Fuel flow restrictor assembly with integral fuel filter and fuel system using same

Abstract

A fuel flow restrictor assembly includes a restrictor body forming a central bore, and includes a shut-off piston within the central bore having a closed hydraulic surface exposed to fluid pressure of a fuel inlet and movable from an open position to a closed position based on a drop in fuel pressure from the fuel inlet to a fuel outlet in the restrictor assembly. A fuel filter is resident in the restrictor assembly and supported in a connector coupled to the restrictor body. The fuel filter is elongate and projects from the connector into a fuel flow path from the fuel inlet to the fuel outlet.

Description

A fuel flow limiter assembly with an integrated fuel filter and a fuel system using the fuel flow limiter assembly. Technical Field

[0001] This disclosure generally relates to a fuel flow limiter assembly in a pressurized fuel system, and more specifically to a fuel flow limiter assembly with an integrated fuel filter. Background Technology

[0002] Pressurized fuel systems are well-known and widely used in internal combustion engines. In one example, pressurized fuel is supplied from a single pump to a pressurized fuel reservoir, which then makes the pressurized fuel available for delivery and injection into the combustion cylinders of the engine via fuel injectors. Other pressurized fuel injection systems utilize so-called unit pumps, in which individual cam-actuated or hydraulically actuated fuel pressurization pumps are associated with each fuel injector. Over the years, various extensions and alternatives to these two basic configurations have been proposed.

[0003] In recent years, there has been a widespread recognition of the need for higher fuel injection pressures. High fuel pressures enable the rapid and precise injection of small amounts of fuel and provide improved atomization and other properties to mitigate certain unwanted emissions.

[0004] However, such systems tend to be highly sensitive to particulate matter, as small particles present in the fuel supplied to the system or generated by components within the system itself can interfere with the movement of fast-moving fuel injector and pump components or otherwise degrade performance. For many years, engineers have experimented with different strategies for filtering fuel to remove particulate matter, including systems that filter all fuel upstream of the pressurized fuel accumulator and systems that filter fuel between the pressurized fuel accumulator and individual fuel injectors. An exemplary pressurized fuel system employing fuel filtration between the pressurized fuel accumulator and fuel injectors is described in U.S. Patent Application Publication No. 20150345448A1, granted to Gerstner et al. While the strategies described in '448 application may have certain advantages and applications, there is always room for improvement and development of alternative strategies. Summary of the Invention

[0005] On one hand, a fuel flow limiter assembly includes a limiter body defining a longitudinal axis extending between a first axial body end and a second axial body end, and including an axially extending central opening and a fuel inlet formed in the first axial body end and fluidly connected to the central opening. The limiter assembly also includes a connector coupled to the second axial body end and including a fuel outlet fluidly coupled to the central opening. The limiter assembly further includes a closing piston within the central opening and including a closed hydraulic surface exposed to fluid pressure from the fuel inlet, and a sealing surface. The closing piston is movable within the central opening from an open position to a closed position along the direction of the second axial body end, in which the sealing surface contacts the connector to block fuel flow from the fuel inlet to the fuel outlet. The limiter assembly also includes a biasing spring and a fuel filter supported in the connector, the biasing spring being clamped between the closing piston and the connector and biasing the closing piston toward the open position. The fuel filter protrudes from the connector along the direction of the first axial body end in the fuel flow path from the fuel inlet to the fuel outlet.

[0006] On the other hand, a fuel system for an internal combustion engine includes a pressurized fuel reservoir, a plurality of fuel injectors fluidly connected to the pressurized fuel reservoir, and a plurality of flow restrictor assemblies, each fluidly positioned between the pressurized fuel reservoir and at least one of the plurality of fuel injectors. Each of the plurality of flow restrictor assemblies defines a longitudinal axis and includes a fuel inlet, a fuel outlet, a central opening, a bias spring, and a closing piston positioned in the central opening and movable to a closed position against bias of the bias spring based on a decrease in fuel pressure from the fuel inlet to the fuel outlet. Each of the plurality of flow restrictor assemblies also includes a fuel filter in the respective flow restrictor assembly, the fuel filter having a filter inlet surface exposed to the fuel flow in the central opening and a filter outlet surface forming a filtered fuel passage extending to the fuel outlet.

