JPH0511041U - Pressure sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide a structure capable of favorably welding a metal diaphragm and a pressure transmission rod. A melted portion 11e is formed on the outer surface of the thick portion 11a of the metal diaphragm 11 around the through hole 11d, and the melted portion is formed on the lower end portion 10a of the pressure transmission rod 10 inserted into the through hole 11d. Since the welding is performed by melting 11e, the main surface of the thick portion 11a is not deformed, and the melt does not flow out to the flexible portion 11c. Therefore, the metal diaphragm is welded by the welding. The degree of flexure of 11 does not change, and stable output characteristics can be generated. Further, the surface area is increased by the molten wall portion 11e, the cooling efficiency is improved at the time of welding, and further, the molten amount is made constant by defining the thickness of the molten wall portion, so that the welding current and the melting Since welding conditions such as time can be made constant, a constant welding result can always be produced.

Description

[Detailed description of the device]

The present invention relates to a pressure sensor for detecting a change in internal cylinder pressure of an internal combustion engine with a piezoelectric element.

[0002]

[Prior Art]

 A detection element consisting of a piezoelectric element, pressure transmission rod, etc. is housed inside a metal shell mounted in a screw hole for mounting a sensor provided in a cylinder block of an internal combustion engine, and a metal diaphragm is attached to the lower end surface located inside the cylinder. There is known a pressure sensor in which the pressure inside the cylinder is sealed, the pressure inside the cylinder is propagated to the piezoelectric element through the pressure transmission rod, and an electric signal proportional to the magnitude of the pressure inside the cylinder is taken out from the element. As this piezoelectric element, a piezoelectric element made of a ceramic material such as lead zirconate titanate or lead titanate is generally used.

In this pressure sensor, the diaphragm has a thick-walled portion on the center side and thin-walled flexible portions formed concentrically around the central portion, and the flexible portion bends to generate internal pressure of the cylinder block. The pressure transmitting rod acts on the piezoelectric element. Further, the connection between the diaphragm and the pressure transmission rod is performed by inserting the pressure transmission rod into the through hole formed in the thick portion and welding the peripheral edge to the peripheral edge of the through hole to seal the shaft hole. ing .

In this structure, the cylinder pressure causes the diaphragm to bend and acts on the pressure transmission rod. Therefore, if the thickness of the flexible portion of the diaphragm is large, the diaphragm does not sufficiently deform following the pressure. , The operation of the pressure transmission rod will be restricted. For this reason, the flexible portion is usually made extremely thin with a thickness of 0.3 mm or less. Further, for the same reason, even if the flexible portion is too small, the cylinder internal pressure does not properly act on the pressure transmission rod. On the other hand, the cylinder pressure is as high as 100 atm, and during use, the diaphragm rises to a maximum of nearly 600 ° C. For this reason, the portion connected to the pressure transmission rod is likely to accumulate heat, so this portion is made thick. For this reason, it is necessary that the metal diaphragm has a concentric thick portion and a flexible portion that are concentric with each other, and that the thickness and diameter of the flexible portion have predetermined values.

[0005]

[Problems to be solved by the device]

 In such a pressure sensor, the tip of the pressure transmission rod is hermetically fixed by melting the thick portion at the periphery of the through hole of the metal diaphragm by argon welding or the like. However, at this time, the thick portion is melted and deformed by the heat during welding, and the damage is likely to occur. Further, the thick portion melts and erodes into the thin flexible portion to restrain the bending. For this reason, there were drawbacks such as inability to maintain stable output. An object of the present invention is to provide a structure in which such a metal diaphragm and a pressure transmission rod can be welded well without the above-mentioned drawbacks.

[0006]

[Means for Solving the Problems]

 According to the present invention, a thick wall portion is formed on the center side of the metal diaphragm, and thin flexible portions are concentrically formed around the metal diaphragm, and a molten wall portion is formed around the through hole on the outer surface of the thick wall portion. It is characterized by being raised.

