JPH08282222A - Tire internal pressure lowering detecting device - Google Patents

Abstract

PURPOSE: To specify a wheel in which the internal pressure of a tire is lowered by comparing and judging the internal pressure of a tire of each wheel from the rotation angular speed of each wheel. CONSTITUTION: When the tire internal pressure of a front left wheel is lowered, the rotation angular speed VWFL is increased, and the front wheel speed right to left ratio PF is increased more than a reference point CA, the wheel load of a rear right wheel is decreased to decrease the rear right wheel speed VWRR, and the wheel load of a rear left wheel is increased to increase the rear left wheel speed VWRL. Accordingly, the rear wheel speed left to right ratio PF is a little increased. On the other hand, when the tire internal pressure of a front right wheel is lowered, and the front wheel speed left to right ratio PF is decreased below a reference point CA, the rear wheel speed left to right ratio PR is a little decreased, and the front and rear wheel speed left to right ratios PF, PR generated in two situations draw a locus of a straight line L1 A passing a fixed reference point CA according to the tire internal pressure lowering rate of each wheel. Similarly, when the rear wheel internal pressure is lowered, a locus of a straight line L2 A is drawn. It is judged whether coordinates PF, PR are included or not in an area A formed by a sum-set of areas where a very small width dA is given to the straight lines L1 A, L2 A formed by the front and rear wheel speed left to right ratios.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire internal pressure drop detecting device for detecting a decrease in air pressure (hereinafter, also referred to as internal pressure) of a tire of each wheel while a vehicle is running, and more particularly to a tire internal pressure drop detecting device. The present invention relates to a tire internal pressure drop detecting device capable of identifying even a wheel whose tire internal pressure is decreasing by comparing and determining the tire internal pressure of each wheel from the rotational angular velocity.

[0002]

2. Description of the Related Art In order to detect a decrease in the tire internal pressure of each wheel while the vehicle is traveling, the fact that the rolling radius of the tire is proportional to the tire internal pressure is utilized to determine the rolling radius of the tire of each wheel. There is one that detects a decrease in internal pressure by making a comparison. That is, to briefly describe the principle, when the rolling radius of the tire becomes smaller along with the decrease in the tire internal pressure, the rotational angular velocity of the tire internal pressure-decreasing wheel in a certain predetermined running state is greater than the rotational angular velocity of the regular internal pressure wheel. Therefore, the rotational angular velocity of each wheel (equivalent to the generally recognized wheel speed) is detected by a wheel speed sensor or the like provided as a wheel speed detecting means of an existing anti-skid control device, and these are mutually detected. By comparison, the wheel whose tire internal pressure is decreasing is specified.

However, the wheel rotational angular velocity detected by the wheel speed sensor or the like is
In a running state such as during deceleration, a change larger than the normally expected change in the wheel rotation angular velocity due to a decrease in tire internal pressure may occur, and a wheel in which the tire internal pressure actually decreases may be erroneously detected. Therefore, changes in the tire internal pressure in these running states are predicted in each running state or derived from vehicle experiment results and the like, and based on the tire internal pressure changes corresponding to the respective running states, the rotational angular velocity of each wheel or As a means for correcting the tire internal pressure based on the calculation result, for example, a tire internal pressure drop detecting device disclosed in Japanese Patent Laid-Open No. 6-8714 has been proposed. According to this tire internal pressure drop detecting device, it is possible to detect the tire internal pressure drop of each wheel in various possible traveling states.

[0004]

However, in the conventional tire internal pressure drop detecting device described above, for example, in order to make it possible to detect the tire internal pressure drop of each wheel in various conceivable running states, it is described in the above publication, for example. Since many corrections such as the calculation process are required, which complicates the calculation process, an error occurs due to a difference between the timing of the correction by the calculation process and the sampling timing of the wheel angular velocity, and the tire internal pressure is reduced. It may cause an erroneous judgment of deterioration. In addition, the calculation time increases due to an increase in the calculation load, and, for example, the calculation processing device cannot be shared with the controller of the anti-skid control device as described above. There is also a problem that the cost is increased because it is necessary to provide them independently.

In order to avoid such a problem, it is detected that the vehicle is not in a traveling state in which a change in wheel angular velocity larger than a change in wheel angular velocity due to a decrease in tire internal pressure as described above is generated, and only at that time, each wheel is detected. It is conceivable to detect the decrease in tire internal pressure. A specific and ideal driving state is a state where the vehicle is traveling straight or almost straight (hereinafter, also referred to as approximate straight traveling), and no intentional acceleration / deceleration is performed or such acceleration / deceleration occurs in the vehicle. It can be mentioned that the vehicle is in a steady running state. However,
At least at the present time, in order to detect the straight traveling or the approximately straight traveling steady traveling, for example, a lateral acceleration sensor or a steering angle sensor for detecting that the vehicle is not turning traveling, or an accelerator opening sensor for detecting that the vehicle is not accelerating. A large number of detecting means such as the above are required, and the structure may be complicated and the cost may be increased accordingly.

The present invention has been developed in view of these problems, and it is an object of the present invention to provide a tire internal pressure drop detecting device capable of reducing the calculation load, simplifying the configuration, and reducing the cost. It is intended.

[0007]

In order to solve the above problems, a tire internal pressure drop detecting device according to a first aspect of the present invention, as shown in the basic configuration diagram of FIG. 1, rotates each wheel of a vehicle. Wheel angular velocity detecting means for detecting the angular velocity, and tire internal pressure drop detecting means for detecting the tire internal pressure drop of each wheel based on the wheel rotational angular velocity detection value detected by the wheel angular velocity detecting means during straight running or near straight running steady running , A wheel load variation detecting means for detecting a variation in wheel load of each wheel, and a condition for detecting a decrease in the internal pressure of the tire of each wheel are defined by the left-right ratio of the rotational angular velocities of the front two wheels of the vehicle and the rotational angular velocity of the rear two wheels of the vehicle. Condition setting means for setting the right / left ratio on the orthogonal coordinate axis and the wheel load variation detecting means, when the wheel load variation detecting means detects a variation in the wheel load of each wheel, a predetermined number of front two wheels detected by the wheel angular velocity detecting means. Angle of rotation Of the right and left ratios of the two detected wheels and the average value of the left and right ratios of the detected wheel rotational angular velocities of the rear two wheels as a variable reference point, passing through the variable reference point and passing through the front and rear wheels. When the rotational angular velocity left / right ratio increases, the region in which the rotational angular velocity left / right ratio of the rear two wheels slightly increases and a region where a small width is given to the straight line passing through the variable reference point and the rotational angular velocity left / right ratio of the rear two wheels increases A variable region setting means for setting a union with a region where a minute width is given to a straight line in which the rotational angular velocity left / right ratio of the two wheels slightly increases, and a variable type determination region set by the variable region setting means, When a coordinate point consisting of the left / right ratio of the wheel rotational angular velocity detection values of the front two wheels and the left / right ratio of the wheel rotational angular velocity detection values of the rear two wheels detected by the wheel angular velocity detection means is included, the internal pressure of the tire of each wheel is included. A change that adds a condition for detecting It is characterized in that a region determination unit.

The tire internal pressure drop detecting device according to claim 2 of the present invention is characterized in that the wheel load fluctuation detecting means is an ON signal of an ignition switch. Further, the tire internal pressure drop detecting device according to claim 3 of the present invention is characterized in that the wheel load variation detecting means is an opening / closing signal of a door switch.

According to a fourth aspect of the present invention, the tire internal pressure drop detecting device is characterized in that the wheel load variation detecting means is an opening / closing signal of a trunk lid switch. Further, the tire internal pressure drop detecting device according to claim 5 of the present invention is characterized in that the wheel load variation detecting means is an opening / closing signal of a fuel lid switch.

Further, in the tire internal pressure drop detecting device according to claim 6 of the present invention, the condition setting means sets the right / left ratio of the rotational angular velocities of the front two wheels and the left / right ratio of the rotational angular velocities of the rear two wheels of the vehicle in an orthogonal coordinate axis. When set to, the coordinate point consisting of the rotational angular velocity left / right ratio of the front two wheels and the rotational angular velocity left / right ratio of the rear two wheels during straight running steady running in a predetermined normal internal pressure state where the tire internal pressures of the four wheels are preset is fixed. As a reference point, the fixed type reference point and a region where a small width is given to a straight line that passes through the fixed type reference point and the rotational angular velocity left / right ratio of the front two wheels slightly increases when the rotational angular velocity left / right ratio increases A fixed fixed determination region that is a set of a straight line and a region in which the left and right rotational angular velocities of the two front wheels slightly increase when the left and right rotational angular velocities of the two rear wheels increase. Detected by angular velocity detection means When a coordinate point consisting of the left / right ratio of the detected wheel rotation angular velocity of the two front wheels and the left / right ratio of the detected wheel rotation angular velocity of the rear two wheels is included, a condition for detecting the decrease in the internal pressure of the tire of each wheel is given. It is characterized in that a fixed area determination means is provided.

Further, in the tire internal pressure drop detecting device according to claim 7 of the present invention, the tire internal pressure drop detecting means comprises:
Coordinate points consisting of the left / right ratio of the wheel rotational angular velocity detection values of the front two wheels detected by the wheel angular velocity detection means and the left / right ratio of the wheel rotational angular velocity detection values of the rear two wheels are the variable determination regions in the variable region determination means. Tire internal pressure that identifies a wheel whose tire internal pressure is decreasing depending on which of the variable reference points or the fixed reference point of the fixed determination area in the fixed area determination means is in the determination area It is characterized in that it is provided with a degraded wheel identifying means.

Further, in the tire internal pressure drop detecting device according to claim 8 of the present invention, the tire internal pressure drop wheel identifying means determines the left-right ratio of the wheel rotational angular velocity detection values of the front two wheels detected by the wheel angular velocity detecting means. And the difference between the left and right ratios of the detected wheel rotational angular velocities of the two rear wheels and the difference between the diagonal ratios of the detected rotational angular velocities of the front and rear left and right wheels, which are diagonally opposite to each other, respectively. It is characterized in that the wheel whose internal pressure of the tire is lower than that of the wheel is specified.

According to a ninth aspect of the present invention, in the tire internal pressure drop detecting device, the tire internal pressure drop wheel identifying means determines the front-rear ratio of the wheel rotational angular velocity detected values of the two left wheels detected by the wheel angular velocity detecting means. And the difference between the front and rear ratios of the detected wheel rotational angular velocities of the two right wheels and the difference between the diagonal ratios of the detected rotational angular velocities of the front and rear left and right wheels that are diagonally opposite to each other It is characterized in that the wheel whose internal pressure of the tire is lower than that of the wheel is specified.

According to a tenth aspect of the present invention, there is provided a tire internal pressure reduction detecting device, wherein the tire internal pressure reduction wheel specifying means sets the variation type reference point and the variation type determination area by the variation area setting means. The difference between the left-right ratio of the wheel rotational angular velocity detection value of the front two wheels detected by the wheel angular velocity detection means and the left-right ratio of the wheel rotational angular velocity detection value of the rear two wheels or the front-back ratio of the wheel rotational angular velocity detection value of the left two wheels The difference between the front-rear ratio of the wheel rotational angular velocity detection values of the two right wheels and the difference between the front-rear left-right wheel rotational angular velocity detection values of the front-rear left-right wheels that are diagonal to each other are set to the variable reference values, respectively. It is what

The tire internal pressure drop detecting device according to claim 11 of the present invention comprises a longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle, and the condition setting means is detected by the longitudinal acceleration detecting means. In addition, the detection condition of the decrease in the internal pressure of the tire is set based on the detected wheel rotation angular velocity values detected by the wheel angular velocity detection means when the longitudinal acceleration detected value is zero or substantially zero.

According to a twelfth aspect of the present invention, there is provided a tire internal pressure drop detecting device, wherein the longitudinal acceleration detecting means detects the front and rear of the vehicle from the differential value of each wheel rotational angular velocity detected value detected by the wheel angular velocity detecting means. It is characterized by detecting directional acceleration. Further, claim 1 of the present invention
In the tire internal pressure drop detecting device according to No. 3, the longitudinal acceleration detecting means detects the longitudinal acceleration of the vehicle from the difference value between the detected wheel rotational angular velocity values detected by the wheel angular velocity detecting means. Is.

[0017]

Thus, in the tire internal pressure drop detecting device of the present invention having the above-described structure, when comparing the wheel rotational angular velocity detection values of the four wheels, the tires of the respective wheels are traveling straight or approximately straight at steady internal pressure. At times, the rotational angular velocity of each wheel becomes a certain predetermined value or a value in the vicinity thereof according to the vehicle speed at that time. However, even when the same vehicle travels straight or near straight at the same vehicle speed, if the internal pressure of the tire of a wheel decreases, the wheel load of the wheel and the wheel corresponding to the diagonal position in the vehicle decreases. , The wheel load of other wheels increases, and among them, the wheel whose wheel load decreases decreases the wheel radius and the wheel rotational angular velocity decreases, and conversely, the wheel whose wheel load increases increases the wheel rotational angular velocity. .
Therefore, each wheel rotation angular velocity will change according to this wheel load change, and each wheel rotation angular velocity detection value,
Since it is possible to determine that the vehicle is traveling straight or approximately straight in a steady state by comparing along with the change in the wheel rotation speed that accompanies this expected change in wheel load, each wheel can be determined based on the determination result. The condition for detecting the decrease in the tire internal pressure is set, that is, by filtering each wheel rotation angular velocity detection value, without performing complicated correction, only when the vehicle is traveling straight or approximately straight straight It is possible to detect a decrease in the internal pressure of the tire of each wheel.

