JP2004322700A - Tire air pressure determination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly determine whether or not an air pressure is normally returned after it is determined that the air pressure of a tire is abnormal in a vehicle. <P>SOLUTION: When it is determined that the air pressure of the tire is abnormal ("abnormal determination" is varied from "0" to "1"), regarding a resonance frequency f of vibration of the tire obtained thereafter and a dynamic load radius reflection value α, it is determined whether or not the previously determined returning determination condition holds. When it holds, it is determined that the air pressure of the tire is returned to the normal state ("returning determination (relative determination)" is varied from "0" to "1"). The returning determination condition holds when respective increase amounts from when it is determined that the air pressure of the tire is abnormal become increase degrees Δf, Δα or more regarding both the resonance frequency f and the dynamic load radius reflection value α. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technology for determining whether or not the tire air pressure in a vehicle is abnormal, and in particular, whether or not the tire pressure has returned to normal after it has been determined that the tire air pressure is abnormal. The present invention relates to an improvement in the technique for determining
[0002]
[Prior art]
2. Description of the Related Art There is already a technology for detecting tire air pressure for the purpose of finding a tire abnormality in a vehicle while the vehicle is running. This technology is classified into a direct detection type and an indirect detection type from the viewpoint of a method of detecting tire pressure.
[0003]
In the direct detection type, a pressure sensor that detects tire air pressure and wirelessly transmits the detected value to the vehicle body is used by being mounted on the tire itself. The tire pressure is directly detected by the pressure sensor.
[0004]
On the other hand, in the indirect detection type, for example, a wheel speed sensor that detects an angular velocity of a wheel configured by mounting a tire on a wheel as a wheel speed is used by being mounted on a vehicle body side. The tire pressure is indirectly detected by the wheel speed sensor.
[0005]
In one specific example, the indirect detection type tire pressure detecting device acquires a tire pressure reflecting value related to the wheel and reflecting the tire pressure based on the wheel speed detected by the wheel speed sensor, and the acquired tire pressure reflecting value. Is configured to include an estimator that estimates the tire pressure based on
[0006]
Some specific systems for detecting the tire pressure by the indirect detection system have already been proposed.
[0007]
One of them is a dynamic load radius method. In this method, if the air pressure of the tire changes, the dynamic load radius of the tire changes, and the angular velocity of the tire, that is, the phenomenon that the wheel speed detected by the wheel speed sensor also changes, is focused on. A dynamic load radius reflection value reflecting the dynamic load radius is calculated based on the wheel speed, and a tire air pressure is detected based on the calculated dynamic load radius reflection value.
[0008]
In this dynamic load radius method, the dynamic load radius reflection value constitutes an example of the air pressure reflection value. A conventional example of the dynamic load radius method is described in Japanese Patent Application Laid-Open No. 8-164720.
[0009]
Another method is a tire vibration method. In this method, if the air pressure of the tire changes, the characteristics of the vibration of the tire change, and attention is paid to the phenomenon that the change is reflected in the wheel speed. A vibration characteristic value is calculated, and a tire air pressure is detected based on the calculated tire vibration characteristic value.
[0010]
In this tire vibration method, the tire vibration characteristic value constitutes an example of the air pressure reflection value.
[0011]
The tire vibration method includes a resonance frequency method and a disturbance observer method.
[0012]
In the resonance frequency method, attention is paid to the phenomenon that the resonance frequency of the vibration of the tire changes when the air pressure of the tire changes, and the resonance frequency is detected as the tire vibration characteristic value based on the wheel speed, and the detection is performed. The tire pressure is estimated based on the obtained resonance frequency. One conventional example of the resonance frequency system is described in Japanese Patent No. 2836652.
[0013]
On the other hand, in the disturbance observer method, based on the knowledge that according to the modern control theory of a disturbance observer, it is possible to estimate a change in tire air pressure as a disturbance to the tire, the disturbance is determined based on the wheel speed. The tire vibration characteristic value is calculated, and the tire pressure is estimated based on the calculated disturbance. A conventional example of the disturbance observer method is described in Japanese Patent Application Laid-Open No. 2000-238516.
[0014]
In any case, when the tire air pressure is detected, it is determined whether or not the tire is abnormal based on the detected value. A device having such a detecting function and a determining function can be referred to as a tire air pressure determining device.
[0015]
When it is determined that the tire pressure is abnormally low by this type of tire pressure determination device, the vehicle user can replenish air into the tire determined to have abnormal tire pressure, or Work such as replacing it with a new one.
[0016]
The tire pressure determination device may need information indicating that the tire pressure has returned to normal. The tire pressure determination device can be designed to wait for an input from the vehicle user and confirm the fact that the tire pressure has returned to normal.
[0017]
However, in this case, for example, even though the tire pressure has actually returned to normal, the user of the vehicle forgets to input information indicating that, or the tire pressure is actually normal. If the user of the vehicle erroneously inputs information indicating that the tire pressure has returned to normal even though the tire pressure has not returned to normal, the normal operation of the tire pressure determination device cannot be guaranteed.
[0018]
Therefore, a technology for automatically detecting that the tire pressure has returned to normal has already been known (see Patent Document 1).
