JP2011022071A - Combustion pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion pressure sensor, capable of reducing a possibility of generating decline in the combustion pressure sealability, plug looseness or the like, based on instability of a seat surface shape caused by plastic working or a weld bead, and also of reducing the possibility of opening of a preload of a pressure detection element caused by deformation of a welded zone, or sensitivity deterioration of the pressure detection element caused by heat during welding. <P>SOLUTION: The combustion pressure sensor stores the pressure detection element inside and has an annular case wherein a mounting screw part of a plug for an engine is inserted into a through-hole provided on the center and penetrating in the axial direction. The case is constituted by welding integrally on the side face part; an upper case having a flat toroidal upper surface; an upper side inner circumferential wall extending downward from the inside of the upper surface; and an upper side outer circumferential wall, extending downward from the outside of the upper surface with a lower case having a flat toroidal lower surface, a lower side inner circumferential wall extending upward from the inside of the lower surface, and a lower side outer circumferential wall extending upward from the outside of the lower surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a combustion pressure sensor for measuring a combustion pressure inside an engine such as an automobile engine.

  Conventionally, as a combustion pressure sensor for measuring the combustion pressure inside the engine, it is installed at the bottom of the plug hole, and the mounting screw portion of the engine plug is inserted into the through hole provided at the center so that the bottom seating surface of the plug hole A combustion pressure sensor having a structure sandwiched between an engine plug and the engine plug is known.

  As the combustion pressure sensor having the above configuration, an insulating plate, an electrode plate, a pressure detection element, a plate packing, etc. formed in an annular shape are stacked and accommodated in a metal annular case, and are sealed. Are known. As a structure for housing and sealing the pressure detection element and the like in the case, the plate material for constituting the inner side wall and bottom of the case is configured in a cylindrical shape, and after the pressure detection element and the like are accommodated in the case, A structure in which the upper side of the cylindrical member is caulked plastically toward the outer peripheral side and plastically deformed, and the outer peripheral end and the outer wall are welded all around is known (see, for example, Patent Document 1). . However, in the combustion pressure sensor having such a configuration, since the bottom portion (seat surface) of the case is formed by plastic working, the shape of the seat surface is likely to vary. Further, since the outer peripheral portion of the seat surface of the case is welded, a weld bead is generated on the seat surface, and this weld bead also causes variations in the shape of the bottom surface. Since the seat surface shape is unstable as described above, there is a possibility that the combustion pressure sealing property is lowered, the plug is loosened, or the like. Further, there is a possibility that the piezoelectric element breaks during plastic processing.

  A combustion pressure sensor having another structure is known in which a seat surface is formed by caulking both open ends of a U-shaped metal case constituent member toward the inside of the U shape (for example, a patent). Reference 2). However, even in the combustion pressure sensor having such a structure, since the seat surface is formed by plastic processing, the shape of the seat surface becomes unstable, and there is a possibility that the combustion pressure sealing performance is deteriorated or the plug is loosened. In order to avoid such a problem, the seat surface is also lapped, but in this case, the number of lapping steps increases, and the seat surface becomes thinner due to the lapping process, resulting in a decrease in strength.

  Furthermore, as a combustion pressure sensor of another structure, the above-described plastic working process is abolished and a seating surface is formed by the annular negative electrode plate, and an inner casing member and an outer casing member are provided on the annular negative electrode plate. Is known which has been laser welded (see, for example, Patent Document 3). However, in the combustion pressure sensor having such a structure, since the welded portion is concentrated at the bottom of the combustion pressure sensor, the preload applied to the pressure detection element may be released due to the deformation of the welded portion. Moreover, since the welding location is the annular negative electrode plate directly below the pressure detection element, there is a possibility that the sensitivity of the pressure detection element may be deteriorated by heat during welding.

