KR20200011085A - Steer-By-Wire Type Steering Apparatus - Google Patents

Abstract

The present embodiments relate to a steer-by-wire steering system. According to the present embodiments, provided is the steer-by-wire steering system including: a sliding bar which has an outer circumferential screw groove on an outer circumferential surface and has a slit groove in an axial direction on an outer surface of the outer circumferential screw groove; a ball nut which has an inner circumferential screw groove corresponding to the outer circumferential screw groove on an inner circumferential surface and is coupled through a ball inserted into the outer circumferential screw groove and the inner circumferential screw groove; a motor in which a hollow motor shaft through which a sliding bar passes is coupled to the ball nut; and a piston member having a protrusion inserted into the slit groove on an inner circumferential surface.

Description

Steer-By-Wire Type Steering Apparatus}

The present embodiment relates to a steer-by-wire steering device, and more particularly, to prevent the rotation of the sliding bar compared to the prior art, the power transmission of the motor is made stable through the ball nut and the sliding bar, and at the same time sliding the sliding bar. The present invention relates to a steering-by-wire steering device that minimizes frictional resistance and can absorb a collision impact between a sliding bar and a cylinder housing even when an impact load is generated from a road surface.

In general, the steering device of the vehicle is developed and applied to assist the driving force of the driver's steering wheel to provide the convenience of driving operation, the power steering is a hydraulic type using the hydraulic pressure, the hydraulic power of the hydraulic and motor at the same time Electro-hydraulics to be used and electric-types using only the electric power of the motor have been developed and applied.

In recent years, instead of removing mechanical connections such as steering columns or universal joints or pinion shafts between the steering wheel and the wheels, steering-by-wire (SBW) enables steering of the vehicle using an electric motor such as a motor. ) Steering system has been developed and applied.

However, since the steering-by-wire steering device does not have a mechanical connection between the steering shaft and the wheels, there is an increasing need for a mechanism configuration for stably transmitting power of an electric motor such as a motor.

Embodiments of the present invention have been made in the above-described background, in a steer-by-wire type steering apparatus, a steer-by-wire type steering apparatus capable of stably transmitting power of a motor through a ball nut and a sliding bar is prevented by rotating the sliding bar. The purpose is to provide.

In addition, the steer-by-wire steering system prevents the rotation of the sliding bar and minimizes the frictional resistance during the sliding of the sliding bar and absorbs the collision impact between the sliding bar and the cylinder housing even when an impact load is generated from the road surface. It is an object to provide a wire steering device.

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 embodiment, an outer circumferential screw groove is provided on an outer circumferential surface and a sliding bar slid in an axial direction by rotation of a ball nut coupled through a ball, a cylinder housing in which a sliding bar is inserted and slid inside, and a ball nut are built in. And a steer-by-wire steering device including a gearbox housing having an intubation portion into which a cylinder housing is inserted at one end, and an insertion member inserted between an outer circumference of the cylinder housing and an inner circumference of the intubation portion and elastically deformed in a radial direction. Can be.

Further, according to the present embodiment, an outer circumferential screw groove is provided on the outer circumferential surface, and a sliding bar slid in the axial direction by the rotation of the ball nut coupled through the ball, and the sliding bar is inserted into the inner side and slid and spaced apart from one end. The cylinder flange portion extending in the radial direction is formed on the outer circumferential side of the position, the cylinder flange portion is provided with a cylinder housing, the ball nut is built in the axial through-hole is formed, and an intubation portion into which one end of the cylinder housing is inserted The gearbox flange portion corresponding to the cylinder flange portion is formed on the outer circumferential side of the intubation portion, and the gearbox flange portion is inserted into the gearbox housing having the axial through hole formed therein, the through hole of the cylinder flange portion, and the gearbox flange portion. Steer-by-wire steering apparatus including an insertion member elastically deformed in the direction can be provided The.

According to the present embodiments as described above, in the steer-by-wire type steering apparatus, the rotation of the sliding bar is prevented, so that the power transmission of the motor is stably achieved through the ball nut and the sliding bar.

In addition, according to the present embodiments, in the steer-by-wire type steering apparatus, while preventing the rotation of the sliding bar, the frictional resistance during the sliding of the sliding bar is minimized and the impact of the sliding bar and the cylinder housing is generated even when an impact load is generated from the road surface. There is an effect that can be absorbed.

