Abstract:
The present invention provides an improved oil injection lubrication system for two-cycle engines. The system includes an oil tank having a recess and a number of raised portions that allow the tank to be mounted to an engine in a compact configuration proximate a flywheel without interference while providing a passageway for control lines and fluid conduits in the recess. In one embodiment, the system is included in an outboard marine motor. In this embodiment, the oil tank is preferably configured to have an inlet that remains above a maximum oil level even when the outboard motor is raised to a fully tilt-up position to prevent backflow or siphoning of oil back into a supply tank in the hull of a watercraft.

Description:
RELATED APPLICATIONS  
         [0001]    This application is a division of U.S. application Ser. No. 09/388,734, filed Sep. 2, 1999, which is hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to oil injection lubrication systems for engines, and more particularly to an oil injection system for lubricating a multiple cylinder engine.  
           [0004]    2. Description of the Related Art  
           [0005]    For two-cycle engines, it is a common practice to mix lubricating oil with induction air to lubricate engine parts. Conventional systems typically mix oil with induction air in the same proportion regardless of engine speed. Such systems also typically deliver the same amount of oil to each cylinder regardless of the engine operating conditions. Under certain conditions, however, some cylinders of some engines require more lubricating oil than other cylinders. Furthermore, operating conditions such as cylinder resting periods, idling periods, rapid acceleration periods, or continuous speed periods often result in variations in the appropriate amount of oil required for each cylinder. Conventional systems do not provide the capability of adjusting the amount of oil delivered to each cylinder to compensate for these situations. Consequently, conventional systems suffer from problems such as smoke generated by the mixture of air and lube oil, odor, and heavy oil consumption.  
           [0006]    Existing systems for single cylinder engines provide a solenoid valve at a discharge side of a mechanical oil pump through which oil delivery can be regulated in response to varying engine operating conditions. In these systems, however, the oil pump is typically configured to supply oil at a constant volume per crankshaft revolution. At extremely low engine speeds, an engine may require much less oil per revolution than at higher speeds. As a consequence, the solenoid valves may have to be actuated in a relatively heavy duty cycle to appropriately regulate the flow of oil at low engine speeds. Actuation of the solenoid valves draws electrical power. Consequently these systems adversely draw a relatively large amount of electrical power during low engine speed periods when it is also more difficult to generate electrical power. Still another disadvantage of existing systems is that they would require a complicated layout of solenoid valves and lines in order to be adapted to multiple cylinder engines.  
           [0007]    In many outboard boat motors having two-cycle engines, an oil tank that supplies oil to the oil injection system is generally mounted below a flywheel on a side of the engine body. This arrangement allows only a small clearance between the oil tank and flywheel because other parts such as a fuel tank, fuel pump and oil filter are crammed into a tight engine compartment. As a result, pipes and wires cannot pass above the oil tank. Further, particularly for direct fuel injection type engines, fuel pipes and wires may have to detour around the oil tank, resulting in undesirably long pipes and wires. Longer pipes and wires are less efficient and more susceptible to damage. Prior art oil tanks are also susceptible to backflow or siphoning of the lubricating oil back into a main tank located in the hull of the boat, when, for example, the oil tank is tilted as the engine is raised out of the water.  
         SUMMARY OF THE INVENTION  
         [0008]    One embodiment of the invention provides an improved oil injection lubrication system for an engine, which has particular application in connection with a multi-cylinder engine.  
           [0009]    In accordance with one aspect of the present invention, the system comprises a variable output oil pump, the output of which can be varied in relation to a throttle valve position. A solenoid valve unit, which includes a plurality of solenoid valves, regulates the flow of oil from the oil pump to each cylinder. An electronic control unit sends control signals to the solenoid valve unit to regulate the flow of oil based upon engine operating conditions in accordance with a control scheme. By adjusting the output from the oil pump in accordance with the throttle position, the volume of oil directed to each cylinder is roughly equal (i.e., approximates) to a predetermined volume of oil required or desired for a given engine speed or operational condition. The solenoid valve unit then regulates the volume flow to each cylinder through the solenoid valves to fine tune the amount of oil delivered to each cylinder (including both the combustion chamber and the corresponding crankcase section) to more precisely equal the predetermined volume, that volume depending upon the engine&#39;s running condition.  
           [0010]    In a preferred mode, one solenoid valve is dedicated to each cylinder. The valve circuitry is configured to permit oil flow from the oil pump to the cylinders when the corresponding solenoid valves are in an inactive state. The ECU powers the solenoid valves to temporarily close the valves and direct a portion of the lubricant flow away from the cylinders (e.g., through a line to an oil tank). By varying the closure times of the valves, the ECU can finely tune the amount of oil delivered to each cylinder in accordance with predetermined control strategies.  
           [0011]    In accordance with this aspect of the present invention, a lubrication system is provided for an engine having a plurality of cylinders. The system comprises a plurality of oil supply pipes, each oil supply pipe being configured to supply oil to one of the plurality of cylinders. A solenoid valve unit is connected to the plurality of oil supply pipes and regulates the flow of oil to the cylinders. An oil pump is connected to the solenoid valve unit to supply oil to the unit, and an electronic control unit is connected to and communicates with the solenoid valve unit to control the operation of the unit.  
           [0012]    In one mode, an oil supply pipe carries a flow of oil from the valve unit to a vapor separator tank for mixture with the fuel supply in order to reduce the formation of deposits on fuel injectors, lubricate the fuel system, and/or prevent corrosion.  
           [0013]    In accordance with a preferred method of controlling oil delivery to the cylinders of an engine, the method comprises producing a base volume flow of oil per crankshaft revolution. The base volume is adjusted per crankshaft revolution to deliver an adjusted volume per crankshaft revolution. This adjusted volume is then fine tuned for each cylinder.  
           [0014]    In a preferred mode of operation, the base volume per crankshaft revolution is supplied through a positive displacement oil pump, and the base volume per crankshaft revolution is adjusted by varying the volume output per revolution by the positive displacement oil pump. The volume supplied per revolution by the positive displacement oil pump is preferably adjusted in relation to a position of a throttle valve of the engine. The adjusted volume is then fine tuned by passing the adjusted volume through a solenoid valve.  
