Fuel injector having a self-contained replaceable pilot valve assembly

A fuel injector device for injecting fuel into a combustion chamber of an internal combustion engine is provided. Included in the fuel injector is a body having a chamber and a pilot valve assembly including a seat retainer configured to be detachably insertable into the chamber of the body. A pilot valve seat is disposed in the seat retainer and substantially enclosed by the seat retainer. A stator assembly is disposed in the seat retainer and at least partially enclosed by the seat retainer. The pilot valve seat and the stator assembly in the pilot valve assembly are replaceable as a single unit of the pilot valve assembly for the fuel injector.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to common-rail fuel injector devices for injecting fuel into a combustion chamber of an internal combustion engine, and more particularly to a fuel injector having a self-contained replaceable pilot valve assembly.

BACKGROUND OF THE DISCLOSURE

An introduction of fuel into cylinders of an internal combustion engine is most commonly achieved using fuel injectors. A commonly used injector is a closed-nozzle injector which includes a nozzle assembly having a spring-biased needle valve element positioned adjacent the injector nozzle for allowing fuel to be injected into the cylinder of an internal combustion engine. The needle valve element also functions to provide a deliberate, abrupt end to fuel injection. The needle valve is positioned in the injector body and although biased downward by a spring force, a hydraulic force acting on the needle valve primarily holds the needle valve in the closed position. When an actuated force exceeds the biasing hydraulic force or causes a change in the magnitude of the hydraulic force, the needle valve element moves to allow fuel to pass through the injector nozzle, thus marking the beginning of the fuel injection event.

Manufacturers have implemented extra high pressure injection systems, also known as XPI, where the pressures can reach 2600 bar. Such high injection pressures cause wear and tear conditions in the injectors. During operation, the fuel injectors may need maintenance and/or replacement work depending on a degree of the wear and tear conditions of components of the injectors. Conventional injectors are typically serviceable only with special tools at designated service locations, and are difficult to replace, thereby increasing maintenance costs and time. Thus, vehicles having the injectors must be brought into the designated service locations and wait for the maintenance crew. Further, as injection pressures increase, greater forces must be applied to the injector components to achieve the required sealing at component interfaces/joints. Conventional injectors often include internal component configurations which are well suited to achieving desired high pressure performance characteristics but do so at high design and manufacturing costs. Accordingly, there is a need for an enhanced fuel injector that addresses one or more of the drawbacks of conventional injectors.

SUMMARY OF THE DISCLOSURE

In one embodiment of the present disclosure, a fuel injector includes a body having a chamber and a pilot valve assembly including a seat retainer configured to be detachably insertable into the chamber of the body. A pilot valve seat is disposed in the seat retainer and substantially enclosed by the seat retainer. A stator assembly is disposed in the seat retainer and at least partially enclosed by the seat retainer. The pilot valve seat and the stator assembly in the pilot valve assembly are replaceable as a single unit of the pilot valve assembly for the fuel injector.

In one aspect of the embodiment, no portion of the pilot valve seat is exposed outside of the seat retainer. In another aspect of the embodiment, the seat retainer and the stator assembly are integrated as a unitary unit. In one embodiment, a lower portion of the seat retainer includes a retainer central passage extending longitudinally from a lower end of the seat retainer toward an upper end of the seat retainer. The pilot valve seat includes a valve seat central passage extending longitudinally from a lower end of the pilot valve seat toward an upper end of the pilot valve seat. The valve seat central passage is fluidly coupled to the retainer central passage of the seat retainer. In another embodiment, an inner cavity within the chamber of the body is configured for receiving, at least partially, a lower end of the seat retainer.

In yet another aspect of the embodiment, the pilot valve assembly includes an armature assembly disposed in the seat retainer and a guide support disposed in the seat retainer between the armature assembly and the pilot valve seat. In one example, the stator assembly includes a solenoid disposed directly above the armature assembly, and the solenoid has an active state in which the armature assembly is in an upward position and an inactive state in which the armature assembly is in a downward position. In another example, the armature assembly is positioned within the chamber and includes a plunger central bore configured for receiving a plunger. In yet another example, the guide support has an inner bore configured to receive an armature spring and a lower end of the armature assembly. In one embodiment, a lower end of the guide support includes a radially inclined inner surface having a wider opening relative to a longitudinal axis of the guide support toward an edge of the lower end. In another embodiment, the radially inclined inner surface of the guide support is configured to matingly receive an upper portion of the pilot valve seat.

