JPH06286429A - Tire pneumatic pressure alarm device - Google Patents

Abstract

PURPOSE:To improve precision and reliability of tire pneumatic pressure judgment by permitting judgment at the time of a vehicle speed range set according to each road surface state when tire pneumatic pressure is judged from four wheel wheel speeds. CONSTITUTION:A control unit 40 receives those signals inputted from wheel speed sensors 27-30, a steering angle sensor 26, a travel distance meter 31, an inclination detecting sensor 32 and an initial setting switch 33, and in the control unit 40, initial setting processing to compensate the manufacturing error of a tire is executed at the time of tire exchange or the like, and afterwards periodical tire pneumatic pressure judgment processing is executed. The initial setting processing is executed at the time of a vehicle speed range set at a map according to each road surface state (a friction state, a bad road state and an inclination state), and the tire pneumatic pressure judgment processing is executed at the time of a vehicle speed range set to another map according to road surface states.

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 vehicle speed range in which tire pressure determination is permitted.
The present invention relates to the thing set according to the road surface condition.

[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]

In the tire pressure alarm device described in the above publication, the tire pressure is not judged during acceleration or deceleration.
There is no suggestion in the above publication regarding the relationship between the road surface condition (friction condition, bad road condition, slope condition) of the traveling road surface and the vehicle speed and the tire pressure determination. By the way, generally, at low speed, the number of data detected by the wheel speed sensor decreases, so that the detection accuracy of the wheel speed decreases, and at high speed, the slip amount of the driving wheels becomes large, and the front and rear wheels have a large slip amount. Since the wheel load varies and the wheel speed detection accuracy decreases, the tire pressure determination accuracy and reliability also decrease.

Particularly, as the road friction state becomes lower μ, the slip amount of the driving wheels becomes larger, the detection accuracy of the wheel speed is lowered and the tire air pressure determination accuracy is lowered. Since the variation in the wheel speed of the driving wheels becomes large, the accuracy of the wheel speed detection decreases, and the accuracy and reliability of the tire air pressure determination decrease. When traveling on an uphill road, the amount of slip of the drive wheels increases and the same state as during acceleration occurs, so the accuracy of wheel speed detection decreases and the accuracy of tire pressure determination decreases. An object of the present invention is to increase the accuracy and reliability of tire air pressure determination by allowing tire air pressure determination in the vehicle speed range set according to the road surface condition of the traveling road surface.

[0006]

A tire pressure warning system according to claim 1 is a tire pressure warning system which detects a decrease in tire pressure using the wheel speeds of four wheels of a vehicle and outputs a warning. Wheel speed detection means for detecting the wheel speed of the wheel, tire air pressure determination means for determining a decrease in tire air pressure using the wheel speed detected by the wheel speed detection means, and road surface state detection for detecting the state of the traveling road surface And a vehicle speed range setting means for setting a vehicle speed range in which the tire air pressure determination by the tire air pressure determination means is permitted according to the state of the road surface detected by the road surface state detection means.

Here, the road surface state detecting means has a means for detecting the frictional state of the road surface, and the vehicle speed range setting means sets the upper limit value of the vehicle speed range to be lower in the low friction state than in the high friction state. According to the above configuration (claim 2), the road surface state detecting means has means for detecting a bad road state of the road surface,
The vehicle speed range setting means is configured to set the upper limit value of the vehicle speed range to be lower on a bad road than on a good road (claim 3), and the road surface state detecting means has a means for detecting a sloped state of the road surface. However, the vehicle speed range setting means can be configured in various modes such as a structure in which the upper limit value of the vehicle speed range is set lower on an uphill than on a flat ground (claim 4).

