KR20080107712A - Active front steering system - Google Patents

Abstract

An activeness front wheel steering system is provided to improve the parking assistant and steering answerability in the low speed and the steering stability in the high speed. An activeness front wheel steering system comprises an AFS ECU(2) in which he information of the sensor unit(1) is input and the actuator control value for the goal steering ratio according to the car speed is turned out, and the result according to the operation of actuator is input; an actuator assay(3) consisting of motor(4), and the worm axis(5) and worm wheel(6); a reducer(7) consisting of the carrier(11) generated the steering output; a housing(12) adapting the motor and worm axis.

Description

Active Front Steering System

1 is a block diagram of an active front wheel steering apparatus according to a first embodiment of the present invention.

2 is a perspective view of the combination of FIG.

3 is a two-input flow chart of the active front wheel steering apparatus according to FIG.

4 is a flow chart of two inputs and one output of the active front wheel steering apparatus according to FIG.

5 is a configuration diagram of an active front wheel steering apparatus using a planetary gear train for adjusting a variable gear ratio as a second embodiment according to the present invention.

6 is a flow chart of two inputs and one output of the active front wheel steering apparatus according to FIG.

7 is a configuration diagram of an active front wheel steering apparatus using a planetary gear train for adjusting a variable gear ratio as a third embodiment according to the present invention.

FIG. 8 is a flow chart of two inputs and one output of the active front wheel steering apparatus according to FIG. 7.

    <Description of the symbols for the main parts of the drawings>

1: sensor unit 2: AFS ECU

3,30,300: Actuator assembly

4,34,304: Motor 5,35,305: Worm shaft

6,36,306: Worm Wheel 7,70,700: Reducer

8,80,800: Input sun gear 9,90,900: Planetary gear set

10,100,1000: ring gear 11,110,1100: carrier

11a, 1100a: carrier plate

11b, 21,1100b: Planetary Gear Shaft

11c: output shaft

12: housing 13: upper case

20,200: Reduction ratio converter 22: Second planetary gear set

23: 2nd ring gear 24,204: output sun gear

201: carrier shaft gear 202,203: first and second slave gears

The present invention relates to an active front wheel steering apparatus, and more particularly, to an active front wheel steering apparatus that allows input and output to be made through a single planetary gear system, thereby simplifying the design and manufacturing.

In general, a power steering device that generates steering force of a vehicle is designed and operated to use hydraulic pressure in order to enable quick steering while making the steering wheel light and smooth.

Such a power steering device can perform steering operation with a small force, can be selected regardless of the operating force of the steering gear ratio, and can absorb the impact from the unevenness of the road surface and prevent it from being transmitted to the handle. There is this.

In addition, in recent years, the electronic control unit (ECU) drives the motor according to the driving conditions of the vehicle detected by the vehicle speed sensor and the steering torque sensor to provide a light and comfortable steering feeling at low speed, and a heavy steering feeling at high speed. It provides directional stability, and uses an electric steering system that provides optimum steering conditions to the driver by allowing quick steering in emergency situations, such as Electro-hydraulic Power Steering (EHPS) or Motor Driven Power Steering (MDPS). The trend is.

In addition, an active front steering control system (AFS), which is an active front wheel steering system, is applied. The AFS is a one-output steering device for two inputs (an input according to a driver's steering wheel operation and an input by a motor). In addition to steering angles by the driver, steering angles can be added or attenuated by the actuator, reducing steering ratios at low speeds to improve steering responsiveness and at higher speeds, allowing the drivers to be more stable at high speeds. Allow to operate.

In addition to the larger steering output and smaller steering output than the driver's steering, which is a feature of AFS, the integrated control is coordinated with systems such as ESC (Electronic Control Suspension system) or Motor Driven Power Steering (MDPS). It is also possible to implement the vehicle active control through.

These AFSs can be divided into actuators that generate additional steering inputs in addition to the driver's steering input due to its driving characteristics, and AFS ECUs that control and vary the steering output.The dual actuators are a key element for implementing AFS performance. It usually consists of a motor and a reducer.