In another embodiment of the present disclosure, a fuel injector includes a body having an upper chamber and a lower chamber, and an armature assembly disposed in the upper chamber. A seat retainer having an inner chamber is configured to receive the armature assembly. A pilot valve seat is inserted into the inner chamber of the seat retainer. In one example, the pilot valve seat is attached to the seat retainer using at least one coupling mechanism to permit replacement of the pilot valve seat and the seat retainer as a single unit for the fuel injector.

In one aspect of the embodiment, the at least one coupling mechanism is a threaded fastener. In another aspect of the embodiment, the at least one coupling mechanism is a snap ring.

While multiple embodiments are disclosed, still other embodiments of the present disclosure will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the present disclosure. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

While the present disclosure is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the present disclosure to the particular embodiments described. On the contrary, the present disclosure is intended to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the present disclosure is practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present disclosure, and it is to be understood that other embodiments can be utilized and that structural changes can be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and their equivalents.

FIG. 1shows a cross-sectional view of a prior art mid-range XPI fuel injector100. Fuel injector100generally includes an armature assembly110, a plunger112, an injector body114, and a needle valve116. Injector body114includes upper chamber146and lower chamber144for receiving a plurality of components therein. The disclosed embodiment provides an inner cavity within lower chamber144for receiving needle valve116, a needle sleeve124, a needle spring150, a needle seal136, a pilot valve seat128, and a check ball122. The disclosed embodiment further provides an inner cavity within upper chamber146for receiving armature assembly110, plunger112, an armature spring152, a spring disk138, and a stator assembly120. Upper chamber146is a low pressure environment of fuel injector100relative to the high pressure environment below check ball122.

Stator assembly120is fixed within the upper chamber146and retained in place by retainer140. In the disclosed embodiment, the bottom surface of stator assembly120is a precision calibrated distance away from armature assembly110. The other end of armature assembly110is supported via abutting engagement with check ball retainer142.

The middle section of plunger112includes an angled shoulder disposed on the upper surface of armature assembly110thereby creating a reciprocal connection such that when armature assembly110moves in the upward direction plunger112moves therewith. Armature spring152is biased against the flanged elements of armature assembly110and biases armature assembly110and plunger112in an upward direction. Armature assembly110is positioned within an inner cavity of upper chamber146and further includes central bore160for receiving the shaft of plunger112there through. The outer diameter of the shaft of plunger112is sized and configured to provide a close or match fit in relation to the inner diameter of central bore160while still permitting sliding movement of plunger112. This close/match fit inhibits fuel leakage between the outer diameter of the shaft of plunger112and the inner diameter of central bore160while permitting relative sliding movement.

Injector body114also includes lower chamber144which further includes an inner cavity that houses needle valve116, needle sleeve124, needle spring150, needle seal136, pilot valve seat128, and check ball122. Needle spring150biases needle valve116in a downward direction and applies a closing spring force to needle valve116thereby preventing fuel from exiting through injector orifice158when solenoid132is inactive. Needle seal136includes control orifices148integrated within the seal. Needle seal136is disposed above needle valve116and includes end points that terminate adjacent needle sleeve124. The surface of the lower end of pilot valve seat128abuts the top surface of needle seal136, while the surface of the upper end of pilot valve seat128is disposed immediately below armature spring152. Pilot valve seat128further includes valve seat central passage129. Valve seat central passage129extends longitudinally from the lower end of pilot valve seat128toward the upper end. Pilot valve seat128is held in place against the upwardly acting fuel pressure by a threaded seat retainer154.

