JPH0518840A - Differential pressure sensor - Google Patents

Abstract

PURPOSE:To provide a hermetic seal mechanism which achieves a high-pressure sealing at a same member as a diaphragm distortion-producing portion and at the same time enable the number of portions to be sealed to be reduced and the manufacture to be eased extremely, and obtain a differential pressure sensor with a highly reliable structure. CONSTITUTION:In a distortion-producing portion 4a of a diaphragm 4 which is formed by a metal plate, an insulation film is formed on one surface and then a protection film is provided on this insulation film, thus providing a distortion gauge film and a wiring film. Then, a title item is so constituted that a fluid pressure is guided to each surface of front and rear surfaces of the diaphragm 4 and a pressure detection signal which is generated at the wiring film is taken out by a wiring which is lead out through a hermetic seal structure which is formed at a non-distortion-producing portion 4b of the diaphragm 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure sensor, and more particularly to the use of a strain gauge provided in a pressure receiving portion to detect the differential pressure of two fluids to be measured applied to each of the two surfaces of the pressure receiving portion. The present invention relates to a differential pressure sensor configured to extract a differential pressure detection signal from a portion formed around a pressure receiving portion.

[0002]

2. Description of the Related Art A configuration example of a conventional differential pressure sensor will be described with reference to FIG. The differential pressure sensor 100 is composed of three block members 100a, 100b, 100c, and these block members have a seal diaphragm 1 between them.
01 is interposed and connected by bolts 102 to form an internal space into which two fluids 103a and 103b are introduced and an internal space filled with silicone oil 104, as shown in the figure. 105a is fluid 1
03a is a hole for introducing the fluid, and 105b is a hole for introducing the fluid 103b. The block member 100b includes the diaphragm member installation location 106 and the silicone oil 10
4 has a hole 107 for communicating with each other. By installing the diaphragm member 108 at the installation place 106, the silicone oil 104 is separated into two parts. The diaphragm member 108 is joined to the block member 100b with an adhesive or the like.

The above-mentioned diaphragm member 108 has a pressure receiving portion. For example, a silicon single crystal film is formed on the upper surface of the pressure receiving portion in FIG. 3, and a strain gauge is formed by utilizing this silicon single crystal film. . At the pressure receiving portion of the diaphragm member 108, the silicone oil 104 comes into contact with both the front and back surfaces, and these two liquid contact surfaces serve as pressure receiving surfaces.
The strain gauge formed on the upper surface of the diaphragm member 108 is covered with a protective film and is connected to the bonding wire 109 via the electrode film. The other end of the bonding wire 109 is connected to a predetermined terminal board 110. Reference numeral 111 is a leader line, and this leader line 1
11 is connected to the terminal board 110 through a hole 112 formed in the block member 100b, and thereby to the bonding wire 109. The hermetic seal 1 is placed in the hole 112 where the lead wire 111 is arranged.
13 is applied to the lead wire 111 and the block member 100b.
And prevents the silicon oil 104 from leaking outside. Although there are a required number of bonding wires and lead wires, only one wire is shown in the illustrated example for convenience.
The lead wire 111 taken out to the outside is connected to an electric circuit section (not shown) that performs signal processing.

In the differential pressure sensor having the above structure, the pressure of the two fluids 103a and 103b is the seal diaphragm 1.
01, and in response to this, each of the two regions of the silicone oil 104 transmits the pressure of the fluid to the corresponding pressure receiving surface of the diaphragm member 108, thereby detecting the differential pressure between the two fluids 103a and 103b to be measured. To be done.
It has an indirect differential pressure detection structure in which a silicone oil 106 is interposed so that the fluid to be measured does not come into direct contact with the pressure detection portion of the diaphragm member 108.

[0005]

In the conventional differential pressure sensor having the structure shown in FIG. 3, in measuring the pressure of each fluid, the fluid pressure is first converted into the hydraulic pressure of the silicone oil 104 to apply the pressure to the diaphragm member. However, since the fluid pressure itself is not measured, the pressure measurement accuracy is reduced. Further, the structure requires the seal diaphragm 101, has a complicated structure as a differential pressure sensor, and has a structure in which the hydraulic pressure of silicon oil or the like directly influences the electrical wiring of the detection unit. A hermetic seal was required as a member.

As another example of the structure of the conventional differential pressure sensor, a stress detecting portion is provided on one surface of the diaphragm, and the stress detecting portion is covered with a protective film to protect the fluid, and the fluid is directly applied to both front and back surfaces of the diaphragm. There is also a structure in which the difference between the two fluid pressures is detected by contacting with. The structure of this sensor requires, as a condition, that the hermetic seal portion that protects the lead wire from fluid pressure is made to withstand high pressure, and in addition, the hermetic seal portion is formed by being exposed to high temperature conditions. The manufacturing process is procedurally restricted due to the relationship with the signal extraction wiring, which deteriorates the manufacturability and further lowers the reliability of the joint between the electric wiring of the stress detection unit and the lead wire. Raise a problem.