Further, the tire air pressure determining means uses the wheel speeds of the four wheels to set a compensation coefficient for compensating a manufacturing error of a newly mounted tire, and the initial setting processing. Compensation coefficient set by means and 4
A configuration including tire air pressure determination processing means for performing tire air pressure determination using the wheel speed of one wheel (Claim 5), wherein the vehicle speed range setting means includes a vehicle speed range for which setting processing in the initial setting processing means is permitted, The vehicle speed range in which the determination processing in the tire air pressure determination processing means is permitted may be set individually (claim 6).

[0009]

In the tire pressure warning device according to the first aspect of the present invention, the wheel speed detecting means detects the wheel speed of the four wheels, and the tire air pressure judging means detects the four wheel wheels detected by the wheel speed detecting means. Determine the decrease in tire air pressure using speed, the road surface state detection means detects the road surface state of the traveling road surface,
The vehicle speed range setting means sets the vehicle speed range in which the tire air pressure determination by the tire air pressure determination means is permitted according to the state of the road surface detected by the road surface state detection means. In this way, by allowing the tire pressure determination only in the vehicle speed range set according to the road surface condition, the wheel speed detection accuracy can be increased, and the tire pressure determination accuracy and reliability can be improved.

According to the second aspect of the present invention, the vehicle speed range setting means sets the upper limit value of the vehicle speed range to be lower in the low friction state than in the high friction state. By eliminating them, the accuracy and reliability of the tire pressure determination can be improved. In the present invention, the vehicle speed range setting means sets the upper limit value of the vehicle speed range to be lower on a bad road than on a good road. The accuracy and reliability can be improved. In claim 4, the vehicle speed range setting means sets the upper limit value of the vehicle speed range to be lower on an uphill than on a level ground. Therefore, the deterioration of the wheel speed detection accuracy due to the slip of the driving wheels is eliminated, and the tire pressure determination accuracy is eliminated. And reliability can be increased.

According to a fifth aspect of the present invention, an initial setting processing means and a tire air pressure determination processing means are provided, and a compensation coefficient for compensating a manufacturing error of a newly mounted tire is set by the initial setting processing means to determine the tire air pressure. Since the processing means determines the tire air pressure using the compensation coefficient, it is possible to improve the accuracy and reliability of the tire air pressure determination through the tire air pressure determination processing that takes tire manufacturing errors into consideration. In the present invention, the vehicle speed range setting means sets the vehicle speed range in which the setting processing in the initial setting processing means is permitted and the vehicle speed range in which the determination processing in the tire air pressure determination processing means is permitted, respectively. The determination process can be executed in each of the suitable vehicle speed ranges.

[0012]

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 vehicle, the left and right front wheels 1 and 2 are driven wheels,
The left and right rear wheels 3 and 4 are the driving wheels, and the output torque of the engine 5 is from the automatic transmission 6 to the propeller shaft 7 and the differential device 8.
And the left and right rear wheels 3 and 4 via the left and right drive shafts 9 and 10. Each of the wheels 1 to 4 includes a disc 11a to 14a that rotates integrally with the wheel, and a braking device 11b that includes a caliper 11b to 14b that receives the supply of a braking pressure to brake the rotation of the disc 11a to 14a. 14 are provided respectively, and a brake control system 15 for operating these braking devices 11-14 is provided.

The brake control system 15 includes a booster device 17 for increasing the stepping force on the brake pedal 16 by the driver.
And a master shilling 18 for generating a braking pressure according to the stepping force increased by the booster 17. Front wheel braking pressure supply line 19 from this master shilling 18
Is branched into two routes, and the front wheel branch braking pressure line 19
a and 19b are connected to the calipers 11b and 12b of the left and right front wheels 1 and 2 of the braking devices 11 and 12, respectively, and the left front wheel 1 of the braking device 11 is connected.
One of the front wheel branch braking pressure lines 19a leading to the
The valve unit 20 is installed and the braking device for the right front wheel 2
A second valve unit 21 similar to the first valve unit 20 is also provided in the other front wheel branch braking pressure line 19b leading to 12.

