JP2002158079A - Ceramic heater and glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater with enough mechanical strength and durability resulting from the superb mechanical strength realizing manufacturing efficiency and these characteristics at low cost, and a glow plug equipped with the ceramic heater. SOLUTION: Mixture powder containing silicon nitride, erbium oxide, silica and tungsten carbide with a binder added is kneaded, which is then molded. A U-shaped unbaked heating resistive element 12' which has buried a tungsten- made lead wire 13a' having a bent part per a piece of wire with a bending angle of 0 deg.<θ<=40 deg. after baking and a tungsten-made lead wire 13b' without a bent part are set up in split-half unbaked insulating base bodies 11a', 11b' and are hot-pressed to make up a coarse ceramic heater. Later, its surface is polished to adjust the exposed surface area per lead wire within the range of 0.07 to 0.60 mm2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to ceramic heaters and glow plugs, and more particularly to impact resistance,
The present invention relates to a ceramic heater and a glow plug having excellent mechanical strength such as bending strength and high durability. The ceramic heater of the present invention can be suitably used as a glow plug as a starting assist device for a diesel engine or a heating source for a combustion type heater, and the glow plug of the present invention is suitable as a glow plug for a diesel engine.

[0002]

2. Description of the Related Art Conventionally, ceramics having high heat resistance and excellent mechanical strength have been used as an insulating ceramic substrate of a ceramic heater used for a glow plug. On the other hand, a metal conductive material is usually used for a lead wire for supplying a current to a heating resistor embedded in the insulating ceramic substrate. The lead wire is buried in the insulating ceramic base together with the heating resistor, one end is connected to the heating resistor, and the other end is exposed on the outer surface of the insulating ceramic base. Electricity is being supplied to the heating resistor.

[0003]

However, no technique has been studied for this exposed part. Further, the shape of the lead wire for exposing the lead wire to the outer surface of the insulating ceramic substrate is disclosed in Japanese Patent Publication No. Hei 6-10039, Japanese Patent Laid-Open No. 7-142153 and Japanese Patent Laid-Open No. 9-18.
No. 4627 is known, but it is not easy to process any lead wire shape, and it is the best when considering workability during production, yield in production, production cost and durability during use. It's not always good.

The present invention has been made in view of the above-mentioned problems, and a ceramic heater has sufficient mechanical strength and durability due to excellent mechanical strength, and at the same time, manufacturing efficiency and these characteristics are reduced at a low cost. It is an object of the present invention to provide a ceramic heater that can be realized and a glow plug including the ceramic heater.

[0005]

SUMMARY OF THE INVENTION Ceramic heaters used for glow plugs and the like require extremely high mechanical strength. This is because, for example, the glow plug is attached to the engine with a high impact tool such as an impact wrench, and the diesel engine operates at a very high compression pressure. It can be seen from the fact that when abnormal combustion occurs, etc., a very large shock is received, and that the fuel cell itself bears a thermal shock due to repeated cold / hot cycles. We have:
Regarding ceramic heaters that can be cut off sufficiently for use in such glow plugs and the like, in particular, the shape of the lead wires embedded inside the insulating ceramic base and the outer surface of the insulating ceramic base for energizing the heating resistor are shown in FIG. The study was repeated on the exposed area per lead wire to be provided.

As a result, the voltage applied to cause the ceramic heater (heating resistor) to generate heat is applied to an external conductive member (glow) brazed to the exposed portion of the lead wire exposed from the outer surface of the insulating ceramic base. In the case of a plug, it is supplied from a protective outer cylinder, a lead coil or a connection lead, etc.), but the exposed area of the lead wire is very small, and the only exposed area is to ensure brazing and conduction. It has been confirmed that it is preferable to increase the size. On the other hand, a material having a large difference in characteristics (thermal expansion coefficient, firing shrinkage rate, etc.) from the insulating ceramic substrate may be used for the lead wires in the insulating ceramic substrate. For this reason, the bending strength at that position tends to decrease as the position of the lead wire in the insulating ceramic substrate approaches the outer surface of the insulating ceramic substrate. In the exposed portion, it was confirmed that if the exposed area was large, the bending strength of the ceramic heater was likely to decrease. From these results, by optimizing the exposed area per lead wire exposed from the insulating ceramic base, it is possible to sufficiently improve both the brazing strength to the external conductive member and the mechanical strength of the ceramic heater itself. The present inventors have found that a ceramic heater satisfying the requirements can be obtained, and have completed the present invention.

