CN1606678A - Glow plug for diesel engine and method of manufacturing the glow plug - Google Patents

Abstract

A glow plug for diesel engine, wherein one end of a ceramic heater 2 is fixed to one end of a metallic outer tube 4 and the negative pole of the heater 2 is electrically connected to the metallic outer tube 4, the positive pole thereof is connected to an outer connection terminal 8 through an electrode extractor 6, the metallic outer tube 4 having the heater 2 and the outer connection terminal 8 therein are inserted into the internal hole 16 of a housing 10 and, after the tip of the heater 2 is positioned relative to the seat face 10a of the housing 10, swading is performed from the outer peripheral side of the housing 10, an annular projected part 10d is formed on the inner peripheral surface of the housing 10 and an annular recessed part 4c fitted to the annular projected part 10d is concurrently formed in the outer peripheral surface of the metallic outer tube 4, whereby the metallic outer tube 4 holding the heater 2 can be firmly fixed to the housing 10, and a cost can be reduced since a high accuracy is not requested for the inner diameter of the housing 10.

Description

Glow plug for diesel engine and manufacturing method thereof

technical field

The present invention relates to a glow plug used as a starting aid for a diesel engine. The present invention particularly relates to a glow plug for a diesel engine and a method for manufacturing the same. The glow plug for a diesel engine is characterized in that it will hold The outer casing of the heater is fixed to the outer casing which is the mount of the cylinder head of the engine.

Background technique

A glow plug for a diesel engine is generally constructed in such a way that the heater is held inside a metal casing, and one end of the casing is inserted into the front end of the cylinder head attachment (cylindrical casing) of the engine. One of the electrodes of the heater is connected to the casing, and the other electrode is installed on the outside through an electrode lead-out piece, and connected to an external connection terminal fixed on the other end of the casing through an insulator.

In the above-mentioned glow plug for a diesel engine, silver soldering or press-fitting is conventionally performed as a method of fixing and holding the jacket and the casing of the heater. When fixing by soldering, a slight gap is formed between the inner peripheral surface of the case and the outer peripheral surface of the case, and molten solder material flows into the gap to join the case and the case. In addition, in the case of press-fitting, in the inner hole of the housing, a portion having a diameter smaller than the outer diameter of the jacket is formed as a press-fit allowance, and the jacket is pressurized inside the smaller-diameter portion to press it. into the fixed.

In the case where the jacket holding the heater is fixed to the inside of the casing by welding, there must be a gap for the solder to enter between the inner peripheral surface of the casing and the outer peripheral surface of the jacket. Problems with concentricity between housing and heater. In addition, since the high heat treatment is repeated, there is also a phenomenon that the jacket holding the heater enters the inside of the casing, and there is a risk of falling out of the casing.

In addition, in the case of fixing the outer cover to the housing by pressing, since the inner diameter of the press-fit part and the length of the press-fit part of the outer cover in the inner surface of the housing must be machined with high precision, usually, by cutting etc. The processing of the inner hole is carried out in a conventional manner, and thus, there is a problem that the processing cost of the casing is very high. In addition, in order to change the distance from the front end of the heater to the seat surface of the cylinder head formed at the front end of the housing in order to correspond to the required performance, it is necessary to form the press-fit part of the inner hole of the housing at different positions. In this way, it is necessary to manufacture a plurality of types of casings corresponding to each type, and the cost is high. When the jacket holding the heater is press-fitted into the case, if the press-fit portion gets caught, etc., the press-fitting load increases, and as a result, the heater and the case may be damaged.

Contents of the invention

The present invention was made in order to solve the above-mentioned problems, and an object of the present invention is to provide a glow plug for a diesel engine and a manufacturing method thereof in which there is no risk of eccentricity when the jacket and the housing of the heater are fixed by welding. , In addition, the axial holding force is firm.

Still another object of the present invention is to provide a glow plug for a diesel engine and a method of manufacturing the same, in which the processing of the housing is relatively inexpensive, and there is no risk of damage to the heater during pressing.

The invention described in the first aspect of the present invention is a glow plug for a diesel engine, wherein one end of a jacket holding a heater is inserted and fixed in an inner hole of a cylindrical casing, and is characterized in that The ring-shaped convex part and the ring-shaped concave part are fitted with each other. The ring-shaped convex part is formed on the inner surface of the casing by plastic working from the outer peripheral surface of the casing. On the outside, the above shell and jacket are secured.

