JP2016187294A - Grommet and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grommet capable of enhancing sound-proof effect without inviting size increase.SOLUTION: A grommet 10 supports a wire harness WH to a panel P by being fixed to the wire harness WH inserted into an opening 1 of the panel P and being fitted to the opening 1 to be mounted. The grommet includes: partition walls 21 and 22 forming a sound-proof space S around the wire harness WH by covering the surrounding of the wire harness WH; and a sound-proof wall 25 formed in the sound-proof space S so as to cross against a longer direction of the wire harness WH.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a grommet for supporting a wire harness passed through an opening of a panel on the panel and a manufacturing method thereof.

  As a grommet for supporting a wire harness passed through an opening of a panel on the panel, one having an air layer formed therein is known (for example, see Patent Documents 1 to 4).

JP2012-125002A JP 2001-153270 A JP 2014-50153 A JP 2002-27641 A

  As described above, the grommet provided with the air layer can suppress the transmitted sound transmitted through the grommet with the air layer. However, in order to increase the soundproofing effect, it is necessary to increase the capacity of the air layer or to increase the thickness of the peripheral wall forming the air layer, leading to an increase in the size of the grommet.

  This invention is made | formed in view of the situation mentioned above, The objective is to provide the grommet which can improve the soundproofing effect, without causing the enlargement, and its manufacturing method.

In order to achieve the above-described object, the grommet according to the present invention is characterized by the following (1) to (8).
(1) A grommet that supports the wire harness on the panel by being fixed to a wire harness that is inserted into the opening of the panel and fitted into the opening.
A peripheral wall that covers the periphery of the wire harness and forms a sound insulation space around the wire harness;
A grommet, comprising: a soundproof wall formed in the sound insulation space so as to intersect with a longitudinal direction of the wire harness.
(2) The grommet according to (1), wherein the plurality of soundproof walls are formed in parallel at intervals.
(3) The grommet according to (2), wherein a sound absorbing material is provided between the sound barriers.
(4) The grommet according to any one of (1) to (3), wherein the soundproof wall has a through hole through which the wire harness passes, and the wire harness and the through hole are in close contact with each other. .
(5) having a long cylindrical portion to be mounted on the outer periphery of the wire harness;
A pair of the peripheral walls formed in a conical shape whose diameter gradually narrows away from the panel fixing part is provided on both sides in the axial direction of the panel fixing part attached to the opening of the panel,
The inner peripheral end of the peripheral wall that is farthest away from the panel fixing portion is disposed adjacent to the outer periphery of the long cylindrical portion in a non-joined state, so that the sound insulation space is defined between the long cylindrical portion and the peripheral wall. Made,
The outer peripheral end of the soundproof wall is coupled to the inner periphery of the panel fixing portion, and the inner peripheral end of the soundproof wall is coupled to the outer periphery of the long cylindrical portion, so that the sound insulating space is pivoted by the soundproof wall. The grommet according to (1), wherein the grommet is divided in a direction.
(6) The grommet according to (5), wherein the soundproof wall is formed as an annular corrugated wall.
(7) The sound insulation space is divided into a plurality in the axial direction by the sound barrier,
(1) to (6) above, wherein the cancellation frequency at which the sound wave is canceled by the axial reflection in the divided sound insulation space is included in the target frequency band of the sound wave to be attenuated. Either grommet.
(8) The grommet according to (7), wherein a ratio of lengths in the axial direction of two sound insulation spaces among the plurality of divided sound insulation spaces is set to 2: 1.

