Embodiments of the invention relate generally to overhead valve (OHV) engines utilizing push rod tubes, and more particularly, to an engine cylinder head and push rod tube configuration.
Overhead valve (OHV) engines use push rods to actuate valves in a cylinder head. The push rods are driven by a camshaft located in the engine block. The push rods actuate one end of a rocker arm which pivots on a trunnion pin or a rocker shaft located above the cylinder head. The other end of the rocker arm actuates an intake or exhaust valve. The rocker assembly is usually encased by a rocker cover.
In some engines, the push rods are contained in push rod tubes which protect the push rods and provide a path for oil to flow between the crankcase and rocker cover. Since push rods typically extend from the cylinder head to the block, when push rod tubes are utilized, they too extend from the cylinder head to the block. This results in requiring an affirmative seal to prevent oil seepage and contamination due to movement and differing expansion and contraction rates. The push rod tubes are therefore either threaded at both ends and screwed into the engine block and the head or the rocker cover, contain o-rings to provide an oil seal, and/or contain annular flanges and gaskets. Unfortunately, these components degrade over time and must be replaced and are time consuming to manufacture and install.
In air cooled internal combustion engines, it may be desirable to position push rod tubes and rocker covers to aid in transferring heat from the cylinder head and block. Air cooled internal combustion engines rely on cooling fins around the periphery of the cylinder block and head to increase surface area over which cooling air flows. However, push rod tubes may become effective cooling devices if they are positioned in the path of cooling air. Also, new enclosure designs for rocker components have the potential to increase surface area available for heat transfer. Rocker covers often act as insulators as they encapsulate the cylinder head, and therefore heat transfer from the cylinder head may be significantly improved with careful design.
Instead of push rod tubes, other engines use push rod passages formed within the cylinder head and block. While push rod passages do not require o-rings and gaskets, they require thicker walls within the cylinder head and block to provide room for the passages and require additional casting or machining steps. The thicker walls increase thermal resistance to heat transfer from the combustion chamber. Push rod tubes formed in the cylinder head also restrict air flow and reduce cooling capacity.
Therefore, it would be desirable to provide push rod tubes without components that degrade over time and that reduce manufacturing and assembly time. It would also be desirable for a cylinder head to have push rod tubes located in a position to maximize heat transfer to the ambient environment and are wholly contained within a single component of the engine. It would be further advantageous if a cylinder head had an enclosure for rocker components that increased heat transfer from the cylinder head.
Embodiments of the invention relate to a cylinder head and push rod tube configuration for an internal combustion engine.
In accordance with one aspect of the invention, a cylinder head for an internal combustion engine includes a first end comprising a recessed rocker arm cavity. The cylinder head also includes a second end opposite the first end and defining an upper end of a combustion chamber. The recessed rocker arm cavity has a lower surface with a pair of push rod tube bores therethrough. The second end of the cylinder head has a pair of push rod tubes positioned in the push rod tube bores between the recessed rocker arm cavity and the second end. An intake port and an exhaust port each extend through the cylinder head to the combustion chamber.
In accordance with another aspect of the invention, a cylinder head assembly includes a cylinder head configured to be operatively coupled to a cylinder block. The cylinder head includes a base portion to contact the cylinder block, an intake port and an exhaust port, and a top portion comprising a recessed valve assembly cavity. The recessed valve assembly cavity and base portion form a gap therebetween along a side of the cylinder head. The cylinder head also includes a pair of push rod tubes extending through the gap from the base portion to the recessed valve assembly cavity. An intake valve and exhaust valve are in communication with the respective intake port and exhaust port. The intake valve and exhaust valve each have a stem extending into the recessed valve assembly cavity. A rocker arm assembly is coupled into the recessed valve assembly cavity. Each of a pair of push rods communicates with the rocker arm assembly and is inserted into a respective push rod tube.
In accordance with a further aspect of the invention, a multi-cylinder internal combustion engine includes a crankcase, a plurality of cylinders, and a plurality of cylinder heads. Each cylinder has a bore and a piston located in the bore. Each cylinder head has a lower end coupled to a respective cylinder and an upper end having a cavity for inclusion of rocker components. A recess is located under the cavity in the cylinder head within which a pair of push rod tubes are positioned and extend from the lower end to the cavity. The cylinder head further includes an intake valve in communication with an intake port and an exhaust valve in communication with an exhaust port, with the intake and exhaust valves each having stems protruding into the cavity. Rocker components are coupled to the inside of each cavity. A push rod is located in each of the push rod tubes and communicates with respective rocker components and the crankcase.
