BACKGROUND Technical Field

The present invention relates generally to the field of high pressure fuel pumps. More particularly, but not exclusively, the present invention concerns engine location spigot adaptor for high pressure diesel fuel pumps.

Description of the Related Art In a high pressure fuel pump, the fuel pump is usually located in relation to a front of the engine block. This is achieved via the location of a spigot (extending from a front plate thereof) into a bore relative to the front of the engine block. The driveshaft passes through the spigot and on the other side of the bore, the driveshaft attaches to a driving gear which rotates the driveshaft in operation. The spigot is retained in position due to the bore adopting a snug fit therearound.

Typically, the bore and the location spigot of the pump have a fixed diameter of relatively small dimensions, e.g. a spigot with a 50 mm or 68 mm diameter and a bore of similar diameter allowing for clearance. However, such small diameters do not allow assembly of the driving gear to the fuel pump before location of the spigot in the engine block.

It is advantageous to allow pre-assembly of the driving gear to the fuel pump, since it enables the fuel pump to be removed from the engine block without requiring access to a rear of the engine block, which often requires the engine to be removed from the vehicle. One solution to the above problem is to increase the diameter of the bore (and therefore, the spigot) to be larger than the driving gear, e.g. greater than 68 mm, in order to allow the driving gear to pass through the bore and the spigot to still fit snugly within the bore. However, this increase in the diameter of the spigot on the pump introduces a further problem, since a spigot often interferes with the screws that fix the pump front plate to the pump housing. In order to tackle this further issue, it is known to use an adaptor between the location spigot on the pump and the bore of the engine block. An adaptor allows the spigot on the pump to remain small, thereby minimising problems with fixing the pump front plate to the pump housing, whilst accommodating a larger bore in the front of the engine block, thereby providing a diameter enabling assembly of the driving gear to the fuel pump before location in the engine block.

Various adapters have been developed for this reason. One such prior art adaptor shown in Figure 1, comprises a loose collar 4 that sits within the bore 2 of the engine block 1 around the spigot 3a of the pump housing 3. The collar 4 comprises a shallow annular design with an outer peripheral o-ring seal 5 located within a groove 6 between the collar 4 and the engine block 1 and an inner o-ring seal 7 between the collar 4 and the spigot 3 a. The inner seal 7 is trapped between the collar 4, the spigot 3a and a front plate 3b of the pump seated within a triangular channel 8 cut into an inner rear corner of the collar 4. The seal 7 is partly retained by a small circular segmental annular hollow 9 cut into the diagonal wall of the channel 8. When the inner seal 7 is compressed, it applies an axial load to the front plate 3b and collar 4 minimising axial movement of the collar 4 within the bore 2. The depth of the collar 4 and the disposal of the inner seal 7 has to be made such that the front plate 3b can seat against the engine block 1 in order to avoid distortion of pump 3 geometry. However, this in turn causes an axial clearance when the inner seal 7 is compressed, which can cause inner seal 7 fretting and failure.

Another issue with the adaptor used in Figure 1 relates to the location of the telltale drilling 10 and cooperating tell-tale hole, the function of which are to help to detect the failure of inner and outer driveshaft seals. In this case the drilling 10 exits on a back of the front plate 3b of the pump housing 3. However, in most other pump arrangements the inner seal 7 blocks a leak path for the tell-tale hole and so the tell-tale function is compromised.

Accordingly, the aim is to provide an engine location spigot adaptor for high pressure diesel fuel pumps able to minimise axial movement within an engine block bore, whilst allowing the pump to be seated against the engine block, and which does not impinge on the function of the 'tell-tale' drilling and hole. Therefore, it is now desired to provide an improved arrangement for high pressure diesel fuel pump to minimise the effects of axial clearances that lead to seal fretting and failure. It is also desired to provide an improved arrangement for high pressure diesel fuel pump to retain the tell-tale function of the pump. SUMMARY OF THE INVENTION

In a first aspect of the present invention there is provided a high pressure diesel fuel pump comprising a pump housing, a location spigot protruding from a front plate of the pump, and a driveshaft protruding from the location spigot, the driveshaft being adapted for assembly with a driving gear of an engine and said location spigot being adapted to be located in a bore relative to a front end of an engine block, the pump further comprising an adaptor for location around said location spigot in said bore between the front plate and the engine block, the adaptor comprising a collar, an outer seal for location between the collar and the engine block, and an inner seal for location between the collar and the locaton spigot, characterised in that the adaptor further comprises a spring means adapted to be located at a bottom end of the collar between said collar and the front plate.

With this arrangement using the spring means, the adaptor is able to be seated firmly against the engine block to minimise or even eliminate axial movement, which would otherwise lead to seal fretting and failure. However, the use of the wave spring leaves the leak path open and un-impinged in order to retain the telltale function of the pump. The spigot can remain small, thereby minimising problems with fixing the pump front plate to the pump housing, whilst allowing for a larger bore in the front of the engine block, to enable assembly of the driving gear to the driveshaft before location in the engine block. Preferably, the spring means is configured to apply an axial load to the front plate when compressed. With this arrangement, the spring means forces the adaptor against the engine block minimising axial movement of the pump within the bore.

