JP2003022884A - Spark plug and mounting structure thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark plug easily mountable to a cylinder head and proper in heat dissipation and heat resistance, and its mounting structure to the cylinder head. SOLUTION: A tip part 12 of the main metal fitting 1 of the spark plug 100 is cylindrically formed, without having a male screw for mounting a plug to be screwed in the cylinder head SH on its own external periphery. A corresponding tip part 36, corresponding to the external peripheral shape of the tip part 12 of the main metal fitting 1, is provided in a plug-hole P formed in the cylinder head SH. In this mounting structure of the spark plug 100 to the cylinder head SH, a sealing agent 25 for transmitting the heat of the main metal fittings 1 to the cylinder head SH is interposed between the tip part 12 of the main metal fitting 1 and the inner wall surface of the corresponding tip part 36 of the plug-hole P. Thereby, heat flowing into the main metal fitting 1 is speedily dissipated to the cylinder head SH.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug that does not need to be screwed into a plug hole when assembling the spark plug into a plug hole formed in a cylinder head, and a structure for mounting the spark plug. Is.

[0002]

2. Description of the Related Art A spark plug 10 used as an ignition source for an air-fuel mixture in a combustion chamber in an internal combustion engine such as an automobile engine has a center electrode 3 extending in an axis O direction, as shown in FIG. It is composed of an insulator 2 that surrounds the periphery thereof and a tubular metal shell 1 that holds the insulator 2.
This metal shell 1 has a flange portion 1 in which a plug seat surface 13 is formed on a tip side (a side where a spark discharge gap g is formed).
1 and a tip portion 12 extending from the plug seat surface 13 toward the tip in the axis O direction. A caulking portion 16, a hexagonal portion 15, and a caulking groove portion 14 are formed on the rear end side of the flange portion 11, and a male screw 12a is formed on the outer periphery of the tip portion 12. On the other hand, on the tip surface of the tip portion 12, the center electrode 3
The ground electrode 4 that forms a spark discharge gap g facing each other is coupled to form a ground electrode coupling portion 17.

The insulator 2 is composed of a head portion 2b having a corrugation 2c formed therein, a diamond portion 2e having the largest diameter, a middle body portion 2g having a diameter smaller than that of the diamond portion 2e, and a leg portion 2i located at the tip. Has been done. Also, the long leg portion 2i and the middle body portion 2
The locking surface 2h corresponding to the connecting portion with g is attached to the metal fitting side engaging portion 18 projecting inward from the inner peripheral surface of the metal shell 1 with the packing 5
It is locked through 1. The locking surface 2h is in close contact with the metal fitting side engaging portion 18 via the packing 51 to maintain airtightness, and the heat flowing into the center electrode 3 and the insulator 2 can be applied to the insulator 2, the packing 51, and the metal fitting side. Engaging portion 18, tip portion 12
Through the (male screw 12a), it becomes a part of the main path that diffuses to the cylinder head described below.

The spark plug 10 as described above is assembled to a cylinder head for use, and in this assembling, the spark plug 10 is inserted into a plug hole formed in the cylinder head to form a metal shell. This is done by applying a plug wrench to the hexagonal portion 15 of No. 1 and screwing the male screw 12a formed at the tip portion 12 of the metal shell 1 into the female screw formed in the plug hole at a predetermined torque.

[0005]

Here, when the spark plug 10 is accurately rotated around the central axis of the plug hole in which the female screw is formed, the spark plug 10 and the spark plug 10 are fastened to each other without any problem. However, when the spark plug 10 is rotated while being tilted from the central axis of the plug hole, the male screw 12
The a and the female screw do not mesh with each other, resulting in a so-called galling state. As a result, the male screw 12a or the female screw is damaged,
In extreme cases, the combustion gas may blow out from the combustion chamber, and the tip 12 of the metal shell 1 and the center electrode 3 may become excessively high in temperature to cause preignition (premature ignition) or electrode melting damage. May occur.

Therefore, the spark plug 10 (the tip portion 1 of the metal shell 1 is formed without forming the male screw 12a on the tip portion 12 of the metal shell 1 and without forming the female screw in the plug hole.
It is conceivable that 2) can be inserted into the plug hole in a loose fitting manner and the spark plug 10 is fixed by a separately provided plug fixing tool or the like. As a result, the spark plug can be easily attached without problems such as the engagement of the screws with each other.

As described above, in the spark plug which does not have the male screw 12a in the metal shell 1, the attachment between the plug hole and the detachability is taken into consideration between the outer peripheral surface of the tip portion 12 and the inner wall surface of the plug hole. It is necessary to provide a clearance in. By the way, in the spark plug 10 having the male screw 12a on the metal shell 1, the heat flowing into the metal shell 1 from the insulator 2 and the center electrode 3 as described above is generated by the tip portion 12
The structure is such that the male screw 12a can be diffused to the cylinder head through the female screw that is in direct contact with the male screw 12a. On the other hand, in the spark plug which does not have the male screw 12a in the metal shell 1, since a gap must be provided between the outer peripheral surface of the tip portion 12 and the inner wall surface of the plug hole, the heat flowing into the metal shell moves. (Dissipation) tends to be difficult. Therefore, there is a new problem that preignition may occur or electrode melting may be caused.

The present invention has been made to solve the above problems, and is a spark plug which can be easily attached to a plug hole formed in a cylinder head and has good heat dissipation and heat resistance. Another object of the present invention is to provide a mounting structure for a spark plug and a cylinder head (plug hole).

[0009]

Means for Solving the Problems and Effects of the Invention In order to solve the above problems, a spark plug mounting structure according to the present invention has a center electrode extending in the axial direction and a center electrode disposed on the tip end side of itself. While holding the insulator surrounding the radial periphery of the insulator and holding the insulator surrounding the radial periphery of the insulator, a flange portion having a plug seat surface on the tip side and an axial tip from the plug seat surface of this flange portion A structure for mounting a spark plug having a metal shell having a tip extending toward the side and a plug hole formed in the cylinder head, wherein the tip of the metal shell has a male screw for mounting a plug on the outer periphery. On the other hand, the plug hole has a shape corresponding to the outer peripheral shape of the flange portion and the tip end portion of the metal shell, respectively. Provided, between the outer surface and the inner wall surface of the tip corresponding portion of the plug hole of the tip portion of the metal shell, the sealing agent for transferring heat of the metal shell to the cylinder head is characterized in that interposed.

Further, the spark plug of the present invention includes a center electrode extending in the axial direction, an insulator surrounding the radial periphery of the center electrode while arranging the center electrode on the tip side of itself, and surrounding the radial periphery of the insulator. Formed on a cylinder head, which holds the insulator and includes a metal shell having a flange portion having a plug seat surface on the tip end side and a tip portion extending from the plug seat surface of the flange portion to the tip end side in the axial direction. It is a spark plug that is attached to a plug hole, and the tip of the metal shell is formed in a tubular shape without having a male screw for attaching the plug on the outer periphery, while the plug hole is
The metal shell is provided with a flange-corresponding portion and a tip-corresponding portion that respectively correspond to the outer peripheral shapes of the flange portion and the tip portion. The outer periphery of the tip portion of the metal shell contacts the inner wall surface of the tip-corresponding portion of the plug hole. It is characterized in that a sealant is provided around the metal shell to transfer the heat of the metal shell to the cylinder head.

