JP2005100898A - Spark plug for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent growth of a flame kernel from being inhibited by a center electrode or a grounding electrode even when a firing part is narrowed for preventing sideward sparking in a spark plug having a plurality of firing parts. <P>SOLUTION: This spark plug is provided with a plurality of center electrodes 12 and 13 and grounding electrodes 20 and 21; each center electrode is insulated and held by an insulator 11; the insulator is housed in a housing 10; and each grounding electrode is jointed to the housing. Center-side chips 18 and 19 thinner than center electrode body parts 121 and 131 are jointed to tip parts of the respective center electrodes 12 and 13; and ground-side chips 22 and 23 projecting toward the center-side chips 18 and 19 are jointed to the respective grounding electrodes 20 and 21. Thereby, distances from the firing parts G1 and G2 to the center electrodes 12 and 13 and the grounding electrodes 20 and 21 are increased to increase each gap for forming a flame kernel. Thereby, inhibition of the growth of the flame kernel by the center electrodes 12 and 13 and the grounding electrodes 20 and 21 is reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ignition plug for an internal combustion engine used for automobiles, cogeneration, gas pressure pumps, and the like.

  For the purpose of improving ignitability and the like, a spark plug has been proposed in which two center electrodes and two ground electrodes are provided to form two ignition portions (discharge gaps) (see, for example, Patent Document 1). This is because by providing a plurality of ignition points in the cylinder, combustion can be promoted and the combustion period can be shortened, that is, the time loss can be reduced by this rapid combustion effect, and the combustion efficiency can be improved.

However, in a spark plug having a plurality of ignition parts, since the pocket gap (gap between the insulator and the housing) becomes narrow, when smoldering, high voltage may travel along the carbon adhering to the insulator surface and short circuit to the housing. Therefore, it is desirable to narrow the discharge gap from the viewpoint of preventing lateral jumping during smoldering.
JP-A-57-193777

  However, when the ignition part is narrowed, the flame nucleus generated in the ignition part is impeded by the center electrode and the ground electrode before it grows sufficiently large, and the growth is also inhibited. End up. Therefore, the ignitability of each ignition part in an ignition plug having a plurality of ignition parts is inferior to that of a general ignition plug having one ignition part. As a result, the effect of simultaneous ignition at multiple points or the effect of phase ignition was improved to some extent by the rapid combustion effect, but the effect was weak.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a spark plug having a plurality of ignition portions, which can obtain good ignitability even when the ignition portion is narrowed to prevent side jumping.

  In order to achieve the above object, in the invention described in claim 1, the plurality of center electrodes (12, 13) are insulated and held by the insulator (11), the insulator is accommodated in the housing (10), and the ground electrode is provided in the housing. In the joined spark plug, the center tip (18, 19) thinner than the body (121, 131) held by the insulator in the center electrode is joined to the electrode tip located on the combustion chamber side in the center electrode. The grounding tip (22, 23) protruding toward the center tip is joined to the ground electrode.

  According to this, since the ignition part is formed between the center side chip and the ground side chip, the distance from the ignition part to the center electrode and the ground electrode is increased, and the gap for forming the flame nucleus is increased. Accordingly, since the growth inhibition of the flame nuclei by the center electrode and the ground electrode is reduced, the growth of the flame nuclei is accelerated and the ignitability is improved.

  As in the second aspect of the present invention, the tip mounting surface (201, 211) facing the tip of the center electrode (12, 13) in the ground electrode (20, 21) is the central axis ( Z1) may be parallel to the plane perpendicular to Z1), or the chip mounting surface facing the tip of the center electrode (12, 13) in the ground electrode (20, 21) as in the invention of claim 3 (201, 211) may be inclined with respect to a plane orthogonal to the central axis (Z1) of the insulator (11).

  In the invention according to claim 4, in the spark plug in which the plurality of center electrodes (12, 13) are insulated and held by the insulator (11) and the insulator is accommodated in the housing (10), the center electrode is positioned on the combustion chamber side. A center side tip (18, 19) thinner than the body (121, 131) held by the insulator of the center electrode is joined to the tip of the electrode to be grounded, and the ground side tip protrudes toward the center side tip in the housing A plurality of (22, 23) are joined.

