U.S. patent application number 11/503118 was filed with the patent office on 2006-12-07 for high pressure pump.
Invention is credited to Marco Ganser.
Application Number | 20060275164 11/503118 |
Document ID | / |
Family ID | 32855128 |
Filed Date | 2006-12-07 |
United States Patent
Application |
20060275164 |
Kind Code |
A1 |
Ganser; Marco |
December 7, 2006 |
High pressure pump
Abstract
A piston (6) of a piston pump unit (2), which can be displaced
in a translatory manner, is guided in a cylinder bore (7). The
piston (6) is driven by a crank drive (13) comprising an eccentric
element (15) which is arranged on a drive shaft (14). A stroke ring
(12) is rotationally mounted on the eccentric element (15) but does
not rotate therewith. A sliding surface (10) of the piston (6) is
arranged on a sliding bearing surface (11) on the stroke ring (12).
A discharge chamber (22) is embodied inside the piston (6) on an
end opposite the stroke ring (12). Said discharge chamber is open
towards the sliding bearing surface (11). The discharge chamber
(22) is connected in a pressure-wise manner to a working chamber
(8) by means of a passage (23) in the piston (6). A displaceable
control piston (25) is guided in a longitudinal bore (24)
pertaining to said passage (23). Said control piston (25) is
impinged upon on one side by a medium in the working chamber (8)
and on the other front side by a pressure medium in the discharge
chamber (22). The control piston (25) separates the medium which is
to be transported from the pressure medium in the discharge chamber
(22) and ensures that the pressure in the discharge chamber (22)
increases if the pressure increases in the working chamber (8).
This results in decompression of the sliding bearing between the
piston (6) and the stroke ring (12).
Inventors: |
Ganser; Marco; (Oberageri,
CH) |
Correspondence
Address: |
HERSHKOVITZ & ASSOCIATES
2845 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
32855128 |
Appl. No.: |
11/503118 |
Filed: |
August 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10544004 |
Aug 1, 2005 |
7108491 |
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PCT/CH03/00802 |
Dec 4, 2003 |
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11503118 |
Aug 14, 2006 |
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Current U.S.
Class: |
417/521 |
Current CPC
Class: |
F04B 1/0408 20130101;
F04B 53/04 20130101; F04B 1/0404 20130101; F02M 2200/16 20130101;
F04B 1/0413 20130101; F02M 59/102 20130101 |
Class at
Publication: |
417/521 |
International
Class: |
F04B 41/06 20060101
F04B041/06 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 11, 2003 |
CH |
202/03 |
Claims
1. A high pressure pump, in particular for a fuel injection system
for internal combustion engines, having at least one piston pump
unit (2, 2') which has a piston (6) guided in a cylinder bore (7)
and delimiting a working chamber (8), having a crank drive (13) for
driving the piston (6), having a stroke ring (12) which is arranged
between the crank drive (13) and the piston (6) and which is
mounted such that it is driven rotatably with respect to the crank
drive (13) but does not rotate and which has a flat sliding bearing
surface (11), on which the piston (6) is supported with a sliding
surface (10), wherein a connecting duct (34, 35) is formed in the
stroke ring (12), said connecting duct (34, 35) opens at one, first
end into the sliding bearing surface (11) and is connected to a
fluid source by means of a fluid feed conduit (31, 32, 33) provided
in the crank drive (13).
2. The high pressure pump as claimed in claim 1, wherein the fluid
is a lubricant and the fluid feed conduct is a lubricant feed
conduct.
3. The high pressure pump as claimed in claim 2, wherein the crank
drive (13) has an eccentric element (15) and wherein the connecting
duct (34, 35) opens at the other, second end into the inner surface
(12a) of the stroke ring (12) which is in contact with the
eccentric element (15), and wherein a lubricating groove (31) is
provided on the circumference of the eccentric element (15), said
lubricating groove (31) is open toward the outside and is connected
to the lubricant source via a connecting line (32, 33) running in
the eccentric element (15) and in the drive shaft (14).
4. The high pressure pump as claimed in claim 3, wherein the
lubricating groove (31) extends over part of the circumference of
the eccentric element (15).
