JP3085797B2 - Pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor incorporated in a gas meter for measuring a gas flow rate and for monitoring whether or not gas supply is normal.

[0002]

2. Description of the Related Art It has been considered to use a semiconductor pressure sensor as a compact pressure sensor provided in a gas meter of this type. FIG. 10 is a cross-sectional view of a conventional semiconductor pressure sensor, which will be described.

In FIG. 10, reference numeral 1 denotes an outer frame of a pressure sensor, which has a gas introduction unit 2. In the outer frame 2, a sensor case 3 is adhered with an adhesive 4 so as to correspond to the gas introduction portion 2. The sensor case 3 has an air introduction section 5 and a pressure detection section inside. The pressure detecting unit comprises a silicon substrate 6, a silicon film 7 having a thickness of several microns provided on the silicon substrate 6 by etching, and a semiconductor resistor formed on the silicon film 7 and having a resistance value that changes due to mechanical strain. It is configured. A gel 8 is coated on the silicon film 7 so as not to come into direct contact with dust or moisture contained in the gas. A printed circuit board 9 on which an electric circuit such as an amplifier circuit is formed is provided in the outer frame 1.
Are provided, and are molded with the plastic resin 10. The printed circuit board 9 has input / output terminals 11. Numeral 12 in the figure indicates the tip of the gas introduction unit 2.

In the above configuration, the silicon film 7 is mechanically distorted due to the difference between the gas pressure applied from the gas inlet 2 and the atmospheric pressure applied from the air inlet 5. The distortion is proportional to the pressure difference between the gas pressure and the atmospheric pressure. When the silicon film 7 is distorted, the resistance value of the semiconductor resistor formed on the silicon film 7 changes in proportion to the magnitude of the distortion. Therefore, by detecting, amplifying and outputting the change in the resistance value, the differential pressure between the gas pressure and the atmospheric pressure can be measured. Further, an electric circuit formed on the printed circuit board 9 has a function of amplifying the change in the resistance value. The input / output terminals 11 are a power supply terminal for supplying power to an electric circuit on the printed circuit board 9 and a resistor on the silicon film 7, an output terminal for amplifying and outputting a change in resistance value, and a ground terminal.

[0005]

However, in the above-described conventional configuration, the silicon film 7 is configured to receive the pressure of the gas through the gel 8, so that the silicon film 7 does not directly touch the gas.
The gel 8, the adhesive 4, and the sensor case 3. Among them, the gel 8 and the adhesive 4 are mainly composed of a polymer material, but are easily eroded by the gas because they are in a portion directly in contact with the gas, swell and transmit the gas, and in the worst case, a molding agent is used. There is a problem that gas leaks to the atmosphere side through a certain plastic resin 10. Also, due to temperature fluctuation,
While the gas repeatedly liquefies and vaporizes, the gel 8, the adhesive 4, the plastic resin 10 and the like are deformed or deteriorated by swelling and shrinking, or adhere to dust in the gas. There has been a problem that the pressure difference from the atmospheric pressure cannot be accurately measured.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and prevents deformation and alteration due to swelling and shrinkage of a material directly in contact with a gas to be measured to prevent gas leakage to the outside of the sensor. It is an object of the present invention to realize a highly reliable pressure sensor in which accurate gas pressure is applied to a silicon film for a long period of time by preventing deterioration of sensor characteristics due to adhesion of dust.

[0007]

The pressure sensor according to the present invention comprises:
To measure the pressure difference between the pressure of the fluid to be measured and the reference pressure
A fluid to be measured introduction unit provided for introducing the fluid to be measured
And a reference fluid guide for introducing a reference fluid having the reference pressure.
Inlet, the measured fluid introduction unit and the reference fluid introduction unit
And a pressure detector for detecting the differential pressure.
Then, the pressure detecting unit is moved over the pressure receiving surface formed on the substrate.
It is composed by coating with a gel layer.
The pressure of the gel layer of the detecting unit and the pressure of the measured fluid introducing unit
Introducing the fluid to be measured from a space between one end on the side of the detection unit
A gas-resistant liquid to the gas of the fluid to be measured
The measured flow is filled at the other end of the measured fluid introduction section.
The liquid spills due to surface tension with a smaller diameter than the body introduction part
A place where the liquid is not filled and is formed with a hole diameter that does not come out
A constant length tip section is formed, and the gas pressure of the fluid to be measured is
The liquid in the fluid introduction section through the hole in the tip section
And acts on the pressure-receiving surface via the gel layer.
It is characterized by having been constituted as follows.

