JP2009040080A - Tire internal pressure drop detecting method and apparatus, and tire internal pressure drop detecting program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire internal pressure drop detecting method realizing quantitative correction of load-induced reduction of a dynamic load radius and accurate determination of a tire internal pressure drop. <P>SOLUTION: In the method, the tire dynamic load radius of a running vehicle is calculated to detect the tire internal pressure drop based on the magnitude of change of the obtained dynamic load radius from its reference value under a normal internal pressure. The method includes the steps of detecting wheel rotation information of each vehicle tire, calculating a wheel speed from the detected wheel rotation information, obtaining a vehicle speed, obtaining the dynamic load radius of each tire from the wheel speed and the vehicle speed, obtaining a vehicle mass, comparing the obtained vehicle mass with a vehicle mass under normal internal pressure and with no load mounted thereon to obtain a wheel load change amount of a predetermined tire to correct the reference value of the dynamic load radius of the predetermined tire based on the wheel load change amount, and determining the tire internal pressure drop when the magnitude of change of the obtained tire dynamic load radius from the corrected reference value exceeds a predetermined threshold value. At the vehicle mass obtaining step, with the vehicle running on a road surface of an inclined angle θ, the vehicle mass is obtained from an equation m(α+gsin(θ))+AV<SP>2</SP>=Fx=T/R wherein m is the vehicle mass, V is the vehicle speed, α is a vehicle acceleration, T is a vehicle axle shaft, Fx is fore and aft force, R is the tire load radius, θ is the road surface inclined angle, A is an aerodynamic drag and g is a gravity acceleration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tire internal pressure drop detection method and apparatus, and a tire internal pressure drop detection program.

  Conventionally, various methods have been proposed as a method for detecting a decrease in the internal pressure of a tire of a vehicle. For example, Patent Document 1 discloses a tire of a running vehicle based on the relationship between the absolute speed of the vehicle and the rotational angular velocity of the tire. The dynamic load radius is calculated, and when the calculated dynamic load radius becomes smaller by a predetermined degree than the initial value (reference value) stored in advance as the dynamic load radius at the normal internal pressure, the internal pressure of the tire is reduced. A method for alarming is disclosed.

  In the method described in Patent Document 1, in order to prevent an alarm from being issued due to a cause other than a decrease in tire internal pressure, the traveling state of the vehicle is limited (limited to a traveling state in which a flat road is traveling straight at a constant speed). In addition, the dynamic load radius obtained in such a state is used as an effective value for detecting a decrease in the internal pressure of the tire.

JP 2007-45295 A

  By the way, the dynamic load radius of a tire changes not only when the vehicle is accelerating or decelerating or turning, but also depending on the magnitude of the load on the person who rides on the vehicle or on the vehicle. However, there has been no conventional method that considers the change in the dynamic load radius due to the load. In particular, in the case of a rear wheel tire, a heavy load is often placed on the trunk, and the load fluctuation is large. Therefore, it is difficult to accurately determine the pressure reduction of the tire.

  The present invention has been made in view of such circumstances, and it is possible to quantitatively correct a decrease in the dynamic load radius due to a load, and to detect a decrease in tire internal pressure accurately. It is an object of the present invention to provide a method and apparatus, and a tire internal pressure drop detection program.

The tire internal pressure drop detection method of the present invention calculates the tire dynamic load radius of a running vehicle, and based on the magnitude of change of the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure. A method for detecting a decrease in tire internal pressure,
Detecting wheel rotation information of each tire of the vehicle;
Calculating the wheel speed from the detected wheel rotation information;
Determining vehicle speed;
Obtaining a dynamic load radius of each tire from the wheel speed and vehicle speed;
Determining the mass of the vehicle;
A wheel load change amount of a predetermined tire is obtained by comparing the obtained vehicle mass with a normal internal pressure and a vehicle mass when no load is mounted, and based on the wheel load change amount, a reference for a dynamic load radius of the predetermined tire is obtained. Correcting the value;
A step of determining a decrease in the internal pressure of the tire when a magnitude of a change from the corrected reference value of the obtained tire dynamic load radius exceeds a predetermined threshold value, and
In the step of determining the vehicle mass, it is assumed that the vehicle is traveling on a road surface with an inclination angle θ, the vehicle mass is m, the vehicle speed is V, the vehicle acceleration is α, the axle shaft of the vehicle is T, and the longitudinal force is When Fx, tire load radius is R, road inclination angle is θ, aerodynamic resistance is A, and gravitational acceleration is g, m (α + gsin (θ)) + AV ² = Fx = T / R
The vehicle mass is obtained by the following.

