KR20090013731A - Spark plug for internal combustion engine and method of manufacturing the same - Google Patents

Abstract

A spark plug for internal combustion engine and a manufacturing method thereof are provided to extend lifetime of a spark plug by preventing exfoliation of a noble metal chip. A spark plug for internal combustion engine comprises the followings: an insulator having an axis hole penetrated into axis line direction; a central electrode inserted in the axis hole; a metal shell installed in an outer circumference of the insulator; and a ground electrode(27) installed in a leading end part of the metal shell.

Description

Spark plug for internal combustion engine and manufacturing method of spark plug {SPARK PLUG FOR INTERNAL COMBUSTION ENGINE AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a spark plug for use in an internal combustion engine and a method of manufacturing the same.

The spark plug for an internal combustion engine is attached to an internal combustion engine (engine) and used for ignition of the mixer in a combustion chamber. In general, a spark plug includes an insulator having a shaft hole, a center electrode inserted into the shaft hole, a metal shell provided at an outer circumference of the insulator, and a spark discharge gap between the center electrode provided at the tip of the metal shell. A ground electrode is provided.

Further, for the purpose of improving flame resistance and flammability, a noble metal chip made of a noble metal alloy such as platinum is bonded to a tip of a ground electrode made of a heat resistant corrosion resistant metal such as a nickel alloy. When joining a noble metal chip to a ground electrode, the technique of spot welding with a laser beam along the outer peripheral part of the junction surface of a ground electrode and a noble metal chip is proposed (for example, refer patent document 1).

Patent Document 1: Japanese Patent No. 3460087

By the way, in recent years, in order to achieve high output of the engine, an engine having a high compression ratio has been developed. In the combustion chamber of such an engine, precious metal chips, ground electrodes, and the like are exposed to higher temperature conditions. In addition, since the heat is hardly dissipated at the tip side of the ground electrode, the closer to the tip side of the ground electrode, the higher the temperature becomes. For this reason, there exists a possibility that a difference may arise in the thermal stress which acts on the front-end side part of a ground electrode, and the thermal stress acting on a base-end side part in a noble metal chip, a ground electrode, and the junction part of both. Furthermore, there is a concern that oxidation scales, cracks, etc. occur at the boundary between the precious metal chip and the ground electrode, and the precious metal chip is dropped from the ground electrode.

In recent years, spark plugs are being miniaturized in response to requests for engine miniaturization, and the metal shell itself tends to have a smaller thickness and diameter. It must be made smaller, so the size must be further reduced. As a result, the heat dissipation performance of the ground electrode is further lowered, and there is a concern that the above-mentioned problem becomes more remarkable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to prevent the dropping of precious metal chips due to the difference in thermal stress, and furthermore, a spark plug for an internal combustion engine and a method of manufacturing the same, which can achieve long life. Is to provide.

Hereinafter, each structure suitable for solving the said objective is divided and demonstrated by item. Moreover, if necessary, the effect peculiar to a corresponding structure is added.

(Configuration 1)

The spark plug for an internal combustion engine of this structure comprises a cylindrical insulator having a shaft hole penetrating in the axial direction, a center electrode inserted into the shaft hole, a tubular metal shell provided at an outer periphery of the insulator, and its tip. A base end of a noble metal chip, the main component of which is a noble metal, is bonded to one side of the side, and a ground electrode is provided at the tip of the metal shell so that the front end of the noble metal chip faces the front end of the center electrode. A spark plug for an internal combustion engine, wherein the precious metal chip is joined by forming a molten portion in which itself and the ground electrode are dissolved in each other, and along the longitudinal direction of the ground electrode, and including a central axis of the precious metal chip. When the molten portion in the cross section is seen, the cross-sectional area of the proximal end molten portion A located at the proximal side of the ground electrode is in contact with the cross section. The total cross-sectional area of the cross-sectional area of the tip-side melt part B located at the tip side of the electrode is 4 mm 2 or more, and the cross-sectional area of the tip-side melt part B is determined by the cross-sectional area of the base-side melt part A. It is characterized by 1.1 to 1.3 times.

In addition, at least one of the base end side melting part A and the front end side melting part B may be formed so that both may be overlapped beyond the central axis of a noble metal chip. In this case, it is preferable to determine the cross-sectional area as follows. That is, in the cross section along the longitudinal direction of the ground electrode and including the central axis of the noble metal chip, an outline for forming the outline of the base-side melt part A and an outline of the tip-side melt part B are formed. The molten part which connected two intersection points of a line in a straight line, and divided | segmented into the proximal side side melting part A side was determined as "the proximal side side melting part A", and the molten part divided into the front side side melting part B side was "a front-end | tip. Side melt portion B ". The precious metal material is not only composed of precious metals such as platinum (Pt) and iridium (Ir) but also includes those having a precious metal as a main component.

According to the above configuration 1, since the noble metal chip is bonded to the tip portion of the ground electrode, the flame resistance and flammability can be improved.

On the other hand, since heat tends to be hard to be dissipated at the front end side of the ground electrode as described above, greater thermal stress is likely to occur at a portion closer to the front end of the ground electrode in the precious metal chip, the melting part, or the like under high temperature conditions. In particular, when attention is paid to the tip side and the base end side starting from the center of the precious metal chip, relatively large thermal stress is generated at the tip side, while relatively small thermal stress is generated at the base side. The molten portion formed by welding between the ground electrode and the precious metal chip absorbs the difference in thermal expansion between the two to prevent peeling off of the precious metal chip from the ground electrode, but the molten portion at the front end side and the molten portion at the rear end side have the same area. In this case, the difference in thermal stress is not absorbed, and there is a fear that the noble metal chip is peeled off at the boundary between the ground electrode and the noble metal chip.

In this regard, in the above-described configuration 1, when the molten portion in the cross section along the longitudinal direction of the ground electrode and including the central axis of the noble metal chip is viewed, the cross-sectional area of the tip-side molten portion B is melted at the proximal side. It becomes 1.1 to 1.3 times the cross-sectional area of the part (A). For this reason, the length of the boundary between the tip side melting part B and the noble metal chip (the contact area of the tip side melting part and the noble metal chip) and the length of the boundary between the tip side melting part B and the ground electrode (the melting on the tip side) The contact area between the part and the ground electrode) can be further increased. Therefore, since it is possible to absorb more energy in the melting portion at the tip side, deformation of the thermal stress applied to the noble metal chip can be alleviated. Thereby, the breakdown of the balance of thermal stress can be suppressed and the peeling resistance (falling resistance) of a noble metal chip can be improved. Furthermore, it becomes possible to extend the lifetime of a spark plug.

In addition, in the said structure 1, the total cross-sectional area of the cross-sectional area of the base end side melting part A and the cross-sectional area of the front end side melting part B is set to 4.Omm <2> or more. As a result, sufficient welding strength can be ensured, and the above-described effects can be obtained more reliably.