           [0015]    In accordance with another aspect of the present invention, the lubrication system comprises an oil tank having a recess and a number of raised portions that allow the tank to be mounted to the engine in a compact configuration proximate the flywheel without interference while providing a passageway for control lines and fluid conduits in the recess. The oil tank is also preferably configured to have an inlet that remains above the maximum oil level to prevent backflow or siphoning of oil back into a supply tank in the hull of a watercraft. Further aspects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiment which follows. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The above-mentioned and other features of the invention will now be described with reference to the drawings of preferred embodiments of the present watercraft. The illustrated embodiments are intended to illustrate, but not to limit the invention. The drawings contain the following figures:  
         [0017]    [0017]FIG. 1 is a schematic view of an engine control system, which is configured in accordance with a preferred embodiment of the present invention as employed on an outboard motor, and illustrates in Section A the outboard motor from a side elevational view, illustrates in Sections B and C a partial schematic view of the engine with associated portions of the oil injection system, illustrates in Section D a sectional view of the engine (as taken along line D-D of the Figure Section B) and a drive shaft housing of the outboard motor, and illustrates an electronic control unit (ECU) of the engine control system communicating with various sensors and controlled components of the engine;  
         [0018]    [0018]FIG. 2 is a top plan view of a power head of the engine showing the engine in solid lines and the cowling in phantom lines;  
         [0019]    [0019]FIG. 3 is a side elevational view of the engine as viewed in the direction of arrow Y of FIG. 2 and illustrates a number of components of the oil injection system;  
         [0020]    [0020]FIG. 4A illustrates a top plan view of a main oil tank of the engine of FIG. 3;  
         [0021]    [0021]FIG. 4B illustrates a side elevational view of the main oil tank as viewed in the direction of arrow X of FIG. 4A;  
         [0022]    [0022]FIG. 4C illustrates a side elevational view of the main oil tank as viewed in the direction of arrow Z of FIG. 4A;  
         [0023]    [0023]FIG. 4D illustrates the side elevational view of the main oil tank of FIG. 4C when the motor is tilted to raise it out of the water;  
         [0024]    [0024]FIG. 5 illustrates an enlarged cross-sectional view of a solenoid valve unit of the engine control system;  
         [0025]    [0025]FIG. 6A is a partial sectional side elevational view of another solenoid valve unit configured in accordance with an additional preferred embodiment of the present invention;  
         [0026]    [0026]FIG. 6B is a top plan view of the solenoid valve unit of FIG. 6A;  
         [0027]    [0027]FIG. 6C illustrates a view of the solenoid valve unit of FIG. 6B as viewed in a direction W;  
         [0028]    [0028]FIG. 7 is a graph of the relationship between engine speed and desired or required oil supply volumes for various cylinders of the disclosed engine in accordance with a preferred embodiment of the invention; and  
         [0029]    FIGS.  8 A-H show eight exemplary timing diagrams for controlling the solenoid valve unit in order to deliver a predetermined amount of oil to the cylinders depending upon the engine&#39;s running condition. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    In the following description, reference is made to the accompanying drawings, which form a part of this written description of the invention, and which show, by way of illustration, specific embodiments in which the invention can be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Where possible, the same reference numbers will be used throughout the drawings to refer to the same or like components. Numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one skilled in the art that the present invention may be practiced without the specific details or with certain alternative equivalent devices and methods to those described herein. In other instances, well-known methods, procedures, components, and devices have not been described in detail so as not to unnecessarily obscure aspects of the present invention.  
         [0031]    In FIG. 1, Section A, an outboard motor constructed and operated in accordance with a preferred embodiment of the invention is depicted in side elevational view and is identified generally by the reference numeral  100 . The entire outboard motor  100  is not depicted in that the swivel bracket and the clamping bracket, which are associated with the drive shaft housing, indicated generally by the reference numeral  102 , are not illustrated. These components are well known in the art, and thus, the specific method by which the outboard motor  100  is mounted to the transom of an associated watercraft is not necessary to permit those skilled in the art to understand or practice the invention.  
         [0032]    The outboard motor  100  includes a power head, indicated generally by the reference numeral  104 . The power head  104  is positioned above the drive shaft housing  102  and includes a powering internal combustion engine, indicated generally by the reference numeral  106 . The engine  106  is shown in more detail in the remaining three views of FIG. 1 and will be described shortly by reference thereto.  
         [0033]    The power head  104  is completed by a protective cowling formed by a main cowling member  108  and a lower tray  110 . The main cowling member  108  is detachably connected to the lower tray  110 . The lower tray  110  encircles an upper portion of the drive shaft housing  102  and a lower end of the engine  106 .  
         [0034]    Positioned beneath the drive shaft housing  102  is a lower unit  112  in which a propeller  114 , which forms the propulsion device for the associated watercraft, is journaled.  
         [0035]    As is typical with outboard motor practice, the engine  106  is supported in the power head  104  so that its crankshaft  116  (see Section B of FIG. 1) rotates about a vertically extending axis. This is done so as to facilitate connection of the crankshaft  116  to a driveshaft which extends into the lower unit  112  and which drives the propeller  114  through a conventional forward, neutral, reverse transmission contained in the lower unit  112 .  
         [0036]    The details of the construction of the outboard motor and the components which are not illustrated may by considered to be conventional or of any type known to those wishing to utilize the invention disclosed herein. Those skilled in the art can readily refer to any known constructions of such with which to practice the invention.  
         [0037]    With reference now in detail to the construction of the engine  106  still by primary reference to FIG. 1, in the illustrated embodiment, the engine  106  is of the V6 type and operates on a two-stroke, crankcase compression principle. Although the invention is described in conjunction with an engine having this cylinder number and cylinder configuration, it will be readily apparent that the invention can be utilized with engines having other cylinder numbers and other cylinder configurations. Also, although the engine  106  will be described as operating on a two stroke principle, it will also be apparent to those skilled in the art that certain facets of the invention can be employed in conjunction with four-stroke engines. Some features of the invention also can be employed with rotary type engines.  
