JPH0365440A - Controller for vehicle - Google Patents

Abstract

PURPOSE:To provide a satisfactory brake by separating the drive systems of front and rear wheels from each other in braking, while operating a change-over means to couple the drive systems of front and rear wheels with each other when the rotational speed for rear wheel is detected slower than that of front wheel. CONSTITUTION:When in braking the rotational speed of rear wheels 3L, 3R is detected slower than that of front wheels 2L, 2R by wheel speed sensors 25-28 in a controller 24, a clutch 21 (change-over means) of a four-wheel drive device is operated to couple the drive system of front and rear wheels with each other in additional to the braking control by an ABS hydraulic control unit 31. Thus, the front and rear sides are changed over to the four-wheel drive condition in which both sides are coupled directly with each other, so that the rotational speed of rear wheels 3L, 3R is increased by the front wheels 2L, 2R. Thus, the rear wheels 3L, 3R are quickly released from the locked condition to be very satisfactorily braked without degrading the stability of a car body in the braking.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a vehicle control device, particularly a four-wheel drive device that drives front and rear wheels using engine output, and a four-wheel drive device that controls braking force to each wheel during brake operation. The present invention relates to a control device for a vehicle equipped with an anti-skid brake system that prevents wheels from locking.

(Prior Art) Generally, anti-skid brake systems (hereinafter referred to as ABS) are designed to prevent each wheel from locking during braking.
) is known. This adjusts the hydraulic pressure (brake fluid pressure) supplied to the braking means of each wheel based on the signal from the wheel speed sensor installed for each wheel to detect the speed of each wheel when the brakes are operated. This improves braking performance by preventing each wheel from locking or skidding during braking.

On the other hand, the four wheels drive the front and rear wheels using the engine output.
There are four-wheel drive vehicles, which have full-time four-wheel drive with a center differential that divides the engine power into a front-wheel drive system that drives the front wheels and a rear-wheel drive system that drives the rear wheels. There are part-time four-wheel drive vehicles that are equipped with a 2-4 switching clutch between the front wheel drive system and the rear wheel drive system for switching between a direct connection state and a separation state. For example, JP-A-6243355
In the publication, a four-wheel drive vehicle as described above is equipped with ABS, and when the brake is operated, that is,
When the ABS is in operation, the braking control by the ABS can be effectively performed by switching from the four-wheel drive state to the two-wheel drive state.

(Problem to be Solved by the Invention) When the brake is operated, for example, if the rotational speed of the rear wheels is slower than the rotational speed of the front wheels, that is, if the rear wheels become locked, the rear wheels The slip ratio of the vehicle exceeds a predetermined value, impairing the stability of the vehicle during braking, and resulting in a reduction in braking performance.

On the other hand, in a vehicle equipped with ABS, when a locked state of the rear wheels is detected as described above, the system is controlled to eliminate the locked state of the rear wheels. There remained issues to be resolved in terms of prompt resolution.

Therefore, in a vehicle equipped with a four-wheel drive system and an ABS, when a locked state of the wheels is detected during braking, particularly when a locked state of the rear wheels is detected,
It is an object of the present invention to provide a vehicle control device that can perform extremely good braking by appropriately switching the driving state of the four-wheel drive device to a two-wheel drive state or a four-wheel drive state in addition to the braking control by S. purpose.

(Means for Solving the Problems) In order to solve the above problems, the present invention is characterized by the following configuration.

That is, a four-wheel drive device including a switching means for switching a front wheel drive system and a rear wheel drive system between a directly coupled state and a separated state;
A vehicle control device having an anti-skid brake system that prevents wheels from locking by controlling braking force based on the speed of each wheel detected by a wheel speed detection means that detects the rotational speed of each wheel during brake operation. When the brakes are operated, the drive systems for the front and rear wheels are separated, and when the wheel speed detection means detects that the rotation speed of the rear wheels is slower than the rotation speed of the front wheels, the drive systems for the front and rear wheels are connected. The present invention is characterized in that a control means is provided for operating the switching means so as to achieve the following.

