JPS633233A - Pressure detector - Google Patents

Abstract

PURPOSE:To accurately measure combustion pressure by providing a quenching body which is made of a material with good heat conductivity and has many air holes across in a pressure intake passage. CONSTITUTION:The pressure intake passage 31 which is open at the tip of a metallic housing 2 is provided in the housing and a pressure receiving diaphragm 4 to which a strain gauge is added is provided at the internal end of the intake passage 31. The quenching body 1 is provided across in the intake passage 31 in its middle and the quenching body 1 is made of the material with good heat conductivity and has many air holes. Then, the combustion pressure is applied to the diaphragm 4 from the intake passage 31 to make the diaphragm deform, and the output corresponding to the deformation strain is outputted by the strain gauge. At this time, flames may enter the intake passage 31 possibly, but when the flames pass through the quenching body 1 provided in the intake passage 31, the heat is absorbed and the flames are extinguished, so that they do not reach the diaphragm 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure detector for high temperatures, and particularly to a pressure detector suitable for use in measuring combustion pressure in internal combustion engines and the like.

[Prior Art] As a typical structure of a pressure detector, a metal housing is fixed to a pressure chamber wall, and a pressure introduction path is provided inside the housing and opens at the tip of the housing, which projects inwardly. It is known that a pressure receiving diaphragm is provided at the inner end, a strain gauge is attached to the pressure receiving diaphragm, and an output signal is output in accordance with the deformation of the diaphragm.

Traditionally, metal strain gauges bonded to pressure-receiving diaphragms with resin have been used, but in recent years semiconductor strain gauges have been used, which provide linear and highly sensitive output and can be extremely miniaturized. is attracting attention.

[Problems to be Solved by the Invention] By the way, there is a limit to the fluid humidity that can be measured with the pressure detector using the above-mentioned metal strain gauge due to the heat resistance of resin etc. Even in the case of a PN junction structure type, there is a limit to the operating temperature due to leakage current that occurs as the temperature rises.

In particular, when measuring the combustion pressure of an internal combustion engine, there is a risk that high-temperature flames may reach the pressure detection part.In order to prevent this, it has been proposed to lengthen the pressure introduction path, but this is not the case. This poses a problem in that it induces air column vibration on the road, reducing measurement accuracy.

SUMMARY OF THE INVENTION In view of these problems, an object of the present invention is to provide a pressure detector that can accurately measure combustion pressure by preventing flame from entering the pressure detection section without increasing the length of the pressure introduction path.

[Means for Solving the Problems] The configuration of the present invention will be explained with reference to FIG.
A pressure introduction passage 31 opening at the tip thereof is necessarily provided inside the pressure introduction passage 31, and a pressure receiving diaphragm 4 equipped with a strain gauge is provided at the inner end of the pressure introduction passage 31.

A flame extinguishing body 1 is provided across the pressure introduction path 31 halfway, and the flame extinguishing body 1 is made of a material with good heat conductivity and has a large number of ventilation holes.

[Operation] Combustion pressure is applied to the pressure receiving diaphragm 4 from the pressure introduction path 31 to deform it, and an output corresponding to the deformation strain is output from the strain gauge. At this time, flame may enter the pressure introduction path 31, but when the flame passes through the flame extinguishing body 1 provided in the introduction path 31, it absorbs heat and is extinguished and does not reach the pressure receiving diaphragm 4. do not have.

Effect] In this way, high-temperature flame is prevented from reaching the pressure receiving diaphragm 4, and the combustion pressure of the internal combustion engine or the like can be measured satisfactorily. According to this structure, the pressure introduction path 31
Since it can be made relatively short, occurrence of air column vibration etc. is prevented and highly accurate pressure measurement is possible.

[Example] FIG. 3 shows the overall structure of a pressure detector. The detector has a cylindrical metal housing 2, and the housing 2 has a mounting thread 2a formed on the outer periphery of the lower half of the small diameter, and has a hexagonal surface on the outer periphery of the upper half of the large diameter. A threaded portion 2b is formed on the inner periphery of the upper half, into which the cylindrical cover body 21 is screwed. A lead wire 8 is inserted through the center of the cover body 21 from above, and is supported by a lead holder 22.

A sensing pod 3 is fitted into the lower end opening of the housing 2, the details of which are shown in FIG.

The sensing tenon 3 is a thick-walled cylindrical body, and its lower outer peripheral edge is fixed to the opening of the housing 2 by welding. The inside of the cylinder of the sensing body 3 has a pressure introduction path 3 with the lower half having a small diameter.
1, and a ceramic substrate 4 which operates as a pressure receiving diaphragm is fitted in the upper half of the large diameter so as to close one end of the introduction path 3]. The substrate 4 has a molybdenum (MO) layer 51, a nickel (N
1) It is bonded and fixed to the inner peripheral stepped portion of the sensing body 3 via the layer 52 and AO-based brazing@53.

A semiconductor strain gauge element is formed on the ceramic substrate 4. This is shown in FIGS. 4 and 5.

In the figure, the substrate 4 has a thickness of 0.3 to 1°0 μm over the entire upper surface.
An 8102 layer 41 is formed to a thickness of about 1 μm by vapor deposition, sputtering, etc., and a polycrystalline silicon layer 42 about 1 μm thick is formed thereon by low pressure CVD. The polycrystalline silicon layer 4
2 is doped with holon (B) or phosphorus (P>) by thermal diffusion, and patterned by dry etching to form strain gauge elements 42a, 42b, 42c, and 42d.