         [0038]    Now, referring primarily to Sections B and D of FIG. 1, the engine  106  comprises a cylinder block  118  that is formed with a pair of cylinder banks  120 . Each of these cylinder banks  120  comprises three vertically spaced, horizontally extending cylinders or cylinder bores  122 A-F. Pistons  124  reciprocate in these cylinder bores  122 A-F. The pistons  124  are, in turn, connected to the upper or small ends of connecting rods  126 . The big ends of these connecting rods are journaled on the throws of the crankshaft  116  in a manner that is well known in this art.  
         [0039]    The crankshaft  116  is journaled in a suitable manner for rotation within a crankcase chamber  128  that is formed in part by a crankcase member  130 . The crankcase member  130  is affixed to the cylinder block  118  in a suitable manner. As is typical with two-cycle engines, the crankshaft  116  and crankcase chamber  128  are formed with seals so that each section of the crankcase, which is associated with one of the cylinder bores  122 A-F, is sealed from the other sections. This type of construction is well known in the art.  
         [0040]    With reference to FIG. 2, a cylinder head assembly, indicated generally by the reference numeral  202 , is affixed to an end of each cylinder bank  120  that is spaced from the crankcase chamber  128 . These cylinder head assemblies  202  comprise a main cylinder head member  204  that defines a plurality of recesses  206  in its lower face. Each of these recesses  206  cooperate with a respective cylinder bore  122  and the head of the piston  124  to define the combustion chambers of the engine, as is well known in the art. A cylinder head cover member  208  completes the cylinder head assembly  202 . The cylinder head members  204 ,  208  are affixed to each other and to the respective cylinder banks  120  in a suitable, known manner.  
         [0041]    With reference again primarily to FIG. 1, Sections B and C, an air induction system, indicated generally by the reference numeral  132  is provided for delivering an air charge to the sections of the crankcase chamber  128  associated with each of the cylinder bores  122 A-F. This communication is via an intake port  134  formed in the crankcase member  130  and registering with each such crankcase chamber section.  
         [0042]    The induction system  132  includes an air silencing and inlet device, shown schematically in this figure and indicated by the reference numeral  136 . In actual physical location, this device  136  is contained within the cowling  108  at the forward end thereof and has a rearwardly facing air inlet opening  138  through which air is drawn. Air is admitted into the interior of the cowling  108  in a known manner, and this is primarily through a pair of rearwardly positioned air inlets that have a construction that is generally well known in the art.  
         [0043]    The air inlet device  136  supplies the induced air to a plurality of throttle bodies  140 , each of which has a throttle valve  142  provided therein. These throttle valves  142  are supported on throttle valve shafts. These throttle valve shafts are linked to each other for simultaneous opening and closing of the throttle valves  142  in a manner that is well known in this art.  
         [0044]    As is also typical in two-cycle engine practice, the intake ports  134  have, provided in them, reed-type check valves  144 . These check valves  144  permit the air to flow into the sections of the crankcase chamber  128  when the pistons  124  are moving upwardly in their respective cylinder bores. However, as the pistons  124  move downwardly, the charge will be compressed in the sections of the crankcase chamber  128 . At that time, the reed type check valve  144  will close so as to permit the charge to be compressed.  
         [0045]    In accordance with a preferred embodiment of the present invention, an oil pump  146  pumps oil to a solenoid valve unit  150 . In the preferred embodiment, the oil pump  146  is driven by the crankshaft  116 ; however, an electric oil pump can be used in the alternative. The solenoid valve unit  150  regulates the delivery of oil to the throttle body  140  of each cylinder  122 . The oil passes through the throttle body  140  and into the crankcase chamber  128  to lubricate the components of each cylinder  122 . An ECU (Electronic Control Unit)  148  sends control signals through a number of drive signal lines  149  to the solenoid valve unit  150  to regulate the timing of oil delivery to each cylinder  122 . The oil delivery system will be described in greater detail below.  
         [0046]    The charge which is compressed in the sections of the crankcase chamber  128  is then transferred to the combustion chamber through a scavenging system (not shown) in a manner that is well known. A spark plug  152  is mounted in the cylinder head assembly  202  for each cylinder bore. The spark plug  152  is fired under the control of the ECU  148 . The ECU  148  receives certain signals for controlling the time of firing of the spark plugs  152  in accordance with any desired control strategy.  
         [0047]    The spark plug  152  ignites a fuel air charge that is formed by mixing fuel directly with the intake air via a fuel injector  154 . The fuel injectors  154  are solenoid type injectors and electrically operated.  
         [0048]    The ECU  148  controls the timing and the duration of fuel injection. The ECU  148  thus controls the opening and closing of the solenoid valves of the fuel injectors  154 , and in particular, controls the selective supply of current to the solenoids of the fuel injectors  154 .  
         [0049]    With reference to Sections C and D of FIG. 1, fuel is supplied to the fuel injectors  154  by a fuel supply system, indicated generally by the reference numeral  156 . The fuel supply system  156  comprises a main fuel supply tank  158  that is provided in the hull  159  of the watercraft with which the outboard motor  100  is associated. Fuel is drawn from this tank  158  through a conduit  160  by a first low pressure pump  162  and a plurality of second low pressure pumps  164 . The first low pressure pump  162  is a manually operated pump and the second low pressure pumps  164  are diaphragm type pumps operated by variations in pressure in the sections of the crankcase chamber  128 , and thus provide a relatively low pressure. A quick disconnect coupling is provided in the conduit  160  and a fuel filter  166  is positioned in the conduit  160  at an appropriate location.  
         [0050]    From the low pressure pump  164 , fuel is supplied to a vapor separator  168  which is mounted on the engine  106  or within the cowling  108  at an appropriate location. This fuel is supplied through a line  169 , and a float valve regulates fuel flow through the line  169 . The float valve is operated by a float that disposed within the vapor separator  168  so as to maintain a generally constant level of fuel in the vapor separator  168 .  
