JP5097438B2 - Tire dynamic load radius reference value initialization method and apparatus, and tire dynamic load radius reference value initialization program - Google Patents

Description

  The present invention relates to a tire dynamic load radius reference value initialization method and apparatus, and a tire dynamic load radius reference value initialization program.

  Conventionally, various methods have been proposed as a method for detecting a decrease in the internal pressure of a tire of a vehicle. For example, Patent Document 1 discloses a tire of a running vehicle based on the relationship between the absolute speed of the vehicle and the rotational angular velocity of the tire. The dynamic load radius is calculated, and when the calculated dynamic load radius becomes smaller by a predetermined degree than the initial value (reference value) stored in advance as the dynamic load radius at the normal internal pressure, the internal pressure of the tire is reduced. A method for alarming is disclosed. In the method described in Patent Document 1, in order to improve the detection accuracy, the running state of the vehicle is limited (limited to a running state in which a flat road is traveling straight at a constant speed), and the dynamic load obtained in such a state The radius is used as an effective value to detect a decrease in tire internal pressure.

  In addition, since the dynamic load radius of the tire depends on the vehicle speed, the applicant of the present invention can detect the decrease in the dynamic load radius in any speed region before the dynamic load radius and the vehicle in a plurality of speed regions. A method of initializing the dynamic load radius using an approximate expression from the relationship with the speed has been proposed (Japanese Patent Application No. 2006-187845).

JP 2007-45295 A

  According to the method proposed in the Japanese Patent Application No. 2006-187845, it is possible to accurately detect a decrease in the dynamic load radius in any speed region, but the measurement data is divided into a plurality of speed regions and accumulated. Since a representative value (average value of dynamic load radii representing each speed region) is obtained when the necessary number of data is collected in the speed region, it may take a long time to complete initialization. . In other words, in this method, the speed dependence in the entire speed region of the tire dynamic load radius can be obtained only by collecting a plurality of representative values, so it is necessary when traveling in the same speed region. Since the representative values of the numbers are not collected, it is difficult to complete initialization.

  In addition, in the speed area divided into several areas, it is not known at which speed in each area, so in order to keep the average value of the dynamic load radius from changing significantly in the speed area, it is fine. It is necessary to set an appropriate speed range. Accordingly, it may take a long travel time to accumulate a predetermined number of data in each of a plurality of finely set speed regions.

  The present invention has been made in view of such circumstances, and a tire dynamic load radius reference value initialization method and apparatus, and a tire, which can shorten the time for initializing the tire dynamic load radius reference value. The purpose is to provide a dynamic load radius reference value initialization program.

The tire dynamic load radius reference value initialization method of the present invention calculates the tire dynamic load radius of a running vehicle, and changes the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure. A method for initializing the reference value when determining a decrease in the internal pressure of a tire based on a size,
Detecting wheel rotation information of each tire of the vehicle when traveling at normal internal pressure;
Calculating the wheel speed from the detected wheel rotation information;
Determining vehicle speed;
Obtaining a dynamic load radius of each tire from the wheel speed and vehicle speed;
Sequentially accumulating the relationship between the vehicle speed and the dynamic load radius of each tire at the vehicle speed;
A step of setting a reference value in the entire speed range by obtaining an approximate expression representing a correlation between the vehicle speed and the dynamic load radius when the number of accumulated vehicle speed data exceeds a predetermined number. And
Obtaining the approximate expression when the accumulated vehicle speed data is dispersed beyond a predetermined range; and
A plurality of speed regions are set, and the approximate expression is obtained when the number of vehicle speed data belonging to each speed region exceeds a predetermined number .

  In the tire dynamic load radius reference value initialization method of the present invention, when the number of accumulated vehicle speed data exceeds a predetermined number, an approximate expression representing the correlation between the vehicle speed and the dynamic load radius is obtained. Since the reference value is set in the entire speed range, the reference value can be initialized in a short traveling time.

