Internal-combustion engines – Igniters – Sparkers
Reexamination Certificate
2002-04-26
2003-12-02
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Igniters
Sparkers
C123S1690EB
Reexamination Certificate
active
06655334
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ignition apparatus for use in an internal combustion engine, the apparatus including one or more spark plugs attached to corresponding cylinders of the internal combustion engine and being adapted to induce spark discharge at the spark plugs for igniting an air-fuel mixture.
2. Description of the Related Art
Conventionally, in an internal combustion engine for use as an automobile engine or a like engine, a spark plug used for igniting an air-fuel mixture generally includes a center electrode inserted into a front end portion of an axial hole formed in an insulator, a metallic shell provided outside the insulator, and a ground electrode whose one end is joined to the metallic shell and whose opposite end faces the center electrode across a spark discharge gap.
Such spark plugs, together with ignition coils, among other components, constitute an ignition apparatus for use in an internal combustion engine. In the ignition apparatus for use in an internal combustion engine, high voltage for ignition is generated at an ignition coil and applied to a spark plug, whereby spark discharge is induced in a spark discharge gap to thereby ignite an air-fuel mixture within a combustion chamber.
A known spark plug is configured such that thread grooves are formed on the outer circumferential surface of the metallic shell for fixedly attaching the spark plug to a cylinder head through screw engagement.
In order to meet recent demands for high efficiency (improvement of fuel economy) and clean emission, some internal combustion engines employ a high air-fuel ratio (lean air-fuel ratio) for an air-fuel mixture. Such an internal combustion engine employing a lean air-fuel ratio involves a problem in that ignition of an air-fuel mixture is impaired when the amount of fuel present in the vicinity of the spark discharge gap is small. In order to cope with this problem, the internal combustion engine employing a lean air-fuel ratio utilizes a turbulent flow (swirl flow or tumble flow) of an air-fuel mixture within a combustion chamber for stabilizing ignition of an air-fuel mixture.
However, when turbulent flow of an air-fuel mixture is generated, the orientation of the ground electrode of a spark plug within a combustion chamber is known to influence ignition of the air-fuel mixture; i.e., when the ground electrode is oriented in a certain direction within the combustion chamber, ignition may be impaired. In connection with ignition of an air-fuel mixture through contact with spark discharge induced in the spark discharge gap of a spark plug, for example, when the ground electrode is located upstream of the spark discharge gap with respect to a turbulent flow of the air-fuel mixture, the ground electrode serves as a block and hinders contact between the air-fuel mixture and spark discharge. As a result, ignition of the air-fuel mixture may be impaired.
In the case of a spark plug which is attached to a cylinder head through screw engagement, the orientation of a ground electrode within a combustion chamber differs among cylinders and is thus uncertain; therefore, difficulty is encountered with such a spark plug in orienting a ground electrode in a specific direction. Also, in the case of a spark plug which is attached to a cylinder head through screw engagement, a slight dimensional error of thread grooves or individual differences cause variation of the orientation of a ground electrode within a combustion chamber at the final stage of attachment. Therefore, such a spark plug encounters difficulty in orienting a ground electrode in a specific direction.
Thus, according to a contemplated structure, a spark plug is loosely fitted into a cylinder head without forming thread grooves for fixation on a metallic shell of the spark plug and without forming internal thread grooves in the cylinder head for engaging the spark plug. Employment of a structure in which a spark plug is loosely fitted into a cylinder head for attachment can avoid variations in the orientation of a ground electrode within a combustion chamber among spark plugs and can facilitate orientation of a ground electrode in a specific direction within a combustion chamber. However, in contrast to a conventional structure in which a spark plug is attached to a cylinder head through screw engagement, in the devised structure, gastightness (seal) must be maintained between a spark plug and a cylinder head, and a spark plug must be held fixedly attached to the cylinder head in a stable condition when combustion pressure is applied to the spark plug from a combustion chamber.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an ignition apparatus for use in an internal combustion engine, which facilitates orientation of a ground electrode within a combustion chamber at the final stage of attachment of a spark plug to a cylinder head, exhibits good gastightness between the spark plug and the cylinder head, and is capable of fixedly attaching the spark plug to the cylinder head in a stable condition by a simple structure.
In order to achieve the above object, the invention provides an ignition apparatus for use in an internal combustion engine, comprising a spark plug, which comprises a center electrode inserted into a front end portion of an axial hole formed in an insulator, a metallic shell provided outside the insulator, and a ground electrode joined to the metallic shell and forming a spark discharge gap between the ground electrode and the center electrode and which is disposed in a plug disposition hole formed in a cylinder head of the internal combustion engine, the ignition apparatus being adapted to induce spark discharge in the spark discharge gap of the spark plug for igniting an air-fuel mixture. The ignition apparatus is characterized in that the metallic shell of the spark plug comprises a flange portion having a plug seat formed on a front end face thereof and adapted to come in contact with the cylinder head directly or indirectly via another member, and a cylindrical front end portion extending axially frontward from the plug seat of the flange portion and having no thread grooves formed on an outer circumferential surface thereof, and in that a plug hole pipe, which is disposed rearward in relation to the plug seat of the metallic shell and is fixedly attached to the cylinder head, causes the plug seat of the metallic shell to be pressed against the cylinder head, whereby the spark plug is fixedly attached to the cylinder head.
A spark plug to be mounted on this ignition apparatus for use in an internal combustion engine has no thread grooves formed on the outer circumferential surface of the front end portion of the metallic shell; i.e., the ignition apparatus does not employ screw engagement for attaching the same to a cylinder head. The front end portion of the metallic shell has no thread grooves formed on the outer circumferential surface thereof, but is formed into a cylindrical shape, whereby the spark plug can be attached to the cylinder head while being loosely fitted into the cylinder head. Thus, when the spark plug is attached to the cylinder head, a position on the metallic shell where the ground electrode is joined can be readily set to a circumferentially specific position about the axis of the plug disposition hole (i.e., the ground electrode can be oriented in a specific direction within a combustion chamber), thereby preventing uncertain orientation of a ground electrode as is the case where a spark plug is screw-engaged with a cylinder head. For example, this spark plug allows orientation of the ground electrode in the following manner: the orientation of the ground electrode within a combustion chamber is set beforehand; and the spark plug is inserted into a cylinder head while the orientation of the ground electrode is maintained, and is then fixed, whereby at the final stage of attachment the ground electrode can be oriented in a specific direction within the combustion chamber.
T
Fuma Tomohiro
Inagaki Hiroshi
Suzuki Takahiro
Argenbright Tony M.
NGK Spark Plug Co. Ltd.
LandOfFree
Ignition apparatus for use in internal combustion engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ignition apparatus for use in internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ignition apparatus for use in internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3181609