  According to this, since the ignition part is formed between the center side chip and the ground side chip, the distance from the ignition part to the center electrode and the housing is increased, and the gap for forming the flame nucleus is increased. Accordingly, since the growth inhibition of the flame nuclei by the center electrode and the ground electrode is reduced, the growth of the flame nuclei is accelerated and the ignitability is improved.

  The invention according to claim 5 is characterized in that the center chip (18, 19) and the ground chip (22, 23) are made of a noble metal. According to this, since each chip is made of a noble metal, durability is improved and the life of the spark plug is improved.

  The invention according to claim 6 is characterized in that the center chip (18, 19) is made of an Ir alloy. According to this, since an Ir alloy, which is a high melting point material, is used for the center side tip having a high spark consumption rate, the wear resistance of the center side tip is improved and the life of the spark plug is greatly improved.

  The invention according to claim 7 is characterized in that the center chip (18, 19) is made of an Ir alloy containing Ir in an amount of 50% by weight or more. According to this, the wear resistance of the center side chip can be further improved.

  The invention according to claim 8 is characterized in that the ground side chip (22, 23) is made of a Pt alloy. According to this, since the Pt alloy having excellent oxidation volatility is used for the grounding tip having a high rate of oxidation volatilization consumption, the oxidation resistance of the grounding tip is improved and the life of the spark plug is greatly improved.

  The invention according to claim 9 is characterized in that the ground side chip (22, 23) is made of a Pt alloy containing Pt in an amount of 50% by weight or more. According to this, the oxidation resistance of the ground side chip can be further improved.

In the invention according to claim 10, the center side chip (18, 19) and the ground side chip (22, 23) are Ir, Pt, Rh, Ni, W, Pd, Ru, Os, Al, Y as additives. , Y ₂ O ₃ is contained. According to this, not only the wear resistance can be further improved, but also the chip strength can be increased, and as a result, chip cracking and cracking due to high temperature can be prevented, which is preferable.

In the invention of claim 11, the area S of the front end surface of the center side tip (18, 19) is not less than 0.12 mm ^{2 and not} more than 0.38 mm ² , and the protruding length A of the center side tip (18, 19). Is 0.8 mm or more and 1.5 mm or less, and the area Q of the tip surface of the ground side chip (22, 23) is 0.12 mm ² or more and 0.65 mm ² or less, and the ground side chip (22, 23) protrudes. The length B is 0.5 mm or more and 1.2 mm or less.

  By the way, the smaller the center chip and the ground chip, the more difficult it is to prevent the growth of flame nuclei. However, when the chip volume is small, the heat resistance is low and there is a problem in durability. Therefore, by making the dimensional relationship between the center side tip and the ground side tip as in the invention described in claim 11, it is possible to ensure practically sufficient durability and maintain good ignitability.

  In the invention described in claim 12, the center electrode (12, 13) is formed narrower than the body (121, 131) and is directed from the body (121, 131) toward the center chip (18, 19). Thinning portions (122, 132) extending in the direction of the body, and boundary portions (124, 134) between the body portions (121, 131) and the thinning portions (122, 132) are arranged in the insulator (11). It is characterized by that.

  As described above, in the spark plug having a plurality of ignition portions, the pocket gap is narrowed, so that the side jump is likely to occur. However, according to the invention of claim 12, the boundary portion and the grounding side tip are formed during the spark discharge. By the sparks generated between the carbons, the carbon adhering to the insulator can be burned out, and by extension, the side jump can be prevented.

  As described above, the specific principle of burning off the carbon adhering to the tip of the insulator by the spark generated at the time of spark discharge is from when a high voltage is applied to the electrode until the moment when the capacitive discharge occurs at the electrode tip. Further, the atmosphere in the vicinity of the electrode is ionized by a leakage current flowing through the attached carbon, and the carbon adhering to the insulator 11 in the vicinity of the center electrodes 12 and 13 is burned out at the time of the induction discharge generated following the capacitive discharge.