In addition, when the total cross-sectional area of the cross-sectional area of the base-side melt part A and the cross-sectional area of the tip-side melt part B is less than 4.O 2 mm, the weld strength is insufficient and there is a concern that the above-described effect may not be sufficiently obtained. have. In addition, when the cross-sectional area of the tip-side melt part B is less than 1.1 times the cross-sectional area of the base-side melt part A, thermal stress at the tip of the ground electrode is not sufficiently relaxed, and the above-described effects may not be sufficiently obtained. There is. On the other hand, when the cross-sectional area of the tip-side melt part B is larger than 1.3 times the cross-sectional area of the base-side melt part A, the thermal stress applied to the noble metal chip at the tip side of the ground electrode may be extremely alleviated. There is. As a result, the thermal stress applied to the noble metal chip at the front end side of the ground electrode is smaller than the thermal stress applied to the noble metal chip at the base end side of the ground electrode, so that the balance of thermal stress may collapse in the opposite direction to the above. have.

(Configuration 2)

In the spark plug for an internal combustion engine of this configuration, in the configuration 1, the precious metal chip has its proximal end embedded in the ground electrode, and the proximal side melted portion A and the proximal side melted portion B are respectively. The noble metal chip side melting parts C1 and C2 on the noble metal chip side and the ground electrode among the areas partitioned by the first virtual outline line among the regions partitioned by the rectangular first virtual outline of the precious metal chip before forming the melted portion. In the region at the side, the electrode is further divided into ground electrode side melt portions D1 and D2 on the ground electrode side partitioned by a second virtual outline of the ground electrode before forming the melt portion, and the proximal side melt portion A ) And the ground electrode side molten portion D1 (D2) in a cross section along the longitudinal direction of the ground electrode and including the central axis of the noble metal chip in at least one of the tip side molten portion B). Cross-sectional area Group noble metal chip side is characterized in that a 1.0 to 2.0-fold in the cross-sectional area of the melt part (C1 (C2)).

According to the above-mentioned structure 2, the cross-sectional area of the ground electrode side melting part D1 (D2) is at least one of the base-side melting part A and the tip-side melting part B, and the noble metal chip side melting part C1 (C2). It becomes 1.0 times-2.0 times the cross-sectional area of)). This prevents the linear expansion coefficient of the melted portion from becoming too close to only the linear expansion coefficient of either the precious metal material or the metal material. In other words, the volume change of the melted portion and the volume change of the noble metal material accompanying thermal expansion are not significantly different, and the volume change of the melted portion and the volume change of the metal material are not significantly different. As a result, an increase in the shear force accompanying thermal expansion at the boundary between the melted portion and the precious metal chip or at the boundary between the melted portion and the ground electrode can be suppressed. Can be suppressed. As a result, further improvement of peeling resistance can be aimed at.

In addition, when the cross-sectional area of the ground electrode side melted portions D1 and D2 is less than 1 times the cross-sectional area of the noble metal chip side melted portions C1 and C2, the coefficient of linear expansion of the melted portion is closer to that of the precious metal material. The difference in linear expansion coefficient between the melted portion and the ground electrode becomes larger. As a result, the shear force at the boundary between the molten portion and the ground electrode increases with thermal expansion, and there is a fear that cracks or the like occur between the molten portion and the ground electrode. On the other hand, when the cross-sectional area of the ground electrode side melted portions D1 and D2 becomes larger than twice the cross-sectional area of the precious metal chip side melted portions C1 and C2, the linear expansion coefficient of the melted portion becomes closer to the linear expansion coefficient of the metal material. Therefore, the shear force at the boundary between the molten portion and the precious metal chip is increased, and there is a possibility that a crack or the like occurs between the molten portion and the precious metal chip.

(Configuration 3)

In the configuration 1 or 2, the spark plug for an internal combustion engine has the proximal end melting at the front end of the precious metal chip in a cross section along the longitudinal direction of the ground electrode and including the central axis of the precious metal chip. When the shortest distance to the portion A is set to E (mm), and the shortest distance from the tip of the precious metal chip to the tip side melted portion B is F (mm), the following equation (1) and It is characterized by satisfying Formula (2).

1.05 ≦ E / F ≦ 1.25... (One)

0.3 mm E 0.5 mm (2)

In general, when the noble metal chip is placed under high temperature conditions, the oxidation resistance is lowered, and further, the wear resistance is lowered. Here, as described above, in the ground electrode, heat is hardly dissipated at the front end side, and since a portion closer to the front end side of the ground electrode tends to be high in temperature, the tip side of the ground electrode is also used for the precious metal chip bonded to the ground electrode. It is easy to become high temperature as it is a site located in. Therefore, the portion located on the tip side of the ground electrode of the noble metal chip is more likely to be consumed due to discharge than the portion located on the proximal side, so that the precious metal chip may be worn down. When the noble metal chip is worn out, the discharge position becomes unstable, and thus there is a fear that dispersion occurs in the direction of spreading the sparks, resulting in a decrease in combustion efficiency.

In this regard, according to the above-described configuration 3, the shortest distance from the tip of the precious metal chip to the proximal side melted portion A is set to E (mm), and from the tip of the precious metal chip to the tip melted portion B. When the shortest distance is set to F (mm), the molten portion is formed so as to satisfy "1.05≤E / F≤1.25". That is, the surface area of the site | part located in the front end side of a ground electrode in a noble metal chip is smaller than the surface area of the site | part located in the base end side of a ground electrode.

Therefore, the amount of heat received by the portion located at the front end side of the ground electrode in the noble metal chip that tends to be higher in temperature can be reduced, and further, the portion and the proximal side located at the front end side of the ground electrode in the noble metal chip. The temperature difference of the site | part located in can be reduced. As a result, uneven wear of the noble metal chip can be effectively prevented, the discharge position can be stabilized, and further, the combustion efficiency can be improved.

By the way, if the surface area of the site | part located in the front end side of a ground electrode in a noble metal chip is made small, the surface area of the site | part located in the front end side of the ground electrode in a melting part will increase. Therefore, it is concerned that the amount of heat received at the said site | part increases and peeling resistance and durability fall. However, in general, the metal material (for example, Ni alloy) forming the ground electrode has a lower thermal conductivity than the precious metal material forming the precious metal chip, so that the molten portion is formed by melting the metal material and the precious metal material forming the ground electrode. The thermal conductivity is smaller than that of the precious metal chip. Therefore, since heat from the combustion gas is relatively difficult to be transferred to the molten portion, the surface area of the molten portion is increased and the heat quantity of the molten portion is extremely increased. .

In addition, when it is set to "1.05> E / F", the amount of heat received by the site | part located in the front end side of the ground electrode in a noble metal chip cannot fully be reduced, Furthermore, the above-mentioned effect will not fully be acquired. There is concern. In the case of " E / F &gt; 1.25 &quot;, the amount of heat received by the portion located at the tip side of the ground electrode in the noble metal chip is extremely reduced, and is located at the proximal side of the ground electrode in the noble metal chip. There is a fear that the consumption at the site to proceed easily.

In the case of "0.3 mm> E", since the molten portion is formed at a position relatively close to the spark discharge gap, discharge is easily generated between the molten portions, and furthermore, There is a fear that stabilization cannot be sufficiently achieved. In addition, in the case of "E> 0.5 mm", since the precious metal chip further protrudes from the ground electrode and the amount of heat received by the precious metal chip increases, the portion located at the front end side and the proximal side of the ground electrode of the precious metal chip is increased. There exists a possibility that the balance of the temperature difference of the site | part located may collapse, and furthermore, the above-mentioned effect may not be fully acquired.

