JPH0325017A - Suspension device for steering wheel - Google Patents

Abstract

PURPOSE:To improve tack-in restraining effect by providing liquid enclosed cylinders responding to the displacement, in the direction of a swinging axis, of a suspension arm, and by connecting the liquid enclosed cylinders of left and right steering wheels to each other by means of a crossing piping. CONSTITUTION:During turning traveling, when transverse force Fs is applied to rear wheels 1L, 1R, swinging axes 5L, 5R directional force FSL, FSR, caused by the transverse force Fs, and applied to suspension arms 3L, 3R are liable to displace the suspension arms 3L, 3R toward the respective correspondent swing axes through the elastic deformation of elastic bushes 4L, 4R. At this time, on account of the directions of the force FSL, FSR, high pressure is produced in the chambers 21L, 21R of the liquid enclosed cylinders 15L, 15R. Neverthless, as both chambers 21L, 21R are communicated with each other by means of a crossing piping 25, the displacement of liquid is not generated. Consequently, displacement in the direction of swing axes is inhibited. Due to this construction, large tack-in restraining effect can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a suspension system for a steering vehicle.

(Prior art) As a suspension device for a rear wheel that assists in steering a steered wheel, for example, when front wheels are being steered, for example, Japanese Utility Model Application Publication No. 1-90673 is used.
There is something like the one described in the publication No.

As shown in Figure 5, this suspension device
, IRt-A type suspension arms 3L, 3R are rotatably and steerably attached to the ends of the suspension arms 3L, 3R, and the base ends of the suspension arms 3L, 3R are swung vertically around the axes 5L, 5R by elastic pushes 4L, 4R. It is movable and supported on the vehicle body suspension member 7. The rear wheels IL, IR are auxiliary steered by the power cylinder 13 via lateral ronds IIL, IIR connected to the respective knuckle arms 9L, 9R.

As shown in Fig. 4, this auxiliary steering is performed while the vehicle is running at a high speed of V or higher, and during this running, the front wheels are steered to increase the lateral acceleration (Fig. 4 illustrates 0.5 G and IG).
When this occurs, a depends on the vehicle speed (when the lateral acceleration is 0.5G)
Or as shown in b (when lateral acceleration IG), the rear wheels IL, I
The power cylinder l3 is hydraulically operated so that R is steered in the same phase.

(Problem to be Solved by the Invention) However, in such a suspension device, the rear wheel LL. When a lateral force is input to the IR, as schematically shown in FIG. 6, the lateral force F. (The illustration shows the lateral force when turning right.) The swing axis (5L, 5
R) Directional force F SL+ F s++ causes suspension arms 3L, 3R to be displaced from the solid line position to the dotted line position through elastic deformation of pushers 4L, 4R, and as a result, knuckle arms 9L, 9R and lateral rods ILL, IIR move ILIR is changed in the heto angle in the same phase direction as the front wheel.

Since the rear wheel steering angle characteristics a and b in Figure 4 are determined in consideration of this toe angle change (congruent steering), the toe angle change does not affect rear wheel steering, but when the vehicle speed is less than V1 While driving at medium to low speeds without steering the wheels, the above-described in-phase toe angle changes tend to cause the vehicle's steering characteristics to tend to understeer, resulting in a lack of sharpness in the steering.

In addition, as is clear from the comparison of the rear wheel positions shown by the solid line and dotted line in Figure 6, this toe angle change is accompanied by a movement of the ground contact point in the front and rear direction, so the camber rigidity and lateral There was a problem that the rigidity was insufficient, and the vehicle behavior near the limit became unnatural. Furthermore, in view of these problems, it is not possible to make the elastic pushers 4L and 4R with a low spring constant, which increases the stiffness of the suspension device in the longitudinal direction, which worsens the ride comfort of the vehicle and reduces the longitudinal force during braking. The amount of toe-in involved was small, and a large tuck-in suppressing effect could not be expected.

The present invention attempts to solve the above-mentioned problem by preventing the toe angle from changing due to the deformation of the elastic push only when a lateral force is input.

(Means for Solving the Problems) For this purpose, the suspension device of the present invention supports a suspension arm to which a steering wheel is rotatably and steerably attached to a vehicle body so as to be swingable in the vertical direction by elastic pushing, and In a vehicle in which the steered wheels are steered by a lateral rond located behind the axle in the longitudinal direction of the vehicle body and extending in the vehicle width direction, a liquid seal cylinder is provided that responds to displacement of the suspension arm in the direction of the swing axis. , the liquid seal cylinders of the left and right steered wheels are interconnected by cross piping.

