JP2010076703A - Method and device for estimating wheel load of tire, and program for estimating wheel load of tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wheel load estimating method for a tire, can exactly calculate the wheel load of each wheel of a vehicle at a low cost. <P>SOLUTION: This wheel load estimating method includes a process for detecting wheel rotation information on each tire, a process for calculating wheel speed, a process for determining vehicle speed, a process for determining a dynamic load radius of each tire from the wheel speed and the vehicle speed, a process for determining a slip ratio of each tire, a process for determining the mass of the vehicle, a process for determining the dynamic load radius of each wheel when longitudinal force is zero using driving stiffness determined from the driving force of each wheel and the slip ratio, the vehicle speed and the wheel speed during initialization and calculating internal pressure sensitivity and/or load sensitivity of each tire based on a relation between the dynamic load radius, wheel load of the tire and initial internal pressure of the tire, and a process for calculating the wheel load of each tire from the relational expression of the driving force of each wheel, the slip ratio and the driving stiffness and the vehicle mass obtained in the process for determining the vehicle mass. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tire wheel load estimation method and apparatus for estimating a wheel load of a tire based on a change in a dynamic load radius of the tire, and a tire wheel load estimation program.

In recent years, stability control systems are frequently used to improve vehicle safety. In this system, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-203300, vehicle information mounted on the vehicle is obtained using sensor information such as yaw rate and lateral acceleration during turning, and distribution of vehicle mass and load. The turning limit is calculated by, and the limit is not exceeded by electronically controlling the brake pressure and traction of each wheel.
In such a conventional system, the distribution of the mass and load of the vehicle is set by default.

JP 2000-203300 A

However, it is usually not possible to estimate the vehicle's mass and load distribution while driving, so when personnel or luggage are loaded on the vehicle, there is a deviation from the default mass / load distribution, resulting in fine control. There is a possibility that it cannot be done.
On the other hand, as a method of knowing the mass and load distribution of the running vehicle, it is conceivable to use sensors for measuring various suspension strokes, but this is not practical because it costs a lot of money.

  The present invention has been made in view of such circumstances, and a wheel load estimation method and apparatus for a tire that can accurately calculate the wheel load of each wheel of a vehicle at low cost, and the wheel load of a tire. The purpose is to provide an estimation program.

A wheel load estimation method for a tire according to a first aspect of the present invention is a method for estimating a wheel load of a tire mounted on a vehicle based on a rotational speed of a wheel mounted on the vehicle,
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;
The step of obtaining the slip ratio of each tire using this dynamic load radius,
Determining the mass of the vehicle;
At the time of initialization, using the driving stiffness and the vehicle speed and the wheel speed obtained from the driving force and slip ratio of each wheel, the dynamic load radius of each wheel when the longitudinal force is zero is obtained, and this dynamic load radius, Calculating the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the wheel load of the tire and the initial internal pressure of the tire;
And a step of calculating a wheel load of each tire from a relational expression of a driving force of each wheel, a slip ratio and a driving stiffness, and a vehicle mass obtained in the step of obtaining the vehicle mass.

  In the tire wheel load estimation method according to the first aspect of the present invention, the tire driving stiffness is proportional to (wheel load / internal pressure), and the tire dynamic load radius when the tire longitudinal force is zero, The relationship between wheel load and internal pressure is used, and even if the internal pressure of each wheel is different, the load distribution ratio of vehicle mass to each tire can be accurately calculated. The wheel load can be accurately calculated.

In the step of calculating the internal pressure sensitivity and / or load sensitivity at the time of initialization, the dynamic load radius of the tire when the longitudinal force is zero is DLR, the wheel load is FZ, the internal pressure is IP, the load sensitivity is b, and the internal pressure sensitivity Is c and the constant is d,
DLR = bFZ + cIP + d
The internal pressure sensitivity and / or load sensitivity can be calculated based on the formula represented by

In the step of determining the vehicle mass, it is assumed that the vehicle is traveling on a road surface having an inclination angle θ, the vehicle mass is m, the vehicle speed is V, the vehicle acceleration is α, the total axle shaft torque of the vehicle is T, and a tire. M (α + gsin (θ)) + AV ² = T / R where R is the load radius, θ is the slope of the road surface, A is the aerodynamic resistance, and g is the acceleration of gravity.
Thus, the vehicle mass can be obtained.

