GB2554845A

GB2554845A - Fuel pump

Info

Publication number: GB2554845A
Application number: GB1608662.1A
Authority: GB
Inventors: T D Mchattie James
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2016-05-17
Filing date: 2016-05-17
Publication date: 2018-04-18
Also published as: GB201608662D0

Abstract

High pressure diesel fuel pump 10 has a bearing cooling arrangement that comprises a pumping head 22 arranged on a cambox 12 having walls defining an inner space filled with diesel fuel. A camshaft 14 is arranged between two aligned bearings 24, 26 adapted to rotate about a camshaft axis Y, a piston 20 slidably arranged in a bore is adapted to perform a pumping cycle perpendicular to the camshaft axis, the piston being provided at an end with a cam follower 18 following an outer face of a cam 16 of the camshaft. A first bearing may be fitted within a bore of a first wall 34 of the cambox and a second within a recess 30 of the camshaft. A fuel return conduit 62 preferably extends through a cylindrical member 54 and fuel may leak from the pumping head in to the cambox and flow out via annular clearance C2 and the conduit. The flow of fuel along this path directly cools cylindrical member 54.

Description

(71) Applicant(s):

Delphi International Operations Luxembourg S.a.r.l. Avenue de Luxembourg, Bascharage L-4940, Luxembourg (72) Inventor(s):

James T.D. McHattie (74) Agent and/or Address for Service:

DELPHI FRANCE SAS

PO Box CS 65059, Bat. Le Raspail,

ZAC Paris Nord II 22, avenue des Nations,

Roissy CDG Cedex 95972,

France (including Overseas Departments and Territori es) (51) INT CL:

F02M 39/00 (2006.01) F02M 39/02 (2006.01) (56) Documents Cited:

GB 1274237 A EP 3073110 A1

DE 102011082729 A1 US 4069799 A

US 20140165957 A1 (58) Field of Search:

INT CL F02M

Other: WPI, EPODOC, TXTA (54) Title of the Invention: Fuel pump Abstract Title: Fuel pump (57) High pressure diesel fuel pump 10 has a bearing cooling arrangement that comprises a pumping head 22 arranged on a cambox 12 having walls defining an inner space filled with diesel fuel. A camshaft 14 is arranged between two aligned bearings 24, 26 adapted to rotate about a camshaft axis Y, a piston 20 slidably arranged in a bore is adapted to perform a pumping cycle perpendicular to the camshaft axis, the piston being provided at an end with a cam follower 18 following an outer face of a cam 16 of the camshaft. A first bearing may be fitted within a bore of a first wall 34 of the cambox and a second within a recess 30 of the camshaft. A fuel return conduit 62 preferably extends through a cylindrical member 54 and fuel may leak from the pumping head in to the cambox and flow out via annular clearance C2 and the conduit. The flow of fuel along this path directly cools cylindrical member 54.

FIG. 1 /2

FIG. 1

2/2

Γ4

FIG.

FUEL PUMP

TECHNICAL FIELD

The present invention relates to a fuel pump having a cambox and, more particularly, it relates to a bearing arrangement of the camshaft rotating in the cambox.

BACKGROUND OF THE INVENTION

In diesel fuel injection equipment, a high pressure fuel pump pressurizes fuel sucked in a low pressure tank and delivers it to a high pressure reservoir to which are connected a plurality of fuel injectors spraying said pressurized fuel into the compression chambers of an internal combustion engine. The pump typically involves a camshaft imparting reciprocal displacement to a piston, the camshaft rotating between two aligned bearings, the piston following a cam between said bearings. Unfortunately in use, the camshaft deflects under the influence of the important forces generated by the piston and, moreover the pump heats up and the bearing, in addition to lubrication, requires cooling which is typically provided by diesel fuel flow.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providinga high pressure diesel fuel pump adapted to be arranged in a fuel injection equipment. The pump has a pumping head arranged on a cambox having walls defining an inner space filled, in use with diesel fuel and wherein, a camshaft arranged between two aligned bearings, is adapted to rotate about a camshaft axis. A piston slidably arranged for reciprocal displacements in a bore is adapted to perform a pumping cycle along a pumping axis perpendicular to the camshaft axis. The piston is provided at an end with a cam follower following the outer face of a cam of the camshaft.

Advantageously, the pump is arranged to enhance bearing cooling when fuel flows in and out of the cambox.

Also, the first of said bearings is press-fitted in a bore of a first wall of the cambox and, the second of said bearings is press-fitted in a recess provided in the camshaft, a fixed cylindrical member protruding from a second wall of the cambox and being complementary engaged within said second bearing.

