JP4289273B2 - Glow plug - Google Patents

Description

  The present invention relates to a glow plug used for preheating a combustion chamber of a diesel engine.

  In conventional glow plugs, a heating element that generates heat when energized is inserted and fixed in a cylindrical protective pipe, and this protective pipe is inserted and fixed in a cylindrical housing, and heat is generated through a central shaft inserted in the housing. It is designed to supply power to the body. Further, the glow plug is fixed to the cylinder head by screwing the male screw formed on the housing with the female screw formed on the cylinder head.

In order to prevent the rotation of the center shaft, the center shaft is held and fixed to the housing by glass welding (for example, see Patent Document 1), or the center shaft is held and fixed to the housing by caulking the housing (for example, Patent Document 1) 2 and 3) are known.
JP-A-8-320118 JP-A-63-311022 JP 2002-327919 A

  However, the glow plug in which the central shaft is held and fixed to the housing by glass welding has the following problems (a) to (c). (A) There are many steps when assembling the glass, and the assembling property is not good. (B) Since the temperature is high (500 ° C.) at the time of glass welding, the strength of the metal part decreases. (C) After glass welding, it is necessary to perform plating to prevent oxidation, and there is a concern of short circuit due to intrusion of the plating solution.

  On the other hand, the glow plug in which the center shaft is held and fixed to the housing by caulking the housing has the following problems (d) and (e). (D) Due to the deformation of the housing due to caulking, the tapered surface of the housing comes into contact with the tapered surface of the cylinder head and the combustion gas leaks. (E) When the housing is deformed by caulking, the heating element is shaken, and if the glow plug is mounted on the cylinder head while the heating element is eccentric, the heating element interferes with the cylinder head and breaks.

  Further, in a glow plug including a combustion pressure sensor that detects the combustion pressure of the engine, the sensitivity of the combustion pressure sensor increases as the center shaft fixing portion and the combustion pressure sensor mounting portion are separated. However, in the case of a glow plug equipped with a combustion pressure sensor that detects the combustion pressure of the engine and the center shaft is held and fixed to the housing by glass welding, the center shaft is fixed at a position very close to the site where the combustion pressure sensor is mounted. There was a problem that the sensitivity of was minimized.

  In addition, when using a glow plug with a combustion pressure sensor that detects the combustion pressure of the engine and the housing is caulked to hold and fix the center shaft to the housing, it can be relatively caulked at the front end of the housing. This is advantageous, but the position of the male screw formed in the housing, that is, the length from the male screw end to the fixed one end of the protective pipe is limited. Further, in the case of a housing having a shape in which the caulking margin cannot be secured, it is not possible to employ a structure in which the center shaft is held and fixed to the housing by caulking the housing.

  The present invention has been made in view of the above points, and an object thereof is to make it possible to solve at least one of the various problems in the conventional glow plug described above.

In order to achieve the above object, according to the first aspect of the present invention, a cylindrical housing (10) attached to the engine so that one end side is located on the combustion chamber side of the engine, and one end side of the housing (10) are provided. The inserted and fixed protective pipe (20), inserted into the protective pipe (20), and heated by a ceramic heating element (30) that generates heat when energized, and inserted into the other end of the housing (10), A glow plug including a middle shaft (50) electrically connected to a heating element (30) includes a sheath tube (40) into which the middle shaft (50) is inserted to hold the middle shaft (50), and a protective pipe (20 ), A hole (22) is formed, and a sheath pipe (40) is inserted into the hole (22) to join the protective pipe (20) and the sheath pipe (40). To do.

  According to this, the middle shaft is held and fixed to the housing via the sheath tube and the protective pipe. That is, the center shaft can be held and fixed to the housing in a non-rotatable manner without performing conventional glass welding or caulking of the housing.

  Therefore, the conventional problems (a) to (e) described above can be solved. Specifically, by eliminating the glass assembly process, it is possible to improve ease of assembly, prevent metal parts from decreasing in strength, and prevent short circuits due to ingress of plating solution. Body breakage can be avoided.

  As in the second aspect of the invention, the protective pipe (20) and the sheath tube (40) can be brazed.

  As in the third aspect of the invention, the housing (10) and the protective pipe (20) can be joined on the combustion chamber side with respect to the joint portion between the protective pipe (20) and the sheath pipe (40). .

