JP2019113381A - 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 accommodated in the housing and provided with a piezoelectric body; and a diaphragm 20 comprising a flexible tabular section 21 fixed to an inner wall of the tip-end cylindrical section, and a rod section 22 disposed between the flexible tabular section and the pressure measurement unit. The pressure sensor also includes a heat shield sphere 70 which is retained inside the tip-end cylindrical section to shield the diaphragm from a 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.

  As a conventional pressure sensor, a cylindrical housing, a sensor element contained in the housing, a diaphragm that closes the housing and deforms according to the pressure of the pressure medium, and force transmission that transmits the pressure received by the diaphragm to the sensor element A pressure sensor is known which employs a plate-like diaphragm provided with a rod and provided with a folded portion defining an annular recess having a substantially V-shaped cross section as a diaphragm (e.g., 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 sensor element through the force transmission rod of the diaphragm, and a signal corresponding to the pressure is output. .

  However, this pressure sensor has a structure in which the diaphragm is directly exposed to the high temperature combustion gas, so that the change in temperature of the combustion gas causes a change in sensor characteristics, and hence a measurement error.

Patent No. 4638659

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reliably shut off the diaphragm from the high-temperature pressure medium to suppress the influence of heat accompanying the temperature change of the pressure medium. An object of the present invention is to provide a pressure sensor capable of detecting the pressure of a high temperature pressure medium with high accuracy.

  The pressure sensor according to the present invention includes a housing having a distal end cylindrical portion, a pressure measurement portion housed in the housing and including a piezoelectric body, a flexible plate-like portion fixed inside the distal end cylindrical portion, and a flexible A diaphragm comprising a rod portion interposed between the plate portion and the pressure measurement portion, and a heat shield spherical body held inside the tip end cylindrical portion to shield the diaphragm from the pressure medium. There is.

  In the pressure sensor having the above configuration, the distal end tubular portion has a distal end annular portion defining an opening having a reduced diameter at its distal end, and the heat shielding spherical body is held by the distal end annular portion. You may

  In the pressure sensor having the above configuration, the distal end annular portion may be formed by bending the opening edge region of the distal end cylindrical portion inward.

  In the pressure sensor having the above-described configuration, the heat shielding spherical body adopts a configuration in which the flexible plate-like portion is held so as to contact with no load in a state where the pressure medium does not receive pressure. May be

  In the pressure sensor having the above configuration, the flexible plate-like portion may adopt a configuration including a positioning portion for positioning the heat shielding spherical body.

  In the pressure sensor having the above-described configuration, the heat shielding spherical body may be fixed to the flexible plate portion.

  In the pressure sensor having the above configuration, the distal end cylindrical portion is formed in a cylindrical shape, the flexible plate-like portion is formed in a disk shape disposed inside the distal end cylindrical portion, and the heat shielding spherical body is A configuration may be employed in which the ball is formed into a sphere having an outer diameter smaller than the inner diameter of the distal end cylindrical portion.

  In the pressure sensor having the above-described configuration, the distal end tubular portion includes a first tubular portion, and a second tubular portion located on the distal end side of the first tubular portion and thinner than the first tubular portion. The flexible plate-like portion is fixed to the step surface, and the second cylindrical portion has a diameter-reduced opening at its tip, including the step surface formed at the boundary between the first tubular portion and the second tubular portion. And the heat shield ball may be held by the tip annulus.

  In the pressure sensor having the above configuration, the distal end annular portion may be formed by a coupling member coupled to the housing so as to define the second tubular portion.

  In the pressure sensor having the above configuration, the tip annular portion is formed as a conical wall that defines an opening at its tip, and the heat shield sphere is held in contact with the conical wall. Good.

  In the pressure sensor having the above-described configuration, the tip annular portion is formed as an annular flat plate defining an opening at the center thereof, and the heat shielding spherical body is held in contact with the inner edge of the opening of the annular flat plate. A configuration may be adopted.