In the grommet having the configuration (1), sound transmitted from one side of the panel to the other side through the opening of the panel can be reduced in the sound insulation space, and further, can be greatly reduced by the soundproof wall. . For example, if a grommet is provided on the dash panel of the vehicle, it is possible to reliably suppress the sound in the engine room from being transmitted into the vehicle through the opening.
Thereby, compared with the case where the sound insulation space is increased or the peripheral wall is thickened in order to enhance the soundproofing effect, the soundproofing effect can be significantly increased and the material cost can be suppressed without increasing the size. Further, the mounting work is not complicated by increasing the thickness of the partition wall.
In the grommet having the configuration (2), a higher soundproofing effect can be obtained by providing a plurality of soundproofing walls.
In the grommet having the configuration (3), the transmitted sound can be absorbed by the sound absorbing material provided between the soundproof walls, and a higher soundproofing effect can be obtained.
In the grommet having the configuration (4), leakage of transmitted sound between the through hole of the soundproof wall and the wire harness can be prevented, and the soundproof effect on the soundproof wall can be obtained with certainty.
In the grommet configured as described in (5) above, the inner peripheral ends of the pair of conical peripheral walls are disposed in close proximity to the outer periphery of the long cylindrical portion attached to the outer periphery of the wire harness. Intrusion of external sound can be reduced and sound insulation can be increased. In addition, since the outer peripheral edge and inner peripheral edge of the soundproof wall arranged inside the sound insulating space are respectively connected to the inner periphery of the panel fixing part and the outer periphery of the long cylindrical part, the sound insulating space can be divided while keeping airtightness. In addition, leakage of transmitted sound between the divided spaces can be prevented, and a soundproof effect can be reliably obtained by the soundproof wall.
In the grommet configured as described above (6), since the soundproof wall is formed as an annular corrugated wall, the incident sound hitting the corrugated wall is reflected while being diffused. Therefore, the waves of the incident sound and the reflected sound are reflected. The cancellation becomes active and the sound insulation is increased. In addition, the sound reduction effect of the soundproof wall can be enhanced without particularly increasing the thickness of the soundproof wall.
In the grommet configured as described above (7), each cancellation frequency of the divided plurality of sound insulation spaces is included in the target frequency band to be attenuated. It can be effectively suppressed.
In the grommet configured as described above (8), the ratio of the lengths in the axial direction of the two sound insulation spaces among the divided sound insulation spaces is set to 2: 1. The sound that is resonance-amplified in one sound insulation space of the ratio can be canceled in the other sound insulation space.

In order to achieve the above-mentioned object, the grommet manufacturing method according to the present invention is characterized by the following (9).
(9) The method for producing a grommet according to any one of (1) to (8) above, wherein an internal mold for forming the internal shape of the grommet is divided into two in the axial direction with the soundproof wall as a boundary, After forming the grommet, one of the two divided internal dies is punched to one side relatively to the molded grommet, and the other of the two divided internal dies. A method for producing a grommet, wherein the inner mold is die-cut relative to the molded grommet on the other side.

  According to the method for manufacturing a grommet having the configuration (9), the divided internal mold can be relatively removed from the grommet without the molded soundproof wall getting in the way. Therefore, an integral structure grommet including the soundproof wall can be easily formed.

  According to the present invention, it is possible to provide a grommet capable of enhancing the soundproofing effect without causing an increase in size.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is a perspective view of a dash panel to which a grommet is attached. FIG. 2 is a cross-sectional view of the grommet according to the first embodiment. FIG. 3 is a cross-sectional view of a grommet according to a reference example. FIG. 4 is a diagram for explaining the soundproof effect by the soundproof wall, and (a) to (c) are schematic cross-sectional views of the soundproof wall, respectively. FIG. 5 is a cross-sectional view of a grommet according to a modification. 6 is a cross-sectional view for explaining an internal mold for molding the grommet of FIG. FIG. 7 is a cross-sectional view for explaining an internal mold for molding a grommet according to another modification. FIG. 8 is a cross-sectional view of the grommet according to the second embodiment. FIG. 9 is a cross-sectional view for explaining an internal mold for molding the grommet of FIG. FIG. 10 is a diagram for explaining the principle when the axial length of the sound insulation space is set. FIG. 10A shows the function of resonance amplification for the sound of the sound insulation space (air column is a model) having a wavelength λ. FIG. 10B is a diagram showing the conditions when the sound insulation space (air column is a model) performs the function of canceling the sound of wavelength λ. FIG. 11 is an explanatory diagram of a setting example of specific dimensions of the grommet according to the embodiment of FIG.

Hereinafter, an example of an embodiment according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a dash panel to which a grommet is attached. FIG. 2 is a cross-sectional view of the grommet according to the first embodiment of the present invention.

  As shown in FIGS. 1 and 2, the grommet 10 according to the first embodiment is mounted on a panel P such as a dash panel of a vehicle such as an automobile. The panel P is provided between the engine room and the vehicle interior. An opening 1 is formed in the panel P, and the wire harness WH is inserted through the opening 1. Thereby, the wire harness WH is wired over the front and back of the panel P. For example, the wire harness WH is configured such that a wire bundle is passed through a tube-shaped exterior.

  The grommet 10 is made of an elastic material such as rubber or elastomer, and has a circular shape in plan view (as viewed from the axial direction). The grommet 10 has harness fixing portions 11 and 12 at both end portions in the axial direction, and a panel fixing portion 13 at an intermediate portion in the axial direction. The harness fixing portions 11 and 12 are arranged with a space therebetween, and the panel fixing portion 13 is arranged at substantially the center of these harness fixing portions 11 and 12. The harness fixing portions 11 and 12 have harness insertion holes 1la and 12a, and the wire harness WH is inserted through the harness insertion holes 11a and 12a.