  In the invention according to claim 4, in the glow plug according to claim 1 or 2, an insulating material is filled between the sheath tube (40) and the middle shaft (50) to form an insulating layer (60), The joint portion between the housing (10) and the protective pipe (20) and the joint portion between the protective pipe (20) and the sheath tube (40) are positions overlapping in the radial direction.

  According to this, since the protective pipe is joined to the sheath pipe that has been filled with the insulating material and has increased rigidity, and the housing and the protective pipe are joined on the outer peripheral side of the joined portion, the central shaft constituted by the heating element, etc. The holding strength of the assembly to the housing can be maintained.

In the invention according to claim 5, a cylindrical housing (10) attached to the engine so that one end side is located on the combustion chamber side of the engine, and a protective pipe (inserted and fixed to one end side of the housing (10)). 20), a ceramic heating element (30) which is inserted into the protective pipe (20) and generates heat when energized, and is inserted into the other end of the housing (10), and a heating element ( 30) and a combustion pressure sensor which is disposed on the other end side of the middle shaft (50) and detects the combustion pressure by transmitting the combustion pressure of the engine via the middle shaft (50). (200) is provided with a sheath tube (40) in which the middle shaft (50) is inserted to hold the middle shaft (50), and a hole (22) is formed at the end of the protective pipe (20), This hole (22 The sheath tube (40) is inserted, the protective pipe (20) and sheath tube (40) and is characterized in that it is joined.

  According to this, the middle shaft is held and fixed to the housing via the sheath tube and the protective pipe. That is, the center shaft can be held and fixed to the housing in a non-rotatable manner without performing conventional glass welding or caulking of the housing. Therefore, an effect similar to that of the first aspect can be obtained.

  Further, since the center shaft can be held and fixed without caulking the housing, it is effective for a glow plug of a housing having a shape in which the caulking margin cannot be secured. Furthermore, the male screw of the housing can be provided on the front end side of the housing (side near the combustion chamber). Furthermore, since the caulking of the housing is unnecessary, the restriction on the length of the glow plug can be eliminated.

  As in the invention described in claim 6, in the glow plug described in claim 5, the protective pipe (20) and the sheath tube (40) can be brazed and joined.

  According to a seventh aspect of the present invention, in the glow plug according to the fifth or sixth aspect, the housing (10) and the protective pipe (20) are more than a joint portion between the protective pipe (20) and the sheath pipe (40). It is joined on the combustion chamber side.

  According to this, the joint between the housing and the protective pipe is close to the front end of the housing, and the sensitivity of the combustion pressure sensor is increased.

  In the invention according to claim 8, in the glow plug according to claim 5 or 6, an insulating material is filled between the sheath tube (40) and the middle shaft (50) to form an insulating layer (60), The joint portion between the housing (10) and the protective pipe (20) and the joint portion between the protective pipe (20) and the sheath tube (40) are positions overlapping in the radial direction.

  According to this, the same effect as in the fourth aspect can be obtained.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing the overall configuration of the glow plug G1 according to the first embodiment, and FIG. 2 is an enlarged cross-sectional view showing the vicinity of the heating element 30 in FIG. In each of the following embodiments, in each part of the glow plug G1, one end corresponds to the lower end in the figure, and the other end corresponds to the upper end in the figure.

  1 and 2, this glow plug G1 is attached to each of a plurality of mounting holes (glow holes) formed in a cylinder head in an automobile diesel engine, for example. Applicable to promote combustion.

  The housing 10 is a cylindrical member that can be attached to the engine, and is made of a conductive material (for example, carbon steel). On the outer peripheral surface between the one end 11 and the other end 12 of the housing 10, a male screw 13 for mounting and a hexagonal portion 14 for screw tightening are formed.

  Although not shown, the glow plug G1 is inserted into the hole of the cylinder head while the one end 11 side of the housing 10 is positioned on the combustion chamber side, and the female screw portion and the male screw 13 formed in the hole portion are screwed. Combined. Thereby, the glow plug G1 is detachably attached to the cylinder head.

  A cylindrical protective pipe 20 is accommodated in the inner hole of the housing 10. The protective pipe 20 has electrical conductivity, and is made of, for example, a heat-resistant / corrosion-resistant alloy such as stainless steel, and is manufactured by cold forging or the like. The protection pipe 20 is inserted into the housing 10 at the other end side with one end side protruding from the one end 11 of the housing 10.

