JP2017020960A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress carbon from inflowing into between a member for receiving heat and a diaphragm.SOLUTION: A pressure sensor comprises: a housing; a diaphragm that bends in accordance with a pressure; a sensor unit that has an electric characteristic varying by the pressure; and a heat reception part that is arranged on a tip end side of the diaphragm, and is directly or indirectly connected to the diaphragm to receive heat. The heat reception part includes: a plate part; and a lateral wall part that protrudes on the tip end side from an edge of the plate pat. In the lateral wall part, a plurality of through-holes is formed that is arranged along the edge of the plate part, in which a length of a direction parallel with an axial line of the plurality of through-holes is equal to or more than 0.3 mm. In a cross section of the lateral wall part vertical to the axial line and not through the plurality of through-holes, when an outer peripheral length of the lateral wall part is an outer peripheral length C1, and in a cross section of the lateral wall part vertical to the axial line and through the plurality of through-holes, when a sum of a length of a part corresponding to an outer peripheral surface is a wall length C2, (C2/C1)≤0.6 is satisfied.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a pressure sensor that measures a pressure in a combustion chamber of an internal combustion engine.

  As a pressure sensor, a metal shell attached to the engine head, a pressure receiving member having a diaphragm and a pressure receiving rod, a press screw screwed into the pressure receiving rod, and a piezoelectric element sandwiched between the head of the press screw and the metal shell. A sensor having a sensor has been proposed. When the diaphragm receives the combustion pressure, the diaphragm is pushed rearward, the pressure receiving rod is contracted and deformed, and the tightening force of the presser screw is reduced. The piezoelectric sensor converts a change in tightening force into a change in electrical output. Here, in order to reduce the amount of thermal deformation of the diaphragm due to the high-temperature combustion gas, a heat shielding plate is disposed on the front surface of the diaphragm.

JP 7-318448 A JP-A-7-19981

  By the way, in the combustion chamber, carbon may be generated by the combustion of fuel. When such carbon flows between the heat receiving member, such as a heat shielding plate, and the diaphragm, a problem may occur. For example, carbon may adhere to the diaphragm and the characteristics of the diaphragm may change.

  The present disclosure discloses a technique capable of suppressing the inflow of carbon between a member for receiving heat and a diaphragm.

  For example, the present disclosure discloses the following application examples.

[Application Example 1]
A cylindrical housing, a diaphragm that is joined to the front end side of the housing and expands in a direction intersecting the axis of the housing and bends according to the received pressure, and an electric that is arranged in the housing and changes depending on the pressure A sensor unit having a characteristic, and a pressure sensor comprising:
A heat receiving portion that receives heat and is disposed on the distal end side of the diaphragm and connected directly or indirectly to the diaphragm;
The heat receiving part is
A plate portion extending in a direction intersecting the axis;
A side wall portion protruding from the edge of the plate portion toward the tip side;
With
The side wall portion is formed over the entire circumference of the edge of the plate portion,
In the side wall portion, a plurality of through holes arranged along the edge of the plate portion are formed,
The maximum value of the length in the direction parallel to the axis of the plurality of through holes is 0.3 mm or more,
In the cross section of the side wall portion that is perpendicular to the axis and does not pass through the plurality of through holes, the outer peripheral length of the side wall portion is defined as an outer peripheral length C1,
In the cross section of the side wall portion perpendicular to the axis and passing through the plurality of through holes, when the total length of the portions corresponding to the outer peripheral surface of the side wall portion is the wall length C2,
(C2 / C1) ≦ 0.6 is satisfied,
Pressure sensor.

  According to this configuration, when the plate portion of the heat receiving portion receives the gas flowing in the combustion chamber, the gas flows from the inner peripheral side of the side wall portion to the outer peripheral side through the plurality of through holes of the side wall portion. As described above, since the gas flows from the through hole in the side wall portion toward the outer peripheral side, it is possible to suppress the carbon generated in the combustion chamber from flowing on the outer peripheral side of the side wall portion and flowing between the heat receiving portion and the diaphragm.

[Application Example 2]
The pressure sensor according to Application Example 1,
The connection portion between the inner peripheral surface of the side wall portion and the front end side surface of the plate portion is rounded,
Pressure sensor.

  According to this configuration, the gas easily flows from the surface on the front end side of the plate portion to the through hole in the side wall portion, so that it is possible to suppress a decrease in the flow velocity of the gas flowing from the through hole to the outer peripheral side. Therefore, it can suppress that carbon flows in the outer peripheral side of a side wall part, and flows in between a heat receiving part and a diaphragm.

[Application Example 3]
The pressure sensor according to Application Example 1 or 2,
Within an angular range in any direction where the central angle around the axis is 90 degrees,
Of the outer peripheral length C1, the length of the portion included in the angle range is a partial outer peripheral length C1a,
When the length of the portion included in the angle range of the wall length C2 is the partial wall length C2a,
(C2a / C1a) ≦ 0.6
Pressure sensor.

  According to this configuration, since the distribution of the plurality of through holes viewed from the axis is suppressed from being biased in a specific direction, the gas flow from the through hole toward the outer peripheral side is part of the entire circumference of the side wall portion. It is suppressed to be biased. Therefore, it can suppress appropriately that carbon flows on the outer peripheral side of a side wall part, and flows in between a heat receiving part and a diaphragm.

[Application Example 4]
The pressure sensor according to any one of Application Examples 1 to 3,
In the plane cross section of the side wall including the axis, among the directions from the inner peripheral side to the outer peripheral side, the angle in the direction perpendicular to the axis is zero degrees, and the angle in the direction inclined toward the tip side is a positive angle And when the angle in the direction inclined to the rear end side is a negative angle, the angle of the inner surface on the rear end side of the through hole is -40 degrees or more and 20 degrees or less.
Pressure sensor.

  According to this structure, it can suppress that carbon flows in between a heat receiving part and a diaphragm with the flow of the gas which goes to an outer peripheral side from a through-hole.

  The technology disclosed in the present specification can be realized in various modes, for example, in a mode of a pressure sensor, an internal combustion engine equipped with the pressure sensor, or the like.

It is explanatory drawing which shows the pressure sensor 10 as 1st Embodiment. 3 is an enlarged cross-sectional view of a tip portion of the pressure sensor 10. FIG. It is explanatory drawing of the heat receiving part. 3 is an exploded perspective view of an element unit 50. FIG. It is explanatory drawing of operation | movement of the pressure sensor 10x of a reference example. It is the schematic of the model used for simulation. It is the schematic of the model used for simulation. It is a graph which shows a simulation result. It is a graph which shows inflow distance dx of a plurality of models. It is explanatory drawing of another embodiment of a heat receiving part. It is explanatory drawing of another embodiment of a heat receiving part. It is a graph which shows a simulation result. 7 is an explanatory diagram of a part of a cross section perpendicular to an axis CL of a side wall portion 92. FIG.

A. First embodiment:
FIG. 1 is an explanatory diagram showing a pressure sensor 10 as the first embodiment. The pressure sensor 10 of this embodiment is attached to an internal combustion engine and used to detect the pressure in the combustion chamber of the internal combustion engine. As shown in FIG. 1, the pressure sensor 10 includes, as main components, a cylindrical first metal fitting 20 and a second metal fitting 30, a pressure receiving part 40, a heat receiving part 90, an element part 50, and a cable 60. It is equipped with. The central axis CL is the central axis of the pressure sensor 10. Hereinafter, the central axis CL is also referred to as an axis line CL, and a direction parallel to the axis line CL is also referred to as an “axis direction”. The radial direction of the circle centered on the axis CL is also simply referred to as “radial direction”, and the circumferential direction of the circle centered on the axis CL is also simply referred to as “circumferential direction”. A direction from the first metal fitting 20 to the second metal fitting 30 along the axis CL is referred to as a “front end direction Df”, and a direction opposite to the front end direction Df is referred to as a “rear end direction Dr”. The front end direction Df side is referred to as “front end side”, and the rear end direction Dr side is also referred to as “rear end side”.

  FIG. 1 shows a cross-sectional configuration on the left side of the axis line CL of the tip side portion of the pressure sensor 10. This cross section is a flat cross section (cross section cut along a plane) including the axis CL. FIG. 1 shows an external configuration of another part of the pressure sensor 10. In the present embodiment, the central axis CL of the pressure sensor 10 is also the central axis of each of the first metal fitting 20, the second metal fitting 30, the pressure receiving part 40, the heat receiving part 90, and the element part 50.

