High-pressure fuel pump

Abstract

The invention relates to a fuel pump (1) comprising a main body (2) that defines: - a pumping chamber (3) with a pumping plunger (4) arranged to reciprocate within the pumping chamber (3); - an inlet passage (5) at least indirectly connecting a low-pressure inlet of the fuel pump (1) to the pumping chamber (3), an inlet valve (6) being adapted to selectively enable flow through the inlet passage (5) to the pumping chamber (3); and - a receptacle (9), which is open towards a distal side (D) and which extends into the main body (2) along an axially aligned outlet axis (A) towards a proximal side (P) so that the receptacle (9) communicates with the pumping chamber (3); wherein an outlet passage (12) at least indirectly connects the pumping chamber (3) to a high-pressure outlet (13) of the fuel pump (1), an outlet valve (25) being adapted to selectively enable flow through the outlet passage (12) to the outlet (13), wherein an outlet-valve body (20), which at least partially defines the outlet passage (12) and comprises an outlet-valve seat (26), is at least partially received in the receptacle (9) and is connected to the main body (2) in a fuel-tight manner, an outlet-valve member (27) being adapted to engage the outlet-valve seat (26) in a closed position to close the outlet passage (12). In order improve the design of a fuel pump with an integrated outlet valve, the invention provides that a main body locking portion (2.1) of the main body (2) and an outlet-valve locking portion (20.1) of the outlet-valve body (20) engage each other via at least one elastic retainer element (15) which establishes a form-fit connection between the main body (2) and the outlet-valve body (20) with respect to the axial direction, whereby removal of the outlet-valve body (20) is prevented.

Description

P-DELPHI-443 / WO 1High-Pressure Fuel PumpFIELD OF THE INVENTION

[0001] The present invention generally relates to fuel delivery systems for combustion engines and more particularly to a fuel pump adapted to pressurize fuel at several hundred bars.BACKGROUND OF THE INVENTION

[0002] Fuel systems in modern internal combustion engines fueled by gasoline, particularly for use in the automotive market, mostly employ gasoline direct injection (GDI). In these systems, fuel injectors inject fuel directly into combustion chambers of the internal combustion engine. Commonly, fuel from a fuel tank is supplied under relatively low pressure by a low-pressure fuel pump which is typically an electric fuel pump located within the fuel tank. The low- pressure fuel pump supplies the fuel to a high-pressure fuel pump (also referred to as GDI pump), which typically includes a pumping plunger which is reciprocated by a camshaft of the internal combustion engine. During an intake stroke, fuel is sucked into the pumping chamber, and in a subsequent pumping stroke, the pumping plunger further pressurizes the fuel so that it can be supplied at high pressure to the fuel injectors.

[0003] For safe operation, the GDI pump includes a relief passage with an embedded relief valve to avoid any overpressure that could burst the pump or any part of the high-pressure system behind the pump (fuel rail, pipes and / or injectors) as well as limiting the pressure so that the pressure never reaches the injector Maximum Opening Pressure (MOP). In order to avoid backflow from the fuel rail into the pumping chamber, the fuel pump also comprises an outlet valve, which is disposed in an outlet passage on a high-pressure side of the pumping chamber. According to one known design, the outlet valve comprises an outletvalve body that is press-fitted into a receptacle of a main body of the fuel pump. Although press-fitting allows for a fuel-tight connection, this connection only relies on frictional forces. It has been observed that during operation of the fuel pump, e.g., due to pressure cycles and intense vibrations over a long period of time, theP-DELPHI-443 / WO 2 press-fit connection may fail. That is the outlet-valve body is displaced, leading to fuel leakage past the outlet valve, which impairs the function of the fuel pump and the entire engine system.OBJECT OF THE INVENTION

[0004] The object of the present invention is to improve the design of a fuel pump with an integrated outlet valve.

[0005] This object is achieved by a fuel pump according to claim 1 .SUMMARY OF THE INVENTION

[0006] The present invention relates to a fuel pump. More specifically, it relates to a fuel pump for an internal combustion engine, in particular for a motor vehicle like a car. The fuel pump may be configured as a high-pressure pump, which receives fuel from a fuel tank via a low-pressure pump. The high-pressure pump then increases the pressure of the fuel, normally to at least 100 bar, sometimes up to 500 to 600 bar or even higher. The fuel pump has been designed for gasoline, but can also be used with other liquid fuels.

[0007] The fuel pump comprises a main body. The main body, which is normally at least partially made of metal to provide the necessary pressure resistance and stability, may be made of a single piece or (normally) several connected pieces. The main body defines an inlet passage, a pumping chamber and a receptacle, which are all volumes or spaces delimited by the main body.

[0008] The main body defines a pumping chamber with a pumping plunger arranged to reciprocate within the pumping chamber. By the action of the pumping plunger, fuel can be sucked into the pumping chamber during an intake stroke and can subsequently be pressurized and expelled from the pumping chamber during a compression stroke or pumping stroke. Accordingly, the fuel enters the pumping chamber at a low pressure and exits the pumping chamber at a high pressure. The pumping plunger can be operated electrically, or it may be mechanically linked to an engine, in particular to the combustion engine that the fuel pump supplies with fuel. E.g., the pumping plunger can be linked to a camshaft of the engine. Since the plunger reciprocates (i.e., moves back andP-DELPHI-443 / WO 3 forth) along a straight line, at least a portion of the pump chamber is cylindrical with a cross-section corresponding to that of the plunger. However, the pumping chamber may comprise at least one portion that is not accessible by the plunger and that may have a non-cylindrical shape. It is understood that the pumping chamber, as well as the passages mentioned hereinafter, are defined inside a housing of the fuel pump.