Also, determine the approximate equation when the accumulated vehicle velocity data were dispersed beyond a predetermined range, and the vehicle speed data varies beyond a predetermined range, and the dynamic load radius data associated with it Based on the above, an approximate expression representing the correlation between the vehicle speed and the dynamic load radius can be obtained, and an approximate expression having a large correlation coefficient, in other words, a high accuracy can be obtained.

Furthermore, setting a plurality of speed regions than the number of vehicle speed data belonging to each speed region determining the approximate expression if it exceeds a predetermined number, it is possible to prevent the variation of the vehicle speed data is biased Thus, an approximate expression with higher accuracy can be obtained.

In addition, the tire dynamic load radius reference value initialization apparatus of the present invention calculates the tire dynamic load radius of a running vehicle, and obtains the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure. A device that initializes the reference value when determining a decrease in the internal pressure of a tire based on the magnitude of change,
Wheel rotation information detection means for detecting wheel rotation information of each tire of the vehicle when traveling at normal internal pressure;
Wheel speed calculation means for calculating wheel speed from the detected wheel rotation information;
Vehicle speed calculation means for determining the vehicle speed;
A dynamic load radius calculating means for determining a dynamic load radius of each tire from the wheel speed and the vehicle speed;
Data accumulation means for sequentially accumulating the relationship between the vehicle speed and the dynamic load radius of each tire at the vehicle speed;
Reference value setting means for setting a reference value in the entire speed region by obtaining an approximate expression representing the correlation between the vehicle speed and the dynamic load radius when the number of accumulated vehicle speed data exceeds a predetermined number It equipped with a door,
The reference value setting means obtains the approximate expression when the accumulated vehicle speed data is dispersed beyond a predetermined range, and
A plurality of speed regions are set, and the approximate expression is obtained when the number of vehicle speed data belonging to each speed region exceeds a predetermined number .

  In the tire dynamic load radius reference value initialization apparatus according to the present invention, when the number of accumulated vehicle speed data exceeds a predetermined number, the reference value setting means represents the correlation between the vehicle speed and the dynamic load radius. Since the reference value is set in the entire speed range by obtaining the approximate expression, the reference value can be initialized in a short traveling time.

Further, the tire dynamic load radius reference value initialization program according to the present invention calculates the tire dynamic load radius of the running vehicle, and obtains the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure. When determining the decrease in the internal pressure of the tire based on the magnitude of the change, the computer is used to initialize the reference value, and the wheel rotation information of each tire of the vehicle detected when the vehicle is running at the normal internal pressure is used. Wheel speed calculation means for calculating a wheel speed, dynamic load radius calculation means for obtaining a dynamic load radius of each tire from the wheel speed and the vehicle speed, a relationship between the vehicle speed and a dynamic load radius of each tire at the vehicle speed Data accumulating means for accumulating sequentially, and when the number of accumulated vehicle speed data exceeds a predetermined number, an approximate expression representing the correlation between the vehicle speed and the dynamic load radius is obtained, thereby obtaining the total speed To function as a reference value setting means for setting the reference value in the range,
The reference value setting means obtains the approximate expression when the accumulated vehicle speed data is dispersed beyond a predetermined range, and
Setting a plurality of speed regions, the number of vehicle speed data belonging to each speed region is characterized that you have been configured to determine the approximate expression if it exceeds a predetermined number.

  In the tire dynamic load radius reference value initialization program according to the present invention, when the number of accumulated vehicle speed data exceeds a predetermined number, an approximate expression representing the correlation between the vehicle speed and the dynamic load radius is obtained. Since the computer is configured to set the reference value in the entire speed range, the reference value can be initialized in a short traveling time.

  According to the tire dynamic load radius reference value initialization method and dynamic load radius reference value initialization program of the present invention, the time for initializing the tire dynamic load radius reference value can be shortened.

