JPH0954004A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate pressure leakage with a simple structure by setting a pressure sensor while making an object to be measured, such as gas or liquid, exist so as not to come into direct contact with a joing face of the sensor. SOLUTION: Regarding the pressure sensor 1 to detect a pressure to be measured in a manner wherein the pressure to be measured supplied from an open part in one end of a pressure introducing pipe is introduced into a pressure introducing pipe 5' and the introduced pressure to be measured is detected by a pressure detecting element 4 installed in an open part in the other end of the pressure introducing pipe 5' and closing the open part in the other end, the peripheral area of the open part in the other end of the pressure introducing pipe 5' is filled with a gel material or an oil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting the pressure of liquid, gas or the like.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a general pressure sensor showing a conventional example. The pressure sensor element 1 includes a stem 2 having a hole 2a formed in the center, a silicon pedestal 3 fixed on the stem 2 and having a hole 3a formed in the center, and a silicon pedestal 3 provided on the silicon pedestal 3. The piezoresistive pressure detection chip 4 using fixed single crystal silicon and the stem 2 are arranged on the side where the detection chip (pressure detection element body) 4 is not located, and a hole 5a is formed in the center. A pressure introducing pipe (pressure introducing path) 5, a connecting lead 7 supported by the stem 2 and connected via a gold wire 6, and a cap 8 covering the silicon pedestal 3, the detection chip 4 and the upper end of the connecting lead 7. It is equipped with. Further, 9 is a sealing means by a soldering means for sealing a small hole for venting the air provided in the cap 8, which keeps the pressure in the cap 8 in a vacuum state after deaeration.

The hole 2a of the stem 2, the hole 3a of the silicon pedestal 3 and the hole 5a of the pressure introducing pipe 5 communicate with each other to form a pressure introducing means, and these holes 2a, 3a and 5a are formed. External pressure acts on the detection chip 4 via the external pressure. Further, the detection chip 4 constitutes a Wheatstone bridge by the semiconductor strain gauges R1, R2, R3 and R4 as shown in FIG. Further, the stem 2 and the pressure introducing pipe 5 are joined by brazing, and the stem 2, the silicon pedestal 3, and the silicon pedestal 3 and the detection chip 4 are Au-S.
They are joined by an i (gold-silicon) eutectic bond.

Next, a pressure detection unit equipped with this pressure sensor will be described with reference to FIG. This pressure detection unit has a case 10, and a connection terminal 11 is fixed to the upper part of the case 10 by insert molding. A guide groove 12 is integrally formed in the case 10, and a coil spring 13 having one end connected to the connection terminal 11 is arranged in the guide groove 12. Further, the case 10 is provided with a screw hole 14.

The pressure detecting unit has a holder 15 as a holding means, and a relay terminal 16 is fixed to the holder 15 by insert molding. And
The holder 15 holds a processing circuit board 18 on which a processing circuit 17 that performs a predetermined processing on an input signal is mounted. The processing circuit board 18 is electrically connected to the relay terminal 16 by soldering. There is. And the pressure sensor 1
The case 1 is fixed by the mounting screw 30 while the stem 2 of the pressure sensor 1 and the edge of the cap 8 are fixed by the holder 15 and the pressing plate 19 by heat caulking and held.
It is fixed at 0. In addition, the connection lead 7 and the relay terminal 1
6 is previously connected by soldering.

Further, the stem 2 is provided on the open surface of the case 10.
0 is fitted, and an O-ring 22 is contracted in a ring groove 21 engraved on the mating surface of the case 10 and the stem 20 to prevent moisture and the like from entering from the mating surface. There is. The central portion of the stem 20 projects downward, and a hole 23 that penetrates in the up-down direction is formed in the center of the projecting portion. A ring-shaped protrusion 24 is integrally formed on the bent portion inside the stem 20. Further, the pressure introducing pipe 5 is inserted into the hole 23, and an O-ring 25 and a seal ring 26 as sealing means are arranged between the pressure introducing pipe 5 and the hole 23 formed in the stem 20. ing. The projection 24 has a function as a stopper that restricts the axial movement and separation of the O-ring 25 and the seal ring 26.

Next, the operation will be described. Note that, here, a case will be described in which the pressure detection element shown in FIG. 3 is mounted on a pipe for feeding a liquid and the pressure of the liquid is measured.
That is, the pressure of the liquid in the pressure introducing pipe 5 is measured by the pressure sensor 1.
It acts on the detection chip 4 through the pressure introduction pipe 5 of 1, and the pressure is converted into an electric signal by the piezoresistive effect of the detection chip 4. This detection signal is sent from the connection lead 7 to the processing circuit board 18 via the relay terminal 16, and the processing circuit board 18 performs a predetermined processing. Then, the processed signal is sent from the processing circuit board 18 to the coil spring 1
It is sent to the connection terminal 11 via 3 and further sent to an external device (not shown) via a lead wire.

