JP7051381B2 - Spark plug - Google Patents

Description

The present invention relates to a spark plug, and more particularly to a spark plug having a built-in resistor.

A spark plug provided with a resistor is known in order to suppress radio wave noise (Patent Document 1). Patent Document 1 incorporates a resistor containing an oxide semiconductor such as SnO ₂ , a metal such as Zn, Sb, Sn, Ag and Ni, and a conductive non-metal such as C, SiC, TiC, WC and ZrC. The spark plug that was used is disclosed.

JP-A-2007-122879A

However, as the output of the internal combustion engine increases, the energy passing through the resistor during discharge tends to increase, so that further improvement in the durability of the resistor is required.

The present invention has been made in order to meet the above-mentioned requirements, and an object of the present invention is to provide a spark plug capable of improving the durability of a resistor.

In order to achieve this object, the spark plug of the present invention has an insulator having a shaft hole extending in the direction of the axis from the tip side to the rear end side, a center electrode arranged on the tip side of the shaft hole, and a shaft hole. It includes a terminal fitting arranged on the rear end side and a resistor that electrically connects the terminal fitting and the center electrode inside the shaft hole. The resistor is composed of a sintered body containing a metal oxide represented by the general formula AaBbCuCOd, and the element A is at least one selected from the Group 3 elements of the periodic table based on the IUPAC 1990 Recommendation (however, the element) . A is excluding actinides) , element B is at least one selected from Ca, Sr and Ba, and satisfies 0 <a≤2,0≤b≤2,1≤c≤3,3 <d <8. ..

According to the spark plug according to claim 1, the resistor is a metal oxide represented by the general formula AaBbCuCOd (provided that element A is at least one selected from Group 3 elements of the periodic table based on the IUPAC 1990 Recommendation. , Element B is at least one selected from Ca, Sr and Ba, and contains 0 <a ≦ 2,0 ≦ b ≦ 2,1 ≦ c ≦ 3,3 <d <8). It consists of a unit. This metal oxide exhibits metallic electrical conduction and is not affected by the number of carriers seen in the case of oxide semiconductors or the oxidation seen in the case of metals, so that the durability of the resistor can be improved.

According to the spark plug according to claim 2, the element A is at least one selected from La, Ce, Pr, Nd, Sm, Gd, Y and Yb. According to the spark plug according to claim 3, the element A is at least one selected from La, Ce, Nd and Gd. As a result, the stability of the metal oxide can be ensured and the durability of the resistor can be further improved.

According to the spark plug according to claim 4, the conductive glass that contacts the center electrode, the resistor and the insulator and electrically connects the center electrode and the insulator is arranged between the resistor and the insulator. It also comprises a conductive glass, a resistor and an insulating glass that comes into contact with the insulator. In any cross section including the axis, the interface between the insulating glass and the conductive glass is located so that the first point where the interface touches the insulator is located at the rear end side of the second point where the interface touches the resistor. , It is located at the same position in the axial direction as the second point or on the rear end side in the axial direction from the second point. As a result, it is possible to alleviate the concentration of the electric field at the second point on the resistor, so that deterioration of the resistor can be suppressed. Therefore, in addition to the effect of any one of claims 1 to 3, the durability of the resistor can be further improved.

It is one side sectional view of the spark plug in 1st Embodiment of this invention. (A) is a cross-sectional view of a spark plug shown by enlarging the portion shown by IIa in FIG. 1, and (b) is a cross-sectional view showing a part of the spark plug according to the second embodiment in an enlarged manner. .. It is a perspective view which shows the resistor schematically. (A) is an enlarged sectional view showing a part of the spark plug in the third embodiment, and (b) is an enlarged sectional view showing a part of the spark plug in the fourth embodiment. be. FIG. 5 is an enlarged cross-sectional view showing a part of the spark plug in the fifth embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a one-sided cross-sectional view of the spark plug 10 in the first embodiment of the present invention with the axis O as a boundary. In FIG. 1, the lower side of the paper surface is referred to as the front end side of the spark plug 10, and the upper side of the paper surface is referred to as the rear end side of the spark plug 10 (the same applies to FIGS. 2 to 5). The spark plug 10 includes an insulator 11, a center electrode 14, and a terminal fitting 15.

The insulator 11 is a ceramic member such as alumina which is excellent in mechanical properties and insulating properties at high temperatures, and an inner peripheral surface 12 is formed by penetrating a shaft hole along the axis O. The inner peripheral surface 12 is provided with a rear end facing surface 13 facing the rear end side on the front end side. The inner diameter of the rear end facing surface 13 gradually decreases toward the tip.

The center electrode 14 is a rod-shaped member extending along the axis O, and a core material containing copper or copper as a main component is covered with nickel or a nickel-based alloy. The center electrode 14 is locked to the rear end facing surface 13, and the tip is exposed from the shaft hole of the insulator 11.