On the other hand, the rear wheel braking pressure supply line 22 from the master cylinder 18 is connected to the first and second valve units 20, 2.
A third valve unit 23 similar to that of 1 is provided. The rear wheel braking pressure supply line 22 is connected to the third valve unit 23.
The branching pressure lines 22a, 22b for the rear wheels are branched into two paths on the downstream side of the brake system 13,1 for the left and right rear wheels 3,4.
The four calipers 13b and 14b are respectively connected. The brake control system 15 variably controls the braking pressure of the brake device 11 for the left front wheel 1 via the first valve unit 20.
The right front wheel 2 through the channel and the second valve unit 21
The second channel that variably controls the braking pressure of the braking device 12 and the third channel that variably controls the braking pressures of both the braking devices 13 and 14 of the left and right rear wheels 3 and 4 via the third valve unit 23. The first to third channels are provided so as to be controlled independently of each other.

The brake control system 15 includes the first to
A control unit 24 for controlling the third channel is provided. The control unit 24 includes a brake signal from a brake switch 25 for detecting ON / OFF of the brake pedal 16 and a steering angle sensor 26 for detecting a steering angle of the steering wheel. Receiving the steering angle signal and the wheel speed signals from the wheel speed sensors 27 to 30 respectively detecting the rotational speeds of the respective wheels, the braking pressure control signals corresponding to these signals are sent to the first to third valve units.
By outputting to 20, 21, 23 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. There is.

Next, the tire pressure warning device peculiar to the present invention will be described. This tire pressure warning device is the same as the above 4
Wheel speed sensors 27 to 30, an inclination detection sensor 32 for detecting the inclination state of the vehicle body (road surface inclination state), and an initial setting switch 33 for instructing the initial setting of tire air pressure determination (this is the instrument Installed on the instrument panel), a warning lamp 34 attached to the instrument panel, a control unit 40, etc., and the control unit 40 includes wheel speed sensors 27-3.
0, brake switch 25, rudder angle sensor 26, odometer 3
1, signals from sensors and switches such as the inclination detection sensor 32, the initial setting switch 33, etc. are supplied to the warning lamp.
The control unit 40 drives and controls 34.

Each of the wheel speed sensors 27 to 30 includes a disk 11
a formed on a -14a or formed on a detection disk (not shown) provided adjacent to the disks 11a -14a
The configuration is such that four detection units are detected by an electromagnetic pickup. The control unit 40 is a wheel speed sensor.
A filter for filtering the detection signal from 27 to 30, a circuit for shaping the waveform of the detection signal filtered by the filter, an AD converter for A / D converting various analog detection signals, an input / output interface, a CPU, a ROM and a 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 time constant of the filter is variable, and the time constant is set to a large value at the time of high speed traveling to prevent the accuracy from deteriorating, and the time constant is set to a small value at the time of low speed traveling to obtain the accuracy.

The tire air pressure determination control executed by the control unit 40 will be described below with reference to FIGS. However, in the figure of the flow chart, each step of reference symbol Si (i = 10, 11, ...) Is shown. First, the outline of the tire air pressure determination control will be described. Basically, the tire air pressure determination is performed based on the wheel speeds Vw1 to Vw4 detected by the four wheel speed sensors 27 to 30, but the use of the vehicle is started. At the time of, or when one or more tires are replaced, an initialization process of the coefficient Cx (this corresponds to a compensation coefficient) is executed to initialize the coefficient Cx for compensating the tire manufacturing error and characteristics. . After that, the tire pressure determination process is executed periodically (for each predetermined mileage or for each predetermined period) to determine whether the tire pressure is abnormal. If the tire pressure is low, a warning lamp is issued. An alarm is output via 34.

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 set separately according to the road surface condition. Run. The tire pressure determination control includes the initial setting process, the tire pressure determination process, the rough road index calculation process, and the road friction coefficient calculation process (the flowchart thereof is omitted).

