KR20160038508A - Discharge pulsation reduction structure of a compressor - Google Patents

Abstract

The present invention relates to a discharge pulsation reduction structure of a compressor. A compressor (1) includes: a cylinder block (10) including a center bore (12) penetrating the center, and multiple cylinder bores (11) formed around the center bore (12); a front housing combined with the front side of the cylinder block (10) to form a crank chamber (21) inside; a rear housing (30) combined with the rear side of the cylinder block (10), wherein an intake chamber (31) connected to an intake port (32) is provided inside the rear housing (30) and a discharge chamber (34) is provided outside the rear housing (30) by a circular partition formed inside; and a rotation shaft (40) installed and rotated by penetrating the crank chamber (21) and the center bore (12), and combined and rotated with a swash plate (44) placed inside the crank chamber (21). The discharge pulsation reduction structure includes a discharge part (100) formed on the outer surface of the cylinder block (10) to discharge a refrigerant, stored in the discharge chamber (34), to the outside of the compressor (1).

Description

Discharge pulsation reduction structure of a compressor < RTI ID = 0.0 >

The present invention relates to a discharge pulsation reduction structure of a compressor, and more particularly, to a variable displacement swash plate type compressor having an expansion portion formed on an upper portion of a discharge portion of a discharge portion, a damping portion communicating with a discharge flow path, The present invention relates to a discharge pulsation reducing structure of a compressor capable of reducing pulsation of a refrigerant discharged from a room, increasing durability of the air conditioner, and reducing noise due to pulsation.

Generally, an automobile is provided with an air conditioner (A / C) for cooling and heating the room. Such an air conditioner includes a compressor that compresses gaseous low-temperature and high-pressure gaseous refrigerant introduced from an evaporator into gaseous refrigerant of high temperature and high pressure and sends it to a condenser.

The compressor includes a reciprocating type compressing the refrigerant by the reciprocating motion of the piston in accordance with the compressing system, and a rotary type compressing by the rotational motion. The reciprocating type includes a crank type in which a crank is used in accordance with a transmission system of a drive source, and a swash plate type in which a crank is transmitted to a plurality of pistons. Rotary types include rotary rotary axes using vanes, vane rotary, rotary scrolling, and scrolling with fixed scrolling.

Among the reciprocating compressors described above, the swash plate type compressor is formed to rotate the swash plate while rotating the rotary shaft by the driving force of the engine, and reciprocate the piston in accordance with the rotation of the swash plate to compress the refrigerant.

Generally, a variable capacity swash plate type compressor refers to a compressor in which a swash plate of a swash plate type compressor is configured to be able to change the inclination angle of swash plate in accordance with the compression capacity.

Such a swash plate type compressor is driven in accordance with on / off of the air conditioner switch. When the compressor is driven, the temperature of the evaporator is lowered, and when the compressor is stopped, the temperature of the evaporator is increased. When the air conditioner switch is turned on, the swash plate type compressor discharges refrigerant having a high pressure according to the relative motion between the piston, the rotary shaft and the swash plate to the condenser outside the compressor.

1 is a cross-sectional view of a conventional variable displacement swash plate type compressor. A schematic configuration of a conventional variable displacement swash plate type compressor will be described with reference to FIG.

The cylinder block 10 forms a part of the skeleton and the outer appearance of the compressor 1. A center bore 12 is formed through the center of the cylinder block. A rotary shaft (40) is rotatably mounted on the center bore (12). A plurality of cylinder bores 11 are formed so as to penetrate the cylinder block 10 radially around the center bore 12. A piston (13) is installed in the cylinder bore (11) so as to reciprocate linearly. Preferably, the piston 13 is formed in a cylindrical shape, and the cylinder bore 11 is formed in a cylindrical space so as to correspond to the shape of the piston 13. Accordingly, the piston 13 linearly reciprocates inside the cylinder bore 11 to compress the refrigerant sucked through the suction chamber 31.

A front housing (20) is installed at one end of the cylinder block (10). The front housing 20 is recessed in a direction opposite to the cylinder block 10 to form a crank chamber 21 together with the cylinder block 10 therein. The crank chamber 21 is kept air-tight with the outside.

A pulley (60) is rotatably installed on one side of the front housing (20). The pulley 60 receives the driving force of the engine and rotates the rotating shaft.

