Ignition apparatus for internal combustion engine

An ignition apparatus for an internal combustion engine includes a center electrode, a ground electrode, an insulator, a housing, and an insulator protective wall portion. The ground electrode is disposed such that a discharge gap is formed between the ground electrode and the center electrode. The insulator holds the center electrode on an inner side of the insulator. The housing holds the insulator on an inner side of the housing. The insulator protective wall portion is arranged to surround an outer circumference side of a distal end portion of the insulator. A distal end of the insulator protective wall portion is positioned further towards a distal end side than a distal end of the insulator is and further towards a proximal end side than a distal end of the center electrode is. The insulator protective wall portion includes an inward protruding portion that protrudes towards a side surface of the center electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2018-124165, filed Jun. 29, 2018. The entire disclosure of the above application is incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure relates to an ignition apparatus for an internal combustion engine.

Related Art

An ignition apparatus for an internal combustion engine ignites an air-fuel mixture present inside a combustion chamber using a spark plug that is mounted in the internal combustion engine. For example, in a direct-injection-type internal combustion engine, fuel that is sprayed from a fuel injection valve is mixed with air in the combustion chamber. The air-fuel mixture is then ignited. Here, preventing fuel spray from attaching to an insulator of the spark plug is desired.

SUMMARY

The present disclosure provides an injection apparatus for an internal combustion engine. The injection apparatus includes: a center electrode; a ground electrode; an insulator that holds the center electrode; a housing that holds the insulator; and an insulator protective wall portion that surrounds an outer circumferential side of a distal end portion of the insulator. A distal end of the insulator protective wall portion is positioned further towards a distal end side than a distal end of the insulator is and further towards a proximal end side than a distal end of the center electrode is. The insulator protective wall portion includes an inward protruding portion that protrudes towards a side surface of the center electrode.

DESCRIPTION OF THE EMBODIMENTS

In related art, a ground electrode is configured to be mounted in the combustion chamber as a separate component from a main body of the spark plug, such that the ground electrode can be arranged in a predetermined position inside the combustion chamber. As a result, the ground electrode is prevented from changing the orientation of the fuel spray. Fuel is prevented from attaching to the insulator.

However, even if arranging the ground electrode in a predetermined position is possible, preventing the fuel from attaching to the insulator is not necessarily easy.

That is, for example, the sprayed fuel reaching the insulator as a result of being carried by air flow or the like inside the combustion chamber can also be considered. In this case, as a result of the fuel attached to the insulator being burned, soot attaches to a surface of the insulator. In addition, even if liquid fuel is not attached to the insulator, soot that is produced by unevaporated fuel being burned near the insulator may attach to the surface of the insulator. When soot attaches to the surface of the insulator in this manner, obstruction of appropriate spark discharge at a discharge gap, that is, occurrence of so-called smoldering becomes a concern.

It is thus desired to provide an ignition apparatus for an internal combustion engine that suppresses the occurrence of smoldering.

An exemplary embodiment of the present disclosure provides an injection apparatus for an internal combustion engine, including a center electrode, a ground electrode, an insulator, a housing, and an insulator protective wall portion. The ground electrode is disposed such that a discharge gap is provided between the ground electrode and the center electrode. The insulator holds the center electrode on an inner side of the insulator. The housing holds the insulator on an inner side of the housing. The insulator protective wall portion is arranged to surround an outer circumferential side of a distal end portion of the insulator. A distal end of the insulator protective wall portion is positioned further towards a distal end side than a distal end of the insulator is and further towards a proximal end side than a distal end of the center electrode is. The insulator protective wall portion includes an inward protruding portion that protrudes towards a side surface of the center electrode.

The above-described ignition apparatus includes the insulator protective wall portion that is configured as described above. In addition, the insulator protective wall portion includes the inward protruding portion that protrudes towards the side surface of the center electrode. As a result, fuel can be prevented from attaching to the insulator. Soot can also be prevented from attaching to the insulator. That is, the insulator protective wall portion can prevent fuel or soot that is blown radially inward from reaching a surface of the insulator or the periphery of the insulator. In addition, the inward protruding portion can prevent fuel or soot from infiltrating the inner side of the housing from the distal end side in an axial direction. As a result, soot attributed to fuel attaching to a surface of the insulator can be suppressed. Consequently, the occurrence of smoldering can be suppressed.

As described above, according to the above-described exemplary embodiment, an ignition apparatus for an internal combustion engine that suppresses the occurrence of smoldering can be provided.

First Embodiment

An ignition apparatus for an internal combustion engine according to a first embodiment will be described with reference toFIG. 1toFIG. 4.

