JP2010139148A - Glow plug with combustion pressure sensor and internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug with a combustion pressure sensor and an internal combustion engine capable of suppressing degradation of combustion pressure detecting sensitivity caused by clogging of soot dust without degrading productivity and increasing the manufacturing cost, suppressing fluctuation of properties as the glow plug, and improving reliability and durability. <P>SOLUTION: In this glow plug with the combustion pressure sensor, an inner peripheral face 8 of an opening 6 of a sheet member 2 has the linear shape from an axial rear end toward an axial distal end, or the shape expanded from the axial rear end toward the axial distal end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a glow plug with a combustion pressure sensor used for an internal combustion engine such as an automobile engine, and an internal combustion engine to which the glow plug is attached.

  2. Description of the Related Art Conventionally, a glow plug with a combustion pressure sensor provided with a combustion pressure sensor for detecting the combustion pressure of the internal combustion engine is known as a glow plug used in an internal combustion engine such as a diesel engine for automobiles.

  In such a glow plug with a combustion pressure sensor, a connecting portion (movable portion) that holds between the heater and the housing that houses the rear end side of the heater while allowing relative displacement in the axial direction of the heater with respect to the housing. ) Must be provided. As this connection part, it is common to make relative displacement easy by reducing the thickness of the member, and to increase the transmission load to the combustion pressure sensor.

  Further, in the glow plug with a combustion pressure sensor, as shown in FIG. 8, a sheet member 2 having a tapered sheet surface 7 is provided at the distal end portion of the housing 1 that houses the heater 20 so that the distal end side protrudes. The sheet surface 7 of the sheet member 2 is brought into pressure contact with a taper sheet provided in the glow hole of the internal combustion engine so as to be airtight. For this reason, in order to avoid the influence of the deformation | transformation etc. by the fastening torque at the time of attaching the glow plug with a combustion pressure sensor itself to an internal combustion engine, the said connection part 11 is provided in the rear end side from the seat surface 7 of the seat member 2. Many. An inner peripheral portion of the connecting portion 11 is a movable portion 12 that is thin (thickness, for example, 0.3 mm). The sheet member 2 has an annular shape having an opening 6 for projecting the heater 20 at the center.

  In this case, the movable portion 12 has a structure in which the heater 20 is easily displaced in the axial direction by reducing the thickness of the member, and the movable portion 12 is airtight. In addition, the front end portion of the sheet member 2 has a structure having a protruding portion 9 that protrudes toward the inner peripheral side so as to narrow the distance between the outer periphery of the heater 20 and the inner periphery of the sheet member 2. For this reason, when a glow plug with a combustion pressure sensor is mounted on an internal combustion engine and used, the inner peripheral surface of the sheet member 2 and the movable portion 12 on the outside of the heater 20 (outside of the heater holding member 10) by the combustion gas. In some cases, the wrinkles are clogged in the space 15 surrounded by the surface on the tip side in the axial direction. When the soot is clogged in the space 15 as described above, the heater 20 is difficult to be displaced in the axial direction, and the detection sensitivity of the combustion pressure is lowered, and the heat transfer state from the heater 20 to the housing 1 changes. As a result, there arises a problem that the characteristics of the glow plug with the combustion pressure sensor vary.

In addition, a technique is known in which a heat-resistant member is packed in advance in the above-described space in order to prevent clogging of wrinkles as described above (for example, see Patent Document 1). However, with this technology, the process of filling the heat-resistant member increases, resulting in a decrease in productivity and an increase in manufacturing cost, and the presence of the heat-resistant member, resulting in a decrease in combustion pressure detection sensitivity and a glow plug with a combustion pressure sensor. There was a problem that fluctuations in characteristics occurred.
WO2007 / 073959A1

  As described above, the glow plug with the combustion pressure sensor has a problem in that the sensitivity of the combustion pressure detection is lowered due to clogging of the soot and the characteristics of the glow plug with the combustion pressure sensor are changed. Moreover, in the technology of prepacking the heat-resistant member in advance, the process of filling the heat-resistant member increases, and therefore the problem of inviting a decrease in productivity and an increase in manufacturing cost, and the presence of the heat-resistant member, There was a problem that the characteristics of the glow plug with the combustion pressure sensor fluctuated.

