KR20220005145A - Electric Power Steering Apparatus for Vehicle - Google Patents

Abstract

The present invention relates to an electric power assisted steering apparatus. The present embodiments relate to the electric power assisted steering apparatus. The electric power assisted steering apparatus may be provided, and comprises: an input shaft wherein one side end is connected to a steering shaft and the other side end has a first gear; an output shaft wherein one side end has a second gear coupled to the first gear and a ball nut is coupled to an outer peripheral side through a ball; and a sector shaft coupled to an outer gear formed on the outer periphery of the ball nut to operate a fitman arm.

Description

Electric Power Steering Apparatus for Vehicle

The present embodiments relate to an electric power-assisted steering system, and more particularly, in the case of a truck or bus requiring a relatively large steering force compared to a passenger car, automatic parking, lane keeping, and road surface control while assisting the driver's steering force It relates to an electric power assist steering system that can increase the convenience of a driver by enabling additional functions such as driving assistance and autonomous driving control according to the state to be used.

In general, a steering system of a car is a device for changing the driving direction of the car at the will of the driver. It is a device that assists the driver to move the car in the desired direction by arbitrarily changing the center of rotation of the front wheel of the car. .

On the other hand, the power-assisted steering system assists the driver in operating the steering wheel by using a booster when the driver operates the steering wheel of the vehicle, so that the driving direction of the vehicle can be easily changed with less force. is a device that

Such a power-assisted steering system is largely divided into an electric power-assisted steering system (EPS) and a hydraulic power-assisted steering system (HPS: Hydraulic Power Steering Apparatus).

In the hydraulic power assist steering system, when the hydraulic pump connected to the engine's rotating shaft supplies hydraulic oil to the operating cylinder connected to the rack bar, the piston of the operating cylinder supplied with the hydraulic oil moves to assist the steering operation force, thereby helping the driver. It is a steering device that allows the steering operation to be performed with a small force.

On the other hand, the electric power assist steering device is a steering device that includes a motor instead of a hydraulic pump and an operating cylinder, and thus assists the operating force of the steering wheel with the power of the motor.

However, in the case of a truck or bus that requires a relatively large steering force compared to a passenger car, a hydraulic power-assisted steering system was used for the reason that high power was required. There was a problem in that functions such as parking, lane keeping, and autonomous driving could not be used.

Accordingly, in the case of a truck or a bus requiring a relatively large steering force compared to a passenger car, there is a need to assist the steering force and enable automatic parking, lane keeping, autonomous driving, etc. using an electronic control device.

Accordingly, the present embodiments have been devised in the background described above, and even in the case of a truck or bus requiring a relatively large steering force compared to a passenger car, automatic parking, lane maintenance, and driving according to the road surface condition to control the vehicle while assisting the driver's steering force An object of the present invention is to provide an electric power assist steering system that can increase driver convenience by enabling additional functions such as assistance and autonomous driving control.

In addition, the purpose of the present embodiments is not limited thereto, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

According to the present embodiments, one end of the input shaft is connected to the steering shaft and the other end is provided with a first gear, one end is provided with a second gear coupled to the first gear, and the outer peripheral side is provided with a ball through a ball. An electric power assist steering device including an output shaft to which a nut is coupled, and a sector shaft coupled to an outer gear formed on an outer peripheral side of the ball nut to operate a fitman arm may be provided.

According to the present exemplary embodiments, additional functions such as automatic parking, lane keeping, and autonomous driving control that assist the driver's steering force and control the vehicle are used even in the case of a truck or bus requiring a relatively large steering force compared to a passenger car. This has the effect of increasing the driver's convenience.

1 is a configuration diagram schematically showing an electric power assist steering device according to the present embodiments;
2 is a perspective view showing a part of the electric power assist steering apparatus according to the present embodiments;
3 is an exploded perspective view showing a part of the electric power assist steering system according to the present embodiments;
4 and 5 are cross-sectional views showing some of the electric power assist steering apparatus according to the present embodiments;
6 is a perspective view showing a part of the electric power assist steering device according to the present embodiments;
7 and 8 are cross-sectional views showing some of the electric power assist steering apparatus according to the present embodiments;
9 is a reference view illustrating a part of the electric power assist steering system according to the present embodiments.

Hereinafter, some embodiments of the present embodiments will be described in detail with reference to exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in the description of the present embodiments, if it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present embodiments, the detailed description thereof will be omitted.