[0008]

[0009]

[0010]

[0011]

[0012]

According to the structure of the present invention, the fluid to be measured is introduced into the fluid introduction section.
The opening on the side in contact with the measurement gas should be
A hole with a smaller diameter that does not allow the liquid to spill out due to surface tension
And a predetermined length that is not filled with liquid.
Because it is the tip section, it can be measured even after long-term use.
Adhesion of dust at the inlet of the tip section of the constant fluid inlet
And maintain a sufficient amount of liquid in a stable
Gel layer can be reliably protected from
As a result, stable measurement performance can be maintained.

[0013]

[0014]

[0015]

[0016]

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same parts as those in the conventional example are denoted by the same reference numerals and described. First Embodiment FIG. 1 is a cross-sectional view of a semiconductor pressure sensor according to a first embodiment.
The feature of this configuration is that a partition 13 is formed between the gas inlet 2 and the pressure detector in the sensor case 3. The partition 13 has gas resistance and chemical resistance, so that it does not cause a swelling phenomenon peculiar to the polymer material.
Since no alteration or the like occurs, the gas does not permeate and does not cause gas leakage. Note that the pressure detecting section is made of a silicon substrate 6, a silicon film 7, a gel 8, and the like. Second Embodiment FIG. 2 is a sectional view of a semiconductor pressure sensor according to a second embodiment.
The feature of this configuration resides in that a liquid partition wall portion 14 made of a fluorine-based oil is filled between the gas introducing portion 2, that is, between the tip 12 of the gas introducing portion and the gel 8 in the pressure detecting portion. The distal end 12 of the gas introduction portion is formed with a hole diameter such that the liquid partition wall (fluorous oil) 14 does not spill out due to surface tension. Since the fluorine-based oil has gas resistance and chemical resistance and has a small volume compression ratio, the gas pressure can be accurately transmitted to the pressure detecting unit. In addition, the characteristics of the polymer material of the gel 8 and the adhesive 4 do not cause a swelling phenomenon, so that a change in volume, deterioration, and the like do not occur, so that gas does not permeate and gas does not leak. Third Embodiment FIG. 3 is a cross-sectional view of a semiconductor pressure sensor according to a third embodiment, and FIG. 4 is a detailed cross-sectional view of a gas introducing portion in FIG. The feature of this configuration is that a metal film (stainless steel 316 having a thickness of 20 mm) is provided between the gas introduction portion 2, that is, the space between the tip 12 of the gas introduction portion and the space having the silicon film 7 which is the pressure-sensitive portion of the pressure sensor.
That is, a partition 15 made of a diaphragm having a size of about 30 microns is provided. The partition 15 is fixed by pressing the partition 15 made of a metal film with a rubber packing 17 at a joint 16 between the front end 12 of the gas inlet and the outer frame 1. The gas passage (the end 12 of the gas introduction part) and the space having the silicon film 7 which is the pressure-sensitive part of the pressure sensor are cut off by the metal film partition part 15, and only the gas pressure is applied to the silicon film 7. Accurately transmitted. The gel 8 and the adhesive 4 do not directly touch the gas and are not attacked by the gas, so they do not swell and the sensor characteristics do not deteriorate due to the adhesion of dust in the gas. In addition, the partition 15 has no restriction on the aperture ratio of the fluid introduction portion to be measured, and has a high degree of freedom in design and manufacture.

In this embodiment, the tip 12 of the gas introduction portion is used.
A case has been described in which the partition 15 that blocks the space between the pressure sensor and the space having the silicon film 7 that is a pressure-sensitive part is formed of a metal film. You may. Fourth Embodiment FIG. 5 is a cross-sectional view of a semiconductor pressure sensor according to a fourth embodiment, and FIG. 6 is a detailed cross-sectional view of a gas introduction part in FIG. This configuration is characterized in that a liquid partition (fluorine-based oil) 14 and a partition 15 made of a metal film are provided side by side. The liquid partition 14 is the same as that of the second embodiment, and the configuration of the partition 15 is the same as that of the third embodiment. The tip portion 12 of the gas introduction portion is formed to have a hole diameter such that in the event that the metal film partition portion 15 is damaged or falls off, the fluid partition wall portion 14 made of fluorine-based oil does not spill due to surface tension. ing. The gas passage (the end 12 of the gas introduction part), the silicon film 7 and the gel 8
The liquid barrier portion 14 made of fluorine-based oil on the front surface is shut off, and only the gas pressure is accurately transmitted to the silicon film 7. The gel 8 and the adhesive 4 do not come into direct contact with the gas, so they are not eroded by the gas, and therefore do not swell, and the sensor characteristics do not deteriorate due to the adhesion of dust in the gas.

Further, even when the partition 15 made of a metal film is broken, the polymer material such as the gel 8 and the adhesive 4 does not come into direct contact with the gas by the liquid partition 14 made of the filled fluorine-based oil. , It is not affected by the gas, and the same effect as above can be obtained.

