JP2020122776A - Cylinder internal pressure sensor - Google Patents

Abstract

To provide a cylinder internal pressure sensor capable of suppressing damage and breakage of a joint section joining a heat receiving plate.SOLUTION: A cylinder internal pressure sensor includes: a cylindrical casing; a membrane that is joined to the casing by a first joint section, closes an opening of the casing while being expanded in a direction crossing an axis of the casing, and is deformed according to a received pressure; a heat receiving plate that is arranged at a tip side than the membrane and joined to the membrane by a second joint section; a diaphragm that is arranged in the casing and generates mechanical strain accompanying deformation of the membrane; and a sensor element that is arranged on the diaphragm and converts an amount of mechanical strain of the diaphragm into an amount of electricity. A circumferential tip portion is provided that is disposed over an outer peripheral surface of the membrane. The tip portion overlaps up to an outer peripheral surface of the heat receiving plate.SELECTED DRAWING: Figure 2

Description

The present invention relates to an in-cylinder pressure sensor that detects the pressure inside a combustion chamber of an internal combustion engine.

As an in-cylinder pressure sensor attached to an internal combustion engine, a cylindrical casing, a membrane that is joined to the casing and that is arranged in an opening of the casing and deforms according to the in-cylinder pressure, and that is arranged in the casing by pressure. A sensor unit having a changing electrical characteristic is known. In this type of in-cylinder pressure sensor, as a result of thermal expansion of the membrane due to high temperature combustion gas, the sensor section detects deformation due to thermal expansion of the membrane, and pressure detection accuracy decreases. Therefore, in order to reduce the thermal effect of the combustion gas on the membrane, a technique has been disclosed in which a heat receiving plate is joined to the membrane and the heat receiving plate is arranged on the tip side of the membrane (Patent Documents 1 and 2).

JP, 2017-40516, A JP, 2017-194358, A

However, in Patent Documents 1 and 2, the interface in which the first joint portion that joins the housing and the membrane and the interface in which the second joint portion that joins the membrane and the heat receiving plate are formed are Exposed outside the sensor. Therefore, the air flow in the combustion chamber flows into these two interfaces, and a force that pulls the membrane or the heat receiving plate away from the membrane works, and as a result, the first joint portion and the second joint portion are damaged or destroyed. May occur.

The present invention has been made to solve this problem, and an object of the present invention is to provide an in-cylinder pressure sensor capable of suppressing damage or destruction of the first joint portion and the second joint portion.

In order to achieve this object, the in-cylinder pressure sensor of the present invention includes a cylindrical casing extending along the axis from the front end side to the rear end side, and the casing connected to the casing by the first joint portion. A membrane that expands in a direction that intersects with the opening and closes the opening of the housing and that is deformed according to the received pressure; a heat receiving plate that is disposed on the tip side of the membrane and that is bonded to the membrane by the second bonding portion; And a sensor element that is disposed on the diaphragm, in which mechanical strain is generated due to the deformation of the membrane, and a sensor element that is disposed on the diaphragm and that converts the mechanical strain amount of the diaphragm into an electrical amount. A peripheral tip portion is arranged over the outer peripheral surface of the membrane, and the tip portion overlaps the outer peripheral surface of the heat receiving plate.

According to the in-cylinder pressure sensor of claim 1, since the distal end portion of the circumferential casing arranged over the outer peripheral surface of the membrane overlaps the outer peripheral surface of the heat receiving plate, the first joint portion is formed. The interface and the interface where the second joint is formed can be placed inside the in-cylinder pressure sensor by covering the interface with the tip. As a result, the airflow in the combustion chamber flowing into the two interfaces can be blocked. As a result, the force of peeling the membrane from the housing and the force of peeling the heat receiving plate from the membrane are suppressed, so that damage or breakage of the first joint portion or the second joint portion can be suppressed.

According to the in-cylinder pressure sensor of the second aspect, since a gap is formed between at least a part of the outer peripheral surface of the heat receiving plate in the circumferential direction and the inner peripheral surface of the tip portion, the heat receiving plate corresponds to the gap. Can be thermally expanded. When the thermal expansion of the heat receiving plate is limited, the heat receiving plate bends, so that the bending of the heat receiving plate is transmitted to the membrane through the second joint, and mechanical strain other than the deformation of the membrane according to the cylinder internal pressure causes the diaphragm. Occurs, which leads to a decrease in pressure detection accuracy. Since this can be suppressed, in addition to the effect of claim 1, the pressure detection accuracy can be improved.

According to the in-cylinder pressure sensor of the third aspect, a gap is formed between the entire outer circumferential surface of the heat receiving plate in the circumferential direction and the inner circumferential surface of the tip portion. Therefore, in addition to the effect of the second aspect, The pressure detection accuracy can be further improved.

