Electrical resistors – Resistance value responsive to a condition – Force-actuated
Reexamination Certificate
2000-12-04
2002-04-16
Donovan, Lincoln (Department: 2832)
Electrical resistors
Resistance value responsive to a condition
Force-actuated
C338S099000, C338S101000
Reexamination Certificate
active
06373373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic pressure-sensitive device for detecting the magnitude of a load as electrical resistance and, in particular, to an electronic pressure-sensitive device capable of detecting the magnitude of a load ranging from a small load to a large load.
2. Description of the Related Art
For example, as shown in
FIG. 7
, in a conventional electronic pressure-sensitive device used in a seat sensor or the like detecting whether a person is sitting on a seat, a first contact portion
52
formed on a flexible first insulating substrate
51
and consisting of a conductive material is opposed to a second contact portion
56
formed on a flexible second insulating substrate
55
and consisting of a conductive material through the intermediation a gap, the width of the gap being maintained by a spacer
54
provided between the first and second insulating substrates.
When a load is applied to the first and second insulating substrates
51
and
55
, the insulating substrates
51
and
55
are deflected toward the gap. And, the load applied to the first and second insulating substrates
51
and
55
exceeds a threshold value, the first contact portion
52
is brought into contact with the second contact portion
56
, and the electronic pressure-sensitive device is turned ON.
In the conventional seat sensor, a plurality of electronic pressure sensitive devices as described above are arranged in the plane of a seat base (the seat base receiving the weight of a person), and, from the in-plane distribution of the electronic pressure-sensitive device which has been turned ON, it is detected whether a person is sitting on the seat or not. And, when the presence of a person sitting on the seat is detected, an air bag is operated when the vehicle undergoes a collision.
However, in the conventional electronic pressure-sensitive device, which is turned ON when a load of a magnitude not less than a threshold value is applied, it is difficult to detect a small load applied to the electronic pressure-sensitive device or variation in the load.
Further, since the first and second insulating substrates
51
and
55
are deflected toward the gap, the burden applied to the first and second insulating substrates
51
and
55
is large, and, when the first and second insulating substrates
51
and
55
are deformed so as to protrude toward the gap, the threshold value varies to thereby cause malfunction.
In a motor-vehicle-mounted seat sensor using this conventional electronic pressure-sensitive device, it is difficult to detect the magnitude of a load, so that it is impossible to sense the physique of the person sitting on the seat, to operate the air bag in conformity with the physique of the person sitting on the seat, some other device is necessary. Further, in the case of a motor-vehicle-mounted sensor, a load can be continuously applied at high temperature, so that it is necessary to use an expensive material such as polyethylene terephthalate, which has a superior heat resistance, for the first and second insulating substrates
51
and
55
, which are continuously deflected by the load (baggage), resulting in a high cost.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an electronic pressure-sensitive device which has a long service life and which is capable of detecting loads of various magnitudes including a minute load in appropriate resistance values.
In accordance with the present invention, there is provided an electronic pressure-sensitive device comprising a first substrate consisting of an insulating material, a first contact portion formed on the first substrate, a first resistive element provided on the surface of the first contact portion, a second substrate consisting of an insulating material and opposed to the first substrate, a second contact portion formed on the second substrate and opposed to the first substrate, a high resistance material, a second resistive element constituting the first contact portion and provided on the surface of the second contact portion, and an adhesive member provided between the first and second substrates and adapted to glue the first and second substrates to each other, wherein the first and second resistive elements are constantly in an electrical contact state, and wherein a press contact force acting between the first and second resistive elements is detected as the electrical resistance between the first and second contact portions by pressurizing the first and second contact portions from at least one side.
In this electronic pressure-sensitive device, the first and second resistive elements consisting of a high resistance material are constantly in an electrical contact state, so that, even when no load is applied to the substrates, the electrical resistance measured between the first and second contact portions is a limited value. When a load is applied to at least one of the first and second substrates, even if it is a minute load, the pressure contact force which acts between the first and second resistive elements according to the load increases, and the electrical contact area of the first and second resistive elements increases, whereby the contact resistance decreases, so that the electrical resistance measured between the first and second contact portions is a value according to the load. Thus, due to the electrical resistance measured between the first and second contact portions, it is possible to detect loads of various magnitudes including those in the proximity of zero.
Further, since there is no need to maintain a gap between the contact portions, there is no need to provide a maintaining member for maintaining a gap, and there is no deterioration in performance due to deformation of the maintaining member. Further, since there is no gap between the contact portions, the amount of deformation (deflection amount) due to the load is small, so that there is little burden on the substrates, thereby providing a long service life.
Further, even when the magnitudes of the press contact forces acting on the first and second resistive elements are the same, the higher the specific resistance of the first and second resistive element materials, the higher the electrical resistance measured between the first and second contact portions, so that, by varying the specific resistance of the first and second resistive element materials according to the magnitude of the load detected by the electronic pressure-sensitive device (the specifications of the electronic pressure-sensitive device), the electrical resistance measured between the first and second contact portions is an appropriate value, making it possible to detect the load according to the specifications in an appropriate electrical resistance.
Further, by gluing together the first and second substrates by an adhesive member, the first and second resistive elements are secured at predetermined positions, and the opposition area of the first and second resistive elements is maintained constant, so that it is possible to reduce the factor leading variation in the detection of the load.
Further, in the electronic pressure-sensitive device of the present invention, the adhesive member is formed at a position deviated from the first and second resistive elements in such a way as to surround the first and second resistive elements.
In this electronic pressure-sensitive device, the adhesive member surrounds the first and second resistive elements with the first and second substrates to make it possible to reduce the influence from the external environment. Further, the electrical contact of the first and second resistive elements is not hindered by the adhesive member.
Further, in the electronic pressure-sensitive device of the present invention, at least one of the first and second substrates is flexible, and the adhesive member consists of a sheet-like member, the gap between the first and second substrates being larger at the positions where the first and second co
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Donovan Lincoln
Lee Kyung S.
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