5. The high pressure pump as claimed in claim 2, further comprising
a relief chamber (22) which is arranged in the region of the
sliding surface (10), is open toward the sliding bearing surface
(11) and is fluidically separated from the working chamber (8).
6. The high pressure pump as claimed in claim 5, wherein an annular
groove (36) is formed in the piston (6), said annular groove (36)
surrounds the relief chamber (22) and is open toward the sliding
bearing surface (11).
7. The high pressure pump as claimed in claim 6, wherein the
annular groove (36) is connected to a chamber (5) in which the
crank drive (13) and the stroke ring (12) are accommodated.
8. The high pressure pump as claimed in claim 5, wherein the
opening of the relief chamber (22) is completely surrounded by the
sliding surface (10) of the piston, said sliding surface (10)
acting together with the sliding bearing surface (11) of the stroke
ring (12).
9. The high pressure pump as claimed in claim 7, wherein a
longitudinal groove (37) is formed in the stroke ring (12) in the
region of the sliding bearing surface (11), said longitudinal
groove (37) is open toward the sliding surface (10) and opens into
said chamber (5), is offset with respect to the relief chamber (22)
in the direction of the axis of rotation (14a) of the drive shaft
(14) and communicates with the annular groove (36).
10. The high pressure pump as claimed in claim 5, wherein the
pressure medium in the relief chamber (22) is a lubricant,
preferably lubricating oil.
11. The high pressure pump as claimed in claim 2, wherein said
connecting duct (34, 35) opens into the sliding bearing surface
(11) at a point such that it is connected to the relief chamber
(22) only in specific positions of the stroke ring (12) with
respect to the piston (6) and is connected periodically to said
lubricant feed conduit (31, 32, 33).
12. The high pressure pump as claimed in claim 11, wherein the
lubricating groove (15) is arranged such that it is connected to
the connecting duct (34, 35) in the stroke ring (12) when this
connecting duct (34, 35) is connected to the relief chamber
(22).
13. The high pressure pump as claimed in claim 5, wherein the
relief chamber (22) is fluidically separated from the working
chamber (8) by a pressure transmission element (25, 41) arranged in
a passage (23) in the piston (6), said pressure transmission
element (25, 41) is pressurized on one side by the medium to be
delivered and on the opposite side by a pressure medium in the
relief chamber (22) and can be displaced in the direction of the
application of pressure under the action of pressure.
14. The high pressure pump as claimed in claim 13, wherein the
pressure transmission element is a control piston (25) which can be
displaced in a longitudinal bore (24) belonging to said passage
(23) and is guided closely in a sliding manner.
15. The high pressure pump as claimed in claim 14, wherein the
control piston (6) on its first end facing the relief chamber (22)
is supported on a compression spring (26) which rests on an
abutment at the other end.
16. The high pressure pump as claimed in claim 15, wherein said
abutment is formed by a supporting element retained in the control
piston (25).
17. The high pressure pump as claimed in claim 16, wherein said
supporting element is a spring ring (27).
18. The high pressure pump as claimed in claim 13, wherein the
pressure transmission element is a diaphragm (41) which can be
deflected elastically, covers the passage (23) and is fixed in a
sealing manner in its edge region.
19. The high pressure pump as claimed in claim 18, wherein the
piston (6) has a piston element (38) guided in the cylinder bore
(7) and a ring (39) which is connected to the piston element (38)
at the end of the latter facing away from the working chamber
(8).
20. The high pressure pump as claimed in claim 19, wherein the
diaphragm (41) is held firmly in its edge region between the piston
element (38) and the ring (39).
21. The high pressure pump as claimed in claim 2, wherein the crank
drive (13) has an eccentric element (15) which is arranged on a
rotatably driven drive shaft (14) with an eccentricity (e) and on
which the stroke ring (12) is mounted such that it does not rotate
with the eccentric element (15).
22. The high pressure pump as claimed in claim 2, wherein an
annular collecting groove (28) is formed in the wall of the
cylinder bore (7), said annular collecting groove (28) is open
toward the piston (6), is used to collect seepage which passes
through the gap between the wall of the cylinder bore (7) and the
piston (6) and to which a discharge conduit (30) is connected.
23. The high pressure pump as claimed in claim 2, wherein the high
pressure pump (1, 1') is designed to deliver fuel.