[0009] The main body further defines an inlet passage at least indirectly connecting a low-pressure inlet of the fuel pump to the pumping chamber, an inlet valve being adapted to control flow through the inlet passage to the pumping chamber. The low-pressure inlet is adapted for connection to a low-pressure fuel source, normally a low-pressure pump. Instead of “low-pressure inlet” this could simply be referred to as an “inlet”, while the term “low-pressure” indicates that the fuel entering the inlet has not yet been pressurized by the fuel pump. Of course, the connection to the fuel source can be indirect, e.g., via a pipe, a hose, or the like. The inlet passage establishes a fluid connection, or fluid communication, between the inlet and the pumping chamber, either directly or indirectly. In case of an indirect connection, the inlet passage is connected to another passage that is connected to the inlet. During an intake stroke of the plunger, fuel is sucked through the inlet passage into the pumping chamber. The term “passage” here and in the following refers to any volume that is suitable for containing fuel and allowing transfer of the fuel from an origin (in this case, the low-pressure inlet) to a destination (in this case, the pumping chamber). Such a passage may have various shapes, e.g., straight, curved and / or angled, and may be branched or unbranched. The inlet valve is adapted to selectively enable flow through the inlet passage to the pumping chamber, “selectively enable” here means that the inlet valve is not always open, but is configured to be closed for the compression stroke and open when a predetermined pressure is reached. Advantageously, the inlet valve is adapted to prevent fuel from flowing in the opposite direction, i.e. , back towards the inlet passage. Preferably, the pressure on an inlet side of the inlet valve has to be greater than the pressure on a pumping-chamber side by at least the specified opening pressure. Additionally, the opening of the inlet valve may be assisted / controlled by an actuator. The inlet valve can be disposedP-DELPHI-443 / WO 4 on or inside the inlet passage, for example close to the inlet, close to the pumping chamber or somewhere in between. In order to minimize the pumping dead volume, it is highly preferred that the inlet valve is disposed close to the pumping chamber. The inlet valve can be received inside the main body or can be regarded as a part of the main body.

[0010] Furthermore, the main body defines a receptacle, which is open towards a distal side, and which extends into the main body along an axially aligned outlet axis towards a proximal side so that the receptacle communicates with the pumping chamber. The receptacle is a recess inside the main body. More specifically, it is an open recess, i.e., it is open towards a distal side (the main body having a receptacle opening at this distal side). The receptacle extends into the main body along an outlet axis the towards a proximal side, which is opposite the first side with respect to the outlet axis. More specifically, it extends into the main body so that it communicates with the pumping chamber. In other words, the pumping chamber and the receptacle are directly or indirectly connected. The outlet axis is aligned axially or in an axial direction. Thus, the outlet axis implicitly also defines a radial direction and a tangential direction. The receptacle may be symmetrical to the outlet axis.

[0011] An outlet passage at least indirectly connects the pumping chamber to a high-pressure outlet of the fuel pump, an outlet valve being adapted to control the flow through the outlet passage to the outlet. The outlet passage is either directly or indirectly connected to the pumping chamber and is either directly or indirectly connected to the high-pressure outlet. Instead of “high-pressure outlet”, this could simply be referred to as an “outlet”, while the term “high-pressure” indicates that the fuel exiting the outlet has been pressurized by the fuel pump. In assembled state, the outlet may be connected to a fuel rail which in turn is connected to a plurality of fuel injectors. During a pumping stroke, fuel is pressurized in the pumping chamber and then expelled from the pumping chamber through the outlet passage. The outlet valve is adapted to selectively enable flow through the outlet passage to the outlet. “Selectively enable” here means that the outlet valve is not always open, but is configured - for the inlet valve function - to be open for an intake stroke and closed for a compressionP-DELPHI-443 / WO 5 stroke. The outlet valve is conventionally a one-way valve (check-valve type) that prevents fuel from flowing in the opposite direction, i.e., towards the pumping chamber. Also, the outlet valve may typically only enable flow towards the outlet if a certain opening pressure is exceeded. The outlet valve can be disposed inside the outlet passage, for example close to the outlet, close to the pumping chamber or somewhere in between.