The terminal fitting 15 is a rod-shaped member to which a high-voltage cable (not shown) is connected, and is made of a conductive metal material (for example, low carbon steel or the like). The terminal fitting 15 is fixed to the rear end of the insulator 11 with the tip end side inserted into the shaft hole.

The main metal fitting 16 is fixed to the tip side of the outer periphery of the insulator 11 with a gap between the terminal metal fitting 15 and the axis O direction. The main metal fitting 16 is a substantially cylindrical member made of a conductive metal material (for example, low carbon steel or the like). The main metal fitting 16 includes a seat portion 17 that projects radially outward in a flange shape, and a screw portion 18 formed on an outer peripheral surface on the tip end side of the seat portion 17. The main metal fitting 16 is fixed by fastening a screw portion 18 to a screw hole (not shown) of an internal combustion engine (cylinder head).

The ground electrode 19 is a metal member (for example, made of a nickel-based alloy) joined to the main metal fitting 16. In the present embodiment, the ground electrode 19 is formed in a rod shape, and the tip side is bent to face the center electrode 14. The ground electrode 19 forms a spark gap with the center electrode 14.

The resistor 20 is a member for suppressing radio wave noise generated during discharge, and is arranged in a shaft hole between the center electrode 14 and the terminal fitting 15. The resistor 20 is electrically connected to the center electrode 14 by a conductive glass 21 in contact with the center electrode 14 and the resistor 20. In this embodiment, the resistor 20 is formed in a columnar shape. Further, the resistor 20 is electrically connected to the terminal fitting 15 by the conductive glass 22 that comes into contact with the terminal fitting 15 and the resistor 20. The resistor 20 absorbs a component of the discharge current in a frequency band that causes radio wave noise. The resistance value of the resistor 20 is preferably, for example, 0.1 kΩ to 30 kΩ, and more preferably 1 kΩ to 20 kΩ.

The resistor 20 is made of a sintered body containing a metal oxide represented by the general formula AaBbCuCOd. However, the element A is one or more selected from the Group 3 elements of the periodic table based on the IUPAC 1990 recommendation. Element B is at least one or more selected from Ca, Sr and Ba selected from Group 2 elements of the Periodic Table based on the IUPAC 1990 Recommendation. The subscripts a, b, c, and d satisfy 0 <a≤2,0≤b≤2,1≤c≤3,3 <d <8. The subscript b = 0 indicates that the element B is not contained.

Examples of the element A include lanthanoids such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb , Sc and Y. In particular, the element A is preferably at least one selected from La, Ce, Pr, Nd, Sm, Gd, Y and Yb, and more preferably at least one selected from La, Ce, Nd and Gd.

Examples of the metal oxide represented by the general formula AaBbCuCOd include La ₂ CuO ₄ , YBa ₂ Cu ₃ O ₇ , La _1.85 Ba _0.15 CuO ₄ , and the like. The metal oxide represented by the general formula AaBbCuCOd exhibits metallic electrical conduction and is not affected by the number of carriers seen in the case of oxide semiconductors or the oxidation seen in the case of metals. Therefore, the resistor 20 Can improve the durability of.

Since the resistor 20 adjusts the resistance value, it can contain a substance having a higher volume resistivity than this metal oxide. Examples of this substance (insulating powder) include metal oxides such as Al ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , mulite, and steatite, metal nitrides such as Si ₃ N ₄ , and B ₂ O ₃ -SiO ₂ . System, BaO-B ₂ O ₃ system, SiO ₂ -B ₂ O ₃ -CaO-BaO system, SiO ₂ -ZNO-B ₂ O ₃ system, SiO ₂ -B ₂ O ₃ -Li ₂ O system and SiO _2- Examples thereof include B ₂ O ₃ -Li ₂ O-BaO type glass. Only one kind of these substances may be used, or two or more kinds thereof may be used in combination.

The resistor 20 is, for example, mixed with a weighed starting material and calcined, then the powder after the calcining is crushed, and if necessary, an insulating substance (insulating powder) is mixed, and then molded and calcined. It is a sintered body obtained by the above. The sintered body is externally processed as necessary.

As the conductive glasses 21 and 22, a fired mixture of glass powder and conductive powder is used. The glass powder constituting the conductive glasses 21 and 22 is B ₂ O ₃ -SiO ₂ system, BaO-B ₂ O ₃ system, SiO ₂ -B ₂ O ₃ -CaO-BaO system, SiO ₂ -ZnO-B ₂ Examples thereof include O ₃ series, SiO ₂ -B ₂ O ₃ -Li ₂ O series and SiO ₂ -B ₂ O ₃ -Li ₂ O-BaO series powders.

Examples of the conductive powder constituting the conductive glasses 21 and 22 include powders made of oxide semiconductors, metals, non-metal conductive materials and the like. Examples of the oxide semiconductor include SnO ₂ , SrTiO ₃ , and the like. Examples of the metal include Zn, Sb, Sn, Ag and Ni. Examples of the non-metal conductive material include amorphous carbon (carbon black), graphite, SiC, TiC, TiN, WC, ZrC and the like. Only one kind of these conductive powders may be used, or two or more kinds thereof may be used in combination. The conductive glasses 21 and 22 may contain semi-conducting inorganic compound powder such as ZnO and TiO ₂ , insulating powder and the like, if necessary.

