JPH0742939A - Ceramic heater type glow plug - Google Patents

Abstract

PURPOSE:To improve assembling properties in the case of assembling a rod-like ceramic heater in a metal holder to be held and to positively electrically connect it at a predetermined position. CONSTITUTION:A large-diameter part 12B to be engaged with an end of a metal holder 13 is formed at a ceramic heater 12 made of insulting ceramic material for embedding a resistor 11. The ceramic heater type glow plug comprises an external connection terminal 15 which is inserted from a rear end of the holder and in which a rear end of the terminal can be brought into contact with a rear end of the heater, and an insulating bush 14 for holding the terminal 15 at the rear end of the holder to be engaged by a caulked part 28. One end of the resistor 11 exposed on the rear end of the heater is electrically connected to an inner end of the terminal. The other end of the resistor 11 is exposed near a step 12C of the large-diameter part of the rear end side of the resistor 11, the stepped part 120 is engaged with an end of the holder via a conductive gasket 27 to be electrically connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow plug used for preheating a sub-combustion chamber or a combustion chamber of a diesel engine, and particularly to a fast plug and self-temperature controllability for a long afterglow. The present invention relates to a ceramic heater type glow plug having an achievable self-temperature control function.

[0002]

2. Description of the Related Art Conventionally, glow plugs having various structures have been known as diesel engine glow plugs. Among them, a ceramic heater type has recently attracted attention because it can function as a fast heating type. ing.

As such a ceramic heater type glow plug, for example, Japanese Patent Laid-Open No. 57-41523 discloses a ceramic in which a heating wire made of tungsten (W), rhenium alloy (Re) or the like is embedded in an insulating ceramic material. A heater is known, which is superior in heat transfer efficiency to the sheath type,
The heat generation characteristic and the temperature rising characteristic are improved, and the performance as a rapid heating type can be obtained.

By the way, in such a conventional ceramic heater type glow plug, the ceramic heater is
Generally, it is fixed by being joined by brazing or the like to the tip of a metal holder as a glow plug body via a metal pipe, and other metal conductors connected to the rear end of this heater by welding or the like. The end is integrally assembled by being welded and connected to an external connection terminal which is held at the rear end of the holder via an insulating bush or the like.

[0005]

However, according to the above-mentioned conventional ceramic heater type glow plug, there are three joining portions such as a brazing portion between the heater and the holder and a welding portion at both ends of the metal conducting wire. Not only is there a fixing part such as caulking of the external connection terminal at the rear end of the holder, the whole assembly work is not only complicated and costly, but also the above-mentioned brazing part and welding part. There was a problem that it caused problems such as peeling and cracking.

This was particularly remarkable at the joint portion between the heater made of a ceramic material and the holder made of a metal material. And, according to such a conventional glow plug, there is a problem in securing the reliability in the operation of each part, and it is desired to take some measures to eliminate these problems. .

Therefore, for example, Japanese Unexamined Patent Publication No. 5-18536
In the publication, a step portion is provided on a metal pipe that holds a ceramic heater by brazing, and the step portion is locked to the tip end portion of the metal holder via a gasket while being fixed to the rear end portion of the heater by brazing. An external connection terminal having a flange portion is inserted from the rear end side of the holder into the opening of the electrode lead-out metal fitting, the front end portion is inserted, and the inner end of the external connection terminal is engaged with the flange portion. There is proposed a glow plug having a structure in which a bush is fitted and the rear end of the holder is caulked in a state where the insulating bush is assembled in the holder so that the whole is integrally assembled.

In such a structure, the holder and the metal pipe, and the electrode lead-out fitting and the external connection terminal can be integrally fixed by pressure joining without brazing. The number of parts is reduced and the assembly is simplified.

However, in such a conventional example, it is necessary to braze a metal pipe and a power take-out fitting to the ceramic heater, which is not only a problem in terms of assembling, but also the ceramic heater and the pipe. Creep is likely to occur in the brazed part, and there was a problem in terms of long-term durability.

Further, in Japanese Patent Laid-Open No. 60-17632, a conductive ceramic material is formed in a film shape on the surface of a cylindrical body made of an insulating ceramic material, and a heater by this is formed on the tip of the holder via a conductive gasket. In addition to locking, the tip of the external connection terminal inserted from the rear end of the holder is fitted into the inner hole of the rear end of this heater, and this external connection terminal is held by an insulating bush. There is disclosed a structure in which the whole is integrally assembled by being locked by the caulking portion.

