JP2015190689A - internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of suppressing the clogging of soot in the clearance between the inner circumferential surface of a storage hole of a main fitting out of a glow plug and the outer circumferential surface of the heater hole interior of a heater.SOLUTION: A glow plug 1 with a pressure sensor constituting an internal combustion engine 101 comprises: a cylindrical main fitting 10 including a storage hole 10h; a rod heater 20 including a heater protrusion 20s and a heater hole interior 20k; and a sensor 50. If a minimum diameter difference is B=min(d1-d2) among diameter differences between an inside diameter d1 of a protrusion surrounding portion 116 of a glow hole 111 and an outside diameter d2 of the heater protrusion 20s in a cross-section and a minimum diameter difference is C=min(d3-d4) out of diameter differences between an inside diameter d3 of a certain inside diameter portion 10hc of the storage hole 10h and an outside diameter d4 of the heater hole interior 20k in the cross-section, a relation of B<C is satisfied.

Description

  The present invention relates to an internal combustion engine in which a glow plug with a pressure sensor is mounted in a glow hole of an engine head.

  Conventionally, as an internal combustion engine, an internal combustion engine in which a glow plug with a pressure sensor is mounted in a glow hole of an engine head is known. Among these, a glow plug with a pressure sensor (hereinafter also simply referred to as a glow plug) has a function of detecting combustion pressure in addition to a function of promoting ignition in a combustion chamber of an internal combustion engine (diesel engine). That is, this glow plug receives the combustion pressure (combustion gas pressure) in the combustion chamber with the heater part, and detects the displacement of the heater part accompanying this by the sensor part having a piezoelectric element, a strain sensor (gauge) and the like.

  This glow plug has, for example, a cylindrical metal shell, and its front end portion (hereinafter also referred to as a heater protrusion) protrudes from the metal shell, and its rear end portion (hereinafter also referred to as the heater hole interior). It has a rod-like heater portion held by the metal shell and a sensor portion in a state of being disposed in the housing hole of the metal shell. Among these, the heater part is arrange | positioned so that a displacement in an axial direction is possible according to combustion pressure, and the displacement of this heater part is detected by a sensor part. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-139148) discloses such a glow plug and an internal combustion engine equipped with the glow plug (see FIG. 6 of Patent Document 1 and the description thereof).

JP 2010-139148 A

  In the glow plug described above, the heater hole inside the heater part is separated from the metal shell in order to hold the heater part axially displaceable in the metal shell (the outer diameter inside the heater hole is the housing hole of the metal shell). Is smaller than the inner diameter of For this reason, a gap is formed between the inner peripheral surface of the housing hole of the metal shell and the outer peripheral surface inside the heater hole. On the other hand, in order to mount the glow plug in the glow hole of the engine head, the outer diameter of the heater protrusion of the heater portion is made smaller than the inner diameter of the glow hole. For this reason, a gap is also formed between the inner peripheral surface of the glow hole and the outer peripheral surface of the heater protrusion.

However, the combustion gas reaches the gap between the inner peripheral surface of the housing hole of the metal shell and the outer peripheral surface inside the heater hole through the gap between the inner peripheral surface of the glow hole and the outer peripheral surface of the heater protrusion. As a result, the gap between the inner peripheral surface of the housing hole of the metal shell and the outer peripheral surface inside the heater hole is likely to be clogged. If the gap is clogged with soot, the heater part is difficult to displace in the axial direction, and the detection sensitivity of the combustion pressure may be reduced.
The present invention has been made in view of such a situation, and an internal combustion engine in which a flaw is unlikely to be clogged in a gap between an inner peripheral surface of a housing hole of a metal shell and an outer peripheral surface inside a heater hole of a heater portion of a glow plug. The purpose is to provide.

  One aspect of the present invention for solving the above problems is an internal combustion engine in which a glow plug with a pressure sensor is mounted in a glow hole of an engine head, and the glow plug with a pressure sensor penetrates in the axial direction. A cylindrical metallic shell having a receiving hole; a heater projecting portion projecting toward the distal end side in the axial direction from the distal end of the metallic shell; and the axially rear end side of the heater projecting portion and the main body In the housing hole of the metal fitting, there is a rod-shaped heater portion that is held in the metal shell so as to be displaceable in the axial direction, and has a heater hole inside that is spaced apart from the metal shell. A sensor portion that detects the displacement, and the housing hole has a constant inner diameter portion having a constant inner diameter in the axial direction following the rear end side in the axial direction of a tip opening edge, and Hall A portion of the heater portion surrounding the heater protrusion from the outside in the radial direction is defined as a protrusion surrounding portion, and the protrusion surrounding portion is a cross section perpendicular to the axial direction in the protrusion surrounding portion and the heater protruding portion. Of the diameter difference (d1−d2) between the inner diameter d1 of the portion and the outer diameter d2 of the heater protrusion, the minimum diameter difference is B = min (d1−d2), and the above inside the constant inner diameter portion and the heater hole. Of the diameter difference (d3−d4) between the inner diameter d3 of the constant inner diameter portion and the outer diameter d4 inside the heater hole in the cross section, when the minimum diameter difference is C = min (d3−d4), In the internal combustion engine, the protruding portion surrounding portion, the heater protruding portion, the constant inner diameter portion, and the heater hole are configured to satisfy B <C.

  In this internal combustion engine, the minimum diameter difference B between the inner diameter d1 of the glow hole projecting portion enclosing portion and the outer diameter d2 of the heater projecting portion of the heater portion, the inner diameter d3 of the constant inner diameter portion of the housing hole, and the inside of the heater hole of the heater portion. As for the minimum diameter difference C from the outer diameter d4, B <C is satisfied. That is, in this internal combustion engine, the inner peripheral surface of the constant inner diameter portion of the housing hole and the heater hole of the heater portion are larger than the gap between the inner peripheral surface of the glow hole projecting portion surrounding portion and the outer peripheral surface of the heater projecting portion of the heater portion. The gap with the inner peripheral surface is larger.