1 is a schematic view showing a steer-by-wire steering apparatus according to the present embodiments;
2 is an exploded perspective view showing a part of a steering-by-wire steering apparatus according to the present embodiments;
3 is a cross-sectional view showing a part of a steering-by-wire steering apparatus according to the present embodiments;
4 and 5 are an exploded perspective view showing a part of the steering-by-wire steering apparatus according to the embodiments;
6 is a cross-sectional view showing a part of a steering-by-wire steering apparatus according to the present embodiments;
FIG. 7 is an enlarged cross-sectional view of a portion A of FIG. 6.

Some embodiments of the present embodiments will now be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used to refer to the same components as much as possible, even if displayed on different drawings. In addition, in describing the present embodiments, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present embodiments, the detailed description thereof will be omitted.

In addition, in describing the components of the present embodiments, terms such as first, second, A, B, (a), and (b) may be used. These terms are only to distinguish the components from other components, and the nature, order or order of the components are not limited by the terms. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but there may be another configuration between each component. It is to be understood that the elements may be "connected", "coupled" or "connected".

1 is a configuration diagram schematically showing a steer-by-wire steering apparatus according to the present embodiments, Figure 2 is an exploded perspective view showing a part of the steering-by-wire steering apparatus according to the present embodiment, Figure 3 is an embodiment 4 and 5 are an exploded perspective view showing a part of the steer-by-wire steering device according to the present embodiments, and FIG. 6 is a steer according to the present embodiments. A cross-sectional view showing a part of the bi-wire steering device, and FIG. 7 is an enlarged cross-sectional view of part A of FIG. 6.

As shown in these drawings, the steer-by-wire steering apparatus according to the present embodiments has an outer circumferential screw groove 120a provided on an outer circumferential surface thereof and is rotated by a ball nut 121 coupled through a ball 121b. A sliding bar 120 sliding in the axial direction, a cylinder housing 130 into which the sliding bar 120 is inserted and sliding inside, a ball nut 121 is embedded, and an intubation part into which the cylinder housing 130 is inserted at one end thereof. 157 is provided between the gear box housing 150, the cylinder member 130 is inserted between the outer peripheral surface and the inner peripheral surface of the intubation portion 157 is inserted member 170 which is elastically deformed in the radial direction.

Steer-by-wire steering device according to the present embodiments, the torque sensor 103 is coupled to one side of the steering shaft connected to the steering wheel 101, the torque sensor for detecting this when the steering wheel 101 of the driver ( 103 transmits an electrical signal to both actuators 110 such that the actuators 110 steer both wheels 115 through the tie rods 119.

Actuator 110 is composed of a motor 113, an electronic controller 111, a sliding bar 120, a ball nut 121, a belt 125, a motor pulley 123, a nut pulley 127, The tie rod 119 is coupled to both sides of the sliding bar 120 by means of an inner ball joint into which a stud is inserted into the ball housing, and the tie rod 119 is coupled to a wheel (knuckle arm 117 connected to the wheel) Steer 115.

And, the electrical signal generated from the torque sensor 103 is sent to the electronic control device 111 of both actuators 110, the electronic control device 111 is transmitted to the electric signal and other vehicles transmitted from the torque sensor 103. The motor 113 is controlled based on electrical signals transmitted from various sensors mounted.

However, in the drawings in the present embodiment, for convenience of description, each of the two actuators 110 is provided with an electronic control device 111, but is not necessarily limited thereto, the torque sensor 103 and various sensors Of course, it is also possible to send an electric signal to the motor 113 of both actuators 110 from one electronic control device 111 that receives the electric signal from the detailed description thereof will be omitted.

Meanwhile, the motor pulley 123 is coupled to the shaft 113a of the motor 113, the nut pulley 127 is coupled to the ball nut 121, and the belt 125 is attached to the motor pulley 123 and the nut pulley 127. ) Is coupled and the driving force of the motor 113 is transmitted to the ball nut 121 through the belt 125 to rotate the ball nut 121.

Then, by rotating the ball nut 121 with the driving force of the motor 113, the sliding bar 120 coupled through the ball 121b is axially slid to be steered through the tie rod 119. It is.