Also, in describing the components of the present embodiments, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the terms. When a component is described as being “connected”, “coupled” or “connected” to another component, the component may be directly connected to or connected to the other component, but another component is between each component. It should be understood that elements may also be “connected,” “coupled,” or “connected.”

1 is a configuration diagram schematically showing an electric power assisted steering system according to the present embodiments, FIG. 2 is a perspective view showing a part of the electric power assisted steering system according to the present embodiments, and FIG. 3 is a configuration diagram according to the present embodiments An exploded perspective view showing a part of the electric power assist steering system, FIGS. 4 and 5 are cross-sectional views showing some of the electric power assist steering system according to the present embodiments, and FIG. 6 is an electric power assist steering system according to the present embodiments A perspective view showing a part, FIGS. 7 and 8 are cross-sectional views showing a part of the electric power-assisted steering system according to the present embodiments, and FIG. 9 is a reference view showing a part of the electric power-assisted steering system according to the present embodiments.

In the electric power assist steering apparatus according to the present embodiments, one end is connected to the steering shaft 103 and the other end is provided with a first gear 203, the input shaft 201, and the first gear ( 203) is provided with a second gear 213 coupled with an output shaft 210 to which a ball nut 260 is coupled via a ball on the outer periphery side, and is coupled with an outer gear formed on the outer periphery of the ball nut 260 It includes a sector shaft 270 that operates a fitman arm 135 .

The electric power assist steering apparatus according to the present embodiments includes an angle sensor 105 and a torque sensor 107 connected to a steering shaft 103 connected to a steering wheel 101, and a driver's steering wheel 101 ) The angle sensor 105 and the torque sensor 107 that detect this during operation transmit an electric signal to the electronic control device 110 , and the electronic control device 110 transmits an operation signal to the drive motor 120 . .

In addition, the electronic control device 110 controls the drive motor 120 based on the electrical signals transmitted from various sensors mounted on the vehicle together with the electrical signals transmitted from the angle sensor 105 and the torque sensor 107. do.

However, in the drawings in the present embodiments, for convenience of explanation, the angle sensor 105, the torque sensor 107, the vehicle speed sensor 104, and the motor rotation angle sensor 106 are illustrated as being provided, but the steering information A motor position sensor for transmitting to the electronic control device 110 and various radar, lidar, camera image sensors, etc. may be provided, and detailed descriptions of these various sensors will be omitted.

The drive motor 120 operates the pitman arm 135 connected to the sector shaft 270 through the power transmission member 130 so that the link 111 connected to the pitman arm 135 is connected to both wheels 119L and 119R. Steering of both wheels 119L and 119R is performed through the links 115 and 117 .

The upper end of the input shaft 201 is connected to the steering shaft 103 to rotate. Here, the input shaft 201 is illustrated as being connected to the steering shaft 103 , but may be replaced with the steering shaft 103 .

That is, when the steering shaft 103 is integrally provided according to the layout of the engine room of the vehicle, the steering shaft 103 itself becomes the input shaft 201, and the steering shaft 103 is bent by a universal joint, etc., and two or more In this case, the steering shaft 103 may be connected to the input shaft 201 .

And, the output shaft 210 is coupled to the driving motor 120 via the power transmission member 130, so that when the driving motor 120 is operated according to a signal input from the electronic control device 110, the driving force of the motor It is transmitted to the output shaft 210 through the power transmission member 130 to reduce or increase the steering force.

The power transmission member 130 for rotating the input shaft 201 with the driving force of the driving motor 120 is provided on the input pulley 121 and the output shaft 210 provided on the shaft 120a of the driving motor 120 . It includes an output pulley 211, an input pulley 121, and a belt member 230 coupled to the output pulley 211.

The input pulley 121 is connected to the shaft 120a of the driving motor 120 and rotates in interlocking motion to rotate the output pulley 211 through the belt member 230, where the input pulley 121 and the output pulley ( 211 may be integrally formed with the shaft 120a and the output shaft 210 of the drive motor 120, respectively, and in the present embodiments, the input pulley 121 and the output pulley 211 are separately manufactured to drive the motor The shaft 120a of the 120 is shown as an example coupled to the output shaft 210 .

