JPH06286428A - Method to detect depressurization of tire furnished to vehicle - Google Patents

Abstract

PURPOSE:To avoid wrong signals and realize detection of depressurization of tires virtually throughout the whole vehicle travel time. CONSTITUTION:This is a method to detect the depressurization of tires furnished to a vehicle by making comparision between radiuses of rotation of tire by mutually comparing angle speed signals from wheel speed sensors fitted to respective wheels individually. An error value (DEL') is calculated, and a correction factor (LAT) is determined, and a corrected error value (DEL) is calculated, and when it is detected that the magnitude of the corrected error value (DEL) is within the range from 0.05 to 0.5, it is indicated that a tire has been depressurized.

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 decompression of a tire mounted on a vehicle. The method of the present invention is suitable for passenger cars and trucks.

[0002]

Prior art applications such as French Patent Publication No. 2568519 and European Patent Publication No. 291217, for example, typically require 48 to 96 pulses per revolution of each wheel. It proposes the use of wheel speed signals emanating from the wheels of the vehicle, such as signals from anti-lock braking systems that are multi-pulse. Prior art systems compare speed-calculated signals in various ways, for example cornering, braking, acceleration that causes a change in speed signal that is greater than the change in speed signal caused by a 0.4 bar decompression of the tire. It aims to overcome errors caused by vehicle factors such as load non-uniformity and changes.

French Patent Publication No. 2568519 discloses:
It is disclosed to avoid this type of error by effectively monitoring the cornering of the vehicle by monitoring the speed of the diagonally opposite pair of wheels over a long period of time or traveling a distance. However, as a result, the operation of the device is very slow and the depressurization of the vehicle cannot be detected until it has traveled many kilometers.

EP-A-291217 uses a fixed four wheel speed signal, a fixed threshold value above which the detection system is suppressed to avoid false signals due to cornering and acceleration. To improve this situation by calculating the lateral and longitudinal accelerations of the vehicle. However, suppressing the detection in this way means that the system can detect a puncture only for a part of the total traveling time of the vehicle. Actually, how much time the system can detect a puncture with respect to the total traveling time of the vehicle depends on the road surface condition and the driving method of the vehicle until then.

The real difficulty with these types of systems is that each vehicle, apart from the lateral acceleration of the vehicle which, when cornering, increases the deflection of the outer pair of wheels compared to the inner pair of wheels, It has different characteristics due to the position of the center of gravity and the type of suspension, which are different in that it causes the outer pair of tires to deflect with respect to the inner pair of tires when cornering.

The vehicle characteristics cause different deflections for each tire. When braking a vehicle, a similar problem arises due to the vehicle characteristics in the deflection of the front wheel pair with respect to the rear wheel pair. Similar problems arise when the vehicle is accelerating due to the vehicle characteristics in the deflection of the rear wheel pair with respect to the front wheel pair.

Prior application by the applicant (UK patent application N
No. 9214951.7, filing date July 11, 1992) discloses a method for detecting the pressure reduction of a tire mounted on a vehicle. In this method, the wheel radii of the tires are compared by comparing the angular velocity signals from the wheel velocity sensors attached to each wheel. This method calculates an error value (DEL ') from four wheel speed signals, determines a correction factor (LAT), calculates a corrected error value (DEL) and then calculates a corrected error value (DEL). ) Is in the range of 0.05 to 0.5, the decompression alarm device is activated to indicate that at least one tire has decompressed.

Here, DEL = DEL'-LAT * A, where A is a constant related to the vehicle. The decompression alarm is attached to the vehicle.

Although the conventional method can detect the tire pressure reduction in most situations, it is extremely difficult to reach the corners such as sudden cornering on a road surface which is wet, slippery, and has no braking force. Under the condition, a false signal is generated.

It is an object of the present invention to provide a method for detecting a tire pressure drop in a vehicle. The method of the present invention allows for the above variations, avoids false signals, and detects decompression for substantially the entire vehicle travel time.

