JPS6393681A - Four-wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To improve driving stability as well as direction changing characteristic by arranging a liquid amount absorbing means for reducing a rear steering amount by communicating said means with a rear cylinder when a piston of the rear cylinder has travelled more than a specified stroke at the time of front steering. CONSTITUTION:If a front wheel 1 is steered during a high speed driving, a steering wheel 13 is operated with a small steering angle and pressure oil from a left or right oil pressure chamber 18 or 19 of a front cylinder 16 is directly supplied passing through a liquid amount absorbing means 84 to either oil pressure chamber 29 or 30 of a rear cylinder 27 to that a rear wheel 4 is steered by a great steering angle in the same direction with the front wheel 1. During a driving at a low speed on the other hand, the steering angle of the steering wheel is great and therefore a travel of a piston 17 of the front cylinder 16 becomes great. As a result, pressure oil from the oil chamber 18 or 19 is supplied with the amount of oil reduced by the oil amount absorbing means 84 to either oil pressure chamber 29 or 30 so that the rear wheel 4 is steered by a small steering angle in the same direction with the front wheel 1. Thus, a stability during high speed driving and direction changing characteristic during low speed driving can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a four-wheel steering system for a vehicle, which steers both the front wheels and the rear wheels through the steering operation of the steered wheels. The present invention relates to a four-wheel steering system that includes a front cylinder that is operated in conjunction with steering, a rear cylinder that steers rear wheels, and a hydraulic path that connects the cylinder spaces of the front cylinder and the rear cylinder.

(Prior art and its problems) Conventionally, as a four-wheel steering system for a vehicle as described above, the eighth
As shown in the figure, there are provided a front cylinder 3 that is operated in conjunction with the steering wheel 2 that steers the front wheels 1.1, and a rear cylinder 5 that steers the rear wheels 4, 4. .5 connected by hydraulic pressure passages 6, 6 has been proposed (see Japanese Patent Laid-Open No. 183351/1983).

This type of device has a large degree of freedom in the layout of the hydraulic pressure path, and is superior in terms of structure (layout) compared to types that transmit steering force to the rear wheels using rotary wheels, etc. be.

This device is a so-called steering angle-sensitive four-wheel steering device in which the steering angle and direction of the rear wheels are controlled according to the magnitude of the steering angle, and the device is a four-wheel steering device of the steering angle sensitive type, in which the steering angle and direction of the rear wheels are controlled according to the magnitude of the steering angle. By manipulating the steering angle, the rear wheels 4.4 are steered in the same direction (same phase) as the front wheels 1.1 (see Figure 6 (a)) to improve driving stability and to improve steering during low speed driving. ring 2
By operating the large steering angle, the rear wheels 4, 4 are steered in the opposite direction (opposite phase) to the front wheels 1, 1 (see Fig. 6 (b)), and the turning performance (turning performance) is changed in the direction 1-. This is how it was done.

However, the above-mentioned four-wheel steering device has a problem in that the control characteristics of the rear wheel steering angle are complicated, and the relative settings between the front wheels and the rear wheels are delicate, making it difficult to set them in a consistent manner.

(Object of the Invention) The present invention provides a steering angle-sensitive four-wheel steering device that has a relatively simple structure and can clearly switch and set rear wheel steering angle characteristics depending on the magnitude of the steering angle. The basic purpose is to provide

(Structure of the Invention) Therefore, the present invention provides a front cylinder that is operated in conjunction with steering of the front wheels, a rear cylinder that steers the rear wheels, and a fluid that connects the front ring and the cylinder space of the rear cylinder. In a four-wheel steering system for a vehicle that is equipped with a pressure path and is configured to steer the front wheels and the rear wheels together with the front wheels by steering operation of the steered wheels, the front cylinder, the rear cylinder, or the hydraulic pressure path is provided with This device is characterized by being provided with means that communicates when the piston strokes beyond a predetermined value and absorbs the amount of liquid in a direction that reduces the amount of rear steering.

(Effects of the Invention) According to the present invention, when a piston strokes more than a predetermined amount due to front steering, communication occurs in the front cylinder, the rear cylinder, or the hydraulic pressure path connecting these cylinders, and the amount of rear steering is reduced. This device is equipped with means for absorbing the amount of liquid in the direction of decreasing the amount of liquid.