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 a 1st 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 front-end | tip cylindrical part, a diaphragm, the spherical body for heat insulation, a pressure measurement part etc. 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 the spherical body for thermal insulation. In the pressure sensor shown in FIG. 1, it is a partially enlarged cross-sectional view showing a state before bending the opening edge region of the tip cylindrical portion and a tip cylindrical portion after bending, a diaphragm, and a heat shield spherical body. . In the pressure sensor shown in FIG. 1, it is a partial expanded sectional view which shows the modification which provided the positioning part in the flexible plate-like part of the diaphragm. It is a sectional view showing a second embodiment of a pressure sensor concerning the present invention. The pressure sensor shown in FIG. 6 WHEREIN: It is a partial expanded sectional view which shows the mutual relationship of the housing which has a tip cylindrical part, a diaphragm, and the ball for thermal insulation. The pressure sensor shown in FIG. 6 WHEREIN: It is a partial expanded sectional view which shows the mutual relationship of a front end cylindrical part, a coupling member, a diaphragm, and the spherical body for thermal insulation. In the pressure sensor shown in FIG. 6, the tip cylindrical portion, the diaphragm, the coupling member, and the heat shielding spherical body in a state before and after coupling to the housing a coupling member that defines a portion of the tip cylindrical portion. It is a partial expanded sectional view which shows. It is a sectional view showing a 3rd embodiment of a pressure sensor concerning the present invention. In the pressure sensor shown in FIG. 10, it is a partially enlarged cross-sectional view showing the mutual relationship between a housing having a tip end cylindrical portion, a diaphragm, and a heat shielding spherical body. In the pressure sensor shown in FIG. 10, it is a partially enlarged cross-sectional view showing the mutual relationship of the tip end cylindrical portion, the coupling member, the diaphragm, and the heat shielding spherical body. It is the graph which compared the sensor output by the pressure sensor which concerns on this invention, and the conventional pressure sensor.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.
The pressure sensor according to the first 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 spherical body 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 front end cylindrical portion 11 is formed in a cylindrical shape having a two-step thickness in a region located on the front end side in the direction of the axis S from the seal portion 12, and the first cylindrical portion 11a, the second cylindrical portion 11b, and the step surface An opening 11e defined by the tip annular portion 11d and the tip annular portion 11d is provided.

The first cylindrical portion 11a defines a cylindrical inner wall surface 11a1, and the outer wall surface of the first cylindrical portion 11a is disposed close to or in close contact with the inner peripheral surface H1 of the mounting hole of the cylinder head H and is difficult to be exposed to combustion gas It is supposed to be.
The second cylindrical portion 11b defines a cylindrical inner wall surface 11b1 having a thickness smaller than that of the first cylindrical portion 11a before being bent.
The inner diameter dimension of the inner wall surface 11b1 is formed to be slightly larger than the outer diameter D of the heat shield spherical body 70.
The step surface 11c is formed as an annular flat surface perpendicular to the axis S at the boundary between the first cylindrical portion 11a and the second cylindrical portion 11b.
And the level | step difference surface 11c functions as a fixed surface which fixes the flexible plate-like-part 21 of the diaphragm 20 by welding etc.

The distal end annular portion 11d is formed as a conical wall which bends the opening edge region of the second cylindrical portion 11b inward to be in contact with the heat shield spherical body 70, and defines a circular opening 11e in its central region.
The opening 11 e is formed to have an inner diameter smaller than the outer diameter D of the heat shield spherical body 70, that is, smaller.
That is, the tip annular portion 11d plays a role of holding the heat shielding spherical body 70 housed inside the second cylindrical portion 11b so as not to drop off.

The seal portion 12 is formed in a conical surface shape at a predetermined position receded from the tip end of the tip 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. It serves to prevent 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 dimension 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 is formed using a metal material such as stainless steel having precipitation hardenability.
The diaphragm 20 is provided with a flexible plate 21 and a rod 22 continuously formed on the flexible plate 21.

The flexible plate-like portion 21 is formed in a disk shape having a plate thickness t 1, and the outer edge region thereof is fixed to the step surface 11 c of the distal cylindrical portion 11 by welding or the like.
The flexible plate-like portion 21 is a region in which a load corresponding to the pressure of the combustion gas is transmitted through the heat shielding spherical body 70 and elastically deformed in the direction of the axis S according to the load.
Here, the thickness t1 of the flexible plate-like portion 21 is about 0.2 mm to 0.6 mm.

