JP2007253943A - Tire air pressure reduction detection method and device and program for tire pressure reduction determination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire air pressure reduction detection method capable of shortening a time for obtaining an effective front/rear wheel ratio. <P>SOLUTION: The tire air pressure reduction detection method for detecting reduction of an internal pressure of the tire based on rotation information obtained from the tire attached to a vehicle includes a step for detecting the rotation information of the respective tires; a step for memorizing the rotation information of the respective tires; a step for calculating the front/rear wheel ratio obtained from the rotation information of the front two wheels of the vehicle and the rotation information of the rear two wheels; a step for calculating drive wheel torque of the vehicle; and a step for obtaining a value of the front/rear wheel ratio when the drive wheel torque is zero from a relationship of the front/rear wheel ratio and the drive wheel torque. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

2. Description of the Related Art Conventionally, there is a tire pressure drop detection device (DWS) that detects tire pressure reduction from rotation (wheel speed) information of a four-wheel tire mounted on a vehicle. This device uses the principle that when the tire is depressurized, the outer diameter (the dynamic load radius of the tire) is smaller than that of a normal pneumatic tire, so that the rotational angular velocity is increased compared to other normal tires. For example, in the method of detecting a decrease in internal pressure from the relative difference in the rotational angular velocity of the tire, as the determination value DEL,
DEL = {(F1 + F4) / 2- (F2 + F3) / 2} / {(F1 + F2
+ F3 + F4) / 4} × 100 (%)
(See Patent Document 1). Here, F1 to F4 are rotational angular velocities of the left front tire FL, the right front tire FR, the left rear tire RL, and the right rear tire RR, respectively.

By the way, since tires are manufactured with variations (initial differences) within the standard, the effective rolling radius of each tire (the value obtained by dividing the distance advanced by one rotation by 2π) is the same for all tires. Even the normal internal pressure is not necessarily the same. Therefore, the rotational angular velocity F _i of each tire will be varied, not a DEL = 0 at a normal internal pressure when calculating the DEL value as such, it may become false alarm.

  Therefore, a process (initialization) for obtaining a correction coefficient for correcting the manufacturing variation of each wheel is performed. Specifically, the following three coefficients are obtained.

F2 = fac1 × F1
F3 = fac3 × F1
F4 = fac3 × fac2 × F1
Here, fac1, fac2, and fac3 are correction coefficients obtained at normal internal pressure, fac1 is a correction coefficient for correcting a difference in effective rolling radius due to an initial difference between the left and right tires FL and FR, and fac2 is a rear wheel. The correction coefficient and fac3 for correcting the difference in effective rolling radius due to the initial difference between the left and right tires RL and RR and fac3 are the average of the front axle wheels ((FL + FR) / 2) and the average of the rear axle wheels ((RL + RR) / 2) Is a correction coefficient for correcting the difference in effective rolling radius due to the initial difference, and these correction coefficients fac1, fac2, and fac3 are obtained by a running test at normal internal pressure.

  Of the correction coefficients, fac3 is the front / rear wheel ratio, which is a value necessary for accurately obtaining the DEL value.

JP 63-305011 A

  The front / rear wheel ratio is obtained from the wheel speeds of the four wheels, and thus is affected by slips caused by driving in addition to tire manufacturing variations. Therefore, since it is difficult to obtain an effective front / rear wheel ratio while traveling on a flat road at a constant speed, it is preferable to obtain it only when the vehicle is in a slow deceleration state.

  However, depending on the driving conditions, “when the vehicle is in a slow deceleration state” may be very rare. Then, since it is almost impossible to acquire an effective front / rear wheel ratio, it takes a lot of time to acquire the front / rear wheel ratio necessary for determining the pressure reduction.

  In view of the circumstances described above, an object of the present invention is to provide a tire pressure drop detection method and apparatus, and a tire decompression determination program that can shorten the time for acquiring an effective front and rear wheel ratio.

  A method for detecting a decrease in tire air pressure according to the present invention is a method for detecting a decrease in internal pressure of a tire based on rotation information obtained from a tire mounted on a vehicle, the step of detecting rotation information of each tire, Storing the rotation information of each tire, calculating the front-rear wheel ratio obtained from the rotation information of the two front wheels and the rotation information of the two rear wheels of the vehicle, and calculating the driving wheel torque of the vehicle A method for detecting a decrease in tire air pressure, comprising: obtaining a value of a front / rear wheel ratio when the driving wheel torque is zero based on a relationship between the front / rear wheel ratio and the driving wheel torque. The step of calculating the ratio is calculated by the ratio of the average wheel speed of the two driving wheels and the average wheel speed of the two driven wheels, and the step of calculating the driving wheel torque without performing a gentle deceleration determination is (engine torque × Engine Calculated by the number of rolling) / (driving wheel rotational speed × driving wheel speed), the relationship between the drive wheel torque and the front and rear wheels ratio, characterized in that it is a regression line.

