Patent Description:
Fuel injectors are used in internal combustion engines to inject fuel into the combustion chamber before the air/fuel mixture is ignited. Such fuel injectors are typically made as assemblies of a plurality of components to aid in their manufacture and repair. For example, fuel injector assemblies are often assembled using a nozzle that interfaces with a fuel injector body, as for example disclosed in <CIT>. A joint may be located between the nozzle and the fuel injector body through which fuel at high pressure may leak.

To avoid the need for a face seal at this interface which creates component stack up uncertainty, which may lead to leaks. Also, machining such a face seal feature may be expensive. Any remedy to these problems may be constrained to a solution that is a "drop-in" replacement. That is to say, the fuel injector assembly with such a solution may need to work in existing engines by fitting into an existing envelope.

Also, these fuel injector assemblies may employ solenoid assemblies that activate the injection of the fuel. In some current designs, an effective path for high pressure fuel to flow to a drain is not provided when a problem occurs in the nozzle (e.g. a component becomes stuck). This may result in contamination of fuel into the oil of the engine. Moreover, damage may also occur to the solenoid assembly or other component of the fuel injector.

Again, a remedy to these problems may be constrained so that the solution is a "drop-in" solution.

A fuel injector body for use with a fuel injector according to an embodiment of the present disclosure is provided. The fuel injector body comprises a body that includes an at least partially annular configuration defining a longitudinal axis, a circumferential direction, and a radial direction. A first end is disposed axially along the longitudinal axis, and a second end is disposed axially along the longitudinal axis. A first counterbore and a first cavity extend from the first end toward the second end, and an external interface portion includes a sealing surface that is disposed axially between the first end and a shoulder. The first cavity defines a bottom surface and a peripheral surface, the peripheral surface defining a first cavity diameter, and the sealing surface defining a sealing surface diameter, and a ratio of the sealing surface diameter to the first cavity diameter ranges from <NUM> to <NUM>, as also disclosed in <CIT>. The body further includes a radially outer surface that is disposed radially outwardly from the shoulder, the radially outer surface defining a low pressure drain groove, and the body defining a leak passage extending from the bottom surface to the low pressure drain groove.

Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. In some cases, a reference number will be indicated in this specification and the drawings will show the reference number followed by a letter for example, 100a, 100b or a prime indicator such as <NUM>', <NUM>"etc. It is to be understood that the use of letters or primes immediately after a reference number indicates that these features are similarly shaped and have similar function as is often the case when geometry is mirrored about a plane of symmetry. For ease of explanation in this specification, letters or primes will often not be included herein but may be shown in the drawings to indicate duplications of features discussed within this written specification.

While the application discussed herein is primarily a common rail unit injector, so-called as the fuel is supplied at high pressure from a common source and is not pressurized in the fuel injector, it is to be understood that in other embodiments the fuel injector that uses the same features described herein may be powered to inject in another manner, such as mechanically, hydraulically, or controlled in another manner, etc. Similarly, the type of fuel injected by the injector may be varied and includes diesel fuel, gasoline, etc. Accordingly, the applications of the embodiments discussed herein are applicable to a host of engine types and to a host of machines driven by such engines.

For example, an internal combustion engine <NUM> is shown in <FIG> that may employ various embodiments of the fuel injector assembly. The engine <NUM> may include an engine block <NUM> in which the piston (not shown) reciprocates, and a cylinder head <NUM> that may contain various engine components for the introduction of fluids into the bore/combustion chamber located in the engine block <NUM>.

Turning to <FIG>, a portion of the engine <NUM> is shown sectioned, revealing the combustion chamber <NUM> that may have a generally cylindrical shape that is defined within a cylinder bore <NUM> formed within the crankcase or engine block <NUM> of the engine <NUM>. The combustion chamber <NUM> is further defined at one end by a flame deck surface <NUM> of the cylinder head <NUM>, and at another end by a crown portion <NUM> of a piston 111a that is reciprocally disposed within the bore <NUM>, and is connected to a connecting rod <NUM>, which in turn is connected to a crank shaft (not shown). A fuel injector <NUM> is mounted in the cylinder head <NUM>. The injector <NUM> has a tip <NUM> that protrudes within the combustion chamber <NUM> through the flame deck surface <NUM> such that it can directly inject fuel into the combustion chamber <NUM>.

