JPH03264846A - Method for measuring road friction coefficient - Google Patents

Abstract

PURPOSE:To judge the friction efficient of a road simply during the running of a vehicle by obtaining a stability factor based on the detected steering angle, lateral acceleration and vehicle speed, and comparing the obtained value with a specified value which is lower than a standard value. CONSTITUTION:A torque operating unit (TCL) computes a stability factor based on a steering angle of the steering wheel of a vehicle that is detected with a steering-wheel sensor 70, a lateral acceleration detected with a linear-G sensor 100 and a vehicle speed detected with rear-wheel rotation sensors 66 and 67. Thus computed stability factor is then compared with a specified value which is lower than a standard stability factor. The detected value of the lateral acceleration when the stability factor agrees with the specified value is estimated to be the friction coefficient of the road surface.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to the friction coefficient between the road surface and the tires while the vehicle is running.
The method for easily measuring the road surface friction coefficient (hereinafter referred to as road surface friction coefficient or road surface μ) is particularly concerned with the method for easily measuring the lateral acceleration (lateral G
) is useful when adjusting the degree of drive torque reduction in accordance with the μ of the road surface in turning control that reduces the drive torque of mu in accordance with μ of the road surface.

<Conventional technology> First, we will outline the turning control.

If the road surface conditions suddenly change while the vehicle is running, or if the vehicle is traveling on a slippery road with a low coefficient of friction, such as a snowy or icy road, the drive wheels may spin, making it extremely difficult to control the vehicle. It becomes difficult.

In such a case, it is extremely difficult for the driver, even for an experienced driver, to adjust the amount of depression of the accelerator pedal and delicately control the output of the engine so that the drive wheels do not spin.

Similarly, when a vehicle is traveling on a turning path, a centrifugal force corresponding to the lateral acceleration in the direction perpendicular to the direction of travel is generated.
If the speed of the vehicle on the turning path is too high, the grip strength of the tires may exceed the limit and the vehicle body may skid.

In such cases, in order to reduce the engine output appropriately and drive the vehicle safely with a turning radius that corresponds to the turning path, it is especially important to In cases where the size of the vehicle is gradually decreasing, extremely advanced driving skills are required.

In general vehicles that have a so-called understeering tendency, it is necessary to gradually increase the amount of steering as the lateral acceleration applied to the vehicle increases, but when this lateral acceleration exceeds a value specific to each vehicle, the amount of steering increases. As mentioned earlier, this property has the property of rapidly increasing the number of times, making safe cornering difficult or impossible.

It is well known that this tendency is particularly noticeable in front-engine, front-wheel drive vehicles, which have a strong tendency to understeering.

For this reason, the idling state of the driving wheels is detected, and when the idling of the driving wheels occurs, the output of the engine is forcibly reduced, regardless of the amount of depression of the accelerator pedal by the driver. Alternatively, an output that detects the lateral acceleration of the vehicle and forcibly reduces the engine output before the turning limit at which the vehicle becomes difficult or unable to turn, regardless of the amount of depression of the accelerator pedal by the driver. A control device is considered, and the driver can select between driving using this output control device as necessary and normal driving in which the engine output is controlled according to the amount of depression of the accelerator pedal. It has been announced.

Among the methods related to vehicle output control based on such viewpoints, conventionally known methods detect the rotational speed of the driving wheel and the rotational speed of the driven wheel, and calculate the difference between these rotational speeds as the slip of the driving wheel. The drive torque of the engine is controlled according to the amount of slip of the vehicle, or the drive torque of the engine is controlled based on the amount of yawing of the vehicle (hereinafter referred to as yaw rate). It is.

In other words, in the latter method, the amount of yawing that mainly occurs during high-speed sharp turns of the vehicle tends to increase rapidly as the vehicle speed increases and the turns become sharper. If detected, or if these exceed predetermined values, the driving torque of the engine is reduced.

In such turning control, it has been found that it is preferable to adjust the degree of drive torque reduction depending on the μ of the road surface, especially when the μ is low.

However, no technology for measuring road surface μ suitable for hawk turning control has been known.

In other words, conventionally, there is a technology that attaches standard tires to a two-wheeled trailer and calculates the road surface μ from the locking braking force, but it requires forcibly locking the tires, and the characteristics of the tires deteriorate as the vehicle travels. Therefore, it is not desirable to apply this to ordinary vehicles. Furthermore, the μ of the road surface depends on the road surface condition (paved road, unpaved road, dry road, wet road, packed snow, frozen road, etc.) and is not constant while driving, so the tires are frequently locked for μ measurement. However, this is not realistic.

<Problems to be Solved by the Invention> In view of the above-mentioned prior art, an object of the present invention is to provide a method that can easily determine μ of a road surface while a vehicle is running.

<Means for Solving the Problems> The method for measuring the coefficient of road friction according to the present invention includes detecting the steering angle of the steering wheels of a vehicle, the lateral acceleration and vehicle speed of the vehicle, and the method based on the detected steering angle, lateral acceleration and vehicle speed. performing a calculation to obtain a stability factor; comparing the calculated value of the stability factor with a predetermined value worse than a standard stability factor; and when the calculated value of the stability factor matches the predetermined value; It is characterized in that the detected value of the lateral acceleration is taken as l@friction coefficient of the road surface.

As is well known, the stability factor is a value determined by the configuration of the vehicle's suspension system, the characteristics of the tires, etc. Specifically, as shown in FIG. 12 [a], for example, the lateral acceleration G generated in the vehicle during a steady circular turn, and the steering angle ratio δH/of the steering wheel shaft (steering shaft) at this time It is expressed as the slope of a tangent in a graph representing the relationship with δHo. Here, the steering angle ratio δ8/δHo is the neutral position δ of the steering shaft. The lateral acceleration GY is 0 based on
This is the ratio of the turning angle δ of the steering shaft during acceleration to the turning angle δHO of the steering shaft in the nearby very low speed running state.

Further, the illustrated example is for a front wheel drive vehicle.

Then, the stability factor can be calculated from the following formula, where A is the stability factor.

However, δζ is the steering angle of the steering wheel, δ is the turning angle of the steering shaft, ρ
8t is the steering gear transmission ratio (known), G7 is the actual lateral acceleration of the vehicle, t is the wheelbase of the vehicle (known), and ■ is the vehicle speed.

Expressing the relationship between lateral acceleration G7 and steering angle ratio δM/δ8o during a steady circular turn on a high μ road such as the song $101 Alt dry mass installation during the 121st mfal, and assuming μ (friction coefficient) of this road surface to be μm, Lateral acceleration GY (unit: g) cannot exceed μm.

Then, in a region where the lateral acceleration G is small to the extent that it is less than the μ-factor, and therefore the vehicle speed V is not very high, the stability factor A is approximately a constant value (for example, A=0.0021,
This is an area with a linear relationship, but the lateral acceleration G7 is μ
, the stability factor A suddenly increases (deteriorates) and the vehicle begins to exhibit an extremely strong tendency to understeering.

In FIG. 12+a+, other curves 102A and 103A.

104A each has a friction coefficient of μ2. μ1. μ4 (μm
〉μ2〉μm〉μ4), that is, a rain-wet road surface (μ2), a packed snow road surface (μ3), and an icy road surface (μ4), the relationship between GY and δH/δHo is shown. In the case of any low μ road surface, the lateral acceleration G cannot exceed the road surface μ, and as it approaches the road surface μ, the stability factor A deviates from the linear relationship and increases rapidly.

