JP5901882B2 - Glow plug with combustion pressure sensor - Google Patents

Description

  The present invention relates to a glow plug, and more particularly to a glow plug with a combustion pressure sensor.

  In a compression ignition type internal combustion engine such as a diesel engine, a glow plug is used as an auxiliary heat source. For example, the glow plugs described in Patent Documents 1 and 2 have a male screw provided in its housing screwed into a female screw formed in a plug mounting hole of the internal combustion engine, and a tapered shape provided at the front end of the housing. This seal surface is brought into surface contact with a tapered seat surface formed in the plug mounting hole of the internal combustion engine, thereby ensuring airtightness from the combustion chamber.

  However, in recent years, a new combustion method such as a premixed combustion method has been proposed in addition to the conventional diffusion combustion method, and accordingly, the combustion pressure of the internal combustion engine tends to increase. Therefore, it may be difficult for a conventional glow plug to ensure sufficient airtightness against a high combustion pressure. In particular, in a glow plug having a pressure sensor for detecting the combustion pressure in an internal combustion engine, it is necessary to incorporate a movable structure of the sensor and heater (a structure capable of relative displacement with respect to the housing) inside, so the thickness of the housing It is difficult to thicken. Therefore, considering the possibility of plastic deformation of the housing, it is difficult to improve the airtightness between the combustion chamber by simply increasing the fastening axial force of the glow plug.

JP 2004-205148 A JP 2002-276842 A

  In view of the above-described problems, the problem to be solved by the present invention is to improve the airtightness in the contact portion with the combustion chamber in the glow plug with the combustion pressure sensor.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
The first aspect of the present invention is:
A housing having a substantially cylindrical trunk extending in the axial direction, and a substantially cylindrical head provided at a distal end of the trunk and having a diameter reduced toward the distal end;
A rod-like heater portion, the rear end portion of which is disposed in the housing, the tip portion projects from the tip of the head, and is movable along the axial direction;
A connecting member that connects the heater portion and the housing in the housing, while allowing the heater portion to move along the axial direction;
A glow plug with a combustion pressure sensor, provided in the housing, and comprising a pressure sensor for detecting a combustion pressure in accordance with a movement amount of the heater section along the axial direction,
On the outer periphery of the head, inside the outermost periphery of the head, a corner that makes a line contact with the seating surface of the plug mounting hole of the internal combustion engine is formed in an annular shape,
The head includes a substantially cylindrical first cylindrical portion on the rear end side of the corner portion,
The thickness of the corner of the head along the direction perpendicular to the axial direction is greater than the thickness of the first cylindrical part along the direction perpendicular to the axial direction.
The connecting member includes a flat portion extending in a radial direction provided on a front end side, and a second cylindrical portion connected to the flat portion and disposed on the rear end side of the flat portion, and the flat portion Is connected to the heater section,
The planar portion is provided in the first cylindrical portion.
This is a glow plug with a combustion pressure sensor.

Application Example 1 A housing having a substantially cylindrical body portion extending in the axial direction, a substantially cylindrical head portion provided at the front end of the body portion and having a diameter reduced toward the front end, and a rear end portion Disposed in the housing, the tip portion protrudes from the tip of the head, and can be moved along the axial direction, and the heater portion can be moved along the axial direction. A connecting member that connects the heater part and the housing in the housing, and a pressure sensor that is provided in the housing and detects a combustion pressure in accordance with a movement amount of the heater part along the axial direction. A glow plug with a combustion pressure sensor provided, wherein an outer periphery of the head is formed with an annular corner portion in line with the seat surface of the plug mounting hole of the internal combustion engine inside the outermost periphery of the head. Combustion characterized by The glow plug with a pressure sensor.

  In such a configuration, the corner portion provided on the head of the housing is in line contact with the seat surface of the plug mounting hole, so that the load is concentrated on the seat surface rather than the surface contact as in the past. Can be applied. Moreover, since the corner is formed inside the outermost periphery of the head, the pressure receiving area of the combustion pressure is reduced. As a result, it becomes possible to improve the airtightness at the contact portion between the glow plug and the combustion chamber.

Application Example 2 A glow plug with a combustion pressure sensor according to Application Example 1, wherein the head includes a substantially cylindrical cylindrical portion on a rear end side, and extends along a direction perpendicular to the axial direction. A glow plug with a combustion pressure sensor, wherein a thickness at the corner of the head is greater than a thickness of the cylindrical portion along a direction perpendicular to the axial direction.

