JPS6230955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steering system for a vehicle, particularly a four-wheeled vehicle.

More specifically, steering means is provided on the rear wheels in addition to the front wheels, and the steered wheels and the rear wheel side steering means are connected by two link members that are slidably engaged with each other, and the steering angle of the steered wheels is adjusted. The present invention relates to a steering device for a vehicle that can steer the front wheels and also steer the rear wheels according to the steering angle, and can change the steering angle ratio between the front wheels and the rear wheels according to the steering angle.

Four-wheeled vehicles are generally steered by turning the front wheels. When a steering operation is performed while the vehicle is running, a slip angle is first generated in the front wheels at the start of steering, and the resulting cornering force causes lateral movement of the vehicle body and yawing around the center of gravity of the vehicle. Next, displacement in the yaw direction begins to occur in the rear wheels due to yawing of the vehicle body, and only at this time does a slip angle occur in the rear wheels. Therefore, the cornering force of the rear wheels is considerably delayed in phase compared to the front wheels. There is a slight time delay from the start of steering until the resultant force of the cornering forces of the front and rear wheels reaches the value intended by the driver, and this makes driving the vehicle difficult.

Additionally, because sideways slipping occurs in the tires while the vehicle is turning, the vehicle does not always travel with the tangent to the trajectory of the vehicle aligned with the vehicle axis, and drivers must be aware of this phenomenon. First, it is necessary to steer the vehicle while taking into consideration the angular deviation between the tangent to the trajectory of the vehicle and the vehicle axis based on previous driving experience.
This fact, along with the time delay in response of the cornering force of the rear wheels to the front wheels mentioned above, requires a considerable amount of driving experience in order to maneuver the vehicle as desired, and these two points are If the dynamic characteristics of a vehicle can be improved, driving the vehicle will become easier.

In view of the problems with the conventional vehicle steering structure as described above, the present inventor has created the present invention to effectively solve the problems.In particular, the rear wheels are steered together with the front wheels, and the steering angle of the rear wheels is The present invention has been developed to control over a wide range as a function of the front wheel steering angle.

Incidentally, the present applicant has already proposed in Japanese Patent Application No. 163681/1987 that the rear wheels be steered in the same phase as the front wheels or in the opposite phase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle in which the front wheels are steered by rotating a steering wheel, in which a steering means is provided on the rear wheels, a rotating shaft is connected to the steered wheel and the steering means, respectively; A link member that rotates while slidably engaging with each other is provided at the end of the rotating shaft of the rear wheel, and the steering operation by the steering wheel is directed to the rear wheel steering means side by the link member via the rotating shaft on the steered wheel side. To provide a steering device for a vehicle that transmits power to a rotating shaft of a vehicle and steers both front wheels and rear wheels.

Therefore, an object of the present invention is to steer the rear wheels in conjunction with the steering of the front wheels, and to change the steering angle ratio between the front wheels and the rear wheels in accordance with the steering angle of the steered wheels, thereby improving cornering of the rear wheels. By solving as much as possible the time delay in force response and the discrepancy between the tangent of the motion trajectory and the vehicle axis, it is possible to make driving operations easier, and to significantly reduce the minimum turning radius of four-wheeled vehicles, making it easier to drive on narrow roads. To provide a steering device for a vehicle that enables parking in narrow spaces.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an outline of a device according to the present invention, and 1 is a steering wheel. The tip of the steered wheel 2 faces the inside of a gearbox 3, which constitutes steering means 5 for the front wheels 4, 4, and is a well-known rack and pinion type mechanism. When the steering wheel 1 is rotated, the tie rod 6 moves left and right, and the front wheels 4 are steered according to the steering angle of the steering wheel 1 by a linkage such as a knuckle arm. 7 is the rear wheel 8,
This gearbox 7 constitutes steering means 9 on the 8 side, and this gearbox 7 is also of a rack and pinion type, and is configured to steer the rear wheels 8, 8 by the left and right movement of the tie rod 10.

