JP6392004B2 - Heater and glow plug - Google Patents

Description

  The present invention relates to a heater and a glow plug.

  A heater provided in a glow plug or the like includes a heating resistor and a support that supports the heating resistor. The heating resistor includes, for example, tungsten carbide as a conductive material and silicon nitride. The support also includes silicon nitride. The heater is manufactured by embedding heating resistors in a support body and sintering them. When sintering, it is difficult to sinter with silicon nitride alone. For example, a sintering aid containing rare earth and silicon is added to the heating resistor and the support, respectively, and liquid phase sintering is performed. (See, for example, Patent Documents 1 and 2).

International Publication No. 03/092330 Japanese Patent No. 3933345

  However, depending on the composition of the sintering aid added to the heating resistor and the support, the temperature at which shrinkage starts between the heating resistor and the support may be different during the sintering of the heater. If the shrinkage start temperature is different between the heating resistor and the support, the respective shrinkage behaviors are also different.Therefore, tensile stress is applied to at least one of the heating resistor and the support, and there is a gap at the interface between the heating resistor and the support. (Crack) may occur. Therefore, there is a demand for a technique that can suppress the occurrence of cracks in the heater.

  Further, when the heater is sintered, a part of the material may volatilize as a gas component. However, in the prior art such as Patent Document 1, such a phenomenon is not taken into consideration, and the blending ratio of materials at the raw material stage of the heater is often shown. Therefore, in the present invention, the inventors have found a condition capable of suppressing the occurrence of cracks based on the composition of the material after the heater is fired.

The present invention has been made to solve the above-described problems, and can be realized as the following forms.
The first aspect of the present invention is:
A heating resistor including a heating portion and a lead portion connected to the heating portion;
A heater comprising silicon nitride and a rare earth, and supporting the heating resistor in contact with the heating resistor,
At least one of the heat generating part and the lead part includes silicon nitride and rare earth,
Of the heat generating portion and the lead portion, when the specific member includes silicon nitride and rare earth,
A value obtained by converting the amount of rare earth contained in the specific member into the molar fraction of the first rare earth oxide is A1, and the oxygen contained in the first rare earth oxide from the amount of oxygen contained in the specific member. The value obtained by subtracting the amount of excess oxygen, which is converted to the molar fraction of silicon dioxide using the amount of silicon contained in the specific member, is B1, and the R1 value is R1 = B1 / (A1 + B1).
The amount of rare earth contained in the support is converted to the molar fraction of the second rare earth oxide as A2, and the oxygen contained in the second rare earth oxide is determined from the amount of oxygen contained in the support. When the amount of surplus oxygen obtained by subtracting the amount is converted to the mole fraction of silicon dioxide using the amount of silicon contained in the support is B1, and the R2 value is R2 = B2 / (A2 + B2) In addition,
The absolute value of the difference between the R1 value and the R2 value is 0.5 or less,
The specific member is the heat generating portion;
A value obtained by converting the amount of rare earth contained in the lead portion into the molar fraction of the third rare earth oxide is A3, and the oxygen contained in the third rare earth oxide from the amount of oxygen contained in the lead portion. When the amount of surplus oxygen obtained by subtracting the amount is converted to the molar fraction of silicon dioxide using the amount of silicon contained in the lead portion is B3, and the R3 value is R3 = B3 / (A3 + B3) In addition,
The absolute value of the difference between the R3 value and the R2 value is 0.5 or less,
The heat generating part and the lead part are each formed of different materials including silicon nitride and rare earth,
The R1 value is greater than or equal to the R3 value. The present invention can also be realized as the following forms.

(1) According to one aspect of the present invention, the heating resistor includes a heat generating portion and a lead portion connected to the heat generating portion; and includes silicon nitride and a rare earth, and is in contact with the heat generating resistor. And a support that supports the heating resistor. In this heater, when at least one of the heat generating part and the lead part includes silicon nitride and a rare earth, and the heat generating part and the lead part including the silicon nitride and the rare earth as a specific member, A value obtained by converting the amount of rare earth contained in the specific member into the molar fraction of the first rare earth oxide is A1, and the amount of oxygen contained in the first rare earth oxide from the amount of oxygen contained in the specific member The value obtained by subtracting the amount of excess oxygen into the molar fraction of silicon dioxide using the amount of silicon contained in the specific member is B1, and the R1 value is R1 = B1 / (A1 + B1). A value obtained by converting the amount of rare earth contained in the body into the molar fraction of the second rare earth oxide is A2, and the amount of oxygen contained in the second rare earth oxide is determined from the amount of oxygen contained in the support. The amount of excess oxygen deducted When the value converted into the mole fraction of silicon dioxide using the amount of silicon contained in the support is B1, and the R2 value is R2 = B2 / (A2 + B2), the R1 value and the R2 value The absolute value of the difference is 0.5 or less. In the case of such a heater, the ratio of silicon dioxide in the sintering aid added to the material of the specific member of the heating resistor during the manufacture of the heater and the sintering added to the material of the support. Since the ratio of silicon dioxide in the binder becomes approximately the same, the temperature at which the liquid phase is generated during firing of the heater is close to the specific member and the support. Therefore, it is possible to align the timing at which the specific member and the support start to shrink, and as a result, it is possible to suppress the occurrence of a gap (crack) at the interface between the specific member and the support.