  The tire pressure drop detecting device of the present invention is a tire pressure drop detecting device for detecting a tire internal pressure drop based on rotation information obtained from a tire mounted on a vehicle, and detects the rotation information of each tire. Rotation information detection means, storage means for storing the rotation information of each tire, and front / rear wheel ratio calculation means for calculating a front / rear wheel ratio obtained from rotation information of two front wheels and rotation information of two rear wheels of the vehicle Torque calculating means for calculating the driving wheel torque of the vehicle; and zero calculating means for obtaining a value of the front and rear wheel ratio when the driving wheel torque is zero from the relationship between the front and rear wheel ratio and the driving wheel torque; And a means for calculating the front-rear wheel ratio is calculated by the ratio of the average wheel speed of the two driving wheels and the average wheel speed of the two driven wheels, and performs a gentle deceleration determination. Drive The means for calculating the wheel torque is calculated by (engine torque × engine speed) / (drive wheel speed × drive wheel number), and the relationship between the front and rear wheel ratio and the drive wheel torque is a regression line. And

  Further, the tire decompression determination program according to the present invention includes a computer for determining a decrease in tire air pressure, storage means for storing rotation information for each tire, rotation information for the two front wheels of the vehicle, and rotation for the two rear wheels. When the driving wheel torque is zero from the relationship between the front and rear wheel ratio calculating means for calculating the front and rear wheel ratio obtained from the information, the torque calculating means for calculating the driving wheel torque of the vehicle, and the front and rear wheel ratio and the driving wheel torque. A tire decompression determination program for functioning as zero calculating means for acquiring a front and rear wheel ratio value, wherein the means for calculating the front and rear wheel ratio includes an average wheel speed of two driving wheels and two driven wheels. A means for calculating the drive wheel torque without calculating a slow deceleration by calculating the ratio of the average wheel speed is calculated by (engine torque × engine speed) / (drive wheel speed × drive wheel number). The relationship between the wheel ratio and the drive wheel torque is a regression line.

  According to the present invention, the time for acquiring an effective front and rear wheel ratio can be shortened.

  Hereinafter, a tire pressure drop detecting method and apparatus and a tire decompression determination program according to the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the tire pressure drop detecting device according to one embodiment of the present invention determines whether or not the air pressures of the four tires FL, FR, RL and RR provided in the four-wheel vehicle are lowered. Is provided with normal rotation information detection means 1 provided in association with each tire.

  The rotation information detection means 1 generates power using rotation like a wheel speed sensor or dynamo that generates a rotation pulse using an electromagnetic pickup or the like and measures the wheel speed (rotation speed) from the number of pulses. An angular velocity sensor including one that measures the wheel speed from this voltage can be used. The output of the rotation information detecting means 1 is given to a control unit 2 which is a computer such as ABS. Connected to the control unit 2 are a liquid crystal display element for notifying a tire whose air pressure has dropped, a display 3 composed of a plasma display element or a CRT, and an initialization switch 4 that can be operated by a driver. .

  As shown in FIG. 2, the control unit 2 stores an I / O interface 2a required for signal exchange with an external device, a CPU 2b functioning 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.

The rotation information detection means 1 outputs a pulse signal (hereinafter referred to as wheel speed pulse) corresponding to the number of rotations of the tire. Further, the CPU 2b calculates the rotational angular velocity F _i of each tire at a predetermined sampling period ΔT (sec), for example, ΔT = 1 second, based on the wheel speed pulse output from the rotation information detecting means 1.

Here, since the tire is manufactured with variations (initial differences) within the standard, as described above, the corrected rotational angular velocity F1 _i is calculated in order to cancel the variations due to the initial differences. In particular,
F1 ₁ = F ₁
F1 ₂ = fac1 × F ₂
F1 ₃ = fac3 × F ₃
F1 ₄ = fac3 × fac2 × F ₄
It is corrected.

  Here, fac1, fac2, and fac3 are correction coefficients obtained at normal internal pressure according to the following equations, and fac1 is a correction for correcting the difference in effective rolling radius due to the initial difference between the front and left tires FL and FR. The coefficient, fac2, is a correction coefficient for correcting the difference in effective rolling radius due to the initial difference between the left and right tires RL, RR, and fac3 is the average of the front wheel ((FL + FR) / 2) and the average of the rear wheel ( (RL + RR) / 2) is a correction coefficient for correcting the difference in effective rolling radius due to the initial difference between (RL + RR) / 2). These correction coefficients fac1, fac2, and fac3 are obtained by initialization running at normal internal pressure, and are stored in the RAM 2d. Stored.