(Configuration 4)

The spark plug manufacturing method of this configuration includes a cylindrical insulator having a shaft hole penetrating in the axial direction, a center electrode inserted into the shaft hole, a cylindrical metal shell provided at an outer periphery of the insulator, and A base end of a noble metal chip composed mainly of a noble metal is joined to one side of the tip side, and a ground electrode provided at the tip of the metal shell so that the front end surface of the noble metal chip faces the front end surface of the center electrode, wherein the precious metal The chip is a method of manufacturing a spark plug which is joined by forming a molten part in which the ground electrode and the ground electrode are melted around each other, and by irradiating a laser beam to the outer edge of the bonding surface of the ground electrode and the precious metal chip. Forming a molten part to bond the noble metal chip to the ground electrode; In the tablet, and the energy for melting of the portion positioned at the front end side of the ground electrode is characterized in that a laser beam to be larger than melting energy for the area which is located on the base end side of the ground electrode.

According to the configuration 4 described above, the portion located at the front end side of the ground electrode in the melting section (the front side melt section B) is larger than the portion located at the proximal side (proximal side melt section A). Therefore, the spark plug which can acquire the effect similar to the structure 1 mentioned above can be manufactured easily and reliably comparatively easily.

(Configuration 5)

The manufacturing method of the spark plug of this structure is a manufacturing method of the spark plug for internal combustion engines of the said structure 1 or structure 2, Comprising: The said melting part is irradiated by irradiating a laser beam with respect to the outer peripheral part of the joining surface of the said ground electrode and the said noble metal chip. And a bonding step of bonding the noble metal chip to the ground electrode, wherein, in the bonding step, the melting energy of a portion located at the front end side of the ground electrode is located at a base end side of the ground electrode. It is characterized by irradiating a laser beam so as to be larger than the melt energy.

According to the configuration 5 described above, basically the same operation and effect as the configuration 4 described above can be obtained.

(Configuration 6)

In the method for manufacturing a spark plug according to the present invention, in the configuration 4, the laser beam is irradiated while increasing the melting energy from a portion located at the proximal side of the ground electrode to a portion located at the distal end side of the ground electrode. It is characterized by.

According to the configuration 6 described above, basically the same operation and effect as the configuration 4 described above can be obtained. Further, according to this configuration 6, the molten portion is formed so as to gradually increase from the portion located on the proximal side of the ground electrode to the portion located on the front end side. As a result, the balance of thermal stress applied to the noble metal chip can be further suppressed, and the peeling resistance of the noble metal chip can be further improved.

(Configuration 7)

In the manufacturing method of the spark plug of this structure, in the said structure 4 or 6, in the said bonding process, the center axis of the said noble metal chip was made into the center axis of the said noble metal chip, and the said ground in the state which fixed the irradiation direction of the laser beam. The melting part may be formed by rotating the noble metal chip and the ground electrode with an axis formed by tilting toward the proximal end of the ground electrode starting from an intersection with a plane including one side of the electrode as a rotation axis.

As a method of realizing the above-described configuration 3, for example, it is conceivable to change the irradiation direction of the laser beam (the position where the laser beam abuts) at the portion located at the front end side and the proximal side of the ground electrode. . However, when this method is used, it is necessary to provide a means for changing the irradiation direction separately, which may lead to a situation of complexity of the device and reduction of production efficiency.

In this regard, by rotating the noble metal chip and the ground electrode with the axis of inclination of the center axis of the noble metal chip as the rotation axis as described above, the above-described configuration 3 can be realized even if the irradiation direction of the laser beam remains fixed. . That is, according to this configuration 7, the above-described configuration 3 can be realized without any special difficulty, and the complexity of the device and the decrease in production efficiency can be prevented more reliably.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

[First embodiment]

1 is a partially broken front view of the spark plug 1. In addition, in FIG. 1, the axial line X direction of the spark plug 1 is made into the up-down direction in a figure, and the lower side is demonstrated as the front end side of the spark plug 1, and the upper side as the rear end side of the spark plug 1. In FIG. .

The spark plug 1 is comprised from the insulator 2 as a cylindrical insulator, the cylindrical metal shell 3 holding this, etc.

A shaft hole 4 is formed through the insulator 2 along the axis X. And the center electrode 5 is inserted and fixed to the front end side of the shaft hole 4, and the terminal electrode 6 is inserted and fixed to the rear end side. A resistor 7 is disposed between the center electrode 5 and the terminal electrode 6 in the shaft hole 4, and both ends of the resistor 7 are formed with conductive glass sealing layers 8, 9. It is electrically connected to the center electrode 5 and the terminal electrode 6, respectively.

The center electrode 5 protrudes from the front end of the insulator 2, and the terminal electrodes 6 are fixed in the state protruding from the rear end of the insulator 2, respectively. The center electrode 5 also has a The noble metal chip 31 is joined to the front end by welding (this will be described later).

On the other hand, the insulator 2 is formed by firing alumina or the like, as is well known, and has a front end side than the rear end side body part 10 and the rear end side body part 10 formed on the rear end side of the outer side part. Larger diameter portion 11 protruding outward in the radial direction, the intermediate body portion 12 formed with a diameter smaller than this at the tip side than the large diameter portion 11, and the intermediate body portion 12 The leg part 13 formed in diameter smaller than this in the front end side is provided. The large diameter portion 11, the middle body portion 12, and most of the leg portions 13 in the insulator 2 are housed inside the metal shell 3. A tapered stepped portion 21 is formed at the junction between the leg portion 13 and the intermediate body portion 12, and the insulator 2 is formed of the metal shell 3 by the stepped portion 21. )

The metal shell 3 is formed in a tubular shape by metal such as low carbon steel, and a threaded portion (male screw portion) 15 for attaching the spark plug 1 to the engine head is formed on the outer circumferential surface thereof. In addition, a seating portion 16 is formed on the outer circumferential surface of the rear end side of the threaded portion 15, and a ring-shaped gasket 18 is fitted into the screw neck 17 of the rear end of the threaded portion 15. In addition, at the rear end side of the metal shell 3, a tool engagement portion 19 having a hexagonal cross section for engaging a tool such as a wrench or the like when the metal shell 3 is attached to the engine head is formed. A caulking portion 20 for holding the insulator 2 is formed.

In addition, a tapered stepped portion 14 for engaging the insulator 2 is formed on the inner circumferential surface of the metal shell 3. Then, the insulator 2 is inserted from the rear end side of the metal shell 3 toward the line end side, and the metal shell with its stepped portion 21 engaged with the stepped portion 14 of the metal shell 3. It is fixed by caulking the opening part of the rear end side of (3) radially inward, ie, forming the said caulking part 20. FIG. An annular flat plate packing 22 is interposed between the stepped portion 21 of the insulator 2 and the stepped portion 14 of the metal shell 3. As a result, fuel air that penetrates into the gap between the leg 13 of the insulator 2 exposed in the combustion chamber and the inner circumferential surface of the metal shell 3 does not leak to the outside, thereby maintaining airtightness in the combustion chamber.

