Tire wear estimation methods and tire wear shape identification methods

Abstract

To provide a method for accurately estimating the wear of a tire during driving, independent of its wear pattern, the wear is estimated using an index of deformation rate at or near the tire contact patch, a contact time ratio, and deflection. The deformation rate index is calculated based on the magnitude of either or both of the positive and negative peaks in the radial acceleration waveform obtained by differentiating the time-series waveform of the tire's radial acceleration detected by an accelerometer mounted on the tire. The contact time ratio is the ratio of the contact time (the time interval between the positive and negative peaks) to the tire's rotation time (the time interval between either the positive or negative peaks). The deflection is the difference between the tire radius (the radius of the tire when unloaded) and the effective radius (the radius of the tire when in motion).

Description

Technical Field

[0001] This invention relates to a method for estimating the wear level of a tire and a method for determining whether the wear pattern of a tire in motion is intermediate wear. Background Technology

[0002] Conventionally, a method for estimating tire wear has been proposed (for example, see Patent Document 1): An acceleration sensor is placed inside the tire; an index is calculated representing the deformation speed at the tire's contact patch, which is the magnitude of either or both of the positive and negative peaks appearing in the differential waveform of the tire's radial acceleration detected by the acceleration sensor; and a contact patch ratio is calculated, which is the ratio of the contact patch time (the time interval between the positive and negative peaks) to the tire's rotation time (the time interval between the peaks of either the positive or negative peaks). The tire's wear level is estimated based on these calculated deformation speed indices and contact patch ratios, and a pre-determined mapping representing the relationship between groove allowance (as a measure of tire wear), deformation speed indices, and contact patch ratios.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: WO2009 / 008502A1 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, the following problem exists: when estimating the tire groove allowance based on the deformation speed index and the ground contact time ratio as in Patent Document 1 mentioned above, if the tire has an intermediate wear pattern, the actual groove allowance detected will be close to the groove allowance when the tire is new (resulting in the estimated wear amount being less than the actual wear amount).

[0008] Figure 12This graph illustrates the relationship between the differential peak of tire radial acceleration and the contact time ratio when a vehicle equipped with four test tires—a brand new tire (□; New), two tires with different wear patterns (○, △; Mid-worm) with half the tread depth of a brand new tire, and a tire worn to near the slip sign (■; Full-worm)—is driven at a constant speed. The ○ symbol represents a tire with intermediate wear, and the △ symbol represents a tire with even wear. In this example, the differential peak of tire radial acceleration is measured for multiple contact time ratios by varying the load.

[0009] As can be seen from the figure, the relationship between the deformation rate index and the contact time ratio of tires with intermediate wear patterns has shifted towards the new tire side.

[0010] The present invention was made in view of the problems of the past, and its object is to provide a method for determining whether the wear pattern of a tire is intermediate wear, and a method for estimating the wear degree of a tire during driving with high accuracy regardless of the wear pattern of the tire.

[0011] Solution for solving the problem

[0012] This invention provides a method for estimating the wear degree (groove allowance or wear amount) of a tire during operation. The method is characterized by using an index of deformation speed at or near the tire contact patch, a contact time ratio, and deflection to estimate tire wear. The deformation speed index is calculated based on the magnitude of either or both of the positive and negative peaks (differential peak value at the contact patch) in the radial acceleration waveform obtained by differentiating the time-series waveform of the tire's radial acceleration detected by an accelerometer mounted on the tire. The contact time ratio is the ratio of the contact time (the time interval between the positive and negative peaks) to the tire's rotation time (the time interval between either the positive or negative peaks). The deflection is the difference between the tire radius (the radius when the tire is unloaded) and the effective radius (the distance between the axle and the road surface) when the tire is in motion.

[0013] In this way, in addition to the indicators of the tire's deformation rate and contact time ratio during driving, the tire's deflection is also used as a measure of wear to estimate the tire's wear level. Therefore, the tire's wear level can be estimated with high accuracy regardless of whether the tire's wear pattern is intermediate wear.

[0014] In addition, the wear degree of the tire can also be calculated based on a pre-determined regression equation with the deformation rate index, contact time ratio and deflection as variables. It can also determine whether the wear pattern is intermediate wear. If it is intermediate wear, the wear degree estimated based on the deformation rate index and contact time ratio can be corrected.

[0015] Alternatively, it can be set to prepare two main curves: one for uniform wear and one for intermediate wear, with the main curve selected based on the wear pattern.

[0016] Furthermore, the above description of the invention does not list all the necessary features of the invention; sub-combinations of these feature groups can also form an invention. Attached Figure Description

[0017] Figure 1 This is a diagram showing the structure of the tire wear estimation device according to Embodiment 1.

