KR100358509B1 - Ceramic heater-type glow plug and method for manufacturing the same - Google Patents

Abstract

According to the present invention, the tip side including the heater portion of the ceramic heater type glow plug is formed to be elongated in the axial direction, and the housing diameter and the heater diameter on the side of the glow plug are made thin to reduce the heat generation of the heat generating element 13. The connection end 14b of one lead portion 14 is exposed to the outer side of the ceramic insulator 12 to be electrically joined to the metal outer cylinder 21. The electrode extraction bracket 18 and the electrode extraction bracket 18 are formed by using the cylindrical ceramic molded body or the sintered body 17 in a position where the connection end 15b of the other lead portion 15 is not exposed from the rear end to the rear end of the ceramic insulator. Electrically bonding is carried out, and this electrode extraction bracket is taken out from the rear end of the ceramic insulator. The electrical connection between the connecting end of the lead portion and the electrode ejection bracket is performed in the ceramic insulator at a position at least five times the diameter dimension of the ceramic insulator from the top end thereof on the rear end side.

Description

Ceramic Heater Type Glow Plugs and Manufacturing Method Thereof {CERAMIC HEATER-TYPE GLOW PLUG AND METHOD FOR MANUFACTURING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a ceramic heater-type glow plug for high temperature, which is used as a starting aid for a diesel engine. In particular, in order to cope with the direct injection multi-valve of a diesel engine, the front end side of the tubular housing and the support thereof The present invention relates to a ceramic heater-type glow plug and a method of manufacturing the same, which are formed by extending the thin portion of the ceramic heater in the axial direction to form a long one and thinning the entire diameter including the tip side thereof.

Conventionally, as a glow plug used as a starting aid for a diesel engine, a metal heating wire made of Ni-Cr (nickel chromium alloy), Fe-Cr (iron chromium alloy) or the like is embedded in a heat-resistant insulating powder such as MgO (magnesia) It is common to use the sheath heater of the structure which covered these with the sheath made of heat-resistant metal.

In addition, in order to cope with the recent long-term exhaust gas regulation, it is necessary to quickly reach the time of reaching 800 ° C, increase the peak temperature and saturation temperature, and lengthen the afterglow time. And in order to respond to these requests, it is necessary for the heating element part to be a high melting point metal material or an inorganic conductive material, and to make the thin part the ceramic which can be used at high temperature from a metal material. For example, Japanese Unexamined Patent Publication No. 62-19034 proposes a glow plug using a ceramic heater in which high melting point metal materials such as W (tungsten) are embedded in ceramics such as silicon nitride having excellent oxidation resistance and thermal shock resistance. .

In recent years, diesel engines are also required to respond to exhaust gas regulations. As a part of this, the combustion method of diesel engines is shifted from a type having a sub-combustion chamber to a direct injection type, a so-called direct type type, and multiplexed. It is done. Accordingly, a glow plug for improving engine startability at low temperatures is also attached to the cylinder head along with the fuel injection nozzle. And it is comprised so that a heater tip part may go to main combustion chamber and preheat this room, and it becomes an ignition assistance source.

Since the glow plug used in such a direct injection diesel engine passes through the wall of the cylinder head to the main combustion chamber, it is necessary to form a longer overall length and a thinner diameter than the type of preheating the subcombustion chamber.

That is, it is necessary to install many supply and exhaust valves on the cylinder head to which such a glow plug is mounted, and to enlarge the area of the valve entrance as much as possible. In addition, it is necessary to increase the thickness of the cylinder head in order to secure the strength of the cylinder head. For this reason, the insertion port for mounting the glow plug is very thin and long, and accordingly, it is necessary to form the glow plug very thin and long.

However, as described above, when all the thinner diameters on the tip side of the glow plug are formed of ceramics, the ceramic parts may be damaged by the force applied when the glow plug is attached to or removed from the cylinder head. It is practically difficult to form a thin part only with a ceramic heater made of ceramics.

