JPH06286430A - Tire pneumatic pressure alarm device - Google Patents

Abstract

(57) [Summary] [Purpose] The tire pressure determination is prohibited when the vehicle and / or the road surface is in a specific state to improve the accuracy and reliability of the tire pressure determination. [Structure] In a tire pressure alarm device that determines a tire pressure using the wheel speeds of four wheels of an automobile, the detection accuracy of the wheel speed decreases and the variation in the wheel speed increases.
The tire pressure determination is prohibited in the specific state illustrated in 100 to S109, when the chain is attached, when a large load is loaded, and the like, and the tire pressure determination is performed only when the vehicle is traveling straight and straight and the wheel speed detection accuracy is high. Run.

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 prohibiting tire pressure determination when the condition of the vehicle and / or the road surface is in a specific state not suitable for the tire pressure determination.

[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 warning device described in the above publication, the tire pressure determination is not executed at the time of acceleration or deceleration. However, in consideration of the road surface state and the vehicle state, the tire pressure No technique has been proposed for improving the accuracy or reliability of judgment. Road surface condition (road surface μ, bad road, slope, cant road surface,
Etc.), the amount of slip of the drive wheels may increase, or
The wheel load of the wheels varies and the wheel speeds of the four wheels vary, so that the wheel speed detection accuracy decreases, and the tire pressure determination accuracy and reliability decrease.

Depending on the state of the vehicle (acceleration / deceleration, load, chain installation, etc.), the slip amount of the drive wheels may increase or the wheel speed detection accuracy may deteriorate due to uneven wheel loads on the front and rear wheels. The wheel speed is detected to be small due to the increase in the tire diameter, and thus the wheel speed detection accuracy decreases, and the tire air pressure determination accuracy and reliability decrease. An object of the present invention is to improve the accuracy and reliability of tire pressure determination by prohibiting the tire pressure determination when the state of the vehicle and / or the road surface is in a specific state.

[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. For detecting a wheel speed of a wheel, a tire air pressure judging means for judging a decrease in tire air pressure using the wheel speed detected by the wheel speed detecting means, and a tire air pressure judgment for a vehicle and / or a road surface. It is provided with a specific state detecting means for detecting an unsuitable specific state and a prohibiting means for prohibiting the tire air pressure determination with respect to the tire air pressure determining means in the specific state detected by the specific state detecting means.

Here, the specific state includes an acceleration / deceleration state (Claim 2), the specific state includes a slope running state (Claim 3), and the specific state is a spin state of driving wheels. (Claim 4), the specific state includes a stack state (Claim 5), the specific state includes a cant road surface running state (Claim 6), and the specific state includes left and right. A configuration including a state in which the wheel speed of the drive wheels is constantly lower than the wheel speed of the driven wheels (claim 7), wherein the specific state is such that the wheel speeds of the left and right driven wheels are compared with the wheel speeds of the drive wheels. And the specific state includes a state in which the wheel loads of the left and right rear wheels are both larger than the wheel loads of the front wheels (claim 9). The state includes a state in which the wheel load of four wheels is equal to or more than a set value (claim 10), The constant state includes a state in which only two bad roads based on the wheel speeds of the left and right drive wheels are determined to be bad roads (claim 11), and the specific state is the wheel speeds of the left and right driven wheels. A configuration including a state in which only two rough road determinations based on the determination are bad roads (claim 12), a configuration in which the specific state includes an ON state of a parking brake (claim 13), and the specific state is anti Various configurations such as a configuration including the operating state of the skid brake device (claim 14) and a configuration including the specific state including the operating state of the traction control device (claim 15) can be adopted.

[0008]

In the tire pressure warning device of the present invention, when the wheel speed detecting means detects the wheel speeds of the four wheels of the vehicle, the tire air pressure determining means uses the detected wheel speeds. Determine the decrease in tire pressure. When the specific state detection means detects a specific state that is not suitable for tire pressure determination on the vehicle and / or the road surface, the prohibiting means prohibits the tire pressure determination means from the tire pressure determination means in the detected specific state. become. The specific states are listed in claims 2 and below, but when the specific state is not suitable for the tire pressure determination, by prohibiting the tire pressure determination, the wheel speed detection accuracy is increased,
The accuracy and reliability of tire pressure determination can be improved.

