JP2002221527A - Wear state detection method and device for tire, and wear determination program for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wear state detection device for a tire capable of relatively correctly detecting the wear state of the tire. SOLUTION: This device is provided with a rotation speed detection means for periodically detecting the rotation speed of the tires of four vehicular wheels, a first calculation means for calculating the vehicular speed and the vehicular acceleration/deceleration from the measurement value of the rotation speed detection means, a second calculation means for calculating slip rates of front and rear wheels, a third calculation means for finding mutual primary regression coefficients and correlation coefficients between the vehicular acceleration/ deceleration and the slip rates, a fourth calculation means for accumulating a predetermined number of the primary regression coefficients when the obtained correlation coefficients are equal to or more than a predetermined value to find the average value of the primary regression coefficients, and a tire wear detection means for detecting the wear state of the tires according to the average value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for detecting a worn state of a tire, and a program for determining a worn state of a tire. More specifically, the present invention relates to a tire wear state detecting device and method capable of improving vehicle performance and safety performance by detecting a tire wear state using tire rotation information, and a tire wear determination program.

[0002]

2. Description of the Related Art A tire is formed with a vertical groove and a horizontal groove in consideration of drainage and the like, so that a rubber block surrounded by these grooves is formed. If the rubber block is large, it is difficult to deform by shearing in the front-rear and left-right directions, and the rigidity is large. Therefore, a tire having a tread pattern composed of a large block is generally referred to as a tire having a large pattern rigidity.

[0003] Since the magnitude of the pattern rigidity has a great effect on the cornering power and the cornering force as well as the slip ratio, a device for improving the vehicle performance and safety performance based on tire rotation information, for example, an ABS (anti-block) is used. In order to estimate the behavior of a vehicle based on tire rotation information in a braking system), TCS (traction control system) or tire pressure drop warning device, it is important to know the pattern rigidity of the tire. It is.

Further, when the tire is worn, the tread rubber of the tire becomes thin, so that the rigidity before and after the pattern becomes large. Wear of the tire affects the performance on snow in winter tires, and also affects hydroplaning performance in summer tires. Therefore, although it is useful to detect wear, these devices are not provided with a function of detecting a worn state of a tire. Therefore, tire wear can be identified only by visual identification, such as by using a depth gauge for measuring the groove depth or by checking a slip sign indicating a wear limit provided on the tire. Since such visual identification requires skill, tire maintenance tends to be complicated, and tire wear may be overlooked at the time of start-up inspection in tire maintenance.

[0005] Japanese Patent Application Laid-Open No. 11-78442 discloses a method of periodically measuring the tire wear state.

According to this method, the rotational speeds of the four tires are periodically measured, and based on the measured rotational speeds,
The ratio of the rotational speed of the front wheel tires to the rotational speed of the rear wheel tires is calculated, and the slope of the relational expression between the ratio of the rotational speeds and the acceleration of the vehicle is obtained. The tire wear state is detected by comparing the slope of the relational expression. That is, in the range where the slip ratio is small (10% or less), there is almost no slippage between the tire and the road surface, and the gradient of the μ-s curve is determined by the longitudinal rigidity of the tread rubber. If so, tire wear can be detected.

[0007]

In fact, the slope of the μ-s curve increases as the rigidity of the tread rubber in the front-rear direction increases, but is greatly affected by the friction coefficient of the road surface, as shown in FIG. Road surface (high μ road R1, middle μ road R
2. As the friction coefficient of the low μ road R3) becomes smaller,
The slope of the μ-s curve, eg, the slope θ of the μ-s curve of R3
Also tend to be smaller. Therefore, even if the time-dependent change of only the gradient of the μ-s curve is measured, for example, the μ-s curve must be compared with that measured on a road surface having the same friction coefficient.
Just because the slope of the curve is larger than the initial one,
It is not possible to judge whether this is due to a worn tire or to a road surface having a higher coefficient of friction than a previously measured road surface.

