Patent Publication Number: US-2022212505-A1

Title: Pneumatic tire

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2021-0001500 filed on Jan. 6, 2021, the disclosures of which are incorporated herein in its entirety by reference for all purposes. 
     TECHNICAL FIELD 
     The present disclosure relates to a pneumatic tire, and more particularly, a pneumatic tire formed so that noise generated from a groove is reduced by disposing a noise reflector in the groove. 
     BACKGROUND 
     Tires are mounted on a variety of vehicles, from small vehicles to heavy-duty vehicles, to support loads of the vehicles, and to perform a power transmission function that transmit power of the vehicles to the ground and a brake function, as well as functions for dampening vibrations and shocks from the ground that occur when the vehicles travel. In order to perform the functions of the tires, an internal air pressure is applied to the tires which play an important part in traveling and braking of the vehicles. 
     SUMMARY 
     The present disclosure provides a pneumatic tire formed so that noise generated from a groove can be reduced. 
     In accordance with an embodiment of the present disclosure, there is provided a pneumatic tire for reducing noise including: a tread portion including: a tread surface for making contacting with a road surface; and a groove recessed inward from the tread surface and extending along a circumferential direction of the pneumatic tire; and a plurality of noise reflectors protruding from the groove and disposed spaced apart from each other along the circumferential direction of the pneumatic tire, wherein the groove includes: a groove bottom surface spaced apart by a predetermined distance from the tread surface in a radial direction of the pneumatic tire; and a plurality of groove side surfaces connected to the groove bottom surface and each including a connection curved surface having a predetermined curvature, wherein each of the noise reflectors includes: a support surface supported by the connection curved surface and the groove bottom surface; and a protrusion surface located on a side opposite to the support surface and disposed to be spaced apart from the connection curved surface, and wherein the protrusion surface includes a protruding curved surface having a shape which goes away from a central virtual plane perpendicular to the groove bottom surface as it goes from the groove bottom surface toward an outer side in the radial direction of the pneumatic tire. 
     The pneumatic tire may have a meridian plane passing through a center of the pneumatic tire and perpendicular to an axial direction of the tire, the plurality of groove side surface may include a first groove side surface and a second groove side surface, the first groove side surface and the second groove side surface may be inclined so that an axial gap therebetween decreases as it goes to the groove bottom surface from the tread surface, and each of the first groove side surface and the second groove side surface may extend to be inclined with respect to the meridian surface. 
     A height of the noise reflector in the radial direction may be ½ or more of a length between the tread surface and the groove bottom surface. 
     A thickness of the noise reflector in the circumferential direction may be equal to or smaller than a separation distance between centers of the plurality of noise reflectors in the circumferential direction. 
     The tread portion may further include a sipe recessed inward from the tread surface and extending in a direction deviating from an extension direction of the groove to be connected to the groove, and the noise reflector may be disposed to be spaced apart from the sipe in the circumferential direction of the pneumatic tire. 
     According to embodiments of the present disclosure, a noise reflector may be disposed in the groove of the pneumatic tire, and thus, noise generated by the groove may be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a pneumatic tire according to a first embodiment of the present disclosure. 
         FIG. 2  is a perspective view of a noise reflector disposed in a groove according to the first embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view of the groove according to the first embodiment of the present disclosure. 
         FIG. 4  is a partial cross-sectional view of a pneumatic tire taken along line IV-IV of  FIG. 1 . 
         FIGS. 5A to 5C  are cross-sectional views of the noise reflector according to the first embodiment of the present disclosure. 
         FIG. 6  is an enlarged view of K illustrated in  FIG. 1 . 
         FIG. 7  is a table illustrating a level of noise generated by the pneumatic tire according to the first embodiment of the present disclosure. 
         FIG. 8  is a graph illustrating a noise evaluation result of the pneumatic tire according to the first embodiment of the present disclosure. 
         FIG. 9  is a table illustrating results of evaluating drainage performance of the pneumatic tire according to the first embodiment of the present disclosure. 
         FIGS. 10A and 10B  are cross-sectional views of side surfaces of a plurality of grooves of a pneumatic tire according to a second embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     With the change of the times, a proportion of unpaved roads gradually decreases, vehicles without an internal combustion engine such as electric vehicles are popularized, and noise is recently being regarded as important among the main performance of tires. The existing tire includes a tread portion in contact with a road surface, and a groove may be formed in the tread portion. The groove improves drainage. However, air flows in the groove as the vehicle travels, and thus, pipe resonance may be generated by the flowing air. There is a problem that the pipe resonance causes noise. 