Here, claims 2 and below will be comprehensively described. In the acceleration state, the slip amount of the drive wheels increases and the wheel speed detection accuracy decreases, and in the deceleration state, the wheel load of the front wheels increases, so the wheel speed accuracy decreases. Also, when driving on a hill, even if the vehicle speed is constant, the wheel speed detection accuracy decreases due to slipping of the drive wheels as in the case of acceleration, and when the drive wheels spin, the slip amount is large. The speed detection accuracy is reduced, and the same is true in the stacking state. While traveling on the cant road surface, the wheel load becomes uneven between the left front wheel and the right front wheel.
Since the wheel speeds of the front and rear wheels on the low level side increase, the wheel speed detection accuracy decreases.

When a chain is attached to the left and right drive wheels, the wheel speeds of the left and right drive wheels are constantly lower than the wheel speeds of the driven wheels, but the wheel speed detection accuracy also deteriorates in this case. If the left and right driven wheels are chained by mistake, the wheel speeds of the left and right driven wheels will be constantly lower than the wheel speeds of the drive wheels. The accuracy decreases. When a heavy load is loaded in the trunk, the wheel load on the left and right rear wheels is larger than the wheel load on the front wheels, but in this case it is the same as the tire pressure drop, making it difficult to judge the tire pressure. However, when a heavy load is loaded in the passenger compartment or the trunk, the wheel load of the four wheels becomes equal to or greater than the set value, and the tire air pressure of the four wheels becomes similar to that of the tire pressure drop. .

When chains are attached to the left and right driving wheels, only two bad roads based on the wheel speeds of the left and right driving wheels are judged to be bad roads. If the chains are attached to the left and right driven wheels due to incorrect mounting, only the two bad road determinations based on the wheel speeds of the left and right driven wheels will be in a state of being determined as a bad road.
Also in this case, the wheel speed detection accuracy is lowered. You may drive with the parking brake ON due to an incorrect operation.
Since the wheel speed accuracy is reduced due to the deceleration state, and the wheel speed of the front wheels increases because the wheel speed is often decelerated during the operation of the anti-skid brake device or the traction control device. Is reduced.

[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, which also executes traction control of a traction control device (not shown), is provided. The control unit 24 is an ON / O switch for the brake pedal 16.
A brake signal from a brake switch 25 that detects FF, a steering angle signal from a steering angle sensor 26 that detects a steering angle, and a wheel speed sensor 27 that detects the rotation speed of each wheel, respectively.
~ 30 to receive the wheel speed signals, the brake pressure control signals corresponding to these signals, the first to third valve units 20, 21, 23.
Output to the left and right front wheels 1, 2 and rear wheels respectively.
First braking control (ABS control) for 3,4 slip
~ It is designed to be performed in parallel for each third channel.

Next, the tire pressure warning device peculiar to the present invention will be described. This tire air pressure alarm device basically has the four wheel speed sensors 27 to 30 and an initial setting switch 33 (which is attached to the instrument panel) for instructing the initial setting of the tire air pressure determination. And a warning lamp 3 attached to the instrument panel
4, equipped with a control unit 40. Here, a control system including the control unit 40 and sensors and switches will be described with reference to FIG.

