JPH099461A - Mounting structure of wire harness for gas sealing grommet - Google Patents

Abstract

PURPOSE: To facilitate insertion work of electric wires in a gas leakage preventing grommet and, at the same time, to make it possible to surely execute sealing. CONSTITUTION: A grommet 12 is mounted to a wire harness for wiring electric wires through an opening provided in a box in the box 10 storing equipments including power supply cell, etc., for an electric automobile and is used for preventing gas leakage from the inside of the box by sealing the opening. A plurality of wire insertion holes 15 inserting electric wires 13 of a group of electric wires forming the wire harness into them one by one are opened in both end faces to pass through and are bored in the grommet, and while each of the wire insertion holes 15 is set larger than the width of each of terminal fixtures 14 connected to the front ends of the wires, a rubber pin 21 is closely contacted with each of the wires and is fitted from the outside, an outside diameter of the rubber pin is set larger than the inside diameter of the electric wire insertion hole mentioned above, and force-fit of the rubber pin into an insertion side of the wire insertion hole is made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire harness mounting structure for a gas seal grommet used in an electric vehicle, and more specifically, hydrogen gas generated when a battery is charged does not enter a required area separated by a partition wall. like,
A wire harness that penetrates the partition is attached to a grommet for gas sealing.

[0002]

2. Description of the Related Art Recently, various electric vehicles have been provided, and hydrogen gas is generated in the electric vehicles when charging a battery. If the hydrogen gas enters a box containing a control device such as a sensor, a spark may be generated in the box, and the invaded hydrogen may be ignited. Therefore, it is necessary to reliably prevent gas from entering through the insertion portion of the wire harness connected to the control device in the box.

Conventionally, when inserting a wire harness through an opening provided in a vehicle body panel or the like, various waterproof and dustproof grommets have been proposed for sealing the opening. This type of grommet has the most general shape shown in FIG. 16, and is made of rubber or elastomer.
The wire harness W / H in which a large number of electric wires w are bundled by tape winding or the like is inserted through the electric wire insertion portion 1a formed of the small diameter cylindrical portion of the grommet 1 by expanding the diameter and passing through the electric wire insertion portion 1a. The locking groove 1c provided on the outer peripheral surface of the vehicle body panel P
The lip 1d, which is engaged with the peripheral edge of the through hole 2 and is provided in the vicinity of the engaging groove 1c, is attached to the vehicle body panel P by pressing.

The grommet presses the inner peripheral surface of the wire insertion portion 1a against the outer peripheral surface of the wire harness W / H to seal between the wire harness W / H and the grommet 1, and
The gap between the grommet 1 and the through hole 2 is sealed by a lip 1d to prevent water from entering from the outside X of the vehicle body into the inside Y of the vehicle body, and also to prevent dust.

[0005]

The conventional grommet shown in FIG. 16 functions sufficiently for waterproofing and dustproofing, but is insufficient for gas sealing. That is, since a large number of electric wires are wrapped with a tape and bound to form a wire harness and are passed through a grommet, gaps are unavoidably generated between the bound electric wires, and these gaps are sealed. Not not. To seal the gaps between the electric wires, a sealant is also filled, but it is very difficult for the sealant to penetrate into all the gaps between the electric wires to completely seal the electric wires. .

Therefore, the grommet shown in FIG. 16 which has been conventionally provided for waterproofing and dustproofing is insufficient in terms of sealing property to be used as a grommet for gas sealing in an electric vehicle. There is a demand for the development of a grommet that can reliably shut off the power.

The present invention meets the above-mentioned demands, and it is an object of the present invention to reliably block the flow of gas and to facilitate wiring work.

[0008]

In order to achieve the above-mentioned object, the present invention is, in claim 1, for attaching to a wire harness penetrating an opening of a partition wall for gas sealing, wherein the grommet is rubber or With a solid body made of an elastic material such as an elastomer, a plurality of electric wire insertion holes for inserting one electric wire of an electric wire group constituting a wire harness are opened at both end faces and penetrated, and each of these electric wire insertion holes is inserted. The hole is set to be larger than the width of the terminal fitting connected to the end of the wire, and each wire is fitted with a rubber stopper closely, and the outer diameter of these rubber stoppers is set to be larger than the inner diameter of the wire insertion hole. ,
Provided is a wire harness mounting structure for a gas seal grommet, characterized in that a rubber plug is press-fitted into an insertion side of an electric wire insertion hole.

