JPH08159900A - Manufacture of pressure sensitive diaphragm for pressure sensor - Google Patents

Abstract

PURPOSE: To provide a manufacturing method for a pressure sensitive diaphragm for pressure sensor by which the effect of the strain and residual stress on the diaphragm in the state that the diaphragm is built in a case of a pressure sensor are lessened and which retains high flatness, is easy to be handled at the time of assembly, and has high reliability. CONSTITUTION: A grooving process to form a pattern corresponding to the outline of a diaphragm is carried out from both sides of a base material 8, which is a thick metal plate 8 by half-etching and while the peripheral joining parts 15 to be joined with a case of a pressure sensor by welding are left as they are, a thin center flat part 13 is formed in the inner circumferential region, and a corrugated part 14 in which projected and recessed parts are arranged is formed concentrically to manufacture a corrugated diaphragm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a pressure-sensitive diaphragm incorporated in a pressure sensor for detecting a slight pressure applied to, for example, leak detection of city gas, particularly a corrugated diaphragm suitable as a diaphragm for a capacitive pressure sensor. Regarding

[0002]

2. Description of the Related Art As a pressure sensor for detecting a slight pressure described above, a capacitive pressure sensor as shown in FIG. 5 is disclosed in Japanese Patent Application No. 5-109.
No. 686 is proposed by the same applicant as the present invention. In the figure, 1 is a metal upper case that also serves as a fixing plate for the pressure-sensitive diaphragm 2, 3 is a lower case made of an insulator that also serves as a printed wiring board substrate, and 4 is provided on the lower case 3 facing the diaphragm 2. Fixed electrode, 5 is connection electrode, 6
Is an electronic circuit component, 7 is an external lead-out terminal, a pressure-conducting hole 1a for the measured pressure is formed in the upper case 1, and an atmospheric pressure-conducting hole 3a is opened in the lower case 3. The peripheral edge of the diaphragm 2 is hermetically welded to the step portion 1b of the upper case 1. The pressure detecting operation of such a capacitive pressure sensor is well known, and the description thereof is omitted here.

On the other hand, in the pressure sensor shown in FIG. 5, a flat diaphragm is used as the diaphragm 2,
Some have adopted a corrugated diaphragm instead of a flat diaphragm. In this corrugated diaphragm, a flat portion facing the fixed electrode 4 shown in FIG. 5 is formed in the central portion of the plate surface,
A ring-shaped concavo-convex surface arranged in concentric circles is formed in a plate surface region between the central flat portion and a peripheral portion welded to the upper case 3 so as to have a corrugated cross section. This corrugated diaphragm is widely used because it is less affected by thermal strain and residual stress due to welding and has excellent pressure / displacement characteristics, which are important characteristics of the diaphragm.

Further, in the case of manufacturing the above-mentioned corrugated diaphragm, according to the conventional manufacturing method, a thin disk-shaped metal foil is pressed to form a corrugated portion, and then the diaphragm is annealed to perform the press processing. The residual stress generated at this time is removed, and the diaphragm manufactured in this way is welded to the metal upper case shown in FIG. 5 in the process of assembling the pressure sensor.

[0005]

By the way, the capacitive pressure sensor assembled by using the corrugated diaphragm manufactured by the above method has the following problems in terms of output characteristics and assemblability. 1) The corrugated diaphragm manufactured through the press working and annealing process is welded to the peripheral edge of the diaphragm in order to incorporate it into the case of the pressure sensor. Due to this welding, the diaphragm itself is mechanically and thermally distorted. Is newly generated. In addition, in this case, the influence of strain is concentrated on the central flat portion of the diaphragm and disturbs the flatness, so that the output characteristic of the pressure sensor tends to vary due to the strain, particularly in the capacitive pressure sensor.

2) Further, since the diaphragm for detecting a slight pressure has a very thin wall thickness (for example, a wall thickness of about 30 μm), it is easily deformed even if a slight impact is applied, and a new strain is generated. It is troublesome to manage the parts because it is necessary to pay close attention to the handling when assembling into the sensor. The present invention has been made in view of the above points, the object is to solve the above problems, strain in the state of being incorporated into the case of the pressure sensor, the effect of residual stress is small, and high flatness can be secured, Moreover, it is another object of the present invention to provide a highly reliable method for manufacturing a pressure-sensitive diaphragm for a pressure sensor, which is easy to handle during assembly.

