JPH06320971A - Driving force control method for vehicle - Google Patents

Abstract

PURPOSE:To enable the behavioral change of a vehicle to be prevented, even upon the occurrence of an error during the control of driving force distribution, by monitoring the operation of a driving force distribution mechanism, and lowering or cutting torque transmitted to a drive shaft. CONSTITUTION:In a vehicle 1, for example, a four-wheel drive vehicle, the torque of an engine 2 is distributed to right and left front wheels 4 and 5, and a propeller shaft 6. Furthermore, the torque of the propeller shaft 6 is distributed to right and left rear wheel drive shafts 11 and 12 via a rear differential gear 7 and each of hydraulic clutches 8 and 9, thereby driving right and left front wheels 13 and 14, and rear wheels 15 and 16. In this case, torque transmitted to the clutches 8 and 9 is adjusted with a hydraulic control valve 18. On the other hand, the operation of the clutches 8 and 9, or the control valve 18 is monitored with a system monitor means 40. When an error is detected with the means 40, torque transmitted to each of the driving wheels 15 and 16 is reduced or cut with a torque limiting means 50 on the basis of a signal for the error.

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 method for a vehicle of the type in which driving force is distributed to the front and rear or to the left and right.

[0002]

2. Description of the Related Art A technique for controlling the front-rear driving force distribution of a four-wheel drive vehicle and a technique for controlling the left-right driving force distribution are known, for example, in Japanese Patent Laid-Open Nos. 1-182128 and 4-321435. .

[0003]

Conventionally, when an abnormality occurs in a sensor unit, a control circuit, a distribution mechanism or the like while the driving force distribution control is being executed, the distribution control is not performed and the normal operation state is set. Due to the return, changes in the behavior of the vehicle may occur. Therefore, an object of the present invention is to provide a technique for coping with a behavior change that is expected to occur.

[0004]

In order to achieve the above object, the present invention reduces the torque transmitted to the drive wheels to a vehicle that transmits the torque of a drive source to the drive wheels via a front-rear or left-right driving force distribution mechanism. Alternatively, it is provided with a torque limiting means for cutting and a system monitoring means for monitoring the operation of the device related to the driving force distribution mechanism. The system monitoring means may reduce or cut the transmission torque when the number of rotations of the drive source is equal to or higher than a predetermined value, and the torque limiting means has at least two stages of large and small, and these are for vehicles. The speed may be switched depending on the speed.

[0005]

When the system monitoring means detects an abnormality, the torque limiting means reduces or cuts the torque transmitted to the drive wheels based on the abnormality signal.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of the reference numerals.
FIG. 1 is a system diagram according to the driving force control method of the present invention. The torque of the engine 2 of the vehicle 1 is distributed to the left and right front wheel drive shafts 4 and 5 and the propulsion shaft 6, and the torque of the propulsion shaft 6 is rear differential. The front wheels 13, 1 are distributed to the left and right rear wheel drive shafts 11, 12 via the device 7 and the hydraulic clutches 8, 9.
4 and the rear wheels 15, 16.

The hydraulic clutches 8 and 9 have a constant relationship between the supplied hydraulic pressure and the transmission torque, and the transmission torque is adjusted by the hydraulic control valve 18. Therefore, the driving force distribution mechanism for the left and right driving rear wheels includes the hydraulic clutches 8 and 9, the hydraulic control valve 18, and the driving force control means 30 described below. The engine 2 is controlled by the engine ECU 20.

The vehicle 1 is provided with a driving force control means 30 for controlling the driving force, a system monitoring means 40, a torque control means 50, and a turning judgment sensor 60, of which the system monitoring means 40 is, for example, sensor monitoring. It comprises a unit 41, a communication monitoring unit 42, a current monitoring unit 43, and a hydraulic pressure monitoring unit 44.

The operation of the driving force control device having the above structure will be described below. In FIG. 1, the engine torque is calculated in STEP1, and in the next STEP2, the front wheels are 60% and the rear wheels are 40%.
Allocate to%.

On the other hand, a steering wheel (not shown)
The turning determination sensor 60, which has obtained information such as the turning angle and the lateral G by turning the steering wheel to the left, outputs the turning information to the driving force control means 3.
Send to 0. In STEP 3, the left and right drive wheels are distributed to the left rear wheel 10% and the right rear wheel 90%, and in STEP 4, the left rear wheel is converted to a current value of 4% and the right rear wheel is 36% in terms of engine torque, and hydraulic control is performed with these. Control valve 18. As a result, 30% of the engine torque is distributed to the left front wheel 13, 30% of the right front wheel 14, 4% of the left rear wheel 15 and 36% of the right rear wheel 16, and a large torque is distributed to the right rear wheel 16 which is the outer rear wheel. Therefore, good turning can be performed without causing understeer.