In the input shaft 201, the first shaft 201a and the second shaft 201b are hollow, and the torsion bar 201c is coupled to the inner space of the first shaft 201a and the second shaft 201b, A torque sensor 107 for detecting a steering torque generated when the driver manipulates the steering wheel is coupled to the outer peripheral side of the first shaft 201a.

Then, the electronic control device 110 compares the signal value input from the torque sensor 107 with preset data, transmits a signal value to the driving motor 120, and adjusts the steering angle when the driver operates the steering wheel 101. The signal value received from the sensing angle sensor 105 is compared with preset data and the signal value is transmitted to the driving motor 120 .

Accordingly, the electronic control device 110 includes electrical signals transmitted from the vehicle speed sensor 104, the motor rotation angle sensor 106, etc. mounted on the vehicle together with the electrical signals transmitted from the angle sensor 105 and the torque sensor 107. The driving motor 120 is controlled based on these.

A first gear 203 is provided at the end of the second shaft 201b and is coupled to the second gear 213 provided on the output shaft 210 to transmit the rotational force of the input shaft 201 to the output shaft 210 . it is made to be

The input shaft 201 and the output shaft 210 are not coaxially coupled but are disposed to form a predetermined angle so that the first gear 203 and the second gear 213 are coupled, and in this embodiment, the first gear ( 203) and the second gear 213 are formed as bevel gears and are coupled at right angles to reduce the volume from the input shaft 201 to the output shaft 210 while accurately transmitting power.

One end of the output shaft 210 protrudes to the outside of the nut housing 130h in which the ball nut 260 is incorporated, and the output pulley 211 and the second gear 213 are at the protruding end of the output shaft 210 . is disposed and provided inside the belt housing in which the belt member 230 is embedded.

The output shaft 210 that is coupled with the first gear 203 of the input shaft 201 and rotates in conjunction with the input shaft 201 has an outer circumferential screw groove formed on its outer circumferential surface, and the output shaft 210 through a ball. The ball nut 260 coupled to the inner circumferential surface has an inner screw groove corresponding to the outer screw groove of the output shaft 210, so that the ball nut 260 slides in the axial direction when the output shaft 210 rotates. is done

In addition, an outer gear is formed on the outer circumferential surface of the ball nut 260 to rotate the sector shaft 270 having gear teeth meshed therewith.

Accordingly, the sector shaft 270 operates the fitman arm 135 while rotating when the ball nut 260 slides in the axial direction.

And, between the upper end outer peripheral surface of the output shaft 210 and the upper inner peripheral surface of the nut housing 130h, the first rotation support member 300 for supporting the rotation of the output shaft 210 and the axial load may be provided.

Here, the first rotation support member 300 is to support the load in the axial direction and the radial direction together with the rotation of the output shaft 210, the inner member 303 to which the outer peripheral surface of the upper end of the output shaft 210 is coupled. , an outer member 301 coupled to the inner circumferential surface of the nut housing 130h, and a cylindrical rolling member 305 provided between the inner member 303 and the outer member 301 .

The upper side of the nut housing 130h in which the output shaft 210 and the ball nut 260 are built in is coupled to the belt housing 220 in which the input pulley 121 and the output pulley 211 are built, and the belt housing 220 ), the cover housing 240 is coupled to the upper side and is coupled to the shaft housing 250 .

An upper stepped portion is formed on the outer peripheral surface of the upper end of the output shaft 210 , and the lower end of the inner member 303 is supported and coupled to the upper stepped portion.

In addition, an output pulley 211 is provided at the upper end of the output shaft 210 on which the inner circumferential surface of the inner member 303 is supported in the radial direction.

Between the inner member 303 and the outer member 301 , an intermediate support member 307 having a seating groove 308 that rotates while the rolling member 305 is supported on the inner circumferential surface may be provided.

A support groove 304 in which the rolling member 305 is supported and rotated is provided on the inner circumferential surface of the inner member 303 , and the support groove 304 and the seating groove 308 are formed as inclined surfaces inclined in the axial direction to form a cylindrical shape. The outer peripheral surface of the upper rolling member 305 is supported by the support groove 304 and the seating groove 308 and rotates.

Here, the locking jaw formed on the upper side of the support groove 304 and the locking jaw formed on the lower side are formed such that a predetermined clearance space is formed with the upper and lower ends of the rolling member 305, so that the intermediate support member 307 and the rolling member ( 305) can be made to flow in the axial direction.