[0011]

According to the present invention, by comparing the angular velocity signals from the wheel velocity sensors attached to each wheel one by one, the turning radii of the tires are compared to reduce the pressure of the tires mounted on the vehicle. A method of detecting is provided. The method of the present invention calculates an error value (DEL '), determines a correction factor (LAT), calculates a corrected error value (DEL), and calculates the magnitude of the corrected error value (DEL). Is detected to be in the range of 0.05 to 0.5, the decompression warning device in the vehicle is activated to indicate that at least one tire has decompressed.

Here, DEL '= [(C1 + C4) / 2- (C2 + C3) /
2] × 100 / [(C1 + C2 + C3 + C4) / 4], where C1, C2, C3, and C4 are the angular velocities of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively.

If the sign of (LAT × A) obtained from the correction factor (LAT) and the constant (A) related to the vehicle is opposite to the sign of the error value (DEL '), the corrected error is detected. Value (DEL) = (DEL '); Correction factor (LA
T) and the constant (A) related to the vehicle (LAT)
The sign of × A) is the same as the sign of the error value (DEL ′), and the absolute value of (LAT × A) is the error value (DEL).
′) Is greater than the absolute value, the corrected error value (DEL) = 0; otherwise, the corrected error value (DEL) = (DEL ′) − LAT × A; is there.

The magnitude of the corrected error value DEL is 0.1.
It is preferred that the decompression alarm be activated when in the range from 0.3 to 0.3.

The constant A relating to the vehicle is -2.0 x 10
It preferably has a value in the range of ^-7 to +2.0 x 10 ^-7 .

The correction factor LAT is derived from the four angular velocity values C1, C2, C3 and C4 as the first, second, third and fourth values.
The respective determinants (MC1, MC2, MC3, MC4) are calculated, the four determinants are summed, and the total value is multiplied by a centralizing constant K to obtain a central determinant (MPSD), The first is the selection of the correction factor LAT.
Or LAT = 2 when the second determinant (MC1 or MC2) is greater than the central determinant (MPSD)
LAT = when the third or fourth determinant (MC3 or MC4) is larger than the central determinant (MPSD) by × (C3-C4) × (C1 + C2 + C3 + C4)
2 × (C1-C2) × (C1 + C2 + C3 + C4),
All of the above determinants (MC1, MC2, MC3, MC
4) is not larger than the central determinant (MPSD), LAT = (C1 + C3-C2-C4) × (C1 +
C2 + C3 + C4) is preferably selected.

Here, MC1 = C1 MC2 = C2 / [(C2 + C4) / (C1 + C3)] MC3 = C3 / [(C3 + C4) / (C1 + C2)] MC4 = C4 / [[(C2 + C4) / (C1 + C3)]
X [(C3 + C4) / (C1 + C2)]].

The centralized constant K used for calculating the central determinant (MPSD) is preferably in the range of 0.250125 to 0.250625, and its value is preferably 0.25025.

A particular tire that has been deflated can be detected by calculating the decompression warning factors IMC1, IMC2, IMC3 and IMC4 respectively for each wheel and selecting the one with the highest value.

The decompression warning factor is calculated as follows.

