JPH02144206A - Rear wheel suspension device for rear wheel steering vehicle - Google Patents

Abstract

PURPOSE:To contrive both the enhancement in the responsiveness in a same- phase steering region and the control in a rear-wheel toe angle by setting the alignment of a rear wheel so that a toe-out moment can be produced around a king-pin axis by the vertical load being input in the center of the wheel. CONSTITUTION:In a rear wheel, for example, the right side rear wheel 11R of a rear wheel steering vehicle, a wheel support 40 provided with a knuckle arm 14R, which is connected to a tie rod 13R projected toward the rear of the vehicle body via a ball joint 50, is supported by both an upper arm 41 and a lower arm 42 via ball joints 43, 44 respectively. In this case, the alignment of the rear wheel 11R is set so that a toe-out moment can be produced around a king-pin axis KP by the vertical load being input in the center of the wheel. Thus, the play of respective ball joints 43, 44 can be eliminated, and the responsiveness in a same-phase steering region can be enhanced, and also the control of a rear-wheel toe angle can be enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel suspension system for a vehicle configured to steer the rear wheels as well as the front wheels.

(Prior Art) Conventionally, four-wheel steered vehicles (AW
S car) is in practical use, but in this AWS car, as disclosed in Japanese Patent Laid-Open No. 6.1-9374, when the steering angle of the steering wheel is large, the left and right rear wheels are used as front wheels. Steering is done in opposite phases to improve turning ability, and when the steering angle of the steering wheel is small, the left and right rear wheels are steered in the same phase as the front wheels to improve running stability.

By the way, in a driving range where the front wheels and the rear wheels are steered in the same phase, the steering angle of the rear wheels is extremely small, so high precision is required for the operation.

On the other hand, in the rear wheel steering mechanism of this type of vehicle, the tie rod is connected to the knuckle arm integrated with the wheel support at -g via a ball joint. Since there is some play, there is a problem in that this play has an adverse effect on the rear wheel steering operation and impairs its responsiveness.

On the other hand, in dWS vehicles, a technique is known that reduces the rear wheel steering force by optimizing the wheel alignment of the rear wheels, as disclosed in, for example, Japanese Unexamined Patent Publication No. 58214463.

(Object of the Invention) Therefore, an object of the present invention is to provide a rear wheel suspension system that completely eliminates the influence of the play of the ball joint and enables improved responsiveness in the in-phase steering region and management of the rear wheel toe angle. purpose.

(Structure of the Invention) The present invention is characterized in that the alignment of the rear wheels is set so that the vertical load input to the wheel center generates a toe-out moment around the kingpin axis.

(Effect of the invention) In a region where the rear wheels are steered in the same phase as the front wheels, the rear wheel on the outside of the turn is steered in the toe-in direction when turning, but when turning, input to the wheel center of the rear wheel on the outside of the turn is The rear wheel is urged in the toe-out direction by the vertical load caused by the
This eliminates play in the ball joint, improves responsiveness in the in-phase steering region, and enables control of the rear wheel toe angle.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a diagram schematically showing the overall configuration of a four-wheel steering system for a vehicle to which the present invention is applied, in which the left and right front wheels IL, I
A front wheel steering device A for steering the vehicle R includes a steering wheel 2, a rack and pinion mechanism 3 that converts the rotational motion of the steering wheel 2 into linear reciprocating motion, and a front wheel steering rod 4 provided with this mechanism 3. and left and right knuckle arms 6L and 6R connected to both left and right ends of the rod 4 via tie rods 5L and 5R, respectively, and a power cylinder equipped with a piston 7 to assist the movement of the rod 4. 8, a control valve 9 that switches oil passages by operating the steering wheel 2, and an oil pump 1O.