Hereinafter, with reference to the accompanying drawings, a tire dynamic load radius reference value initialization method (hereinafter also simply referred to as “initialization method”) and device (hereinafter also simply referred to as “initialization device”) of the present invention, and An embodiment of a tire dynamic load radius reference value initialization program will be described in detail.
As shown in FIG. 1, the initialization apparatus according to an embodiment of the present invention detects wheel rotation information of four tires FL, FR, RL, and RR provided in a four-wheel vehicle. There is provided a normal wheel speed detecting means (wheel rotation information detecting means) 1 provided in connection with.

  The wheel speed detection means 1 generates power using rotation like a wheel speed sensor or dynamo for generating rotation pulses using an electromagnetic pickup or the like and measuring the rotation angular speed and wheel speed from the number of pulses. It is possible to use an angular velocity sensor including that for measuring the rotational angular velocity and the wheel speed from this voltage. The output of the wheel speed detecting means 1 is given to a control unit 2 which is a computer such as ABS. The control unit 2 is connected to a GPS device 3 constituting vehicle speed calculation means.

  As shown in FIG. 2, the control unit 2 stores an I / O interface 2a necessary for passing signals to and from an external device, a CPU 2b that functions 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. In FIG. 2, 3a is a GPS antenna.

  The wheel speed detection means 1 outputs a pulse signal corresponding to the number of rotations of the tire (hereinafter referred to as “wheel speed pulse”). Further, the CPU 2b calculates the rotation angular velocity of each tire at a predetermined sampling period ΔT (sec), for example, ΔT = 0.05 seconds, based on the wheel speed pulse output from the wheel speed detecting means 1.

  The vehicle speed can be obtained using, for example, a GPS speedometer. With the widespread use of car navigation systems, GPS devices are attached to many vehicles. As a result, positioning technology using a GPS device has also been improved, and a device specialized in calculating speed (GPS speedometer VBOX (trade name) manufactured by Race Logic, UK) is now on the market. The speed calculated by the speedometer using such GPS information can be used as the vehicle speed.

  The initialization apparatus according to the present embodiment includes a wheel speed detection unit (wheel rotation information detection unit) 1, a wheel speed calculation unit that calculates a wheel speed from the detected wheel rotation information of each tire of the vehicle, and a vehicle speed. The GPS speedometer for obtaining the vehicle, the dynamic load radius calculating means for obtaining the dynamic load radius of each tire from the wheel speed and the vehicle speed, and the relationship between the vehicle speed and the dynamic load radius of each tire at the vehicle speed are sequentially accumulated. When the number of accumulated vehicle speed data and the number of accumulated vehicle speed data exceeds a predetermined number, the reference value is set in the entire speed range by obtaining an approximate expression representing the correlation between the vehicle speed and the dynamic load radius. And a reference value setting means for performing. Then, the tire dynamic load radius reference value initialization program causes the control unit 2 to function as wheel speed calculation means, dynamic load radius calculation means, data accumulation means, and reference value setting means.

  The tire dynamic load radius (R) of the traveling vehicle can be calculated by V = R × ω from the relationship between the absolute speed (V) of the vehicle and the rotational angular velocity (ω) of the tire. The tire dynamic load radius (R) is known to decrease as the tire internal pressure decreases, and this is used to estimate the decrease in tire internal pressure from the decrease in tire dynamic load radius (R). Can do.

  Incidentally, the dynamic load radius (R) of the tire has a dependency on the vehicle speed (V), and changes depending on the vehicle speed (V) even if the tire internal pressure does not change. That is, as the tire rotates at higher speeds, the centrifugal force increases due to the mass of the tire tread, and the dynamic load radius (R) increases as a function of speed (generally proportional to the square of speed).