Preferably, the spring means is adapted to be accommodated substantially within the bottom end of the collar. Preferably, the collar comprises a recess to accommodate said spring means. Preferably, the collar comprises a shallow annular design comprising a centrally disposed axial bore therethrough.

Preferably, the recess comprises an annular groove in said collar. Preferably, the recess communicates with the bore of the collar. Therefore, most preferably, the recess is disposed at a bottom inner corner of said collar open to said bore.

Preferably, the spring means comprises a wave spring. Preferably, the wave spring comprises a round wire profile. Preferably, the wave spring comprises a single-turn, e.g. one layer of wire.

The wave spring may be configured to provide between approximately 5 ON and approximately 2000N working load. Preferably, the wave spring is configured to provide between approximately 700N and approximately 1000N working load, more preferably between approximately 800N and 900N.

The inner and outer seals may be located diametrically opposite one another on said collar, e.g. on the same diametric plane. Preferably, the seals are disposed towards an upper end of the collar.

Preferably, the outer seal comprises an o-ring of suitable sealing material. Preferably, the outer seal is located within a groove in the outer circumference of the collar.

Preferably, the inner seal comprises an o-ring of suitable sealing material. Preferably, the inner seal is located within a groove in the location spigot. Alternatively, the inner seal may be located within a groove in the bore of the collar.

Preferably, the collar comprises a main portion of first outer diameter comprising said upper end of the collar. Preferably, the collar comprises a secondary portion of second larger outer diameter comprising said bottom end of the collar. Preferably, the secondary portion is adapted to be seated within a wider secondary bore as part of a bottom end of the bore of the engine block, e.g. the engine block is adapted to provide a recess.

Preferably, the first outer diameter of the collar is larger than the driving gear. The adaptor may convert a 80 mm engine bore diameter to approximately a 50 mm diameter. The adaptor may therefore, comprise approximately a 50 mm inner diameter and approximately a 80 mm outer diameter.

In a second aspect of the present invention there is provided an adaptor for a high pressure diesel fuel pump, the adaptor being adapted for location within a bore relative to a front end of an engine block around a location spigot protruding from a front plate, the adaptor comprising a collar, an outer seal for location between the collar and the engine block, and an inner seal for location between the collar and the location spigot, characterised in that the adaptor further comprises a spring means adapted to be located at a bottom end of the collar between said collar and the front plate.

It will be appreciated that the relevant preferred features described in relation to the first aspect of the invention apply to the second aspect of the invention.

In a third aspect of the present invention there is provided a high pressure diesel fuel pump and drive gear assembly, the pump comprising a housing, a location spigot protruding from a front plate, and a driveshaft protruding from the location spigot, the driveshaft being adapted for assembly with the driving gear of an engine and said location spigot being adapted to be located in a bore relative to a front end of an engine block, the assembly further comprising an adaptor for location around said location spigot in said bore between the front plate and the engine block, the adaptor comprising a collar, an outer seal for location between the collar and the engine block, and an inner seal for location between the collar and the location spigot, characterised in that the adaptor further comprises a spring means adapted to be located at a bottom end of the collar between said collar and the front plate.

It will be appreciated that the relevant preferred features described in relation to the first and second aspects of the invention apply to the third aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show how exemplary embodiments may be carried into effect, reference will now be made to the accompanying drawings in which: Figure 1 is a cross-sectional view of a high pressure diesel fuel pump assembled within a bore of an engine block and a prior art adaptor;

Figure 2 is a cross-sectional side view of a high pressure diesel fuel pump assembled with a driving gear and seated within a bore of an engine block with an adaptor according to an embodiment of the invention; Figure 3 is a perspective view of the adaptor according to the invention as shown in Figure 2;

Figure 4 is an exploded cross-sectional side view of a portion of Figure 2; and

Figure 5 is a perspective front view of the adaptor of Figure 3 installed on a high pressure diesel fuel pump.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Figures 2 to 5 show a preferred embodiment of the present invention in which a high pressure diesel fuel pump 20 comprises a pump housing 21, a location spigot 24 protruding from a front plate 23 of the pump 20 and a driveshaft 22 protruding from the location spigot 24, the driveshaft 22 being adapted for assembly with a driving gear 31 of an engine and said location spigot 24 being adapted to be located in a bore 32 relative to a front end of an engine block 30, the pump 20 further comprising an adaptor 40 for location around said location spigot 24 in said bore 32 between the front plate 23 and the engine block 30, the adaptor 40 comprising a collar 43, an outer seal 45 for location between the collar 43 and the engine block 30, and an inner seal 47 for location between the collar 43 and the location spigot 24, characterised in that the adaptor 40 further comprises a spring means 49 adapted to be located at a bottom end 41 of the collar 43 between said collar 43 and the front plate 23.