IMC1 = C1 The first determinant MC1 is the central determinant (MPSD)
IMC2 = C2 / [((C4 / C3) / 2) +0.5] IMC3 = C3 / [((C4 / C2) / 2) +0.5] IMC4 = C4 / [[(( C4 / C3) / 2) +0.5]
× [((C4 / C2) / 2) +0.5]]; the second determinant MC2 is the central determinant (MPSD)
IMC2 = C2 / [((C4 / C3) / 2) +0.5] IMC3 = C3 / [((C3 / C1) / 2) +0.5] IMC4 = C4 / [[(( C4 / C3) / 2) +0.5]
× [((C3 / C1) / 2) +0.5]]; the third determinant MC3 is the central determinant (MPSD)
IMC2 = C2 / [((C2 / C1) / 2) +0.5] IMC3 = C3 / [((C4 / C2) / 2) +0.5] IMC4 = C4 / [[(( C2 / C1) / 2) +0.5]
× [((C4 / C2) / 2) +0.5]]; the fourth determinant MC4 is the central determinant (MPSD)
IMC2 = C2 / [((C2 / C1) / 2) +0.5] IMC3 = C3 / [((C3 / C1) / 2) +0.5] IMC4 = C4 / [[(( C2 / C1) / 2) +0.5]
× [((C3 / C1) / 2) +0.5]]; All of the determinants (MC1, MC2, MC3, MC4)
Is not larger than the central determinant (MPSD), IMC2 = C2 / [(((C2 + C4) / (C1 + C
3)) / 2) +0.5] IMC3 = C3 / [(((C3 + C4) / (C1 + C
2)) / 2) +0.5] IMC4 = C4 / [[((C3 + C4) / (C1 + C
2) / 2) +0.5] × [((C2 + C4) / (C1 + C
3) / 2) +0.5]] The present invention actually compares the angular velocities of the wheels, which is the comparison of the time it takes for each wheel to make one complete revolution, or the multipulse wheel speed. It should be understood that this is done by comparing the digital signals for the signal generator.

An initialization process is performed to allow different size tires from different manufacturers. This step monitors the signal under normal driving conditions and makes it possible to calculate a constant for allowing the variation for each wheel.

[0023]

In the present invention, the error value (DEL ') is calculated from each angular velocity of each wheel, the correction factor (LAT) is determined, and the error value (DEL') is corrected to correct the error value (DEL '). DEL). Then, when this value is within a predetermined range, a warning of depressurization is issued.

[0024]

Further aspects of the invention will become apparent from the following description, which is given by way of illustration only.

The device shown in FIG. 1 has four wheels 1,
3 is a decompression warning device for a vehicle having 2, 3, and 4.
Wheels 1 and 2 are a left front wheel and a right front wheel, respectively. Wheels 3,
Reference numerals 4 are a left rear wheel and a right rear wheel, respectively. Each wheel has a toothed wheel device that is designed to fit itself and that produces a digital signal, which device is a lateral magnetic pickup.
etic pick-up) and is suitable for an electronic type anti-skid system generally known as an ABS braking system. In this example, each pickup is further connected to a decompression warning detection system that uses the same digital signal as the ABS system.

The electrical signals from each of the four wheels are routed via cable 5 to a separate input (i) of the central processing unit 10.
nput) Carried to 6, 7, 8, and 9. Four separate indicator lights 12, 13, 14, 15 are provided, one for each wheel 1, 2, 3, 4. These indicator lights are most conveniently mounted on the vehicle dashboard.

The central processing unit 10 is basically a microprocessor. The microprocessor monitors the four signals and compares them to determine if an outward signal should be sent to activate an indicator light warning of tire pressure reduction. In the case of a vehicle already equipped with an ABS system, the microprocessor 10 may be the same as the microprocessor of the ABS system, but a separate microprocessor may be installed instead.

The total values of the digital pulse signals from the respective wheels 1, 2, 3, 4 for 5 seconds are C1, respectively.
C2, C3, and C4. The central processing unit 10 calculates these frequency values in the manner described below to determine whether to issue a depressurization warning signal to one of the warning lights 12, 13, 14, 15.

The operating sequence used for this calculation is shown in FIG.

The first function of the method according to the invention is to calculate the error value DEL 'from the actual wheel speed values C1 to C4.

Here, DEL '= [(C1 + C4) / 2- (C2 + C3) /
2] × 100 / [(C1 + C2 + C3 + C4) / 4].

However, the actual wheel speed values are distorted by vehicle factors such as cornering, braking, acceleration or load non-uniformity. These vehicle factors have a greater impact than those caused by tire pressure reduction. Therefore,
It is necessary to correct the calculated error value to remove the vehicle factor.

In order to correct the error value DEL ', the central determinant M of the determinants MC1 to MC4 for each wheel
The correction factor LAT is calculated according to the magnitude compared to the PSD. The central determinant MPSD is equal to the sum of the four determinants MC1-MC4 multiplied by the centralization constant K. As the value of the centralization constant K, 0.25025 is selected in this embodiment. After that, the value of the correction factor LAT is calculated as follows.