According to the structure of the present invention, the tip portion of the metal shell forming the spark plug is formed in a tubular shape without having a male screw for mounting the plug on the outer periphery, while the plug hole is formed in the metal shell. It has a flange-corresponding portion and a tip-corresponding portion having shapes corresponding to the flange portion and the tip portion, respectively. A clearance is formed between the outer peripheral surface of the tip of the metal shell and the inner wall surface of the end corresponding portion of the plug hole. As a result, when installing the spark plug, it suffices to insert the spark plug into the plug hole in a loose-fitting manner, screw tightening work is unnecessary, and the spark plug can be easily and stably installed in the plug hole.

In particular, in the mainstream DOHC engine in recent years, a large-sized intake / exhaust valve is often provided, and the plug hole is designed deeply. The spark plug of the present invention loosely fits into such a plug hole. It can be installed simply by inserting it in a shape. Therefore, the spark plug can be easily attached, and the plug can be easily attached and detached at the time of exchanging the plug, and there is no fear of a problem caused by the engagement of the male screw of the metal shell and the female screw of the plug hole. In the present invention, since it is not necessary to form a female screw portion in the plug hole of the cylinder head corresponding to the tip portion of the metal shell, the diameter (inner diameter) of the plug hole is smaller than that of the conventional female screw portion. Can also be reduced. As a result, it is easy to install the large-area intake / exhaust valve as described above on the cylinder side, and it is easy to design for installing them.

By the way, the tip of the metal shell is formed into a tubular shape without forming a male screw for attaching the plug on the outer periphery, and the outer peripheral surface of the tip and the portion corresponding to the tip of the plug hole are secured in order to secure the attachability of the spark plug. By providing the clearance with the wall surface within a predetermined range, the heat of the metal shell, which was conventionally able to escape from the male screw formed at the tip to the cylinder head (wall surface inside the plug hole), is dissipated. It will be difficult. That is, when the outer peripheral surface of the tip portion of the metal shell and the inner wall surface of the plug hole are in contact with each other through the engagement of the screws as in the conventional case, the heat of the metal shell can be dissipated directly to the cylinder head. Since the male thread for attaching the plug is not formed at the tip of the metal fitting, there is a clearance between the outer peripheral surface of the tip of the metal shell and the inner wall surface of the corresponding end of the plug hole, and the heat dissipation path of the metal shell Is insufficient.

More specifically, if there is a clearance between the outer peripheral surface of the tip of the metal shell and the inner wall surface of the plug hole (corresponding to the tip of the plug hole), an air layer (a layer formed by air) is present in the clearance. ) Will intervene. Then, this air layer functions as a heat insulating layer by being exposed to a high temperature by combustion gas and the like, and prevents the heat flowing into the metal shell from being dissipated to the inner wall surface of the plug hole. Therefore, problems such as pre-ignition and electrode melting damage are likely to occur.

On the other hand, according to the present invention, the center electrode, the insulator, or the like is used as the metal shell in the clearance (clearance) formed between the tip of the metal shell and the inner wall surface of the end corresponding portion of the plug hole. It should be noted that the sealant for transmitting the inflowing heat to the cylinder head is interposed.

By interposing the sealant in this way,
The outer peripheral surface of the tip portion of the metal shell and the inner wall surface of the tip corresponding portion of the plug hole are indirectly contacted with each other through the sealant, and the air layer is prevented from intervening. As a result, the heat flowing into the metal shell from the insulator or the center electrode is quickly dissipated to the cylinder head through the tip and the sealant. As a result, the temperature of the center electrode and insulator is kept low, and the heat resistance (pre-ignition resistance) is equal to or higher than the conventional one with a male screw formed on the tip.
It is possible to obtain a spark plug which suppresses preignition and electrode melting damage.

Further, by interposing the sealant, it is possible to suppress variations in heat resistance of the spark plug due to variations in the clearance amount. Furthermore, by interposing a sealant on the outer peripheral surface of the tip of the metal shell and the inner wall surface of the plug hole, it is possible to more reliably suppress the blowout of combustion gas from the combustion chamber, and the airtightness of the spark plug mounting structure. The effect of further improving

In the present invention, the outer diameter of the tip portion of the metal shell is adjusted in order to interpose the sealant between the tip portion of the metal shell and the inner wall surface of the corresponding portion of the plug hole tip. Clearance amount (φD-φd), where φd is the diameter of the plug hole corresponding to the tip
Preferably satisfies the relationship of 0.005 to 0.50 mm. As a result, it is possible to realize a spark plug having good heat resistance for all internal combustion engines including high-power engines. In addition, the clearance amount when the sealant is interposed is 0.075 to 0.4.
It is preferable to satisfy the relationship of 0 mm, and especially 0.0
It is preferable to satisfy 75 to 0.15 mm in consideration of the attachment property of the spark plug and the improvement of heat resistance. Further, regarding the sealing agent, although the internal combustion engine is subjected to high temperature use, it preferably has a heat resistance of 400 ° C. or higher, although it varies depending on the characteristics of the internal combustion engine.

By constructing the present invention,
The spark plug in which the ground electrode facing the center electrode and forming the spark discharge gap is coupled to the metal shell has the following effects. It is generally known that in the combustion chamber, there is an optimum positional relationship between the swirl flow direction and the formation position of the ground electrode coupling portion so that the ground electrode does not interfere with the swirl flow generated during the compression stroke. . However, when a male screw is formed on the metal shell as in the conventional case, the metal shell is screwed into the cylinder head, which makes it difficult to identify the direction of the ground electrode (the position of the ground electrode coupling portion) in the combustion chamber. was there. On the other hand, in the configuration of the present invention, as described above, since the tip of the metal shell is formed in the outer peripheral tubular shape and the plug hole is formed in a shape corresponding to this metal shell, it is necessary to screw it into the cylinder head. Therefore, there is an advantage that it is easy to identify the direction of the ground electrode in the combustion chamber.

The sealant preferably contains at least one kind of metal powder, alloy powder and ceramic powder having a thermal conductivity of 20 W / mK or more. In this way, the sealant that transfers the heat flowing into the metal shell to the inner wall surface of the plug hole has a thermal conductivity of 20 W / m.
By including the metal powder, the alloy powder, and the ceramic powder of K or more, the heat of the metal shell can be dissipated more quickly. In addition, specifically, these metal powder, alloy powder, and ceramic powder can be used as a sealing agent by containing them in a viscous substance or an elastic material.

The metal powder may be copper, aluminum, molybdenum, etc., the alloy powder may be molybdenum disulfide, etc., and the ceramic powder may be aluminum nitride, boron nitride, etc. Is not limited to the above as long as it satisfies 20 W / mK or more. The viscous substance may be lubricating oil such as grease, silicone oil, mechanical oil, mineral oil, dibasic acid ester, etc., and the elastic material may be heat resistant rubber or the like.

