JPH05272371A - Drive force control device for vehicle - Google Patents

Abstract

PURPOSE:To secure running stability of a vehicle to be excellent even when an irregularity in a running road surface is large by decreasing drive torque when an acceleration degree of the vehicle exceeds a reference value, and decreasing the reference value more as the irregularity in the running road surface is larger. CONSTITUTION:In controlling drive force of a vehicle, an acceleration degree of the vehicle is detected by an acceleration detection means 100 first. Next, when the detected acceleration degree exceeds a specified reference value which is preliminarily determined, drive torque of the vehicle is decreased by a torque decreasing means 102. Irregularity in a running road surface is then detected by a road surface irregularity detection means 104. The reference value is controlled by a reference value control means 106 to decrease the specified reference value more as the detected irregularity is larger. Running stability of the vehicle can thus be secured to be excellent even when the irregularity in the running road surface is large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle driving force control device.

[0002]

2. Description of the Related Art JP-A-61-253228 discloses
When the acceleration acting on the vehicle (composition of the lateral acceleration of the vehicle and the longitudinal acceleration) exceeds a predetermined reference value,
A drive force control device for a vehicle is disclosed that reduces the drive torque of the vehicle.

[0003]

However, since this apparatus does not consider the unevenness of the traveling road surface, the degree of unevenness is the same as the reference value when traveling on a flat road (good road) with almost no unevenness. If it is used during traveling on a large road (bad road), the ground contact of the wheels will deteriorate when the vehicle travels on a bad road, resulting in a problem that the running stability of the vehicle will deteriorate.

[0004]

In order to solve the above problems, according to the present invention, as shown in the block diagram of the invention of FIG. 1, an acceleration detecting means 100 for detecting the acceleration of a vehicle,
A torque reducing means 102 for reducing the driving torque of the vehicle when the acceleration of the vehicle detected by the acceleration detecting means 100 exceeds a predetermined reference value, and a road surface unevenness state detecting means 104 for detecting the unevenness state of the traveling road surface. The reference value control means 106 reduces the reference value as the degree of unevenness of the traveling road surface detected by the road surface unevenness state detection means 104 increases.

[0005]

[Function] The reference value is reduced as the degree of unevenness of the road surface is increased. For this reason, when the acceleration of the vehicle exceeds the reduced reference value, the driving torque is reduced, so that the allowable acceleration of the vehicle is reduced.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows an overall view of a vehicle adopting one embodiment of the driving force control device of the present invention. Referring to FIG. 2, 1
Is a rear-wheel drive vehicle, 2 is an engine, 3 is an intake passage of the engine 2, 4 is a throttle valve which is arranged in the intake passage 3 and is driven by a step motor 5, 6 is a transmission, and 7 and 8 are drive wheels. Rear wheel and left rear wheel, 9
Are drive shafts for transmitting the driving force of the engine 2 to the rear wheels 7, 8 and 10 and 11 are right front wheels and left front wheels which are not drive wheels, respectively.

The electronic control unit 20 is composed of a digital computer, and has a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, a CPU (Microprocessor) 24, and an input port 25 which are mutually connected by a bidirectional bus 21. And an output port 26. RR wheel speed sensor 35, LR wheel speed sensor 3
6, RF wheel speed sensor 37, and LF wheel speed sensor 3
8 detects the wheel speed of each of the right rear wheel 7, the left rear wheel 8, the right front wheel 10, and the left front wheel 11, and each detection signal is input to the input port 25. The vehicle speed sensor 39 detects the vehicle speed, and its output signal is input to the input port 25. The steering angle sensor 40 detects the rotation angle of the steering shaft, and its output signal is input to the input port 25. A load sensor 41 that generates an output voltage proportional to the depression amount of the accelerator pedal 12 is connected to the accelerator pedal 12, and the output voltage of the load sensor 41 is input to the input port 25 via the AD converter 27.

The yaw rate sensor 42 outputs a detection signal representing the yaw rate γ acting on the vehicle body by detecting the rotational speed of the vehicle body about the vertical axis of the center of gravity, and this output signal is input through the AD converter 28 to the input port 25. Entered in.
The front-rear direction G sensor 43 detects the front-rear direction acceleration acting on the vehicle, and the detection signal is input to the input port 25 via the AD converter 29. The lateral G sensor 44 detects lateral acceleration acting on the vehicle, and the detection signal is input to the input port 25 via the AD converter 30. Brake switch 45 that turns on when the brake pedal is depressed
Is connected to the input port 25. The engine speed sensor 46 detects the engine speed, and the detection signal is input to the input port 25.