[0012] An outlet-valve body, which at least partially defines the outlet passage and comprises an outlet-valve seat, is at least partially received in the receptacle and is connected to the main body in a fuel-tight manner, an outletvalve member being adapted to engage the outlet-valve seat in a closed position to close the outlet passage. Generally speaking, the term “outlet-valve body” is used for distinction and is not to be construed in any limiting way. However, the outlet-valve body defines the outlet-valve seat, which is part of the outlet valve. In some embodiments, the outlet-valve body is symmetric with respect to the outlet axis. The outlet-valve member is movable relative to the outlet-valve body. In a closed position, it engages the outlet-valve seat to block the outlet passage. In an open position, it is removed / lifted from the outlet-valve seat to enable fuel flow through the outlet passage. The outlet-valve body is at least partially disposed inside the receptacle. Furthermore, the outlet-valve body at least partially defines the outlet passage. In some embodiments, a part of the outlet passage may be defined by a different element. At least a part of the outlet passage may be a cavity or recess inside the outlet-valve body. This part may be referred to as an “outlet-valve cavity”. The outlet module is at least partially received in the receptacle, which is defined by the main body, and is connected to the main body in a fuel-tight manner. Accordingly, fuel cannot pass through any gap between the main body and the outlet-valve body. However, if the outlet valve is open, fuel can pass through the outlet-valve body, e.g., through the abovementioned outlet-valve cavity. The fuel-tight connection ensures that the fuel flow can be controlled by the outlet valve.

[0013] According to the invention, a main-body locking portion of the main body and an outlet-valve locking portion of the outlet-valve body engage each other via at least one elastic retainer element which establishes a form-fitP-DELPHI-443 / WO 6 connection between the main body and the outlet-valve body, whereby removal of the outlet-valve body in the axial direction is prevented. As will be understood, a form-fit connection is a connection between two elements in which one element blocks a potential movement path of the other element. In this case, the form-fit connection established through the at least one retainer element at least blocks an axial movement path of the outlet-valve body relative to the main body. It can also be referred to as an axial form-fit connection. The main-body locking portion of the main body and the outlet-valve locking portion of the outlet-valve body interact via the at least one retainer element. The respective retainer element is adapted to at least transfer an axial force between the locking portions. The retainer element is elastic, i.e., elastically deformable. Specifically, it may be elastically deformable in the radial direction. Due to its elastic properties, it can be deformed into an assembly position (transitorily) for an assembly process, which assembly position does not establish the form-fit connection. Then, when the outlet-valve body has reached its intended position in the receptacle, elastic restoring forces can move the retainer element into a locking position, in which it establishes the form-fit connection. The form-fit connection prevents the outletvalve body from being removed from the receptacle. Depending on embodiments, the retainer element may be made of metal, in particular steel or stainless steel, or from a suitable polymer. The use of a metallic retainer element is advantageous in that the intrinsic elasticity of steel allows some expansion / compression during assembly while ensuring a return to a rather stable shape when the external forces disappear (due to elastic restoring forces).

[0014] Due to the form-fit connection, the outlet-valve body is securely attached to the main body. In contrast to a press-fit connection, the form-fit connection does not rely on frictional forces and cannot be removed by vibrations. Therefore, the inventive design guarantees a long-time operability of the outlet valve.

[0015] Beside the abovementioned features, the fuel pump preferably also comprises a relief passage that at least indirectly connects the outlet passage, downstream of the outlet valve, to the pumping chamber. The relief passage originates (directly or indirectly) from the outlet passage downstream of the outletP-DELPHI-443 / WO 7 valve and leads (directly or indirectly) to the pumping chamber. Accordingly, fuel can be released from the outlet passage into the pumping chamber through the relief passage. The function of the relief passage is to prevent excessive overpressure in the outlet passage and / or for example a fuel rail connected to the outlet passage. The fuel pump may further comprise a relief valve that is adapted to selectively enable flow through the relief passage to the pumping chamber. More specifically, the relief valve is a one-way valve that prevents fuel from flowing in the opposite direction, i.e. , towards the outlet passage. Also, the relief valve only enables fuel flow towards the pumping chamber if a certain opening pressure is exceeded. In other words, if the pressure difference between the outlet passage and the pumping chamber is high enough, the relief valve opens to release fuel from the outlet passage through the relief passage. The relief valve can be disposed inside the relief passage, for example close to the outlet passage, close to the pumping chamber or somewhere in between.

[0016] A particularly preferred embodiment provides that the outlet-valve body is made of a single piece, preferably a piece of metal. In other words, a single piece (of metal) is used for the outlet-valve body, which normally undergoes various machining operations, e.g., for providing the outlet-valve cavity, the outlet-valve locking portion, the valve seat, or other features. However, at least some features can be defined by an initial casting process. Specifically, the outlet-valve locking portion and the valve seat are part of a single piece. The single-piece design facilitates assembly of the outlet valve and increases the structural stability of the outlet-valve body.

[0017] In some embodiments, it is conceivable that even the form-fit connection allows for some axial movement of the outlet-valve body. In such a case it could rely on an additional connection to prevent such movement. However, it is highly preferred that the form-fit connection prevents any axial movement of the outlet-valve body. It will be understood that this does not exclude axial movement of a magnitude that is relevant for the operation of the fuel pump. One could say that the form-fit connection allows for no or only negligible axial movement. In this embodiment, the form-fit connection fixes the axial position of the outlet-valve body relative to the main body.P-DELPHI-443 / WO 8

[0018] The fluid-tight connection between the main body and the outletvalve body could be established in various ways. It is conceivable that the at least one retainer element establishes fluid tightness. In other embodiments, an elastomeric element could be interposed between the main body and the outletvalve body. According to a preferred embodiment, the outlet-valve body is press- fitted into the receptacle, with at least one press-fit surface of the outlet-valve body engaging the main body. The press-fit connection not only establishes fluidtightness, but also prevents radial and tangential movement of the outlet-valve body. It may also reduce the strain on the form-fit connection. Specifically, the main body may comprise a main-body press-fit surface, which engages an outletvalve press-fit surface of the outlet-valve body. Optionally both the main body and the outlet-valve body could comprise a plurality of press-fit surfaces. Each of the above-mentioned press-fit surfaces is normally parallel to the outlet axis or inclined by less than 2° or less than 1 ° with respect to the outlet axis. Preferably, at least one press-fit surface is preferably disposed distally of the outlet-valve locking portion.

