JPH0740718A - Tire air pressure alarm device - Google Patents

Abstract

PURPOSE:To prevent an erroneous decision of deciding the tire air pressure and enhance the reliability and accuracy. CONSTITUTION:The pulse signals from wheel speed sensors to detect the wheel speeds of four wheels respectively are detected in 48 pulses at every detecting cycle per one rotations of the wheels, and by counting the detected signals of the wheel speed sensors, one rotation times of the wheels are detected repeatedly, so as to find an average one rotation times of the wheels (the wheel speed corresponding values), and a deciding variable D to decide the tire air pressure is found by using the one rotation times of the wheels. And when the difference of the deciding variable D and a deciding variable specific value D0 is larger than a specific threshold value epsilonXDELTA, it is decided that the tire air pressure is reduced. When the variation amount of the deciding variable D is large, the tire air pressure deciding is prohibited so as to prevent an error decision owing to an influence of the slip and the noise of a driving wheel, and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure warning device, and more particularly to a device for improving the reliability of wheel speed data detected by a wheel speed sensor.

[0002]

2. Description of the Related Art Since it is not preferable to drive a vehicle in which the air pressure of the tire has dropped to some extent, various tire air pressure warning devices have been proposed. For example, the tire pressure is detected by a sensor to determine a decrease in the tire pressure, or when the tire pressure decreases, the number of rotations of the wheel whose pressure has decreased decreases. It has been proposed that a wheel speed sensor for detecting is provided and a decrease in tire air pressure is determined based on the wheel speed detected by these wheel speed sensors.

For example, in Japanese Patent Laid-Open No. 63-305011, the outputs from the wheel speed sensors of the four wheels are used to calculate the total wheel speed of a pair of wheels on the diagonal line and the other wheel on the other diagonal line. When the difference between the total wheel speed of a pair of wheels is greater than or equal to a predetermined value, it is determined that the tire pressure of any one of the pair of wheels with the larger total wheel speed has decreased, and When the larger one of the wheel speeds of the wheels is higher than the average value of the wheel speeds of the four wheels by a predetermined value or more, it is determined that the air pressure of the wheel has decreased, and the determination result is warned. A configured tire pressure warning device is described.

[0004]

The manufacturing error of the vehicle tire is about 0.3%, but the variation of the tire dynamic radius due to the decrease in tire air pressure is also about 0.3%. Therefore, it is necessary to control the tire air pressure with high accuracy. The tire air pressure determination is executed based on the detection signal of the wheel speed sensor in the steady running state of the vehicle.However, even when the vehicle is in the steady running state, the driving wheel The slip amount becomes large, and the slip amount of the drive wheels becomes large due to the gravel, snow, etc. that are present on the road surface intermittently.
The slip amount of the drive wheels may increase due to other factors.

The object of the present invention is to decrease the tire speed detection accuracy and the tire air pressure judgment accuracy due to the influence of noise generated in the detection signal from the wheel speed sensor and the slip amount of the driving wheel. It is to prevent the erroneous determination of and improve the reliability and accuracy of the tire air pressure determination.

A tire air pressure warning device according to a first aspect of the present invention is a tire air pressure warning device which detects a decrease in tire air pressure by using detection signals of wheel speed sensors of four wheels of a vehicle and outputs an alarm. A wheel speed sensor for detecting each wheel speed, a wheel speed calculating means for obtaining a wheel speed equivalent value of four wheels based on detection signals from the four wheel speed sensors in a steady traveling state of the vehicle, and the wheel speed calculating means. Using a plurality of wheel speed equivalent values obtained in to determine the determination variable to determine the decrease in tire air pressure, the air pressure determination means to determine the decrease in tire pressure based on the determination variable, the previous value of the current value of the determination variable When the amount of change from the value is large, the prohibition means for prohibiting the application of the current value is provided.

Here, the air pressure judging means calculates an initial value of a judging variable corresponding to the initial state of the tire by using a plurality of wheel speed corresponding values obtained by the wheel speed calculating means, and the judging variable and the judging variable. A configuration in which a decrease in tire air pressure is determined based on a deviation from an initial value (claim 2 dependent on claim 1), and the air pressure determination means, when calculating the determination variable initial value, A configuration in which the determination variable initial value is calculated by using a plurality of wheel speed equivalent values that are larger than when the determination variable is calculated (claim 3 dependent on claim 2),
The air pressure determination means can be configured in various modes such as a configuration in which the determination variable initial value is determined from an average value of a plurality of determination variable initial values (claim 4 dependent on claim 2).

[0008]

In the tire pressure warning device according to the first aspect of the present invention, the wheel speed calculating means has the wheel speed equivalent value of four wheels based on the detection signals from the four wheel speed sensors in the steady running state of the vehicle. Ask for. The air pressure determination means obtains a determination variable for determining a decrease in tire air pressure using a plurality of wheel speed equivalent values, and determines a decrease in tire air pressure based on the determination variable. The prohibition unit prohibits the application of the current value when the change amount of the current value of the determination variable from the previous value is large. For example, the determination variable fluctuates due to the influence of slip of driving wheels, noise generated in the detection signal, and the like, and the determination variable also fluctuates when the tire air pressure decreases.

However, by prohibiting the application of the current value of the judgment variable when the change amount of the judgment variable is large, when the judgment variable temporarily fluctuates due to the influence of the slip of the driving wheels or noise, It is possible to reliably prevent erroneous determination of a decrease in air pressure. When the tire air pressure actually drops, it is possible to reliably determine the tire air pressure drop based on the next determination variable that does not change significantly from the current determination variable. As a result, the reliability and accuracy of tire pressure determination can be improved.

Here, in claim 2, the air pressure determination means calculates the determination variable initial value corresponding to the initial state of the tire using a plurality of wheel speed equivalent values, and determines the determination variable and the determination variable initial value. Since the decrease of the tire air pressure is determined based on the deviation, the tire air pressure can be determined in consideration of the initial state of the tire. In the third aspect, the air pressure determination means calculates the determination variable initial value by using a plurality of wheel speed equivalent values, which are larger than when the determination variable is calculated, when calculating the determination variable initial value. The initial value of the variable can be obtained with high accuracy, and the reliability of tire pressure determination can be improved. According to the fourth aspect, the air pressure determination means determines the determination variable initial value from the average value of the plurality of determination variable initial values. Therefore, the determination variable initial value can be accurately obtained, and the reliability of the tire pressure determination can be improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is an embodiment in which the present invention is applied to a tire pressure warning device for a rear-wheel-drive type vehicle for passenger use equipped with an anti-skid brake device. As shown in FIG. 1, in this automobile, the left and right front wheels 1 and 2 are driven wheels, and the left and right rear wheels 3 and 4 are driving wheels, and the output torque of the engine 5 is from the automatic transmission 6 to the propeller shaft 7. It is configured to be transmitted to the left and right rear wheels 3 and 4 via the differential device 8 and the left and right drive shafts 9 and 10. Each wheel 1-4
Include disks 11 to 14 that rotate integrally with the wheels,
Brake devices 31 to 34 including calipers 21 to 224 for braking the rotation of the disks 11 to 14 in response to the supply of the braking pressure are provided respectively, and a brake control system for operating the brake devices 31 to 34 is provided. ing.

