| Fuel system with variable discharge pump -> Monitor Keywords |
|
|
 
Fuel system with variable discharge pumpRelated Patent Categories: Pumps, With Condition Responsive Pumped Fluid Control, Pressure Responsive Relief Or Bypass ValveFuel system with variable discharge pump description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070086899, Fuel system with variable discharge pump. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATION TO OTHER PATENT APPLICATION [0001] This application is a divisional of patent application Ser. No. 10/314,879, filed Dec. 9, 2002, with the title Variable Discharge Pump, now U.S. Pat. No. ______. TECHNICAL FIELD [0002] The present invention relates generally to variable discharge pumps, and more particularly to variable discharge pumps having a pair of pumping plungers for use in a fuel system for an engine. BACKGROUND [0003] In one class of fluid systems, such as common rail fuel systems for internal combustion engines, a variable discharge pump is utilized to maintain a pressurized fluid supply for a plurality of fuel injectors. For instance, European Patent Specification EP 0,516,196 teaches a variable discharge high pressure pump for use in a common rail fuel injection system. The pump maintains the common rail at a desired pressure by controllably displacing fluid from the pump to either the high pressure common rail or toward a low pressure reservoir with each pumping stroke of each pump piston. This is accomplished by associating an electronically controlled spill valve with each pump piston. When the pump piston is undergoing its pumping stroke, the fluid displaced is initially pushed into a low pressure reservoir past a spill control valve. When the spill control valve is energized, it closes the spill passageway causing fluid in the pumping chamber to quickly rise in pressure. The fluid in the pumping chamber is then pushed past a check valve into a high pressure line connected to the common rail. In this type of system, the pump typically includes several pump pistons or the system is maintained with several individual unit pumps. The various pump pistons are preferably out of phase with one another so that at least one piston is pumping at about the same time one of the hydraulic devices is consuming fluid from the common rail. This strategy allows the pressure in the common rail to be more steadily controlled in a highly dynamic environment. [0004] As stated, in the pump of the above identified patent, fluid is initially displaced from each pump chamber through a spill control valve toward a low pressure reservoir when the individual pump pistons begin their pumping stroke. When the spill control valve is energized, this spill passageway is closed allowing fluid pressure to build and be pushed past a check valve toward the high pressure common rail. Like many pumps of its type, the spill control valve is a pressure latching type valve in which the valve member is held in its closed position via fluid pressure so that the actuator can be deenergized after the spill control valve has been closed, which can conserve electrical energy. In other words, the fluid pressure in the pumping chamber itself holds the spill control valve closed until that pressure drops toward the end of the pumping stroke, where a spring or other bias pushes the spill control valve back to its open position. When the pump piston undergoes its retracting stroke, fresh fluid is drawn into the pumping chamber past the spill control valve. Thus, the identified patent teaches a spill control valve that both fills the pump cavity with inlet fluid and spills the pump cavity during the time preceding the closing of the valve and the commencement of pump discharge toward the high pressure common rail. [0005] One problem associated with pumps of the type previously described is that the process of filling the pumping chamber and that of spilling the pumping chamber before high pressure pumping begins tend to conflict with one another. Optimizing the spill control valve details for spilling requires designing the valve and valve body geometry to, among other things, avoid shutting the valve due to flow forces before the electrical actuator is energized. [0006] This design criteria often conflicts with the need to fill the pumping chamber through the same fluid circuit. Thus, the pump previously described suffers from two potential drawbacks in that a separate spill control valve is needed for each pumping plunger, and each pump cavity both fills and spills through the spill control valve, resulting in design compromises to efficiently achieve both effective spilling and filling. [0007] The present invention is directed to overcoming one or more of the problems set forth above. SUMMARY OF THE INVENTION [0008] In one aspect, a fuel system for an engine includes a high pressure pump with an inlet and an outlet, which is fluidly connected to a fuel rail. A plurality of fuel injectors are fluidly connected to the fuel rail via respective branch passages. An electronic control module is in control communication with the high pressure pump via an electrical actuator. The high pressure pump includes a first plunger within a first pumping chamber, and a second plunger within a second pumping chamber. The first pumping chamber and the second pumping chamber share a common spill valve, and the spill valve is movable in response to the electrical actuator. A shuttle valve is movable between a first position in which the first pumping chamber is in fluid communication with the spill valve, and a second position in which the second pumping chamber is in fluid communication with spill valve. The shuttle valve is configured to be moved to the first position when the first plunger is in a pumping stroke, and to be moved to the second position when the second plunger is in a pumping stroke. [0009] In another aspect, a method of operating a fuel system includes supplying high pressure fuel to a common rail by reciprocating a first plunger within a first pumping chamber and a second plunger within a second pumping chamber. The high pressure fuel displaced from the first and second pumping chambers is controlled with a shared spill valve. The spill valve is closed by energizing an electrical actuator coupled to the spill valve. A shuttle valve is moved to a first position when the first plunger is in a pumping stroke, and the shuttle valve is moved to a second position when the second plunger is in a pumping stroke. Fuel to the plurality of fuel injectors are supplied from the common rail via individual branch passages. BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG. 1 is a schematic illustration of a common rail fuel system according to one aspect of the present invention; [0011] FIG. 2 is a front sectioned view of a pump from the fuel system