24. The high pressure pump as claimed in claim 23, wherein the high
pressure pump (1, 1') is designed to deliver diesel fuel.
Description
[0001] This application is a continuation of co-pending application
U.S. Ser. No. 10/544,004, the subject matter of which is
incorporated herein by reference in its entirety.
[0002] The invention relates to a high pressure pump, which is
suitable in particular for use in a fuel injection system for
internal combustion engines.
[0003] In DE-A-197 05 205 and the corresponding U.S. Pat. No.
6,077,056, a generic high pressure pump for a fuel injection device
for internal combustion engines is described in which the piston of
a piston pump unit is driven harmonically by an eccentric drive. At
its end facing away from the working chamber of the piston pump
unit, the piston bears a sliding shoe which rests with a sliding
surface against a sliding bearing surface of a stroke ring. The
stroke ring is rotatably mounted on an eccentric journal of a drive
shaft and is driven rotatably but does not rotate. The drive shaft,
the eccentric journal, the stroke ring and the sliding shoe are all
accommodated in a low pressure chamber, which is used as a feed
chamber for the medium to be delivered, that is to say fuel. Formed
in the sliding shoe is a relief chamber, which is open toward the
sliding bearing surface and has a direct hydraulic connection to
the working chamber via a passage which extends in the longitudinal
direction of the pump piston. The relief chamber is accordingly
filled with the fuel to be delivered.
[0004] During the delivery stroke of the piston pump unit, the
piston and the sliding shoe fixed to the latter are pressed against
the stroke ring by the pressure acting in the working chamber. At
the same time, there is also an increase in the pressure in the
relief chamber connected to the working chamber, as a result of
which the force acting on the sliding shoe and directed away from
the stroke ring is increased. Relief of the load on the sliding
bearing between the sliding shoe and the stroke ring is therefore
achieved. This hydrostatic relief of the load on the sliding
bearing leads to a reduction in the friction between the sliding
surface on the sliding shoe and the sliding bearing surface on the
stroke ring.
[0005] The lubrication of the sliding bearing between the sliding
shoe and the stroke ring is carried out by the fuel in the relief
chamber. The bearing between the eccentric journal and the stroke
ring is lubricated by the fuel in the low pressure chamber.
However, as is known, fuel has poor lubricating properties and is
therefore able to develop only a restricted lubricating action.
[0006] The present invention is, then, based on the object of
providing a high pressure pump of the type mentioned at the
beginning for very high delivery pressures and large delivery
quantities, whose production costs are as low as possible and which
is able to satisfy high requirements on the operational reliability
and on the lifetime.
[0007] This object is achieved by a high pressure pump having the
features of claim 1.
[0008] The relief chamber is divided off from the working chamber
by the pressure transmission element arranged in the passage in the
piston. Therefore, the medium to be delivered, which is fuel, for
example, is also separated from the medium in the relief chamber.
There is thus no longer any restriction to using the medium to be
delivered for the pressure relief and the lubrication of the
sliding bearing between the stroke ring and the piston. Instead, a
medium which is much more suitable for these tasks can be chosen,
which means one with excellent lubricating properties, for example
lubrication oil. With the considerably improved lubrication of the
sliding bearing and also the bearing between the stroke ring and
the crank drive, the risk of these bearings seizing, even under
high loading, is reduced sharply, which in turn contributes to
increased operational reliability and a long lifetime.
[0009] Since the pressure transmission element is pressurized on
one side by the medium to be delivered and can be displaced in the
direction of the application of pressure, the pressure in the
working chamber is transmitted to the medium in the relief chamber,
that is to say, when the pressure in the working chamber rises, the
pressure in the relief chamber also rises. Therefore, relief of the
load on the sliding bearing between stroke ring and piston is
achieved which becomes greater as the delivery pressure becomes
greater, as is known from the aforementioned prior art. This relief
of the load on the sliding bearing not only permits higher delivery
pressures but also allows an enlargement of the piston area and
therefore an increase in the delivery rate without the number of
piston pump units necessarily having to be increased for this
purpose. This has a beneficial effect on the production costs.
[0010] Preferred further refinements of the high pressure pump
according to the invention form the subject matter of the dependent
claims.
