JP2019113382A - Pressure sensor - Google Patents

Abstract

To provide a pressure sensor capable of suppressing influence of heat to accurately sense pressure of a high-temperature pressure medium.SOLUTION: A pressure sensor comprises: a housing 10 having a tip-end cylindrical section 11; a pressure measurement unit 30 with a piezoelectric body 32 accommodated in the housing; and a bottomed diaphragm 20 comprising an inner cylindrical section 22 disposed inside the tip-end cylindrical section and configured to extend toward the pressure measurement unit, and a pressure-receiving bottom section 23 integrally formed with the inner cylindrical section and configured to be in contact with the pressure measurement unit. The pressure sensor also includes a heat shield cover member 70, 170 which is formed to shield the inner cylindrical section 22 from a pressure medium and expose the pressure-receiving bottom section 23 to the pressure medium. Such an arrangement allows for suppressing influence of heat to accurately sense pressure of the pressure medium.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pressure sensor for detecting the pressure of a pressure medium, and more particularly to a pressure sensor for detecting the pressure of a high temperature pressure medium such as combustion gas in a combustion chamber of an engine.

  The conventional pressure sensor includes a tubular housing having a distal end tubular portion, a measuring unit housed in the housing, and a pressure transmitting member for closing the housing and transmitting the pressure of the pressure medium to the measuring unit. There is known a pressure sensor employing, as a member, a concave diaphragm having an inner cylindrical portion disposed inside a distal end cylindrical portion and a pressure receiving bottom portion (for example, Patent Document 1).

  In this pressure sensor, when the pressure of the high temperature combustion gas is applied to the diaphragm, the pressure is transmitted to the measuring unit through the pressure receiving bottom of the diaphragm, and a signal corresponding to the pressure is output by the piezoelectric body of the measuring unit. It is supposed to be.

  In this pressure sensor, the tip cylindrical portion and the diaphragm are directly exposed to the high temperature combustion gas, so by providing the inner cylindrical portion on the diaphragm, the measurement error due to thermal deformation is suppressed. There is room for improvement to further reduce the measurement error.

JP, 2016-205842, A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a pressure sensor capable of detecting the pressure of a high-temperature pressure medium with high accuracy while suppressing the influence of heat. It is.

  The pressure sensor according to the present invention comprises a housing having a distal end cylindrical portion, a pressure measurement portion including a piezoelectric body accommodated in the housing, and an inner side disposed inside the distal end cylindrical portion and extending toward the pressure measurement portion. A bottomed diaphragm integrally formed with the cylindrical portion and the inner cylindrical portion and having a pressure receiving bottom portion contacting the pressure measuring portion, and shielding the inner cylindrical portion from the pressure medium and exposing the pressure receiving bottom to the pressure medium And the formed heat shielding cover member.

  In the pressure sensor having the above configuration, the heat shield cover member adopts a configuration including a cylindrical cover portion disposed so as to cover the inner wall surface of the inner cylindrical portion, and an opening portion for exposing the pressure receiving bottom portion. It is also good.

  In the pressure sensor having the above configuration, the heat shield cover member has an annular bottom which is continuously formed on the cylindrical cover and which defines the opening, and the cylindrical cover is opposed to the inner cylindrical portion. The configuration may be adopted, which is disposed with a predetermined gap, and the annular bottom is disposed in close contact with the pressure receiving bottom.

  In the pressure sensor having the above-described configuration, the cylindrical cover portion of the heat shield cover member is disposed so as to define an opening on one end side toward the pressure receiving bottom portion and not in contact with the pressure receiving bottom portion and in close contact with the inner cylindrical portion. The configuration may be adopted.

  In the pressure sensor having the above configuration, the diaphragm has an annular flange portion continuously formed on the inner cylindrical portion and fixed to the end face of the distal end cylindrical portion, and the heat shield cover member is continuous on the cylindrical cover portion It is also possible to adopt a configuration that includes a flange cover portion that is formed and fixed to be superimposed on the annular flange portion.

