JP6693711B2 - Soundproof structure for automobiles - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soundproof structure for automobiles, and more particularly to the structure of a sound absorbing material.

  Various types of sound absorbing materials are provided in many parts (on the panel separating the inside and outside of the vehicle) of the vehicle to reduce noise in the vehicle interior. As the sound absorbing material, a fibrous structure or a foam having flexibility that follows fine irregularities of the panel and having many voids is preferably used. The sound absorbing material exerts a sound absorbing action by taking in a sound wave inside the void and attenuating the sound wave. The sound absorbing material also reflects sound waves and prevents sound waves from entering the vehicle interior, thereby exhibiting sound insulation.

  A soundproof structure for an automobile generally has a panel, components such as an instrument panel attached to the vehicle compartment side of the panel, and a sound absorbing material located between the panels (Patent Document 1). 1). The panel that separates the engine room and the passenger compartment in front of the vehicle is called the dash panel, and the sound absorbing material attached to the dash panel is called the dash silencer.

JP, 2002-73036, A

  In order to reduce the noise in the passenger compartment of an automobile, it is important not only to block engine noise and other noise generated outside the passenger compartment but also to suppress noise that attempts to enter the passenger compartment. Part of the noise that enters the vehicle interior is due to the vibration generated by the panels and parts. Panels and parts vibrate due to engine vibrations and vibrations transmitted from the road surface to the vehicle body, generating noise. In the soundproof structure for automobiles disclosed in Patent Document 1, suppression of vibration of panels and parts is not sufficiently taken into consideration.

  In order to suppress the vibration of the panel and the parts, it is considered that the parts are pressure-bonded to the sound absorbing material and the sound absorbing material is elastically compressed between the parts and the panel. As a result, the panel and the parts are pressed down by the sound absorbing material, and vibration is less likely to occur. However, the elastic repulsive force generated by elastically compressing the sound absorbing material may cause deterioration in the mountability of the component or a mounting defect.

  It is an object of the present invention to provide a soundproof structure for an automobile, which can secure good attachment of parts and can suppress vibration of parts and panels.

The soundproof structure for an automobile of the present invention includes a panel that separates the interior and exterior of the vehicle compartment, a component that is located inside the vehicle compartment and fixed to the vehicle, and a sound absorbing material that is sandwiched between the panel and the component. A part of the sound absorbing material has a deformed portion which is pressed by the component and the panel and elastically compressed. Deformations, the whole of the deformation portion, the distance to the two parts is provided in a short position from the deformable portion than the distance between the two closest parts from deformable portion.

  A part of the sound absorbing material is elastically compressed and pressed between the component and the panel. For this reason, the effect of restraining the panel and parts is enhanced, and the vibrations generated by these are suppressed. Since only a part of the sound absorbing material is elastically compressed, the elastic repulsive force of the sound absorbing material is generated only partially. For this reason, it is less likely that the attachment of the component will be deteriorated and the attachment will not be caused due to the elastic repulsive force of the sound absorbing material.

  According to the present invention, it is possible to provide a soundproof structure for an automobile, which can secure good mountability of parts and can suppress vibration of parts and panels.

1 is an external view of a soundproof structure for an automobile according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the automobile soundproof structure taken along line AA of FIG. 1. It is a typical perspective view which expands and shows the convex part integrally formed in the sound-absorbing material. It is a typical sectional view of a convex part of a sound absorbing material. It is a typical perspective view of other embodiment of the convex part of a sound-absorbing material. It is a typical perspective view of other embodiment of the convex part of a sound-absorbing material. FIG. 2 is a schematic cross-sectional view of the automobile soundproof structure taken along the line BB of FIG. 1. FIG. 2 is a schematic cross-sectional view of the automobile soundproof structure taken along the line C-C of FIG. 1. It is a conceptual diagram which shows the positional relationship of a deformation part and two studs. FIG. 9 is a schematic cross-sectional view showing another embodiment of the automobile soundproof structure shown in FIG. 8. It is a typical sectional view of the soundproofing structure for vehicles concerning other embodiments of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Parts and elements having the same function are given the same number, and the description thereof may be omitted.