  The inner peripheral surface of the protective pipe 20 has a stepped shape, and a small diameter hole 21 and a large diameter hole 22 are formed. Further, the outer peripheral surface of the protective pipe 20 has a stepped shape, and a large-diameter portion 23 having the maximum diameter is formed in the middle portion in the longitudinal direction. The small-diameter hole 21 houses a ceramic rod-shaped heating element 30 that generates heat when energized. The heating element 30 is inserted into the protective pipe 20 at the other end 32 side with one end 31 protruding from one end of the protective pipe 20. Here, the heating element 30 is fixed and held on the protective pipe 20 by brazing the insertion portion or the like.

  The heat generating body 30 is formed by embedding a heat generating portion 33 having conductivity in an insulator 35 made of an insulating ceramic. Specifically, the heating element 30 includes a U-shaped heating part 33 and a pair of lead wires 34 that are electrically connected to the heating part 33 and energize the heating part 33. Reference numeral 33 denotes a sintered body in which the lead wire 34 and the lead wire 34 are embedded in the insulator 35.

  Here, the heat generating portion 33 is made of a conductive ceramic containing, for example, silicon nitride and tungsten carbide as components, and the pair of lead wires 34 is made of a metal wire made of tungsten or the like, for example. Is made of an insulating ceramic containing silicon nitride as a component, for example.

  A cylindrical sheath tube 40 and a rod-shaped inner shaft 50 are accommodated on the other end 12 side of the housing 10 in the inner hole of the housing 10. The sheath tube 40 is made of a metal such as stainless steel, the middle shaft 50 is inserted into the sheath tube 40, and an insulating layer 60 made of, for example, magnesia powder is formed between the sheath tube 40 and the middle shaft 50. Is held by the sheath tube 40 via the insulating layer 60.

  The middle shaft 50 is made of a conductive metal such as carbon steel, and is processed by cutting and cold forging, for example. A recess 51 into which the other end 32 of the heating element 30 is inserted is formed on one end side of the middle shaft 50. One end side of the sheath tube 40 and one end side of the middle shaft 50 are inserted into the large-diameter hole 22 of the protective pipe 20.

  One end of the lead wire 34 of the heating element 30 is exposed on the outer peripheral surface of the insulator 35, and the other end 32 of the heating element 30 is inserted into the recess 51 of the intermediate shaft 50, thereby At the exposed portion of the lead wire 34, one lead wire 34 of the heating element 30 and the middle shaft 50 are electrically connected. The recess 51 and the other end 32 of the heating element 30 are pressure-bonded and held by shrink fitting through a brazing material such as silver-copper brazing.

  The other end of the lead wire 34 is exposed on the outer peripheral surface of the insulator 35 in the protective pipe 20, and the exposed end and the protective pipe 20 are made of a brazing material such as silver-copper solder. It is pressure-bonded and electrically connected by shrink fitting through a material. As a result, the other lead wire 34 is grounded to the housing 10 via the protective pipe 20.

  In addition, a screw pin 70 made of a conductive metal such as carbon steel is joined to the other end side of the middle shaft 50. A part of the screw pin 70 protrudes from the other end 12 of the housing 10, and a terminal screw portion 71 is formed on the protruding portion. A nut 72 is screwed into the terminal screw portion 71, and an insulating bush 73 is disposed between the nut 72 and the housing 10. In addition, an external wiring member (not shown) that is electrically connected to a power source (not shown) via a terminal nut is separately disposed on the nut 72. Between the screw pin 70 and the housing 10, an annular rubber ring 80 for holding, fixing and centering the screw pin 70 is interposed.

  Next, a method for manufacturing the glow plug G1 having the above configuration will be described. FIG. 3 is a process diagram showing the assembly process of the glow plug G1, and FIG. 4 is an enlarged sectional view showing a state immediately before the brazing process shown in FIG.

  First, as shown in FIG. 3A, the central shaft 50 is inserted into the sheath tube 40, and the lower end opening side of the sheath tube 40 is closed with a plug 100 made of silicon rubber.

