JPH092031A - Tire inflation pressure estimation device - Google Patents

Abstract

PURPOSE: To surely estimate the inflation pressure of a tire regardless of wheel speed by estimating the inflation pressure of the tire based on the dynamic load radius of the tire in the case of high wheel speed. CONSTITUTION: A first tire pressure estimation block 18 obtains the spring constant of tires from the vibration content of wheel speed signals supplied from wheel speed sensors 12FL-12RR, and estimates the tire pressure based on them. A second tire pressure estimation block 20 obtains the dynamic load radius of the tire from the wheel speed signal, and estimates the tire pressure. A discrimination block 22 discriminates whether the vehicle speed is high or not. A selection block 24 lets the first tire pressure estimation block 18 to estimate the tire pressure in the case of not high speed running, and lets the second tire pressure estimation block 20 to estimate the tire pressure in the case of high speed running. Hereby, the tire pressure can be surely estimated regardless of the wheel speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire air pressure estimating device for estimating a tire air pressure of an automobile or the like, and more particularly to a tire air pressure estimating device for estimating a tire air pressure based on a wheel speed signal.

[0002]

2. Description of the Related Art There is a constant relationship between a tire air pressure and a tire spring constant, and a constant relationship between a tire spring constant and a tire resonance frequency is utilized to obtain a wheel. Tire frequency estimation apparatus for obtaining the tire resonance frequency in the up-down direction or the front-rear direction based on the vibration component of the speed signal and estimating the tire air pressure from this has been proposed in various configurations from the past, and one example thereof is JP-A-5
No. 133831.

According to such a tire air pressure estimating device, a sensor for detecting the pressure inside the tire is provided on a rotating wheel, and a means for wirelessly transmitting a signal indicating the detection result from the sensor is not required. The air pressure can be estimated.

[0004]

However, if the vehicle speed is 1
When the wheel speed exceeds a predetermined value as in the case of 20 km / h or more, it becomes difficult to distinguish the tire vibration phenomenon.
Depending on the so-called FFT type conventional tire air pressure estimating device that estimates the tire air pressure based on the tire resonance frequency, or the so-called disturbance observer type conventional tire air pressure estimating device that estimates the tire air pressure based on the detection result of the disturbance torque, There is a problem that the tire pressure cannot be estimated.

The present invention has been made in view of the above-mentioned problems in the conventional tire air pressure estimating device, and the main problem of the present invention is based on the dynamic load radius of the tire when the wheel speed is high. By estimating the tire air pressure, it is possible to reliably estimate the tire air pressure regardless of the wheel speed.

[0006]

In the tire air pressure estimating device for estimating the tire air pressure on the basis of the wheel speed signal, the main problem described above is the tire pressure sensor based on the vibration component of the wheel speed signal. And a second tire air pressure estimating means for estimating the tire air pressure based on the obtained spring constant and a tire dynamic pressure radius based on the wheel speed signal for estimating the tire dynamic pressure. And a means for determining whether or not the vehicle speed is a high speed traveling at a predetermined value or more, and when the vehicle is not traveling at a high speed, the tire pressure is estimated by the first tire pressure estimating means, and when the vehicle is traveling at a high speed. And a selecting means for estimating the tire air pressure by the second tire air pressure estimating means.

According to the present invention, in order to effectively achieve the above-mentioned main problems, in the structure of claim 1, it is determined that the second tire air pressure estimating means is operating at a high speed. A tire based on the ratio R / Ro of the dynamic load radius R of the current tire to the dynamic load radius Ro of the immediately preceding tire and the tire air pressure Po estimated by the first tire air pressure estimating means when not running at high speed. Is configured to calculate the air pressure of.

[0008]

According to the above-mentioned structure of claim 1, when the vehicle is not traveling at a high speed, the first tire air pressure estimating means obtains the spring constant of the tire from the vibration component of the wheel speed signal, and the air pressure of the tire is estimated based on the spring constant. When the vehicle is traveling at high speed, the tire dynamic pressure radius is obtained from the wheel speed signal by the second tire pressure estimating means, and the tire air pressure is estimated based on this, so the first tire pressure estimation is conducted when not traveling at high speed. The tire pressure is accurately estimated by the means, and the tire pressure is surely estimated by the second tire pressure estimating means when the vehicle is traveling at high speed.