  The soundproof structure 1 for a vehicle of the present invention is generally applicable to a soundproof structure for a vehicle. Here, the dash panel 20 that separates the engine room and the vehicle room in front of the vehicle and the sound absorbing material 10 (dash silencer) mounted on the dash panel 20 will be described as an example.

  FIG. 1 is a perspective view showing the overall structure of a sound absorbing material 10 attached to a dash panel 20 of an automobile. FIG. 1 is a view of the sound absorbing material 10 as viewed from the passenger compartment side. The left side corresponds to the left front seat of the vehicle and the right side corresponds to the right front seat of the vehicle. The sound absorbing material 10 is attached to the dash panel 20 along the surface of the dash panel 20 on the vehicle interior side. The sound absorbing material 10 is provided between the dash panel 20 and parts (not shown) such as an air conditioner unit and an instrument panel. The sound absorbing material 10 is covered with these components and cannot be visually recognized from the vehicle interior. The sound absorbing material 10 has a soundproof function of insulating or absorbing noise transmitted from the outside of the vehicle compartment, and a vibration damping function of suppressing vibration generated in the dash panel 20 and components. The parts are fixed to the dash panel 20 in a suitable manner and fixed to the vehicle.

  The dash panel 20 is provided with a plurality of openings 20a through which air conditioner ducts, wire harnesses, steering shafts, etc. penetrate, and the sound absorbing material 10 is also provided with openings 10a corresponding thereto. As described in detail later, a stud 40 is attached to the surface of the dash panel 20 on the vehicle interior side, and the sound absorbing material 10 is formed with an opening 10b and a notch 10c. The stud 40 is passed through the opening 10b and the cutout 10c of the sound absorbing material 10, and a fixture (not shown) such as a clip or a nut is locked to the stud 40. Thereby, the sound absorbing material 10 is fixed to the dash panel 20.

As the material of the sound absorbing material 10, foams made of various soft resins or fiber molded bodies made of non-woven fabric are preferably used, and a particularly preferable material is a foam made of soft urethane resin. The sound absorbing material 10 is preferably a density of ^{0.01g / cm 3 ~0.1g / cm 3} , hardness 25N～650N (Evaluation method JIS K 6400-2), more preferably 150～400N. In the present invention, the hardness of the sound absorbing material 10 is particularly important. If the hardness is smaller than the above numerical range (i.e., soft), the rigidity of the sound absorbing material 10 as a whole is insufficient, so that the mounting property of the sound absorbing material 10 on a vehicle may be deteriorated. If the hardness is larger than the above numerical range (if it is hard), the required vibration damping performance for the panel may not be obtained, and when a part of the sound absorbing material 10 is elastically compressed by the component 30, the sound absorbing material is The elastic repulsion force of 10 becomes too strong, and there is a risk of defective mounting of parts or deterioration of mounting workability.

  The lower part of the sound absorbing material 10 is covered with the shock absorbing material 41. The shock absorbing material 41 is arranged in a region in the passenger compartment where the occupant's feet are placed. The front portion of the shock absorbing material 41 is placed on the sound absorbing material 10, and the rear portion thereof is installed on the floor panel. A floor carpet (not shown) is laid on the upper surface of the shock absorber 41, and the shock absorber 41 cannot be visually recognized from the passenger compartment. As a result, the appearance and appearance of the vehicle interior are kept good. The shock absorber 41 is made of a foam material such as polypropylene (PP), polystyrene (PS), and urethane. The shock absorber 41 is placed on the floor panel without using a fixture, but may be fixed to the floor panel with a fixture such as a clip. The shock absorbing material 41 may be incorporated in the floor carpet and placed or fixed on the floor panel together with the floor carpet. The shock absorbing material 41 is provided on each of the left front seat and the right front seat of the vehicle, and the floor tunnel 42 is provided between them.

  The shape and size of the sound absorbing material 10 are determined by the shape and size of the dash panel 20 provided with the sound absorbing material 10. In the case of the embodiment shown in FIG. 1, the shape of the sound absorbing material 10 in a mounted state is a horizontally long rectangular shape, the width (horizontal length) is 900 mm to 1800 mm, and the height (vertical length) is 400 mm. ~ 1200 mm.