However, in the glow plug provided with the tubular ceramic heater using such a film-shaped heating element, the portion requiring the combustion pressure seal is retained by the heater in the holder via the gasket. Part, the fitting part of the external connection terminal to the rear end of the heater or the flange on the terminal side and the rear end surface of the heater, the structure is complicated and lacks reliability, and problems such as high cost occur. It was inevitable.

Further, in such a structure, the large-diameter locking portion on the rear end side of the heater is locked to the holder side via the gasket to establish electrical connection on the ground side. Since the whole is a heating element, this heating element is required over the entire circumference of the heater. Therefore, the contact of the external connection terminal that press-contacts this heater to the holder side must be uniform over the entire circumference of this locking portion. However, there is also a problem that the resistance becomes non-uniform and a uniform temperature distribution of the heater cannot be obtained, and it is desired to take some measures against such a problem.

In particular, in this kind of glow plug, a so-called after glow system has been adopted in recent years in which the energized state of the glow plug is maintained for a certain period of time even after the engine is started to enhance the engine combustion effect. In this case, it is necessary to take measures for obtaining a glow plug that can be obtained with reliability and durability in operation, and can be manufactured easily and can be reduced in cost.

The present invention has been made in view of the above circumstances, and the ceramic heater is locked and held at the front end of the metal holder, and is integrally assembled by simple caulking at the rear end of the holder. The purpose is to obtain a ceramic heater type glow plug that can be assembled, can be manufactured at low cost, is excellent in reliability, can easily and reliably perform combustion pressure sealing, and has a large degree of freedom in design. .

[0015]

In order to meet the above-mentioned demand, a ceramic heater type glow plug according to the present invention comprises:
A rod-shaped ceramic heater having a large-diameter portion on the rear end side that is locked to the front end of the metal holder and formed by embedding a resistor in an insulating ceramic material, and a rod-shaped ceramic heater inserted from the rear end of the holder. An external connection terminal whose front end is formed so as to be able to come into contact with the rear end surface of the ceramic heater and a holder rear end part which is assembled by being fitted to this external connection terminal while being held by the holder rear end part. The ceramic bush has an insulating bush that is locked by the caulking part and exposes one end of the resistor in the ceramic heater to the rear end face of the heater, and the inner end of the external connection terminal directly or at the inner end of the conductive metal. While electrically connecting via a piece, expose the other end of the resistor to the outer peripheral surface near the stepped portion due to the large diameter portion on the rear end side of the heater,
The stepped portion is locked to the tip of the holder via a conductive gasket so that the stepped portion is electrically connected.

Further, in the ceramic heater type glow plug according to the present invention, the rod-shaped ceramic heater is connected in series to the first heating element made of a conductive ceramic material buried in the heater tip side and the first heating element. And a second heating element made of a conductive metal material having a positive temperature coefficient of resistance larger than that of the first heating element, and one end of the resistor formed by the first and second heating elements, and after the heater. The first lead portion extends to the end portion and is exposed to the rear end surface of the heater, and the second lead portion is connected to the other end of the resistor and is exposed to a portion near the rear end of the heater.

[0017]

According to the present invention, the gasket is attached to the step inside the tip of the holder, and then the rod-shaped ceramic heater is attached.
Insert the external connection terminal, which is inserted into the metal holder and the step portion near the rear end is locked to the tip of the holder through the gasket, and the metal piece is temporarily fixed to the tip from the rear end of the holder. A heater that forms a glow plug by inserting the insulation bush that is fitted into the external connection terminal with the caulking portion at the rear end of the holder in the state that the front end is pressed against the rear end of the heater. The external connection terminals and the like are assembled and held in the metal holder without the need for brazing, and the glow plug can be easily and reliably assembled.

According to the present invention, in the initial stage of energization, a large amount of electric power is supplied to the first heating element on the tip side of the ceramic heater so that the first heating element can rapidly generate heat to exhibit its performance as a rapid heating type and for a predetermined time. After the lapse of time, the electric power supplied to the first heating element is supplied by the second heating element which is a power control resistor embedded in the rear end side of the ceramic heater, so that the function as a fast heating type can be exerted and it is appropriate. Saturation temperature characteristics can be obtained, and overshoot characteristics capable of performing afterglow for a long time can be obtained.