Furthermore, in order to expose a part of the lead wire on the outer surface of the insulating ceramic substrate, the lead wire is connected to the heating resistor at any point on the lead wire extending from one end to the other end. It is usual to provide a converter. However, since lead wires require high heat resistance, relatively brittle metals such as tungsten and tungsten alloys must be used in many cases. For this reason, the formation of the direction change portion itself tends to be a heavy burden on the lead wire. Further, while having such brittleness, it is a small part, so precision of processing is required, and the processing is not easy, and it is costly to apply such processing to a plurality of locations of one lead wire. Is also not preferred.

However, up to now, the lead wire has been prevented from peeling off from the insulating ceramic substrate due to the difference in the material of the insulating ceramic substrate and the lead wire at the exposed portion of the insulating ceramic substrate, and has been reliably connected to the external conductive member. Processing such as providing two or more direction conversion portions on the lead wire is performed in order to achieve a proper connection and the like. On the other hand, the present inventors do not necessarily need to have two or more direction change portions in the lead wire, and furthermore, the expression per lead wire exposed from the insulating ceramic base as described above. By optimizing the area, it was found that the brazing strength with the external conductive member, the mechanical strength of the ceramic heater itself, and also the cost problem could be solved, and the present invention was completed.

The ceramic heater of the present invention is embedded in the insulating ceramic base together with the insulating ceramic base and a heating resistor which generates heat when energized. One end of the ceramic heater is connected to the heating resistor to energize the heating resistor. And a lead wire whose other end is exposed on the outer surface of the insulating ceramic substrate, and the area of the lead wire exposed on the outer surface of the insulating ceramic substrate is 0.07 to 0. .60mm
It is characterized by being ² .

Although the above-mentioned "insulating ceramic substrate" can be selected variously depending on the purpose, silicon nitride-based ceramics are frequently used. In particular, silicon nitride obtained by containing at least one rare earth element such as Er and Yb is used as an insulating material. Preferably, the content is 90% by mass or more based on the entire ceramic base. In addition, silicon nitride includes a wide range of substances containing silicon nitride as a main component, and in addition to silicon nitride, aluminum nitride, alumina, sialon, and the like can be contained. In order to reduce the difference in the coefficient of thermal expansion from the conductive component contained in the heating resistor, a small amount of the conductive component may be contained in the insulating ceramic substrate.

The above-mentioned "heating resistor" is a resistor which generates heat when energized, and is composed of an insulating component and a conductive component. Silicon nitride is often used as an insulating component.
On the other hand, as conductive components, W, Ta, Nb, Ti, M
At least one of silicide, carbide, nitride and the like of one or more metal elements selected from o, Zr, Hf, V, Cr and the like can be used. Above all, it is preferable that the difference in the coefficient of thermal expansion from silicon nitride, which is frequently used as an insulating component of the heating resistor and also as an insulating ceramic substrate, is small, and further, the heat resistance temperature is high. As a result, the maximum temperature of the ceramic heater can be improved, and the occurrence of cracks due to the difference in the coefficient of thermal expansion hardly occurs. Such conductive components include WC, Mo
Si ₂ , TiN, WSi _{2 and the} like can be mentioned. In addition, the ratio between the insulating component and the conductive component is not particularly limited,
When the heating resistor is 100% by volume, the conductive component is 1
It can be 5 to 40% by volume (particularly 20 to 30% by volume).