As shown inFIG. 1andFIG. 2, an ignition apparatus1according to the present embodiment includes a center electrode2, a ground electrode3, an insulator4, a housing5, and an insulator protective wall portion6. The ground electrode3is disposed such that a discharge gap11is provided between the ground electrode3and the center electrode2. The insulator4has a cylindrical shape and holds the center electrode2on an inner side of the insulator4. The housing5has a cylindrical shape and holds the insulator4on an inner side of the housing5. The insulator protective wall portion6is arranged to surround an outer circumferential side of a distal end portion of the insulator4.

A distal end601of the insulator protective wall portion6is positioned further towards a distal end side Z1than a distal end401of the insulator4is and further towards a proximal end side Z2than a distal end201of the center electrode2is.

The insulator protective wall portion6has an inward protruding portion61that protrudes towards a side surface of the center electrode2.

For example, the ignition apparatus1can be used as an igniting means in an internal combustion engine for a vehicle such as an automobile. The ignition apparatus1is configured such that a spark plug10is fixed to a cylinder head71. According to the present embodiment, the spark plug10includes the center electrode2, the ground electrode3, the insulator4, the housing5, and the insulator protective wall portion6. In addition, the spark plug10is mounted to the internal combustion engine by an attachment screw portion51that is formed in an outer circumference of the housing5being screwed into a plug hole711in the cylinder head71.

In the present specification, a side on which the spark plug10is inserted into a combustion chamber72in an axial direction Z of the spark plug10is a distal end side (tip end side) Z1. A side opposite the distal end side Z1is a proximal end side (base end side) Z2.

The insulator protective wall portion6is formed in a distal end portion of the housing5. That is, the distal end portion of the housing5is extended towards the distal end side Z1and thereby configures the insulator protective wall portion6. The insulator protective wall portion6protrudes towards the combustion chamber72.

As shown inFIG. 2, the insulator protective wall portion6has the inward protruding portion61in a distal end portion of the insulator protective wall portion6. The inward protruding portion61is configured such that an overall inner-side end surface611is present further towards the distal end side Z1than the distal end401of the insulator4is. In addition, the overall inner-side end surface611of the inward protruding portion61opposes the side surface of the center electrode2. The inner-side end surface611is approximately parallel to the axial direction Z.

As shown inFIG. 3, the inward protruding portion61is formed to surround the outer circumference of the center electrode2. As shown inFIG. 3, in terms of a cross-sectional shape at a cross-section taken on a plane that is perpendicular to the axial direction Z and passes through the center electrode2and the inward protruding portion61, an outer circumferential surface of the center electrode2and the inner-side end surface611of the inward protruding portion61are formed into approximately concentric circles. Therefore, a distance d1between the center electrode2and the inward protruding portion61is approximately equal at any position in the circumferential direction.

As shown inFIG. 1,FIG. 2, andFIG. 4, the ground electrode3is fixed to the housing5. That is, a fixed end31of the ground electrode3is fixed to a distal end portion of the insulator protective wall portion6that is formed in the distal end portion of the housing5. As shown inFIG. 2, the ground electrode3extends from the housing5towards the distal end side Z1and bends towards a center axis side of the spark plug10. In addition, the periphery of an end portion on the side opposite the fixed end31of the ground electrode3opposes the center electrode2in the axial direction Z. As a result, the discharge gap11is formed between the center electrode2and the ground electrode3.

The inward protruding portion61includes metal. As shown inFIG. 2, the distance d1between the inward protruding portion61and the center electrode2is greater than a dimension D of the discharge gap11.

The inward protruding portion61is formed as a portion of the insulator protective wall portion6. In addition, the insulator protective wall portion6is integrally formed with the housing5. That is, according to the present embodiment, the inward protruding portion61is integrally formed with the housing5that includes metal. For example, the housing5includes a nickel alloy. In addition, the ground electrode3also includes a nickel alloy.

The center electrode2includes an electrode base material21and a noble metal chip22that is joined to a distal end of the electrode base material21. A portion of the electrode base material21protrudes from the insulator4towards the distal end side Z1. The outer circumferential surface of the portion of the electrode base material21that protrudes towards the distal end side Z1of the insulator4opposes the inner end surface611of the inward protruding portion61in a radial direction.

Here, according to the present embodiment, for example, the ignition apparatus1can be applied to a direct-injection-type internal combustion engine in which fuel is directly injected into the combustion chamber72. That is, for example, the configuration may be such that a fuel injection valve (not shown) is disposed, together with the spark plug10, in the cylinder head71.

Next, working effects according to the present embodiment will be described.

