JP6948247B2 - Pressure sensor - Google Patents

Description

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

Conventional pressure sensors include a tubular housing, a sensor element housed in the housing, a diaphragm that closes the housing and deforms according to the pressure of the pressure medium, and a force transmission that transmits the pressure received by the diaphragm to the sensor element. A pressure sensor having a rod and having a plate-shaped diaphragm provided with a folded-shaped portion for defining an annular recess having a substantially V-shaped cross section is known as a diaphragm (for example, Patent Document 1).

In this pressure sensor, when the pressure of high-temperature combustion gas is applied to the diaphragm, the pressure is transmitted to the sensor element via the force transmission rod of the diaphragm, and a signal corresponding to the pressure is output. ..

However, in this pressure sensor, since the diaphragm is directly exposed to the high-temperature combustion gas, the sensor characteristics change with the temperature change of the combustion gas, and therefore, a measurement error occurs.

Japanese Patent No. 46386559

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 a high-temperature pressure medium and suppress the influence of heat due to a temperature change of the pressure medium. It is an object of the present invention to provide a pressure sensor capable of detecting the pressure of a high temperature pressure medium with high accuracy.

The pressure sensor of the present invention includes a housing having a tip tubular portion, a pressure measuring portion housed in the housing and containing a piezoelectric body, a flexible plate-shaped portion fixed inside the tip tubular portion, and a flexible plate. It is configured to include a diaphragm having a rod portion interposed between the plate-shaped portion and the pressure measuring portion, and a heat-shielding spherical body held inside the tip tubular portion to shield the diaphragm from the pressure medium. There is.

In the pressure sensor having the above configuration, the tip cylindrical portion has a tip annular portion that defines a reduced diameter opening at the tip thereof, and the heat shield spherical body is held by the tip annular portion. You may.

In the pressure sensor having the above configuration, the tip annular portion may adopt a configuration in which the opening edge region of the tip tubular portion is bent inward.

In the pressure sensor having the above configuration, the heat shield spherical body is held so as to be in contact with the flexible plate-like portion without a load in a state where it is not subjected to the pressure of the pressure medium. You may.

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

In the pressure sensor having the above configuration, the heat shield spherical body may adopt a configuration in which it is fixed to a flexible plate-like portion.

In the pressure sensor having the above configuration, the tip tubular portion is formed in a cylindrical shape, the flexible plate-shaped portion is formed in a disk shape arranged inside the tip tubular portion, and the heat shield sphere is formed. , A configuration may be adopted in which a sphere having an outer diameter smaller than the inner diameter of the tip cylindrical portion is formed.

In the pressure sensor having the above configuration, the tip tubular portion includes a first tubular portion and a second tubular portion having a wall thickness thinner than the first tubular portion and located on the tip side of the first tubular portion. , The flexible plate-shaped portion is fixed to the stepped surface, and the second tubular portion has a reduced diameter opening at the tip thereof, including the stepped surface formed at the boundary between the first tubular portion and the second tubular portion. The structure may be adopted, which has an annular portion at the tip and is held by the annular portion at the tip of the heat shield.

In the pressure sensor having the above configuration, the tip annular portion may adopt a configuration in which the tip annular portion is formed by a coupling member coupled to the housing to define the second tubular portion.

In the pressure sensor having the above configuration, the tip annular portion is formed as a conical wall defining an opening at the tip thereof, and the heat shield spherical body is held in contact with the conical wall, even if the configuration is adopted. good.

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

In the pressure sensor having the above configuration, the pressure measuring unit has a first electrode, a piezoelectric body, and a second electrode that are sequentially laminated from the tip side of the tip tubular 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 suppressing the influence of heat and detecting the pressure of the high temperature pressure medium with high accuracy.

