JP4615791B2 - Tire pressure drop detection method and apparatus, and tire decompression determination program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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 air pressure drop detection method and apparatus capable of improving the accuracy of pressure reduction detection, and a tire pressure reduction determination program.
[0002]
[Background Art and Problems to be Solved by the Invention]
A conventional apparatus (DWS system) for detecting a decrease in tire air pressure has four ABS wheel speed sensors based on the fact that the wheel speed increases when the tire dynamic load radius decreases when the tire air pressure decreases. The tire pressure is judged from the wheel speed. In the tire pressure reduction determination in this apparatus, a determination value obtained by comparing the difference between the two diagonal sums of the wheel speed of the front tire and the wheel speed of the rear tire is used.
[0003]
Here, 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 always the same.
[0004]
Therefore, it is necessary to learn the initial value of the tire. For this reason, the DWS is provided with a process called “initialization”, and an initial value for correcting variations in manufacturing of the tire is learned by this process. In addition, the learned initial value is stored in a non-volatile storage device (hereinafter referred to as EEPROM) so that it does not disappear even if the ignition switch of the vehicle is turned off.
[0005]
Conventionally, each time the initial value is updated, the updated initial value is stored in the EEPROM.
[0006]
However, when the DWS is mounted on a microcomputer for a vehicle control system such as ABS, the processing time becomes a problem with the above-described method.
[0007]
In other words, writing to the EEPROM takes a considerable amount of time, but when the processing time is measured by a commonly used microcomputer, the processing time required for initial value learning and air pressure alarm determination in the one-second processing of DWS. It was found that writing to the EEPROM requires about 200 msec for a storage capacity of about 50 bytes, while it is about 100 msec.
[0008]
When the processing capacity of the microcomputer is sufficient, the time required for the writing does not matter. However, when ABS and DWS are processed simultaneously by one microcomputer, the writing time is long (long Too much) may be overtime.
[0009]
Normally, when the DWS processing time is over, the next one-second processing is canceled. For this reason, it is considered that the running data for one second is discarded due to the writing time of the EEPROM.
[0010]
In view of the above circumstances, 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 improve the accuracy of tire decompression detection.
[0011]
[Means for Solving the Problems]
The tire pressure drop detecting method of the present invention is a tire pressure drop detecting method for detecting a tire internal pressure drop based on rotation information obtained from a tire mounted on a vehicle, and updates the initial value of the tire, A method for detecting a decrease in tire air pressure, comprising a step of writing the updated initial value to the EEPROM from the relationship between the count of the request for writing the updated initial value to the EEPROM and the speed of the vehicle.
[0012]
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. A rotation information detecting means; a rotation information storing means for storing the rotation information of each tire; an update determining means for determining whether or not to update an initial value of the tire; a vehicle speed calculating means for calculating a vehicle speed; Vehicle speed determining means for determining whether the vehicle speed is low speed driving or high speed driving when the vehicle is stopped, counter means for counting a write request to the EEPROM of the updated initial value, and the initial value of the tire After the update, the update initial value is written to the EEPROM from the relationship between the count of the write request for the update initial value to the EEPROM and the speed of the vehicle. A write execution means for performing, characterized by comprising a decompression judging means for judging a decreased air pressure of the tire.
[0013]
Further, the tire decompression determination program of the present invention is a computer for determining a decrease in tire air pressure, a rotation information storage means for storing rotation information of each tire, and an update for determining whether or not to update the initial value of the tire. Determining means; vehicle speed calculating means for calculating vehicle speed; vehicle speed determining means for determining whether the vehicle speed is low speed driving or high speed driving when the vehicle is stopped; a request to write the updated initial value to the EEPROM After updating the initial value of the tire, the counter means for counting the initial value of the updated initial value to the nonvolatile storage device of the updated initial value from the relationship between the count of the write request to the EEPROM and the speed of the vehicle It is characterized by functioning as writing execution means for performing writing, and pressure reduction determination means for determining a decrease in tire air pressure.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
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.
[0015]
FIG. 1 is a block diagram showing an embodiment of a tire pressure drop detecting device of the present invention, FIG. 2 is a block diagram showing an electrical configuration of the tire pressure drop detecting device of FIG. 1, and FIG. 3 is related to this embodiment. It is an example of a flowchart.
[0016]
As shown in FIG. 1, a tire pressure drop detecting device according to an embodiment of the present invention includes, for example, 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 rotation information detection means 1 provided in association with each other.