As shown in FIG. 2, the control unit 40 includes a brake switch signal BSs from the brake switch 25, a steering angle θh signal from the steering angle sensor 26, and a wheel speed Vw1 from the wheel speed sensors 27 to 30. .About.Vw4 signal, mileage signal 31 from the odometer 31, tilt angle .theta.k signal from a tilt detection sensor 32 for detecting the tilt state of the vehicle body (road surface tilt state), initial setting switch 33
Initial setting command signal ISs from the lateral acceleration sensor 35, lateral acceleration Gh signal from the lateral acceleration sensor 35, yaw rate ψv signal from the yaw rate sensor 36, 4 of the active suspension device.
Oil pressure sensor that detects the oil pressure in the hydraulic working chamber for wheel height adjustment
Hydraulic pressure signals P1 to P4 from 41 to 44, P brake switch signal PBs from the parking brake switch 37 of the parking brake device, ABS / TRC control unit 24 for performing anti-skid control and traction control
Various signals such as a signal indicating that the ABS is in operation and a signal indicating that the TRC is in operation are supplied from the above, and the warning lamp 34 is drive-controlled by the control unit 40.

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 the drawings starting from FIG. 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, and the coefficient Cx for compensating the tire manufacturing error is initialized. afterwards,
Periodically (every predetermined mileage, or every predetermined period), the tire pressure determination process is executed to determine an abnormal tire pressure, and when the tire pressure is low, the warning lamp 34 is turned on. An alarm is output via.

The initialization process is executed when the vehicle speed range is set according to the road surface condition, and is prohibited when the road surface condition or the vehicle condition is a specific condition not suitable for the initialization process. . The tire pressure determination process,
This is executed in the vehicle speed range that is separately set according to the road surface state, and is prohibited when the road surface state or the vehicle state is a specific state that is not suitable for the tire air pressure determination processing. still,
The tire air pressure determination control includes the initial setting process, the tire air pressure determination process, the rough road index calculation process, and the road surface friction coefficient calculation process (the flowchart thereof is omitted).

Next, the initial setting process of the coefficient Cx will be described with reference to FIG. This initial setting process of the coefficient Cx is performed by turning on the a-contact type initial setting switch 33 attached to the instrument panel when the tire is replaced.
It is started when operated, then various data obtained by digitizing the signals from the sensors and switches are read (S10), and next, in order to show that the initialization process is being executed,
The warning lamp 34 is turned on, and the flag F is reset to 0 to prohibit the tire pressure determination process (S
11).

Next, in S12, it is determined whether or not the initial setting condition of the coefficient Cx is satisfied. The subroutine of this determination will be described with reference to the flowcharts of FIGS. 6 and 7. First, in S100, the P brake switch signal PBs from the parking brake switch 37
When the parking brake is ON, the parking brake is determined based on the above (when the vehicle is traveling with the parking brake ON due to an erroneous operation).
Corresponds to the braking state, the wheel loads of the front wheels and the rear wheels become non-uniform, and the wheel speed detection accuracy decreases, so it is determined that the condition is not satisfied in S118.

Next, in S101, it is determined whether acceleration or deceleration is being performed. 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 S118 that the condition is not satisfied.

Next, at S102, it is judged whether or not the vehicle is turning based on the signal of the steering angle θh from the steering angle sensor 26.
When the vehicle is turning, the difference in wheel speed between the inner wheel and the outer wheel becomes large and it is not desirable to execute the tire pressure determination.
At 118, it is determined that the condition is not satisfied. Next, S10
3, it is determined whether or not the ABS is in operation based on the signal indicating that the ABS is in operation from the ABS / TRC control unit 24. When the ABS is in operation, the braking state is often generated and the wheel speed detection accuracy is deteriorated. Therefore, S118
It is determined that the condition is not satisfied in. Next, in S104, T from the ABS / TRC control unit 24
Whether or not the TRC is in operation is determined based on the signal indicating that the RC is in operation. When the TRC is in operation, a braking state is often generated, and the wheel speed detection accuracy deteriorates. Therefore, it is determined in S118 that the condition is not satisfied.

Next, in S105, it is determined whether the road surface on which the vehicle is traveling is an uphill road based on the signal of the road surface inclination θk from the inclination detection sensor 32. When the road surface is an uphill road, the wheel speed detection accuracy is the same as in the acceleration state. Since it decreases, it is determined in S117 that the condition is not satisfied. Next, in S106,
Based on a rough road index (a rough road flag Fak), which will be described later, which is an average of four rough road indexes, it is determined whether or not the road surface on which the vehicle is running is a rough road. If not, the variations in the four wheel speeds increase, so S11
In 8, it is determined that the condition is not satisfied.