In the glow plug for a diesel engine of the present invention, since the annular convex portion of the casing formed by plastic working is firmly engaged with the annular concave portion of the casing, there is no danger of the casing moving in the axial direction of the casing, and there is no risk of the casing moving from entering the casing. inside or from the enclosure. In addition, there is no risk of eccentricity of the housing and the jacket. In addition, it is not necessary to process the inner hole of the housing with high precision, and the cost of machining the housing is low.

Furthermore, the invention according to the second aspect of the present invention is characterized in that the annular convex portion and the annular concave portion formed by the above-mentioned plastic working are constituted by surfaces parallel to the axis of the housing.

Furthermore, the invention according to claim 3 of the present invention is characterized in that the annular convex portion and the annular concave portion formed by the above-mentioned plastic working are constituted by surfaces inclined with respect to the axis of the housing.

In the solution of the present invention, the diameters of the annular convex portion and the annular concave portion change continuously from the larger diameter portion to the smaller diameter portion, compared with the case of having the same diameter in the entire range of the axial length. , easy to maintain the airtight state between the shell and the jacket.

Furthermore, the invention according to claim 4 of the present invention is characterized in that a plurality of annular convex portions and annular concave portions formed by the above-mentioned plastic working are provided along the axial direction.

In addition, the invention described in the fifth aspect of the present invention relates to a method of manufacturing a glow plug for a diesel engine. In the inner hole of the cylindrical case, one end of the jacket holding the heater is inserted and fixed, and one end of the jacket is inserted into the In the inner hole of the casing, after positioning the front end of the heater held in the casing with the seat surface of the cylinder head provided on the casing, plastic processing is performed on the outer peripheral surface of the casing, thereby, on the inner surface of the casing, An annular convex portion is formed, and an annular concave portion into which the annular convex portion is fitted is formed on the outer surface of the casing, and the casing is fixed to the casing.

According to the method of the invention, since the manufactured glow plug for a diesel engine is firmly engaged with the annular convex portion of the casing formed by plastic working and the annular concave portion of the casing, there is no danger of the casing moving in the axial direction of the casing. , and there is no danger of eccentricity. In addition, since it is not necessary to process the housing with high precision, the cost of machining the housing is low. In addition, since the distance between the front end of the heater and the seating surface of the housing can be set arbitrarily when the heater is joined to the housing, it is possible to manufacture various types of heating wires with a single size of housing and heater. stuffed.

The method of manufacturing a glow plug for a diesel engine according to the sixth aspect of the present invention is characterized in that one end of the outer casing is inserted into the inner hole of the outer casing, and the outer peripheral surface of the outer casing is plastically processed, thereby forming a glow plug on the inner surface of the outer casing. An annular convex portion, and an annular concave portion for fitting the annular convex portion is formed on the outer surface of the casing to fix the casing to the casing, and at the same time, a seat surface of the cylinder head is formed on the front end surface of the casing.

According to the method of this invention, since the seating surface of the casing is simultaneously formed when the casing and the heater are joined by the plastic working, the dimensional accuracy from the tip of the heater to the seating surface of the casing can be further improved.

The method for manufacturing a glow plug for a diesel engine according to the seventh aspect of the present invention is characterized in that one end of the outer casing is inserted into the inner hole of the outer casing, an insulator is interposed between the inner surface of the outer casing and the outer surface of the outer casing, and the pair is held in the outer casing. The front end of the heater is positioned with the seat surface of the cylinder head provided on the above-mentioned casing, and then plastic processing is performed from the outer side of the casing to form a ring-shaped convex part on the inner surface of the casing, through the above-mentioned insulator, the The above-mentioned coat is fixed on the shell.

Since the insulator is interposed between the inner surface of the casing and the outer surface of the casing in the glow plug for a diesel engine manufactured according to the method of the invention, and both are fixed in an insulated state, it can be used as an ion sensor as it is.