Here, if the left / right ratio of the rotational angular velocities of the front two wheels and the left / right ratio of the rotational angular velocities of the rear two wheels are set on the orthogonal coordinate axes, the four wheels will be in front of straight running steady running in a predetermined normal internal pressure state. Using the rotational angular velocity left / right ratio of the two wheels and the rear two wheels as a reference point, even in the same straight traveling or approximate straight traveling state, a linear change line of the rotational angular velocity left / right ratio corresponding to the wheel load change that occurs with the decrease in tire internal pressure A determination area on the orthogonal coordinate axis with a small width is added, and this determination area includes coordinate points consisting of the left / right ratio of the wheel rotation angular velocity detection values of the front two wheels and the left / right ratio of the wheel rotation angular velocity detection values of the rear two wheels. When the vehicle is running, it can be determined that the vehicle is traveling straight or approximately straight.

However, as described above, the wheel rotational angular velocity increases and decreases as the wheel load increases and decreases. Therefore, even if the four wheels are in the same straight traveling or approximate straight traveling state with a predetermined normal internal pressure, If the load or the like changes, the wheel load also changes, and as a result, the coordinate points of the rotational angular velocity left / right ratios of the front two wheels and the rear two wheels corresponding to the reference points of the Cartesian coordinate system also change. Therefore, the input signals such as the ON signal of the ignition switch, the opening / closing signal of the door switch, the opening / closing signal of the trunk lid switch, the opening / closing signal of the fuel lid switch, etc., which may cause the wheel load to fluctuate, are used as triggers to detect each wheel rotation angular velocity thereafter. The coordinate points of the left and right rotational angular velocities of the front two wheels and the rear two wheels consisting of the values are set as the variable reference points, and the same determination area as above is set for the variable reference points. , It is determined whether or not the coordinate points of the left and right rotational angular velocities of the front two wheels and the rear two wheels, which consist of the detected rotational velocities of the respective wheels, are included. It is possible to accurately detect the decrease in the internal pressure of the tire.

On the other hand, when the tire internal pressure of a certain wheel has already dropped by the time the variable type determination area is set as described above, both the variable type reference point and the variable type determination area are set. However, it is unsuitable for determining whether the vehicle is traveling straight or approximately straight, or detecting a decrease in tire internal pressure of the wheel. Therefore, the fixed type reference point is a coordinate point formed by the rotational angular velocity left / right ratio of the two front wheels and the rotational angular velocity left / right ratio of the rear two wheels during straight running steady running in a predetermined normal internal pressure state in which the tire internal pressures of the four wheels are set in advance. Then, a fixed type determination area is set for this fixed type reference point in the same manner as described above, and whether or not the fixed type determination area includes a coordinate point composed of the left / right ratio of the wheel rotation angular velocity detection values of the front and rear wheels. If it is determined that the wheel load fluctuation element cannot be completely eliminated, at least the decrease in the tire internal pressure of the certain wheel can be accurately detected.

Further, the change in the wheel rotational angular velocity due to the change in the wheel load of the other wheel accompanying the decrease in the tire internal pressure of the certain wheel is substantially smaller than the change in the wheel rotational angular velocity of the wheel whose tire internal pressure is decreased. A left-right ratio of the wheel rotational angular velocity detection values of the front two wheels and a left-right ratio of the wheel rotational angular velocity detection values of the rear two wheels with respect to the variable reference point of the variable determination area or the fixed reference point of the fixed determination area. The existence point of the coordinate point is different depending on the wheel whose tire internal pressure is decreasing, and by using this, the wheel whose tire internal pressure is decreasing can be accurately specified.

At this time, for example, when the decrease in tire internal pressure of each wheel is determined using the variable type determination region, the front and rear wheel rotational angular velocity detection values when the variable type reference point and the variable type determination region are set. The difference between the right-and-left ratios, the difference between the front-rear ratios of the left and right wheel rotation angular velocity detection values, and the difference in the diagonal ratios of the diagonal wheel rotation angular velocity detection values are respectively set to the variable reference values, and the fixed-type determination region is set. For these, these numerical values obtained in advance from the vehicle specifications are set as fixed type reference values, and the difference between the left-right ratio of the wheel rotational angular velocity detection values of the front two wheels and the left-right ratio of the wheel rotational angular velocity detection values of the rear two wheels is set. , Or by comparing the difference between the front-rear ratio of the detected wheel rotational angular velocities of the left two wheels and the front-rear ratio of the detected wheel rotational angular velocities of the right two wheels with the variable reference value or the fixed reference value, the diagonal positions of the vehicle You can specify the two wheels that will be By comparing the difference in the diagonal ratio of the rotational angular velocity detection values of the front and rear wheels that are diagonally opposite to each other on both sides with the fixed reference value or the variable reference value, whichever of those diagonal positions It is possible to specify whether the tire internal pressure has decreased, and since the comparison with the variable reference value will be the determination result according to the wheel load state in particular, it is possible to specify the wheel with decreased tire internal pressure more accurately. Become.

Further, in the case where the differential limiting device is provided between the driving left and right wheels, when the driving force applied to the driving wheel is increased, the left-right difference between the rotational angular velocities of the driving wheels is decreased, and when the driving force is decreased, Because the difference becomes large, if the longitudinal acceleration detection value is zero or substantially zero, from each wheel rotation angular velocity detection value, if the detection condition for the tire internal pressure decrease is set as described above, the tire internal pressure decreases. It is possible to avoid an erroneous determination when identifying the wheel in which the tire is located or when detecting that the tire internal pressure is low.

At this time, if the longitudinal acceleration of the vehicle is to be detected from the differential value of each wheel rotation angular velocity detection value detected by the wheel angular velocity detection means or the difference value thereof,
It is not necessary to separately provide a detector such as a longitudinal acceleration sensor, which is advantageous in terms of cost.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the tire internal pressure drop detecting device of the present invention is applied to a front-wheel drive vehicle will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing a tire internal pressure drop detecting device of this vehicle. The front left and right wheels 9L and 9R as driving wheels and the rear left and right wheels 6L and 6R as non-driving wheels are respectively rotated. Wheel speed sensor 46FL to 46R for detecting angular velocity
R is provided. This wheel speed sensor 46FL-46
Like the existing wheel speed sensor, the RR includes, for example, a rotor made of a magnetic material having serrations on the outer periphery and rotating together with each axle, and a magnet facing the rotor is built in to generate an induced electromotive voltage due to a magnetic flux between the two. The induced electromotive force having a frequency corresponding to the circumferential movement speed of the serration, that is, the rotational angular velocity of the rotor is output as the rotational angular velocities Vw _{FL to} Vw _RR of the wheels.

Further, the brake pedal 21 is provided with a brake switch 45 for detecting whether or not the brake pedal 21 is depressed. This brake switch 45
Is the same as a normal brake lamp switch when the brake pedal 21 is depressed and the logical value "1" is ON.
Turns off the logical value "0" when the signal is not stepped on
The signal is output as a brake signal S _BRK having a digital value. Further, for each door (not shown), a door signal S _DOOR having a digital value of an ON signal having a logical value “1” when the door is open and an OFF signal having a logical value “0” when all the doors are closed. A door switch 42 for outputting as is attached. Further, a trunk lid switch (not shown) outputs an ON signal having a logical value "1" in the open state and an OFF signal having a logical value "0" in the closed state as a trunk lid signal S _TR having a digital value. 43 is attached. In addition, the so-called hatchback vehicle that does not have an independent trunk lid corresponds to the open / close state of the rear door. Further, a fuel lid (not shown) is provided with an ON signal having a logical value "1" in its open state.
A fuel lid switch 44 that outputs an OFF signal having a logical value "0" in a closed state as a fuel lid signal S _FL having a digital value is attached.

In addition, on the instrument panel of the vehicle
Is the front left wheel 9L, front right wheel 9R, rear left wheel 6L, rear right
Wheel display lamps 35FL to 35RR showing the respective wheels 6R
Is provided. Each wheel display lamp 35FL-3
5RR is a drive from the control unit 40 described later.
Motion signal LD_FL~ LD_RRIs flickered by. Also the vehicle
Based on the detection signals from each sensor,
The decrease in tire pressure has been detected and the tire pressure has decreased.
For wheels, the drive signal LD _FL~ LD_RRON state
As a state, the respective wheel display lamps 35FL to 35RR are turned on.
A control unit 40 for killing is provided.

This control unit 40 is shown in FIG.
As clearly shown, the microcomputer 51 and the drive circuit
The roads 53FL to 53RR are provided. Of these, Mike
The computer 51 has at least the wheel speed sensor 4
Wheel rotation consisting of sinusoidal voltage signal from 6FL to 46RR
Rolling speed Vw_FL~ Vw_RRWaveform shaping function and A / D conversion function
Input interface circuit 51a including a microphone and the like
Arithmetic processing unit consisting of a processor unit (MPU), etc.
A processing unit (CPU) 51b, ROM, RAM, etc.
Storage device 51c and output with D / A conversion function
And an interface circuit 51d. And
The input interface circuit 51a includes the wheel speed sensors.
Wheel angular velocity detected by sensors 46FL to 46RR
(This wheel rotation angular velocity is constant when the tire rolling radius is constant.
When I think that there is, I can recognize it in the control unit
Since it is equivalent to the wheel speed,
S) Vw_FL~ Vw_RR, Door signal from door switch 42
S_DOOR, Trunk lid from the trunk lid switch 43
Dead signal S_TR, Fuel lid switch 44
Fuel lid signal S_FLFrom the brake switch 45
Brake signal S_BRKInput and output interface
From the circuit 51d, the wheels with low tire internal pressure
Towards the corresponding wheel display lamps 35FL to 35RR
Drive signal LD _FL~ LD_RRIs output.

The arithmetic processing unit 51b executes the arithmetic processing shown in FIG. 4, which will be described later, and at each predetermined sampling time ΔT, each detected value from each sensor and switch or ON-OFF.
The signal is read, and predetermined arithmetic processing is performed on the basis of these values and signals to detect the wheel whose tire internal pressure is decreasing. Further, the storage device 51c stores in advance programs necessary for the arithmetic processing of the arithmetic processing device 51b, each set value, a control map, and the like, and sequentially stores the arithmetic results required in the arithmetic process.

Further, the drive circuits 53FL to 53RR
When the tire internal pressure attention control signal F _Ci (i = FL to RR) output from the microcomputer 51, which will be described later, is in the ON state of the logical value “1”, each wheel display lamp 35FL to When 35RR is blinked and the tire internal pressure warning control signal F _{Wi, which} is also output from the microcomputer 51, is in the ON state of the logical value "1", each wheel display lamp 35F of the corresponding wheel is also turned on.
The drive signal LD _i for lighting the L to 35RR is output to the corresponding wheel display lamps 35FL to 35RR.
Each drive circuit 53FL to 53RR has a sample hold function, and turns ON / OFF the tire internal pressure caution control signal F _Ci or the tire internal pressure warning control signal F _Wi input last time.
Until the state is switched, the lamp drive signal LD _i corresponding to the control signals F _Ci and F _Wi is continuously transmitted.

Next, the arithmetic processing executed by the arithmetic processing unit 51b of the microcomputer 51 will be described with reference to the flowchart of FIG. This calculation process is executed by a timer interrupt process for each predetermined sampling time (for example, 5 msec.) ΔT. In this flowchart, each internal pressure caution control signal F _Ci (i = FL to RR), internal pressure warning control signal F _Wi , variable internal pressure caution control signal F _CBi ,
Fluctuating internal pressure warning control signal F _WBi , fixed internal pressure caution control signal F _CAi , fixed internal pressure warning control signal F _WAi , control flags F ₁ , F ₂ , fluctuation reference values D ₁₁₀ , D ₃₁₀ , wheel speed ratio difference Average value of aveD _1A , aveD _3A , aveD _1B , aveD _3B ,
Accumulation differential value .SIGMA.D _1, .SIGMA.D _3, the counters n, N _i, in the present embodiment are reset respectively the initial value (= 0) when the ignition switch is again ON from OFF. In addition, in this flowchart, the fixed type determination area A
Is a determination region in which the front-rear wheel speed left-right ratios P _F and P _R when the tire internal pressure changes are orthogonal coordinate axes, which are set in advance by experiments or the like in a straight traveling state of the vehicle or an approximately straight traveling steady traveling state. In addition, in this flowchart, the steps necessary for communication are not provided, but the information necessary for the arithmetic processing is
It is read from the storage device 51c into the buffer of the arithmetic processing device 51b, and the arithmetic result of the arithmetic processing device 51b is updated and stored in the storage device 51c at any time.

In this calculation process, first, in step S1, the calculation process of FIG. 5, which will be described later, is called, and the internal pressure caution counters N _Ai , N _Bi and the wheel speed ratio difference cumulative value ΣD of each wheel are called.
Clear ₁ and ΣD ₃ . Next, in step S2, the arithmetic processing of FIG. 6 which will be described later is called to calculate and set the front / rear wheel speed left / right ratios P _F and P _R.