(2) In the heater of the above aspect, both the R1 value and the R2 value may be 0.55 or more. In such a form, it is possible to suppress generation of a crystal layer containing nitrogen (such as a melilite phase or a J phase) in the heater, thereby improving the oxidation resistance which is the basic performance of the heater. be able to.

(3) In the heater of the above aspect, both the R1 value and the R2 value may be 0.85 or less. With such a configuration, it is possible to suppress the SiO ₂ phase from being excessively formed in the heater, and thus it is possible to improve the heat resistance, which is the basic performance of the heater.

(4) In the heater of the above aspect, a value obtained by subtracting the R1 value from the R2 value may be −0.08 or more and 0.1 or less. In such a form, it is possible to suppress the concentration (segregation) of the grain boundary layer at the interface between the specific member and the support, and therefore, the occurrence of migration is suppressed. Therefore, the change in the resistance value of the specific member can be reduced.

(5) In the heater of the above aspect, the specific member is the heat generating portion, and a value obtained by converting the amount of rare earth contained in the lead portion into a molar fraction of a third rare earth oxide is A3, and the lead The amount of excess oxygen obtained by subtracting the amount of oxygen contained in the third rare earth oxide from the amount of oxygen contained in the part was converted to the mole fraction of silicon dioxide using the amount of silicon contained in the lead part. When the value is B3 and the R3 value is R3 = B3 / (A3 + B3), the absolute value of the difference between the R3 value and the R2 value may be 0.5 or less. In such a form, the absolute value of the difference between the R1 value and the R2 value and the absolute value of the difference between the R3 value and the R2 value are both 0.5 or less. Therefore, it is possible to more effectively suppress the occurrence of a gap (crack) at the interface between the heating resistor and the support.

(6) In the heater according to the above aspect, the heat generating portion and the lead portion may be formed of different materials including silicon nitride and rare earth, and the R1 value may be equal to or greater than the R3 value. With such a configuration, when the heater is sintered, the heat generating portion contracts faster than the lead portion, so that the heat generating portion is suppressed from being pulled by the contraction of the lead portion. Therefore, it is possible to suppress the occurrence of a gap (crack) between the heat generating portion and the lead portion. Here, the concept of “different materials including silicon nitride and rare earth” includes materials in which elements included other than silicon nitride and rare earth are completely different, and the elements included are the same. Materials with different element contents are also included.

(7) According to the other form of this invention, a glow plug provided with the heater of the form in any one of the said forms is provided. With such a configuration, a highly durable glow plug can be provided.

  The present invention is not limited to the form as the heater or glow plug described above, and can be realized in various forms. For example, it can be realized in the form of a heater, a glow plug manufacturing method, an ignition device including a glow plug, a vehicle, or the like.

It is explanatory drawing which shows the partial cross section of a glow plug. It is explanatory drawing which shows the detailed structure of a heater. It is a perspective view which shows the outline | summary of the preparation methods of a heater. It is explanatory drawing which shows the structure of the heater produced with two materials.

A. Embodiment:
FIG. 1 is an explanatory view showing a partial cross section of a glow plug 10 as an embodiment of the present invention. In FIG. 1, with the axis SC of the glow plug 10 as a boundary, the appearance shape of the glow plug 10 is generally illustrated on the right side of the drawing, 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 “front end side”, and the upper side of FIG. 1 is referred to as “rear end side”.

  The glow plug 10 includes a heater 800 that generates heat. The heater 800 functions as a heat source that assists ignition when starting the internal combustion engine 90 such as a diesel engine. In addition to the heater 800, the glow plug 10 includes a middle shaft 200, a metal shell 500, and an outer cylinder 700. The axis SC of the glow plug 10 is also the axis of each member constituting the glow plug 10.

  The middle shaft 200 is a metal body having conductivity. The middle shaft 200 has a cylindrical shape extending around the axis SC. The middle shaft 200 relays electric power supplied from the outside of the glow plug 10 to the heater 800. The middle shaft 200 receives power from the outside of the glow plug 10 via the terminal 100 on the rear end side of the middle shaft 200. In another embodiment, the middle shaft 200 may receive power supply directly from the outside of the glow plug 10 on the rear end side of the middle shaft 200. In the present embodiment, the middle shaft 200 is electrically connected to one of the two electrode portions 838 (FIG. 2) provided on the heater 800 via the cylindrical ring 600 on the distal end side of the middle shaft 200. . In another embodiment, the middle shaft 200 may be directly connected to the heater 800 on the distal end side of the middle shaft 200.