During operation of the engine <NUM>, air is admitted into the combustion chamber <NUM> via an air inlet passage <NUM> when one or more intake valves <NUM> (one shown) are open during an intake stroke. In a known configuration, high pressure fuel is permitted to flow through nozzle openings in the tip <NUM> to form fuel jets that enter the combustion chamber <NUM>. Each nozzle opening creates a fuel jet <NUM> that generally disperses to create a predetermined fuel/air mixture, which in a compression ignition engine as shown in <FIG> and <FIG> auto-ignites and combusts. The fuel jets <NUM> may be provided from the injector at an included angle β of between <NUM> and <NUM> degrees, but other angles may also be used. In some embodiments, a single nozzle opening may be provided, etc. Following combustion, exhaust gas is expelled from the combustion chamber through an exhaust conduit <NUM> when one or more exhaust valves <NUM> (one shown) is/are open during an exhaust stroke.

The uniformity and extent of fuel/air mixing in the combustion cylinder is relevant to the combustion efficiency as well as to the amount and type of combustion byproducts that are formed. For example, fuel-rich mixtures, which may be locally present within the combustion chamber <NUM> during a combustion event due to insufficient mixing, may lead to higher soot emissions and lower combustion efficiency.

Turning now to <FIG>, a fuel injector assembly <NUM> according to an embodiment of the present disclosure that may be used in the engine <NUM> just described will now be discussed in general terms concerning its construction and operation.

In <FIG>, the fuel injector assembly <NUM> includes a fuel injector body <NUM> that defines a common rail inlet <NUM>, and a nozzle <NUM> that includes an injection outlet <NUM>.

Focusing on fuel injector body <NUM> in <FIG>, it can be seen that it includes a drain outlet <NUM> and a low pressure drain groove 322b that is in fluid communication with the drain outlet <NUM>. The common rail inlet <NUM> may take the form of a conical seat to sealingly engage a quill fluidly connected to a common rail pressure source, but not necessarily so. A solenoid actuator <NUM> (may be an assembly) may be disposed in the injector body <NUM>, and includes an armature <NUM> that moves with respect to a stator assembly <NUM>. Stator assembly <NUM> includes a pole piece <NUM> and a stop pin <NUM> that are flush at an air gap plane <NUM> (only shown in <FIG>).

In <FIG>, the stator assembly <NUM> may be substantially free of empty space between pole piece <NUM> and a centerline (may be the same as the longitudinal axis <NUM> of the fuel injector body <NUM>, but not necessarily so). In addition, the stop pin <NUM> may be surrounded by, but radially spaced apart from, the pole piece <NUM>, such as by a plastic filler material that may also serve to magnetically isolate the stop pin <NUM> from the pole piece <NUM>.

Looking at <FIG> and <FIG> together, the solenoid actuator <NUM> is operably coupled to a check valve member <NUM> that includes a closing hydraulic surface <NUM> exposed to fluid pressure in a pressurized fuel chamber <NUM> that is disposed in the nozzle <NUM>. The check valve member <NUM> is movable between a closed position (as shown) blocking the injection outlet <NUM>, and an open position fluidly connecting the common rail inlet <NUM> to the injection outlet <NUM>. The check valve member <NUM> also includes an opening hydraulic surface <NUM> that is exposed to fluid pressure in the common rail inlet <NUM>, which corresponds to pressure in a common rail (not shown).

As best seen in <FIG>, a control valve member <NUM> may be provide (e.g. a ball) that is unattached to, but trapped between, a push pin <NUM> and a seat <NUM> of a valve plate <NUM>. Control valve member <NUM> is movable between a closed position (as shown) in contact with seat <NUM>, and an open position out of contact with seat <NUM> to fluidly connect the pressurized fuel chamber <NUM> to the drain outlet <NUM>. The push pin <NUM> interacts at one end with armature <NUM> and at its opposite end with control valve member <NUM> to facilitate movement of control valve member <NUM> between its closed and open positions responsive to deenergizing and energizing the solenoid actuator <NUM>, respectively.