  With such a configuration, it is possible to increase the rigidity of the corner portion to which a load is intensively applied when the plug mounting hole contacts the seat surface.

Application Example 3 A glow plug with a combustion pressure sensor according to Application Example 1 or Application Example 2, wherein the connecting member is provided in the head. .

  If it is such a structure, the area of a connection member can be expanded rather than arrange | positioning a connection member in a trunk | drum by making the thickness of the part which provides the connection member of a head thinner than a trunk | drum. As a result, the movable range of the heater section can be increased, and the performance of the pressure sensor can be improved.

[Application Example 4] The glow plug with a combustion pressure sensor according to any one of Application Example 1 to Application Example 3, wherein the corner portion is provided at the forefront of the head. Glow plug with combustion pressure sensor.

  With such a configuration, it is possible to improve the airtightness from the combustion chamber without performing special processing on the head.

  In addition to the above-described configuration as a glow plug with a combustion pressure sensor, the present invention can also be configured as a method for manufacturing a glow plug with a combustion pressure sensor, an internal combustion engine including a glow plug with a combustion pressure sensor, and the like.

It is explanatory drawing which shows the structure of the glow plug as one Embodiment of this invention. It is an expanded sectional view near a cap part. It is a figure which shows the pressure-receiving area of a combustion pressure. It is a figure which shows other embodiment of a glow plug. It is a figure which shows other embodiment of a glow plug.

  FIG. 1 is an explanatory diagram showing a configuration of a glow plug 100 as an embodiment of the present invention. 1A shows the overall configuration of the glow plug 100, and FIG. 1B shows a partial cross-sectional configuration. FIG. 2 is an enlarged cross-sectional view in the vicinity of a cap portion 120 described later. In the following description, the lower side of the axis O of the glow plug 100 in FIGS. 1 and 2 is the front end side of the glow plug 100 and the upper side is the rear end side. A downward direction along the axis O of the glow plug 100 is defined as an axial direction OD. As shown in FIGS. 1A and 1B, the glow plug 100 includes a housing 130 having a metal shell 110 and a cap portion 120, and a heater portion 150. The metal shell 110 corresponds to the “body” of the present application, and the cap 120 corresponds to the “head”.

  The metal shell 110 is a substantially cylindrical metal member formed of carbon steel or stainless steel. A tool engaging portion 112 is formed at the rear end of the metal shell 110 and engages with a tool for attaching the glow plug 100 to the internal combustion engine. Further, a screw portion 114 formed with a screw groove (not shown) for fixing the glow plug 100 to the cylinder head is provided on the tip side of the tool engaging portion 112. A plurality of wirings 116 that are electrically connected to an integrated circuit 166 (described later) and a central shaft 170 (described later) in the housing 130 are inserted into the rear end portion of the tool engaging portion 112.

  A cap portion 120 is disposed at the tip of the metal shell 110. The cap part 120 is an annular metal member formed of carbon steel or stainless steel. On the rear end side of the cap portion 120, a cylindrical portion 122 whose thickness is smaller than that of the metal shell 110 and having a substantially constant outer diameter is formed, and on the front end side, a tapered portion 124 whose diameter decreases toward the front end is formed. (See FIG. 2). In the present embodiment, a corner 126 that makes line contact with a tapered seat surface 210 formed at the bottom of the plug mounting hole 200 of the internal combustion engine (not shown) is annularly formed around the axis O on the outer periphery of the tapered portion 124. Is formed. In the present embodiment, the corner portion 126 is formed at the boundary by forming a two-step tapered surface in the tapered portion 124 so that the taper angle becomes larger toward the tip side. Here, the taper angle refers to a narrow angle formed by the axis O and the taper surface. In the present embodiment, the thickness T1 at the corner portion 126 of the cap portion 120 along the direction perpendicular to the axis O is thicker than the thickness T2 of the cylindrical portion 122 along the direction perpendicular to the axis O. The thickness T2 can be set to 0.5 mm, for example, and the thickness T1 can be set to 0.75 mm or more. The corner portion 126 is formed by, for example, cutting the tapered portion 124 of the cap portion 120 having a uniform initial taper angle from the position where the corner portion 126 is formed toward the tip side, and a taper angle larger than the initial taper angle. It can form easily by forming the part which becomes.