(Function) According to the above configuration, when the wheel speed detection means detects that the rotation speed of the rear wheels is slower than the rotation speed of the front wheels during brake operation, in addition to braking control by the anti-skid brake system, , the switching means in the four-wheel drive system is operated by the control means to bring the drive systems of the front and rear wheels into a coupled state, thereby switching to a four-wheel drive state in which the front wheels and the rear wheels are directly coupled. As a result, the rotation of the rear wheels, which have a lower rotational speed than the front wheels and are in a locked state, is pulled up by the front wheels. As a result, the locked state of the rear wheels is quickly released, and extremely good braking can be achieved without reducing the stability of the vehicle body during braking.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an overall schematic elliptical diagram of a full-time four-wheel drive vehicle having a center differential and equipped with a vehicle control device according to the present invention.
The left and right rear wheels 3L and 3R are both drive wheels, and the output of a power unit 4 consisting of an engine, a transmission, etc. is input to a center differential input gear 7 via a drive gear 5, and the center differential 6 is Gear machine 1118
The signal is transmitted to the front wheels 2L, 2R and the rear wheels 3L, 3R. And the front wheel 2L,
The output to the 2R side is provided by a first drive shaft 9. which extends forward from the center differential 6. Front differential 1° and left and right front axles 1
1.12 to the left and right front wheels 2L, 2R, and the output to the rear wheels 3L, 3R is transmitted to the second drive shaft 13 extending rearward from the center differential 6, the rear differential 14, and the left and right rear axles 15. The first drive shaft 9, front differential 10, and front axle 11.12 constitute a front wheel drive system 17. The rear wheel drive system 1 includes the second drive shaft 13, the rear differential 14 and the rear axle 15.16.
8 are made up.

Further, a clutch 21 is interposed between a pair of gear transmissions 119.20 driven by the center differential 6, and this clutch 21 is connected to a clutch actuator 2.
2, a differential-free state that allows relative rotation between the front wheel drive system 17 and the rear wheel drive system 18 by intermittent connection as necessary, and a differential lock that directly connects the front and rear wheel drive systems 17 and 18. It is possible to switch between the states.

Further, the left and right front axles 11.12 and the left and right rear axles 15.16 have disc rotors 23a...23a that rotate integrally therewith, and when braking pressure (brake fluid pressure) is supplied. Brake devices 23, . . . , 23, each including a caliper 23b, .

On the other hand, this vehicle 1 is equipped with a controller 24, and this controller 24 includes each of the left, right, front and rear wheels 2.
Signals a1 to a4 from wheel speed sensors 25 to 28 that detect the rotational speeds of L, 2R, 13L, and 3R, signals a5 from the accelerator sensor 29 that detects the state of depression of the accelerator pedal, and detection of the state of depression of the brake pedal. The signal a6 from the brake sensor 30 is input, and the controller 24 inputs each of the input signals a1 to a6.
Based on the ABS (anti-skid brake system) hydraulic control unit 31 and the above clutch 2
Clutch actuation actuator 2 for connecting and connecting 1
2 and control signals bl, b2 for controlling their operation.
is now output. When the controller 24 outputs the control signal bl to the ABS hydraulic control unit 31, the ABS hydraulic control unit 31 outputs the control signal bl to each wheel 2L, 2 during braking.
Each brake device 23 depending on the rotational state of R13L and 3R.
By adjusting the braking pressure supplied to the wheel, the locked state of the wheels is released.

Next, the operation of this embodiment will be explained based on the flowchart of FIG. It is determined whether the pedal is in the OFF state, that is, the accelerator pedal is not depressed. When it is determined that the accelerator pedal is in the OFF state, the clutch actuator 2 is activated in step S2.
2 and outputs a signal b2 to turn the clutch 21 into the OFF state. As a result, the center differential 6 becomes free, and the first drive shaft 9 and the second drive shaft 13 are able to rotate relative to each other with a rotational difference. Note that when the accelerator pedal is in the OFF state as described above, as shown in FIG. 24 is the brake sensor 3 in step S.
Based on the signal b6 from 0, it is determined whether the brake pedal is in the ON state. That is, it is determined whether the brake pedal is depressed or not, and when it is determined that the brake pedal is depressed, that is, when the wheel speed Vl begins to decrease as shown in (b) in FIG. In step S4, the signals al to a from each wheel speed sensor 25 to 28 are
4, the speed of each wheel 2L, 2R13L, and 3R is detected. Note that this detection will be performed in the area indicated by (c) in FIG. 3.In step S, each wheel 2L, 2 detected in step S4
Based on the rotational speeds of R13L and 3R, it is determined whether or not there is a wheel in a locked state, that is, a wheel whose slip rate during braking is equal to or higher than a predetermined value. If there is a wheel in a locked state, that wheel is removed in step S6. A signal bl is output to the ABS hydraulic control unit 31 so as to reduce the braking pressure supplied to the brake means 23. As a result, as shown in FIG. 3 (d), the wheel speed Vl of the wheels in the locked state starts to increase again. After that, in step S7, the rear wheels 3L,
Determine whether the 3R side is in the locked state, and lock the rear wheels 3L and 3R.
When it is determined that the side is not in the locked state, step S
8, the clutch is turned off as set in step S2 above.
maintain the condition. Further, if it is determined that the rear wheels 3L and 3R are in the locked state, step S9 is executed, and a signal b2 is output to the clutch actuation actuator 22,
The clutch 21 is turned on. As a result, the center differential 6 becomes locked, and a four-wheel drive state is established in which the first drive shaft 9 and the second drive shaft 13 are coupled. As a result, the rotation of the rear wheels 3L and 3R, which are in the locked state, is reduced to that of the front wheels 2.
As a result, the wheel speed V of the rear wheels 3L and 3R increases as shown by (d) in Fig. 3.
The locked state is released by quickly bringing l closer to the reference wheel speed Vo. As described above, in this embodiment, when the locked state of the rear wheels 3L, 3R is detected, in addition to the control by the ABS hydraulic control unit 31, the rotation of the rear wheels 3L, 3R is controlled to the front wheels 2L, 2R. By pulling up the rear wheels 3L and 3R, the locked state of the rear wheels 3L and 3R is quickly released, allowing extremely good braking without reducing vehicle stability during braking.