However, AFS can make various changes in actuator configuration and operation method by controlling driver's steering input by using motor power, but in particular, reducer that is operated by double input of motor and driver's input is usually planetary. According to the reduction gear method, not only the structure is very complicated, but also the limitation of design and development is difficult when the input part of the motor is composed of the sun gear.

Accordingly, the present invention has been invented in view of the above, and transmits the driver input input to the sun gear to the steering output through the rotation and revolution of the sun gear and the planetary gear, and the motor input to the ring using the ring gear As the gear wheel is integrated with the worm wheel and transmitted to the steering output through the rotation and revolution of the ring gear and the planetary gear, it has a very simple structure by using a single planetary gear and the input of the motor is sequentially transferred through the ring gear. Its purpose is to simplify the design and manufacture since it is transmitted to the planetary gear and carrier.

In addition, the present invention simply changes the input ratio of 3: 1 (three steering wheels: one output shaft rotation) input to output ratio of the reducer that generates the final output through the driver input and the actuator input. The purpose is to give.

The present invention for achieving the above object, the active front-wheel steering device receives the information of the sensor unit to obtain a measurement value for obtaining the steering output, calculates the actuator control value for the target steering ratio according to the vehicle speed, the actuator operation An AFS ECU receiving the feedback according to the feedback;

With a motor mounted on the steering column via a housing mounted on the steering column, the motor generates a rotational drive force under the control of the AFS ECU, a worm shaft coupled to the motor to generate the rotational force, and a worm wheel engaged with the worm shaft. An actuator assembly;

The input sun gear receiving the steering force of the steering wheel through the steering column, the planetary gear set which is arranged around the input sun gear so as to be circumscribed and rotated together through the input sun gear, and the planetary gear set is inscribed so as to rotate. A reducer comprising a ring gear rotated to transmit a target steering input calculated from the AFS ECU through a worm wheel forming a sway, and a carrier shaft-coupled with the planetary gear set to rotate with the planetary gear set to generate a steering output value;

A housing housing an output shaft of a carrier while accommodating the reducer, and accommodating an actuator assembly at a side thereof to accommodate an worm shaft;

Characterized in that consisting of.

The planetary gear set is arranged to be circumscribed to the input sun gear with a 120 ° spacing and inscribed to the ring gear, and the carrier protrudes vertically with a 120 ° spacing of the planetary gear shaft on the carrier plate. Each planetary gear of the planetary gear set is fixed to the gear shaft and rotates together with the planetary gear set, and an output shaft that protrudes vertically from the center to the opposite side of the carrier plate and delivers the final output value to the gear box Is formed.

In addition, the reducer further comprises a reduction ratio converter for increasing the output in the reducer such that the input-to-output ratio occurs below 3: 1.

In addition, the reduction ratio converter may include a second planetary gear set axially fixed via a planetary gear shaft 21 formed as an opposite surface of the carrier on which the planetary gear set is axially fixed, and a second ring in which the second planetary gear set is inscribed. A gear and the second planetary gear set are externally configured to generate an output sun gear which generates a final steering output for the steering input of the driver and the target following steering input of the AFS ECU toward the gear box, and the second planetary gear set is 120 The second ring gear, which is arranged to be circumscribed to the output sun gear at an interval, and in which the second planetary gear set is inscribed, is simply coupled to the housing to position the second planetary gear set.

In addition, the reduction ratio converter is a carrier shaft gear protruding planetary gear set to the opposite surface of the carrier fixed to the shaft, the first and second slave gears external to the carrier shaft gear and the gearbox to deliver the final output to the gear box; The first and second subordinate gears are spur gear type and are connected to each other by shafts, and are compared to the first subordinate gears external to the carrier shaft gear. A second slave gear circumscribed to the gear is formed with a larger diameter.

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

1 is a configuration diagram of an active front wheel steering apparatus according to a first embodiment of the present invention, and FIG. 2 shows a combined perspective view of FIG. 1. The active front wheel steering apparatus according to the present invention provides a steering output. AFS ECU 2 which calculates actuator control value for target steering ratio according to vehicle speed by receiving the information of sensor unit 1 which obtains the measured value, and is driven through AFS ECU 2 to input driver's steering wheel Separately from the actuator assembly (3) that generates the steering input and the driver's steering wheel input is received to generate a driver steering output value, and receives the motor steering input of the actuator assembly (3) to generate an actuator steering output value The reducer 7 is comprised.

