Measuring and testing – Fluid pressure gauge – Electrical
Reexamination Certificate
1999-03-04
2001-01-23
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Fluid pressure gauge
Electrical
Reexamination Certificate
active
06176137
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pressure sensor, and particularly, to a pressure sensor having a housing for storing a sensor element and a connector case, the sensor adopting an absolute pressure method or a sealed gauge pressure method, which is free from any effects caused by electromagnetic noise.
Further, the present invention relates to a pressure sensor wherein the sensor element being stored inside a housing is welded thereto with advantageous airtightness.
DESCRIPTION OF THE RELATED ART
A strain gage-type semiconductor pressure sensor of the prior art is disclosed, for example, in Japanese Laid-Open Patent Publication No. 7-29435. In this prior art pressure sensor, a pressure sensor element (pressure sensor chip) is mounted on a concave formed on a body (corresponding to the housing of the present invention) through a metallic base (corresponding to the base plate of the present invention) and a glass base. Pressure is impressed to the pressure sensor element through a penetrating hole formed concentrically on the body, the metallic base and the glass base, respectively. The metallic base is fixed to the body by a laser welding technique.
The applicant of the present invention filed a Japanese patent application No. 9-185141 which disclosed a pressure sensor for sensing the pressure of a fluid. The disclosed pressure sensor comprises a metallic housing having an interior space being communicated to a pressure sensing space and further having a thin rising portion on the upper end thereof, a cylindrical metallic pressure case having an interior space, a separation wall for vertically separating the interior space, and a thin rising portion on the upper end thereof, and a connector case formed of an insulating material, wherein the housing, the pressure case and the connector case are stacked up, the rising portions of each member being caulked so as to form an integrated body, and an electrical circuit and a sensor element for sensing pressure are stored inside the interior space formed in said integrated body. The housing comprises a fluid introducing hole formed on the bottom portion of the interior space which is communicated to the pressure sensing space, and an annular protrusion formed surrounding the opening of the pressure introducing hole on the bottom portion. The sensor element is formed by layering a pressure sensing element formed on a semiconductor board, an upper base made of glass, a lower base made of silicon, and a metallic base plate. The pressure case comprises an opening to which the penetrating condenser is inserted. The bottom surface of the base plate of the sensor element is mounted on the annular protrusion, and both members are welded together and fixed airtightly by an electrical resistance welding.
SUMMARY OF THE INVENTION
When the prior art sensor was used in the refrigeration cycle of an air conditioner mounted on vehicles, the variation in the atmospheric pressure based on the difference in altitude had effects on the sensing of pressure, and there was fear that a deviation may be generated in the pressure being sensed. Therefore, high demand exists for pressure sensors adopting an absolute pressure method where no effect will be caused by the atmospheric pressure, or a sealed gauge pressure method and the like where the reference pressure is sealed at atmospheric pressure, which is used as reference when measuring pressure.
The present invention aims at responding to such demand, and the object of the invention is to provide a pressure sensor adopting either the absolute pressure method or the sealed gauge pressure method.
Further, the object of the present invention is to provide a pressure sensor enabling the sensor element and the housing to be formed of different metallic materials, when creating the reference pressure space by welding.
Even further, the object of the present invention is to provide a pressure sensor enabling the sensor element and the housing to be formed of different metallic materials, when welding and supporting the sensor element.
In order to solve the problem, the pressure sensor according to the present invention relates to a pressure sensor for sensing pressure by a sensor element formed of a semiconductor element having a piezoresistance effect; wherein said sensor element is airtightly fixed to a holder using a base plate for mounting said sensor element, said holder being airtightly fixed to a pressure case having an electromagnetic shield function and forming a reference pressure space by covering said sensor element, and said holder being supported by a housing having a pressure introducing hole.
Further, the pressure sensor according to the present invention relates to a pressure sensor comprising a housing having a pressure introducing hole, a sensor element formed of a semiconductor element having a piezoresistance effect, a holder to which said sensor element is fixed, and a pressure case having a ceiling portion, said sensor element, said holder and said pressure case being welded airtightly together to form a reference pressure space; wherein said sensor element is formed by layering said semiconductor element, an upper base made of glass, a lower base made of silicon, and a metallic base plate; said holder includes an opening formed in the center portion thereof, an annular protrusion positioned surrounding said opening at the lower surface thereof, and a flat surface formed on the peak surface of the rising portion formed around said holder; said pressure case includes a collar portion where the lower end of the surrounding wall hanging from said ceiling portion is bent outwardly; said base plate of said sensor element is welded and fixed airtightly to said annular protrusion of said holder; and said collar portion of said pressure case is welded and fixed airtightly to said peak surface of said holder.
According to the pressure sensor mentioned above, the holder being provided not only enables to define a reference pressure space, but it also works to prevent the direct airtight welding of the heading and the housing, which makes it possible to select the material of each member optionally, and therefore, different kinds of metal may be used to form the base plate and the housing.
Moreover, the pressure sensor according to the present invention relates to a pressure sensor comprising a metallic housing having a pressure introducing hole, a sensor element formed of a semiconductor element having a piezoresistance effect, a holder to which said sensor element is airtightly fixed, and a metallic pressure case having a ceiling portion, said sensor element, said holder and said pressure case being welded airtightly together to form a reference pressure space; wherein said sensor element is formed by layering said semiconductor element, an upper base made of glass, a lower base made of silicon, and a metallic base plate; said holder comprises an interior space, an opening formed in the center portion thereof, an annular protrusion positioned surrounding said opening at the lower surface thereof, and a flat surface formed on the peak surface of the rising portion formed around said holder; said pressure case comprises a collar portion where the lower end of the surrounding wall hanging from said ceiling portion is bent outwardly; said base plate is welded and fixed airtightly to said annular protrusion of said holder; and said collar portion of said pressure case is welded and fixed airtightly to said peak surface of said holder.
By mounting a collar portion to the pressure case, the collar portion and the holder may be welded and fixed together in a more secure manner.
Moreover, the pressure sensor according to the present invention relates to a pressure sensor, wherein said pressure case is equipped with an airtight penetrating condenser, and said penetrating condenser guides the output from said sensor element to a predetermined exterior terminal.
Even further, the penetrating condenser is positioned inside said reference pressure space and being connected to a circuit bo
Miyano Jun-ichi
Sasaki Keiji
Sawada Akira
Armstrong, Westerman Hattori, McLeland & Naughton
Aw-Musse Abdullahi
Fujikoki Corporation
Fuller Benjamin R.
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