JP2008018940A - Method and device for detecting lowering of tire pressure, and program for determining reduction of tire pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting lowering of tire pressure capable of determining simultaneous reduction of tire pressure of two front wheels, two rear wheels, or four wheels. <P>SOLUTION: The method of determining reduction of tire pressure includes a process of detecting wheel speed information of each tire, a process of storing the wheel speed information of each tire, a process of determining whether driving force is applied to each tire during the travelling or not, a process of computing car speed when driving force is applied to each tire, a process of computing a slip ratio when driving force is applied to each tire, a process of obtaining a relation between car speed and slip ratio, a process of comparing the relation between car speed and slip ratio when driving force is applied to the tires at a previously obtained normal pressure, a process of determining simultaneous reduction of tire pressure of the two front wheels, the two rear wheels or the four wheels. <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. More specifically, the present invention relates to a tire pressure drop detection method and apparatus capable of determining simultaneous decompression of front two-wheel tires, simultaneous decompression of rear two-wheel tires or simultaneous decompression of four-wheel tires, 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 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, and therefore the rotational speed and rotational angular speed are increased compared to other normal tires. For example, in a method of detecting a decrease in internal pressure from a relative difference in tire rotation angular velocity (see Patent Document 1), as the determination value DEL,
DEL = {(F1 + F4) / 2- (F2 + F3) / 2} / {(F1 + F2
+ F3 + F4) / 4} × 100 (%)
Is used. Here, F1 to F4 are rotational angular velocities of the front left tire, the front right tire, the rear left tire, and the rear right tire, respectively.

  Moreover, since each tire is manufactured with variations (initial differences) within the standard, the effective rolling radius of each tire is not necessarily the same even if all tires have normal internal pressure. Therefore, the rotational angular speed of each tire varies. Therefore, for example, in the technique described in Patent Document 2, after obtaining an initial correction coefficient for eliminating the difference in effective rolling radius on the rotational angular velocity, the speed of each tire is corrected using the initial correction coefficient. The determination of the decompression of the tire is performed based on the determination value DEL.

  However, since this method determines the pressure reduction from the difference between the sum of the rotational angular velocities at the four wheels diagonally, it cannot determine the simultaneous pressure reduction of the front two-wheel tire or the simultaneous pressure reduction of the rear two-wheel tire. . For this reason, there is a problem that by continuing to run without knowing that the tire is depressurized, fuel consumption is deteriorated due to an increase in rolling resistance of the tire, leading to a burst.

JP 63-305011 A JP-A-10-206460

  In view of the above circumstances, the present invention relates to a tire pressure drop detection method and apparatus capable of determining simultaneous decompression of front two-wheel tires, simultaneous decompression of rear two-wheel tires or simultaneous decompression of four-wheel tires, and tires. An object of the present invention is to provide a decompression determination program.

  The tire pressure drop detection method of the present invention is a tire pressure drop detection method for detecting a tire pressure drop based on wheel speed information obtained from a tire mounted on a vehicle, and detects wheel speed information of each tire. A process, a step of storing wheel speed information of each tire, a step of determining whether or not a driving force is applied to each running tire, and a driving force applied to each tire based on the wheel speed information. A step of calculating a vehicle body speed when the vehicle is running, a step of calculating a slip ratio when a driving force is applied to each tire when the vehicle body acceleration is within a predetermined range based on the wheel speed information, A step of obtaining a relationship between the vehicle body speed and the slip ratio, and a step of comparing the relationship with a relationship between the vehicle body speed and the slip ratio obtained in advance when a driving force is applied to a tire at a normal internal pressure. And the two A method for detecting a decrease in tire air pressure including a step of determining simultaneous decompression of front two-wheel tires, simultaneous decompression of rear two-wheel tires or simultaneous decompression of four-wheel tires based on the relationship, The step of comparing the relationship is obtained by calculating a regression curve using the average value of the relationship between a predetermined number of vehicle speeds and slip ratios for each speed region of the vehicle speed, It is characterized by comparing with relational data.