The heel is likely to be clogged in the portion where the gap is reduced, and is difficult to clog the portion where the gap is increased. Therefore, by setting B <C as described above, the gap between the inner peripheral surface of the constant inner diameter portion of the accommodation hole and the outer peripheral surface inside the heater hole of the heater hole is relatively large. It becomes difficult to clog the candy. Therefore, in this internal combustion engine, the heater portion is difficult to be displaced in the axial direction due to clogging of the gap between the inner peripheral surface of the inner diameter portion of the accommodation hole and the outer peripheral surface of the heater portion inside the heater hole. Thus, it is possible to prevent the detection sensitivity of the combustion pressure from being lowered.
In addition, the clearance gap between the internal peripheral surface of the protrusion part surrounding part of a glow hole, and the outer peripheral surface of the heater protrusion part of a heater part is relatively small. However, since the protruding portion surrounding portion and the heater protruding portion are close to the combustion chamber and become high temperature, even if soot accumulates in these gaps, they are burned by heat and disappear. For this reason, it is hard to clog these gaps.

The difference in diameter (d1-d2) is a difference in diameter when the protruding portion surrounding portion and the heater protruding portion are viewed in each cross section orthogonal to the axial direction. Therefore, the minimum diameter difference B = min (d1-d2) is not the difference between the smallest value of the inner diameter d1 and the largest value of the outer diameter d2, but the difference in diameter (d1-d2) in the cross section in the axial direction. It refers to the smallest value obtained when measured while moving.
Similarly, the diameter difference (d3-d4) is a diameter difference when the constant inner diameter portion and the heater hole are viewed in each cross section orthogonal to the axial direction. Therefore, the minimum diameter difference C = min (d3−d4) is not the difference between the smallest value of the inner diameter d3 and the largest value of the outer diameter d4, but the difference in diameter (d3−d4) in the cross section in the axial direction. The smallest value obtained when measured while moving.

  As the “heater part”, for example, a ceramic heater main body in which a ceramic base made of an insulating ceramic and a heating resistor are integrated, and a cylindrical metal outer cylinder holding the ceramic heater main body inside itself. The ceramic heater part which has these. Furthermore, examples of the ceramic heater body include a form in which a heating resistor is embedded in the ceramic base. Moreover, as a heating resistor, what consists of metals, such as a conductive ceramic and W (tungsten), is mentioned, for example. Further, examples of the “heater portion” include a sheathed heater portion having a bottomed cylindrical metal sheath tube whose axial end is closed and a rear end is opened, and a heat generating coil disposed in the sheath tube. .

  The “sensor unit” includes, for example, a strain sensor (strain gauge), a semiconductor strain gauge having a piezoresistor, a displacement sensor such as a piezoelectric element, and a member that guides the displacement of the heater unit to the displacement sensor. Is mentioned.

  Furthermore, in the internal combustion engine described above, the heater section has a ceramic heater body in which a ceramic base made of insulating ceramic and a heating resistor are integrated, and a cylindrical shape in which the ceramic heater body is held inside itself. A ceramic heater part, wherein the outer cylinder is located at least inside the constant inner diameter part of the accommodation hole over the entire axial direction, and the outer diameter d2 is the ceramic heater part. An outer diameter of a portion of the heater body or the outer cylinder that forms the outer peripheral surface of the heater protrusion, and the outer diameter d4 is an outer diameter of a portion of the outer cylinder that forms the heater hole. Good.

  In this internal combustion engine, the heater part is a ceramic heater part having a ceramic heater body and an outer cylinder, and the outer cylinder is located at least inside the constant inner diameter part of the accommodation hole over the entire axial direction. Thus, in the form in which the outer cylinder exists inside the constant inner diameter portion, the outer diameter d4 inside the heater hole tends to be large, and the minimum diameter difference C = min (d3−d4) tends to be small. However, since the internal combustion engine is configured to satisfy B <C as described above, the inner circumference of the constant inner diameter portion of the accommodation hole is provided even though the outer cylinder exists inside the constant inner diameter portion of the accommodation hole. The gap between the surface and the outer peripheral surface inside the heater hole of the heater portion is less likely to become clogged.

  Alternatively, in the internal combustion engine, the heater unit includes a bottomed cylindrical metal sheath tube having a closed end in the axial direction and an open rear end, and a heating coil disposed in the sheath tube. The outer diameter d2 is the outer diameter of the portion of the sheath tube that forms the heater protrusion, and the outer diameter d4 is the interior of the heater hole of the sheath tube. An internal combustion engine having the outer diameter of the part is preferable.

  In this internal combustion engine, the heater portion is a sheathed heater portion in which a heat generating coil is disposed in the sheath tube. Even in the internal combustion engine having such a sheathed heater portion, as described above, by satisfying B <C, the inner peripheral surface of the constant inner diameter portion of the accommodation hole and the outer peripheral surface inside the heater hole of the heater portion are formed. It becomes difficult for clogs to clog the gap.

