JPH0747821A - Tire pressure alarm device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a tire pressure warning device capable of reliably determining a simultaneous decrease in tire pressure of a pair of wheels on the same side in front, rear, left and right. [Structure] Signals from four wheel speed sensors 51 to 54, a trunk lid switch 58, door switches 59a to 59d, etc. are supplied to a control unit 50 of a tire air pressure detection device, and the control unit 50 is in motion while the vehicle is running. In addition, when the wheel speed ratio of the wheel speed of a pair of wheels on the same side in the front-rear direction or the left-right direction to the four-wheel average wheel speed changes to a predetermined threshold value or more, the tire air pressures of the pair of wheels simultaneously. In order to prevent the erroneous determination due to the influence of the weight of the baggage and the like, it is also determined that the air pressure is reduced by using the opening / closing of the opening / closing body as a determination factor.

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 capable of judging a decrease in tire pressure of a pair of wheels on the same side in front, rear, left and right.

[0002]

2. Description of the Related Art Since it is not preferable to drive a vehicle with the tire air pressure lowered to a certain extent or more, various tire air pressure alarm devices (tire air pressure determination devices) have been conventionally 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]

In the conventional tire pressure determination device, the difference between the total wheel speed of a pair of wheels on a diagonal line and the total wheel speed of a pair of wheels on another diagonal line. Since it is a configuration that detects a decrease in air pressure from the left and right, tire pressure drop of the left and right front wheels, tire pressure drop of the left and right rear wheels, tire pressure drop of the left and right front wheels, tire pressure drop of the right and left front wheels, etc. When the tire air pressures of the pair of wheels on the left and right sides are the same, there is a problem that it cannot be reliably detected. Moreover, even if luggage is loaded in the luggage compartment or the weight of the occupants in the rear seats is increased, the radii of movement of the rear wheels on the left and right become smaller. ,
It is a very difficult task to detect the decrease in tire air pressure by distinguishing the decrease in tire air pressure between the left and right rear wheels.
An object of the present invention is to provide a tire pressure warning device that can reliably determine the tire pressures of a pair of wheels on the same side in front, rear, left and right.

[0005]

A tire pressure warning device according to claim 1 is a tire pressure warning device for detecting a decrease in tire pressure using a detection signal of a wheel speed sensor of four wheels of a vehicle and outputting an alarm. , A wheel speed sensor for detecting the wheel speed of each of the four wheels of the vehicle, and a detection signal from the wheel speed sensor, the moving radii of a pair of wheels on the same side in the front, rear, left and right, while the vehicle is traveling. And a pneumatic pressure determination means for determining that the tire pneumatic pressures of the pair of wheels have dropped when the tire pressures have changed.

A tire pressure warning device according to a second aspect is the device according to the first aspect, wherein the air pressure determining means uses the wheel speeds of the four wheels to calculate the four wheel average wheels of the wheel speeds of the pair of wheels. It is configured to detect the change in the radius of gyration of the pair of wheels from the ratio of the wheel speed to the speed. A tire pressure warning device according to a third aspect is the device according to the first aspect, further comprising an opening / closing detection means for detecting opening / closing of the opening / closing body when the vehicle is stopped, and the air pressure determining means uses an output from the opening / closing detection means. It is configured to determine a decrease in tire air pressure.

[0007]

According to the tire pressure warning device of the present invention, the air pressure judging means receives the detection signals from the wheel speed sensors for detecting the wheel speeds of the four wheels of the vehicle, respectively.
It is determined that the tire air pressure has decreased when the radii of movement of the pair of wheels on the same side in the front-rear direction or the left-right direction change while the vehicle is traveling. Since the radius of gyration of the pair of wheels during traveling is not due to the loading of luggage but due to the decrease in tire air pressure, the air pressure determination means ensures the decrease in tire air pressure of the pair of wheels. Can be detected.

