JP3286389B2 - Vehicle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a vehicle, and more particularly to an improved traction control by a traction control device when a decrease in tire pressure is determined by a tire pressure determination device.

[0002]

2. Description of the Related Art Conventionally, in order to prevent the driving wheels from slipping due to excessive driving torque and deteriorating the acceleration during vehicle acceleration, the slip amount of the driving wheels is detected and the slip amount of the driving wheels is set to a target value. The traction control technology configured to control the engine output and the application of the braking force to the wheels so as to obtain a value (reduce the engine output or increase the braking force) is generally put to practical use. And a traction control device (see, for example, JP-A-1-197160).

[0003] On the other hand, various tire pressure judging devices have been conventionally proposed. For example, when 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 with the decreased pressure increases, so that the wheel speeds of the four wheels are respectively adjusted. There has been proposed a device provided with a wheel speed sensor for detecting, and determining a decrease in tire air pressure based on the wheel speed detected by the wheel speed sensor.

[0004] For example, Japanese Patent Application Laid-Open No. 63-305011 discloses that the sum of the wheel speeds of a pair of wheels on a diagonal line and the values of the sum of the wheel speeds on the other diagonal lines are obtained by using outputs from wheel speed sensors of four wheels. When the difference from the sum of the wheel speeds of a certain pair of wheels is equal to or greater than a predetermined value, it is determined that the air pressure of any one of the pair of wheels having the larger total wheel speed has decreased, and When the larger one of the wheel speeds of the wheels is larger 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 conventional traction control (slip control), control is performed on the assumption that the tire air pressure is normal. However, the tire air pressure of any one of the four wheels is controlled. When the tire pressure decreases, the running resistance of the tire with reduced air pressure increases, so if the same traction control is performed as in the case where the tire pressure is normal, the wear of the wheel with reduced air pressure due to the increase in tire load will progress. In addition, there is a problem that the understeer tendency becomes remarkable during turning.

On the other hand, when the air pressure of the tire is reduced moderately, the grip force of the wheel whose air pressure has been reduced is improved. However, when the traction control is performed in the same manner as in the case where the air pressure is normal, the acceleration is reduced. There is a problem that it cannot be increased sufficiently. An object of the present invention is to reduce the load on a tire whose air pressure has decreased in a vehicle equipped with a traction control device and a tire pressure determination device, to suppress an understeer tendency at the time of an air pressure decrease, and to improve acceleration. And so on.

[0007]

According to a first aspect of the present invention, a control device for a vehicle suppresses a slip of a drive wheel with respect to a road surface.
The engine output according to the degree of slip of the drive wheels.
And a traction control device for controlling the traction control device and a tire pressure determination device for determining a decrease in tire pressure of a wheel. Control amount changing means for comparing a control amount corresponding to the degree of control slip with a normal tire pressure and changing the engine output in a direction to suppress the engine output is provided.

Here, the tire air pressure judging device includes abnormal wheel detecting means for detecting a wheel having a decreased tire air pressure, and the control amount changing means includes a tire for driving wheels based on an output from the abnormal wheel detecting means. A configuration in which the control amount is changed only when the air pressure is reduced (Claim 2) , turning detection means for detecting the turning traveling state of the vehicle based on the steering angle of the vehicle, When the vehicle is in a turning traveling state detected by the turning detecting means, an output changing means for changing the engine output to the suppression direction may be provided (claim 3).

According to a fourth aspect of the present invention, there is provided a vehicle control device for controlling a road surface.
The slip of the driving wheel is controlled so as to suppress the slip of the driving wheel.
Control to suppress engine output according to the degree of stop
A traction control device for varying the amount, in a vehicle equipped with a tire air pressure determining apparatus determining a decrease in tire air pressure of a wheel, the tire from the tire air pressure determining apparatus grayed
Control amount changing means for changing a control amount corresponding to a slip degree of traction control in the traction control device in a direction to enhance engine output in response to a determination of a decrease in tire air pressure that increases the lip force is provided. Things. Here, the tire pressure determining device includes an abnormal wheel detecting unit that detects a wheel having a decreased tire pressure, and the control amount changing unit reduces a tire pressure of a driving wheel based on an output from the abnormal wheel detecting unit. have a structure which is adapted to change the control amount only (claim 5) when
Is also good.

[0010]

In the vehicle control device according to the first aspect, when the tire pressure determination device determines that the tire pressure of the wheel has decreased, the control amount changing means controls the slip of the traction control in the traction control device.
When the tire pressure is normal , adjust the control amount according to the degree.
In comparison, the engine output is changed in a direction to suppress. Therefore, it is possible to reduce the load on the tire whose air pressure has been reduced and to suppress the damage to the tire.

Here, when the abnormal wheel detecting means provided in the tire air pressure judging device detects a wheel whose tire air pressure has decreased, the control amount changing means adjusts the tire air pressure of the driving wheel. The control amount is changed only when it has decreased. When the slip amount of the drive wheel is larger than that of the driven wheel and the tire pressure of the drive wheel decreases, the load on the tire increases, but by controlling as described above, the drive wheel whose air pressure has decreased Tire load can be reduced.

According to the third aspect, when the turning detection means detects the turning traveling state, the output changing means changes the engine output in the restraining direction, so that the load on the tire with reduced air pressure is reduced, and the air pressure is reduced. An understeer tendency due to an increase in resistance due to the decrease can be suppressed.

In the vehicle control device according to the fourth aspect, the tire gripping force is increased by the tire air pressure determining device.
When it is determined that the tire pressure of the wheel is
The control amount changing means changes the control amount according to the degree of slip of the traction control in the traction control device in a direction to enhance the engine output. When the tire air pressure decreases (especially when the tire air pressure decreases moderately), the gripping force of the tire increases due to the decrease in the air pressure, so that the acceleration performance can be enhanced by enhancing the engine output.

