JPH1182091A - Driving force control system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress slips of the driving wheels of a vehicle without causing problems including overheat of the catalyst, and prevent a reduction in speed and acceleration performance of the vehicle caused by a fuel cut. SOLUTION: The number of fuel-cut cylinders Nfc is computed which is required for the reduction of an average slippage SLr of the left and right rear wheels down to a specified value. (S10-S80) It the engine is low-loaded or runs at low speed or the required number of fuel-cut cylinders Nfc exceeds the limited number of fuel-cut cylinders Nfco (S90, 100), fuel is cut at the number of the cylinders Nfc. If the engine is high-loaded and runs at high speed and that the required cylinder number Nfc is not larger than the limited cylinder number Nfco (S90, 100), Nfc is corrected up to Nfco for correction when the coefficient of friction μ of the road surface is small (S130). Nfc is corrected down to zero when this friction coefficient μ of the road surface is relatively large (S140).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force control device for a vehicle, and more particularly, to a driving force control device for suppressing a driving slip of a driving wheel by cutting fuel.

[0002]

2. Description of the Related Art As one of driving force control devices for a vehicle such as an automobile, when the driving slip of a driving wheel is excessive, a fuel cut of an engine is performed with a required number of fuel cut cylinders corresponding to a degree of the driving slip. For example, Japanese Patent Application Laid-Open No. 8-112210 discloses a driving force control device that suppresses a driving slip of a driving wheel. A driving force control device configured to prohibit the fuel cut of a small number of cylinders when such a situation occurs is described.

According to such a driving force control device, for example, when the required number of fuel cut cylinders is small and the operating state of the engine is an operating state in which the exhaust gas reduction catalyst may be overheated, the fuel cut is prohibited. Therefore, it is possible to reduce the possibility that a problem such as overheating of the catalyst due to the fuel cut will occur.

[0004] Further, as one of the fuel cut type driving force control devices, the fuel cut of a small number of cylinders is prohibited when there is a risk of overheating of the catalyst. A driving force control device has been proposed in which the number of fuel cut cylinders is increased and corrected, thereby suppressing the occurrence of problems such as overheating of the catalyst and suppressing the driving slip of the driving wheels.

[0005]

In general, even when the driving slip of the driving wheels is excessive, when the friction coefficient of the road surface is very low such as an icy and snowy road surface, the driving slip of the driving wheels is reduced and the driving wheels are reduced. It is difficult to recover the grip of the road, but when the coefficient of friction of the road is not as low as that of an icy and snowy road such as a wet road, the drive slip of the drive wheels can be reduced relatively quickly to recover the grip of the drive wheels. .

However, in the driving force control device according to the above-mentioned proposal, since the friction coefficient of the road surface is not taken into consideration, the driving slip of the driving wheels is surely reduced even when the friction coefficient of the road surface is very low. In order to recover the grip of the drive wheel early, the required number of fuel cut cylinders increases, so the drive torque of the drive wheel becomes too low in a situation where the vehicle runs on a wet road surface, so that the vehicle There is a problem that the vehicle stalls or the acceleration performance of the vehicle deteriorates.

The present invention has been made in view of the above-mentioned problems in a fuel cut type driving force control device, and
The main problem of the present invention is that when the number of required fuel cut cylinders is equal to or less than the limit number of fuel cut cylinders determined by the operation state of the engine, the required number of fuel cut cylinders is increased or decreased according to the road surface friction coefficient to increase or decrease the number of required catalysts. It is an object of the present invention to suppress a drive slip of a drive wheel while avoiding a problem such as overheating, and to prevent a vehicle from stalling or deteriorating a vehicle's acceleration performance due to a fuel cut.

[0008]

According to the present invention, there is provided a driving force control apparatus for a vehicle which suppresses a driving slip of a driving wheel by a fuel cut according to the present invention. Means for calculating the required number of fuel cut cylinders based on the magnitude of the wheel drive slip; means for calculating the limit number of fuel cut cylinders based on the operating state of the engine; means for estimating the road surface friction coefficient; When the number of cylinders is equal to or less than the limit fuel cut cylinder number, the required fuel cut cylinder number is corrected to 0 if the road surface friction coefficient is equal to or more than a predetermined value, and if the road surface friction coefficient is less than a predetermined value. Means for correcting the required number of fuel cut cylinders to the limit number of fuel cut cylinders.

