TECHNICAL FIELD OF INVENTION The present disclosure relates to a fuel pump which supplies fuel to an internal combustion engine, more particularly to such a fuel pump which includes a pumping plunger which reciprocates in a pumping chamber, and even more particularly to a damper cup which houses a pulsation damper for such a fuel pump.

BACKGROUND OF INVENTION

Fuel systems in modem internal combustion engines fueled by gasoline, particularly for use in the automotive market, employ gasoline direct injection (GDi) where fuel injectors are provided which inject fuel directly into combustion chambers of the internal combustion engine. In such systems employing GDi, 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 which typically includes a pumping plunger which is reciprocated by a camshaft of the internal combustion engine. Reciprocation of the pumping plunger further pressurizes the fuel in a pumping chamber of the high-pressure fuel pump in order to be supplied to fuel injectors which inject the fuel directly into the combustion chambers of the internal combustion engine. The high-pressure fuel pump includes an electrically actuated inlet valve which allows fuel to enter the pumping chamber during an intake stroke of the plunger. During a compression stroke of the plunger, the inlet valve is closed, thereby allowing the plunger to decrease the volume of the pumping chamber, consequently pressurizing the fuel. When the fuel reaches a predetermined pressure, an outlet valve is opened under the force of the pressurized fuel and the fuel is communicated to the fuel rail and fuel injectors. In order to vary the pressure generated by the high-pressure fuel pump, the inlet valve can be commanded to remain open for a portion of the compression stroke of the plunger, thereby decreasing the fuel pressure generated by the high-pressure fuel pump in order to accommodate different operating conditions of the internal combustion engine. However, when the inlet valve remains open during a portion of the compression stroke of the plunger, pressure pulsations generated by the plunger can propagate upstream of the spill valve which can have undesirable effects on the low-pressure fuel pump and other components in the fuel system. Consequently, these pressure pulsations need to be attenuated.

In order to mitigate the pressure pulsations, it is known for the high-pressure fuel pump to include a pulsation damper located within a fuel volume which is defined by a damper cup and which is exposed to the pressure pulsations. Known pulsation dampers typically include first and second halves which define a sealed damping volume such that the first and second halves each include a damper wall that is configured to flex in response to pressure pulsations. In order to allow the damper walls to flex in response to the pressure pulsations, it is important that the damper walls be exposed to the fuel within fuel volume, and as a result, the pulsation damper must be suspended in the fuel volume. US Patent Application Publication No. US 2011/0110807 A1 to Kobayashi et al. illustrates using a multi-piece supporting member, separate from the pulsation damper, which is used to suspend the pulsation damper within the fuel volume. This supporting member adds parts to the system, and as a result increases cost, manufacturing time, and complexity. US Patent Application No. US 2008/0289713 A1 to Munakata et al. seeks to simplify suspending the pulsation damper within the fuel volume by providing the damper cup with circumferentially spaced features which engage an outer periphery of the pulsation damper. While the arrangement of Munakata et al. may minimize the number of components in comparison to Kobayashi et al., the arrangement of Munakata et al. raises other issues. First, extreme care must be taken during installation of the pulsation damper within the damper cup because if the pulsation damper is tipped, the outer periphery of the pulsation damper has the potential of dropping beyond the support features of the damper cup, thereby requiring removal and repositioning of the pulsation damper. Second, contact area between the pulsation damper and the support features of the damper cup is minimal, thereby increasing contact stress. This high contact stress, together with vibrations which are experienced during the operational life of the high- pressure fuel pump, can lead to decreased durability.

What is needed is a fuel pump and a damper cup thereof which minimize or eliminate one or more of the shortcomings as set forth above.

SUMMARY OF THE INVENTION

Briefly described, in one aspect the present disclosure provides a fuel pump including a fuel pump housing with a pumping chamber defined therein; a pumping plunger which reciprocates within a plunger bore along a plunger bore axis such that an intake stroke of the pumping plunger increases volume of the pumping chamber and a compression stroke of the pumping plunger decreases volume of the pumping chamber; a damper cup which defines a fuel volume together with the fuel pump housing, the damper cup having a sidewall which is annular in shape and which extends along a damper cup axis from a sidewall first end to a sidewall second end, the damper cup also having an end wall which closes the sidewall second end, wherein the sidewall incudes a support shoulder which is transverse to the damper cup axis and which is a segment of an annulus extending uninterrupted about the damper cup axis from a shoulder first end to a shoulder second end such that the shoulder first end and the shoulder second end are separated from each other by a gap which is uninterrupted; and a pulsation damper located within the fuel volume and defining a damping volume which is fluidly segregated from the fuel volume, the pulsation damper having at least one damper wall which is flexible in response to pressure pulsations within the fuel volume, wherein an outer periphery of the pulsation damper is supported by the support shoulder.