  The first metal fitting 20 and the second metal fitting 30 have a cylindrical shape in which a cross section perpendicular to the central axis CL (hereinafter also referred to as a transverse cross section) is annular and extends in the axial direction. In the present embodiment, the first metal fitting 20 and the second metal fitting 30 are made of stainless steel. However, other materials (for example, steel such as low carbon steel, various metal materials) may be adopted.

  The first metal fitting 20 is formed with a shaft hole 21 that is a through-hole centered on the central axis CL. In addition, a screw portion 22 and a tool engagement portion 24 are provided on the outer peripheral surface of the first metal fitting 20 on the rear end side. The screw portion 22 includes a screw thread for fixing the pressure sensor 10 to the mounting hole 510 of the cylinder head 500 of the internal combustion engine. The tool engaging portion 24 has an outer peripheral shape (for example, a hexagonal cross section) that engages with a tool (not shown) used for attaching and detaching the pressure sensor 10.

  FIG. 2 is an enlarged cross-sectional view of the distal end portion of the pressure sensor 10, specifically, the portion indicated as the region X in FIG. This cross section is a flat cross section including the axis CL. The second metal fitting 30 is disposed on the front end side of the first metal fitting 20, and is joined to the front end of the first metal fitting 20 via the melting portion 26. The melted portion 26 is a melted portion during welding (for example, laser welding) between the first metal fitting 20 and the second metal fitting 30. A diameter-expanded portion 34 that increases in diameter from the front end side toward the rear end side is formed at the front end portion of the second metal fitting 30. When the pressure sensor 10 is attached to the internal combustion engine, the enlarged diameter portion 34 is in close contact with the seal surface 520 of the attachment hole 510 of the cylinder head 500 of the internal combustion engine. Further, the second metal fitting 30 is formed with a shaft hole 31 which is a through hole centered on the central axis CL. The shaft hole 31 includes a large inner diameter portion 35 and a small inner diameter portion 36 connected to the rear end side of the large inner diameter portion 35 and having an inner diameter smaller than the inner diameter of the large inner diameter portion 35. A step portion 39 is provided between the large inner diameter portion 35 and the small inner diameter portion 36. The step portion 39 forms a surface facing the tip direction Df side. In the shaft hole 31, the pressure receiving part 40 and the element part 50 are arrange | positioned in order toward the rear end side from the front end side.

  The pressure receiving unit 40 includes a diaphragm 42 and a rod 44. The diaphragm 42 is a substantially circular film centered on the axis line CL. The outer edge 42o of the diaphragm 42 is welded to the tip of the second metal fitting 30 over the entire circumference (for example, laser welding). A rod 44 is connected to the center of the surface on the rear end side of the diaphragm 42. The rod 44 is a cylindrical portion centering on the axis CL, and extends from the diaphragm 42 toward the rear end direction Dr. The element portion 50 is connected to the rear end portion 49 of the rod 44. The diaphragm 42 and the rod 44 are integrally formed using stainless steel (for example, forging or shaving). However, after the diaphragm 42 and the rod 44 are separately formed, the diaphragm 42 and the rod 44 may be integrated by welding or the like. Moreover, you may employ | adopt other materials (For example, steel, such as low carbon steel, various metal materials).

  A heat receiving portion 90 is joined to the surface on the distal end side of the diaphragm 42 (for example, laser welding). FIG. 3 is an explanatory diagram of the heat receiving unit 90. 3A shows a perspective view of the heat receiving unit 90, and FIG. 3B shows a flat cross section including the axis CL of the heat receiving unit 90. FIG. The heat receiving portion 90 includes a disc-shaped plate portion 93 centered on the axis CL, a cylindrical side wall portion 92 projecting from the outer peripheral edge 93o of the plate portion 93 toward the distal direction Df, and a central portion of the plate portion 93. Column-shaped leg part 98 which protrudes from the rear end direction Dr side. Hereinafter, the entire side wall portion 92 and the plate portion 93 are also referred to as a “main portion 91”. The outer diameter of the leg portion 98 is smaller than the outer diameter of the main portion 91.

  The side wall portion 92 is formed over the entire circumference of the edge 93 o of the plate portion 93. A plurality of through holes 97 are formed in the side wall portion 92 along the edge 93o of the plate portion 93 (that is, along the circumferential direction). In the present embodiment, the through hole 97 is a substantially rectangular hole surrounded by two inner surfaces perpendicular to the axis line CL and two inner surfaces parallel to the axis line CL.

  A size H1 in FIG. 3B is the size of the through hole 97 in the axial direction, and is the maximum value of the length (ie, size) of the plurality of through holes 97 in the direction parallel to the axis CL. The size of one through-hole 97 in the axial direction is the maximum value of the length of the line segment connecting the two points when a straight line parallel to the axis CL passes through two points on the inner surface of one through-hole 97. is there. The size H1 is the maximum value of the sizes in the axial direction of the plurality of through holes 97. In the embodiment of FIG. 3B, the through hole 97 extends along the radial direction. Therefore, the size H1 is the same as the length of the through hole 97 in the direction parallel to the axis CL.

  3C and 3D show a cross section perpendicular to the axis CL of the side wall portion 92. 3C shows a first cross section CS1 that does not pass through the plurality of through holes 97, and FIG. 3D shows a second cross section CS2 that passes through the plurality of through holes 97.

  The outer peripheral length C1 shown in FIG. 3C is the outer peripheral length of the side wall portion 92 in the first cross section CS1. In the present embodiment, since the shape of the side wall portion 92 is a substantially cylindrical shape extending along the axis line CL, the outer peripheral length C1 is the same as the peripheral length of the circle calculated from the outer diameter D2 of the heat receiving portion 90.

  The wall length C2 shown in FIG. 3D is the total length of portions corresponding to the outer peripheral surface of the side wall portion 92 in the second cross section CS2. In FIG. 3D, the wall length C2 is the sum of the lengths of the portions indicated by bold lines. The wall length C2 is the remainder obtained by subtracting the circumferential length of the through hole 97 from the outer peripheral length C1. In the first embodiment, the plurality of through holes 97 are arranged so as to be evenly distributed along the circumferential direction.

  The side wall portion 92, the plate portion 93, and the leg portion 98 are integrally formed using stainless steel (for example, forging or shaving). After forming two parts of the side wall part 92, the plate part 93, and the leg part 98, or three parts separately, these parts may be integrated by welding or the like. Moreover, you may employ | adopt other materials (For example, steel, such as low carbon steel, various metal materials).

  As shown in FIG. 2, the heat receiving part 90 is joined to the diaphragm 42 (and thus the pressure receiving part 40) via the melting part 99. The melting part 99 is a part melted during welding of the heat receiving part 90 and the diaphragm 42 (and thus the pressure receiving part 40) (for example, laser welding). The melting part 99 is formed at the center of the heat receiving part 90.

  Further, as shown in the figure, the heat receiving portion 90 is disposed in the mounting hole 510 of the cylinder head 500. Specifically, the heat receiving portion 90 is located in the portion 530 on the tip end direction Df side of the attachment hole 510 (also referred to as “tip portion 530”). The outer peripheral surface 922 of the side wall portion 92 faces the inner peripheral surface of the distal end portion 530 of the attachment hole 510.

  The diaphragm 42 closes the shaft hole 31 at the tip of the second metal fitting 30. The diaphragm 42 is exposed in the combustion chamber of the internal combustion engine, and the surface 42f on the tip end direction Df side of the diaphragm 42 forms a pressure receiving surface. In the present embodiment, the pressure receiving surface 42 f can receive the pressure in the combustion chamber through the gap between the diaphragm 42 and the heat receiving portion 90. Further, the diaphragm 42 can receive a load corresponding to the pressure in the combustion chamber through the heat receiving portion 90. And the diaphragm 42 deform | transforms according to the pressure in a combustion chamber. The rod 44 is displaced along the axis CL according to the deformation of the diaphragm 42, thereby transmitting a load corresponding to the pressure received by the diaphragm 42 to the element portion 50 on the rear end side. As the diaphragm 42 is made thinner, the diaphragm 42 is more easily deformed, so that the sensitivity of the pressure sensor 10 can be increased.

