GB2550882A

GB2550882A - Pressure regulator

Info

Publication number: GB2550882A
Application number: GB1609349.4A
Authority: GB
Inventors: T D Mchattie James; Lyon Matthew
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2016-05-26
Filing date: 2016-05-26
Publication date: 2017-12-06
Also published as: GB201609349D0

Abstract

An arrangement 10 of a fuel pump body 16 and a pressure regulator 12, the fuel pump body 16 being provided with a cylindrical main bore 20 in which is positioned the pressure regulator 12. The main bore 20 extends along a main axis (X) and has a peripheral cylindrical face 22 and a transverse bottom face 24. The pressure regulator 12 has a body 38 with a cylindrical peripheral wall (50, Fig. 2) and a transverse end wall (52, Fig. 2), said walls defining an inner bore having a cylindrical peripheral face and a transverse end face. A piston 40 is slidably arranged in the inner bore urged in contact against said bottom face by a spring 42 compressed between said piston 40 and a cap 44 fixed in the pump body 16 and axially closing the main bore 20. The arrangement 10 comprises a spacer 46 defining a first clearance (C1) between the transverse bottom face 24 of the bore and the transverse end wall of the regulator body. The spacer may allow for thermal expansion between the regulator and the pump body, thus reducing the need for high precision when manufacturing the arrangement, which may reduce production costs.

Description

PRESSURE REGULATOR

TECHNICAL FIELD

The present invention relates to a high pressure fuel pump and more particularly to an arrangement of the body of the pump and a pressure regulator arranged in said body.

BACKGROUND OF THE INVENTION

In a fuel injection equipment, a high pressure fuel pump is typically arranged downstream a lift pump and upstream a high pressure injection unit. The high pressure fuel pump typically comprises a pressurizing unit wherein fuel is pressurized by a piston reciprocating in a bore and varying the volume of a compression chamber, said piston cooperating with a camshaft rotating between aligned bearings set in the body of a cambox. The body is further provided with a plurality of internal conduit defining a lubrication circuit and a return circuit enabling lubricant to flow around the camshaft, along the bearings and flow toward return outlet. Furthermore, to amortize pressure spikes that would be detrimental to the lift pump and to the injection unit performance, a pressure regulator is arranged in said return circuit.

The regulator comprises a body arranged in a bore of the pump body and, a piston slidably arranged in an internal bore provided inside said regulator body. The piston is urged toward a first position by a spring and, said piston only moves under the influence of a pressure spike.

In use the cambox heats up and to accommodate thermal expansion between the cambox and the regulator, said regulators although being fairly simple in design are difficult to manufacture with high precision parts leading to be expensive components.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing an arrangement of a fuel pump body and a pressure regulator, the fuel pump body being provided with a cylindrical main bore in which is positioned the pressure regulator. The main bore extends along a main axis and has a peripheral cylindrical face and a transverse bottom face and, the pressure regulator has a regulator body with a cylindrical peripheral wall and an transverse end wall. Said walls define an inner bore having a cylindrical peripheral face and a transverse end face and in which, is slidably arranged a piston urged in contact against said bottom face by a spring compressed between said piston and a cap fixed in the pump body and axially closing the main bore.

Advantageously, the arrangement further comprises a first spacer defining a first clearance between the transverse bottom face of the bore and the transverse end wall of the regulator body.

Also, the pressure regulator body is compressed between the cap and the first spacer.

Also, the main bore opens in a recess provided in the pump body, and in which is engaged and fixed the cap, the engagement of the cap in the recess compressing the first spacer.

Also, the cap is screwed in the recess.

Also, the arrangement further comprises a second spacer defining a second clearance between the peripheral cylindrical wall of the regulator and the peripheral face of the main bore.

Also, said second spacer is arranged between the cap and a shoulder face of the recess.

More precisely, the first and second spacer are resilient O-rings.

Also, the arrangement may further comprise guiding means arranged within said second clearance, without closing said second clearance, said means guiding the insertion of the regulator body within the main bore.