This brake control system includes a booster device 2 for increasing the stepping force on the brake pedal 25 by the driver.
6 and a master shilling 27 that generates a braking pressure according to the stepping force increased by the booster 26. The front wheel braking pressure supply line 28 from the master shilling 27 is branched into two paths, and the front wheel branch braking pressure lines 29 and 30 are respectively connected to the calipers 21 and 22 of the left and right front wheel 1 and 2 braking devices 31 and 32. A front valve branch braking pressure line 29 that is connected and communicates with the brake device 31 of the left front wheel 1 is provided with a first valve unit 36, and the other front wheel branch braking pressure line that communicates with the brake device 32 of the right front wheel 2. A second valve unit 37 similar to the first valve unit 36 is also provided in the unit 30.

On the other hand, the rear wheel braking pressure supply line 40 from the master cylinder 27 is provided with a third valve unit 43 similar to the first and second valve units 36 and 37. The rear wheel braking pressure supply line 40 is branched into two paths on the downstream side of the third valve unit 43, and the rear wheel branch braking pressure lines 41, 42 are divided into left and right rear wheels 3, 4.
Are connected to the calipers 23 and 24 of the braking devices 33 and 34, respectively. This brake control system, the first channel that variably controls the braking pressure of the braking device 31 of the left front wheel 1 via the first valve unit 36, and the braking pressure of the braking device 32 of the right front wheel 2 via the second valve unit 37. Through the second channel for variably controlling the vehicle and the third valve unit 43 for the both brake devices 3 for the left and right rear wheels 3 and 4.
A third channel for variably controlling the braking pressures of 3, 34 is provided, and these first to third channels are controlled independently of each other.

The brake control system is provided with a control unit 44 for controlling the first to third channels, and the control unit 44 detects the ON / OFF state of the brake pedal 25.
In response to the brake signal from the steering wheel 6, the steering angle signal from the steering angle sensor 47 that detects the steering angle, and the wheel speed signals from the wheel speed sensors 51 to 54 that detect the rotation speeds of the wheels, respectively, The braking pressure control signal corresponding to the signal of
By outputting to the third valve units 36, 37, 43 respectively, braking control (ABS control) for slips of the left and right front wheels 1, 2 and rear wheels 3, 4 is performed in parallel for each of the first to third channels. .

Next, the tire pressure warning device peculiar to the present invention will be described. This tire pressure warning device is the same as the above 4
Wheel speed sensors 51 to 54 and an initial setting switch 55 for instructing the initial setting of tire pressure determination (this is
Attached to the instrument panel) and a warning lamp 56 attached to the instrument panel,
The control unit 50 is provided with signals from the wheel speed sensors 51 to 54, the initial setting switch 55, and the like, and the warning lamp 56 is driven and controlled by the control unit 50.

Each of the wheel speed sensors 51 to 54 has 48 detecting portions formed on the disks 21 to 24 or adjacent to the disks 21 to 24, which are not shown in the drawing, and are electromagnetically detected by 48 detecting portions. It is configured to be detected by a pickup. The control unit 50 includes a filter for filtering the detection signals from the wheel speed sensors 51 to 54, and a circuit for shaping the waveform of the detection signals filtered by the filter.
An AD converter for A / D converting various analog detection signals,
Input / output interface, CPU, ROM, RAM
And a control program and a map for tire air pressure determination control, which will be described later, are stored in advance in the ROM, and the RAM includes various memories (buffer, memory, Flags, counters, soft timers, etc.). The filter has a variable time constant, and its time constant is set to a large value in order to prevent the accuracy from deteriorating during high speed running, and is set to a small value in order to obtain accuracy during low speed running.

The tire air pressure determination control executed by the control unit 50 will be described below with reference to the drawings starting from FIG. However, in the flow chart, the reference symbol Si (i = 1, 2, ...) Indicates each step. 2 and 3 show the wheel speed sensors 51 to 54.
It shows a detection signal reading process of reading a pulse-shaped detection signal from the device and storing it in a memory. This detection signal reading process is basically always executed while the vehicle is running, but an outline of this process is as follows:
Since the wheel speed sensors 51 to 54 output 48 pulse signals P1 to P4 (wheel speed pulses) per one rotation of the wheel, the counters I1 to P1 count the number of pulse signals P1 to P4.
I4 counts each, and the time when 48 pulse signals P1 to P4 are output (that is, the time when the wheel makes one rotation) is
Time is measured by the timers TC1 to TC4, and the measured time is stored in the memory as wheel speed data.

However, when the four pulse signals P1 to P4 are not input within a predetermined time (time ts shown in FIG. 11) after the start of counting the pulse signals P1 to P4, the road surface condition is not constant and the wheel rotation condition is not constant. Is unstable, so reset the count and clock. Similarly, the pulse signal P1
When the four pulse signals P1 to P4 are not input within a predetermined time (time te shown in FIG. 11) at the end of counting P4 to P4, the road surface condition is not constant and the wheel rotation condition is unstable. To reset. Further, the above counting and timing are executed in the steady running state of the vehicle, in order to improve the reliability of the wheel speed data, the wheel speed data in the predetermined period before the transition to the non-steady running state is erased, and Do not collect wheel speed data in a predetermined period after the unsteady running state is resolved.

Next, the detection signal reading process will be described with reference to the flow charts of FIGS. 2 and 3. After the start of control, timers TC1 to TC corresponding to the four wheels 1 to 4
4 is reset, and the flags F1 to F4 are reset (S1), then the pulse signals P1 to P4 from the wheel speed sensors 51 to 54 are read (S2), and then S2.
It is determined whether the flags Fg3 and Fg4 set in 8 and S32 are both 0 (S3). If the determination is Yes, the process proceeds to S4, and if the determination is No, the process proceeds to S23.