  In the tire internal pressure drop detection method of the present invention, the axle shaft torque of the vehicle, which is CAN (Control Area Network) information, for example, the vehicle speed calculated from GPS, the vehicle acceleration calculated therefrom, and the vehicle travels. The vehicle mass is calculated (estimated) using the inclination angle α of the road surface. Then, a wheel load change amount of a predetermined tire is obtained by comparing the estimated vehicle mass with a vehicle mass at a normal internal pressure and when no load is mounted, and based on the wheel load change amount, the movement of the predetermined tire is calculated. The reference value of the load radius is corrected, and it is determined that the tire internal pressure is reduced when the dynamic load radius becomes smaller than the decrease in the dynamic load radius due to the wheel load. That is, by calculating the mass of the running vehicle, the amount of decrease in the dynamic load radius due to the wheel load can be grasped for a predetermined tire (for example, a rear wheel tire when a load is placed on the trunk). Only when the dynamic load radius decreases due to a decrease in internal pressure, a determination of a decrease in internal pressure can be made. Thereby, a false alarm can be prevented and the detection accuracy of the internal pressure drop can be improved.

  In the step of correcting the reference value, the load sensitivity of the dynamic load radius indicating the contribution of the wheel load to the change of the dynamic load radius obtained from the relationship between the wheel load and the dynamic load radius of the tire obtained in advance is used. Thus, the reference value can be corrected.

In addition, the tire internal pressure drop detecting device of the present invention calculates the tire dynamic load radius of the running vehicle, and changes the magnitude of the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure. A device for detecting a decrease in tire internal pressure based on
Wheel rotation information detecting means for detecting wheel rotation information of each tire of the vehicle;
Wheel speed calculation means for calculating wheel speed from the detected wheel rotation information;
Vehicle speed calculation means for determining the vehicle speed;
A dynamic load radius calculating means for determining a dynamic load radius of each tire from the wheel speed and the vehicle speed;
Vehicle mass calculating means for determining the mass of the vehicle;
A wheel load change amount of a predetermined tire is obtained by comparing the obtained vehicle mass with a normal internal pressure and a vehicle mass when no load is mounted, and based on the wheel load change amount, a reference for a dynamic load radius of the predetermined tire is obtained. A reference value correcting means for correcting the value;
Determination means for determining a decrease in the internal pressure of the tire when the magnitude of a change in the tire dynamic load radius obtained from the corrected reference value exceeds a predetermined threshold,
The vehicle mass calculation means assumes that the vehicle is traveling on a road surface with an inclination angle θ, the vehicle mass is m, the vehicle speed is V, the vehicle acceleration is α, the axle shaft of the vehicle is T, and the longitudinal force is Fx. M (α + gsin (θ)) + AV ² = Fx = T / R where R is the tire load radius, θ is the slope of the road surface, A is the aerodynamic resistance, and g is the acceleration of gravity.
The vehicle mass is obtained by the following.

Further, the tire internal pressure drop detection program according to the present invention calculates the tire dynamic load radius of the running vehicle, and changes the obtained dynamic load radius to the magnitude of change from the reference value of the dynamic load radius at normal internal pressure. Based on the wheel speed calculation means for calculating the wheel speed from the wheel rotation information of each tire of the vehicle, and the dynamic load for determining the dynamic load radius of each tire from the wheel speed and the vehicle speed. Radius calculation means, vehicle mass calculation means for determining the mass of the vehicle, a wheel load change amount of a predetermined tire is obtained by comparing the obtained vehicle mass with a vehicle mass at a normal internal pressure and when no load is mounted. Reference value correction means for correcting the reference value of the dynamic load radius of the predetermined tire based on the load change amount, and a large change from the corrected reference value of the obtained tire dynamic load radius. The vehicle mass calculation means is assumed to be running on a road surface with an inclination angle θ, and the vehicle mass calculation means Mass is m, vehicle speed is V, vehicle acceleration is α, vehicle axle shaft is T, longitudinal force is Fx, tire load radius is R, road slope is θ, aerodynamic resistance is A, and gravitational acceleration is g. Sometimes m (α + gsin (θ)) + AV ² = Fx = T / R
The vehicle mass is obtained by the above.