According to the second aspect of the present invention, the second tire air pressure estimating means sets the dynamic load radius R of the current tire with respect to the dynamic load radius Ro of the tire immediately before it is determined that the vehicle is traveling at high speed. Since the tire air pressure is calculated based on the ratio R / Ro and the tire air pressure Po estimated by the first tire air pressure estimating means when the vehicle is not traveling at a high speed, for example, the present tire with respect to the dynamic load radius of the standard tire is calculated. In comparison with the case where the tire air pressure is calculated based on the ratio of the dynamic load radius and the standard tire air pressure, the tire air pressure during high speed traveling is calculated accurately.

[0010]

According to a preferred embodiment of the present invention, in the structure of claim 1, the second tire pressure estimating means is a ratio of the dynamic load radius of the present tire to the dynamic load radius of the standard tire. The tire pressure is configured to be calculated based on the standard tire pressure. With this configuration, it is not necessary to store and update the tire air pressure Po estimated by the first tire air pressure estimating means when the vehicle is not traveling at a high speed.

In any of the structures of claims 1 and 2, the dynamic load radius of the tire is obtained in order to estimate the tire air pressure, and the ratio of the dynamic load radius of the tire is obtained. For example, since the tire air pressure can be estimated, the "dynamic load radius of the tire" is the dynamic load radius in the narrow sense,
That is, the concept includes not only the dynamic load radius itself but also a value corresponding to the dynamic load radius in a narrow sense.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 1 is a schematic configuration diagram (A) and a block diagram (B) showing a first embodiment of a tire air pressure estimating device according to the present invention.

In FIG. 1A, the wheel speed Vwi (i = FL, FR, RL, RR) of the wheels corresponding to the left front wheel 10FL, the right front wheel 10FR, the left rear wheel 10RL, and the right rear wheel 10RR, respectively. Wheel speed sensors 12FL, 12FR, 12RL,
12RR is provided. A signal indicating the wheel speed Vwi is input to the tire air pressure estimation device 14, and the tire air pressure estimation device 14 estimates the tire air pressure Pi (i = FL, FR, RL, RR) of each wheel based on the wheel speed Vwi as described later. Calculate,
By outputting a control signal to the alarm device 16 as needed, an occupant of the vehicle is alerted.

As shown in FIG. 1 (B), the tire air pressure estimating device 14 obtains the tire spring constant from the vibration component of the wheel speed signal supplied from the wheel speed sensors 12FL to 12RR, and based on this, the tire air pressure is calculated. The first tire air pressure estimation block 18 for estimating Pi and the tire dynamic load radius is calculated from the wheel speed signal, and the tire air pressure Pi is calculated based on this.
The second tire pressure estimation block 20 for estimating the tire, the determination block 22 for determining whether or not the vehicle speed is at a high speed traveling at a predetermined value or more, and the tire pressure estimation 18 for the tire when the high speed traveling is not performed. And a selection block 24 for estimating the tire air pressure by the second tire air pressure estimation block 20 when the vehicle is traveling at a high speed.

The tire pressure estimation device 14 is actually a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM).
And an input / output port device, which may be connected to each other by a bidirectional common bus, and this is the same in the second embodiment described later.

The tire air pressure estimating device 14 of the first embodiment calculates the tire air pressure Pi of each wheel by estimation according to the routine shown in FIG. The routine shown in FIG. 2 is repeatedly executed every predetermined time.

First, in step 10, a signal indicating the wheel speed Vwi is read, in step 20, the average wheel speed Va is calculated as the average value of the wheel speeds Vwi of the four wheels, and in step 30. Then, it is determined whether or not the average wheel speed Va is, for example, a reference value Vac (a positive constant) corresponding to the vehicle speed of 120 km / h, that is, whether or not the vehicle is traveling at high speed, and a positive determination is made. Step 50 when done
If the determination is negative, the process proceeds to step 40.

In step 40, the spring constant of each tire is obtained from the vibration component of the wheel speed signal of each wheel by the disturbance observer method or the FFT method, and the air pressure Pi of each tire is estimated and calculated based on this. At 50, Pni (i = FL, FR, RL, RR) is used as a standard constant tire pressure, and the tire pressure Pi of each tire is calculated by estimation according to the following equation 1.

## EQU1 ## Pi = (Va / Vwi) * Pni

Generally, in the estimation of tire air pressure by the disturbance observer method, the estimated disturbance is obtained from the wheel speed signal by the disturbance observer, the spring constant of the tire is obtained from the estimated disturbance, and the tire air pressure is estimated based on this. Further, in the tire pressure estimation by the FFT method, the signal indicating the vibration component of the wheel speed is extracted from the wheel speed signal and the frequency analysis is performed on the signal to calculate the resonance frequency of the tire. The tire spring constant is calculated based on the resonance frequency to calculate the tire air pressure. The procedure for estimating the tire air pressure by the disturbance observer method and the FFT method is well known in the art, and Since various types have been proposed, detailed description thereof will be omitted.