  The heater unit 150 includes a sheath tube 152, a heating coil 154, and insulating powder 155. The sheath tube 152 is made of stainless steel or the like excellent in heat resistance and corrosion resistance, and has a tip end closed in a hemispherical shape and a rear end opened in the metal shell 110. The heating coil 154 is a wire-wound resistor and is disposed inside the distal end side of the sheath tube 152. A middle shaft 170 that is a metal bar-like member is inserted into the heater unit 150, and the rear end of the heating coil 154 is fixed to the tip of the middle shaft 170. Electric power is supplied to the heating coil 154 from the outside through the wiring 116 and the central shaft 170. The sheath tube 152 is filled with insulating powder 155 such as magnesium oxide having heat resistance in a gap with the heating coil 154. A seal member 156 for sealing the insulating powder 155 in the sheath tube 152 is inserted between the opened rear end of the sheath tube 152 and the middle shaft 170. The sheath tube 152 is subjected to a swaging process, whereby the denseness of the insulating powder 155 filled therein is enhanced, and the heat conduction efficiency is improved. The heater part 150 having such a configuration is arranged such that the rear end side is disposed in the metal shell 110 and the front end side is projected from the opening 125 of the cap part 120 toward the axial direction OD.

  In the housing 130, an annular pressure sensor 160 (see FIG. 1) disposed on the rear end side of the heater unit 150, a sensor fixing member 132 for fixing the pressure sensor 160 in the housing 130, and the heater unit A transmission sleeve 134 for transmitting the displacement along the axis O of 150 to the pressure sensor 160 and a connecting member 180 for connecting the outer periphery of the heater unit 150 to the inside of the housing 130 are provided.

  The sensor fixing member 132 is a substantially cylindrical member formed of stainless steel or the like. The sensor fixing member 132 is disposed along the inner periphery of the metallic shell 110, and a flange-shaped flange portion 133 is formed at the tip thereof. The flange portion 133 is welded to the front end surface of the metal shell 110. The outer periphery of the pressure sensor 160 is welded to the rear end of the sensor fixing member 132. In the present embodiment, the pressure sensor 160 is fixed near the central portion in the housing 130 by the sensor fixing member 132.

  The transmission sleeve 134 is a substantially cylindrical member formed of stainless steel or the like. The transmission sleeve 134 is disposed between the sensor fixing member 132 and the heater unit 150. The distal end of the transmission sleeve 134 is welded to the outer periphery of the heater portion 150 in the vicinity of the position where the flange portion 133 of the sensor fixing member 132 is formed. Further, the rear end of the transmission sleeve 134 is welded to the inner peripheral portion of the annular pressure sensor 160. The displacement along the axis O of the heater portion 150 is transmitted to the inner peripheral portion of the pressure sensor 160 by the transmission sleeve 134.

  The connecting member 180 (see FIG. 2) is an elastic annular member formed of stainless steel, nickel alloy, or the like. The connecting member 180 includes a flange-like flange portion 182 provided on the rear end side, a thin-film-like flat portion 183 provided on the front end side, and a cylindrical portion 184 that connects the flange portion 182 and the flat portion 183. Have. The flange portion 182 has an upper surface (rear end side surface) welded to the flange portion 133 of the sensor fixing member 132, and a lower surface (front end side surface) welded to the rear end surface of the cap portion 120. As shown in FIG. 2, the flat portion 183 has a folded portion 185 that is folded toward the distal end side at the inner peripheral portion thereof. The connecting member 180 is welded to the outer periphery of the heater unit 150 at the folded portion 185. In the present embodiment, the flat portion 183 of the connecting member 180 is disposed in the cylindrical portion 122 of the cap portion 120. The heater unit 150 is connected to the housing 130 by the connecting member 180, and displacement along the axis O is allowed by the elastic force of the connecting member 180. The connecting member 180 also serves to ensure airtightness from the combustion chamber into the metal shell 110 by connecting the heater portion 150 and the housing 130.

  The pressure sensor 160 (see FIG. 1) includes an annular metal diaphragm 162 provided in the center with an opening 161 through which the central shaft 170 passes, and a piezoresistive element 164 joined to the upper surface (rear end surface) of the metal diaphragm 162. And. The metal diaphragm 162 is made of, for example, stainless steel. An integrated circuit 166 provided at a predetermined position in the housing 130 is electrically connected to the piezoresistive element 164. As described above, the rear end of the transmission sleeve 134 connected to the heater unit 150 is joined to the inner periphery of the metal diaphragm 162. Therefore, when the heater unit 150 is displaced along the axis O by receiving the combustion pressure, the displacement amount is transmitted to the metal diaphragm 162 by the transmission sleeve 134 and the metal diaphragm 162 is bent. The integrated circuit 166 detects the combustion pressure of the internal combustion engine by detecting the deformation of the metal diaphragm 162 using the piezoresistive element 164. The integrated circuit 166 outputs an electrical signal indicating the combustion pressure thus detected to an external ECU or the like through the wiring 116 inserted at the rear end of the metal shell 110.