The total weight of the above-mentioned metal powder, alloy powder and ceramic powder is 2 in terms of the weight ratio of the whole sealing agent.
It is preferable to be in the range of 0 to 80%. If the total weight is less than 20% of the total weight of the sealant, the function of the sealant itself that transfers the heat flowing into the metal shell to the inner wall surface of the plug hole may not be exhibited well. Further, when the total weight exceeds 80% in terms of the weight ratio of the entire sealing agent, the function of the sealing agent itself for transmitting the heat flowing into the metal shell to the inner wall surface of the plug hole may be improved, but the metal powder, The effect of viscous or elastic force due to viscous substances or elastic bodies containing alloy powder and ceramic powder may be weakened, and the effect of sealing between the outer peripheral surface of the tip of the metal shell and the inner wall surface of the plug hole may be reduced. . The metal powder, the alloy powder, and the ceramic powder are contained so as to satisfy the above range in the weight ratio of the entire sealing agent, and the average particle diameter is a value of half or less of the clearance amount (φD-φd). Is preferably adjusted as follows. By adjusting the average particle size of the powder in this manner, the viscosity or elastic force of the sealant can be maintained well.

Further, in the spark plug of the present invention, one or a plurality of ones are arranged such that one end is coupled to the metal shell to form a ground electrode coupling portion, and the other end is opposed to the center electrode with a spark discharge gap therebetween. When the spark plug is inserted in the plug hole and rotated around the axial direction while at least one of the main body and the tip of the metal shell is equipped with the ground electrode of While at least one of the corresponding parts has a fitting position limiting shape that fits at one or more locations,
The relationship between the formation position of the one or more ground electrode coupling portions and the body portion or the tip portion having the fitting position limiting shape is substantially the same when looking at the spark plug of the same part number. Good.

With such a structure, the position of the ground electrode coupling portion is limited to a predetermined position (predetermined direction) in the combustion chamber by inserting the spark plug into the plug hole in a loose fit manner and fitting the spark plug. You can As described above, it is known that there is an optimum positional relationship between the swirl flow direction and the formation position of the ground electrode coupling portion. Therefore, while considering the positional relationship between the swirl flow direction and the ground electrode coupling portion in advance, set the relationship between the formation position of the ground electrode coupling portion and the flange portion or the tip portion having the fitting position limiting shape. Thus, the relationship between the swirl flow direction and the formation position of the ground electrode coupling portion can be kept constant (optimal position) for each internal combustion engine (each cylinder). As a result, the ignitability does not vary for each internal combustion engine or cylinder, and a uniform air-fuel ratio (A /
It is possible to drive with F), and it is also possible to drive with a lean air-fuel ratio.

Here, the fitting position limiting shape is such a shape that when the metal shell is inserted into the plug hole and is rotated about the axial direction of the metal shell, the metal shells are fitted to each other at one or more places. I wish I had. To give a concrete example,
A key hole that extends in the axial direction is formed in the plug hole, and a key protrusion (a strip or a protrusion) that fits into the key groove is provided on the metal shell side, or conversely, a key protrusion on the plug hole, the metal shell side Key groove provided, chamfered end of the metal shell and plug hole shaped to match this chamfer, and the cross-sectional shapes of the tip and plug hole are egg-shaped, oval-shaped, and polygonal, respectively. Examples include shapes. When the fitting position limiting shape is to be provided between the tip of the metal shell and the corresponding portion of the plug hole, it is interposed between the outer peripheral surface of the tip of the metal shell and the inner wall surface of the plug hole. The sealing agent may be interposed according to the fitting position limiting shape.

Further, in the present invention, the tip of the metal shell is formed in a cylindrical shape, but the shape is not limited to a cylindrical shape. For example, the tip of the metal shell is
It may be formed by a combination of a cylindrical shape and a shape which is adjacent to the tip end side of the column shape and whose outer diameter is reduced continuously or stepwise toward the tip end side. When the shape of the tip of the metal shell is not cylindrical, the “outer diameter φd of the tip of the metal shell” in this specification refers to the maximum outer diameter of the tip.
At this time, the “hole diameter φD at the tip of the plug hole” in this specification refers to the hole diameter of the portion facing the maximum outer diameter of the tip. Further, the sealant provided around the outer peripheral surface of the tip portion of the metal shell does not need to be entirely provided around the outer peripheral surface of the tip portion, and may be partially provided.

By the way, when the sealing agent can be partially provided on the outer peripheral surface of the tip of the metal shell, the metal shell side engaging portion for locking the insulator is formed on the inner peripheral surface of the metal shell. In addition, the distance L (unit: mm) measured from the tip side edge of the plug seat surface to the tip end in the axial direction from the base end side edge of the locking surface of the metal fitting side engaging portion satisfies L ≧ 0. The sealant is provided around the outer peripheral surface of the tip of the metal shell, at least in the outer peripheral area corresponding to the area of the inner peripheral surface of the metal shell where the metal fitting side engaging portion is formed. It is preferable.

The spark plug generally has a structure in which the heat flowing into the center electrode and the insulator flows into the metal fitting side engaging portion of the metal shell as described above. Therefore, while forming the metal fitting side engaging portion on the inner peripheral surface of the tip end portion located closer to the tip end than the plug seat surface, the metal fitting side engaging portion is formed on the outer peripheral area of the tip end portion corresponding to the area where the metal fitting side engaging portion is formed. By interposing at least the sealant, the heat flowing from the insulator or the center electrode into the metal shell can be more quickly dissipated to the sealant through the metal fitting side engaging portion. As a result, the heat flowing into the metal shell can be dissipated to the cylinder head more quickly. The "outer peripheral area corresponding to the area in which the metal fitting side engaging portion is formed in the outer peripheral surface at the tip of the metal shell" refers to the area from the base end side edge to the tip end side edge of the metal fitting side engaging portion. The region in the circumferential direction between the regions is a region in the circumferential direction that overlaps with the outer peripheral surface of the tip when the region in the radial direction of the tip is enlarged.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are a partially cutaway sectional view and a sectional view showing an internal structure of a spark plug 100 according to the present embodiment. This spark plug 100
A so-called unipolar type in which only one ground electrode 4 is formed, which is a flat sheet type in which sealing is performed by a plug seat surface 13 which constitutes a plane provided between the flange portion 11 and the tip portion 12 of the metal shell 1. It is a thing. A ring-shaped gasket G is attached to the plug seat surface 13.

The spark plug 100 comprises a center electrode 3 extending in the direction of the axis O, an insulator 2 surrounding the center electrode 3,
The metal shell 1 holds the insulator 2.
This metal shell 1 is made of carbon steel, and has a flange portion 11 having a plug seat surface 13 formed on the front end side and the plug seat surface 1
3 and a front end portion 12 extending from the shaft 3 in the direction of the axis O.
The tip portion 12 does not have a male screw on the outer circumference, and has a substantially cylindrical outer circumference. One end of the ground electrode 4 is coupled to the tip surface of the tip portion 12 to form a ground electrode coupling portion 17. The other end of the ground electrode 4 extends toward the tip surface of the center electrode 3 and faces the center electrode 3 with a spark discharge gap g therebetween. Further, the caulking groove portion 14, the hexagonal portion 15, and the caulking portion 16 are provided on the rear end side (base end side) of the flange portion 11.
Are formed. In this specification, the side where the spark discharge gap g is formed is the front side (tip side) and the opposite side is the rear side (base end side) in the direction of the axis O.