In order to better understand the rapid increase in stability factor A, FIG. 12 [b] is a rewritten version of FIG. 12 (al), with the vertical axis representing stability factor A1 and the horizontal axis representing lateral acceleration GY.

In Figure 12(b), the song is $1018+! Curve 1i102B shows the relationship when the road surface IIIWA coefficient is μm, curve 103B shows the relationship when it is μ3, curve 1
04B represents the relationship in the case of μ4.

Then, the actual lateral acceleration GY1. when a predetermined value AL (for example, A, = 0.005) is larger than the standard stability factor (A = 0.002) in a region with a linear relationship. Gv2. GV3. GY4 If you find them, they are the friction coefficient μm of the road surface.

μ2. μ1. The value is extremely close to μ4. Gvl-μm
.

G72-μ27 GY3-μ3Pcv, =μ4° or more applies to vehicles that tend to understeering, but the same can be said for vehicles that tend to oversteering.

Therefore, (a) Rudder angle δ of the steering wheel of the vehicle, lateral acceleration GY of the vehicle
and vehicle speed V, (bl) Calculate the stability factor based on the detected steering angle δ, lateral acceleration GY, and vehicle speed (C) Calculate the calculated value A of the stability factor using standard stability By comparing the detected value G7 of the lateral acceleration when the calculated value A of the stability factor matches the predetermined value 9 with the predetermined value 9, the detected value G7 of the stability factor can be estimated as the coefficient of friction μ of the road surface. reactor.

In order to prevent errors due to disturbances, etc., set a large value of lateral acceleration GVTH, e.g. 0.5 (gl), in advance.
In the case of Y>GvTH, it is better not to perform measurement or simply to estimate that μ is high. Also, in the case of A<AL, it is preferable not to perform measurement or simply to estimate that μ is high.

Embodiment An embodiment in which the present invention is applied to a front wheel drive type vehicle will be described with reference to FIG. 1 and FIG. 22.

In FIG. 1, a torque calculation unit (hereinafter referred to as Jl and abbreviated as TCL) 58 is means for calculating the target driving torque of the engine 11, and this TCL 58 performs calculations to measure the friction coefficient of the road surface. Therefore, the TCL 58 includes a rear wheel rotation sensor 66, 67, a steering angle sensor 70, and a linear G (lateral acceleration) sensor 10 that calculates the actual lateral acceleration GY.
0 is connected, and the steering gear speed ratio ρ8, vehicle wheelbase l, predetermined threshold, ) value A, and GvTH are set in advance.

Then, the TCL 58 calculates the vehicle speed V using the following formula based on the detection signal from the rear wheel rotation sensor 66 and 67.

However, VFIL and VRFI each have a pair of left and right rear wheels 6.
The circumferential speed is 4.65 (see Figure 2).

In addition, since the TCL5g has the steering angle sensor 70 on the steering shaft 69 (see Fig. 2), the steering wheel (
The steering angle δ of the front wheels is calculated. δ8 is the turning angle of the steering shaft.

The μ measurement operation of the TCL 58 will be explained with reference to FIG. First, in step 201, a stability factor A is calculated using the following formula.

Next, in step 202, the calculated value A of the stability factor is compared with a predetermined value AL, for example 0.005, and the detected value G7 of the lateral acceleration is compared with a predetermined value G, for example 0.5 (g).

Then, in step 203, if A>AL and G<G, it is determined that the road surface on which the vehicle is traveling has a low μ, and in step 204, the detected value G of the lateral acceleration when A=A,
Let (g) be the friction coefficient μ of the road surface. however,
In the case of AL or GAG, it is determined that the road surface has a high μ, and μ is not estimated.

The TCL 58 repeatedly executes steps 201 to 204 described above at a predetermined sampling period, thereby determining the μ of the road surface at all times during driving.

Note that the means for detecting the actual loss acceleration GY is not limited to the linear G sensor 100, and other means may be used. For example, the circumferential speed difference between a pair of left and right driven wheels (rear wheels) is 1v1. The actual loss acceleration G7 may be detected by calculating the following formula from lL-■,1 and the tread b.

Next, vehicle output control (turning control and slip control) to which the method of measuring the road surface friction coefficient according to the present invention is applied will be explained.

As shown in FIG. 1 and FIG. 2 showing the schematic structure of the vehicle, there is an intake passage 1 formed by the intake pipe 13 in the middle of the intake pipe 13 connected to the combustion chamber 12 of the engine 11.
A throttle body 16 incorporating a throttle valve 15 for adjusting the amount of intake air supplied into the combustion chamber 12 by changing the opening degree of the combustion chamber 12 is interposed.

As shown in FIG. 1 and FIG. 3, which shows an enlarged cross-sectional structure of the cylindrical throttle body 16, both ends of a throttle shaft 17 with a throttle valve 15 fixed thereto are rotatable. freely supported. An accelerator lever 18 and a throttle lever 19 are coaxially fitted into one end of the throttle shaft 17 that protrudes into the intake passage 14 .

The cylindrical portion 20 of the throttle shaft 17 and the accelerator lever 18
A bunyu 21 and a spacer 22 are interposed between the
This allows the accelerator bar 18 to rotate freely with respect to the throttle shaft 17. Furthermore, the throttle shaft 17
on the washer 23 and nut 24 attached to one end of the
This prevents the accelerator lever 18 from being removed from the throttle shaft 17.

Also, a cable receiver 25 integrated with this accelerator lever 18
An accelerator pedal 26 operated by the driver is connected via a cable 27 to the accelerator pedal 2.
The accelerator lever 18 rotates with respect to the throttle shaft 17 according to the amount of depression of the throttle lever 6.

On the other hand, the throttle lever 19 is fixed integrally with the throttle shaft 17, and therefore the throttle lever 19 is fixed integrally with the throttle shaft 17.
By operating 9, the throttle valve 15 rotates together with the throttle shaft 17. Further, a collar 28 is coaxially fitted into the cylindrical portion 20 of the accelerator lever 18, and a claw portion 29 formed on a portion of the collar 28 is engaged with the tip portion of the throttle lever 19. A stopper 30 that can be stopped is formed. These claws 29 and stoppers 30
is set in a positional relationship such that when the throttle lever 19 is rotated in the direction in which the throttle valve 15 opens, or the accelerator lever 18 is rotated in the direction in which the throttle valve 15 is closed, they are mutually locked. ing.

A stopper 30 of the throttle lever 19 is pressed against the claw portion 29 of the accelerator lever 18 to close the throttle valve 15 between the throttle body 16 and the throttle lever 19.
A torsion coil spring 31 biasing in the opening direction is attached to a pair of cylindrical spring receivers 32 fitted to the throttle shaft 17.
, 33, and is mounted coaxially with this throttle shaft 17. Also, between the stopper pin 34 protruding from the throttle body 16 and the accelerator lever 18,
Push the claw part 29 of the accelerator lever 18 into the throttle lever 19.
A torsion fill spring 35 is applied to the cylindrical portion 2° of the accelerator lever 18 via the collar 28 to urge the throttle valve 15 in the closing direction by pressing against the stopper 30 of the accelerator pedal 26 and to impart a detent feeling to the accelerator pedal 26. It is mounted coaxially with the throttle shaft 17.

