JPS629476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a steering system for a vehicle, particularly a four-wheeled vehicle.

(Prior Art) Steering in a four-wheeled vehicle is generally performed by steering only the front wheels. When the front wheels start turning when the vehicle is running, a slip angle is first generated in the front wheels, and the resulting cornering force causes lateral movement of the vehicle body and yawing around the center of gravity of the vehicle.

The rear wheels develop a slip angle only after displacement in the yaw direction begins to occur as a result of the yaw movement of the vehicle body. Therefore, there is a phase lag in the cornering force generated by the rear wheels compared to the front wheels, and there is always a slight time delay before the resultant force of the cornering forces of the front and rear wheels reaches the value intended by the driver. This is the reason why steering a four-wheeled vehicle requires skill.

Furthermore, while a four-wheeled vehicle is making a turning motion due to steering, side slip occurs in the wheels, so the tangent to the turning trajectory and the vehicle axis do not always match, and this is also a problem for four-wheeled vehicles. There is a reason why steering requires skill.

Therefore, the driver of a four-wheel vehicle is required to perform steering by empirically recognizing the time delay in steering the rear wheels and the angle deviation between the turning trajectory and the vehicle axis in order to steer the vehicle appropriately. Driving a car requires a certain amount of driving experience.

As a means to solve the problems with such conventional steering devices, it has been proposed to steer the front wheels and the rear wheels. For example, Japanese Patent Publication No. 40-10728 discloses a method of giving the rear wheels a steering angle proportional to the sideslip angle of the rear wheels, and U.S. Patent No. 2910131 discloses a method of giving the rear wheels a steering angle proportional to the sideslip angle of the rear wheels. A method for controlling the amount of steering is disclosed.

(Problems to be Solved by the Invention) However, these known techniques not only have technical problems with the sideslip angle or G sensor that controls the steering of the rear wheels, but also all of them have problems due to the steering of the front wheels. Since this method corrects the steering of the rear wheels based on the factors that occur, a delay in response occurs in steering.

In addition, technology that steers both the front and rear wheels has been used in special vehicles, etc., but in both cases, the purpose is to reduce the turning radius and improve the maneuverability of the vehicle. The purpose is simply achieved by switching the control mode (for example, British Patent No. 523656,
No. 26732).

Therefore, an object of the present invention is to focus on the fact that in four-wheeled vehicles, the amount of front wheel steering at medium to high speeds is generally in a relatively small range, and to solve the problems of conventional devices in steering at medium to high speeds. The amount of steering of the rear wheels can be reduced by using a factor that easily detects the response delay of hot steering without using complicated sensors and mechanisms, and without having to correct rear wheel steering due to generated lateral force, etc. achieved by predicting
The purpose of the present invention is to provide a steering device that provides ease and stability in steering, reduces the turning radius without requiring switching operations of the device, and improves maneuverability of the vehicle. .

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a front wheel steering device that is linked to steering wheel operation, a rear wheel steering device that is mechanically interlocked and connected to the front wheel steering device, and a front wheel steering device that is connected to the front wheel steering device. A rear wheel steering angle function generating device that is provided in a power transmission path from the device to a rear wheel steering device and that varies a ratio between a front wheel turning amount and a rear wheel turning amount based on the front wheel turning amount. , and a rear wheel steering direction converting device which is provided in the same power transmission path and controls the steering of the rear wheels to be in the same phase or opposite phase to the front wheels based on a predetermined amount of steering of the front wheels.

Specifically, the rear wheel steering angle function generating device and the rear wheel steering direction converting device are formed on a cam that is approximately S in plan view.
It consists of a cam groove in the shape of a letter or inverted S, and a pin engaged with the cam groove.

(Function) In order to obtain the lateral acceleration necessary for turning the vehicle, a large steering angle is required when driving at low speeds, but at high speeds, the required steering angle gradually becomes smaller. Therefore, according to the steering system according to the present invention, the front and rear wheels are steered in the same phase at a small steering angle, so when operating at high speed, a slip angle is generated in the rear wheels at the same time as the front wheels, and the cornering force is changed. Because it occurs,
The vehicle's lateral acceleration reaches the value intended by the driver in a short time, and steering response is significantly improved.

When the required steering angle increases as the vehicle speed decreases, the amount of steering angle of the rear wheels decreases, and therefore the degree of improvement in response described above also decreases, but this is not as important for steering response at low speeds. There is no problem in practice.

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. 3 to 6.

Although all the figures are shown with two wheels, there is no risk of impairing the validity of the explanation if the turning radius is sufficiently large compared to the wheel width of a general four-wheeled vehicle.

FIGS. 3 and 4 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 orientation of the tires, so the direction of the vehicle faces outward from the tangent to the turning trajectory, as shown in FIG. When 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 points outward from the plane of the tire. Therefore, the turning center of the vehicle gradually moves forward, and the tangent to the turning locus begins to point outward with respect to the tangent to the vehicle. That is, as shown in FIG. 4, the direction of the vehicle body is directed inward from the tangent to the turning trajectory.

In the steering system according to the present invention, since a region with a large steering angle is used when turning at low speed, the front and rear wheels are steered in opposite phases. As shown in the figure, the difference between the direction of the vehicle and the tangent to the turning trajectory can be made sufficiently small.

