GB2578166A

GB2578166A - A fuel pump

Info

Publication number: GB2578166A
Application number: GB1817096.9A
Authority: GB
Inventors: Buckley Paul
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-10-19
Filing date: 2018-10-19
Publication date: 2020-04-22
Anticipated expiration: 2038-10-19
Also published as: GB2578166B; GB201817096D0

Abstract

A fuel pump 10 assembly for controlling the flow of pressurised fuel to a common rail fuel volume, the pump 10 assembly comprises a pump housing 22 defining an inlet and an outlet; a valve seat 46 formed in the pump housing 22; a valve member 36 disposed in the pump housing 22 and having a closed position to engage the valve seat 46 to prevent fuel from flowing through the outlet; a valve stop 48 arranged to engage with the valve member 36 when the valve member is in an open position; a spring 44 configured to urge the valve member towards the valve seat 46; and a damper (72, Fig. 4a) arranged to dampen the movement of the valve member as it moves towards the valve stop. The damper (72, Fig. 4a) is integrally formed with the valve member. The damper may include damping apertures which allows for reduced stiffness of the valve body without reducing its sidewall thickness.

Description

A FUEL PUMP

FIELD OF THE INVENTION

This invention relates to a fuel pump for controlling the flow of pressurised fuel to a common rail volume. In particular, but not exclusively, the present invention relates to a fuel pump comprising a valve member having an integral damper.

BACKGROUND

Fuel pumps are employed in a variety of engine systems. Common rail fuel injection systems for compression ignition (diesel) internal combustion engines provide excellent control of all aspects of engine operation and require a pump to act as a source of high pressure fuel.

One known common rail fuel pump is of radial pump design and includes three pumping plungers arranged at equi-angularly spaced locations around an engine driven cam. Each plunger is mounted within a plunger bore provided in a pump head mounted to a main pump housing. As the cam is driven in use, the plungers are caused to reciprocate within their bores in a phased, cyclical manner. As the plungers reciprocate, each causes pressurisation of fuel within a pump chamber defined at one end of the associated plunger bore in the pump head.

Fuel that is pressurised within the pump chambers is delivered to a common high pressure supply line and, from there, is supplied to a common rail or other accumulator volume, for delivery to the downstream injectors of the common rail fuel system.

Such a fuel pump has an outlet valve for controlling the flow of the pressurised fuel from the pump chamber. The outlet valve is a non-return valve, having a valve member which is arranged within a valve housing of the fuel pump. The valve member may be a ball or a pintel type closing member which is biased towards a valve seat by a spring. A first end of the closing member is arranged to seal off an aperture disposed in the valve seat when the valve member is arranged in a closed positon. A second surface of the valve member may be arranged to engage with the valve stop when the valve member is moved to an open position. Movement of the valve member is generally limited in the fluid flow direction by a valve stop (or backstop) arranged in a pump housing. The valve stop engaging surface of the valve member forms an impact surface which is arranged to collide against the valve stop each time the valve opens. The repeated collisions between the impact surface and the valve stop can cause fatigue in the body of the valve member leading to degradation and ultimately, failure of the outlet valve. It is against this background that the invention has been devised.

STATEMENTS OF INVENTION

According to an aspect of the present invention there is provided a fuel pump assembly for controlling the flow of pressurised fuel to a common rail fuel volume. The pump assembly comprises a pump housing defining a passageway having an inlet and an outlet; a valve seat formed in the pump housing; a valve member disposed in the pump housing and having a closed position to engage the valve seat to prevent fuel from flowing through the outlet; a valve stop arranged to engage with the valve member when the valve member is in an open position; a spring configured to urge the valve member towards the valve seat; and a damper arranged to dampen the movement of the valve member as it moves towards the valve stop. The damper is integrally formed with the valve member.

Advantageously, the integrally formed damper enables the valve member to absorb energy when the valve member impacts with the valve stop of the pump housing during actuation of the outlet valve. The damper thereby prevents fatigue in the valve member and extends the working life of the fuel pump.