2 is a partial cross-sectional view of a portion in the vicinity of a glow plug with a pressure sensor in the internal combustion engine according to Embodiment 1. FIG. FIG. 3 is an enlarged vertical cross-sectional view in which a portion in the vicinity of a heater protrusion is enlarged in the glow plug with a pressure sensor according to the first embodiment. FIG. 3 is an enlarged vertical cross-sectional view in which a portion in the vicinity of the inside of a heater hole is enlarged in the glow plug with a pressure sensor according to the first embodiment. FIG. 4 is an enlarged vertical cross-sectional view in which a portion of the glow plug with pressure sensor according to the first embodiment in the vicinity of the connecting ring and the center shaft tip is enlarged. FIG. 3 is an enlarged cross-sectional view of an internal combustion engine according to the first embodiment, in which a portion in the vicinity of a seat surface of a glow hole is enlarged. 6 is a partial cross-sectional view of a portion in the vicinity of a glow plug with a pressure sensor in an internal combustion engine according to Embodiment 2. FIG. FIG. 6 is an enlarged vertical cross-sectional view in which a portion in the vicinity of a heater protrusion is enlarged in a glow plug with a pressure sensor according to the second embodiment. FIG. 6 is an enlarged vertical cross-sectional view of a glow plug with a pressure sensor according to the second embodiment, in which a portion in the vicinity of a tip side inside a heater hole is enlarged. FIG. 6 is an enlarged longitudinal sectional view of a glow plug with a pressure sensor according to the second embodiment, in which a portion in the vicinity of a rear end side in a heater hole is enlarged. FIG. 5 is an enlarged cross-sectional view of an internal combustion engine according to a second embodiment, in which a portion near a seating surface of a glow hole is enlarged.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 5 show an internal combustion engine (diesel engine) 101 according to the first embodiment. 2 to 4 show a glow plug 1 with a pressure sensor (hereinafter also simply referred to as a glow plug 1). 1 to 5, the direction along the axis AX of the glow plug 1 and its metal shell 10 is defined as the axial direction HJ, and the side of the axial direction HJ where the ceramic heater section (heater section) 20 is disposed (see FIG. The middle lower side is the front end side GS, and the opposite side (upper side in the figure) is the rear end side GK.

  The internal combustion engine 101 (see FIGS. 1 and 5) includes an engine block (not shown) in which a piston, a crank, and the like are accommodated, and an engine head 110 attached to the engine block. The engine head 110 is provided with an unillustrated intake port, exhaust port, cooling water passage, and the like. Further, the engine head 110 is provided with a nozzle mounting hole (not shown) through which a fuel injection device is inserted and fixed. Further, the engine head 110 is provided with a glow hole 111, through which the glow plug 1 is inserted and fixed.

First, the glow plug 1 will be described (FIGS. 1 to 4). The glow plug 1 detects the combustion pressure (combustion gas pressure) in the combustion chamber in addition to promoting the ignition of fuel in the internal combustion engine 101. The glow plug 1 includes a metal shell 10, a ceramic heater section 20, a holding member 40, a sensor section 50, and the like.
Of these, the metal shell 10 is a cylindrical metal member (specifically, carbon steel) having a housing hole 10h penetrating in the axial direction HJ. The housing hole 10h is narrowed at the front end side GS, and a portion of the front end side GS has a constant inner diameter d3 in the axial direction HJ following the rear end side GK of the chamfered front end opening edge 10hs. An inner diameter portion 10hc is provided. In the first embodiment, the inner diameter d3 of the constant inner diameter portion 10hc is d3 = 6.0 mm.

  Further, the metal shell 10 includes a cylindrical front end cap member 11 positioned on the front end side GS, a cylindrical rear end cap member 18 positioned on the rear end side GK, and an axial direction HJ positioned therebetween. It consists of a cylindrical metal fitting body member 17 that extends (see FIG. 1). The rear end portion 11k of the front end cap member 11 and the front end portion 17s of the metal fitting body member 17 are joined (specifically, welded) via a flange portion 53c of a sensor support member 53 described later (see FIG. 3). . The rear end portion 17k of the metal fitting body member 17 and the front end portion 18s of the rear end cap member 18 are also joined (specifically, welded) (see FIG. 1).

  The distal end cap member 11 (see FIG. 3) is located on the cylindrical distal end side portion 12 having a tapered shape with a smaller diameter toward the distal end side GS and the rear end side GK, and has a constant outer diameter. It consists of a cylindrical rear end side portion 13. The tapered outer peripheral surface 12m of the distal end side portion 12 is pressed against the seat surface 113n (see FIG. 5) of the glow hole 111 when the glow plug 1 is attached to the engine head 110, as will be described later. Airtightness in the chamber NS is secured.

  Further, as shown in FIG. 1, a mounting portion 17 d having a male screw for mounting the glow plug 1 to the engine head 110 is provided in a portion of the metal shell 10 on the rear end side GK of the metal shell 10. It has been. Further, a portion of the rear end cap member 18 on the rear end side GK is provided with a tool engaging portion 18e that has a hexagonal cross section and that engages a tool when the glow plug 1 is attached to the engine head 110. ing. In addition, the rear end cap member 18 is loaded with a cylindrical resin member 19 for wiring extraction that protrudes to the rear end side GK from the rear end 18 b of the rear end cap member 18.

  Next, the ceramic heater unit 20 will be described. The ceramic heater portion 20 has a rod shape in which a portion on the front end side GS and a portion on the rear end side GK are thinner than the intermediate portion therebetween. For this reason, as will be described later, the outer diameter d2 of the heater protrusion 20s is larger than the outer diameter d22 of the rear end side GK portion (rear end side portion 20sb) of the front end side GS (front end side portion 20sa). The outer diameter d21 is small (d21 <d22) (see FIG. 2). Further, the outer diameter d4 of the heater hole interior 20k is larger than the outer diameter d42 of the rear end side GK portion (rear end side portion 20kb) than the outer diameter d41 of the front end side GS portion (front end side portion 20ka). The diameter is small (d42 <d41) (see FIG. 3). Further, the outer diameter d21 of the front end side GS portion (front end side portion 20sa) of the heater protrusion 20s and the outer diameter d42 of the rear end side GK portion (rear end side portion 20kb) inside the heater hole 20k are equal ( d21 = d42), the outer diameter d22 of the rear end side GK portion (rear end side portion 20sb) of the heater protrusion 20s and the outer diameter d41 of the front end side GS portion (front end side portion 20ka) of the heater hole inside 20k are Are equal (d22 = d41).

  The ceramic heater unit 20 includes a ceramic heater body 21 and an outer cylinder 31. Among these, the ceramic heater main body 21 is a ceramic heater having a round bar shape extending in the axial direction HJ and having a shape whose tip is curved into a hemispherical shape. Specifically, the ceramic heater body 21 contains a conductive ceramic (specifically, tungsten carbide as a conductive component) inside a ceramic base 26 made of an insulating ceramic (specifically, a silicon nitride ceramic). A heating resistor 27 made of silicon nitride ceramic) is embedded.