FIG. 2A is a cross-sectional view of the spark plug 10 in which the portion shown by IIa in FIG. 1 is enlarged. Arrow F in FIG. 2A indicates the tip side in the axial direction, arrow B indicates the rear end side in the axial direction, and arrow P indicates the inside in the direction perpendicular to the axis orthogonal to the axis O (see FIG. 1) (FIG. 2). (B), FIG. 3, FIG. 4 (a), FIG. 4 (b) and FIG. 5).

As shown in FIG. 2A, in the spark plug 10, the insulating glass 23 is arranged between the side surface 20b of the resistor 20 and the inner peripheral surface 12 of the insulator 11. The insulating glass 23 comes into contact with the conductive glass 21, the resistor 20, and the insulator 11. By interposing the insulating glass 23 between the resistor 20 and the insulator 11, it is possible to prevent the resistor 20 from being damaged by vibration.

As the material of the insulating glass 23, the melting point is lower than the melting point of the insulator 11, for example, B ₂ O ₃ -SiO ₂ system, BaO-B ₂ O ₃ system, SiO ₂ -B ₂ O ₃ -CaO-BaO. Examples thereof include SiO ₂ -ZO-B ₂ O ₃ system, SiO ₂ -B ₂ O ₃ -Li ₂ O system and SiO ₂ -B ₂ O ₃ -Li ₂ O-BaO system. Only one of these may be used, or two or more thereof may be used in combination. The insulating glass 23 may contain an inorganic compound such as alumina, silicon nitride, mullite and steatite.

The conductive glass 21 contacts a part of the bottom surface 20a and the side surface 20b of the resistor 20 and also contacts the insulator 11. When the conductive glass 21 comes into contact with the insulator 11, the combustion gas in the combustion chamber of the internal combustion engine (not shown) to which the spark plug 10 is mounted can be prevented from leaking from the shaft hole of the insulator 11.

The insulating glass 23 is interposed between the conductive glass 21 and the conductive glass 22. Since the volume resistivity of the insulating glass 23 is higher than the volume resistivity of the resistor 20 and the conductive glass 21, the conductive glasses 21 and 22 can be prevented from being short-circuited via the insulating glass 23.

The spark plug 10 is manufactured, for example, by the following method. First, the center electrode 14 is inserted into the shaft hole of the insulator 11, and the center electrode 14 is locked by the rear end facing surface 13. Next, the raw material powder of the conductive glass 21 is put in through the shaft hole and filled around the center electrode 14. Using a compression bar (not shown), the raw material powder of the conductive glass 21 packed around the center electrode 14 is precompressed.

Next, a glass tube made of the material of the insulating glass 23 containing the resistor 20 (sintered body) is inserted into the shaft hole and placed on the molded body of the raw material powder of the conductive glass 21. .. After placing a molded body obtained by molding the raw material powder of the conductive glass 22 into pellets on the resistor 20 and the glass tube, the insulator 11 is transferred into the furnace, for example, the raw material powder of the conductive glass 21 and 22. And the temperature is higher than the softening point of the glass component contained in the material of the insulating glass 23. After heating, the terminal fitting 15 is inserted into the shaft hole of the insulator 11, and the raw material powder of the conductive glass 21 and 22 and the material of the insulating glass 23 are axially compressed by the tip of the terminal fitting 15. As a result, they are compressed and sintered, and the resistor 20, the conductive glasses 21 and 22, and the insulating glass 23 are formed inside the insulator 11.

Next, the insulator 11 is transferred to the outside of the furnace, and the main metal fitting 16 is attached to the outer periphery of the insulator 11. After joining the ground electrode 19 to the main metal fitting 16, the ground electrode 19 is bent so that the tip of the ground electrode 19 faces the center electrode 14 to obtain a spark plug 10.

In this manufacturing method, instead of inserting the glass tube containing the resistor 20 into the shaft hole, after inserting the resistor 20 (sintered body) into the shaft hole, the raw material of the insulating glass 23 is placed around the resistor 20. Of course it is possible to fill with powder. Further, instead of using the previously sintered resistor 20, the resistor 20 (molded body) is fired together with the conductive glasses 21 and 22 and the insulating glass 23 inside the insulator 11 and inside the shaft hole. Of course, it is possible to bring the softened conductive glass 21 and 22 and the insulating glass 23 into contact with the resistor 20. Further, instead of inserting the molded body of the raw material powder of the conductive glass 22 into the shaft hole, it is naturally possible to fill the shaft hole with the raw material powder of the conductive glass 22.

