Abstract: There is provided manufacturing method of a spark plug that includes a center electrode and a ground electrode with a discharge gap left therebetween. At least one of the center electrode and the ground electrode has an electrode body containing a base metal and a noble metal tip welded to the electrode body. The spark plug manufacturing method includes a laser welding step for welding the noble metal tip and the electrode body by placing the noble metal tip at a given position on the electrode body, irradiating a pulsed laser onto the noble metal tip and the electrode body and thereby sequentially forming welding spots corresponding to pulses of the laser in a circumferential direction of the noble metal tip, wherein at least one of the laser pulses is an initially increasing type laser pulse having a laser intensity waveform in which a laser intensity increases with time during a predetermined initial period from a pulse start time.

Abstract: There are provided a spark plug in which a plating film applied to a ground electrode can be relatively easily removed, without cost increase, to prevent deterioration in ignition performance, and a process for producing the spark plug. A spark plug 1 has a metal shell 3, a ground electrode 27 made of a Ni alloy and a Ni plating layer 28 containing Ni as a main component and applied to surfaces of at least a rear end portion of the ground electrode 27 and of the metal shell 3. A Ni plating film 41 applied to a center-electrode-side part of a portion of the ground electrode 27 to be bent has been irradiated with a laser beam or the like, thereby forming a molten layer 29 in which metal materials of the Ni plating film 41 and the ground electrode 27 are molten together on the center-electrode-side part of the portion of the ground electrode 27 to be bent. The Ni plating layer 28 is formed on a part of the ground electrode 27 other than the part irradiated with the laser beam.

Abstract: A method for manufacturing a spark plug is a method for manufacturing the spark plug having an electrode base member and a noble metal tip welded thereto by means of a laser or an electrode base member, a tip base member joined thereto, and a noble metal tip welded to the tip bases material by means of a laser, and the method includes a laser welding process of welding the electrode base member or the tip base member to the noble metal tip by means of a laser and through use of a laser beam whose BBP value assumes 25 mm·mrad (a radius·a half angle) or less at a time point when a laser beam enters a transfer optical system for guiding the laser beam to areas to be welded where laser welding is to be performed.

Abstract: There are provided a spark plug in which a plating film applied to a ground electrode can be relatively easily removed, without cost increase, to prevent deterioration in ignition performance, and a process for producing the spark plug. A spark plug 1 has a metal shell 3, a ground electrode 27 made of a Ni alloy and a Ni plating layer 28 containing Ni as a main component and applied to surfaces of at least a rear end portion of the ground electrode 27 and of the metal shell 3. A Ni plating film 41 applied to a center-electrode-side part of a portion of the ground electrode 27 to be bent has been irradiated with a laser beam or the like, thereby forming a molten layer 29 in which metal materials of the Ni plating film 41 and the ground electrode 27 are molten together on the center-electrode-side part of the portion of the ground electrode 27 to be bent. The Ni plating layer 28 is formed on a part of the ground electrode 27 other than the part irradiated with the laser beam.

Abstract: A method for manufacturing a spark plug is a method for manufacturing the spark plug having an electrode base member and a noble metal tip welded thereto by means of a laser or an electrode base member, a tip base member joined thereto, and a noble metal tip welded to the tip bases material by means of a laser, and the method includes a laser welding process of welding the electrode base member or the tip base member to the noble metal tip by means of a laser and through use of a laser beam whose BBP value assumes 25 mm·mrad (a radius·a half angle) or less at a time point when a laser beam enters a transfer optical system for guiding the laser beam to areas to be welded where laser welding is to be performed.

Abstract: There is provided manufacturing method of a spark plug that includes a center electrode and a ground electrode with a discharge gap left therebetween. At least one of the center electrode and the ground electrode has an electrode body containing a base metal and a noble metal tip welded to the electrode body. The spark plug manufacturing method includes a laser welding step for welding the noble metal tip and the electrode body by placing the noble metal tip at a given position on the electrode body, irradiating a pulsed laser onto the noble metal tip and the electrode body and thereby sequentially forming welding spots corresponding to pulses of the laser in a circumferential direction of the noble metal tip, wherein at least one of the laser pulses is an initially increasing type laser pulse having a laser intensity waveform in which a laser intensity increases with time during a predetermined initial period from a pulse start time.

Abstract: There is provided a method for producing a spark plug in which welding strength between a noble metal tip and an electrode joined by laser welding can be restrained from becoming weak. A noble metal tip (90) to be joined to a center electrode (2) or ground electrode of a spark plug to form a spark discharge gap is resistance-welded to each electrode containing no noble metal and then laser-welded. In the noble metal tip (90) exposed under a severe environment involving spark discharge, a molten portion (80) formed in such a manner that a portion of the noble metal tip (90) and a portion of the electrode are melted by laser welding and a non-molten portion (95) on the noble metal tip (90) side are apt to be peeled from each other in a boundary surface (83) between the molten portion (80) and the non-molten portion (95).

Abstract: A laser ignition device for irradiating and condensing laser beams in a combustion chamber of an internal combustion engine so as to ignite fuel particles within the combustion chamber, includes: a laser beam generating unit for emitting the laser beams; and a condensing optical member for guiding the laser beams into the combustion chamber such that the laser beams are condensed in the combustion chamber, wherein the laser beam generating unit comprises a Beam Parameter Product (BPP) laser beam generating unit which emits the laser beams with a BPP value of no more than 20 mm·mrad (radius·half angle).

Abstract: There is provided a method for producing a spark plug in which welding strength between a noble metal tip and an electrode joined by laser welding can be restrained from becoming weak. A noble metal tip (90) to be joined to a center electrode (2) or ground electrode of a spark plug to form a spark discharge gap is resistance-welded to each electrode containing no noble metal and then laser-welded. In the noble metal tip (90) exposed under a severe environment involving spark discharge, a molten portion (80) formed in such a manner that a portion of the noble metal tip (90) and a portion of the electrode are melted by laser welding and a non-molten portion (95) on the noble metal tip (90) side are apt to be peeled from each other in a boundary surface (83) between the molten portion (80) and the non-molten portion (95).