JPH06286632A - Controller for vehicle - Google Patents

Abstract

PURPOSE:To enable a driver to surely recognize the lowering of the tire pneumatic pressure by securing the steering performance in the lowering of the pneumatic pressure, as for a vehicle equipped with a power steering device and a tire pneumatic pressure judging device. CONSTITUTION:Into a controller 8 for executing the tire pneumatic pressure judgement control by using each wheel speed of four wheels, each signal supplied from the wheel speed sensors 9a-9d, steering angle sensor 10, brake switch 11, traveling distance meter 12, and an initiallizing switch 13 for instructing the start of the initiallization processing for a tire. Though, when it is judged by the controller 8 that the tire pnematic pressure is reduced, the instruction for intensifying the power assisting force is outputted for the controller 50 of a power steering device, the power assisting force is intensified only in the case where each tire pnematic pressure of the front wheels 2a and 2b lowers, or when the reduction of the pneumatic pressure is judged, the power assisting force may be lowered, when the reduction of the tire pneumatic pressure is judged, in order to allow a driver to surely recognize the reduction of the pneumatic pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle control device, and more particularly to an improved control system for assisting force of a power steering device when a tire air pressure determination device determines a decrease in tire air pressure.

[0002]

2. Description of the Related Art Conventionally, various power steering devices for assisting steering of a steering wheel have been put into practical use, and the hydraulic pressure supply amount to the power cylinder (that is, the magnitude of the assist force) is set by using the vehicle speed as a parameter. The hydraulic pressure supply amount is reduced in accordance with the increase of the vehicle speed, and the hydraulic power supply amount is kept constant at a vehicle speed equal to or higher than a predetermined vehicle speed (for example, 80 Km / H) so that the assist force is controlled not to become too small. There is.

On the other hand, conventionally, various tire air pressure determination 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 Laid-Open Patent Publication 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 determination device is described.

[0005]

In the control of the conventional power steering system, control is performed on the assumption that the tire pressure is normal. However, when the tire pressure is reduced, the resistance of the tire whose pressure is reduced is reduced. Therefore, there is a problem that the steering becomes heavier and the tendency becomes remarkable especially when the tire pressure of the front wheels decreases. By the way, since the tire air pressure determination device only displays an alarm on the warning lamp when it determines a decrease in air pressure, it is conceivable that the driver will continue to drive without noticing even if an alarm is displayed on the warning lamp. An object of the present invention is to enhance the steerability when it is determined that the tire pressure has dropped, and to make the driver surely notice the tire pressure drop.

[0006]

According to a first aspect of the present invention, there is provided a vehicle control device including a power steering device and a tire air pressure determination device for determining a decrease in tire air pressure of a wheel. The control means is provided for greatly changing the assist force of the power steering device when it is determined that the tire air pressure has dropped.

According to a second aspect of the present invention, there is provided a vehicle control device according to the first aspect, wherein the tire air pressure determination device includes an abnormal wheel detection means for detecting an abnormal wheel in which the tire air pressure has dropped. The assisting force is changed only when the abnormal wheel is the front wheel by receiving the data regarding the abnormal wheel from the abnormal wheel detecting means. The vehicle control device according to claim 3 is a vehicle including a power steering device and a tire air pressure determination device that determines a decrease in tire air pressure of a wheel, when the tire air pressure determination device determines that the tire air pressure is low. In addition, a control means for changing the assisting force of the power steering device to a small value is provided.

[0008]

In the vehicle control system according to the first aspect of the present invention, when the tire air pressure determination device determines that the tire air pressure of any one of the four wheels has dropped, the control means assists the power steering device. Greatly change the power.
As a result, it is possible to prevent an increase in steering resistance due to the resistance of the tire whose air pressure has dropped, and prevent an increase in the steering burden on the driver, and to prevent deterioration in steering performance.

According to a second aspect of the present invention, there is provided the vehicle control system according to the first aspect, wherein the abnormal wheel detecting means provided in the tire air pressure determination device detects an abnormal wheel having a decreased tire air pressure. The control means receives the data on the abnormal wheel and changes the assist force only when the abnormal wheel is the front wheel. That is, when the tire pressure of the front wheels decreases, the steering resistance increases and the steering performance deteriorates, but this can be prevented.