  The panel fixing portion 13 has an engagement groove 13a extending in the circumferential direction, and the edge portion of the opening 1 of the panel P is engaged with the engagement groove 13a. Thereby, the grommet 10 is attached to the panel P.

  In the grommet 10, the harness fixing portions 11 and 12 and the panel fixing portion 13 are connected by partition walls (peripheral walls) 21 and 22. Each of the partition walls 21 and 22 has a conical shape that narrows from the panel fixing portion 13 toward the harness fixing portions 11 and 12. The grommet 10 has a sound insulation space S in the space surrounded by the partition walls 21 and 22.

  The grommet 10 has two soundproof walls 25 in the sound insulation space S. These soundproof walls 25 are integrally formed on the inner peripheral side of the panel fixing portion 13 which is an engagement portion engaged with the edge of the opening 1 by fitting the grommet 10 into the opening 1. The soundproof wall 25 is disposed so as to intersect the longitudinal direction (axial direction) of the wire harness WH. These soundproof walls 25 are arranged with a gap therebetween. The sound insulation space S surrounded by the partition walls 21 and 22 is divided into a plurality of sound insulation walls 25.

  Each soundproof wall 25 is formed with through holes 25a, and the wire harness WH is inserted through these through holes 25a. The inner peripheral portion of the through hole 25a is in close contact with the outer peripheral surface of the wire harness WH without a gap.

  The grommet 10 is fitted to the panel P by being fitted into the opening 1 of the panel P and engaging the edge of the opening 1 with the engaging groove 13a, whereby the wire harness WH is attached by the grommet 10. Supported by panel P. Thus, when the grommet 10 is fitted into the opening 1 of the panel P, the opening 1 is sealed with the grommet 10.

  The grommet 10 has a sound insulation space S, and further has a sound insulation wall 25 in the sound insulation space S. Therefore, the sound of the engine room is reduced in the sound insulation space S and further greatly reduced in the soundproof wall 25. Thereby, it is suppressed that the sound of an engine room is transmitted through the opening part 1 into a vehicle interior.

Here, the grommet 100 which concerns on a reference example is demonstrated.
FIG. 3 is a cross-sectional view of a grommet according to a reference example.

  As shown in FIG. 3, the grommet 100 according to the reference example has no soundproof wall 25 in the sound insulation space S. In this grommet 100, the sound of the engine room is reduced in the sound insulation space S, but the sound insulation effect by the sound insulation wall 25 cannot be obtained.

  In the grommet 100 having such a structure, the soundproofing effect can be slightly increased by increasing the sound insulation space S or increasing the thickness of the partition walls 21 and 22. However, if the sound insulation space S is increased or the thicknesses of the partition walls 21 and 22 are increased, an increase in the size of the grommet 100 cannot be avoided, and the material cost increases. In addition, when the partition walls 21 and 22 are thickened, it becomes difficult to elastically deform the grommet 10O, and the mounting operation of the panel P to the opening 1 becomes complicated.

  On the other hand, according to the grommet 10 according to the present embodiment, the soundproofing effect can be greatly enhanced by forming the soundproofing wall 25 without increasing the soundproofing space S or thickening the partition walls 21 and 22. it can. That is, the soundproofing effect can be significantly increased and the material cost can be suppressed without enlarging the sound insulation space S or increasing the thickness of the partition walls 21 and 22. In addition, the mounting work is not complicated by increasing the thickness of the partition walls 21 and 22.

  In addition, since the plurality of soundproof walls 25 are formed in parallel at intervals, a high soundproof effect can be obtained by the plurality of soundproof walls 25.

  In addition, since the soundproof wall 25 is formed on the inner peripheral side of the panel fixing portion 13 that is an engagement portion where the edge of the opening 1 is engaged by fitting the grommet 10 into the opening 1, the grommet The transmitted sound that passes through 10 will surely pass through the soundproof wall 25. Thereby, the soundproof effect can be reliably obtained by the soundproof wall 25.

  Further, since the wire harness WH and the through hole 25a are in close contact with each other, leakage of transmitted sound between the through hole 25a of the soundproof wall 25 and the wire harness WH is prevented, and the soundproof effect at the soundproof wall 25 is ensured. Can be obtained.

  In the above embodiment, the case where the two soundproof walls 25 are provided has been described as an example. However, the soundproof wall 25 may be one, or may be three or more. By increasing the number of the soundproof walls 25, a higher soundproofing effect can be obtained.

Hereinafter, a specific soundproof effect will be described.
FIG. 4 is a diagram for explaining the soundproof effect by the soundproof wall, and (a) to (c) are schematic cross-sectional views of the soundproof wall, respectively.

