Internal-combustion engines – Particular piston and enclosing cylinder construction – Cylinder head
Reexamination Certificate
2000-04-13
2001-04-03
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Cylinder head
Reexamination Certificate
active
06209506
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cylinder head for an internal combustion engine, and particularly to the improvements of a cylinder head structure for a spark-ignited internal combustion engine capable of more compactly mounting related parts, such as intake and exhaust valves, a spark plug, and engine valve operating units, in place.
2. Description of the Prior Art
As is generally known, the installation position of a spark plug on an engine cylinder head (relating to the shape of a combustion chamber) plays a very important part in a combustion quality. For maximizing engine performance, a pent-roof type is often used as a typical combustion-chamber shape. In such high-performance engines with pent-roof combustion chambers, a spark plug is generally located substantially in the center of the pent-roof combustion chamber, for shortening a flame propagation distance and thus promoting good combustion. Also, on engines with pent-roof combustion chambers, a spark-plug hole bored or drilled in an engine cylinder head for spark-plug installation/removal, is usually formed as a straight through-opening which communicates the substantially center of the pent-roof combustion chamber and is drilled downwards from the upper part of the engine. However, in such engines having straight spark-plug holes, engine-valve's related parts mounted on the cylinder head are restricted in layout due to the necessity for providing a desired thickness between the spark-plug hole and each of the valve's related parts. To put it concretely, the installation position of the valve operating unit, which operates intake and/or exhaust valves, is limited by the straight spark-plug-holes drilled in the cylinder head. The engine valve must be arranged in due consideration of the shape of the combustion chamber. Also, it is desirable to produce an optimal gas flow (of less energy loss) both on intake stroke and on exhaust stroke. For the reasons mentioned above, the inclination and size (particularly, the size of valve head) of intake valve is designed to be usually different from those of exhaust valve. Usually, the inclination of intake valve is steeper than that of exhaust valve. Thus, if the spark plug is arranged in the cylinder head in a manner so as to satisfy the combustion quality as discussed above, respective valve operating units related to intake and exhaust valves would be arranged in the cylinder head far away from the combustion chamber, owing to the design difference between the intake and exhaust valves. In recent years, there have been proposed and developed various automotive electromagnetically-powered valve operating apparatus each having electromagnetically-operated valve units for electromagnetically opening and closing intake and exhaust valves. On engines with electromagnetically-powered valve operating apparatus, there is an increased tendency for valve units to be arranged far away from the combustion chamber. Commonly, a combination of the electromagnetically-powered valve operating apparatus and the previously-noted straight spark-plug hole opening to the combustion chamber, results in an increased cylinder-head overall height (consequently, an increased engine overall height). This is contrary to demands for lightweight, small-sizing, and reduced engine production costs.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a cylinder head for an internal combustion engine, which avoids the aforementioned disadvantages of the prior art.
It is another object of the invention to provide a cylinder head for a spark-ignition internal combustion engine, which is capable of more compactly mounting a variety of related parts, such as intake and exhaust valves, a spark plug, and engine valve operating units, without deteriorating the combustion quality, by virtue of a specific spark-plug hole and cylinder-head structure.
In order to accomplish the aforementioned and other objects of the present invention, a cylinder head of a spark-ignition engine having at least one spark-plug hole through which a spark plug is screwed into a tapped hole portion, comprises a division wall portion which divides the cylinder head into an upper cylinder head portion and a lower cylinder head portion, an upper spark-plug hole formed in the upper cylinder head portion, and a lower spark-plug hole formed in the lower cylinder head portion, wherein an axis of the upper spark-plug hole and an axis of the lower spark-plug hole are offset from each other.
According to another aspect of the invention, a method for removing a spark plug from a tapped hole portion formed in a cylinder head of a spark-ignition engine having at least one spark-plug hole through which the spark plug is screwed into the tapped hole portion, in which the cylinder head includes a division wall portion for dividing the cylinder head into an upper cylinder head portion and a lower cylinder head portion, an upper spark-plug hole formed in the upper cylinder head portion, and a lower spark-plug hole formed in the lower cylinder head portion, and wherein an axis of the upper spark-plug hole and an axis of the lower spark-plug hole are offset from each other, the method comprises removing the spark plug from the tapped hole portion by a plug wrench, drawing the spark plug upwardly after removal of the spark plug from the tapped hole portion, and further drawing up the spark plug towards within the upper spark-plug hole via the division wall portion.
According to another aspect of the invention, a method for installing a spark plug into a tapped hole portion formed in a cylinder head of a spark-ignition engine having at least one spark-plug hole through which the spark plug is screwed into the tapped hole portion, in which the cylinder head includes a division wall portion for dividing the cylinder head into an upper cylinder head portion and a lower cylinder head portion, an upper spark-plug hole formed in the upper cylinder head portion, and a lower spark-plug hole formed in the lower cylinder head portion, and wherein an axis of the upper spark-plug hole and an axis of the lower spark-plug hole are offset from each other, the method comprises inserting the spark plug downwardly into the upper spark-plug hole by a plug wrench, further inserting the spark plug downwardly towards within the lower spark-plug hole via the division wall portion, and screwing the spark plug into the tapped hole portion formed in the lower cylinder head portion.
REFERENCES:
patent: 5101777 (1992-04-01), Onishi et al.
patent: 5307785 (1994-05-01), Yoshikawa
patent: 5775288 (1998-07-01), Suzuki et al.
patent: 344597 (1989-12-01), None
patent: 0422277 (1991-04-01), None
Foley & Lardner
McMahon Marguerite
Nissan Motor Co,. Ltd.
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