On the other hand, a rear wheel steering device B for steering the left and right rear wheels 11L and IIR includes a rear wheel steering rod 12 and a
Tie rods +3L and 131' on both left and right ends respectively. Left and right knuckle arms 14L and 14R connected via
By moving the rear wheel drying steering rod 12 in the left-right direction, the rear wheels 11L and 11R are steered. Further, a power steering wheel for assisting the movement of the rod 12 is integrally attached to the rear wheel steering rod 12, so that the rod 12 passes through the inside of the power cylinder 15 and is attached to the rear wheel steering rod 12. The piston 16 of the power cylinder 15 is fixed. Furthermore, the rear wheel steering rod 12 has a fail-safe function.
A centering spring 19 is attached to urge the rod 12 to the intermediate position.

This rear wheel steering device B has a rear wheel 11L and a front wheel IL of IIR.
, steering ratio θ, /θ, (θ is the rear wheel steering angle,
As shown in FIG. 4, the vehicle is equipped with a variable steering ratio mechanism C that changes the front wheel steering angle (θ is the front wheel steering angle) in accordance with the vehicle speed. 17 is an input shaft of this mechanism C, 18 is a control rod as its output shaft, and the linear movement of the front wheel steering rod 4 in response to the operation of the steering wheel 2 is controlled by a second rank and pinion provided on the rod 4. The mechanism 20 converts it into a rotational movement, and this rotational movement is converted into a rotational movement by the universal joint 2122.
and is transmitted to the human power shaft 17 of the variable steering ratio mechanism C via the connecting rod 23. On the other hand, a control rod 18 serving as an output shaft is provided so as to move in parallel to the rear wheel steering rod 12. The variable steering ratio mechanism C has steering ratios θ, /θ,
A stepping motor 25 is connected to change the vehicle speed sensor 26.
．． A control circuit (CPU) 27 is provided with an output signal corresponding to the vehicle speed detected by the 26 (two are provided to improve safety), and the direction and amount of the rotation are controlled according to the vehicle speed. It is controlled accordingly.

28 is a steering ratio sensor included in the variable steering ratio mechanism C;
The output of this sensor 28 is given to a control circuit 27 to perform feedbank control of the stepping motor 25. Regarding the configuration and operation of this variable steering ratio mechanism C,
For example, as detailed in Japanese Patent Laid-Open No. 59-48054 filed by the present applicant, further explanation will be omitted here, but the control rod 18, which is the output shaft of the variable steering ratio mechanism C, The spool valve type control pulp 30 of the rear wheel power steering device is activated, and as a result, as is clear from FIG. It is controlled so that it is in a neutral 2WS state at around 35 km/h and in the same phase at 35 km/h or more.

Control valve 30 of rear wheel power steering device
Oil is supplied from an oil pump 31 to the oil passageway, and a solenoid valve 32 is interposed in the middle of this oil passage. In the unlikely event that an abnormality occurs in the control system, this solenoid valve 32 is activated by a signal from the control circuit 27 to stop the supply of pressure oil to the control valve 30. The hydraulic pressure in 15 disappears, and the rear wheel steering loft 12 returns to the neutral position by the spring force of the centering spring 19.

Therefore, if an abnormality occurs in the control system, the rear wheel 11
L and IIR are configured so that they are never steered, and even if they are steered, they immediately return to the neutral position.

In addition to the above configuration, a bypass passage is provided between the oil passage from the oil pump 31 to the control valve 30 and the oil passage returning from the control valve 30 to the oil tank, and the solenoid valve 32 is provided in this bypass passage.
may be provided.

