JPS61181776A - Steering gear for front and rear wheels - Google Patents

Abstract

PURPOSE:To reduce steering force to some extent, by installing a power output member for a rear-wheel steering system separate from a front-wheel steering output member, while gearing it with a steering shaft, and connecting this power output member to a power takeoff shaft with a variable gear ratio mechanism. CONSTITUTION:A rack 8 to be engaged with a pinion 5 installed in a steering shaft 4 is installed in a rack shaft 7. A knuckle arm supporting a front wheel is connected to both ends of this rack shaft with a tie rod. And, a rack shaft 11 forming a power output member for a rear-wheel steering system is parallelly set up in a lower part of the rack shaft 7. A rack 12 is installed in the front of one half part of the rack shaft 11, while a pinion 15 to be engaged with the rack 12 is installed in a lower part of the steering shaft 4. And, the rack shaft 11 is connected to a pinion shaft 18 forming a power takeoff shaft for a rear-wheel steering system with variable gear ratio mechanisms 13 and 19.

Description

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

(Prior art) In front and rear wheel steering of a vehicle, that is, in a four-wheel steering (4WS) system, a steering shaft that rotates in conjunction with a steering wheel and a front wheel steering output member are gear-engaged, and the front wheel steering system is connected to the steering shaft. A power take-off shaft for the rear wheel steering system that rotates in conjunction with the rear wheel steering system is provided, and the power take-off shaft and the input shaft of the rear wheel steering system are interlocked and connected via a linkage shaft, and the rear wheel steering output is connected to the input shaft. A patent application filed in 1982 provides a vehicle steering system in which an eccentric shaft is provided as a member, and the steering of the rear wheels can be varied between the same phase and the opposite phase as the front wheels depending on the magnitude of the steering angle by rotation of the eccentric shaft. It is known from No.-93394 (Japanese Unexamined Patent Publication No. 58-209657).

The rear wheel steering characteristic by such a 4WS device is shown by a sine waveform as shown in characteristic (a) in FIG. 6(C). On the other hand, since the gear ratio characteristic between the steering shaft and the front wheel steering output member is constant as shown in the characteristic (a) in Fig. 6(a), the front wheel steering characteristic is as shown in Fig. 6(b).
) shows a proportional linear line as shown in (a).

(Problems to be Solved by the Invention) By the way, the steering force by a normal two-wheel steering (2WS) device that steers only the front wheels without steering the rear wheels has the characteristics (b) shown in Figure 6(d). Compared to this, the steering force by the 4WS device is generally heavier as shown in characteristic (a) in FIG. 6(d).

The weight of such steering force can be reduced by installing a power steering device, but this increases the price and increases the size of the device, so it is recommended not to install a power steering device, especially for small and light vehicles. The challenge was to reduce the steering force.

Therefore, an object of the present invention is to be able to reduce the steering force in the above-mentioned 4WS system by applying a relatively simple modification to the mechanism inside the gear box of the front wheel steering system. To provide a steering device for front and rear wheels that can fully take advantage of the advantages of the system, such as good turning ability at a large steering angle and good maneuverability at a small steering angle.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides the above-mentioned 4WS device with a steering shaft (4) and gears (12), (1) shown in FIG.
5) A power output member (11) to the rear wheel steering system that meshes is provided, and the power output member (11) and the power output shaft (18) to the rear wheel steering system are connected to a variable gear ratio mechanism (13), (IS)
The steering shaft (4) and the front wheel turning output member (7) are interlocked and connected by variable gear ratio mechanisms (5) and (8).

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

Fig. 1 is a schematic perspective view of the entire steering system, Fig. 2 is an enlarged perspective view of the rear wheel steering system, and Fig. 3 is an enlarged front view of the gear mechanism section in the gear box provided in the front wheel steering system. .

There is a universal joint (3) at the lower end of the support shaft (2) of the handle (1).
The steering shaft (4) is connected to the steering shaft (4) through the rack and pinion steering gear box (6), and the steering shaft (4) is connected to the rack shaft (4) which forms the front wheel steering output member. 7) are interlocked and connected by a variable gear ratio mechanism.