[0008]

The conventional pressure sensor has the following problems.
As described above, since the inside of the cap 8 is configured to be maintained in a low pressure state such as a vacuum, the joint surface between the stem 2 and the silicon pedestal 3 or the silicon pedestal 3 and the detection chip 4 is formed.
There is no problem as long as the joint surface with and is closely joined without a minute gap, but during a long period of time, gas, liquid, etc. to be measured leaks into the cap 8 through the minute gap. It is considered that the characteristics may be deteriorated (for example, the characteristics change from a solid line to a broken line as shown in FIG. 6) or cause a failure. In particular, when the measurement target is gas, there is a fear that the gas is likely to leak. The present invention has been made in order to solve the above-mentioned problems, in which the gas to be measured does not come into direct contact with the bonding surface, and an object consisting of molecules larger than the gap is interposed so that the pressure is reduced. The purpose is to reduce the leakage of.

[0009]

In the pressure sensor according to the present invention, the pressure to be measured supplied from the one end opening of the pressure introducing pipe 5 is introduced into the pressure introducing pipe 5, and the introduced pressure to be measured is introduced. A pressure sensor that is provided by welding to the other end opening of the pressure introducing path and that detects the measured pressure by a pressure detection element that closes the other end opening, the other end opening in the pressure introducing path The vicinity was filled with a gel-like member or oil.

[0010]

In the pressure sensor according to the present invention, since the pressure detecting element is attached and the vicinity of the other end opening closed by the pressure detecting element is filled with the gel member or the oil, a minute gap is closed. Thus, the pressure of the gas to be measured can reduce leakage.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same or equivalent components as those described in the description of the conventional example are denoted by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described below. explain.

That is, in FIG. 1, reference numeral 31 is a pressure transmission medium such as silicon gel or silicone oil, which is a gel-like substance with little pressure loss due to pressure transmission, and is filled in the entire tip portion of the pressure introducing pipe 5. Then, it is injected up to the position of the joint surface between the stem 2 and the silicon pedestal 3 with a syringe or the like. As a result, the pressure of the gas to be measured is transmitted to the pressure detection element 4 indirectly via the pressure introduction pipe 5, that is, via the pressure transmission medium 31 made of silicon gel, silicon oil, etc. Since it does not directly contact the joint surfaces formed on the upper and lower end surfaces of 3, it is possible to prevent pressure leakage.

Further, in FIG. 2, the pressure transmission medium 31 such as silicon gel or silicon oil covers the joint surface between the silicon pedestal 3 and the pressure detecting element 4, that is, the pressure introducing pipe 5 '.
Is filled so as to cover the front end opening of the. in this case,
The pressure introducing pipe 5 ′ has a shape in which the silicon pedestal 3 and the pressure introducing pipe 5 ′ in FIG. 1 are integrated, that is, the step portion 5 having a stopper function in the circumferential direction of the tip end portion of the pressure introducing pipe 5 ′.
Since a'is formed and the pressure introducing pipe 5'penetrates through the hole 2a of the stem 2 and is brazed, the number of places where pressure leaks is smaller than that shown in FIG.

[0014]

As described above, according to the present invention, it is possible to reduce the pressure leak easily and with a simple structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is a sectional explanatory view of a pressure sensor showing another embodiment of the present invention.

FIG. 3 is a cross-sectional explanatory view of a conventional pressure sensor.

FIG. 4 is an explanatory diagram showing a Wheatstone bridge structure which is a method of detecting a detection chip of a pressure sensor.

FIG. 5 is an explanatory cross-sectional view of a pressure detection unit incorporating a pressure sensor.

FIG. 6 is a characteristic explanatory view for explaining a problem of the conventional pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 pressure sensor 4 pressure detection element 5, 5'pressure introduction pipe 10 case 15 holder 16 relay terminal 18 processing circuit board 20 stem 22, 25 O ring 26 seal ring

Claims (1)

[Claims] 1. A pressure to be measured supplied from an opening at one end of the pressure introducing path is introduced into the pressure introducing path, and the introduced pressure to be measured is welded to an opening at the other end of the pressure introducing path. In a pressure sensor that is provided and detects the measured pressure by a pressure detection element that closes the other end opening, a gel-like member or oil is filled in the vicinity of the other end opening in the pressure introduction path. Pressure sensor.