In the meantime, in the system monitoring means 40, the sensor monitoring section 41 monitors the output signal of the turning determination sensor 60, the communication monitoring section 42 monitors the communication from the engine ECU 20 to the driving force control means 30, and the current monitoring. The section 43 monitors the current value to the hydraulic control valve 18, and the hydraulic pressure monitoring section 44 monitors the hydraulic pressure to the hydraulic clutches 8 and 9.

The current monitoring unit 43 is given a planned current value from the information of STEP 3 (left and right driving force distribution) and STEP 4 (determination of left and right driving force), and the error between the planned current value and the actually measured current value is within an allowable range. (For example, plus or minus 20
%), It is judged to be abnormal, an "abnormal judgment" is made, and a warning signal is sent to the torque limiting means 50. The other sensor monitoring unit 41, the communication monitoring unit 42, and the hydraulic pressure monitoring unit 44 are similarly given respective judgment criteria, and when the reference values are exceeded, an "abnormality judgment" is made and a warning signal is sent to the torque limiting means 50. When this warning signal is issued, the warning lamp is lit via the "warning lamp lighting" circuit, and the occupants such as the driver are made to recognize that the abnormality judgment has been made.

Further, when the warning signal is received, the torque limiting means 50 determines in STEP 5 that torque limiting is to be executed, and in the next STEP 6, the number of cylinders of the engine is changed, and a fuel cut signal for the cylinder is sent to the engine ECU 20.
Send to. The engine ECU 20 cuts fuel quickly.
Reduce the engine speed. Alternatively, if the engine 2 has a supercharger, the supercharging is stopped in STEP7. Further, other than STEP 8, the driving force is reduced by a method such as reducing the driving current if the vehicle 1 is an electric vehicle or limiting the driving force if the vehicle 1 is a vehicle with a driving force limiting system. squeeze. Further, as other things, throttle reduction, braking, and shifting to a higher gear in an AT (automatic) vehicle can be mentioned. These series of operations will be described in more detail with reference to FIG.

FIG. 2 is a flowchart relating to the torque limitation of the present invention, and so as not to be confused with the STEP number of FIG.
ST (abbreviation of step) Numbers from 11 are added. Hereinafter, description will be given based on this number. In ST11, the presence or absence of an abnormal signal is confirmed. If an alarm signal is output from the system monitoring means 40 of FIG. 1, the process proceeds to ST12, in which the presence or absence of a flag determines whether or not it is the first control. If the flag is not raised, F is different from 1, so the process proceeds to ST13, where a warning lamp (corresponding to the warning lamp in FIG. 1) is turned on.

At ST14, it is confirmed whether or not the engine speed Ne is equal to or higher than a predetermined value (for example, 1,500 to 2,000 rpm). This may cause an engine stall if the torque is limited at low speed. Therefore,
The engine speed Ne is a predetermined value (for example, 1,500 to
When the rotation speed is lower than 2,000 rpm, torque limitation is not performed.

In ST15, the T timer is started. T
Is the constant elapsed time from the occurrence of the abnormality. When this time T has passed, stable running can be obtained. Next, in ST16, the time T corresponding to the vehicle speed is calculated on the map. Specifically,
The relationship between the vehicle speed and the time T1 during which the torque limit is greatly increased according to the present invention is obtained from the vehicle speed. In addition, 50 and 100 on the horizontal axis are reference values. The meaning of FIG. 3 is as follows. When an abnormality occurs at low speed, the distribution control mechanism is cut off so as to return to a normal running state. However, at low speeds, the wheels may run idle due to the high reduction ratio and large driving torque. Therefore, in the low speed range, the time T1 during which the torque is limited is increased to prevent idling. The time T1 is set shorter than the time T.