  In the present embodiment described above, a tool is engaged with the tool engaging portion 112 of the glow plug 100, and the screw portion 114 is screwed into the plug mounting hole 200 of the internal combustion engine, whereby the cap portion 120 is connected to the internal combustion engine. The glow plug 100 is fixed to the internal combustion engine in contact with the seating surface 210 of the plug mounting hole 200. At this time, since the corner portion 126 provided in the cap portion 120 is in line contact with the seat surface 210 of the plug attachment hole 200, a load can be applied to the seat surface 210 more intensively than in surface contact. Therefore, it becomes possible to improve the airtightness between the combustion chamber and the cap part 120.

  Further, in the present embodiment, the corner 126 that makes line contact with the seating surface 210 of the plug mounting hole 200 is provided not on the outermost periphery (cylindrical portion 122) of the cap portion 120 but on the tapered portion 124 inside thereof. Yes. Therefore, for example, as shown on the left side of FIG. 3, this embodiment shown on the right side of FIG. 3 rather than the pressure receiving area A2 of the glow plug that is in line contact with the seat surface 210 of the plug mounting hole 200 on the outermost periphery of the cap part. In the glow plug 100, the pressure receiving area A1 can be reduced. As a result, according to this embodiment, even if the combustion pressure is increased, the airtightness between the combustion chamber and the cap portion 120 can be improved without increasing the tightening axial force of the glow plug 100. . For example, if the glow plug configured to contact the seat surface 210 at the outermost periphery of the cap portion 120 can withstand a combustion pressure of 20 MPa, the pressure receiving area is 0.8 times (0.894 times if the diameter). If the corner portion 126 is formed in the cap portion 120 of the glow plug, the glow plug 100 that can withstand a pressure of 25 MPa can be obtained.

  Further, in the present embodiment, the thickness T1 at the corner portion 126 of the cap portion 120 is thicker than the thickness T2 at the cylindrical portion 122 of the cap portion 120. Therefore, it is possible to increase the rigidity of the corner portion 126 to which a load is concentrated.

  In the present embodiment, the flat portion 183 of the connecting member 180 is provided in the cylindrical portion 122 of the cap portion 120. Since the thickness of the cylindrical portion 122 is thinner than the thickness of the metal shell 110, the area of the flat surface portion 183 can be made larger than providing the flat surface portion 183 in the metal shell 110. As a result, the spring constant of the connecting member 180 is lowered, and the amount of movement of the heater unit 150 along the axial direction can be increased. Therefore, the performance (for example, S / N ratio) of the pressure sensor 160 can be improved.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to such Embodiment, A various structure can be taken in the range which does not deviate from the meaning. For example, the thickness of the corner portion 126 of the cap portion 120 may be equal to or less than the thickness of the cylindrical portion 122. Further, the flat portion 183 of the connecting member 180 can be provided in the metal shell 110. In addition, the following various aspects can be adopted.

  4 and 5 are views showing another embodiment of the glow plug. FIG. 4 shows a glow plug 100b in which a corner portion 126b is formed by making the tapered portion 124b of the cap portion 120b polygonal. Specifically, by providing a step portion 128b perpendicular to the axis O between the cylindrical portion 122b and the taper portion 124b of the cap portion 120b, the rear end side of the corner portion 126b becomes a surface substantially parallel to the axis O. A cap portion 120b is formed on the surface. Further, FIG. 5 shows a glow plug 100c that is brought into contact with the seat surface 210 of the plug mounting hole 200 with the tip of the outer peripheral surface of the cap portion 120c as a corner portion 126c. As shown in these drawings, the corner portion that contacts the seating surface 210 of the plug attachment hole 200 may be formed in any manner as long as it is provided in the cap portion 120 other than the outermost periphery thereof. For example, the step portion 128b in FIG. 4 may not be perpendicular to the axis O. Further, if the corner is in line contact with the seating surface 210, the corner may be rounded. In addition, according to the structure shown in FIG. 5, the effect similar to embodiment mentioned above can be acquired, without performing special process with respect to the taper part 124c.