     Hereinafter, specific embodiments for implementing the technical spirit of the present disclosure will be described with reference to the accompanying drawings. 
     In describing the embodiments of the present disclosure, the detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed descriptions of well-known functions or configurations may unnecessarily make obscure the spirit of the present disclosure. 
     When an element is referred to as being ‘connected’ to, or ‘contacted’ with another element, it should be understood that the element may be directly connected to, or contacted with the other element, but that other elements may exist in the middle. 
     The terms used in the present disclosure are only used for describing specific embodiments, and are not intended to limit the present disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise. 
     In addition, in the present disclosure, expressions such as an upper side, a lower side, and a side surface are described with reference to the drawings, and it should be noted in advance that if the direction of the object is changed, it may be expressed differently. For the same reason, some components in the accompanying drawings are exaggerated, omitted, or schematically illustrated, and the size of each component does not entirely reflect the actual size. 
     The terms used herein, including ordinal numbers such as “first” and “second” may be used to describe, and not to limit, various components. The terms simply distinguish the components from one another. 
     The meaning of “including” as used in the specification specifies a specific characteristic, region, integer, step, action, element and/or component, but does not exclude the existence or addition of other specific characteristic, region, integer, step, action, element, component and/or group. 
     Meanwhile, a radial direction “R” described below means a radial direction of a tire. An axis may mean a rotation axis of the tire, and an axial direction “A” means a direction parallel to the rotation axis of the tire. The axial direction does not necessarily pass through a center of the rotation axis of the tire, and includes a direction parallel to an extension direction of the rotation axis of the tire. In addition, a circumferential direction “C” is a direction along an outer circumferential surface of the tire and means a direction perpendicular to the radial direction. The circumferential direction may be either the clockwise direction or counterclockwise direction when viewed from a side surface of the tire. 
     Meanwhile, unless otherwise specified, the directions include both positive and negative directions. 
     Hereinafter, a pneumatic tire  1  according to a first embodiment of the present disclosure will be described with reference to the drawings. 
     Referring to  FIG. 1 , the pneumatic tire  1  according to the first embodiment of the present disclosure may include a tread portion  100  and a noise reflector  200 . 
     The tread portion  100  is disposed on an outer portion of the pneumatic tire  1 , corresponds to a thick rubber layer having a configuration in which the road surface is directly grounded, and may be formed of a rubber material having strong cut, impact, and abrasion resistance to protect an inside of the tire. A surface of the tread portion  100  may extend toward a side wall (not illustrated) of the pneumatic tire  1  as a portion contacting the road surface. In addition, the tread portion  100  may include a groove  110  and a sipe  120  to improve water discharge performance, conditional friction performance, or the like. 
     Referring further to  FIG. 2 , the groove  110  may be recessed inward from the surface of the tread portion  100 . The groove  110  may be formed in the circumferential direction or the axial direction of the pneumatic tire  1 , or may be extended in a direction deviating from the circumferential direction or the axial direction of the pneumatic tire  1 . Hereinafter, the groove  110  will be described on the basis of being formed in the circumferential direction, but is not limited thereto. In addition, the groove  110  may include a plurality of grooves  110  and the plurality of grooves  110  may be disposed to be spaced apart from each other. For example, the plurality of grooves  110  formed in the circumferential direction of the pneumatic tire  1  may be disposed to be spaced apart from each other in the axial direction of the pneumatic tire  1 . In addition, a width of the groove  110  perpendicular to an extension direction of the groove  110  may be 1.1 mm or more. The groove  110  may include a plurality of groove side surfaces  111  and  112  and a groove bottom surface  113 . 