The sensor unit 1 includes an input angle sensor for detecting a steering input angle of a steering input shaft, an output angle sensor for detecting a steering output angle of a steering output shaft, a motor position sensor for detecting a position of a motor, and a vehicle speed while driving. The vehicle speed sensor is configured to detect information about a change in the vehicle being driven.

In addition, the AFS ECU 2 calculates an actuator control value by setting a target steering gear ratio according to the vehicle speed, that is, receiving a vehicle speed of the driving vehicle and receiving a target steering gear ratio (decelerator) for each vehicle speed through a setting map of the target steering gear ratio. The steering gear ratio is set, the output angle is calculated from the set steering gear ratio and the output angle, and the position control of the actuator is performed to follow the calculated output angle.

The actuator assembly 3 is coupled to the motor 4 to generate a rotational drive force under the control of the AFS ECU 2 while being mounted to the steering column via the housing, and coupled to the motor 4 to generate the rotational force. It consists of a worm shaft (5) and a worm wheel (6) is engaged with the worm shaft (5) to rotate, to provide a steering input calculated through the AFS ECU (2) toward the reducer (7).

In addition, the actuator assembly 3 detects a rotation angle of the motor 4 which is rotated through the AFS ECU 2 and feeds it back to the AFS ECU 2. The detection rotation angle of (4) is reflected in the correction of the control value via the AFS ECU 2.

In addition, the speed reducer 7 is arranged around the input sun gear 8 and the input sun gear 8, which receives the operating force of the steering wheel through the steering column, and is externally circumferentially arranged together through the input sun gear 8. The planetary gear set 9 that is rotated, the ring gear 10 that is inscribed to rotate the planetary gear set 9 and the planetary gear set 9 are axially coupled to rotate together with the planetary gear set 9 to steer output. It consists of a carrier 11 which generates a value.

In addition, the reducer 7 receives the ring gear 10 and the entire reducer 7 is mounted into the inner space through the housing 12 which surrounds the output shaft portion of the carrier 11. The input sun gear 8 side forming the upper part is covered by the upper case 13 which is coupled to the housing 12 and wraps the steering column.

At this time, the housing 12 and the upper case 13 are fastened using a bolt or the like.

In addition, the housing 12 accommodates the motor 4 constituting the actuator assembly 3 as a side portion in which the reducer 7 is accommodated, and is coupled to the motor 4 and positioned at the side portion of the reducer 7. An accommodation portion is formed to accommodate the worm shaft 5 to be formed.

The planetary gear 9 is arranged to be circumscribed to the input sun gear 8 with a spacing of about 120 ° and inscribed in the ring gear 10, and the ring gear 10 is actuator actuator 3. It is pressed into the worm wheel (6) forming a, and receives the rotational force from the worm wheel (6) rotated with the motor (4) to rotate the ring gear (10).

In addition, the carrier 11 has a planetary gear shaft 11b projecting vertically on the carrier plate 11a with a spacing of about 120 ° so that each planet of the planetary gear set 9 is formed on the planetary gear shaft 11b. The gear is fixed to the shaft to rotate with the planetary gear set 9, the output shaft for transmitting the output value to the steering column connected to the gear box protruding perpendicularly from the center of the carrier plate (11a) to the opposite side ( 11c) is formed.

The active front-wheel steering device configured as described above has an actuator assembly 3 driven through the AFS ECU 2 and the reducer 7 mounted on the steering column to interact with the reducer 7. The driver's steering wheel operation force and the motor operation force through the actuator are input together as separate processes.

That is, when the driver steering manipulation force enters the input sun gear 8 through the steering column as shown in FIG. 3 (a), the carrier is set through the planetary gear set 9 circumscribed to the input sun gear 8. It is outputted to (11).

In contrast, the motor rotational force of the actuator assembly 3 driven through the AFS ECU 2 is transferred to the worm wheel 6 through the worm shaft 5 coupled to the motor 4, as shown in FIG. ), And the worm wheel 6 is output to the carrier 11 through the planetary gear set 9 inscribed by rotating the ring gear 10.