In addition, the inner peripheral surface of the outer member 301 and the outer peripheral surface of the intermediate support member 307 are formed with inclined surfaces corresponding to the support groove 304 and the seating groove 308 .

In addition, the elastic protrusions 309 are spaced apart from each other in the circumferential direction on the outer circumferential surface of the intermediate support member 307 and are formed to protrude, so that they are elastically supported on the inner circumferential surface of the outer member 301 .

Therefore, when the flow in the axial direction is generated by the impact load reversely input to the output shaft 210 through the sector shaft 270, the elastic protrusion 309 is elastically deformed and the flow in the axial direction is made to absorb the impact load. be able to

In addition, a second rotation support member 310 for supporting the rotation of the output shaft 210 may be provided between the outer peripheral surface of the lower end of the output shaft 210 and the nut housing 130h.

And, an inner bush 322 is coupled between the outer peripheral surface of the lower end of the output shaft 210 and the second rotation support member 310, and between the inner peripheral surface of the nut housing 130h and the second rotation support member 310 An outer bush 316 may be coupled thereto.

Here, the second rotation support member 310 is to support the load in the axial direction and the radial direction together with the rotation of the output shaft 210 , is formed in the same shape as the first rotation support member 300 , and is formed in the first rotation It is coupled to the support member 300 in a vertical symmetrical direction.

That is, the second rotation support member 310 includes an inner member 313 coupled to the outer periphery of the inner bush 322 , an outer member 311 coupled to the inner periphery of the outer bush, the inner member 313 and the outer A rolling member 317 provided between the members 311 is included.

A lower stepped portion is formed on the outer peripheral surface of the lower end of the output shaft 210 , and the upper end of the inner bush 322 is supported and coupled to the lower stepped portion of the output shaft 210 .

And, between the inner member 313 and the outer member 311, the rolling member 317 is supported on the inner circumferential surface, the intermediate support member 315 in which the rotating seating groove 318 is formed may be provided.

A support groove 314 in which the rolling member 317 is supported and rotated is provided on the inner circumferential surface of the inner member 313, and the support groove 314 and the seating groove 318 are formed as inclined surfaces inclined to the axial direction, and are formed in a cylindrical shape. The outer peripheral surface of the upper rolling member 317 is supported by the support groove 314 and the seating groove 318 and rotates.

Here, the locking jaw formed on the upper side and the lower side of the support groove 314 is formed so that a predetermined clearance space is formed with the upper and lower ends of the rolling member 317, so that the intermediate support member 315 and the rolling member ( 317) can be made to flow in the axial direction.

And, the inner circumferential surface of the outer member 311 and the outer circumferential surface of the intermediate support member 315 are formed with inclined surfaces corresponding to the support grooves 314 and the seating grooves 318 , and these inclined surfaces are directed upward of the output shaft 210 . It is formed in a direction in which the diameter increases as it goes on.

In addition, the elastic protrusions 319 are spaced apart from each other in the circumferential direction on the outer circumferential surface of the intermediate support member 315 and are formed to protrude, so that they are elastically supported on the inner circumferential surface of the outer member 301 .

Therefore, when a load in the axial direction is generated by an impact load reversely input to the output shaft 210 through the sector shaft 270, the elastic protrusion 319 is elastically deformed and flows in the axial direction to absorb the impact load. do.

In addition, an axial support member 320 for supporting the second rotation support member 310 in the axial direction is coupled to the inner circumferential surface of the lower end of the nut housing 130h to support the second rotation support member 310 in the axial direction. The support force in the axial direction is also applied to the first rotation support member 300 coupled to the upper end of the output shaft 210 .

Accordingly, the first rotation support member 300 and the second rotation support member 310 are prevented from being wasted or noise caused by the clearance between the output shaft 210 or the nut housing 130h.

In addition, the inclined directions of the support grooves and the seating grooves of the first rotation support member 300 and the second rotation support member 310 are vertically symmetrical, that is, the inclined direction of the first rotation support member 300 is In a direction in which the diameter increases in the lower direction of the output shaft 210 , and the inclined direction of the second rotation support member 310 is formed in a direction in which the diameter increases in the upper direction of the output shaft 210 , the output shaft 210 is a vertical direction between the nut housing 130h in which the outer member 301 of the first rotation support member 300 is supported and the axial support member 320 in which the second rotation support member 310 is supported. An axial flow can be achieved.