In embodiments, said support shoulder may extend around said damper cup axis for an angular distance of 270° ± 60°. In embodiments, said damper cup includes an inlet fitting which is tubular and which provides a fuel inlet into said fuel volume, said inlet fitting being positioned through said sidewall such that said inlet fitting is positioned within said gap.

By way of example, the inlet fitting may be positioned between said sidewall first end and said sidewall second end to be aligned with said support shoulder.

The sidewall may also include an exterior shoulder which is transverse to said damper cup axis extending uninterrupted about said damper cup axis from an exterior shoulder first end to an exterior shoulder second end. In this way the exterior shoulder first end and said exterior shoulder second end may be separated from each other by a cylindrical surface segment. For example, the exterior shoulder may extend around said damper cup axis for an angular distance of 270° ± 60°.

In embodiments, the damper cup may include an inlet fitting which is tubular and which provides a fuel inlet into said fuel volume, said inlet fitting being positioned through said sidewall at said cylindrical surface segment.

By way of example, the inlet fitting is positioned between said sidewall first end and said sidewall second end to be aligned with said exterior shoulder. The exterior shoulder may be axially aligned with said sidewall first end in a direction parallel to said damper cup axis.

In another aspect, the present disclosure also provides a damper cup for housing a pulsation damper of a fuel pump, wherein the damper cup defines a fuel volume together with a fuel pump housing of the fuel pump. The damper cup includes a sidewall which is annular in shape and which extends along a damper cup axis from a sidewall first end to a sidewall second end; and an end wall which closes the sidewall second end, wherein the sidewall incudes a support shoulder which is transverse to the damper cup axis and which is a segment of an annulus extending uninterrupted about the damper cup axis from a shoulder first end to a shoulder second end such that the shoulder first end and the shoulder second end are separated from each other by a gap which is uninterrupted.

By way of example, the support shoulder may extend around said damper cup axis for an angular distance of 270° ± 60°.

The damper cup may include an inlet fitting which is tubular and which provides a fuel inlet into said fuel volume. The inlet fitting may be positioned through said sidewall such that said inlet fitting is positioned within said gap.

The inlet fitting may be positioned axially along said damper cup axis between said sidewall first end and said sidewall second end to be aligned with said support shoulder.

In embodiments, the sidewall also includes an exterior shoulder which is transverse to said damper cup axis extending uninterrupted about said damper cup axis from an exterior shoulder first end to an exterior shoulder second end. In this way the exterior shoulder first end and said exterior shoulder second end may be separated from each other by a cylindrical surface segment. The exterior shoulder may extend around said damper cup axis for an angular distance of 270° ± 60°.

In embodiments, the damper cup may include an inlet fitting which is tubular and which provides a fuel inlet into said fuel volume. The inlet fitting may be positioned through said sidewall at said cylindrical surface segment. The inlet fitting may be positioned between said sidewall first end and said sidewall second end to be aligned with said exterior shoulder. The exterior shoulder may be axially aligned with said sidewall first end in a direction parallel to said damper cup axis.

The fuel pump with damper cup as described herein provides for ease of installation of the pulsation damper into the damper cup while ensuring proper positioning of the pulsation damper. Furthermore, durability is increased by increasing surface area contact between the pulsation damper and the damper cup, thereby minimizing contact stress. Also furthermore, rigidity of the damper cup is increased, thereby minimizing flexing in use which minimizes acoustic noise. Still even furthermore, installation of the damper cup on the fuel pump housing is eased by providing features which ensure proper orientation and which provide increased surface area to press the damper cup onto the fuel pump housing.

Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS This disclosure will be further described with reference to the accompanying drawings in which:

FIG. 1 is a schematic view of a fuel system including a fuel pump in accordance with the present disclosure; FIG. 2 is an enlarged cross-sectional view of the fuel pump of FIG. 1;

FIG. 3 is a cross-sectional view of an outlet and pressure relief valve assembly of the fuel pump of FIG. 1 ;

FIGS. 4 and 5 are exploded isometric views of the outlet and pressure relief valve assembly of FIG. 3 taken from different perspectives; FIG. 6 is the cross-sectional view of FIG. 3 shown with an outlet valve member in an unseated position and arrows to show the path of fuel flow;

FIG. 7 is the cross-sectional view of FIG. 3 shown with a pressure relief valve member in an unseated position and arrows to show the path of fuel flow;

FIG. 8 is an enlarged portion of FIG. 2 showing a pulsation damper and a damper cup of the fuel pump;