Next, the process proceeds to step S3, and the step
Front-rear wheel left-right ratio P calculated in step S2 _F, P_RBefore consists of
Rear wheel left / right ratio coordinates (P_F, P_R) Is the solid state of FIG.
It is an element of the fixed form determination area A, that is, the coordinate (P_F, P
_R) Is included in the fixed type determination area A.
However, the front / rear wheel left / right ratio coordinates (P_F, P_R) Is a fixed type
If it is included in the area A, move to step S4
If not, it returns to the main program.

In step S4, the wheel speed ratio cumulative counter n is incremented. Next, the process proceeds to step S5, and the calculation process of FIG. 7 described later is called to calculate and set the wheel speed ratio difference cumulative values ΣD ₁ and ΣD ₃ . Then step S
6, the arithmetic processing of FIG. 8 described later is called to determine whether to reset the variable determination area B of FIG. 17 described later.

Next, in step S7, the arithmetic processing of FIG. 9 which will be described later is called to call the variable type judgment area B of FIG.
Make the settings for Next, in step S8, the wheel speed ratio cumulative counter n is set to a predetermined count value n set in advance.
_It is determined whether or not the _{value is} greater than _0. If the wheel speed ratio cumulative counter n is greater than the predetermined count value n _{0, the process} proceeds to step S9, and if not, the process returns to the main program.

In step S9, the arithmetic processing of FIG. 10 which will be described later is called, and the evaluation value aveD _{1A of} the inner pressure reduction wheel is calculated.
aveD _3A , aveD _1B , and aveD _3B are calculated, and their reference values D ₁₁₀ and D ₃₁₀ are set. Next, in step S10, the arithmetic processing of FIG. 11 which will be described later is called to identify the wheel with reduced internal pressure in the fixed type determination area A.

Next, in step S11, the front / rear wheel left / right ratio coordinates (P _F , P _R ) composed of the front / rear wheel left / right ratios P _F , P _R calculated in step S2 are the variable type shown in FIG. It is an element of the determination area B, that is, the coordinate (P _F ,
P _R ) is included in the variable determination region B, and if the front / rear wheel left / right ratio coordinates (P _F , P _R ) are included in the variable determination region B, the process proceeds to step S12. Migrate, otherwise return to main program.

In step S12, the process shown in FIG.
The arithmetic processing of (1) is called to identify the wheel with reduced internal pressure in the variable type determination area B. Next, in step S13, the internal pressure caution control signal F _{Ci is called} by calling the arithmetic processing of FIG. 13 described later.
Also, the internal pressure warning control signal F _Wi is set. Next, in step S14, the internal pressure caution control signal F _Ci and the internal pressure warning control signal F _Wi set in step S13 are output and then the process returns to the main program.

Next, the minor program executed in step S1 will be described with reference to the flowchart of FIG. In this minor program, first step S
In 101, each internal pressure attention control signal F _Ci is OF of logical value “0”
It is determined whether the F state or not, and each internal pressure attention control signal F _Ci
Is OFF, the process proceeds to step S102, and if not, the process proceeds to step S103.

[0040] Step If at the step S102, the pressure warning control signal F _Wi is determined whether the OFF state of the logical value "0", each individual pressure warning control signal F _Wi is OFF If it is not, the process proceeds to step S103. Step S1
In 04, the internal pressure caution counter N _Ai for the fixed type determination area (hereinafter, also simply referred to as fixed) and the internal pressure caution counter N _Bi for the variable type determination area (hereinafter, also simply referred to as variable) are cleared to “0”. Then, the process proceeds to step S103.

In step S103, it is determined whether or not the wheel speed ratio cumulative counter n is in the clear state of "0". If the wheel speed ratio cumulative counter n is in the clear state, the process proceeds to step S105. If not, it returns to the main program. Step S105
In, clear the accumulation differential value .SIGMA.D ₃ of the accumulation differential value .SIGMA.D ₁ and diagonal wheel speed ratio value D ₃ of the right and left wheel velocity ratio the differential D ₁ respectively to "0", the process proceeds to step S2 .

Next, the minor program executed in step S2 will be described with reference to the flowchart of FIG. In this minor program, first step S
In 201, the wheel speed (wheel rotation angular velocity equivalent) of the wheel speed sensors 46FL~46RR Vw _{i (i} = FL~R
R) and the brake signal S _BRK of the brake switch 45 are read.

[0043] and then proceeds to step S202, using the wheel speed Vw _i, to calculate the present value V _C of the average vehicle speed _(n) according to the following 1 formula. _{V C (n) = (Vw} FL + Vw FR + Vw RL + Vw RR) / 4 ......... (1) then the process proceeds to step S203, the current value V _{C (n)} and its previous value V of the average vehicle speed _{Using C (n-1)} , the vehicle body longitudinal acceleration Xg is calculated from these differential values (or difference values) according to the following two equations.

Xg = (VC _(n) -VC _(n-1) ) / ΔT (2) Next, in step S204, the current value V _{C (n)} of the average vehicle speed is set. The storage device 5 is used as the previous value V _{C (n-1).}
It is updated and stored in 1c. At the next step S205, the brake signal S _BRK it is determined whether the OFF state of the logical value "0", the brake signal S _BRK is O
If it is in the FF state, the process proceeds to step S206, and if not, the process returns to the main program.

In step S206, it is determined whether or not the absolute value | Xg | of the vehicle body longitudinal acceleration is smaller than a preset predetermined longitudinal acceleration value Xg ₀ , and the absolute value | Xg | of the vehicle body longitudinal acceleration is predetermined. If it is smaller than the longitudinal acceleration value Xg _{0, the process} proceeds to step S207, and if not, the process returns to the main program. Step S2
In 07, using the wheel speeds Vw _i, shifts wheel speed lateral ratio P _F according to Equation 3 below and 4 wherein after calculating a rear wheel speed lateral ratio P _R in the process of the step S3.

P _F = Vw _FL / Vw _FR (3) P _R = Vw _RL / Vw _RR (4) Next, regarding the minor program executed in step S5, referring to the flowchart of FIG. explain.

[0047] In this minor program first in step S501, using the wheel speeds Vw _i, to calculate the left and right wheel speed ratio the differential D ₁ according to Formula 5 below. D ₁ = Vw _FL / Vw _FR −Vw _RL / Vw _RR (5) Next, the process proceeds to step S502, and the wheel speeds Vwi _{i are set.}
Using, the diagonal wheel speed ratio difference D ₃ is calculated according to the following six equations.

D ₃ = Vw _FL / Vw _RR −Vw _FR / Vw _RL (6) Next, the process proceeds to step S 503, and the difference accumulation of the left and right wheel speed ratio front-back difference D ₁ is performed according to the following equations 7 and 8. After calculating the difference cumulative value ΣD ₃ of the value ΣD ₁ and the diagonal wheel speed ratio difference D ₃ , the process proceeds to step S6. ΣD ₁ = ΣD ₁ + D ₁ (7) ΣD ₃ = ΣD ₃ + D ₃ (8) Next, the minor program executed in step S6 will be described with reference to the flowchart of FIG.

In this minor program, first in step S601, the door signal S from the door switch 42 is sent.
_DOOR is equal to or in the closed state of the logical value "0", step S6 when the door signal S _DOOR is closed
02, otherwise moves to step S603. In step S602, it is determined whether or not the trunk lid signal S _TR from the trunk lid switch 43 is in the closed state with a logical value "0". If the trunk lid signal S _TR is in the closed state, step S602 is executed. S60
No. 4, otherwise, to step S603.

In step S604, the fuel lid signal S _FL from the fuel lid switch 44 is sent.
Is in the closed state of the logical value "0", and if the fuel lid signal S _FL is in the closed state, the process proceeds to step S7, and if not, the process proceeds to step S603. To do. In the step S603, the transition from resetting the variable-determination region setting prohibition flag F ₁ and variable-reference-value setting prohibition flag F ₂ are both "0" in step S605.

In step S605, the wheel speed ratio cumulative counter n is cleared to "0", and then step S6.
Move to 06. In the step S606, both the fluctuation internal pressure caution control signal F _CBi and the fluctuation internal pressure warning control signal F _WBi are reset to “0”, and _{then the} step S606 is performed.
The process shifts to 7.

Next, the minor program executed in step S7 will be described with reference to the flowchart of FIG. In this minor program, first step S
The front wheel speed left / right ratio P _F and the rear wheel speed left / right ratio P _R are respectively added to the front wheel speed left / right ratio cumulative value ΣP _F and the rear wheel speed left / right ratio cumulative value ΣP _R , which are updated and stored in the storage device 51c at 701. was added respectively values, a new front wheel speed lateral ratio cumulative value .SIGMA.P _F, updates stored in the storage device 51c as the rear wheel speed lateral ratio cumulative value .SIGMA.P _R.

Next, the process proceeds to step S702 and the variable type
Judgment area setting prohibition flag F₁Is in the reset state of "0"
Whether or not there is a variable type determination area setting prohibition flag
Gu F ₁Is reset to "0", step
If it is not, the process proceeds to step S703.
The process shifts to the process of 8. In step S703, the wheels are
The speed ratio cumulative counter n is a preset cumulative count set in advance.
Value n_DIt is determined whether or not the above, and the wheel speed ratio cumulative power is concerned.
Unter n is the predetermined cumulative count value n_DIf more than
If no, go to step S704.
The process proceeds to step S8.

In step S704, the variable front / rear wheel speed left / right ratio reference value P _F0B ,
After calculating P _R0B , the _{process proceeds} to step S705. P _F0B = ΣP _F / n _D (21) P _R0B = ΣP _R / n _D (22) In step S705, according to a minor program (not shown), the variable front and rear wheels are used as shown in FIG. speed lateral ratio reference value P _f0B, P _R0B (or its coordinates (P _f0B, P _R0B)) was set to variable-reference point C _B, the variable-reference point C _B street and front wheel speed lateral ratio P _F front wheel speed lateral ratio P _F is slightly with the straight line L _1B of the rear wheel speed lateral ratio P _R is slightly, the increase in the variable-reference point C _B street and the rear wheel speed lateral ratio P _R with increasing to the straight line L _2B, the transition from creating sets the variable-determination region B plus a preset minute width d _B in step S706.

In the step S706, the variable type determination area setting prohibition flag F ₁ is set to "1", and then the process proceeds to the step S8. Next, the step S
The minor program executed in 9 will be described with reference to the flowchart of FIG. In this minor program, first, in step S901, using the difference accumulated value ΣD ₁ of the left-right wheel speed ratio front-back difference, the average value aveD of the left-right wheel speed ratio front-back difference for the fixed type determination area (for fixation) is calculated according to the following nine equations.
Calculate _1A . In the equation, D ₁₀₀ is an initial value of the front-rear difference between the left and right wheel speed ratios when the four wheels are traveling straight in a normal internal pressure state.

AveD _1A = ΣD ₁ / n ₀ −D ₁₀₀ (9) Next, the process proceeds to step S902 and the difference cumulative value ΣD ₃ of the diagonal wheel speed ratio differences is used according to the following formula (10). Calculate the average value aveD _3A of the fixed diagonal wheel speed ratio difference. In the formula, D ₃₀₀ is the initial value of the diagonal wheel speed ratio difference when the four wheels are traveling straight in the normal internal pressure state.

AveD _3A = ΣD ₃ / n ₀ −D ₃₀₀ (10) Next, the process proceeds to step S903, and it is determined whether or not the variable determination region setting prohibition flag F ₁ is set to “1”. If the variable determination area setting prohibition flag F ₁ is in the set state of "1", the process proceeds to step S904, and if not, the process proceeds to step S905.

In step S904, the variable group
Quasi-value setting prohibition flag F₂Is set to "1"
It is determined whether or not the variable reference value setting prohibition flag F.₂But
If it is in the set state of "1", go to step S906.
If not, move to step S905
It In step S906, in step S901
Average value of front-rear difference for fixed left / right wheel speed ratio calculated in step aveD_1A
The left / right wheel speed ratio front-back difference reference value D for fluctuation₁₁₀When set to
And the fixed diagonal wheel speed calculated in step S902.
Average value of ratio difference aveD _3ADiagonal wheel speed ratio difference reference value for fluctuation D
₃₁₀After setting to, shifts to step S907.

In step S907, the variable reference value setting prohibition flag F ₂ is set to "1", and then the process proceeds to step S905. In the step S905, the process proceeds from calculating the average value AVED _1B of the right and left wheel velocity ratio difference before and after a change in accordance with the following 23 formula to Step S908. aveD _1B = aveD _1A −D ₁₁₀ (23) In step S908, the average value aveD _3B of the varying diagonal wheel speed ratio differences is calculated according to the following equation 24, and then the process proceeds to step S10.

AveD _3B = aveD _3A −D ₃₁₀ (24) Next, the minor program executed in step S 10 will be described with reference to the flowchart of FIG. 11. In this minor program, first, step S100
1, the average value aveD _{1A of the} fixed left / right wheel speed ratio front / rear difference is a preset negative value of the predetermined left / right wheel speed ratio front / rear difference for the front wheel (−
_D1F0 ) is smaller than the predetermined value, and if the average value aveD _{1A of the} fixed left / right wheel speed ratio front-rear difference is smaller than the negative value of the front wheel predetermined left / right wheel speed ratio front-rear difference (-D _1F0 ). The process moves to step S1002, and if not, step S1
Move to 003.

In step S1002, it is determined whether or not the average value aveD _{3A of the} fixed diagonal wheel speed ratio difference is smaller than the preset negative value (-D ₃₀ ) of the predetermined diagonal wheel speed ratio difference. If the average value aveD _{3A of the} fixed diagonal wheel speed ratio difference is smaller than the negative value (−D ₃₀ ) of the predetermined diagonal wheel speed ratio difference, the process proceeds to step S1004, and if not, step S1004. The process moves to S1005.

