JPH062469B2 - Rear wheel steering actuator for front and rear wheel steering system of vehicle - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering actuator in a front / rear wheel steering device of a vehicle capable of variably controlling a steered angle of a rear wheel with respect to a front wheel.

<Prior Art> The present applicant has already steered the rear wheels in relation to the steering of the front wheels and, at the same time, steered the vehicle by changing the steering angle or the steering angle ratio of the rear wheels to the front wheels according to the vehicle speed ( Japanese Patent Application No. 57-13
Various proposals have been made such as 4888 (see JP-A-59-26363). In such a device, at low speeds, the rear wheels are steered to the opposite phase or substantially zero to the front wheels, while at high speeds, on the contrary, the rear wheels are steered to the same phase as the front wheels. I am trying to let you. If desired, the function characteristic of the steering angle ratio of the rear wheels with respect to the vehicle speed can be changed according to the acceleration of the vehicle or manually, or the fixed mode can be selected by manual selection.

As a result, at a low speed, the minimum turning radius of the vehicle and the inner ring difference are greatly reduced, and the vehicle is put in the garage, traveling on a narrow bend and
It is possible to dramatically improve the maneuverability of the vehicle at the time of turn, and at the same time, at the high speed, it is possible to dramatically improve the maneuvering response at the time of changing lanes.

Generally, in a front wheel steering system, a force applied from the road surface to the front wheels is transmitted to the steering wheel to some extent, and a caster angle provided on the front wheels obtains a force for restoring the front wheels to the straight traveling position. It makes driving the vehicle easier. However, such an action is not necessary for the rear wheels, and the movement of the vehicle may be disturbed when the rear wheels are steered due to disturbance such as unevenness of the road surface.

<Problems to be Solved by the Invention> In view of the above-mentioned drawbacks of the conventional technology, the main object of the present invention is to prevent the rear wheels from being steered even when an external force is applied to the rear wheels, so that the vehicle is always turned. To provide a rear-wheel steering actuator in a front-rear wheel steering device that enables stable running of the vehicle.

<Means for Solving Problems> According to the present invention, such an object is to provide a rear-wheel steering actuator in a front-rear wheel steering device for a vehicle, which variably controls a rear-wheel steering angle according to a certain condition. And an electric motor, a screw rod fixed to the output shaft of the electric motor and extending in the left-right direction, and screwed onto the screw rod so as to be displaceable in the left-right direction, and the left and right tie rods are connected. And a slider member, and the screw rod has a lead angle smaller than a friction angle, thereby providing a rear wheel steering actuator.

<Operation> Since the slider member is not displaced unless the screw rod rotates in this way, the rear wheel is always fixed at a position determined by the state of the actuator, and the rear wheel can be steered by an external force applied thereto. Absent.

<Embodiment> FIG. 1 shows an embodiment of a rear wheel steering actuator according to the present invention. An electric motor 1 is fixed to a vehicle body portion near a center position of a rear portion of a vehicle, and a screw rod 2 is fixed to an output shaft of the motor. The screw rod 2 is screwed with an inner screw cut on the convex portion 3 of the slider 5. The slider 5 is supported by the vehicle body so as to be able to slide in the left-right direction and is connected to one end of the tie rod 6 via a ball joint 6a. The other end of the tie rod 6 is also connected to a knuckle arm 7 of a rear wheel 8 via a ball joint 6b. A hexagonal rod portion 2a is integrally formed at the free end of the screw rod 2.

Here, the lead angle of the screw of the screw rod 2 is set to be smaller than the friction angle, and the rear wheel 8 can be steered by driving the slider 5 by the rotation of the screw rod 2. The screw rod 2 is not driven by the external force.

The motor 1 is connected to an in-vehicle computer 9, and the motor 1 is driven to realize a predetermined rear wheel steering angle based on a predetermined control program. When the motor 1 is rotationally driven, the slider 5 is displaced in the left-right direction via the screw mechanism, and the rear wheel 8 can be steered.

When the motor 1 cannot be operated for some reason and the rear wheels 8 are stopped while being steered in a certain direction, it becomes difficult to drive the vehicle. The rear wheel 8 can be restored and fixed to the neutral position by engaging with the screw 2a and rotating the screw rod 2 in a desired direction.

<Effect> As described above, according to the present invention, the external force applied to the rear wheels from the road surface is not transmitted to the input end of the rear wheel steering actuator. The movement is not disturbed, and it is possible to obtain the effect of enabling stable running of the vehicle at all times. Further, by extending the screw rod in the left-right direction in parallel with the displacement direction of the slider member, the slider member drive mechanism can be made compact. Moreover, by directly driving the slider member using the screws, a relatively small number of elements causing rattling can be obtained, so that higher rigidity can be obtained and the number of parts can be kept low.

[Brief description of drawings]

FIG. 1 is a perspective view showing a simplified rear wheel steering mechanism to which a rear wheel steering actuator according to the present invention is applied. DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Screw rod 2a ... Hexagonal bar part 3 ... Convex part 5 ... Slider 6 ... Tie rod 6a, 6b ... Ball joint 7 ... Knuckle arm 8 ... Rear wheel 9 ... Computer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Hamada 6-8-7 Motoimaizumi Utsunomiya City, Tochigi Prefecture No. 201 Eder Heights 201 (72) Inventor Manuya Serizawa 773-5, Sukugocho, Utsunomiya City, Tochigi Prefecture 2 Izumi Mansion 2 -201 (56) Reference JP-A-61-146682 (JP, A)

Claims (1)

[Claims] 1. A rear wheel steering actuator in a front and rear wheel steering device of a vehicle, which variably controls a steering angle of a rear wheel according to a certain condition, the actuator being fixed to an electric motor and an output shaft of the electric motor. And a slider member that extends in the left-right direction and a slider member that is screwed onto the screw rod and that can be displaced in the left-right direction and that is connected to the left and right tie rods, and the screw rod has a smaller friction angle. An actuator for steering rear wheels in a front and rear wheel steering device of a vehicle, which has a lead angle.