[0011] In the following text, by using the drawings, exemplary
embodiments of the subject matter of the invention will be
explained in more detail. In the drawings, purely
schematically:
[0012] FIG. 1 shows a first embodiment of a high pressure pump
having two piston pump units, in a longitudinal section,
[0013] FIGS. 2 and 3 show one of the two piston pump units with the
pump piston in various operating positions, in an illustration
corresponding to FIG. 1 and on an enlarged scale,
[0014] FIG. 4 shows a section along the line A-A in FIG. 3, and
[0015] FIG. 5 shows a second embodiment of a high pressure pump in
an illustration corresponding to FIG. 2.
[0016] The high pressure delivery pump 1 shown in FIGS. 1-4, which
is intended for use in a fuel injection system for internal
combustion engines, has two mutually diametrically opposite piston
pump units 2, 2' (plunger pump units), which are constructionally
identical and operate in antiphase. Each piston pump unit 2, 2' has
a housing block 3, which is firmly connected to a pump casing 4 and
projects into the interior 5 of this pump casing 4. Each piston
pump unit 2, 2' has a piston 6 (plunger), which is guided such that
it can move linearly with a close sliding fit in a cylinder bore 7
in the housing block 3. With one end face 6a, the piston 6 delimits
a working chamber 8 and, at its opposite end, widens to form a base
part 9. This base part 9 has a flat sliding surface 10, which rests
on a sliding bearing surface 11 which is provided on a stroke ring
12. This stroke ring 12 is common to both piston pump units 2, 2'.
Provided for the harmonic drive of the pistons 6 of the two piston
pump units 2, 2' is a crank drive 13, which has a drive shaft 14,
illustrated dashed, and an eccentric element 15 firmly connected to
the latter. The drive shaft 14 is driven in rotation about its axis
of rotation 14a (FIG. 1). The stroke ring 12 is seated rotatably
but not so as to corotate on the eccentric element 15. The
eccentric element 15 is arranged with an eccentricity e (FIG. 1)
with respect to the axis of rotation 14a of the drive shaft 14.
During rotation of the drive shaft 14, the stroke ring 12 is moved
firstly parallel to the sliding bearing surfaces 12 and secondly at
right angles to the axis of rotation 14a of the drive shaft 14,
specifically by the amount 2e in each direction. During operation,
the stroke ring 12 is thus displaced to and fro with respect to the
base part 9 of the piston 6. The pistons 6 of the piston pump units
2, 2' execute a stroke which is likewise 2e, that is to say twice
the eccentricity e.
[0017] Seated on the base part 9 of the piston 6 is a bearing ring
16, which is used as an abutment for a compression spring 17 which
is supported at the other end on the housing block 3. The
compression spring 17 keeps the associated piston 6 in continuous
contact with the stroke ring 12.
[0018] Formed in the housing block 3 is an inlet conduit 18, which
is connected to the working chamber 8 via a pressure-controlled
inlet valve 19 (FIG. 1). The inlet conduit 18 is connected to a
feed line, not illustrated, which is connected to a liquid
reservoir, that is to say in the present case to a fuel tank, for
example via a pre-delivery pump. In the housing block 3 there is
also an outlet conduit 20, which is connected to the working
chamber 8 via a pressure-controlled outlet valve 21 (FIG. 1). The
outlet conduit 20 is connected to a high pressure chamber, for
example the common rail of a fuel injection system.
[0019] Formed in the region of the sliding surface 10 in the base
part 9 of the piston 6 is a relief chamber 22, which is open toward
the sliding bearing surface 11.
[0020] In the longitudinal direction of the piston 6 there extends
a continuous, coaxial passage 23, which on one side is open toward
the working chamber 8 and on the other side is open toward the
relief chamber 22 (the passage 23 could also be placed off-axis).
Belonging to this passage 23, whose diameter changes, is a
longitudinal bore 24, in which a control piston 25, which serves as
a pressure transmission element, is displaceably guided with a
close sliding fit. The control piston 25 rests on a compression
spring 26, which is supported at the other end on a spring ring 27
(FIG. 2), which is retained in the piston 6.