The ignition apparatus1includes the insulator protective wall portion6. In addition, the insulator protective wall portion6includes the inward protruding portion61. As a result, fuel can be prevented from attaching to the insulator4. Soot attaching to the insulator4can also be prevented. That is, the insulator protective wall portion6can prevent fuel or soot that is blown radially inward from reaching the surface of the insulator4or the periphery of the insulator4. In addition, the inward protruding portion6can prevent fuel or soot from infiltrating the inner side of the housing5from the distal end side Z1in the axial direction.

In this manner, infiltration of fuel or soot into a space (hereinafter referred to as a pocket portion14, as appropriate) on the inner side of the housing5and the outer side of the insulator4can be prevented. As a result, soot attributed to fuel attaching to the surface of the insulator4can be suppressed. Consequently, the occurrence of smoldering can be suppressed.

In addition, the inward protruding portion61is formed to surround the outer circumference of the center electrode2. As a result, infiltration of fuel or soot into the inner side of the housing5(that is, the pocket portion14) from the distal end side Z1can be further effectively suppressed.

Furthermore, the distance d1between the inward protruding portion61and the center electrode2is greater than the dimension D of the discharge gap11. As a result, the occurrence of discharge between the inward protruding portion61and the center electrode2can be effectively suppressed. That is, discharge in the discharge gap11can be made to occur reliably. As a result, ignitability of the ignition apparatus1can be ensured.

In addition, the insulator protective wall portion6is formed in the distal end portion of the housing5. As a result, the insulator protective wall portion6can be easily and accurately formed. In accompaniment, manufacturing cost of the ignition apparatus1can be reduced.

The ground electrode3is fixed to the housing5. As a result, the discharge gap11can be accurately formed. That is, as a result of the center electrode2and the ground electrode3being formed as a portion of the spark plug10, during manufacturing of the spark plug10, the discharge gap11can be formed into a predetermined size. As a result, the discharge gap11can be accurately formed and ignitability can be improved.

As described above, according to the present embodiment, an ignition apparatus for an internal combustion engine that suppresses the occurrence of smoldering can be provided.

Second Embodiment

According to a second embodiment, as shown inFIG. 5, the inward protruding portion61is arranged to oppose only a portion of the outer circumference of the center electrode2.

That is, according to the first embodiment, as shown inFIG. 3andFIG. 4, the inward protruding portion61is formed to surround the outer circumference of the center electrode2. However, according to the present embodiment, as shown inFIG. 5, the inward protruding portion61opposes only a portion of the outer circumference of the center electrode2.

According to the present embodiment, the inward protruding portion61is formed over an angular area of about half of the overall circumference, that is, about 180 degrees. In addition, the inward protruding portion61is formed in an area on the fixed end31side of the ground electrode3.

Other configurations are similar to those according to the first embodiment. Here, of the reference numbers that are used according to the second and subsequent embodiments, the reference numbers that are the same as those used in a previous embodiment indicate constituent elements and the like that are similar to those according to the previous embodiment, unless otherwise noted.

According to the present embodiment, ventilation of the pocket portion14is facilitated. That is, when high-temperature gas stagnates in the pocket portion14, self-ignition of the air-fuel mixture in the pocket portion14becomes a concern. According to the present embodiment, an advantage in that such stagnation of high-temperature gas in the pocket portion14is easily suppressed is achieved. Therefore, if infiltration of fuel and soot into the pocket portion14is sufficiently preventable as a result of the partial inward protruding portion61being formed, in terms of the foregoing, the ignitability of the ignition apparatus1can be easily improved.

Other working effects are similar to those according to the first embodiment.

Here, as a variation example according to the present embodiment, the inward protruding portion61may be formed in an area on the side opposite the fixed end31of the ground electrode3.

When the inward protruding portion61is formed only in a portion of the outer circumference of the center electrode2, for example, the formation area of the inward protruding portion61can be set as appropriate based on a scattering direction of liquid fuel and the like within the combustion chamber72.

Third Embodiment

According to a third embodiment, as shown inFIG. 6toFIG. 8, the inward protruding portion61has an opposing insulating portion613in a portion opposing the center electrode2. The opposing insulating portion613includes an insulating material.

For example, the opposing insulating portion613can include a ceramic such as alumina.

An outer circumferential portion of the opposing insulating portion613is held by the insulator protective wall portion6that includes a metal. In addition, a protruding metal portion612that configures a portion of the inward protruding portion61is provided in the distal end portion of the insulator protective wall portion6. The protruding metal portion612protrudes inward from the insulator protective wall portion6. However, an inner-side end surface of the protruding metal portion612is more radially outside than the inner-side end surface of the opposing insulating portion613. That is, the inner-side end surface611of the inward protruding portion61is configured by the inner-side end surface of the opposing insulating portion613.