Note that when the front wheels 2L and 2R are in a locked state during braking, the clutch 21 is turned off, that is, a differential-free state is established in which relative rotation between the first drive shaft 9 and the second drive shaft 13 is allowed. This means that when the front wheels 2L and 2R are in the locked state and the first and second drive shafts 9.13 are in the coupled state, the rear wheels 3L and 3R [ [The rotation of l is the front wheels 2L and 2R.
The rotational speed of the rear wheels 3L, 3R decreases, and as a result, the rotational speed of the rear wheels 3L, 3R also decreases.
This is to prevent the vehicle from being locked together with the R side and losing stability of the vehicle body during braking.

In addition, as shown in FIG. 4, the output of the power unit 4' is transmitted to the front differential 10' and the rear differential 14' via the first drive shaft 9' and the second drive shaft 13'. Each wheel (not shown) is driven, and the first drive shaft 9' and the front differential 10'
It is interposed between a front wheel drive system 17' consisting of a second drive shaft 13', a rear differential 14', etc., and a rear wheel drive system 18' consisting of a second drive shaft 13', a rear differential 14', etc. In a part-time four-wheel drive vehicle equipped with a 2-4 switching clutch 21' that switches between By controlling the front wheel drive system 17' and the rear wheel drive system 18' to be directly connected through the 2-4 switching clutch 21', the rotation of the rear wheels in the locked state is changed to the front wheels. As a result, the locked state of the rear wheels is quickly released, and as a result, it is possible to brake extremely well without reducing the stability of the vehicle body during braking.

(Effects of the Invention) As described above, according to the vehicle control device according to the present invention,
During brake operation, when the wheel speed detection means detects that the rotational speed of the rear wheels is slower than the rotational speed of the front wheels, in addition to braking control by the anti-skid brake system, the control means also controls the switching means in the four-wheel drive system. By operating the front and rear wheel drive systems in a coupled state, the front and rear wheels are switched to a four-wheel drive state in which they are directly coupled, resulting in a rotation speed that is lower than that of the front wheels. The rotation of the rear wheel, which is slow and locked, is pulled up by the front wheel. As a result, the locked state of the rear wheels is quickly released, and extremely good braking can be achieved without reducing the stability of the vehicle body during braking.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is an overall schematic diagram of a full-time four-wheel drive vehicle equipped with a vehicle control device according to the embodiment, and Fig. 2 shows control operations by the controller. FIG. 3 is a graph showing changes in vehicle speed and wheel speed during control operation, and FIG. 4 is a flowchart showing a part-time four-wheel drive vehicle equipped with the vehicle control device according to the present embodiment. FIG. 2 is a schematic configuration diagram of main parts. 2L, 2R...front wheel, 3L, 3R...rear wheel, 17.
17'...Front wheel drive system, 18.18'...Rear wheel drive system, 25-28...Wheel speed detection means (wheel speed sensor), 21.21'...Switching means (clutch, 2 -4 switching clutch), 24° 31... Anti-skid brake system (controller, ABS hydraulic control unit), 24... Control means (controller). Figure 2 Figure I Time

Claims (1)

[Claims] (1) A four-wheel drive device equipped with a switching means that switches the front wheel drive system and the rear wheel drive system between a directly coupled state and a separated state;
An anti-skid brake system that prevents wheels from locking by controlling braking force based on the speed difference between each wheel detected by a wheel speed detection means that detects the rotational speed of each wheel during brake operation. The control device separates the drive systems of the front and rear wheels when the brake is operated, and drives the front and rear wheels when the wheel speed detection means detects that the rotational speed of the rear wheels is slower than the rotational speed of the front wheels. A control device for a vehicle, comprising control means for operating the switching means to bring the system into a coupled state.