[0019]

1 and 2 show an embodiment of a ceramic heater type glow plug according to the present invention. First, a general structure of a glow plug generally designated by the numeral 10 is shown in FIG.
This glow plug 10 will be briefly described with reference to FIG.
Is a resistor 1 including two kinds of heating elements and their lead portions.
1 is provided with a rod-shaped ceramic heater 12 which is embedded in an insulating ceramic material such as silicon nitride (Si ₃ N ₄ ) and a metal holder 13 having a substantially tubular shape which holds the heater 12 at its tip. There is. The metal holder 13 is made of a material resistant to creep, for example, carbon steel such as S45C or a similar material.

A rod-shaped external connection terminal 15 is fitted and held on the rear end side of the holder 13 via an insulating bush 14 made of an insulating ceramic material or the like.
The inner end of the external connection terminal 15 is brought into contact with the rear end surface of the ceramic heater 12 via a metal piece 16 made of a conductive metal material described later, and one lead portion (which is embedded in the heater 12 ( It will be described later).

Reference numeral 13a in the drawing denotes a screw portion formed on the outer periphery of the holder 13, which is screwed into a screw hole on the engine cylinder head side (not shown) so that the tip of the heater 12 is projected into the auxiliary combustion chamber (combustion chamber). It is for placing in a state. Further, reference numeral 17a in the drawing denotes an insulating ring penetrating the external connection terminal 15 extending from the rear end of the holder 13.
Reference numeral 7b denotes a metal ring fixed by caulking or the like on the external connection terminal 15 in a state where the insulating ring 17a is brought into contact with the rear end of the holder 13, and 18 is not shown between the metal ring 17b and the metal ring 17b. It is a tightening nut for connecting the lead wire from the battery.

Further, the above-mentioned ceramic heater 12 is
The ceramic powder is formed as a round bar having a substantially circular cross section and is filled with the resistor 11 held in a mold by hot pressing or the like. In this case, the material of the ceramic heater 12 is preferably a material having excellent insulating properties and thermal conductivity, for example, a silicon nitride such as silicon nitride, but it is needless to say that silicon carbide or the like may be used. Yes.

Further, according to the present embodiment, in the ceramic heater type glow plug 10 having the above-described structure, the tip end side of the rod-shaped ceramic heater 12 made of an insulating ceramic material, as is apparent from FIG. A first heating element 20 formed of a conductive sialon so as to have a substantially U-shape as a conductive ceramic material is embedded as a heating resistor, and the first heat generation is performed on the rear end side of the heater 12. The first heating element 2 is used as a power control resistor that is connected in series to both ends of the body 20.
The ceramic heater 12 is configured by embedding the second heating elements 21 and 21 made of a metal material having a positive resistance temperature coefficient larger than 0, for example, tungsten (W).

The first and second lead portions 22 and 23 are connected to the rear ends of the second heating elements 21 and 21 in the ceramic heater 12, and the lead portions 22 and 23 are connected to each other. It extends in the axial direction of the ceramic heater 12. The rear end of the first lead portion 22 is exposed to the rear end surface of the ceramic heater 12 so as to be externally connectable (exposed portion 22a), and the rear end of the second lead portion 23 is exposed to the ceramic heater 12 described later. The exposed portion is formed so as to be externally connectable to the step portion between the large diameter portion formed in the portion near the rear end and exposed (exposed portion 23a).

Here, as the conductive ceramic material forming the above-mentioned first heating element 20, for example, silicon nitride is used.
By increasing or decreasing the content of titanium nitride (TiN) as a conductivity-imparting material in β sialon whose main component is (Si ₃ N ₄ ) or sialon in which α and β are mixed, the specific resistance can be increased. Conductive sialon that can be arbitrarily selected and used
(SiAlON) or the like is preferably used.

However, such a conductive ceramic material is not limited to the above-mentioned conductive sialon, and it is essential that the performance is stable even in a high temperature state (for example, up to about 1200 ° C.), and the second heat generation is relatively large. Any ceramic material may be used as long as it has a smaller temperature coefficient of resistance than the body 21 and is excellent in thermal shock resistance, and may be, for example, SiC and 4a group of the periodic table, 5
Sialon firing containing at least one selected from the group of non-oxide conductive materials such as carbides, borides, nitrides or carbonitrides of Group a or Group 6a elements and Al or Al compounds as sintering binders Consolidation is possible. When the first heating element 20 made of a conductive ceramic material of this kind is embedded in the insulating ceramic material, the conductive ceramic material is mixed in a powder state or a preformed one is embedded. You may.