  The heating resistor 27 includes a heating part 27c, a pair of lead parts 27d and 27e, and a pair of electrode extraction parts 27f and 27g. The heat generating portion 27c (see FIG. 2) is disposed on the distal end side GS, has a U-shaped bent shape, and generates a high temperature when energized. The pair of lead portions 27d and 27e (see FIGS. 2 to 4) is connected to both ends of the heat generating portion 27c and extends in parallel to the rear end side GK. The pair of electrode extraction portions 27f and 27g (see FIGS. 3 and 4) are connected to the pair of lead portions 27d and 27e on the rear end side GK, respectively, and are exposed to the outer peripheral surface 26m of the ceramic base 26. One electrode extraction portion 27g is arranged on the rear end side GK with respect to the other electrode extraction portion 27f.

  The outer cylinder 31 (see FIGS. 2 to 4) is a cylindrical metal member extending in the axial direction HJ. The outer cylinder 31 includes a cylindrical metal body (specifically, stainless steel) outer cylinder body 37 and a metal layer 38 formed by Au plating on the inner peripheral surface of the outer cylinder body 37. Is done. The outer cylinder 31 holds the ceramic heater body 21 by press-fitting (interference fitting) into the inside (diameter inside). Specifically, in the ceramic heater main body 21, the main body front end portion 21s (see FIG. 2) protrudes toward the front end side GS from the front end 31a of the outer cylinder 31, and the main body rear end portion 21k (see FIGS. 3 and 4). A main body middle portion 21c (see FIGS. 2 to 4) that protrudes to the rear end side GK from the rear end 31b of the outer cylinder 31 and is located between the main body front end 21s and the main body rear end 21k is a diameter of the outer cylinder 31. The outer cylinder 31 holds the ceramic heater body 21 in a form arranged on the inner side in the direction. As a result, one electrode extraction portion 27 f of the ceramic heater body 21 is in contact with the metal layer 38 of the outer cylinder 31 and is electrically connected to the outer cylinder 31.

  The ceramic heater section 20 including the ceramic heater body 21 and the outer cylinder 31 is held by the metal shell 10 so as to be displaceable in the axial direction HJ. Specifically, the heater protrusion 20s (see FIG. 2) protrudes toward the front end GS from the front end 11sa of the metal shell 10, and the heater hole interior 20k (see FIGS. 3 and 4) is inside the housing hole 10h of the metal shell 10. The metal shell 10 is held by the metal shell 10 so as to be displaceable in the axial direction HJ via a holding member 40, a displacement transmitting member 51, a sensor support member 53, and the like, which will be described later. .

Out of the heater protrusions 20s, the tip side part 20sa located on the tip side GS has no outer cylinder 31, and consists only of the body tip part 21s of the ceramic heater body 21 (the body tip part 21s is the outer peripheral surface of the heater protrusion part 20s). 20 sm). Of the outer diameter d2 of the heater protrusion 20s, the outer diameter d21 of the tip side portion 20sa is constant in the axial direction HJ, and d21 = 3.1 mm.
On the other hand, among the heater protrusions 20 s, the rear end side portion 20 sb located on the rear end side GK of the front end side portion 20 sa is the main body intermediate portion 21 c of the ceramic heater main body 21 and the front end 11 sa of the metal shell 10 of the outer cylinder 31. The outer cylinder tip side portion 31s protrudes further toward the tip side GS. Of the outer diameter d2 of the heater protruding portion 20s, the outer diameter d22 of the rear end side portion 20sb is constant in the axial direction HJ and larger than the outer diameter d21 of the front end side portion 20sa (d22> d21), d22 = 4.0 mm.

Further, of the heater hole inside 20k, the tip side portion 20ka located on the tip side GS is a main body intermediate portion 21c of the ceramic heater main body 21 and an outer cylinder located in the housing hole 10h of the metal shell 10 of the outer cylinder 31. It consists of a rear end side portion 31k. Of the outer diameter d4 of the heater hole inside 20k, the outer diameter d41 of the tip side portion 20ka is constant in the axial direction HJ and is equal to the outer diameter d22 of the rear end side portion 20sb of the heater protrusion 20s (d41 = d22). ), D41 = 4.0 mm.
On the other hand, the rear end side portion 20 kb located on the rear end side GK in the heater hole inside 20 k does not have the outer cylinder 31 and consists only of the main body rear end portion 21 k of the ceramic heater main body 21. Of the outer diameter d4 of the heater hole inside 20k, the outer diameter d42 of the rear end side 20kb is constant in the axial direction HJ and is equal to the outer diameter d21 of the front end side 20sa of the heater protrusion 20s (d42 = d21). ), D42 = 3.1 mm.

  Inside the fixed inner diameter portion 10hc of the housing hole 10h of the metal shell 10, a tip side portion 20ka of the heater hole inside 20k is arranged over the entire axial direction HJ (outside of the outer cylinder 31 over the entire axial direction HJ). A cylinder rear end side portion 31k is disposed). As described above, the constant inner diameter portion 10hc of the accommodation hole 10h has an inner diameter d3 = 6.0 mm. Therefore, the difference in diameter (d3−d4) between the inner diameter d3 of the constant inner diameter portion 10hc and the outer diameter d4 of the heater hole inner portion 20k in a cross section perpendicular to the axial direction HJ in the constant inner diameter portion 10hc and the heater hole inner portion 20k is. It is constant regardless of the position in the axial direction HJ, and the diameter difference (d3-d4) = d3-d41 = 6.0-4.0 = 2.0 mm. Therefore, in this Embodiment 1, the minimum diameter difference C = min (d3-d4) of the diameter differences (d3-d4) is also C = 2.0 mm.