(Function) The steering wheel allows the vehicle to travel by rotating, and the vehicle can be steered by turning with the lateral rod.

By the way, when the vehicle is running and a lateral force is generated, even if the suspension arm attempts to displace in the direction of the rocking axis through elastic deformation due to the lateral force, the liquid seal cylinders of the left and right steering wheels transfer this displacement to each other through cross piping. Block because it is connected. Therefore, when a lateral force is input, the steered wheels do not change the toe angle in the in-phase direction (congruent steering), and it is possible to prevent the tendency of understeer that accompanies this in-phase congruent steering, thereby avoiding a lack of sharpness. . At the same time, this means that there is no movement of the grounding point of the steered wheels in the longitudinal direction, which prevents the camber stiffness and lateral stiffness from becoming insufficient, and prevents the vehicle behavior from becoming unnatural near the limit. . In addition, from these reasons, it is no problem to make the elastic push highly elastic, which can reduce the longitudinal stiffness of the suspension device to improve ride comfort and increase the amount of toe-in associated with longitudinal force during braking. It is possible to achieve a large tuck-in suppressing effect.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the suspension system of the present invention, in which the same parts as in FIG. 5 are designated by the same reference numerals. Lateral rods are attached to the knuckle arms 9L and 9R of the left and right rear wheels IL and IR, which are rotatably and steerably attached to the tips of the A-type suspension arms 3L and 3R]. IL and IIR are articulated, and these lateral rods extend in the vehicle width direction behind the rear wheel axle in the longitudinal direction of the vehicle body. The lateral rods 11L and IIR are connected by a power cylinder 13 fixed to the vehicle suspension member 7. The power cylinder l3 uses built-in springs 13a and 13b to set the rear wheels IL and IR to a non-steering neutral position, and when supplying hydraulic pressure to the chamber 13c or 13d, turns the rear wheels 1L and IR to the left or to the left by a steering angle corresponding to the pressure value. It can be steered to the right.

The base ends of the suspension arms 3L, 3R are supported by the vehicle body suspension member 7 so as to be swingable in the vertical direction of the vehicle body (direction perpendicular to the drawing) around the axes 5L, 5R via elastic pushers 4L, 4R. The swing axes 5L and 5R are inclined so as to approach each other toward the rear of the vehicle body. Such axis line 5L
, 5R, the liquid seal cylinders 15L, 15
An extension arm 1 in which the piston rods of cylinders 15L and 15R are extended to suspension arms 3L and 3R, with R fixedly attached to the vehicle body suspension member 7.
7L, 17R and ball joint 19L. It is articulated via 19R.

The cylinders 15L and 15R are connected to each other by a cross pipe 25, so that the extension chambers 21L and 21 of both cylinders are connected to each other by a cross pipe 25.
R are communicated with contraction chambers 23R and 23L, respectively. Of course, the cross pipe 25 must also be filled with liquid.

The operation of the above embodiment will be explained next.

During turning, when lateral force is applied to the rear wheels IL and IR, the second
As schematically shown in the figure, the lateral force F. (The illustration shows lateral force when turning right)
The accompanying force Fst+ Rs* in the direction of the tg movement axis (5L, 5R) on the suspension arms 3L, 3R attempts to displace the suspension arms 3L, 3R in the direction of the corresponding rocking axis through the elastic deformation of the elastic pushes 4L, 4R. do. At this time, due to the direction of the force F sL + R s*, the chambers 21L and 23R of the liquid seal cylinders 15L and 15R are brought to high pressure, respectively, but since these chambers are connected through the cross piping 25, the pressure in the cylinders 15L and 15R is high. Suspension arms 3L, 3R force F3L without causing fluid flow between them.
+ Prevents displacement in the swing axis direction due to R3R.

Therefore, the rear wheels IL and IR are affected by the lateral force F. However, the convergence steer described above with reference to FIG. 6 does not occur. For this reason, when steering the rear wheels using the power cylinder l3, conventionally the rear wheel steering angle using the power cylinder l3 is set as a in Fig. 4 in anticipation of this conformance steering (in the same phase direction).
, b, but in this example, by giving an extra in-phase steering angle of the rear wheels by the power cylinder 3 as shown in c and d in the same figure, since in-phase direction coherent steering does not occur, The effect of improving vehicle dynamic characteristics by rear wheel steering can be achieved as before.