  The present invention has been made to solve the above problems. The present invention can suppress a decrease in combustion pressure detection sensitivity due to clogging of soot without causing a decrease in productivity and an increase in manufacturing cost, and can suppress a variation in characteristics as a glow plug, It is an object of the present invention to provide a glow plug with a combustion pressure sensor and an internal combustion engine capable of improving reliability and durability.

  A glow plug with a combustion pressure sensor of the present invention has a cylindrical housing, a pressure detection element disposed in the housing, and a columnar outer shape extending in the axial direction, and a tip side of the housing A heater that protrudes from the tip and is provided so that the rear end is accommodated in the housing, the tip surface is a pressure receiving surface, a combustion pressure is transmitted to the pressure detection element, and a cylindrical portion that holds the heater; The cylindrical portion and the housing are connected directly or through another member, and the connecting portion has a portion that allows relative displacement in the axial direction of the heater with respect to the housing and is exposed to combustion gas. An annular shape having a heater holding member and an opening for projecting the heater in the radial center portion is located on the tip side in the axial direction with respect to the connecting portion, and is provided in the internal combustion engine. A glow plug with a combustion pressure sensor, wherein the shape of the inner peripheral surface of the opening of the seat member is axial from the rear end in the axial direction. It is characterized by having a linear shape toward the tip or a shape that expands from the rear end in the axial direction toward the tip in the axial direction.

  In the glow plug with a combustion pressure sensor of the present invention, the shape of the inner peripheral surface of the opening of the seat member is a linear shape from the axial rear end to the axial front end, or from the axial rear end to the axial front end. It is set as the shape which expands toward it. As a result, it is possible to prevent the combustion gas from staying in the space surrounded by the inner peripheral surface of the sheet member and the axially distal end surface of the connecting portion (movable portion) on the outer side of the heater. Since the soot can be prevented from being clogged in this space, it is possible to suppress the deterioration of the combustion pressure detection sensitivity due to the clogging of the soot, and to suppress the fluctuation of the characteristics as the glow plug. And durability can be improved. In addition, there is no increase in the number of steps such as packing the heat-resistant member, and no reduction in productivity or increase in manufacturing cost is caused.

  Further, the internal combustion engine of the present invention has a cylindrical housing, a pressure detecting element disposed in the housing, and a columnar outer shape extending in the axial direction, and a distal end side is a distal end portion of the housing. And a rear end side is provided so as to be accommodated in the housing, a front end surface is a pressure receiving surface, a heater that transmits combustion pressure to the pressure detection element, a cylindrical portion that holds the heater, and the cylinder And a housing having a portion that allows a relative displacement in the axial direction of the heater relative to the housing and that is exposed to combustion gas. A taper sheet provided in the internal combustion engine, having a member and an annular shape having an opening for projecting the heater at a radially central portion, located on the axial front end side with respect to the connecting portion; A sheet member having a tapered sheet surface to be touched, and the shape of the inner peripheral surface of the opening of the sheet member is a linear shape from the rear end in the axial direction toward the front end in the axial direction, or in the axial direction A glow plug with a combustion pressure sensor, which has a shape that expands from the rear end toward the front end in the axial direction, is an internal combustion engine that is mounted in a glow hole that leads to a combustion chamber, and is provided in the glow hole. The diameter of the glow hole closer to the combustion chamber than the tapered sheet is larger than the diameter of the tip of the opening in the axial direction.