According to another aspect of the tire pressure warning device of the present invention, the air pressure determining means uses the wheel speeds of the four wheels and calculates the wheel speed from the wheel speed ratio of the wheel speed of the pair of wheels to the four-wheel average wheel speed. , Detecting changes in the radii of movement of the pair of wheels. In this way, it is possible to detect a change in the radius vector of the pair of wheels by a simple calculation process. In the tire pressure warning device according to claim 3, in the device according to claim 2, the opening / closing detection means detects opening / closing of the opening / closing body when the vehicle is stopped, and the air pressure determination means uses the output from the opening / closing detection means. To detect a decrease in tire pressure. As a result, it is possible to prevent erroneous determination of a change in the tire radius of movement due to loading of luggage as a decrease in tire air pressure.

[0009]

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

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

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

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

Next, the tire pressure warning device peculiar to the present invention will be described. This tire pressure determination device is
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 has a control unit 50, etc., and the control unit 50 has an absolute clock for calculating the absolute date and time. The control unit 50 has wheel speed sensors 51 to 54, an initial setting switch 55, an odometer. 5
7, trunk lid switch 58, four door switches 59a to 59d, parking brake switch 60, 4
Signals are supplied from four ultrasonic-type vehicle height sensors 60a to 60d that detect the vehicle height at the wheel positions, and the warning lamp 56 is drive-controlled by the control unit 50.

Each of the wheel speed sensors 51 to 54 has 48 detecting portions formed on the disks 21 to 24 or adjacent to the disks 21 to 24, which are not shown in the drawing, and are electromagnetically detected by 48 detecting portions. It is configured to be detected by a pickup. The control unit 50 includes a filter for filtering the detection signals from the wheel speed sensors 51 to 54, and a circuit for shaping the waveform of the detection signals filtered by the filter.
An AD converter for A / D converting various analog detection signals,
Input / output interface, CPU, ROM, RAM
The ROM is pre-stored with a control program for tire pressure determination control, which will be described later, and the RAM includes various memories (buffer, memory, flag, Counter, etc.) is provided. 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. This tire pressure determination control is, for example, when the tire is replaced or when the use of the vehicle is started.
Initial value setting processing for setting the initial value of the determination variable described below when the tire pressure is normal, air pressure determination processing for determining the tire pressure during actual traveling, and initial for detecting the time to set the initial value It consists of a value setting timing detection process.

First, the initial value setting timing detection process will be described with reference to FIGS. 2 and 3. This initial value setting time detection process is a process for detecting that an initial value setting process for determining an initial value D0 of the determination variable D, which will be described later, should be executed, and notifying the driver of the determination. = 10,
11, ...) Indicates each step. This process is a process which is always executed when the vehicle is not used as well as when it is not used. First, various signals necessary for the following arithmetic processing are read (S10), and then in S11, The distance D traveled from the initial value setting process of
C1 (however, C1 is a predetermined value of about 1000 km, α is
Variable coefficient) or more. The traveling distance is counted by the counter based on the signal from the traveling distance meter 57.

When the determination in S11 is Yes, it is time to execute the initial value setting, and after S17 and S18, S2 is set.
Move to 3. Next, when the determination in S11 is No,
In S12, it is determined whether or not the time elapsed from the previous initial value setting process to the present is α · C2 (where C2 is a predetermined value in January) or more. If the determination is Yes, the initial value setting is performed. Is the time to execute, S17, S1
After 8, the process proceeds to S23.

When the determination in S12 is No, it is determined in S13 and S14 whether tire replacement has been executed. In S13, it is determined whether the ignition switch is ON and / or the parking switch 60 is ON. Yes if any tires have been replaced
Therefore, the process proceeds to S14, and it is determined whether or not any wheel has fully rebounded. This determination is made based on the detection signals from the vehicle height sensors 60a-60d.
When replacing the tire of any wheel, S
Since the determination of 14 is Yes, the process proceeds to S17 and S18 and then S
Move to 23.

Next, the determination in S13 is No or S14
If the determination is No, it is determined in S15 whether the wheel speed Vw1 of the front wheels 1 is zero and the wheel speed Vw2 of the front wheels 2 is positive. If the determination is Yes, it is possible that the tires of the front wheels 2 will be replaced. Is high, the process moves to S17, and S15
When the determination is No, it is determined in S16 whether the wheel speed Vw1 of the front wheels 1 is positive and the wheel speed Vw2 of the front wheels 2 is zero. When the determination is Yes, it is possible to replace the tires of the front wheels 1. Since the property is high, the process proceeds to S17. The wheel speeds Vw1 and Vw2 are calculated based on the detection signals from the wheel speed sensors 51 and 52.

