GB2570290A

GB2570290A - Fuel pump

Info

Publication number: GB2570290A
Application number: GB1800346.7A
Authority: GB
Inventors: J Maclane Stephen; J Pedley Toby
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-01-09
Filing date: 2018-01-09
Publication date: 2019-07-24
Anticipated expiration: 2038-01-09
Also published as: GB201800346D0; GB2570290B

Abstract

High pressure fuel pump 10 having a body 12 provided with a bore 22 coaxial to a turret 18 and a plunger 26, a spring seat member 30 fixed to the plunger 26, and a spring 36, wherein said spring seat member 30 defines a bucket adapted to collect fuel leaking between the plunger and the bore. This arrangement allows for a clearance between the plunger 26 and bore 22 such that the chance of seizure is reduced, while minimising pressure loss due to leakage.

Description

TECHNICAL FIELD

The present invention relates to a diesel fuel pump and particularly to an arrangement tending to limit the fuel leaks.

BACKGROUND OF THE INVENTION

The hydraulic performance of diesel fuel injection pumps that have a plunger reciprocating in a bore in a pumping head relies on a close clearance between the plunger and the bore to minimise the fuel leakage. This leakage constitutes the largest hydraulic loss and reduction in performance at high pressures.

A simple method of improving the performance of a pump is to reduce this clearance, however, as the clearance gets smaller the likelihood of the plunger seizing in the bore increases. As a consequence of the leakage and associated pressure drop along the clearance heat is released.

As the pressures get higher and higher so the pressure drops and leakage flows also increase leading to more and more heat release.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a high pressure fuel pump of a diesel injection system having a body with a main member from a face of which a turret protrudes and extends along a main axis toward a distant end face. Said body is provided with a bore coaxial to the turret and extending between an opening in said turret end face and an inner end partially defining a compression chamber.

The pump further comprises

- a plunger guided in said bore for reciprocating between BDC and TDC. The plunger extends between an upper end also partially defining said compression chamber and a lower end protruding outside said bore opening and extending along said main axis.

- a spring seat member fixed to said part of the plunger that extends outside the bore and with,

- a spring arranged around the turret and compressed between the spring seat integral to the spring seat member and the face of the pump body main member.

Said spring seat member comprises a disc-like base which annular peripheral area defines said spring seat and which central area defines the bottom of a bucket adapted to collect, in use, fuel leaking between the plunger and the bore, said bucket comprising a cylindrical peripheral wall upwardly extending from said base and upwardly extending toward a distant edge.

Said peripheral wall defines with the turret an annular clearance enabling, in use, fuel present in the bucket to exit the bucket by flowing through said clearance wetting the peripheral face to the turret.

Said clearance may be about 1 mm to the radius.

Between the base and the distant edge said peripheral wall may axially extends along a height a little superior to the travel distance of the plunger between TDC and BDC.

When in BDC, the edge of the bucket peripheral wall just surrounds the distant end face of the turret and where, in TDC, the bucket is pulled-up by the plunger and the peripheral wall of the bucket surrounds the end of the turret which distant end face is close to the bottom of the bucket.

The peripheral wall may be integral to the base, the spring seat member being a monobloc part.

In another alternative, the peripheral wall is a tubular sleeve fixed to the base.

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 an axial section of a pump as per the invention, the plunger of the pump being in BDC.

Figure 2 is similar to figure 1, the plunger being in TDC.

Figure 3 is a view magnified on a spring seat member of the pump of figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to the figures is described a diesel pumping head 10 comprising a body 12 that has a main member 14 from an under face 16 of which a turret 18 extends along a main axis A toward a distant end face 20. Said body 12 is further provided with a bore 22 extending along said main axis A between an upper blind end partially defining a compression chamber 24 and a lower end centrally opening in said turret end face 20.

In the compression chamber 24 open a controlled inlet and a controlled outlet and, in the bore 22 a plunger 26 is guided, having an upper end also partially defining said compression chamber 24 and a lower end portion protruding from said bore opening and extending along said main axis A toward a lower end 28. In use, said lower end 28 cooperates with a camshaft, not shown, that rotates and imparts to the plunger 26 reciprocal displacements between BDC, as shown on figure 2, and TDC, as shown on figure 3.

Moreover, a spring seat member 30 is fixed at said lower end 28 of the plunger, said spring seat member 30 having a disc-like base 32 centrally holed for the plunger to extend through and which outer peripheral area defines a spring seat 34, a spring 36 engaged around the turret 18 being compressed between said spring seat 34 and the under face 16 of the body main member so that the spring 36 imparts a force pulling the plunger 26 toward BDC.