Lower chamber144further includes fuel entry orifice156which is configured to supply fuel to the inner cavity of lower chamber144. The inner cavity as well as cross drilled fluid channels126in needle valve116facilitates fuel flow throughout lower chamber144. The fuel supply pressure may be within a pressure range of approximately 500-2600 bar. Control orifices148function to route fuel flow up valve seat central passage129. When coils118are de-energized and solenoid132is in an inactive state, check ball122is in sealing engagement with pilot valve seat128. Check ball122also functions as a moveable valve member and thus moves out of sealing engagement with pilot valve seat128. When check ball122is in sealing engagement with pilot valve seat128, fuel from lower chamber144is blocked from entering upper chamber146. When fuel is supplied to lower chamber144and check ball122is in sealing engagement with pilot valve seat128the inner cavity of lower chamber144becomes a highly pressurized volume. When check ball122functions as a moveable valve member and moves out of sealing engagement with pilot valve seat128, high pressure fuel flows up valve seat central passage129through pilot valve seat128and into the inner cavity of upper chamber146.

Injector100utilizes needle valve116in a normally closed position. When needle valve116is in its normally closed position, coils118are de-energized and solenoid132is in an inactive state. Additionally, plunger return spring162exerts a spring force downwardly such that plunger112and armature assembly110exert a downward force on check ball retainer142which thus secures and retains check ball122into sealing engagement with pilot valve seat128. Pressurized fuel is continuously supplied to the inner cavity of lower chamber144.

When coils118are de-energized fuel from lower chamber144is blocked from entering upper chamber146thus the inner cavity of lower chamber144becomes highly pressurized. Due to the fuel supply pressure acting downwardly on needle valve116, a large downward hydraulic force pushes needle valve116in the downward direction. Needle spring150also is positioned in the inner cavity of lower chamber144and is compressed about the upper end of needle valve116such that when solenoid132is inactive, high pressure fuel as well as a downward spring force on needle valve116both act to secure needle valve116against needle valve seat164. Securing needle valve116against needle valve seat164prevents high pressure fuel from exiting injector100via injector orifice158.

For a fuel injection, injector100requires an intermediate pressure or force loss, such as depressurizing the pressurized control volume by creating a low pressure drain flow from the control volume. The beginning of an injection event is initiated by energizing coils118with an electric current. As coils118of solenoid132are energized the solenoid acts as a type of electromagnet which then causes armature assembly110to rapidly move upwardly in magnetic attraction with solenoid132. Because plunger112is disposed atop armature assembly110, the strength of the solenoid's magnetic force acting on armature assembly110further causes plunger112to move upwardly against the downward biasing force of plunger return spring162. When coils118are energized solenoid132is in an active state thereby causing armature assembly110and plunger112to move to an upward position, permitting movement of check ball122out of sealing engagement with pilot valve seat128. During an injection event, check ball122functions as a moveable valve member, and when it moves out of sealing engagement with pilot valve seat128, high pressure fuel residing in valve seat central passage129flows through pilot valve seat128into the inner cavity of upper chamber146.

The flow of high pressure fuel from the inner cavity of lower chamber144to the inner cavity of upper chamber146creates a pressure differential. The pressure difference between the high fuel supply pressure in lower chamber144and the low pressure in upper chamber146results in significant hydraulic force acting in a direction to lift needle valve116and allow an injection event. Needle valve116is therefore lifted off needle valve seat164allowing fuel to be injected into the engine combustion chamber via injector orifice158which may contain various spray outlet arrangements.

The fuel injection event is ended by de-energizing coils118, which results in solenoid132being inactive and thus causing the downward force of plunger return spring162to force plunger112to exert a downward force on armature assembly110. The downward force exerted on armature assembly110via plunger return spring162forces check ball122back into sealing engagement with pilot valve seat128. When check ball122is in sealing engagement with pilot valve seat128, high pressure fuel from lower chamber144is once again blocked from entering the inner cavity of upper chamber146. As fuel is continuously supplied to lower chamber144and with check ball122in sealing engagement with pilot valve seat128, the inner cavity of lower chamber144again becomes highly pressurized. The seal created by check ball122as well as the high pressure fuel supplied to the inner cavity of lower chamber144both combine to produce a highly pressurized control volume in lower chamber144. Due to the fuel supply pressure acting downwardly on needle valve116, a large downward hydraulic force pushes needle valve116back to the downward direction. Needle spring150further applies a downward biasing spring force in order to expedite seating needle valve116against needle valve seat164, thus preventing high pressure fuel from exiting injector100and ending the injection event.

