JPH0396481A - Steering device for vehicle - Google Patents

Abstract

PURPOSE:To improve stability at the time of braking a vehicle in a high-speed forward travel, or the like by installing an actuator for assisting the steering of an auxiliary steering wheel in such a way as to steer the vehicle in a direction opposite to yawing moment generated due to a braking force difference between right and left wheels. CONSTITUTION:When a brake pedal is stepped down and disc brakes 33L and 33R are thereby actuated for braking front wheels 11L and 11R under running, a braking force is transmitted from the front wheels 11L and 11R running in contact with a ground surface to a body 17 via tension rods 16L and 16R. In this case, when there is any difference in the braking force of the disc brakes 33L and 33R, due to a difference in coefficient of friction between the brake discs 32L and 32R, and a brake pad, or between the front wheels 11L and 11R, and the ground surface, yawing moment is generated for turning a vehicle toward a large braking force. On the other hand, however, the front wheels 11L and 11R are steered in such a way that the oil chambers of mount units 21L and 21generate differential pressure, corresponding to the aforesaid braking force difference, and the vehicle is turned with a hydraulic actuator 35 in a direction opposite to the action of the yawing moment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle steering system, and more particularly to a vehicle steering system that slightly steers steered wheels in order to stabilize vehicle behavior during high-speed straight braking. .

(Prior Art) Conventionally, there have been proposed methods for improving turning performance by steering the rear wheels according to the front wheel steering state and changes in vehicle speed when turning a vehicle, for example, Japanese Utility Model Application Publication No. 57-19172 and Japanese Patent Application Laid-Open No. 1987-1917. Showa 5
There is one described in No. 7--60974. These devices detect deceleration or acceleration when the vehicle is turning, and perform rear wheel steering according to the detection results. This is to prevent the flow spin phenomenon.

(Problem to be Solved by the Invention) However, with such conventional vehicle steering systems, rear wheel auxiliary steering is performed according to the deceleration and acceleration of the vehicle during a turn, so During braking, mainly due to the variation in the friction coefficient of the brake pads (usually about ±10%), for example, as shown in Fig. 6, the left and right front wheels IL,
Even if a difference ΔF occurs between the IR braking force F and Ffl, and the vehicle's yaw moment M (around the center of gravity CG) occurs,
In contrast, there has been a problem in that an effective auxiliary steering effect cannot be obtained, resulting in vehicle behavior that is not intended by the driver. In particular, vehicle behavior that is not intended by the driver due to the difference between the left and right brake torques becomes more pronounced as the speed increases and as the brakes become more abrupt.

Furthermore, even if the difference in the coefficient of friction between the left and right brake pads is small, if there is a difference in the coefficient of friction between the road surface and the tires, the same problem as mentioned above will occur due to the difference in braking force FrLsFr*. .

Furthermore, when the scrub radius (king bin offset) of the front suspension is positive, as shown in Fig. 7, the wheel IL with the greater braking force is displaced (δ,〉) in the toe-out direction due to the braking force of the left and right wheels. δR)
This also tended to increase the yaw moment of the vehicle.

A technique for reducing such a yaw moment of a vehicle by auxiliary steering of the rear wheels is disclosed in Japanese Patent Laid-Open No. 1-168577. However, the configuration shown in the above document requires a controller, a hydraulic pressure generating means, a control valve, a sensor, etc. in order to perform auxiliary steering of the rear wheels, resulting in a complicated configuration and increased cost. Furthermore, since the rear wheels are auxilially steered based on electrical signals from the controller, a fail-safe means must be provided in case an electrical failure such as a runaway of the controller occurs, which further complicates the structure.

(Purpose of the Invention) Therefore, the present invention performs minute steering according to the difference in braking force between the left and right steered wheels to offset the vehicle yaw moment generated by the difference in braking force by mechanical means without using electrical control means. In this way, the purpose is to improve stability during high-speed straight-line braking.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a steering device for a vehicle that performs auxiliary steering of at least one of the front wheels and rear wheels of the vehicle, and which applies braking force from the wheels. left and right suspension members that receive and transmit the braking force to the vehicle body, left and right hydraulic pressure generation means that independently generate hydraulic pressure in response to the braking force applied to the vehicle body from each suspension member, and both hydraulic pressure generation means. The present invention is characterized by comprising an actuator that operates in response to a hydraulic pressure difference and performs auxiliary steering of an auxiliary steering wheel so as to steer the vehicle in a direction opposite to the vehicle yaw moment caused by the difference in braking force between the left and right wheels. It is something.

(Function) In the present invention, different hydraulic pressures are generated on the left and right sides according to the difference in the braking force applied from the wheels to the left and right suspension members during braking, and the actuators on the left and right sides are operated according to the differential pressure between the two hydraulic pressures. Auxiliary steering wheels are used to perform auxiliary steering to steer the vehicle in a direction opposite to the yaw moment of the vehicle caused by the difference in braking force. Therefore, the yaw moment caused by the difference in braking force between the left and right sides is offset by the yaw moment generated by steering by the actuator, preventing vehicle behavior that is not intended by the driver, and improving stability during high-speed straight braking.