  As shown in FIG. 4A, when two soundproof walls 25 having a soundproof effect of 10 dB for reducing a sound of 60 dB to 50 dB are arranged in parallel as shown in FIG. Soundproofing effect (10 dB + 10 dB) can be obtained. Thus, by arranging a plurality of soundproof walls 25, it is possible to obtain a soundproof effect obtained by adding the number of soundproof effects. Further, as shown in FIG. 4C, when the soundproof wall 25 having a thickness of 4 mm, which is twice the thickness, is provided, a soundproof effect of 16 dB (10 dB + 20 log 102 dB) can be obtained. Thus, the soundproof effect can be enhanced by increasing the thickness of the soundproof wall 25.

Next, a modified example of the grommet according to the present embodiment will be described.
Note that the same components as those of the grommet 10 described above are denoted by the same reference numerals and description thereof is omitted.
FIG. 5 is a cross-sectional view of a grommet according to a modification.

  As illustrated in FIG. 5, the grommet 10 </ b> A according to the modification includes a sound absorbing material 31 such as glass wool or urethane foam between the soundproof walls 25. According to the grommet 10A in which the sound absorbing material 31 is provided between the soundproof walls 25, the transmitted sound can be absorbed by the soundproof wall 25 and the sound absorbing material 31, and a higher soundproofing effect can be obtained.

Next, the manufacturing method of the grommet 10 (10A) of the said embodiment is demonstrated.
The grommet 10 is obtained as a molded product by injecting a molten material into a cavity in a mold and releasing the mold after the material is solidified. As the mold, an external mold for forming the shape of the outer peripheral surface of the grommet 10 and an internal mold for forming the shape of the inner peripheral surface are used.

FIG. 6 shows the relationship between the grommet 10 and the inner molds 40A and 40B.
As shown in FIG. 6, in the manufacturing method of the grommet 10 of this embodiment, the internal metal mold | die which shape | molds the internal shape of the grommet 10 is divided into 2 in the axial direction on the boundary of the soundproof wall 25. As shown in FIG. Then, after the grommet 10 is molded, one of the two divided inner dies 40A is die-cut relative to the molded grommet 10 on one side in the axial direction (arrow A direction). In addition, the other inner mold 40 </ b> B of the two divided inner molds is die-cut to the other axial side (arrow B direction) relative to the molded grommet 10. Thus, the grommet 10 as a molded product can be obtained.

  By manufacturing in this way, the divided internal dies 40A and 40B can be relatively removed from the grommet 10. Therefore, it is possible to easily mold the grommet 10 having an integral structure including the soundproof wall 25.

  In the case of the example shown in FIG. 6, since the two soundproof walls 25 are provided, the mold can be released by expanding the soundproof wall 25 on one side. As shown in FIG. 7, when there is one soundproof wall 25, the internal dies 41A and 41B can be more easily pulled out in the directions of arrows A and B.

  When releasing the internal mold, if the air is blown between the grommet 10 and the internal molds 40A, 40B, 41A, 41B to expand the grommet 10, the internal mold 40A, 40B, 41A, 41B can be pulled out.

Next, a grommet and a manufacturing method thereof according to another embodiment of the present invention will be described.
FIG. 8 is a cross-sectional view showing the configuration of the grommet according to the second embodiment of the present invention, and FIG. 9 is a cross-sectional view for explaining an internal mold for molding the grommet.

  As shown in FIG. 8, the grommet 50 is made of an elastic material such as rubber or elastomer, and is attached to the opening 1 of the panel P. The grommet 50 includes a pair of annular peripheral walls (partition walls) 61 and 62 that form a sound insulation space S around the wire harness WH, an annular panel fixing portion 53 that is positioned at an intermediate portion in the axial direction of the grommet 50, and a peripheral wall 61, 62 and a cylindrical long cylindrical portion 54 that is disposed on the inner peripheral side of the wire harness WH and is mounted on the outer periphery of the wire harness WH.

  The panel fixing portion 53 has an engaging groove 53a extending in the circumferential direction, and the grommet 50 is attached to the panel P by engaging the edge of the opening 1 of the panel P with the engaging groove 53a. . The pair of peripheral walls 61 and 62 are connected to both sides in the axial direction of the panel fixing portion 53 attached to the opening 1 of the panel P, and have a conical shape (tapered tube) whose diameter gradually decreases as the distance from the panel fixing portion 53 increases. Formed). And the cylindrical part 51, 52 concentric with the long cylinder part 54 is provided in the inner peripheral end farthest from the panel fixing | fixed part 53 of these cone-shaped surrounding walls 61, 62, and these cylindrical parts 51, 52 are long cylinders. Annular gaps 56 and 57 are formed on the outer periphery of the portion 54 so as to be adjacent to each other in a non-joined state. Thereby, a sound insulation space S is defined between the long cylindrical portion 54 and the peripheral walls 61 and 62.