Although other structures would fall within the intended scope of the present disclosure, the pressurized fuel chamber <NUM> is shown partially defined by a sleeve <NUM> and an orifice piece <NUM>. A biasing spring <NUM> (see <FIG>) may be operably positioned to simultaneously bias the sleeve <NUM> into contact with the orifice piece <NUM>, and bias the check valve member <NUM> toward its downward closed position, as shown. Other springs 230a, 230b (see <FIG>) may be provided to bias the push pin <NUM> into contact with the seat <NUM>, and to bias the armature <NUM> toward contact with the push pin <NUM> respectively.

When fuel injector assembly <NUM> is in the injection configuration, the common rail inlet <NUM> is fluidly connected (fluid communication) to the drain outlet <NUM> through orifices <NUM> of the orifice piece <NUM> (see <FIG>). These orifices may assist in more abruptly ending injection events by fluidly connecting the pressurized fuel chamber <NUM> to the high pressure in common rail inlet <NUM> at the end of an injection event. That is to say, these orifices <NUM> may be sized to influence the rate at which the needle/check valve member <NUM> lifts from its closed position to its open position by influencing the rate at which fuel escapes to drain outlet <NUM> past control valve member <NUM>. These features may be omitted in other embodiments of the present disclosure.

The operation of this fuel injector assembly <NUM> during an injection event will be discussed later herein in more detail.

With continued reference to <FIG> and <FIG>, an embodiment of a fuel injector assembly <NUM> that may have features for limiting or dealing with leaks will now be discussed.

Starting with <FIG>, the fuel injector assembly <NUM> may comprise a fuel injector component (e.g. a nozzle <NUM>, a sleeve <NUM>) that defines a pressurized fuel chamber <NUM>, and a check valve assembly 214a that is in fluid communication with the pressurized fuel chamber <NUM>. This check valve assembly <NUM> may be disposed in the nozzle <NUM> or sleeve <NUM>, etc..

Also as best seen in <FIG>, a fuel injector body <NUM> may be provided that includes an at least partially annular configuration defining a longitudinal axis <NUM> (may be a centerline), a circumferential direction <NUM>, and a radial direction <NUM>. A first end <NUM> may be disposed along the longitudinal axis, as well as a second end 312a (see <FIG>). The fuel injector body <NUM> may further define a first counterbore <NUM>, and a first cavity 314a (see <FIG>) that extends longitudinally from the first end <NUM> toward the second end 312a, terminating short thereof.

In addition, a nozzle <NUM> may be provided that defines a first longitudinal end <NUM> (see <FIG>), and a second longitudinal end 404a (see FIG. 4a) that is disposed longitudinally adjacent to the first end <NUM> of the fuel injector body <NUM>. The nozzle may define a second counterbore <NUM> with a second cavity 406a that extends longitudinally from the second longitudinal end 404a toward the first longitudinal end <NUM>.

When assembled as best seen in <FIG>, the first end <NUM> of the fuel injector body <NUM> may be disposed in the second counterbore <NUM>, and the second cavity 406a of the nozzle <NUM>, forming an interface region <NUM> with the nozzle <NUM>, and a seam <NUM> between the fuel injector body <NUM> and the nozzle <NUM>. In this region, the fuel injector assembly <NUM> may further define a radial seal receiving groove <NUM> disposed longitudinally along the seam <NUM>. This groove <NUM> may be formed on either the fuel injector body <NUM> or the nozzle <NUM>. Before being assembled into the engine, a seal <NUM> would typically be disposed in the radial seal receiving groove <NUM>.

For the embodiment shown in <FIG>, the second cavity 406a of the nozzle <NUM> includes a radially inner circumferential surface <NUM> that defines the radial seal receiving groove <NUM>.

To provide a robust design, the fuel injector assembly <NUM> may define a minimum seal receiving groove inner diameter <NUM>, a minimum first cavity diameter <NUM> that is defined by a first cavity circumferential surface <NUM>, and a ratio of the minimum seal receiving groove inner diameter <NUM> to the minimum first cavity diameter may range from <NUM> to <NUM>.

