JPH1071939A - Vehicle behavior controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a reduction in the side force of rear wheels and the occurrence of an unstable vehicle behavior caused by the movement of a load during engine braking in a rear wheel driven vehicle. SOLUTION: In a rear wheel driven vehicle, during engine braking (110: YES), a deviation ΔV (=VR-VF) between the average wheel speed VR of rear wheels and the average wheel speed VF of front wheels is calculated (120 to 140) and, if the deviation ΔV is lower than a first determining value KH (positive value) (150: YES, 170: NO), the braking hydraulic pressure of the front wheel is gradually increased by ΔP (160). If the deviation ΔV is within a range of the first determining value KH to a larger second determining value KR, the braking hydraulic pressure of the front wheel is held (180: NO→190) and, when the deviation ΔV is larger than the second determining value KR, the braking hydraulic pressure of the front wheel is reduced (180: YES→200). Thus, during engine braking, a relationship between a front wheel braking force and a rear wheel braking force is controlled in the stable region of an ideal braking force distribution and the unstable motion of the vehicle following a reduction in the side force of the rear wheel is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle behavior control device for controlling vehicle behavior when a braking force by an engine brake is applied to driving wheels.

[0002]

2. Description of the Related Art Conventionally, in a vehicle such as a rear-wheel drive vehicle or a four-wheel drive vehicle, in which at least the rear wheel of the vehicle is a drive wheel, the driving force applied to the drive wheel is reduced. When the driving wheels are in the engine braking state, the load moves forward of the vehicle body, the grip force of the rear wheels on the road surface is reduced, and the rotation speed of the rear wheels is reduced by the braking force applied to the rear wheels by the engine brake. There was a thing that it was greatly reduced.

Therefore, in a vehicle having rear wheels as driving wheels, during engine braking, the rear wheels tend to slip ahead of the front wheels, reducing the side force exerted by the rear wheels and adversely affecting the behavior of the vehicle body. Could give. That is, in this type of vehicle, spin and the like are likely to occur during engine braking.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and in a vehicle having at least a rear wheel as a driving wheel, a side force of the rear wheel is reduced due to a load shift at the time of engine braking, and the vehicle behavior becomes unstable. The purpose is to prevent the

[0005]

According to a first aspect of the present invention, there is provided a vehicle behavior control apparatus comprising: a vehicle having at least a rear wheel as a driving wheel; When the driving wheels are in an engine braking state due to a decrease in the applied driving force, a wheel braking force is applied to the front wheels by a brake fluid pressure according to the load movement of the vehicle body by the engine braking.

That is, in the vehicle behavior control apparatus according to the first aspect, in a rear-wheel drive or a four-wheel drive vehicle, the wheels on the front wheel side are subjected to brake hydraulic pressure according to the load movement of the vehicle body during engine braking. By applying the braking force, the braking force applied to the front wheels of the vehicle is increased, and the side force of the front wheels is reduced.

As a result, even if the side force of the rear wheel is reduced due to the load movement during engine braking, the side force of the front wheel is also reduced accordingly, and the lateral force on the front wheel side and the rear wheel side of the vehicle is reduced. Can be balanced, and the running stability of the vehicle can be improved.

Particularly, in a rear-wheel drive vehicle, when the drive wheel (rear wheel) is in an engine braking state, no braking force is applied to the front wheels, so that the vehicle behavior becomes more unstable than in a four-wheel drive vehicle. According to the present invention (claim 1), since the braking force is applied to the front wheels during engine braking, the relationship between the front wheel braking force and the rear wheel braking force is shown in FIG. By controlling to the stable region of the distribution diagram, the running stability of the vehicle can be improved, and the effect can be more exhibited.

The ideal braking force distribution diagram shown in FIG.
It shows the relationship between the rear wheel braking force and the front wheel braking force that can stably and quickly brake the vehicle. In the region where the rear wheel braking force is larger than the braking force distribution defined by this ideal braking force distribution diagram, This indicates that the vehicle becomes unstable and spins or the like are likely to occur, and the vehicle is in a stable state in a region where the front wheel braking force is larger than this braking force distribution.

