Abstract:
A four-cycle, fuel lubricated, internal combustion engine system suited for a vehicle includes a fuel tank containing fuel at a remote location from the engine, a first fluid path for transporting fuel to the lubrication system of the engine, and a second fluid path for transporting fuel to said combustion system of the engine. In this way, the engine&#39;s fuel serves as the lubricant and the combustive agent.

Description:
This is a continuation of application Ser. No. 08/810,244, filed on Mar. 3, 1997, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a four-cycle, internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     In a conventional four-cycle internal combustion engine, the fuel and lubricating systems are maintained completely separate. Despite wide use, this division in the modern engine entails a number of shortcomings. For example, the oil is relied upon to not only reduce friction and wear, but also to serve as a coolant, an oxidation and corrosion inhibitor, and a transport fluid that removes wear metal particles and blow-by products (e.g., carbon, sludge, varnish, unburned fuel, and other combustion products) for subsequent filtration. Due to these requirements on the oil, the engine oil additives become depleted and the important characteristics of the lubricant are degraded. As a result, the oil over time will tend to experience an increase in viscosity and an accumulation of abrasive particles and oxides which, in turn, leads to the corrosion of engine components and increased wear. Moreover, replacement of the oil creates an added expense and a disposal problem with regard to the used oil. Finally, vehicles which are old or poorly maintained can experience considerable burning of the oil which leads to tailpipe emission problems. 
     A few engine systems have mixed oil and fuel together to facilitate oil replacement while the engine is in use. For instance, U.S. Pat. Nos. 5,431,138, 4,421,078, 4,869,346 and 4,495,909 disclose systems which pump a quantity of used oil into a fuel return line as the engine operates. Fresh oil in predetermined batches is also fed into the lubricating system to offset the oil which is removed. However, the maintenance of two fluid systems is still required. Moreover, as discussed above, the burning of oil creates undesirable pollution problems. 
     U.S. Pat. Nos. 4,572,120 and 4,615,305 to Matsumoto each discloses an outboard motor provided with a lubricant delivery tank mounted on the motor, and a storage tank which is mounted in the hull and fluidly coupled to the delivery tank. A pump feeds the lubricant in the delivery tank into the intake manifold of the motor. However, the outboard motor is a two-cycle engine, rather than a four-cycle engine. Moreover, this system requires the maintenance of separate oil and fuel systems and involves the burning of oil in the motor. 
     Other two-cycle, internal combustion engines have been produced which use an oil-fuel mixture for both lubrication and powering of the motor. However, these two-cycle engines are much different than modern four-cycle, internal combustion engines. For instance, these engines lack valves, rely upon oil-rich mixtures, and are very dirty engines which are not suitable for the high pollution standards now in existence for vehicles and other large engine applications. 
     Also, fuel lubrication is known to have advantages for an internal combustion engine, especially a diesel fuel engine. As a result, most diesel fuels have high lubricity, or contain lubrous additives, to ensure that the fuel injector pump and fuel injectors are adequately lubricated during normal operation. However, no four-cycle, internal combustion engine has been used in which the fuel serves as the lubricant for the engine. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide a four-cycle, internal combustion engine in which the engine&#39;s fuel serves as the lubricant and the combustive agent. 
     A further object of the present invention is to provide a fuel lubricated, four-cycle, internal combustion engine which has a system for maintaining a desired quantity of clean lubricant (fuel) in the lubrication system. 
     These as well as other objects are accomplished by an engine system which comprises a fuel tank containing fuel at a remote location from the engine, a first fuel path to convey fuel to the lubricating system of the engine, and a second fuel path to convey fuel to the engine for combustion. In one preferred construction, the fuel is first directed into the lubricating system for lubricating the engine, and then to the combustion system for powering the engine. 
     In an alternative construction, the fuel tank is fluidly coupled to provide fresh fuel to both the lubricating system and the combustion system. A fuel return line is also provided to transport fuel used in the lubricating system to the fuel supply line for powering the engine with a mixture of fresh fuel and fuel used as a lubricant. 
     By using a single fluid to power and lubricate an engine, the expense of maintaining two separate systems is eliminated. Since the lubricating fluid is constantly removed and replaced with fresh fuel, oil changing and disposal problems are eliminated. The constant exchange of fuel in the lubricating system also keeps contaminants in the lubricant to a low level which permits the elimination of an oil filter. Moreover, in view of the constant turn over of lubricant in the lubricating system and the low level of contaminants, the lubricant is not subject to undue degradation. Finally, the undesired exhaust produced from burning oil is completely obviated in the present system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of an engine system of a preferred embodiment of the present invention. 
     FIGS. 2 and 3 are alternative embodiments of an engine system. 
     FIGS. 4 and 5 are schematic views of alternate fuel delivery systems. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention pertains to a four-cycle, internal combustion engine that is lubricated by the fuel. The inventive system is best suited for a diesel engine, but could also be used in gasoline or alternative fuel (e.g., natural gas, biodiesel, etc.) powered, four-cycle, internal combustion engines. 