The present invention has been made in view of the above circumstances, and has as its object to provide a tire wear state detecting device and method capable of more accurately detecting a tire wear state, and a tire wear determination program.

[0009]

SUMMARY OF THE INVENTION A tire wear state detecting apparatus according to the present invention comprises: a rotational speed detecting means for periodically detecting rotational speeds of four tires of a vehicle; First calculating means for calculating the speed of the vehicle and the acceleration / deceleration of the vehicle, second calculating means for calculating the slip ratio of the front and rear wheels, and a first-order regression of the acceleration / deceleration and the slip ratio of the vehicle. A third calculating means for obtaining a coefficient and a correlation coefficient, a predetermined number of the first-order regression coefficients when the obtained correlation coefficient is equal to or more than a predetermined value, and an average value of the first-order regression coefficients And a tire wear detecting means for detecting a wear state of the tire according to the average value.

Further, the method of detecting a worn state of a tire according to the present invention includes a rotation speed detecting means for periodically detecting the rotation speeds of the four tires of the vehicle, and a speed and a speed of the vehicle based on values measured by the rotation speed detection means. Calculating the acceleration / deceleration of the vehicle, calculating the slip ratio of the front and rear wheels, and calculating the first-order regression coefficient and correlation coefficient of the acceleration / deceleration and the slip ratio of the vehicle. When the correlation coefficient obtained is equal to or more than a predetermined value, a predetermined number of the primary regression coefficients are accumulated,
The method is characterized by comprising a step of obtaining an average value of the following regression coefficients, and a step of detecting a tire wear state according to the average value.

The program for determining tire wear according to the present invention comprises a first computer for calculating a vehicle speed and a vehicle acceleration / deceleration from a value measured by a rotation speed detecting means in order to determine a tire wear state. Means, second calculating means for calculating the slip ratio of the front and rear wheels, third calculating means for obtaining a mutual primary regression coefficient and correlation coefficient of the acceleration / deceleration of the vehicle and the slip ratio, and the obtained phase. Fourth arithmetic means for accumulating a predetermined number of the primary regression coefficients when the number of relations is equal to or more than a predetermined value, and obtaining an average value of the primary regression coefficients, and a tire wear state according to the average value It is characterized by functioning as a tire wear detecting means for detecting tire wear.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tire wear state detecting device and method and a tire wear determination program according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a tire wear state detecting device according to the present invention, FIG. 2 is a block diagram showing an electrical configuration of the tire wear state detecting device in FIG. 1, and FIGS. FIG. 5 is an example of a flowchart of the present invention, FIG. 5 is a diagram showing a time-dependent change of a tire wear index in a new tire FF1, a 40% worn tire FF2, and an 80% worn tire FF3 mounted on a front wheel drive vehicle, and FIG. New tire FR1 mounted on a wheel drive vehicle, approximately 40% worn tire FR
FIG. 2 is a graph showing a change over time in a tire wear index of an approximately 80% worn tire FR3.

As shown in FIG. 1, a tire wear state detecting apparatus according to one embodiment of the present invention measures the rotational speeds of wheel tires provided on tires FL, FR, RL and RR of a four-wheeled vehicle. It is provided with a rotational speed detecting means for detecting periodically, and the output of the rotational speed detecting means is A
The information is transmitted to the control unit 2 which is a computer such as a BS. Reference numeral 3 denotes a wear alarm which issues an alarm according to the tire wear state.

The rotation speed detecting means generates a rotation pulse using an electromagnetic pickup or the like and measures the rotation speed from the number of pulses, or a wheel speed sensor 1 such as a dynamo to generate electric power. Alternatively, an angular velocity sensor or the like including one that measures the rotation speed from this voltage can be used.

As shown in FIG. 2, the control unit 2 includes an I / O interface 2a required for transmitting and receiving signals to and from an external device, and a C functioning as a center of arithmetic processing.
A PU 2b, a ROM 2c in which a control operation program of the CPU 1b is stored, and a RAM 2d into which data or the like is temporarily written when the CPU 2b performs a control operation, and from which the written data is read. I have.