[0019] In some embodiments, a retainer element may be part of the main body or the outlet-valve body. Preferably, at least one retainer element is manufactured separately from the main body and the outlet-valve body and form- fittingly engages both locking portions. In other words, the respective retainer element is a dedicated element that is not permanently connected / joined to either of the main body of the outlet-valve body. However, it is in contact with both bodies in that it establishes a form-fit connection with the main body as well as with the outlet-valve body. Considering the flow of force, the retainer element is interposed between the main body and the outlet-valve body. It can transfer a force between these bodies to prevent axial movement of the outlet-valve body.

[0020] It is preferred that at least one of locking portions defines a radially extending recess in which at least one retainer element is at least partially received. The recess is defined by a surface of the respective locking portion that is recessed in the radial direction. In case of a recess in the main-body locking portion, the surface recedes radially outwards whereas in case of a recess in the outlet-valve locking portion, the surface recedes radially inwards. It will beP-DELPHI-443 / WO 9 appreciated that the recess also extends in the tangential direction and in the axial direction. However, the relation between the radial, tangential and axial dimension of the recess can be chosen in various ways. Specifically, the tangential dimension of the recess may be greater than its radial and axial dimension, but this is not imperative. In assembled state, at least one retainer element is at least partially received in the recess. Thus, the radial positions of the retainer element and the respective locking portion overlap, whereby the form-fit is established. It is preferred that each of the locking portions defines a recess. These may be referred to as a main-body recess of the main-body locking portion and an outlet-valve recess of the outlet-valve locking portion. In this case, at least one retainer element is at least partially received in both recesses.

[0021] According to one embodiment, at least one retainer element has a ring-like shape and extends tangentially around the outlet-valve body. The term “ring-like” does not imply that the retainer element has to extend a full 360° in the tangential direction. Insofar, it is to be understood in the sense of “at least similar to a ring”. In any way it extends tangentially around the outlet-valve body. In other words, it is disposed radially outwards of the outlet-valve body and at least partially surrounds it. If a ring-like retainer element is used, it is preferred that this is the only retainer element, i.e. , that the fuel pump comprises a single retainer element between the main body and the outlet-valve body.

[0022] Specifically, at least one retainer element can be an open ring. In other words, the retainer element, at least in its undeformed shape, does not extend 360° in the tangential direction. Typically, it may extend over 270° to 355° or over 300° to 350°. The open shape allows the retainer element to be expanded to a greater radial dimension as well to be compressed to a smaller radial dimension. It should be noted, though, that there are other possibilities. For instance, the retainer element could correspond to a closed ring which has a meandering or wavelike structure which allows for compression as well as expansion. Preferably, the retainer element is a metal ring, e.g. made of steel or stainless steel.

[0023] The ring-like retainer element may have various types of crosssections. This includes the possibility that the cross-section is constant in all partsP-DELPHI-443 / WO 10 of the retainer element or that it varies along the tangential direction. In one preferred embodiment, the ring-like retainer element has a circular cross-section, i.e. the cross-section corresponds to a circle. According to another embodiment, it has a rectangular cross-section, i.e. the cross-section corresponds to a rectangle, e.g., a square. It will be understood that the cross-section of the recess may correspond to the cross-section of the retainer element. If the cross-section of the retainer element is circular, the cross-section of the recess may also be at least partially circular, e.g. semi-circular. If the cross-section of the retainer element is rectangular, the same may be true for the cross-section of the recess.

[0024] Preferably, at least one recess has an annular shape. In other words, the recess extends circumferentially in the tangential direction. Such a shape is easy to produce e.g. by milling or turning, and it is well adapted for a combination with a ring-like retainer element. Preferably, both locking portions each comprise and annular recess.

[0025] It is preferred that one of the locking portions defines a stowage recess adapted so that at least one retainer element is elastically deformable to be further received in the stowage recess during an assembly process (i.e. transitorily) rather than in an assembled state. The stowage recess is one of the above-mentioned recesses in which the retainer element is partially received in assembled state. However, the size of the stowage recess is large enough to receive a larger portion of the retainer element, or even the entire retainer element during the assembly process. In other words, the retainer element can be received or stowed in the stowage recess. During assembly, the retainer element is elastically deformed so that it is moved into the stowage recess. For instance, if the main-body locking portion defines the stowage recess, the retainer element is elastically expanded in the radial direction to move into the stowage recess. If the outlet-valve locking portion defines the stowage recess, the elastic element is compressed in the radial direction to move into the stowage recess. During assembly, the elastic deformation is maintained by contact of the retainer element with the outlet-valve body (if the main-body locking portion comprises the stowage recess) or with the main body (if the outlet-valve locking portion comprises the stowage recess). Then, when the outlet-valve body has reachedP-DELPHI-443 / WO 11 its intended position, the retainer element is aligned with the recess of the other locking portion. Accordingly, following the elastic restoring force, it moves partially out of the stowage recess and into the other recess, thereby establishing the form-fit connection.