Further, the vehicle behavior control device of the present invention (claim 1) secures the running stability of the vehicle by applying a braking force to the front wheels at the time of engine braking. The vehicle deceleration (negative acceleration) can be increased, and for example, the maneuverability of the vehicle when downhill (during downhill traveling) while applying engine brake can be improved.

In other words, if only the stability at the time of engine braking is to be improved, for example, it is conceivable to increase the driving force of the drive wheels to suppress the movement of the load. The braking characteristics of the vehicle are impaired. In particular, when traveling downhill using the engine brake, the braking force by the engine brake is insufficient, and a brake operation is required. On the other hand, according to the present invention (claim 1), since the braking force is applied to the front wheels during engine braking, the vehicle deceleration can be increased. Therefore, when traveling downhill, it is not necessary to frequently perform the brake operation, and the maneuverability of the vehicle can be improved.

Next, a vehicle behavior control device according to a second aspect of the present invention provides a vehicle having a rear wheel as a drive wheel and a front wheel as a driven wheel (ie, a rear wheel drive vehicle). When the drive wheels are in an engine brake state with the decrease, a wheel braking force equal to or greater than the wheel braking force applied to the drive wheels by the engine brake is applied to the driven wheels by brake fluid pressure.

Therefore, according to the present invention (claim 2),
In a rear-wheel drive vehicle, when a braking force is applied to a rear wheel (drive wheel) by an engine brake, a wheel braking force equal to or greater than the braking force is applied to the front wheel (driven wheel), and the front wheel braking force and the rear wheel The relationship with the braking force can be controlled in the stable region of the ideal braking force distribution diagram shown in FIG. 5, and the same effect as the vehicle behavior control device according to the first aspect can be obtained.

According to a third aspect of the present invention, there is provided a vehicle behavior control device for controlling vehicle behavior during engine braking in a rear-wheel drive vehicle, similarly to the vehicle behavior control device according to the second aspect. When the vehicle is in the engine braking state, the wheel braking force is applied to the driven wheels by the brake fluid pressure so that the wheel braking force on the driven wheels is equal to or greater than the wheel braking force on the driving wheels.

That is, when the drive wheels are in the engine brake state, the drive wheels are subjected to the braking force by the engine brake, but the braking force other than the engine brake is also applied by the driver's brake operation or the like. is there. Therefore, in the present invention (claim 3), at the time of engine braking, a braking force equal to or greater than the total braking force of the driving wheels including the braking force applied to the driving wheels by the engine brake is provided.
It is added to the driven wheel.

As a result, according to the present invention (claim 3),
Compared with the vehicle behavior control device according to claim 2, the relationship between the front wheel braking force and the rear wheel braking force is more reliably controlled by the stability region of the ideal braking force distribution diagram shown in FIG. Performance can be improved.

Next, a vehicle behavior control device according to a fourth aspect of the present invention generates wheel braking force generating means provided on each wheel of a vehicle, and generates a brake fluid pressure applied to each wheel braking force generating means. In a vehicle including a brake fluid pressure generating unit and a driving force generating unit that generates a driving force for driving at least a rear wheel, a driving force generated by the driving force generating unit is reduced and the driving wheels are reduced. When the engine brake state is detected by the detection means, the control means operates the brake fluid pressure generation means to control the front wheel side wheel control. A brake fluid pressure is applied to the power generating means to generate a braking force on the front wheels.

Therefore, according to the vehicle behavior control device of the present invention (claim 4), similarly to the device of claim 1, in a rear-wheel drive or a four-wheel drive vehicle, the front wheel of the vehicle at the time of engine braking. The running stability of the vehicle can be improved by increasing the applied braking force to reduce the side force of the front wheels and balance the front and rear side forces, thereby improving the running stability of the vehicle. The effect can be obtained.

In the vehicle behavior control apparatus according to the fourth aspect, when the detection means detects the engine brake state, the control means generates a vehicle body by the engine brake. The brake fluid pressure may be generated from the brake fluid pressure generating means in accordance with the load movement to be applied to the front wheel side wheel braking force generating means.