On the other hand, the output port 26 is connected to the step motor 5 via a drive circuit 31. 3 and 4 show a routine for obtaining the target throttle valve opening. This routine is executed by interruption at regular time intervals. Referring to FIGS. 3 and 4, first, in step 50, the longitudinal acceleration G _X (m / s ² ) of the vehicle detected by the longitudinal G sensor 43 and the lateral direction of the vehicle detected by the lateral G sensor 44. Acceleration G _Y (m / s ² ) is read. The G sensors 43 and 44 do not have to be provided to obtain the longitudinal acceleration G _X and the lateral acceleration G _Y, and the estimated values may be obtained by the following equations.

G _X = ΔV / Δt G _Y = V _SO · V _MNS / L ΔV: Amount of change in vehicle speed between time Δt V _SO : Even when wheels are slipping on the road surface, Estimated value of relative speed (estimated vehicle speed) V _MNS : Front wheel left / right wheel speed difference L: Tread space Next, at step 51, the acceleration G (m
/ S ² ) (vehicle longitudinal acceleration G _X and lateral acceleration G
(Composition with _Y ) is calculated from the following equation.

G = (G _X ² + G _Y ² ) ^{1/2 In} step 52, the yaw rate γ calculated based on the detection signal of the yaw rate sensor 42 is read. In step 53, the friction coefficient μ of the road surface is obtained based on the longitudinal acceleration G _X read in step 50.
The friction coefficient μ is estimated as shown in Table 1.

[0012]

[Table 1]

Referring to Table 1, | G _X | <1.5 m /
In the case of s ² , the friction coefficient μ was determined to be extremely low, and 1.5
When m / s ² ≦ | G _X | <3 m / s ² , friction coefficient μ
Is determined to be low, and 3 m / s ² ≦ | G _X | <5 m / s ²
In the case of, the coefficient of friction μ is judged to be medium and 5 m / s
^{When 2} ≦ | G _X |, it is determined that the friction coefficient μ is high.

In step 54, the unevenness of the road surface is estimated. The unevenness of the road surface is estimated as follows. The number of times that the wheel acceleration α _FW exceeds the first reference value G _N is less than or equal to 3 times per second for both front wheels 10 and 11, and the wheel acceleration α _RW is the first for both rear wheels 7 and 8. Reference value G
_{When the} number of times exceeding _N is 4 times or less per second, it is determined that the degree of unevenness of the road surface is small and it is determined that the road is good. Here, the first reference value G _N is, for example, +20 m / s ² .

On the other hand, one of the front wheels 10 and 11 is
And the wheel acceleration α_FWIs the first reference value G_NThe number of times exceeds
More than twice in 0.24 seconds or both rear wheels 7,
For one of the eight, the wheel acceleration α_RWIs the first reference value
G_NWhen the number of times exceeds 3 times or more in 0.24 seconds
It is judged that the road surface is uneven and the road is bad.
Or both front wheels 10 and 11
Acceleration α_FWIs the second reference value G_WOver 1 second
8 times or less, and for both rear wheels 7 and 8,
Acceleration α_RWIs the second reference value G_W9 times per second
If it is less than or equal to the number of times, it is determined to be a bad road. here
Then, the second reference value G_WIs + 60m / s ²Is.

Further, for one of the front wheels 10 and 11, the number of times that the acceleration α _FW of the wheel exceeds the second reference value G _W is four or more times in 0.336 seconds, or both the rear wheels 7 and 11. When the number of times that the wheel acceleration α _RW exceeds the second reference value G _W is 5 times or more in 0.336 seconds, the degree of unevenness of the road surface is determined to be extremely large, and one of the It is determined that

In step 55, the running environment is estimated. The estimation of the traveling environment is performed as follows, for example. The average vehicle speed between T _ST (for example, 300 seconds) is 70 km / h or more, and the minimum vehicle speed between T _ST is 60 km / h.
More than km / h, the maximum steering angle between T _ST is 60de
When it is less than or equal to g and when it is determined that the road condition is good between T _ST , it is determined that the vehicle is running at high speed.

On the other hand, the average vehicle speed between T _ST is 20 km /
h or less, the maximum vehicle speed between T _ST is 30 km / h or less, the number of times the brake switch is turned on between T _ST is one or more, and the engine speed between T _ST is the idle speed or more. It is determined that the vehicle is running in a traffic jam. Further, the average vehicle speed between T _ST is 50 km / h or less, and the absolute value of the lateral acceleration G _Y is 4 between T _ST.
When the number of times m / s ² or more is 5 or more, the maximum steering angle between T _ST is 90 deg or more, and the number of times the brake switch is turned on between T _ST is 3 or more,
It is determined that the mountain is running.

If the vehicle is not traveling at a high speed, is not traveling in a traffic jam and is not traveling in the mountains, or if the vehicle speed after ignition is not 5 km / h or more, it is determined that the vehicle is traveling on a city road. In step 56, the reference acceleration G _SH which is the reference value is obtained from the following equation. As will be described later, when the acceleration G is larger than the reference acceleration G _SH , the throttle valve opening is reduced.