In this embodiment, the rotational speed detecting means includes:
First calculating means for calculating the speed of the vehicle and the acceleration / deceleration of the vehicle from the measured value by the rotation speed detecting means; second calculating means for calculating the slip ratio of the front and rear wheels; A third calculating means for obtaining a first-order regression coefficient and a correlation coefficient with respect to the ratio, and storing a predetermined number of the first-order regression coefficients when the obtained correlation coefficient is equal to or more than a predetermined value; A fourth calculating means for calculating an average value of the primary regression coefficients; and a tire wear detecting means for detecting a tire wear state according to the average value. The tire wear determination program according to the present embodiment includes a control unit 2 that calculates a vehicle speed and a vehicle acceleration / deceleration from a measured value obtained by the wheel speed sensor 1; Second calculating means for calculating (the ratio of the wheel speed of the front wheel tires to the wheel speed of the rear wheel tires); and a second calculating means for calculating mutual regression coefficients and correlation coefficients of the acceleration / deceleration and the slip ratio of the vehicle. A third calculating means, a fourth calculating means for accumulating a predetermined number of the primary regression coefficients when the obtained correlation coefficient is equal to or more than a predetermined value, and obtaining an average value of the primary regression coefficients; It functions as tire wear detecting means for detecting the state of wear of the tire according to the average value.

It is preferable that a fifth arithmetic means is provided for obtaining a tire wear index indicating a degree of tire wear by multiplying the average value by the weight of the drive shaft / the weight of the vehicle.

In the present embodiment, the rotational speed of the four tires is detected in one second or less. The acceleration / deceleration of the vehicle is G
Although it can be measured by a sensor, it is preferable to calculate from the average wheel speed of four wheels or driven wheels from the viewpoint of cost.

Then, the acceleration / deceleration and slip ratio of the vehicle are determined by moving-averaging every sampling time as an average value of data for a fixed time, for example, data for 2 seconds or more. Acceleration and deceleration and slip ratio) of the vehicle.

Further, the data of the moving averaged acceleration / deceleration and slip ratio of the vehicle, for example, when the traveling distance is 50
Accumulate until 0 m. In the present invention, data may be stored for a certain period of time, for example, 30 seconds, instead of the traveling distance, or until the number of data reaches 100. The first-order regression coefficient and correlation coefficient of the accumulated acceleration / deceleration and slip ratio of the vehicle are obtained. here,
Each time a predetermined number of primary regression coefficients, for example, 100, are accumulated when the correlation coefficient is a predetermined value, for example, 0.9 or more, an average value of the primary regression coefficients is obtained. Next, a vehicle coefficient (weight of drive shaft / weight of vehicle) Md is added to the average value.
/ M to determine the tire wear index W. If the tire wear index is equal to or less than a predetermined value Wo (W <Wo), it is determined that the tire is in a worn state, and the driver is notified as an alarm.

Hereinafter, the operation of the tire wear state detecting device according to the present embodiment will be described in accordance with procedures (1) to (10).

(1) The wheel speeds (V1 _n , V1 _n ) are calculated from the rotation speeds of the four-wheel tires FL, FR, RL and RR of the vehicle.
V2 _n , V3 _n , V4 _n ) are calculated. For example, AB
The respective wheel tires FL of the vehicle obtained from sensors such as S sensor and FR, RL, wheel speeds _V1 n the wheel speed data of the point in the _RR, and _{V2 n, V3 n, V4 n} .