In this way, in order for the control means to generate the brake fluid pressure in accordance with the load movement from the brake fluid pressure generating means, the load movement is controlled by the front wheel speed and the wheel speed. Judgment may be made from the wheel speed difference from the wheel speed of the rear wheel, and the brake fluid pressure applied to the front wheel side wheel braking force generating means may be controlled in accordance with the wheel speed difference.

That is, when a load shift occurs in the vehicle body due to the engine brake and the grip force of the rear wheels on the road surface is reduced, the engine may be driven in either a rear-wheel drive vehicle or a four-wheel drive vehicle. Due to the braking force applied to the rear wheel by the brake, the wheel speed of the rear wheel becomes lower than the wheel speed of the front wheel.

Therefore, the load transfer by the engine brake can be determined from the difference between the front wheel speed and the rear wheel speed.
If the brake fluid pressure applied to the front wheels is controlled according to the wheel speed difference, the braking force applied to the front wheels by the brake fluid pressure can be controlled according to the braking force applied to the rear wheels. As a result, the lateral force generated on the front wheel side of the vehicle can be controlled to a desired state in accordance with the lateral force generated on the rear wheel side, and the running stability of the vehicle can be improved. Become.

In particular, when the brake fluid pressure of the front wheels is controlled according to the wheel speed difference between the front wheels and the rear wheels,
When the wheel speed of the front wheel is lower than the wheel speed of the rear wheel by a predetermined value or more, the braking force applied to the front wheel is applied to the rear wheel by prohibiting an increase in the brake fluid pressure. It is also possible to prevent the vehicle from becoming too large as compared with the braking force and the vehicle becoming unstable.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic configuration diagram showing a configuration of an entire control system of a rear wheel drive vehicle to which the present invention is applied.

As shown in FIG. 1, each wheel of the vehicle (left front wheel F
L, the front right wheel FR, the rear left wheel RL, and the rear right wheel RR) are hydraulic brake devices (hereinafter referred to as wheel cylinders) as wheel braking force generating means for applying a braking force to each of the wheels FL to RR.
W / C) 2FL, 2FR, 2RL, 2RR are provided respectively, and wheel speed sensors 4FL, 4FR, 4R for detecting the rotational speed of each wheel (hereinafter also referred to as wheel speed).
L and 4RR are provided respectively.

Further, a transmission (T / M) 8
The driving force (driving torque) of the vehicle output via the right and left wheels is distributed to the left and right rear wheels (drive wheels) RL and RR via the propeller shaft 11 and the differential gear 10. The engine 6 is provided with an accelerator switch 12 which is turned on when the vehicle driver operates the accelerator pedal.
Signals from the wheel speed sensors 4FL to 4RR, etc., are supplied to an electronic control unit (hereinafter referred to as an ECU).
20.

The ECU 20 is a master cylinder (hereinafter referred to as M) for discharging brake oil when the brake pedal 32 is depressed.
/ C) 34 to W / C2FL of each wheel FL-RR
By controlling various actuators in a hydraulic circuit 40 provided in a hydraulic path leading to 2RR, anti-skid control for suppressing slip generated on wheels during vehicle braking is executed, and at the same time, the engine 6 controls the drive wheels RL and RR. By detecting the engine brake state of the drive wheels RL, RR accompanying the decrease in the transmitted drive force, the braking force is applied to the front wheels (follower wheels) FL, FR by controlling various actuators in the hydraulic circuit 40 during the engine brake. The added vehicle behavior control is executed.

The ECU 20 includes a CPU, ROM, RA
The microcomputer 20 is mainly configured with a microcomputer including an M and the like. A detection signal from a brake switch 36 that is turned on when the brake pedal 32 is operated is also input to the ECU 20. Next, the hydraulic circuit 40 will be described. The hydraulic circuit 40 corresponds to a brake fluid pressure generating means according to the present invention (claim 4).