Next, the initial setting process of the coefficient Cx will be described with reference to the flowchart of FIG. This initial setting process of the coefficient Cx is started when the a-contact type initial setting switch 33 attached to the instrument panel is turned on when the tire is replaced, and then the sensors 27 to 30, 26, 32 are set. Various data obtained by digitizing the signal from the switch 25 is read (S10), the warning lamp 34 is turned on to indicate that the initialization process is being executed, and the tire pressure determination process is prohibited. The flag F is reset to 0 (S11). Next, the coefficient Cx
It is determined whether the initial setting condition of is satisfied (S1).
2) is that the vehicle is not in an acceleration / deceleration state, is in a steady straight traveling state, and the vehicle speed V is within the initial permitted vehicle speed range of the coefficient Cx set according to the road surface state shown in the map of FIG. Is satisfied, the condition is determined to be satisfied, and the process proceeds to S13. When the condition is not satisfied, the process directly returns. 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. 6 is set to a predetermined value which is not excessively low (for example, 20 km / H), and the upper limit of the initially permitted vehicle speed range is set. The value is set to a value in the range of 40 to 50 Km / H according to the road surface state of the traveling road surface (road surface frictional state, bad road degree, road surface gradient). With respect to 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 lowered, and thus the 20 km It is desirable to set a predetermined value in the / H position.

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 50 km / h when the road is light (good road), and from 40 km / h when the uphill is large to small uphill (flat road or downhill). It is set to linearly increase to 50 km / H.
Note that μ is the friction coefficient of the road surface. And 50 km / h
At super high speeds, the amount of slip on the drive wheels may increase,
The wheel load of the front wheels 1 and 2 and the rear wheels 3 and 4 changes, and the detection accuracy of the wheel speeds Vw1 to Vw4 decreases. Therefore, execute the initial setting process when the vehicle speed is 50 Km / H or less. When the vehicle speed is 40 Km / H or less, it is desirable to perform the initialization process because the slip amount of the driving wheels increases when the value of μ is low, and when the degree of bad road is heavy. Since the variations in the wheel speeds Vw1 to Vw4 are large,
It is desirable to execute the initial setting process when the vehicle speed is 40 Km / H or less.

The slope of the traveling road surface is calculated from the detection signal of the inclination detection sensor 32, and the calculation method of the road surface μ and the calculation method of the rough road index (flag Fak) indicating the rough road condition will be described later. . Next, when it is determined in S12 that the condition is satisfied, in S13, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement is added with the wheel production speed of the four wheels Vw1 to 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 sum of the wheel speeds of the right front wheel 2 and left rear wheel 3 in the other diagonal relationship (Vw2 + Vw3) ) Is calculated by the following equation. 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 tire manufacturing error is 0.3% at the 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, S15
The coefficient Cx rewriting process is executed in this step, the previous Cx (i-1) is given the current Cx (i), the warning lamp 34 is turned off, and a flag is set to permit the tire pressure determination process. F is set to 1, then S1
Move to 9. On the other hand, when the determination result of S14 is No,
In S17, it is determined whether or not the coefficient Cx is indefinite, and when it is indefinite, the process proceeds to S12 and S12 and subsequent steps are reexecuted.
If not indefinite, the warning lamp 34 blinks in S18 for a predetermined time (for example, 2 seconds), and then the process proceeds to S19. In S19, it is determined whether or not the flag F is 1, and if the determination is No, the process returns, and
If the determination is Yes, this process ends. However, 1
It is also possible to execute a plurality of initial setting processes based on the ON operation of the switch 33 a plurality of times to obtain a plurality of coefficients Cx, and to determine the final coefficient Cx from the average value of the plurality of coefficients Cx. It is possible. Thus, the coefficient C for compensating the initial state of the four tires at the time of tire replacement, etc.
x is determined and stored in the RAM memory.

Here, 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 initially set. 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 start of acceleration,
The vehicle body acceleration Vg is calculated by the following equation.