     Referring further to  FIG. 3 , the plurality of groove side surfaces  111  and  112  may be recessed from the surface of the tread portion  100 . The plurality of groove side surfaces  111  and  112  are connected to the groove bottom surface  113  and portions connected to the groove bottom surface  113  may have a predetermined curvature. The predetermined curvature may be equal to or less than R 5  (5 mm), for example. In addition, the plurality of groove side surfaces  111  and  112  may include a first groove side surface  111  and a second groove side surface  112 . The second groove side surface  112  may be disposed at a position more spaced apart from a center of the tread portion  100  than the first groove side surface  111 . For example, in the plurality of groove side surfaces  111  and  112  of the groove  110 , the second groove side surface  112  located on one side (left side of  FIG. 1 ) in the axial direction of the pneumatic tire  1  with respect to a meridian plane “m” is located on one side (left side of  FIG. 1 ) of the first groove side surface  111  in the axial direction of the pneumatic tire  1 . In addition, in the plurality of groove side surfaces  111  and  112  of the groove  110 , the second groove side surface  112  located on the other side (right side of  FIG. 1 ) in the axial direction of the pneumatic tire  1  with respect to the meridian surface “m” is located on the other side (right side of  FIG. 1 ) of the first groove side surface  111  in the axial direction of the pneumatic tire  1 . In the present specification, the meridian plane “m” refers to a plane perpendicular to the axial direction while passing through a center of the pneumatic tire  1 . In other words, in each of the grooves  110 , the second groove side surface  112  is disposed to be farther from the meridian surface “m” than the first groove side surface  111  in the axial direction of the pneumatic tire  1 . 
     In addition, the first groove side surface  111  and the second groove side surface  112  may be inclined so that a gap therebetween decreases in a direction closer to the groove bottom surface  113 . For example, an angle “g” at which the first groove side surface  111  and the second groove side surface  112  are inclined may be in a range of 5° to 30° with respect to the radial direction of the pneumatic tire  1 . In other words, the angle “g” formed between each of the first groove side surface  111  and the second groove side surface  112  and the meridian surface “m” may be in a range of 5° to 30°. In addition, the plurality of groove side surfaces  111  and  112  may include connection curved surfaces  111   a  and  112   a  and inclined surfaces  111   b  and  112   b,  respectively. 
     As described above, the connection curved surfaces  111   a  and  112   a  are portions of the groove side surfaces that are connected to the groove bottom surface  113  and formed with a predetermined curvature. The connection curved surfaces  111   a  and  112   a  may support the noise reflector  200 . The first groove side surface  111  may include the first connection curved surface  111   a  connected to the groove bottom surface  113 , and the second groove side surface  112  may include the second connection curved surface  112   a  connected to the groove bottom surface  113 . 
     The inclined surfaces  111   b  and  112   b  may be located between the connection curved surfaces  111   a  and  112   a  and the surface of the tread portion  100 . In addition, the inclined surfaces  111   b  and  112   b  are surfaces that may be connected to a second connection unit  220   b  of the noise reflector  200  to be described below. In addition, the inclined surfaces  111   b  and  112   b  may be inclined to form the angle “g” with the meridian surface “m” as described above. In other words, the first groove side surface  111  may include the first inclined surface  111   b  connected to the first connection curved surface  111   a,  and the second groove side surface  112  may include the second inclined surface  112   b  connected to the second connection curved surface  112   a.  In addition, the first inclined surface  111   b  and the second inclined surface  112   b  may be inclined so that an axial gap therebetween gradually decreases toward the groove bottom surface  113 . For example, an angle “g 1 ” between the first inclined surface  111   b  and the meridian surface “m” and an angle g 2  between the second inclined surface  112   b  and the meridian surface “m” may be in a range of 5° to 30°. The angle “g 1 ” and the angle “g 2 ” may be the same or different from each other. 
     The groove bottom surface  113  may be connected to the plurality of groove side surfaces  111  and  112  and may extend in a direction parallel to the surface of the tread portion  100 . In other words, the groove bottom surface  113  may be located between the first groove side surface  111  and the second groove side surface  112 . 
