EP3402979B1

EP3402979B1 - Fuel pump

Info

Publication number: EP3402979B1
Application number: EP17700137.7A
Authority: EP
Inventors: Levent AKIN
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2016-01-15
Filing date: 2017-01-06
Publication date: 2020-03-18
Anticipated expiration: 2037-01-06
Also published as: CN108603478B; WO2017121690A1; EP3402979A1; GB201600766D0; CN108603478A

Description

TECHNICAL FIELD

The present invention relates to a cam actuated high pressure fuel pump adapted to be arranged in a fuel injection equipment of an internal combustion engine. The invention particularly focuses on the arrangement of a spring seat onto the extremity of a plunger.

BACKGROUND OF THE INVENTION

Fuel injection equipment comprise high pressure pump aiming at pressurizing fuel at several thousands of bars prior to flow said fuel to injectors that spray the fuel in combustion chambers of an internal combustion engine.
US2002/0085936 and DE2314596 are relevant prior art. A known high pressure fuel pump comprises a pumping head provided with a bore in which a piston translates along a pumping axis of the bore performing a pumping cycle. The piston, also identified as a plunger, performs the pumping cycle between a Top Dead Centre (TDC) position around which fuel in the compression chamber is compressed and, a Bottom Dead Centre (BDC) position around which fuel is aspired in the chamber. The piston reciprocates under the influence of a cam rotating about a cam axis perpendicular to the pumping axis. The cam is followed by a cam follower combined to an external extremity of the piston, said cam follower typically having a cup-like body member in which a roller is free to rotate about a rolling axis perpendicular to the piston axis and parallel to the cam axis.
A spring arranged around the plunger and compressed between the pumping head and a spring seat cooperating with the cam follower and fixed to the extremity of the plunger maintains the roller in contact against the outer track of the cam. The spring permanently bias the cam follower against the cam and it also pulls the piston as it travels from the Top Dead Centre (TDC) position to the Bottom Dead Centre (BDC) position thanks to the engagement of the spring seat member and the plunger.
The spring seat is an axisymmetric part having a central circular portion, for complementary arrangement to the extremity of the plunger, a perpendicular cylindrical portion axially extending from the circular edge of the central portion and, a peripheral annular disc portion for receiving the spring. The central and peripheral portions extend in parallel plans separated from each other by the cylindrical portion.
In known arrangements, the spring seat is mounted to an outer diameter of the piston by pressing. The spring seat member may be fixedly mounted to the piston such that relative movement is inhibited.
Alternatively, a mounting collar may be fixedly mounted to an outer diameter of the piston to support the spring seat member, for example by press fitting. In this arrangement, the spring seat member may be movable relative to the piston, but is operatively biased against the collar by the action of the spring. Also, the spring seat and the collar may both be press-fitted on the plunger. Although this solves certain issues, for instance packaging issues, a problem with this type of arrangement is that the piston and seat member is not modular since to disassemble the spring seat, the collar needs to be disassembled first.
A further alternative is to form a keyed interface for mounting the spring seat member to the piston. The keyed interface may not require a press fit arrangement, but machining is required to form the keyed interface on the piston and/or the spring seat member.
These assemblies require high precision and costly manufacturing of both the plunger and the spring seat.

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 wherein a spring engaged around a cylindrical plunger is compressed between a spring seat arranged and retained at an extremity of the plunger and a pumping head in which the plunger is slidably guided and arranged to perform a pumping cycle.
More precisely, the spring seat comprises a central portion surrounded with a peripheral disc portion for receiving the spring, the central portion being provided with a central aperture allowing the plunger to pass therethrough and be positioned in a final position.
The spring seat further comprises an engagement aperture enabling through engagement of the extremity of the plunger in a preliminary engagement position distinct from the final position, said engagement aperture opening into the central aperture so that the plunger can be moved from the engagement position to the final position.
The extremity of the plunger is provided with a transverse diametral through hole in which is engaged a pin protruding from both extremities of the hole, the engagement aperture enabling passage of said pin until final positioning of the plunger in the central aperture.
The engagement aperture has a rectangular section forming diametrally opposed slots radially extending from the circular central aperture so that the plunger and the pin can be engaged therethrough said central and engagement apertures prior to be rotated to the final position.
The spring seat is further provided with rectangular notches forming recess in the central portion of the spring seat, the notches radially extending from the circular central opening, so that the pin can position in said notches when the plunger is in final position.
In a preferred embodiment, the final position is 90° apart from the engagement position.
More precisely, the spring seat may comprise a cylindrical portion axially extending from a first circular edge to an opposed second circular edge, the central portion wherein is arranged the central opening inwardly radially extending from the first circular edge and, the peripheral disc portion for receiving the spring outwardly radially extending from the second circular edge.
In further embodiment, the engagement aperture partially opens in the wall of said cylindrical portion.