According to a fifth aspect of the present invention, when the abnormal wheel detecting means provided in the tire air pressure judging device detects a wheel whose tire air pressure has decreased, the control amount changing means changes the tire air pressure of the driving wheel. The control amount is changed only when it has decreased. When the tire pressure of the drive wheel decreases,
Since the slip of the driving wheels is suppressed, the engine output can be increased to enhance the acceleration.

[0015]

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 vehicle including a traction control device that performs traction control (hereinafter, referred to as slip control) for an engine and a tire pressure determination device that determines a decrease in tire pressure. First, the traction control device will be described, and then the tire pressure determination device will be described.

As shown in FIG. 1, a vehicle 1 has left and right front wheels 2.
a and 2b are driving wheels, and left and right rear wheels 3a and 3b are driven wheels. A V-type 6-cylinder engine 4 is mounted on the front part of the vehicle body, and the driving torque from this engine 4 is transmitted to the left front wheel 2a via the left driving shaft 7a via the automatic transmission 5 and the differential device 6 and to the right driving shaft 7b. The transmission is transmitted to each of the right front wheels 2b via the right wheel.

A control device 8 is provided for executing fuel injection control and ignition timing control of the engine 4, slip control of the vehicle (corresponding to engine traction control), and tire pressure determination control described later. The device 8 is provided with an engine control unit for executing fuel injection control and ignition timing control, a slip control unit for executing slip control, and an air pressure judgment control unit for executing tire air pressure judgment control.

The sensors include an engine speed sensor for detecting the number of revolutions of the engine 4, a steering angle sensor 10 for detecting the steering angle of the steering wheel, a brake switch 11 for detecting the braking state of the four wheels 2a to 3b, and a four wheel 2a. ~ 3b wheel speed Vw
Wheel speed sensors 9a to 9 for detecting 1, Vw2, Vw3, Vw4
d, an initial setting switch 13 for starting an initial setting process in the tire air pressure determination control, a warning lamp 14 for outputting an alarm when the tire air pressure decreases, a detection signal from these sensors and an odometer. Signals from 12 are supplied to the control device 8.

The controller 8 includes an input interface for receiving detection signals from the sensors, three microcomputers including a CPU, a ROM, and a RAM, an output interface, and a drive for an igniter and a fuel injector. It is composed of circuits and the like. These three microcomputers are for engine control,
One for traction control and one for tire air pressure determination control. In the ROM of the microcomputer of the engine control unit, a control program for fuel injection control and ignition timing control and tables and maps associated therewith are stored in advance, and in the ROM of the microcomputer of the slip control unit, A control program for the slip control and various tables and maps for the slip control are stored in advance, and the RAM is provided with various memories and soft counters.

The outline of the slip control executed by the slip control section of the control device 8 will be described first.
Using the detection signals from the sensors, the actual turning radius Rr, the turning radius corresponding to the steering angle Ri, the vehicle speed V (vehicle speed), the road surface friction coefficient μ
And a lateral acceleration G, and a correction coefficient k for correcting the slip determination threshold value and the control target value T so as to decrease as the lateral acceleration G increases is determined based on the lateral acceleration G. Thereafter, calculation of slip amount, slip determination, control target value T
, And calculation of a control level FC for adjusting the engine output, and the like, and outputs a control signal of slip control for fuel control and ignition timing control.

Hereinafter, slip control (engine traction control) executed in the slip control section will be described with reference to FIGS. However, in the flow chart, the symbol Si (i = 1, 2, 3,...) Indicates each step. When the engine 4 is started, the slip control is started, and various detection signals such as a detected steering angle θ are read from the sensors (S1). Next, in S2, the actual turning radius Rr, the turning angle corresponding turning radius Ri, and the vehicle speed V are detected. , Is calculated. The actual turning radius Rr is calculated by the following equation (1) based on the wheel speeds Vw3, Vw4 of the driven wheels 3a, 3b detected by the wheel speed sensors 9c, 9d.
Here, Td is the tread (for example, 1.7 m) of the vehicle.

Rr = Min (Vw3, Vw4) × Td ÷ | Vw3−Vw4 | + 0.5Td (1) The turning radius corresponding to the steering angle Ri substantially corresponds to the turning radius in the neutral steering, and this is the current detection. Based on the absolute value of the steering angle θ, it is obtained by linear interpolation from the table shown in Table 1 below.

[0023]

[Table 1]

The vehicle speed V is determined by the wheel speed sensors 9c and 9c.
The wheel speeds Vw3, Vw4 of the driven wheels 3a, 3b detected from d.
Of the road surface friction coefficient μ
Is calculated based on the vehicle speed V and its acceleration Vg. A 100 msec count timer and a 500 msec count timer are used in the calculation of the road surface friction coefficient μ, and the change in the vehicle speed V between 100 msec every 100 msec from the start of the slip control until 500 msec when the vehicle acceleration Vg does not become sufficiently large. From the following equation (2), the vehicle body acceleration Vg is obtained by the following equation (2). After 500 msec elapses when the vehicle body acceleration Vg becomes sufficiently large, the vehicle body acceleration Vg is calculated by the following equation (3) from the change in the vehicle speed V for 500 msec every 100 msec. Ask. Note that V (k) is currently
V (k-100) is 100 msec before, V (k-50)
0) is the vehicle speed 500 msec before, and K1 and K2 are predetermined constants, respectively.