In the step of obtaining the dynamic load radius of each wheel when the longitudinal force is zero, the dynamic load radius is DLR, the driving force is FX, the driving stiffness obtained from the slip ratio is D, the vehicle speed is V, and the wheel speed is ω. And when
FX = D × {1-V / (ωDLR)}
Thus, the dynamic load radius can be obtained.

The tire wheel load estimation device of the present invention is a device for estimating the wheel load of a tire mounted on the vehicle based on the rotational speed of the wheel mounted on the vehicle,
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;
Slip rate calculating means for determining the slip rate of each tire using the dynamic load radius;
Vehicle mass calculating means for determining the mass of the vehicle;
At the time of initialization, using the driving stiffness and the vehicle speed and the wheel speed obtained from the driving force and slip ratio of each wheel, the dynamic load radius of each wheel when the longitudinal force is zero is obtained, and this dynamic load radius, Tire sensitivity calculation means for calculating the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the wheel load of the tire and the initial internal pressure of the tire;
Tire wheel load calculating means for calculating the wheel load of each tire from the relational expression of the driving force, slip ratio and driving stiffness of each wheel and the vehicle mass obtained in the step of obtaining the vehicle mass. .

  Further, the tire wheel load estimation program according to the present invention provides a computer for estimating the wheel load of the tire mounted on the vehicle based on the rotational speed of the wheel mounted on the vehicle, and the wheel rotation of each tire of the vehicle. Wheel speed calculating means for calculating wheel speed from information, dynamic load radius calculating means for calculating a dynamic load radius of each tire from the wheel speed and vehicle speed, and a slip ratio calculation for determining a slip ratio of each tire using the dynamic load radius Means, vehicle mass calculation means for determining the mass of the vehicle, and each wheel when the longitudinal force is zero using the driving stiffness, vehicle speed and wheel speed determined from the driving force and slip ratio of each wheel at the time of initialization. , And based on the relationship between the dynamic load radius, the wheel load of the tire, and the initial internal pressure of the tire, the internal pressure sensitivity of each tire and / or Tire sensitivity calculating means for calculating heavy sensitivity, a relational expression of driving force, slip ratio and driving stiffness of each wheel, and a tire wheel load for calculating a wheel load of each tire from a vehicle mass obtained in the vehicle mass obtaining step It is characterized by functioning as a calculation means.

  In the tire wheel load estimation device and the tire wheel load estimation program of the present invention, the tire driving stiffness is proportional to (wheel load / internal pressure), and the front and rear of the tire, as in the tire wheel load estimation method. Using the relationship between the tire dynamic load radius when the force is zero, the wheel load and the internal pressure, even if the internal pressure of each wheel is different, the load distribution ratio of the vehicle mass to each tire Can be calculated accurately, and the wheel load of each wheel can be calculated accurately.

Further, the tire wheel load estimation method according to the second aspect of the present invention is a method for estimating the wheel load of the tire mounted on the vehicle based on the rotational speed of the wheel mounted on the vehicle,
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;
The step of obtaining the slip ratio of each tire using this dynamic load radius,
Determining the mass of the vehicle;
At the time of initialization, using the driving stiffness, vehicle speed and wheel speed obtained from the braking force and slip ratio of each wheel, the dynamic load radius of each wheel when the longitudinal force is zero is obtained, and this dynamic load radius, Calculating the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the wheel load of the tire and the initial internal pressure of the tire;
And a step of calculating a wheel load of each tire from a relational expression of a braking force, a slip ratio and a driving stiffness of each wheel and a vehicle mass obtained in the step of obtaining the vehicle mass.

