1. Field of the Invention
The present invention relates to an internal combustion engine with novel cooling passages located within the cylinder head.
2. Disclosure Information
Liquid-cooled internal combustion engines have been in continuous use for more than a century. In the beginning, cooling systems for single cylinder engines relied upon a reservoir incorporated in the cylinder of the engine to flood an external portion of the cylinder with water, which was allowed to boil off. Later cooling system designs, although using radiators, employed steam generated within the engine to force the coolant through various passages. Finally, pumped cooling came to the fore.
The demands placed on engine cooling systems, defined to include the various cooling passages within the cylinder block and cylinder head of an engine, are not too great in the case of engines which are operated at low specific output. However, engines which are operated at high levels of specific output require large amounts of fuel, and therefore place heavy demands on their cooling systems. Moreover, cooling system design is critical with respect to particular areas of an engine's cylinder head, such as the bridge area extending between adjacent valves. This bridge area is particularly prone to thermal stress and cylinder head fire deck cracking, in the case of either two-valve engines with a single intake and exhaust in each cylinder head unit, or with multiple valve engines having, for example, two intake valves and a single exhaust valve, or even engines with two or more intake valves and two or more exhaust valves.
As used herein, the term “cylinder head unit” means a specific portion of a cylinder head having a single combustion chamber dedicated to a single engine cylinder. Thus, a cylinder head for a four-cylinder inline engine would have four cylinder head units. Following this convention, a cylinder head for a V-6 engine would have three cylinder head units.
A cylinder head having directed cooling according to the present invention permits operation at high specific output by applying the circulating coolant to the areas of the cylinder head which are either subject to the greatest heat flux, measured in terms of units of heat energy per unit of surface area, or which are prone to damage, such as the previously mentioned bridge area extending between adjacent valves in a given cylinder head unit. As a result, the present cylinder head is said to have “directed” cooling.
An internal combustion engine cylinder head includes a number of intake ports extending upwardly from a fire deck and a number of partially conjoined exhaust ports extending upwardly from the fire deck. A common coolant passage extends between the exhaust ports. A first coolant flow director extends into the common coolant passage, so as to cause coolant flowing within the common coolant passage to remain attached upon an upper surface of the fire deck between the exhaust ports. The first coolant flow director further causes coolant to flow about an outer surface of each of the exhaust ports.
According to another aspect of the present invention, a first coolant flow director includes a flow splitter depending from an upper wall of the common coolant passage. The flow splitter may divide at least a portion of the common coolant passage into three sub-passages.
According to another aspect of the present invention, an internal combustion engine may further include a second coolant passage extending about a radially outward portion of the cylinder head unit. The second coolant passage preferably includes a second coolant flow director extending into the second coolant passage from a rear wall of the second coolant passage so as to cause coolant flowing within the second coolant passage to impinge upon an upper surface of the fire deck, as well as upon at least an outboard portion of one of the exhaust ports. In this embodiment, the second coolant flow director preferably comprises a truncated bulk flow displacer.
In general, the present invention is applicable to any cylinder head unit including a number of gas flow ports extending upwardly from a fire deck, where a common flow passage extends between adjacent ports. The ports may include either two intake ports, two exhaust ports, or an intake port and an exhaust port.
It is an advantage of a cylinder head unit according to the present invention that the durability of the cylinder head is enhanced by the capability to cool the bridge area between adjacent valves in an enhanced manner.
It is a further advantage of a cylinder head according to the present invention that an engine with this invention should have a lower octane requirement because of the likelihood that the cylinder head's combustion chamber will have a more uniform temperature distribution.
It is yet another advantage according to the present invention that the ability to control and manage cylinder head heat distribution will improve fuel economy of the engine by allowing optimal spark timing.
Other advantages, as well as features and objects of the present invention will become apparent to the reader of this specification.
As shown in
Those skilled in the art will appreciate in view of this disclosure that ports 34 are illustrative of not only two exhaust ports, but alternatively depict two intake ports, or a single intake port and a single exhaust port. In any event, common coolant passage 38 extends between exhaust ports 34, which are partially conjoined. In other words, exhaust ports 34 are attached very closely to one another at the section line 3-3. First coolant flow director 42 is shown in
First coolant flow director 42 causes the coolant flow within common coolant passage 38 to remain attached to upper surface 24 of fire deck 20. This is shown with particularity in
While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.
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