Abstract:
A cylinder block assembly for an internal combustion engine having a cylinder block and a plurality of cylinders includes an oil port in each of the cylinders. An annular groove is located in each cylinder wall so that oil flowing from the oil port flows into the annular groove to lubricate the skirt of the piston. An opening may be located in the piston so that oil flowing from the oil port flows into and through the piston opening when the piston is at a predetermined position, thereby directly injecting oil into the piston to lubricate the wrist pin of the piston.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application and claims priority of U.S. application Ser. No. 09/267,481, filed Mar. 11, 1999 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to outboard engines, and more particularly, to the oil injection systems for two-stroke internal combustion engines. 
     Known v-type internal combustion engines for marine use include a cylinder block having a crankcase and two banks of cylinders extend radially from the crankcase. In a six cylinder engine, for example, each cylinder bank includes three cylinders. Each cylinder includes a sleeve and a piston moves relative to the sleeve between top dead center and bottom dead center positions. A main exhaust passageway and cooling water passageway are located between the first and second cylinder banks. 
     In operation, the friction between the pistons and the sleeves can result in generation of heat and wear of both the pistons and the sleeves. To reduce such heat generation and wear, oil should be dispersed between the pistons and the sleeves. The clearance between the pistons and the sleeves, however, is only about 0.004 to 0.010 inches. Dispersing oil between the pistons and the sleeves is difficult due to such small clearance. 
     Known attempts to introduce oil directly into the clearance space between the sleeves and the pistons have not been successful. Specifically, the oil supply hole for each cylinder must be located at the outer side of each cylinder due to the location of the exhaust and water passageways. Therefore, the oil supply holes for both banks of cylinders must be located in the outer cylinder walls. 
     In a v-type engine, and as the crankshaft rotates in a clockwise direction, the pistons in the first cylinder bank are thrust against the inner cylinder walls, and the pistons in the second cylinder bank are thrust against the outer cylinder walls. The second cylinder bank pistons thrust against the outer cylinder walls, and therefore against the oil supply holes in the outer cylinder walls, inhibit oil from being introduced into the cylinder through such holes. As a result, the second cylinder bank may be starved for lubrication. 
     It would be desirable to provide an oil injection system which injects oil directly between the pistons and the cylinder sleeves in a v-type engine. It also would be desirable to provide such a system which does not add significant costs or complexity to fabrication and assembly of the engine. 
     BRIEF SUMMARY OF THE INVENTION 
     These and other objects may be attained by oil injection apparatus and methods for injecting oil directly between the cylinder sleeves and the pistons of both cylinder banks in a v-type engine. In one embodiment, an oil port in the engine block extends to an annular groove in the cylinder wall. An oil pump supplies lubricating oil to the port via a conduit and under the control of a control unit. 
     In operation, if the piston is thrust into the cylinder wall at the location of the groove when the oil is being injected, the oil flows into the groove and is dispersed as the piston moves past the groove on the next stroke. If the piston is not thrust into the cylinder wall at the time oil is introduced, the oil flows into the cylinder and is dispersed by the piston. 
     Such direct injection of the oil at a location between the piston and the cylinder wall provides the advantage that lubricating oil is located between the piston and the cylinder in each cylinder. As a result, there is less friction between the pistons and the cylinders as compared to the friction if no lubricant is provided between the pistons and cylinders. Therefore, less heat is generated (i.e., less energy loss) due to such friction, and wear of the pistons and cylinders is reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic, partial cross-sectional illustration of a known internal combustion engine for marine use. 
     FIG. 2 illustrates a portion of a two-stroke internal combustion engine in accordance with one embodiment of the present invention. 
     FIG. 3 illustrates a portion of a two-stroke internal combustion engine in accordance with another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a schematic, partial cross-sectional illustration of a known internal combustion engine  10  for marine use. Engine  10  is shown schematically primarily to describe one known engine configuration. The present invention is not limited to practice in engine  10 , and can be used in connection with many other engine arrangements. For example, the present invention can be used in both two stroke and four stroke engines. Further, although the present invention is described herein in connection with a single fluid, pressure surge direct in-cylinder fuel injection system, the invention can be used in connection with many other fuel injection systems including, for example, dual fluid, air-assisted direct in-cylinder fuel injection systems. 
     Engine  10  includes a cylinder block  12  having a crankcase  14 . Cylinder block  12  also includes a main exhaust passageway  16  intermediate first and second cylinders  18  and  20  which extend radially from crankcase  14 . Cylinders  18  and  20  include cylinder walls  22  and  24 , respectively. Block  12  further includes a water passageway  26  intermediate cylinders  18  and  20 . 
     A crankshaft  28  is supported in crankcase  14  for rotation about a crankshaft axis  30 . Angularly spaced first and second crankpins  32  and  34  are coupled to crankshaft  28 . Pistons  36  and  38  are connected to crankpins  32  and  34  by connecting rods  40  and  42 . Pistons  36  and  38  are reciprocally movable in first and second cylinders  18  and  20  toward and away from crankshaft  28  and between top dead center and bottom dead center positions. 
     Sleeves  44  and  46  are located in cylinders  22  and  24 , and pistons  36  and  38  are in sliding contact with sleeves  44  and  46 . The friction between aluminum pistons  36  and  38  and sleeves  44  and  46  can result in generation of heat and wear of both pistons  36  and  38  and sleeves  44  and  46 . To reduce such heat generation and wear, oil should be dispersed between pistons  36  and  38  and sleeves  44  and  46 . The clearance between pistons  36  and  38  and sleeves  44  and  46 , however, is only about 0.004 to 0.010 inches. In addition, lubricating oil is typically introduced into an air stream flowing into crankcase  14  or is dribelled into crankcase  14  at a location that allows crankshaft  28 , connecting rod  40  and  42 , or pistons  36  and  38  to hit and disperse the oil. 