In step S1005, it is determined whether the average value aveD _{3A of the} fixed diagonal wheel speed ratio difference is larger than the positive value D _{30 of} the preset predetermined diagonal wheel speed ratio difference value, If the average value aveD _{3A of the} fixed diagonal wheel speed ratio difference is larger than the positive value D _{30 of the} predetermined diagonal wheel speed ratio difference, step S
The process proceeds to 1006, and if not, the process returns to the main program.

In step S1006, it is determined whether or not the average value aveD _{1A of the} fixed left / right wheel speed ratio front-rear difference is smaller than a preset negative value (-D _1R0 ) of the predetermined rear wheel left / right wheel speed ratio front-rear difference. If the average value aveD _{1A of the} fixed left / right wheel speed ratio front-rear difference is smaller than the negative value of the rear wheel predetermined left / right wheel speed ratio front-rear difference (−D _1R0 ), the process proceeds to step S1007. If not, it returns to the main program.

In step S1007, after the fixed rear left wheel internal pressure caution counter N _ARL is incremented,
The process moves to step S1008. Step S100
In 8, it is determined whether the left rear wheel pressure note counter N _ARL or is set greater than a predetermined count value N ₀ in advance for the fixing, after for that fixed left wheel pressure note counter N _ARL is greater than a predetermined count value N ₀ In this case, step S1009
Otherwise, to step S1010.

In step S1009, the fixed rear left wheel internal pressure warning control signal F _WARL is set to the ON state of the logical value "1", and the fixed internal pressure warning control signal F _CAi and the fixed internal pressure warning control signal F _{WAi of the} other wheels are set. Are all logical O "0"
After the FF state, the process shifts to step S11. In step S1010, the fixed rear left wheel internal pressure caution control signal F _CARL is set to the ON state of the logical value "1", and the fixed internal pressure caution control signal F _CAi and the fixed internal pressure warning control signal F _WAi of the other wheels are set. O of all logical values "0"
After the FF state, the process shifts to step S11.

On the other hand, in step S1004, the fixed front right wheel internal pressure caution counter N _AFR is incremented and then the process proceeds to step S1011. Step S1
In 011, the fixed front right wheel internal pressure caution counter N _AFR
Is greater than the predetermined count value N ₀ ,
If the fixed front right wheel internal pressure caution counter N _AFR is larger than the predetermined count value N _{0, the process} proceeds to step S1012, and if not, the process proceeds to step S1013.

In step S1012, the fixed front right wheel internal pressure warning control signal F _WAFR is set to the ON state of the logical value "1", and the fixed internal pressure caution control signal F _CAi and the fixed internal pressure warning control signal F of the other wheels are set. _WAi is all O of logical value "0"
After the FF state, the process shifts to step S11. In step S1013, the fixing front right wheel pressure caution control signal F _CAFR is set to the ON state of the logical value "1", and the fixing _inner pressure caution control signal F _CAi and the fixing _inner pressure warning control signal F _{WAi of the} other wheels are set. Are all logical O "0"
After the FF state, the process shifts to step S11.

On the other hand, in step S1003, it is determined whether or not the average value aveD _{1A of the} fixed left / right wheel speed ratio front / rear difference is larger than the _preset positive value D _{1F0 of the} predetermined front / rear predetermined left / right wheel speed ratio front / rear difference. If the average value aveD _1A of the front and rear fixed left and right wheel speed ratio differences is greater than the positive value D _1F0 of the front and rear predetermined left and right wheel speed ratio front and rear differences, the _{process proceeds} to step S1014, and otherwise. The process moves to step S1015.

In step S1015, all wheels are
Internal pressure caution control signal F for fixing_CAiAnd fixed internal pressure warning system
Signal F_WAiBefore turning off the logical value "0"
The process moves to step S11. In addition, the step
In step S1014, the average value of the fixed diagonal wheel speed ratio difference a
veD _3AIs a positive value of the preset predetermined diagonal wheel speed ratio difference value
D₃₀It is determined whether or not it is greater than the fixed diagonal wheel speed ratio.
Average difference aveD_3AIs a positive value D of the predetermined diagonal wheel speed ratio difference value₃₀Yo
If it is larger, the process moves to step S1016,
If not, the process moves to step S1017.

In step S1016, the fixed front left wheel internal pressure caution counter N _AFL is incremented, and then the process proceeds to step S1018. Step S1018
In the fixing front left wheel pressure note counter N _AFL, it is determined whether or not larger than the predetermined count value N _0, before for the fixed left wheel pressure note counter N _AFL predetermined count value N
If it is greater than _{0, the} process proceeds to step S1019, and if not, the process proceeds to step S1020.

In step S1019, the fixed front left wheel internal pressure warning control signal F _WAFL is set to the ON state of the logical value "1", and the fixed internal pressure caution control signal F _CAi and the fixed internal pressure warning control signal F _{WAi of the} other wheels are set. Are all logical O "0"
After the FF state, the process shifts to step S11. In step S1020, the fixed front left wheel internal pressure caution control signal F _CAFL is set to the ON state of the logical value “1”, and the fixed internal pressure caution control signal F _CAi and the fixed internal pressure warning control signal F _WAi of the other wheels are set. O of all logical values "0"
After the FF state, the process shifts to step S11.

On the other hand, in step S1017,
Average value of fixed diagonal wheel speed ratio difference aveD _3AIs preset
Value of the predetermined diagonal wheel speed ratio difference value (-D₃₀) Less than
It is determined whether or not the average value of the fixed diagonal wheel speed ratio difference aveD
_3AIs a negative value of the predetermined diagonal wheel speed ratio difference value (-D₃₀) Smaller field
If so, the process proceeds to step S1021; otherwise,
Returns to the main program.

In step S1021, it is determined whether or not the average value aveD _{1A of the} fixed left / right wheel speed ratio front-rear difference is greater than a preset positive value D _1R0 of the rear wheel predetermined left / right wheel speed ratio front-rear difference. However, the average value of the front-rear difference between the fixed left and right wheel speed ratio a
If veD _1A is larger than the positive value D _1R0 of the front / rear difference of the predetermined left / right wheel speed ratio for the rear wheels, the process proceeds to step S1022, and if not, the process returns to the main program.

In step S1022, after the fixed rear right wheel internal pressure caution counter N _ARR is incremented,
The process moves to step S1023. Step S102
3, the right wheel pressure note counter N _ARR after fixing it is determined whether the set is greater than a predetermined count value N ₀ in advance, after for that fixed right wheel pressure note counter N _ARR predetermined count value N ₀ If larger, step S1024
Otherwise, to step S1025.

In step S1024, the fixed rear right wheel internal pressure warning control signal F _WARR is set to the ON state of the logical value "1", and the fixed internal pressure warning control signal F _CAi and the fixed internal pressure warning control signal F of the other wheels are set. _WAi is all O of logical value "0"
After the FF state, the process shifts to step S11. Further, in the step S1025, the fixed rear right wheel internal pressure caution control signal F _CARR is set to the ON state of the logical value "1", and the fixing internal pressure caution control signal F _CAi and the fixed internal pressure warning control signal F _{WAi of the} other wheels are set. Are all logical O "0"
After the FF state, the process shifts to step S11.

Next, the minor program executed in step S12 will be described with reference to the flowchart of FIG. This minor program, first step wherein the variable-reference-value setting prohibition flag F ₂ in S1200 it is determined whether the set state of "1", the variable-reference-value setting prohibition flag F ₂ is "1" If it is in the set state, the process proceeds to step S1201, and if not, the process returns to the main program.

In step S1201, it is determined whether or not the average value aveD _{1B of the} front-rear difference for the left / right wheel speed ratio for fluctuation is smaller than the _preset negative value (-D _1F0 ) for the front / rear predetermined left / right wheel speed ratio for the front wheel. If the average value aveD _1B of the front-rear difference of the left and right wheel speed ratios for fluctuation is smaller than the negative value (−D _1F0 ) of the predetermined front-rear difference of the left and right wheel speed ratios for the front wheel, the process _proceeds to step S1202. In that case, the process proceeds to step S1203.

In step S1202, it is determined whether the average value aveD _3B of the variable diagonal wheel speed ratio differences is smaller than a preset negative value (-D ₃₀ ) of the predetermined diagonal wheel speed ratio differences. If the average value aveD _{3B of the} variable diagonal wheel speed ratio difference is smaller than the negative value (−D ₃₀ ) of the predetermined diagonal wheel speed ratio difference, the process proceeds to step S1204, and if not, the step S1204. The process moves to S1205.

In step S1205, it is determined whether or not the average value aveD _3B of the varying diagonal wheel speed ratio difference is greater than the positive value D _{30 of} the preset predetermined diagonal wheel speed ratio difference value, If the average value aveD _3B of the varying diagonal wheel speed ratio difference is larger than the positive value D _{30 of the} predetermined diagonal wheel speed ratio difference, step S
The procedure moves to 1206, and if not, the procedure returns to the main program.

In step S1206, it is determined whether or not the average value aveD _{1B of the} front-rear difference for the left and right wheel speed ratios for fluctuation is smaller than the preset negative value (-D _1R0 ) of the predetermined front-rear difference for the left and right wheel speed ratios for the rear wheels. If the average value aveD _{1B of the} front-rear difference of the left / right wheel speed ratio for fluctuation is smaller than the negative value (−D _1R0 ) of the predetermined front / rear difference of the left / right wheel speed ratio for the rear wheel, the process proceeds to step S1207, If not, it returns to the main program.

In step S1207, after the variation left rear wheel internal pressure caution counter N _BRL is incremented,
The process moves to step S1208. Step S120
In 8, it is determined whether the left rear wheel pressure note counter N _BRL is preset predetermined count value N ₀ is greater than for the variation, left wheel pressure after for the variations noted counter N _BRL is greater than a predetermined count value N ₀ In that case, step S1209
Otherwise, to step S1210.

[0082] In step S1209, the left wheel pressure warning control signal F _WBrl after a change to the ON state of the logical value "1", and other variations for pressure Note control signals of the wheel F _CBi and variations for pressure warning control signal F _WBi Are all logical O "0"
After the FF state, the process shifts to step S13. Further, in step S1210, the left wheel pressure Note control signal F _CBRL after a change to the ON state of the logical value "1", and other variations for pressure Note control signal F _CBi and variations for pressure warning control signal F _WBi wheel O of all logical values "0"
After the FF state, the process shifts to step S13.

On the other hand, in step S1204, the variable front right wheel internal pressure caution counter N _BFR is incremented, and then the process proceeds to step S1211. Step S1
In 211, the front right wheel pressure caution counter for fluctuation N _BFR
Is greater than the predetermined count value N ₀ ,
If the variable front right wheel internal pressure caution counter N _BFR is greater than the predetermined count value N _{0, the process} proceeds to step S1212, and if not, the process proceeds to step S1213.

In step S1212, the variable front right wheel internal pressure warning control signal F _WBFR is set to the ON state with the logical value "1", and the variable internal pressure caution control signal F _CBi and the variable internal pressure warning control signal F are changed. All _WBi are O with logical value "0"
After the FF state, the process shifts to step S13. Further, the step S1213, the front right wheel pressure Note control signal F _CBFR for fluctuating an ON state of a logical value "1", the other wheels of change for pressure Note control signal F _CBi and variations for pressure warning control signal F _WBi Are all logical O "0"
After the FF state, the process shifts to step S13.

On the other hand, in step S1203, it is determined whether or not the average value aveD _{1B of the} fluctuation left-right wheel speed ratio front-back differences is greater than the _preset positive value D _{1F0 of the} predetermined front-wheel predetermined left-right wheel speed ratio front-rear differences. If the average value aveD _1B of the front-rear difference of the left / right wheel speed ratio for fluctuation is larger than the positive value D _1F0 of the front / rear difference of the left / right wheel speed ratio for the front wheel, the _{process proceeds} to step _S1214. The process moves to step S1215.

In step S1215, all wheels are
Internal pressure caution control signal F for fluctuation of_CBiAnd internal pressure warning system for fluctuations
Signal F_WBiBefore turning off the logical value "0"
The process proceeds to step S13. In addition, the step
In step S1214, the average value of the variation diagonal wheel speed ratio difference a
veD _3BIs a positive value of the preset predetermined diagonal wheel speed ratio difference value
D₃₀It is determined whether or not it is larger, and the diagonal wheel speed ratio for fluctuation is determined.
Average difference aveD_3BIs a positive value D of the predetermined diagonal wheel speed ratio difference value₃₀Yo
If it is larger, the process moves to step S1216,
If not, the process moves to step S1217.

In step S1216, the variable front left wheel internal pressure caution counter N _BFL is incremented, and then the process proceeds to step S1218. Step S1218
Then, it is determined whether or not the fluctuation front left wheel internal pressure caution counter N _BFL is larger than the predetermined count value N ₀ , and the fluctuation front left wheel internal pressure caution counter N _BFL is determined by the predetermined count value N _0.
If it is greater than _{0, the process} proceeds to step S1219, and if not, the process proceeds to step S1220.