  The main body rear end 21k of the ceramic heater main body 21 of the ceramic heater section 20 is connected to the middle shaft member 63 (see FIG. 4) via a connection ring 61 (see FIGS. 3 and 4). The connection ring 61 is a cylindrical metal member (specifically, stainless steel member) extending in the axial direction HJ. The connection ring 61 is disposed on the radially inner side of the displacement transmission member 51 and the sensor support member 53 described later in the housing hole 10 h of the metal shell 10. A main body rear end portion 21k of the ceramic heater main body 21 is press-fitted into a portion of the connecting ring 61 on the front end side GS. On the other hand, a fitting portion 63sa of the middle shaft front end portion 63s of the middle shaft member 63 is press-fitted into a portion of the connection ring 61 on the rear end side GK. Thereby, one electrode extraction part 27 g of the ceramic heater main body 21 is electrically connected to the central shaft member 63 via the connection ring 61.

  The middle shaft member 63 is a round bar-shaped metal member (specifically, stainless steel member) extending in the axial direction HJ. The central shaft member 63 is inserted into the housing hole 10 h of the metal shell 10 in a state of being separated from the metal shell 10. Further, a portion of the middle shaft member 63 on the front end side GS is disposed on the radially inner side of a displacement transmission member 51 and a sensor support member 53 which will be described later and spaced apart from these. The middle shaft member 63 includes a middle shaft front end portion 63s having a large diameter located on the front end side GS, and a middle shaft body portion 63c having a smaller diameter than the middle shaft front end portion 63s and extending from the middle shaft front end portion 63s to the rear end side GK. . As described above, the connection ring 61 is press-fitted into the fitting portion 63sa on the distal end side GS in the middle shaft distal end portion 63s.

  Next, the holding member 40 will be described. The holding member 40 (see FIG. 3) is a cylindrical member made of metal (specifically, stainless steel). The holding member 40 is disposed in an annular space KA between the inner peripheral surface of the metal shell 10 (specifically, the inner peripheral surface 11n of the tip cap member 11) and the outer peripheral surface 20m of the ceramic heater unit 20. While this holding member 40 is held by the metal shell 10, it is welded to the outer cylinder 31 of the ceramic heater portion 20 at the tip side GS from the position held by the metal shell 10.

  The holding member 40 holds the ceramic heater portion 20 in a state in which the ceramic heater portion 20 can be displaced in the axial direction HJ on the radially inner side thereof. Specifically, the holding member 40 includes an outer cylinder side part 41, a metal part side part 45, and an intermediate deformation part 43 positioned therebetween. Outer cylinder side part 41 of holding member 40 is a cylindrical part located in tip side GS, and holds ceramic heater part 20 inside itself in the diameter direction. Specifically, the outer cylinder side portion 41 is welded to the outer cylinder 31 over the entire circumference. Further, the metal part side portion 45 is a part having a cylindrical shape larger in diameter than the outer cylinder side part 41 and located on the rear end side GK, and is held by the metal shell 10 via a sensor support member 53 described later. Specifically, the metal side part 45 is externally fitted to the support front end part 53 s of the sensor support member 53 and is welded over the entire circumference. Further, since the sensor support member 53 is welded to the metal shell 10 over the entire circumference in the circumferential direction as will be described later, the metal fitting side portion 45 of the holding member 40 is indirectly fixed to the metal shell 10 by welding. .

Furthermore, the intermediate deformation portion 43 of the holding member 40 is a portion that deforms with the displacement of the ceramic heater portion 20 in the axial direction HJ. Specifically, the intermediate deformation portion 43 forms an annular plate-like diaphragm (thin film), and the intermediate deformation portion 43 is deformed to allow displacement of the ceramic heater portion 20 in the axial direction HJ.
Since the holding member 40 also electrically connects the outer cylinder 31 and the metal shell 10, one electrode extraction portion 27 f of the ceramic heater main body 21 is interposed via the outer cylinder 31 and the holding member 40. , And electrically connected to the metal shell 10.

  Next, the sensor unit 50 will be described. The sensor unit 50 includes a displacement transmission member 51, a sensor support member 53, a diaphragm member 55, a sensor element 57, a pair of wirings 58, and an integrated circuit 59. Of these members, the displacement transmission member 51 (see FIGS. 3 and 4) is a cylindrical metal member (specifically, stainless steel member) extending in the axial direction HJ. The displacement transmission member 51 is disposed inside the housing hole 10 h of the metal shell 10 on the radially inner side of the sensor support member 53 and on the rear end side GK with respect to the holding member 40. The displacement transmission member 51 is welded to the outer cylinder 31 over the entire circumference. On the other hand, a diaphragm member 55 is connected to the rear end side GK of the displacement transmitting member 51.

  The sensor support member 53 (see FIGS. 3 and 4) is a cylindrical metal member (specifically, stainless steel) that extends in the axial direction HJ. The sensor support member 53 is disposed on the radially outer side of the displacement transmission member 51 in the housing hole 10 h of the metal shell 10. The sensor support member 53 includes a cylindrical support front end portion 53s, a large flange portion 53c located on the rear end side GK, and a cylindrical support main body portion 53k extending from the flange portion 53c to the rear end side GK. Consists of. Among these, the metal fitting side portion 45 of the holding member 40 is externally fitted and welded to the support tip portion 53s as described above. The flange portion 53 c is welded to the metal shell 10 while being sandwiched between the rear end portion 11 k of the front end cap member 11 of the metal shell 10 and the tip portion 17 s of the metal body member 17. Further, a diaphragm member 55 is connected to the rear end side GK of the support main body portion 53k.

  The diaphragm member 55 (see FIG. 4) is a metal (specifically, stainless steel) member, and the sensor element 57 is joined to the main surface of the rear end side GK. The sensor element 57 is a semiconductor strain gauge having a piezoresistor, and its own resistance value changes as the diaphragm member 55 is bent and deformed. Further, the integrated circuit 59 is disposed inside the rear end cap member 18 of the metal shell 10 as indicated by a broken line in FIG. 1, and a pair of wirings 58 drawn from the sensor element 57 to the rear end side GK. The sensor element 57 is connected via The integrated circuit 59 outputs an electrical signal to the outside using the resistance value of the sensor element 57.