The above-mentioned "lead wire" is a conductive wire for supplying a current to the heating resistor, and is generally provided with two wires. This lead wire can be formed of one kind of metal selected from W, Re, Ta, Mo, Nb and the like, or an alloy of two or more kinds. The shape of the lead wire is not particularly limited, and the cross-sectional shape is not particularly limited. Further, the wire diameter is not particularly limited.
0 to 0.60 mm (more preferably 0.35 to 0.55
mm, more preferably 0.40 to 0.50 mm). If the wire diameter is less than 0.30 mm, it tends to be difficult to handle during manufacture,
The relative resistance with respect to the amount of energization increases, and the lead wire itself tends to generate heat. On the other hand, it is not necessary to be thicker than 0.60 mm, which is not preferable because the mechanical strength of the ceramic heater tends to decrease.

The ceramic heater of the present invention has lead wires 13a 'and 13b' at predetermined positions as shown in FIG.
U-shaped unfired heating resistor 1 having one end connected to
2 ′ is a half-shaped unsintered insulative ceramic substrate 11a ′ and 11b ′ in which a non-sintered heating resistor and a lead wire-shaped recess are formed as shown in FIG. The green ceramic heater assembly 11 'is formed by sandwiching the lead wires 12' and the lead wires 13a 'and 13b', and then fired integrally. Further, by polishing a predetermined amount of the surface of the obtained sintered body, the other ends of the lead wires 13a 'and 13b' are exposed from the outer surface of the insulating ceramic base 11 (see FIG. 3). As a result, a ceramic heater extending in the axial direction is formed. The location where the lead wire is exposed on the outer surface of the insulating ceramic substrate varies depending on the shape of the lead wire and the like. The side on which the resistor is disposed is referred to as a tip side).

The area of this lead wire exposed on the outer surface of the insulating ceramic substrate is 0.07 to 0.07
0.60 mm ² (more preferably 0.20 to 0.50 m
m ² , particularly preferably 0.30 to 0.40 mm ² ). If this area is less than 0.07 mm ² ,
Since there are few regions to be brazed to the external conductive member, there may be cases where poor conductivity occurs, or even if the conduction is sufficient, the durability may be insufficient. On the other hand, 0.60
If it exceeds mm ² , the mechanical strength of the ceramic heater tends to decrease, which is not preferable.

If the area is 0.07 mm ² or more, even if 200 cycles or more are imposed in the accelerated cold / hot cycle endurance test, sufficient brazing strength is maintained so that the brazing portion does not peel off from the external conductive member. can do. On the other hand, if this area is 0.60 mm ² or less, the three-point bending strength (span 12 mm, cross At a head speed of 5 mm / min), a ceramic heater having a pressure of 400 MPa or more and excellent mechanical strength can be obtained.

[0016] The cold / hot cycle endurance test means that a ceramic heater is put into a tubular furnace and the temperature of the ceramic heater itself is raised from room temperature to 400 ° C. As one cycle, this 1
This is a test in which the cycle is repeated several times. In this cold / hot cycle durability test, when the ceramic heater is used as a glow plug, the maximum temperature of the brazed portion when mounted on the engine is usually 250 to 300 ° C. Therefore, this test is an accelerated durability test for the ceramic heater.

The ceramic heater according to the present invention is embedded in the insulating ceramic base together with the insulating ceramic base and a heating resistor which generates heat when energized, and one end of the ceramic heater is connected to the heating resistor to energize the heating resistor. And a lead wire having the other end exposed on the outer surface of the insulating ceramic substrate, at least one of the leads extending from the one end and being changed in direction to reach the other end. It has only one direction changing part, and the bending angle θ of the direction changing part is 0 ° <θ
≦ 40 °.

