Aluminum alloy cylinder block
Aluminum alloy cylinder block for use in a water-cooled internal combustion engine has a cylinder with a bore into which a piston is to be movably fitted. A water jacket provided on the outer side wall of the cylinder is adapted to allow the passage of water therein for cooling the engine. The depth of the water jacket from the top of the cylinder block is preferably from 0.2 to 0.5 times the length of the cylinder. A crank case has a side wall connected to the bottom of the water jacket, and a cylinder rib extends from the inside of the side wall of the crank case toward the water jacket.
It is known that a reduction in engine weight can be attained most effectively by making an engine cylinder block of aluminum alloy instead of cast iron. If the aluminum alloy cylinder block duplicates the usual structure of a cast iron cylinderblock, however, this change in material brings about various unfavorable results because the coefficient of thermal expansion of aluminum is twice as large as that of cast iron.
An object of the present invention is, therefore, to provide an aluminum alloy cylinder block free from the above mentioned drawbacks.
More specifically, the principal object of the present invention is to provide an aluminum alloy cylinder block in which thermal deformation of the cylinder bores is restrained to almost the same level as in the case of a conventional cast ironcylinder block, thereby lowering consumption of oil and diminishing scuffing and seizing between the bores and pistons.
Still another object of the present invention is to provide an aluminum alloy cylinder block having such a structure as to reinforce the mechanical strength of the upper and/or lower portion of the cylinder block.
A further object of the present invention is to provide an aluminum alloy cylinder block which provides reduced thermal deformation between the adjacent cylinders of a multicylinder engine.
Still another object of the present invention is to provide an aluminum alloy cylinder block which is simple in structure and easy to manufacture.
The present invention is characterized in that a cylinder rib is provided extending from the inner wall of the crank case to each cylinder. In addition, preferably the depth of a water jacket from the upper end of the cylinder block isdesigned to extend from 0.2 to 0.5 times as long as the length of the cylinder. Further, in the present invention, a horizontal rib having a length of from 0.6 to 1.0 times as long as the length of the cylinder block may be provided on the lower sidewall of the cylinder block. In addition, a transverse rib may be provided bridging a depression or groove between adjacent cylinders, and also a vertical rib having a length more than 0.2 times the height of the cylinder block may be provided on theouter wall of the cylinder block and along a cylinder head bolt hole.
The aluminum alloy cylinder block according to the present invention can be manufactured, for instance, by die casting or by low pressure casting.
As mentioned above, in the present invention, the depth of the water jacket from the upper end of the cylinder block is designed preferably to be from 0.2 to 0.5, preferably 0.3 to 0.45, times the length of the cylinder, and the cylinder ribextends from the side wall of the crank case to the cylinder. Therefore, the upper portion of the cylinder, which is heated up to higher temperatures, is adapted to be cooled by water circulating in the water jacket, while the heat is dissipated via theliner rib in the lower portion of the cylinder, which stays at relatively lower temperatures.
Furthermore, the thermal deformation of the cylinder is directly exerted upon the water jacket and the cylinder rib. Thus, according to the present invention, the aluminum alloy cylinder block can be easily manufactured with a slight change in the conventionalstructure, the distortion of the bore can be held to the level of the cast iron block, oil consumption can be reduced, and scuffing and seizure between the bore and the piston can be effectively prevented.
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