(Example) Hereinafter, the present invention will be explained based on the drawings.

1 to 3 show a first embodiment of the invention.

First, the structure will be explained. In FIG. 1, IIL, ll
R is a left and right front wheel that is both a main steering wheel and an auxiliary steering wheel, and 12L and 12R are left and right rear wheels.

The front wheels 11L and IIR are steered by a rack-and-pinion type steering gear 14 in accordance with the operation of the steering wheel H via steering linkages 13L and 13R consisting of side wheels, etc., and transverse links 15L and 115R and tension. It is connected to the vehicle body 17 via suspension members such as rondos 161, 16R.

These tension brakes 16L and 16R receive the braking force as tension from the front wheels 11L and IIR when the vehicle is braking, and the mount unit 21L attached to the front end receives the braking force as tension.
It is transmitted to the vehicle body 17 via 21R (hydraulic pressure generating means).

As shown in FIG. 2, mount units 21L and 21R
are tension rods 16L and 16R and car body l7 respectively.
It is interposed between the side brackets 22, and each mount unit 21L, 21R has a first push 23 (hydraulic pressure generating means) which is compressed by the displacement of the tension rods 16L, 16R in the direction of arrow P during forward braking. , made of elastic material such as rubber, and tension rod 16 during reverse braking.
The second push 24 is compressed by the displacement of L and 16R in the direction of the arrow Q, the one-shears 25A, 25B, 26A, 26B that come into contact with both axial surfaces of both pushes 23 and 24, and both pushes 23 and 24 are attached to the bracket 22. The waffle 27A is connected to the tension rods 16L and 16R while applying narrow pressure.
, 27B and a nant 28, and a collar 29 interposed between the inner peripheral portions of both the pushers 23, 24 and the tension rods 16L, 16R. The first push 23 has an oil chamber 30 inside an annular elastic body, and the front wheels 11L and 11R are braked by known disc brakes 33L and 33R, which are composed of caliper abutments 31L and 31R and brake discs 32L and 32R. When the first push 23 receives the force from the tension rods 16L and 16R, it pressurizes the hydraulic oil (not shown) in the oil chamber 30 and transmits the force to the vehicle body 17.

In addition, a pair of oil chambers 3 of the mount units 21L and 21R
0 communicates with the hydraulic chambers 35a, 35b of the hydraulic actuator 35 via hydraulic pipes 34A, 34B, and the actuator piston 36 of the hydraulic actuator 35 communicates with the hydraulic pressure difference between the two hydraulic chambers 35a, 35b, that is, the pair of oil Room 3
According to the differential pressure of 0, the centering springs 37A, 37
It is displaced against the urging force of one of B. The actuator piston 36 is connected to a rank housing 38 of the steering gear 14, and the rack housing 38, which is elastically supported by the vehicle body 17 via rank mount insulators 39A and 39B, is connected to the actuator piston 3.
The front wheels ILL and IIR are displaced in the vehicle width direction in response to the thrust from 6, and are
It is designed to steer the ship. In this embodiment, the steering linkages 13L and 13R are connected to the front wheel 1.
Since it is arranged on the rear side of 1L and IIR, the hydraulic pipes 34A and 34B are crossed and the disc brake 3
The vehicle yaw moment generated due to the difference in braking force between the front wheels ILL and IIR caused by 3L and 33R and the vehicle yaw moment generated due to steering by the hydraulic actuator 35 are designed to cancel each other out.

Next, the effect will be explained.

When the brake pedal (not shown) is depressed, the disc brakes 33L, 33R are activated, and the front wheels 1L, I
When IR is braked, the front wheels 11L and IIR that are in contact with the road surface
from the vehicle body l7 via tension rods 16L and 16R.
Braking force is transmitted to. At this time, disc brake 3
If there is a difference in the braking force between the disc brakes 33L and 33R due to the difference in the friction coefficient between the brake disc 32A132B of 3L and 33R and the brake pad (not shown), or the difference in the friction coefficient between the front wheels ILL and IIR and the road surface, the braking force will be reduced. A vehicle yaw moment is generated that tries to turn the vehicle toward the side with greater power, but on the other hand, the mount unit 21L,
The hydraulic actuator 35 causes the hydraulic actuator 35 to steer the vehicle in the opposite direction to the vehicle yaw moment.
L and 11R are steered.

? For example, if a large braking force FfL (FfL>F■) is applied to the front wheel ILL due to braking during high-speed straight running, conventionally the front M11t,...
IIR was displaced, and the reaction force of the tension rods 16L and 16R was also larger for the tension rod 16L, but in this example, the tension rod 1, which has a larger braking force,
6L generates a large hydraulic pressure PL (PL > Rll) in the oil chamber 30 in the mount unit 21L, and the oil chamber 30
The differential pressure PL-P. The hydraulic actuator 35 is actuated by a stroke S corresponding to , and the hydraulic actuator 35 steers the front wheels 11L and IIR by an angle δ from the dashed line position to the solid line position so as to keep the vehicle traveling straight. In this state, the steering wheel H is in a stable state, so that the vehicle does not behave unintentionally by the driver.
Stability during braking is ensured.

