JPH09184627A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater having a structure where an electrode part is prevented from being positionally displaced during manufacture. SOLUTION: This ceramic heater 1 includes a ceramic substrate 13, a ceramic heater 10 buried in the ceramic substrate 13 and producing heat through its resistance by being supplied with electric power, and linear electrode parts 11, 12 connected at its one end with the ceramic heater 10 for supplying the ceramic heater 10 with electric power and buried in the ceramic substrate 13 together with the ceramic heater 10. U shaped folded-back parts 11b, 12b are formed at ends of the electrodes 11, 12 not connected with the ceramic heater 10.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a ceramic heater, and more particularly to a ceramic heater used for a ceramic glow plug or the like.

[0002]

2. Description of the Related Art Heretofore, as a ceramic heater used for a ceramic glow plug, there has been known a ceramic heater having a structure in which an insulating ceramic substrate is embedded with a ceramic heating element which generates heat by resistance. One end of a linear or rod-shaped electrode portion is embedded in the ceramic heating element for energization thereof.

The ceramic heater as described above is manufactured, for example, as follows. That is, FIG.
As shown in (a), first, the conductive ceramic powder forming the ceramic heating element is injected into the electrode portion 13 by injection molding.
Integrally molded with 0 to make an integral injection molded body 135. on the other hand,
Separately from this, the divided preforms 136 and 137 in which the concave portions 138 for accommodating the integral injection-molded body 135 are formed on the mating surfaces thereof are previously press-molded by using the ceramic powder for forming the ceramic base. Etc. Then, the integral injection-molded body 13 is formed in the recess 138.
5 is housed and the divided preforms 136 and 137 are matched with each other, and then these are pressed and integrated by using a mold to form a composite molded body 139 shown in FIG. A ceramic heater can be obtained by further firing and polishing. As shown in FIG. 8A, a linear portion 130a is formed along the outer peripheral surface of the divided preforms 136 and 137 at the end of each electrode portion 130 by bending the electrode portion 130 outward in a polygonal line shape. Has been done. These linear portions 130a are exposed on the surface of the ceramic substrate after firing / polishing to form power supply terminal portions for the ceramic heating element.

[0004]

In the ceramic heater manufactured as described above, the straight portion 130a of the electrode portion 130 (that is, the power supply terminal portion) corresponds to the mating surface of the divided preforms 136 and 137. Will be formed at the position. By the way, in the case where the straight line portion 130a is formed by a bent line-shaped bending process, the bent portions may not necessarily form a perfect flat surface. Therefore, as shown in FIG. 8C, the terminal portion of the electrode portion 130 on which the linear portion 130a is formed is lifted from the mating surface 139a, and when the composite molded body 139 is formed by press molding, the lifted portion is There is a case where the linear preform 130a is displaced from the mating surface 139a by cutting into the divided preforms 136 or 137, as shown in FIG. When such a positional deviation occurs, the power supply terminal portion of the ceramic heater is not formed at a proper position, and when this is used for a glow plug or the like, conduction failure may occur, or the position of the terminal portion may vary depending on the product. As a result of the variation, there may occur a problem that it becomes difficult to automate the heater resistance value measurement and the like in the inspection process.

An object of the present invention is to provide a ceramic heater having a structure in which displacement of the electrode portion is unlikely to occur during its manufacture.

[0006]

In order to solve the above-mentioned problems, the ceramic heater of the present invention comprises a ceramic base, a heating element embedded in the ceramic base, which generates resistance heat when energized, and An end of the electrode portion, which is not connected to the heating element, is provided with one end connected to the heating element for energizing the heating element and having a linear electrode portion embedded in the ceramic base together with the heating element. The bent portion is formed in the portion.

The heating element can be made of conductive ceramics, but it can also be made of a refractory metal material such as tungsten or a tungsten alloy.

For example, when the heating element is made of conductive ceramics, in order to manufacture the ceramic heater,
For example, the following composite powder compacts can be used. That is, the composite powder molded body is an integrated molded body having an electrode portion and a conductive ceramic powder molded portion in which one end side of the electrode portion is embedded and integrated, and a base ceramic powder molded portion covering the outside of the integrated molded body. It is configured to include and. Here, the above-described bent-back portion is formed at the end of the electrode portion that is not embedded in the conductive ceramic powder molding portion. Such a composite powder compact can be manufactured, for example, as follows. First, a divided preform having a recess for accommodating the above-mentioned integrally formed body formed on its mating surface is made of the base ceramic powder, and the above-mentioned integrally formed body is accommodated in the depression, and then the divided preform is formed. Are aligned on the mating surface. Then, the integrated molded body and the divided pre-molded body, which have been matched with each other, are further integrated by press molding to obtain a composite powder molded body. By firing this composite powder compact, the conductive ceramic powder compact becomes a heating element, and the base ceramic powder compact becomes a ceramic base to manufacture the ceramic heater of the present invention.