[0017]
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 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.
[0018]
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 includes 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 the initial learning value and the updated initial value are written. Yes.
[0019]
Based on the wheel speed pulse output from the rotation information detecting means 1, the CPU 2b calculates the rotation angular velocity F _i of each tire Wi every predetermined sampling period ΔT (sec), for example, ΔT = 1 second. Then, the vehicle speed is calculated from the rotational angular speed F _i of each tire Wi.
[0020]
A part of the storage area of the RAM 2d is used as a counter used in writing to the EEPROM 2e. The reason why the initial learning value (update initial value) is written in the EEPROM 2e is to hold the learning value even when the ignition switch of the vehicle is turned off. Normally, the driver does not turn off the ignition while traveling, so the initial learning value and the updated initial value may be stored before the driver turns off the ignition.
[0021]
Since the initial value is usually manufactured including variations (initial differences) within the standard, the correction coefficient for canceling the variations due to the initial differences given to the initial tires Wi is a left-right wheel ratio correction coefficient. Fac1, Fac2, front and rear wheel ratio correction coefficient Fac3, and the like.
[0022]
Here, Fac1 = (V _FL / V _FR )
Fac2 = (V _RL / V _RR )
Fac3 = (V _FL + V _FR ) / (V _RL + V _RR )
It is.
[0023]
Then, an initial value for correcting the variation in manufacturing of the tire is learned at the time of DWS initialization processing. Further, the initial values Fac1 and Fac2 are updated when the state regarded as straight traveling continues for 6 seconds, and the initial value Fac3 is updated when neutral traveling (state where the engine torque is regarded as zero) continues for 2 seconds. The When this initial value is updated, the write request counter is incremented. Once the data is written to the EEPROM 2e, the count becomes zero. However, even if there is a write request, the data is not written to the EEPROM 2e during high speed running, so the count number is accumulated.
[0024]
The process until the driver turns off the ignition is usually as follows: ignition on → travel → ... deceleration → stop → ignition off. The process of stopping is included.
[0025]
The DWS cannot perform air pressure judgment at low speeds, for example, about 30 km / h or less, so if writing to the EEPROM 2e when stopping from low speeds, even if the DWS processing time is over, the running data for one second is saved. Even if thrown away, the air pressure cannot be determined in the speed range, so there is no substantial disadvantage. On the other hand, when traveling data is obtained without time-over, the number of traveling data used for determination increases, more efficient air pressure determination can be performed, and the detection accuracy of tire decompression can be improved.
[0026]
In the present embodiment, the rotation information detection means 1 for detecting the rotation information of each tire Wi, the rotation information storage means for storing the rotation information of each tire Wi, and the initial value of the tire Wi are updated. An update determination means for determining whether the vehicle speed is a low speed running or a high speed running when the vehicle is stopped, and the update. Counter means for counting a request for writing the initial value into the nonvolatile storage device, and after updating the initial value of the tire, the number of requests for writing the updated initial value into the nonvolatile storage device and the vehicle speed Therefore, there are provided a writing execution means for writing the updated initial value to a nonvolatile storage device, and a decompression determination means for determining a decrease in tire air pressure.
[0027]
In addition, the writing means may write the updated initial value to the EEPROM 2e when the vehicle is stopped or running at a low speed or the count number is equal to or greater than a predetermined value until the count number is less than a predetermined value by the counter means. In this case, the updated initial value may be written to the EEPROM 2e when the vehicle is stopped, when traveling at a low speed, or when traveling at a high speed.
[0028]
In determining the count number and the vehicle speed, for example, when the count number is a predetermined value 30 or more, writing to the EEPROM 2e is performed when the vehicle is stopped, when traveling at a low speed, or when traveling at a high speed. This is because the initial learning value in the middle stage is stored even if the ignition is turned off during the driving.
[0029]
Further, the decompression determination value (DEL) for detecting the decrease in the air pressure of the tire Wi is, for example, a difference between two diagonal sums of a front tire and a rear tire, and is a pair of diagonal lines. The sum of the signals from the other pair of wheels on the diagonal line is subtracted from the sum of the signals from the wheels, and the ratio between the result and the average value of the two sums is obtained from the following equation (1).
