Spark plug with riveted sleeve

A spark plug comprising a housing, a ceramic insulator and a sleeve is provided. The housing has an inner cavity while the ceramic insulator encloses a central electrode. The ceramic insulator is disposed inside the inner cavity and maintain from the housing with a gap. The sleeve is provided enclosing an inner wall of the housing and corresponds to an opening of the inner cavity. The level of an edge surface of the housing corresponding to the opening of the inner cavity is disposed higher than the level of an edge surface of the central electrode, and the level of the center electrode is also higher than the level of the edge surface of the ceramic insulator.

This application claims priority based on both Taiwanese patent applications No. 096215065 filed on Sep. 7, 2007 and No. 097209856 filed on Jun. 4, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spark plug, and more particularly to a spark plug that can protect a discharge spark.

2. Description of the Relative Art

A motorcycle or gasoline vehicle's engine is equipped with spark plugs to ignite fire and generate power. Generally, when spark plugs form a high discharge voltage, the engine introduces air via an intake manifold to form a fuel-air mixture into a cylinder almost at the same time, and generates power by igniting fuel-air mixture by discharge spark. However, the forms of the spark plug are different according to engine's design.

FIG. 1shows a conventional spark plug10. As shown inFIG. 1, the spark plug10includes a housing12, a ceramic insulator14, and a central electrode16. One end of the housing12extends and forms a ground contacted electrode18. The ground contacted electrode18is perpendicular to the central electrode16and is apart from the central electrode16with a gap24. The gap24is where a high voltage discharge spark formed (not shown). Besides, the other end of the spark plug10covers by an insulator20for preventing a short circuit or electric leakage. The insulator20further connects to a connecting head22. The ceramic insulator14may enclose a sealing material such as aluminum oxide and a seal ring between the ceramic insulator14and the housing12in assembly such that the ceramic insulator14and the housing12may form an air-seal structure for preventing pressure from leaking out from the engine while assembles the housing12.

Referring toFIG. 2, the conventional spark plug10is disposed on an engine30, and a discharge spark26forms between the central electrode16and the ground contacted electrode18. When fuel-air mixture40enter into a combustion chamber32and the piston34go up to Top Center Point, the air fuel mixture40ignites by the exposed discharge spark26in the combustion chamber32of the engine30directly, thereby drives a piston34of the engine30to generate power. However, when stepping on the gas pedal heavily to speed up suddenly or other circumstances, a large amount of high pressure fuel-air mixture40will enter into the combustion chamber32speedily and breach the discharge spark26. Therefore, the discharge spark26may snuff out and affect the ignited efficiency of the spark plug10, such that causes the moving motorcycle or vehicle cannot speed up smoothly.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a spark plug that can enable a moving vehicle to speed up smoothly.

It is another objective of the present invention to provide a spark plug with a long life span.

It is still another objective of the present invention to provide a spark plug that can protect a discharge spark form.

It is another objective of the present invention to provide a spark plug whose discharge spark is not affected by the fuel-air mixture.

A spark plug of the present invention includes a housing, a ceramic insulator and a sleeve. The housing has an inner cavity while the ceramic insulator encloses a central electrode. The ceramic insulator is disposed in the inner cavity and maintain from the housing with a gap. The sleeve encloses an inner wall and corresponds to the opening of the inner cavity. The level of the housing corresponding to the edge surface of the opening of the inner cavity is higher than the level of the edge surface of the central electrode, and the level of the edge surface of the central electrode is also higher than the level of the edge surface of the ceramic insulator.

In other words, the housing corresponding to the outer sidewall of the opening of the inner cavity protrudes out from the edge surface of the central electrode, and the edge surface of the central electrode also protrudes out from the edge surface of the ceramic insulator. From another point of view, the level of the edge surface of the central electrode is lower than the level of the edge surface of the housing corresponding to opening of the inner cavity, and the level of the edge surface of the ceramic insulator is also lower than the level of the edge surface of the central electrode.