  Next, as shown in FIG. 3B, after filling the insulating material 110 such as magnesia powder between the sheath tube 40 and the middle shaft 50, vibration is applied to increase the filling density of the insulating material 110. Do.

  Next, as shown in FIG. 3C, liquid silicon is injected from the upper end opening of the sheath tube 40 to form the sealing layer 120, and the upper end opening of the sheath tube 40 is sealed.

  Next, as shown in FIG. 3D, the entire sheath tube 40 is swaged to increase the density of the insulating material 110, solidify the insulating material 110, and form the insulating layer 60. The intermediate shaft 50 is firmly held by the sheath tube 40 through the insulating layer 60. Further, the small diameter portion 41 is formed on the outer diameter on the lower end side of the sheath tube 40 by swaging or cutting. The small diameter portion 41 is formed in a size that can be inserted into the large diameter hole 22 of the protective pipe 20.

  Next, as shown in FIG. 3E, the stopper 100 and the sealing layer 120 are incinerated.

  Next, as shown in FIG. 3F, each part is brazed. In this brazing step, first, as shown in FIG. 4, each component is temporarily assembled, and brazing materials 130, 131, 132 such as copper brazing or silver-copper brazing are disposed at predetermined positions. Specifically, in order to join the sheath tube 40 and the protective pipe 20, a coil-shaped brazing material 130 is disposed on the annular relief portion 24 formed in the protective pipe 20. In order to hold and fix the heating element 30 and the middle shaft 50, a plate-like brazing material 131 is disposed in the recess 51 of the middle shaft 50. In order to hold and fix the protective pipe 20 and the heating element 30, a ring-shaped brazing material 132 is disposed at the bottom in the large-diameter hole 22 of the protective pipe 20.

  After arranging the brazing materials 130, 131, 132 in this way, the respective parts are joined, held and fixed by a single vacuum brazing. What was obtained by the process of FIG.3 (f) is hereafter called a protection pipe assembly.

  Next, as shown in FIG. 3G, the screw pin 70 is joined to the protective pipe assembly. Incidentally, when swaging the sheath tube 40, the central shaft 50 is also extended through the insulating layer 60 as the entire length of the sheath tube 40 is extended. Therefore, in this step, after the middle shaft 50 extended by swaging is cut into a predetermined length, the middle shaft 50 and the screw pin 70 in the protective pipe assembly are joined by plasma welding. What was obtained in the process of FIG. 3G is hereinafter referred to as a central shaft assembly.

  Next, as shown in FIG. 3 (h), the large-diameter portion 23 of the protective pipe 20 in the center shaft assembly and the inner peripheral surface on the one end 11 side of the housing 10 are joined by, for example, silver-copper brazing. . In other words, the housing 10 and the protective pipe 20 are joined on the combustion chamber side with respect to the joint portion between the protective pipe 20 and the sheath tube 40.

  Next, the nut 72 (see FIG. 1), the bush 73 (see FIG. 1), and the ring 80 (see FIG. 1) are assembled to complete the glow plug G1 shown in FIG.

  In the present embodiment, the middle shaft 50 is held and fixed to the housing 10 via the insulating layer 60, the sheath tube 40, and the protective pipe 20. That is, the intermediate shaft 50 can be held and fixed to the housing 10 so as not to rotate without performing conventional glass welding or caulking of the housing 10.

  Therefore, by eliminating the glass assembling process, it is possible to improve the assembling performance, to prevent the strength of metal parts from being reduced, and to prevent a short circuit due to the penetration of the plating solution, and by eliminating the housing caulking process, combustion gas leakage and heating element 30 can be prevented. Breakage can be avoided.

(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 5 is a cross-sectional view showing a state immediately before the brazing process of the glow plug G1 according to the second embodiment. The same or equivalent parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the step of FIG. 3F in the first embodiment, when the vertical direction of the temporary assembly when performing vacuum brazing is reversed, the brazing materials 130, 131, and 132 are disposed as in the present embodiment.

  That is, as shown in FIG. 5, in order to join the sheath tube 40 and the protective pipe 20, a coil-shaped brazing material 130 is disposed in an annular relief portion 42 formed in the sheath tube 40. In order to hold and fix the heating element 30 and the middle shaft 50, a plate-like brazing material 131 is disposed in the recess 51 of the middle shaft 50. In order to hold and fix the protective pipe 20 and the heating element 30, a ring-shaped brazing material 132 is disposed at the end of the protective pipe 20 on the combustion chamber side. After arranging the brazing materials 130, 131, 132 in this way, the respective parts are joined by one vacuum brazing.