The rear housing 30 is installed to face the front housing 20 at the other end of the cylinder block 10, that is, the cylinder block 10. A suction chamber 31 is formed inside the rear housing 30 by a circular partition wall formed therein to communicate with the suction port 32 through a suction passage 33. The suction chamber 31 functions to transfer the refrigerant to be compressed into the cylinder bore 11. The discharge chamber 34 is formed on the outer side of the rear housing 30 by a circular partition wall formed therein. The discharge chamber 34 functions to temporarily store the compressed refrigerant before being discharged to the outside of the compressor.

The center bore 12 and the crank chamber 21 of the front housing 20 to be rotatable. The rotary shaft (40) is rotated by the driving force transmitted from the engine. A rotor 41 is provided on the rotary shaft 40. The rotor 41 penetrates the center of the rotating shaft 40 and is installed in the crank chamber 21 so as to rotate integrally with the rotating shaft 40. The rotor 41 is fixed to the rotary shaft 40 in a substantially disc shape and the hinge arm 42 protrudes from one surface of the rotor 41.

The swash plate 44 is installed to be connected to the rotary shaft 40 by a shoe 45. The swash plate 44 is hinged to the rotor 41 and rotates together with the rotor 41. The swash plate 44 is installed at a position between a state in which the swash plate 44 is perpendicular to the longitudinal direction of the rotary shaft 40 and a state in which the swash plate 44 is inclined at a predetermined angle with respect to the rotary shaft 40 do.

A semi-inclined spring 43, which is a coil spring, is installed on the rotary shaft 40 so as to surround the rotary shaft 40. The anti-tilt spring 43 exerts an elastic force between the rotor 41 and the swash plate 44. That is, the semi-inclined spring 43 functions to absorb the force acting on the swash plate 44 when the operation of the compressor 1 is stopped, by applying an elastic force in a direction in which the inclination angle of the swash plate 44 is reduced .

A valve assembly (50) is provided between the cylinder block (10) and the rear housing (30) for controlling the flow of the refrigerant.

In the conventional compressor, in particular, the variable displacement swash plate type compressor, pulsation occurs due to the reciprocating motion of the piston in the refrigerant stored in the discharge chamber (34). That is, there is a problem that pulsation occurs in the discharge chamber due to the time difference due to the reciprocating motion of the piston due to the compression stroke and the suction stroke at the time of driving the compressor.

Further, the refrigerant in the discharge chamber is in a state of high temperature and high pressure, and the pulsation generated in the refrigerant in the discharge chamber acts with a large impact force to deteriorate the durability of the air conditioner.

Further, the pulsation generated in the refrigerant in the discharge chamber causes various pipes of the air conditioner to vibrate, causing noise due to the vibration, and such noise causes a problem to the driver or the passenger.

Korean Patent Laid-Open Publication No. 10-2014-0025909

SUMMARY OF THE INVENTION It is an object of the present invention to provide a variable displacement swash plate type compressor in which an expansion portion is formed on an upper portion of a body portion of a compressor and the expansion portion is communicated with a discharge passage, A damping portion is formed to reduce the pulsation of the refrigerant discharged along the discharge passage in the discharge chamber to increase the durability of the air conditioner and to reduce the noise caused by the pulsation to minimize the discomfort of the driver or the occupant, Structure.

In order to accomplish the object of the present invention, a discharge pulsation reduction structure of a compressor according to a preferred embodiment of the present invention includes a cylinder block having a center bore formed through the center thereof and having a plurality of cylinder bores formed around the center bore, A front housing connected to the front of the cylinder block to form a crank chamber therein and a suction chamber connected to the suction port at the inner side by a circular partition wall which is coupled to the rear of the cylinder block and formed therein, A compressor comprising a rear housing in which a discharge chamber is formed, and a rotating shaft which rotates together with a swash plate which is installed through the center bore and the crank chamber and rotated and located in the crank chamber, the compressor comprising: And a discharge unit for discharging the refrigerant stored in the discharge chamber to the outside of the compressor Can.

In another preferred embodiment of the discharge pulsation reduction structure of the compressor according to the present invention, the discharge portion of the discharge pulsation reduction structure of the compressor includes a body portion; An extension formed on an upper portion of the body portion; A discharge port provided on one side of the body portion; A discharge channel formed inside the body so that one side is connected to the discharge chamber and the other side is connected to the discharge port; And a damping portion formed in the expansion portion to communicate with the discharge passage.