[0018] Figure 2 This is a diagram showing the installation location of the accelerometer and the direction of acceleration detection.

[0019] Figure 3 This is a diagram showing an example of the radial acceleration waveform and the differential acceleration waveform of a tire, as well as the calculation method for rotation time and contact time.

[0020] Figure 4 It shows R c -V R A diagram of an example of mapping.

[0021] Figure 5 This is a flowchart illustrating the tire wear estimation method according to Embodiment 1.

[0022] Figure 6 It is a graph showing the time-varying waveforms of tire radial acceleration, tire circumferential acceleration, tire circumferential velocity, and rotational angular velocity.

[0023] Figure 7 It is a graph showing the time-varying waveforms of the rotation angle, forward and backward acceleration, and up and down acceleration of the measurement point.

[0024] Figure 8 It is a graph showing the time-varying waveforms of the forward and backward velocities and the vertical velocities of the measurement point.

[0025] Figure 9 It is a graph showing the time-varying waveforms of the displacement of the measurement point in the forward and backward directions and the displacement in the up and down directions, as well as the trajectory of the measurement point.

[0026] Figure 10 This is a diagram showing the structure of the tire wear estimation device according to Embodiment 2.

[0027] Figure 11 This is a schematic diagram showing the distribution of characteristic quantities and the identification function as the separating plane.

[0028] Figure 12 It is a mapping that shows the relationship between the deformation rate of tires with different groove allowances and the contact time ratio. Detailed Implementation

[0029] Implementation method 1.

[0030] Figure 1 This is a diagram showing the structure of the tire wear estimation device 10 according to Embodiment 1. The tire wear estimation device 10 includes a first acceleration sensor 11A, a second acceleration sensor 11B, an acceleration differential waveform calculation unit 12, a differential peak value calculation unit 13, a ground contact time ratio calculation unit 14, an angular velocity estimation unit 15, a deflection calculation unit 16, a storage unit 17, and a groove margin estimation unit 18.

[0031] Each unit of the acceleration differential waveform calculation unit 12 to the groove margin estimation unit 18 is composed of, for example, computer software and memory such as RAM. Hereinafter, each unit of these acceleration differential waveform calculation units 12 to the groove margin estimation unit 18 will be referred to as the calculation unit 10B. In this example, the calculation unit 10B is located on the side of the vehicle body, but it could also be located inside the tire.

[0032] like Figure 2 As shown in (a) and (b), the first acceleration sensor 11A and the second acceleration sensor 11B are both housed in a sensor box 11 located approximately in the center of the inner liner portion 2 of the tire 1 on the side near the tire chamber 3, and detect the vibration input from the road surface to the tread 4 as acceleration.

[0033] The first acceleration sensor 11A is configured with the detection direction being the tire radial direction to detect the tire radial acceleration a input from the road surface. R (t), the second acceleration sensor 11B is configured with the detection direction being the tire circumferential direction to detect the tire circumferential acceleration a. T (t). In addition, in each figure, the x-direction is the vehicle's direction of travel, the y-direction is the vehicle's width direction (tire width direction), and the z-direction is the up and down direction.

[0034] Furthermore, although the figures are omitted, the sensor box 11 houses an amplifier that amplifies the outputs of the first acceleration sensor 11A and the second acceleration sensor 11B, an A / D converter, and a transmitter that sends the A / D converted signal to the arithmetic unit 10B. Moreover, when the arithmetic unit 10B is installed inside the tire 1, such as in the sensor box 11, the estimation result obtained by the arithmetic unit 10B can be sent to a vehicle control device (not shown) installed on the side of the vehicle body.

[0035] The first acceleration sensor 11A and the second acceleration sensor 11B are much smaller than the size of the tire 1, and therefore can be considered to be in approximately the same position. Below, Figure 2 The positions of the first accelerometer 11A and the second accelerometer 11B shown at point A in (b) are called measurement points.

[0036] The acceleration differential waveform calculation unit 12 extracts the time sequence waveform of the tire radial acceleration detected by the first acceleration sensor 11A, i.e., the radial acceleration waveform, and calculates the waveform obtained by time differentiation of the extracted radial acceleration waveform, i.e., the acceleration differential waveform.

[0037] Figure 3 Figure (a) is a diagram showing an example of a radial acceleration waveform, with the horizontal axis representing time [sec.] and the vertical axis representing acceleration [G]. The portion of the diagram enclosed by the dashed line with the largest negative slope represents the grounding terminal p on the step-in side. f The part p with the largest positive slope k It is the grounding terminal on the push-off side.