In S17, the flag Fic indicating that the initial value setting should be executed is set, and the process proceeds from S16 or S17 to S18. In S18, it is determined whether or not the flag Fic is in the set state, and if No, in S19, it is determined whether or not the season is summer based on the absolute clock. In summer, the outside air temperature is high and the tire air pressure is likely to decrease due to the expansion of air inside the tire. Therefore, in S20, the coefficient α is set to 0.7. α is set to 1.0, and then the process returns.

When the determination in S18 is Yes, the driver is notified when the vehicle is stopped. Therefore, in S22, it is determined whether or not the ignition switch is ON and the vehicle speed V is zero. If the determination is Yes, No. When the process returns and the determination is Yes, the warning lamp 56 blinks in S23 for a predetermined time (for example, 5 seconds), whereby the triber knows that the initial value setting process is necessary. When the driver turns on the initial setting switch 55 while seeing the blinking of the warning lamp 56, the initial value setting process is executed during the subsequent traveling of the vehicle, and after the execution, a command notifying the completion of the initial value setting is issued. This initial value setting time detection processing is supplied.

In S24, it is determined whether or not the initial value setting is completed based on the command notifying the completion of the initial value setting. If No, the determination is made in S25 at predetermined time intervals (for example, one hour). , S23, the warning lamp 56 blinks, and then, when the initial value setting is completed, the process proceeds to S26, the counter D for counting the traveling distance D is reset to 0, and the counter for measuring elapsed time is also provided. T is reset to 0 and the flag Fic is set to 0.
After that, the process returns, and thereafter the initial value setting time detection process is executed even when the vehicle is not in use.

As described above, according to the initial value setting timing detection process, when the tire is replaced, the tire replacement is detected by paying attention to the fact that the wheels are in a full rebound state, and the necessity of the initial value setting can be notified. However, at the time of tire replacement, regarding the driven wheel, the tire replacement is detected by noting that the other wheel may rotate while one wheel is stopped,
The necessity of setting the initial value can be notified.

Here, when the vehicle height detected by the vehicle height sensors 60a to 60d exceeds a predetermined value while the vehicle is stopped, it is determined that the tire has been replaced, and the process proceeds to S17. You may comprise. Alternatively, a sensor that horizontally emits ultrasonic waves toward the wheels may be provided in a region of the vehicle body on the inner side of each wheel, and tire replacement may be detected from the detection signal of the sensor, and the process may proceed to S17. Good. Also, when the tires are filled with air, it is necessary to set the initial values.The method for detecting the filling of air is to check the vehicle height without opening the trunk lid or door while the vehicle is stopped. When is changed, it may be determined that the air is filled, and the process may proceed to S17.
In the above-described embodiment, the warning lamp 56 is configured to blink for a predetermined time in S23, but the initial value setting is required on the display of the instrument panel together with or instead of blinking the warning lamp 56. It may be configured to display a message indicating that the initialization switch needs to be turned on.

Next, the initial value setting process for setting the initial value of the judgment variable will be described with reference to FIG.
In the figure, reference numeral Si (i = 30, 31, ...) Indicates each step. This initial value setting process is a process that is executed while the vehicle is running after the initial setting switch 55 is turned on. First, it is determined whether the initial setting switch 55 is on (S30), and then When the determination is Yes, various signals (mainly wheel speed signals) are read in S31. Next, it is determined whether the road is a low μ road (low friction road surface) (S32) and whether the road is a bad road (S33).
Then, it is determined whether or not the vehicle is in a steady straight traveling state (S34), and the process proceeds to S35 only when the vehicle is in a steady traveling straight traveling state, not on a low μ road, on a bad road. The determination of the low μ road and the determination of the rough road will be described later with reference to FIGS. 7 and 8, but the determination of whether or not the vehicle is in a steady running straight state is determined based on the wheel speeds of the driven wheels 1 and 2. To be done.