In the vehicle control device of the third aspect, when the tire air pressure determination device determines that the air pressure of any one of the four wheels has dropped, the control means changes the assist force of the power steering device to a small value. To do. Therefore, when the air pressure decreases, steering of the steering wheel becomes heavy,
It is possible to make the driver notice that the tire pressure has dropped.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is an example in which the present invention is applied to a control device for an automobile equipped with a power steering device and a tire air pressure determination device that determines a decrease in tire air pressure. As shown in FIG. 1, in this vehicle, the left and right front wheels 2a and 2b are drive wheels, and the left and right rear wheels 3a and 2b are
3b is a driven wheel, and a V-type 6-cylinder engine 4 on the front of the vehicle
The drive torque from the engine is passed through the automatic transmission 5 and the differential 6 via the left drive shaft 7a and the left front wheel 2 is mounted.
a and to the right front wheel 2b via the right drive shaft 7b, respectively.

Here, the power steering device provided in the automobile will be described with reference to FIGS. As shown in FIGS. 2 and 3, in this power steering device 20, tie rods 22a and 22b are connected to the knuckle arms of the wheel supports 21a and 21b of the left and right front wheels 2a and 2b.
a and 22b are rack shafts 2 having racks 23a
3, the rack shaft 23 is meshed with the pinion 28 at the lower end of the lower shaft 27, and the steering shaft 25 extending from the steering handle 24 is connected to the lower shaft 27 via the intermediate shaft 26. . Piston 3 fixed to the rack shaft 23
2 is provided, the rack shaft 23 is inserted through a cylinder body 31 of the power cylinder 30 in an oil-tight manner, and the cylinder body 31 is fixed to the vehicle body.

Regarding the hydraulic system of the power steering device 20, a gear control valve 37 is attached to the lower shaft 27, and an oil chamber 33 of the power cylinder 30,
34 is connected to a gear control valve 37 via oil passages 35 and 36, and a supply oil passage 38 extending from a pump 40 driven by an engine to the gear control valve 37, and extending from the gear control valve 37 to a tank 41. A drain oil passage 39, a flow rate control valve 42 provided in the supply oil passage 38, and a pressure control valve 43 bypassing the flow rate control valve 42 and connected to the supply oil passage 38 are provided.

As shown in FIGS. 3 and 4, the flow control valve 42 is provided with a valve body 45, a solenoid 46, and a spring 47 for urging the valve body 45 in the valve closing direction in a case 44. The valve flange 45a of the valve element 45 faces the ring-shaped valve seat 48 of the case 44, and the valve flange 45a is formed with a fixed orifice 49. The solenoid 46
The gap h between the valve collar 45a and the valve seat 48 increases with an increase in the exciting current to increase the hydraulic pressure supply amount, and the assist force by the power cylinder 30 increases. When the exciting current is reduced to a predetermined value or less, the elastic force of the spring 47 lowers the valve element 45 and the gap h between the valve collar portion 45a and the valve seat 48 becomes zero. Supplied. The pressure adjusting valve 43 is the flow control valve 42.
A part of the hydraulic pressure is drained according to the increase in the pressure difference between the upstream side and the downstream side.

A power steering control device 50 for controlling the flow control valve 32 is provided, and the control device 50 is provided.
Controls the exciting current of the solenoid 46 based on the vehicle speed V detected by the vehicle speed sensor 51 based on a predetermined map or table. The relationship between the vehicle speed V and the hydraulic pressure supply amount is as shown in FIG. . When steering to the left with respect to the automobile (when steering the front wheels 2a, 2b in the direction of arrow L), the oil passage 36 is connected to the oil supply passage 38 via the gear control valve 37, 35 is connected to the drain oil passage 39 via the gear control valve 37. On the contrary, when steering to the right (the front wheels 2a, 2b are indicated by the arrow R
When the steering wheel is turned in the direction of, the oil passage 35 is connected to the supply oil passage 38 via the gear control valve 37, and the oil passage 36 is connected to the drain oil passage 39 via the gear control valve 37. Further, when the steering angle is substantially zero, the supply oil passage 38 is connected to the drain oil passage 39 via the gear control valve 37.

As described above, when the vehicle speed V is low, the hydraulic pressure supply amount is large, so a strong assist force is generated according to the vehicle speed V, and the hydraulic pressure supply amount decreases as the vehicle speed V increases. When the vehicle speed V becomes equal to or higher than a predetermined value (for example, 80 Km / H) as the assisting force decreases, the flow rate control valve 32 enters the state shown in FIG. 4, so that a substantially constant small hydraulic pressure supply flowing through the fixed orifice 49 is supplied. As a result, a constant small assist force is generated.