  And like invention of Claim 13, a boundary part (124, 134) is located in the range of 0.1 mm-1.2 mm from the front end by the side of a combustion chamber in an insulator (11), and capacity discharge is carried out. It is possible to reliably perform ionization due to the leakage current before the occurrence of.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, the present invention will be described based on embodiments. 1A is a front cross-sectional view showing the overall configuration of the spark plug according to the first embodiment of the present invention, FIG. 1B is a bottom view of FIG. 1A, and FIG. 2 is the spark plug of FIG. It is an expanded sectional view near an ignition part.

  The spark plug 1 shown in FIGS. 1 and 2 is formed with a pair of ignition portions (discharge gaps) G1 and G2 in order to perform one-cylinder two-point ignition. Then, these ignition parts G1 and G2 are mounted on the cylinder head so as to face one combustion chamber of an internal combustion engine (not shown), and are discharged by the ignition parts G1 and G2 to ignite the air-fuel mixture in the combustion chamber. It is.

  The spark plug 1 has a substantially cylindrical housing 10 made of a conductive steel material. The housing 10 includes a male screw 101 that is screwed into a female screw of a cylinder head in an internal combustion engine. An insulator 11 made of alumina ceramic is fixed inside the housing 10, and both ends of the insulator 11 protrude from the housing 10.

  The insulator 11 is provided with two holes 111, 112 extending in the direction of the central axis Z1 of the insulator 11. In each of the holes 111, 112, cylindrical center electrodes 12, 13 made of a conductive steel material, carbon Resistors 14 and 15 and columnar stems 16 and 17 made of a conductive steel material are embedded, and a sealing glass is sealed between these components.

  Each of the center electrodes 12 and 13 includes columnar body parts 121 and 131 held by the insulator 11 and thinned parts 122 and 132 having a diameter smaller than that of the body parts 121 and 131. The narrowing parts 122 and 132 are formed at the end of the body parts 121 and 131 on the combustion chamber side, and in this example, are formed in a conical shape.

  Cylindrical center-side tips 18 and 19 having a diameter smaller than those of the body portions 121 and 131 and the narrowing portions 122 and 132 are joined to the distal end surfaces of the narrowing portions 122 and 132 by laser welding. Since the joining form of the center-side tips 18 and 19 is laser welding, between the center-side tips 18 and 19 and the tip portions of the narrowed portions 122 and 132, there are melted portions 123 and 133 in which both of them melt together. Is formed. The center electrodes 12 and 13 and the center side chips 18 and 19 are bonded and fixed via the melting portions 123 and 133.

  The center side chips 18 and 19 are made of a noble metal or an alloy thereof, and for example, Ir—Rh which is a high melting point material can be used, and more specifically, Ir-10Rh can be used. From the viewpoint of wear resistance, it is desirable that the center-side chips 18 and 19 are made of an Ir alloy containing 50% by weight or more of Ir.

  The heads of the stems 16 and 17 are each provided with a terminal to which a line for guiding a high voltage is connected. The terminals are formed integrally or separately with the stems 16 and 17. Further, the terminals 16 and 17 are buried in the insulator 11 in order to maintain an insulation distance between the terminals.

  On the other hand, a pair of ground electrodes 20 and 21 made of a conductive steel material are joined to the end of the housing 10. The chip mounting surfaces 201 and 211 facing the center-side chips 18 and 19 in the ground electrodes 20 and 21 are parallel to a plane orthogonal to the insulator center axis Z1, and the ground electrodes 20 and 21 are of a so-called overhang type.

  Cylindrical ground-side chips 22 and 23 that protrude toward the center-side chips 18 and 19 are joined to the chip mounting surfaces 201 and 211. The ground side chips 22 and 23 are made of a noble metal or an alloy thereof, and for example, Pt—Rh, which is a high melting point material having excellent oxidation volatility, can be used, and more specifically, Pt-20Rh can be used. . From the standpoint of oxidation resistance, the ground side chips 22 and 23 are preferably made of a Pt alloy containing 50 wt% or more of Pt.