  The metal shell 500 is a conductive metal body. The metal shell 500 has a cylindrical shape extending about the axis SC. The metal shell 500 includes a shaft hole 510, a tool engaging portion 520, and a male screw portion 540.

  The shaft hole 510 is a through hole extending around the axis SC. The inner diameter of the shaft hole 510 is larger than the outer shape of the middle shaft 200. Inside the shaft hole 510, the middle shaft 200 is positioned on the shaft center SC, and a gap that electrically insulates the shaft hole 510 and the middle shaft 200 is formed between the shaft hole 510 and the middle shaft 200. In the present embodiment, the middle shaft 200 is attached to the rear end side of the shaft hole 510 via a cylindrical insulating member 300 and an annular insulating member 400.

  The tool engaging portion 520 is configured to be engageable with a tool (not shown) used for attaching and removing the glow plug 10 to and from the internal combustion engine 90. The male thread portion 540 of the metal shell 500 is configured to be fixed to the internal combustion engine 90 by fitting with a female thread formed in the internal combustion engine 90.

  The outer cylinder 700 is a metal body having conductivity. The outer cylinder 700 has a cylindrical shape extending around the axis SC. The rear end side of the outer cylinder 700 is welded to the front end side of the metal shell 500. A heater 800 protrudes from the distal end side of the outer cylinder 700. The material of the outer cylinder 700 is an iron-based alloy, and in this embodiment, is a phyllite-based stainless steel (for example, SUS430). In another embodiment, the material of the outer cylinder 700 may be precipitation hardened stainless steel (for example, SUS630, SUS631, etc.). The outer cylinder 700 has an inner peripheral surface 710 that forms a shaft hole of the outer cylinder 700. A heater 800 is tightly fitted to the inner peripheral surface 710. As a result, the heater 800 is held on the inner peripheral surface 710.

  FIG. 2 is an explanatory diagram showing a detailed configuration of the heater 800. In FIG. 2, the region corresponding to the support 810 is hatched. The heater 800 is a heating element (heating device) made of a ceramic composition. The heater 800 includes a support 810 and a heating resistor 820. The heating resistor 820 includes a heating part 830 and a lead part 836. The heat generating portion 830 is a portion of the heat generating resistor 820 that reaches the maximum temperature when heat is generated.

  The heat generating part 830 includes a folded part 832 and a pair of linear parts 834. A pair of lead portions 836 is connected to the heat generating portion 830. Each lead portion 836 is provided with an electrode portion 838.

  The folded portion 832 of the heat generating portion 830 is provided on the distal end side of the support body 810. The folded portion 832 is a portion that forms a linear shape folded in an arc shape. The folded portion 832 connects between the tips of the pair of linear portions 834. The pair of linear portions 834 are portions extending from both ends of the folded portion 832 to the rear end side.

  The pair of lead portions 836 is a portion extending from each of the pair of linear portions 834 to the rear end side. Two electrode portions 838 provided in the pair of lead portions 836 are exposed on the surface of the support 810. In the present embodiment, in a state where the heater 800 is assembled to the metal shell 500, one of the electrode portions 838 is electrically connected to the central shaft 200 via the ring 600 (FIG. 1), and the other is connected to the outer cylinder 700. Electrically connected.

  The cross section of the heat generating portion 830 (the folded portion 832 and the linear portion 834) is smaller than the cross section of the lead portion 836. Therefore, the electric resistance of the heat generating part 830 is larger than the lead part 836. Therefore, the heater 800 generates heat mainly in the heat generating portion 830 among the lead portion 836 and the heat generating portion 830.

The support 810 is an insulating ceramic made of an electrically insulating ceramic material. The support 810 contacts the heat generating resistor 820 and supports the heat generating resistor 820. The support 810 electrically insulates the heat generating resistor 820 from the outside of the glow plug 10 and transmits heat of the heat generating resistor 820 to the outside of the glow plug 10. In the present embodiment, the support 810 is mainly made of silicon nitride (Si ₃ N ₄ ). For example, the support 810 contains 85 to 95 mass% silicon nitride. The support 810 is, for example, a rare earth (for example, erbium (Er) or ytterbium (Yb)) compound (for example, an oxide) and a silicon (Si) compound (for example, an oxide) as the remaining 5 to 15% by mass. ) And. Rare earth and silicon in these compounds are components contained in the sintering aid blended in the material of the support 810 when the support 810 is produced. In another embodiment, among the silicon nitride included in the support 810, at least part of silicon may be replaced with aluminum (Al), and at least part of nitrogen is replaced with oxygen (O). Also good.