[0026] In order to facilitate assembly of the fuel pump, it is preferred that the outlet-valve body has a guide portion disposed proximally of the outlet-valve locking portion, which guide portion has a radial dimension that increases in the distal direction. Preferably, a surface of the guide portion is at least partially inclined relative to the axial direction and the radial direction. The shape of the guide portion may at least partially be frusto-conical. On the one hand, the guide portion can facilitate insertion of the outlet-valve body into the receptacle. Since those parts of the guide portion that are disposed further to the proximal side have a smaller radial dimension, they are easier to insert, even if the alignment between the outlet-valve body and the receptacle is not perfect. Then, as the radial dimension increases towards the distal side, the alignment of the outletvalve body automatically improves as it is inserted further into the receptacle. Moreover, in an embodiment in which the retainer element has to be radially expanded during the assembly process, the increasing radial dimension of the guide portion can facilitate the expansion of the retainer element.

[0027] The outlet valve may comprise a spring element for biasing the outlet-valve member against the outlet-valve seat, and spring-retainer element connected to the outlet-valve body, the spring element engaging the springretainer element. The spring element may e.g. be a helical spring. It exerts a restoring force on the outlet-valve member, thereby biasing it against the outletvalve seat. While in some embodiments, the spring element could rest against the outlet-valve body, this embodiment provides that there is a dedicated element, namely the spring-retainer element. The spring-retainer element forms an abutment for the spring element. Accordingly, the spring element transfers a force between the valve member and the spring-retainer element. The springretainer element in turn is connected to the outlet-valve body. This connection should be rigid but does not have to be fluid tight. The spring-retainer element may form a case, sleeve or cage around the spring element and may also provideP-DELPHI-443 / WO 12 a guiding function for the spring element. However, in order to enable fuel flow through the valve in its open state, the spring-retainer element may comprise at least one opening, preferably a plurality of openings.

[0028] Preferably, the outlet-valve seat is disposed on the distal side of the outlet-valve body and the outlet-valve member is at least partially disposed outside of the outlet-valve body. With this configuration, it is possible to assemble the outlet valve after the outlet-valve body has been inserted into the receptacle and the form-fit connection has been established. This is because the outlet-valve seat is facing the distal opening of the receptacle and is therefore still accessible. For instance, the above-mentioned valve element, the spring element and the spring-retainer element could be assembled to the outlet-valve body after it has been inserted into the main body. However, even with this configuration, it is possible to assemble the outlet valve before the outlet-valve body is inserted into the receptacle.

[0029] When the fuel pump is installed e.g. in a vehicle and is used to supply fuel to an engine, the outlet passage can be connected to a fuel rail. The portion of the fuel pump that is adapted for the connection could be part of the main body or of the outlet-valve body. Preferably though, there is a dedicated element adapted for such a connection. According to a preferred embodiment, the fuel pump comprises an outlet fitting which is connected to the main body and is distally offset from the outlet-valve body. An axial position of the outlet fitting may overlap with an axial position of the outlet-valve body, but the outlet fitting is disposed further to the distal side. The outlet fitting can be adapted for a connection to a downstream element that receives fuel from the fuel pump, e.g. a fuel rail. For this purpose, the outlet fitting may be provided with a threading. The outlet fitting may at least partially be received inside the receptacle. It may be connected to the main body by an outer threading that engages an inner threading of the main body. As a rule, the outlet fitting is connected to the main body in a fuel-tight manner.P-DELPHI-443 / WO 13BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 : is a sectional view of an inventive fuel pump according to a first embodiment;Fig. 2: is a detail view of fig.1 ;Fig. 3: is a sectional detail view of an inventive fuel pump according to a second embodiment;Fig. 4: is a sectional detail view of an inventive fuel pump according to a third embodiment;Fig. 5: is a sectional detail view of an inventive fuel pump according to a fourth embodiment;Fig. 6A-6D: are sectional views illustrating an assembly process of the fuel pump from figs. 1 and 2; andFig. 7A-7F: are sectional views illustrating an assembly process of the fuel pump from fig.3.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] Fig.1 shows a fuel pump 1 according to a first embodiment of the present invention. The general structure and operating principle of the fuel pump 1 are generally known and thus will only be briefly described here. Fuel pump 1 is typically part of a fuel system (not shown) of an internal combustion engine, which generally includes a fuel tank holding a volume of liquid fuel to be supplied to the engine for operation thereof. A low-pressure fuel pump draws fuel from the fuel tank and elevates the pressure of the fuel (e.g. up to 5 bar) for delivery to the (high-pressure) fuel pump 1 , which in turn further elevates the pressure of the fuel (typically several hundred bars and here up to 500 to 600 bars)for delivery toP-DELPHI-443 / WO 14 a fuel rail to which the fuel injectors are coupled. The fuel injectors then directly inject the fuel into the combustion chambers of the cylinders of the engine.