According to the first aspect of the present invention, when the required number of fuel cut cylinders calculated based on the magnitude of the drive slip of the drive wheels is equal to or less than the limit fuel cut cylinder, the friction coefficient of the road surface is reduced. Is equal to or greater than a predetermined value, the required number of fuel cut cylinders is corrected to 0 and fuel cut is prohibited, so the vehicle stalls due to fuel cut when the road surface friction coefficient is not a very low value. If the friction coefficient of the road surface is less than a predetermined value, the required fuel cut cylinder number is corrected to increase to the limit fuel cut cylinder number. This reliably suppresses the occurrence of problems such as overheating of the catalyst and the like.

[0010]

According to a preferred aspect of the present invention, in the above-described configuration, the magnitude of the driving slip of the driving wheel is a driving slip amount or a driving slip ratio. (Preferred embodiment 1).

According to another preferred aspect of the present invention, in the configuration of the first aspect, the means for calculating the limit fuel cut cylinder number based on the operating state of the engine is provided when the operating state of the engine is a predetermined number. When the engine is in the high-load and high-speed operation state, the limit fuel cut cylinder number is set to a preset value (preferred mode 2).

According to another preferred embodiment of the present invention, in the configuration of the first aspect, the means for estimating the friction coefficient of the road surface includes the coefficient of friction of the road surface based on the longitudinal acceleration and the lateral acceleration of the vehicle. (Preferred embodiment 3).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing one embodiment of a driving force control device according to the present invention applied to a rear wheel drive vehicle.

In FIG. 1, reference numeral 10 denotes an engine, and a driving force of the engine 10 is transmitted to a propeller shaft 14 via an automatic transmission 12 including a torque converter and a transmission. The driving force of the propeller shaft 14 is controlled by the differential 16 to the left rear wheel axle 18L.
And the right rear wheel axle 18R, whereby the right and left rear wheels 20RL and 20RR as drive wheels are rotationally driven.

On the other hand, the left and right front wheels 20FL and 20FR are both driven wheels and steered wheels. Tie rods are provided by a rack-and-pinion type power steering device 24 driven in response to the driver turning the steering wheel 22. Steered via 26L and 26R.

The output of the engine 10 is controlled by a throttle valve 30 provided in the intake passage 28. The throttle valve 30 is controlled in accordance with the depression amount of an accelerator pedal (not shown in FIG. 1) operated by the driver. You. A fuel injection device 32 is provided in the intake passage 28 for each cylinder in proximity to the engine 10, and each fuel injection device 32 is controlled by an engine control computer 34.

A signal indicating the opening degree φ of the throttle valve 30 is input from the throttle position sensor 36 to the engine control computer 34, and a signal indicating the amount of intake air and other engine control information is input from another sensor 38. Further, a fuel cut request signal, which will be described later, is input to the engine control computer 34 from the traction control computer 40 as necessary. The computer 34 responds to the fuel cut request signal by operating the fuel injection device 32 having the required fuel cut cylinder number Nfc. The fuel cut is performed by stopping the operation.

The traction control computer 40 has left and right front wheels 20FL, 20FR and left and right rear wheels 20RL, 20RR.
Wheel speed sensors 42FL, 42FR, 42RL provided in the
Wheel speed Vwi (i = fl, fr, rl, input from 42RR)
rr), a signal indicating the vehicle speed V from the vehicle speed sensor 44, a signal indicating the yaw rate γ of the vehicle from the yaw rate sensor 46, the longitudinal acceleration sensor 48 and the lateral acceleration sensor 50.
Thus, signals indicating the longitudinal acceleration Gx and the lateral acceleration Gy of the vehicle are input.