A through hole 6 is formed in the insulator 2 in the direction of the axis O. The terminal electrode 5 is inserted and fixed on the rear side of the through hole 6, and the center electrode 3 is inserted and fixed on the front side of the through hole 6. In addition, the terminal electrode 5 in the through hole 6
A ceramic resistor 7 is disposed between the center electrode 3 and the center electrode 3, and both ends of the ceramic resistor 7 are electrically connected to the terminal electrode 5 and the center electrode 3 through conductive glass seal layers 8 and 9, respectively. The ceramic resistor 7 may be omitted, and the central electrode 3 and the terminal electrode 5 may be connected by a single conductive glass seal layer.

Further, as shown in detail in FIG. 2, the insulator 2 is provided with a diamond portion 2e projecting outward in the circumferential direction at a substantially intermediate portion in the axis O direction. The rear side of the diamond portion 2e is a head portion 2b having a smaller diameter than this. On the other hand, on the front side of the diamond portion 2e, a middle trunk portion 2g having a smaller diameter than this and a leg long portion 2 having a smaller diameter than the middle trunk portion 2g.
i are formed adjacent to each other. A glaze layer 2d is formed on the outer surface of the head 2b, and a corrugation 2c is formed on the outer surface on the rear side of the head 2b. Further, the outer surface of the long leg portion 2i located on the most front side in the axis O direction of the insulator 2 has a substantially conical shape whose diameter decreases toward the tip.

Next, the through hole 6 of the insulator 2 is formed into the first portion 6
a and a second portion 6b having a diameter larger than that on the rear side of the first portion 6a. Terminal electrode 5 and ceramic resistor 7
Is housed in the second part 6b and the center electrode 3 is
It is inserted in a. A convex portion 3a is formed at the base end portion of the center electrode 3 so as to project outward from the outer peripheral surface thereof.
Then, the first portion 6a and the second portion 6b of the through hole 6 are connected to each other in the middle body portion 2g, and at the connecting position, the convex portion receiving surface for receiving the convex portion 3a of the center electrode 3 is formed. 6c
Is formed in a tapered surface or an R surface shape.

The connecting portion between the middle body portion 2g and the long leg portion 2i forms a stepped locking surface 2h, and the locking surface 2h is formed.
Is a plate packing 51 with respect to the locking surface 18a of the metal fitting side engaging portion 18 formed so as to project inward on the inner peripheral surface of the metal shell 1.
By engaging with the insulating member 2 through the shaft, the insulator 2 is prevented from being pulled out to the front side in the direction of the axis O. On the other hand, between the inner peripheral surface rear side of the metal shell 1 and the outer peripheral surface of the insulator 2, an annular wire packing 22 and a talc 23 which are engaged with the diamond portion 2e are arranged. By crimping the side edge toward the outer surface of the insulator 2, the crimp portion 16 is formed, and the insulator 2 is held to the metal shell 1.

Here, the metal fitting side engaging portion 18 heats the heat flowing into the center electrode 3 and the insulator 2 (leg long portion 2i), the insulator 2 (insulator locking surface 2h), the packing 51, the metal shell. 1
It constitutes a part of the main path of heat dissipation to the tip 12, the sealing agent 25 described later, and further to the cylinder head SH (inner wall surface of the plug hole P). In addition,
As shown in the blowout diagram of FIG. 2, the distance L (unit: mm) measured from the tip side edge of the plug seat surface 13 to the base end side edge of the metal fitting side engaging portion 18 toward the tip side in the axis O direction. Also relates to the degree of heat dissipation into the center electrode 3 and the insulator 2 (note that the gasket G is omitted in the blowout diagram of FIG. 2). It is preferable that the distance L satisfies the relationship of L ≧ 0. The reason for this is that the metal fitting side engaging portion 18 is formed on the tip end portion 12 which is located on the tip end side in the axis O direction with respect to the plug seat surface 13, so that the sealing agent 2 described later is formed.
This is because it becomes easy to dissipate the heat flowing into the metal shell 1 via the cylinder head SH to the cylinder head SH. In addition, the distance L
More preferably satisfies 0 ≦ L ≦ 6. By setting the distance L in such a specific range, the heat flowing into the metal shell 1 is added to the sealing agent 25 to be described later, and the plug seat surface 1
It is also possible to dissipate heat to the cylinder head SH from No. 3, and it can be expected that further heat dissipation can be secured. In the spark plug 100 of this embodiment, the distance L is set to 0.5 mm.

Further, a key projection 19 is formed on a part of the outer peripheral surface of the tip portion 12 of the metal shell 1. For this reason, the tip end portion 12 has a tip groove corresponding to the key protrusion 19 in a plug hole P formed in a cylinder head SH, which will be described later.
, And can be fitted to each other at one position in the circumferential direction.

In this embodiment, when mounting the spark plug 100 on the cylinder head SH which will be described later, as shown in FIGS. 1 and 2, the outer peripheral surface of the tip portion 12 of the metal shell 1 (specifically, the key projection 19). 12 including the
The sealant 25 is provided (applied) around the outer peripheral surface.
The sealing agent 25 is applied to the outer peripheral surface of the tip portion 12 in whole or in part. In the case of partial application, the application is applied to the front side of the outer peripheral surface of the tip portion 12 and the spark plug 100 is inserted into the plug hole P to push up the sealing agent 25 to the rear side, and the tip end in the mounted state. The coating may be applied to almost the entire outer peripheral surface of the portion 12.

Further, the above-mentioned distance L (see FIG. 2) is L ≧
In the spark plug that satisfies the relationship of 0, when the spark plug is attached to the cylinder head SH, the sealing agent 25 is a metal fitting on the inner peripheral surface of the metal shell 1 among the outer peripheral surfaces of the tip portion 12 of the metal shell 1. Outer peripheral area 12a corresponding to the area where the side engaging portion 18 is formed (see FIG. 2)
It is preferable that it is configured to be located at least in the position. With such a configuration, the metal shell 1
The heat flowing into the can be efficiently dissipated through the metal fitting side engaging portion 18 and the sealant 25.

Here, the sealant 25 used in this embodiment is composed of mineral oil containing copper powder, and when the sealant 25 is viewed as a whole, the copper powder is 40% by weight. There is. The heat resistance of the sealant 25 itself is about 400 ° C.

Next, the cylinder head SH according to this embodiment will be described with reference to FIG. The head body 31 of the cylinder head SH includes a plug hole P penetrating between the head upper surface 32 and the combustion chamber surface 33,
Further, screw holes 32a to 32d for screwing a plug fixing tool 41, which will be described later, are formed in the head upper surface 32 around this. The plug hole P is a spark plug 1
00 is a depth at which the head is completely inserted, and the head upper surface 32 is formed of three round holes having a diameter decreasing in order.

