JP3346447B2 - Manufacturing method of ceramic heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of a ceramic heater used for a glow plug for a diesel engine, a heating element for burning a burner or an oxygen sensor, and the like.
About the method .

[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 configuration in which a ceramic heating element which generates resistance by energization is embedded in an insulating ceramic substrate. One end of a linear or rod-shaped electrode portion is buried in the ceramic heating element for energization.

The above-described ceramic heater is manufactured, for example, as follows. That is, FIG.
As shown in (a), first, an integrally molded body 135 of a U-shaped conductive ceramic powder molded body 134 (which becomes a ceramic heating element after firing) and an electrode portion 130 by injection molding or the like.
make. On the other hand, separately from this, divided preforms 136 and 137 having recesses 138 for accommodating the integrally formed body 135 formed on their mating surfaces (to be a ceramic base after firing) are formed using base ceramic powder. It is produced by press molding or the like. Next, after the integrally formed body 135 is accommodated in the concave portion 138 and the divided preformed bodies 136 and 137 are mold-matched, they are pressed and integrated using a mold, as shown in FIG. 9B. A composite molded body 139 is obtained. Here, as shown in FIG. 10A, the pressing direction is the mating surface 13 of the divided preforms 136 and 137.
9a is set substantially at a right angle. The thus obtained composite molded body 139 is subjected to a hot press treatment of performing firing while applying pressure in the same direction as the above-mentioned pressing direction, as shown in FIG. The ceramic heater 10 shown in FIG.
0 is obtained.

[0004]

According to the above-described manufacturing method, as shown in FIG. 9A, in the composite molded body 139, the two linear portions 134b of the U-shaped conductive ceramic powder molded body 134 are formed. Are arranged on the mating surface 139a of the divided preforms 136 and 137. Then, in the hot pressing, a pressing force is applied to the composite molded body 139 in a direction perpendicular to the mating surface 139a, and as shown in FIG.
The cross-sectional shape of each of the 0 linear portions 110b is formed in a long elliptical shape in the facing direction. As a result, the distance from the surface of the linear portion 110b to the surface of the heater 100 becomes uneven, and as shown in FIG. 11, the difference between the distance L1 in the elliptical short axis direction and the distance L2 in the long axis direction increases. As a result, there is a disadvantage that the temperature distribution on the heater surface tends to be uneven. Thus, as shown in FIG. 10D, it is conceivable to reduce the cross-sectional dimension of the heater 100 in the direction of the elliptical minor axis of the cross section of the linear portion 110b. In addition to being troublesome, for example, when assembling the heater 100 to a glow plug or the like, the cross-sectional shape of the outer cylinder or the like accommodating the heater 100 must also have a shape corresponding to this, resulting in an increase in the manufacturing cost of the plug. Problems arise.

An object of the present invention is to manufacture a ceramic heater which has a good temperature distribution on the surface of the heater and which can be assembled at low cost to an application product such as a glow plug.
It is to provide a method .

According to the present invention, there is provided a ceramic base and a ceramic heating element which is embedded in the ceramic base and which generates resistance heat when energized through electrodes connected to both ends thereof, extends from one base end, A direction change portion that changes the direction at the portion and reaches the other base end portion, and two straight portions extending in the same direction from each base end portion of the direction change portion. According to a method for manufacturing a ceramic heater which is formed in an elliptical shape compressed in a direction opposite to a straight portion, in order to solve the above-mentioned problem, the direction is changed at a distal end and extended from one proximal end, and the other proximal end is changed. Integrated body comprising a conductive ceramic powder molding part having a direction changing part reaching the first direction, two linear parts extending in the same direction from each base end of the direction changing part, and electrode parts connected to both ends thereof. The first part of manufacturing a compact Forming a divided preform having a concave portion for accommodating an integrated molded body such that the two linear portions of the conductive ceramic powder molded portion are arranged on a surface thereof, using a base ceramic powder; In the state in which the above-mentioned integrated molded body is accommodated, the outside of the integrated molded body is covered with the base ceramic powder and then compressed, whereby the integrated molded body is embedded and integrated in the base ceramic powder molded part. A second molding step for producing a composite molded body, and firing the composite molded body while pressing it in a direction along the surface of the divided preformed body where the above-mentioned concave portion is formed, thereby forming a conductive member having a circular cross section. sex ceramic powder molding portion is a ceramic heating element having an elliptical cross section which is compressed in the opposite direction of the linear portion, the fired body base ceramic powder molding portion is a ceramic substrate A firing step that, characterized in that it comprises a.