Next, in S35, a wheel speed signal for 400 rotations of the wheel is read from the wheel speed sensors 513 to 54, and next, using the wheel speed signal, the four wheels 1 to 4 are read.
The wheel speeds Vw1, Vw2, Vw3, Vw4 of 4 are calculated and stored in the memory (S36). Next, in S37, the initial value D0 of the judgment variable is calculated by the formula shown and stored in the memory. Then, an instruction to complete the initial value setting is output to the initial value setting timing detection processing, and then this processing ends.

Next, the air pressure determination process executed while the vehicle is in use will be described with reference to FIGS. 5 and 6.
In the figure, reference numeral Si (i = 40, 41, ...) Indicates each step. After the start of processing, various signals (wheel speed signals, trunk lid switch and door switch signals, etc.) are displayed first.
Is read (S40), and then, in S41, it is determined whether or not the vehicle is running based on the signals from the wheel speed sensors 51 to 54. When the vehicle is not running, the process proceeds to S42 and the trunk lid switch is activated. 58 and door switch 5
Based on the detection signals from 9a to 59d, it is determined whether or not an opening / closing body such as a trunk lid or a door has been opened / closed. When the determination is Yes, the flag Fop is set to 1 in S43 and the process proceeds to S45. When the opening / closing body is not opened or closed, the flag Fop is reset to 0 in S44, the flag F is reset to 0 in S45, and then the process proceeds to S64.

When the determination in S41 is Yes, it is determined whether the road is a low μ road (S46) and whether the road is a bad road (S47).
Then, it is determined whether or not the vehicle is in a steady straight traveling state (S48). If the vehicle is not in a low μ road, is not a bad road, and is in a steady straight traveling state, the process proceeds to S49. The determination in S46 to S48 is the same as in the case of the initial value setting process,
This will be described later with reference to FIGS. 7 and 8. Next, in S49, the wheel speed signal for 400 rotations of the wheel is detected by the wheel speed sensor 5
13-54, and then using the wheel speed signals, the wheel speeds Vw1, Vw2, Vw3, V of the four wheels 1-4.
w4 is calculated and stored in the memory (S50), then S
At 51, the decision variable D is calculated by the formula shown.

Next, in S52, the judgment variable D
And the initial value D0 of the determination variable obtained by the initial value setting process and stored in the memory, the absolute value of (D−D0) is a predetermined value Δ (for example, Δ is 0.02 to 0.05). Or more), and if the result is Yes,
In S53, it is determined that the tire air pressure of one of the wheels has dropped, then in S54, the warning lamp 56 is lit for a predetermined time (for example, 5 seconds), and then the process proceeds to S64. Here, when the tire pressures of the four wheels are normal, the determination variable D becomes a value that is substantially equal to its initial value D0, so the absolute value of (D−D0) becomes a value less than Δ. When the tire pressure of the front wheels 1 decreases, the radius of gyration of the front wheels 1 decreases, so that the wheel speed Vw1
Becomes larger and the (D−D0) absolute value becomes Δ or more, so that the determination of S52 makes it possible to determine a decrease in tire air pressure.

By the way, when both the tire pressures of the left and right front wheels 1 and 2 decrease, when the tire pressures of the left and right rear wheels 3 and 4 decrease, the tire pressures of the left and right front wheels 1 and 3 both decrease. In this case, in a special case such as when the tire pressures of the right and left front wheels 2 and 4 both decrease, the influence of the decrease in the air pressure is not reflected in the judgment variable D. Determine the special decrease in air pressure. When the determination in S52 is No, the process proceeds to S55, and in S55, the average wheel speed Vm, which is the average value of the wheel speeds Vw1 to Vw4, is calculated by the formula shown, and then S5.
6, it is determined whether the wheel speed ratio Vw1 / Vm is a predetermined value α or more and the wheel speed ratio Vw2 / Vm is a predetermined value α or more. When the determination is Yes, the air pressure of the left and right front wheels 1 and 2 is determined. Is highly likely to have decreased, the process proceeds to S63.
When the determination in S56 is No, in S57, the wheel speed ratio Vw3 / Vm is equal to or greater than the predetermined value α and the wheel speed ratio Vw4
It is determined whether or not / Vm is greater than or equal to the predetermined value α, and the determination is Yes.
In the case of, there is a high possibility that the air pressures of the left and right rear wheels 3, 4 have dropped, so the routine proceeds to S63.