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 high pressure pump as per the invention.
Figure 2 is a magnified section of the pump of figure 1 particularly magnifying the invention comprising a plunger and spring seat arrangement.
Figures 3, 4 and 5 are isometric and bottom views of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

In reference to figure 1 is generally described a high pressure fuel pump 10 having a pumping head 12 wherein fuel at low pressure enters via an inlet into a compression chamber wherefrom it is expelled pressurized via an outlet, after a cylindrical piston 14, having diameter D14, reciprocally translating in a bore 16 along a pumping axis X has performed a pumping cycle.
Although the invention has first been thought for a diesel fuel pump where "low" pressure is in the range of few bars, less than ten and, "high" pressure ranges up to three thousand bars, the invention as described can be applied to gasoline pump, or even any type of cam actuated fluid pump.
As it is known in the art, the piston 14 protrudes outside the pumping head 12 and extends toward an external extremity 18 where is arranged a spring seat 20 cooperating with a cam-follower 22 permanently maintained in contact against the outer track of a rotating cam 24 by a spring 26 that is compressed between a face of the pumping head 12 and the spring seat 20. As in use the cam 24 rotates, the follower 22 imparts to the piston 14 a reciprocating movement generating said pumping cycle.
The piston 14 is described having a constant diameter D14 throughout its length from the extremity inside the bore 16 to the external extremity. In alternative design the external extremity of the plunger may have a slightly smaller diameter than the upper extremity that slides in the bore.
More precisely, in reference to figures 2 to 5, the spring seat 20 comprises a central circular portion 28, a perpendicular cylindrical portion 30 axially extending from the peripheral circular edge of the central circular portion 28 to another distant circular edge and, a peripheral annular disc portion 32 outwardly extending from said another distant circular edge. The central 28 and the peripheral 32 portions extend in parallel plans transverse to the pumping axis X, and are separated from each other by the height of the cylindrical portion 30. While the central portion 28 is adapted to be arranged on the plunger, the peripheral annular disc portion 32 is adapted to receive the spring 26. This defines an orientation of the spring seat 20 where an upper-side faces the pumping head, best shown on figure 4, is opposed to an under-side facing the cam, best shown on figure 5. The terms such as upper and under are only utilized to ease and clarify the description without any intent to limit the scope of the invention.
As visible on the figures the under-side has a concave shape, the cylindrical portion defining an under space S.
The extremity 18 of the plunger is provided with a pin 36 fixedly arranged in a diametral through hole 38 pierced in said external extremity of the plunger. The pin 36 symmetrically protruding from both sides of the plunger is, in a preferred embodiment, an elastic pin enabling press engagement and fixation in the hole 38 via elastic contact pressure. Coiled pin, slotted elastic pin or solid cylindrical rod are also possible alternatives.
The central portion 28 of the spring seat is provided with a circular central aperture 34 of diameter D34 slightly superior to the diameter D14 of the plunger. From said central aperture 34 radially extend two diametrally opposed lateral rectangular apertures 40 having dimensions slightly superior to the dimensions of the pin in order to enable through passage of the pin 36. The lateral rectangular apertures 40 are also identified as engagement aperture 34.
As shown in figures 3, 4 and 5, in a preferred embodiment, the lateral rectangular extensions 40 extend within the central portion 28 of the spring seat and do not cut into the cylindrical portion 30. In a non-represented alternative the lateral rectangular extensions 40 may extend to the cylindrical portion and cut out said lateral face of the spring seat. Also, the extensions 40 and designated "rectangular" even if, as shown on the figures, the angles of said extensions are rounded.
For arranging this embodiment, the pin 36 is firstly engaged in the hole 38 of the plunger so that said pin 36 symmetrically protrudes from both sides of the hole. Secondly, the plunger and pin assembly is placed before the spring seat oriented and axially aligned with the central aperture 34 and its lateral rectangular extensions 40 then, thirdly, the plunger and pin assembly is axially X engaged through the central portion of the spring seat, the plunger 14 passing through the central aperture 34 and the pin 36 passing through the lateral rectangular extensions 40. This intermediate position where the pin is aligned with the lateral apertures is identified as the engagement position. Fourthly, once the pin 36 is in the under-side of the spring seat in said engagement position, the plunger is rotated about the axis X by 90°, so that the pin 36 is no longer aligned with the lateral rectangular extensions 40. Said position where the spring seat cannot disengage from the shaft is identified as being the final position.
Furthermore, in order to secure the final position of said plunger and pin assembly and to prevent later rotations that would re-align the pin 36 with the lateral rectangular extensions 40 and enable dis-engagement of the spring seat, the under-side of the central portion of the spring seat is provided with two lateral notches 42 diametrally opposed and radially extending from the central aperture 34. Said notches 42, arranged 90° apart from the lateral extensions 34, set the final position, the pin 36 being complementary arranged in the notches. In the alternative shown on figure 4, the machining of the notches 42 is done radially from the outside of the spring seat so that round openings in the peripheral cylindrical face 30 are made and are visible. In another alternative shown on figure 3, the machining of said notches 42 is entirely done via the underside of the spring seat without leaving openings in the cylindrical face.
The angle between the engagement position and the final position of the spring seat is described as 90° but other angles are possible, provided said other angle is sufficient to keep the pin distant from the lateral extensions.
Also, as visible on figure 2, in the described embodiment the height of the space S is adjusted to the length of the extremity of the plunger protruding in the under-side of the central portion. Other arrangements where the plunger is slightly longer and extends below the spring seat or, to the contrary where the plunger is shorter are also possible.