[0021] Formed in the housing block 3 is an annular groove 28, which
extends around the piston 6 and is open toward the cylinder bore 7.
In the piston 6 there is a transverse bore 29, which passes through
the piston 6 and which is connected to the annular groove 28 at
both ends. Connected to the annular groove 28 is a discharge
conduit 30, which extends in the housing block 3 and which is
connected to a return line, not shown, which leads to a collecting
reservoir, which can be the fuel tank. Seepage, which is fed back
via the discharge conduit 30, collects in the annular groove 28 in
a manner still to be described.
[0022] The eccentric element 15 is provided with a lubricating
groove 31, which extends along a part of the circumference and is
open toward the stroke ring 12. The lubricating groove 31 is
connected via a radial bore 32 in the eccentric element 15 to a
feed duct 33, which extends in the direction of the axis of
rotation 14a of the drive shaft 14 and which is connected to a
lubricant reservoir via a lubricant pump, not shown. Via this feed
duct 33, a lubricant, preferably lubricating oil, is supplied at a
pressure of, for example, 2-6 bar. Formed in the stroke ring 12 are
two connecting ducts 34, 35, each of which leads from the inner
surface 12a of the stroke ring 12 to one of the sliding bearing
surfaces 11. The lubricating groove 31, which is permanently
connected to the feed duct 33, is, however, connected to a
connecting duct 34, 35 only in specific rotational positions of the
eccentric element 15, as can be seen from FIGS. 1-3.
[0023] The functioning of the high pressure pump 1 will now be
described in more detail by using FIGS. 1-4.
[0024] FIG. 1 shows that rotational position of the eccentric
element 15 in which the piston 6 of the one piston pump unit 2, the
upper one in the figures, is located in the lower end position,
that is to say at the end of the suction stroke. The piston 6 of
the other, lower piston pump unit 2' has reached the end of the
delivery stroke and therefore its upper end position. The
connecting ducts 34, 35 are connected neither to the lubricating
groove 31 nor to the associated relief chamber 22.
[0025] Starting from this initial position, only the operation of
the upper piston pump unit 2 will be described below. The operation
of the other, lower piston pump unit 2' is equal but opposite.
[0026] If the drive shaft 14 rotates in the counterclockwise
direction, then the delivery stroke begins for the piston 6 of the
upper piston pump unit 2, that is to say the piston 6 will be
displaced upward in the direction of the arrow A (FIG. 2). During
this delivery stroke, the inlet valve 19 is closed, which also
applies to the outlet valve 21 at the beginning of the delivery
stroke. The pressure in the working chamber 8 rises, the control
piston 25, which is pressurized on its end face facing the working
chamber 8 by the pressure of the liquid in the working chamber 8,
is moved downward in the direction of the arrow D in FIG. 2,
counter to the action of the compression spring 26. The result of
this is that the pressure of the lubricant which is located in the
relief chamber 22 and in the region of the passage 23 underneath
the control piston 25 is increased. As a result, a force is exerted
on the piston 6 which is directed away from the stroke ring 12 and
which counteracts the force exerted on the piston 6 by the liquid
in the working chamber 8. In this way, hydrostatic relief of the
load on the sliding bearing formed by the sliding surface 10 on the
base part 9 and the sliding bearing surface 11 on the stroke ring
12 is achieved, as described in DE-A-197 05 205 and U.S. Pat. No.
6,077,056 already mentioned. An optimum relief action is achieved
when the diameter DA of the relief chamber 22 is slightly smaller
than the diameter DP of the end face 6a of the piston 6 which faces
the working chamber 8 (see FIG. 2).
[0027] The situation following a rotation of the drive shaft 14
through 90.degree. is illustrated in FIG. 2. The piston 6 has
reached its middle position during the delivery stroke. There is no
connection between the lubricating groove 31 and the relief chamber
22 of the upper piston pump unit 2. By contrast, in the lower
piston pump unit 2', not shown, the relief chamber 22 is connected
to the lubricating groove 31. After the rotation of the drive shaft
14 through 90.degree., illustrated in FIG. 2, the stroke ring 12
assumes its right-hand end position, which is illustrated dashed in
FIG. 4 and is designated 12'.