Therefore, during high-speed driving, the liquid volume is not absorbed due to the small stroke of the piston due to the small steering angle operation of the steered wheels, and the rear steering amount is not reduced, so the rear wheels are largely steered in the same direction as the front wheels, improving driving stability. At the same time, during low-speed driving, the large stroke of the piston's designated tool L due to large steering angle operation of the steered wheels [1-] absorbs the liquid volume and reduces the rear steering amount, so the rear wheels are the same as the front wheels. A large turning in the direction is suppressed and turning performance is improved.

In this way, by using the means for absorbing the amount of liquid, it is possible to change the ratio of the rear steering amount to the one-point steering wheel, thereby achieving simple four-wheel steering that is responsive to the steering angle.

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

FIG. 4 shows the basic configuration of a four-wheel steering system for a vehicle.

As shown in the figure, a rack case 10 extending in the vehicle width direction is arranged on the front side of the vehicle, and a rack bar (front steering rod) 11 is fitted into the rack case 10 so as to be slidable left and right. A pinion (not shown) in a gear box 12 meshes with a rack portion (not shown) of the rack bar 11, and a steering wheel (handle) 13 is connected to the pinion.

In addition, in the drawing, the steering wheel I3 is the rack 10.
It is depicted in a more forward position.

Knuckle arms 14 are attached to both ends of the rack bar 11.
14 are connected to each other, and a front wheel 1.1 is connected to each knuckle arm 14.1.

Therefore, when the steering wheel 13 is operated, the pinion,
The rack bar 11 is slid left and right by the rack portion, and the front wheels 1.1 are steered via the knuckle arms 14.14.

A front cylinder 16 is installed in parallel to the rack case IO, and a piston 1 is installed in the front noring 16.
7 is fitted so that it can slide left and right.

It is partitioned into right hydraulic chambers 18 and 19, and the piston rod 20 of the piston 17 is connected to the rack bar 11 via a connecting member 2I.

Therefore, the piston 17 can be slid left and right in conjunction with the rack bar 11.

A reserve tank 22 is attached to the front cylinder 16, and the reserve tank 22 and the left and right hydraulic chambers 1
8.19 is the supply passage 23. which replenishes leaked oil.
It is communicated with 23.

On the other hand, a rod case 25 extending in the vehicle width direction is arranged on the rear side of the vehicle, and a rear steering rod 26 is fitted into the rod case 25 so as to be slidable left and right. , a piston 28 that fits into a rear cylinder 27 formed in the rod case 25 is provided, and the piston 28 allows the rear cylinder 27 to be connected to the left and right hydraulic chambers 29.3.
It is partitioned into 0.

The left and right hydraulic chambers 29,30 are provided with stoppers 31,32 for regulating the left and right sliding positions of the piston 28.

Inside the rod case 25, there is a large diameter portion 26 of the rod 26.
Centering springs 33 and 34 are compressed to bias the piston 28 in the opposite direction and center the piston 28.

Knuckle arms 35° and 35° are provided at both ends of the rod 26.
are connected to each other, and the rear wheel 4 is connected to each knuckle arm 35.

The left hydraulic chamber 29 of the rear cylinder 27 and the left hydraulic chamber 18 of the front cylinder 16 are connected by a first hydraulic path 36, and the right hydraulic chamber 30 of the rear cylinder 27 and the right hydraulic chamber 19 of the front cylinder 16 are connected. are connected by a second hydraulic path 37.

Therefore, when steering the front wheel 1.1 to the left,
When the piston 17 of the front cylinder I6 slides to the left, hydraulic pressure is supplied to the left hydraulic chamber 29 of the rear cylinder 27 via the first hydraulic path 36, and the piston 28 slides to the right, causing the rod 26 to slide to the right. As a result, the rear wheels 4.4 are steered to the left via the knuckle arms 35, 35.

Conversely, when the front wheel 1.1 is steered to the right, if the piston 17 of the front cylinder 16 is slid to the right, the second
Hydraulic pressure is supplied to the right hydraulic chamber 30 of the rear cylinder 27 through the hydraulic path 37, and the piston 28 is slid to the left, causing the rod 2
6 is slid to the left, and the rear wheels 4.4 are steered to the right via the knuckle arms 35, 35.

