JP5165603B2 - Tire running state estimation method, steady running state estimation device, tire wear estimation method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for estimating the running state of a tire, and a method and apparatus for estimating the degree of tire wear.

When the tires wear, the drainage performance decreases, causing a decrease in braking / driving performance on a wet road surface. In addition, with a studless tire, the grip performance on an icy and snowy road surface is greatly reduced due to wear. Excessive wear is very dangerous because water can enter the tread belt and cause tire destruction.
In the case of a small passenger car, rubber protrusions called slip signs appear in the groove when the remaining groove amount of the tire is 1.6 mm. Considering the driving safety of the vehicle, tires should be replaced before the appearance of the slip sign, but there are not many drivers who are indifferent to such maintenance.
Therefore, a technique for automatically detecting tire wear is required for warning the driver. In terms of vehicle control, it is expected to grasp changes in tire characteristics due to wear and realize safer control.

As a method of estimating tire wear, conventionally, the tire dynamic radius is calculated by calculating the absolute speed of the vehicle using a GPS or an optical sensor and comparing it with the wheel rotation speed. There is known a method for obtaining a tire wear amount from a difference from the tire radius (see, for example, Patent Documents 1 and 2).
However, even if the tire is completely worn, the difference between the rotational speed of the tire and the rotational speed of a new tire is at most about 1%. In actual driving, it includes stable inner and outer wheel errors during turning, errors due to acceleration slip during braking and driving, and errors due to gradients. It was difficult to do.

  On the other hand, a tire is worn by embedding a transponder or IC tag in the tire tread, and placing a receiver on the vehicle body side. (See, for example, Patent Documents 3 to 5), or a detection body made of a magnetic material or conductive rubber is embedded in a tire tread, a sensor is disposed on the vehicle body side, and the detection body is caused by tire wear. There has been proposed a method of estimating tire wear by detecting that the detection signal of the sensor changes due to wear (see, for example, Patent Documents 6 and 7).

  However, in the method of embedding a transponder, IC tag, magnetic material, conductive rubber or the like in the tire tread, the detector and the sensor are exposed to the grounding surface as wear progresses, so there is a concern that the tire durability may be adversely affected. In addition, when a rubber having physical properties different from that of the tread rubber is exposed on the surface of the tire tread, there is a problem that the grip strength of the tire is reduced.

Therefore, the present applicant arranges an acceleration sensor in the tire tread portion, and uses the time series waveform of the acceleration of the tire tread portion detected by the acceleration sensor, and the amount of deformation in the tire radial direction at the tire contact end portion of the tread. Alternatively, a method has been proposed in which a deformation speed is calculated and the degree of wear of the tire is estimated using the calculated deformation amount or deformation speed in the tire radial direction (Japanese Patent Application No. 2007-182254).
Thus, if the deformation of the tread is directly measured to estimate the degree of wear of the tire, the wear form of the tire is such that, for example, the shoulder portion is more worn than the center portion. Even in different cases, the wear of the tire can be accurately estimated.

JP-A-6-278419 JP 7-164830 A Japanese Patent Laid-Open No. 10-307981 JP 2004-205437 A US2002 / 0116992A1 JP 2003-214808 A JP 2005-28950 A

  However, as a result of subsequent studies, in the wear estimation method proposed by the applicant, an error occurs in the estimated degree of wear when a certain degree of acceleration or steering force is applied when the vehicle travels. It turns out that there is a tendency to. In other words, in order to stably estimate the degree of wear, it is preferable to estimate only at a constant speed, a straight running in a straight line, or a state close thereto (hereinafter referred to as a steady running state).

As one method, a method of determining a steady running state using an acceleration sensor normally provided in a vehicle and transmitting the information to a tire can be considered. However, in this case, there is a problem that a transmission system from the vehicle to the tire and a reception system on the tire side are newly required, and the system configuration becomes complicated.
Also, in the steady running state determined from the information of the acceleration sensor mounted on the vehicle body, the state where no longitudinal force or lateral force is input to the tire where the acceleration sensor for estimating the degree of wear of the tire is installed Therefore, when estimating the state of tire wear based on tire tread information, it is better to assume that the steady running state is the case where the tire is in the steady running state. It is considered that the degree can be estimated more accurately.

  On the other hand, it is possible to send data every time from the tire side without sending steady running information to the tire side, and to select these data on the vehicle side, but in this case, delay the data every time Therefore, a large amount of energy is required for transmission on the tire side. For this reason, a large power generation device is required for the tire, which is also not preferable.

  The present invention has been made in view of conventional problems, and estimates whether the tire is in a steady running state on the tire side and improves the estimation accuracy of the tire wear degree with a simple system configuration. With the goal.

FIG. 15 is a schematic view showing the outer shape of the tire when the tire 1 is bent by applying a load. When a load is applied to the tire, a portion where the tire is in contact with the road surface (ground contact surface) is pushed in toward the tire center, and the periphery of the tire is deformed so as to bulge outward from the initial profile indicated by a one-dot chain line in FIG. Here, the point at which the tire 1 swells to the outermost side outside the ground contact surface is defined as the bulging point, and the end of the ground contact surface of the tire 1 is defined as the ground contact end.
As a result of examining the difference in deformation between a new tire and a worn tire, the present inventors have found that when the same amount of deflection is given, the worn tire has a tread radial direction at the ground contact end such as a stepping end or a kicking end. It was found that the deformation speed was higher than that of a new tire. The reason for this is considered that the worn tire has less tread rubber, and therefore the out-of-plane bending deformation rigidity of the tread is low.
Therefore, an acceleration sensor is attached to the tire tread portion, and an index of the deformation rate in the tire radial direction near the contact end of the tire tread or in the vicinity of the contact end is measured, and this deformation rate index is used as an estimated measure of tire wear. By doing so, the degree of wear of the tire can be estimated accurately and stably.

Incidentally, the estimation accuracy of the degree of wear estimated using the index of deformation speed is affected by acceleration and steering, that is, the longitudinal force and lateral force input to the tire. This is because the ground contact surface of the tire moves back and forth due to longitudinal force and lateral force, and at the same time, vibration due to slip occurs on the contact surface, so that the deformation of the contact end changes from the steady running state. Due to
For inputs below a certain level, it is possible to reduce the influence of longitudinal force and lateral force by using the average value of the index of deformation speed on the stepping side and kicking side. However, when the input is increased, the estimated value of the degree of wear is shifted. Therefore, it is better not to use the driving state data with a large input because it causes an error (noise).
Since tire wear is a slow change unless the circuit travels, there is no need to constantly detect wear data, and there is no problem even if measurement is not performed in a state other than steady travel. Rather, it is desirable to measure only when the vehicle is surely in a steady running state.