For this reason, in the glow plug using such a ceramic heater, actually making the screw diameter of the tubular housing of a glow plug thin like M10 to M8 is performed. In other words, the tubular housing of the glow plug is made as thin as possible. In addition, in the conventional ceramic heater type glow plug, the diameter dimension of the ceramic heater serving as the heat generating portion is not less than ø3.4 mm in total, so as to ensure sufficient strength against external force, and to maintain the amount of protrusion to the combustion chamber described above. It can not be helped.

That is, when the diameter of the tubular housing is made thin, not only the problem of lowering the strength but also the diameter of the ceramic heater do not change, so that a metal wire is exposed at the end of the conventional heater element and the terminal cap is soldered to the metal wire (Japan The space between the tubular housing is small in the case of Japanese Patent Application Laid-Open No. 60-30608) or a method of fixing a spirally wound metal wire by soldering or the like (Japanese Patent Laid-Open No. 60-114631). Even withdrawal of the electrode was impossible.

Further, Japanese Patent Laid-Open No. 62-295382 discloses a structure in which an end portion of a lead portion of a heating element is spirally twisted, an insertion hole is formed in the portion thereof, and the electrode ejection bracket is electrically connected to each other by soldering or the like. However, in such a structure, it is impossible to make the lead portion wound in the ceramics if the portion made of the insulating ceramics is about 3.5 mm. In addition, it is also very difficult to open a hole for inserting the electrode extraction bracket in a portion made of ceramics, and there is also a problem of high manufacturing cost.

In addition, Japanese Patent Application Laid-Open No. 2-28044 describes a structure in which a step is provided at the rear end of the ceramic heater and joined to the terminal bracket. However, processing to form a step in the cylindrical ceramic sintered body is very difficult as described above, and manufacturing costs are high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and the length of the glow plug is lengthened, the tubular housing is made thin, the so-called attachment screw diameter is as thin as M10 to M8, and the diameter of the ceramic heater is ø3. It is an object of the present invention to obtain a ceramic heater-type glow plug which can be easily connected to the electrode extracting means and which does not cost a manufacturing cost even if it is about 5 mm.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view for explaining the outline of a ceramic heater, showing one embodiment of a ceramic heater-type glow plug and a manufacturing method thereof according to the present invention;

(A) is a figure which shows the rear end surface of the ceramic heater of FIG. 1, (b) is a figure which shows the modification example,

Fig. 3A is an enlarged cross-sectional view of the junction portion between the lead and the electrode extraction bracket when the cylindrical ceramic molded body or the sintered body is formed of insulating ceramic in the electrode extraction portion at the rear end of the ceramic heater; An enlarged sectional view showing a modification thereof,

Fig. 4A is an enlarged cross-sectional view of the junction portion between the lead and the electrode extraction bracket when the cylindrical ceramic molded body or the sintered body is formed of conductive ceramic in the electrode extraction portion at the rear end of the ceramic heater; An enlarged sectional view showing a modification thereof,

5 (a), 5 (b) and 5 (c) are cross-sectional views of the main parts of the ceramic heater-type glow plug according to the present invention, illustrating the attachment structure to the tubular housing side and a modification thereof;

Fig. 6 is an overall sectional view showing one embodiment of a ceramic heater-type glow plug and a method of manufacturing the same according to the present invention;

7 is a cross-sectional view showing an example of a ceramic heater in the ceramic heater-type glow plug according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: ceramic heater type glow plug 11: ceramic heater