As shown inFIG. 7andFIG. 8, according to the present embodiment as well, the inward protruding portion61is formed to surround the outer circumference of the center electrode2. In addition, the opposing insulating portion613is also formed to surround the outer circumference of the center electrode2. The opposing insulating portion613is configured by a circular ring-shaped insulating member. In addition, the opposing insulating portion613is held in the protruding metal portion612such that a portion of the circular ring-shaped member on the inner circumferential side is exposed towards the inner side from the circular ring-shaped protruding metal portion612.

A distance d2between the inward protruding portion61and the center electrode2is equal to or less than the dimension D of the discharge gap11. In particular, according to the present embodiment, the distance d2is less than the dimension D of the discharge gap11.

Other configurations are similar to those according to the first embodiment. Here, of the reference numbers that are used according to the second and subsequent embodiments, the reference numbers that are the same as those used in a previous embodiment indicate constituent elements and the like that are similar to those according to the previous embodiment, unless otherwise noted.

According to the present embodiment, the inward protruding portion61includes the opposing insulating portion613. Therefore, the occurrence of discharge between the inward protruding portion61and the center electrode2can be prevented. As a result, discharge in the discharge gap11can be easily ensured. In accompaniment, the space between the inward protruding portion61and the center electrode2can be decreased. That is, as shown inFIG. 6, the distance d2can be easily shortened. As a result, infiltration of fuel or soot from the distal end side Z1into the inner side (that is, the pocket portion14) of the housing5can be more effectively prevented.

In addition, as a result of the distance d2being set to be equal to or less than the dimension D of the discharge gap11, the above-described effects can be easily achieved. In particular, according to the present embodiment, the distance d2is less than the dimension D. Therefore, infiltration of fuel or soot into the inner side of the housing5can be easily prevented. Smoldering can be even more reliably prevented.

Other working effects are similar to those according to the first embodiment.

Here, as a variation example according to the present embodiment, a configuration in which the distance d2is 0, that is, the inner-side end surface of the opposing insulating portion613is in contact with the outer circumferential surface of the center electrode2is also possible. In this case, infiltration of fuel from the distal end side Z1into the inner side of the housing5can be even more reliably prevented.

Furthermore, as another variation example according to the present embodiment, the distance d2can be greater than the dimension D. For example, in cases in which the dimension D of the discharge gap11is particularly small, the distance d2may be set to be greater than the dimension D.

Fourth Embodiment

According to a fourth embodiment, as shown inFIG. 9andFIG. 10, the inward protruding portion61is configured by a member that has air permeability in a thickness direction.

In other words, the inward protruding portion61has air permeability in the thickness direction, that is, the axial direction Z of the spark plug10. For example, as shown inFIG. 9, the inward protruding portion61can be formed by a circular ring-shaped member that is formed to have a grid-like structure. Alternatively, for example, as shown inFIG. 10, the inward protruding portion61may be formed by a circular ring-shaped member through which numerous slits pass.

Here, the size of the grid or the width of the slits in the inward protruding portion61is made small enough that liquid fuel, soot, and the like are prevented from passing. Meanwhile, the size of the grid or the width of the slit is made large enough that gas, such as air, can smoothly pass.

In addition, according to the present embodiment, the inward protruding portion61may be formed by an insulating member or a metal member.

Other configurations are similar to those according to the first embodiment.

According to the present embodiment, ventilation of the pocket portion14is facilitated. In addition, infiltration of fuel and soot into the pocket portion14can be effectively inhibited. That is, infiltration of fuel and soot can be inhibited even though the inward protruding portion61has air permeability. In other words, if the size of the grid, the width of the slits, or the like are made sufficiently small, as described above, liquid fuel and soot can be prevented from passing through the grid or the slits. As a result, the pocket portion14can be easily ventilated while preventing the infiltration of fuel and soot into the pocket portion14. Consequently, the ignition apparatus1that has excellent ignitability can be achieved.

Other working effects are similar to those according to the first embodiment.

Fifth Embodiment

According to a fifth embodiment, as shown inFIG. 11, the ignition apparatus1is configured such that the inward protruding portion61and the ground electrode3are attached to the cylinder head71.

That is, according to the present embodiment, neither the inward protruding portion61nor the ground electrode3is formed in the spark plug10.

In addition, according to the present embodiment, the insulator protective wall portion6is also configured by a portion of the cylinder head71. That is, the distal end601of the insulator protective wall portion6is positioned further towards the distal end side Z1than the distal end401of the insulator is and further towards the proximal end side Z2than the distal end201of the center electrode2is. A configuration that meets this state is a portion of the cylinder head71that surrounds the periphery of the distal end portion of the insulator4from the outer side in the radial direction.

