GB2581488A

GB2581488A - Sealing assembly

Info

Publication number: GB2581488A
Application number: GB1902148.4A
Authority: GB
Inventors: Coxon Jack
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2019-02-15
Filing date: 2019-02-15
Publication date: 2020-08-26
Also published as: GB201902148D0

Abstract

A high-pressure fuel pump (14, figure 1), for a vehicle, comprises a first component 10, 20 with a first sealing face 52, 54 and a second component 10, 20 with a second sealing face 52, 54 that is engaged with the first sealing face to define a high-pressure fluid seal 50 around a fluid chamber 48 of the fuel pump. A surface of the first component adjacent to the first sealing face comprises a recess 56 that is spaced from the seal and is disposed outside the chamber. The recess being shaped to increase the compliance of the first sealing face to a predetermined extent. The recess may extend continuously around the seal, is preferably axisymmetric and / or annular and / or may comprises a groove. The recess is preferably shaped so that the first sealing face has substantially uniform stiffness. Multiple recesses may be employed. The first component may be a valve body and the second component may be a pump body. A method of fabrication is also claimed.

Description

Sealing Assembly

S Field of the Invention

This invention relates to a sealing assembly for a vehicle device such as a high-pressure fuel pump, and in particular to a sealing assembly for a high-pressure fluid seal subject to cyclic loading.

Background to the Invention

In automotive devices that operate in a reciprocating manner, such as fuel injectors and fuel pumps, various components of the devices are subject to cyclic loading in use. For example, the walls of a pumping chamber in a fuel pump experience cyclic loading as fuel is repeatedly pressurised and then released.

Cyclic loading of this type can induce corresponding cyclic deformation of surfaces exposed to high pressure, which in turn may cause relative movement between neighbouring components of the device.

Such relative movement will tend to cause wear at engaging faces of the neighbouring components. This may pose a particular problem where those faces are required to provide a fluid seal, as the wear will degrade the integrity of the seal over fime.

It is against this background that the invention has been devised.

Summary of the Invention

In broad terms, the invention provides a sealing assembly for a vehicle device configured to handle high-pressure fuel. The sealing assembly comprises a first component comprising a first sealing face and a second component comprising a second sealing face, the second sealing face being engaged with the first sealing face to define a high-pressure fluid seal around a fluid chamber of the device. A surface of the first component adjacent to the first sealing face comprises a recess that is spaced from the seal and is disposed outside the chamber. The recess is shaped to increase the compliance of the first sealing face to a predetermined extent.

An aspect of the invention provides a high-pressure fuel pump for a vehicle. The fuel pump comprises a first component comprising a first sealing face, and a second component comprising a second sealing face that is engaged with the first sealing face to define a high-pressure fluid seal around a fluid chamber of the fuel pump. A surface of the first component adjacent to the first sealing face comprises a recess that is spaced from the seal and is disposed outside the chamber, the recess being shaped to increase the compliance of the first sealing face to a predetermined extent.

By virtue of the recess, the compliance of the first sealing face can be controlled to ensure that the first sealing face complies with deformation of the second sealing face when the first and second components are subjected to high pressure by fluid contained in the fluid chamber. When that high pressure is cyclic, as for a pumping chamber of the pump for example, enabling the first and second faces to deform together reduces relative movement between the two and the associated wear at the seal.

In this respect, increasing the compliance of the first sealing face to a predetermined extent entails providing the correct level of compliance in the first sealing face for the first and second sealing faces to deform together in a complementary manner. If the increase in compliance of the first sealing face is too small or too great, wear at the seal will not be addressed and may even be exacerbated.

Optionally, the recess extends continuously around the seal. For example, the recess may be axisymmetric and/or annular.

The recess may comprise a groove.

The recess may be shaped such that the first sealing face has substantially uniform stiffness.

In some embodiments, the surface of the first component adjacent to the first sealing face comprises multiple recesses that are spaced from the seal and are disposed outside the chamber, the recesses collectively being configured to increase the compliance of the first sealing face. For example, the fuel pump or sealing assembly may comprise two or more discrete recesses angularly spaced around the seal.

A surface of the second component adjacent to the second sealing face optionally comprises a recess that is spaced from the seal and is disposed outside the chamber, the recess being shaped to increase the compliance of the second sealing face to a predetermined extent.

The second component may comprise a bore defining the fluid chamber.

The first component may be a valve body, for example, in which case the second component may be a pump body and the chamber a pumping chamber.