At S4, the pulse signal Pi (however,
i = 1 to 4) is input, that is, whether any of the pulse signals P1 to P4 is input, and Yes
In the case of, the counter Ii (where i = 1 to 4) for counting the input pulse signal Pi is incremented (S5). On the other hand, when the determination in S4 is No, the process proceeds to S12. In S6, it is determined whether or not the flag Fi (where i = 1 to 4) corresponding to the counter Ii is 0 (whether or not before the start of counting). When the flag Fi is 0, the counter Ii is corresponded in S7. The timer TCi to be started is reset and then started, and then the flag Fi is set to 1 (S8). If the result of the determination in S6 is No, the process proceeds to S12.

In S9, it is determined whether or not the flag Fg1 is 0. When the flag Fg1 = 0 at first, the timer TM1 is reset and then started in S10, then the flag Fg1 is set to 1 (S11), and thereafter. S12
Move to. In this way, the timer TM1 starts timing from the input of any of the pulse signals Pi, and each pulse signal P1 to
When P4 is input, the corresponding flags F1 to F4
Is set, and timers TC1 to T corresponding to the flags are set.
C4 starts, and the counter I1 corresponding to the flag
~ Counting by I4 is performed.

Next, in S12, it is determined whether or not the four pulse signals P1 to P4 are input within a very short predetermined time (ts in FIG. 11) measured by the timer TM1, and flags F1 to F4.
If the result of the determination is Yes, S
At 14, it is determined whether or not the count value Ii of the counter Ii = 48 pulses. If No, the process proceeds to S2.
When i = 48 pulses, the timer TCi corresponding to the counter Ii is stopped in S15. still,
When the determination result in S12 is No, the counter K is incremented in S13 and the process returns to S1.

Thus, when the rotation states of the wheels 1 to 4 are unstable and four pulse signals P1 to P4 are not input within a predetermined time after the start of counting every 48 pulse signals P1 to P4, the pulse signals P1 to P1 are input. The count of P4 is reset, and S1 and the subsequent steps are repeatedly executed, but when four pulse signals P1 to P4 are input within a predetermined time,
The timers TC1 to TC4 are sequentially stopped from the timers TC1 to TC4 corresponding to the counter Ii that has counted the 48 pulse signals P1 to P4. In this way, the four wheels 1
The times T1 to T4 required for one rotation of the four wheels are detected.

Next, one of the timers TCi (where i =
1 to 4) are stopped, the flag Fg2 is set in S16.
Is 0, and if the result is Yes, S
At 17, the timer TM2 is reset and then started, then the flag Fg2 is set to 1 (S18), that is, when any one of the pulse signals P1 to P4 is inputted, the timer TM2 is reset and then started. . Next, in S19, it is determined whether or not all the counters I1 to I4 have reached 48 pulses or more within a very short predetermined time (te in FIG. 11) measured by the timer TM2. If the determination result is Yes, In S20, four wheels 1
Data of one rotation time T1 to T4 (hereinafter referred to as wheel speed data (T1 to T4)) are stored in the memory, the counter J is incremented (S21), and then the process proceeds to S23.

However, when the result of the determination in S19 is No, the counter L is incremented in S22 and the process returns to S1 and S1 and subsequent steps are repeated.
Thus, when the rotation states of the wheels 1 to 4 are unstable and four pulse signals P1 to P4 are not input within a predetermined time at the end of counting every 48 pulse signals P1 to P4 (each detection cycle), The speed data (T1 to T4) is not stored in the memory, and S1 and subsequent steps are repeatedly executed.

Next, after S21, the routine proceeds to S23 in FIG. 3, where it is judged at S23 whether the running condition of the vehicle is a turning condition, and at S24 it is judged whether it is an acceleration / deceleration condition, and S25. At S29, it is determined whether or not the vehicle is traveling on a low μ road (a road surface in a low friction state), and at S29 subsequent to S25, it is determined whether or not the vehicle is traveling on a rough road. It should be noted that S23 to S25 and S29 are routines for determining whether or not the vehicle is in a steady traveling state, and these determination routines will be described later with reference to FIGS.

In the turning state, in the acceleration / deceleration state, or in the low μ road traveling state, the routine proceeds to S26, where it is determined whether the flag Fg3 is 0 or not, and the flag Fg3 =
When it is 0, the latest wheel speed data T1 to T4 for 10 revolutions of the wheel speed data (T1 to T4) stored in the memory is erased from the memory in S27, and accordingly, the count of the counter J is increased. The value J is changed to (J-10), then the flag Fg3 is set to 1 in S28, and then the process returns to S1. If the result of the determination in S26 is No, the process directly returns to S1 (Fig. 12). Then, once the flag Fg3 is set, it is determined as No in the next determination in S3.
The process proceeds from S3 to S23 and returns to S1 via S26 as long as the turning state, the acceleration / deceleration state, or the low μ road traveling state continues. Therefore, during this period, wheel speed data (T1 to
T4) is never stored in the memory (see FIG. 12).

When the vehicle is traveling on a rough road according to the determination in S29, it is determined in S30 whether the flag Fg4 is 0. If the flag Fg4 = 0, in S31 the wheel speed data (T1 to T4) stored in the memory is determined. The latest wheel speed data for 15 revolutions (T1 to T4) of () are erased from the memory, and accordingly, the count value J of the counter J is changed to (J-15). Next, in S32, After the flag Fg4 is set to 1, the process returns to S1, and when the determination in S30 is No, the process directly returns to S1 (see FIG. 13).

Then, once the flag Fg4 is set, it is determined as No in the next determination in S3, so S3 is performed.
From S to S23, as long as the rough road running condition continues, S
After 30, the process returns to S1. Therefore, the wheel speed data (T1 to T4) is not stored in the memory while the rough road traveling state continues (see FIG. 13). In this way, wheel speed data (T1 to T
Even in the case of 4), the predetermined number of wheel speed data (T1 to T4) immediately before the transition to the unsteady running state is deleted.
The reliability of the wheel speed data (T1 to T4) can be improved.

Next, S33 to S39 are routines for prohibiting the accumulation of the wheel speed data (T1 to T4) for a predetermined time after the unsteady running state is resolved, and When the steady running state is switched to the steady running state, the determination result in S29 is No.
Move to 33. In S33, the flag Fg3 = 0
Then, it is determined whether or not the flag Fg4 = 0, and when the process does not proceed to S26 or S30 (that is, when the unsteady traveling state is not switched), or the flag Fg3 and the flag Fg4 are reset in S38. After that, since the determination result of S33 is Yes, the process returns from S33 to S1.

On the other hand, once the vehicle transits to the unsteady running state, S2
8 or S32, the flag Fg3 or the flag Fg4
Is set to 1 and then the vehicle is switched to the steady running state, the determination result in S33 is No and the process proceeds to S34. In S34, it is determined whether or not the flag Fg5 is 0. If the determination is Yes, S35 is performed. In, the timer TM3 is reset and then started, then the flag Fg5 is set to 1 (S36), and then the process proceeds to S37.
If the determination result in S34 is No, the process proceeds to S37.