When the determination in S57 is No, in S58, the wheel speed ratio Vw1 / Vm is equal to or greater than the predetermined value α, and
It is determined whether or not the wheel speed ratio Vw3 / Vm is equal to or greater than the predetermined value α, and when the determination is Yes, it is highly possible that the air pressure of the left and right front wheels 1 and 3 has decreased, so the process proceeds to S63. S5
When the determination in No. 8 is No, in S59, the wheel speed ratio Vw2 / Vm is not less than the predetermined value α and the wheel speed ratio Vw4 / V
It is determined whether or not m is equal to or greater than the predetermined value α, and when the determination is Yes, there is a high possibility that the air pressure of the right and left front wheels 2 and 4 has decreased, so the process proceeds to S63.

When the determination in S59 is No, it is determined in S60 that the air pressures of all the tires are normal, then the flag F is set to 1 in S61, and the counter If is set in S62. It is incremented, and then, in S66, it is determined whether or not the ignition switch is OFF. If No, the process returns to S40, and if the ignition switch is turned ON, in S67, the flags Fop and F are reset and Since the counter If is reset and the automobile is in the non-use state, this process ends.

As shown in S61, when the decrease in air pressure is not detected while the vehicle is running, the flag F is set. In S63, it is determined whether or not the flag F is 1, and the flag F is set to 1. If it is, it is possible that the air pressure has decreased during the current travel because the determination in any of S56 to S59 was determined to be Yes this time, even though the air pressure was previously determined to be normal. Since the property is very high, the process proceeds to S53, it is determined that the tire air pressure has dropped, and the warning lamp 56 is lit for a predetermined time in S54.

As a result of the determination in S63, when the flag F is 0, it is not determined that the air pressure is normal during the traveling this time.
It is highly possible that the determination in S59 is Yes. Therefore,
In S63, it is determined whether or not the flag Fop is set to 1. If the flag Fop is 1, the opening / closing body has been opened and closed during the stop before the current running, and the load and the weight of the occupant increase. Since it is highly probable that the operation has been performed, the process proceeds from S64 to S66. On the other hand, when the flag Fop is not set to 1, it cannot be considered that the load or the weight of the occupant has increased because the opening / closing body has not been opened / closed during the previous stop. Shifts to S65, and in S65,
It is determined whether or not the count value If of the counter If is positive.

Even after the start of use of the car this time, S
When the process proceeds to 60 or S61, the count value If becomes positive regardless of the stop on the way. However, if the count value If is not positive, the load or the occupant may affect the start of use of the vehicle this time. , S56 and S59 are likely to be Yes, the process proceeds to S66. On the other hand, S
If the judgment of 65 is Yes, after starting to use the car this time,
Even though the opening / closing body was not opened and closed during the previous stop and the count value If is positive, the determinations in S56 to S59 are
Since the answer is Yes, it is highly probable that the tire air pressure has dropped, so the process proceeds to S53. In this way, it is possible to almost surely determine the decrease in tire air pressure of the pair of wheels on the same side in front, rear, left and right. Here, S56 to S5
In Fig. 9, the wheel speed ratio is used as a parameter for the wheel 1
This is to detect the change in the radius vector of 4 to S45, S5.
Through steps 6 to S59, S62, and S63, a change in the radiuses of movement of the pair of wheels on the same side in the front, rear, left, and right while the vehicle is traveling is detected.

Next, the low μ road determination processing executed in the interrupt processing, which is the low μ road determination processing in S32 and S46, will be described with reference to FIG. First, a predetermined number of wheel speeds and wheel speeds are read (S110),
Next, in S111, the front wheel wheel speeds Vw1 and Vw2 are calculated based on the wheel speed signals of the front wheels 1 and 2, and the rear wheel wheels are calculated based on the respective average values of the wheel speed signals of the rear wheels 3 and 4. The speeds Vw3 and Vw4 are calculated, and the vehicle speed V (vehicle body speed) is calculated as an average value of the front wheel speeds Vw1 and Vw2. next,
In S112, the slip ratio SL3 of the rear wheel 3 = (Vw
3-V) / V and the slip ratio SL4 of the rear wheel 4 = (Vw4
−V) / V is 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 determination result in S113 is No, it is determined in S115 that the vehicle is traveling on a high μ road, the flag Fμ is set to 0, and the process ends. Incidentally, S3
The determinations of 2 and S46 are 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 S33 and S47 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, similarly to S110 and S111, the wheel speeds Vw1 to Vw4 of the four wheels and the front wheel wheel accelerations AVw1 and AVw2 are calculated, and then acceleration / deceleration is performed based on the average wheel speed of the four wheels. It is determined whether or not the state is S122 (S122).
When the routine returns to 120 and the acceleration / deceleration state is not established, it is determined in S123 whether the flag Fa is 1 or not. When the 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 (S125), and the process proceeds to S126. Incidentally, S123
If the determination is Yes, the process proceeds 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 determinations of S33 and S47 are executed based on the flag Fak.