     Referring further to  FIG. 4 , the sipe  120  may be recessed inwardly from the surface of the tread portion  100 , and may be connected to the groove  110  by extending in a direction that deviates from a direction in which the groove  110  is extended. For example, the sipe  120  may extend in a direction close to the sidewall or in the axial direction of the pneumatic tire  1 . In addition, a width of the sipe  120  perpendicular to an extension direction of the sipe  120  may be 1.0 mm or less. One side of the sipe  120  may be connected to the first groove side surface  111  or the second groove side surface  112  of the groove  110 . In addition, the sipe  120  may be spaced apart from the noise reflector  200  in the circumferential direction of the pneumatic tire  1 . In addition, some of the plurality of sipes  120  may be connected to one groove  110 . The plurality of sipes  120  are connected to the groove  110 , and thus, a plurality of pitches  130  may be formed on the surface of the tread portion  100 . The plurality of noise reflectors  200  may be disposed between the plurality of sipes  120 . In addition, the noise reflector  200  may be disposed to be spaced apart from the sipe  120  in the circumferential direction. For example, a gap “E” between the sipe  120  and the noise reflector  200  may be in a range between 1.5 mm and 3.0 mm. The gap “E” may be a gap between the sipe  120  and the noise reflector  200  formed closest to the sipe  120  among the plurality of noise reflectors  200 . The sipe  120  may include a plurality of sipe side surfaces  121  and  122  and a sipe bottom surface  123 . 
     The plurality of sipe side surfaces  121  and  122  may be recessed inward from the surface of the tread portion  10 . In addition, the plurality of sipe side surfaces  121  and  122  may be connected to any one of the plurality of groove side surfaces  111  and  112 . The gap “E” between the sipe  120  and the noise reflector  200  described above by the plurality of sipe side surfaces  121  and  122  may be a gap between any one of the plurality of noise reflector  200  and any one of the plurality of sipe side surfaces  121  and  122  formed closest thereto. 
     The sipe bottom surface  123  is connected to the plurality of sipe side surfaces  121  and  122  and may be formed in a direction parallel to the surface of the tread portion  100 . In other words, the sipe bottom surface  123  may be located between the plurality of sipe bottom surfaces  123 . At least a portion of the plurality of sipe bottom surfaces  123  may be disposed at different positions according to the length of the plurality of sipe side surfaces  121  and  122  being recessed from the surface of the tread portion  100 . In other words, the sipe bottom surface  123  may be connected to any one of the plurality of groove side surfaces  111  and  112  or the groove bottom surface  113 . 
     Referring further to  FIGS. 5A to 5C , the noise reflector  200  may reduce noise by reducing pipe resonance generated by air flowing in the groove  110 . The noise reflector  200  may protrude from the groove  110 , and the plurality of noise reflectors  200  may be provided and disposed to be spaced apart from each other along the circumferential direction of the pneumatic tire  1 . In addition, the noise reflector  200  may protrude from at least one of the first groove side surface  111  and the second groove side surface  112 . For example, the noise reflectors  200  may protrude from the first groove side surface  111  and the groove bottom surface  113  and may be spaced apart from each other along the circumferential direction of the pneumatic tire  1 . As another example, the plurality of noise reflectors  200  may protrude from the second groove side surface  112  and the groove bottom surface  113  and may be spaced apart from each other along the circumferential direction of the pneumatic tire  1 . As still another example, first noise reflectors  200   a  which are some of the plurality of noise reflectors  200  may protrude from the first groove side surface  111  and the groove bottom surface  113  and may be disposed to be spaced apart from each other along the circumferential direction of the pneumatic tire  1 , and second noise reflectors  200   b  which are the remainder thereof may protrude from the second groove side surface  112  and the groove bottom surface  113  and may be spaced apart from each other along the circumferential direction of the pneumatic tire  1 . In addition, the first noise reflectors  200   a  and the second noise reflectors  200   b  may be spaced apart from each other. 
     Referring further to  FIGS. 3, 4 and 6 , a height “b” of the noise reflector  200  may be formed to be ½ or more of a length “B” from the surface of the tread portion  100  to the groove bottom surface  113  in the radial direction of the pneumatic tire  1 . For example, the height “b” of the noise reflector  200  may be 65% or more and 75% or less of the length “B” from the surface of the tread portion  100  to the groove bottom surface  113  in the radial direction of the pneumatic tire  1 . A thickness “W” of the noise reflector  200  in the circumferential direction of the pneumatic tire  1  may be 3% to 10% or less of a length of the gap between the plurality of sipes  120  or the pitch between the plurality of sipes  120 , but is not limited thereto. For example, the thickness W of the noise reflector  200  may be in a range of 1.0 mm to 3.0 mm In addition, the thickness W of the noise reflector  200  may be less than or equal to a circumferential separation distance L between the centers of the plurality of noise reflectors  200 . In other words, the circumferential separation distance L between the centers of the plurality of noise reflectors  200  may be 1 or more times and less than 2 times the thickness “W” of the noise reflector  200 . For example, the separation distance L may be 1.0 mm or more and 6.0 mm or less. In addition, the plurality of noise reflectors  200  may be disposed in the groove  110  in a number of 300 or more and 1000 or less. The noise reflector  200  may include a support surface  210  and a protrusion surface  220 . 