At S37, the time measured by the timer TM3 TM
3 is equal to or more than a short predetermined time C (see FIGS. 12 and 13), and when the time count TM3 is less than the predetermined time C,
The process returns from S37 to S1, but the next determination in S3 is No, so the process moves from S3 to S23, and then S2.
Since 3 to S25, S29, and S33 to S37 are repeatedly returned, the wheel speed data (T1 to T4) is not stored in the memory before the predetermined time C has elapsed (FIG. 1).
2, see FIG. 13). Then, when the predetermined time C has passed,
When the determination in S37 is Yes, the process proceeds to S38, the flags Fg3 and Fg4 are reset to 0 (S38), the flag Fg5 is next reset to 0, and then the process returns to S1. Next time, since the determination in S3 is Yes, S3 to S
It will move to 4. Thus, since the wheel speed data (T1 to T4) is not accumulated until the predetermined time C elapses after shifting from the unsteady running state to the steady running state, the reliability of the wheel speed data (T1 to T4) is You can improve your sex.

Next, the turning determination processing for determining the turning state in S23 will be described with reference to FIG. still,
This processing is executed by interruption processing every predetermined short time. First, a predetermined number of wheel speed data (T1 ...
(T4) is read (S90), then the front wheel speeds Vw1 and Vw2 are calculated based on the respective average values of the wheel speed data (T1 and T2) of the front wheels 1 and 2, and the rear wheels 3 and 4 are calculated. Rear wheel wheel speeds Vw3 and Vw4 are calculated based on the respective average values of the wheel speed data (T3 and T4) (S91). Next, S92
, The absolute value ΔVw of the wheel speed difference (Vw1-Vw2) of the front wheels, the wheel speed difference ΔVwf of the front wheels = (Vw1-Vw)
2), the wheel speed difference ΔVwr = (Vw3−Vw4) of the rear wheels is calculated.

Next, it is judged whether or not the absolute value ΔVw of the wheel speed difference between the front wheels is 0.5 Km / h or less (S93). If the result of the judgment is Yes, it is judged in S96 that the vehicle is not turning, and the flag Ft is set. Is set to 0 and then ends. On the other hand, when ΔVw is not 0.5 Km / h or less, it is determined in S94 whether ΔVwf and ΔVwr have the same sign, and it is determined whether ΔVwf × ΔVwr> 0. If Yes, in S95, It is determined that the vehicle is in a turning state, the flag Ft is set to 1, and then the process ends. If the determination result of S94 is No, S
At 96, it is determined that the vehicle is in the non-turning state, the flag Ft is set to 0, and then the processing ends. The determination in S23 is executed based on the flag Ft.

Next, the acceleration / deceleration determination process for determining the acceleration / deceleration state in S24 will be described with reference to FIG. It should be noted that this process is executed as an interrupt process every predetermined short time. First, from the memory a predetermined number of front wheels 1, 2
Wheel speed data (T1, T2) is read (S10
0), then the front wheel speeds Vw1, Vw2 are calculated based on the respective average values of the wheel speed data (T1, T2) of the front wheels 1, 2, and the front wheel speeds Vw1, Vw2 are differentiated with respect to time. The accelerations AVw1 and AVw2 are calculated (S10
1) Next, it is determined whether or not the absolute values of the front wheel accelerations AVw1 and AVw2 are both equal to or greater than a predetermined value a (S10).
2) If the determination result is Yes, it is determined in S103 that the vehicle is in the acceleration / deceleration state, the flag Fad is set to 1 and the processing ends, and if the determination result in S102 is No, the non-acceleration / deceleration state is set in S104. Is determined, the flag Fad is set to 0, and the process ends. The determination in S24 is performed based on the flag Fad.

Next, the low μ road determination processing for determining the low μ road traveling state in S25 will be described with reference to FIG. It should be noted that this process is executed as an interrupt process every predetermined short time. First, a predetermined number of wheel speed data (T1 to T4) are read from the memory (S110), and then, in S111, the wheel speed data (T1) of the front wheels 1 and 2 (T1).
1, T2) based on each average value, front wheel speed Vw1, V
w2 is calculated, and the wheel speed data (T
3, T4) based on each average value, the rear wheel speed Vw3, V
w4 is calculated, and the vehicle speed V (vehicle body speed) is the front wheel speed Vw.
It is calculated as an average value of 1 and Vw2. Next, S112
At, the slip ratio SL3 of the rear wheel 3 = (Vw3-V)
/ V and the slip ratio SL4 of the rear wheel 4 = (Vw4-V) /
V and are calculated.

Next, in S113, the slip ratio SL
It is determined whether or not both 3 and SL4 are equal to or greater than the predetermined value SL0. If Yes, it is determined that the vehicle is traveling on a low μ road, and the flag F
When μ is set to 1 and the process ends, and when the result of the determination in S113 is No, it is determined that the vehicle is traveling on a high μ road, and the flag Fμ
Is set to 0 and the process ends. The determination in S25 is executed based on the flag Fμ.

Next, the rough road determination processing for determining whether or not the vehicle is traveling on a rough road in S29 will be described with reference to FIG. It should be noted that this process is executed as an interrupt process every predetermined short time. First, in S120 and S121,
Similar to S100 and S111, the front wheel wheel acceleration AV
w1 and AVw2 are calculated, and then the acceleration / deceleration flag Fad
Is 0 (that is, whether it is not in the acceleration / deceleration state) (S122). If it is in the acceleration / deceleration state, the process returns to S120. If it is not in the acceleration / deceleration state, in S123, whether the flag Fa is 1 or not. To be judged. Flag Fa
Is 0, the counters M and N are set to 0 in S124, the timer Tc is reset and then started, and then the flag Fa is set to 1 (S12).
5) and shifts to S126. Note that the determination in S123 is Yes
In case of, it shifts from S123 to S126.

In S126, it is determined whether or not the absolute value of the wheel acceleration AVw1 of the front wheels 1 is equal to or greater than the predetermined value Ao. If the determination is Yes, the process proceeds to S127 and the counter M is incremented. In S128, it is determined whether or not the absolute value of the wheel acceleration AVw2 of the front wheels 2 is equal to or greater than the predetermined value Ao. If the determination is Yes, the process proceeds to S129 and the counter N is incremented. next,
In S130, the measured time Tc of the timer Tc is the predetermined time T
It is determined whether or not it is 0 or more, and the process returns from S130 to S120 repeatedly until the predetermined time T0 elapses, and when the measured time Tc becomes the predetermined time T0 or more, S1
The process proceeds from S30 to S131, and the flag F is sent in S131.
a is reset to 0, and then, in S132, it is determined whether the count value M of the counter M is less than or equal to the predetermined value m and the count value N of the counter N is less than or equal to the predetermined value m.