The rod portion 22 is formed in a cylindrical shape extending in the direction of the axis S from a substantially central region of the flexible plate-like portion 21.
The outer peripheral surface of the rod portion 22 is disposed with a predetermined gap from the inner wall surfaces 11a1 and 16 of the housing 10, and the end surface of the rod portion 22 is disposed to abut the piezoelectric body 32 of the pressure measuring portion 30. ing.
That is, the rod portion 22 is interposed between the flexible plate-like portion 21 and the piezoelectric body 32 of the pressure measuring portion 30, and functions to transmit the force received by the flexible plate-like portion 21 to the piezoelectric body 32.

  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 rod portion 22 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 first electrode 31, that is, the rod portion 22 of the diaphragm 20 and the second electrode 33, and outputs an electrical 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 shielding spherical body 70 is disposed inside the distal end cylindrical portion 11 so as to shield the diaphragm 20 from the combustion gas which is a pressure medium, and is formed using a material having heat resistance and low thermal conductivity. It is done.
Here, as a material of the heat shield spherical body 70, a material having low thermal conductivity, excellent in durability, and high rigidity is preferable, and in addition to stainless steel, a nickel-plated carbon steel, a nickel alloy, Iron-based alloys, titanium alloys, or ceramics can be used.

Further, the heat shielding spherical body 70 is formed as a spherical body having an outer diameter D which is slightly smaller than the inner diameter of the inner wall surface 11b1 of the distal end cylindrical portion 11 (second cylindrical portion 11b).
Here, the heat shield spherical body 70 is not limited to a sphere, and may be in the form of a sphere which is extended in one direction or collapsed in one direction.
Thus, by adopting the heat shield spherical body 70, it is possible to exhibit the function of transmitting only the pressure of the combustion gas to the flexible plate-like portion 21 while blocking the heat of the combustion gas.

  The heat shielding spherical body 70 is inserted into the second cylindrical portion 11b of the distal end cylindrical portion 11 as shown in FIG. 4, and then the bending heat machine M is used to form the second cylindrical portion 11b. It is hold | maintained inside the 2nd cylindrical part 11b so that it may not drop | omit outside by the front-end | tip annular part 11d which the opening edge area | region bend | folded inward and was formed.

Here, the heat shielding spherical body 70 is in contact with the conical wall of the tip annular portion 12 so as to contact the flexible plate-like portion 21 with no load in a state where it receives no pressure of combustion gas. It is held.
Further, the outer diameter D is larger than the effective diameter of the flexible plate-like portion 21 which functions as a diaphragm so that the heat shielding spherical body 70 does not become immobile due to sticking, sticking or the like inside the second cylindrical portion 11b. It is large and smaller than the inner diameter of the second cylindrical portion 11b.

In addition, although the spherical body 70 for thermal insulation is hold | maintained so that it may contact with respect to the flexible plate-like part 21 by no load, it may be fixed with respect to the flexible plate-like part 21 by welding etc. .
In this case, the heat shield spherical body 70 can be prevented from vibrating due to the pressure of the combustion gas. Thereby, in the sensor output of the pressure measurement part 30, it can prevent that the noise accompanying the vibration generate | occur | produces.
As described above, in the configuration in which the heat shielding spherical body 70 is fixed to the flexible plate-like portion 21 by welding, when the heat shielding spherical body 70 is formed of ceramics, the metal spheres of the ceramic are covered with a metal layer. The welding process can be easily performed by applying the rising.

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 and the spacer 61, and the heat shielding spherical body 70 are prepared.

Subsequently, the diaphragm 20 is assembled to the housing 10. That is, the flexible plate-like portion 21 is joined to the step surface 11 c of the distal end cylindrical portion 11 and fixed by welding or the like.
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.

Subsequently, the heat shielding spherical body 70 is assembled so as to be held inside the distal end cylindrical portion 11 of the housing 10. Here, “holding” means not being fixed in the distal end cylindrical portion 11 but supported so as not to drop off.
That is, the heat shielding spherical body 70 is disposed inside the second cylindrical portion 11 b of the distal end cylindrical portion 11.
Subsequently, as shown in FIG. 4, the opening edge region of the second cylindrical portion 11 b is bent inward using a predetermined bending processing machine M, and the tip annular portion 11 d is formed. Here, an opening 11 e having a diameter smaller than the outer diameter D of the heat shield spherical body 70 is defined by the tip annular portion 11 d.