Description of drawings

Fig. 1 is a longitudinal sectional view of a glow plug for a diesel engine according to an embodiment of the present invention;

Fig. 2 is an enlarged view of the main part (part A in Fig. 1 ) of the above-mentioned glow plug for a diesel engine;

Fig. 3 is a longitudinal sectional view illustrating an assembly process of the above-mentioned glow plug for a diesel engine;

Fig. 4 is a longitudinal sectional view showing the next process of Fig. 3;

Fig. 5 is a longitudinal sectional view showing the next process of Fig. 4;

Fig. 6 is a longitudinal sectional view of a glow plug for a diesel engine of a second embodiment;

7 is a longitudinal sectional view illustrating an assembly process of the glow plug for a diesel engine of the second embodiment;

Fig. 8 is a longitudinal sectional view illustrating the next step of Fig. 7;

Fig. 9 is a circuit diagram showing an operating circuit of a glow plug for a diesel engine according to a second embodiment.

Detailed ways

The present invention will be described below through the embodiments shown in the accompanying drawings. Fig. 1 is a longitudinal sectional view of a glow plug for a diesel engine according to an embodiment of the present invention (the whole is indicated by a symbol 1), and Fig. 2 is an enlarged view of its main part (part A in Fig. 1). The glow plug 1 of this embodiment is a ceramic heater type glow plug in which a ceramic heater 2 is used as a heating element.

This ceramic heater 2 is a conventionally known scheme, and its details are not shown in the figure. Inside the ceramic insulator constituting the main part, for example, tungsten (W) and other high-melting-point metals are embedded in a spiral shape. A heating wire is connected to one end of the heating wire with a lead wire on the negative electrode side, and to the other end of which is connected to a lead wire on the positive electrode side. The lead wire on the negative electrode side is led out to the outer peripheral surface of the ceramic insulator, and is electrically connected to the casing 4 (metal outer cylinder) described later by welding. On the other hand, the positive electrode-side lead wire extends on the end side opposite to the position where the heating wire is buried (the left end in FIG. 1 ), and is connected to the electrode lead-out member 6 by welding inside the mounting hole 2b formed on the end surface. The front end is turned on. In addition, the rear end portion of the electrode lead-out member 6 is fixed to the front end portion of the external connection terminal 8 .

The ceramic heater 2 of the above-mentioned aspect is joined to the inside of the casing (metal outer cylinder) 4 by welding, and is fixed to the cylindrical casing 10 as a mounting member of the cylinder head through the metal outer cylinder 4 . In this embodiment, in the metal outer cylinder 4, the diameter of the part 4a on the front end side is slightly smaller, and the diameter on the rear part 4b side is larger, and a ceramic heater is inserted into the inside of the smaller diameter part 4a. 2 and joined by welding or the like. In addition, on the housing 10, a seat surface 10a of the cylinder head of the engine is formed at the front end (the left end in FIG. Fixed nut part 10c etc.

One end of the external connection terminal 8, which is electrically connected to the positive-side lead wire of the above-mentioned ceramic heater 2 through the electrode lead-out member 6, is fixed to the inside of the metal outer cylinder 4 by swaging, and the lower face is fixed to the outside by the swaging. The process of connecting the terminal 8 will be briefly described. First, the electrode lead-out member 6 is inserted into the mounting hole 2b of the ceramic heater 2, and the electrode lead-out member 6 and the positive electrode of the ceramic heater 2 are bonded with a wire by welding and the ceramic heater 2 is brought close to the metal heater 2 by welding. The end portion of the outer cylinder 4 on the side where the ceramic heater is fixed (the end portion on the side of the smaller diameter portion 4 a ) is fixed. At this time, the heat generating portion 2 a near the tip portion of the ceramic heater 2 in which the heating wire is embedded is exposed outside the metal outer cylinder 4 .

After fixing the ceramic heater 2 inside the small diameter portion 4a of the metal outer cylinder 4, insert the front end of the external connection terminal 8 from the opening 4c on the side of the larger diameter portion 4b of the metal outer cylinder 4, and insert it. It is joined to the other end of the above-mentioned electrode lead-out member 6 . Then, from the opening 4c of the metal outer cylinder 4, heat-resistant insulating powder (for example, MgO) 12 is filled into the space in which the connecting portion of the electrode lead 6 and the external connection terminal 8 is accommodated. Next, a rubber sealing member (silicone rubber, fluororubber, etc.) 14 is attached to the opening 4c of the metal outer cylinder 4 . By attaching the sealing member 14 inside the opening 4c of the metal outer cylinder 4, it is possible to prevent the above-mentioned heat-resistant insulating powder 12 from overflowing when swaging is performed in a later step. In addition, it is also possible to prevent the electrode lead-out material 6 from coming into contact with the metal outer cylinder 4 .