  In the pressure sensor having the above-mentioned configuration, the diaphragm includes a bending area continuous from the inner cylindrical portion to the annular flange portion, and the heat shield cover member includes a bending cover area continuous from the cylindrical cover portion to the flange cover portion The bent cover area of the heat shield cover member may be arranged with a predetermined gap with respect to the bent area of the diaphragm.

  In the pressure sensor having the above configuration, the inner cylindrical portion of the diaphragm may be arranged with a predetermined gap with respect to the inner wall surface of the distal end cylindrical portion.

  In the pressure sensor having the above configuration, the pressure measurement unit has a first electrode, a piezoelectric body, and a second electrode sequentially stacked from the tip end side of the tip cylindrical portion, and the diaphragm also serves as the first electrode. May be adopted.

  According to the pressure sensor having the above configuration, it is possible to obtain a pressure sensor capable of detecting the pressure of the high-temperature pressure medium with high accuracy while suppressing the influence of heat.

It is a sectional view showing one embodiment of a pressure sensor concerning the present invention. The pressure sensor shown in FIG. 1 WHEREIN: It is a partial expanded sectional view which shows the housing which has a tip cylindrical part, a diaphragm, a heat insulation cover member, a pressure measurement part, etc. FIG. In a pressure sensor shown in Drawing 1, it is an exploded perspective view showing a diaphragm and a thermal insulation cover member. The pressure sensor shown in FIG. 1 WHEREIN: It is a partial expanded sectional view which shows the mutual relationship of a tip cylindrical part, a diaphragm, and a thermal insulation cover member. It is a partial expanded sectional view which shows other embodiment of the pressure sensor which concerns on this invention. The pressure sensor shown in FIG. 5 WHEREIN: It is a disassembled perspective view which shows a diaphragm and a thermal insulation cover member. The pressure sensor shown in FIG. 5 WHEREIN: It is a partial expanded sectional view which shows the mutual relationship of a tip cylindrical part, a diaphragm, and a thermal insulation cover member. It is the graph which compared the sensor output by the pressure sensor which concerns on this invention, and the pressure sensor which is not equipped with a thermal insulation cover member.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.
The pressure sensor according to this embodiment is attached to the cylinder head H of the engine, and detects the pressure of the combustion gas in the combustion chamber as a pressure medium.
As shown in FIGS. 1 and 2, the pressure sensor includes a housing 10, a diaphragm 20, a pressure measurement unit 30, a pressing member 40, lead wires 50, a connector 60, and a heat shield cover member 70.

The housing 10 is formed in a multistage cylindrical shape that defines an internal space A extending in the direction of the axis S by using a metal material such as a precipitation hardening system or a ferritic stainless steel.
The housing 10 includes a distal end cylindrical portion 11, a seal portion 12, an external thread 13, an opening end 14, an inner wall surface 15, 16, and an internal thread 17.

The end cylindrical portion 11 is formed in a cylindrical shape having the same thickness in a region located on the end side in the direction of the axis S from the seal portion 12, and includes an end surface 11a and an inner wall surface 11b having the same diameter as the inner wall surface 16. .
An outer wall surface of the distal end cylindrical portion 11 is disposed close to or in close contact with the inner peripheral surface H1 of the mounting hole of the cylinder head H, so that it is difficult to be exposed to the combustion gas.

The seal portion 12 is formed in a conical surface shape at a predetermined position receding from the end face 11a of the tip end cylindrical portion 11 in the direction of the axis S, and abuts on the seal surface H2 of the cylinder head H to burn combustion gas in the combustion chamber CH. Plays a role in preventing leakage.
The male screw portion 13 is formed in an enlarged diameter area receding from the seal portion 12 in the direction of the axis S so as to fix the housing 10 by screwing with the female screw portion H3 of the mounting hole provided in the cylinder head H .
The opening end portion 14 functions as an insertion port when attaching the pressing member 40 and the like, and is formed so that the connector 60 is fixed via the spacer 61.

