JPH0740720A - Tire air pressure alarm device - Google Patents

Abstract

PURPOSE:To enhance the reliability and accuracy of the tire air pressure decision by selecting the detecting signals from wheel speed sensors accurately. CONSTITUTION:The pulse signals from wheel speed sensors to detect the wheel speeds of four wheels respectively are detected in 48 pluses at every detecting cycle per one rotation of the wheels, and by counting the detecting 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 the tire air pressures are decided by using the one rotation times of the four wheels. When the four pulse signals are not detected in a specific time ts at the count starting time of each detecting cycle, the count of the pulse signals in the detecting cycle is reset, in order to select accurately the pulse signals when the running condition of the wheels is not stable, and the count of the pulse signals in the detecting cycle is reset when the four pulse signals are not detected for a specific time te in the count finishing time of each detecting cycle.

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 pressure determination is performed 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 increases, the slip amount of the drive wheels increases due to gravel, snow, and the like that are intermittently present on the road surface, and the slip amount of the drive wheels may increase due to other factors.

When the slip amount of the driving wheels is large, the detection accuracy of the wheel speed is reduced and the accuracy of the tire air pressure determination is decreased. Therefore, the detection signals detected by the wheel speed sensor are carefully selected and a truly effective detection signal is selected. Unless the wheel speed is obtained with high accuracy by using, it is difficult to increase the reliability and accuracy of tire pressure determination. An object of the present invention is to improve the reliability and accuracy of tire pressure determination by carefully selecting the detection signals from the wheel speed sensor.

[0006]

A tire pressure warning device according to claim 1 is a tire pressure warning device which detects a decrease in tire pressure using a detection signal of a wheel speed sensor of four wheels of a vehicle and outputs a warning. , A wheel speed sensor for detecting the wheel speed of each of the four wheels of the vehicle, and pulsed detection signals from the four wheel speed sensors are read and counted, and each time the count value reaches a predetermined number. Data collection means for storing the obtained wheel speed equivalent data of the four wheels in a memory, and detection from the four wheel speed sensors within a first predetermined time at the start of reading the detection signals from the four wheel speed sensors. When no signal is input, the data collection means is provided with start reset means for resetting the count values of the four detection signals.

According to a second aspect of the present invention, there is provided the tire pressure warning device according to the first aspect, further comprising count restarting means for causing the data collecting means to restart counting of each detection signal after the start resetting means resets the count of detection signals. It is provided. The tire air pressure warning device according to claim 3 is a tire air pressure warning device that detects a decrease in tire air pressure using a detection signal of a wheel speed sensor of four wheels of a vehicle and outputs an alarm. A wheel speed sensor for detecting each wheel and pulse-shaped detection signals from the four wheel speed sensors are read and counted, and wheel speed equivalent data of four wheels obtained each time each count value reaches a predetermined number. Within a second predetermined time from the time when the count value of the detection signal from any one of the wheel speed sensors stored in the memory reaches the predetermined number, the detection signals from the other wheel speed sensors are detected. When the count value does not reach the predetermined number, the data collection means is provided with end reset means for resetting the count values of the four detection signals.

A tire air pressure warning device according to a fourth aspect of the present invention is a tire air pressure warning device which detects a decrease in tire air pressure using a detection signal of a wheel speed sensor of four wheels of a vehicle and outputs an alarm. A wheel speed sensor for detecting the wheel speeds respectively, and pulse-like detection signals from the four wheel speed sensors are read and counted, and the wheel speeds of four wheels are obtained each time each count value reaches a predetermined number. When the detection signals from the four wheel speed sensors are not input within the first predetermined time at the start of reading the detection signals from the data collection means for storing the data in the memory and the four wheel speed sensors, the data Start resetting means for causing the collecting means to reset the count values of the four detection signals, and the time when the count value of the detection signals from any of the wheel speed sensors reaches the predetermined number. Then, when the count value of the detection signals from the other wheel speed sensors does not reach the predetermined number within the second predetermined time, the data collecting means is provided with end reset means for resetting the count values of the four detection signals. Be prepared.

[0009]

According to the tire pressure warning device of the present invention, the data collecting means reads and counts pulse-like detection signals from the four wheel speed sensors,
The data corresponding to the wheel speeds of the four wheels is stored in the memory each time each count value reaches a predetermined number. The start resetting means resets the count values of the four detection signals to the data collecting means when the detection signals from the four wheel speed sensors are not input within the first predetermined time at the start of reading the detection signals. That is, when the wheel rotation state is unstable and the wheel speed of any driven wheel decreases or the wheel speed of any driving wheel increases, the four wheel speed sensors are detected within the first predetermined time. In this case, by resetting the count values of the four detection signals, the detection of the wheel speed in the unstable state of the wheel rotation is stopped and the reliability of the detection signal is reduced. Therefore, the reliability and accuracy of the tire pressure determination can be improved.

In the tire pressure warning device according to a second aspect of the present invention, in the device according to the first aspect, the count resuming means causes the data collecting means to resume the counting of each detection signal after the start resetting means resets the count of the detection signals. ,
Detection from the wheel speed sensor will not be delayed.

According to another aspect of the tire pressure warning device of the present invention, the data collecting means reads and counts pulse-like detection signals from the four wheel speed sensors, and counts each time the count value reaches a predetermined number. The obtained data corresponding to the wheel speeds of the four wheels is stored in the memory. The end resetting means is configured such that, within a second predetermined time from the time when the count value of the detection signal from any of the wheel speed sensors reaches the predetermined number, the count value of the detection signals from the other wheel speed sensors is equal to the predetermined number. If not, the data collection means is caused to reset the count values of the four detection signals. Similarly to claim 1, when the rotational state of the wheel is unstable, the count value of the four detection signals does not reach the predetermined number within the second predetermined time. Therefore, in this case as well, the count of the four detection signals is counted. By resetting the value, it is possible to stop the detection of the wheel speed when the rotation state of the wheel is unstable and improve the reliability of the detection signal, and thereby improve the reliability and accuracy of the tire pressure determination. You can

In the tire pressure warning device according to claim 4, since the data collecting means, the start resetting means, and the end resetting means are provided as in the first and second aspects, the counting start time and the counting start time are counted. At both ends, the detection signals can be carefully selected to improve the reliability of the detection signals and the reliability and accuracy of the tire air pressure determination.

[0013]

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 unique to the present application 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, for detecting 48 electromagnetic waves. 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. 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.

In 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 have been 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 the 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 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 in an acceleration / deceleration condition, and S25. In S, it is determined whether or not the vehicle is traveling on a low μ road (road surface in a low friction state), and in S29 subsequent to S25, it is determined whether or not the vehicle is traveling on a bad 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 or not the flag Fg3 is 0, 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. When 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).

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 from the time when 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 an 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.

In S37, the time measured TM of the timer TM3
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 determined 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 determination is Yes, it is determined 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 running 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 process 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 process returns, and when J ≧ 400, the process proceeds to S52 and 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.

If the determination result 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) is not obtained.
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.

In S64, it is determined whether or not the wheel speed changes of the left and right front wheels are in the same direction and the wheel speed changes of the right front wheel are in the same direction.
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 corresponding 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 drops, 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 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).

Furthermore, through steps S64 to S67, it is possible to reliably prevent the reliability and accuracy of 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, the 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 modifications 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 a predetermined value ν and the absolute value of (Tm4-Tm) is less than or equal to a 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) Incidentally, as the timer in the above embodiment, a counter for counting the clock signal from the CPU or a predetermined period 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.

I] First Alternative Embodiment Next, a first alternative embodiment of the tire air pressure determination control and its modification will be described with reference to Table 1 and the drawings of FIGS. However, in the flow chart, the reference symbol Si (i
= 310, 311, ...) Indicates each step. First, an outline of the tire air pressure determination control will be described. Basically, four wheel speed sensors 51 to 54 are basically provided.
The tire air pressure is determined based on the wheel speeds Vw1 to Vw4 detected in Step 1. However, when the vehicle is started to be used or one or more tires are replaced, the initialization process of the compensation coefficient Cx is executed. , Initialize a compensation coefficient Cx for compensating for tire manufacturing error and characteristics. After that, the tire pressure determination process is executed regularly (every predetermined mileage, or every predetermined period) to determine an abnormal tire pressure of any tire,
When the tire pressure is low, an alarm is output via the warning lamp 56.

The initial setting process is executed in the vehicle speed range set according to the road surface condition, and the tire air pressure determination process is executed in the vehicle speed range separately set according to the road surface condition. The tire air pressure determination control includes an initial setting process, a tire air pressure determination process, a rough road index calculation process, and a road surface friction coefficient calculation process (the flowchart of which is omitted). Further, the flag and counter timer in this other embodiment are independent of the flag and counter in the above embodiment.

