JPH11180118A - Method for sensing change in tire air pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensing accuracy by calculating the measured wheel speed difference and comparing that to the wheel speed difference data for each wheel and determining the steering wheel position, calculating the difference between the wheel speed difference data at the steering wheel position and the measured wheel speed difference of each wheel, and sensing the wheel in which there is a change in air pressure. SOLUTION: The lowest wheel speed is gathered at an electronic control unit 5 from the wheel speed sensed by wheel speed sensors 51-54, which are located at each wheel 1-4. A measurement of wheel speed difference is then done for each wheel based on the lowest wheel speed and each wheel speed. Next, each measured wheel speed difference and the measurement values for each wheel at the steering wheel position previously recorded are averaged and compared to the wheel speed difference data. The revolutions and air pressure change are then determined and the air pressure change parameters are then calculated. Next, the mean value of the air pressure change parameters is measured and a check is done to see whether the mean value exceeds the threshold value. If the mean value exceeds the threshold value, the air pressure of the tire is determined to have changed and a warning lamp lights.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a change in tire air pressure.

[0002]

2. Description of the Related Art Conventionally, there are the following methods for detecting a change in tire pressure of each wheel of a vehicle. A method in which a pressure sensor is embedded in the tire itself and the change in air pressure is directly measured by the pressure sensor. A method in which a steering angle sensor is used to check the straight running state of a vehicle to measure each wheel speed, and various wheel speed differences are subjected to various numerical conversions and filters to detect a wheel with a low air pressure. When measuring changes in tire pressure by these methods,
In the above method, it is technically difficult to embed the pressure sensor directly in a wheel or a tire. In the above method, an accurate wheel speed difference cannot be measured unless the vehicle is in a straight running state, so that a steering angle sensor for detecting the straight running state of the vehicle is required.

[0003]

[Problems to be solved by the invention]

<A> The present invention provides a method for detecting a change in tire air pressure of a vehicle. <B> The present invention also provides a method for identifying a tire with reduced air pressure from among wheels of a vehicle. <C> There is provided a method of detecting a linear state and detecting a change in tire air pressure without requiring any steering angle sensor.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a wheel speed of each wheel of a vehicle is determined, a minimum wheel speed among the wheel speeds of the wheels is determined, and a difference between the minimum wheel speed and each wheel speed is determined at a minimum. Divide by the wheel speed to obtain the measured wheel speed difference, compare the measured wheel speed difference with the wheel speed difference data of each wheel at the previously measured steering angle position, and determine the steering angle position of the vehicle based on the comparison. And
A method for detecting a change in tire air pressure, characterized by judging a difference between wheel speed difference data at the determined steering angle position and an actually measured wheel speed difference of each wheel, and detecting a wheel having an air pressure change.

Further, the present invention is characterized in that in the above-described method for detecting a change in tire air pressure, a measured wheel speed difference is measured a predetermined number of times or for a predetermined time, averaged for each wheel, and compared with wheel speed difference data of each wheel. This is a method for detecting a change in tire air pressure. Further, according to the present invention, in the method for detecting a change in tire air pressure described above, only the actually measured wheel speed difference of each wheel when the steering angle is substantially in a straight-ahead state is compared with the wheel speed difference data at the steering angle position. A tire pressure change change detecting method characterized by detecting a change in tire air pressure by comparing with the wheel speed difference data.

According to the present invention, in any one of the tire pressure change detecting methods described above, the measured wheel speed difference of each wheel is obtained when the vehicle is not in an acceleration state or in a deceleration state at a constant speed. This is a change detection method. Further, in any of the tire pressure change detecting methods described above, the present invention compares the measured wheel speed difference of each wheel with the wheel speed difference data of each wheel at a steering angle position measured in advance to determine turning and reduce air pressure. A tire pressure change detection method, comprising: determining a tire pressure change signal from a determination and obtaining an air pressure change signal; and notifying a change in tire air pressure when an average value of a predetermined time or a predetermined number of times of the air pressure change signal exceeds a threshold value. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire pressure change detecting method according to the present invention obtains wheel speeds using wheel speed sensors 51 to 54 provided on wheels 1 to 4 of a vehicle as shown in FIG. The electronic control unit 5 obtains the minimum wheel speed from each wheel speed, and based on the minimum wheel speed and each wheel speed, obtains the measured wheel speed difference of each wheel. The wheel speed difference data (hereinafter referred to as wheel speed difference data) obtained by averaging the measured values of each wheel at the steering angle position input to the vehicle, and comparing the measured wheel speed difference of each wheel and the wheel speed difference data of each wheel From the deviation, the tire whose air pressure has changed is identified.

Hereinafter, an example of a method of detecting a change in tire air pressure will be described in detail with reference to a flowchart shown in FIG.