The heat generating portion 830 and the lead portion 836 are conductive ceramics made of a ceramic material having conductivity. In this embodiment, the heat generating portion 830 and the lead portion 836 have the same composition, and are mainly composed of tungsten carbide (WC) as a conductive material and silicon nitride. The heat generating part 830 and the lead part 836 contain, for example, 55 to 70% by mass of tungsten carbide and 28 to 35% by mass of silicon nitride. The exothermic part 830 and the lead part 836 contain, for example, a rare earth (eg, erbium or ytterbium) compound (eg, oxide) and a silicon compound (eg, oxide) as the remaining 2 to 10% by mass. . The rare earth and silicon in these compounds are components contained in the sintering aid blended in these materials when the heat generating portion 830 and the lead portion 836 are produced. In another embodiment, the heat generating portion 830 and the lead portion 836 may be a composition mainly composed of molybdenum disilicide (MoSi ₂ ). In addition, when the lead portion 836 is formed by a printing method or the like, the lead portion 836 may not include silicon nitride.

FIG. 3 is a perspective view showing an outline of a method for manufacturing the heater 800. The manufacturing method of the heater 800 is well known, but is generally as follows. First, a compound obtained by kneading a powder material containing tungsten carbide, silicon nitride, and a sintering aid and an organic binder is melted and fluidized by heating, and this is injection-molded. And the loop-shaped 1st molded object 351 used as the original form of the lead part 836 is formed. Next, the material formed by mixing silicon nitride and sintering aid is press-molded to form the lower second molded body 352a of the second divided molded body 352 that is the original shape of the support 810. To do. Thereafter, the first molded body 351 is accommodated (embedded) in the concave portion 353 formed on the upper surface of the lower second molded body 352a, and a material that becomes the upper second molded body 352b is covered from above, and calcined. And the original form 801 of the heater 800 is integrally formed by performing baking by a hot press method. Thereafter, the shape of the original shape 801 of the heater 800 is processed into a shape shown in FIG. 2 (a columnar shape with a rounded tip) by polishing, and corresponds to the rear end portion of the loop-shaped first molded body 351. The heater 800 is formed by removing the portion. The calcining of the original shape 801 of the heater 800 is performed at a temperature of 600 to 800 ° C., for example. For example, the hot pressing is performed in a non-oxidizing atmosphere in an environment of a temperature of 1700 to 1850 ° C. and a pressure of 350 kgf / cm ² for 1 to 2 hours. The reason why the first molded body 351, which is the original shape of the heat generating portion 830 and the lead portion 836, is formed in a loop shape is to suppress the occurrence of misalignment during press molding. The blending ratio of each material of the first molded body 351 and the blending ratio of each material of the second molded body 352 at the time of manufacture are set in advance so that the content of each material after firing and polishing satisfies each condition described later. Find it experimentally.

  In the heater 800 of this embodiment manufactured as described above, the R1 value and the R2 value defined by the following (1) to (6) satisfy the following condition 1. If the R1 value and the R2 value satisfy the following condition 1, it is possible to suppress the occurrence of cracks at the interface F1 (see FIG. 2) between the heat generating portion 830 of the heat generating resistor 820 and the support 810. it can. The reason why the occurrence of cracks can be suppressed will be described later. In addition, when the heat generating part 830 and the lead part 836 are formed with the same composition (when both the heat generating part 830 and the lead part 836 correspond to the “specific member” in the claims), the R1 value And R2 value satisfy the following condition 1, naturally, cracks are generated not only at the interface between the heat generating portion 830 and the support 810 but also at the interface between the lead portion 836 and the support 810. It is possible to suppress.

<Condition 1> The absolute value of the difference between the R1 value and the R2 value is 0.5 or less.

(1) A1 is a value obtained by converting the amount of rare earth contained in the heat generating portion 830 into the molar fraction of the rare earth oxide (first rare earth oxide).
(2) The amount of oxygen (the amount of surplus oxygen) obtained by subtracting the amount of oxygen contained in the rare earth oxide (first rare earth oxide) of (1) from the amount of oxygen contained in the heat generating portion 830 is determined as the heat generating portion. The value converted into the mole fraction of silicon dioxide using the amount of silicon contained in 830 is defined as B1.
(3) The R1 value is R1 = B1 / (A1 + B1).
(4) A2 is a value obtained by converting the amount of rare earth contained in the support 810 into the molar fraction of the rare earth oxide (second rare earth oxide).
(5) The amount of oxygen (the amount of surplus oxygen) obtained by subtracting the amount of oxygen contained in the rare earth oxide (second rare earth oxide) of (4) above from the amount of oxygen contained in the support 810, A value converted into a mole fraction of silicon dioxide using the amount of silicon contained in 810 is defined as B1.
(6) The R2 value is R2 = B2 / (A2 + B2).

  Moreover, in the said embodiment, it is preferable that R1 value and R2 value further satisfy | fill one or more conditions of the following conditions 2-4. The reason why it is preferable to satisfy these conditions will be described later.