An electrode pattern 43 made of PT is formed on the polycrystalline silicon layer 42, and the entire structure is 3 i 3 N except for the pad portion 431 for bonding the wire line 62 (FIG. 1).
It is covered with a passivation film 44 such as No. 4. The strain gauge elements 428 to 42d are located directly above the peripheral edge of the closed end of the pressure introduction path 31, forming a full bridge circuit.

In FIG. 1, a pressure introduction path 31 leading to the ceramic substrate 4 is provided with a flame extinguisher 1 midway.

The flame extinguishing body 1 is a disk-shaped wire mesh structure as shown in FIG. 2, and a large number of mesh-like ventilation holes 1a are formed in the structure. Stainless steel wire, Ni alloy wire, etc. can be used as the wire material constituting the wire mesh structure.

The outer peripheral edge of the upper surface of the flame extinguishing body 1 is brought into contact with the stepped portion of the pressure introduction path 31, and the lower surface is positioned and fixed by a circlip 11.

In FIG. 3, a columnar insulator 61 made of a glass material is disposed within the housing 2, and the wire wire 62 is inserted into a through hole of the insulator 61.

The wire wire 62 has an upper end connected to a lead pin 63 erected on the insulator 61, and a lower end connected to the pad portion 431 on the ceramic substrate 4 (FIG. 5). The lead pins 63 support the ceramic substrate 7 and are electrically connected to a signal processing circuit for amplification and temperature compensation formed thereon.

One end of the lead wire 8 inserted through the cylindrical cover 21 is connected to this signal processing circuit.

Combustion pressure is applied to the ceramic substrate 4 through the pressure introduction path 31, causing it to deform. The resistance value of each of the strain gauge elements 42a to 42d on the substrate 4 changes due to the deformation strain at this time, and is taken out as a pressure signal by the 1-node line 8 via the signal processing circuit.

Flame may enter the introduction passage 31 when measuring the combustion pressure between the internal combustion chambers. However, in the pressure detector of the present invention, the flame that has entered comes into contact with the flame extinguishing body 1 and is removed with heat and extinguished, and does not reach the ceramic substrate 4. The heat removed by the flame extinguishing body 1 is transferred to the sensing mortise 3 and the housing 2.
It is then dissipated onto the combustion chamber wall to which the housing 2 is fixed.

According to this structure, high-temperature flame is prevented from entering the ceramic substrate 4, and the combustion pressure of an internal combustion engine or the like can be measured satisfactorily. Furthermore, since the pressure introduction path 31 can be made relatively short, highly accurate pressure measurement is possible without causing any atmospheric vibrations.

In addition, in the above embodiment, the semiconductor strain gauge element was formed by doping the polycrystalline silicon layer on the ceramic substrate with impurities, so the PN junction, such as when forming the semiconductor strain gauge element on the single crystal silicon substrate, is This allows use in higher temperature atmospheres.

As the flame extinguishing body 1, as shown in FIG. 6, a honeycomb structure having a large number of ventilation holes 1a penetrating through the main body can be used as the flame extinguishing body 1, and the material of the structure may be stainless steel, stainless steel,
Metal materials such as Ni-based alloys, or ceramic materials with excellent heat transfer properties such as SiC and IN can be used. Note that the porosity of the honeycomb structure is preferably 60 to 90%. In addition, especially ceramic structures are preferably fixed via plate springs 12 as shown in the figure.

Furthermore, as the flame extinguishing body 1, a punching metal or the like in which a large number of small holes are provided in a metal plate can also be used.

The flame extinguisher 1 may be fixed by welding or adhesive.

[Brief explanation of the drawing]

Fig. 1 is an enlarged sectional view of the tip of a detector housing showing a practical example of the present invention, Fig. 2 is a perspective view of a flame extinguisher, Fig. 3 is an overall sectional view of the pressure detector, and Fig. 4 is a ceramic substrate. 5 is a cross-sectional view taken along the line IV-IV in FIG. 5, FIG. 5 is a plan view of the ceramic substrate, and FIG. 6 is an enlarged sectional view of the tip of the detector housing showing another embodiment of the present invention. is. 1...Flame extinguishing body 1a...Vent hole 2...Metal housing 3...Sensing body 31...Pressure introduction path 4... ... Ceramic substrate (pressure receiving diaphragm) 4
2...Polycrystalline silicon layers 42a, 42b, 42G, 42d...Strain gauge element FIG. 1 F, 2

Claims (7)

[Claims] (1) It has a metal housing that is fixed to the combustion chamber wall and has a tip facing into the combustion chamber, and a pressure introduction passage that opens at the tip is provided inside the housing, and an inner end of the pressure introduction passage is provided. In a pressure sensor equipped with a pressure-receiving diaphragm equipped with a strain gauge, a flame-extinguishing body made of a material with good heat conductivity and having a large number of ventilation holes is provided halfway across the pressure introduction path, and the flame extinguisher is made of a material with good heat conductivity and has a large number of ventilation holes. A pressure detector designed to prevent flame from entering. (2) The pressure detector according to claim 1, wherein the flame extinguishing body is constructed of a wire mesh structure. (3) The pressure sensor according to claim 2, wherein the wire mesh structure is made of stainless steel wire or Ni alloy wire. (4) The pressure detector according to claim 1, wherein the flame extinguisher is made of a ceramic honeycomb structure with good heat conductivity. (5) The pressure sensor according to claim 4, wherein the honeycomb structure is made of SiC or AlN ceramic. (6) The pressure sensor according to claim 1, wherein the flame extinguishing body is made of a metal honeycomb structure. (7) The pressure detector according to claim 1, wherein the flame extinguishing body is made of punched metal.