Of these, the insertion portion 34 on the head upper surface 32 side
Is a round hole that extends from the head upper surface 32 to the vicinity of the combustion chamber surface 33 and has a diameter larger than that of the flange portion 11 having the largest diameter in the metal shell 1 so that the plug 100 can be inserted loosely. It is like this. Then, the tip end corresponding portion 36 on the side of the combustion chamber surface 33 is a portion into which only the tip end portion 12 of the metal shell 1 is loosely inserted when the spark plug 100 is inserted. Further, the flange corresponding portion 35 is located between the insertion portion 34 and the tip corresponding portion 36, and when the spark plug 100 is inserted, the flange portion 11 of the metal shell 1 is inserted.
Constitutes a portion to be inserted loosely. The sealing surface 37, which is the boundary between the flange corresponding portion 35 and the tip corresponding portion 36, is a surface that seals when the gasket G abuts. Further, as can be seen from FIG. 3A, a key groove 39 having a width and a depth adapted to the key protrusion 19 of the metal shell 1 is formed in the distal end side corresponding portion 36. In addition, the cylinder head SH has a circulation hole 3 for circulating cooling water.
8 is formed.

In the present embodiment, the key groove 39 and the key protrusion 19 are formed so as to be fixed in a fixed positional relationship while taking into consideration the formation position of the ground electrode coupling portion 17. Here, if the ground electrode 4 prevents the swirl from flowing into the spark discharge gap g, ignition will occur only with a relatively rich air-fuel mixture. Therefore, in the present embodiment, when the spark plug 100 is attached to the plug hole P, the formation position of the ground electrode coupling portion 17 and the tip portion 12 are adjusted so that the swirl flow direction and the ground electrode 4 satisfy the optimum positional relationship. The key protrusion 19 and the key groove 39 are formed so that the formation position of the key protrusion 19 and the formation position of the key protrusion 19 and the formation position of the key groove 39 of the tip end corresponding portion 36 have a fixed positional relationship. There is.

Next, the plug fixture 41 according to this embodiment will be described with reference to FIG. The plug fixture 41 is made of metal and includes a protrusion 42 for fixing itself to the cylinder head SH, and a tubular portion 43 having a substantially cylindrical shape. Although not shown, the protrusion 42 has a plurality of mounting holes formed at positions corresponding to the screw holes 32a to 32d of the cylinder head SH. The outer peripheral surface of the tubular portion 43 is slightly smaller in diameter than the insertion portion 34 of the cylinder head SH, and the tip end surface 43a at the tip thereof is a base end surface of the flange portion 11 of the metal shell 1 as described later. In order to be able to press, the inner peripheral surface is made larger in diameter than the hexagonal portion 15.

Then, as shown in FIG.
3, a coil core 44, a primary winding L1, a secondary winding L2, and a connection terminal 45 for supplying the discharge electrode high voltage generated in the secondary winding L2 to the terminal electrode 5. The ignition coil unit 50 is housed. Inside the tubular portion 43, the head 2 of the insulator 2 made of heat resistant rubber is used.
An insulating holding member 46 that contacts b is provided so as to cover the periphery of the connection terminal 45. Further, the spring-shaped connection terminal 45 electrically connected to one end of the secondary winding L2 is electrically connected to the terminal electrode 5 by being in contact with the terminal electrode 5 in a compressed form in the axis O direction. At this time, the insulating holding member 46
Comes into contact with the head 2b of the insulator 2 and has a function of ensuring insulation between the ignition coil unit 50 and the spark plug 100.

The plug fixing tool 41 includes an ignition coil unit 50.
As described later, the spark plug 10 has a built-in
At the same time that 0 is fixed in the plug hole P, the ignition coil portion 50 can be arranged in the plug hole P, and the connection between the spark plug 100 and the ignition coil portion 50 can be completed. Further, when such a plug fixture 41 is used, the spark plug 100 and the ignition coil unit 50 are directly connected to each other, so that a high tension cable or the like for connecting them is not required, and noise generation can be reduced. . In addition, this plug fixture 41
Is a power supply device or an EC because it has a built-in ignition coil unit 50.
A connector portion 47 for connecting to an external device such as U and an ignition unit 48 are provided. This ignition unit 48
Includes a switching element (not shown) for energizing / disconnecting the energizing current supplied from the power supply device to the primary winding L1 based on the ignition signal. The ignition unit 48 is electrically connected to the connector portion 47 and the ignition coil portion 50.

Below, with respect to the cylinder head SH,
On the outer peripheral surface of the tip portion 12 of the metallic shell 1, the above-mentioned sealing agent 25
A method of attaching the spark plug 100 having the circles, and further attaching the plug fixture 41 will be described. First, as shown in FIG. 4, the spark plug 100 is loosely inserted into the plug hole P of the cylinder head SH. At this time, the spark plug 100 is inserted while rotating around the axis O direction, the key protrusion 19 is fitted into the key groove 39, and the spark plug 100 is fitted into the plug hole P. That is, by the key projection 19 and the key groove 39, the tip portion 12 of the metal shell 1 and the tip corresponding portion 36 of the plug hole P.
And will fit together. As a result, the gasket G contacts the sealing surface 37. And at the same time,
Sealing agent 2 provided around the outer peripheral surface of the tip 12 of the metallic shell 1.
5 exhibits its own viscosity, and the tip 12 of the metal shell 1
The outer peripheral surface and the inner wall surface of the tip end corresponding portion 36 of the plug hole P are in contact with each other and are interposed between them.
At this time, the sealant 25 is applied to the tip portion 1 of the metal shell 1.
Of the outer peripheral surface of 2, the metal shell 1 is located in the outer peripheral area 12a corresponding to the area in which the metal fitting side engaging portion 18 is formed.

Then, the spark plug 100 is fixed to the cylinder head SH by using the above-mentioned plug fixture 41. First, as shown in FIG. 4, the tubular portion 43 of the plug fixture 41 is inserted into the plug hole P. The outer peripheral surface of the tubular portion 43 is slightly smaller in diameter than the insertion portion 34, so that the tubular portion 43 can be inserted loosely, and the tip end surface 43a of the tubular portion 43 abuts on the base end surface of the flange portion 11 of the metal shell 1. . At this time, inside the tubular portion 43, the connection terminal 45 contacts the terminal electrode 5 in a pressure contact state.

Then, as shown in FIG. 4, the projecting portions 42 of the plug fixture 41 are aligned so that the four bolts (see FIG.
Then, the plug fixture 41 is screwed into the screw holes 32a to 32d (see FIG. 3) of the head upper surface 32 of the cylinder head SH using only two bolts 49a and 49c. Then, the flange portion 11 of the metal shell 1 is pressed in the axis O direction by the tip end surface 43 a via the tubular portion 43, and the seal between the plug seat surface 13 and the seal surface 37 is performed via the gasket G. The length (height) of the tubular portion 43 is adjusted in advance in consideration of the dimensions of the spark plug 100 and the plug hole P so that the cylindrical plug 43 can be pressed with an appropriate pressure.