According to the in-cylinder pressure sensor of the fourth aspect, the front end surface of the heat receiving plate is located closer to the front end side than the front end portion, and the front end portion overlaps at least half or more of the distance in the axial direction of the outer peripheral surface of the heat receiving plate. Thereby, the airflow flowing into the interface where the second joint portion is formed can be further blocked, and the force for peeling the heat receiving plate from the membrane is further suppressed. Therefore, in addition to the effect according to any one of claims 1 to 3, Therefore, it is possible to further suppress the breakage or breakage of the second joint portion.

According to the in-cylinder pressure sensor of claim 5, the main body portion of the membrane is joined to the heat receiving plate via the second joint portion, and the edge portion located on the outer periphery of the main body portion is joined to the housing via the first joint portion. To be joined. Since the distance D in the axial direction of the outer peripheral surface of the heat receiving plate and the thickness T of the main body portion satisfy D/T≦1, the thickness of the heat receiving plate can be equal to or less than the thickness T of the main body portion. Since it is possible to prevent the heat receiving plate from becoming thicker than the main body portion, it is difficult for the heat receiving plate to prevent the deformation of the main body portion. Therefore, in addition to the effect of the fourth aspect, it is possible to prevent the pressure detection sensitivity from decreasing.

According to the in-cylinder pressure sensor of the sixth aspect, since 0.33≦D/T≦1 is satisfied, the heat receiving plate can be prevented from becoming too thin. Thereby, in addition to the effect of the fifth aspect, it is possible to suppress the interface of the second joint and the damage of the second joint due to the force of peeling the heat receiving plate from the membrane.

FIG. 3 is a partial cross-sectional view of the in-cylinder pressure sensor according to the first embodiment. It is sectional drawing of a cylinder pressure sensor. FIG. 3 is an enlarged view of a portion indicated by III in FIG. 2. FIG. 4 is a front view of the in-cylinder pressure sensor seen from the direction of arrow IV in FIG. 1. It is a fragmentary sectional view of the in-cylinder pressure sensor in the second embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a partial sectional view of an in-cylinder pressure sensor 10 according to the first embodiment. 2 is a sectional view including the axis O of the in-cylinder pressure sensor 10, and FIG. 3 is an enlarged view of a portion indicated by III in FIG. In FIG. 2, illustration of the rear end side of the in-cylinder pressure sensor 10 is omitted. The lower side of the paper surface of FIG. 1 is referred to as the front end side of the in-cylinder pressure sensor 10, and the upper side of the paper surface is referred to as the rear end side of the in-cylinder pressure sensor 10 (also in FIGS. 2, 3 and 5). As shown in FIG. 1, the cylinder pressure sensor 10 mainly includes a housing 11, a membrane 30, and a diaphragm 43. In FIG. 1, illustration of the cables arranged inside the housing 11 is omitted (the same applies to FIG. 2 ).

The housing 11 is a cylindrical member extending along the axis O formed of a metal material having heat resistance and gas resistance (for example, stainless steel or low carbon steel). In the present embodiment, the cross section of the inner peripheral surface 12 of the housing 11 perpendicular to the axis O is circular. A screw portion 21 and a tool engagement portion 22 are provided on the outer peripheral surface of the housing 11. The screw portion 21 is a male screw attached to a screw hole formed in an internal combustion engine (not shown). The tool engagement portion 22 is a portion with which a tool (not shown) such as a wrench used for attaching and detaching the in-cylinder pressure sensor 10 to the internal combustion engine engages.

As shown in FIG. 2, the housing 11 has a first member 13 and a second member 14 arranged in order from the rear end side to the front end side. The first member 13 is a member having a cylindrical shape at least at its tip. The second member 14 is an annular member having an outer peripheral surface whose diameter decreases toward the tip side. The second member 14 constitutes an opening 16 on the front end side of the housing 11.

As shown in FIG. 3, the second member 14 is provided with a cylindrical tip portion 18 located outside the membrane 30 in the radial direction. The tip portion 18 is formed with a ring-shaped tip end surface 17 centered on the axis O. The tip end surface 17 communicates with the opening 16 of the second member 14. The tip surface 19 of the tip portion 18 is located closer to the tip side than the tip facing surface 17.

The membrane 30 is a thin metal circular film that closes the opening 16 of the housing 11. The membrane 30 is integrally formed with a disc-shaped main body 31 and an annular edge portion 32 located on the outer periphery of the main body 31. In the present embodiment, the tip surface 30a of the membrane 30 is a plane perpendicular to the axis O. The thickness of the edge portion 32 is smaller than the thickness T of the main body portion 31. The edge portion 32 is in contact with the tip end facing surface 17 of the tip end portion 18. The body portion 31 is arranged inside the tip portion 18 in the radial direction. The outer peripheral surface 31 a of the body portion 31 is in contact with the tip portion 18.

