JP2615806B2 - Acceleration slip control device for four-wheel drive vehicle - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration slip control device for preventing generation of excessive slip on wheels during acceleration in a four-wheel drive vehicle, and more particularly to reduction of cost. It is.

2. Description of the Related Art In some four-wheel drive vehicles, front left and right wheels and rear left and right wheels are driven by a common power source, and the power of the power source is distributed to a front wheel shaft and a rear wheel shaft by a differential device. . This differential device has a function of absorbing a difference between the rotational speeds of the front wheel shaft and the rear wheel shaft.

In such a four-wheel drive vehicle, there is a possibility that slippage may occur during acceleration (including when starting) for all four wheels. In order to suppress slippage during acceleration, for example, "Toyota Crown New Model Vehicle Manual 9/1987"
Month (published by the Service Department of Toyota Motor Corporation), a brake that suppresses the rotation of the wheels is applied to reduce the number of rotations of the wheels.
If the rotational speed of each of the left and right front wheels and the left and right rear wheels is reduced by the action of the brake, the acceleration slip of the four wheels can be suppressed.

However, in this case, it is necessary to provide a brake for acceleration slip control on both the left and right front wheels and the left and right rear wheels, and to provide a means for controlling the brakes. Inevitably increases the cost. If the rotation of only one of the left and right front wheels and the left and right rear wheels is suppressed by the action of the brake, it is possible to suppress the increase in cost, but the wheel on the side where the rotation is not suppressed by the brake has an acceleration slip. An uncontrolled problem arises.

In addition, a differential limiting device such as a wet multi-plate clutch is provided in the differential device to control the distribution of driving force between the front wheels and the rear wheels according to the slip condition of the four wheels, and to distribute the driving force to the slipping side. It is conceivable to suppress the rotation by reducing the driving force to be applied, but in this case, there is a problem that the acceleration slip cannot be suppressed when all four wheels are in a slip state, for example, the entire road surface is frozen.

An object of the present invention is to provide an inexpensive device capable of performing acceleration slip control for any of the four drive wheels.

Means for Solving the Problems In order to solve the above-described problems, the present invention provides a four-wheel drive vehicle including the left and right front wheels, the left and right rear wheels, a common power source, a differential device, and the like. As shown in FIG.
A differential stop device for stopping the differential function of the differential device,
(B) a brake for suppressing rotation of one of the left and right front wheels and the left and right rear wheels, and (c) acceleration slip detection means for detecting at least one of the left and right front wheels and the right and left rear wheels. (D) first acceleration slip suppression means for activating a differential function stop device when excessive acceleration slip is detected by the acceleration slip detection means;
A second acceleration slip suppression means for activating a brake when the acceleration slip suppression by the first acceleration slip suppression means is insufficient.

In the acceleration slip control device configured as described above, when an excessive acceleration slip is detected, first, the first acceleration slip suppression means operates the operation function stopping device,
Stop the differential function of the differential. By stopping the differential function, the left and right front wheels and the left and right rear wheels are restrained from each other, and their respective average rotation speeds (average of the rotation speed of the right wheel and the rotation speed of the left wheel) become equal. If the acceleration slip of some wheels is excessive but the rotation speed of the other wheels is not excessive, the rotation of wheels with excessive acceleration slip and high rotation speed is suppressed by other wheels. Because
Thereby, an acceleration slip suppression effect is obtained.

However, if the acceleration slip suppression effect is not sufficient, the second acceleration slip suppression means operates the brake to suppress the rotation of the wheel provided with the brake. At this point, since the differential function stop device has already stopped the differential function of the differential device, the rotation speed of one of the left and right wheels is reduced by the action of the brake, so that the average rotation speed of the other left and right wheel is also reduced. It is reduced, and the slip of both the left and right front wheels and the left and right rear wheels is controlled to an appropriate range. How the rotation of the four wheels is suppressed depends on the condition of the road surface, which will be described later in embodiments.

