Patent Publication Number: US-6701900-B1

Title: Quick priming fuel system and common passageway housing for same

Description:
RELATION TO OTHER PATENT APPLICATION 
     This is a continuation of application Ser. No. 10/335,594 filed Dec. 31, 2002 with the same title, now abandoned. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to fuel systems for internal combustion engines, and more particularly to fuel systems with features to encourage quick priming. 
     BACKGROUND 
     In one class of fuel systems, most or all of the fuel system needs to be primed before fuel injectors will operate properly to start an engine. The difficulty and time consumed in priming a fuel system can sometimes be harmful to the fuel system and/or engine components, and is usually annoying to an operator. Long priming times can sometimes create new situations in which damage can occur. For instance, when a fuel filter is changed, there are sometimes attempts to refill the filter before attaching the filter canister to its head assembly. Maintaining the filter canister full of fuel during attachment to a head assembly is difficult and may result in debris entering the filter opening. In addition, the new filter is sometimes filled with the contents of the old filter, which can also introduce contaminates into the clean side of the filter. This debris can potentially be pushed toward fuel injectors without being filtered. 
     Hand pumps are sometimes provided for priming an engine after servicing, such as after replacement of a fuel filter or fuel injector. Although these pumps can be effective, an operator does not always have the knowledge or the patience to pump a number of strokes necessary to properly prime the engine before attempting to start the same. 
     Diesel engines are typically hard to start if any vapor or air is entrained in the fuel system. After changing a fuel filter, it is typical for an operator to bleed the air out of the system by loosening some fittings (injectors or lines). This is almost always a messy and time consuming process, and often requires manual operation by a skilled mechanic. In many diesel systems, there are several potential parts that could fail and therefore leak air into the system causing hard or no start conditions. Among these might be fuel injector O rings, pressure regulating check valves, bypass check valves, hand priming fuel pumps, transfer fuel pumps, fuel fitting seals, other fittings and seals, etc. Problems associated with air in fuel lines has sometimes been approached in the past by an arguably excessive use of check valves intended to keep fuel in the system, and thereby keep air out. Unfortunately, this approach to the problem can sometimes cause system failure from air leaks. In addition, the system might also be sensitive to the check valve seal wearing out. 
     Over the years, engineers have incorporated various features in fuel systems in order to assist in priming the same. For instance, it is known to include a bypass passage around a pressure regulating valve in the hopes of hastening the time needed to evacuate air or vapor from a fuel system. This bypass passageway typically includes a flow restriction or orifice that allows gas to pass without restriction, but is relatively restrictive to liquid flow. This restriction to liquid flow serves to prevent the bypass passage from undermining system pressure. Another known strategy is to include a bypass passage that circumvents both the fuel injectors and the pressure regulating valve. In this known system, the bypass passageway is fluidly connected on the upstream side of the fuel system between the fuel filter and the fuel injectors and connected on the downstream side between the pressure regulating valve and the fuel tank. The bypass passage includes a hand manipulated valve that is only opened when the engine is off and being primed via a hand priming pump. The manual valve has an intentional leaking feature such that an operator can determine that the system is primed when fuel begins to squirt out of the leakage opening. Upon noticing this, the operator then closes the manual valve and cranks the engine to start in a conventional manner. In still another strategy, a bleed valve is positioned in a bypass passage around a pressure regulating valve. the bleed valve has a relatively low opening pressure threshold. The bypass passage also includes a flow restriction or orifice that passes gas without restriction but passes liquid with restriction, so as not to undermine the system pressure and the functioning of the pressure regulating valve. Although these systems have performed satisfactorily, there remains room for improvement. 
     The present invention is directed to real and/or perceived priming problems in fuel systems. 
     SUMMARY OF THE INVENTION 
     In one aspect, a fuel system includes a supply pump positioned between a fuel tank and at least one fuel injector. A pressure regulating valve is fluidly positioned between the fuel injector and the fuel tank. A first bypass passageway circumvents the fuel injector(s), and a second bypass passageway circumvents the pressure regulating valve. 
     In another aspect, a method of priming a fuel system includes a step of circumventing gas around at least one fuel injector via a first bypass passageway. Circumventing gas around a pressure regulating valve via a second bypass passageway. 
