JP5002203B2 - Initialization method of tire dynamic load radius reference value - Google Patents

Description

  The present invention measures the tire dynamic load radius of a running vehicle, and initializes the reference value when determining a decrease in tire internal pressure based on the magnitude of change from the dynamic load radius reference value at the reference internal pressure. Related to the method.

  Conventionally, Patent Documents 1 to 3 disclose a method for detecting a decrease in the internal pressure of a tire from the vehicle speed and distance calculated from GPS information and the rotation speed of the tire. However, in order to detect a decrease in tire internal pressure from the vehicle speed and tire rotation speed calculated from GPS information, it is necessary to detect a change in tire rotation speed due to only a decrease in internal pressure. In other words, it is necessary to eliminate the rotational speed change due to the running state of the vehicle.

  Patent Document 1 discloses a method for detecting a decrease in tire air pressure by comparing a vehicle travel locus calculated from tire rotation information with a vehicle travel locus obtained from vehicle position information by GPS or the like. However, it does not show that the change in the rotational speed due to the running state of the vehicle is excluded. In Patent Document 2 and Patent Document 3, the running state is specified by comparing the rotation states of the tires. However, when a decrease in the internal pressure of the tire occurs, the relationship between the rotational speeds of the four wheels is already out of balance. Therefore, it is impossible to specify the exact driving state. Also known is a method of detecting a decrease in tire air pressure by calculating the tire dynamic load radius from the travel distance calculated from GPS information and the tire rotation speed. Is not accurate enough.

  Therefore, the running condition of the vehicle is limited, the effective value of the measured dynamic load radius at that time is selected, the average value is set as the dynamic load radius during running, and when the dynamic load radius becomes smaller than the reference value, the internal pressure A method for alarming the drop has been proposed. In addition, this method considers the influence of the dynamic load radius measurement value due to the road surface μ and load, and if there is a possibility of such influence, it should be noted that there is an influence of the road surface or the load in parallel with the warning of a decrease in internal pressure. A method of prompting is disclosed. However, in this method, it is necessary to set in advance a reference value in a speed range for determining a decrease in internal pressure.

JP 2003-94920 A JP 2005-186739 A JP 2003-146037 A

  According to the present invention, it is not necessary to set in advance a reference value in a speed range in which a decrease in tire internal pressure is to be determined, and it is determined from tire dynamic load radius data when the vehicle travels at a normal internal pressure. It is an object of the present invention to provide a reference value initialization method capable of setting a reference value.

  That is, according to the present invention, the tire dynamic load radius of the running vehicle is calculated from the vehicle speed information and tire rotation speed information by GPS, and the tire is determined by the magnitude of the change from the reference value of the dynamic load radius at the reference internal pressure. A method for initializing the reference value when determining a decrease in the internal pressure of the vehicle, wherein the measurement value of the dynamic load radius of the vehicle at the reference internal pressure is distributed and accumulated for each predetermined speed region, The present invention also relates to a tire dynamic load radius reference value initialization method including a step of calculating a reference value for each speed region when a certain number of measurement values are accumulated.

  The reference value is preferably calculated by a weighted arithmetic moving average method.

  Further, the present invention is a tire internal pressure drop determination method including the tire dynamic load radius reference value initialization method, wherein the vehicle speed and the dynamic load radius in any one of the speed regions are measured, and the average of the obtained data The present invention also relates to a tire internal pressure decrease determination method including a step of obtaining a dynamic load radius corresponding to a vehicle speed by the conversion and comparing with a reference value set at the vehicle speed.

  Furthermore, the present invention calculates the tire dynamic load radius of the running vehicle from the vehicle speed information by GPS and the tire rotation speed information, and determines the tire load according to the magnitude of the change from the reference value of the dynamic load radius at the reference internal pressure. An apparatus for initializing the reference value when determining a decrease in internal pressure, and means for distributing and storing measured values of the dynamic load radius of the vehicle at the time of the reference internal pressure for each predetermined speed region; and The present invention relates to a tire dynamic load radius reference value initialization device including means for calculating a reference value for each speed region when a certain number of measurement values are accumulated.