  The first center side chip 18 and the first ground side chip 22 face each other across the first ignition part G1, and the second center side chip 19 and the second ground side chip 23 face each other across the second ignition part G2. doing.

  Next, the ignitability of the evaluation products 1 to 5 having the specifications shown in Chart 3 was evaluated. Evaluation product No1 is an ignition plug with one ignition part and an overhang type grounding electrode, which includes a center side tip and no grounding side tip. Evaluation product No2 is obtained by changing the specifications of the discharge gap and the center side chip of evaluation product No1. Evaluation product No4 is obtained by providing a grounding tip on the spark plug of evaluation product No2. Evaluation product No. 3 is an ignition plug with two ignition parts and an overhang type ground electrode, which has a center side tip and no ground side tip. Evaluation product No5 is a spark plug provided with a grounding tip on the spark plug of evaluation product No3 and having the configuration of this embodiment. The center side chip is made of Ir-Rh, and the ground side chip is made of Pt-Rh.

  The evaluation test was carried out under the conditions of cold idling by mounting the evaluation product on an internal combustion engine having a displacement of 1800 cc. The ignitability was evaluated by the flame volume with respect to the elapsed time from the start of discharge at the ignition part.

  FIG. 4 shows the result. Based on the evaluation product No1 which is the most general configuration and specification, the evaluation product No2 having a narrow discharge gap has a small gap for forming the flame nucleus, so that the flame kernel is Difficult to spread. Although the evaluation product No. 4 is provided with the ground side chip, the distance from the ignition part to the ground electrode is increased, and the gap for forming the flame nuclei is increased, but the growth rate of the flame is about the same as that of the evaluation product No. 1. is there.

  Since the evaluation product No3 has two ignition parts, the flame kernel grows from two points, and thus a large flame nucleus is obtained earlier than the evaluation product No1. Evaluation product No5 has two ignition parts, so that the flame kernel grows from two points, and the provision of the ground-side tip increases the gap for forming the flame nucleus, resulting in a flame caused by the center electrode and the ground electrode. Since the growth inhibition of the nucleus is reduced, a large flame nucleus is obtained earlier than the evaluation product No3.

  By the way, the smaller the center side chips 18 and 19 and the ground side chips 22 and 23, the more difficult it is to prevent the growth of flame nuclei. However, when the chip volume is small, the heat resistance is low and there is a problem in durability. Therefore, evaluation is performed from the viewpoint of durability of the center side chips 18, 19 and the ground side chips 22, 23, and various dimensions A, B, Q, S of the center side chips 18, 19 and the ground side chips 22, 23 are determined. The desired range was examined.

  Incidentally, the dimension S is the area of the tip surface of the center side chips 18 and 19, and the dimension A is the protruding length of the center side chips 18 and 19. As shown in FIG. 2, the protrusion length A when the center side tips 18 and 19 are laser-welded as in this example is as shown in FIG. 2 from the tip of the center side tips 18 and 19 to the center electrodes 12 and 13. The length includes up to the melting parts 123 and 133. In the case where the melted portions 123 and 133 do not substantially exist, the protruding length A is the length of the center side tips 18 and 19.

  The dimension Q is the area of the tip surface of the ground side chips 22 and 23. The dimension B is the protruding length B of the ground-side chips 22 and 23. More specifically, the dimension B is the length from the chip mounting surfaces 201 and 211 of the ground electrodes 20 and 21 to the tip surfaces of the ground-side chips 22 and 23. is there.

As a result of experimental study conducted by the present inventors, the area S of the front end surface of the center-side chip 18, 19 0.12 mm ² or more 0.38 mm ² or less, the projection length A of the center-side chip 18 and 19 0.8 mm or more and 1.5 mm or less, the area Q of the tip surface of the ground side chips 22 and 23 is 0.12 mm ² or more and 0.65 mm ² or less, and the protruding length B of the ground side chips 22 and 23 is 0.5 mm or more and 1 When the thickness is 2 mm or less, sufficient practical durability can be secured and good ignitability can be maintained.