The damper may be defined by an aperture arranged in a sidewall of the valve member. The aperture may be formed by any suitable means including drilling, for example. The aperture may comprise a depth which extends into a body of the valve member its outer surface. Advantageously, the aperture reduces the material in the body of the valve member, which thereby reduces the stiffness of the valve member such that it may be capable of greater elastic deformation when during an impact with the valve seat, as the valve member moves towards its closed position.

The aperture may be a non-fluid flow carrying channel in the sidewall of the valve member. The valve member may comprise a number of fluid-carrying channels for allowing fluid to pass through the valve member when it is arranged in its closed position, i.e. when the outlet valve is open. By contrast, the non-fluid carrying apertures may be arranged such that the fluid cannot be directed through the aperture in order to pass through the valve member and/or the outlet valve.

The valve member may comprise an axial bore. The aperture may extend through the sidewall of the valve member to the axial bore. The axial bore may be arranged with an opening at the end of the valve member which engages with the valve seat. An internal wall of the valve member's sidewall may define an internal wall of the axial bore.

The axial bore may be configured to accommodate the spring of the valve member. The damper may comprise a plurality of apertures and at least one of the plurality of apertures may be substantially elliptical. At least one of the plurality of apertures may be substantially circular. The substantially curved outline of the aperture advantageously distributes the stresses within the sidewall of the valve member around the aperture. In particular, an aperture comprising sharp corners (such as a square) would produce a concentration of stress in the corners, which could lead to failure of the valve member.

Each of the plurality of apertures may lie in a substantially transverse plane to the axial bore. The axial bore may comprise a central axis which is aligned with the longitudinal direction of the valve member. The aperture may define an axis which is orthogonally aligned with the central axis of the axial bore.

Each of the plurality of the apertures may have substantially the same radius in the transverse plane of the axial bore. In this way, each of the apertures represents the absence of the same volume of material from the sidewall of the valve member. Each aperture causes an equivalent reduction in the stiffness of the valve member which reduces any concentration of stress within the sidewall of the valve member when in use.

The plurality of apertures may be spaced equidistantly around the circumference of the axial bore. When each of the plurality of the apertures has substantially the same radius in the transverse plane of the axial bore, a spacing between each of the plurality of apertures may be substantially equal to the radius of curvature of each aperture in the transverse plane of the axial bore.

The spring may be integrally formed with the valve member. The valve member may comprise an axial bore having a sidewall, the sidewall comprising a substantially helical aperture which defines the damper of the valve member. The helical valve member may be arranged such that it defines both the spring and the damper of the valve member. The spring and/or damping effect of the helical aperture may be determined by the number of turns of the helical aperture around the valve member. The helical aperture may comprise at least two turns around the valve member.

The damper may be arranged substantially towards an end of the valve member which is arranged to engage with the valve stop. The aperture of the present invention may be configured to act as a spring and/or a damper of the valve member. Arranging the aperture towards the end of the valve member which engages with the valve stop, thereby conveniently reduces the un-sprung and/or un-damped mass of the valve member.

The valve member may define a closing member of an outlet valve of the fuel pump.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the invention will now be described, by way of example only, with reference to the accompanying drawing, in which: Figure 1 is a fragmentary elevational view of a fuel pump, according to the present invention; Figures 2 and 3 are enlarged fragmentary elevational views of an outlet valve of the fuel pump of Figure 1 illustrating a valve member of the outlet valve in an open and a closed position, respectively; Figures 4a and 4b are side views of the valve member shown in Figure 2; Figure 5 is a longitudinal-sectional view of the valve member shown in Figure 2; Figure 6 is a side view of a valve member for use in a fuel pump according to an alternative embodiment of the present invention; Figure 7 is a longitudinal-sectional view of the valve member shown in Figure 6; and Figure 8 is a side view of a valve member for use in a fuel pump according to a further embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings and in particular Figures 1 to 5, one embodiment of a fuel pump 10, according to the present invention, is shown. The fuel pump 10 is suitable for controlling the supply of pressurised fuel to a common rail fuel injection system of a compression ignition (diesel) internal combustion engine of a vehicle (not shown). The fuel pump 10 includes an outlet valve member having an integral damper which is configured to allow the valve member to withstand the forces that are exerted upon it during operation of the fuel pump 10.