The adaptor 40 comprises a substantially annular collar 43 with a centrally- disposed axial through-bore 46. The collar 43 comprises aluminium to minimise mass and reduce the load demand on the spring means 49.

The collar 43 comprises a first bottom end 41 which sits close to the pump housing 21 and a second upper end 42. The collar 43 comprises a main portion 43a of a first external diameter encompassing the upper end 42 and a shallow secondary portion 43b of a second larger external diameter encompassing the bottom end 41. This provides a stepped outer profile to the collar 43 between the bottom end 41 and the upper end 42.

The engine block 30 is adapted to receive the stepped outer profile of the adaptor 40 by comprising a secondary bore 32b concentric with the primary bore 32a and of larger diameter to accommodate the outer diameter of the secondary portion 43b.

The main portion 43a of the collar 43 comprises an outer circumferential groove 44 disposed near to the upper end 42 for accommodating the outer seal 45. The outer seal 45 comprises an o-ring of suitable sealing material that is held within the groove 44 in order to provide a sealing interface between the collar 43 and bore 32 of the engine block 30.

Within the main portion 43a of the collar 43, the bore 46 comprises a substantially straight and un-profiled internal wall 46a.

In contrast, within the secondary portion 43b of the collar 43, the bore 46 comprises a profiled internal wall 46b. Accordingly, the secondary portion 43b of the collar 43 comprises an inner circumferential recess 48 disposed within the bore 46 and open to the bottom end 41 of the collar 43. The recess 48 comprises a substantially square profile in cross-section. Where the recess 48 re-joins the internal wall 46b of the bore 46, the recess 48 comprises a short, steep tapered section 51, configured to provide a short conical portion and a diminishing gap 61 between the location spigot 24 and the internal wall 46b. Furthermore, where the recess 48 re-joins the bottom end 41 of the collar 43, the recess 48 comprises a second short, outwardly tapered section 52, configured to provide a short shallow conical portion and a wider mouth 62 between the front plate 23 and the bottom end 41 of the adaptor 40. The mouth 62, recess 48 and gap 61 work together to provide a flow path through the bore 46 between the front plate 23 and the collar 43 up to the point at where the inner seal 47 is located.

The spring means 49 comprises a single-turn, round wire wave spring. The wave spring 49 is adapted to be located within the recess 48 of the collar 43. Due to the shape of the recess 48 and the mouth 62 and gap 61, there is a flow path around the spring 49 in any compression state of the spring 49.

During assembly, the inner seal 47 is first located within the groove 25 provided by the location spigot 24. The outer seal 45 is located within the groove 44 of the collar 43 and the wave spring 49 is located within the recess 48 of the collar 43. The adaptor 40 is then assembled on the pump 20, by passing the bottom end 41 over the driveshaft 22 and then over the location spigot 24. The bottom end 41 of the collar 43 is brought close to, but generally does not abut the front plate 23 with the wave spring 49 in uncompressed ('free') form, causing the bottom end 41 to stand off of the front plate 23. The collar 43 is machined to have a low clearance fit (10-85 microns diametrically) around the location spigot 24 of the pump 20. This helps to reduce eccentricity errors that could be detrimental to the drivetrain of the pump 20. The pressure provided by the outer seal 45 and the inner seal 47 aids in keeping the adaptor 40 concentric within the engine block bore 32 and the location spigot 24 concentric within the adaptor 40 bore 46.

The adaptor is held in position on the front plate 23 due to the friction between the inner seal 47 and the collar 43 and the groove 25.

Once the adaptor 40 is in position on the pump 20, the driveshaft 22 can then be assembled with the driving gear 31. The driving gear 31 can then be passed through the bore 32 of the front end of the engine block 30, followed by the driveshaft 22. The adaptor 40 and encompassed location spigot 24 pass into the bore 32, until the secondary portion 43b of the collar 43 abuts an upper wall of the secondary bore 32b.

The pump 20-adaptor 40 assembly is then mounted on the engine block 30 by engaging and tightening bolts (not shown). This pulls the front plate 23 of the pump 20 closer to the bottom end 41 of the adaptor 40 and compresses the wave spring 49. The adaptor 40 is then captive between the engine block 30 and the front plate 24 within the engine block bore 32 and does not need to be bolted itself to the pump 20 or the engine block 30.

Since the wave spring 49 is then in compressed form, the adaptor collar 43 is unable to vibrate, which minimises seal 45, 47 fretting and failure.

In addition, the mouth 62 and the gap 61 as part of the recess 48 around the wave spring 49 are in communication with one another around the wave spring 49, which maintains the tell-tale leak path.

The adaptor 40 is space efficient and quick to install when compared with prior art adaptors, since it does not require separate bolting to the pump 20 or the engine block 30, and the collar 43 of the adaptor is instead retained on the location spigot 24 during pre-assembly via the inner seal 47. Furthermore, the wave spring 49 is capable of provide higher axial loading, which reduces the risk of seal fretting and failure. Finally, the tell-tale leak path is maintained since the wave spring 49 does not provide a block at the bottom end 41 of the adaptor 40.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.