  Further, the grommet 50 has a soundproof wall 75 formed as one annular corrugated wall in the sound insulation space S. The soundproof wall 75 is arranged on the inner peripheral side of the panel fixing portion 13 so as to intersect the longitudinal direction of the wire harness WH. The outer peripheral end 75 a of the soundproof wall 75 is coupled to the inner periphery of the panel fixing portion 53. In addition, the inner peripheral end 75 b of the soundproof wall 75 is coupled to the outer periphery of the long cylindrical portion 54. Thereby, the sound insulation space S surrounded by the peripheral walls 61 and 62 is divided into two sound insulation spaces S1 and S2 in the axial direction by the sound insulation wall 75.

  Here, the annular corrugated wall forming the soundproof wall 75 is obtained by forming an annular wall plate into a concentric corrugated waveform. The waveform includes a bellows shape.

  The grommet 50 is attached to the panel P by fitting into the opening 1 of the panel P and engaging the edge of the opening 1 with the engaging groove 53 a of the panel fixing portion 53. Thereby, the wire harness WH is supported by the panel P by the grommet 50. As described above, when the grommet 50 is fitted into the opening 1 of the panel P, the opening 1 is sealed with the grommet 50.

  The grommet 50 has a sound insulation space S surrounded by the peripheral walls 61 and 62, and further has a sound insulation wall 75 in the sound insulation space S. Therefore, the sound of the engine room is reduced by the two peripheral walls 61 and 62 and the one soundproof wall 75 which are multiple soundproof walls, and is also reduced by the sound insulation space S. Thereby, it is suppressed that the sound of an engine room is transmitted through the opening part 1 into a vehicle interior.

  In particular, since the soundproof wall 75 is formed as an annular corrugated wall, incident sound hitting the corrugated wall is reflected while being diffused. Therefore, the cancellation of the waves of the incident sound and the reflected sound becomes active and the sound insulation is improved. In addition, since the soundproof wall 75 is disposed at the panel fitting position in the center of the grommet 50 through which the transmitted sound always passes, reliable soundproof performance can be exhibited. Therefore, even if the thickness of the soundproof wall 75 is not particularly increased, a high sound reduction effect by the soundproof wall 75 can be obtained.

  Moreover, in this grommet 50, since the cylindrical parts 51 and 52 provided in the inner peripheral end of a pair of surrounding wall are arrange | positioned close to the outer periphery of the long cylinder part 54 with which the outer periphery of a wire harness is mounted | worn, it is sound-insulating Intrusion of external sound into the space S can be reduced as much as possible, and sound insulation can be increased. Further, after passing WH inside the long cylindrical portion 54, if the cylindrical portions 51, 52 are tightened together with the long cylindrical portion 54 with a tie band or tape 78, the space between the cylindrical portions 51, 52 and the long cylindrical portion 54 is obtained. Since the intrusion of sound from the annular gaps 56 and 57 can be blocked, further improvement in soundproofing can be achieved. In this case, a band retaining portion 85 for preventing the tie band or tape 78 from falling off at the axially distal end of the cylindrical portion 52, that is, the position farthest from the panel fixing portion 53, is integrated with the cylindrical portion 52. It is preferable to stand upright.

  Further, since the soundproof wall 75 disposed inside the sound insulation space S has the outer peripheral end 75a and the inner peripheral end 75b coupled to the inner periphery of the panel fixing portion 53 and the outer periphery of the long cylindrical portion 54, respectively. S can be divided into two while being airtight. Therefore, leakage of transmitted sound between the two sound insulation spaces S1 and S2 divided into two can be reliably prevented, and the soundproof effect by the soundproof wall 75 can be further enhanced.

  As a result, the soundproofing effect can be greatly increased without increasing the size as compared with the case where the soundproofing space S is increased or the peripheral walls 61 and 62 are thickened in order to enhance the soundproofing effect. Costs can be reduced. Further, the mounting work by increasing the thickness of the peripheral walls 61 and 62 is not complicated.

  Also in the grommet 50, by filling the sound insulating space S with a sound absorbing material, the transmitted sound can be further absorbed, and a higher soundproofing effect can be obtained.