Next, the tire pressure determining device will be described. As shown in FIG. 1, this tire air pressure determination device includes four wheel speed sensors 9a to 9d for respectively detecting the rotational speeds of front wheels 2a and 2b and rear wheels 3a and 3b of an automobile, and an initial setting process for tire air pressure determination. An initial setting switch 13 (which is attached to the instrument panel) for starting the operation, a warning lamp 14 attached to the instrument panel, a control device 8 and the like,
The control device 8 is supplied with signals from sensors and switches such as the wheel speed sensors 9a to 9d, the steering angle sensor 10, the brake switch 11, the odometer 12, the initial setting switch 13, and the like, and the warning lamp 14 controls The drive is controlled by the device 8.

The wheel speed sensors 9a to 9d are formed on a brake disc or a detection disc (not shown) provided adjacent to the brake disc.
The configuration is such that four detection units are detected by an electromagnetic pickup. ROM of the control device 8 microcomputer
A tire air pressure determination control control program and map are input and stored in advance, and the RAM is provided with various memories (buffer, memory, flag, counter, soft timer, etc.) necessary for the control. There is.

The tire air pressure determination control executed by the controller 8 will be described below with reference to the drawings starting from FIG. However, in the flow chart, the reference numeral Si (i = 1,
2, 3, ...) Each step 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 9a to 9d. Initialization of a coefficient Cx (which corresponds to a compensation coefficient) for compensating a tire manufacturing error and characteristics is performed when one or a plurality of tires are replaced.

After that, at regular intervals (every predetermined mileage, or
(Every predetermined period), or at all times, the tire pressure determination process is executed to determine whether or not there is an abnormality in the tire pressure.
When the tire pressure is low, an alarm is output via the warning lamp 14, and an exciting current change command for increasing the assist force is output to the control device 50 of the power steering device 20 so that the control device 50 causes the power steering device 20 to increase. Increase assist power. The initial setting process is executed in the vehicle speed range set according to the road surface friction state, and the tire air pressure determination process is executed in the vehicle speed range set separately according to the road surface friction state. The tire air pressure determination control includes the initial setting process and the tire air pressure determination process.

Next, the initial setting process of the coefficient Cx will be described with reference to the flowchart of FIG. The initial setting process of the coefficient Cx is started when the a-contact type initial setting switch 13 attached to the instrument panel is turned on when the tire is replaced, and then the sensors 9a to 9d, 10 and 12 are started. Various data obtained by digitizing the signals from the switches 11 and 13 are read (S
1) Next, the warning lamp 14 is turned on to indicate that the initialization process is being executed, and the flag F is reset to 0 to prohibit the tire air pressure determination process (S).
2).

Next, it is determined whether or not the initial setting condition of the coefficient Cx is satisfied (S3), but the vehicle is not in the acceleration / deceleration state, is in the steady straight traveling state, and the vehicle speed V is as shown in FIG.
Coefficient C set according to the road friction state shown in the map of
When it is satisfied that the vehicle speed is within the initial setting permission vehicle speed range of x, it is determined that the condition is satisfied and the process proceeds to S4, and when the condition is not satisfied, the process proceeds to S10. The vehicle speed V in the tire air pressure determination control is set equal to the average value of the wheel speeds Vw3 and Vw4 of the left and right driven wheels 3a and 3b, and 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. 10 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 to 5 depending on the road friction on the road surface.
It is set to a value in the range of 0 Km / H. Regarding the upper limit value, 40 km / H in the low μ state to 5 in the high μ state
It is set to increase linearly to 0 Km / H. Fifty
In the high speed state exceeding Km / H, the slip amount of the driving wheels increases, the wheel loads of the front wheels 2a and 2b and the rear wheels 3a and 3b change, and the detection accuracy of the wheel speeds Vw1 to Vw4 decreases. Therefore, it is desirable to execute the initialization process when the vehicle speed is 50 Km / H or less, and since the slip amount of the driving wheels increases when the vehicle speed is low μ, the initialization process is performed when the vehicle speed is 40 Km / H or less. It is desirable to perform processing.