  The element unit 50 includes two electrodes 52, a piezoelectric element 51 sandwiched between the two electrodes 52, a pressing plate 54 disposed on the front end side of the front end electrode 52, and an electrode 52 on the rear end side. A lead portion 53, a pressing plate 54, and an insulating plate 55 are arranged in order in the rear end direction Dr. As shown in FIG. 2, the pressing plate 54, the electrode 52, the piezoelectric element 51, the electrode 52, the lead portion 53, the pressing plate 54, and the insulating plate 55 are laminated in this order from the front end side to the rear end side. Yes. The rear end surface of the insulating plate 55 is supported by the step 39 of the second metal fitting 30. The rear end portion 49 of the rod 44 is in contact with the front end surface of the front end holding plate 54. As will be described later, the pressing plate 54 has a through-hole 54h centered on the axis CL. The rear end portion 49 of the rod 44 has a protruding portion that is inserted into the through hole 54h. The rear end surface of the projecting portion is in contact with the front surface of the front electrode 52. The piezoelectric element 51 is connected to the rod 44 via a tip-side electrode 52 and a pressing plate 54. The whole of the rod 44, the holding plate 54 on the distal end side, and the electrode 52 forms a connection portion 100 that connects the diaphragm 42 and the piezoelectric element 51.

  FIG. 4 is an exploded perspective view of the element unit 50. As shown in the drawing, the piezoelectric element 51 and the electrode 52 are disk-shaped plate members centered on the axis CL. The holding plate 54 and the insulating plate 55 are annular plate-like members centered on the axis line CL. The piezoelectric element 51 is formed using quartz in the present embodiment, but a piezoelectric element formed of another material may be adopted. On the piezoelectric element 51, an electric charge is generated according to the load transmitted through the rod 44 from the pressure receiving portion 40 (FIG. 2). The piezoelectric element 51 outputs an electric charge (for example, an electric signal) corresponding to the load through the two electrodes 52. Based on the output electric signal, the deformation amount of the diaphragm 42, that is, the pressure in the combustion chamber can be specified. Thus, the piezoelectric element 51 has an electrical characteristic that varies depending on the pressure received by the pressure receiving unit 40. The electrode 52 and the pressing plate 54 are formed using stainless steel in the present embodiment, but may be formed using other metals. The insulating plate 55 is a member for insulating between the lead portion 53 and the second metal fitting 30 (FIG. 2). In this embodiment, the insulating plate 55 is formed of alumina, but may be formed of other types of insulating materials.

  The lead part 53 includes a disk part 57 that is a substantially disk-shaped plate member, and a terminal part 56 that extends from the center part of the disk part 57 toward the rear end direction Dr. The terminal portion 56 passes through the through hole 54h of the pressing plate 54 and the through hole 55h of the insulating plate 55 and protrudes toward the rear end direction Dr (FIG. 2). The lead portion 53 is formed using stainless steel in the present embodiment, but may be formed using other metals. The lead part 53 can be produced by punching out the shape of the disk part 57 and the terminal part 56 from a stainless steel flat plate, and then bending the part to be the terminal part 56.

  In the shaft hole 31 of the second metal fitting 30 (FIG. 2), the lead portion 53 is disposed such that the disk portion 57 is in surface contact with the electrode 52 and the terminal portion 56 extends to the rear end side. The terminal portion 56 passes through the through hole 54 h at the center of the pressing plate 54 and the through hole 55 h at the center of the insulating plate 55. The rear end portion of the terminal portion 56 is disposed in the small inner diameter portion 36 in a state of being separated from the inner wall surface of the small inner diameter portion 36 of the second metal fitting 30.

  Each member (excluding the insulating plate 55) constituting the element unit 50 is disposed in the shaft hole 31 of the second metal fitting 30 so as to be separated from the inner wall surface of the second metal fitting 30. The electrode 52 on the rear end side of the piezoelectric element 51 is electrically connected to a lead portion 53 (in this embodiment, further, a holding plate 54), and is electrically connected from the first metal fitting 20 and the second metal fitting 30. Away. The electrode 52 on the distal end side of the piezoelectric element 51 is electrically connected to the second metal fitting 30 through the holding plate 54 on the distal end side, the rod 44 and the pressure receiving portion 40. In the present embodiment, in order to make the distribution of the load applied to the piezoelectric element 51 uniform, the pressing plate 54 is disposed not only on the rear end side but also on the front end side of the piezoelectric element 51.

  A cable 60 is disposed in the shaft hole 21 of the first metal fitting 20. The cable 60 is a member for transmitting the electric charge of the piezoelectric element 51 to an electric circuit (not shown) for detecting the combustion pressure of the internal combustion engine based on the electric charge of the piezoelectric element 51. In this embodiment, noise is reduced by using a so-called shielded wire having a multilayer structure as the cable 60. The cable 60 includes an inner conductor 65, an insulator 64, a conductive coating 63, an outer conductor 62, and a jacket 61 arranged from the center toward the outer peripheral side. The inner conductor 65 is composed of a plurality of conductive wires. The outer side of the inner conductor 65 in the radial direction is surrounded by an insulator 64. A conductive coating 63 is provided on the outer peripheral surface of the insulator 64. An outer conductor 62 that is a mesh shield is provided on the outer side in the radial direction of the conductive coating 63. The outer peripheral surface of the outer conductor 62 is covered with a jacket 61. A cable including a plurality of members arranged coaxially in this way is also called a coaxial cable.

  As shown in FIG. 2, the outer conductor 62 that is not covered by the jacket 61 is exposed from the portion covered by the jacket 61 toward the distal end side at the distal end portion of the cable 60. Further, the insulator 64 that is not covered by the external conductor 62 is exposed from the portion where the external conductor 62 is exposed toward the tip side. Further, the inner conductor 65 that is not covered by the insulator 64 is exposed from the portion where the insulator 64 is exposed toward the tip side.

  The internal conductor 65 exposed at the distal end portion of the cable 60 is connected to the terminal portion 56 of the element portion 50 through the flat plate conductive wire 75 and the small diameter conductive wire 74. Specifically, the flat conductor 75 is welded to the tip of the inner conductor 65, and the rear end of the thin conductor 74 wound in a coil shape is welded to the tip of the flat conductor 75, The distal end of the small diameter conductive wire 74 is welded to the rear end portion of the terminal portion 56. The flat conductive wire 75 and the thin conductive wire 74 can transmit the electric charge of the piezoelectric element 51 from the terminal portion 56 to the internal conductor 65. In addition, as a structure for connecting the internal conductor 65 and the terminal part 56, it replaces with the structure using the flat conducting wire 75 and the thin diameter conducting wire 74, and can employ | adopt other arbitrary structures.

  From the tip of the terminal portion 56 to the position on the rear end side of the welded portion connecting the terminal portion 56 and the thin wire 74, the range including the entire terminal portion 56 and the tip of the thin wire 74 is Covered by a heat-shrinkable tube 72. Thereby, the reliability of the electrical insulation between the terminal part 56 and the 2nd metal fitting 30 (especially small inner diameter part 36) is improved. When manufacturing the pressure sensor 10, the integration of the lead portion 53 having the terminal portion 56 and the thin lead wire 74 by welding and the covering with the heat shrinkable tube 72 may be performed prior to the entire assembly.

  A grounding conductor 76 extending from the distal end of the external conductor 62 to the distal end side is connected to the distal end portion of the external conductor 62. The grounding conductor 76 is composed of a stranded wire formed continuously from the outer conductor 62. The front end portion of the grounding conductor 76 is welded to the rear end portion of the second metal fitting 30. Thereby, the outer conductor 62 is grounded through the grounding conductor 76, the second metal fitting 30, and the cylinder head of the internal combustion engine.