In addition, as shown in Fig. 5, the rear rod case 25
The inner rod 26 is divided into two left and right, each rod 26A,
The rear cylinder 2 of the rod case 25 is attached to the inner end of the rod case 26B.
Pistons 28A and 28B are provided which fit into the independent left and right hydraulic chambers 29 and 30 formed in the left hydraulic chamber 2.
If the configuration is such that the second hydraulic path 37 is connected to the right hydraulic chamber 30 and the first hydraulic path 36 is connected to the right hydraulic chamber 30, when the front wheels 1.1 are steered to the left, the rear Hydraulic pressure is supplied only to the right hydraulic chamber 30 of the cylinder 27, the piston 28B is slid to the right, the rod 26B is slid to the right, and only the right rear wheel 4 is steered to the left (toe-in direction) via the nasicle arm 35. Since the left rear wheel 4 is prevented from being steered to the left (toe-out direction) by the stopper portion 26b of the rod 26B (see FIG. 7(a)), the rear wheels 4, 4 are prevented from being steered in the event of oil failure. Changes to the stable side can be reliably prevented.

Similarly, when steering the front wheels 1.1 to the right, only the left rear wheel 4 is steered to the right (toe-in direction),
The right rear wheel 4 is turned rightward (
steering in the toe-out direction) is prevented (Fig. 7 (
b)).

A first embodiment of means (hereinafter referred to as oil amount absorbing means) that communicates when the piston strokes more than a predetermined amount due to front steering and absorbs the amount of oil in the direction of reducing the amount of rear steering. As shown in FIG.
A case 84 has a first cylinder 80 partitioned into an oil pressure chamber 79 and a hydraulic chamber 79, and a second cylinder 83 in which a piston 8I is oil-tightly fitted using a sliding packing to form an oil reservoir chamber 82. 1 installed in the middle of the hydraulic path 36, the first cylinder 80
The piston 77 has a spring 8 compressed in the hydraulic chamber 79.
5 is biased toward the large hydraulic chamber 78 and stopped by the stopper ring 86, and the piston 81 of the second cylinder 83 is pushed against the piston 77 by the spring 88 compressed in the atmospheric pressure chamber 87.
While the first cylinder 80 and the second cylinder 83 are biased in the same direction, the first cylinder 80 and the second cylinder 83 are equipped with a check valve that allows oil to return only from the oil reservoir chamber 82 of the second cylinder 83 to the large hydraulic chamber 78 of the first cylinder 80. 89 is normally in communication with the service hydraulic chamber 79 of the first cylinder 80, and only when the screw 77 of the first cylinder 80 strokes toward the service hydraulic chamber 79 by a predetermined amount or more. A second communication passage 91 communicating with the left hydraulic chamber 78 is connected to the left hydraulic chamber 78 . And the first hydraulic path 3
6, the left hydraulic chamber 78 of the first cylinder 80 is on the front cylinder 16 side, and the output 411 pressure chamber 7 is on the rear cylinder 27 side.
9 are connected to each other (see Fig. 4). Note that the second hydraulic path 37 is also configured in the same manner.

With this configuration, when the front wheels 1, 1 are steered, for example, to the left, the steered wheels 13 are operated by a small steering angle if the vehicle is traveling at high speed, so the left hydraulic chamber 1 of the front cylinder 16
8 to the left hydraulic chamber 78 of the first cylinder 80 of the case 84. Since the piston 77 of the 17th ring 80 slides only by one small stroke, the second communication passage 9
1 is not communicated with the left hydraulic chamber 78, and the amount of oil sent from the output Aft pressure chamber 79 to the left hydraulic chamber 29 of the rear cylinder 27 is not reduced.

Therefore, since the front steering amount and the rear steering amount almost correspond to each other (see a in Figure 3), the rear wheel 4.4 will be significantly steered in the same direction as the front wheel 1.1, which will cause it to rise during high-speed driving. The running stability of the vehicle is improved.

Furthermore, when the vehicle is traveling at low speed, the steered wheels 13 are operated to a large steering angle, so the piston 17 of the front cylinder I6 slides with a large stroke.

Therefore, the piston 77 of the first cylinder 80 slides with a large stroke by the hydraulic pressure sent from the left hydraulic chamber 18 of the front cylinder 16 to the left hydraulic chamber 78 of the first cylinder 80 of the case 84, and the piston 77 of the first cylinder 80 slides with a large stroke. Passage 91 communicates with left hydraulic chamber 78 . Therefore, the pressure oil sent into the left hydraulic chamber 78 flows into the oil reservoir chamber 82, and the piston 81 is moved back against the spring force of the coil spring 87 according to the amount of inflow, and as a result, the peak pressure All is no longer delivered from the chamber 73 to the left hydraulic chamber 29 of the rear cylinder 27.

Therefore, since the rear steering amount is reduced relative to the front steering amount (see b in FIG. 3), the front wheels 1.
If the vehicle is steered in the same direction as 1, the amount of steering will be smaller, and the turning performance during low speed driving will be less.