[0032] The fuel pump 1 comprises a main body 2 with various parts, most of which are made of metal, e.g., stainless steel. The main body 2 defines a pumping chamber 3 with a pumping plunger 4, which is adapted to reciprocate within the pumping chamber and may be mechanically linked to a rotating camshaft (not shown) of the engine. The pumping chamber 3 is connected to an inlet passage 5 with an inlet valve 6. Conventionally, the inlet passage 5 is connected to a low-pressure inlet 7 (fitting) of the fuel pump 1 , via which the fuel pump 1 can be connected to the abovementioned low-pressure pump. Fuel enters the pump 1 via the low-pressure inlet 7, flows through a damping volume 8, which is defined by a damper cup mounted to the main body 2, as is known in the art, and then enters the inlet passage 5. Although not shown in detail, the inlet valve 6 typically comprises a seat member 6.1 defining one or more flow orifices 6.2 that can be sealed by a flexible disk valve member 6.3 that can be raised from the seat member by means of an actuating rod 6.4 controlled by a solenoid actuator 6.5. This is only one conventional example of inlet valve and should not be construed as limiting.

[0033] The main body 2 also defines a receptacle 9 that is aligned along an outlet axis A and opens to an outside of the main body 2 at a receptacle opening 10. The receptacle opening 10 is disposed on a distal side D with respect to the outlet axis A, and the receptacle extends into the main body 2 towards a proximal side P so that it communicates with the pumping chamber 3. An outletvalve body 20, which is made of a single piece of stainless steel, is received in the receptacle 9. An outlet passage 12, which is partially defined by the outletvalve body 20, connects the pumping chamber 3 to a high-pressure outlet 13 of the fuel pump 1 .The fuel pump 1 comprises an outlet valve 25. The outlet valve 25 is here designed as a one-way valve that enables fuel flow from the pumping chamber 3 to the outlet 13 if the pressure difference between the pumping chamber 3 and the outlet passage 12 (or rather, the portion downstream of the outlet valve 25) exceeds a predefined outlet pressure.P-DELPHI-443 / WO 15

[0034] The fuel pump 1 may comprises a relief valve (not shown) arranged in a relief passage 37, which is only partially shown, connecting the outlet passage 12 - downstream of the outlet valve 25- to the pumping chamber 3. The relief valve is a one-way valve that enables flow from the outlet passage 12 through the relief passage 37 to the pumping chamber 3 if the pressure in the outlet passage 12 (downstream of valve 25) exceeds the pressure in the pumping chamber 3 and the difference is greater than a defined relief opening pressure.

[0035] During operation, the reciprocating movement of the pumping plunger 4 causes fuel to be drawn from the inlet passage 5 into the pumping chamber 3 during an intake stroke. During a following pumping or compression stroke, the fuel in the pumping chamber 3 is pressurized and expelled through the outlet valve 25 and the outlet passage 12. The fuel can then be supplied via the outlet 13 to the fuel rail and then the injectors, as indicated above. During the compression stroke, the inlet valve 6 is closed and prevents backflow through the inlet passage 5. If at any time the pressure in the outlet passage 12 exceeds the predefined relief opening pressure, the relief valve opens to release fuel from the outlet passage 12 through the relief passage 37 into the pump chamber 3, thereby preventing possible damage to any components downstream of the fuel pump 1 .

[0036] Details of the outlet valve 25 and neighbouring components will now be discussed with reference to fig. 2. The outlet-valve body 20 is symmetrical with respect to the outlet axis A. It defines an outlet-valve cavity 21 that is a part of the outlet passage 12. Furthermore, the outlet-valve body 20 comprises an outletvalve locking portion 20.1 that defines an annular outlet-valve recess 20.2. An elastic retainer element 15 is partially disposed in the outlet-valve recess 20.2. Radially opposite the outlet-valve recess 20.2, a main-body recess 2.2 is formed in a main-body locking portion 2.1 of the main body 2. The main-body recess 2.2 is also annular and also receives a portion of the retainer element 15. In this embodiment, the retainer element 15 is an open ring made of steel, preferably spring type stainless steel, and has a circular cross-section. The retainer element hence has an annular gap that allows its expansion / compression during installation. Since both locking portions 2.1 , 20.1 engage the retainer element 15,P-DELPHI-443 / WO 16 a form-fit connection between the outlet-valve body 20 and the main body 2 is established with respect to the axial direction. That is, the outlet-valve body 20 and the main body 2 are locked in place relative to one another by the retainer element 15. Be a proper sizing of outlet-valve recess 20.2 and a main-body recess 2.2, a precise axial positioning of the outlet valve body 20 is achieved.

[0037] Therefore, the outlet-valve body 20 cannot be removed without deforming or destroying the retainer element 15. Proximal of the locking portions 2.1 , 20.1 , a main-body press-fit surface 2.3 engages an outlet-valve press-fit surface 20.3. Accordingly, the main body 2 and the outlets-valve body 20 are connected by a press-fit connection that is fuel-tight. Even further to the proximal side P, the outlet-valve body 20 comprises a guide portion 20.4 with a radial dimension that increases towards the distal side D.