Furthermore, in order to more completely seal by caulking, on the rear end side of the metal shell 3, annular ring members 23 and 24 are interposed between the metal shell 3 and the insulator 2, The powder of talc (talc) 25 is filled between these ring members 23 and 24. That is, the metal shell 3 holds the insulator 2 via the flat plate packing 22, the ring members 23 and 24, and the talc 25.

Further, a ground electrode 27 having a substantially L shape is joined to the tip portion 26 of the metal shell 3. That is, the ground electrode 27 is welded to the front end portion 26 of the metal shell 3, the front end side is bent, and the side end is the front end portion of the center electrode 5 (the precious metal chip 31). It is arranged to face with. In the present embodiment, the ground electrode 27 is formed of Ni-23Cr-14.4Fe-1.4Al (Incone 1601 (Japan registered trademark)), and the thermal conductivity of this metal material is about 0.111 W / cm. It is K.

In addition, the noble metal chip 32 is joined to the ground electrode 27 so as to face the noble metal chip 31 (this will be described later). The gap between these precious metal chips 31 and 32 is the spark discharge gap 33. In the present embodiment, the noble metal chip 31 is made of a known noble metal material (for example, Pt-Ir alloy or the like), and the noble metal chip 32 is made of Pt-20Ir-5Rh alloy. Formed. In addition, the thermal conductivity of the noble metal material is about 0.262 W / cm · K, and has a higher thermal conductivity than the metal material constituting the ground electrode 27.

The center electrode 5 is constituted by an inner layer 5A made of copper or a copper alloy and an outer layer 5B made of a nickel (Ni) alloy. In addition, the ground electrode 27 is made of Ni alloy.

The diameter of the center electrode 5 gradually decreases toward the tip side, but forms a rod shape (cylindrical shape) as a whole, and the tip end surface is flat. The noble metal chip 31 and the center electrode 5 are joined to each other by superimposing the noble metal chip 31 forming a cylindrical shape and performing laser welding, electron beam welding, or resistance welding along the outer edge of the joining surface.

On the other hand, the precious metal chip 32 facing the precious metal chip 31 is embedded in the ground electrode 27 by resistance welding in a state where it is positioned at a predetermined position of the ground electrode 27. Spot welding is performed with the laser beam along the outer edge of the joint surface. As a result, a molten portion 34 in which the noble metal material and the Ni alloy are melted is formed, and the ground electrode 27 and the noble metal chip 32 are joined. The noble metal chip 31 on the side of the center electrode 5 may be omitted. In this case, a spark discharge gap 33 is formed between the tip of the center electrode 5 and the precious metal chip 32.

In addition, in this embodiment, the melting part 34 is the front end side of the ground electrode 27 in the proximal side melting part A located in the proximal side (left side of the figure) of the ground electrode 27 (right side of the figure). It is formed so that the volume (melt amount) may gradually increase over the front-end side melt part B located in (circle). More specifically, as shown in FIG. 2, the cross section along the longitudinal direction of the ground electrode 27 and including the central axis Y of the noble metal chip 32 (hereinafter referred to as “center axis cross section”). WHEREIN: It is formed so that the cross-sectional area of the front end side melt part B may be 1.1-1.3 times (for example, 1.2 time) of the cross-sectional area of the base end side melt part A. FIG. Moreover, the sum total cross-sectional area of the cross-sectional area of the said base side melting part A and the cross-sectional area of the front side side melting part B is set to 4.Omm <2> or more (for example, 5.Omm <2>).

As shown in Fig. 3, the proximal end melted part A and the proximal end melted part B are each formed before the melting part 34 (the proximal end of the precious metal chip 32 is connected to the ground electrode 27). The noble metal chip side melting parts C1 and C2 on the noble metal chip 32 side and the first virtual outline in the region partitioned by the rectangular first virtual outline N1 of the precious metal chip 32 in the buried state}. The ground electrode further partitioned by a second virtual outline line N2 of the ground electrode 27 before the melting portion 34 is formed in the region partitioned by the line N1 on the side of the ground electrode 27. It is divided into the melting parts D1 and D2 of the ground electrode side on the (27) side. In addition, the noble metal chip side melt portions C1 and C2 are shown by oblique lines slanting from the lower left side to the upper right portion, and the ground electrode side melt portions D1 and D2 are shown as oblique lines slanting from the upper left side to the lower right portion. .

Further, in the cross section of the central axis, the cross-sectional area of the ground electrode side melting portion D1 is 1.0 to 2.0 times (for example, 1.5 times) the cross-sectional area of the noble metal chip side melting portion C1, and the ground electrode side The cross-sectional area of the molten portion D2 is 1.0 to 2.0 times (for example, 1.7 times) of the cross-sectional area of the noble metal chip side molten portion C2.

Next, the manufacturing method of the spark plug 1 comprised as mentioned above is demonstrated.

First, the metal shell 3 is processed beforehand. In other words, a cylindrical shape metal material (for example, iron-based material or stainless steel material such as S17C or S25C) is formed by cold forging while forming a through hole. Thereafter, the outer shape is adjusted by cutting to obtain a metal shell intermediate.

Subsequently, a ground electrode 27 made of a Ni alloy (for example, an Inconel alloy or the like) is resistance welded to the front end surface of the metal shell intermediate. Since the so-called "drip" occurs at the time of welding, after removing this "drip", the screw part 15 is formed by rolling in the predetermined part of the metal shell intermediate body. As a result, the metal shell 3 to which the ground electrode 27 is welded is obtained. In addition, after providing the noble metal chip 32 mentioned later to the ground electrode 27, you may weld the ground electrode 27 to a metal shell intermediate body. The metal shell 3 to which the ground electrode 27 is welded is subjected to zinc plating or nickel plating. In addition, in order to improve corrosion resistance, the surface may further be chromated.

In addition, the above-described precious metal chip 32 is bonded to the tip portion of the ground electrode 27. More specifically, first, the base of the precious metal chip 32 is temporarily fixed to the predetermined portion of the ground electrode 27 by resistance welding in a state of being embedded in the ground electrode 27. Then, the laser is applied to the outer edge of the joint surface of the ground electrode 27 and the precious metal chip 32 while rotating the precious metal chip 32 relative to the laser irradiation means with the central axis Y of the precious metal chip 32 as the rotation axis. The beam is intermittently irradiated. More specifically, the laser beam is irradiated a predetermined number of times (for example, eight times) such that the intervals between the centers of the melting points at which the laser beam is irradiated are approximately equal. As a result, a plurality of melting points (melting portions 34) connected in an annular shape when viewed from the front end side of the noble metal chip 32 are formed so that the ground electrode 27 and the noble metal chip 32 are joined (spot welding method). ).

Moreover, when irradiating a laser beam, a laser beam is irradiated at the predetermined angle with respect to the said outer peripheral surface part, increasing or decreasing an output energy step by step. Specifically, a relatively low energy laser beam is irradiated to a portion located at the proximal side of the ground electrode 27 among the outer edge portions of the bonding surface, while a relatively high energy is applied to a portion located at the distal end side of the ground electrode 27. Laser beam is irradiated. Thereby, the amount of melting of the tip side melting part B formed in the front end side of the ground electrode 27 is larger than the amount of melting of the base end side melting part A formed in the base end side of the ground electrode 27. You lose.

As described above, the melt amount of the base-side melt part A and the tip-side melt part B may be increased or decreased by changing the focal length of the laser beam without increasing or decreasing the output energy.