More specifically, the fuel injector body <NUM> may define a radial wall thickness <NUM> that is disposed radially between the radial seal receiving groove <NUM>, and the first cavity circumferential surface <NUM> that ranges from <NUM> to <NUM>.

Likewise, the nozzle <NUM> may define a radially outer circumferential surface <NUM>, and a minimum radial wall thickness <NUM> measured radially from the radially outer circumferential surface <NUM> to the radial seal receiving groove <NUM> that ranges from <NUM> to <NUM>.

Looking more closely at the interface region <NUM> in <FIG>, it can be seen that this region includes meshing threads <NUM>. It is contemplated that other forms of interfacing or attaching the nozzle to the fuel injector body are possible, as well as other ratios and dimensional ranges in other embodiments of the present disclosure.

The fuel injector assembly may further comprise a valve plate <NUM> that is disposed in the first cavity 314a, an orifice piece <NUM> that is disposed in the nozzle <NUM> contacting the valve plate <NUM>, and a control valve <NUM> disposed in the fuel injector body <NUM> above the valve plate <NUM> and the orifice piece <NUM>. Other constructions are possible in other embodiments of the present disclosure.

According to the invention as best seen in <FIG> and <FIG>, the fuel injector body <NUM> defines a drain passage <NUM> that is in communication with the first cavity 314a of the fuel injector body <NUM>, as well as a low pressure drain cavity <NUM>.

More particularly as best seen in <FIG>, the fuel injector body <NUM> further defines a radially outer circumferential surface <NUM>, and the low pressure drain cavity <NUM> takes the form of a circumferential groove 322a disposed on the radially outer circumferential surface <NUM> axially between an upper seal <NUM> (see <FIG>), and a lower seal <NUM>.

Focusing on <FIG>, the first cavity 314a may be defined by a bottom surface <NUM> (e.g. a planar annular surface) and the drain passage <NUM> is a bore (e.g. drilled using a convention drill or Electric Discharge Machining, etc.) that extends from the bottom surface <NUM> to the circumferential groove 322a along a direction that forms an oblique angle <NUM> with the longitudinal axis <NUM> in a plane containing the longitudinal axis <NUM>, and the radial direction <NUM> (e.g. the sectioned plane of <FIG>). Other orientations and configurations are possible for the bore in other embodiments of the present disclosure.

Next, components such as a fuel injector body and/or a nozzle that may be supplied as a replacement part to repair, refurbish, or retrofit a fuel injector assembly will now be discussed with reference to <FIG> and <FIG>.

Such a fuel injector body <NUM> shown in <FIG> may include an external interface portion <NUM> including a sealing surface <NUM> that is disposed axially between the first end <NUM>, and a shoulder <NUM>. More particularly, an externally threaded portion <NUM> may be disposed axially between the sealing surface <NUM>, and the shoulder <NUM>.

As mentioned previously, the first cavity 314a defines a bottom surface <NUM>, and a peripheral surface <NUM> defining a first cavity diameter 316a. Also, the sealing surface <NUM> may define a sealing surface diameter <NUM>, and a ratio of the sealing surface diameter <NUM> to the first cavity diameter <NUM> may range from <NUM> to <NUM> in some embodiments. In such embodiments, the body may define a radial thickness <NUM> from the sealing surface <NUM> to the peripheral surface <NUM> ranging from <NUM> to <NUM>. This may not be the case in other embodiments of the present disclosure.

According to the invention, the first cavity 314a may define a first cavity axial depth <NUM> from the bottom surface <NUM> to the first end <NUM>, and a ratio of the sealing surface diameter <NUM> to the first cavity axial depth <NUM> ranges from <NUM> to <NUM>. In such a case, the first cavity axial depth <NUM> may range from <NUM> to <NUM>. Other configurations, dimensions, and ratios are possible in other embodiments of the present disclosure.

As also alluded to earlier herein, a radially outer surface 324a is disposed radially outwardly from the shoulder <NUM> that defines a low pressure drain groove 322b (see <FIG>). A leak passage 320a extends from the bottom surface <NUM> to the low pressure drain groove 322b, which in turn is in communication with the drain outlet <NUM> (see <FIG>). High pressure may thus be relieved when a problem occurs, minimizing the risk of further damage to the components of the fuel injector assembly.