     The support surface  210  may be supported by the groove bottom surface  113  and one of the first groove side surface  111  and the second groove side surface  112 . In addition, the support surface  210  may also be formed into a curved surface corresponding to the connection curved surfaces  111   a  and  112   a.  In other words, the support surface  210  may be formed in a curved surface to be supported by the connection curved surfaces  111   a  and  112   a,  the inclined surfaces  111   b  and  112   b,  and the groove bottom surface  113 . For example, the support surface  210  may be supported by the first connection curved surface  111   a,  the first inclined surface  111   b,  and the groove bottom surface  113 , or may be supported by the second connection curved surface  112   a,  the second inclined surface  112   b,  and the groove bottom surface  113 . 
     The protrusion surface  220  may be located on a side opposite to the support surface  210  and may be spaced apart from the connection curved surfaces  111   a  and  112   a.  The protrusion surface  220  may be connected to the groove bottom surface  113  and one of the first groove side surface  111  and the second groove side surface  112 . The protrusion surface  220  may include one side that is connected to the groove bottom surface  113  and the other side that is located on a side opposite to one side and connected to the first groove side surface  111  or the second groove side surface  112 . Hereinafter, one side of the protrusion surface  220  will be referred to as a first connection portion  220   a,  and the other side of the protrusion surface  220  will be referred to as a second connection portion  220   b.  The first connection portion  220   a  and the second connection portion  220   b  of the protrusion surface  220  may be connected to the support surface  210 . In addition, the protrusion surface  220  may include a protruding curved surface having a shape that goes away from a first virtual surface “V”, which is a virtual plane perpendicular to the groove bottom surface  113 , toward an outer side in the radial direction of the pneumatic tire  1 . In other words, the first connection portion  220   a  may be closer to the first virtual surface V than the second connection portion  220   b.  In addition, the protrusion surface  220  may be in contact with a second virtual surface “S”, which is a virtual plane that is perpendicular to the groove bottom surface  113  and passes through the first connection portion  220   a  of the protrusion surface  220 . 
     A length “a” from the second virtual surface “S” to the second connection portion  220   b  of the protrusion surface  220  based on the axial direction of the pneumatic tire  1  may be 20% or more and 30% or less of a maximum gap “I” between the first groove side surface  111  and the second groove side surface  112 . In other words, the noise reflector  200  may be 20% or more and 30% or less of the maximum distance “I” between the first groove side surface  111  and the second groove side surface  112  and may protrude from the groove bottom surface  113  and any one of the first groove side surfaces  111  and the second groove side surface  112 . 
     Hereinafter, operations and effects of the pneumatic tire  1  according to the first embodiment of the present disclosure will be described with further reference to  FIGS. 7 to 9 . 
     Since the noise reflector  200  is disposed in the groove  110  of the pneumatic tire  1  according to the first embodiment of the present disclosure, noise caused by the flow of air flowing in the groove  110  can be reduced. 
     V 1 , V 2 , and V 3  illustrated in  FIG. 7  are grooves having different shapes, and V 4  and V 5  are grooves in which different types of noise reflectors are disposed. Even when the shapes of the grooves are different, there is no change in a noise level and a noise level per unit volume. Meanwhile, as the noise reflector is provided, the noise level per unit volume was improved by 4% in V 4  and by 6% or more in V 5 . In addition, in the noise level and the noise level per unit volume, V 5  including the noise reflector formed long in the radial direction of the pneumatic tire  1  were further improved than V 4 . In other words, as the noise reflector  200  is provided on the groove bottom surface  113  and the groove side surfaces  111  and  112  as in V 5 , noise can be efficiently reduced. 
     In addition, as illustrated in  FIG. 8 , when the noise reflector  200  is applied to the groove  110 , noise can be reduced in a band of 500 hz to 800 hz than when the noise reflector  200  is not applied. 