  In the above embodiment, the housing 130 is constituted by the metal shell 110 and the cap portion 120 which are independent members. On the other hand, the housing 130 may have a configuration in which the metal shell 110 and the cap portion 120 are integrally formed by, for example, tapering the tip of the metal shell 110.

  In the above-described embodiment, the heater unit 150 is configured by embedding the heating coil 154 in the sheath tube 152, but other configurations are possible. For example, the heater unit 150 may be configured as a ceramic heater in which a conductive ceramic is embedded in an insulating ceramic.

  In the above embodiment, the pressure sensor 160 is configured by the annular metal diaphragm 162 and the piezoresistive element 164. However, the configuration of the pressure sensor 160 is not limited to this, and a well-known pressure sensor employed in a glow plug with a combustion pressure sensor can be appropriately applied.

  In the above embodiment, the housing 130 and the heater unit 150 are connected by the connecting member 180 having the thin film-like flat part 183. On the other hand, for example, the housing 130 and the heater unit 150 may be coupled by a bellows (bellows) -shaped member.

  In the above embodiment, the heater unit 150 and the pressure sensor 160 are connected via the transmission sleeve 134. However, the rear end portion of the heater unit 150 is directly connected to the pressure sensor 160. Also good.

  In the above embodiment, power is supplied to the heater unit 150 through the middle shaft 170, but the middle shaft 170 may be omitted and power may be directly supplied from the wiring 116 to the heater unit 150.

DESCRIPTION OF SYMBOLS 100, 100b, 100c ... Glow plug 110 ... Main metal fitting 112 ... Tool engaging part 114 ... Screw part 116 ... Wiring 120, 120b, 120c ... Cap part 122, 122b ... Cylindrical part 124, 124b, 124c ... Tapered part 125 ... Opening 126, 126b, 126c ... Corner 128b ... Step 130 ... Housing 132 ... Sensor fixing member 133 ... Flange 134 ... Transmission sleeve 150 ... Heater 152 ... Sheath tube 154 ... Heating coil 155 ... Insulating powder 156 ... Sealing member 160 ... Pressure sensor 161 ... Opening part 162 ... Metal diaphragm 164 ... Piezoresistive element 166 ... Integrated circuit 170 ... Central shaft 180 ... Connecting member 182 ... Flange part 183 ... Planar part 184 ... Cylindrical part 185 ... Folding part 200 ... Plug mounting hole 210 ... seat

Claims (3)

A housing having a substantially cylindrical trunk extending in the axial direction, and a substantially cylindrical head provided at a distal end of the trunk and having a diameter reduced toward the distal end;
A rod-like heater portion, the rear end portion of which is disposed in the housing, the tip portion projects from the tip of the head, and is movable along the axial direction;
A connecting member that connects the heater portion and the housing in the housing, while allowing the heater portion to move along the axial direction;
A glow plug with a combustion pressure sensor, provided in the housing, and comprising a pressure sensor for detecting a combustion pressure in accordance with a movement amount of the heater section along the axial direction,
On the outer periphery of the head, inside the outermost periphery of the head, a corner that makes a line contact with the seating surface of the plug mounting hole of the internal combustion engine is formed in an annular shape ,
The head includes a substantially cylindrical first cylindrical portion on the rear end side of the corner portion,
The thickness of the corner of the head along the direction perpendicular to the axial direction is greater than the thickness of the first cylindrical part along the direction perpendicular to the axial direction.
The connecting member includes a flat portion extending in a radial direction provided on a front end side, and a second cylindrical portion connected to the flat portion and disposed on the rear end side of the flat portion, and the flat portion Is connected to the heater section,
The planar portion is provided in the first cylindrical portion.
A glow plug with a combustion pressure sensor. A glow plug with a combustion pressure sensor according to claim 1,
The connecting member has a flange-like flange portion connected to the second cylindrical portion and provided on the rear end side of the second cylindrical portion ,
The front end surface of the flange portion is joined to the rear end surface of the head,
A glow plug with a combustion pressure sensor, wherein a joint portion between the connecting member and the heater portion is located on the front end side of the rear end surface of the head. A glow plug with a combustion pressure sensor according to claim 1 or 2 ,
A glow plug with a combustion pressure sensor, wherein the corner portion is provided at the forefront of the head.

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