[0028] As soon as the pressure in the working chamber 8 in the
course of the delivery stroke of the piston reaches a value which
is greater than the closing force of the outlet valve 21, the
latter is opened and the liquid is expelled from the working
chamber 8 into the outlet conduit 20 and then into the high
pressure chamber.
[0029] Following a rotation of the drive shaft 14 through
180.degree. from the position shown in FIG. 1, the delivery stroke
of the piston 6 is completed. The piston 6 is then moved downward
in the opposite direction, that is to say in the direction of the
arrow B (FIG. 3), for the suction stroke. During this suction
stroke, the outlet valve 21 remains closed. During the downward
movement of the piston 6 in the direction of the arrow B, a
negative pressure is produced in the working chamber 8, which
results in the inlet valve 19 opening and allowing liquid to flow
into the working chamber 8. The pressure prevailing in the relief
chamber 22 and the region of the passage 23 underneath the control
piston 28, together with the compression spring 26, effects upward
displacement of the control piston 25 in the direction of the arrow
E (FIG. 3). The situation following the rotation of the drive shaft
14 through a total of now 270.degree. is illustrated in FIG. 3. The
piston 6 has reached its middle position during the suction stroke.
The stroke ring 12 now assumes its left-hand end position, which is
illustrated by continuous lines in FIG. 4. This FIG. 4 reveals that
the stroke ring 12 executes a total stroke C in the direction of
the sliding bearing surface 11 which is equal to 2e, that is to say
twice the eccentricity e. In this left-hand end position of the
stroke ring 12, shown in FIGS. 3 and 4, the connecting duct 34 in
the stroke ring 12 is now connected to the relief chamber 22 and
the lubricating groove 31. This means that pressurized oil can get
into the relief chamber 22 via the feed duct 33, the radial bore
32, the lubricating groove 31 and the connecting duct 34. In this
way, the lubricant which has been lost during the delivery stroke
as a result of leakage along the sliding bearing surface 11 and
along the outer surface of the control piston 25 is replaced.
[0030] Following a rotation of the drive shaft 14 through a total
of 360.degree., the piston 6 is located at the end of the suction
stroke and assumes the lower end position illustrated in FIG. 1
again. The operating cycle described starts from the beginning.
[0031] Although the piston 6 is guided in the cylinder bore 7 with
a close sliding fit, on the one hand liquid, that is to say fuel,
can pass through the gap between the piston 6 and the wall of the
cylinder bore 7 and, on the other hand, lubricant, that is to say
lubricating oil, can pass out of the interior 5 of the pump casing
4. This seepage is collected in the annular groove 28 as a
liquid-lubricant mixture, that is to say as a fuel-lubricating oil
mixture.
[0032] In addition, it is possible that liquid (fuel) can pass out
of the working chamber 8 via the upper section of the passage 23
and through the very small gap between the control piston 25 and
the wall of the longitudinal bore 24. This seepage likewise passes
into the annular groove 28 via the transverse bore 29 in the piston
6. Furthermore, lubricant (lubricating oil) from the relief chamber
22 can pass through the narrow gap between the control piston 25
and the wall of the longitudinal bore 24. This leakage-lubricant
likewise passes into the annular groove 28 via the transverse bore
29.
[0033] The mixture of liquid (fuel and lubricant (lubricating oil))
in the annular groove 28 is led away via the discharge conduit 30
and, for example, led back into the liquid reservoir, that is to
say the fuel tank.
[0034] In the following text, a variant of the embodiment shown in
FIGS. 1 and 2 will be described in which, in the base part 9 of the
piston 6, in the region of the sliding surface 10, an annular
groove 36 is additionally formed, which is arranged coaxially with
respect to the relief chamber 22 and is open toward the sliding
bearing surface 11. This annular groove 36 is connected to a
longitudinal groove 37 which is formed in the stroke ring 12 and
which is open toward the sliding surface 10. This longitudinal
groove 37 is offset with respect to the section plane of FIG. 3
(which extends at right angles to the axis of rotation 14a and in
the center of the stroke ring 12) in the direction of the axis of
rotation 14a of the drive shaft 14 and opens into the interior 5 of
the pump casing 4 at both ends (FIG. 4). The seepage (lubricating
oil) entering this annular groove 36 is led back into the interior
5 via the longitudinal groove 37.