It is sectional drawing which shows the 1st Embodiment of the pressure sensor which concerns on this invention. In the pressure sensor shown in FIG. 1, it is a partially enlarged cross-sectional view showing a housing having a tip cylindrical portion, a diaphragm, a heat shield spherical body, a pressure measuring portion, and the like. FIG. 5 is a partially enlarged cross-sectional view showing the mutual relationship between the tip cylindrical portion, the diaphragm, and the heat shield spherical body in the pressure sensor shown in FIG. 1. 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 tubular portion, a tip tubular portion after bending, a diaphragm, and a sphere for heat shielding. .. FIG. 5 is a partially enlarged cross-sectional view showing a modified example in which a positioning portion is provided on a flexible plate-shaped portion of a diaphragm in the pressure sensor shown in FIG. It is sectional drawing which shows the 2nd Embodiment of the pressure sensor which concerns on this invention. FIG. 6 is a partially enlarged cross-sectional view showing the mutual relationship between a housing having a tubular tip, a diaphragm, and a heat-shielding spherical body in the pressure sensor shown in FIG. FIG. 6 is a partially enlarged cross-sectional view showing the mutual relationship between the tip cylindrical portion, the coupling member, the diaphragm, and the heat shield spherical body in the pressure sensor shown in FIG. In the pressure sensor shown in FIG. 6, the tip tubular portion, the diaphragm, the coupling member, and the heat shield spherical body in the state before and after the coupling member defining a part of the tip tubular portion are connected to the housing. It is a partially enlarged sectional view which shows. It is sectional drawing which shows the 3rd Embodiment of the pressure sensor which concerns on this invention. FIG. 5 is a partially enlarged cross-sectional view showing the mutual relationship between a housing having a tubular tip, a diaphragm, and a heat-shielding spherical body in the pressure sensor shown in FIG. FIG. 5 is a partially enlarged cross-sectional view showing the mutual relationship between the tip cylindrical portion, the coupling member, the diaphragm, and the heat shield spherical body in the pressure sensor shown in FIG. It is a graph which compared the sensor output with 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 accompanying 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, this pressure sensor includes a housing 10, a diaphragm 20, a pressure measuring unit 30, a pressing member 40, a lead wire 50, a connector 60, and a heat shield spherical body 70.

The housing 10 is formed in a multi-stage cylindrical shape that defines an internal space A extending in the axis S direction by using a metal material such as precipitation hardening stainless steel or ferritic stainless steel.
The housing 10 includes a tip cylindrical portion 11, a seal portion 12, a male screw portion 13, an open end portion 14, inner wall surfaces 15 and 16, and a female screw portion 17.

The tip tubular portion 11 is a region located on the tip side in the axial direction S direction from the seal portion 12, and is formed in a two-step thick cylindrical shape, and is formed by a first tubular portion 11a, a second tubular portion 11b, and a stepped surface. It has an opening 11e defined by 11c, an annular portion 11d at the tip, and an annular portion 11d at the tip.

The first tubular portion 11a defines a cylindrical inner wall surface 11a1, and the outer wall surface thereof is arranged 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 has become like.
The second tubular portion 11b defines a cylindrical inner wall surface 11b1 having a wall thickness thinner than the wall thickness of the first tubular portion 11a in a state before being bent.
The inner diameter 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 stepped surface 11c is formed as an annular plane perpendicular to the axis S at the boundary between the first cylindrical portion 11a and the second tubular portion 11b.
The stepped surface 11c functions as a fixing surface for fixing the flexible plate-shaped portion 21 of the diaphragm 20 by welding or the like.

The tip annular portion 11d is formed as a conical wall in which the opening edge region of the second tubular portion 11b is bent inward to come into contact with the heat shield spherical body 70, and a circular opening 11e is defined in the central region thereof.
The opening 11e is formed to have a diameter smaller than the outer diameter D of the heat shield spherical body 70, that is, an inner diameter smaller than that of the outer diameter D.
That is, the tip annular portion 11d serves to hold the heat shield spherical body 70 housed inside the second tubular portion 11b so as not to fall off.