As shown in FIG. 2A, the bottom surface 20a of the resistor 20 comes into contact with the conductive glass 21. In any cross section including the axis O (see FIG. 1), the interface 24 between the conductive glass 21 and the insulating glass 23 has a first point 25 in contact with the inner peripheral surface 12 of the insulator 11 and the side surface of the resistor 20. The second point 26 touches 20b. In the present embodiment, the interface 24 is linearly inclined from the first point 25 to the second point 26. The shape of the interface 24 and the positions of the first point 25 and the second point 26 are the pressure when each material is compressed in the axial direction using the terminal fitting 15, and the shape of the material (glass tube) of the insulating glass 23. It can be appropriately set by adjusting the amount of the raw material powder of the insulating glass 23 and the insulating glass 23.

For example, the bottom surface 20a of the resistor 20 can be embedded in the conductive glass 21 by increasing the pressure when compressing each material in the axial direction by using the terminal fitting 15. The softened conductive glass 21 passes through the insulator 11 and enters the gap between the insulating glass 23 and the insulator 11. As a result, the interface 24 between the conductive glass 21 and the insulating glass 23 rises from the resistor 20 toward the insulator 11.

In the interface 24, the first point 25 is located on the rear end side (arrow B direction) in the axial direction from the second point 26, and at any two points on the interface 24, the inside in the axis perpendicular direction (arrow P direction). Is located on the tip side (arrow F direction) in the axial direction with respect to the point on the outside (counter-arrow P direction) perpendicular to the axis. The angle (angle on the conductive glass 21 side) between the interface 24 and the resistor 20 (side surface 20b) is set to 90 ° or more, and the angle (conductivity) between the interface 24 and the insulator 11 (inner peripheral surface 12) is set to 90 ° or more. The angle on the glass 21 side) is set to less than 90 °. This relationship holds for any (in any case) cross section including axis O (see FIG. 1). As a result, it is possible to alleviate the concentration of the electric field at the second point 26. Since the current density at the time of discharging the second point 26 can be suppressed and the deterioration of the resistor 20 can be suppressed, the durability of the resistor 20 can be improved.

FIG. 3 is a perspective view schematically showing the resistor 20. Since the interface 24 (see FIG. 2A) is in contact with the side surface 20b of the resistor 20 in any (in any case) cross section including the axis O, in FIG. 3, the boundary line 27 in which the resistor 20 and the interface 24 are in contact is provided. , Notated as a continuous curve. The boundary line 27 is a set of the second points 26 (see FIG. 2A).

The spark plug 10 has a point 28 (last end position) located on the rearmost end side (arrow B direction) and a point located on the most tip side (arrow F direction) of the boundary line 27 on the side surface 20b of the resistor 20. D / L obtained by dividing the distance D in the axis O direction from 29 (the most advanced position) by the maximum length L in the axis O direction of the resistor 20 satisfies 0 ≦ D / L ≦ 0.1. Is preferable.

The maximum length L of the resistor 20 refers to the distance between the two planes when the resistor 20 is sandwiched in the axis O direction by the two planes orthogonal to the axis O. Further, the shape of the interface 24, the positions of the first point 25 and the second point 26, the distance D and the length L are determined by microscopic observation of the cut surface of the sample and non-destructive inspection using a CT scanner (X-ray fluoroscope). Can be measured.

By satisfying 0 ≦ D / L ≦ 0.1, it is possible to suppress variations in the circumferential direction of the contact area of the conductive glass 21 in contact with the side surface 20b of the resistor 20. Therefore, it is possible to suppress variations in the resistance value of the resistor 20. Further, by satisfying 0 ≦ D / L ≦ 0.1, the variation in the current density of the side surface 20b of the resistor 20 can be suppressed, so that the deterioration of the resistor 20 can be suppressed. Therefore, the durability of the resistor 20 can be further improved.

Next, the second embodiment will be described with reference to FIG. 2 (b). In the first embodiment, the case where the interface 24 is in contact with the side surface 20b of the resistor 20 has been described. On the other hand, in the second embodiment, the case where the interface 34 touches the corner between the bottom surface 20a and the side surface 20b of the resistor 20 will be described. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 2B is an enlarged cross-sectional view showing a part of the spark plug 30 in the second embodiment.

As shown in FIG. 2B, the bottom surface 20a of the resistor 20 comes into contact with the conductive glass 31. In any cross section including the axis O (see FIG. 1), the interface 34 between the conductive glass 31 and the insulating glass 33 has a first point 35 in contact with the insulator 11 and has a bottom surface 20a and a side surface 20b of the resistor 20. The second point 36 touches the corner or the side surface 20b of the. In the present embodiment, in at least one of the above arbitrary cross sections, the interface 34 between the conductive glass 31 and the insulating glass 33 has a second point 36 at the corner between the bottom surface 20a and the side surface 20b of the resistor 20. Contact. The interface 34 is linearly inclined from the first point 35 to the second point 36.