[0038] in addition, Figure 3 Figure (b) is a graph showing an example of the differential acceleration waveform, with the horizontal axis representing time [sec.] and the vertical axis representing the differential acceleration value [G / sec.]. Two peaks appear in this differential acceleration waveform. The first peak in time, on the leading side of the waveform, is the step-in peak P. f The peak that appears later in time is the peak P on the side of the kick-off end. k The ground terminal p of the radial acceleration waveform f p k The greater the slope at a point, the greater the peak P in the differential acceleration waveform. f P k The larger the size.

[0039] like Figure 3 As shown in (c), the peak P on the step-in side of the differential acceleration waveform f Peak P on the side of the push-off end k The interval is the grounding time T. t The peaks P on the two adjacent push-off ends in time k Pk+1 The interval is the time it takes for the tire to rotate once, i.e., the rotation time T. r Alternatively, the rotation time T can be calculated based on the time interval between the peaks on the stepping side. r .

[0040] In the differential peak calculation unit 13, the peak P on the step-in side is calculated. f The magnitude is the differential peak value V on the step-in end side. Rf And use it as the deformation rate index V R Send to the groove allowance estimation unit 18. Furthermore, V is used as the deformation rate index. R Alternatively, the differential value of the acceleration at the push-off end can be used, i.e., the peak differential value V at the push-off end. Rk Alternatively, the differential peak value V on the step-in side can be used. Rf Differential peak value V at the push-off end Rk The average value.

[0041] In the grounding time ratio calculation unit 14, the calculation is performed. Figure 3 (c) shows the peak P on the push-off side. k The rotational time T is the time difference between the time T1 when the peak appears and the time T2 when the peak on the pedal end side reappears after one revolution of tire 1. r And as the peak P on the step-in end side f Peak P on the side of the push-off end k The grounding time T between t And calculate the calculated grounding time T. t Divide by rotation time T r The obtained grounding time is greater than R c The calculated grounding time is higher than R. c It is sent to the trench margin estimation unit 18.

[0042] In addition, T r =T2-T1, R c =(T t / T r ).

[0043] Angular velocity estimation unit 15 estimates the tire radial acceleration α detected by the first acceleration sensor 11A. R (t) and the tire circumferential acceleration a detected by the second acceleration sensor 11B T We use (t) to estimate the rotational angular velocity ω(t) of tire 1.

[0044] The deflection calculation unit 16 calculates the tire radial acceleration a detected by the first acceleration sensor 11A. R (t), the tire circumferential acceleration a detected by the second acceleration sensor 11BT The trajectory of measurement point A is calculated using the angular velocity ω(t) estimated by the angular velocity estimation unit 15, and the shape of the tire 1 as the longitudinal cross-section shape of the tire 1 during driving is obtained. The deflection d is estimated based on the shape of the tire 1. The tire radius, which is the radius of the tire 1 when it is unloaded, is set as R, and the effective radius, which is the radius of the tire when it is in motion, is set as R... eff At that time, the deflection d can be expressed as d = RR eff .

[0045] The methods for estimating the rotational angular velocity ω(t) and calculating the deflection d will be described later.

[0046] Storage unit 17 stores multiple pre-calculated R values. c -V R Mapping 17M1~17M n R c -V R Mapping 17M1~17M n It is a mapping used to estimate the wear level of tire 1, and it is for each deflection d. k (k = 1 to n) is used. Furthermore, in this example, the groove allowance H is used as the degree of wear, but the wear amount M can also be used as the degree of wear. When the groove depth of the tire 1 when it is new is set to H0 and the groove allowance is set to H, the wear amount M is represented by M = H0 - H.

[0047] like Figure 4 As shown, the deflection is d k R c -V R Mapping 17M k The pre-calculated groove allowance is H. j The wear tire's contact time with the ground is longer than R c With deformation rate index V R The main line of the relationship L j Plotted with the horizontal axis set to the grounding time ratio R c And set the vertical axis as the deformation rate index V. R The plane obtained, in this example, is the principal line L. j The range can be set to 4 lines: H1 = 8mm (new), H2 = 6mm, H3 = 4mm, and H4 = 2mm (whole worm) (j = 1 to 4). However, it can also be set to 3 lines (new, medium worm, and whole worm), or even more than 5 lines.

[0048] R c -V R Mapping 17M1~17M n It uses a groove allowance H that includes both new tires (new) and tires worn to near the wear indicator (full worm).M Vehicles with multiple test tires of different wear patterns under various load conditions underwent a road contact time comparison with R. c Data, deformation rate index V R The data was obtained from the data of the bending amount d.

[0049] Furthermore, in the case of shoulder wear, if the groove allowance in the middle section is approximately the same as the groove allowance in uniform wear, the contact time will be longer than that of R. c Deformation speed index V R Since the deflection d is roughly the same as that of uniform wear, in this example, the wear shape is set to two types: intermediate wear and uniform wear.