     In still another aspect, a common housing for a fuel system includes an adapter having a supply passage and a return passage disposed there through. A first bypass passageway is disposed in the adapter and fluidly connects the supply passage to the return passage. A second bypass passageway is disposed in the adapter and fluidly connects an upstream portion to a downstream portion of the return passage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a fuel system according to an embodiment of the present invention; 
     FIG. 2 is a partial isometric view of a filter assembly according to another aspect of the present invention; 
     FIG. 3 is an isometric view from a different perspective the filter head assembly of FIG. 2; and 
     FIG. 4 is an isometric view of an adapter for the filter head assembly of FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a fuel system  10  includes a supply pump  16  fluidly positioned between a fuel tank  18  and a plurality of fuel injectors  12 . Fuel system  10  also includes a filter assembly  22  that includes filter(s)  24 , a system pressure regulating valve  26  and an optional priming pump  28 . Fuel system  10  also includes an electronic control module  20  that can control various aspects of the fuel system in a conventional manner, such as by controlling fuel injection timing and quantity. In the illustrated embodiment, fuel flows through the electronic control module  20  to cool the same. In the illustrated embodiment, fuel injectors  12  are mounted in an cylinder head  14  for direct injection into an engine cylinder for compression ignition operation. Nevertheless, those skilled in the art will appreciate that the present invention could be applied to fuel systems for any type of internal combustion engine. 
     Fuel is drawn by supply pump  16  from fuel tank  18  via pump supply passage  31 . The outlet of supply pump  16  is connected to pump outlet passage  32 , where it passes through filter assembly  22  into injector supply passage  33 . After flowing through injectors  12 , fuel passes back to filter assembly  22  via return passage  34 . After passing pressure regulating valve  26 , the fuel enters drain passage  35  for eventual return to fuel tank  18 . A separate priming supply passage  30  is connected to fuel tank  18  upstream from supply pump  16 , and connected to injector supply passage  33  via a separate fluid circuit. Although not necessary, the present invention preferably arranges the filter assembly  22  to be a fluid crossroads for both fuel being supplied to fuel injectors  12  and fuel returning to tank  18  from the same. 
     Referring in addition in FIGS. 2 and 3, filter assembly  22  includes a filter head assembly  23  attached to at least one fuel filter  24 . Filter head assembly  23  acts as a common housing for various components and passageways. For instance, a pressure differential sensor  70 , an absolute pressure sensor  71  and a temperature sensor  72  are all mounted to filter head assembly  23 . In addition to various components attached to filter head assembly  23 , it also includes various internal passageways and includes five ports attached to various other passageways of fuel system  10 . Referring in addition to FIG. 4, four of these ports can be located in an adapter  61 , and a filter outlet port  44  can be located in a separate portion of filter head assembly  23 . Filter head assembly  23  and adapter  61  include a priming inlet port  40  fluidly connected to the priming supply passage  30 , a filter inlet port  41  fluidly connected to pump outlet passage  32 , and an injector return port  43  fluidly connected to return passage  34 . In addition, filter head assembly  23  includes a tank return port  42  fluidly connected to drain passage  35 , and a filter outlet port  44  fluidly connected to injector supply passage  33 . 
     Priming pump  28  is illustrated as a hand priming pump that is optional. However, those skilled in the art will appreciate that another priming pump, such as electronically operated priming pump could be substituted in place of hand priming pump  28 . In other systems, a priming pump  28  can be excluded all together. In the illustrated embodiment, priming pump  28  operates by drawing fluid in through priming inlet port  40  into an internal priming inlet  50  past a check valve  51 . Fluid leaving priming pump  28  passes through an internal priming outlet  52  past a check valve  53  into a filter supply passage  54 , which is directly connected to filter inlet port  41 . Fluid in filter supply passage  54  is filtered in filter(s)  24  and then passes into filter outlet passage  55  before leaving filter assembly  22  via filter outlet port  44 . Priming pump  28  fluidly circumvents supply pump  16  by being directly connected to tank  18 . 
     A first bypass passage  48  is defined by adapter  61 , and fluidly connects the injector supply passage  33  to return passage  34  at internal return passage  56 . Fluid in internal return passage  56  passes to drain passage  35  either through pressure regulating valve  26  or around the same via second bypass passageway  49 . Thus, first bypass passageway  48  can be thought of as circumventing the fuel injectors  12 , while second bypass passageway  49  can be thought of as fluidly connecting an upstream portion to a downstream portion of the drain/return passage to circumvent pressure regulating valve  26 . 