[0007] In another aspect, a fuel feed subsystem for a fuel injector includes a leak containment housing configured to connect with a pressurized fuel reservoir, and a fuel flow restrictor assembly within the leak containment housing. The fuel flow restrictor assembly includes a restrictor body defining a longitudinal axis and a connector coupled to the restrictor body. The restrictor body has a fuel inlet formed therein and an axially extending central opening fluidly connected to the fuel inlet. The connector has a fuel outlet formed therein and fluidly connected to the central opening. The fuel flow restrictor assembly also includes a biasing spring and a closing piston, the closing piston including a closed hydraulic surface exposed to fluid pressure from the fuel inlet and a sealing surface. The closing piston is movable from an open position to a closed position within the central opening against the biasing force of the biasing spring to block fuel flow from the fuel inlet to the fuel outlet. The subsystem also includes a fuel filter residing in the fuel flow restrictor assembly and supported in the connector, such that the fuel filter protrudes from the connector in an upstream direction relative to the fuel flow path from the fuel inlet to the fuel outlet. Attached Figure Description

[0008] Figure 1 is a schematic view of an internal combustion engine system according to one embodiment;

[0009] Figure 2 is a partial cross-sectional schematic view of a fuel feed subsystem according to one embodiment;

[0010] Figure 3 is an exploded view of a fuel flow limiter assembly according to one embodiment;

[0011] Figure 4 is a cross-sectional side view of the fuel flow limiter assembly in its open configuration; and

[0012] Figure 5 is a cross-sectional side view of a fuel flow limiter assembly in a closed configuration. Detailed Implementation

[0013] Referring to Figure 1, an internal combustion engine system 10 according to one embodiment is shown. The internal combustion engine system 10 includes an engine 12 comprising a plurality of combustion cylinders 14. Each of the combustion cylinders 14 is associated with a piston (not shown) configured to compress a mixture of fuel and air for combustion to rotate a crankshaft in a generally conventional manner. The engine system 10 may be implemented in mobile machinery, stationary generator sets for generating electricity, pumps, compressors, or in a variety of other applications. The engine system 10 may be configured to operate on liquid fuels (e.g., liquid diesel distillate fuels) and is typically operated by compression ignition in a conventional four-cycle mode, but this disclosure is not limited thereto. The engine 12 may include any number of cylinders in any suitable arrangement.

[0014] Engine system 10 also includes a pressurized fuel system 16 having a fuel reservoir 18, a low-pressure pump 20, a high-pressure pump 22, and a pressurized fuel accumulator 24. A plurality of fuel injectors 26 are coupled to the pressurized fuel accumulator 24 and positioned to inject liquid fuel directly into combustion cylinders 14. Each fuel injector 26 includes an outlet check valve 28 and an electrically actuated control valve assembly 30. Fuel system 16 also includes a plurality of fuel feed lines 32 extending between the accumulator 24 and the fuel injectors 26. In one embodiment, the feed lines 32 may include so-called sleeve connectors. Pressure sensors 38 may be coupled to the accumulator 24 and configured to monitor fuel pressure therein in a generally known manner. Fuel system 16 may be implemented as a so-called common-track fuel system, wherein a single integral pressurized fuel accumulator is provided to simultaneously supply pressurized fuel to all fuel injectors 26 at injection pressure. In other embodiments, a plurality of separate pressurized fuel accumulators with accumulator characteristics may be used, each pressurized fuel accumulator associated with one or more fuel injectors. Electronic control unit 40 is shown connected to each of the high-pressure pump 24, pressure sensor 38, and fuel injector 26 to monitor and electronically control the operation of these and other components in a generally known manner. Based on the pressure signal from pressure sensor 38, electronic control unit 40 can control high-pressure fuel pump 24 to maintain fuel pressure at a desired level. Fuel system 16 also includes a plurality of fuel flow restrictor assemblies 34, each fluidly positioned between pressurized fuel reservoir 24 and one of the fuel injectors 26, the features and functions of which will become further apparent from the following description in the illustrated embodiment.