If any one of the four determinants MC1 to MC4 is larger than the central determinant MPSD If MC1 or MC2 is larger than MPSD LAT = 2 × (C3-C4) × (C1 + C2 + C3 + C
4) When MC3 or MC4 is larger than MPSD LAT = 2 × (C1-C2) × (C1 + C2 + C3 + C
4) In other cases LAT = (C1 + C3-C2-C4) × (C1 + C2 +
C3 + C4) This sequence is shown in FIG.

The calculated error value (DEL ') is further modified by a vehicle-related constant A to eliminate the vehicle factor. This constant A allows for vehicle factors, particularly those related to lateral tilt, such as road surface and suspension dimensions and characteristics. The value of this constant A for a particular vehicle is determined by experiment. Examples of established values for the constant A are +1.3 x 10 ^-7 for the Jaguar XJ6, -0.6 x 10 ^-7 for the Peugeot 405 and -2.0 x 10 ^-7 for the Audi 100. and so on.

The purpose of using the constant A associated with the vehicle is to
Appropriate modification of DEL 'with respect to vehicle characteristics, and the value is reflected in vehicle performance under an average driving condition on a normal road surface. However, in extreme driving situations such as high-speed running, sudden cornering, and running on a road surface that is slippery and does not exert braking force, the value of the constant A becomes unsuitable, and DEL 'cannot be properly corrected. Therefore, it is first necessary to test whether it is appropriate to use the constant A to modify DEL '.

The first stage of these tests is to modify factor L
It is obtained from AT and a constant A related to the vehicle (LAT x
Comparing the sign of A) with the sign of the calculated error value (DEL '). If the signs of these two values are different, the error value (DEL ') is not subject to any modification and the modified error value (DEL) is equal to (DEL').

When the code of (LAT × A) and the code of (DEL ') are the same, the second stage test is performed. In the second stage, the absolute values of (LAT × A) and (DEL ') are compared. If the value of (LAT × A) is larger than the value of (DEL '), the corrected error value (DE
The value of L) is set to zero. The value of (LAT x A) is (DE
If the value of (DEL ') is smaller than the value of (L') or both values are equal, the value of (DEL ') is completely corrected,
L) = (DEL ′) − (LAT × A).

This sequence is shown in FIG.

Once the corrected error value DEL has been calculated, the central processing unit 10 determines if the value of DEL is in the range 0.05 to 0.5. When the value of DEL is within this range, one of the tires is decompressed.

When the value of DEL is less than 0.05, it is a statistically small fluctuation of the count from each wheel.
When the value of DEL is larger than 0.5, it means that an abnormality such as wheel spin or lock has occurred, which is larger than the influence of the flat tire.

The central processing unit 10 makes the corrected error value D
Recognizing that the EL is in the range of 0.05 to 0.5, the method of the present invention proceeds to the next step of determining which tire is deflated. Otherwise, the system continues to monitor wheel speed.

In order to determine which tire was decompressed, the central processing unit 10 calculates decompression warning factors IMC1 to IMC4 for each wheel. These factors are calculated as follows.