[0050] The groove allowance estimation unit 18 uses the deformation rate index V calculated by the differential peak calculation unit 13. R The grounding time ratio R calculated by the grounding time ratio calculation unit 14 c The deflection d calculated by the deflection calculation unit 16 and the R stored in the storage unit 17 c -V R Mapping 17M1~17M n To estimate the groove allowance H as the wear degree of the tire 1.

[0051] As mentioned above, R c -P maps 17M1 to 17M n It is the radial acceleration a of the tires measured by driving vehicles equipped with test tires having different groove allowances H and different wear patterns. R (t) and tire circumferential acceleration a T (t) is obtained, therefore if R is used c -V R Mapping 17M1~17M n It can estimate the groove allowance H with high accuracy, regardless of whether the wear shape is intermediate wear.

[0052] In addition, such as Figure 4 As shown, it can also replace R. c -V R Mapping 17M1~17M n Using a pre-calculated grounding time ratio R c Deformation speed index V R The regression equation for the groove allowance H, which has three variables as variables, is H = F(R). c V R The regression equation is H = F(R, d) to estimate the groove allowance H of tire 1. c V R d) is also related to the above R c -VR Mapping 17M1~17M n Similarly, the radial acceleration a of the tires was measured by driving vehicles equipped with test tires having different groove allowances H and different wear patterns. R (t) and tire circumferential acceleration a T The value was obtained using (t). Therefore, the regression equation H = F(R) is used. c V R ,d) can also estimate the groove allowance H of the tire 1 with high accuracy.

[0053] Next, refer to Figure 5 The tire wear estimation method according to Embodiment 1 will be described using a flowchart. Furthermore, when estimating the degree of wear, it is assumed that the vehicle equipped with tire 1 is traveling straight at a constant speed V0 on a flat road surface.

[0054] First, the radial acceleration a of the tire input from the road surface to the tire 1 is detected by the first acceleration sensor 11A and the second acceleration sensor 11B installed in the inner liner portion 2 of the tire 1. R (t) and tire circumferential acceleration a T (t)(Step S10).

[0055] Next, the radial acceleration a of the tire is calculated. R (t) The waveform obtained by time differentiation is the acceleration differential waveform (step S11). Calculate the peak P on the step-in side of this acceleration differential waveform. f The magnitude is the peak value of the differential on the step-in end side, V. Rf And use it as the deformation rate index V R (Step S12). Furthermore, the peak P on the step-in side of the differential acceleration waveform is calculated. f Peak P on the side of the push-off end k The grounding time T of the interval t And the two push-off peaks P in the differential acceleration waveform k1 P k2 The rotation time T of the interval r (Step S13), then, the calculated grounding time T is calculated. t With rotation time T r The ratio of the grounding time to R c (Step S14). Grounding time ratio R c Able to use T t / T r To express.

[0056] Next, based on the tire radial acceleration a detected in step S10 above... R (t) and tire circumferential acceleration a TThe rotational angular velocity ω(t) of tire 1 is calculated using (t) (step S15). Then, based on the tire radial acceleration a R (t), tire circumferential acceleration a T The deflection d of tire 1 is calculated using the rotational angular velocity ω(t) and the rotational angular velocity ω(t) (step S16).

[0057] In addition, the deformation rate index V R The calculation and grounding time ratio R c The calculation of the angular velocity and the deflection d do not necessarily have to be performed in this order; the order can be changed, and they can be processed in parallel.

[0058] Finally, the deformation rate index V calculated in step S13 is used. R The grounding time ratio R calculated in step S15 c The deflection d calculated in steps S16-S17, and the pre-calculated R stored in the database. c -V R Mapping 17M1~17M n To estimate the groove allowance H as the wear degree of the tire 1 (step S17).

[0059] The method for estimating the rotational angular velocity ω(t) in step S15 is as follows.

[0060] First, such as Figure 6 As shown in (a) and (b), from the radial acceleration a of the tire R (t) and tire circumferential acceleration a T (t) captures the waveform of the amount of time the tire rotates one revolution.

[0061] Next, based on the tire circumferential acceleration a T (t), use the following equation (1) to calculate the tire circumferential velocity v(t).

[0062] [Number 1]

[0063]

[0064] Here, V0 represents the vehicle speed, which can be calculated based on the tire's rotational period, tire radius, and GPS data. Sometimes, preprocessing such as centering is also performed on v(t).

[0065] like Figure 6 As shown in (c), the tire circumferential velocity v(t) decreases as it approaches the pedal end, increases again when it enters the contact area, but decreases again from near the center of the contact area, and becomes the minimum at the pedal end, and then rises.

[0066] Next, based on the tire radial acceleration a RThe rotational angular velocity ω(t) of tire 1 is estimated by the following equation (2) using the tire circumferential velocity v(t) and the tire circumferential velocity v(t).