FIG. 2shows an exemplary embodiment of the present disclosure designed to overcome one or more shortcomings of conventional injectors and/or offer features noted herein below. Like reference numerals represent like elements shown inFIG. 1. Fuel injector200includes a self-contained replaceable pilot valve assembly202being detachably insertable into upper chamber146of injector body114. Advantageously, self-contained replaceable pilot valve assembly202is readily exchangeable from fuel injector200to another injector as desired. In this configuration, stator assembly120and a pilot valve seat204are constructed and arranged to be replaceable as a single unit in self-contained replaceable pilot valve assembly202. As such, self-contained replaceable pilot valve assembly202is exchangeable while operating in the field without having to be replaced in the designated service locations by the maintenance crew. Another advantage is that self-contained replaceable pilot valve assembly202can also be installed in a conventional injector, such as fuel injector100. In other words, originals parts of the conventional injector can be removed and exchanged with self-contained replaceable pilot valve assembly202out in the field.

More specifically, pilot valve seat204of fuel injector200is smaller than pilot valve seat128of fuel injector100, and is disposed within a seat retainer206of self-contained replaceable pilot valve assembly202. Seat retainer206can be threadably attached to injector body114, but can also be attached by, for example, glue, friction fit, snap fit, or other similar rigid coupling mechanism. In this example, pilot valve seat204is substantially enclosed by seat retainer206such that no portion of pilot valve seat204is exposed outside of seat retainer206. In another example, pilot valve seat204is fully enclosed by seat retainer206. For example, seat retainer206and stator assembly120are fully integrated as a unitary unit. In contrast, as shown inFIG. 1, a lower portion of pilot valve seat128of fuel injector100is exposed out of threaded retainer154. This particular configuration of pilot valve seat204and seat retainer206allows for easy replacement of damaged or worn-out self-contained replaceable pilot valve assembly202. A lower portion of seat retainer206includes a retainer central passage208extending longitudinally from a lower end of seat retainer206toward an upper end of seat retainer206. When assembled, a valve seat central passage210of pilot valve seat204is fluidly coupled to retainer central passage208of seat retainer206such that fuel can flow up from control orifices148of needle seal136to an inner chamber of seat retainer206via retainer central passage208and valve seat central passage210.

Self-contained replaceable pilot valve assembly202generally includes pilot valve seat204, seat retainer206, armature assembly110, plunger112, stator assembly120, and a guide support220. Other components, such as check ball122, check ball retainer142, armature spring152, spring disk138, and the like, as shown inFIG. 2, are also included in self-contained replaceable pilot valve assembly202. Pilot valve seat204further includes an inlet end212, an outlet end214, and valve seat central passage210. As discussed above, injector body114includes upper chamber146and lower chamber144for receiving a plurality of components therein, such as self-contained replaceable pilot valve assembly202. The disclosed embodiment provides an inner cavity within upper chamber146for receiving stator assembly120, solenoid132, coil118, armature spring152, and plunger return spring162. In this example, an inner cavity within upper chamber146is configured for receiving, at least partially, the lower end of seat retainer206. As with fuel injector100, upper chamber146is a low pressure environment of fuel injector200relative to the high pressure environment below pilot valve seat204and the lower end of seat retainer206.

In one embodiment, a bottom surface of stator assembly120has a precision calibrated distance from one end of armature assembly110. The distance between stator assembly120and armature assembly110is indicated by a stroke gap216. An exemplary distance of stroke gap216is approximately 47 microns. After extended use of fuel injector200, the distance of stroke gap216can change over time (e.g., become larger or smaller) causing an inaccurate operation of the fuel injection event. Recalibrating stroke gap216in the field can be difficult without proper tools. However, it is advantageous that an old self-contained replaceable pilot valve assembly202can readily be replaced with a new self-contained replaceable pilot valve assembly202for either fuel injector200or fuel injector100.