IMC1 = C1 The first determinant MC1 is the central determinant (MPSD)
IMC2 = C2 / [((C4 / C3) / 2) +0.5] IMC3 = C3 / [((C4 / C2) / 2) +0.5] IMC4 = C4 / [[(( C4 / C3) / 2) +0.5]
× [((C4 / C2) / 2) +0.5]]; the second determinant MC2 is the central determinant (MPSD)
IMC2 = C2 / [((C4 / C3) / 2) +0.5] IMC3 = C3 / [((C3 / C1) / 2) +0.5] IMC4 = C4 / [[(( C4 / C3) / 2) +0.5]
× [((C3 / C1) / 2) +0.5]]; the third determinant MC3 is the central determinant (MPSD)
IMC2 = C2 / [((C2 / C1) / 2) +0.5] IMC3 = C3 / [((C4 / C2) / 2) +0.5] IMC4 = C4 / [[(( C2 / C1) / 2) +0.5]
× [((C4 / C2) / 2) +0.5]]; the fourth determinant MC4 is the central determinant (MPSD)
IMC2 = C2 / [((C2 / C1) / 2) +0.5] IMC3 = C3 / [((C3 / C1) / 2) +0.5] IMC4 = C4 / [[(( C2 / C1) / 2) +0.5]
× [((C3 / C1) / 2) +0.5]]; All of the determinants (MC1, MC2, MC3, MC4)
Is not larger than the central determinant (MPSD), IMC2 = C2 / [(((C2 + C4) / (C1 + C
3)) / 2) +0.5] IMC3 = C3 / [(((C3 + C4) / (C1 + C
2)) / 2) +0.5] IMC4 = C4 / [[((C3 + C4) / (C1 + C
2) / 2) +0.5] × [((C2 + C4) / (C1 + C
3) / 2) +0.5]] In this way, when the decompression warning factor for each of the four wheels is obtained, the central processing unit 10 compares them and determines which wheel has the largest factor. To do. A signal is then sent and the indicator light corresponding to that wheel is activated to alert the driver that the tire is deflated. In the preferred arrangement, a warning signal is sent only when all three decompression indicator factors calculated from consecutive wheel speed data indicate that a particular tire is decompressing.

In the above embodiments, typically, a multi-toothere generates 48 or 96 pulses per wheel revolution.
d) Although the method of the present invention has been described using single data from a wheel system, the method of the present invention can be used with other wheel speed sensing systems as well. For example, using a simple system that uses one single pulse per wheel revolution to calculate the time interval required for one wheel revolution. In this case, it is necessary to multiply the wheel speed by a constant factor to obtain the required form of data.

[0046]

According to the method of the present invention, erroneous signals can be avoided and the decompression can be detected for substantially the entire vehicle travel time.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a decompression warning device for a vehicle with four wheels.

FIG. 2 is a schematic diagram showing the sequence of calculations used to determine if a deflated tire is present and which tire was deflated.

FIG. 3 is a schematic diagram showing a calculation sequence used when determining a correction factor LAT.

[Explanation of symbols]

 1 left front wheel 2 right front wheel 3 left rear wheel 4 right rear wheel 5 cable 10 central processing unit 12, 13, 14, 15 indicator light

Claims (10)