In another preferred embodiment of the discharge pulsation reduction structure of the compressor according to the present invention, the discharge pulsation reduction structure of the compressor includes a connection flow path communicating with the discharge port of the discharge portion, and a connector portion ; And a refrigerant pipe provided at one side of the connector portion to communicate with a connection flow path of the connector portion to transfer the refrigerant discharged from the discharge portion to the outside of the compressor.

Further, in another preferred embodiment of the discharge pulsation reducing structure of the compressor according to the present invention, the damping portion of the discharge portion of the discharge pulsation reduction structure of the compressor is formed so as to extend at the tip end of the discharge flow path so as to be perpendicular to the discharge port .

In another preferred embodiment of the discharge pulsation reducing structure of the compressor according to the present invention, the damping portion of the discharge portion of the discharge pulsation reduction structure of the compressor includes a first damping portion extending from the distal end of the discharge path within the expansion portion; And a second damping portion extending from the distal end of the first damping portion so as to be orthogonal to the first damping portion inside the extension portion.

Further, in another preferred embodiment of the discharge pulsation reduction structure of the compressor according to the present invention, the discharge portion of the discharge pulsation reduction structure of the compressor may further include a cap member coupled to the tip of the second damping portion.

Further, in another preferred embodiment of the discharge pulsation reduction structure of the compressor according to the present invention, the discharge pulsation reduction structure of the compressor is such that the damping portion of the compressor is formed such that the depth of the damping portion is 2 mm or more and 8 mm or less.

The discharge pulsation reduction structure of the compressor according to the present invention has the effect of reducing the pulsation of the refrigerant discharged from the discharge chamber to the outside of the compressor through the discharge portion.

Further, the discharge pulsation reduction structure of the compressor according to the present invention has the effect of enhancing the durability of the air conditioner through reduction of pulsation of the refrigerant, thereby increasing the service life of the air conditioner and reducing the maintenance cost.

Further, the discharge pulsation reduction structure of the compressor according to the present invention minimizes noise due to pulsation reduction of the refrigerant, thereby preventing burning of the driver or occupant.

In addition, the discharge pulsation reduction structure of the compressor according to the present invention has the effect of forming an expansion part in the main body part and further forming a damping part when the discharge flow path is formed by drilling, thereby reducing the manufacturing cost for pulsation reduction have.

1 is a cross-sectional view of a conventional variable swash plate type compressor.
2 is a perspective view of a cylinder block in which a discharge portion of a discharge pulsation reduction structure of a compressor according to an embodiment of the present invention is formed.
3 is a cross-sectional view of the discharge portion shown in Fig.
4 is a cross-sectional view of a discharge unit according to another embodiment of the present invention.
FIGS. 5 to 7 are cross-sectional views illustrating a state in which a connector portion having various types of chambers and a refrigerant pipe are coupled to the discharge portion shown in FIG.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals are used to refer to like elements throughout.

FIG. 2 is a perspective view of a cylinder block in which a discharge portion of a discharge pulsation reduction structure of a compressor according to an embodiment of the present invention is formed, FIG. 3 is a sectional view of the discharge portion shown in FIG. 2, 1 is a cross-sectional view of a discharge portion according to an embodiment. FIGS. 5 to 7 are cross-sectional views illustrating a state in which a connector portion having various types of chambers and a refrigerant pipe are coupled to the discharge portion shown in FIG.

2 to 3, a discharge pulsation reducing structure of a compressor according to a preferred embodiment of the present invention will be described. 2 to 3, the discharge pulsation reduction structure of the compressor according to the first preferred embodiment of the present invention includes the discharge portion 100. [

A compressor according to a preferred embodiment of the present invention includes a cylinder block 10, a front housing 20, a rear housing 30, a rotary shaft 40, a valve assembly 50, and a pulley 60. The cylinder block 10 includes a center bore 12 formed through the center of the cylinder block 10 and a plurality of cylinder bores 11 formed around the center bore 12. The front housing 20 is coupled to the front of the cylinder block 10 and has a crank chamber 21 formed therein. The rear housing 30 is coupled to the rear of the cylinder block 10. The rear housing 30 is provided with a suction chamber 31 communicating with the suction port 32 on the inner side by a circular partition wall formed therein, And a discharge chamber (34) formed in the discharge chamber (34). The rotary shaft 40 is installed through the center bore 12 and the crank chamber 21 of the front housing 20 and is rotated. Further, a swash plate 44, which is coupled to the rotary shaft 40 by the rotor 41 and the shoe 45, is provided.

