JPH0634470A - Diaphragm pressure sensor - Google Patents

Abstract

PURPOSE:To obtain the assembling structure of a diaphragm pressure sensor that can improve the reliability of the sensor by enabling the sensor to perform measurement even in a high-temperature environment and can easily lead out the lead wires of strain gauges while the gauges are protected. CONSTITUTION:A diaphragm 2 composed of metallic foil is put on the opened surface of a cup-like metallic case 1 and joined to the surface by resistance welding and strain gauges 4 are stuck to the front-side surface of the diaphragm 2. Then, after a hollow ring 7 is put on the diaphragm 2 so that the peripheral margin of the diaphragm 2 can be sandwiched between the ring 7 and case 1 and the whole outer peripheral surface of this sensor assembly including the ring 7 is coated with a solder layer 8, they are integrally joined to each other and sealed. In addition, the lead wires 4a of the gauges 4 are directly lead out through the opened surface of the ring 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm type pressure sensor.

[0002]

2. Description of the Related Art As the above-mentioned diaphragm type pressure sensor, the opening surface of a cup-shaped metal case is covered with a diaphragm made of a metal foil having a strain gauge attached thereto, and the metal case and the periphery of the diaphragm are sealed and joined. Things are known. FIG. 3 shows a conventional structure of such a diaphragm type pressure sensor. In the figure, 1 is a cup-shaped metal case, 2 is a flat plate-shaped diaphragm made of a metal foil adhered to the opening end surface of the metal case 1, Reference numeral 3 denotes a solder layer in which an end surface (upper surface) of the metal case 1 and a peripheral edge of the diaphragm 2 superposed on the same are sealed and joined, and 4 is a strain gauge attached to a back surface (inside the metal case) of the diaphragm 2
Is a lead wire for taking out a signal connected to the strain gauge 4, and 5 is a sealing resin such as an epoxy resin that closes the lead hole of the lead wire 4a formed in the side wall of the metal case 1.

With such a structure, a gas phase of 1 atm, for example, is enclosed in a sealed space surrounded by the metal case 1 and the diaphragm 2. When a measurement pressure is applied from the outside with the diaphragm 2 as the pressure receiving surface, the diaphragm 2 is deformed due to the pressure difference between the inside and the outside, and the deformation amount is converted into an electric signal by the strain gauge 4 and taken out, and the gauge pressure is measured by an external measurement circuit. It is converted to and measured.

[0004]

However, the conventional structure of the diaphragm type pressure sensor described above has the following problems in terms of structure and environmental resistance. That is, (1) Since the peripheral edges of the metal case 1 and the diaphragm 2 are seal-joined with the solder 3, for example, the ambient temperature is 100 ° C.
When used in the above high temperature environment, the gas phase enclosed in the inner space of the metal case 1 expands in volume and the diaphragm 2 bends outward as shown by the chain line in FIG. A stress is applied to the solder joint in the direction of peeling the joint surface. On the other hand, when the solder layer 3 is exposed to a high temperature, the bonding force decreases, and as a result, the solder bonding surface is easily peeled off and the sealing function between the metal case 1 and the diaphragm 2 is lost, making pressure measurement impossible. Trouble occurs.

(2) The strain gauge 4 is attached to the back surface of the diaphragm 2 in order to protect the strain gauge. In this structure, the lead wire 4a of the strain gauge is attached to the side surface of the metal case 1 to be pulled out. Since it is necessary to form a lead-out hole for the lead wire and further to lead out the lead wire 4a, the lead-out hole needs to be closed with the sealing resin 5, which is troublesome to manufacture. The present invention has been made in view of the above points, and an object thereof is to solve the problems described above, to improve reliability by enabling measurement in a high temperature environment, and to further simplify the lead wire while protecting the strain gauge. It is an object of the present invention to provide a diaphragm type pressure sensor that can be pulled out to the outside, and particularly to provide an assembly structure thereof.

[0006]

In order to achieve the above object, in the pressure sensor of the present invention, the cup-shaped metal case and the diaphragm are joined by resistance welding, and the periphery of the diaphragm is sandwiched. Then, a hollow ring is superposed on the side opposite to the metal case, and the outer peripheral surface of the sensor assembly including the hollow ring is integrally sealed with a joint sealing material.

In addition, solder is used as the joint sealing material in the above construction, and a solder layer is applied to the entire outer peripheral surface of the sensor assembly consisting of the metal case, the diaphragm and the hollow ring to seal the parts from each other. Good to do. Further, in order to simplify the lead wire drawing structure of the strain gauge, there is a structure in which the strain gauge is attached to the front surface of the diaphragm and the lead wire of the strain gauge is drawn to the outside from the opening surface of the hollow ring.

[0008]

In the above structure, first, resistance welding is performed between the metal case and the peripheral edge of the diaphragm, so that the joint strength between the two is significantly increased as compared with the solder joint, and the welded joint is sandwiched between them. By fixing the hollow ring by overlapping it on the side opposite to the metal case, the curvature of the diaphragm caused by the vapor phase expansion in the metal case in the high temperature environment is restricted to the inner surface area of the hollow ring. Therefore, undue stress such as peeling off the joint surface is not applied to the resistance welding portion.