Looking at <FIG>, a replacement nozzle <NUM> (may be an assembly as shown) may include a body that includes at least a partially stepped annular configuration that defines a radial direction, a circumferential direction, and a longitudinal axis as previously described with reference to the fuel injector body <NUM>.

The nozzle <NUM> may include a first longitudinal end <NUM>, and a second longitudinal and 404a. An attachment portion <NUM> may be disposed at the second longitudinal end 404a, while a tip portion <NUM> with the injection outlet <NUM> may be disposed at the first longitudinal end <NUM>.

Specifically as best seen in <FIG>, the attachment portion <NUM> may include a fuel injector body receiving cavity <NUM> defining an inner circumferential surface <NUM> (may include any surface of revolution including conical, cylindrical, etc.) that includes internal threads <NUM> extending from the second longitudinal end 404a, and that defines a seal receiving groove <NUM> that is disposed axially below the internal threads <NUM>.

To provide a robust design, the attachment portion <NUM> may include a maximum radial wall thickness <NUM> (e.g. slightly above or below the seal receiving groove <NUM>) disposed circumferentially about the fuel injector body receiving cavity <NUM>, and a minimum radial wall thickness <NUM> disposed circumferentially about the fuel injector body receiving cavity <NUM> (e.g. at the seal receiving groove <NUM>). A ratio of the maximum radial wall thickness <NUM> to the minimum radial wall thickness <NUM> may range from <NUM> to <NUM> in some embodiments. In such a case, the maximum radial wall thickness <NUM> may range from <NUM> to <NUM>, while the minimum radial wall thickness <NUM> may range from <NUM> to <NUM>. In order to provide adequate sealing, the seal receiving groove <NUM> may be spaced away from the internal threads <NUM> a minimum axial distance <NUM> (see <FIG>) that ranges from <NUM> to <NUM>. Other configurations, dimensional ratios, and dimensions are possible in other embodiments of the present disclosure.

Now, another embodiment of a fuel injector focused on providing pressure relief in the nozzle and the nozzle/fuel injector body interface will be discussed while looking at <FIG> and <FIG>.

As alluded to earlier herein, the fuel injector body <NUM> of the fuel injector assembly <NUM> may be disposed in the second counterbore <NUM>, and the second cavity 406a of the nozzle <NUM>, forming an interface region <NUM> with the nozzle <NUM>, and a seam <NUM> between the fuel injector body <NUM>, and the nozzle <NUM>. The fuel injector body may further define a supply passage <NUM> in communication with the pressurized fuel chamber <NUM> and the common rail inlet <NUM> for supplying the fuel. Also, a leak passage 320a may extend from the first cavity 314a.

As best seen in <FIG>, the fuel injector body <NUM> defines a bottom surface <NUM> of the first cavity 314a, and the leak passage 320a may extend from the bottom surface <NUM> radially on one side of the longitudinal axis <NUM>, while the supply passage <NUM> extends to the bottom surface <NUM> radially on the other side of the longitudinal axis <NUM> in a plane containing the radial direction <NUM>, and the longitudinal axis <NUM> (e.g. in the sectioned plane of <FIG>).

In addition in <FIG>, the fuel injector body <NUM> may include an outer peripheral surface <NUM> that that is disposed radially outwardly from the nozzle <NUM>. The outer peripheral surface <NUM> may define a low pressure drain groove 322b that is in communication with the leak passage 320a. A valve plate <NUM> may be disposed in the first cavity 314a, including an abutting sealing surface <NUM> facing the bottom surface <NUM> of the first cavity 314a. This abutting sealing surface <NUM> may define a reservoir <NUM> that is in communication with the leak passage 320a, as well as a thru-passage <NUM> (see <FIG>) that fluidly connects the supply passage <NUM> to the pressurized fuel chamber <NUM>. The leak passage, the thru-passage, and the supply passage may all extend along directions that are oblique to the longitudinal axis and radial direction. Also, the supply passage and thru-passage may be oblique to each other (i.e. not straight with respect to each other). Other configurations are possible in other embodiments of the present disclosure.