  Next, the glow hole 111 provided in the engine head 110 will be described (see FIGS. 1 and 5). The glow hole 111 is provided so as to penetrate the inside and outside of the engine head 110, and includes a front end side circular hole portion 112, a tapered hole portion 113, and a rear end side circular hole portion 114. Among these, the distal end side circular hole portion 112 is a cylindrical hole that is located on the distal end side GS and opens into the combustion chamber NS and has a constant inner diameter d11 in the axial direction HJ. In the first embodiment, the inner diameter d11 of the distal end side circular hole portion 112 is d11 = 5.8 mm.

Further, the tapered hole 113 is a portion that is located on the rear end side GK of the front end side circular hole portion 112 and has a tapered shape with a smaller diameter toward the combustion chamber NS side (downward in the drawing). A taper-shaped outer peripheral surface 12m of the distal end side portion 12 of the tip cap member 11 in the metal shell 10 of the glow plug 1 is in pressure contact with the seat surface 113n forming the inner peripheral surface of the tapered hole portion 113.
The rear end side circular hole portion 114 is a cylindrical hole that is located on the rear end side GK of the tapered hole portion 113 and opens to the outside of the internal combustion engine 101 and has a constant inner diameter in the axial direction HJ. An attachment portion 114d having a female screw for attaching the glow plug 1 is provided at a portion of the rear end side circular hole portion 114 on the rear end side GK.

  The glow plug 1 is inserted into the glow hole 111 in such a manner that a part of the tip side GS of the heater projection 20s of the ceramic heater unit 20 projects into the combustion chamber NS. The glow plug 1 is fixed to the glow hole 111 by the male screw of the attachment portion 17 d of the glow plug 1 being screwed into the female screw of the attachment portion 114 d of the glow hole 111.

  Here, in the glow hole 111, a portion surrounding the heater protrusion 20s of the ceramic heater portion 20 from the outside in the radial direction is a protrusion surrounding portion 116, and a portion surrounding the metal shell 10 from the outside in the radial direction is a metal surrounding portion 117. . That is, the projecting portion surrounding portion 116 is configured by the front end side circular hole portion 112 of the glow hole 111 and the front end side hole portion 113 s of the tapered hole portion 113. On the other hand, the bracket surrounding portion 117 includes a rear end side hole portion 113k and a rear end side circular hole portion 114 of the tapered hole portion 113.

Regarding the inner diameter d1 of the projecting portion surrounding portion 116, the inner diameter d11 of the tip side circular hole portion 112 in the projecting portion surrounding portion 116 is d11 = 5.8 mm as described above. Further, the inner diameter of the tip side hole 113s of the taper hole 113 is larger than the inner diameter d11 of the tip side circular hole 112. On the other hand, of the outer diameter d2 of the heater protrusion 20s, the outer diameter d21 of the front end side portion 20sa is d21 = 3.1 mm as described above, and the outer diameter d22 of the rear end side portion 20sb is the front end side portion. It is larger than the outer diameter d21 of 20sa (d22> d21), and d22 = 4.0 mm. Accordingly, the difference in diameter (d1−d2) between the inner diameter d1 of the protruding portion surrounding portion 116 and the outer diameter d2 of the heater protruding portion 20s in the cross section orthogonal to the axial direction HJ in the protruding portion surrounding portion 116 and the heater protruding portion 20s. ), The minimum diameter difference B = min (d1−d2) is B = d11−d22 = 5.8−4.0 = 1.8 mm. Moreover, among the above-mentioned diameter differences (d1−d2), the maximum diameter difference D = max (d1−d2) is D = d11−d21 = 5.8−3.1 = 2.7 mm.
On the other hand, as described above, the minimum difference C = min (d3−d4) between the inner diameter d3 of the constant inner diameter portion 10hc and the outer diameter d4 of the heater hole inside 20k in the cross section is C = d3−d41 = 2.0 mm. It is. Therefore, in this internal combustion engine 101, B <C is satisfied.

  As described above, in the internal combustion engine 101 of the first embodiment, the minimum diameter difference B between the inner diameter d1 of the protruding portion surrounding portion 116 of the glow hole 111 and the outer diameter d2 of the heater protruding portion 20s of the ceramic heater portion 20 is The minimum diameter difference C between the inner diameter d3 of the constant inner diameter portion 10hc of the housing hole 10h of the metal shell 10 and the outer diameter d4 of the heater hole inside 20k of the ceramic heater portion 20 satisfies B <C. That is, in the internal combustion engine 101 (see FIG. 5), the housing hole is more than the gap SA between the inner peripheral surface 116n of the protruding portion surrounding portion 116 of the glow hole 111 and the outer peripheral surface 20sm of the heater protruding portion 20s of the ceramic heater portion 20. The clearance SB between the inner peripheral surface 10hcn of the constant inner diameter portion 10hc of 10h and the outer peripheral surface 20km of the heater hole inside 20k of the ceramic heater portion 20 is larger.

The heel is likely to be clogged in the portion where the gap is reduced, and is difficult to clog the portion where the gap is increased. Therefore, by setting B <C as described above, the outer peripheral surface of the inner peripheral surface 10hcn of the constant inner diameter portion 10hc of the accommodation hole 10h and the heater hole inner portion 20k of the ceramic heater portion 20 is relatively large. The gap SB with 20 km is less likely to be clogged with soot. Therefore, the clogging is caused in the gap SB between the inner peripheral surface 10hcn of the constant inner diameter portion 10hc of the accommodation hole 10h and the outer peripheral surface 20km of the heater hole inside 20k of the ceramic heater portion 20, so that the ceramic heater portion 20 is in the axial direction. It can be prevented that the detection sensitivity of the combustion pressure is lowered due to difficulty in displacement to HJ.
The gap SA between the inner peripheral surface 116n of the protruding portion surrounding portion 116 of the glow hole 111 and the outer peripheral surface 20sm of the heater protruding portion 20s of the ceramic heater portion 20 is relatively small. However, since the protruding portion surrounding portion 116 and the heater protruding portion 20s are close to the combustion chamber NS and become high temperature, even if soot accumulates in these gaps SA, they are burned by heat and disappear. For this reason, it is hard to clog these gaps SA.