FIG. 1 is a perspective view showing a first embodiment of a rear wheel suspension system to which the present invention is applied in a vehicle equipped with the rear wheel steering system B described above. Figure 1 shows the suspension system for the right rear wheel 11R.
A knuckle arm 1 projects toward the rear of the vehicle body and is connected to a tie rod 13R via a ball joint 50.
Wheel support (hub carrier) with integrated 4R
40 has ball joints 43 and 44 on one I-type amber arm 41 and one I-type lower arm 42, respectively.
It is supported through a double wishbone structure. Upper arm 41 and lower arm 42
are supported on the vehicle body via elastic bushes 51 and 52, respectively. Furthermore, the rear ends of trailing links 48 and 49 are connected to the upper arm 41 and the lower arm 42, respectively, and the front end of the trailing link 49 is supported by the vehicle body via an elastic bushing 53. In this case, the kingpin shaft KP connecting the centers of the two ball joints 43 and 44 tilts forward as it goes upwards when viewed from inside the vehicle body, as shown in Fig. 2 (=1). It is sloped and the caster trail is negative. The tie rod 13R is connected to the wheel support 40 behind the king pin shaft KP. Further, as shown in FIG. 2 fbl, when viewed from the front side of the vehicle body, the king pin shaft KP is provided inward from the wheel center of the rear wheel 11R, and is inclined inwardly as it goes upward.

With this configuration, the load input from below to the wheel center generates a toe-out moment around the king pin axis KP, and this toe-out moment is applied to the tie rod 13R connected to the rear of the king pin axis KP. This acts as a force in the direction of pressing the tie rod 13R and the wheel support 40.
The ball joint 50 interposed between the two is pushed to one side and its play is lost. By the way, when the vehicle body turns to the left in the same-phase steering region, the right rear wheel 11R on the outside of the turn is steered in the toe-in direction by the tie rod L3R, so the play of the ball joint 50 remains suppressed. The movement of the tie rod 13R is immediately transmitted to the wheel support 40. Therefore, responsiveness in the same phase region can be improved.

Next, FIG. 5 fal and fbl are explanatory diagrams showing the second embodiment of the present invention in correspondence with FIG. 2 (al and (bl). In this embodiment, as shown in FIG. When viewed from the inside of the vehicle body, the king pin shaft KP is tilted upwards and rearward, and the caster rail is positive.Also, as shown in Figure 5 (bl), When viewed from the side, the king pin shaft KP is the rear wheel 11R.
The king pin shaft KP in such a configuration is provided outward from the wheel center of the wheel center and is inclined outward as it goes upward. Ball joint 43 at the tip of
Rather than a straight line connecting the center of the I-type lower arm 42 and the center of the ball joint 44 at the tip of the I-type lower arm 42, for example, the intersection point on the extended line of the two upper arms, which are configured so that the distance becomes narrower as they move outward, The virtual king pin axis is located at the intersection point on the extension line of the two lower arms, which are configured so that the distance becomes narrower as they move outward.

It is clear that the configuration of the second embodiment of the present invention provides the same effects as the first embodiment described above.

The above-mentioned embodiment is a case in which the present invention is applied to a double wishbone type rear wheel suspension system. Type rear wheel: Can also be applied to suspension equipment.

It should be noted that the rear wheel shock absorber according to the present invention only needs to have the alignment of each of its components in the states shown in FIGS. 2 and 5 at least in the normal driving range, and different behavior outside the normal driving range will not be a problem. There's no need.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the first embodiment of the present invention, FIG. 2 is ta+,
[b) is an explanatory diagram, Fig. 3 is a system diagram of the steering system, Fig. 4 is a graph showing the relationship between vehicle speed and steering ratio, and Fig. 5 ia+
, (ill is an explanatory diagram of the second embodiment of the present invention. Rear wheel steering rod power cylinder human power shaft 18 control rond centering spring steering motion vehicle speed sensor 27-control circuit steering ratio sensor control balf wheel support 43 .44.50-Pole joint

Claims (1)

[Claims] In a rear wheel suspension system of a rear wheel steered vehicle configured to steer the rear wheels at the same time as the front wheels are steered, the alignment of the rear wheels is determined by the vertical load input to the wheel center creating a toe-out moment around the kingpin axis. A rear wheel suspension system for a vehicle with rear wheel steering, characterized in that the rear wheel suspension is set so that the rear wheel steering occurs.