  Moreover, in the grommet 50 shown in FIG. 8, in order to relieve | assemble the assembly stress at the time of making it fit in the panel P, the curved part 83 curved in the S shape in the peripheral wall 62 at the panel fixing | fixed part 53 side of the cylindrical part 52. Are connected. Of course, the curved portion 83 may be employed in other grommets such as the grommets 10 and 10A described above, and the assembly stress can be alleviated in any case.

Next, a method for manufacturing the grommet 50 will be described.
The grommet 50 is obtained as a molded product by injecting a molten material into a cavity in a mold and releasing the mold after the material is solidified. As the mold, an external mold that molds the shape of the outer peripheral surface of the grommet 50 and an internal mold that molds the shape of the inner peripheral surface are used.

FIG. 9 shows the relationship between the grommet 50 and the internal molds 80A, 80B, 80C.
As shown in FIG. 9, in the manufacturing method of the grommet 50 of this embodiment, the three internal metal mold | die which shape | molds the internal shape of the grommet 50 is used. That is, the internal mold that forms the sound insulation space S (see FIG. 8) is divided into two axially with the soundproof wall 75 as a boundary, and the first internal mold 80A on one side in the axial direction and the first internal mold 80A on the other side in the axial direction. The second internal mold 80B is used. Further, a third internal mold 80C for molding the inner periphery of the long cylindrical portion 54 is used.

  After forming the grommet 50 using the first to third internal molds 80A to 80C, the first internal mold 80A is divided into two divided internal molds. Then, the die is removed in one axial direction (arrow A direction) relative to the molded grommet 50. In addition, the second internal mold 80 </ b> B of the two internal molds is die-cut to the other axial side (arrow B direction) relative to the formed grommet 50. Further, the third internal mold 80C is die-cut to one side (arrow C direction) or the other side. Thus, the grommet 50 as a molded product can be obtained.

  When the grommet 50 is manufactured in this way, the divided internal molds 60A and 80B can be relatively removed from the grommet 50 without the molded soundproof wall 75 being in the way. Therefore, the grommet 50 having an integral structure including the soundproof wall 75 can be easily formed.

  Also in this case, when the inner molds 80A to 80C are released, if the air is blown between the grommet 50 and the inner molds 80A and 80B to expand the grommet 50, the inner mold 80A can be more easily removed from the grommet 50. 80B can be pulled out.

  By the way, in the case of a grommet having a sound insulation space (also referred to as an air layer or an air chamber) as described above (common to the grommets of each embodiment), the sound waves cancel each other due to the influence of sound reflection in the sound insulation space. Or, conversely, resonance amplification of sound waves may occur. As a result, there exists a sound having a frequency that is easily attenuated by grommet and a frequency that is easily transmitted.

For example, consider a condition that causes resonance amplification of sound using an air column model.
FIG. 10 is a diagram for explaining the principle when the axial length of the sound insulation space is set. FIG. 10A shows the function of resonance amplification for the sound of the sound insulation space (air column is a model) having a wavelength λ. FIG. 10B is a diagram showing the conditions when the sound insulation space (air column is a model) performs the function of canceling the sound of wavelength λ.

  In the case of the air column model of both ends occlusion type, as shown in FIG. 10A, when the length of the air column is L = λ / 2 with respect to the sound of wavelength λ, a standing wave having nodes at both ends is generated. Under these conditions, resonance amplification occurs. The same thing occurs when L = (λ / 2) · N (where N = 1, 2, 3,...).

  On the other hand, considering the conditions opposite to those in the case of resonance amplification, as shown in FIG. 10B, when the air column length L = λ / 4 with respect to the sound of wavelength λ, the canceling action by the reflected sound is exerted. Occur. In this case, the same thing occurs when L = (λ / 4) · N (where N = 1, 3, 5,...).

Expressing the above two conditions with different equations,
The condition for resonance amplification is f = (cN) / (2L) (1)
・ The condition for cancellation is f = (cN) / (4L) (2)
It becomes.

Where f: frequency (Hz)
L: Length of sound insulation space in the axial direction (m)
c: speed of sound (m / sec) = about 340 m / s
λ: Wavelength (m)
N in the formula (1) is N = 1, 2, 3,.
N in the formula (2) is N = 1, 3, 5,.
It is.

  According to the principle explained in the above air column model, in the grommets of the above embodiments, each cancellation frequency of the sound insulation space S (S1, S2) divided into a plurality by the sound insulation wall tends to attenuate. It is desirable to be included in the target frequency band.

  For example, if the frequency band (target frequency band) of the sound whose transmission is to be suppressed is 2000 to 6000 Hz among the frequencies of the sound to be transmitted from the vehicle interior to the vehicle interior, the above case where f = 2000 to 6000 is used. If the length in the axial direction of each sound insulation space is set to the length L obtained from the equation (2), it is possible to effectively suppress the transmission of sound in the target frequency band.