The "insulating ceramic substrate" and the "heating resistor" are the same as those described above, and the "lead wire"
Is the same as described above, except that after changing the direction by extending from one end side, the direction changing portion reaching the other end side has the above-mentioned bending angle. The above-mentioned "direction changing part" indicates a part where the direction of a center line extending from one end connected to the heating resistor in the lead wire changes. This change in direction may be linear or curvilinear. If the number of the direction change portions is two or more as in the conventional case, the cost of processing the lead wire is high, and the insulating ceramic base may be slightly displaced in the insulating ceramic substrate during the manufacturing process. The area exposed on the external surface of the body tends to be large, and the mechanical strength of the ceramic heater itself tends to decrease.

The bending angle of the direction changing portion is 5 ° ≦ θ.
≦ 40 ° (more preferably 10 ° ≦ θ ≦ 35 °, further preferably 15 ° ≦ θ ≦ 30 °).
The bending angle θ of the direction changing portion refers to a bending angle after a lead wire connected to one end of the unfired heating resistor is buried in the unfired ceramic substrate and these are integrally fired. . If the bending angle after firing exceeds 40 °, the direction changing portion of the lead wire before firing must be set larger than the bending angle after firing in consideration of the firing shrinkage. There is a tendency that a strongly bent portion called a buckling portion as shown in FIG. Even if this buckling portion occurs in the lead wire with a bending angle exceeding 40 °, there is no problem in the initial stage of use of the ceramic heater, but as the use time increases, the possibility of disconnection gradually decreases and the mechanical strength of the ceramic heater itself decreases. It is not preferable because it invites.

As described above, in order to make the bending angle θ of the direction changing portion of the fired lead wire 0 ° <θ ≦ 40 °,
The bending angle θ ′ of the direction changing portion of the lead wire before firing is 0.
It is preferable that {<θ ′ ≦ 55}. For example, when the bending angle θ ′ before firing is about 20 °, the angle after firing is about 15 °, and when θ ′ is about 30 °, θ is about 20 °.
When θ ′ is about 45 °, θ is about 30 °, and when θ ′ is about 55 °, θ is about 40 °.

The bending angle at which the direction of the center line of the lead wire changes with respect to the bending angle of the direction changing portion of the lead wire before and after firing is, as shown in FIG. The center line extending from the one end F and its extension are denoted by l1, the point p1 at which the direction of the center line of the lead wire changes, and the other end B where the center line is exposed on the outer surface of the insulating ceramic substrate. When the straight line connecting the point p2 to the point p2 is defined as l2, θ corresponds to the angle bent to expose the other end side B of the lead wire from the outer surface of the insulating ceramic substrate among the angles sandwiched between l1 and l2. Shall be referred to.

In the ceramic heater according to the present invention, the area of the other end of the lead wire exposed on the outer surface of the insulating ceramic base per lead wire is 0.07.
０．６0.60 mm ² (more preferably 0.20 to 0.50
mm ^2, and even more preferably from 0.30~0.40mm ^2). If the area is more than 0.07 mm ² or less than 0.60 mm ² are not preferable as well as the.

The location where the lead wire is exposed is not particularly limited as long as it is the outer surface of the insulating ceramic base. It is exposed behind the rear end of the resistor. That is, all the lead wires can be exposed from the outer surface of the insulating ceramic base, at least one of the lead wires is exposed on the outer surface of the insulating ceramic base, and at least one is insulated. Can be exposed on the rear end surface of the conductive ceramic substrate. Here, the outer surface refers to the outer surface of the insulating ceramic substrate in the circumferential direction around the axis of the insulating ceramic substrate formed so as to extend in the axial direction.