[0007]

The above object can be achieved by the present invention by the following manufacturing method. (1) First invention: A thick metal flat plate is used as a base material, and etching grooves are formed on both surfaces of the base material in a pattern corresponding to the contour of the diaphragm, and the outer peripheral joint portion of the diaphragm is the same as the base material plate thickness. Remainingly, a thin central flat portion and a corrugated portion in which concavo-convex surfaces are arranged concentrically are formed in the inner peripheral surface area. Specifically, in the first etching step, concentric circles are formed on one surface of the base material. A ring-shaped groove formed in parallel is processed, and in the second etching process, a ring-shaped groove formed in a concentric pattern is formed on the opposite side of the base material by shifting a half pitch from the groove formed in the first etching process. The corrugated part shall be formed.

(2) Second invention: A flat disk-shaped metal foil is placed on a metal diaphragm fixing plate which is a pressure sensor case, and a ring-shaped projection and a metal foil formed on the fixing plate. Then, the diaphragm corrugated portion is formed by press working on the metal foil in this state, and then the residual stress of the metal foil is removed by gas pressurizing in the direction opposite to the press working.

Further, as the press forming method of the diaphragm corrugated portion in the above, a method of press-molding the diaphragm corrugated portion on the metal foil using the fixing plate itself as a press die, or a combination of a dedicated press die with the fixing plate is used. There is a method of press-forming the corrugated portion of the diaphragm on the metal foil.

[0010]

According to the first aspect of the present invention, the outer peripheral joint of the diaphragm is left thick with respect to the thick plate-shaped base material, and the thin central flat portion and the corrugation are formed in the inner peripheral surface area. By forming the portion by the etching groove processing, there is no possibility of strain as seen in the press working method, and high flatness can be secured in the central flat portion of the diaphragm that functions as a pressure sensitive portion. On the other hand, the outer peripheral joint of the diaphragm is thick and has large rigidity and heat capacity. Therefore, even if the peripheral edge of the diaphragm is welded to the case when it is assembled into the pressure sensor, the effect of thermal strain and residual stress is on the corrugated part and the central flat part. Since it has almost no effect on the pressure-sensitive portion and the outer peripheral edge portion is thick and has high mechanical strength, the diaphragm can be easily handled.

According to the second aspect of the present invention, a flat plate-shaped metal foil serving as a corrugated diaphragm is welded and joined to the diaphragm fixing plate which is a part of the case of the pressure sensor along the entire outer peripheral edge thereof, and then the metal foil is kept in this state. By forming the corrugated portion by performing press working on the, the welding strain (the strain is unevenly distributed) generated during welding is made uniform by the pressing operation of the corrugated portion. However, the residual stress newly generated by the press working remains. Therefore, if high pressure air, nitrogen gas, etc. is applied to the plate surface of the diaphragm from the side opposite to the press working,
The residual stress is released, and almost no strain or residual stress remains. This has been confirmed by the results of experiments conducted by the inventors. Moreover, in this manufacturing method,
Without handling the corrugated diaphragm as a single part,
Welding of the diaphragm to the case of the pressure sensor and press forming of the corrugated portion of the diaphragm can be performed simultaneously in the same process, and a troublesome annealing process is not necessary. Note that, instead of performing the above-mentioned gas pressurization, if annealing is performed after press-molding the corrugated portion in a state where the peripheral edge of the diaphragm is welded to the case and constrained, the strain increases conversely from the experimental results. It is clear.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIGS. 1 and 2 show an embodiment corresponding to claims 1 and 2 of the present invention, and a manufacturing method thereof will be described in the order of steps with reference to FIGS. 1 (a) to 1 (d).

First, in the first etching step, half-etching is performed from one side (top surface) of the base material 8 using the thick metal flat plate (thickness of about 0.3 mm) shown in FIG. Grooving is performed to form a ring-shaped peripheral notch 9 having a pattern corresponding to the outer shape of the diaphragm, a circular flat groove 10 at the center, and concentric ring-shaped concave grooves 11 as shown in FIG. Put in. In addition, the connecting portion 9a is left uncut at several places around the cut groove 9. In the subsequent second etching step, as shown in FIG. 6C, half-etching is performed from the rear surface side (lower surface) of the base material 8 and the ring-shaped concave grooves 12 are arranged in concentric circles with a half pitch offset from the concave grooves 11. Dig in. Finally, the connecting portion 9a is cut to complete the corrugated diaphragm shown in FIG. In addition, in FIG.
13 is a central flat portion facing the fixed electrode 4 described in FIG.
Reference numeral 14 is a diaphragm corrugated portion, and 15 is a peripheral edge joint portion.
Here, the thickness of the central flat portion 13 and the corrugated portion 14 is 30 μm.
The joint portion 15 is not etched, and the plate thickness of the base material 8 (about 0.3 mm) is left as it is. FIG. 2 is a plan view of the completed corrugated diaphragm. Although the wave number of the corrugated portion 14 is two in the illustrated example, this wave number is not limited to the number in the illustrated example, and a desired pressure / displacement characteristic can be obtained in relation to the thickness of the diaphragm. It can be decided appropriately.