The sliding bar 120 is provided with an outer circumferential screw groove 120a through which the ball 121b is circulated on the outer circumferential surface, and an inner circumferential screw corresponding to the outer circumferential screw groove 120a of the sliding bar 120 on the inner circumferential surface of the ball nut 121. Since the groove 121a is provided, the sliding bar 120 is coupled to the outer circumferential screw groove 120a and the ball 121b inserted into the inner circumferential screw groove 121a.

Accordingly, the sliding bar 120 is slid in the axial direction by the rotation of the ball nut 121 in the cylinder housing 130.

In the steering-by-wire steering device, the piston member 140 is provided to prevent the sliding bar 120 from interlocking when the ball nut 121 rotates. Referring to FIGS. The cylinder housing 130 in which the sliding bar 120 is inserted and slid has a housing protrusion 133a and a housing recess 133b formed on an inner circumferential surface thereof.

The piston member 140 coupled to the end of the sliding bar 120 is provided with a piston groove 149a corresponding to the housing protrusion 133a or a piston protrusion 149b corresponding to the housing groove 133b. Formed.

Here, the housing protrusion 133a and the piston groove 149a or the housing groove 133b and the piston protrusion 149b corresponding to each other may be provided in plural and spaced apart in the circumferential direction, respectively. In the drawings, for convenience of description, a plurality of housing protrusions 133a and housing recesses 133b are formed in the cylinder housing 130, and a plurality of piston protrusions 149b and piston grooves 149a are formed in the piston member 140 as well. As shown.

An insertion groove 145a recessed in the axial direction is formed at one end of the sliding bar 120, and an extension part 145 inserted into the insertion groove 145a of the sliding bar 120 at one end of the piston member 140. May be formed and press-coupled to each other.

In this case, a thread is formed on the inner circumferential surface of the insertion groove 145a of the sliding bar 120 and the outer circumferential surface of the extension part 145 of the piston member 140 such that the sliding bar 120 and the piston member 140 may be screwed together.

In addition, a first hole 147a formed in the axial direction is formed at an end of the sliding bar 120, and a second hole 147 communicating with the first hole 147a of the sliding bar 120 in the piston member 140. ) Is formed and the fastening member 161 penetrating the first hole 147a and the second hole 147 may be coupled to the sliding bar 120 and the piston member 140.

In addition, a threaded portion may be formed in the inner circumferential surface of the first hole 147a of the sliding bar 120 and the second hole 147 of the piston member 140 to be screwed to the fastening member 161.

The gearbox housing 150 has a gearbox flange portion 151 extending in the radial direction on the outer circumferential side of the intubation portion 157 provided at one side end, and the cylinder housing 130 is the gearbox housing 150. The cylinder flange portion 131 corresponding to the gearbox flange portion 151 is formed on the outer circumferential side of the position spaced from the end inserted into the intubation portion 157 of the.

In addition, an extension flange portion 171 of which diameter is extended is formed at one end of the insertion member 170 formed in a cylindrical shape, and the extension flange portion 171 is a gearbox flange portion 151 and a cylinder flange portion 131. Are coupled between.

The gearbox flange portion 151, the cylinder flange portion 131, and the extension flange portion 171 of the insertion member 170 are formed with through holes 151a, 131a, and 171a penetrating in the axial direction, and thus the fastening member 160. Is coupled to, the through-hole (151a) of the gearbox flange portion 151 is formed with a screw may be screwed with the fastening member 160.

The insertion member 170 has a radial elastic deformation between the cylinder housing 130 and the gearbox housing 150 while the impact load is input from the road surface and transmitted to the sliding bar 120. ) And the cylinder housing 130 are instantaneously displaced from the coaxial and it is possible to prevent the high friction force is generated between the piston member 140 and the cylinder housing 130.

That is, even when the impact load from the road surface is input, the cylinder housing 130 can be made to flow while elastically deforming in the radial direction between the cylinder housing 130 and the gearbox housing 150. The gearbox housing 150 can be easily restored to the coaxial state, thereby preventing the operating force of the sliding bar 120 from being momentarily increased.