Although these may be in any form, FIGS. 6 and 7 show a case where a ceramic heater in which the other ends of all the lead wires are exposed from the outer surface of the insulating ceramic substrate is assembled to the glow plug. It is necessary to provide a gap between the insulating ceramic base 11 and the metal shell 22 for inserting the lead coil 24 as shown in FIG. Therefore, it is not suitable for the purpose of obtaining a thinner glow plug. On the other hand, in the ceramic heater of the present invention, as shown in FIGS. 8 and 9, for example, the connection leads 2 are linearly extended from the rear end face of the insulating ceramic base 11 to the terminal fittings.
3 can be connected, so that a glow plug having a small diameter can be obtained with little need for a gap between the insulating ceramic base 11 and the metal shell 22. Note that the lead wire exposed from the rear end face of the insulating ceramic substrate does not need to have the direction changing portion, and has the direction changing portion in which the bending angle θ is 0 ° <θ ≦ 40 °. Is also good.

A glow plug according to the present invention is characterized by including the ceramic heater. Glow plugs equipped with these ceramic heaters have high durability due to the excellent mechanical strength of the ceramic heater itself, and have excellent brazing strength between a lead wire constituting the ceramic heater and an external conductive member. Can be used stably for a long time. A glow plug having a ceramic heater in which at least one of the lead wires is exposed on the outer surface of the insulating ceramic base and at least one of the lead wires is exposed on the rear end surface of the insulating ceramic base can be made particularly small in diameter. Is as described above.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the ceramic heater and glow plug of the present invention will be described in more detail with reference to embodiments. (1) Preparation of ceramic heater 86% by mass of silicon nitride raw material
A mass% of Er ₂ O ₃ powder and 4 mass% of SiO ₂ powder were blended to obtain a raw material for an insulating component. This insulating material 40
After wet mixing 72% by mass and WC powder 60% by mass as a raw material for a conductive component for 72 hours, the mixture was dried to obtain a mixed powder. Thereafter, the mixed powder and the binder were put into a kneader and kneaded for 4 hours. Next, the obtained kneaded material was cut into pellets. On the other hand, after a predetermined tungsten lead wire having a circular cross section shown in Tables 1 and 2 is installed at a predetermined position of an injection molding die, the above-mentioned pellet-shaped kneaded material is injected by an injection molding machine, and the lead wire is injected. A U-shaped unfired heating resistor having one end connected to both ends was obtained. still,
For the lead wires, L1 to L8 shown in Table 1 were used in combinations shown in Table 2.

On the other hand, 84% by mass of silicon nitride raw material powder
As a sintering aid, 10% by mass of Er ₂ O ₃ powder, 4% by mass of SiO ₂ powder and 2% by mass of MoSi ₂ powder are blended.
The mixture obtained by wet mixing for 0 hour was granulated by a spray drier method, and two half molds each having a non-fired heating resistor obtained by compacting the granulated material and a concave portion for accommodating a lead wire were prepared.
Thereafter, the unfired heating resistor is placed at a predetermined position between the two half molds, press-molded and embedded, and then these are heated to 7M.
Pressurization was performed integrally at a pressure of Pa to obtain an unfired ceramic heater assembly. Next, the unfired ceramic heater assembly was degreased at 600 ° C., set on a graphite pressing die, and hot-press fired at 1800 ° C. for 1.5 hours in a nitrogen atmosphere to form a circle having a diameter of 3.5 mm. A crude ceramic heater having a cross section was obtained. Thereafter, the surface of the obtained crude ceramic heater is polished by a predetermined amount, and the other end side of each lead wire is exposed from the outer surface of the insulating ceramic substrate to extend in the axial direction (Experimental Examples 1 to 4). 7,
(See Table 2).

[0028]

[Table 1] L8 has two direction change parts, and a distance from the rear direction change part to the rear end of the lead wire is 1 mm.

[0029]

[Table 2]

Further, Table 3 shows the amount of polishing of the surface of the crude ceramic heater in the above polishing, and the area exposed from the outer surface of the insulating ceramic substrate (the exposed area of L5 to L8) by this polishing.

