Trapped volume isolation check valve assembly in a fuel injector

Abstract

A fuel system includes a fuel injector having a split check assembly with a control member, an outlet member, and a check sleeve. A trapped volume is formed within the check sleeve between the control member and the outlet member, hydraulically coupling the control member to the outlet member. A start rate shaping gap fluidly connects the trapped volume to a fuel cavity and is formed between the check sleeve and one of the control member or the outlet member received in the check sleeve, and regulates a start rate shape of fuel injection from the fuel injector. Related methods are disclosed.

Description

Technical Field

[0001] This disclosure generally relates to pressurized fuel systems, and more specifically to fuel injectors in pressurized fuel systems having a separate check valve assembly having a cut-off volume and an initial rate shaping gap for adjusting the fuel injection rate shape. Background Technology

[0002] In recent decades, emission requirements for internal combustion engines have become increasingly stringent. Engine manufacturers and component suppliers continue to seek strategies to reduce undesirable emissions such as particulate matter and nitrogen oxides, or "NOx." Various strategies are known for reducing such emissions in engine exhaust aftertreatment systems, as well as for limiting the generation of such emissions in the combustion process itself. Most modern internal combustion engine systems employ a combination of strategies to limit emissions, and also capture or treat emissions that are still always generated.

[0003] A common goal in reducing the generation of certain emissions is to improve the processes and parameters of fuel delivery to engine cylinders, particularly in the case of direct fuel injection in compression-ignition diesel engines. Various well-known technologies employ a pressurized fuel reservoir, often referred to as a common rail, which allows fuel to be injected at the desired injection pressure and also actuates various moving parts within the fuel injector. Common rail and related strategies have enabled engineers to develop systems capable of controlling the timing, quantity, and rate profile of fuel injection with relatively high precision, but various limitations remain. It has been observed that optimal operation and performance can be achieved, at least theoretically, when relatively small amounts of fuel can be precisely injected. Fuel injection systems are typically designed to achieve robust performance under rated loads but may be subject to certain limitations when operating at lower loads. In other words, while the engine and fuel system can operate as desired most of the time, there are still situations where the inherent hardware limitations of known systems prevent them from actually providing or supporting optimal performance. One known common rail fuel injection system is known from U.S. Patent No. 7,278,593 to Wang et al. Summary of the Invention

[0004] On one hand, a fuel injector includes an injector housing defining a longitudinal axis and having a high-pressure inlet formed therein, a fuel chamber fluidly connected to the high-pressure inlet, a low-pressure outlet, and a check control chamber. The injector housing further includes a nozzle having a plurality of injection orifices formed therein. The fuel injector also includes an injection control valve assembly including a control valve movable from a closed position to an open position, in which the control valve isolates the check control chamber from the low-pressure outlet. The fuel injector further includes a split check assembly within the injector housing and including: a control having a check top surface exposed to the check control chamber, an outlet coaxially arranged with the control, and a check sleeve receiving at least one of the control or the outlet therein. The outlet element includes a tip that contacts the injector housing to isolate the injection outlet from the fuel chamber, and the control element and the outlet element are movable from a forward position to a retracted position based on the control valve moving from the closed position to the open position to allow the injection outlet to access the fuel chamber. A trapping volume is formed within the check sleeve between the control element and the outlet element, and hydraulically connects the control element to the outlet element. An initial rate setting gap fluidly connects the trapping volume to the fuel chamber and is formed between the check sleeve and at least one of the control element or the outlet element received in the check sleeve.

