Seat position sensor

Details Seat position sensor Seat position sensor

2002-05-14

2004-01-27

JeanGlaude, Jean (Department: 2819)

Coded data generation or conversion

Digital pattern reading type converter

Magnetic, inductive or capacitive

C280S735000, C324S207240, C324S207260

Reexamination Certificate

active

06683544

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a seat position sensor which is served for detecting a position of a seat of an automobile or the like and for controlling an inflation of an airbag or the like.
2. Description of the Related Art
To explain a conventional seat position sensor using drawings,
FIG. 10
is a perspective view showing the conventional seat position sensor in a mounted state,
FIG. 11
is an enlarged perspective view showing the conventional seat position sensor in the mounted state,
FIG. 12
is a cross-sectional view of an essential part of the conventional seat position sensor in the mounted state, and
FIG. 13
is a cross-sectional view of the essential part of the conventional seat position sensor.
To explain the conventional seat position sensor in conjunction with
FIG. 10
to
FIG. 13
, each first rail
51
is constituted by bending a metal plate in an approximately U shape and a pair of these first rails
51
are fixed to both sides of a lower surface of a seat
60
. A shielding plate
54
is constituted by bending a metal plate in an L shape and includes an elongated planer base
54
a
and a side wall
54
b
which is formed by being bent and extended downwardly from an end of the base
54
a,
wherein the base
54
a
is fixed to the first rail
51
and the shielding plate
54
is slidably moved together with the first rail
51
.
A second rail
52
is constituted by bending a metal sheet in an approximately U shape and is combined with the first rail
51
such that the second rail
52
forms an inversely projecting shape as shown in FIG.
12
. The second rail
52
is fixed to an indoor floor surface of a vehicle using a holding strut
53
bent in an L shape.
A seat position sensor
55
is formed of a molded product made of synthetic resin and includes a base body
55
a
which is formed in a U shape, a rectangular magnet
56
which is embedded into a first side wall
55
b
of the base body
55
a,
and a rectangular Hall IC
57
which is embedded into a second side wall
55
c
which is formed in an opposed manner with respect to the first side wall
55
b
and faces the magnet
56
in an opposed manner. As the magnet
56
, a magnet having a strong magnetic force such as samarium or cobalt can be used. The seat position sensor
55
having such a constitution is mounted on the second rail
52
by means of a stay
58
.
In the state that seat position sensor
55
is mounted, the side wall
54
b
of the shielding plate
54
can enter into or exit from a space
55
d
defined between the first and second side walls
55
b,
55
c,
wherein when the shielding plate
54
is positioned inside the space
55
d,
a magnetic field generated by the magnet
56
is shielded by the shielding plate
54
so that the magnetic flux density which the Hall IC
57
receives is lowered thus generating the changeover of an output of the Hall IC
57
.
To explain the manner of operation of the conventional seat position sensor
55
having the abovementioned constitution and the mounting state, when the seat
60
is moved, the shielding plate
54
enters into or exits from the space
55
d
of the seat position sensor
55
so that the changeover of the output of the Hall IC
57
is performed. Due to this changeover of the signal, a gas flow-out quantity at the time of inflation of an airbag (not shown in the drawing), for example, is changed so that an airbag is adjusted.
In the conventional seat position sensor which has the abovementioned constitution and performs the abovementioned operation, as explained above, when the shielding plate
54
is positioned inside the space
55
d,
the flux density which the Hall IC
57
receives is lowered. However, since a gap is formed between the side wall
54
b
of the shielding plate
54
and the space
55
d
and the magnetism leaks from this gap. Here, the Hall ICs
57
have considerable irregularities with respect to sensitivity, that is, the Hall ICs
57
have the considerable irregularities with respect to the magnetic flux density at the time of changeover so that when the Hall IC having a favorable sensitivity (the Hall IC which is changed over with small magnetic flux density) is used, there arises a problem that the changeover of the output of the Hall IC is not performed due to the influence of the leaked magnetic flux. Although it may be possible to use the Hall IC having a poor sensitivity (the Hall IC which is changed over with large magnetic flux density) to cope with such a problem, there arises a problem that the yield rate is drastically decreased.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a seat position sensor which can ensure a high yield rate by reducing influence of leaked magnetic flux using a bias magnet, by ensuring changeover of a magnetoelectric converting element by controlling a magnetic flux density and further by using a magnetoelectric converting element in a wide range.
According to a first aspect of the present invention to solve the abovementioned problems, a seat position sensor of the present invention includes a housing, a magnetoelectric converting element which is held by the housing and performs changeover of an output at a given magnetic field intensity, and a magnet which is held by the housing at a position where the magnet faces the magnetoelectric converting element in an opposed manner, wherein a shielding plate is capable of entering into or exiting from a space defined between the magnetoelectric converting element and the magnet, and an inverse bias magnet which applies a magnetic field of an inverse direction to the magnet is provided at a side opposite to the magnet side while sandwiching the magnetoelectric converting element therebetween.
Further, according to a second aspect of the present invention to solve the abovementioned problems, the housing of the seat position sensor of the present invention includes a first side wall, a second side wall which faces the first side wall in an opposed manner, and a connection wall which connects the first with the second side walls and form the space into a recess, wherein the magnetoelectric converting element and the magnet are respectively mounted on either one of the first and the second side walls, the shielding plate is formed in a planar shape and is allowed to be disposed inside the recess from an opening side of the recess toward the connecting wall, and an end surface of the shielding plate at the connection wall side is positioned closer to the connection wall side than the magnet.
Further, according to a third aspect of the present invention to solve the abovementioned problems, the housing is arranged such that the open-side of the recess of the space of the seat position sensor of the present invention is positioned downwardly.
Further, according to a fourth aspect of the present invention to solve the abovementioned problems, the bias magnet is arranged at the first or the second side wall on which the magnetoelectric converting element of the seat position sensor of the present invention is arranged and the bias magnet, the magnetoelectric converting element and the magnet are positioned on one straight line.
Further, according to a fifth aspect of the present invention to solve the abovementioned problems, the magnetoelectric converting element of the seat position sensor of the present invention is constituted of a Hall element and a magnetization surface of the magnet is parallel to the shielding plate.
Further, according to a sixth aspect of the present invention to solve the abovementioned problems, the changeover of the output of the magnetoelectric converting element is performed only once with respect to movement in an exiting direction or in an entering direction of the shielding plate which is capable of entering into or exiting from the space of the seat position sensor of the present invention.
Further, according to a seventh aspect of the present invention to solve the abovementioned problems, the housing of the seat position sens

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