  In the tire internal pressure decrease detection device and the tire internal pressure decrease detection program of the present invention, the axle shaft torque of the vehicle, which is CAN information, for example, the vehicle speed calculated from GPS, the vehicle acceleration calculated therefrom, and the vehicle travels. The vehicle mass is calculated using the inclination angle α of the road surface. Then, a wheel load change amount of a predetermined tire is obtained by comparing the estimated vehicle mass with a vehicle mass at a normal internal pressure and when no load is mounted, and based on the wheel load change amount, the movement of the predetermined tire is calculated. The reference value of the load radius is corrected, and it is determined that the tire internal pressure is reduced when the dynamic load radius becomes smaller than the decrease in the dynamic load radius due to the wheel load. That is, by calculating the mass of a running vehicle, the amount of decrease in the dynamic load radius due to wheel load can be grasped for a given tire, and the internal pressure decreases only when the dynamic load radius decreases due to a decrease in tire internal pressure. Can be determined. Thereby, a false alarm can be prevented and the detection accuracy of the internal pressure drop can be improved.

  According to the tire internal pressure drop detection method and apparatus and the tire internal pressure drop detection program of the present invention, the decrease in the dynamic load radius due to the load can be corrected quantitatively, and the tire internal pressure drop can be accurately determined. .

Hereinafter, with reference to the accompanying drawings, a tire internal pressure drop detection method (hereinafter also simply referred to as “detection method”) and device (hereinafter also simply referred to as “detection device”), and a tire internal pressure drop detection program according to the present invention will be described. Will be described in detail.
As shown in FIG. 1, the detection apparatus according to an embodiment of the present invention includes four tires FL (left front wheel), FR (right front wheel), RL (left rear wheel), and In order to detect wheel rotation information of the RR (right rear wheel), normal wheel speed detection means (wheel rotation information detection means) 1 provided in association with each tire is provided.

  The wheel speed detection means 1 generates power using rotation like a wheel speed sensor or dynamo for generating rotation pulses using an electromagnetic pickup or the like and measuring the rotation angular speed and wheel speed from the number of pulses. It is possible to use an angular velocity sensor including that for measuring the rotational angular velocity and the wheel speed from this voltage. The output of the wheel speed detecting means 1 is given to a control unit 2 which is a computer such as ABS. The control unit 2 includes a liquid crystal display element for informing a tire whose internal pressure has decreased, a display 3 composed of a plasma display element or a CRT, an initialization button 4 that can be operated by a driver, and a decrease in tire internal pressure. Are connected to a GPS device 6 that constitutes a vehicle speed calculation means.

As shown in FIG. 2, the control unit 2 stores an I / O interface 2a necessary for passing signals to and from an external device, a CPU 2b that functions as a center of arithmetic processing, and a control operation program for the CPU 2b. The ROM 2c and the RAM 2d from which data is temporarily written or the written data is read when the CPU 2b performs a control operation. In FIG. 2, 6a is a GPS antenna.
The wheel speed detection means 1 outputs a pulse signal corresponding to the number of rotations of the tire (hereinafter also referred to as “wheel speed pulse”). Further, the CPU 2b calculates the rotation angular velocity of each tire at a predetermined sampling period ΔT (sec), for example, ΔT = 0.05 seconds, based on the wheel speed pulse output from the wheel speed detecting means 1.

  The vehicle speed can be obtained using, for example, a GPS speedometer. With the widespread use of car navigation systems, GPS devices are attached to many vehicles. As a result, positioning technology using a GPS device has also been improved, and a device specialized in calculating speed (GPS speedometer VBOX (trade name) manufactured by Race Logic, UK) is now on the market. The speed calculated by the speedometer using such GPS information can be used as the vehicle speed. In addition, the absolute speed of the vehicle obtained by different methods, such as ground speed, can be used other than the absolute speed of the vehicle obtained by the GPS device.

  The detection device according to the present embodiment includes wheel speed detection means (wheel rotation information detection means) 1, wheel speed calculation means for calculating wheel speed from the detected wheel rotation information of each tire of the vehicle, and vehicle speed. GPS speedometer to be calculated, dynamic load radius calculating means for determining the dynamic load radius of each tire from wheel speed and vehicle speed, vehicle mass calculating means for determining the mass of the vehicle, obtained vehicle mass, and normal internal pressure And a reference value correcting means for obtaining a wheel load change amount of a predetermined tire by comparison with a vehicle mass when no load is mounted, and correcting a reference value of a dynamic load radius of the predetermined tire based on the wheel load change amount. And determining means for determining a decrease in the internal pressure of the tire when the magnitude of the change in the tire dynamic load radius from the corrected reference value exceeds a predetermined threshold value. The tire internal pressure drop detection program causes the control unit 2 to function as wheel speed calculation means, dynamic load radius calculation means, vehicle mass calculation means, reference value correction means, and determination means.