Next, the initial setting process of the compensation coefficient Cx will be described with reference to the flowchart of FIG. This processing is started when the initial setting switch 55 is turned on, and then from the wheel speed sensors 51 to 56, the switch 55, and an inclination detection sensor (a sensor that detects the inclination in the front-rear direction of the vehicle body) not shown. Various data obtained by digitizing the signal of
Wheel speeds Vw1 to V of wheels 1 to 4 based on the detection signal from
w4 is calculated (S310), then the warning lamp 56 is turned on to indicate that the initialization process is being executed, and the flag F is reset to 0 to prohibit the tire air pressure determination process (S311). ..

Next, it is determined whether or not the initial setting condition of the coefficient Cx is satisfied (S312), but the vehicle is not in the acceleration / deceleration state, is in the steady straight traveling state, and the vehicle speed V is as shown in FIG. When it is satisfied that the vehicle is in the initial setting permission vehicle speed range of the coefficient Cx set according to the road surface condition shown in the map, it is determined that the condition is satisfied, the process proceeds to S313, and when the condition is not satisfied, the condition is maintained. To return.
The vehicle speed V will be described later, and the acceleration / deceleration is detected from the change in the vehicle speed V.

Here, the lower limit value of the initially permitted vehicle speed range of the coefficient Cx shown in FIG. 30 is set to a predetermined value which is not excessively low speed (for example, 20 Km / H), and the upper limit value of the initially permitted vehicle speed range is The value is set to a value in the range of 40 to 50 km / H according to the road surface condition of the traveling road surface (road surface frictional state, bad road degree, road surface gradient). Regarding the lower limit value, in an excessively low speed state, since the number of pulse signals from the wheel speed sensor is small, the detection accuracy of the wheel speeds Vw1 to Vw4 decreases,
It is desirable to set it to a predetermined value of about 20 Km / H.

Regarding the upper limit value, 4 in the low μ state
It is set to increase linearly from 0 Km / H to 50 Km / H in the high μ condition, and 40 Km in the case of heavy road load.
It is set to linearly increase from / H to 50km / h when the road is light (good road) and 40km when the uphill is large.
50km from / H to a small uphill (flat road or downhill)
It is set to increase linearly to / H, where μ is the friction coefficient of the road surface. In a high speed state of more than 50 km / H, the slip amount of the driving wheels increases, the wheel loads of the front wheels 1, 2 and the rear wheels 3, 4 change, and the detection accuracy of the wheel speeds Vw1 to Vw4 decreases. Therefore, it is desirable to execute the initialization process when the vehicle speed is 50 Km / H or less, and the slip amount of the driving wheels increases when the vehicle speed is low μ, so the initialization process is performed when the vehicle speed is 40 Km / H or less. It is desirable to execute the initial setting process when the vehicle speed is 40 Km / H or less because the wheel speeds Vw1 to Vw4 vary greatly even when the degree of rough road is heavy.

The gradient of the traveling road surface is calculated from the detection signal of the inclination detecting sensor, and the method of calculating the road surface μ and the method of calculating the rough road index (flag Fak) indicating the rough road condition will be described later. Next, when it is determined in S312 that the condition is satisfied, in S313, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement and the like is added with the tire manufacturing error, and the wheel speed Vw1 of the four wheels is Using Vw4,
The sum of the wheel speeds of the left front wheel 1 and the right rear wheel 4 (Vw1 + Vw4) in one diagonal relationship, and the right front wheel 2 in the other diagonal relationship
And the sum of the wheel speeds of the left rear wheel 3 (Vw2 + Vw3),
It is calculated by the following formula. Compensation coefficient Cx = (Vw1 + Vw4) / (Vw2 + Vw3) Next, it is determined whether or not the coefficient Cx is an appropriate value. However, since the tire diameter error due to the tire manufacturing error is 0.3% at maximum, the coefficient Cx is approximately 1 Predetermined range (for example, 0.95 to 1.0
When the value is in 5), it is determined that the coefficient Cx is an appropriate value.

When the coefficient Cx is a proper value, S31
In step 5, the coefficient Cx is rewritten, the previous coefficient Cx (i-1) is given the current Cx (i), the warning lamp 56 is turned off, and the tire pressure determination processing is permitted. Flag F is set to 1, then S
Move to 319. On the other hand, if the determination result in S314 is No, it is determined in S317 whether or not the coefficient Cx is indefinite. If it is indefinite, the process proceeds to S312. If the coefficient Cx is not indefinite, the warning lamp 5 is output in S318.
6 blinks for a predetermined time (for example, 2 seconds), and then S3
Move to 19. In S319, it is determined whether or not the flag F is 1, and if the determination is No, the process returns and the determination is
If Yes, this process ends. However, based on one ON operation of the switch 55, a plurality of initial setting processes may be executed to obtain a plurality of coefficients Cx, and the final coefficient Cx may be determined from the average value of the plurality of coefficients Cx. . In this way, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement is determined and stored in the memory of the RAM.

Now, the calculation processing for obtaining the road surface μ of the traveling road surface will be described. First, the vehicle speed is applied as the vehicle speed V, and this vehicle speed V is basically set equal to the average value of the wheel speeds Vw1 and Vw2 of the driven wheels (front wheels 1 and 2), and the vehicle speed V is set to the initial value. It is applied to the setting process and the tire air pressure determination process. The road surface μ is the vehicle speed V and its acceleration V
It is calculated based on g and 500 ms for this calculation.
Using a timer of 100 ms and a timer of 100 ms, from the change of the vehicle speed V for 100 ms every 100 ms until the vehicle body acceleration Vg does not become sufficiently large after the acceleration starts,
The vehicle body acceleration Vg is calculated by the following equation.

Vg = K1 × [V (i) −V (i-100)] After the lapse of 500 ms when the vehicle body acceleration Vg becomes sufficiently large, from the change of the vehicle speed V for 500 ms every 100 ms,
The vehicle body acceleration Vg is calculated by the following equation. Vg = K2 × [V (i) -V (i-500)] In the above equation, V (i) is the current vehicle speed, V (i-1).
00) is the vehicle speed 100 ms before, V (i-500) is 50
The vehicle speed before 0 ms, K1 and K2 are predetermined constants.
The road surface μ is calculated by three-dimensional complementation from the μ table shown in Table 1 using the vehicle speed V and the vehicle body acceleration Vg obtained as described above, and the road surface μ is subjected to the initialization processing and the tire air pressure determination processing. Applied to.

[0085]

[Table 1]

Now, the calculation process for obtaining the rough road index indicating the rough road condition of the traveling road surface will be described with reference to the flowchart of FIG. This calculation process is, for example,
This is a process for determining using the wheel speed Vw1, and after the start of this rough road index calculation process, various data are read (S35).
0) Next, in S351, it is determined whether or not the flag FA is 0. Since the flag FA is set to 0 at the time of initialization, the first determination result is Yes and the process proceeds to S352. In S352, the counter K is cleared and the timer T
Is reset and then started, then the flag FA is set to 1 in S353, and then the process proceeds to S354. When the determination result of S351 is No, S352 and S3
Step 53 is skipped and the process proceeds to S354. In S354, the wheel acceleration AVw1 (including the wheel deceleration) of the left front wheel 1 is calculated by differentiating the wheel speed Vw1 with respect to time.

Next, in S355, the wheel acceleration AV
It is determined whether or not the absolute value of w1 is equal to or greater than a predetermined rough road determination threshold value A0. If the determination result is Yes, the counter K is incremented (S356), and then the process proceeds to S357, and the determination result is If No, S356 is skipped and the process proceeds to S357. In S357, the count time T of the timer T is the predetermined time T1 (for example, 1000 ms).
It is determined whether or not the above, and before the predetermined time T1 has elapsed,
Repeating the return from S357, the predetermined time T
The counter K counts the number of times that the absolute value of the wheel acceleration AVw1 becomes equal to or more than the rough road determination threshold value A0 during the period of 1.

When the predetermined time T1 has elapsed, the process proceeds from S357 to S358, and the flag FA is reset to 0 for the next count of the predetermined time and the number of times, and then S35.
In 9 to S363, based on the count value K of the counter K, the bad road flag Fak (bad road index) is 0 when K ≦ 3.
Is set, and when 3 <K ≦ 7, the rough road flag Fak is set.
Is set to 1 and when 7 <K, the rough road flag Fak
Is set to 2. However, the numerical values 3 and 7 are set in relation to the predetermined time T1. In this way, the left front wheel 1 is rotated every predetermined time T1 during the initialization process.
The rough road flag Fak based on the wheel speed Vw1 is set to one of 0, 1, and 2. Similarly to the above, the rough road flag Fak is set to any one of 0, 1, and 2 based on the wheel speeds Vw2 to Vw4, and the average value of these four rough road flags Fak is rounded off. Thus, the rough road index for the initialization process and the tire air pressure determination process is calculated.

Next, the tire pressure determination process will be described with reference to the flowcharts of FIGS. 27 and 28.
This tire air pressure determination processing is, for example, processing executed for each traveling distance of 500 Km, and after the start of this processing,
Various data obtained by digitizing the signals from the sensors 51 to 54 and the switch 55 are read (S320), and then it is determined whether or not the flag F is 1 (S321). If Yes, the tire pressure determination condition is determined in S322. It is determined whether or not it is established. Regarding the tire pressure determination conditions, the vehicle is not in an acceleration / deceleration state, is in a steady straight traveling state, and the vehicle speed is within the tire pressure determination permission vehicle speed range set according to the road surface condition shown in the map of FIG. , Are satisfied, it is determined that the condition is satisfied and S
If the condition is not satisfied, the process proceeds to S324.