The steady running state of the tire needs to be easily determined within the tire, that is, from the behavior of the tire. The time series waveform of the radial acceleration of the tire tread (hereinafter referred to as the radial acceleration waveform) output from the acceleration sensor used to estimate the degree of wear of the tire was examined. It was found that the following characteristics appear in the radial acceleration waveform.
The first feature is that the front and rear bulge point levels outside the contact surface, that is, the acceleration level of the bulge point (front bulge point) that appears in front of the tread end of the tire tread and the bulge that appears behind the kick end. The acceleration level of the point (rear bulging point) changes relatively.
The second feature is that high-frequency vibration caused by tire slip occurs behind the tire contact surface.

  Therefore, an acceleration sensor is arranged in the tire tread portion to extract a radial acceleration waveform, and by detecting an acceleration level of a bulging point appearing in the radial acceleration waveform or a vibration level of high-frequency vibration behind the tire contact surface. It can be estimated whether the running state of the tire is a steady running state in which the longitudinal force and the lateral force are not input to the tire.

  That is, according to the present invention, from the time series waveform of the acceleration signal in the tire radial direction output from the acceleration sensor arranged in the tire tread portion, the front bulge point which is the bulge point on the tread end side of the tire tread or the above-mentioned The front bulge point level that is the output level near the front bulge point and the rear bulge point that is the bulge point on the kicking end side or the rear bulge point level that is the output level near the rear bulge point And the two bulging point levels are compared to estimate whether or not the tire running state is a steady running state, so that the longitudinal force and lateral force are input to the tire. It can be reliably estimated in the tire. Therefore, it is possible to accurately estimate whether or not the running state of the tire is a steady running state without complicating the system.

  Further, the vibration level in the specific frequency range behind the tire contact surface is detected from the time series waveform of the acceleration signal in the tire radial direction output from the acceleration sensor arranged in the tire tread portion, and the detected specific frequency range is detected. Even if it is estimated whether the running state of the tire is a steady running state based on the vibration level, it is possible to estimate whether the longitudinal force or the lateral force is input to the tire.

  Further, vibration levels in a specific frequency range at the front of the tire contact surface and at the rear of the tire contact surface are detected from the time-series waveform of the acceleration signal in the tire radial direction output from the acceleration sensor arranged in the tire tread portion, respectively. It is also possible to estimate whether the running state of the tire is a steady running state by comparing the two vibration levels. As a result, the influence of disturbance such as road surface unevenness can be eliminated, so that the estimation accuracy of the running condition of the tire can be further improved as compared with the case where only the vibration level behind the tire contact surface is used.

Further, when detecting the input of longitudinal force and lateral force to the tire using the vibration level of high-frequency vibration, the vibration level is a vibration in a specific frequency range selected from a frequency range of 200 Hz to 10,000 Hz. If the level is set, it is possible to reliably detect the input of the longitudinal force and the lateral force, so that the estimation accuracy of the running state of the tire can be further improved.
In addition, by using the bulging point level information and the vibration level information in the specific frequency range in combination, the steady running state can be estimated more reliably.
Furthermore, the time from when the peak appearing in the time series waveform of the acceleration signal or the time differential waveform or the time integration waveform of the time series waveform has elapsed until the peak occurs at the same position after one revolution of the tire. By measuring the time and using this measured time as the rotation time of the tire and correcting the bulge point level or vibration level using this rotation time, the influence of speed can be eliminated. And input of lateral force can be detected more reliably.

  Further, the tire running state estimation device according to the present invention includes an acceleration sensor that is mounted on a tire tread portion and detects acceleration in a tire radial direction, and a time series waveform of the detected acceleration on a tire tread step end side. A front bulging point that is a bulging point or an output level in the vicinity of the front bulging point and a rear bulging point that is a bulging point on the kicking end side or the vicinity of the rear bulging point The bulging point level detecting means for detecting the rear bulging point level, the comparing means for comparing the two bulging point levels, and the tire running state based on the comparison result. If it comprises the steady running state estimating means for estimating whether or not it is in the running state, it can be reliably estimated whether or not the running state of the tire is in the steady running state.

  Further, the tire running state estimating device according to the present invention includes an acceleration sensor mounted on a tire tread portion for detecting acceleration in a tire radial direction, and a vibration in front of the ground contact surface of the tire tread from the time series waveform of the detected acceleration. A vibration level detecting means for detecting a vibration level in a specific frequency range selected from a frequency range of 200 Hz to 10,000 Hz, and a vibration level behind the ground surface and a contact level of the detected tire tread. The same effect can be obtained even when the comparison means for comparing the vibration levels before and after the ground and the steady running state estimation means for estimating whether or not the running state of the tire is the steady running state based on the comparison result. Can be obtained.

  In addition, from the magnitude of the peak of the radial acceleration waveform obtained by differentiating the time-series waveform of the acceleration signal in the tire radial direction output from the acceleration sensor arranged in the tire tread portion, at the tire ground contact edge or in the vicinity of the tire ground contact edge When calculating the deformation speed index and detecting the wear of the tire based on the calculated deformation speed index, the tire running state estimation method according to any one of claims 1 to 5, If tire wear is detected only when it is estimated that the running state of a tire is a steady running state in which no longitudinal force or lateral force is input to the tire, the input of longitudinal force or lateral force is possible. Therefore, the degree of wear can be stably estimated.

  A tire wear estimation device that estimates the degree of tire wear is a time series of accelerations output from a steady running state estimation device according to claim 6 or an acceleration sensor provided in the steady running state estimation device. An acceleration differential waveform calculation means for differentiating the waveform and calculating a differential waveform of the radial acceleration, and a tire radial direction near the tire contact edge or the tire contact edge based on the peak size of the differential waveform of the radial acceleration. Deformation speed index measuring means for measuring an index of deformation speed, and wear estimation means for estimating the degree of wear of the tire based on the measured deformation speed index, wherein the wear estimation means is the steady state If the configuration is such that the degree of wear of the tire is estimated only when the steady running state estimation means of the running state estimation device estimates that the tire is in a steady running state, Fit a it can be estimated in a stable manner.