Vg = K1 × [V (k) −V (k−100)] (2) Vg = K2 × [V (k) −V (k−500)] (3) The road surface friction coefficient μ is: The vehicle speed V obtained as described above,
The calculation is performed by three-dimensional interpolation from the μ table shown in Table 2 using the vehicle body acceleration Vg.

[0026]

[Table 2]

Next, in S3, a lateral acceleration G and a correction coefficient k corresponding to the lateral acceleration G are calculated. The lateral acceleration G is determined by the turning radius and the vehicle speed V. To determine the lateral acceleration G, the actual turning radius Rr and the turning radius corresponding to the steering angle Ri are selectively used. Based on the road surface condition and the driving condition, the magnitude of the tendency to deviate from the travel line at the steering angle-corresponding turning radius Ri when the vehicle turns is determined, and when the tendency is large, the steering angle-corresponding turning radius Ri is selected. When the tendency is not large, the actual turning radius Rr is selected.

That is, when the absolute value of the current detected steering angle θ is equal to or more than the predetermined value θo, the vehicle speed V is equal to or more than the predetermined value Vo, and the road surface friction coefficient μ is equal to or less than the predetermined value μo (when the tendency of understeer is strong). In ()), the lateral acceleration G is calculated from the turning radius corresponding to the steering angle Ri. When the absolute value of the current detected steering angle θ is less than the predetermined value θo, or the vehicle speed V is less than the predetermined value Vo, or the road surface friction coefficient μ is larger than the predetermined value μo,
The lateral acceleration G is calculated from the actual turning radius Rr. The lateral acceleration G is determined by the vehicle speed V and the turning radius R (the turning radius R corresponding to the steering angle).
i or the actual turning radius Rr) is calculated by the following equation. G = V × V × (1 / R) × (1/127) (4) Next, based on the lateral acceleration G obtained as described above, the correction coefficient k is calculated from the correction coefficient table of Table 3. .

[0029]

[Table 3]

Next, in step S4 in the flowchart of FIG. 2, a threshold value for slip determination is set. The threshold value for slip determination is set to a basic threshold value × a correction coefficient k. The threshold value is obtained by using the vehicle speed V and the road surface friction coefficient μ as parameters,
(For slip control start) or three-dimensional interpolation from the basic threshold value table 2 of Table 5 (for slip control continuation). It should be noted that the control target basic threshold value table 1 in Table 4 is for determining whether to start the slip control, and the control target basic threshold value table 2 in Table 5 is for determining whether to continue the slip control. Things.

[0031]

[Table 4]

[Table 5]

Next, in S5, calculation of the average slip amount and the maximum slip amount is executed. The apparent slip amounts SL and SR of the front wheels 2a and 2b, which are the left and right driving wheels, are obtained by subtracting the vehicle speed V from the wheel speeds Vw1 and Vw2 of the left and right front wheels 2a and 2b. = (V
w2−V), and then the average slip amount SAv
Is the average value of the slip amount of the left and right drive wheels (SL + SR)
/ 2, and then calculates the maximum slip amount SHi from the maximum value of the slip amounts SL and SR of the left and right drive wheels.
Is calculated.

Next, in S6 of FIG. 2, slip determination is performed. In the slip determination, the following (6) is performed based on the maximum slip amount SHi and the threshold value for slip determination.
When the equation is satisfied, it is determined that the slip control is necessary, and the slip flag SFL is set to 1.

SHi ≧ Slip Determination Threshold (6) As the slip determination threshold, the non-control state (CFL = 0) is determined in step S134 of the flowchart of FIG. 3 showing the subroutine of S9. When the slip control is being performed (CFL = 1), the control target basic threshold value for continuation shown in Table 5 is used. .

[0035]

[Table 6]

[Table 7]

Next, in S7, it is determined whether or not the flag CFL = 1, and if CFL = 0 (the slip control is not being executed), the routine immediately returns. On the other hand, in S7, CFL
= 1 (during the execution of the slip control), S8
Then, the control target value T is set. The control target value T is a target value as the slip amount of the front wheels 2a and 2b. The control target basic value obtained by three-dimensional interpolation from the control target basic value table of Table 6 using the vehicle speed V and the road friction coefficient μ as parameters. It is calculated from the value and the correction coefficient k by the following equation. Control target value T = Control target basic value × k (7)

Next, a control level FC is calculated in S9. Regarding this control level FC, the deviation EN of the average slip amount SAv from the control target value T and the rate of change D thereof
The basic control level FCB is determined based on EN, and the basic control level FCB is set in the range of 0 to 15 in consideration of the feedback correction and the first correction of the previous value FC (k-1). The first correction is
It is (+5) until the change rate DSAv of the average slip amount SAv becomes 0 for the first time.
Is (+2) until is becomes zero. The routine of S9 will be described with reference to the flowchart of FIG. First, in S131, the deviation EN and the deviation change rate DEN are determined.
Are calculated by the following equations (8) and (9), respectively. Deviation EN = SAv (k) −Control target value T (8) Deviation change rate DEN = DSAv = SAv (k) −SAv (k−1) (9)

Next, in S132, the basic control level FCB is calculated from the basic control level table of Table 7 based on the deviation EN and the deviation change rate DEN. Next, S13
At 3, the feedback correction for adding the previous control level FC (k-1) to the current control level FC (k) is performed, then the slip control determination is performed at S134, and then the first slip control determination is performed at S135. Then, in S136, an initial correction amount for forcibly increasing the control level from when the slip of the front wheels 2a, 2b is first determined until the first slip determination is eliminated is calculated.