In the preferable embodiment, the housing further has a protrusion and corresponds to the opening of the inner cavity. The level of the protrusion is higher than the edge surface of the central electrode, and the inner diameter of the protrusion is smaller than the inner diameter of the inner cavity. An inclined surface is disposed outside the edge surface of the housing and has a top end surface. The protrusion has a plane connects to the top end surface, and the plane is parallel to a central axis of the central electrode. The sleeve has a bending portion in contacts with the top end surface for positioning on the inner wall of the protrusion. Moreover, the side of the housing is further machined process at least one through hole. The through hole is parallelly communicated with the gap from the outer sidewall of the housing, and the level of the through hole is lower than the edge surface of the ceramic insulator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a spark plug that can enable a smooth ignition process of an engine even when a large amount of fuel-air mixture is generated suddenly. In other words, when hardly stepping (Kick down) on the gas pedal (e.g. speeding up or climbing a slope), a discharge spark would not snuff out by of the breach of the large amount of fuel-air mixture and thereby the ignition process is smoothly without interruption. In the preferable embodiment, the spark plug can be applied to motorcycles, vehicles, internal combustion engines and agricultural car. The preferred embodiments of the present invention are illustrated hereunder with attached drawings.

Referring toFIG. 3, a spark plug100of the present invention includes a housing102, a ceramic insulator120, and a sleeve300. The housing102is shaped a hollow shell and forms an inner cavity100thereof. The inner cavity110accommodates the ceramic insulator120and a central electrode130enclosed by the ceramic insulator120. In the present embodiment, the outer sidewall of the housing102has an inclined surface104and an outside screw108. The inclined surface104preferably intersects the horizontal with a 60-degrees angle. However, the angle may include between 45 degrees and 60 degrees by the inclined surface104and the horizontal, and the inclined surface104may be shaped cruciform or other shapes. The outside screw108connects with the inclined surface104for engaging with the engine (not shown). The central electrode130is preferably a straight stick; however, in other embodiments, the central electrode130may be shaped a cone at the top end or in other shapes. A gap forms132between the ceramic insulator120and the housing102and with a certain level.

The housing102corresponding to the edge surface of the opening of the inner cavity110is preferably higher than the level of the edge surface of the central electrode130, and the level of the edge surface of the central electrode130is also higher than the level of the edge surface of the ceramic insulator120. In other words, the housing102corresponding to the outer sidewall105of the opening of the inner cavity110protrudes out from the edge surface of the central electrode130, and the edge surface of the central electrode130may also protrude out from the edge surface of the ceramic insulator120. In the present embodiment, the outer sidewall105of the housing102protrudes out from the edge surface of the central electrode130including 5 mm to 20 mm. From another point of view, the level of the edge surface of the central electrode130is lower than the level edge surface of the housing102corresponding to the opening of the inner cavity110, and the level of the edge surface of the ceramic insulator120may also lower than the level of the edge surface of the central electrode130. Therefore, when the spark plug100is electrically conducted, the discharge spark (not shown) may form inside the inner cavity110. In other words, the discharge spark is hided inside the housing of the spark plug100.

FIG. 4illustrates another embodiment of the present invention. In the present embodiment, the housing102includes at least one through hole150. However, in the embodiment shown inFIG. 5, the housing102may include a plurality of through holes150. The through hole150is parallelly communicated through the gap132from the outer sidewall105of the housing102, and the level of the through hole150is disposed lower than the level of the edge surface of the ceramic insulator120. However, in other embodiments, the level of the through hole150may also be disposed the same as the level of the edge surface of the ceramic insulator120. In the embodiment shown inFIG. 4, the diameter of the through hole150is preferably between 2 mm and 14 mm.

Moreover, the inclined surface104of the housing102further connects to the top end surface106. The top end surface106is a plane parallel to the horizontal. The housing102further has a protrusion160corresponding to the inner cavity110. The level of the protrusion160is disposed higher than the edge surface of the central electrode130, and an inner diameter of the protrusion160is smaller than an inner diameter of the inner cavity110. In the present embodiment, the protrusion160further has a plane162and an inclined surface164. The plane162connects with the top end surface106and is preferably perpendicular to the top end surface106. The inclined surface164connects with the plane162. However, in other embodiments, the plane162may be a plane not perpendicular to the horizontal, and the inclined surface164may be parallel to the horizontal. One end of the sleeve300further has a bending portion310bent outward and in contacts with the top end surface106, so as to position at the inner sidewall of the housing102. That is, the sleeve300has a through hole330and a sidewall320surrounding the through hole330. The through hole330corresponds to the opening of the inner cavity110, i.e., the diameter of the through hole330is smaller than or substantially equal to the diameter of the opening of the inner cavity110. The side wall320of the sleeve300is disposed parallel against to the inner wall of the housing102.

The mentioned-above of the sleeve300is preferably be a rivet, and the material of the sleeve300preferably includes nickel, nickel alloy, nickel copper alloy, titanium alloy, yttrium alloy, chromium alloy, platinum, or other conductive materials.