  The tire dynamic load radius (R) of the traveling vehicle can be calculated by V = R × ω from the relationship between the absolute speed (V) of the vehicle and the rotational angular velocity (ω) of the tire. The tire dynamic load radius (R) is known to decrease as the tire internal pressure decreases, and this is used to estimate the decrease in tire internal pressure from the decrease in tire dynamic load radius (R). Can do.

  As described above, the tire dynamic load radius is reduced not only by a decrease in tire internal pressure but also by a wheel load acting on the tire. The wheel load varies depending on the position of the person or baggage on the vehicle. In the present invention, the vehicle axle shaft torque, which is CAN information, for example, the vehicle speed calculated from GPS, and the vehicle calculated from the vehicle speed. The amount of change in the wheel load of a given tire is obtained by comparing the vehicle mass calculated based on the acceleration of the vehicle, the inclination angle α of the road surface on which the vehicle is traveling, and the vehicle mass at normal internal pressure and when no load is mounted. Based on this wheel load change amount, the reference value of the dynamic load radius, which is a criterion for determining whether or not the tire is depressurized, is corrected. Specifically, a reference value of the dynamic load radius is set in consideration of the decrease in the dynamic load radius due to the wheel load. In this specification, “when the load is not mounted” means that a person other than the driver or the load is not substantially mounted on the vehicle, that is, a weight that can affect the dynamic load radius of the tire. It means the state where it is not installed.

Hereinafter, the procedure for calculating the vehicle mass and the procedure for correcting the reference value of the dynamic load radius will be described in detail.
[Calculation of vehicle mass]
The total mass of the vehicle can be estimated using the balance of forces in the vehicle front-rear direction acting on the vehicle traveling on the road surface (slope) with the inclination angle θ at the acceleration α (see FIG. 3). That is, the vehicle mass m is calculated from the following equation (1) using the vehicle axle shaft torque, which is CAN information, the speed calculated from the GPS, the acceleration calculated therefrom, and the inclination angle of the road surface. Can do.
m (α + gsin (θ)) + AV ² = Fx = T / R (1)
Here, T is the axle shaft torque, R is the tire load radius, Fx is the longitudinal force, g is the gravitational acceleration, V is the vehicle speed, A is the aerodynamic resistance, and α is the vehicle acceleration.

θ is an inclination angle of the road surface on which the vehicle is traveling, and θ is expressed by θ = arctan (Vxy / Vz) where Vxy (= V) is a plane speed of the vehicle and Vz is a vertical speed. The vehicle acceleration α is expressed by α = dVxy / dt / sin θ.
From the above, the vehicle mass m and the aerodynamic resistance A can be calculated by regression.

From the difference between the estimated vehicle mass m thus obtained and the estimated vehicle mass at the reference time (when only one driver is in the vehicle), it is possible to obtain an increase in the wheel load on the predetermined tire. For example, when a load is placed on the trunk of a vehicle, the load due to this load is substantially borne by both rear wheels, so it can be considered that the wheel load of each rear wheel increases by one half of the difference. .
Normally, a passenger sits on the passenger seat and the load is about 100 kg at the maximum, but there is a possibility that a load of about 100 to 300 kg may be put on the rear seat and the trunk. The rear wheel tire is considered to have a larger load fluctuation than the front wheel tire. Therefore, even if it is assumed that the rear wheel tire bears all the increase in vehicle mass, that is, the wheel load of the rear wheel tire increases, it is considered that the detection accuracy of the internal pressure drop is improved. In this regard, the present inventor assumed that when the vehicle mass increased under various loading conditions, all of the load increments were on the rear wheel tire, and compared with the separately obtained wheel load actual measurement values for each wheel. . As a result, the deviation from the measured wheel load when all the increase in vehicle mass is assumed to be an increase in the load on the rear tire is compared to the deviation from the measured wheel load when no increase in load is taken into account. As for the front wheel tire, it is almost the same, but for the rear wheel tire, it is clear that the increase in load is assumed to have been on the rear wheel tire rather than the case where no increase in load is considered. Has been confirmed to be smaller. From this, it is understood that the detection accuracy of the internal pressure drop is improved even if it is assumed that the rear tires bear all the increments of the vehicle mass.