The inner wall surface 15 is formed as a cylindrical inner peripheral surface having an inner diameter dimension into which the pressing member 40 can be inserted.
The inner wall surface 16 is formed as a cylindrical inner peripheral surface having an inner diameter smaller than the inner wall surface 15, and the pressure measurement unit 30 is accommodated in this region.
The female screw portion 17 is formed in the region between the inner wall surface 15 and the inner wall surface 16 in order to screw and fix the pressing member 40.

The diaphragm 20 has a precipitation hardening property, and is formed in a concaved shape by pressing using a metal material such as a stainless steel plate having a thickness t1. The plate thickness t1 is, for example, about 0.2 mm to 0.6 mm.
The diaphragm 20 is provided with an annular flange portion 21, an inner cylindrical portion 22, a pressure receiving bottom portion 23, and a bending area 24.

The annular flange portion 21 is formed in an annular plate shape having an outer diameter substantially the same as the outer diameter of the distal end cylindrical portion 11 so as to be joined so as to cover the end surface 11 a of the distal end cylindrical portion 11.
The annular flange portion 21 is fixed to the end face 11 a by welding or the like.

The inner cylindrical portion 22 has an outer diameter smaller than the inner diameter of the inner wall surface 11b of the distal end cylindrical portion 11, and is disposed inside the distal end cylindrical portion 11 and extends in the direction of the axis S toward the pressure measurement portion 30. It is formed in a cylindrical shape.
That is, the inner cylindrical portion 22 is formed to be arranged with respect to the inner wall surface 11 b of the distal end cylindrical portion 11 with a predetermined gap C1.
Here, the gap C1 is set to a dimension that can suppress the heat transfer from the inner wall surface 11b of the distal end cylindrical portion 11 to the inner cylindrical portion 22 and prevent the influence of heat.

The pressure receiving bottom portion 23 is integrally formed with the inner cylindrical portion 22 and formed in a disk shape that abuts on the piezoelectric body 32 of the pressure measuring portion 30.
The pressure receiving bottom portion 23 is a region having a function of receiving the pressure of the combustion gas in the direction of the axis S, and is disposed in close contact with the piezoelectric body 32 of the pressure measuring portion 30, and directly loads the load according to the pressure of the combustion gas. It is supposed to be transmitted to the body 32.
The bending area 24 is an area in which the annular flange portion 21 and the inner cylindrical portion 22 are integrally continued, and is formed as a curved surface having a predetermined curvature radius R1.

  The pressure measurement unit 30 functions as a piezoelectric element, and as shown in FIG. 2, the first electrode 31, the piezoelectric body 32, and the first electrode 31 are sequentially stacked in the direction of the axis S from the tip end side of the tip cylindrical portion 11. Two electrodes 33 are provided.

The first electrode 31 is formed of a conductive metal material, and in this embodiment, the diaphragm 20 also serves as the role.
The pressure receiving bottom portion 23 of the first electrode 31, that is, the diaphragm 20 is disposed in close contact with the piezoelectric body 32, and is electrically connected to the ground (minus side) via the housing 10 and the cylinder head H.

The piezoelectric body 32 is formed in a square pole shape, is sandwiched between the pressure receiving bottom 23 of the first electrode 31, ie, the diaphragm 20 and the second electrode 33, and outputs an electric signal based on the strain due to the load received in the axis S direction. Piezo elements, zinc oxide, quartz, etc. are applied.
The second electrode 33 is formed of a conductive metal material in a cylindrical or disk shape, disposed in close contact with the piezoelectric body 32, and electrically connected to the positive side via the lead wire 50.

In the pressure measurement unit 30 described above, since the diaphragm 20 doubles as the first electrode 31, the number of parts can be reduced and the structure can be simplified as compared with the case where a dedicated electrode is provided.
The present invention is not limited to this configuration, and an electrode different from the diaphragm 20 may be interposed as the first electrode 31.