<Condition 2> R1 value and R2 value are both 0.55 or more.
<Condition 3> Both the R1 value and the R2 value are 0.85 or less.
<Condition 4> The value obtained by subtracting the R1 value from the R2 value is not less than −0.08 and not more than 0.1.

  FIG. 4 is an explanatory diagram showing a configuration of a heater 800a made of two kinds of materials. In the above embodiment, in the heater 800, the heat generating portion 830 and the lead portion 836 are formed of the same material. On the other hand, the heat generating portion 830 and the lead portion 836 may be formed of different materials containing rare earth and silicon, respectively (in this embodiment, materials having the same components but different compositions). In this case, the heat generating portion 830 and the lead portion 836 are manufactured and joined by performing injection molding step by step using different materials. Thus, when the heat generating portion 830 and the lead portion 836 are formed of different materials, the R1 value preferably satisfies the following condition 5 in addition to the above condition 1 and the like. The R3 value is a value defined by the following (7) to (9). If the condition 5 is satisfied, it is possible to suppress the occurrence of cracks at the interface F2 between the heat generating portion 830 and the lead portion 836 formed of different materials. The reason why the generation of cracks can be suppressed will be described later.

<Condition 5> The R1 value in the heat generating portion 830 is equal to or greater than the R3 value in the lead portion 836.

(7) A3 is a value obtained by converting the amount of rare earth contained in the lead portion 836 into the molar fraction of the rare earth oxide (third rare earth oxide).
(8) The amount of oxygen (the amount of surplus oxygen) obtained by subtracting the amount of oxygen contained in the rare earth oxide (third rare earth oxide) of (7) from the amount of oxygen contained in the lead portion 836 is determined as the lead portion. The value converted into the mole fraction of silicon dioxide using the amount of silicon contained in 836 is defined as B3.
(9) The R3 value is R3 = B3 / (A3 + B3).

  The R3 value described above preferably satisfies the following condition 1b, which is the same condition as the above condition 1. According to the above condition 1, it is possible to suppress the occurrence of cracks in the “heating portion 830” of the heating resistor 820 and the interface F1 (FIG. 2) between the support 810, whereas Under this condition 1b, it is possible to suppress the occurrence of cracks at the interface F3 (FIG. 4) between the “lead portion 836” of the heating resistor 820 and the support 810. The reason will be described later.

<Condition 1b> The absolute value of the difference between the R3 value and the R2 value is 0.5 or less.

The above conditions are summarized as follows.
<Condition 1> The absolute value of the difference between the R1 value and the R2 value is 0.5 or less.
<Condition 1b> The absolute value of the difference between the R3 value and the R2 value is 0.5 or less.
<Condition 2> R1 value and R2 value are both 0.55 or more.
<Condition 3> R1 value and R2 value are both 0.85 or less.
<Condition 4> The value obtained by subtracting the R1 value from the R2 value is -0.08 or more and 0.1 or less.
<Condition 5> R1 value is R3 value or more.

B. Experimental result:
Hereinafter, the reason why it is preferable that the R1 value, the R2 value, and the R3 value satisfy the above conditions 1 to 5 will be described based on experimental results. In this experiment, 32 types of samples of the glow plug 10 having different compositions of the heat generating portion 830, the support 810, and the lead portion 836 were prepared. The composition of each sample is shown in Table 1 below. Of these samples, sample no. In Nos. 1 to 26, the heat generating portion 830 and the lead portion 836 are made of the same material. In contrast, sample no. In Nos. 27 to 32, the heat generating portion 830 and the lead portion 836 are made of different materials (different compositions).

Table 1 shows the molar fractions of tungsten carbide and silicon nitride for the heat generating portion 830, and also shows the A1, B1, and R1 values. Moreover, about the support body 810, while showing the mole fraction of silicon nitride, A2 value, B2 value, and R2 value are shown. Furthermore, sample no. About 27-32, while showing the mole fraction of tungsten carbide and silicon nitride about lead part 836, A3 value, B3 value, and R3 value are shown. Each of the heat generating portion 830, the support 810, and the lead portion 836 of each sample contains erbium (Er) as a rare earth. Therefore, A1 value, A2 value, and A3 value represent the mole fraction of erbium oxide (Er ₂ O ₃ ).

  The composition of each sample is the EPMA (electron beam microanalyzer) for each sample site (heating unit 830, support 810, lead part 836) at an acceleration voltage of 20 kV, a magnification of 500 times, and a 10 μm square field of view. And by quantitative analysis using EDS (energy dispersive X-ray spectrometer). In addition, the A1 to A3 values, the B1 to B3 values, and the R1 to R3 values were calculated according to the rules (1) to (9) based on the results of this quantitative analysis.

  Each sample shown in Table 1 was evaluated for crack generation rate, oxidation resistance, and resistance change rate. The results of the pass / fail determination based on these evaluations are shown in Table 2 below.