The seal portion 12 is formed in a conical surface shape at a predetermined position recessed from the tip of the tip cylindrical portion 11 in the axial direction S, and abuts on the seal surface H2 of the cylinder head H to allow combustion gas in the combustion chamber CH to come into contact with the seal surface H2. It plays a role in preventing leakage.
The male screw portion 13 is formed in a diameter-expanded region recessed from the seal portion 12 in the axial direction S so as to be screwed with the female screw portion H3 of the mounting hole provided in the cylinder head H to fix the housing 10. ..
The open end portion 14 functions as an insertion port when the pressing member 40 or the like is attached, 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 that of the inner wall surface 15, and the pressure measuring unit 30 is accommodated in this region.
The female screw portion 17 is formed in a 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 by using a metal material such as stainless steel having precipitation hardening property.
The diaphragm 20 includes a flexible plate-shaped portion 21 and a rod portion 22 continuously formed on the flexible plate-shaped portion 21.

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

The rod portion 22 is formed in a columnar shape extending in the axis S direction from a substantially central region of the flexible plate-shaped portion 21.
The outer peripheral surface of the rod portion 22 is arranged 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 arranged so as to abut on the piezoelectric body 32 of the pressure measuring unit 30. ing.
That is, the rod portion 22 is interposed between the flexible plate-shaped portion 21 and the piezoelectric body 32 of the pressure measuring unit 30, and functions to transmit the force received by the flexible plate-shaped portion 21 to the piezoelectric body 32.

The pressure measuring 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, the piezoelectric body 32, which are sequentially laminated from the tip side of the tip cylindrical portion 11 in the axial direction S direction. It includes two electrodes 33.

The first electrode 31 is formed of a conductive metal material, and in this embodiment, the diaphragm 20 also serves as the first electrode 31.
The rod portion 22 of the first electrode 31, that is, the diaphragm 20, is arranged 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 columnar shape, is sandwiched between the rod portion 22 of the first electrode 31, that is, 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 in a cylindrical or disk shape by a conductive metal material, is arranged in close contact with the piezoelectric body 32, and is electrically connected to the positive side via a lead wire 50.

In the pressure measuring unit 30, since the diaphragm 20 also serves 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 configuration is not limited to this, 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 composed of a screw member 41 and an insulating member 42.
The screw member 41 is formed in a substantially columnar shape using a metal material such as precipitation hardening stainless steel or ferritic stainless steel, and the male screw portion 41a and the lead wire 50 screwed into the female screw portion 17 of the housing 10 are passed through the screw member 41. It is provided with a through hole 41b and a contact surface 41c that comes into contact with the insulating member 42.
The insulating member 42 is formed in a substantially columnar shape using an electrically insulating material having high insulating properties, for example, alumina, and abuts on the end surface 42a and the second electrode 33 that abut on the abutting surface 41c of the screw member 41. It is provided with a through hole 42c through which an end surface 42b and a lead wire 50 pass.

Then, as shown in FIGS. 1 and 2, the insulating member 42 is fitted in the state where the pressure measuring unit 30 is arranged at a predetermined position, 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 axis S direction, and the pressure measuring unit 30 is positioned and held at a predetermined position in the housing 10.

As shown in FIG. 1, the lead wire 50 is electrically connected to the second electrode 33 of the pressure measuring unit 30, and is electrically connected to 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. Is led to the connector 60.
The connector 60 is formed as a receptacle, is coupled to the open end 14 of the housing 10 via a spacer 61, and is detachably connected to an external connector (plug).

The heat shield spherical body 70 is arranged inside the tip cylindrical portion 11 so as to shield the diaphragm 20 from the combustion gas which is a pressure medium, and is formed by using a material having heat resistance and low thermal conductivity. Has been done.
Here, as the material of the heat shield spherical body 70, a material having low thermal conductivity, excellent durability, and high rigidity is preferable, and in addition to stainless steel, nickel-plated carbon steel, nickel alloy, etc. Iron-based alloys, titanium alloys, ceramics and the like can be used.

Further, the heat shield sphere 70 is formed as a sphere having an outer diameter D slightly smaller than the inner diameter of the inner wall surface 11b1 of the tip cylindrical portion 11 (second tubular portion 11b).
Here, the heat shield sphere 70 is not limited to the sphere, and may have a spherical shape extending in one direction or crushed in one direction.
In this way, by adopting the heat shield spherical body 70, it is possible to exert the function of transmitting only the pressure of the combustion gas to the flexible plate-shaped portion 21 while blocking the heat of the combustion gas.

