Measuring and testing – Fluid pressure gauge – Diaphragm
Reexamination Certificate
2001-11-29
2003-07-01
Williams, Hezron (Department: 2855)
Measuring and testing
Fluid pressure gauge
Diaphragm
C073S756000, C073S718000, C073S721000
Reexamination Certificate
active
06584851
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pressure sensor for converting a fluid pressure into an electric signal to output to outside, which more specifically relates to an improvement in an assembly structure and signal-processing circuit board thereof.
2. Description of Related Art
In general, a pressure sensor for detecting a fluid pressure has a joint having a pressure port, a pressure detecting device attached to the joint for converting the fluid pressure introduced to the pressure port to an electric signal, a circuit board disposed immediately above the pressure detecting device and having a circuit for processing the electric signal from the pressure detecting device, and a housing for protecting the pressure detecting device and the circuit board (see, for instance, Japanese Patent Laid-Open Publication No. Hei 11-142267 and 11-237291).
FIG. 25
shows a structure of a conventional pressure sensor.
The pressure sensor has a joint
1
screwed to a mount A such as a tube shown in dotted line, a pressure detecting device
2
welded to the joint
1
and an output means
4
for outputting an electric signal toward outside in accordance with the pressure detected by the pressure detecting device
2
.
The joint
1
is provided with a pressure port
13
for introducing fluid pressure at a center of a body
12
formed with a male thread
11
screwed to the mount A on an outer wall thereof, and a butt welding portion
15
widening in tapered manner projects upward from a surface of the joint
1
at the upper center of the joint
1
. A flange
14
is integrally formed on an upper portion of the body
12
, where a thin crimping part
1
A is carved on an upper outer wall of the flange
14
.
The pressure detecting device
2
is welded to the butt welding portion
15
and a metal case
1
B is welded to an upper surface of the flange
14
. A lower end of the housing
5
as a connector is fitted between the case
1
B and the crimping part
1
A through an O-ring
38
and is caulked by the crimping part
1
A.
A cylindrical base
1
D surrounding the pressure detecting device
2
is held by a projection
1
C formed by bending a part of the case
1
B. A support piece
1
E is formed by cutting and raising an upper inside of the case
1
B. A circuit board
7
connected to the pressure detecting device
2
is supported by the support piece
1
E.
Since the body
12
and the flange
14
of the joint
1
are integrated in the conventional pressure sensor, following disadvantages occurred.
In order to weld the pressure detecting device
2
to the butt welding portion
15
, the butt welding portion
15
has to be projected above the surface of the flange
14
. It is because, when the butt welding portion
15
is retracted relative to the flange
14
, the pressure detecting device
2
has to be welded from obliquely above in a narrow space, which makes welding management such as weld line alignment difficult. However, when the butt welding portion
15
is projected above the surface of the flange
14
, the entire length of the pressure sensor and size thereof can be increased accordingly.
In order to restrain enlargement of the outer diameter of the pressure sensor, the circuit board
7
may preferably be located above the pressure detecting device
2
. However, in the conventional arrangement, since the pressure detecting device
2
projects above the surface of the flange
14
, the circuit board
7
has to be supported by the support piece
1
E to be away from the pressure detecting device
2
, thus lengthening the pressure sensor.
Further, since the crimping part
1
A for fixing the housing
5
is carved to be a thin portion, much work is necessary for processing, thereby increasing production cost.
Elimination of the above disadvantage of the conventional pressure sensor has been strongly desired, where the entire length can be shortened, weld line alignment work can be facilitated and eliminating the need for machining work of the crimping part to reduce production cost.
On the other hand, in a pressure sensor according to the above-described Japanese Patent Laid-Open Publication No. Hei 11-142267 (first conventional art), since a hole for accommodating the pressure detecting device is formed at the center of the circuit board, a circuit component such as integrated circuit has to be located outside the circuit board, so that the outer diameter of the circuit board are increased, thereby making it difficult to reduce the size (diameter) of the product.
In a pressure sensor according to the above-described Japanese Patent Laid-Open Publication No. Hei 11-237291 (second conventional art), since the integrated circuit opposes the pressure detecting device and the pressure detecting device and the circuit board are connected through a spacer, the number of the component and assembly process is increased, thereby also making it difficult to reduce the size (height) of the product.
When a pressure sensor is disposed under an environment with much electromagnetic wave noise, an electric component weak in noise, such as an integrated circuit, has to be protected against foreign noise. When an electro-conductive lid member covering the electric component is separately provided in order to protect the electric component such as integrated circuit from the foreign noise, size reduction becomes difficult. Accordingly, a technique has been proposed where a ground-plane is provided to an intermediate layer of a multi-layered board to form a shielded space (Japanese Patent Laid-Open Publication No. 2000-214040).
Such multi-layered board may be applied to the circuit board of a pressure sensor as shown in, for instance, FIG.
26
and FIG.
27
.
The pressure sensor shown in
FIG. 26
has a joint
1
, a pressure detecting device
2
welded to the joint
1
, and a multi-layered circuit board
7
held on the joint
1
and having a ground-plane layer
71
thereinside. The circuit board
7
has an opening
72
for the pressure detecting device
2
to be accommodated at the center thereof. An input/output terminal
77
and a filter circuit
82
are respectively provided on the upper surface of the circuit board
7
, and an integrated circuit
81
is mounted on the lower side thereof. The pressure detecting device
2
and the circuit board
7
are connected via a bonding wire
80
.
The pressure sensor
27
shown in
FIG. 27
has a joint
1
, a pressure detecting device
2
welded to the joint
1
, and a multi-layered circuit board
7
held on the joint
1
and immediately above the pressure detecting device
2
, the circuit board
7
having a ground-plane layer
71
thereinside. The pressure detecting device
2
and the circuit board
7
are connected by a bonding wire
80
via a through-hole opening
72
formed on the circuit board
7
.
Since the pressure sensor shown in
FIG. 26
can accommodate the pressure detecting device
2
in the opening
72
of the circuit board
7
, the height thereof can be reduced and the entire length of the pressure sensor can be shortened. On the other hand, since the diameter of the circuit board
7
in width diameter can be enlarged as in the first conventional art, thereby making it difficult to reduce the size of the pressure sensor.
In the pressure sensor having structure as shown in
FIG. 27
, since the circuit board
7
is located immediately above the pressure detecting device
2
, the diameter of the circuit board
7
in width direction can be reduced and external diameter of the pressure sensor can be reduced. On the other hand, the height thereof is increased, thereby making it difficult to reduce size of the pressure sensor as in the second conventional art. Further, since the distance between the circuit board
7
and the pressure detecting device
2
is increased, the bonding wire
80
is lengthened, thereby deteriorating efficiency in bonding the wiring, and resonance frequency of the wiring is lowered to deteriorate anti-vibration properties thereof.
Accordingly, a pressure sensor having improved circuit board capable of
Imai Atsushi
Tomomatsu Yoshihiro
Yamagishi Kouzou
Flynn ,Thiel, Boutell & Tanis, P.C.
Jenkins Jermaine
Nagano Keiki Co. Ltd.
Williams Hezron
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