LIST OF REFERENCES

X: pumping axis
10: pump
12: pumping head
14: piston - plunger
16: bore
18: extremity of the piston
20: spring seat
22: cam follower
24: cam
26: spring
28: central portion of the spring seat
30: cylindrical portion
32: annular disc portion
34: central aperture
36: pin
38: hole
40: lateral rectangular extensions
42: notches
D14: diameter of the plunger
D34: diameter of the central aperture
S: space

Claims

High pressure fuel pump (10) wherein a spring (26) engaged around a cylindrical plunger (14) is compressed between a spring seat (20) arranged and retained at an extremity (18) of the plunger and a pumping head (12) in which the plunger (14) is slidably guided and arranged to perform a pumping cycle,
the spring seat (20) comprising a central portion (28) surrounded by a peripheral disc portion (32) for receiving the spring (26), the central portion (28) being provided with a central aperture (34) allowing the plunger (14) to pass therethrough and be positioned in a final position,
characterized in that
the spring seat (20) further comprises a engagement aperture (34) enabling through engagement of the extremity (18) of the plunger in a preliminary engagement position distinct from the final position, said engagement aperture (34) opening into the central aperture (34) so that the plunger (14) can be moved from the engagement position to the final position and wherein,
the extremity (18) of the plunger is provided with a transverse diametral through hole (38) in which is engaged a pin (36) protruding from both extremities of the hole (38), the engagement aperture (34) enabling passage of said pin until final positioning of the plunger (14) in the central aperture (34) and,
wherein the engagement aperture (34) has a rectangular section forming diametrally opposed slots radially extending from the circular central aperture (34) so that the plunger (14) and the pin (36) can be engaged therethrough said central (34) and engagement (34) apertures prior to be rotated to the final position and,
wherein the spring seat (20) is further provided with rectangular notches (42) forming recess in the central portion (32) of the spring seat, the notches (42) radially extending from the circular central opening (34), so that the pin (36) can position in said notches (42) when the plunger is in final position.
High pressure fuel pump (10) as claimed the claim 1 wherein the final position is 90° apart from the engagement position.
High pressure fuel pump (10) as claimed in any one of the preceding claims wherein the spring seat (20) comprises an cylindrical portion (30) axially extending from a first circular edge to an opposed second circular edge, the central portion (28) wherein is arranged the central opening inwardly radially extending from the first circular edge and, the peripheral disc portion (32) for receiving the spring (26) outwardly radially extending from the second circular edge.
High pressure fuel pump (10) as claimed in claim 3 wherein the engagement aperture (34) partially opens in the wall of said cylindrical portion (30).