[0038] The outlet-valve body 20 also defines an outlet-valve seat 26 disposed at the distal side D. A ball-shaped outlet-valve element 27 cooperates with the outlet-valve seat 26 in a closed position (which is shown in fig. 2) to block fuel flow through the outlet passage 12. A spring element 28, which rests against a spring-retainer element 29, biases the outlet-valve element 27 towards the closed position. The shell-like spring-retainer element 29 is here formed as a porous outlet cap 58, that is fixed (e.g. crimped) to a collar radially protruding around the distal end of outlet valve cavity 21. The shell-like spring-retainer element 29 is partially surrounded by an outlet fitting 40 by which the fuel pump 1 can be connected to the above-mentioned fuel rail. The outlet fitting 40 defines a fitting cavity 41 which is a part of the outlet passage 12. It also comprises an outer threading 42 that engages a corresponding inner threading 11 on an inside of the receptacle 9. The outlet fitting 40 is screwed in abutment against an annular shoulder 23 in the receptacle. Although not visible, the outlet fitting 40 advantageously comprises an annular knife edge on an annular, proximal front surface, which engages shoulder 23.

[0039] Figs. 6A to 6D illustrate an assembly process of the fuel pump 1 , specifically the installation of the outlet-valve body 20. Before the outlet-valve body 20 is inserted into the receptacle 9, the retainer element 15 is placed in theP-DELPHI-443 / WO 17 outlet-valve recess 20.2. Then, the shape of the guide portion 20.4 facilitates insertion of the outlet-valve body 20, which is illustrated in fig. 6A. I.e. as the outlet-valve body 20 moves further the to the proximal side P, it automatically aligns within the receptacle 9. It will be understood that the retainer element 15 moves along with the outlet-valve body 20. In fig. 6B, the retainer element 15 has reached a position in which the radial dimension of the receptacle 9 becomes smaller than the radial dimension of the retainer element 15 in its undeformed state. At this stage, the retainer element 15 can be compressed using a tool (not shown) so that it is fully received in the outlet-valve recess 20.2. Alternatively, the radial dimension of the receptacle 9 could decrease gradually towards the proximal side P so that the retainer element 15 is compressed by the proximal movement of the outlet-valve body 20. It should be noted that the outlet-valve recess 2.2 in this embodiment is a stowage recess 16 that is large enough to receive the retainer element 15 completely. When the retainer element 15 is in a position inside the stowage recess 16, which may be referred to as an assembly position, the outlet-valve body 20 can be moved further to the proximal side P, as shown in fig. 6C. Finally, when the axial positions of the outlet-valve recess 20.2 and the main-body recess 2.2 coincide, the retainer element 15 can expand into the main-body recess 2.2 due to elastic restoring forces. Thus, the abovedescribed form-fit connection is established. Also, during the last stages of the proximal movement, the press-fit connection between the outlet-valve press-fit surface 20.3 and the main-body press-fit surface 2.3 is established.

[0040] Fig. 3 shows a detail of a second embodiment of an inventive fuel pump 1 that is mostly identical to the first embodiment. However, in this embodiment, the outlet-valve recess 20.2 is somewhat smaller so that it can only receive a part of the retainer element 15, while the main-body recess 2.2 is sized to be a stowage recess 16. Accordingly, the assembly process is somewhat different, as will now be described with reference to figs. 7A to 7F. Before the outlet-valve body 20 is inserted into the receptacle 9, the retainer element 15 is placed in the main-body recess 2.2. Again, the shape of the guide portion 20.4 facilitates insertion of the outlet-valve body 20 as shown in fig. 7A. Furthermore, as the outlet-valve body 20 moves further to the proximal side P, the guide portionP-DELPHI-443 / WO 18 gets into contact with the retainer element 15 and begins to expand it, as shown in figs.7B and 7C. In fig. 7D, the retainer element 15 has reached a position in which it has been expanded such that it is partially received in the stowage recess 16 on either side of the outlet-valve body 20.

[0041] When the outlet-valve body 20 moves further to the proximal side, the retainer element 15 is fully displaced into the main-body recess 2.2, as shown in fig. 7E. At this stage, the outlet-valve press-fit surface 20.3 passes through the retainer element 15. Finally, when the axial positions of the outlet-valve recess20.2 and the main-body recess 2.2 coincide, the retainer element 15 can contract into the outlet-valve recess 20.2 due to elastic restoring forces, establishing the form-fit connection. Also, during the last stages of the proximal movement, the press-fit connection between the outlet-valve press-fit surface 20.3 and the main- body press-fit surface 2.3 is established.

[0042] While in the first and second embodiment, the retainer element 15 has a circular cross-section, figs. 4 and 5 show a third and fourth embodiment in which the retainer element has a rectangular cross-section. Correspondingly, the cross-sections of the main-body recess 2.2 and the outlet-valve recess 20.2 are also rectangular. In the third embodiment of fig. 4, the outlet-valve recess 20.2 is formed as a stowage recess 16, while in the fourth embodiment of fig. 5, the main- body recess 2.2 is formed as a stowage recess 16.