The heat receiving plate 34 is a thin metal circular plate that covers the front end surface 30 a of the membrane 30. The tip portion 18 overlaps the outer peripheral surfaces 31 a and 33 of the membrane 30, and further overlaps the outer peripheral surface 35 of the heat receiving plate 34.

The entire periphery of the edge portion 32 of the membrane 30 is joined to the tip end surface 17 of the second member 14 by the first joining portion 36. In the present embodiment, the first joint portion 36 is a welded portion formed by the laser beam with which the edge portion 32 of the tip surface 30a of the membrane 30 is irradiated. The heat receiving plate 34 is joined to the portion of the membrane 30 that is radially inward of the first joining portion 36 by the second joining portion 37. In the present embodiment, the second joint portion 37 is a spot-like welded portion formed by the laser beam with which the center of the heat receiving plate 34 is irradiated. Since the second joint portion 37 is formed at the center of the heat receiving plate 34, the second joint portion 37 can make it difficult for the second joint portion 37 to exert the influence of the thermal expansion and contraction of the heat receiving plate 34 in the radial direction on the membrane 30.

A portion 36 a of the first joining portion 36 exposed on the tip surface 30 a of the membrane 30 is located radially inward of the outer peripheral surface 35 of the heat receiving plate 34 and is separated from the outer peripheral surface 35 of the heat receiving plate 34. The outer peripheral surface 33 of the membrane 30 is not melted in the first joint portion 36, and the entire outer peripheral surface 33 remains.

The front end surface 30 a of the membrane 30 is located on the rear end side of the front end surface 19 of the front end portion 18. The front end surface 34 a of the heat receiving plate 34 is located closer to the front end side than the front end surface 19 of the front end portion 18. The tip portion 18 overlaps at least half the distance D in the axial direction of the outer peripheral surface 35 of the heat receiving plate 34. A gap 38 is formed between at least a part of the outer peripheral surface 35 of the heat receiving plate 34 and the inner peripheral surface 20 of the tip portion 18. The distance D is less than or equal to the thickness T of the main body 31.

FIG. 4 is a front view of the in-cylinder pressure sensor 10 as seen from the direction of arrow IV in FIG. As shown in FIG. 4, the gap 38 is formed between the entire outer peripheral surface 35 (see FIG. 3) of the heat receiving plate 34 and the inner peripheral surface 20 (see FIG. 3) of the tip portion 18.

It returns to FIG. 2 and demonstrates. The membrane 30 is provided with a cylindrical transmission member 40 extending from the center of the main body 31 of the membrane 30 to the rear end side along the axis O. In this embodiment, the membrane 30 and the transmission member 40 are integrally formed by using a metal material such as stainless steel by, for example, forging or cutting. However, the invention is not limited to this, and it is naturally possible to integrally form the membrane 30 and the transmission member 40 by welding after forming the membrane 30 and the transmission member 40 separately.

The connection member 41 and the diaphragm 43 are arranged between the transmission member 40 and the inner peripheral surface 12 of the housing 11. The connection member 41 is a metallic cylindrical member that is arranged along the transmission member 40 outside the transmission member 40 in the radial direction. The connecting member 41 is provided with an annular first protruding portion 42 that protrudes outward in the radial direction from the tip of the connecting member 41.

The diaphragm 43 is a metallic annular member arranged between the connecting member 41 and the inner peripheral surface 12 of the housing 11. The diaphragm 43 has a disk-shaped film portion 44 arranged perpendicularly to the axis O, and a cylindrical first projection extending from the portion of the film portion 44 on the transmission member 40 side to the distal end side along the transmission member 40. The portion 45 and the cylindrical second convex portion 46 extending from the portion of the film portion 44 on the housing 11 side toward the tip side along the inner peripheral surface 12 of the housing 11 are provided. The axial length of the second convex portion 46 is shorter than the axial length of the first convex portion 45. The second protrusion 46 is provided with an annular second protrusion 47 that extends radially outward from the vicinity of the center of the second protrusion 46 in the axial direction.

The first convex portion 45 is arranged on the rear end side of the first projecting portion 42 of the connecting member 41. The tip of the first convex portion 45 is abutted against the first overhanging portion 42. The second overhanging portion 47 of the diaphragm 43 is arranged between the first member 13 and the second member 14. The film portion 44, the first convex portion 45, the second convex portion 46, and the second overhanging portion 47 are integrally formed.