(2) Then, average wheel speeds (Vf _n , Vd _n ) of the driven wheels and the drive wheels are calculated. For front wheel drive,
The average wheel speed Vf _n of the driven wheel and the driving wheel at a certain time,
Equation vd _n the following (1), obtained by (2). _{Vf n = (V3 n + V4} n) / 2 ··· (1) Vd n = (V1 n + V2 n) / 2 ··· (2)

[0025] (3) followed average wheel acceleration of the driven wheels (i.e. acceleration or deceleration of the vehicle) is calculated Af _n. The average one from the previous wheel speed data from the wheel speed Vf _n of the following wheels and the average wheel speed Vf _n-1, the average wheel acceleration Af _n of the driven wheel is calculated by the respective following formula (3). Af _n = (Vf _n −Vf _n−1 ) / Δt / g (3) where Δt is the wheel speed V calculated from the wheel speed data.
a f _n and _{Vf n-1} time interval (sampling time), g is the gravitational acceleration. The sampling time is set to 0.1 in order to reduce data variation.
Seconds or less are preferred.

(4) Next, the acceleration / deceleration Af of the vehicle_nThe value of the
The slip ratio is calculated according to. First, in an accelerated state,
When the vehicle is slipping with the drive wheels locked (Vd_n=
0, Vf_n≠ 0) or when the vehicle is stopped in a deceleration state
When the driving wheel is causing wheel spin (Vf_n=
0, Vd_n(≠ 0) is a slip
Ratio S_nIs calculated from the following equations (4) and (5). Af_n≧ 0 and Vd_nIf ≠ 0, S_n= (Vf_n-Vd_n) / Vd _n ... (4) Af_n<0 and Vf_nIf ≠ 0, S_n= (Vf_n-Vd_n) / Vf _n ... (5) In cases other than the above, S_n= 1.

(5) Next, the data of the acceleration / deceleration of the vehicle and the slip ratio are subjected to a moving average process for each sampling time. When performing linear regression, the reliability of the obtained first-order regression coefficients is poor unless the number of data exceeds a certain value. Therefore,
For example, by sampling data at intervals of several tens of ms and moving-averaging the data having a large variation obtained during this sampling time, the variation in the data can be reduced without reducing the number of data. Regarding the slip ratio, MS _n = (S ₁ + S ₂ +... + S _n ) / N (6) MS _{n + 1} = (S ₂ + S ₃ +... + S _{n + 1} ) / N (7) MS _{n + 2} = (S ₃ + S ₄ +... + S _{n + 2} ) / N (8) Regarding the acceleration / deceleration of the vehicle, MAf _n = (Af ₁ + Af ₂ +... + Af _n ) / N (9) MAf _{n + 1} = (Af ₂ + Af ₃ +... + Af _{n + 1} ) / N (10) MAf _{n + 2} = (Af ₃ + Af ₄ +... + Af _{n + 2} ) / N (11)

(6) Next, the first-order regression coefficient of the vehicle acceleration / deceleration and the slip ratio, ie, the first-order regression coefficient K1 of the slip ratio for the vehicle acceleration / deceleration and the first-order regression coefficient of the vehicle acceleration / deceleration for the slip ratio. Is obtained from the following equations (12) and (13), respectively.

[0029]

(Equation 1)

[0030]

[Table 1]

The correlation coefficient R is as follows: R = K1 × K2 (14)

(7) The value of the primary regression coefficient K1 (or K2) obtained by the procedure (6) is stored for a predetermined time or a predetermined number. Hereinafter, the first-order regression coefficient K1 will be described. At this time, it is determined whether or not to store the data of the first-order regression coefficient K1 according to the value of the correlation coefficient R. The value of the correlation coefficient R serving as a threshold value of the data accumulation is not particularly limited. However, if the value is too small, data with inferior measurement accuracy may be accumulated. , 0.9 or more, data is hardly accumulated, so that about 0.7 is preferable. Note that the data storage amount is determined by the travel distance, the measurement time, or the number of stored data, as described above. The accumulated amount is not particularly limited, but may be accumulated for a certain measurement time, for example, 30 seconds. Further, when evaluating the wear state of the tire, the wear hardly progresses rapidly in units of several minutes or several hours, so that there is no particular problem in increasing the measurement time to 30 minutes or one hour. However, because of the data capacity, it is preferable to set it within a practical range. In addition, for example, measurement for several minutes is repeated about several times, and the average can be evaluated, or data having large variations can be deleted and evaluated.