Another aspect of the invention provides a method of fabricating a high-pressure fuel pump for a vehicle. The fuel pump comprises a first component comprising a first sealing face, and a second component comprising a second sealing face that engages with the first sealing face to define a high-pressure fluid seal around a fluid chamber of the fuel pump. The method comprises forming a recess in a surface of the first component adjacent to the first sealing face such that the recess is spaced from the seal and disposed outside the chamber once the fuel pump is assembled, the recess being shaped to increase the compliance of the first sealing face to a predetermined extent.

It will be appreciated that preferred and/or optional features of each aspect of the invention may be incorporated alone or in appropriate combination in the other aspects of the invention also.

Brief Description of the Drawings

In order that the invention may be more readily understood, preferred non-limiting embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which like features are assigned like reference numbers, and in which: Figure 1 shows in schematic axial cross-section a fuel pump according to an embodiment of the invention; and Figures 2 and 3 correspond to Figure 1 but show detail views of a sealing interface of the fuel pump in side and perspective views respectively.

Detailed Description of Embodiments of the Invention In general terms, embodiments of the invention address the above described problem of wear between neighbouring components of a fuel pump or fuel injector due to cyclic loading, by modifying a surface of at least one of the engaged components to increase the compliance of that surface at its point of contact with the neighbouring component.

In such arrangements, the compliant surface is deformed by the surface that it engages as the latter deforms under cyclic loading. By encouraging the engaged surfaces to deform together in a complementary manner, relative movement between the two is reduced, in turn minimising wear.

Such embodiments find particular application where the point of contact between neighbouring components is a sealing interface that provides a high-pressure fluid seal. By reducing wear at the sealing interface, the integrity of the seal is preserved.

Modifying the engaged surface for increased compliance typically involves adding a recess or other discontinuity to that surface, for example in the form of a groove surrounding the portion of the surface that defines part of a sealing interface, as in the embodiment that is described below. Such a groove or similar feature can expand or contract more readily than a plain surface to accommodate deformation of the surface beside it, thereby increasing the compliance of that surface.

Advantageously, compliance-enhancing features may be positioned on the dry side of a fluid seal and therefore be protected from high-pressure fluid and the stress concentrations that could arise were the feature to be positioned within a high-pressure chamber.

Figure 1 shows an example of where this problem may arise, specifically a sealing interface between a pump body 10 and an inlet valve 12 in a fuel pump 14. The apparatus shown in Figure 1 includes features to address the problem of wear at the interface caused by cyclic loading, as shall become clear in the

description that follows.

First, the precise manner in which that problem manifests in the fuel pump 14 of Figure 1 shall be considered, to establish the context for the invention and to illustrate the benefits that it provides. Conventional components of the pump 14 shall only be described in overview to avoid obscuring the invention.

In the example shown in Figure 1, the pump body 10 is of steel and is generally tubular, having a plunger bore 16 extending along its central axis 17 that receives a linearly reciprocating plunger 18.

The inlet valve 12 comprises a generally cylindrical inlet valve body 20, also of steel, which is coupled to the pump body 10 end-to-end in coaxial relation. The inlet valve body 20 includes a valve bore 22 that extends fully through the inlet valve body 20 with varying diameter to accommodate a valve member 24, an annular collar 25 fixed to an upper end of the valve member 24, and a valve spring 26 that acts between a shoulder of the valve bore 22 and the collar 25.

A lower end of the valve member 24 is enlarged to define a valve head 27, which is biased by the valve spring 26 into engagement with a valve seat 28 defined by an end of the valve bore 22, to close the inlet valve 12.

When the inlet valve body 20 is assembled with the pump body 10, respective openings of the valve bore 22 and the plunger bore 16 align so that the plunger bore 16 communicates with the valve bore 22 when the inlet valve 12 is open.

In this respect, movement of the valve member 24 between an open position, in which the valve head 27 is spaced from the valve seat 28, and a closed position, in which the valve head 27 engages the valve seat 28, is controlled passively by a combination of the valve spring 26 and fluid pressure. Specifically, when a filling stroke of the plunger 18 begins pressure in the plunger bore 16 is below the feed pressure. This gives rise to a pressure differential across the valve head 27 that creates a force that overcomes the biasing force provided by the valve spring 26. Accordingly, the valve head 27 lifts away from the valve seat 28, thus opening the inlet valve 12 and allowing fuel to flow into the plunger bore 16. Then, as the plunger bore 16 fills with fuel and the pressure equalises with the feed pressure, the pressure differential across the valve head 26 drops until the valve spring 26 is able to return the valve head 27 into engagement with the valve seat 28. This closes the inlet valve 12, thus preventing backflow of fuel into the valve bore 22 during subsequent compression.