As described above, according to the acceleration slip control device according to the present invention, when the acceleration slip becomes excessive, first, the differential function of the differential device is stopped by the differential function stop device. The stopping of the differential function itself can be expected to have the effect of suppressing the acceleration slip, and if the suppressing effect is sufficient, the brake is not operated. Therefore, it is possible to prevent the driving force of the driving source from being wasted by the operation of the brake, and to improve the acceleration and fuel efficiency of the four-wheel drive vehicle, and to suppress the brake for suppressing the acceleration slip. Life can be extended.

Further, the brakes for suppressing the acceleration slip can be suppressed only for one of the left and right front wheels and the left and right rear wheels, and the acceleration slip can be suppressed for the four wheels, so that an inexpensive control device having a simple structure can be obtained. .

Furthermore, in the acceleration slip control device of the present invention,
Since the rotation of the wheels is suppressed by the action of the brake to eliminate the slip, the freezing of the road surface, etc.
Even when all of the wheels fall into the slip state, the acceleration slip cannot be suppressed as in the case where only the driving force distribution to the front wheel side and the rear wheel side is controlled.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram schematically showing a power transmission path to wheels of a vehicle provided with an acceleration slip control device according to one embodiment of the present invention. In the figure, 10 is a front left wheel, 12 is a front right wheel, 14 is a rear left wheel, 16 is a rear right wheel, and these wheels 10, 12, 14, 16 are front wheel shafts 18, 20, front differential 22, and center They are connected to each other by a power transmission device including a differential device 24, a propeller shaft 26, a rear differential device 28, rear wheel shafts 30, 32, and the like, and are also connected to an engine 34 that is a common power source. Center differential
The 24 distributes the driving force of the engine 34 to the front wheel driving force and the rear wheel driving force, while allowing a difference in rotation speed between the left and right front wheels 10, 12 and the left and right rear wheels 14, 16. The driving force distributed by the center differential device 24 is further distributed to the left and right front wheels 10, 12 by the front differential device 22 on the front wheel side, and to the left and right rear wheels 14, 12 by the rear differential device 28 on the rear wheel side. Distributed to 16. Front differential 22, center differential 24 and engine 34
Is located at the front of the car and has a propeller shaft 26
Extends long along the longitudinal direction of the car. Further, the center differential device 24 is provided with a differential function stopping device 36 for stopping the differential function. This differential stop device 36
Is already known, for example, as described on page 41 of "Automotive Engineering" (March 1987), and a detailed description thereof will be omitted.

The output of the engine 34 is controlled by depressing an accelerator pedal 40 shown in FIG. In the intake manifold 42 of the engine 34, a main throttle valve 44 and a sub throttle valve 46 are provided in series. The main throttle valve 44 is opened and closed by operating the accelerator pedal 40, and its opening is detected by a main throttle valve opening sensor 48. The opening and closing of the auxiliary throttle valve 46 is performed by a motor 49. The opening of the sub throttle valve 46 is set based on the opening of the main throttle valve 44 detected by the sensor 48 during the acceleration slip control, and is opened smaller than the main throttle valve 44.

The rotation of the wheels 10, 12, 14, 16 is suppressed by the hydraulic brake device shown in FIG. In the figure, reference numeral 50 denotes a brake pedal, and a hydraulic pressure is generated in two independent pressurizing chambers 54 and 56 of a master cylinder 52 via a hydraulic pressure booster 51 based on a depression operation of the pedal 50. The hydraulic pressure generated in one pressurizing chamber 54 is
The hydraulic pressure supplied to the front wheel cylinders (not shown) of the brakes provided in the respective 10 and 12 and the hydraulic pressure generated in the other pressurizing chamber 56 is applied to the rear wheel cylinders of the brakes provided in the left and right rear wheels 14 and 16. Supplied to 58,60. This hydraulic brake system is of a front and rear two-system type, and the wheels 10, 12, 14, and 16 are independently subjected to anti-skid control. Hereinafter, the anti-skid control of the left and right rear wheels 14, 16 will be representatively described.

