JP2007085577A - Glow plug with combustion pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug with a combustion pressure sensor, hardly being effected by deformation of an engine head, capable of obtaining a good sensor sensitivity and having a small diameter. <P>SOLUTION: An intermediate sleeve 95, a pressure detecting sleeve 90, and a rear end side subject fitting 60 are connected to a heater supporting member 70 into which a ceramic heater 20 of a heater member 10 is press-fitted, and a cylindrical body having a shaft inserted therein is structured. A tip end side subject fitting 50 is connected to the rear end side subject fitting 60 in a state of surrounding the cylindrical body. When the engine head 200 is deformed by combustion pressure, a barrel part 56 of the tip end side subject fitting 50 deforms, but no displacement occurs in the heater member 10. On the other hand, displacement occurs in the heater member 10 when a flexible part 93 of the pressure detecting sleeve 90 deforms due to the effect of direct pressuring force to the ceramic heater 20 by combustion pressure, and the displacement is detected by the combustion pressure sensor as combustion pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glow plug with a combustion pressure sensor that is integrally provided with a combustion pressure sensor for detecting a change in the combustion pressure of the internal combustion engine and assists starting of the internal combustion engine.

  2. Description of the Related Art A known glow plug for assisting the start of an internal combustion engine is provided with a combustion pressure sensor for detecting the combustion pressure of the internal combustion engine. In such a glow plug with a combustion pressure sensor, piezoelectric ceramics are generally used as a sensor element for detecting the combustion pressure. And the heater member which joined the heater to the tip of the middle shaft inserted through the shaft hole of the metal shell is fixed at the tip of the metal shell, and between the rear end of the heater member and the rear end of the metal shell The piezoelectric ceramic is held in a preloaded state.

  When such a glow plug with a combustion pressure sensor is attached to the mounting hole of the engine head, the outer peripheral surface of the front end of the metal shell is also brought into contact with the inner peripheral surface of the mounting hole on the combustion chamber side as a seal Thus, the male screw portion formed on the outer periphery of the metal shell is screwed into the female screw portion of the mounting hole. That is, the metal shell is locked to the engine head by the tip portion and the male screw portion. When the engine head is deformed by the combustion pressure generated when the internal combustion engine is driven, the metal shell receives a pressing force at the tip portion and is compressed between the male screw portion, so that the body portion expands in the radial direction. It is elastically deformed. As a result, the distance between the front end portion of the metal shell and the male screw portion is shortened, and the heater member fixed to the front end portion is displaced relative to the metal shell. Then, the preload applied to the piezoelectric ceramic is reduced, and the combustion pressure is detected by detecting the change in the electric charge of the piezoelectric ceramic at that time.

  However, since the deformation of the body of the metal shell that causes the displacement between the metal shell and the heater member is due to the deformation of the engine head, the deformation of the engine head when combustion pressure is generated in other cylinders Displacement may occur and may be detected as noise. Further, the magnitude of the displacement depends on the rigidity of the engine head that causes deformation of the metal shell. In other words, different outputs (detection values of the combustion pressure) may be obtained depending on the engine head to which the glow plug with the combustion pressure sensor is attached, and calibration needs to be performed after the glow plug with the combustion pressure sensor is attached.

Therefore, for example, a film is provided in the metal shell so that the heater member (heating rod) can be displaced with respect to the metal shell (glow plug body), and the metal shell and the heater member are joined via the film. . That is, the heater member is supported by the film in the metal shell. In this way, even if the metal shell is deformed due to the deformation of the engine head, it is difficult for the heater member to be displaced. On the other hand, when the heater member receives a direct pressing force due to the combustion pressure, A deflection | deviation can be produced in a heater member because a film | membrane bends in the thickness direction (for example, refer patent document 1).
JP 2005-90954 A

  By the way, in the form in which the heater member is supported by the film in the metal shell as in Patent Document 1, the sensor sensitivity depends on the size of the heater member that can be displaced. Depending on the size that can be flexed, the size that the membrane can flex depends on the clearance between the inner peripheral surface of the metal shell and the outer peripheral surface of the heater member. However, the clearance is not sufficiently large, and there is a problem that good sensor sensitivity cannot be obtained. Further, in order to improve the sensor sensitivity, it is necessary to increase the clearance, and it is difficult to reduce the diameter of the glow plug with a combustion pressure sensor.

  The present invention has been made in order to solve the above-described problems, and is a glow plug with a combustion pressure sensor that is not easily affected by deformation of the engine head, can obtain good sensor sensitivity, and can be reduced in diameter. The purpose is to provide.

  In order to achieve the above object, a glow plug with a combustion pressure sensor according to a first aspect of the present invention includes a metal shell having an axial hole extending along the axial direction, a heater that generates heat when energized, and a rear end side of the heater. A heater member positioned and electrically connected to the heater, the heater member disposed in the shaft hole so as to be displaced along the axial direction; and a combustion pressure of the internal combustion engine And a combustion pressure sensor for detecting a combustion pressure transmitted through the heater member that is displaced in the axial direction in response, a convex portion projecting from the inner wall surface of the shaft hole, and a leading end side in the axial direction from the convex portion or And a protrusion having a connecting portion that extends toward the rear end side and holds the heater member.