  Further, the tire pressure drop detecting device of the present invention is a tire pressure drop detecting device for detecting a tire pressure drop based on wheel speed information obtained from a tire mounted on a vehicle, wherein the wheel speed information of each tire is obtained. Wheel speed information detecting means for detecting, memory means for storing wheel speed information of each tire, driving force determining means for determining whether or not driving force is acting on each running tire, and the wheel speed information Based on the first calculation means for calculating the vehicle body speed when the driving force is applied to each tire, and based on the wheel speed information, the driving force is applied to each tire when the vehicle body acceleration is within a predetermined range. Second calculating means for calculating the slip ratio when working, third calculating means for determining the relationship between the vehicle body speed and the slip ratio, the relationship, and the driving force applied to the tire at the normal internal pressure previously determined Is working A comparison means for comparing the relationship between the vehicle body speed and the slip ratio, and based on the two relations, simultaneous decompression of the front two-wheel tire, simultaneous decompression of the rear two-wheel tire or simultaneous decompression of the four-wheel tire is determined. And a decompression determination means for comparing the vehicle body speed and the slip ratio, wherein the comparison means compares the relationship between the vehicle body speed and the slip ratio. A regression curve is obtained using an average value of the relational data, and is compared with the relational data obtained at the normal internal pressure obtained in advance.

  Further, the tire decompression determination program of the present invention uses a computer to determine a decrease in tire air pressure, memory means for storing wheel speed information of each tire, and whether or not driving force is acting on each running tire. Driving force determining means for determining, first calculating means for calculating vehicle body speed when driving force is applied to each tire based on the wheel speed information, vehicle acceleration in a predetermined range based on the wheel speed information Second calculating means for calculating the slip ratio when the driving force is applied to each tire when the vehicle is within, third calculating means for calculating the relationship between the vehicle body speed and the slip ratio, and the relationship Comparison means for comparing the relationship between the vehicle body speed and the slip ratio when the driving force is applied to the tire at the normal internal pressure, and based on the two relationships, simultaneous decompression of the front two-wheel tire, Simultaneous decompression Is a tire decompression determination program for functioning as a decompression determination means for determining simultaneous decompression of a four-wheel tire, and a comparison means for comparing the relationship between the vehicle body speed and the slip ratio is provided for each speed region of the vehicle body speed. A regression curve is obtained by using an average value of data on the relationship between a predetermined number of vehicle body speeds and slip ratios, and is compared with the data on the relationship at normal internal pressure, which has been obtained in advance.

  As described above, according to the present invention, it is possible to determine simultaneous decompression of the front two-wheel tire, simultaneous decompression of the rear two-wheel tire, or simultaneous decompression of the four-wheel tire.

  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 includes four tires FL, FR, RL and RR (hereinafter collectively referred to as Wi) provided in a four-wheel vehicle. Here, i = 1 to 4, 1: front left tire, 2: front right tire, 3: rear left tire, 4: rear right tire) is detected whether or not the air pressure is reduced. Are provided with normal wheel speed information detection means 1 provided in association with each other.

  The wheel speed information detecting means 1 generates a rotation pulse by using an electromagnetic pickup or the like, and rotates like a wheel speed sensor or dynamo that measures the wheel speed (rotation speed) as wheel speed information from the number of pulses. It is possible to use an angular velocity sensor or the like including one that generates power using this voltage and measures the wheel speed from this voltage. The output of the wheel speed 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 the tire Wi whose air pressure has been reduced, a display 3 composed of a plasma display element or CRT, and an initialization switch 4 that can be operated by a driver. Yes.

  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 is composed of a RAM 2d in which data is temporarily written when the CPU 2b performs a control operation, and the written data is read out, and an EEPROM 2e in which an initial value is written.

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

Here, since the tires Wi are manufactured with variations (initial differences) within the standard, the effective rolling radius of each tire Wi (the value obtained by dividing the distance advanced by one rotation by 2π) Even if the tire Wi has normal air pressure, it is not necessarily the same. Therefore, the rotational angular velocity F _i of each tire Wi varies. Therefore, the corrected rotational angular velocity F1 _i is calculated in order to cancel the variation due to the initial difference. In particular,
F1 ₁ = F ₁
F1 ₂ = mF ₂
F1 ₃ = F ₃
F1 ₄ = nF ₄
It is corrected. The correction factor m, n, for example the vehicle calculates the rotational angular velocity F _i under the condition that it is traveling straight, based on the rotational angular velocities F _i The _{calculated, m = F 1 / F 2} , n = Obtained as F ₃ / F ₄ . And based on said F1 _i , the wheel speed Vi of the tire of each wheel is calculated.

