Metal working – Method of mechanical manufacture – Combined manufacture including applying or shaping of fluent...
Reexamination Certificate
2001-01-17
2004-07-06
Cuda-Rosenbaum, I (Department: 3726)
Metal working
Method of mechanical manufacture
Combined manufacture including applying or shaping of fluent...
C029S527100, C264S328120, C264S271100, C264S272110, C249S097000, C249S085000, C425S542000
Reexamination Certificate
active
06757960
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of Japanese Patent Applications No. 2000-17820 filed on Jan. 21, 2000, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for manufacturing a (O-shaped ring sealing type) pressure detecting apparatus with a pressure detection chamber that is hermetically sealed by a resin-molded first case and a second case assembled together with an O-shaped ring interposed therebetween, and to a molding device suitably used for manufacturing the pressure detecting apparatus.
2. Description of the Related Art
As this kind of pressure detecting apparatus, for example, JP-A-7-209115 and JP-A-7-243926 propose seal diaphragm type semiconductor pressure detecting apparatuses and methods for manufacturing the same with a decreased number of parts, simplified manufacturing process, high reliability and low cost. The pressure detecting apparatuses are generally used for detecting refrigerant pressures of a vehicle air conditioner, power steering oil pressure, and the like, a detection pressure range of which is 0 to about 10 MPa.
FIG. 5A
shows a cross-sectional shape of an O-shaped ring sealing type pressure detecting apparatus. A pressure detection chamber J
5
is provided by assembling a molded resin case (first case) J
2
holding connector pins J
1
therein, and a metallic housing (second case) J
4
having a seal diaphragm J
3
. A sensor element (integrated element) J
6
fixed to a base is held in the pressure detection chamber J
5
that is filled with oil J
7
for transmitting pressure from the seal diaphragm J
3
.
At an outer periphery of the pressure detection chamber J
5
, an O-shaped ring J
8
is fit in a groove (O-shaped ring groove) formed on an end surface of the resin case J
2
in a state where it is sandwiched between a metallic pushing plate J
9
of the housing J
4
and the resin case J
2
. The O-shaped ring J
8
hermetically seals the pressure detection chamber J
5
.
The above-described pressure detecting apparatus is generally manufactured as follows. First, the resin case is formed by injection molding with a die. The pressure detection chamber J
5
holding the sensor element J
6
therein is formed by assembling the resin case J
2
having a recess filled with the oil J
7
for the pressure detection chamber J
5
, and the housing J
4
. At that time, the O-shaped ring J
8
is sandwiched and crushed between the case J
2
and the housing J
4
at the outer periphery of the pressure detection chamber J
5
, and the case J
2
and the housing J
4
are fixedly assembled together by caulking fixation or the like. Thus, the basic structure of the pressure detecting apparatus is manufactured.
A detecting operation of this pressure detecting apparatus is as follows. That is, pressure introduced from a pressure conduction hole J
10
of the housing J
4
is received by the seal diaphragm J
3
and is transmitted to the oil J
7
. Then, the sensor element J
6
detects the pressure of this oil J
7
, and outputs an output signal proportional to the pressure.
In the above-described detecting operation, however, if the oil J
7
is leaked from the pressure detection chamber J
5
, the pressure cannot be transmitted appropriately. Because of this, in this kind of pressure detecting apparatus, the hermetic sealing of the pressure detection chamber J
5
, i.e., the sealing of the oil J
7
by the O-shaped ring J
8
is important. Here,
FIG. 5B
is an enlarged view of a portion indicated by arrow VB in
FIG. 5A
, and
FIG. 5C
is a cross-section of the O-shaped ring J
8
in the radial direction thereof.
In general, the sealing property of the O-shaped ring J
8
is secured by surface roughness and flatness of seal surfaces J
21
, J
41
of the resin case J
2
and the housing J
4
sandwiching the O-shaped ring J
8
, and the compressibility of the O-shaped ring J
18
compressed by the seal surfaces J
21
, J
41
. Here, the surface roughness and the flatness are set to be 12.5 S or less, and 0.05 mm or less, respectively, as values based on JIS (Japanese Industrial Standards).
The compressibility is generally in a range of 10 to 30%, which is a value represented by 100×(D1−D2)/D1(%). Incidentally, D1 is a diameter of the cross-section of the O-shaped ring J
8
in the radial direction thereof, D2 is a diameter of the radial direction cross-section of the O-shaped ring J
8
in the compressive direction. This compressibility of the O-shaped ring J
8
varies due to flatness of the respective seal surfaces J
21
, J
41
. When the seal surfaces have irregularities, the compressibility varies on the circumference of the O-shaped ring J
8
to have large variations. Therefore, it is important to make the respective seal surfaces flat.
The seal surface J
41
of the housing J
4
that is formed form metallic plate by welding can readily have satisfactory surface roughness and flatness. However, because the seal surface J
21
of the resin case J
2
is formed from resin by molding, the surface roughness and flatness are readily affected by its molded state. That is, in the O-shaped ring sealing type pressure detecting apparatus described above, the satisfactory surface roughness and flatness of the O-shaped ring seal surface at the resin case side cannot be attained stably.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to provide a pressure detecting apparatus composed of first and second cases assembled together to form a hermetically sealed pressure detection chamber with an O-shaped ring with a sufficient sealing property. Another object of the present invention is to provide a method and a device for forming the first case from resin with a seal surface having satisfactory surface roughness and flatness.
According to the present invention, briefly, a molding die used for forming a first case has a seal correspondence surface for forming a seal surface of the first case, and a gate for injecting resin. The gate is provided at a position capable of injecting resin so that the resin flows in the molding die approximately in parallel with the seal correspondence surface. Accordingly, the resin is suppressed from hitting the seal correspondence surface of the molding die, and the seal surface formed by this molding die can have sufficient surface roughness and flatness stably.
REFERENCES:
patent: 4293182 (1981-10-01), Schwartz
patent: 5585061 (1996-12-01), Hara et al.
patent: 5595939 (1997-01-01), Otake et al.
patent: 5604372 (1997-02-01), Yamaguchi
patent: 5926952 (1999-07-01), Ito
patent: 6219913 (2001-04-01), Uchiyama
patent: 2 118 477 (1983-11-01), None
patent: 58-25931 (1981-08-01), None
patent: 7-209115 (1995-08-01), None
patent: A-H10-138310 (1998-05-01), None
Chiku Kazuhiro
Ootake Seiichirou
Cuda-Rosenbaum I
Jimenez Marc
Posz & Bethards, PLC
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