  According to a second aspect of the present invention, the glow plug with a combustion pressure sensor includes the flexible portion in addition to the configuration of the first aspect of the invention.

  A glow plug with a combustion pressure sensor according to a third aspect of the invention is characterized in that, in addition to the configuration of the invention according to the first or second aspect, the connecting portion extends toward the distal end side in the axial direction. To do.

  According to a fourth aspect of the present invention, a glow plug with a combustion pressure sensor includes a mounting hole of an internal combustion engine on an outer peripheral surface of the metal shell in addition to the configuration of the first aspect of the present invention. A screw part to be screwed and a seal part that contacts the inner peripheral surface of the mounting hole on the tip side from the screw part are formed, and of the convex part, a coupling site with the inner wall surface of the shaft hole is: It exists between the said thread part and the said seal part, It is characterized by the above-mentioned.

  A glow plug with a combustion pressure sensor according to a fifth aspect of the present invention is the glow plug with a combustion pressure sensor according to the fourth aspect of the present invention. The more distal portion has a portion whose thickness is formed thinner than the thickness of the portion on the rear end side from the binding portion.

  According to a sixth aspect of the present invention, in the glow plug with a combustion pressure sensor, in addition to the configuration of the fourth aspect of the present invention, in the metal shell, the coupling site between the seal portion and the screw portion. The more distal portion has a portion configured such that its hardness is lower than the hardness of the portion on the rear end side from the coupling portion.

  According to a seventh aspect of the present invention, the glow plug with a combustion pressure sensor includes a mounting hole for an internal combustion engine on the outer peripheral surface of the metal shell. A screw part to be screwed and a seal part that abuts on the inner peripheral surface of the mounting hole on the tip side with respect to the screw part are formed, and, of the convex part, the coupling site with the inner wall surface of the shaft hole is , Being on the rear end side with respect to the threaded portion.

  According to an eighth aspect of the present invention, the glow plug with a combustion pressure sensor includes the tip of the metal shell, the tip of which forms a distal end portion in the axial direction, in addition to the structure of the first aspect of the invention. It is comprised from the side metal shell and the rear end side metal shell which makes | forms the site | part of a rear end side, The said convex part is couple | bonded with the said rear end side metal shell, It is characterized by the above-mentioned.

  A glow plug with a combustion pressure sensor according to a ninth aspect of the invention is the glow plug with a combustion pressure sensor according to any one of the first to eighth aspects, wherein the protruding portion is disposed in the shaft hole via the protruding portion. The airtightness in the shaft hole is maintained so that the combustion gas does not flow.

  A glow plug with a combustion pressure sensor according to a tenth aspect of the invention is characterized in that, in addition to the configuration of the invention according to any one of the first to ninth aspects, the connecting portion is formed in a cylindrical shape. To do.

  In the glow plug with a combustion pressure sensor according to the first aspect of the present invention, the heater member disposed in the shaft hole of the metal shell is coupled to the metal shell via the protruding portion and is not directly fixed to the metal shell. Even if the metal shell is deformed as the engine head is deformed, the heater member is hardly displaced. On the other hand, when the heater member receives a direct pressing force, the protrusion can be deformed to cause the heater member to be displaced. Thereby, it is difficult to be affected by the deformation of the engine head caused by the combustion pressure generated in the other cylinders, and it is possible to reduce the superimposition of noise on the detection result of the combustion pressure, and the attached engine head It is possible to detect a combustion pressure that does not depend on rigidity. Further, by deforming the connecting portion of the projecting portion, the deformed portion becomes larger than the membrane, so that the distance that the heater member can be displaced can be increased, and as a result, the sensitivity of the combustion pressure sensor can be improved. . Moreover, even if the clearance between the metal shell and the heater member is reduced, by adjusting the hardness, length, and thickness of the connecting portion, the deformable size of the connecting portion, that is, the distance by which the heater member can be displaced Therefore, it is possible to reduce the diameter of the glow plug with the combustion pressure sensor while sufficiently ensuring the sensitivity of the combustion pressure sensor.

  And if the flexible part is provided in a connection part like the glow plug with a combustion pressure sensor of the invention which concerns on Claim 2, a protrusion part will deform | transform elastically by bending in a radial direction in a flexible part. Can do. Furthermore, by adjusting the hardness, length, and thickness of the connecting portion, the amount of deformation in the axial direction of the protruding portion can be easily increased without increasing the clearance between the metal shell and the heater member. it can. Accordingly, the distance that the heater member can be displaced can be increased, and the sensitivity of the combustion pressure sensor can be improved.

  Further, as in the glow plug with a combustion pressure sensor of the invention according to claim 3, if the connecting portion extends toward the tip end side in the axial direction and is coupled to the heater member at the end portion on the tip end side, the heater is generated by the combustion pressure. When the member is pressed to the rear end side of the metal shell, the connecting portion can be compressed in the axial direction. Thereby, compared with the case where it is set as the form which expands a connection part, the displacement amount of a heater member can be enlarged easily.

  In addition, combustion gas may enter between the metal shell and the heater member from the combustion chamber side. However, as in the glow plug with a combustion pressure sensor according to claim 4 of the invention, the shaft hole has a shaft hole. Since the joint portion with the inner wall surface is between the screw portion and the seal portion of the metal shell, the combustion gas is less likely to enter the rear end side than the joint portion. Therefore, the site | part in which the thread part of the metal shell was formed is not easily exposed to high-temperature combustion gas. Thereby, the possibility that the screw loosening due to the thermal expansion of the screw portion may occur can be reduced.