[0007]

[Action]

 At the time of welding, the molten wall portion formed on the outer surface of the thick wall portion is melted by the welding heat and bonded to the periphery of the tip of the pressure transmission rod. By the way, since this molten wall portion is formed in advance on the assumption that it will be melted, by optimizing this thickness, it is possible to avoid deformation of the main surface of the thick wall portion, and further The melt does not flow out into the part. Therefore, the welding quality can be made constant and the welding conditions can be made constant.

[0008]

【Example】

 FIG. 1 shows an embodiment of the present invention, in which a male screw 2 for screwing into a cylinder block is formed on the outer periphery of a lower end 1a, and a hexagonal portion 3 suitable for a tightening tool such as a spanner is formed on the outer periphery of an upper end 1b. A metal shell having a bolt structure, in which a shaft hole 4 is formed in the vertical direction. The shaft hole 4 is a connecting hole of different diameter holes 4a and 4b penetrating the lower end 1a side and a large diameter hole 4c penetrating the upper end 1b side. Of the different-diameter holes 4a and 4b, the larger-diameter side hole 4a has an electrical insulating ring 5, a first terminal member 6, and electrodes (not shown) on the front and back sides from the side closer to the smaller-diameter side hole 4b. The piezoelectric element 7 and the second terminal member 8 to which the) is applied are sequentially housed in layers, and are insulated from the metal shell 1 by the insulating material 9 which covers the periphery of the laminate. Further, a connecting hand 6a for connecting to a signal carrying cable 12, which will be described later, is projected from the upper surface of the first terminal member 6 by inserting the insulating ring 5 therethrough.

Further, a pressure transmission rod 10 is inserted into the large-diameter side hole 4a, the large-diameter portion of the upper end of the pressure-transmitting rod 10 is pressed against the second terminal member 8, and the lower end of the small-diameter portion is mainly formed as described later. The lower end 1a of the metal fitting 1 is penetrated and welded to a metal diaphragm 11 joined so as to hermetically seal it. The metal diaphragm 11 needs to have heat resistance, and for example, a material such as Inconel or a heat resistant metal material equivalent to SUS630 is preferable.

A stepped seat 4c ′ is formed on the inner surface of the large diameter hole 4c on the side of the hexagonal part 3 and a metal sleeve 13 having a flange 13a for seating the stepped seat 4c ′ is fitted into the stepped seat 4c ′ and the upper end of the hexagonal part 3 is fitted. It is tightened by bending the annular thin piece 3a protruding from the inside.

One end of a signal carrying cable 12 is inserted and fixed inside the metal sleeve 13, and a core wire 12 a exposed from the cable 12 is connected to a terminal member 6 via an insulating conductor wire 14 for insulation. Has been done. However, one electrode of the piezoelectric element 7 is connected to the core wire 12a of the cable 12 through the terminal member 6 and the relay lead wire 14, and the other electrode is grounded to the metal shell 1 through the terminal member 8, the transmission rod 10 and the metal diaphragm 11. It is connected.

Further, between the terminal member 6 and the terminal member 8, a piezoelectric element 7 having electrodes on its front and back surfaces is arranged. The piezoelectric element 7 is made of lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ) or a single crystal piezoelectric material having the same effect as those single crystal materials, and has an outer dimension of 0.3 mm to 1.5 mm. A circular or rectangular plate-shaped piezoelectric element having the same can be used.

Next, a main part of the present invention will be described. The metal diaphragm 11 has a lid-like structure having a peripheral wall on the periphery thereof, and as shown in FIGS. 1 and 2, is provided with a thick portion 11a near the center thereof and a joint portion 11b for connecting the peripheral wall to the metal shell 1. The thin flexible portion 11c is defined by the space s between the inner diameter A of the joint portion 11b and the outer diameter B of the thick portion 11a. A through hole 11d is formed at the center of the thick portion 11a, and the lower end 10a of the pressure transmission rod 10 is inserted into the through hole 11d. The metal diaphragm 11 may be plate-shaped, and its peripheral edge may be joined to the lower edge of the metal shell 1.

Although the above is the conventional configuration, the present invention is characterized in that the melted portion 11e is formed on the outer surface of the thick portion 11a around the through hole 11d as shown in FIG. ..