It is a functional block diagram which shows the structure of the tire wear estimation system which concerns on Embodiment 1 of this invention. It is a figure which shows the example of attachment of an acceleration sensor. It is a figure which shows the tire radial direction acceleration waveform detected with the acceleration sensor. It is a figure which shows the radial direction acceleration waveform at the time of steady driving | running | working state, braking force provision, and driving force provision. It is a figure which shows the relationship between the longitudinal force input into a tire, and a bulging point level ratio. It is a figure which shows the relationship between a slip angle and a bulging point level ratio. It is a figure which shows an example of the differential waveform of radial direction acceleration. It is a figure which shows the relationship between a contact time ratio and a normalization deformation speed parameter | index. It is a figure which shows the relationship between the contact time ratio when a braking force is provided, and the standardized deformation speed index. It is a functional block diagram which shows the structure of the tire wear estimation system which concerns on this Embodiment 2. FIG. It is a figure which shows a steady running state and the radial direction acceleration waveform at the time of braking force provision. It is a figure which shows the radial direction acceleration waveform before and behind a band pass filter. It is a figure which shows the relationship between the longitudinal force input into a tire, and a vibration level ratio. It is a figure which shows the relationship between a slip angle and a vibration level ratio. It is a schematic diagram which shows the external shape change of the tire at the time of a load load.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a functional block diagram showing the configuration of the tire wear estimation system according to the first embodiment. The tire wear estimation system estimates the degree of tire wear and the steady running state estimation device 10 that estimates whether the running state of the tire is a steady running state in which longitudinal force and lateral force are not input to the tire. And a tire wear estimation device 20 that performs the same.
The steady running state estimating device 10 includes an acceleration sensor 11, a radial acceleration waveform extracting unit 12, a bulging point level detecting unit 13, a bulging point level ratio calculating unit 14, a first storage unit 15, and a steady running. State estimation means 16.
The tire wear estimation device 20 includes an acceleration sensor 11, a radial acceleration waveform extraction means 12, an acceleration differential waveform calculation means 22, a deformation speed calculation means 23, a rotation time calculation means 24, a contact time calculation means 25, A contact time ratio calculating unit 26, a standardized deformation speed index calculating unit 27, a second storage unit 28, and a tire wear estimating unit 29 are provided.
The acceleration sensor 11 and the radial acceleration waveform extraction means 12 are common components of the steady running state estimation device 10 and the tire wear estimation device 20.

In this example, both the running state of the tire and the degree of wear are estimated from the output of one acceleration sensor 11.
The acceleration sensor 11 is a sensor that detects acceleration input to the tire tread portion. The acceleration sensor 11 constitutes the sensor portion 10A of the tire wear estimation system of the present invention, and the steady acceleration state estimation means from the radial acceleration waveform extraction means 12. Each means up to 16 constitutes the first calculation unit 10B, and each means from the acceleration differential waveform calculation means 22 to the tire wear estimation means 29 constitutes the second calculation part 20B.
In this example, as shown in FIG. 2, the acceleration sensor 11 is disposed at the center in the tire width direction on the inner surface side of the inner liner portion 2 of the tire 1 so that the detection direction is the tire radial direction. Hereinafter, the tire radial acceleration acting on the tread 3 is detected.
Further, the first and second calculation units 10B and 20B are also mounted in the tire 1.

  As a configuration for transmitting the determination result of the tire wear estimation means 29 to a vehicle control device (not shown) provided on the vehicle body side, for example, as shown in FIG. do it. At this time, if the first and second arithmetic units 10B and 20B are provided on the same substrate as the transmitter 11F and the acceleration sensor 11 and the substrate are housed in the same case, unnecessary wiring can be eliminated. Therefore, it is preferable. In addition, you may provide the 1st and 2nd calculating parts 10B and 20B on the board | substrate different from the transmitter 11F by the side of the tire 1. FIG.

The radial acceleration waveform extracting means 12 extracts a time series waveform of tire radial acceleration (hereinafter referred to as radial acceleration) acting on the tread 3 detected by the acceleration sensor 11.
FIG. 3 shows a flat belt test of a summer tire with a size of 205 / 65R15 with an acceleration sensor 11 attached to the center of the inner liner 2 in the tire width direction under conditions of a speed of 40 km / hr, a load of 5 kN, and an internal pressure of 230 kPa. It is a figure which shows an example of the radial direction acceleration waveform detected with the acceleration sensor 11 when it was made to drive | work on a machine, and a horizontal axis is time [sec.] And a vertical axis | shaft is the magnitude [g] of radial acceleration.
When the acceleration value is positive, acceleration occurs outside the tire, and when the acceleration value is negative, acceleration occurs in the tire center direction. Since this acceleration is generated almost in proportion to the force that the tread 3 receives in the radial direction, it is an index of the amount of deformation in the radial direction.
In the figure, points P _f and P _k respectively correspond to the tread edge and the kick edge that are the two ground contact edges of the tire 1. Radial acceleration waveform of the positive side of the two p _f point indicating the peak, p _k neighborhood is outside the ground plane, since the tread 3 is under a force of deformed outward in the tire, two peaks p _f , P _k is the peak of the bulging point.
Front acceleration waveform, i.e., at the peak of the front bulge point is bulging points of the side of the leading edge of the peak p _f is a tire tread appearing earlier in time, the peak p _k appearing temporally after the tire tread This is the peak of the rear bulge point, which is the bulge point on the kicking end side.

The bulging point level detecting means 13 detects the bulging point level which is the magnitude of acceleration at two bulging points of the radial acceleration waveform.
FIG. 4 is a diagram showing a radial acceleration waveform in a steady running state, when a braking force of 1.5 kN is applied, and when a driving force of 1.5 kN is applied. All speeds are 40 km / hr, and the conditions other than the longitudinal force are the same. Here, in order to make the radial acceleration waveform easy to see, a low-pass filter with a low frequency (200 Hz) is applied.
When braking force is applied, the ground contact surface moves rearward in the vehicle traveling direction from the center of the tire. As a result, the acceleration level at the bulging point (front bulging point) that appears in front of the tread end of the tire tread is reduced, and the acceleration level at the bulging point (rear bulging point) that appears behind the kicking end. Becomes larger. Conversely, during driving, the acceleration level at the front bulge point increases and the acceleration level at the rear bulge point decreases.
Therefore, it is possible to estimate whether or not the tire is in a steady running state by calculating the level difference or ratio of these peaks and comparing it with a preset threshold value.