  Therefore, when estimating the decrease in tire internal pressure from the decrease in tire dynamic load radius (R), it is necessary to grasp the dependency of the tire dynamic load radius (R) on the vehicle speed (V) at the normal internal pressure. . In the initialization method of the present invention, the dependence on the vehicle speed (V) is taken into account when determining the reference value of the tire dynamic load radius (R) at the normal internal pressure, which is a reference for estimating the decrease in the internal pressure of the tire. When the number of vehicle speed data exceeds a predetermined number, the reference value is set in the entire speed range by obtaining an approximate expression representing the correlation between the vehicle speed (V) and the tire dynamic load radius (R). Is doing. Specifically, the reference value of the tire dynamic load radius (R) can be initialized by the following procedure.

(1) First, based on the output signal (pulse signal) of the wheel speed detecting means 1, the rotational angular velocity (ω) of each tire at normal internal pressure is calculated by the following equation (1).
Rotational angular velocity (ω) = 2π × Freq (Hz) / N (pieces) (1)
Here, N is the number of teeth per one rotation of the axle of the wheel speed detecting means 1, and Freq (Hz) is a numerical value obtained by counting the teeth of the wheel speed detecting means 1 per second.

  (2) On the other hand, the vehicle speed (V) is obtained from the GPS speedometer. The vehicle speed (V) is directly output to the control unit 2 as serial data. For either one of the calculation time of the rotational angular velocity (ω) and the calculation time of the vehicle speed (V), the numerical value at the same time as the other is interpolated and the numerical values at the same time are calculated and synchronized with each other. For example, can be taken into the control unit 2 as digital data every 50 msec.

  The tire dynamic load radius also changes depending on factors other than the decrease in tire internal pressure, such as acceleration / deceleration, turning, and running on slopes, but changes in the tire dynamic load radius due to these other factors are excluded from the data for determining internal pressure decrease. By doing so, it is possible to accurately determine a decrease in internal pressure. Correspondingly, the vehicle speed data and dynamic load radius data when initializing the dynamic load radius reference value are also limited to the vehicle travel state (limited to the travel state where the flat road is traveling straight at a constant speed). It is preferable to adopt the data obtained in such a state as valid data.

  Specifically, whether or not the driving condition satisfies conditions such as constant speed driving, flat road driving, and straight driving is compared with each judgment condition, and the data obtained during actual driving is used for setting the reference value. It is determined whether the data is suitable for the data. If the data is inappropriate, the data is excluded without being used as the reference value setting data. As the determination conditions, for example, the vehicle front-rear direction | G | <0.05G, the direction change is 1 degree or less, the road surface gradient is 5% or less, and the brake is not stepped on.

  (3) Next, the dynamic load radius (R) of each tire is calculated from the rotational angular velocity (ω) and the vehicle speed (V) of each tire, and the vehicle speed (V) data and the motion at the vehicle speed (V) are calculated. Load radius (R) data is accumulated sequentially.

  (4) And when the number of vehicle speed (V) data, in other words, the number of dynamic load radius (R) data at the vehicle speed (V) is stored in a predetermined number, for example, 120, all Is used to obtain an approximate expression indicating the correlation between the vehicle speed (V) and the dynamic load radius (R) by the least square method or the like. With this approximate expression, the reference value of the dynamic load radius (R) in the entire speed region can be set.

Next, examples of the initialization method of the present invention will be described. However, the present invention is not limited to such examples.
[Example 1]
In order to obtain the rotational angular velocity of each tire mounted on the vehicle, the rotational angular velocity used for ABS control was converted into the rotational angular velocity. Further, in order to obtain the absolute speed of the vehicle, a VBOX (trade name, a GPS speedometer manufactured by Race Logic, UK) was attached to the vehicle. The vehicle speed is directly output as serial data to a PC (personal computer), and the vehicle speed information and the rotational speed information are synchronized with each other as digital data every 50 msec and can be taken into the PC. And the tire dynamic load radius was calculated every 50 msec from these two pieces of information, and calculated as an average value per second. The test conditions were as follows:

<Test conditions>
Vehicle: Four-wheel drive vehicle Tire: 215 / 45R17 SP9000
Road surface: General road and Okayama test course initialized by Sumitomo Rubber Industries Co., Ltd. Driving condition: One passenger rides at standard internal pressure (230 kPa) Also, as driving conditions, it is judged that the vehicle is traveling straight on a flat road at a constant speed The case was selected, and the dynamic load radius was calculated for the case where this running condition was satisfied, and the obtained data was accumulated. Specifically, from GPS information, the front-rear direction | G | <0.05G, direction change of 1 degree or less, road surface gradient of 5% or less, and clearing of all conditions, provided that the brake is not depressed, Only data obtained when the GPS reception state is good and the speed information is normally output is adopted as valid data.