[0088] In step S1219, the pre-use variable left wheel pressure warning control signal F _WBfl the ON state of the logical value "1", and other variations for pressure Note control signals of the wheel F _CBi and variations for pressure warning control signal F _WBi Are all logical O "0"
After the FF state, the process shifts to step S13. Further, in step S1220, the pre-use variable left wheel pressure Note control signal F _CBFl the ON state of the logical value "1", and other variations for pressure Note control signal F _CBi and variations for pressure warning control signal F _WBi wheel O of all logical values "0"
After the FF state, the process shifts to step S13.

On the other hand, in step S1217,
Average value of diagonal wheel speed ratio difference for fluctuation aveD _3BIs preset
Value of the predetermined diagonal wheel speed ratio difference value (-D₃₀) Less than
It is judged whether or not the average value aveD of the variation diagonal wheel speed ratio difference.
_3BIs a negative value of the predetermined diagonal wheel speed ratio difference value (-D₃₀) Smaller field
If so, the process proceeds to step S1221; otherwise,
Returns to the main program.

In step S1221, it is determined whether or not the average value aveD _{1B of the} front-rear difference of the left / right wheel speed ratio for fluctuation is larger than a preset positive value D _{1R0 of the} predetermined front / rear difference of the left / right wheel speed ratio for the rear wheel. However, the average value of the difference between the left and right wheel speed ratios for fluctuation a
If veD _1B is greater than the positive value D _1R0 of the rear wheel predetermined left / right wheel speed ratio front / rear difference value, the process proceeds to step S1222, and if not, the process returns to the main program.

In step S1222, the variable rear right wheel internal pressure caution counter N _BRR is incremented, and then the
The process moves to step S1223. Step S122
In 3, the right wheel pressure note counter N _BRR after a change to determine whether the set is greater than a predetermined count value N ₀ in advance, the right wheel pressure after for the variations noted counter N _BRR predetermined count value N ₀ If so, step S1224
Otherwise, to step S1225.

[0092] In step S1224, the right wheel pressure warning control signal F _WBrr after a change to the ON state of the logical value "1", and other variations for pressure Note control wheel signal F _CBi and variations for pressure warning control signal F All _WBi are O with logical value "0"
After the FF state, the process shifts to step S13. Further, the step S1225, the right wheel pressure Note control signal F _CBRR after a change to the ON state of the logical value "1", the other wheels of change for pressure Note control signal F _CBi and variations for pressure warning control signal F _WBi Are all logical O "0"
After the FF state, the process shifts to step S13.

Next, the minor program executed in step S13 will be described with reference to the flowchart of FIG. In this minor program, first, in step S1301, the fixing internal pressure caution control signal F for each wheel is set.
It is determined whether or not _CAi is in the set state of "1". If the fixed internal pressure attention control signal F _CAi is in the set state of "1", the process proceeds to step S1302, and if not, the step is performed. The procedure moves to S1303.

[0094] At step S1303, it is determined whether the reset state of each wheel the variation for pressure Note control signal F _CBi "0", for the variation pressure Note control signal F _{CB i} is "0" If it is in the reset state, the process proceeds to step S1304, and if not, the process proceeds to step S1302. In step S1304,
It is determined whether the reset state of each wheel the fixed inner pressure warning control signal F _WAi for "0", when the fixing pressure warning control signal F _{WA i} is reset state of "0" The process moves to step S1305, and if not, the process moves to step S1306.

In step S1305, the front of each wheel is
Internal pressure warning control signal F for fluctuation_WBiIs a reset state of "0"
It is judged whether or not it is in the state of
F_{WB i}Is reset to "0", step
If not, the procedure proceeds to step S1307.
The procedure moves to S1306. On the other hand, step S1302
Then, the fixing internal pressure warning control signal F of each wheel is _WAiBut
It is judged whether or not it is in the set state of "1", and
Internal pressure warning control signal F_WAiIs set to “1”
If so, the process proceeds to step S1306, and if not,
If so, the process proceeds to step S1308.

In step S1308, in front of each wheel.
Internal pressure warning control signal F for fixing_WBiIs a reset state of "0"
It is judged whether or not it is in the state of
F_{WB i}Is in the reset state of “0”,
If not, move to step S1309.
Then, the process proceeds to step S1306. In step S1307
Is the internal pressure caution control signal F_CiAnd internal pressure warning control signal F _WiTo
After the reset state of both "0", the above step S1
The process shifts to the process of No. 4.

In step S1306, the internal pressure warning control signal F _Ci is reset to "0", and the internal pressure warning control signal F _Wi is set to "1". Then, the process proceeds to step S14. . Then, in step S1309, the internal pressure caution control signal F _Ci is set to "1" and the internal pressure warning control signal F _Ci is set.
_{After Wi} is reset to "0", the step S1 is performed.
The process shifts to the process of No. 4.

Here, the wheel speed sensors 46FL to 46FL.
RR and step S2 of the arithmetic processing of FIG. 4 and step S201 of the arithmetic processing of FIG. 6 executed therein constitute the wheel angular velocity detecting means of the tire internal pressure drop detecting device of the present invention,
Similarly, the step S2 of the calculation process of FIG. 4 and the step S203 of the calculation process of FIG. 6 executed therein constitute the longitudinal acceleration detecting means, and the step S2 of the calculation process of FIG. Step S of the calculation processing of
207 and step S3 of the arithmetic processing of FIG. 4 constitute the fixed area determination means, and step S6 of the arithmetic processing of FIG. 4 and the entire arithmetic processing of FIG. 8 executed therein constitutes the wheel load variation detecting means. 9 and the entire calculation process of FIG. 9 executed therein constitutes the variable region setting means, and step S2 of the calculation process of FIG. 4 and step S207 of the calculation process of FIG. The step S11 of the arithmetic processing of FIG. 4 constitutes the variable region determining means, and the step S2 of the arithmetic processing of FIG. 4 and the steps S205 to S207 of the arithmetic processing of FIG. 6 executed therein and the step S3 of the arithmetic processing of FIG. And step S7 and step S11, and the entire arithmetic processing of FIG. 9 executed therein constitutes the condition setting means, and step S5 of the arithmetic processing of FIG. Step S9 and Step S10 and Step S12 and S12 of the arithmetic processing in step S1001 through step S1006 and step S1017 and step S1021, and 11 of the arithmetic processing of the arithmetic processing and the entire 10 of Figure 7 to be executed by its respective
01 to step S1206, step S1217, and step S1221 constitute tire internal pressure reduction wheel specifying means, and step S4 and step S of the arithmetic processing of FIG.
5 and Step S9 and Step S10 and Step S
12 and FIG. 7 and FIG. 10 and FIG.
The entire calculation process of 1 constitutes the tire internal pressure drop detecting means.

Next, the operation of the tire internal pressure drop detecting device of this embodiment will be described. First, in step S3 of the arithmetic processing of FIG. 4, the coordinates (P
_F , P _R ) is included in the determination area A in FIG. Perform and set the conditions for that.

Here, before and after calculated as described above.
Left-to-right ratio P of wheel speed (= front and rear wheel rotation angular velocity)_F, P_RTo each other
When the orthogonal coordinate axes shown in Fig. 14 are set,
Tires rolling with all wheels under normal internal pressure
With a stable radius and a stable road surface condition, for example,
In the present embodiment, the drive wheels applied to the front wheels 9L and 9R are driven.
Power (accelerating force) is stable and at the same time engine braking
The braking force (deceleration force) applied to the drive wheels is stable, and
The braking force from the wheel cylinder is not acting.
In the normal straight running condition, the rotational angular velocity of each wheel is
Since the ratio of is constant, it is defined by the above equations 3 and 4.
The coordinates (P _F, P_R) Is
Fixed reference point C in FIG._AMatches

On the other hand, in the tire of any one of the four wheels
When the pressure drops, the rolling radius of the tire on that wheel decreases.
Therefore, the wheel load of each wheel changes. Specifically
Wheels with reduced pressure and wheels located diagonally to the vehicle
Wheel load for two wheels with reduced load and diagonally opposite the other vehicle
Will increase. At this time, if the wheel load increases,
Because the rolling radius of the tire decreases, the angular velocity of the wheel rotation
If the wheel load decreases, the angular velocity of the wheel
Decrease. However, the wheel whose actual tire pressure is low
Compared to changes in the rotational angular velocity (wheel speed) of the
The change in the wheel rotation angular velocity (wheel speed) accompanying it is small and practical
Suspension spring constant, tire spring constant, car
Depending on the rigidity of the body, the front / rear wheel speed left / right ratio increases
Then, the remaining wheel speed left / right ratio slightly increases. Obedience
Therefore, the front-rear wheel speed left-right ratio is used as the orthogonal coordinate axis as described above.
In the coordinate system, for example, as shown in FIG.
P _FAnd the vertical axis represents the rear wheel speed left / right ratio P_RIf you take
And the tire internal pressure of the front left wheel 9L decreases and
(Front left wheel speed) Vw_FLAs a result, the front-wheel speed left-right ratio
P_FIs greater than the reference point C, the load on the rear right wheel 6R
Weight decreases and rear right wheel speed Vw_RRDecreased and the left rear wheel 6L
Wheel load increases and rear left wheel speed Vw_RLWill increase, so the rear wheels
Speed ratio P_RIs slightly increased, and the tire pressure of the front right wheel 9R is
Lower right front wheel speed Vw_FRAs a result, front wheel speed left
Right ratio P_FIs lower than the reference point C, the rear wheel speed left / right ratio
P_RThe front and rear wheel speeds left and right that occur in two situations
Coordinates (P_F, P_R) Indicates that the vehicle is traveling straight ahead
Under each situation, depending on the tire pressure drop rate of each wheel,
Fixed type reference point C in FIG._AStraight line L passing through_1ADraw the trajectory of
Ku. In addition, the tire internal pressure of either of the rear left and right wheels 6L, 6R
When it decreases, the coordinates of the front-rear wheel speed left-right ratio
(P_F, P_R) Indicates that the vehicle is running straight ahead.
Then, according to the tire internal pressure drop rate of each wheel
Mold reference point C_AStraight line L passing through _2ADraw the trajectory of. These things
Is the wheel speed right / left ratio, that is, P _F,
P_REven if you change the denominator / numerator of
Also, for example, the right and left wheels of the vehicle, that is, the front-rear ratio of the right wheel, and the vehicle left
The front / rear ratio of the side wheel, that is, the left wheel is defined as the orthogonal coordinate axis as described above.
It can be seen that the same tendency is exhibited when set to.

Therefore, step S of the arithmetic processing of FIG.
3, the orthogonal coordinate system of the straight line L _1A of Figure 14 consisting of front and rear wheel speed lateral ratio, the fixed determination region A composed of a union of the regions gave minute width d _A to L _2A, the front and rear wheel speed lateral It is determined whether or not the coordinates (P _F , P _R ) composed of the ratio are included, and the coordinates (P _F , P _R ) composed of the front-rear wheel speed left-right ratio are included in the fixed determination region A. In addition, by performing the tire internal pressure drop determination after that, the vehicle is
It is possible to determine that the vehicle is in a straight traveling state or an approximately straight traveling steady traveling state that is sufficient to accurately detect a decrease in tire internal pressure.
That is, according to this calculation process, the input value for detecting the decrease in the tire internal pressure, that is, the wheel rotation angular velocity (wheel speed), the calculated tire internal pressure, and the like are complicated according to the running state of the vehicle as in the conventional case. Instead of applying a correction, the input value consisting of the wheel rotation angular velocity for detecting the decrease in the tire internal pressure,
By applying the filter in consideration of the wheel load, it is possible to improve the accuracy of detecting the decrease in the tire internal pressure.

However, as described above, the coordinates (P _F , P _R ) composed of the front-rear wheel speed left-right ratio are not limited to wheel load fluctuations due to a decrease in tire internal pressure, and, for example, the number of wheels depending on the number of occupants or the load or the state thereof. Since the influence of the load variation is also exerted, the minute width d _A forming the fixed type determination area _A is relatively large so that the wheel load variation corresponding to the expected number of occupants, the loading amount or the state thereof is absorbed. And have to. Therefore, not only the determination of the straight traveling state or the approximate straight traveling steady traveling state of the vehicle may be unstable, but also the identification of the tire internal pressure-decreasing wheel described later may be unstable.

Therefore, in the present embodiment, step S of the arithmetic processing of FIG. 8 executed in step S6 of the arithmetic processing of FIG.
When the door signal S _DOOR has a logical value "1" indicating an open state at 601, or when the trunk lid signal S _TR has a logical value "1" indicating an open state at step S602, or the fuel lid signal S at step S603. _{When FL} is a logical value "1" indicating an open state and when an ON signal is supplied from the ignition switch, it is considered that there is a possibility that the wheel load state of each wheel may fluctuate.
In 03, both the variable determination area setting prohibition flag F ₁ and the variable reference value setting prohibition flag F ₂ are reset to “0”,
Then the wheel speed ratio accumulation counter n at the same step S605 is cleared to "0", then the variation for pressure Note control signal F _CBi and variations for pressure warning control signal F _WBi in the step S606 is reset to both "0" . When the coordinates (P _F , P _R ) including at least the front-rear wheel speed left-right ratio are included in the fixed determination region A, the wheel speed ratio cumulative counter that is incremented in step S4 of the calculation process of FIG. n is a preset cumulative count value n set in advance
_When it becomes _D or more, the process proceeds from step S703 of the calculation process of FIG. 9 executed in step S7 of FIG. 4 to step S704, and as shown in FIG. As to the coordinates (P _F0B , P _R0B ) consisting of the front-rear wheel speed left-right ratio reference values, the variable reference point C is set in step S705 as shown in FIG.
_B , similar to the above, front and rear wheel speed left / right ratio variation straight lines L _1B and L _2B due to a decrease in tire internal pressure in a straight traveling steady running state passing through the variable reference point C _B are given, and further to both straight lines L _1B and L _2B . set the variable-determination region B consisting of union plus a small width d _B, from the variable-determined region setting prohibition flag F ₁ in the next step S706 is set to "1", it is opened and closed again the door The variable determination area B is maintained unless the trunk lid is opened or closed, the fuel lid is opened or closed, or the engine is restarted.