(8) Next, a predetermined number of primary regression coefficients K1 when the correlation coefficient R is equal to or more than a predetermined value are accumulated, and the average value is obtained. For example, each time a predetermined number of primary regression coefficients K1, for example, 100, are accumulated, the average value K1m of the primary regression coefficients K1 is calculated.

(9) Next, the tire wear index W is obtained by multiplying the average value K1m by the vehicle coefficient (drive shaft weight / vehicle weight) Md / M.

(10) If the tire wear index is equal to or less than a predetermined value Wo (W <Wo), it is determined that the tire is in a worn state. The predetermined value Wo varies depending on the type of the tire. However, considering a tire wear state, for example, a state in which the degree of wear of the tire is about 70% wear and a tire replacement is desired, the tire wear index W is Wo = 0. If it is not more than 015, it is determined that the tire is in a worn state.
When it is determined that the tire is in a worn state, the wear alarm 3 informs the driver.

[0036]

Next, the present invention will be described based on examples, but the present invention is not limited to only these examples.

Examples 1 and 2 First, a new tire, a tire worn by about 40% or a tire worn by about 80% was mounted on a front wheel drive vehicle.
The tire at this time was FM901 manufactured by Sumitomo Rubber Industries, Ltd.
It is. Then, each tire was driven on a dry asphalt road for 4 hours (Example 1). In addition, a running test similar to that of Example 1 was performed by mounting the new tire, the tire worn by about 40% or the tire worn by about 80% on the rear wheel drive vehicle instead of the front wheel drive vehicle (Example). 2).

In this traveling, as shown in FIG. 3, based on the wheel speed pulse output from the wheel speed sensor,
The wheel speed is taken every 0.1 second (step S1), the average wheel speed of the driven wheels is calculated as the vehicle speed Fs, and the travel time T and the travel distance D are calculated (step S1).
2). Then, the acceleration / deceleration Fac and the slip ratio SR of the vehicle every 0.1 second were calculated (steps S3 and S4). Regarding the acceleration / deceleration Fac and the slip ratio SR of the vehicle, values FacM and SRM obtained by performing a moving average process on the data for 2 seconds for each sampling time were obtained (steps S5 and S6).

Then, FacM and SRM are accumulated for each traveling distance D of D1 = 500 m (steps S7, S7).
8) A first-order regression coefficient K1 and a correlation coefficient R of the vehicle acceleration with respect to the slip ratio were obtained (step S9). It is determined whether or not the correlation coefficient R is equal to or greater than R1 = 0.9 (steps S10 and S11). Each time X = 100 primary regression coefficients K1 when R1 = 0.9 or greater are accumulated. Then, the average value K1m is obtained (steps S11 to S14).

Next, the vehicle coefficient Md / M is added to the average value K1m.
(The front-wheel drive vehicle of Example 1 is 0.651, and Example 2
Is 0.462 for the rear wheel drive vehicle) to obtain a tire wear index W (step S15), and it is determined whether or not an alarm is issued based on the value of the tire wear coefficient W. = 0.015 or less, a tire wear warning is issued (steps S16 to S1).
8).

As a result, in the case of Example 1, the tire wear index of the new tire FF1 constantly changes from 0.024 to 0.025 based on the change with time of the tire wear index shown in FIG. For the tire FF2 which is about 40% worn, it constantly changes between 0.016 and 0.017. Also about 8
0% wear tire FF3 constantly 0.011-0.01
2.

In the case of the second embodiment, the tire wear index of the new tire FR1 constantly changes from 0.025 to 0.027, while the tire wear index changes from 0.025 to 0.027, as shown in FIG. For the 40% worn tire FR2, it constantly changes between 0.017 and 0.018. About 80%
For the worn tire FR3, it is constantly 0.012 to 0.013.