Also, said guiding means comprises at least one O-ring surrounding the regulator body.

Also, said guiding means comprises at least one lip integral to the regulator body, axially extending and radially protruding from the peripheral cylindrical wall.

Also, the pump body is further provided an inlet channel opening in the bottom face of the main bore and also with an outlet channel opening in the peripheral cylindrical face of the main bore and wherein, the pressure regulator is further provided with an inlet opening arranged in the end transverse wall and also with an outlet opening arranged in the peripheral wall of the regulator body.

Also, the pressure regulator is further provided with a groove arranged in the peripheral cylindrical face of the internal bore of the regulator body, said groove extending from the outlet opening to a distant end arranged at a predetermined distance D from the bottom transverse face.

Said, said groove defines a fluid communication between the inlet channel and the outlet channel, said fluid communication being widely open only when the distance between the transverse bottom face of the regulator body and the piston is superior to said predetermined distance D.

Also, the regulator body and the piston are plastic moulded parts.

Also, the cap is metallic.

The invention further extend to a fuel pump having pump body and a pressure regulator forming an arrangement as previously described.

More precisely, the fuel pump is a high pressure diesel fuel pump adapted to be arranged in diesel fuel injection equipment of an internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

Figure 1 is section of a pressure regulator arranged, as per the invention, in a pump body, said regulator being in a first position.

Figure 2 is the arrangement of figure 1 with the regulator in a second position.

Figure 3 is an exploded view of the regulator of figures 1 or 2.

Figure 4 is a section of the arrangement provided with insertion guiding means.

Figure 5 is a section of the arrangement provided another embodiment of an insertion guiding means.

Figure 6 is a transverse section of the arrangement of figure 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to the figures is described a new arrangement 10 of a pressure regulator 12 in a body 16. Although the arrangement 10 can be implemented within many products for regulating pressure of many different fluid, for purpose of clarity and illustration, the description is done in the context of a diesel fuel high pressure pump 14 arranged in a fuel injection equipment, also known as a common rail system. Such fuel injection equipment comprises a low pressure system wherein a lift pump sucks fuel in a tank and delivers it to the high pressure pump 14. In turn said fuel is pressurized and delivered to a high pressure injection delivering system comprising a common rail and a plurality of fuel injectors.

The high pressure pump 14 typically comprises a pumping head wherein a piston reciprocally translates in a bore thus performing a pumping cycle in varying the volume of a compression chamber. The pumping head is fixed on a cambox having a body 16 wherein a camshaft rotates between aligned bearings and imparts said reciprocating displacement to the piston. In use, fuel leaks between the piston and the bore and gets in an inner volume defined in the cambox body 16. Said body 16 is further provided with conduits defining a return circuit 18 enabling fuel that, in use, fills said inner volume, to flow along the bearings and to return toward the low pressure system. The pressure regulator 12 is arranged in said return circuit 18 and is adapted to damp pressure spikes generated by the piston displacements that could damage the lift pump or, could alter the injection performance.

More in details, the regulator 12 is arranged in a main bore 20 of diameter D20 extending along a main axis X and having a peripheral cylindrical face 22 and a transverse end face 24. Opposed to said transverse end face 24, the main bore 20 centrally opens in the transverse bottom face of a recess 26, said bottom face being limited to a annular shoulder face 28 surrounding said opening of the bore. The recess 26 further has a peripheral cylindrical threaded face 30 axially extending between said shoulder face 28 and the outer face 32 of the cambox body 16. Furthermore, an upstream portion of the return circuit 18 forms an inlet channel 34 centrally opening in the transverse end face 24 of the bore and, a downstream portion of the return circuit 18 forms an outlet channel 36 radially opening in the cylindrical peripheral face 22 of the bore.

Inside the main bore 20 is arranged the pressure regulator 12 which comprises a cylindrical hollow body 38, a piston 40, a spring 42, a cap 44, a first O-ring 46 and a second O-ring 48.