In order to further ensure welding, plating of the welded portion is removed prior to the welding or masked on the weld preliminary portion during the plating process. The welding of the noble metal chip 32 may be performed after assembling which will be described later.

On the other hand, the insulator 2 is formed and molded separately from the metal shell 3. For example, a cylindrical molded product is obtained by preparing a granulated body for molding using a material powder containing alumina as a main body and using a binder and the like, and performing rubber press molding using this. . Grinding is performed and shape | molded about the obtained molded object. And the shape | mold is put into a kiln, and it bakes. After firing, the insulating insulator 2 is obtained by performing various polishing processes.

In addition, the center electrode 5 is manufactured separately from the metal shell 3 and the insulator 2. That is, Ni alloy is forged and the inner layer 5A which consists of a copper alloy is formed in the center part in order to improve heat dissipation. The noble metal chip 31 described above is joined to the tip portion by resistance welding, laser welding, or the like.

Then, the insulator 2, the center electrode 5, the resistor 7 and the terminal electrode 6 obtained as described above are hermetically fixed by the glass sealing layers 8,9. Generally as the glass sealing layers 8 and 9, borosilicate glass and metal powder are mixed and prepared, and this preparation is injected into the shaft hole 4 of the insulator 2 with the resistor 7 interposed therebetween, and After the terminal electrode 6 is pressed in the rear, it is baked and hardened in a kiln. At this time, the glaze layer may be simultaneously fired on the surface of the rear end side body portion 10 of the insulator 2, or the glaze layer may be formed in advance.

Thereafter, the insulator 2 including the center electrode 5 and the terminal electrode 6 prepared as described above and the metal shell 3 including the ground electrode 27 are assembled. More specifically, the opening on the rear end side of the metal shell 3, which is formed relatively thin, is fixed by caulking inwardly in the radial direction, that is, by forming the caulking portion 20. FIG.

Finally, by bending the ground electrode 27, the spark discharge gap 33 between the noble metal chip 31 provided on the tip of the center electrode 5 and the noble metal chip 32 provided on the ground electrode 27. Machining to adjust is carried out.

Thus, the spark plug 1 which has the structure mentioned above is manufactured by passing through a series of processes.

Next, in order to confirm the effect by which this embodiment is obtained, the following test was done.

That is, when the noble metal chip is joined to the ground electrode, along the longitudinal direction of the ground electrode, and the molten part in the cross section passing through the central axis of the noble metal chip, the cross-sectional area of the base-side molten part (hereinafter referred to as "SA") Total cross-sectional area (hereinafter referred to as "SA + SB"), cross-sectional area ratio of SA and SB (hereinafter referred to as "SB / SA"), and tip side The cross sectional area ratio (hereinafter referred to as "SC") of the noble metal chip side melted portion on the melted portion side and the cross-sectional area of the melted portion on the ground electrode side (hereinafter referred to as "SD") at the tip side melted portion side (hereinafter referred to as "SD / SC"). The sample of the spark plug which changed various) was produced, and the peeling resistance evaluation test was done about each sample. The result of this test is shown by the line graph and contour line graph of FIGS.

Here, the outline of the peeling resistance evaluation test is as follows. That is, a sample of each spark plug is attached to a 2000 kW series 6-cylinder engine, and it is set as 1 cycle after making it into a 1 minute full load state (engine speed = 5000rpm) for 1 minute, and peeling a chip | tip in a precious metal The number of cycles (the number of chip peel cycles) until the occurrence of was measured. In addition, in the said test, it was decided that it had sufficient peeling-resistant performance when the number of chip peel cycles became 10000 cycles or more.

4 and 5 show a line graph and a contour graph when SA + SB is 3 mm 2, and a line graph and contour graph when SA + SB is 4 mm 2 in FIGS. 6 and 7. In Fig. 9, a line graph and a contour graph when SA + SB is 6 mm 2 are shown, respectively.

4, 6, and 8, the vertical axis represents the number of chip peel cycles, the horizontal axis represents SD / SC, and the sample with SB / SA of "1.0" is a circular black spot. A sample of "1.1" is composed of a triangle black dot, a sample of "1.2" is a rhombic black spot, a sample of "1.3" is a square black dot, and a sample of "1.4" is composed of a x mark. In addition, a thick line indicates 10000 cycles which can be evaluated as having sufficient peeling resistance.

In addition, in each contour graph (FIG. 5, FIG. 7, FIG. 9), the vertical axis | shaft is SB / SA, the horizontal axis is SD / SC, and the area | region where the number of chip peel cycles became 10000 cycles or more is displayed in white. Here, since it is recognized that when the number of chip peel cycles becomes 13000 cycles or more, it is recognized to have extremely excellent peeling resistance, the intersecting line in the region is particularly indicated by a dotted line. On the other hand, when the number of chip peel cycles is less than 10,000 cycles, the peeling resistance is not sufficient, and the inside of the area is displayed in a shape scattered with dots. In this case, the larger the density of the point (the higher the concentration), the less the peeling performance.

As shown in Fig. 4 to Fig. 9, by removing SB / SA from " 1.1 to 1.3 " without depending on the value of SA + SB, the chip peel cycle is compared with the case of SB / SA being " 1.0 " It was confirmed that the number of times increased. This is because the boundary area between the tip-side melt part and the precious metal chip and the border area between the tip-side melt part and the ground electrode are further increased, so that the thermal stress applied to the precious metal chip at the melt part or the ground electrode part located at the tip side of the ground electrode is increased. It is thought that this is due to the relaxation of the thermal stress at the front end side of the ground electrode and further relaxation of the ground electrode.

Moreover, it became clear that the number of chip peel cycles further increased by setting SD / SC to "1.0-2.0". This is because the coefficient of linear expansion of the melted portion does not become too close to only the coefficient of linear expansion of either the precious metal material or the metal material, so that the shear force at the boundary between the melted portion and the precious metal chip or the boundary between the melted portion and the ground electrode is increased. It can be suppressed, and furthermore, it is thought that it was based on being able to suppress generation | occurrence | production of the oxidation scale, a crack, etc. in each boundary.

On the other hand, as shown in Figs. 4 and 5, when SA + SB is 3 mm 2, improvement in peeling resistance was recognized by setting SB / SA to "1.1 to 1.3" or SD / SC to "1.0 to 2.0", but sufficient resistance was obtained. It was not recognized until it had peeling performance. This is considered to be due to insufficient welding strength because the melt amount of the melt portion is too small.

On the other hand, when SA + SB is 4 mm <2> as shown to FIG. 6 and FIG. 7, SB / SA is set to "1.1-1.3" and SD / SC is set to "1.0-2.0" (bold in FIG. 7). In the area enclosed by lines), the number of chip peel cycles exceeded 10,000 cycles, and it was confirmed that sufficient peeling resistance could be realized.

As shown in Figs. 8 and 9, when SA + SB is 6 mm2, the area where SB / SA is "1.1 to 1.3" and SD / SC is "1.0 to 2.0" (enclosed by a thick line in Fig. 9). In the region where the number of chip peel cycles exceeded 13,000 cycles occupy most of the region, it was confirmed that very excellent peeling resistance could be realized.