shown in FIG. 1; [0012] FIG. 3 is a side sectioned view of the pump of FIG. 2; [0013] FIG. 4 is an enlarged front sectioned view of the fill and spill portion of the pump of FIGS. 2 and 3; and [0014] FIG. 5 is a schematic illustration of a pump according to another embodiment of the present invention. DETAILED DESCRIPTION [0015] Referring to FIG. 1, a fuel system 10 includes a plurality of fuel injectors 22, which are each connected to a high pressure fuel rail 20 via an individual branch passage 21. The high pressure fuel rail 20 is supplied with high pressure fuel from a high pressure pump 16, which is supplied with relatively low pressure fluid by a fuel transfer pump 14. Fuel transfer pump 14 draws fuel from a fuel tank 12, which is also fluidly connected to the fuel injectors 22 via a leak return passage 23. Fuel system 10 is controlled in its operation in a conventional manner via an electronic control module 18 which is connected to an electrical actuator 28 of pump 16 via a control communication line 29, and connected to the individual fuel injectors 22 via other communication lines (not shown). When in operation, control signals generated by electronic control module 18 determine when and how much fuel displaced by pump 16 is forced into common rail 20, as well as when and for what duration (fuel injection quantity) that fuel injectors 22 operate. [0016] Referring in addition to FIGS. 2 and 3, high pressure pump 16 includes a high pressure outlet 30 fluidly connected to the high pressure rail 20, a low pressure outlet 32 connected to fuel tank 12, and an inlet 33 fluidly connected to fuel transfer pump 14. Pump 16 also includes a first plunger 45 positioned to reciprocate in a first pumping chamber 46 of a first barrel 44. In addition, pump 16 includes a second plunger 55 positioned to reciprocate in a second pumping chamber 56 of a second barrel 54. Although not necessary, first and second barrels 44, 54 are preferably portions of a common pump housing 40. A pair of cams 34 and 35 are operable to cause plungers 45 and 55 to reciprocate out of phase with one another. In this embodiment, cams 34 and 35 each include three lobes such that one of the plungers 45 or 55 is undergoing a pumping stroke at about the time that one of the fuel injectors 22 is injecting fuel. Thus, cams 34 and 35 are preferably driven to rotate directly by the engine at a rate that preferably synchronizes pumping activity to fuel injection activity in a conventional manner. [0017] When plunger 45 is undergoing its retracting stroke, fresh low pressure fuel is drawn into pumping chamber 46 past a first inlet check valve 48 from a low pressure gallery 37 that is fluidly connected to inlet 33. Likewise, when plunger 55 is undergoing its retracting stroke, fresh low pressure fuel is drawn into the second pumping chamber 56 past a second inlet check valve 58 from the shared low pressure gallery 37. When first plunger 45 is undergoing its pumping stroke, fluid is displaced from pumping chamber 46 either into low pressure gallery 37 via first spill passage 41 and spill control valve 38, or into high pressure gallery 39 past first outlet check valve 47. Likewise, when second plunger 55 is undergoing its pumping stroke, fuel is displaced from second pumping chamber 56 either into low pressure gallery 37 via second spill passage 51 and spill control valve 38, or into high pressure gallery 39 past second outlet check valve 57. [0018] Referring now in addition to FIG. 4, only one of the pumping chambers 46 or 56 is fluidly connected to spill control valve 38 at a time. These fluid connections are controlled by a shuttle valve member 80 that includes a first hydraulic surface 81 exposed to fluid pressure in first pumping chamber 46, and a second hydraulic surface 82, which is oriented in opposition to first hydraulic surface 81 and exposed to fluid pressure in second pumping chamber 56. Because pumping plungers 44 and 54 are out of phase with one another, one pumping chamber will be at low pressure (retracting) when the other pumping chamber is at high pressure (advancing), and vice versa. This action is exploited to move shuttle valve member 80 back and forth to connect either first spill passage 41 to spill control valve 38, or fluidly connect second spill passage 51 to spill control valve 38. Thus, first hydraulic surface 81 and second hydraulic surface 82 actually define a portion of first spill passage 41 and second spill passage 51, respectively. This allows pumping chambers 46 and 56 to share a common spill control valve 38. In other words, when first plunger 44 is undergoing its pumping stroke while second plunger 54 is undergoing its retracting stroke, shuttle valve member 80 will be in a position shown in FIG. 4 in which first pumping chamber 56 is fluidly connected to spill control valve 38. This is caused by hydraulic fluid pressure acting on first hydraulic surface 81 from pumping chamber 44 pushing shuttle valve member 80 to the right to close second spill passage 51. The affect of this is twofold. First, a single spill control valve 38 can be used to control high pressure discharge from two separate pumping chambers. And second, second pumping chamber 56 is refilled past a second inlet check valve 58 rather than past the spill control valve as in the prior art. These features allow the spill control valve 38 to be optimized for flow in one direction, namely in the spill direction without requiring it to also perform the duty of reverse flow to fill a pumping chamber(s). In addition, this strategy also allows for the usage of a simple cartridge check valve 58 for controlling low pressure fill into the second pumping chamber 56. When second plunger 54 is undergoing its pumping stroke and first plunger 44 is undergoing its retracting stroke, shuttle valve member 80 moves to the left to connect second spill passage 51 to spill control valve 38, while low pressure fuel refills first pumping chamber 46 past first inlet check valve 48. Continue reading about Fuel system with variable discharge pump... Full patent description for Fuel system with variable discharge pump Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Fuel system with variable discharge pump patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Fuel system with variable discharge pump or other areas of interest. ### Previous Patent Application: Microfluidic device utilizing magnetohydrodynamics and method for fabrication thereof Next Patent Application: Air barrel of air compressor Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Fuel system with variable discharge pump patent info. IP-related news and info Results in 0.14872 seconds Other interesting Feshpatents.com categories: Electronics: Semiconductor , Audio , Illumination , Connectors , Crypto , 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