In view of the above problems, an object of the present invention is to provide a hermetic sealing mechanism capable of high-pressure sealing in the same member as the diaphragm straining portion, reduce the number of sealing points, and make the manufacturing extremely easy and reliable. It is to provide a differential pressure sensor having a high structure.

[0008]

In order to achieve the above object, a differential pressure sensor according to the present invention has an insulating film formed on one surface of a strain-flexing portion of a diaphragm formed of a metal plate,
A strain gauge film and a wiring film are provided on this insulating film, and fluid pressure is guided to each of the front and back surfaces of the diaphragm, and a pressure detection signal generated in the wiring film is formed in the non-strain portion of the diaphragm. The wiring is drawn through the hermetically sealed structure, and is configured to be taken out.

In the differential pressure sensor according to the present invention, in the above structure, preferably, the insulating material used in the hermetic seal structure is glass, ceramics, thermoplastic resin,
Any one of the thermosetting resins is used.

[0010]

The differential pressure sensor according to the present invention has a structure in which two fluids are brought into direct contact with the strain-causing portion of the diaphragm to enhance the measurement sensitivity and the quick response of the measurement. In addition, a strain generating portion of the diaphragm having a stress detecting portion for detecting the differential pressure,
A hermetic seal part for drawing out a signal line for taking out a signal from the stress detecting part is formed on the same diaphragm member to facilitate the manufacturing process and the assembling property.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view of a differential pressure sensor according to the present invention. In FIG. 1, 1 is a case for accommodating the differential pressure sensor, and 2 is a case cover. The case 1 and the case cover 2 are connected by, for example, a bolt member 3. The external shape of the entire member including the case 1 and the case cover 2 is a columnar body.

When connecting the case 1 and the case cover 2, the large-diameter concave portion 1a formed in the lower portion of the case 1 in FIG. 1 and the convex portion 2a formed in the case cover 2 are fitted together. The concave portion 1a of the case 1 and the convex portion 2a of the case cover 2 are formed in a stepped shape with different diameters.

A diaphragm member 4 made of a metal material is attached to the tip of the case cover 2. The diaphragm member 4 is formed of a strain-generating portion 4a of a thin circular plate in the center and a ring-shaped non-strain-generating portion 4b located around the strain-generating portion 4a. The non-strained portion 4b has a required thickness. The diaphragm member 4 and the tip of the case cover 2 are fixed to each other in a fitting relationship. As shown in FIG. 1, when the case 1 and the case cover 2 are assembled, the diaphragm member 4 is fixed by the stepped portion on the inner surface of the recess of the case 1 and the case cover 2. Further, in the same assembled state, the tip projection of the case cover 2 and the diaphragm member 4 are
, And O-rings 5 and 6 are respectively provided between the diaphragm member 4 and the case 1 to exert a sealing function. The O-rings 5 and 6 are arranged in the ring-shaped grooves.

An insulating film is formed on the upper surface of the strain generating portion 4a of the diaphragm member 4, and a strain gauge film and a wiring film are formed on the insulating film. As a result, the stress detecting portion 7 for detecting the stress generated in the strain-flexing portion 4a due to the fluid pressure is formed. The stress detecting portion formed on the strain-flexing portion 4a of the diaphragm member 4 is covered with a protective film to be protected from fluid pressure.

A port 8 is formed in the case 1, and a fluid pressure such as pressure oil is introduced into the strain-flexing portion 4a of the diaphragm member 4 through the port 8 and applied to one surface (front surface) thereof. A port 9 is formed in the case cover 2, and another fluid pressure is generated through the port 9 through a small-diameter hole 9a formed inside the tip projection of the projection.
And is applied to the other surface (back surface) of the strain-flexing portion 4a. Therefore, the strain-flexing portion 4a of the diaphragm member 4 can detect the difference between the two fluid pressures applied to the front and back surfaces.

In the non-strain portion 4b of the diaphragm member 4,
A plurality of hermetic seal parts 10 are formed. Each hermetic seal portion 10 holds a lead-out signal line 11 for taking out the detected signal to the outside. One end of the signal line 11 is electrically connected to the strain gauge included in the stress detecting unit 7 via the bonding wire 12 in one fluid. The other end of the signal line 11 is connected to the hermetic seal portion 10 of the case cover 2.
To the outside through a hole 13 formed at a position corresponding to.

In the differential pressure sensor having the above structure, the fluid can be brought into direct contact with the strain-flexing portion 4a of the diaphragm member 4 provided with the stress detecting portion 7 through the protective film. Therefore, the sensitivity of the differential pressure sensor is improved, and the responsiveness and reliability of pressure measurement are improved. Further, since the hermetic seal portion 10 is formed on the non-straining portion 4b of the diaphragm member 4, the strain generating portion and the hermetic sealing portion are integrated. As a result, the lead-out signal line 11 and the stress detecting portion 7 can be joined by the wire bonding 12, and the production is facilitated and the joining can be performed with high reliability. In this way, the differential pressure sensor can be easily wired, easily manufactured, improved in operation reliability, and improved in response to gauge output.