The hollow body 38 extends along the main axis X and comprises a peripheral cylindrical wall 50 of diameter D50 axially extending from a transverse end wall 52, left of figure 1, to an annular end face 54, said walls 50, 52 defining an inner regulator bore 56 having a peripheral cylindrical face 58, that is the inner face of the peripheral wall 50 and, a transverse bottom face 60, that is the inner face of the transverse end wall 52. The regulator body 38 further comprises an inlet opening 62 centrally pierced through the end wall 52, and therefore aligned to the inlet channel 34 and, an outlet opening 64 radially pierced through the peripheral wall 50, in the vicinity of the annular end face 54. Alternatively, particularly visible on figure 4, the outlet opening 64 can form an indent in the peripheral wall 50, opening in said end face 54. On figure 4 the outlet opening 64 forms four indents in the wall 50. The hollow body 38 further comprises a groove 66 axially provided in the peripheral face 58 of the regulator bore from the outlet opening 64 to a distant end 68 that remains at a distance D from the bottom face 60 of the inner regulator bore. As shown the groove 66 can be straight or, alternatively, could be curved, the major characteristic being its ends in the outlet and at distance D from the bottom face. The regulator body 38 is made of plastic material such as polyamide or glass reinforced Nylon, integrally molded or alternatively machined.

The piston 40 is also a plastic molded integral cylindrical part comprising a cylindrical wall 70 and a bottom wall 72 defining an inner cavity. The cylindrical wall has an outer face 74 adjusted to slide with a small functional clearance of about 30pm against the peripheral face 58 of the bore. From the face of the bottom wall 72 opposed to the inner cavity, centrally extends a cylindrical protrusion 76 adapted to receive the lasts turns of the spring 42. Alternatively, the piston 40 could be a plain part but, in plastic molded part, it is commonly preferred for manufacturing purposes to keep substantially constant wall thicknesses.

The cap 44 is a metallic integral part comprising a cylindrical head 78 complementary threaded in the recess 26, a cylindrical base 80 centrally extending from the under face 82 of the head to an transverse face 84, the head 78 having substantially the same diameter D50 as the regulator body 38 so that said head 78 engages in the main bore 20 and, the transverse face 84 abuts against the annular end face 54 of the peripheral wall of the regulator body. From said transverse face 84 centrally extends another cylindrical protrusion 86 also adapted to receive the lasts turns of the spring 42.

The first O-ring 46 is typically a synthetic rubber O-ring, for instance such as the well-known Viton O-rings, and is arranged between the transverse end face 24 of the main bore and the transverse wall 52 of the regulator body. As visible on the figure, an annular groove surrounding the inlet opening 62 is provided in said transverse wall 52 of the regulator body, the first O-ring 46 being positioned in said groove.

The second O-ring 48 is also a synthetic rubber O-ring and is arranged between the under face 82 of the head of the cap and the annular shoulder face 28 of the recess.

The spring 42 is a coil spring engaged at both ends around the cylindrical protrusions 76, 86 and which pushes the piston 40 toward the transverse end wall 52 of the regulator body.

As visible on figure 1, when assembled in place, the cap 44 is screwed in the recess 26 and it compresses the second O-ring 48. Also, as the cap engages it pushes the regulator body 38 which in turn compresses the first O-ring 46, that serves as a first spacer 46 keeping apart the regulator end wall 52 of the regulator from the transverse end face 24 of the bore thus defining a first clearance Cl between said faces.

Also, the diameter D20 being much larger than the diameter D50 of the regulator body, a second peripheral clearance C2 is defined between said cylindrical faces.

The regulator body 38 not being able to move since it is compressed by the cap 44, said first Cl and second C2 clearances are always open and, the inlet channel 34 opens in the first clearance Cl and, the outlet channel 36 opens in the second clearance.

Conclusive tests have been performed with arrangement having the following characteristics:

Piston outer diameter 7mm

Piston total axial length 12mm

Piston to body functional clearance between 10pm and 50pm.

