Measuring and testing – Fluid pressure gauge – Mounting and connection
Reexamination Certificate
2002-04-12
2003-08-12
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
Mounting and connection
Reexamination Certificate
active
06604430
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pressure sensor that converts pressure into an electric signal and outputs it, and a pressure sensor housing for housing the pressure sensor. In particular, the present invention relates to a pressure sensor that is suitably applied to automobiles and the like, and a pressure sensor housing for housing the pressure sensor.
BACKGROUND OF THE INVENTION
Generally, a semiconductor sensor chip based on the piezo resistance effect is employed in a pressure sensor for use in automobiles. The semiconductor pressure sensor is constructed such that a plurality of semiconductor distortion gages made of materials producing the piezo resistance effect are connected together to form a bridge circuit on a diaphragm formed of single crystal silicon or the like. If the diaphragm is deformed due to a change in pressure, the resistance of the semiconductor distortion gages varies according to the change in pressure. The change in resistance is withdrawn as a voltage signal from the bridge circuit.
FIG. 4
shows the exterior of the above-described conventional pressure sensor, and
FIG. 5
is a sectional view taken along line V—V in FIG.
4
. The pressure sensor is constructed such that a semiconductor sensor chip
13
is housed in a concave sensor mount portion
12
formed in a housing body
11
, and a pressure port
14
is attached to the housing body
11
. The semiconductor pressure sensor chip
13
is electrically connected to a lead terminal (lead frame)
15
, which is used for conduction to external devices and is inserted into and integrated with the housing body
11
, via a bonding wire
16
. The pressure sensor includes a gel protective portion
17
that protects the surface of the semiconductor pressure sensor chip
13
and the bonding wire
16
from contaminated substances included in a medium whose pressure is to be measured. A space between the housing body
11
and the base of the pressure port
14
serves as a pressure detecting chamber
18
.
In the pressure sensor constructed in the above-mentioned manner, however, the part of the gel protective member
17
, which covers the semiconductor pressure sensor chip
13
, is exposed into the pressure port
14
. Therefore, degraded and solidified foreign matter such as oil and gasoline included in the medium to be measured may enter the pressure detecting chamber
18
via the pressure port
14
to directly collide with the gel protective member
17
. If the foreign matter collides with the gel protective member
17
, the impact of the collision is transmitted to the semiconductor pressure sensor chip
13
to cause the deformation amount of the diaphragm to deviate from accuracy. This results in inaccurate measurement of pressure.
Therefore, it would be desirable to provide a pressure sensor that is capable of preventing foreign matter included in a medium to be measured from entering a pressure detecting chamber housing a sensor element that converts pressure into an electric signal so as to eliminate the adversary effect caused by collision of the foreign matter with the sensor element or the like and enable accurate measurement of pressure. It would further be desirable to provide a pressure sensor housing that is capable of preventing foreign matter from entering a pressure detecting chamber housing a sensor element that converts pressure into an electric signal.
SUMMARY OF THE INVENTION
In accordance with the present invention, a pressure sensor is provided which includes a sensor element that converts pressure into an electric signal, a pressure detecting chamber that houses the sensor element, a pressure port that allows communication of the pressure detecting chamber and a space in which pressure is to be measured, and a protective portion provided inside the pressure port in such a position as to substantially close an inlet of the pressure detecting chamber in the state in which the pressure detecting chamber and the space in which pressure is to be measured are in communication with each other. According to the present invention, the protective portion provided inside the pressure port substantially closes the inlet of the pressure detecting chamber housing the pressure sensor element in the state in which the pressure detecting chamber and the space in which pressure is to be measured are communication with each other. Therefore, the protective portion prevents foreign matter from entering the pressure detecting chamber
REFERENCES:
patent: 4546785 (1985-10-01), Sanderford
patent: 4682499 (1987-07-01), Baker
patent: 5307684 (1994-05-01), Moss et al.
patent: 5583294 (1996-12-01), Karas
patent: 5602338 (1997-02-01), Tamai et al.
patent: 6131467 (2000-10-01), Miyano et al.
patent: 63-175736 (1988-07-01), None
Ashino Kimihiro
Saito Kazunori
Ueyanagi Katsumichi
Fuji Electric & Co., Ltd.
Oen William
Rossi & Associates
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