Next, in S107, it is judged whether or not the vehicle is on the cant road surface. When the vehicle is traveling on the cant road surface, the wheels of the left front wheels 1 and 3 and the left front wheels 2 and 4 are generated although the yaw rate ψv is not generated. Since a speed difference or lateral acceleration occurs, the yaw rate ψv detected by the yaw rate sensor 36, the wheel speeds Vw1 to Vw4 detected by the wheel speed sensors 27 to 30, and the lateral acceleration sensor 35 are detected. Lateral acceleration G
Based on h, 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 load of the front and rear wheels on the low level side becomes large and the wheel speed detection accuracy deteriorates. It

Next, in S108, 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. The vehicle is in a stack based on the wheel speeds Vw1 to Vw4 and the vehicle speed V. It is determined whether or not the condition is not satisfied in S118 because an abnormal wheel speed is detected and it is difficult to determine the tire pressure when the vehicle is stuck. next,
In S109, 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 S118 that the condition is not satisfied.

Next, in S110, it is judged whether or not only the rear wheels are the bad road judgment. In the bad road judgment described later, the bad road judgment corresponding to the left rear wheel 3 and the bad road judgment corresponding to the right rear wheel 4 If it is determined that only one of the roads is a bad road, it is highly possible that chains are attached to both the rear wheels 3 and 4, and in this case the detection accuracy of the wheel speed decreases, so it is determined that the condition is not satisfied in S118. Next, in S111, it is determined whether or not only the front wheels are both bad roads. If only the bad road determination corresponding to the left front wheel 1 and the bad road determination corresponding to the right front wheel 2 are bad roads, There is a high possibility that the front wheels 1 and 2 are erroneously attached to the chain, and in this case, the detection accuracy of the wheel speed is lowered, so that the condition is determined not to be satisfied in S118.

Next, in S112, it is judged whether or not the wheel speeds of both rear wheels are lower than the wheel speeds of both front wheels, but it is highly possible that chains are attached to both rear wheels 3 and 4. In this case, since the wheel speed detection accuracy decreases, it is determined in S118 that the condition is not satisfied. Next, in S113, it is determined whether or not the wheel speeds of both front wheels are lower than the wheel speeds of both rear wheels, but it is highly possible that chains are attached to both front wheels 1 and 2, and in this case the wheels are Since the speed detection accuracy decreases, it is determined in S118 that the condition is not satisfied. Next, S1
14, the hydraulic pressure P1 detected by the hydraulic pressure sensors 41 to 44
It is determined whether or not all of P4 to P4 are equal to or more than the set values, and if a large load is loaded in the passenger compartment or the trunk and the wheel load becomes excessive, the detection accuracy of the wheel speed decreases, so the condition is not satisfied in S118. Is determined.

Next, at S115, the oil pressures P1 to P are set.
Among the four, only the hydraulic pressures P3 and P4 corresponding to both rear wheels are determined to be higher than the hydraulic pressures P1 and P2 corresponding to both front wheels, and the hydraulic pressure P3 is set in a state where a heavy load is loaded on the trunk. , P4 alone is high, the wheel load of the rear wheels is large and the wheel speed detection accuracy decreases, so it is determined in S118 that the condition is not satisfied. Next, in S116, it is determined whether the vehicle speed V is within the permitted vehicle speed range. As shown in FIG. 9, the permitted vehicle speed range is the initially set permitted vehicle speed range of the coefficient Cx set according to the frictional condition of the road surface. When the result of the determination is No, the condition is not satisfied in S118. Is determined. Then, S100 to S115
All judgment results are No, and the judgment result in S116 is Ye.
When s, the wheel speeds Vw1 to Vw4 can be detected with high accuracy, so that the condition is determined to be satisfied in S117.