12 ceramic insulator 13 heating element

13a, 13b: end portion 14, 15: lead portion

14a, 15a: once 14b, 15b: connection end

17: cylindrical ceramic molded body or sintered body

17a, 17b, 17c: hole 18: electrode withdrawal bracket

18a, 18b: Connection end 21: Metal outer cylinder

22 tubular housing 22a threaded portion

24: external connection terminal 24a: connection terminal

25: insulation bush 28: solder filler

In order to meet the above object, the ceramic heater type glow plug according to the present invention is a ceramic heater type in which a metal outer tube or tubular housing and an electrode extraction bracket are attached to a ceramic insulator in which a heating element made of an inorganic conductive material or a high melting point metal material is embedded in ceramics. In a glow plug, a connection end of one lead portion of the heating element is exposed to an outer portion of the ceramic insulator, and is electrically connected to the metal outer tube or tubular housing, and a connection end of the other lead portion is connected to a rear end portion of the ceramic insulator. The electrode end bracket is electrically connected to the electrode extraction bracket at a position not exposed at the last end, and the electrode extraction bracket is configured to be taken out from the rear end of the ceramic insulator, and the electrical connection between the connection end of the other lead portion and the electrode extraction bracket is performed. Its maximum in ceramic insulators Characterized in that from the ends it is configured to perform at a location in at least 5 times or more rear end side of the diameter dimension of the ceramic insulator.

Moreover, the ceramic heater type glow plug which concerns on this invention is characterized by the different material of the lead part of the said heat generating body, and the said electrode taking-out bracket.

The ceramic heater-type glow plug according to the present invention is characterized in that electrical joining of the electrode ejection bracket and the lead portion of the heating element is performed through a ceramic molded body or a sintered body made of ceramics including an inorganic conductive material or a high melting point metal material.

The ceramic heater-type glow plug according to the present invention is characterized in that the last end of the ceramic insulator is placed in the metal outer cylinder.

The ceramic heater type glow plug according to the present invention is a ceramic heater type glow plug having a metal outer cylinder or tubular housing and an electrode extraction bracket attached to a ceramic insulator in which a heating element made of an inorganic conductive material or a high melting point metal material is embedded in ceramics. As a manufacturing method of the present invention, a cylindrical ceramic molded body or a sintered body is embedded in a ceramic powder, a part of the heating element lead portion made of an inorganic conductive material or a high melting point metal material is passed through the cylindrical ceramic molded body or a sintered body, and then these are used as ceramic heaters. A hot press is performed to integrate.

Moreover, the manufacturing method of the ceramic heater type glow plug which concerns on this invention is characterized in that the said cylindrical ceramic molded object or sintered compact consists of ceramics containing an inorganic conductive material or a high melting-point metal material.

According to the present invention, the electrode lead portion of the other lead portion of the heating element embedded in the ceramic insulator constituting the ceramic heater is constructed by using a cylindrical ceramic molded body or sintered body embedded in the rear end of the ceramic insulator and the electrode take-out bracket bonded thereto. Therefore, even if the diameter dimension of the ceramic insulator made of the ceramic heater is about ø3.5 mm, it is possible to obtain a ceramic heater-type glow plug that can be easily and reliably made electrically coupled and inexpensive.

In addition, according to the present invention, since the electrical coupling between the lead portion of the heating element and the electrode ejection bracket is performed on the rear end side not affected by the heating element in the ceramic sintered body, the strength in the ceramic heater can be improved. As a result, in a glow plug, the diameter of a ceramic heater, the metal outer cylinder which supports it, or a tubular housing can be made thin and lengthened.

Further, according to the present invention, the thickness of the tubular housing of the glow plug is made thin so that the so-called attachment screw diameter is from M10 to M8, and in the ceramic heater type glow plug, even if the diameter of the ceramic heater is about ø3.5 mm, Since the joining can be easily performed, the diameter of the entire glow plug can be made thin and the length can be increased.

Here, the ceramics which form the ceramic insulator which comprises a ceramic heater refer to the thing of the general inorganic material. Examples include alumina, zirconia, cordierite, silicon nitride, silicon carbide or their composites. In particular, among these, silicon nitride and silicon carbide which are sintered through the liquid layer, have high temperature strength and are excellent in heat shock resistance are preferred.

Ceramic molded body means what hardened the ceramic powder. What is necessary is just to employ | adopt the general shaping | molding method of a ceramic, such as extrusion molding, a casting shaping | molding, a press shaping | molding, a CIP shaping | molding method, and shape | molding to the shape with an open hole.

The ceramic sintered body is obtained by firing the above-mentioned molded body, and also includes a semi-baked body. Either the molded body or the sintered body is selected depending on whether the ceramic molded body or the sintered body in the shape of the hole has an open strength is easy to handle.