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 shielding spherical body 70 have the arrangement relationship shown in FIG.
That is, the heat shielding spherical body 70 is in contact with the conical wall of the tip annular portion 12 in a state of not receiving the pressure of the combustion gas so as to contact the flexible plate portion 21 with no load. It is held inside the distal end cylindrical portion 11 and disposed outside the diaphragm 20.
Therefore, when the heat shield spherical body 70 receives the pressure of the combustion gas through the opening 11 e, a load corresponding to the pressure is immediately applied to the flexible plate 21 through the heat shield spherical body 70. Then, the diaphragm 20 is shielded from the combustion gas by the heat shielding spherical body 70, and is deformed according to the received load.

Thereby, the heat of the combustion gas is substantially blocked by the heat shielding spherical body 70, and the heat transfer to the diaphragm 20 side is suppressed or prevented. Therefore, the flexible plate-like portion 21 of the diaphragm 20 receives or suppresses substantially only the pressure of the combustion gas with the influence of the heat by the combustion gas being suppressed or prevented.
Further, since the heat shielding spherical body 70 is disposed to be in contact with the flexible plate-like portion 21, an impact force or an impact sound accompanying the movement thereof is suppressed or prevented, and the characteristics of the diaphragm 20 are obtained. It has no effect.

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 rod portion 22 of the diaphragm 20 and the piezoelectric body 32 of the pressure measurement 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 heat spherical body 70, the pressure can be detected with high accuracy by heat blocking → suppressing thermal deformation of the diaphragm 20 → preventing fluctuation of preload.

FIG. 5 shows a modification in which a positioning portion is provided on the flexible plate-like portion 21 of the diaphragm 20 in the above embodiment.
In this modification, the flexible plate-like portion 21 is provided with a conical recess 23 having a center on the axis S as a positioning portion.
The conical recess 23 receives the heat shield ball 70 and positions the center of the heat shield ball 70 on the axis S.
Thereby, positioning and assembly of the heat shield spherical body 70 can be easily performed.
The heat shielding spherical body 70 may be fixed to the flexible plate 21 by welding or the like in a state of being positioned in the conical recess 23.

FIGS. 6 to 9 show a second embodiment of the pressure sensor according to the present invention, and the above-described embodiment is carried out except that the second cylindrical portion 11b holding the heat shielding spherical body 70 described above is changed. It has the same configuration as the form. Therefore, about the same structure, the same code | symbol is attached | subjected and description is abbreviate | omitted.
The pressure sensor according to this embodiment includes a housing 100, a diaphragm 20, a pressure measurement unit 30, a pressing member 40, a lead wire 50, a connector 60, and a heat shield spherical body 70.

The housing 100 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 100 includes the coupling member 120 coupled to the distal end cylindrical portion 110, the seal portion 12, the male screw portion 13, the opening end portion 14, the inner wall surfaces 15 and 16, the female screw portion 17, and the distal end cylindrical portion 110. Have.

The distal cylindrical portion 110 is formed in a cylindrical shape having a two-step thickness in a region located on the distal end side in the direction of the axis S from the seal portion 12 and is coupled to the first cylindrical portion 111, the end surface 112, and the end surface 112. A coupling member 120 is provided.
Then, the coupling member 120 includes a second cylindrical portion 121 coupled to the first cylindrical portion 111 so that the outer peripheral wall is continuous, a distal end annular portion 122 formed on the distal end side of the second cylindrical portion 121, and An end surface 123 formed on the rear end side of the two cylindrical portions 121 and an opening 124 defined by a tip annular portion 122 are provided.

The first cylindrical portion 111 defines a cylindrical inner wall surface 111a, and the outer wall surface thereof 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 combustion gas It is supposed to be.
The end surface 112 defines a step surface forming an annular flat surface perpendicular to the axis S at the boundary between the first cylindrical portion 111 and the second cylindrical portion 121 in a state where the first cylindrical portion 111 and the second cylindrical portion 121 are coupled.
The step surface located in the inner edge region of the end surface 112 functions as a fixing surface for fixing the flexible plate-like portion 21 of the diaphragm 20 by welding or the like.