In the interface 34, the first point 35 is located on the rear end side (arrow B direction) in the axial direction from the second point 36, and at any two points on the interface 34, the inside in the axial perpendicular direction (arrow P direction). Is located on the tip side (arrow F direction) in the axial direction with respect to the point on the outside (counter-arrow P direction) perpendicular to the axis. The angle (angle on the conductive glass 31 side) formed by the interface 34 and the resistor 20 (bottom surface 20a or side surface 20b) is set to 90 ° or more, and the angle formed by the interface 34 and the insulator 11 (inner peripheral surface 12). (Angle on the conductive glass 31 side) is set to less than 90 °. This relationship holds for any (in any case) cross section including axis O (see FIG. 1). Therefore, it is possible to alleviate the concentration of the electric field at the second point 36 and suppress the deterioration of the resistor 20.

The third embodiment will be described with reference to FIG. 4A. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 4A is an enlarged cross-sectional view showing a part of the spark plug 40 in the third embodiment.

As shown in FIG. 4A, the bottom surface 20a of the resistor 20 comes into contact with the conductive glass 41. In any cross section including the axis O (see FIG. 1), the interface 44 between the conductive glass 41 and the insulating glass 43 has a first point 45 in contact with the insulator 11 and a second point on the side surface 20b of the resistor 20. 46 touches. In the present embodiment, in at least one of the above arbitrary cross sections, the interface 44 is a curve convex toward the tip side (arrow F direction).

In the interface 44, the first point 45 is located on the rear end side (arrow B direction) in the axial direction from the second point 46, and at any two points on the interface 44, the inside in the axis perpendicular direction (arrow P direction). Is located at the same position in the axial direction or on the tip side in the axial direction (in the direction of arrow F) with respect to the point on the outside in the direction perpendicular to the axis (direction of counter arrow P). The angle (angle on the conductive glass 41 side) between the interface 44 and the resistor 20 (side surface 20b) is set to 90 ° or more, and the angle (conductivity) between the interface 44 and the insulator 11 (inner peripheral surface 12) is set to 90 ° or more. The angle on the glass 41 side) is set to less than 90 °. This relationship holds for any (in any case) cross section including axis O (see FIG. 1). Therefore, it is possible to alleviate the concentration of the electric field at the second point 46 and suppress the deterioration of the resistor 20.

The fourth embodiment will be described with reference to FIG. 4 (b). The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 4B is an enlarged cross-sectional view showing a part of the spark plug 50 in the fourth embodiment.

As shown in FIG. 4B, the bottom surface 20a of the resistor 20 comes into contact with the conductive glass 51. In any cross section including the axis O (see FIG. 1), the interface 54 between the conductive glass 51 and the insulating glass 53 has a first point 55 in contact with the insulator 11 and a second point on the side surface 20b of the resistor 20. 56 touches. In the present embodiment, in at least one of the above arbitrary cross sections, the interface 54 is a curve in which the state of unevenness changes near the center.

In the interface 54, the first point 55 is located on the rear end side (arrow B direction) in the axial direction from the second point 56, and at any two points on the interface 54, the inside in the axis perpendicular direction (arrow P direction). Is located at the same position in the axial direction or on the tip side in the axial direction (in the direction of arrow F) with respect to the point on the outside in the direction perpendicular to the axis (direction of counter arrow P). The angle (angle on the conductive glass 51 side) between the interface 54 and the resistor 20 (side surface 20b) is set to 90 ° or more, and the angle (conductivity) between the interface 54 and the insulator 11 (inner peripheral surface 12) is set to 90 ° or more. The angle on the glass 51 side) is set to less than 90 °. This relationship holds for any (in any case) cross section including axis O (see FIG. 1). Therefore, it is possible to alleviate the concentration of the electric field at the second point 56 and suppress the deterioration of the resistor 20.

The fifth embodiment will be described with reference to FIG. Unlike the other embodiments, the spark plug 60 in the fifth embodiment omits the insulating glass, and the resistor 62 is sintered inside the insulator 11. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 5 is an enlarged cross-sectional view showing a part of the spark plug 60 in the fifth embodiment.

As shown in FIG. 5, in the spark plug 60, the conductive glass 61 and the resistor 62 are arranged in the shaft hole (inside of the inner peripheral surface 12) of the insulator 11. The resistor 62 is connected to the terminal fitting 15 by the conductive glass 22.

The resistor 62 is made of a sintered body containing a metal oxide represented by the general formula AaBbCuCOd, similarly to the resistor 20 described in the first embodiment. However, the element A is one or more selected from the Group 3 elements of the periodic table based on the IUPAC 1990 recommendation. The element B is at least one or more selected from Ca, Sr and Ba. The subscripts a, b, c, and d satisfy 0 <a≤2,0≤b≤2,1≤c≤3,3 <d <8.

The spark plug 60 is manufactured, for example, by the following method. First, the center electrode 14 is inserted into the shaft hole of the insulator 11, and the center electrode 14 is locked by the rear end facing surface 13. Next, the raw material powder of the conductive glass 21 is put in through the shaft hole and filled around the center electrode 14. Using a compression bar (not shown), the raw material powder of the conductive glass 21 packed around the center electrode 14 is precompressed.