[0030]
DEL = {(V1 + V4) / 2- (V2 + V3) / 2} / {(V1 + V2)
+ V3 + V4) / 4} × 100 (%) (1)
[0031]
The tire decompression determination program in the present embodiment updates the control unit 2 to determine whether or not the rotation information storage means for storing the rotation information of each tire Wi and the initial value of the tire Wi have been updated. Determining means; vehicle speed calculating means for calculating vehicle speed; vehicle speed determining means for determining whether the vehicle speed is low speed driving or high speed driving when the vehicle is stopped; a request to write the updated initial value to the EEPROM After updating the initial value of the tire, the counter means for counting the initial value of the updated initial value to the nonvolatile storage device of the updated initial value from the relationship between the count of the write request to the EEPROM and the speed of the vehicle It is made to function as writing execution means for writing and pressure reduction determination means for determining a decrease in tire air pressure.
[0032]
In addition, the control unit 2 counts the number of requests for writing the updated initial value into the EEPROM 2e, and the counter means counts the number of requests for writing the updated initial value into the EEPROM 2e. In this case, it is further made to function as second writing execution means for writing the updated initial value to the EEPROM 2e regardless of whether the vehicle is stopped or traveling at a low speed.
[0033]
Next, the present invention will be described based on examples, but the present invention is not limited to such examples.
[0034]
Example A vehicle equipped with tires with normal air pressure (2.2 × 10 ⁴ Pa) was prepared. The tire size is 185 / 70R14. Further, the vehicle was run on a test course while swinging the vehicle speed randomly (10 km / h to 100 km / h).
[0035]
Then, as shown in FIG. 3, first, as the initial value learning of the tire while running the vehicle, the Fac1, Fac2, and Fac3 conditions are determined and the values are calculated (step S1), and then the initial value learning is performed in step S2. Whether or not the above condition is satisfied is determined. If the condition is satisfied, the initial value is calculated and the initial value is updated. When updating the initial value, the write request counter is counted up and the count number is accumulated (step S3). Then, an EEPROM write determination process is performed.
[0036]
In the write determination process, the following procedure is performed as shown in FIG. That is, when the vehicle speed is 30 km / h or less and the count value is 1 or more, writing to the EEPROM is performed (steps S4 and S5).
[0037]
Further, in this embodiment, as described above, even if the ignition is turned off during driving, the updated initial value in the middle is stored, so when the count value is 30 or more, the vehicle speed is set. Regardless, writing to the EEPROM was performed (steps S4 and S6). Thereafter, the count number is set to zero.
[0038]
In this embodiment, the obtained vehicle travel data is stored in a DAT (Digital Audio Tape) recorder, then processed by a microcomputer storing a program for writing to EEPROM, and the time until initialization is completed is calculated. .
[0039]
Further, as shown in FIG. 5 as a comparative example, after updating the initial value in the same manner as in the prior art (steps S11 and S12), the writing process to the EEPROM was immediately performed (step S13). The same amount of travel data as in the previous embodiment was processed by a microcomputer storing the program for writing to the EEPROM, and the time until completion of initialization was calculated (comparative example).
[0040]
Next, the time until the completion of initialization using the same traveling data was compared between the present example and the comparative example. As a result, in this example, the initial value learning was completed at 1 hour 32 minutes 49 seconds, whereas in the comparative example, the initial value learning was completed in 1 hour 47 minutes 12 seconds longer than this example. As a result, this embodiment can prevent the running data from being discarded due to the excessive processing time due to the writing time to the EEPROM, and thus it can be seen that the time until the initialization is completed is shortened. .
[0041]
【The invention's effect】
As described above, according to the present invention, the EEPROM is written based on the relationship between the count number and the vehicle speed, and more efficient air pressure determination can be performed without wasting the number of travel data. Become. Thereby, the detection accuracy of tire decompression can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a tire pressure drop detecting device according to the present invention.
FIG. 2 is a block diagram showing an electrical configuration of the tire pressure drop detecting device of FIG. 1;
FIG. 3 is an example of a flowchart up to an EEPROM write determination process according to the present embodiment.