As shown in FIG. 2, the pressing member 40 is configured by a screw member 41 and an insulating member 42.
The screw member 41 is formed in a substantially cylindrical shape using a metal material such as a precipitation-hardening system or a ferritic stainless steel, and the male screw portion 41a screwed to the female screw portion 17 of the housing 10 and the lead wire 50 pass through. The through hole 41 b and an abutting surface 41 c that abuts on the insulating member 42 are provided.
The insulating member 42 is formed in a substantially cylindrical shape using an insulating material having high electrical insulation, such as alumina, and abuts on the end face 42 a that abuts on the abutment surface 41 c of the screw member 41 and the second electrode 33. An end surface 42 b and a through hole 42 c for passing the lead wire 50 are provided.

  Then, as shown in FIGS. 1 and 2, with the pressure measurement unit 30 being disposed at a predetermined position, the insulating member 42 is fitted, and the screw member 41 is screwed in from above the insulating member 42, A preload is applied to the pressure measuring unit 30 in the direction of the axis S, and the pressure measuring unit 30 is positioned and held at a predetermined position in the housing 10.

The lead wire 50 is electrically connected to the second electrode 33 of the pressure measurement unit 30, as shown in FIG. 1, and the through hole 42c of the insulating member 42, the through hole 41b of the screw member 41, and the internal space A of the housing 10 Through to the connector 60.
The connector 60 is formed as a receptacle and is coupled to the open end 14 of the housing 10 via the spacer 61 so as to be detachably connected to an external connector (plug).

The heat shield cover member 70 is formed in a concaved shape by pressing using a metal material having heat resistance and low thermal conductivity, for example, a stainless steel plate having precipitation hardenability. The plate thickness t2 is, for example, about 0.2 mm to 0.5 mm.
Further, as shown in FIGS. 2 and 3, the heat shield cover member 70 includes a flange cover portion 71, a cylindrical cover portion 72, an annular bottom portion 73 which defines the opening portion 73a, and a bending cover region 74.

The flange cover portion 71 is formed in an annular plate shape having an outer diameter substantially the same as the outer diameter of the annular flange portion 21 so as to be joined to cover the annular flange portion 21.
The flange cover portion 71 is fixed together with the annular flange portion 21 to the end surface 11 a of the distal end cylindrical portion 11 by welding or the like.

The cylindrical cover portion 72 has an outer diameter smaller than the inner wall surface 22a of the inner cylindrical portion 22, and is disposed inside the inner cylindrical portion 22 and has a cylindrical shape extending in the direction of the axis S toward the pressure receiving bottom portion 23. It is formed.
That is, the cylindrical cover portion 72 is formed to be disposed with respect to the inner wall surface 22a of the inner cylindrical portion 22 with a predetermined gap C2.

The annular bottom portion 73 is integrally formed with the cylindrical cover portion 72 so as to abut the pressure receiving bottom portion 23 of the diaphragm 20 and to define a circular opening 73a in the central region thereof.
The opening 73 a is formed to expose the pressure receiving bottom 23 of the diaphragm 20 and expose it to the combustion gas.
The bending cover area 74 is an area in which the flange cover 71 and the cylindrical cover 72 are integrally continued, and is formed as a curved surface having a curvature radius R2 (<R1).

Next, assembly of the pressure sensor having the above configuration will be described.
First, the housing 10, the diaphragm 20, the piezoelectric body 32, the second electrode 33 to which the lead wire 50 is connected, the screw member 41, the insulating member 42, the connector 60, the spacer 61, and the heat shielding cover member 70 are prepared.

Subsequently, the diaphragm 20 is assembled to the housing 10. That is, the annular flange portion 21 is joined and held to the end face 11 a of the distal end cylindrical portion 11.
Subsequently, the heat shield cover member 70 is assembled to the housing 10. That is, the flange cover portion 71 is overlapped and joined to the annular flange portion 21 so that the cylindrical cover portion 72 faces the inner cylindrical portion 22 and the annular bottom portion 73 faces the pressure receiving bottom portion 23.
Then, the flange cover portion 71 and the annular flange portion 21 are welded together and fixed to the end surface 11 a of the distal end cylindrical portion 11.