  In general, in a state where the driving force is applied to the tire at the normal internal pressure, the driving wheel rotates faster than the driven wheel, so that the slip ratio (wheel speed of the driving wheel / wheel speed of the driven wheel) increases.

  Similarly, for example, in the case of simultaneous reduction of four wheels, it is considered that when the driving force is applied, the driving wheel tends to rotate faster than the driven wheel, so that the slip ratio increases. However, the driving wheel pressure-reducing wheel has a gripping force on the tire compared to the normal internal pressure wheel, and is less slippery (the slope of the μ-s characteristic is larger than that at normal internal pressure due to the reduced pressure). In this way, the force that tends to rotate quickly due to the driving force and the increase in the grip amount of the tire due to the reduced pressure cancel out the force that makes it difficult to rotate, and the slip rate is reduced compared to the case of normal internal pressure.

  Therefore, since the relationship between the vehicle body speed and the slip ratio when the driving force is applied to the tire is different between the normal internal pressure and the simultaneous four-wheel pressure reduction, it is possible to determine the tire pressure abnormality during the four-wheel simultaneous pressure reduction. it can. Similarly, it is possible to determine an abnormality in tire air pressure when the two driving wheels are simultaneously depressurized.

  Therefore, in the present embodiment, the wheel speed information detecting means 1, the driving force determining means for determining whether or not the driving force is acting on each running tire Wi, and the driving force acting on each tire Wi. First calculation means and second calculation means for calculating the vehicle body speed and the slip ratio when the vehicle is in operation, third calculation means for determining the relationship between the vehicle body speed and the slip ratio, the relationship, and the normal internal pressure previously determined Means for comparing the relationship between the vehicle speed and the slip ratio when the driving force is applied to the tire of the vehicle, and simultaneous decompression of the front two-wheel tire and simultaneous decompression of the rear two-wheel tire based on the two relationships Alternatively, a decompression determination unit that determines simultaneous decompression of the four-wheel tire is provided.

  The tire decompression determination program according to the present embodiment includes a control unit 2, a computer for determining a decrease in air pressure of each tire Wi tire, memory means for storing wheel speed information of each tire, Driving force determining means for determining whether or not driving force is applied to each tire, first calculating means for calculating a vehicle body speed when driving force is applied to each tire, and when driving force is applied to each tire Second calculating means for calculating the slip ratio of the vehicle, third calculating means for determining the relationship between the vehicle body speed and the slip ratio, the relationship, and the vehicle body when the driving force is acting on the previously obtained tire at normal internal pressure Comparing means for comparing the relationship between the speed and the slip ratio, and based on the two relationships, a reduction for determining simultaneous decompression of the front two-wheel tire, simultaneous decompression of the rear two-wheel tire or simultaneous decompression of the four-wheel tire. To function as a determination unit.

  The slip ratio can be expressed as a ratio (wheel speed of the driving wheel / wheel speed of the driven wheel) or a difference between the wheel speed of the driving wheel and the wheel speed of the driven wheel.

  Further, the relationship between the vehicle body speed and the slip ratio obtained at the normal internal pressure is saved in an EEPROM so that it can be remembered even if the ignition key of the vehicle is turned off. The decompression determination means in the tire pressure drop detection device is executed by the control unit 2 every sampling period ΔT by the CPU 2b operating according to a predetermined program stored in the ROM 2c.

  Further, whether or not driving force is acting on each tire can also be determined from information on vehicle body acceleration, accelerator opening, throttle opening, wheel torque, or engine torque.

  Hereinafter, the operation of the tire pressure drop detecting device according to the present embodiment will be described as an example along the procedures (1) to (9).

(1) Each wheel speed (V1 _n , V2 _n , V3 _n , V4 _n ) of the four-wheel tire Wi of the vehicle is calculated.
For example, wheel speed data at a certain point in time for each wheel tire Wi of the vehicle obtained from a sensor such as an ABS sensor is set as wheel speeds V1 _n , V2 _n , V3 _n , V4 _n .

(2) Then the case of a front-wheel drive, wherein the average wheel speed Vf _n of the following wheels and the driving wheels at a certain time, the Vd _n of the following (1), obtained by (2).
Vf _n = (V3 _n + V4 _n ) / 2 (1)
Vd _n = (V1 _n + V2 _n ) / 2 (2)

(3) Next, the vehicle body speed is calculated. For two-wheel drive vehicle, the average wheel speed Vf _n of the following wheels.