  At this time, it is preferable that the resonance amplification conditions do not overlap among the plurality of sound insulation spaces. Specifically, when the axial lengths of the plurality of sound insulation spaces are different, for example, the condition is set by changing the cancellation frequency of the large sound insulation space to 3000 Hz and the cancellation frequency of the small sound insulation space to 5000 Hz. .

  In particular, when the ratio of the length of the large sound insulation space to the length of the small sound insulation space is set to 2: 1, it becomes possible to cancel the sound amplified in resonance in one sound insulation space in the other sound insulation space. Can cover a wide range.

FIG. 11 is an explanatory diagram of a setting example of specific dimensions of the grommet according to the embodiment shown in FIG.
The cylindrical portions 51 and 52 at both ends are tightened together with the long cylindrical portion 54 with a tie band or tape 78 (see FIG. 8) after passing the wire harness WH through the long cylindrical portion 54. By doing so, the annular gaps 56 and 57 between the cylindrical portions 51 and 52 and the long cylindrical portion 54 are sealed.

  The length in the axial direction of the sound insulation space S1 on one side (eg, engine room) OUT of the panel P where sound enters is L1, and the length of the sound insulation space S2 on the other side (eg, vehicle interior side) IN of the panel P. Is set to L2, L1 and L2 are calculated and set by the above equation (2) based on the target frequency f. At that time, it is preferable to set L1: L2 to 2: 1. For example, when L1 = 40 mm, L1 = 20 mm.

  Actually, in view of the above-described principle of resonance and cancellation, L1 and L2 should be optimized through experiments.

  Next, a suitable material for the grommet for further improving soundproofing will be described. Here, the grommet 10 will be described as an example, but the same applies to the grommets 10A and 50.

It is known that the soundproofing performance of a wall made of a dense and uniform material is represented by the following formula (3).
TLo = 20 log (f × M) -42.5 (dB) (3)
Here, TLo means transmission loss (dB), f means frequency (Hz), and M means material density (kg / m ³ ).

As described above, rubber is generally used for the grommet 10, but as is clear from the equation (3), by increasing the material density M, it is possible to increase sound transmission loss and improve soundproofing. Become. Accordingly, the density of the grommet 10 is increased by mixing an inorganic substance such as a calcium carbonate-based material into rubber or elastomer. Alternatively, a material with high density such as polysulfide rubber or fluororubber may be used. The material density is preferably 1100 kg / m ³ or more.

  Moreover, since the vibration of the grommet 10 is also suppressed by increasing the material hardness, the soundproofness can be improved. The hardness is preferably 45 or more.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimensions, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  For example, in the above-described embodiment, the case where the grommets 10, 10A, 50 are mounted on the panel P including the dash panel has been described as an example. However, the panel P on which the grommets 10, 10A, 50 are mounted is not limited to the dash panel. . For example, if the grommets 10, 10A, 50 are attached to a rear panel provided at the rear part of the vehicle or a door panel provided at the door of the vehicle, noise transmitted to the rear of the vehicle or through the door can be suppressed.