The routine for determining the slip control in step S134 will be described with reference to the flowchart of FIG. 4. First, in step S140, it is determined whether the slip flag SFL = 1 and the vehicle is not in the brake state, and the conditions are satisfied. At this time, the control flag CFL indicating that the slip control is being performed is set in S141, and the flow shifts to S135. On the other hand, when No is determined in S140, S1
At 42, a first counter provided in the slip control unit for counting the duration of the signal of the slip flag SFL = 0.
When the count value t1 of the counter and FC ≦ 3 and DSAv
When the count value t2 of the second counter that counts the duration in which the condition of ≦ 0.3 g is satisfied is read, and the count value t1 is 1000 msec or more (S
143: Yes) or the count value t2 is 500 ms
If not less than c (S145: Yes), the control flag CF
L is reset, and the routine goes to S135.

The routine of the initial slip control determination in S135 will be described with reference to the flowchart of FIG. 5. First, in S150, the current control flag CFL is determined.
(K) = 1 and the previous control flag CFL (k-1) =
It is determined whether it is 0 or not. When these conditions are satisfied, the initial flag STFL is set in S151, and the flow shifts to S136. On the other hand, when No is determined in S150, in S152, the current slip flag SFL (k) = 0 and the previous slip flag SF
It is determined whether or not L (k-1) = 1, and when these conditions are satisfied, the initial flag STFL is set in S153.
Is reset, and the routine goes to S136. Incidentally, in S152
When the determination is No, the process proceeds to S136.

In S136, the first flag STF
L signal and average slip amount change rate DSA shown in equation (9)
Based on v, when STFL = 1 and DSAv <0, the initial correction amount (+2) is determined. Next, in S137 , the current final control level FC (k) is changed to the next (10)
As shown in the equation, the level is set to 0 to 15. FC (k) = FC (k−1) + δ (10) where the previous control level FC (k−1) is actually S
133, but the current control level F
C (k) is described for clarity. The δ is
If there is an initial correction to the basic control level FCB obtained in S132, this corresponds to a value obtained by adding the initial correction.

As described above, when the lateral acceleration G is large, the correction coefficient k is small, and the threshold value (for starting, for continuing)
And the control target value (T) is set small, and the control level of the slip control is set high. When the road surface μ is large, the threshold value is set high, but the control level of the slip control is set high. Also, when the wheel speed difference ΔV is large, the maximum slip amount SHi becomes large, so that the control level of the slip control is set high.

Next, in S10 of the flowchart of FIG. 2, a slip control signal is output from the slip control unit to the engine control unit. The control signal includes a control signal for retarding the ignition timing and a control signal for instructing a fuel cut. Regarding the ignition timing, see FIG.
And determines and outputs the retard amount according to the control level FC. In this case, the maximum retard amount is limited in the region where the engine speed is high based on the map shown in FIG. Regarding the fuel cut, based on the control level FC, the pattern 0 in the fuel cut table in Table 8 is used.
~ 12, but the control level FC
Is higher, the pattern number is larger. In addition, × in Table 8
The mark indicates the fuel cut, and as shown in FIG. 8, the fuel cut is limited in a region where the engine speed is low.
Fuel cut prohibition conditions are set for each control level.

[0044]

[Table 8]

Next, the operation of the slip control will be described. As shown in the time chart of FIG. 9, the threshold value for starting the slip control is set to a relatively high threshold value Sh based on the basic threshold value table for starting, and the wheel speed of the driving wheel is reduced due to disturbance or the like. Even if it becomes high, the slip control is not started unless the threshold value Sh is exceeded. When the wheel speed of the drive wheel exceeds the threshold value Sh, the slip flag SFL
Is set, and if the brake is not in operation, the control flag CFL and the initial flag STFL are set and the slip control is started.

In the turning operation of the vehicle, when it is determined that the understeer tendency is strong, the lateral acceleration G becomes larger and the correction coefficient k becomes smaller due to the steering angle-corresponding turning radius Ri smaller than the actual turning radius Rr. Threshold S
h becomes lower. As a result, the slip control is started early, and the excessive understeer tendency can be suppressed. On the other hand, when the understeer tendency is not large, the lateral acceleration G is calculated based on the actual turning radius Rr, and the threshold value for slip determination and the control target value T are accurately set to match the actual lateral acceleration.

The reason why the initial flag STFL becomes 0 is as follows.
This is the point in time when the maximum slip amount Shi becomes equal to or less than the threshold value Sc for continuation determination of the slip control, and at this point the slip control is temporarily stopped. The continuation threshold value Sc is set to a relatively low value by calculating its basic value from the continuation basic value table, and the slip reliably converges.

The wheel speed of the higher driving wheel is equal to the continuation threshold value S.
c, the control flag CFL is maintained in the set state if the state does not continue for one second or longer, and the wheel speed of the drive wheel increases again with the suspension of the slip control, and the continuation threshold Sc Exceeds the slip flag SFL
Is set, and the slip control is restarted. In this case, the initial flag STFL is not set, and the control level F
No initial correction of C is made. Therefore, the control level FC
Is initially set only at the basic control level based on the deviation EN and the deviation change rate DEN, and thereafter, the value obtained by adding the previous value to the basic control level by feedback correction is set as the control level FC. As described above, if the slip converges and the state in which the slip flag SFL is not set for one second or more continues, the control flag CFL is reset, and one cycle of slip control ends.

Next, a tire pressure judging device will be described. As shown in FIG. 1, the tire pressure judging device includes, as shown in FIG. 1, the four wheel speed sensors 9a to 9d and an initial setting switch 13 (which is provided on an instrument panel) for starting an initial setting process for tire pressure judgment. ), A warning lamp 14 attached to the instrument panel, an air pressure judgment control unit of the control device 8, and the like. The air pressure judgment control unit of the control device 8 includes wheel speed sensors 9a to 9d, a steering angle. Signals from sensors and switches such as a sensor 10, a brake switch 11, an odometer 12, and an initial setting switch 13 are supplied, and the warning lamp 14 is driven and controlled by an air pressure determination control unit.