[0005] On the other hand, a fuel injector includes an injector housing defining a longitudinal axis and having a high-pressure inlet formed therein, a fuel chamber fluidly connected to the high-pressure inlet, a low-pressure discharge port, and a check control chamber. The injector housing further includes a nozzle having a plurality of injection outlets formed therein. The fuel injector further includes an injection control valve assembly having a control valve movable from a closed position to an open position, in which the control valve isolates the check control chamber from the low-pressure discharge port. The fuel injector also includes a split check assembly within the injector housing and having: a control member having a check top surface exposed to the check control chamber; and an outlet member coaxially arranged with the control member and having a tip that contacts the injector housing to isolate the injection outlet from the fuel chamber. The split check assembly further includes a check sleeve receiving the control member and the outlet member therein and forming a trap volume together with the control member and the outlet member. The trapping volume hydraulically connects the control element and the outlet element from an advance position to a retracted position based on the movement of the control valve from the closed position to the open position, so that the injection outlet opens to the fuel chamber. An initial rate setting gap is formed between the check sleeve and at least one of the control element or the outlet element, and fluidly connects the trapping volume to the fuel chamber.

[0006] In another aspect, a method of operating a fuel system includes: moving a control element in a split check assembly in a fuel injector from an advance position toward a retracted position; and opening an outlet element of the split check assembly hydraulically coupled to the control element based on the movement of the control element toward the retracted position. The method further includes, during the opening of the outlet element, leaking fuel between a fuel chamber in the fuel injector and a retaining volume formed between the control element and the outlet element through an initial rate-setting gap formed between the check sleeve and at least one of the control element or the outlet element. The method further includes, based on the fuel leakage between the fuel chamber and the retaining volume, setting a fuel injection rate through an injection outlet in the fuel injector opened by the outlet element. Attached Figure Description

[0007] Figure 1 This is a schematic view of an internal combustion engine system according to one embodiment;

[0008] Figure 2 This is a cut-out side view of a fuel injector according to one embodiment;

[0009] Figure 3 yes Figure 2A cut-out side view of a portion of the fuel injector;

[0010] Figure 4 This is a schematic view of an outlet component for a split check valve assembly according to one embodiment;

[0011] Figure 5 This is a cut-out side view of a portion of a fuel injector according to one embodiment;

[0012] Figure 6 This is a schematic view of a control element for a split check valve assembly according to one embodiment;

[0013] Figure 7 This is a cut-out side view of a portion of a fuel injector according to one embodiment;

[0014] Figure 8 This is a schematic view of a check sleeve for a split check assembly according to one embodiment;

[0015] Figure 9 This is a cut-out side view of a portion of a fuel injector according to one embodiment;

[0016] Figure 10 This is a schematic view of an outlet component for a split check valve assembly according to one embodiment;

[0017] Figure 11 This is a cut-out side view of a fuel injector according to one embodiment;

[0018] Figure 12 yes Figure 11 A cut-out side view of a portion of the fuel injector;

[0019] Figure 13 This is a schematic diagram of a fuel injector according to one embodiment; and

[0020] Figure 14 It is a graph of the component position of the separate check valve assembly according to this disclosure relative to time, compared with the position of the check valve in a known design. Detailed Implementation

[0021] refer to Figure 1An internal combustion engine system 10 according to one embodiment is illustrated. Engine system 10 includes a cylinder block 12 having a plurality of cylinders 14 formed therein. The cylinders 14 may include any number of cylinders in any suitable arrangement, such as an inline pattern, a V-shaped pattern, or another as shown. Engine system 10 may include a direct injection compression ignition engine configured to operate with a liquid fuel (such as liquid diesel distillate fuel), however, this disclosure is not limited thereto. Engine system 10 may be a single-fuel engine; however, this disclosure is not limited in this respect, and in some embodiments, engine system 10 may be a gas and liquid dual-fuel engine. Engine system 10 further includes a fuel system 16 having a liquid fuel supply source or fuel tank 18, a low-pressure delivery pump 20, and a high-pressure pump 22, the high-pressure pump being configured to pressurize the fuel and supply it to a pressurized fuel reservoir or common rail 24. Common rail 24 may include a single integral fuel reservoir, but may include a plurality of separate fuel reservoirs having accumulator characteristics and / or a plurality of separate pressurized lines connected together in a so-called daisy-chain arrangement, etc. Pressure sensor 34 can be generally conventionally coupled to common rail 24 and communicate with electronic control unit 36. Electronic control unit 36 ​​can receive pressure signals from pressure sensor 34 and responsively operate high-pressure pump 22 to maintain fuel pressure in common rail 24 at a desired level, or to regulate fuel pressure to a desired level for various purposes. Common rail 24 is fluidly connected to a plurality of fuel injectors 26, each positioned to extend into and fluidly communicate with a corresponding one of cylinders 14. Fuel injectors 26 can be substantially identical to each other. Each of fuel injectors 26 includes an injector housing 28 and has an injection control valve assembly 32 within the corresponding injector housing 28, or the injection control valve assembly is coupled to the corresponding injector housing 28. Each injection control valve assembly 32 can be generally conventionally electrically actuated by a control current generated by electronic control unit 36. Each fuel injector 26 may further include a separate check valve assembly 30 within the corresponding injector housing 28, the details and function of which are further discussed herein. As will become further apparent from the following description, each separate check valve assembly 30 may be configured to improve the minimum delivery and fuel injection rate profile, including the initial fuel injection rate profile.