Two electromagnetic control valves 62 and 64 are provided in the main liquid passage for supplying hydraulic pressure from the pressurizing chamber 56 to the rear hole cylinders 58 and 60, so that the master cylinder side passage 66 and the wheel cylinder side passage 68 , 70. Electromagnetic on-off valves 72 and 74 are provided in the wheel cylinder side passages 68 and 70, respectively, so that communication between the rear wheel cylinders 58 and 60 and the electromagnetic control valves 62 and 64 is allowed and cut off.
The anti-skid control uses solenoids 7 of solenoid on-off valves 72 and 74.
6, 78 are not excited, and the rear wheel cylinders 58, 60 and the electromagnetic control valves 62, 64 are communicated with each other. Electromagnetic control valves 62, 6 from electromagnetic on-off valves 72, 74 in wheel cylinder side passages 68, 70
The part on the side of the fourth side and the part on the side of the rear wheel cylinders 58, 60 are connected by supply passages 84, 86 provided with check valves 80, 82, respectively. Are solenoid on-off valves 72 and 74 and supply passage 8
The air is supplied to the rear wheel cylinders 58, 60 through both the wheels 4,86.

A reservoir 92 is connected to the electromagnetic control valves 62 and 64 via reservoir passages 88 and 90, and return passages 94 and 96 are provided between the master cylinder side passage 66 and the wheel cylinder side passages 68 and 70, respectively. Is connected. This return passage 94,96
Are provided with check valves 98 and 100, respectively, which allow the flow of the brake fluid from the wheel cylinder side passages 68 and 70 to the master cylinder side passage 66 but prevent the flow in the opposite direction. The brake fluid in the cylinders 58 and 60 is quickly supplied to the master cylinder side passage 66.

These control valves 62 and 64 are three-position directional control valves, and connect the rear wheel cylinders 58 and 60 to the pressurizing chamber 56 to increase the hydraulic pressure, and to communicate with the reservoir 84 to reduce the hydraulic pressure. The state can be switched between a state in which the fluid pressure is maintained and a state in which the fluid pressure is maintained at a constant level without communicating with any of them. When the rear wheel cylinders 58 and 60 communicate with the reservoir 92, the brake fluid discharged from the rear wheel cylinders 58 and 60 is stored in the reservoir 92. The brake fluid stored in the reservoir 92 is pumped up by the pump 102 and supplied to the master cylinder side passage 66 via the pump passage 104.

Although the rear system has been described above, the front system is similarly configured. However, the solenoid valves 72 and 74, the check valves 80 and 82, and the supply passages 84 and 86 are not provided.

Furthermore, the rotation speed of each wheel 10, 12, 14, 16 is respectively
The rotation is detected by the rotation sensors 110, 112, 114, 116, and the detection signal is supplied to the anti-skid control circuit 120. The control circuit 120 includes the rotation sensors 110 to 116
Then, the slip ratio of each wheel is calculated based on the detection signal from the ECU, and based on the result, the electromagnetic control valves 62 and 64 of the rear system and the electromagnetic control valve of the front system are controlled.

The rotation of the left and right rear wheels 14, 16 is further suppressed to perform acceleration slip control. This control is performed in a state where the solenoids 76, 78 of the electromagnetic on-off valves 72, 74 are excited and the communication between the rear wheel cylinders 58, 60 and the electromagnetic control valves 62, 64 is cut off.
8,70 solenoid on-off valves 72,74 and the rear wheel cylinders 58,60 are provided with acceleration slip control displacement control valves 124,12
6 is connected. The configurations of these capacity control valves 124 and 126 are the same. Hereinafter, the capacity control valve 124 of the left rear wheel system will be representatively described, and the constituent members of the capacity control valve 126 of the right rear wheel system will be the same as those of the capacity control valve 124. The reference numerals of the members are denoted by A.