In this embodiment, the tip 12 of the gas introduction portion is used.
A case has been described in which the metal film is used to form the partition that blocks the space having the silicon film 7 that is the pressure-sensitive part of the pressure sensor. It may be a resin film partition part having. Fifth Embodiment FIG. 7 is a sectional view of a semiconductor pressure sensor according to a fifth embodiment.
The feature of this configuration is that dangerous gas such as corrosive gas is prevented from directly touching the sensor element. In particular,
A sensor element 19 made of a silicon semiconductor is provided in a sensor case 18, and the sensor element 19 is bonded to a glass base 20 by an anodic bonding portion 21. The glass base 20 is fixed in the sensor case 18 by an adhesive 25 of a silicone resin.
The sensor case 18 is made of a heat-resistant resin such as PPS resin, in which a lead frame 30 is insert-molded, and a gold wire 28 is bonded between the lead frame 30 and the sensor element 19. An atmospheric pressure introducing cylinder 18a is formed integrally with the sensor case 18, and a potting agent 24 is filled on the surface side of the sensor element 19 opposite to the atmospheric pressure introducing cylinder 18a, and the sensor element 19 is embedded. I have.

A printed board 27 is mounted on the sensor case 18 via a lead frame 30.
The terminal 31 is fixed to. The sensor case 18 is fixed to a central portion of a housing 29 made of a PBT resin or the like as an accommodating member with an epoxy adhesive 26, and the surface side of the sensor element 19 covered with the potting agent 24 faces the pressure introducing cylinder 29a of the housing 29. Mounted facing. In the housing 29, the sensor case 18 includes a silicone resin filler 23,
Soft epoxy resin filler further filled on it
22 are formed so that the atmospheric pressure introducing cylinder 18a and the terminal 31 protrude.

A bellows 32 is fixed to the pressure introducing cylinder 29a of the housing 29. The bellows 32 separates the outside of the atmospheric pressure introducing cylinder 18a from the inside of the housing 29. Bellows 32
Is a flexible thin film made of rubber or synthetic resin, and is formed in a bottomed cylindrical shape. The side surface of the bellows 32 is formed in a wavy state, and is formed so as to be flexible and deformable. The base end peripheral edge portion 32a of the bellows 32 is fitted into a mounting groove 29b in the inner wall of the pressure introducing cylinder 29a, and is mounted in an airtight state over the entire circumference. Further, as the material of the bellows 32, a material which is durable against toxic gas such as corrosive gas and has high safety is selected. In a space interposed between the bellows 32 and the sensor element 19, air is stored in an airtight state.

In the operation of the pressure sensor of this embodiment, the pressure introducing cylinder 29a is connected so that the pressure of the gas to be measured is applied, and the atmospheric pressure introducing cylinder 18a is connected to a rubber tube such that the atmospheric pressure is applied. When the pressure of the gas to be measured is applied to the pressure introducing cylinder 29a, the bellows 32 expands at that pressure, and the bellows 32 is brought into a state in which the pressure of the air in the space between the sensor element 19 and the bellows 32 becomes equal to the gas pressure. 32 transforms. As a result, the pressure of the gas to be measured is transmitted to the sensor element 19 via the pressure of the bellows 32 and the air inside the bellows 32, and the pressure of the gas to be measured is detected.

According to the pressure sensor of this embodiment, a dangerous gas such as a corrosive gas does not directly touch the sensor element 19, and the number of locations where gas leakage may occur in the sensor can be reduced. It will be safe. Embodiment 6 A sixth embodiment will be described with reference to FIG. The characteristic configuration of the present embodiment is such that the peripheral portion of the bellows 32 in the configuration of the above-described fifth embodiment is fixed by being sandwiched between two divided pressure introducing cylinders 29a and 29c. In the drawing, reference numeral 33 denotes a junction between the two divided pressure introducing cylinders 29a and 29c.

As a result, the base peripheral portion 32 of the bellows 32 is
a is more securely attached to the pressure introducing cylinder 29 in an airtight state, so that the airtightness of the space between the bellows 32 and the sensor element 19 is higher, and the safety can be higher. Embodiment 7 A seventh embodiment will be described with reference to FIG. The characteristic configuration of the present embodiment is that the base end peripheral portion 32a of the bellows 32 is fixed by being sandwiched between the connection portions between the sensor case 18 and the housing 29.

As a result, the bellows 32 is more securely fixed, and the number of mounting steps is reduced.