[0022] Still referencing Figure 2-4Each fuel injector 26 referred to hereinafter in the singular includes the injector housing 28 as described above. The injector housing 28 may include multiple housings or pressure-retaining components, and multiple internal components movable relative to the housings and pressure-retaining components. The injector housing 28 defines a longitudinal axis 38 and has a high-pressure inlet 40 formed therein and fluidly connected to a common rail 24, a fuel chamber 42 fluidly connected to the high-pressure inlet 40, a low-pressure discharge port 44, and a check valve control chamber 46. The injector housing 28 further includes a nozzle 48 having multiple injection outlets 50 formed therein. In the illustrated embodiment, the nozzle 48 includes a tip 52 positioned within a housing 54 defining an injection outlet 50. Various other injector housing components (not labeled) are clamped together within the injector housing 28. The low-pressure discharge port 44 may be or fluidly connected to a low-pressure return line (not shown) that returns fuel used to actuate the fuel injector 26 to the fuel tank 18, or discharges to a fuel supply line normally fluidly connected between the delivery pump 20 and the high-pressure pump 22. The high-pressure inlet 40 can be fluidly connected to the common rail 24 in any suitable manner, for example, by means of a so-called sleeve connector that clamps into a sealing contact with the injector housing 28.

[0023] The fuel injector 26 further includes an injection control valve assembly 32 having a control valve 56 movable from a closed position to an open position. In the closed position, the control valve 56 isolates the check control chamber 46 from the low-pressure discharge port 44; in the open position, the control valve 56 does not isolate the check control chamber 46 from the low-pressure discharge port 44. The control valve assembly 32 may also include an electric actuator 62, an armature 60 movable relative to the electric actuator 62, and a rod connected between the armature 60 and the control valve 56. The control valve 56 may include a ball control valve, a hemispherical control valve, a flat valve, a three-way lift valve, or any other suitable valve type that can establish and disconnect various fluid connections in a suitable manner. The control valve assembly 32 may also include a valve seat orifice plate 58 contacted by the control valve 56 in the closed position and not contacted by the control valve 56 in the open position. The valve seat orifice plate 58 may include a plurality of orifices (unnumbered) formed therein for pressurizing and depressurizing the check control chamber 46 in a suitable manner.

[0024] As described above, the split check assembly 30 is located within the injector housing 28. The split check assembly 30 includes a control element 64 that moves within a guide 92, for example, against a closing bias of a bias spring 90. The control element 64 further includes a check top surface 66 exposed to the check control chamber 46. The split check assembly 30 also includes an outlet 68 arranged coaxially with the control element 64, and a check sleeve 70 that receives at least one of the control element 64 or the outlet 68 therein. The outlet 68 includes a tip 72 that contacts the injector housing 28 to isolate the injection outlet 50 from the fuel chamber 42, and the control element 64 and the outlet 68 are movable from an advance position to a retracted position based on the control valve 56 moving from a closed position to an open position to allow the injection outlet 50 to access the fuel chamber 42. When the control element 68 is raised and disengaged from contact with the injector housing 28 blocking the injection outlet 50, the injection outlet 50 is fluidly connected to the fuel chamber 42 where pressurized fuel is located. Tip 72 may be part of needle 69 of export part 68.