  Further, the present invention calculates the tire dynamic load radius of the running vehicle from the vehicle speed information and the tire rotational speed information by GPS, and determines the tire load according to the magnitude of the change from the reference value of the dynamic load radius at the reference internal pressure. A program for initializing the reference value when determining a decrease in internal pressure, and storing the measured value of the dynamic load radius of the vehicle at the reference internal pressure for each predetermined speed region in a computer. The present invention relates to a program for initializing a reference value of a tire dynamic load radius by executing a procedure and a procedure for calculating a reference value for each speed region when a certain number of measurement values are accumulated.

  According to the present invention, there is no need to set a reference value in a speed range in which a decrease in tire internal pressure is to be determined in advance, and a measured value of the dynamic load radius of the vehicle at the reference internal pressure is distributed for each predetermined speed region. By storing and calculating a reference value for each speed region when a certain number of measurement values are stored, it is possible to set a reference value according to the vehicle.

  Hereinafter, a tire dynamic load radius reference value initialization method and apparatus and a program for initializing a tire dynamic load radius reference value according to the present invention will be described with reference to the accompanying drawings.

  1 and 2 are block diagrams showing an embodiment of an initialization apparatus of the present invention.

  As shown in FIG. 1, in the initialization apparatus according to the embodiment of the present invention, in order to detect wheel speed rotation information of the four tires FL, FR, RL and RR provided in the four-wheel vehicle, A normal wheel speed detecting means 1 provided in association with each tire is provided. The wheel speed detection means 1 generates power using rotation like a wheel speed sensor or dynamo that generates rotation pulses using an electromagnetic pickup or the like and measures wheel speed rotation information from the number of pulses. An angular velocity sensor including one that measures tire speed rotation information from voltage can be used.

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

  The output of the wheel speed detecting means 1 is given to a control unit 2 which is a computer such as ABS. A GPS device 3 is connected to the control unit 2 as a vehicle speed detection device.

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

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

  However, the tire dynamic load radius (R) is dependent on speed. That is, the faster the tire rotates, the greater the centrifugal force due to the mass of the tire tread, and the dynamic load radius increases as a function of speed (roughly proportional to the square of the speed). Therefore, it is necessary to determine the reference value for each of several speed regions.

  In addition, measurement error is included in the vehicle speed by GPS, and the difference in road surface unevenness and slipperiness affects the rotational angular velocity. Therefore, it is preferable to perform an averaging process to remove such errors. The calculation of the reference value can be realized with high accuracy in a short time by using the statistical method based on the amount of variation in the dynamic load radius due to the decrease in internal pressure and the variation in measurement. As a variation factor of the measured value, a factor due to the rotation order component of the tire is dominant, and this is a periodic variation. From such a viewpoint, it is preferable to use a weighted arithmetic moving average method as the averaging method. The number of sampling data necessary for the averaging process for calculating the reference value can be determined for each vehicle or tire. A specific method will be described later.

  In addition, since the travel distance in a fixed time becomes long, so that vehicle speed is high, the influence of an error changes with speeds. Therefore, it is desirable to change the number of data to be averaged for each speed region. If the reference value is obtained in each speed region, it is possible to determine the pressure reduction in that speed region.

  An embodiment of a calculation program for initializing the reference value of the tire dynamic load radius based on the technical matters described here will be described based on the flowchart of FIG.

  First, in step S1, vehicle travel conditions (flat road, straight line constant speed, etc.) are limited.

  Next, in steps S2 and S3, the rotation speed of each wheel at the reference internal pressure is acquired (calculated) based on the output signal of the wheel rotation speed detection device.

  In steps S4 and S5, the traveling speed of the vehicle based on the GPS information is acquired (calculated).

  In step S6, the dynamic load radius of each wheel is calculated from the rotational speed of each wheel and the GPS speed of the vehicle.

  In step S7, a combination of the dynamic load radius and the GPS speed is acquired and databased under various driving conditions.

  In step S8, the obtained dynamic load radius and GPS speed are allocated to each preset speed region.

