KR20040102888A - steering actuator of independent steer-by-wire system - Google Patents

Abstract

PURPOSE: A steering actuator of an independent steer-by-wire system is provided to improve the performance of the driving actuator and to control steering accurately by generating driving force from an ultrasonic motor. CONSTITUTION: A ring gear(12) is fixed to a housing(11) fastened to a vehicle body, and an ultrasonic motor(13) is mounted in the ring gear. Planetary gears(15) are installed to a rotor(13b) of the ultrasonic motor, and used as a carrier. The planetary gear is engaged with a sun gear(16), and a worm gear(16a) is formed in the inner periphery of the sun gear. A rack(17a) is engaged with the worm gear, and formed in a steering rod(17). A tie rod is connected to the outer end of the housing of the steering rod. Steering is performed by driving force of the ultrasonic motor. The size and the weight of the ultrasonic motor are reduced, and reversion is restricted by the ultrasonic motor.

Description

Steering actuator of independent steer-by-wire system

The present invention relates to a steering by wire system, and more particularly to a steering actuator for the implementation of a stand alone steering by wire system.

The vehicle's power steering system is hydraulic to electrohydraulic, and now electric power steering system is widely used, and in the near future, a steer-by-wire system by advanced electronic control will be put to practical use.

Steer-by-wire system removes the steering column part from the existing electric power steering system, but detects the driver's steering intention by installing a sensor that measures torque and steering angle in the steering wheel, and accordingly, the actuator such as a motor It is operated to generate steering force.

That is, since the steering force transmission is not performed directly through the steering column, the steering parts on both sides do not need to be mechanically connected through the link.

Therefore, by developing a separate steer-by-wire system with separate steering parts, it is possible to secure a wider space in the engine room. To this end, it is necessary to provide steering power to each of the independent steering parts. There is a need for a steering actuator that satisfies conditions such as not being reversed by the transmitted force, or capable of precise control for safety.

Accordingly, an object of the present invention is to provide a steering actuator that satisfies the above conditions for implementing a standalone steer-by-wire system.

1 is a schematic configuration diagram of a standalone steer-by-wire system;

2 is a block diagram of a steering actuator according to the present invention;

3 is a side view of FIG. 2.

** Description of the symbols for the main parts of the drawings **

1: knuckle, 2: tie rod,

3: steering wheel, 4: steering control signal generator,

10: steering actuator, 11: housing,

12: ring gear, 13: ultrasonic motor,

13a: stator, 13b: rotor,

14: pin, 15: planetary gear,

16: sun gear, 16a: worm gear,

17: steering rod, 17a: rack.

The present invention for achieving the above object is an ultrasonic wave having a housing fixed to the vehicle body, a ring gear fixed to the inside of the housing, a stator fixed to the ring gear and a rotor that rotates with respect to the stator when the current is applied Motor, planetary gears installed on the rotor of the ultrasonic motor via pins and engaged with the inner circumferential surface of the ring gear, sun gears with the planetary gears engaged with the outer circumferential surface and a worm gear formed on the inner circumferential surface, the worm gear on the inner circumferential surface of the sun gear The rack formed on the upper surface is engaged and includes an steering rod which is connected to the tie rod and an end extending out of the housing.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

1 is a schematic configuration diagram of a standalone steer-by-wire system, in which the steering portion of both wheels including a knuckle 1 equipped with a wheel and a tie rod 2 for moving the knuckle 1 is independently constructed without being interconnected; It can be seen that.

Therefore, the conventional rack bar or other links that cross the engine room is not present, so that a large space can be secured in the engine room (not shown 3 includes a steering wheel, 4 a torque sensor and a steering angle sensor). Steering control signal generator.)

On the other hand, in order to apply the steering force to the steering portion independently configured to each of the two wheels as described above, as shown, a steering actuator 10 for inputting the steering force through the tie rods 2, the steering actuator according to the present invention (10) is comprised as follows.

As shown in FIG. 2 and FIG. 3, the steering actuator 10 basically has a structure in which a stator and a rotor of an ultrasonic motor are combined in a planetary gear assembly inside the housing 11.

The housing 11 is mounted at an appropriate position of the peripheral vehicle body (or frame) which is easily connected to the tie rods 2 of the independent one side steering part.

The ring gear 12 is fixed to the inner circumferential surface of the housing 11 in a non-rotating state.