As mentioned above, SA + SB is 4 mm <2> or more, and SB / SA is "1.1-1.3" and SD / SC is "1.0-2.0", and it can be said that the peeling resistance of a noble metal chip can be improved sufficiently. have.

[2nd Embodiment]

Next, 2nd Embodiment is described with reference to FIGS. 11-16. In addition, in this embodiment, since the structure of the fusion | melting part 34 and the joining method of the ground electrode 27 and the noble metal chip 32 are different from 1st Embodiment mentioned above, it demonstrates centering on these below.

Also in the present embodiment, similarly to the first embodiment described above, in the cross section of the central axis, the cross-sectional area of the tip-side melt part B is formed so as to be 1.1 to 1.3 times the cross-sectional area of the base-side melt part A. The total cross-sectional area of the cross-sectional area of the base-side melt part A and the cross-sectional area of the tip-side melt part B is at least 4.0 mm 2. Further, in the cross section of the central axis, the cross-sectional area of the ground electrode side melt parts D1 and D2 is 1.0 to 2.0 times the cross-sectional area of the noble metal chip side melt parts C1 and C2.

Hereinafter, the structure of the melting part 34 peculiar to this 2nd Embodiment is demonstrated.

As shown in FIG. 11, the melting part 34 in this embodiment is located in the front end side in the site | part where the edge of the edge located in the front end side of the noble metal chip 32 is located in the base end side of the ground electrode 27. As shown in FIG. It is formed to approach the tip of the noble metal chip 32 gradually toward the site. That is, as shown in FIG. 12, compared with the base end side melting part A, the front side side melting part B is formed in the state which approached the front end of the noble metal chip 32 further. More specifically, the shortest distance from the tip of the precious metal chip 32 to the proximal end melted portion A in the cross section of the central axis is called E (mm), and the tip side of the precious metal chip 32 at the tip side. When the shortest distance to the fusion | melting part B is set to F (mm), the fusion | melting part 34 which satisfy | fills 1.05 <= E / F <= 1.25 is formed. In addition, in this embodiment, the melting part 34 which satisfies 0.3 mm <= E <= 0.5mm is formed.

As shown in Fig. 12, the precious metal chip 32 is joined so that its front end surface 32f is parallel to the end face 27b of the center electrode 5 side of the ground electrode 27. As shown in Figs. That is, the precious metal chip between the front end side end portion 32f1 located at the front end side of the ground electrode 27 in the front end surface 32f of the precious metal chip 32 and the end face 27b of the ground electrode 27. A base (proximal end length) L1 along the central axis Y of the base 32, and a proximal end positioned on the proximal end of the ground electrode 27 in the distal end surface 32f of the noble metal chip 32; The distance along the central axis Y of the noble metal chip 32 between the side end portion 32f2 and the end surface 27b of the ground electrode 27 is the same (proximal end length) L2.

The noble metal chip 32 is joined so that its front end face 32f protrudes 0.8 mm along the central axis Y from the end face 27b of the ground electrode 27.

Next, the bonding method of the ground electrode 27 and the noble metal chip 32 is demonstrated.

First, the base end of the noble metal chip 32 is temporarily fixed to the ground electrode 27 in a predetermined portion of the ground electrode 27 by resistance welding.

13 and 14, an intersection point BP of the central axis Y of the noble metal chip 32 between the central axis Y and a plane including one side surface of the ground electrode 27 is defined. A laser beam in which the irradiation direction is fixed while relatively rotating the ground electrode 27 and the noble metal chip 32 with the axis AR formed by tilting the base AR of the ground electrode 27 by a predetermined angle as a starting point. LB) is intermittently irradiated to the outer edge of the bonding surface of the ground electrode 27 and the noble metal chip 32.

As a result, the laser beam LB is irradiated at a position relatively near the distal end of the noble metal chip 32 at the portion located at the distal end side of the ground electrode 27, while being located at the proximal end of the ground electrode 27. At the position where the laser beam is located, the laser beam LB is irradiated at a relatively separated position from the tip of the precious metal chip 32. Therefore, the tip-side melting part B is formed in a state closer to the tip of the precious metal chip 32, and the base-side melting part A is formed at a position relatively separated from the tip of the precious metal chip 32. .

As described above, by using the above-described manufacturing method, the end edge located at the front end side of the noble metal chip 32 in the melting section 34 is not caused to complicate the device and lower the production efficiency. The melting part 34 can be formed so as to approach the tip of the noble metal chip 32 gradually from the site located at the proximal side of the back side to the site located at the front end side.

Next, in order to confirm the operation and effect obtained by this embodiment, as shown in FIG. 15, the shortest distance between the front-end | tip of the noble metal chip 32 on the ground electrode 27 side, and the front-end side melting part B " The ratio ("SE / SF") of the shortest distance "SE" between the tip of the said noble metal chip 32 and the base side side melting part A with respect to SF ", and the said shortest distance" SE "are variously changed. A sample of one spark plug was produced and the durability evaluation test was done about each sample. The outline of the durability evaluation test is as follows.

That is, a sample of each spark plug was attached to a 2000 kPa inline 6-cylinder engine, and the engine was operated over 100 hours in a full load state (engine rotation speed = 5000 rpm). Thereafter, with respect to the precious metal chip 31 on the side of the center electrode 5 and the precious metal chip 32 on the ground electrode 27 side, the distance "G1" between the portions located at the proximal side of the ground electrode and the ground electrode While the distance "G2" of the parts located in the front end side was measured, the absolute value (| G1-G2 |) of the difference of both was computed. 16 is a graph showing a relationship between SE / SF and | G1-G2 |.

In Fig. 16, the test results when the SE is 0.3 mm are formed in a rhombus, the test results when the SE is 0.4 mm is formed in a triangle, and the test results when the SE is 0.5 mm. It consisted of a circle and the test result when SE was set to 0.6 mm was comprised by the x mark. The precious metal chip was formed of Pt-20Ir-5Rh alloy, and the ground electrode was formed of Incone1601 (Japanese registered trademark).

As shown in Fig. 16, for samples having SE of 0.3 mm or more and 0.5 mm or less and SE / SF of 1.05 or more and 1.25 or less, | Gl-G2 | It can be seen that can effectively suppress the. This is because when the SE / SF is set to 1.05 or more and 1.25 or less, the surface area of the portion located on the front end side of the ground electrode in the precious metal chip on the ground electrode side becomes smaller than the surface area of the portion located on the proximal side of the ground electrode. In addition, it is possible to reduce the amount of heat received by the portion located at the tip side of the ground electrode, which tends to become higher, and furthermore, to reduce the temperature difference between the portion located at the tip side of the ground electrode and the portion located at the base end. I think it is by thing.

On the other hand, for samples having a SE / SF of less than 1.05 and samples having a SE / SF of more than 1.25, | G1-G2 | became over 0.05 mm, and it became clear that noble metal chips had a single wear. This is considered to be based on the following reason. In other words, when the SE / SF is less than 1.05, the amount of heat received by the portion located at the tip side of the ground electrode in the noble metal chip is not sufficiently reduced, and it is considered that the consumption at this portion is easily performed. do. On the other hand, when the SE / SF exceeds 1.25, since the amount of heat received by the portion located at the tip side of the ground electrode in the noble metal chip is extremely reduced, the consumption at the portion located at the base end side of the ground electrode is easy. It seems to be due to what went on.