A sensor element 48 is fixed to the diaphragm 43. The sensor element 48 is a piezoresistive strain gauge that converts the mechanical strain amount of the diaphragm 43 into an electric amount. Two sensor elements 48 are fixed at two locations sandwiching the axis O of the film portion 44.

The sensor element 48 is fixed on the film portion 44 by a connecting portion 49 formed of a bonding material such as an adhesive. The connecting portion 49 is formed on the surface facing the rear end side of the film portion 44. The output signal of the sensor element 48 is transmitted to an electric circuit (not shown) built in the cylinder pressure sensor 10 by a cable (not shown) connected to the sensor element 48, and the cylinder circuit pressure is increased by the electric circuit. Is calculated.

The third joint portion 50 joins the rear end portion of the transmission member 40 to the rear end portion of the connection member 41. The fourth joint portion 51 joins the tip portion of the connecting member 41 to the tip portion of the first convex portion 45. The third joint portion 50 is located on the rear end side of the fourth joint portion 51. In the present embodiment, the third joint portion 50 and the fourth joint portion 51 are welded portions formed by laser beam irradiation. The fourth joint portion 51 is located closer to the tip end side than the tip end portion of the second convex portion 46. The connecting portion 49 is located closer to the tip side than the third joining portion 50. The connection portion 49 is located on the rear end side of the fourth joint portion 51.

The fifth joint portion 52 joins the rear end portion of the second member 14 to the second overhang portion 47 over the entire circumference. The sixth joint portion 53 joins the tip end portion of the first member 13 to the second overhang portion 47 over the entire circumference. In the present embodiment, the fifth joint portion 52 and the sixth joint portion 53 are welded portions formed by laser beam irradiation.

A gap 55 is formed between the connection member 41 and a portion of the first convex portion 45 of the diaphragm 43 on the rear end side of the fourth joint portion 51. The gap 55 is formed over the entire circumference of the first convex portion 45. A gap 56 is formed between the first member 13 and a portion of the second protrusion 46 of the diaphragm 43 on the rear end side of the sixth joint 53. The gap 56 is formed over the entire circumference of the first member 13.

The housing 11, the membrane 30, the transmission member 40, the connection member 41, and the diaphragm 43 of the in-cylinder pressure sensor 10 are joined in the following order, for example. First, the connecting member 41 is inserted into the diaphragm 43 from the tip side of the diaphragm 43, and then the diaphragm 43 and the connecting member 41 are connected by the fourth joint portion 51.

Separately from this, after the edge portion 32 of the membrane 30 provided with the transmission member 40 is brought into contact with the distal end facing surface 17 of the second member 14, the edge portion 32 is joined to the second member 14 by the first joining portion 36. To do. Then, the heat receiving plate 34 is bonded to the membrane 30 by the second bonding portion 37. The transmission member 40 is inserted into the connection member 41, the rear end portion of the second member 14 is abutted against the second overhanging portion 47, and then the transmission member 40 and the connection member 41 are joined by the third joining portion 50. Finally, the second member 14 and the second overhanging portion 47 are joined by the fifth joining portion 52, and then the first member 13 and the diaphragm 43 are joined by the sixth joining portion 53.

In the in-cylinder pressure sensor 10, when the screw portion 21 is attached to the screw hole formed in the internal combustion engine (not shown), the outer peripheral surface of the second member 14 is pressed against the internal combustion engine, and the distal end surface 19 of the distal end portion 18 and The heat receiving plate 34 is exposed to the combustion chamber. The tip surface 19 and the heat receiving plate 34 exposed in the combustion chamber are exposed to the airflow (swirl, tumble, etc.) in the combustion chamber.

In the in-cylinder pressure sensor 10, when the membrane 30 bends due to the pressure in the combustion chamber (in-cylinder pressure), the transmission member 40 is displaced in the axial direction. The displacement of the transmission member 40 is transmitted to the first convex portion 45 of the diaphragm 43 via the third joint portion 50, the connecting member 41, and the fourth joint portion 51. Since the second overhanging portion 47 provided on the second convex portion 46 of the diaphragm 43 is fixed to the housing 11, the axial displacement of the first convex portion 45 causes mechanical strain in the film portion 44. The sensor element 48 generates an output signal according to the mechanical strain amount of the film portion 44. An electric circuit (not shown) built in the cylinder pressure sensor 10 calculates the cylinder pressure based on the output signal of the sensor element 48.

However, since the edge portion 32 of the membrane 30 is joined to the housing 11 via the first joining portion 36, when the membrane 30 is thermally expanded by the high temperature combustion gas, the membrane 30 is bent by the expanded amount. When the flexure of the membrane 30 according to the in-cylinder pressure is applied to the flexure due to thermal expansion, mechanical strain other than the deformation of the membrane 30 according to the in-cylinder pressure is generated in the diaphragm 43, which leads to a decrease in pressure detection accuracy. .. In order to prevent this, the heat receiving plate 34 is joined to the membrane 30 via the second joining portion 37. The heat receiving plate 34 arranged on the tip side of the membrane 30 reduces the thermal influence of the combustion gas on the membrane 30.