         [0051]    A high pressure electric fuel pump  170  is provided in the vapor separator  168  and pressurizes fuel that is delivered through a fuel supply line  171  to a high pressure fuel pump, indicated generally by the reference numeral  172 . The electric fuel pump  170 , which is driven by an electric motor, develops a pressure such as 3 to 10 kg/cm 2 . A low pressure regulator  170   a  is positioned in the line  171  at the vapor separator  168  and limits the pressure that is delivered to the high pressure fuel pump  172  by dumping the fuel back to the vapor separator  168 .  
         [0052]    With reference to Section D of FIG. 1, fuel is supplied from the high pressure fuel pump  172  to a pair of vertically extending fuel rails  173  through a flexible pipe  173   a . The pressure in the high pressure delivery system  172  is regulated by a high pressure regulator  174  which dumps fuel back to the vapor separator  168  through a pressure relief line  175  in which a fuel heat exchanger or cooler  176  is provided.  
         [0053]    After the fuel charge has been formed in the combustion chamber by the injection of fuel from the fuel injectors  154 , the charge is fired by firing the spark plugs  152 . The injection timing and duration, as well as the control for the timing of firing of the spark plugs  152 , are controlled by the ECU  148 .  
         [0054]    Once the charge burns and expands, the pistons  124  will be driven toward the crankcase in the cylinder bores until the pistons  124  reach the lowermost position (i.e., Bottom Dead Center). Through this movement, an exhaust port (not shown) is opened to communicate with an exhaust passage  177  (see the lower left-hand view) formed in the cylinder block  118 .  
         [0055]    The exhaust gases flow through the exhaust passages  177  to collector sections of respective exhaust manifolds that are formed within the cylinder block  118 . These exhaust manifold collector sections communicate with exhaust passages formed in an exhaust guide plate on which the engine  106  is mounted.  
         [0056]    A pair of exhaust pipes  178  extend the exhaust passages  177  into an expansion chamber  179  formed in the drive shaft housing  102 . From this expansion chamber  179 , the exhaust gases are discharged to the atmosphere through a suitable exhaust system. As is well known in outboard motor practice, this may include an underwater, high speed exhaust gas discharge and an above the water, low speed exhaust gas discharge. Since these types of systems are well known in the art, a further description of them is not believed to be necessary to permit those skilled in the art to practice the invention.  
         [0057]    Any type of desired control strategy can be employed for controlling the time and duration of fuel injection from the injector  154  and timing of firing of the spark plug  152 ; however, a general discussion of some engine conditions that can be sensed and some other ambient conditions that can be sensed for engine control will follow. It is to be understood, however, that those skilled in the art will readily understand how various control strategies can be employed in conjunction with the components of the invention.  
         [0058]    The control for the fuel air ratio preferably includes a feedback control system. Thus, a combustion condition or oxygen sensor  180  is provided and determines the in-cylinder combustion conditions by sensing the residual amount of oxygen in the combustion products at about a time when the exhaust port is opened. This output signal is carried by a line to the ECU  148 , as schematically illustrated in FIG. 1.  
         [0059]    As seem in Section B of FIG. 1, a crank angle position sensor  181  measures the crank angle and transmits it to the ECU  148 , as schematically indicated. Engine load, as determined by throttle angle of the throttle valve  142 , is sensed by a throttle position sensor  182  which outputs a throttle position or load signal to the ECU  148 .  
         [0060]    There is also provided a pressure sensor  183  communicating with the fuel line connected to the pressure regulator  174 . This pressure sensor  183  outputs the high pressure fuel signal to the ECU  148  (signal line is omitted). There also may be provided a trim angle sensor  184  (see the lower right-hand view) which outputs the trim angle of the motor to the ECU  148 . Further, an intake air temperature sensor  185  (see the upper view) may be provided and this sensor  185  outputs an intake air temperature signal to the ECU  148 . There may also be provided a back-pressure sensor  186  that outputs exhaust back pressure to the ECU  148 .  
         [0061]    The sensed conditions are merely some of those conditions which may be sensed for engine control and it is, of course, practicable to provide other sensors such as, for example, but without limitation, an engine height sensor, a knock sensor, a neutral sensor, a watercraft pitch sensor and an atmospheric temperature sensor in accordance with various control strategies.  
         [0062]    The ECU  148  computes and processes the detection signals of each sensor based on a control map. The ECU  148  forwards control signals to the fuel injector  154 , spark plug  152 , the electromagnetic solenoid valve unit  150 , and the high pressure electric fuel pump  170  for their respective control. These control signals are carried by respective control lines that are indicated schematically in FIG. 1.  
         [0063]    With reference to FIG. 2, a pump drive unit  210  is provided for driving the high pressure fuel pump  172 . The high pressure fuel pump  172  is mounted on the pump drive unit 210 with bolts. The high pressure fuel pump  172  can develop a pressure of, for example, 50 to 100 kg/cm 2  or more.  
         [0064]    The pump drive unit  210  is attached through a stay  211  to the cylinder block  118  with bolts  212 ,  213 . The pump drive unit  210  is further affixed to the cylinder block  118  directly by bolt  214 . The pump drive unit  210  thus overhangs between the two banks  120  of the V-cylinder arrangement. A pulley  215  is affixed to a pump drive shaft  216  of the pump drive unit  210 . The pulley  215  is driven by a drive pulley  217  affixed to the crankshaft  116  by means of a drive belt  218 . The pump drive shaft  216  is provided with a camdisk extending horizontally for pushing plungers which are disposed on the high pressure fuel pump  172 .  
         [0065]    The driving pulley  217  in the pump drive unit  210  of the high pressure fuel pump  172  is mounted on the crankshaft  116 , while the driven pulley  215  is mounted on the pump drive shaft  216  of the pump drive unit  210 . The driving pulley  217  drives the driven pulley  215  by means of the drive belt  218 . A belt tensioner  218   a  maintains tension in the drive belt  218 . The high pressure pump  172  is mounted on either side of the pump drive unit  210  and is driven by the drive unit  210  in a manner described above.  