The discharge portion 100 is formed on the outer circumferential surface of the cylinder block 10 so as to discharge the refrigerant stored in the discharge chamber 34 to the outside of the compressor 1. [

3, the discharge unit 100 of the discharge pulsation reduction structure of the compressor according to the preferred embodiment of the present invention includes a body 110, an extension 120, a discharge port 130, a discharge passage 140 And a damping unit 150. The damping unit 150 includes a damping unit 150,

The body 110 forms the outer shape of the discharge part 100 and the lower end of the body part 110 protrudes on the outer circumferential surface of the cylinder block 10.

The extension 120 is formed on the top of the body 110. Although not limited thereto, the extension 120 is formed integrally with the body 110. The extension 120 functions to provide a space for forming the damping unit 150, which will be described later.

And a discharge port 130 is provided on one side of the body portion.

One side of the discharge passage 140 is connected to the discharge chamber 34 and the discharge passage 140 is formed inside the body 110 so that the other side of the discharge passage 140 is connected to one side of the discharge port 140 do. The discharge passage 140 may be formed in the body 110 through drilling, and is formed in a cylindrical pipe-like shape.

The damping portion 150 is formed inside the expansion portion 120 so as to communicate with the upper end portion of the discharge flow passage 140. The damping portion 150 can be formed by further deepening the processing depth when drilling the discharge passage 140, and is preferably formed in the shape of a cylindrical pipe having the same diameter as the discharge passage 140.

More preferably, the damping portion 150 is formed at the tip of the discharge passage 140, that is, at the upper end of the discharge passage 140 so as to be orthogonal to the discharge port 130 inside the expansion portion 120.

The damping unit 150 is a space for receiving the refrigerant flowing into the discharge passage 140. The refrigerant flowing in the discharge chamber 34 through the discharge passage 140 has a relatively long flow path, The refrigerant flowing into the damping unit 150 is mixed with the refrigerant flowing out of the damping unit 150 while being collided with the refrigerant flowing out of the damping unit 150. In this process, the pulsation of the refrigerant is reduced. That is, before the refrigerant passes through the discharge port 130 by the damping unit 150, the pulsation of the refrigerant is relieved by the damping unit 150, thereby reducing noise due to pulsation.

Evaluation condition Evaluation results (dBA) BASE Damping volume Noise Difference Value (dBA)
Pd pressure
16mbar 18.8 17.8 -1.0 21 mbar 19.4 17.9 -1.5 26mbar 20.6 16.1 -.45

In Table 1, Pd represents the pressure of the discharge portion, and (-) represents a state where the noise is reduced in the noise difference value. As shown in Table 1, when the depth h of the damping portion 150 is 8 mm, it is confirmed that the noise inside the vehicle is reduced.

3 and Table 1, it is preferable that the damping portion 150 is formed such that the depth h of the damping portion 150 is 2 mm or more and 8 mm or less. When the depth h of the damping portion 150 is less than 2 mm, there is a problem that the working time increases due to the drilling work and the ripple effect is not generated to the increase of the cost. When the depth h of the damping portion 150 is greater than 8 mm, the depth of the damping portion 150 is increased to accommodate the damping portion 150, The size of the compressor 120 can not be reduced, and interference with other components may occur on the installation of the compressor.

2 to 7, the discharge pulsation reducing structure of the compressor according to another preferred embodiment of the present invention further includes a connector portion 200 and a refrigerant pipe 300.

The connector unit 200 includes a connection passage 220 communicating with the discharge port 130 of the discharge unit 100. The connector 200 is installed at one side of the discharge unit 100 so that the connection passage 220 is connected to the discharge tray 130. In order to minimize the size of the connector, the connection channel 220 of the connector unit 200 is formed to be bent in a L-shape.

The refrigerant pipeline 300 is installed at one side of the connector unit 200 so as to communicate with the connection flow path 220 of the connector unit 200 in order to transfer the refrigerant discharged from the discharge unit 100 to the outside of the compressor 1 .