The metal wire rod (lead) inserted into the pores of the ceramic molded body or the sintered body and joined may be made of, for example, a high melting point metal material having a melting point of 2000 ° C. or higher, but is not limited thereto.

Embodiment of the Invention

1 to 7 show one embodiment of a ceramic heater-type glow plug and a method of manufacturing the same according to the present invention. In these drawings, the outline of the ceramic heater type glow plug in which the entirety is indicated by reference numeral 10 will be described below with reference to Figs.

In the drawing, reference numeral 11 denotes a ceramic heater made of ceramics having insulating properties described later, 21 a metallic outer cylinder made of a pipe or the like inserted into the outer peripheral portion of the ceramic heater 11 and joined by soldering or the like, and 22 a metallic outer cylinder 21. It is a tubular housing which supports to the front-end | tip and becomes an attachment bracket to the engine head of the glow plug 10. The rear end side outer peripheral part of this tubular housing 22 is provided with the screw part 22a which is a screw fastening means to the attachment hole of an engine head.

24 is an external connection terminal supported by the insulating bush 25 at the rear end of the tubular housing 22. The inner end portion of the external connection terminal 24 is subjected to an insulation treatment, and is connected to a connection end 18b of the electrode extraction bracket 18 that makes electrical connection with the ceramic heater 11 ( 24a) is formed.

Here, in such a ceramic heater type glow plug 10, at least the threaded portion 22a is removed from the outer circumferential portion of the tubular housing 22 having the threaded portion 22a for screwing and fixing to the attachment hole provided in the cylinder head. In this case, high frequency quenching may be performed as a heat treatment on the portion leading to the sheet surface portion.

In addition, since the structure and function of such a glow plug 10 are conventionally widely known, description is abbreviate | omitted here.

Among the ceramic insulators 12 constituting the ceramic heater 11, as shown in FIGS. 1, 6, and 7, a heating element 13 made of an inorganic conductive material or a high melting point metal material, and both ends of the heating element 13 ( One end 14a, 15a is connected to 13a, 13b, and the lead parts 14, 15 which take out electrodes with respect to the exterior of a heater are embedded in ceramics.

And the connection end 14b of one lead part 14 is exposed to the outer peripheral part near the rear end part of the ceramic insulator 12, and is electrically connected with the metal outer cylinder 21 by soldering etc. This electrical junction generally becomes a cathode. In addition, the exposed portion of the lead portion connecting portion 14b has a conductive layer (a portion corresponding to the connecting portion 14b) around the ceramic insulator 12 so as to reliably perform electrical bonding with the metal outer cylinder 21. Not shown).

In addition, the connecting end 15b of the other lead portion 15 is a cylindrical ceramic molded body or a sintered body 17 (hereinafter referred to as the molded body 17) at a position where the rear end of the ceramic insulator 12 is not exposed to the last end. It is electrically connected to the electrode extraction bracket 18 through the following. This electrical junction generally becomes an anode. This electrode extraction bracket 18 is taken out from the rear end of the ceramic insulator 12 and extends backward.

In addition, as shown in Figs. 2A and 2B, the cylindrical ceramic molded body 17 has a cylindrical shape or a cylindrical shape, whereby the lead portion 15 is connected to the inner hole 17a. Hot pressing is performed while the stage 15b is inserted, and then the connecting end 18a of the electrode extraction bracket 18 is inserted into a hole opened in one of the cylindrical ceramic molded bodies 17 and soldered. The whole is integrated and joined.

According to the present invention, the electrode withdrawing portion at the rear end of the ceramic heater 11 described above is configured as shown in Figs. That is, in the ceramic heater 11, the connection end of the lead part 15 is electrically connected with the electrode extraction bracket 18 at the position which is not exposed from the rear end of the ceramic insulator 12 to the last end. The electrical connection is performed from the uppermost end of the ceramic insulator 12 at a position on the rear end side of at least five times (for example, 20 mm or more) the diameter dimension of the ceramic insulator 12 (for example, ø3.5 mm). It is comprised so that it is not affected by the heat of (13).