From the input value Vi of the wheel speed of each wheel of the vehicle,
The minimum wheel speed VL is calculated (S1). Subsequently, an actually measured wheel speed difference ΔV of each wheel speed Vi is obtained from the minimum wheel speed VL of the vehicle (S2). This actually measured wheel speed difference ΔV is ΔV = (V
i-VL) / VL. The measured wheel speed difference ΔV of each wheel speed Vi obtained from the minimum wheel speed VL is averaged, so that a predetermined number of samples are measured every short time in which the change in vehicle behavior is small (S3). The short time here is, for example, 0.7 seconds, and 100 samples of the measured wheel speed difference ΔV for each short time are measured for each of the four wheels. At this time, if 100 samples of the measured wheel speed difference ΔV have not been measured, the measurement is started again from the beginning.

Subsequently, it is checked whether the brake lamp switch is off during the measurement of the measured wheel speed difference ΔV (S4). Thus, it is confirmed that the values of the wheel speed Vi and the minimum wheel speed VL have changed due to the deceleration of the vehicle due to the brake operation during the measurement of the measured wheel speed difference ΔV. Therefore, if the brake lamp switch is not turned off, it is possible to decelerate the vehicle due to the brake operation during the measurement of the measured wheel speed difference ΔV, so that correct averaging cannot be achieved. Start the measurement again from the beginning.

If the brake lamp switch is turned off during the measurement of the measured wheel speed difference ΔV, it is checked whether the fluctuation width of the estimated vehicle speed Vref is within a predetermined range (S5). The fluctuation range of the estimated vehicle speed Vref at this time means that the vehicle is in an acceleration state in which the driving wheels slip significantly, the difference in wheel speed between the non-driving wheels due to the slipping of the driving wheels increases, and This is a width for confirming that the speed difference ΔV does not exceed an allowable range. That is, that the fluctuation range of the estimated vehicle speed Vref exceeds a predetermined range (permissible range) indicates an increase in the slip ratio (acceleration state), and a comparison between the measured wheel speed difference ΔV at the steering angle position described later and the average value data. Refers to the inability to Therefore, when the estimated vehicle speed Vref exceeds the allowable range, the measured wheel speed difference ΔV is cleared and the measurement is started again from the beginning.

If the vehicle speed is almost constant (not accelerating) from the above-described measurement of the fluctuation width of the estimated vehicle speed Vref, 100 samples of the measured wheel speed difference ΔV are averaged (S6). The averaged measured wheel speed difference ΔV is 1
The 00 sample is compared with the wheel speed difference data (FIG. 3) of each wheel at the steering angle position that has been determined in advance by the measurement, and the turning determination and the air pressure change determination are performed to obtain the air pressure change parameter Pi (S6). In the wheel speed difference data of each wheel at the steering angle position used at this time (FIG. 3), the surrounding portion allows a measurement error in the numerical values near the straight line of the front wheel speed and rear wheel speed data wheel speed differences ΔV1 to ΔV4. The air pressure change parameter Pi is obtained from 100 samples of the measured wheel speed difference ΔV obtained by averaging the measured values corresponding to the surrounding portion.

The wheel speed difference data of each wheel at the steering angle position shown in FIG. 3 is an example of data of an FF vehicle. The encircled portion described in this data shows a portion where the vehicle is substantially in a straight line. The fact that the measured wheel speed difference ΔV of each wheel speed of the vehicle is within this range indicates that the vehicle is in a straight running state. This data range is a portion including the starting point at which the change due to steering appears in the measured wheel speed difference ΔV of each wheel, and is a portion where the change of the measured wheel speed difference ΔV of the wheel is converged. It can be said that this is a portion where it is easy to detect an abnormality when comparing with the wheel speed difference data. Therefore, in this embodiment, the tire pressure change is detected by extracting only the measured wheel speed difference ΔV of the wheel speed in the data range where the vehicle is in a substantially straight line state. That is, the turning determination at this time means whether or not the steering angle of the vehicle is in a straight running state (an almost straight running state with an error within a predetermined width, indicating an encircled portion in FIG. 3) at an assumed value. Indicates a check (S7).

At this time, the steering angle is checked by comparing the measured wheel speed difference ΔV of each wheel with the wheel speed difference data at the steering angle position. For example, the measured wheel speeds of three or more wheels among the four wheels are checked. If ΔV coincides with the same steering angle on the wheel speed difference data, the steering angle of the vehicle is specified at that position. If it is determined that the steering angle of the vehicle is not in the straight running state at the assumed value, the measured wheel speed difference ΔV is cleared and the measurement is started again from the beginning. The determination of the air pressure drop is made when the average of 100 samples of the measured wheel speed difference ΔV is substantially in a straight-ahead state (encircled portion in FIG. 3 data) as compared with the wheel speed difference data of each wheel at the steering angle (FIG. 3). The average value of 100 samples of the measured wheel speed difference ΔV of each wheel is compared with the wheel speed difference data of each wheel at the steering angle position to check for a change in air pressure (S7). The measured wheel speed difference ΔV that clears the turning judgment and the air pressure change judgment is output as an air pressure change parameter Pi.