  In the internal combustion engine of the present invention, the glow hole diameter on the combustion chamber side from the taper sheet provided in the glow hole is larger than the diameter of the tip end in the axial direction of the opening of the glow plug with the combustion pressure sensor. As a result, in the glow plug with a combustion pressure sensor, the combustion gas stays in a space surrounded by the inner peripheral surface of the sheet member and the axially distal end surface of the connecting portion (movable portion) on the outer side of the heater. This can be further suppressed, and the clogging of this space can be further suppressed.

  According to the present invention, it is possible to suppress a decrease in combustion pressure detection sensitivity due to clogging of soot and to suppress fluctuations in characteristics as a glow plug without causing a decrease in productivity and an increase in manufacturing cost. It is possible to provide a glow plug with a combustion pressure sensor and an internal combustion engine that can improve reliability and durability.

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a configuration of a glow plug 100 with a combustion pressure sensor according to an embodiment of the present invention, and FIG. 1 (a) is a side view showing the overall configuration of the glow plug 100 with a combustion pressure sensor. 1 (b) is a cross-sectional view showing the overall configuration of the glow plug 100 with a combustion pressure sensor, and FIG. 2 is an enlarged cross-sectional view showing the main part of FIG. 1 (b). In addition, the dashed-dotted line O shown in FIG. 1, FIG. 2 is an axis which shows an axial direction.

  As shown in FIG. 1, the glow plug 100 with a combustion pressure sensor is made of a high-strength metal such as carbon steel (S45C, etc.), stainless steel (eg, SUS430, SUS630, etc.), and is formed in a substantially cylindrical shape. A housing 1 is provided. A sheet member 2 is provided at the axial end of the housing 1 (the lower end in FIG. 1).

  As shown in FIG. 1 (a), a threaded portion 4 for attaching the glow plug 100 with a combustion pressure sensor to an internal combustion engine (engine) (not shown) is formed on the outer peripheral surface of the housing 1. A tool engaging portion 5 for engaging a tool such as a spanner or a wrench when the housing 1 is attached to the engine is provided on the outer peripheral portion on the axial rear end side (upper side in FIG. 1) of the screw portion 4. Yes. The housing 1 is provided with a heater 20 so that the front end protrudes from the front end of the housing 1 and the rear end is accommodated in the housing 1. The heater 20 has a columnar shape extending in the axial direction.

  The seat member 2 has an annular shape having an opening 6 for projecting the heater 20 from the front end of the housing 1, and the axial front end side end surface thereof is an internal combustion engine such as an automobile diesel engine. A tapered sheet surface 7 is formed in close contact with the sheet. In the opening 6, a heater support member (cylindrical portion) 10 made of a metal such as stainless steel (for example, SUS430, SUS630, etc.) and formed in a substantially cylindrical shape is provided. The heater 20 is held on the surface. A substrate 62 on which an IC (ASIC) 61 is mounted is disposed on the rear end side in the housing 1. The substrate 62 constitutes a signal processing circuit for processing a pressure detection signal of the pressure detection element 46 described later.

  As shown in FIG. 2, the heater 20 is composed of a ceramic heater (made of silicon nitride, alumina or the like) having a structure in which a conductive ceramic 22 is embedded in an insulating ceramic 21 as an insulating base material. On the side peripheral surface of the heater 20, an exposed portion (cathode side) 23 and an exposed portion (anode side) 24 where the conductive ceramic 22 is exposed are provided. Among these, the exposed portion (cathode side) 23 provided on the more distal end side in the axial direction is covered by the heater support member 10, and the exposed portion (cathode side) 23 and the heater support member 10 are electrically connected. . Since the ceramic heater 20 and the metal heater support member 10 cannot be joined by welding, they are joined by brazing or press fitting (in this embodiment, press fitting).

  On the other hand, the exposed portion (anode side) 24 provided on the rear end side in the axial direction from the exposed portion (cathode side) 23 is made of a metal such as stainless steel (for example, SUS430, SUS630, etc.) and is formed in a substantially cylindrical shape. The exposed portion (anode side) 24 is electrically connected to the ring member 30. The heater 20 and the ring member 30 are also joined by brazing or press-fitting (press-fitting in this embodiment). The tip surface 25 of the heater 20 shown in FIG. 1 is a pressure receiving surface that receives the combustion pressure in the combustion chamber.