  By the way, the metal shell is fixed to the mounting hole by bringing the seal portion into contact with the mounting hole of the internal combustion engine and screwing the screw portion. When the engine head is deformed by the combustion pressure, the metal shell is screwed. The portion is compressed between the seal portion and the seal portion to cause deformation. In the glow plug with the combustion pressure sensor of the invention according to claim 5, the coupling portion of the convex portion is between the screw portion and the seal portion. By having a portion where the thickness is formed thinner than the thickness of the portion on the rear end side in the portion on the tip side than the portion, the deformation of the metal shell is thinner on the tip side than the coupling portion, that is, This is likely to occur at low rigidity parts. In other words, since the metal shell is less likely to be deformed at the coupling site and the rear end portion, the relationship between the position of the coupling site with the inner wall surface of the shaft hole and the position of the heater member is the main component. It is possible to detect a combustion pressure that hardly changes depending on the deformation of the metal fitting and does not depend on the rigidity of the engine head to be attached.

  Such an effect, like the glow plug with a combustion pressure sensor of the invention according to claim 6, has a hardness of the metal shell between the seal part and the screw part at the tip side of the joint part. Can also be obtained by having a portion configured lower than the hardness of the portion on the rear end side.

  On the other hand, as in the glow plug with a combustion pressure sensor of the invention according to claim 7, when configured so that the coupling portion of the convex portion with the inner wall surface of the shaft hole is located on the rear end side of the screw portion, It is possible to prevent the coupling portion from being arranged at a portion from the seal portion to the screw portion that may cause deformation of the metal shell as the engine head is deformed. In this way, the relationship between the position of the coupling part and the position of the heater member is kept constant without making the structure of the metal shell different between the part on the front end side and the part on the rear end side of the coupling part. Therefore, it is possible to detect the combustion pressure which does not depend on the rigidity of the engine head to be attached.

  In the glow plug with a combustion pressure sensor according to the eighth aspect of the present invention, the metal shell is composed of a front metal shell and a rear metal shell, and a protrusion is coupled to the rear metal shell. With such a configuration, the protruding portion can be easily interposed between the metal shell and the heater member, and the labor for manufacturing can be reduced. In a state where the rear end side metal fitting and the projecting portion are coupled, a heater member is disposed therein to couple with the projection portion, and further, the front end side metal fitting and the rear end side metal fitting are joined to each other. If they are integrally formed, the protruding portion can be easily interposed between the metal shell and the heater member disposed in the shaft hole.

  In addition, as in the glow plug with a combustion pressure sensor according to the ninth aspect of the present invention, by holding the airtightness in the shaft hole by the projecting portion, the combustion gas enters the shaft hole from the tip end side of the shaft hole of the metal shell. Even if it enters, it does not reach the rear end side from the protrusion. Thereby, the airtightness in the combustion chamber through the shaft hole can be maintained, and it is possible to prevent the gas from being lost and the combustion pressure sensor from being exposed to high-temperature combustion gas.

  In addition, as in the glow plug with a combustion pressure sensor according to the tenth aspect of the present invention, when the connecting portion is formed in a cylindrical shape, the internal stress applied to the connecting portion when the heater member is displaced is centered on the axis. Can be even. In this way, since the heater member can be displaced in a direction parallel to the axial direction without generating a radial component of the connecting portion as a displacement direction component of the heater member, a stable combustion pressure detection result is obtained. be able to. Further, unlike the square tube, there is no portion where stress such as corners is concentrated, so that the durability of the connecting portion can be enhanced.

  Hereinafter, an embodiment of a glow plug with a combustion pressure sensor embodying the present invention will be described with reference to the drawings. First, the structure of the glow plug 1 of the present embodiment as an example of a glow plug with a combustion pressure sensor will be described with reference to FIGS. FIG. 1 is a partially cutaway longitudinal sectional view of the glow plug 1. FIG. 2 is an enlarged cross-sectional view of the tip side of the glow plug 1 attached to the engine head 200. In the direction of the axis O, the side where the ceramic heater 20 is disposed (the lower side in FIG. 1) is the front end side of the glow plug 1, and the side where the combustion pressure sensor 100 is disposed (the upper side in FIG. 1) is the rear end side. explain.

  The glow plug 1 of the present embodiment is attached to, for example, an engine head of a diesel engine, and is used as a heat source that assists ignition at the start of the engine. As shown in FIG. 1, the ceramic heater 20 is disposed in the direction of the axis O on the front end side of the metal shell 40, and is mechanically connected to the middle shaft 30 inserted through the shaft holes 51 and 61 of the metal shell 40. The heater member 10 is integrated. The ceramic heater 20 of the heater member 10 is exposed at the front end side in the combustion chamber, and is displaced in the direction of the axis O when receiving a pressing force due to the combustion pressure, and the pressing pressure is provided on the rear end side of the metal shell 40. It is comprised so that it may be transmitted.