[0043] Legend of Reference Numbers:1 fuel pump2 main body2.1 main-body locking portion2.2 main-body recess2.3 main-body press-fit surface3 pumping chamber4 pumping plunger5 inlet passage6 inlet valve8 damping volumeP-DELPHI-443 / WO 199 receptacle10 receptacle opening11 inner threading12 outlet passage13 outlet15 retainer element16 stowage recess20 outlet-valve body20.1 outlet-valve locking portion20.2 outlet-valve recess20.3 outlet-valve press-fit surface20.4 guide portion21 outlet-valve cavity25 outlet valve26 outlet-valve seat27 outlet-valve member28 spring element29 spring-retainer element37 relief passage40 outlet fitting41 fitting cavity42 outer threading44 drive profileA outlet axisD distal sideP proximal side

Claims

P-DELPHI-443 / WO 20CLAIMS1 . A fuel pump (1 ) comprising a main body (2) that defines:- a pumping chamber (3) with a pumping plunger (4) arranged to reciprocate within the pumping chamber (3);- an inlet passage (5) at least indirectly connecting a low-pressure inlet of the fuel pump (1 ) to the pumping chamber (3), an inlet valve (6) being adapted to control flow through the inlet passage (5) to the pumping chamber (3); and- a receptacle (9), which is open towards a distal side (D) and which extends into the main body (2) along an axially aligned outlet axis (A) towards a proximal side (P) so that the receptacle (9) communicates with the pumping chamber (3); wherein an outlet passage (12) at least indirectly connects the pumping chamber (3) to a high-pressure outlet (13) of the fuel pump (1 ), an outlet valve (25) being adapted to control flow through the outlet passage (12) to the outlet (13), wherein an outlet-valve body (20), which at least partially defines the outlet passage (12) and comprises an outlet-valve seat (26), is at least partially received in the receptacle (9) and is connected to the main body (2) in a fuel-tight manner, an outlet-valve member (27) being adapted to engage the outlet-valve seat (26) in a closed position to close the outlet passage (12), characterized in that a main-body locking portion (2.1 ) of the main body (2) and an outlet-valve locking portion (20.1 ) of the outlet-valve body (20) engage each other via at least one elastic retainer element (15) which establishes a form-fit connection between the main body (2) and the outlet-valve body (20) with respect to the axial direction, whereby removal of the outlet-valve body (20) is prevented.

2. The fuel pump according to claim 1 , wherein the outlet-valve body (20) is made of a single piece.

3. The fuel pump according to any of the preceding claims, wherein the form-fit connection prevents any axial movement of the outlet-valve body (20).P-DELPHI-443 / WO 214. The fuel pump according to any of the preceding claims, wherein the outletvalve body (20) is press-fitted into the receptacle (9), with at least one press- fit surface (20.3) of the outlet-valve body (20) engaging the main body (2), wherein preferably at least one press-fit surface (20.3) is disposed distally of the outlet-valve locking portion (20.1 ).

5. The fuel pump according to any of the preceding claims, wherein at least one retainer element (15) is manufactured separately from the main body (2) and the outlet-valve body (20) and form-fittingly engages both locking portions (2.1 , 20.1 ).

6. The fuel pump according to any of the preceding claims, wherein at least one of locking portions (2.1 , 20.1 ) defines a radially extending recess (2.2, 20.2) in which at least one retainer element (15) is at least partially received, wherein preferably each of the locking portions (2.1 , 20.1 ) defines a recess (2.2, 20.2).

7. The fuel pump according to any of the preceding claims, wherein at least one retainer element (15) has a ring-like shape and extends tangentially around the outlet-valve body (20).

8. The fuel pump according to any one of the preceding claims, wherein at least one retainer element (15) is an open ring.

9. The fuel pump according to any of the preceding claims, wherein the ring-like retainer element (15) has a circular cross-section or a rectangular crosssection.

10. The fuel pump according to any one of the preceding claims, wherein at least one recess (2.2, 20.2) has an annular shape.P-DELPHI-443 / WO 2211 . The fuel pump according to any of the preceding claims, wherein one of the locking portions (2.1 , 20.1 ) defines a stowage recess (16) adapted so that at least one retainer element (15) is elastically deformable to be further received in the stowage recess (16) during an assembly process than in an assembled state.

12. The fuel pump according to any of the preceding claims, wherein the outletvalve body (20) has a guide portion (20.4) disposed proximally of the outletvalve locking portion (20.1 ), which guide portion (20.4) has a radial dimension that increases in the distal direction.

13. The fuel pump according to any of the preceding claims, wherein the outlet valve (25) comprises a spring element (28) for biasing the outlet-valve member (27) against the outlet-valve seat (26), and a spring-retainer element (29) connected to the outlet-valve body, the spring element (28) engaging the spring-retainer element (29).

14. The fuel pump according to any one of the preceding claims, wherein the outlet-valve seat (26) is disposed on the distal side (D) of the outlet-valve body (20) and the outlet-valve member (27) is at least partially disposed outside of the outlet-valve body (20).

15. The fuel pump according to any of the preceding claims, comprising an outlet fitting (40) which is connected to the main body (2) and is distally offset from the outlet-valve body (20).

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