[Correction of standard value of dynamic load radius]
(1) Prior to correction, the amount of decrease in the dynamic load radius due to the load of the relevant tire is obtained by experiment and is grasped as an initial value. Specifically, for example, on a tire to be mounted on a vehicle, a table top dynamic load radius measurement is performed using a flat belt, and a reduction amount of the dynamic load radius due to the load is measured. Based on the dynamic load radius at the reference load and the reference internal pressure, the dynamic load radius that decreases as the mass increases by 1 kg, that is, the mass sensitivity (% / kg) of the dynamic load radius is obtained. The unit of the numerator is (%) because the decrease in the dynamic load radius is evaluated by (dynamic load radius change / value of the dynamic load radius at the reference load and reference internal pressure). is there.

  (2) Next, an increase in the wheel load of the predetermined tire is calculated from the difference between the estimated vehicle mass obtained in the above-described “calculation of vehicle mass” and the estimated vehicle mass at the reference time. By multiplying the increase (kg) by the mass sensitivity (% / kg) of the dynamic load radius obtained as the initial value, the decrease (%) of the dynamic load radius due to the load can be calculated. For example, when a heavy load is loaded on the trunk of the vehicle, the increase in the estimated vehicle mass is considered to be borne by the rear wheel tire, so the dynamic load radius reference value is corrected for this rear wheel tire (predetermined tire). .

  By reducing this reduction amount (%) from 100%, it is possible to correct the reference value of the dynamic load radius, which is a criterion for determining whether or not the tire internal pressure is reduced. For example, if the increase in the wheel load of the tire is 20 kg and the mass sensitivity is 0.003% / kg, the amount of decrease in the dynamic load radius due to the load is 20 × 0.003 = 0.06%. Therefore, the corrected reference value is 100−0.06 = 99.4 (%), and a decrease in tire internal pressure is determined by comparing this reference value with the actually measured dynamic load radius. By subtracting the decrease due to the increase in the wheel load from the decrease in the dynamic load radius, it is possible to accurately determine whether or not the decrease is due to the decrease in the tire internal pressure.

[Internal pressure drop detection method]
Hereinafter, the detection method of the present invention will be described.
(1) First, based on the output signal (pulse signal) of the wheel speed detecting means 1, the rotational angular velocity (ω) of each tire is calculated by the following equation (2).
Rotational angular velocity (ω) = 2π × Freq (Hz) / N (pieces) (2)
Here, N is the number of teeth per one rotation of the axle of the wheel speed detecting means 1, and Freq (Hz) is a numerical value obtained by counting the teeth of the wheel speed detecting means 1 per second.

  (2) On the other hand, the vehicle speed (V) is obtained from the GPS speedometer. The vehicle speed (V) is directly output to the control unit 2 as serial data. For either one of the calculation time of the rotational angular velocity (ω) and the calculation time of the vehicle speed (V), the numerical value at the same time as the other is interpolated and the numerical values at the same time are calculated and synchronized with each other. For example, can be taken into the control unit 2 as digital data every 50 msec. The dynamic load radius is calculated every 50 msec from the digital data every 50 msec, and can be calculated, for example, as an average value per second.

  (3) From the obtained rotational angular velocity (ω) and vehicle speed (V), the tire dynamic load radius (R) is calculated by R = V / ω, and the reference load and the reference set in advance by actual vehicle running or the like. The ratio (%) to the dynamic load radius at internal pressure is obtained.

The tire dynamic load radius also changes due to factors other than a decrease in tire internal pressure, such as acceleration / deceleration, turning, and running on a slope, so the vehicle's running condition is limited (running on a flat road at a constant speed) It is preferable to adopt the data obtained in such a state as valid data, and in this way, by excluding changes in the tire dynamic load radius due to other factors from the data for determining the internal pressure drop, A decrease in internal pressure can be determined.
Specifically, whether or not the driving condition satisfies conditions such as constant speed driving, flat road driving, and straight driving is compared with each judgment condition, and the data obtained during actual driving is used for setting the reference value. It is determined whether the data is suitable for the data. If the data is inappropriate, the data is excluded without being used as the reference value setting data. As the determination conditions, for example, the vehicle front-rear direction | G | <0.05G, the direction change is 1 degree or less, the road surface gradient is 5% or less, and the brake is not stepped on.