The manufacturing method of the ceramic heater 11 including such an electrode extraction part is demonstrated below.

That is, the heat generating element 13 and the lead parts 14 and 15 are embedded in the ceramic molded body for forming the ceramic insulator 12. As this embedding method, an extrusion molding method, a uniaxial press method, a casting molding method, a gel casting method, etc. which are conventionally known general methods can be adopted. Among them, the uniaxial press method is most preferable in terms of yield, formability, automation and the like.

In detail, about half of the granular powder of the ceramic insulator 12 is placed in the mold, and the W filament serving as the heating element 13 and the lead portions 14 and 15 is placed thereon. The connecting end 15b of the lead portion 15 extending to the end portion is partially passed through the ceramic molded body (or sintered body) 17 formed into a cylindrical shape, and the other half of the granular powder is covered and molded thereon.

At this time, the other end of the hole 17a of the cylindrical ceramic molded body 17 may not be exposed to the last end portion of the ceramic insulator 12 so that the lead portion 15 does not oxidize. What is necessary is just to be able to cut | disconnect the last end of this ceramic insulator 12, and to expose the open end of the hole 17a after hot press mentioned later.

After deforming the molded object which becomes the ceramic insulator 12 shape | molded as mentioned above, hot press baking is performed. The molded bodies are arranged in a graphite form and hot-pressed at 1700 ° C to 2000 ° C. When hot pressing at a temperature lower than 1700 ° C, the ceramic sintering does not proceed sufficiently, and when the ceramic is silicon nitride, the α phase remains in the sintered body, and the characteristics such as strength deteriorate. Moreover, when hot-pressing at the temperature higher than 2000 degreeC, the pure W silicization will advance too much and resistance will increase. For this reason, hot press temperature must be in the range of 1700 degreeC-2000 degreeC.

Thereafter, the ceramic insulator 12 having the heat generating element 13 embedded therein is circumferentially shaped, and the top end thereof is ground in a hemispherical shape. Since the cylindrical ceramic molded body 17 is embedded in the last end part, the hole 17a is open. As described above, when the opening portion of the hole 17a of the cylindrical ceramic molded body 17 is not exposed at the end so that the lead portion 15 does not oxidize, the last end of the insulator 12 is cut off. The hole 17a is exposed.

And the electrode which consists of Ni wire strong in oxidation different from the material of the lead part 15, for example in the hole 17a of the cylindrical ceramic molded object 17 exposed to the last end of the ceramic insulator 12 in this way. An electrical conduction can be obtained by passing the ejection bracket 18 through contact with the W (lead portion 15) contained in the hole 17a.

Here, the electrical junction part by the cylindrical ceramic molded object 17 is unsuitable in the position which the heat_generation temperature in the ceramic heater 11 becomes high. That is, as described above, the electrical junction must be separated from the ceramic insulator 12 having a diameter of ø3.5 mm by a distance of 5 to 12 times (for example, 20 mm to 40 mm) more than its uppermost end.

In addition, the material of the leads 14 and 15 described above is the same as that of the heating element 13, and is formed of an inorganic conductive material or a high melting point metal material, for example, W. The electrode ejection brackets 18 are different materials, for example. For example, it is made of Ni (nickel). However, according to the present invention, as described above, electrical bonding is performed using the cylindrical ceramic molded body 17, so that a reliable bonding state can be obtained.

The inorganic conductive material for forming such a heating element 13 refers to a conductive inorganic material containing at least one of nitrides, silicides, carbides, and borides of Groups 4a, 5a, and 6a of the Periodic Table of Elements. Further, the high melting point metal material refers to metals such as W (tungsten), Mo (molybdenum), Hf (hafnium), and Re (renium) and their alloys having a melting point of 2000 ° C or higher.

As the electrode extraction bracket 18, a Ni wire, a Ni-plated Fe wire, a stainless wire, or the like can be used, and is excellent in oxidation resistance.

In addition, the metal outer cylinder 21 may be stainless steel or inconel, which is a known heat resistant steel.