Subsequently, the piezoelectric body 32, the second electrode 33, the insulating member 42, and the screw member 41 are inserted into the housing 10 from the opening end 14 so as to sequentially overlap.
The piezoelectric body 32, the second electrode 33, and the insulating member 42 may be stacked in advance and temporarily assembled.
Then, the screw member 41 is appropriately screwed in, and a predetermined preload is applied to give the pressure measurement unit 30 a linear characteristic as a sensor.

Subsequently, the spacer 61 is fixed to the open end 14 of the housing 10, the lead wire 50 drawn out is connected to the connector 60, and the connector 60 is connected to the spacer 61.
Thus, the assembly of the pressure sensor is completed.
In addition, the said assembly | attachment procedure is an example, Comprising: It is not limited to this, You may employ | adopt another assembly | attachment procedure.

In the pressure sensor having the above-described configuration, the tip end cylindrical portion 11, the diaphragm 20, and the heat shield cover member 70 have the arrangement relationship shown in FIG.
That is, in the diaphragm 20, the annular flange portion 21 is fixed to the end surface 11a of the distal end cylindrical portion 11, and the inner cylindrical portion 22 is disposed with a gap C1 to the inner wall surface 11b of the distal end cylindrical portion 11.
Thereby, the heat transfer from the distal end cylindrical portion 11 to the inner cylindrical portion 22 can be suppressed or prevented.

  In addition, the heat shield cover member 70 is disposed outside the diaphragm 20. Then, the flange cover portion 71 is overlapped and fixed so as to cover the annular flange portion 21, the cylindrical cover portion 72 covers the inner cylindrical portion 22 with a gap C 2, and the annular bottom portion 73 is in the vicinity of the peripheral edge of the pressure receiving bottom portion 23. Close to the region, the opening 73 a provided in the annular bottom 73 exposes the pressure receiving bottom 23.

Therefore, the annular flange portion 21 of the diaphragm 20 is shielded from the combustion gas by the flange cover portion 71 of the heat shield cover member 70.
Further, the inner cylindrical portion 22 of the diaphragm 20 is shielded from the combustion gas by the cylindrical cover portion 72 and the annular bottom portion 73 of the heat shield cover member 70.
On the other hand, the pressure receiving bottom portion 23 is exposed to the combustion gas through the opening 73a.

Thereby, the heat of the combustion gas is substantially shut off by the heat shield cover member 70, the heat transfer to the diaphragm 20 side is suppressed, and the pressure receiving bottom portion 23 receives only the pressure of the combustion gas.
In particular, since the inner cylindrical portion 22 is covered by the heat shielding cover member 70, it is possible to prevent thermal deformation in the direction of the axis S of the inner cylindrical portion 22.

On the other hand, since the pressure of the combustion gas directly acts on the pressure receiving bottom 23 through the opening 73a, the pressure receiving bottom 23 is deformed according to the pressure of the combustion gas without being affected by the heat shield cover member 70.
Although the pressure receiving bottom portion 23 is also exposed to the heat of the combustion gas, the shape thereof is a thin plate, and the thermal deformation in the direction of the axis S is small, so it does not affect the preload.

Further, the bending cover area 74 of the heat shield cover member 70 is disposed with a gap C3 with respect to the bending area 24 of the diaphragm 20.
Thereby, even if the heat shield cover member 70 is thermally deformed, the interference between the both, or the like can be prevented.

As described above, deformation of the diaphragm 20 due to heat can be suppressed even in a measurement environment exposed to a high-temperature pressure medium, and the contact position between the pressure receiving bottom 23 of the diaphragm 20 and the piezoelectric body 32 of the pressure measuring unit 30 can be It can be maintained at the desired setting state.
Therefore, the fluctuation of the preload applied to the pressure measuring unit 30 can be prevented, and the output noise from the piezoelectric body 32 caused by the fluctuation of the preload can be prevented.
Therefore, the pressure of the combustion gas in the combustion chamber CH of the engine can be detected with high accuracy while suppressing measurement errors due to thermal deformation and the like.