The fuel pump 10, also referred to as the fuel pump assembly, comprises an inlet valve 12 to allow low pressure fuel into the fuel pump assembly 10 and an outlet valve 14 to allow high pressure fuel to leave the fuel pump assembly 10 once it has been pressurised. The fuel is pressurised in a fuel chamber 16 by a pumping plunger 18 reciprocating in a plunger bore 20 provided in a pump housing 22, also referred to as a pump body. This plunger may, for example, be driven by a cam (not shown) and is used to pressurise the fuel.

The inlet valve 12 comprises an inlet valve member 24 in the form of a valve pin.

The inlet valve member 24 reciprocates in an inlet bore 26 of the pump housing 22. The inlet bore 26 joins the fuel chamber 16 at a valve aperture 27, which defines an inlet valve seat 28. A valve closure end 32 of the valve member 24 is biased to seat against the inlet valve seat 28 by an inlet biasing arrangement in the form of a spring 30. The inlet biasing spring 30 works in compression, one end located in an annular groove 34 on the pump housing 22 and the other end fixed to a part of the inlet valve member 24 remote from the valve seat 28.

The outlet valve 14 comprises an outlet valve member 36 in the form of a bullet nosed closing element, or pintel. The outlet valve member 36 is located in an outlet bore 38 which is formed within the pump housing 22 and is fluidly connected to the fuel chamber 16 at a first valve aperture 40, which defines a valve seat 46. A second valve aperture 42 located at the other end of the outlet bore 38 provides a fluid connection to the common fuel rail located downstream. In this way, the first valve aperture 40 and the second valve aperture 42 defines an inlet and an outlet of the outlet valve 14, respectively.

The outlet valve member 36 is biased to close the first valve aperture 40 by an outlet biasing arrangement, also in the form of a spring 44. The biasing spring 44 works in compression, one end being arranged to engage within the outlet valve member 36 whilst the other end is fixed to a portion of the outlet bore 38 which is remote from the first valve aperture 40.

Both the inlet valve 12 and the outlet valve 14 are non-return valves, sometimes alternatively referred to in the art as check valves. Each valve is biased so that it will only open at a distinct opening pressure. The opening pressure for the inlet valve 12 is lower than the opening pressure for the outlet valve 14. The fuel pump works in the following way. When the plunger 18 moves down, it expands the size of the fuel chamber 16 and lowers the pressure of the fuel within it. When the pressure is sufficiently low, the difference in pressure between the fuel inlet pressure and the fuel chamber pressure becomes sufficient for the inlet valve 12 to open and for fuel to be admitted into the fuel chamber 16. When the fuel chamber 16 fills and the plunger 18 starts to move upwards, the pressure in the fuel chamber 16 increases. When the inlet fuel pressure no longer exceeds the fuel chamber pressure sufficiently to hold the inlet valve 12 open, the inlet valve 12 closes.

Throughout these stages, the outlet valve 14 has been closed as there has not been sufficient fuel chamber pressure to open it. As the plunger 18 continues to move upwards in the plunger bore 20, the pressure in the fuel chamber 16 rises to the point where it is sufficient to open the outlet valve 14. When the outlet valve 14 opens, pressurised fuel passes through the outlet valve 14 until the fuel chamber pressure drops to the point when the outlet valve 14 closes again. The cycle described above then starts again and repeats.

The outlet valve 14 will now be described in more detail with reference to Figures 2 to 5. The outlet valve 14 comprises the valve member 36 and the spring 44 which are both disposed in the outlet bore 38 of the fuel pump 10. The outlet bore 38 is formed in the pump housing 22 which thereby defines a valve housing of the outlet valve 14. The outlet bore 38 has a generally circular cross-sectional shape which allows it to receive the substantially cylindrical valve member 36.

Both the valve member 36 and the surrounding pump housing 22 are made from a rigid material such as a metal or metal alloy.