Vg = K1 × [V (i) −V (i-100)] Then, the vehicle body acceleration Vg becomes sufficiently large 500 m
After the elapse of s, the vehicle body acceleration Vg is calculated by the following equation from the change of the vehicle speed V every 100 ms for 500 ms. 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.

[0027]

[Table 1]

Now, the calculation processing 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, a process of making a determination using the wheel speed Vw1, and after the start of this rough road index calculation process, various data are read (S50),
Next, in S51, 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 S52. S52
Then, the counter K is cleared, the timer T is reset and then started, then the flag FA is set to 1 in S53, and then the process proceeds to S54. When the determination result of S51 is No, S52 and S53 are skipped and S54 is executed.
Move to. In S54, the wheel acceleration AV of the left front wheel 1
w1 (including wheel deceleration) is calculated by differentiating the wheel speed Vw1 with respect to time.

Next, in S55, the wheel acceleration AVw1
It is determined whether or not the absolute value of is greater than or equal to a predetermined rough road determination threshold value A0. If the determination result is Yes, the counter K is incremented (S56), and then the process proceeds to S57,
When the determination result is No, S56 is skipped and S5 is executed.
Move to 7. In S57, the count time T of the timer T
Is determined to be equal to or longer than a predetermined time T1 (for example, 1000 ms). If the predetermined time T1 has not elapsed, the process returns from S57 repeatedly, and during the predetermined time T1, the absolute value of the wheel acceleration AVw1 is determined as a rough road. The counter K counts the number of times the threshold value is A0 or more.

When the predetermined time T1 has elapsed, the process proceeds from S57 to S58, the flag FA is reset to 0 for the next predetermined time and count, and then S59 to S58.
At 63, based on the count value K of the counter K, K
The bad road flag Fak (bad road index) is set to 0 when ≦ 3, the bad road flag Fak is set to 1 when 3 <K ≦ 7, and the bad road is set when 7 <K. The 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 wheel speed V of the left front wheel 1 is set every predetermined time T1 during the initialization process.
The rough road flag Fak based on w1 is set to any one of 0, 1, and 2. Similarly to the above, each wheel speed Vw2 ~
The bad road flag Fak is set to one of 0, 1, and 2 based on Vw4, and the average value of these four bad road flags Fak is rounded off to perform the initial setting process and the tire air pressure determination process. The rough road index for is calculated.

Next, the tire pressure determination process will be described with reference to the flowcharts of FIGS. 3 and 4. This tire air pressure determination process is, for example, a process that is executed for each mileage of 500 Km, and after the start of this process, various signals from the sensors 27 to 30, 26, 31, 32 and the switch 25 are digitized. The data is read (S20), then it is determined whether the flag F is 1 (S21), Yes.
In case of, it is determined in S22 whether or not the tire air pressure determination condition is satisfied. 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 S2 is satisfied.
If the condition is not satisfied, the process proceeds to S24.

Here, the lower limit value of the tire pressure determination permission vehicle speed range shown in FIG. 7 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 according to the road surface condition of the traveling road surface (road surface frictional state, bad road degree, road surface gradient). With respect to 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 to some extent, 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. Also, when the value of μ is low, the slip amount of the drive wheels increases, so 40 km / H
It is desirable to execute the tire air pressure determination process at the following vehicle speeds, and the variation of the wheel speeds Vw1 to Vw4 becomes large even at the time of a bad road degree, so when the vehicle speed is 40 Km / H or less, It is desirable to execute the tire pressure determination process.

In S23, the tire pressure determination subroutine of FIG. 4 is executed, and then the process returns and S2 is executed.
If the determination result in 1 or S22 is No, the timer T in the tire pressure determination subroutine is determined in S24.
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 S23 will be described with reference to FIG. First, it is determined whether or not the flag Ft is 1 (S30), and at first,
Since it is No, the timer T is started in S31, the flag Ft is set to 1, and the process proceeds to S32. When the flag Ft is set to 1, S3
The process proceeds from 0 to S32. Next, in S32, the air pressure determination variable D is calculated by the equation shown, that is, the following equation.