A control rod 3 whose base end is fixed to a diaphragm 37 of an actuator 36 is attached to the tip of the slotted lever 19.
The tips of 8 are connected. This actuator 36
The throttle valve 1 is inserted into the pressure chamber 39 formed therein by pressing the stopper 3° of the throttle lever 19 together with the torsion coil spring 31 against the claw portion 29 of the accelerator lever 18.
A compression coil spring 40 is incorporated which biases the opening of the opening 5 in the direction of opening. The spring force of the torsion coil spring 35 is set to be greater than the sum of the spring forces of these two springs 31 and 40, so that when the accelerator pedal 26 is depressed or the pressure in the pressure chamber 39 is The throttle valve 15 will not open unless the negative pressure is greater than the sum of the spring forces of the two springs 31 and 40.

A surge tank 41 connected to the downstream side of the throttle body 16 and forming a part of the intake passage 14 is connected to a vacuum tank 43 via a connecting pipe 42 . A check valve 44 that only allows air to move from the vacuum tank 43 to the surge tank 41 is interposed between the vacuum tank 43 and the surge tank 41 . As a result, the pressure within the vacuum tank 43 is set to a negative pressure approximately equal to the lowest pressure within the surge tank 41.

Inside these vacuum tanks 43 and the actuator 3
The pressure chamber 39 of No. 6 is in communication with the pressure chamber 39 through a pipe 45, and a first torque control solenoid valve 46 of a type that is closed when energized is provided in the middle of the pipe 45. In other words,
This torque control electromagnetic valve 46 has a built-in spring 49 that biases the plunger 47 against the valve seat 48 so as to close the pipe 45.

Further, a pipe 50 communicating with the intake passage 14 on the upstream side of the throttle valve 15 is connected to the pipe 45 between the first torque control solenoid valve 46 and the actuator 36 . A second torque control solenoid valve 51 of a dispersion type when not energized is provided in the middle of the pipe 50. That is, this torque control solenoid valve 51 includes a spring 53 that biases the plunger 52 to open the pipe 50.

The two torque control solenoid valves 46 and 51 include the engine 1
An electronic control unit 54 (hereinafter referred to as ECU) that controls the operating state of the
Torque control solenoid valve 46 based on commands from CU 34
The ON and OFF of the current supply to .degree.

For example, when the duty rate of the torque control solenoid valves 46 and 51 is 0%, the pressure in the pressure chamber 39 of the actuator 36 becomes atmospheric pressure (which is approximately equal to the pressure in the intake passage 14 on the upstream side of the throttle valve 15), The opening degree of the throttle valve 15 corresponds one-to-one to the amount of depression of the accelerator pedal 26.

Conversely, when the duty ratio of the torque control solenoid valves 46 and 51 is 100%, the pressure chamber 39 of the actuator 36 becomes a negative pressure almost equal to the pressure inside the vacuum tank 43,
As a result of the control rod 38 being pulled up diagonally to the left in FIG. 1, the throttle valve 15 is closed regardless of the amount of depression of the accelerator pedal 26, and the driving torque of the engine 11 is forcibly reduced. In this way, by adjusting the duty ratio of the torque control solenoid valves 46 and 51, the opening degree of the throttle valve 15 is changed regardless of the amount of depression of the accelerator pedal 26, and the driving torque of the engine 11 is arbitrarily adjusted. can do.

The ECU 34 includes a crank angle sensor 55 that is attached to the engine 11 and detects the engine rotation speed, a throttle opening sensor 56 that is attached to the throttle body 16 and detects the opening of the throttle lever 19, and a throttle opening sensor 56 that is attached to the throttle body 16 and detects the opening of the throttle lever 19. An idle switch 57 for detecting a fully closed state is connected, and output signals from the crank angle sensor 55, throttle opening sensor 56, and idle switch 57 are sent, respectively.

Further, the torque calculation unit (TCL) 58 that calculates the target driving torque of the engine 11 includes an accelerator that is attached to the throttle body 16 together with the throttle opening sensor 56 and the idle switch 57 to detect the opening of the accelerator lever 18. An opening sensor 59, front wheel rotation sensors 62 and 63 that respectively detect the rotational speed of a pair of left and right front wheels 60 and 61 that are driving wheels, and a pair of left and right rear wheels 6 that are driven wheels.
Rear wheel rotation sensors 66 and 67 that detect rotational speeds of 4.65, respectively, and a steering angle sensor 7 that detects the turning angle of the steering shaft 69 when turning based on the straight-ahead state of the vehicle 68.
0 and the linear G sensor 100 are connected, and output signals from these sensors 59, 62, 63, 66, 67, 70, and 100 are sent, respectively.

The ECU 34 and the TCL 58 are connected via a cable 71, and the ECU 34 sends information on the operating state of the engine 11, such as the amount of intake air, in addition to the engine speed and detection signals from the idle switch 57 to the TCL 5B. sent to. Conversely, the TCL 58 sends information regarding the target drive torque calculated by the TCL 58 to the ECU 34.

As shown in FIG. 4, which shows the general flow of control according to this embodiment, in this embodiment, the engine 1
1 and the target drive torque T of the engine 11 when performing turning control. The TCL 58 always calculates these two target drive torques T0. ．．
Optimal final target drive torque T from ToH. is selected so that the driving torque of the engine 11 can be reduced as necessary.

Specifically, the control program of this embodiment is started by turning on the ignition key (not shown), and the initial value δ of the steering shaft turning position is first read in Ml, and various flags are reset or this control is sampled. Initial settings such as starting the main timer's count every 15 milliseconds are performed.

Then, in M2, the TCL 58 calculates the vehicle speed V, etc. based on the detection signals from various sensors, and then calculates the neutral position δ of the steering shaft 69. is learned and corrected in M3. Neutral position δ of the steering shaft 69 of this vehicle 68. is the initial value δ□ every time the ignition key is turned on. , is read, but this initial value δ□. ) is learned and corrected only when the vehicle 68 satisfies straight running conditions, which will be described later, and this initial value δ is learned and corrected until the ignition key is turned off.

Next, TCL58 is M4 with front wheels 60, 61 (&k
jI Target drive torque T when performing slip control that regulates the drive torque of the engine 11 based on the rotation difference between 64 and 65. 5 is calculated, and target drive torque T of the engine 11 when turning control aa is performed with M5. , is calculated as follows.

Then, at M6, the TCL 58 receives these target drive torques T0. ．． After selecting the optimal final target drive torque T0 from To, by the method described later, the ECU 34 adjusts the duty of the pair of torque control solenoid valves 46 and 51 so that the drive torque of the engine 11 becomes the final target drive torque T. The rate is controlled, thereby allowing the vehicle 68 to travel smoothly and safely.

In this way, the driving torque of the engine 11 is controlled by M7 until the countdown of the main timer ends, and from then on, the driving torque of the engine 11 is controlled by M7.
At step 8, the main timer starts counting down again, and the steps from M2 to M8 are repeated until the ignition key is turned off.

Neutral position δ of the steering shaft 69. The reason why the learning correction is performed in step 9M3 is that the amount of turning of the steering shaft 69 and the steering wheel may change due to changes in the toe-in of the front wheels 60 and 61 during maintenance of the vehicle 68 or due to aging such as wear of the steering gear (not shown). A deviation occurs between the actual steering angle δ of certain front wheels 60 and 61, and the steering shaft 69 reaches a neutral position δ. This is because it may change. The stability factor A is determined using the steering shaft turning angle δ□ after the learning correction.

As shown in FIG. 5, which shows the procedure for learning and correcting the neutral position δ of the steering shaft 69, the TCL 58 is connected to the rear wheel rotation sensor 6.
Based on the detection signal from 6.67, the vehicle speed ■ is calculated at C1 using the following formula (1).

v +V ■-8L'''''' 2 (1) However, in the above formula, V, L, V, l, and I are the circumferential speeds of the pair of left and right rear wheels 64 and 65, respectively.