  As for the crack occurrence rate, first, 160 heaters prepared under the same conditions were prepared for each sample. The 160 heaters were each subjected to ultrasonic flaw inspection, and the ratio of those in which cracks were confirmed to be generated was obtained for each sample.

For oxidation resistance, first, two heaters prepared for each sample under the same conditions were prepared. Then, these heaters are left in an electric furnace heated to 1350 ° C. in an air atmosphere for 100 hours, and the weight increase before and after heating is measured for each heater, and the weight increase is divided by the heater surface area. The average was obtained and evaluated. Specifically, when the amount of weight increase is less than 0.4 mg / cm ² , it is determined as pass (“A”), and when it is 0.4 mg / cm ² or more, it is determined as fail (“X”). Judged. This oxidation resistance was evaluated only for samples with a crack occurrence rate of 0.0%.

  Regarding the resistance change rate, first, for each sample, ten glow plugs prepared under the same conditions as the sample were prepared. Then, the cycle of heating to 1350 ° C. in 1 second and then cooling by air cooling for 30 seconds without energization is repeated 100,000 times for each sample, and the resistance value of the heater 800 before and after repeating the cycle 100,000 times The average rate of change was measured. In the case where there was a disconnection after 100,000 cycles, Table 2 describes “disconnection”. The rate of change in resistance was evaluated only for the samples with the oxidation resistance determination result “A”.

  Regarding the determination result, the above-described crack occurrence rate of 0.0%, oxidation resistance “A”, and resistance change rate of 5% or less were determined as “A” having the highest evaluation. Moreover, the crack occurrence rate of 0.0%, oxidation resistance of “A”, and resistance change rate of more than 5% and 10% or less were determined as “B” having the highest evaluation after “A”. For the case where the crack occurrence rate exceeds 0.0%, the oxidation resistance is “X”, and the resistance change rate is “disconnected” or exceeds 10%, the determination result is “ C ”. According to this evaluation standard, a sample with an evaluation of “A” 24 to 26, 28 to 32. Samples with an evaluation of “B” are sample nos. 17, 18, 20, 22, 23, 27. Samples with an evaluation of “C” are sample nos. 1-16, 19, 21.

<Regarding Condition 1 and Condition 1b>
As shown in “Condition 1” in Table 2, for samples (sample Nos. 1, 3, 5, and 7) in which the absolute value of the difference between the R1 value and the R2 value exceeds 0.5, However, the crack occurrence rate exceeds 0.0%. Therefore, if the absolute value of the difference between the R1 value and the R2 value is 0.5 or less as in Condition 1, the occurrence of cracks can be suppressed. This is considered to be due to the following reason. If the difference between the R1 value of the heat generating part 830 and the R2 value of the support 810 is 0.5 or less, the ratio of silicon dioxide in the sintering aid blended with the material of the heat generating part 830 at the time of manufacturing the heater And the ratio of silicon dioxide in the sintering aid to be mixed with the material of the support 810, the temperature at which the liquid phase is generated when the heater 800 is fired is the temperature of the heating unit 830 and the support 810. And get closer. Therefore, it is possible to align the timing at which the heat generating portion 830 and the support 810 start to contract, and as a result, it is possible to suppress the occurrence of a gap (crack) at the interface F1 between the heat generating portion 830 and the support 810. is there.

  In addition, sample No. Referring to “Condition 1b” of 27 to 32, the absolute value of the difference between the R3 value and the R2 value is 0.5 or less, and the crack occurrence rate is 0.0%. Therefore, even if the absolute value of the difference between the R3 value and the R2 value is 0.5 or less, the generation of cracks (specifically, cracks at the interface F3 between the lead portion 836 and the support 810) is suppressed. be able to. That is, when the specific member is the one containing silicon nitride and rare earth among the heat generating portion 830 and the lead portion 836, even if the specific member is the heat generating portion 830, the specific member is the lead portion 836. However, as in Condition 1, the absolute value of the difference between the R1 value (or R3 value) and the R2 value is preferably 0.5 or less. If the absolute value of the difference between the R1 value and the R2 value and the absolute value of the difference between the R3 value and the R2 value are both 0.5 or less, the interfaces F1, F3 between the heating resistor 820 and the support 810 It is possible to more effectively suppress the occurrence of gaps (cracks).

<Condition 2>
As shown in Table 2, samples in which at least one of R1 value and R2 value is less than 0.55 (Sample Nos. 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12) , 13, 14, 15, 16), the determination result was “C”. Therefore, it is preferable that the R1 value and the R2 value are both 0.55 or more as in Condition 2 above. This is because when the R1 value and the R2 value are less than 0.55, the ratio of silicon dioxide in the sintering aid used at the time of manufacturing the heater 800 is small, which causes a decrease in sinterability, and nitrogen. This is considered to be due to the fact that a crystal layer (such as a melilite phase or a J phase) containing phosphine is likely to be generated, resulting in a decrease in oxidation resistance. Therefore, if the R1 value and the R2 value are both 0.55 or more, the durability and oxidation resistance of the heater 800 can be improved.