The capacity control valve 124 includes a capacity changer 130. The variable capacity device 130 is configured such that a piston 134 is fitted in a housing in a liquid-tight and slidable manner, and hydraulic chambers 136 and 138 are formed on both sides thereof. One hydraulic chamber 136 has a spring 1
The piston 40 is urged toward the other hydraulic chamber 138 and is connected to the rear wheel cylinder side passage 68. The hydraulic chamber 138 is connected to an accumulator 144 by a liquid passage 142, and is connected to a reservoir 148 by a hydraulic passage 146. By changing the capacity of the hydraulic chamber 138, the hydraulic pressure of the rear wheel cylinder 58 is changed. And the rotation of the left rear wheel 14 can be controlled. accumulator
Reference numeral 144 also functions as a hydraulic pressure source of the hydraulic booster 51. A pump 150 pumps up a hydraulic fluid in a reservoir 148, and stores the hydraulic fluid in an accumulator 144 via a pump passage 151. A pressure switch 152 activates the pump 150 when the hydraulic pressure of the accumulator 144 becomes equal to or lower than the set lower limit, and stops the pump when the liquid pressure becomes equal to or higher than the set upper limit. Reference numeral 153 denotes a level warning switch, which issues a warning signal when the volume of the hydraulic fluid in the reservoir 146 becomes equal to or less than a predetermined amount.

In the middle of the liquid passage 142, a proportioning valve 154 and a high-pressure side solenoid on-off valve 156 for reducing the liquid pressure supplied from the accumulator 124 at a fixed ratio are provided.
A low-pressure side solenoid on-off valve 158 is provided in the middle of the liquid passage 146,
A capacity control valve 124 is configured together with the capacity variable device 130. When the solenoid is excited, the high-pressure side solenoid valve 156 is opened,
When the low pressure side solenoid on-off valve 158 is closed, the hydraulic pressure chamber 138
Is communicated with the accumulator 144 to supply the hydraulic fluid, and the hydraulic pressure of the rear wheel cylinder 58 is increased.
Also, the on-off valve 156 is closed by the demagnetization of the solenoid,
When the on-off valve 158 is open, the hydraulic chamber 138 is
The hydraulic fluid is discharged by being communicated with 8, and the hydraulic pressure of the rear wheel cylinder 58 is reduced. In addition, on-off valve 156,
When both 158 are closed, the hydraulic chamber 138 does not communicate with either the accumulator 144 or the reservoir 148, and the hydraulic pressure of the rear wheel cylinder 58 is kept constant. Excitation of the high-pressure solenoid valve 156 and demagnetization of the low-pressure solenoid valve 158 are duty-controlled in two stages, respectively.
The pressure increase and the pressure reduction of the rear wheel cylinder 58 are, respectively, a gradual pressure increase and a pressure decrease in which the fluid pressure gradually increases or decreases,
It is performed in two stages, namely, a sudden increase and a sudden decrease in the hydraulic pressure.

The capacity control valves 124 and 126 are connected to the acceleration slip control circuit 160.
Is controlled by As shown in FIG. 4, the control device 160 is mainly composed of a computer having a CPU 162, a ROM 164, a RAM 166 and a bus 168 connecting them. An input interface 170 is connected to the bus 168, and the main throttle valve opening sensor 48, the anti-liquid control circuit 120, and the like are connected to the input interface 170. The bus 168 also has an output interface 172
Through the differential function stopping device 3 of the center differential device 24.
6, while the auxiliary throttle valve opening / closing motor 49 is connected, the electromagnetic opening / closing valves 72, 74, the high-pressure side electromagnetic opening / closing valves 156, 156A, and the low-pressure side electromagnetic opening / closing valve closing valves 158, 158A are connected. Also,
The ROM 164 stores various control programs in addition to the program for suppressing the rotation of the wheels during the acceleration slip control shown in the flowchart in FIG. The wheel rotation suppressing program is executed by interrupting the main program every 10 ms. Hereinafter, the acceleration slip control will be described based on the flowchart shown in FIG.