In <FIG>, the leak passage 320a may take the form of a straight bore (e.g. cylindrical) that is machined or otherwise formed into the fuel injector body <NUM>. As such, the leak passage 320a may define a passage diameter <NUM>, and the first cavity 314a may define a first cavity diameter 316a (see <FIG>). A ratio of the first cavity diameter 316a to the passage diameter <NUM> may range from <NUM> to <NUM> in certain embodiments of the present disclosure. In such a case, the leak passage diameter may range from <NUM> to <NUM>. Other ranges are possible in other embodiments of the present disclosure.

For some embodiments of the fuel injector body of the present disclosure, these following features may also be present.

As alluded to previously, the fuel injector assembly <NUM> may further define a radial seal receiving groove <NUM> that is disposed longitudinally along the seam <NUM> (see <FIG>) with a seal <NUM> that is disposed in the radial seal receiving groove <NUM>. The radial seal receiving groove may be disposed axially below the bottom surface <NUM> of the first cavity 314a, but not necessarily so. For the embodiment shown in the figures, the second cavity 406a of the nozzle <NUM> includes a radially inner circumferential surface 422a that defines the radial seal receiving groove <NUM>. This may not be the case for other embodiments of the present disclosure.

Various embodiments of a fuel injector body that may be provided as a replacement part, etc. for the fuel injector assembly just described will now be discussed with reference to <FIG>.

The fuel injector body <NUM> may include an external interface portion <NUM> including a sealing surface <NUM> that is disposed axially between the first end <NUM> and a shoulder <NUM>. The first cavity 314a defines a bottom surface <NUM> and a peripheral surface <NUM>, while a leak passage 320a extends from the bottom surface <NUM> that is in communication with the first cavity 314a.

In some embodiments, the leak passage 320a extends along a direction that is oblique to the radial direction <NUM>, and the longitudinal axis <NUM>. In particular embodiments, the direction along which the leak passage extends is in the same plane as the radial direction and the longitudinal axis (e.g. the sectioned plane of <FIG>). This may not be the case in other embodiments of the present disclosure. The fuel injector body <NUM> may further define a supply passage <NUM> that extends to the first cavity 314a as seen in <FIG>, but not necessarily so.

In certain embodiments as seen in <FIG>, the fuel injector body <NUM> may include a stepped configuration including a side circumferential surface 324b (e.g. any surface of revolution including a conical surface, a cylindrical surface) that is spaced radially and axially away from the shoulder <NUM>, and the external interface portion <NUM>. The side circumferential surface 324b defines a low pressure drain groove 322b, and the leak passage 320a extends to the low pressure drain groove <NUM>. More specifically, the low pressure drain groove 322b defines a corner <NUM>, and the leak passage 320a may extend to the corner <NUM> as shown, or some other portion of the groove such as its bottom surface, its side surface, etc..

In other embodiments, the fuel injector body <NUM> has an external male attachment portion 334a including a sealing surface <NUM> that is disposed axially between the first end <NUM>, and a shoulder <NUM>.

The peripheral surface <NUM> defines a cavity diameter 316a, and the sealing surface defines a sealing surface diameter <NUM>, and a ratio of the sealing surface diameter <NUM> to the cavity diameter <NUM> may range from <NUM> to <NUM> in some embodiments of the present disclosure.

The external male attachment portion 334a includes external threads 344a that are disposed axially between the sealing surface <NUM> and the shoulder <NUM>. A wall <NUM> is disposed circumferentially about the first cavity 314a, defining a minimum radial wall thickness 318a, and a maximum axial wall height <NUM> (see <FIG>). In such a case, the minimum radial wall thickness 318a may range from <NUM> to <NUM>, and the maximum axial wall height <NUM> may range from <NUM> to <NUM>.

The fuel injector body and the nozzle may be made from similar materials such as steel.

In practice, a nozzle, a fuel injector body and/or a fuel injector assembly according to any embodiment described herein may be provided, sold, manufactured, and bought etc. to refurbish, retrofit or remanufacture existing fuel injector assemblies in the field. Similarly, a fuel injector assembly may also be provided, sold, manufactured, and bought, etc. to provide a new fuel injector that includes such a nozzle, a fuel injector body, or a fuel injector assembly. The fuel injector body, the nozzle, or fuel injector assembly may be new or refurbished, remanufactured, etc..