Here, the axial support member 320 is provided with a first support end 323b that protrudes in the axial direction from the outer circumferential surface and is formed to increase in the circumferential direction, and is inserted into the inner circumferential surface of the lower end of the nut housing 130h. The first support member 323 for supporting the second rotation support member 310 in the axial direction, the second support protrudes in a shape corresponding to the first support end 323b and engages the first support end 323b. An end portion 321a is provided, and between the second support member 321 and the first support member 323 and the second support member 321 coupled to the inner circumferential surface of the lower end of the nut housing 130h, one end is the second support member 321 . It includes an elastic member 325 coupled to the first support member 323 and the other end coupled to the second support member 321 to generate an elastic force in the circumferential direction.

Accordingly, the first supporting end 323b rotates along the second supporting end 321a by the circumferential elastic force of the elastic member 325 and the first supporting member 323 is allowed to flow in the axial direction.

That is, the second support member 321 is press-fitted or screwed to the nut housing 130h to be fixed, and the first support member 323 is elastically compressed to the second support member 321 via the elastic member 325 as a medium. It is movably inserted into the inner peripheral surface of the lower end of the nut housing (130h) in the coupled state.

And, when the second support member 321 is fixed to the position of the nut housing 130h, the rotational force is transferred to the first support member 323 by the elastic restoring force of the elastic member 325, and forms an inclined surface in the circumferential direction. The first support member 323 rotates along the inclined surface of the second support end 321a along the inclined surface of the first support end 323b and presses the second rotation support member 310 while flowing in the axial direction.

Here, the second support member 321 may be press-fitted or screwed into the nut housing 130h, but in the present embodiments, a screw portion is formed in the second support member 321 to be screwed to the nut housing 130h. shown as an example.

The first support member 323 and the second support member 321 are assembled in a state in which the elastic member 325 is elastically compressed in the circumferential direction, and at this time, the positions of the first support end 323b and the second support end 321a are Each of the stop ends is assembled in abutting state, and the second support member 321 is screwed in a direction in which the stop end of the second support member 321 presses the stop end of the first support member 323 .

In addition, one end of the elastic member 325 is fixed to the engaging portion 323a of the first support member 323 and the other end of the elastic member 325 is fixed to the second support member so that the elastic member 325 is not separated and elastically deformed in the circumferential direction. It is fixed to the locking part 321a of the 321.

To enable the locking structure of the elastic member 370 in this way, the first and second support members 323 and 321 are provided with protruding locking portions 323a and 321a, respectively.

And, a pressing member 327 that is screwed to the second support member 321 to directly support the first support member 323 in the axial direction is provided, so that the first support member 323 is rotated after the durability progresses. When a defect occurs, such as when the elastic restoring force of the elastic member 325 is insufficient or the first support member 323 is fixed to the second support member 321, the pressure member 327 without replacement of the axial support member 320 is It is possible to directly support the first support member 323 in the axial direction by adjusting the screw tightening amount.

In the electric power assist steering apparatus according to these embodiments, the angle sensor 105 and the torque sensor 107 that detect the driver's operation of the steering wheel 101 transmit electrical signals to the electronic control device 110 and The electronic control device 110 transmits an operation signal to the driving motor 120 .

The electronic control device 110 is based on various electrical signals transmitted from the vehicle speed sensor 104, the motor rotation angle sensor 106, etc. in addition to the electrical signals transmitted from the angle sensor 105 and the torque sensor 107, the driving motor ( 120) will be controlled.

As described above, according to the present embodiments, it is possible to assist the driver's steering force even in the case of a truck or bus requiring a relatively large steering force compared to a passenger car, and automatic parking, lane maintenance, and road surface conditions for controlling the vehicle Additional functions such as driving assistance and autonomous driving control can be used according to the driver's convenience, which has the effect of increasing the driver's convenience.

In the above, even though it has been described that all components constituting the embodiments of the present embodiments are combined or operated in combination, the present embodiments are not necessarily limited to these embodiments. That is, within the scope of the purpose of the present embodiments, all of the components may operate by selectively combining one or more.

The above description is merely illustrative of the technical idea of the present embodiments, and those of ordinary skill in the art to which the present embodiments pertain may make various modifications and variations without departing from the essential characteristics of the present embodiments. will be. Accordingly, the embodiments disclosed in the present embodiments are for explanation rather than limiting the technical spirit of the present embodiments, and the scope of the technical spirit of the present embodiments is not limited by these embodiments. The protection scope of the present embodiments should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present embodiments.