[0007] By making the cross-sectional shape of the two straight portions of the ceramic heating element as described above, the unevenness of the distance from the surface of the straight portion to the heater surface is corrected, and the temperature distribution on the heater surface becomes uneven. Is less likely to occur. In particular,
For its elliptical cross section, its major axis length P and minor axis length Q
Is set within the range of 1.2 to 2.5, the unevenness of the temperature distribution is further reduced. It is more preferable to set P / Q to 1.6 to 2.0.

Here, the cross section of the ceramic base can be formed in a circular shape having its center at a position where the distance between the axes of the two linear portions of the ceramic heating element is substantially equally divided.
Thereby, the difference in the distance from the surface of the linear portion to the surface of the heater between the short axis direction and the long axis direction of the cross section of the linear portion is reduced, and the temperature distribution on the heater surface is made more uniform. be able to. In addition, by making the cross-sectional shape of the ceramic base circular, polishing of the outer peripheral surface of the heater becomes easy, and when assembling the ceramic heater to an applied product such as a glow plug, a component such as an outer cylinder holding the heater is required. Manufacturing is facilitated, and the manufacturing cost of the applied product is reduced.

[0009]

According to this manufacturing method, the conductive ceramic powder molded portion is fired while applying a pressing force in a direction along the surface of the divided preform in which the concave portion is formed, so that the cross-sectional shape of the linear portion is obtained. However, it is possible to easily obtain a ceramic heating element having an elliptical shape compressed in the direction opposite to the linear portion, and to manufacture the ceramic heater of the present invention with high efficiency. Further, by using the divided preform, the positioning of the conductive ceramic powder forming portion with respect to the base ceramic powder forming portion can be performed extremely easily, which contributes to the improvement of the manufacturing efficiency of the ceramic heater.

[0011] More specifically, the second molding step may include the following steps. A divided preform having a concave portion for accommodating an integral molded body formed on the mating surface and having an integrated molded body formed thereon such that two linear portions of the conductive ceramic powder molded portion are arranged on the mating surface is formed on a substrate. It is made of ceramic powder. The split preform is mold-matched with the integrally formed body accommodated in the recess. The combined molded body and the divided preformed body are pressed and integrated in a direction substantially perpendicular to the mating surface to form a composite molded body. In this case, in the firing step, the composite molded body is pressed in a direction along the mating surface of the divided preliminary molded bodies.

[0012] According to the above method, the two mating surfaces are mutually separated.
The use of the divided preforms that are matched to each other makes it possible to extremely easily position the conductive ceramic powder molding portion with respect to the base ceramic powder molding portion, thereby contributing to an improvement in the production efficiency of the ceramic heater.

[0013]

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. Also, at the rear end of the ceramic heater 1,
Coupling member 5 whose both ends are formed in a helical spring shape by a metal wire
Is fitted from the outside, and the other end is fitted to a corresponding end of the metal shaft 6 inserted into the metal housing 4. The other end of the metal shaft 6 extends outside the metal housing 4, and a nut 7 is screwed into a screw portion 6 a formed on the outer peripheral surface of the metal shaft 6. 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 to an engine block (not shown) is formed.

As shown in FIG. 2, the ceramic heater 1 includes a direction changing portion 10a extending from one base end and changing its direction at the front end to reach the other base end.
a, a U-shaped ceramic heating element 10 having two linear portions 10b extending in the same direction from the respective base ends of the end portions of the linear or rod-shaped electrode portions 11 and 12 at both ends thereof. Are embedded, and the entire ceramic heating element 10 and the electrode portions 11 and 12 are embedded in a rod-shaped ceramic base 13 having a circular cross section. Further, the ceramic heating element 10 includes a
It is arranged so that it may be located at the terminal side of. Further, each of the electrode portions 11 and 12 extends in a direction away from the ceramic heating element 10 in the ceramic base 13, one of which (12) is in the outer cylinder 3 and the other (11) is in the ceramic base. In the vicinity of the other end of the substrate 13, the rear end is exposed to the surface of the ceramic base 13 to form exposed portions 11a and 12a.