  When manufacturing the pressure sensor 10, the element portion 50 is inserted into the shaft hole 31 (specifically, the large inner diameter portion 35) from the distal end side of the second metal fitting 30. The terminal portion 56 of the lead portion 53 of the element portion 50 is integrated with the small-diameter conductive wire 74 and the heat shrinkable tube 72 in advance. And the thin diameter conducting wire 74 is inserted from the front end side of the small inner diameter portion 36 of the second metal fitting 30, and the small diameter conducting wire 74 is drawn out from the rear end side of the small inner diameter portion 36. Further, the pressure receiving part 40 is disposed on the tip side of the element part 50. And the edge 42o of the diaphragm 42 and the 2nd metal fitting 30 are welded, and the fusion | melting part 45 is formed. The length of the rod 44 is determined in advance so that an appropriate preload is applied to the element unit 50. Thereafter, the heat receiving portion 90 is welded to the diaphragm 42 to form the melting portion 99.

  Then, the rear end of the small-diameter conductive wire 74 drawn from the rear end side of the second metal fitting 30 (specifically, the small inner diameter portion 36) and the front end of the internal conductor 65 are welded to the flat plate conductive wire 75. Further, the front end portion of the grounding conductor 76 and the rear end portion of the second metal fitting 30 are welded. Further, the cable 60 is passed through the shaft hole 21 of the first metal fitting 20, and the front end of the first metal fitting 20 and the rear end of the second metal fitting 30 are welded to form the melting portion 26. Thereafter, molten rubber is injected into the shaft hole 21 of the first metal fitting 20 to fill the shaft hole 21 with a rubber layer (not shown), and the pressure sensor 10 is completed. By forming the rubber layer, the waterproof property in the pressure sensor 10 is improved and the vibration proof property is also improved. Note that molten resin may be injected into the shaft hole 21 instead of the molten rubber.

B. About thermal expansion of diaphragm 42:
The pressure receiving surface 42f of the diaphragm 42 (FIG. 2) passes through a gap 951 between the side wall 92 of the heat receiving part 90 and the cylinder head 500, and a gap 952 between the plate part 93 of the heat receiving part 90 and the diaphragm 42. The pressure Pc in the combustion chamber can be received. Further, the diaphragm 42 can receive a load corresponding to the pressure Pc through the heat receiving portion 90. The diaphragm 42 bends (deforms) according to the pressure Pc in the combustion chamber. In the embodiment of FIG. 2, the diaphragm 42 bends in a direction parallel to the axis CL. The rod 44 is displaced approximately parallel to the axis CL in accordance with the bending (deformation) of the diaphragm 42. As a result, the rod 44 transmits a load corresponding to the pressure Pc to the element unit 50.

  Further, the heat receiving portion 90 is disposed on the tip side of the diaphragm 42, that is, on the combustion chamber side. The heat receiving unit 90 can receive heat from the combustion chamber instead of the diaphragm 42. For example, the heat generated by the combustion of the fuel can be conducted to the surface on the front end side of the heat receiving unit 90 through the gas in the combustion chamber. Further, high-temperature combustion gas can come into contact with the surface on the front end side of the heat receiving unit 90. As described above, the temperature of the heat receiving unit 90 (particularly, the tip side surface) can be increased. Since the diaphragm 42 is disposed on the rear end side of the heat receiving unit 90, it is less likely to receive heat from the combustion chamber than the heat receiving unit 90. Therefore, the thermal expansion of the diaphragm 42 is suppressed.

  FIG. 5 is an explanatory diagram of the operation of the pressure sensor 10x of the reference example. In the drawing, a plane cross section including an axis CL of a part of the tip side of the pressure sensor 10x is shown. The only difference from the pressure sensor 10 of the embodiment of FIG. 2 is that the heat receiving portion 90 is omitted. The configuration of the other part of the pressure sensor 10x is the same as the configuration of the corresponding part of the pressure sensor 10 of the embodiment.

  The pressure receiving surface 42f of the diaphragm 42 receives the pressure Pc in the combustion chamber, similarly to the pressure receiving surface 42f of the embodiment of FIG. Further, in the reference example of FIG. 5, unlike the embodiment of FIG. 2, the heat receiving portion 90 is omitted, so that the portion (for example, the pressure receiving surface 42 f) on the tip end direction Df side of the diaphragm 42 is from the combustion chamber. Receive heat. Thereby, the part by the side of the front-end | tip direction Df among the diaphragms 42 can be thermally expanded locally. In the reference example, the outer edge 42 o of the diaphragm 42 is joined to the second metal fitting 30. Therefore, the diaphragm 42 tends to extend toward the inner peripheral side by thermal expansion. In this case, the thermal expansion of the diaphragm 42 can apply a force parallel to the axis CL to the rod 44. For example, in the reference example of FIG. 5, the thermal expansion of the pressure receiving surface 42 f of the diaphragm 42 applies a force F in the distal direction Df to the rod 44. Thereby, the load applied to the element part 50 becomes small. As described above, in the pressure sensor 10x of the reference example, the load applied to the element unit 50 can fluctuate greatly depending on the temperature of the combustion gas, so that the error of the signal from the element unit 50 increases.

  In the embodiment shown in FIG. 2, thermal expansion of the diaphragm 42 is suppressed by the heat receiving unit 90. Therefore, as compared with the reference example of FIG. 5, in the first embodiment, the error of the signal from the element unit 50 can be reduced.

C. Regarding the through hole 97 of the side wall 92:
C1. About simulation:
In order to examine the relationship between the through hole 97 in the side wall 92 of the heat receiving unit 90 and the gas flow, a simulation was performed. 6 and 7 are schematic views of the model used for the simulation. FIG. 6 shows a model of the pressure sensor 10 of the embodiment, and FIG. 7 shows a model of the pressure sensor 10z of the reference example. In the drawing, a part of a flat cross section including the axis CL is shown. The flat cross section of FIG. 6 shows a flat cross section passing through the through hole 97. The small arrows in the figure indicate the direction of gas flow. The gas flow shown shows the result of simulation by the finite element method. In the drawing, the illustration of the gas flowing direction in the gap 952 between the heat receiving portion 90 and the diaphragm 42 is omitted.

FIG. 6 shows a plane cross section including the axis CL of a part of each of the tip end portion 530 of the mounting hole 510 of the cylinder head 500, the second metal fitting 30, the diaphragm 42, and the heat receiving portion 90 of the pressure sensor 10. Yes. The diaphragm 42 and the second metal fitting 30 are simplified to one member filled with contents. In the simulation, the dimensions shown were set to the following values.
Inner diameter D1 of the side wall portion 92 = 7.85 mm
Outer diameter D2 of the side wall portion 92 = 8.45 mm
Inner diameter D3 of the tip 530 of the mounting hole 510 = 9 mm
Cylinder head 500 outer diameter D4 = 20 mm
First clearance CL1 = 0.275mm
Second clearance CL2 = 0.5mm
The first clearance CL1 is a radial distance of the gap 951 between the side wall 92 and the tip 530 of the heat receiving unit 90. The second clearance CL2 is a distance in a direction parallel to the axis CL of the gap 952 between the plate portion 93 of the heat receiving portion 90 and the diaphragm 42.

  In the pressure sensor 10z of the reference example illustrated in FIG. 7, the heat receiving unit 90 of FIG. 6 is replaced with the heat receiving unit 90z of the reference example. The structure of the other part of the model of the reference example is the same as the structure of the corresponding part of the model of the embodiment of FIG. The heat receiving part 90z is a disk-shaped plate part centering on the axis line CL, and is different from the heat receiving part 90 in that the side wall part 92 is not provided. The outer diameter D2 of the heat receiving portion 90z is the same as the outer diameter D2 of the heat receiving portion 90 in FIG. The thickness of the heat receiving portion 90z in the direction parallel to the axis CL is the same as the thickness of the main portion 91 in FIG.

  In each model of FIGS. 6 and 7, the parameters D2, D3, D4, CL1, and CL2 are common. The tip side of the cylinder head 500 is the combustion chamber 600. The gaps between the members 500, 90, 90z, 42, and 30 and the combustion chamber 600 are filled with standard air. It was assumed that there was no gas movement through the outer surface of each member 500, 90, 90z, 42, 30. A maximum pressure of 16 MPa was applied from the combustion chamber 600 toward the rear end direction Dr. The time-dependent change of the air flow by the application of this pressure was simulated.

  As shown in FIG. 6, in the model of the embodiment, gas flows from the combustion chamber 600 toward the rear end direction Dr. And in the vicinity of the heat receiving part 90, the direction of the gas flow changes to the outside in the radial direction. Particularly, in the model of the embodiment, the gas flows toward the outside in the radial direction along the surface 931 on the tip end direction Df side of the plate portion 93 on the inner peripheral side of the side wall portion 92. Then, the gas flows out from the through hole 97 into the gap 951 between the side wall 92 and the cylinder head 500.