As described above, the configuration of this embodiment is a mechanical configuration that uses only hydraulic pressure, has a simple structure, and does not cause electrical failure.

4 and 5 are diagrams showing a second embodiment of the present invention, and show an example in which the present invention is applied to a four-wheel steering vehicle.

In this example, the tension rod 16L116R
Mount units 41L, 41 between and bracket 22
R is interposed, and the mount units 41L and 41R are connected to the first push 23 of the mount units l-21L and 21R.
And hydraulic piston 4 in place of wasosha 25A, 26A
It has 2. The hydraulic piston 42 has an annular piston member 43 and a cylinder member 44 that define an oil chamber 45. During braking, the piston member 43, which receives the force from the tension rods 16L and 16R, drains the hydraulic oil in the oil chamber 45. Braking force is transmitted from the cylinder member 44 to the vehicle body 17 while being pressurized. On the other hand, the pair of oil chambers 45 are connected to hydraulic pipes 46A, 4
Hydraulic chamber 47a of hydraulic actuator 47 via 6B,
47b, the front wheel 11L is the main steering wheel,
When a pressure difference occurs between the oil pressures PL and PR in the pair of oil chambers 45 due to the difference in braking force acting on the IIR, the actuator piston 48 moves the centering spring 49 in response to the pressure difference.
It is displaced against the biasing force of either of the rear wheels A and 49B, and steers the rear wheels 12L and 12R, which are auxiliary steering wheels, via the left and right side wheels 50L and 50R. For example, when the braking force of the front wheel 11L is greater than that of the front wheel 11R, the oil pressure in the hydraulic chamber 47a of the hydraulic actuator 47 increases,
The rear wheels 12L and 12R are slightly steered to the left. Even in this case, the same effects as in the first embodiment can be obtained.

In addition to what is shown in this embodiment, both the front wheels 11L, 11R and the rear wheels 12L, 12R may be slightly steered by the difference in braking force between the front wheels 11L and IIR, which are the main steering wheels. In addition, the rear wheels 12L, 12, which are auxiliary steering wheels,
Hydraulic pressure is generated according to the difference in braking force between the R and 11LSI front wheels.
At least one of the IR and the rear wheels 12L and 12R may be slightly steered.

(Effects) According to the present invention, different hydraulic pressures are generated on the left and right sides by the hydraulic pressure generation means according to the difference in braking force applied from the wheels to the left and right suspension members during braking, and the actuator is actuated according to the differential pressure between the two hydraulic pressures. Since the vehicle is steered in the opposite direction to the vehicle yaw moment caused by the difference in braking force, the yaw moment caused by the difference in left and right braking forces is offset by the auxiliary steering of the actuator, thereby preventing vehicle behavior that is not intended by the driver. This makes it possible to improve stability during high-speed straight-line braking.

Here, the structure of the present invention is a simple mechanical structure using only hydraulic pressure, which reduces costs and does not cause electrical failure.

[Brief explanation of drawings]

1 to 3 are diagrams showing a first embodiment of the vehicle steering system according to the present invention, in which FIG. 1 is an overall configuration diagram thereof, FIG. 2 is a detailed sectional view of its main parts, and FIG. 3 is its Action diagram, 4th and 5th
The figures are diagrams showing a second embodiment of the vehicle steering system according to the present invention, FIG. 4 is a diagram of its overall configuration, and FIG. 5 is a detailed cross-sectional view of its essential parts. 6 and 7 are explanatory diagrams of the conventional problems, respectively. lIL, IIR...Front wheel, 12L, 12R...Rear wheel, 16L, 16R...Tension Rondo (suspension 3-in member), 21L, 21R... Mount unit (hydraulic generating means), 35... Hydraulic actuator, 41L, 41R
...Mount unit, (hydraulic pressure generating means), 47...Hydraulic actuator.

Claims (1)

[Claims] A steering system for a vehicle that assists in steering at least one of the front wheels and rear wheels of a vehicle, comprising left and right suspension members that receive braking force from the wheels and transmit the braking force to the vehicle body, and a suspension member that applies braking force to the vehicle body from each suspension member. The left and right hydraulic pressure generating means independently generate hydraulic pressure according to the braking force, and the hydraulic pressure generating means operates according to the differential pressure between the hydraulic pressure generated by both hydraulic pressure generating means, and it acts in opposition to the vehicle yaw moment caused by the difference in braking force between the left and right wheels. 1. A vehicle steering device comprising: an actuator that performs auxiliary steering of an auxiliary steering wheel so as to steer the vehicle in a direction.