As shown in FIG. 2, the second embodiment of the oil amount absorbing means has the left and right hydraulic chambers 29 and 30 of the rear cylinder 27 shown in FIG.
are divided by pistons 28A and 2813, respectively, and the left,
Hydraulic chambers 29a facing the right hydraulic chambers 29 and 30, respectively;
30a (hydraulic chamber 29a is not shown),
A case 96 in which a piston 93 is fitted to form a reservoir chamber 94 is connected to the outer peripheral wall of the rod case 25 from a right angle, and a spring 98 in which the piston 93 is compressed into an atmospheric chamber 97 is used to generate left and right hydraulic pressure. While chamber 29.30 biases towards the left.

The right hydraulic chamber 29, 30 and the oil sump chamber 94 of the case 96 are:
A first communication passage 1 having a check valve 99 that allows oil to return only from the oil reservoir chamber 94 to the left and right hydraulic chambers 29 and 30.
00, left and right hydraulic chambers 29.30 pistons 28A, 2
8B is configured to communicate with the left and right hydraulic chambers 29, 30 through a second communication passage 101 when the pressure chamber 8B strokes toward the 'A11 pressure chambers 29a, 30a by a predetermined amount or more.

With this configuration, when steering the front wheels 1.1 to the left, for example, when driving at high speed, the steered wheels 13 are operated by a small steering angle, so the left hydraulic chamber I of the front cylinder 16
8 to the right hydraulic chamber 30 of the rear cylinder 27, the piston 28B of the right hydraulic chamber 30 only slides with a small stroke, so the second communication passage 101 is connected to the right hydraulic chamber 30.
Since the piston 28B does not communicate with the piston 28B, the piston 28B slides with approximately the same stroke as the piston 17 of the front nolinder 16.

Therefore, since the front steering amount and the rear steering amount approximately correspond to each other (see a in FIG. 3), the right rear wheel 4 is steered in the same direction as the front wheel 1.1.

Furthermore, when the vehicle is running at low speed, the steered wheels 13 are operated to a large steering angle, so the piston 17 of the front cylinder I6 slides with a large stroke.

Therefore, the piston 28B slides through the large stroke by the hydraulic pressure sent from the left hydraulic chamber 18 of the front cylinder 16 to the right hydraulic chamber 30 of the rear cylinder 27, and the second communication passage 101
is now in communication with the right hydraulic chamber 30, and oil is stored in the oil reservoir chamber 94, so the piston 28B no longer slides.

Therefore, since the rear steering amount is reduced relative to the front steering amount (see b in FIG. 3), the front wheel 1.1 of the right rear wheel 4 is
The amount of steering that is steered in the same direction becomes smaller.

In the above embodiments, the oil amount absorbing means is provided in the hydraulic passage 36 (37) or the rear cylinder 27, but it goes without saying that it may be provided in the front cylinder side.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the oil amount absorption means according to the present invention, FIG. 2 is a sectional view of the second embodiment, and FIG. 3 is a graph showing the relationship between the front steering angle and the rear steering angle. FIG. 4 is a basic configuration diagram of a four-wheel steering system, FIG. 5 is a sectional view showing another embodiment of the rear cylinder shown in FIG. 4, FIG. 6(a) is a plan view showing same-phase steering, and FIG. Figure 6(b) is a plan view showing anti-phase steering;
FIG. 7(a) is a plan view showing leftward steering by the rear cylinder in FIG. 5, FIG. 7(b) is a plan view showing rightward steering with respect to FIG. 7(a), and FIG. FIG. 2 is a perspective view of a conventional four-wheel steering device. 1. Front wheel, 4. Rear wheel, 16. Front cylinder, 27. Rear cylinder, 36.37. Hydraulic path, 81.9
3. Piston, 82.94. Oil sump chamber, 84.96...
・Case, 89.99 ・Check valve, 90.1
00...First communication path, 91.101...Second communication path.

Claims (1)

[Claims] (1) Equipped with a front cylinder that is operated in conjunction with the steering of the front wheels, a rear cylinder that steers the rear wheels, and a hydraulic pressure path that connects the cylinder spaces of the front cylinder and the rear cylinder to operate the steering wheel. In a four-wheel steering system for a vehicle that steers the rear wheels together with the front wheels, there is a connection between the front cylinder, rear cylinder, or hydraulic pressure path when the piston strokes more than a predetermined amount due to front steering. A four-wheel steering system for a vehicle, characterized in that a means for absorbing a liquid amount in a direction that reduces a rear steering amount is provided.