Grommet and method for manufacturing same

1. A grommet which is fixed to a wire harness to be inserted through an opening portion of a vehicle panel, and which is then fitted and mounted in the opening portion so that the wire harness is supported in the vehicle panel, the grommet including:

a panel fixation portion mounted in the opening portion of the vehicle panel,

circumferential walls which cover the circumference of the wire harness to form a sound insulation space around the wire harness; and

soundproof walls formed inside the sound insulation space so as to intersect with a longitudinal direction of the wire harness,

wherein: the soundproof walls have through holes penetrated by the wire harness, and the wire harness and the through holes are brought into tight contact with each other, and

an outer circumference of the soundproof walls and through holes are positioned at an inner circumferential side of the panel fixation portion.

2. A grommet according to claim 1 , wherein: the soundproof walls are formed in parallel at intervals.

3. A grommet according to claim 2 , wherein: a sound absorbing material is provided among the soundproof walls.

4. A grommet according to claim 1 , further including:

a long cylinder portion which is mounted on an outer circumference of the wire harness; wherein:

the circumferential walls include a pair of circumferential walls which are formed into conical shapes having diameters gradually smaller as their distances from the panel fixation portion mounted in the opening portion of the vehicle panel are larger are provided on axially opposite sides of the panel fixation portion;

inner circumferential ends of the circumferential walls separated at maximum distances from the panel fixation portion are disposed adjacently to an outer circumference of the long cylinder portion in a non-contact state so that the sound insulation space can be defined between the long cylinder portion and the circumferential walls; and

an outer circumferential end of each soundproof wall is connected to an inner circumference of the panel fixation portion and an inner circumferential end of each soundproof wall is connected to the outer circumference of the long cylinder portion, so that the sound insulation space is divided axially by the soundproof wall.

5. A grommet according to claim 4 , wherein: each soundproof wall is formed as an annular corrugated wall.

6. A grommet according to claim 1 , wherein:

the sound insulation space is divided into a plurality of sections in an axial direction by the soundproof walls; and

all cancellation frequencies at which sound waves can cancel each other due to reflection in the axial direction within the divided sound insulation space sections are included in a target frequency band of sound waves to be attenuated.

7. A method for manufacturing a grommet according to claim 1 , wherein:

an internal mold for molding an internal shape of the grommet is axially divided into two parts with the soundproof walls as a boundary, one internal mold part of the divided two internal mold parts is removed toward one side relatively to the molded grommet after the grommet is molded, and the other internal mold part of the divided two internal mold parts is removed toward the other side relatively to the molded grommet.

8. A grommet including:

a large diameter cylinder portion which is provided with a panel engagement portion at its outer circumference, the panel engagement portion being engaged with an inner circumferential edge of a through hole of a vehicle panel;

two small diameter cylinder portions which are disposed on axially opposite sides of the large diameter cylinder portion and tightly fitted to an outer circumference of a cable passed through the through hole respectively; and

two coupling shield walls which have outer circumferential edges connected to the large diameter cylinder portion and inner circumferential edges connected to the small diameter cylinder portions, so that the coupling shield walls shield annular spaces between the large diameter cylinder portion and the small diameter cylinder portions respectively;

the large diameter cylinder portion, the two small diameter cylinder portions, and the two coupling shield walls forming a grommet body, which is made of an elastic material; wherein:

a sound insulation plate which is formed separately from the grommet body and tightly fitted to the outer circumference of the cable is disposed inside the grommet body to partition the inside of the grommet body into a plurality of hermetically sealed spaces;

an annular fitting groove is formed internally in the grommet body, and an outer circumferential edge of the sound insulation plate integrated with the cable is fitted to the annular fitting groove; and

the annular fitting groove is provided in an inner circumferential side position corresponding to the panel engagement portion.

9. A grommet which is fixed to a wire harness to be inserted through a through hole of a vehicle panel, and which is fitted into the through hole so as to be mounted in the vehicle panel so that the wire harness is supported in the vehicle panel, the grommet including:

a large diameter cylinder portion which is provided with a panel fixation portion fixed to the through hole of the vehicle panel;

two coupling shield walls which extend from the large diameter cylinder portion toward axially opposite sides to have diameters gradually smaller as their distances from the large diameter cylinder portion are larger so that, of the two coupling shield walls, inner circumferential ends are disposed adjacently to or in tight contact with an outer circumference of the wire harness, and which therefore define a sound insulation space around the wire harness;

an inner cylinder portion which has at least one axial side end portion inserted into a corresponding one of the inner circumferential ends of the coupling shield walls and which is tightly fitted to the outer circumference of the wire harness; and

a sound insulation wall which is provided inside the sound insulation space and which has an outer circumferential end coupled to an inner circumference of the large diameter cylinder portion or to an inner circumference of one of the coupling shield walls close to the inner circumference of the large diameter cylinder portion, and an inner circumferential end coupled to the inner cylinder portion so that the sound insulation wall defines the sound insulation space axially, wherein:

a water sealing portion is provided partially on one side of the panel fixation portion in the inner cylinder portion so that gaps among electric wires of the wire harness to which the inner cylinder portion is tightly fitted and a gap between the electric wires and an inner circumference of the inner cylinder portion is sealed with a water sealant in the water sealing portion.