The second heating elements 21 and 21 are set so that the positive temperature coefficient of resistance is relatively larger than that of the conductive sialon forming the first heating element 20. It is preferable to form the obtained tungsten (W) wire. Furthermore, the electrical resistance of the first and second lead portions 22 and 23 extending from the rear end portions of the second heating elements 21 and 21 to the rear end side of the ceramic heater 12 is as small as possible. As described above, it is preferable to use a wire in which the cross-sectional area of the tungsten wire is larger than that of the heating elements 21 and 21.

The second heating elements 21 and 21 described above are used.
Are both end portions of the first heating element 20 and the lead portions 2 described above.
The end portions of the heaters 2 and 23 are connected to each other in a wound state, and are formed in a spiral shape along the longitudinal direction of the heater 12 and embedded in the heater 12. However, the connection method is not limited to this, and the connection may be made by embedding in the conductive sialon forming the first heating element 20. Depending on the method, an appropriate connection method can be considered. That is, in this embodiment, the first and second lead portions 22 and 23 are
The wire-shaped one is exemplified as the second heating element 21, 2.
For example, tungsten having a sufficiently large wire diameter is used.

Then, as described above, the ceramic heater 12 is provided with the first heating element 20 as a heating resistor and the second heating elements 21, 21 connected in series to this as a power control resistor. According to this, in the initial stage of energization, a large amount of electric power can be supplied to the first heating element 20 on the tip side of the ceramic heater 12 to rapidly generate heat to exhibit the performance as a rapid heating type, and after a predetermined time has elapsed. The second heating element 21, which serves as a power control resistor embedded in the rear end side of the ceramic heater 12, is supplied with the electric power supplied to the first heating element 20,
As can be seen from the heat generation characteristics of the glow plug shown in FIG. 7, the function as a fast heating type can be exhibited, an appropriate saturation temperature characteristic can be obtained, and afterglow for a long time can be performed. It is possible to obtain the overshoot characteristic.

According to the present invention, in the ceramic heater glow plug 10 described above, the rear end portion of the ceramic heater 12 provided with the lead portions 22 and 23 is connected to the first and second heating elements 20; 21 is configured as a large diameter portion 12B having a larger diameter than the tip side small diameter portion 12A, and a step portion 12C between the small diameter portion 12A and the large diameter portion 12B is provided at the tip portion of the holder 13. It is configured such that it can be locked by the step portion 26 formed by the heater insertion hole 25 having a small diameter, and the ring-shaped gasket 27 made of a conductive metal material having a combustion pressure sealing function is interposed in this portion. Then, the second lead portion 2 in this portion
The exposed side 23a of No. 3 and the holder 13 can be electrically connected to the ground side, and the combustion pressure can be sealed at this part.

Further, according to the present invention, the external connection terminal 15
The inner end portion of the insulating bush 14 is formed with a large diameter portion 15A and the rear end side portion thereof is formed with a small diameter portion 15B, and the tip portion of the insulating bush 14 can be locked to the step portion 15C therebetween. Further, at the tip (inner end) of the external connection terminal 15, the conductive metal piece 16 is inserted into the insertion hole 16a (see FIG. 3), or water, a creamy liquid or the like is applied. Then, it is temporarily fixed by being attached. In this case, this metal piece 16 should not come off from the tip portion of the external connection terminal 15 when assembled.

By inserting the external connection terminal 15 into the holder 13 in this temporarily fixed state, the metal piece 16 is abutted against the rear end surface of the heater 12, and the first lead portion 22 exposed at this portion is exposed. It is configured so that electrical connection on the anode side with the portion 22a can be surely made.

An insulating bush 14 is fitted to the rear end side small diameter portion 15B of the external connection terminal 15, the inner end of which is locked to the step portion 15C, and the rear end portion is Caulking portion 28 by caulking the cylindrical rear end portion 13b (see FIG. 2) of the holder 13 with knurling
It is designed to be locked by.