The bulging point level ratio calculating means 14 calculates the ratio of the detected rear bulging point level to the front bulging point level. The acceleration level at the bulging point (front bulging point) that appears in front of the tread edge of the tire tread is the front bulging point level _Af, and the bulging point (rear bulging point) that appears behind the kicking end. Is the rear bulge point level A _k , the bulge point level ratio can be expressed as P _a = (A _k / A _f ).
In the steady running state estimator 16, based on the bulge point level ratio calculated at the bulge point level ratio calculating unit 14 P _a and the longitudinal force stored in the first storage means 15 map 15F and slip angle map 15S Then, it is estimated whether or not the tire is in a steady running state in which no longitudinal force or lateral force is input to the tire.

The longitudinal force map 15F is a map showing the relationship between the longitudinal force input to the tire when a braking force or driving force is applied and the bulging point level ratio P _a = (A _k / A _f ). For example, as shown in FIG. The (+) longitudinal force is the longitudinal force during driving, and the (−) longitudinal force is the longitudinal force during braking. From this graph, it can be seen that in a nearly linear relationship between the longitudinal force and the bulge point level ratio P _a. Therefore, examined on the size of the bulge point level ratio P _a, provided under two threshold values, calculated bulge point level ratio P _a is above whether between the lower two threshold values, It can be estimated whether the longitudinal force is input to the tire. The above graph is the result when a new tire is used as a test tire, but the same result is obtained even when a worn product is used.

On the other hand, whether or not lateral force is input is evaluated by the slip angle θ. The slip angle θ is an angle formed by the traveling direction of the vehicle and the rolling direction of the wheel. When a lateral force is input to the tire 1, the slip angle θ increases.
The slip angle map 15S is a map showing the relationship between the slip angle θ and the bulging point level ratio P _a = (A _k / A _f ). If this is represented by a graph, for example, it is as shown in FIG. Thus, the relationship between the slip angle and the bulge point level ratio P _a is approximately linear relationship. Thus, either the even slip angle, the upper and the lower two threshold is the size of the bulge point level ratio P _a, calculated bulge point level ratio P _a is above lies between the lower two thresholds Whether or not a lateral force is input to the tire can be estimated.
Instead of the slip angle theta, preparing a map showing the relationship between the lateral force and the bulge point level ratio P _a, it may be estimated whether the lateral force is inputted to the tire.
From FIG. 5 and FIG. 6, the bulging point level ratio P _a has almost the same influence on both the longitudinal force and the lateral force, but based on the result of the larger influence depending on the tire. If the threshold value of the steady / unsteady running state is set as appropriate, data during steady running can be stably collected. In other words, it is possible to reliably exclude data in a state that is not in a steady running state. Further, since it is not always necessary to use all the data of the steady running state, the threshold value may be set as appropriate according to the tire.

On the other hand, the acceleration differential waveform calculation means 22 obtains a differential waveform of radial acceleration by time-differentiating the time series waveform of radial acceleration extracted by the radial acceleration waveform extraction means 12.
FIG. 7 is a diagram illustrating an example of a differential waveform of radial acceleration, and two peaks appear in the differential waveform of radial acceleration. The front side of the differential waveform, that is, the peak indicated by the point P _f that appears first in time is the differential peak value on the step-in end side, and the point P _k that appears later in time is the differential peak value on the kicking end.
The deformation speed calculation means 23 detects the differential peak value on the stepping end side and sets this as the tread deformation speed V _tf on the stepping end side, detects the differential peak value on the kicking end side, and calculates this as the kicking end side. By calculating the deformation speed V _tk of the tread at, the deformation speed at each contact end is calculated.

By the way, the acceleration level is greatly influenced by the speed. The radial acceleration of the tire inner surface is proportional to the centrifugal force, that is, the square of the speed. Therefore, it is preferable to perform correction to reduce the influence of speed on the detected acceleration level.
Also in this case, it is preferable to detect the information related to the speed not on the vehicle side but on the tire side. Therefore, the influence of the speed can be reduced by calculating the tire rotation time from the tire radial acceleration waveform measured by the acceleration sensor and correcting the vibration level based on this information.

Specifically, in the tire radial acceleration waveform, or in the waveform of these time differentiation and time integration, the time at which a certain peak occurs is used as a reference until the peak at the same position after one rotation of the tire occurs. The elapsed time is measured, and this is set as the rotation time. For example, in the time differential waveform of the tire radial direction acceleration waveform, since the peak level of the rear contact end (kick-out contact end) is large, stable rotation time measurement can be performed by using this peak.
Multiply this by the travel distance per tire lap to get the tire speed. Therefore, if the magnitude of the acceleration is normalized by dividing the measured magnitude of the acceleration by the square of the tire speed, the influence of the speed can be corrected appropriately.
As another method, since the rotational speed of the tire is in inverse proportion to the rotational time of the tire, the magnitude of acceleration may be normalized by multiplying the square of the rotational time.

In the rotation time calculation means 24, the time T ₁ at which the peak P _{k on} the kicking end side of the two peaks appears and the time until the peak on the kicking end side appears again after the tire 1 has made one revolution. It calculates the time difference T _r = T ₂ -T ₁ and T _2. This time difference _Tr is the rotation time required for one turn of the tire. Hereinafter, the _{Tr is referred} to as a rotation time.
The contact time calculation means 25 calculates a contact time T _t that is a time between two peaks corresponding to the deformation at the contact end of the tread 3.
The contact time ratio calculating means 26 calculates the contact time ratio by dividing the contact time T _t by the rotation time _Tr . In this example, the contact time ratio is used as the contact length index _Lt , which is used to correct the influence of the load and the like.

The standardized deformation speed index calculation means 27 is the rotation time _Tr calculated by the rotation time calculation means 24 using the stepping end side and kicking end side deformation speeds V _tf and V _tk calculated by the deformation speed calculation means 23. Are used to calculate the standardized deformation speed V ⁿ _tf on the stepping-end side and the standardized deformation speed V ⁿ _tk on the kick-out side, and the standardized deformation speed V on the stepping-end side By averaging ⁿ _tf and the standardized deformation speed V ⁿ _tk on the kicking end side, a standardized deformation speed index (standardized deformation speed index) V ⁿ _t is calculated. In this example, the deformation speed, which is the peak value of the differential waveform, is multiplied by the cube of the rotation time.
The second storage means 28 shows the relationship between the standardized deformation speed index V ⁿ _t (M) and the contact length index L _t (M) for each degree of tire wear M obtained in advance. The V (M) -L map 28M is stored.