  In this embodiment, the same effect as that of the first embodiment can be obtained.

(Third embodiment)
A third embodiment of the present invention will be described. In this embodiment, a combustion pressure sensor 200 is added to the glow plug G1 of the first embodiment. FIG. 6 is a cross-sectional view showing the overall configuration of the glow plug G1 according to the third embodiment, and FIG. 7 is an enlarged cross-sectional view showing the vicinity of the combustion pressure sensor 200 in FIG. In addition, the same code | symbol is attached | subjected to the same or equivalent part as 1st Embodiment, and the description is abbreviate | omitted.

  As shown in FIG. 6, the glow plug G1 of the present embodiment includes a combustion pressure sensor 200 that detects the combustion pressure by transmitting the combustion pressure of the engine through the middle shaft 50 or the like to the inside of the hexagonal portion 14 in the housing 10. It is stored. The combustion pressure sensor 200 is fixedly held between the insulating bush 73 and the housing 10 by tightening the fixing nut 74, and a preload is applied to the piezoelectric element 201.

  As shown in FIG. 7, in the combustion pressure sensor 200, two annular piezoelectric elements 201 made of lead titanate or lead zirconate titanate are disposed with an annular electrode 202 interposed therebetween, and are electrically connected. Are connected in parallel. Both the piezoelectric element 201 and the electrode 202 are sandwiched between a sensor housing 203 and a pedestal 204 formed of a conductive metal in a substantially annular shape.

  The shielded electric wire 205 for taking out the signal of the combustion pressure sensor 200 has a core wire connected to the electrode 202, and a shield wire insulated from the core wire is connected to the sensor housing 203 and is grounded. The shield electric wire 205 passes through holes formed in the sensor housing 203 and the insulating bush 73.

  An O-ring 206 is disposed between the inner peripheral surface of the hole of the sensor housing 203 and the shield electric wire 205, and an O-ring is provided between the outer peripheral surface of the sensor housing 203 and the inner peripheral surface of the hexagonal portion 14 in the housing 10. 207 is disposed, and a cylindrical ring 208 is disposed between the inner peripheral surface of the sensor housing 203 and the outer peripheral surface of the screw pin 70.

  Here, the O-rings 206 and 207 are intended to ensure waterproofness and airtightness, and the cylindrical ring 208 is intended to suppress vibration of the screw pin 70 and ensure waterproofness and airtightness. The O-rings 206 and 207 and the cylindrical ring 208 are made of silicon rubber, fluorine rubber, EPDM, NBR, H-NBR, or the like.

  In the glow plug G1 configured as described above, the combustion pressure generated in the combustion chamber of the engine is transmitted to the combustion pressure sensor 200 via the heating element 30, the middle shaft 50, the screw pin 70, the fixing nut 74, the insulating bush 73, and the like. .

  As a result, the preload preliminarily applied to the piezoelectric element 201 by the fixing nut 74 is relaxed. Since the load state applied to the piezoelectric element 201 changes, the generated electric charge as an electric signal output along with the piezoelectric characteristics changes, and the electric signal is output to an ECU (not shown) via the shield wire 205. The

  In the present embodiment, the middle shaft 50 is held and fixed to the housing 10 via the insulating layer 60, the sheath tube 40, and the protective pipe 20. That is, the intermediate shaft 50 can be held and fixed to the housing 10 so as not to rotate without performing conventional glass welding or caulking of the housing 10. Therefore, the same effect as that of the first embodiment can be obtained.

  Further, since the middle shaft 50 can be held and fixed without caulking the housing 10, it is effective for a glow plug of a housing having a shape in which the caulking margin cannot be secured. Furthermore, the male screw 13 of the housing 10 can be provided on the housing front end side (side closer to the combustion chamber). Furthermore, since the caulking of the housing is unnecessary, the restriction on the length of the glow plug can be eliminated.

