1. Field of the Invention
This invention relates to a grommet, and more particularly relates to a grommet that is mounted on a wire harness to be arranged in a motor vehicle and is attached to a burred through-hole in a vehicle body panel.
2. Description of the Related Art
A wire harness that extends from an outer compartment of a motor vehicle, such as an engine compartment, to an inner compartment, such as a driver's compartment, passes through a through hole in a vehicle body panel that partitions the outer and inner compartments. A grommet is mounted on the wire harness and is attached to the through-hole to effect waterproof, dustproof, and soundproof functions.
The prior art includes various kinds of grommets, including, a one-body grommet made of a rubber or an elastomer, and a two-body grommet that has a grommet main body made of a rubber or an elastomer and a resin inner incorporated with the grommet main body.
JP HEI 9 (1997)-27226 A and FIGS. 6A to 6B herein disclose a two-body grommet that is used when a through-hole in a vehicle body panel is a burred hole. With reference to FIG. 6A, a two-body grommet 100 includes a grommet main body 110 made of a rubber and a resin inner support 120. The grommet main body 110 includes a waterproof sealing portion 111 that contacts a vehicle body panel P. On the other hand, a flange 122 projects from an end of an inner side cylindrical portion 121 of the resin inner support 120 and is inserted into an annular recess 112 in the grommet main body 110. A latch pawl 123 is formed by turning the other end of the inner side cylindrical portion 121 outward. The latch pawl 123 contacts and latches with a burr B projecting from a peripheral edge around a through-hole H in the vehicle body panel P.
An O-ring-like portion 111b is provided on the distal end of the waterproof sealing portion 111 of the grommet main body 110 and has a ball shape in cross section. The ball-like ring portion 111b is pressed onto the vehicle body panel P to effect a waterproof action. JP HEI 9 (1997)-27226 also discloses an example with another O-ring-like waterproof sealing portion 115 inside the waterproof sealing portion 111 (see FIG. 6B) and an example in which a lip-like waterproof sealing portion 116 is provided outside the O-ring-like waterproof sealing portion 115 (see FIG. 6C). These two waterproof sealing portions 115 and 116 project from an outer peripheral wall at the same height from the annular recess 112 and are oblique to the wall.
As shown in FIGS. 6B and 6C, the conventional grommet includes two waterproof sealing portions with equal projecting heights H1. One waterproof sealing portion can exert its waterproof function even if the other waterproof sealing portion bites foreign particles and curls up to lose its waterproof function.
As shown in FIG. 7A, a burred hole formed in the vehicle body panel P has a burr B that projects from an inner peripheral edge around the through-hole H in the vehicle body panel P. A height (a) of the burr B is likely to be random, as shown in FIGS. 7B, 7C, and 7D. On the other hand, a height H3 between the latch pawl 123 of the resin inner support 120 and a lip 111r on a distal end of the waterproof sealing portion 111 of the grommet main body 110 are constant.
Accordingly, as shown in FIG. 7C, if the projecting height (a) of the burr B is formed into a designed height precisely, the lip 111r of the waterproof sealing portion 111 is pressed onto the vehicle body panel P by a given contact pressure. However, as shown in FIG. 7B, if the height (a) of the burr B is small, the lip 111r of the waterproof portion 111 lightly contacts the vehicle body panel P and is not pressed onto the panel P by the given contact pressure. This may cause a clearance between the lip 111r and the panel P. As shown in FIG. 7D, if the projecting height (a) of the burr B is great, a contact wall 111a of the waterproof sealing portion 111 contacts the vehicle body panel P and the lip 111r does not push the panel P. This will cause a clearance between the lip 111r and the panel P or this will exert less than the given contact pressure between the lip 111r and the panel P.
Accordingly, even if two waterproof sealing portions are provided on the grommet main body, as shown in FIGS. 6B and 6C, they cannot reply to the random projecting heights of the burrs, since the projecting heights of the two waterproof sealing portions are same.
In view of the above problems, an object of the invention is to provide a grommet that can provide a high waterproof function at a burred through-hole in a vehicle body panel even if projecting heights of the burrs are random.