With particular reference to Figures 4a and 4b, the valve member 36 is shown to have a substantially cylindrical body 50 with a first end 52 consisting of a rounded dome, and a second end 54 having a substantially flat surface. It should be appreciated that the cylindrical body 50 of the valve member 36 has a close fit to the interior wall of the outlet bore 38 so as to form a sealed interface to prevent the passage of fuel. The first end 52 of the valve member 36 faces against the flow of fuel and thus defines a leading end of the valve member 36. The second end 54 of the valve member 36 faces substantially towards the direction in which fuel flows during operation of the outlet valve 14 such that the second end 54 defines a trailing end of the valve member 36.

The spring 44 is of a coil type, also known as a helical spring. The spring 44 is fixed, at one end, to a portion of the outlet bore 38 which is remote from the inlet valve aperture 40. The fixed end of the spring 44 is held in place by a spring seat which is disposed within the outlet bore 38. A free end of the spring 44 is disposed within an axial bore 60 provided in the valve member 36. The spring 44 is arranged to bias the valve member 36 towards the second aperture 42 of the outlet valve 14. It should be appreciated that the spring 44 is conventional and known in the art. The spring 44 is installed within the valve member 36 by pressing it's free end into the axial bore 60 and forcing it to a position such that it exerts the necessary biasing force upon the valve member 36.

The outlet valve 14 includes a valve stop 48 disposed at the opposite end of the outlet bore 38 to the valve seat 46. The valve member 36 is configured to move reciprocally between the valve seat 46 and the valve stop 48. It should be appreciated that both the valve seat 46 and the valve stop 48 are integral portions of the pump housing 22 and together they form a single monolithic structure.

The valve seat 46 has a generally frusta-conical cross-sectional shape and is arranged to receive a leading end of the valve member 36. The biasing spring 44 urges the valve member 36 toward the valve seat 46 so that the valve member 36 engages the valve seat 46 when valve member 36 is arranged in a closed position, as illustrated in Figure 2. Hence, the valve member 36 seals off the first valve aperture 40, when in its closed position, thereby preventing fuel from flowing into the outlet bore 38.

The valve stop 48 is arranged to engage with the trailing end of the valve member 36 when the valve member 36 is in an open position, as illustrated in Figure 3. The valve stop 48 is arranged to limit the movement of the valve member 36 in the fluid flow direction. The valve stop 48 comprises a resilient lip which extends in a radially inward direction from the interior wall of the outlet bore 38. The resilient lip provides a rigid obstacle to the valve member 36 as it moves under the force of the pressurised fuel moving in the fluid flow direction.

Accordingly, the flat surface at the trailing end of the valve member 36 is configured to impact against the valve stop 48 as the valve member 36 assumes its open position. The flat surface at the trailing end of the valve member 36 defines an impact surface 56 of the valve member 36.

The valve member 36 further includes a number of circular damping apertures 72 arranged in a sidewall 70 of the valve body 50. The sidewall 70 is comprised of a tubular portion of the valve body 50 which also defines the interior wall of the axial bore 60. The valve body 50 defines a pintel shape comprising a domed portion at one end and a hollow tube portion at the other end. The damping apertures 72 are formed by drilling holes in a substantially radial direction through the sidewall 70 from an exterior surface 74 of the valve body 50 through to the interior wall of the axial bore 60.

The damping apertures 72 are non-fluid flow carrying channels disposed in the sidewall 70 of the valve member 36. The damping apertures 72 reduce the stiffness of the sidewall 70 making the valve body 50 more compliant when a force is applied to the valve body in a substantially longitudinal direction. Hence, the damping apertures 72 collectively define an integral damper in the sidewall 70 of the valve member 36, which enables the valve member 36 to absorb energy when the impact surface of the 56 collides with the valve stop 46. The effect of the inclusion of the damper within the valve member 36 is to reduce the stiffness of valve body 50 by approximately 50%. In embodiments, the damping apertures 72 are configured such that they cause a reduction in the stiffness of valve body 50 of between 30% and 60%.

The valve member 36 shown in Figures 4a and 4b comprises four circular damping apertures 72 arranged in two sets of opposing pairs. The centre point of each damping aperture 72 is separated from its neighbour about the circumference of the axial bore 60 by an angle of 90°. The four damping apertures 72 are arranged in a symmetrical fashion around the circumference of the valve body 50 in order to balance the pressures that are exerted on the sidewall 70 of the valve member 36 during operation of the outlet valve 14. In an alternative embodiment, the valve member 36 comprises three damping apertures 72, which are equally spaced around the valve body 50 and are separated from each other, about the circumference of the axial bore 60, by an angle of 120°.