The tire wear estimation unit 29 estimates the degree of tire wear when the steady running state estimation unit 16 determines that the tire state is a steady running state where no longitudinal force is input to the tire. Specifically, the index L _t of contact length with the standardized deformation speed index V ⁿ _t calculated in the standardized deformation speed index calculating means 27 calculated in contact time ratio calculating means 26, V (M) -L map 28M From this, the degree M of wear of the tire is estimated.

Next, a tire wear estimation method according to the present embodiment will be described.
First, the steady running state estimation device 10 is used to estimate whether or not the tire is in a steady running state in which no longitudinal force and lateral force are input to the tire.
First, a radial acceleration waveform is extracted from an acceleration signal in the tire radial direction on the inner surface of the inner liner portion 2 that is deformed with the deformation of the tread 3 detected by the acceleration sensor 11.

Then, the radial acceleration waveform side bulge point level after an acceleration of magnitude in the size of the front bulge point level A _f and the rear-side expansion point p _k of the acceleration in the front bulged point p _f from A _k is detected respectively. Then, the expanded point level ratio is the ratio front bulge point level of the detected side bulge point level after P _a = seeking (A _k / A _f), the expanded point level ratio P _a and the longitudinal From the force map 15F or the slip angle map 15S, it is estimated whether or not the state of the tire is a steady running state where no longitudinal force or lateral force is input to the tire. This estimation result is sent to the tire wear estimation device 20.

The tire wear estimation device 20 estimates the degree of tire wear only when it is estimated that the tire is in a steady running state.
Hereinafter, a method for estimating the degree of tire wear using the tire wear estimation device 20 will be described.
First, a differential waveform, which is a time series waveform of a value obtained by differentiating the radial acceleration waveform extracted by the radial acceleration waveform extraction unit 12 of the steady running state estimation device 10, is obtained by calculation.

Next, the values of the two peaks P _f and P _k (hereinafter referred to as differential peak values) V _tf and V _tk of the differential waveform are calculated, and these data are obtained at the step-in end side and the kick-out end side. The tread deformation speeds are V _tf and V _tk .
In peak detection, depending on the sensitivity of the acceleration sensor 11, data is more stable when peak detection is performed after applying an appropriate low-pass filter. That is, more stable wear estimation can be performed. Further, the time interval between the peaks P _f and P _k varies greatly depending on the rotational speed of the tire. Therefore, changing the frequency of the low-pass filter in accordance with the rotational speed of the tire can make the waveform shape at each speed the same, so that more stable estimation can be performed. Moreover, as a deformation | transformation speed, you may use what averaged the differential value of the specific range of the peak vicinity, especially the differential value of the peak periphery centering on the said peak instead of the said peak value.

On the other hand, the time difference between the time T ₁ when the peak P _k on the kicking end side appears from the differential waveform and the time T ₂ until the peak P _k on the kicking end side appears again after the tire 1 makes one revolution. T _r is calculated, and this data is set as the rotation time T _{r of the} tire 1. The rotation time T _r of the tire 1 may be calculated using the peak P _f on the depression end side.
Further, the time interval T _t between the two peaks P _f and P _k is calculated, and this data is used as the contact time T _{t of the} tire.
Thus, in this example, from the acceleration in the tire radial direction detected by the acceleration sensor 11, the deformation speeds V _tf and V _{tk of} the tread 3, the rotation time _{Tr of the} tire 1, and the contact time T _{t of the} tire and calculates a standardized deformation speed index V ⁿ _t using these values.

Next, the method for calculating the standardized deformation speed index V ⁿ _t be described.
In order to examine not only the amount of wear but also the influence of the wear shape, the following four types of test tires were prepared. Needless to say, there are variations in the wear shape on the market, and it is important that the estimation error is small even if the wear shape is different.
The test tire 1 is a new tire, and the groove depth of the circumferential groove 5 shown in FIG. 2 is about 8 mm.
The test tire 2 is a tire in which the remaining groove depth of the circumferential groove 5 is about 4 mm, and the shoulder portion 6 is slightly worn.
The test tire 3 is a tire in which the circumferential groove 5 has a remaining groove depth of about 4 mm, the center portion 7 is worn out, and the shoulder portion 6 remains.
The test tire 4 is a tire having a remaining groove depth of about 2 mm in the circumferential groove 5 and worn almost uniformly to a level close to a slip sign.

Using the above four types of test tires, the load was 5 kN, the acceleration at a speed of 40 km / hr was detected, the time differential value of the acceleration was calculated, and the peak level was used as an index of the deformation speed. The deformation speed on the stepping end side is V _rf, and the deformation speed on the kicking end side is V _tk . In this example, after calculating the standardized deformation speeds V ⁿ _tf and V ⁿ _tk obtained by standardizing the deformation speeds V _rf and V _tk using the rotation time _Tr calculated by the rotation time calculation means 24, the following calculating the average standardized deformation speed using equation (1), which was used as the reference deformation speed index V ⁿ _t.
V ⁿ _t = (| V ⁿ _tf | + | V ⁿ _tk |) / 2 (1)
The acceleration is proportional to the square of the speed, but the deformation speed that is a differential value of the acceleration is proportional to the cube of the speed. That is, the deformation speed is inversely proportional to the cube of the tire rotation time _Tr . In this example, the normalized deformation speeds V ⁿ _tf and V ⁿ _tk are calculated using the following equations (2) and (3).
V ⁿ _tf = V _tf · T _r ³ (2)
V ⁿ _tk = V _tk · _Tr ³ (3)
Thus, as a standardized deformation speed index V ⁿ _t, the use of the average standardized deformation speed is the average value of the end-side kick the leading edge side, the influence of longitudinal force and lateral force input to the tire 1 Since it becomes difficult, stable estimation can be performed except when the longitudinal force and lateral force are large. Incidentally, V ⁿ _tf the calculation of standardized deformation speed index V ⁿ _t, was using the absolute value of V ⁿ _tk positive and negative reversed between the end side code deforming speed V _t of the tread kicking the leading edge side Because it becomes.

