JPH05254406A - Brake system for vehicle - Google Patents

Abstract

PURPOSE:To provide a brake system for a vehicle capable of improving the driving stability at the time of a turning travel. CONSTITUTION:A brake system is provided with a foot brake system 16 generating the liquid pressure with a master cylinder 12 interlocked with a brake pedal 11 and an automatic brake system 100 generating the braking liquid pressure when the behavior of a vehicle tends to exceed the turn limit at the time of a turning travel. The foot brake system 16 and the automatic brake system 100 are connected to braking force distributing devices 13, 14 via direction control valves 115, 116. The braking force distributing devices 13, 14 distribute the liquid pressure to the wheel cylinders of an inner wheel and an outer wheel at the braking ratio capable of suppressing the excessive under-steering or over-steering during the turning travel. The direction control valves 115, 116 communicate the foot brake system 16 with the braking force distributing devices 13, 14 when the brake pedal 11 is depressed and connect the automatic brake system 100 to the braking force distributing devices 13, 14 when the brake pedal 11 is not depressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic brake system for vehicles such as automobiles, and more particularly to a brake system having a braking force distribution function.

[0002]

2. Description of the Related Art It is known that when a vehicle turns, the cornering motion characteristics differ depending on the vehicle type. In other words, there are characteristics such as understeer and oversteer.These movement characteristics depend on driving conditions such as vehicle speed and turning radius.When the turning plunge speed is too high, the behavior of the vehicle may exceed the turning limit. come.
In addition, when braking is performed during turning, the above-mentioned motion characteristics may be changed by the braking force acting on the wheel on the inside of the turn (inner wheel) and the wheel on the outside of the turn (outer wheel).

Therefore, when it is likely to exceed the turning limit or when braking is performed during turning, it is desirable to suppress the occurrence of excessive understeer or oversteer to improve steering stability.

[0004]

[Problems to be Solved by the Invention] Conventionally, so-called TCL
Although a system has been developed for performing engine output control when there is a possibility that the turning limit will be exceeded as described above, there was no idea to increase the turning limit by using the braking force. For example, engine output control such as TCL does not raise the turning limit, and therefore, when a driver wants to aggressively enter a corner, the driver may feel a slight discomfort in the driving feeling. Therefore, an object of the present invention is to provide a vehicle brake system that can improve steering stability by utilizing a braking force during turning.

[0005]

SUMMARY OF THE INVENTION A brake system of the present invention developed to achieve the above object comprises a foot brake system for generating hydraulic pressure during braking by a master cylinder interlocked with a brake pedal, and a vehicle during turning. The automatic braking system that supplies hydraulic pressure for braking when there is a possibility that the behavior of the vehicle will exceed the turning limit, and the inside of the turning with a braking ratio that makes the actual behavior of the vehicle that occurs during cornering approach the desired cornering motion characteristics. Braking force distribution device that distributes the hydraulic pressure for braking to the wheel cylinder of the wheel and the wheel cylinder of the wheel on the outside of the turn, and the hydraulic pressure of the foot brake system is supplied to the braking force distribution device when the brake pedal is depressed. When the brake pedal is not depressed, the foot brake system is connected so that the hydraulic pressure of the automatic brake system is supplied to the braking force distribution device. It is provided with a switching means for switching operation of the dynamic braking system.

[0006]

When the brake pedal is depressed, the hydraulic pressure generated in the master cylinder according to the depression amount of the pedal is transmitted to the left wheel wheel cylinder and the right wheel wheel cylinder through the braking force distribution device. When the brake pedal is pressed during turning, for example, when the yaw rate sensor system shows an understeer tendency, the braking force distribution is adjusted so that the braking force of the outer wheel becomes lower than the braking force of the inner wheel. The device distributes hydraulic pressure to the left and right wheel cylinders. When the tendency of oversteering is recognized, the braking force distribution device operates so that the braking force of the inner wheel is lower than the braking force of the outer wheel, contrary to the above.

When the behavior of the vehicle may exceed the turning limit when the brake pedal is not depressed, the braking hydraulic pressure generated in the automatic braking system is applied to the wheels of the inner and outer wheels via the braking force distribution device. It is distributed to the cylinders and the braking ratio of the inner and outer wheels is adjusted so as to suppress excessive understeer or oversteer, as in the case of the foot brake system.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. A vehicle brake system 10 shown in FIG. 1 includes a master cylinder 12 that is interlocked with a brake pedal 11 and a front braking force distribution device 1.
3 and a rear braking force distribution device 14. The master cylinder 12 produces a braking hydraulic pressure in accordance with the amount of depression of the brake pedal 11, as is well known. In the vicinity of the brake pedal 11, the brake pedal 1
A brake switch 15 is provided to detect that 1 is stepped on. Brake pedal 11 and master cylinder 1
2 constitutes a foot brake system 16.