[0035] As a result of the provision of the annular groove 36, the
pressure distribution on the sliding surface 10 and the sliding
bearing 37 in the radial direction toward the outside from the
relief chamber 22 is changed, which has a beneficial influence on
the amount of the seepage.
[0036] The second embodiment of a high pressure pump 1', shown in
FIG. 5, differs from the first embodiment according to FIGS. 1-4
through a different configuration of the pressure transmission
element arranged in the piston 6. In this FIG. 5, which in terms of
illustration corresponds to FIG. 2, the same designations as in
FIGS. 1-4 are used for parts which are the same in both
embodiments.
[0037] In this second embodiment according to FIG. 5, the piston 6
comprises a piston element 38 guided in the cylinder bore 7 and a
ring 39, which is firmly connected to the piston element 38 at the
end of the latter facing away from the working chamber 8, for
example by being pressed on or shrunk on. The ring 39 rests with a
sliding surface 10 on the sliding bearing surface 11 on the stroke
ring 12 and has a flange 40, on which the compression spring 17 is
supported. As described by using FIGS. 1-3, this compression spring
17 ensures that the ring 39 remains in contact with the stroke ring
12. The sliding surface 10 is formed on the ring 39. The flange 40
could also be formed as a separate part, analogous to the bearing
ring 16 of FIG. 2.
[0038] Arranged between the ring 39 and the piston element 38 is a
diaphragm 41 which can be deflected elastically and is clamped
firmly in a sealing manner along its edge region between the ring
39 and the piston element 38. This diaphragm 41, serving as a
pressure transmission element, spans the relief chamber 22
delimited by the inner wall 39a of the ring and divides this relief
chamber 22 from a chamber 42 formed in the piston element 38. Into
this chamber 42 there opens a longitudinal bore 43, which extends
in the direction of the longitudinal axis of the piston element 38
and via which the chamber 42 is connected to the working chamber 8.
The longitudinal bore 43 and the chamber 42 form the passage 23.
The chamber 42 is filled with the liquid to be delivered, that is
to say with fuel.
[0039] The pressure in the chamber 42 changes in the same direction
as the pressure in the working chamber 8. With increasing pressure
in the chamber 42, the diaphragm 41 is deflected downward in the
direction of the application of pressure, that is to say toward the
sliding bearing surface 11. This leads to an increasing pressure in
the relief chamber 22 containing lubricant, and therefore to
hydrostatic pressure relief, as has already been described by using
FIGS. 1-4. Since the pressures on both sides of the diaphragm 41
are virtually identical, the stressing of the diaphragm 41 is low.
The latter can therefore be thin-walled and elastic.
[0040] In the variant according to FIG. 5, the annular groove 28
together with discharge conduit 30 for collecting and leading
seepage away, present in the first exemplary embodiment according
to FIGS. 1-3, is not shown but can likewise be provided if
required.
[0041] In a further variant, not illustrated, the diaphragm 41 is
fitted to the end surface 6a of the piston 6 facing away from the
working chamber 8. The diaphragm 41 could be fixed by welding the
same on or, in a manner analogous to that in FIG. 5, could be fixed
with a screwed, pressed or shrunk retaining part. The passage 23 is
then located underneath the diaphragm 41, it is filled with the
lubricant and communicates directly with the relief chamber 22.
[0042] The action of the embodiment illustrated in FIG. 5
corresponds to the mode of operation described by using FIGS.
1-4.
[0043] The exemplary embodiments of a high pressure pump 1, 1'
according to the invention, described in conjunction with FIGS.
1-5, have the advantage that, as a result of arranging a pressure
transmission element, that is to say a control piston 25 or
diaphragm 41, in the passage 23 connecting the working chamber 8
and the relief chamber 22, the media in the working chamber 8 and
in the relief chamber 22 are separated from each other. This
permits the use of a suitable lubricant in the region of the stroke
ring 12 and of the crank drive 13, irrespective of the medium
(fuel) to be delivered. In addition, without great constructional
expenditure, the desired pressure relief of the sliding bearing
which is formed by the sliding surface 10 of the piston 6 and the
sliding bearing surface 11 on the stroke ring 12 is achieved.