Regulator body outer diameter 12mm

Regulator body, length of bore 24mm

Regulator body length 30mm

Distance D of piston travel before opening flow path 4mm O-ring diameter 2mm

Clearances Cl, C2, between the regulator body and the pump between 1mm and 3mm.

In operation, when pressure upstream the inlet channel 34 is below a pressure threshold, the piston 40 is urged by the spring 42 into a position wherein, as shown on figure 1, the outer face 74 of the piston is close to the bottom face 60 of the regulator body, within a distance smaller than distance D. Therefore, the peripheral wall 70 of the piston closes the distant end 68 of the groove. In such configuration, the return fuel flow reaches the inlet channel 34, fills the first clearance Cl, enters the regulator body 38 via the inlet opening 62 and flows through the functional clearance around the piston 40 prior to exit the regulator via the outlet opening 64 and the outlet channel 36. Said functional clearance provides a viscosity controlled cooling flow for the pump.

When pressure upstream the inlet channel 34 surpasses said pressure threshold, the piston 40 moves backward in the direction of the cap 44 and uncovers the distant end 38 of the groove then, a fluid communication between the inlet channel and outlet channel widely opens enabling larger fuel flow to flow toward the outlet channel 36.

As the pressure in the return circuit 18 oscillates and pressure spikes travel in the return flow, the piston 40 moves back and forth within the regulator body 38 and damps said spikes to attenuate detrimental effects.

When assembling the pressure regular 12 within the main bore 20, to ensure correct positioning and avoid bias assembly, guiding means 88 can be provided. A first possible embodiment is presented on figure 4 and it comprises two parallel O-rings surrounding the regulator body 38, elastically maintained around the regulator. During the assembly process, said O-rings ease the centering of the regulator and, once the cap is tightened and the regulator fixed in place, said two O-rings do not contact the peripheral face 22 of the main bore and, the second clearance C2 remains a continuous uninterrupted space.

Another embodiment of a guiding means 88 is presented on figures 5 and 6 where said means 88 comprises axial lips, four being presented on the figures, outwardly protruding from the peripheral wall 50 of the regulator. Once in place, similarly to the previously presented two O-rings, the lips do not contact the peripheral face 22 of the main bore and, the second clearance C2 remains a continuous uninterrupted space.

During operation of the pump 14 important heat is generated and, all the parts thermally expand. The pump body 16 and the cap 44 being both metallic expand similarly. The regulator body 38 and the piston 40 both being plastic molded using same plastic material also expand similarly and, the sliding adjustment of the piston within the regulator body is kept. Thanks to the first Cl and second C2 clearances the plastic molded regulator is allowed to expand more than the metallic pump body.

LIST OF REFERENCES X main axis - regulator axis D20 diameter of the bore D50 diameter of the regulator body D distance

Cl first clearance C2 second clearance 10 Arrangement 12 pressure regulator 14 high pressure pump 16 pump body - cambox body 18 return circuit 20 main bore 22 peripheral face of the bore 24 transverse end face of the bore 26 recess 28 annular shoulder face 30 peripheral threaded face of the recess 32 outer face of the cambox 34 inlet channel 36 outlet channel 3 8 regulator hollow body 40 piston 42 spring 44 cap 46 first O-ring / first spacer 48 second O-ring / second spacer 50 peripheral wall of the regulator body 52 transverse end wall of the regulator body 54 annular end face of the peripheral wall 56 inner regulator bore 58 peripheral face of the bore 60 bottom face 62 inlet opening 64 outlet opening 66 groove 68 distant end of the groove 70 peripheral wall of the piston 72 bottom wall of the piston 74 outer face of the piston 76 cylindrical protrusion of the piston 78 head of the cap 80 cylindrical base of the cap 82 under face of the head of the cap 84 transverse face of the base 86 cylindrical protrusion of the cap 88 guiding means

Claims

CLAIMS:

1. Arrangement (10) of a fuel pump body (16) and a pressure regulator (12), the fuel pump body (16) being provided with a cylindrical main bore (20) in which is positioned the pressure regulator (12), the main bore (20) extending along a main axis (X) and having a peripheral cylindrical face (22) and a transverse bottom face (24), the pressure regulator (12) having a regulator body (38) with a cylindrical peripheral wall (50) and an transverse end wall (52), said walls defining an inner bore (56) having a cylindrical peripheral face (58) and a transverse end face (60) and in which, is slidably arranged a piston (40) urged in contact against said bottom face (60) by a spring (42) compressed between said piston (40) and a cap (44) fixed in the pump body (16) and axially closing the main bore (20), characterized in that the arrangement (10) further comprises a first spacer (46) defining a first clearance (Cl) between the transverse bottom face (24) of the bore and the transverse end wall (52) of the regulator body.

2. Arrangement (10) as claimed in the preceding claim wherein the pressure regulator body (38) is compressed between the cap (44) and the first spacer (46).

3. Arrangement (10) as claimed in claim 2 wherein the main bore (20) opens in a recess (26) provided in the pump body (16), and in which is engaged and fixed the cap (44), the engagement of the cap in the recess compressing the first spacer (46).

4. Arrangement (10) as claimed in claim 3 wherein the cap (44) is screwed in the recess.

5. Arrangement (10) as claimed in any one of the preceding claims further comprising a second spacer (48) defining a second clearance (C2) between the peripheral cylindrical wall (50) of the regulator (12) and the peripheral face (22) of the main bore.

6. Arrangement (10) as claimed in claim 5 when taken in combination with any one of the claims 3 or 4 wherein said second spacer (48) is arranged between the cap (44) and a shoulder face (28) of the recess.

7. Arrangement (10) as claimed in any one of the claims 5 or 6 wherein the first and second spacer are resilient O-rings.

8. Arrangement (10) as claimed in any one of the claims 5 to 7 further comprising guiding means (88) arranged within said second clearance (C2), without closing said second clearance, said means (88) guiding the insertion of the regulator body within the main bore.

9. Arrangement (10) as claimed in claim 8 wherein said guiding means (88) comprises at least one O-ring surrounding the regulator body.

10. Arrangement (10) as claimed in claim 8 wherein said guiding means (88) comprises at least one lip integral to the regulator body (38), axially extending and radially protruding from the peripheral cylindrical wall.

11. Arrangement (10) as claimed in any one of the preceding claims wherein the pump body is further provided an inlet channel (34) opening in the bottom face of the main bore and also with an outlet channel (36) opening in the peripheral cylindrical face of the main bore and wherein, the pressure regulator is further provided with an inlet opening (62) arranged in the end transverse wall and also with an outlet opening (64) arranged in the peripheral wall of the regulator body.

12. Arrangement (10) as claimed in claim 11 wherein the pressure regulator (12) is further provided with a groove (66) arranged in the peripheral cylindrical face (58) of the internal bore of the regulator body, said groove (66) extending from the outlet opening to a distant end (68) arranged at a predetermined distance (D) from the bottom transverse face.

13. Arrangement (10) as claimed in claim 12 wherein, said groove (66) defines a fluid communication between the inlet channel (34) and the outlet channel (36), said fluid communication being widely open only when the distance between the transverse bottom face of the regulator body and the piston is superior to said predetermined distance (D).

14. Arrangement (10) as claimed in any one of the preceding claims wherein the regulator body (38) and the piston (40) are plastic moulded parts.

15. Arrangement (10) as claimed in any one of the preceding claims wherein the cap (44) is metallic.

16. Fuel pump (14) having pump body (16) and a pressure regulator (12) forming an arrangement (10) as claimed in any one of the preceding claims.

17. Fuel pump (14) as claimed in claim 16 wherein said pump is a high pressure diesel fuel pump adapted to be arranged in diesel fuel injection equipment of an internal combustion engine.