  The metal shell 40 is a long and thin cylindrical metal member having shaft holes 51 and 61 penetrating in the direction of the axis O, and two components divided in the direction of the axis O being welded at the joint portion 41. On the distal end side metal shell 50 on the distal end side from the joint portion 41, a screw portion 52 for attaching the glow plug 1 to the mounting hole 210 (see FIG. 2) of the engine head 200 is formed on the outer peripheral surface on the rear end side. Yes. The inner diameter of the shaft hole 51 of the distal end side metal shell 50 is reduced at the distal end portion 55, and a seal portion 53 having a tapered surface 54 that tapers toward the distal end side is formed at the distal end portion 55. The seal portion 53 abuts the tapered surface 54 on a locking surface 220 (see FIG. 2) formed on the tip end side (lower combustion chamber side in the drawing) of the mounting hole 210, and the inner peripheral surface of the mounting hole 210. This is a part for preventing combustion gas from entering between the outer peripheral surface of the metal shell 40 and the outer peripheral surface of the metal shell 40.

  In addition, a tool engaging portion 66 that engages a tool used for attachment to the engine head 200 is formed in the rear end side metal shell 60 on the rear end side from the joint portion 41. On the rear end side of the tool engaging portion 66, a combustion pressure sensor 100 to be described later is fixed to the rear end side metal shell 60, so that the cross section orthogonal to the axis O is annular and directed toward the rear end side in the axis O direction. A base end portion 62 that protrudes like a wall is provided. Further, the inner diameter of the shaft hole 61 of the rear end side metal shell 60 is expanded in the tool engaging portion 66, and is configured as a diameter expanded portion 63.

  A convex portion 64 that protrudes from the inner wall surface of the shaft hole 51 is formed at the distal end portion (near the joint portion 41) of the rear end side metal shell 60. Furthermore, the outer diameter of the front end side of the convex portion 64 is reduced in two stages, and a rear end portion 92 of a pressure detection sleeve 90 described later is engaged with the outer periphery of the small diameter portion 65 on the most front end side.

  A metal center shaft 30 made of an iron-based material (for example, Fe—Cr—Mo steel) extending in the direction of the axis O is inserted into the shaft holes 51 and 61 of the metal shell 40. A small-diameter engaging portion 31 is formed at the tip of the middle shaft 30, and a metal cylindrical connection ring 15 is fitted into the engaging portion 31. A rear end portion 29 of a ceramic heater 20 to be described later is press-fitted into the connection ring 15 to mechanically connect the center shaft 30 and the ceramic heater 20 via the connection ring 15, so that the heater member 10 is integrated. Composed.

  Further, a small-diameter rear end portion 32 is formed on the rear end side of the middle shaft 30. The rear end portion 32 is disposed at a position where the rear end portion 32 is inserted through a combustion pressure sensor 100 described later, and the rear end portion is exposed behind the combustion pressure sensor 100. A connection terminal 80 for electrical connection with an external circuit for energizing the ceramic heater 20 is fixed to the exposed portion of the rear end portion 32 by caulking.

  Next, the combustion pressure sensor 100 is provided at the base end portion 62 of the rear end side metal shell 60. The combustion pressure sensor 100 includes a known semiconductor strain gauge (a strain detection element 120 described later) in which a piezoresistive element is formed on a semiconductor substrate such as silicon, for example, and is disposed on the diaphragm. It is a sensor that detects the combustion pressure by bending. The strain member 110 fixed to the base end portion 62 of the rear end side metal shell 60 includes a ring-shaped locking portion 111 that surrounds and engages with the outer periphery of the base end portion 62, and an edge of the locking portion 111. It is comprised from the diaphragm part 112 which consists of a thin annular | circular metal plate which makes it a periphery and makes an axis line O direction into a thickness direction. The diaphragm portion 112 has flexibility and has an opening at the center, and is inserted so that the rear end portion 32 of the middle shaft 30 does not contact the opening.

  A plurality of strain detection elements 120 are pasted on the diaphragm portion 112 of the strain member 110. The strain detecting element 120 is distorted when the diaphragm portion 112 is bent, and its own resistance value changes according to the degree of the distortion. Further, a relay substrate 130 is disposed on the rear end side of the strain member 110 so as to face the diaphragm portion 112. On the relay substrate 130, an ASIC 131 or the like including a known electric circuit for converting the resistance value of the strain detection element 120 into a voltage value, amplifying it, and outputting it as a detection value is disposed. The strain detecting element 120 is electrically connected to the relay substrate 130 by a gold wire or a flexible cable (not shown). In addition, a connection cable 132 for making an electrical connection with an external circuit (not shown) such as an ECU is connected to the relay board 130.

  Further, a cylindrical tube member 140 made of an insulating ceramic is fitted to the rear end portion 32 of the middle shaft 30, and the front end is in contact with a stepped boundary portion where the rear end portion 32 of the middle shaft 30 is formed. It is fixed in the state. The rear end of the tubular member 140 is in contact with the peripheral edge of the central opening portion of the diaphragm portion 112 of the strain member 110. When the middle shaft 30 of the heater member 10 is displaced toward the rear end side in the direction of the axis O due to the combustion pressure, the opening portion of the diaphragm portion 112 is pressed by the cylindrical member 140 and the diaphragm portion 112 is bent. Yes.