101: steering wheel 103: steering shaft
110: electronic control device 120: drive motor
121: input pulley 130: power transmission member
201: input shaft 203: first gear
210: output shaft 211: output pulley
213: second gear 230: belt member

Claims (20)

an input shaft connected to the steering shaft at one end and provided with a first gear at the other end;
an output shaft having a second gear coupled to the first gear at one end and a ball nut coupled to an outer peripheral side through a ball;
a sector shaft coupled to an outer gear formed on the outer periphery of the ball nut to operate a fitman arm;
Electric power assist steering system comprising a. The method of claim 1,
The output shaft is an electric power assist steering device, characterized in that coupled to the drive motor via a power transmission member. 3. The method of claim 2,
The power transmission member,
an input pulley provided on the shaft of the driving motor;
an output pulley provided on the output shaft;
a belt member coupled to the input pulley and the output pulley;
Electric motion assistance steering system comprising a. The method of claim 1,
The input shaft is
a first shaft connected to the steering shaft;
a second shaft coupled to the first shaft;
a torsion bar coupled to the inside of the first shaft and the second shaft;
Electric power assist steering system comprising a. 5. The method of claim 4,
An electric power assist steering device having a torque sensor coupled to an outer periphery of the first shaft to detect a steering torque generated when a driver operates a steering wheel. 6. The method of claim 5,
The electric power-assisted steering apparatus further comprising an electronic control device that compares the signal value input from the torque sensor with preset data and transmits a signal value to the driving motor. 7. The method of claim 6,
The electronic control device compares a signal value received from an angle sensor that detects a steering angle when a driver operates a steering wheel with preset data and transmits a signal value to the driving motor. The method of claim 1,
The input shaft and the output shaft are arranged to form a predetermined angle, the electric power assist steering device to which the first gear and the second gear are coupled. 4. The method of claim 3,
One end of the output shaft protrudes to the outside of the nut housing in which the ball nut is embedded, and the output pulley and the second gear are disposed at the protruding end of the output shaft. Electric power assist steering system provided. The method of claim 1,
Electric power-assisted steering, characterized in that the upper end of the output shaft is supported on the inner peripheral surface of the upper end of the nut housing in which the ball nut is built in, the first rotation support member for supporting the rotation of the output shaft and the axial load is provided. Device. 11. The method of claim 10,
The first rotation support member,
Electric power assist steering device comprising an inner member coupled to an outer circumferential surface of the upper end of the output shaft, an outer member coupled to the inner circumferential surface of the nut housing, and a rolling member provided between the inner member and the outer member . 12. The method of claim 11,
An upper stepped portion is formed on an outer peripheral surface of the upper end of the output shaft, and a lower end of the inner member is supported and coupled to the upper stepped portion. 12. The method of claim 11,
Between the inner member and the outer member, the electric power assist steering device, characterized in that the intermediate support member is provided with a seating groove is formed to rotate the rolling member is supported on an inner circumferential surface. 14. The method of claim 13,
The inner peripheral surface of the inner member is provided with a support groove in which the rolling member is supported and rotated, and the support groove and the seating groove are formed as inclined surfaces inclined in the axial direction. 15. The method of claim 14,
The electric power assist steering device, characterized in that the inner peripheral surface of the outer member and the outer peripheral surface of the intermediate support member are formed as inclined surfaces corresponding to the support groove and the seating groove. The method of claim 1,
A second rotation support member for supporting the rotation of the output shaft is provided between the outer peripheral surface of the lower end of the output shaft and the nut housing in which the ball nut is incorporated. 17. The method of claim 16,
An inner bush is coupled between the outer peripheral surface of the lower end of the output shaft and the second rotation support member. 18. The method of claim 17,
An outer bushing is coupled between the inner circumferential surface of the nut housing and the second rotation support member. 19. The method of claim 18,
The second rotation support member,
Electric power assist steering device comprising an inner member coupled to the outer circumferential surface of the lower end of the output shaft, an outer member coupled to the inner circumferential surface of the nut housing, and a rolling member provided between the inner member and the outer member . 20. The method of claim 19,
An axial support member for supporting the second rotation support member in the axial direction is coupled to an inner circumferential surface of the lower end of the nut housing.

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