Abstract: The present invention provides a method of manufacturing a spark plug which is capable of securing a bonding strength at the middle of a chip while suppressing an occurrence of scattering. The method of manufacturing the spark plug having a ground electrode to which a bonding surface of a chip is welded, has a machining process of machining the ground electrode such that an area located inside an edge of a welding-planned part where the chip is welded on the ground electrode and including a center of the welding-planned part is rougher than a section except the area of the welding-planned part, and a bonding process of bonding the chip to the welding-planned part of the ground electrode after undergoing the machining process by resistance welding.

Abstract: The present invention provides a method of manufacturing a spark plug which is capable of securing a bonding strength at the middle of a chip while suppressing an occurrence of scattering. The method of manufacturing the spark plug having a ground electrode to which a bonding surface of a chip is welded, has a machining process of machining the ground electrode such that an area located inside an edge of a welding-planned part where the chip is welded on the ground electrode and including a center of the welding-planned part is rougher than a section except the area of the welding-planned part, and a bonding process of bonding the chip to the welding-planned part of the ground electrode after undergoing the machining process by resistance welding.

Abstract: A method for manufacturing a spark plug so as to make welded portions uniform. A method, for manufacturing a spark plug having a ground electrode to which a tip is welded, includes: a preparation step of preparing the ground electrode in which a plating layer is formed so as to at least exclude a first portion to which the tip is to be welded; an application step of applying a laser beam or electron beam to the first portion of the ground electrode after the preparation step; and a joining step of joining the tip to the first portion of the ground electrode by resistance welding after the application step.

Abstract: Disclosed is a method for manufacturing a spark plug of the type in which a tip is joined to a ground electrode. In a positioning step, the ground electrode is positioned with respect to a first electrode by means of a pressing member. In a tip pressing step, the tip is pressed against a tip weld site of the ground electrode by means of a second electrode. In a welding step, the tip is resistance welded to the tip weld site of the ground electrode by the passage of electric current between the first and second electrodes.

Abstract: A method for manufacturing a spark plug so as to make welded portions uniform. A method, for manufacturing a spark plug having a ground electrode to which a tip is welded, includes: a preparation step of preparing the ground electrode in which a plating layer is formed so as to at least exclude a first portion to which the tip is to be welded; an application step of applying a laser beam or electron beam to the first portion of the ground electrode after the preparation step; and a joining step of joining the tip to the first portion of the ground electrode by resistance welding after the application step.

Abstract: An ignition plug such as a spark plug or a glow plug configured to ignite an air-fuel mixture in an internal combustion engine includes a mark that is formed of an oxide film generated on the surface of a metal member or is formed of the metal member and the oxide film. The mark is formed by promoting formation of the oxide film on the surface of the metal member or removing the oxide film through radiation of a laser beam onto the surface of the metal member.

Abstract: An ignition plug such as a spark plug or a glow plug configured to ignite an air-fuel mixture in an internal combustion engine includes a mark that is formed of an oxide film generated on the surface of a metal member or is formed of the metal member and the oxide film. The mark is formed by promoting formation of the oxide film on the surface of the metal member or removing the oxide film through radiation of a laser beam onto the surface of the metal member.

Abstract: A spark plug includes a tubular metal shell having a tapered portion that projects radially outward with respect to an external thread and is provided on a rear end side of the metal shell with respect to the external thread, a center electrode held in an insulated manner at a center of the metal shell on a front end side thereof, and a ground electrode connected to the metal shell to form a spark gap between the ground electrode and the center electrode. The tapered portion has a contact portion that contacts the inner surface of a plug hole formed in an engine when the external thread is tightened into a threaded hole in the plug hole. The Vickers hardness of the contact portion is higher than the Vickers hardness of at least a part of a portion between the contact portion and the external thread.

Abstract: A spark plug includes a tubular metal shell having a tapered portion that projects radially outward with respect to an external thread and is provided on a rear end side of the metal shell with respect to the external thread, a center electrode held in an insulated manner at a center of the metal shell on a front end side thereof, and a ground electrode connected to the metal shell to form a spark gap between the ground electrode and the center electrode. The tapered portion has a contact portion that contacts the inner surface of a plug hole formed in an engine when the external thread is tightened into a threaded hole in the plug hole. The Vickers hardness of the contact portion is higher than the Vickers hardness of at least a part of a portion between the contact portion and the external thread.

Abstract: An ignition plug such as a spark plug or a glow plug configured to ignite an air-fuel mixture in an internal combustion engine includes a mark that is formed of an oxide film generated on the surface of a metal member or is formed of the metal member and the oxide film. The mark is formed by promoting formation of the oxide film on the surface of the metal member or removing the oxide film through radiation of a laser beam onto the surface of the metal member.

Abstract: An ignition plug such as a spark plug or a glow plug configured to ignite an air-fuel mixture in an internal combustion engine includes a mark that is formed of an oxide film generated on the surface of a metal member or is formed of the metal member and the oxide film. The mark is formed by promoting formation of the oxide film on the surface of the metal member or removing the oxide film through radiation of a laser beam onto the surface of the metal member.

Abstract: Disclosed is a method for manufacturing a spark plug of the type in which a tip is joined to a ground electrode. In a positioning step, the ground electrode is positioned with respect to a first electrode by means of a pressing member. In a tip pressing step, the tip is pressed against a tip weld site of the ground electrode by means of a second electrode. In a welding step, the tip is resistance welded to the tip weld site of the ground electrode by the passage of electric current between the first and second electrodes.

Abstract: Disclosed is a method for manufacturing a spark plug in which a tip is welded to a ground electrode. After the tip is welded to a distal end portion of the ground electrode, polishing treatment or grinding treatment is performed on at least a part of an edge region of a distal end face of the ground electrode. After the polishing or grinding treatment, an image of the distal end face of the ground electrode and the tip is taken with the use of reflected light and then analyzed by image processing.

Abstract: A method for manufacturing a spark plug comprises: welding a ground electrode to a tip of a metal shell (metallic shell); and removing a welding sag formed on and over inner surfaces of the ground electrode and the metal shell from a work in which the ground electrode is welded to the tip of the metal shell, the welding step including: cutting the welding sag using a working tool while a control unit controls a working position of the working tool with respect to the work; and measuring a remaining quantity of the welding sag after the cutting step and the control unit performing a feedback of a measured value of the remaining quantity of the welding sag measured in the measuring step to a working position of a working tool in the cutting step for the subsequent work.

Abstract: A method for manufacturing a spark plug comprises: welding a ground electrode to a tip of a metal shell (metallic shell); and removing a welding sag formed on and over inner surfaces of the ground electrode and the metal shell from a work in which the ground electrode is welded to the tip of the metal shell, the welding step including: cutting the welding sag using a working tool while a control unit controls a working position of the working tool with respect to the work; and measuring a remaining quantity of the welding sag after the cutting step and the control unit performing a feedback of a measured value of the remaining quantity of the welding sag measured in the measuring step to a working position of a working tool in the cutting step for the subsequent work.