[0019]
[Patent Document 1]
JP-A-10-250324
According to the technology described in Patent Literature 1, when it is determined that the tire air pressure is abnormal, it is then determined whether the dynamic load radius reflection value is less than a constant value near zero. In this conventional technique, the dynamic load radius reflection value is defined to be 0 when the tire air pressure is normal, that is, when the tire pressure is equal to the set pressure. In this prior art, when it is determined that the dynamic load radius reflection value is less than a certain value near 0, it is determined that the tire pressure has returned to normal.
[0020]
Therefore, according to this conventional technique, it is possible to detect that the tire pressure has returned to normal without any specific input by the vehicle user.
[0021]
[Problems to be solved by the invention]
However, when implementing this conventional technique, it is not determined that the tire air pressure has returned to normal unless the tire air pressure recovers above the set pressure. That is, when air is replenished in the tire because the air pressure of the tire is determined to be abnormally low, if the air pressure does not increase beyond the set pressure, even if the air pressure increases to some extent after the abnormality determination, It is not determined that the tire pressure has returned to normal.
[0022]
Therefore, when the conventional technique is implemented, the accuracy of the return determination is emphasized, but the responsiveness of the return determination to a change in the tire air pressure is sacrificed.
[0023]
Based on the findings described above, the present invention has been made to provide an object to quickly determine whether or not the tire pressure in the vehicle is abnormal after the tire pressure is determined to be abnormal.
[0024]
Means for Solving the Problems and Effects of the Invention
The following aspects are obtained by the present invention. Each aspect is divided into sections, each section is numbered, and if necessary, described in a form in which the numbers of other sections are cited. This is to facilitate understanding of some of the technical features described in the present specification and some of the combinations thereof, and the technical features and the combinations thereof described in the present specification have the following aspects. It should not be construed as limited.
(1) A device is provided in a vehicle having a wheel configured such that air is sealed under pressure inside a tire mounted on a wheel, and determines whether or not the air pressure of the tire is abnormal.
An air pressure reflection value acquisition unit that acquires a value reflecting the air pressure as a plurality of air pressure reflection values according to a plurality of predetermined acquisition rules, respectively,
For a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit, when a predetermined abnormality determination condition is satisfied, an abnormality determination unit that determines that the tire air pressure is abnormal,
When a plurality of types of air pressure reflection values obtained by the air pressure reflection value obtaining unit after the air pressure of the tire is determined to be abnormal by the abnormality determination unit, a predetermined return determination condition is satisfied, A return determining unit that determines that the tire pressure has returned to normal;
A tire pressure determination device, wherein the return determination unit includes condition changing means for changing the return determination condition based on at least one of the plurality of types of air pressure reflection values.
[0025]
If the return determination condition to be satisfied to determine that the tire pressure has returned to normal after the determination that the tire air pressure is abnormal is set as a fixed condition, the return determination condition may be excessive depending on the timing. It can be strict.
[0026]
On the other hand, if the return determination condition is set to change based on at least one of the plurality of types of air pressure reflection values, the return determination condition should flexibly follow the at least one air pressure reflection value. It becomes.
[0027]
Therefore, according to this setting, it is easy to reduce the possibility that the return determination condition becomes excessively strict. That is, it is desirable to change the return determination condition so as to conform to at least one of the plurality of types of air pressure reflection values in order to improve the responsiveness of the return determination to a change in tire air pressure after the abnormality determination.
[0028]
Based on such knowledge, in the device according to this section, the return determination condition is changed based on at least one of a plurality of types of air pressure reflection values.
(2) The condition changing means is based on at least one of a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit when the abnormality judgment unit judges that the tire air pressure is abnormal. (1) The tire pressure judging device according to (1), further comprising means for changing the return judging condition.
[0029]
According to this device, when the abnormality determination unit determines that the tire air pressure is abnormal, the abnormality determination is performed based on at least one of the plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit. A return determination condition that should be satisfied later to determine that the tire pressure has returned to normal is relatively determined.
[0030]
Therefore, according to this device, the change in the tire air pressure after the abnormality determination is at least one of a plurality of types of air pressure reflection values when the tire air pressure is determined to be abnormal, and is not a fixed value but a variable. It is possible to relatively grasp based on the value.
[0031]
Therefore, according to this device, as a result, instead of relying on the absolute value of the air pressure reflection value after the abnormality determination, it is based on the relative value to the air pressure reflection value when the tire air pressure is determined to be abnormal. It is determined whether or not the tire pressure has returned to normal.
(3) The return determination unit further determines whether the return determination condition is satisfied by comparing corresponding ones of the plurality of types of air pressure reflection values and the plurality of return determination thresholds. The condition changing means determines at least one of the plurality of return determination thresholds as a variable value based on a corresponding one of the plurality of types of air pressure reflection values. The tire pressure judging device according to item (2), including a threshold value determining unit.
[0032]
In this device, the success or failure of the return determination condition is determined by comparing mutually corresponding ones of the plurality of types of air pressure reflection values and the plurality of return determination thresholds. Further, at least one of the plurality of return determination thresholds is determined as a variable value based on a corresponding one of the plurality of types of air pressure reflection values. As a result, the return determination condition is eventually changed based on at least one of the plurality of types of air pressure reflection values.
