JPH0244616Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a four-wheel steering device that steers both the front wheels and the rear wheels by steering the front wheels of an automobile.

(Prior Art) Conventionally, most automobiles have been steered by turning only the front wheels, and although the rear wheels may have some toe-in or toe-out, there has been no steering of the rear wheels actively. However, if a four-wheel steering device is used in which the rear wheels are also steered in response to the front wheels being steered, maneuverability and stability can be significantly improved. For example, when maneuvering a vehicle at extremely low speeds such as parallel parking or parking in a garage, it is possible to significantly change the direction of the vehicle by steering the rear wheels in the opposite direction to the front wheels (this is called anti-phase). This makes it possible or easy to park in narrow spaces, which was previously impossible or extremely difficult. Further, in a U-turn, the minimum turning radius can be made small, which is advantageous. Furthermore, by steering the rear wheels in a phase opposite to that of the front wheels, the difference between the inner wheels can be minimized or eliminated, which is advantageous when turning a narrow corner. In addition, when steering a vehicle at extremely low speeds, if the rear wheels are steered in the same direction as the front wheels (this is called in-phase), it is possible to move the entire vehicle in parallel, making it easier to park and park. It is often convenient when parking in the garage.

On the other hand, when changing lanes while driving at medium to high speeds, if four-wheel steering is performed in the same phase, lateral force is applied to the front and rear wheels at the same time, making it possible to change lanes smoothly without phase lag, resulting in yawing. Therefore, you can change lanes at high speed without fear. Furthermore, when cornering, the direction of the vehicle can be effectively changed by steering the rear wheels in opposite phases.

In view of these circumstances, various four-wheel steering devices have been proposed recently. For example, there is a system in which the freely steerable front and rear wheels are connected by a link mechanism, and the rear wheels are steered in the opposite phase in response to the steering of the front wheels (Japanese Patent Application Laid-open No. 15301/1983), and a rod that works in conjunction with the front wheels. The cam plate is moved in accordance with the steering angle of the front wheels, and the pin fixed to the rear wheel steering member is held movably within the cam groove to steer both the front and rear wheels, and the pin fixed to the rear wheel steering member is moved in accordance with the steering angle of the front wheels. Things that change the angular ratio (Japanese Patent Application Laid-Open No. 55-91458
No.) etc. are known.

In this way, many specific configurations have been considered for a four-wheel steering system, but in each case, the rear wheel support part needs to have the same structure as the front wheels in order to be able to steer the rear wheels. . In other words, a knuckle that supports the rear wheels rotatably and rotatably with respect to the vehicle body, a tie rod that transmits steering force to this knuckle, and a means for giving movement in the vehicle width direction to this tie rod are required. It is a complex and expensive mechanism with a large number of parts compared to the rear wheels, which do not steer.
Therefore, there is a problem in that it is difficult to use common rear wheel parts between two-wheel steering (front wheel steering) vehicles and four-wheel steering vehicles. Furthermore, because the tie rods that transmit the steering force are connected to the nutcle by ball joints, road noise from the tires is transmitted through the tie rods and directly to the vehicle body, causing an increase in vibration and noise inside the vehicle. . In particular, a steering device for steering the front wheels and a rear wheel steering device for steering the rear wheels are mechanically connected by a transmission shaft, and a rear wheel steering characteristic changing section for changing the steering characteristics is provided on the transmission shaft. In the case of a four-wheel steering system, there is a problem that road noise from the tires is transmitted to the rear wheel steering characteristic changing section via the transmission shaft, and the changing section is damaged due to vibration.

On the other hand, apart from the purpose of turning the rear wheels significantly at low speeds to make it easier to park in a garage or parallel park, the purpose is to perform quick lane changes at high speeds and to obtain smooth cornering characteristics. For this purpose, the effect can be obtained even if the steering angle of the rear wheels is small (within a few degrees). For this reason, the rear wheel steering angle range is kept small and the rear wheel steering device is simplified instead.
There is also a desire to have common parts with two-wheel steering vehicles and to reduce costs.

(Purpose of the invention) This invention was made in view of the above circumstances.
The front wheels are steered by the steering device by moving multiple support points of a suspension arm (hereinafter referred to as the arm) that supports the rear wheels relative to the vehicle body via an elastic body in the vehicle width direction to give the rear wheels a turning angle. It is an object of the present invention to provide a four-wheel steering device for a vehicle, which enables steering of the rear wheels and blocks road noise transmitted from the rear wheels by the elastic body. .