[0025] Also in the illustrated embodiment, the outlet member 68 is guided within a guide opening 87 formed in the tip member 52. The control member 64 may be guided within an opening 94 formed in the outlet member 68, and as described above, within the guide member 92. The control member 64 may be guided primarily through interaction with the outlet member 68. A bias spring 90 may be compressively held between the guide member 92 and the control member 64. The outlet member 68 may further include a plurality of guide surfaces 86 configured to contact the tip member 52 and have guide gaps therewith. A plurality of flow surfaces 88 may be arranged alternately with the guide surfaces 86 around the longitudinal axis 38. Thus, as shown, the guide gap 84 can be understood as being formed between the check sleeve 70 and the injector housing 28, and between the check sleeve 70 and the tip member 52. A fuel supply gap larger than the guide gap 84 may be formed between the check sleeve 70 and the injector housing 28, as shown between the flow surfaces 88 and the tip member 52, and extending between the fuel chamber 42 and the injection outlet 50. In other embodiments, different piping strategies can be used to supply pressurized fuel to the injection outlet 50, in addition to the movable part of the separate check valve assembly 30 and the injector housing 28.

[0026] As further discussed herein, a retaining volume 74 is formed within the check sleeve 70 between the control member 64 and the outlet member 68, and hydraulically connects the control member 64 to the outlet member 68. An initial rate shaping gap 76 fluidly connects the retaining volume 74 to the fuel chamber 42 and is formed between the check sleeve 70 and at least one of the control member 64 and the outlet member 68 received within the check sleeve. The control member 64 may further include a check end surface 78 opposite to the check top surface 66. The outlet member 68 includes a second check top surface 80 opposite to the tip 72, and the retaining volume 74 may be formed between the check end surface 78 and the second check top surface 80. The check end surface 78 may have a larger surface area exposed to the fluid pressure of the retaining volume 74, and the second check top surface 80 may have a smaller surface area exposed to the fluid pressure of the retaining volume 74.

[0027] Also in the illustrated embodiment, an initial rate setting gap 76 is formed peripherally between the check sleeve 70 and one of the control element 64 and the outlet element 68 received within the check sleeve. The initial rate setting gap 76 may extend circumferentially about the longitudinal axis 38, and the trapping volume 74 may be fluidly connected to the fuel chamber 42 solely through the initial rate setting gap 76. (Further details will be provided...) Figure 2-4 Note that the check sleeve 70 is movable within the injector housing 28 and integrally formed with the outlet member 68, such that the check sleeve 70 and the outlet member 68 move together between the forward and retracted positions. In other embodiments further discussed herein, the check sleeve is integrally formed with the control member and moves together with the control member between the forward and retracted positions. It will also be further understood from the following description that the difference in movement between the outlet member and the control member between the forward and retracted positions (e.g., fuel leakage adjustment via the initial rate shaping gap 76) contributes to achieving the desired initial rate shape of fuel injection and improved minimum delivery capability.

[0028] Now for reference Figure 5A fuel injector 126 according to another embodiment is shown. Fuel injector 126 shares some similarities with fuel injector 26 discussed above, but also has some differences. Fuel injector 126 includes an injector housing 128 defining a longitudinal axis 138. A split check valve assembly 130 is located within the injector housing 128 and functions generally similarly to the split check valve assembly 30 discussed above. A control element 164, an outlet element 168, and a check sleeve 170 define a trap volume 174. The outlet element 168 is partially positioned within the check sleeve 170, and an initial rate shaping gap 176 fluidly connects the trap volume 174 to the fuel chamber 142. In contrast to the split check valve assembly 30, in the split check valve assembly 130, the check sleeve 170 is integrally formed with the control element 164, rather than the check sleeve being integrally formed with the outlet element. Therefore, the check sleeve 170 forms an opening 194 that receives the outlet 168, and the initial rate setting gap 176 fluidly connects the trapping volume 174 to the fuel chamber 142 below the connection of the corresponding control and outlet.