[0015] Referring now to Figure 2, additional features of the fuel system 16 are shown in more detail. Each fuel flow restrictor assembly 34 (hereinafter referred to in the singular) may be part of a fuel feed subsystem 36 configured to restrict the fuel flow to one or more fuel injectors 26 and also filter that fuel flow via an integrated fuel filter 82. The fuel feed subsystem 36 includes a leak containment housing 46 configured to be coupled to the pressurized fuel reservoir 24. The fuel system 16 may include multiple similar or identical fuel feed subsystems and multiple leak containment housings receiving multiple flow restrictor assemblies, all configured similarly or identically to the components shown in Figure 2. Multiple seals, to be described, fluidly seal the flow restrictor assemblies within their respective leak containment housings. As can be seen in Figure 2, the pressurized fuel reservoir 24 defines a fuel chamber 42 and forms an inner wall 43 that contains pressurized fuel within the fuel chamber 42. The housing 46 is coupled to the reservoir 24 and forms an outer wall 42 such that a leakage chamber 48 extends between the inner wall 43 and the outer wall 44 to contain any escaped, leaked, or otherwise discharged fuel, and to return the fuel to the fuel tank 18, for example, via a return line 56. The housing 46 may form a first housing member 47. A second housing member 50 of the housing 46 is coupled to the first housing member 47, for example, by clamping with fasteners not shown in FIG. 2. A feed line / sleeve connector 32 is shown supported in the second housing member 50, wherein a seal, such as an O-ring seal 52, fluidly seals between the second housing member 50 and the feed line / sleeve connector 32. Another seal 54 fluidly seals between the first housing member 47 and the second housing member 50.

[0016] Referring now to FIG. 3, the flow limiter assembly 34 includes a limiter body 58 with a longitudinal axis 60 extending between a first axial body end 62 and a second axial body end 64. The flow limiter assembly 34 also includes a connector 70, which engages with the second axial body end 64 when the flow limiter assembly 34 is assembled for use. The flow limiter assembly 34 also includes a shut-off piston 74 having a closed hydraulic surface 76 and a sealing surface 78. A bias spring 80 is clamped between the shut-off piston 74 and the connector 70 when assembled for use. A spacer 107 is also shown in FIG. 3 when assembled for use between the connector 70 and the bias spring 80. A groove 112 extends circumferentially around the connector 70. The shut-off piston 74 may include various configurations and, in the illustrated embodiment, includes a flow channel 114 configured to allow fuel to flow around and through the shut-off piston 74 for feeding fuel through a fuel filter 82 and ultimately to one or more fuel injectors 26.

[0017] Figure 3 also shows a detailed enlarged view of a portion of the fuel filter 82. The fuel filter 82 includes an elongated perforated filter body 83 with perforated cylindrical walls 88 and a plurality of holes 90 formed therein. The holes 90 communicate between a filter inlet surface 92 formed on the wall 88 and a filter outlet surface 94 formed on the wall 88 and forming a fuel filtration passage 96. The fuel filter 82 may be a single metal piece in which the holes 90 are laser-drilled, but certain other filter types and manufacturing methods may be used. The cylindrical wall 88 extends circumferentially about a longitudinal axis 60 when assembled for use.

[0018] Referring now to Figure 4, a flow restrictor assembly 34 is shown that can be present in the open position. As discussed above, the restrictor body 58 includes a first axial body end 62 and a second axial body end 64. The restrictor body 58 also includes an axially extending central opening 66 and a fuel inlet 68 formed in the first axial body end 62 and fluidly connected to the central opening 66. The central opening 66 may or may not be centered on the longitudinal axis 60, but the longitudinal axis 60 will generally pass through the central opening 66. The fuel inlet 68 may be formed in a sealing protrusion 110 extending axially outward from the first axial body end 62 and may be ball-shaped or otherwise profiled to form a line contact metal-to-metal seal with the pressurized fuel reservoir 24. A connector 70 is coupled to the second axial body end 64 and includes a fuel outlet 72 fluidly connected to the central opening 66. The fuel inlet 68 and the fuel outlet 72 may be centered on the longitudinal axis 60. A filtered fuel passage 96 extends to the fuel outlet 72. The closing piston 74 is positioned within the central opening 66, exposing the closed hydraulic surface 76 to the fluid pressure of the fuel inlet 68. The closing piston 74 is movable within the central opening 66 from the open position as shown in FIG4 along the direction of the second axial body end 64.