First, in step S1 (hereinafter abbreviated as S1; the same applies to other steps), the four wheels 10, 12, 14, 1
Among the rotation speeds V _FR , V _FL , V _RR , and V _RL of 6, the lowest rotation speed V _{MIN (N)} is selected. The rotation speed of the wheel is calculated in the calculation unit of the anti-skid control circuit 120,
Here, the calculation result is read and the rotation speed is selected. Next, in S2, an estimated vehicle speed (hereinafter, referred to as an estimated vehicle speed) V _S0 is obtained. The estimated vehicle speed V _S0 is S1
Estimated vehicle speed V _{S0 (n-1)} to change the amount ΔVα therebetween vehicle speed when the V _{MIN (n)} obtained, the S2 is performed last in
And the smaller of the two. In this case α
Is a set acceleration set based on the acceleration that the vehicle can output, and ΔVα is a change amount of the vehicle speed for 10 ms when the vehicle speed increases at the set acceleration α. If a wheel slips, the rotation speed increases, but is reduced by performing brake control as described below,
It changes as shown by the solid line in FIG. While the minimum rotation speed of the four wheels is low, it is used as the estimated vehicle speed,
If the four wheels slip and the rotational speed increases, the actual vehicle speed cannot change that way, so the estimated vehicle speed
The value obtained by adding ΔVα to V _{S0 (n−1)} is set as the estimated vehicle speed V _S0, and the estimated vehicle speed V _S0 changes as shown by a dashed line in FIG. If the rotational speed of the slipped wheel is reduced by the brake control and becomes smaller than the vehicle speed obtained from the set acceleration α, the estimated vehicle speed is set to V _S0 . FIG. 7 shows such an estimated vehicle speed V _S0 in relation to time.

Then the reference value VT ₁ for performing the acceleration slip control stepwise in S3, VT _2, VT ₃ is obtained. These are obtained by adding ΔV ₁ , ΔV ₂ , and ΔV ₃ to the estimated vehicle speed V _S0 , respectively. ΔV ₁ indicates that the slip generated on the wheels is small,
ΔV ₂ is a value that sets a rotational speed range in which brakes are required in addition to throttle valve control, in which the slip generated on the wheels is large and throttle control is required. is there. ΔV ₃ is larger than ΔV ₂ and is a value for setting a boundary for switching between increasing and decreasing the hydraulic pressure of the rear wheel cylinders 58 and 60 during the brake control. In S4, the rotational speeds V _RR , V
_RI it is determined whether or not larger than the reference value VT ₁ respectively performed. If at least one of the wheels has slipped, the determination result is YES, and the throttle valve control is performed in S5. Sub throttle valve opening / closing motor
49 is activated, and the opening of the sub throttle valve 46 is set to a size set based on the opening of the main throttle valve 44, whereby the output of the engine 34 is reduced, and the wheels 10, 12, The rotational speed of 14,16 is reduced. S6
, The differential function stopping device 36 is operated, and the differential function of the center differential device 24 is stopped. As a result, the rotation of the left and right front wheels 10, 12 and the rotation of the left and right rear wheels 14, 16 are mutually restricted, and the respective average rotation speeds become equal.

Each rotation speed V _RL of the left and right rear wheels 14 and 16 at S7, V _RR is made is determined whether larger than the reference value VT _2, respectively, when large brake control is performed at S8 for that wheel. Assuming that the rotation speed V _RL of the left rear wheel 14 is higher than VT ₂ , the solenoid on-off valve 72 is excited, the rear wheel cylinder 58 is cut off from the solenoid control valve 62, and the high-pressure side solenoid on-off valve 156 and the low-pressure side The opening and closing of the solenoid on-off valve 158 is performed.
Opening and closing of these on-off valves 156 and 158 is performed by the rear wheel cylinder 5
The liquid pressure of No. 8 is set so as to be determined based on the magnitude of the rotation speed V and the acceleration α as shown in the table below.

However, I: V> region of VT ₃ II: area of _{VT 2 <V ≦ VT 3 III} : VT 1 < area of _{V ≦ VT 2 IV: V S0} < regions of V ≦ VT ₁ V: the V ≦ V _S0 Area FU: Sudden pressure increase SU: Slow pressure increase FD: Sudden pressure reduction SD: Slow pressure reduction H: Hold The switching of the increase and decrease of the rear wheel cylinder fluid pressure shown in the above table is stored in the ROM 164 in advance. If the left rear wheel 14 slips, the change in the hydraulic pressure of the rear wheel cylinder 58 is switched as shown in FIG. 8 according to the above table.