  Furthermore, in this Embodiment 1, the heater part is the ceramic heater part 20 which has the ceramic heater main body 21 and the outer cylinder 31, and the outer cylinder 31 is an axial direction HJ inside the fixed internal diameter part 10hc of the accommodation hole 10h. Located throughout. Thus, in the form in which the outer cylinder 31 exists inside the constant inner diameter portion 10hc, the outer diameter d4 (d41) of the heater hole inside 20k tends to be large, and the minimum diameter difference C = min (d3-d4) is small. Tend to. However, since the internal combustion engine 101 is configured to satisfy B <C, as described above, the constant amount of the accommodation hole 10h is constant even though the outer cylinder 31 exists inside the constant inner diameter portion 10hc of the accommodation hole 10h. The SB is less likely to be clogged in the gap SB between the inner peripheral surface 10hcn of the inner diameter portion 10hc and the outer peripheral surface 20km of the heater hole inside 20k of the ceramic heater portion 20.

(Embodiment 2)
Next, a second embodiment will be described (see FIGS. 6 to 10). In the first embodiment, the heater portion of the glow plug 1 with a pressure sensor constituting the internal combustion engine 101 is the ceramic heater portion 20, whereas in the second embodiment, the glow plug 201 with a pressure sensor constituting the internal combustion engine 301 is used. This heater part is greatly different in that it is a sheathed heater part 220. In addition, the same code | symbol as Embodiment 1 is attached | subjected to the site | part which makes the form fundamentally similar to Embodiment 1, and the description is abbreviate | omitted or simplified.

  Of the glow plug 201 with pressure sensor of the second embodiment (hereinafter also simply referred to as the glow plug 201), the sheathed heater portion 220 has a rod shape in which the tip side GS portion is slightly thinner than the rear end side GK portion. Eggplant (see FIG. 7). For this reason, as will be described later, the outer diameter d2 of the heater protrusion 220s is smaller than the outer diameter d22 of the rear end side GK portion (d21 <d22).

  The sheathed heater unit 220 includes a sheathed tube 221, a heating coil 227, and insulating powder 228. The sheath tube 221 is a bottomed cylindrical metal member (specifically, an iron-nickel alloy product) that extends in the axial direction HJ and has a closed end 221a and an open rear end 221b. The heat generating coil 227 is disposed in the sheath tube 221 together with the insulating powder 228, the coil tip 227 s is connected to the inside of the tip 221 a of the sheath tube 221, and the coil rear end 227 k is the center shaft of the center shaft member 263. It is connected to the tip 263s.

  The middle shaft member 263 is a round bar-like metal member (specifically, stainless steel member) extending in the axial direction HJ. A portion of the middle shaft member 263 on the front end side GS is disposed in the sheath tube 221, and the coil rear end portion 227 k of the heating coil 227 is wound around and connected to the middle shaft front end portion 263 s (see FIG. 7). ). On the other hand, a portion of the middle shaft member 263 on the rear end side GK protrudes toward the rear end side GK from the rear end 221b of the sheath tube 221 (see FIG. 9).

  The sheathed heater 220 is held by the metal shell 10 so as to be displaceable in the axial direction HJ. Specifically, the heater protrusion 220s (see FIG. 7) protrudes toward the front end GS from the front end 11sa of the metal shell 10, and the heater hole interior 220k (see FIGS. 8 and 9) is inside the housing hole 10h of the metal shell 10. The metal shell 10 is held by the metal shell 10 so as to be displaceable in the axial direction HJ via the holding member 40, the displacement transmission member 51, the sensor support member 53, and the like.

  Of these, the outer diameter of the heater hole interior 220k (the outer diameter of the tube rear end side portion 221k forming the heater hole interior 220k of the sheath tube 221) d4 is constant in the axial direction HJ, and d4 = 4.0 mm. On the other hand, the inner diameter d3 of the constant inner diameter portion 10hc of the accommodation hole 10h is d3 = 6.0 mm in the second embodiment. Therefore, the diameter difference (d3-d4) between the inner diameter d3 of the constant inner diameter portion 10hc and the outer diameter d4 of the heater hole inner portion 220k in a cross section perpendicular to the axial direction HJ in the constant inner diameter portion 10hc and the heater hole inner portion 220k is It is constant regardless of the position in the axial direction HJ, and the diameter difference (d3-d4) = d3-d4 = 6.0-4.0 = 2.0 mm. Therefore, the minimum diameter difference C = min (d3-d4) in the diameter difference (d3-d4) is also C = 2.0 mm.

  Further, regarding the outer diameter d2 of the heater protrusion 220s, the outer diameter of the rear end side GK portion of the heater protrusion 220s (the outer diameter of the tube tip side portion 221s that forms the heater protrusion 220s of the sheath tube 221) d22. Is equal to the outer diameter d4 of the heater hole interior 220k (d22 = d4), and d22 = 4.0 mm. On the other hand, the outer diameter d21 of the heater protrusion 220s on the tip side GS is smaller than the inner diameter of the heater hole 220k and the like, and d21 = 3.5 mm.

  On the other hand, regarding the inner diameter d1 of the protruding portion surrounding portion 116 of the glow hole 111, the inner diameter d11 of the tip side circular hole portion 112 in the protruding portion surrounding portion 116 is d11 = 5.8 mm in the second embodiment. . Accordingly, the difference in diameter (d1-d2) between the inner diameter d1 of the protruding portion surrounding portion 116 and the outer diameter d2 of the heater protruding portion 220s in a cross section orthogonal to the axial direction HJ in the protruding portion surrounding portion 116 and the heater protruding portion 220s. Among them, the minimum diameter difference B = min (d1-d2) is B = d11-d22 = 5.8-4.0 = 1.8 mm. Of the above-mentioned diameter differences (d1−d2), the maximum diameter difference D = max (d1−d2) is D = d11−d21 = 5.8−3.5 = 2.3 mm. Therefore, the internal combustion engine 301 of the second embodiment also satisfies B <C.