[0019] Referring also to Figure 5, a shut-off piston 74 is shown in a closed position, where a sealing surface 78 contacts a connector 70 to block fuel flow from fuel inlet 68 to fuel outlet 72. A biasing spring 80 is clamped between the shut-off piston 74 and the connector 70 and biases the shut-off piston 74 toward the open position, such that the shut-off piston 74 is moved to the closed position against the biasing force of the biasing spring 80. The fuel filter 82 includes an elongated filter body 83 as described above, having an open outlet end 84 supported in the connector 70 and an unsupported second end 86 opposite the open outlet end 84 and positioned within a central opening 66. In an end view, the open outlet end 84 forms a circular opening leading to a filtered fuel passage 96. In an end view of the second end 86, the filter body is closed, but the opening 90 may not be visible to the naked eye. In the illustrated embodiment, comparing Figures 4 and 5, it can be noted that the second end 86 is within the shut-off piston 74 at both the open and closed positions. A perforated cylindrical wall 88 extends between the outlet end 84 and the second end 86. The fuel filter 80 may have perforations 90 at various points, but this disclosure is not limited thereto. For example, the outlet end 84 may be interference-fitted with the connector 70 within the fuel outlet 72 and may be non-perforated.

[0020] Also in the illustrated embodiment, the limiter body 58 includes a countersunk hole 98 formed in the second axial body end 64. The connector 70 may be formed as a single-piece engagement block positioned in the countersunk hole 98 and has a connector seat 100, such as a conical seat, formed therein and extending circumferentially around the fuel outlet 72. The connector 70, including the single-piece engagement block as described above but possibly having multiple parts, includes a spring opening 102 arranged coaxially with the fuel outlet 72 about a longitudinal axis 60 and extending between the fuel outlet 72 and a central opening 66.

[0021] Further exemplary details of the shut-off piston 74 are also visible in Figures 4 and 5. The shut-off piston 74 includes a head portion 104 having a closed hydraulic surface 76 formed thereon and a skirt portion 106 extending circumferentially about a longitudinal axis 60. A biasing spring 80 is partially received within the skirt portion 106 and partially received within a spring opening 102. A spacer 107 may include an annular spacer extending circumferentially about the fuel filter 82 and sandwiched between the biasing spring 80 and the connector 70 within the spring opening 102. A sealing surface 78 may include an annular sealing edge forming the end 108 of the skirt portion 106. The fuel filter 84, biasing spring 80, and shut-off piston 74 may be arranged coaxially about the longitudinal axis 60. It should also be appreciated that each of the filter inlet surface 92 and the filter outlet surface 94 may extend circumferentially about the longitudinal axis 60. As described above, the fuel filter 84 may be interference-fitted with the connector / engagement block 70 within the fuel outlet 72. The single-end support of the fuel filter 82 allows it to protrude substantially unobstructed from the connector 70 in an upstream direction relative to the first axial body end 62 of the fuel flow path from fuel inlet 68 to fuel outlet 72. The elongated structure of the fuel filter 82 and its protrusion along the first axial body end 62 allow fuel to flow through the orifice 90 in a generally radially inward direction into the filtered fuel passage 96, where particles larger than the orifice 90 are excluded, and optimizes the fuel filter flow area available for filtration to limit pressure drop across the fuel filter 82.