         [0066]    The stay  211  is affixed to the cylinder block  118  with bolts so as to extend from the cylinder block  118  and between both cylinder banks  120 . The pump drive unit  210  is then partly affixed to the stay  211  with bolts  212 ,  213  and partly directly affixed to a boss of the cylinder block  118  so that the pump drive unit  210  is mounted on the cylinder block  118  as overhanging between the two banks  120  of the V arrangement.  
         [0067]    The high pressure pump  172  is mounted on the pump drive unit  210  with bolts  219  at both side of the pump drive unit  210 . In this regard, a diameter of the bolt receiving openings on the pump drive unit  210  is slightly larger than a diameter of the bolts  219 . Thus, the mounting condition of the high pressure pump  172  on the pump drive unit  210  is adjustable within a gap made between the opening and the bolt  219 . The respective high pressure pump  172  has a unified fuel inlet and outlet module  220  which is mounted on a side wall of the pressure pump  172 . A flexible pipe  221  delivers fuel from the unified fuel inlet and outlet module  220  to the fuel rails  173 . The flexible pipe is connected at each end by connectors  222 .  
         [0068]    In order to start the motor  100 , a starter motor  223  engages with and rotates a flywheel  224  that is connected to the crankshaft  116 .  
         [0069]    The key components of the oil injection system of the present invention will now be described, first with reference to FIG. 1. As best viewed in Section C of FIG. 1, an oil sub tank  187  located in the hull of the watercraft serves as a reservoir of lubrication oil for the engine  106 . A suitable delivery pump supplies oil from the oil sub tank  187  through an oil supply pipe  187   a  to a main oil tank  188  mounted to the side of the cylinder block  118 . The delivery pump can, for example, be located within the oil sub tank  187  or can be positioned within the supply pipe  187   a , and can be either electrically or mechanically driven. An oil feed pipe  189  supplies oil from the bottom of the main oil tank  188  to the oil pump  146 . The oil pump  146  in turn supplies oil to the solenoid valve unit  150 , which regulates the flow of oil to the cylinders  122 A-F. The solenoid valve unit  150  is preferably controlled via control signals from the ECU  148 . As best viewed in Section A of FIG. 1, an oil level sensor  191  relays the level of oil in the main oil tank  188  to the ECU  148 .  
         [0070]    In the preferred embodiment, the solenoid valve unit  150  also regulates the flow of oil to the vapor separator tank  168  through an oil supply pipe  190  for mixture with fuel. The addition of a small amount of oil to the fuel of a fuel injected engine has been found to inhibit the formation of deposits on fuel injectors and to extend their useful life. The addition of oil may also help prevent corrosion when water is present in the system. The oil delivered directly to the combustion chamber with the fuel charge may also help to lubricate the components of the fuel system.  
         [0071]    The main oil tank  188  is mounted to one side of the cylinder block  118 . The main oil tank  188  has elevated portions  188   a ,  188   b  that are separated by a recess  188   c  in the tank  188 . The elevated portions  188   a ,  188   b  are designed to provide increased volume in the tank. The inner elevated portion  188   a  is designed to fit below the flywheel  224 . The outer elevated portion  188   b  is located adjacent the flywheel  224  and extends above the level of the flywheel  224 . The recess  188   c  is configured to allow a number of pipes, conduits, and wires to pass over the recess  188   c  of the tank but under the flywheel  224 . These pipes, conduits, and wires comprise an overflow pipe  225 , the pressure relief line  175 , the fuel supply line  171 , a portion of a wiring harness  226 , and an oil mist outlet hose  227 . The oil mist outlet hose  227  directs oil vapor from the main oil tank  188  to the air inlet device  136 . A bracket  228  holds the pipes, conduits and wires in place in the recess  188   c.    
         [0072]    As seen in FIG. 3, a filter  302  filters lubricating oil before it passes through an outlet on the bottom of the main oil tank  188  and into the oil feed pipe  189 . The oil feed pipe  189  delivers the oil to the oil pump  146 . The oil pump  146  supplies oil through a number of oil delivery pipes  304  to the solenoid valve unit  150 . The number of oil delivery pipes  304  preferably corresponds to the number of cylinders  122  in the engine  106 . Alternatively, fewer oil delivery pipes  304  (e.g., one) can be used with an inlet manifold that feed the individual parts of the valve unit  150 . A number of oil supply pipes  306  supply oil from the solenoid valve unit  150  to each cylinder  122  through the air induction system  132 . The number of oil supply pipes  306  preferably corresponds to the number of cylinders  122  in the engine  106 . The oil supply pipes  306  are preferably configured so that their lengths are as short as possible to minimize the distance the oil must travel to the air induction system  132  for each cylinder  122 . The solenoid valve unit  150  also delivers an amount of oil to the vapor separator tank  168  through the oil supply pipe  190  preferably for mixture with fuel. Any unused oil not delivered to the cylinders  122  or the vapor separator tank  168  is returned to the main oil tank  188  via an oil return pipe  308 .  
         [0073]    In the preferred embodiment, the oil pump  146  is a positive displacement type oil pump that is driven by the crankshaft  116 . A positive displacement type oil pump delivers a volume of oil for each crankshaft revolution as opposed to, for example, an impeller type pump that supplies an approximate pressure of oil based upon engine speed. The oil pump  146  preferably also has an adjustment lever  310  that is configured to adjust the discharge rate per crankshaft revolution of the oil pump  146 . The adjustment lever  310  is preferably interconnected with the throttle to vary the discharge rate in relation to the throttle level.  
         [0074]    In the preferred embodiment, the adjustment lever  310  allows the oil pump  146  to deliver slightly more than the required amount of oil. The oil delivery is then fine tuned appropriately for each cylinder by the ECU  148  through the solenoid valve unit  150 . Typical positive displacement pumps deliver a constant volume of oil per crankshaft revolution, regardless of engine speed or throttle position. The oil required per crankshaft revolution, however, is typically lower at slower engine speeds (i.e., at lesser open throttle positions) and higher at higher engine speeds (i.e., at more open throttle positions). Accordingly, the oil delivery rate of a typical positive displacement type pump would have to be reduced by a greater proportion at lower engine speeds in order to supply the appropriate amount of oil. The adjustment lever  310  of the preferred embodiment, however, allows the oil pump  146  to deliver proportionally more oil per revolution as the throttle position is opened. Increased engine speeds are associated with increased throttle positions, and in this manner the amount of oil to be delivered per revolution can be increased in relation to engine speed. The adjustment lever  310 , by allowing the oil pump to supply reduced amount of oil per revolution at lower engine speeds, allows the solenoid valve unit  150  to appropriately regulate, through fine tuning, an oil supply that is already approximate the correct amount.  