Japanese Patent Laid-Open No. 2002-24369 No. 6-746 JP 2008-185419 A

  As described above, with the conventional combustion pressure sensor, there is a risk of deterioration of the combustion pressure sealability or plug loosening due to instability of the seat shape due to plastic working or welding beads, and pressure due to deformation of the welded part. There have been problems such as opening of the preload of the detection element and the possibility of deterioration of sensitivity of the pressure detection element due to heat during welding.

  The present invention has been made in response to the above-described conventional circumstances. The present invention can reduce the risk of occurrence of combustion pressure sealing deterioration and plug loosening due to instability of the seating surface shape due to plastic working or welding beads, and preloading of the pressure detection element due to deformation of the welded portion. It is an object of the present invention to provide a combustion pressure sensor that can reduce the risk of deterioration in sensitivity of the pressure detection element due to heat release and heat during welding.

  A combustion pressure sensor according to the present invention includes a pressure detection element for detecting a combustion pressure, and an attachment screw portion for an engine plug in a through-hole that accommodates the pressure detection element in the axial direction and is provided in the center. A combustion pressure sensor in which the case is installed at the bottom of a plug hole provided in the engine, and the case includes a flat annular upper surface, and an upper surface of the upper surface. An upper case having an upper inner peripheral wall extending downward from the inner side, an upper outer peripheral wall extending downward from the outer side of the upper surface, a flat annular lower surface, and extending upward from the inner side of the lower surface A lower case having a lower inner peripheral wall and a lower outer peripheral wall extending upward from the outside of the lower surface, and the upper case and the lower case are welded and integrated at a side surface portion. It is characterized by being.

  In the combustion pressure sensor of the present invention configured as described above, the case includes a flat annular upper surface, an upper inner peripheral wall extending downward from the inner side of the upper surface, and an upper outer peripheral wall extending downward from the outer side of the upper surface. And an upper case, a flat annular lower surface, a lower inner peripheral wall extending upward from the inner side of the lower surface, and a lower outer peripheral wall extending upward from the outer side of the lower surface A lower case is provided, and the upper case and the lower case are integrated by welding at a side surface portion. As a result, the case can be integrated without performing plastic working in the assembly process of the case and without generating a weld bead at the bottom of the case. It is possible to reduce the possibility of occurrence of pressure sealability deterioration and plug loosening. In addition, since the welded portion is not provided at the bottom of the case, it is possible to reduce the possibility of pressure sensor element preload opening due to deformation of the welded part and sensitivity deterioration of the pressure sensor element due to heat during welding.

  In the combustion pressure sensor of the present invention configured as described above, the length of the portion of the upper inner peripheral wall and the lower inner peripheral wall overlapping in the axial direction, and the upper outer peripheral wall and the lower outer peripheral wall overlap in the axial direction. The length of the portion is less than half of the thickness of the case. As a result, the combustion pressure in the combustion chamber applied in the thickness direction of the case can be prevented from being hindered by the inner peripheral wall and the outer peripheral wall of the case, and can be efficiently applied to the pressure detection element. The combustion pressure can be detected with high sensitivity.

  In the combustion pressure sensor of the present invention having the above-described configuration, the upper inner peripheral wall and the upper outer peripheral wall have the same axial length, and the lower inner peripheral wall and the lower outer peripheral wall have an axial length. Are the same. Thereby, the height of the welding position in the side part of a case can be made the same height, and laser welding etc. can be performed efficiently.

  Further, in the combustion pressure sensor of the present invention having the above-described configuration, an insulating member is accommodated in the case in a state of being stacked with the pressure detection element, and the upper case and the lower case are disposed at lateral positions of the insulating member. Is welded. In this way, by performing welding at the side position of the insulating member, it is possible to suppress the transfer of heat due to welding to the pressure detection element, and reduce the risk of sensitivity deterioration of the pressure detection element due to heat during welding. can do.