Here, the lower limit value of the tire pressure determination permission vehicle speed range shown in FIG. 31 is set to a predetermined value which is not excessively low speed (for example, 20 Km / H), and the upper limit value of the tire pressure determination permission vehicle speed range. Is set to a value in the range of 40 Km / H to the maximum vehicle speed in accordance with the road surface condition of the traveling road surface (road surface frictional state, bad road degree, road gradient). Regarding the lower limit value, in an excessively low speed state, since the number of pulse signals from the wheel speed sensors 27 to 30 is small (the number of data is small), the detection accuracy of the wheel speeds Vw1 to Vw4 is reduced.
It is desirable to set it to a predetermined value of Km / H.

Regarding the upper limit value, 4 in the low μ state
It is set to increase linearly from 0 Km / H to the maximum vehicle speed in the high μ condition, and 40 when the degree of rough road is heavy.
It is set to increase linearly from Km / H to the maximum vehicle speed when the degree of bad road is light (good road), and small uphill slope (flat road or downhill) from 40 Km / H when the uphill slope is large. It is set to increase linearly to the maximum vehicle speed at. Then, in the high speed state of more than 50 km / h, the slip amount of the driving wheels increases and the detection accuracy of the wheel speeds Vw1 to Vw4 decreases, but even if the accuracy decreases somewhat, the high speed running state of more than 50 km / h. Since it is desirable to detect the decrease of the tire air pressure in the above, the setting is made as described above. Since the slip amount of the drive wheels increases when the μ is low, it is desirable to execute the tire air pressure determination processing when the vehicle speed is 40 Km / H or less, and also when the road speed Vw1 ~
Since the variation of Vw4 becomes large, it is desirable to execute the tire air pressure determination processing when the vehicle speed is 40 Km / H or less.

In S323, the tire air pressure determination subroutine of FIG. 28 is executed, and then the process returns.
If the determination result of S321 or S322 is No, S32
At 4, the timer T in the tire air pressure determination subroutine is reset, the flags Fa and Ft are reset to 0, the counters I and J are reset to 0, and then the process returns. Next, the subroutine for determining the tire pressure in S323 will be described with reference to FIG. First, it is determined whether the flag Ft is 1 (S33).
0), since it is No at first, the timer T is started and the flag Ft is set to 1 in S331, and S332 is set.
Move to. Further, when the flag Ft is set to 1, the process proceeds from S330 to S332. Then S
At 332, the air pressure determination variable E is calculated by the equation shown, that is, the following equation.

E = 2 × [Cx (Vw2 + Vw3)-(Vw1 + Vw4)]
/ [Vw1 + Vw2 + Vw3 + Vw4] In the above equation, the coefficient Cx is set in advance so as to compensate for the initial state of the tire. Therefore, when the tire air pressure is normal, the air pressure determination variable E becomes a value substantially equal to 0. However, when the tire air pressure of the right front wheel 2 or the left rear wheel 3 is decreasing, the wheel speed Vw2 or the wheel speed Vw3 increases, so the air pressure determination variable E increases in the positive direction, and the left front wheel 1 or When the tire air pressure of the right rear wheel 4 is decreasing, the wheel speed Vw1 or the wheel speed Vw4 increases, so the air pressure determination variable E increases in the negative direction.

Next, in S333, it is judged whether or not the judgment variable E is a predetermined value Δ0 (for example, a predetermined value in the range of 0.020 to 0.050), and if the judgment result is Yes, whether the flag Fa is 1 or not. It is determined (S334) and the flag Fa is 1
If not, the counter I that counts the number of times the judgment variable E is a predetermined value Δ0 or more is set to 1 and the flag F is set.
a is set to 1 (S335), and then the process proceeds to S341. With the flag Fa set to 1,
The process moves from S334 to S336, the counter I is incremented, and then the process proceeds to S341.

On the other hand, if the determination result in S333 is No,
In step S337, it is determined whether the judgment variable E is equal to or less than the predetermined value −Δ0. If Yes, it is determined whether the flag Fa is 2 (S338). If flag Fa is not 2, the judgment variable E is the predetermined value. The counter J which counts the number of times equal to or smaller than −Δ0 is set to 1 and the flag Fa is set to 2 (S339), and then the process proceeds to S341. When the flag Fa is set to 2, the process proceeds from S338 to S340 and the counter J is incremented,
Then, the process proceeds to S341.

Next, in S341, it is determined whether or not the count value T of the timer T has passed a predetermined time T0 (for example, 2 seconds). In the beginning, since the determination result is No, S341 From S320 to S322 and S330 to S341 in FIG. 3 are repeatedly executed, the count value T of the timer T and the count value I of the counter I or the count value J of the counter J are repeated. Increase. Note that FIG. 32 illustrates the behavior of the air pressure determination variable E when the tire pressure is normal, and FIG. 33 illustrates the behavior of the air pressure determination variable E when the tire pressure of the right front wheel 2 or the left rear wheel 3 is abnormal. There is.

When the predetermined time T0 has elapsed, S34
Since the determination result of 1 is Yes, the process proceeds to S342, and it is determined whether the count value I of the counter I is the predetermined value K0 or more or the count value J of the counter J is the predetermined value K0 or more. When the result is No, the tire pressure is determined to be normal in S343 and the process proceeds to S346.
If the determination result in S342 is Yes, S344
It is determined that the tire pressure is abnormal (decreased) in step S34.
In 5, the warning lamp 56 is turned on for a predetermined time (for example, 2 seconds) to warn the driver of a decrease in tire air pressure, and the process proceeds to S346. In S346, the timer T,
The flag Fa, the flag Ft, the counter I, and the counter J are
Each is reset to 0, and the tire air pressure determination processing this time is completed.

Next, the operation of the tire air pressure determination control described above will be described. An initial setting switch 55 is provided on the instrument panel, and by operating the switch 55, an initial setting process for initializing the coefficient Cx is executed when necessary, such as when the tire is replaced.
It is possible to set the coefficient Cx that compensates for the manufacturing error of the wheel tire. Since the initial setting process is executed in the vehicle speed range set according to the road surface condition of the traveling road surface,
The error factors due to the slip of the driving wheel on the low μ road, the variation of the wheel speed on the bad road, the slip of the driving wheel on the uphill, the fluctuation of the wheel load, etc. are eliminated as much as possible, and the coefficient Cx
Can be initialized with high accuracy.

After the initial setting process, the tire air pressure determination process is always executed using the compensation coefficient Cx while the vehicle is running. This tire air pressure determination process is executed when the vehicle is traveling straight and in the vehicle speed range set according to the road surface condition of the traveling road surface.Therefore, similar to the case of the initial setting process, the driving wheels on the low μ road are It is possible to enhance the accuracy and reliability of tire air pressure determination by eliminating error factors caused by slip, variations in wheel speed on bad roads, slips of driving wheels on uphills, fluctuations in wheel load, etc. as much as possible.
In the tire pressure determination process, the timer T, the counter I, and the counter J are used to count the count value I that satisfies E ≧ Δ0 and the count value J that satisfies E ≦ −Δ0 at the predetermined time T0. When the count values I and J are equal to or greater than the predetermined value K0, it is determined that the tire pressure is abnormal, so that the tire pressure can be determined accurately based on a large amount of sampling data.

Next, three modified examples in which a part of this another embodiment is modified will be described. 1) First modification (see FIGS. 34 and 35) FIG. 34 is a flowchart of the initial value setting process corresponding to FIG. 26, and the same steps as those in FIG. To do. In this modification, the compensation coefficient C
Instead of x, the initial value E0 for compensating the tire manufacturing error, characteristics, etc. is applied, and in S312A, S3
Similar to 12, it is determined whether or not the initial value E0 initial setting condition is satisfied. When the condition is satisfied, the initial value E0 is calculated by the equation shown in S313A. S314A
Then, it is determined whether or not the initial value E0 is an appropriate value. For example, when the initial value E0 is in the range of −0.05 to 0.05, it is determined to be an appropriate value, and the rewriting process of the initial value E0 is executed in S315A. When the initial value E0 is not an appropriate value, S
In 317A, it is determined whether the initial value E0 is indefinite,
It is executed in the same manner as S317.

Next, the tire air pressure determination subroutine of the tire air pressure determination processing of FIG. 27 will be described with reference to FIG.
35 is a diagram corresponding to FIG. 28, and the same steps as those in FIG. 28 are designated by the same reference numerals and the description thereof will be omitted. The tire air pressure determination variable E in this modified example is calculated by the equation shown in S332A, it is determined in S333A whether (E-E0) is equal to or greater than a predetermined value Δ0, and in S337A, (E-E0) is predetermined. It is determined whether or not the value is −Δ0 or less. If the initial value E0 is used as in this modification, the arithmetic processing is simplified.