Then, in S11 of the arithmetic processing of FIG. 4, the coordinate (P
_F , P _R ) is included to determine whether or not the vehicle is in a straight traveling state or an approximately straight traveling steady traveling state. This variable type determination region B is from the initial setting state of the wheel load at that time. Since it is according to the fluctuation state, the given minute width d
_{Even if B} is reduced, as long as the vehicle is in a straight traveling or near straight traveling steady state, the coordinates (P _F ,
P _R) is to not deviate from the variable-determination region B, it is possible to accurately determine the straight or approximate straight steady running state of the vehicle smaller the minute width d _B reversed. Further, the variable type determination area B is opened or closed, the trunk lid is opened or closed, the fuel lid is opened or closed, or the engine is restarted, that is, the wheel load variation may occur. since the re-set, the minute width d _B is may be set relatively small constant value. However, in the present embodiment, the fixed type judgment area A
The determination of a straight traveling state or an approximate straight traveling steady traveling state by is also performed. This is because the coordinates (P _F , P _R ) consisting of the front-rear wheel speed left-right ratio sampled until the variable determination region B is set, that is, the coordinates consisting of the front-rear wheel speed left-right ratio reference value (P _F0B , _This is to avoid the problem that when the tire internal pressure of a certain wheel is already reduced, P _R0B ), it becomes impossible to identify the wheel whose tire internal pressure is to be reduced, which will be described later.

Prior to this, step S of the arithmetic processing of FIG. 6 executed in step S2 of the arithmetic processing of FIG.
In 205, it is determined whether or not the brake signal S _BRK read in step S201 is in the OFF state of the logical value "0", and in step S206, it is determined in step S206.
It is determined whether or not the absolute value | Xg | of the vehicle longitudinal acceleration calculated in 8 is smaller than a preset predetermined longitudinal acceleration value Xg _0, and when these two conditions are satisfied, that is, the braking control described above is performed. power does not act, and when a large acceleration force and deceleration forces to the drive wheel is not acting, the consist front and rear wheel speed lateral ratio coordinates (P _F, P _R) determination of the rectilinear or approximately rectilinear steady running state by By performing the above, it is possible to improve the accuracy of detecting the decrease in the tire internal pressure.

Incidentally, when the longitudinal acceleration of the vehicle body is zero or substantially zero, it is necessary to detect the decrease of the tire internal pressure.
There is also the following action. That is, particularly when a differential limiting device is added between the driving left and right wheels, and in the present embodiment between the front left and right wheels 9L and 9R, the differential limiting device increases the driving force applied to the driving wheels and reduces the driving left and right. Since it has the effect of reducing the difference in the wheel rotation angular velocity (wheel speed) between the wheels, the inclusion of the coordinates (P _F , P _R ) consisting of the front-rear wheel speed left-right ratio in the fixed determination region A or the variable determination region B. Not only the determination becomes ambiguous, but also the left / right wheel speed ratio front / rear difference D ₁ and the diagonal wheel speed ratio difference D ₃ for specifying the wheel whose tire internal pressure is reduced, which will be described later.
There is a possibility that the value of will also vary, and the identification of the wheel whose tire internal pressure is decreasing will be inaccurate. Therefore, when the longitudinal acceleration of the vehicle body is zero or substantially zero, the erroneous determination can be avoided by detecting the decrease in the tire internal pressure thereafter.

[0108] Further, if the act uniformly on the four wheels all the braking force by the brake, since the reduction ratio of each wheel rotational angular velocity becomes uniform, the wheel speeds Vw _{i (i} = FL~RR)
It is reduced to the same rate, for example, from the front and rear wheel speed lateral ratio coordinates (P _F, P _R) in at least rectilinear or approximately straight running condition, a constant value regardless of the braking by the brake. However, the braking force of the brake that actually acts on each wheel is not uniform depending on, for example, the road surface condition or the wheel load condition, and therefore, it is more likely that the decrease rate of each wheel rotation angular velocity will fluctuate. Therefore, if the tire pressure drop detection is not performed when the brake signal S _BRK is in the ON state, the tire pressure drop detection accuracy can be improved as a result.

Next, in the arithmetic processing of FIG. 4, when the condition for detecting the decrease in tire internal pressure in the fixed type determination area A is set as described above, the arithmetic processing of FIG. 7 executed in step S5 is executed. The cumulative counter n becomes larger than the predetermined count value n ₀ in the same step S8 as the fixed left / right wheel ratio front-rear difference D ₁ calculated in step S501 and the fixed diagonal wheel speed ratio difference D ₃ calculated in step S502. Up to step S503, the accumulated difference values ΣD ₁ , ΣD
₃ is calculated, and further, in steps S901 and S902 of the arithmetic processing of FIG. 10 executed in step S9,
The average value of the difference between the front and rear wheel speed ratio for fixing ave
D _1A , the average value of the fixed diagonal wheel speed ratio difference aveD _3A is calculated. Further, as described above, the variable determination area B is set, the variable determination area setting prohibition flag F ₁ is set to "1", and the variable reference value setting prohibition flag F ₂ is reset to "0". 10 is executed in step S9 of the calculation process of FIG. 4, the steps S903 to S904 and step S904 are executed.
906, and the average value aveD _{1A of} the fixed left / right wheel speed ratio front-back difference and the average value of the fixed diagonal wheel speed ratio difference aveD _3A calculated at that time are respectively the variable left / right wheel speed ratio front-back difference. Since the reference value D ₁₁₀ and the variable diagonal wheel speed ratio difference reference value D ₃₁₀ are set, and then the variable reference value setting prohibition flag F ₂ is set to “1” in step S907, the same step S905 is performed thereafter. Then, from the average value of the front-rear difference between the fixed left and right wheel speed ratios aveD _1A to the reference value D of the front-rear difference between the left and right wheel speed ratios for the fluctuations
_The value obtained by subtracting ₁₁₀ is the average value of the difference between the front and rear wheel ratios for fluctuation ave
It is calculated and set as D _1B , and in the same step S906, the value obtained by subtracting the variable diagonal wheel speed ratio difference reference value D ₃₁₀ from the average fixed wheel diagonal wheel speed ratio difference aveD _3A is the variable diagonal wheel speed ratio. It is calculated and set as the average value aveD _3B of the differences. At this time, by averaging the front-rear wheel speed ratio front-rear difference D ₁ and the diagonal wheel speed ratio difference D ₃ , the coordinates (P _F , P
Rang each wheel speed (wheel rotation angular velocity) Vw _{i when R)} is included in the fixed-type determination area A or variable-determination region B, decreases drop detection accuracy of the tire pressure due to a temporary wheel speed variation It can be suppressed and prevented.

By the way, in the Cartesian coordinate system defined above, all four tires are in the normal internal pressure state,
Coordinates (P _F , P _R ) composed of the front-rear wheel speed left-right ratios during equivalent straight traveling or near straight traveling steady running have a relatively strong positive correlation as shown in FIG. 15, but this correlation is the orthogonal coordinates. As described above, in the system, as the tire pressure in the front left wheel decreases (decompresses), it moves to the right of the reference point, that is, to the region where the front wheel speed left / right ratio increases, and to the left of the reference point as the front right wheel depressurizes. , Ie, moving to the front wheel speed left / right ratio decreasing area, above the reference point as the rear left wheel depressurizes, ie, moving to the rear wheel speed left / right increasing area, lowering to the reference point as the rear right wheel depressurizing That is, the vehicle moves to a region where the rear wheel speed left / right ratio decreases. Although FIG. 15 shows a change in the front / rear wheel left / right ratio with respect to the fixed determination region A, it is obvious that this tendency is the same for the variable determination region B.

Here, for example, in the fixed type determination area A, the front-rear difference D ₁ between the left and right wheel speed ratios calculated in accordance with the above equation 5 in step S501 in the calculation process of FIG. 7 in step S5 of the calculation process of FIG. Focusing on, the change in the wheel rotation angular velocity (wheel speed) due to the decrease in the tire internal pressure,
When the tire internal pressure of the front left wheel 9L decreases according to the increasing / decreasing tendency of the wheel speed change due to the wheel load change and the magnitude thereof, the front left wheel speed is higher than the change rate of the wheel speed due to the wheel load change of the other wheels. Since the increase rate of Vw _FL is larger, the first term on the right side of the equation 5 becomes larger, and the left-right wheel speed ratio front-back difference D
₁ increases, and also when the tire internal pressure of the rear right wheel 6R decreases, the second term on the right side of the equation 5 decreases, and the left / right wheel speed ratio front-rear difference D ₁ increases. Conversely, when the tire internal pressure of the front right wheel 9R decreases or when the tire internal pressure of the rear left wheel 6L decreases, the left / right wheel speed ratio front-rear difference D ₁ decreases. The result of verifying this by experiment is FIG. 18a.

[0112] Therefore, the initial value D ₁₀₀ of the right and left wheel velocity ratio respective differential D _1, left and right wheel speed ratio before and after difference when the four-wheel is in the normal internal pressure
Then, in step S901 of the calculation process of FIG. 8, which is executed in step S9 of the calculation process of FIG. 4, the initial value D _{100 is} calculated from the average value (ΣD ₁ / n ₀ ) of the difference cumulative values in accordance with the equation (9). When the average value aveD _{1A of the} front-rear difference between the fixed type left and right wheel speed ratios obtained by subtracting the positive value exceeds the dead zone and increases, it means that the tire internal pressure of the front left wheel 9L or the rear right wheel 6R is decreasing. When the average value aveD _{1A of the} front-rear difference of the fixed left / right wheel speed ratio becomes a negative value exceeding the dead zone and decreases, it means that the tire pressure in the front right wheel 9R or the rear left wheel 6L has decreased. Therefore, in step S1001 the processing of FIG. 11 executed by the decreased internal pressure wheel particular step S10 in the arithmetic processing of Fig. 4, the average value AVED _1A predetermined left and right wheels speed ratio for the front wheels of the fixed lateral wheel speed ratio before and after differential When the difference between the front and rear is smaller than the negative value (-D _1F0 ), it is determined and specified in which step the front right wheel 9R or the rear left wheel 6L has decreased tire pressure in the subsequent steps, and the same step S1 is performed.
In 003, the average value of the fixed type left / right wheel speed ratio before and after difference aveD _1A
Is greater than the positive value D _1F0 of the front / rear predetermined left / right wheel speed ratio, the tire internal pressure of the front left wheel 9L or the rear right wheel 6R is determined and specified in the subsequent steps. If none of them, it is determined in step S1015 that the tire internal pressures of all the wheels are at or near the normal internal pressures, and the fixed internal pressure caution control signal F _CAi and the fixed internal pressure warning control signal F _WAi are set to the OFF state. Will be done.

In the present embodiment, as shown in FIG. 18a, even when the tire internal pressure reduction rate is the same, the tire internal pressure of the front wheels decreases and the tire internal pressure of the rear wheels decreases. The amount of change in the front-rear difference D ₁ of the left / right wheel speed ratio is different. This is largely due to the front / rear wheel load distribution of the vehicle, but according to this characteristic, in this embodiment, the rear left wheel 6 is processed in step S1006 after step S1001 described later.
When it is determined and specified that the tire internal pressure of L has decreased, the average value aveD _{1A of the} fixed left / right wheel speed ratio front-rear difference is the negative value of the rear wheel predetermined left / right wheel speed ratio front-rear difference (−D). _1R0 ) and it is confirmed that it is small, and the above-mentioned step S100 described later is performed.
When it is determined and specified that the tire internal pressure of the rear right wheel 6R has decreased in step S1021 after Step 3, the average value aveD _{1A of the} fixed left / right wheel speed ratio front-rear difference is the predetermined left / right wheel speed for the rear wheel. It has been confirmed that the difference between the front and rear ratios exceeds the positive value D _1R0 and is large.

Further, the front / rear wheel speed left / right ratio D ₂ calculated by the following equation 11 may be used in place of the left / right wheel speed ratio front / rear difference D ₁ . D ₂ = Vw _FL / Vw _RL −Vw _FR / Vw _RR (11) Even when this front-rear wheel speed left-right ratio D ₂ is used, a change in the wheel rotation angular velocity (wheel speed) due to the decrease in the tire internal pressure, and When the tire internal pressure of the front left wheel 9L decreases according to the increasing and decreasing tendency of the change of the wheel speed due to the change of the wheel load and its magnitude,
The first term on the right-hand side of Equation 11 increases, the front-rear wheel speed ratio left-right difference D ₂ increases, and also when the tire internal pressure of the rear right wheel 6R decreases, the second term on the right-hand side of Equation 11 decreases. As a result, the front / rear wheel speed ratio left / right difference D ₃ increases. On the contrary, when the tire internal pressure of the front right wheel 9R is reduced, the second term on the right side of the equation 11 is increased, the front / rear wheel speed ratio left / right difference D ₂ is reduced, and the tire internal pressure of the rear left wheel 6L is reduced. In this case, the first term on the right side of the equation 11 becomes smaller and the front-rear wheel speed ratio left-right difference D ₂
Decreases. The result of verifying this by experiment is FIG. 8b (however, in the figure, since the vertical axis is represented by the negative value (−D ₂ ) of the front-rear wheel speed ratio left-right difference, the direction of increase and decrease is apparently reversed. ing).

