Measuring and testing – Fluid pressure gauge – Mounting and connection
Reexamination Certificate
1998-07-06
2001-02-13
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
Mounting and connection
Reexamination Certificate
active
06186009
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to pressure sensors and, more particularly, to semiconductor pressure sensors preferable for sensing fluid pressure such as refrigerant of refrigerating/cooling devices.
BACKGROUND OF THE INVENTION
In the prior art, these kinds of pressure sensors comprising semiconductor chips were, as is disclosed in Japanese Patent Application Laid-Open No. H3-226638, equipped with a housing and a stem fixed to the lower portion of said housing and having a semiconductor chip storage chamber, wherein a glass seat is connected to the concave portion of said storage room, and a semiconductor chip is connected airtightly to said glass seat said semiconductor chip measuring the pressure of the refrigerant introduced through a pressure induction hole of said stem and a pressure induction hole of said glass seat.
In the above type of pressure sensors, a borosilicate glass is used as the material of the glass seat, and an iron-nickel (Fe—Ni) system alloy is used as the material of the stem, and these materials differ greatly in their temperature characteristics such as the thermal expansion coefficient. When temperature change occurs to a pressure sensor with such glass seat and metal stem connected to each other, the connection may be separated by the difference in the thermal expansion coefficient, which may lead to a problem where pressure could not be added accurately to the pressure sensing element.
In order to prevent such problems, the connection between the outer peripheral of the glass seat and the inner wall of the concave portion of the stem is provided by a low-melting glass having a thermal expansion coefficient which is at the middle of the thermal expansion coefficient of the glass seat and the thermal expansion coefficient of the stem, so that when the pressure sensor is used for a long period of time and repeated temperature changes occur to the connection of the glass seat and the stem, the connection will not separate or exfoliate, and the glass seat could be connected firmly to the upper portion of the stem.
The prior art pressure sensor of the above comprising the pressure sensing element formed of semiconductor chips had a problem in that the connection of the glass seat and the stem was troublesome and time-consuming, since the glass seat and the stem could not be connected by one step, having to place low-melting glass material to the gap between the outer peripheral of the glass seat and the concave of the stem, and then sealing the connection of the stem and the glass seat by melting said low-melting glass material.
Further, since the above-mentioned prior art technique connects the glass seat and the stem by a low-melting glass having a thermal expansion coefficient that is in the middle of the thermal expansion coefficient of each member, there is a need to select a glass material having a certain thermal expansion coefficient, which is inconvenient in that only a limited glass material could be used.
Further, the above technique solves the problem based on the difference in said expansion coefficient by selecting a certain glass material for the connection. However, the glass seat and the stem naturally differ in their thermal expansion coefficient based on the difference in material, so even when a low-melting glass having a thermal expansion coefficient in the middle of the thermal expansion coefficient of the glass seat and that of the stem is used, the connection provided by such technique may not be perfect when the pressure sensor is used for a long time.
In order to overcome the above problems, the present applicant proposed a pressure sensor including a connection of a stem and a seat for fitting a pressure sensing element of a semiconductor chip characterized in that the sensor is constituted so that the assembly and mounting of members could easily be done, and that the connected members do not separate or exfoliate under temperature change in Japanese patent application No. H8-268927.
The structure of the pressure sensor according to the above invention is explained hereinafter with reference to FIG.
3
.
FIG. 3
is a vertical cross-sectional view of the pressure sensor
10
according to the above-explained invention. The pressure sensor
10
comprises a housing
11
of a metal material at the outer portion and an electric connector
12
which is fit and connected to said housing
11
, and placed in the inner area formed by said housing
11
and said electric connector
12
is a semiconductor chip
13
with a pressure sensing element having a strain gage formed on the upper surface and an electric circuit board (print board)
14
with a calculating circuit and the like for converting an output from said semiconductor chip to an electric output of a voltage or a current.
Said housing
11
is formed of a metal such as iron (Fe) or stainless steel (SUS), and comprises a pipe-like screw
11
c
having a refrigerant liquid induction hole
11
d
on its lower portion and a receiving open pipe
11
a
on its upper portion, and further comprising a funnel-like supporting portion
11
b
in its middle interior portion, and said funnel-like supporting portion
11
b
includes a flat bottom
11
e
on its lower portion.
Said electric connector
12
is formed by an electrical insulating material of artificial resin such as polybutylene terephthalate reinforced by glass, comprising a guide pipe
12
b
for the fitting and separating of a connector on the upper portion, and an enlarging fitting pipe
12
a
on the lower portion. In the interior of said electric connector
12
, three connector terminals
17
(two of which are not shown) penetrating the inner area of the enlarging fitting pipe
12
a
from the inner area of the guide pipe
12
b
are fixed.
Said electric circuit board
14
is placed to fit into an inner ring portion
11
f
of said receiving open pipe
11
a
of the housing
11
, and an o-ring
15
is positioned on said electric circuit board
14
for waterproofing and supporting of the board
14
, which is fit into said ring portion
11
f
. The fitting pipe
12
a
of said electric connector
12
fits to the upper end of said receiving open pipe
11
a
of the housing
11
, and in a state where a lower inclining portion
12
c
of said fitting pipe
12
a
of the electric connector
12
presses said electric circuit board
14
through said o-ring
15
, an opening peripheral portion
11
a
′ at the end of said receiving open pipe
11
a
of the housing
11
stakes a shoulder portion
12
d
of said enlarging fitting pipe
12
a
of the electric connector. By such method, the housing
11
and the electric connector
12
are fit and connected together, and the electric circuit board
14
is fixed and held firmly inside the inner area formed by the housing and the electric connector.
A connecting conductive sleeve
18
is connected and fixed to a lower angled end
17
a
of said connector terminal
17
by a spot welding and the like, and on said connecting conductive sleeve
18
, an upper portion
19
b
of a pin terminal
19
is inserted, and a lower portion
19
a
of said pin terminal
19
is fixed onto said electric circuit board
14
by soldering and the like. Said pin terminal
19
transmits electric signals from said electric circuit board to said connector terminal
17
.
A stem
20
of an iron-nickel (Fe—Ni) alloy such as
42
alloy is fit and fixed to the funnel-like supporting portion
11
b
placed in the interior of said housing
11
.
Said stem
20
comprises a lower pipe
20
a
which fits in the liquid induction hole
11
d
of said housing
11
, a protruding collar
20
b
placed on a flat surface
11
e
of said funnel-like supporting portion
11
b
, and an upper mounting portion
20
c
for placing the seat
21
, and further comprising a penetrating hole
20
d
in the upper and lower direction as a liquid path, wherein at least the surface contacting the seat
21
is gold (Au) plated with a thickness of approximately 1 &mgr;m. Said stem
20
is welded firmly onto the plan surface
11
e
of said housing
Miyano Jun-ichi
Sasaki Keiji
Sawada Akira
Armstrong, Westerman Hattori, McLeland & Naughton
Fujikoki Corporation
Oen William
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