  In addition, sample No. 27 to 32, the R3 value and the R2 value are both 0.55 or more, and the determination result is the sample No. Except for 27 being “B”, all were “A”. Therefore, when either one of the heat generating portion 830 and the lead portion 836 (one containing silicon nitride and rare earth) is used as the specific member, even if the specific member is the heat generating portion 830, the specific member is the lead. Even in the portion 836, it is preferable that both the R1 value (or R3 value) and the R2 value are 0.55 or more as in the above condition 2.

<Regarding condition 3>
As shown in Table 2, all of the samples (sample Nos. 3, 4, 7, 8, 10, 19, 21) in which at least one of the R1 value and the R2 value exceeds 0.85 are used. The determination result was “C”. Therefore, it is preferable that the R1 value and the R2 value are both 0.85 or less as in Condition 3 above. This is because when the R1 value and the R2 value exceed 0.85, the proportion of silicon dioxide in the sintering aid used during the manufacture of the heater 800 increases, and the heat resistance decreases due to excessive SiO ₂ phase. It is thought that it is to do. Therefore, if the R1 value and the R2 value are both 0.85 or less, the heat resistance of the heater 800 can be improved.

  In addition, sample No. 27 to 32, both of the R3 value and the R2 value are 0.85 or less. Except for 27 being “B”, all were “A”. Therefore, when either one of the heat generating portion 830 and the lead portion 836 (one containing silicon nitride and rare earth) is used as the specific member, even if the specific member is the heat generating portion 830, the specific member is the lead. Even in the portion 836, it is preferable that both the R1 value (or R3 value) and the R2 value are 0.85 or less as in the condition 3 above.

<Condition 4>
As shown in “Condition 4” in Table 2, samples in which the value obtained by subtracting the R1 value from the R2 value is −0.08 or more and 0.1 or less (sample Nos. 9, 10, 11, 14, 17 , 22, 24, 25, 26, 30, 31, 32) are sample nos. With the exception of 9, 10, 11, and 14, all the determination results were “A” or “B”. Therefore, the value obtained by subtracting the R1 value from the R2 value is preferably −0.08 or more and 0.1 or less as in the above condition 4. This is because if the R1 value and the R2 value are in such a relationship, the concentration (segregation) of the grain boundary layer on the interface F1 between the heat generating portion 830 and the support 810 is suppressed, thereby causing a decrease in durability. This is considered to be because it is difficult for the migration to occur, and as a result, an increase in resistance value and disconnection of the heat generating portion 830 can be suppressed.

  In addition, sample No. With reference to “Condition 4b” of 27 to 32, the value obtained by subtracting the R3 value from the R2 value is −0.08 or more and 0.1 or less except for the samples N0.27 and 28. Were all “A”. Therefore, when either one of the heat generating portion 830 and the lead portion 836 (one containing silicon nitride and rare earth) is used as the specific member, even if the specific member is the heat generating portion 830, the specific member is the lead. Even in the part 836, as in Condition 4 above, the value obtained by subtracting the R1 value (or R3 value) from the R2 value is preferably −0.08 or more and 0.1 or less.

<Condition 5>
Referring to “Condition 5” in Table 2, for samples (sample Nos. 27 to 32) having different compositions in the heat generating portion 830 and the lead portion 836, the R1 value in the heat generating portion 830 is the R3 value in the lead portion 836. The above samples, that is, the samples whose R1-R3 values are 0 or more (sample Nos. 28, 29, 31, 32) have generally better determination results than the other samples (samples No. 27, 30). It became. Specifically, any sample having an R1 value equal to or greater than the R3 value has a crack generation rate of 0%, a good oxidation resistance evaluation result, and a resistance change rate of 1 to 3%. became. Therefore, when the heat generating part 830 and the lead part 836 have different compositions, it is preferable that the R1 value in the heat generating part 830 is equal to or greater than the R3 value in the lead part 836 as in Condition 5 above. This is considered to be due to the following reason. The heat generating part 830 is usually thinner than the lead part 836 in order to concentrate heat generation. In this case, the lead part 836 pulls the heat generating part 830 due to shrinkage during sintering. Therefore, generally, cracks are likely to occur at the interface F2 between the lead portion 836 and the heat generating portion 830. However, if the R1 value in the heat generating portion 830 is equal to or greater than the R3 value in the lead portion 836, the heat generating portion 830 contracts faster than the lead portion 836 during the sintering of the heater 800a. It is because it can suppress that the heat-emitting part 830 is pulled by this, and can suppress that a crack generate | occur | produces in those interfaces F2. Further, in the sample in which the R1 value is equal to or greater than the R3 value, as described above, since the tension between the lead portion 836 and the heat generating portion 830 that causes the generation of cracks is suppressed, the grain boundary layer is formed in the gap generated by the tension. Is prevented from segregating. For this reason, migration that causes a decrease in durability is less likely to occur, and as a result, the durability of the heating resistor 820 is improved and the rate of change in resistance can be reduced.