Next, when it is determined in S3 that the condition is satisfied, in S4, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement, etc. is added to the four wheels in consideration of the manufacturing error and characteristics of the tire. Using the wheel speeds Vw1 to Vw4 of
As a ratio of the sum of the wheel speeds of the left front wheel 2a and the right rear wheel 3b (Vw1 + Vw4), which are diagonally related to each other, and the sum of the wheel speeds of the right front wheel 2b and the left rear wheel 3a (Vw2 + Vw3), which are diagonally related to each other It is calculated by the following formula. Coefficient Cx = (Vw1 + Vw4) / (Vw2 + Vw3) Next, in S5, it is determined whether or not the coefficient Cx is an appropriate value, but the tire diameter error due to the tire manufacturing error is 0.
Since it is 3%, it is determined that the coefficient Cx is an appropriate value when the coefficient Cx is within a predetermined range of approximately 1 (for example, 0.95 to 1.05).

When the coefficient Cx is a proper value, the coefficient Cx is rewritten in S6, the previous coefficient Cx (i-1) is given the current Cx (i), and then the warning lamp is added in S7. 14 is turned off, and the flag F is set to 1 to allow the tire pressure determination process,
Then, the process proceeds to S10. On the other hand, if the determination result in S5 is No, it is determined in S8 whether or not the coefficient Cx is indefinite. If it is indefinite, the process proceeds to S10. If it is not indefinite, in S9 the warning lamp 14 is operated for a predetermined time (for example, Flashes for 2 seconds, and then proceeds to S10. In S10, it is determined whether or not the flag F is 1, and if the determination is No, the process returns and the processing is repeated, and if the determination is Yes, this processing ends.

However, based on one ON operation of the switch 13, a plurality of initialization processes are executed to obtain a plurality of coefficients Cx.
Can be obtained and the final coefficient Cx can be determined from the average value of the plurality of coefficients Cx. In this way, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement is determined and stored in the memory of the RAM.

Here, the calculation processing for obtaining the road surface μ of the traveling road surface will be described. First, the vehicle speed V is the driven wheels 3a, 3
It is set equal to the average value of the wheel speeds Vw3 and Vw4 of b, and the vehicle speed V is applied to the initial setting process and the tire air pressure determination process. The road surface μ is calculated on the basis of the vehicle speed V and its acceleration Vg. For this calculation, a 500 ms timer and a 100 ms timer are used, and after the acceleration starts, the vehicle body acceleration Vg does not become sufficiently large until 500 ms elapses. 10
The vehicle body acceleration Vg is calculated by the following equation from the change of the vehicle speed V for 100 ms every 0 ms.

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

[0029]

[Table 1]

Next, the tire air pressure determination process will be described with reference to the flowcharts of FIGS. 7 to 9 and FIGS. 11 to 13. This tire air pressure determination process, for example,
This is a process executed for each mileage of 10 km, and after starting this process, various data obtained by digitizing the signals from the sensors 9a to 9d, 10, 12 and the switch 11 are read (S40), and then, It is determined whether the flag F is 1 (S41), and if Yes, it is determined in S42 whether the tire air pressure determination condition is satisfied. Regarding this tire pressure determination condition, the vehicle is not in the acceleration / deceleration state, is in the steady straight traveling state, and the vehicle speed is within the tire pressure determination permission vehicle speed range set according to the road surface friction state shown in the map of FIG. If is satisfied, the condition is determined to be satisfied and the process proceeds to S43, and if the condition is not satisfied, the process proceeds to S44.

Here, the lower limit value of the tire pressure determination permission vehicle speed range shown in FIG. 11 is set to a predetermined value (for example, 20 Km / H) which is not excessively low, and the upper limit value of the tire pressure determination permission vehicle speed range. Is 4 depending on the road friction on the road surface.
It is set to a value in the range of 0 Km / H to maximum vehicle speed.

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 state. Then, in a high speed state of over 50 Km / H, the slip amount of the drive wheels increases and the wheel speeds Vw1 to Vw
Although the detection accuracy of w4 decreases, it is desirable to detect the decrease in tire air pressure in a high-speed running state of more than 50 Km / H even if there is some decrease in accuracy, so the setting is made as described above. Further, since the slip amount of the driving wheels increases when the μ is low, it is desirable to execute the tire air pressure determination processing when the vehicle speed is 40 Km / H or less.