As shown in FIG. 2, the hydraulic circuit 40 has an M / C
There are provided two hydraulic paths 42 and 44 for supplying the brake oil pumped from the two oil passages 34 to the left front wheel FL and the right rear wheel RR and the right front wheel FR and the left rear wheel RL, respectively. .
Then, in the hydraulic path 42, the W / C2 of the left front wheel FL
The path 42FL leading to the FL and the path 42RR leading to the W / C2RR of the right rear wheel RR are each provided with an electromagnetic switchable between a pressure increasing position connecting the paths 42FL and 42RR and a holding position blocking the path. Type pressure increase control valves 46FL, 46RR and each W / C
Electromagnetic pressure reducing control valves 48FL, 48RR for discharging the brake oil in the 2FL, 2RR are provided.

Similarly, in the hydraulic path 44, a path 44FR leading to the W / C2FR of the right front wheel FR and a path 44RL leading to the W / C2RL of the left rear wheel RL are respectively provided in the path 4RL.
The electromagnetic pressure-increasing control valve 46FR, 4 which can be switched between a pressure-increasing position for communicating the 4FR, 44RL and a holding position for interrupting the path.
6RL and electromagnetic pressure reducing control valves 48FR, 48RL for discharging brake oil in each W / C2FR, 2RL are provided.

The pressure increase control valves 46FL, 46FR, 46RL,
46RR is normally a pressure increasing position, and is switched to a holding position by energization from the ECU 20. The pressure reduction control valves 48FL, 48FR, 48RL, and 48RR are normally in a shut-off state, and are in a communicating state by energization from the ECU 20, and discharge the brake oil in the corresponding W / C2FL to 2RR.

On the other hand, in the hydraulic path 42, a master cylinder cut valve (hereinafter, referred to as an SM valve) 50a is provided on a path on the M / C 34 side of the pressure increase control valves 46FL, 46RR to connect / disconnect the path. ing. And
In parallel with the SM valve 50a, when the oil pressure on the M / C 34 side is higher than the oil pressure on the pressure increase control valves 46FL and 46RR, the pressure oil output from the M / C 34 is communicated with the pressure increase control valve 46FL. , 46RR are connected to a relief valve 54a to be supplied.

Similarly, in the hydraulic path 44, a path on the M / C 34 side of the pressure increase control valves 46FR and 46RL is also provided.
An SM valve 50b for communicating and shutting off the path is provided. Then, in parallel with the SM valve 50b, when the oil pressure on the M / C 34 side becomes higher than the oil pressure on the pressure increase control valves 46FR, 46RL, the pressure oil outputted from the M / C 34 is increased. Relief valve 5 to supply to valves 46FR and 46RL
4b is connected.

The SM valves 50a and 50b are powered off.
Sometimes the communication state is established, and the state is switched to the cut-off state by energization from the ECU 20. SM valve 50a, 50b
Are connected in parallel with differential pressure valves PRVa and PRVb, respectively. Each differential pressure valve PRVa and PRVb is connected to the M / C3
4 prohibits the flow of brake oil from the W / C side to the W / C
The flow of the brake oil from the side to the M / C 34 is allowed when the brake oil pressure on the W / C side becomes higher than the pressure on the M / C 34 by a predetermined pressure or more. The predetermined pressure is 50 atm.
差 200 atm, and each differential pressure valve PRVa,
The PRVb protects the pipeline so that the pressure in the pipeline on the W / C side with respect to the SM valves 50a and 50b does not exceed a predetermined pressure when the pumps 60 and 62 described later discharge.

In FIG. 2, the SM valves 50a and 50b are provided with parallel pipes, and the differential pressure valves PRVa and PRVb are provided in these pipes.
, But instead of such a configuration,
Even when a configuration is adopted in which the valve elements at the shut-off positions of the SM valves 50a and 50b are differential pressure valves having a predetermined relief pressure (opening pressure), and the differential pressure valves PRVa and PRVb are built in each of the SM valves 50a and 50b. Good.