Next, the TCL58 moves to the left and right rear wheels 6 at C2. i, 6
5 circumferential speed difference (hereinafter referred to as rear wheel speed difference)”
FIL-VRFI” calculation.

Thereafter, the TCL 58 determines at C3 whether the vehicle speed ■ is greater than a preset threshold value VA. This operation
This is necessary because the rear wheel speed difference VRL 'RR' due to steering cannot be detected unless the vehicle 68 reaches a certain high speed. For example, set it as appropriate, such as 201 oa per hour.

Then, when it is determined that the vehicle speed ■ is equal to or higher than the threshold value VA, TCL58 adjusts the rear wheel speed difference "FIL 'R" at C4.
It is determined whether R' is smaller than a preset threshold (2), such as 0.1 km/hour, that is, whether the vehicle 68 is traveling straight. Here, set the threshold value ■6 to OK every hour.
The reason why the left and right rear wheels 64 and 65 are not equal in tire pressure is that even though the vehicle 68 is traveling straight, the circumferential speed VRL of the pair of left and right rear wheels 64,65 is not equal to n.
, are different.

At this step C4, rear wheel speed difference IVFIL-v1. l
□! If it is determined that is below the threshold V8, TCL5
8 determines whether the current steering shaft turning position δ is the same as the previous steering shaft turning position δm (n−11) detected by the steering angle sensor 701ζ at C5. In order to avoid being affected by
It is desirable to set the turning detection resolution of the steering shaft 69 by the steering angle sensor 70 to, for example, about 5 degrees.

In Step B, C5, the current steering shaft turning position δ is the same as the previous steering shaft turning position δ...(nl

If it is determined that IN+n-11-, TCL5
8, it is determined at C6 that the vehicle 68 is currently traveling straight, and a learning timer (not shown) built in the TCL 58 starts counting, and this continues for, for example, 0.5 seconds.

Next, at C7, the TCL 58 determines whether 0.5 seconds have elapsed since the learning timer started counting, that is, whether the vehicle 68 has been traveling straight for 0.5 seconds. in this case,
At the beginning of the vehicle 68's travel, 0.5 seconds have not yet elapsed since the start of counting of the learning timer t, so that at the beginning of the vehicle 68's travel, steps C1 to C7 are repeated.

When it is determined that 0.5 seconds have passed since the learning timer started counting, the TCL58 determines whether the steering angle neutral position learned flag F is set in C8, that is, if the current learning control is the first time. Determine whether it exists or not.

In step 08, the steering angle neutral position learned flag FH
If it is determined that is not set, the current steering shaft turning position δ is determined at C9. 3. , , is the new neutral position δ of the steering shaft 69. ,. , and reads this into the memory in the TCL 58, and sets the steering angle neutral position learned flag F8.

In this way, the new neutral position δ6 of the steering shaft 69. ．．
．． After setting the neutral position δ□ of this steering shaft 69,
While calculating the turning angle δ8 of the steering shaft 69 using , as a reference, the count of the learning timer is cleared in the CIO, and the steering angle neutral position learning is performed again.

In step C8, the steering angle neutral position learned flag FH
is set, that is, if it is determined that the steering angle neutral position learning is being performed for the second time or later, the TCL58 changes the current steering axis turning position δ111111 to the previous steering axis 6 at C1l.
equal to the neutral position δ of 9, i.e. gate +n-.

Determine whether δ = δ m (nl M In-11. Then, if it is determined that the current steering shaft turning position δ, i) is equal to the previous neutral position δM-1, of the steering shaft 69. For example, the process directly returns to step C10 and the next steering angle neutral position learning is performed again.

In step C11, the current steering shaft turning position δ1. ,,
If it is determined that the bar (n-11) is not equal to the previous neutral position δ of the steering shaft 69 due to play in the steering system, etc., the current steering shaft turning position δ□.

The new neutral position δ□ of the steering shaft 69 is maintained. .

If the absolute value of these differences differs by a preset correction limit amount of 68 or more, the previous steering axis 82
neutral position δ□. -1, by subtracting or adding this correction limit amount Δδ, and set it as a new neutral position δ of the steering shaft 69, which is then read into the memory in the TCL 58.

That is, the TCL 58 changes from the current steering shaft turning position δ□, . . . to the previous neutral position δ of the steering shaft 69 at C12. ,. −
The value obtained by subtracting 8 is the preset negative correction limit amount -Δδ
Determine whether it is smaller than . Then, if it is determined that the value subtracted in step C12 is smaller than the negative correction limit amount -Δδ, a new steering axis 6 is set in step C13.
9 neutral position δ,. ) is the previous neutral position δ of the steering shaft 69. From the negative correction limit -Δδ+11-11, δ = δ -Δδ tri gate (n-11) to ensure that the learning correction amount per - time does not unconditionally increase to the negative side. .

As a result, even if an abnormal detection signal is output from the steering angle controller 70 for some reason, the neutral position δ of the steering shaft 69 will not change suddenly, making it possible to quickly respond to this abnormality. can.

On the other hand, if it is determined that the value subtracted in the step C12 is larger than the negative correction limit amount -Δδ, the current steering shaft turning position δm (from nl to the previous steering shaft 69
It is determined whether the value obtained by subtracting the neutral position δMin-11 of is larger than the positive correction limit amount Δδ. And this C
If it is determined that the value subtracted in step C14 is larger than the positive correction limit amount Δδ, a new neutral position δ1 of the steering shaft 69 is set in C15. , , is changed from the previous neutral position δM(n-1) of the steering shaft 69 and the positive correction limit amount Δδ to δ = δ + Δδ gate in) M fn-1, and the learned correction amount per - time is nil. Care has been taken to ensure that the conditions do not increase to the positive side.

As a result, even if an abnormal detection signal is output from the steering angle sensor 70 for some reason, the neutral position δ6 of the steering shaft 69 (does not change suddenly), and this abnormality can be dealt with quickly.

However, if it is determined that the value subtracted in step C14 is smaller than the positive correction limit amount Δδ, the current steering shaft turning position δ is read out as is as the new neutral position δ of the steering shaft 69 in C16. .

Therefore, when the stopped vehicle 68 starts with the front wheels turning at 60% or 61%, as shown in FIG.
When the learning control of the neutral position δ of the steering shaft 69 is performed for the first time, the initial value δ of the steering shaft turning position in the step Ml mentioned above.
Although the amount of correction from the second time onwards is the neutral position δ of the steering shaft 69. is suppressed by the operations in steps C13 and C14.

In this way, the neutral position δ of the steering shaft 69 is established. After learning and correcting, the vehicle speed V and the peripheral speeds of the front wheels 60, 61 VFL, VF,
Target drive torque T when performing slip control that regulates the drive torque of the engine 11 based on the difference between T and I. , is calculated.

By the way, in order to make the driving torque generated by the engine 11 work effectively, as shown in FIG. 7, which shows the relationship between the friction coefficient between the tires and the road surface and the slip rate of the tires
The front wheels 60, 61 are adjusted so that the slip rate S of the tires of the front wheels 60, 61 during running is at or near the target slip rate S0 corresponding to the maximum value of the coefficient of friction between the tires and the road surface.
It is desirable to adjust the slip amount S of the vehicle 61 so as not to impair the additive performance of the vehicle 68.