Returning to FIG. 2, the T1 timer is started in ST17, and waits for counting up in ST18. FIG. 4 is a diagram for stepwise implementing the torque limitation according to the present invention, in which the horizontal axis represents the time t from the occurrence of abnormality, and the vertical axis represents the degree of torque limitation. The present embodiment is characterized in that the torque limit “large” is selected before the time T1 has elapsed, the torque limit “slow” is selected until the time T has elapsed, and the torque limit is not performed thereafter. Here, the torque limit “large” means taking measures such as stopping the fuel supply to all cylinders or 2/3 cylinders of the engine, activating the brake, and fully closing the throttle. Further, the torque limit "slow" is, for example, stopping the fuel supply to the 1/2 cylinder of the engine, delaying the ignition timing, raising the gear of the AT one step, half-closing the throttle, stopping supercharging, etc. It means taking action.

Returning to FIG. 2, ST18 → ST19 → ST
Torque limit is set to "large" on route 21 and ST18 →
Set the torque limit to "loose" on the route from ST20 to ST21,
When the time T has elapsed, the flag F is set to 1 in ST22,
Return to (Start) via (Return).

If no abnormality is found while repeating the control loop of FIG. 2, the route to ST24 is selected in ST11, and the fracture F is reset in ST24. The same applies when no abnormality has occurred from the beginning.

If the flag = 1 in ST2, ST
The route to No. 23 is selected, and the maximum engine output is limited to 70% in ST23, for example. At this time, since the time T has passed and the vehicle is in a stable traveling state,
After that, the maximum output of the engine is limited to a predetermined amount (for example, 70%), and stable running is continued. To limit the maximum output of the engine, for example, the engine speed Ne is set to 3
There are methods such as limiting to 000 rpm, controlling throttle or ignition or fuel, and stopping supercharging.

The contents of the system monitoring means 40 and the torque limiting means 50 are not limited to those in the above embodiment, but the system monitoring means 40 is for monitoring the operation of the device relating to the driving force distribution mechanism. The torque limiting means 50 may be of any type as long as it limits the transmission of torque to the drive wheels.

[0022]

As described above, the present invention provides a vehicle having a front-rear or left-right driving force distribution mechanism for transmission, a torque limiting means for reducing or cutting transmission torque to driving wheels, and a driving force distribution mechanism. System monitoring means for monitoring the operation of the device, and when the system monitoring means detects an abnormality, the torque limiting means reduces or cuts the torque transmitted to the drive wheels based on the abnormality signal. Therefore, even if an abnormality occurs during the driving force distribution control, it is possible to prevent the behavior change of the vehicle from occurring.

Further, if the system monitoring means is configured to reduce or cut the transmission torque when the rotation speed of the drive source is equal to or higher than a predetermined value (see ST14 in FIG. 2), the torque is limited when the rotation speed is low. If you do this, you will not have to worry about engine stalls. Further, the torque limiting means is switched in at least two stages according to the speed of the vehicle (ST1 in FIG. 2).
8 to ST21), the wheels can be prevented from idling at low speed.

[Brief description of drawings]

FIG. 1 is a system diagram according to a driving force control method of the present invention.

FIG. 2 is a flowchart relating to torque limitation of the present invention.

FIG. 3 is a time T during which a large torque limitation is performed according to the present invention.
Relationship between 1 and vehicle speed

FIG. 4 is a diagram for carrying out stepwise torque limitation according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Drive source (engine), 8, 9 ... Hydraulic clutch which concerns on driving force distribution mechanism, 15, 16 ... Driving wheel (rear wheel), 18 ... Hydraulic control valve which concerns driving force distribution mechanism, 30 ...
Driving force control means relating to the driving force distribution mechanism, 40 ... System monitoring means, 50 ... Torque control means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Miyashita 1-4-1 Chuo, Wako City, Saitama Stock Company Honda R & D Co., Ltd.

Claims (3)

[Claims] 1. A vehicle for transmitting torque of a drive source such as an engine or a motor to front and rear or left and right drive wheels via a drive force distribution mechanism, and torque limiting means for reducing or cutting the transmission torque to the drive wheels. A system monitoring means for monitoring the operation of the device relating to the driving force distribution mechanism, and when the system monitoring means detects an abnormality, the torque limiting means transmits the torque to the drive wheel based on the abnormality signal. A driving force control method for a vehicle, characterized by reducing or cutting torque. 2. The driving force control method for a vehicle according to claim 1, wherein the system monitoring means reduces or cuts the transmission torque when the rotation speed of the drive source is equal to or higher than a predetermined value. 3. The torque limiting means is at least large and small 2
2. The driving force control method for a vehicle according to claim 1, further comprising steps, which are switched according to the speed of the vehicle.