[0029] Also refer to Figure 6 The control element 164 may have a guide clearance with the injector housing 128 and includes a guide surface 186 configured to contact the injector housing 128. The control element 164 may have a fuel supply gap formed between the fuel supply surface 188 and the injector housing 128 that is larger than the guide clearance. The guide surface 186 may be arranged alternately with the fuel supply surface 188 circumferentially around the longitudinal axis 138. A check valve top surface 166 is formed on the control element 164 and exposed in the check valve control chamber within the fuel injector 126. A spring flange or stop 196 is also formed on the control element 164 and is generally similar to the foregoing embodiments, configured to contact the bias spring within the fuel injector 126.

[0030] Now for reference Figure 7-8A portion of a fuel injector 226 and its components according to another embodiment are shown. Although not depicted, it should be understood that the fuel injector 226 may include control valve assemblies and other features similar to those used in other embodiments described herein. Similarly, other embodiments discussed below will generally include many of the same or similar parts and / or functions, even if not specifically shown. The fuel injector 226 includes an injector housing 228 defining a longitudinal axis 238. A trapping volume 274 is formed within a split check assembly 230 between a control member 264 and an outlet member 268, and hydraulically connects the control member 264 to the outlet member 268. The split check assembly 230 also includes a check sleeve 270. The check sleeve 270 contacts the injector housing 228 and, in the illustrated embodiment, contacts a tip member 252. The check sleeve 270 has an axially extending opening formed by a first opening section 294 receiving the control member 264 and a second opening section 295 receiving the outlet member 268. The check valve end surface 278 of the control element 264 is exposed to the fluid pressure of the trap volume 274. The check valve top surface 280 of the outlet element 268 is also exposed to the fluid pressure of the trap volume 274. The check valve end surface 278 may have a larger surface area exposed to the fluid pressure of the trap volume 274, and the check valve top surface 280 may have a smaller surface area exposed to the fluid pressure of the trap volume. An initial rate setting gap 276 is formed between the first opening section 294 and the control element 264. A second initial rate setting gap 277 is formed between the second opening section 295 and the outlet element 268. Another opening 287 is formed in the tip element 252. The check valve sleeve 270 may have a guide gap with the injector housing 228 and a guide gap with the tip element 252, the tip element being configured, for example, to contact the guide surface 286 of the check valve sleeve 270. The guide surface 286 may be arranged alternately with the fuel supply surface 288 circumferentially around the longitudinal axis 238, thereby forming a fuel supply gap with the injector housing 228 that is larger than the corresponding guide gap. The flange or other protrusion 296 of the check sleeve 270 extends radially outward and contacts the tip 252 to position the check sleeve 270 within the injector housing 228. A bias spring 290 contacts the check sleeve 270 and may be kept compressed within the injector housing 228 to hold the check sleeve 270 in place as needed.

[0031] Now for reference Figure 9 and 10A fuel injector 326 according to yet another embodiment is shown, and includes an injector housing 328 defining a longitudinal axis 338. A split check valve assembly 330 is located within the injector housing 328 and includes a control member 364, an outlet member 368, and a check valve sleeve 370. A trapping volume 374 is formed within the check valve sleeve 370 between the control member 364 and the outlet member 368, and hydraulically connects the control member 364 to the outlet member 368. The check valve sleeve 370 includes an axially extending opening formed by a first opening section 394 and a second opening section 395 that respectively receive the control member 364 and the outlet member 368. A first initial rate setting gap 376 fluidly connects the trapping volume 374 to the fuel chamber 342. The first initial rate setting gap 376 is formed between the check valve sleeve 370 and the control member 364. A second initial rate shaping gap 377 fluidly connects the choke volume 374 to the fuel chamber 342 and is formed between the check sleeve 370 and the outlet member 368. The outlet member 368 may have a guide gap 384 with the injector housing 328 and, as shown, a guide gap with the tip 352 of the injector housing 328. A biasing spring 390 is compressively held between the check sleeve 370 and the outlet member 368. Based on the biasing force of the biasing spring 390, the check sleeve 370 is kept in contact with the protruding flange or other protrusion 396 of the control member 364. The control member 364 includes a check end surface 378, which may have a larger surface area exposed to the fluid pressure of the choke volume 374. The outlet member 368 includes a check top surface 380, which may have a smaller surface area exposed to the fluid pressure of the choke volume 374. Figure 10 As shown, the outlet component 368 includes a needle 369 with a tip 372 configured to contact the injector housing 328 for opening and closing the injection outlet. A check valve shaft 371 extends to a check valve top surface 380. The outlet component 368 also includes a guide surface 386, which is arranged circumferentially around a longitudinal axis 338 alternately with the fuel supply surface 388, and is constructed and functions similarly to similar structures in other embodiments described herein.