Due to the point discharge phenomenon of electricity forms selectively an electric current at the position of the lowest resistance when the spark plug100is electrically conducted. However, in other circumstances, the electricity may form selectively a discharge spark along a shortest path. AsFIG. 5shown, when the spark plug100conducts and form an electric circuit, the discharge spark170may form between an end of the sleeve300and the edge surface of the central electrode130, i.e. the bending portion310corresponding to a point between the plane162of the wall surface of the sleeve300and the edge surface of the central electrode130(170a.) However, in other embodiments, the discharge spark170amay form between the sleeve300corresponding to any points of the inner wall surface of the plane162and the edge surface of the central electrode130.

The discharge spark170bmay form along a point of the shortest path between the edge surface of the central electrode130and the sleeve300. In the embodiment of shown inFIG. 5, the discharge spark170bpreferably forms between the bending point of the sleeve300and the edge surface of the central electrode130. The mentioned-above of the bending point of the sleeve300is a point which connects corresponding to the surface162of the protrusion160and the inclined surface164.

Furthermore, in the preferable embodiment, a plurality of through holes150are disposed on the housing102, and the level of the through hole150is lower than the level of the edge surface of the ceramic insulator120. The fuel-air mixture may enter from the opening of the inner cavity110or enter from the through hole150while a large of the fuel-air mixture diffuse all around of the spark plug100. When the fuel-air mixture230enter from the through hole150, the fuel-air mixture230may impact the sidewall of the ceramic insulator120and would not directly affects the discharge sparks170a,170bwhich forms between the edge surface of the central electrode130and the inner sidewall of the sleeve300or between the edge surface of the central electrode130and the bending point of the sleeve300. Besides, the disposed of the through hole150may help the fuel-air mixture230entering into the inner cavity110and assists the spark plug100to ignite fire. The accumulation of greasy filth may overfill form the through hole150and would not affect the formed discharge spark170.

When the fuel-air mixture230enter from the opening of the inner cavity110, the fuel-air mixture230may enter into the inner cavity110before impact the plane104indirectly, and then ignites fire with the formed discharge spark170, thus the fuel-air mixture230would not affect the discharge spark170directly. In addiction, the protrusion160of the housing102protrudes towards the inner cavity110, so as to increase the moveable length of the fuel-air mixture230. In other words, the disposed of the protrusion160can increase the protection of the discharge spark170and would not snuff out by the large amount of the fuel-air mixture230.

AsFIG. 6shown, an inclined continuous surface180, the discharge spark170, is preferably formed between the inner sidewall of the sleeve300and the edge surface of the central electrode130. The mentioned-above of the continuous surface180includes forming in the inner cavity110at any ranges for 360 degrees. In fact, the range of angles of the discharge spark170may depend on the different electricity, the material of the sleeve300or other facts. Therefore, in other embodiments, the discharge spark170formed on the continuous surface180may also be a portion, a segment or other incompleted discharge spark.

FIG. 7illustrates a perspective view of the sleeve assembling the spark plug of the present invention. The step of assemble methods of the sleeve300are, the sleeve300assembles upwards from bottom end of the inner cavity110of the housing102until engages with the protrusion160of the housing102. AsFIG. 8aandFIG. 8bshown, the housing102may fabricate on a machine tool600, and utilizes a pressed device500to press a top end of the sleeve300, the top end of the sleeve300becomes a bending portion310so as to position at the inner sidewall of the housing102, shows inFIG. 8b. AsFIG. 8cshown, after finished the pressing method, they can be assembled the ceramic insulator120, the central electrode130and other elements.

FIG. 9illustrates an embodiment view of the spark plug disposed on the engine of the present invention. The spark100engages with a cylinder of the engine200by uses the outside screw108of the housing102. When the fuel-air mixture230enters into the combustion chamber210, the inclined surface104will guide the fuel-air mixture230spread rapidly, and speedily contacts and ignites the formed discharge spark170. More particularly, when treads on the gas pedal hardly, the large amount of the high pressure fuel-air mixture230will enter into the combustion chamber210rapidly. Because the protection of the protrusion160of the housing102, the discharge spark170which hides and forms between the inner sidewall of the sleeve300and the central electrode130would not impact or snuffed out by the fuel-air mixture230directly.

The fuel-air mixture230may indeed enter into the inner cavity110from the through hole150rapidly, but block by the ceramic insulator120to reduce the impaction of the large amount of the fuel-air mixture230. In other words, the spark100may still ignite fire smoothly and the engine200may keep on operating in this circumstance.