     The present invention, in one aspect, provides that oil is injected directly between the cylinder sleeves and the pistons of both cylinder banks in a v-type engine. Particularly, and referring to FIG. 2 which illustrates a portion of a two-stroke internal combustion engine  100 , engine  100  includes a cylinder block  102  and a cylinder head  104 . Block  102  includes cylinder  106  having piston  108  therein. Although not shown in FIG. 2, a sleeve is located between piston  108  the wall of cylinder  106 . Block  102 , of course, includes other cylinders and pistons configured the same as cylinder  106  and piston  108 . Cylinder  106  includes a combustion chamber  110 , and an exhaust manifold  112  communicates with combustion chamber  110 . 
     A crankcase cover  114  forms a sealed crankcase  116 , and a crankshaft  118  is supported in crankcase  116  for rotation. A connecting rod  120  extends from crankshaft  118  and is engaged to piston  108 . Piston  108  is reciprocally movable toward and away from crankshaft  118  and between top dead center and bottom dead center positions. 
     A fuel injector  122  communicates directly with combustion chamber  110  and periodically injects fuel unmixed with air directly in chamber  110 . A spark plug  124  extends into combustion chamber  110 , and is operable to periodically ignite the fuel charges in combustion chamber  110 . A control unit  126 , which in one embodiment includes an electronic control unit, controls operations of injector  122  and spark plug  124 . Additional details regarding the above described engine components are set forth, for example, in U.S. Pat. No. 5,730,099, which is assigned to the present assignee. 
     In accordance with the present invention, an oil induction port  128  is located at an outer wall  130  of cylinder  106 , and port  128  is in flow communication with an annular groove  132 , or notch, in cylinder wall  134 . Groove  132  extends radially 360 degrees, i.e., is coextensive with wall  134 . The sleeve (not shown) includes an annular opening therein that is substantially coextensive with groove  132 . 
     An oil injection circuit  136  supplies oil to port  128 . Injection circuit  136  includes an oil pump  138  and an oil distribution manifold  140 . An oil supply conduit  142  extends from port  128  to pump  138 , and another oil supply conduit  144  extends from pump  138  to manifold  140 . Oil pump  138  is coupled to, and controlled by, control unit  126 , as is well known in the art. 
     The particular dimensions of port  128  and groove  132  are selected depending upon the desired amount of oil to be injected during each cycle. The dimensions can be determined empirically. Groove  132  can be machined into block  102 , or may be formed when block  102  is fabricated, e.g., during casting operations. 
     In operation, pump  138  draws oil from manifold  140  and pumps oil through conduit  142  to port  128 . If piston  108  is thrust into cylinder wall  134  at the location of port  126  and when oil is being injected, the oil flows into groove  132  and is dispersed as piston  108  moves past groove  132  on the next stroke. If piston  108  is not thrust into cylinder wall  134  at the time oil is introduced, the oil flows into cylinder  106  and is dispersed by piston  108 . 
     Such direct injection of oil at a location between the piston and the cylinder wall provides the advantage that lubricating oil is located between the piston and the cylinder wall in each cylinder. As a result, there is less friction between the pistons and cylinders as compared to the friction if no lubricant is provided between the pistons and cylinders. Therefore, less heat is generated (i.e., less energy loss) due to such friction, and wear of the pistons and cylinders is reduced. 
     FIG. 3 illustrates another embodiment of an engine  200  in accordance with the present invention. Engine components in FIG. 3 which are identical to the engine components illustrated in FIG. 2 are identified in FIG. 3 using the same reference numerals as used in FIG.  2 . In the embodiment shown in FIG. 3, an oil induction port  202  is located at outer wall  130  of cylinder  106 . The sleeve (not shown) includes an opening therein that is aligned with port  202 . A piston  204  located in cylinder  106  includes an oil flow opening  206  that aligns with port  202  at least for a portion of the movement of piston  204  between top dead center and bottom dead center. In one embodiment, opening  206  aligns with port  202  when piston  204  is at bottom dead center. 
     The particular dimensions of port  202  and opening  206  are selected depending upon the desired amount of oil to be injected during each cycle. The dimensions can be determined empirically. In addition, opening  206  may be formed in piston  204  by drilling or other machining operations. Alternatively, opening  206  may be formed when piston  204  is fabricated, e.g., during casting operations. 
     In operation, pump  138  draws oil from manifold  140  and pumps oil through conduit  142  to port  202 . If opening  206  in piston  204  is aligned with port  202  when oil is being injected, the oil flows through opening  206 , drops onto the piston wrist pin boss, and is dispersed. At least some of the oil will be dispersed against cylinder wall  134  so that lubricating oil is between piston  204  and wall  134 . If opening  206  is not aligned with port  202  when oil is being injected, the oil may be prevented from entering into cylinder  106  by piston  204 , or some oil may flow between piston  204  and cylinder wall  134 . 
     The above described oil injection systems provide the advantage that oil is dispersed against the cylinder walls of the cylinders in a v-type engine. By providing lubricating oil between the pistons and cylinder walls or sleeves, less friction is generated between the pistons and the sleeves, which facilitates reduced energy loss and wear. 
     From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. For example, as explained above, the present invention can be used in both two stroke and four stroke engines, and in connection with single fluid, pressure surge direct in-cylinder fuel injection systems, dual fluid, air-assisted direct in-cylinder fuel injection systems, and other injection systems. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.