(4) The threshold value determination unit acquires the at least one return determination threshold value by the air pressure reflection value acquisition unit when the abnormality determination unit determines that the tire air pressure is abnormal. The tire pressure judging device according to item (3), further including a unit that relatively determines a corresponding one of the plurality of types of reflected air pressure values.
[0033]
According to this device, the return determination threshold value is determined so as to follow a corresponding one of a plurality of types of air pressure reflection values when it is determined that the tire air pressure is abnormal.
[0034]
Therefore, according to this device, as a result, not by the absolute value of the air pressure reflection value after abnormality determination, but by relying on the relative value to the air pressure reflection value when it is determined that the tire air pressure is abnormal. It is determined whether or not the tire pressure has returned to normal.
(5) the vehicle includes a wheel speed sensor that detects an angular speed of the wheel as a wheel speed;
The plurality of types of air pressure reflection values include a dynamic load radius reflection value reflecting a dynamic load radius of the tire, and a tire vibration characteristic value reflecting characteristics of vibration of the tire,
The air pressure reflection value acquisition unit includes means for acquiring the dynamic load radius reflection value and the tire vibration characteristic value based on a wheel speed detected by the wheel speed sensor,
Thus, the tire pressure determination device according to any one of (1) to (4), wherein the tire pressure is indirectly detected and determined.
(6) The tire pressure judging device according to (5), wherein the tire vibration characteristic value includes a resonance frequency of vibration of the tire.
(7) The tire pressure determination device according to (6), wherein the condition changing unit includes a unit that changes the return determination condition based on the resonance frequency.
[0035]
When the dynamic load radius reflection value and the tire vibration resonance frequency are compared with each other, there is a tendency that, for various reasons, the determined value of the resonance frequency can be obtained in a shorter time than the dynamic load radius reflection value. Therefore, if the return determination condition is changed based on the resonance frequency, the responsiveness of the return determination condition is improved, and it is possible to quickly determine that the tire pressure has returned to normal. .
[0036]
Based on such knowledge, in the device according to this section, the return determination condition is changed based on the resonance frequency of the tire vibration.
(8) An apparatus provided in a vehicle having a wheel configured such that air is sealed under pressure inside a tire mounted on a wheel, and configured to determine whether or not the air pressure of the tire is abnormal,
An air pressure reflection value acquisition unit that acquires a value reflecting the air pressure as a plurality of air pressure reflection values according to a plurality of predetermined acquisition rules, respectively,
For a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit, when a predetermined abnormality determination condition is satisfied, an abnormality determination unit that determines that the tire air pressure is abnormal,
When a plurality of types of air pressure reflection values obtained by the air pressure reflection value obtaining unit after the air pressure of the tire is determined to be abnormal by the abnormality determination unit, a predetermined return determination condition is satisfied, A return determining unit that determines that the tire pressure has returned to normal;
And, the return determination condition is related to at least one of the plurality of types of air pressure reflection values, and the amount of change from when the air pressure of the tire is determined to be abnormal by the abnormality determination unit is a set amount. A tire pressure judging device that is established when the tire pressure has been reached.
[0037]
According to this device, the tire air pressure is not based on the absolute value of the air pressure reflected value after the abnormality determination, but on the amount of change in the air pressure reflected value from when the tire air pressure is determined to be abnormal. It is possible to determine whether or not the normal state has been restored.
(9) A device which is provided in a vehicle having a wheel configured such that air is sealed under pressure inside a tire mounted on a wheel and determines whether or not the tire pressure is abnormal,
An air pressure reflection value acquisition unit that acquires a value reflecting the air pressure as a plurality of air pressure reflection values according to a plurality of predetermined acquisition rules, respectively,
For a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit, when a predetermined abnormality determination condition is satisfied, an abnormality determination unit that determines that the tire air pressure is abnormal,
When a plurality of types of air pressure reflection values obtained by the air pressure reflection value obtaining unit after the air pressure of the tire is determined to be abnormal by the abnormality determination unit, a predetermined return determination condition is satisfied, A return determining unit that determines that the tire pressure has returned to normal;
And, the return determination condition, the plurality of types of air pressure from a value that matches a preset pressure set in advance for the tire to function normally to a value that is shifted to the side where the tire air pressure is abnormal A tire pressure determination device that is established when at least one of the reflection values has reached.
[0038]
In this device, the same event related to the tire pressure is observed by a plurality of kinds of pressure reflection values. On the other hand, when the same event is comprehensively determined by a plurality of types of air pressure reflection values, compared with a case where the same event is solely determined by one air pressure reflection value, the final judgment result is an error of one air pressure reflection value. You don't have to be so affected.
[0039]
Therefore, when the same event is comprehensively determined by a plurality of types of air pressure reflection values, it is easy to improve the accuracy of the determination. Therefore, even if the conditions to be satisfied by a plurality of types of air pressure reflection values are relaxed in order to determine that the tire air pressure has returned to normal, a large error does not occur in the final judgment.
[0040]
In short, when observing the same event with a plurality of types of air pressure reflection values, it is necessary to improve the responsiveness of the recovery determination with respect to the change in the tire air pressure while ensuring the accuracy of the recovery determination that the tire air pressure has returned to normal. It is easy to improve.