  FIG. 2 shows a schematic cross-sectional view taken along the line AA of FIG. The protrusion 13 described below is compressed by the component 30 at the time of mounting, but for convenience, the protrusion 13 in the uncompressed state is shown superimposed on the component 30 (the same applies to FIGS. 7 and 8). The overlapping part is hatched. Referring to part A of FIG. 2, the dash panel 20 and the sound absorbing material 10 have openings 20a and 10a, and the component 30 is attached to the dash panel 20 so as to cover these openings 20a and 10a. The component 30 is fixed to the vehicle. In one example, with the end of the component 30 in contact with the dash panel 20, the component 30 is passed through the stud 40 attached to the dash panel 20, and the nut 43 is fastened to the stud 40. In the present embodiment, the component 30 is an air conditioner unit, but the component is not limited to this, and any component may be used as long as the sound absorbing material 10 is sandwiched between the component 30 and the dash panel 20.

  A convex portion (projection) 13 is provided on the surface 10 d of the sound absorbing material 10 on the vehicle interior side, that is, on the surface of the sound absorbing material 10 opposite to the dash panel 20. Although the convex portion 13 is integrally formed with the constant-thickness portion of the sound absorbing material 10 (hereinafter referred to as the main body 14), the convex portion 13 may be fixed to the main body 14 by an adhesive, fusion bonding, or the like. FIG. 3 shows a perspective view of the convex portion 13. The convex portion 13 has a central opening that substantially coincides with the opening 20a of the dash panel 20 and the opening 10a of the main body 14 of the sound absorbing material 10, and is provided along the entire circumference of the peripheral portion of the opening 10a of the main body 14 of the sound absorbing material 10. There is. The convex portion 13 may be provided partially or intermittently along the peripheral portion of the opening 10a of the main body 14 of the sound absorbing material 10.

  The component 30 is attached to the dash panel 20 so as to press the convex portion 13. As a result, the convex portion 13 of the sound absorbing material 10 and its surroundings are elastically compressed. The other parts of the sound absorbing material 10 are not elastically compressed by the component 30. In the following description, a portion of the sound absorbing material 10 that is pressed between the component 30 and the dash panel 20 and elastically compressed is referred to as a deformed portion 12, and other portions are referred to as a general portion 11. The deforming portion 12 includes a convex portion 13 of the sound absorbing material 10 that is pressed by the component 30. The surface of the sound absorbing material 10 opposite to the convex portion 13 is in contact with the dash panel 20. The general portion 11 of the sound absorbing material 10 may be in contact with the dash panel 20 or may be separated from the dash panel 20.

  The thickness of the general portion 11 of the sound absorbing material 10 is preferably 10 mm to 120 mm, and particularly preferably 20 mm to 80 mm. If the thickness of the general portion 11 is smaller than the above numerical range, it is difficult to secure sound absorption, and if the thickness is larger than the above numerical range, the sound absorbing material 10 is arranged along the dash panel 20 due to lack of flexibility. Becomes difficult. The thickness of the general portion 11 is constant, but may vary depending on the location.

  The thickness of the convex portion 13 of the sound absorbing material 10 is preferably 1 mm to 30 mm, and particularly preferably 5 mm to 20 mm. The amount of compression of the protrusion 13 (the amount of change in thickness due to the pressing of the component 30) is preferably 0 mm to 10 mm (excluding 0 mm), and particularly preferably 2 mm to 6 mm. If the amount of compression of the convex portion 13 is smaller than the above numerical range, the elastic repulsion force is insufficient and sufficient vibration damping performance cannot be obtained. If the compression amount is larger than the above numerical range, the elastic repulsion force becomes too large, and the attachment property is liable to deteriorate and a problem is likely to occur.

  The conventional sound absorbing material is attached to the dash panel and parts without being pressed. Therefore, depending on the dimensional accuracy and mounting accuracy of the sound absorbing material, the sound absorbing material is separated from the component, and engine noise or road noise easily enters the vehicle interior through the gap between the sound absorbing material and the component. According to the present embodiment, the deformable portion 12 of the sound absorbing material 10 has the convex portion 13 and is thicker than the general portion 11. Therefore, the sound absorbing material 10 is elastically compressed by the deforming portion 12, and is strongly adhered to the dash panel 20 and the component 30. Since the convex portion 13 is continuously provided along the opening 10a of the sound absorbing material 10 from which vibration easily enters from the outside of the vehicle interior, the engine enters the vehicle interior through the gap between the opening 10a of the sound absorbing material 10 and the component 30. Noise and road noise are effectively shielded. Moreover, since the dash panel 20 and the component 30 are constrained by the elastic repulsive force of the compressed sound absorbing material 10, these vibrations are suppressed.