Here, the insertion member 170 is NR (Natural Rubber), BR (Butadiene Rubber), NBR (Nitrile Butadiene Rubber), CR (Chloroprene Rubber), EPDM (Ethylene Propylene Diene Monomer rubber) to facilitate elastic deformation in the axial and radial directions. ), SBR (Styrene Butadine Rubber), CSM (Chlorosulphonated Polyethylene), fluororubber, silicone, urethane, thermoplastic polyurethane (TPU) and the like may be formed of at least one or more of the materials.

Meanwhile, referring to FIGS. 5 to 7, the steer-by-wire steering apparatus according to the present embodiments includes a ball nut 121 having an outer circumferential screw groove 120a formed on an outer circumferential surface thereof and coupled through a ball 121b. Sliding bar 120 is slid in the axial direction by the rotation of the sliding bar 120 is inserted into the inner sliding and the cylinder flange portion 131 extending in the radial direction on the outer peripheral side of the position spaced from one end is formed The cylinder flange portion 131 has a cylinder housing 130 and a ball nut 121 in which an axial through hole 131a is formed, and an intubation portion into which an end of the cylinder housing 130 is inserted at one end thereof ( 157 is provided and a gearbox flange portion 151 corresponding to the cylinder flange portion 131 is formed on the outer circumferential side of the intubation portion 157 and the through-hole 151a in the axial direction is formed in the gearbox flange portion 151. Gear box housing 150, the cylinder flange portion 131 is formed Air is inserted into the through-hole (131a, 151a) of the box, the flange 151 may include an insertion member 180 is elastically deformed in the radial direction.

The cylinder housing 130 in which the sliding bar 120 is inserted and slid inward has a housing protrusion 133a and a housing recess 133b formed on an inner circumferential surface thereof.

The piston member 140 coupled to the end of the sliding bar 120 is provided with a piston groove 149a corresponding to the housing protrusion 133a or a piston protrusion 149b corresponding to the housing groove 133b. Formed.

Here, the housing protrusion 133a and the piston groove 149a or the housing groove 133b and the piston protrusion 149b corresponding to each other may be provided in plural and spaced apart in the circumferential direction, respectively. In the drawings, for convenience of description, a plurality of housing protrusions 133a and housing recesses 133b are formed in the cylinder housing 130, and a plurality of piston protrusions 149b and piston grooves 149a are formed in the piston member 140 as well. As shown.

In addition, the through-holes 131a and 151a of the cylinder flange portion 131 and the gearbox flange portion 151 are arranged in pairs corresponding to positions opposing each other in the radial direction with respect to the central axis so as to correspond to the cylinder housing 130 and the gears. The coaxial holding of the box housing 150 can be supported by a uniform holding force.

On the outer circumferential side of the insertion member 180 formed in a cylindrical shape, an enlarged diameter portion 181 having an expanded diameter is formed, and the enlarged diameter portion 181 is coupled between the gearbox flange portion 151 and the cylinder flange portion 131.

In addition, the cylinder housing 130 and the gearbox housing are formed by the fastening member 160 penetrating the through holes 131a and 151a of the cylinder flange portion 131 and the gearbox flange portion 151 and the inner circumferential surface of the insertion member 180. 150 may be combined.

In addition, the through hole 151a of the gearbox flange part 151 may be provided with a screw part to be screwed to the fastening member 160.

Here, in the state where the cylinder housing 130 and the gearbox housing 150 are coupled, a radial gap d is formed between the end outer circumferential surface of the cylinder housing 130 and the inner circumferential surface of the intubation portion 157 of the gearbox housing 150. It is provided.

Therefore, when the impact load is input from the road surface and is transmitted to the sliding bar 120, the sliding bar 120 and the cylinder housing 130 are instantaneously displaced from the coaxial and a high friction force is generated between the piston member and the cylinder housing 130. Can be prevented.

That is, even when the impact load from the road surface is input, the insertion member 180 is elastically deformed in the axial direction and the radial direction, and is formed between the outer peripheral surface of the end of the cylinder housing 130 and the inner peripheral surface of the inlet 157 of the gear box housing 150. The flow of the cylinder housing 130 can be made as much as the gap (d) of the cylinder housing 130 and the gearbox housing 150 is easily restored to the coaxial state, the operating force of the sliding bar 120 is instantaneous It is possible to prevent the increase.