[0041]
Based on the knowledge described above, in the device according to this section, after it is determined that the tire air pressure is abnormal, a predetermined set pressure (hereinafter simply referred to as “tire setting”) for the tire to function normally is used. When at least one of the plurality of types of air pressure reflection values reaches a value that deviates from the value that matches the "pressure") to the side where the air pressure of the tire is abnormal, it is determined that the air pressure of the tire has returned to normal. .
[0042]
Therefore, according to this device, it is determined that the tire pressure has returned to normal without waiting for at least one of the plurality of types of air pressure reflection values to reach a value matching the set pressure of the tire.
[0043]
Therefore, according to this device, it is easy to improve the responsiveness of the return determination to a change in the tire air pressure while ensuring the accuracy of the return determination that the tire air pressure has returned to normal.
(10) The return determination unit determines whether the return determination condition is satisfied by comparing corresponding ones of the plurality of types of air pressure reflection values and the plurality of return determination thresholds. Means, and
The tire air pressure judging device according to item (9), wherein at least one of the plurality of return judgment threshold values is a value shifted from a value matching the set pressure to a side where the air pressure of the tire is abnormal.
[0044]
According to this device, after it is determined that the tire pressure is abnormal, the tire pressure returns to normal without waiting for at least one return determination threshold to reach a value matching the set pressure. It is possible to determine that it has been done.
(11) The return determination condition includes a plurality of individual return determination conditions that are predetermined with respect to the plurality of types of air pressure reflection values, respectively, and the return determination unit performs all of the plurality of individual return determination conditions. The tire pressure judging device according to any one of (1) to (10), including means for judging that the air pressure of the tire has returned to normal when the condition (1) is satisfied.
[0045]
When the return determination condition is formed from only one predetermined condition for one air pressure reflection value, it is desirable that the return determination condition be strictly defined in order to improve the accuracy of the return determination. For example, it is desirable to define the return determination condition so that the condition is satisfied when the air pressure of the tire certainly exceeds the set pressure after the abnormality determination. However, when the return determination condition defined in this manner is used, the tire pressure has increased to some extent after the abnormality determination, and a state in which the fact that air has been replenished in the tire after the abnormality determination can be estimated. Even if there is, it cannot be determined that the tire pressure has returned to normal.
[0046]
In contrast, when the return determination condition is configured to include a plurality of predetermined individual return determination conditions for a plurality of types of air pressure reflection values, the same event related to the tire pressure is reflected by the plurality of types of air pressure reflection values. Since the values can be comprehensively determined, it is possible to correctly detect the fact that the tire pressure has returned to normal even if the individual return determination conditions are relaxed.
[0047]
Therefore, in the device according to this section, the return determination condition includes a plurality of individual return determination conditions that are respectively predetermined for a plurality of types of air pressure reflection values, and the plurality of individual return determination conditions Is satisfied, it is determined that the tire pressure has returned to normal.
(12) The abnormality determination condition includes a plurality of individual abnormality determination conditions each of which is predetermined with respect to the plurality of types of air pressure reflection values, and the abnormality determination unit determines all of the plurality of individual abnormality determination conditions. The tire pressure judging device according to any one of (1) to (11), including means for judging that the air pressure of the tire is abnormal when the condition is satisfied.
(13) The abnormality determination condition includes a plurality of individual abnormality determination conditions each of which is predetermined with respect to the plurality of types of air pressure reflection values, and the abnormality determination unit determines at least one of the plurality of individual abnormality determination conditions. The tire pressure determination device according to any one of (1) to (11), further including a unit that determines that the tire pressure is abnormal when one of the conditions is satisfied.
[0048]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, one of more specific embodiments of the present invention will be described in detail with reference to the drawings.
[0049]
FIG. 1 is a block diagram conceptually showing a hardware configuration of a tire abnormality determination device according to an embodiment of the present invention. This tire abnormality determination device is mounted on a vehicle.
[0050]
The vehicle has wheels on the front, rear, left and right sides thereof. In FIG. 1, "FL" indicates a front left wheel, "FR" indicates a front right wheel, "RL" indicates a rear left wheel, and "RR" indicates a rear right wheel. The total number of wheels is four.
[0051]
As is well known, each wheel is configured such that air is sealed under pressure inside a rubber tire mounted on a metal wheel.
[0052]
As shown in FIG. 1, the tire abnormality determination device includes a wheel speed sensor 10 for each wheel. As is well known, each wheel speed sensor 10 is a sensor that detects an angular speed of each wheel as a wheel speed. Specifically, the wheel speed sensor 10 is an electromagnetic pickup, and outputs a voltage signal that changes periodically according to the passage of a large number of teeth formed on the outer periphery of the rotor that rotates with the wheels.
[0053]
The four wheel speed sensors 10 are electrically connected to a determiner 20, as shown in FIG. The determiner 20 is mainly composed of a computer 22. Based on the output signals of the four wheel speed sensors 10, the determiner 20 determines whether a wheel having abnormally low tire pressure is present among a plurality of wheels. Device.
[0054]
In addition, in addition, in the following description, the term tire abnormality is used as a term meaning that the tire pressure is abnormally low.