The glow plug 10 having such a structure
Inserts the conductive gasket 27 into the holder 13 and puts the rod-shaped ceramic heater 12 into the metal holder 13 in a state where the conductive gasket 27 is placed on the step portion 26 on the front end side.
C is locked to the stepped portion 26 at the tip of the holder 13 via the gasket 27, and the external connection terminal 15 with the metal piece 16 temporarily fixed to the tip is inserted from the rear end of the holder 13, and the tip is heated by the heater. 12 Insulation bush 1 fitted to this external connection terminal 15 while being pressed against the rear end
4 is locked by the caulking portion 28 at the rear end portion of the holder 13 to integrally assemble.

Here, according to the glow plug 10 assembled in this way, the large-diameter hole portion on the rear end side of the holder 13 is insulated when the caulking portion 28 is caulked, as is apparent from FIG. It is preferable to provide a gap that allows the bush 14 to move in the axial direction.

According to the above structure, the ceramic heater 12, the external connection terminal 15 and the insulating bush 1 are provided in the holder 13.
4. Further, the conductive gasket 27 and the conductive metal piece 16 are simply incorporated, and the rear end portion 13b of the holder 13 is swaged so that the rear end of the insulating bush 14 is locked by the swaged portion 28. The entire glow plug 10 can be assembled and held very easily without the need for such brazing work, and the glow plug 10 as a whole can be integrally assembled. This simplifies the assembling process as compared with the conventional one and greatly reduces the manufacturing cost. Can be realized.

Further, in such a structure, the step portion 12C formed by the large diameter portion 12B on the rear end side of the ceramic heater 12 is formed.
To the tip of the holder 13 via the conductive gasket 27, and the insulating bush 14, the external connection terminal 15, and the conductive metal piece 16 which are locked by the caulking portion 28 on the rear end side of the holder 13. By pressing through, the electrical connection and combustion pressure sealing at the gasket 27 portion can be easily and reliably performed.

In particular, according to such a structure, since the combustion pressure seal need only be provided in one place as described above, it is simple and inexpensive in cost. Further, in such a configuration, the heater 12, the gasket 27, the metal piece 16, the external connection terminal 1
5, the insulating bush 14 and the like are individually divided, and relative positional deviation between them can be tolerated to some extent, which is excellent in assemblability and advantageous in terms of manufacturing cost.

Further, with such a structure, the stepped portion 12C of the heater 12 can be pressed uniformly over the entire circumference, and the electrical connection is exposed to the exposed portion 23a of the lead portion 23.
Since there is only one position in the circumferential direction at which the heater 12 is exposed, the required electrical connection can be obtained, and as a result, a uniform temperature distribution of the heater 12 can be obtained.

Further, according to the above-mentioned structure, since there is no brazing joint portion, there are no restrictions in designing the glow plug 10, and the second power control resistor is used in the conventional brazing joint. There is also an advantage that it is not necessary to shift the position of the second heating element in the axial direction from the brazing joint so that the brazing portion does not melt due to the heat effect of the heating element.

In addition, in the above-mentioned structure, the metal piece 16 at the tip of the external connection terminal 15 has a simple disk shape as shown in FIGS. 1 to 3 and FIG. 4A. However, if a metal piece 16A having elasticity such as a disc spring shape as shown in FIG. 4B or a hemispherical metal piece 16B as shown in FIG. 4C is used,
Creep or the like at the caulking portion 28 at the rear end of the holder 13 for integrally assembling the whole through the insulating bush 14 can be absorbed, and the problem of contact failure due to such creep can be solved, and reliable electrical connection can be achieved. There is also an advantage that it can be obtained.
This is also effective in absorbing the dimensional tolerance of each part.

Further, in the structure described above, in the ceramic heater 12, the first and second heating elements 20, 21 are formed.
Since a simple pressure contact structure in which a gasket 27 is interposed is used to hold the above at the tip of the metal holder 13, when adopting brazing joining as in the conventional case,
It is possible to prevent thermal influence on the brazed joint between the heater 12 and the holder 13 or the like due to the temperature rise of the two heating elements 20 and 21, which is a great advantage.

Further, in the above-mentioned structure, the first heating element 20 as the heating resistor is formed of the conductive ceramic material, so that it is excellent in heat resistance strength and durability is improved.
Afterglow can be achieved for a long time. Since the glow plug 10 generates heat only at the ceramic heater 12 part, there is no need to generate heat at an extra portion, there is no wasteful power consumption, and the heat resistance and the like are also excellent in terms of reliability. There is also.