G _SH = G μ · K γ · K _f · K _e where G μ is the basic acceleration based on the friction coefficient μ of the road surface and is given by Table 2.

[0021]

[Table 2]

Referring to Table 2, the smaller the friction coefficient μ, that is, the lower the grip force of the wheel, the smaller Gμ, and thereby the smaller the reference acceleration G _SH . As a result, the allowable acceleration of the vehicle is reduced.
Kγ is a coefficient based on the yaw rate γ and is given by Table 3.

[0023]

[Table 3]

Referring to Table 3, Kγ decreases as the yaw rate increases, and therefore the reference acceleration G _SH decreases as the yaw rate increases. K _f is a coefficient based on the unevenness of the road surface, and is given by Table 4.

[0025]

[Table 4]

Referring to Table 4, as the degree of road surface irregularities is large, i.e., to deteriorate the ground of the tire is higher running stability of the vehicle is deteriorated, decreasing the K _f, whereby reference acceleration G _SH Is small. K _e is a coefficient based on the driving environment and is given by Table 5.

[0027]

[Table 5]

Referring to Table 5, in these cases, K _{e is set} to 1.0 on the basis of the congested road and the city road, and K _e is increased to 1.1 because the curvature of the curve is large on the highway.
On the other hand, on a mountain road where the curvature of the curve is small, K _e is reduced to 0.9. In step 57, the basic throttle valve opening θ _M is obtained from the map based on the accelerator pedal depression amount L. FIG. 5 shows the relationship between the accelerator pedal depression amount L and the basic throttle valve opening θ _M. The throttle valve opening degree θ _M is increased as the accelerator pedal depression amount L increases.

Referring again to FIGS. 3 and 4, at step 58 it is determined whether the vehicle acceleration G is greater than the reference acceleration G _SH . If G ≦ G _SH , that is, if the acceleration G of the vehicle is less than the allowable acceleration and there is no risk of the wheels slipping, the routine proceeds to step 59, where the target throttle opening θ _TH
The basic throttle opening θ _M is stored in. In a routine (not shown), the step motor 5 is controlled so that the throttle valve opening becomes the target throttle valve opening θ _TH .

On the other hand, G> G_SH, That is, of the vehicle
The acceleration G may exceed the allowable acceleration and the wheels may slip.
If so, go to step 60 and open the target throttle valve.
Degree θ _THIs the previous throttle valve opening θ_TH0.9 times less
Be punished. G> G_SHTarget throttle valve as long as
Opening θ_THIs reduced by 0.9 times. By this
Reduce the drive torque of the vehicle and prevent the wheels from slipping.
Can be suppressed. In step 61, the target slot is
Torque valve opening θ_THIs the basic throttle valve opening θ_MWhether or not
To be judged. θ_TH≤ θ_M, Then θ_THIs in step 60
The calculated value remains as it is, and other routines (not shown)
At θ_THThe throttle valve opening is controlled based on
Be done.

On the other hand, when θ _TH > θ _M , that is, when the accelerator pedal 12 is released when the vehicle starts to slip due to large acceleration of the vehicle, θ _M becomes small. Gives priority to θ _M. Therefore, the process proceeds to step 59, is stored theta _M in theta _TH, the throttle valve opening is made to control the other routines (not shown) based on the theta _TH.

As described above, according to this embodiment, when the acceleration G of the vehicle is larger than the reference acceleration G _SH , the wheels may slip, so the throttle valve opening is reduced and the driving torque of the vehicle is reduced. Therefore, it is possible to prevent the wheel from slipping and the traveling stability from being deteriorated. Further, as the degree of unevenness of the road surface is increased, the reference acceleration G _SH is reduced to reduce the allowable acceleration of the vehicle. It is possible to suppress deterioration of running stability of the vehicle.

[0033]

Since the allowable acceleration of the vehicle is reduced as the degree of unevenness on the traveling road surface is reduced, deterioration of the running stability of the vehicle can be suppressed even if the degree of unevenness on the traveling road surface is increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is an overall view of a vehicle that employs an embodiment of the driving force control device of the present invention.

FIG. 3 is a flowchart for obtaining a target throttle valve opening.

FIG. 4 is a flowchart for obtaining a target throttle valve opening.

FIG. 5 is a diagram showing a relationship between an accelerator pedal depression amount L and a basic throttle valve opening θ _M.

[Explanation of symbols]

 4 ... Throttle valve

Claims (1)

[Claims] 1. An acceleration detecting means for detecting an acceleration of a vehicle, and a torque reducing means for reducing a driving torque of the vehicle when the acceleration of the vehicle detected by the acceleration detecting means exceeds a predetermined reference value. A vehicle including: a road surface unevenness state detecting means for detecting a road surface unevenness state; and a reference value control means for reducing the reference value as the degree of the road surface unevenness detected by the road surface unevenness state detecting means increases. Drive force control device.