[0031]

[Table 3]

(2) Evaluation of Ceramic Heater Three-Point Bending Strength Lead wires (L5 to L5) exposed from the outer surface of the insulating ceramic substrate on the ceramic heater surfaces of Experimental Examples 1 to 4.
L8), with the center of the exposed part as the load point, JISR16
According to No. 01, the three-point bending strength (span 12 mm, crosshead speed 5 mm per minute) was measured. The results are shown in Table 3.

Presence or absence of buckling of lead wire due to firing After measuring the three-point bending strength, the ceramic heaters of Experimental Examples 1 to 4 were oriented in a direction parallel to the axial direction of the ceramic heater, including the direction change portion of the lead wire. Was cut, and the presence or absence of buckling of each lead wire (L5 to L8) was examined in the cross section. The results are also shown in Table 3.

(3) Manufacture of glow plug Each ceramic heater obtained in (1) and (2) is brazed to a protective outer cylinder and a connection lead, and then the protective outer cylinder is brazed to a metallic shell. The connection lead was obtained by welding to the center shaft. Incidentally, 20 glow plugs were manufactured for each of the ceramic heaters of Experimental Examples 1 to 7.

The glow plug obtained is shown in FIG.
The configuration shown in FIG. That is, the glow plug 2 has a configuration in which the heating resistor 12 is disposed on the tip end side and the ceramic heater 1 is formed.
The ceramic heater 1 is inserted through a metal protective outer cylinder 21. At the same time, one lead wire (L5 to L8) exposed from the outer surface of the ceramic heater is electrically connected to the protective outer cylinder by a brazing material. It is connected. The protective outer cylinder 21 is further fixed to the distal end side of the metal shell 22 by brazing. Further, the other lead wire (L
1 to L4) are electrically connected to the connection leads 23 by brazing, further connected to the center shaft 25, and further connected to terminal fittings 26. In addition, on the outer periphery of the metal shell 22,
A mounting screw portion 27 for screwing the glow plug into the engine is threaded, and a hexagonal tool engaging portion 28 for addressing the impact wrench when screwing the glow plug is formed.

(4) Evaluation of crack resistance and breakage resistance by impact wrench Of the obtained glow plugs, glow plugs using the ceramic heaters of Experimental Examples 1 to 4 were replaced with impact wrenches (Uryu, model “u610”). Use, air pressure 0.5M
The engine was actually mounted on the engine at a setting of Pa and a rotation speed of about 5000 rpm. Thereafter, the glow plug was removed and disassembled, and the resistance value before and after attachment of the ceramic heater was checked for breakage, and the presence or absence of cracks was observed by fluorescent flaw detection. As a result, Table 3 also shows the number of ceramic heaters having cracks and breaks per 20 tubes.

(5) Cold / hot cycle durability of the brazing portion Further, among the obtained glow plugs, protective metal fittings for the glow plugs provided with the ceramic heaters of Experimental Examples 1 and 5 to 7 and connection leads and lead wires. The correlation with the exposed area was evaluated based on the durability of the brazed part. A cycle in which each of the above five glow plugs is placed in a tubular furnace (high-temperature furnace) and heated from room temperature to 400 ° C. for 60 seconds, and then cooled with a fan and cooled to room temperature over about 5 minutes. 200 cycles were repeated as one cycle. The resistance value of each brazed portion was measured every 10 cycles by a DC four-terminal method using a milliohm high tester (model “3227” manufactured by Hioki Electric Co., Ltd.). When the resistance value changed by 10 mΩ or more, it was evaluated that the resistance value changed, and the results are shown in Table 4. Table 4 also shows the area of each lead wire exposed from the insulating ceramic substrate. As the change in resistance value increases, the strength of the brazed portion tends to decrease.

[0038]

[Table 4] The evaluation was evaluated as ○ when the number of endurance cycles (average of 5 lines) was 200 cycles, Δ when the number was 150 cycles or more and less than 200 cycles, and × when the number was less than 150 cycles.