[0067] ω(t)=a R (t) / v(t)……(2)

[0068] Figure 6 (d) shows the time variation of the estimated rotational angular velocity ω(t).

[0069] Equation (2) above is derived assuming that the sensor (measuring point A) is undergoing uniform circular motion at a certain time t, and the acceleration a of measuring point A during uniform circular motion is... R The velocity v(t) and the velocity v(t) can be expressed by the following formula.

[0070] a R (t)=v 2 (t) / R(t)

[0071] v(t)=R(t)ω(t)

[0072] Here, R(t) is the radius of curvature at time t.

[0073] Eliminating R(t) from the two equations above and solving for ω(t) yields equation (2).

[0074] Next, the calculation method for the deflection d in step S16 will be explained.

[0075] In this example, the deflection d is calculated based on the trajectory of measurement point A.

[0076] First, integrate the estimated value of the rotational angular velocity ω(t) using the following equation (3) to obtain the time-varying waveform of the rotational angle θ. For example... Figure 7 As shown in (a), the rotation angle θ of the measuring point is the rotation angle of the measuring point A when viewed from the center of the tire 1. The initial value θ0 can be set to an appropriate value such as 0 (grounding center) or -π (topmost part).

[0077] [Number 2]

[0078]

[0079] Figure 7 (a) is a graph showing the time variation of the rotation angle θ(t). It can be seen that the rotation angle θ(t) changes approximately linearly, but near the ground center surrounded by the circle in the graph (around t = 0.1 seconds), the change becomes smaller, corresponding to the decrease in the rotation angular velocity ω(t).

[0080] Next, as shown in equations (4) and (5) below, using the aforementioned rotation angle θ(t), the tire radial acceleration a is... R (t) and tire circumferential acceleration a T (t) is transformed into forward and backward acceleration a, which is the acceleration in the global coordinate system (x, z). x (t) and vertical acceleration a z (t). The global coordinate system (x, z) is Figure 2 As shown in (a) and (b), a coordinate system is established where the x-direction is the vehicle's direction of travel, the y-direction is the vehicle's width direction (tire width direction), and the z-direction is the up-down direction.

[0081] [Number 3]

[0082] a x (t)=a T (t)cosθ(t)-a R (t)sinθ(t)……(4)

[0083] a z (t)=a T (t)sinθ(t)+a R (t)cosθ(t)......(5)

[0084] exist Figure 7 (b) shows the forward and backward acceleration a. x The time-varying waveform of (t) is shown in Figure 7 (c) shows the vertical acceleration a. z The time-varying waveform of (t).

[0085] Next, the acceleration transformed into the global coordinate system is integrated, and the forward and backward velocities v of the measurement point A are calculated using the following equations (6) and (7). x (t) and vertical velocity v z (t).

[0086] [Number 4]

[0087]

[0088]

[0089] Among them, a x (t), a z (t) is sometimes accompanied by preprocessing such as centering. Additionally, the initial value v x0 v z0 It can be set to any value.

[0090] exist Figure 8(a) shows the forward and backward velocities v. x The time-varying waveform of (t) is shown in Figure 8 (b) shows the vertical velocity v. z The time-varying waveform of (t).

[0091] Furthermore, by integrating the velocity, the displacement u in the forward and backward directions of the measurement point A is calculated using the following equations (8) and (9). x (t) and displacement u in the vertical direction z (t).

[0092] [Number 5]

[0093]

[0094]

[0095] Among them, v x (t), v z (t) is sometimes accompanied by preprocessing such as centering. Additionally, the initial value u... x0 u z0 It can be set to any value.

[0096] exist Figure 9 (a) shows the displacement u in the forward and backward directions. x The time-varying waveform of (t) is shown in Figure 9 (b) shows the displacement u above and below. z The time-varying waveform of (t).

[0097] Then, by removing the time component and shifting u x (t), u z (t) is plotted on a two-dimensional plane, resulting in the following: Figure 9 The trajectory of measurement point A as shown in (c).

[0098] The regression circle C is obtained by fitting the trajectory of the measurement point A with a circle. fit Find the regression circle C. fit The regression radius R fit And determine the effective radius R, which represents the radius of tire 1 in a state of deflection. eff In this example, as Figure 9 As shown in the schematic diagram of (d), the effective radius R eff Let C be the regression circle shown by the dashed line in the figure. fit The minimum distance from the center O to the measurement point A.

[0099] Finally, the deflection d is calculated using the following formula.

[0100] d = R fit-R eff

[0101] Furthermore, the deflection d used to estimate the degree of wear or as a characteristic quantity used in the intermediate wear determination described later can be either the deflection d or the deflection rate k. d =d / R fit .

[0102] Implementation method 2.