The insertion member 180 is provided with a small diameter portion 183 at one end thereof with respect to the enlarged diameter portion 181 and a larger diameter portion 185 having a larger diameter than the small diameter portion 183 at the other end thereof.

The large diameter portion 185 of the insertion member 180 is inserted into the through hole 131a of the cylinder flange portion 131, and the head portion 161 of the fastening member 160 is supported by the large diameter portion 185 and coupled thereto. Therefore, the bearing force in both the axial direction and the radial direction can be adjusted by the fastening amount of the fastening member 160.

That is, when the head 161 of the fastening member 160 is supported by the cylinder flange portion 131 and is fastened, only the axial support force is adjusted, but the head 161 of the fastening member 160 is inserted into the insertion member 180. By supporting the large diameter portion 185 of the large diameter portion 185 and the elastic deformation in the axial and radial directions of the large diameter portion 185, the bearing force of both the axial direction and the radial direction can be adjusted, and the insertion member when transmitting the impact load from the road surface ( The elastic deformation amount of 180) can be adjusted.

In addition, in the through hole 151a of the gearbox flange part 151, a seating groove 151b having a diameter larger than an inner circumferential surface to which the body portion 163 of the fastening member 160 is coupled is formed, thereby inserting the member 180. The small diameter portion 183 is supported by the seating groove 151b and is coupled to the seating groove 151b when the fastening member 160 is fastened, thereby enabling elastic deformation in the axial direction.

Here, the insertion member 180 is NR (Natural Rubber), BR (Butadiene Rubber), NBR (Nitrile Butadiene Rubber), CR (Chloroprene Rubber), EPDM (Ethylene Propylene Diene Monomer rubber) to facilitate elastic deformation in the axial and radial directions. ), SBR (Styrene Butadine Rubber), CSM (Chlorosulphonated Polyethylene), fluororubber, silicone, urethane, thermoplastic polyurethane (TPU) and the like may be formed of at least one or more of the materials.

As described above, according to the present embodiments, in the steer-by-wire type steering apparatus, the rotation of the sliding bar is prevented so that power transmission of the motor is stably achieved through the ball nut and the sliding bar.

In addition, according to the present embodiments, in the steer-by-wire type steering apparatus, while preventing the rotation of the sliding bar, the frictional resistance during the sliding of the sliding bar is minimized and the impact of the sliding bar and the cylinder housing is generated even when an impact load is generated from the road surface. There is an effect that can be absorbed.

In the above description, it is described that all the components constituting the present embodiments are combined or operated in one, but the present embodiments are not necessarily limited to such an embodiment. In other words, within the scope of the present embodiments, all of the components may be selectively operated in combination with one or more of them.

The above description is merely illustrative of the technical spirit of the present embodiments, and those skilled in the art to which the present embodiments belong may make various modifications and changes without departing from the essential characteristics of the present embodiments. will be. Therefore, the embodiments disclosed in the present embodiments are not intended to limit the technical spirit of the present embodiments, but to explain, and the scope of the technical spirit of the present embodiments is not limited by these embodiments. The scope of protection of the present embodiments should be construed by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present embodiments.

101: steering wheel 110: actuator
111: electronic control device 113: motor
120: sliding bar 121: ball nut
123: motor pulley 125: belt
127: nut pulley 130: cylinder housing
131: cylinder flange portion 140: piston member
150: gearbox housing 151: gearbox flange
170,180: insertion member

Claims (20)