Stator assembly120further includes solenoid132disposed directly above armature assembly110, wherein solenoid132has an active state in which armature assembly110moves to an upward position and an inactive state in which armature assembly110moves to a downward position. Armature assembly110is positioned within the inner cavity of upper chamber146and further includes a plunger central bore218for receiving plunger112there through.

Plunger112includes a shaft portion disposed within plunger central bore218of armature assembly110for creating a reciprocal connection such that when armature assembly110moves in the upward direction, plunger112moves therewith. An outer diameter of the shaft of plunger112is sized and configured to provide a close or match fit in relation to an inner diameter of plunger central bore218while still permitting sliding movement of plunger112. This close/match fit inhibits fuel leakage between the outer diameter of the shaft of plunger112and the inner diameter of plunger central bore218while permitting relative sliding movement. Armature assembly110further includes flanged elements disposed directly below solenoid132and coils118. Armature spring152is biased against the flanged elements of armature assembly110and biases armature assembly110and plunger112in an upwardly direction.

Guide support220is disposed below the flanged elements of armature assembly100between spring disk138and pilot valve seat204, and has an inner bore222configured to receive armature spring152and a lower end of armature assembly110. In one embodiment, a lower end of guide support220includes a radially inclined inner surface224having a wider opening relative to a longitudinal axis of guide support220toward an edge of the lower end. Radially inclined inner surface224is configured to matingly receive an upper portion of pilot valve seat204having a corresponding sloped or angled outer surface226such that pilot valve seat204is securely held by guide support220during operation.

As similarly with fuel injector100, when coils118are de-energized and solenoid132is in an inactive state, check ball122is in sealing engagement with pilot valve seat204. Check ball122also functions as a moveable valve member and thus moves out of sealing engagement with pilot valve seat204. When check ball122is in sealing engagement with pilot valve seat204, fuel from lower chamber144is blocked from entering upper chamber146. When fuel is supplied to lower chamber144and check ball122is in sealing engagement with pilot valve seat204, the inner cavity of lower chamber144becomes a highly pressurized volume. When check ball122functions as a moveable valve member and moves out of sealing engagement with pilot valve seat204, high pressure fuel flows up retainer central passage208and valve seat central passage210and into the inner chamber of seat retainer206.

When coils118are energized solenoid132is in an active state thereby causing armature assembly110and plunger112to move to an upward position, permitting movement of check ball122out of sealing engagement with pilot valve seat204. During an injection event, check ball122functions as a moveable valve member, and when it moves out of sealing engagement with pilot valve seat204, high pressure fuel residing in retainer central passage208and valve seat central passage210flows through seat retainer206and pilot valve seat204into the inner chamber of seat retainer206.

FIG. 3is a cross-sectional view of fuel injector300which includes a plurality of fasteners302according to the present disclosure. Fuel injector300is a variant of fuel injector200and generally includes elements of fuel injector100. Like reference numerals represent like elements shown inFIG. 1. One aspect of fuel injector300is that a first coupling mechanism, such as fasteners302, are used to fixedly and removably attach threaded retainer154to pilot valve seat128. In this example, fasteners302are threaded bolts, but any other suitable fastener types known in the art can be used to suit different applications. In this configuration, components associated with threaded retainer154and pilot valve seat128are replaceable as a single unit.

FIG. 4is a cross-sectional view of fuel injector400which includes at least one snap ring402according to the present disclosure. Fuel injector400is another variant of fuel injector200and generally includes elements of fuel injector100. Like reference numerals represent like elements shown inFIG. 1. One aspect of fuel injector400is that a second coupling mechanism, such as a snap ring402, is used to fixedly and removably attach threaded retainer154to pilot valve seat128. In this example, snap ring402is disposed between an inner surface of threaded retainer154and an outer surface of pilot valve seat128for facilitating secure attachment between threaded retainer154and pilot valve seat128. Again, in this configuration, components associated with threaded retainer154and pilot valve seat128are replaceable as a single unit.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. For example, it is contemplated that features described in association with one embodiment are optionally employed in addition or as an alternative to features described in associate with another embodiment. The scope of the present disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.