In addition, for the sample having SE of 0.6 mm, | G1-G2 | became larger than 0.05 mm regardless of the value of SE / SF, and it became clear that uneven wear occurred in the noble metal chip. Since the precious metal chip on the ground electrode side protrudes further from the ground electrode, the amount of heat received by the precious metal chip increases, and furthermore, the precious metal chip is located at the proximal side and the portion located at the front end side of the ground electrode. It is considered that the balance of the temperature difference between the sites is collapsed.

In addition, this invention is not limited to description of said embodiment, For example, you may carry out as follows. Of course, other applications and modifications not exemplified below are naturally possible.

(a) In the above-described embodiment, the proximal end melted portion A and the proximal side melted portion B are formed without exceeding the central axis Y of the noble metal chip 32, but the proximal end melted portion A And at least one of the tip side melted portions B may be formed beyond the central axis Y. At this time, as shown in Fig. 10A, the proximal side melted portion A and the proximal side melted portion B may overlap each other. In this case, the proximal end melted portion A is formed as follows. It is preferable to determine the cross-sectional area of the cross section and the cross-sectional area of the tip-side melt part (B). That is, as shown to Fig.10 (b), in the said central-axis cross section, forming the external shape of the outline line H1 which forms the external shape of the base end side melt part A, and the front side side melt part B. Two intersections K1 and K2 of the outline line H2 are connected by an imaginary straight line S. Then, as shown in Fig. 10C, the molten portion A1 divided into the proximal side melted portion A side is determined as the "proximal side melted portion A", and the molten portion A1 toward the proximal side melted portion B side. The divided melted portion B1 is determined as the "front side melted portion B".

(b) In the above embodiment, the cross-sectional area of the ground electrode side melting part D1 in the base-side melting part A becomes 1.0 to 2.0 times the cross-sectional area of the precious metal chip side melting part C1, and the tip-side melting is performed. The cross-sectional area of the ground electrode side melted portion D2 in the portion B is 1.0 to 2.0 times the cross-sectional area of the noble metal chip side melted portion C2. On the other hand, the cross-sectional area of the ground electrode side melting part D1 (D2) in either one of the proximal side melting part A and the tip side melting part B is determined by the noble metal chip side melting part C1 (C2). It may be set to 1.0 to 2.0 times the cross-sectional area.

(c) Although not specifically mentioned in the above embodiment, the cross-sectional area of the tip portion of the ground electrode 27 is relatively small (for example, 2.0 mm 2 or more and 3.5 mm 2 or less) in consideration of recent requests for miniaturization of spark plugs. ) May be used. In this case, when the cross-sectional area is relatively small, the heat dissipation performance of the ground electrode 27 decreases, so that the ground electrode 27 tends to be higher in temperature, and further, the balance of the thermal stress applied to the noble metal chip 32 is further increased. There is a concern that it becomes easy to collapse. By adopting the above configuration in this regard, it is possible to stably suppress the collapse of the balance of the thermal stress. That is, the effect by setting it as the above structure on the conditions which the ground electrode 27 tends to become high temperature can be acquired more effectively.

(d) In the above embodiment, the precious metal chip 32 is formed of Pt-20Ir-5Rh alloy, but the precious metal chip 32 may be formed of another precious metal or precious metal alloy. Therefore, you may form with Pt-20Rh alloy, for example.

By the way, the thermal conductivity of the fusion | melting part 34 can be changed by changing the composition of the noble metal chip 32. FIG. Here, in order to confirm whether the effect of the above-described embodiment is obtained when the composition of the noble metal chip 32 is changed, the noble metal chip made of Pt-20Rh alloy is provided, and the tip of the noble metal chip on the ground electrode side and The ratio (SE / SF) of the shortest distance "SE" between the tip of the precious metal chip and the base-side melted part with respect to the shortest distance "SF" between the tip melted part and the shortest distance "SE" are various. The sample of the spark plug changed into was produced, and the above-mentioned durability evaluation test was done about each sample. The result of this evaluation test is shown in FIG. In addition, the thermal conductivity of the Pt-20Rh alloy is about 0.372 W / cm · K. The ground electrode was formed by Incone1601 (Japanese registered trademark).

As shown in Fig. 17, the precious metal chip made of the Pt-20Rh alloy was similarly to the above-described embodiment, and the sample made SE of 0.3 mm or more and 0.5 mm or less and SE / SF of 1.05 or more and 1.25 or less. It became clear that | G1-G2 | became 0.05 mm or less and can effectively suppress the single-wear of a noble metal chip. That is, it is thought that the effect in the above-mentioned embodiment is obtained by forming a noble metal chip from the noble metal material which has a thermal conductivity larger than the thermal conductivity of the metal material which forms a ground electrode. Therefore, as long as such a relationship is satisfied, it is not limited to the alloy containing Pt as the main component described above, and even the precious metal chips formed by the alloy containing Ir as a main component can be said to have the same effect. .

(e) In the above embodiment, the ground electrode 27 is formed by Incone1601 (registered trademark in Japan), but the metal material constituting the ground electrode 27 is not limited to this. In addition, from the viewpoint of effectively suppressing the single wear of the noble metal chip 32, it is preferable to form the ground electrode 27 by a metal material having a thermal conductivity smaller than that of the noble metal material constituting the noble metal chip 32. Therefore, for example, the ground electrode 27 may be formed of a Ni-15.5Cr-8Fe alloy (Incone 1600) manufactured by a metal material having a relatively low thermal conductivity of about 0.149 W / cm · K. .

(f) In the second embodiment described above, the end face 32f of the ground electrode 27 and the front end face 32f of the noble metal chip 32 are parallel to each other, that is, the tip end protrusion length L1 and the proximal end protrusion length. Although the noble metal chip 32 is bonded to the ground electrode 27 so that L2 is the same, the noble metal chip 32 has the ground electrode 27 so that the end face 32f and the front end face 32f are substantially parallel. It is good to be bonded to). Therefore, the precious metal chip 32 is bonded to the ground electrode 27 so that the difference between the tip-side protrusion length Ll and the base-side protrusion length L2 is within a predetermined range (for example, 0.05 mm). It may be used.

(g) In the above embodiment, the case where the ground electrode 27 is bonded to the tip end portion 26 of the metal shell 3 is specified. However, a tip shell which is previously welded to the metal shell (or the metal shell is pre-welded). It is also applicable to the case where the ground electrode is formed by scraping off a portion of the metal sheet (for example, Japanese Patent Laid-Open No. 2006-236906, etc.).

(h) Although the tool engagement part 19 has a hexagonal cross section in the above-mentioned embodiment, the shape of the tool engagement part 19 is not limited to this shape. For example, it may be a Bi-HEX (deformation 12 angle) shape [ISO22977: 2005 (E)].

1 is a partially broken front view illustrating a spark plug according to the present embodiment.

2 is a partially enlarged cross-sectional view showing a cross section of a melted part or the like according to the present embodiment.

Fig. 3 is a partially enlarged schematic diagram showing the noble metal chip side melting part and the ground electrode side melting part according to the present embodiment.