4, the damping portion 150 of the discharge portion 100 of the discharge pulsation reduction structure of the compressor according to another preferred embodiment of the present invention includes a first damping portion 150 and a second damping portion 152 ).

The first damping portion 151 is formed to extend from the distal end of the discharge passage 140 in the expansion portion 120. The first damping portion 151 is formed by deepening the processing depth when the discharge passage 140 is drilled.

The second damping portion 152 is formed at the tip of the first damping portion 151 so as to be orthogonal to the first damping portion 151 inside the expansion portion 120. That is, the second damping portion 152 is formed by drilling one side of the extending portion 120 in a direction orthogonal to the first damping portion 151. The second damping portion 152 is formed through drilling to be perpendicular to the first damping portion 151 after the first damping portion 151 is machined.

4, the discharge part 100 of the discharge pulsation reduction structure of the compressor according to another preferred embodiment of the present invention is coupled to the tip of the second damping part 152 to prevent the refrigerant from flowing out And a cap member (160). The cap member 160 is fastened to the expansion portion 120 through a known fastening means such as a bolt to prevent the refrigerant from flowing out of the second damping portion 152. Further, although not shown in the figure, a sealing member may be further provided between the cap member and the second damping portion 152 to block refrigerant outflow.

The structure of another embodiment of the discharge pulsation reducing structure of the compressor according to the present invention will be described with reference to Figs. 5 to 7. Fig.

5, the connector 200 includes a body 210, a connection channel 220 formed in a lattice shape inside the body 210, and a connector 220 connected to one side of the connection channel 220 And a chamber 230 is provided.

A refrigerant transport pipe 300 for transporting the refrigerant discharged from the discharge unit 100 to an external air conditioning unit is connected to one side of the body 210.

A connection passage 220 connecting the discharge port 130 of the discharge unit 100 and the refrigerant transfer pipe 300 is formed in the body 210. [ The refrigerant discharged from the discharge part 100 is transferred to the refrigerant transfer pipe 300 through the coupling flow path 210 of the body part 210.

The chamber 230 is formed to extend from the tip of the connection passage 210. The chamber 230 is formed by deepening the processing depth when drilling the coupling flow path 220.

The chamber 230 is a space for secondarily receiving the refrigerant flowing into the connection channel 220 in the same manner as the damping unit 150. The chamber 230 is connected to the connection channel 220 through the discharge port 130, The pulsation is further reduced by the chamber 230, so that the shock is mitigated. The pulsation is reduced when the flow path is lengthened or bent into a labyrinth shape.

The refrigerant flowing into the chamber 230 flows into and out of the chamber 230 because the refrigerant flows into and out of the chamber 230. The refrigerant flowing into the chamber 230 collides with the refrigerant discharged from the chamber 230, Mixed. In the process, the pulsation is canceled and the shock is mitigated.

6, the connection channel 220 of the connector unit 200 includes a first connection channel 221 connected to the discharge port 130 and a second connection channel 222 connected to the refrigerant transfer pipe 300 ).

The first connection passage 221 is formed parallel to the refrigerant discharge direction X of the discharge port 130 and the second connection passage 222 is formed perpendicular to the tip of the first connection passage 221.

The chamber 230 includes a first chamber 231 formed at the tip of the first connection channel 221 and extending along the refrigerant discharge direction X and a first chamber 231 formed at the tip of the first chamber 231, And a second chamber 232 formed to extend in a direction crossing the first chamber 232.

The first chamber 231 is formed by deepening the processing depth when the first connection channel 221 is drilled.

The second chamber 232 is formed by drilling a tip of the first chamber 231 in a direction transverse to the refrigerant discharge direction X. [ After the first chamber 231 is machined, the second chamber 232 is vertically drilled. After processing the second chamber 232, the closing member 240 is engaged to seal the space.

The second chamber 232 is bent and extended at the tip of the first chamber 231 so that the flow path is bent and elongated. Accordingly, the refrigerant flowing into the first chamber 231 flows into the second chamber 232 and is further relaxed when the pulsation is formed only by the damping portion 150.

7, the connection channel 220 of the connector unit 200 includes a first connection channel 221 connected to the discharge port 130 and a second connection channel 222 connected to the refrigerant transfer pipe 300 ).

The first connection passage 221 is formed parallel to the refrigerant discharge direction X of the discharge port 130 and the second connection passage 222 is formed perpendicular to the tip of the first connection passage 221.