With respect to the material of each portion of the differential pressure sensor having the above-mentioned structure, the hermetic seal portion 10 provided on the non-straining portion 4b of the diaphragm member 4 is preferably formed of glass or ceramic, and in addition, thermoplastic It is also possible to use a resin or a thermosetting resin.

When glass is used for the hermetic seal portion 10, the diaphragm member 4 first forms the hermetic seal portion 10 and then forms a film on the upper surface of the strain generating portion 4a to form the stress detecting portion 7. To do. When a resin is used for the hermetic seal portion 10, the film is formed on the upper surface of the strain generating portion 4a to form the stress detecting portion 7, and then the hermetic seal portion 10 is formed.

FIG. 2 shows an embodiment in which the differential pressure sensor according to the present invention is incorporated in a hydraulic device. In FIG. 2, FIG.
Elements that are substantially the same as the elements described in 1 are assigned the same reference numerals. 21 is two ports 22 and 23 in the lateral direction.
Is a case having a substantially cylindrical shape. A circular hole 24 having an open top is formed around the center axis of the case 21. The ports 22 and 23 communicate with the holes 24, respectively. Ring-shaped grooves 25 and 26 are formed in the inner openings of the ports 22 and 23 along the inner peripheral surface of the hole 24.

In the hole 24, the diaphragm member 4 described above is provided.
However, as compared with the above-described embodiment, the upper and lower positions thereof are reversed and arranged. The diaphragm member 4 is placed at a predetermined position in the hole 24.
Two spacer members 27 and 28 are provided for arranging. A space for disposing the bonding wire 12 is secured between the lower spacer member 27 and the diaphragm member 4. The spacer member 27 is
The pressure oil P ₁ given from the port 23 is introduced into one surface of the strain-flexing part 4 a of the diaphragm member 4 and applied. The upper spacer member 28 has a structure in which the diaphragm member 4 is pressed from the upper side and another pressure oil P ₂ given from the port 22 is introduced to the other surface of the strain-flexing part 4 a of the diaphragm member 4 and applied. In this embodiment, the signal line 11 that is inserted through and drawn out from the hermetic seal portion 10 of the diaphragm member 4 is formed to have a short drawn-out portion, and the tip thereof is connected to an FPC (flexible printed circuit) 34. The spacer member 28 has a hole 28 through which the FPC 31 is inserted and taken out to the outside.
a is formed. FPC31 taken out
Is connected to the amplifier 29.

A case cover 30 is fixed to the case 21 with a bolt member 3. A large diameter hole 30a is formed in the center of the case cover 30, and an output line 29a from the amplifier 29 is drawn out. The O-ring 3 is provided on the peripheral surfaces of the diaphragm member 4 and the spacer member 28 arranged in the hole 24.
1, 32, 33 are arranged to perform sealing.

[0024]

As is apparent from the above description, according to the present invention, the strain generating portion of the diaphragm in which the stress detecting portion for detecting the differential pressure is formed, and the signal for extracting the signal from the stress detecting portion. By forming the hermetic seal part that draws out the wire on the same diaphragm member, the stress detection part and the seal part of the signal wire lead-out can be easily manufactured, and the number of places where the adhesive or O-ring is used is reduced. It is possible to improve the operation reliability. Further, since the two strains have a structure in which the two fluids come into direct contact with the strain-generating part of the diaphragm member, the structure of the measurement accuracy is improved and the responsiveness is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a differential pressure sensor according to the present invention.

FIG. 2 is a vertical sectional view showing an actual usage state of the differential pressure sensor according to the present invention.

FIG. 3 is a vertical cross-sectional view illustrating the structure of a conventional differential pressure sensor.

[Explanation of symbols]

1 case 2 case cover 4 Diaphragm member 4a Strain part 4b Non-strain element 5,6 O-ring 8, 9 ports 10 Hermetically sealed part 11 signal line 12 Bonding wire

Continued front page    (72) Inventor Kiyoshi Tanaka             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory (72) Inventor Fujio Sato             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory (72) Inventor Yukio Sakamoto             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory (72) Inventor Hisashi Hashimoto             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory (72) Inventor Onomasa Yomasa             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory

Claims (3)

[Claims] 1. An insulating film is formed on one surface of a strain-generating part of a diaphragm formed of a metal plate, a strain gauge film and a wiring film are provided on the insulating film, and both surfaces of the diaphragm are provided. The fluid pressure is guided to the wiring, and the pressure detection signal generated in the wiring film is taken out by the wiring drawn out through the hermetic seal structure formed in the non-strain portion of the diaphragm. Pressure sensor. 2. The differential pressure sensor according to claim 1, wherein one of glass and ceramics is used as an insulating material used in the hermetic seal structure. 3. The differential pressure sensor according to claim 1, wherein either one of a thermoplastic resin and a thermosetting resin is used as an insulating material used in the hermetic seal structure. .