The braking force distribution device 13 for the front side and the braking force distribution device 14 for the rear side are connected to the master cylinder 12 via the brake pipes 20 and 21, respectively.
26 are provided. These primary hydraulic chambers 25, 26 are provided with primary hydraulic pistons 27, 28 which are moved by the hydraulic pressure generated in the master cylinder 12 during braking.

The front braking force distribution device 13 includes a hydraulic chamber 30 for the front left wheel and a hydraulic chamber 3 for the front right wheel.
1 is provided. A front left wheel secondary side piston 32 and a front right wheel secondary side piston 33 are provided in these hydraulic chambers 30, 31. The front left wheel hydraulic chamber 30 is connected to a front left wheel wheel cylinder 36 via a hydraulic pipe 35. The front right wheel hydraulic chamber 31 is connected to a front right wheel wheel cylinder 38 via a hydraulic pipe 37.

The braking force distribution device 14 for the rear includes a hydraulic chamber 40 for the rear left wheel and a hydraulic chamber 41 for the rear right wheel. A rear left-wheel secondary piston 42 and a rear right-wheel secondary piston 43 are provided in these hydraulic chambers 40 and 41. The rear left wheel hydraulic chamber 40 is connected to a rear left wheel wheel cylinder 46 via a hydraulic pipe 45. The rear right wheel hydraulic chamber 41 is connected to a rear right wheel wheel cylinder 48 via a hydraulic pipe 47.

As shown in FIG. 2 as a representative of one braking force distribution device 13, the braking force distribution device 13 includes a housing 50. Inside the housing 50, the movable frame 5
1 is housed so as to be movable in the left-right direction in the drawing. One end 52 of the movable frame 51 is connected to the rod 53 of the primary hydraulic piston 27. Therefore, the movable frame 51
Moves in the left-right direction in the drawing in conjunction with the primary hydraulic piston 27.

The hydraulic chambers 30 and 31 partitioned by the secondary side pistons 32 and 33 have the above-mentioned hydraulic pipes 35 and 3, respectively.
Connected to 7. The secondary side pistons 32 and 33 include piston rods 62 and 63 connected by universal joints 60 and 61 such as pillow ball joints. The piston rods 62 and 63 extend in parallel with each other inside the housing 50.

The ends of the piston rods 62 and 63 are connected to each other by a link 65. The connecting portions of the piston rods 62, 63 and the link 65 are connected by rotatable joints 66, 67 such as pillow ball joints.

The link 65 is driven by the movable pusher 70. The movable pusher 70 includes the secondary piston 3
The links 65 are in contact with the link 65 from the directions in which the piston rods 62, 63 of 2, 33 can be pressed simultaneously. Movable pusher 70
Is slidably held by the guide member 71 so that it can be moved in the length direction of the link 65, that is, in the directions of arrows A and B in FIG. 2 along the guide member 71 provided on the movable frame 51.

The movable pusher 70 of the illustrated example is a rotary type that rotates about a shaft 72 and rolls on the surface of the link 65, and uses a bearing such as a roller bearing. Instead of, the slide type of sliding on the surface of the link 65 may be adopted. The guide member 71 is fixed to the movable frame 51 so as to be parallel to the link 65.

The movable pusher 70 can be moved to a desired target position by a servo mechanism 81 having an actuator 80. Servo mechanism 8
One example is a forward / reverse rotatable DC servo motor as the actuator 80, a slider 85 provided with the movable pressing element 70, and a force transmission means 86 for converting the rotational movement of the actuator 80 into a linear movement of the slider 85. And a position detector 87 such as a potentiometer for detecting the position of the slider 85. Movable pusher 7
0 is integrated with the slider 85 and is indicated by an arrow A or B in FIG.
Move in the direction.

The force transmission means 86 of the illustrated example comprises a gear unit 90 rotated by an actuator 80, a lead screw 91 rotated by the gear unit 90, a nut member 92 screwed to the lead screw 91, and the like. Depending on the rotation direction and the rotation amount of the actuator 80, the nut member 92 moves the lead screw 9
The movable pusher 70 is moved to a desired target position by being screwed in the axial direction of 1.

Position of the nut member 92, that is, the slider 8
The position of 5 is detected by the position detector 87 and fed back to the controller 95. Controller 95
Controls the rotation of the actuator 80 based on the feedback information on the position of the slider 85 output by the position detector 87 so that the movable pusher 70 reaches the target position.