Each of the damping apertures 72 lies in a common transverse plane T with respect to the axial bore 60 of the valve member 36. The damping apertures 72 each have the same radius r0 in the common transverse plane of the axial bore 60. The damping apertures 72 are also spaced equidistantly apart from each other around the circumference of the valve body 50. The circumferential spacing S between each of the neighbouring damping apertures 72 is substantially equal to the radius n25 each damping aperture in the transverse plane of the axial bore 60.

The damping apertures 72 are substantially circular such that the continuous curvature of the circular damping aperture 72 prevents a concentration of stress at any single point within the sidewall 70 of the valve body 50, which could otherwise lead to stress fatigue and even premature failure of the valve member 36. Alternatively, the damping apertures 72 can be ellipses.

The damping apertures 72 are arranged towards the trailing end of the valve member 36, i.e. towards the impact surface 56 that is configured to collide with the valve stop 48 as the valve member 36 approaches its closed position. Locating the damping apertures 72 towards the trailing end of the valve member 36 advantageously reduces the sprung mass of the remaining valve body 50, which thereby improves the stability of the valve member 36 during operation of the outlet valve 14. A further advantage of the integral damper is to prevent the valve body 50 from radially expanding during the longitudinal compression of the valve member 36, when in use, which would otherwise lead to further instability of the outlet valve 14.

It will be appreciated that the physical characteristics of the damper, as defined by the damping apertures 72, may be tuned in order to adjust the stiffness of the sidewall 70. Such physical characteristics may include the radius of each damping aperture 72, the spacing between each damping aperture 72 and the relative position of each damping aperture 72 in a transverse and/or longitudinal direction along the valve body 50.

The valve members 36 shown in Figures 1 to 5 all comprise a single row of damping apertures 72. However, it will be appreciated that the valve body 50 may comprise multiple rows of damping apertures 72. The damping apertures 72 from each row may be aligned in a longitudinal direction with respect to the apertures of the adjacent row. Alternatively, each row of damping apertures 72 may be suitably offset with respect to a neighbouring row of apertures, in accordance with the stiffness requirements of a particular valve member 36.

The integral damper prevents the valve member 36 from becoming fatigued due to repeated collisions between the impact surface 56 and the valve stop 48. By integrating the damper into the valve member 36, the present invention also removes the need to provide a separate damper in the outlet valve 14 assembly, which would otherwise increase the complexity and cost of manufacturing the fuel pump 10. The damping apertures 72 allow the stiffness of the valve body 50 to be reduced without reducing the thickness of the sidewall 70, i.e. by increasing the diameter of the axial bore 60. Hence, the present invention provides a simple and convenient means of introducing compliance into the valve body 50 without weakening the sidewall 70 of the valve member 36, which would otherwise increase the complexity of the valve member's manufacture and assembly within the fuel pump 10.

Figure 5 shows a longitudinal-section of the valve member 36 in which it can be seen that the axial bore 60 extends into the body 50 of the valve member 36 from its trailing end. The axial bore 60 thereby forms an opening 76 at the second end 54 of the valve member 36. At the opposing end of the axial bore 60, a turret 80 extends further into the valve member body 12. The turret 80 projects, longitudinally, into the valve body 50 from an end of the axial bore 60 which is distal to the opening 76 of the valve member 36. The turret 80 is fluidly connected to the exterior surface 74 of the valve body 50 via three equi-angularly spaced radial fluid channels 78. In contrast to the damping apertures 72 described above, these fluid channels 78 are arranged to allow fuel to flow through the valve member 36 in accordance with the fluid flow direction of the outlet valve 14.