  As described above, if the heater 800 satisfying at least the condition 1 among the above conditions 1 to 5 is manufactured, the heater 800 can be prevented from being cracked. It becomes possible to provide. Moreover, each said condition is derived | led-out by analyzing the composition of the heater 800 after the heater 800 was manufactured instead of the compounding ratio of the material at the time of manufacture of the heater 800. This is because part of the material of the heater 800 may volatilize during sintering, and the mixing ratio of each material may be different during production (before firing) and after production (after firing). It is. Therefore, for example, even if a part of the material of the heater 800 volatilizes during sintering, it can be easily determined whether or not the above conditions are met.

  The present invention is not limited to the above-described embodiments and examples, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features of the embodiments and examples corresponding to the technical features in each form described in the summary section of the invention are intended to solve part or all of the above-described problems or to achieve the above-described effects. In order to achieve part or all of the above, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

For example, in the above-described embodiment, erbium (Er) and ytterbium (Yb) are given as examples of the rare earth contained in the support 810, the heat generating part 830, and the lead part 836. Yttrium (Y), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho) At least one of thulium (Tm) and lutetium (Lu) may be included. The R1 to R3 values may be calculated using these rare earth trivalent oxides. That is, when calculating the R1 to R3 values, the rare earth oxide may be calculated as RE ₂ O ₃ (RE is a rare earth).

DESCRIPTION OF SYMBOLS 10 ... Glow plug 90 ... Internal combustion engine 100 ... Terminal 200 ... Medium shaft 300 ... Insulating member 351 ... 1st molded object 352 ... 2nd molded object 353 ... Recessed part 400 ... Insulating member 500 ... Main metal fitting 510 ... Shaft hole 520 ... Tool engagement 540 ... Male thread 600 ... Ring 700 ... Outer cylinder 710 ... Inner peripheral surface 800, 800a ... Heater 801 ... Heater original 810 ... Support 820 ... Heat generating resistor 830 ... Heat generating part 832 ... Folded part 834 ... Linear part 836 ... Lead part 838 ... Electrode part F1, F2, F3 ... Interface SC ... Axle

Claims (6)

A heating resistor including a heating portion and a lead portion connected to the heating portion;
A heater comprising silicon nitride and a rare earth, and supporting the heating resistor in contact with the heating resistor,
At least one of the heat generating part and the lead part includes silicon nitride and rare earth,
Of the heat generating portion and the lead portion, when the specific member includes silicon nitride and rare earth,
A value obtained by converting the amount of rare earth contained in the specific member into the molar fraction of the first rare earth oxide is A1, and the oxygen contained in the first rare earth oxide from the amount of oxygen contained in the specific member. The value obtained by subtracting the amount of excess oxygen, which is converted to the molar fraction of silicon dioxide using the amount of silicon contained in the specific member, is B1, and the R1 value is R1 = B1 / (A1 + B1).
The amount of rare earth contained in the support is converted to the molar fraction of the second rare earth oxide as A2, and the oxygen contained in the second rare earth oxide is determined from the amount of oxygen contained in the support. When the amount of surplus oxygen obtained by subtracting the amount is converted to the mole fraction of silicon dioxide using the amount of silicon contained in the support is B1, and the R2 value is R2 = B2 / (A2 + B2) In addition,
Ri absolute value der 0.5 or less of a difference between the R2 value and the R1 values,
The specific member is the heat generating portion;
A value obtained by converting the amount of rare earth contained in the lead portion into the molar fraction of the third rare earth oxide is A3, and the oxygen contained in the third rare earth oxide from the amount of oxygen contained in the lead portion. When the amount of surplus oxygen obtained by subtracting the amount is converted to the molar fraction of silicon dioxide using the amount of silicon contained in the lead portion is B3, and the R3 value is R3 = B3 / (A3 + B3) In addition,
The absolute value of the difference between the R3 value and the R2 value is 0.5 or less,
The heat generating part and the lead part are each formed of different materials including silicon nitride and rare earth,
The R1 value is equal to or greater than the R3 value . The heater according to claim 1,
Both the R1 value and the R2 value are 0.55 or more. The heater according to claim 1 or 2,
Both the R1 value and the R2 value are 0.85 or less. A heater according to any one of claims 1 to 3, wherein
A value obtained by subtracting the R1 value from the R2 value is -0.08 or more and 0.1 or less.   A heater according to any one of claims 1 to 4,
  The heater, wherein the heat generating part is narrower than the lead part. A glow plug comprising the heater according to any one of claims 1 to 5 .

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