  A flanged cylindrical insulating member 150 is disposed in the gap between the outer periphery of the cylindrical member 140 and the middle shaft 30 and the inner periphery of the enlarged diameter portion 63 of the rear end side metal shell 60. 30 is insulated. Further, an O-ring 160 made of, for example, silicon rubber is formed in a gap surrounded by the distal end surface of the insulating member 150, the stepped surface on the distal end side of the enlarged diameter portion 63 of the shaft hole 61, and the outer peripheral surface of the middle shaft 30. The intermediate shaft 30 is positioned so that the airtightness in the shaft holes 51 and 61 of the metal shell 40 is maintained and the outer peripheral surface of the middle shaft 30 is not in contact with the inner wall surfaces of the shaft holes 51 and 61. .

  In addition, a cover 170 is provided to cover the outer periphery and upper side (rear end side) of the strain member 110 and the relay substrate 130 disposed at the base end portion 62 of the rear end side metal shell 60. The entire outer periphery is laser-welded while being engaged with the outer periphery of the portion 111, thereby being fixed integrally with the rear end side metal shell 60. An annular insulating rubber 180 is interposed between the cover 170 and the connection terminal 80 fixed to the rear end portion 32 of the middle shaft 30 so as to insulate the two.

  Next, as shown in FIG. 2, the ceramic heater 20 disposed on the distal end side in the shaft hole 51 of the distal end side metal shell 50 has a round bar shape, and is made of an insulating ceramic in which the distal end portion 28 is processed into a curved surface shape. A heating element 24 having a substantially U-shaped cross section made of a conductive ceramic is embedded in the base 25. The heating element 24 is disposed at the tip portion 28 of the ceramic heater 20, and is connected to the heating element 21 whose both ends are folded back in a substantially U shape in accordance with the curved surface thereof, and to both ends of the heating element 21, respectively. It is comprised from the lead parts 22 and 23 embed | buried substantially parallel along the axis O toward the rear-end part 29. As shown in FIG. The heating element 21 is formed so that its cross-sectional area is smaller than the cross-sectional area of the lead portions 22 and 23, and heat is generated mainly in the heating element 21 when energized. In addition, on the outer peripheral surface of the rear end portion 29 of the ceramic heater 20, electrode extraction portions 26 and 27 protruding from the lead portions 22 and 23 are exposed at positions shifted from each other in the axis O direction. The ceramic heater 20 corresponds to the “heater” in the present invention.

  A cylindrical heater support member 70 is disposed around the outer periphery of the body portion of the ceramic heater 20. The heater support member 70 is made of a conductive metal member, and the ceramic heater 20 is fixed by press-fitting with the electrode extraction portion 26 of the rear end portion 29 exposed rearward. The electrode extraction portion 27 of the ceramic heater 20 is in contact with the inner peripheral surface of the heater support member 70, and the heater support member 70 and the lead portion 23 of the ceramic heater 20 are electrically connected. On the other hand, the electrode extraction portion 26 is in contact with the inner peripheral surface of the connection ring 15 fitted to the rear end portion 29 of the ceramic heater 20. Further, a flange 71 projecting outward is formed on the rear end side of the heater support member 70 over the entire circumference. The flange portion 71 functions as a positioning when the front end portion 96 of the intermediate sleeve 95 is engaged on the outer periphery of the engagement portion 72 on the rear end side of the flange portion 71.

  Next, the intermediate sleeve 95 surrounds the rear end portion 29 of the ceramic heater 20 fixed to the heater support member 70 and the front end portion of the intermediate shaft 30 mechanically connected to the ceramic heater 20 through the connection ring 15. The front end portion 96 is welded to the engaging portion 72 of the heater support member 70 as a tubular member. The intermediate sleeve 95 is fixed in a non-contact state with the middle shaft 30, and the two are insulated with a gap. The rear end portion 97 is formed in a step shape with a small diameter, and the front end portion 91 of the pressure detection sleeve 90 is engaged and welded thereto.

  The pressure detection sleeve 90 is a cylindrical member made of metal such as SUS, which is thinner than the intermediate sleeve 95, and is insulated from the middle shaft 30 with a gap, like the intermediate sleeve 95. The front end portion 91 of the pressure detection sleeve 90 is engaged with the rear end portion 97 of the intermediate sleeve 95, and the rear end portion 92 is engaged with the small-diameter portion 65 at the front end of the rear end side metal shell 60. Has been. Further, the portion between the front end portion 91 and the rear end portion 92 of the pressure detection sleeve 90 bends so as to spread in the radial direction when a pressure compressed in the axis O direction is applied, and the shaft of the pressure detection sleeve 90 It is configured as a flexible part 93 that can shorten the length in the direction. The pressure detection sleeve 90 and the intermediate sleeve 95 correspond to the “connecting portion” in the present invention, and the convex portion 64 corresponds to the “convex portion” in the present invention. In other words, the “projection” in the present invention is configured by the pressure detection sleeve 90, the intermediate sleeve 95, and the convex portion 64 in the present embodiment. In the present invention, the “joining portion of the convex portion with the inner wall surface of the shaft hole” is a portion in the vicinity of the base of the convex portion 64 protruding from the shaft holes 51 and 61 of the metal shell 40. In FIG. 4, the portion near the joint 41 corresponds, but the joint portion and the joint 41 do not necessarily coincide with each other, and the portion near the boundary between the shaft hole and the protruding portion corresponds. Of course, in this embodiment, the pressure detection sleeve 90, the intermediate sleeve 95, the heater support member 70, and the convex portion 64 are composed of a plurality of members including a part of the rear end side metal shell 60. These members may be used, or may be integrated with the rear end side metal shell 60. Moreover, although the convex part 64 is united with the rear-end side metal shell 60, another member may be sufficient. For example, when one end of a single member or a plurality of members corresponding to the pressure detection sleeve 90 and the intermediate sleeve 95 is directly joined to the inner wall surfaces of the shaft holes 51 and 61 of the metal shell 40, one end thereof The portion corresponds to the “convex portion” in the present invention, and the joining site corresponds to the “binding site” in the present invention.