The operation implementation of the active front wheel steering apparatus of the present invention having such a configuration is shown in FIG. 4, in which the driver's steering wheel operation is transmitted to the input sun gear 8 through the steering column and passes through the speed reducer 7 and then the carrier. The vehicle information, which is output to 11 and at the same time, measured by the sensor unit 1 made of various sensors mounted on the vehicle, is input to the AFS ECU 2, and an actuator for correcting the steering output through steering wheel operation. The motor output of the assembly 3 is input to the reducer 7 side.

That is, as the steering wheel input of the driver rotates the input sun gear 8, when the planetary gear set 9 which is external to the input sun gear 8 and inscribed in the ring gear 10 is rotated, the planetary gear is rotated. The carriers 11 which fix each planetary gear constituting the gear set 9 to the planetary gear shaft 11b are rotated together.

At the same time, the AFS ECU 2 having received the respective information according to the turning measured by the sensor unit 1 calculates the actuator control value for the target steering ratio, and then the reducer 7 driven by the driver's steering input. The motor rotational force of the actuator assembly 3 is inputted to the side.

That is, when the motor 4 constituting the actuator assembly 3 is driven through the AFS ECU 2, the worm wheel 6 engaged with the worm shaft 5 coupled to the motor 4 is rotated. As the rotational force of the worm wheel 6 rotates the ring gear 10 fixed to the worm wheel 6, the planetary gear set 9 inscribed in the ring gear 10 is rotated. The carrier 11 in which the planetary gear is fixed to the planetary gear shaft 11b is rotated.

In this way, the carrier 11 constituting the reducer 7 receives and outputs an input through two different paths, which is a planetary gear set 9 external to the input sun gear 8 according to a steering wheel operation. In addition to being rotated through the actual steering input value, which is directly input, the planetary gear set 9 is rotated through the worm wheel 6 of the actuator assembly 3 for the target following of the AFS ECU 2. As inscribed in (10), it is rotated through the target following steering input value through the actuator assay (3).

Accordingly, the planetary gear set 9 receives the rotational force of the input sun gear 8 through the steering column and the rotational force of the ring gear 10 through the actuator assembly 3 at the same time. The shaft 11 is fixed to the carrier 11, the rotation of the carrier 11 is provided to the gear box as the output value of the reducer 7 through the output shaft (11c) formed integrally with the carrier (11) Lose.

The output value of the speed reducer 7 acts to increase or decrease the steering force applied by the driver through the control of the AFS ECU 2, which indicates the current vehicle speed and steering angle information when the AFS ECU 2 controls the driver. When calculating the steering angle that is optimal for the current driving condition, if the currently required steering angle output needs to be larger than the steering input entered by the driver (slow speed, parking mode), the AFS ECU 2 determines the actuator assembly 3. The direction of rotation of the motor 4 constituting the motor is in the same direction as the direction of the driver steering input, that is, the direction of increasing the rotational force of the planetary gear set 9 circumscribed to the input sun gear 8 through the steering column. By rotating 4), the output value through the reducer 7 is controlled to have a steering angle output larger than the driver's steering input.

However, when the current condition is to reduce the steering output than the steering angle input of the driver, the AFS ECU 2 rotates the motor 4 constituting the actuator assembly 3 in the reverse direction with respect to the direction of the driver steering input. This reduces the torque of the planetary gear set 9 external to the input sun gear 8 through the steering column so that the output value through the reducer 7 has a smaller steering angle output than the driver's steering input. Control.

When the decelerator 7 is driven, the AFS ECU 2 performs continuous feedback control by using the detection information on the rotation angle according to the rotation of the motor 4 of the actuator assembly 3.

However, in the structure of the speed reducer 7, there is a limit to reducing the input-to-output ratio to about 3: 1 (three steering wheel rotations: one output shaft rotation) or less, even if the gear ratio of the gearbox is changed. Since there is a structural aspect that there is a limit to the change of the present invention, to solve this, the present invention adjusts the input-to-output ratio through a reducer that receives an input and generates an output.