The present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part of the glow plug 10 can be freely modified and changed, and various modifications can be considered.

For example, FIG. 8 shows another embodiment of the present invention. In this embodiment, in order to maintain the insulating property inside the holder 13 at the large diameter portion 15A of the external connection terminal 15 inserted into the holder 13, Insulation tube 4 made of glass, glass fiber, etc.
This is the case where 0 is fitted. By doing so, the reliable insulation between the external connection terminal 15 and the holder 13 can be maintained, and concentric positioning with the heater 12 can be easily performed when the external connection terminal 15 is inserted into the holder 13. There are advantages.

Further, in the above-described embodiment, the second heating elements 21 and 21 have a larger positive resistance temperature coefficient than the conductive sialon as the conductive ceramic material forming the first heating element 20. Although the case of forming the tungsten (W) wire rod that can be set as above is shown, the present invention is not limited to this, and the positive temperature coefficient of resistance is higher than that of the conductive ceramic material forming the first heating element 20 described above. It may be formed of a metal material large enough to maintain the above relationship, for example, a tungsten alloy material.

Further, in the above-described embodiment, in the ceramic heater glow plug 10, the exposed portion 22a of the first lead portion 22 exposed on the rear end surface of the ceramic heater 12 in the holder 13 and the tip of the external connection terminal 15 are exposed. The conductive metal piece 16 is used for electrical connection with the heater 12. However, the conductive metal piece 16 is omitted and the heater 12
Of course, the exposed portion 22a of the first lead portion 22 and the inner end of the external connection terminal 15 may be electrically connected to the rear end surface of the first lead portion 22 by direct contact.

[0048]

As described above, according to the ceramic heater type glow plug according to the present invention, the rod-shaped ceramic made of an insulating ceramic material having a large diameter portion on the rear end side that is engaged with the front end of the metal holder. The heater and the external connection terminal that can be inserted from the rear end of the holder so that the tip can abut the rear end surface of the ceramic heater, and the external connection terminal that is fitted to this and held at the rear end of the holder. Equipped with an insulating bush that is locked by the caulking part of the end, expose one end of the resistor embedded in the ceramic heater to the rear end surface of the heater, and directly or internally to the inner end of the external connection terminal. In addition to electrically connecting through the provided conductive metal piece, expose the other end of the resistor to the outer peripheral surface near the stepped portion due to the large diameter portion on the rear end side of the heater, and attach this stepped portion to the tip of the holder. Conductive gas Since so as to electrically connected through this by locking through a socket, in spite of the simple structure, excellent effects as follows.

That is, according to the above configuration, the ceramic heater, the external connection terminal, the insulating bush, the
Furthermore, by simply incorporating a conductive gasket or a conductive metal piece and caulking the rear end of the holder to caulk and lock the rear end of the insulating bush, the entire glow plug can be assembled as a whole. The brazing process required at the time of assembling the glow plug can be omitted, the assembling property can be simplified, and the manufacturing cost can be greatly reduced.

Further, in the above-mentioned structure, the conductive gasket is interposed between the step portion formed by the large diameter portion on the rear end side of the ceramic heater and the tip portion of the holder, and the conductive gasket is locked by the caulking portion on the rear end side of the holder. The insulation bush, the external connection terminal, and the conductive metal piece are pressed into contact,
There is an advantage that the electrical connection can be surely made at the gasket portion and the combustion pressure sealing can be easily and surely made at this portion. In particular, since such a combustion pressure seal may be provided at one place, it is simple and inexpensive in cost.

Further, according to the above-mentioned structure, since there is no brazing joint portion, there is an advantage that there is no restriction in designing the glow plug. That is, conventionally,
In brazing, the second heating element is axially separated from the brazing joint so that the brazing point does not melt due to the heat generated by the second heating element, which is a power control resistor. However, according to the present invention, there is no such need.