  Further, since the housing 10 and the protection pipe 20 are joined on the combustion chamber side with respect to the joint portion between the protection pipe 20 and the sheath tube 40, the sensitivity of the combustion pressure sensor 200 is increased.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. In the present embodiment, the joining position of the housing 10 and the protective pipe 20 is different from that of the first embodiment. FIG. 8 is a cross-sectional view showing a configuration of a main part of a glow plug G1 according to the fourth embodiment. In addition, the same code | symbol is attached | subjected to the same or equivalent part as 1st Embodiment, and the description is abbreviate | omitted.

  As shown in FIG. 8, the sheath tube 40 and the protection pipe 20 are joined at a fitting portion between the small diameter portion 41 of the sheath tube 40 and the large diameter hole 22 of the protection pipe 20 as in the first embodiment. Yes. Here, the insulating layer 60 is formed up to the inside of the small-diameter portion 41 of the sheath tube 40, whereby the small-diameter portion 41 of the sheath tube 40 has high rigidity.

  A small diameter portion 15 is formed on the outer peripheral side of the joint portion between the sheath tube 40 and the protective pipe 20 on the inner peripheral surface of the housing 10. The large diameter portion 23 of the protection pipe 20 extends from the middle portion in the longitudinal direction to the other end. The housing 10 and the protective pipe 20 are joined by, for example, silver-copper brazing at a fitting portion between the small diameter portion 15 of the housing 10 and the large diameter portion 23 of the protective pipe 20.

  In other words, the joint portion between the sheath tube 40 and the protective pipe 20, the joint portion between the housing 10 and the protective pipe 20, and the insulating layer 60 are in a position overlapping in the radial direction.

  In this way, the protective pipe 20 is joined to the sheath tube 40 that has been filled with the insulating material and has increased rigidity, and the housing 10 and the protective pipe 20 are joined on the outer peripheral side of the joined portion, whereby the heating element 30 and the like. The holding | maintenance intensity | strength to the housing 10 of the center axis | shaft assembly comprised from can be maintained.

  In the present embodiment, the position of the small-diameter hole 21 of the protective pipe 20 that holds the heating element 30 does not overlap with the joint portion between the housing 10 and the protective pipe 20 in the radial direction. Even if 20 is joined by press-fitting, there is almost no increase in stress of the heating element 30 due to the press-fitting.

  Therefore, the housing 10 and the protective pipe 20 may be joined by press fitting. In this case, first, a middle shaft assembly and a pre-plated housing 10 are prepared. It is assumed that the outer diameter of the large diameter portion 23 of the protective pipe 20 in the prepared intermediate shaft assembly is slightly larger than the inner diameter of the small diameter portion 15 of the housing 10 and has a dimensional difference of, for example, +60 to +140 μm.

  Then, the protective pipe 20 in the middle shaft assembly is fitted into the housing 10 with a length of 10 mm, for example, and the housing 10 and the protective pipe 20 are fixed and sealed by mutual elastic force. By this press-fitting, the pulling strength between the housing 10 and the protective pipe 20, that is, the holding force is secured at 4 kN or more, and the housing 10 and the protective pipe 20 are joined and integrated.

  As described above, when the housing 10 and the protective pipe 20 are joined by press fitting, the following advantages can be obtained as compared with the case of joining by brazing.

  First, by eliminating the influence of heat on the housing 10, a decrease in material strength can be prevented. This eliminates buckling / deformation of the housing 10 when the glow plug G1 is mounted on the engine, and particularly eliminates the contribution to the occurrence of vibration of the heating element 30. It leads to improvement.

  Further, in the press-fitting method, since the housing 10 is plated in advance as a single unit, the plating liquid does not enter the housing 10 during manufacture. As a result, it is possible to significantly reduce the processes such as removal of flux and oxide film after brazing, waterproofing measures during plating processing, insulation inspection after assembly, etc., which were carried out by the brazing method. Simplification and manufacturing cost reduction.

  FIG. 9 shows a first modification of the fourth embodiment. The narrow diameter portion 15 of the housing 10 is provided at a position closer to the one end 11 of the housing 10 than the fourth embodiment. The joint portion between the protective pipe 20 and the joint portion between the housing 10 and the protective pipe 20 are moved to a position near the one end 11 of the housing 10.

  In this way, by changing the position of the joint portion, the protrusion amount x can be adjusted even with the heating element 30 having the same size. As a result, there is no need to line up the heat generating elements 30 having different element lengths y for each engine having a different protrusion amount x as in the prior art, and a single type of heat generating element 30 can be used in common. Can be greatly reduced.