         [0075]    As illustrated in FIGS.  4 A-B, the main oil tank  188  comprises a hollow tank body  400  for containing oil. The oil supply pipe  187   a  supplies oil to the main oil tank  188  through the inlet  402 . The oil mist outlet  404  provides an outlet for oil vapor, mist, and overflow through oil mist outlet hose  227 . The oil level sensor  191  is shown at the top of the main oil tank  188  in FIG. 4A. The elevated portions  188   a ,  188   b  and the recess  188   c  of the main oil tank  188  are clearly shown in FIGS.  4 A-B.  
         [0076]    The tank  188  is mounted to the cylinder block  118  by a number of stays  406 . FIG. 4B shows the bracket  228 , which holds the overflow pipe  225 , the pressure relief line  175 , the fuel supply line  171 , the portion of a wiring harness  226 , and the oil mist outlet hose  227  in place in a region indicated by P. The bracket has a side portion  228   a  and a top portion  228   b . The bracket  228  is held in place relative to the tank  188  by a bolt  407  that secures the tank  188  and bracket  228  through a stay  406 . FIGS.  4 B-C depict an outlet  408  that supplies oil to the oil pump  146  through the oil feed pipe  189  to which the outlet  408  is connected. Any unused oil returning from the solenoid valve unit  150  through the oil return pipe  308  enters through the return port  410  to which the oil return pipe  308  is connected.  
         [0077]    FIGS.  4 C-D illustrate the orientation of the main oil tank  188  as the motor  100  is tilted from a drive position in FIG. 4C to a raised position in FIG. 4D. Arrows indicate the directions towards the front and rear of a watercraft upon which the motor  100  is preferably mounted. As the motor  100  is tilted, the oil tank  188  tilts through an angle towards the front of the watercraft. The maximum oil level in the tank  188  is indicated by the line M. In one embodiment, the maximum oil level is maintained by the ECU  148  by turning on a pump in the sub tank  187  in response to a low reading from the oil level sensor  191 . The main oil tank  188  is configured such that the inlet  402  and mist outlet  404  remain above the maximum oil level M between the tilted and raised positions. In this manner, spillage of oil from the tank  188  into the air inlet device  136  and backflow or siphoning of oil into the oil sub tank  187  is avoided.  
         [0078]    [0078]FIG. 5 illustrates a cross section view of a preferred embodiment of the solenoid valve unit  150  viewed from the same perspective as FIG. 3. In the preferred embodiment, the solenoid valve unit  150 , as driven by the ECU  148 , appropriately fine tunes for each cylinder based upon engine conditions, an approximately correct amount of oil supplied by the oil pump  146 . The body  502  of the valve unit  150  houses a number of oil passages and valves for regulating the flow of oil to the cylinders  122  and to the vapor separator tank  168 . A number of oil inlet ports  504  located on the exterior of the body  502  are connected to the oil delivery pipes  304 . The oil delivery pipes  304  deliver oil from the oil pump  146  to the solenoid valve unit  150 . Oil passes through the oil inlet ports  504  and through a filter  506  associated with each oil inlet port  504 . From each filter  506 , oil flows through an inlet passage  507  within the body  502  to one of a number of solenoid valves indicated generally by the number  508 . Each solenoid valve  508  comprises a control valve  509 , which is actuated through a magnetic field generated by a coil  510 . The current in each coil  510  is regulated by a driving circuit  512  preferably containing a switching transistor. The switching transistors of the driving circuits  512  are in turn connected to the drive signal lines  149  that carry control signals from the ECU  148 . In this manner, the ECU can control the actuation of each solenoid valve  508 .  
         [0079]    In the preferred embodiment, each solenoid valve  508  is configured to switch the passage of oil to either a supply port  516  or an oil return port  518 . When the solenoid is off, or in other words when the coil  510  is not carrying a current, the solenoid valve  508  is “open” and allows oil to pass through a supply passage  517  to its associated supply port  516 . The supply ports  516  are connected to the oil supply pipes  306  in order to supply oil to the cylinders  122 . When the solenoid is on or carrying a current, the solenoid valve  508  is “closed” and directs the passage of oil through a return passage  519  to a junction with a common oil return port  520 . A check valve  518  is installed in-line in the return passage  519  between the solenoid valve  508  and the junction with the common oil return port  520  to prevent backflow of oil through the passage  519 . The oil return port  520  is connected to the oil return pipe  308  to return excess oil to the main oil tank  188 .  
         [0080]    An additional supply passage  521  branches off from of one of the return passages  519  to supply an amount of oil to an additional oil supply port  522 . The additional oil supply port  522  is connected to the oil supply pipe  190 , which delivers the oil to the vapor separator tank  168  for mixture with fuel. Two adjustment orifices  524  are provided to regulate the proportion of oil that is directed to the oil supply port  522  as opposed to the common oil return port  520 . One adjustment orifice  524  is positioned in the additional supply passage  521 . The other adjustment orifice  524  is positioned in the corresponding return passage  519  between the branch and the junction with the common oil return port  520 . The adjustment orifices  524  can be selected so that an appropriate amount of oil is delivered to the fuel injection system to inhibit deposit buildup on the fuel injectors, rust, and/or corrosion. In another variation, the additional supply passage  521  can be configured to branch off after the junction between the return passages  519  and the common oil return port  520 .  