When the determination in S132 is Yes, S13
If it is determined to be a good road in step 4, the flag Fak is set to 0, and the processing ends, and if the determination in S132 is No, S
In 133, it is determined that the road is rough, the flag Fak is set to 1, and the process ends. That is, when traveling on a rough road, the number of times that the wheel accelerations and decelerations of the left and right front wheels 1 and 2 are abnormally increased within a predetermined time T0 in view of the fact that the wheel speeds of the driven wheels 1 and 2 are likely to change. The vehicle is counted, and the traveling state on the rough road is determined from the count values M and N. The determination in S29 is performed based on the flag Fak.

Next, a group of wheel speed data (T1 to T1) collected by the detection signal reading processing shown in FIGS.
A tire air pressure determination process for determining a decrease in tire air pressure using T4) and outputting an alarm for the decrease in air pressure will be described with reference to FIGS. 4 and 5. Note that this process is executed as an interrupt process for the wheel speed data reading process or a parallel process, and is basically always executed while the vehicle is traveling.

First, various data stored in the memory (wheel speed data necessary for the following control, counter data, etc.) are read (S50), and then the count value J of the counter J is 400 or more. It is determined whether or not (S51), and when the determination is No, the routine returns, and when J ≧ 400, the routine proceeds to S52, where it is determined whether or not the flag Fg6 is 0. When the flag Fg6 = 0, in S53, The total value of the count values K and L of the counters K and L (K +
L) ≦ 80 is determined.

The count value K is the pulse signals P1 to P
The count value L indicates the number of times the counting start of 4 has been stopped.
Indicates the number of times the storage of the wheel speed data (T1 to T4) is stopped at the end of counting the pulse signals P1 to P4, and the total value (K + L) is a parameter indicating an unstable rotational state of the wheels 1 to 4. , That is, wheel speed data (T1 to T
This is a parameter indicating the reliability of 4) (see the mark x in FIG. 14). For example, when the road surface condition is good, the rotation states of the wheels 1 to 4 are stable, and the data is accumulated smoothly, the total value (K + L) becomes a small value, and the road surface is not limited to a bad road distance. When the condition is not good, the total value (K + L) becomes a large value.

When the determination in S53 is Yes, the set value J0 of the data number of the wheel speed data (T1 to T4) used for the tire pressure determination is set to 400 (S54). In this case, the tire air pressure determination is performed using the wheel speed data (T1 to T4) for the 400 rotations of the four wheels. If the determination result in S53 is No, it is determined in S55 whether or not the total value (K + L) is 120 or less. If the determination is Yes, the set value J0 is set to 500 (S56), and then the flag Fg6 is set. After setting to 1, return. If the determination result in S55 is No, S
At 58, it is determined whether the total value (K + L) is 160 or less, and if the determination is Yes, the set value J0 is 60.
The flag Fg6 is set to 0 (S59), the flag Fg6 is set to 1, and then the process returns.

When the result of the determination in S58 is No, the accumulated wheel speed data (T1 to T4) for 400 revolutions is too low in reliability, and therefore the wheel speed data (T1 to T4).
In order to prohibit the application of 4), the process proceeds to S68, the counters J, K and L are reset to 0, and the set value J0 is 4
00, the wheel speed data (T1 to T4) stored in the memory since J = 0 is erased (S68), and then the process returns. When the total value (K + L) is 80 or less, it is determined in S61 whether the count value J of the counter J is the set value J0 or more. In this case, the wheels 40
Since the wheel speed data (T1 to T4) for 0 revolutions has already been accumulated, the determination is Yes and the process proceeds to S62. In S62, the flag Fg6 is set to 0. still,
When the total value (K + L) is 80 or less, the flag Fg6
Remains 0.

On the other hand, when returning from S57,
When S50 to S52 and S61 are repeated and 100 sets of wheel speed data (T1 to T4) corresponding to 100 rotations of the wheel are added, the determination in S61 becomes Yes, the process proceeds to S62, and the flag Fg6 is set. It is reset to 0. Also, S6
When returning from 0, S50 to S52, S61
When 200 sets of wheel speed data (T1 to T4) corresponding to 200 rotations of the wheel are added, the determination result of S61 becomes Yes, the process proceeds to S62, and the flag Fg6 is entered.
Is reset to 0.

In this way, when a group of wheel speed data (T1 to T4) used for tire pressure determination is prepared, S63
At 400 wheels or 500 rotations or 60
Total time Tt of wheel speed data (T1 to T4) for 0 rotation
1 to Tt4 and average times Tm1 to Tm4 per one rotation are calculated. As described above, even if the wheel speed data (T1 to T4) is collected under various conditions, for example, when the vehicle travels uphill, the slip amount of the driving wheels becomes large, and the tire pressure is increased. The reliability of the judgment is reduced, and although it is not a low μ road, the slip of the drive wheel may occur due to the influence of water, gravel, snow, and unevenness that are present intermittently on the road surface. In view of the fact that the drive wheels on one side may slip even on the split road surface and that the wheel speed data (T1 to T4) may vary due to the effects of the occupant and the load, the average of 1 in S64 to S67. It is determined whether the rotation times Tm1 to Tm4 can be applied to the tire pressure determination. That is, S64 to S67
It is a wheel speed data suitability determination routine.

At S64, it is determined whether or not the changes in the wheel speeds of the left and right front and rear wheels are in the same direction, and whether the changes in the wheel speeds of the right and left front and rear wheels are in the same direction. ΔTm1 × ΔTm
It is determined whether 3 ≧ 0 and ΔTm2 × ΔTm4 ≧ 0. However, as shown in FIG. 15, ΔTmi (where i =
1 to 4) are change amounts of the present value with respect to the previous value. S
When the result of determination at No. 64 is No, there is an abnormal change in the four wheel speeds, and therefore the process proceeds to S68, and in S68, it is prohibited to apply the average one revolution time Tm1 to Tm4 of this time to the tire pressure determination. Counter J, K, L is 0
Is reset, the set value J0 is set to 400, and J =
Wheel speed data (T1 to
T4) is erased and then the process returns.

