U.S. patent application number 10/560461 was filed with the patent office on 2006-09-28 for radial piston pump for providing high pressure in fuel injection systems of internal combustion engines.
This patent application is currently assigned to Endress+ Hauser GmbH + Co. KG. Invention is credited to Gerhard Breuer, Claudia Kohler, Franz Ruckert, Karl-Heinz Thiemann.
Application Number | 20060216157 10/560461 |
Document ID | / |
Family ID | 33482895 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060216157 |
Kind Code |
A1 |
Breuer; Gerhard ; et
al. |
September 28, 2006 |
Radial piston pump for providing high pressure in fuel injection
systems of internal combustion engines
Abstract
The invention relates to a radial piston pump (1) for
high-pressure fuel generation in fuel injection systems of internal
combustion engines, in particular in a common rail injection
system, having a drive shaft (4) which is mounted in a pump casing
(2) and has an eccentric shaft section (6) on which a running
roller (8) is mounted, and having preferably a plurality of pistons
(16), which are arranged in a respective cylinder (14) radially
with respect to the drive shaft (4) and each have a piston
footplate (18), which makes contact with the circumferential
surface (10, 12) of the running roller (8), at their ends facing
the running roller (8). The invention provides that at least that
surface (28) of the piston footplate (18) which is in contact with
the circumferential surface (10, 12) of the running roller (8)
consists of a wear-resistant material, namely of hard metal, a
ceramic material, a cast carbide material, or cermet.
Inventors: |
Breuer; Gerhard;
(Grossbettlingen, DE) ; Kohler; Claudia;
(Stuttgart, DE) ; Ruckert; Franz; (Ostfildern,
DE) ; Thiemann; Karl-Heinz; (Korb, DE) |
Correspondence
Address: |
WILLIAM COLLARD;COLLARD & ROE, P.C.
1077 NORTHERN BOULEVARD
ROSLYN
NY
11576
US
|
Assignee: |
Endress+ Hauser GmbH + Co.
KG
Maulburg
DE
|
Family ID: |
33482895 |
Appl. No.: |
10/560461 |
Filed: |
June 11, 2004 |
PCT Filed: |
June 11, 2004 |
PCT NO: |
PCT/EP04/06338 |
371 Date: |
April 3, 2006 |
Current U.S.
Class: |
417/273 |
Current CPC
Class: |
F04B 1/0426 20130101;
F05C 2203/0843 20130101; F04B 1/0413 20130101; F05C 2251/10
20130101; F05C 2203/08 20130101 |
Class at
Publication: |
417/273 |
International
Class: |
F04B 1/04 20060101
F04B001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 2003 |
DE |
103 26 863.4 |
Claims
1-8. (canceled)
9. A radial piston pump (1) for high-pressure fuel generation in
fuel injection systems of internal combustion engines, in
particular in a common rail injection system, having a drive shaft
(4) which is mounted in a pump casing (2) and has an eccentric
shaft section (6) on which a running roller (8) is mounted, and
having preferably a plurality of pistons (16), which are arranged
in a respective cylinder (14) radially with respect to the drive
shaft (4) and each have a piston footplate (18), which makes
contact with the circumferential surface (10, 12) of the running
roller (8), at their ends facing the running roller (8), wherein at
least that surface (28, 31) of the piston footplate (18) which is
in contact with the circumferential surface (10, 12) of the running
roller (8) consists of hard metal, a cast carbide material, or
cermet.
10. The radial piston pump as claimed in claim 9, wherein the
piston footplate (18), on its surface (31) facing the running
roller (8), bears at least one insert (30) made from hard metal,
from a cast carbide material or from cermet.
11. The radial piston pump as claimed in claim 9, wherein the hard
metal contains G20, GC37 or GC20 and has a surface roughness
R.sub.z of between 0.3 .mu.m and 1.0 .mu.m.
12. The radial piston pump as claimed in claim 9, wherein the cast
carbide material contains a chilled cast iron material, in
particular GGH or SoGGH, and has a surface roughness R.sub.z of
between 0.5 .mu.m and 2.0 .mu.m.
13. The radial piston pump as claimed in claim 9, wherein the
piston footplate (18), on its surface (31) facing the running
roller (8), has at least two grooves (50) which cross one
another.
14. The radial piston pump as claimed in claim 13, wherein one such
groove (50) is in each case arranged in the center of a depression
(39), forming a groove run-out, in the surface (31).
15. The radial piston pump as claimed in claim 9, wherein the
surface of the piston footplate (18) and/or of the running roller
(8) has a surface roughness R.sub.z of between 0.15 .mu.m and 2
.mu.m.
Description
[0001] The invention is based on a radial piston pump for
high-pressure fuel generation in fuel injection systems of internal
combustion engines, in particular in a common rail injection
system, having a drive shaft which is mounted in a pump casing and
has an eccentric shaft section on which a running roller is
mounted, and having preferably a plurality of pistons, which are
arranged in a respective cylinder radially with respect to the
drive shaft and each have a piston footplate, which makes contact
with the circumferential surface of the running roller, at their
ends facing the running roller, in accordance with the preamble of
claim 1.