Here, the lower limit value of the initially permitted vehicle speed range of the coefficient Cx shown in FIG. 9 is set to a predetermined value (for example, 20 km / H) that is not excessively low, and the upper limit of the initially permitted vehicle speed range is set. The value is 40-5 depending on the frictional condition of the road surface.
It is set to a value in the range of 0 Km / H. The method of calculating the road surface μ and the method of calculating the rough road index (flag Fak) indicating the rough road state will be described later.

Next, as a result of executing the subroutines of FIG. 6 and FIG. 7, when it is determined that the condition is satisfied in S12 of FIG. 3, the four tires at the time of tire replacement etc. are considered in consideration of the manufacturing error of the tire in S13. Using the wheel speeds Vw1 to Vw4 of the four wheels having the coefficient Cx for compensating for the initial state, the sum of the wheel speeds of the left front wheel 1 and the right rear wheel 4 (Vw1 + Vw4) and the diagonal line of the other are used. The ratio of the sum of the wheel speeds of the right front wheel 2 and the left rear wheel 3 (Vw2 + Vw3), which are related, 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, the previous coefficient Cx (i-1) is rewritten with the current Cx (i), and then
The warning lamp 34 is turned off and the flag F is set to 1 to permit the tire air pressure determination process, and then the process proceeds to S19. On the other hand, if the determination result in S14 is No, it is determined in S17 whether the coefficient Cx is indefinite,
When it is not fixed, the process proceeds to S12 and S12 and subsequent steps are re-executed. When it is not fixed, the warning lamp 34 is blinked for a predetermined time (for example, 2 seconds) in S18, and then the process proceeds to S19. In S19, it is determined whether the flag F is 1, and if the determination is No, the process returns,
If the determination is Yes, this process ends. However, based on one ON operation of the switch 33, a plurality of initialization processes are executed to obtain a plurality of coefficients Cx, and the final coefficient Cx is determined from the average value of the plurality of coefficients Cx. It is also possible to do so. 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, as already mentioned, the vehicle speed V
Is basically the wheel speed Vw1, Vw2 of the driven wheels (front wheels 1, 2)
Is set to be equal to the average value of, and the vehicle speed V is applied to the initial setting process and the tire air pressure determination process. Road surface μ
Is calculated based on the vehicle speed V and its acceleration Vg,
For this calculation, a timer of 500 ms and a timer of 100 ms are used, and after the start of acceleration, the vehicle body acceleration Vg does not become sufficiently large.
From the change of the vehicle speed V during s, 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.

[0036]

[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, 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 count of the predetermined time and the number of times, and then S59 to S59.
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 average rough road index for is calculated. However, the rough road index corresponding to each wheel is also stored, and S11 of FIG.
0 and used in S111.

Next, the tire pressure determination process will be described with reference to the flowcharts of FIGS. 4 and 5. This tire air pressure determination process is, for example, a process that is executed for each mileage of 500 km, and after starting this process, various data obtained by digitizing the signals from the sensors and switches is read (S20), Next, the flag F
Is determined to be 1 (S21), and if Yes, S2
In 2, it is determined whether or not the tire air pressure determination condition is satisfied. The tire pressure determination conditions are the same as those in the subroutines shown in FIGS. 6 and 7, and therefore the description of the tire pressure determination conditions will be omitted. However, S1 in FIG.
The permitted vehicle speed range in 15 is the tire pressure determination permitted vehicle speed range shown in FIG. 10 that is set to a vehicle speed range of 40 km / H to the maximum vehicle speed according to the frictional state of the road surface. If the determination result in S22 is Yes, the process proceeds to S23, and if the condition is not satisfied, the process proceeds to S24.