Also, an annular clearance is defined between the inner face of said second bearing and the outer face of the said cylindrical member.

Also, said clearance C is between 5 pm and 40 pm, preferably around 25 pm to the diameter.

Also, said cylindrical member is provided with a through return conduit extending from an outer opening in the outer face of the second wall of the cambox, said outer opening being adapted to connect to a return pipe to, an inner opening in the end face of said cylindrical member.

Also, a chamber is defined between the bottom face of the recess and the end face of the cylindrical member, the inner aperture opening in said chamber.

Also, in use, fuel flows in and out of the cambox by flowing through said annular clearance, in said chamber and through said return conduit.

Also, the second bearing is inside the cam.

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 a section of a high pressure pump as per the invention.

Figure 2 is an isometric view of the camshaft of the pump of figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the invention is now described in reference to the figures where a diesel high pressure fuel pump 10 comprises a cambox 12 wherein is arranged a camshaft 14 provided with a cam 16 adapted, when rotating about a camshaft axis Y, to impart via a cam follower 18 reciprocal displacements, along a pumping axis X perpendicular to the camshaft axis Y, to a piston 20 slidably arranged in a bore of a pumping head 22, therein performing a pumping cycle, the pumping head 22 being fixed on the top said cambox 12. Direction indications, such as “top” may be utilized in reference to the figures for clarity and simplicity of the description and without any limiting nor binding intentions.

The camshaft 14 is arranged between a first bearing 24, on the left of figure 1, and a second bearing 26, said bearings being aligned along the camshaft axis Y. Both bearings 24, 26, are solid sleeve bushings, for instance made of steelbacked PTFE-coated bronze or PEEK.

The first bearing 24 is press-fitted in a first opening 28 provided in a first peripheral wall 34 of the cambox. The second bearing 26 is press-fitted in a recess 30 provided in the camshaft 14 itself.

In the embodiment presented on figure 1, said first opening 28 is actually provided in a first flange member 32 complementary adjusted and fixed to the first peripheral wall 34 of the cambox.

The camshaft 14 comprises, left of the figure, a tapered portion 36 outwardly protruding from said first bearing 24, said tapered portion 36 being adapted to complementary receive a driving component, such as a pulley, fixedly secured by a nut tightened at the very end of the camshaft 14. The camshaft 14 further comprises a first cylindrical journal face 38 complementary engaged in the first bearing 24, a first functional clearance Cl being defined between said journal face 38 and the inner face 39 of the first bearing 24. The first clearance Cl typically ranges between 40 pm and 70 pm to the diameter. The camshaft 14 extends inside the cambox 12 and comprises, next to the first journal face 38, a thin disc-flange member 40 and the cam 16 which axially Y extends to the transverse end face 42 of the camshaft, said transverse end face 42 being inside the cambox 12. The cam 16 is defined by the profile of the cam face 44 against which roll a roller of the cam follower 18, said cam journal face 44 axially Y extending from the disc-flange 40 to the transverse end face 42. Moreover, in the transverse end face 42 opens the recess 30 which is coaxial to the camshaft axis Y and which extends inside the cam 16 toward a transverse bottom face 46 that is beneath the disc-flange 40, said opening of the recess 30 in the transverse end face 42 limiting the transverse end face 42 to an annular area peripheral to the opening of the recess. The recess 30 defines a peripheral wall 48 which outer face is the cam journal face 44 and which inner face 50 is a cylinder of revolution coaxial to the camshaft axis Y. Consequently, the radial thickness of said wall 48 varies as the profile of the cam varies. In the embodiment presented on figure 1, the recess 30 is provided with a shoulder member 52 arranged near the bottom face 46, said shoulder member 52 limiting the axial extent of the inner face 50 to the axial extent of the cam journal face 44.

In said recess 30 is press-fitted the second bearing 26 which, as shown on the figure, lies right beneath the cam journal face 44.

Opposite the first bearing 24, the cambox 12 is provided with a male cylindrical member 54 inwardly protruding from a second peripheral wall 56, opposed to the first peripheral wall 34. Said cylindrical member 54 has an outer face defining a second journal face 58 complementary adjusted in the second bearing 26, the member 54 axially extending from the wall 56 to a transverse end face 60 that is close to the bottom face 46 of the recess. Thanks to this arrangement, an efficient support is provided to the camshaft 14 and deflection is prevented since the force generated by the piston 20 is directly received by said cylindrical member 54 and transmitted to the wall of the cambox 12.