A sliding bar provided on an outer circumferential surface thereof and sliding in an axial direction by rotation of a ball nut coupled through a ball;
A cylinder housing in which the sliding bar is inserted and slid inside;
A gear box housing having the ball nut embedded therein and having an intubation portion into which the cylinder housing is inserted;
An insertion member inserted between an outer circumferential surface of the cylinder housing and an inner circumferential surface of the intubation portion to elastically deform in a radial direction;
Steer-by-wire steering device comprising a. The method of claim 1,
Steering-by-wire steering device, characterized in that the housing projection or the housing groove is formed on the inner peripheral surface of the cylinder housing. The method of claim 2,
Steer-by-wire further comprises a piston member coupled to an end of the sliding bar to form a piston recess groove portion corresponding to the housing protrusion portion or a piston protrusion portion corresponding to the housing recess portion on an outer circumferential surface of the sliding bar to prevent rotation of the sliding bar. Type steering system. The method of claim 3, wherein
A first hole formed in the axial direction is formed at the end of the sliding bar and a second hole communicating with the first hole is formed in the piston member, so that the fastening member is coupled to the first hole and the second hole. Steer-by-wire steering system. The method of claim 1,
The gearbox housing is a steering-by-wire steering device, characterized in that the gearbox flange portion extending in the radial direction on the outer peripheral side of the intubation portion is formed. The method of claim 5, wherein
The cylinder housing is a steer-by-wire steering device, characterized in that the cylinder flange portion corresponding to the gearbox flange portion is formed on the outer peripheral side of the position spaced apart from the end inserted into the intubation portion. The method of claim 6,
An extension flange portion having an extended diameter is formed at one end of the insertion member, and the extension flange portion is connected between the gearbox flange portion and the cylinder flange portion. The method of claim 7, wherein
Steer-by-wire steering device characterized in that the through-hole penetrating in the axial direction is formed in the gearbox flange portion, the cylinder flange portion and the extension flange portion is coupled to the fastening member. The method of claim 8,
Steering-by-wire steering device, characterized in that the through-hole of the gearbox flange portion is formed with a screw portion is screwed to the fastening member. A sliding bar provided on an outer circumferential surface thereof and sliding in an axial direction by rotation of a ball nut coupled through a ball;
A cylinder housing in which the sliding bar is inserted and slid inward, and a cylinder flange portion extending in the radial direction is formed on an outer circumferential side of the position spaced apart from one end, and the cylinder flange portion is formed with an axial through hole;
The ball nut has a built-in intubation portion having one end inserted into the cylinder housing at one end thereof, and a gearbox flange portion corresponding to the cylinder flange portion is formed on the outer circumferential side of the intubation portion, and the gearbox flange portion has an axial through hole. Gear box housing is formed;
An insertion member inserted into the through-hole of the cylinder flange portion and the gearbox flange portion to elastically deform in a radial direction;
Steer-by-wire steering device comprising a. The method of claim 10,
Steering-by-wire steering device, characterized in that the housing projection or the housing groove is formed on the inner peripheral surface of the cylinder housing. The method of claim 11,
Steer-by-wire further comprises a piston member coupled to an end of the sliding bar to form a piston recess groove portion corresponding to the housing protrusion portion or a piston protrusion portion corresponding to the housing recess portion on an outer circumferential surface of the sliding bar to prevent rotation of the sliding bar. Type steering system. The method of claim 10,
Steering-by-wire steering device, characterized in that the through-holes of the cylinder flange portion and the gearbox flange portion are arranged in pairs corresponding to positions opposite to each other in the radial direction with respect to the central axis. The method of claim 10,
A steer-by-wire steering device, characterized in that an enlarged diameter portion having an enlarged diameter is formed on an outer circumferential side of the insertion member, and the enlarged diameter portion is coupled between the gearbox flange portion and the cylinder flange portion. The method of claim 14,
Steer-by-wire steering device, characterized in that coupled to the through-hole and the inner circumferential surface of the insertion member of the cylinder flange portion and the gearbox flange portion. The method of claim 15,
Steering-by-wire steering device, characterized in that the through-hole of the gearbox flange portion is formed with a screw portion is screwed to the fastening member. The method of claim 16,
Steer-by-wire steering device, characterized in that the radial gap is provided between the outer peripheral surface of the end of the cylinder housing and the inner peripheral surface of the intubation portion of the gearbox housing. The method of claim 17,
Steering-by-wire steering device, characterized in that the insertion member is provided with a small diameter portion at one end portion on the basis of the enlarged diameter portion, and a large diameter portion having a larger diameter than the small diameter portion at the other end portion. The method of claim 18,
Steer-by-wire steering device, characterized in that the large diameter portion of the insertion member is inserted into the through hole of the cylinder flange and the head of the fastening member is supported and coupled to the large diameter portion. The method of claim 19,
Steering-by-wire steering, characterized in that the through-hole of the gearbox flange is formed with a seating groove having a diameter larger than the inner circumferential surface to which the body portion of the fastening member is coupled so that the small diameter portion of the insertion member is supported and coupled to the seating groove. Device.

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