In addition, the inward protruding portion61is formed from the insulator protective wall portion6configured by a portion of the cylinder head71towards the center electrode2. As described above, the inward protruding portion61is also a portion of the cylinder head71. According to the present embodiment, a small opening portion712of which an inner diameter is smaller than an inner circumferential contour of the housing5is formed in a distal end portion of the plug hole711that is formed in the cylinder head71.

An inner circumferential surface of the small opening portion712serves as the inner-side end surface611of the inward protruding portion611and opposes the center electrode2in the radial direction. A shape of the small opening portion712when viewed in the axial direction Z is a circle.

In addition, the ground electrode3is configured such that the fixed end31is joined to a distal end surface of the cylinder head71. Furthermore, the ground electrode3protrudes from the distal end surface (that is, an inner wall surface of the combustion chamber72) of the cylinder head71towards the distal end side Z1, and bends towards the small opening portion712. The periphery of the end portion of the ground electrode3on the side opposite the fixed end31opposes the center electrode2from the axial direction Z. As a result, the discharge gap11is formed between the ground electrode3and the center electrode2.

Other configurations are similar to those according to the first embodiment.

According to the present embodiment, the insulator protective wall portion6that includes the inward protruding portion61is not required to be provided. Therefore, manufacturing cost of the spark plug10can be reduced.

Other working effects are similar to those according to the first embodiment.

Sixth Embodiment

According to a sixth embodiment, as shown inFIG. 12, the ignition apparatus1includes an auxiliary chamber formation body12.

That is, the auxiliary chamber formation body12includes an auxiliary chamber121on an inner side of the auxiliary chamber formation body12. In addition, the auxiliary chamber formation body12includes a plug holding portion122and an injection valve holding portion123on the proximal end side Z2of the auxiliary chamber121. The auxiliary chamber121protrudes into the combustion chamber72in a state in which the auxiliary chamber formation body12is fixed to the cylinder head71.

The auxiliary chamber121and the combustion chamber72are partitioned by the auxiliary chamber formation body12. A nozzle hole124that opens into the combustion chamber72from the auxiliary chamber121is formed in the auxiliary chamber formation body12.

The spark plug10is attached to the plug holding portion122of the auxiliary chamber formation body12. In addition, a fuel injection valve13is attached to the injection valve holding portion123of the auxiliary chamber formation body12. The auxiliary chamber121communicates between the plug holding portion122and the injection valve holding portion123.

In the ignition apparatus1according to the present embodiment, fuel that is injected from the fuel injection valve13mixes with air inside the auxiliary chamber121. A high-concentration air-fuel mixture is formed. The air-fuel mixture is then ignited by discharge from the spark plug10. As a result, a flame is formed inside the auxiliary chamber121. In addition, the flame is injected into the combustion chamber72from the nozzle hole124. Consequently, combustion occurs in the combustion chamber72.

According to the present embodiment, in the ignition apparatus1configured as described above, the inward protruding portion61and the ground electrode3are provided in a portion of the auxiliary chamber formation body12. In addition, a portion of the auxiliary chamber formation body12serves as the insulator protective wall portion6. That is, a portion of the auxiliary chamber formation body12that is formed to surround the periphery of the distal end portion of the insulator4from the outer circumferential side serves as the insulator protective wall portion6. In addition, the circular ring-shaped inward protruding portion61is attached to protrude towards the center electrode2from the periphery of the distal end portion of the plug holding portion122.

Furthermore, the ground electrode3is formed further towards the distal end side Z1than the inward protruding portion61, so as to protrude towards the inner side of the auxiliary chamber121. The ground electrode3protrudes from an inner-side wall surface of the auxiliary chamber formation body12in an approximately straight manner. The protruding end of the ground electrode3opposes the center electrode2from the distal end side Z1. As a result, the discharge gap11is formed between the ground electrode3and the center electrode2.

Other configurations are similar to those according to the first embodiment.

According to the present embodiment, a spray of fuel that is injected into the auxiliary chamber121from the fuel injection valve13is more easily present near the distal end portion of the spark plug10that is set inside the auxiliary chamber formation body12. However, as a result of the inward protruding portion61being formed, the fuel can be prevented from infiltrating the periphery of the insulator4of the spark plug10. In addition, soot that is produced as a result of unevaporated fuel being burned inside the auxiliary chamber121reaching the insulator4can be suppressed.

Other working effects are similar to those according to the first embodiment.

The present disclosure is not limited to the above-described embodiments. Various embodiments are applicable without departing from the spirit of the present disclosure.