Patent Application
20110214642
The present disclosure relates generally to common rail fuel systems, and more particularly to a pump and rail assembly with interchangeable components for a range of engines.
Engine manufacturers are constantly seeking ways to reduce costs. One possible way of reducing costs can be by utilizing common interchangeable components to yield economies of scale. However, such a strategy can be especially problematic when a range of potential engine applications is extremely broad. For instance, Caterpillar Inc. of Peoria Ill. manufactures a broad range of compression ignition engines from as small as 4.4 liter four cylinder engines up to 106 liter 20 cylinder engines, and larger. Although these engines differ from each other in size, shape, configuration and many components, they share some features in common. Among these common features are usage of the same type of distillate diesel fuel, and the engines share in common the fact that the fuel system represents a large fraction of the cost for the engine. It is these common aspects that may represent an opportunity for finding a way to potentially utilize common components in the fuel systems for a broad range of engines.
The present disclosure is directed toward one or more of the problems set forth above.
In one aspect, a pump and rail assembly includes a pump that defines a plurality of quill seats. An output rail also defines a plurality of quill seats. Each of a plurality of quills has one end in contact with the quill seat of the pump, and an opposite end in contact with a quill seat of the output rail. At least one clamp is positioned to compress the quills between the pump and the output rail.
In another aspect, a fuel system includes a pump and rail assembly with a plurality of quills, a plurality of pumping elements positioned in a pump housing, and an output rail. A first injection bank includes a plurality of fuel injectors fluidly connected to a first common rail. A second injection bank includes a plurality of fuel injectors fluidly connected to a second common rail. Each of the first and second common rails are fluidly connected to the output rail.
In still another aspect, a plurality of engines have different numbers of cylinders but common components. A plurality of first engines each have a small number of cylinders and a first fuel system with a first pump and rail assembly. A plurality of second engines each have a large number of cylinders and a second fuel system with a second pump and rail assembly. The first and second pump and rail assemblies each include a plurality of quills, a plurality of pumping elements positioned in a pump housing, and an output rail. The plurality of quills for each of the first and second pump and rail assemblies are interchangeable but differ in number. The plurality of pumping elements for each of the first and second pump and rail assemblies are interchangeable but differ in number.
Referring to
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Those skilled in the art will appreciate that the pump and rail assemblies for the different engines shown in
The pump and rail assembly aspect of the present disclosure finds potential use in any pump application, but especially finds potential application in common rail fuel systems for compression ignition engines. The pump and rail assembly structure also finds potential application for scaling across a large range of engines. In particular, the different pump and rail assemblies for different sized engines may differ in pump speed rate, the number of pumping elements and the number of associated quills and the size of the housing. The pump and rail assemblies may find similarity using interchangeable quills, interchangeable pumping elements, output rails formed from different lengths of a similar base material, utilize interchangeable rail pressure sensors, rail pressure control valves and even inlet throttle valves. By utilizing common components across many different sized engine applications, one can expect reduced product costs and development costs as well as reduced risk, by leveraging a common solution across many applications and by yielding economies of scale and quality within a supply chain.
For many four, five and six cylinder applications, the pump and rail assembly strategy of the present disclosure prescribes a pump having two or three pumping elements, each connected to a single high pressure rail through high pressure lines. For a larger V engine application, the solution may be more complicated. The fueling levels and number of cylinders in these applications require more pump capacity. To accomplish this, the high pressure pump configuration is selected to have anywhere from four to ten pumping elements depending upon the engine configuration. With V configurations, two or four outboard high pressure rails are positioned one or two each adjacent to a group of cylinders and their associated fuel injectors. One means to connect the high pressure pump output to the outboard rails is via high pressure lines. By utilizing the intermediate rail (output rail) concept of the present disclosure, output from all of the pumping elements is collected in the intermediate rail first, and subsequently flows to the appropriate outbound rails via connecting high pressure lines, and then later consumed by the fuel injectors in the firing order sequence of the engine. The intermediate rail also serves as an effective hydraulic dampener, softening the pressure pulses emitted from the high pressure pump elements. It also reduces tendency for Helmholtz resonance and other pressure wave interactions between the outboard injector rails. As one specific example, if the system illustrated in
The intermediate output rail 76 of the present disclosure may also serve as a means to reduce the effects of stack up tolerances. The short interchangeable quills 84 having spherical seats on opposite ends may be used on complimentary conical seats 108 and 109 in the output rail 36 and pumping element assemblies 94 to provide the required high pressure sealing. By utilizing a clamping strategy with a leak containment vessel 101, any leakage that does occur can be captured and returned to tank consistent with Marine Classification Society regulations. The selected sphere on cone joint design provides for good tolerance to misalignment in the horizontal plane between seats on the pumping element 94 and the output rail 36. Regarding differences in vertical distance between the conical seats 108 and 109, the assembly has been aligned so that quill clamps comprising four bolts 98 pull the individual pumping element 94 against one end of the quill 84, with the other end of the quill 84 seen against the cone in the output rail 76, which in turn pushes against the inner wall of the leakage containment vessel 101. This closes the load path and provides the required preloading for sealing each pumping element 94 to the intermediate output rail 76. The result in overall intermediate rail/containment vessel/pumping element subassembly is attached to the pump housing 100 by two attachment bolts 114 per pumping element location, providing an abutment to react to loads applied to the plungers of the pump elements 94 by the lifter assemblies as they move in response to the rotating cam shaft 97.
Either end of the output rail 76 may serve as a connection point for a rail pressure control valve 77 and rail pressure sensor 79. In the illustrated embodiment, the rail pressure control valve 77 is shown in control communication with the electronic controller 65. This aspect of the disclosure is intended to accommodate low leakage fuel injectors 72 which may be so fluidly tight that reductions in rail pressure, such as dropping an engine from a high to a low load condition, may be difficult to achieve without actually spilling some fuel from the output rail. Thus, the electronic aspect of rail pressure control valve 77 is optional. In addition, the rail pressure control valve 77 may include a conventional spring biased overpressurization valve that opens in the unlikely event that pressure in the output rail exceeds some predetermined maximum pressure for the system.
Each of the pump and rail assemblies 13, 18, 23, 30, 37, 45, 54 and 63 may also include an interchangeable inlet throttle valve 95 in which fuel to a fuel gallery within the pump 75 is controlled, to control output from the pump 75 and hence to control pressure in the output rail 76. Each of the pumping elements 94 for a given pumping rail assembly 54 would draw fuel from the common fuel inlet manifold within the pump housing 100. Thus, the illustrated embodiment has the advantage of utilizing a single throttle inlet valve 95 regardless of the number of pumping elements for a given pump and rail assembly application. Nevertheless, those skilled in the art will appreciate the alternative pump output control strategies could be utilized, such as individual spill valves associated with each pumping element.
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 disclosure in any way. For instance, the total number of pumping elements need not necessarily equal the number of fuel injectors in each injection bank for the V configuration engine 25, 32, 40, 47 and 56. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.
