TECHNICAL FIELD
[0001] 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
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] These assemblies require high precision and costly manufacturing of both the plunger
and the spring seat.
SUMMARY OF THE INVENTION
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] In a preferred embodiment, the final position is 90° apart from the engagement position.
[0017] 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.
[0018] In further embodiment, the engagement aperture partially opens in the wall of said
cylindrical portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] 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
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] As visible on the figures the under-side has a concave shape, the cylindrical portion
defining an under space S.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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
[0033]
- 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
1. 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.
2. High pressure fuel pump (10) as claimed the claim 1 wherein the final position is
90° apart from the engagement position.
3. 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.
4. 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).
1. Hochdruckkraftstoffpumpe (10), wobei eine um einen zylindrischen Kolben (14) eingreifende
Feder (26) zwischen einem an einem Ende (18) des Kolbens angeordneten und gehaltenen
Federsitz (20) und einem Pumpenkopf (12) zusammengedrückt wird, in dem der Kolben
(14) verschiebbar geführt und angeordnet ist, um einen Pumpzyklus durchzuführen,
wobei der Federsitz (20) einen Mittelteil (28) aufweist, der von einem Umfangsscheibenteil
(32) zum Aufnehmen der Feder (26) umgeben ist, wobei der Mittelteil (28) mit einer
zentralen Öffnung (34) versehen ist, durch die der Kolben (14) hindurchgehen und in
einer endgültigen Position positioniert werden kann, dadurch gekennzeichnet, dass
der Federsitz (20) weiter eine Eingriffsöffnung (34) aufweist, die ein Durchgreifen
des Endes (18) des Kolbens in einer von der endgültigen Position verschiedenen vorläufigen
Eingriffsposition ermöglicht, wobei sich die Eingriffsöffnung (34) in die zentrale
Öffnung (34) öffnet, so dass der Kolben (14) von der Eingriffsposition in die endgültige
Position bewegt werden kann, und wobei
das Ende (18) des Kolbens mit einem quer verlaufenden diametralen Durchgangsloch (38)
versehen ist, in das ein Stift (36) eingreift, der von beiden Enden des Lochs (38)
vorsteht, wobei die Eingriffsöffnung (34) einen Durchtritt des Stifts bis zu einer
endgültigen Positionierung des Kolbens (14) in der zentralen Öffnung (34) ermöglicht,
und
wobei die Eingriffsöffnung (34) einen rechteckigen Abschnitt hat, der diametral gegenüberliegende
Schlitze bildet, die sich radial von der kreisförmigen zentralen Öffnung (34) erstrecken,
so dass der Kolben (14) und der Stift (36) durch die zentrale Öffnung (34) und die
Eingriffsöffnung (34) in Eingriff gebracht werden können, vor einer Rotation in die
endgültige Position, und
wobei der Federsitz (20) weiter mit rechteckigen Kerben (42) versehen ist, die eine
Aussparung in dem Mittelteil (32) des Federsitzes bilden, wobei sich die Kerben (42)
radial von der kreisförmigen zentralen Öffnung (34) erstrecken, so dass der Stift
(36) in den Kerben (42) positioniert werden kann, wenn der Kolben in der endgültigen
Position ist.
2. Hochdruckkraftstoffpumpe (10) gemäß Anspruch 1, wobei die endgültige Position 90°
entfernt von der Eingriffsposition ist.
3. Hochdruckkraftstoffpumpe (10) gemäß einem der vorhergehenden Ansprüche, wobei der
Federsitz (20) einen zylindrischen Teil (30) aufweist, der sich axial von einem ersten
kreisförmigen Rand zu einem gegenüberliegenden zweiten kreisförmigen Rand erstreckt,
wobei sich der zentrale Teil (28), in dem die zentrale Öffnung angeordnet ist, von
dem ersten kreisförmigen Rand radial nach innen erstreckt und sich der Umfangsscheibenteil
(32) zum Aufnehmen der Feder (26) von dem zweiten kreisförmigen Rand radial nach außen
erstreckt.
4. Hochdruckkraftstoffpumpe (10) gemäß Anspruch 3, wobei sich die Eingriffsöffnung (34)
teilweise in der Wand des zylindrischen Teils (30) öffnet.
1. Pompe à carburant à haute pression (10) dans laquelle un ressort (26) engagé autour
d'un piston cylindrique (14) est comprimé entre un siège de ressort (20) agencé et
retenu à une extrémité (18) du piston et une tête de pompage (12) dans laquelle le
piston (14) est guidé en coulissement et agencé pour effectuer un cycle de pompage,
le siège de ressort (20) comprend une portion centrale (28) entourée par une portion
en disque périphérique (32) pour recevoir le ressort (26), la portion centrale (28)
étant dotée d'une ouverture centrale (34) permettant au piston (14) de passer à travers
celle-ci et d'être positionné dans une position finale,
caractérisée en ce que
le siège de ressort (20) comprend en outre une ouverture d'engagement (34) permettant
un engagement traversant de l'extrémité (18) du piston dans une position d'engagement
préliminaire distincte de la position finale, ladite ouverture d'engagement (34) s'ouvrant
dans l'ouverture centrale (34) de sorte que le piston (14) peut être déplacé depuis
la position d'engagement jusqu'à la position finale, et dans laquelle
l'extrémité (18) du piston est dotée d'un trou traversant diamétral transversal (38)
dans lequel est engagée une broche (36) qui se projette depuis les deux extrémités
du trou (38), l'ouverture d'engagement (34) permettant le passage de ladite broche
jusqu'à un positionnement final du piston (14) dans l'ouverture centrale (34) et
dans laquelle l'ouverture d'engagement (34) possède une section rectangulaire formant
des fentes diamétralement opposées qui s'étendent radialement depuis l'ouverture centrale
circulaire (34) de sorte que le piston (14) et la broche (36) peuvent être engagés
à travers ladite ouverture centrale (34) et ladite ouverture d'engagement (34) avant
d'être tournés à la position finale, et
dans laquelle le siège de ressort (20) est en outre doté d'encoches rectangulaires
(42) formant un évidement dans la portion centrale (32) du siège de ressort, les encoches
(42) s'étendant radialement depuis l'ouverture centrale circulaire (34), de sorte
que la broche (36) peut être positionnée dans lesdites encoches (42) quand le piston
est dans la position finale.
2. Pompe à carburant à haute pression (10) selon la revendication 1, dans laquelle la
position finale est écartée de 90° de la position d'engagement.
3. Pompe à carburant à haute pression (10) selon l'une quelconque des revendications
précédentes, dans laquelle le siège de ressort (20) comprend une portion cylindrique
(30) qui s'étend axialement depuis une première bordure circulaire jusqu'à une seconde
bordure circulaire opposée, la portion centrale (28) dans laquelle l'ouverture centrale
est agencée s'étendant radialement vers l'intérieur depuis la première bordure circulaire,
et la portion en disque périphérique (32) destinée à recevoir le ressort (26) s'étendant
radialement vers l'extérieur depuis la seconde bordure circulaire.
4. Pompe à carburant à haute pression (10) selon la revendication 3, dans laquelle l'ouverture
d'engagement (34) s'ouvre partiellement dans la paroi de ladite portion cylindrique
(30).