A prechamber spark plug for an internal combustion engine with the following features: a body with an external thread at its front end for screwing the spark plug into the engine; the external thread has a center line and begins with a thread start at the front end; the body has a passage in which an insulator is fastened and a center electrode protrudes from the front end of this insulator; at the front end of the body, a prechamber-forming cap is provided, which delimits a prechamber and shields the center electrode from a combustion chamber of the engine after the spark plug has been installed in the engine; the cap has at least one opening, which has a predefined orientation in relation to the thread start and is oriented obliquely to the center line of the external thread so as to permit a gas exchange between the prechamber and the space outside the prechamber.

A metallic shell for a spark plug which metallic shell achieves suppressed elution of hexavalent chromium, and a spark plug including the metallic shell. The spark plug has a metallic shell. The metallic shell includes a tubular metallic shell body; a metal plating layer provided on a surface of the metallic shell body; and a chromium-containing chemical conversion coating layer provided to cover the metal plating layer. The chemical conversion coating layer has a zirconium component content of 0.1 mass % or more.

A metallic shell for a spark plug which metallic shell achieves suppressed elution of hexavalent chromium, and a spark plug including the metallic shell. The spark plug has a metallic shell. The metallic shell includes a tubular metallic shell body; a metal plating layer provided on a surface of the metallic shell body; and a chromium-containing chemical conversion coating layer provided to cover the metal plating layer. The chemical conversion coating layer has a zirconium component content of 0.1 mass % or more.

A spark plug includes a plug cover provided at a tip end portion of a housing to cover an auxiliary combustion chamber where an electrical discharge gap is located. The plug cover has a curved surface portion. The curved surface portion includes an outer curved surface convexly curved outward. The curved surface portion has an inclined injection hole formed therein to allow communication between the auxiliary combustion chamber and an outside. The inclined injection hole is opened to be inclined, relative to a plug axial direction, outward in a plug radial direction toward a tip end side. In a cross section including a central axis of the inclined injection hole and along the plug axial direction, a tangent line of a portion of the outer curved surface that overlaps an extended line of the central axis of the inclined injection hole is orthogonal to the extended line.

A spark plug includes a plug cover provided at a tip end portion of a housing to cover an auxiliary combustion chamber where an electrical discharge gap is located. The plug cover has a curved surface portion. The curved surface portion includes an outer curved surface convexly curved outward. The curved surface portion has an inclined injection hole formed therein to allow communication between the auxiliary combustion chamber and an outside. The inclined injection hole is opened to be inclined, relative to a plug axial direction, outward in a plug radial direction toward a tip end side. In a cross section including a central axis of the inclined injection hole and along the plug axial direction, a tangent line of a portion of the outer curved surface that overlaps an extended line of the central axis of the inclined injection hole is orthogonal to the extended line.

The present invention pertains to a spark plug for an internal combustion engine, comprising a metal outer shell extending in a longitudinal direction from a proximal end to a distal tip end configured to be oriented towards a combustion chamber, said outer shell comprising a fixation portion for attachment of the spark plug to a metal sleeve of the internal combustion engine and arranged at a region proximal of the tip end, wherein the outer shell furthermore comprises a first contact surface arranged at a region distal of the fixation portion and configured to contact a distal end of the sleeve, when the spark plug is attached to the sleeve.

The present invention pertains to a spark plug for an internal combustion engine, comprising a metal outer shell extending in a longitudinal direction from a proximal end to a distal tip end configured to be oriented towards a combustion chamber, said outer shell comprising a fixation portion for attachment of the spark plug to a metal sleeve of the internal combustion engine and arranged at a region proximal of the tip end, wherein the outer shell furthermore comprises a first contact surface arranged at a region distal of the fixation portion and configured to contact a distal end of the sleeve, when the spark plug is attached to the sleeve.

The spark plug includes a cylindrical insulator, a center electrode provided in the insulator, and a cylindrical metal shell provided around the insulator. A ledge portion of the metal shell has a frontward facing surface facing a front side, a rearward facing surface facing a rear side, and a connection surface connecting the rearward facing surface and the frontward facing surface. The rearward facing surface engages with a step portion of the insulator. The metal shell includes a front cylindrical portion connected to the front side of the ledge portion. The inner circumferential surface of the front cylindrical portion is connected to the frontward facing surface of the ledge portion via a chamfered surface or a rounded surface. A corner at which the connection surface and the frontward facing surface are connected is located on the front side with respect to a front end of the insulator.

The spark plug includes a cylindrical insulator, a center electrode provided in the insulator, and a cylindrical metal shell provided around the insulator. A ledge portion of the metal shell has a frontward facing surface facing a front side, a rearward facing surface facing a rear side, and a connection surface connecting the rearward facing surface and the frontward facing surface. The rearward facing surface engages with a step portion of the insulator. The metal shell includes a front cylindrical portion connected to the front side of the ledge portion. The inner circumferential surface of the front cylindrical portion is connected to the frontward facing surface of the ledge portion via a chamfered surface or a rounded surface. A corner at which the connection surface and the frontward facing surface are connected is located on the front side with respect to a front end of the insulator.

A spark plug housing. The spark plug housing includes an inner side, an outer side, and a longitudinal axis, which extends from an end of the spark plug housing facing toward the combustion chamber up to an end of the spark plug housing facing away from the combustion chamber. The spark plug housing includes a circumferential shoulder on its inner side, which is designed so that a spark plug insulator rests thereon, and a corrosion protection layer on its inner side, which is formed on a section of the inner side of the spark plug housing, the section extending from the end of the spark plug housing facing toward the combustion chamber to at least over the shoulder and along the inner circumference of the spark plug housing.