An enlarged view of the vicinity of the gap 951 is shown in the lower part of FIG. A position CP in the figure shows an example of a passing position of carbon particles (hereinafter, the carbon particles are also simply referred to as “particles”). The position SP indicates the start position of the carbon particles. In the simulation, carbon particles were arranged at four start positions SP. The particles arranged at the start position SP moved to another position by the gas flow. In the simulation, the arrangement of the particles at the start position SP was repeated a plurality of times, and the change with time of the position of each particle was calculated. In the simulation, the particle size of the carbon particles was set to 1 × 10 ⁻⁹ m, and the density of the carbon particles was set to 2 kg / m ³ .

  Specifically, the four start positions SP are arranged in the vicinity of the end portion on the tip end direction Df side of the side wall portion 92 of the heat receiving portion 90. The four start positions SP are arranged at intervals of 0.1 mm along the radial direction. Two start positions SP on the inner peripheral side are located on the tip direction Df side of the side wall 92, and two start positions SP on the outer periphery side are located on the tip direction Df side of the gap 951. These four start positions SP are located in the front end portion 530 of the mounting hole 510 of the cylinder head 500. In the simulation, 100 particles are evenly distributed at such four start positions SP within a time of 0.1 ms from the start of pressure application (in this simulation, every 0.001 ms). 1 particle was placed). 100 particles were evenly distributed at the four starting positions SP.

  The innermost position CPm in the figure is the position on the most rear end direction Dr side among the plurality of positions through which the particles have passed. The inflow distance dx is a distance parallel to the axis CL up to a position in a direction parallel to the axis CL of the innermost position CPm with respect to the surface 932 on the rear end direction Dr side of the plate portion 93 of the heat receiving unit 90. The inflow distance of particles is shown. “Dx = 0” indicates that the innermost position CPm of the carbon particles is at the same position as the surface 932. “Dx> 0” indicates that the innermost position CPm of the carbon particles is at a position on the rear end direction Dr side from the surface 932, and “dx <0” indicates that the innermost position CPm of the carbon particles is from the surface 932. Is also located at the tip direction Df side.

  As shown in FIG. 6, in the model of the embodiment, gas flows out from the through hole 97 into the gap 951. The gas flowing out of the through hole 97 into the gap 951 functions as an air curtain that suppresses carbon particles from passing through the gap 951. As described above, the gas flowing through the through-hole 97 prevents the carbon particles from flowing into the gap 952 through the gap 951.

  As shown in FIG. 7, in the model of the reference example, the gas flows from the combustion chamber 600 toward the rear end direction Dr. Then, in the vicinity of the heat receiving portion 90z, the direction of gas flow changes to the outside in the radial direction. Unlike the model of the embodiment of FIG. 6, the gas flows through the gap 951 between the outer peripheral surface of the heat receiving portion 90 z and the cylinder head 500 toward the rear end direction Dr.

  An enlarged view of the vicinity of the gap 951 is shown in the lower part of FIG. Also in the simulation of the reference example, the carbon particles were arranged at the four start positions SP under the same conditions as the simulation of the embodiment of FIG. Unlike the model of FIG. 6, in the model of the reference example, the carbon particles reach the gap 952 between the heat receiving portion 90 z and the diaphragm 42 through the gap 951 from the start position SP. The innermost position CPm is located closer to the rear end direction Dr than the surface 932z on the rear end direction Dr side of the heat receiving portion 90z (dx> 0). The shape and position of the surface 932z of the heat receiving portion 90z are the same as the shape and position of the surface 932 on the rear end direction Dr side of the plate portion 93 in FIG. The inflow distance dx indicates the inflow distance of carbon particles with respect to the surface 932z.

  In general, when the carbon particles reach the gap 952, an error in a signal from the element unit 50 may increase. Specifically, the carbon particles that have reached the gap 952 can adhere to the diaphragm 42. When carbon particles adhere to the diaphragm 42, the physical characteristics of the diaphragm 42 may change. For example, as in the case where the thickness of the diaphragm 42 is increased, the deformation amount of the diaphragm 42 with respect to the pressure in the combustion chamber can be reduced. As a result, the error of the signal from the element unit 50 can increase.

  In order to suppress an error in a signal from the element unit 50, it is preferable that the carbon particles do not reach the gap 952. For example, the inflow distance dx in FIGS. 6 and 7 is preferably zero or less. FIG. 8 is a graph showing simulation results of the inflow distance dx of the pressure sensor 10 of the embodiment of FIG. 6 and the pressure sensor 10z of the reference example of FIG. As illustrated, the inflow distance dx of the pressure sensor 10 of the embodiment was smaller than zero. On the other hand, the inflow distance dx of the pressure sensor 10z of the reference example was larger than zero. As described above, the heat receiving portion 90 includes the plate portion 93 and the side wall portion 92 protruding from the edge of the plate portion 93 toward the front end direction Df, and the side wall portion 92 is provided along the edge of the plate portion 93. By forming the plurality of through holes 97 arranged side by side, it was possible to suppress the inflow of carbon to the rear end direction Dr side of the heat receiving unit 90 (the gap 952 between the heat receiving unit 90 and the diaphragm 42).

C2. For size H1 and ratio C2 / C1:
FIG. 9 is a graph showing inflow distances dx of a plurality of models having different combinations of the ratio of the wall length C2 to the outer peripheral length C1 and the size H1 of the through hole 97. The horizontal axis indicates the ratio (C2 / C1), and the vertical axis indicates the inflow distance dx. One data point represents the simulation result of one type of model. The size H1 was either 0.2 mm, 0.3 mm, or 0.5 mm. The ratio C2 / C1 was either 0.4, 0.5, 0.6, or 0.7. The ratio C2 / C1 was adjusted by adjusting the wall length C2 (that is, the circumferential length of the through hole 97). The values of the parameters D1, D2, D3, D4, CL1, and CL2 (FIG. 6) were the same as the values of the model described in FIG. In the model of the pressure sensor 10 of FIG. 8, the size H1 was 0.3 mm, and the ratio C2 / C1 was 0.6.

  As shown in FIG. 9, when the size H1 is the same, the smaller the ratio C2 / C1, the smaller the inflow distance dx. The reason is estimated as follows. The smaller the ratio C2 / C1, the longer the circumferential length of the through hole 97 is. As described above, in the gap 951 on the outer peripheral side of the side wall 92, in the vicinity of the through hole 97, the inflow of carbon is suppressed by the gas flowing out from the through hole 97. Therefore, the smaller the ratio C2 / C1, the more difficult the carbon particles pass through the gap 951 and reach the gap 952.

  When the ratio C2 / C1 is the same, the inflow distance dx is smaller as the size H1 is larger. The reason is estimated as follows. The larger the size H1, the larger the through hole 97, so the amount of gas flowing from the through hole 97 to the gap 951 per unit time increases. This increase in the amount of gas suppresses the inflow of carbon. Therefore, the larger the size H1, the more difficult it is for the carbon particles to pass through the gap 951 and reach the gap 952.

In addition, as shown in the graph of FIG. 9, the combinations of the size H1 and the ratio C2 / C1 that realized the inflow distance dx of zero or less were as follows.
H1 = 0.2 mm: C2 / C1 = 0.4, 0.5
H1 = 0.3 mm: C2 / C1 = 0.4, 0.5, 0.6
H1 = 0.5 mm: C2 / C1 = 0.5, 0.6, 0.7

  A preferable range between the size H1 and the ratio C2 / C1 may be determined using the values of the above eight types of models. For example, a range in which the size H1 is 0.3 mm or more and the ratio C2 / C1 is 0.6 or less may be adopted. Moreover, you may employ | adopt the range whose size H1 is 0.2 mm or more and ratio C2 / C1 is 0.5 or less. Moreover, you may employ | adopt the range whose size H1 is 0.5 mm or more and ratio C2 / C1 is 0.7 or less.