The stator 13a which is one component of the ultrasonic motor 13 is integrally coupled to one side of the ring gear 12.

A rotor 13b constituting the ultrasonic motor 13 is located on the side of the stator 13a, and the planetary gears 15 are rotatably connected to the rotor 13b via a pin 14. Is mounted.

The planetary gears 15 are simultaneously engaged with gears formed on the inner circumferential surface of the ring gear 12 and gear teeth formed on the outer circumferential surface of the sun gear 16 located inside them.

A worm gear 16a is formed on an inner circumferential surface of the sun gear 16, and a rack 17a formed on an upper surface of the steering rod 17 positioned inside the sun gear 16 is engaged with the worm gear 16a.

The end of the steering rod 17 is connected in a mutually rotatable state of the tie rod 2 extending to the outside of the housing 11 to become an input end of the steering portion.

The operation of the present invention will be described below.

The sensor output from the steering control signal generator 4 is input to a separate control unit, and finally controls the current supplied to the ultrasonic motor 13 through a calculation process.

An ultrasonic motor (USM) is composed of a stator and a rotor attached in a pressed state by piezoelectric ceramic. When an electrical signal is applied to the piezoelectric ceramic, the stator vibrates in an elliptical shape (ultrasonic vibration of 20 kHz or more). Vibration has the effect of pushing the rotor pressed against the stator. By the same principle, the rotor is driven and can be used as a steering actuator because the direction of rotation can be changed as desired by the electric signal applied to the piezoelectric ceramic.

Therefore, when the control current is applied to the stator 13a, the rotor 13b rotates, and the inner circumferential surface of the ring gear 12 on which the planetary gear 15 is fixed by the rotation of the rotor 13b. By rotating while rotating along the rotation, the sun gear 16 engaged with the planetary gear 15 rotates (ie, the rotor 13b acts as a carrier in the general planetary gear assembly. The process is the same as for planetary gear assembly.)

When the sun gear 16 is rotated as described above, the worm gear 16a and the steering rod 17 formed inside the sun gear 16 and the rack 17a formed on the upper surface of the sun gear 16 depend on the rotation direction of the sun gear 16. Since the steering rod 17 moves forward and backward, the driving direction of the wheel can be adjusted because an operation of pushing or pulling the tie rod 2 connected to the end of the steering rod 17 can be performed.

On the other hand, the ultrasonic motor 13 has a low speed & low torque (the general motor has a high speed & low torque characteristics, while the ultrasonic motor has the opposite characteristics, it can be operated at a low speed of 10 ~ 100rpm by itself Therefore, it does not need a separate deceleration mechanism.), 2.Self-fixing (Ultrasonic motors maintain a strong fixed state when no electric signal is applied.) Therefore, a separate magnetic brake is required because it acts as a brake by itself. High responsiveness and high controllability (The motor's own inertia and braking force make it very responsive. It has very short time delay of less than 1/1000 sec. And speed control.), 4.Magnetic field (No magnetic field is used, so no magnetic field is generated.) 5.Small size, light weight, With the characteristics of noise (no coil is present, the structure is simple, light, small size and small driving noise), the above conditions to be provided as a steering actuator of a stand alone steer-by-wire system (1. Lightweight, 2. Reversal prevented, 3. High precision control) can be satisfied.

As described above, according to the present invention, by providing a steering actuator that satisfies the condition, the left and right steering parts are separated, thereby enabling the implementation of a stand-alone steer-by-wire system that enables additional securing of space in the engine room.

Claims (1)

A housing 11 fixed to the vehicle body, a ring gear 12 fixed inside the housing 11, a stator 13a fixed to the ring gear 12 and a rotation with respect to the stator 13a when a current is applied; Ultrasonic motor 13 having a rotor (13b), the planetary gear which is installed on the rotor (13b) of the ultrasonic motor 13 via the pin 14 through the inner peripheral surface of the ring gear 12 (15), the sun gear 16 is meshed to the outer peripheral surface and the worm gear 16a is formed on the inner peripheral surface, the rack 17a formed on the upper surface of the worm gear 16a of the inner peripheral surface of the sun gear 16 is A steering actuator of a stand alone steer-by-wire system comprising a steering rod (17) that is engaged and extends outwardly of the housing (11) to a tie rod (2).