Further, the tip end portion 18 is arranged over the outer peripheral surface 33 of the membrane 30, and the tip end portion 18 overlaps with the outer peripheral surface 35 of the heat receiving plate 34. Therefore, the in-cylinder pressure sensor 10 is covered by covering the interface S1 (see FIG. 3) where the first joint portion 36 is formed and the interface S2 (see FIG. 3) where the second joint portion 37 is formed with the tip portion 18. Can be placed inside. Thereby, the air flow in the combustion chamber flowing into the two interfaces S1 and S2 can be blocked. As a result, the force for peeling off the membrane 30 from the second member 14 and the force for peeling off the heat receiving plate 34 from the membrane 30 are suppressed, so that the first joint portion 36 and the second joint portion 37 are damaged. And damage can be suppressed.

Since the tip portion 18 overlaps at least half or more of the distance D in the axial direction of the outer peripheral surface 35 of the heat receiving plate 34, when the tip portion 18 overlaps a portion of the outer peripheral surface 35 of the heat receiving plate 34 that is less than half of the distance D. In comparison, the airflow flowing into the interface S2 where the second joint portion 37 is formed can be further blocked. Since it is possible to further suppress the force of peeling the heat receiving plate 34 from the membrane 30, it is possible to further suppress damage or destruction of the second joint portion 37.

Since the gap 38 is formed between at least a part of the outer circumferential surface 35 of the heat receiving plate 34 in the circumferential direction and the inner circumferential surface 20 of the tip end portion 18, the heat receiving plate 34 can be thermally expanded by the amount of the gap 38. When the thermal expansion of the heat receiving plate 34 is limited by the tip portion 18, the heat receiving plate 34 bends, so that the bending of the heat receiving plate 34 is transmitted to the membrane 30 via the second joint portion 37, and the membrane according to the pressure in the cylinder. Mechanical strain other than the deformation of 30 is generated in the diaphragm 43, leading to a reduction in pressure detection accuracy. Since this can be suppressed, the pressure detection accuracy can be improved. In particular, since the gap 38 is formed between the entire outer circumferential surface 35 of the heat receiving plate 34 in the circumferential direction and the inner circumferential surface 20 of the tip portion 18, the pressure detection accuracy can be further improved.

Since the thickness D of the heat receiving plate 34 is equal to or less than the thickness T of the main body 31 of the membrane 30, it is difficult for the heat receiving plate 34 to prevent deformation of the main body 31. Therefore, it is possible to prevent the pressure detection sensitivity from decreasing.

A portion 36a of the first joint portion 36 exposed to the tip surface 30a of the membrane 30 is located radially inward of the outer peripheral surface 35 of the heat receiving plate 34, and the entire first joint portion 36 is the outer periphery of the heat receiving plate 34. Since it is separated from the surface 35, it is possible to prevent the first joint portion 36 from being exposed to the combustion gas. As a result, deterioration of the first joint portion 36 due to the influence of combustion gas can be suppressed.

Since the tip end surface 17 is formed on the tip end portion 18 of the housing 11, when the in-cylinder pressure sensor 10 is manufactured, the membrane 30 can be brought into contact with the tip end surface 17 to position the membrane 30 in the axial direction. .. Therefore, the membrane 30 and the second member 14 can be easily joined via the first joining portion 36.

Since the edge portion 32 of the membrane 30 which is thinner than the main body portion 31 and the front end facing surface 17 are joined by the first joining portion 36, the width of the first joining portion 36 (dimension in the direction perpendicular to the axis O). ) Is narrow, the penetration depth of the first joint 36 can be secured, and the mechanical strength of the first joint 36 can be secured. Since the width of the first joint portion 36 can be reduced, the entire first joint portion 36 can be easily separated from the outer peripheral surface 35 of the heat receiving plate 34. As a result, it is possible to make it difficult for the first joint portion 36 to be exposed to the combustion gas. Furthermore, since the outer peripheral surface 31a of the main body 31 that is thicker than the edge 32 is in contact with the second member 14, the main body 31 ensures the mechanical strength of the membrane 30.

A second embodiment will be described with reference to FIG. In the first embodiment, the case where the membrane 30 is bonded to the front end facing surface 17 of the housing 11 has been described. On the other hand, in the second embodiment, a case where the membrane 67 is joined to the inner peripheral surface 66 of the tip portion 64 will be described. The same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 5 is a partial cross-sectional view including the axis O of the in-cylinder pressure sensor 60 according to the second embodiment. In FIG. 5, illustration of a half of the in-cylinder pressure sensor 60 with the axis O as a boundary and illustration of the rear end side in the axial direction are omitted.