In the ceramic heater of the present invention, the bent portion is formed on the terminal side of the electrode portion where the power supply terminal portion is to be formed. For example, when the composite powder compact is manufactured by the above-mentioned method, the bent portion is bent. The portion forms a flat surface portion that follows the mating surface of the divided preform. This allows
Even if the terminal part of the electrode part is lifted from the mating surface, it is less likely that the bent-back part will bite into the side of the divided preform due to press molding, and as a result, the misalignment of the power supply terminal part can be suppressed. You can bear.

When the heating element is formed of a refractory metal, the electrode section and the refractory metal heating element are integrated instead of the integral molding of the electrode section and the conductive ceramic powder molding section. A heating element unit may be used. In this case, the recess formed in the divided preformed body accommodates the heating element unit.

In the bent portion, the electrode portion may have a linear shape in which one of both side portions sandwiching the bent bottom portion is exposed on the surface of the ceramic base. This straight portion can be used as a power supply terminal portion for the heating element.

In the above structure, the ceramic substrate can be formed in a rod shape. In this case, the heating element includes a direction changing part extending from one base end part and changing direction at the tip part to reach the other base end part, and two heat generating elements extending in the same direction from each base end part of the direction changing part. And a linear portion, and the direction changing portion side is embedded in the rod-shaped ceramic base so as to be located at the tip end side of the ceramic base. Further, the linear electrode portions are connected to the respective end portions of the ceramic heating element. Such a ceramic heater can be suitably used for glow plugs of diesel engines and the like. Further, the electrode portions are arranged in the ceramic base body along an axial direction on an imaginary dividing surface set substantially parallel to the axis thereof, and the respective end portions thereof are outward on the dividing surface. The bent portion can be formed by bending back. In this case, the bent end portion is formed in a linear shape exposed on the surface of the ceramic substrate. Here, the virtual divided surface can be set corresponding to the mating surface of the divided preformed body.

The electrode portion may be made of a refractory metal such as tungsten (W) or a tungsten-rhenium (Re) alloy. Here, the refractory metal as described above is generally a brittle material, and the strength against acute-angle bending may not always be sufficient.
Therefore, it is desirable that the tip portion of the bent back is formed in a gently curved shape, for example, a U-shape, while avoiding a shape with an acute angle as much as possible. Such a U-shaped bent portion has a simple shape and has an advantage that it can be easily formed by working.

[0014]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows a glow plug using a ceramic heater according to the present invention, together with its internal structure. That is, the glow plug 50 includes a ceramic heater 1 provided at one end thereof, a metal outer cylinder 3 that covers the outer peripheral surface of the ceramic heater 1 so that a tip end portion 2 of the ceramic heater 1 projects, and further includes the outer cylinder 3. A cylindrical metal housing 4 and the like, which are covered from the outside, are provided. The ceramic heater 1 and the outer cylinder 3 and the outer cylinder 3 and the metal housing 4 are respectively joined by brazing. In addition, at the rear end of the ceramic heater 1,
Coupling member 5 whose ends are formed in a spiral spring shape by metal wires
While one end of is fitted from the outside, the other end is fitted to the corresponding end of the metal shaft 6 inserted in the metal housing 4. The other end portion side of the metal shaft 6 extends to the outside of the metal housing 4, and a nut 7 is screwed into a screw portion 6a formed on the outer peripheral surface of the metal shaft 4, and the nut 7 is tightened toward the metal housing 4. The shaft 6 is fixed to the metal housing 4. Also, nut 7
An insulating bush 8 is fitted between the housing and the metal housing 4. Then, on the outer peripheral surface of the metal housing 4,
A screw portion 5a for fixing the glow plug 50 is formed on an engine block (not shown).

As shown in FIG. 2A, the ceramic heater 1 includes a direction changing portion 10a which extends from one base end portion and changes direction at the tip portion to reach the other base end portion, and the direction changing portion 10a. Two straight portions 10 extending in the same direction from the respective base end portions of the
b-shaped ceramic heating element 10 having b and one end of each of the linear or rod-shaped electrode portions 11 and 12 is embedded at each end thereof, and the ceramic heating element 10 and the electrode portions 11 and 12 are The whole is embedded in a rod-shaped ceramic base 13 having a circular cross section. The ceramic heating element 10 is arranged such that the direction changing portion 10 a is located on the tip side of the ceramic base 13.

As shown in FIG. 2B, the electrode portions 11 and 12 are arranged along the axial direction on a virtual division plane P set in the ceramic base 13 substantially parallel to the axial line. It is located in. Then, as shown in (a) of the figure, the rear end of each is bent back on the dividing surface P, whereby the U-shaped bent portion 11 is formed.
b and 12b are formed, and each of the bent end portions is exposed on the surface of the ceramic base 13 in a linear shape.
a and 12a. These exposed portions 11a and 1
2a functions as a power supply terminal portion to the ceramic heating element 10. In addition, the exposed portion 12a is provided in the outer cylinder 3 in the same manner.
a is formed in the vicinity of the end of the ceramic base 13 on the side where the ceramic heating element 10 is not located. Here, as shown in FIG. 3, the end portion of the electrode portion 11 (12) is bent toward the outer peripheral surface 13a of the ceramic base 13 to form the linear portion 1.
1a (12a) is formed and the outer peripheral surface 1
3a may be exposed to form an exposed portion, and the tip end side may be further bent back inward to form the bent portion 11b (12b).

The ceramic heating element is a conductive ceramic such as tungsten carbide (WC), molybdenum silicate (Mo ₂ Si ₃ ), tungsten carbide and silicon nitride (S).
i ₃ N ₄ ) and the like, but semiconductor ceramics such as silicon carbide (SiC) can also be used. The electrode parts 11 and 12 are made of tungsten (W).
Alternatively, it is made of a refractory metal material such as a tungsten-rhenium (Re) alloy. On the other hand, the ceramic base 13
Are mainly insulating ceramics such as alumina (Al
₂ O ₃ ), silica (SiO ₂ ), zirconia (ZrO ₂ ),
Titania (TiO ₂ ), magnesia (MgO), mullite (3Al ₂ O ₃ .2SiO ₂ ), zircon (ZrO ₂ .S)
iO ₂ ) and cordierite (2MgO · 2Al ₂ O ₃ · 5)
SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN) and the like.

In FIG. 2A, the ceramic base 13
A thin metal layer (not shown) of nickel or the like is formed in a region including the exposed portion 12a of the electrode portion 12 by a predetermined method (for example, plating or vapor deposition) on the surface of The ceramic base 13 and the outer cylinder 3 are joined by brazing via a thin layer, and the electrode portion 12 is electrically connected to the outer cylinder 3 via these joints. The electrode section 11
Similarly, a thin metal layer is formed in a region including the exposed portion 11a, and the joining member 5 is brazed to the thin metal layer. With this configuration, the ceramic heating element 10 is energized from the power source (not shown) through the metal shaft 6 (FIG. 1), the coupling member 5 and the electrode portion 11, and further the electrode portion 12,
It is grounded through the outer cylinder 3, the metal housing 4 (FIG. 1), and an engine block (not shown).

The method of manufacturing the ceramic heater 1 will be described below. First, as shown in FIG. 4A, an electrode material 30 is inserted into a mold 31 having a U-shaped cavity 32 corresponding to the ceramic heating element 10, and one end of the electrode material 30 is inserted into the cavity 32. To arrange. on the other hand,
On the other end side of each electrode material 30, a bent back portion 30a (FIG. 7B) is formed. Then, in this state, a compound 33 containing a conductive ceramic powder and a binder is injected, so that the electrode material 30 and the U-shaped conductive ceramic powder molding portion 34 are formed as shown in FIG. Integral injection molded body (integral molded body) 3
Create 5.

On the other hand, separately from this, the ceramic powder for forming the ceramic base 13 is press-molded in advance with a die to separately form the divided preforms 36 as shown in FIG. Prepare 37. These divided preforms 36 and 37 are the same as the integral injection-molded body 3 described above.
5 is formed in the mating surface 39a. Then, the integral injection molded body 35 is housed in the recess 38, the divided preformed bodies 36 and 37 are matched with each other on the mold matching surface 39a, and in this state, the divided preformed bodies 36 and 37 and the integrated injection molded body are formed. Three
By further pressing and unifying 5 using a die, a composite molded body 39 as shown in FIG. 5B is created.