The outlet bore 38 defines a passageway through which pressurised fuel from the fuel chamber 16 can flow between the first and second valve apertures 40, 42 of the outlet bore 38, when the valve member 36 is in an open position. During operation of the fuel pump 10, the plunger 18 rises in the plunger bore 20 thereby increasing the pressure of the fuel in the fuel chamber 16, thereby allowing the fuel to overcome the biasing force of the spring 44. The valve member 36 is dislodged from its closed position by the force exerted upon it by the pressurised fuel, and is urged to travel in the flow direction away from the valve seat 46.

In normal operating conditions, the output of the fuel pump 10 is greater than 2,500 bar (250 MPa). Fuel which has been pressurised to such a degree by the plunger 18 is able to flow through the outlet valve 14, which causes the valve member 36 to move away from the valve seat 46 and towards the valve stop 48.

The fluid from the fuel chamber 16 flows through the first aperture 40 into the portion of the outlet bore 38 which lies immediately adjacent to the second aperture 42. From here, the fuel then flows through the fluid channels 78 of the valve member 36, into the turret 80, and then through the axial bore 60 before exiting the valve member 36 through the opening 76 at its trailing end. The fuel exits the outlet valve 14 through the second valve aperture 42 of the outlet bore 38 before travelling onward to the common rail located downstream.

With reference to Figures 6 and 7, an alternative embodiment of the valve member 136 is shown in which the damper comprises a single aperture 172, which forms a helix, or helical shape, that coils around the valve body 150 of the valve member 136. In this way, the remaining portion of the sidewall 170 is configured similarly to a wire of a conventional coiled spring, such that it is arranged to flex in compression due to the forces that are exerted upon the valve member 136 during operation of the outlet valve 14. In this way, the helical aperture 172 defines a coiled portion 180 of the valve body 150. The coiled portion 180 of the valve body 150 is dimensioned to control the damping force of the damper during operation of the outlet valve 14, as the trailing end of the valve member 136 collides with the valve stop 48 of the outlet bore 38.

The helical aperture 172 extends from an exterior surface of the valve body 150 through to the interior surface of the axial bore 160 that is formed within the valve member 136. The helical damping aperture 172 makes two complete turns around the valve body 150. The damping aperture 172 is disposed towards the trailing end of the valve member 136 so as to minimise the un-sprung mass of the valve body 150. The helical damping aperture 172 is formed by electron discharge machining (EMD). However, it will be appreciated by the skilled person that other suitable methods of forming a coiled aperture may be used.

With reference to Figures 6 and 7, the coiled portion 180 of the sidewall 170 is defined by a height H and a thickness T. The coiled portion 180 defines a coil of the valve body 150, the coil being defined by a diameter D and a number of turns of the coiled portion 180. The valve body 150 as shown is arranged such that the thickness T of the coiled portion 180 is equal to D/8. Put another way, the thickness T of the sidewall 170 in the coiled region is 12.5% of the diameter D of the coil. In embodiments, the coiled portion 180 may be configured such that the thickness T is within a range of D/5 and D/10 relative to the diameter D of the coil (i.e. approximately within 10% and 20% of the diameter D). The coiled portion 180 of the valve member 136 is arranged such that its height H is approximately double the thickness T. Alternatively, the relative height H of the coiled portion may be configured to be any suitable value within a range of T to 3T.

All other aspects of the valve member 136 are the same as per previously described embodiments in that the axial bore 160 is arranged to receive the spring 44, which is thereby configured to bias the valve member against the valve seat 46 when it is arranged in the outlet bore 38 of the fuel pump 10.

As with the valve member 36 described in Figures 4a and 4b, the dimensions of the helical aperture 172 controls the stiffness of the valve body 150. The spring behaviour of the valve body 150 is determined in dependence on the relative dimensions of the coiled portion 180 of the sidewall 170. The dimensions of the coiled portion 180 are related to the elastic behaviour according to known spring equations, as would be readily appreciated by the skilled person. In particular, any increase or decrease in the number of turns of the helical spring will result in a corresponding change in the stiffness of the sidewall 170 of the valve member 136. For example, increasing the number of turns of the helical damping aperture 172 leads to a corresponding increase in the ability of the valve body 150 to elastically absorb kinetic energy during the collisions between the valve member 136 and the valve stop 48.