As shown in FIG. 4, the heat shield spherical body 70 is inserted into the inside of the second cylindrical portion 11b of the tip cylindrical portion 11, and then the bending machine M is used to form the second tubular portion 11b. The tip annular portion 11d formed by bending the opening edge region inward holds the opening edge region inside the second cylindrical portion 11b so as not to fall off to the outside.

Here, the heat shield spherical body 70 comes into contact with the conical wall of the tip annular portion 12 so as to come into contact with the flexible plate-shaped portion 21 without a load in a state where it is not subjected to the pressure of the combustion gas. Be retained.
Further, the outer diameter D thereof is larger than the effective diameter of the flexible plate-shaped portion 21 that functions as a diaphragm so that the heat-shielding spherical body 70 does not become immobile due to galling, sticking, or the like inside the second tubular portion 11b. It is large and smaller than the inner diameter of the second tubular portion 11b.

Although the heat shield spherical body 70 is held so as to come into contact with the flexible plate-shaped portion 21 without a load, it may be fixed to the flexible plate-shaped portion 21 by welding or the like. ..
In this case, it is possible to prevent the heat shield spherical body 70 from vibrating under the pressure of the combustion gas. As a result, it is possible to prevent noise due to the vibration from being generated in the sensor output of the pressure measuring unit 30.
In this way, in the configuration in which the heat shield sphere 70 is fixed to the flexible plate-shaped portion 21 by welding, when the heat shield sphere 70 is formed of ceramics, the metal that covers the ceramic sphere with a metal layer. By applying the rising, the welding process can be easily performed.

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

Subsequently, the diaphragm 20 is assembled to the housing 10. That is, the flexible plate-shaped portion 21 is joined to the stepped surface 11c of the tip 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 each other.
The piezoelectric body 32, the second electrode 33, and the insulating member 42 may be laminated in advance and temporarily assembled.

Then, the screw member 41 is appropriately screwed in, and a predetermined preload is applied to the pressure measuring unit 30 in order to give linear characteristics as a sensor.
Subsequently, the spacer 61 is fixed to the open end 14 of the housing 10, the lead wire 50 led out is connected to the connector 60, and the connector 60 is connected to the spacer 61.

Subsequently, the heat shield spherical body 70 is assembled so as to be held inside the tip cylindrical portion 11 of the housing 10. Here, "holding" means that the tip is not fixed in the cylindrical portion 11 but is supported so as not to fall off.
That is, the heat shield spherical body 70 is arranged inside the second cylindrical portion 11b of the tip tubular portion 11.
Subsequently, as shown in FIG. 4, the opening edge region of the second cylindrical portion 11b is bent inward using a predetermined bending machine M to form the tip annular portion 11d. Here, the tip annular portion 11d defines an opening 11e whose diameter is smaller than the outer diameter D of the heat shield spherical body 70.

This completes the assembly of the pressure sensor.
The above assembly procedure is an example and is not limited to this, and other assembly procedures may be adopted.

In the pressure sensor having the above configuration, the tip cylindrical portion 11, the diaphragm 20, and the heat shield spherical body 70 have the arrangement relationship shown in FIG.
That is, the heat shield sphere 70 contacts the conical wall of the tip annular portion 12 in a state where it is not subjected to the pressure of the combustion gas, and contacts the flexible plate-shaped portion 21 with no load. It is held inside the tip tubular portion 11 and arranged outside the diaphragm 20.
Therefore, when the heat shield sphere 70 receives the pressure of the combustion gas through the opening 11e, the load corresponding to the pressure is immediately applied to the flexible plate-shaped portion 21 via the heat shield sphere 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.