On the other hand, as the cylindrical ceramic molded body (or sintered body) 17, it is preferable that an inorganic conductive material or a high melting point metal is contained. An inorganic conductive material is a conductive inorganic material containing at least one of nitrides, silicides, carbides, and borides of Groups 4a, 5a, and 6a. For example, when a high melting point metal material is included, the melting point is 2000 ° C or higher. Metallic materials, such as W, Mo, Hf, and Re, are dispersed in an inorganic substance and are said to have electroconductivity.

In the case of manufacturing the ceramic heater 11 of the above structure, the combination of the heat generating element 13 and the lead parts 14 and 15 to the ceramic insulator 12 is, for example, as shown in FIG. Both ends 13a and 13b and lead portions 14 of the metal wire made of a heating element 13 inserted into the holes 19a and 19b opened in parallel to the ceramic body 19 using the sieve 19. The ends 14a and 15a of the metal wire to be 15) are embedded in the ceramic powder and fired, so that the metal wires can be sequentially joined.

According to such a structure, the ceramic body 9 which opened the hole 19a, 19b was used, and the metal wire (heating body 13) is wound up and attached in a spiral shape, and the metal which becomes a lead in each is provided. The wires 14 and 15 are connected and embedded in a ceramic powder body, and then fired in any one of vacuum, nitrogen, inert atmosphere, and reducing atmosphere, thereby joining portions necessary for shrinkage of the ceramic by the firing step. The end is pressed, and the joined body which is satisfactory both in strength and electrically can be obtained.

In the ceramic heater 11 described above, the electrode extraction bracket 18 can be connected to the electrode extraction portion provided at the rear end of the ceramic insulator 12 as shown in Figs. 3 and 4. . 3 (a), (b), 4 (a), and (b) show a cylindrical ceramic molded body 17 which is combined to take out electrodes at the rear end of the ceramic insulator 12, In practice, the molded body 17 is integrated so as to be indistinguishable from the ceramic insulator 12 after firing.

In the ceramic insulator 12 to be the ceramic heater 11 formed as described above, the connection end 18a of the electrode extraction bracket 18 is inserted into the hole 17a exposed at the rear end face. At the same time, the part exposed from the hole 17a may be soldered and joined by the solder filler 28. In this way, the electrode extraction bracket 18 can be integrally coupled to the ceramic heater 11.

Here, Fig. 3 (a) shows the case where the inner diameter of the hole 17a of the tubular ceramic molded body 17 formed of insulating ceramics is constant, and Fig. 3 (b) gives a step to the inner diameter of the hole 17a to give an electrode. The case where the take-out bracket 18 is thickened and buckling does not occur in the middle is shown.

4 (a) and 4 (b) show a case in which the cylindrical ceramic molded body 17 formed of conductive ceramics is molded from a ceramic conductive material. Thus, when the molded object 17 is formed with a electrically conductive material, it is not necessary to contact the lead part 15 and the connection end 15a, 18a of the electrode extraction bracket 18, and can separate them. In addition, in Fig. 4 (b), holes 17b and 17c are opened in the cylindrical ceramic molded body 17, and the connecting ends 15b of the lead portions 15 and the connecting ends of the electrode extraction brackets 18 are respectively opened. 18a) is inserted.

In addition, the ceramic heater 11 molded as mentioned above can be combined with the tubular housing 22 as shown to FIG. 5 (a), (b), (c). That is, FIG. 5 (a) shows the case where the metal outer cylinder 21 provided on the outer circumference of the ceramic heater 11 is formed long, and the rear end of the outer cylinder 21 is supported at the tip of the tubular housing 22. FIG. The diameter of the front end side of the glow plug 10 can be made narrow, and length can be comprised long.

In addition, Fig. 5 (b) is a case where the metal outer cylinder 21 is coupled to the central portion in the longitudinal direction of the ceramic heater 11 and supported on the tip of the tubular housing 22, and Fig. 5 (c) has been described above. The case where the metal outer cylinder 21 is abbreviate | omitted and the tubular housing 22 is used instead of a metal outer cylinder, and the ceramic heater 11 is directly supported by the front end is shown.