Thus, the spark plug 100 is attached to the cylinder head SH, but in the present embodiment, as shown in FIG. 4, the outer diameter of the tip portion 12 of the metal shell 1 is φd (unit: mm), the plug is Hole P corresponding to the tip 3
When the hole diameter of 6 is φD (unit: mm), the clearance amount (φD−φd) is 0.005 ≦ φD−φd ≦
The relationship of 0.50 is satisfied. The hole diameter φD of the tip end corresponding portion 36 of the plug hole P has various sizes for each cylinder head SH design, and the tip end portion of the metal shell 1 satisfies the above range (relationship) for any plug hole P. The outer diameter φd of 12 is appropriately determined. In the present embodiment, for example, φD = 13.70 mm, φ
d = 13.55 mm, φD−φd = 0.15 m
It is supposed to be m. However, as in this embodiment, the key protrusion 1
9 and the key groove 39 are not included in the outer diameter φd of the tip portion 12 and the hole diameter φD of the tip corresponding portion 36 of the plug hole P.

In this embodiment, the clearance amount (φD-φd) is 0.005≤φD-φd≤0.5.
The relationship of 0 is satisfied (for example, φD−φd =
0.15 mm), the sealing agent 25 is interposed between the outer peripheral surface of the tip portion 12 of the metal shell 1 and the inner peripheral surface of the tip corresponding portion 36 of the plug hole P. As a result, the heat flowing from the insulator 2, the center electrode 3, and the ground electrode 4 into the metal shell 1 (tip 12) is passed through the sealant 25 having excellent thermal conductivity,
It is possible to quickly disperse on the inner wall surface (cylinder head SH) of the tip corresponding portion 36 of the plug hole P. Further, in the present embodiment, the metal fitting side engaging portion 18 is formed on the inner peripheral surface of the tip end portion 12 located on the tip end side with respect to the plug seating surface 13, and at the region where the metal fitting side engaging portion 18 is formed. The sealant is positioned in the outer peripheral area of the corresponding tip portion 12, so that the heat flowing into the metal shell 1 can be prevented from flowing into the metal fitting side engaging portion 1
8. Through the sealant 25, the cylinder head SH can be quickly treated.

As a result, the temperature of the center electrode 3, the insulator 2 (leg portion 2i), and the ground electrode 4 is kept low,
It is possible to obtain heat resistance equal to or higher than that of the conventional tip portion 12 formed with a male screw, and it is possible to suppress the occurrence of preignition and electrode melting damage. The amount of clearance (φD−φd) was changed after interposing the sealing agent 25 between the outer peripheral surface of the tip portion 12 of the metal shell 1 and the inner wall surface of the tip corresponding portion 36 of the plug hole P. The effect of improving the heat resistance of the spark plug will be described later.

Further, with the spark plug 100 attached to the cylinder head SH as described above, the relationship between the flow direction of the swirl and the ground electrode 4 will be examined. Here, in the present embodiment, the spark plug 1
When 00 is attached to the plug hole P, the formation position of the ground electrode coupling portion 17 is as described above so that the swirl flow direction and the ground electrode coupling portion 17 satisfy the optimum positional relationship.
Each of the formation positions of the key protrusion 19 and the key groove 39 is set to have a predetermined positional relationship. As a result, when the spark plug 100 is attached to the plug hole P, the position of the ground electrode 4 is always limited to a fixed position. Therefore, the ground electrode 4 (ground electrode coupling portion 17) is specified at a position that does not hinder the swirl flow, and the swirl can be effectively brought into contact with the flame nucleus due to the spark discharge generated in the spark discharge gap g. Good ignitability is obtained. Furthermore, the internal combustion engine can always be driven with a lean air-fuel ratio by using any combination of the spark plug and the cylinder head having the same product number, and the fuel consumption can be improved.

Although the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to the above embodiments and can be appropriately modified without departing from the scope of the invention.
For example, in the above-described embodiment, the spark plug 100 is the one-pole type having only one ground electrode 4, but it may be a multi-pole type in which a plurality of ground electrodes 4 are coupled to the metal shell 1. . Further, as the structure of the spark plug 100, the plug seat surface 13 forming the tapered surface provided between the flange portion 11 and the tip portion 12 of the metal shell 1 seals directly to the cylinder head without the gasket G. It may be of a conical sheet type.

Specifically, FIG. 5 shows a spark plug mounting structure in which the structure of the spark plug is different from that of the above embodiment.
The items shown in are listed. In this mounting structure, especially the shape of the tip portion 12 of the metal shell 1 is different from that of the above-mentioned embodiment, and the description will be focused on the portions different from the above-mentioned embodiment, and the similar portions will be denoted by the same symbols and numbers and will be described. Is omitted.

FIG. 5 is a partial cross-sectional view showing the mounting structure of the spark plug 200 and the cylinder head SH. In FIG. 6, the ignition coil unit is shown in FIG. 4 explained in the above embodiment for simplification of description. Illustration of the 50 and the plug fixture 40 is omitted. In FIG. 6, the spark plug 2
The outer peripheral surface shape of the tip portion 12 of the metal shell 1 at 00 is a first columnar portion 12a extending from the gas sealing surface 13 of the flange portion 11 toward the tip side in the axis O direction, and the first columnar portion 12a.
And a second columnar portion 12c adjacent to the reduced portion 12b, the outer diameter of which is continuously reduced toward the front side of the reduced portion 12b. Moreover, the outer diameter of the hexagonal portion 15 is smaller than that of the flange portion 11, and the tip portion 12 is not provided with a key protrusion or the like as in the above embodiment.

The shape of the inner peripheral surface of the plug hole P1 on the cylinder head SH1 side is appropriately adjusted according to the outer peripheral shape of the metal shell 1. Specifically, the inner peripheral surface (inner wall surface) of the tip corresponding portion 36 of the plug hole P1 is
First cylindrical portion 12a, reduced portion 12b, second cylindrical portion 12
It is formed so as to correspond to the outer peripheral shape of the tip portion 12 of the metal shell 1 made of c, and the inner diameter continuously decreases toward the front side while being in contact with the contraction portion 12b on the front side of the plug hole P1. The second contracted portion 36b is formed, the rear side of the second contracted portion 36a faces the first cylindrical portion 12a, and the second contracted portion 36b is in front of the second cylindrical portion 12b.
A second columnar corresponding portion 36c facing c is formed.
In addition, a flange corresponding portion 35 corresponding to the outer peripheral shape of the flange portion 11 of the metal shell 1 is formed in the plug hole P1. In this embodiment, the insertion portion 34 adjacent to the flange corresponding portion 35 is not formed as in the above-described embodiment, and the plug hole P1 is composed of two round holes.