Next, the raw material powder of the resistor 62 is filled on the raw material powder of the conductive glass 21, and then the raw material powder of the resistor 62 is precompressed using a compression rod (not shown). Next, after the raw material powder of the conductive glass 22 is filled on the raw material powder of the resistor 62, the insulator 11 is transferred into the furnace, and for example, the glass component contained in the raw material powder of the conductive glass 21 and 22 is softened. Heat to a temperature above the point. After heating, the terminal fitting 15 is inserted into the shaft hole of the insulator 11, and the raw material powders of the conductive glass 21 and 22 and the resistor 62 are axially compressed by the tip of the terminal fitting 15. As a result, they are compressed and sintered, and the resistor 62 and the conductive glasses 21 and 22 are formed inside the insulator 11.

Next, the insulator 11 is transferred to the outside of the furnace, and the main metal fitting 16 is attached to the outer periphery of the insulator 11. After joining the ground electrode 19 to the main metal fitting 16, the ground electrode 19 is bent so that the tip of the ground electrode 19 faces the center electrode 14 to obtain a spark plug 60.

Also in the spark plug 60 according to the fifth embodiment, the metal oxide represented by the general formula AaBbCucOd contained in the resistor 62 exhibits metallic electrical conduction, and is affected by the number of carriers seen in the case of the oxide semiconductor. It can be prevented from being affected by the oxidation seen in the case of metal. Therefore, the durability of the resistor 62 can be improved.

The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
Various resistors 20 were produced by the solid phase reaction method as follows. First, various raw materials were weighed so as to have a predetermined composition ratio, and wet-mixed. The obtained slurry was dried and then calcined in the air at 600 to 1100 ° C. _A predetermined amount of insulating powder ₍ Y2O3) for adjusting the resistance value was added to the powder after calcination as needed, and the powder was mixed in a wet manner at the same time as pulverization. The mixture (slurry) was dried, a binder was added, and granulation was performed. The granulated powder was press-molded into a columnar shape and then fired in the air at 800 to 1300 ° C. to obtain a resistor 20 containing various metal oxides (No. 1 to 10) shown in Table 1. The resistor 20 was externally processed as needed.

The phase of the resistor 20 was identified by powder X-ray diffraction (XRD). In this example, an X-ray diffractometer manufactured by Rigaku Co., Ltd. was used, and measurement was performed with CuKα rays (λ1.54 Å).

表１には、Ｎｏ．１～１０の抵抗体に含まれる金属酸化物の組成式、及び、その組成式に示された元素Ａ、元素Ｂ及び添え字の値を記した。なお、表１のＮｏ．１１及び１２は比較例である。Ｎｏ．１１の抵抗体はＴｉＮ粉末と絶縁性のガラス粉末とを混合した後、円柱状にプレス成形して大気中で焼成することにより得た。Ｎｏ．１２の抵抗体はＺｎＯ粉末を円柱状にプレス成形して大気中で焼成することにより得た。

Table 1 shows No. The composition formulas of the metal oxides contained in the resistors 1 to 10 and the values of the element A, the element B and the subscripts shown in the composition formula are described. No. in Table 1 11 and 12 are comparative examples. No. The resistor 11 was obtained by mixing TiN powder and insulating glass powder, press-molding them into a columnar shape, and firing them in the air. No. The resistor of 12 was obtained by press-molding ZnO powder into a cylinder and firing it in the atmosphere.

Next, a sample of the spark plug 10 described in the first embodiment was prepared. In the sample, first, the center electrode 14 is inserted into the shaft hole of the insulator 11, and then the raw material powder of the conductive glass 21 in which the conductive powder and the glass powder are mixed is inserted from the shaft hole and around the center electrode 14. Filled. Next, a glass tube made of the material of the insulating glass 23 containing the resistor 20 was inserted into the shaft hole and placed on the raw material powder of the conductive glass 21. Next, a molded body obtained by molding the raw material powder of the conductive glass 22 into pellets was placed on the resistor 20 and the glass tube, and then the insulator 11 was heated to soften the glass powder and the glass tube. Next, glass powder or the like was pressed by the terminal fitting 15 press-fitted into the shaft hole, and the resistor 20, the conductive glass 21 and 22, and the insulating glass 23 were sintered. The main metal fitting 16 to which the ground electrode 19 was joined was assembled to the insulator 11 to obtain samples 1 to 12 of the spark plug 10.

Using an X-ray fluoroscope, the morphology of the interface 24 between the conductive glass 21 and the insulating glass 23 of each sample was observed. As a result, in all the samples, as in the first embodiment, the interface 24 between the conductive glass 21 and the insulating glass 23 is linear, and in the range of 70% or more of the entire circumference (360 °). The interface 24 was in contact with the side surface 20b of the resistor 20.

