Denso Corporation

Tsunetoshi Goto

Keiji Kanao

Nobuo Abe

Ken Hanashi

Takehiro Watarai

Yasushi Kawashima

Yoshinobu Hirose

A glow plug with combustion pressure sensor is disclosed having a cover and a housing with which a piezoelectric element is hermetically accommodated. A lead wire having flexibility is employed to supply electric power to a heating member. The lead wire, fixedly connected to the heating member, extends through an insertion bore of the cover and is hermetically bonded to an inner circumferential wall of the insertion bore. When the heating member is axially displaced upon receipt of a combustion pressure, the lead wire flexes to absorb the resulting displacement, causing a joint portion between the cover and the lead wire to have no drag against the displacement. This allows the piezoelectric element to detect the combustion pressure with high precision.

Glow plug with combustion pressure sensor

A spark plug is provided which is designed to be compact without sacrificing a mechanical strength of a porcelain insulator. The spark plug includes a metal shell having a base end and a top end. The porcelain insulator is made of a hollow cylinder which includes a body and an insulator head. The body is retained within the metal shell. The insulator head extends from the base end of the metal shell in a lengthwise direction of the porcelain insulator and has a length made up of a major body leading to the body of the porcelain insulator and an end portion lying far away from the body. The major body has an outer diameter D, an inner diameter D, and a section modulus Z at a smallest-outer diameter portion thereof which meet relations of 7.1 mm&#x2266;D&#x2266;8.8 mm, D&#x2267;2.8 mm, and Z&#x2267;33 mm.

Spark plug with increased durability

Ir alloy firing tips are bonded on opposed surfaces of a center electrode and a ground electrode facing to a discharge gap. The configuration of a cross-sectional area of the Ir alloy firing tip taken along a plane perpendicular to the axis of the Ir alloy firing tip is out of round. In this cross-sectional area of this Ir alloy firing tip, when it is assumed that a circumscribed circle has a largest diameter A among virtual circles each contacting at least three portions of a visible outline of the cross-sectional area and an inscribed circle has a largest diameter B among inscribed circles each being coaxial with the circumscribed circle, a ratio of the diameter B to the diameter A (i.e., B/A) is equal to or larger than 0.8 and is less than 1.0.

Spark plug and its manufacturing method

In a spark plug, a chip made of Ir alloy is partly buried into and bonded by laser beam welding on the ground electrode made of Ni base alloy. A molten portion is extended from the inside of the ground electrode through a junction of the chip and the electrode into the inside of the chip, but not formed on the spark discharge surface of the chip. Where A is a maximum length from the end of the junction on the side of the center electrode to the end of the molten portion on the junction on the side opposite to the center electrode, within the length A, B is a length of both ends of the molten portion, t is a length of the chip perpendicularly extending from the junction and d is a sum of the length t and a length of the molten portion protruding from the junction into the ground electrode, a ratio of A/B is not less than 0.5 and a ratio of d/t is not less than 2, but more than 4. When an end surface of the chip is the spark discharge surface, laser beam welding is conducted from the ground electrode toward a side of the other end surface or from the longitudinal side surface of the chip toward the ground electrode.

Growing community of inventors

Handa, Japan

Tsunetoshi Goto