D = 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 D 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 D 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 D increases in the negative direction. Next, in S33, it is judged whether or not the judgment variable D is a predetermined value D0 (for example, a predetermined value in the range of 0.020 to 0.050) or more, and the judgment result is Yes.
If it is, it is determined whether the flag Fa is 1 (S34),
When the flag Fa is not 1, the judgment variable D is the predetermined value D.
The counter I that counts the number of times 0 or more is set to 1 and the flag Fa is set to 1 (S35), and then the process proceeds to S41. Further, when the flag Fa is set to 1, the process proceeds from S34 to S36, the counter I is incremented, and then the process proceeds to S41.

On the other hand, when the result of the determination in S33 is No, S
37, it is determined whether the determination variable D is less than or equal to the predetermined value −D0. If Yes, it is determined whether the flag Fa is 2 (S38). If the flag Fa is not 2, the determination variable D is the predetermined value. -Counter J for counting the number of times D0 or less
Is set to 1 and the flag Fa is set to 2 (S
39) and then the process moves to S41. Further, when the flag Fa is set to 2, the process proceeds from S38 to S40, the counter J is incremented, and then S41.
Go to F. Next, in S41, it is determined whether or not the count value T of the timer T has passed a predetermined time T0 (for example, 2 seconds), but since the determination result is No at the beginning, the process returns from S41. By repeating
S20 to S22 and S30 to S41 of FIG. 3 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 increase. 8 illustrates the behavior of the air pressure determination variable D when the tire pressure is normal, and FIG. 9 illustrates the behavior of the air pressure determination variable D 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, S41
Since the determination result of No is Yes, the process proceeds to S42, and the count value I of the counter I is equal to or greater than the predetermined value K0 or the counter J
It is determined whether or not the count value J is equal to or greater than the predetermined value K0. If the determination result is No, it is determined in S43 that the tire air pressure is normal, and the process proceeds to S46.
When the determination result of 42 is Yes, it is determined in S44 that the tire pressure is abnormal (decreased), and in S45, the warning lamp 34 is lit for a predetermined time (for example, 2 seconds) in order to warn the driver of the decrease in tire pressure.
The process moves to S46. In S46, the timer T, the flag Fa, the flag Ft, the counter I, and the counter J are reset to 0 in preparation for the next tire air pressure determination processing, and the tire air pressure determination processing this time is completed.

Next, the operation of the tire pressure alarm device described above will be described. An initial setting switch 33 is provided on the instrument panel, and by operating the switch 33, the 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 the manufacturing error. Since the initial setting process is executed in the vehicle speed range set according to the road surface condition of the traveling road surface, low μ
The coefficient Cx can be initialized with high accuracy by eliminating as much as possible the error factors due to the slip of the drive wheels on the road, the variation of the wheel speed on the bad road, the slip of the drive wheels on the uphill, the fluctuation of the wheel load, and the like.

After the initial setting process, the tire air pressure determination process is executed using the coefficient Cx each time a predetermined distance travels or a predetermined period elapses. This tire air pressure determination process is executed when the vehicle is traveling straight and in a 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 slip,
It is possible to enhance the accuracy and reliability of tire air pressure determination by eliminating error factors caused by variations in wheel speed on rough roads, slipping of drive wheels on uphill roads, fluctuations in wheel load, etc. as much as possible. In the tire air pressure determination process, the timer T, the counter I, and the counter J are used, and the count value I that satisfies D ≧ D0 and D ≦ D at the predetermined time T0.
Counting the count value J that becomes −D0, 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. You can