[0044] It goes without saying that various variants of the
exemplary embodiments shown are possible. Reference will be made to
some of these variants below.
[0045] In a further embodiment, the piston 6 has no transverse bore
29. Because of the close sliding fit and the pressure relationships
achieved according to the invention on both sides of the control
piston 25, the leakage from the side facing the working chamber 8
into the relief chamber 22 can be kept very low.
[0046] Under certain circumstances, it is also possible to dispense
with measures for collecting and discharging seepage along the
outside of the piston 6, that is to say to dispense with the
annular groove 28 and the discharge conduit 30 in the housing block
3, if no noticeable leakage occurs as a result of the prevailing
pressure conditions.
[0047] In a further variant, not illustrated, the control piston 25
has a larger diameter than illustrated in FIGS. 1-3. The
longitudinal bore 24 for guiding the control piston 25 with a close
sliding fit can be open at the top in the direction of the working
chamber 8. In this case, the part of the passage 23 which has a
narrower cross section is again located under the control piston 25
and communicates directly with the relief chamber 22. The control
piston 25 is installed in the piston 6 from above. A spring ring,
analogous to the spring ring 27 according to FIG. 2, then prevents
the control piston emerging above the end surface 6a. The
longitudinal bore 24 can also be continuous in the piston 6. In
this case, the remaining part of the passage 23 has the same
diameter as the longitudinal bore 24. It is also conceivable to
form the remaining section of the passage 23 slightly larger than
the diameter of the longitudinal bore 24.
[0048] Furthermore, there is also a need to keep the lubrication
losses from the relief chamber 22 into the interior 5 of the
housing low. One means for this purpose is illustrated in the
embodiment of FIGS. 3 and 4 (annular groove 36 and longitudinal
groove 37). If the flat sliding surface 10 of the base part 9 and
the sliding surface 11 of the stroke ring 12 do not rest exactly on
each other, for example because of a forced skewed position of the
two sliding surfaces 10 and 11, the lubrication losses are
detrimentally affected. Constructional measures for preventing such
a state can be: forming the base part 9 with a certain elasticity,
such that the sliding surface 10 can adapt to the sliding surface
11 by means of slight elastic deformation of the base part 9.
Division of base part 9 and piston 6 into two parts, in a manner
analogous to that in DE-A-197 05 205 and the corresponding U.S.
Pat. No. 6,077,056 in FIG. 4, can also be applied. In addition, the
inner surface 12a of the stroke ring 12, together with the
associated surface of the eccentric element 15, could be slightly
convex in the direction of the axis of rotation 14a or even
slightly spherical in the longitudinal and transverse direction. In
this case, it is recommended to configure the stroke ring 12 in two
parts for installation reasons.
[0049] Instead of two piston pump units 2, 2', as shown in FIG. 1,
only one piston pump unit 2 can also be provided. Conversely, more
than two piston pump units with corresponding sliding surfaces 11
of the stroke ring 12 can also be fitted radially, for example 3
piston pump units offset by 120.degree., or 4 offset by 90.degree.,
or 6 offset by 60.degree., with a common stroke ring 12.
[0050] In addition, it is also possible to arrange two or more
individual piston pump units or two or more pairs of mutually
opposite piston pump units 2, 2' operating in antiphase one after
another in the direction of the axis of rotation 14a of the drive
shaft 14.
[0051] Although the high-pressure pumps 1, 1' described are
provided for use in fuel injection systems of internal combustion
engines, in particular of diesel engines, these pumps can also find
applications in other fields.
[0052] It is also possible to dispense with the compression spring
26 and the spring ring 27 supporting the latter.
[0053] In this case, the control piston 25 is moved solely by the
compressive forces acting on the two ends.
[0054] Finally, it is also possible to form the control piston 25
with two different diameters. Then, if the end face facing the
working chamber 8 is larger than that facing the relief chamber, a
step up in pressure takes place; in the opposite case a step down
in pressure. In the case of these refinements, it may be
advantageous to form the control piston 25 from two separate parts
each having the appropriate diameter. If the bore having the
correspondingly larger diameter and that having the correspondingly
smaller diameter are not aligned exactly, tolerance and friction
problems can be prevented in this way.
* * * * *