As an example, as shown in FIG. 5 showing a second embodiment of an active front wheel steering apparatus using planetary gear trains for variable gear ratio adjustment, an input value for the target steering output is controlled by the AFS ECU 2. It is composed of an actuator assembly 30 for generating a, and a reducer 70 mounted on the steering column to receive a driver steering input directly and generate a steering output through a steering input of the driver steering input and the actuator assembly 30. .

Here, the actuator assembly 30 has the same configuration as the first embodiment of the present invention, that is, a worm coupled to the motor 34 accommodated in the housing 12 mounted to the steering column to generate a rotational driving force. In addition to the shaft 35, it is composed of a worm wheel 36 which is engaged with the worm shaft 35 and provides a steering input calculated through the AFS ECU 2 toward the reducer 70.

At this time, the reducer 70 forms the same configuration as the first embodiment of the present invention, and configures the reducer 70 to reduce the input-to-output ratio to about 3: 1 or less. A planetary gear set 90 which is external to the input sun gear 80 receiving the driver's steering input and inscribed in the ring gear 100 is provided, and the planetary gear set 90 is rotated by fixing each planet gear axially. In addition to the carrier 110 to generate a steering output value, the carrier 110 is rotated together with the carrier 110, the reduction ratio converter for supplying the speed of the rotation of the planetary gear set 90 to the gear box ( 20) is further provided.

In addition, the reduction gear ratio converter 20 includes a second planetary gear set 22 fixed to the shaft via a planetary gear shaft 21 formed as an opposite surface of the carrier 110 on which the planetary gear set 90 is fixed to the shaft, The second ring gear 23 and the second planetary gear set 22 in which the second planetary gear set 22 is inscribed are circumscribed so that a steering input of the driver and a target following steering input of the AFS ECU 2 are directed to the gear box. Consists of an output sun gear 24 which generates a final steering output for

Here, in order to reduce the input-to-output ratio of the reduction gear 70 through the reduction ratio converter 20 to 3: 1 or less, the second planetary gear set 22, the second ring gear 23, and the output line engaged with each other are engaged. The number of gear teeth of the gear 24 is determined, which is determined at design time according to the exact requirements of the input to output ratio value.

The second planetary gear set 22 is also arranged to be external to the output sun gear 24 with a spacing of about 120 ° in the same manner as the planetary gear set 90, and the second planetary gear set 22 is inscribed. The second ring gear 23 is coupled to the housing 12 to simply position the second planetary gear set 22.

The operation of the active front wheel steering apparatus according to the second embodiment of the present invention is implemented in the same manner as the first embodiment of the present invention, except that only the final output through the speed reducer 70 is different from the first embodiment. Will have

That is, as shown in FIG. 6, the steering wheel input of the driver is input through the input sun gear 80 and the target steering of the AFS ECU 2 as shown in FIG. 6. When the input is input to the ring gear 100 through the motor 34, the worm shaft 35, and the worm wheel 36 of the actuator assembly 30, the planetary gear set external to the input sun gear 80 ( 90 rotates the carrier 110 while the rotation of the planetary gear set 90 increases (same direction) or decreases (reverse direction) through the rotation direction of the inscribed ring gear 100.

As the carrier 110 is rotated together with the planetary gear set 90 as described above, the reduction gear ratio 20 of the carrier 110 is also rotated, that is, the carrier 110 forming the reduction gear ratio 20. The second planetary gear set 22, which is fixed to the shaft via the planetary gear shaft 21 formed on the opposite side of the carrier, rotates together as the carrier 110 rotates.

Accordingly, the output sun gear 24 having the second planetary gear set 22 circumscribed generates an output for the input, and the final steering output of the output sun gear 24 is the second planetary gear set 22. The ratio of the gears to the power output ratio of the output power is lower than that of the first embodiment (the input to output ratio of 3: 1), that is, the input-to-output ratio is reduced to 3: 1 or less.

On the other hand, the configuration of the speed reducer having an input-to-output ratio of 3: 1 or less can implement the same performance while configuring the second embodiment, that is, as shown in FIG. The deceleration ratio converter to be determined is configured by using a spur gear having a different gear ratio than the planetary gear.