Since the amount of bending and wear shape and load changes changes, also changes the value of the standardized deformation speed index V ⁿ _t. In this example, in order to reduce these influences, information on the contact length index _Lt is also used for estimation. Specifically, the contact time ratio R = (T _t / T _r ) obtained by dividing the contact time T _t by the rotation time T _r calculated by the rotation time calculation means 24 is used as the contact length index L _t . .

When estimating the tire wear, and data of an indicator of the contact length L _t of the data and the standardized deformation speed index V ⁿ _t, for each degree M of tire wear, the index of scaled deformation speed V ⁿ A V (M) -L map 28M indicating the relationship between _t (M) and the contact length index L _t (M) is used.
Figure 8 is a diagram showing an example of V (M) -L map 28M to be used for estimation of the tire wear, the horizontal axis represents the contact time ratio is an index L _t of contact length R, the vertical axis, standardized deformation speed which is an index V ⁿ _t.
The tires used to create the V (M) -L map 28M are the above four types of test tires (test tires 1 to 4), and the load is changed from 3 to 7 kN here. From the figure, it is understood that the line indicating the relationship between the contact time ratio R and the standardized deformation speed index V ⁿ _t is divided into every wear amount.
Therefore, comparing the contact time ratio R and the standardized deformation speed index V ⁿ _t, i.e., by previously preparing a graph as a map, without being affected by the load, is possible to estimate the degree M of wear it can. Further, in the above graph, two lines having different wear shapes, such as the tires of “Test Tire 2” and “Test Tire 3”, are almost similar values, so even if the wear shapes are different, It can be seen that the degree of wear M can be estimated stably.

In this way, by using the index L _t of contact length, for example, even if the wear shapes such shoulder drop and centers wear different, the degree M of wear can be accurately estimated. That is, when the tire wear estimation unit 29 sets the normalized deformation rate index calculated by the normalized deformation rate index calculation unit 27 to V ⁿ _t and the contact length index calculated by the contact time ratio calculation unit 26 to L _t. , (L _t , V ⁿ _t ) is on which line of the V (M) -L map 28M different among the plurality of lines depending on the degree of wear M, or of the plurality of lines By examining which line is between which lines, the degree of wear M of the tire can be accurately estimated.

FIG. 9 is a diagram showing the results when the tires shown in FIG. 8 are detected while applying a braking force of 1.5 kN. For reference, the results of FIG. 8 are also included (results of FIG. 8). Is indicated by a broken line).
When (−) longitudinal force is input to the tire by the braking force, each line is shifted downward. That is, it can be seen that in comparison to the state where no input is longitudinal force, both standardized deformation speed index V ⁿ _t is small. As described above, when the braking force is applied, that is, when wear estimation is performed when the longitudinal force is input to the tire, the error increases. The same applies when the driving force is applied, and when the input is somewhat large, the line shifts to the opposite side of FIG.
In addition, the lateral force also shifts when the input becomes large to some extent, so in these unsteady running states, wear estimation is not performed, and if wear estimation is performed only during steady running, accuracy can be improved. High wear estimation can be performed.
In the tire wear estimation device 20 of the present example, the tire wear degree only when the steady running state estimation device 10 estimates that the tire state is a steady running state in which no longitudinal force or lateral force is input to the tire. Therefore, it is possible to estimate wear with high accuracy.

As described above, in the first embodiment, the acceleration sensor 11 is provided in the inner liner portion 2 of the tire 1 to detect the acceleration in the tire radial direction of the tread 3, and the time series waveform of the tire radial acceleration is extracted. the radial acceleration waveform and a side bulge point level a _k after the acceleration magnitude in the front bulged point level a _f and the rear-side expansion point p _k is the magnitude of the acceleration in the front bulged point p _f After each detection, the bulging point level ratio P _a = (A _k / A _f ), which is the ratio of these, is calculated, and the bulging point level ratio P _a and the previously obtained longitudinal force map 15F or slip Since it is estimated from the angle map 15S whether the tire is in a steady running state where no longitudinal force or lateral force is input to the tire, it is determined whether the tire is in a steady running state. Estimate accurately in the tire Can. Further, since the degree of tire wear is estimated only when the tire is in a steady running state, tire wear estimation can be performed stably.
That is, the levels of the peaks P _f and P _k of the tread end side and the kick end side of the tread 3 appearing in the differential waveform of the radial acceleration waveform extracted at the time of estimating the steady running state are respectively calculated and calculated. Since the deformation speeds V _tf and V _tk are estimated and the degree of wear of the tire is estimated from the deformation speeds V _tf and V _tk , the tire wear can be accurately estimated.

At this time, the rotation time T _r of the tire from the period of the end-side peak P _k kicking above from seeking contact time T _t from the time difference between the peak P _k end side kick peak P _f of leading edge side , end-side standardized deformation respectively kicking and the scaled leading edge side standardized deformation speed V ⁿ _tf using information deforming speed V _tf of the leading edge side and the trailing end side, the V _tk rotation time T _r calculates a standardized deformation speed index V ⁿ _t from the average of the absolute value of the velocity V ⁿ _tk, the contact time ratio of the contact time T _t divided by the rotation time T _r as an index L _t of contact length, and metrics L _t of the standardized deformation speed index V ⁿ _t and the contact length, previously obtained standardized deformation speed index V ⁿ _t and V showing the relationship between the index L _t of contact length (M) -L Since the degree of wear M of the tire is estimated from the map 28M, Even if the case and the load and speed of wear shape different Ya is varied, it is possible to accurately estimate the wear of the tire.

Embodiment 2. FIG.
FIG. 10 is a functional block diagram showing the configuration of the tire wear estimation system according to the second embodiment. In FIG. 10, 30 is a steady running state estimation device, and 20 is a tire wear estimation device.
The steady running state estimating device 30 includes an acceleration sensor 11, a radial acceleration waveform extracting unit 12, a vibration level detecting unit 33, a vibration level ratio calculating unit 34, a third storage unit 35, and a steady running state estimating unit. 36.
Note that reference numeral 30B in the figure is a calculation unit corresponding to the first calculation unit 10B of the first embodiment, and the acceleration sensor 11 and the radial acceleration waveform extraction means 12 are constituent elements of the steady running state estimation device 30 of this example. And since the tire wear estimation apparatus 20 is the same structure as Embodiment 1, the description is abbreviate | omitted.