As shown in FIG. 5, the housing 61 of the in-cylinder pressure sensor 60 includes a second member 62 joined to the first member 13 via the second overhanging portion 47 of the diaphragm 43 (see FIG. 2). The second member 62 constitutes an opening 63 on the front end side of the housing 61. The second member 62 has a cylindrical tip portion 64 located outside the membrane 67 in the radial direction.

The membrane 67 is a thin metal circular film that closes the opening 63 of the housing 61. The membrane 67 is provided with a cylindrical transmission member 40 extending from the center of the membrane 67 to the rear end side along the axis O. The tip portion 64 is located over the entire circumference of the outer peripheral surface 68 of the membrane 67. The heat receiving plate 69 is a thin circular plate made of metal that covers the front end surface 67 c of the membrane 67. The tip portion 64 overlaps with the outer peripheral surface 68 of the membrane 67 and further with the outer peripheral surface 70 of the heat receiving plate 69.

The entire periphery of the outer peripheral surface 68 of the membrane 67 is joined to the second member 62 via the first joining portion 71. Since the first joint portion 71 is formed on the outer side in the radial direction of the membrane 67, it can be said that the first joint portion 71 is formed on the edge portion 67b of the membrane 67. The edge portion 67b of the membrane 67 is a portion of the membrane 67 from the radially inner end of the first joint portion 71 to the outer peripheral surface 68.

In the present embodiment, the first joint portion 71 is a welded portion formed by the laser beam emitted from the distal end surface 67c of the membrane 67 toward the second member 62. The heat receiving plate 69 is joined to the portion of the membrane 67 radially inside the first joining portion 71 via the second joining portion 72. In the present embodiment, the second joint portion 72 is provided at a position where the heat receiving plate 69 intersects the axis O. The second joint portion 72 is a welded portion formed by the laser beam with which the center of the heat receiving plate 69 is irradiated.

A portion 71a of the first bonding portion 71 exposed on the tip surface 67c of the membrane 67 is located radially inward of the outer peripheral surface 70 of the heat receiving plate 69 and is separated from the outer peripheral surface 70 of the heat receiving plate 69. The outer peripheral surface 68 of the membrane 67, part of which disappears (melts) due to the formation of the first bonding portion 71, remains part of the entire length in the axial direction.

The front end surface 67c of the membrane 67 is located rearward of the front end surface 65 of the front end portion 64. The front end surface 69a of the heat receiving plate 69 is located closer to the front end side than the front end surface 65 of the front end portion 64. The tip 64 overlaps at least half the distance D in the axial direction of the outer peripheral surface 70 of the heat receiving plate 69. A gap 73 is formed between at least a portion of the outer peripheral surface 70 of the heat receiving plate 69 in the circumferential direction and the inner peripheral surface 66 of the tip portion 64. The distance D is equal to or less than the thickness T of the main body 67a of the membrane 67. The main body portion 67a refers to a portion radially inward of the edge portion 67b of the membrane 67 in which the first joint portion 71 is formed. In the present embodiment, the gap 73 is formed between the entire outer circumferential surface 70 of the heat receiving plate 69 in the circumferential direction and the inner circumferential surface 66 of the tip portion 64.

According to the in-cylinder pressure sensor 60, the front end portion 64 of the housing 61 is located over the outer peripheral surface 68 of the membrane 67 and overlaps with the outer peripheral surface 70 of the heat receiving plate 69, so that the first joint portion 71 is formed. The interface S3 and the interface S4 on which the second joint portion 72 is formed can be arranged inside the cylinder pressure sensor 60 by covering them with the tip 64. Thereby, the air flow in the combustion chamber flowing into the two interfaces S3 and S4 can be blocked. As a result, the force for peeling off the membrane 67 from the second member 62 and the force for peeling off the heat receiving plate 69 from the membrane 67 are suppressed, so that the first joint portion 71 and the second joint portion 72 are damaged. And damage can be suppressed.

A portion 71a of the first joining portion 71 exposed on the tip surface 67c of the membrane 67 is located radially inward of the outer peripheral surface 70 of the heat receiving plate 69, and a portion 71a of the first joining portion 71 is located on the heat receiving plate 69. Since it is separated from the outer peripheral surface 70, it is possible to make it difficult for the first joint portion 71 to be exposed to the combustion gas. As a result, the deterioration of the first joint 71 due to the influence of the combustion gas can be suppressed.

Since the thickness D of the heat receiving plate 69 is equal to or less than the thickness T of the main body portion 67a of the membrane 67, it is difficult for the heat receiving plate 69 to prevent the deformation of the main body portion 67a. Therefore, it is possible to prevent the pressure detection sensitivity from decreasing.

The present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

(Test 1)
Various samples 1-18 having different thicknesses T of the main body 31 and the distance D in the axial direction of the outer peripheral surface 35 of the heat receiving plate 34 of the in-cylinder pressure sensor according to the first embodiment were produced. In each sample, the length of the tip portion 18 in the axial direction was set so that the tip surface 19 of the tip portion 18 was located at a position half the distance D. In each sample, dimensions other than the thickness T, the distance D, and the axial length of the tip portion 18 were constant.

Each sample was attached to the engine to measure the pressure in the combustion chamber of a 1.3 liter inline 4-cylinder engine. The waveform of the voltage output by the sensor element 48 of each sample was acquired under the conditions of an engine speed of 1500 rpm and a torque of 40 Nm. Under the same conditions, the waveform of the voltage output by the reference sensor (for example, ZI31 manufactured by AVL) was acquired, and the difference (error) between the measurement value of the reference sensor and the measurement value of each sample was obtained. Table 1 shows D (mm), T (mm), D/T, and error (%) of Sample 1-18.

表１に示すようにＤ／Ｔ≦１．０のサンプル１−１４は誤差が２．０％未満であった。これに対し、Ｄ／Ｔ＞１．０のサンプル１５−１８は誤差が２．０％以上であった。Ｄ／Ｔ≦１．０を満たすことにより、圧力の検知感度を確保できることが明らかになった。Ｄ／Ｔ≦１を満たせば受熱板３４の厚さを本体部３１の厚さＴ以下にできるので、本体部３１よりも受熱板３４が厚くならないようにできる。その結果、本体部３１の変形を受熱板３４が妨げ難くなり、圧力の検知感度を確保できたと推察される。

As shown in Table 1, sample 1-14 with D/T≦1.0 had an error of less than 2.0%. On the other hand, in Samples 15-18 with D/T>1.0, the error was 2.0% or more. It has been clarified that the pressure detection sensitivity can be secured by satisfying D/T≦1.0. If D/T≦1 is satisfied, the thickness of the heat receiving plate 34 can be made equal to or less than the thickness T of the main body portion 31, so that the heat receiving plate 34 can be prevented from being thicker than the main body portion 31. As a result, it is presumed that the heat receiving plate 34 is less likely to interfere with the deformation of the main body 31 and the pressure detection sensitivity can be secured.

(Test 2)
Each sample in Sample 1-18 was attached to an in-line 4-cylinder engine having a capacity of 1.3 liters, and the engine was idling for 1 minute and WOT (intake throttle valve fully open) for 1 minute, and operated for 100 hours. After that, the cut surface of the second joint portion 37 including the axis O of each sample is observed with a microscope, and the ratio of the length of the destroyed interface to the total length of the interface between the second joint portion 37 and the heat receiving plate 34. Was calculated. Since the destroyed interface is oxidized, it is possible to distinguish the interface where the bonding is maintained and the interface where peeling has occurred. Among Samples 1-18, a sample in which the interface destruction was 50% or more was evaluated as B, and a sample in which the interface destruction was less than 50% was evaluated as A. The results are shown in the "breakdown" column of Table 1.

As shown in Table 1, the samples 6-18 with D/T≧0.33 were evaluated as A. Since it is possible to prevent the heat receiving plate 34 from becoming too thin in the sample 6-18, it is presumed that the strength of the second joint portion 37 could be secured. According to Test 1 and Test 2, it was revealed that satisfying 0.33≦D/T≦1 can secure the pressure detection sensitivity and improve the reliability. The same applies to the in-cylinder pressure sensor according to the second embodiment.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and various improvements and modifications are possible without departing from the spirit of the present invention. It can be easily guessed.

In the embodiment, the case in which the housings 11 and 61 include the first member 13 and the second members 14 and 62 arranged in the axial direction has been described, but the present invention is not necessarily limited to this. The shape and the number of members forming the housings 11 and 61 can be set appropriately.

In the embodiment, the case where the cylindrical connection member 41 is arranged between the transmission member 40 that transmits the deformation of the membranes 30 and 67 to the rear end side of the housings 11 and 61 and the diaphragm 43 has been described. It is not limited to this. The shape of the connecting member 41 can be set arbitrarily.

In the embodiment, the case where the connection member 41 is arranged between the transmission member 40 and the diaphragm 43 has been described, but the present invention is not limited to this. It is of course possible to omit the connecting member 41 and directly join the diaphragm 43 to the transmitting member 40.