As a result, the heat of the combustion gas is substantially blocked by the heat shield spherical body 70, and heat transfer to the diaphragm 20 side is suppressed or prevented. Therefore, the flexible plate-shaped portion 21 of the diaphragm 20 is suppressed or prevented from being affected by heat by the combustion gas, and substantially receives only the pressure of the combustion gas.
Further, since the heat shield spherical body 70 is arranged so as to be in contact with the flexible plate-shaped portion 21, the impact force and the impact sound due to the movement are suppressed or prevented, and the characteristics of the diaphragm 20 are improved. 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 measuring portion 30 can be adjusted. It can be maintained in the desired setting state.
Therefore, it is possible to prevent the fluctuation of the preload applied to the pressure measuring unit 30 and prevent the output noise from the piezoelectric body 32 due to the fluctuation of the preload.
Therefore, it is possible to suppress the measurement error due to thermal deformation or the like and detect the pressure of the combustion gas in the combustion chamber CH of the engine with high accuracy.

That is, as a mechanism, if the diaphragm 20 is deformed by heat, the preload applied to the pressure measuring unit 30 will fluctuate, and the accuracy of the detected pressure will decrease. Since the thermal sphere 70 suppresses the deformation of the diaphragm 20 due to heat, the pressure can be detected with high accuracy by cutting off the heat → suppressing the thermal deformation of the diaphragm 20 → preventing the fluctuation of the preload.

FIG. 5 shows a modified example in which the positioning portion is provided on the flexible plate-shaped portion 21 of the diaphragm 20 in the above embodiment.
In this modification, the flexible plate-shaped portion 21 is provided with a conical recess 23 as a positioning portion having a center on the axis S.
The conical recess 23 receives the heat shield sphere 70 and positions the center of the heat shield sphere 70 on the axis S.
This makes it possible to easily position and assemble the heat shield spherical body 70.
The heat shield spherical body 70 may be fixed to the flexible plate-shaped portion 21 by welding or the like while being positioned in the conical recess 23.

6 to 9 show a second embodiment of the pressure sensor according to the present invention, and the above-described embodiment is described except that the second tubular portion 11b for holding the heat-shielding spherical body 70 is changed. It has the same structure as the form. Therefore, the same components are designated by the same reference numerals and the description thereof will be omitted.
The pressure sensor according to this embodiment includes a housing 100, a diaphragm 20, a pressure measuring 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 multi-stage cylindrical shape that defines an internal space A extending in the axis S direction by using a metal material such as precipitation hardening stainless steel or ferritic stainless steel.
Then, the housing 100 has a connecting member 120 coupled to the tip cylindrical portion 110, the sealing portion 12, the male screw portion 13, the open end portion 14, the inner wall surfaces 15, 16, the female screw portion 17, and the tip tubular portion 110. I have.

The tip tubular portion 110 is a region located on the tip side in the axial direction S direction from the seal portion 12, is formed in a two-step thick cylindrical shape, and is coupled to the first tubular portion 111, the end face 112, and the end face 112. It includes a coupling member 120.
Then, the coupling member 120 includes a second cylindrical portion 121 in which the first cylindrical portion 111 and the outer peripheral wall are continuously connected, and a tip annular portion 122 and a second annular portion 122 formed on the distal end side of the second tubular portion 121. The end surface 123 formed on the rear end side of the two cylindrical portions 121 and the opening 124 defined by the 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 arranged 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 has become like.
The end surface 112 defines a stepped surface forming an annular plane perpendicular to the axis S at the boundary between the first cylindrical portion 111 and the second tubular portion 121 in a connected state.
The stepped surface located in the inner edge region of the end surface 112 functions as a fixing surface for fixing the flexible plate-shaped portion 21 of the diaphragm 20 by welding or the like.

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

Here, the heat shield spherical body 70 contacts the inner edge of the opening 124 of the tip annular portion 122 so as to contact the flexible plate-shaped portion 21 with no load in a state where it is not subjected to the pressure of the combustion gas. Is held.
Further, the outer diameter D thereof is larger than the effective diameter of the flexible plate-shaped portion 21 that functions as a diaphragm so that the heat-shielding spherical body 70 does not become immobile due to galling, sticking, or the like inside the second tubular portion 121. It is large and smaller than the inner diameter of the second tubular portion 121.
Although the heat shield spherical body 70 is held so as to come into contact with the flexible plate-shaped portion 21 without a load, it may be fixed to the flexible plate-shaped portion 21 by welding or the like. ..