In the mounting structure of the spark plug 200 and the cylinder head SH1 as well, as shown in FIG. 6, the first cylindrical portion 12 of the tip portion 12 of the metal shell 1 is provided.
a Outer peripheral surface and the inner wall surface of the tip end corresponding portion 36 of the plug hole P1 (specifically, the first cylindrical portion 3 of the tip end corresponding portion 36)
6a) clearance amount (φD-φd) is 0.005
It is set to satisfy the relationship of ≦ φD−φd ≦ 0.50. Along with that, the first cylindrical portion 12a of the tip portion 12
Between the substantially entire outer peripheral surface of the plug and the inner wall surface (first cylindrical corresponding portion 36a) of the tip corresponding portion 36 of the plug hole P1.
5 are intervening. Further, although not shown, the metal fitting side engaging portion for locking the insulator 2 is located inside the first cylindrical portion 12a of the tip portion 12 located on the tip side in the axis O direction with respect to the plug seat surface 13. It is formed on the peripheral surface. As a result, the heat flowing into the metal shell 1 (tip 12) is quickly dissipated to the inner wall surface (cylinder head SH1) of the plug hole P1 through the sealing agent 25 having excellent thermal conductivity, and the spark is generated. The heat resistance of the plug 200 can be improved. The spark plug 200 can be fixed appropriately by using a separate plug fixing tool (not shown).

Further, in this other embodiment, the spark plug 200 is attached in such a manner that the reduced portion 12b of the tip portion 12 of the metal shell 1 contacts the second reduced portion 36b on the front side of the plug hole P1. This reliably prevents the sealing agent 25, which is in contact with the first cylindrical portion 12a of the tip portion 12 of the metal shell 1, from dropping into the combustion chamber when the spark plug 200 is used, and is highly reliable. A mounting structure for the spark plug 200 can be provided.

(Embodiment) In order to confirm the effect of the present invention, the outer diameter φ of the tip portion 12 of the metal shell 1 shown in FIG.
While changing d, the tip corresponding portion 3 of the plug hole P
The heat resistance (preignition resistance) of the spark plug 100 was evaluated by changing the value of the clearance amount (φD−φd) while keeping the hole diameter φD of 6 constant (13.7 mm). As the spark plug 100 of this evaluation, the length T1 of the tip portion 12 in the direction of the axis O = 15.0 mm, the inner diameter φd1 of the tip portion 12 = 8.4 mm, and the minimum inner diameter φd2 of the metal fitting engaging portion 18 = 7.5 mm. The dimensions were set for each and evaluated (see FIG. 1). Further, the distance L (see FIG. 2) measured from the tip side edge of the plug seating surface 13 to the base side edge of the metal fitting side engaging portion 18 toward the tip in the axis O direction is +
The size was set to 0.5 mm. Furthermore, in this evaluation,
The distance T2 of the long leg portion 2i of the insulator 2 is T2 = 17 mm
(The outer diameter φd3 of the tip of the long leg portion 2i = 5.1 mm) was set (see FIG. 1).

The evaluation of this heat resistance is as shown in FIG.
It was performed by fixing the spark plug 100 to the cylinder head SH using the plug fixing tool 41 from which the centers of the ignition coil portion 50 and the protruding portion 42 were removed. This plug fixture 41 is formed by forming a through hole 43a connected to the inner peripheral surface of the cylindrical portion 43 in the projecting portion 42, and an insulating holding member 46 having a connection terminal 45 connected to the cable 51 therein. The connection terminal 45 and the terminal electrode 5 are brought into contact with each other in a pressure contact state by being inserted through the through hole 43a. This cable 51
Is connected to an ignition circuit (not shown) via a diode 52 and is connected to a pre-ignition tester (not shown) via a diode 53.

This preignition tester measures so-called ion current. That is, when the spark discharge gap g is surrounded by the flame when preignition occurs, the spark discharge gap g is generated by the ions in the flame.
The spaces are in conduction. Therefore, if a voltage of several hundred V is applied in advance to the spark discharge gap g, an ionic current will flow when preignition occurs. Therefore, it is possible to determine that preignition has occurred when the ionic current is detected before the discharge is performed in the ignition circuit.

Then, as described above, the spark plug 10
After fixing 0 to the cylinder head SH, drive the internal combustion engine (2000 cc, in-line 4 cylinders, throttle fully open state), change the over-advance angle one by one from the regular ignition timing, hold for 2 minutes, Whether or not preignition occurred during that time was measured, and the over-advance angle at which preignition occurred was measured for the first time. Then, the outer diameter φ of the tip portion 12 of the metal shell 1 is applied without applying the sealant 25 to the outer periphery of itself.
d is changed similarly to the case where the sealing agent 25 is applied, and the hole diameter φD of the end corresponding portion 36 of the plug hole P is changed.
Is constant (13.7 mm), the clearance amount (φD
The heat resistance (preignition resistance) of the spark plug 100 was evaluated by changing −φd).

Then, a similar clearance amount (φD-φ
Regarding the spark plug 100 of d) (the mounting structure of the spark plug 100), the sealing agent 25 is applied from the over-advanced angle at which preignition occurs.
FIG. 7 shows the difference value of the over-advanced angle in which pre-ignition occurred although the coating was not applied.

From the result of FIG. 7, the clearance amount (φ
D-φd) is in the range of 0.005 to 0.50 mm, and the sealing agent 25 is present between the metal shell 1 and the plug hole P (spark plug 100 (spark plug 10)).
It can be seen that, for the mounting structure of 0), the over-advance angle at which preignition occurs for the first time is improved as compared with the case where the seal agent 25 is not applied. Accordingly, when the outer diameter of the tip portion 12 of the metal shell 1 is φd and the hole diameter of the tip corresponding portion 36 of the plug hole P is φD, the clearance amount (φD−φd) is 0.005 to 0.50 mm.
It is understood that the heat resistance (pre-ignition resistance) is improved by satisfying the relationship (1) and by having the sealant 25 interposed between the tip portion 12 of the metal shell 1 and the plug hole P. Further, particularly when the sealing agent 25 is interposed between the tip portion 12 of the metal shell 1 and the plug hole P and the clearance amount (φD−φd) satisfies the relationship of 0.075 to 0.40 mm, the heat resistance is further improved. It can be seen that the property improves.

[Brief description of drawings]

FIG. 1 is a partially cutaway sectional view showing an overall shape of a spark plug of an embodiment.

FIG. 2 is an axial cross-sectional view showing the internal structure of the spark plug of the embodiment.

3A and 3B are a plan view and an axial sectional view showing the structure of the cylinder head of the embodiment.

FIG. 4 is an explanatory view (partially cutaway sectional view) showing a mounting structure in which the spark plug of the embodiment is inserted into a plug hole of a cylinder head and fitted.

FIG. 5 is an explanatory view (partially cutaway sectional view) showing a spark plug mounting structure in a state where a spark plug of another embodiment is inserted into a plug hole of a cylinder head and fitted.

FIG. 6 is an explanatory view showing a state in a preignition test of the spark plug (spark plug attachment structure) of the embodiment.

FIG. 7 is a preignition test shown in FIG.
Regarding the spark plug mounting structure shown in Fig. 4 in which the clearance amount (φD-φd) is the same, the seal agent is present between the tip of the metallic shell and the plug hole, but the seal is changed from the over-advanced angle at which preignition occurs for the first time. 6 is a graph showing a difference value of an over-advance angle at which preignition occurs for the first time without an agent.