Here, the characteristics of the embodiment of the grommet according to the present invention and the characteristics of the manufacturing method thereof are briefly summarized and listed in the following (1) to (9), respectively.
(1) It is fixed to the wire harness (WH) inserted through the opening (1) of the panel (P),
A grommet (10, 10A, 50) that supports the wire harness (WH) on the panel (P) by being fitted and fitted into the opening (1),
A peripheral wall (partition walls 21, 22, 61, 62) that covers the periphery of the wire harness (WH) and forms a sound insulation space (S) around the wire harness (WH);
And a soundproof wall (25, 75) formed in the sound insulation space (S) so as to intersect the longitudinal direction of the wire harness (WH).
(2) The grommet according to (1), wherein the plurality of soundproof walls (25) are formed in parallel at intervals.
(3) The grommet according to (2), wherein a sound absorbing material (31) is provided between the soundproof walls (25).
(4) The soundproof wall (25) has a through hole (25a) through which the wire harness (WH) passes, and the wire harness (WH) and the through hole (25a) are in close contact with each other. The grommet according to any one of (1) to (3).
(5) having a long cylindrical portion (54) attached to the outer periphery of the wire harness (WH);
A pair of conical shapes whose diameter gradually narrows with increasing distance from the panel fixing portion (53) on both sides in the axial direction of the panel fixing portion (53) attached to the opening (1) of the panel (P). The peripheral walls (61, 62) are provided;
Inner peripheral ends (cylindrical portions 51, 52) of the peripheral walls (61, 62) spaced apart from the panel fixing portion (53) are arranged close to the outer periphery of the long cylindrical portion (54) in a non-bonded state. And the sound insulation space (S) is defined between the long cylindrical portion (54) and the peripheral wall (61, 62).
The outer peripheral end (75a) of the soundproof wall (75) is coupled to the inner periphery of the panel fixing portion (53), and the inner peripheral end (75b) of the soundproof wall (75) is the long cylindrical portion (54). The grommet according to claim 1, wherein the sound insulation space (S) is divided in the axial direction by the soundproof wall (75) by being coupled to an outer periphery of the grommet.
(6) The grommet according to claim 5, wherein the soundproof wall (75) is formed as an annular corrugated wall.
(7) The sound insulation space (S) is divided into a plurality of portions in the axial direction by the sound barriers (25, 75),
The canceling frequency at which the sound wave is canceled by the reflection in the axial direction in the divided sound insulating space (S1, S2) is included in the target frequency band of the sound wave to be attenuated. The grommet according to any one of 6.
(8) The ratio of the lengths (L1, L2) in the axial direction of the two sound insulation spaces (S1, S2) among the divided sound insulation spaces (S1, S2) is set to 2: 1. The grommet according to claim 7 characterized by things.
(9) The method for producing a grommet according to any one of (1) to (8) above,
An internal mold for forming the internal shape of the grommet (10, 10A, 50) is divided into two axially with the soundproof wall (25, 75) as a boundary, and the grommet (10, 10A, 50) is formed. After that, one of the two inner molds (40A, 41A, 80A) is die-cut relative to the molded grommet (10, 10A, 50) on one side, The other internal mold (40B, 41B, 81B) of the two divided internal molds is die-cut relative to the molded grommet (10, 10A, 50) on the other side. Grommet manufacturing method.

1 Opening 10, 10A Grommet 21, 22 Partition (peripheral wall)
25 Soundproof wall 25a Through hole 31 Sound absorbing material 50 Grommet 51, 52 Cylindrical portion (inner peripheral end)
53 Panel fixing part 54 Long cylindrical part 61, 62 Peripheral wall 75 Soundproof wall 75a Outer peripheral end 75b Inner peripheral end P Panel S, S1, S2 Sound insulation space L1, L2 Axial length WH Wire harness

Claims (9)

A grommet that supports the wire harness on the panel by being fixed to a wire harness that is inserted through the opening of the panel, and fitted into the opening.
A peripheral wall that covers the periphery of the wire harness and forms a sound insulation space around the wire harness;
A grommet, comprising: a soundproof wall formed in the sound insulation space so as to intersect with a longitudinal direction of the wire harness. The grommet according to claim 1, wherein the plurality of soundproof walls are formed in parallel at intervals. The grommet according to claim 2, wherein a sound absorbing material is provided between the soundproof walls. The grommet according to any one of claims 1 to 3, wherein the soundproof wall has a through hole through which the wire harness passes, and the wire harness and the through hole are in close contact with each other. It has a long cylindrical portion that is attached to the outer periphery of the wire harness,
A pair of the peripheral walls formed in a conical shape whose diameter gradually narrows away from the panel fixing part is provided on both sides in the axial direction of the panel fixing part attached to the opening of the panel,
The inner peripheral end of the peripheral wall that is farthest away from the panel fixing portion is disposed adjacent to the outer periphery of the long cylindrical portion in a non-joined state, so that the sound insulation space is defined between the long cylindrical portion and the peripheral wall. Made,
The outer peripheral end of the soundproof wall is coupled to the inner periphery of the panel fixing portion, and the inner peripheral end of the soundproof wall is coupled to the outer periphery of the long cylindrical portion, so that the sound insulating space is pivoted by the soundproof wall. The grommet according to claim 1, wherein the grommet is divided in a direction. The grommet according to claim 5, wherein the soundproof wall is formed as an annular corrugated wall. The sound insulation space is divided into a plurality of axial directions by the sound barrier,
The canceling frequency at which the sound wave is canceled by the reflection in the axial direction in the divided sound insulation space is included in the target frequency band of the sound wave to be attenuated. Grommet according to item. The grommet according to claim 7, wherein a ratio of lengths in the axial direction of two sound insulation spaces among the plurality of divided sound insulation spaces is set to 2: 1. A method for producing a grommet according to any one of claims 1 to 8,
An internal mold that molds the internal shape of the grommet is divided into two in the axial direction with the soundproof wall as a boundary. After forming the grommet, one of the divided internal molds is molded. The die is cut on one side relatively to the grommet, and the other inner die is cut on the other side relative to the already formed grommet. A method for producing a grommet characterized by the above.

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