JP3189516B2 - Gas pressure detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas pressure detecting device for LP gas and city gas.

[0002]

2. Description of the Related Art A conventional semiconductor pressure sensing device will be described with reference to a sectional view of FIG.

In FIG. 3, 1 is an outer frame, 2 is a pressure inlet,
Reference numeral 3 denotes a semiconductor sensor element, which is a diaphragm film having a thickness of several microns provided by etching on a silicon substrate, on which a semiconductor resistor whose resistance value changes due to mechanical strain is formed. Reference numeral 4 denotes a pedestal which is usually made of metal or glass having a coefficient of thermal expansion close to the coefficient of thermal expansion of the semiconductor sensor element 1, and is used as a buffer for strain. A lead frame 5 electrically connects the semiconductor sensor element 1 to the circuit board 8 and fixes the circuit board 8.
Numeral 6 denotes a bonding portion where the bonding is performed at a high temperature of 200 ° C. or more, such as eutectic bonding. Numeral 7 denotes a sensor case, in which a differential pressure hole 12 communicating with the atmosphere is provided at an upper portion. 8 is a circuit board on which an electric circuit such as an amplifier circuit is formed, 9 is an outer frame 1 and a sensor case 7
The adhesive 10 is molded with a plastic resin, and the semiconductor sensor element 3 is coated with a gel 11 so as to prevent direct contact with dust and moisture contained in the fluid to be measured.

[0004] Based on the above configuration, the operation will be described below. The semiconductor sensor element 3 generates mechanical strain due to a differential pressure from the atmospheric pressure detected by a differential pressure hole 12 in the upper part of the pressure sensor case 7 applied from the pressure inlet 2 in the lower part of the outer frame 1, and the mechanical distortion is It is proportional to the pressure difference between the applied pressure and the atmospheric pressure. When the semiconductor sensor element 3 generates distortion, the semiconductor sensor element 3
The resistance value of the semiconductor resistor formed above changes in proportion to the magnitude of the strain. The change in the resistance value is detected, amplified and output to measure the differential pressure between the applied pressure and the atmospheric pressure.

[0005]

However, in the above configuration, the gas directly touches the sensor case 7, the adhesive 9, and the gel 11, and the adhesive 9 is mainly made of a polymer material. However, there is a problem in that the gas directly contacts the gas, so that it is easily eroded by the gas, swells and transmits the gas, and in the worst case, the gas continuously leaks to the atmosphere via the resin mold 9. Further, while the gas repeatedly undergoes liquefaction and vaporization due to temperature fluctuations, the gas undergoes deformation and deterioration due to swelling and shrinkage, and as a result, there has been a problem that the differential pressure between the gas pressure and the atmosphere cannot be measured accurately.

The present invention solves the above-mentioned problems, and prevents a material directly in contact with a gas to be measured (LP gas, city gas) from being deformed or deteriorated due to swelling and shrinkage, thereby preventing the material from being exposed to the outside of the gas pressure detecting device. Prevent gas leakage. Also, in the event of a gas leak, the first object is to limit the amount of leaked gas to the minimum and to realize a gas pressure detecting device capable of detecting a gas leak by always reducing the detection pressure in the event of a gas leak. I have.

A second object is to constantly detect the gas pressure in the gas passage to be measured by a gas pressure detecting device having gas resistance and compare and judge the gas pressure to be measured with a predetermined appropriate gas pressure stored in advance. Another object of the present invention is to provide a highly reliable abnormality detection device that accurately detects gas leakage.

[0008]

Means for Solving the Problems In order to achieve the above-mentioned first object, a gas pressure detecting device according to the present invention comprises a semiconductor pressure sensor element and a pressure sensor element.
Pressure of gas-resistant adhesive on the upper surface and pressure of the resin case on the outer peripheral surface of the lower end
Gas resistance interposed airtight between the inner wall of the inlet and the inner wall
Fixed by hanging from surrounding members with rubber seal material
And a gas pressure detection passage enclosed in an airtight state with the surroundings.
A pressure introducing tube formed of a gas-resistant material to be formed , a lead frame electrically connected to the pressure sensor element via a lead, and the pressure introducing tube and the lead frame integrally formed of resin. A sensor case, and a circuit board electrically connected to the sensor case and the lead frame via the lead frame;
A resin case made of a gas-resistant material having a pressure chamber formed by holding the sensor case in an airtight state through an adhesive around the pressure adjusting hole.

[0009]

[0010]

According to the present invention, the following effects can be obtained by the above configuration.

According to the configuration of the first problem solving means, the fluid to be measured (LP gas, city gas) passes through the pressure introducing portion of the resin case (gas resistant material) and the gas resistant rubber sealing material and the pressure introducing pipe (gas resistant gas). Material), and contacts only the back surface of the pressure sensor element, and the other constituents include the pressure medium to be measured (LP gas,
Gas (LP) is designed to prevent contact with city gas.
(Gas, city gas) to prevent material deterioration. Also, if a gas leak occurs from the gas-resistant adhesive under the pressure sensor element, the gas leaks into the pressure chamber,
The gas amount corresponding to the opening area of the pressure adjusting hole leaks to the outside, and the pressure of the pressure chamber corresponding to the opening area is applied to the surface opposite to the pressure receiving surface of the pressure sensor element. Therefore, if the opening degree is determined so that the opening area of the pressure adjusting hole becomes a leakage flow rate equal to or less than the explosion limit of the fluid to be measured (LP gas, city gas), the gas explosion accident can be prevented and the pressure chamber can be reversed. When leakage occurs due to the application of pressure, the detected pressure decreases, and abnormality can be detected.