It is preferable that the inner diameter of the wire insertion hole is set to be 10% to 20% larger than the width of the terminal fitting, and the outer diameter of the rubber plug is set to be 10% to 20% larger than the inner diameter of the wire insertion hole. . (Claim 2) Further, it is preferable that a plurality of annular ribs are provided on the outer peripheral surface of the rubber plug so as to project, and the annular ribs are crushed and pressed against the inner peripheral surface of the wire insertion hole. (Claim 3)

Further, the rubber plug has a large-diameter portion whose outer diameter is larger than the inner diameter of the electric wire insertion hole and a small-diameter portion whose outer diameter is smaller than the inner diameter of the electric wire insertion hole. It is preferable that the portion is fixed to the electric wire using a crimp terminal or wound with a tape, and the large diameter portion of the rubber plug is press-fitted into the insertion side of the electric wire insertion hole. (Claim 4)

Further, the rubber plug is provided with a pull-out piece extending in the axial direction from one end face thereof, and the pull-out piece is set to be longer than the axial length of the grommet, and the pull-out piece penetrating the wire insertion hole of the grommet. It is preferable that the rubber plug is pushed to the inlet side of the wire insertion hole by pulling.
(Claim 5) It is preferable that the lead-out piece has a semi-annular shape having an outer diameter smaller than the inner diameter of the wire insertion hole and is attached so as to surround the outer circumference of the wire. (Claim 6)

Furthermore, an opening provided in a partition wall composed of an outer wall of a box or the like on which the grommet is mounted is made into a cylindrical portion, and a cylindrical solid body into which the grommet is inserted into the cylindrical portion is formed. An annular rib that presses against the peripheral surface is projected, and a locking groove that locks with the locking projection that projects from the inner peripheral surface of the cylindrical part is provided, and the insertion side into the cylindrical part is gradually contracted. It is preferable to have a diameter. The opening provided in the box is not limited to a cylindrical opening, and the relationship between the opening provided in the box and the outer shape of the grommet can be internally fitted in a state where the grommet is in close contact with the opening.
Any shape may be used.

[0013]

In the grommet according to the first aspect of the present invention, the electric wires are separated one by one and passed through the electric wire insertion holes of the grommet, and the rubber plugs are pressed into the electric wire insertion holes to seal the electric wires. Thus, it is possible to eliminate the gap between the electric wires that occurs when the electric wire is inserted into the grommet. In this way, since the gap generated between the electric wires can be completely eliminated, it is possible to prevent the gas from leaking from the inside of the box. Further, since each electric wire insertion hole is set larger than the terminal fitting, the electric wire can be easily passed through the electric wire insertion hole, and since it is only necessary to press fit the grommet at the place where the rubber plug is attached,
The electric wire can be easily passed through the electric wire insertion hole.

When the relationship between the inner diameter of the wire insertion hole and the width of the terminal fitting is set as described in claim 2, the wire can be inserted very easily, while the outer diameter of the rubber plug and the wire insertion hole When the relationship of inner diameters is set as described in claim 2,
It is possible to surely seal each wire insertion hole. Furthermore, when a plurality of annular ribs are provided on the rubber plug as described in claim 3, the sealing positions are plural, and the sealing is performed more reliably.

Further, when the rubber plug is provided with a small diameter portion and the small diameter portion is crimped and fixed to the electric wire by using a crimp terminal or fixed to the electric wire by tape winding, the grommet electric wire insertion can be performed. Even if you pull it when inserting the wire in the hole,
The rubber stopper can be inserted into the wire insertion hole at the inlet side without displacement.

Still further, as described in claim 5, a rubber plug is provided with a lead-out piece, and the lead-out piece penetrates through the wire insertion hole to project. When the lead-out piece is pulled, the rubber plug is inserted into the wire insertion hole. It can be pushed into the inlet side, and the rubber stopper can be inserted easily and securely. Moreover, as described in claim 6, when the lead-out piece is formed in a semi-annular shape so as to surround the outer circumference of the electric wire, when the electric wire is inserted into the electric wire insertion hole of the grommet, the electric wire insertion hole is formed together with the electric wire. It can penetrate smoothly and project from the outlet side. Moreover, since the cross-sectional area of the pull-out piece is made large as a semi-annular shape, the pull-out piece will not be torn when pulled.

[0017]

The present invention will be described in detail below with reference to an embodiment in which a wire harness is routed through a gas-sealing grommet to a control-device housing box installed near the battery of an electric vehicle.