Based on the wheel speed Vwi, the traction control computer 40 drives the right and left rear wheels 20RL and 20RL.
The average drive slip amount SLr of 0RR is calculated, the target torque Tet of the engine is calculated based on the average drive slip amount SLr, etc., and the output torque Tea of the engine is calculated based on the throttle opening φ and the engine speed Ne. The required fuel cut cylinder number Nfc is calculated based on the target torque Tet, the output torque Tea, and the like, and a fuel cut request signal including the required fuel cut cylinder number is output to the engine control computer 34.

Note that the engine control computer 34 and the traction control computer 40 are actually
It may be a microcomputer having a well-known configuration including a PU, a ROM, a RAM, and an input / output port device, and may be integrated if necessary.

Next, the fuel cut cylinder number calculation routine executed by the traction control computer 40 will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, in step 10, the wheel speed V
A signal indicating wi is read, and in step 20, the average wheel speed Vwf of the left and right front wheels is calculated according to the following equation (1).
In step 30, the average wheel speed Vwr of the left and right rear wheels is calculated according to the following equation (2).
At 0, the average driving slip amount SLr of the left and right rear wheels is calculated according to the following equation (3).

[0024]

## EQU1 ## Vwf = (Vwfr + Vwfl) / 2

## EQU2 ## Vwr = (Vwrr + Vwrl) / 2

## EQU3 ## SLr = Vwr-Vwf

In step 50, it is necessary to determine whether or not the average driving slip amount SLr of the left and right rear wheels is equal to or greater than a reference value SLro (positive constant), that is, to reduce the driving wheel driving force by fuel cut. If a negative determination is made, the required fuel cut cylinder number Nfc is set to 0 in step 60, and if an affirmative determination is made, the routine proceeds to step 70.

In step 70, based on the average driving slip amount SLr of the left and right rear wheels, the slip angle β of the vehicle body, the engine speed Ne, the engine intake air amount A, etc., the engine is operated in a manner known in the art. In step 80, the target torque Tet of the engine is calculated based on the throttle opening φ and the engine speed Ne.
Is calculated, and the required fuel cut cylinder number Nfc is calculated based on the target torque Tet, the output torque Tea, and the friction torque Tef of the engine.

The slip angle β of the vehicle body is, for example, a deviation Gy between the product V · γ of the lateral acceleration Gy and the vehicle speed V and the yaw rate γ.
By calculating the deviation of the lateral acceleration as −V · γ, that is, the side slip acceleration Vyd of the vehicle, and calculating the side slip velocity Vy of the vehicle body by integrating the deviation Vyd of the lateral acceleration,
It may be calculated as the ratio Vy / V of the side slip speed Vy of the vehicle body to the vehicle speed V.

In step 90, it is determined whether or not the engine 10 is in a high-load and high-speed operation state of a predetermined value or more based on the engine intake air amount A and the engine speed Ne. Step 1 when done
Proceeds to 50, and if a positive determination is made, step 10
Go to 0.

In step 100, the limit fuel cut cylinder required to prevent overheating of the catalyst incorporated in the exhaust system of the engine 10 when the engine 10 is in a high-load and high-speed operation state exceeding a predetermined value. Assuming that the number is Nfco (a positive constant integer), it is determined whether or not the required fuel cut cylinder number Nfc calculated in step 80 is equal to or less than the limit fuel cut cylinder number Nfco, and a negative determination is made. If the determination is affirmative, the process proceeds to step 110.

The required fuel cut cylinder number Nfc is equal to the engine 1
If the number of cylinders of 0 is Ne, it is 1 to Ne, and the limit fuel cut cylinder number Nfco is 3 when the engine is, for example, a 4-cylinder engine.

In step 110, the friction coefficient μ of the road surface is estimated based on the longitudinal acceleration Gx and the lateral acceleration Gy of the vehicle in accordance with the routine shown in FIG.
At 0, it is determined whether or not the friction coefficient μ of the road surface is equal to or more than the reference value μo (positive constant), that is, whether or not the friction coefficient of the road surface is a relatively high value is determined. When the determination is made, the fuel cut cylinder number Nfc is rounded up to Nfco in step 130, and when the affirmative determination is made, the fuel cut cylinder number Nfc is determined in step 140.
fc is rounded down to zero.