[0032] Now for reference Figure 11 and 12The image shows a fuel injector 426 according to yet another embodiment, and includes an injector housing 428 having a split check assembly 430 positioned therein. The split check assembly 430 includes a control member 464, an outlet member 468, and a check sleeve 470. The injector housing 428 defines a longitudinal axis 438. A trapping volume 474 is formed between the control member 464 and the outlet member 468, and hydraulically connects the control member 464 to the outlet member 468. The check sleeve 470 has an axially extending opening formed by a first opening section 494 receiving the control member 464 and a second opening section 495 receiving the outlet member 468. The check sleeve 470 includes a first axial end surface 473 (first stop surface) that contacts a shoulder 496 of the control member 464. The check sleeve 470 also includes a second axial end surface 475 (second stop surface) that contacts a shoulder 479 of the outlet member 468. A first initial rate setting gap 476 is formed between the check sleeve 470 and the control member 464, and fluidly connects the trapping volume 474 to the fuel chamber 442. A second initial rate setting gap 477 is formed between the outlet member 468 and the check sleeve 470, and fluidly connects the trapping volume 474 to the fuel chamber 442. At least in the forward position of the control member 464 and the outlet member 468, and possibly in their respective retracted positions, the check sleeve 470 remains engaged between the control member 464 and the outlet member 468, contacting each of the stop surfaces 496 and 479. When the control member 464 and the outlet member 468 are in their respective forward and retracted positions, the trapping volume 474 extends axially between the check end surface 478 and the check top surface 480.

[0033] refer to Figure 13 A fuel injector 526 according to yet another embodiment is shown, and the fuel injector includes an injector housing 528 and a separate check assembly 530, the separate check assembly including a control member 564, an outlet member 568, and a check sleeve 570. The control member 564 includes a check end surface 578, and the outlet member 568 includes a check top surface 580. An injection control valve assembly is shown at 532. Within the check sleeve 570, a trap volume 574 is formed between the control member 564 and the outlet member 568. A first initial rate shaping gap 576 extends between the control member 564 and the check sleeve 570, and a second initial rate shaping gap 577 extends between the outlet member 568 and the check sleeve 570. The initial rate shaping gaps 576 and 577 fluidly connect the trap volume 574 to the fuel chamber 542. When in the forward position, the control element 564 contacts the stop element 581 formed by the check sleeve 570.

[0034] Industrial applicability

[0035] Generally refer to the attached diagram, but also refer to... Figure 14 A graph 600 is shown, illustrating the check position 610 on the X-axis as time progresses along the Y-axis for a known one-piece check element. The position of the control element in the separate check assembly according to this disclosure is shown at line 615, and the position of the outlet element in the separate check assembly according to this disclosure is shown at line 620. During operation of the separate check assembly according to this disclosure, when the control valve assembly is energized to fluidly connect the check control chamber to the low pressure, the top surface of the check element in the control element is exposed to the reduced pressure in the check control chamber and begins to move relatively quickly from the forward position toward the retracted position, generally as indicated by reference numeral 625. The movement of the control element tends to produce a pressure drop in the trap volume extending between the control element and the outlet element as described herein. Then, due to this pressure drop, the control element tends to begin to slow down, as can be seen generally through the portion of line 615 identified by reference numeral 625. As a sufficient pressure drop occurs in the trap volume, the outlet element will begin to move based on the movement of the control element, and begin to open. As shown by reference numeral 630 in the attached figure, the initial opening speed of the exit component can be generally seen along line 620. The movement of the exit component can then begin to provide impingement to the control component, causing its speed to increase from the initial speed. The increased speed of the control component then enables the exit component to accelerate.