     In the preferred embodiment, the present engine system  10  (FIG. 1) includes a fuel tank  12  which contains fuel at a location that is remote from a four-cycle, internal combustion, diesel engine  14 . A diesel fuel, such as JP-8 (a fuel commonly used in military vehicles) or a fuel of similar lubricity can be used in an engine manufactured in accordance with the present invention. It is believed that a fuel having a viscosity in the range of about 1.5 to 4.5 centistokes would be suitable for use in the present invention. However, any fuel for an internal combustion engine which has sufficient lubricity to enable its use in the lubrication system of a four-cycle, internal combustion engine could be used in the present system. 
     In a preferred construction, a first fuel line  16  fluidly connects fuel tank  12  to the lubrication system  18  of engine  14 . Fuel line  16  is preferably coupled to an inlet port  20  formed in the lubricant pan  22 . Lubricant pan  22  defines a reservoir of the fuel to be used in lubricating the engine. Fuel pump  24  is installed along fuel line  16  to pump the fuel from tank  12  to pan  22 . A conventional lubrication pump (not shown) would be used to convey the fuel through the lubrication system. 
     A second fuel line  26  couples the lubrication system  18  to the combustion system  27  of engine  14  in order to transport fuel, for example, to a fuel injector  29 . Fuel line  26  draws fuel from pan  22  via outlet port  28 . The turbulence within pan  22  is generally sufficient to amply mix the fuel and prevent channeling whereby the fresh fuel would flow directly from inlet port  20  to outlet port  28 . Nonetheless, fuel line  26  could alternatively be connected to the lubrication system  18  via a port located outside of pan  22 . For instance, line  26  could connect to a port at a location where the conventional oil filter would ordinarily mount. 
     Since fresh fuel is continually circulated into and out of the lubrication system, fouling and degradation of the lubricant (i.e., fuel) is avoided. Moreover, the conventional lubricant filter can be eliminated. Nevertheless, if desired, a filter could still be included in the lubrication system for additional protection. A conventional fuel filter  30  is positioned in line  26  to remove contaminants. Although diesel fuel is normally suitable for direct use as an engine lubricant, a fuel filter in fuel line  37 , downstream of fuel pump  51 , could be used to remove contaminants from the fresh fuel to be used as a lubricant. 
     Pan  22  includes a fluid level sensor (not shown) which senses when the fuel reaches a predetermined lower level. The sensor would be used to not only activate a warning light and/or gauge, but also to close valve  32  in fuel line  26  to prevent the removal of too much fuel from the lubrication system. A float valve (not shown) is also preferably included in pan  22  to regulate the flow of fuel into pan  22  through port  20 . The float valve acts to close port  20  as the volume of fuel in pan  22  reaches a predetermined upper limit, and open the port as the level of fuel drops in the pan. Alternatively, an upper level sensor (not shown), similar to the low level sensor, can be used to sense a predetermined volume of fluid in pan  22  and electrically signal a valve  33  in line  16  to open and close as needed. 
     In accordance with engine system  10 , fuel in tank  12  is pumped through fuel line  16  by pump  24  and transported to pan  22 . Preferably a float valve associated with port  20  regulates the amount of fuel fed into pan  22 . While a one-way valve could be provided in line  16  to prevent reverse flow of the fuel to the tank, the pressure produced by pump  24  is generally sufficient to prevent the flow of fluid out of pan  22  and into fuel line  16 . A pump (not shown) is used to pump the fuel in pan  22  through the lubrication system  18 . A second fuel line  26  is provided to transport fuel from pan  22  to the combustion system  27  of the engine as the sole source of fuel for powering the engine. The pressure in lubricating system  27  is generally suitable for transporting the fuel through line  26  if the line is coupled to the system outside of the pan, such as where the lubrication filter is ordinarily attached. Nevertheless, an additional fuel pump  31  is used to pump the fuel through line  26  when the fuel is drawn from pan  22 . Valve  32  is generally open, unless the fuel in pan  22  reaches the predetermined lower limit. 
     In an alternative engine system  35  (FIG.  2 ), fuel line  37  transports fuel from fuel tank  39  to combustion system  40  of engine  41  to power the engine. A fuel or lubrication line  47  is joined to fuel supply line  37  by T-connector  49  to transport fresh fuel to the lubricant pan  43  in order to provide fuel to the lubrication system  45 . A fuel pump  51  is installed along fuel line  37 , upstream of T-connector  49 , to pump the fuel through both lines  37  and  47 . As an alternative, lubricant line  47  could be fluidly coupled to tank  39  independent of fuel supply line  37 . However, this alternative construction would require an additional pump. 