In FIG. 1, reference numeral 10 denotes a box accommodating a control device (not shown) such as a sensor, which is arranged inside a large battery box (not shown) accommodating a battery. Reference numeral 11 denotes a cylindrical portion having an opening 11a at the tip protrudingly provided on the outer wall of the box 10 serving as a partition wall, 12 a grommet fitted into the cylindrical portion 11, and 13 a grommet 12
A plurality of electric wires that form a wire harness W / H that is inserted into the wire harness. Terminals 14 are crimped to the ends of the electric wires 13, and the terminal fittings 14 are connected to the control device in the box 10.

The grommet 12 is formed of rubber or elastomer as a substantially cylindrical solid body, and has an electric wire insertion hole 15 for inserting the plurality of electric wires 13 one by one.
Are formed so as to penetrate in the front-rear direction from the front end face 12a to the rear end face 12b, and the electric wire insertion holes 15 are provided at required intervals.

As shown in the enlarged view of FIG. 1 (B), each wire insertion hole 15 has its inner diameter W1 set to be 10% to 20% larger than the width W2 of the terminal fitting 14 connected to the wire 13. That is, in this embodiment, the width W2 of the terminal fitting 14 is about 5
mm, and the inner diameter W1 of the wire insertion hole 15 is about 6 to 7 mm.
And

On the outer peripheral surface of the grommet 12, three annular ribs 18 are provided at intervals in the axial direction, and an annular engaging groove 19 is provided behind the ribs 18. Further, the diameter of the rear portion 12c of the locking groove 19 is gradually reduced.

The outer diameter of the annular rib 18 is set to be slightly larger than the inner diameter of the box cylindrical portion 11 so that the annular rib 18 is pressed and brought into pressure contact with the inner peripheral surface of the cylindrical portion 11. . Further, a locking projection 20 is provided so as to project from the inner peripheral surface of the cylindrical portion 11, and the locking groove 1 of the grommet 12 is provided.
It fits inside 9.

On the other hand, a rubber plug 21 is previously attached to the electric wire 13 so that the electric wire 13 is fitted into the inlet side 15a of the electric wire insertion hole 15 when attached to the grommet 12. The rubber stopper 2
1 is a substantially cylindrical shape, the inner diameter W3 of which is the outer diameter W4 of the wire 13.
Set slightly smaller, expand the diameter of the rubber plug 21 and
3, the rubber plug 21 is externally fitted to the outer peripheral surface of the electric wire 13 in close contact therewith. Further, the outer diameter W4 of the rubber plug 21 is set to be 10% to 20% larger than the inner diameter W1 of the wire insertion hole 15 and is set to 7 to 8 mm in this embodiment.

The operation of passing the electric wire 13 through the grommet 12 and the attachment of the grommet 12 to the box 10 will be described. First, as shown in FIG. 3 (A), each electric wire 13 is passed through a rubber stopper 21, These rubber plugs 21 are positioned at the required positions of the electric wire 13. At this time, the rubber plug 21 is the electric wire 1
Since it is in close contact with 3, it is held at the required position.

Then, as shown in FIG. 3B, the electric wires 13 having the rubber plugs 21 attached thereto are inserted into the electric wire insertion holes 15 of the grommet 12. At this time, since the inner diameter of the wire insertion hole 13 is larger than that of the terminal metal fitting 14 at the tip, it can be easily inserted. Electric wire 1 with rubber plug 21 attached
When the part of 3 reaches the entrance 15a side of the wire insertion hole 15,
Since the outer diameter of the rubber plug 21 is larger than the inner diameter of the wire insertion hole 15, the rubber plug 21 is press-fitted. The entire rubber plug 21 may be inserted into the wire insertion hole 15, or a part may be forcibly inserted and the remaining part may be projected from the end face of the grommet 12 as shown in FIG. 3C.

As shown in FIG. 3C, the electric wire 13 is attached to the grommet 12, and the electric wire 13 is attached to the box 10. At that time, first, the electric wire 13 pulled out from the grommet 12 is inserted through the cylindrical portion 11. Next, the diameter-reduced rear portion 12c of the grommet 12 is replaced with the cylindrical portion 11
To insert. Since the outer periphery of the rear portion 12c is smaller than the inner diameter of the cylindrical portion 11, it can be easily inserted.