  In any case, the larger the size H1, the larger the amount of gas flowing from the through hole 97 to the gap 951. Therefore, the larger the size H1, the more the carbon particles are suppressed from flowing into the gap 952 through the gap 951. . Therefore, it is estimated that an arbitrary value smaller than the length in the direction parallel to the axis CL of the side wall portion 92 of the heat receiving portion 90 can be adopted as the upper limit of the size H1.

  In addition, the smaller the ratio C2 / C1, the smaller the portion of the gap 951 through which the carbon particles easily pass (that is, the portion without the through hole 97). Therefore, the smaller the ratio C2 / C1, the more the carbon particles pass through the gap 951. Inflow through the gap 952 is suppressed. Therefore, various values larger than zero can be adopted as the lower limit of the ratio C2 / C1. In general, the smaller the ratio C2 / C1, the lower the strength of the side wall 92. Therefore, the lower limit of the ratio C2 / C1 should be a value that can realize the practical strength of the side wall 92. Is preferred.

  In addition, it is estimated that the preferable range of size H1 and ratio C2 / C1 is applicable not only to the structure of said model but to other various structures. For example, the values of parameters such as the inner diameter D1 and outer diameter D2 of the heat receiving portion 90, the inner diameter D3 of the tip portion 530 of the mounting hole 510, and the first clearance CL1 may be different from the values of the above model. Also in this case, when the size H1 and the ratio C2 / C1 are within the above preferable range, it is estimated that the inflow distance dx can be made smaller than when the size H1 is outside the preferable range.

C3. About the connection part of the side wall part 92 and the board part 93:
FIG. 10 is an explanatory diagram of the second embodiment of the heat receiving portion. In the drawing, a part of a flat cross section including the axis CL of the heat receiving portion 90b is shown. The difference from the heat receiving portion 90 of the first embodiment shown in FIG. 3 is that the connecting portion 940b between the inner peripheral surface 921 of the side wall portion 92 and the surface 931 of the plate portion 93 on the tip end direction Df side is rounded. (In the embodiment of FIG. 3, the connecting portion 940 between the inner peripheral surface 921 of the side wall portion 92 and the surface 931 of the plate portion 93 on the tip end direction Df side forms a right-angled corner. ing). The structure of the other part of the heat receiving part 90b is the same as the structure of the corresponding part of the heat receiving part 90 of FIG.

  The radius R in the figure is the radius of an arc that forms the connecting portion 940b (that is, the inner peripheral corner 940b) of the surfaces 921 and 931 in the plane cross section including the axis CL. The rounded corner 940 b can smoothly guide the gas GS flowing toward the outer side in the radial direction along the surface 931 on the front end direction Df side of the plate portion 93 to the through hole 97. Thus, the rounded corner 940b can suppress a decrease in the flow velocity of the gas flowing out from the through hole 97 to the outer peripheral side.

  A data point Db in the graph of FIG. 9 indicates a simulation result of a model using the heat receiving unit 90b of FIG. This model replaces the connecting portion 940 (FIG. 6) of the first embodiment model with H1 = 0.3 mm and C2 / C1 = 0.7 by a rounded connecting portion 940b (FIG. 10). can get. Compared with the data point Da of the model of the first embodiment, the inflow distance dx is small. In this way, the rounded connection portion 940b was able to suppress the inflow of carbon particles compared to the right-angled connection portion 940. The reason for this is presumed to be that a decrease in the flow velocity of the gas flowing out from the through hole 97 toward the outer periphery can be suppressed.

  Note that the rounded connection portion 940b has a plate portion regardless of the configuration of each portion of the heat receiving portion such as the values of parameters D1, D2, D3, D4, CL1, CL2, C1, and C2 (FIGS. 3 and 6). The gas flowing toward the outer side in the radial direction along the surface 931 on the tip end direction Df side of 93 can be smoothly guided to the through hole 97. Therefore, it is estimated that by using the rounded connection portion 940b, the inflow of carbon particles can be suppressed regardless of the configuration of each part of the heat receiving part. In any case, it is estimated that the larger the radius R, the higher the effect of suppressing the inflow of carbon particles. For example, the radius R of the rounded connection portion is preferably 0.2 mm or more. As the upper limit of the radius R, various values can be adopted. For example, a distance dd or less in the direction parallel to the axis CL between the end 97e on the rear end direction Dr side of the through hole 97 of the side wall 92 (FIG. 10) and the surface 931 on the front end direction Df side of the plate part 93. The value of may be adopted.

C4. About the direction of the through hole 97:
FIG. 11 is an explanatory diagram of another embodiment of the heat receiving unit. 11A and 11B show a part of a flat cross section including the axis CL of the heat receiving portions 90c and 90d and passing through the through holes 97c and 97d. An angle Ah in the figure indicates an angle in a direction from the inner peripheral side to the outer peripheral side with respect to a direction perpendicular to the axis CL. “Ah = 0” indicates a direction perpendicular to the axis CL. “Ah <0” indicates a direction obliquely toward the rear end direction Dr (FIG. 11A). “Ah> 0” indicates a direction oblique to the tip direction Df (FIG. 11B).

  In 3rd Embodiment of FIG. 11 (A), the through-hole 97c is provided in the side wall part 92c of the heat receiving part 90c. An angle Ah in a direction in which the through hole 97c extends is smaller than zero. Specifically, the angle Ah in the extending direction of the inner surface 97c1 on the rear end direction Dr side of the through hole 97c is smaller than zero. Although not shown, the angle Ah in the extending direction of the inner surface 97c2 on the front end direction Df side of the through hole 97c is the same as the angle Ah of the inner surface 97c1 on the rear end direction Dr side. The structure of the other part of the heat receiving part 90c is the same as the structure of the corresponding part of the heat receiving part 90 shown in FIG.

  In the fourth embodiment of FIG. 11B, a through hole 97d is provided in the side wall portion 92d of the heat receiving portion 90d. An angle Ah in the extending direction of the through hole 97d is larger than zero. Specifically, the angle Ah in the extending direction of the inner surface 97d1 on the rear end direction Dr side of the through hole 97d is larger than zero. Although illustration is omitted, the angle Ah in the extending direction of the inner surface 97d2 on the front end direction Df side of the through hole 97d is also the same as the angle Ah of the inner surface 97d1 on the rear end direction Dr side. The structure of the other part of the heat receiving part 90d is the same as the structure of the corresponding part of the heat receiving part 90 shown in FIG.

  FIG. 12 is a graph showing a simulation result using the model of the embodiment of FIG. 11A and the model of the embodiment of FIG. The horizontal axis represents the angle Ah of the inner surfaces 97c1, 97d1 on the rear end direction Dr side of the through holes 97c, 97d, and the vertical axis represents the inflow distance dx. As the angle Ah, five values of −50, −40, −20, 0, and +20 (degrees) were evaluated. In the five types of models, the size H1 of the through holes 97c and 97d (the maximum length (ie, the size) in the direction parallel to the axis CL of the plurality of through holes 97c and 97d) is 0.5 mm. Yes, the ratio C2 / C1 was 0.6. The configuration of other parts (for example, parameters D1, D2, D3, D4, CL1, CL2) was the same as the configuration of the corresponding part of the model described in FIG.

  As shown in FIG. 12, the inflow distance dx was smaller when the angle Ah was larger than when the angle Ah was small. The reason is estimated as follows. The gas flowing out from the through holes 97c, 97d to the outer peripheral side tends to flow in the direction of the angle Ah. Therefore, when the angle Ah is large, the gas tends to flow toward the distal end direction Df side on the outer peripheral side of the side wall portions 92c and 92d, compared to when the angle Ah is small. For example, the gas easily flows from the through holes 97c and 97d through the gap 951 (FIG. 6) toward the tip direction Df. Therefore, when the angle Ah is large, the carbon particles move on the outer peripheral side (for example, the gap 951 (FIG. 6)) of the side walls 92c and 92d toward the rear end direction Dr as compared with the case where the angle Ah is small. Can be suppressed. As a result, the carbon particles can be prevented from flowing into the gap 952 between the plate portion 93 and the diaphragm 42.

  Further, as shown in the drawing, even when the angle Ah is smaller than zero, an inflow distance dx smaller than zero can be realized. The reason is estimated as follows. The space (including the gap 952) on the rear end direction Dr side from the gap 951 is smaller than that of the combustion chamber 600. The amount of gas that can move from the through hole 97c to the rear end direction Dr side through the gap 951 is only a part of the amount of gas that has flowed out of the through hole 97c into the gap 951. Therefore, even when the angle Ah is smaller than zero, a part of the gas flowing out from the through hole 97c can flow in the gap 951 toward the tip direction Df. As a result, the movement of the carbon particles in the gap 951 toward the rear end direction Dr is suppressed.