  Since the convex portion 13 is locally formed (that is, the sound absorbing material 10 is locally thick), the mountability of the component 30 to the dash panel 20 or the vehicle can be enhanced. When the sound absorbing material is thickly formed on the entire surface, the sound absorbing material is compressed on the entire surface. As a result, the elastic repulsive force that the component 30 receives from the sound absorbing material increases, and the load required to attach the component 30 increases and the workability is likely to deteriorate. On the other hand, in this embodiment, since the convex portion 13 is locally formed, the elastic repulsive force of the sound absorbing material 10 is limited. Therefore, it is possible to improve the vibration damping performance without deteriorating the mountability of the component 30. Even if the dimensions and the positioning accuracy of the sound absorbing material 10 and the component 30 vary, it is possible to avoid a large variation in the elastic repulsive force of the sound absorbing material 10. On the other hand, since the convex portion 13 is formed, the sound absorbing material 10 is reliably pressed between the dash panel 20 and the component 30 even if the dimensions and the positioning accuracy of the sound absorbing material 10 and the component 30 change. Therefore, it is possible to reliably provide the soundproofing performance of the sound absorbing material 10 and the vibration damping performance for the dash panel 20 and the component 30.

  FIG. 4A shows a cross-sectional shape of the convex portion 13 taken along the line DD of FIG. The cross-sectional shape of the convex portion 13 is rectangular or square. The cross-sectional shape of the convex portion 13 is a trapezoidal shape shown in FIG. 4B, a rectangular shape with rounded corners shown in FIG. 4C, a triangular shape with rounded top shown in FIG. 4D, It is also possible to use the semicircular shape shown in FIG. The convex portion 13 shown in FIGS. 4B to 4E has a tapered cross section in which the width gradually decreases toward the tip. Therefore, the strength of the convex portion 13 is increased, the possibility that the convex portion 13 is broken is reduced, and the moldability is improved, and the possibility that defective molding such as a loss of the convex portion 13 occurs is reduced.

  As shown in part B of FIG. 2, the convex portion 13 is provided on the sound absorbing material 10 even when the component 30 is fixed at a position where the opening 20a of the dash panel 20 does not exist. The component 30 is fixed to the vehicle by fixing means (not shown). The convex portion 13 is pressed between the component 30 and the dash panel 20 and elastically compressed. Since the sound absorbing material 10 restrains the dash panel 20 and the component 30, the damping effect on the dash panel 20 and the component 30 is enhanced. The convex portion 13 in the portion B of FIG. 2 has a shape including the concave portion 13a as shown in FIG. 3, and the contact portion between the convex portion 13 and the component 30 is provided along the outer edge of the component 30. Compared to the case where the contact portion is provided in the center of the component 30, the component 30 can be reliably restrained in a wider range, so that the damping effect on the component 30 is enhanced. On the other hand, since the concave portion 13a is provided, the contact area between the convex portion 13 and the component 30 does not increase significantly. Therefore, the elastic repulsive force of the sound absorbing material 10 is limited, and it becomes possible to improve the attachment property. As a result, it is possible to achieve both a vibration damping effect and an attachability that are contradictory to each other.

  FIG. 5 shows another mode applicable to the convex portion 13 of the B part. The convex portion 13 is a set of a plurality of convex portions arranged at intervals shown in FIG. 5 (a), a cross shape shown in FIG. 5 (b), an X shape shown in FIG. 5 (c), and FIG. 5 (d). The S-shape shown in FIG. 5 and the polygonal line shape having a right-angled bent portion shown in FIG. With such a configuration, it is possible to limit the contact area between the component 30 and the convex portion 13 while ensuring the range in which the component 30 is constrained.

  FIG. 6 shows still another aspect applicable to the convex portion 13 of the B portion. The convex portion 13 has a rectangular parallelepiped shape shown in FIG. 6 (a), a cylindrical shape (disc shape) shown in FIG. 6 (b), and a rectangular parallelepiped shape with rounded corners shown in FIG. 6 (c). It may have a truncated cone shape as shown. Also in these modes, increasing the contact area between the component 30 and the convex portion 13 enhances the effect of restraining the dash panel 20 and the component 30.