  FIG. 10 shows a second modification of the fourth embodiment, and uses a heating element 30 having an element length y shorter than that of the fourth embodiment. In this way, when combined with the heating element 30 having a short element length y, the adjustment range of the protruding amount x can be further expanded, and all direct injection diesel engines that are currently becoming mainstream can be handled.

  The fourth embodiment can also be applied to a glow plug G1 having a combustion pressure sensor 200 (see FIG. 6).

It is sectional drawing which shows the whole structure of the glow plug G1 which concerns on 1st Embodiment of this invention. It is sectional drawing which expands and shows the vicinity of the heat generating body 30 in FIG. It is process drawing which shows the assembly | attachment process of the glow plug G1 of FIG. It is an expanded sectional view which shows the state immediately before the brazing process shown in FIG.3 (f). It is sectional drawing which shows the state just before the brazing process in the glow plug G1 which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the whole structure of the glow plug G1 which concerns on 3rd Embodiment of this invention. It is sectional drawing which expands and shows the vicinity of the combustion pressure sensor 200 in FIG. It is sectional drawing which shows the structure of the principal part of the glow plug G1 which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the 1st modification of 4th Embodiment. It is sectional drawing which shows the 2nd modification of 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Housing, 20 ... Protection pipe, 30 ... Heat generating body, 40 ... Sheath pipe | tube, 50 ... Medium shaft.

Claims (8)

A cylindrical housing (10) attached to the engine such that one end side is located on the combustion chamber side of the engine;
A protective pipe (20) inserted and fixed to one end of the housing (10);
A ceramic heating element (30) inserted into the protective pipe (20) and generating heat when energized;
In a glow plug that is inserted into the other end of the housing (10) and includes a middle shaft (50) electrically connected to the heating element (30),
A sheath tube (40) in which the middle shaft (50) is inserted to hold the middle shaft (50);
A hole (22) is formed at the end of the protective pipe (20), and the sheath pipe (40) is inserted into the hole (22), so that the protective pipe (20) and the sheath pipe (40) are connected. Glow plug characterized by being joined. The glow plug according to claim 1, wherein the protective pipe (20) and the sheath tube (40) are brazed. The said housing (10) and the said protective pipe (20) are joined by the said combustion chamber side rather than the junction part of the said protective pipe (20) and the said sheath pipe | tube (40). The glow plug according to 1 or 2. An insulating material is filled between the sheath tube (40) and the middle shaft (50) to form an insulating layer (60),
The joint portion between the housing (10) and the protective pipe (20) and the joint portion between the protective pipe (20) and the sheath tube (40) are positions that overlap in the radial direction. Item 3. A glow plug according to item 1 or 2. A cylindrical housing (10) attached to the engine such that one end side is located on the combustion chamber side of the engine;
A protective pipe (20) inserted and fixed to one end of the housing (10);
A ceramic heating element (30) inserted into the protective pipe (20) and generating heat when energized;
A middle shaft (50) inserted into the other end of the housing (10) and electrically connected to the heating element (30) at one end;
In a glow plug comprising a combustion pressure sensor (200) disposed on the other end side of the middle shaft (50) and detecting the combustion pressure when the combustion pressure of the engine is transmitted through the middle shaft (50).
A sheath tube (40) in which the middle shaft (50) is inserted to hold the middle shaft (50);
A hole (22) is formed at the end of the protective pipe (20), and the sheath pipe (40) is inserted into the hole (22), so that the protective pipe (20) and the sheath pipe (40) are connected. Glow plug characterized by being joined. The glow plug according to claim 5, wherein the protective pipe (20) and the sheath tube (40) are joined by brazing. The said housing (10) and the said protective pipe (20) are joined by the combustion chamber side rather than the junction part of the said protective pipe (20) and the said sheath pipe | tube (40). Or the glow plug of 6. An insulating material is filled between the sheath tube (40) and the middle shaft (50) to form an insulating layer (60),
The joint portion between the housing (10) and the protective pipe (20) and the joint portion between the protective pipe (20) and the sheath tube (40) are positions that overlap in the radial direction. Item 7. The glow plug according to Item 5 or 6.

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