This third embodiment of the present invention is the same configuration as the second embodiment except for the gear ratio converter, that is, the actuator assembly 30 is accommodated in the housing 12 mounted to the steering column to generate a rotational driving force In addition to a worm shaft 305 coupled to 304, it is composed of a worm wheel 306 meshed with the worm shaft 305 and providing a steering input calculated through the AFS ECU 2 toward the reducer 700. Lose.

In addition, the speed reducer 700 is provided with a planetary gear set 900 which is external to the input sun gear 800 that receives the driver's steering input and is inscribed in the ring gear 1000, and the planetary gear set 900 includes each planetary planetary gear. It consists of a carrier 1100 that is axially fixed and rotates together to produce a steering output value.

In addition, the speed reducer 700 is configured to further include a reduction ratio converter 200 which is rotated together with the carrier 1100 to supply an output of increasing the rotation of the planetary gear set 900 to the gear box.

That is, the reduction ratio converter 200 has a carrier shaft gear 201 protruding to the opposite surface of the carrier 1100 is fixed to the planetary gear set 900, the speed of rotation of the planetary gear set 900 The first and second slave gears 202 and 203 are circumscribed to the carrier shaft gear 201, and the output sun gear 204 which transmits the final output toward the gearbox is circumscribed to the first and second slave gears 202 and 203 to rotate. do.

At this time, the first and second slave gears 202 and 203 are spur gear types connected to each other by shafts, and are external to the output sun gear 204 as compared with the first slave gear 202 external to the carrier shaft gear 201. The second slave gear 203 has a larger diameter.

The reduction ratio converter 200 having such a structure includes a carrier shaft gear 201 and first and second slave gears 202 and 203 engaged with each other to reduce the input-to-output ratio of the reduction gear 700 to 3: 1 or less. The number of gear teeth of the output sun gear 204 is determined, which is determined at design time according to the exact requirements of the input to output ratio value.

In addition, the first and second slave gears 202 and 203 and the output sun gear 204 are coupled to each other so as to be positioned in the housing 12.

The operation of the active front wheel steering apparatus according to the third embodiment of the present invention is implemented in the same manner as the second embodiment of the present invention, except that only the final output through the reducer 700 is different from the first embodiment, and the second As in the embodiment, the output value has an input-to-output ratio of 3: 1 or less.

That is, in the third embodiment of the present invention, as shown in FIG. 8, the steering wheel input of the driver is input through the input sun gear 800, and the target steering input of the AFS ECU 2 is applied to the actuator assembly. When input to the ring gear 1008 through the motor 384 and the worm shaft 385 and the worm wheel 386 of the 300, the planetary gear set 900 external to the input sun gear 800 is inscribed ring The rotation of the planetary gear set 900 is rotated through the rotation direction of the gear 1000 to rotate the carrier 1100 while increasing (same direction) or decreasing (reverse direction).

The rotation of the carrier 1100 rotates the output sun gear 204 through the first and second slave gears 202 and 203 circumscribed to the shaft gear 201, and the rotation of the output sun gear 204 is a reduction gear ( A final output of 700 is transmitted to the gearbox, where the final steering output of the output sun gear 204 is via the first and second slave gears 202 and 203 as a first input (3: 1 input to output). It has a smaller input-to-output ratio than 3: 1.

As described above, according to the present invention, the steering input of the driver is input to the reducer through the input sun gear when the operation is implemented, and the target following steering input through the AFS ECU is transmitted through a ring gear that is rotated through the motor forming the actuator. As the final output is transmitted to the gearbox from the reducer, which is simultaneously input to the reducer and two different inputs are input separately, the reducer can be configured in a single planetary gear type, so that the structure is simple and active front wheel steering system. There is an effect that can be configured.

In addition, the present invention uses a single planetary gear reducer that generates two different inputs separately to generate an output, so that the design is simple, the manufacturing process is simple, and the weight is reduced as the number of parts is reduced. This improves steering stability at high speeds while increasing parking assistance and steering response at low speeds.