  Also in the tire wheel load estimation method according to the second aspect of the present invention, the tire driving stiffness is proportional to (wheel load / internal pressure), and the tire dynamic load radius when the tire longitudinal force is zero The load distribution ratio of the vehicle mass to each tire can be accurately calculated even when the internal pressure of each wheel is different, using the relationship between the wheel load and the internal pressure. The wheel load can be accurately calculated.

  According to the tire wheel load estimation method and apparatus and the tire wheel load estimation program of the present invention, the wheel load of each wheel of the vehicle can be calculated accurately and at low cost even when the internal pressure of each tire is different. can do.

Hereinafter, a tire wheel load estimation method (hereinafter also simply referred to as “estimation method”) and apparatus (hereinafter also simply referred to as “estimation device”), and a tire wheel load estimation program according to the present invention, with reference to the accompanying drawings The embodiment will be described in detail.
As shown in FIG. 1, the estimation apparatus according to an embodiment of the present invention is equipped with a drive control device 4 that controls the ratio at which the drive torque of the engine of the vehicle is distributed to the front axle and the rear axle, respectively. Estimates wheel loads of four tires FL (left front wheel), FR (right front wheel), RL (left rear wheel) and RR (right rear wheel) provided in a wheeled vehicle (four-wheel drive vehicle) In order to detect wheel rotation information of the tire, normal wheel speed detection means (wheel rotation information detection means) 1 provided in association with each tire is provided. The drive control device improves the travelability (motion characteristics) of the vehicle, and the front and rear torque distribution rate can be known by communication such as CAN (Control Area Network) if it is of an electronic control type. . Moreover, even if it is a mechanical type, if its characteristics are understood, it can be predicted to some extent from the running state of the vehicle. For example, if the front and rear torque distribution is almost determined by the engine torque, the torque distribution can be estimated by obtaining the engine torque.

  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 is connected to an initialization button 3 that can be operated by a driver and a GPS device 4 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, 4a 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 estimation apparatus 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. A GPS speedometer to be obtained; a dynamic load radius calculating means for obtaining a dynamic load radius of each tire from the wheel speed and the vehicle speed; a slip ratio calculating means for obtaining a slip ratio of each tire using the dynamic load radius; Tire load ratio calculating means for calculating the total driving force obtained from the axle shaft, the distribution before and after the driving force, and the load ratio of other tires with respect to a reference tire using the slip ratio, and vehicle mass calculating means for determining the mass of the vehicle And at the time of initialization, the longitudinal force is zero using the driving stiffness, vehicle speed and wheel speed obtained from the driving force and slip ratio of each wheel. Tire sensitivity calculation that calculates the dynamic load radius of each wheel and calculates the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the dynamic load radius, the wheel load of the tire, and the initial internal pressure of the tire And tire wheel load calculation means for calculating the wheel load of each tire from the relational expression of the driving force, slip ratio and driving stiffness of each wheel and the vehicle mass obtained in the step of obtaining the vehicle mass. Yes. The tire wheel load estimation program functions the control unit 2 as wheel speed calculation means, dynamic load radius calculation means, slip ratio calculation means, vehicle mass calculation means, tire sensitivity calculation means, and tire wheel load calculation means. Let

  The tire dynamic load radius (DLR) of the traveling vehicle can be calculated by V = DLR × ω from the relationship between the absolute speed (V) of the vehicle and the rotational angular velocity (ω) of the tire.

  In the present embodiment, the slip ratio (slp) is calculated from the tire dynamic load radius (DLR) of each wheel obtained from the vehicle speed (V) calculated from the GPS and the rotation speed (ω) of the tire. Driving stiffness (driving force at the unit slip ratio) (D) is calculated from the slip ratio (slp) and the driving force (FX) of each wheel, and the wheel load of each wheel is calculated from these.

More specifically, (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 (1).
Rotational angular velocity (ω) = 2π × Freq (Hz) / N (pieces) (1)
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 (DLR) is calculated by DLR = V / ω.
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 effective data, and thus, by excluding changes in the tire dynamic load radius due to other factors from the tire wheel load estimation data, Can be estimated.