  According to the above-described embodiment, since the firing parts G1 and G2 are formed between the center side chips 18 and 19 and the ground side chips 22 and 23, the center electrodes 12 and 13 and the ground electrodes are grounded from the firing parts G1 and G2. The distance to the electrodes 20 and 21 is increased, and the gap for forming the flame nuclei is increased. Therefore, flame nucleus growth inhibition by the center electrodes 12 and 13 and the ground electrodes 20 and 21 is reduced, so that the growth of the flame nucleus is accelerated and the ignitability is improved.

  Further, since Ir-Rh, which is a high melting point material, is used for the center-side chips 18 and 19 having a high spark consumption rate, the wear resistance of the center-side chips 18 and 19 is improved and the rate of oxidation and volatilization consumption is high. Since Pt-Rh having excellent oxidation volatility is used for the ground side chips 22 and 23, the oxidation resistance of the ground side chips 22 and 23 is improved, and therefore the life of the spark plug is greatly improved.

When the center-side chips 18 and 19 and the ground-side chips 22 and 23 are alloys, Ir (iridium), Pt (platinum, platinum), Rh (rhodium), Ni (nickel), W (tungsten) are used as additives. , Pd (palladium), Ru (ruthenium), Os (osmium), Al (aluminum), Y (yttrium), Y ₂ O ₃ (diyttrium trioxide, yttria) is preferable. According to this, not only the wear resistance can be further improved, but also the chip strength can be increased. As a result, chip cracking and cracking due to high temperature can be prevented.

  Further, by appropriately setting the various dimensions A, B, Q, and S of the center side chips 18 and 19 and the ground side chips 22 and 23, practically sufficient durability is secured and good ignitability is maintained. be able to.

(Second Embodiment)
FIG. 5 is a cross-sectional view of a main part of the spark plug according to the second embodiment of the present invention. In the first embodiment, the chip mounting surfaces 201 and 211 of the ground electrodes 20 and 21 are parallel to the surface orthogonal to the insulator central axis Z1, but in this embodiment, the chip mounting surfaces 201 and 211 are connected to the insulator central axis. Inclined with respect to the plane orthogonal to Z1, the center side chips 18, 19 and the ground side chips 22, 23 are diagonally opposed. Other points are common to the first embodiment. And the effect similar to 1st Embodiment is acquired also in the spark plug of this embodiment.

(Third embodiment)
FIG. 6 is a cross-sectional view of a main part of the spark plug according to the third embodiment of the present invention. In the first embodiment, the ground side chips 22 and 23 are arranged on the chip mounting surfaces 201 and 211 parallel to the plane orthogonal to the insulator central axis Z1, but in this embodiment, the arrangement positions of the ground side chips 22 and 23 are arranged. Has changed. Other points are common to the first embodiment.

  As shown in FIG. 6, in this embodiment, the free ends of the ground electrodes 20 and 21 extend in a direction perpendicular to the insulator center axis Z1, and the ground-side chips 22 and 23 are joined to the tip portions 202 and 212, respectively. The center side chips 18 and 19 and the ground side chips 22 and 23 face each other at a right angle. And the effect similar to 1st Embodiment is acquired also in the spark plug of this embodiment.

(Fourth embodiment)
FIG. 7 is a cross-sectional view of a main part of a spark plug according to the fourth embodiment of the present invention. In the first embodiment, the two ground-side chips 22 and 23 are disposed on the chip mounting surfaces 201 and 211 parallel to the surface orthogonal to the insulator central axis Z1, but in the present embodiment, the second ground-side chip 23 is disposed. The placement position of has been changed. Other points are common to the first embodiment.

  As shown in FIG. 7, in this embodiment, the free end side of the second ground electrode 21 extends in a direction orthogonal to the insulator central axis Z1, and the second ground side chip 23 is joined to the tip end portion 212 thereof. The second center side chip 19 and the second ground side chip 23 face each other at a right angle. And the effect similar to 1st Embodiment is acquired also in the spark plug of this embodiment.