  With such a configuration, the rear end side metal shell 60, the pressure detection sleeve 90, the intermediate sleeve 95, and the heater support member 70 are connected to each other, and the respective connected portions are integrated to maintain high airtightness. It is configured in the form of a cylindrical body. A heater member 10 composed of a ceramic heater 20 and a central shaft 30 that are integrally joined by a connection ring 15 is disposed in the cylindrical body. The ceramic heater 20 of the heater member 10 is fixed to the heater support member 70 on the front end side of the cylindrical body, and the middle shaft 30 is not in contact with the cylindrical body by an O-ring 160 disposed on the rear end side of the cylindrical body. Is supported by positioning.

  Further, the boundary portion between the front end side metal shell 50 and the rear end side main metal plate 60 is joined by welding in a state where the front end side metal shell 50 surrounds the outer periphery of the cylindrical body (that is, the welded boundary portion is The metal shell 40 is formed by integrating the front-end side metal shell 50 and the rear-end side metal shell 60. At this time, the seal portion 53 of the distal end side metal shell 50 is disposed at a position surrounding the outer periphery of the heater support member 70, but does not hold (fix) the heater support member 70. Moreover, although the inner wall surface of the shaft hole 51 of the front end side metal shell 50 and the outer wall surface of the convex portion 64 are in close contact with each other, they are not necessarily in close contact with each other and have a slight gap.

  Further, as described above, the heater support member 70 is electrically connected to the lead portion 23 via the electrode extraction portion 27 of the ceramic heater 20 inside, and the rear end side metal shell 60 and the pressure detection sleeve 90 are electrically connected. The cylindrical body comprising the intermediate sleeve 95 and the heater support member 70 functions as one electrode for applying a voltage to the heating element 21. On the other hand, the engaging portion 31 of the middle shaft 30 and the rear end portion 29 of the ceramic heater 20 are connected by a metal connection ring 15. Thereby, the lead part 22 of the ceramic heater 20 and the middle shaft 30 are electrically connected, and the middle shaft 30 functions as the other electrode for applying a voltage to the heating element 21. That is, the metal shell 40 and the central shaft 30 function as two electrodes for applying a voltage to the heating element 24 of the ceramic heater 20.

  Next, the operation of the glow plug 1 when detecting the combustion pressure of the engine will be described with reference to FIGS. FIG. 3 is an enlarged cross-sectional view of the tip end side of the glow plug 1 that has been deformed due to the pressing force due to the combustion pressure. In FIG. 3, for the sake of explanation, the bending that occurs in the distal end side metal shell 50 and the pressure detection sleeve 90 is drawn exaggerating the actual size.

  As shown in FIG. 2, when the glow plug 1 is attached to the attachment hole 210 of the engine head 200 of the internal combustion engine, the tip side metal shell 50 of the tip side metal fitting 50 is exposed with the tip portion 28 of the ceramic heater 20 exposed in the combustion chamber. The screw part 52 is screwed together. At this time, the tapered surface 54 of the seal portion 53 is brought into contact with the locking surface 220 provided on the combustion chamber side of the mounting hole 210, and the metal shell 40 is fixed to the engine head 200.

  If the pressure in the combustion chamber increases with the operation of the engine, the engine head 200 may be deformed by the combustion pressure. As shown in FIG. 3, when the seal portion 53 receives a pressing force (indicated by an arrow C in the figure) along with this deformation, the metal shell 40 is locked to the seal portion 53 and the mounting hole 210. Compressed between the screw portions 52. Then, the distal end side metal shell 50 of the metal shell 40 that has received a pressing force compressed in the direction of the axis O is bent in the radial direction at the trunk portion 56 (the portion between the seal portion 53 and the screw portion 52) (see FIG. Middle arrow A). However, the rear end side metal shell 60 joined to the front end side metal shell 50 on the rear end side in the axis O direction with respect to the screw portion 52 is hardly affected by internal stress due to the deformation of the engine head 200. Therefore, the pressure detection sleeve 90, the intermediate sleeve 95, the heater support member 70, and the heater member 10 joined to the rear end side metal shell 60 are hardly affected by the internal stress accompanying the deformation of the engine head 200. Since the heater member 10 is not fixed to the front end side metal shell 50, the displacement of the heater member 10 due to the deformation of the engine head 200 hardly occurs.