FIG. 8 is a partially cutaway sectional view showing the overall shape of a conventional spark plug.

[Explanation of symbols]

100, 200 ... Spark plug, 1 ... Metal shell, 11
... Flange portion, 12 ... Tip portion, 17 ... Ground electrode coupling portion,
18 ... Metal fitting side engaging portion, 19 ... Key protrusion, 2 ... Insulator,
3 ... center electrode, 4 ... ground electrode, 5 ... terminal electrode, 25, sealant, 35 ... flange corresponding part, 36 ... tip corresponding part, 3
9 ... Key groove, 41 ... Plug fixture, 50 ... Ignition coil part, SH ... Cylinder head, P ... Plug hole, g ...
Spark discharge gap

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01T 13/16 H01T 13/16 (72) Inventor Kazuya Iwata 14-18 Takatsuji-cho, Mizuho-ku, Aichi Prefecture Nagoya City No. F-Term in Nihon Special Ceramics Co., Ltd. (reference) 3G019 KA01 KA12 KB09 3G024 AA04 BA20 DA01 FA00 4H017 AA23 AA27 AC01 AD06 AE05 5G059 AA03 AA10 JJ28

Claims (12)

[Claims] 1. A center electrode extending in the axial direction, an insulator surrounding the radial periphery of the center electrode while arranging the center electrode on its tip side, and holding the insulator surrounding the radial periphery of the insulator. And a spark plug having a metal shell having a flange portion having a plug seat surface on the tip side and a tip portion extending from the plug seat surface of the flange portion to the tip side in the axial direction, and a plug hole formed in the cylinder head. And the tip portion of the metal shell is formed in a tubular shape without a male screw for mounting the plug on the outer periphery, while the plug hole is formed on the flange portion and the tip portion of the metal shell. A flange-corresponding part and a tip-corresponding part each having a shape corresponding to the outer peripheral shape of the metal shell. A mounting structure of a spark plug sealant for transferring heat of the metal shell in the cylinder head is characterized in that interposed. 2. The outer diameter of the tip portion of the metal shell is φd (unit: mm), and the hole diameter of the corresponding portion of the plug hole tip is φ.
The spark plug mounting structure according to claim 1, wherein the relationship of 0.005 ≦ φD−φd ≦ 0.50 is satisfied when D (unit: mm). 3. The sealant has a thermal conductivity of 20 W / m.
The method according to claim 1 or 2, containing at least one kind of metal powder of K or more, alloy powder and ceramic powder.
Spark plug mounting structure described in. 4. The total weight of the metal powder, the alloy powder and the ceramic powder is contained within a range of 20 to 80% in weight ratio when viewed from the whole sealing agent. Spark plug mounting structure. 5. A columnar portion extending from the plug seating surface of the flange portion toward the tip end in the axial direction, the tip portion of the metal shell comprising:
The plug hole has a reduced portion which is located closer to the tip side than the cylindrical portion and whose outer diameter is continuously reduced toward the tip side, while the tip corresponding portion of the plug hole is in contact with the reduced portion of the metal shell. Has a second reduced portion whose inner diameter continuously decreases toward the tip end side, and is arranged between the outer peripheral surface of the cylindrical portion of the metal shell and the inner wall surface of the tip corresponding portion of the plug hole. The spark according to any one of claims 1 to 4, wherein a sealant is interposed, and the reduced portion of the metal shell and the second reduced portion of the plug hole are in contact with each other directly or through another member. Plug mounting structure. 6. A metal fitting side engaging portion for locking the insulator is formed on an inner peripheral surface of the metal shell, and the metal fitting side engaging portion is formed from a front end side edge of the plug seating surface. The distance L (unit: mm) measured toward the tip in the axial direction to the base end side edge of the locking surface satisfies L ≧ 0, and the sealing agent is one of the outer peripheral surfaces at the tip of the metal shell. The spark plug mounting structure according to any one of claims 1 to 5, wherein the spark plug mounting structure is located at least in an outer peripheral region corresponding to a region in which the metal fitting side engaging portion is formed on an inner peripheral surface of the metal shell. 7. A center electrode extending in the axial direction, an insulator surrounding the radial periphery of the center electrode while arranging the center electrode on the tip side thereof, and holding the insulator surrounding the radial periphery of the insulator. And a metal shell having a flange portion having a plug bearing surface on the tip side and a tip portion extending axially toward the tip side in the axial direction from the plug bearing surface of the flange portion, and attached to a plug hole formed in the cylinder head. In the spark plug, the tip of the metal shell is formed in a tubular shape without a male screw for mounting a plug on the outer circumference, while the plug hole is the outer circumference of the flange and the tip of the metal shell. Equipped with a flange-corresponding portion and a tip-corresponding portion, each of which has a shape corresponding to the shape, and the outer periphery of the tip portion of the metal shell contacts the inner wall surface of the tip-corresponding portion of the plug hole Spark plug, characterized in that the heat of the metal shell is sealant for transmitting to the cylinder head are circumferentially provided Te. 8. The outer diameter of the tip portion of the metal shell is φd (unit: mm), and the hole diameter of the corresponding portion of the plug hole tip is φ.
The tip of the metal shell is arranged in the plug hole so as to satisfy a relationship of 0.005 ≦ φD−φd ≦ 0.50, where D (unit: mm). Spark plug. 9. The sealant has a thermal conductivity of 20 W / m.
The spark plug according to claim 7 or 8, containing at least one kind of metal powder of K or more, alloy powder, and ceramic powder. 10. The total weight of the metal powder, the alloy powder, and the ceramic powder is contained within a range of 20 to 80% in weight ratio when viewed from the whole sealing agent. Spark plug. 11. A metal fitting side engaging portion for locking the insulator is formed on an inner peripheral surface of the metal shell, and the metal fitting side engaging portion is formed from a front end side edge of the plug seating surface. Distance L measured toward the tip in the axial direction to the base side edge of the locking surface
(Unit: mm) satisfies L ≧ 0, and at least the metal fitting side engagement portion is formed on the inner peripheral surface of the metal shell of the sealant, in the outer peripheral surface of the tip of the metal shell. The spark plug according to any one of claims 7 to 10, which is provided around an outer peripheral region corresponding to the region. 12. One or more ground electrodes, one end of which is coupled to the metal shell to form a ground electrode coupling portion, and the other end of which is disposed so as to face the center electrode with a spark discharge gap therebetween. At least one of a body portion and a tip portion of the metal shell corresponds to the body-corresponding portion and the tip portion of the plug hole when the spark plug is rotated about the axial direction while being inserted into the plug hole. At least one of the portions has a fitting position limiting shape that fits with each other at one or more locations, while one or more of the formation positions of the ground electrode coupling portion and the fitting position limiting shape are provided. 12. The spark plugs of the same product number have substantially the same relationship with the main body part or the tip part, when viewed from the same part number, as claimed in any one of claims 7 to 11. Spark plug.