[0103] Figure 10 This is a diagram showing the structure of the tire wear estimation device 20 according to Embodiment 2. In this diagram, 11A is a first acceleration sensor, 11B is a second acceleration sensor, 12 is an acceleration differential waveform calculation unit, 13 is a differential peak value calculation unit, 14 is a ground contact time ratio calculation unit, 15 is an angular velocity estimation unit, 16 is a deflection calculation unit, 21 is an identification model storage unit, 22 is a wear shape discrimination unit, 23 is an RV mapping storage unit, and 24 is a groove margin estimation unit.

[0104] For the first acceleration sensor 11A and the second acceleration sensor 11B to the deflection calculation unit 16, the structure of each unit with the same reference numerals as in Embodiment 1 is the same as in Embodiment 1, so their description is omitted.

[0105] The identification model storage unit 21 stores the pre-determined wear shape identification model 21M.

[0106] like Figure 11 As shown, the wear shape recognition model 21M has a reference feature vector Y. ZSV and the baseline eigenvector Y ZSV Weighted Lagrange multiplier λ Z (Z = N or M), the baseline eigenvector Y ZSV The identification function f is used to determine whether the wear pattern of tire 1 is uniform wear (N state) or center wear (M state). NM (x) is used for separation.

[0107] The contact time ratio R was calculated when vehicles equipped with multiple test tires of different groove allowances H and wear patterns were driven under various load conditions. c Data, deformation rate index V R The data and the data of the deflection d are used as the feature vector Y of the components. Z =(R cZ V RZ d Z After that, these feature vectors Y ZThe baseline feature vector Y is obtained by using a Support Vector Machine (SVM) as training data. ZSV and the Lagrange multiplier λ Z .

[0108] Wear shape discrimination unit 22 uses the deformation rate index V calculated by differential peak calculation unit 13. R The grounding time ratio R calculated by the grounding time ratio calculation unit 14 c The deflection d calculated by the deflection calculation unit 16 is used as the characteristic vector X(R) of the component. c V R d) Support vectors Y recorded in the recognition model storage unit 21 NSV and Y MSVV and the Lagrange multiplier λ N , λ M Calculate the kernel function K N (X, Y) NSV ), K M (X, Y) MSVV After that, use these kernel functions K N (X, Y) NSV ), K M (X, Y) MSVV To find the recognition function f used to identify tire wear patterns. NM The value of (x) is determined by the recognition function f. NM The value of (x) is used to determine whether the wear shape of tire 1 is N-state (uniform wear) or M-state (intermediate wear). The determination result of wear shape determination unit 22 is sent to groove allowance estimation unit 24.

[0109] Furthermore, as the kernel function K N K M For example, the Gaussian kernel function can be preferred.

[0110] RV mapping memory unit 23 stores the first mainline L calculated in advance. Nj Plotted with the horizontal axis set to the grounding time ratio R c And set the vertical axis as the deformation rate index V. R The first R obtained on the plane c -V R Mapping 23N (Even-Map) and the pre-calculated second principal line L Mj The second R obtained by drawing on this plane c -V R Mapping 23M (Center-Map), the first mainline L Nj The groove allowance is H.j Furthermore, the contact time of a tire with uniform wear pattern is longer than that of a tire with uniform wear pattern. c With deformation rate index V R The relationship, the second main line L Mj The groove allowance is H. j Furthermore, the contact time of a worn tire with an intermediate wear pattern is longer than that of a tire with an intermediate wear pattern. c With deformation rate index V R The relationship.

[0111] First R c -V R Mapping 23N and the second R c -V R Mapping 23M is used based on the grounding time ratio R c and deformation rate index V R To estimate the degree of wear, the first R c -V R Mapping 21N is a test vehicle that uses multiple test tires with uniform wear patterns and different groove allowances H to perform ground contact time ratios under various load conditions. c Data and deformation rate index V R The data was obtained from this.

[0112] On the other hand, the second R c -V R Mapping 21M is a test that uses multiple test tires with different wear patterns (intermediate wear and different groove allowances H) to measure the contact time ratio during driving under various load conditions. c Data and deformation rate index V R The data was obtained from this.

[0113] The groove allowance estimation unit 24 uses the deformation rate index V calculated by the differential peak calculation unit 13. R The grounding time ratio R calculated by the grounding time ratio calculation unit 14 c and the first R stored in RV mapping storage unit 23 c -V R Mapping 23N or the second R c -V R Map 23M to estimate the groove allowance H as the wear level of tire 1.

[0114] Specifically, when the wear shape discrimination unit 22 determines that the wear shape of the tire 1 is uniform wear, the calculated deformation rate index V is used. R and grounding time ratio R c and the first R c -V RThe groove allowance H, representing the wear degree of tire 1, is estimated by mapping 23N. If the wear pattern is determined to be intermediate wear, the calculated deformation rate index V is used. R and grounding time ratio R c and the second R c -V R Map 23M to estimate the groove allowance H as the wear level of tire 1.