Next, a first alternative embodiment in which a part of the above embodiment is modified will be described with reference to FIGS. FIG. 10 is a flowchart of the initialization process corresponding to FIG. 2, and the same steps as those in FIG. In this embodiment, the coefficient Cx
Instead of, the initial deviation Δ for compensating the tire manufacturing error, characteristics, etc. is applied, and in S12A, it is determined whether or not the initial deviation Δ initial setting condition is satisfied, as in S12, and the condition is satisfied. At this time, in S13A, the initial deviation Δ is calculated by the equation shown. In S14A, whether or not the initial deviation Δ is an appropriate value is determined. For example, −0.05 to 0.
When it is in the range of 05, it is determined to be an appropriate value, and the rewriting process of the initial deviation Δ is executed in S15A. If the initial deviation Δ is not an appropriate value, in S17A,
The determination as to whether the initial deviation Δ is indefinite is performed in the same manner as in S17.

Next, the tire air pressure determination subroutine of the tire air pressure determination processing of FIG. 3 will be described with reference to FIG. 11. FIG. 11 corresponds to FIG.
The same steps as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. The tire pressure determination variable D in this embodiment is
It is calculated by the formula shown in S32A, and in S33A, (D-
Whether Δ) is greater than or equal to a predetermined value D0 is determined, and
In S37A, it is determined whether (D-Δ) is less than or equal to the predetermined value -D0. The use of the initial deviation Δ as in this embodiment has an advantage that the arithmetic processing is somewhat simplified.

Next, a second alternative embodiment of the tire air pressure determination control will be described with reference to FIGS. 12 and 13. In this tire air pressure determination control, the number of pulses of the pulse signals Pw1 to Pw4 supplied from the wheel speed sensors 27 to 30 is counted over a period of a predetermined time or more, and the total value of the number of pulses for each wheel is compared, It is designed to determine whether the tire pressure is abnormal. This tire pressure determination control is shown in FIG.
The pulse signal reading process of No. 2 and the tire pressure determination process of FIG. The wheel speed sensors 27 to 30, respectively,
The wheel speed sensor 27 is configured to output 44 pulse signals each time the wheel makes one rotation.
There are provided four buffers (B1 to B4) for temporarily storing the pulse signals output from ˜30.

In the flowchart of FIG. 12, when the routine is started for each predetermined traveling distance, the wheel speed sensor 27
~ 30,26,31,32 and various data from the switch 25 are read (S70), and then, similarly to S22, it is determined whether or not the tire pressure determination condition is satisfied (S71). When is Yes, in S72, for example, 8
During ms, the reading of the pulse signals Pw1 to Pw4 is executed, the data is temporarily stored in the buffers (B1 to B4), and then returns and is repeatedly executed.
When the judgment result of 1 is No, the process is returned as it is and repeatedly executed. In this way, when the tire pressure determination condition is satisfied, the buffer (B1 to B4) is set to 8 m.
The pulse signals Pw1 to Pw4 between s are stored while being updated.

Next, in parallel with the pulse signal reading process, the tire air pressure determination process of FIG. 13 is executed. Figure 1
When the routine of No. 3 is started, the buffer (B1 to B4)
Data is read (S80), the counter I that counts the number of readings is incremented to count the number of readings (S81), and then the number of pulses Nw1 to Nw4 of the pulse signals Pw1 to Pw4 is calculated in S82. 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 (S83), and if the determination result is No, the process returns to S80 and S80 and subsequent steps are performed, and when the determination result in S83 becomes Yes, in S84, the number of pulses Nw1 to Nw4. Maximum value Nwmax and pulse number N
The average value Nwm of w1 to Nw4 is calculated. Next, (Nwmax
-Nwm) is greater than or equal to a predetermined value C, and if the determination result is No, the process proceeds to S86, and if the determination result is Yes, it is determined in S87 that the tire pressure is abnormal (decreased).
Next, the warning lamp 34 is turned on for a predetermined time (S8
8) Next, the memory for storing the pulse numbers Nw1 to Nw4 and the counter I are cleared (S88).