Further, when the grommet 12 is pushed into the cylindrical portion 11, the locking projection 20 of the cylindrical portion 11 is inserted and positioned and fixed in the locking groove 19 on the outer periphery thereof, and the annular rib 18 is crushed. In this state, the inner peripheral surface of the cylindrical portion 11 is pressed. Therefore, the outer peripheral surface of the grommet 12 and the box 10
There is surely no gap between the inner peripheral surface of the cylindrical portion 11 and the inner peripheral surface.

In this way, the gap between the electric wire 13 and the grommet 12 is sealed by the rubber plug 21, while the grommet 1
Since the annular rib 18 completely seals between 2 and the cylindrical portion 11 of the box 10, it is possible to prevent gas such as hydrogen gas from entering the box 10.

FIG. 4 shows a modified example of the rubber plug 21, in which two annular ribs 30 are provided on the outer peripheral surface of the rubber plug 21 at intervals in the axial direction. The outer diameter of the annular rib 30 is 8 to 9 m.
m. When the rubber plug 21 is attached to the electric wire 13, when the rubber plug 21 is press-fitted into the electric wire insertion hole 15 of the grommet 12, the annular rib 30 is pressed and brought into pressure contact with the inner peripheral surface of the electric wire insertion hole 15. In addition, since there are two annular ribs 30, sealing is performed at two places, and more reliable sealing can be performed.

5 to 9 show a second embodiment. In the second embodiment, a rubber plug 21 has a large diameter portion 22 having the same outer diameter as the outer diameter of the rubber stopper of the first embodiment and a small diameter portion. 23 is formed continuously. The large diameter portion 22 and the small diameter portion 23 have the same inner diameter W3, and are set to be slightly smaller than the outer diameter W4 of the electric wire 13, and the rubber plug 21 is expanded to pass the electric wire 13 through.
The rubber plug 21 is externally fitted to the outer peripheral surface thereof in a state of being in close contact.

The outer diameter W5 of the large-diameter portion 22 of the rubber plug 21 is 7 to 8 mm, and the outer diameter W6 of the small-diameter portion 23 is 5 mm, which is set smaller than the inner diameter W1 of the wire insertion hole 15, and is set on the outer peripheral surface thereof. As shown in FIG. 6 (A), the crimp terminal 2 made of metal
5 is crimped and fixed to the electric wire 13 by crimping.

More specifically, the crimp terminal 25 has a shape in which a pair of left and right barrels 25a are provided at two positions in the front and rear. The barrels 25a are positioned on the outer circumference of the small diameter portion 23 and crimped by a crimping crimping machine (not shown). Small diameter part 23 of rubber stopper 21
Is crimped and fixed to the outer peripheral surface of the electric wire 13. Note that FIG.
As shown in (B), from the outer periphery of the small diameter portion of the rubber plug to the electric wire 1
The rubber plug 21 may be positioned and fixed to the electric wire by wrapping the tape 26 around the outer circumference of 3.

The work of passing the electric wire 13 through the grommet 12 and the attachment of the grommet 12 to the box 10 are the first steps.
This is the same as the embodiment, and first, as shown in FIGS. 6A and 6B, each electric wire 13 is passed through a rubber plug 21, and the small diameter portion 23 of the rubber plug 21 is crimped to the crimp terminal 25 or the tape 26.
Is used to position and fix the electric wire 13 at a required position.

Then, as shown in FIG. 8, the electric wires 13 to which the rubber plugs 21 are attached are respectively passed through the electric wire insertion holes 15 of the grommet 12. At this time, since the inner diameter of the wire insertion hole 13 is larger than that of the terminal metal fitting 14 at the tip, it can be easily inserted. Further, even if the electric wire 13 is pulled from the pull-out side, since the rubber plug 21 is fixed to the electric wire 13 by using the crimp terminal 25 or the tape 26, the rubber plug 21 is not displaced.

When the portion of the electric wire 13 to which the rubber plug 21 is attached reaches the entrance 15a side of the electric wire insertion hole 15, the crimp terminal 2
5 or the outer diameter of the small diameter portion 23 to which the tape 26 is attached is slightly smaller than the inner diameter of the wire insertion hole 15, so that it can be easily inserted. However, when the large diameter portion 22 reaches the inlet 15a, the outer diameter of the wire insertion hole 15 is reduced. Since it is larger than the inner diameter of 15, it is pressed in. Since the post-process and the operation are the same as those in the first embodiment, the description thereof will be omitted.