[0115] In this way, the deformation rate index V is calculated by the differential peak calculation unit 13. R The grounding time ratio R is calculated by the grounding time ratio calculation unit 14. c After the deflection amount d is calculated by the deflection calculation unit 16, the deformation rate index V calculated above is then applied. R Grounding time ratio R c And the eigenvector X(R) with the deflection d as a component c V R d), and the feature vectors, i.e. support vectors, pre-calculated for each wear shape. Z =(R cZ V RZ d Z The discrimination model (wear shape recognition model 21M) constructed using the learning data uses machine learning algorithms to determine whether the wear shape of the above tire is uniform wear or intermediate wear, thus enabling high-precision determination of the wear shape of the tire 1.

[0116] Furthermore, since the wear pattern is taken into account when estimating the wear degree of the tire 1, the wear degree of the tire during driving can be estimated with high accuracy regardless of the wear pattern of the tire.

[0117] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. Various modifications or improvements can be made to the above embodiments, as will be apparent to those skilled in the art. It is evident from the claims that methods obtained by making such modifications or improvements can also be included within the technical scope of the present invention.

[0118] For example, in embodiments 1 and 2 described above, based on the tire radial acceleration a R (t) and tire circumferential acceleration a T The rotational angular velocity ω(t) can be estimated using (t), but it can also be directly measured using an angular velocity sensor such as a vibrating gyroscope. Preferably, the angular velocity sensor is located at the measurement point A.

[0119] Alternatively, the deflection amount d can be calculated by installing a distance sensor on the vehicle equipped with tire 1 to measure the distance between the vehicle and the road surface, and then calculating the deflection amount d based on this distance. Specifically, the distance between the distance sensor's location and the road surface is converted into the distance between the axle and the road surface, and this distance is used as the effective radius R. eff The difference between the effective radius and the tire radius R can be taken as the deflection d.

[0120] In addition, in the above-described embodiment 2, the wear shape discrimination unit 22 is composed of support vector machine (SVM), but other machine learning algorithms such as logistic regression, random forest, and neural network can also be used.

[0121] Furthermore, in the above-described embodiment 2, the mapping for estimating the degree of wear is selected based on the wear shape; however, it could also be configured to prepare only the first R. c -V R Map 23N, and pre-calculate the grounding time ratio R. c and deformation speed index V R Under the same conditions, the groove allowance H when the wear shape is uniform wear N Groove allowance H when the wear shape is intermediate wear M The correction amount ΔH for the difference, in the case of intermediate wear, will be obtained through the first R. c -V R The groove allowance H' calculated by mapping 23N is corrected to H = H' + ΔH and then output. Furthermore, if the wear shape is not intermediate wear, no correction is needed, and H' can be output directly.

[0122] Explanation of reference numerals in the attached figures

[0123] 1: Tire; 2: Inner liner layer; 3: Tire chamber; 4: Tread; 10: Tire wear estimation device; 11: Sensor box; 11A: First acceleration sensor; 11B: Second acceleration sensor; 12: Acceleration differential waveform calculation unit; 13: Differential peak value calculation unit; 14: Ground contact time ratio calculation unit; 15: Angular velocity estimation unit; 16: Deflection calculation unit; 17: Storage unit; 17M1~17M n Rc-V R Mapping; 18: Trench margin estimation unit.

Claims

1. A tire wear estimation method in which, an indicator of a deformation velocity at a tire ground contact end or in the vicinity thereof, a ground contact time ratio, and a deflection amount are used to estimate a wear degree of a tire, the indicator of the deformation velocity being calculated from a magnitude of either one or both of a positive peak and a negative peak appearing in a radial acceleration waveform obtained by differentiating a time series waveform of a tire radial acceleration detected by an acceleration sensor mounted to the tire, the ground contact time ratio being a ratio of a ground contact time, which is a time interval between the positive peak and the negative peak, to a tire rotation time, which is a time interval of either one of the peaks, the deflection amount being a difference between a tire radius, which is a radius when the tire is unloaded, and an effective radius, which is a radius when the tire is running, the tire wear estimation method comprising: a discrimination step of discriminating, based on the indicator of the deformation velocity, the ground contact time ratio, and the deflection amount as characteristic quantities, whether a wear shape of the tire is intermediate wear by a machine learning algorithm; and a step of estimating the wear degree of the tire, in the discrimination step, whether the wear shape of the tire is intermediate wear is discriminated based on the characteristic quantities and a discrimination model that is a model constructed using, as learning data, characteristic quantities of a tire whose wear shape is intermediate wear and characteristic quantities of a tire whose wear shape is not intermediate wear, in the step of estimating the wear degree of the tire, in a case where it is discriminated that the wear shape of the tire is intermediate wear, the wear degree of the tire is estimated using the calculated indicator of the deformation velocity, the ground contact time ratio, and a relationship between the indicator of the deformation velocity, the ground contact time ratio, and the wear degree of a tire whose wear shape is intermediate wear, which is obtained in advance, in a case where it is discriminated that the wear shape of the tire is not intermediate wear, the wear degree of the tire is estimated using the calculated indicator of the deformation velocity, the ground contact time ratio, and a relationship between the indicator of the deformation velocity, the ground contact time ratio, and the wear degree of a tire whose wear shape is not intermediate wear, which is obtained in advance.