Further, according to the present invention, a first heating element made of a conductive ceramic material such as a conductive sialon is embedded as a heating resistor at the tip side of the ceramic heater made of an insulating ceramic material. As a power control resistor connected in series to the first heating element on the rear end side of the heater, a second element made of a conductive metal material or a conductive ceramic material having a positive temperature coefficient of resistance larger than that of the first heating element. By constructing a ceramic heater by burying the heating element of, the structure is simple, the reliability is excellent, and the cost is low, but the heat generation characteristics and durability as a glow plug, Furthermore, there are advantages such that the self-temperature control function can be exerted and afterglow can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an overall schematic configuration showing an embodiment of a ceramic heater type glow plug according to the present invention.

FIG. 2 is a schematic exploded perspective view for explaining an assembling process of the glow plug according to the present invention.

FIG. 3 is an enlarged view of a portion where a conductive metal piece is attached to the tip of the external connection terminal in the glow plug of the present invention.

FIG. 4 shows a conductive metal piece and its modification (a),
It is a schematic perspective view illustrated to (b) and (c).

FIG. 5 is a schematic view showing a state where (b) of FIG. 4 is used as a conductive metal piece.

FIG. 6 is a schematic perspective view showing a conductive gasket which is interposed between the heater tip and the stepped portion of the heater.

FIG. 7 is a characteristic diagram showing heat generation temperature characteristics in the ceramic heater type glow plug according to the present invention.

FIG. 8 is a schematic cross-sectional view showing another embodiment of the ceramic heater type glow plug according to the present invention.

[Explanation of symbols]

 10 Ceramic Heater Type Glow Plug 11 Resistor 12 Ceramic Heater 12B Large Diameter Part 12C Stepped Part 13 Metal Holder 15 External Connection Terminal 15A Large Diameter Part 16 Conductive Metal Piece 20 First Heating Element Made of Conductive Ceramic Material 21 Conductivity Second heating element made of metal material 22 First lead portion 23 Second lead portion 26 Holder-side step portion 27 Conductive gasket 28 Caulking portion 40 Insulation tube

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[Procedure amendment]

[Submission date] November 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

Claims (4)

[Claims] 1. A rod-shaped ceramic heater having a large-diameter portion on the rear end side that is engaged with the front end portion of a metal holder and formed by embedding a resistor in an insulating ceramic material, An external connection terminal, which is inserted from the rear end of the holder and whose front end is formed so as to be able to contact the rear end surface of the ceramic heater, and the external connection terminal that is fitted to the external connection terminal to connect the external connection terminal to the rear end of the holder. An insulating bush that is retained by the caulking portion at the rear end of the holder in a state of being held by the holder, one end of the resistor in the ceramic heater is exposed to the rear end surface of the heater, and the inner end of the external connection terminal is provided. Is electrically connected via a conductive metal piece provided at the other end of the resistor to the outer peripheral surface near the step between the large diameter portion on the rear end side of the heater and the small diameter portion on the front end side. Exposed, this step is in front The ceramic heater is electrically connected through the gasket by being locked to the holder tip through the gasket, and the step portion of the ceramic heater is locked to the holder tip through the gasket. In addition, the insulating bush is fixed by being locked by the caulking portion of the holder rear end portion while the external connection terminal is pressed to the rear end portion via the metal piece. Ceramic heater type glow plug. 2. The ceramic heater glow plug according to claim 1, wherein the inner end of the external connection terminal is connected to one end of the resistor exposed at the rear end face of the ceramic heater via a metal piece having conductivity. A ceramic heater glow plug characterized by being electrically connected. 3. The ceramic heater glow plug according to claim 1 or 2, wherein the rod-shaped ceramic heater includes a first heating element made of a conductive ceramic material, which is embedded in a tip end side of the heater, and a first heating element. A second heating element which is connected in series to the first heating element and is made of a conductive metal material having a positive temperature coefficient of resistance larger than that of the first heating element; and a resistor formed by the first and second heating elements. A first lead portion connected to one end and extending to the heater rear end portion and exposed to the heater rear end surface, and a second lead portion connected to the other end of the resistor and exposed to the heater rear end portion.
And a ceramic heater type glow plug. 4. The ceramic heater glow plug according to claim 3, wherein the conductive ceramic material forming the first heating element in the ceramic heater is β-sialon containing silicon nitride (Si ₃ N ₄ ) as a main component, or Conductive sialon (SiAlON) whose specific resistance can be arbitrarily selected by increasing / decreasing the content of titanium nitride (TiN) as a conductivity-imparting material is added to α-β mixed-phase sialon. A ceramic heater glow plug characterized by being used.