  As shown in FIG. 2, the heater support member 10 includes a connecting portion 11 formed of a flange protruding outward in a bowl shape at the rear end portion. Moreover, the inner peripheral part of this connection part 11 is made into the movable part 12 made thin (for example, thickness 0.3mm). The movable portion 12 has a function of displacing the heater 20 in the axial direction by elastically deforming according to the combustion pressure applied to the pressure receiving surface 25 of the heater 20.

  In the sheet member 2 constituting the front end portion of the housing 1, the shape of the inner peripheral surface 8 of the opening 6 is linear from the rear end in the axial direction toward the front end in the axial direction. As shown in FIG. 3, the shape of the inner peripheral surface 8 of the opening 6 of the sheet member 2 may be a shape (tapered shape) that increases in diameter from the rear end in the axial direction toward the front end in the axial direction. That is, the shape of the inner peripheral surface 8 of the opening 6 of the sheet member 2 is a shape in which the inner diameter on the front end side does not become smaller when two portions adjacent in the axial direction are compared. By adopting such a shape, the space 15 surrounded by the inner peripheral surface 8 of the sheet member 2 and the surface on the front end side in the axial direction of the movable portion 12 (the portion exposed to the combustion gas) of the outer portion of the heater 20. It is possible to suppress the combustion gas from staying inside, and to suppress the clogging of the soot in the space 15. Accordingly, it is possible to suppress a decrease in combustion pressure detection sensitivity due to clogging of soot, and to suppress fluctuations in characteristics as a glow plug, thereby improving reliability and durability. In addition, there is no increase in the number of steps such as packing the heat-resistant member, and no reduction in productivity or increase in manufacturing cost is caused.

  A cylindrical member 40 that extends in a cylindrical shape toward the rear end side and holds the pressure detection element is provided on the rear end side of the connecting portion 11 of the heater support member 10. A flange portion 41 is formed on the outer side of the cylindrical member 40 in the axial direction so as to protrude outwardly in a bowl shape. And this flange part 41 and the outer peripheral part of the connection part 11 of the above-mentioned heater support member 10 are fixed by welding etc. in the state interposed between the sheet | seat member 2 and the housing 1, and thereby a cylindrical member 40 and the heater support member 10 are connected to the housing 1.

  An insulating plate 42 formed in a disc shape is fixed to a rear end side end portion of the cylindrical member 40 by a cylindrical body 45 provided on the rear end side. As shown in FIG. 4, the insulating plate 42 is provided with a glow electrode 43 and a plurality of (for example, three) element electrodes 44 penetrating the insulating plate 42.

  A pressure detection element 46 is disposed on the surface on the tip side of the insulating plate 42. The pressure detection element 46 is fixed to the front surface of the insulating plate 42 via a lower insulating plate 47 such as glass. Further, an upper insulating plate 48 such as glass is provided on the surface of the pressure detecting element 46 on the tip side. Each element electrode 44 and the pressure detection element 46 are connected by a bonding wire 49.

  As shown in FIG. 2, the pressure detecting element 46 includes a hemispherical member 50 made of bearing steel or the like and formed in a hemispherical shape on the front end side, and a rear end side made of an insulating material such as ceramic, in accordance with the shape of the hemispherical member 50. It is fixed with an initial load applied to the rear end of the heater 20 via the insulating member 51 having the shape.