In S43, the tire air pressure determination subroutine of FIG. 8 is executed, and then the process returns and S41 is executed.
Or, if the determination result in S42 is No, in S44,
The timer T in the tire air pressure determination subroutine is reset, the flags Fa and Ft, and the counters I and J are reset to 0, and then the process returns. Next, the tire pressure determination subroutine of S43 will be described with reference to FIG. First, it is determined whether the flag Ft is 1 (S5
0), since it is initially No, the timer T is started in S51, the flag Ft is set to 1, and the process proceeds to S52. Further, when the flag Ft is set to 1, the process proceeds from S50 to S52. Next, in S52, 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 formula, the coefficient Cx is set in advance so as to compensate for the initial state of the tire, so that the tire pressure is normal. In some cases, the air pressure determination variable D has a value substantially equal to 0, but when the tire air pressure of the right front wheel 2b or the left rear wheel 3a is low, the wheel speed Vw2 or the wheel speed Vw3 is high. The air pressure determination variable D increases in the positive direction, and when the tire air pressure of the left front wheel 2a or the right rear wheel 3b decreases, the wheel speed Vw1 or the wheel speed Vw4 increases, so the air pressure determination variable D is negative. Increase in the direction.

Next, in S53, 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), and if the judgment result is Yes, the flag F
It is determined whether or not a is 1 (S54), and when the flag Fa is not 1, the counter I that counts the number of times the determination variable D is the predetermined value D0 or more is set to 1 and the flag Fa is set to 1 (S55). , And then the process proceeds to S61.
When the flag Fa is set to 1, S
The routine moves from 54 to S56, the counter I is incremented, and then the routine proceeds to S61.

On the other hand, if the determination result in S53 is No, S
57, it is determined whether or not the determination variable D is less than or equal to the predetermined value −D0. If Yes, it is determined whether or not the flag Fa is 2 (S58). 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
59) and then the process moves to S61. Further, when the flag Fa is set to 2, the process proceeds from S58 to S60, the counter J is incremented, and then S61.
Go to F.

Next, in S61, 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 in the beginning, the determination result is No, so S61. Repeatedly returning from
7. S40 to S42 and S50 to S61 of FIG. 7 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. 12 shows the behavior of the air pressure determination variable D when the tire pressure is normal, and FIG. 13 shows the air pressure determination variable D when the tire pressure of the right front wheel 2b or the left rear wheel 3a is abnormal.
The behavior of is illustrated.

When the predetermined time T0 has elapsed, S61
Since the determination result of No is Yes, the process proceeds to S62, 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 the count value J of is equal to or more than the predetermined value K0. If the determination result is No, it is determined in S63 that the tire pressure is normal, and the process proceeds to S67.
When the result of the determination in 62 is Yes, it is determined in S64 that the tire pressure is abnormal (decrease), and in S65, the warning lamp 14 is turned on for a predetermined time (for example, 2 seconds) in order to warn the driver of the decrease in tire pressure. .

In S66, the data of the exciting current change command for increasing the exciting current of the solenoid 46 by the predetermined value A in order to strengthen the assisting force is output to the power steering controller 50. The predetermined value A is
It becomes smaller as the vehicle speed V increases, and becomes a predetermined vehicle speed (for example,
It may be set to be constant above 80 Km / H).
After that, the routine proceeds to S67, where the timer T, the flag Fa, and the flag Fa are prepared for the next tire air pressure determination processing.
The flag Ft, the counter I, and the counter J are reset to 0, respectively, and the tire air pressure determination processing this time is completed.

Here, the abnormal air pressure wheel detection processing for identifying the wheel whose air pressure has decreased will be described with reference to FIG. The abnormal wheel detection process is a calculation process at every minute time, which is the same as the routine of FIG. 8, and is executed as an interrupt process for the routine of FIG. After start, wheel speed Vw1 ≧ V
It is determined whether or not w4 (S110) and whether or not the wheel speed Vw2 ≧ Vw3 (S113), and the counters K1 to K4 that are determined to be larger are incremented (S1).
11-S115).