The operation of the tire air pressure determination control described above will be described. Regarding the initial value setting time detection processing, the coefficient α is corrected to be small in the summer when the tire air pressure is likely to decrease, through steps S19 and S20.
The reliability of this detection process can be increased, and S1
The tire replacement can be detected through the simple steps of S3 and S14, and the driver is informed through the step of S22 that the warning lamp 56 is blinked while the vehicle is stopped to set the initial value. It does not impair safety, and the warning lamp 5 is set at predetermined intervals until the initial value setting is completed through step S25.
Since 6 is blinked to notify the user, it is possible to set the initial value.

With respect to the air pressure determination process, it is possible to reliably determine the tire pressure drop of only one wheel, and it is also possible to almost reliably detect the tire pressure drop of a pair of wheels on the same side in front, rear, left and right. In particular, in the steps of S56 to S59, the change in the radius of movement is detected by using the wheel speed ratio of the wheel speed of the pair of wheels on the same side to the four-wheel average wheel speed. Therefore, it is possible to surely detect. By providing the flag Fop indicating whether or not the opening / closing body is opened / closed and the counter If and making the determinations in S64 and S65, it is possible to improve the accuracy of the determination of the decrease in air pressure.

Regarding the flowchart of FIG. 6, S6
2 and S65 may be omitted, and when the determination in S64 is No, the process may proceed to S53. That is, if the air pressure drops while the vehicle is stopped, S60,
Since the flag Fop is not set because the flag Fop is 0 and the opening / closing body has not been opened and closed without shifting to S61, it is highly possible that the air pressure has decreased, rather than the cargo or occupant having changed, so to S53. Transition.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an automobile anti-skid brake device and a tire pressure warning device according to an embodiment.

FIG. 2 is a part of a flowchart of an initial value setting timing detection process of the tire pressure warning device of FIG.

FIG. 3 is the rest of the flowchart of the initial value setting timing detection process of the tire pressure warning device of FIG.

FIG. 4 is a part of a flowchart of an initial value setting process of the tire pressure warning device of FIG.

5 is a part of a flowchart of an air pressure determination process of the tire air pressure alarm device of FIG.

6 is the rest of the flowchart of the air pressure determination processing of the tire air pressure alarm device of FIG.

FIG. 7 is a flowchart of a low μ road determination process of the tire pressure warning device of FIG.

8 is a flowchart of a rough road determination process of the tire pressure warning device of FIG.

[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 58 trunk lid switch 59a-59d door switch

Claims (3)

[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. In response to detection signals from the sensor and the wheel speed sensor, the tire air pressures of the pair of wheels are changed when the dynamic radius of the pair of wheels on the same side is changed in the front-rear direction or the left-right direction while the vehicle is traveling. A tire air pressure warning device comprising: an air pressure judging means for judging that the tire pressure has dropped. 2. The air pressure determination means uses the wheel speeds of the four wheels to calculate a radius of a pair of wheels from a wheel speed ratio of the wheel speeds of the pair of wheels to an average wheel speed of four wheels. The tire pressure alarm device according to claim 1, wherein the tire pressure alarm device is configured to detect a change in the tire pressure. 3. An opening / closing detection means for detecting opening / closing of an opening / closing body while the vehicle is stopped is provided, and the air pressure determination means is configured to determine a decrease in tire air pressure using an output from the opening / closing detection means. The tire pressure warning device according to claim 2, wherein the tire pressure warning device is provided.