Here, the slip rate S of the tire is as follows, and this slip rate S is a target slip rate S corresponding to the maximum value of the coefficient of friction between the tire and the road surface. Or the target drive torque T of the machine R11 so that it is in the vicinity of ζ. The calculation procedure for setting all S settings is as follows. First, TCL58! The current vehicle speed V calculated using the above formula (1) and the previous vehicle speed C] ■. 1. From this, the current longitudinal acceleration G9 of the vehicle 68 is calculated using the following formula.

v −■ − × 3.6·Δt−g However, Δt is 15 milliseconds, which is the sampling period of the main timer, and g is the gravitational acceleration.

Then, the driving torque T of the engine 11 at this time is calculated using the following formula (2
) is calculated.

T = G - W - r + T - (21 Here, GxF is the corrected longitudinal acceleration passed through a low-pass filter that delays the change in the longitudinal acceleration Gx mentioned above. The low-pass filter allows the longitudinal acceleration GX of the vehicle 68 to be Since the longitudinal acceleration Gy of the vehicle 68 changes, the tire slip rate S changes to the target slip rate S corresponding to the maximum value of the friction coefficient between the tire and the road surface, or the Even when the tire is about to deviate from the vicinity, the slip rate S of one tire is set to the target slip rate S0 corresponding to the maximum value of the friction coefficient between the tire and the road surface.
It has a function of correcting the longitudinal acceleration G8 so as to maintain it at or near that value. Also, the tow is the vehicle weight, r is the front wheel 6
The effective radius of 0.61 and T8 are running resistance, and this running resistance TR can be calculated as a function of vehicle speed (2), but in this embodiment, it is calculated from a map as shown in FIG.

On the other hand, while the vehicle 68 is accelerating, it is normal that the wheels always slip about 3% with respect to the road surface, and
When driving on a rough road such as a gravel road, the maximum value of the coefficient of friction between the tire and the road surface corresponding to the target slip ratio S is generally larger than when driving on a low μ road. Therefore, taking into consideration the amount of slip and road surface conditions, the front wheel 6
Target drive wheel speed ■, which is a peripheral speed of 0.61. The following formula (
Calculate according to 3).

V = 1.03・V+V・(3)
However, vK is a road surface correction amount that is preset corresponding to the corrected longitudinal acceleration GxP, and should have a tendency to increase stepwise as the value of the corrected longitudinal acceleration GXF increases. This road surface correction amount (3) is determined from a map as shown in FIG. 9, which was created based on driving tests and the like.

Next, the slip amount S, which is the difference between the vehicle speed V and the target driving wheel speed vFo, is calculated using the following formula (
Calculate according to 4).

■F, +■FR s = 2 V p. ...(4)
Then, as shown in equation (5) below, this slip amount S is integrated while being multiplied by an integral coefficient by 1 every sampling period of the main timer, and the target drive torque T is obtained. Integral correction torque T to improve control stability for S (however, T≦0
) is calculated.

T = Σ K −s −(
5) Similarly, the target drive torque T0. which is proportional to the slip amount S as shown in equation (6) below. A proportional correction torque TP for alleviating control delay is calculated while being multiplied by a proportional coefficient KP.

T=to-s...(6) And,
The target drive torque T of the engine 11 is calculated by the following equation (7) using the above equations (21, (51, and (6)).

In the above equation, ρ is a gear ratio of a transmission (not shown), and ρ6 is a reduction ratio of a differential gear.

The vehicle 68 is provided with a manual switch (not shown) for the driver to select slip control, and when the driver selects slip control by operating this manual switch, the slip control operation described below is performed. I do.

As shown in FIG. 1, which shows the flow of this slip control process, the TCL 58 first detects and calculates the various data described above at Sl to obtain the target drive torque T. S is calculated, but this calculation operation is performed independently of the operation of the manual switch.

Next, in S2, it is determined whether or not the slip control flag F is set. First, if the slip control flag FS is not set, the TCL58 detects a slip amount of 60°61 for the front wheels in S3. It is determined whether S is larger than a preset wi value, for example 2 km/h.

If it is determined in step 33 that the slip amount S is greater than 2 km/h, the TCL 58 determines in S4 whether the rate of change G5 of the slip amount S is greater than 0.2 g.

In this step 84, the slip amount change rate G5 is 0.2
If it is determined that it is larger than g, the slip control flag FS is set in s5, and the slip fIiJII is set in S6.
It is determined again whether or not the flag Fs during II is set.

In step 36, the slip control flag F is set.
If it is determined that the engine 11 is in the process of sowing, the target drive torque T of the engine 11 is set in S7. One example is the target drive torque T for slip control calculated in advance using equation (7). Adopt S.

Also, in the step S6, the slip control flag F,
If it is determined that the TCL58 has been reset, the TCL58
is the target drive torque T. S, the maximum torque of the engine 11 is output at 58, and as a result, the ECU 54 lowers the duty ratio of the torque control solenoid valves 46, 51 to the 0% side. Generates driving torque according to the amount.

Note that the reason why the TCL 58 outputs the maximum torque of the engine 11 in step 38 is due to the E
CtJ54 always sets the duty rate of the torque control solenoid valves 46 and 51 to 0% side, that is, the torque control solenoid valves 46 and 51.
This is because the engineer 1 works in the direction of cutting off the current to the engine so that the engine engineer 1 can reliably generate a driving torque corresponding to the amount of depression of the accelerator pedal 26 by the driver.

In step S3, the slip amount S of the front wheels 60 and 61 is
If it is determined that the slip amount change rate GS is smaller than 2 kha per hour, or if it is determined in step S4 that the slip amount change rate GS is smaller than 0.2 g, the process directly proceeds to step S6, and the TCL 58 adjusts to the target drive. Torque T. , the maximum torque of the engine 11 is output in step S8, and as a result, the EC1J 54 activates the torque control solenoid valve 46.
．． As a result, the engine 11 generates a driving torque corresponding to the amount of depression of the accelerator pedal 26 by the driver.

On the other hand, in step S2, the slip control flag F
If it is determined that , is set, it is determined in S9 whether the idle switch 57 is on, that is, the throttle valve 15 is fully closed.

If it is determined that the idle switch 57 is on in this step S9, since the driver has not depressed the accelerator pedal 26, the slip control flag F is reset in S10, and the process moves to step S6.

If it is determined in step S9 that the idle switch 57 is off, it is determined again in step S6 whether or not the slip control flag F5 is set.

Note that if the driver does not operate the manual switch for selecting slip IJ knob control, TCL5g is set to target drive torque T0. for slip control as described above. After calculating
The target drive torque of the engine 11 when performing turning control is calculated.

When controlling the turning of the vehicle 68, the TCL 58 calculates the target lateral acceleration GY of the vehicle 68 from the steering shaft turning angle δ8 and the vehicle speed ■.
0 is calculated, and an acceleration in the longitudinal direction of the vehicle body that does not cause extreme understeering of the vehicle 68, that is, a target longitudinal acceleration G8o is set based on the target lateral acceleration GYo. And this target 81 & acceleration G work. The target driving torque of the engine 11 corresponding to the target driving torque is calculated.

By the way, the lateral acceleration G,,l of the vehicle 68 and the rear wheel speed difference 1
■RL It can actually be calculated using 'RR', but by using the steering shaft turning angle δ',
Since the value of the lateral acceleration GY acting on the vehicle 68 can be predicted, there is an advantage that quick control can be performed.