Each of the hydraulic paths 42, 44 is provided with a reservoir 56, 58 for temporarily storing the brake oil discharged from the pressure reducing control valves 48FL to 48RR, and further increases the brake oil with the SM valve 50a. Pumps 60 and 62 are provided for pumping the pressure between the pressure control valves 46FL and 46RR and the path between the SM valve 50b and the pressure increase control valves 46FR and RL, respectively. In addition, accumulators 64 and 66 for suppressing the pulsation of the internal hydraulic pressure are provided in the discharge path of the brake oil from the pumps 60 and 62, respectively.

Next, when the vehicle behavior control described later is executed, the M / C 34
/ C34 to the pump 6 from the reservoir 68
Oil supply paths 42P and 44P for directly supplying brake oil to the oil supply passages 0 and 62 are provided. Each of the oil supply paths 42P and 44P has a reservoir cut valve (hereinafter, referred to as an SR valve) for communicating and shutting off the paths. 70a, 70b
Are arranged respectively.

The SR valves 70a and 70b are normally in a shut-off state, and are switched to a communication state by energization from the ECU 20. Each of the pumps 60 and 62 is driven via the motor 80 when performing the anti-skid control and the vehicle behavior control. Next, the anti-skid control and the vehicle behavior control performed by the ECU 20 will be briefly described. When the anti-skid control and the vehicle behavior control are not performed, all the solenoid valves of the hydraulic circuit 40 are off (OFF), and FIG. 2 shows the non-control state.

Anti-skid control For example, when the driver suddenly operates the brake, each wheel F
When a slip occurs in L to RR, the anti-skid control is started, and the SM valves 50a and 50b are set to the communication positions (OFF).
In addition, while the SR valves 70a and 70b remain at the shut-off position (OFF), the motor 80 is driven to operate the pumps 60 and 62, and the pressure increase control valves 46FL to 46RR and the pressure decrease control valve 48
By turning ON / OFF (energized / de-energized) each of FL-48RR, the brake oil pressure in each W / C2FL-2RR is reduced, maintained, and increased according to the slip state of each wheel FL-RR. Switch appropriately.

More specifically, when it is determined that the wheels have a tendency to lock, the pressure increase control valves 46FL to 46FL corresponding to the wheels are determined.
RR is shut off (ON) and the pressure reduction control valves 48FL-48
The RR is communicated (ON) to reduce the hydraulic pressure of the corresponding W / C2FL to 2RR to prevent the wheels from being locked. At this time, the amount of oil decompressed from the W / C2FL-2RR is discharged to the reservoirs 56, 58 via the pressure-reducing control valves 48FL-48RR, and further driven by the motor 80 to store the oil in the reservoir 5.
The brake oil accumulated in 6,58 is returned to the normal brake system.

When it is determined that the locking tendency of the wheel has been eliminated during the anti-skid control, the pressure increase control valves 46FL to 46RR corresponding to the wheel are communicated (OFF) and the pressure reduction control valves 48FL to 48RR are shut off ( OFF) to increase the hydraulic pressure of the corresponding W / C2FL-2RR.
In this case, if the W / C oil pressure is suddenly increased, the wheels tend to lock, so that both the pressure increase control valves 46FL to 46RR and the pressure decrease control valves 48FL to 48RR are shut off (the pressure increase control valve 4).
6 = ON, pressure reducing control valve 48 = OFF) to create a state in which the W / C hydraulic pressure is maintained. By such control, the W / C oil pressure is gradually increased, and the stability of the vehicle is secured while preventing the wheels from being locked.

After the end of the anti-skid control,
In order to smoothly perform the next anti-skid control, the motor 80 is driven for a predetermined period to pump out the brake oil in the reservoirs 56 and 58. Vehicle Behavior Control (Brake Force Control of Front Wheels FL and FR) Vehicle behavior control is performed when the rear wheels RL and RR, which are driving wheels, enter an engine braking state by moving a load, as described in the section of "Prior Art". Since the side force of the rear wheels RL and RR may decrease and the vehicle behavior may become unstable, in order to prevent such a phenomenon, the braking force according to the load movement is applied to the front wheels FL and FR during engine braking. In addition, the control is performed so that the braking force of the rear wheels RL and RR and the braking force of the front wheels FL and FR fall within the stable region of the ideal braking force distribution diagram shown in FIG.