[0012]

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a sectional view of a pressure detecting device according to Embodiment 1. In FIG. 1, reference numeral 1 denotes a semiconductor pressure sensor element, which is a diaphragm film having a thickness of several microns provided by etching on a silicon substrate, on which a semiconductor resistor whose resistance value changes due to mechanical strain is formed. I have. The pressure sensor element 1 is connected to the lead frame 3 and the pressure introducing pipe (gas-resistant material) via the gas-resistant adhesive 2.
4 is held in a gas-tight state on the upper surface of the pressure introducing pipe 4 of the sensor case 5 formed integrally, and forms a pressure detecting passage. Electrically, they are connected by the pressure sensor element 1 to the lead 8 to the lead frame 3 to the circuit board 10, and the lead frame 3 also holds the circuit board 10. The circuit board 10 has an electric circuit such as an amplifier circuit formed thereon.
Reference numeral 6 denotes a resin case which accommodates the sensor case 5 and a circuit board 10 having a surface coated with a potting agent 11, and a pressure adjusting hole 12 on an upper portion and an adhesive 9 around the pressure adjusting hole 12. A pressure chamber 13 is provided by holding the sensor case 5 in an airtight state via the pressure chamber 13. 7 is a gas-resistant rubber sealing material and a pressure introduction pipe 4
Is airtightly interposed between the outer wall surface of the resin case 6 and the inner wall surface of the pressure introducing portion of the resin case 6.

The operation based on the above configuration will be described below. The pressure sensor element 1 generates a mechanical strain due to a differential pressure between the pressure applied from the pressure introducing portion at the lower portion of the resin case 6 and the atmospheric pressure, and the mechanical strain is proportional to the differential pressure between the applied pressure and the atmospheric pressure. When the pressure sensor element 1 generates a strain, the resistance value of the semiconductor resistor formed on the pressure sensor element 1 changes in proportion to the magnitude of the strain. The change in the resistance value is detected, amplified by an amplifier circuit provided on the circuit board 10 and output, thereby measuring the differential pressure between the applied pressure and the atmospheric pressure.
If a gas leaks from the gas-resistant adhesive 2 under the pressure sensor element 1, the gas leaks into the pressure chamber 13, and the gas amount corresponding to the opening area of the pressure adjusting hole 12 becomes outside. At the same time, the pressure of the pressure chamber 13 corresponding to the opening area is applied to the surface of the pressure sensor element 1 opposite to the pressure receiving surface, and the detection pressure is reduced.

(Embodiment 2) FIG. 2 is a control block diagram in which an abnormality detection device is added to the gas pressure detection device of the first embodiment. In FIG. 2, a gas pressure detecting device 22 for detecting the pressure of the gas flow path 21 includes a reference fluid introducing portion (pressure adjusting hole) 23.
To the atmosphere, and connected to detect a pressure difference with the atmosphere. A gas meter 24 for measuring a gas flow rate is provided on the gas flow path 21 on the downstream side of the gas pressure detecting device 22 mounting position.
Further, a shutoff valve 25 for shutting off gas is connected downstream of the valve. Reference numeral 26 denotes a pressure abnormality detection unit, and the gas pressure detection device 2
2, a pressure detection signal is input and compared with a predetermined appropriate pressure.
Connected to output.

The operation based on the above configuration will be described below. When the gas pressure detecting device 22 of the first embodiment leaks gas, the gas pressure detecting device 22 outputs a detection signal of a decrease in gas pressure, is input to the pressure abnormality detection unit 26, and outputs a cutoff signal from the pressure abnormality detection unit 26. Is output to the shutoff valve to shut off.

[0018]

As described above, the gas pressure detecting device of the present invention has the following effects.

According to the first aspect, the portion in contact with the pressure medium to be measured (LP gas, city gas) is subjected to a gas resistance treatment, and the other components are not contacted by the medium to be measured (LP gas, city gas). By doing so, gas leakage due to swelling of the material is prevented. In addition, it is possible to prevent liquefaction (shrinkage) and deformation due to gasification (expansion) of the gas due to temperature fluctuation and deterioration of characteristics due to deterioration. Even if a gas leak occurs, it is possible to limit the amount of gas leak below the explosion limit of the fluid to be measured (LP gas, city gas) and to detect the leak. As described above, a safe and highly reliable gas pressure detection device can be realized.

[0020]

[Brief description of the drawings]

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

FIG. 2 is a control block diagram of a gas pressure detecting device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional semiconductor pressure detecting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure sensor element 3 Lead frame 4 Pressure introduction pipe (gas-resistant material) 5 Sensor case 6 Resin case (gas-resistant material) 7 Gas-resistant rubber sealing material 8 Lead 9 Adhesive 10 Circuit board 11 Potting agent (gelling) 12 Pressure adjustment hole 13 Pressure chamber 26 Pressure abnormality detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-102036 (JP, A) JP-A-5-196532 (JP, A) JP-A-2-170032 (JP, A) 6042 (JP, U) Hira 4-47642 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01L 9/04 G01L 19/00

Claims (1)

(57) [Claims] 1. A pressure sensor element made of a semiconductor, a gas-resistant adhesive on the upper surface, and a resin cover on a lower peripheral surface.
Airtight between the inner wall of the pressure
Suspended from surrounding members with a gas-resistant rubber seal material
Gas pressure sensor, which is fixed in
Pressure introduction pipe made of gas-resistant material that constitutes the knowledge passage
If, through a lead frame are electrically connected via the pressure sensor element and the lead, a sensor case formed integrally molding the pressure inlet pipe and the lead frame with a resin, said lead frame with the sensor casing And a pressure chamber formed by holding the sensor case in an airtight state through a pressure adjusting hole and an adhesive around the pressure adjusting hole. And a resin case made of a gas-resistant material.