2) Second Modification (Refer to FIGS. 36 and 37) In the tire air pressure determination control of the second modification, the pulse numbers of the pulse signals P1 to P4 supplied from the wheel speed sensors 51 to 54 are set for a predetermined time. Count over the above period,
By comparing the total value of the number of pulses for each wheel, an abnormality in tire air pressure is determined. This tire air pressure determination control includes the pulse signal reading process of FIG.
The tire pressure determination process of FIG. 37. Each of the wheel speed sensors 51 to 54 has four wheels each time the wheel makes one rotation.
Although eight pulse signals are output, the RAM is provided with four buffers (B1 to B4) for temporarily storing the pulse signals output from the wheel speed sensors 51 to 54.

In the flowchart of FIG. 36, when the routine is started for each predetermined traveling distance, various data are read in the same manner as described above (S370), and then, similarly to S322, whether or not the tire air pressure determination condition is satisfied. The determination is executed (S371), and when the determination result is Yes, S372
In, for example, the pulse signals P1 to P4 are read for 8 ms, the data is temporarily stored in the buffers (B1 to B4), and then the process is returned and repeatedly executed.
If the determination result in S371 is No, the process is returned as it is and repeatedly executed. In this way, when the tire air pressure determination condition is satisfied, the buffer (B1 to
The pulse signals P1 to P4 for 8 ms are stored in B4) while being updated.

Next, in parallel with the pulse signal reading process, the tire air pressure determination process of FIG. 37 is executed. Figure 3
When the routine of 7 is started, the buffer (B1 to B4)
Data is read (S380), the counter I for counting the number of readings is incremented to count the number of readings (S381), and then the number of pulses Nw1 to Nw4 of the pulse signals P1 to P4 is calculated in S382. It The calculation of the pulse numbers Nw1 to Nw4 is executed by adding the current pulse numbers Δw1 to Δw4 to the previous total pulse numbers Nw1 to Nw4, respectively.

Next, the counter I has a predetermined value I0 (for example,
100) or more is determined (S383), and when the determination result is No, the process returns to S380 and S380 and subsequent steps are performed, and when the determination result in S383 is Yes, S3 is performed.
At 84, the maximum value Nwmax of the pulse numbers Nw1 to Nw4,
The average value Nwm of the pulse numbers Nw1 to Nw4 is calculated. Next, it is determined whether (Nwmax-Nwm) is greater than or equal to a predetermined value C,
If the determination result is No, the process proceeds to S386. If the determination result is Yes, it is determined in S387 that the tire pressure is abnormal (decreased), then the warning lamp 56 is lit for a predetermined time (S388), and then the number of pulses. The memory for storing Nw1 to Nw4 and the counter I are each cleared (S38).
8).

Since the number of rotations of the wheel whose tire air pressure has dropped becomes large, the number of pulses from the wheel speed sensor of the wheel whose tire air pressure has dropped becomes maximum, so that (Nwmax-Nwm) is predetermined as described above. By judging whether it is more than the value,
A tire pressure abnormality can be detected. In this modification, the initial setting process after the tire replacement is not executed, but after the tire replacement, the same initial setting process as in FIGS. 36 and 37 is executed to obtain the total initial pulse numbers INw1 to INw4. Even if the tire pressure abnormality is detected using the ratio (Nw1 / INw1) to (Nw4 / INw4) of the number of pulses Nw1 to Nw4 and the total number of initial pulses INw1 to INw4 obtained in the tire pressure determination process as a parameter. Good. In this case, the ratio (Nw1 / INw1) to (Nw4 / INw4)
The tire pressure is determined to be abnormal when is equal to or more than a predetermined value. Since the vehicle speed V during the initial setting process and the vehicle speed V during the tire air pressure determination process are not always the same,
It is necessary to use the ratios (Nw1 / INw1) to (Nw4 / INw4) mentioned above.

In this embodiment, the pulse number Nw1
The pulse numbers Nw1 to Nw4 are calculated.
And the number of pulses per wheel rotation of 48 and the count value I
The time Tw1 to Tw4 per one rotation of the four wheels 1 to 4 is calculated based on the data of 0 and the wheel speed reading time of 8 ms per one time, and the tire pressure abnormality is calculated using the time Tw1 to Tw4 as a parameter. May be configured to be determined. Then, also in this case, similarly to the above, the initialization process is executed, and the times ITw1 to ITw4 per one rotation of the wheel at the time of the initialization process are obtained in advance, and the time Tw
Ratio of w1 to Tw4 and time ITw1 to ITw4 (Tw1 / ITw1)
The tire pressure abnormality may be determined using (Tw4 / ITw4) as a parameter.

3) Third Modification (Refer to FIGS. 38 and 39) The determination as to whether or not the initial setting condition in S312 or the tire air pressure determination condition in S322 is satisfied is shown in FIG.
8 may be executed by the determination subroutine shown in FIG. However, in order to execute this processing, the brake signal BSs from the brake switch and the steering angle signal θ from the steering angle sensor
h, traveling distance signal DD from the odometer, inclination signal θ from an inclination detection sensor that detects the inclination of the vehicle body in the longitudinal direction
k, a lateral acceleration signal Gh from a lateral acceleration sensor that detects a lateral acceleration acting on the vehicle body, a yaw rate signal ψv from a yaw rate sensor, and a hydraulic pressure sensor that detects the hydraulic pressures of four vehicle height adjusting hydraulic working chambers in the active suspension device. Various signals such as hydraulic signals Hp1 to Hp4 from the vehicle, parking brake signal PBs from the parking brake switch, ABS operating signal and TRC operating signal from the control unit 44 for performing anti-skid control and traction control (TRC control) are also controlled. It is assumed that the unit 50 is supplied.

First, in S400, it is determined whether or not the parking brake is ON. When the parking brake is ON (when the vehicle is traveling with the parking brake ON due to an erroneous operation), it corresponds to the braking state, and the front wheels and the rear wheels are Since the wheel load is uneven and the wheel speed detection accuracy is reduced, it is determined in S418 that the condition is not satisfied.

Next, in S401, it is determined whether or not acceleration / deceleration is being performed. However, the vehicle speed is applied as the vehicle speed V, and the vehicle speed V is the wheel speed of the left and right driven wheels (front wheels 1 and 2). It is set equal to the average value of Vw1 and Vw2, and it is determined from the change of the vehicle speed V whether acceleration or deceleration is being performed. When acceleration or deceleration is being performed, the wheel loads of the front wheels and the rear wheels become uneven, or the driving wheels Since the slip amount increases and the wheel speed detection accuracy decreases, it is determined in S418 that the condition is not satisfied.

Next, at S402, it is determined whether or not the vehicle is turning based on the steering angle signal θh. When the vehicle is turning, the difference in wheel speed between the inner wheel and the outer wheel becomes large, and the tire pressure determination is executed. Since it is not desirable, it is determined in S418 that the condition is not satisfied. Next, in S403, it is determined based on the ABS operation signal whether or not the ABS is in operation. When the ABS is in operation, the braking state often occurs, and the wheel speed detection accuracy deteriorates. Therefore, in S418, it is determined that the condition is not satisfied. To be done. Next, in S404, it is determined whether or not the TRC is operating based on the TRC operating signal. When the TRC is operating, the braking state is often generated, and the wheel speed detection accuracy deteriorates. Therefore, it is determined in S418 that the condition is not satisfied. To be done.

Next, in S405, it is determined whether the road surface on which the vehicle is traveling is an uphill road, based on the road surface inclination signal θk from the inclination detection sensor, and when the road is an uphill road, the wheel speed detection accuracy is reduced as in the acceleration state. Therefore, it is determined that the condition is not satisfied in S418. Next, in step S406, it is determined whether or not the road surface on which the vehicle is traveling is a bad road based on the average value of the bad road flags Fak calculated for each of the four wheels as in the case of the bad road. Since the four wheel speeds vary greatly, it is determined in S418 that the condition is not satisfied.

Next, in S407, it is determined whether or not the vehicle is on the cant road surface. When the vehicle is traveling on the cant road surface, the wheel speeds of the left and right front wheels 1, 3 and the left front and rear wheels 2, 4 are set even though yaw rate is not generated. Difference or lateral acceleration occurs, the yaw rate signal ψv and the wheel speeds Vw1 to Vw.
4. Based on the lateral acceleration signal Gh, it is determined whether or not the vehicle is on the cant road surface, and when the vehicle is traveling on the cant road surface, the wheel load of the front and rear wheels on the low level side increases and the wheel speed detection accuracy decreases, so S418 is performed. It is determined that the condition is not satisfied.

Next, in S408, it is determined whether or not both drive wheels 3 and 4 are in a spin state while traveling on a snowy road or the like. If it is in the stack, an abnormal wheel speed is detected and it becomes difficult to determine the tire air pressure. Therefore, it is determined in S418 that the condition is not satisfied. next,
In S409, it is determined whether or not the rear wheels 3 and 4 are slipping. Based on the wheel speeds Vw3 and Vw4 of the rear wheels and the vehicle speed V,
It is determined whether or not the rear wheels 3 and 4 are slipping. When the rear wheels are slipping, an abnormal wheel speed is detected and the tire air pressure cannot be determined. Therefore, it is determined in S418 that the condition is not satisfied.