  On the other hand, when the front end portion 28 of the ceramic heater 20 exposed in the combustion chamber receives a pressing force (indicated by an arrow D in the figure) due to the combustion pressure, the rear end side metal shell 60, the pressure detection sleeve 90, the intermediate sleeve 95, and After the pressure detection sleeve 90 having the thinnest thickness and the lowest rigidity among the heater support members 70 is engaged with the front end 91 and the rear end side metal shell 60 engaged with the intermediate sleeve 95 under the action of the pressing force. A flexure (indicated by an arrow B in the figure) that expands in the radial direction is generated at the flexible portion 93 between the end portion 92. By this bending, the heater member 10 is displaced toward the rear end side in the axis O direction with respect to the rear end side metal shell 60. Then, the periphery of the opening portion of the diaphragm portion 112 of the strain member 110 is pressed toward the rear end side in the axis O direction on the rear end of the cylindrical member 140 fixed to the rear end portion 32 of the middle shaft 30. As a result, the diaphragm portion 112 bends, and strain is generated in the strain detection element 120 attached to the diaphragm portion 112. A voltage supplied from an external circuit (not shown) is applied to the strain detection element 120, and the resistance value of the strain detection element 120 that changes according to the magnitude of the distortion, that is, the magnitude of the displacement of the heater member 10. It is detected as a change in voltage value and output to the external circuit as a detected value of combustion pressure.

  The present invention can be variously modified. For example, as shown in FIG. 4, the division position of the front end side metal shell 350 and the rear end side metal shell 360, that is, the joint portion 341 may be provided on the front end side in the axis O direction with respect to the screw portion 362. As described above, the heater support member 70 is not held (fixed) by the seal portion 353 of the distal end side metal shell 350 in order to allow the heater member 10 to be displaced in the direction of the axis O. For this reason, when the engine is operated, high-temperature combustion gas passes through the gap between the seal portion 353 and the heater support member 70, and the inner circumference of the front end side metal shell 350, the rear end side metal shell 360, the pressure In some cases, the detection sleeve 90, the intermediate sleeve 95, and the heater support member 70 may enter the outer periphery of the cylindrical body. At this time, the combustion gas reaches the joint portion 341 between the front end side metal shell 350 and the rear end side metal shell 360, but since the joint portion 341 is located on the front side from the screw portion 362 as described above, Never reach. With such a configuration, it is difficult for the thermal load due to the combustion gas to be applied to the screw portion 362, and it is possible to prevent occurrence of loose mounting of the screw portion 362 due to thermal expansion.

  Further, as shown in FIG. 5, the division position of the front end side metal shell 450 and the rear end side metal shell 460, that is, the joint portion 441 may be further provided on the front end side than in the modification of FIG. 4. If comprised in this way, the heat load by the above combustion gas can be made hard to apply to the thread part 462 more. At this time, if the thickness F of the body portion 456 of the front end side metal shell 450 is made smaller than the thickness E of the body portion 466 of the rear end side metal shell 460, the front end of the rear end side metal shell 460 will be more distal than the body portion 466. The rigidity of the body 456 of the side metal shell 450 can be reduced. Then, when the metal shell 440 is compressed between the seal portion 453 and the screw portion 462 by the pressing force due to the combustion pressure, the body portion 456 can be reliably bent, and the same effect as the present embodiment. Can be obtained. In this case, if a sufficient distance cannot be provided between the rear end side metal shell 460 and the heater support member 70, the intermediate sleeve 95 of the present embodiment is omitted from the configuration, and the pressure detection sleeve 90 causes the heater to be removed. The support member 70 and the convex portion 64 of the rear end side metal shell 460 may be connected.

  In the modification shown in FIG. 5, the hardness of the body 456 of the front end metal shell 450 may be lower than the hardness of the body 466 of the rear end metal shell 460. In this way, as in the above modification, when the metal shell 440 is compressed between the seal portion 453 and the screw portion 462 by the pressing force due to the combustion pressure, the body portion 456 can be reliably bent. it can. Further, the above modifications may be combined so that the thickness F and hardness of the body 456 of the front end side metal shell 450 are thinner and lower than the thickness E and hardness of the body 466 of the rear end side metal shell 460. . That is, when the metallic shell 440 is compressed between the seal portion 453 and the screw portion 462 by the pressing force due to the combustion pressure, the body of the distal metallic shell 450 which is a portion closer to the distal side than the joint portion 441 between them. The portion 456 may be configured to be more easily bent than the body portion 466 of the rear end side metal shell 460, which is a portion on the rear end side from the joint portion 441.

  In this embodiment, a piezoresistive element is used as the strain detecting element 120 of the combustion pressure sensor 100. However, when a resistor made of a metal such as copper or nickel alloy is formed on a thin insulating plate, it is meandered. For example, a strain gauge configured to increase the distance between the electrodes may be used. Alternatively, a piezoelectric charge type element may be used as the strain detection element 120. In this case, the piezoelectric charge-type element may be pressed when the center shaft is displaced by the pressing force due to the combustion pressure, and the generated charge may be output as a detection value. Alternatively, a preload may be applied to the piezoelectric charge element in advance, and the generated load may be output as a detection value so that the preload is relaxed when the center shaft is displaced by the pressing force due to the combustion pressure. Alternatively, an optical position sensor may be used to measure the displacement amount and displacement speed (or acceleration) of the central shaft, and the combustion pressure may be calculated based on the measurement result.