Then, the larger-diameter portion 4b of the metal outer cylinder 4 that accommodates the connecting portion of the electrode lead 6 and the external connection terminal 8 is swaged to reduce the outer diameter of the metal outer cylinder 4 and improve heat resistance. The density of the insulating powder 12 fixes the external connection terminal 8 inside the metal outer cylinder 4 .

The metal outer cylinder 4 to which the above-mentioned ceramic heater 2, electrode lead-out member 6 and external connection terminal 8 are fixed is inserted and fixed by inserting the large-diameter portion 4b on the rear side into the cylindrical casing 10. In this embodiment, the portion near the front end portion of the casing 10 is located on the outer periphery of the portion close to the small diameter portion 4a of the larger diameter portion 4b of the metal outer cylinder 4, and from the outer peripheral side of the casing 10 to the Swaging is partly carried out (the swaged part is represented by S), and an annular convex portion 10d is formed on the inner peripheral side (see FIG. 2 showing A portion of FIG. 1 in an enlarged manner). The forging process also forms an annular concave portion 4c on the outer peripheral surface of the metal outer cylinder 4, and the annular convex portion 10d of the housing 10 and the annular concave portion 4c of the metal outer cylinder 4 are fitted together. The ring-shaped convex portion 10d formed by swaging in this way is in close contact with the ring-shaped recessed portion 4c, thereby fixing the casing 10 and the metal outer cylinder 4 and maintaining an airtight state.

Since the casing 10 and the metal outer cylinder 4 are fixed by performing swage processing from the outer peripheral side of the casing 10 as described above, the casing 10 and the metal outer cylinder 4 are completely in close contact, and there is no possibility of eccentricity between the two. Danger. In addition, an airtight state is surely maintained between the casing 10 and the metal outer cylinder 4 . In addition, since the annular convex portion 10d is engaged with the annular concave portion 4c, the holding force in the axial direction is strong, and the ceramic heater 2 held on the metal outer cylinder 4 does not come out of the casing 10 or enter the inside of the casing 10. Case.

The assembling procedure of the glow plug 1 for a diesel engine with the above-mentioned structure will be described below with reference to Fig. 1 , Fig. 2 and Fig. 3 to Fig. 5 . First, with the threaded portion 8a side of the external connection terminal 8 as the front end, the assembly formed by the ceramic heater 2 fixed to the inside of the metal outer cylinder 4, the electrode lead-out member 6 and the external connection terminal 8 is viewed from the front end side of the housing 10. (the seat surface 10a side of the cylinder head) is inserted into the inner hole 16 (refer to FIG. 3 ). In this case 10, in the state before assembly, the inner diameter of the inner hole 16 as a whole is a size that allows the large-diameter portion 4b of the metal outer cylinder 4 to pass through.

As mentioned above, the external connection terminal 8 is inserted into the inner hole 16 of the housing 10 from the threaded portion 8a side, and the larger diameter portion 4b side of the metal outer cylinder 4 is also inserted into the inner hole 16 of the housing 10. . A seat surface 10a of a cylinder head of the engine is formed at the front end of the housing 10, and is positioned so that the distance L1 between the seat surface 10a and the front end of the ceramic heater 2 becomes a predetermined dimension (see FIG. 4).

In this state, swaging is performed on a portion slightly on the front side of the front end portion of the housing 10 from the outer peripheral side (refer to the symbol S in FIG. 5 ). By swaging, as shown in an enlarged form in FIG. 2 , the outer peripheral surface of the housing 10 is dented, and an annular convex portion 10 d is formed on the inner surface side. In addition, the plastic deformation of the casing 10 also forms an annular recess 4 c on the outer surface of the metal outer cylinder 4 . Through this swaging process, the casing 10 and the metal outer cylinder 4 are joined so as to be firmly and tightly fitted.