Here, as shown in FIG. 5A, the bent portion 30a of the electrode material 30 is divided into preforms 36 and 37.
A flat surface portion is formed that follows the mating surface 39a. As a result, as shown in FIG. 3C, the bent portion 3 of the electrode material 30 is
0a is lifted from the mating surface 39a, it is difficult for the bent portion 30a to bite into the side of the divided preforms 36 to 37 due to press molding, and as shown in FIG. Bent portion 30a is mating surface 39a
The composite molded body 39 accurately positioned above is obtained.

The composite molded body 39 thus obtained is first calcined in order to remove the binder component and the like, and then, as shown in FIG.
As shown in (a), hot press firing is performed at a predetermined temperature while pressurizing between molding dies 40 made of graphite or the like, so that a fired body 4 as shown in FIG.
It becomes 1. At this time, the conductive ceramic powder molding portion 34 shown in FIG. 5B forms the ceramic heating element 10, and the divided preliminary molding bodies 36 and 37 form the ceramic base 13. Further, each electrode material 30 becomes the electrode portions 11 and 12, respectively. Further, the mating surface 39a of the divided preformed bodies 36 and 37 is the virtual divided surface P described above.
(FIG. 2B) is formed. After that, the outer surface of the fired body 41 is subjected to processing such as polishing, if necessary.
A ceramic heater 1 as shown in is obtained.

In the ceramic heater 1, instead of the ceramic heating element 10, tungsten or a tungsten alloy (for example, a tungsten-rhenium alloy) is used.
Alternatively, the high melting point metal material may be used. A specific example is shown in FIG. 7 together with its manufacturing method. In addition, in this embodiment, since both the configuration and the manufacturing method have many parts in common with the case where the heating element is made of ceramics, hereinafter, the different points will be mainly described, and the description of the common parts will be omitted. That is, the coiled high melting point metal material wire rod 60 as shown in FIG.
Bend into a letter shape and insert the electrode material 30 inside both ends.
The heating element unit 61 is formed by the integration.
Then, in FIG. 5, the heating element unit 61 is mounted in the recesses 38 of the divided preforms 36 and 37 in place of the integral injection-molded body 35, and the composite molded body obtained by pressing and integrating this is hot-press fired. Then, as shown in FIG. 7C, the ceramic heater 1 in which the high melting point metal material wire rod 60 as the heating element is embedded in the ceramic base 13 can be obtained.

[Brief description of the drawings]

FIG. 1 is a front partial cross-sectional view showing an example of a glow plug adopting a ceramic heater of the present invention.

FIG. 2 is a front sectional view and AA of the ceramic heater.
Sectional view.

FIG. 3 is a cross-sectional view showing a modified example of a U-shaped bent portion.

FIG. 4 is an explanatory view of the manufacturing process of the ceramic heater.

FIG. 5 is a process explanatory view following FIG. 4;

FIG. 6 is a process explanatory view following FIG. 5;

FIG. 7 is an explanatory view showing an example in which the heating element is made of a refractory metal wire together with its manufacturing method.

FIG. 8 is an explanatory view of a manufacturing process of a conventional ceramic heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic heater 10 Ceramic heating element 11, 12 Electrode part 11a, 12a Exposed part 11b, 12b Curved part 13 Ceramic base P Virtual dividing surface 30 Electrode material 50 Glow plug 60 High melting point metal material Wire material (heating element)

Claims (4)

[Claims] 1. A ceramic base, a heating element embedded in the ceramic base, which generates resistance heat when energized, one end of which is connected to the heating element to energize the heating element, and the ceramic base together with the heating element. And a linear electrode portion embedded therein, wherein a bent portion is formed at an end portion of the electrode portion that is not connected to the heating element. 2. The ceramic heater according to claim 1, wherein the heating element is made of conductive ceramics. 3. The electrode portion of the bent portion has a linear shape in which one of both side portions sandwiching the bent bottom portion is exposed on the surface of the ceramic substrate. Ceramic heater. 4. The ceramic base is formed in a rod shape, and the heating element extends from one base end portion and changes direction at a tip end portion to another base end portion, and a direction change portion thereof. And a straight line portion extending in the same direction from each base end portion of the rod portion, the direction changing portion side being embedded in the ceramic base so as to be located at the tip end side of the ceramic base. The linear electrode portions are respectively connected to the respective end portions of the heating element, and the respective electrode portions are arranged on the virtual dividing plane set in the ceramic base substantially parallel to the axial line. Linearly arranged so as to extend along the direction, and the bent end portions are formed by bending back end portions of the bent end portions outward on the dividing surface, and the bent end portions are exposed on the surface of the ceramic base. Formed in The ceramic heater according to claim 3,