[0036] Fuel leakage through one or more initial rate-determining gaps between the choke volume and the fuel chamber can help these components achieve the required independent but hydraulically coupled movement as the corresponding components of the separate check assembly move from the forward position to the retracted position. As a result, a slow initial rate of fuel injection can be observed, as the outlet component opens relatively gradually, its initial opening speed limited by fuel leakage, but then begins to accelerate at least briefly to increase the injection rate. This contrasts with some known designs, including the known single-piece check design shown, where the initial speed of the check movement is relatively slow but remains relatively slow. It should also be remembered that the surface area of ​​the control component exposed to the choke volume, as discussed herein, can be relatively larger than the surface area of ​​the outlet component exposed to the choke volume. As a result, the movement of the control component may require a relatively large volume of fluid displacement, resulting in some hydraulic assistance to pull the outlet component. When the check control chamber is pressure-restored by isolating it from the low-pressure barrier, in Figure 14 Shortly after time 2 in the diagram, the control element will be pushed down to increase the pressure in the choke volume and push the outlet element to close to end fuel injection.

[0037] 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 injector, comprising: An injector housing that defines a longitudinal axis and has a high-pressure inlet formed therein, a fuel chamber fluidly connected to the high-pressure inlet, a low-pressure outlet and a check valve control chamber, and the injector housing further includes a nozzle having a plurality of injection outlets formed therein, the nozzle including a tip defining the injection outlets; An injection control valve assembly, the injection control valve assembly including a control valve capable of moving from a closed position to an open position, wherein in the closed position the control valve isolates the check control chamber from the low-pressure discharge port; A separate check valve assembly, located within the injector housing, includes: a control having a top surface of the check valve exposed to the check valve control chamber; an outlet coaxially arranged with the control; and a check valve sleeve receiving at least one of the control or the outlet. The outlet component has a tip that contacts the injector housing to isolate the injection outlet from the fuel chamber, and the control component and the outlet component are capable of moving from a forward position to a retracted position based on the control valve moving from the closed position to the open position to allow the injection outlet to access the fuel chamber; as well as A retaining volume, formed within the check sleeve between the control element and the outlet element, hydraulically connects the control element to the outlet element, and an initial rate setting gap fluidly connects the retaining volume to the fuel chamber, and is formed between the check sleeve and at least one of the control element or the outlet element received within the check sleeve. The check sleeve is movable together with one of the control element or the outlet element within the injector housing between an advancing position and a retracted position. A guide gap is formed between the check sleeve and the injector housing, and a fuel supply gap is formed between the check sleeve and the injector housing, extending between the fuel chamber and the plurality of injection outlets. The control element or outlet element includes a plurality of guide surfaces configured to contact the tip element and having a guide gap therebetween.

2. The fuel injector according to claim 1, wherein: The control element includes a check valve end surface opposite to the top check valve surface; The outlet component includes a second check valve top surface opposite the tip, and the retention volume is formed between the check valve end surface and the second check valve top surface.

3. The fuel injector according to claim 2, wherein: The check valve surface has a large surface area exposed to the fluid pressure of the trapping volume; The second check valve top surface has a smaller surface area exposed to the fluid pressure of the trap volume; The initial rate setting gap is formed peripherally between the check sleeve and one of the control element or the outlet element received in the check sleeve, and extends circumferentially around the longitudinal axis; and The choke volume is fluidly connected to the fuel chamber only by the initial rate-defined gap.