When the determination result of S64 is Yes, S6
5, it is determined whether the absolute value of ΔTmi (where i = 1 to 4) is equal to or less than the predetermined value α, and when one or more absolute values of ΔTm1 to ΔTm4 are larger than the predetermined value α, Since the change in the wheel speed is abnormal, the process proceeds to S68. When the determination in S65 is Yes, in S66,
Slip rate SL of left driving wheel (rear wheel 3) SL = (Tm1-T
m3) / Tm1 and the slip ratio SR = (Tm2-Tm4) / Tm2 of the right drive wheel (rear wheel 4) are calculated. Next, in S67, it is determined whether or not the slip ratios SL and SR are 0 or more and less than or equal to the predetermined value β. If the result of the determination is No, the slip amount of the drive wheels is excessive due to the influence of an uphill road or the like. Then, the process proceeds to S68.

If the determination result in S67 is Yes, it is determined that the average one rotation time Tm1 to Tm4 obtained this time can be applied to the tire air pressure determination, and the process proceeds to S69 in FIG.
In S69, the determination variable D for the tire pressure determination is
The determination variable D is calculated by the calculation formula shown, and the determination variable D is stored in the memory as the determination variable D (i) of this time. Next, S7
At 0, it is determined whether or not the absolute value of the difference between the previous determination variable D (i-1) and the current determination variable D (i) is less than or equal to a predetermined value γ. If the determination result is No, the current determination is The variable D (i) changes abnormally compared to the previous determination variable D (i-1), and it is not preferable to immediately determine that the tire pressure is low using the determination variable D (i).
In S71, the tire pressure determination based on the determination variable D (i) this time is prohibited. Then, in S72, the counters J, K, and L are reset to 0, and the set value J0 is 400.
, The wheel speed data (T1 to T4) stored in the memory since J = 0 is erased, and then the process returns (see FIG. 16).

Next, when the determination in S70 is Yes, in order to set the determination threshold value ε × Δ according to the set value J0 of the number of data, the set value J0 = 4 is set in S73 and S74.
When 00, ε = 1.0 is set, and S75
And S76, when the set value J0 = 500, ε =
The value is set to 4/3, and if S77 and S78 set value J0 = 600, ε = 5/3 is set, and then the process proceeds to S79. In S79, the absolute value of the difference between the current decision variable D and the decision variable initial value D0 is the decision threshold ε × Δ (where Δ is a predetermined constant, 0.02 to 0.02).
It is determined whether or not it is a value in the range of 0.05) or more.
The routine for the calculation processing of the initial value of the determination variable D0 will be described later with reference to FIG. When the determination in S79 is No, the tire pressures of the four wheels are determined to be normal, and then the process proceeds to S83. In S83, the counters J, K, and L are reset to 0 as in S72, and the set value J0 is set to 4
00, wheel speed data in memory (T1 to T4)
Is erased and then returns.

Next, if the determination in S79 is Yes, S
At 81, it is determined that the tire air pressure of any of the four wheels is abnormal (decreased state).
6 is turned on for a predetermined time, and then the process proceeds to S83. Here, as shown in FIG. 16, when the tire air pressure is normal, the absolute value of (D−D0) is equal to or smaller than the determination threshold value ε × Δ. That is, when the tire air pressure decreases, the wheel speed of the wheel with the decreased air pressure increases. For example, when the air pressure of the front wheels 2 or the rear wheels 3 decreases, the judgment variable D becomes larger than the initial value D0, and when the air pressure of the front wheels 1 or the rear wheels 4 decreases, the judgment variables D Since D becomes smaller than the initial value D0, it is possible to determine the decrease in tire air pressure by comparing the absolute value of (D−D0) with the determination threshold value ε × Δ.

When the tire air pressure decreases, the decision variable D fluctuates greatly as shown by the black circles in FIG. 16. However, the decision variable D is temporarily changed due to variations in wheel speed data and variations in running conditions. It can change greatly. Therefore, in order to increase the reliability of the air pressure determination, S7
0 is provided, and the air pressure determination is prohibited when the determination variable D largely changes from the previous value. However, when the air pressure of any of the tires actually drops, the difference between the present judgment variable D and the next judgment variable D does not become large, and S
The determination in 70 is Yes, and it is possible to reliably determine the decrease in air pressure in S79.

As described above, according to the tire air pressure determination control, the reliability of the wheel speed data is calculated at each pulse detection cycle, that is, at each wheel rotation, at the pulse signal count start stage and the count end stage. It is possible to improve the reliability of the wheel speed data by prohibiting the accumulation of the wheel speed data during the period of the unsteady traveling state and the periods before and after the unsteady traveling state. Further, in steps S54, S56, and S59, the set value J0 is increased in response to the decrease in the reliability of the wheel speed data (T1 to T4), and the number of wheel speed data used for one air pressure determination is set. Since the number is increased, it is possible to compensate for the decrease in reliability of the wheel speed data (T1 to T4).

Further, through steps S64 to S67, it is possible to reliably prevent the reliability and accuracy of the tire air pressure determination from being lowered due to variations in road surface conditions and running conditions. Further, in S70, when the determination variable D largely changes from the previous value, the air pressure determination by the determination variable D is prohibited, so that the tire air pressure can be prevented from being erroneously determined, and the reliability and accuracy of the air pressure determination can be improved. Furthermore, S73-S
Since the determination threshold value ε × Δ is set to be large in accordance with the reliability of the wheel speed data (T1 to T4) being reduced in step 78, erroneous determination of tire air pressure is prevented, and reliability of air pressure determination is reduced. The accuracy and precision can be improved.

Next, an initial value setting process for obtaining the judgment variable initial value D0 will be described with reference to FIG.
This initial value setting process is performed when the state of the tires of the four wheels is changed, such as when the vehicle is newly used, when any one of the tires of the four wheels is replaced, or when the tires wear or the like. When the initial setting switch 55 is operated, for example, when the state of the tires of the four wheels changes due to the progress of. First, in S140, the initial setting switch 5
It is determined whether or not No. 5 has been operated. If No, the process returns and if the initial setting switch 55 is operated, S14
1, the same processing as S1 to S68 in FIGS. 1, 2, and 3 is executed.

Next, in S142, the current decision variable D (i) is calculated by the illustrated arithmetic expression and stored in the memory, and then in S143, the absolute value of the decision variable D (i) is a predetermined value. It is judged whether it is C0 or less, and the judgment result is N
When it is o, it is highly possible that the decision variable D (i) was inappropriate due to the influence of the road surface condition and the running condition.
In step S150, the decision variable D (i) is erased from the memory, then the counters J, K, L are reset to 0 in step S150, the set value J0 is set to 400, and then the process returns. .