When the movable pusher 70 moves in the direction of the arrow A, the distance L1 from the movable pusher 70 to the secondary piston 32 for the left wheel and the distance R to the secondary piston 33 for the right wheel.
The link ratio with 1 (L1: R1) is from 50:50 to 0: 100
To change to. Therefore, the pressing force of the movable pressing member 70 is larger in the left wheel secondary side piston 32 in inverse proportion to the link ratio. When the movable pusher 70 moves in the direction of arrow B, the link ratio (L1: R1) becomes
It changes from 50:50 to 100: 0. Therefore, the pressing force of the movable pressing element 70 is increased toward the right wheel secondary side piston 33 in inverse proportion to the link ratio.

As shown in FIG. 1, the controller 95
Is an arithmetic processing unit 96 using a microcomputer or the like.
Included in. Information about the on / off operation of the brake switch 15 and information about the steering operation angle and speed information output from the steering angle sensor 97 and the vehicle speed sensor 98 as an example of the yaw rate sensor system are input to the arithmetic processing unit 96. It has become so. Also,
The target yaw rate during turning traveling, which is obtained in advance from the relationship between the steering angle and the vehicle speed, is input to the arithmetic processing unit 96.

The brake system 10 also includes an automatic brake system 100. Automatic braking system 100
Includes a power cylinder 101, a pressure control valve 102, a pump 103, an accumulator 104, and the like.
The pressure of the accumulator 104 is detected by the pressure switch 105, and when the pressure falls below a predetermined value, the pump controller 106 activates the pump 103. When the pressure control valve 102 is switched to the valve opening direction, the pressure stored in the accumulator 104 acts on the power cylinder 101.

On the output side of the power cylinder 101, a front brake pipe 110 and a rear brake pipe 1 are provided.
11 and 11 are connected. Front brake piping 1
10 and the brake pipe 20 of the above-described foot brake system 16 are electromagnetic directional control valves 115 as an example of switching means.
It is adapted to be selectively communicated with the primary hydraulic chamber 25 of the front braking force distribution device 13 via the. Further, the rear brake pipe 111 and the rear brake pipe 21 of the foot brake system 16 are also connected to the primary side hydraulic pressure of the rear braking force distribution device 14 via an electromagnetic directional control valve 116 as an example of a switching means. It is adapted to selectively communicate with the chamber 26.

Next, the operation of the brake system 10 having the foot brake system 16 and the automatic brake system 100 having the above-mentioned configuration will be described with reference to the flowchart of FIG. Since the front braking force distribution device 13 and the rear braking force distribution device 14 have the same operation, the front braking force distribution device 13 will be described as a representative.

When the brake pedal 11 is stepped on, the brake switch 15 is turned on, whereby the directional control valve 11
5, 116 are kept off (state of FIG. 1). In this case, the hydraulic pressure of the master cylinder 12 is the braking force distribution device 13,
14 to act on the foot brake system 1
6 exerts a braking function.

When the brake pedal 11 is not depressed, the brake switch 15 remains off, so that the directional control valves 115 and 116 are turned on, that is, the hydraulic pressure of the power cylinder 101 is applied to the braking force distribution devices 13 and 14. Since the operation is switched so that the automatic braking system 100 is in the standby state. The foot brake system 16 is prioritized when the hydraulic pressure is lost.

When the foot brake system 16 exerts a braking function by the depression of the brake pedal 11, the hydraulic pressure generated in the master cylinder 12 in accordance with the depression amount of the brake pedal 11 causes the primary side hydraulic pressure of the braking force distribution device 13. The piston 27 is driven. And the primary side hydraulic piston 2
By transmitting the movement of 7 to the movable frame 51, the movable pressing element 70 moves in the same direction as the movable frame 51. The movable pusher 70 pushes the link 65 to drive the left-wheel secondary piston 32 and the right-wheel secondary piston 33 simultaneously. Therefore, the hydraulic pressure in the left wheel hydraulic chamber 30 and the right wheel hydraulic chamber 31 is increased, and the left wheel side wheel cylinder 36 and the right wheel side wheel cylinder 38 are driven to exert a braking force.

At the time of braking, the movable pusher 70 is linked to the link 6
When located in the center of 5, link ratio (L1: R1)
Is 50:50, the pressing force of the movable pusher 70 is evenly distributed to the left-wheel secondary piston 32 and the right-wheel secondary piston 33. Therefore, the same braking force is exerted on both the left and right wheel cylinders 36, 38.

When the brake pedal 11 is depressed during turning, the actual yaw rate is calculated from the information input to the arithmetic processing unit 96 from, for example, the steering angle sensor 97 and the vehicle speed sensor 98, and this is compared with the target yaw rate. It As a result of the yaw rate deviation calculation, when it is determined that the understeer is performed, the movable pusher 70 is moved so as to reduce the outer wheel braking ratio.