The vibration level detection means 33 detects vibration levels in a specific frequency band in front of the tire tread and at the rear of the contact surface from the radial acceleration waveform detected by the acceleration sensor 11 and extracted by the radial acceleration waveform extraction means 12. . Here, the front of the ground plane refers to the front of the intermediate point between the stepping end P _f and the kicking end P _k of the radial acceleration waveform shown in FIG. 3, and the rear of the ground plane is the rear of the intermediate point. Point to.
FIGS. 11A and 11B are diagrams showing time-series waveforms (radial acceleration waveforms) of tire radial acceleration when a steady running state and a braking force of 1.5 kN are applied, respectively. All speeds are 40 km / hr, and the conditions other than the longitudinal force are the same. Here, no low-pass filter is applied to show that high-frequency vibration is included in the radial acceleration waveform. As can be seen from the figure, high-frequency vibration is generated in the rear area of the ground plane due to the application of the longitudinal force.

It is considered that the high-frequency vibration generated in the rear surface area of the contact surface is vibration caused by slip generated on the tire contact surface.
Conventionally, as an index of tire slip, a slip ratio which is a value obtained by dividing a difference between a tire speed (rω; r is a tire radius, ω is a tire rotation angular speed) and a vehicle speed (road surface speed) by a vehicle speed, or a vehicle A slip angle which is an angle formed by the traveling direction of the wheel and the rolling direction of the wheel is used. As the slip ratio increases or the slip angle increases, the adhesion area on the contact surface decreases, and the slip area increases from the rear portion of the contact surface. As a result of examining such a phenomenon, it has been found that high-frequency vibration caused by the slip occurs behind the tire contact surface.

Therefore, steady / unsteady running can be estimated by quantifying the high-frequency vibration level shown in FIG. However, since the vibration level at the rear (kicking end side) is affected by the road surface roughness and the like, in this example, the vibration level at the front (stepping side) similarly affected by the road surface roughness is also detected, By comparing these, steady / unsteady running is estimated. That is, the vibration level detection means 33 detects both the vibration level in front of the ground plane and the vibration level in the rear of the ground plane. Therefore, the vibration level detection means 33 applies a band-pass filter with cutoff frequencies of 500 Hz and 2 kHz to the radial acceleration waveform to detect the vibration level in front of the ground plane and the vibration level behind the ground plane.
12 (a) and 12 (b) are diagrams showing a radial acceleration waveform before applying the bandpass filter and a radial acceleration waveform after applying the bandpass filter, respectively, and FIG. 12 (b) shows the radial acceleration waveform. Is divided into a front region Z _{f in} front of the stepping end and a rear region Z _k behind the kicking end, and RMS average values in the respective regions Z _f and Z _k are calculated. The vibration level is B _f and the rear vibration level is B _k .

The vibration level ratio calculating means 34 calculates a vibration level ratio P _b = (B _k / B _f ) which is a ratio of the rear vibration level B _{k to} the front vibration level B _f .
In the steady running state estimator 36, based on the longitudinal force map 35F and slip angle map 35S the calculated vibration level ratio P _b and stored in the third memory means 35 with the vibration level ratio calculating means 34, the state of the tire However, it is estimated whether the vehicle is in a steady running state where no longitudinal force or lateral force is input to the tire.

The longitudinal force map 35F is a map showing the relationship between the longitudinal force input to the tire when the braking force or the driving force is applied and the vibration level ratio P _b = (B _k / B _f ). For example, as shown in FIG. The vibration level ratio P _b is greatly changed by the longitudinal force, by checking the vibration level ratio P _b, it is possible to estimate whether the steady running state.
On the other hand, the slip angle map 35S is a map showing the relationship between the slip angle θ and the vibration level ratio P _b = (B _k / B _f ). If this is represented by a graph, for example, it is as shown in FIG. In this figure, a band-pass filter with cutoff frequencies of 2 kHz and 5 kHz is applied to the radial acceleration waveform to detect a vibration level in front of the ground plane and a vibration level in the rear of the ground plane. The vibration level ratio P _b is greatly changed by the slip angle, by checking the vibration level ratio P _b, it is possible to estimate whether the steady running state.
The steady running state estimation means 36 refers to the longitudinal force map 35F or the slip angle map 35S stored in the third storage means 35 and calculates the vibration level ratio P _b = (B _k / B _f ). Then, it is estimated whether or not the tire is in a steady running state in which no longitudinal force or lateral force is input to the tire, and this estimation result is sent to the tire wear estimation device 20.

Next, the tire wear estimation device 20 is used to estimate the degree of tire wear.
In addition, since the estimation method of the tire wear degree using the tire wear estimation apparatus 20 is the same as Embodiment 1, description is abbreviate | omitted.

As described above, in the second embodiment, the acceleration sensor 11 detects the acceleration in the tire radial direction on the inner surface of the inner liner portion 2 that is deformed as the tread 3 is deformed, and extracts the radial acceleration waveform. Thereafter, the front side vibration level B _f which is the vibration level in the front region Z _f forward from the stepping end of the radial acceleration waveform and the rear side vibration level B _k which is the vibration level in the rear region Z _k behind the kicking end. And the vibration level ratio P _b = (B _k / B _f ) is calculated. Based on the calculated vibration level ratio P _b and the longitudinal force map 35F and the slip angle map 35S, the tire state is calculated. The tire wear level is estimated only when the steady running state is estimated and only when the steady running state is estimated, so the tire wear can be accurately estimated. The

In the second embodiment, the front vibration level B _f and the rear vibration level B _k are detected, and the vibration level ratio P _b = (B _k / B _f ), which is the ratio of these vibration levels, determines the tire. It is estimated whether or not the vehicle is in a steady running state, but other comparison methods such as estimating whether the tire state is in a steady running state from the vibration level difference Δ _b = B _k −B _f are used. May be selected.
In addition, since high-frequency vibration caused by slip occurs mainly in the rear surface area of the contact surface, the rear vibration level B _k is detected and the threshold K is set, and the rear vibration level B _k is equal to or lower than the threshold K. In addition, it may be estimated that the tire is in a steady running state.
However, since the vibration level is greatly influenced by the speed, it is preferable to correct the detected vibration level so as to reduce the influence of the speed.
Since the road surface roughness is affected by both vibration levels before and after the ground contact surface, when steady / unsteady is estimated from only the rear vibration level B _k , the vibration level ratio P _{b of the} second embodiment is used. Therefore, the estimation accuracy is slightly lower than when steady / non-stationary is estimated from the above.