4. The fuel injector according to any one of claims 1-3, wherein: One of the control element or the outlet element is integrally formed with the check sleeve.

5. A fuel injector, comprising: An injector housing that defines a longitudinal axis and has a high-pressure inlet formed therein, a fuel chamber fluidly connected to the high-pressure inlet, a low-pressure outlet and a check valve control chamber, and the injector housing further includes a nozzle having a plurality of injection outlets formed therein, the nozzle including a tip defining the injection outlets; An injection control valve assembly, the injection control valve assembly including a control valve capable of moving from a closed position to an open position, wherein in the closed position the control valve isolates the check control chamber from the low-pressure discharge port; A separate check valve assembly, located within the injector housing, includes: a control having a top surface of the check valve exposed to the check valve control chamber, and an outlet member coaxially arranged with the control and having a tip that contacts the injector housing to isolate the injection outlet from the fuel chamber. The separate check valve assembly further includes a check valve sleeve that receives the control element and the outlet element therein, and together with the control element and the outlet element, forms a trapping volume; The retention volume is hydraulically coupled to the movement of the control element and the outlet element from the forward position to the retracted position based on the movement of the control valve from the closed position to the open position, so that the injection outlet opens to the fuel chamber; and An initial rate setting gap is formed between the check sleeve and at least one of the control element or outlet element, and fluidly connects the trapping volume to the fuel chamber. The control element further includes a check valve end surface opposite the check valve top surface and exposed to the fluid pressure of the choke volume, and the outlet element includes a second check valve top surface exposed to the fluid pressure of the choke volume; and The check valve end surface has a large surface area, while the second check valve top surface has a small surface area. The control element or outlet element includes a plurality of guide surfaces configured to contact the tip element and having a guide gap therebetween, the guide gap being formed between the check sleeve and the injector housing.

6. The fuel injector according to claim 5, wherein: The initial rate setting gap is formed peripherally between the check sleeve and the control element, and the second initial rate setting gap is formed peripherally between the check sleeve and the outlet element.

7. The fuel injector according to claim 5 or claim 6, wherein: A fuel supply gap is formed between the check sleeve and the injector housing, and extends between the fuel chamber and the plurality of injection outlets.

8. The fuel injector according to any one of claims 5-6, wherein: The control element includes a first stop surface, and the outlet element includes a second stop surface; and When the control element and the outlet element are in their respective forward positions, the check sleeve contacts each of the first stop surface and the second stop surface.

9. A method of operating a fuel system, comprising: Move the control element in the separate check valve assembly of the fuel injector from the forward position toward the retracted position; The outlet of the split check assembly is opened based on the movement of the control element toward the retracted position, and the outlet is hydraulically connected to the control element; During the opening of the outlet, fuel leaks between the fuel chamber in the fuel injector and the trapping volume formed between the control element and the outlet through an initial rate-setting gap formed between the check sleeve and at least one of the control element or the outlet; and Based on fuel leakage between the containment volume and the fuel chamber, the fuel injection rate through the injection outlet in the fuel injector is determined, the injection outlet being opened by the opening of the outlet element. The check sleeve, together with one of the control element or outlet element, is guided to move between an advance position and a retracted position through a guide gap formed between the check sleeve and the injector housing of the fuel injector. The control element or outlet element includes a plurality of guide surfaces configured to contact and have a guide gap with a tip element that defines the injection outlet. as well as Injected fuel is supplied through a fuel supply gap formed between the check sleeve and the injector housing, extending between the fuel chamber and multiple injection outlets.

10. The method of claim 9, further comprising: The initial opening speed of the outlet component is limited due to the fuel leakage. as well as The opening speed of the exit component is increased from the initial opening speed.

11. The method according to claim 9 or claim 10, wherein: The movement of the control element includes moving a control element having a check valve surface, the check valve surface having a large surface area exposed to the fluid pressure of the trap volume; and Opening the outlet includes opening the outlet having a check valve top surface, the check valve top surface having a small surface area exposed to the trapping volume.

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