In this vehicle behavior control, first, the motor 80 is driven to operate the pumps 60 and 62, and the SM valves 50a and 50b and the SR valves 70a and 70b are turned on (energized). That is, the SM valves 50a, 50b are set to the shut-off position, and the SR valves 70a, 70b are set to the communication position, from the reservoir 68 provided above the M / C 34 to the pressure increase control valves 46FL to 46RR by the pumps 60, 62. Make the brake oil pumpable.

In this vehicle behavior control, the front wheels FL,
A pressure increase control valve 46 for increasing / decreasing the oil pressure of the W / C2FL, 2FR of the front wheels FL, FR according to the wheel speed difference ΔV between the average wheel speed VF of FR and the average wheel speed VR of the rear wheels RL, RR.
ON of FL, 46FR and pressure reducing control valve 48FL, 48FR
By performing F, the front wheel average wheel speed VF is controlled to be lower than the rear wheel average wheel speed VR.

More specifically, the pressure increase control valves 46FL, 46FR and the pressure decrease control valves 48FL, 48FR are driven to drive the front wheels FL, F
Switch the brake hydraulic pressure of R to pressure increase / hold / pressure reduction as appropriate,
Thus, the braking force of the front wheels FL and FR is changed, and the front wheel average wheel speed VF is adjusted based on the rear wheel average wheel speed VR.

Next, a vehicle behavior control process executed by the ECU 20 to perform such vehicle behavior control will be described with reference to a flowchart shown in FIG. still,
This process is periodically executed at predetermined time intervals when an ignition switch (not shown) of the vehicle is turned on.

As shown in FIG. 3, when the vehicle behavior control process is started, first, in S110 (S: representing step), for example, whether or not both the accelerator switch 12 and the brake switch 36 are off is determined. Is determined, the drive wheels RL and RR are currently in an engine braking state. This processing (S110)
Corresponds to the detecting means of the present invention (described in claim 4).

If the driver is performing an accelerator operation or a brake operation and the engine is not currently being braked, the process is immediately terminated. Conversely, the driver is not performing the accelerator operation or the brake operation. If the engine is currently being braked, the processing after S120 (corresponding to the control means of the present invention) is executed.

When it is determined in S110 that the drive wheels RL and RR are in the engine braking state, the vehicle behavior control process controls the brake oil pressure of the front wheels FL and FR. By driving the motor 80 to operate the pumps 60 and 62, the SM valves 50a and 5
0b and the SR valves 70a and 70b are turned ON, and the brake oil pressure feed control is separately executed.

Next, in S120, the average wheel speed VR of the left and right rear wheels RL, RR is calculated based on the detection signals from the wheel speed sensors 4RL, 4RR provided on the rear wheels RL, RR. Further, in S130, the average wheel speed VF of the left and right rear wheels FL, FR is calculated based on the detection signals from the wheel speed sensors 4FL, 4FR provided on the front wheels FL, FR. Then, in subsequent S140, S120 and S130
Rear wheel average wheel speed VR and front wheel average wheel speed VF
(Where ΔV = VR−VF).

When the deviation ΔV between the rear wheel average wheel speed VR and the front wheel average wheel speed VF is obtained in this manner, S
The routine proceeds to 150, where it is determined whether the deviation ΔV is a negative value smaller than “0” and the rear wheel average wheel speed VR is lower than the front wheel average wheel speed VF. And the deviation ΔV
Is a negative value, and if the rear wheel average wheel speed VR is lower than the front wheel average wheel speed VF, the process shifts to S160 to increase the brake oil pressure for the front wheels FL, FR for W / C2FL, 2FR by a predetermined amount ΔP. Pressure increase control valves 46FL, 46FR to increase pressure
Is turned on, and the pressure-reducing control valves 48FL, 48FR are turned off, and the process is once ended.