F2 = fac1 × F1
F3 = fac3 × F1
F4 = fac3 × fac2 × F1

  Of the correction factors, the front / rear wheel ratio (fac3) is estimated by predicting the front / rear wheel ratio value in a state in which the drive wheel torque is close to zero based on the relationship between the vehicle front / rear wheel ratio and the drive wheel torque. Thus, acquisition of an effective front / rear wheel ratio used for warning of a decrease in tire air pressure can be completed earlier.

  Therefore, in the present embodiment, the rotation information detecting means 1, the storage means for storing the rotation information of each tire, the front and rear obtained from the rotation information of the two front wheels and the rotation information of the two rear wheels of the vehicle. The front and rear wheel ratio calculating means for calculating the wheel ratio, the torque calculating means for calculating the driving wheel torque of the vehicle, and the front and rear wheels when the driving wheel torque is zero based on the relationship between the front and rear wheel ratio and the driving wheel torque. It is comprised from the zero calculating means which acquires the value of ratio.

  Further, the tire decompression determination program in the present embodiment obtains the control unit 2 from the storage means for storing the rotation information of each tire, the rotation information of the two front wheels of the vehicle, and the rotation information of the two rear wheels. A front / rear wheel ratio calculating means for calculating a front / rear wheel ratio, a torque calculating means for calculating a driving wheel torque of the vehicle, and a front / rear wheel when the driving wheel torque is zero based on a relationship between the front / rear wheel ratio and the driving wheel torque. It is made to function as a zero calculating means for acquiring the ratio value.

Each wheel speed (V1 _n , V2 _n , V3 _n , V4 _n ) of the four-wheel tire of the vehicle is obtained from wheel speed data at a certain point of each wheel tire of the vehicle obtained from a sensor such as an ABS sensor. V1 _n , V2 _n , V3 _n , and V4 _n are wheel speeds of the front left tire, the front right tire, the rear left tire, and the rear right tire, respectively. These wheel speed ratio (front and rear wheel ratio) S of the front and rear wheels and the average wheel speed Vf _n of the average wheel speed Vd _n and the driven wheel of the driving wheel in the case of front-wheel drive, by the following equation (1) It can be calculated.

_{S = Vd n / Vf n ···} (1)
Here, Vd _n is _{(V1 n + V2 n) /} 2, Vf n is _{(V3 n + V4 n) /} 2.

  The driving wheel torque can be derived from the engine torque and the rotational speed obtained from the engine control device. For example, the driving wheel torque T per driving wheel is expressed by the following equation (2).

T = (engine torque × engine speed) / (drive wheel speed × drive wheel number)
... (2)

  In this formula (2), (engine speed / drive wheel speed) is the gear ratio or shift position (L, 2, 3,. For example, you can find out which gear you are driving, and if you store the gear ratios, you can know (engine speed) / (drive wheel speed) only from the shift position) Can be calculated.

  The relationship between the front and rear wheel ratio S and the drive wheel torque T is, for example, a regression line when the vertical axis is the front and rear wheel ratio S and the horizontal axis is the drive wheel torque T. From this regression line The value of the front and rear wheel ratio when the driving wheel torque is zero is obtained.

  Therefore, in the procedure (flow chart) of the present embodiment, for example, as shown in FIG. 3, the driving wheel torque of the vehicle is calculated from the equation (2) (step S1). Next, after sampling the rotational angular velocities of the four wheels to determine whether or not to reject the rotational angular velocities, the front / rear wheel ratio is calculated from the equation (1) using the wheel speeds of the respective tires (step S2). As a method for determining the rejection, for example, there is a method of determining whether or not the road is a rough road and whether or not the vehicle is within a predetermined range of longitudinal acceleration, low speed and turning radius. Then, a regression line is obtained by performing regression analysis (least square method) on the data of the driving wheel torque and the front and rear wheel ratio (step S3). Next, a value of the front and rear wheel ratio when the driving wheel torque is zero is obtained from this regression line (step S4).

  Next, the present invention will be described based on examples, but the present invention is not limited to such examples.

Example An FF (front engine / front drive) vehicle equipped with tires of normal air pressure (2.2 × 10 ⁵ Pa) was prepared as a vehicle. The tire size is 185 / 70R14. Further, in the running test of the vehicle, the tire pressure drop detecting device programmed with the tire decompression determination in the above embodiment was mounted, and then the initialization was performed with the normal air pressure. Subsequently, the vehicle traveled on an urban highway at 60 to 80 km / h, and the front-rear wheel ratio was obtained by the procedure shown in FIG.