         [0081]    The driving circuits  512 , solenoid valves  508 , ECU  148 , and control lines  149  are preferably configured such that an active control signal from the ECU  148  and an active power supply to the solenoid valve unit  150  are required to redirect the oil flow away from the supply ports  516  that supply lubricant to the cylinders  122 . This configuration serves as a safety feature in that if one or more of the signals from the ECU  148  are prevented from reaching the solenoid valve unit  148 , oil is still supplied to the cylinders  122 . Furthermore, if power to the solenoid valve unit  148  is disrupted, oil will also still be supplied to the cylinders  122 .  
         [0082]    In the preferred embodiment, the solenoid valve unit  150  draws power through the solenoid coils  510  whenever oil is not supplied to the cylinders  122 . At very low engine speeds, less oil needs to be delivered to the cylinders  122 . Instead of limiting oil supply through the solenoid valve unit  150 , which draws power, oil flow is limited through the flow adjustment lever  310  of the oil pump  146  by linking it to the throttle. The oil pump  146  is preferably mechanically controlled to deliver slightly more than the required volume of oil at each engine speed. Accordingly, the solenoid valves  508  need be used less frequently to limit the flow of oil resulting in a lower electrical power consumption.  
         [0083]    FIGS.  6 A-C illustrate an additional embodiment of the solenoid valve unit  150 . FIG. 6A is an elevational view that shows the oil inlet ports  504  entering from the right side of the unit  150 . The unit  150  is secured through a number of mounting brackets  602 . In the illustrated embodiment, each solenoid valve  508  is a removable unit that fits into a matching cavity in the body  502 . Each valve  508  is sealed within the body by a number of seals  604 . An electrical connector  606  supplies power to the coils  510  and conveys the ECU control signals from the drive signal lines  149  to the solenoid valve unit  150 .  
         [0084]    [0084]FIG. 6B is a top plan view of the solenoid valve unit  150  showing two banks of solenoid valves  508 . A stopper plate  608 , which is fastened to the body  502  by two bolts  610 , secures each of the valves  508  in place within the body  502  of the unit  150 . A rubber damper  612 , through which the solenoid valve unit  150  is mounted via its mounting brackets  602 , helps insulate the unit  150  from vibration. FIG. 6C illustrates a view of the solenoid valve unit along a direction W as indicated in FIG. 6B.  
         [0085]    [0085]FIG. 7 is a graph of the relationship between engine speed and desired or required oil supply volume for various cylinders of the disclosed engine in an exemplary embodiment. The plot with square points indicates the required oil supply to the upper cylinders  122 A and  122 D. The plot with circular points indicates the required oil supply to the middle cylinders  122 B and  122 E. The plot with triangular points indicates the required oil supply to the lower cylinders  122 C and  122 F. At lower engine speeds, the required oil volume for each cylinder is substantially the same. At intermediate speeds, the upper cylinders require more oil than the lower oil cylinders. At higher engine speeds, the lower cylinders require more oil than the upper cylinders.  
         [0086]    In two-cycle engines in general, different cylinders intake varying amounts of air per combustion cycle as engine speed varies. These varying amounts of inducted air are a result of different tuning frequencies for the exhaust passages of different cylinders. In order to maintain a constant mixture ratio of air to oil in the intake system, the amount of oil supplied per combustion cycle can be varied in relation to the amount of air introduced during each cycle.  
         [0087]    In the preferred embodiment, the oil pump  146  supplies slightly more than a maximum required amount of oil for any cylinder under a given operating condition. That is, for example with reference to FIG. 7, the oil pump  146  supplies slightly more than 230 cc/hr to each cylinder when running at 3000 rpm. The ECU  148  then uses a control map, such as those embodied in the timing diagrams to be discussed below, to fine tune, through the solenoid valve unit  150 , the amount of oil actually delivered to each cylinder  122 A-F.  
         [0088]    FIGS.  8 A-H show eight exemplary timing diagrams for controlling the solenoid valve unit  150  in order to deliver an appropriate amount of oil to the cylinders  122 . Representations of these timing diagrams are preferably integrated into the control map and stored into a memory of the control system with which the ECU  148  communicates. The ECU  148  controls the operation of the individual valves of the solenoid valve unit  150  based upon the stored control maps.  
         [0089]    At the top of each timing diagram is a reference signal that has pulses at 60 crankshaft rotation increments. These timing signals can be produced by the crankshaft sensor  181  reading marks placed at 60° intervals about the flywheel  224 . The timing lines are numbered  1  through  6  and correspond to the opening of the solenoid valves  508  that regulate oil delivery to the air induction systems  132  associated with the cylinders as follows: lines  1  and  2  correspond to the top two cylinders  122 A and  122 D, lines  3  and  4  correspond to the middle two cylinders  122 B and  122 E, and lines  5  and  6  correspond to the bottom two cylinders  122 C and  122 F. The timing lines indicate an open solenoid valve sending oil to the cylinder when high, and indicate a closed solenoid valve redirecting oil to the main oil tank  188  when low. The timing lines are also illustrative of the control signals that would be produced by the ECU  148  and passed through the drive signal lines  149  to the solenoid valve unit  150 . In this regard, however, a low timing line is indicative of an active signal and a high timing line is indicative of an inactive signal. This is the case since an active signal from the ECU  148  to the solenoid valve  508  cuts off oil flow to the cylinder  122  in the preferred embodiment. Other configurations could, however, be used to suit other applications.  
         [0090]    [0090]FIG. 8A illustrates a timing diagram that is preferably used under conditions of rapid acceleration. The indicating reference TR indicates a resting time for the solenoid valve  508  during which it is not carrying current and is open, supplying oil to the respective cylinder. The indicating references T 1 -T 6  indicate the time periods during which each of the solenoid valves  508  are activated to intermittently switch off oil supply to the respective cylinders  122 . In the preferred embodiment, the time periods during which oil is intermittently switched off commence contemporaneously with the ticks on the reference signal. In this manner, the switching off time periods can be synchronized with the same point in the combustion cycle for each cylinder  122 . Note that the total off time increases gradually from the top cylinder  1  to the bottom cylinder  6 . This delivery scheme is in accordance with the higher oil volume requirements of the top cylinders. During the periods T 1 -T 4  the oil flow is intermittently switched back on three times for the top and middle cylinders. During the periods T 5 -T 6  the oil flow is only switched on twice for the two lower cylinders. Note that the intermittent switching off periods only occur during every second crankshaft revolution as the next off period for cylinder  1  is twelve reference ticks from its first.  