  As described above, the internal combustion engine 301 of the second embodiment also has a minimum diameter difference B between the inner diameter d1 of the protruding portion surrounding portion 116 of the glow hole 111 and the outer diameter d2 of the heater protruding portion 220s of the sheathed heater portion 220. The minimum diameter difference C between the inner diameter d3 of the constant inner diameter portion 10hc of the accommodation hole 10h and the outer diameter d4 of the heater hole inner portion 220k of the sheathed heater portion 220 satisfies B <C. That is, the internal combustion engine 301 (see FIG. 10) also has an accommodation hole that is larger than the gap SA between the inner peripheral surface 116n of the protruding portion surrounding portion 116 of the glow hole 111 and the outer peripheral surface 220sm of the heater protruding portion 220s of the sheathed heater portion 220. The gap SB between the inner peripheral surface 10hcn of the constant inner diameter portion 10hc of 10h and the outer peripheral surface 220km of the heater hole interior 220k of the sheathed heater portion 220 is larger. For this reason, the gap SB between the inner peripheral surface 10hcn of the constant inner diameter portion 10hc of the accommodation hole 10h and the outer peripheral surface 220km of the heater hole inside 220k of the sheathed heater portion 220 that has a relatively large gap is less likely to be clogged with soot. Therefore, the sheath heater 220 is axially displaced due to the clogging of the gap SB between the inner peripheral surface 10hcn of the constant inner diameter portion 10hc of the accommodation hole 10h and the outer peripheral surface 220km of the heater hole interior 220k of the sheath heater 220. It can be prevented that the detection sensitivity of the combustion pressure is lowered due to difficulty in displacement to HJ. In addition, the same part as Embodiment 1 has the same effect as Embodiment 1. FIG.

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

1,201 Glow plug 10 Metal shell 10h Accommodating hole 10hc Inner peripheral surface 10hcn (of constant inner diameter) Inner peripheral surface 10hs Tip opening edge 11 Tip cap member 11sa Tip (of metal fitting and tip cap member) 12 (tip cap member) ) Tip side 20 Ceramic heater (heater)
220 Seeds heater (heater)
20s, 220s Heater protrusion 20k, 220k Heater hole inside 21 Ceramic heater body 26 Ceramic base 27 Heating resistor 221 Sheath tube 221a (Seeds tube) tip 221b (Seeds tube) rear end 227 Heating coil 31 Outer tube 40 Holding member 50 Sensor parts 101, 301 Internal combustion engine 110 Engine head 111 Glow hole 112 Front end side circular hole part 113 Tapered hole part 113s (a tapered hole part) Front end side hole part 113k (a taper hole part) Rear end side hole part 114 Rear end Side circular hole portion 116 Projection portion surrounding portion 117 Bracket surrounding portion AX (main metal fitting) axis HJ Axial direction GS (axial direction) tip side GK (axial direction) rear end side NS Combustion chamber d1 (projection portion surrounding portion) ) Inner diameter d2 (outer part of heater) outer diameter d3 (constant inner diameter part) inner diameter d4 (inside heater hole) ) Outer diameter

Claims (3)

An internal combustion engine in which a glow plug with a pressure sensor is mounted in a glow hole of an engine head,
The glow plug with pressure sensor is
A cylindrical metal shell having a housing hole penetrating in the axial direction;
A heater protrusion protruding toward the tip end side in the axial direction from the tip end of the metal shell, and the metal shell on the rear end side in the axial direction of the heater protrusion and in the accommodation hole of the metal shell. And a rod-shaped heater portion that is held in the metal shell so as to be displaceable in the axial direction, with the inside of the heater hole being disposed apart from the heater hole,
A sensor unit for detecting the displacement of the heater unit,
The accommodation hole is
Continuing from the rear end side in the axial direction of the front end opening edge, and having a constant inner diameter portion having a constant inner diameter in the axial direction,
Of the glow hole, a portion surrounding the heater protrusion of the heater portion from the outside in the radial direction is a protrusion surrounding portion,
The difference in diameter (d1-d2) between the inner diameter d1 of the protruding portion surrounding portion and the outer diameter d2 of the heater protruding portion in a cross section orthogonal to the axial direction in the protruding portion surrounding portion and the heater protruding portion. Among them, the minimum diameter difference is B = min (d1-d2),
Of the difference in diameter (d3−d4) between the inner diameter d3 of the constant inner diameter portion and the outer diameter d4 inside the heater hole in the cross section inside the constant inner diameter portion and the heater hole, the minimum diameter difference is C = When min (d3-d4),
An internal combustion engine in which the protruding portion surrounding portion, the heater protruding portion, the constant inner diameter portion, and the heater hole are configured to satisfy B <C. The internal combustion engine according to claim 1,
The heater part is
A ceramic heater body in which a ceramic base made of insulating ceramic and a heating resistor are integrated;
A ceramic heater part having a cylindrical and metal outer cylinder holding the ceramic heater body inside itself,
The outer cylinder is located over the entire axial direction inside at least the constant inner diameter portion of the accommodation hole,
The outer diameter d2 is an outer diameter of a portion of the ceramic heater main body or the outer cylinder that forms the outer peripheral surface of the heater protrusion,
The outer diameter d4 is an internal combustion engine that is an outer diameter of a portion of the outer cylinder that forms the heater hole. The internal combustion engine according to claim 1,
The heater part is
A metal tube with a bottomed cylindrical shape with a closed end in the axial direction and an open rear end; and
A sheathed heater section having a heating coil disposed in the sheath tube,
The outer diameter d2 is an outer diameter of a portion of the sheath tube that forms the heater protrusion,
The outer diameter d4 is an internal combustion engine that is an outer diameter of a portion of the sheath tube that forms the inside of the heater hole.

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