     A fuel return line  53  is provided to transport fuel from lubrication system  45  to combustion system  40  of engine  41  in order to reuse the lubricating fuel for combustion. Fuel return line  53  is preferably coupled to lubricant pan  43 , although other connections to the lubrication system could be made. More specifically, return line  53  draws fuel from pan  43  via port  55  and transports the fuel to supply line  37  via T-connector  57 . A one-way valve  59  is provided in line  37 , upstream of T-connector  57 , to prevent a reverse flow of the fuel used as a lubricant to fuel tank  39 . Preferably valve  59  is positioned between connectors  49  and  57  to also prevent recycling of the fuel in line  53  back to pan  43 . Sensors and valves for regulating the volume of fuel in the lubricating system  45 , as described above for engine system  10 , would also be applicable to engine system  35 . A fuel filter  61  in fuel line  37 , downstream of T-connector  57 , removes contaminants from the mixture of fresh fuel and the fuel used as a lubricant. A one-way valve (not shown) could optionally be provided in line  53  to prevent reverse flow of the fluid to pan  43 , but is generally unnecessary due to the pressure in line  53 . Pressure in line  53  is provided by a separate fuel pump  58 , or, by the standard lubricant (oil) pump if exit port  55  is at the normal oil filter location. 
     As another alternative (FIG.  3 ), a valve  64  is provided in return line  53   a  to regulate the flow of fuel from the lubricant pan  43   a  to the fuel supply line  37   a.  Valve  64  is opened intermittently based upon signals from a timer in control module  66 . When valve  64  is open, the pressure generated by the lubricating pump (not shown) of the lubrication system  45   a  is sufficient to convey fuel through line  53   a  to mix with the fuel in supply line  37   a.  A valve  68  can also, optionally, be installed in lubrication line  47   a  in place of a float valve. In this arrangement, valve  68  is intermittently opened in response to a regular, periodic signal generated by control module  66 . In this way, valve  68  thereby regulates the flow of fluid from the fuel tank  39   a  to the lubricant pan  43   a . 
     In this alternative, control module  66  generates a regular, periodic signal at preset time intervals during engine operation to regulate the addition and removal of fuel to and from the engine lubrication system. An impulse timer within the control module  66  dictates the frequency at which a signal is generated. Varying frequencies can be selected by changing the position of a dial  70  located on the control module  66 . Accordingly, valves  64  and  68  are intermittently operable in response to this signal during engine operation. The signals to valves  64  and  68  are provided through the electrical connection of the control module  66  with the valves. Specifically, leads  71  and  72  connect module  66  and valves  64 ,  68 . A lead  73  runs from control module  66  to ignition switch  74  and is connected to a lead  72  from valves  64  and  68  at node  75 . Lead  76  connects control module  66  to a constant power source  77 , such as is readily available in a motor vehicle. 
     A low fluid sensor  67  is preferably provided in pan  43   a  to indicate when the fuel in pan has reached a predetermined low level. Sensor  67  is electrically coupled to control module  66  (or control valve  64 ) to override the periodic signal to open valve  64 , and thereby prevents any further removal of fuel from the pan  43   a . The operation of sensor  67  and valve  64  thus prevents emptying of fuel from the lubricating system as fuel in fuel tank  39   a  runs low. A second sensor  69  can also be provided in pan  43   a  to sense when the fuel reaches a predetermined upper limit. The activation of sensor  69  overrides control module  66  (or control valve  68 ) and prevents valve  68  from being opened and admitting additional fuel into pan  43   a . Sensors  67 ,  69  are electrically, by leads  78 - 81 , coupled to valves  64 ,  68  and control module  66 . 
     The present invention may also be used in conjunction with other known engine systems. For example, a lubrication line  108  and return line  109  may be interconnected via connectors  114 ,  117  to a fuel supply line  107  in engine system  100  (FIG.  4 ). Engine system  100  includes a fuel tank  105 , a fuel pump  138  and a fuel filter  139  located along line  107 , and a fuel injection pump  150  located in the engine (not shown). A fuel return  152  extends from the fuel injector pump  150  to the fuel tank  105 . An injection line  154  also extends from the injection pump  150  to an injection nozzle  156 . As with the earlier systems, connectors  114 ,  117  are located between the fuel pump and the fuel filter. While a one-way valve  110  is preferably still provided between connectors  114 ,  117 , it is not necessary. In this embodiment, fuel return line  152  permits fuel used as a lubricant to return to fuel tank  105 . 
     As a second example, the use of lubrication line  178  and return line  179  can be used with engine system  175  (FIG.  5 ). In this system, fuel supply line  177  extends between fuel tank  176  and injector pump  180 . An electric solenoid pump  182  and a filter water separator/coalescer  184  are provided along fuel line  177 . Connectors  186 ,  188  are provided downstream of pump  182  to couple lubrication and return lines  178 ,  179  to fuel supply line  177 . One-way valve  190  is preferably provided between connectors  186  and  188  to prevent reverse flow of the fuel used as a lubricant to the fuel tank or to the lubrication system. 
     As the above description is merely exemplary in nature, being merely illustrative of the invention, many variations will become apparent to those of skill in the art. Such variations, however, are included within the spirit and scope of this invention as defined by the following appended claims.