In addition, this invention is not limited to the structure demonstrated by embodiment mentioned above, Needless to say, obtaining by deform | transforming and changing suitably the shape, structure, etc. of each part. For example, in the above-mentioned embodiment, an example is shown as a structure of the ceramic heater 11, the metal outer cylinder 21, the tubular housing 22, etc. of the ceramic heater type glow plug 10, but this invention is not limited to this. In addition, it is free to employ | adopt a modification suitably.

In addition to the combined state of the heat generating element 13 in the ceramic heater 11 and the heat generating element 13, a resistor that also acts as an electrode control function may be combined together.

Moreover, the structure widely known conventionally can also be employ | adopted as the structure of the tubular housing 22. As shown in FIG.

For example, in the ceramic heater-type glow plug 10 which concerns on this invention, while attaching to a cylinder head of an engine by a screw part, airtightness can be ensured to a part of tubular housing 22, and this pipe What is necessary is just a structure which can ensure the airtightness between the ceramic heaters 11 which are supported directly or through the metal outer cylinder 21 with respect to the shape housing 22. As shown in FIG.

In the ceramic heater 11, the cylindrical ceramic molded body 17 to be combined on the rear end side of the ceramic insulator 12 may have a cylindrical shape or a cylindrical shape as shown in Figs. 2A and 2B. do.

<Example>

Example 1

91 wt% of silicon nitride, 5 wt% of yttrium, 4 wt% of alumina, a binder, and a silicon nitride pole were placed in a silicon nitride pot, and mixed and ground with isopropyl alcohol as a kneading medium for 24 hours. Thereafter, the slurry produced by mixing was dried with a spray dryer to produce granules of about 100 μm.

The lead portion 15 having a diameter of 0.5 mm connected to the heat generator 13 is passed through the cylindrical ceramic sintered body 17 having an outer diameter of 2.5 mm, an inner diameter of 0.6 mm, and a length of 20 mm, and embedded as shown in FIG. Then, the sample was hot-pressed at 1800 degreeC, and it grind | grinded, and set it as the glow plug tip part 3.5 mm (ceramic heater 11 used as a heat generating body part).

Since the cylindrical ceramic sintered body 17 is embedded in the last end part, the hole 17a is open. Ni wire (electrode extraction bracket 18) of ø0.5 mm was passed through it, and bonding was performed by silver lead BAg-8. In addition, the metal outer cylinder 21 was also bonded with silver lead BAg-8 after metallizing the ceramic insulator 12. As a result, the portion that becomes the cathode can be electrically bonded. Thereafter, the tubular housing 22 having a length of 200 mm whose diameter of the mounting screw portion 22a is M8 was assembled, and the ceramic heater-type glow plug 10 of FIG. 6 was produced.

Heat-cooling cycle test by 30 seconds of air cooling by heat-generating by turning on a power supply for 30 second so that the saturation temperature at the point of 2 mm from the front-end | tip of such a ceramic heater type glow plug 10 may be 1300 degreeC at 14V. Was performed 50,000 times (this test guarantees approximately 100,000 km under actual vehicle conditions).

As a result of such a test, the heating part disconnection, the disconnection of the lead and the bracket, the bending of the tubular housing 22 and the metal outer cylinder 21 did not occur, and cleared 50,000 tests.

In addition, the pin point is defined at a point (load point) of 3 mm from the uppermost end of the ceramic heater 11 with the whole supported at the rear end (point position in FIG. 6) of the ceramic heater-type glow plug 10 described above. Antistatic strength was investigated by applying a load.

In this embodiment, the portion of the ceramic heater 11 described above was not destroyed at all, and was bent at the portion of the metal outer cylinder 21 into which the ceramic insulator 12 was not inserted. This indicates that, in the event of attachment, even if bent at the time of manufacture, it is possible to fix again.

Example 2

In the same manner as in Example 1 described above, a ceramic heater-type glow plug 10 was manufactured.