For each sample, a DC voltage of 5 V is applied between the terminal fitting 15 and the center electrode 14, the resistance value is measured, and the resistance temperature characteristics measured in advance are used to measure the resistance at 20 ° C. Corrected to the value. The resistance value at this time was 1 kΩ for each sample.

Next, each sample was placed in an environment of 425 ° C., the discharge voltage was set to 45 kV, and a test was conducted in which sparks were blown between the center electrode 14 and the ground electrode 19 at a rate of 100 times per second for 200 hours. .. After the test, the mixture was left for 1 hour, the resistance value was measured in the same manner as before the test, and the measured value at that time was corrected to the resistance value at 20 ° C. Samples with a resistance change rate of less than ± 10% before and after the test were evaluated as A, samples with a change rate of ± 10% or more and less than ± 30% were evaluated as B, and samples with a change rate of ± 30% or more were evaluated as C. ..

As shown in Table 1, the evaluation was A for samples 1 to 5, B for samples 6 to 10, and C for samples 11 and 12. In Samples 1 to 10, the resistor 20 has a general formula AaBbCucOd (wherein element A is at least one selected from Group 3 elements in the periodic table, and element B is at least one selected from Ca, Sr and Ba). Since it is composed of a sintered body containing a metal oxide represented by 0 <a≤2,0≤b≤2,1≤c≤3,3 <d <8), the sample 11 and It is presumed that the durability of the resistor could be improved as compared with 12.

In Samples 1 to 5 having an evaluation of A, the element A of the metal oxide (general formula AaBbCucOd) contained in the resistor 20 was at least one selected from La, Ce, Nd and Gd. .. Of these elements, La, Ce and Nd have almost the same ionic radius, so it is presumed that this led to the stabilization of the crystal structure of the metal oxide and contributed to the improvement of the durability of the resistor 20.

(Example 2)
No. 1 described in Example 1. Using the resistor 20 of 3, the spark plugs in the samples 13 to 17 were prepared. The D and L (see FIG. 3) of each sample were measured using an X-ray fluoroscope, and the D / L was calculated. Table 2 shows the morphology of the interface of the samples 13 to 17, the value (D / L) obtained by dividing the distance D by the length L, and the evaluation.

第１実施の形態のように、導電性ガラスと絶縁性ガラスとの界面が直線状で、その界面が抵抗体の側面に接触するものを表２に形態１と表記し、第２実施の形態のように、導電性ガラスと絶縁性ガラスとの界面が抵抗体の角に接触するものを形態２と表記した。また、第３実施の形態のように、導電性ガラスと絶縁性ガラスとの界面が曲線状で、その界面が抵抗体の側面に接触するものを形態３と表記した。形態１から３のいずれかに分類されたサンプルの界面は、全周（３６０°）のうち７０％以上の範囲において、分類されたその形態であった。

As in the first embodiment, the interface between the conductive glass and the insulating glass is linear, and the interface in contact with the side surface of the resistor is described as the first embodiment in Table 2, and the second embodiment is described. The interface between the conductive glass and the insulating glass in contact with the corners of the resistor as described above is referred to as Form 2. Further, as in the third embodiment, the interface between the conductive glass and the insulating glass is curved, and the interface in contact with the side surface of the resistor is described as the third embodiment. The interface of the sample classified into any of morphology 1 to 3 was the morphology classified in the range of 70% or more of the entire circumference (360 °).

Samples 13 to 17 were subjected to the same test as in Example 1 and evaluated in the same manner as in Example 1. As shown in Table 2, all the samples 13 to 17 were evaluated as A regardless of the D / L value. It is presumed that the samples 13 to 17 were able to alleviate the concentration of the electric field at the second points 26, 36, 46, and thus could suppress the deterioration of the resistor 20.

(Example 3)
No. 1 described in Example 1. Using the resistor 20 of No. 3, samples having different D / L values were prepared. The sample was obtained by placing the resistor 20 in a glass tube made of an insulating glass material, inserting the resistor 20 into the shaft hole of the insulator 11 together with the glass tube, and then melting the glass tube. The average resistance value of the resistor 20 was set to 1 kΩ.

Samples of the first embodiment and the third embodiment (forms 1 and 3) are prepared, and D / L of the samples are measured using an X-ray fluoroscope in the same manner as in Example 2, and D / L is measured. Calculated. Furthermore, the resistance value of the sample (resistance value of the resistor) was measured, and the standard deviation (σ) was calculated. A sufficient number of samples were prepared and measured to evaluate the standard deviation. In the evaluation of variation, 3σ ≤ 0.20 kΩ is "excellent (A)", 0.2 <3σ ≤ 0.35 kΩ is "good (B)", and 3σ> 0.35 kΩ is "inferior (C)". bottom. The results are shown in Table 3.