Until the time T counted by the timer T in FIG. 8 reaches the predetermined time T0, S110 to S116 are repeatedly executed and the counters K1 to K4 are incremented. Then, when a predetermined time T0 has elapsed after the start of the tire air pressure determination processing, the same determination as in S62 of FIG. 8 is made in S117, and when the determination result is No, S1 is set.
25, the flag FA is reset to 0, and S
When the determination result of 117 is Yes and the tire pressure is abnormal, it is determined in S118 whether the flag Fa is 1 (S118), and when the flag Fa is 1, S119 is executed.
In, it is determined whether or not the count value K2 is greater than or equal to the count value K3. If K2 ≧ K3, it is determined in S120 that the tire pressure of the right front wheel 2b is abnormal, and the flag FA is set to 2. If the determination result of S119 is not K2 ≧ K3, the tire pressure of the left rear wheel 3a is determined to be abnormal in S121, and the flag FA is set to 3.

When the determination result of S118 is No,
That is, when the flag Fa is 2, it is determined in S122 whether the count value K1 is greater than or equal to the count value K4, and K
When 1 ≧ K4, the tire pressure of the left front wheel 2a is determined to be abnormal in S123, and the flag FA is set to 1. If the determination result in S122 is not K1 ≧ K4, it is determined in S124 that the tire pressure of the right rear wheel 3b is abnormal, and the flag FA is set to 4. Incidentally, S1
At 25, the counters K1 to K4 are cleared and this process ends.

As described above, the air pressure reduction flag FA is set to 1 when the air pressure of the left front wheel 2a is decreased, set to 2 when the air pressure of the right front wheel 2b is decreased, and set to 3 when the air pressure of the left rear wheel 3a is decreased. When the air pressure of the right rear wheel 3b decreases, it is set to 4, and when the air pressure of all four wheels is normal, it is set to 0. Using the data of this air pressure decrease flag FA, in S66 of FIG. 8, the tire pressure of the front wheels 2a, 2b is set. The excitation current to the specified value A only when
It may be configured to output an exciting current change command to be increased only to the control device 50.

Next, the operation of the vehicle control device described above will be described. In the tire air pressure determination device, the instrument panel is provided with the initial setting switch 13, and by operating the switch, 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 for the manufacturing error of the four-wheel tire. Since the initial setting process is executed in the vehicle speed range set according to the road surface state of the traveling road surface in the steady straight traveling state,
The coefficient Cx can be initialized with high accuracy by eliminating as much as possible the error factors caused by the slip of the driving wheel on the low μ road, 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 every time a predetermined distance travels or a predetermined period elapses. This tire air pressure determination process is executed in the vehicle speed range set according to the road friction state of the traveling road surface in the steady straight traveling state, so that the slip of the driving wheel on the low μ road is performed as in the case of the initial setting process. It is possible to enhance the accuracy and reliability of tire air pressure determination by eliminating as much as possible an error factor due to fluctuations in wheel load. Then, in this tire air pressure determination process, the timer T, the counter I, and the counter J are used, and the predetermined time T0
The count value I that satisfies D ≧ D0 and the count value J that satisfies D ≦ −D0 are counted, and when these count values I and J are greater than or equal to the predetermined value K0, it is determined that the tire pressure is abnormal, so many The tire pressure can be accurately determined based on the sampling data.

Moreover, when it is determined that the tire pressure has dropped, a command to increase the exciting current of the solenoid 46 by a predetermined value A is output to the control device 50 of the power steering device 20 to strongly change the assist force. Therefore, it is possible to offset the increase in steering resistance due to the decrease in tire air pressure and reduce the burden on the driver. In particular, it detects abnormal wheels whose air pressure has dropped due to abnormal air pressure wheel detection processing,
Only when the tire pressure of the front wheels 2a, 2b drops,
When the assisting force of the power steering device 20 is strengthened, the driver's burden is surely reduced.

Next, a modified example in which a part of the above embodiment is modified will be described. 1] In the above-described embodiment, when it is determined that the tire pressure has decreased, the assisting force of the power steering device 20 is strengthened in order to reduce the steering burden on the driver. In S66 of 8, the exciting current changing command for decreasing the exciting current by the predetermined value A is output to the control device 50. In this case, since the steering becomes abnormally heavy due to the decrease in the assisting force, the driver can be made sure to notice the decrease in the tire air pressure.