In S23, the tire pressure determination subroutine of FIG. 5 is executed, and then the process returns and S21 is executed.
Or, if the determination result in S22 is No, in S24,
The timer T in the tire 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 S23 will be described with reference to FIG. First, it is determined whether or not the flag Ft is 1 (S30). Since it is initially No, the timer T is started and the flag Ft is set to 1 in S31, and the process proceeds to S32. Further, in a state where the flag Ft is set to 1, S30 to S
Move to 32. 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 determined whether or not the determination variable D is equal to or greater than a predetermined value D0 (eg, 0.050). If the determination result is Yes, it is determined whether or not the flag Fa is 1 (S34), and the flag Fa is 1 If not, the counter I for counting the number of times the judgment variable D is equal to or larger than the predetermined value D0 is set to 1 and the flag Fa is set to 1 (S35), and then the process proceeds to S41. When the flag Fa is set to 1, S3
Then, the process proceeds from S4 to S36, the counter I is incremented, and then the process proceeds to S41.

On the other hand, if the determination result of 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). However, since the determination result is No at the beginning, S41 Repeatedly returning from
The steps S20 to S22 and S30 to S41 of FIG. 4 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 increased. Note that FIG. 11 illustrates the behavior of the air pressure determination variable D when the tire pressure is normal, and FIG. 12 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 air 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. Then, as shown in FIGS. 6 and 7, the initialization process is prohibited when the road surface state, the load state of the vehicle, the operating state of the vehicle, or the like corresponds to a specific state that is not suitable for the tire pressure determination. It is executed only in the steady straight running state in the vehicle speed range set according to the road friction state of the running road surface, which does not correspond to the state, so that the wheel speed due to drive wheel slip, wheel speed variation, and wheel load unevenness The coefficient Cx can be initialized with high accuracy by eliminating as much as possible the error factors caused by the fluctuations and variations of the above.

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 processing, as shown in FIGS. 6 and 7, is similar to the initial setting processing.
A vehicle speed range that is prohibited when the condition of the road surface, the condition of the load, the condition of the vehicle, etc. correspond to a specific condition that is not suitable for tire pressure determination, and which does not correspond to the specific condition and is set according to the road friction condition of the traveling road surface. Since it is executed only in the steady straight running state in, the slip of the drive wheels, the variation of the wheel speed, the variation and the variation of the wheel speed due to the non-uniformity of the wheel load,
It is possible to improve the accuracy and reliability of the tire pressure determination by eliminating the error factors caused by the above 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 D ≧ D0 and the count value J that satisfies D ≦ −D0 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, a first another embodiment in which a part of the above embodiment is modified will be described with reference to FIGS. 13 and 14. FIG. 12 is a flowchart of the initialization process corresponding to FIG. 3, and the same steps as those in FIG. In this embodiment, the coefficient Cx
Instead of, the initial deviation Δ for compensating a tire manufacturing error or the like is applied, and in S12A, it is determined whether or not the initial deviation Δ initial setting condition is satisfied as in S12, and when the condition is satisfied, , S13A, the initial deviation Δ is calculated by the illustrated formula. In S14A, the initial deviation Δ
Is determined to be an appropriate value. For example, it is determined to be an appropriate value in the range of −0.05 to 0.05, and the rewriting process of the initial deviation Δ is executed in S15A. When the initial deviation Δ is not an appropriate value, in S17A, it is determined whether the initial deviation Δ is indefinite or not, as in S17.

Next, the tire air pressure determination subroutine of the tire air pressure determination processing of FIG. 4 will be described with reference to FIG. 14, which is a diagram corresponding to FIG.
The same steps as those in FIG. 5 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. 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.
5, and the tire air pressure determination process of FIG. 16. 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. 15, when the routine is started for each predetermined traveling distance, various data from wheel speed sensors and switches are read (S7).
0) Next, similarly to S22, it is determined whether or not the tire air pressure determination condition is satisfied (S71). If the determination result is Yes, in S72, for example, for 8 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 determination result of S71 is No, it returns as it is and repeats. To be executed. In this way, when the tire air pressure determination condition is satisfied, the pulse signals Pw1 to Pw4 for 8 ms are stored in the buffer (B1 to B4) while being updated.