Next, the 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 shield spherical body 70 are prepared. Will be done.

Subsequently, the diaphragm 20 is assembled to the housing 100. That is, the flexible plate-shaped portion 21 is joined to the end surface 112 of the tip 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 each other.
The piezoelectric body 32, the second electrode 33, and the insulating member 42 may be laminated in advance and temporarily assembled.

Then, the screw member 41 is appropriately screwed in, and a predetermined preload is applied to the pressure measuring unit 30 in order to give linear characteristics as a sensor.
Subsequently, the spacer 61 is fixed to the open end 14 of the housing 100, the lead wire 50 led 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 where the heat shield spherical body 70 is housed inside the connecting member 120, the end surface 123 of the connecting member 120 is joined to the end surface 112 of the tip cylindrical portion 110 and welded or the like. Is fixed by.
As a result, the heat shield spherical body 70 is assembled so as to be held inside the tip cylindrical portion 110 of the housing 100.
Here, "holding" means that the tip is not fixed in the cylindrical portion 110 but is supported so as not to fall off.

This completes the assembly of the pressure sensor.
The above assembly procedure is an example and is not limited to this, and other assembly procedures may be adopted.

In the pressure sensor having the above configuration, the tip cylindrical portion 110, the diaphragm 20, and the heat shield spherical body 70 have the arrangement relationship shown in FIG.
That is, the heat shield sphere 70 contacts the inner edge of the opening 124 of the tip annular portion 122 and contacts the flexible plate-shaped portion 21 with no load in a state where it is not subjected to the pressure of the combustion gas. It is held inside the tip cylindrical portion 110 and arranged outside the diaphragm 20.
Therefore, when the heat shield sphere 70 receives the pressure of the combustion gas through the opening 124, the load corresponding to the pressure is immediately applied to the flexible plate-shaped portion 21 via the heat shield sphere 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.

As a result, the heat of the combustion gas is substantially blocked by the heat shield spherical body 70, and heat transfer to the diaphragm 20 side is suppressed or prevented. Therefore, the flexible plate-shaped portion 21 of the diaphragm 20 is suppressed or prevented from being affected by heat by the combustion gas, and substantially receives only the pressure of the combustion gas.
Further, since the heat shield spherical body 70 is arranged so as to be in contact with the flexible plate-shaped portion 21, the impact force and the impact sound due to the movement are suppressed or prevented, and the characteristics of the diaphragm 20 are improved. 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 measuring portion 30 can be adjusted. It can be maintained in the desired setting state.
Therefore, it is possible to prevent the fluctuation of the preload applied to the pressure measuring unit 30 and prevent the output noise from the piezoelectric body 32 due to the fluctuation of the preload.
Therefore, it is possible to suppress the measurement error due to thermal deformation or the like and detect the pressure of the combustion gas in the combustion chamber CH of the engine with high accuracy.

10 to 12 show a third embodiment of the pressure sensor according to the present invention, and are described above except that the heat shield sphere 70 and the coupling member 120 according to the second embodiment are modified. It has the same configuration as the embodiment. Therefore, the same components are designated by the same reference numerals and the description thereof will be omitted, and the assembly procedure will be the same and will be omitted.
The pressure sensor according to this embodiment includes a housing 100, a diaphragm 20, a pressure measuring 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 tip tubular portion 110, a seal portion 12, a male screw portion 13, an open end portion 14, inner wall surfaces 15, 16, a female screw portion 17, and a coupling member 130 coupled to the tip tubular portion 110. There is.

The heat shield sphere 71 is formed as a sphere smaller than the heat shield sphere 70. Therefore, the heat shield sphere 71 is lighter in weight than the heat shield sphere 70, and the impact force exerted on other members when pressure is applied is also smaller.