In step 150, a fuel cut request signal including the required fuel cut cylinder number Nfc is output to the engine control computer 34, whereby the operation of the fuel injection device 32 for the required fuel cut cylinder number Nfc is stopped. Cuts the fuel. When Nfc is 0, no fuel cut is performed.

In step 111 of the road friction coefficient μ calculation routine, the horizontal acceleration Gxy of the vehicle for calculating the estimated value μ of the road surface friction coefficient based on the longitudinal acceleration Gx and the lateral acceleration Gy of the vehicle is as follows. It is calculated according to the equation

## EQU4 ## Gxy = (Gx ² + Gy ² ) ^1/2

In step 112, the horizontal acceleration Gxy
Is determined to be equal to or more than the estimated value μ (n-1) of the friction coefficient of the road surface one cycle before, and when a positive determination is made, the coefficient K is set to 1 in step 113, When a negative determination is made, the coefficient K is set to 0.01 in step 114. In step 115, the estimated value μ of the road surface friction coefficient is calculated according to the following equation (5).

Μ = (1−K) · μ (n−1) + K · Gxy

In the illustrated embodiment, the coefficient of friction of the road surface is calculated as the square root of the sum of the squares of Gx and Gy, but may be calculated by any method known in the art. For example, it may be estimated from the absolute value of the lateral acceleration Gy of the vehicle, and lateral acceleration components Gyfy and Gyry at the front wheel position and the rear wheel position generated by yawing of the vehicle are calculated, and these components and the vehicle are calculated. The lateral acceleration components Gyf and Gyr at the front wheel position and the rear wheel position are calculated as the sum of the lateral accelerations Gy, and the larger value of Gyf and Gyr is calculated as the lateral acceleration Gys, and the square root of the sum of squares of Gx and Gys is calculated. It may be calculated.

Thus, according to the illustrated embodiment, in steps 10 to 40, the average driving slip amount S of the left and right rear wheels is set.
Lr is calculated, and it is determined in step 50 whether or not the drive wheel driving force needs to be reduced by fuel cut. If a negative determination is made, in step 60 the required fuel cut cylinder number Nfc is determined. Is set to 0. However, if an affirmative determination is made in step 50, a target engine torque Tet required to reduce the drive slip of the left and right rear wheels to a required value is calculated in step 70,
In step 80, the number N of fuel cut cylinders required to set the output torque of the engine 10 to the target engine torque Tet
fc is calculated.

In step 90, it is determined whether or not the engine 10 is in a high-load and high-speed operation state of a predetermined value or more, and in step 100, the required fuel cut cylinder number Nfc is set to the limit fuel cut. It is determined whether or not the number of cylinders is equal to or less than Nfco. If it is determined in step 90 that the engine 10 is not in a predetermined high load and high rotation operating state, or in step 100, If it is determined that the number of fuel cut cylinders Nfc is larger than the limit number of fuel cut cylinders Nfco, the required fuel cut indicating the required number of fuel cut cylinders Nfc calculated in step 80 in step 150. The cylinder number signal is sent from the traction control computer 40 to the engine control computer 3.
4 is output.

On the other hand, in step 90, it is determined that the engine 10 is in a predetermined high-load and high-speed operation state, and in step 100, the number of fuel cut cylinders Nfc is reduced to the limit number of fuel cut cylinders Nfco. If the following is determined, the friction coefficient μ of the road surface is estimated in step 110. Then, in step 120, it is determined whether or not the friction coefficient of the road surface is a relatively high value. If a negative determination is made, in step 130, the required fuel cut cylinder number Nfc is rounded up to Nfco and corrected. If an affirmative determination is made, the required fuel cut cylinder number Nfc is corrected to be rounded down to 0 in step 140, and the required fuel cut cylinder number signal indicating the corrected required fuel cut cylinder number Nfc is corrected in step 150. Output from the control computer 40 to the engine control computer 34.

