Abstract: A method for manufacturing a spark plug includes: a preparation step of preparing a specimen provided with a center electrode, an insulator, a metal shell, and a ground electrode; and an inspection step of applying a predetermined voltage between the ground electrode and the center electrode of the prepared specimen, and determining whether dielectric breakdown is caused in the insulator. The inspection step includes a calculation step and a judgment step. The calculation step involves receiving an oscillating wave generated from the specimen upon application of the predetermined voltage to the specimen, obtaining a power spectrum by subjecting an oscillating wave signal representing the oscillating wave to fast Fourier transform, and then calculating an integral of a predetermined frequency range in the power spectrum. In the judgment step, whether discharge is caused by dielectric breakdown of the insulator is judged by utilizing the integral.

Abstract: An object of the invention is to restrain separation of an electrode tip from a ground electrode or from a center electrode. A spark plug satisfies a condition 0.8?A1/A2?1.9, where, as viewed on a section which contains a center axis (O) of an electrode tip, A1 [Hv] is hardness of the electrode tip as measured outside a circle having a radius of 0.2 mm, with a boundary point (PA) on a surface of the spark plug between a fusion zone and the electrode tip serving as the center of the circle, and A2 [Hv] is hardness of the electrode tip as measured within the circle having a radius of 0.2 mm.

Abstract: A method of manufacturing a spark plug includes a joining step of joining a first member and a second member which constitute the spark plug. In the joining step, a first welding electrode in contact with the first member and a second welding electrode which has an elastically deformable intermediate portion and which is in contact with the second member are electrically connected through the first member and the second member, whereby the first member and the second member are joined together by resistance welding.

Abstract: In a method of manufacturing a sensor, firstly, a plate-type detection element is inserted through an element-insertion through-hole of a first powder-compacted ring. Secondly, a flange section including at least the first powder-compacted ring is integrally assembled to the plate-type detection element, applying axially compressive pressure to the first powder-compacted ring so as to compressively deform the first powder-compacted ring such that the cross-sectional area of the element-insertion through-hole is reduced. Thirdly, the flange section is engaged, directly or via an intermediate member, with the stepped portion of the metallic shell at the time of disposing of the plate-type detection element in the through-hole of the metallic shell. A sensor prepared by the method is also disclosed.

Abstract: An intermediate substrate is provided which reduces the effect of the difference in the coefficients of linear expansion between the terminals of the substrate and those of a semiconductor integrated circuit device, and which thus lowers the likelihood of disconnection due to thermal stress. The intermediate substrate, which is a planar member made of a polymeric material, includes a substrate core including a main core body having formed therein a sub-core compartment, and a ceramic sub-core section accommodated in the compartment. A first terminal array on the first principal surface side includes two types of terminals, functioning either as power source terminals or ground terminals, and a signal terminal. The array occupies an area entirely included within an orthogonally projected region of the sub-core section projected onto a reference plane parallel to the planar surface of the substrate core.

Abstract: A spark plug comprising: a center electrode; a metal shell; and an alumina ceramic insulator disposed between the center electrode and the metal shell, wherein at least part of the surface of the insulator is covered with a glaze layer comprising oxides, wherein the glaze layer comprises: 1 mol % or less of a Pb component in terms of PbO; 30 to 60 mol % of a Si component in terms of SiO2; 20 to 50 mol % of a B component in terms of B2O3; 0.5 to 25 mol % of a Zn component in terms of ZnO; 0.5 to 15 mol % in total of at least one of Ba and Sr components in terms of BaO and SrO, respectively; 2 to 12 mol % in total of at least two alkaline metal components of Na, K and Li, in terms of Na2O, K2O, and Li2O, respectively, wherein K and Li is essential; and 0.1 to 10 mol % of a F component in terms of F2.