表３に示すように０≦Ｄ／Ｌ≦０．１を満たすことで、抵抗値のばらつきを小さくできることがわかった。特に０≦Ｄ／Ｌ≦０．０５を満たすことで、抵抗値のばらつきを特に小さくできることがわかった。

As shown in Table 3, it was found that the variation in resistance value can be reduced by satisfying 0 ≦ D / L ≦ 0.1. In particular, it was found that the variation in resistance value can be made particularly small by satisfying 0 ≦ D / L ≦ 0.05.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It is easy to guess.

In the first to fourth embodiments, the interfaces 24, 34, 44, 54 have points inside (arrow P direction) in the direction perpendicular to the axis at any two points on the interfaces 24, 34, 44, 54. The case where the point is located at the same position in the axial direction or on the tip side in the axial direction (in the direction of arrow F) with respect to the point on the outside in the direction perpendicular to the axis (direction of counter arrow P) has been described, but the present invention is not limited to this. For example, at the interfaces 24, 34, 44, 54, the point on the inside (arrow P direction) in the direction perpendicular to the axis is on the rear end side (arrow) in the axis direction with respect to the point on the outside (counter arrow P direction) in the direction perpendicular to the axis. It may have a portion located in the B direction).

That is, the first points 25, 35, 45, 55 where the interfaces 24, 34, 44, 54 contact the insulator 11, and the second points 26, 36, 46 where the interfaces 24, 34, 44, 54 contact the resistor 20. , 56 located on the rear end side (arrow B direction), and the interface 24, 34, 44, 54 is at the same position as the second point 26, 36, 46, 56 in the axial direction or the second point 26, 36, It suffices if it is located on the rear end side (direction of arrow B) from 46 and 56. If the interfaces 24, 34, 44, 54 are positioned in this way, the angle between the interfaces 24, 34, 44, 54 and the side surface 20b of the resistor 20 is set to 90 ° or more, and the interfaces 24, 34, The angle formed by the 44, 54 and the insulator 11 is set to less than 90 °. Therefore, it is possible to alleviate the concentration of the electric field at the second points 26, 36, 46, 56 and improve the effect of suppressing the deterioration of the resistor 20.

In the first to fourth embodiments, the case where the resistor 20 is formed in a columnar shape has been described, but the present invention is not limited to this. Since the resistor 20 may have a size and shape that can be inserted into the shaft hole, it is naturally possible to adopt a resistor 20 formed in a rectangular parallelepiped shape, for example.

In the embodiment, the case where the resistors 20 and 62 are connected to the terminal fitting 15 by the conductive glass 22 has been described, but the present invention is not limited to this. For example, instead of the conductive glass 22, an elastic body such as a conductive spring is interposed between the resistors 20 and 62 and the terminal fitting 15, and the resistors 20 and 62 and the terminal fitting 15 are electrically connected to each other. Of course it is possible to connect to.

In the embodiment, the spark plugs 10, 30, 40, 50, 60 in which the ground electrode 19 faces the tip of the center electrode 14 have been described, but the structure of the spark plug is not necessarily limited to this. Other structures of the spark plug include, for example, a spark plug in which the ground electrode 19 faces the side surface of the center electrode 14, and a multi-pole spark plug in which a plurality of ground electrodes 19 are joined to the main metal fitting 16.

10,30,40,50,60 Spark plug 11 Insulator 14 Center electrode 20,62 Resistor 21,31,41,51 Conductive glass 23,33,43,53 Insulator glass 24,34,44,54 Interface 25,35,45,55 1st point 26,36,46,56 2nd point O-axis

Claims (4)

An insulator having a shaft hole extending in the direction of the axis from the front end side to the rear end side,
The center electrode arranged on the tip side of the shaft hole and
The terminal fittings arranged on the rear end side of the shaft hole and
A spark plug comprising a resistor that electrically connects the terminal fitting and the center electrode inside the shaft hole.
The resistor is made of a sintered body containing a metal oxide represented by the general formula AaBbCuCOd.
Element A is at least one selected from Group 3 elements of the Periodic Table based on the IUPAC 1990 Recommendation (however, Element A excludes actinides) and Element B is at least one selected from Ca, Sr and Ba. can be,
A spark plug that satisfies 0 <a≤2,0≤b≤2,1≤c≤3,3 <d <8. The spark plug according to claim 1, wherein the element A is at least one selected from La, Ce, Pr, Nd, Sm, Gd, Y and Yb. The spark plug according to claim 2, wherein the element A is at least one selected from La, Ce, Nd and Gd. Conductive glass that comes into contact with the center electrode, the resistor, and the insulator and electrically connects the center electrode and the resistor.
The conductive glass, the resistor and the insulating glass in contact with the insulator, which are arranged between the resistor and the insulator, are provided.
In any cross section including the axis, the interface between the insulating glass and the conductive glass is such that the first point where the interface touches the insulator is behind the second point where the interface touches the resistor. Located on the side,
The spark plug according to any one of claims 1 to 3, wherein the interface is located at the same position in the axial direction of the second point or on the rear end side in the axial direction of the second point.

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