In this structure, in order to join the pressure transmission rod 10 and the metal diaphragm 11, the lower end portion 10a of the pressure transmission rod 10 is penetrated through the metal diaphragm 11 as shown in FIG. Insert through the hole 11d. Then, the molten wall portion 11e is melted by the argon welding from the direction of the arrow x in FIG. 2, and the entire circumference is welded to the lower end portion of the pressure transmitting rod 10 as shown in FIG. Thus, the pressure transmission rod 10 and the metal diaphragm 11 are connected. Next, the pressure transmission rod 10 is inserted into the shaft hole 4 of the metal shell 1 in which the piezoelectric element 7 and the like are already housed, and the peripheral wall (joint portion 11b) of the metal diaphragm 11 is attached to the lower end of the metal shell 1. Weld to the peripheral surface by the same means. This completes the assembly.

As described above, in the above embodiment, the molten wall portion 11e is formed differently from the thick wall portion 11a, and the molten wall portion 11e is melted and welded. It is not necessary to melt the surface side, and further, the melt does not flow out to the flexible portion 11c. Further, since the surface area is increased by the molten wall portion 11e, the cooling efficiency at the time of welding is improved. Further, the amount of melting becomes constant by defining the thickness of the molten wall portion. Therefore, welding conditions such as welding current and melting time can be made constant. As a result, a constant welding result can be always produced, the degree of flexure of the metal diaphragm 11 is constant, and stable output characteristics can be produced.

The relationship between the outer diameter C and the inner diameter D of the molten wall portion 11e, the inner diameter A of the joint portion 11b, and the outer diameter B of the thick portion 11a, and the thickness t _{1 of the} thick portion 11a and the molten wall portion 11e The relationship with the thickness t ₂ (see FIG. 2) is preferably the following relationship according to various experiments. φB-φD ≧ (φC−φD) × 2 φB ≧ φD × 1.5 t ₂ ≧ t ₁ × 1.3

[0018]

[Effect of the device]

 In the pressure sensor of the present invention, the molten wall portion 11e is formed on the outer surface of the thick portion 11a of the metal diaphragm 11 around the through hole 11d, and the lower end portion of the pressure transmission rod 10 inserted into the through hole 11d. Since the welded portion 11e is welded to the welded portion 10a, the main surface of the thick portion 11a is not deformed, and the melt does not flow out to the flexible portion 11c. Due to the welding, the degree of flexure of the metal diaphragm 11 does not change, and stable output characteristics can be produced. Further, the melted portion 11e increases the surface area, improves the cooling efficiency at the time of welding, and further regulates the thickness of the molten portion so that the amount of melting becomes constant, so that the welding current and the melting Since the welding conditions such as time can be made constant, a constant welding result can be always produced, and the metal diaphragm 11 is not damaged. Thus, there is an excellent effect that the optimum pressure sensor having high durability and reliability can be put on the market.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing a state in which a lower end portion 10a of a pressure transmission rod 10 is inserted into a through hole 11d of a metal diaphragm 11.

FIG. 3 is an enlarged vertical sectional side view of a main part showing a mounted state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal shell 4 Axial hole 7 Piezoelectric element 10 Pressure transmission rod 11 Metal diaphragm 11a Thick part 11b Joint part 11c Annular flexible part 11d Through hole 11e Melt part

Continued Front Page (72) Inventor Hirofumi Hasako 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Nippon Special Ceramics Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A metal shell mounted on a cylinder of an internal combustion engine, comprising a shaft hole in which a detection opening is located in the cylinder,
At least a piezoelectric element and a pressure transmission rod that applies pressure to the piezoelectric element are housed inside the shaft hole, and the opening end of the shaft hole is sealed with a metal diaphragm, and a penetrating hole formed in the center thereof. In a pressure sensor in which the tip of the pressure transmission rod is inserted into the hole and the periphery of the pressure transmission rod is welded to the periphery of the through hole to seal the shaft hole, the metal diaphragm has a thick portion on the center side thereof. A pressure sensor, characterized in that thin-walled flexible portions are formed concentrically around each of them, and further a molten-wall portion is formed around the through-hole on the outer surface of the thick-walled portion.