  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, from the obtained dynamic load radius (DLR) of each tire and the dynamic load radius (DLR ₀ ) when the total driving force (FX ALL) of the vehicle is zero, according to the following equation (2): The slip ratio (slp) is calculated.
slp = (DLR ₀ −DLR) / DLR ₀ (2)

(5) Moreover, if the total axle shaft torque (T) of the vehicle can be obtained, the total driving force can be calculated from the tire load radius (R) by the following equation (3).
FX ALL = T / R (3)

(6) On the other hand, the driving stiffness (D) is a proportional constant of the driving force with respect to the slip ratio, and can be expressed as FX = D × slp.
Here, the driving stiffness is related to the ground contact shape of the tire. If the ground contact area of the tire is S and the longitudinal rigidity per unit area is G, it can be approximated by D = G × S.
Furthermore, since the contact area S is proportional to the tire load (FZ) and the tire internal pressure (IP), if the proportionality constant is p, it can be expressed as S = p × FZ / IP.

From the above, the driving force of each wheel is 4 when subscripts 1, 2, 3, and 4 are FL (left front wheel), FR (right front wheel), RL (left rear wheel), and RR (right rear wheel), respectively. In the case of a wheel drive vehicle, if the driving force front / rear distribution (AWDP) = front shaft driving force / total driving force is known,
FX1 = AWDP × FX ALL / 2 = pG (FZ1 / IP1) slp1 (4)
FX2 = AWDP × FX ALL / 2 = pG (FZ2 / IP2) slp2 (5)
FX3 = (1-AWDP) × FX ALL / 2 = pG (FZ3 / IP3) slp3 (6)
FX4 = (1-AWDP) × FX ALL / 2 = pG (FZ4 / IP4) slp4 (7)
It can be expressed as.
As described above, the driving force front-rear distribution (AWDP) can be known by communication such as CAN if an electronically controlled drive control device is provided.

When FL (left front wheel) is a reference wheel, the load ratio of FR (right front wheel), RL (left rear wheel) and RR (right rear wheel) with respect to the FL (left front wheel) is calculated based on equations (4) to (7). Can be expressed by the following formulas (8) to (10).
FZ2 / FZ1 = (IP2 / IP1) (slp1 / slp2) (8)
FZ3 / FZ1 = {(1-AWDP) / AWDP} (IP3 / IP1) (slp1 / slp
3) ... (9)
FZ4 / FZ1 = {(1-AWDP) / AWDP} (IP4 / IP1) (slp1 / slp
4) ... (10)
Therefore, by performing initialization at the normal internal pressure where the tire internal pressure is known, each wheel load ratio at the time of initialization can be obtained by the equations (8) to (10).

(7) Further, the total mass (estimated mass) of the vehicle is calculated using the acceleration, speed, and tilt angle of the vehicle. That is, the vehicle mass m is calculated from the following equation (11) using the vehicle axle shaft torque that is CAN information, the speed calculated from the GPS, the acceleration calculated therefrom, and the inclination angle of the slope. Can do.
m (α + gsin (θ)) + AV ² = T / R (11)
Here, T is the total axle shaft torque, R is the tire load radius, g is the gravitational acceleration, V is the vehicle speed, A is the aerodynamic resistance, and α is the vehicle acceleration.
θ is the inclination angle of the slope on which the vehicle is traveling, and θ is expressed by θ = arctan (Vz / Vxy), where Vxy (= V) is the plane speed of the vehicle and Vz is the 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.

(8) On the other hand, the dynamic load radius (DLR) of each wheel is such that the tire load sensitivity is b, the internal pressure sensitivity is c, and the constant is d.
DLR1 = bFZ1 + cIP1 + d
DLR2 = bFZ2 + cIP2 + d
DLR3 = bFZ3 + cIP3 + d
DLR4 = bFZ4 + cIP4 + d
It can be expressed as. “Load sensitivity” refers to the amount of change in the dynamic load radius relative to the load, and “internal pressure sensitivity” refers to the amount of change in the dynamic load radius relative to the internal pressure.