Therefore, similarly to the above, the front-rear wheel speed ratio left-right difference D ₂ when the four wheels are at the normal internal pressure is set to the initial value D ₂₀₀ of the front-rear wheel speed ratio left-right difference, and is the same as the calculation processing of FIG. Then, the average value aveD _{2A of the} fixed front-rear wheel speed ratio left-right difference obtained by subtracting this initial value D ₂₀₀ from the average value of the difference accumulated values (ΣD ₂ / n ₀ ) becomes a positive value exceeding the dead zone. When it increases, it can be determined by specifying that the tire internal pressure of the front left wheel 9L or the rear right wheel 6R is decreasing, and the average value aveD _{2A of the} fixed left / right wheel speed ratio front and rear difference exceeds the dead zone. When it decreases as a negative value, front right wheel 9R or rear left wheel 6L
It is possible to determine and determine that the tire internal pressure is decreased.

On the other hand, step S1 of the arithmetic processing shown in FIG.
Focusing on the diagonal wheel speed ratio difference D ₃ calculated according to the above equation 6 in step S502 of the calculation processing of FIG. 7 executed at 0, the change in the wheel rotation angular speed (wheel speed) due to the decrease in the tire internal pressure, and the wheel When the tire internal pressure of the front left wheel 9L decreases in accordance with the increasing / decreasing tendency of the wheel speed change due to the load change and its magnitude, the first term on the right side of the equation 6 becomes large and the diagonal wheel speed ratio difference D ₃ becomes Also, when the tire internal pressure of the rear left wheel 6L decreases, the second term on the right side of the equation 6 decreases, and the diagonal wheel speed ratio difference D ₃ increases. On the contrary, front right wheel 9
In the case where the R tire internal pressure decreases, the second term on the right side of the equation 6 increases, the diagonal wheel speed ratio difference D ₃ decreases, and even when the rear right wheel 6R tire internal pressure decreases, The first term on the right side of Equation 6 becomes smaller and the diagonal wheel speed ratio difference D ₃ decreases. The result of verifying this by experiment is FIG. 18c.

Therefore, the diagonal wheel speed ratio difference D ₃ when the four wheels are at the normal internal pressure is set to the initial value D ₃₀₀ of the diagonal wheel speed ratio difference, and is executed in step S9 of the arithmetic processing of FIG. according to the 10 formula in step S902 of the calculation processing of FIG. 10, from the average value of the difference accumulated value (ΣD ₃ / n _0), the initial value D
Average value of the fixed diagonal wheel speed ratio difference obtained by subtracting ₃₀₀ ave
When D _3A increases as a positive value that exceeds the dead zone, it means that the tire internal pressure of the front left wheel 9L or the rear left wheel 6L has decreased, and the average value of the fixed diagonal wheel speed ratio front-back difference aveD
_{When 3A} becomes a negative value exceeding the dead zone and decreases, it means that the tire internal pressure of the front right wheel 9R or the rear right wheel 6R has decreased. Therefore, in step S1002 after step S1001 of the calculation process of FIG. 11 that is executed by specifying the internal pressure-decreasing wheel in step S10 of the calculation process of FIG. 4, the average value aveD _{3A of} the fixed diagonal wheel speed ratio difference is the predetermined diagonal. When the wheel speed ratio difference is smaller than the negative value (-D ₃₀ ) and is small, it is determined that the tire internal pressure of the front right wheel 9R is determined to be low, and otherwise specified, the tire internal pressure of the rear left wheel 6L is reduced. On the other hand, in step S1014 after step S1003, the mean value aveD _{3A of} the fixed diagonal wheel speed ratio difference exceeds the positive value D ₃₀ of the predetermined diagonal wheel speed ratio difference and is large. Sometimes, it is determined and specified that the tire internal pressure of the front left wheel 9L has decreased, and if not, the rear right wheel 6
It is determined and specified that the R tire internal pressure has decreased. However, step S1 after step S1002
In step 005, the average value aveD _3A of the fixed diagonal wheel speed ratio difference is not larger than the positive value D ₃₀ of the predetermined diagonal wheel speed ratio difference, or when the fixed diagonal wheel speed difference is determined in step S1017 after step S1014. When the average value aveD _3A of the ratio differences is not smaller than the negative value (−D ₃₀ ) of the predetermined diagonal wheel speed ratio difference, the tire internal pressure is in a condition contrary to the principle of specifying the wheel, and hence the tire internal pressure thereafter. Return to the main program without specifying the degraded wheel.

In this way, the tire internal pressure is reduced.
Each time the wheel is identified, that is, the front and rear wheel speed
Coordinates (P_F, P_R) Is the fixed type determination area A
Left / right wheel speed ratio front-back difference D when included in₁And diagonal wheel speed
Ratio D₃The predetermined count value n ₀Sampled individually
Average value of front / rear difference of fixed left / right wheel speed ratio aveD_1AAnd fixed pair
Average value of square wheel speed ratio difference aveD_3ADecrease in tire pressure
Each time a wheel that is running is identified, the tire pressure drops
Internal pressure caution counter N for fixing the running wheel_Ai(I = FL
To RR) in step S100 of the arithmetic processing of FIG.
4 or step S1007 or step S1016 or
Increment in step S1022
Pressure caution counter N_AiIs the predetermined count value N₀Is less than
First, the same step S1010 or step S1013
Alternatively, in step S1020 or step S1025,
Internal pressure caution control signal F for fixing wheels_CAiIs turned on,
This internal pressure caution counter N for fixation_AiIs the predetermined count value N₀
If it becomes larger, the same step S1009 or step
S1012 or Step S1019 or Step S10
At 24, the internal pressure warning control signal F for fixing the wheel concerned_WAiON
State.

On the other hand, the average value aveD _1B of the fluctuation left / right wheel speed ratio front-back difference and the average value of the fluctuation diagonal wheel speed ratio difference executed by the calculation process of FIG. 12 executed in step S12 of the calculation process of FIG. The principle of specifying a tire internal pressure reduction wheel using aveD _3B is basically the same as the average value of the front-rear difference between the fixed left and right wheel speed ratios.
aveD _1A and the average value of the fixed diagonal wheel speed ratio difference aveD _3A is exactly the same as the specific principle of the wheel with reduced tire internal pressure,
Specifically, in the explanation of the operation by the calculation process of FIG. 11, the step number S1000 is changed to S1200, the description "fixed" is changed to "variable", and the subscript "A" is changed to " B ”as a result, and as a result, the wheel in which the tire internal pressure is reduced according to the average value aveD _{1B of the} front-rear difference of the left and right wheel speed ratios for fluctuation and the average value aveD _3B of the diagonal wheel speed ratio difference for fluctuations Each time is specified, the internal pressure caution counter N _Bi (i = FL to R for fluctuation of the wheel whose tire internal pressure is decreasing)
R) is incremented in step S1204, step S1207, step S1216 or step S1222 of the arithmetic processing of FIG. 11, and when the fluctuation internal pressure caution counter N _Bi is equal to or less than the predetermined count value N ₀ , step S1210 or step S1213 or step S1220 or variations for pressure Note control signal F _CBi of the wheel and turned ON at step S1225, when the variation for pressure note counter N _Bi is greater than the predetermined count value N _0, the step S1209 or step S1
212 or Step S1219 or Step S1224
Then, the internal pressure warning control signal F _WBi for fluctuation of the wheel is turned on. However, step S12 of the arithmetic processing of FIG.
In 00, the fluctuation reference value setting prohibition flag F ₂ is set to “1” to set the fluctuation type determination region B, the fluctuation left / right wheel speed ratio front-back difference reference value D _110, and the fluctuation diagonal wheel speed ratio difference. If the reference value D ₃₁₀ is not set, the main program is returned to, and thus the wheel with the decreased tire internal pressure is not specified as described above.

Here, the above-mentioned variation left / right wheel speed ratio front-back difference reference
Value D₁₁₀And diagonal wheel speed ratio difference reference value D for fluctuation₃₁₀And strange
Average value of front / rear difference of dynamic left / right wheel speed ratio aveD_1BAnd diagonal for fluctuation
Average wheel speed ratio difference aveD_3BConsidering the above,
As shown in the figure, the reference value D₁₁₀And for fluctuation
Diagonal wheel speed ratio difference reference value D₃₁₀Is the variable judgment area setting prohibited
Flag F₁Is set to "1" and the variable reference value is set
Prohibition flag F₂When is reset to “0”,
The cumulative counter n is a predetermined cumulative count value n _DBecomes
Fixed left and right wheel speeds when the variable determination area B is set
Average value of difference before and after ratio aveD_1A， Average of fixed diagonal wheel speed ratio difference
Value aveD_3AIt is set from. Therefore, the left and right wheels for this fluctuation
Speed ratio front-back difference reference value D₁₁₀And diagonal wheel speed ratio difference reference value for fluctuation
D₃₁₀Is a preset initial value D_Ten, D₃₀₀Except
It is the difference in each wheel speed ratio according to the wheel load fluctuation of the traveling vehicle,
The average value of the accumulated difference values (ΣD₁/ N₀) From the initial
Value D₁₀₀Fixed left / right wheel speed ratio before and after difference aveD_1AFrom
Further, the left / right wheel speed ratio front-back difference reference value D for fluctuation₁₁₀Subtract
Average value of front and rear difference of left and right wheel speed ratio for fluctuation obtained aveD_1BOr
The average value of the accumulated difference values (ΣD₃/ N₀) From the initial
Value D₃₀₀Average value of fixed diagonal wheel speed ratio difference aveD_3A
To further diagonal wheel speed ratio difference reference value D₃₁₀Is obtained by subtracting
Average value of dynamic speed ratio difference aveD_3BAs mentioned above
Tire pressure drop in a vehicle where the load seems to fluctuate
It can be seen that this is the optimum evaluation value for specifying the wheel.
Therefore, similar to the above, the average value of the difference between the left and right wheel speed ratios for fluctuations
 aveD _1BAnd the average value of the diagonal wheel speed ratio difference for fluctuation aveD_3BFor
And the tire internal pressure is low by comparing with each predetermined value.
It is possible to accurately identify the wheel that is descending. However,
When the variable type determination area B is set, a certain wheel is already present.
In consideration of the possibility that the tire internal pressure of
In the example, the average value aveD of the front-rear difference between the fixed left and right wheel speed ratios_1AOver
And the average value of the fixed diagonal wheel speed ratio difference aveD_3ATires using
Wheels with low internal pressure are identified in parallel.

Then, step S13 of the arithmetic processing of FIG.
In the arithmetic processing of FIG. 13 to be executed, the all control signals F _CAi, F _CBi, F _WAi, when the F _WBi is OFF, the internal pressure noted control in the step S1307 signal F
_Ci and the internal pressure warning control signal F _Wi are also set to the OFF state,
When either the fixed internal pressure caution control signal F _CAi or the variable internal pressure caution control signal F _CBi is in the ON state, only the internal pressure caution control signal F _Ci is turned on in step S1309, and the fixed internal pressure warning control signal is set. When either F _WAi or the fluctuating internal pressure warning control signal F _WBi is in the ON state, only the internal pressure warning control signal F _Wi is turned ON in the same step S1306.
By this, the drive signals LD _{FL to} LD _RR for blinking the corresponding wheel display lamps 35 _{FL to} 35 _RR are output from the drive circuits 53 _{FL to} 53 _RR to which the internal pressure caution control signal F _Ci in the ON state is input. Corresponding wheel indicator lamps 35FL to 35R on the instrument panel
R blinks, and the drive signals LD _{FL to} LD _RR for turning on the corresponding wheel display lamps 35 _{FL to} 35 _RR are output from the drive circuits 53 _{FL to} 53 _RR to which the internal pressure warning control signal F _Wi in the ON state has been input, and the installation is performed. Since the corresponding wheel display lamps 35FL to 35RR on the instrument panel are turned on, an occupant including the driver can recognize that the tire internal pressure of the wheel is reduced.

The wheel rotational angular velocity ratios defined in this embodiment show the same tendency even if the numerator / denominator are exchanged as described above. Therefore, the wheel rotational angular velocity ratios obtained by exchanging the numerator / denominator are changed. May be used to detect a decrease in tire internal pressure. Further, even if the numerator / denominator of the wheel rotation angular velocity ratio is replaced, the difference value shows a uniform tendency according to the decrease rate of the tire internal pressure. Therefore, the calculation of the difference value of each wheel rotation angular velocity ratio is: It is not limited to the above.

Further, in the present embodiment, the details will be described only in the case where the determination of the straight traveling or the approximate straight traveling steady running state using the fixed type determination region and the specification of the tire pressure lowering wheel from the wheel speed ratio coordinate in the fixed type determination region are used together. As described above, the tire internal pressure drop detecting device of the present invention does not necessarily have to be used together. Further, in the present embodiment, the ON signal of the ignition switch, the door signal, the trunk lid signal, and the fuel lid signal are all adopted as the input signals having the possibility of wheel load fluctuation. It is also possible to adopt any one of them or two or more at the same time.