  In step S9, necessary n and m numbers are accumulated for each speed region, which will be described later, these are compared with a reference value, and if smaller than the reference value, the process returns to the re-measurement routine. When n and m reach the reference value, in step S10, the average value of the dynamic load radii R for each speed region is calculated, and the reference value is determined. Next, tire pressure reduction determination is started based on the reference value.

  Note that initialization of the reference value ends when the reference value is calculated in all the predetermined speed regions, but the reference value is calculated in a certain speed region and the reference value calculation in the other speed region ends. If the initialization is not completed because it is not, the decompression determination may be performed only in the speed region where the reference value calculation is completed.

  Next, an embodiment of a calculation program for determining a decrease in internal pressure of a tire using the reference value initialization method will be described based on the flowchart of FIG.

  Similar to the initialization program for the tire dynamic load radius reference value in FIG. 3, in S1 to S8, the average value of the dynamic load radius in the predetermined speed region is calculated. Here, the tire dynamic load radius calculation method necessary for the pressure reduction determination is preferably the same as the calculation method and the number of sample data used at the time of initialization in the corresponding speed region.

  In S9, a difference D between the average value of the obtained dynamic load radii and the dynamic load radius reference value in the allocated speed region is calculated. If D is equal to or greater than a preset threshold, an internal pressure drop alarm is issued. If D is smaller than the threshold value, the process returns to the re-measurement routine without issuing an internal pressure drop alarm.

  It should be noted that the tire internal pressure decrease determination can be performed for each wheel individually.

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

  In order to detect the rotational angular velocity of the tire, the rotational angular velocity information used for ABS control was used and converted into the rotational angular velocity. A GPS speedometer (manufactured by Race Logic) was attached to obtain the absolute speed of the vehicle. The vehicle speed was directly output to the PC as serial data.

  These two pieces of information can be taken into the PC in synchronism as digital data every 50 msec. The dynamic load radius is calculated every 50 msec from these two pieces of information, and is calculated as an average value per second.

<Test conditions>
Vehicle: FF car Tire: 185 / 70R14 SP10
Road surface: General roads and highways in Kobe City Initial driving conditions: 1 person rides at standard internal pressure (210 kPa) Decompression test: 1 person rides at RL wheel 25% decompression (158 kPa)

<Determination of speed area>
(1) 20-40km / h
(2) 40-60km / h
(3) 60-70 km / h
(4) 70-80 km / h
(5) 80-85km / h
(6) 85-90 km / h
(7) 90-95km / h
(8) 95-100km / h
8 regions.

<Limitation of driving conditions>
The conditions determined to be traveling straight at a constant speed on a flat road were selected, the dynamic load radius was calculated, and the data was accumulated. Here, GPS information indicates that GPS reception is good and speed information is normal on condition that | G | <0.05G, azimuth change is 1 degree or less, road surface gradient is 5% or less, and the brake is not depressed. It was decided to adopt only when output.

<Data accumulation method>
The data was assigned to the previously determined 8-speed area based on GPS speed information.

<Calculation of reference value>
As a reference value averaging method, a weighted arithmetic moving average method was employed, and an average value of 10 data was further averaged to calculate a reference value in the speed range. A method of determining the average number for calculating the reference value is shown below.
(1) Sampling a large number of data in a certain speed range in the initialization running condition.
(2) A moving average is performed for several n numbers to obtain time-series data X.
(3) The data X is further subjected to moving average for some m numbers to obtain time series data Y.
(4) Any number of Y is possible depending on the combination of n and m, and the standard deviation σ is obtained for the time series data Ynm.
(5) The dynamic load radius of the tire can be measured by performing a drum experiment. The dynamic load radius was measured at a target speed by applying a load corresponding to the axle load of the target vehicle. The internal pressure was measured at two levels: normal pressure and pressure targeted for detection. In the case of this example, the tire was 185 / 70R14 SP10, the load was 2.5 kPa, the internal pressure was 210 kPa and 158 kPa, and the speed was the center speed of the above eight regions. At this time, the reduction margin of the dynamic load radius due to the reduction of the internal pressure was about 0.6 mm.
(6) As shown in FIG. 5, for each data group at the time of reduced pressure and normal internal pressure, when 3σ (σ is a standard deviation) is 0.1 mm or less, each data group has a probability of 99.9% or more. As a result, the distance d is 0.4 mm or more. Therefore, in order to accurately detect that the difference D between the average values of each data group is 0.6 mm or more, the target value of σ is set to 0.033 mm or less.
(7) From the combination of (4), the minimum (n + m) that achieves the above (6) was obtained, and n and m were set as the optimum number of samples for averaging.