The inlet valve body 20 further includes a fuel outlet channel 29 extending between planar end faces of the inlet valve body 20 at an inclination relative to the valve bore 22, the outlet channel 29 being configured to open into the plunger bore 16 when the inlet valve body 20 is assembled with the pump body 10.

A fuel inlet channel 30 extends orthogonally from the valve bore 22 through the inlet valve body 20 to provide an entry route for fuel when the inlet valve 12 is open during a filling stroke of the plunger 18. As the inlet valve 12 is passive, typically an external inlet metering valve (not shown) is also used to regulate the volume of fuel admitted to the fuel pump 14 on each pumping cycle.

Figure 1 also shows a connection body 32 that is coupled to the upper end of the inlet valve body 20, so that the inlet valve 12 is disposed between the connection body 32 and the pump body 10. The connection body 32 includes a protrusion 34 providing a connection point for a fuel line (not shown) that supplies high-pressure fuel output by the pump 14 to a fuel rail.

The connection body 32 further includes a connection channel 36 extending from one axial end of the connection body 32 to the other, to provide fluid communication between the protrusion 34 and a face of the connection body 32 that engages the inlet valve body 20. The connection channel 36 aligns with the fuel outlet channel 29 of the inlet valve body 20 when the pump 14 is assembled, to complete a fuel outlet path between the protrusion 34 and the plunger bore 16 of the pump body 10.

The connection body 32 is coupled to the pump body 10 by a cap nut 38, which provides a clamping action to press the pump body 10, the connection body 32 and the inlet valve body 20 into tight engagement. In this respect, the cap nut 38 engages an external annular shoulder 40 of the pump body 10 at one end, and the connection body 32 includes an external thread 42 onto which the cap nut 38 secures at its other end. In this way, the cap nut 38 acts as a clamping mechanism to provide the required clamping force to hold the elements of the fuel pump 14 together.

Movement of the plunger 18 is controlled by a plunger spring 44, which is received on a cylindrical outer surface of a lower portion of the pump body 10 and is coupled to the lower end of the plunger 18, as viewed in Figure 1, by a spring cap 46. A lower end face of the cap nut 38 provides an abutment that the upper end of the plunger spring 44 engages to control its position.

In use, as the plunger 18 undergoes a filling stroke fuel is drawn through the fuel inlet channel 30 into the plunger bore 16 while the inlet valve 12 is open. The inlet valve 12 then closes as the fuel pressure rises to prevent backflow into the fuel inlet channel 30 while fuel is compressed by the plunger 18 in a compression stroke, during which high-pressure fuel exits through the fuel outlet channel 29 to be fed to a fuel rail. For example, fuel may enter the plunger bore 16 at a feed pressure of around 7 bars and then exit at around 3000 bars.

Accordingly, the uppermost portion of the plunger bore 16 that is not occupied by the plunger 18 defines a pumping chamber 48 in which fuel is compressed. The pumping chamber 48 is therefore enclosed by the cylindrical side walls of the plunger bore 16, a planar end face of the plunger 18 and a portion of the face of an engagement face of the inlet valve body 20 that engages the pump body 10 and falls within the boundary of the plunger bore 16.

A fluid seal is required around the openings of the plunger bore 16 and the valve bore 22 to avoid fuel leakage from the pumping chamber 48 between the pump body 10 and the inlet valve body 20, which would inhibit the ability of the pump 14 to pressurise fuel. Due to the high pressures involved, ordinary sealing options such as 0-rings cannot be used. Accordingly, a high-pressure seal 50 is created by direct, metal-to-metal engagement between opposed faces of the pump body 10 and the inlet valve body 20.

In this respect, the engaging face of the pump body 10 includes a portion around the opening to the plunger bore 16 that is formed slightly proud of the remainder of the face, defining an annular, planar engagement surface referred to as a 'sealing pad' 52. The inlet valve body 20 may include a complementary sealing pad, although in the embodiment shown in Figure 1 the engaging face of the inlet valve body 20 is planar, without any protrusion. Instead, an annular portion of the engaging face of the inlet valve body 20 that engages the sealing pad 52 of the pump body 10 defines a sealing face 54. The sealing pad 52 and the sealing face 54 engage one another when the pump body 10 is assembled with the inlet valve body 20, thereby controlling the point of contact between the engaging surfaces.