(Structure of the invention) The four-wheel steering device of the invention is a vehicle in which the rear wheels are supported on the vehicle body by suspension arms at multiple support points via elastic bodies, and includes: a steering device for steering the front wheels; a rear wheel steering device including an output member that is moved in the width direction; a transmission shaft that mechanically connects the steering device and the output member of the rear wheel steering device; and a steering transmission device that moves the output member in the vehicle width direction as the front wheels are steered, the output member having a U-shape at both ends thereof. A pair of support points corresponding in the vehicle width direction among the plurality of support points of the suspension arm are connected to the fork portion through an elastic body so that the suspension arm can swing freely in the vertical direction. The support point of the suspension arm connected to the fork portion is supported by the vehicle body via the elastic body and the output member.

(Effects of the invention) According to the invention, the plurality of support points that support the rear wheel via the suspension arm are all connected to the output member or the vehicle body via the elastic body, so that the load transmitted to the vehicle body is reduced. Noise and vibration can be reduced by these elastic bodies, and it is possible to reduce vibration noise and improve riding comfort. In addition, since the support point of the suspension arm is connected to the output member via the elastic body, it is possible to reduce vibrations transmitted from the tires to the rear wheel steering characteristic changing unit via the output member and the transmission shaft. Damage to the changing portion due to the vibration can be prevented, and durability can be improved. Furthermore, since the rear wheels can be steered by the elastic deformation of the elastic body, there is no need to use expensive ball joint parts for each connection, and there is no need for the use of expensive ball joint parts, which are conventionally required for steering wheels such as knuckles. This eliminates the need for other parts, which simplifies the structure and reduces costs, and allows the suspension arm and other parts to be the same as those used in cars that do not steer the rear wheels.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of an automobile having a four-wheel steering system according to the present invention. The steering device 1 includes a steering wheel 3 that is steered by a driver, a pinion 4 that converts the rotational power of the steering wheel 3 into reciprocating motion in the vehicle width direction, and a first rack member 5.
A rack part 5a, tie rods 6, 6 whose base ends are connected to each end of the rack member 5, a knuckle arm 7 whose one end is connected to the tips of the tie rods 6, 6, and the other end is connected to the left and right front wheels 2L, 2R, 7, and in accordance with the steering of the steering wheel 3, the front wheels 2L, 2R are steered as is well known.

Rear wheels 22L and 22R are rear wheel suspension 21
It is supported by the vehicle body, but since it is symmetrical, only the right side will be explained below. The rear wheel suspension 21 includes a wheel support 23 that rotatably supports a rear wheel 22R, and a front arm 2 that is rotatably connected to the wheel support 23 at one end and the subframe 20 at the other end via a rubber bushing 27.
5, one end is attached to the wheel support 23 and the other end is attached to the output member 34 of the rear wheel steering device 30, and a rubber bush 28
The rear arm 24 is connected to the rear arm 24 so as to be swingable in the vertical direction via a rubber bushing 29, and the leading arm 26 extends longitudinally and has one end connected to the wheel support 23 and the other end connected to the vehicle body via a rubber bushing 29. As shown in the cross section of FIG. 2, the connecting portion of the rear arm 24 with the output member 34 (the portion indicated by arrow A) holds the rubber bushing 28 within a cylindrical body 24a that is joined to the other end of the rear arm 24. The rubber button 28 is inserted through the center of the rubber button 28.
The protruding portions at both ends of the pin 28a attached to the fork portion 34a are joined to the end portion of the output member 34.
The rear arm 24 and the output member 34 are rotatably connected.

By moving this output member 34 in the width direction of the vehicle body, the rear wheels 22R are steered (movement indicated by arrow θ _R in the figure), which engages with a third rack 34b formed on this output member 34. after pinion 5
The output member 34 performs the above-mentioned movement in response to the rotation of 3a. Note that in order to assist the movement of the output member 34, a piston 34 coupled to the output member 34 is provided.
A cylinder 33 having a diameter is fixed to the vehicle body. Hydraulic pressure sent from the hydraulic pump 31 through the oil passage 31a is controlled by a control valve 54 provided on the rear transmission shaft 53 having the rear pinion 53a at the rear end, and is controlled by the piston 34a within the cylinder 33. Left and right cylinder chambers 33 divided into two
The hydraulic pressure generated in either the left or right cylinder chambers 33a or 33b assists the movement of the output member 34. Ru.
In this way, the output member 34, the cylinder 33, the control valve 54, etc. constitute the rear wheel steering device 30.