  (4) Next, an estimated vehicle mass is obtained according to the procedure in “Calculation of vehicle mass” described above, and the difference between the estimated vehicle mass and the total vehicle mass at the reference time (when only one driver is on board) Find the increase in wheel load. Then, the decrease amount (%) of the dynamic load radius due to the load is calculated from the obtained increase in the wheel load and the mass sensitivity (% / kg) of the dynamic load radius obtained as the initial value.

Next, by reducing this reduction amount (%) from 100%, the reference value of the dynamic load radius, which is a criterion for determining whether or not the tire internal pressure is reduced, is corrected.
Then, by comparing the corrected dynamic load radius (%) with the actually measured dynamic load radius (%), it is determined whether or not the tire internal pressure has decreased. Specifically, when determining the mass sensitivity (% / kg) of the dynamic load radius described above, the pressure reduction sensitivity of the dynamic load radius (dynamic load radius (%) that decreases when the internal pressure decreases by 1%) is also obtained. The degree of pressure reduction relative to the reference internal pressure (%) is determined by dividing the difference between the actually measured dynamic load radius (%) and the corrected dynamic load radius (%) by the pressure reduction sensitivity (% /%). ). The degree of decompression obtained is compared with a threshold value (for example, 30%). If the degree of decompression is greater than the threshold value, it is determined that the tire internal pressure has decreased, and the decompressed tire is displayed on the display 3. At the same time, the alarm 5 gives an alarm to the driver.

Next, examples of the detection method of the present invention will be described. However, the present invention is not limited to such examples.
[Example]
In order to obtain the rotational angular velocity of each tire mounted on the vehicle, the rotational angular velocity used for ABS control was converted into the rotational angular velocity. Further, in order to obtain the absolute speed of the vehicle, a VBOX (trade name, a GPS speedometer manufactured by Race Logic, UK) was attached to the vehicle. The vehicle speed is directly output to a PC (personal computer) as serial data, and the vehicle speed information, the rotation speed information, and the axle shaft torque information of the vehicle can be synchronously captured as digital data every 50 msec. . And the tire dynamic load radius was calculated every 50 msec from vehicle speed information and rotational speed information, and it calculated as an average value for every second.

[Pre-test]
The onboard dynamic load radius was measured using a flat belt, and the amount of decrease in the dynamic load radius due to the load of the corresponding tire and reduced pressure was measured and input as an initial value to the storage unit of the detection device.
Based on the dynamic load radius at the standard load (3.5 kN) and the standard internal pressure (210 kPa), the dynamic load radius that decreases as the mass (load) increases by 1 kg, that is, the mass sensitivity of the dynamic load radius (% / kg) ), And the dynamic load radius that decreases when the internal pressure decreases by 1%, that is, the pressure reduction sensitivity (% /%) of the dynamic load radius. As a result, the mass sensitivity (% / kg) of the dynamic load radius was 0.0029% / kg, and the reduced pressure sensitivity (% /%) was 0.0172% /%. The unit of the numerator is (%) because the decrease in the dynamic load radius is evaluated by (dynamic load radius change / value of the dynamic load radius at the reference load and reference internal pressure). is there.

[Real car test]
Tires (215 / 45R17 SP9000) were mounted on a 4WD vehicle, and the following four cases were tested in actual vehicles at the Okayama test course of Sumitomo Rubber Industries, Ltd.
Case 1: 1 person rides at standard internal pressure (front wheel: 230 kPa, rear wheel: 210 kPa). In the present invention
It corresponds to normal internal pressure and reference load (or reference time).
Case 2: Reduce the pressure of the rear wheel by 30% (front wheel: 230 kPa, rear wheel: 147 kPa)
One person rides.
Case 3: One passenger rides at a standard internal pressure (front wheel: 230 kPa, rear wheel: 210 kPa). further,
190kg weight on the trunk.
Case 4: In case 3, the rear wheel was decompressed by 30% (front wheel: 230 kPa, rear wheel: 147 kPa).