The planar engagement surfaces of the sealing pad 52 and sealing face 54 are machined to a smooth finish and are pressed into tight engagement by the cap nut 38, thus providing a robust fluid seal 50 that can withstand high pressure.

The components contributing to the formation of the seal 50, namely the inlet valve body 20, the pump body 10, the connection body 32 and the cap nut 38, may therefore be regarded as a sealing assembly.

All of the features described thus far are conventional and will be familiar to the skilled person. However, as noted above, it has been identified that cyclic loading of the pumping chamber 48 as the pump 14 operates induces corresponding cyclic deformation of the pump body 10 and inlet valve body 20, albeit at a very small scale. This cyclic deformation results in relative movement at the sealing interface between the pump body 10 and inlet valve 12, causing wear and therefore degradation of seal integrity.

The cyclic loading is complicated by the fact that movement of the plunger 18 varies the surface area of the pumping chamber 48 that is exposed to high pressure. So, for example, when the plunger 18 nears the end of a pressurising stroke, high-pressure fuel is concentrated in the uppermost end of the plunger bore 16, as viewed in Figure 1. In that scenario, the fuel pressure deforms the walls of that uppermost end of the plunger bore 16, which causes the sealing pad 52 of the pump body 10 to expand radially and tilt outwardly in a manner that tends to cause its outer periphery to disengage the sealing face 54 of the inlet valve body 20.

Conversely, when the plunger 18 is near the start of the pressurising stroke, a larger portion of the plunger bore 16 is exposed to high-pressure fuel. This can result in a barrelling effect, in which a mid-region of the bore 16 expands radially, inducing contraction in the uppermost end of the bore 16 in response. This produces a pinching effect in the vicinity of the sealing pad 52, in which the wall of the plunger bore 16 bends radially inwardly so that the sealing pad 52 contracts and tilts in a manner that tends to disengage the inner periphery of the sealing pad 52 from the sealing face 54 of the inlet valve body 20.

Accordingly, as the fuel pump 14 operates over successive pumping cycles the sealing pad 52 of the pump body 10 undergoes oscillatory radial deformation at a frequency corresponding to the pumping speed.

Meanwhile, a portion of the engagement face of the inlet valve body 20 disposed within the pumping chamber 48 is also exposed to the high-pressure fuel, which tends to deform the face into a concave shape, before relaxing to its initial planar configuration when the pressure subsequently drops. Accordingly, the engagement face of the inlet valve body 20 cycles between concave and planar states.

The respective deformations induced in the pump body 10 and the inlet valve body 20 are therefore quite different to one another, resulting in relative movement at the interface between the sealing pad 52 and the sealing face 54.

Indeed, as the plunger 18 nears the end of a pressurising stroke the deformation of the engagement face of the inlet valve body 20 causes it to move in almost the opposite direction to the movement of the sealing pad 52 of the pump body 10, exacerbating relative movement between them.

Although it will be appreciated that these deformations are miniscule in practice, typically measured in microns, as the cyclic loading occurs at a frequency corresponding to the rate at which the fuel pump 14 operates the deformations are nonetheless sufficient to generate wear between the engaged sealing surfaces of the pump body 10 and inlet valve body 20. Over time, this may compromise the integrity of the seal.

To address this, as noted above embodiments of the invention provide features in sealing surfaces of the sealing assembly to increase the compliance of at least one of those faces to help it to deform in a manner that is complementary to deformation of the face that it engages, thus reducing relative movement between the faces and the associated wear. It is noted that such features are configured to modify stiffness locally, i.e. the stiffness of the sealing surface, without significantly impacting the overall stiffness of the component to which they are added.

In the embodiment shown in Figure 1, and as best seen in the detail views provided by Figures 2 and 3, this feature takes the form of a recess in the engagement face of the inlet valve body 20. More specifically, the recess is embodied as an annular groove 56 surrounding the portion of the engagement face that defines the sealing face 54.

As the figures show, in axial cross-section the groove 56 has straight side walls 58 of equal axial extent that both lie generally parallel to a central axis of the inlet valve body 20, those side walls 58 terminating in and being joined by an end surface 60 of semi-circular profile The groove 56 creates a discontinuity in the surface of the inlet valve body 20, which reduces the stiffness of the adjacent sealing face 54 of the inlet valve body 20 and therefore increases its compliance, allowing the groove 56 to expand or contract more readily than a continuous surface and thereby absorb deformation of the sealing face 54. Specifically, the groove 56 can expand through outward radial deflection of its side walls 58, and conversely contract through inward radial deflection of the side walls 58, which accommodates deformation of the sealing face 54 to a greater extent than if the groove 56 were not present. L1.