FIG. 9 is an isometric view of the damper cup; and

FIG. 10 is an elevation view of the damper cup looking into a fuel volume of the damper cup. DETAILED DESCRIPTION OF INVENTION

In accordance with a preferred embodiment of this disclosure and referring initially to FIG. 1, a fuel system 10 for an internal combustion engine 12 is shown in schematic form. Fuel system 10 generally includes a fuel tank 14 which holds a volume of fuel to be supplied to internal combustion engine 12 for operation thereof; a plurality of fuel injectors 16 which inject fuel directly into respective combustion chambers (not shown) of internal combustion engine 12; a low-pressure fuel pump 18; and a high-pressure fuel pump 20 where the low-pressure fuel pump 18 draws fuel from fuel tank 14 and elevates the pressure of the fuel for delivery to high-pressure fuel pump 20 where the high- pressure fuel pump 20 further elevates the pressure of the fuel for delivery to fuel injectors 16. By way of non-limiting example only, low-pressure fuel pump 18 may elevate the pressure of the fuel to about 500 kPa or less and high-pressure fuel pump 20 may elevate the pressure of the fuel to above about 14 MPa and may be about 35 MPa or even higher depending on the operational needs of internal combustion engine 12. While four fuel injectors 16 have been illustrated, it should be understood that a lesser or greater number of fuel injectors 16 may be provided.

As shown, low-pressure fuel pump 18 may be provided within fuel tank 14, however low-pressure fuel pump 18 may alternatively be provided outside of fuel tank 14. Low- pressure fuel pump 18 may be an electric fuel pump as are well known to a practitioner of ordinary skill in the art. A low-pressure fuel supply passage 22 provides fluid communication from low-pressure fuel pump 18 to high-pressure fuel pump 20. A fuel pressure regulator 24 may be provided such that fuel pressure regulator 24 maintains a substantially uniform pressure within low-pressure fuel supply passage 22 by returning a portion of the fuel supplied by low-pressure fuel pump 18 to fuel tank 14 through a fuel return passage 26. While fuel pressure regulator 24 has been illustrated in low-pressure fuel supply passage 22 outside of fuel tank 14, it should be understood that fuel pressure regulator 24 may be located within fuel tank 14 and may be integrated with low-pressure fuel pump 18.

Now with additional reference to FIG. 2, high-pressure fuel pump 20 includes a fuel pump housing 28 which includes a plunger bore 30 which extends along, and is centered about, a plunger bore axis 32. As shown, plunger bore 30 may be defined by a combination of an insert and directly by fuel pump housing 28 but may alternatively be formed only, and directly by, fuel pump housing 28. High-pressure fuel pump 20 also includes a pumping plunger 34 which is located within plunger bore 30 and reciprocates within plunger bore 30 along plunger bore axis 32 based on input from a rotating camshaft 36 of internal combustion engine 12 (shown only in FIG. 1). A pumping chamber 38 is defined within fuel pump housing 28. An inlet valve assembly 40 of high- pressure fuel pump 20 is located within a pump housing inlet passage 41 of fuel pump housing 28 and selectively allows fuel from low-pressure fuel pump 18 to enter pumping chamber 38 while an outlet and pressure relief valve assembly 42 is located within an outlet valve bore 43 of fuel pump housing 28 and selectively allows fuel to be communicated from pumping chamber 38 to fuel injectors 16 via a fuel rail 44 to which each fuel injector 16 is in fluid communication. Outlet and pressure relief valve assembly 42 also provides a fluid path back to pumping chamber 38 if the pressure downstream of outlet and pressure relief valve assembly 42, i.e. between outlet and pressure relief valve assembly 42 and fuel injectors 16, reaches a predetermined limit which may pose an unsafe operating condition if left unmitigated. Outlet valve bore 43 is centered about, and extends along, an outlet valve bore axis 43a. In operation, reciprocation of pumping plunger 34 causes the volume of pumping chamber 38 to increase during an intake stroke of pumping plunger 34 (downward as oriented in FIG. 2) in which a plunger return spring 46 causes pumping plunger 34 to move downward, and conversely, the volume of pumping chamber 38 decreases during a compression stroke (upward as oriented in FIG. 2) in which camshaft 36 causes pumping plunger 34 to move upward against the force of plunger return spring 46. In this way, fuel is drawn into pumping chamber 38 during the intake stroke, and conversely, fuel is pressurized within pumping chamber 38 by pumping plunger 34 during the compression stroke, depending on the state of operation of inlet valve assembly 40 as will be described in greater detail later, and discharged through outlet and pressure relief valve assembly 42 under pressure to fuel rail 44 and fuel injectors 16. For clarity, a portion of pumping plunger 34 is shown in phantom lines in FIG. 2 to represent the intake stroke at a bottom dead center position (volume of pumping chamber 38 is maximized) and pumping plunger 34 is shown in solid lines in FIG. 2 to represent the compression stroke at a top dead center position (volume of pumping chamber 38 is minimized) such that pumping plunger 34 reciprocates between the bottom dead center position and the top dead center position.