  The angles Ah that achieved an inflow distance dx of zero or less were −40, −20, 0, and +20 (degrees). A preferable range (range between the lower limit and the upper limit) of the angle Ah may be determined using the above four values. Specifically, any value of the above four values may be adopted as the lower limit of the preferable range of the angle Ah. For example, the angle Ah is preferably −40 degrees or more, particularly preferably −20 degrees or more, and most preferably zero degrees or more. Moreover, you may employ | adopt the arbitrary values more than the minimum among these values as an upper limit. For example, the angle Ah is preferably +20 degrees or less.

  As the angle Ah increases, the gas tends to flow toward the tip end direction Df side on the outer peripheral side of the side walls 92c and 92d. Therefore, the angle Ah may be larger than +20 degrees which is the maximum value among the above four values. However, when the angle Ah is excessively large, it is difficult to manufacture the heat receiving portion. Therefore, the upper limit of the angle Ah is preferably determined so that the heat receiving part can be easily manufactured. For example, the angle Ah is preferably 45 degrees or less.

  In addition, it is estimated that the preferable range of the angle Ah is applicable not only to the configuration of the above model but also to various other configurations. For example, the configuration of the parameters D1, D2, D3, D4, CL1, CL2, C1, C2, and H1 may be different from the values of the model. Also in this case, when the angle Ah is within the above preferable range, it is estimated that the inflow distance dx can be made smaller than when the angle Ah is outside the preferable range.

C5. About the circumferential distribution of through-holes:
FIG. 13 shows a part of a cross section perpendicular to the axis CL of the side wall 92. In the drawing, a portion CS3 included in an angle range AR in which the central angle with respect to the axis CL is 90 degrees is shown (also referred to as “partial cross section CS3”). The partial cross section CS <b> 3 is a cross section passing through the through hole 97. The partial outer peripheral length C1a in the drawing is the length of the portion included in the angular range AR (that is, the partial cross section CS) in the outer peripheral length C1 described with reference to FIGS. 3 (A) and 3 (C). In the embodiment of FIG. 13, the shape of the side wall 92 is substantially cylindrical. Therefore, the partial outer peripheral length C1a is a quarter of the outer peripheral length C1. The partial wall length C2a is the length of the portion included in the angle range AR (that is, the partial cross section CS) in the wall length C2 described with reference to FIGS. 3 (A) and 3 (D).

  In order to suppress the inflow of the carbon particles over the entire circumference of the annular gap 951 (FIG. 6) surrounding the axis CL, it is preferable that the plurality of through holes 97 are distributed approximately evenly along the circumferential direction. . For example, it is preferable that the ratio C2a / C1a is equal to or less than a predetermined upper limit within an angle range AR in an arbitrary direction in which the central angle about the axis CL is 90 degrees. According to this structure, it is suppressed that ratio C2a / C1a becomes large too much in a part direction seeing from the axis line CL. That is, it is possible to prevent the gas flow from the through hole 97 toward the outer peripheral side from being biased to a part of the entire circumference of the side wall portion 92. Therefore, it is possible to suppress the formation of a portion in which the carbon particles easily move toward the rear end direction Dr in the annular gap 951. As a result, it is possible to suppress the carbon particles from flowing on the outer peripheral side of the side wall portion 92 and flowing into the gap 952 between the heat receiving portion 90 and the diaphragm 42. In each simulation model described above, the plurality of through holes were evenly distributed along the circumferential direction. Therefore, the ratio C2a / C1a is approximately the same as the ratio C2 / C1 within the angle range AR in an arbitrary direction.

  In consideration of the simulation result of FIG. 9, the ratio C2a / C1a is preferably 0.7 or less, particularly preferably 0.6 or less, and most preferably 0.5 or less. As the lower limit of the ratio C2a / C1a, various values larger than zero can be adopted. Here, it is preferable to employ a value that can realize a practical strength of the side wall portion 92.

  The preferable range of the ratio C2a / C1a is not limited to the embodiment of FIG. 3, but can be applied to other various configurations (for example, the embodiments of FIGS. 10, 11A, and 11B). . In any case, if the ratio C2a / C1a is within the above-mentioned preferable range within the angle range AR in an arbitrary direction whose center angle about the axis CL is 90 degrees, compared to the case outside the preferable range. Thus, it is estimated that the inflow distance dx can be reduced.

D. Variations:
(1) As a structure of a heat receiving part, it can change to the structure of said each embodiment, and can employ | adopt other various structures. For example, in the embodiment of FIGS. 11A and 11B, the angle Ah of the inner surfaces 97c2 and 97d2 on the front end side of the through holes 97c and 97d is different from the angle Ah of the inner surfaces 97c1 and 97d1 on the rear end side. May be. The angle Ah of the inner surfaces 97c1 and 97d1 on the rear end side may be within the above preferable range, and the angle Ah of the inner surfaces 97c2 and 97d2 on the front end side may be outside the above preferable range. In any case, the gas GS flowing toward the side wall portions 92c and 92d along the front end side surface 931 of the plate portion 93 is not the front end inner surfaces 97c2 and 97d2, but the rear end inner surface 97c1, 97d1 is reached. Therefore, the gas flowing from the through holes 97c and 97d to the outer peripheral side tends to flow toward the extending direction of the inner surfaces 97c1 and 97d1 on the rear end side (that is, the direction of the angle Ah of the inner surfaces 97c1 and 97d1 on the rear end side). Therefore, if the angle Ah of the inner surfaces 97c1 and 97d1 on the rear end side is within the above-described preferable range, the carbon particles move around the outer peripheral side (for example, the gap 951 (FIG. 6)) of the side wall portions 92c and 92d. It can suppress moving toward. However, the angle Ah of the inner surfaces 97c1 and 97d1 on the rear end side may be outside the above preferable range.

(2) As a cross-sectional shape of the through hole in the side wall (a cross-sectional shape perpendicular to the extending direction of the through hole), any other shape can be adopted instead of the rectangular shape. For example, a circular shape may be adopted. In any case, when the angle Ah of the inner surface on the rear end side of the through hole is specified, the plane cross section including the axis line CL is parallel to the axis line CL between the inner surface on the rear end side and the inner surface on the front end side. What is necessary is just to employ | adopt the inner surface of the rear-end side of the through-hole in the plane cross section where the distance of an arbitrary direction becomes largest.

  Further, the shape may be different among the plurality of through holes. Moreover, the circumferential length may be different among the plurality of through holes. Moreover, the size of an axial direction may differ between several through-holes. In any case, the maximum value of the length in the direction parallel to the axis CL of the plurality of through holes, that is, the largest size among the sizes in the axial direction of the plurality of through holes is preferable for the size H1 described above. It is preferable to be within the range. According to this configuration, since the gas easily flows from the through hole in the side wall portion toward the outer peripheral side, the carbon particles can be prevented from flowing between the heat receiving portion and the diaphragm through the outer peripheral side of the side wall portion. .

(3) When the wall length C2 described in FIG. 3D changes according to the position in the direction parallel to the axis CL of the second cross section CS2, the minimum value may be adopted as the wall length C2. Further, when the partial wall length C2a described in FIG. 13 changes according to the position in the direction parallel to the axis CL of the partial cross section CS3, the minimum value may be adopted as the partial wall length C2a.

(4) The rounded connection portion 940b described with reference to FIG. 10 can be applied to various other configurations in place of the configuration of the embodiment of FIG. For example, you may apply the rounded connection part 940b to embodiment of FIG. 11 (A) and FIG. 11 (B).

(5) The preferable range of the ratio C2a / C1a described in FIG. 13 can be applied to other various configurations in place of the configuration of the embodiment of FIG. For example, the preferred range of the ratio C2a / C1a may be applied to the embodiments of FIGS. 10, 11A, and 11B. However, the ratio C2a / C1a may exceed the above upper limit within the angular range AR in some directions.