The wheel speed sensors 9a to 9d are formed on a brake disk or a detection disk (not shown) provided adjacent to the brake disk.
In this configuration, four detection units are detected by an electromagnetic pickup. In the ROM of the microcomputer of the air pressure determination control unit of the control device 8, a control program and a map for the tire pressure determination control are previously input and stored.
Is provided with various memories (buffers, memories, flags, counters, soft timers, etc.) necessary for the control.

Hereinafter, the tire pressure judgment control executed by the air pressure judgment control unit will be described with reference to FIG. 10 and subsequent drawings. However, in the flow chart, the symbol Si
(I = 1, 2, 3,...) Indicates each step. First, the outline of the tire pressure determination control will be described. Basically, the tire pressure determination is performed based on the wheel speeds Vw1 to Vw4 detected by the four wheel speed sensors 9a to 9d. At the time, when one or a plurality of tires are replaced, etc., an initial setting of a coefficient Cx (corresponding to a compensation coefficient) for compensating a tire manufacturing error and characteristics is executed.

Thereafter, at regular intervals (every predetermined traveling distance, or
The tire pressure determination process is executed at predetermined intervals) to determine whether any one of the tires has an abnormal pressure. If the tire pressure is low, an alarm is output via a warning lamp 14 and slip control is performed. A control level change command is output to the
Change C.

The initial setting process is executed when the vehicle speed range is set according to the road surface friction state, and the tire pressure determination process is executed when the vehicle speed region is set separately according to the road surface friction state. Is done. The tire pressure determination control includes the initial setting process and the tire pressure determination process, and information on the road surface friction coefficient μ is supplied from the slip control unit to the air pressure determination control unit.

Next, the initial setting process of the coefficient Cx will be described with reference to the flowchart of FIG. This initial setting process of the coefficient Cx is started when the a-contact type initial setting switch 13 attached to the instrument panel is turned ON when the tire is replaced or the like, and then the sensors 9a to 9d, 10, and 12 are set. And various data obtained by digitizing signals from the switches 11 and 13 are read (S20). Next, in order to indicate that the initial setting process is being executed,
The warning lamp 14 is turned on, and the flag F is reset to 0 to prohibit the tire pressure determination process (S21).

Next, it is determined whether or not the condition for initial setting of the coefficient Cx is satisfied (S22). It is determined that the vehicle is not in the acceleration / deceleration state, the vehicle is in the steady straight running state, and the vehicle speed V is lower than that in FIG.
If the condition that the coefficient Cx set according to the road surface friction state shown in the map of FIG. 4 is within the initial setting permission vehicle speed range is satisfied, it is determined that the condition is satisfied, and the process proceeds to S23.
If the condition is not satisfied, the flow shifts to S29. The vehicle speed V in the tire air pressure determination control is set to be 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 a change in the vehicle speed V.

Here, the lower limit of the initial setting permitted vehicle speed range of the coefficient Cx shown in FIG. 14 is set to a predetermined value (for example, 20 km / H) which is not excessively low, and the upper limit of the initial setting permitted vehicle speed range. The value ranges from 40 to 5 depending on the road surface friction state of the running road surface.
It is set to a value in the range of 0 km / H. Regarding the upper limit value, from 40 km / H in the low μ state to 5 km in the high μ state.
It is set to increase linearly to 0 km / H. 50
In a high-speed state exceeding Km / H, the slip amount of the drive wheels increases, and the wheel loads of the front wheels 2a, 2b and the rear wheels 3a, 3b change, so that the detection accuracy of the wheel speeds Vw1 to Vw4 decreases. Therefore, it is desirable to execute the initial setting process when the vehicle speed is 50 km / H or less, and when the vehicle speed is 40 km / H or less, the slip amount of the drive wheels increases when the vehicle speed is low μ. It is desirable to perform the processing.

Next, when it is determined in S22 that the condition is satisfied, in S23, a coefficient Cx for compensating the initial state of the four tires at the time of tire replacement or the like is taken into consideration in consideration of tire manufacturing errors and characteristics. Using the wheel speeds Vw1 to Vw4, the sum (Vw1 + Vw4) of the wheel speeds of the left front wheel 2a and the right rear wheel 3b in one diagonal relationship, and the wheels of the right front wheel 2b and the left rear wheel 3a in the other diagonal relationship. It is calculated by the following equation as a ratio to the sum of the speeds (Vw2 + Vw3). Coefficient Cx = (Vw1 + Vw4) / (Vw2 + Vw3) Next, it is determined whether or not the coefficient Cx is an appropriate value. Since the error of the tire diameter due to a tire manufacturing error is 0.3% at the maximum, the coefficient Cx is substantially equal to 1. A predetermined range (for example, 0.95 to 1.0
If 5), the coefficient Cx is determined to be an appropriate value.

If the coefficient Cx is an appropriate value, the process goes to S25.
The rewriting process of the coefficient Cx is executed, the current coefficient Cx (i-1) is given to the previous coefficient Cx (i-1), and then the warning lamp 14 is turned off and a flag is set to permit the tire pressure determination processing. F is set to 1 and then S2
Move to 9. On the other hand, when the determination result of S24 is No,
In S27, it is determined whether or not the coefficient Cx is indeterminate. If uncertain, the process proceeds to S29. If not, the warning lamp 14 flashes in S28 for a predetermined time (for example, 2 seconds), and then proceeds to S29. In S29, it is determined whether the flag F is 1 or not. When the determination is No, the process returns and the process is repeated. When the determination is Yes, the process ends.