In addition, the present invention is to vary the final output of the reducer to a single planetary gear type reducer in which two different inputs are input separately to generate an output, that is to add a separate planetary gear train or spur gear train to the reducer Therefore, the input-to-output ratio of the reducer can be reduced to 3: 1 (three steering wheel rotations: one output shaft rotation) or less, and it is not possible to change the rack shape of the gear box, which is structurally limited in changing the gear ratio. It is possible to easily adjust the input-to-output ratio of the reducer without having to.

Claims (9)

AFS ECU 2 which receives the information of the sensor unit 1 which obtains the measurement value to obtain the steering output, calculates the actuator control value for the target steering ratio according to the vehicle speed, and feeds back the result according to the actuator operation. ; A motor 4 for generating a rotational drive force under the control of the AFS ECU 2 and a worm shaft 5 coupled to the motor 4 to generate a rotational force while being mounted to the steering column via a housing mounted on the steering column. And an actuator assembly (3) composed of a worm wheel (6) which is engaged with the worm shaft (5) and rotates; An input sun gear 8 that receives the steering force of the steering wheel through the steering column and a planetary gear set 9 which is arranged around the input sun gear 8 so as to be circumscribed and rotated together through the input sun gear 8. The ring gear 10 rotates to transmit the target steering input calculated by the AFS ECU 2 through the worm wheel 6 constituting the actuator assembly 3 while the planetary gear set 9 is rotated. A reduction gear (7) comprising a carrier (11) in which the planetary gear set (9) is axially coupled and rotated together with the planetary gear set (9) to generate a steering output value; While the upper case 13 surrounding the input sun gear 8 is fastened, the motor is configured to surround the output shaft of the carrier 11 while accommodating the reducer 7 and form an actuator assembly 3 at the side. 4) and a housing (12) for receiving the worm shaft (5). 2. The active front wheel steering apparatus according to claim 1, wherein the planetary gear set is arranged to be circumscribed to the input sun gear at intervals of 120 ° and inscribed to the ring gear. 10. 2. The carrier 11 according to claim 1, wherein the planetary gear shaft 11b protrudes vertically on the carrier plate 11a with a 120 [deg.] Interval so that the planetary gear set 9 can be moved to the planetary gear shaft 11b. Each planetary gear is axially fixed to rotate together with the planetary gear set 9, and the output shaft 11c protrudes perpendicularly from the center to the opposite side of the carrier plate 11a to transmit the final output value to the gear box. Active front wheel steering device, characterized in that formed. The active front wheel steering apparatus according to claim 1, wherein the reducer further comprises a reduction ratio converter for increasing the output in the reducer such that an input-to-output ratio occurs below 3: 1. 5. The gear set according to claim 4, wherein the reduction ratio converter (20) comprises a second planetary gear set (22) axially fixed via a planetary gear shaft (21) formed on the opposite side of the carrier on which the planetary gear set is axially fixed; A second ring gear 23 into which the second planetary gear set 22 is inscribed; An output sun gear 24 having the second planetary gear set 22 circumscribed to generate a final steering output for the steering input of the driver and the target following steering input of the AFS ECU 2 towards the gearbox; Active front wheel steering device, characterized in that consisting of. The second ring gear (23) according to claim 5, wherein the second planetary gear set (22) is arranged to be circumscribed to the output sun gear (24) with a spacing of 120 °, and the second ring gear (23) to which the second planetary gear set (22) is inscribed. ) Is simply coupled to the housing (12) to position the second planetary gear set (22). 5. The gear ratio converter according to claim 4, wherein the reduction ratio converter includes a carrier shaft gear 201 protruding to the opposite surface of the carrier on which the planetary gear set is fixed to the shaft, and first and second slave gears 202 and 203 which are external to the carrier shaft gear 201. And an output sun gear 204 circumscribed to the first and second slave gears 202 and 203 so as to deliver a final output toward the gear box. The method according to claim 7, wherein the first and second slave gears 202 and 203 are connected to each other by a shaft, and are external to the output sun gear 204 compared to the first slave gear 202 external to the carrier shaft gear 201. Active front wheel steering device, characterized in that the second slave gear (203) is formed in a larger diameter. 9. The active front wheel steering apparatus according to claim 8, wherein the first and second slave gears (202, 203) are spur gear type.

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