Meanwhile, the groove 56 has a negligible impact on the stiffness of the inlet valve body 20 as a whole, and so does not cause unwanted side effects in this respect.

The increased compliance of the sealing face 54 means that it will deform readily as the sealing pad 52 of the pump body 10 exerts pressure on it due to the tight engagement between the two surfaces under the clamping action of the cap nut 38, so that if the sealing pad 52 moves the sealing face 54 moves with it. In contrast, without the groove 56 the stiffness of the sealing face 54 resists movement under action of the sealing pad 52, resulting in relative sliding movement.

Accordingly, as the sealing pad 52 moves and changes shape due to deformation of the walls of the plunger bore 16, the sealing face 54 of the inlet valve body 20 is deformed by the sealing pad 52 to comply with the movement of the sealing pad 52. As a result, the sealing face 54 deforms in a complementary manner to the sealing pad 52 to compensate for deformation and movement of the latter. This greatly reduces relative movement between the sealing pad 52 and the sealing face 54, thus minimising wear and preserving the integrity of the seal.

It is noted, however, that if the sealing face 54 becomes too compliant the problem of relative movement may be exacerbated rather than mitigated. Accordingly, the dimensions and geometry of the groove 56, in particular its width and depth, are optimised to provide the correct level of compliance in the sealing face 54 of the inlet valve body 20 for minimised relative movement as the pump 14 operates. In other words, the groove 56 is shaped to increase the compliance of the sealing face 54 of the inlet valve body 20 to a predetermined extent relative to a plain surface, to provide the correct stiffness in the sealing face 54.

In practice, the shape of the groove 56 or alternative recess may be determined using a finite element analysis package, for example.

In this embodiment, the groove 56 has a width and depth of approximately 0.5mm and 1mm respectively, although this will differ for each application depending on the characteristics of the pump or injector. Similarly, the profile of the groove 56 may vary, for example by having side walls that are wholly or partially inclined with respect to the central axis of the inlet valve body 20. In another alternative, the groove may have curved walls, for example having a semi-circular cross-section.

It is apparent from the Figures that the groove 56 is broadly similar to grooves used for 0-rings in low-pressure sealing arrangements. However, the considerations that determine the characteristics of the groove 56 of this embodiment are entirely different to those that govern 0-ring groove design, resulting in different geometry and dimensions. In general terms, a groove designed to receive an 0-ring will be significantly wider than the groove 56 of this embodiment. This would lead to the surface within the boundary of the 0-ring groove becoming too complaint for the purposes of compensating for deformation under cyclic loading; although an 0-ring groove would not be used in a context where such issues arise.

Another difference between the groove 56 of this embodiment and an 0-ring groove is that the latter is located at the sealing interface and so is exposed to fluid pressure, since the 0-ring itself provides the seal. In contrast, the groove 56 of this embodiment lies outside the seal 50 and is therefore isolated from the high pressures arising within the pumping chamber 48. If the groove 56 were positioned inside the high-pressure environment, its geometry would create stress concentrations that could lead to failure of the component in the extreme case. Positioning the groove 56 outside the high-pressure environment and spaced from the seal 50 as in the present embodiment therefore beneficially avoids this risk.

It will be appreciated by a person skilled in the art that the invention could be modified to take many alternative forms to that described herein, without departing from the scope of the appended claims.

For example, in a simple variant of the above embodiment, a groove could be provided around the sealing pad of the pump body instead of, or in addition to, the groove around the sealing face of the inlet valve body. The decision as to where to position the groove may be dictated by practical considerations. In some cases, including grooves or alternative recesses around both of the sealing faces may enhance the ability to control compliance at the sealing interface. This may particularly apply where only a very small increase in compliance is required, which may be difficult to achieve with a single recess as it would entail a very small recess that would be impractical to machine. In this situation, the engaged components may be provided with recesses of different sizes to increase compliance in each sealing face to a different extent to provide the required deformation behaviour.

Also, although in the above described embodiment the recess takes the form of a continuous groove extending around the sealing interface, in other embodiments one or more discrete recesses could be used to achieve a similar effect. For example, the groove described above could be replaced by a ring of angularly-spaced axial drillings. However, it must be noted that uneven deformation in the sealing faces must be avoided to preserve the integrity of the seal. While this applies to all embodiments, this consideration is particularly relevant to discontinuous recesses.