  Further, a temperature sensing element capable of detecting the temperature is provided on the substrate of the strain sensing element 120, and the detected value of the combustion pressure detected by the strain sensing element 120 is corrected based on the temperature information detected by the temperature sensing element. A temperature compensation circuit may be provided in the ASIC 131.

  The heater member provided in the glow plug 1 is provided with the ceramic heater 20 in the present embodiment. However, a sheath in which a coil-shaped heating resistor and a control coil are disposed in a sheath tube whose tip is closed in a hemispherical shape. A heater may be used.

  The pressure detection sleeve 90 can be a plate spring-like member or a spring-like member, and the same effect can be obtained, but from the viewpoint of maintaining the airtightness in the shaft hole 61 of the rear end side metal shell 60. It is preferable that it is a cylindrical member. In this case, a square tube may be used, and the cylinder may be a perfect circle or an ellipse. However, the direction component orthogonal to the axis O of the internal stress applied to the pressure detection sleeve 90 is uniform around the axis O. In order to keep the displacement direction of the central shaft 30 of the heater member 10 constant, it is desirable that no bias be provided. More desirably, it is preferably a cylinder.

  In addition, a bellows-like cylindrical body may be used as the pressure detection sleeve, and the amount of displacement may be increased by causing bending at a plurality of locations in the axis O direction. The same effect may be obtained by forming it thinly. A plurality of pressure detection sleeves may be disposed in the direction of the axis O.

  The present invention can be used for a combustion pressure sensor that detects the combustion pressure of an internal combustion engine, a glow plug equipped with a combustion pressure sensor, a temperature sensor, and the like.

2 is a partially cutaway longitudinal sectional view of the glow plug 1. FIG. 2 is an enlarged cross-sectional view of the tip side of a glow plug 1 attached to an engine head 200. FIG. FIG. 3 is an enlarged cross-sectional view of the tip side of the glow plug 1 that is deformed by receiving a pressing force due to combustion pressure. It is a partially cutaway longitudinal cross-sectional view of the glow plug 300 as a modification. It is a partially cutaway longitudinal cross-sectional view of the glow plug 400 as a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glow plug 10 Heater member 20 Ceramic heater 30 Middle shaft 40 Main metal fitting 41 Joining part 50 Front end side main metal fitting 51,61 Shaft hole 52 Screw part 53 Sealing part 60 Rear end side main metal fitting 90 Pressure detection sleeve 91 Front end part 92 Rear end part 93 Flexible part 100 Combustion pressure sensor

Claims (10)

A metal shell having an axial hole extending along the axial direction;
A heater member having a heater that generates heat by energization and a middle shaft that is located on the rear end side of the heater and is electrically connected to the heater, and is disposed in the shaft hole so as to be displaced along the axial direction. A heater member to be disposed;
A combustion pressure sensor that detects a combustion pressure transmitted through the heater member that is displaced in the axial direction in accordance with a combustion pressure of an internal combustion engine;
A projection that protrudes from the inner wall surface of the shaft hole and a projection that extends from the projection toward the front end side or the rear end side in the axial direction and that holds the heater member. A glow plug with a combustion pressure sensor.   The glow plug with a combustion pressure sensor according to claim 1, wherein the connecting portion includes a flexible portion having flexibility.   The glow plug with a combustion pressure sensor according to claim 1 or 2, wherein the connecting portion extends toward a tip end side in the axial direction. On the outer peripheral surface of the metal shell, there are formed a screw portion that is screwed into the mounting hole of the internal combustion engine, and a seal portion that is in contact with the inner peripheral surface of the mounting hole on the tip side from the screw portion,
4. The combustion pressure sensor according to claim 1, wherein a connecting portion of the convex portion with the inner wall surface of the shaft hole is between the screw portion and the seal portion. Glow plug.   Of the metal shell, between the seal part and the threaded part, the part formed on the front end side of the joint part is thinner than the part on the rear end side of the joint part. The glow plug with a combustion pressure sensor according to claim 4, comprising:   Of the metal shell, between the seal part and the threaded part, the part of the tip side from the joint part is configured so that the hardness is lower than the hardness of the part at the rear end side from the joint part. The glow plug with a combustion pressure sensor according to claim 4, comprising: On the outer peripheral surface of the metal shell, there are formed a screw portion that is screwed into a mounting hole of the internal combustion engine, and a seal portion that is in contact with the inner peripheral surface of the mounting hole on the tip side of the screw portion,
The glow plug with a combustion pressure sensor according to any one of claims 1 to 3, wherein a connecting portion of the convex portion with the inner wall surface of the shaft hole is located on a rear end side with respect to the screw portion. The metal shell is composed of a front-end-side metal shell that forms a front-side portion in the axial direction, and a rear-end-side metal shell that forms a rear-end side portion,
The glow plug with a combustion pressure sensor according to any one of claims 1 to 7, wherein the convex portion is coupled to the rear end side metal shell.   9. The projecting portion according to claim 1, wherein the projecting portion maintains airtightness in the shaft hole so that combustion gas does not flow through the projecting portion through the projecting portion. Glow plug with combustion pressure sensor as described. The glow plug with a combustion pressure sensor according to claim 1, wherein the connecting portion is formed in a cylindrical shape.

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