  That is, as the mechanism, if the diaphragm 20 is deformed due to heat, the preload applied to the pressure measurement unit 30 is fluctuated, and the accuracy of the detected pressure is lowered. Since thermal deformation of the diaphragm 20 is suppressed by the thermal cover member 70, the pressure can be detected with high accuracy by heat blocking → suppressing thermal deformation of the diaphragm 20 → preventing fluctuation of preload.

5 to 7 show another embodiment of the pressure sensor according to the present invention, which has the same configuration as that of the above-described embodiment except that the above-described heat shield cover member 70 is changed. . Therefore, the same reference numerals are given to the same configuration and the description is omitted. Further, the assembly procedure is also the same as that of the above-described embodiment, and the description thereof is omitted.
The pressure sensor according to this embodiment includes a housing 10, a diaphragm 20, a pressure measurement unit 30, a pressing member 40, a lead wire 50, a connector 60, and a heat shielding cover member 170.

The heat shield cover member 170 is formed into a crimped cylindrical shape by pressing using a metal material having heat resistance and low thermal conductivity, for example, a stainless steel plate having precipitation hardenability. The plate thickness t2 is preferably, for example, about 0.2 mm to 0.5 mm.
Further, as shown in FIGS. 5 and 6, the heat shield cover member 170 has a flange cover 171, a cylindrical cover 172, a circular opening 173 defined on one end side of the cylindrical cover 172, and a bending cover. An area 174 is provided.

The flange cover portion 171 is formed in an annular plate shape having an outer diameter substantially the same as the outer diameter of the annular flange portion 21 so as to be joined to cover the annular flange portion 21.
The flange cover portion 171 is fixed to the end face 11 a of the distal end cylindrical portion 11 together with the annular flange portion 21 by welding or the like.

The cylindrical cover portion 172 has an outer diameter substantially the same as the inner wall surface 22a of the inner cylindrical portion 22, is disposed inside the inner cylindrical portion 22, and extends in the direction of the axis S toward the pressure receiving bottom portion 23. At one end towards the bottom 23 it is cylindrical in shape defining an opening 173.
That is, the cylindrical cover portion 172 is formed so as not to be in contact with the pressure receiving bottom portion 23 and in close contact with the inner wall surface 22 a of the inner cylindrical portion 22.

The opening portion 173 is formed to expose the pressure receiving bottom portion 23 of the diaphragm 20 substantially over the entire area to be exposed to the combustion gas.
The bending cover area 174 is an area in which the flange cover portion 171 and the cylindrical cover portion 172 are integrally continued, and is formed as a curved surface having a curvature radius R2 (<R1).

In the pressure sensor having the above-described configuration, the tip end cylindrical portion 11, the diaphragm 20, and the heat shield cover member 170 have the arrangement relationship shown in FIG.
That is, in the diaphragm 20, the annular flange portion 21 is fixed to the end surface 11a of the distal end cylindrical portion 11, and the inner cylindrical portion 22 is disposed with a gap C1 to the inner wall surface 11b of the distal end cylindrical portion 11.
Thereby, the heat transfer from the distal end cylindrical portion 11 to the inner cylindrical portion 22 can be suppressed or prevented.

  Further, the heat shield cover member 170 is disposed outside the diaphragm 20. Then, the flange cover portion 171 is overlapped and fixed so as to cover the annular flange portion 21, the cylindrical cover portion 172 is not in contact with the pressure receiving bottom portion 23 and closely in contact with the inner cylindrical portion 22, and the opening portion 173 is the pressure receiving bottom portion 23. Will be exposed.