By performing the brake control in this manner, the rotation speed of the wheels is reduced, and the average rotation speed of the left and right rear wheels 14, 16 is reduced. During the brake control, the differential function of the center differential device 24 is stopped, so that the average rotation speed of the left and right front wheels 10, 12 is also reduced. The slip is suppressed by reducing the rotation speed.

Hereinafter, how the acceleration slip control is performed according to the road surface condition will be described.

As shown in FIG. 9, when the road surface is a left / right split road in which the left side friction coefficient is larger than the right side friction coefficient in the wheel traveling direction indicated by the arrow, the rotation speed of the right rear wheel 16 increases. If the result of the determination in S4 is YES, throttle valve control is performed and the differential function of the center differential device 24 is stopped. If throttle valve control is performed in this state, the average rotation speed of the left and right front wheels 10, 12 and the average rotation speed of the left and right rear wheels 14, 16 are reduced. Left front wheel 10,
Since the left rear wheel 14 is on a road surface having a large friction coefficient, the rotation speed does not change, and the right front wheel 12,
The rotation speed of the right rear wheel 16 is reduced, and the slip is suppressed. There is a difference in the slip situation of the right front wheel 12 and the right rear wheel 16,
Even if there is a difference in the number of revolutions, the differential function of the center differential 24 is stopped, and the average number of revolutions of the left and right front wheels 10, 12 and the left and right rear wheels 1
By performing the throttle valve control in a state where the average rotational speeds of the wheels 4 and 16 are the same, the effect of suppressing the wheel having the higher rotational speed is large, and the slip is effectively suppressed.

If the slip is not eliminated only by the throttle valve control, the brake control is performed to reduce the rotation speed. Since the left rear wheel 14 is traveling on a portion of the road where the coefficient of friction is large, the rotation speed does not change, and the average rotation speed of the left and right rear wheels 14 and 16 is reduced by performing the brake control on the right rear wheel 16. The average rotational speed of the left and right front wheels 10, 12 is also reduced. Although it is permitted that a rotational speed difference occurs between the left front wheel 10 and the right front wheel 12 by the front differential device 22,
Since the average rotation speed of both is reduced, and the rotation speed of the left front wheel 10 traveling in the portion where the friction coefficient is large does not change, the rotation speed of the right front wheel 12 is reduced and the slip is suppressed. Becomes

Further, as shown in FIG. 10, when the road surface has a high friction coefficient on the front side of the vehicle and a low front and rear split road on the rear side in the wheel traveling direction indicated by the arrow in the figure, the left rear wheel 14, The throttle valve control is performed by increasing the rotation speed of the right rear wheel 16, and the differential function of the center differential device 24 is stopped. In this case, the left and right front wheels
10 and 12 are on a road surface having a high coefficient of friction and do not slip. Therefore, when the differential function of the center differential 24 is stopped, the average rotational speed of the left and right rear wheels 14 and 16 is equal to that of the left and right front wheels 10 and 12. The rotational speed is reduced to the average rotational speed, and the slip is suppressed. In the state where the differential function of the center differential device 24 is stopped, the left and right front wheels 10, 12 and the left and right rear wheels 14, 16 can only rotate so that their respective average rotational speeds are the same,
The left and right front wheels 10, 12 having no slip and having a small number of revolutions play a role of a brake. In addition, since the rotation speed is reduced by the throttle valve control, the slip of the left and right rear wheels 14, 16 is effectively suppressed.
If the suppression is still insufficient and the rotational speeds of the left and right rear wheels 14, 16 are large, the brake control is performed, and the slip is quickly eliminated. The same applies when only the right rear wheel 16 is on a road surface having a low friction coefficient.

Furthermore, the coefficient of friction of the entire road surface is small due to freezing, etc.,
If any of the four wheels slips, the brake control is performed on the left and right rear wheels 14, 16 in a state where the differential function is stopped, so that the rotation speed of all four wheels is reduced, The slip condition is eliminated.

Once the brake control has been performed, the left and right rear wheels 14,1
If the determination result of S7 becomes NO due to the decrease in the rotation speed of 6, the electromagnetic on-off valves 156, 156A, 158, 158A are demagnetized and return to the state shown in FIG. In this case, demagnetization of the solenoid valves 158, 158A is not duty control, but is to completely demagnetize the solenoid.