A gear 2a is fixed to the steering shaft 2 of the steering wheel 1, and a rotating shaft 12 includes a gear 11 that meshes with the gear 2a.
extends to the rear of the vehicle. Another rotating shaft 13 extends toward the front of the vehicle body from the steering means 9 on the rear wheel side, and both rotating shafts 12 and 13 are connected by two links 15 and 16 built into a link case 14. FIG. 2 is a detailed view of the link case 14, in which the link 15 is attached perpendicularly to the end of the rotating shaft 12 on the steering wheel 1 side, and the other link is attached to the end of the rotating shaft 13 on the rear wheel steering means 9 side. The links 16 are also installed orthogonally. A linear cam groove 16a is formed in the link 16 in its length direction, and a pin-shaped cam 15a protrudes from the link 15 to be inserted into and engaged with the cam groove 16a. As described above, the two links 15 and 16 are slidably engaged with each other by the cam 15a and the cam groove 16a, and the steering wheel side rotation shaft 12 and the rear wheel steering means side rotation shaft 13 are connected.

When the steering wheel 1 is rotated in either the left or right direction, the front wheels 4 are steered in this direction as described above. This rotation also passes through gears 2a and 11 to the rotating shaft 1.
2, further transmitted to the rotating shaft 13 through two links 15 and 16, and input to the rear wheel steering means 9. The rear wheels 8, 8 are therefore steered together with the front wheels 4, 4.

FIG. 3 is a principle diagram showing the operation of both links 15 and 16 within the link case 14 and showing that the steering angle ratio of the front wheels and rear wheels changes depending on the steering angle of the steered wheel 1.

FIG. 3a shows the state when the vehicle is traveling straight ahead, that is, before the steering wheel 1 is operated, and in this case, the two links 1
5 and 16 both exist on the straight line XX connecting the centers of the rotating shafts 12 and 13, and the cam 1 of the short link 15
5a is engaged with the end A position of the cam groove 16a of the long link 16. From this point on, when the rotating shaft 12 rotates _{counterclockwise} in the figure by an angle α and reaches the state shown in FIG. 3b, the cam 15a of the link 15
In order to proceed on the Pituchi Circle PC concentric with
The link 16, which has a cam groove 16a on which the cam 15a slides, rotates in the same counterclockwise direction by an angle β ₁ minute depending on the distance between the rotating shafts 12 and 13, etc.
3 also rotates by the same angle _β . When the rotating shaft 12 is further rotated and the position of the cam 15a passes through the contact point B of the tangent line from the rotating shaft 13 to the pitch circle PC shown in FIG. The rotation angle of the rotating shaft 13 in the counterclockwise direction is maximum at point B, and decreases thereafter. When the position of the cam 15a reaches point C on the straight line XX, the amount of rotational displacement of the rotating shaft 13 returns to zero, and the rotational angle of the rotating shaft 12 becomes _α2 exceeding 180°, and the cam 15a passes point C as shown in FIG. 3c, the rotation axis 13 moves clockwise at an angle β ₂
Rotate.

Figure 4 shows the above operation graphically.
The horizontal axis is the rotation angle α of the rotation axis 12, and the vertical axis is the rotation axis 13.
The rotation angle is β. As is clear from this graph, in the region where the rotation angle α of the rotation shaft 12 on the steering wheel 1 side is small, the rotation shaft 13 on the rear wheel steering means 9 side is
2 rotates in the same direction and in the same phase, reaches a maximum at point B and then decreases, and after point C, even though the rotating shaft 12 continues to rotate in the same direction, the rotating shaft 13 is in the opposite phase. The steering angle ratio of the front wheels 4 and rear wheels 8 can be changed according to the steering angle of the steered wheels 1, and the phases of the front wheels 4 and rear wheels 8 can be changed from the same phase to opposite phases as the steering angle of the steered wheels 1 increases. can turn to.

In the above, the front wheels 4 and rear wheels 8 are steered in the same direction in a region where the steered wheel 1 is not rotated so much, and the front wheels 4 and rear wheels 8 are steered in the opposite direction in a region where the steering angle of the steered wheel 1 is large. In order to
The distance from the front wheel 4 to the rotation axis 1 is determined appropriately.
2 and the gear ratio of the steering force transmission system from the rotating shaft 13 to the rear wheels 8 may be determined as appropriate.

Next, the relationship between the direction of the vehicle and the turning locus when the steering system according to the present invention is used will be explained with reference to FIGS. 5 to 8. Although all the figures are shown using two wheels, this does not impair the validity of the explanation if the turning radius is sufficiently large compared to the tread, as in a general four-wheeled vehicle.