[0055]
FIG. 2 conceptually shows a hardware configuration of the computer 22 in a block diagram. As is well known, the computer 22 includes a CPU 30 (an example of a processor), a ROM 32 (an example of a memory), and a RAM 34 (an example of a memory) connected to each other via a bus 36. Although not shown, a rewritable nonvolatile memory is formed in the ROM 32. One example is an EEPROM or flash ROM.
[0056]
2, various programs such as a tire abnormality determination program, a normal return determination program, and a return determination threshold value determination program are stored in the ROM 32 in advance.
[0057]
The tire abnormality determination program is a program that is executed to determine whether an abnormal tire is present among a plurality of tires in a vehicle. The normal return determination program determines whether or not the tire pressure determined to be abnormal is restored to normal after the tire abnormality determination program is executed and after it is determined that there is a tire with abnormal air pressure. Is a program that is executed to The return determination threshold value determination program is a program executed to determine a return determination threshold value used for performing a normal return determination in the normal return determination program.
[0058]
As shown in FIG. 1, an alarm 40 is further connected to the determiner 20. The alarm 40 is activated to visually or audibly notify the driver of the vehicle that a wheel having abnormally low tire pressure is present among the plurality of wheels.
[0059]
FIG. 3 conceptually illustrates the contents of the tire abnormality determination program in a flowchart.
[0060]
First, in brief, in the tire abnormality determination program, the resonance frequency f of tire vibration and the dynamic load radius reflection value α are detected based on the wheel speed. Further, when all of the two individual abnormality determination conditions predetermined for the resonance frequency f and the dynamic load radius reflection value α are satisfied, it is determined that the tire air pressure is abnormal.
[0061]
The tire abnormality determination program is repeatedly executed by the computer 22. In each execution, first, in step S1 (hereinafter simply referred to as "S1"; the same applies to the other steps), the wheel speed of each wheel is determined based on the signal from the wheel speed sensor 10. Is calculated.
[0062]
Next, in S2, the resonance frequency f of the tire vibration is calculated as one value representing four wheels. The resonance frequency fs is calculated as a representative value (for example, a simple average value or a weighted average value) of a plurality of resonance frequencies calculated based on the wheel speeds for a plurality of wheels, or one wheel representing four wheels. Can be calculated as one resonance frequency calculated based on the wheel speed.
[0063]
FIG. 4A is a graph showing an example of the relationship between the tire pressure P and the resonance frequency f. In this example, as the tire pressure P decreases from the set pressure P0, the resonance frequency f decreases from the initial value f0.
[0064]
Subsequently, in S3 of FIG. 3, the abnormality determination threshold value fth0 is read from the ROM 32. Further, it is determined whether or not the calculated resonance frequency f is lower than the read abnormality determination threshold value fth0. In the present embodiment, the first individual abnormality determination condition is that the resonance frequency f is lower than the abnormality determination threshold value fth0.
[0065]
In addition, it is determined whether the first individual abnormality determination condition is satisfied by determining whether the amount of change of the resonance frequency f from its initial value f0 exceeds a reference value. The invention can be implemented in embodiments.
[0066]
In this case, assuming that the resonance frequency f is not lower than the abnormality determination threshold value fth0, the determination in S3 is NO, and one cycle of the tire abnormality determination program is immediately terminated.
[0067]
In contrast, this time, if it is assumed that the resonance frequency f is lower than the abnormality determination threshold value fth0, the determination in S3 is YES, and the process proceeds to S4. In S4, a dynamic load radius reflection value α that reflects the dynamic load radius of the tire is calculated based on the wheel speed detected by the wheel speed sensor 10. In the present embodiment, the dynamic load radius reflection value α is calculated as a composite value of a plurality of wheel speeds detected by the wheel speed sensors 10 for each wheel, one for each of the plurality of wheels. .
[0068]
FIG. 4B is a graph showing an example of the relationship between the tire pressure P and the absolute value of the dynamic load radius reflection value α. In this example, as the tire pressure P decreases from the set pressure P0, the absolute value of the dynamic load radius reflection value α decreases from the initial value α0.
[0069]
In addition, in this embodiment, in light of the fact that the direction in which the dynamic load radius R of the tire changes as the tire pressure P decreases is a decreasing direction, the dynamic range is set to decrease as the tire pressure P decreases. Although the load radius reflection value α is defined, for example, as shown in a graph in FIG. 5, a mode in which the dynamic load radius reflection value α is defined so as to increase from 0 as the tire pressure P decreases from the set pressure P0. It is possible to carry out the present invention.
[0070]
In this embodiment, the dynamic load radius reflection value α is, for example, the difference between the ratio between the left and right front wheels, which is the ratio of the wheel speed between the left and right front wheels, and the ratio between the right and left rear wheels, which is the ratio between the wheel speeds and the left and right wheels. Is calculated using
[0071]
The dynamic load radius reflection value α is calculated by, for example, the following equation.
[0072]
α = f (V _FL , V _FR , V _RL , V _RR ) = (V _FR / V _FL )-(V _RR / V _RL )
However,
f (): function
V _FL : Wheel speed of left front wheel
V _FR : Wheel speed of right front wheel
V _RL : Wheel speed of left rear wheel
V _RR : Wheel speed of right rear wheel
Thereafter, in S5 of FIG. 3, the abnormality determination threshold value αth0 is read from the ROM 32. Further, it is determined whether or not the absolute value of the dynamic load radius reflection value α calculated as described above is smaller than the abnormality determination threshold αth0. In the present embodiment, the second individual abnormality determination condition is that the absolute value of the dynamic load radius reflection value α is smaller than the abnormality determination threshold αth0.