The junction position of the lead part 15 and the Ni wire which is the electrode extraction bracket 18 was set to 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, and 40 mm from the highest end of the ceramic heater 11. In addition, joining to the rear end part of the heater 11 of Ni wire was performed with active silver solder.

Thereafter, a saturation temperature at a point of 2 mm from the tip of the ceramic heater type glow plug 10 is set to 1300 ° C. at 14 V, and each of them is turned on for 30 seconds to generate heat, and a heat-cooling cycle test by air cooling for 30 seconds is performed. 50,000 times was performed. (This test is equivalent to approximately 100,000 Km in actual vehicle conditions, and it becomes possible to guarantee the durability of 100,000 Km).

The said test result is shown in following Table 1, and it is confirmed that the joining position of the electrode extraction bracket 18 should just be 20 mm or more.

<Table 1>

As explained above, according to the ceramic heater type glow plug which concerns on this invention, and its manufacturing method, the other lead part of the heat generating body embedded in the ceramic insulator which comprises a ceramic heater, and the junction part for electrode extraction of an electrode extraction bracket are attached to a ceramic insulator. Therefore, since it is carried out at the rear end side separated from the heat generating element so as not to be affected by heat, it is possible to realize a long after-growth without disconnection, and to significantly improve the durability of the glow plug, for example, no need to replace it. You can.

In addition, according to the present invention, since the other lead portion of the heating element embedded in the ceramic insulator which is a ceramic heater and the electrode extraction portion of the electrode extraction bracket are formed by using a cylindrical ceramic molded body or a sintered body embedded in the rear end of the ceramic insulator, The thickness of the tubular housing of the glow plug is made thin so that the so-called attachment screw diameter is M10 to M8, and in the ceramic heater type glow plug, the ceramic heater can be easily connected even if the diameter of the ceramic heater is, for example, about ø3.5 mm. I can do it. Therefore, the whole glow plug can be made thin and long, and the ceramic heater type glow plug which is not costly can be obtained.

Claims (6)

In the ceramic heater type glow plug which attaches a metal outer cylinder or tubular housing, and an electrode extraction bracket to the ceramic insulator which embedded the heat generating body which consists of an inorganic conductive material or a high melting point metal material in ceramics, The connecting end of one lead portion of the heating element is exposed to the outer portion of the ceramic insulator and is electrically joined to the metallic outer cylinder or tubular housing, The connecting end of the other lead portion is electrically connected to the electrode extraction bracket at a position which is not exposed at the rear end of the ceramic insulator, and the electrode extraction bracket is taken out from the rear end of the ceramic insulator, The electrical connection between the connection end of the other lead portion and the electrode extraction bracket is performed at a position within the ceramic insulator at the rear end side of at least five times the diameter dimension of the ceramic insulator from the uppermost end of the ceramic insulator. A ceramic heater-type glow plug, wherein a material of the lead portion of the heating element and the electrode ejection bracket is different. delete The method of claim 1, The ceramic heater type glow plug, wherein the electrode extraction bracket and the lead portion of the heating element are electrically connected through a ceramic molded body or a sintered body made of ceramics including an inorganic conductive material or a high melting point metal material. The method according to claim 1 or 3, A ceramic heater-type glow plug, wherein the last end of the ceramic insulator is placed in the metal outer cylinder. In the manufacturing method of the ceramic heater type glow plug which attaches the metal outer cylinder or tubular housing, and the electrode extraction bracket to the ceramic insulator which embedded the heat generating body which consists of an inorganic conductive material or a high melting point metal material in ceramics, A cylindrical ceramic molded body or sintered body is embedded in the ceramic powder body, A portion of the lead portion of the heating element made of the inorganic conductive material or the high melting point metal material is passed through the cylindrical ceramic formed body or the sintered body, Thereafter, hot pressing is performed to integrate these as ceramic heaters. The method of claim 5, A method of manufacturing a ceramic heater-type glow plug, wherein the tubular ceramic molded body or sintered body is made of ceramics containing an inorganic conductive material or a high melting point metal material.