That is, a helical type pinion (5) is provided on the steering shaft (4), and a helical type rack (8) that meshes with this pinion (5) is provided on the front surface of the negative half of the rack shaft (7). The pitch of the teeth (8a) of this rack (8) is the largest in the center and becomes smallest toward both ends, and in the neutral steering state, the pinion (5) is connected to the variable gear ratio rack. (8) Position it in the center.

Both ends of the rack shaft (7) protruding from the gear box (8) and the knuckle arms (22), (22) supporting the front wheels (21), (21) are connected to the tie rods (23).
) and (23).

Furthermore, a second rack shaft (11) is disposed in parallel below the rack shaft (7) in the gear box (6). This rack shaft (11) constitutes a power output member to the rear wheel steering system, and a helical type rack (12) with a constant gear ratio is provided on the front side of the negative half of the rack shaft (11). A helical pinion (15) that meshes with the rack (12) is provided at the bottom of the shaft (4).

The second rack shaft (11) and a pinion shaft (18) forming a power output shaft for the rear wheel steering system are interlocked and connected by the same variable gear ratio mechanism as described above.

That is, a helical rack (13) is provided on the lower surface of the other part of the rack shaft (11) as shown in FIG.
3) The pitch of the teeth (13a) is largest in the center and becomes smallest toward both ends, and a helical-type pinion (19) is attached to this rack (13).
and the pinion shaft (18) is connected to the gearbox (1
3) protrudes backwards. In the neutral steering state, the pinion (1θ) is positioned at the center of the variable gear ratio rack (13).

A long linkage shaft (25) is connected to the pinion shaft (18) via a universal joint (24), and a rear end of the linkage shaft (25) is connected to the rear end of the linkage shaft (25) via a universal joint (26). Connect the input shaft (27) of the wheel steering system. Input shaft (27)
is supported by a bearing bladder (y) (31), and this input shaft (
27) An eccentric shaft (28) constituting a rear wheel steering output member is protruded through a flange (27) at the rear end, and the eccentric shaft (28)
29), the joint member (32) is fitted and assembled so as to be relatively rotatable. Between this joint member (32) and the vehicle body side, there is an arm (33) extending to one side and a link (
34) erect a link mechanism consisting of:

Both ends of the joint member (32) and the rear wheel (3B
), (3B) supporting knuckle arms (37), (3
? ) are connected with tie rods (38) and (38).

In the neutral steering state, the eccentric shaft (28) is connected to the input shaft (27).
) located vertically above.

The above 4WS device rotates the rear wheels (3B), (3B) to the front wheels (21), (2
It is steered in the same phase as 1), but in the opposite phase from 1/2 rotation to 38 rotations, which is the practical range of use.

As described above, the steering shaft (4) and the rack shaft (7) forming the front wheel steering output member are interlocked and connected by the variable gear ratio mechanism (5), (8), that is, the small reduction ratio is set near the neutral steering position. In addition, since a large reduction ratio is achieved near a large steering angle, the gear ratio characteristics change as shown in Figure 6 (a) (/\), and the front wheel steering characteristics also change as shown in Figure 6 (b). Particularly in the small steering angle range, as shown in (c), it becomes nonlinear.

Then, a new rack shaft (11) is installed that serves as a power output member to the rear wheel steering system, and this rack shaft (11) and the steering shaft (4
) are meshed with gears (12) and (15) having a regular constant gear ratio, and power to the rear wheel steering system is obtained from a separate system from the front wheel steering system, and from the rack shaft (11). Since the variable gear ratio mechanisms (13) and (19) similar to those described above are used to extract rotation from the pinion shaft (18) that forms the power output shaft for the rear wheel steering system, the rear wheel steering characteristics are as shown in Figure 6 ( The characteristics (c) in Fig. 6(d) change as shown in the characteristic (c) of C), and especially the steering force changes over the entire range as shown in the characteristic (c) of Fig. 6(d).
In particular, the steering force after the initial stage of steering can be significantly reduced.

In addition, as is clear from the rear wheel steering characteristics (c) in Figure 6 (C), the maximum steering angle of each rear wheel is maintained equal when the front wheels are in opposite phase and in the same phase. A delayed characteristic is obtained, and it is possible to change the rear wheel steering angle of the conventional 4WS characteristic (a) as α) with respect to the ratio angle (α0) at the initial stage of steering.