Various other features and advantages will be made apparent from the following detailed description and the drawings.
The drawings illustrate embodiments presently contemplated for carrying out the invention.
In the drawings:
Embodiments of the invention are directed to an intake port of a cylinder head of an air cooled internal combustion engine; a push rod tube configuration within the cylinder head of the air cooled combustion engine; and an air guide for directing cooling air to the cylinder head of the air cooled combustion engine. The various embodiments of the invention are incorporated into the air cooled internal combustion engine, which in turn is incorporated as a prime mover/prime power source in any of a number of various applications, including but not limited to, power generators, lawnmowers, power washers, recreational vehicles, and boats, as just some examples. While embodiments of the invention are described below, it is to be understood that such disclosure is not meant to be limiting but set forth examples of implementation of the inventions. The scope of the inventions is meant to encompass various embodiments and any suitable application in which a general purpose internal combustion engine can benefit from the inventions shown and described herein. It is understood that certain aspects of the inventions may equally be applicable to non-air cooled internal combustion engines as well and such is within the scope of the present inventions.
Referring first to
Cylinder head 14 includes push rod tubes 60 that are pressed fit into respective bores 62 of cylinder head 14. Each push rod tube 60 has two outside diameters 64, 66 that are received into bore 62 of cylinder head 14 such that the smaller diameter 66 passes unobstructed through the bore 62 until the larger diameter 64 reaches the top of bore 62 to allow an even press-in fit. As is shown in further detail and will be described hereinafter with respect to
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As one skilled in the art will now readily recognize, by eliminating push rod passages that are usually cast into the cylinder head, and minimizing the push rod tubes, a substantial amount of the casting can be eliminated resulting in new open areas that can be utilized for additional cooling. The new push rod tubes of the present invention allow for more cooling air to communicate with the combustion chamber and exhaust port.
Therefore, according to one embodiment of the invention, a cylinder head for an internal combustion engine includes a first end comprising a recessed rocker arm cavity. The cylinder head also includes a second end opposite the first end and defining an upper end of a combustion chamber. The recessed rocker arm cavity has a lower surface with a pair of push rod tube bores therethrough. The second end of the cylinder head has a pair of push rod tubes positioned in the push rod tube bores between the recessed rocker arm cavity and the second end. An intake port and an exhaust port each extend through the cylinder head to the combustion chamber.
According to another embodiment of the invention, a cylinder head assembly includes a cylinder head configured to be operatively coupled to a cylinder block. The cylinder head includes a base portion to contact the cylinder block, an intake port and an exhaust port, and a top portion comprising a recessed valve assembly cavity. The recessed valve assembly cavity and base portion form a gap therebetween along a side of the cylinder head. The cylinder head also includes a pair of push rod tubes extending through the gap from the base portion to the recessed valve assembly cavity. An intake valve and exhaust valve are in communication with the respective intake port and exhaust port. The intake valve and exhaust valve each have a stem extending into the recessed valve assembly cavity. A rocker arm assembly is coupled into the recessed valve assembly cavity. Each of a pair of push rods communicates with the rocker arm assembly and is inserted into a respective push rod tube.
According to yet another embodiment of the invention, a multi-cylinder internal combustion engine includes a crankcase, a plurality of cylinders, and a plurality of cylinder heads. Each cylinder has a bore and a piston located in the bore. Each cylinder head has a lower end coupled to a respective cylinder and an upper end having a cavity for inclusion of rocker components. A recess is located under the cavity in the cylinder head within which a pair of push rod tubes are positioned and extend from the lower end to the cavity. The cylinder head further includes an intake valve in communication with an intake port and an exhaust valve in communication with an exhaust port, with the intake and exhaust valves each having stems protruding into the cavity. Rocker components are coupled to the inside of each cavity. A push rod is located in each of the push rod tubes and communicates with respective rocker components and the crankcase.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
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20150322882 A1 | Nov 2015 | US |