On the other hand, the joint sealing material (solder layer) integrally covering the outer periphery of the sensor assembly consisting of the metal case, the diaphragm and the hollow ring is used for the joint between the metal case and the hollow ring, and the metal case and the diaphragm. Plays a role of hermetically sealing the joint surface between and. Moreover, by additionally installing the hollow ring as described above, even if the diaphragm itself is curved, there is no risk of any stress being applied to the sealing layer covering the outer peripheral surface, and this ensures the high sealing performance.

Further, the hollow ring also serves as a peripheral wall for protection against a strain gauge attached to the front surface of the diaphragm. Moreover, by attaching the strain gauge to the front surface of the diaphragm, the lead wire can be directly pulled out through the opening surface of the hollow ring without taking the troublesome means of penetrating the metal case. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. In the figure, the same members corresponding to those in FIG. 3 are designated by the same reference numerals. In the illustrated embodiment, first, the peripheral edge of the diaphragm 2 to which the strain gauge 4 is attached on the front surface (pressure receiving surface side) is fixed to the end surface of the metal case 1 by seam welding or spot welding by resistance welding. 6
Indicates a resistance weld. Further, a hollow ring 7 is superposed on the side opposite to the metal case 1 with the peripheral edge of the diaphragm 2 sandwiched between them, and a bonding sealing material is provided on the outer peripheral surface of the sensor assembly including the hollow ring 7. As a result, a solder layer 8 is deposited by a depping method, and the solder layer 8 integrally joins the metal case 1 and the hollow ring 7 and seals the metal case 1 and the diaphragm 2. Further, the lead wire 4a of the strain gauge 4 is drawn out through the opening surface of the hollow ring 7.

With the above structure, the measured pressure is applied to the diaphragm 2 through the opening surface of the hollow ring 7, and the strain gauge 4 measures the strain amount of the diaphragm 2 based on the differential pressure from the gas phase pressure enclosed in the metal case 1. To be detected. Further, when the ambient temperature becomes high (100 ° C. or higher), the diaphragm 2 is convexly curved and deformed due to the expansion of the gas phase in the metal case 1, but the peripheral edge of the diaphragm is between the metal case 1 and the hollow ring 7. Since they are sandwiched and constrained in a sandwiched manner, no stress is applied to the resistance welding portion 6 and the solder layer 8 on the outer peripheral surface so as to separate the joint surface.
The sealing function between the diaphragm 2 and the diaphragm 2 is reliably retained. Further, the hollow ring 7 also serves as a protective partition for the strain gauge 4, and prevents the strain gauge 4 from being touched and damaged when the pressure sensor is used or handled.

Regarding the above point, according to an actual machine test conducted by the inventors, in the conventional structure of FIG. 3, when the ambient temperature exceeds 80 ° C., the sealing function of the diaphragm 2 is lost and the pressure measurement becomes impossible. According to the structure of FIG. 1, it has been confirmed that the ambient temperature can be safely measured even at 160 ° C., which is twice the ambient temperature. At the time of actual pressure measurement, by subtracting the deformation amount ε _a of the diaphragm 2 due to the change of the ambient temperature from the indicated value ε _m , the deformation amount ε _{p of the} diaphragm generated according to the pressure at high temperature ε _p = [epsilon] _{m- [} epsilon] _a is obtained, and the amount of deformation [epsilon] _p is introduced into a predetermined calibration formula P = a [epsilon] _p + b (where a and b are coefficients) to be converted into pressure P.

[0014]

As described above, according to the structure of the present invention, the measurement can be performed in a high temperature environment as compared with the conventional assembly structure, and the lead wire can be easily pulled out while protecting the strain gauge. It is possible to provide a diaphragm-type pressure sensor that is highly reliable and easy to assemble.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is an exploded perspective view of FIG.

FIG. 3 is a sectional view showing the configuration of a conventional diaphragm type pressure sensor.

[Explanation of symbols]

 1 Metal Case 2 Diaphragm 4 Strain Gauge 4a Lead Wire 6 Resistance Welding Part 7 Hollow Ring 8 Solder Layer (Joint Sealing Material)

Claims (3)

[Claims] 1. A diaphragm-type pressure sensor comprising a cup-shaped metal case, an opening surface of which is covered with a diaphragm made of a metal foil having a strain gauge attached thereto, and a metal case and a peripheral edge of the diaphragm being sealed and joined together. And the diaphragm are joined by resistance welding, and the outer periphery of the sensor assembly including the hollow ring is joined and sealed by stacking a hollow ring on the side opposite to the metal case while sandwiching the periphery of the diaphragm in a sandwich shape. A diaphragm type pressure sensor, which is integrally sealed with a stopper. 2. The pressure sensor according to claim 1, wherein solder is used as a joint sealing material, and a solder layer is applied to the entire outer peripheral surface of a sensor assembly including a metal case, a diaphragm, and a hollow ring. A diaphragm-type pressure sensor characterized by sealing between each other. 3. The pressure sensor according to claim 1, wherein a strain gauge is attached to the front surface of the diaphragm, and the lead wire of the strain gauge is drawn out from the opening surface of the hollow ring to the outside. Sensor.