The present disclosure finds general applicability to fuel injectors for common rail fueling applications. The present disclosure finds specific application to common rail fuel injectors used in compression ignition engines. However, other applications in other types of engines and other types of fuel injectors are contemplated to be within the scope of the present disclosure.

In operation between injection events, fuel injector assembly <NUM> will be in a rest configuration, as shown. When in the rest configuration, solenoid actuator <NUM> is de-energized, armature <NUM> is in contact with push pin <NUM>, and control valve member <NUM> is in its closed position in contact with the seat <NUM>. In addition, in the rest configuration the check valve member <NUM> is in its downward closed position blocking the nozzle injection outlet <NUM>. Also, in the rest configuration the pressure in the pressurized fuel chamber <NUM> is high such that rail pressure may be acting on both the closing hydraulic surface <NUM> and the opening hydraulic surface <NUM>.

An injection event is initiated by energizing solenoid actuator <NUM>. When this occurs, the pole piece <NUM> magnetically attracts the armature <NUM>. As the armature <NUM> begins moving toward stator assembly <NUM>, push pin <NUM> is lifted to allow the high pressure in pressurized fuel chamber <NUM> to push control valve member <NUM> off of the seat <NUM> to fluidly connect the pressurized fuel chamber <NUM> to the low pressure of drain outlet <NUM>. The motion of armature <NUM> will stop when sit contacts the stop pin <NUM>. When pressure in pressurized fuel chamber <NUM> drops sufficiently, the high pressure acting on opening hydraulic surface <NUM> pushes check valve member <NUM> upward against the action of biasing spring <NUM> to commence an injection event. When fuel injector is in the injection configuration, check valve member <NUM> is in its upward open position, control valve member <NUM> is in its open position out of contact with the seat <NUM>, and push pin <NUM> is in contact with stop pin <NUM> and armature <NUM>, with armature <NUM> being at a final air gap distance away from stator assembly <NUM>.

During the injection event, pressures in the nozzle and fuel injector body may be high. The embodiments discussed herein may help to prevent the leaking of fuel at the interface between the nozzle and the fuel injector body, and/or may help to provide pressure relief so that fuel injector components are not damaged if a problem occurs such as a stuck component. In some applications such as common rail applications, the pressure in the nozzle and high pressure passage in the body may be high, not just during the injection event. When the ball (which may take the form of a flattened geometry to form a seat as shown in the drawings) lifts, the pressure on top of the check valve may be evacuated, inducing a pressure imbalance, allowing the check valve ball to lift, opening the tip to the check valve seat, allowing the injection event to occur.

It will be appreciated that the foregoing description provides examples of the disclosed assembly and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.

Claim 1:
A fuel injector body (<NUM>) for use with a fuel injector, the fuel injector body (<NUM>) comprising:
a body that includes an at least partially annular configuration defining a longitudinal axis (<NUM>), a circumferential direction (<NUM>), and a radial direction (<NUM>);
a first end (<NUM>) that is disposed axially along the longitudinal axis (<NUM>), and a second end (312a) that is disposed axially along the longitudinal axis (<NUM>);
a first counterbore (<NUM>) and a first cavity that extends from the first end (<NUM>) toward the second end (312a); and
an external interface portion (<NUM>) including a sealing surface (<NUM>) that is disposed axially between the first end (<NUM>) and a shoulder (<NUM>);
wherein the first cavity (314a) defines a bottom surface (<NUM>) and a peripheral surface (<NUM>), the peripheral surface (<NUM>) defining a first cavity diameter (316a), and the sealing surface (<NUM>) defining a sealing surface diameter (<NUM>), and a ratio of the sealing surface diameter (<NUM>) to the first cavity diameter (316a) ranges from <NUM> to <NUM>;
characterised in that the body further includes a radially outer surface (324a) that is disposed radially outwardly from the shoulder (<NUM>), the radially outer surface (324a) defining a low pressure drain groove (322b), and the body defining a leak passage (320a) extending from the bottom surface (<NUM>) to the low pressure drain groove (322b).