(4) Next, the vehicle body acceleration Taf _{n of the} vehicle is calculated.
Wherein the vehicle speed Vf _n 1 preceding wheel speed data from, when the vehicle speed Vf _n-1, determined by the equation of the vehicle body acceleration Taf _n Hatsugi vehicle (3).
Taf _n = (Vf _n −Vf _n−1 ) / Δt / G (3)
Here, Δt is a time interval (sampling time) between the average rotational speeds Tf _n and Tf _n−1 calculated from the wheel speed data, for example, 1 second.

(5) Next, it is determined whether or not the driving force is acting on the tire. For example, the determination is made based on whether or not the vehicle body acceleration Taf _{n of the} vehicle is within a predetermined range (for example, 0 to 0.03 G).
Here, the determination using the vehicle body acceleration is performed in order to suppress the variation in the slip ratio by limiting the vehicle body acceleration, for example. In addition, these conditions may change with the speed area | region during driving | running | working. In addition to the determination based on the vehicle body acceleration, it is also possible to determine whether or not the driving force is acting on the tire from the information on the accelerator opening, the throttle opening, the wheel torque, or the engine torque as described above.

From the ratio of front and rear wheels of the average wheel speed Vf _n of the average wheel speed Vd _n and the driven wheels (6) followed the drive wheel, calculates the slip ratio S _n, for example by the following equation (4), the speed of the vehicle speed Add each area (for example, a speed area in increments of 10 km / h) and average the data including the previous data.
S _n = Vd _n / Vf _n (4)

(7) Next, it is determined whether there are, for example, four or more vehicle body speed regions in which a predetermined number (for example, 10 or more) of data is accumulated for each speed region.

(8) Next, the relationship between the vehicle speed and the slip ratio of the vehicle currently running is obtained, and compared with the relationship between the vehicle speed and the slip ratio at normal internal pressure, which has been obtained in advance, whether the two relationships are different or not. to decide.
As a determination method, for example, there is a method of comparing slopes by obtaining regression curves using data on the relationship between the vehicle speed and the slip ratio. Other than that, a method of comparing the difference in slip rate for each vehicle speed region or the slip rate when a driving force is applied to a tire for a long time (for example, 2 hours) is averaged for each vehicle speed region and obtained in advance. There is also a method of comparing with the average value of the slip rate at the normal internal pressure. Accordingly, it is possible to determine the pressure reduction even when the vehicle travels for a long time at a constant speed. Here, the reason why the vehicle travels for a long time is to cancel the change of the slip rate when the vehicle climbs up and down.

(9) Next, simultaneous decompression of the front two-wheel tire, simultaneous decompression of the rear two-wheel tire or simultaneous decompression of the four-wheel tire is determined.

  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 215 / 50R17. In addition, the vehicle traveling conditions were such that two passengers traveled on a general road for about an hour. A running test was carried out on a vehicle equipped with a tire at normal internal pressure and a vehicle in which the pressure of a four-wheel tire was reduced by 30%.

  First, the wheel speeds of the four wheels are sampled during traveling. Regarding the sampling time of the wheel speed of the wheel, in order to increase the number of data and to eliminate variations and measurement errors, it was set to 1 second.

  Then, as shown in FIG. 3, the average wheel speed of the driven wheel is set as the vehicle body speed, and then the vehicle body speed is differentiated by the sampling time to obtain the vehicle body acceleration (steps S1 and S2).

  Next, it is determined whether the vehicle body acceleration is within a predetermined range, for example, 0 to 0.03G (step S3). If it is within the predetermined range, the slip ratio is obtained. In this embodiment, the ratio of the wheel speeds of the drive wheel tire and the driven wheel tire is used as the slip ratio. Then, the slip rate is added to the current slip rate and averaged for each vehicle speed region, for example, 30 km / h, 60 km / h, 90 km / h, and 120 km / h in 10 km / h increments (step S4). It is determined whether there are four or more vehicle body speed areas in which 10 or more data are accumulated in each speed area (step S5). When there are four or more, the relationship between the vehicle speed and the slip ratio currently being traveled is compared with the relationship between the vehicle speed and the slip ratio obtained at the normal internal pressure obtained in advance, and it is determined whether or not they are different. (Step S6). As a determination method, a regression curve was obtained using data on the relationship between the vehicle speed and the slip ratio, and the inclination was compared. As shown in FIG. 4, the relationship NT between the vehicle body speed and the slip ratio of the tire at normal internal pressure determined by actual vehicle travel and the relationship DT between the vehicle body speed and the slip ratio of a four-wheel tire with the air pressure reduced by 30%. In this embodiment, it can be determined that the four-wheel tires are simultaneously depressurized (step S7).

