JPS62187660A - Front and rear wheels steering device for vehicle - Google Patents

Abstract

PURPOSE:To restrict the maximum steering angle of the rear wheels in the same phase as the front wheels, and secure the driving response without losing a capability of small sharp turns, by composing a rotation pickup piston, a rotation input piston, and racks to gear therewith in variable gear mechanisms respectively. CONSTITUTION:While a straight rack 7 furnished at the front side of one half of a rack shaft 6 is geared to a pinion 5 of a pinion shaft 4 linked to the steering shaft, a pinion 16 of a rotation pickup pinion shaft 15 is geared to a variable rack 8 with a different pitch furnished at the lower side of the other half of the rack shaft 6, to compose the first variable gear ratio mechanism I. And a variable rack 25 is furnished at the lower side of a rack shaft 24 to gear with a pinion 22 of a rotation input pinion shaft 21 which is linked to the pinion shaft 15, to form the second variable gear mechanism II. Therefore, even though the rear wheel turning angle to the handle steering angle is made larger, the maximum steering angle of the wheels in the same phase as the front wheels can be restricted.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a front and rear wheel steering device for a vehicle.

(Prior art) In vehicles, in order to improve the turning performance at low speeds and the steering response at high speeds, steering wheels are also changed to the rear wheels. , a front and rear vehicle in which a pinion shaft for taking out rotation provided on a rack and pinion type steering gear for steering the front wheels and a pinion shaft for inputting rotation provided on a rack and pinion type steering gear for steering the rear wheels are connected via a linkage shaft. Wheel steering devices are known.

(Problem to be Solved by the Invention) By the way, for example, in order to improve steering response near straight-ahead driving, if the rear wheel turning angle (α) with respect to the steering wheel steering angle is increased as shown in characteristic (a) in Fig. 5, In the case of a conventional strain steering wheel, the maximum steering angle of the rear wheels in the same phase as the front wheels becomes large, and this results in a sacrifice in small turning performance.

(Means for solving the problem) In order to solve the problem, the present invention provides a front and rear wheel steering system of the type described above, in which the rotation take-off pinion (16) and the rack (8) meshing with the pinion are connected to a variable gear. It is composed of a ratio gear 4W (1), a 5-rotation input pinion (22) and a gear ratio mechanism (25) that matches 11 rotations with the pinion (22).
).

(effect) Both pinions (18) for rotation extraction and rotation input.

(22) both mesh with barrier pull ranks (8) and (25), so for example both barrier pull racks (8) and (2
If the tooth pinch of 5) is largest at the center and smallest toward both ends, then the characteristic shown in FIG. 5 (b) is obtained.

As shown in (c), the rear wheel turning angle (α
), it is possible to keep the maximum steering angle of the rear wheels in the same phase as the front wheels small. Therefore, a maneuvering response of +/1 can be ensured without significantly sacrificing the turning performance.

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

Figure 1 is a schematic perspective view of the front and rear wheel steering system.
) steering shaft (2) is incorporated into a rack and pinion type front steering gear box (3),
It is connected to the pinion shaft (4) shown in the figure. This pinion shaft (
4) is equipped with a helical pinion (5), and a straight rank (7) with a constant helical tooth pinch that meshes with this pinion (5) is sunk in the front half of the rack shaft (8). I get kicked. Both ends of this rack shaft (6) and the knuckle arm (+2) supporting the front wheels (11), (11)
) and (12) are connected by tie rods (13) and (13).

Furthermore, on the lower surface of the other half of the rack shaft (6), there is a barrier pull rack (8) which is also helical in shape and has a different tooth pitch.
), and a rotary extraction pinion shaft (15) equipped with a helical pinion (16) that meshes with this barrier pull rack (8) is assembled into the gear box (3) and protrudes rearward. Specifically, as shown in Fig. 2, the rear pull rack (8) is formed so that the tooth pitch is the largest at the center where it meshes with the pinion (1B) in the neutral steering state, and becomes the smallest towards both ends. .

Thus, in the front steering gear box (3), the barrier pull rack (8) and the rotation extraction pinion (16) constitute the first variable gear ratio mechanism (I).

In addition, the rotation extraction pinion shaft (15) has a universal joint (17).
), and a rotational input pinion shaft (21) is connected to this linkage shaft (18) via a universal joint (18). This rotational input pinion shaft (21) is provided with a helical pinion (22) as shown in FIG. 3, and is also incorporated into a rack and pinion type gear steering gear box (23).

The same barrier pull rack (2) as described above is also placed on the lower surface of the rack shaft (24) that meshes with the rotation input pinion (22).
5), and both ends of this rack shaft (24) and the rear wheel (2
B), (2B) supporting knuckle arm (27), (
27) with tie rods (28) and (2B). That is, the tooth pitch of the barrier pull rack (25) is also formed so that, as shown in FIG. 3, the tooth pitch is the largest at the center portion where the pinion (22) meshes in the neutral steering state, and becomes the smallest toward both ends.

Thus, in the rear steering gear box (23), the rotation input pinion (22) and the barrier pull rack (25) constitute a second variable gear ratio mechanism (n).

The above front and rear wheel steering system is as shown in Fig. 4, and the steering wheel steering angle (A) is controlled by the front wheel steering mechanism (B) consisting of the pinion (5) and straight rack (7) in the front steering gear box (3). The output is then output as a front wheel steering angle (C), and is converted by the variable gear ratio mechanism (1) in the same gear box (3), and the output is input into the gear steering gear box (23). Then, after being converted again by the variable gear ratio mechanism (II) in the gear box (23), it is output as the rear wheel steering angle (D).

Note that the characteristics (b) and (c) in FIG. 5 are merely examples, and desired rear wheel steering characteristics can be obtained by changing the barrier pull rack or the tooth pitch of the pinion.

(Effects of the Invention) As described above, according to the present invention, since a variable gear ratio mechanism is adopted for both the rotation take-out and rotation input pinions and the respective ranks, for example, the rear wheel Even if the steering angle is increased, the maximum steering angle of the rear wheels in the same phase as the front wheels can be kept small, ensuring maneuvering responsiveness without significantly sacrificing tight turning performance, allowing for arbitrary rear wheel steering characteristics. It will be done.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view of the front and rear wheel steering device, Fig. 2 is a front view of the gear mechanism in the front steering gear box, Fig. 3 is a bottom view of the gear mechanism in the beam steering gear box, and Fig. 4 is a front and rear view. A system configuration diagram of wheel steering, and FIG. 5 is a rear wheel steering characteristic diagram. In the drawing, (8) and (24) are rack axes, (8) and (
25) is a barrier pull rack, (11) and (21) are pinion shafts, (12) and (22) are pinions, (1B) is a linkage shaft, and (I) and (II) are variable gear ratio mechanisms.

Claims (1)

[Scope of Claims] A pinion shaft for taking out rotation provided in a rack and pinion type steering gear for steering the front wheels and a pinion shaft for inputting rotation provided in a rack and pinion type steering gear for steering the rear wheels are connected via a linkage shaft. In the front and rear wheel steering systems of connected vehicles, the rotation output pinion and the rack that meshes with it are configured with a variable gear ratio mechanism, and the rotation input pinion and the rack that meshes with it are also configured with a variable gear ratio mechanism. Features: Front and rear wheel steering system for vehicles.