JP2003021332A - Manufacturing method of ceramic heater, ceramic heater, and glow plug provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a ceramic heater, in which heating is uniform, the heater can be minimized, performance of temperature rise is improved, and electric-power saving can be attained, and provide further a ceramic heater and a glow plug provided therewith. SOLUTION: In the manufacturing method of the ceramic heater, the width of a heating unit 22 in the cross section image is obtained, and the position passing the center of the width is calculated to obtain a rotation axis 25 of the ceramic heater 20 before rough polishing. The unpolished ceramic heater 20 is roughly polished in its outer periphery with the rotation axis 25 as the center, and then it is finally polished by the centerless polishing to obtain an aimed ceramic heater 2. In the ceramic heater 2 thus produced and the glow plug I provided therewith, the heating unit 22 is positioned radially in the center of the ceramic sintered body 21, it can accordingly perform a uniform heating. Further, miniaturization of the heater and improvement in performance of temperature rise, etc., can be easily attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a ceramic heater capable of generating heat when energized, a ceramic heater manufactured by this manufacturing method, and a glow plug including the same. More specifically, the present invention relates to a method for manufacturing a ceramic heater, which has uniform heat generation, and is capable of downsizing the ceramic heater, improving temperature rising performance, and saving power consumption, a ceramic heater, and a glow plug including the same. The present invention is
It can be suitably used as a ceramic heater used for promoting ignition and combustion of a combustible fluid and a glow plug including the ceramic heater.

[0002]

2. Description of the Related Art A general ceramic heater has a structure in which a heating element is embedded in a ceramic sintered body. Since the ceramic sintered body has excellent heat resistance, it is possible to rapidly generate heat by heating and raise the temperature. An application product using this ceramic heater is a glow plug used for starting assistance of a diesel engine. In this glow plug, as shown in FIGS. 1 and 2, a heating element 22 and lead wires 23, 24 for supplying power to the heating element 22 are embedded in a ceramic sintered body 21 and a ceramic heater 2 is attached to a metal fitting 11. It has been provided. In addition, as specific examples of glow plugs, Japanese Patent No. 3004134 and Japanese Unexamined Patent Publication No. HEI 1
0-110951, JP 2000-121055 A
JP, JP-A 2000-130754, and JP 2
No. 000-193241 can be mentioned.

In order to produce such a ceramic heater, an unfired heating element produced by an injection molding method or the like is embedded in a ceramic powder, and a rod-shaped unfired ceramic molding is made by a press molding method or the like. Form the body. Next, this unfired ceramic compact is fired by a known firing method such as a hot press firing method to obtain a pre-polishing ceramic heater 20 as illustrated in FIG. Thereafter, polishing processing such as centerless polishing is performed on the outer peripheral surface of the pre-polishing ceramic heater 20 to obtain the ceramic heater 2.

The glow plug 1 incorporating the ceramic heater 2 is desired to generate heat evenly over the entire circumference of the ceramic heater in order to accelerate ignition and combustion of a combustible fluid such as fuel. .
Further, in order to generate heat uniformly, it is preferable to position the heating element at the center of the axis of the ceramic sintered body. This is because the distance from the heating element to the surface of the ceramic heater is substantially the same, and the heat conduction becomes uniform. However, the heating element 22 in the ceramic sintered body 21 cannot easily improve the positional accuracy during burying and may be offset during burying, resulting in temperature unevenness and sufficient uniform heat generation. There's a problem. In order to solve this problem, Japanese Unexamined Patent Publication No. 9-180863 discloses a ceramic heater in which the particle size and particle size composition of a conductive material serving as a heating element are regulated to make the heating temperature distribution in the effective heating portion region uniform. ing. Also, after the ceramic heater is once heated to measure the temperature distribution on the surface of the ceramic heater by the temperature detecting means, the ceramic sintered body in the low temperature portion is cut based on the obtained temperature distribution to form a thin layer. Japanese Unexamined Patent Publication (Kokai) No. 11-162620 discloses a ceramic heater whose temperature is soaked.

[0005]

However, due to the problem of the accuracy of the embedded position of the heating element in the ceramic heater, the heating element may be arranged offset, and the thermal uniformity of the ceramic heater may deteriorate. This is mainly due to the positional accuracy of the heating element and the processing accuracy during the centerless polishing in the stage of manufacturing the ceramic sintered body.