For example, when it is determined that the understeer is occurring during the left turn, the movable pusher 70 moves in the direction of arrow A in FIG. In this case, the braking force transmitted from the primary side hydraulic piston 27 to the movable pusher 70 is equal to the link ratio (L1
: R1) has a large effect on the left-wheel piston 32 in inverse proportion to R1), so that the braking force of the left wheel (inner wheel side) becomes larger than the braking force of the right wheel (outer wheel side), and understeer is eliminated. ..

When it is determined that the steering is oversteer during a left turn, the movable pusher 70 is driven in the direction of arrow B, as opposed to understeer, so that the braking force of the inner wheel is greater than the braking force of the outer wheel. By controlling the braking ratio to be low, oversteering is eliminated. In any of the above cases, it goes without saying that control is performed in the opposite direction when turning to the right as when turning to the left.

As described above, the braking ratio of the outer wheel or the inner wheel is reduced according to the understeer or oversteer during turning, but the reduced hydraulic pressure is exerted as an increase in the braking force of the wheel on the opposite side. Therefore, the braking force generated in the master cylinder 12 by depressing the brake pedal 11 is fully exerted.

On the other hand, when the brake pedal 11 is not depressed, that is, when the automatic braking system 100 is in the standby state, the liquid generated in the power cylinder 101 when the behavior of the vehicle may exceed the turning limit. The pressure passes through the directional control valves 115 and 116, the braking force distribution device 13,
14 is transmitted to the primary side hydraulic pistons 27, 2
8 is driven. Then, as in the case of braking by the foot brake system 16, the link 65 is pushed through the movable frame 51 and the movable pressing element 70, and the left wheel secondary side piston 32 and the right wheel secondary side piston 33 are driven.

In this case as well, the actual yaw rate generated during turning is compared with the target yaw rate by the arithmetic processing unit 96. As a result of the yaw rate deviation calculation, when it is determined that the understeer is occurring, the link ratio (L1: R1 = 0: 100) is set so that the inner wheels are braked.
In this case, the braking force acting on the primary side hydraulic piston 27 substantially acts only on the left wheel piston 32, so that understeer is suppressed. When it is determined that the oversteer is performed, the link ratio (L1: R1 = is 100: 0) for braking the outer wheels is set contrary to the above, so that the oversteer is suppressed.

When the left / right slip ratio Δs exceeds the set value, it is determined that excessive slip has occurred. Further, when the front-rear direction G exceeds the set value, it is determined that the deceleration is too strong. In these cases, the pressure control valve 102
A process of reducing the braking hydraulic pressure by the process and a process of changing the link ratio are performed. The above braking force control is sequentially executed in real time during turning, and the braking force distribution devices 13, 1 are provided so that desired cornering motion characteristics can be obtained.
The link ratio (L1: R1) in 4 is 0: 100 to 5
It is variably set in the range of 0:50 to 100: 0.

[0036]

According to the present invention, the cornering motion characteristics can be improved by increasing or decreasing the braking force distributed to the inner wheel and the outer wheel during turning, and the safety and steering stability during turning can be improved. You can improve your sex.

[Brief description of drawings]

FIG. 1 is a system diagram of a brake system showing an embodiment of the present invention.

2 is a cross-sectional view of a braking force distribution device used in the braking system shown in FIG.

3 is a flowchart showing an example of control by a controller of the brake system shown in FIG.

[Explanation of symbols]

11 ... Brake pedal, 12 ... Master cylinder, 13,
14 ... Braking force distribution device, 16 ... Foot brake system, 3
6, 38 ... Wheel cylinders, 46, 48 ... Wheel cylinders, 96 ... Arithmetic processing unit, 100 ... Automatic braking system, 115, 116 ... Direction control valves (switching means).

Claims (1)

[Claims] 1. A foot brake system that generates hydraulic pressure during braking by a master cylinder that interlocks with a brake pedal,
The automatic braking system that supplies hydraulic pressure for braking when the behavior of the vehicle may exceed the turning limit during turning, and the actual behavior of the vehicle that occurs during turning approaches the desired cornering motion characteristics. A braking force distribution device that distributes the braking hydraulic pressure to the wheel cylinder of the wheel on the inside of the turn and the wheel cylinder of the wheel on the outside of the turn at a braking ratio, and the hydraulic pressure of the foot brake system when the brake pedal is depressed. A switching means for switching between the footbrake system and the automatic braking system so that the hydraulic pressure of the automatic braking system is supplied to the braking force distributing device when the brake pedal is not depressed. A vehicle braking system characterized by the above.