Outlet and pressure relief valve assembly 42 will now be discussed with continued reference to FIGS. 1 and 2 and additionally with particular reference to FIGS. 3-7. Outlet and pressure relief valve assembly 42 generally includes a valve housing 48 which is tubular and extends along outlet valve bore axis 43a from an inner end 48a, which is proximal to pumping chamber 38, to an outer end 48b, which is distal from pumping chamber 38 and outside of fuel pump housing 28. A valve housing bore 48c extends into valve housing 48 from inner end 48a along outlet valve bore axis 43a such that valve housing bore 48c is centered about outlet valve bore axis 43a. Valve housing bore 48c extends from inner end 48a to a shoulder 48d which is transverse to outlet valve bore axis 43a and which faces toward inner end 48a. A valve housing outlet passage 48e extends from shoulder 48d to outer end 48b such that valve housing outlet passage 48e provides fluid communication from valve housing bore 48c to outer end 48b. The inner periphery of valve housing bore 48c and valve housing outlet passage 48e are each surfaces of revolution centered about outlet valve bore axis 43a. Similarly, the outer periphery of valve housing 48 is a surface of revolution centered about outlet valve bore axis 43a. Furthermore, the outer periphery of valve housing 48 includes an external shoulder 48f which is annular in shape and which is transverse to outlet valve bore axis 43a such that external shoulder 48f engages a complementary internal shoulder 43b of outlet valve bore 43, thereby providing a stop to establish a position of outlet and pressure relief valve assembly 42 within outlet valve bore 43.

Outlet and pressure relief valve assembly 42 also includes a valve seat 50 which is located within valve housing bore 48c and is positioned either directly or indirectly by shoulder 48d. As illustrated herein, shoulder 48d indirectly positions valve seat 50 because an intermediate element, which will be described later, is disposed between valve seat 50 and shoulder 48d such that the intermediate member acts as an extension of shoulder 48d to provide a positive stop for valve seat 50, however, it is anticipated that valve seat 50 could alternatively directly contact shoulder 48d. Valve seat 50 includes a valve seat end wall 50a which is transverse to outlet valve bore axis 43a. Valve seat 50 also includes a valve seat sidewall 50b which is annular in shape and which extends away from valve seat end wall 50a such that valve seat sidewall 50b spaces valve seat end wall 50a away from shoulder 48d. An outlet flow passage 50c extends through valve seat end wall 50a such that outlet flow passage 50c is centered about outlet valve bore axis 43a and such that outlet flow passage 50c provides a path for fuel through valve seat end wall 50a when fuel flows from inner end 48a to outer end 48b in order to communicate pressurized fuel from pumping chamber 38 to fuel injectors 16. Furthermore, one or more pressure relief flow passages 50d extend through valve seat end wall 50a such that each pressure relief flow passage 50d is laterally spaced from outlet flow passage 50c relative to outlet valve bore axis 43a. In this way, pressure relief flow passages 50d are arranged in a polar array which is centered about outlet valve bore axis 43a. Pressure relief flow passages 50d provide a path for fuel through valve seat end wall 50a when fuel flows from outer end 48b to inner end 48a during an over-pressure condition downstream of outlet and pressure relief valve assembly 42. While two pressure relief flow passages 50d have been illustrated in the figures, it should be understood that different quantities may be used. The inner periphery of valve seat sidewall 50b includes a plurality of circumferentially alternating flow channels 50e and valve guides 5 Of such that flow channels 50e provide a path for fuel to flow therethrough. Valve seat 50 is sealed to valve housing 48 such that flow is prevented radially between the outer periphery of valve seat 50 and the inner periphery of valve housing bore 48c. For example, the outer periphery of valve seat 50 may engage the inner periphery of valve housing bore 48c in an interference fit. Outlet and pressure relief valve assembly 42 also includes an outlet valve member 52 which is located within valve seat sidewall 50b and which is moveable between 1) a seated position, shown in FIGS. 3 and 7, against said valve seat end wall 50a which prevents flow through valve housing 48 by way of outlet flow passage 50c in a first direction from outer end 48b to inner end 48a and 2) an unseated position, shown in FIG. 6, spaced apart from valve seat end wall 50a which allows flow through valve housing 48 by way of outlet flow passage 50c in a second direction from inner end 48a to outer end 48b. Movement of outlet valve member 52 in a direction laterally relative to outlet valve bore axis 43a is limited by valve guides 5 Of while flow channels 50e provide a path to flow around outlet valve member 52 when outlet valve member 52 is unseated. As illustrated herein, outlet valve member 52 is spherical. While outlet valve member 52 may be illustrated herein as a full sphere, spherical as used herein includes a portion of a sphere, such as a frustum of a sphere, a spherical cap, or a spherical segment. Alternatively, outlet valve member 52 may be conical or frustoconical. Outlet valve member 52 is biased toward valve seat end wall 50a by an outlet valve spring 54 which is grounded to valve housing 48 through an outlet valve spring seat 56 and which is located entirely within valve seat sidewall 50b. Outlet valve spring 54 is a coil compression spring and outlet valve spring seat 56 is a disk with one or more outlet valve spring seat apertures 56a extending therethrough to allow passage of fuel. Outlet valve spring seat apertures 56a are arranged in a polar array centered about outlet valve bore axis 43a, thereby allow the central portion of outlet valve spring seat 56 to remain solid to provide a surface for outlet valve spring 54 to engage. While five outlet valve spring seat apertures 56a have been illustrated in the figures, it should be understood that different quantities may be used. The outer edge of outlet valve spring seat 56 is captured axially between valve seat sidewall 50b and shoulder 48d such that outlet valve spring seat 56 engages both valve seat sidewall 50b and shoulder 48d. Since the outer edge of outlet valve spring seat 56 is captured axially between valve seat sidewall 50b and shoulder 48d such that outlet valve spring seat 56 engages both valve seat sidewall 50b and shoulder 48d, shoulder 48d indirectly positions valve seat 50 within valve housing bore 48c. In this way, valve seat 50 is pressed into place during assembly of outlet and pressure relief valve assembly 42 until it is stopped by shoulder 48d and outlet valve spring seat 56.