         [0091]    As illustrated in FIG. 8A, the oil supply is switched off for a first duration that is the same for each cylinder. The oil supply is then switched on for a second duration that is the same for each cylinder. Next, the oil supply is again switched off for a third duration that is the same for each cylinder. Next, the oil supply is switched on again for a fourth duration that is the same for each cylinder. Next, for cylinders  1  through  4 , the oil supply is again switched off and on for fifth and sixth durations that are the same for each cylinder. Next, for cylinders  1  through  4 , the oil supply is switched off for a duration that increases gradually from cylinders  1  to  4  in accordance with the lesser oil requirements of the lower cylinders. Finally, for cylinders  1  to  4 , the oil supply is switched on again until the end of the cycle. For cylinders  5  and  6 , after the fourth duration, the oil supply is switched off again for a duration that is less for cylinder  5  and greater for cylinder  6 . Finally, for cylinders  5  and  6 , the oil supply is switched on again until the end of the cycle.  
         [0092]    [0092]FIG. 8B illustrates a second timing diagram in which the periods T 1 -T 6  represent a constant shutoff of oil flow to the respective cylinder during the duration. The diagram is titled “Intermittent Cycle Driving” as the solenoids are only activated on intermittent or alternate crankshaft revolutions. The period of the off time increases gradually from the top cylinder  1  to the bottom cylinder  6  in accordance with the higher oil requirements of the upper cylinders.  
         [0093]    The timing diagram of FIG. 8C is similar to that of FIG. 8B; however, it illustrates a timing scenario that can be used in conjunction with cylinder “resting” periods. As is well known in the art, some engines employ resting periods for certain cylinders during idle or low power situations or during abnormal running conditions (e.g. engine overheating). During a resting period, one or more cylinders of a multiple cylinder engine will not fire on each crankshaft revolution. The revolution during which a cylinder does not fire is known as a resting period. One method by which cylinder resting can be achieved in a fuel injected engine is to suspend injection to selected cylinders. Another method by which cylinder resting can be achieved is through misfiring or adjusting the timing of the firing of the spark plugs for selected cylinders.  
         [0094]    In the timing diagram depicted in FIG. 8C, cylinders  2 ,  3 , and  5  are in resting periods. During a resting period, a cylinder typically requires less oil than during a normal crankshaft revolution. The timing diagram, therefore, depicts an increased duration during which the oil flow to cylinders  2 ,  3 , and  5  is switched off. The difference between the normal on duration, as indicated in phantom, and the “resting” on duration is identified by a small arrow in the timing lines of cylinders  2 ,  3 , and  5 .  
         [0095]    The timing diagram of FIG. 8D is also similar to that of FIG. 8B; however, the solenoid valves  508  shut off the oil flow once during each crankshaft revolution, but for a shorter duration of time. Accordingly the diagram is titled “Every Cycle Driving” to indicate that the solenoid valves are driven every crankshaft revolution. As in the timing diagram of FIG. 8B, the off period is greater for the lower cylinders.  
         [0096]    [0096]FIG. 8E illustrates a timing diagram titled “Driving for Predetermined Time 1” in which the shutoff periods are not necessarily synchronized with the turning of the crankshaft or a reference signal. In this timing diagram each cylinder has a respective off period, T 1 -T 6 , which is greater for the lower cylinders. The on period, TR, however, is the same for each cylinder. Accordingly, the on-off cycle time for the lower cylinders is greater than that of the upper cylinders. One method by which this timing scenario could be implemented involves the use of timers that are alternately reset to count down an off period (one of T 1 -T 6 ) and the on period (TR). The on-off cycle time for certain cylinders in this case will likely not correspond to a whole number of crankshaft revolutions. In an additional embodiment, the on period could also be varied for the various cylinders.  
         [0097]    [0097]FIG. 8F illustrates a timing diagram titled “Driving for Predetermined Time 2” in which, like the previous diagram, the shutoff periods are not necessarily synchronized with the reference signal. Unlike the previous diagram, however, the cycle periods are the same for all cylinders. The sum of the off duration, T 1 -T 6 , and the on duration TR 1 -TR 6 , therefore, is the same for each cylinder. The upper cylinders have a shutoff duration that occupies a lesser portion of the period than the lower cylinders. Accordingly, more oil is delivered to the upper cylinders. In this timing diagram, the shutoff period also begins substantially at the same time for each cylinder. Therefore, the shutoff period may occupy a different portion of the two stroke cycle for each cylinder. One method by which this timing scenario could be implemented involves the use of timers that are alternately reset to count down an off period (one of T 1 -T 6 ) and an on period (one of TR 1 -TR 6 ).  
         [0098]    [0098]FIG. 8G illustrates a timing diagram that is similar to FIG. 8F; however, the beginning of the shutoff duration is synchronized with the reference signal. The shutoff duration is also longer and occurs less frequently. Accordingly the diagram is titled “Intermittent Cycle Driving.” This timing diagram is an alternative to that of FIG. 8F that delivers approximately the same amount of oil using less frequent shutoff periods.  
         [0099]    [0099]FIG. 8H illustrates a timing diagram that is similar to FIG. 8B; however, the off periods are adjusted to provide an increased amount of oil under conditions of rapid acceleration. The normal periods of oil supply are indicated by phantom lines, while the increased oil supply under rapid acceleration is indicated by solid lines. An arrow also indicates the added duration of oil supply for each cylinder.  
         [0100]    While certain exemplary preferred embodiments, and variations thereof, have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention. Further, it is to be understood that this invention shall not be limited to the specific construction and arrangements shown and described since various modifications or changes may occur to those of ordinary skill in the art without departing from the spirit and scope of the invention as claimed. For instance, the present lubrication injection and control system can be used with two-cycle engines employed in applications other than outboard motors, as well as with engines operating on other than a two-cycle combustion principle. It is intended that the scope of the invention be limited not by this detailed description but by the claims appended hereto.