  According to the present invention, it is possible to reduce the possibility of occurrence of combustion pressure sealing deterioration or plug loosening due to instability of the seating surface shape due to plastic working or welding beads, and the pressure detection element due to deformation of the welded portion. It is possible to provide a combustion pressure sensor that can reduce the risk of sensitivity deterioration of the pressure detection element due to the opening of the preload and heat during welding.

1 is a longitudinal sectional view showing an overall schematic configuration of a combustion pressure sensor according to an embodiment of the present invention. The top view of the combustion pressure sensor of FIG. The longitudinal cross-sectional view which expands and shows the AA cross section of FIG. The longitudinal cross-sectional view which expands and shows the principal part structure of the combustion pressure sensor of other embodiment.

  Hereinafter, details of the present invention will be described with reference to the drawings.

  1 is a diagram showing an overall schematic configuration of a combustion pressure sensor according to an embodiment of the present invention, FIG. 2 is a top view of the combustion pressure sensor of FIG. 1, and FIG. 3 is a cross-sectional view taken along line AA of FIG. It is a longitudinal cross-sectional view shown expanding. As shown in FIGS. 1 and 2, the combustion pressure sensor 1 includes a case 2 formed in an annular shape. At the center of the case 2 is provided a through-hole 3 that penetrates in the direction of the axis (indicated by a one-dot chain line G in the figure), and an attachment screw portion 101 of the engine plug 100 is inserted into the through-hole 3. It has come to be.

  As shown in FIG. 3, a pressure detection element 4 for detecting the combustion pressure is accommodated in the case 2. The pressure detection element 4 is made of a piezoelectric ceramic element or the like and is formed in an annular shape. A plate packing 5 formed in an annular shape from a metal flat plate is disposed below the pressure detection element 4 so as to be stacked with the pressure detection element 4. 3 and FIG. 4 to be described later, the side (left side in the figure) on which the axis indicated by the alternate long and short dash line G is drawn is the inner side of the combustion pressure sensor 1.

  In addition, an electrode 6 formed in an annular shape from a metal flat plate and an insulating plate 7 formed in an annular shape from insulating ceramics are laminated on the upper side of the pressure detecting element 4 in the case 2. Has been placed. An insulating member 8 made of a heat-shrinkable tube or the like is disposed on the inner wall portion on the inner peripheral side of the case 2.

  The case 2 includes an upper case 10 and a lower case 20. The upper case 10 has a flat annular upper surface 11, an upper inner peripheral wall 12 that extends downward from the inside of the upper surface 11, and an upper outer peripheral wall 13 that extends downward from the outer surface of the upper surface 11. The lower case 20 includes a flat annular lower surface 21, a lower inner peripheral wall 22 extending upward from the inner side of the lower surface 21, and a lower outer peripheral wall 23 extending upward from the outer side of the lower surface 21. Have

  And the upper case 10 and the lower case 20 are welded and integrated by the side part. That is, the upper inner peripheral wall 12 and the upper outer peripheral wall 13 of the upper case 10 are arranged so as to cover the inner side of the lower inner peripheral wall 22 of the lower case 20 and the outer side of the lower outer peripheral wall 23, and Along the lower end portion, the upper inner peripheral wall 12 and the lower inner peripheral wall 22 are welded and fixed all around the welded portion 31 by laser welding. Further, along the lower end portion of the upper outer peripheral wall 13, the upper outer peripheral wall 13 and the lower outer peripheral wall 23 are all welded and fixed by laser welding at the welding portion 32. Thereby, the upper case 10 and the lower case 20 are integrated.

  As described above, in the present embodiment, in the assembly process of the case 2, the insulating member 8 is disposed in the lower case 20 formed in advance in a predetermined shape, and the plate packing 5, the pressure detection element 4, the electrode 6, the insulation After arrange | positioning so that the board | plate 7 may be laminated | stacked, it can integrate by covering the upper case 10 on these and carrying out the laser welding of the side wall part over the perimeter.

  Therefore, as in the prior art, after placing the pressure detection element or the like in the case, the case 2 is formed without performing plastic processing such as caulking on the open portion of the case, and without generating a weld bead at the bottom of the case. Can be integrated. As a result, the shape of the seating surface of the case 2 can be stabilized, and the possibility of occurrence of deterioration in the combustion pressure sealing property, loose plug, and the like can be reduced. In addition, since the welded portions 31 and 32 are not on the bottom portion of the case 2 but on the side wall portion, it is possible to reduce the risk of sensitivity deterioration of the pressure detecting element 4 due to opening of the preload of the pressure detecting element 4 due to deformation of the welded portions 31 and 32. Can do.

  Further, for example, when welding is performed in the vicinity of the bottom (seat surface) of the case 2, heat at the time of welding is transmitted to the pressure detection element 4 via the metal plate packing 5 having high thermal conductivity, and the pressure detection element 4. However, in this embodiment, since the welds 31 and 32 are located on the side wall of the case 2, there is a possibility that the sensitivity of the pressure detection element 4 may be deteriorated due to heat during welding. Can be reduced. Furthermore, as shown in FIG. 3, in the case of this embodiment, the welded portions 31 and 32 are provided so as to be located on the side of the insulating plate 7 made of insulating ceramics or the like and having a low thermal conductivity. For this reason, it can suppress that the heat at the time of welding is transmitted to the pressure detection element 4 still more.

  Moreover, in this embodiment, the length (L1 shown in FIG. 3) of the part which overlaps with the axial direction of the upper side inner peripheral wall 12 and the lower side inner peripheral wall 22, and the axis line of the upper side outer peripheral wall 13 and the lower side outer peripheral wall 23 The length of the portion overlapping in the direction (L2 shown in FIG. 3) is less than half of the thickness of the case 2 (D shown in FIG. 3). In the present embodiment, specifically, D shown in FIG. 3 is about 5 mm, and L1 and L2 are about 1 mm. Accordingly, the combustion pressure in the combustion chamber applied in the thickness direction of the case 2 can be suppressed from being inhibited by the inner peripheral wall and the outer peripheral wall of the case 2, and the pressure detection element 4 can be efficiently applied. Therefore, the combustion pressure can be detected with high sensitivity. In addition, when said L1, L2 becomes long, it acts similarly to the plate | board thickness of the side wall of case 2 becoming thick, and the combustion pressure in the combustion chamber added to the pressure detection element 4 will be prevented by this thick side wall. Become.

  As shown in FIG. 3, in the present embodiment, the upper inner peripheral wall 12 and the upper outer peripheral wall 13 have the same axial length, and the lower inner peripheral wall 22 and the lower outer peripheral wall 23 have an axial length. Are the same. Thereby, the height of the welding position with respect to the welding parts 31 and 32 of the side part of case 2 can be made the same height, and laser welding can be performed efficiently.

  As described above, after the upper case 10 and the lower case 20 are integrated by welding all around the welded portions 31 and 32, the empty space in the case 2 is filled with an insulating material such as rubber 9. As shown in FIGS. 1 and 2, the electrode 6 is formed with a protruding portion 60 protruding outward at a part of the outer peripheral portion, and the protruding portion 60 is provided on the outer peripheral side of the case 2. It is in a state protruding from the portion 30. And the front-end | tip part of the lead wire 40 adheres to this protrusion part 60, and the pressure detection signal of the pressure detection element 4 is taken out outside. Note that the protrusions 60 and the leading ends of the lead wires 40 are covered with a resin 41 such as silicon. In FIG. 1, a part of the resin 41 is cut out to show the inside.

  The combustion pressure sensor 1 having the above-described configuration is provided at the bottom of a plug hole provided in the engine, the mounting screw portion 101 of the engine plug 100 is inserted into the through hole 3, and the engine plug 100 and the bottom of the plug hole are inserted. It is sandwiched between and fixed. The mounting screw portion 101 of the engine plug 100 is screwed into a female screw portion provided at the bottom of the engine plug hole, and the engine plug 100 and the combustion pressure sensor 1 are mounted on the engine.

  Then, the lead wire 40 is pulled out to the outside of the plug hole, and is electrically connected to a control unit or the like provided outside. In this state, when the engine plug 100 is pressed outwardly by the combustion pressure in the combustion chamber of the engine, the pressure is pressed by the combustion pressure sensor 1 sandwiched between the engine and the engine plug 100. Is detected as the combustion pressure. When measuring the combustion pressure in the combustion chamber of the engine in this way, the combustion pressure sensor 1 does not perform plastic working as described above, and the case 2 without generating a weld bead at the bottom of the case. Since they are integrated, the shape of the seating surface of the case 2 is stabilized, and it is possible to reduce the possibility that the combustion pressure sealing performance is lowered or the plug is loosened. In addition, since it is possible to reduce the possibility of preload opening of the pressure detection element 4 due to deformation of the welded portion and sensitivity deterioration of the pressure detection element 4 due to heat during welding, the combustion pressure can be detected with high accuracy.

  In addition, this invention is not limited to said embodiment, Of course, various deformation | transformation are possible. For example, as shown in FIG. 4, the upper inner peripheral wall 12 of the upper case 10 is disposed so as to cover the outer side of the lower inner peripheral wall 22 of the lower case 20, and the upper outer peripheral wall 13 of the upper case 10 is It is good also as the case 200 of the structure comprised so that it might be arrange | positioned inside the lower outer peripheral wall 23. FIG. In FIG. 4, parts corresponding to those in FIG.

  DESCRIPTION OF SYMBOLS 1 ... Combustion pressure sensor, 2 ... Case, 4 ... Pressure detection element, 5 ... Plate packing, 6 ... Electrode, 7 ... Insulating plate, 8 ... Insulating member, 9 ... Rubber, 10 ... Upper case, 11 ... Upper surface, 12 ... Upper inner peripheral wall, 13 ... Upper outer peripheral wall, 20 ... Lower case, 21 ... Lower surface, 22 ... Lower inner peripheral wall, 23 ... Lower outer peripheral wall, 31 , 32 ... welded part, 40 ... lead wire, 60 ... projecting part, 100 ... engine plug.

Claims (4)

A pressure detection element for detecting a combustion pressure; and an annular case that houses the pressure detection element therein and that has an engine plug mounting screw inserted through a through hole that is provided in the center and extends in the axial direction. A combustion pressure sensor in which the case is installed at the bottom of a plug hole provided in the engine,
The case is
An upper case having a flat annular upper surface, an upper inner peripheral wall extending downward from the inner side of the upper surface, and an upper outer peripheral wall extending downward from the outer side of the upper surface;
A lower ring having a flat annular lower surface, a lower inner peripheral wall extending upward from the inside of the lower surface, and a lower outer peripheral wall extending upward from the outer side of the lower surface;
The combustion pressure sensor, wherein the upper case and the lower case are welded and integrated at a side surface portion.   The length of the portion overlapping in the axial direction between the upper inner peripheral wall and the lower inner peripheral wall, and the length of the portion overlapping in the axial direction between the upper outer peripheral wall and the lower outer peripheral wall are the thickness of the case. The combustion pressure sensor according to claim 1, wherein the combustion pressure sensor is less than half of the combustion pressure sensor.   2. The axial lengths of the upper inner peripheral wall and the upper outer peripheral wall are the same, and the axial lengths of the lower inner peripheral wall and the lower outer peripheral wall are the same. 2. The combustion pressure sensor according to 2.   The insulating member is accommodated in the case in a state of being laminated with the pressure detecting element, and the upper case and the lower case are welded at a side position of the insulating member. The combustion pressure sensor according to any one of?

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