Generally, the required steering angle decreases as the vehicle speed increases, so the steering angle of the rear wheels changes from the opposite phase to the steering angle O and the same phase, and as shown in Figure 6, the vehicle direction and turning trajectory are maintained even at high speeds. It is possible to keep the difference between the tangent line and the tangent line small. Furthermore, according to the steering system of the present invention, the minimum turning radius can be reduced. In other words, the turning radius of a vehicle decreases as the steering angle of the steered wheels increases, but due to dimensional constraints such as brake hoses connected between the wheels and the vehicle body, dimensional constraints of the wheel house protruding into the vehicle interior, and further When the steering wheel is also a driving wheel, the maximum steering angle is limited due to constraints on the flexibility angle of the shaft joint, and therefore there is a limit to the minimum turning radius. According to the steering system of the present invention, since the front and rear wheels are steered in opposite phases at low speeds, the minimum turning radius is reduced by nearly 1/2, and the difference between the inner wheels is also significantly reduced, making it easy to maneuver on narrow roads. This makes it easier to drive and park in tight spaces.

(Example) Examples will be described below based on the accompanying drawings.

FIG. 1 is a schematic plan view showing an embodiment of the steering system of the present invention, in which the front wheels 8 and 9 are rotated by a gearbox using a well-known method such as a rack and pinion to rotate a steering shaft 7a by steering the steering wheel 7. 12, the linear motion is transmitted by a known linkage such as a tie rod, knuckle arm 13, etc., and the front wheels 8, 9 are steered. The steering mechanism for the front wheels 8 and 9 described above is completely the same as the conventional one.

A cam plate 3 having a rod 1 connected to a point 14 which is linked to the steering of the front wheels 8 and 9 extends rearward, and is slidably housed in a cam case 2 provided at the rear.
The rod 1 is connected to. The cam plate 3 is provided with a substantially inverted S-shaped cam groove 4 as shown enlarged in FIG. 2, and a pin 6 is engaged in the cam groove 4 so as to slide along the groove. A rear wheel tie rod 5 arranged to connect both rear wheels 10 and 11 and steer both rear wheels 10 and 11 by movement in the axial direction is joined to a pin 6 that moves in a cam groove 4, pin 6
By moving the cam groove 4, the rear wheel tie rod 5 moves in the axial direction according to the shape of the cam groove, and the rear wheel is steered.

Next, the operation of the steering system according to the present invention will be explained.

In the figure, when the steering wheel 7 is steered to the right, the front wheels 8 and 9 are steered to the right. At the same time, the rod 1 is pushed rearward, causing the cam plate 3 connected to the rod 1 to slide rearward within the cam case 2. As shown in FIG. 2, the cam groove 4 provided in the cam plate 3 is formed in an inverted S-shape with both end portions 4b and 4c extending substantially linearly from an intermediate curved portion 4a. When it begins to slide rearward, the pin 6 moves to the right in the figure, moves the rear wheel tie rod 5 in the right axial direction, and steers the rear wheels 10, 11 to the right. When the steering wheel is further rotated to the right, the cam plate 3 slides further rearward, and due to the movement of the pin 6 that moves along the cam groove 4, the steering angle of the rear wheel to the right reaches its maximum value and gradually decreases. Initially, as the steering angle of the steered wheels increases further, the rear wheels begin to turn to the opposite left, and near the maximum steering angle of the steered wheels, the steering angle of the rear wheels is almost the same as the front wheel steering angle, and It becomes a turning point in the direction.

It is clear from the figure that when the steered wheels are steered to the left in the figure, a similar operation is shown, only that the steering direction of the front and rear wheels is reversed.

(Effects of the Invention) As described above, according to the present invention, it is possible to eliminate the delay in steering response, which was a problem with conventional devices, especially in steering at medium and high speeds, without using complicated sensors and mechanisms. This is achieved by steering the rear wheels in response to the same phase as the front wheel steering direction based on the amount of front wheel steering that can be easily detected, without having to correct the rear wheel steering due to generated lateral force, etc. Therefore, with a simple configuration, it is possible to perform steering control of the front and rear wheels with excellent steering response at medium and high speeds, and to obtain ease and stability of steering. By making it smaller, it is also possible to improve the maneuverability of the vehicle.

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view showing one embodiment of the steering device of the present invention, Fig. 2 is an enlarged view of the cam, Figs. FIG. 6 is a schematic diagram illustrating the advantages of the present invention. In the drawings, 1 is a rod, 3 is a cam plate, 4 is a cam groove, 5 is a rear wheel steering member, 6 is a pin, 8 and 9 are front wheels, and 10 and 11 are rear wheels.

Claims (1)

[Scope of Claims] 1. A front wheel steering device that is linked to steering wheel operation, a rear wheel steering device that is mechanically interlocked and connected to the front wheel steering device, and a power transmission path from the front wheel steering device to the rear wheel steering device. A rear wheel steering angle function generating device is provided in the same power transmission path and makes the ratio between the front wheel turning amount and the rear wheel turning amount variable based on the front wheel turning amount. A vehicle steering device comprising a rear wheel steering direction conversion device that controls steering of the rear wheels to be in the same phase or opposite phase to the front wheels based on the amount of steering. 2. The rear wheel steering angle function generating device and the rear wheel steering direction converting device include a cam groove formed in a cam and having an approximately S-shape or inverted S-shape in plan view, and a pin engaged with the cam groove. A steering system for a vehicle according to item 1.