In this way, it is also possible to make the rear wheel steering characteristics variable, which also contributes to improving the rear wheel steering characteristics.

The above 4WS system is shown in Figure 5.

The steering angle (I) is determined by the steering gear box (6
) is converted by the variable gear ratio mechanism (II) of the front wheel steering system, and its output is output as the front wheel steering angle (III). Separately from this, the steering wheel steering angle (I) is converted by a variable gear ratio mechanism (IV) that forms the power output mechanism for the rear wheel steering system installed in the gear box (6), and the output is transferred to the rear wheel steering system. It is converted again by the steering mechanism (V), and its output is output as a rear wheel turning angle (Vl).

Since such a system can reduce the steering force as described above, there is no need to add a power steering device, and costs can be kept low. Therefore, it is possible to equip even small and light vehicles with the 4WS device.

By the way, the variable gear ratio mechanism is not limited to the one in the embodiment, and other suitable ones may be adopted. Furthermore, the gear ratio characteristic (c) is just an example; if the gear ratio at the initial stage of steering is set to LOW CARD compared to the conventional gear ratio characteristic (a), the steering force at the initial stage of steering can be further reduced.

(Effects of the Invention) As described above, according to the present invention, the steering shaft and the front wheel steering output member are interlocked and connected by the variable gear ratio mechanism, and the front wheel steering output member is separately connected to the rear wheel steering system. A power output member is provided and geared to the steering shaft, and this power output member and a power take-off shaft for the rear wheel steering system are further interlocked and connected by a variable gear ratio mechanism, which eliminates the need for a power steering device and is relatively efficient. It has a simple structure that reduces steering force, and is especially small.

It is possible to equip light vehicles with inexpensive 4WS devices.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of the entire steering system, FIG. 2 is an enlarged perspective view of the rear wheel steering system, FIG. 3 is an enlarged front view of the gear mechanism in the gear box provided in the front wheel steering system, and FIG. The figure is a partial bottom view in the Z direction of Figure 3, Figure 5 is a diagram of the steering system for the front and rear wheels, Figure 6 is a characteristic diagram for each steering wheel steering angle, Figure 6 (a) is a gear ratio characteristic diagram, Figure 6(b) is a front wheel steering angle characteristic diagram, Figure 6(c) is a rear wheel steering angle characteristic diagram, and Figure 6(d) is a characteristic diagram of the front wheel steering angle.
) is a steering force characteristic diagram. In the drawing, (1) is a handle, and (4) is a steering shaft. (5), (8) are variable gear ratio mechanisms, (6) are steering gear boxes, (11) are front wheel steering output members, (11) are
) is the power output member to the rear wheel steering system, (13), (19
) is a variable gear ratio mechanism, (18) is a power take-off shaft, (21)
is the front wheel, (25) is the linkage shaft, (27) is the input shaft,
(29) is an eccentric shaft, and (36) is a rear wheel. Patent applicant: Agent for Honda Motor Co., Ltd.
Patent Attorney Part 2 1) Yong-Immediate Question Patent Attorney Kuni Ohashi Department Attorney Yu Koyama Figure 2 Back Silver R p

Claims (1)

[Claims] A steering shaft that rotates in conjunction with the steering wheel and a front wheel steering output member are gear-engaged, a power output shaft for the rear wheel steering system that rotates in conjunction with the steering shaft is provided in the front wheel steering system, and the power is The take-out shaft and the input shaft of the rear wheel steering system are interlocked and connected via a linkage shaft, and the input shaft is provided with an eccentric shaft that constitutes a rear wheel steering output member, and the rotation of the eccentric shaft adjusts the steering angle of the steering wheel. In a vehicle steering system in which the steering of the rear wheels is variable between the same phase and the opposite phase as the front wheels according to A steering device for front and rear wheels, in which the power take-off shaft is interlocked and connected by a variable gear ratio mechanism, and the steering shaft and a front wheel turning output member are interlocked and connected by a variable gear ratio mechanism.