On the other hand, when the vehicle speed is less than V+ (see Figure 4) and the rear wheels are not being steered at medium to low speeds, the rear wheels IL and I
Due to the fact that the in-phase direction conformance steering of R does not occur, the equivalent cornering power of the rear wheels is reduced, the tendency of the vehicle to understeer is prevented, and a lack of sharpness can be avoided. At the same time, this eliminates the movement of the ground contact point of the rear wheels IL and IR in the longitudinal direction as described above with reference to FIG. can be prevented from becoming.

Further, from these reasons, it is no problem to make the elastic pushers 4L and 4R of a low spring constant, and the longitudinal stiffness of the suspension device can be reduced accordingly, thereby improving riding comfort.

Furthermore, by making the elastic pushers 4L and 4R soft as described above, there are also advantages during braking. It will be done. That is,
As shown schematically in FIG. The force in the direction of the swing axis (5L, 5R) on the suspension arms 3I, 3R due to FIIL. F■ is suspension arm 3 L1
3 R elastic push 4L 4R elastic deformation 3rd
An attempt is made to displace it from the solid line position in the figure to the dotted line position in the direction of the corresponding swing axis. At this time, due to the directions of the forces F, L, F
21R is brought to high pressure, but the chambers 23R and 23L, which are connected to these chambers by the cross piping 25, are heated on the low pressure side, allowing liquid to flow between the cylinders 15L and 15R, and the suspension arm 3L, 3R power F BL+
The above-mentioned oscillating axial displacement by F 1111 is possible.

This displacement causes the rear wheels IL and IR to change by one angle in the toe-in direction as shown by the dotted line, but the amount of toe-in during braking is increased by the elastic pushes 4L and 4R having a low spring constant as described above. obtain. Therefore, it is possible to increase the effect of suppressing the winding during braking while driving at medium to low speeds without steering the rear wheels.

(Effects of the Invention) Thus, the suspension device of the present invention has the elastic push 4L. Since the liquid seal cylinders 15L and 15R that respond to the rocking Idl m direction displacement of the suspension arms 3L and 3R through the elastic deformation of 4R are provided, and these cylinders are interconnected by the cross piping 25,
Only when the lateral force (F3) is input, changes in the toe angle in the same phase direction (congruent steering) of the steered wheels (rear wheels IL, IR in the illustrated example) due to the deformation of the elastic pushes 4L and 4R are prevented, and the steering wheel is It is possible to prevent the tendency of understeer during non-steering, thereby eliminating the lack of sharpness. At the same time, this eliminates the movement of the grounding point of the steered wheels in the longitudinal direction, so that the camber stiffness and lateral stiffness do not become insufficient, and it is possible to prevent the vehicle behavior from becoming unnatural near the limit. In addition, from these reasons, it is no problem to make the elastic pushers 4L and 4R with a low spring constant, which can reduce the longitudinal stiffness of the suspension device to improve ride comfort and reduce the longitudinal force associated with braking. By increasing the toe-in amount, a large cook-in suppressing effect can be achieved.

[Brief explanation of drawings]

Fig. 1 is a plan view showing one embodiment of the suspension device of the present invention, Figs. 2 and 3 are schematic diagrams for explaining the behavior of the same example during turning and braking, respectively, and Fig. 4 is a diagram showing rear wheel steering. An in-phase steering angle change characteristic diagram, FIG. 5 is a plan view illustrating a conventional suspension device, and FIG. 6 is a schematic diagram for explaining the behavior when turning. IL, IR...Rear wheel (steering wheel) 3L, 3R...Suspension arm 4L, 4R...
・Elastic push 5L, 5R...suspension arm swing M&i7・
...Vehicle suspension members 11L, IIR...Lateral rod 13...Power cylinders 15L, 15R...Liquid seal cylinder 25...Cross piping Same as Figure 1

Claims (1)

[Scope of Claims] 1. A suspension arm to which a steering wheel is rotatably and steerably attached is supported on the vehicle body so as to be swingable in the vertical direction by elastic push, and is located behind the axle of the steering wheel in the longitudinal direction of the vehicle body. In a vehicle in which the steered wheels are steered by a lateral rod extending in the width direction, a liquid seal cylinder that responds to the displacement of the suspension arm in the swing axis direction is provided, and a cross is provided between the liquid seal cylinders of the left and right steered wheels. A steering wheel suspension device characterized by being interconnected by piping.