(Fifth embodiment)
FIG. 8A is a front cross-sectional view showing the main configuration of the spark plug according to the fifth embodiment of the present invention, and FIG. 8B is a bottom view of FIG. 8A. In the first embodiment, the ground-side tips 22 and 23 are joined to the ground electrodes 20 and 21. However, in this embodiment, the ground-side electrodes 20 and 21 are eliminated and the ground-side tips 22 and 23 are replaced with the combustion chamber in the housing 10. It is joined to the end of the side. The ground-side chips 22 and 23 extend from the housing 10 toward the center-side chips 18 and 19, and the first center-side chip 18 and the first ground-side chip 22 face each other across the first ignition part G1, The 2 center side chip | tip 19 and the 2nd earthing | grounding side chip | tip 23 are opposed across the 2nd ignition part G2. Other points are common to the first embodiment.

  According to the present embodiment, since the ignition parts G1 and G2 are formed between the center side chips 18 and 19 and the ground side chips 22 and 23, from the ignition parts G1 and G2 to the center electrodes 12 and 13 and the housing 10. Increases the gap for flame nucleation. Accordingly, since the growth inhibition of the flame nuclei by the center electrodes 12 and 13 and the housing 10 is reduced, the growth of the flame nuclei is accelerated and the ignitability is improved.

(Sixth embodiment)
FIG. 9 is a cross-sectional view of a main part of a spark plug according to the sixth embodiment of the present invention. Compared to the first embodiment, the positional relationship between the insulator 11 and the center electrodes 12 and 13 in the insulator central axis Z1 direction is changed. Other points are common to the first embodiment.

  As shown in FIG. 9, the narrowing portions 122 and 132 of the center electrodes 12 and 13 are located in the insulator 11, and the protrusion amount L of the center side chips 18 and 19 from the tip of the insulator 11 is −0.5 mm to It is set to 0.5 mm. Further, the gap X between the outer peripheral surface of the center side chips 18 and 19 and the inner peripheral surface of the distal end side of the insulator 11 is set to 0.1 mm or more. Further, boundary portions 124, 134 between the body portions 121, 131 and the narrowing portions 122, 132 in the center electrodes 12, 13 are disposed in the insulator 11, and the boundary portion 124, The dimension C between 134 is set to 0.1 mm to 1.2 mm. In addition, when the thin parts 122 and 132 are formed in a conical shape, the maximum diameter part corresponds to the boundary part.

  As described above, in the spark plug having a plurality of ignition portions, the pocket gap is narrowed, so that when the smoldering occurs, a side jump is likely to occur through the carbon adhering to the insulator 11. The sparks generated between the narrowing parts 122 and 132 and the ground-side chips 22 and 23 at the time of discharge can burn out carbon adhering to the insulator 11, thereby preventing the side jump.

  As described above, the specific principle of burning off the carbon adhering to the tip of the insulator 11 by the spark generated at the time of spark discharge is from when a high voltage is applied to the electrode until the moment when capacitive discharge occurs at the electrode tip. Further, the atmosphere in the vicinity of the electrode is ionized by a leakage current flowing through the attached carbon, and the carbon adhering to the insulator 11 in the vicinity of the center electrodes 12 and 13 is burned out at the time of the induction discharge generated following the capacitive discharge. The boundary portions 124 and 134 between the body portions 121 and 131 and the narrowing portions 122 and 132 are positioned in the insulator 11 to promote ionization due to the above-described leakage current. By setting the dimension C between the front end and the boundary portions 124 and 134 to 0.1 mm to 1.2 mm, ionization due to leakage current before capacitive discharge can be reliably performed.

(A) is front sectional drawing which shows the whole structure of the ignition plug which concerns on 1st Embodiment of this invention, (b) is a bottom view of (a). It is an expanded sectional view of the ignition part vicinity in the ignition plug of FIG. It is a chart which shows the specification of evaluation goods 1-5 which evaluated ignitability. It is a figure which shows the evaluation result regarding the ignitability of an evaluation product. It is sectional drawing of the principal part of the spark plug which concerns on 2nd Embodiment of this invention. It is sectional drawing of the principal part of the spark plug which concerns on 3rd Embodiment of this invention. It is sectional drawing of the principal part of the spark plug which concerns on 4th Embodiment of this invention. (A) is front sectional drawing which shows the principal part structure of the spark plug which concerns on 5th Embodiment of this invention, (b) is a bottom view of (a). It is sectional drawing of the principal part of the spark plug which concerns on 6th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Housing, 11 ... insulator, 12, 13 ... center electrode, 19 ... center side chip | tip, 20, 21 ... ground electrode, 18, 22, 23 ... ground side chip | tip, 121, 131 ... trunk | drum.

