Abstract: To provide a fabrication method for a porous glass base material for optical fiber, the method including performing deposition of glass fine particles generated by using a burner for glass fine particle synthesis to form a porous glass base material, and heating this porous glass base material to be transformed into transparent glass to obtain a glass base material hardly containing any air bubbles. Provided is a fabrication method for a porous glass base material for optical fiber by depositing glass fine particles, which is generated in flame formed by ejecting a glass raw material gas and a combustible gas from a burner, on a rotating starting material, in which the burner continuously ejects inert gas for at least a predetermined period immediately after the end of the deposition of the glass fine particles.

Abstract: To provide a fabrication method for a porous glass base material for optical fiber, the method including performing deposition of glass fine particles generated by using a burner for glass fine particle synthesis to form a porous glass base material, and heating this porous glass base material to be transformed into transparent glass to obtain a glass base material hardly containing any air bubbles. Provided is a fabrication method for a porous glass base material for optical fiber by depositing glass fine particles, which is generated in flame formed by ejecting a glass raw material gas and a combustible gas from a burner, on a rotating starting material, in which the burner continuously ejects inert gas for at least a predetermined period immediately after the end of the deposition of the glass fine particles.

Abstract: An optical fiber base material manufacturing apparatus including a reaction chamber; a burner that has a portion thereof inserted into the reaction chamber through an insertion opening that creates a connection between the inside and outside of the reaction chamber, and emits a flame toward a starting member positioned within the reaction chamber; and a seal connection member that creates an air-tight seal between the burner and the reaction chamber at the insertion opening. One end of the seal connection member firmly contacts the burner inserted therethrough, another end of the seal connection member firmly contacts the reaction chamber and has a through-hole formed therein through which the burner is inserted without contacting the seal connection member, and the seal connection member includes a connecting portion that connects the one end to the other end, while preventing transfer of stress between the one end and the other end.

Abstract: An optical fiber base material manufacturing apparatus including a reaction chamber; a burner that has a portion thereof inserted into the reaction chamber through an insertion opening that creates a connection between the inside and outside of the reaction chamber, and emits a flame toward a starting member positioned within the reaction chamber; and a seal connection member that creates an air-tight seal between the burner and the reaction chamber at the insertion opening. One end of the seal connection member firmly contacts the burner inserted therethrough, another end of the seal connection member firmly contacts the reaction chamber and has a through-hole formed therein through which the burner is inserted without contacting the seal connection member, and the seal connection member includes a connecting portion that connects the one end to the other end, while preventing transfer of stress between the one end and the other end.

Abstract: A tip that contains a noble metal is joined to a joining surface of an electrode base material of a ground electrode via a welded portion. On cross-sections of the tip and the electrode base material in a longitudinal direction of the joining surface, the welded portion has a void above the joining surface, and a continuous distance of the welded portion on the joining surface is less than or equal to 0.5 mm, whereby thermal stress due to a difference in thermal expansion between the tip and the electrode base material can be reduced. A total of continuous distances of the welded portions on the joining surface, are 0.4 times to 0.8 times a length from an end of the tip to another end thereof, whereby joining strength of the welded portion can be assured. Peeling at the tip or falling-off of the tip due to thermal stress can be less likely to occur, whereby durability of the ground electrode can be improved.

Abstract: A tip that contains a noble metal is joined to a joining surface of an electrode base material of a ground electrode via a welded portion. On cross-sections of the tip and the electrode base material in a longitudinal direction of the joining surface, the welded portion has a void above the joining surface, and a continuous distance of the welded portion on the joining surface is less than or equal to 0.5 mm, whereby thermal stress due to a difference in thermal expansion between the tip and the electrode base material can be reduced. A total of continuous distances of the welded portions on the joining surface, are 0.4 times to 0.8 times a length from an end of the tip to another end thereof, whereby joining strength of the welded portion can be assured. Peeling at the tip or falling-off of the tip due to thermal stress can be less likely to occur, whereby durability of the ground electrode can be improved.

Abstract: An optical fiber base material manufacturing apparatus including a reaction chamber; a burner that has a portion thereof inserted into the reaction chamber through an insertion opening that creates a connection between the inside and outside of the reaction chamber, and emits a flame toward a starting member positioned within the reaction chamber; and a seal connection member that creates an air-tight seal between the burner and the reaction chamber at the insertion opening. One end of the seal connection member firmly contacts the burner inserted therethrough, another end of the seal connection member firmly contacts the reaction chamber and has a through-hole formed therein through which the burner is inserted without contacting the seal connection member, and the seal connection member includes a connecting portion that connects the one end to the other end, while preventing transfer of stress between the one end and the other end.

Abstract: In a device for producing a large-sized porous base material by a VAD process, the cracking and variation of the outer diameter of the base material are suppressed by forming a smooth tapered part, without changing the length of a non-effective part. In producing the porous base material by a VAD process, the time for a gas to reach a flow amount of the gas in a steady state from starting of the deposition is extended more in a burner that deposits glass microparticles on a layer closer to the outside of the base material.

Abstract: A spark plug (1) includes an insulator (2) having an axial hole (4), a center electrode (5) inserted into the axial hole (4), a metallic shell (3) provided around the insulator (2), a ground electrode (27) whose base end portion is fixed to the metallic shell (3) and which has an annular portion (27A) formed at a forward end portion thereof, the center electrode (5) being disposed radially inward of the annular portion (27A), and an annular tip (32) which is joined to the inner circumference of the annular portion (27A) and which forms a spark discharge gap (28) between the center electrode (5) and the inner circumferential surface of the annular tip (32). Recesses (35) are provided on at least one of the inner and outer circumferences of the annular portion (27A).