(9) Since the internal pressure sensitivity c and the load sensitivity b are in a proportional relationship (c = eb), at least one tire, preferably about three tires with different sizes are measured, and the proportionality constant (e ), The dynamic load radius of each wheel can be expressed by the following equations (12) to (15).
DLR1 = b (FZ1 + eIP1) + d (12)
DLR2 = b (FZ2 + eIP2) + d (13)
DLR3 = b (FZ3 + eIP3) + d (14)
DLR4 = b (FZ4 + eIP4) + d (15)

(10) Here, the dynamic load radius (DLR) expressed using the load sensitivity and the internal pressure sensitivity in the formulas (12) to (15) is when the longitudinal force is not generated in the tire (between the road surface and the tire). The dynamic load radius value when no slip occurs), and the dynamic load radius value is expressed by the following equation (16) among the slip ratio (slp), the vehicle speed (V), and the wheel speed (ω). Satisfied.
slp = 1-V / (ωDLR) (16)
Also, since FX = D × slp,
FX = D × {1-V / (ωDLR)} (17)
Is established. The DLR when the longitudinal force is zero can be calculated by regressing FX with V / ω.

  At the time of initialization of the detection device, the relational expressions (12) to (15) of the dynamic load radius (DLR), the wheel load (FZ) and the internal pressure (IP) were obtained by the expressions (8) to (11). By substituting each wheel load and each wheel internal pressure (initial time = normal internal pressure), load sensitivity (b), constant (d), and proportionality constant (e) can be calculated. Further, from c = eb The internal pressure sensitivity (c) can be calculated.

(11) During normal driving (non-initialization), since the internal pressure of each wheel is not known, it is expressed as IP = (DLR-d-bFZ) / c from equations (12) to (15), Substituting into equations (8) to (10), equations (18) to (20) are obtained, respectively.
FZ2 / FZ1 = {(DLR2-d-bFZ2) / (DLR1-d-bFZ1)} × (sl
p1 / slp2) (18)
FZ3 / FZ1 = {(1-AWDP) / AWDP} × {(DLR3-d-bFZ3) / (D
LR1-d-bFZ1)} × (slp1 / slp3) (19)
FZ4 / FZ1 = {(1-AWDP) / AWDP} × {(DLR4-d-bFZ4) / (D
LR1-d-bFZ1)} × (slp1 / slp4) (20)
(12) Moreover, vehicle mass (m) is calculated | required from Formula (11). This vehicle mass (m) is
mg = FZ1 + FZ2 + FZ3 + FZ4 (21)
Therefore, FZ1, FZ3, and FZ4 are expressed by FZ1 in equations (18) to (20), respectively, and are substituted into equation (21) and solved by FZ1 to obtain FZ1. . Next, FZ2, FZ3, and FZ4 can be obtained from the equations (18) to (20), respectively. Thus, the wheel load of each tire can be calculated (estimated).

Next, examples of the estimation 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 personal computer (PC) as serial data. The vehicle speed information, the rotational speed information, the front / rear driving force distribution information, and the vehicle axle shaft torque information are synchronized as digital data every 50 msec. I was able to import to PC. 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]
We measured the dynamic load radius on the table using a flat belt, measured the load on the tire and the decrease in the dynamic load radius due to reduced pressure, and investigated the relationship between the load sensitivity of the tire and the internal pressure sensitivity.

  For the three types of tires shown in Table 1, load sensitivity (change in dynamic load radius per 1 kN change in load (mm)) and internal pressure sensitivity (change in dynamic load radius per 1 kPa change in internal pressure (mm)) Examined. The load applied to the tire was set at three levels of 2.5 kN, 3.5 kN, and 4.5 kN, and the tire load was changed at four levels (150 kPa, 180 kPa, 210 kPa, and 240 kPa), and the dynamic load radius was measured.

  The load sensitivity and the internal pressure sensitivity of the three types of tires are as shown in Table 1 and FIG. 3. From this, it was found that the relationship between the two sensitivities is internal pressure sensitivity = −0.0369 × load sensitivity. Therefore, e = −0.0369 is preset in the estimation device as the proportionality constant (e) between the internal pressure sensitivity and the load sensitivity.