However, depending on the steering shaft turning angle δ8 and the vehicle speed ■,
Merely determining the target drive torque of the engine 11 does not reflect the driver's intention at all, and there is a risk that the driver may remain dissatisfied with the maneuverability of the vehicle 68. Therefore, it is desirable to determine the required drive torque L of the engine 11 desired by the driver from the amount of depression of the accelerator pedal 26, and set the target drive torque of the engine 11 in consideration of this required drive torque Td. Furthermore, if the increase or decrease in the target drive torque of the engine 11, which is set every 15 milliseconds, is extremely large, a shock will occur as the vehicle 68 accelerates and decelerates, resulting in a reduction in ride comfort. The increase/decrease in target drive torque of 11 is vehicle 6.
If the target drive torque becomes large enough to cause a decrease in the ride comfort of the vehicle, it is necessary to regulate the increase/decrease of this target drive torque.

Furthermore, if the target drive torque of the engine 11 is not changed depending on the μ of the road surface, for example, if the engine 11 is operated with the target drive torque for a high μ road while driving on a low μ road, the front wheels 60, 61 will slip. Since there is a possibility that safe driving may become impossible, TCL58 sets the target drive torque T according to the μ of the road surface. It is desirable to calculate H in advance.

As shown in FIG. 11, which shows a calculation block for turning control in consideration of the above knowledge, the TCL 58 calculates the vehicle speed V from the outputs of the pair of rear wheel rotation sensors 66 and 67 using equation (1) above, and also performs steering control. Based on the detection signal from the angle sensor 70, the steering angle δ of the front wheels 60, 61 is calculated using the following formula (8), and the target lateral acceleration G7° of the vehicle 68 at this time... (8) However, δ□ is the steering angle Shaft turning angle, ρ8 is steering gear gear ratio, l
is the wheelbase of the vehicle 68, and A is the stability factor of the vehicle.

This stability factor A is, as is well known, the vehicle 68
This value is determined by the configuration of the suspension system, tire characteristics, etc. Specifically, it is expressed as the slope of a tangent line in a graph as shown in FIG. 12 (al), for example.
In the case of a high μ road such as song 1j101A in Figure 12+al,
In a region where the lateral acceleration GY is small and the vehicle speed V is not very high, the stability factor A is approximately constant (A = 0.00
2), but when the lateral acceleration GY exceeds 0.6 g, the stability factor A rapidly increases, and the vehicle 68 begins to exhibit a strong understeering tendency.

Based on the above, when based on the curve 101A on the high μ road surface in Fig. 12 (a), the stability factor is set to a value AH of 0.002 or less and calculated using equation (9). Target lateral acceleration GY0 of vehicle 68゛ is 016g
The driving torque of the engine 11 is controlled so that the torque is less than the following.

Then, in order to adjust the driving torque of the engine 11 according to the μ of the road surface, the estimated value μ of the road surface friction coefficient measured by the method of the present invention described above is used to obtain the target lateral acceleration GY according to equation (9).
0 is converted to G'Yo=GY0/μ, and the driving torque of the engine 11 is controlled so that the converted target lateral acceleration G',o becomes less than 0.6 g. In addition, in the case of a high μ road, μ = 1 and G′7° = Gv
It is set to 0.

If the target lateral acceleration G'7o=Gv0/μ is calculated in this way, this target lateral acceleration G', in advance.

The target longitudinal acceleration Gx0 of the vehicle 68 set according to the magnitude of
Obtain this target longitudinal acceleration G from the map shown in the figure. The standard driving torque T8 of the engine 11 is calculated by the following formula (lO).
Calculated by

However, TL is the road surface resistance obtained as a function of the lateral acceleration G of the vehicle 68.
oad) Torque, which is obtained from a map as shown in FIG. 14 in this embodiment.

Next, in order to determine the adoption ratio of the reference drive torque T,
This reference drive torque TB is multiplied by a weighting coefficient a to obtain a corrected reference drive torque. The weighting coefficient a is set empirically by turning the vehicle 68, but on high μ roads, a value of around 0.6 is adopted, and if necessary, the weighting coefficient
Change according to the measured value.

On the other hand, the required driving torque T6 desired by the driver is determined by a map as shown in FIG. Then, the corrected required driving torque corresponding to the weighting coefficient α is set to the required driving torque Td (1-a)9! Calculated by multiplying. For example, if a=0.6 is set, the adoption ratio of the standard drive torque T8 and the required drive torque Td is 6.
It will be 4 against 4.

Therefore, the target drive torque T of the engine 11. ,,l is the following formula (
11).

T = a ・T + (1-a) ・T − (
The Ill vehicle 68 is provided with a manual switch (not shown) for the driver to select turning control, and when the driver selects turning control by operating this manual switch,
The turning control operation described below is performed.

Target drive torque T for this turning control. As shown in FIG. 16, which shows the flow of control for determining the target drive torque T, the target drive torque T is determined by the detection and arithmetic processing of the various data described above in Hl. Although H is calculated, this operation is performed independently of the operation of the manual switch.

Next, whether or not the vehicle 68 is under turning control at H2;
In other words, the turning control flag F:1. Determine if is set. Since it is not under turning control at first,
It is determined that the turning control flag F is in the reset state,
Target drive is performed at H3. A threshold value set in advance by H,
For example, it is determined whether it is less than or equal to (Td-2). In other words, the target drive torque T is maintained even when the vehicle 68 is traveling straight. 8 can be calculated, but the value is based on the driver's required driving torque T,
It is normal for it to be slightly larger than the previous year. However, since this required drive torque Td generally becomes smaller when the vehicle 68 turns, the target drive torque T. 8 is less than the threshold value (T, -2), this is set as the start condition for turning control.

Note that this threshold value is set to (T, -2) as a hysteresis to prevent control hunting.

Target drive torque T at step H3. l( is the threshold (T
If it is determined that it is below d-2), the TCL 58 determines in H4 whether or not the idle switch 57 is in the off state.

If it is determined in this step H4 that the idle switch 57 is in the off state, that is, the accelerator pedal 26 is depressed by the driver, the turning control flag F is determined in U5.
. H is set. Next, in H6, it is determined whether the steering angle neutral position learned flag FH is set, that is, the reliability of the steering angle δ detected by the steering angle sensor 70 is determined.

If it is determined that the steering angle neutral position learned flag F is set in step H6, the turning control flag F is set in Hl. It is determined again whether H is set.

In the above procedure, the turning control flag F is set in step U5. 8 is set, it is determined that the turning control flag FCH is set in step Hl,
Target drive torque T of formula 01) calculated earlier in H8.

H should be adopted.

On the other hand, if it is determined that the steering angle neutral position learned flag FH is not set in step H6, then the steering angle δ calculated by equation (8) is not valid, so (!1) Target drive torque T calculated using the formula. , without adopting TC
L58 is target drive torque T. , the maximum torque of the engine 11 is output at H9, and as a result, the ECU 54 lowers the duty ratio of the torque control solenoid valves 46, 51 to the 0% side. Generates driving torque according to the amount.

Further, the target drive torque T is set in step H3. If it is determined that H is not below the threshold value (Td-2), the transition is made from step H6 or Hl to step H9 without transitioning to turning control, and TCL58 is the target drive torque T. 8, the maximum torque of the engine 11 is outputted, and as a result, the ECU 34 lowers the duty ratio of the torque control solenoid valves 46, 51 to the 0% side, and as a result, the engine 11 responds to the amount of depression of the accelerator pedal 26 by the driver. Generates driving torque.

Similarly, when it is determined in step H4 that the idle switch 56 is on, that is, the accelerator pedal 26 is not depressed by the driver, the TCL 58 outputs the maximum torque of the engine 11 as the target drive torque ToH. , this causes the ECLI 54 to operate as the torque control solenoid valve 46.
．． As a result of reducing the duty rate of 51 to 0% side, the machine R
11 generates a driving torque according to the amount of depression of the accelerator pedal 26 by the driver and does not shift to turning 1lIIat+.