Claims (13)

In a spark plug in which a plurality of center electrodes (12, 13) are insulated and held by an insulator (11), the insulator is accommodated in a housing (10), and a ground electrode is joined to the housing,
A center tip (18, 19) thinner than the body (121, 131) held by the insulator in the center electrode is joined to the electrode tip located on the combustion chamber side in the center electrode,
A spark plug for an internal combustion engine, characterized in that a ground side tip (22, 23) protruding toward the center side tip is joined to the ground electrode. A tip mounting surface (201, 211) facing the electrode tip of the center electrode (12, 13) in the ground electrode (20, 21) is a surface orthogonal to the center axis (Z1) of the insulator (11). The spark plug for an internal combustion engine according to claim 1, wherein the spark plug is parallel. The tip mounting surface (201, 211) facing the electrode tip of the center electrode (12, 13) in the ground electrode (20, 21) is a surface orthogonal to the central axis (Z1) of the insulator (11). 2. The spark plug for an internal combustion engine according to claim 1, wherein the spark plug is inclined with respect to the internal combustion engine. In the spark plug in which the plurality of center electrodes (12, 13) are insulated and held by the insulator (11), and the insulator is accommodated in the housing (10),
A center tip (18, 19) thinner than the body (121, 131) held by the insulator in the center electrode is joined to the electrode tip located on the combustion chamber side in the center electrode,
A spark plug for an internal combustion engine, wherein a plurality of ground side tips (22, 23) projecting toward the center side tip are joined to the housing. The ignition plug for an internal combustion engine according to any one of claims 1 to 4, wherein the center side tip (18, 19) and the ground side tip (22, 23) are made of a noble metal. 6. The spark plug for an internal combustion engine according to claim 5, wherein the center tip (18, 19) is made of an Ir alloy. The ignition plug for an internal combustion engine according to claim 6, wherein the center side tip (18, 19) is made of an Ir alloy containing Ir of 50 wt% or more. 6. The ignition plug for an internal combustion engine according to claim 5, wherein the grounding tip (22, 23) is made of a Pt alloy. The spark plug for an internal combustion engine according to claim 8, wherein the grounding tip (22, 23) is made of a Pt alloy containing Pt by 50 wt% or more. The center side chip (18, 19) and the ground side chip (22, 23) may be any of Ir, Pt, Rh, Ni, W, Pd, Ru, Os, Al, Y, Y ₂ O ₃ as additives. The ignition plug for an internal combustion engine according to any one of claims 5 to 9, wherein the ignition plug is contained. Area S of the front end surface of the center-side chip (18, 19) is at 0.12 mm ² or more 0.38 mm ² or less,
The projecting length A of the center chip (18, 19) is 0.8 mm or more and 1.5 mm or less,
The area Q of the front end surface of the ground side chip (22, 23) is 0.12 mm ² or more and 0.65 mm ² or less,
11. The ignition plug for an internal combustion engine according to claim 1, wherein a protruding length B of the grounding tip (22, 23) is not less than 0.5 mm and not more than 1.2 mm. The center electrode (12, 13) is formed thinner than the body (121, 131) and extends from the body (121, 131) toward the center chip (18, 19). (122, 132), and the boundary portions (124, 134) between the body portions (121, 131) and the narrowed portions (122, 132) are disposed in the insulator (11). The spark plug for an internal combustion engine according to any one of claims 1 to 11, wherein the spark plug is an internal combustion engine. 13. The ignition plug for an internal combustion engine according to claim 12, wherein the boundary portion (124, 134) is located in a range of 0.1 mm to 1.2 mm from a tip of the insulator (11) on the combustion chamber side. .

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