2. The tire wear estimation method according to claim 1, wherein, the tire radial acceleration, the tire circumferential acceleration, and the rotational angular velocity of the tire are measured, and the deflection amount is estimated from a trajectory of displacement of the tire calculated using the measured tire radial acceleration, tire circumferential acceleration, and rotational angular velocity.

3. The tire wear estimation method according to claim 1, wherein, the tire radial acceleration and the tire circumferential acceleration of the tire are measured, the rotational angular velocity of the tire is estimated from the measured tire radial acceleration and tire circumferential acceleration, and the deflection amount is estimated from a trajectory of displacement of the tire calculated using the measured tire radial acceleration and tire circumferential acceleration, and the estimated rotational angular velocity.

4. The tire wear estimation method according to claim 1, characterized in that, the effective radius is calculated based on a distance between the vehicle and a road surface detected by a distance sensor mounted in the vehicle on which the tire is mounted.

5. A tire wear estimation method wherein, an indicator of a deformation speed at a tire ground contact end portion or in the vicinity thereof, a ground contact time ratio, and a deflection amount are used to estimate a degree of wear of a tire, the indicator of the deformation speed being calculated based on a size of either or both of a positive peak and a negative peak appearing in a radial acceleration waveform obtained by differentiating a time series waveform of a tire radial acceleration detected by an acceleration sensor mounted to the tire, the ground contact time ratio being a ratio of a ground contact time, which is a time interval between the positive peak and the negative peak, to a rotation time of the tire, which is a time interval of either of the positive peak and the negative peak, the deflection amount being a difference between a tire radius, which is a radius when the tire is unloaded, and an effective radius, which is a radius when the tire is running, the tire wear estimation method comprising: an estimation step of estimating the degree of wear of the tire using the indicator of the deformation speed and the ground contact time ratio; a discrimination step of discriminating whether a wear shape of the tire is intermediate wear based on the indicator of the deformation speed, the ground contact time ratio, and the deflection amount by a machine learning algorithm; and a correction step of correcting the estimated degree of wear when the wear shape of the tire is discriminated as intermediate wear, in the discrimination step, whether the wear shape of the tire is intermediate wear is discriminated based on the characteristic quantities and a discrimination model obtained in advance, the discrimination model being a model constructed using characteristic quantities of a tire whose wear shape is intermediate wear and characteristic quantities of a tire whose wear shape is not intermediate wear as learning data, in the correction step, the estimated degree of wear is corrected using a difference between a degree of wear of a tire whose wear shape is intermediate wear and a degree of wear of a tire whose wear shape is not intermediate wear obtained in advance.

6. A tire wear shape discrimination method for discriminating whether a wear shape of a tire running is intermediate wear, the tire wear shape discrimination method comprising: obtaining an indicator of a deformation speed at a tire ground contact end portion or in the vicinity thereof, the indicator of the deformation speed being calculated based on a size of either or both of a positive peak and a negative peak appearing in a radial acceleration waveform obtained by differentiating a time series waveform of a tire radial acceleration detected by an acceleration sensor mounted to the tire; obtaining a ground contact time ratio, the ground contact time ratio being a ratio of a ground contact time, which is a time interval between the positive peak and the negative peak, to a rotation time of the tire, which is a time interval of either of the positive peak and the negative peak; obtaining a deflection amount, the deflection amount being a difference between a tire radius, which is a radius when the tire is unloaded, and an effective radius, which is a radius when the tire is running; and ​ In a discrimination step, whether the wear shape of the tire is intermediate wear is discriminated by a machine learning algorithm based on the index of the deformation speed, the grounding time ratio, and the deflection amount as characteristic quantities. In the discrimination step, Whether the wear shape of the tire is intermediate wear is discriminated based on the characteristic quantities and a discrimination model that is constructed based on characteristic quantities of tires whose wear shape is intermediate wear and characteristic quantities of tires whose wear shape is not intermediate wear as learning data.

Images