The chamber 230 includes a first chamber 231 formed at the tip of the first connection channel 221 and extending along the refrigerant discharge direction X and a second chamber 231 formed at the tip of the first chamber 231, And a second chamber 232 extending in a direction transverse to the second chamber 232.

The first chamber 231 is formed by deepening the processing depth when the first connection channel 221 is drilled.

The second chamber 232 is formed at the tip of the second connection passage 222 and extends in the direction crossing the refrigerant discharge direction X. [ The second chamber 232 is formed by deepening the processing depth when the second connection channel 231 is drilled.

The second chamber 232 together with the first chamber 231 serves to mitigate the impact by reducing pulsation. That is, the pulsation of the refrigerant discharged from the discharge chamber is primarily reduced by the damping unit 150, and the pulsation of the refrigerant is additionally reduced by the first and second chambers 231 and 232 of the chamber 230 secondarily. So that the durability of the air conditioner can be increased and the noise can be remarkably reduced.

The present invention is not limited to the modifications shown in the drawings and the embodiments described above, but may be extended to other embodiments falling within the scope of the appended claims.

1: compressor, 10: cylinder block,
11: cylinder bore, 12: center bore,
13: piston, 20: front housing,
21: crank chamber, 30: rear housing,
31: suction chamber, 32: suction port,
33: suction channel, 34: discharge chamber,
40: rotation shaft, 41: rotor,
42: a hinge arm, 43: a semi-inclined spring,
44: swash plate, 45: shoe,
50: valve assembly, 60: poly,
100: discharging portion, 110: body portion,
120: extension part, 130: discharge port,
140: discharge flow path, 150: damping portion,
151: first damping portion, 152: second damping portion,
160: cap member,
200: connector portion, 210: body portion,
220: connection channel, 221: first connection channel,
222: second connection channel, 230: chamber,
231: first chamber, 232: second chamber,
240: closing member, 300: refrigerant pipe,
h: Damping depth.

Claims (7)

A cylinder block 10 through which a center bore 12 is formed to penetrate the center and a plurality of cylinder bores 11 are formed around the center bore 12; A suction chamber communicating with the suction port 32 is formed on the inner side by a circular partition wall which is coupled to the rear of the cylinder block 10 and forms therein a crank chamber 21, 31 and a discharge chamber 34 is formed on the outer side of the crank chamber 21 and a rear housing 30 which is installed through the center bore 12 and the crank chamber 21, (1) comprising a rotating shaft (40) which rotates together with a rotating shaft (44)
And a discharge part (100) formed on an outer circumferential surface of the cylinder block (10) for discharging the refrigerant stored in the discharge chamber (34) to the outside of the compressor (1) . The method according to claim 1,
The discharging unit (100)
A body part 110;
An extension 120 formed at an upper portion of the body 110;
A discharge port 130 installed at one side of the body 110;
A discharge passage 140 formed in the body 110 so that one side is connected to the discharge chamber 34 and the other side is connected to the discharge port 130; And
And a damping part (150) formed in the expansion part (120) to communicate with the discharge flow path (140). 3. The method of claim 2,
A connector unit 200 having a connection channel 220 communicated with the discharge port 130 of the discharge unit 100 and installed at one side of the discharge unit 100; And
A refrigerant pipe provided at one side of the connector unit 200 to communicate with the connection channel 220 of the connector unit 200 to transfer the refrigerant discharged from the discharge unit 100 to the outside of the compressor 1, (300) for reducing the discharge pulsation of the compressor. 3. The method of claim 2,
Wherein the damping part (150) is formed at the tip of the discharge passage (140) so as to be perpendicular to the discharge port (130) inside the expansion part (120). 5. The method of claim 4,
The damping unit 150 includes:
A first damping portion 151 extending from a distal end of the discharge passage 140 in the extension portion 120; And
And a second damping part (152) extending from the tip of the first damping part (151) so as to be perpendicular to the first damping part (151) inside the expansion part (120) Discharge pulsation reduction structure. The method of claim 5, wherein
Wherein the discharge unit (100) further includes a cap member (160) coupled to a tip of the second damping unit (152). 5. The method of claim 4,
Wherein the damping part (150) is formed such that the depth (h) of the damping part (150) is 2 mm or more and 8 mm or less.

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