First, the dynamic load radius of the rear wheel tire was calculated from the rotational angular velocity of the rear wheel tire and the vehicle speed, and the ratio (%) to the calculated value (dynamic load radius) in case 1, which is the reference time, was obtained. The results are shown in Table 1. For example, in case 2, the measured value of the dynamic load radius was 99.48%.
Subsequently, the estimated vehicle mass was calculated | required according to said Formula (1) about each of cases 1-4. FIG. 4 is a diagram in which test results for estimating the vehicle mass in case 2 are plotted, in which the horizontal axis is (α + g sin θ) and the vertical axis is (Fx−AV ² ). From the equation (1), the slope of the regression line obtained from the plotted data is the estimated vehicle mass. In the case of the illustrated example, the regression line is y = 1571x, and the estimated vehicle mass is 1571 (kg). Similarly, the estimated vehicle masses of Case 1, Case 3, and Case 4 were 1578 (kg), 1758 (kg), and 1765 (kg), respectively. The “total vehicle mass” in Table 1 is a vehicle mass obtained by actual measurement.

  Next, with respect to the estimated vehicle mass obtained in case 1, for each of cases 2 to 4, the reference value of the dynamic load radius of the rear wheel tire is corrected in accordance with the increase or decrease of the wheel load of the rear wheel tire. It was. For example, in case 2, since the wheel load of the rear tire is reduced by (1578-1571) /2=3.5 (kg) in calculation, the reference value after correcting the dynamic load radius is 3 .5 (kg) × 0.0029 (% / kg) ≈0.01 (%) is increased to 100.01 (%). In the case 3, since the wheel load of the rear tire is increased by (1758-1578) / 2 = 90 (kg), the reference value after correcting the dynamic load radius is 90 (kg) × 0. .0029 (% / kg) ≈0.26 (%) is reduced to 99.74 (%).

  The difference between the corrected dynamic load radius reference value obtained in this way and the actually measured dynamic load radius is calculated, and then this difference and the reduced pressure sensitivity (% /%) of the dynamic load radius obtained in the preliminary test are calculated. ) And the decompression value (%) of the rear tire of each case. For example, in case 2, the measured dynamic load radius (99.48%) is 0.53% smaller than the corrected dynamic load radius reference value (100.01%). Therefore, the reduced pressure value is 0.53 (%) ÷ 0.0172 (% /%) ≈31 (%). In case 3, the measured dynamic load radius (99.72%) is 0.02% smaller than the corrected dynamic load radius reference value (99.74%). Accordingly, the reduced pressure value is 0.02 (%) ÷ 0.0172 (% /%) ≈1 (%). In the other cases, the estimated reduced pressure value of the rear tire was calculated in the same manner. The results are shown in Table 1.

  When the difference between the actual reduced pressure value (0% for cases 1 and 3 and 30% for cases 2 and 4) and the calculated estimated reduced pressure value is less than 5%, “good (OK) ) ", It was" OK "for all the rear wheel tires of cases 1-4.

[Comparative example]
The estimated reduced pressure value was calculated in the same manner as in the example except that the decrease due to the load was not taken into account (corrected) for the reference value of the dynamic load radius when determining the tire internal pressure. The results are shown in Table 1.
When the difference between the actual reduced pressure value (0% for cases 1 and 3 and 30% for cases 2 and 4) and the calculated estimated reduced pressure value is less than 5%, “good (OK) ”), It was estimated that the cases 3 and 4 in which the load was loaded on the trunk were respectively decompressed by 16% more than the actual, and were“ bad ”(NG).
From the above, it can be seen that the decrease in the internal pressure of the tire can be accurately determined by correcting the reference value of the dynamic load radius in consideration of the reduced pressure reduction due to the load mounting.

It is a block diagram which shows one Embodiment of the detection apparatus of this invention. It is a block diagram which shows the electrical structure of the detection apparatus shown by FIG. It is a figure which shows the force which acts on the vehicle which drive | works the road surface of the inclination angle (alpha). It is the figure which plotted the test result for estimating vehicle mass.