[0073]
It should be noted that whether the second individual abnormality determination condition is satisfied is determined by determining whether the amount of change in the dynamic load radius reflection value α from its initial value α0 exceeds a reference value. It is possible to implement the present invention in a mode in which is determined.
[0074]
In this case, assuming that the absolute value of the dynamic load radius reflection value α is not smaller than the abnormality determination threshold αth0, the determination in S5 is NO, and one cycle of the tire abnormality determination program is immediately terminated. .
[0075]
On the other hand, this time, if it is assumed that the absolute value of the dynamic load radius reflection value α is smaller than the abnormality determination threshold αth0, the determination in S5 becomes YES, and in S6, the tire pressure It is determined that there is a wheel whose P is abnormal. Thereafter, in S7, the alarm 40 is turned on to notify the driver of the situation. Thus, one execution of the tire abnormality determination program ends.
[0076]
FIG. 6 is a flowchart conceptually showing the contents of the normal return determination program. This normal return determination program is repeatedly executed by the computer 22. At the time of each execution, first, in S31, the wheel speed is calculated for each wheel based on the signal from the wheel speed sensor 10 in the same manner as in S1.
[0077]
Next, in S32, in the same manner as in S2, the resonance frequency f of the tire vibration is calculated as one value representing four wheels.
[0078]
Subsequently, in S33, the return determination threshold value fth1 is read from the rewritable nonvolatile memory. The return determination threshold value fth1 is determined in advance by executing the return determination threshold value determination program.
[0079]
Thereafter, in S34, it is determined whether or not the calculated resonance frequency f is higher than the read return determination threshold value fth1. In the present embodiment, the first individual return determination condition is that the resonance frequency f is higher than the return determination threshold value fth1.
[0080]
In this case, assuming that the resonance frequency f is not higher than the return determination threshold value fth1, the determination in S34 is NO, and one execution of the normal return determination program is immediately terminated.
[0081]
On the other hand, assuming that the resonance frequency f is higher than the return determination threshold value fth1 this time, the determination in S34 becomes YES, and the process proceeds to S35. In S35, a dynamic load radius reflection value α that reflects the dynamic load radius of the tire is calculated based on the wheel speed detected by the wheel speed sensor 10, as in S4.
[0082]
Subsequently, in S36, the return determination threshold value αth1 is read from the rewritable nonvolatile memory. The return determination threshold value αth1 is determined in advance by executing the return determination threshold value determination program. Thereafter, in S37, it is determined whether or not the calculated absolute value of the dynamic load radius reflection value α is larger than the readout return determination threshold αth1. In the present embodiment, the second individual return determination condition is that the dynamic load radius reflection value α is larger than the return determination threshold αth1.
[0083]
In this case, assuming that the dynamic load radius reflection value α is not larger than the return determination threshold value αth1, the determination in S37 becomes NO, and one execution of the normal return determination program is immediately terminated.
[0084]
On the other hand, if it is assumed that the dynamic load radius reflection value α is larger than the return determination threshold αth1, the determination in S37 is YES, and the process proceeds to S38. In S38, it is determined that the tire pressure P of the wheel whose tire pressure P has been determined to be abnormal has returned to normal. Thereafter, in S39, the alarm 40 is turned off to notify the driver of the fact. This completes one execution of the normal return determination program.
[0085]
FIG. 7 is a flowchart conceptually showing the contents of the return determination threshold value determination program. This return determination threshold value determination program is repeatedly executed by the computer 22. In each execution, first, in S51, it is determined whether or not the alarm device 40 has just changed from OFF to ON. In this case, assuming that this is not the case, the determination is NO, and one execution of the return determination threshold determination program is immediately terminated.
[0086]
On the other hand, assuming that this time is immediately after the alarm device 40 changes from OFF to ON, the determination in S51 becomes YES, and the process proceeds to S52.
[0087]
In S52, the current value of the resonance frequency f (resonance frequency representing the four wheels) is calculated as described above, and the sum of the current value and the set increment Δf (this is an example of the set amount). Is calculated as the return determination threshold value fth1.
[0088]
Subsequently, in S53, the current value of the dynamic load radius reflection value α is calculated as described above, and the return determination is performed as the sum of the current value and the set increment Δα (this is an example of the set amount). The threshold value αth1 is calculated.
[0089]
Thereafter, in S54, the calculated return determination thresholds fth1 and αth1 are stored in the rewritable nonvolatile memory. Thus, one execution of the return determination threshold determination program is completed.
[0090]
FIG. 8 is a graph conceptually showing an example of the effect of the present embodiment. In the same figure, the respective time transitions of the resonance frequency f and the dynamic load radius reflection value α are represented by respective graphs. In this example, both the resonance frequency f and the dynamic load radius reflection value α start decreasing at time t0. First, the resonance frequency f falls below the abnormality determination threshold value fth0 at time t1. Falls below the abnormality determination threshold αth0 at time t2. At time t2, it is determined that there is a wheel whose tire pressure P is abnormal. In FIG. 8, the two abnormality determination thresholds fth0 and αth0 are shown to have the same value for convenience of explanation. The same applies to the relationship between the return determination threshold value fth ′ and αth ′, which will be described later.