Outlet and pressure relief valve assembly 42 also includes a pressure relief valve member 58 located within valve housing bore 48c between valve seat 50 and inner end 48a such that pressure relief valve member 58 is moveable between 1) a seated position, shown in FIGS. 3 and 6, against valve seat end wall 50a which prevents flow through valve housing 48 in the second direction from inner end 48a to outer end 48b by way of pressure relief flow passages 50d and 2) an unseated position, shown in FIG. 7, spaced apart from valve seat end wall 50a which allows flow through valve housing 48 in the first direction from outer end 48b to inner end 48a by way of pressure relief flow passages 50d. Pressure relief valve member 58 is centered about outlet valve bore axis 43a such that pressure relief valve member 58 extends along outlet valve bore axis 43a from a pressure relief valve member inner end 58a, which is proximal to inner end 48a, to a pressure relief valve member outer end 58b, which is distal from inner end 48a. A pressure relief valve member outlet flow passage 58c extends axially through pressure relief valve member 58 from pressure relief valve member inner end 58a to pressure relief valve member outer end 58b such that pressure relief valve member outlet flow passage 58c provides a path for fuel to flow when outlet valve member 52 is unseated. Pressure relief valve member outlet flow passage 58c is centered about outlet valve bore axis 43a. The outer periphery of pressure relief valve member 58 is a surface of revolution about outlet valve bore axis 43a such that the outer periphery is stepped in diameter, thereby forming a pressure relief valve spring seat 58d which is annular in shape and which is transverse to outlet valve bore axis 43a, and is preferably perpendicular to outlet valve bore axis 43a. Pressure relief valve member outer end 58b is annular in shape, is planar, and projects over the entirety of pressure relief flow passages 50d such that pressure relief valve member 58 prevents fluid communication through pressure relief flow passages 50d when pressure relief valve member 58 is in the seated position.

Outlet and pressure relief valve assembly 42 also includes a pressure relief valve spring 60 which is located within valve housing bore 48c. It should be noted that pressure relief valve spring 60 is surrounded directly by valve seat sidewall 50b, i.e. there are no intermediate elements located radially between pressure relief valve spring 60 and valve seat sidewall 50b, thereby allowing any radial shift of pressure relief valve spring 60 to be controlled directly by valve housing 48. Pressure relief valve spring 60 is a coil compression spring which is held in pression by pressure relief valve spring seat 58d and a pressure relief valve spring retainer 62. Pressure relief valve spring retainer 62 is located within valve housing bore 48c and is annular in shape such that a pressure relief valve spring retainer outlet passage 62a extends axially, i.e. along outlet valve bore axis 43a, through pressure relief valve spring retainer 62, thereby providing a path for fuel to flow when outlet valve member 52 is unseated. Pressure relief valve spring retainer outlet passage 62a is centered about outlet valve bore axis 43a. The outer periphery of pressure relief valve spring retainer 62 is engaged with the inner periphery of valve housing bore 48c and during assembly of outlet and pressure relief valve assembly 42, pressure relief valve spring retainer 62 is pressed into valve housing bore 48c until a predetermined compression force, within an acceptable tolerance range, of pressure relief valve spring 60 is achieved. In this way, pressure relief valve member 58 is unseated from valve seat 50 when a predetermined pressure downstream of outlet and pressure relief valve assembly 42 occurs.