In this embodiment, the inner diameter of the inner hole 16 of the housing 10 may be slightly larger than the outer diameter thereof so that the larger diameter portion 4b of the metal outer cylinder 4 can pass through. Since high precision is not required, it can be processed at extremely low cost compared with the case of fixing by press-fitting. In addition, since the distance L1 between the seat surface 10a of the casing 10 and the front end of the ceramic heater 2 can be set arbitrarily during bonding, it is possible to manufacture heating wires with various performances through the casing 10 and the ceramic heater 2 of one size. Glow plug 1, the cost is extremely low. In addition, there is no danger of damage to the ceramic heater 2 as in the case of fixing by press-fitting.

In addition, in the above-mentioned embodiment, the casing 10 and the metal outer cylinder 4 can be fixed by performing swage processing from the outer peripheral surface of the casing 10 to simultaneously deform the casing 10 and the metal outer cylinder 4, but it is not limited to the swaging processing. The annular convex portion 10d and the annular concave portion 4c that are fitted to each other can be formed on the housing 10 and the metal outer cylinder 4 by other plastic working methods such as roll forming. In addition, at present, solid steel is used as a material, and the shell with the inner hole is manufactured by cutting. However, in this embodiment, the inner hole 16 of the shell 10 does not require high-precision processing, and a low-priced pipe is used. The mounting screw portion 10b facing the engine, the nut portion 10c at the rear end, and the seating surface 10a at the front end are formed by roll forming or the like, thereby also achieving cost reduction.

In the hot wire igniter 1 of the above-described embodiment, the portion deformed by plastic working is constituted by a surface parallel to the axis of the housing 10 . That is, the swaged portion S has the same diameter in the longitudinal direction of the housing 10 . The annular convex portion 10a and the annular concave portion 4c are not limited to having the same diameter in the longitudinal direction as described above, but may be formed of surfaces inclined to the axis of the housing 10 with their diameters continuously changing.

Also, on the front end of the casing 10, a seat surface 10a is formed, and the seat surface 10a is used to be installed on the cylinder head of the engine, but not only is formed on the casing 10 in advance like the foregoing embodiment, but also is passed through The seating surface 10 a may be formed simultaneously when the casing 10 and the metal outer cylinder 4 are fixed by plastic working such as swaging or roll forming as described above. Thus, by simultaneously forming the seating surface 10a of the housing 10, the dimensional accuracy between the tip portion of the ceramic heater 2 and the seating surface 10a of the housing 10 can be improved.

In addition, the smooth R-shape connects the plastic-worked portion of the outer periphery of the housing 10 to the adjacent portion, thereby preventing peeling of the anti-rust plating of the housing 10 during swaging.

In addition, in the foregoing description, the inside of the metal outer cylinder 4 is filled with heat-resistant insulating powder 12 and swaged, thereby fixing the external connection terminal 8 connected to the electrode lead-out member 6 to the metal outer cylinder 4 . However, this swaging process may be omitted, and a swaging process for simultaneously fixing the outer casing 10 and the metal outer cylinder 4 may be employed. In this case, airtightness does not need to be required, but the electrode on the positive electrode side can be reliably fixed, swaging can be omitted, and cost reduction can be achieved.

6 is a longitudinal sectional view showing a second embodiment of a glow plug 101 for a diesel engine. The glow plug 101 is integrally formed with an ion sensor on the glow plug 1 for a diesel engine having the above-mentioned structure. The ion sensor detects an ion current. , to detect the combustion state of the engine.

In the ceramic heater 102 of the glow plug 101, a heating element 102b is embedded in a ceramic insulator 102a, a negative lead 102c is connected to one end, and a positive lead 102d is connected to the other end. The front end 102ba of the heating element 102b is exposed outside the ceramic insulator 102a so as to be used as an electrode for ion detection.

The above-mentioned lead wire 102c on the negative electrode side is installed on the side surface of the ceramic insulator 102a, and conducts with the inner surface of the casing (metal outer cylinder) 104, and the lead wire 102d on the positive electrode side is inside the ceramic insulator 102a, and conducts with one end of the electrode lead-out member 106. In addition, the other end of the electrode lead 106 is connected to an external connection terminal 108 .