From the results shown in Table 3, it can be seen that the direction of the lead wire is changed in one place, and the smaller the exposed area of the lead wire exposed from the outer surface of the insulating ceramic substrate, that is, the smaller the exposed area is, It can be seen that the three-point bending strength of the ceramic heater increases when the thickness is equal to or less than .60 mm ² . If the exposed area of the lead wire is within the range of the present invention, a high value of 400 MPa or more is obtained in the above three-point bending strength. Furthermore, from the results in Table 4, the exposed area of the lead wire is 0.
It can be seen that if the thickness is 07 mm ² or more, sufficiently high durability (high brazing strength against cold and hot cycles) can be exhibited even at the brazing portion.

[0040]

According to the ceramic heater of the present invention, a glow plug having high durability can be obtained at low cost. Further, according to the glow plug of the present invention, the engine can be started and idling stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a front view of an unfired body in which a lead wire is provided on a heating resistor.

FIG. 2 is an explanatory diagram illustrating a manufacturing process of the ceramic heater.

FIG. 3 is a sectional view of a ceramic heater.

FIG. 4 is an explanatory diagram illustrating buckling.

FIG. 5 is an explanatory diagram illustrating a bending angle.

FIG. 6 is a cross-sectional end view of an example glow plug including the ceramic heater of the present invention.

FIG. 7 is a front end sectional view of another example of a glow plug including the ceramic heater of the present invention.

FIG. 8 is a cross-sectional end view of another example of a glow plug including the ceramic heater of the present invention.

FIG. 9 is a cross-sectional end view of a glow plug according to still another example including the ceramic heater of the present invention.

FIG. 10 is a cross-sectional view of an example of the glow plug of the present invention.

[Explanation of symbols]

1; ceramic heater, 11; insulating ceramic substrate (11 '; unfired insulator), 12; heating resistor (1
2 '; unfired heating resistor), 13a, 13b; lead wire (13a', 13b '; unfired lead wire), 2; glow plug, 21; protective outer cylinder, 22; metal shell, 23; , 24; lead coil, 25; center shaft, 26; terminal fitting, 27; mounting screw portion, 28;

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 3/48 H05B 3/48 F term (Reference) 3K092 PP15 PP16 QA01 QB11 QB13 QB18 QB20 QB32 QB74 QC16 QC42 QC43 QC52 RA02 RB03 RB22 RD02 TT08 TT25 VV31 VV34

Claims (5)

[Claims] 1. An insulating ceramic substrate and a heat generating resistor which generates heat when energized are embedded in the insulating ceramic substrate, one end of which is connected to the heat generating resistor to energize the heat generating resistor, and the other end of which is connected to the heat generating resistor. And a lead wire exposed on the outer surface of the insulating ceramic substrate, and an area of the lead wire exposed on the outer surface of the insulating ceramic substrate is 0.07 to 0.60 mm ² . A ceramic heater, characterized in that: 2. An insulating ceramic base and a heating resistor which generates heat by energization are embedded in the insulating ceramic base, and one end is connected to the heating resistor to energize the heating resistor, and the other end is connected to the heating ceramic. And a lead wire exposed on the outer surface of the insulating ceramic substrate, at least one of the lead wires extending from the one end side, and having a direction changing part which is changed in direction and reaches the other end side. And a bending angle θ of the direction changing portion is 0 ° <θ ≦ 40 °. 3. The method according to claim 3, wherein the other end of the lead wire is
Outer surface of the above insulating ceramic substrate per lead wire
The area exposed on the surface is 0.07 to 0.60 mm ^TwoWho is
The ceramic heater according to claim 2. 4. When the side of the insulating ceramic substrate in which the heating resistor is embedded is a tip end, at least one of the lead wires is exposed on the outer surface of the insulating ceramic substrate. 4. The ceramic heater according to claim 2, wherein at least one of the ceramic heaters is exposed on a rear end face of the insulating ceramic substrate. 5. A glow plug comprising the ceramic heater according to claim 1. Description: