Steering wheel and horn switch assembly for the steering wheel

Details Steering wheel and horn switch assembly for the steering wheel Steering wheel and horn switch assembly for the steering wheel

2000-02-28

2001-03-13

Mai, Lanna (Department: 3619)

Land vehicles

Wheeled

Running gear

C280S731000, C074S552000

Reexamination Certificate

active

06199908

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle steering wheel which has a horn switch assembly and an air bag module, the vehicle steering wheel can sufficiently absorb an impact force which acts on the back side of the ring portion of the steering wheel in the forward direction.
2. Description of the Related Art
A horn switch assembly which is arranged in a vehicle steering wheel while supporting an air bag module, is disclosed in Japanese Utility Model Publication No. Hei. 2-143734, Japanese Patent Publication No. Hei. 8-225051 or the like as shown in
FIGS. 21
to
23
.
In the above vehicle steering wheel W, horn switch mechanisms
200
are disposed on both sides of the air bag module
201
as shown in FIG.
23
.
Each of the horn switch mechanisms
200
comprises an elongated movable plate
202
coupled with the air bag module
201
, a fixed plate
203
coupled with the vehicle steering wheel body under the movable plate
202
and being in association with the movable plate
202
, metal coiled springs
204
for upwardly urging the movable plate
202
apart from the fixed plate
203
, and mounting bolts
205
which are screwed to a vehicle steering wheel body while engaging the movable plate
202
to put a distance from the fixed plate
203
to the movable plate
202
at a fixed distance.
Movable contacts
206
are provided at both ends of the movable plate
202
, while fixed contacts are provided at both ends of the fixed plate
203
in association with the movable contacts
206
, respectively.
The number of the mounting bolts
205
used in each of the horn switch mechanisms
200
is two. Those mounting bolts
205
are located near to both ends of said movable plate
202
and slightly closer to the center of said movable plate
202
than the locations of said movable contacts
206
. The coiled springs
204
are respectively placed around the mounting bolts
205
while being coaxial with the mounting bolts
205
.
The movable contacts
206
are located at both ends of the movable plate
202
in order to avoid such a state that the air bag module
201
is excessively declined to the depressing side of the air bag module, viz., a rolling of the air bag module
201
downward. To this end, a measure is used to prevent such a situation that after the movable contacts
206
are brought into contact with the fixed contacts
207
when the horn is operated, the depressing side of the air bag module
201
further descends. Let us consider a case where the movable contacts
206
are placed at positions on the movable plate
202
, which are greatly apart from the urging means and the mounting bolts
205
, not at both ends of the movable plate
202
. In this case, after the movable contacts
206
are brought into contact with the fixed contacts
207
, with progression of the deformation of the ends of the movable plate
202
, the urging means is compressed, and the depressing side of the air bag module
201
will possibly descend (downward rolling).
The mounting bolts
205
and the coiled springs
204
are placed at the positions near to the movable contacts
206
located at the ends of the movable plate
202
, in order to prevent an upward rolling of the air bag module
201
. If the mounting bolts
205
and the coiled springs
204
are placed at positions that are located closer to the center of the movable and fixed plates
202
,
203
and apart from the movable contacts
206
, the side of the air bag module
201
opposite to the depressing side thereof is excessively inclined upward, viz., an upward rolling of the air bag module
201
tends to occur.
Further, the movable plate
202
includes a substantially rectangular base member
208
disposed above the fixed plate
203
and a mounting plate
209
extending upward from the edge of the central part of the base member
208
and being coupled with and supporting the air bag module
201
by connection bolts
210
to be screwed into the side surfaces of the air bag module
201
. The movable plate
202
includes engaging holes
211
provided near to both ends of the base member
208
.
The movable plate
202
is upward urged apart from the fixed plate
203
and the heads of two mounting bolts
205
to be screwed into the vehicle steering wheel body are brought into engagement with engaging holes
211
of the movable plate
202
, whereby a distance from the movable plate
202
to the fixed plate
203
is put at a fixed distance.
Temporary fastening holes
214
are provided near to the center of the base member
208
of the movable plate
202
in order to temporarily fasten the air bag module
201
before the air bag module
201
is coupled with the mounting plate
209
by utilization of the connection bolts
210
. To fasten, the engaging leg portions
213
extended from the air bag module
201
are inserted into the temporary fastening holes
214
. In this case, the number of temporarily fastening holes
214
is two since two engaging leg portions
213
extended from the air bag module
201
are provided on each side of the air bag module
201
. The engaging leg portions
213
are located closer to the center of the base member
208
than the engaging holes
211
so as not to interfere with the mounting bolts
205
.
However, in the aforementioned conventional horn switch mechanisms, the two mounting bolts are screwed into the vehicle steering wheel body to which the fixed plate is fixed. The heads of those mounting bolts are brought into engagement with the edges of the engaging holes of the movable plate. Therefore, those mounting bolts must be electrically insulated from the base member of the movable plate. The insulating spacers
215
,
216
are placed around the edges of the engaging holes, respectively. Two insulating spacers and two coiled springs corresponding in number to the number of the mounting bolts are used. This leads to an increase of the number of required component parts.
Actually, each of the two insulating spacers has two members, which are put on the upper and lower sides of each engaging hole. A total of four members are used for the insulating spacers.
A possible measure to reduce the number of the component parts is to use a single plate spring in place of the two coiled springs. However, the necessity of preventing a rolling of the air bag module when the horn is depressed makes it difficult to substitute one plate spring for the two coiled springs.
In the horn switch mechanisms, two holes for temporarily fastening the air bag module, provided in the base member of the movable plate, are located close to the center of the base member. For this reason, a temporary fastening strength of the air bag module is weak.
To fasten the air bag module by means of the connection bolts, the connection bolt of one of the horn switch mechanisms, disposed on both sides of the air bag module, is screwed into the corresponding threaded hole of the air bag module. Then, the connection bolt of the other horn switch mechanism is screwed into the corresponding threaded hole of the air bag module. The air bag module is easy to turn by a torque developed when the bolt is tighten into one of the threaded holes. The mounting plate to which the connection bolts are attached is disposed close to the center of the base member of the movable plate, and the temporary fastening holes for the air bag module are also formed close to the center of the base member. Therefore, the center (position of the connection bolt) of the torque of the air bag module is near to the temporary fastening hole. Therefore, the temporary fastening strength of the air bag module is weak.
A possible measure to increase the temporary fastening strength is to increase the length of the base member of the movable plate and to form the temporary fastening holes at locations near both ends of the elongated base member which correspond to the engaging leg portions of the air bag module. In this case, the movable contacts are located at positions greatly apart from and within both ends of the movable plate. When the horn is dep

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