Fig. 4 is a graph showing test results when the total cross-sectional area of the cross-sectional area of the noble metal chip side melted portion and the ground electrode side melted portion is 3 mm 2 in the peeling resistance evaluation test.

Fig. 5 is a contour graph showing test results when the total cross-sectional area of the cross-sectional area of the noble metal chip side melted portion and the ground electrode side melted portion is 3 mm 2 in the peeling resistance evaluation test.

Fig. 6 is a graph showing test results when the total cross-sectional area of the cross-sectional area of the noble metal chip side melted portion and the ground electrode side melted portion is 4 mm 2 in the peeling resistance evaluation test.

Fig. 7 is a contour graph showing the test results when the total cross-sectional area of the cross-sectional area of the noble metal chip side melted portion and the ground electrode side melted portion is 4 mm 2 in the peeling resistance evaluation test.

Fig. 8 is a graph showing test results when the total cross-sectional area of the cross-sectional area of the noble metal chip side melted portion and the ground electrode side melted portion is 6 mm 2 in the peeling resistance evaluation test.

Fig. 9 is a contour graph showing test results when the total cross-sectional area of the cross-sectional area of the noble metal chip side melted portion and the ground electrode side melted portion is 6 mm 2 in the peeling resistance evaluation test.

In FIG. 10, (a) is the partial expanded sectional drawing which shows the front side melt part, the base side melt part, etc. in another embodiment, (b), (c) is the cross-sectional area of the front side melt part in another embodiment. And schematic diagram for explaining the method for determining the cross-sectional area of the proximal side melted portion.

Fig. 11 is a partially enlarged front view showing the structure of the melting section of the ground electrode and the noble metal chip in the second embodiment.

12 is a partial cross-sectional view showing the positional relationship between the proximal end melted portion, the distal end melted portion, and the precious metal chip according to the second embodiment;

FIG. 13 is a schematic sectional view referred to for describing the bonding method for the ground electrode and the noble metal chip according to the second embodiment; FIG.

14 is a schematic cross-sectional view for explaining a bonding method between a ground electrode and a noble metal chip according to the second embodiment.

15 is a cross-sectional view for explaining the concept of a sample used in the durability evaluation test (however, hatching is omitted for convenience).

16 is a graph showing the results of the endurance evaluation test for the samples in which SE and SE / SF are variously changed.

17 is a graph showing the results of durability evaluation tests of samples in which SE and SE / SF are variously changed in other precious metal chips.

Explanation of symbols on the main parts of the drawings

1-spark plug for internal combustion engine 2-insulator (insulator)

3-metal shell 4-shaft hole

5-center electrode 26-tip of metal shell

27-Grounding Electrode 32-Precious Metal Chip

33-flame discharge gap 34-melt

A-Proximal Melt B-Proximal Melt

Cl, C2-Melt side of precious metal chip Dl, D2-Melt side of ground electrode

Nl-the first virtual outline N2-the second virtual outline

X-axis Y-center axis

Claims (7)

A cylindrical insulator having an axial hole penetrating in the axial direction, a center electrode inserted into the shaft hole, a cylindrical metal shell provided at an outer circumference of the insulator, and precious metal mainly on one side of its tip side A spark plug for an internal combustion engine having a ground electrode provided at a distal end of the metal shell such that the proximal end of the precious metal chip is joined and the distal end face of the precious metal chip faces the distal end surface of the center electrode. The noble metal chip is joined by forming a molten portion in which itself and the ground electrode are dissolved with each other, and formed around the same. The cross-sectional area of the proximal side melted portion A located at the proximal end of the grounded electrode and the grounded electrode when the molten portion in the cross section along the longitudinal direction of the grounded electrode and including the central axis of the precious metal chip is viewed. The total cross-sectional area of the cross-sectional area of the tip-side molten portion B located at the tip side of is set to 4 mm 2 or more, and the cross-sectional area of the tip-side molten portion B is 1.1 of the cross-sectional area of the base-side molten portion A. A spark plug for an internal combustion engine, characterized in that ˜1.3 times. The method according to claim 1, The precious metal chip has its base end embedded in the ground electrode, The proximal side melted portion A and the proximal side melted portion B each have a noble metal chip side melted portion C1 on the noble metal chip side of a region partitioned by a rectangular first virtual outline of the noble metal chip before forming the melted portion. , C2) and a ground electrode side of the ground electrode side partitioned by a second virtual outline line of the ground electrode before forming the melting part in a region of the ground electrode side among the regions partitioned by the first virtual outline line. It is further divided into melting parts (D1, D2), In at least one of the proximal side melted portion (A) and the proximal side melted portion (B), the ground electrode side is melted in a cross section along the longitudinal direction of the ground electrode and including a central axis of the noble metal chip. A spark plug for an internal combustion engine, wherein the cross-sectional area of the portion D1 (D2) is set to 1.0 to 2.0 times the cross-sectional area of the noble metal chip side melting portion C1 (C2). The method according to claim 1 or 2, In the cross section along the longitudinal direction of the ground electrode and including the central axis of the precious metal chip, the shortest distance from the tip of the precious metal chip to the proximal side melted portion A is set to E (mm), and the precious metal The spark plug for an internal combustion engine characterized by following Formula (1) and Formula (2), when the shortest distance from the tip of a chip | tip to the said tip side melting part B is set to F (mm). 1.05 ≦ E / F ≦ 1.25... (One) 0.3 mm E 0.5 mm (2) A cylindrical insulator having a shaft hole penetrating in the axial direction, A center electrode inserted into the shaft hole and installed; A cylindrical metal shell provided on an outer circumference of the insulator, A proximal end of the noble metal chip, the main component of which is a noble metal, is bonded to one side of its front end side, and a ground electrode provided at the distal end of the metal shell so that the distal end surface of the noble metal chip faces the distal end surface of the center electrode; The precious metal chip is a method of manufacturing a spark plug which is joined by forming a molten portion in which itself and the ground electrode are melted with each other are formed around them. And a joining process of joining the noble metal chip to the ground electrode by forming the molten part by irradiating a laser beam to the outer edge of the bonding surface of the ground electrode and the noble metal chip. In the joining process, the laser beam is irradiated so that the melting energy of the portion located at the tip end side of the ground electrode is greater than the melting energy of the portion located at the base end side of the ground electrode. Manufacturing method. As a manufacturing method of the spark plug for internal combustion engines of Claim 1 or 2, And a joining process of joining the noble metal chip to the ground electrode by forming the molten part by irradiating a laser beam to the outer edge of the bonding surface of the ground electrode and the noble metal chip. In the joining process, the laser beam is irradiated so that the melting energy of the portion located at the tip end side of the ground electrode is greater than the melting energy of the portion located at the base end side of the ground electrode. Manufacturing method. The method according to claim 4, And a laser beam is irradiated while increasing the melting energy from a portion located at the proximal side of the ground electrode to a portion located at the front end side of the ground electrode. The method according to claim 4 or 6, In the joining process, In a state where the irradiation direction of the laser beam is fixed, The precious metal chip and the ground electrode are rotated with an axis formed by tilting the central axis of the precious metal chip at an intersection point between the central axis of the precious metal chip and a plane including one side surface of the ground electrode. Method for producing a spark plug, characterized in that for forming the molten portion by rotating.

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