However, based on one ON operation of the switch 13, a plurality of initial setting processes are executed to obtain a plurality of coefficients Cx
, And the final coefficient Cx may be determined from the average value of the plurality of coefficients Cx. Thus, the coefficient Cx for compensating the initial state of the four tires at the time of tire replacement or the like is determined and stored in the memory of the RAM.

Next, the tire pressure determination processing will be described with reference to the flowcharts of FIGS.
The tire pressure determination process is, for example, a process executed for each traveling distance of 100 km, and after the start of the process,
Various data obtained by digitizing signals from the sensors 9a to 9d, 10, 12 and the switch 11 are read (S
40) Then, it is determined whether or not the flag F is 1 (S4).
1) If Yes, it is determined in S42 whether or not the tire pressure determination condition is satisfied. Regarding the tire pressure determination conditions, the vehicle is not in the acceleration / deceleration state, is in the steady straight running 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. Is satisfied, it is determined that the condition is satisfied, and the process proceeds to S43. If the condition is not satisfied, the process proceeds to S44.

Here, the lower limit value of the tire pressure determination permitted vehicle speed range shown in FIG. 15 is set to a predetermined value that is not excessively low (for example, 20 km / H), and the upper limit value of the tire pressure determination permitted vehicle speed range. Is 4 depending on the road surface friction state of the running road surface.
It is set to a value in the range from 0 km / H to the maximum vehicle speed.

Regarding the upper limit value, 4 in the low μ state
It is set so as to linearly increase from 0 km / H to the maximum vehicle speed in the high μ state. In a high-speed state of more than 50 km / H, the slip amount of the drive wheel increases and the wheel speeds Vw1 to Vw1
Although the detection accuracy of w4 is reduced, it is desirable to detect a decrease in tire air pressure in a high-speed running state of more than 50 km / H even if the accuracy is slightly reduced. When the vehicle speed is low μ, the slip amount of the drive wheels increases. Therefore, it is desirable to execute the tire pressure determination process at a vehicle speed of 40 km / H or less.

In S43, the tire pressure determination subroutine of FIG. 12 is executed, and thereafter, the routine returns to S4.
If the determination result of 1 or S42 is No, in S44, the timer T in the tire pressure determination subroutine is reset, and the flags Fa, Ft and the counters I, J are set to 0.
And then return. Next, the tire pressure determination subroutine of S43 will be described with reference to FIG. First, it is determined whether or not the flag Ft is 1 (S50).
Is started and the flag Ft is set to 1 and S5
Move to 2. When the flag Ft is set to 1, the process proceeds from S50 to S52. Next, S5
In FIG. 2, the air pressure determination variable D is determined by the equation shown in the drawing, that is,
It is calculated by 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. 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 increases. When the tire pressure of the left front wheel 2a or the right rear wheel 3b decreases, the wheel pressure Vw1 or the wheel speed Vw4 increases, and the air pressure determination variable D becomes negative. Increase in the direction.

Next, in S53, it is determined whether or not the determination variable D is equal to or more than a predetermined value D0 (for example, a predetermined value in the range of 0.020 to 0.050). If the determination 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 for counting the number of times the determination variable D is equal to or more than the predetermined value D0 is set to 1 and the flag Fa is set to 1 (S55). Thereafter, the flow shifts to S61.
When the flag Fa is set to 1, S
The process proceeds from S to S56, where the counter I is incremented, and then proceeds to S61.

On the other hand, if the decision result in S53 is No, S
57, it is determined whether or not the determination variable D is equal to or less than a 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 set to a predetermined value. Counter J for counting the number of times equal to or less than -D0
Is set to 1 and the flag Fa is set to 2 (S
59) Thereafter, the flow shifts to S61. When the flag Fa is set to 2, the process proceeds from S58 to S60, where the counter J is incremented.
Move 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). Initially, the determination result is No. From returning to
S40 to S42 and S50 to S61 in FIG. 11 are repeatedly executed, and the count value T of the timer T and the count value I of the counter I or the count value J of the counter J increase. FIG. 16 shows the behavior of the air pressure judgment variable D when the tire pressure is normal, and FIG. 17 shows the air pressure judgment variable D when the tire pressure of the right front wheel 2b or the left rear wheel 3a is abnormal.
Is illustrated.

When the predetermined time T0 has elapsed, S61
Is determined to be Yes, the flow shifts to S62, and the count value I of the counter I is equal to or larger than the predetermined value K0 or the counter J
Is determined whether or not the count value J is equal to or greater than a predetermined value K0. If the determination result is No, the tire pressure is determined to be normal in S63, and the process proceeds to S67.
If the determination result at 62 is Yes, it is determined that the tire pressure is abnormal (reduced) in S64, and in S65, the warning lamp 14 is turned on for a predetermined time (for example, 2 seconds) to alert the driver of the reduced tire pressure. .

In step S66, the control level FC is set to a predetermined value A (for example, +2 to +4) for the slip control unit.
A change command to suppress the engine output by increasing the output is output, and δ in the equation (10) in the slip control unit is set to (δ + A). Then, the process proceeds to S67,
In S67, a timer T, a flag Fa, a flag Ft, a counter I,
The counters J are reset to 0, respectively, and the current tire pressure determination processing ends.

Here, the abnormal air pressure wheel detection processing for specifying the wheel whose air pressure has decreased will be described with reference to FIG. This abnormal wheel detection process is a calculation process for each minute time, which is the same as the routine of FIG. 12, and is executed by an interrupt process to the routine of FIG. After the start, the wheel speed Vw1
Determination of whether or not ≧ Vw4 (S110), and wheel speed Vw2 ≧ Vw3
The determination (S113) is performed, and the counters K1 to K4 determined to be larger are incremented (S111 to S115).