The width of the helical aperture 172 also affects the compliance of the valve member 136, such that any increase in the width (wA) of the helical aperture 172, relative to the width (wS) of the coiled portion 180, leads to a reduction in the stiffness of the valve body 150. The wA is also configured to change as the valve member 136 is compressed as it collides with the valve stop 48. The valve member 136 is shown in Figure 7 as being in an uncompressed configuration, in which the helical aperture width wA is approximately equal to the thickness T of the coiled portion. In embodiments, the helical aperture width wA of the uncompressed valve body 150 is substantially less than the thickness T of the sidewall 170.

A further embodiment of the outlet valve 14 is shown in Figure 8 in which a valve member 236 is once again provided with a damper in the form of a helical aperture 272. In this embodiment, the helical aperture 272 comprises three complete turns about its valve body 250. The three turns of the helical aperture 272 leads to a substantial increase in the compliance of the valve body 250 such that there is no longer the need to provide a separate spring in the outlet valve 14 assembly. Rather, the helical aperture 272 enables the valve member 236 to bias its leading end towards the valve seat 46. In this way, both the damper and the spring are integrally formed within the body 250 of the valve member 236. It will be appreciated that the coil of the valve body 250 may be configured to comprise any number of turns without departing from the scope of the present invention. In particular, the coil may also be configured to have less than one complete turn. For example, the coil may have half a complete turn.

It should be appreciated that the valve housing is shown as being integral with the pump housing however, the outlet valve 14 may also comprise a separate valve housing which can be adapted to be disposed within, or at least fluidly connected to, the fuel pump 10. Thus, the valve housing of the outlet valve 14 may be separate to the rest of the pump housing.

The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.

Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than as specifically described.

Claims

CLAIMS: 1. A fuel pump assembly for controlling the flow of pressurised fuel to a common rail fuel volume, the pump assembly comprising: a pump housing defining a passageway having an inlet and an outlet; a valve seat formed in the pump housing; a valve member disposed in the pump housing and having a closed position to engage the valve seat to prevent fuel from flowing through the outlet; a valve stop arranged to engage with the valve member when the valve member is in an open position; a spring configured to urge the valve member towards the valve seat; and a damper arranged to dampen the movement of the valve member as it moves towards the valve stop; wherein the damper is integrally formed with the valve member.
2. The fuel pump according to claim 1, and the damper is defined by an aperture arranged in a sidewall of the valve member.
3. The fuel pump according to claim 2, wherein the aperture is a non-fluid flow carrying channel in the sidewall of the valve member.
4. The fuel pump according to claim 3, wherein the valve member comprises an axial bore, the aperture extending through the sidewall of the valve member to the axial bore.
5. The fuel pump according to claim 4, wherein the axial bore is configured to accommodate the spring, the damper comprising a plurality of apertures and at least one of the plurality of apertures is substantially elliptical.
6. The fuel pump according to claim 5, wherein at least one of the plurality of apertures is substantially circular.
7. The fuel pump according to any of claim 5 or claim 6, wherein each of the plurality of apertures lies in a substantially transverse plane to the axial bore.
8. The fuel pump according to claim 7, wherein each of the plurality of the apertures has substantially the same radius in the transverse plane of the axial bore.
9. The fuel pump according to any of claims 5 to 8, wherein the plurality of apertures are spaced equidistantly around the circumference of the axial bore.
10. The fuel pump according to claim 9, when dependent through 8, wherein a spacing between each of the plurality of apertures is substantially equal to the radius of curvature of each aperture in the transverse plane of the axial bore.
11. The fuel pump according to any one of claims 1 to 4, wherein the spring is integrally formed with the valve member.
12. The fuel pump according to claim 11, wherein the valve member comprises an axial bore having a sidewall, the sidewall comprising a substantially helical aperture which defines the damper of the valve member.
13. The fuel pump according to claim 12, wherein the helical aperture comprises at least two turns around the valve member.
14. The fuel pump according to any preceding claim, wherein the damper is arranged substantially towards an end of the valve member which is arranged to engage with the valve stop.
15. The fuel pump according to any preceding claim, wherein the valve member defines a closing member of an outlet valve of the fuel pump.