The pinion 53a that can move the output member 34 is rotated according to the steering angle (θ _H ) of the steering device 3 via a steering transmission device 50 that mechanically connects the steering device 1 and the rear wheel steering device 30. This steering transmission device 50 includes a front pinion 51a that meshes with a second rack 5b formed on the rack member 5.
A front transmission shaft 51 whose front end is connected to the front pinion 51a and extends back and forth; and a rear wheel steering characteristic changing section which is connected to the rear end of the front transmission shaft 51 and mechanically changes the rotational characteristics of the front transmission shaft 51. a mechanical control box 52, a rear transmission shaft 53 whose front end is connected to the mechanical control box 52 and receives the changed rotation, and a rear pinion 53a connected to the rear end of the rear transmission shaft 53, The front pinion 5 responds to the steering of the steering wheel 3.
1a is rotated, and this rotation is appropriately adjusted by the mechanical control box 52 and transmitted to the rear pinion 53a, whereby the output member 34
is moved in the vehicle width direction, and the rear wheels 22L and 22R are steered.

At this time, it is preferable to adjust the rotation by the mechanical control box 52 as shown in FIG. 3, for example. That is, when the steering angle (θ _H ) of the steering wheel 3 is small, the rear wheels are steered in the same phase,
When the steering angle (θ _H ) exceeds a certain value (θ _Ha ), it is preferable to gradually steer the rear wheels to the opposite phase side with respect to the steering angle (θ _H ). In this way, in a region where the steering angle is small, there are many lane changes, etc., and smooth lateral movement is enabled by in-phase steering, and in a region where the steering angle is large, turning performance can be improved by anti-phase steering.

In the case of the present invention, since the rear wheels are steered by deforming the rubber bushings, it is difficult to increase the rear wheel steered angle (θ _R ), so the above effect is not so great. However, when turning, the wheels on the outside of the turning radius receive a large lateral force, and when the steering angle (θ _H ) is small relative to this lateral force, steering to the same phase increases the amount of toe-in, resulting in stable driving. Sexuality improves. On the other hand, when the steering angle increases and the vehicle is steered to the opposite phase side, the amount of toe-in decreases and the turning performance of the vehicle improves.
Normally, at high speeds, the steering angle (θ _H ) is used only in a small range, and at medium and low speeds, the steering angle (θ _H )
Since the range of speed is also widened, by steering the rear wheels as described above, it is possible to achieve both running stability at high speeds and turning performance at medium and low speeds.

As explained above, the present invention enables rear wheel steering by deforming the rubber bush at the end of the suspension arm that supports the rear wheels, eliminating the need for expensive parts such as ball joints and knuckles. , the structure is simplified and the cost can be reduced.
Also, the front arm 25, the rear arm 24, the leading arm 26, and the rubber buttons 27, 2 at the ends thereof.
For 8, 29, etc., common parts can be used even when the rear wheels are not steered. Furthermore, these rubber bushes can reduce road noise, vibration, etc. Furthermore, since the suspension arm 24 is connected to the output member 34 via the rubber bush 28, it is possible to reduce vibrations transmitted from the tires to the vehicle body and rear wheel steering characteristic changing unit via the output member 34. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an automobile having a four-wheel steering system according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing a connecting portion of a rear arm indicated by an arrow in FIG. 1. FIG. 3 is a graph showing the relationship between the steering angle and the rear wheel turning angle. DESCRIPTION OF SYMBOLS 1... Steering device, 3... Steering, 5... Rack member, 21... Rear wheel suspension, 30... Rear wheel steering device, 50... Steering transmission device.

Claims (1)

[Scope of Claim for Utility Model Registration] A steering device that steers the front wheels and an output that moves the front wheels in the width direction of a vehicle in which the rear wheels are supported by a suspension arm on the vehicle body at multiple support points via elastic bodies. a transmission shaft that mechanically connects the steering device and an output member of the rear wheel steering device; and a transmission shaft that is provided on the transmission shaft and that changes steering characteristics of the rear wheels. and a steering transmission device that moves the output member in the vehicle width direction as the front wheels are steered, and the output member is provided with U-shaped fork portions at both ends thereof. A pair of support points corresponding in the vehicle width direction among the plurality of support points of the suspension arm are connected to the fork portion via an elastic body so that the suspension arm can swing vertically. A four-wheel steering system for a vehicle, wherein a support point of a suspension arm connected to a fork portion is supported by a vehicle body via the elastic body and the output member.