The cambox 12 is further provided with a return conduit 62 extending through the cylindrical member 54 from an outer end where said conduit 62 opens in the outer face of the second peripheral wall 56 to, an opposite inner end where the conduit 62 opens in the transverse end face 60 of the cylindrical member 60. On the outer face of the second peripheral wall 56 a return pipe, not represented, can be connected for joining a low pressure tank.

Actually, in the embodiment presented on figure 1, the cylindrical member 54 is integral the second peripheral wall 56 of the cambox 12. In a nonrepresented alternative, the cylindrical member 54 could be integral to a second flange member complementary adjusted and fixed to the second peripheral wall 56, said adjustment ensuring the alignment of the cylindrical member 54 with the first bearing 24 along the camshaft axis Y.

The second journal face 58 complementary adjusted to the inner face 66 of the second bearing 26 defines a second functional clearance C2 comprised between 40 pm and 70 pm between said second bearing inner face 66 and said second journal face 58. Moreover, as presented on the figure, a chamber C is defined at the bottom of the recess 30, between the end face 60 of the cylindrical member and the bottom face 46 of the recess, the return conduit 62 opening in said chamber C.

In operation, as the camshafts 14 rotates about its axis Y, the first bearing 24 fixed in the first opening 28 does not rotate, while the second bearing 26 fixed in the recess 30 of the camshaft rotates with said camshaft 14.

Also, as fuel leaks from the pumping head 22, the cambox 12 is filled with diesel fuel that lubricates the mechanism of the pump, in particular, diesel fuel flows from the cam and roller area through the second clearance C2, fills the chamber C and evacuates via the return conduit 62 and the return pipe.

Thanks to this fluid path, in addition to efficient lubrication of the second bearing 26, the cylindrical member 54 is directly cooled by the continuous fuel flow.

LIST OF REFERENCES high pressure diesel pump cambox camshaft cam cam follower piston pumping head first bearing second bearing first opening recess flange first peripheral wall of the cambox tapered portion fir st j ournal face inner face of the first bearing first flange end face of the camshaft cam journal face bottom face of the recess peripheral wall

50	inner face of the recess
52	shoulder
54	cylindrical member
56	second peripheral wall
58	second journal face - outer face of the cylindrical member
60	end face of the cylindrical member
62	return conduit
66	inner face of the second bearing
X	pumping axis
Y	camshaft axis
Cl	first clearance
C2	second clearance
c	chamber

Claims

1. High pressure diesel fuel pump (10) adapted to be arranged in a fuel injection equipment, the pump having a pumping head (22) arranged on a cambox (12) having walls defining an inner space filled, in use with diesel fuel and wherein, a camshaft (14) arranged between two aligned bearings (24, 26) is adapted to rotate about a camshaft axis (Y), a piston (20) slidably arranged for reciprocal displacements in a bore is adapted to perform a pumping cycle along a pumping axis (X) perpendicular to the camshaft axis (Y), the piston (20) being provided at an end with a cam follower (18) following the outer face of a cam (16) of the camshaft, characterized in that the pump (10) is arranged to enhance bearing cooling when fuel flows in and out of the cambox (12).

2. High pressure fuel pump (10) as claimed in the preceding claim wherein, the first of said bearings (24) is press-fitted in a bore of a first wall (34) of the cambox and, the second of said bearings (26) is press-fitted in a recess (30) provided in the camshaft (14), a fixed cylindrical member (54) protruding from a second wall (56) of the cambox and being complementary engaged within said second bearing (26).

3. High pressure fuel pump (10) as claimed in claim 2 wherein an annular clearance (C2) is defined between the inner face (66) of said second bearing and the outer face (58) of the said cylindrical member.

4. High pressure fuel pump (10) as claimed in claim 3 wherein said clearance (C2) is between 5 pm and 40 pm, preferably around 25 pm to the diameter.

5. High pressure fuel pump (10) as claimed in any one of the claims 2 to 4 wherein said cylindrical member (54) is provided with a through return conduit (62) extending from an outer opening in the outer face of the second wall of the cambox, said outer opening being adapted to connect to a return pipe to, an inner opening in the end face (60) of said cylindrical member.

6. High pressure fuel pump (10) as claimed in claim 5 wherein a chamber

5 (C) is defined between the bottom face (46) of the recess and the end face (60) of the cylindrical member, the inner aperture opening in said chamber (C).

7. High pressure fuel pump (10) as claimed in claim 6 wherein, in use, fuel flows in and out of the cambox (12) by flowing through said annular clearance

10 (C2), in said chamber (C) and through said return conduit (62).

8. High pressure fuel pump (10) as claimed in any one of the preceding claims wherein the second bearing (26) is inside the cam (16).

Intellectual

Property

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