The corrugated diaphragm manufactured as described above is mounted on the metal case of the pressure sensor as described with reference to FIG. 5, and the peripheral edge joint portion 15 is welded and assembled to the case to assemble. Further, it is possible to manufacture many diaphragms from one base material 8 at the same time. Example 2 FIG. 3 shows an example corresponding to claims 3 and 4 of the present invention, and (a) to (c) show the manufacturing steps in order. First, in FIG. 3A, a metal fixing plate 16 which also serves as a case of the pressure sensor (the fixing plate 16 corresponds to the upper case 1 in FIG. 5, and a pressure guiding hole 16a is opened in the center) is provided. In advance, a ring-shaped projection (projection) 16b that is welded to the peripheral edge of the diaphragm and a ring-shaped molding groove 16c that serves as a mold for press-molding the corrugated portion of the diaphragm are formed by a forging method or the like. Then, on the ring-shaped projection 16a formed on the fixing plate 16 in the first step, a thin wall (thickness 3
A disk-shaped metal foil 17 (about 0 μm) is placed, the welding electrode 18 is applied to the disk-shaped metal foil 17, and a current is supplied from the welding power source 19 to pass between the peripheral edge of the metal foil 17 and the ring-shaped projection 16b. Resistance welding is performed over the entire circumference. Next, the second shown in FIG.
In the step (1), the metal foil 17 is pressed from above by the ring-shaped punch 20 conforming to the shape of the molding groove 16c to form the corrugated portion 17a of the diaphragm on the plate surface of the metal foil 17. Then, in the third step shown in FIG.
Place the stopper plate 21 on 6 and fix the fixed plate 1 in this state.
High-pressure air or nitrogen gas is introduced through the pressure guiding holes 16a of the metal foil 6, and the metal foil 17 is placed on the lower surface side (direction opposite to press working).
Pressurize with gas. As a result, the strain and residual stress generated in the metal foil 17 in the pressing step are removed. In this case, the stopper 21 is the metal foil 1 associated with gas pressurization.
7 serves as a protective member for preventing the transitional bending of 7.

Then, the assembly of the fixed plate and the corrugated diaphragm manufactured by the above method is attached to the lower case 3 of the pressure sensor described in FIG. 5 and assembled. Third Embodiment: FIG. 4 shows an application example of the above-mentioned second embodiment corresponding to claim 5 of the present invention. In this embodiment, the fixing plate 16 is an annular frame body, and the corrugated portion is press-molded on the metal foil 17 by using a dedicated press die. It demonstrates in order in (c). First, in the first step shown in FIG. 7A, the ring-shaped protrusion 16b formed on the fixing plate 16 in the same manner as in the second embodiment.
A thin disk-shaped metal foil 17 is placed on the metal foil 17, and resistance welding is performed between the ring-shaped protrusion 16b and the peripheral edge of the metal foil 17 in this state. In the subsequent second step, as shown in FIG. 3B, the fixing plate 16 is attached to a dedicated press die (die) 22 for forming a corrugated portion.
The punch 20 is pressed from above to form the corrugated portion 17a. 22a is a press die 2
Formed groove 2 (corresponding to formed groove 16c in FIG. 3)
Is. Then, after molding the corrugated portion 17a, (c)
In the third step shown in the figure, the lid member 16d (represented by a chain line) having the pressure guiding hole 16a opened is attached to the central opening of the fixed plate 16, and the stopper plate 21 is set on the opposite end face. In this state, gas pressurization is applied from the outside in the same manner as in Example 2 to remove the strain and residual stress generated in the metal foil 17 by the pressing operation.

In this embodiment, since the dedicated press die 22 is used for forming the corrugated portion of the diaphragm, the second embodiment is used.
High productivity can be obtained compared with. In the second and third embodiments, it is possible to continuously perform the steps of supplying the metal foil 17, punching, welding and joining to the fixed plate 16, press molding, and gas pressurization.