[0022] Industrial applicability

[0023] Referring generally to the accompanying drawings, the engine system 10 is operated by reciprocating a piston in combustion cylinder 14 and injecting pressurized fuel supplied from pressurized fuel reservoir 24 directly into combustion cylinder 14. Under normal operation, the outlet check valve 28 in each fuel injector 26 remains closed between injection events, and is commanded to open by electronic control unit 40 to energize control valve assembly 30 for fuel injection. During a fuel injection event, fuel flows through each of the corresponding flow restrictor assemblies 34 to the associated fuel injector 26. Based on the decrease in fuel pressure across each flow restrictor assembly 34 during fuel injection, the corresponding closing piston 74 can move away from the open position against the biasing force of bias spring 80. Normally, the fuel injection event ends, and bias spring 80 pushes the closing piston 74 back towards the fully open position, without reaching its closed portion. Fuel filter 82 filters fuel flowing to fuel outlet 72 through central opening 66 in a manner generally described herein.

[0024] In some cases, fuel injectors may experience performance degradation or damage, including valve jamming, electric actuator failure, problems caused by debris, or other issues leading to excessive or unrelieved fuel flow from the pressurized fuel reservoir 24 into the associated combustion cylinder 14. In such cases, the shut-off piston 74 moves to a fully closed position based on the decrease in fuel pressure from fuel inlet 68 to fuel outlet 72, rather than returning to an open or fully open position at the end of the fuel injection event, so that the sealing surface 78 in contact with connector 70 effectively shuts off the fuel flow and closes the associated combustion cylinder. Integrating flow restriction and filtration functions can reduce the number of parts and components required in a fuel system such as fuel system 16, while achieving or maintaining complete fuel shut-off functionality associated with each combustion cylinder.

[0025] This specification is for illustrative purposes only and should not be construed as limiting the scope of this disclosure in any way. Therefore, those skilled in the art will recognize that various modifications may be made to the embodiments currently disclosed without departing from the full and reasonable scope and spirit of this disclosure. Other aspects, features, and advantages will become apparent from the accompanying drawings and claims. As used herein, the articles “a” and “an” are intended to include one or more items and are interchangeable with “one or more”. The term “one” or similar language is used when intended to indicate only one item. Furthermore, as used herein, the terms “has,” “have,” “having,” etc., are intended to be open-ended terms. Additionally, the phrase “based on” is intended to mean “at least partially based on”, unless otherwise expressly stated.

Claims

1. A fuel flow limiter assembly, comprising: A limiter body defining a longitudinal axis extending between a first axial body end and a second axial body end, and including an axially extending central opening and a fuel inlet formed in the first axial body end and fluidly connected to the central opening; a connector coupled to the second axial body end, and including a fuel outlet fluidly connected to the central opening and a connector seat formed in the connector and extending circumferentially around the fuel outlet; a closing piston within the central opening, and including a closed hydraulic surface exposed to fluid pressure from the fuel inlet and a sealing surface, and the closing piston being movable within the central opening from an open position to a closed position along the direction of the second axial body end, in which the sealing surface contacts the connector to block fuel flow from the fuel inlet to the fuel outlet; A biasing spring is clamped between the closing piston and the connector, and biases the closing piston toward the open position; And a fuel filter, which is supported in the connector and protrudes from the connector in the direction of the first axial body end in the fuel flow path from the fuel inlet to the fuel outlet.

2. The fuel flow limiter assembly according to claim 1, wherein: The fuel filter includes an elongated filter body having an open outlet end supported in the connector and an unsupported second end opposite the open outlet end and positioned within the central opening; the limiter body also includes a countersunk hole formed in the second axial body end, and the connector includes an engagement block positioned in the countersunk hole and having a connector seat extending circumferentially around the fuel outlet; the outlet end is interference-fitted with the connector within the fuel outlet; and the fuel filter includes a perforated cylindrical wall extending between the outlet end and the second end and circumferentially around the longitudinal axis.

3. The fuel flow limiter assembly according to claim 2, wherein: The engagement block includes a spring opening arranged coaxially with the fuel outlet around the longitudinal axis and extending between the fuel outlet and the central opening; the closing piston includes a head portion and a skirt portion, the head portion having a closed hydraulic surface formed on the head portion, and the skirt portion extending circumferentially around the longitudinal axis; The bias spring is received within the skirt portion and the spring opening; and the sealing surface includes an annular sealing edge forming the end of the skirt portion.