Next, in S410, it is determined whether or not only the rear wheels are bad roads. Only the bad road judgment corresponding to the left rear wheel 3 and the bad road judgment corresponding to the right rear wheel 4 are judged as bad roads. If so, there is a high possibility that chains are attached to both the rear wheels 3 and 4, and in this case the detection accuracy of the wheel speed decreases,
It is determined in S418 that the condition is not satisfied. Next, S4
In 11, it is determined whether or not only the front wheels are bad roads.
When only the bad road judgment corresponding to the left front wheel 1 and the bad road judgment corresponding to the right front wheel 2 are judged as bad roads, both front wheels 1, 2
There is a high possibility that the chain is erroneously attached to the vehicle, and in this case the detection accuracy of the wheel speed is reduced, so that the condition is determined not to be satisfied in S418.

Next, in S412, it is judged whether or not the wheel speeds of the both rear wheels are lower than the wheel speeds of the both front wheels. In this case, since the wheel speed detection accuracy is reduced, it is determined in S418 that the condition is not satisfied. Next, in S413, it is determined whether or not the wheel speeds of both front wheels are lower than the wheel speeds of both rear wheels. Since the speed detection accuracy decreases, it is determined in S418 that the condition is not satisfied. Next, S4
14, the hydraulic pressures Hp1 to Hp of the vehicle height adjusting hydraulic working chamber
If it is determined whether or not all of p4 are equal to or more than the set value, and the wheel load becomes excessive when a large load is loaded in the passenger compartment or the trunk, the detection accuracy of the wheel speed decreases, so that the condition is not satisfied in S418. To be judged.

Next, in S415, the hydraulic pressure Hp1.
Of the Hp4, it is determined whether or not only the hydraulic pressures Hp3 and Hp4 corresponding to both the rear wheels are higher than the hydraulic pressures Hp1 and Hp2 corresponding to the front wheels, and the hydraulic pressure Hp3 is set in a state where a large load is loaded on the trunk. , Hp4 is high, the wheel load of the rear wheels is large and the wheel speed detection accuracy is reduced.
At 418, it is determined that the condition is not satisfied. Next, S41
At 6, it is determined whether the vehicle speed V is within the permitted vehicle speed range. The permitted vehicle speed range is the initially set permitted vehicle speed range of the coefficient Cx shown in FIG. 30 or the tire air pressure determination permitted vehicle speed range shown in FIG. 31. Is determined. When the determination results of S400 to S415 are all No and the determination result of S416 is Yes, the wheel speeds Vw1 to Vw
Since w4 can be detected with high accuracy, it is determined in S417 that the condition is satisfied.

II] Second Alternative Example A second alternative example of the tire air pressure determination control executed by the control unit 50 will be described below with reference to FIGS. 40 to 46. However, in the flow chart, the reference numeral Si (i = 501, 502, ...) Indicates each step. Since the second alternative embodiment corresponds to a partial modification of the first alternative embodiment, the matters already described in the first alternative embodiment will be briefly described.

First, the outline of the tire air pressure determination control will be described. The initialization process for setting the compensation coefficient Cx is performed in the first vehicle speed range for initialization (for example, 10 to 10).
55 Km / H), the tire pressure determination process is
It is executed in the second vehicle speed range for air pressure determination (for example, 10 km / H to the maximum vehicle speed). The tire air pressure determination control includes the initial setting process and the tire air pressure determination process.

Next, the initial setting process of the coefficient Cx will be described with reference to the flowchart of FIG. The initial setting process of the coefficient Cx is started when the initial setting switch 55 is turned on when the tire is replaced,
Next, various data obtained by digitizing the signals from the wheel speed sensors 51 to 54 and the switch 55 are read, and the four wheels 1 to 4 are read based on the detection signals from the wheel speed sensors 51 to 54.
Wheel speeds Vw1 to Vw4 are calculated (S501), and then the warning lamp 56 is displayed to indicate that the initialization process is being executed.
Is turned on, and the flag F is reset to 0 in order to prohibit the tire air pressure determination processing (S502).

Next, it is determined whether or not the initial setting condition of the coefficient Cx is satisfied (S503). However, the vehicle speed is not the acceleration / deceleration state, the steady straight traveling state, and the initial setting vehicle speed. If it is satisfied that the condition is within the range, it is determined that the condition is satisfied, the process proceeds to S504, and if the condition is not satisfied, the process directly returns. The vehicle speed V is the same as above. If the determination in S503 is Yes, in S504 to S509, the determination threshold value for the tire air pressure determination (α in S533 and S537 in FIG. 42) is determined.
A correction coefficient α for correcting βΔ0) is set as follows.

When the vehicle speed V is in the vehicle speed range of 10 km / H or more and less than 25 km / H, the correction coefficient α is obtained by S504 and S505.
Is set to 1.10, and when the vehicle speed V is 25 km / H or more, 40
When the vehicle speed range is less than Km / H, the correction coefficient α is set to 1.05 in S506 and S507, and the vehicle speed V is 40 km.
When the vehicle speed range is above / H and below 55 km / H, S508,
The correction coefficient α is set to 1.00 by S509 (FIG. 43).
reference). That is, when the vehicle speed V is 40 km / H or more and less than 55 km / H, the detection accuracy of the wheel speeds Vw1 to Vw4 becomes highest,
As the vehicle speed V decreases, the detection accuracy of the wheel speeds Vw1 to Vw4 decreases. Therefore, when the vehicle speed V decreases, α
Is increased to largely correct the judgment threshold value for tire pressure judgment. The above values 1.10, 1.05
Indicates an example and is not limited to these numerical values.

From S505, S507 or S509, the process proceeds to S510, and in S510, the coefficient Cx for compensating the initial condition of the four tires at the time of tire replacement is added with consideration of tire manufacturing error and characteristics. The wheel speeds Vw1 to Vw4 of the wheels are used for the calculation according to the illustrated calculation formula. Next, in S511, it is determined whether or not the coefficient Cx is an appropriate value. Since the tire diameter error due to a tire manufacturing error is 0.3% at the maximum, the coefficient Cx is within a predetermined range of approximately 1 (for example, 0.95 to 1.05), the coefficient C
It is determined that x is a proper value.

When the coefficient Cx is an appropriate value, S51
2, the coefficient Cx rewriting process is executed, the previous coefficient Cx (i-1) is rewritten with the current Cx (i), then, in S513, the warning lamp 56 is turned off and the tire pressure determination process is permitted. Therefore flag F is 1
Is set to, and then the process proceeds to S516. On the other hand, S5
When the determination result of 11 is No, the coefficient C is determined in S514.
It is determined whether or not x is indefinite, and when it is indefinite, the process proceeds to S503 and is re-executed after S503. When it is not indefinite, the warning lamp 56 is blinked for a predetermined time (for example, 2 seconds) in S515, and then S516. Move to. In S516, it is determined whether or not the flag F is 1, and when the determination is No, the process returns, and when the determination is Yes, this process ends.

However, on the basis of one ON operation of the switch 55, a plurality of coefficients Cx are obtained by executing initialization processing a plurality of times in the same vehicle speed range.
It is also possible to determine the final coefficient Cx from the average value of In this way, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement is determined and stored in the memory of the RAM. The initial setting process may be prohibited when traveling on a low μ road, traveling on a bad road, or traveling on a slope.

Next, the tire pressure determination process will be described with reference to the flow charts of FIGS. 41 and 42.
This tire air pressure determination process is a process that is always executed while the vehicle is running. After the start of this process, various data are read and the wheel speeds Vw1 ... Vw4 is calculated (S520), then it is determined whether or not the flag F is 1 (S521), and Ye
When s, it is determined in S522 whether or not the tire air pressure determination condition is satisfied. Regarding the tire pressure determination condition, when the condition that the vehicle is not in the acceleration / deceleration state, that the vehicle is in the steady straight running state, and is in the vehicle speed range for determining the tire pressure is satisfied, it is determined that the condition is satisfied and S is satisfied.
If the condition is not satisfied, the process proceeds to S523.

Next, if the conditions are satisfied, S523 to S523.
At 527, a correction coefficient β for correcting the determination threshold value is set according to the vehicle speed V at the time of tire pressure determination.
When the vehicle speed V is 10 Km / H or more and less than 50 Km / H, the correction coefficient β is set to 1.00 by S523 and S524, and when the vehicle speed V is 50 Km / H or more and less than 100 Km / H. , S523, S524 set the correction coefficient β to 1.10, and when the vehicle speed V is in the vehicle speed range of 100 km / H or more, the correction coefficient β is set to 1.20 in S527 (see FIG. 44).

That is, when the vehicle speed V is 10 Km / H or more and less than 50 Km / H, the tire pressure determination is executed when the vehicle speed is close to the vehicle speed V in the initialization process.
Since the correction coefficient β is set to 1.00 and the vehicle speed V largely deviates from the vehicle speed V in the initial setting process as the vehicle speed V increases, the tire pressure determination is executed. In view of the large error in the air pressure determination variable D, the correction coefficient β is set to a large value as the vehicle speed V increases. The numerical values 1.10 and 1.20 described above are merely examples, and the present invention is not limited to these numerical values.

Next, in S528, the subroutine for tire pressure determination of FIG. 42 is executed and then returns, and if the determination result of S521 or S522 is No, S
At 529, the timer T in the tire air pressure determination subroutine is reset, the flags Fa and Ft are reset to 0, the counters I and J are reset to 0, and then the process returns. Next, the tire pressure determination subroutine of S528 will be described with reference to the flowchart of FIG. First, it is determined whether or not the flag Ft is 1 (S530). Since it is initially No, the timer T is started and the flag Ft is set to 1 in S531, and the process proceeds to S532. Further, the flag Ft is 1
In the state where it is set to, the process proceeds from S530 to S532. Next, in S532, the air pressure determination variable E
Is calculated by the equation shown, that is, the following equation.

E = 2 × [Cx (Vw2 + Vw3)-(Vw1 + Vw4)]
/ [Vw1 + Vw2 + Vw3 + Vw4] In the above formula, the coefficient Cx is set in advance so as to compensate for the initial state of the tire. Therefore, when the tire air pressure is normal, the air pressure determination variable E becomes a value substantially equal to 0. However, when the tire air pressure of the right front wheel 2 or the left rear wheel 3 is decreasing, the wheel speed Vw2 or the wheel speed Vw3 increases, so the air pressure determination variable E increases in the positive direction, and the left front wheel 1 Alternatively, when the tire air pressure of the right rear wheel 4 is decreasing, the wheel speed Vw1 or the wheel speed Vw4 increases, so the air pressure determination variable E increases in the negative direction.

Next, in S533, it is judged whether or not the judgment variable E is the judgment threshold value αβΔ0 (however, the predetermined basic value Δ0 is, for example, a value in the range of 0.020 to 0.050), and the judgment result is obtained. Is Yes, it is determined whether or not the flag Fa is 1 (S534). If the flag Fa is not 1, the counter I for counting the number of times the judgment variable E is the judgment threshold value αβΔ0 or more is set to 1 and the flag Fa is set. F
a is set to 1 (S535), and then the process proceeds to S541. When the flag Fa is set to 1, the process proceeds from S534 to S536, the counter I is incremented, and then the process proceeds to S541.

On the other hand, if the determination result in S533 is No,
After shifting to S537, the judgment variable E is the judgment threshold value −αβ.
It is determined whether or not Δ0 or less. If Yes, the flag Fa is 2
It is determined whether or not (S538), and if the flag Fa is not 2, the counter J that counts the number of times the determination variable E is the determination threshold value -αβΔ0 or less is set to 1 and the flag Fa is set to 2 (S539). , Then S541
Move to. When the flag Fa is set to 2, the process proceeds from S538 to S540 and the counter J
Is incremented, and then the process proceeds to S541.

Next, in S541, it is determined whether or not the count value T of the timer T has passed a predetermined time T0 (for example, 2 seconds). In the beginning, since the determination result is No, S541 The process is repeated from S520 to S527 and S530 to S541 in FIG.
Are repeatedly executed, and the count value T of the timer T and the count value I of the counter I or the count value J of the counter J are
Will increase.

When the predetermined time T0 has elapsed, S54
Since the determination result of 1 is Yes, the process proceeds to S542, and it is determined whether the count value I of the counter I is the predetermined value K0 or more or the count value J of the counter J is the predetermined value K0 or more. When the result is No, the tire pressure is determined to be normal in S543 and the process proceeds to S546.
If the determination result in S542 is Yes, S544
It is determined that the tire pressure is abnormal (decreased) in S54,
In 5, the warning lamp 56 is lit for a predetermined time (for example, 2 seconds) to warn the driver of a decrease in tire air pressure, and the process proceeds to S546. In step S546, the timer T,
The flag Fa, the flag Ft, the counter I, and the counter J are
Each is reset to 0, and the tire air pressure determination processing this time is completed. Note that the tire pressure determination may be prohibited when traveling on a low μ road, traveling on a bad road, or traveling on a slope.

Next, the operation of the tire air pressure determination control described above will be described. In this initial setting process, the correction coefficient α is set according to the vehicle speed V when the initial setting process is executed so that the lower the vehicle speed is, the larger the correction coefficient α becomes, and the judgment coefficient α is used for the determination. Since the value is corrected, the probability of erroneous determination in tire pressure determination can be reduced, and the accuracy and reliability of tire pressure determination can be improved.

This tire air pressure determination processing is executed when the vehicle is running straight and in a steady state and is in the second vehicle speed range of 10 km / H to the maximum vehicle speed. The second vehicle speed range is wider than the first vehicle speed range. Since the tire pressure is set so as to include the vehicle speed range, the tire air pressure determination can be performed in almost the entire vehicle speed range, which is excellent in practicality. Here, when the vehicle speed V becomes 60 km / H or more,
In view of the fact that the detection accuracy of the wheel speed decreases due to the influence of the slip of the driving wheels, the correction coefficient β is set so that the vehicle speed at the time of executing the tire pressure determination increases as the distance from the first vehicle speed range increases. Since the determination threshold value is corrected by the correction coefficient β, the probability of erroneous determination in the tire air pressure determination can be reduced, and the accuracy and reliability of the tire air pressure determination can be improved.

In this tire air pressure determination process, the timer T, the counter I, and the counter J are used, and the count value I that satisfies E ≧ αβΔ0 and E ≦ −αβ at the predetermined time T0.
The count value J that is Δ0 is counted, and when the count values I and J are equal to or greater than the predetermined value K0, it is determined that the tire pressure is abnormal. Therefore, it is possible to accurately determine the tire pressure based on many sampling data. it can.

Next, two modifications will be described in which a part of the tire air pressure determination processing in the second alternative embodiment is modified. 1) First Modified Example (see FIG. 45) FIG. 45 shows a modified part of the flowchart of FIG. 42. In this modified example, the correction coefficients α and β are used.
In addition, the learning correction coefficient γ is applied to set the determination threshold value to αβγΔ0, and the learning correction coefficient γ is set to 1 when the initial setting is completed.

First, referring to FIG. 45, S5
Next to 43, in S570, the present determination flag H (i)
Is reset to 0, then in S571, it is determined whether or not the previous determination flag H (i-1) is 1, and the previous time it was determined that the tire pressure was normal and the determination flag H (i-1) was 0. S
In 572, the learning correction coefficient γ is held unchanged,
Next, in S579, the warning lamp 56 is turned off, and then the process proceeds to S546.

When the result of the determination in S571 is Yes, S5
Whether the previous β (i-1) is equal to the current β (i) at 73 (that is, the vehicle speed range at the time of the previous tire pressure determination is the same as the vehicle speed range at the time of this tire pressure determination) Whether or not) is made, and the result of the judgment is Yes,
Despite the fact that the vehicle speed range is the same, the tire pressure is abnormal last time and it is determined to be normal this time, so in view of the fail-safe viewpoint, the determination threshold value may be slightly too large. In this case, the learning correction coefficient γ is changed to a small value by a predetermined value 0.05 in S574, and then S5.
After 79, the process proceeds to S546.

On the other hand, when the result of the determination in S573 is No,
If the vehicle speed range is different between the previous time and this time, it is determined in S575 whether or not the previous determination flag H (i-2) is 1,
If the determination result is Yes, that is, the tire pressure is abnormal at the previous time and the previous time, and it is determined that the tire pressure is normal at this time. In view of this, in this case, the learning correction coefficient γ is changed to a small value by a predetermined value 0.05 in S574, and then S
After 579, the flow shifts to S546. If the determination result in S575 is No, the tire pressure was normal the previous time,
Since it is determined that the previous time is abnormal and the current time is normal, it is considered that the learning correction coefficient γ is substantially appropriate.
In, the learning correction coefficient γ is held without change, and then the process proceeds to S546 via S579.

2) Second Modification (Refer to FIG. 46) FIG. 46 shows a modified part of the flowchart of FIG. Next, referring to FIG. 46, when it is determined that the tire pressure is abnormal in S542, the present determination flag H (i) is set to 1 in S580, and then the previous determination flag H (i-1) is set. If it is 1 and the result of the determination is Yes, in S582, it is determined whether or not β (i-1) of the previous time and β (i) of the current time are not equal (that is, the previous tire air pressure determination (Whether the vehicle speed range at this time is different from the vehicle speed range at the time of this tire pressure determination) is determined, and if the determination result is Yes,
Since abnormalities are continuously detected in different vehicle speed zones, S58
3, it is determined that the tire pressure is abnormal, and the warning lamp 56 is held in the lighting state. Then, in S585, the learning correction coefficient γ is held without change, and then in S54.
Go to 6.

If the determination result in S582 is No, the vehicle speed range is the same between the previous time and this time, and it is difficult to determine that the tire pressure is abnormal. Therefore, in S584, the tire pressure is determined to be semi-abnormal and the warning lamp 56 blinks. The state is maintained, and then the process proceeds to S585. On the other hand, if the result of the determination in S581 is No, that is, if the tire pressure was normal the previous time and abnormal this time, it is determined in S586 whether the previous β (i-1) and the current β (i) are equal. If the determination result is Yes, the vehicle speed range is the same between the previous time and this time, but it is determined that the tire pressure is normal the previous time and abnormal this time. The air pressure is judged to be semi-abnormal and the warning lamp 56
Is kept blinking.

If the determination result in S586 is No, it is possible that the tire pressure is abnormal in this determination because the vehicle speed range is different between the previous time and this time. Therefore, in S587, it is determined whether or not the previous determination flag H (i-2) is 1, and if the determination result is No, and the previous previous tire pressure was also determined to be normal, then the tire air pressure decreases. Since there is a high possibility that the tire pressure has been quasi-abnormal, the warning lamp 56 is held in a blinking state.

On the other hand, when the result of the determination in S587 is Yes,
In other words, tire pressure was abnormal the previous time, normal last time,
Since it is determined to be abnormal this time, in view of the possibility that the determination threshold value is too low, the learning correction coefficient γ is significantly changed by a predetermined value 0.05 in S588, and then S
Move to 546. In this way, the learning correction coefficient γ is introduced, and the learning correction coefficient γ is learned by the above-described logic, whereby the probability of erroneous determination of tire air pressure determination can be reduced.

III] Third Alternative Example Next, another alternative example of the initialization process of the compensation coefficient Cx of the first alternative example will be described with reference to the flowcharts of FIGS. 47 and 48 and FIGS. 49 and 50. explain. This coefficient C
The initial setting process of x is started when the initial setting switch 55 is turned on, and then the timer T that measures the elapsed time from the time of turning on the switch 55 is started.
Also, the switch 55 is turned on based on the signal from the odometer.
The distance counter Dc that counts the traveling distance from the time of the operation is reset to 0 (S601), then various data obtained by digitizing the signals from the sensors 51 to 54 and the switch 55 is read, and the four wheels 1 to 4 are read. Wheel speed Vw1 ~
Vw4 is calculated (S602), then the warning lamp 56 is turned on to indicate that the initialization process is being executed, and the flag F is reset to 0 to prohibit the tire air pressure determination process (S603). .

Next, in S604, the count-up of the timer T and the count-up of the distance counter Dc are executed, and then it is judged in the steps of S605 to S616 whether or not the initial setting condition of the coefficient Cx is satisfied. To be judged. Basically, the initial setting conditions are that the vehicle is not in an acceleration / deceleration state, is in a steady straight traveling state, and the vehicle speed V is the initial value of the coefficient Cx set according to the road surface friction shown in FIG. It is necessary to be within the setting permission vehicle speed range, but the initial setting process is not executed smoothly when either one of the wheels is fitted with temper tires or when traveling on a cout road. Also, the initial setting process is surely executed.

First, in S605, the vehicle speed V is as shown in FIG.
The determination is made as to whether or not the vehicle speed is within the predetermined vehicle speed range, as shown in (4). As the vehicle speed V, the average value of the wheel speeds Vw1, Vw2 of the left and right driven wheels (front wheels 1, 2) is applied. As a result of the determination in S605, if Yes, the process proceeds to S606, and if No, the process returns to S602. In S606, it is determined whether or not the time T counted by the timer T is equal to or greater than the predetermined value T0. However, the determination result is No in the beginning, so in S607, the count value Dc of the distance counter D is the predetermined value. It is determined whether D0 or more. Since it is determined to be No at the beginning, the process proceeds to S608 and the initial setting switch 55 is turned on again.
It is determined whether N operations have been performed. However, initially the initial setting switch 55 is not turned on again, so at the beginning
When it is determined No, the process proceeds to S609.

Next, in S609, it is determined whether or not the rate of change of the vehicle speed V is substantially zero (that is, whether or not the vehicle is in a steady running state), and Ye
When s, the process proceeds to S610 and whether the steering angle θh detected by the steering angle sensor is substantially 0 (that is, whether the vehicle is in a straight traveling state).
If it is determined that the vehicle is traveling straight, the process proceeds to S611.
In S611, as shown in the illustrated formula, the different-diameter wheel determination variable R for determining the mounting state of the temper tire is the difference between the sum of the left wheel speeds Vw1 and Vw3 and the sum of the right wheel speeds Vw2 and Vw4. Is calculated as a ratio of the absolute value of V to the vehicle speed V, and it is determined whether the different diameter wheel determination variable R is equal to or less than a predetermined threshold value β.

That is, in the case of the normal tires for all four wheels, if the vehicle is in a steady straight traveling state, as shown in FIG. 49, the different diameter wheel determination variable R becomes equal to or less than the threshold value β, so the determination result of S611. Becomes Yes. However, in the state in which one tempered tire is mounted in addition to the three normal tires, the sum of the left wheel speeds Vw1 and Vw3 is not equal to the sum of the right wheel speeds Vw2 and Vw4. As shown in, since the different diameter wheel determination variable R becomes larger than the predetermined threshold value β, S
The determination result of 611 is No and S611 to S614
Move to.

When the result of the determination in S610 is No, S61
In 2, it is determined whether the steering angle θh is equal to or less than a predetermined value α, and if the determination result is No, it is determined that the vehicle is turning, and S602.
Return to. If the determination result in S612 is Yes, it is determined in S613 whether or not the steering angle θh is continuously constant for a predetermined time tα or more in order to determine whether or not the vehicle is traveling on the couch road surface. However, this determination is actually executed through the start of the timer, the setting of the flag after the timer is started, and the counting of the timer by the arithmetic processing performed a plurality of times. When the vehicle is not traveling on the couch road surface, the determination result of S613 is No and the process proceeds to S602, but when the vehicle is traveling on the cout road surface, the determination result of S613 is Yes. Then, in this case also, in order to enable the initial setting process, when the result in S613 is Yes, S613 to S611.
Move to.

If the judgment result in S611 is No, it is judged in S614 whether or not the temper tire is mounted.
At, it is determined whether the different diameter wheel determination variable R is continuously constant for a predetermined time or longer. However, this determination is actually executed through a plurality of times of arithmetic processing, by starting the timer, setting a flag after the timer is started, and counting the timer. When the temper tires are mounted, the different diameter wheel determination variable R becomes constant for a predetermined time or longer even in the steady straight running state, so that the initial setting process can be performed in this case as well. So that
If Yes in S614, from S614 to S617 in FIG.
Move to.

On the other hand, after the initialization process is started, the initialization process is not completed even if a predetermined time has passed or a predetermined distance has been traveled, or the initialization process is not completed, and thus the initialization process is completed. When the switch 55 is turned on again, the predetermined time tα is shortened and
The initial setting process is completed by largely correcting the threshold value β.

That is, as a result of the determination in S606, when the time T counted by the timer T is equal to or longer than the predetermined time T0, the process proceeds to S616, the predetermined time tα becomes 0.95tα, and the threshold β
Is rewritten to 1.05β and the process returns to S602.
As a result of the determination in 7, when the traveling distance Dc counted by the distance counter Dc is equal to or greater than the predetermined value Dc0, the process proceeds to S616, the predetermined time tα is 0.95tα, and the threshold β is
It is rewritten to 1.05β and returns to S602. If the result of determination in S608 is that the initial setting switch 55 has been turned ON again, in S615 the timer T is reset and then started, the distance counter Dc is reset to 0, and then the process proceeds to S16 and the predetermined time is elapsed. tα is 0.95tα
And the threshold value β is rewritten to 1.05β and S602
Return to.

Next, when the determination result in S611 is Yes,
Alternatively, when the determination result in S614 is Yes, S6 in FIG.
Then, the processing shifts to S17, and S617 and subsequent steps are executed. In S617, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement in consideration of the manufacturing error and characteristics of the tire has one diagonal relationship using the wheel speeds Vw1 to Vw4 of the four wheels. Sum of wheel speeds of front left wheel 1 and rear right wheel 4 (Vw1 +
Vw4) and the right front wheel 2 and the left rear wheel 3 which are diagonally related to each other
Is calculated by the following equation as a ratio with the sum of the wheel speeds (Vw2 + Vw3). Coefficient Cx = (Vw1 + Vw4) / (Vw2 + Vw3) Next, in S618, it is determined whether or not the coefficient Cx is an appropriate value. However, since the tire diameter error due to the tire manufacturing error is 0.3% at the maximum, the coefficient Cx is When it is within a predetermined range of approximately 1 (for example, 0.95 to 1.05), the coefficient Cx
Is determined to be an appropriate value.