Accordingly, when the driving slip amounts of the left and right rear wheels are not excessive, a negative determination is made in step 50, and the required fuel cut cylinder number Nfc is set to 0 in step 60. It is not executed, and therefore, the driving wheel driving force is not reduced by the fuel cut.

On the other hand, if the drive slip amounts of the left and right rear wheels become excessive, an affirmative determination is first made in step 50, and when the engine 10 is not in the predetermined high load and high speed operation state or when the required fuel If the cut cylinder number Nfc is greater than the limit fuel cut cylinder number Nfco, a negative determination is made in step 90 or 100, and the drive wheel drive by fuel cut is performed without increasing or decreasing the required fuel cut cylinder number Nfc. A reduction in force is provided.

Further, when the engine 10 is in a predetermined high-load and high-speed operation state and the required fuel cut cylinder number Nfc is equal to or less than the limit fuel cut cylinder number Nfco, a positive determination is made in steps 90 and 100. Done. When the coefficient of friction μ of the road surface is relatively high, step 130
In this case, the required fuel cut cylinder number Nfc is rounded up to Nfco so that the number of fuel cut cylinders is set to be equal to or less than the limit fuel cut cylinder number Nfco and fuel cut is performed. When the friction coefficient μ of the road surface is low, the required fuel cut cylinder number Nfc is corrected to be reduced to 0 in step 140, and the reduction of the driving wheel driving force due to the fuel cut is prevented. By not performing, the stall and deterioration of the acceleration performance of the vehicle are reliably prevented.

While the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are within the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the illustrated embodiment, the magnitude of the drive slip of the drive wheel is calculated as the deviation between the average wheel speed Vwr of the left and right rear wheels and the average wheel speed Vwf of the left and right front wheels according to the equations (1) to (3). Although the average driving slip amount SLr is used, the magnitude of the driving slip may be a driving slip ratio, and the driving slip amount and the driving slip ratio are calculated based on the reference wheel speed of the driving wheel obtained based on the vehicle body speed. May be done.

In the illustrated embodiment, the vehicle is a rear wheel drive vehicle, but the present invention may be applied to a front wheel drive vehicle or a four wheel drive vehicle.

[0045]

As is apparent from the above description, according to the present invention, in a situation where the coefficient of friction of the road surface is not a very low value such as a wet road surface, the vehicle may stall due to fuel cut or the like. It is possible to prevent the acceleration performance of the vehicle from deteriorating.In addition, when the coefficient of friction of the road surface is extremely low such as an icy snowy road surface, the drive slip of the drive wheels is surely suppressed, and problems such as overheating of the catalyst are caused. Occurrence can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a driving force control device according to the present invention applied to a rear wheel drive vehicle.

FIG. 2 is a flowchart illustrating a fuel cut cylinder number Nfc calculation routine in the embodiment.

FIG. 3 is a flowchart showing a subroutine for calculating a friction coefficient μ of a road surface in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Engine 12 ... Automatic transmission 16 ... Differential 32 ... Fuel injection device 34 ... Engine control computer 36 ... Throttle position sensor 40 ... Traction control computer 42FL-42RR ... Wheel speed sensor 44 ... Vehicle speed sensor 46 ... Yaw rate sensor 48 ... Front-back acceleration Sensor 50: Lateral acceleration sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/36 F02D 41/36 A

Claims (1)

[Claims] 1. A driving force control apparatus for a vehicle, which suppresses a driving slip of a driving wheel by a fuel cut, means for calculating a required number of fuel cut cylinders based on a magnitude of a driving slip of the driving wheel, and an operating state of the engine. A means for calculating the limit fuel cut cylinder number based on, a means for estimating a road surface friction coefficient, and when the required fuel cut cylinder number is not more than the limit fuel cut cylinder number, the road surface friction coefficient is not less than a predetermined value. If so, the required fuel cut cylinder number is corrected to 0,
Means for correcting the required number of fuel cut cylinders to the limit number of fuel cut cylinders if the coefficient of friction of the road surface is less than a predetermined value.