4. The fuel flow limiter assembly of claim 3 further includes a spacer, the spacer being sandwiched between the bias spring and the connector within the spring opening.

5. A fuel system for an internal combustion engine, comprising: A pressurized fuel reservoir; a plurality of fuel injectors fluidly connected to the pressurized fuel reservoir; A plurality of flow restrictor assemblies, each a fuel flow restrictor assembly according to any one of claims 1 to 4, wherein each of the plurality of flow restrictor assemblies is fluidly positioned between the pressurized fuel reservoir and at least one of the plurality of fuel injectors; each of the plurality of flow restrictor assemblies defines a longitudinal axis and includes a fuel inlet, a fuel outlet, a central opening, a bias spring, and a closing piston, the closing piston being positioned in the central opening and being movable to a closed position against bias of the bias spring based on a decrease in fuel pressure from the fuel inlet to the fuel outlet; and each of the plurality of flow restrictor assemblies has a fuel filter in the respective flow restrictor assembly having a filter inlet surface exposed to the fuel flow in the central opening and a filter outlet surface forming a filtered fuel passage extending to the fuel outlet.

6. The fuel system according to claim 5, wherein: In the respective flow restrictor assembly, the filter inlet surface and the filter outlet surface each extend circumferentially about a longitudinal axis; each of the fuel filters includes a perforated wall having a filter inlet surface and a filter outlet surface formed thereon, and extends between an open outlet end supported in the respective flow restrictor assembly and an unsupported second end positioned in the central opening; each of the flow restrictor assemblies includes a restrictor body and a connecting block, the connecting block being coupled to the restrictor body and having a fuel outlet formed therein; each of the fuel filters is interference-fitted with the connecting block within the fuel outlet; in the respective flow restrictor assembly, the connecting block includes a spring opening receiving the bias spring and arranged coaxially with the fuel outlet about the longitudinal axis; and the shut-off piston includes a head portion and a skirt portion, the head portion having a closed hydraulic surface exposed to the fluid pressure of the fuel inlet, and the skirt portion including a sealing surface that contacts the connecting block at the closed position of the shut-off piston.

7. The fuel system of claim 5 or 6 further includes a plurality of leak containment housings for receiving the plurality of flow limiter assemblies, and a plurality of seals for fluidly sealing the plurality of flow limiter assemblies within the plurality of leak containment housings.

8. A fuel feed subsystem for a fuel injector, comprising: A leak containment housing configured to be coupled to a pressurized fuel reservoir; a fuel flow restrictor assembly within the leak containment housing, comprising a restrictor body defining a longitudinal axis and a connector coupled to the restrictor body; the restrictor body having a fuel inlet formed in the restrictor body and an axially extending central opening fluidly connected to the fuel inlet; The connector has a fuel outlet formed in the connector and fluidly connected to the central opening, and a connector seat formed in the connector and extending circumferentially around the fuel outlet; the fuel flow restrictor assembly also includes a bias spring and a closing piston, the closing piston including a closed hydraulic surface exposed to fluid pressure at the fuel inlet and a sealing surface, and is movable from an open position to a closed position within the central opening against the biasing force of the bias spring to block fuel flow from the fuel inlet to the fuel outlet; And a fuel filter, which resides in the fuel flow restrictor assembly and is supported in the connector such that the fuel filter protrudes from the connector in an upstream direction relative to the fuel flow path from the fuel inlet to the fuel outlet.

9. The fuel feed subsystem of claim 8, wherein the fuel filter includes an elongated perforated body supported within the connector.

10. The fuel feeding subsystem according to claim 9, wherein: The fuel filter, the bias spring, and the shut-off piston are arranged coaxially, with the bias spring partially received within the shut-off piston and partially received within the connector; and the fuel filter includes an open outlet end that is interference-fitted within the fuel outlet, and an opposing unsupported end that is axially located within the shut-off piston in the open position and in the closed position.

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