FIGS. 5 and 6 are examples of conventional steering devices that steer only the front wheels. When turning at very low speeds, the direction of movement of the vehicle coincides with the direction of the tires, so the direction of the vehicle faces outward from the tangent to the turning trajectory, as shown in FIG. As the vehicle speed increases, a slip angle occurs in the front and rear wheels, and the direction of motion of the front and rear wheels begins to point outward from the plane of the tires. Therefore, the center of the turning trajectory of the vehicle gradually moves forward, and the tangent to the turning trajectory begins to point outward with respect to the vehicle axis.
That is, as shown in FIG. 6, the direction of the vehicle body is directed inward from the tangent to the turning trajectory, and throughout the above, the vehicle axis line and the tangent to the motion turning trajectory do not match.

In the steering system according to the present invention, when turning at low speed, the steering wheel 1 uses a large steering angle range, so the front wheels and rear wheels are in opposite phases due to the above-mentioned structure, and the direction of the vehicle and the turning are adjusted as shown in FIG. The difference between the trajectory and the tangent can be made sufficiently small. As the vehicle speed increases, the steering angle of the steered wheels 1 is generally required to be smaller, so the steering angle of the rear wheels changes from the opposite phase to zero, and then to the same phase as the front wheels, as shown in Fig. 8. This makes it possible to maintain a small difference between the direction of the vehicle and the tangent to the turning trajectory even when the vehicle is moving.

By the way, in order to obtain the same lateral acceleration due to the dynamic characteristics of an automobile when turning, a large steering angle is required at low speeds, but this steering angle may be small at high speeds. Regarding this point, according to the present invention, in the case of a small steering angle at high speed, the front wheels and rear wheels are steered in the same phase, and even immediately after the start of steering, a slip angle occurs in the rear wheels at the same time as the front wheels, and the cornering force is is also generated at the rear wheels at the same time, so the vehicle's lateral acceleration reaches the intended value in a short time, significantly improving responsiveness compared to before. According to the embodiment of the present invention described above, if the required steering angle for turning increases as the vehicle speed decreases, the amount of steering angle of the rear wheels decreases and this improved responsiveness also decreases; There is no problem with this point because if it decreases, there will be more time to operate the car and the importance of improving responsiveness will decrease.

In addition, the turning radius for a vehicle to turn becomes smaller as the steering angle of the steered wheels increases, but due to dimensional constraints such as the brake hose connected between the vehicle body and the wheels, and the wheels protruding into the vehicle interior. Conventionally, there is a limit to the minimum radius of rotation that can be achieved due to restrictions on the dimensions of the house and, if the steered wheels are drive wheels, restrictions on the flexibility angle of the shaft coupling. In this regard, according to the present invention, the front and rear wheels can be steered in opposite phases over a wide steering angle range at low speeds, so the minimum turning radius can be significantly reduced to nearly half compared to conventional devices that steer only the front wheels. This makes it possible to make the vehicle smaller, and the difference between the inner wheels can be significantly reduced, making it easier to drive on narrow roads and park in narrow spaces.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, FIG. 1 is a schematic diagram showing the outline of the device of the present invention, FIG. 2 is a perspective view of two link member parts, and FIGS. 3 a, b, and c are links. Figure 4 is a diagram of the operating principle of the member; Figure 4 is a graph of operation based on this principle; Figures 5 and 6 are diagrams pointing out the problems of the conventional technology; Figures 7 and 8 explain the advantages of the present invention. It is a diagram. In the drawings, 1 is a steering wheel, 4 is a front wheel, 5 is a front wheel steering means, 8 is a rear wheel, 9 is a rear wheel steering means, 1
2 and 13 are rotating shafts, and 15 and 16 are link members.

Claims (1)

[Claims] 1. In a vehicle in which the front wheels are steered by rotating the steering wheels, a steering means is provided on the rear wheels, a rotating shaft is connected to each of the steering wheels and the steering means, and an end of each rotating shaft is connected to the steering wheel. A link member that rotates while slidably engaging with each other is provided in the section to connect the rotating shaft on the steering wheel side and the rotating shaft on the rear wheel steering means side, and the rotation operation by the steering wheel is performed by rotation of the link member. A steering device for a vehicle, characterized in that the information is transmitted to a rear wheel steering means to steer the rear wheels together with the front wheels.