As is clear from the above description, in the present embodiment, the rotation sensors 110, 112, 114, and 116, the portions of the acceleration slip control circuit 160 that store S1 to S4 and S7 in the ROM 164, the portion of the CPU 162 that executes those steps, and the like detect acceleration slip. A portion for storing S6 of the ROM 164, a portion for executing S6 of the CPU 162, and the like constitute first acceleration slip suppression means, and a capacity control valve 124, 126 for acceleration slip control, an area for storing S8 of the ROM 164, and a CPU 162. The part that executes S8 constitutes the second acceleration slip suppression means.

In the above embodiment, it is determined whether or not a slip has occurred in the left and right rear wheels 14, 16, and the acceleration slip control is performed. However, the determination may be made for all four wheels. In this case, when the road surface is a front / rear split road having a low friction coefficient on the front side and a high friction coefficient on the rear side in the vehicle traveling direction, a slip is detected due to an increase in the rotational speed of the left and right front wheels. By suppressing the rotation of the wheels 14, 16, the rotation of the left and right front wheels 10, 12 is suppressed, and the slip is suppressed.

Further, in the above-described embodiment, the rotation of the left and right rear wheels 14 and 16 is suppressed by the brake during the acceleration slip, but the brakes of the left and right front wheels 10 and 12 may be applied.

Although not specifically exemplified, the present invention can be implemented in various modified and improved embodiments based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing the configuration of the present invention. FIG. 2 is a system diagram showing a power transmission path to wheels of a vehicle provided with an acceleration slip control device according to one embodiment of the present invention. FIG. 3 is a system diagram showing the acceleration slip control device together with an anti-skid control type hydraulic brake device. FIG. 4 is a block diagram showing a control circuit of the acceleration slip control device. FIG. 5 is a flowchart showing a program extracted from a program stored in a ROM of a computer, which is a main component of the control circuit, which is relevant to the present invention. FIG. 6 is a graph showing the relationship between the rotational speed and the estimated vehicle speed and time when a slip occurs on the wheel of the vehicle. FIG. 7 is a graph showing the relationship between the estimated vehicle speed of the vehicle and three types of reference vehicle speeds for acceleration slip control and time. FIG. 8 is a diagram showing the relationship between the rotational speed and acceleration of the wheel and the brake control during the acceleration slip control. FIG. 9 is a diagram for explaining acceleration slip control when the vehicle travels on a left-right split road. No.
FIG. 10 is a diagram for explaining acceleration slip control when the vehicle travels on a front-back split road. 10: Left front wheel, 12: Right front wheel 14: Left rear wheel, 16: Right rear wheel 18, 20: Front wheel axle, 24: Center differential 30, 32: Rear axle, 34: Engine 36: Differential function stop 58, 60: Rear wheel cylinders 110, 112, 114, 116: Rotation sensors 124, 126: Capacity control valves for acceleration slip control 130, 130A: Variable capacity 144: Accumulator, 148: Reservoirs 156, 156A: High pressure side solenoid on / off valve 158, 158A: Low pressure side solenoid on / off valve

Claims (1)

(57) [Claims] 1. A four-wheel drive vehicle in which left and right front wheels and right and left rear wheels are driven by a common power source, and the power of the power source is distributed to a front wheel shaft and a rear wheel shaft by a differential device. A device for controlling the acceleration slip of the left and right front wheels and the left and right rear wheels, a differential function stopping device for stopping a differential function of the differential device; and one of the left and right front wheels and the left and right rear wheels A brake that suppresses rotation of the left and right wheels, acceleration slip detection means for detecting at least one of the left and right front wheels and right and left rear wheels, and an excessive acceleration slip detected by the acceleration slip detection means. First acceleration slip suppression means for operating the differential function stop device; and second actuation of the brake when acceleration slip suppression by the first acceleration slip suppression means is insufficient. Acceleration slip control device for a four-wheel drive vehicle which comprises a quick slip suppressing means.