[0091]
Thereafter, air is replenished into the tires of the wheels whose tire pressure P is abnormal. As a result, both the resonance frequency f and the dynamic load radius reflection value α start to increase.
[0092]
In this example, first, the dynamic load radius reflection value α exceeds the return determination threshold αth1 at time t3. The return determination threshold value αth1 is set as a value that is increased by an increment Δα from the dynamic load radius reflection value α when it is determined that there is a wheel with abnormal tire pressure P. .
[0093]
In this example, thereafter, the resonance frequency f exceeds the return determination threshold value fth1 at time t4. The return determination threshold value fth1 is set as a value that is increased by an increment Δf from the resonance frequency f when it is determined that a wheel having an abnormal tire pressure P exists.
[0094]
In this example, at time t4, it is determined that the tire pressure P of the wheel whose tire pressure P has been determined to be abnormal has returned to normal.
[0095]
FIG. 8 also shows a comparative example for the present embodiment. In this comparative example, the return determination thresholds fth ′ and αth ′ are set to reflect the resonance frequency f and the dynamic load radius when it is determined that there is a wheel having an abnormal tire pressure P for the normal return determination. It is set as a fixed value irrespective of the value α. The return determination threshold values fth ′ and αth ′ are set as values that the resonance frequency f and the dynamic load radius reflection value α should take when the tire pressure P is the set pressure P0.
[0096]
Furthermore, in the present embodiment, the return determination threshold values fth1 and αth1 are set smaller than the above-described return determination threshold values fth ′ and αth ′, whereby the tire pressure P is abnormal. Is set off.
[0097]
Therefore, in this comparative example, first, the dynamic load radius reflection value α exceeds the return determination threshold αth ′ at time t5, and thereafter, the resonance frequency f exceeds the return determination threshold fth ′ at time t6. At time t6, it is determined that the tire pressure P of the wheel whose tire pressure P has been determined to be abnormal has returned to normal.
[0098]
In this comparative example, the resonance frequency f and the dynamic load radius reflection value α are each compared with a threshold value, which is an absolute value, to determine whether or not the tire pressure has returned to normal. That is, an absolute determination is made. In contrast, in the present embodiment, the resonance frequency f and the dynamic load radius reflection value α are each compared with a threshold value, which is a relative value, to determine whether or not the tire pressure has returned to normal. Is done. That is, a relative determination is made.
[0099]
As a result, according to the present embodiment, as illustrated in FIG. 8, it is determined that the tire air pressure has returned to normal earlier than in the comparative example in which an absolute determination is made.
[0100]
As in the comparative example, when the tire pressure P is at the set pressure P0, a threshold value for return determination is set as a value to be taken by the tire pressure reflection value, and the threshold value is compared with the tire pressure reflection value. When determining whether or not the air pressure P has returned to normal, for example, as shown in the graph of FIG. 9, the tire pressure P is abnormal because the tire pressure reflection value has fallen below the abnormality determination threshold value. Is determined, the tire pressure P is not determined to have returned to normal unless the tire pressure reflection value is restored to the return determination threshold value. This means that it takes time until it is determined that the tire pressure has returned to normal.
[0101]
On the other hand, according to the present embodiment, as shown in FIG. 8, even when the resonance frequency f and the dynamic load radius reflection value α do not recover to values that match the set pressure P0, the tire air pressure P becomes normal. Is determined to have returned.
[0102]
It should be noted that, in this embodiment, the first individual return determination condition is that the change amount of the resonance frequency f from the time when the tire air pressure is determined to be abnormal becomes equal to or more than the increment Δf. Is equivalent to the condition that holds. Further, the second individual return determination condition is equivalent to a condition that is satisfied when the amount of change in the dynamic load radius reflection value α from the time when the tire air pressure is determined to be abnormal is equal to or greater than the increment Δα. It is.
[0103]
As is apparent from the above description, in the present embodiment, the tire abnormality determination device forms an example of the “tire pressure determination device” according to the present invention, and the computer 22 includes S1, S2, and S4 in FIG. The part that executes S31, S32, and S35 of FIG. 6 constitutes an example of the “pneumatic pressure reflection value acquisition unit” in the above item (1) or (5), and the part that executes S3, S5, and S6 of FIG. An example of the “abnormality determination unit” in the item (1) or (12) is configured, and the part that executes S33, S34, S36, S37, and S38 in FIG. The part that executes the return determination threshold value determination program of FIG. 7 constitutes an example of the “return determination unit”, and the example of the “condition changing means” in the above item (1), (2) or (7). Make up Is are you.
[0104]
Further, in the present embodiment, the part of the computer 22 that executes S34 and S37 in FIG. 6 constitutes an example of the "success / failure determination means" in the above item (3), and the return determination threshold value determination in FIG. The part that executes the program constitutes an example of the “threshold value determining means” in the above item or the item (4).
[0105]
Further, in the present embodiment, S34 and S37 in FIG. 6 are steps for determining whether or not an example of the “return determination condition” in the above item (8), (9) or (11) is satisfied.