FIG. 9 shows a modified example of the rubber plug 21 of the second embodiment, in which two annular ribs 30 are provided on the outer peripheral surface of the large diameter portion 22 of the rubber plug 21 so as to be spaced apart in the axial direction. There is. When the annular rib 30 is provided, like the grommet in FIG. 4,
A reliable seal can be made.

10 to 14 show a third embodiment of the present invention. In the third embodiment, as shown in FIG. 10, the rubber plug 21 has a shape in which a pull-out piece 31 is continuously provided from the cylindrical portion 22. The pull-out piece 31 of the rubber plug 21 has a cylindrical portion 22.
It has a semi-annular shape protruding from one end surface 22a on the grommet insertion side along the semi-periphery of the hole 22b, and the outer diameter is about 5 m.
m is set so that the wire 13 can be inserted into the wire insertion hole 15 while surrounding half of the outer peripheral surface of the wire 13. The length L1 is set to be larger than the axial length L2 of the grommet 12. That is, in this embodiment, L2 is 1
It is 4 mm and L1 is 25 mm.

The operation of passing the electric wire 13 through the grommet 12 and the attachment of the grommet 12 to the box 10 will be described. First, as shown in FIG. 11, each electric wire 13 is passed through a rubber plug 21. Next, as shown in FIG. 12 (A), the electric wires 13 with the rubber plugs 21 attached are inserted into the electric wire insertion holes 15 of the grommets 12. At this time, since the inner diameter of the wire insertion hole 13 is larger than that of the terminal metal fitting 14 at the tip, it can be easily inserted. Also, rubber stopper 2
The drawing piece 31 of No. 1 smoothly penetrates the wire insertion hole 15 together with the wire 13 in a state of surrounding the outer circumference of the wire 13, and is drawn out from the outlet 15b of the wire insertion hole 15.

When the portion of the electric wire 13 to which the cylindrical portion 22 of the rubber stopper 21 is attached reaches the inlet 15a side of the electric wire insertion hole 15, the pull-out piece 31 protruding from the outlet 15b is pulled. As a result, the cylindrical portion 22 of the rubber stopper 21 is pushed into the inlet 15b of the wire insertion hole 15. At that time, the cylindrical portion 22
May be put in the wire insertion hole 15 as shown in FIG.
As shown in (B), a part of the grommet 12 may be pushed in and the remaining part may be projected from the end surface of the grommet 12. With the electric wire 13 attached to the grommet 12 as shown in FIG.
As shown in FIG. 4, it is attached to the box 10.

FIG. 15 shows a modified example of the rubber plug 21 of the third embodiment. As in the first and second embodiments, the outer peripheral surface of the cylindrical portion 22 of the rubber plug 21 is axially spaced. 2
Individual annular ribs 30 are provided so as to project.

[0041]

As is apparent from the above description, in the grommet according to the first aspect of the present invention, unlike the conventional one, the electric wires are divided into individual wires, which are inserted into the electric wire insertion holes of the grommet and attached to the respective electric wires. Since the rubber plug is pressed against the wire insertion hole to seal it, the gap between the wires that occurs when binding the conventional wires and inserting them into the grommet can be eliminated without fail. It is possible to prevent gas leakage such as. Further, since the electric wire insertion hole is larger than the terminal fitting, the electric wire can be inserted into the electric wire insertion hole of the grommet very easily, and the work efficiency can be improved.

Specifically, when the inner diameter of the wire insertion hole, the width of the terminal fitting, and the outer diameter of the rubber plug are set as set forth in claim 2, the wire can be easily inserted and the rubber plug seals. Can be done reliably.

Further, when the rubber plug is provided with the annular rib as described in claim 3, the rubber plug can be easily press-fitted into the wire insertion hole of the grommet and the sealing property can be improved.

Further, as described in claim 4, when the rubber plug is provided with a small diameter portion and the small diameter portion is crimped to the electric wire by using a crimp terminal or fixed by winding tape, the electric wire is a grommet electric wire. Even if you pull it when inserting it into the insertion hole,
The rubber stopper will not come off. Therefore, the rubber plug can be reliably positioned so as to be inserted into the inlet side of the wire insertion hole.

Furthermore, when the rubber plug is provided with a pull-out piece as described in claim 5, the cylindrical portion can be easily pushed into the wire insertion hole by pulling the pull-out piece.
Further, as in claim 6, since the lead-out piece is formed in a semi-annular shape so as to surround the electric wire, it can be smoothly passed together with the electric wire through the electric wire insertion hole of the grommet.
Moreover, since the cross-sectional area of the pull-out piece is large, it is possible to prevent the pull-out piece from being broken when pulled.