On the other hand, when the determination in S143 is Yes,
In S144, it is determined whether or not the absolute value of the difference between the previous determination variable D (i-1) and the current determination variable D (i) is less than or equal to a predetermined value γ. If the determination result is No, the previous determination variable is Since the variation amount of the determination variable D (i) for this time with respect to D (i-1) is large and lacks reliability, the process proceeds to S149. When the determination in S144 is Yes, the counter Ka is incremented. The counter Ka is initially set to 0 at the start of control.

Next, in S146, it is determined whether or not the count value Ka of the counter Ka is 10 or more. If the determination result is No, S141 (that is, S1 in FIG. 2).
The process returns to and the above processing is repeated, 10 judgment variables D are accumulated in the memory, and the judgment in S146 is Yes.
Then, in S147, the determination variable initial value D0 is
The 10 decision variables D (i-9), D (i-8),
... Calculated as the average value of D (i), the decision variable initial value D0 is stored in the memory, and then the counter Ka
Is reset to 0, and this initialization processing ends. As described above, the initial value of the decision variable D0 is selected 1
Since the calculation is performed from the average value of 0 determination variables D, the reliability of the determination variable initial value D0 can be improved.

Next, various modified examples in which a part of the above embodiment is modified will be described. First, S64 to S6 in FIG.
Six examples of wheel speed data suitability determination routines that can be applied instead of step 7 will be described with reference to FIGS. 1) First Modification (See FIGS. 17 and 18) As shown in FIGS. 17 and 18, S160 to S162 are
Since the steps are the same as steps S64 to S66 in FIG. 4, description thereof will be omitted. In S163, the slip ratio SL, SR
The smoothed values SLf and SRf are calculated by the illustrated calculation formula.

Next, in S164, (SL-SL
It is determined whether the absolute value of f) is less than or equal to a predetermined value δ (where δ is a value of about 0.001) and the absolute value of (SR-SRf) is less than or equal to the predetermined value δ. If the result is No, the process proceeds to S165, and the determination result of S164 is
If Yes, the process proceeds to S69 in FIG. Incidentally, S16
Step 5 is the same step as S68 in FIG. 4, so description thereof will be omitted. That is, as shown in FIG. 18, the slip ratio S
The wheel speed data (T1 to T4) of the group (wheels 400 or 500 or 600 rotations) is provided only when the slip ratios SL and SR largely change by δ or more as compared with the smoothed values SLf and SRf of L and SR. ) Is not adopted, tire pressure determination based on the data is prohibited, and the wheel speed data (T1 to T4) of the group is deleted.

2) Second Modification (See FIG. 19) As shown in FIG. 19, in S170, the average of four wheels is 1
The rotation time Tm is calculated by the calculation formula shown, and then S
171, the slip ratio S of the left and right drive wheels 3, 4
L and SR are calculated by the calculation formula shown, and then S17
2, the changing direction of the current slip rate SL (i) with respect to the previous slip rate SL (i-1) and the current slip rate SR with respect to the previous slip rate SR (i-1).
Whether or not the changing direction of (i) is changing in the same direction is judged by the inequalities shown, and the judgment result is N
When it is o, the process shifts to S174 similar to S68.

When the result of the determination in S172 is Yes, S
In 173, the change rate of the current slip rate SL (i) with respect to the previous slip rate SL (i−1) is a predetermined value λ.
Whether (? Is about 0.003) or less and the rate of change of the current slip rate SR (i) with respect to the previous slip rate SR (i-1) is less than or equal to a predetermined value? It is judged by the two inequalities shown and the judgment result is No.
When it is, the amount of slip of the drive wheels is large, so S174
If the judgment result is Yes, the process proceeds to FIG.
Then, the process proceeds to S69.

3) Third Modification (See FIG. 20) As shown in FIG. 20, in S180, the wheel speed ratio FRr of the front and rear wheels is calculated by the following calculation formula. FRr = (Tm1 + Tm2) / (Tm3 + Tm4) Next, in calculation 181, the smoothed value FRrf of the wheel speed ratio FRr is calculated by the following calculation formula. FRrf = (7 × FRrf + FRr) / 8 Next, in S182, it is determined whether or not the absolute value of (FRr−FRrf) is less than or equal to a predetermined value C1, and the determination result is N.
When it is o, the slip amount of the driving wheel is large, so S6
The process proceeds to S183, which is the same as step 8, and the determination result is Yes.
When s, the process proceeds to S69 in FIG.

4) Fourth Modification (Refer to FIG. 21) As shown in FIG. 21, in S190, the one-revolution time difference ΔF between the front wheels 1 and 2 and the one-revolution time difference ΔR between the rear wheels 3 and 4 are shown. Is calculated by the formula, and then in S191,
It is determined whether the absolute value of ΔF is less than or equal to the absolute value of ΔR. When the determination is No, the slip amount of the driving wheels is large, so the process proceeds to S192 similar to S68, and when the determination is Yes, The process proceeds to S69 in FIG.

5) Fifth Modification (Refer to FIG. 22) As shown in FIG. 22, the average one rotation time Tm of the left and right front wheels 1 and 2 is calculated by the equation Tm = (Tm1 + Tm2) / 2, and then , S201, it is determined whether the absolute value of (Tm3-Tm) is less than or equal to the predetermined value ν and the absolute value of (Tm4-Tm) is less than or equal to the predetermined value ν. If the determination is No, the drive wheels are Since the slip amount is large, the process shifts to S202 similar to S8, and when the determination is Yes,
The process proceeds to S69 in FIG. 6) Sixth modification (see FIG. 23) As shown in FIG. 23, in calculation 210, the change amount ΔTm1, ΔTm2, ΔTm3, ΔTm4 of the current value of the average one rotation time Tm1 to Tm4 for each wheel with respect to the previous value.
Are calculated by the equation shown in the figure, and then, in S211, the change amounts ΔTm1, ΔTm2, ΔTm3, and ΔTm4 thereof are calculated.
Is determined to have the same sign. If the result of the determination is No, the rotation of the wheels is unstable, so S
When the determination result is Yes, the process proceeds to S212. In S212, it is determined whether or not the absolute values of the change amounts ΔTm1, ΔTm2, ΔTm3, and ΔTm4 are equal to or less than a predetermined value C2, and when the determination result is No, the acceleration / deceleration state or the slip amount of the driving wheel is determined. Since it is large, the process proceeds to S213, and when the determination result is Yes, the process proceeds to 69 in FIG.

7) Seventh Modification (See FIG. 24) A determination variable setting routine which is an alternative to S69 to S78 in FIG. 5 will be described. As shown in FIG. 24, S22
0, S221, S222, S224, S226, S22
9 are S69, S70, S73, S75 of FIG. 5, respectively.
Since the steps are the same as S77 and S72, description thereof will be omitted. S228 is a case where the judgment variable D (i) of this time is inappropriate, and in this S228, the judgment variable D of this time is
The previous decision variable D (i-1) is added to (i), and S2
Move to 29.