2] Instead of the coefficient Cx, it is also possible to apply an initial deviation Δ for compensating a tire manufacturing error, characteristics, etc., which is expressed by the following equation. Δ = 2 [(Vw1 + Vw4) − (Vw2 + Vw3)] / (Vw1 + Vw2 + Vw3 + Vw4) When the initial deviation Δ is applied, the air pressure determination variable D in the tire air pressure determination process is calculated by the following equation. D = 2 [(Vw1 + Vw4)-(Vw2 + Vw3)] / (Vw1 + Vw2 + Vw3 + Vw4) When using the initial deviation Δ and the air pressure determination variable D, the determination of S53 in FIG. 8 is (D−Δ) ≧ Whether or not it is D0 is determined, and the determination in S57 is (D-Δ).
It is determined whether ≦ −D0.

3] Tire pressure determination is performed using the number Nw1 to Nw4 of cumulative output pulses of the wheel speed sensors 27 to 30 in a continuous or intermittent predetermined period as a parameter without using the wheel speed as in the above embodiment. It is also possible to run
Further, it is also possible to execute the tire pressure determination with the time Tw1 to Tw4 per one wheel rotation calculated from the predetermined period and the number of pulses Nw1 to Nw4 as a parameter. Then, in this case, similarly to the above, the initial setting process is executed, and the cumulative wheel speed sensor 27 in the continuous or intermittent predetermined period (the predetermined period is the same or different predetermined period).
It is also possible to determine the number INw1 to INw4 of the output pulses of .about.30 and to perform the tire pressure determination using the pulse number ratios (Nw1 / INw1) to (Nw4 / INw4) as parameters. 4] Instead of the tire air pressure determination device in the above embodiment, a tire air pressure determination device that detects the tire air pressure via an air pressure sensor may be applied.

For reference, in a vehicle equipped with a suspension device such as an active suspension device whose suspension characteristics can be changed, or a suspension device capable of controlling the orifice characteristic inside the suspension damper through an electric actuator. The tire air pressure determination device detects a decrease in tire air pressure, and by the abnormal air pressure wheel detection process, when a wheel whose air pressure has decreased is specified, the suspension characteristics of the wheel whose air pressure has decreased are changed to be hard. Alternatively, it may be configured to be changed softly. When changing the suspension characteristics to be stiff, it is possible to suppress the decrease in riding comfort by supplementing the decrease in tire air pressure with the suspension, and when changing the suspension characteristics to be soft, the burden on the tires with reduced air pressure. Can be reduced and the damage can be suppressed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an automobile tire pressure determination device according to an embodiment.

FIG. 2 is a configuration diagram of a power steering device of the automobile.

3 is a cross-sectional view of a flow control valve of the power steering device of FIG.

4 is a sectional view of a flow control valve of the power steering device of FIG.

5 is a characteristic diagram of a hydraulic pressure supply amount of the power steering device of FIG.

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

FIG. 7 is a flowchart of tire air pressure determination processing of tire air pressure determination control.

FIG. 8 is a flowchart of a tire pressure determination subroutine of FIG.

FIG. 9 is a flowchart of an abnormal pressure wheel detection process of tire pressure determination control.

FIG. 10 is a diagram showing a map of an initially permitted vehicle speed range of a coefficient Cx.

FIG. 11 is a diagram showing a map of a vehicle speed range in which tire pressure determination is permitted.

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

FIG. 13 is a diagram showing the behavior of the air pressure determination variable D when the tire air pressure is abnormal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Car 2a, 2b Front wheels 3a, 3b Rear wheel 8 Control device for tire pressure determination device 9a-9d Wheel speed sensor 10 Steering angle sensor 11 Brake switch 12 Odometer 13 Initial setting switch 14 Warning lamp 20 Power steering device 50 Power steering Equipment control device

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B62D 113: 00 137: 00

Claims (3)

[Claims] 1. A vehicle including a power steering device and a tire air pressure determination device for determining a decrease in tire air pressure of a wheel, wherein the power steering system is provided when the tire air pressure determination device determines that a tire air pressure has decreased. A control device for a vehicle, which is provided with control means for greatly changing the assisting force of the device. 2. The tire pressure determination device comprises abnormal wheel detection means for detecting an abnormal wheel in which the tire air pressure has dropped, and the control means receives data on the abnormal wheel from the abnormal wheel detection means. The vehicle control device according to claim 1, wherein the assist force is changed only when the front wheel is a front wheel. 3. A vehicle including a power steering device and a tire air pressure determination device for determining a decrease in tire air pressure of a wheel, wherein the power steering device is used when the tire air pressure determination device determines that a tire air pressure has decreased. A control device for a vehicle, comprising a control means for changing the assisting force of the device to a small value.