If it is determined in step H2 that the turning I11 control flag FCH is set, the target drive torque T calculated this time in HIO. It is determined whether the difference ΔT between H(nl and the previously calculated target drive torque T.,.-3, is larger than a preset increase/decrease allowable amount TK. The amount of torque change is such that no acceleration/deceleration shock is felt, and for example, if it is desired to suppress the target longitudinal acceleration G of the vehicle 68 to 0.1 g/s, the above four formulas are used.

Target drive torque T calculated this time in the HIO step. H(nl and the previously calculated target drive torque T.Hl.

-1, if it is determined that the difference ΔT is not larger than the preset allowable increase/decrease amount TK, then the target drive torque T is set at Hll. Yes, the target drive torque T calculated last time. ,
. It is determined whether the difference ΔT from -1l is larger than the negative increase/decrease allowance TK.

The current target drive torque T and the previously calculated target drive torque T in step Hll. If it is determined that the difference ΔT from H(n-110Hfnl is larger than the negative increase/decrease tolerance TK, the target drive torque To1.lL,,l
, and the target drive torque TOM+ calculated last time, 1-11
Since the absolute value of the difference 1ΔT1 is smaller than the allowable increase/decrease amount TK, the current target drive torque T is calculated. H(, l is directly adopted as the target drive torque T.H.

Also, the target drive torque T calculated this time in step Hll. ,. , and the target drive torque T calculated last time. ,. - If it is determined that the difference Δt from 〇 is not larger than the negative increase/decrease allowance 1, the current target drive torque T is determined at Hl2. H. ,
is set by the following formula.

T = T - T OHinl OHfn-11K In other words, the amount of decrease with respect to the previously calculated target drive torque TOH (n-11) is regulated by the allowable increase/decrease amount TK, and the deceleration sink due to the reduction in the drive torque of the engine 11 is reduced.

On the other hand, the target drive torque T calculated this time in the HIO step. H(nl and the previously calculated target drive torque T.

,,. If it is determined that the difference Δt from −1 is greater than the allowable increase/decrease amount TK, the current target drive torque T is determined at Hl3. Hl
,,l are set by the following formula.

T = T + T ON fnl OH1n-11K In other words, in the case of increase in drive torque, as in the case of decrease in drive torque described above, the target drive torque T calculated this time and the target QH (nl drive torque T. □, The difference ∆ from .-1 is the allowable increase/decrease amount -
If it exceeds the previously calculated target drive torque T. □
. -4, is regulated by the allowable increase/decrease amount T, thereby reducing the acceleration shock caused by the increase in the drive torque of the engine 11.

In this way, the target drive torque T. Steering shaft turning angle δ8, target longitudinal acceleration Gxo, and target drive torque T when the increase/decrease of H is regulated. As shown in FIG. 17, which shows the state of change between H and the actual longitudinal acceleration Gx, the target drive torque T
. Compared to the case where the increase or decrease of H is not regulated as shown by the broken line,
It can be seen that the actual longitudinal acceleration Gx changes smoothly, and the acceleration/deceleration shock is eliminated.

The target drive torque T is obtained as described above. When H is set, the TCL58 sets this target drive torque T at Hl4. It is determined whether H is larger than the driver's requested driving torque Td.

Here, the turning control flag F is set. If H is set, target drive torque T. , i.e., the requested drive of the M driver) and the torque T, it is determined at H2S whether or not the idle switch 57 is in the on state.

If it is determined in this step H2S that the idle switch 57 is not in the on state, this means that turning control is required, so the process moves to step H6.

Also, the target drive torque T is set at step H14 in fJ.

If it is determined that H is larger than the driver's requested drive torque T, this means that the turning movement of the vehicle 68 has ended, so the TCL 58 sets the turning control flag F at H2S. 1
．． Reset l. Similarly, when it is determined in step H2S that the idle switch 57 is in the on state,
Since the accelerator pedal 26 is not depressed, the process moves to step H2S and the turning control flag F is set.

Reset 8.

Turning control flag F in Otsu's H2S. When H is set, TCL58 sets engine 1 as target drive torque ToH.
The maximum torque of 1 is output at H9, which causes the ECU
As a result, the engine 11 generates a driving torque corresponding to the amount of depression of the accelerator pedal 26 by the driver.

Note that it is naturally possible to ignore the driver's requested drive torque L in order to simplify the above-mentioned turning control procedure, and in this case, the target drive torque is set to the reference drive torque that can be calculated using Equation 10. TB may be adopted.Furthermore, even when the driver's required drive torque T is taken into account as in this embodiment, instead of setting the weighting coefficient a to a fixed value, the Zζ control is started as shown in FIG. Then, the value of the coefficient α is gradually decreased as time passes, or as shown in FIG. 19, it is gradually decreased according to the vehicle speed, and the proportion of the driver's requested driving torque T6 is gradually increased. Similarly, as shown in FIG. angle δ
It is also possible to increase the value of the coefficient a as the value of 8 increases, so that the vehicle 68 can be driven safely, especially on turning roads where the radius of curvature gradually becomes smaller. Furthermore, the smaller the measured value of the road surface μ, the larger the coefficient α may be.

In addition, in the arithmetic processing method described above, in order to prevent acceleration/deceleration shock due to sudden fluctuations in the driving torque of the m function 11,
Target drive torque T. When calculating the target drive torque T, the allowable increase/decrease amount T is used. Although the target longitudinal acceleration Gxo is restricted, this restriction may be applied to the target longitudinal acceleration Gxo. When the allowable increase/decrease amount in this case is GK, n
Target longitudinal acceleration Gxo at the time of rotation. .

The calculation process is shown below.

G8゜,,, -G,xo,,, If >GK, C,
=G. -1l+GK
=G - G

Target drive torque T for the above-mentioned turning control. After calculating the fraud, TCL58 calculates these two target drive torques Tos+
Optimal final target drive torque T from TOH. and output it to ECTJ 54. In this case, in consideration of the running safety of the vehicle 68, priority is given to outputting the target drive torque having the smallest numerical value. However, - target drive torque T for slip control for boat fishing. , is the target drive torque T for turning control. Because it is always smaller than □, it is used for slip control,
Final target drive torque T in order of turning ff1J use. All you have to do is choose.

As shown in FIG. 21 showing the flow of this process, the two target drive torques T mentioned above in Mll. ,, After calculating ToH, it is determined in M12 whether or not the slip control flag F is set.

If it is determined in this step M12 that the slip control flag F9 is set, the TCL 58 selects the target drive torque T for slip control as the final target drive torque T in M13, and sends this to the ECU 54. Output.

The ECU 34 stores a map for determining the throttle opening θa using the engine speed N5 and the driving torque of the engine 11 as parameters.
Using this map, calculate the target throttle opening θ corresponding to the current engine speed N6 and this target drive torque Tas.

Read out. Next, the ECU 34 determines this target throttle opening degree θ□. The deviation between the actual throttle opening θ outputted from the throttle opening sensor 56 is determined, and the duty ratio of the pair of torque control solenoid valves 46° 51 is set to a value commensurate with the deviation. Current is applied to the solenoids of the plungers 47 and 52 of the solenoid valves 46 and 51, and the actuator 36 operates to adjust the actual throttle opening θ.
Control is performed so that □ falls to the target value θ7°.

If it is determined in step M12 that the slip control flag F is not set, it is determined in M2S whether the turning control flag F is set.