On the other hand, if it is determined in S150 that the deviation ΔV is equal to or greater than “0”, the flow shifts to S170, where the deviation ΔV is determined.
It is determined whether V is greater than a first determination value KH (positive value) set in advance and whether the front wheel average wheel speed VF is lower than the rear wheel average wheel speed VR by a first determination value KH or more. This first determination value KH is determined at S160 by the front wheels FL,
By increasing the brake hydraulic pressure of FR, the front wheels FL,
This is a determination value for determining whether or not the braking force applied to the FR has been controlled to be equal to or greater than the braking force applied to the rear wheels RL and RR.
If the difference ΔV is equal to or smaller than the first determination value KH, the process of S160 is executed, and then the process is temporarily terminated.
When V is larger than the first determination value KH, the process proceeds to S180.

At S180, the deviation ΔV is larger than a second judgment value KR (positive value) set to a value larger than the first judgment value KH, and the front wheel average wheel speed VF
Is determined to be smaller than the rear wheel average wheel speed VR by a second determination value KR or more. This second determination value KH
Is to determine whether the braking force applied to the front wheels FL, FR has become too large with respect to the braking force applied to the rear wheels RL, RR by increasing the brake oil pressure of the front wheels FL, FR in S160. If the difference ΔV is equal to or smaller than the second determination value KR (that is, within the range from the first determination value KH to the second determination value KR), in S190, the pressure increase control valves 46FL, 46FR ON state, pressure reducing control valve 48FL, 48
FR is controlled to the OFF state, and W / C2 of the front wheels FL and FR is controlled.
After the brake oil pressure for FL and 2FR is maintained in the current state, the process is temporarily terminated.

Conversely, when the deviation ΔV is larger than the second determination value KR, the braking force applied to the front wheels FL, FR becomes too large, and the front wheels FL, FR tend to lock, and the vehicle behavior becomes poor. Since there is a risk of becoming stable, the process proceeds to S200, in order to reduce the brake oil pressure of the front wheels FL, FR, the pressure increase control valves 46FL, 46FR are turned on, and the pressure reduction control valves 48FL, 48FL,
48FR is controlled to be in the ON state, and the process is temporarily terminated.

As shown in FIG. 4, in the rear-wheel drive vehicle of this embodiment in which the vehicle behavior control is executed, the drive wheels (rear wheels) RL and RR enter an engine braking state (time t).
0), the rear wheel average wheel speed VR decreases, and the deviation ΔV between this and the front wheel average wheel speed VF becomes a negative value (time t).
1) The brake oil pressure of the front wheels FL and FR is gradually increased, and a braking force is applied to the front wheels FL and FR.

When the front wheel average wheel speed VF becomes lower than the rear wheel average wheel speed VR and the deviation ΔV becomes larger than the first determination value KH due to the increase of the brake oil pressure, when the front wheels FL and FR are increased. Brake oil pressure is maintained,
Further, when the deviation ΔV becomes larger than the second determination value KR,
When the brake hydraulic pressure of the front wheels FL and FR is reduced, the front wheels F
The braking force applied to L and FR is reduced.

Therefore, according to the present embodiment, the braking force applied to the front wheels FL and FR during engine braking is determined by determining whether the front wheel average wheel speed VF is equal to the first determination value K from the rear wheel average wheel speed VR.
The engine is controlled so as to be within the speed range from the speed (VR-KH) obtained by subtracting H to the speed (VR-KR) obtained by subtracting the second determination value KR from the average rear wheel speed VR. The vehicle deceleration at the time of engine braking can be increased as compared with a conventional device that does not control the braking force of the front wheels FL and FR during braking (see FIG. 4).

As described above, in this embodiment, the rear wheels RL, R
A braking force equal to or greater than the braking force applied to the front wheels FL, FR
, The braking force of the rear wheels RL and RR and the front wheel F
The relationship between L and FR and the braking force can be controlled within the stable region of the ideal braking force distribution diagram shown in FIG. 5, and the running stability of the vehicle can be improved.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various embodiments can be adopted. For example, in the above-described embodiment, a description has been given of a case in which a braking force is applied to the front wheels during engine braking of a rear-wheel drive vehicle to improve the running stability of the vehicle. When the rear wheel side force is reduced, braking force is applied to the front wheels to reduce the front wheel side force and balance the lateral forces on the front and rear wheels of the vehicle. Even when the present invention is applied to a driving vehicle, the running stability of the vehicle can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of an entire control system of a rear-wheel drive vehicle according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a configuration of a hydraulic circuit according to an embodiment.