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 embodiment, the initial setting process after the tire replacement is not executed, but after the tire replacement, the same initial setting process as in FIGS. 12 and 13 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 number of pulses Nw1
The pulse numbers Nw1 to Nw4 are calculated.
And the number of pulses per wheel rotation 44, 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. 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. Note that the tire air pressure determination processing of the tire air pressure determination control may be executed at all times while the vehicle is running.

[Brief description of drawings]

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

FIG. 2 is a flowchart of an initial setting process of a coefficient Cx of tire air pressure determination control.

FIG. 3 is a flowchart of tire air pressure determination processing of tire air pressure determination control.

FIG. 4 is a flowchart of a tire pressure determination subroutine of FIG.

FIG. 5 is a flowchart of rough road index calculation processing.

FIG. 6 is a diagram showing a map of an initially permitted vehicle speed range of a coefficient Cx.

FIG. 7 is a diagram showing a map of a vehicle speed range in which tire pressure determination is permitted.

FIG. 8 is a diagram showing the behavior of the air pressure determination variable D when the tire air pressure is normal.

FIG. 9 is a diagram showing a behavior of an air pressure determination variable D when a tire air pressure is abnormal.

FIG. 10 is a diagram corresponding to FIG. 2 in the tire air pressure determination control according to the first alternative embodiment.

FIG. 11 is a flowchart of a subroutine of tire air pressure determination processing according to the first alternative embodiment.

FIG. 12 is a flowchart of pulse signal reading processing in tire air pressure determination control according to a second alternative embodiment.

FIG. 13 is a flowchart of a tire air pressure determination process according to a second alternative embodiment.

[Explanation of symbols]

 1, 2 front wheels 3, 4 rear wheels 25 brake switch 26 steering angle sensor 27-30 wheel speed sensor 31 odometer 32 tilt detection sensor 33 initial setting switch 34 warning lamp 40 control unit

Claims (6)

[Claims] 1. A tire air pressure alarm device for detecting a decrease in tire air pressure by using wheel speeds of four wheels of a vehicle and outputting an alarm, wheel speed detecting means for detecting wheel speeds of four wheels of the vehicle, Tire pressure determination means for determining a decrease in tire air pressure using the wheel speed detected by the wheel speed detection means, road surface state detection means for detecting the state of the traveling road surface, and road surface state detection means for detecting the road surface state A tire pressure warning device comprising: a vehicle speed range setting unit that sets a vehicle speed range in which the tire pressure determination unit permits the tire pressure determination in accordance with the state. 2. The road surface state detecting means has means for detecting a frictional state of the road surface, and the vehicle speed range setting means sets the upper limit value of the vehicle speed range to be lower in the low friction state than in the high friction state. The tire pressure warning device according to claim 1, wherein the tire pressure warning device is configured as follows. 3. The road surface condition detecting means has means for detecting a bad road condition of the road surface, and the vehicle speed range setting means sets the upper limit value of the vehicle speed range to be lower on a bad road than on a good road. The tire pressure alarm device according to claim 1, wherein the tire pressure alarm device is configured. 4. The road surface condition detecting means has a means for detecting a sloped condition of the road surface, and the vehicle speed range setting means is configured to set an upper limit value of the vehicle speed range lower on an uphill than on a level ground. The tire pressure warning device according to claim 1, wherein the tire pressure warning device is provided. 5. The tire air pressure determination means uses an wheel speed of four wheels to set a compensation coefficient for compensating a manufacturing error of a newly mounted tire, and the initial setting processing. The tire pressure warning device according to claim 1, further comprising: a tire pressure determination processing unit that determines a tire pressure using the compensation coefficient set by the means and the wheel speeds of the four wheels. 6. The vehicle speed range setting means includes a vehicle speed range in which a setting process in the initial setting processing means is permitted and a vehicle speed range in which a determination process in the tire air pressure determination processing means is permitted.
The tire pressure alarm device according to claim 5, wherein the tire pressure alarm device is configured to be set respectively.