Subsequently, it is checked whether or not the air pressure change parameter Pi has been measured over a certain number of samples (S).
8). As the number of samples of the air pressure change parameter Pi, for example, it is conceivable to measure 10 samples.
If the air pressure change parameter Pi has not been measured more than the number of samples, the measured wheel speed difference ΔV is cleared and the measurement is started again from the beginning. If the air pressure change parameter Pi can be measured more than the number of samples, an average value of the air pressure change parameter Pi is measured, and it is checked whether or not the average value exceeds a threshold value (S9). At this time, if the average value of the air pressure change parameter Pi does not exceed the threshold value, it is determined that there is no change in the tire air pressure, the measured wheel speed difference ΔV is cleared, and the measurement is started again from the beginning. If the average value of the air pressure change parameter Pi exceeds the threshold value, a warning lamp is turned on to notify the driver of the change in the tire air pressure because the tire air pressure has changed.

[0016]

Embodiment 2 Hereinafter, another embodiment of the tire pressure change detecting method described in Embodiment 1 of the present invention will be described.

In the first embodiment of the present invention, the estimated vehicle speed Vref fluctuation range is set to determine that the vehicle is not in an acceleration state that causes the driving wheels to slip significantly during the method of detecting the tire pressure change. There is a step (S5) of checking that the value is within a predetermined range (the accelerator opening of the vehicle is constant). In this check (S5), it is sufficient to determine that the driving wheels of the vehicle slip significantly, that is, not to open the accelerator, so that the fluctuation range of the estimated vehicle speed Vref is within a predetermined range. Instead of the check (S5), it is conceivable to check whether the accelerator is off.

[0018]

Embodiment 3 Hereinafter, another embodiment of the tire pressure change detecting method described in Embodiments 1 and 2 of the present invention will be described.

In the first and second embodiments of the invention,
When the measured wheel speed difference ΔV obtained by averaging the measured values is compared with the wheel speed difference data of each wheel at a known steering angle position, a turning judgment is performed, and the vehicle is in a straight running state at an assumed steering angle. Discloses a method of detecting a change in tire air pressure by comparing the measured wheel speed difference ΔV with the averaged measured wheel speed difference ΔV. On the other hand, in the third embodiment of the present invention, in the wheel speed difference data of each wheel at the steering angle position, the data of the specific area during turning and the data of each wheel of the vehicle obtained during the actual traveling are used. By comparing the measured wheel speed difference ΔV with the actual wheel speed difference, it is possible to detect a wheel whose tire pressure has changed, regardless of the direction in which the vehicle is not traveling straight and is steered in any direction. In this case as well, it is necessary to set an upper limit of how many wheels match or are close to existing data in the measured wheel speed difference ΔV of each wheel.

[0020]

As described above, the present invention has the following effects. <A> The present invention can detect a change in tire pressure of a vehicle. <B> The present invention makes it possible to specify a tire with reduced air pressure from among the wheels of a vehicle. <C> A change in tire air pressure can be detected without a steering angle sensor.

[Brief description of the drawings]

FIG. 1 is a layout diagram of a wheel speed sensor and an electronic control unit.

FIG. 2 is a flowchart of tire pressure change detection.

FIG. 3 is a data table of a deviation ΔV at a steering angle position.

[Explanation of symbols]

 1-4 Wheel 5 Electronic control device 51-54 Wheel speed sensor

Claims (5)

[Claims] Determining a wheel speed of each wheel of a vehicle; determining a minimum wheel speed among the wheel speeds of each wheel; dividing a difference between the minimum wheel speed and each wheel speed by a minimum wheel speed;
Obtain the measured wheel speed difference, compare the measured wheel speed difference with the wheel speed difference data of each wheel at the pre-measured steering angle position, determine the steering angle position of the vehicle based on the comparison, and find out A method for detecting a change in tire air pressure, comprising determining a deviation between wheel speed difference data at a steering angle position and an actually measured wheel speed difference of each wheel, and detecting a wheel having an air pressure change. 2. The method according to claim 1, wherein the measured wheel speed difference is measured a predetermined number of times or for a predetermined time, averaged for each wheel, and compared with the wheel speed difference data of each wheel. A method for detecting a change in tire air pressure, which is a feature. 3. The tire pressure change detecting method according to claim 1, wherein each of the wheels is measured when the steering angle is substantially in a straight-ahead state by collating with the wheel speed difference data at the steering angle position. A method for detecting a change in tire air pressure, comprising detecting a change in tire air pressure by comparing only a wheel speed difference with wheel speed difference data of each wheel. 4. The tire pressure change detecting method according to claim 1, wherein the measured wheel speed difference of each wheel is obtained when the vehicle is not in an acceleration state or a deceleration state and is in a constant velocity state. A method for detecting a change in tire air pressure. 5. The tire pressure change detecting method according to claim 1, wherein the measured wheel speed difference of each wheel is obtained by comparing the wheel speed difference data of each wheel at a steering angle position measured in advance. By comparing and determining a pneumatic pressure change signal from the turning judgment and the pneumatic pressure decrease judgment, when the average value of the pneumatic pressure change signal for a certain period of time or a certain number of times exceeds a threshold value, a change in tire air pressure is notified. , Tire pressure change detection method.