  FIG. 7 shows a cross-sectional view taken along the line BB of FIG. As shown in part C of FIG. 7, the dash panel 20 is not provided with an opening, and only the sound absorbing material 10 is provided with an opening 10 a. A first fixing member 21 and a second fixing member 22 facing the first fixing member 21 are provided in the opening 10a. The base portion 21a of the first fixing member 21 is welded to the surface of the dash panel 20 on the vehicle interior side. The first fixing member 21 has a first top plate 21b protruding toward the vehicle compartment. The second fixing member 22 has a base portion 22a and a second top plate 22b pulled in from the vehicle compartment side. The first top plate 21b and the second top plate 22b face each other and are fixed to each other by bolts or screws 23. Therefore, the distance between the base portion 21a of the first fixing member 21 and the base portion 22a of the second fixing member 22 is kept constant. The sound absorbing material 10 is sandwiched between the base portion 21 a of the first fixing member 21 and the base portion 22 a of the second fixing member 22. A rib-shaped convex portion 13 surrounding the opening 10a is formed at an edge portion of the sound absorbing material 10 along the opening 10a, that is, a contact portion of the sound absorbing material 10 with the base portion 22a of the second fixing member 22. The convex portion 13 is compressed between the base portion 21a of the first fixing member 21 and the base portion 22a of the second fixing member 22, so that the convex portion 13 is removed from the gap between the base portion 22a of the second fixing member 22 and the sound absorbing material 10. Prevents noise from entering the passenger compartment. The convex portion 13 has the same shape as that shown in FIG. 3, and can take various sectional shapes shown in FIG.

  A similar configuration is also possible when the component 30 is fixed to the dash panel 20 through the opening 10a of the sound absorbing material 10 as shown in part D of FIG. That is, the bottom surface 30 a of the component 30 is fixed to the dash panel 20, and the sound absorbing material 10 is sandwiched between the flange portion 30 b of the component 30 and the dash panel 20. The component 30 is fixed to the vehicle by fixing means (not shown). Although the distance between the bottom surface 30a of the component 30 and the flange portion 30b is constant, the shape is not limited to this and may be a shape that follows the shape of the sound absorbing material 10. A rib-shaped convex portion 13 that surrounds the opening 10a is formed at an edge portion of the sound absorbing material 10 along the opening 10a, that is, a contact portion between the sound absorbing material 10 and the flange portion 30b of the component 30. The convex portion 13 is compressed between the dash panel 20 and the flange portion 30b of the component 30, and blocks noise that enters the vehicle interior through the gap between the flange portion 30b of the component 30 and the sound absorbing material 10. The convex portion 13 has the same shape as that in FIG. 3, and can take various sectional shapes shown in FIG.

  The component 30 may not be directly fixed to the dash panel 20, as shown in part E of FIG. 7. A similar vibration damping effect can be obtained by compressing the sound absorbing material 10 with a component 30 that is fixed at a predetermined position in the vehicle compartment, such as an electrical component such as a harness. The convex portion 13 can have various sectional shapes shown in FIGS.

  FIG. 8 shows a cross-sectional view taken along the line CC of FIG. The dash panel 20 is provided with a fixing portion (stud 40) for fixing the sound absorbing material 10. The stud 40 is welded to the dash panel 20. The stud 40 penetrates the opening 10b provided in the sound absorbing material 10. The claw 51 of the clip 50 is locked in the groove of the stud 40, and the sound absorbing material 10 is fixed to the dash panel 20. The convex portion 13 of the sound absorbing material 10 is provided on the surface on the dash panel 20 side. That is, the deformable portion 12 includes the convex portion 13 provided on the contact portion of the sound absorbing material 10 with the dash panel 20. The deformable portion 12 is provided between the two studs 40. As shown in FIG. 1, the sound absorbing material 10 is supported by the dash panel 20 in a vertical direction or in a posture close to the vertical direction, so that the sound absorbing material 10 is easily separated from the dash panel 20 at a position between the two studs 40. Since the convex portion 13 presses the dash panel 20 even when the sound absorbing material 10 moves in a direction away from the dash panel 20, in addition to the vibration damping effect of the dash panel 20 by the stud 40, the vibration damping effect is obtained even at a position where the stud 40 is not present. Occurs.