From the direction changing portion 10a of the ceramic heating element 10, two straight portions 10b extend almost in parallel, and as shown in FIG. It is an elliptical shape compressed in the facing direction. The cross section of the ceramic base 13 is formed in a circular shape whose center is located at a position O where the distance between the axes of the two linear portions 10b of the ceramic heating element 10 is substantially equally divided. Thereby, for example, as compared with the conventional ceramic heater 100 shown in FIG. 11, the distance from the surface of the linear portion 10b to the heater surface is smaller between the elliptical short axis direction (L1) and the long axis direction (L2) of the cross section. The difference is smaller. The cross-sectional shape of the ceramic base 13 is circular, and the outer cylinder 3 of the glow plug 50 holding the ceramic base 13 is also cylindrical. Further, each linear portion 10b has a ratio P / Q of the major axis length P to the minor axis length Q of the elliptical cross section of 1.2 to 2.5, more preferably 1.6 to 2.5.
It is set in the range of 2.0.

The ceramic heating element is made of a conductive ceramic such as tungsten carbide (WC), molybdenum silicide (Mo ₂ Si ₃ ), tungsten carbide and silicon nitride (S).
composed of composite products of the i ₃ N ₄₎ is also possible to use a semiconductor ceramic such as silicon carbide (SiC). The electrodes 11 and 12 are made of tungsten (W).
Alternatively, it is made of a high melting point metal material such as a tungsten-rhenium (Re) alloy. On the other hand, the ceramic base 13
Is mainly made of 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), cordierite _{(2MgO · 2Al 2 O 3 ·} 5
It is made of SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN) or the like.

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

Hereinafter, a method for manufacturing the ceramic heater 1 will be described. 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 enters the cavity 32. So that Then, in this state, by injecting a compound 33 containing the conductive ceramic powder and the binder, the electrode material 30 and the U-shaped conductive ceramic powder molding part 34 are formed as shown in FIG. Integrated body 35 in which is integrated
Create The conductive ceramic powder molding part 34 is formed to have a substantially circular cross section.

On the other hand, separately from this, the ceramic preform for forming the ceramic base 13 is pre-press-molded, so that the divided preformed body 36 and the divided preformed body 36 formed separately as shown in FIG. Prepare 37. Each of the divided preforms 36 and 37 has a concave portion 38 having a shape corresponding to the shape of the integral molded body 35 formed on its mating surface 39a. Next, the integrally formed body 35 is accommodated in the recess 38, and the divided preformed bodies 36 and 37 are fitted to the molding surfaces 39.
Match in a. Then, as shown in FIG. 6A, the divided preformed bodies 36 and 37 and the integrally formed body 35 are housed in the cavity 61a of the mold 61 in this state, and are pressed by the punches 62 and 63. By compressing, as shown in FIG. 5B and FIG. 7A, a composite molded body 39 in which these are integrated is formed. Here, the pressing direction is set substantially perpendicular to the mating surface 39a of the divided preforms 36 and 37.

The composite molded body 39 thus obtained is first calcined at a predetermined temperature (for example, about 800 ° C.) in order to remove a binder component and the like, and a calcined body 39 ′ shown in FIG.
It is said. Subsequently, as shown in FIG. 6B, the calcined body 39 'is set in cavities 65a and 66a of hot press molds 65 and 66 made of graphite or the like. The calcined body 39 ′ is placed in the furnace 64 by the two molds 65.
And 66 at a predetermined temperature (for example, about 1
By firing at 800 ° C.), a fired body 70 as shown in FIG. At this time, the conductive ceramic powder molding part 34 shown in FIG.
0, the divided preforms 36 and 37 are
3 will be formed respectively. In addition, each electrode material 30
Are electrode portions 11 and 12, respectively.

Here, as shown in FIG. 6B, the calcined body 39 'is a mating surface 39 of the divided preforms 36 and 37.
The sintered body 70 is formed while being compressed in the direction along a. Then, as shown in FIG. 7 (c), the linear portion 34b of the conductive ceramic powder molded portion 34 is deformed so that its circular cross section is crushed in the above-described compression direction. The straight portion 10b of the body 10 is formed. Next, as shown in FIG. 7D, the outer peripheral surface of the fired body 70 is polished or the like, whereby the cross section of the ceramic base 13 is shaped into a circle, and the final ceramic heater 1 is obtained.

The ceramic heater of the present invention is not limited to a glow plug, but can be used for a burner ignition or a heating element for an oxygen sensor.

[0023]

EXAMPLE For the ceramic heater 1 obtained as described above and the conventional ceramic heater 100 having the cross-sectional structure shown in FIG. When the temperature was raised to 900 ° C. in 3 seconds, the temperature distribution on the heater surface was examined. As shown in FIG. 8, the temperature measurement points are:
With a straight line connecting the axes of the two straight portions 10b to 110b as a reference line, A: near the intersection of the reference line and the heater surface;
B: near the intersection of a straight line passing through the center of the cross section of the heater and orthogonal to the reference line and the heater surface; and C: near the midpoint of the line connecting A and B on the heater surface. That is, in the ceramic heater 1 according to the embodiment, the temperature at each measurement point decreases in the order of A>B> C, but the temperature difference between A and C is as small as 10 ° C., and a relatively uniform temperature distribution is obtained. Obtained. On the other hand, in the ceramic heater 100 of the comparative example, the temperature decreased in the order of A>C> B, and the temperature difference between B and A was 40 ° C., indicating a rather uneven temperature distribution.

[Brief description of the drawings]

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

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

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a view illustrating a manufacturing process of a 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 a schematic view showing a change in cross-sectional shape of a composite molded body and a fired body in the method for manufacturing a ceramic heater of the present invention.

FIG. 8 is an explanatory diagram showing the results of an experiment in which the surface temperature distribution of a ceramic heater as one embodiment of the present invention was measured in comparison with a conventional ceramic heater.

FIG. 9 is an explanatory view of a manufacturing process of a conventional ceramic heater.

FIG. 10 is a schematic view showing a change in cross-sectional shape of a composite molded body and a fired body in a conventional method for manufacturing a ceramic heater.

FIG. 11 is a sectional view of a conventional ceramic heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic heater 10 Ceramic heating element 11, 12 Electrode part 10b Linear part 13 Ceramic base 34 Conductive ceramic powder molding part 35 Integral molded body 36, 37 Split pre-molded body 39 Composite molded body 70 Fired body 50 Glow plug

Claims (2)

(57) [Claims] 1. A ceramic base and a ceramic heating element buried in the ceramic base and generating resistance heat by being energized through electrodes connected to both ends thereof extend from one base end and extend at one end. A direction change portion that changes direction and reaches the other base end portion; and two straight portions extending in the same direction from the base end portions of the direction change portion. Compressed in the opposite direction of
A method of manufacturing a ceramic heater having an elliptical shape , comprising: a direction changing portion extending from one base end and changing direction at a tip to reach another base end; and each base end of the direction changing portion. A first molding step of manufacturing an integrated molded body having a conductive ceramic powder molded part having two linear parts extending in the same direction from the above, and electrode parts connected to both ends thereof; A divided preform having a concave portion for accommodating the integral molded body is formed from the base ceramic powder so that the two linear portions of the conductive ceramic powder molded portion are arranged, and the integral molded body is formed in the concave portion. The composite molded body in which the integrated molded body is embedded and integrated in the base ceramic powder molded portion is manufactured by covering the outside of the integrated molded body with the base ceramic powder and compressing the molded body. First A molding step of, the composite molding, by sintering under pressure in the direction along the recess formed surface of the divided preform, said conductive ceramic powder molding portion a straight line having a circular cross-section A ceramic heater, wherein the ceramic heating element has an elliptical cross-section compressed in a direction facing the part, and a firing step is performed to obtain a fired body in which the base ceramic powder molded part is the ceramic base. Manufacturing method. 2. The step of forming a second part of the conductive ceramic powder molded part on the mating surface, wherein the second molding step includes forming a mold on the mating surface.
A step of forming a divided preform formed with a concave portion for accommodating the integral molded body so that the linear portions are arranged using the base ceramic powder; and, in a state in which the integral molded body is accommodated in the concave portion, A step of matching the divided preforms, and pressing and integrating the matched preformed bodies and the divided preforms in a direction substantially orthogonal to the mating surface to form the composite. The method of manufacturing a ceramic heater according to claim 1, further comprising a step of forming a molded body, wherein in the firing step, the composite molded body is pressed in a direction along a mating surface of the divided preformed bodies.