In order to improve the positional accuracy of the heating element when buried, it is necessary to manage and control a number of parameters such as molding pressure, weight of the sintered body and dimensional accuracy of the sintered body. If these management controls are performed, the number of manufacturing steps of the ceramic heater increases, which hinders the reduction of manufacturing cost. Further, the centerless polishing process is performed in order to perform polishing along the outer periphery of the sintered body,
Even if the positional accuracy of the heating element in the sintered body before polishing was low and there was a deviation, it could not be corrected,
The position of the heating element will be offset even after processing. Therefore, the soaking property of the ceramic heater is deteriorated.

Further, by making the diameter of the ceramic sintered body to be larger, even if the heating element is embedded in a biased manner, a certain thickness can be secured between the surface of the ceramic sintered body and the heating element. Had to do. Therefore, it is difficult to reduce the size of the ceramic heater by the amount of the extra thickness secured, and the heat capacity of the ceramic sintered body is increased, which causes a problem that it is difficult to save power and improve the temperature raising performance.

The present invention solves the above problems, and a method of manufacturing a ceramic heater which has uniform heat generation and is easy to downsize, improve temperature rising performance, and save power, and this manufacturing method. Ceramic heater manufactured by the method,
And a glow plug including the same.

[0009]

A method of manufacturing a ceramic heater according to the present invention comprises a firing step for obtaining a ceramic sintered body having a heating element embedded therein, and the heat generation embedded in the ceramic sintered body by an image processing means. The method is characterized by including a detection step of obtaining a rotation axis passing through the center of the body, and a polishing step of polishing the outer periphery of the ceramic sintered body so that the rotation axis becomes the center. Further, the detecting step may be a step of obtaining the rotation axis based on the contour position of the heating element obtained by the image processing means.

The "image processing means" is a means for detecting the position of the heating element embedded in the ceramic sintered body produced in the firing step and determining the center of the heating element. By polishing so that the central portion is located at the axial center of the ceramic sintered body, it is possible to obtain a ceramic heater that evenly generates heat. Further, in order to detect the position of the heating element embedded in the ceramic sintered body, a known nondestructive inspection device such as an X-ray inspection device and an ultrasonic flaw detector can be used. Of these, it is preferable to use the X-ray inspection apparatus in consideration of productivity.

Further, as an X-ray inspection apparatus used in the image processing means, an X-ray generator and an X-ray detection apparatus which are arranged opposite to each other with a ceramic sintered body having a heating element embedded therein, and a ceramic having a heating element embedded therein. Rotation control means for controlling rotation of the sintered body and X-ray capable of photographing a cross-sectional image by processing the X-ray image transmitted through the ceramic sintered body in which the heating element is embedded and displaying the photographed cross-sectional image. Micro focus device and X-ray C
A T device can be exemplified. Further, as a concrete system, an X-ray detection system 3 as illustrated in FIG.
Can be mentioned. In this X-ray detection system 3, an X-ray detection system 3 for producing a substantially cylindrical ceramic heater 2 by polishing the heating element 22 embedded in the ceramic sintered body 21 so that the central portion thereof is on the rotation axis. And
An X-ray detection unit 31, a rotation control unit 32, and an X-ray transmission image processing unit 33 are provided, and the X-ray detection unit applies X to the ceramic sintered body.
X-ray irradiation unit 311 that performs X-ray irradiation and X-ray transmission image detection unit 31 that detects an X-ray transmission image transmitted through the ceramic sintered body.
2, the rotation control section 32 rotates the ceramic sintered body while holding it, and the X-ray transmission image processing section 33 is rotated.
A contour detecting section 332 for image-processing the X-ray transmission image obtained from the X-ray transmission image detecting section to obtain a contour of the heating element;
A rotation instructing section 335 for instructing the rotation control section to perform the rotation operation corresponding to the contour obtained by the contour detecting section;
A rotation axis output unit 333 that outputs a straight line passing through the center of the contour detected by the contour detection unit as a rotation axis.

The image processing means uses a method of determining the rotation axis at the time of polishing based on the contour position of the heating element acquired by using the X-ray detection system 3 as an example. here,
FIG. 4 shows a cross-sectional view of the pre-polishing ceramic heater 20 obtained by the firing process. As shown in FIG. 4, the pre-polishing ceramic heater 20 has a ceramic sintered body 21 in which a heating element 22 and linear lead wires 23 and 24 for energizing the heating element are embedded. In the conventional manufacturing method, as shown in FIG.
As shown in FIG. 5, the rotating shaft 25 passing through the central portion of the heating element 22 is deviated from the center of the ceramic sintered body 21, which may cause uneven heating.

In order to solve the above problem, the width of the heating element 22 in an arbitrary cross-sectional image obtained by rotating the ceramic sintered body and photographing by X-ray is obtained. Although there is no limitation on the orientation of the cross-sectional image to be photographed, as shown in FIGS.
It is advisable to use a cross section in which the maximum width (100 and 101 in FIG. 5) and the minimum width (102 and 103 in FIG. 7) of 2 are obtained. The width can be improved in accuracy by obtaining at least two positions for one cross-sectional image.

With respect to the sectional image showing the contour of the heating element 22, the rotation axis passing through the center of the heating element is determined from the point where the width is determined. When the maximum width and the minimum width of the heating element 22 are used, as shown in FIGS. 5 and 7, the maximum width (100, 101 in FIG. 5) and the minimum width (102, 103 in FIG. 7) of the heating element 22 are set. The rotation axis passing through the central portion of the heating element 22 can be obtained from the data of each two points, that is, four points in total. By polishing the outer peripheral surface of the ceramic sintered body 40 according to this rotation axis, the positional accuracy of the heating element can be dramatically improved.

The above-mentioned "polishing step" may be any method as long as the ceramic sintered body can be processed into a substantially cylindrical shape by an arbitrary rotation axis, and a method of polishing by traverse grinding with a cylindrical grinder is exemplified. be able to. Further, the polishing step is a step of performing rough polishing and centerless polishing in this order, and in the rough polishing, the outer periphery of the ceramic sintered body is polished so that the central portion of the heating element is the rotation axis. it can. In other words, polishing by traverse grinding takes a lot of polishing time, so rough polishing by traverse grinding etc. is performed until the shape of the ceramic sintered body becomes roughly cylindrical, and then main polishing by centerless polishing etc. It is possible to polish a large amount in a short time while maintaining high positional accuracy. This is because, in centerless polishing, the outer peripheral surface is polished to a uniform thickness, so if the cross-sectional shape before polishing is a substantially perfect circle, it will be a perfect circle even after polishing, and there will be almost no center deviation.

The polishing allowance for centerless polishing is usually 200.
To 300 μm (preferably 50 to 190 μm, more preferably 80 to 180 μm, still more preferably 100 to 16)
It is often set in the range of 0 μm). Further, in the present invention, since the centerless polishing process is performed along the rotation axis passing through the center of the heating element detected by the image processing means, it is possible to set the polishing allowance of 200 μm or less. By reducing the setting of the polishing allowance, the time required for the polishing process can be shortened. If the tip of the ceramic heater is previously rounded by polishing, as in the ceramic heater after the polishing step shown in FIG. 3, chipping can be effectively prevented.

The above-mentioned "firing process" includes injection molding,
A ceramic sintered body in which a heating element is embedded is formed using a known integral molding method such as a press molding method, and then the ceramic sintered body is fired using a known firing method such as a hot press firing method to obtain a ceramic. A known process for obtaining a sintered body can be used. Further, the accuracy of the embedded position of the heating element is required as long as the thickness from the surface of the ceramic sintered body to the heating element in the unheated ceramic heater obtained by firing is the minimum required. do not do. This is because by using this manufacturing method, the heating element can be manufactured so as to be located on the central axis in the radial direction of the ceramic sintered body.

The ceramic heater of the present invention is characterized by being manufactured by the above-described method for manufacturing a ceramic heater. Further, the glow plug of the present invention is characterized by including the ceramic heater. The above-mentioned "heating element" that constitutes the ceramic heater is W, Ta, Nb, Ti, M.
It can be formed by firing from at least one kind of silicide, carbide, nitride or the like of one or more metal elements selected from o, Zr, Hf, V and Cr. The "ceramic sintered body" is usually a silicon nitride sintered body containing silicon nitride as a main component, but it may contain a small amount of aluminum nitride, alumina, or the like. It may also be Sialon. Further, it is preferable that the heating element and the ceramic sintered body do not have a large difference in their thermal expansion coefficients. This is because if the difference in the coefficient of thermal expansion is small, the occurrence of cracks near the interface between the heating element and the ceramic sintered body can be suppressed when the heater is used.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for manufacturing a ceramic heater according to the present invention, a ceramic heater manufactured by this manufacturing method, and a glow plug including the same will be described in more detail with reference to Examples with reference to FIGS. 1. Method of Manufacturing Ceramic Heater (1) Firing Step First, silicon nitride powder mixed with tungsten carbide and a sintering aid is granulated by a spray dryer method to produce granulated powder. Next, this granulated powder is press-molded to produce a U-shaped unfired heating element. Separately, silicon nitride powder mixed with a sintering aid is granulated by a spray dryer method to produce granulated powder. After embedding the unsintered heating element and the electrode terminals in the granulated powder, the unsintered ceramic heater is integrated by press molding. Furthermore, the unfired ceramic heater is set to 600 ° C.
By calcination for 2 hours in the nitrogen atmosphere, the binder is removed and a ceramic calcined body is obtained.

On the other hand, a release agent is applied to the surface of the graphite mold used for hot pressing. This release agent is a paste-like material in which the main component, boron nitride powder, the silicon nitride powder and the sintering aid used in the above granulated powder, and a binder are mixed with ethanol. Using the above mold, the ceramic calcined body is sintered by hot pressing under a nitrogen atmosphere,
As shown in FIGS. 4 and 6, a substantially rectangular unpolished ceramic heater 20 having a heating element embedded therein is obtained.

(2) Detection step The contour image of the heating element 22 in the pre-polishing ceramic heater 20 obtained in "(1) Firing step" is determined by the X-ray detection system 3 shown in FIG. Detect the axis of rotation.
The X-ray detection system 3 includes an X-ray detection unit 31, a rotation control unit 32, and an X-ray transmission image processing unit 33. The X-ray detection unit 31 includes an X-ray irradiation unit 311 and an X-ray transmission image detection unit 312.
An X-ray microfocus device including Also,
The X-ray irradiation unit 311 is the X-axis of the ceramic heater 20 before polishing.
An X-ray source for detecting a transmission image. Further, the X-ray transmission image detection unit 312 detects the X-ray transmission image emitted from the X-ray irradiation unit 311 and transmitted through the pre-polishing ceramic heater 20, and transmits the obtained signal to 331. The rotation control unit 32 is a device that rotates the ceramic heater 20 before polishing for detecting an X-ray transmission image by the X-ray detection unit 31 while rotating the ceramic heater 20 by an arbitrary angle.

The X-ray transmission image processing section 33 includes an image signal capturing section 331, a contour detecting section 332, an image output section 333, an image display section 334 and a rotation instructing section 335. The image signal acquisition unit 331 acquires the X-ray transmission image signal transmitted from the X-ray transmission image detection unit 312. In addition, the contour detection unit 332
Is an apparatus for performing image processing on the X-ray transmission image signal obtained by the image signal capturing unit 331 to obtain the contour of the heating element.
Further, the image output unit 333 is a rotation axis output unit, obtains the width from the detected contour and obtains the corresponding rotation axis, superimposes the display on the X-ray transmission image, and displays the position of the rotation axis and the image data. This is a device for outputting to the image display unit 334. The rotation instructing unit 335 is a device that instructs the rotation control unit 32 to control the rotation operation corresponding to the contour detected by the contour detecting unit 332.

The procedure for determining the rotation axis during polishing using the X-ray detection system 3 will be described in order. The contour images of the ceramic sintered body 21 and the heating element 22 (see FIG. 4) that can be obtained from the X-ray transmission image of the pre-polishing ceramic heater 20 are not limited to one kind, and the longitudinal direction of the pre-polishing ceramic heater 20 is the axis. As shown in FIG. 4 and FIG.
As shown in, it is possible to obtain different contour images depending on the shooting direction. Further, since the heating element 22 has a U-shape, the widths 261 and 262 are maximum when the contour image is a plane image having a U-shape as shown in FIG.
As shown in FIG. 7, when the contour image is a side image that looks like a rod, the widths 263 and 264 are the smallest.

That is, the pre-polishing ceramic heater 20 is rotated by the rotation control unit 32 to obtain two types of X-ray transmission images in which the contour width of the heating element 22 is minimum and maximum. It is possible to specify the position of the heating element 22 necessary for determining the position of the. Further, a straight line that passes through the midpoints of two transverse lines (261 and 262 in FIG. 6 and 263 and 264 in FIG. 7) that intersect the contour images of the heating element 22 in these two types of X-ray transmission images. Reference numeral 25 is a line passing through the central portion of the heating element 22 which is a heating element, and by outputting this as the rotation axis during polishing, the rotation axis during polishing can be determined.

A specific procedure for determining the rotation axis during polishing will be described below. First, the pre-polishing ceramic heater 20 for determining the rotation axis is attached to the rotation control unit 32 so that the longitudinal direction thereof is the rotation axis. Further, an X-ray transmission image of the pre-polishing ceramic heater 20 is acquired using the X-ray detection unit 31,
It is transmitted to the contour detection unit 332 via the image signal capturing unit 331, and the contour detection unit 332 obtains contour images of the ceramic sintered body 21 and the heating element 22 (see FIG. 4). Further, the transverse line of the heating element 22 (261, 262 in FIG. 5, FIG.
263, 264 in the above), and sends an instruction to the rotation control unit 32 via the rotation instruction unit 335 to rotate the pre-polishing ceramic heater 20 until the contour image having the minimum or maximum line length is obtained.

Next, the image output unit 333 obtains a straight line 25 passing through the respective midpoints of the obtained maximum transverse lines 261 and 262 and the minimum transverse lines 263 and 264 as a rotation axis, and displays the display on an X-ray transmission image. The image is superimposed and output to the image display unit 334. The position of the rotary shaft obtained on the pre-polishing ceramic heater 20 is stored so that it can be used during polishing. As an example of this, it is possible to engrave the position of the rotating shaft by laser light on the surface where the rotating shaft of the pre-polishing ceramic heater 20 is exposed, or to transmit the position of the rotating shaft as reproducible coordinate information to a fixing device during polishing. Can be mentioned.

(3) Polishing step The ceramic sintered body 21 is fixed to a cylindrical grinder so that the rotation axis obtained in "(2) Detection step" is the center of rotation,
The outer periphery of the ceramic sintered body 21 is roughly polished by traverse grinding. Then, main polishing by centerless polishing is performed to obtain the target ceramic heater 2. In the produced ceramic heater 2, as shown in FIG. 3, the heating element 22 is located on the radial central axis on the tip side in the ceramic sintered body 21, and a lead for passing an electric current through the heating element 22. The wires 23 and 24 are connected to each other to form the ceramic sintered body 21.
Is led to the outer circumference of.

(4) Production of Glow Plug The ceramic heater 2 produced by the above steps (1) to (3) is inserted and fixed in the metal fitting 11, and the glow plug 1 as shown in FIG. 1 is obtained. Create. The glow plug 1 includes a ceramic heater 2 in which a heating element 22 is arranged on the tip side, which is a portion that generates heat. The ceramic heater 2 is penetrated and held by an outer cylinder 12 made of metal.
On the other hand, the outer cylinder 12 is fixed to the tip of the metal fitting 11 by brazing. A mounting screw portion 13 for mounting the glow plug 1 on the engine is threaded on the outer periphery of the metal fitting 11, and a hexagonal tool engaging portion 14 for applying an impact wrench when mounting is further formed. .

2. Examination of core runout Ceramic heaters of an example with a diameter of 3.34 mm produced by the present manufacturing method and a comparative example with a diameter of 3.5 mm that was subjected to centerless polishing without performing rough polishing were prepared. The embedded portion is cut, the displacement of the rotation axis passing through the central portion of the heating element with respect to the central axis of the ceramic heater (hereinafter referred to as "core deflection", see FIG. 15) is measured, and the plotted results are shown. Shown in FIGS. 9 and 10 are plots of core runout of the ceramic heater of the example, FIG. 9 is the tip side (262 in FIG. 5), and FIG. 10 is the terminal side (261 in FIG. 5). The positions are 5 mm and 10 mm from the tip of the ceramic heater, respectively. On the other hand, FIGS. 11 and 12 are plots of core runout of the ceramic heater of the comparative example. FIG.
Is the terminal side. The minimum thickness between the heating element and the surface of the ceramic sintered body is 0.1 in both the examples and the comparative examples.
It is 6 mm or more.

As shown in FIG. 9 and FIG. 10, in the ceramic heater of this embodiment, the runout on both the heater tip side and the terminal side of the heating element is within about 0.04 mm, which is about ± 1%.
It can be seen that it is within the error of. On the other hand, as shown in FIGS. 11 and 12, in the ceramic heater of the comparative example, an error of about ± 3% occurs within about 0.1 mm, and it can be seen that the deviation of the heating element is larger than that of the example. .
As described above, in the ceramic heater in which the center runout is small and the heating element is located at the center, the distance from the outer circumference of the ceramic sintered body to the heating element is uniform, and uniform heating can be performed.

3. Examination of heat generation characteristics Under the conditions of applied voltages of 10 V and 11 V, the heat generation characteristics of the ceramic heaters of the same examples and comparative examples as in “2. Examination of core runout” were obtained, and shown in FIGS. 13 and 14. As shown in FIG. 13, when the applied voltage is 10 V, the heating temperature of the ceramic heater of the comparative example is 1120 to 1160 ° C., but the runout is small and the outer shape can be made thin.
In the ceramic heater of this example, which has a small surface area and a small loss due to heat escape, a high temperature of 1170 to 1210 ° C. could be obtained. The average power of the comparative example is 8
The average power of the embodiment is 80.0, while it is 1.5 W.
It was W and low power consumption. Further, as shown in FIG. 14, when the applied voltage is 11 V, the comparative example is 1230 to 1280.
C., 93.2 W, while this example is 1290-
A ceramic heater having a high temperature of 1330 ° C. and low power consumption could be obtained.

4. Effect of Ceramic Heater Manufacturing Method, Ceramic Heater, and Glow Plug In this ceramic heater manufacturing method, the rotation axis passing through the center of the heating element embedded in the ceramic sintered body can be obtained by the image processing means. By polishing the outer periphery of the ceramic sintered body with its rotation axis on the central axis in the radial direction, the ceramic sintered body can be sintered without strict precision control when manufacturing the ceramic sintered body. The accuracy of the center position of the heating element embedded in the body can be improved.
In addition, the ceramic heater manufactured by the method for manufacturing a ceramic heater does not need to secure an extra thickness between the surface of the ceramic sintered body and the heating element in consideration of the case where the heating element is embedded while being offset. The diameter can be made smaller by using the heating element, and the miniaturization becomes easier than before. As a result, the heat generated from the heating element is conducted to the outer periphery of the ceramic sintered body in a shorter time, and the temperature raising performance of the ceramic heater is improved. Also, shortening the heat transfer time,
By reducing the unevenness of heat generation and the heat capacity, it is possible to reduce the electric power required for the required heat generation.

Further, in the ceramic heater manufacturing method of the present invention, it is necessary to strictly control the accuracy of the embedded position of the heating element in the press molding process for manufacturing the divided preformed body or the composite molded body as in the conventional manufacturing method. Therefore, the manufacturing yield can be improved and the manufacturing cost can be reduced. Also,
A glow plug using such a ceramic heater is
Temperature unevenness during heat generation is unlikely to occur, and when used as an ignition member of an internal combustion engine such as a diesel engine, it is possible to improve ignitability.

The present invention is not limited to the above embodiments, but various modifications may be made within the scope of the present invention according to the purpose and application. That is, the shapes of the ceramic sintered body and the heating element are not limited to the rectangular parallelepiped shape and the U-shape shown in the embodiments, and may have any shape, and the materials of the heating element and the lead wire may be arbitrarily selected. it can.
For example, the shape of the heating element may be a coil shape, a composite type in which a heating coil is wound around a U-shaped heating wire, and a plate type. Further, a low resistance ceramic conductor can be used for the lead wire. Further, the heating element can be configured by using a plurality of ceramic conductors having different resistances. Further, the ceramic heater may be separately provided with an electrode for detecting an external ion current.

Further, in this embodiment, the transverse lines 261, 26
The rotation axis was determined using two types of X-ray transmission images in which 2 and the like are maximum and minimum, but the present invention is not limited to this, and the rotation axis is determined using two types of X-ray transmission images obtained with different standards. can do. For example, two types of X-ray transmission images based on the directions of the ceramic sintered body (for example, positions that are a plane and a side surface) are used, and the transverse lines 261 and 262 are obtained from these X-ray transmission images.
Etc., the rotation axis can be determined from a straight line passing through the intermediate points.

[0036]

According to the method for manufacturing a ceramic heater of the present invention, since the heating element is located at the axial center of the ceramic sintered body thus produced, uniform heat generation can be obtained. Further, it is easy to reduce the size, improve the temperature raising performance, and save power. Further, the same effect can be obtained also in the ceramic heater manufactured by this manufacturing method and the glow plug including the same.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining a glow plug including a ceramic heater.

FIG. 2 is a partial enlarged cross-sectional view for explaining a ceramic heater portion of a glow plug.

FIG. 3 is a schematic cross-sectional view seen from a plane for explaining a preferable position of a heating element in a ceramic heater.

FIG. 4 is a schematic cross-sectional view seen from a plane for explaining the shape of a ceramic sintered body before polishing and the position of a heating element.

FIG. 5 is a schematic cross-sectional view seen from a plane for explaining the position of the transverse line of the heating element.

FIG. 6 is a schematic cross-sectional view seen from a plane for explaining the shape of a ceramic sintered body before polishing and the position of a heating element.

FIG. 7 is a schematic cross-sectional view seen from a plane for explaining the position of the transverse line of the heating element.

FIG. 8 is a block diagram for explaining a configuration of a manufacturing apparatus of the present ceramic heater.

FIG. 9 is a plot diagram of core runout of the heating element obtained on the tip side (101 in FIG. 5) of the ceramic heater of the example. The X-axis is the horizontal direction in FIG. 5, and the Y-axis is the horizontal direction in FIG.

FIG. 10 is a plot diagram of core runout of the heating element obtained on the terminal side (100 in FIG. 5) of the ceramic heater of the example. The X-axis is the horizontal direction in FIG. 5, and the Y-axis is the horizontal direction in FIG.

FIG. 11 is a plot diagram of core runout of the heating element obtained on the tip side (101 in FIG. 5) of the ceramic heater of the comparative example. The X-axis is the horizontal direction in FIG. 5, and the Y-axis is the horizontal direction in FIG.

FIG. 12 is a plot diagram of core runout of the heating element obtained on the terminal side (100 in FIG. 5) of the ceramic heater of the comparative example. The X-axis is the horizontal direction in FIG. 5, and the Y-axis is the horizontal direction in FIG.

FIG. 13 shows the ceramic heaters of Examples and Comparative Examples.
It is a graph which shows tip temperature when V power supply is connected.

FIG. 14 shows the ceramic heaters of Examples and Comparative Examples.
It is a graph which shows tip temperature when V power supply is connected.

FIG. 15 is a schematic diagram for explaining a state of center runout.

[Explanation of reference numerals] 1; glow plug, 11; metal fitting, 12; outer cylinder, 2; ceramic heater, 20; ceramic heater before polishing, 21;
Ceramic sintered body, 22; heating element, 23, 24; lead wire, 25; rotating shaft, 3; X-ray detection system, 31; X-ray detection unit, 311; X-ray irradiation unit, 312; X-ray transmission image detection Section, 32; rotation control section, 33; X-ray transmission image processing section, 33
1; image signal acquisition unit, 332; contour detection unit, 333; image output unit, 334; image display unit, 335; rotation instruction unit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takaya Yoshikawa             14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi Japan special             Within Toyo Co., Ltd. (72) Inventor Masaya Ito             14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi Japan special             Within Toyo Co., Ltd. F term (reference) 3K092 PP16 QA03 QB10 QB74 RE03                       RE09 SS31 VV22

Claims (5)

[Claims] 1. A firing step of obtaining a ceramic sintered body in which a heating element is embedded, and a detection step of obtaining a rotation axis passing through a central portion of the heating element embedded in the ceramic sintered body by an image processing means, And a polishing step of polishing the outer periphery of the ceramic sintered body so that the rotation axis becomes the center. 2. The method of manufacturing a ceramic heater according to claim 1, wherein the detecting step is a step of obtaining the rotation axis based on a contour position of the heating element obtained by the image processing means. 3. The polishing step is a step of performing rough polishing and centerless polishing in this order, and in the rough polishing, the outer periphery of the ceramic sintered body is polished so that the central portion of the heating element is the rotation axis. The method for manufacturing a ceramic heater according to claim 1 or 2. 4. A ceramic heater manufactured by the method for manufacturing a ceramic heater according to any one of claims 1 to 3. 5. A glow plug comprising the ceramic heater according to claim 4.