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

The tip annular portion 132 is formed in an annular flat plate shape on the tip side of the second tubular portion 131, and defines a circular opening 134 in the central region thereof.
The end face 133 is formed on an annular plane that is joined to the outer peripheral region of the end face 112.
The opening 134 is formed to have a diameter smaller than the inner diameter of the second cylindrical portion 131 as the tip cylindrical portion so that the inner diameter is smaller than the outer diameter D of the heat shield spherical body 71.
That is, the tip annular portion 132 serves to hold the heat shield spherical body 71 housed inside the second tubular portion 131 so as not to fall off.

Here, the heat shield spherical body 71 contacts the inner edge of the opening 134 of the tip annular portion 132 so as to contact the flexible plate-shaped portion 21 with no load in a state where it is not subjected to the pressure of the combustion gas. Is held.
Further, the outer diameter D thereof is larger than the effective diameter of the flexible plate-shaped portion 21 that functions as a diaphragm so that the heat-shielding spherical body 71 does not become immobile due to galling, sticking, or the like inside the second tubular portion 131. It is large and smaller than the inner diameter of the second tubular portion 131 (inner wall surface 131a).
Although the heat shield spherical body 71 is held so as to come into contact with the flexible plate-shaped portion 21 without a load, it may be fixed to the flexible plate-shaped portion 21 by welding or the like. ..

In the pressure sensor having the above configuration, the tip cylindrical portion 110, the diaphragm 20, and the heat shield spherical body 71 have the arrangement relationship shown in FIG.
That is, the heat shield sphere 71 contacts the inner edge of the opening 134 of the tip annular portion 132 and contacts the flexible plate-shaped portion 21 with no load in a state where it is not subjected to the pressure of the combustion gas. It is held inside the tip cylindrical portion 110 and arranged outside the diaphragm 20.
Therefore, when the heat shield sphere 71 receives the pressure of the combustion gas through the opening 134, the load corresponding to the pressure is immediately applied to the flexible plate-shaped portion 21 via the heat shield sphere 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, the impact force and the like can be further suppressed or prevented, and only the pressure of the combustion gas can be transmitted to the flexible plate-shaped portion 21 while ensuring the heat-shielding action. can.

That is, the heat of the combustion gas is substantially blocked by the heat shield spherical body 71, and the heat transfer to the diaphragm 20 side is suppressed or prevented. Therefore, the flexible plate-shaped portion 21 of the diaphragm 20 is suppressed or prevented from being affected by heat by the combustion gas, and substantially receives only the pressure of the combustion gas.
Further, since the heat shield sphere 71 is smaller than the heat shield sphere 70 and is arranged so as to come into contact with the flexible plate-like portion 21, impact force, impact sound, etc. due to the movement thereof 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 measuring portion 30 can be adjusted. It can be maintained in the desired setting state.
Therefore, it is possible to prevent the fluctuation of the preload applied to the pressure measuring unit 30 and prevent the output noise from the piezoelectric body 32 due to the fluctuation of the preload.
Therefore, it is possible to suppress the measurement error due to thermal deformation or the like and detect the pressure of the combustion gas in the combustion chamber CH of the engine with high accuracy.

FIG. 13 is a graph showing comparative test data in which the pressure of the combustion gas in the combustion chamber of the engine is measured by the pressure sensor according to the present invention and the conventional pressure sensor.
-Engine used: 2-cylinder gasoline engine, displacement 1000cc
・ Operating conditions: Engine speed 5000 rpm, full load ・ Reference sensor: Sensor for precision analysis (manufactured by AVL)
-Result data: dotted line-> sensor for precision analysis (actual combustion pressure), solid line-> pressure sensor of the present invention, single-point chain line-> conventional pressure sensor As is clear from the results shown in FIG. 13, the heat shield spherical body 70 In the pressure sensor of the present invention provided with the above, the amount of deviation from the actual combustion pressure, that is, the measurement error is smaller than that of the conventional pressure sensor.
Even 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 embodiment, the diaphragm 20 including the flexible plate-shaped portion 21 and the rod portion 22 integrally is shown as the diaphragm, but the present invention is not limited to this, and the flexible plate-shaped portion 21 and the rod portion are not limited thereto. 22 may be formed separately, the flexible plate-shaped portion 21 may function as a diaphragm, and the rod portion 22 may function as a force transmission member.