  When the reference value is obtained, the initialization in the speed region is finished and the region is closed. Here, if the reference value is obtained in a certain speed region before the reference value is obtained in all speed regions (8 regions), the pressure reduction determination is executed.

<Decompression judgment>
The measurement value calculation method for determining the reduced pressure used 10 and 50 moving averages determined in the initialization. At this time, an alarm is issued when it is judged that the criterion is reduced by 0.4 mm or more.

<Running results>
The initialization of the speed range: 40 to 60 km / h was completed after traveling for about 20 minutes. Thereafter, when the vehicle was driven in a 25% reduced pressure state, the reduced pressure was detected in about 3 minutes.

It is a block diagram which shows one Embodiment of the reference value initialization apparatus of the tire dynamic load radius of this invention. It is a block diagram which shows the electric constitution of the reference value initialization apparatus of FIG. It is a flowchart which shows one Embodiment of the calculation program for initializing the reference value of the tire dynamic load radius concerning this invention. It is a flowchart which shows one Embodiment of the calculation program for the tire internal pressure fall determination concerning this invention. It is a schematic diagram which shows distribution of the sampling data of a tire dynamic load radius.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wheel speed detection means 2 Control unit 3 GPS apparatus 3a GPS antenna

Claims (4)

The tire dynamic load radius of the running vehicle is calculated from the vehicle speed information by GPS and the tire rotation speed information, and the decrease in the internal pressure of the tire is determined by the magnitude of the change from the reference value of the dynamic load radius at the time of the reference internal pressure. A method for initializing the reference value,
A process of distributing and accumulating the measured value of the dynamic load radius of the vehicle at the time of the reference internal pressure for each predetermined speed area, and a reference value for each speed area when a certain number of the measured values are accumulated , look including the step of calculating the averaging process by the weighted arithmetic moving average method,
A tire dynamic load radius reference value initialization method for changing the number of measurement values to be averaged for each speed region . A tire pressure drop judging method including the reference value initialization method of the tire dynamic load radius of claim 1 Symbol placement,
The vehicle speed and the dynamic load radius in any one of the speed regions are measured, and the dynamic load radius corresponding to the vehicle speed is obtained by averaging the obtained data, and compared with the reference value set at the vehicle speed. A method for determining a decrease in internal pressure of a tire including a step. The tire dynamic load radius of the running vehicle is calculated from the vehicle speed information by GPS and the tire rotation speed information, and the decrease in the internal pressure of the tire is determined by the magnitude of the change from the reference value of the dynamic load radius at the time of the reference internal pressure. A device for initializing the reference value,
Means for allocating and storing the measured value of the dynamic load radius of the vehicle at the reference internal pressure for each predetermined speed region, and a reference value for each speed region when a certain number of the measured values are accumulated , look including a means for calculating by averaging by the weighted arithmetic moving average method,
A tire dynamic load radius reference value initialization device for changing the number of measurement values to be averaged for each speed region . The tire dynamic load radius of the running vehicle is calculated from the vehicle speed information by GPS and the tire rotation speed information, and the decrease in the internal pressure of the tire is determined by the magnitude of the change from the reference value of the dynamic load radius at the time of the reference internal pressure. A program for initializing the reference value,
Procedures for storing and storing the measured value of the dynamic load radius of the vehicle at the reference internal pressure for each predetermined speed area in the computer, and the reference for each speed area when a certain number of the measured values are accumulated values by the Turkey to execute the steps of calculating by averaging by the weighted arithmetic moving average method, a program for initializing a reference value of the radius tire dynamic load,
A program for initializing the tire dynamic load radius reference value that changes the number of measured values to be averaged for each speed region .

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