  When a predetermined number (120) of dynamic load radius values calculated as an average value for 1 second were accumulated, an approximate curve was calculated by the least square method using all the accumulated data. The approximate expression can be calculated by running for about 10 minutes in a state where GPS can be received. The results are shown in FIG. As can be seen from FIG. 3, in this example, the speed was sufficiently varied, and the obtained results were not inferior to the comparative examples described later.

[Example 2]
Test running was carried out in the same manner as in Example 1, and dynamic load radius values obtained under predetermined running conditions were stored as effective data.
More than a predetermined number (120) of dynamic load radius values calculated as an average value for one second are accumulated, and a difference between the maximum value and the minimum value of the vehicle speed at that time is a predetermined value (50 km / When h) was exceeded, an approximated curve was calculated by the least square method using all the accumulated data. The approximate expression can be calculated by running for about 15 minutes in a state where GPS can be received. The results are shown in FIG. As can be seen from FIG. 4, in this example, there was no large deviation in speed variation, and the obtained results were not inferior to the comparative examples described later.

[Example 3]
Test running was carried out in the same manner as in Example 1, and dynamic load radius values obtained under predetermined running conditions were stored as effective data.
The vehicle speed area is divided into three areas in advance (less than 60 km / h, less than 60 km / h to less than 80 km / h, and more than 80 km / h), and the dynamic load radius value calculated as the average value per second is The vehicle traveled until 60 were accumulated, and an approximate curve was calculated by the least square method using all accumulated data. The approximate expression can be calculated by running for about 30 minutes in a state where GPS can be received. The results are shown in FIG. As can be seen from FIG. 5, in this example, there was no large deviation in speed variation, and the obtained results were not inferior to the comparative examples described later.

[Comparative example]
Test running was carried out in the same manner as in Example 1, and dynamic load radius values obtained under predetermined running conditions were stored as effective data.
The vehicle speed area of 20-100 km / h is divided into 13 areas in advance (3 areas in increments of 10 km / h from 20 to 50 km / h, 10 areas in increments of 5 km / h from 50 to 100 km / h). As a representative value in each area, when 60 data were accumulated in each speed area, an average value of dynamic load radii was obtained. Then, when five representative values were collected, an approximate curve was calculated by the least square method from the average value for the speed in each speed region and the average value of the dynamic load radius.

Theoretically, an approximate expression can be calculated with 60 (pieces / area) × 5 (area) × 1 (seconds / piece) = 300 (seconds) at the shortest. In addition, since data may be accumulated in five or more of the 13 regions, it took about 1 hour to calculate an approximate expression even in a state where GPS can be received. The results are shown in FIG.
As described above, according to the initialization method of the present invention, the reference value can be initialized in a shorter time than the conventional method of storing a predetermined number of data for each region, and the obtained approximate expression is the conventional equation. It turns out that there is no inferiority compared with the thing of.

  In the above-described embodiment, the absolute speed of the vehicle obtained by the GPS device is used. However, the present invention is not limited to this, and the absolute speed of the vehicle obtained by a different method such as the ground speed is used. Can be used.