[0017]

As described above, the manufacturing method of the present invention has the following effects. (1) The corrugated diaphragm manufactured by adopting the etching method according to claims 1 and 2 has almost no strain as seen in the press-molded product, and the flatness of the central flat portion is high. Variations in displacement characteristics are small and product yield is improved. Moreover, since the peripheral portion of the diaphragm is thick, it is easy to handle and install the pressure sensor in the case, and it is hardly affected by thermal strain and residual stress due to welding and joining to the case. The advantages of

(2) Further, by adopting the manufacturing method according to claims 3 to 5, the diaphragm can be press-molded and the pressure sensor can be assembled into the case without treating the corrugated diaphragm as a single component as in the conventional case. High productivity can be obtained in the same process, and distortion and residual stress generated in the diaphragm due to welding and joining to the case are removed by press forming of the corrugated part and gas pressurization performed thereafter, and pressure with little variation. / Displacement characteristics can be secured. Moreover, unlike the conventional manufacturing method, a complicated annealing process is not required, and a corrugated diaphragm with high pressure detection accuracy can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a corrugated diaphragm corresponding to a first embodiment of the present invention, in which (a) to (d) are diagrams showing respective processes in order.

FIG. 2 is a plan view of a corrugated diaphragm manufactured by the manufacturing method of FIG.

3A to 3C are manufacturing process diagrams of a corrugated diaphragm corresponding to Example 2 of the invention, and FIGS. 3A to 3C are diagrams showing respective processes in order.

FIG. 4 is a manufacturing process drawing of a corrugated diaphragm corresponding to Embodiment 3 of the present invention, in which (a) to (c) are views sequentially showing the respective processes.

FIG. 5 is a conventional configuration diagram of a capacitive pressure sensor to which the present invention is applied, in which (a) is a vertical sectional view and (b) is a plan view.

[Explanation of symbols]

 8 Base Material 9 Peripheral Cut Groove 10 Flat Groove in Central Part 11 Ring-Shaped Groove 12 Ring-Shaped Groove 13 Central Flat Part 14 Corrugated Part 15 Peripheral Joint 16 Fixing Plate 16a Pressure-Producing Hole 16b Ring-Shaped Protrusion 16c Forming Groove 17 Metal foil 17a Corrugated part 18 Welding electrode 20 Punch 22 Dedicated press die

Claims (5)

[Claims] 1. A method of manufacturing a pressure-sensitive diaphragm having a corrugated cross-section, which is used by being incorporated in a pressure sensor, wherein a thick metal flat plate is used as a base material, and etching grooves having a pattern corresponding to the contour of the diaphragm are formed on both surfaces of the base material. The pressure sensor is characterized in that the outer peripheral joint of the diaphragm is left as the plate thickness of the base material, and a thin central flat portion and a corrugated portion where concavo-convex surfaces are concentrically arranged are formed in the inner peripheral surface area. For manufacturing pressure sensitive diaphragms for automobiles. 2. The manufacturing method according to claim 1, wherein in the first etching step, concentric ring-shaped grooves are formed on one surface of the base material, and in the second etching step, an opposite side surface of the base material is processed. A method for manufacturing a pressure-sensitive diaphragm for a pressure sensor, comprising forming a corrugated portion by processing ring-shaped concave grooves arranged concentrically with a shift of a half pitch from the concave grooves formed in the first etching step. 3. A method of manufacturing a pressure-sensitive diaphragm having a corrugated cross-section for use in a pressure sensor, wherein a flat disc-shaped metal foil is placed on a metal diaphragm fixing plate which is a pressure sensor case, and The ring-shaped protrusion formed on the fixed plate and the peripheral edge of the metal foil are welded and joined, and in this state, the diaphragm corrugated part is formed by pressing, and then the metal foil is pressed with gas from the opposite direction to the pressing. A method for manufacturing a pressure-sensitive diaphragm for a pressure sensor, which comprises removing residual stress of the pressure sensor. 4. The method for manufacturing a pressure-sensitive diaphragm for a pressure sensor according to claim 3, wherein the fixed plate itself is used as a press die to press-form the corrugated portion of the diaphragm on the metal foil. 5. The method for manufacturing a pressure-sensitive diaphragm of a pressure sensor according to claim 3, wherein a fixed press plate is combined with a dedicated press die to press-form the corrugated diaphragm portion on the metal foil. .