[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.
The conditions for initialization and evaluation were as follows. The front-rear distribution of driving force was 45 (front): 55 (rear).
Initialization One person was boarded at the standard internal pressure (front wheel: 230 kPa, rear wheel: 210 kPa).
At the time of evaluation: Evaluation was performed for the case of one person riding and a case where a load was loaded (vehicle loading). The load was 290 kg in total including the front seat (90 kg), the rear seat (100 kg), and the trunk (100 kg). Then, the internal pressures of the front wheels and the rear wheels were changed as shown in Table 3 for evaluation.

[When initializing]
From the dynamic load radius of each tire and the dynamic load radius (R ₀ ) when the total driving force (FX ALL) of the vehicle is zero, the slip ratio (slp) was calculated according to the equation (2).
Then, at the time of initialization, since the tire internal pressure is a reference value (front wheel: 230 kPa, rear wheel: 210 kPa), FL (left front wheel) is obtained using the obtained slip ratio according to the above formulas (8) to (10). ) (FR front right wheel), RL (left rear wheel) and RR (right rear wheel) load ratio (wheel load ratio) is calculated, and the vehicle mass (estimated mass) obtained from the equation (11) is used. Thus, the wheel load (estimated wheel load) of each wheel was calculated.

Further, the dynamic load radius (DLR) when the longitudinal force is zero is obtained from the equation (17), and the dynamic load radius, the wheel load and the internal pressure are substituted into the equations (12) to (15). The load sensitivity (b) and the constant (d) were obtained, and the internal pressure sensitivity (c) was calculated from the preset internal pressure sensitivity and the proportional constant (e) of the load sensitivity.
The results are shown in Table 2.

[At the time of evaluation]
The dynamic load radius when the slip ratio and the longitudinal force were zero was calculated in the same manner as at the time of initialization. Moreover, the wheel load (estimated wheel load) of each wheel was calculated using the wheel load ratio obtained by the equations (18) to (20) and the vehicle mass obtained by the equation (11). The results are shown in Table 3. Table 3 shows the difference between the actual wheel load and the estimated wheel load.

  As can be seen from Table 3, the wheel load error (difference between the estimated wheel load and the actual wheel load) of each wheel estimated (calculated) by the estimation method of the present invention is about 20 to 30 kg, that is, the error {(estimated Wheel load−actual wheel load) × 100 / actual wheel load} is about ± several percent, and the accuracy has no practical problem.

  In the above embodiment, a four-wheel drive vehicle has been described as an example. However, the present invention is not limited to this and can be applied to a two-wheel drive vehicle. That is, in the case of a two-wheel drive vehicle, the driving force acts on only two wheels, but the braking force (when the brake is depressed) acts on the four wheels. Therefore, if the braking force can be known from, for example, the braking force of each wheel, the above-described calculation can be performed by using “braking force” instead of “driving force” in the above-described calculation.

It is a block diagram which shows one Embodiment of the estimation apparatus of this invention. It is a block diagram which shows the electric constitution of the estimation apparatus shown by FIG. It is a figure which shows the relationship between load sensitivity and internal pressure sensitivity.

Explanation of symbols

1 Wheel speed detection means 2 Control unit 2a Interface 2b CPU
2c ROM
2d RAM
3 Initialization button 4 GPS device 4a GPS antenna

Claims (7)