In step 60, the tire air pressure P
It is determined whether i is less than the reference value Pci (a positive constant). If a negative determination is made, the process returns to step 10. If an affirmative determination is made, the alarm device 16 is activated in step 70. A control signal to cause the vehicle occupant is output, and an occupant of the vehicle is alerted that the tire pressure is abnormal. Incidentally, step 60 is executed for the air pressure Pi of each tire, and step 70 is executed when a positive determination is made for at least one air pressure.

Thus, in this embodiment, when the vehicle is not traveling at a high speed, a negative determination is made in step 30, and in step 40, the tire air pressure Pi of each wheel is based on the wheel speed Vwi as a disturbance observer system or It is accurately estimated by being calculated by the FFT method. When the vehicle is traveling at a high speed, a positive determination is made in step 30, and in step 50, the ratio Va / Vwi equal to the ratio of the dynamic load radius of the tire and the standard Based on the tire air pressure Pni, the tire air pressure Pi of each wheel is reliably estimated according to the equation (1).

FIG. 3 is a schematic configuration diagram (A) and a block diagram (B) showing a second embodiment of the tire air pressure estimating apparatus according to the present invention, and FIG. 4 shows a tire air pressure calculation routine of the second embodiment. It is a flowchart. Incidentally, in FIG. 3, the portions corresponding to the portions shown in FIG. 1 are denoted by the same reference numerals as those given in FIG. 1, and in FIG.
Steps corresponding to the steps shown in FIG. 2 have the same step numbers as the step numbers given in FIG.

In this embodiment, the first tire pressure estimation 18 determines the tire spring constant from the vibration component of the wheel speed signal when the vehicle is not traveling at high speed, and estimates the tire pressure Pi based on the spring constant. The tire dynamic load radius Roi is calculated from the wheel speed signal, and the second tire pressure estimation block 20 calculates the tire dynamic load radius Ri from the wheel speed signal when the vehicle is running at high speed, and is also running at high speed. The ratio Ri / Roi of the dynamic load radius Ri of the present tire to the dynamic load radius Roi of the tire immediately before being determined as and the tire air pressure Poi estimated by the first tire air pressure estimation block when not traveling at high speed. Based on this, the tire air pressure Pi is calculated.

In step 40 of the tire air pressure calculation routine of this embodiment, the air pressure Pi of each tire is estimated and calculated by the disturbance observer method or the FFT method, and the air pressure Pi is stored in a storage means such as a RAM. And step 42 executed after step 40
In this case, the dynamic load radius Roi of the tire is calculated according to the following equation 2 based on the wheel speed Vwi and stored in the storage means.

[Equation 2] Roi = Vwi / 2π

If a positive determination is made in step 30, that is, it is determined that the vehicle speed is high, step 4 is executed.
In step 4, the tire air pressure Pi calculated and stored in step 40 described above is rewritten to Poi, and in step 46, the current tire dynamic load radius Ri is calculated according to the same formula as in the above equation 2. In step 50, the air pressure Pi of each tire is calculated by estimation according to the following equation (3).

## EQU3 ## Pi = (Ri / Roi) * Poi

Therefore, in this embodiment, when the vehicle is not traveling at a high speed, the same step 3 as in the first embodiment is performed.
A negative determination is made at 0, and at step 40, the tire air pressure Pi of each wheel is accurately estimated based on the wheel speed Vwi by the disturbance observer method or the FFT method. If yes, an affirmative determination is made in step 30, the tire dynamic load radius ratio Ri / Roi in step 50, and the last tire air pressure calculated in step 40 when not running at high speed. Based on Poi, the tire air pressure Pi of each wheel is reliably estimated according to equation (3).

In the illustrated first and second embodiments, whether the vehicle speed is high is determined by determining in step 30 whether the average wheel speed Va of the four wheels is equal to or higher than the reference value Vac. The determination as to whether or not the vehicle is at a high vehicle speed may be made based on the vehicle speed detected by the vehicle speed sensor, for example.

The determination in step 30 is executed for each wheel speed, and corresponding to this, steps 30-70 are executed.
Each of the routines may be configured to be executed in time series in the order of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel.

In the illustrated first and second embodiments, steps 40 and 50 are selectively executed depending on whether or not the vehicle is traveling at high speed. Steps 40 and 50 are executed irrespective of whether the vehicle is running at high speed, the tire pressure is the air pressure calculated at Step 40 when not running at high speed, and the tire pressure calculated at Step 50 is running when running at high speed. May be configured.