Therefore, the annular flange portion 21 of the diaphragm 20 is shielded from the combustion gas by the flange cover portion 171 of the heat shield cover member 170.
Further, the inner cylindrical portion 22 of the diaphragm 20 is shielded from the combustion gas by the cylindrical cover portion 172 of the heat shielding cover member 170.
On the other hand, the pressure receiving bottom portion 23 is exposed to the combustion gas through the opening portion 173.

Thereby, the heat of the combustion gas is substantially shut off by the heat shield cover member 170, the heat transfer to the diaphragm 20 side is suppressed, and the pressure receiving bottom portion 23 receives only the pressure of the combustion gas.
In particular, since the inner cylindrical portion 22 is covered by the heat shielding cover member 170, thermal deformation in the direction of the axis S of the inner cylindrical portion 22 can be prevented.

On the other hand, since the pressure of the combustion gas directly acts on the pressure receiving bottom portion 23 through the opening portion 173, the pressure receiving bottom portion 23 is deformed according to the pressure of the combustion gas without being affected by the heat shield cover member 170.
Although the pressure receiving bottom portion 23 is also exposed to the heat of the combustion gas, the shape thereof is a thin plate, and the thermal deformation in the direction of the axis S is small, so it does not affect the preload.

Further, the bending cover area 174 of the heat shield cover member 170 is disposed with a gap C3 with respect to the bending area 24 of the diaphragm 20.
As a result, even if the heat shield cover member 170 is thermally deformed, it is possible to prevent the interference between the two and the like.

As described above, deformation of the diaphragm 20 due to heat can be suppressed even in a measurement environment exposed to a high-temperature pressure medium, and the contact position between the pressure receiving bottom 23 of the diaphragm 20 and the piezoelectric body 32 of the pressure measuring unit 30 can be It can be maintained at the desired setting state.
Therefore, the fluctuation of the preload applied to the pressure measuring unit 30 can be prevented, and the output noise from the piezoelectric body 32 caused by the fluctuation of the preload can be prevented.
Therefore, the pressure of the combustion gas in the combustion chamber CH of the engine can be detected with high accuracy while suppressing measurement errors due to thermal deformation and the like.

  Further, since the cylindrical cover portion 172 of the heat shield cover member 170 is not in contact with the pressure receiving bottom portion 23, management of the length dimension of the cylindrical cover portion 172 in the direction of the axis S is simplified. When assembling, it is possible to easily assemble the tubular cover portion 172 only by fitting the tubular cover portion 172 to the inner tubular portion 22.

FIG. 8 is a graph showing comparative test data obtained by measuring the pressure of combustion gas of the engine with the pressure sensor according to the present invention and the pressure sensor with the heat shield cover member 70 eliminated.
Here, the conditions of the comparison test are as follows.
・ Use engine: Two cylinder gasoline engine, 1000cc displacement
・ Operating conditions: Engine rpm 5000rpm, full load ・ Reference sensor: Sensor for precision analysis (AVL)
Result data: dotted line → sensor for precise analysis (actual combustion pressure), solid line → pressure sensor of the present invention, one-dot chain line → conventional pressure sensor As is apparent from the results shown in FIG. In the pressure sensor according to the present invention, the amount of deviation from the actual combustion pressure, that is, the measurement error is smaller than that of the conventional pressure sensor.
In the present invention provided with the heat shield cover member 170, the same effect as the result shown in FIG. 8 can be obtained.
As described above, according to the pressure sensor of the present invention, the sensor accuracy is improved, and the pressure of the pressure medium such as the combustion gas in the combustion chamber of the engine can be detected with high accuracy.

In the above embodiment, as the diaphragm, the annular flange portion 21 has an annular shape, the inner cylindrical portion 22 has a cylindrical shape, and the pressure receiving bottom portion 23 has a disc shape, but the present invention is limited thereto. If it is a form fixed to the tip part of tip cylindrical part 11 instead of an annular flange part, a form other than an annular flange may be adopted, and cylindrical shape of tip cylindrical part 11 of housing 10 other than a cylinder may be adopted. If it is, it is good also as a shape which adapts to it.
In this case, the heat shield cover member is also preferably configured to be compatible with the diaphragm in the form.