  FIG. 5 shows a part of the manufacturing process of the glow plug 100 with the combustion pressure sensor having the above structure. As shown in FIG. 5A, from the state in which the heater 20 to which the heater support member 10 and the cylindrical member 40 are fixed is fixed to the housing 1, first, the insulating member 51 and the hemispherical member 50 are disposed on the rear end side of the heater 20. (B). Next, the insulating plate 42 shown in FIG. 4 on which the pressure detecting element 46 and the like are mounted is disposed on the rear end side of the hemispherical member 50 (c). Thereafter, the cylindrical body 45 is disposed on the rear end side of the insulating plate 42, and the cylindrical body 45 on the rear end side is welded to the cylindrical member 40 in a state where an initial load is applied (d). Through such a process, the pressure detection element 46 is fixed in a state in which the combustion pressure can be detected by the axial displacement of the heater 20. The glow electrode 43 is fixed to the cylindrical member 40 side in advance, and is assembled so that the glow electrode 43 is positioned in a through hole provided in the insulating plate 42.

  As described above, when the axial displacement of the heater 20 due to the combustion pressure is detected by the pressure detection element 46, the pressure detection element 46 is composed of, for example, a piezoresistive element such as an Si element or an SOI element, and pressure is applied. What was comprised so that the electrical signal according to the distortion at the time of output may be used can be used. When such a pressure detection element 46 is configured, a structure in which an element such as an Si element or an SOI element is bonded to a substrate made of glass, metal, or the like can be used. A piezoresistor is formed on the surface of the element, and pressure is detected from a change in resistance value when the element is strained and deformed. In addition, piezoelectric elements such as PZT and quartz can also be used.

  The detection signal of the pressure detection element 46 is processed by a signal processing circuit provided on the substrate 62 built in the glow plug 100 with the combustion pressure sensor, or a signal processing circuit provided outside, and then a control device such as an ECU. And a change in the combustion pressure in the engine is detected.

  In the glow plug 100 with the combustion pressure sensor configured as described above, as shown in FIG. 1, the front end portion of the heater 20 protrudes from the front end portion of the housing 1. Then, as shown in FIG. 6, the glow plug 100 is inserted into the glow hole 201 leading to the combustion chamber (not shown) of the internal combustion engine 200, and the screw portion 4 shown in FIG. Airtightness is secured by bringing the seat surface 7 into contact with a taper seat 203 provided in the glow hole 201 of the internal combustion engine 200 by tightening to a mounting screw (not shown). In this state, the heater 20 is attached to the internal combustion engine so that the front end side is located in the combustion chamber, and the heater 20 is energized to generate heat, thereby assisting in starting the internal combustion engine.

  Here, in the internal combustion engine 200 shown in FIG. 6, the diameter R of the glow hole 202 on the combustion chamber side (lower side in FIG. 6) from the taper sheet 203 is larger than the diameter r of the opening 6 of the seat member 2. It is configured. Therefore, ventilation between the combustion chamber (not shown) of the internal combustion engine 200 and the space 15 of the glow plug 100 is further promoted, and the retention of combustion gas in the space 15 can be further suppressed. As a result, it is possible to further suppress clogging of the soot in the space 15.

  When the combustion pressure is applied to the front end surface (pressure receiving surface) 25 of the heater 20 with the glow plug 100 attached to the internal combustion engine 200 as described above, the movable portion 12 is elastically deformed (flexed). The heater 20 is displaced in the axial direction toward the rear, and the pressure detecting element 46 is pressed through the insulating member 51 and the hemispherical member 50. The insulating plate 42 on which the pressure detection element 46 is arranged is held on the axial rear end side by a cylindrical body 45 welded to the cylindrical member 40 all around the cylindrical member 40. Since the pressure detection element 46 receives a pressing force, an output signal corresponding to the pressing force is generated. The output signal of the pressure detection element 46 is transmitted to the signal processing circuit provided on the substrate 62 by the sensor terminal 44 and amplified by the signal processing circuit.