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 an example of the flowchart which shows operation | movement of the tire air pressure fall detection apparatus of this invention. It is a figure which shows the relationship between the vehicle body speed and slip ratio in the one aspect | mode concerning the tire air pressure fall detection apparatus of this invention.

Explanation of symbols

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

Claims (3)

A method for detecting a decrease in tire air pressure based on wheel speed information obtained from a tire mounted on a vehicle, the step of detecting wheel speed information for each tire, and the wheel speed information for each tire. A step of storing, a step of determining whether or not a driving force is applied to each running tire, and a step of calculating a vehicle body speed when the driving force is applied to each tire based on the wheel speed information And calculating the slip ratio when the driving force is applied to each tire when the vehicle body acceleration is within a predetermined range based on the wheel speed information, and the relationship between the vehicle body speed and the slip ratio. Based on these two relationships, the step of obtaining, the relationship, and the step of comparing the relationship between the vehicle speed and the slip ratio obtained in advance when the driving force is acting on the tire at the normal internal pressure, Same as front tires A method for detecting a decrease in tire air pressure including a step of determining decompression, simultaneous decompression of two-wheel tires or simultaneous decompression of four-wheel tires, and the step of comparing the relationship between the vehicle body speed and the slip ratio A regression curve is obtained by using an average value of data on the relationship between a predetermined number of vehicle body speeds and slip ratios for each speed region, and is compared with the data on the relationship obtained at normal internal pressure, which is obtained in advance. Tire pressure drop detection method. A tire air pressure drop detecting device for detecting a tire air pressure drop based on wheel speed information obtained from a tire mounted on a vehicle, the wheel speed information detecting means for detecting the wheel speed information of each tire, Memory means for storing wheel speed information, driving force judging means for judging whether or not driving force is acting on each running tire, and driving force acting on each tire based on the wheel speed information First calculating means for calculating the vehicle body speed at the time, and second calculating the slip ratio when the driving force is applied to each tire when the vehicle body acceleration is within a predetermined range based on the wheel speed information. A calculation means; a third calculation means for obtaining a relationship between the vehicle body speed and the slip ratio; and the relationship between the vehicle speed and the slip ratio when the driving force is applied to the tire at the normal internal pressure, which is obtained in advance. Compare with relationship Tire pressure drop detection comprising comparison means and pressure reduction determination means for determining simultaneous decompression of front two-wheel tires, simultaneous decompression of rear two-wheel tires or simultaneous decompression of four-wheel tires based on the two relationships Comparing means for comparing the relationship between the vehicle body speed and the slip ratio is to obtain a regression curve by using an average value of a predetermined number of vehicle body speed and slip ratio data for each speed region of the vehicle body speed. A tire air pressure drop detecting device, which is compared with the data of the relationship at the time of normal internal pressure obtained in advance. A computer for determining a decrease in tire air pressure, a memory means for storing wheel speed information of each tire, a driving force judgment means for judging whether or not a driving force is acting on each running tire, and the wheel speed information Based on the first calculation means for calculating the vehicle body speed when the driving force is applied to each tire, and based on the wheel speed information, the driving force is applied to each tire when the vehicle body acceleration is within a predetermined range. Second computing means for calculating the slip ratio when working, third computing means for obtaining the relationship between the vehicle body speed and the slip ratio, the relationship, and the driving force acting on the tire at the normal internal pressure previously obtained Comparison means for comparing the vehicle speed and the slip ratio when the vehicle is in operation. Based on the two relationships, the simultaneous decompression of the front two-wheel tire, the simultaneous decompression of the rear two-wheel tire or the simultaneous decompression of the four-wheel tire is determined. Depressurization judgment hand A tire decompression determination program for functioning as a vehicle, wherein the comparison means for comparing the relationship between the vehicle body speed and the slip ratio is a data of the relationship between a predetermined number of vehicle body speed and slip ratio for each speed region of the vehicle body speed. A tire decompression determination program characterized in that a regression curve is obtained using an average value and compared with the data of the relationship obtained at normal internal pressure obtained in advance.

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