Explanation of symbols

1 Wheel speed detection means 2 Control unit 2a Interface 2b CPU
2c ROM
2d RAM
3 Display 4 Initialization Button 5 Alarm 6 GPS Device 6a GPS Antenna

Claims (4)

This is a method of calculating the tire dynamic load radius of a running vehicle and detecting the decrease in tire internal pressure based on the magnitude of change of the obtained dynamic load radius from the standard value of the dynamic load radius at normal internal pressure. And
Detecting wheel rotation information of each tire of the vehicle;
Calculating the wheel speed from the detected wheel rotation information;
Determining vehicle speed;
Obtaining a dynamic load radius of each tire from the wheel speed and vehicle speed;
Determining the mass of the vehicle;
A wheel load change amount of a predetermined tire is obtained by comparing the obtained vehicle mass with a normal internal pressure and a vehicle mass when no load is mounted, and based on the wheel load change amount, a reference for a dynamic load radius of the predetermined tire is obtained. Correcting the value;
Determining the decrease in internal pressure of the tire when the magnitude of change in the tire dynamic load radius obtained from the corrected reference value exceeds a predetermined threshold,
In the step of determining the vehicle mass, it is assumed that the vehicle is traveling on a road surface with an inclination angle θ, the vehicle mass is m, the vehicle speed is V, the vehicle acceleration is α, the axle shaft of the vehicle is T, and the longitudinal force is When Fx, tire load radius is R, road inclination angle is θ, aerodynamic resistance is A, and gravitational acceleration is g, m (α + gsin (θ)) + AV ² = Fx = T / R
A method for detecting a decrease in tire internal pressure, characterized in that the vehicle mass is obtained by:   In the step of correcting the reference value, the load sensitivity of the dynamic load radius indicating the contribution of the wheel load to the change of the dynamic load radius obtained from the relationship between the wheel load and the dynamic load radius of the tire obtained in advance is used. The method for detecting a decrease in tire internal pressure according to claim 1, wherein the reference value is corrected. This is a device that calculates the tire dynamic load radius of a running vehicle and detects the decrease in tire internal pressure based on the magnitude of the change of the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure. And
Wheel rotation information detecting means for detecting wheel rotation information of each tire of the vehicle;
Wheel speed calculation means for calculating wheel speed from the detected wheel rotation information;
Vehicle speed calculation means for determining the vehicle speed;
A dynamic load radius calculating means for determining a dynamic load radius of each tire from the wheel speed and the vehicle speed;
Vehicle mass calculating means for determining the mass of the vehicle;
A wheel load change amount of a predetermined tire is obtained by comparing the obtained vehicle mass with a normal internal pressure and a vehicle mass when no load is mounted, and based on the wheel load change amount, a reference for a dynamic load radius of the predetermined tire is obtained. A reference value correcting means for correcting the value;
Determination means for determining a decrease in the internal pressure of the tire when the magnitude of a change in the tire dynamic load radius obtained from the corrected reference value exceeds a predetermined threshold,
The vehicle mass calculation means assumes that the vehicle is traveling on a road surface with an inclination angle θ, the vehicle mass is m, the vehicle speed is V, the vehicle acceleration is α, the axle shaft of the vehicle is T, and the longitudinal force is Fx. M (α + gsin (θ)) + AV ² = Fx = T / R where R is the tire load radius, θ is the slope of the road surface, A is the aerodynamic resistance, and g is the acceleration of gravity.
A tire internal pressure drop detecting device, characterized in that the vehicle mass is obtained by the following. A computer for calculating a tire dynamic load radius of a running vehicle and detecting a decrease in the internal pressure of the tire based on a magnitude of a change of the obtained dynamic load radius from a reference value of the dynamic load radius at a normal internal pressure. A wheel speed calculating means for calculating a wheel speed from wheel rotation information of each tire of the vehicle, a dynamic load radius calculating means for calculating a dynamic load radius of each tire from the wheel speed and the vehicle speed, and a vehicle mass for determining the mass of the vehicle. The calculation means calculates the wheel load change amount of the predetermined tire by comparing the obtained vehicle mass with the normal internal pressure and the vehicle mass when the load is not mounted, and based on the wheel load change amount, the dynamic load of the predetermined tire is obtained. Reference value correction means for correcting the reference value of the radius, and when the magnitude of change of the obtained tire dynamic load radius from the corrected reference value exceeds a predetermined threshold, the internal pressure of the tire is reduced. The vehicle mass calculation means is assumed to be traveling on a road surface with an inclination angle θ, the vehicle mass is m, the vehicle speed is V, the vehicle acceleration is α, the vehicle M (α + gsin (θ)) + AV ² = Fx = T where T is the axle shaft, Fx is the longitudinal force, R is the tire load radius, θ is the slope of the road, A is the aerodynamic resistance, and g is the gravitational acceleration. / R
A vehicle internal pressure drop detection program characterized in that the vehicle mass is determined by

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