The second cylindrical portion 121 defines a cylindrical inner wall surface 121 a having a thickness smaller than that of the first cylindrical portion 111. The inner diameter of the inner circumferential wall 121 a is slightly larger than the outer diameter D of the heat shield spherical body 70.
The distal end annular portion 122 is formed in an annular flat plate shape on the distal end side of the second cylindrical portion 121, and defines a circular opening 124 in a central region thereof.
The end surface 123 is formed in an annular flat surface joined to the outer peripheral region of the end surface 112.
The opening 124 is formed to have a diameter smaller than the inner diameter of the second cylindrical portion 121 as the distal end cylindrical portion so as to have an inner diameter smaller than the outer diameter D of the heat shield spherical body 70.
That is, the tip end annular portion 122 plays a role of holding the heat shielding spherical body 70 housed inside the second cylindrical portion 121 so as not to drop off.

Here, the heat shielding spherical body 70 contacts the inner edge of the opening 124 of the distal end annular portion 122 so as to contact the flexible plate-like portion 21 with no load in a state where it receives no pressure of combustion gas. To be held.
Further, the outer diameter D is larger than the effective diameter of the flexible plate-like portion 21 which functions as a diaphragm so that the heat shielding spherical body 70 does not become immobile by sticking, sticking or the like inside the second cylindrical portion 121. It is large and smaller than the inner diameter of the second tubular portion 121.
In addition, although the spherical body 70 for thermal insulation is hold | maintained so that it may contact with respect to the flexible plate-like part 21 by no load, it may be fixed with respect to the flexible plate-like part 21 by welding etc. .

Next, assembly of the pressure sensor having the above configuration will be described.
First, the housing 100, the coupling member 120, 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 and the spacer 61, and the heat shielding spherical body 70 are prepared. Be done.

Subsequently, the diaphragm 20 is assembled to the housing 100. That is, the flexible plate-like portion 21 is joined to the end surface 112 of the distal end cylindrical portion 110 and fixed by welding or the like.
Subsequently, the piezoelectric body 32, the second electrode 33, the insulating member 42, and the screw member 41 are inserted into the housing 100 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 100, the lead wire 50 drawn out is connected to the connector 60, and the connector 60 is connected to the spacer 61.

Subsequently, as shown in FIG. 9, in a state in which the heat shielding spherical body 70 is accommodated inside the coupling member 120, the end surface 123 of the coupling member 120 is joined to the end surface 112 of the tip cylindrical portion 110, and welding etc. Fixed by
Thus, the heat shield spherical body 70 is assembled so as to be held inside the distal end cylindrical portion 110 of the housing 100.
Here, "holding" means not being fixed in the distal end cylindrical portion 110, but supported so as not to come off.

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 110, the diaphragm 20, and the heat shield spherical body 70 have the arrangement relationship shown in FIG.
That is, the heat shielding spherical body 70 contacts the inner edge of the opening 124 of the tip annular portion 122 in a state where it does not receive the pressure of the combustion gas, and contacts the flexible plate portion 21 with no load. , And is disposed outside the diaphragm 20 while being held inside the distal end tubular portion 110.
Therefore, when the heat shield spherical body 70 receives the pressure of the combustion gas through the opening 124, a load corresponding to the pressure is immediately applied to the flexible plate 21 through the heat shield spherical body 70. Then, the diaphragm 20 is shielded from the combustion gas by the heat shielding spherical body 70, and is deformed according to the received load.

Thereby, the heat of the combustion gas is substantially blocked by the heat shielding spherical body 70, and the heat transfer to the diaphragm 20 side is suppressed or prevented. Therefore, the flexible plate-like portion 21 of the diaphragm 20 receives or suppresses substantially only the pressure of the combustion gas with the influence of the heat by the combustion gas being suppressed or prevented.
Further, since the heat shielding spherical body 70 is disposed to be in contact with the flexible plate-like portion 21, an impact force or an impact sound accompanying the movement thereof is suppressed or prevented, and the characteristics of the diaphragm 20 are obtained. It has no effect.

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 rod portion 22 of the diaphragm 20 and the piezoelectric body 32 of the pressure measurement 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.