  In addition, the connection part 11 may be the structure which connects the heater support member 10 and the housing 1 via another member in addition to what connects the heater support member 10 and the housing 1 directly. For example, as shown in FIG. 7, the connecting portion 11 may be connected to the housing 1 via a cylindrical member 40.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

The figure which shows the whole glow plug with a combustion pressure sensor which concerns on embodiment of this invention, and a cross-sectional structure. The figure which shows the cross-sectional structure of the principal part of the glow plug with a combustion pressure sensor of FIG. The figure which shows the cross-sectional structure of the principal part of the modification of the glow plug with a combustion pressure sensor of FIG. The perspective view which shows the principal part structure of the glow plug with a combustion pressure sensor of FIG. The figure which shows the manufacturing process of the glow plug with a combustion pressure sensor of FIG. The figure which shows the cross-sectional structure of the principal part of the internal combustion engine which concerns on embodiment of this invention. The figure which shows the cross-sectional structure of the principal part of the modification of embodiment of this invention. The figure which shows the cross-sectional structure of the principal part of the conventional glow plug with a combustion pressure sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Sheet member, 4 ... Screw part, 5 ... Tool engaging part, 6 ... Opening, 7 ... Sheet surface, 8 ... Inner peripheral surface, 10 ... Heater support member, DESCRIPTION OF SYMBOLS 11 ... Connecting part, 12 ... Moving part, 15 ... Space, 20 ... Heater, 21 ... Insulating ceramic, 22 ... Conductive ceramic, 23, 24 ... Exposed part, 25 ... Pressure-receiving surface, DESCRIPTION OF SYMBOLS 40 ... Cylindrical member, 41 ... Flange part, 42 ... Insulating plate, 45 ... Cylindrical body, 46 ... Pressure detection element, 100 ... Glow plug with a combustion pressure sensor.

Claims (2)

A housing formed in a cylindrical shape;
A pressure sensing element disposed within the housing;
The pressure detecting element has a columnar outer shape extending in the axial direction, the front end side protrudes from the front end portion of the housing, the rear end side is accommodated in the housing, the front end surface is a pressure receiving surface, A heater that transmits combustion pressure to
The cylindrical portion that holds the heater, and the cylindrical portion and the housing are connected directly or via another member, allow relative displacement in the axial direction of the heater with respect to the housing, and are exposed to combustion gas. A heater holding member comprising a connecting portion having a portion;
A tapered seat surface that has an annular shape having an opening for projecting the heater at a radially central portion, is positioned on the axial front end side with respect to the connecting portion, and contacts a tapered seat provided in the internal combustion engine A sheet member having
A glow plug with a combustion pressure sensor comprising:
The shape of the inner peripheral surface of the opening of the sheet member is a linear shape from the rear end in the axial direction toward the front end in the axial direction, or a shape that expands from the rear end in the axial direction toward the front end in the axial direction. A glow plug with a combustion pressure sensor. A housing formed in a cylindrical shape;
A pressure sensing element disposed within the housing;
The pressure detecting element has a columnar outer shape extending in the axial direction, the front end side protrudes from the front end portion of the housing, the rear end side is accommodated in the housing, the front end surface is a pressure receiving surface, A heater that transmits combustion pressure to
The cylindrical portion that holds the heater, and the cylindrical portion and the housing are connected directly or via another member, allow relative displacement in the axial direction of the heater with respect to the housing, and are exposed to combustion gas. A heater holding member comprising a connecting portion having a portion;
A tapered seat surface that has an annular shape having an opening for projecting the heater at a radially central portion, is positioned on the axial front end side with respect to the connecting portion, and contacts a tapered seat provided in the internal combustion engine A sheet member having
The shape of the inner peripheral surface of the opening of the sheet member is a linear shape from the rear end in the axial direction toward the front end in the axial direction, or a shape that expands from the rear end in the axial direction toward the front end in the axial direction. A combustion plug with a combustion pressure sensor is an internal combustion engine mounted in a glow hole that leads to a combustion chamber,
An internal combustion engine characterized in that a glow hole diameter on the combustion chamber side of the tapered sheet provided in the glow hole is larger than a diameter of an axial tip of the opening.

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