  In the above embodiment, although the configuration in which the diaphragm 20 doubles as the first electrode 31 of the pressure measurement unit 30 is shown, the present invention is not limited to this, and a configuration in which a dedicated electrode is provided as the first electrode 31 is adopted. It is also good.

  As described above, the pressure sensor of the present invention can detect the pressure of the high-temperature pressure medium with high accuracy by suppressing the influence of heat, and in particular, the pressure of the high-temperature pressure medium such as combustion gas in the combustion chamber of the engine As well as being applicable as a pressure sensor for detecting the pressure, it is also useful as a pressure sensor for detecting the pressure of a high temperature pressure medium other than the combustion gas or other pressure medium.

Reference Signs List 10 housing 11 tip cylindrical portion 11a end surface 11b inner wall surface 20 diaphragm t1 plate thickness 21 annular flange portion 22 inner cylindrical portion C1 gap 22a inner wall surface 23 pressure receiving bottom portion 24 bending region 30 pressure measuring portion 31 first electrode 32 piezoelectric body 33 2 Electrode 70 Heat shielding cover member t2 Plate thickness 71 Flange cover portion 72 Tubular cover portion C2 Gap 73 Annular bottom portion 73a Opening portion 74 Bending cover area C3 Gap 170 Heat shielding cover member 171 Flange cover portion 172 Tubular cover portion 173 Opening portion 174 bend cover area

Claims (8)

A housing having a distal tubular portion;
A pressure measurement unit including a piezoelectric body housed in the housing;
An inner cylindrical portion disposed inside the distal end cylindrical portion and extending toward the front pressure measuring portion, and a bottomed portion including a pressure receiving bottom portion integrally formed with the inner cylindrical portion and abutting on the pressure measuring portion With the diaphragm,
A heat shield cover member formed to shield the inner cylindrical portion from the pressure medium and to expose the pressure receiving bottom to the pressure medium;
A pressure sensor characterized by The heat shield cover member includes a cylindrical cover portion arranged to cover an inner wall surface of the inner cylindrical portion, and an opening portion for exposing the pressure receiving bottom portion.
The pressure sensor according to claim 1, characterized in that: The heat shield cover member has an annular bottom which is formed continuously with the cylindrical cover and which defines the opening.
The cylindrical cover portion is disposed with a predetermined gap with respect to the inner cylindrical portion,
The annular bottom is disposed closely to the pressure receiving bottom.
The pressure sensor according to claim 2, characterized in that. The cylindrical cover portion of the heat shield cover member is disposed so as to define the opening on one end side toward the pressure receiving bottom portion and in non-contact with the pressure receiving bottom portion and in close contact with the inner cylindrical portion. ,
The pressure sensor according to claim 2, characterized in that. The diaphragm has an annular flange portion which is continuously formed on the inner cylindrical portion and fixed to an end surface of the distal cylindrical portion.
The heat shield cover member includes a flange cover portion which is formed continuously with the cylindrical cover portion and is overlapped and fixed to the annular flange portion.
The pressure sensor according to any one of claims 2 to 4, characterized in that. The diaphragm includes a bending region continuous from the inner tubular portion to the annular flange portion,
The heat shield cover member includes a bending cover region that is continuous with the flange cover portion from the cylindrical cover portion,
The bending cover area is disposed with a predetermined gap with respect to the bending area.
The pressure sensor according to claim 5, characterized in that: The inner cylindrical portion of the diaphragm is disposed with a predetermined gap with respect to the inner wall surface of the distal end cylindrical portion.
The pressure sensor according to any one of claims 1 to 6, characterized in that. The pressure measurement unit has a first electrode, a piezoelectric body, and a second electrode sequentially stacked from the tip side of the tip cylindrical portion,
The diaphragm also serves as the first electrode.
The pressure sensor according to any one of claims 1 to 7, characterized in that.

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