In the above embodiment, the diaphragm 20 also serves as the first electrode 31 of the pressure measuring unit 30, but 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. May be good.

As described above, since the pressure sensor of the present invention can suppress the influence of heat and detect the pressure of the high temperature pressure medium with high accuracy, the pressure of the high temperature pressure medium such as the combustion gas in the combustion chamber of the engine is particularly high. Of course, it can be applied as a pressure sensor for detecting pressure, and it is also useful as a pressure sensor for detecting the pressure of a high-temperature pressure medium other than combustion gas or other pressure medium.

10 Housing 11 Tip cylindrical portion 11a First tubular portion 11b Second tubular portion 11c Stepped surface 11d Tip annular portion (conical wall)
11e Aperture 20 Diaphragm 21 Flexible plate-shaped part 22 Rod part 23 Conical recess (positioning part)
30 Pressure measuring unit 31 First electrode 32 Piezoelectric body 33 Second electrode 70,71 Heat shield spherical body 100 Housing 110 Tip cylindrical part 111 First tubular part 112 End face (step surface)
120 Coupling member 121 Second cylindrical portion 122 Tip annular portion (annular flat plate)
124 Aperture 124
130 Coupling member 131 Second cylindrical part 132 Tip annular part (annular flat plate)
134 opening

Claims (12)

A housing with a cylindrical tip and
A pressure measuring unit housed in the housing and containing a piezoelectric body,
A diaphragm having a flexible plate-shaped portion fixed to the inside of the tip cylindrical portion and a rod portion interposed between the flexible plate-shaped portion and the pressure measuring portion, and
It is provided with a heat-shielding spherical body held inside the tip cylindrical portion so as to shield the diaphragm from the pressure medium.
A pressure sensor characterized by that. The tip cylindrical portion has a tip annular portion that defines a reduced diameter opening at the tip thereof.
The heat shield spherical body is held by the tip annular portion.
The pressure sensor according to claim 1. The tip annular portion is formed by bending the opening edge region of the tip tubular portion inward.
The pressure sensor according to claim 2. The heat shield sphere is held so as to come into contact with the flexible plate-like portion without a load in a state where it is not subjected to the pressure of the pressure medium.
The pressure sensor according to any one of claims 1 to 3. The flexible plate-shaped portion includes a positioning portion for positioning the heat shield spherical body.
The pressure sensor according to claim 4. The heat shield spherical body is fixed to the flexible plate-like portion.
The pressure sensor according to claim 4 or 5. The tip tubular portion is formed in a cylindrical shape.
The flexible plate-shaped portion is formed in a disk shape arranged inside the tip cylindrical portion.
The heat shield sphere is formed into a sphere having an outer diameter smaller than the inner diameter of the tip cylindrical portion.
The pressure sensor according to any one of claims 2 to 6, wherein the pressure sensor. The tip cylindrical portion includes a first cylindrical 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 cylinder. Includes a stepped surface formed at the boundary between the shaped portion and the second cylindrical portion.
The flexible plate-like portion is fixed to the stepped surface and
The second cylindrical portion has a tip annular portion that defines a reduced diameter opening at the tip thereof.
The heat shield spherical body is held by the tip annular portion.
The pressure sensor according to any one of claims 1 to 7. The tip annular portion is formed by a coupling member coupled to the housing to define the second tubular portion.
The pressure sensor according to claim 8. The tip annular portion is formed at its tip as a conical wall defining the opening.
The heat shield sphere is held in contact with the conical wall.
The pressure sensor according to claim 3 or 9. The tip annular portion is formed as an annular flat plate defining the opening in the center thereof.
The heat shield sphere 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. The pressure measuring unit has a first electrode, a piezoelectric body, and a second electrode that are sequentially laminated 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.

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