Further, in the present embodiment, the vehicle body longitudinal acceleration is calculated and detected from the differential value or the difference value of the wheel speed (= vehicle body angular velocity). However, for example, a longitudinal acceleration sensor is directly provided in the vehicle body. You may make it detect. However, in that case, it should be noted that the cost of the longitudinal acceleration sensor becomes high. In the above embodiment, the vehicle body speed V _C, which is the average wheel speed, is differentiated according to the equations (1) and (2) to calculate the average vehicle longitudinal acceleration Xg. The vehicle body longitudinal acceleration may be calculated from the average value. Then, in that case, it may be determined that slip occurs in a wheel having a rotational acceleration that is too large or too small, and the vehicle body longitudinal acceleration may be calculated without using the wheel rotational acceleration.

Further, in these embodiments, the case where the tire internal pressure drop detecting device is constituted by the microcomputer has been described, but it may be constituted by combining an electronic circuit such as an arithmetic circuit. Further, the wheel speed sensor as the wheel angular velocity detecting means may be shared with another vehicle motion control device such as a so-called anti-skid control device. In addition, along with this, it becomes possible to share the arithmetic processing unit composed of the microcomputer or the like.

[0126]

As described above, according to the tire internal pressure drop detecting device of the present invention, the right / left ratio of the rotational angular velocities of the front two wheels and the left / right ratio of the rotational angular velocities of the rear two wheels are set on the orthogonal coordinate axes, and the occupant is set. The right-and-left ratio of the detected wheel rotational angular velocity values of the front two wheels is set in the variable type judgment area consisting of the union of the slightly increased straight line passing through the reference point and the minute width When the coordinate point consisting of the left and right wheel rotation angular velocity detection values of the two rear wheels is included, it can be accurately determined that the vehicle is traveling straight or approximately straight.

Further, the variable determination region corresponding to the change in the wheel load of the other wheel caused by the change in the internal pressure of the tire of a certain wheel includes the coordinate points of the front-rear wheel rotation angular velocity left / right ratio. It is possible to determine that the vehicle is traveling straight ahead or approximately straight ahead steadily by simply determining that.Therefore, set the conditions for detecting the decrease in the tire internal pressure of each wheel based on the determination result. Thus, it is possible to accurately detect the decrease in the internal pressure of the tire of each wheel only when the vehicle is traveling straight ahead or approximately straight ahead steadily without complicated correction.

Further, it is determined that the preset fixed-type determination area at the time of normal internal pressure of the four wheels includes the coordinate points of the front-rear wheel rotational angular velocity left-right ratio, and the vehicle goes straight or approximates accordingly. If it is determined that the vehicle is traveling straight ahead steadily, it is also possible to detect that a decrease in tire internal pressure has occurred before the variable determination region is set. Further, from the existence region of the coordinate points consisting of the left / right ratio of the wheel rotational angular velocity detection values of the front two wheels and the left / right ratio of the wheel rotational angular velocity detection values of the rear two wheels with respect to the reference point, the wheel in which the tire internal pressure is lowered is accurately determined. Can be specified.

Further, the difference between the left / right ratio of the wheel rotational angular velocity detection values of the front two wheels and the left / right ratio of the wheel rotational angular velocity detection values of the rear two wheels, or the front / rear ratio of the wheel rotational angular velocity detection values of the left two wheels and the right two wheels. By comparing the difference between the detected front and rear ratio of the rotational angular velocity with the reference value, it is possible to identify the two wheels that are diagonally opposite to each other in the vehicle, and the rotational angular velocity of the front and rear wheels that are diagonally opposite to each other in the vehicle. By comparing the difference in the diagonal ratio of the detected values with the reference value, it becomes possible to identify which of the diagonal positions of the wheels the tire internal pressure is decreasing.

Further, a differential limiting device is provided between the driving left and right wheels by setting the detection condition of the tire internal pressure drop from the detected wheel rotational angular velocity values when the longitudinal acceleration detected value is zero or substantially zero. In this case, the variable element of the left-right difference between the rotational velocities of the driving wheels is eliminated to identify the erroneous judgment when identifying the wheel whose tire internal pressure is decreasing or when detecting that the tire internal pressure is decreasing. It can be avoided.

If the longitudinal acceleration of the vehicle is detected from the differential value of each wheel rotational angular velocity detection value or its difference value, it is not necessary to separately provide a detector such as a longitudinal acceleration sensor, and the cost is reduced. Will be advantageous.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a tire internal pressure drop detecting device of the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of a tire internal pressure drop detecting device of the present invention.

FIG. 3 is a block diagram showing a control unit of FIG.

FIG. 4 is a flowchart of a calculation process executed by the control unit of FIG.

FIG. 5 is a flowchart of arithmetic processing by a minor program executed as part of the arithmetic processing of FIG.

FIG. 6 is a flowchart of arithmetic processing by a minor program executed as a part of the arithmetic processing of FIG.

FIG. 7 is a flowchart of arithmetic processing by a minor program executed as part of the arithmetic processing of FIG.

FIG. 8 is a flowchart of arithmetic processing by a minor program executed as part of the arithmetic processing of FIG.

FIG. 9 is a flowchart of arithmetic processing by a minor program executed as part of the arithmetic processing of FIG.

FIG. 10 is a flowchart of arithmetic processing by a minor program executed as a part of the arithmetic processing of FIG.

11 is a flowchart of the arithmetic processing by a minor program executed as a part of the arithmetic processing of FIG.

FIG. 12 is a flowchart of arithmetic processing by a minor program executed as part of the arithmetic processing of FIG.

13 is a flowchart of arithmetic processing by a minor program executed as a part of the arithmetic processing of FIG.

14 is an explanatory diagram of a fixed determination region of front-rear wheel speed left-right ratio used in the flowchart of FIG.

FIG. 15 is an explanatory diagram showing a state of change in front-rear wheel speed left-right ratio coordinates when each wheel is decompressed in the coordinate system of FIG.

16 is an explanatory diagram showing a change state of front-rear wheel speed left-right ratio coordinates when the wheel load of each wheel changes in the coordinate system of FIG.

17 is an explanatory diagram of a front-rear wheel speed left / right ratio variable determination region used in the flowchart of FIG. 4. FIG.

FIG. 18 is an explanatory diagram of a difference value of a wheel rotation angular velocity ratio for identifying a wheel whose tire internal pressure is low.

[Explanation of symbols]

 6L and 6R are rear left and right wheels 9L and 9R are front left and right wheels 35FL to 35RR are wheel display lamps 40 are control units 42 are door switches 43 are trunk lid switches 44 are fuel lid switches 45 are brake switches 46FL to 46RR are wheel speed sensors 51 Is a microcomputer 53FL to 53RR is a drive circuit

Claims (13)

[Claims] 1. A wheel angular velocity detecting means for detecting a rotational angular velocity of each wheel of a vehicle, and a tire internal pressure drop of each wheel based on a detected value of the wheel rotational angular velocity detected by the wheel angular velocity detecting means to advance straight or approximately straight forward. The tire internal pressure drop detection means that detects when the vehicle is running steadily, the wheel load fluctuation detection means that detects the fluctuation of the wheel load of each wheel, and the conditions for detecting the tire internal pressure drop of each wheel are the rotation of the two front wheels of the vehicle. Condition setting means for setting the left / right ratio of the angular velocities and the left / right ratio of the rotational angular velocities of the two rear wheels on the orthogonal coordinate axes; and the wheel load variation detection means, when the wheel load variation of each wheel is detected, the wheel angular velocity detection means The coordinate point consisting of the average value of the left / right ratios of the wheel rotational angular velocity detection values of the specified number of front two wheels and the average value of the left / right ratio of the detected wheel rotational angular velocity values of the specified number of rear two wheels detected as , The fluctuation A region in which a small width is given to a straight line that passes through the mold reference point and the rotational angular velocity left / right ratio of the front two wheels slightly increases, and the rotation of the rear two wheels passing through the variable type reference point When the angular velocity left / right ratio increases, the variable region setting means for setting the union with the region in which the straight line in which the rotational angular velocity left / right ratio of the front two wheels slightly increases increases the minute width is set in the variable type determination region, and the variable region setting means. The set variable type determination area includes coordinate points consisting of the left / right ratio of the wheel rotational angular velocity detection values of the front two wheels detected by the wheel angular velocity detection means and the left / right ratio of the wheel rotational angular velocity detection values of the rear two wheels. A tire internal pressure drop detecting device, comprising: a variable region determining means that applies a condition for detecting a decrease in tire internal pressure of each wheel. 2. The tire internal pressure drop detecting device according to claim 1, wherein the wheel load variation detecting means is an ON signal of an ignition switch. 3. The tire internal pressure drop detecting device according to claim 1, wherein the wheel load variation detecting means is an opening / closing signal of a door switch. 4. The tire internal pressure drop detecting device according to claim 1, wherein the wheel load variation detecting means is an opening / closing signal of a trunk lid switch. 5. The tire internal pressure drop detecting device according to claim 1, wherein the wheel load variation detecting means is an opening / closing signal of a fuel lid switch. 6. The condition setting means sets a tire internal pressure of each of the four wheels to a predetermined value when the left / right ratio of the rotational angular velocities of the two front wheels and the left / right ratio of the rotational angular velocities of the rear two wheels of the vehicle are set on the orthogonal coordinate axes. The fixed type reference point is a coordinate point that consists of the rotational angular velocity left / right ratio of the two front wheels and the rotational angular velocity left / right ratio of the rear two wheels during steady-state straight running in the normal internal pressure state, and the rotation of the front two wheels passes through the fixed type reference point. A region in which a small width is given to a straight line where the rotational angular velocity left / right ratio slightly increases when the angular velocity left / right ratio increases, and the front two wheels that pass through the fixed reference point and the rotational angular velocity left / right ratio of the rear two wheels increases Of the rotational angular velocity left / right ratio of the front two wheels of the wheel rotational angular velocity detection value of the front two wheels detected by the wheel angular velocity detection means in a preset fixed type determination region consisting of an union with a region in which a straight line with a minute width is given. Left-right ratio and wheel rotation of the rear two wheels 6. A fixed area determining means for applying a condition for detecting a decrease in the internal pressure of the tire of each wheel when a coordinate point consisting of the lateral ratio of the detected angular velocity values is included, wherein the fixed area determining means is provided. The tire internal pressure drop detection device according to any one of claims. 7. The tire internal pressure drop detecting means is a coordinate point composed of a left / right ratio of wheel rotational angular velocity detection values of the front two wheels detected by the wheel angular velocity detecting means and a left / right ratio of wheel rotational angular velocity detection values of the rear two wheels. Is a tire depending on which region of the determination region relative to the variable reference point of the variable determination region in the variable region determination unit or the fixed reference point of the fixed determination region in the fixed region determination unit. 7. The tire internal pressure drop detecting device according to claim 1, further comprising a tire internal pressure drop wheel identifying means for identifying a wheel whose internal pressure has dropped. 8. The tire internal pressure drop wheel identifying means determines a difference between a left / right ratio of wheel rotation angular velocity detection values of the front two wheels detected by the wheel angular velocity detection means and a left / right ratio of wheel rotation angular velocity detection values of the rear two wheels. , The difference in the diagonal ratio of the rotational angular velocity detection values of the front, rear, left, and right wheels, which are diagonally opposite to each other, is compared with a variable reference value or a fixed reference value, respectively, to identify the wheel whose tire internal pressure is decreasing. The tire internal pressure drop detecting device according to claim 7, wherein. 9. The tire internal pressure drop wheel identifying means determines a difference between a front-rear ratio of wheel rotational angular velocity detection values of the two left wheels detected by the wheel angular velocity detecting means and a front-rear ratio of wheel rotational angular velocity detection values of the right two wheels. , The difference in the diagonal ratio of the rotational angular velocity detection values of the front, rear, left, and right wheels, which are diagonally opposite to each other, is compared with a variable reference value or a fixed reference value, respectively, to identify the wheel whose tire internal pressure is decreasing. The tire internal pressure drop detecting device according to claim 7, wherein. 10. The tire internal pressure reduction wheel identifying means is
The lateral ratio of the wheel rotational angular velocity detection value of the front two wheels detected by the wheel angular velocity detection means when the variable region setting means sets the variable reference point and the variable determination area, and the wheel rotational angular velocity detection value of the rear two wheels. Or the difference between the front-rear ratio of the wheel rotation angular velocity detection values of the left two wheels and the front-rear ratio of the wheel rotation angular velocity detection values of the right two wheels, and the rotation angular velocity detection values of the front and rear left and right wheels that are diagonal to each other. 9. The difference between the diagonal ratios of the two is set to the variable reference value, respectively.
Or the tire internal pressure drop detection device according to item 9. 11. A longitudinal acceleration detecting means for detecting a longitudinal acceleration of a vehicle, wherein the condition setting means is the wheel when the longitudinal acceleration detection value detected by the longitudinal acceleration detecting means is zero or substantially zero. The tire internal pressure drop detecting device according to any one of claims 1 to 10, wherein a detection condition of the tire internal pressure drop is set from each wheel rotation angular velocity detection value detected by the angular velocity detecting means. 12. The longitudinal acceleration detecting means detects the longitudinal acceleration of the vehicle from a differential value of each wheel rotation angular velocity detected value detected by the wheel angular velocity detecting means. Tire pressure drop detection device. 13. The longitudinal acceleration detecting means detects the longitudinal acceleration of the vehicle from a difference value between the wheel rotational angular velocity detection values detected by the wheel angular velocity detecting means. Tire pressure drop detection device.