When the set value J0 = 400, S222
To S223, the decision variable D is set as the moving average value of the past two decision variables, and the set value J is set.
When 0 = 500, the process proceeds from S224 to S225, and the determination variable D is set as a moving average value of the past three determination variables. When the setting value J0 = 600, S226 to S227. And the decision variable D is
It is set as the moving average value of the past four judgment variables, and S
The process proceeds from S223 or S225 or S227 to S79. As described above, the reliability of the determination variable D can be increased by increasing the number of pieces of data for which the moving average is calculated as the reliability of the wheel speed data decreases.

8) Eighth Modification (See FIG. 25) A determination variable setting routine instead of S69 to S78 of FIG. 5 will be described. As shown in FIG. 25, S24
0, S241, S242, S244, S246, S25
9 are S69, S70, S73, S75 of FIG. 5, respectively.
Since the steps are the same as S77 and S72, description thereof will be omitted. S249 is a case where the current decision variable D (i) is inappropriate, and in this S249, the current decision variable D (i) is
The previous decision variable D (i-1) is added to (i), and S2
Move to 50.

When the set value J0 = 400, S242
From S243 to the smoothed value Df of the judgment variable D
Is calculated by a quintuple smoothed arithmetic expression as shown in the figure,
When the set value J0 = 500, S244 to S244
245, the smoothed value Df of the judgment variable D is calculated by the 6-times smoothed arithmetic expression as shown in the figure, and when the set value J0 = 600, the processing shifts from S246 to S247. , The averaged value Df of the determination variable D is calculated by a 7-times averaged arithmetic expression as shown in S243 or S2.
45 or S247, the process proceeds to S248, where the determination variable D is set equal to the smoothed value Df calculated this time, and then the process proceeds to S79. in this way,
Since the degree of smoothing is increased as the set value J0 increases, the reliability of the determination variable D can be increased.

9) As the timer in the above embodiment, a counter for counting the clock signal from the CPU, or a predetermined cycle in the ABS control device (for example,
A counter or the like that counts the control cycle of 8 ms) may be applied. Further, even during each cycle of detecting the pulse signals P1 to P4 from the wheel speed sensors 51 to 54, it is constantly monitored whether or not the input state of the pulse signals P1 to P4 becomes unstable, and the input state is not detected. When stable, it may be configured to return to S1 of FIG. 2 and restart the counting.

The wheel speed data (T
1 to T4), that is, one rotation time (T1 to T4),
It corresponds to the “wheel speed equivalent value”, but instead of this one rotation time (T1 to T4), the wheel speed (Vw1 to Vw)
4) may be applied to the air pressure determination control.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an automobile tire pressure determination device (tire pressure alarm device) and an anti-skid brake device according to an embodiment.

FIG. 2 is a part of a flowchart of a detection signal reading process of a wheel speed sensor.

FIG. 3 is the rest of the flowchart of the detection signal reading processing of the wheel speed sensor.

FIG. 4 is a part of a flowchart of tire pressure determination processing.

FIG. 5 is the rest of the flowchart of the tire pressure determination process.

FIG. 6 is a flowchart of turning determination processing by interrupt processing.

FIG. 7 is a flowchart of acceleration / deceleration determination processing by interrupt processing.

FIG. 8 is a flowchart of low μ road determination processing by interrupt processing.

FIG. 9 is a flowchart of rough road determination processing by interrupt processing.

FIG. 10 is a flowchart of an initial value setting process.

FIG. 11 is a time chart of wheel speed pulses.

FIG. 12 is a time chart of data detection timing at the time of turning, acceleration / deceleration, and low μ road.

FIG. 13 is a time chart of data detection timing on a rough road.

FIG. 14 is a time chart of data detection timing for 400 rotations of wheels.

FIG. 15 is a time chart of the average time for one wheel rotation (wheel speed data).

FIG. 16 shows a difference (DD) between a judgment variable and an initial value of the judgment variable.
It is a time chart of 0).

FIG. 17 is a flowchart of a wheel speed data suitability determination routine according to a first modification.

FIG. 18 is a time chart showing a slip ratio, its smoothed value, and data acceptance / rejection.

FIG. 19 is a flowchart of a wheel speed data suitability determination routine according to a second modification.

FIG. 20 is a flowchart of a wheel speed data suitability determination routine according to a third modified example.

FIG. 21 is a flowchart of a wheel speed data suitability determination routine according to a fourth modified example.

FIG. 22 is a flowchart of a wheel speed data suitability determination routine according to a fifth modified example.

FIG. 23 is a flowchart of a wheel speed data suitability determination routine according to a sixth modified example.

FIG. 24 is a flowchart of a determination variable setting routine according to a seventh modified example.

FIG. 25 is a flowchart of a determination variable setting routine according to an eighth modified example.

[Explanation of symbols]

 1, 2 front wheels 3, 4 rear wheels 50 control unit 51-54 wheel speed sensor 55 initial setting switch 56 warning lamp

Claims (4)

[Claims] 1. A tire air pressure alarm device for detecting a decrease in tire air pressure using a detection signal of a wheel speed sensor for four wheels of a vehicle and outputting an alarm, the wheel speed for detecting each wheel speed of four wheels of a vehicle. A sensor, a wheel speed calculation means for obtaining a wheel speed equivalent value of four wheels based on detection signals from four wheel speed sensors in a steady traveling state of the vehicle, and a plurality of wheel speed equivalents obtained by the wheel speed calculation means. A determination variable for determining a decrease in tire air pressure using a value is obtained, and an air pressure determination means for determining a decrease in tire air pressure based on the determination variable, when the amount of change from the previous value of the present value of the determination variable is large. A tire pressure warning device comprising: a prohibiting means for prohibiting the application of the current value. 2. The air pressure judging means calculates a judgment variable initial value corresponding to the initial state of the tire by using a plurality of wheel speed equivalent values obtained by the wheel speed calculating means, and the judgment variable and the judgment variable initial value. 3. The method according to claim 1, wherein the decrease in tire pressure is determined based on the deviation from the value.
The tire air pressure alarm device described in. 3. The air pressure determination means, when calculating the determination variable initial value, calculates the determination variable initial value using more than a plurality of wheel speed equivalent values than when calculating the determination variable. It is constituted as follows.
The tire air pressure alarm device described in. 4. The tire pressure warning device according to claim 2, wherein the air pressure determination means is configured to determine the initial value of the determination variable from the average value of the plurality of initial values of the determination variable.