This invention relates generally to internal combustion engines and, more particularly, to cylinder sleeves that provide bores that receive the pistons of such engines.
An internal combustion engine generates a great amount of heat as a result of the combustion processes taking place in the engine block. Pistons move within cylinder bores toward and away from a cylinder head that includes intake and exhaust valves. The cylinder head seals the top end of a cylinder bore. The cylinder bores, head, and pistons form combustion chambers of the engine. As a piston travels upwardly toward the top of the cylinder bore, a gas/fuel mixture is compressed within the cylinder. The cylinder pressure can be as high as 10,000 psi. Prior to reaching the top of the piston travel, a spark and the compression of the mixture causes a controlled burn that can reach as high as 1400xc2x0 C. The controlled burning of the compressed gas/fuel mixture pushes the piston downward in the cylinder, thereby rotating a crankshaft. The burning of the gas/fuel mixture generates a significant amount of heat within the engine.
The operating temperature of an engine can generally be maintained within acceptable limits by the circulation of coolant in the engine block, around the cylinders, and through portions of the cylinder head. Demands for greater horsepower output of engines, and for reduced hydrocarbon emissions in conjunction with catalyst systems, have both resulted in substantially increased combustion temperatures and hotter running engines. The increased temperatures occur primarily within the engine block, especially near the most highly heated top portions of the cylinders, near the cylinder head.
Some engines utilize cylinder sleeves that are inserted within the cylinder bores of an engine block. Alternatively, the block can be cast around the cylinder sleeves. If the sleeves come in contact with engine coolant, then the sleeves are referred to as wet sleeves. In other configurations, the cylinder sleeves might be located totally within an existing cylinder bore of the engine, such that coolant does not come into contact with the cylinder sleeve. These sleeves are referred to as dry sleeves. Unfortunately, without coolant contact, the most highly heated portion of the cylinder sleeve might not be adequately cooled. Some aftermarket applications provide a cylinder sleeve that is inserted within an existing cylinder bore of an engine block, to strengthen the engine and improve performance. Cylinder sleeves are typically made of high-strength metal compositions for increased performance.
Other configurations of cylinder sleeves can improve cooling flow. For example, some cylinder sleeves are provided with an upper collar or flange. The flange includes holes configured as vertical passageways that permit coolant to pass through the flange and into the cylinder head. This improves cooling of the selected upper flange area of the cylinder sleeve, but heat can still build up along the uppermost portion of the sleeve and in the hottest portions of high performance engines.
FIG. 1 illustrates a partial cross-sectional view of a conventional internal combustion engine 100 that includes an engine block 106, a cylinder sleeve 102, a cylinder head 130, and a piston 110. The cylinder sleeve 102 includes a flange portion 108. The sleeve is slidably inserted into a cylinder bore 104 within the engine block 106 until a support shoulder 112 of the cylinder sleeve comes in contact with a ledge 114 of the engine block 106. The ledge positions the top surface 120 of the cylinder sleeve 102 to be substantially flush with the cylinder head seating surface 122 formed by the engine block 106 and top of the flange 108. Those skilled in the art will appreciate that a gasket (not illustrated) can be positioned between the lower surface of the cylinder head 130 and the cylinder head seating surface 122 to provide improved combustion chamber sealing.
The inner wall 126 of the cylinder sleeve 102, the lower surface of the cylinder head 130, and the top surface of the piston 110 form a combustion chamber 124. On the piston intake stroke, the piston 110 moves downwardly, away from the cylinder head, and a mixture of air and vaporized fuel is drawn into the combustion chamber 124 through an intake valve port 132. Approximately when the piston 110 reaches the lower limit of the piston travel area 116, an intake valve is closed, shutting off the intake port 132 and sealing off the combustion chamber 124. The piston then begins upward movement, toward the cylinder head. As the piston moves upwardly, the air/fuel mixture is compressed as the combustion chamber 124 is reduced in volume. The compression of the air/fuel mixture increases the pressure in the combustion chamber 124, and also increases the mixture temperature. Approximately as the piston 110 reaches the top position of its travel (as shown in FIG. 1, also referred to as xe2x80x9ctop dead centerxe2x80x9d), the air/fuel mixture is ignited with a controlled bum. The ignition creates an exhaust in the combustion chamber that presses against the piston 110 and moves the piston rod 128 down to rotate the crankshaft (not illustrated). The burned exhaust gas is forced out through the exhaust valve port 134.
For engine cooling of the FIG. 1 configuration, coolant is circulated into and out of an annular coolant gap 136 via coolant passages (not illustrated) in the block 106. The most highly heated portion of the cylinder sleeve 102 and the cylinder head 130 is the area adjacent to the combustion chamber 124 near the flange 108. It should be apparent in FIG. 1 that the most highly heated portion is not effectively cooled, because coolant in the coolant gap 136 is generally not in contact with this most highly heated portion of the sleeve 102, but rather is restricted to contact below the flange 108.
It is known to circulate coolant within an annular gap 140 located within the flange 108. Coolant passages (not illustrated) permit coolant to circulate into and out of the annular gap 140. This improves cooling of the sleeve flange, but more thorough cooling of the sleeve with greater control of the cooling is desirable.
From the discussion above, it should be apparent that there is a need for more efficient and controlled cooling of the most highly heated portions of internal combustion engines. The present invention solves this need.
The present invention overcomes the above-described shortcomings by providing a cylinder sleeve for an internal combustion engine having an engine block and a cylinder head, wherein the cylinder sleeve includes a cylindrical section having a top portion and a bottom portion, and a flange section adjacent to the top portion, such that the flange section is configured to include a coolant groove and at least one coolant hole that provides a passageway for coolant to pass through the flange and into the coolant groove. The coolant groove provides improved cooling of the flange and the upper portion of the cylinder sleeve. In this way, the cylinder sleeve provides more efficient and controlled cooling of the most highly heated portions of internal combustion engines.
In one aspect, an internal combustion engine can be provided with cylinder sleeves so that the engine includes an engine block having at least one bore, a cylinder head including at least one coolant port, and at least one cylinder sleeve that corresponds to the cylinder bore of the block. Each of the cylinder sleeves includes a cylindrical inner surface having a longitudinally extending axis, an outer surface, and at least one coolant passageway. The outer surface of the sleeve has a lower mating region that is adapted to be at least partially fitted into a cylinder bore of an engine block of the internal combustion engine. The outer surface is in communication with a flow of coolant. The flow of coolant can pass from the outer surface of the sleeve into coolant ports, through the sleeve flange, and into a cylinder head of the internal combustion engine. The coolant passageway includes a groove that provides lateral flow of coolant through the flange and into the cylinder head.
In another aspect, a method for cooling highly heated portions of a cylinder sleeve and a cylinder head is described. Coolant flows into a groove configured about an upper portion of the flange section in the cylinder sleeve. Once inside the groove, the coolant is directed about the upper portion of the flange section and can be channeled into an area of the cylinder head disposed above the groove.
Other features and advantages of the present invention should be apparent from the following description of the preferred embodiments, which illustrates, by way of example, the principles of the invention.