[Claims] 1. A method for detecting decompression of a tire mounted on a vehicle by comparing the turning radii of tires by comparing angular velocity signals from wheel speed sensors attached to each wheel one by one. Of the left front wheel, right front wheel, left rear wheel, and right rear wheel of C1, C2, C3, and C respectively.
4, the formula DEL ′ = [(C1 + C4) / 2− (C2
+ C3) / 2] × 100 / [(C1 + C2 + C3 + C4)
/ 4], the error value (DEL ′) is calculated, the correction factor (LAT) is determined, and the sign of (LAT × A) obtained from the correction factor (LAT) and the constant (A) related to the vehicle is an error. If the sign of the value (DEL ') is opposite, the corrected error value (DEL) = (DEL'); obtained from the correction factor (LAT) and the constant (A) related to the vehicle (LAT x A). Is the same as the sign of the error value (DEL ′) and the absolute value of (LAT × A) is larger than the absolute value of the error value (DEL ′), the corrected error value ( DEL) = 0; otherwise, the corrected error value (DEL) = (DEL ′) − LAT ×
A; A corrected error value (DEL) is calculated so as to be A; and when it is detected that the magnitude of the corrected error value (DEL) is in the range of 0.05 to 0.5, Activating the tire warning indicator of (4) to indicate that at least one tire has been depressurized. 2. The correction factor (LAT) is selected from the four angular velocity values C1, C2, C3, C4 by the formula: MC1 = C1, MC2 = C2 / [(C2 + C4) / (C1 + C3)], MC3. = C3 / [(C3 + C4) / (C1 + C2)], MC4 = C4 / [[(C2 + C4) / (C1 + C3)]
× [(C3 + C4) / (C1 + C2)]], the first, second, third, and fourth determinants (MC1,
MC2, MC3, MC4) respectively, summing the four determinants and multiplying the sum by a centralization constant (K) to obtain the central determinant (MPSD), and then the first or second If the determinant of (MC1 or MC2) is larger than the central determinant (MPSD), LAT =
2 × (C3-C4) × (C1 + C2 + C3 + C4),
The third or fourth determinant (MC3 or MC4)
Is larger than the central determinant (MPSD), L
AT = 2 × (C1-C2) × (C1 + C2 + C3 + C
4) and all of the above determinants (MC1, MC2, MC
3, MC4) is not larger than the central determinant (MPSD), LAT = (C1 + C3-C2-C4) ×
The method according to claim 1, wherein the method is performed so that (C1 + C2 + C3 + C4). 3. A method according to claim 2, wherein the value of the centralization factor (K) is in the range 0.250125 to 0.250625. 4. A method according to claim 2, wherein the value of the centralization factor (K) is 0.25025. 5. The formula: IMC1 = C1 where the first determinant MC1 is the central determinant (MPSD).
Greater than, IMC2 = C2 / [((C4 / C3) / 2) +0.5], IMC3 = C3 / [((C4 / C2) / 2) +0.5], IMC4 = C4 / [[ ((C4 / C3) / 2) +0.5]
× [((C4 / C2) / 2) +0.5]], the second determinant MC2 is the central determinant (MPSD)
Greater than, IMC2 = C2 / [((C4 / C3) / 2) +0.5], IMC3 = C3 / [((C3 / C1) / 2) +0.5], IMC4 = C4 / [[ ((C4 / C3) / 2) +0.5]
× [((C3 / C1) / 2) +0.5]], the third determinant MC3 is the central determinant (MPSD)
Greater than, IMC2 = C2 / [((C2 / C1) / 2) +0.5], IMC3 = C3 / [((C4 / C2) / 2) +0.5], IMC4 = C4 / [[ ((C2 / C1) / 2) +0.5]
× [((C4 / C2) / 2) +0.5]], the fourth determinant MC4 is the central determinant (MPSD)
Greater than, IMC2 = C2 / [((C2 / C1) / 2) +0.5], IMC3 = C3 / [((C3 / C1) / 2) +0.5], IMC4 = C4 / [[ ((C2 / C1) / 2) +0.5]
× [((C3 / C1) / 2) +0.5]], all of the determinants (MC1, MC2, MC3, MC4)
Is not larger than the central determinant (MPSD), IMC2 = C2 / [(((C2 + C4) / (C1 + C
3)) / 2) +0.5], IMC3 = C3 / [(((C3 + C4) / (C1 + C
2)) / 2) +0.5], IMC4 = C4 / [[((C3 + C4) / (C1 + C
2) / 2) +0.5] × [((C2 + C4) / (C1 + C
3) / 2) +0.5]], the decompression warning factor (IMC1, IMC2, IMC3,
5. A method according to claim 2, 3 or 4, wherein IMC4) is calculated for each wheel respectively and the wheel with the highest decompression warning factor is warned for decompression. 6. The tire warning indicator is activated when it is detected that the magnitude of the corrected error value (DEL) is in the range of 0.1 to 0.3.
The method according to 3, 4, or 5. 7. The value of a constant (A) related to the vehicle is −
2.0 × claim 1 in 10 ^-7 to +2.0 × 10 ^-7 in the range of,
The method according to 2, 3, 4, 5 or 6. 8. The value of a constant (A) associated with the vehicle is −
The method according to claim 1, 2, 3, 4, 5, or 6, which is 2.0 × 10 ⁻⁷ . 9. The value of a constant (A) related to the vehicle is −
The method of claim 1, 2, 3, 4, 5, or 6, which is 0.6 × 10 ^-7 . 10. The value of the constant (A) relating to the vehicle is + 1.3 × 10 ⁻⁷ , 1, 2, 3, 4, 5 or 6.
The method described.