When the coefficient Cx is an appropriate value, S61
In step 9, the coefficient Cx is rewritten, the previous coefficient Cx (i-1) is rewritten with the current value Cx (i), and then, in S620, the warning lamp 56 is turned off and the tire pressure determination processing is permitted. Therefore flag F is 1
Is set to, and then the process proceeds to S621. On the other hand, S6
If the determination result in 18 is No, the coefficient C is determined in S622.
It is determined whether or not x is indefinite, and if it is indefinite, the process proceeds to S621. If it is not indefinite, the warning lamp 56 is blinked for a predetermined time (for example, 2 seconds) in S623, and then the process proceeds to S621.

In S621, it is determined whether or not the flag F is 1, and when the setting of the coefficient Cx is completed and the flag F is 1, this initial setting process ends, but the coefficient Cx
47 is not completed and the flag F is 0, FIG.
Return to S602. However, based on one ON operation of the switch 33, a plurality of initial setting processes are executed to obtain a plurality of coefficients Cx, and a final coefficient Cx is determined from an average value of the plurality of coefficients Cx. It is also possible to do so. As described above, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement is determined,
It is stored in the RAM memory.

In the initial setting process, S60
When the determination result in S6, S607, and S608 is Yes, in the step corresponding to S611, (R-
It may be configured to determine whether δ) is less than or equal to a predetermined threshold value γ. However, δ is a predetermined value of about 0.05β,
γ is a threshold value substantially equal to β (see FIG. 50).

IV] Fourth Alternative Embodiment Next, a tire air pressure determination timing detection process applicable to the first alternative embodiment will be described with reference to the flowchart of FIG. In the first alternative embodiment, the tire air pressure determination is always performed while the automobile is running. However, the tire air pressure determination timing detection process according to the fourth alternative embodiment is performed in response to a command from the tire air pressure determination timing detection process. It may be configured to execute the air pressure determination.

When this process is started when the ignition switch of the automobile engine is turned on, first S72 is executed.
At 0, it is determined whether or not the flag F is 1, and the flag F
When is 1, various data necessary for this processing is read in S721, and then, in S722, the flag Fo is read.
Is determined to be 1 or not. This flag Fo is set in S735 and initially 0, so it is determined in S723 whether or not the flag F has been switched from 0 to 1, and immediately after the end of the initial setting process, Since the determination result is Yes, the process proceeds from S723 to S724,
The timer T is started and the distance counter Dc that counts the traveling distance based on the signal from the odometer is reset.

Next, in S725, the cow canter FK for counting the number of times the fuel is supplied to the fuel tank is reset, and then the process proceeds to S726. On the other hand, when the determination result in S723 is No, the process proceeds to S726 and S7
In 26, the count-up of the timer T and the distance counter D
Counting up c is executed. In S727, based on the signal from the fuel supply detection switch, it is determined whether or not fuel is supplied. If No, the process proceeds to S729 and Ye
If s, the counter FK is incremented in S728 and then the process proceeds to S729. However, the fuel supply detection switch is turned on when the fuel cap of the fuel tank or the opening / closing lid outside the fuel cap is opened.
Is a switch. Next, in S729, the timer T
It is determined whether or not the count time T of K is a predetermined value C1 (for example, 30 days) or more, and in S730, it is determined whether or not the count value Dc of the distance counter Dc is a predetermined value (for example, 50 Km) or more. , S731, it is determined whether the fuel supply frequency FK is a predetermined value (for example, twice) or more.

At first, the determination results of S729 to S731 are
Since the answer is No, the process proceeds to S732, the flag Fo is reset to 0, and the process returns to S721. After that, S721 to
After S723, the process proceeds to S726, and S726 to S731.
Is repeatedly executed, and S729, S73
0, if any of the determinations in S731 is Yes, S733
In step S733, the warning lamp 56 is turned on for a predetermined time (for example, 5 seconds) in order to notify the user that it is time to execute the tire pressure determination process and to prompt the driver to visually check the tire pressure. ), Then a start command for starting the tire pressure determination process is output in S734, the flag Fo is set to 1 in S735, and then the process proceeds to S721.

By the above tire air pressure determination timing detection processing, the time when the tire air pressure determination processing should be executed is detected and displayed by the warning lamp 56. If the vehicle is running, based on the start command output in S734. Then, the tire air pressure determination process is started. However, when the vehicle is stopped, the tire pressure determination process is started after the start of running. When the flag Fo is set to 1 in S735 and the process proceeds to S721, the determination result in S722 is Ye.
Since s is reached, the process proceeds to S726 through S724 and S725, so that the time after that point, the mileage, and the number of times of fuel supply are counted, and the same procedure as described above is repeated. However, since the flag Fo is reset to 0 during the initialization process, the tire air pressure determination timing detection process is not executed.

[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.

FIG. 26 is a flowchart of a process for initializing a coefficient Cx for tire air pressure determination control according to the first alternative embodiment.

FIG. 27 is a flowchart of tire air pressure determination processing of tire air pressure determination control according to the first alternative embodiment.

28 is a flowchart of a tire air pressure determination subroutine of FIG. 27.

FIG. 29 is a flowchart of rough road index calculation processing.

FIG. 30 is a diagram showing a map of an initially permitted vehicle speed range of a coefficient Cx.

FIG. 31 is a diagram showing a map of a vehicle speed range in which tire pressure determination is permitted.

FIG. 32 is a diagram showing the behavior of the air pressure determination variable E when the tire air pressure is normal.

FIG. 33 is a diagram showing the behavior of the air pressure determination variable E when the tire air pressure is abnormal.

FIG. 34 is a diagram corresponding to FIG. 2 in the tire air pressure determination control of the first modified example.

FIG. 35 is a flowchart of a subroutine of tire air pressure determination processing of the first modified example.

FIG. 36 is a flowchart of a pulse signal reading process in the tire air pressure determination control of the second modified example.

FIG. 37 is a flowchart of a tire air pressure determination process of the second modified example.

FIG. 38 is a part of a flowchart of a condition satisfaction determination subroutine of the third modified example.

FIG. 39 is the rest of the flowchart of the condition satisfaction determination subroutine of the third modified example.

FIG. 40 is a flowchart of an initial setting process of a coefficient Cx for tire pressure determination according to the second alternative embodiment.

FIG. 41 is a flowchart of tire air pressure determination processing of tire air pressure determination control according to the second alternative embodiment.

FIG. 42 is a flowchart of a tire pressure determination subroutine of FIG. 41.

FIG. 43 is a characteristic diagram of the correction coefficient α.

FIG. 44 is a characteristic diagram of the correction coefficient β.

FIG. 45 is a flowchart of a part of a tire air pressure determination subroutine of the first modified example.

FIG. 46 is a flowchart of a tire air pressure determination subroutine of the second modification.

FIG. 47 is a part of a flowchart of an initial setting process of a coefficient Cx for tire pressure determination according to the third example.

FIG. 48 is the rest of the flowchart of the initialization process of the coefficient Cx for tire pressure determination according to the third example.

FIG. 49 is a time chart of the different diameter wheel determination variable R in the third alternative embodiment.

FIG. 50 is a time chart of the different diameter wheel determination variable R in the third alternative embodiment.

FIG. 51 is a flowchart of tire air pressure determination timing detection processing according to the fourth alternative embodiment.

[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 speeds for respectively detecting the wheel speeds of four wheels of a vehicle. The sensor and the pulse-shaped detection signals from the four wheel speed sensors are read and counted, and the wheel speed equivalent data of the four wheels obtained each time each count value reaches a predetermined number is stored in the memory. When the detection signals from the four wheel speed sensors are not input within the first predetermined time at the start of reading the detection signals from the four wheel speed sensors, the data collection means 4
A tire pressure warning device, comprising: a start resetting means for resetting the count value of one detection signal. 2. The tire air pressure according to claim 1, wherein after the start resetting means resets the count of the detection signals, the data collecting means is provided with count restarting means for restarting the count of each detection signal. Alarm device. 3. 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 speeds for respectively detecting the wheel speeds of four wheels of a vehicle. Sensors and pulse-shaped detection signals from the four wheel speed sensors are read and counted, and wheel speed equivalent data of four wheels obtained each time each count value reaches a predetermined number is stored in a memory. Within a second predetermined time from the time when the count value of the detection signal from any one of the wheel speed sensors reaches the predetermined number, the count value of the detection signal from the other wheel speed sensor is set to the predetermined value. A tire pressure warning device, characterized in that, when the number is not reached, the data collecting means is provided with an end resetting means for resetting count values of four detection signals. 4. 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 speeds for respectively detecting the wheel speeds of four wheels of a vehicle. Sensors and pulse-shaped detection signals from the four wheel speed sensors are read and counted, and wheel speed equivalent data of four wheels obtained each time each count value reaches a predetermined number is stored in a memory. When the detection signals from the four wheel speed sensors are not inputted within the first predetermined time at the start of reading the detection signals from the data collection means and the four wheel speed sensors, the data collection means
Start reset means for resetting the count value of one detection signal, and within a second predetermined time from the time when the count value of the detection signal from one of the wheel speed sensors reaches the above-mentioned predetermined number, A tire pressure warning device, characterized in that: when the count value of the detection signal does not reach the predetermined number, the data collection means includes termination reset means for resetting the count values of the four detection signals.