Next, in parallel with the pulse signal reading process, the tire pressure determination process of FIG. 16 is executed. Figure 1
When the routine of No. 6 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. 15 and 16 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. The tire air pressure determination process of the tire air pressure determination control may be configured to be constantly executed while the vehicle is traveling.

[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 configuration diagram of a control system of a tire air pressure alarm device.

FIG. 3 is a flowchart of an initial setting process of a coefficient Cx of tire air pressure determination control.

FIG. 4 is a flowchart of tire air pressure determination processing of tire air pressure determination control.

5 is a flowchart of a tire air pressure determination subroutine of FIG.

6 is a part of a flowchart of a subroutine of S12 of FIG. 3 and S22 of FIG.

7 is the rest of the flowchart of the subroutine of S12 of FIG. 3 and S22 of FIG.

FIG. 8 is a flowchart of rough road index calculation processing.

FIG. 9 is a diagram showing a map of an initially permitted vehicle speed range of a coefficient Cx.

FIG. 10 is a diagram showing a map of a vehicle speed range in which tire pressure determination is permitted.

FIG. 11 is a diagram showing the behavior of the air pressure determination variable D when the tire air pressure is normal.

FIG. 12 is a diagram showing a behavior of an air pressure determination variable D when a tire air pressure is abnormal.

FIG. 13 is a diagram corresponding to FIG. 2 in the tire air pressure determination control according to the first alternative embodiment.

FIG. 14 is a flowchart of a tire pressure determination subroutine according to the first alternative embodiment.

FIG. 15 is a flowchart of a pulse signal reading process in the tire air pressure determination control according to the second alternative embodiment.

FIG. 16 is a flowchart of tire air pressure determination processing according to a second alternative embodiment.

[Explanation of symbols]

 1, 2 front wheels 3, 4 rear wheels 24 ABS / TRC control unit 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 35 lateral acceleration sensor 36 yaw rate sensor 37 Parking brake switch 40 Control unit

Claims (15)

[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, A 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 a specific state detection means for detecting a specific state not suitable for tire air pressure determination for the vehicle and / or road surface, When the specific state detected by the specific state detection means,
A tire pressure warning device comprising: a prohibition unit that prohibits the tire pressure determination unit from making a tire pressure determination. 2. The tire pressure warning device according to claim 1, wherein the specific state includes an acceleration / deceleration state. 3. The tire pressure warning device according to claim 1, wherein the specific state includes a hill running state. 4. The tire pressure warning device according to claim 1, wherein the specific state includes a spin state of a drive wheel. 5. The tire pressure warning device according to claim 1, wherein the specific state includes a stuck state. 6. The tire pressure warning device according to claim 1, wherein the specific state includes a cant road surface running state. 7. The tire pressure warning device according to claim 1, wherein the specific state includes a state in which the wheel speeds of the left and right driving wheels are constantly lower than the wheel speeds of the driven wheels. 8. The tire pressure warning device according to claim 1, wherein the specific state includes a state in which the wheel speeds of the left and right driven wheels are constantly lower than the wheel speeds of the driving wheels. 9. The tire pressure warning device according to claim 1, wherein the specific state includes a state in which the wheel loads of the left and right rear wheels are both larger than the wheel loads of the front wheels. 10. The tire pressure warning device according to claim 1, wherein the specific state includes a state in which the wheel loads of four wheels are equal to or more than a set value. 11. The tire pressure warning according to claim 1, wherein the specific state includes a state in which only two bad road determinations based on the wheel speeds of the left and right driving wheels are determined to be bad roads. apparatus. 12. The tire pressure warning according to claim 1, wherein the specific state includes a state in which only two bad road determinations based on the wheel speeds of the left and right driven wheels are determined to be bad roads. apparatus. 13. The tire pressure warning device according to claim 1, wherein the specific state includes an ON state of a parking brake. 14. The tire pressure warning device according to claim 1, wherein the specific state includes a state in which an anti-skid brake device is in operation. 15. The tire pressure warning device according to claim 1, wherein the specific state includes a state in which a traction control device is operating.