At this M2S step, the turning control flag F is set. If it is determined that H is set, the target drive torque T for turning control is set as the final target drive torque T0. , M2S
, and proceed to step M14.

On the other hand, the turning control flag F is set in step M15.

, 4 is not set, TCL5
8 outputs the maximum torque of the engine 11 as the final target drive torque T, which causes the ECU 54 to reduce the duty rate of the torque control solenoid valve 46.51 to the 0% side. A driving torque corresponding to the amount of depression of 26 is generated. In this case, in this embodiment, the duty rate of the pair of torque control solenoid valves 46 and 51 is not unconditionally set to 0%, and the ECU 34 adjusts the actual accelerator opening θ9 and the maximum throttle opening regulation value. In comparison, if the accelerator opening θ6 exceeds the maximum throttle opening regulation value, the pair of torque i#lI!l solenoid valves 4 is set so that the accelerator opening θ6 exceeds the maximum throttle opening regulation value.
Determine the duty rate of 6,51 and set the plunger at 47°5.
Drive 2. This maximum throttle opening regulation value is a function of the engine speed N5, and is set to a certain value (for example, 2000 rp
m) In the above cases, the opening is set at or near full open, but in the low rotation range below this, the opening should be gradually reduced to several tens of percent as the engine speed NE decreases. be.

The reason for regulating the throttle opening θ is that T
This is to improve the responsiveness of control when the CL 58 determines that there is a need to reduce the driving torque of the engine 11. That is, according to the current design policy 1 of the vehicle 68, in order to improve the acceleration performance and maximum output of the vehicle 68, there is a tendency to make the bore diameter (passage cross section IN) of the throttle body 16 extremely large, and the engine 11 is in the low rotation region. In this case, the intake air amount becomes saturated when the throttle opening degree θ1 is about several tens of percent. Therefore, rather than setting the throttle opening θ1 at or near full wI depending on the amount of depression of the accelerator pedal 26, by regulating it to a predetermined position, the target when a drive torque reduction command is issued. Throttle opening θ
This is because the deviation between 1o and the actual throttle opening θ is reduced, and the throttle opening can be quickly lowered to the target throttle opening θTo.

According to the above-described vehicle output control method, the magnitude of the lateral acceleration that occurs when the vehicle turns is calculated based on the detection signals from the steering angle sensor and the vehicle speed sensor, and the Since this method reduces the engine drive torque, it is possible to estimate the magnitude of lateral acceleration more quickly than the conventional method of detecting the magnitude of lateral acceleration based on the yaw rate, etc. that actually occurs in the vehicle. . As a result, there is almost no control delay when turning, and it is possible to appropriately suppress the lateral acceleration of the vehicle and safely and reliably run through the turning path. Further, by using this torque control device, it is also possible to reduce shocks and the like during gear changes in an automatic transmission. Furthermore, since the degree of reduction of the engine drive torque is adjusted in accordance with the μ of the road surface, it is possible to turn extremely safely.

<Effects of the Invention> According to the present invention, the stability factor is calculated based on the steering angle, lateral acceleration, and vehicle speed of the vehicle, and the lateral acceleration (unit: g) when the calculated value matches a predetermined value is used to calculate the stability factor of the road surface. Since the coefficient of friction is estimated, it can be easily measured while the vehicle is running.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an embodiment of an engine control system that can realize the method of the present invention, Fig. 2 is a conceptual diagram thereof, Fig. 3 is a sectional view showing the drive mechanism of the throttle valve, and Fig. 4 is a flowchart showing the overall flow of the control, Fig. 5 is a flowchart showing the flow of the neutral position learning correction control of the steering shaft, and Fig. 6 is a flowchart showing the correction state of the learned value when learning and correcting the neutral position of the steering shaft. A graph showing an example, Fig. 7 is a graph showing the relationship between the coefficient of friction between the tire and the road surface and the slip rate of this tire, Fig. 8 is a map showing the relationship between vehicle speed and running resistance, and Fig. 9 is a map showing the relationship between the corrected longitudinal acceleration and the speed correction amount, Fig. 10 is a flowchart showing the flow of slip control, Fig. 11 is a block diagram showing the procedure for calculating the target drive torque for turning, and Fig. 12 is a A graph explaining the present invention in detail from the stability factor, road surface μ, and lateral acceleration, Fig. 13 is a map showing the relationship between target lateral acceleration, target longitudinal acceleration, and vehicle speed, and Fig. 14 is a graph showing the relationship between the target lateral acceleration, target longitudinal acceleration, and vehicle speed. Figure 15 is a map showing the relationship between engine speed, accelerator opening, and required drive torque; Figure 16 is a flowchart showing the flow of turning control; Figure 17 is a flowchart showing the flow of turning control. Graphs showing the relationship between angle, target drive torque, and longitudinal acceleration, Figures 18 and 20 are graphs showing the relationship between time after control start and weighting coefficients, and Figure 19 shows vehicle speed and weighting coefficients. FIG. 21 is a flow chart showing an example of the final target torque selection operation, and FIG. 22 is a flow chart showing an example of road surface μ measurement. Also, in the figure, 11 is the engine, 12 is the combustion chamber, 13 is the intake pipe, 14i, t @ air passage 15 is the throttle valve, 17
is the throttle shaft, 18 is the accelerator lever, 19 is the throttle lever, 26 is the accelerator pedal, 27 is the cable, 2
9 is a claw part, 30 is a stopper, 36 is an actuator,
38 is a control rod, 42 is a connection pipe, 43 is a vacuum tank, 44 is a check valve, 45 and 50 are pipes, 46.51 is a J:4 magnetic valve for torque control, and 54 is an ECU. 55 is a crank angle sensor, 56 is a throttle opening sensor, 57 is an idle switch, 58 is a TCL, 59 is a 7
ri-t'le opening sensor, 60, 61 are front wheels, 62,
63 is the front wheel rotation sensor, 64°65 (rear wheel, 66.6
7 is a rear wheel rotation sensor, 68 is a vehicle, 69 is a steering shaft, 70
1 ma I! ! ! Rudder angle sensor, 71 communication cable, 100
is the linear G sensor, A is the stability factor,
μ is the *g coefficient of the road surface, Fljl is the turning control flag, F
, are flags under control control, Fl, l are flags that have learned the steering neutral position, Fo are flags under turning control, GXl, ti1
'iI rear acceleration, G8o is target longitudinal acceleration, G7 is lateral acceleration, Gvo is target lateral acceleration, G'Y. +yo μ is the corrected target lateral acceleration, g is the gravitational acceleration, To is the target drive torque for slip control, and T08 is the target iI for turning control! Dynamic torque, To. is the target drive torque for turning control, T. is the final target drive torque, and T6 is the base! ! ! ! driving torque,
Td is required driving torque, ■ is vehicle speed, S is slip amount, θ
8 is the accelerator opening, θ is the throttle opening, θ is the target throttle opening, δ is the steering angle of the front wheels, δ is the turning angle of the steering shaft, and δ is the neutral position of the steering shaft. Agent for patent applicant Mitsubishi Motors Corporation

Claims (1)

[Scope of Claims] Detecting a steering angle of a steering wheel of a vehicle, lateral acceleration and vehicle speed of a vehicle; Performing a calculation to obtain a stability factor based on the detected steering angle, lateral acceleration and vehicle speed; Stability factor Compare the calculated value of the stability factor with a predetermined value worse than the standard stability factor, and use the detected value of the lateral acceleration when the calculated value of the stability factor matches the predetermined value as the coefficient of friction of the road surface. A method for measuring a road surface friction coefficient.