[0027]

As described above, according to the pressure sensor of the present invention.
And the differential pressure between the pressure of the fluid to be measured and the reference pressure is measured.
A fluid to be measured that is provided for introducing the fluid to be measured
Part and a reference fluid for introducing a reference fluid having the reference pressure
Introducing section, the measured fluid introducing section and the reference fluid introducing section
And a pressure detector for detecting the differential pressure.
Then, the pressure detecting unit is moved over the pressure receiving surface formed on the substrate.
It is composed by coating with a gel layer.
The pressure of the gel layer of the detecting unit and the pressure of the measured fluid introducing unit
Introducing the fluid to be measured from a space between one end on the side of the detection unit
A gas-resistant liquid to the gas of the fluid to be measured
The measured flow is filled at the other end of the measured fluid introduction section.
The liquid spills due to surface tension with a smaller diameter than the body introduction part
A place where the liquid is not filled and is formed with a hole diameter that does not come out
A constant length tip section is formed, and the gas pressure of the fluid to be measured is
The liquid in the fluid introduction section through the hole in the tip section
And acts on the pressure-receiving surface via the gel layer.
With this configuration, it comes in contact with the gas to be measured at the fluid introduction section.
The opening on the side to be measured is smaller in diameter than the
If the hole diameter does not allow the liquid to spill due to surface tension,
In addition, the end section of a predetermined length that is not filled with liquid
The fluid to be measured
No dust adheres to the inlet at the tip of
A gel layer is formed from the gas to be measured by holding a sufficient amount of liquid stably.
Can be reliably protected and stable for a long time
Measurement performance can be maintained and stable measurement performance over a long period of time
It is highly reliable that can maintain performance.

[0028]

[0029]

[0030]

[0031]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the structure of a pressure sensor according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a structure of a pressure sensor according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing details of the vicinity of a gas introduction portion of the pressure sensor according to the third embodiment.

FIG. 5 is a sectional view showing a structure of a pressure sensor according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing details of the vicinity of a gas introduction portion of the pressure sensor according to the fourth embodiment.

FIG. 7 is a sectional view showing the structure of a pressure sensor according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view showing a structure of a pressure sensor according to a sixth embodiment of the present invention.

FIG. 9 is a sectional view showing the structure of a pressure sensor according to a seventh embodiment of the present invention.

FIG. 10 is a cross-sectional view showing the structure of a conventional pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer frame 2 Gas introduction part (measurement fluid introduction part) 3 Sensor case 4 Adhesive 5 Atmosphere introduction part (reference fluid introduction part) 6 Silicon substrate 7 Silicon film (pressure detection part) 8 Gel 13 Partition part

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tokuyoshi Ohashi 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Kosaku Kubo 1006 Kazuma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd. (72) Inventor Nao Uno 1006 Okadoma Kadoma, Kadoma, Osaka Pref. Yoshiyuki Nakamizo 3158 Shimo-Okubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Inside Hokuriku Electric Industry Co., Ltd. No. 3158 Shimo-Okubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Inside Hokuriku Electric Industry Co., Ltd. (72) Inventor Hiroyuki Ishiwari Toyama 3158 Shimo-Okubo, Osawano-machi, Shinkawa-gun Hokuriku Electric Industry Co., Ltd. (56) References JP-A-2-120634 (JP, A) JP-A-2-170032 (JP, A) JP-A-3-264830 (JP, A) Japanese Unexamined Patent Publication No. 4-125438 (JP, A) Japanese Utility Model Showa 62-131454 (JP, U) Japanese Utility Model Showa 63-199044 (JP, U) Japanese Utility Model Showa 60-48136 (JP, U) Japanese Utility Model Showa 62 -201035 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 9/04 101

Claims (2)

(57) [Claims] 1. A measuring fluid introducing section (2) provided for measuring a differential pressure between a pressure of a measuring fluid and a reference pressure, for introducing the measuring fluid, and introducing a reference fluid serving as the reference pressure. Reference fluid inlet
(5) , the measured fluid introduction unit (2) and the reference fluid introduction unit
(5) a pressure detecting unit for detecting the differential pressure
(7) , wherein the pressure detecting section (7) is formed by coating a pressure receiving surface formed on a substrate with a gel layer (8) , and the gel of the pressure detecting section (7) is formed. Layer (8) and said measured
One end of the fluid introduction section (2) on the pressure detection section (7) side;
From the space between the target fluid introduction part (2)
Filled with gas-resistant liquid (14) against gas of measurement fluid
And the other end of the fluid to be measured (2) is connected to the fluid to be measured.
The liquid (14) is smaller in diameter than the inlet (2) and has a surface tension.
The liquid (14) is formed to have a hole diameter that does not spill out by the liquid (14).
A tip section (12) of a predetermined length not filled with is formed
And the gas pressure of the fluid to be measured is increased through the hole in the tip section (12).
Acts on the liquid (14) of the fluid introduction part (2) to be measured
And a pressure sensor configured to act on the pressure receiving surface via the gel layer (8 ). 2. A fluorinated oil as the liquid (14).
The pressure sensor according to claim 1, wherein: