JP6426338B2 - Glow plug - Google Patents

Description

  The present invention relates to glow plugs.

  As a glow plug, a ceramic glow plug using a ceramic heater is known (see, for example, Patent Document 1). The ceramic heater of the ceramic glow plug comprises a heating resistor and a support. The heating resistor is made of a ceramic composition having conductivity and generates heat by energization. The support is made of an electrically insulating ceramic composition, in which the heating resistor is embedded and supports the heating resistor.

  In Patent Document 2, in order to prevent damage to the ceramic heater due to the difference in thermal expansion between the heating resistor and the support, the heating resistor is covered with a coating layer having a hardness and density lower than those of the heating resistor and the support. It has been described that. The covering layer of Patent Document 2 mainly comprises boron nitride (BN), and its coefficient of thermal expansion is lower than that of the heating resistor and the support.

  As generally known, the coefficient of thermal expansion of the material constituting the heating resistor is larger than the material constituting the support (see, for example, Patent Document 3).

  The glow plug is required to have a rapid temperature rise characteristic of rapidly raising the temperature from the start of energization to a desired temperature in order to shorten the start time of the internal combustion engine. The rapid temperature rising characteristic of the glow plug requires about 2 seconds as an arrival time up to 1000 ° C., and in recent years, the required level has been increased to about 1 second. In order to improve the rapid temperature rising characteristics, it is necessary to reduce the initial resistance of the heat generating resistor by increasing the content of the conductive component in the heat generating resistor.

JP, 2009-287920, A JP, 2011-66020, A JP, 2010-108606, A

  In the glow plug of Patent Document 1, when the content of the conductive component in the heating resistor is increased to improve the rapid temperature rising characteristic, the thermal stress of the heating resistor due to the difference in thermal expansion with the support increases. Therefore, there is a problem that the heat generating resistor is easily deteriorated. The resistance value of the heating resistor increases with deterioration. Also in the glow plug of Patent Document 2, when the content of the conductive component in the heat generating resistor is increased, the thermal stress generated in the heat generating resistor can not be alleviated by the covering layer, and the heat generating resistor is easily degraded. there were. Furthermore, in the glow plug of Patent Document 2, there is a problem that the strength of the ceramic heater can not be sufficiently secured because the strength of the covering layer covering the heating resistor is relatively low.

The present invention has been made to solve the above-described problems, and can be realized as the following modes.
According to one aspect of the present invention, a glow plug is provided. Glow plug of this embodiment: comprises a first ceramic composition, the heating resistor and that generates heat when energized; a second ceramic composition different from the first ceramic composition, silicon nitride (Si ₃ A glow plug mainly comprising a second ceramic composition containing N ₄ ) as a main component, in which the heat generating resistor is embedded, and which supports the heat generating resistor. The support is a third ceramic having a thermal expansion coefficient higher than that of silicon nitride (Si ₃ N ₄ ) in the adjacent region adjacent to the heating resistor, in the solid phase made of the second ceramic composition. A plurality of particles made of the composition include adjacent regions dispersed unevenly distributed on the heating resistor side.
According to one aspect of the present invention, a glow plug is provided. Glow plug of this embodiment comprises a first ceramic composition, the heating resistor and that generates heat when energized; a second ceramic composition different from the first ceramic composition, silicon nitride (Si ₃ A support mainly composed of a second ceramic composition containing N ₄ ) as a main component, in which the heating resistor is embedded, and supporting the heating resistor is provided. In the glow plug of this aspect, the support is an adjacent region adjacent to the heat generating resistor, and a plurality of particles having a component having a thermal expansion coefficient higher than that of silicon nitride (Si ₃ N ₄ ) are present. It includes an adjacent region dispersed unevenly distributed on the heating resistor side. According to the glow plug of this aspect, the thermal stress of the heat generating resistor caused by the difference in the thermal expansion with the support is suppressed by the difference in the thermal expansion between the heat generating resistor and the support being mitigated in the adjacent region. it can. As a result, the durability of the heat generating resistor can be improved.
In the glow plug of the above aspect, the components present in the particles dispersed in the adjacent region are chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), and zirconium (Zr). And at least one element of tantalum (Ta) or silicon carbide (SiC). According to the glow plug of this aspect, the durability of the heating resistor supported by the support can be effectively improved.

(1) According to one aspect of the present invention, a glow plug is provided. The glow plug of this aspect is made of a first ceramic composition, mainly composed of a heat generating resistor which generates heat when energized, and a second ceramic composition having a thermal expansion coefficient lower than that of the first ceramic composition. The heat generating resistor is embedded, and a support for supporting the heat generating resistor is provided. In the glow plug of this aspect, the support includes an adjacent region adjacent to the heat generating resistor and in which a plurality of particles are dispersed, and the plurality of particles are more than the second ceramic composition. The third ceramic composition has a high coefficient of thermal expansion. According to the glow plug of this aspect, the thermal stress of the heat generating resistor caused by the difference in the thermal expansion with the support is suppressed by the difference in the thermal expansion between the heat generating resistor and the support being mitigated in the adjacent region. it can. As a result, the durability of the heat generating resistor can be improved.

(2) In the glow plug according to the above aspect, the thickness of the adjacent area may be 10 to 200 μm from the heating resistor. According to the glow plug of this aspect, the thermal stress of the heat generating resistor can be effectively suppressed by the adjacent region.

(3) In the glow plug of the above aspect, the thickness of the adjacent region may be 20 to 100 μm from the heat generating resistor. According to the glow plug of this aspect, the thermal stress of the heat generating resistor can be more effectively suppressed by the adjacent region.

(4) In the glow plug of the above aspect, the average particle diameter of the plurality of particles may be 5 μm or less. According to the glow plug of this aspect, the formation of pores in the adjacent region can be suppressed. In addition, it is possible to suppress fine cracks (fine cracks) generated around the particles due to the thermal expansion difference between the particles and the periphery thereof. As a result of these, the durability of the adjacent region can be improved, and in turn, the durability of the heating resistor can be improved.

(5) In the glow plug of the above aspect, the second ceramic composition is silicon nitride, and the main components of the third ceramic composition are chromium (Cr), molybdenum (Mo), tungsten ( It may be at least one silicide of W), titanium (Ti), zirconium (Zr) and tantalum (Ta), or silicon carbide (SiC). According to the glow plug of this aspect, it is possible to improve the durability of the heat generating resistor supported by the support mainly made of silicon nitride.

(6) In the glow plug of the above aspect, the relationship between the cross-sectional area S1 of the heat-generating resistor cut at the position where the adjacent region is formed and the cross-sectional area S2 of the support is 0.5% ≦ S1 / (S1 + S2) × 100% ≦ 25% may be satisfied. According to the glow plug of this aspect, it is possible to improve the durability of the heat generating resistor while securing the rapid temperature rise characteristic.

(7) In the glow plug of the above embodiment, the relationship between the cross-sectional area S1 of the heating resistor cut at the position where the adjacent region is formed, the cross-sectional area S2 of the support and the thickness T of the adjacent region is And T · (S1 + S2) / S1 ≧ 67 μm may be satisfied. According to the glow plug of this aspect, the thermal stress of the heating resistor can be sufficiently suppressed by the adjacent region.

(8) In the glow plug of the above aspect, the heat generating resistor includes a folded back portion having a folded shape; and a conductive portion having a cross section larger than the folded back portion and connected to the folded back portion; The area may be at least an area adjacent to the turnback portion. According to the glow plug of this aspect, it is possible to suppress the thermal stress generated in the folded portion having a relatively large amount of heat generation.

(9) In the glow plug of the above aspect, the heat generating resistor may be a member formed by an injection molding method or a printing method. According to the glow plug of this aspect, the durability of the heating resistor molded by the injection molding method or the printing method can be improved.

(10) In the glow plug of the above aspect, the first ceramic composition and the second ceramic composition may contain common components. According to the glow plug of this aspect, the mechanical strength of the heat generating resistor can be improved by strengthening the bonding force between the heat generating resistor and the support. Therefore, the durability of the heat generating resistor can be further improved.

(11) In the blow plug of the above aspect, the second ceramic composition may contain a rare earth element and an aluminum (Al) element. According to the glow plug of this aspect, the durability of the heat generating resistor can be further improved.

  The present invention can also be realized in various forms other than glow plugs. For example, the present invention can be realized in the form of a member constituting a glow plug, a manufacturing method of manufacturing the glow plug, or the like.

It is explanatory drawing which shows the partial cross section of a glow plug. It is an explanatory view showing a section of a ceramic heater. It is an explanatory view showing a section of a ceramic heater. It is explanatory drawing which shows an example of the structure of a ceramic heater. It is explanatory drawing which shows an example of the structure of a ceramic heater. It is explanatory drawing which shows an example of the structure of a ceramic heater. It is process drawing which shows the manufacturing method of a glow plug. It is a table | surface which shows the result of having evaluated the performance of the glow plug. It is a table | surface which shows the result of having evaluated the performance of the glow plug. It is explanatory drawing which shows the cross section of the ceramic heater in 2nd Embodiment. It is process drawing which shows the manufacturing method of the glow plug in 2nd Embodiment. It is explanatory drawing which shows an example of the image used for analysis of the sample.

A. First embodiment:
A1. Glow plug configuration:
FIG. 1 is an explanatory view showing a partial cross section of the glow plug 10. In FIG. 1, the outer shape of the glow plug 10 is illustrated on the right side of the drawing with the axis SC of the glow plug 10 as a boundary, and the cross-sectional shape of the glow plug 10 is illustrated on the left side of the drawing. In the description of the present embodiment, the lower side of the glow plug 10 in FIG. 1 is referred to as the “front end side”, and the upper side of FIG. 1 is referred to as the “rear end side”.

  The glow plug 10 includes a ceramic heater 800 for generating heat and functions as a heat source for assisting ignition at the start of the internal combustion engine 90 including a diesel engine. The glow plug 10 includes, in addition to the ceramic heater 800, an inner shaft 200, a metal shell 500, and an outer cylinder 700. The axial center SC of the glow plug 10 is also the axial center of each member constituting the glow plug 10.

  The central axis 200 of the glow plug 10 is a metal body having conductivity. The center shaft 200 has a cylindrical shape extending around the axis SC. The center shaft 200 relays the power supplied from the outside of the glow plug 10 to the ceramic heater 800.

  In the present embodiment, the center shaft 200 receives power feeding from the outside of the glow plug 10 via the terminal 100 on the rear end side of the center shaft 200. In another embodiment, the center shaft 200 may receive power directly from the outside of the glow plug 10 on the rear end side of the center shaft 200.

  In the present embodiment, the center shaft 200 is electrically connected to the ceramic heater 800 via the ring 600 on the tip side of the center shaft 200. In another embodiment, the center shaft 200 may be directly connected to the ceramic heater 800 on the tip side of the center shaft 200.

  The metal shell 500 of the glow plug 10 is a conductive metal body. The metal shell 500 has a tubular shape extending around the axial center SC. The metal shell 500 includes an axial hole 510, a tool engagement portion 520, and an external thread portion 540.

  The axial hole 510 of the metal shell 500 is a through hole extending around the axial center SC. The inner diameter of the shaft hole 510 is larger than the outer diameter of the middle shaft 200. Inside the shaft hole 510, the middle shaft 200 is positioned on the shaft center SC, and a space is formed between the shaft hole 510 and the middle shaft 200 to electrically insulate the shaft hole 510 from the middle shaft 200. In the present embodiment, the center shaft 200 is attached to the rear end side of the shaft hole 510 via the cylindrical insulating member 300 and the annular insulating member 400.

  The tool engagement portion 520 of the metal shell 500 is configured to be engageable with a tool (not shown) used for attaching and detaching the glow plug 10 to the internal combustion engine 90. The male screw portion 540 of the metal shell 500 is configured to be fixable to the internal combustion engine 90 by being fitted to a female screw formed in the internal combustion engine 90.

  The outer cylinder 700 of the glow plug 10 is a conductive metal body. The outer cylinder 700 has a cylindrical shape extending around the axis SC. The outer cylinder 700 is provided with an axial hole 710 for holding the ceramic heater 800. The rear end side of the outer cylinder 700 is welded to the front end side of the metal shell 500. A ceramic heater 800 protrudes from the front end side of the outer cylinder 700.

  The ceramic heater 800 of the glow plug 10 is a heat generating element (heat generating device) made of a ceramic composition. The ceramic heater 800 includes a heating resistor 810 and a support 860.

  The heating resistor 810 of the ceramic heater 800 is a conductive ceramic made of the first ceramic composition having conductivity. The heat generating resistor 810 generates heat by energization. In the present embodiment, the heating resistor 810 is a member molded by an injection molding method.

In the present embodiment, the first ceramic composition forming the heating resistor 810 mainly comprises tungsten carbide (WC). In the present embodiment, the first ceramic composition contains silicon nitride (Si ₃ N ₄ ) in addition to tungsten carbide. The first ceramic composition contains 55 to 70% by weight of tungsten carbide and 28 to 35% by weight of silicon nitride, and the remaining 2 to 10% by weight of erbium oxide (Er ₂ O ₃ ) and silicon oxide it may contain (SiO _2). In another embodiment, the first ceramic composition may be a composition consisting primarily of molybdenum disilicide (MoSi ₂ ).

  The support 860 of the ceramic heater 800 is an insulating ceramic mainly made of the second ceramic composition having electrical insulation. In the support 860, the heating resistor 810 is embedded, and the support 860 supports the heating resistor 810. The support 860 electrically insulates the heating resistor 810 from the outside of the glow plug 10 and transfers the heat of the heating resistor 810 to the outside of the glow plug 10.

In the present embodiment, the second ceramic composition forming the support 860 mainly comprises silicon nitride (Si ₃ N ₄ ). In another embodiment, at least a portion of silicon (Si) of the silicon nitride (Si ₃ N ₄ ) forming the support 860 is replaced with aluminum (Al), and at least a portion of nitrogen (N) is oxygen (O) may be substituted. The second ceramic composition forming the support 860 contains, as a sintering aid, a rare earth oxide (eg, ytterbium (Yb) oxide, erbium (Er) oxide, etc.) and aluminum (Al) oxide. You may contain.

  FIG. 2 is an explanatory view showing a cross section of the ceramic heater 800. As shown in FIG. The cross section of FIG. 2 is a cross section of the ceramic heater 800 cut along a plane passing through the axial center SC. The heating resistor 810 of the ceramic heater 800 includes a terminal portion 811, a conductive portion 812, a folded back portion 815, a conductive portion 818, and a terminal portion 819.

  The terminal portion 811 of the heating resistor 810 is provided on the rear end side of the conductive portion 812 and exposed from the support 860. The terminal portion 811 is electrically connected to the center shaft 200 in a state where the ceramic heater 800 is assembled to the metal shell 500.

  The conductive portion 812 of the heating resistor 810 has a linear shape along the axis SC, and connects between the terminal portion 811 and the folded portion 815. The cross section of the conductive portion 812 is larger than that of the folded portion 815.

  The folded back portion 815 of the heating resistor 810 has a U-shaped shape, and is connected to the conductive portion 812 at one end of the U-shaped portion and connected to the conductive portion 818 at the other end of the U-shaped portion. Since the cross section of the folded portion 815 is smaller than the conductive portion 812 and the conductive portion 818, the electrical resistance of the folded portion 815 is larger than that of the conductive portions 812 and 818. Therefore, the heating resistor 810 generates heat centering on the folded portion 815 by energization.

  The conductive portion 818 of the heat generating resistor 810 has a linear shape along the axis SC, and connects between the folded portion 815 and the terminal portion 819. The cross section of the conductive portion 818 is larger than that of the folded portion 815.

  The terminal portion 819 of the heat generating resistor 810 is provided on the rear end side of the conductive portion 818 and exposed from the support 860. The terminal portion 819 is electrically connected to the outer cylinder 700 in a state where the ceramic heater 800 is assembled to the metal shell 500.

  FIG. 3 is an explanatory view showing a cross section of the ceramic heater 800. As shown in FIG. The cross section of FIG. 3 is a cross section of the ceramic heater 800 cut along a plane orthogonal to the axial center SC in the folded portion 815, and corresponds to the F3-F3 cross section of FIG.

  The diameter of the ceramic heater 800 is preferably 2.5 to 4.0 mm (millimeters). The diameter of the ceramic heater 800 may be smaller than 2.5 mm or larger than 4.0 mm.

  The major diameter L1 of the folded portion 815 in the heating resistor 810 is preferably 0.3 to 1.8 mm. The major diameter L1 of the folded back portion 815 may be smaller than 0.3 or larger than 1.8 mm.

  The minor diameter L2 of the folded portion 815 in the heating resistor 810 is preferably 0.2 to 1.0 mm. The major diameter L1 of the folded back portion 815 may be smaller than 0.2 or larger than 1.0 mm.

  4A and 4B are explanatory views showing an example of the structure of the ceramic heater 800. FIG. The structure of FIGS. 4A and 4B is a structure at the periphery of the boundary where the turnback portion 815 and the support 860 are adjacent to each other, and corresponds to the portion F4 of FIG.

The support 860 of the ceramic heater 800 comprises an adjacent region 866 adjacent to the heating resistor 810. In the adjacent region 866, the solid phase 862 of the second ceramic composition forming the support 860 has a plurality of particles 868 of the third ceramic composition having a thermal expansion coefficient higher than that of the second ceramic composition. scatter. The main components of the third ceramic composition forming particles 868 are chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), zirconium (Zr) and tantalum (Ta). And at least one silicide or silicon carbide (SiC). In the particles 868, components of the support 860 (eg, Si ₃ N ₄ ) may be mixed, or components of the support 860 may not be mixed.

  In the example of FIG. 4A, the particles 868 are formed by diffusing the components of the particles 868 added to the intermediate of the heating resistor 810 before firing from the heating resistor 810 to the support 860 during firing of the ceramic heater 800. Be done. Therefore, the particle size of the particles 868 tends to become smaller as it gets farther from the heating resistor 810.

  In the example of FIG. 4B, the particles 868 are formed by dispersing the components of the particles 868 applied to the intermediate of the heating resistor 810 before firing on the support 860 when the ceramic heater 800 is fired. Therefore, the particle size of particles 868 is approximately the same throughout.

  FIG. 4C is an explanatory view showing an example of the structure of the ceramic heater 800. As shown in FIG. The structure of FIG. 4C is a structure at the periphery of the boundary where the folded back portion 815 and the support 860 are adjacent to each other, and corresponds to the portion F4 of FIG. The drawing of column (A) in FIG. 4C schematically shows the structure of the ceramic heater 800. The drawing in column (B) in FIG. 4C corresponds to the structure in column (A), and specifically shows crystal grains in the support 860.

In the ceramic heater 800 of FIG. 4C, the support 860 is a second ceramic composition different from the first ceramic composition forming the heating resistor 810 and is mainly composed of silicon nitride (Si ₃ N ₄ ). Mainly consisting of the second ceramic composition contained as In the support 860, a plurality of particles 862p different from silicon nitride (Si ₃ N ₄ ) are dispersed as a second ceramic composition. The particles 862 p are crystal particles relatively smaller than crystal particles of silicon nitride (Si ₃ N ₄ ). The support 860 comprises an adjacent region 866 adjacent to the heating resistor 810.

A plurality of particles 868 are dispersed in the adjacent area 866 of FIG. 4C. In particle 868, a component different from the component included in the second ceramic composition (ie, silicon nitride (Si ₃ N ₄ ) and a component contained in the second ceramic composition as a component for reducing the thermal expansion difference between heating resistor 810 and support 860) There is a component different from particles 862p) and having a thermal expansion coefficient higher than that of silicon nitride (Si ₃ N ₄ ). The components present in the particles 868 are at least one element of chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), zirconium (Zr) and tantalum (Ta), Alternatively, silicon carbide (SiC) is preferable.

  In the adjacent region 866 in FIG. 4C, particles 862 p and particles 868 may be mixed. The concentration of particles 868 in adjacent region 866 in FIG. 4C may increase as it approaches heating resistor 810 and may decrease as it moves away from heating resistor 810.

  In the present embodiment, the adjacent region 866 in which the plurality of particles 868 are dispersed is formed only in the folded portion 815. The adjacent region 866 may be at least a region formed in the folded portion 815. The adjacent region 866 may be a region formed in a part of the folded portion 815, or may be a region formed in the whole of the folded portion 815. The adjacent region 866 may be a region formed in part of the conductive portions 812 and 818 in addition to the folded portion 815, or may be a region formed on the entire of the conductive portions 812 and 818.

  The thickness T of the adjacent region 866 is preferably 10 to 200 μm (micrometers) from the heating resistor 810. More preferably, the thickness T of the adjacent region 866 is 20 to 100 μm from the heating resistor 810. The evaluation of the thickness T of the adjacent region 866 will be described later.

  The average particle size of the plurality of particles 868 is preferably 5 μm or less. The evaluation of the average particle diameter of the particles 868 will be described later.

  The relationship between the cross-sectional area S1 of the heating resistor 810 cut at the position where the adjacent region 866 is formed and the cross-sectional area S2 of the support 860 is 0.5% ≦ S1 / (S1 + S2) × 100% ≦ 25% It is preferable to satisfy. The cross-sectional area S1 is a cross-sectional area obtained by adding the cross-sectional area S1a of one of the folded portions 815 and the cross-sectional area S1b of one of the folded portions 815 (see FIG. 3). Cross-sectional area S2 is a cross-sectional area including adjacent region 866. S1 / (S1 + S2) is a resistor cross-sectional ratio Rs indicating the ratio of the cross-sectional area of the heating resistor 810 to the cross-sectional area of the ceramic heater 800. The evaluation of the resistor cross-sectional ratio Rs will be described later.

  The relationship between the cross-sectional area S1 of the heating resistor 810, the cross-sectional area S2 of the support 860, and the thickness T of the adjacent region 866 preferably satisfies T · (S1 + S2) / S1 ≧ 67 μm. In other words, the relationship between the resistor cross-sectional ratio Rs and the thickness T of the adjacent region 866 preferably satisfies T / RsT67 μm. The evaluation of the value T / Rs will be described later.

A2. How to make glow plugs:
FIG. 5 is a process chart showing a method of manufacturing the glow plug 10. In producing the glow plug 10, first, the manufacturer produces an intermediate product of the heating resistor 810 by an injection molding method (process P110).

  After producing the intermediate product of the heating resistor 810 (Step P110), the manufacturer applies the particle material which is the material of the particles 868 to the folded portion 815 in the intermediate of the heating resistor 810 (Step P120). In the present embodiment, the manufacturer applies the particulate material to the intermediate product of the heating resistor 810 by immersing the intermediate product of the heating resistor 810 in the liquid particle material.

  After applying the particulate material to the intermediate product of the heating resistor 810 (process P120), the manufacturer produces an intermediate product of the support 860 by a die press molding method (process P130). In the present embodiment, the intermediate product of the support 860 is composed of two members divided in a plane passing through the axial center SC, and a groove into which the intermediate product of the heating resistor 810 is fitted is formed inside these members It is done. In another embodiment, the preparation of the intermediate product of the support 860 (step P130) is either the preparation of the intermediate product of the heating resistor 810 (step P110) and the application of the particulate material (step P120). May be implemented prior to the

  After producing the intermediate product of the support 860 (process P130), the manufacturer produces a composite molded body combining the intermediate of the heating resistor 810 and the intermediate product of the support 860 (process P140).

  After producing the composite molded body (process P140), the manufacturer bakes the composite molded body to produce the ceramic heater 800 (process P150). After producing the ceramic heater 800 (process P150), the manufacturer assembles the ceramic heater 800 into another component (the center shaft 200, the metal shell 500, the outer cylinder 700, etc.) that constitutes the glow plug 10 (process P190). . Thus, the glow plug 10 is completed.

  If the melting point of the component forming particle 868 is lower than the firing temperature in the firing (process P150), the manufacturer uses the injection molding material to which the particle material which is the raw material of particle 868 is added. The intermediate product of may be prepared by injection molding (process P115). The particulate material contained in the intermediate of the heating resistor 810 forms an adjacent region 866 by diffusing to the support 860 in the firing (process P150). In this case, the particle size of the particles 868 tends to decrease with distance from the heating resistor 810 as shown in FIG. 4A. When the firing temperature in the firing (step P150) is 1700 to 1900 ° C., the particulate material that can be added to the injection molding material is at least one element of chromium (Cr), titanium (Ti) and zirconium (Zr), Or at least one silicide or oxide of these elements.

A3. Glow plug rating:
6 and 7 are tables showing the results of evaluating the performance of the glow plug 10. In the evaluation tests of FIG. 6 and FIG. 7, the tester evaluated the samples 1 to 25 which are the glow plugs 10 having different specifications of the ceramic heater 800.

The cross-sectional area (S1 + S2) of the ceramic heater 800 in the samples 1 to 25 is constant at 7.54 mm ² . In the ceramic heater 800 of the sample 1, the adjacent region 866 is not formed. An adjacent region 866 is formed in the ceramic heater 800 of the samples 2 to 25.

The material of the support 860 in the samples 1 to 22 contains silicon nitride (Si ₃ N ₄ ) as a main component, and contains erbium (Er) oxide and silicon dioxide (SiO ₂ ) as a sintering aid. The material of the support 860 in the samples 23 and 24 contains silicon nitride (Si ₃ N ₄ ) as a main component, and ytterbium (Yb) oxide and aluminum oxide (Al ₂ O ₃ ) as sintering aids. And molybdenum silicide (MoSi ₂ ) as an additive component for adjusting the thermal expansion difference with the heating resistor 810. The material of the support 860 may contain tungsten disilicide (WSi ₂ ) as an additive component for adjusting the difference in thermal expansion with the heating resistor 810. The material of the support 860 in the sample 25 contains silicon nitride (Si ₃ N ₄ ) as a main component, and contains erbium (Er) oxide and aluminum oxide (Al ₂ O ₃ ) as a sintering aid. At grain boundaries in the support 860 of Samples 1 to 25, components (for example, rare earth elements and aluminum elements) derived from the respective sintering aids are present. The component derived from the rare earth oxide of the sintering aid may be at least one of a rare earth element-containing disilicate and a monosilicate.

Samples 1～22,24,25 is produced by firing in nitrogen (N _2). The sample 23 is produced by firing in argon (Ar).

In Samples 2 to 11 and 16 to 22, the particle material which is the material of the particle 868 is any of chromium (Cr), molybdenum (Mo), tungsten (W), and chromium oxide (Cr ₂ O ₃ ), and ceramic It becomes a silicide by reacting with the silicon nitride of the support 860 in the firing step in manufacturing the heater 800. The particle material of the sample 12 is silicon carbide (SiC), which is a particle composition that is the main component of the particles 868. The particulate material of sample 13 is chromium silicide (CrSi ₂ ). The particulate material of sample 14 is molybdenum silicide (MoSi ₂ ). The particulate material of the sample 15 is tungsten silicide (WSi ₂ ).

In sample 23, the particle material which is the material of particles 868 is chromium (Cr). As shown in FIG. 4C, a plurality of particles 862 p made of molybdenum silicide (MoSi ₂ ) are dispersed in crystal particles made of silicon nitride (Si ₃ N ₄ ) on a support 860 of sample 23. A plurality of particles 868 are dispersed in an adjacent region 866 in the support 860 of the sample 23. The tester used molybdenum (Mo) and silicon (Mo) as a component present in the particles 868 of the sample 23 using an electron probe microanalyzer (EPMA) and a scanning electron microscope (SEM). The presence of each component of Si) and chromium (Cr) was confirmed. In the sample 23, the component localized in the adjacent region 866 among the components of the particle 868 is chromium (Cr).

In sample 24, the particulate material that is the material of particles 868 is chromium (Cr). As shown in FIG. 4C, a plurality of particles 862p made of molybdenum silicide carbide (Mo _4.8 Si ₃ C _0.6 ) are contained in crystal particles made of silicon nitride (Si ₃ N ₄ ) on the support 860 of sample 24. scatter. A plurality of particles 868 are dispersed in an adjacent region 866 in the support 860 of the sample 24. The tester uses EPMA and SEM to detect the presence of each component of molybdenum (Mo), silicon (Si), carbon (C) and chromium (Cr) as components present in the particle 868 of the sample 24. It was confirmed. Of the components of the particle 868 in the sample 24, the component localized in the adjacent region 866 is chromium (Cr). The carbon (C) in the particles 862p and the particles 868 is considered to be derived from a heating aid 810 and a forming aid (binder) added when forming the support 860.

In sample 25, the particle material which is the material of particles 868 is chromium (Cr), and chromium silicide (CrSi ₂ ) reacts by reacting with silicon nitride of support 860 in the firing step of producing ceramic heater 800. become.

  The examiner observed the cross section of the ceramic heater 800 cut along a plane orthogonal to the axial center SC using Samples Electron Beam Microanalyzer (EPMA: Electron Probe MicroAnalyzer) for Samples 1 to 25. The tester calculated the thickness T of the adjacent region 866, the average particle diameter of the particles 868, the resistor cross-sectional ratio Rs, and the value T / Rs by image analysis of the image by EPMA.

  The examiner prepares a plurality of samples for each of the samples 2 to 25 and uses the scanning electron microscope (SEM: Scanning Electron Microscope) to cut the ceramic heater 800 along a plane orthogonal to the axial center SC. The adjacent area 866 was observed at a magnification of 3000 times. The examiner calculated the proportion of the sample in which the pores of 0.1 μm or more which can be confirmed in the image by SEM are present in the adjacent region 866 as the proportion of the porous sample by image analysis of the image by SEM.

  FIG. 10 is an explanatory view showing an example of an image used for analysis of a sample. The analysis images shown in FIGS. 10A, 10B, and 10C are images obtained by analyzing the same portion in the cross section of the sample 24 cut along a plane orthogonal to the axial center SC.

  FIG. 10A is an image of a cross section of the ceramic heater 800 taken using an SEM. FIG. 10B is a mapping image showing the distribution of chromium (Cr) in the cross section of the ceramic heater 800 using EPMA. FIG. 10C is a mapping image showing the distribution of molybdenum (Mo) in the cross section of the ceramic heater 800 using EPMA.

  In the image analysis using EPMA, qualitative analysis on the cross section of the ceramic heater 800 was performed as a first step using a wavelength dispersive X-ray spectrometer (WDS) provided in EPMA. The elements contained in the cross section of the ceramic heater 800 were identified by this qualitative analysis.

  As a second step, measurement conditions for obtaining a mapping image representing the distribution of each element identified in the first step were determined. The analysis interval and the irradiation beam diameter were determined as measurement conditions of the mapping image by subdividing the observation area into a grid shape to the extent that the required analysis accuracy can be ensured. As a measurement condition of the mapping image, the flow rate and the uptake time of the irradiation beam were determined so as to obtain an X-ray intensity (count number) capable of visually recognizing a change in the detected amount of trace element as a color tone change.

Specific measurement conditions are shown below.
・ Acceleration voltage: 15kV (kilovolt)
Probe current: 1.0 × 10 ^-7 A (ampere)
Beam irradiation diameter (minimum diameter): less than 0.003 μm Observation area (longitudinal × horizontal): 100 μm × 100 μm
Analysis interval: 0.4 μm
・ Measurement point: 250 points x 250 points (62,500 points)
Main peak acquisition time: 15 ms (milliseconds)
・ Background capture time: 15 ms

  As a third step, for each element identified in the first step, the detection amount in the observation region was measured under the measurement conditions determined in the second step. Specifically, at each measurement point in the observation area, after capturing the main peak, the background at the low angle side is captured. A two-dimensional display of the X-ray intensity obtained by removing the background from the main peak of each measurement point was obtained as a color tone change to obtain a mapping image of each element (see FIGS. 10B and 10C). .

  From the comparison between FIG. 10A and FIG. 10C, it can be seen that a plurality of particles containing a molybdenum (Mo) element are dispersed in a support 860. From the comparison of FIG. 10A, FIG. 10B and FIG. 10C, in the adjacent region 866 adjacent to the turnback portion 815 of the heating resistor 810, the chromium (Cr) element as well as the molybdenum (Mo) element It can be seen that a plurality of existing particles are distributed unevenly on the side of the heating resistor 810.

The tester measured the resistance value of the glow plug 10 which was an unused sample. Thereafter, the tester raises the surface temperature of the ceramic heater 800 to 1000 ° C. one second after the start of energization by applying a voltage of 11 V to the glow plug 10, and further raises the temperature to 1350 ° C. The Thereafter, the tester forcibly cooled the ceramic heater 800 using air. The tester carried out an endurance test repeated 50,000 times with one cycle from temperature increase to cooling of the ceramic heater 800 for each sample. After the endurance test, the tester again measures the resistance value of the glow plug 10 to calculate the rate of increase in resistance, which indicates the rate at which the resistance value of the glow plug 10 increases before and after the endurance test. The increase in the resistance value of the glow plug 10 is considered to be due to the deterioration of the heating resistor 810 (in particular, the folded portion 815). The examiner evaluated the durability of each sample based on the following evaluation criteria.
優 (Excellent): Resistance increase rate 10% or less ○ (Good): Resistance increase rate 10% or more and 20% or less × (Not applicable): Resistance increase rate 20% or more

  According to the comparison between Samples 1, 2 and 9 and Samples 3 and 5 to 8, the thickness T of the adjacent region 866 is 10 to 200 μm from the heating resistor 810 from the viewpoint of securing the durability of the heating resistor 810. Is preferred. Furthermore, according to the comparison between Samples 3 and 8 and Samples 5 to 8, the thickness T of the adjacent region 866 is more preferably 20 to 100 μm from the heating resistor 810 from the viewpoint of securing durability.

  From the viewpoint of securing the durability of the heating resistor 810, the average particle diameter of the particles 868 is preferably 5 μm or less according to the comparison between the samples 5 and 10 to the samples 18 and 19. In the samples 18 and 19 in which the average particle diameter of the particles 868 exceeds 5 μm, the pores in the adjacent region 866 are considered to be one of the factors causing deterioration of the heating resistor 810 because the pores are present in the adjacent region 866.

According to the comparison between Sample 18 and Sample 25, from the viewpoint of suppressing the pores in the adjacent region 866, the support 860 contains a component derived from erbium (Er) oxide and aluminum oxide (Al ₂ O ₃ ). Is preferred. Thereby, the durability of the heat generating resistor 810 can be improved.

  According to the comparison between the samples 4, 5, 21 and the sample 20, the rate of increase in resistance of the sample 20 having the resistor cross-sectional ratio Rs less than 0.5% is larger than that of the samples 4, 5, 21. In the case of the sample 22 in which the resistance cross section ratio Rs exceeds 25%, the resistance value of the folded portion 815 can not be sufficiently secured, so that the sample 22 can not achieve the rapid temperature rising characteristic reaching 1000 ° C. one second after energization. . Therefore, from the viewpoint of securing the durability of the heating resistor 810 while securing the rapid temperature rising characteristic, the resistor cross-sectional ratio Rs is preferably 0.5% or more and 25% or less.

  From the viewpoint of securing the durability of the heating resistor 810, the value T / Rs is preferably 67 μm or more according to the comparison between the sample 2 and the samples 3 to 8 and 10 to 22.

  According to the comparison between the sample 5 and the sample 13, the comparison between the sample 10 and the sample 14, and the comparison between the sample 11 and the sample 15, even if the particle material is a material that becomes a silicide by firing, It can be seen that the durability of the heating resistor 810 can be equally secured even with a material that is a silicide.

  According to the results of Samples 23 and 24, as shown in FIG. 4C, it can be seen that the durability of the heating resistor 810 can be improved even with the structure of the support 860 in which the particles 862p and the particles 868 are dispersed.

A4. effect:
According to the first embodiment described above, the thermal expansion difference between the heating resistor 810 and the support 860 is alleviated in the adjacent region 866, whereby the heat generation resistance due to the thermal expansion difference from the support 860 is obtained. The thermal stress of the body 810 can be suppressed. As a result, the durability of the heat generating resistor 810 can be improved.

  When the thickness T of the adjacent region 866 is 10 to 200 μm from the heating resistor 810, the adjacent region 866 can effectively suppress the thermal stress of the heating resistor 810. Furthermore, when the thickness T of the adjacent region 866 is 20 to 100 μm from the heating resistor 810, the adjacent region 866 can more effectively suppress the thermal stress of the heating resistor 810.

  In addition, when the average particle diameter of the plurality of particles 868 is 5 μm or less, the formation of pores in the adjacent region 866 can be suppressed. In addition, it is possible to suppress fine cracks generated around the particles 868 due to the thermal expansion difference between the particles 868 and the periphery thereof. As a result, the durability of the adjacent region 866 can be improved, which in turn can improve the durability of the heating resistor 810.

  When the resistor cross-sectional ratio Rs satisfies 0.5% ≦ Rs ≦ 25%, the durability of the heat generating resistor 810 can be improved while securing the rapid temperature rising characteristic.

  In addition, when the value T / Rs satisfies 67 μm or more, the thermal stress of the heating resistor 810 can be sufficiently suppressed by the adjacent region 866.

  Further, since the adjacent region 866 is a region adjacent to at least the turn-back portion 815, it is possible to suppress the thermal stress generated in the turn-back portion 815 having a relatively large amount of heat generation.

  Further, since the first ceramic composition forming the heating resistor 810 and the second ceramic composition forming the support 860 contain silicon nitride as a common component, the heating resistor 810 and the support The mechanical strength of the heat generating resistor 810 can be improved by strengthening the bonding force between 860 and 860. Therefore, the durability of the heat generating resistor 810 can be further improved.

B. Second embodiment:
FIG. 8 is an explanatory view showing a cross section of a ceramic heater 800B in the second embodiment. The glow plug 10 of the second embodiment is the same as the first embodiment except that a ceramic heater 800B is provided instead of the ceramic heater 800 of the first embodiment.

  The ceramic heater 800B of the second embodiment is the same as the first embodiment except that the shape of the heating resistor 810 is different. The heating resistor 810 of the second embodiment is a member formed by printing, and is the same as the first embodiment except that the cross-sectional shape cut along a plane orthogonal to the axial center SC is different.

  The major diameter L1 of the folded portion 815 in the heating resistor 810 is preferably 0.4 to 1.0 mm. The major diameter L1 of the folded back portion 815 may be smaller than 0.4 or larger than 1.0 mm.

  The short diameter L2 of the folded portion 815 in the heating resistor 810 is preferably 0.02 to 0.3 mm. The major diameter L1 of the folded back portion 815 may be smaller than 0.02 or larger than 0.3 mm.