Inlet valve assembly 40 will now be described with particular reference to FIG. 2. Inlet valve assembly 40 generally includes an inlet valve member 40a, an inlet valve seat 40b, and a solenoid assembly 40c. Inlet valve member 40a and inlet valve seat 40b act together as a check valve which normally allows fuel to flow into pumping chamber 38 from pump housing inlet passage 41 when pumping plunger 34 is moving to expand the volume of pumping chamber 38, i.e. moving downward as oriented in the figures during the intake stroke, but prevents fuel from flowing from pumping chamber 38 to pump housing inlet passage 41 when pumping plunger 34 is moving to decrease the volume of pumping chamber 38, i.e. upward as oriented during the compression stroke. However, an electronic control unit 64, in conjunction with feedback from a pressure sensor 66 which senses pressure within fuel rail 44, may be used to time the supply of an electric current to solenoid assembly 40c during the compression stroke, thereby varying the proportion of fuel from the compression stroke that is supplied to fuel injectors 16 and the proportion of fuel from the compression stroke that is spilled back to pump housing inlet passage 41. When an electric current is supplied to solenoid assembly 40c, inlet valve member 40a and inlet valve seat 40b act together as a check valve, i.e. fuel can flow into pumping chamber 38 through inlet valve assembly 40 but fuel cannot flow out of pumping chamber 38 through inlet valve assembly 40. Conversely, when no electric current is supplied to solenoid assembly 40c, inlet valve member 40a is held open, thereby allowing fuel to flow back to pump housing inlet passage 41 during a portion of the compression stroke, thereby allowing for the appropriate pressure and volume of fuel to be provided to fuel injectors 16. Inlet valve assembly 40 will not be describe further herein, however, further details may be found in United States Patent Application Publication No. US 2020/0011279 A1 to Dauer et al, the disclosure of which is hereby incorporated by reference in its entirety.

In operation, and with particular reference to FIGS. 2 and 6, when inlet valve assembly 40 is closed and pumping plunger 34 is in the compression stroke, pressure within pumping chamber 38 is elevated, thereby resulting in a force sufficient to cause outlet valve member 52 to unseat from valve seat end wall 50a. Consequently, outlet flow passage 50c is opened, thereby allowing fuel to flow from pumping chamber 38 to fuel injectors 16. It should be noted that the coaxial nature of pressure relief valve spring retainer outlet passage 62a, pressure relief valve member outlet flow passage 58c, and outlet flow passage 50c provides an unobstructed passage, in a direction parallel to outlet valve bore axis 43a, from inner end 48a to outlet valve member 52. As a result, the fuel passing through pressure relief valve assembly 42 from pumping chamber 38 to fuel injectors 16 departs from linear flow to flow around outlet valve member 52, however, the spherical nature of outlet valve member 52 provides for a smooth transition, thereby minimizing restriction to the outlet flow of fuel. It should also be noted that outlet valve member 52 is located entirely within fuel pump housing 28 which minimizes transmission of audible noise which may otherwise be transmitted to an operator of a motor vehicle containing internal combustion engine 12. Furthermore, valve housing 48 extends into pumping chamber 38 such that a portion of valve housing 48 is aligned with pumping plunger 34 in a direction parallel to plunger bore axis 32. This relationship minimizes the volume of pumping chamber 38 which is formed larger than necessary in order to accommodate installation of inlet valve seat 40b. If pumping chamber 38 is too large in volume, pumping efficiency can be reduced.