In the embodiment, the case in which the diaphragm 43 in which the first convex portion 45 and the second convex portion 46 protrude from the film portion 44 to which the sensor element 48 is fixed toward the tip side is described, but the present invention is not limited thereto. is not. It is of course possible to use the diaphragm 43 in which either or both of the first convex portion 45 and the second convex portion 46 project from the film portion 44 to the rear end side.

In the embodiment, the case where at least a part of the outer peripheral surfaces 35 and 68 of the membranes 30 and 67 remains due to the formation of the first bonding portions 36 and 71 has been described, but the present invention is not limited to this. Of course, it is possible to form the first bonding portions 36 and 71 and to eliminate (melt) all the outer peripheral surfaces 35 and 68 of the membranes 30 and 67. When the outer peripheral surfaces 35 and 68 of the membranes 30 and 67 are all melted in the first joint portions 36 and 71, the "outer peripheral surface of the membrane" described in "the tip located over the outer peripheral surface of the membrane" Means the interface between the membrane and the first joint.

In the embodiment, the gaps 38 and 73 between the outer peripheral surfaces 35 and 70 of the heat receiving plates 34 and 69 and the inner peripheral surfaces 20 and 66 of the tip portions 18 and 64 are the entire circumferences of the outer peripheral surfaces 35 and 70 of the heat receiving plates 34 and 69. Although the case of being provided over the entire length has been described, the present invention is not necessarily limited to this. Part of the outer peripheral surfaces 35, 70 of the heat receiving plates 34, 69 in the circumferential direction may be in contact with the inner peripheral surfaces 20, 66 of the tip portions 18, 64.

In the embodiment, the case where the first joint portions 36, 71 and the second joint portions 37, 72 are formed by laser welding has been described, but the present invention is not limited to this. It is of course possible to form the joint portion by another joining method. Other joining methods include, for example, electron beam welding.

In the embodiment, the case where the dot-shaped second joint portions 37 and 72 are formed at the centers of the heat receiving plates 34 and 69 has been described, but the present invention is not limited to this. Of course, the second joint portions 37 and 72 may have other shapes such as a ring shape.

In the first embodiment, the case where the edge portion 32 thinner than the main body portion 31 is provided in the membrane 30 has been described, but the present invention is not limited to this. It is naturally possible to make the thickness of the edge portion 32 the same as the thickness of the main body portion 31.

10,60 In-cylinder pressure sensor 11,61 Housing 12 Inner surface of housing 16,63 Housing opening 18,64 Tip portion 20,66 Inner surface of tip portion 30,67 Membrane 31,67a Main body portion 32, 67b Edge portion 33,68 Membrane outer peripheral surface 34,69 Heat receiving plate 35,70 Heat receiving plate outer peripheral surface 36,71 First joint portion 37,72 Second joint portion 38,73 Gap 43 Diaphragm 48 Sensor element D Distance O axis T Body thickness

Claims (6)

A cylindrical casing extending along the axis from the front end side to the rear end side,
A membrane that is joined to the housing by the first joining portion, closes the opening of the housing while expanding in a direction intersecting the axis of the housing, and deforms according to the pressure received.
A heat receiving plate arranged on the tip side of the membrane and joined to the membrane by a second joining portion;
A diaphragm that is disposed in the housing and in which mechanical strain is generated along with the deformation of the membrane,
A cylinder pressure sensor provided on the diaphragm, comprising: a sensor element that converts a mechanical strain amount of the diaphragm into an electric amount,
The casing includes a circumferential tip portion arranged over the outer peripheral surface of the membrane,
The in-cylinder pressure sensor in which the tip portion overlaps with the outer peripheral surface of the heat receiving plate. The in-cylinder pressure sensor according to claim 1, wherein a gap is formed between at least a part of the outer peripheral surface of the heat receiving plate in the circumferential direction and the inner peripheral surface of the tip portion. The in-cylinder pressure sensor according to claim 2, wherein a gap is formed between the entire outer circumferential surface of the heat receiving plate in the circumferential direction and the inner circumferential surface of the tip portion. The tip surface of the heat receiving plate is located closer to the tip side than the tip portion,
The in-cylinder pressure sensor according to any one of claims 1 to 3, wherein the tip portion overlaps with at least half the distance D in the axial direction of the outer peripheral surface of the heat receiving plate. The membrane includes a main body portion joined to the heat receiving plate via the second joint portion, and an edge portion located on the outer periphery of the main body portion and joined to the housing via the first joint portion, Equipped with
The cylinder pressure sensor according to claim 4, wherein the distance D and the thickness T of the body portion satisfy D/T≦1. The in-cylinder pressure sensor according to claim 5, wherein 0.33≦D/T≦1 is satisfied.

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