FIG. 3 is a flowchart illustrating vehicle behavior control performed by an ECU during engine braking.

FIG. 4 is a timing chart illustrating an operation of vehicle behavior control performed by an ECU.

FIG. 5 is an ideal braking force distribution diagram for front wheels and rear wheels of the vehicle.

[Explanation of symbols]

FL: Left front wheel FR: Right front wheel RL: Left rear wheel R
R: right rear wheel 2: brake device (wheel cylinder: W / C) 4
... wheel speed sensor 6 ... engine 8 ... transmission 10 ... differential gear 11 ... propeller shaft 12 ... accelerator switch 20 ... electronic control unit (ECU) 32 ... brake pedal 34 ... master cylinder (M / C) 36 ... brake switch 40 ... Hydraulic circuits 42, 44 Hydraulic path 46 Pressure increasing control valve 48 Pressure reducing control valve 54a, 54b Relief valve 50a, 50b Master cylinder cut valve (SM
Valves) 56, 58, 68 Reservoir 60, 62 Pump 64, 66 Accumulator 80 Motor 70a, 70b Reservoir cut valve (SR valve)

Claims (7)

[Claims] In a vehicle having at least a rear wheel as a driving wheel, when the driving wheel is in an engine braking state due to a decrease in driving force applied to the driving wheel, a load transfer of the vehicle body by the engine brake is performed. A vehicle behavior control device characterized by applying a wheel braking force by a brake fluid pressure to a front wheel according to the following. 2. A vehicle in which a rear wheel is configured as a drive wheel and a front wheel is configured as a driven wheel. A vehicle behavior control device characterized in that a wheel braking force equal to or greater than a wheel braking force applied to a driving wheel is applied to the driven wheel by a brake fluid pressure. 3. In a vehicle in which a rear wheel is a driving wheel and a front wheel is a driven wheel, when the driving wheel is in an engine braking state with a decrease in driving force applied to the driving wheel, a wheel on the driven wheel is provided. A vehicle behavior control device, wherein a wheel braking force is applied to the driven wheel by a brake fluid pressure so that a braking force is equal to or greater than a wheel braking force of the driving wheel. 4. A wheel braking force generating means provided on each wheel of a vehicle for generating a braking force in accordance with a brake fluid pressure on each wheel, and a brake fluid pressure applied to each wheel braking force generating means. The vehicle is provided with a brake fluid pressure generating means and a driving force generating means for generating a driving force for driving at least a rear wheel, and the driving force generated by the driving force generating means is reduced. A vehicle behavior control device that controls the behavior of the vehicle when the drive wheels are in an engine braking state, wherein a detecting means for detecting the engine braking state; and the detecting means detects the engine braking state. When,
Control means for operating the brake fluid pressure generating means to apply brake fluid pressure to the front wheel side wheel braking force generating means to generate a braking force on the front wheels of the vehicle. Control device. 5. The control means, when the engine brake state is detected by the detection means, causes the brake hydraulic pressure generation means to generate a brake hydraulic pressure according to a load shift generated in the vehicle body by the engine brake. The vehicle behavior control device according to claim 4, wherein the vehicle behavior control device is applied to the front wheel side wheel braking force generating means. 6. The control means judges the load movement from a wheel speed difference between a wheel speed of a front wheel and a wheel speed of a rear wheel, and generates a wheel braking force on the front wheel according to the wheel speed difference. The vehicle behavior control device according to claim 5, wherein brake fluid pressure applied to the vehicle is controlled. 7. The vehicle according to claim 6, wherein the control means prohibits an increase in the brake fluid pressure when a wheel speed of a front wheel is lower than a wheel speed of a rear wheel by a predetermined value or more. Behavior control device.