Until the counted time T of the timer T in FIG. 12 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 process, in S117, S62 in FIG.
Is determined in the same way as above, and if the determination result is No,
In S125, the flag FA is reset to 0, and when the result of determination in S117 is Yes and the tire pressure is abnormal, it is determined in S118 whether or not the flag Fa is 1 (S118). Sometimes, S
At 119, it is determined whether or not the count value K2 is equal to or greater than the count value K3. If K2 ≧ K3, the tire pressure of the right front wheel 2b is determined to be abnormal at S120, and the flag FA is set to 2. As a result of the determination in S119, K2 ≧
If it is not K3, it is determined in S121 that the tire air pressure of the left rear wheel 3a is abnormal, and the flag FA is set to 3.

When the result of the determination in S118 is No,
That is, when the flag Fa is 2, it is determined in S122 whether or not the count value K1 is equal to or greater than the count value K4.
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 K1 ≧ K4 is not satisfied as a result of the determination in S122, the tire pressure of the right rear wheel 3b is determined to be abnormal in S124, and the flag FA is set to 4. S1
At 25, the arithmetic processing ends after the counters K1 to K4 are cleared.

As described above, the air pressure reduction flag FA is set to 1 when the air pressure of the left front wheel 2a is reduced, set to 2 when the air pressure of the right front wheel 2b is reduced, and set to 3 when the air pressure of the left rear wheel 3a is reduced. 12 is set when the air pressure of the right rear wheel 3b is low, and is set to 0 when the air pressure is normal for all four wheels. Using the data of the air pressure reduction flag FA, the driving wheels 2a, 2b are determined in S66 of FIG.
The command to increase the control level FC of the slip control by the predetermined value A may be output to the slip control unit only when the tire air pressure of the tire falls.

Next, the operation of the tire pressure judging device described above will be described. An initial setting switch 13 is provided on the instrument panel, and by operating the switch, an initial setting process for initial setting the coefficient Cx is performed when necessary such as when replacing a tire. An error-compensated coefficient Cx can be set. Since the initial setting process is executed in a vehicle speed range that is set according to the road surface friction state of the running road surface in the steady straight running state, the initial setting process is caused by a slip of the drive wheels on a low μ road, a change in wheel load, and the like. The coefficient Cx can be initialized with high accuracy by eliminating the error factors that occur as much as possible.

After the initial setting process, the tire pressure determination process is performed using the coefficient Cx every time the vehicle travels a predetermined distance or every time a predetermined period elapses. Since this tire air pressure determination process is performed in a vehicle speed range that is set according to the road surface condition of the traveling road surface in a steady straight running state, similarly to the case of the initial setting process, the slip of the drive wheel on a low μ road, An error factor due to a variation in wheel load or the like can be eliminated as much as possible, and the accuracy and reliability of the tire pressure determination can be improved. In this tire pressure determination process, a count value I satisfying D ≧ D0 and a count value J satisfying D ≦ −D0 at a predetermined time T0 are counted using a timer T, a counter I, and a counter J. Count value I,
When J is equal to or more than the predetermined value K0, it is determined that the tire pressure is abnormal, so that the tire pressure can be accurately determined based on a large amount of sampling data.

Further, when it is determined that the tire air pressure has decreased, the control level FC is given to the slip control unit by a predetermined value A.
Since the command to increase the output is output only and the engine output is changed in the decreasing direction, the load on the tire with reduced air pressure can be reduced. If the abnormal wheel detection processing detects an abnormal wheel whose air pressure has decreased and changes the engine output in the decreasing direction only when the tire pressure of the driving wheel decreases, the air pressure of the driving wheel with a large tire load decreases. The load on the tire can be reduced, and the damage to the tire can be reliably suppressed.

Next, a description will be given of a modification in which a part of the above embodiment is changed. 1) In the turning traveling state, in consideration of the fact that the load on the tire is significantly increased, in the tire pressure judging processing, a decrease in the tire air pressure is determined in the steady straight traveling state. In response, a control level change command for further suppressing the engine output is output. In this case, the steering angle sensor 1
It is determined whether or not the vehicle is turning based on the detection signal from 0. If the vehicle is turning, the slip control unit increases and corrects the control level FC by a predetermined value B (for example, +2 to +4). It is configured to output a change command. in this case,
When the vehicle is turning, δ in the above equation (10) is changed to (δ + A + B). in this way,
By further suppressing the engine output during turning after the determination of a decrease in tire air pressure, the load on the tire with reduced air pressure can be further reduced and its wear can be suppressed.

2) In the above-described embodiment, the control level FC of the slip control is configured to be increased when the decrease in the tire air pressure is determined. On the contrary, when the decrease in the tire air pressure is determined. Alternatively, the control level FC of the slip control may be reduced and corrected to enhance the engine output. In this case, in S66 of FIG. 12, a command to reduce the control level FC by a predetermined value -A (for example, A is 2 to 4) is output to the slip control unit. As a result, in the slip control unit, δ in the equation (10) is changed to (δ−A). That is, when the tire air pressure is reduced appropriately, the grip force of the tire increases, so that the engine output can be enhanced and the acceleration can be improved.

3) As described in the above [2], when it is determined that the tire air pressure has decreased, when the control level FC is changed in a direction to enhance the engine output, only when the tire air pressure of the driving wheel decreases, The control level FC may be changed. In this case, only when the abnormal wheel detected by the abnormal wheel detection processing is a driving wheel, the control level FC is set to the predetermined value -A
(For example, A is reduced by 2 to 4).