Abstract: In a device for producing a large-sized porous base material by a VAD process, the cracking and variation of the outer diameter of the base material are suppressed by forming a smooth tapered part, without changing the length of a non-effective part. In producing the porous base material by a VAD process, the time for a gas to reach a flow amount of the gas in a steady state from starting of the deposition is extended more in a burner that deposits glass microparticles on a layer closer to the outside of the base material.

Abstract: An optical fiber base material manufacturing apparatus including a reaction chamber; a burner that has a portion thereof inserted into the reaction chamber through an insertion opening that creates a connection between the inside and outside of the reaction chamber, and emits a flame toward a starting member positioned within the reaction chamber; and a seal connection member that creates an air-tight seal between the burner and the reaction chamber at the insertion opening. One end of the seal connection member firmly contacts the burner inserted therethrough, another end of the seal connection member firmly contacts the reaction chamber and has a through-hole formed therein through which the burner is inserted without contacting the seal connection member, and the seal connection member includes a connecting portion that connects the one end to the other end, while preventing transfer of stress between the one end and the other end.

Abstract: A spark plug (1) includes an insulator (2) having an axial hole (4), a center electrode (5) inserted into the axial hole (4), a metallic shell (3) provided around the insulator (2), a ground electrode (27) whose base end portion is fixed to the metallic shell (3) and which has an annular portion (27A) formed at a forward end portion thereof, the center electrode (5) being disposed radially inward of the annular portion (27A), and an annular tip (32) which is joined to the inner circumference of the annular portion (27A) and which forms a spark discharge gap (28) between the center electrode (5) and the inner circumferential surface of the annular tip (32). Recesses (35) are provided on at least one of the inner and outer circumferences of the annular portion (27A).

Abstract: An ignition plug having a metallic shell with a through hole extending therethrough in an axial direction, an insulator fitted into the through hole of the metallic shell and having an axial hole extending in the axial direction, and a center electrode fitted into the axial hole of the insulator. The ignition plug further includes a cap member which covers a front end opening of the metallic shell, provided on a front end side thereof where the center electrode is disposed, to thereby form an ignition chamber at the front end portion of the metallic shell, and a ground electrode disposed within the ignition chamber and facing a circumferential surface of the center electrode directly or indirectly.

Abstract: A technique of reducing occurrence of multiple discharge in a spark plug. The spark plug has a main ground electrode and three auxiliary ground electrodes. The position at which first auxiliary ground electrode is joined to a metallic shell is located opposite the position at which main ground electrode is joined to the metallic shell, with respect to a center electrode. The positions at which second and third auxiliary ground electrodes are joined to the metallic shell are located opposite to each other with respect to the center electrode. When the width of first auxiliary ground electrode is represented by W, the shortest distance between second auxiliary ground electrode and third auxiliary ground electrode is represented by T, and a distance which is a component of the shortest distance T in a direction orthogonal to first auxiliary ground electrode is represented by Tp, a relation W?Tp is satisfied.

Abstract: An ignition plug having enhanced seal performance, while suppressing deformation of a metallic shell thereof. The ignition plug includes a metallic shell having a crimp portion, a male screw portion, a seat portion, and a bent portion. The bent portion has a largest outer diameter (OD) portion, and first and second smallest OD portions, wherein 0.01?(L2+L3?L1)/(L2+L3)?0.3 is satisfied. L1 is distance between a point in the first smallest OD portion farthest from center axis and a point in the second smallest OD portion farthest from center axis, L2 is distance between the point in the first smallest OD portion farthest from center axis and a point in the largest OD portion farthest from center axis, and L3 is distance between the point in the second smallest OD portion farthest from center axis and the point in the largest OD portion farthest from center axis.

Abstract: An ignition plug having enhanced seal performance, while suppressing deformation of a metallic shell thereof. The ignition plug includes a metallic shell having a crimp portion, a male screw portion, a seat portion, and a bent portion. The bent portion has a largest outer diameter (OD) portion, and first and second smallest OD portions, wherein 0.01?(L2+L3?L1)/(L2+L3)?0.3 is satisfied. L1 is distance between a point in the first smallest OD portion farthest from center axis and a point in the second smallest OD portion farthest from center axis, L2 is distance between the point in the first smallest OD portion farthest from center axis and a point in the largest OD portion farthest from center axis, and L3 is distance between the point in the second smallest OD portion farthest from center axis and the point in the largest OD portion farthest from center axis.

Abstract: A technique of reducing occurrence of multiple discharge in a spark plug provided. The spark plug has a main ground electrode and three auxiliary ground electrodes. The position at which first auxiliary ground electrode is joined to a metallic shell is located opposite the position at which main ground electrode is joined to the metallic shell, with respect to a center electrode. The positions at which second and third auxiliary ground electrodes are joined to the metallic shell are located opposite to each other with respect to the center electrode. When the width of first auxiliary ground electrode is represented by W, the shortest distance between second auxiliary ground electrode and third auxiliary ground electrode is represented by T, and a distance which is a component of the shortest distance T in a direction orthogonal to first auxiliary ground electrode is represented by Tp, a relation W?Tp is satisfied.

Abstract: An ignition plug having a metallic shell with a through hole extending therethrough in an axial direction, an insulator fitted into the through hole of the metallic shell and having an axial hole extending in the axial direction, and a center electrode fitted into the axial hole of the insulator. The ignition plug further includes a cap member which covers a front end opening of the metallic shell, provided on a front end side thereof where the center electrode is disposed, to thereby form an ignition chamber at the front end portion of the metallic shell, and a ground electrode disposed within the ignition chamber and facing a circumferential surface of the center electrode directly or indirectly.