Even if the recess is a groove extending continuously around the seal it may not follow a circular profile and be axisymmetric as in the described embodiment, but may instead have an irregular shape. This may assist with providing even stiffness across the enclosed sealing face when that surface includes apertures and other features that may cause local stiffness variations. Another possibility within the inventive concept is to include multiple continuous recesses, for example in the form of concentric rings. A mixture of continuous and discrete recesses may also be employed to provide the required deformation characteristics.

Moreover, while the plunger bore of a pump body has been used as an example, there are many other sealing interfaces in fuel pumps or fuel injectors that are vulnerable to wear due to cyclic loading in the manner outlined above, to which suitable embodiments of the invention may be applied to mitigate the problem. Indeed, the principles of the invention are applicable more widely than in fuel injectors and pumps, and may find application in sealing interfaces of any type of device that is subject to cyclic deformation.

References used: 10-pump body 12-inlet valve 14 -fuel pump 16-plunger bore 18-plunger -inlet valve body 22 -valve bore 24 -valve member -collar 26 -valve spring 27 -valve head 28 -valve seat 29 -fuel outlet channel -fuel inlet channel 32 -connection body 34 -protrusion 36 -connection channel 38 -cap nut -shoulder (of pump body) 42 -external thread (of pump body) 44 -plunger spring 46 -spring cap 48 -pumping chamber -seal 52 -sealing pad 54 -sealing face 56 -groove 58 -groove side wall -groove end surface

Claims

Claims: 1. A high-pressure fuel pump (14) for a vehicle, the fuel pump (14) comprising: a first component (10, 20) comprising a first sealing face (52, 54); and a second component (10, 20) comprising a second sealing face (52, 54) that is engaged with the first sealing face (52, 54) to define a high-pressure fluid seal (50) around a fluid chamber (48) of the fuel pump (14); wherein a surface of the first component (10, 20) adjacent to the first sealing face (52, 54) comprises a recess (56) that is spaced from the seal (50) and is disposed outside the chamber (48), the recess (56) being shaped to increase the compliance of the first sealing face (52, 54) to a predetermined extent.
The fuel pump (14) of claim 1, wherein the recess (56) extends continuously around the seal (50).
The fuel pump (14) of claim 2, wherein the recess (56) is axisymmetric.
The fuel pump (14) of claim 2 or claim 3, wherein the recess (56) is annular.
The fuel pump (14) of any preceding claim, wherein the recess (56) comprises a groove.
The fuel pump (14) of any preceding claim, wherein the recess (56) is shaped such that the first sealing face (52, 54) has substantially uniform stiffness.
7. The fuel pump (14) of any preceding claim, wherein the surface of the first component (10, 20) adjacent to the first sealing face (52, 54) comprises multiple recesses (56) that are spaced from the seal (50) and are disposed outside the chamber (48), the recesses (56) collectively being configured to increase the compliance of the first sealing face (52, 54). 2. 3. 4. 5.
The fuel pump (14) of claim 7, comprising two or more discrete recesses angularly spaced around the seal (50).
9. The fuel pump (14) of any preceding claim, wherein a surface of the second component (10, 20) adjacent to the second sealing face (52, 54) comprises a recess (56) that is spaced from the seal (50) and is disposed outside the chamber (48), the recess (56) being shaped to increase the compliance of the second sealing face (52, 54) to a predetermined extent.The fuel pump (14) of any preceding claim, wherein the second component (10, 20) comprises a bore (16) defining the fluid chamber (48).The fuel pump (14) of any preceding claim, wherein the first component is a valve body (20), the second component is a pump body (10), and the chamber is a pumping chamber (48).A method of fabricating a high-pressure fuel pump (14) for a vehicle, the fuel pump (14) comprising a first component (10, 20) comprising a first sealing face (52, 54), and a second component (10, 20) comprising a second sealing face (52, 54) that engages with the first sealing face (52, 54) to define a high-pressure fluid seal (50) around a fluid chamber (48) of the fuel pump (14); wherein the method comprises forming a recess (56) in a surface of the first component (10, 20) adjacent to the first sealing face (52, 54) such that the recess (56) is spaced from the seal (50) and disposed outside the chamber (48) once the fuel pump (14) is assembled, the recess (56) being shaped to increase the compliance of the first sealing face (52, 54) to a predetermined extent. 10.