It is a block diagram which shows one Embodiment of the initialization apparatus of this invention. It is a block diagram which shows the electrical structure of the initialization apparatus shown by FIG. It is a figure which shows the approximate expression showing the correlation of the vehicle speed data and dynamic load radius data in embodiment of this invention. It is a figure which shows the approximate expression showing the correlation of the vehicle speed data and dynamic load radius data in embodiment of this invention. It is a figure which shows the approximate expression showing the correlation of the vehicle speed data and dynamic load radius data in embodiment of this invention. It is a figure which shows the approximate expression showing the correlation of the vehicle speed data and dynamic load radius data in a prior art.

Explanation of symbols

1 Wheel speed detection means 2 Control unit 2a Interface 2b CPU
2c ROM
2d RAM
3 GPS device 3a GPS antenna

Claims (3)

When calculating the tire dynamic load radius of the running vehicle and determining the decrease in the internal pressure of the tire based on the magnitude of the change of the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure, A method of initializing the reference value,
Detecting wheel rotation information of each tire of the vehicle when traveling at normal internal pressure;
Calculating the wheel speed from the detected wheel rotation information;
Determining vehicle speed;
Obtaining a dynamic load radius of each tire from the wheel speed and vehicle speed;
Sequentially accumulating the relationship between the vehicle speed and the dynamic load radius of each tire at the vehicle speed;
A step of setting a reference value in the entire speed range by obtaining an approximate expression representing a correlation between the vehicle speed and the dynamic load radius when the number of accumulated vehicle speed data exceeds a predetermined number. And
Obtaining the approximate expression when the accumulated vehicle speed data is dispersed beyond a predetermined range; and
A tire dynamic load radius reference value initialization method , wherein a plurality of speed regions are set, and the approximate expression is obtained when the number of vehicle speed data belonging to each speed region exceeds a predetermined number . When calculating the tire dynamic load radius of the running vehicle and determining the decrease in the internal pressure of the tire based on the magnitude of the change of the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure, An apparatus for initializing the reference value,
Wheel rotation information detection means for detecting wheel rotation information of each tire of the vehicle when traveling at normal internal pressure;
Wheel speed calculation means for calculating wheel speed from the detected wheel rotation information;
Vehicle speed calculation means for determining the vehicle speed;
A dynamic load radius calculating means for determining a dynamic load radius of each tire from the wheel speed and the vehicle speed;
Data accumulation means for sequentially accumulating the relationship between the vehicle speed and the dynamic load radius of each tire at the vehicle speed;
Reference value setting means for setting a reference value in the entire speed region by obtaining an approximate expression representing the correlation between the vehicle speed and the dynamic load radius when the number of accumulated vehicle speed data exceeds a predetermined number It equipped with a door,
The reference value setting means obtains the approximate expression when the accumulated vehicle speed data is dispersed beyond a predetermined range, and
A reference value initialization of a tire dynamic load radius , wherein a plurality of speed regions are set and the approximate expression is obtained when the number of vehicle speed data belonging to each speed region exceeds a predetermined number apparatus. When calculating the tire dynamic load radius of the running vehicle and determining the decrease in the internal pressure of the tire based on the magnitude of the change of the obtained dynamic load radius from the reference value of the dynamic load radius at normal internal pressure, In order to initialize the reference value, a wheel speed calculating means for calculating a wheel speed from wheel rotation information of each tire of the vehicle detected when the vehicle is running at a normal internal pressure, from the wheel speed and the vehicle speed Dynamic load radius calculation means for determining the dynamic load radius of each tire, data accumulation means for sequentially accumulating the relationship between the vehicle speed and the dynamic load radius of each tire at the vehicle speed, and the number of accumulated vehicle speed data If but exceeds a predetermined number, by obtaining an approximate expression representing the correlation between the vehicle speed and the dynamic load radius to function as the reference value setting means for setting the reference value in all speed ranges
The reference value setting means obtains the approximate expression when the accumulated vehicle speed data is dispersed beyond a predetermined range, and
A reference value initialization of a tire dynamic load radius , wherein a plurality of speed regions are set and the approximate expression is obtained when the number of vehicle speed data belonging to each speed region exceeds a predetermined number program.

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