  FIG. 9 is a process chart showing a method of manufacturing the glow plug 10 in the second embodiment. In producing the glow plug 10, first, the manufacturer produces an intermediate product of the support 860 by a die press molding method (process P210). In the present embodiment, the intermediate product of the support 860 is composed of two members divided by a plane passing through the axial center SC, and a groove corresponding to the heating resistor 810 is formed inside these members. .

  After producing the intermediate product of the support 860 (process P210), the manufacturer applies the particulate material to the groove of one member which is the intermediate of the support 860 by printing (process P220).

  After applying the particulate material to the intermediate of the heating resistor 810 (Step P220), the manufacturer prints the heating resistor 810 by printing on the particulate material applied to the intermediate of the support 860 (Step P220) Process P230).

  After printing the heating resistor 810 on the intermediate product of the heating resistor 810 (step P230), the manufacturer applies the particulate material by printing on the heating resistor 810 printed on the intermediate of the support 860. Then (process P240).

  After applying the particulate material to the intermediate product of the heating resistor 810 (Step P240), the manufacturer forms a composite molded body in which the heating resistor 810 is sandwiched between two members which are the intermediate of the heating resistor 810. Perform (Step P250).

  After producing the composite molded body (process P250), the manufacturer bakes the composite molded body to produce the ceramic heater 800B (process P260). After producing the ceramic heater 800B (process P260), the manufacturer assembles the ceramic heater 800B into another component (the center shaft 200, the metal shell 500, the outer cylinder 700, etc.) constituting the glow plug 10 (process P290). . Thus, the glow plug 10 is completed.

  If an intermediate product of the support 860 is prepared (Step P210), the manufacturer can produce particles, which are the raw material of the particles 868, if the melting point of the silicide forming the particles 868 is lower than the calcination temperature in calcination (Step P260). Using the printing material to which the material is added, the heating resistor 810 may be printed by a printing method in the groove of one member which is an intermediate product of the support 860 (process P235). The particulate material contained in the intermediate of the heating resistor 810 forms an adjacent region 866 by diffusing to the support 860 in the firing (step P260). In this case, the particle size of the particles 868 tends to decrease with distance from the heating resistor 810 as shown in FIG. 4A. When the firing temperature in the firing (step P260) is 1700 to 1900 ° C., the particulate material that can be added to the printing material is at least one silicide of chromium (Cr), titanium (Ti) and zirconium (Zr) Or oxide.

  According to the second embodiment described above, the durability of the heat generating resistor 810 can be improved as in the first embodiment.

C. Other embodiments:
The present invention is not limited to the above-described embodiments, examples, and modifications, and can be implemented with various configurations without departing from the scope of the invention. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in the respective forms described in the section of the summary of the invention are for solving some or all of the problems described above, or It is possible to replace or combine as appropriate in order to achieve part or all of the above-mentioned effects. Also, if the technical features are not described as essential in the present specification, they can be deleted as appropriate.

10: glow plug 90: internal combustion engine 100: terminal 200: central shaft 300: insulating member 400: insulating member 500: main metal fitting 510: axial hole 520: tool engagement portion 540: external thread portion 600: ring 700: outer cylinder 710 ... Axial hole 800: ceramic heater 800 B: ceramic heater 810: heating resistor 811: terminal portion 812: conductive portion 815: folded portion 818: conductive portion 819: terminal portion 860: support 862: solid phase 862 p: particles 866: adjacent region 868 ... particle

Claims (11)

A heating resistor made of a first ceramic composition and generating heat when energized;
A second ceramic composition different from the first ceramic composition, which mainly comprises a second ceramic composition containing silicon nitride (Si ₃ N ₄ ) as a main component, and the heat generating resistor comprises A support embedded and supporting the heating resistor;
The support is a third ceramic having a thermal expansion coefficient higher than that of silicon nitride (Si ₃ N ₄ ) in the adjacent region adjacent to the heating resistor, in the solid phase made of the second ceramic composition. A glow plug characterized in that a plurality of particles made of a composition include adjacent regions dispersed in a localized manner on the heat generating resistor side. The third ceramic composition comprises at least one element of chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), zirconium (Zr), and tantalum (Ta). The glow plug according to claim 1, wherein the glow plug comprises silicon carbide (SiC).   The glow plug according to claim 1, wherein a thickness of the adjacent region is 10 to 200 μm from the heating resistor.   The glow plug according to any one of claims 1 to 3, wherein the thickness of the adjacent region is 20 to 100 m from the heat generating resistor.   The glow plug according to any one of claims 1 to 4, wherein an average particle diameter of the plurality of particles is 5 m or less.   The relationship between the cross-sectional area S1 of the heat-generating resistor cut at the position where the adjacent area is formed and the cross-sectional area S2 of the support is 0.5% ≦ S1 / (S1 + S2) × 100% ≦ 25% The glow plug according to any one of claims 1 to 5, wherein the glow plug is filled.   The relationship between the cross-sectional area S1 of the heating resistor cut at the position where the adjacent area is formed, the cross-sectional area S2 of the support, and the thickness T of the adjacent area is T · (S1 + S2) / S1 ≧ 67 μm The glow plug according to any one of claims 1 to 6, wherein A glow plug according to any one of claims 1 to 7, wherein
The heating resistor is
A folded portion having a folded shape,
And a conductive portion having a cross section larger than the turnaround portion and connected to the turnaround portion;
The glow plug, wherein the adjacent area is an area adjacent to at least the folded portion.   The glow plug according to any one of claims 1 to 8, wherein the heat generating resistor is a member formed by an injection molding method or a printing method.   The glow plug according to any one of claims 1 to 9, wherein the first ceramic composition and the second ceramic composition contain common components.   The glow plug according to any one of claims 1 to 10, wherein the second ceramic composition contains a rare earth element and an aluminum (Al) element.