In operation, and with particular reference to FIGS. 2 and 7, if the pressure downstream of pressure relief valve assembly 42 exceeds a predetermined threshold, the force of pressure relief valve spring 60 is overcome, thereby allowing pressure relief valve member 58 to unseat from valve seat end wall 50a. Consequently, pressure relief flow passages 50d are opened, thereby allowing fuel pressure to be relieved back to pumping chamber 38, thereby mitigating the over-pressure condition downstream of pressure relief valve assembly 42. While pressure relief valve member 58 should rarely, if ever, open during the life of high-pressure fuel pump 20, it should be noted that pressure relief valve member 58 is located entirely within fuel pump housing 28 which minimizes transmission of audible noise which may otherwise be transmitted to an operator of a motor vehicle containing internal combustion engine 12. It should also be noted that the planar mating nature of pressure relief valve assembly 42 and valve seat end wall 50a, which may be more likely to produce noise, is more easily tolerated applied to the pressure relief function because of its low use over its lifetime. When inlet valve member 40a is held open during a portion of the compression stroke, thereby allowing fuel to flow back to pump housing inlet passage 41, pressure pulsations may be generated within high-pressure fuel pump 20. If left unmitigated, these pressure pulsations may propagate upstream from inlet valve assembly 40 and cause undesirable effects on low-pressure fuel pump 18 and other components in fuel system 10 as well as producing undesirable audible noise. In order to mitigate these pressure pulsations, and now with particular reference to FIGS. 2 and 8-10, high-pressure fuel pump 20 includes a pulsation damper 68 located within a fuel volume 70 defined by a damper cup 72 and by fuel pump housing 28 such that fuel volume 70 is in fluid communication with inlet valve assembly 40 and is also in fluid communication with pumping chamber 38 when inlet valve assembly 40 is open. In the paragraphs that follow, pulsation damper 68 and damper cup 72 will be described in greater detail.

Pulsation damper 68 is a two-piece assembly comprising a pulsation damper first half 68a and a pulsation damper second half 68b which are sealingly joined together to define a damping volume 68c between pulsation damper first half 68a and pulsation damper second half 68b. Pulsation damper first half 68a is defined by first damper wall 68d which is flexible in response to the pressure pulsations within fuel volume 70 such that first damper wall 68d is centered about a damper axis 68e. Pulsation damper first half 68a is also defined by a first attachment flange 68f which is spaced axially from first damper wall 68d such that a first connecting wall 68g joins first damper wall 68d and first attachment flange 68f, consequently, pulsation damper first half 68a defines a first recess 68h. First attachment flange 68f is substantially planar and may be annular in shape. Similarly, pulsation damper second half 68b is defined by a second damper wall 68i which is flexible in response to the pressure pulsations within fuel volume 70 such that second damper wall 68i is centered about damper axis 68e. Pulsation damper second half 68b is also defined by a second attachment flange 68j which is spaced axially from second damper wall 68i such that a second connecting wall 68k joins second damper wall 68i and second attachment flange 68j, consequently, pulsation damper second half 68b defines a second recess 681. Second attachment flange 68j is substantially planar and may be annular in shape. Pulsation damper first half 68a and pulsation damper second half 68b sealingly mate together at first attachment flange 68f and second attachment flange 68j such that first recess 68h and second recess 681 face each other and together comprise damping volume 68c. First attachment flange 68f and second attachment flange 68j may be sealed together, by way of non-limiting example only, by welding, thereby fluidly segregating damping volume 68c from fuel volume 70. Damping volume 68c may be filled with ambient air or an inert gas such as pressurized nitrogen or other media which contracts to damp pressure pulsations and then expands when the pressure pulsation subsides. Alternatively, another method may be used such as a spring or foam within damping volume 68c in order to provide desirable damping characteristics without permanent deformation.

Damper cup 72 includes a sidewall 72a which extends along a damper cup axis 72b from a sidewall first end 72c to a sidewall second end 72d such that sidewall 72a is annular in shape. Damper cup 72 also includes an end wall 72e which closes sidewall second end 72d. Sidewall first end 72c is closed by fuel pump housing 28. For example, as illustrated in the figures, fuel pump housing 28 incudes a fuel pump housing extension 28a which is cylindrical and which extends into sidewall first end 72c. Damper cup 72 is sealingly fixed to fuel pump housing 28, for example by circumferentially welding sidewall 72a to fuel pump housing extension 28a as indicated by weld 74. Alternatively, or additionally, damper cup 72 may be fixed to fuel pump housing 28 using mechanical fasteners and sealing members such as O-rings or other mechanical seals known to those of ordinary skill in the art.