A method for estimating a wheel load of a tire mounted on a vehicle based on a rotation speed of a wheel mounted on the vehicle,
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;
The step of obtaining the slip ratio of each tire using this dynamic load radius,
Determining the mass of the vehicle;
At the time of initialization, using the driving stiffness and the vehicle speed and the wheel speed obtained from the driving force and slip ratio of each wheel, the dynamic load radius of each wheel when the longitudinal force is zero is obtained, and this dynamic load radius, Calculating the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the wheel load of the tire and the initial internal pressure of the tire;
A wheel load of the tire, comprising: a relational expression of a driving force of each wheel, a slip ratio and a driving stiffness, and a step of calculating a wheel load of each tire from the vehicle mass obtained in the step of obtaining the vehicle mass. Estimation method. In the step of calculating the internal pressure sensitivity and / or load sensitivity at the time of initialization, when the internal pressure sensitivity and / or load sensitivity is zero, the dynamic load radius of the tire when the longitudinal force is zero is DLR, the wheel load is FZ, the internal pressure Is IP, load sensitivity is b, internal pressure sensitivity is c, and constant is d,
DLR = bFZ + cIP + d
The tire wheel load estimation method according to claim 1, which is calculated based on an expression represented by: In the step of determining the vehicle mass, it is assumed that the vehicle is traveling on a road surface having an inclination angle θ, the vehicle mass is m, the vehicle speed is V, the vehicle acceleration is α, the total axle shaft torque of the vehicle is T, and a tire. M (α + gsin (θ)) + AV ² = T / R where R is the load radius, θ is the slope of the road surface, A is the aerodynamic resistance, and g is the acceleration of gravity.
The wheel load estimation method for a tire according to claim 1, wherein the vehicle mass is obtained by: In the step of obtaining the dynamic load radius of each wheel when the longitudinal force is zero, the dynamic load radius is DLR, the driving force is FX, the driving stiffness obtained from the slip ratio is D, the vehicle speed is V, and the wheel speed is ω. And when
FX = D × {1-V / (ωDLR)}
The method for estimating a wheel load of a tire according to claim 1, wherein a dynamic load radius is obtained by: An apparatus for estimating a wheel load of a tire mounted on a vehicle based on a rotation speed of a wheel mounted on the vehicle,
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;
Slip rate calculating means for determining the slip rate of each tire using the dynamic load radius;
Vehicle mass calculating means for determining the mass of the vehicle;
At the time of initialization, using the driving stiffness and the vehicle speed and the wheel speed obtained from the driving force and slip ratio of each wheel, the dynamic load radius of each wheel when the longitudinal force is zero is obtained, and this dynamic load radius, Tire sensitivity calculation means for calculating the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the wheel load of the tire and the initial internal pressure of the tire;
Tire wheel load calculating means for calculating the wheel load of each tire from the relational expression of the driving force, slip ratio and driving stiffness of each wheel and the vehicle mass obtained in the step of determining the vehicle mass. Tire wheel load estimation device.   A wheel speed calculating means for calculating a wheel speed from wheel rotation information of each tire of the vehicle, a computer for estimating a wheel load of the tire mounted on the vehicle based on a rotation speed of the wheel mounted on the vehicle, Dynamic load radius calculating means for determining the dynamic load radius of each tire from the wheel speed and vehicle speed, slip ratio calculating means for determining the slip ratio of each tire using this dynamic load radius, vehicle mass calculating means for determining the mass of the vehicle, At the time of initialization, using the driving stiffness and the vehicle speed and the wheel speed obtained from the driving force and slip ratio of each wheel, the dynamic load radius of each wheel when the longitudinal force is zero is obtained, and this dynamic load radius, Tire sensitivity calculation means for calculating the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the wheel load of the tire and the initial internal pressure of the tire, driving of each wheel , A relational expression of slip ratio and driving stiffness, and a tire wheel load calculating means for calculating a wheel load of each tire from a vehicle mass obtained in the step of obtaining the vehicle mass. program. A method for estimating a wheel load of a tire mounted on a vehicle based on a rotation speed of a wheel mounted on the vehicle,
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;
The step of obtaining the slip ratio of each tire using this dynamic load radius,
Determining the mass of the vehicle;
At the time of initialization, using the driving stiffness, vehicle speed and wheel speed obtained from the braking force and slip ratio of each wheel, the dynamic load radius of each wheel when the longitudinal force is zero is obtained, and this dynamic load radius, Calculating the internal pressure sensitivity and / or load sensitivity of each tire based on the relationship between the wheel load of the tire and the initial internal pressure of the tire;
A wheel load of a tire, comprising: a relational expression of braking force, slip ratio and driving stiffness of each wheel; and a step of calculating a wheel load of each tire from the vehicle mass obtained in the step of obtaining the vehicle mass. Estimation method.

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