The metal outer cylinder 104 to which the above-mentioned ceramic heater 102 is fixed is different from the aforementioned first embodiment in that its overall length is longer than that of the casing 110. The end portion 104e on the opposite side to the portion 104d reaches the rear end portion of the casing 110 . The inside of the metal outer cylinder 104 is filled with heat-resistant insulating powder 112, and the density is increased by swaging to fix the above-mentioned external connection terminal 108, and connect the positive-side external connection terminal 108 and the negative-side metal casing. The barrel 104 is insulated.

A ceramic heater 102 is fixed to one end 104d, and a metal outer cylinder 104 extending with an external connection terminal 108 is inserted into an inner hole 116 of the cylindrical case 110 at the other end 104e. An insulator 118 is inserted between the inner surface of the portion near the front end of the housing 110 and the outer surface of the metal outer cylinder 104 to electrically insulate the housing 110 and the metal outer cylinder 104 . In this embodiment, the portion filled with the insulator 118 is swaged from the outer peripheral side of the case 110 (refer to the symbol S in FIG. 6 ), and an annular convex portion 110d is formed on the inner peripheral side. The metal outer cylinder 104 of the swaged portion S is fixed to the case 110 .

Next, the process of assembling the ion sensor-integrated glow plug 101 will be described with reference to FIGS. 6 , 7 and 8 . With the threaded portion 108a side of the external connection terminal 108 as the front side, the internal ceramic heater 102 held by the metal outer cylinder 104, the electrode lead-out member 106, and the external connection terminal 108 are integrally formed from the front end portion of the housing 110 ( The ceramic heater 102 is inserted on the mounting side end) side (refer to FIG. 7 ).

After positioning so that the distance L2 between the front end of the ceramic heater 2 and the seat surface 110a of the cylinder head formed at the front end of the housing 110 becomes a predetermined size, the front end of the housing 110 and the outer periphery of the metal outer cylinder 104 A sealing member 120 is installed between the surfaces, and a sealing member 122 is fitted after filling the heat-resistant insulating powder 118 on the opening side from the rear of the housing 110 (see FIG. 8 ). Then, swaging is performed on the outer peripheral side of the portion filled with the heat-resistant insulating powder 118 to plastically deform the case 110 to form a ring-shaped convex portion 110d on the inner peripheral surface, and to improve the strength of the heat-resistant insulating powder 118. Density, fixed metal outer cylinder 104 (state of FIG. 6 ).

In the ion sensor integrated type glow plug 101 described above, the metal outer cylinder 104 that conducts with the negative electrode side lead 102c of the ceramic heater 102 is connected to the negative electrode side terminal 124 at the rear end side of the casing 110, and passes through the electrode lead-out member 106. On the other hand, the external connection terminal 108 that conducts with the positive electrode-side lead wire 102 d is connected to the positive electrode-side terminal 126 . In addition, an insulating ring 128 is interposed between the negative-side terminal 124 and the case 110 which are connected to the metal outer cylinder 104, and an insulator 130 is interposed between the negative-side terminal 124 and the positive-side terminal 126 to electrically insulate the two. .

The positive side terminal 126 is connected to the positive side of the battery 132 through the first relay 134A as shown in FIG. 9 , and the negative side terminal 124 is connected to the negative side of the battery 132 through the second relay 134B. Then, through the positive pole of the above-mentioned battery 132, the first relay 134A, the positive pole side terminal 126, the external connection terminal 108, the electrode lead-out member 106, the positive pole side lead 102d of the ceramic heater 102, the heating element 102b, the negative pole side lead 102c, the metal The outer cylinder 104, the negative terminal 124, the second relay 134B, and the negative electrode of the battery 132 form an electric circuit of the glow plug.

In addition, the casing 110 is fixed to the cylinder head 136 of the engine, the negative electrode of the battery 132 is connected to the cylinder head 136 in a grounded manner, and a current flows between the positive electrode of the battery 132 and the positive terminal 126 of the glow plug 101. The detection mechanism 138 and the sensor are connected by a relay 140 . Then, through the positive pole of the above-mentioned battery 132, the current detection mechanism 138 and the sensor relay 140, the positive side terminal 126, the external connection terminal 108, the electrode lead-out member 106, the heating element 102b as the electrode for ion detection and the grounding of the cylinder head 136, Form the circuit for the ion sensor.

When the ion sensor-integrated glow plug 101 is used as a glow plug, the first and second glow plug relays 134A and 134B are turned on, and the sensor relay 140 is turned off. Then, an electric current flows through the circuit for the glow plug, and the heating element 102b generates heat to warm up the engine.