Accordingly, it can be seen that both Examples 1 and 2 accurately identify the degree of tire wear. Also,
Since Example 1 and Example 2 show almost the same tire wear index even when the vehicle changes, it is understood that it is not necessary to separately include identification for each vehicle.

[0044]

As described above, according to the present invention,
Since the wear state of the tire can be accurately detected, the performance and safety performance of the vehicle can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a tire wear state detecting device according to the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the tire wear state detecting device in FIG.

FIG. 3 is an example of a flowchart of the present invention.

FIG. 4 is an example of a flowchart of the present invention.

FIG. 5 is a diagram showing a change over time in a tire wear index of a new tire FF1, a tire 40% worn, and a tire FF3 worn about 40%, which are mounted on a front wheel drive vehicle.

FIG. 6 is a graph showing a change over time in a tire wear index of a new tire FR1, a tire 40% worn, and a tire FR3 worn about 80%, which are mounted on a rear wheel drive vehicle.

FIG. 7 is a schematic diagram showing a relationship between a road surface μ and a slip ratio s.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wheel speed sensor (rotation speed detection means) 2 Control unit 3 Wear alarm FL, FR, RL, RR Tire

Claims (5)

[Claims] A rotation speed detecting means for periodically detecting rotation speeds of four tires of a vehicle, and a first speed calculating means for calculating a speed of the vehicle and an acceleration / deceleration of the vehicle based on a value measured by the rotation speed detecting means. Calculating means, second calculating means for calculating a slip ratio of the front and rear wheels, third calculating means for calculating a mutual primary regression coefficient and correlation coefficient between the acceleration / deceleration and the slip ratio of the vehicle, A fourth calculating means for accumulating a predetermined number of the primary regression coefficients when the obtained correlation coefficient is equal to or more than a predetermined value and obtaining an average value of the primary regression coefficients; A tire wear state detecting device, comprising: a tire wear detecting means for detecting a tire wear state. 2. The vehicle according to claim 1, further comprising: fifth calculating means for multiplying the average value by a weight of the drive shaft / the weight of the vehicle to obtain a tire wear index indicating a degree of tire wear. The wear state detecting device according to claim 1, wherein when the tire wear index is equal to or less than a predetermined value, the wear of the tire is determined. 3. A rotational speed detecting means for periodically detecting rotational speeds of four tires of the vehicle, and a step of calculating a vehicle speed and a vehicle acceleration / deceleration from a value measured by the rotational speed detecting means. Calculating the slip ratio of the front and rear wheels;
Obtaining a mutual primary regression coefficient and a correlation coefficient between the acceleration / deceleration and the slip ratio of the vehicle, and determining the primary regression coefficient when the obtained correlation coefficient is a predetermined value or more by a predetermined number. A method for detecting a worn state of a tire, comprising: a step of accumulating and calculating an average value of the primary regression coefficients; and a step of detecting a worn state of the tire according to the average value. 4. A tire wear index indicating the degree of tire wear is obtained by multiplying the average value by the weight of the drive shaft / the weight of the vehicle. When the tire wear index is equal to or less than a predetermined value, the tire wear is evaluated. 4. The method according to claim 3, wherein the determination is made. 5. A first calculating means for calculating a vehicle speed and a vehicle acceleration / deceleration from a measured value by a rotation speed detecting means, for calculating a tire wear state, and calculating a slip ratio of front and rear wheels. A second calculating means for calculating a first-order regression coefficient and a correlation coefficient of the acceleration / deceleration and the slip ratio of the vehicle, and a third calculating means for obtaining a correlation coefficient of not less than a predetermined value A fourth calculating means for accumulating a predetermined number of the primary regression coefficients and calculating an average value of the primary regression coefficients, and a tire wear detecting means for detecting a tire wear state according to the average value A program to determine the wear of tires.