FIGS. 10 to 12 show a third embodiment of the pressure sensor according to the present invention, which is the same as the above except that the heat shielding spherical body 70 and the coupling member 120 according to the second embodiment described above are changed. It has the same configuration as that of the embodiment. Therefore, the same components are denoted by the same reference numerals and the description thereof will be omitted, and the assembling procedure is also the same.
The pressure sensor according to this embodiment includes a housing 100, a diaphragm 20, a pressure measurement unit 30, a pressing member 40, a lead wire 50, a connector 60, and a heat shield spherical body 71.

  The housing 100 includes a distal end cylindrical portion 110, a seal portion 12, an external thread portion 13, an open end portion 14, an inner wall surface 15, 16, an internal thread portion 17, and a coupling member 130 coupled to the distal end cylindrical portion 110. There is.

  The heat shielding spherical body 71 is formed as a sphere smaller than the heat shielding spherical body 70. Therefore, the weight of the heat shielding spherical body 71 is smaller than that of the heat shielding spherical body 70, and the impact force or the like exerted on another member when pressure is applied is also reduced.

The distal cylindrical portion 110 includes a first cylindrical portion 111, an end surface 112, and a coupling member 130 coupled to the end surface 112.
The coupling member 130 includes a two-stage cylindrical second cylindrical portion 131 having a thickness smaller than the thickness of the first cylindrical portion 111, a tip annular portion 132, an end surface 133, and an opening 124.
The second cylindrical portion 131 includes the same diameter region having the same diameter as the first cylindrical portion 111 and the reduced diameter region, and defines a cylindrical inner wall surface 131 a in the reduced diameter region. The inner diameter of the inner circumferential wall 131 a is slightly larger than the outer diameter D of the heat shielding spherical body 71.

The tip annular portion 132 is formed in an annular flat plate shape on the tip side of the second cylindrical portion 131, and defines a circular opening 134 in the central region thereof.
The end surface 133 is formed in an annular flat surface joined to the outer peripheral region of the end surface 112.
The opening 134 is formed smaller in diameter than the inner diameter of the second cylindrical portion 131 as the distal end cylindrical portion so as to have an inner diameter smaller than the outer diameter D of the heat shield spherical body 71.
That is, the tip annular portion 132 plays a role of holding the heat shielding spherical body 71 housed inside the second cylindrical portion 131 so as not to drop off.

Here, the heat shielding spherical body 71 contacts the inner edge of the opening 134 of the tip annular portion 132 so as to contact the flexible plate-like portion 21 with no load in a state where it receives no pressure of combustion gas. To be held.
Further, the outer diameter D is larger than the effective diameter of the flexible plate-like portion 21 which functions as a diaphragm so that the heat shielding spherical body 71 does not become immobile by sticking, sticking or the like inside the second cylindrical portion 131. It is large and smaller than the inner diameter of the second cylindrical portion 131 (inner wall surface 131a).
In addition, although the spherical body 71 for thermal insulation is hold | maintained so that it may contact with respect to the flexible plate-like part 21 by no load, it may be fixed with respect to the flexible plate-like part 21 by welding etc. .

In the pressure sensor having the above-described configuration, the tip end cylindrical portion 110, the diaphragm 20, and the heat shield spherical body 71 have the arrangement relationship shown in FIG.
That is, the heat shielding spherical body 71 is in contact with the inner edge of the opening 134 of the tip annular portion 132 in a state of not receiving the pressure of the combustion gas, and contacts the flexible plate 21 with no load. , And is disposed outside the diaphragm 20 while being held inside the distal end tubular portion 110.
Therefore, when the heat shield spherical body 71 receives the pressure of the combustion gas through the opening 134, a load corresponding to the pressure is immediately applied to the flexible plate 21 through the heat shield spherical body 71. Then, the diaphragm 20 is shielded from the combustion gas by the heat shielding spherical body 71 and is deformed according to the received load.
Here, in particular, since the heat shielding spherical body 71 is small, it is possible to further suppress or prevent the impact force etc., and to transmit only the pressure of the combustion gas to the flexible plate portion 21 while securing the heat shielding effect. it can.

That is, the heat of the combustion gas is substantially blocked by the heat shielding spherical body 71, and the heat transfer to the diaphragm 20 side is suppressed or prevented. Therefore, the flexible plate-like portion 21 of the diaphragm 20 receives or suppresses substantially only the pressure of the combustion gas with the influence of the heat by the combustion gas being suppressed or prevented.
In addition, since the heat shield spherical body 71 is smaller than the heat shield spherical body 70 and disposed so as to be in contact with the flexible plate-like portion 21, an impact force, an impact sound, etc. accompanying the movement are generated. It is suppressed or prevented, and does not affect the characteristics of the diaphragm 20.