     First bypass passageway  48  is preferably located above the fuel injectors  12  so that any air introduced into the system, such as by changing a filter  24  can be quickly passed into return passage  56  without having to be pushed through fuel injectors  12 . Although first bypass passageway  48  has its end connected upstream from pressure regulating valve  26 , those skilled in the art will appreciate that the downstream end of first bypass passageway  48  could be connected directly to drain passage  35  anywhere downstream of pressure regulating valve  26 , including a possible connection directly into second bypass passageway  49 . First bypass passageway  48  preferably has a relatively small flow area so that gases, including air and/or vapor, are easily passed therethrough, but is relatively restrictive to liquid fuel flow so that the normal supply of fuel at a proper pressure to fuel injectors  12  via injector supply passage  33  is not substantially undermined. Those skilled in the art will recognize that the flow area restriction can be accomplished by positioning a flow restriction orifice of a suitable diameter in the passageway, as shown in the schematic. In other words, bypass passageway  48  should be sized for reduced liquid flow, to avoid fuel from bypassing the fuel injectors. First bypass passageway  48  is also preferably arranged to create a siphon break with respect to fuel located in cylinder head  14 . Nevertheless, those skilled in the art will recognize that the same principals can be applied to systems with fuel rails separated from the cylinder head. This is preferably accomplished by locating first bypass passageway  48  at a location elevationally above the inlet ports to cylinder head  14 , as shown in FIG.  1 . This helps enable fuel to remain in cylinder head  14  (common rail) at all times to further hasten priming and engine start up. 
     Second bypass passage  49  preferably has a relatively small flow area that is sufficiently large to allow for quick free flow of air and/or vapor, but relatively restrictive to liquid fuel flow so as to not undermine system pressure via an undermining of the functioning of pressure regulating valve  26 . This can be accomplished by incorporating a flow restriction orifice into the passageway, as shown in the schematic. Second bypass passageway  49  helps to evacuate gases from system  10  without forcing the fuel lines to a pressure that will open pressure regulating valve  26 . Together, bypass passageways  48  and  49  are portions of a bypass flow path that allows gas, which may originate in the area of filter  24  due to a filter change, to circumvent both of the fuel injectors  12  and pressure regulating valve  26  during engine priming and start up. In other words, air can be evacuated from system  10  at a relatively low pressure. Bypass passageway  49  may be incorporated into the valve member for regulating valve  26 . 
     Referring now to FIG. 4, both first bypass passageway  48  and second bypass passageway  49  are preferably defined by an adapter  61  that is a portion of filter head assembly  23 . Adaptor  61  can be made from any suitable material but is preferably cast and machined to include the various passageways and fastener pores illustrated in FIG.  4 . Among these are a cavity  47  for receiving the temperature sensor  72 , and a cavity  46  for receiving pressure regulating valve  26 . In addition, adapter  61  defines a pressure sensor passage  59  that allows pressure differential sensor  70  (FIGS. 2 and 3) to sense the pressure differential across the cylinder head  14 . 
     INDUSTRIAL APPLICABILITY 
     When in operation, system  10  can be primed in at least one of two ways. First, priming pump  28  can be operated to push any air in filters  24  back to tank via a bypass flowpath that includes first bypass passageway  48 , internal return passage  56  and second bypass passageway  49 . It is likely that an operator using hand pump  28  would be able to quickly detect, via the back pressure feel when the system was primed. In addition, this priming should not take very much effort as priming pump  28  need not pump fluid through supply pump  16 , and most often need not push air and/or fuel through fuel injectors  12 . Alternatively, the system can be primed by cranking the engine to start supply pump  16 , which is preferably a gear driven pump directly coupled to the engine. Because the air can be evacuated at a relatively low pressure, substantially shorter cranking times should be required in order to evacuate any air from system  10  back to tank  18  in order to start the engine. In addition, there is preferably enough fuel remaining in cylinder head  14  to start the engine. In fact, there is preferably enough fuel in one of the cylinder heads to enable the engine to start with only half of its injectors operating if an injector in the other head is replaced due to servicing or another reason rendering that head in need of being primed. 
     By channeling both supply flow and return flow through the filter head assembly, the bypass passageways of the present invention can be added simply via small cross drilled bores in an adapter through which both supply and return passages pass. This strategy should allow the quick priming features of the present invention to be easily implemented in a way that renders the fuel system more easily serviced in the future. Although the bypass passageways are shown in the illustrated embodiment as being unobstructed, in some applications it might be desirable to include a check valve or a spring loaded check valve. However, the pre-load on the check valves should be preferably relatively low in order to allow them to open and allow air to be evacuated from the system at a relatively low pressure. 
     It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. Thus, those skilled in the art will appreciate that other aspects of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.