     As illustrated in  FIG. 9 , even when the noise reflector  200  is disposed in the groove  110 , drainage performance of the groove  110  is hardly affected. V 1  illustrated in  FIG. 9  represents the drainage performance of the tire in which the noise reflector is not present, and V 5  represents the drainage performance of the tire to which the noise reflector  200  of the present disclosure is applied. In addition, V 2 , V 3 , and V 4  represent the tire drainage performance in a state in which protrusions of different shapes are applied to the groove. ST represents tire drainage performance in a straight traveling state, and CO represents tire drainage performance in a cornering state. According to  FIG. 9 , it can be seen that V 5  to which the noise reflector  200  of the present disclosure is applied has drainage performance better than those of V 2 , V 3 , and V 4  in ST and CO states. In addition, the drainage performance of V 5  may be close to the drainage performance of V 1 . In other words, even when the noise reflector  200  of the present disclosure is applied to the groove  110 , the groove  110  can efficiently discharge water. 
     Hereinafter, a pneumatic tire  1  according to a second embodiment of the present disclosure will be described with reference to  FIGS. 10A and 10B . As compared with the first embodiment described above, in the second embodiment of the present disclosure, at least one of the plurality of groove side surfaces  111  and  112  may further include surface connection surfaces  111   c  and  112   c.  Hereinafter, these differences will be mainly described, and the same description and reference numerals refer to the above-described embodiments. 
     The surface connection surfaces  111   c  and  112   c  may be located between the inclined surfaces  111   b  and  112   b  and the surface of the tread portion  100 . A length “d” of each of the surface connection surfaces  111   c  and  112   c  in the radial direction of the pneumatic tire  1  may be 25% or less of a length “B” from the surface of the tread portion  100  to the groove bottom surface  113 . In addition, the surface connection surfaces  111   c  and  112   c  may be inclined to be further away from the virtual surface “V” in order to form a predetermined angle “f” with the inclined surfaces  111   b  and  112   b.  For example, the angle “f” of each of the inclined surface connection surfaces  111   c  and  112   c  may be 30° or less based on the inclined surfaces  111   b  and  112   b.  In other words, the surface connection surfaces  111   c  and  112   c  may be inclined more than the inclined surfaces  111   b  and  112   b  with respect to the virtual surface V. 
     These surface connection surfaces  111   c  and  112   c  may be included in one or more of the plurality of groove side surfaces  111  and  112 . As an example, referring to  FIG. 10A , the first groove side surface  111  may include a first surface connection surface  111   c  disposed between the first inclined surface  111   b  and the surface of the tread portion  100 , and the second groove side surface  112  may include a second surface connection surface  112   c  disposed between the second inclined surface  112   b  and the surface of the tread portion  100 . As another example, referring to  FIG. 10B , the first groove side surface  111  may include a first surface connection surface  111   c,  and the second inclined surface  112   b  of the second groove side surface  112  may be directly connected to the surface of the tread portion  20 . As still another example, the second groove side  112  may include a second surface connection surface  112   c,  and the first inclined surface  111   b  of the first groove side surface  111  may be directly connected to the surface of the tread portion  100 . In addition, the angle “f 1 ” between the first surface connection surface  111   c  and the first inclined surface  111   b  and the angle “f 2 ” between the second surface connection surface  112   c  and the second inclined surface  112   b  may be formed equal to or different from each other. 
     Hereinafter, operation and effects of the pneumatic tire  1  according to the second embodiment of the present disclosure will be described. 
     When the noise reflector  200  is applied to the groove  110 , an area of the groove  110  may be reduced, and thus, the drainage performance may be reduced compared to V 1  as described above. When at least one of the plurality of groove side surfaces  111  and  112  includes the surface connection surfaces  111   c  and  112   c,  an area of the groove  110  can be further secured (the area is increased), and thus, reduced drainage performance can be supplemented. 
     The examples of the present disclosure have been described above as specific embodiments, but these are only examples, and the present disclosure is not limited thereto, and should be construed as having the widest scope according to the technical spirit disclosed in the present specification. A person skilled in the art may combine/substitute the disclosed embodiments to implement a pattern of a shape that is not disclosed, but it also does not depart from the scope of the present disclosure. In addition, those skilled in the art can easily change or modify the disclosed embodiments based on the present specification, and it is clear that such changes or modifications also belong to the scope of the present disclosure.