In the above example, the frequency band for extracting high-frequency vibrations can be set as appropriate according to the tire and use conditions. However, in the region lower than 500 Hz, the influence of disturbance such as road surface roughness becomes strong, which is not preferable. Further, in a region higher than 10000 Hz, the signal level is low and stable detection cannot be performed, which is not preferable. Therefore, the frequency range for detecting the vibration level is preferably a specific frequency range selected from a frequency range of 200 Hz to 10,000 Hz. A specific frequency range selected from a frequency range of 400 Hz to 5000 Hz is more preferable.
Further, the set frequency range may be changed for the longitudinal force and the lateral force.
In the above example, the vibration level in the set frequency range is extracted using the bandpass filter, but other frequency analysis methods such as FFT analysis may be used.

As described above, according to the present invention, since the steady running state is estimated using the feature amount of the acceleration waveform of the tire tread, the running of the tire can be performed within the tire without complicating the system configuration. It can be estimated whether the state is a steady running state.
Further, since the degree of tire wear is estimated only when the tire is in a steady running state, tire wear can be detected accurately and stably. Therefore, if the driver recognizes the wear of the tire using, for example, an alarm means, the traveling safety of the vehicle can be improved.

1 tire, 2 inner liner, 3 tire tread, 4 wheel,
5 circumferential groove, 6 shoulder, 7 center,
10 steady running state estimation device, 10A sensor unit, 10B first calculation unit,
11 acceleration sensor, 11F transmitter, 12 radial acceleration waveform extraction means,
13 bulging point level detecting means, 14 bulging point level ratio calculating means, 15 first storage means, 15F longitudinal force map, 15S slip angle map, 16 steady running state estimating means,
20 tire wear estimation apparatus, 20B 2nd calculating part, 22 acceleration differential waveform calculating means,
23 deformation speed calculation means, 24 rotation time calculation means, 25 contact time calculation means,
26 contact time ratio calculating means, 27 standardized deformation speed index calculating means,
28 Second storage means, 28MV (M) -L map, 29 tire wear estimation means.

Claims (9)

  From the time series waveform of the acceleration signal in the tire radial direction output from the acceleration sensor arranged in the tire tread portion, the front bulge point which is the bulge point on the tire tread step end side or the vicinity of the front bulge point Detecting a front bulging point level that is an output level and a rear bulging point that is a bulging point on the kicking end side or a rear bulging point level that is an output level in the vicinity of the rear bulging point; Comparing the two bulging point levels, it is estimated whether the running state of the tire is a steady running state where no longitudinal force or lateral force is input to the tire. Method.   The vibration level in the specific frequency range behind the tire contact surface is detected from the time series waveform of the acceleration signal in the tire radial direction output from the acceleration sensor arranged in the tire tread portion, and the vibration level in the detected specific frequency range is detected. The tire running state estimation method characterized by estimating whether or not the running state of the tire is a steady running state in which no longitudinal force or lateral force is input to the tire.   From the time series waveform of the acceleration signal in the tire radial direction output from the acceleration sensor arranged in the tire tread portion, vibration levels in a specific frequency range in front of the tire contact surface and in the rear of the tire contact surface are detected, respectively. A tire running state estimation method characterized by comparing levels to estimate whether the running state of a tire is a steady running state in which no longitudinal force or lateral force is input to the tire.   The tire running state estimation method according to claim 2 or 3, wherein the vibration level is a vibration level in a specific frequency range selected from a frequency range of 200 Hz to 10,000 Hz.   The elapsed time from the time when the peak appearing in the time series waveform of the acceleration signal or the time differential waveform or the time integration waveform of the time series waveform occurs until the peak occurs at the same position after one revolution of the tire. The measurement is performed, and the measured time is set as the rotation time of the tire, and the bulging point level or the vibration level is corrected using the rotation time. A method for estimating a tire running state according to claim 1. An acceleration sensor mounted on the tire tread portion to detect acceleration in the tire radial direction;
From the time series waveform of the detected acceleration, the front bulge point which is the bulge point on the tread end side of the tire tread, or the front bulge point level which is the output level in the vicinity of the front bulge point and the kick end side A bulging point level detection means for detecting a rear bulging point that is a bulging point of the rear bulging point or a rear bulging point level that is an output level in the vicinity of the rear bulging point;
A comparison means for comparing the two bulge point levels;
And a steady running state estimating means for estimating whether the running state of the tire is a steady running state in which no longitudinal force or lateral force is input to the tire based on the comparison result. Steady running state estimation device. An acceleration sensor mounted on the tire tread portion to detect acceleration in the tire radial direction;
From the time series waveform of the detected acceleration, the vibration level in front of the contact surface of the tire tread and the vibration level in the rear of the contact surface, and a specific frequency range selected from a frequency range of 200 Hz to 10,000 Hz. Vibration level detection means for detecting the vibration level;
Comparison means for comparing vibration levels before and after the ground contact surface of the detected tire tread;
And a steady running state estimating means for estimating whether the running state of the tire is a steady running state in which no longitudinal force or lateral force is input to the tire based on the comparison result. Steady running state estimation device.   Deformation speed at or near the tire ground contact edge based on the peak magnitude of the radial acceleration waveform obtained by differentiating the time series waveform of the tire radial acceleration signal output from the acceleration sensor arranged in the tire tread A tire wear estimation method for detecting wear of the tire based on the calculated deformation speed index, wherein the tire running state estimation according to any one of claims 1 to 5 is performed. A tire wear estimation method characterized by detecting wear of a tire only when it is estimated by the method that the running state of the tire is a steady running state in which no longitudinal force or lateral force is input to the tire. . The steady running state estimation device according to claim 6 or 7,
An acceleration differential waveform calculating means for calculating a differential waveform of radial acceleration by differentiating a time series waveform of acceleration output from the acceleration sensor;
From the magnitude of the peak of the differential waveform of the radial acceleration, a deformation speed index measuring means for measuring an index of the deformation speed in the tire radial direction near the tire ground contact edge or the tire ground contact edge;
Wear estimation means for estimating the degree of wear of the tire based on the measured index of deformation speed,
The wear estimation unit estimates the degree of wear of the tire only when the steady running state estimation unit of the steady running state estimation device estimates that the tire is in a steady running state. apparatus.

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