(6) As shown in FIG. 2, in each of the above embodiments, the heat receiving part (for example, the heat receiving parts 90, 90 b, 90 c, 90 d) is provided when the pressure sensor is attached to the attachment hole 510 of the cylinder head 500. The mounting hole 510 (specifically, the tip portion 530) is disposed. However, at least a part of the heat receiving portion may be disposed outside the attachment hole 510 (specifically, on the combustion chamber side with respect to the opening 510o on the combustion chamber side of the attachment hole). Also in this case, it is possible to suppress the inflow of carbon particles between the heat receiving portion and the diaphragm by the gas flowing from the through hole in the side wall portion of the heat receiving portion to the outer peripheral side. In order to suppress the inflow of carbon particles, it is preferable that at least a part (particularly, the part on the rear end direction Dr side) of the side wall part of the heat receiving part is disposed in the attachment hole 510. According to this configuration, the carbon particles can be prevented from flowing through the gap between the side wall portion and the attachment hole 510 (for example, the gap 951 in FIG. 2) by the gas flowing out from the through hole.

(7) Various configurations can be adopted as a configuration for connecting the heat receiving portion and the diaphragm. For example, the leg portion 98 in FIG. 2 may be omitted, and the plate portion 93 may be directly connected to the diaphragm 42. Moreover, the heat receiving part may be connected to the diaphragm 42 via another member.

(8) As the configuration of the connecting portion for connecting the diaphragm 42 and the piezoelectric element 51, other various configurations can be adopted instead of the configuration of the connecting portion 100 in FIG. For example, the holding plate 54 on the distal end side may be omitted, and the rod 44 may be in contact with only the electrode 52 on the distal end side among the elements of the element unit 50. Further, the pressing plate 54 and the electrode 52 on the distal end side may be omitted, and the piezoelectric element 51 may be directly connected to the rod 44. In this case, the rod 44 functions as an electrode.

(9) As the configuration of the element unit 50, various other configurations can be adopted instead of the configurations of FIGS. For example, at least one of the front end side pressing plate 54 and the rear end side pressing plate 54 may be omitted. Further, the terminal portion 56 may be directly connected to the electrode 52. In addition, the electrode 52 and the piezoelectric element 51 may be an annular plate member surrounding the axis CL, instead of a disk-shaped plate member disposed on the axis CL, and a specific circumferential axis CL. The member arrange | positioned in the position away from may be sufficient. In general, the element unit 50 preferably includes a piezoelectric element and is configured to output a signal from the piezoelectric element to the outside of the pressure sensor. In addition, as an apparatus having an electrical characteristic that changes depending on the pressure received by the diaphragm, an electrical characteristic that changes according to the load received through the diaphragm and the connecting portion instead of the piezoelectric element (for example, voltage, resistance value, etc.) Various devices having the above can be employed. For example, a strain gauge may be employed.

(10) As the configuration of the housing that accommodates the piezoelectric element 51, various cylindrical configurations can be employed instead of the configuration of the second metal fitting 30 described in FIG. For example, the large inner diameter portion 35 and the small inner diameter portion 36 may be separate members separated from each other. In this case, for example, a female screw is formed on the inner peripheral surface of the large inner diameter portion 35, a male screw is formed on the outer peripheral surface of the small inner diameter portion 36, and the small inner diameter portion 36 is connected to the large inner diameter portion 35 from the rear end side of the large inner diameter portion 35. It may be screwed in. In this case, the preload can be adjusted by adjusting the rotational speed of the small inner diameter portion 36 when the small inner diameter portion 36 is screwed. In either case, the diaphragm may be connected to the front end side of the housing by welding.

(11) As a configuration for guiding the signal from the element unit 50 to the outside of the pressure sensor, various other configurations can be adopted instead of the configuration using the cable 60. For example, a terminal metal fitting may be disposed on the rear end side of the pressure sensor 10, and the terminal metal fitting and the terminal portion 56 of the element unit 50 may be connected by a middle shaft. In this case, a signal from the element unit 50 can be acquired through the terminal fitting and the first fitting 20.

  As mentioned above, although this invention was demonstrated based on embodiment and a modification, embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

10, 10x, 10z ... Pressure sensor, 20 ... 1st metal fitting, 21 ... Shaft hole, 22 ... Screw part, 24 ... Tool engaging part, 26 ... Melting part, 30 ... second fitting, 31 ... shaft hole, 34 ... expanded diameter part, 35 ... large inner diameter part, 36 ... small inner diameter part, 39 ... step part, 40 ... pressure receiving Part, 41 ... fixing part, 42 ... diaphragm, 42f ... pressure-receiving surface, 42o ... edge, 44 ... rod, 45, 46 ... melting part, 49 ... rear end part , 50 ... Element part, 51 ... Piezoelectric element, 52 ... Electrode, 53 ... Lead part, 54 ... Holding plate, 54h ... Through-hole, 55 ... Insulating plate, 55h ... through hole, 56 ... terminal part, 57 ... disk part, 60 ... cable, 61 ... jacket, 62 ... outer conductor, 63 ... conductive coating, 64 ... Insulator, 65 ... inner conductor, 72 ... heat-shrinkable tube, 74 ... small-diameter conductor, 75 ... flat conductor, 76 ... ground conductor, 90, 90b, 90c, 90 , 90z ... heat receiving part, 91 ... main part, 92, 92c, 92d ... side wall part, 93 ... plate part, 93o ... edge, 96 ... cylindrical part, 97, 97c, 97d, 97e ... end, 97c1, 97c2 ... inner surface, 98 ... leg part, 99 ... melting part, 100 ... connection part, 500 ... cylinder head, 510 ... mounting hole , 510o ... opening, 520 ... sealing surface, 530 ... tip, 600 ... combustion chamber, 921 ... surface, 922 ... outer peripheral surface, 931, 932, 932z ... surface , 940, 940b ... Connection part (corner), 951, 952 ... Gap, 97d1, 97d2 ... Inner surface, X ... area, CL ... Axis (center axis), CP ... Pass Position, SP ... start position, AR ... angle range, Pc ... pressure, Df ... front end direction, Dr ... rear end direction, Ah ... angle, dx ... inflow distance, CPm ... deepest position

Claims (4)

A cylindrical housing, a diaphragm that is joined to the front end side of the housing and expands in a direction intersecting the axis of the housing and bends according to the received pressure, and an electric that is arranged in the housing and changes depending on the pressure A sensor unit having a characteristic, and a pressure sensor comprising:
A heat receiving portion that receives heat and is disposed on the distal end side of the diaphragm and connected directly or indirectly to the diaphragm;
The heat receiving part is
A plate portion extending in a direction intersecting the axis;
A side wall portion protruding from the edge of the plate portion toward the tip side;
With
The side wall portion is formed over the entire circumference of the edge of the plate portion,
In the side wall portion, a plurality of through holes arranged along the edge of the plate portion are formed,
The maximum value of the length in the direction parallel to the axis of the plurality of through holes is 0.3 mm or more,
In the cross section of the side wall portion that is perpendicular to the axis and does not pass through the plurality of through holes, the outer peripheral length of the side wall portion is defined as an outer peripheral length C1,
In the cross section of the side wall portion perpendicular to the axis and passing through the plurality of through holes, when the total length of the portions corresponding to the outer peripheral surface of the side wall portion is the wall length C2,
(C2 / C1) ≦ 0.6 is satisfied,
Pressure sensor. The pressure sensor according to claim 1,
The connection portion between the inner peripheral surface of the side wall portion and the front end side surface of the plate portion is rounded,
Pressure sensor. The pressure sensor according to claim 1 or 2,
Within an angular range in any direction where the central angle around the axis is 90 degrees,
Of the outer peripheral length C1, the length of the portion included in the angle range is a partial outer peripheral length C1a,
When the length of the portion included in the angle range of the wall length C2 is the partial wall length C2a,
(C2a / C1a) ≦ 0.6
Pressure sensor. The pressure sensor according to any one of claims 1 to 3,
In the plane cross section of the side wall including the axis, among the directions from the inner peripheral side to the outer peripheral side, the angle in the direction perpendicular to the axis is zero degrees, and the angle in the direction inclined toward the tip side is a positive angle And when the angle in the direction inclined to the rear end side is a negative angle, the angle of the inner surface on the rear end side of the through hole is -40 degrees or more and 20 degrees or less.
Pressure sensor.

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