The spring seat member 30 further comprises a cylindrical wall 38 upwardly extending from the base 32 toward a distant circular end 40. In a first embodiment presented on figure 2, said wall is an independent sleeve 42 fixed to the base 32. In a second embodiment shown on figures 1 and 3 the spring seat member 30 is made monobloc, said wall 38 being integral to the base 32.

Whichever the embodiment, the spring seat member 30 has a cup-like shape defining a bucket B surrounded by the wall 38, said bucket having a cylindrical inner space S through which axially extends the plunger, the spring seat 34 forming a collar outside said wall 38.

The turret 18 has a diameter DI8 slightly smaller than the inner diameter D38 of the peripheral wall defining between them a small annular clearance C.

C = D38 - D18. Typically, said clearance is about 1mm to the radius.

Moreover, the height H38 of the wall, between the base 32 and the distant circular edge 40 is just slightly superior to the plunger travel distance between BDC and TDC.

As shown on figure 2, when the plunger is in BDC, the base member 32 is at a distance from the turret end face 20 which is just engaged within the peripheral wall 38. The bucket inner space S is maximised, the turret not moving and the plunger being at BDC. The space S is almost closed by the turret which slightly engages in said wall 38 leaving between them the annular opening of said clearance C. In use, fuel leaking between the plunger 26 and the bore 22 exits the bore and is collected in the bucket B.

As the plunger 26 moves from BDC to TDC the turret 18 further engages in the bucket, reducing said inner space S, the fuel therein collected exiting the bucket B via said annular clearance C as shown by the arrows of figure 3.

When reaching TDC, figure 3, the inner space S is almost fully occupied by the turret 18 that has engaged in the wall 38, the turret end face 20 being very close to the base 32.

A major advantage of this spring seat member defining a bucket is that when the fuel exits the bucket and wets the turret, the heat loss to the surroundings from the pumping head is reduced. This has the effect of stabilising the temperature difference between the plunger and the head and thus preventing a thermal imbalance between the two components.

LIST OF REFERENCES

A main axis

TDC Top Dead Center position

BDC Bottom Dead Center position

B bucket

S inner space

D18 diameter of the turret

D38 diameter of the wall

H38 height of the wall

C clearance pump body main member under face turret end face bore compression chamber plunger lower end of the piston spring seat member disc-like base spring seat spring peripheral wall distant edge sleeve

Claims

CLAIMS:

1. High pressure fuel pump (10) of a diesel injection system having a body (12) with a main member (14) from a face (16) of which a turret (18) protrudes and extends along a main axis (A) toward a distant end face (20), said body (12) being provided with a bore (22) coaxial to the turret (18) and extending between an opening in said turret end face (20) and an inner end partially defining a compression chamber (24), the pump further comprising

- a plunger (26) guided in said bore for reciprocating between BDC and TDC, the plunger extending between an upper end also partially defining said compression chamber and a lower end (28) protruding outside said bore (22) opening and extending along said main axis (A) and,

- a spring seat member (30) fixed to said part of the plunger that extends outside the bore and with,

- a spring (36) arranged around the turret (18) and compressed between the spring seat (34) integral to the spring seat member (30) and the face (16) of the pump body main member and wherein, said spring seat member (30) comprises a disc-like base (32) which annular peripheral area defines said spring seat (34) and which central area defines the bottom of a bucket (B) adapted to collect, in use, fuel leaking between the plunger and the bore, said bucket comprising a cylindrical peripheral wall (38) upwardly extending from said base and upwardly extending toward a distant edge (40).

2. High pressure pump (10) as claimed in the preceding claims said peripheral wall (38) defining with the turret (18) an annular clearance (C) enabling, in use, fuel present in the bucket (B) to exit the bucket by flowing through said clearance wetting the peripheral face to the turret.

3. High pressure pump (10) as claimed in claim 2 wherein said clearance (C) is of about 1mm to the radius.

4. High pressure pump (10) as claimed in the preceding claims wherein between the base (32) and the distant edge (40) said peripheral wall (38) axially extends along a height (H38) a little superior to the travel distance of the plunger between TDC and BDC.

5. High pressure pump (10) as claimed in claim 4 wherein, when in BDC, the edge (40) of the bucket peripheral wall just surrounds the distant end face (20) of the turret and where, in TDC, the bucket (B) is pulled-up by the plunger and the peripheral wall (38) of the bucket surrounds the end of the turret which distant end face (20) is close to the bottom of the bucket.

6. High pressure pump (10) as claimed in the preceding claims wherein the peripheral wall (38) is integral to the base (32), the spring seat member (30) being a monobloc part.

7. High pressure pump (10) as claimed in any one of the claims 1 to 5 wherein the peripheral wall (38) is a tubular sleeve (42) fixed to the base (32).