  As shown in FIG. 9A, the deformable portion 12 provided with the convex portion 13 is closer to the center of the deformable portion 12 than the center distance L between the two studs 40 a and 40 b closest to the center of the deformable portion 12. It is preferable that the distances L1 and L2 to the centers of the studs 40a and 40b are shorter, and the distances L1 and L2 are provided within hatched areas in the drawing. More preferably, the deformable portion 12 is provided within a range surrounded by the two arcs 44a and 44b, as shown in FIG. 9B. Here, the two arcs 44a and 44b pass through the two studs 40a and 40b, respectively, with the center-to-center distance L between the two studs 40a and 40b closest to the center of the deforming portion 12 as the radius. With such a configuration, it is possible to prevent the sound absorbing material 10 from separating from the dash panel 20 at the deforming portion 12 and to exert a vibration damping function.

  The convex portion may be formed on the dash panel 20 or the component 30 instead of the sound absorbing material 10. An example is shown in FIG. FIG. 10 is a modification of the embodiment shown in FIG. In the present modification, the dash panel 20 is provided with the convex portion 24. In the example shown in FIG. 10A, the convex portion 24 is formed integrally with the dash panel 20. As shown in FIG. 10 (b), the convex portion 24 may be welded to the dash panel 20 by a convex reinforcement 25 that is separate from the dash panel 20, or as shown in FIG. 10 (c). You may weld the stud-shaped convex part 24 to the panel 20. By pressing the clip 50 against the sound absorbing material 10, the portion of the sound absorbing material 10 that is in contact with the convex portion 24 is compressed and the deformed portion 12 is formed. Although not shown, the deformable portion 12 can be formed by forming a convex portion on the surface of the clip 50 on the sound absorbing material 10 side and pressing the clip 50 against the sound absorbing material 10. That is, the deforming portion 12 is provided at a contact portion of the dash panel 20 or the clip 50 (more generally, the component 30 fixed to the vehicle) with the sound absorbing material 10, and the deforming portion 12 of the sound absorbing material 10 is provided. It may be a convex portion that presses.

  In the example of FIGS. 8 and 10, the clip 50 is pushed into the stud 40 until the distance between the clip 50 and the dash panel 20 becomes substantially equal to the thickness of the sound absorbing material 10, and is locked to the stud 40. The sound absorbing material 10 may be elastically compressed by further pressing the clip 50. With such a configuration, the vibration damping performance can be further enhanced.

  Furthermore, the present invention does not need to have a convex portion, and it is sufficient that a part of the sound absorbing material 10 has the deforming portion 12 that is pressed between the component 30 and the dash panel 20 and elastically compressed. As shown in FIG. 11, by bringing the mounting position of the component 30 closer to the dash panel 20, a part of the sound absorbing material 10 can be pressed by the component 30 to form the deformed portion 12 in the sound absorbing material 10.

1 Soundproof Structure for Automobile 10 Sound Absorbing Material 10a Opening 10b Notch 11 General Part 12 Deforming Part 13, 24 Convex Part 20 Dash Panel 20a Opening 30 Parts 41 Shock Absorbing Material 50 Stud

Claims (5)

A panel that separates the interior and exterior of the vehicle, a component that is located inside the vehicle and fixed to the vehicle, and a sound absorbing material that is sandwiched between the panel and the component,
The portion of the sound absorbing material, said component and having a deformable portion which is being pressed resiliently compressed by said panel, the deformable portion is entirely of the deformable portion, the nearest two of said components from the flexible portion A soundproof structure for an automobile, which is provided at a position where a distance from the deformed portion to the two components is shorter than a distance therebetween.   The soundproof structure for an automobile according to claim 1, wherein the deformed portion of the sound absorbing material has a convex portion.   The soundproof structure for an automobile according to claim 1, wherein the panel or the component has a convex portion that presses the deformed portion of the sound absorbing material.   The vehicle soundproofing structure according to claim 2, wherein the convex portion is provided along an opening of the sound absorbing material.   The soundproof structure for a vehicle according to claim 4, wherein the convex portion extends along the entire circumference of the opening.

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