In addition, when the glow plug 101 of the above structure is used as an ion sensor, the relays 134A and 134B for glow plugs are turned off, and the relay 140 for ion sensors is turned on. Then, a voltage is applied between the heating element 102b of the ceramic heater 102 serving as an electrode for ion detection and the cylinder head 136, and a current flows through the sensor circuit through ions in the combustion chamber generated during engine combustion. The electric current is detected by the electric current detecting means 138, and the engine is feedback-controlled.

Also in the glow plug 101 for a diesel engine of this embodiment, as in the above-mentioned first embodiment, since the structure of the housing 110 is simple, the housing 110 can be manufactured at a relatively low cost. In addition, even without changing the shape of the housing 110, the distance L2 between the seat surface 110a of the cylinder head 136 of the housing 110 and the front end of the ceramic heater 102 can be set arbitrarily, which can greatly reduce the cost.

In addition, the insulator interposed between the housing 110 and the metal outer cylinder 104 is not limited to the case where the density of the heat-insulating insulating powder 118 is increased by swaging as described above, for example, other insulators such as resin may be used.

In addition, in each of the above-mentioned embodiments, the ceramic heater type glow plug 1, 101 in which the ceramic heater 2, 102 is used as the heating element has been described, however, it is not limited to the ceramic heater, and the present invention can also be used for Glow plugs for metal heaters.

Claims (7)

1. used for diesel engine glow plug wherein, in the internal holes of cylinder-like shell, is fixed with an end of the overcoat that keeps heater with inserted mode, it is characterized in that:

Annular convex and annular recessed portion are chimeric mutually, and this annular convex is by the outer peripheral face from shell, and the mode of carrying out plastic working is formed on its inner face, this annular recessed portion is by above-mentioned plastic working, by shell, be formed on the outside of overcoat, above-mentioned shell and overcoat are fixed.

2. used for diesel engine glow plug according to claim 1 is characterized in that: annular convex that forms by above-mentioned plastic working and annular recessed portion are made of the face with the parallel axes of shell.

3. used for diesel engine glow plug according to claim 1 is characterized in that: annular convex that forms by above-mentioned plastic working and annular recessed portion are made of the face that the axis of opposite shell tilts.

4. used for diesel engine glow plug according to claim 1 is characterized in that: be provided with along axis direction a plurality of, the annular convex and the annular recessed portion that form by above-mentioned plastic working.

5. the manufacture method of a used for diesel engine glow plug in the internal holes of cylinder-like shell, is fixed with an end of the overcoat that keeps heater with inserted mode, it is characterized in that:

One end of above-mentioned overcoat is inserted the internal holes of above-mentioned shell, the front end of the heater in this overcoat will be remained in, behind the seat surface location that is arranged at the cylinder cap on the shell, outer peripheral face to shell, carry out plastic working, thus, in the inner face formation annular convex of shell, and on the outside of overcoat, form above-mentioned annular convex chimeric annular recessed portion, above-mentioned overcoat is fixed on the shell.

6. the manufacture method of a used for diesel engine glow plug in the internal holes of cylinder-like shell, is fixed with an end of the overcoat that keeps heater with inserted mode, it is characterized in that:

One end of above-mentioned overcoat is inserted the internal holes of above-mentioned shell, outer peripheral face to shell carries out plastic working, thus, on the inner face of shell, form annular convex, and on the outside of overcoat, form above-mentioned annular convex chimeric annular recessed portion, above-mentioned overcoat is fixed on the shell, simultaneously, on the front end face of above-mentioned shell, form the seat surface of cylinder cap.

7. the manufacture method of a used for diesel engine glow plug in the internal holes of cylinder-like shell, is fixed with an end of the overcoat that keeps heater with inserted mode, it is characterized in that:

One end of above-mentioned overcoat is inserted the internal holes of above-mentioned shell, with insulator between the outside of the inner face of shell and overcoat, to remaining in the front end of the heater in the overcoat, position with the seat surface that is arranged at the cylinder cap on the above-mentioned shell, then, carry out plastic working, on the inner face of shell, form annular convex thus from the exterior side of shell, by above-mentioned insulator, above-mentioned overcoat is fixed on the shell.

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