As a modification of the above-described embodiment, an initial deviation Δ for compensating a tire manufacturing error or the like, which is represented by the following equation, is applied instead of the coefficient Cx. Is also possible. 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 pressure determination process is calculated by the following equation. D = 2 [(Vw1 + Vw4)-(Vw2 + Vw3)] / (Vw1 + Vw2 + Vw3 + Vw4) When the above-mentioned initial deviation Δ and the air pressure determination variable D are used, the determination of S53 in FIG. 12 is (D−Δ) ≧ D0 or not, and the determination in S57 is (D−
Δ) ≦ −D0.

Here, instead of using the wheel speed as in the above-described embodiment, the tire number is set using the number Nw1 to Nw4 of the cumulative output pulses of the wheel speed sensors 27 to 30 in the continuous or intermittent predetermined period as a parameter. It is also possible to execute the air pressure judgment, and it is also possible to execute the tire pressure judgment using the time Tw1 to Tw4 per wheel rotation calculated from the predetermined period and the pulse numbers Nw1 to Nw4 as parameters. . Then, in this case, similarly to the above, the initial setting process is executed, and the cumulative output of the wheel speed sensors 27 to 30 in a continuous or intermittent predetermined period (the predetermined period is the same or different from the predetermined period). Find the number of pulses INw1 to INw4,
Tire pressure determination can also be performed using the pulse number ratios (Nw1 / INw1) to (Nw4 / INw4) as parameters. It should be noted that the tire air pressure determination control may be configured to be constantly executed while the vehicle is running. Also,
As a matter of course, a tire pressure determination device of a type that detects a tire pressure by a pneumatic sensor can be applied as the tire pressure determination device.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a vehicle slip control device and a tire air pressure determination device according to an embodiment.

FIG. 2 is a flowchart of a slip control routine.

FIG. 3 is a flowchart of step S9 in FIG. 2;

FIG. 4 is a flowchart of a slip control determination in S134 of FIG. 3;

FIG. 5 is a flowchart of a first slip control determination in S135 of FIG. 3;

FIG. 6 is a diagram of a map of an ignition retard amount with respect to a control level.

FIG. 7 is a diagram of a map of an ignition retard amount with respect to an engine speed;

FIG. 8 is an explanatory diagram of a fuel cut prohibition region with respect to a control level and an engine speed.

FIG. 9 is an overall operation time chart of the slip control.

FIG. 10 is a flowchart of an initial setting process of a coefficient Cx of the tire air pressure determination control.

FIG. 11 is a flowchart of a tire pressure determination process of the tire pressure determination control.

FIG. 12 is a flowchart of a tire air pressure determination subroutine of FIG. 11;

FIG. 13 is a flowchart of abnormal wheel detection processing in tire air pressure determination control.

FIG. 14 is a diagram showing a map of a vehicle speed range in which an initial setting of a coefficient Cx is permitted.

FIG. 15 is a diagram showing a map of a vehicle speed range in which tire pressure determination is permitted.

FIG. 16 is a graph showing the behavior of a tire pressure determination variable D when the tire pressure is normal.

FIG. 17 is a diagram showing a behavior of an air pressure determination variable D when a tire air pressure is abnormal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vehicle 2a, 2b Front wheel 3a, 3b Rear wheel 4 Engine 8 Control device 9a-9d Wheel speed sensor 10 Steering angle sensor 11 Brake switch 12 Odometer 13 Initial setting switch 14 Warning lamp

Continuation of the front page (56) References JP-A-6-8785 (JP, A) JP-A-63-305011 (JP, A) JP-A-1-197160 (JP, A) JP-A-6-249035 (JP) , A) Real opening 63-83442 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 29/02 311 B60C 23/06-23/08

Claims (5)

(57) [Claims] 1. Suppression of slip of a drive wheel with respect to a road surface
The engine according to the degree of slip of the drive wheels
In a vehicle provided with a traction control device that controls output and a tire pressure determination device that determines a decrease in tire pressure of a wheel, receiving a determination of a decrease in tire pressure from the tire pressure determination device, a control amount corresponding to the slip degree of the traction control, tire
A control device for a vehicle, comprising: a control amount changing unit that changes a direction in which an engine output is suppressed as compared with a case where an air pressure is normal . 2. The tire pressure judging device includes abnormal wheel detecting means for detecting a wheel having a decreased tire pressure, and the control amount changing means includes a tire pressure of a driving wheel based on an output from the abnormal wheel detecting means. The vehicle control device according to claim 1, wherein the control amount is changed only when the control value decreases. A turning detection means for detecting a turning state of the vehicle 3. Based on the steering angle of the vehicles, when the turning traveling state which is detected by this pivot detecting means changes the engine output to suppress direction The control device for a vehicle according to claim 1, further comprising an output changing unit. 4. Suppression of slip of a driving wheel with respect to a road surface.
The engine according to the degree of slip of the drive wheels
In a vehicle including a traction control device that changes a control amount for suppressing an output and a tire pressure determination device that determines a decrease in a tire pressure of a wheel, the tire gripping force increases from the tire pressure determination device.
In response to determination of the decrease in the degree of the tire air pressure large to, traction control in the traction control device Seri
A control device for a vehicle, comprising: a control amount changing unit that changes a control amount according to a stop degree in a direction to enhance engine output. 5. The tire pressure judging device includes abnormal wheel detecting means for detecting a wheel having a decreased tire pressure, and the control amount changing means includes a tire pressure of a driving wheel based on an output from the abnormal wheel detecting means. The control device for a vehicle according to claim 4, wherein the control amount is changed only when the control value decreases.