In the second embodiment shown in the figure, the dynamic load radius of the tire is calculated in accordance with equation 2, but V is the vehicle speed and Ni is the rotation speed of each wheel, and V /
It may be calculated by (2πNi) or may be calculated by V / Ni as a value corresponding to the dynamic load radius.

Further, the relationship between the tire air pressure and the ratio of the tire dynamic load radius changes depending on the reference tire air pressure. Therefore, in order to estimate the tire air pressure more accurately, It is preferable that the expression 3 is changed to the following expression 4 and expression 5, respectively. In the equations 4 and 5, K1 and K2 are constants determined by Pni,
K3 and K4 are constants determined by Poi.

[0033]

[Equation 4] Pi = K1 * (Va / Vwi) + K2

## EQU5 ## Pi = K3 * (Ri / Roi) + K4

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments within the scope of the present invention. It will be apparent to those skilled in the art that

For example, in the illustrated first and second embodiments, in step 40, the tire air pressure Pi is calculated by the disturbance observer method or the FFT method. In this step, The calculation of the tire air pressure may be performed in any manner as long as the tire spring constant is obtained from the vibration component of the wheel speed signal and the tire air pressure is calculated based on this.

[0036]

As is apparent from the above description, according to the configuration of claim 1 of the present invention, the tire air pressure is accurately estimated by the first tire air pressure estimating means when the vehicle is not traveling at high speed, and the vehicle is traveling at high speed. When it is time, the tire pressure can be reliably estimated by the second tire pressure estimation means, and thus the tire pressure can be estimated regardless of the wheel speed.

According to the second aspect of the present invention, the second tire air pressure estimating means sets the current dynamic load radius R of the tire with respect to the dynamic load radius Ro of the tire immediately before it is determined that the vehicle is traveling at high speed. Since the tire air pressure is calculated based on the ratio R / Ro and the tire air pressure Po estimated by the first tire air pressure estimating means when the vehicle is not traveling at a high speed, for example, the present tire with respect to the dynamic load radius of the standard tire is calculated. In comparison with the case where the tire air pressure is calculated based on the ratio of the dynamic load radius and the standard tire air pressure, the tire air pressure during high speed traveling can be calculated accurately.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram (A) and a block diagram (B) showing a first embodiment of a tire air pressure estimating device according to the present invention.

FIG. 2 is a flowchart showing a tire air pressure calculation routine of the first embodiment.

FIG. 3 is a schematic configuration diagram (A) and a block diagram (B) showing a second embodiment of the tire air pressure estimating device according to the present invention.

FIG. 4 is a flowchart showing a tire air pressure calculation routine of a second embodiment.

[Explanation of symbols]

 12FL-12RR ... Wheel speed sensor 14 ... Tire pressure calculation device 16 ... Warning device 18 ... First tire pressure estimation block 20 ... Second tire pressure estimation block 22 ... Judgment block 24 ... Selection block

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Ohashi 1st Toyota-cho, Toyota-shi, Aichi Toyota Motor Corporation (72) Inventor Koji Umeno 1-share, 41st side road, Nagakute-cho, Aichi-gun, Aichi-gun Toyota Central Research Institute (72) Inventor Shunji Naito 1-1, Showa-cho, Kariya city, Aichi Nihondenso Co., Ltd.

Claims (2)

[Claims] 1. A tire air pressure estimating device for estimating a tire air pressure based on a wheel speed signal, wherein a tire spring constant is obtained from a vibration component of a wheel speed signal and the tire air pressure is estimated based on the spring constant. Air pressure estimating means, a second tire air pressure estimating means for estimating the tire air pressure based on the dynamic load radius of the tire obtained from the wheel speed signal,
A means for determining whether or not the vehicle speed is at a high speed traveling at a predetermined value or more, and the tire pressure is estimated by the first tire air pressure estimating means when the vehicle is not traveling at a high speed, and when the vehicle is traveling at a high speed, A tire air pressure estimating device, comprising: a selecting means for estimating a tire air pressure by a second tire air pressure estimating means. 2. The tire air pressure estimating device according to claim 1, wherein the second tire air pressure estimating means is the dynamic load radius Ro of the present tire immediately before the dynamic load radius Ro of the tire immediately before it is determined that the vehicle is traveling at a high speed. The tire air pressure is calculated based on the ratio R / Ro of the radius R and the tire air pressure Po estimated by the first tire air pressure estimating means when the vehicle is not traveling at a high speed. Tire pressure estimation device.