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 rod portion 22 of the diaphragm 20 and the piezoelectric body 32 of the pressure measurement 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.

FIG. 13 is a graph showing comparative test data obtained by measuring the pressure of combustion gas in the combustion chamber of the engine with the pressure sensor according to the present invention and the conventional pressure sensor.
・ 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 spherical body 71, the same effect as the result shown in FIG. 13 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-mentioned embodiment, although diaphragm 20 which provided flexible plate-like part 21 and rod part 22 integrally as a diaphragm was shown, it is not limited to this, flexible plate-like part 21 and a rod part 22 may be separately formed, and the flexible plate-like portion 21 may function as a diaphragm, and the rod portion 22 may function as a force transmission member.

  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.

DESCRIPTION OF SYMBOLS 10 Housing 11 tip cylindrical part 11a 1st cylindrical part 11b 2nd cylindrical part 11c Step surface 11d tip annular part (conical wall)
11e Opening 20 Diaphragm 21 Flexible plate-like portion 22 Rod portion 23 Conical recess (positioning portion)
Reference Signs List 30 pressure measurement unit 31 first electrode 32 piezoelectric body 33 second electrode 70, 71 heat shielding spherical body 100 housing 110 tip cylindrical portion 111 first cylindrical portion 112 end surface (step surface)
120 coupling member 121 second cylindrical portion 122 tip annular portion (annular flat plate)
124 Opening 124
130 Coupling member 131 second cylindrical portion 132 tip annular portion (annular flat plate)
134 opening

Claims (12)

A housing having a distal tubular portion;
A pressure measurement unit housed in the housing and including a piezoelectric body;
A flexible plate-like portion fixed inside the distal end cylindrical portion, and a diaphragm having a rod portion interposed between the flexible plate-like portion and the pressure measuring portion;
A heat shield ball held inside the tip tubular portion to shield the diaphragm from the pressure medium;
A pressure sensor characterized by The tip tube has a tip annulus defining a reduced diameter opening at its tip,
The heat shielding spherical body is held by the tip annular portion.
The pressure sensor according to claim 1, characterized in that: The tip annular portion is formed by bending an opening edge area of the tip cylindrical portion inward.
The pressure sensor according to claim 2, characterized in that. The heat shielding spherical body is held so as to be in non-load contact with the flexible plate-like portion without receiving the pressure of the pressure medium.
The pressure sensor according to any one of claims 1 to 3, characterized in that. The flexible plate portion includes a positioning portion for positioning the heat shielding spherical body.
The pressure sensor according to claim 4, characterized in that: The heat shielding spherical body is fixed to the flexible plate portion.
The pressure sensor according to claim 4 or 5, characterized in that: The tip cylindrical portion is formed in a cylindrical shape,
The flexible plate-like portion is formed in a disk shape disposed inside the distal end cylindrical portion,
The heat shielding spherical body is formed into a sphere having an outer diameter smaller than the inner diameter of the distal end cylindrical portion.
The pressure sensor according to any one of claims 2 to 6, characterized in that. The tip tubular portion is a first tubular portion, a second tubular portion located on the tip side of the first tubular portion and thinner than the first tubular portion, and the first tubular portion. A stepped surface formed at the boundary between the second portion and the second portion;
The flexible plate portion is fixed to the stepped surface,
The second tubular portion has a tip annulus defining a reduced diameter opening at its tip,
The heat shielding spherical body is held by the tip annular portion.
The pressure sensor according to any one of claims 1 to 7, characterized in that. The tip annulus is formed by a coupling member coupled to the housing to define the second tubular portion.
The pressure sensor according to claim 8, characterized in that. The tip annulus is formed as a conical wall defining the opening at its tip,
The heat shield ball is held in contact with the conical wall,
The pressure sensor according to claim 3 or 9, characterized in that: The tip annulus is formed as an annular flat plate defining the opening at its center,
The heat shielding spherical body is held in contact with the inner edge of the opening of the annular flat plate.
The pressure sensor according to claim 3 or 9, 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 11, characterized in that.

Images