[0106]
As mentioned above, one embodiment of the present invention has been described in detail with reference to the drawings. However, this is an exemplification, and the embodiment described in the above-mentioned "Means for Solving the Problems and Effects of the Invention" will be described. The present invention can be implemented in other forms with various modifications and improvements based on the knowledge of the trader.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a hardware configuration of a tire abnormality determination device according to one embodiment of the present invention.
FIG. 2 is a block diagram showing a hardware configuration of a computer in FIG.
FIG. 3 is a flowchart conceptually showing the contents of a tire abnormality determination program in FIG.
FIG. 4 is a graph for explaining each definition of a resonance frequency f and a dynamic load radius reflection value α in FIG. 3;
FIG. 5 is a graph for explaining another definition of the dynamic load radius reflection value α in FIG. 3;
FIG. 6 is a flowchart conceptually showing the content of a normal return determination program in FIG.
FIG. 7 is a flowchart conceptually showing the contents of a return determination threshold value determination program in FIG. 2;
FIG. 8 is a graph illustrating an example of an effect of the tire abnormality determination device according to the embodiment.
FIG. 9 is a graph for explaining a problem of a comparative example with respect to the tire abnormality determination device according to the embodiment.

Claims (6)

Apparatus provided in a vehicle having a wheel configured to be sealed under pressure with air inside the tire mounted on the wheel, a device for determining whether the tire pressure is abnormal,
An air pressure reflection value acquisition unit that acquires a value reflecting the air pressure as a plurality of air pressure reflection values according to a plurality of predetermined acquisition rules, respectively,
For a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit, when a predetermined abnormality determination condition is satisfied, an abnormality determination unit that determines that the tire air pressure is abnormal,
When a plurality of types of air pressure reflection values obtained by the air pressure reflection value obtaining unit after the air pressure of the tire is determined to be abnormal by the abnormality determination unit, a predetermined return determination condition is satisfied, A condition determining unit that includes a return determining unit that determines that the tire pressure has returned to normal, and the return determining unit changes the return determination condition based on at least one of the plurality of types of air pressure reflection values. A tire pressure determination device including: The condition changing unit performs the return based on at least one of a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit when the abnormality judgment unit determines that the air pressure of the tire is abnormal. The tire pressure judging device according to claim 1, further comprising means for changing a judging condition. The vehicle includes a wheel speed sensor that detects an angular speed of the wheel as a wheel speed,
The plurality of types of air pressure reflection values include a dynamic load radius reflection value reflecting a dynamic load radius of the tire, and a tire vibration characteristic value reflecting characteristics of vibration of the tire,
The air pressure reflection value acquisition unit includes means for acquiring the dynamic load radius reflection value and the tire vibration characteristic value based on a wheel speed detected by the wheel speed sensor,
The tire pressure determination device according to claim 1, wherein the tire pressure is indirectly detected and determined. Apparatus provided in a vehicle having a wheel configured to be sealed under pressure with air inside the tire mounted on the wheel, a device for determining whether the tire pressure is abnormal,
An air pressure reflection value acquisition unit that acquires a value reflecting the air pressure as a plurality of air pressure reflection values according to a plurality of predetermined acquisition rules, respectively,
For a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit, when a predetermined abnormality determination condition is satisfied, an abnormality determination unit that determines that the tire air pressure is abnormal,
When a plurality of types of air pressure reflection values obtained by the air pressure reflection value obtaining unit after the air pressure of the tire is determined to be abnormal by the abnormality determination unit, a predetermined return determination condition is satisfied, A return determination unit that determines that the tire pressure has returned to normal, and the return determination condition is related to at least one of the plurality of types of air pressure reflection values, and the abnormality determination unit determines that the tire pressure is abnormal. A tire pressure determination device that is established when the amount of change from when it is determined that the tire pressure reaches a set amount. Apparatus provided in a vehicle having a wheel configured to be sealed under pressure with air inside the tire mounted on the wheel, a device for determining whether the tire pressure is abnormal,
An air pressure reflection value acquisition unit that acquires a value reflecting the air pressure as a plurality of air pressure reflection values according to a plurality of predetermined acquisition rules, respectively,
For a plurality of types of air pressure reflection values acquired by the air pressure reflection value acquisition unit, when a predetermined abnormality determination condition is satisfied, an abnormality determination unit that determines that the tire air pressure is abnormal,
When a plurality of types of air pressure reflection values obtained by the air pressure reflection value obtaining unit after the air pressure of the tire is determined to be abnormal by the abnormality determination unit, a predetermined return determination condition is satisfied, A return determining unit that determines that the tire pressure has returned to normal, and wherein the return determination condition is based on a value that matches a preset pressure set in advance for the tire to function normally. A tire pressure determination device that is established when at least one of the plurality of types of air pressure reflection values reaches a value shifted to a side where an abnormality is detected. The return determination condition includes a plurality of individual return determination conditions that are respectively predetermined for the plurality of types of air pressure reflection values, and the return determination unit has satisfied all of the plurality of individual return determination conditions. 6. The tire pressure judging device according to claim 1, further comprising means for judging that the air pressure of the tire has returned to normal in such a case.

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