4 is an example of a flowchart of an EEPROM write determination process in FIG. 3;
FIG. 5 is an example of a flowchart up to a conventional writing process to an EEPROM;
[Explanation of symbols]
1 Rotation information detection means 2 Control unit 3 Display 4 Initialization switch

Claims (6)

A tire pressure drop detecting method for detecting a drop in tire internal pressure based on rotation information obtained from a tire mounted on a vehicle, wherein the initial value of the tire is updated, and then the updated initial value is stored in a nonvolatile storage device From the relationship between the count of the write request and the vehicle speed, a method for detecting a decrease in tire air pressure including a step of writing the updated initial value to a nonvolatile storage device,
Said count number to less than the predetermined value, the update initial value nonvolatile line song tire pressure drop detecting method to write when the vehicle stopped or low-speed running of the storage device. A tire pressure drop detecting method for detecting a drop in tire internal pressure based on rotation information obtained from a tire mounted on a vehicle, wherein the initial value of the tire is updated, and then the updated initial value is stored in a nonvolatile storage device From the relationship between the count of the write request and the vehicle speed, a method for detecting a decrease in tire air pressure including a step of writing the updated initial value to a nonvolatile storage device,
Wherein when the count number is equal to or greater than a predetermined value, the time of writing the vehicle stop to the nonvolatile storage device updates the initial value, the row song tire pressure drop detecting method at the time of low-speed running time or high-speed running. 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. Rotation information storage means for storing the vehicle, update determination means for determining whether or not to update the initial value of the tire, vehicle speed calculation means for calculating the vehicle speed, and when the vehicle speed is stopped, the vehicle runs at low speed or high speed. Vehicle speed judgment means for judging whether or not the counter, counter means for counting a write request to the nonvolatile storage device of the updated initial value, and the initial value of the tire after updating the initial value Write execution means for writing the updated initial value to the non-volatile storage device from the relationship between the count of the write request to the non-volatile storage device and the vehicle speed The a tire pressure drop detecting device including a determining decompression judging means for lowering tire pressure,
It said write implementation means, by said counter means, the count number to less than the predetermined value, the updating the initial value of the non-volatile means der filter tire air pressure for writing when the vehicle stopped or low-speed running to the storage device Drop detection device. 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. Rotation information storage means for storing the vehicle, update determination means for determining whether or not to update the initial value of the tire, vehicle speed calculation means for calculating the vehicle speed, and when the vehicle speed is stopped, the vehicle runs at low speed or high speed. Vehicle speed judgment means for judging whether or not the counter, counter means for counting a write request to the nonvolatile storage device of the updated initial value, and the initial value of the tire after updating the initial value Write execution means for writing the updated initial value to the non-volatile storage device from the relationship between the count of the write request to the non-volatile storage device and the vehicle speed The a tire pressure drop detecting device including a determining decompression judging means for lowering tire pressure,
Means for writing the updated initial value to a non-volatile storage device when the vehicle is stopped, at a low speed or at a high speed, when the count means has a count value greater than or equal to a predetermined value by the counter means; der Ruta tire pressure drop detecting device. Computer for determining a decrease in tire air pressure, rotation information storage means for storing rotation information of each tire, update determination means for determining whether or not to update the initial value of the tire, vehicle speed calculation means for calculating the vehicle speed Vehicle speed determining means for determining whether the vehicle speed is low speed driving or high speed driving when the vehicle is stopped, counter means for counting a write request to the nonvolatile storage device for the updated initial value, After updating the initial value of the tire, the updated initial value is written to the nonvolatile storage device based on the relationship between the count of the request for writing the updated initial value to the nonvolatile storage device and the vehicle speed. Write execution means, a tire decompression determination program for functioning as a decompression determination means for determining a decrease in tire air pressure,
Said write implementation means, said by the counter means, the count number to less than a predetermined value, said updated initial value to write to the nonvolatile storage device rows songs unpleasant deflation judgment when the vehicle is stopped or low-speed traveling program. Computer for determining a decrease in tire air pressure, rotation information storage means for storing rotation information of each tire, update determination means for determining whether or not to update the initial value of the tire, vehicle speed calculation means for calculating the vehicle speed Vehicle speed determining means for determining whether the vehicle speed is low speed driving or high speed driving when the vehicle is stopped, counter means for counting a write request to the nonvolatile storage device for the updated initial value, After updating the initial value of the tire, the updated initial value is written to the nonvolatile storage device based on the relationship between the count of the request for writing the updated initial value to the nonvolatile storage device and the vehicle speed. Write execution means, a tire decompression determination program for functioning as a decompression determination means for determining a decrease in tire air pressure,
The writing execution means writes the updated initial value to the nonvolatile storage device when the vehicle is stopped, at low speed driving or at high speed driving when the counter means counts a predetermined value or more. song hate judging decompression of the program.

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