  In addition, the vehicle was equipped with a device that acquires the front-rear wheel ratio only when the vehicle is in a moderate deceleration state as in the prior art, and the same running test as in this example was also performed (comparative example). Acquisition of the front-rear wheel ratio in this comparative example was performed by a procedure for determining a rejection and determining whether or not the vehicle is in a moderate deceleration state.

  In this comparative example, as a procedure for acquiring the front-rear wheel ratio, it is determined whether or not the vehicle is in a moderate deceleration state, that is, whether or not -0.1 <front-rear acceleration <-0.05. Therefore, while traveling at a constant speed, this deceleration judgment was not met, and the acquisition time of the front and rear wheel ratio was as long as 1 hour 15 minutes. This acquisition time is determined by whether or not the valid data has reached a specified number.

  On the other hand, the acquisition time of the front-rear wheel ratio in this example was 17 minutes, which was less than that of the comparative example. This is because the value of the front and rear wheel ratio when the driving wheel torque is zero is obtained from the regression line without performing the deceleration determination.

It is a block diagram which shows one Embodiment of the tire pressure fall detection apparatus of this invention. FIG. 2 is a block diagram showing an electrical configuration of the tire pressure drop detecting device of FIG. 1. It is a flowchart which shows an example of the procedure for calculating | requiring the value of the front-rear wheel ratio of one embodiment of this invention.

Explanation of symbols

1 Rotation information detection means 2 Control unit 3 Display 4 Initialization switch

Claims (3)

A tire pressure drop detection method for detecting a drop in tire internal pressure based on rotation information obtained from a tire mounted on a vehicle, the step of detecting the rotation information of each tire, and storing the rotation information of each tire A step of calculating a front / rear wheel ratio obtained from rotation information of two front wheels and rotation information of two rear wheels of the vehicle, a step of calculating driving wheel torque of the vehicle, and the front / rear wheel ratio and driving A method for detecting a decrease in tire air pressure including a step of obtaining a value of a front and rear wheel ratio when the driving wheel torque is zero based on a relationship with a wheel torque, wherein the step of calculating the front and rear wheel ratio includes: The process of calculating the drive wheel torque without calculating the slow deceleration by calculating the ratio of the average wheel speed of the wheel and the average wheel speed of the two driven wheels is (engine torque × engine speed) / (drive wheel rotation). Number x number of drive wheels) The tire pressure drop detecting method characterized in that the relationship between the front and rear wheel ratio and the drive wheel torque is a regression line. A tire pressure drop detecting device for detecting a drop in tire internal pressure based on rotation information obtained from a tire mounted on a vehicle, the rotation information detecting means for detecting the rotation information of each tire, and the rotation information of each tire. Storage means for storing the vehicle, front / rear wheel ratio calculation means for calculating the front / rear wheel ratio obtained from the rotation information of the two front wheels of the vehicle and the rotation information of the two rear wheels, and torque for calculating the drive wheel torque of the vehicle A tire pressure drop detecting device comprising: a calculating means; and a zero calculating means for obtaining a value of a front and rear wheel ratio when the driving wheel torque is zero from a relationship between the front and rear wheel ratio and the driving wheel torque, The means for calculating the front-rear wheel ratio is calculated by the ratio of the average wheel speed of the two driving wheels to the average wheel speed of the two driven wheels, and the means for calculating the driving wheel torque without performing a gradual deceleration determination is ( Engine torque × engine speed) / (calculated by the drive wheel rotation speed × driving wheel speed), the relationship between the drive wheel torque and the front and rear wheels ratio, tire pressure drop detecting device, characterized in that the regression line. Before and after calculating the front-rear wheel ratio obtained from the storage means for storing the rotation information of each tire, the rotation information of the front two wheels and the rotation information of the two rear wheels of the vehicle, in order to determine the tire pressure drop Wheel ratio calculation means, torque calculation means for calculating the drive wheel torque of the vehicle, and zero calculation for obtaining the front and rear wheel ratio value when the drive wheel torque is zero from the relationship between the front and rear wheel ratio and the drive wheel torque A tire decompression determination program for functioning as a means, wherein the means for calculating the front-rear wheel ratio is calculated by a ratio of an average wheel speed of two driving wheels and an average wheel speed of two driven wheels, and is moderate. A means for calculating drive wheel torque without performing deceleration determination is calculated by (engine torque × engine speed) / (drive wheel speed × drive wheel number), and the relationship between the front and rear wheel ratio and the drive wheel torque is Regression line A tire pressure drop detection program.

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