[Brief description of drawings]

1A is a perspective view showing a state in which a grommet of the present invention is attached to a box, and FIG. 1B is a sectional view.

2A is a perspective view of the grommet of FIG. 1, and FIG.
FIG. 4 is a perspective view of a rubber stopper.

3A is a perspective view showing a state where a rubber plug is attached to an electric wire, FIG. 3B is a perspective view in which the electric wire is inserted into a grommet, and FIG. 3C is a rubber plug pushed into an electric wire insertion hole of the grommet. It is a rear perspective view.

FIG. 4 is a perspective view showing a modified example of a rubber plug.

FIG. 5 is a perspective view of a rubber plug used in a second embodiment.

6A and 6B are perspective views showing a fixed state of a rubber plug and an electric wire according to a second embodiment.

FIG. 7A is a perspective view showing a state in which an electric wire is inserted into the grommet of the second embodiment, and FIG. 7B is a sectional view after the rubber plug is pushed into the grommet.

FIG. 8 is a cross-sectional view of a state in which the grommet of the second embodiment is attached to the box.

FIG. 9 is a perspective view showing a modified example of the rubber plug of the second embodiment.

FIG. 10 is a perspective view of a grommet used in the third embodiment.

FIG. 11 is a perspective view showing a state where an electric wire is inserted through the rubber plug of the third embodiment.

FIG. 12 is a perspective view showing a state in which the electric wire of the third embodiment is inserted into a grommet.

FIG. 13A is a perspective view showing a state where the rubber plug of the third embodiment is pushed into the grommet, and FIG. 13B is a sectional view of a main part.

FIG. 14 is a cross-sectional view showing a state in which the grommet of the third embodiment is attached to the box.

FIG. 15 is a perspective view showing a modified example of the rubber plug of the third embodiment.

FIG. 16 is a cross-sectional view showing a conventional grommet.

[Explanation of reference numerals] 10 box 11 cylindrical portion 11a opening 12 grommet 13 electric wire 14 terminal fitting 15 electric wire insertion hole 18 annular rib 19 locking groove 20 locking projection 21 rubber plug 23 small diameter portion 25 crimp terminal 26 tape 30 annular rib 31 Drawer

Claims (6)

[Claims] 1. A gas harness which is attached to a wire harness penetrating an opening of a partition wall for gas sealing. The grommet is a solid body made of an elastic material such as rubber or elastomer. A plurality of wire insertion holes that are inserted one by one are opened by penetrating through both end faces, and each of these wire insertion holes is set to be wider than the width of the terminal fitting connected to the tip of the wire. A gas seal characterized in that a rubber plug is closely fitted to the electric wire and the outer diameter of these rubber plugs is made larger than the inner diameter of the electric wire insertion hole, and the rubber plug is press-fitted into the insertion side of the electric wire insertion hole. Mounting structure of wire harness to the grommet for car. 2. The inner diameter of the wire insertion hole is set to be 10% to 20% larger than the width of the terminal fitting, and the outer diameter of the rubber plug is set to be 10% to 20% larger than the inner diameter of the wire insertion hole. The mounting structure according to claim 1. 3. The mounting structure according to claim 1, wherein a plurality of annular ribs are provided on the outer peripheral surface of the rubber plug, and the annular ribs are crushed and pressed against the inner peripheral surface of the wire insertion hole. 4. The rubber plug is provided with a large-diameter portion having an outer diameter larger than the inner diameter of the wire insertion hole and a small-diameter portion having an outer diameter smaller than the inner diameter of the wire insertion hole in a continuous manner. 2. The mounting structure according to claim 1, wherein the portion is fixed to the electric wire by using a crimp terminal or wound with a tape, and the large diameter portion of the rubber plug is press-fitted into the insertion side of the electric wire insertion hole. 5. The rubber plug is provided with a pull-out piece extending axially from one end face thereof, and the pull-out piece is set to be longer than the axial length of the grommet, and the pull-out piece penetrating an electric wire insertion hole of the grommet. The mounting structure according to claim 1, wherein the rubber plug is pushed into the inlet side of the electric wire insertion hole by pulling. 6. The mounting structure according to claim 5, wherein the lead-out piece has a semi-annular shape having an outer diameter smaller than the inner diameter of the wire insertion hole, and is attached so as to surround the outer circumference of the wire.