In order to suspend pulsation damper 68 within fuel volume 70 such that first damper wall 68d and second damper wall 68i are exposed to the fuel within fuel volume 70, damper cup 72 includes a support shoulder 72f within fuel volume 70 upon which first attachment flange 68f is supported. Support shoulder 72f is transverse to damper cup axis 72b and is a segment of an annulus extending uninterrupted about, i.e. around, damper cup axis 72b from a shoulder first end 72g to a shoulder second end 72h such that shoulder first end 72g and shoulder second end 72h are separated from each other by a gap 72i which is uninterrupted. Support shoulder 72f extends from shoulder first end 72g to shoulder second end 72h for an angular distance of 270° ± 60 ⁰ around damper cup axis 72b with the remainder of the angular distance around damper cup axis 72b being provided by gap 72i. In other words, the sum of the angular distances about damper cup axis 72b of support shoulder 72f and gap 72i is 360°. Gap 72i provides fluid communication around pulsation damper 68 in order to allow both first damper wall 68d and second damper wall 68i to be exposed to the pressure pulsations during operation. Damper cup 72 also includes an inlet fitting 72j which is connected to low-pressure fuel supply passage 22 down stream of fuel pressure regulator 24. In this way, fuel enters high-pressure fuel pump 20 through inlet fitting 72j such that inlet fitting 72j provides a fuel inlet into fuel volume 70. Inlet fitting 72j is tubular and is connected to sidewall 72a such that inlet fitting 72j is positioned within gap 72i, thereby providing unrestricted passage of fuel. As can be seen in the figures, inlet fitting 72j is positioned through sidewall 72a such that inlet fitting 72j is positioned axially between sidewall first end 72c and sidewall second end 72d to be aligned with support shoulder 72f. Alternatively, but not shown, inlet fitting 72j may be connected to end wall 72e or may be omitted from damper cup 72 entirely by providing an inlet fitting elsewhere on fuel pump housing 28.

Sidewall 72a and end wall 72e are formed from a single piece of material through one or more of deep drawing and stamping of a piece of sheet metal. Consequently, sidewall 72a also includes an exterior shoulder 72k on the outer periphery thereof which is complementary to support shoulder 72f and which is transverse to damper cup axis 72b. As a result, exterior shoulder 72k extends uninterrupted about damper cup axis 72b from an exterior shoulder first end 721 to an exterior shoulder second end 72m for an angular distance of 270° ± 60°. As can be seen in the figures, at least a portion of exterior shoulder 72k is axially aligned, i.e. in a direction parallel to damper cup axis 72b, with sidewall first end 72c which allows exterior shoulder 72k to be used as a surface to press against when installing damper cup 72 to fuel pump housing extension 28a. By having at least a portion of exterior shoulder 72k axially aligned with sidewall first end 72c, the press force is applied in a straight line through sidewall 72a, i.e. there is no bending moment applied. A cylindrical surface segment 72n extends from exterior shoulder first end 721 and exterior shoulder second end 72m such that inlet fitting 72j is connected to cylindrical surface segment 72n and such that inlet fitting 72j is positioned between sidewall first end 72c and sidewall second end 72d to be aligned with exterior shoulder 72k, i.e. inlet fitting 72j and exterior shoulder 72k are at the same elevation in a direction parallel to damper cup axis 72b.

A positioning member, illustrated herein as spring 76, is provided in order to keep first attachment flange 68f in contact with support shoulder 72f. More specifically, spring 76 has been illustrated herein as a wave spring, however, other resilient and compliant or rigid alternatives are anticipated, for example, coil compression spring or solid spacers. Spring 76 is held in compression against second attachment flange 68j and the axial end of fuel pump housing extension 28a. Consequently, the position of pulsation damper 68 is maintained within fuel volume 70 which ensures that pulsation damper 68 does not move during operation, regardless of pressure pulsations or vibration forces.

High-pressure fuel pump 20 which includes damper cup 72 provides several advantages over known arrangements. Support shoulder 72f extending uninterrupted for an angular distance of 270° ± 60° around damper cup axis 72b with the remainder of the angular distance around damper cup axis 72b being provided by gap 72i ensures that pulsation damper 68 can be dropped into position without the possibility of being misassembled between discrete support features which are spaced circumferentially as is known in the prior art, thereby acting similar to a manhole cover in that pulsation damper 68 cannot be positioned between support shoulder 72f and end wall 72e in such a way as to prevent assembly of, or allow improper assembly of, pulsation damper 68 and damper cup 72 with fuel pump housing 28. Support shoulder 72f extending uninterrupted for an angular distance of 270° ± 60° around damper cup axis 72b provides increased surface contact between support shoulder 72f and pulsation damper 68, thereby minimizing contact stress that could potentially negatively impact durability. The addition of support shoulder 72f and exterior shoulder 72k also increases the rigidity of damper cup 72, thereby minimizing flexing of damper cup 72 which minimizes audible noise. Furthermore, exterior shoulder 72k provides increased surface contact with tooling (not shown) that is used to press damper cup 72 onto fuel pump housing extension 28a and allows the force to be transferred straight through sidewall 72a. Also furthermore, the tooling used to press damper cup 72 onto fuel pump housing extension 28a can be used to orient damper cup 72 with respect to fuel pump housing 28 since the length of exterior shoulder 72k ensures a unique orientation which ensures that inlet fitting 72j is in the required radial orientation position. While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.