[0002] A radial piston pump of this type is known, for example,
from DE 198 09 315 A1. The piston footplate and the running roller
of the known radial piston pump generally consist of case-hardened
steel or of heat-treated steel. Over the course of time, however,
sliding wear to these components can occur as a result of adhesion,
abrasion or surface spalling. This undesirable wear can lead to
failure of the radial piston pump and therefore also to failure of
the internal combustion engine.
[0003] By contrast, the present invention is based on the object of
further developing a radial piston pump of the type described in
the introduction in such a manner as to increase its
reliability.
[0004] This object is achieved according to the invention by the
characterizing features of claim 1.
[0005] The susceptibility of the piston footplate/running roller
sliding pairing to wear is significantly reduced by virtue of the
fact that, for the first time, at least that surface of the piston
footplate which is in contact with the circumferential surface of
the running roller consists of a wear-resistant material, namely of
hard metal, a ceramic material, a cast carbide material or cermet.
The materials listed have a significantly higher modulus of
elasticity compared to the steel materials used hitherto, which
results in reduced deformation under load and consequently also in
a more uniform surface pressure without significant stress peaks.
If ceramic materials are used, in particular their lower weight
plays an advantageous role, since the piston footplate together
with the piston is accelerated and decelerated at a high frequency,
and consequently the mass inertia is significantly reduced.
[0006] The piston footplate may be made entirely from the
wear-resistant material, or else it consists, as hitherto, of
case-hardened steel or heat-treated steel but bears at least one
insert made from the wear-resistant material on its surface facing
the running roller. The use of inserts brings the advantage of a
modular structure, i.e. a standardized piston footplate can be
provided with inserts made from different material, so that
numerous variants can be produced.
[0007] If a ceramic material is used, this material preferably
contains silicon nitride Si.sub.3N.sub.4 and has a surface
roughness R.sub.z of between 0.15 .mu.m and 0.5 .mu.m. Hard metals
may consist, for example, of G20, GC37 or GC20 and may have a
surface roughness R.sub.z of between 0.3 .mu.m and 1.0 .mu.m, while
the cast carbide material is formed by a chilled cast iron
material, in particular by GGH or SoGGH, which has a surface
roughness R.sub.z of between 0.5 .mu.m and 2.0 .mu.m.
[0008] It is particularly preferable for the piston footplate, on
its surface facing the running roller, to have at least two grooves
which cross one another. This eliminates the overlap region of
piston foot disk and running roller without a supply of lubricant.
Fuel can accumulate in the grooves, which act as build-up gaps, and
this fuel, on account of the sliding velocity between the running
roller and the piston footplate, promotes the formation of a
hydrodynamic sliding film, which further reduces the wear to the
sliding surfaces.
[0009] Exemplary embodiments of the invention are illustrated in
the drawings and explained in more detail in the description which
follows. In the drawings:
[0010] FIG. 1 shows a cross-sectional illustration of a radial
piston pump with a piston footplate and a drive shaft in accordance
with a first embodiment of the invention;
[0011] FIG. 2 shows a large cross-sectional illustration of a
piston and piston footplate in accordance with a further
embodiment.
[0012] FIG. 2a shows an enlarged excerpt from FIG. 2;
[0013] FIG. 2b shows a further enlarged excerpt from FIG. 2;
[0014] FIG. 3 shows a view of the piston footplate from FIG. 2 from
below;
[0015] FIG. 4 shows a cross-sectional illustration of a piston with
piston footplate and a drive shaft in accordance with a further
embodiment;
[0016] FIG. 5 shows a cross-sectional illustration of a drive shaft
in accordance with a further embodiment;
[0017] FIG. 6 shows a view on line VI-VI from FIG. 5;
[0018] FIG. 7 shows a view on line VII-VII from FIG. 6.
[0019] The radial piston pump 1 shown in FIG. 1 is preferably used
to generate the system pressure for the high-pressure reservoir
(rail) of a common rail injection system of a compression-ignition
internal combustion engine. It comprises a drive shaft 4 mounted in
a pump casing 2 with an eccentric shaft section 6, on which a
polygonal running roller 8, which can rotate with respect to the
shaft section 6, is mounted. The polygonal running roller 8 has
planar flat sections 12 arranged at a circumferential distance from
one another along its circumferential surface 10.
[0020] The piston footplate 18 of a piston 16 guided radially with
respect to the drive shaft 4 in a cylinder 14 is supported on each
of the flat sections 12 of the running roller 8. The piston
footplate 18 is preferably pivotably connected, by means of a
spherical bearing 20, to the end of the piston 16 which faces
towards the drive shaft 4. The spherical bearing 20 is realized,
for example, by the end of the piston being designed as a partial
ball 22 which engages in a spherical recess 24 of complementary
design in the piston footplate 18. Furthermore, the piston
footplate 18, together with the piston 16, is prestressed by a
spring 26 onto the associated flat section 12 of the running roller
8. The way in which a radial piston pump 1 of this type functions
is described, for example, in DE 198 02 475 A1 and therefore will
not be dealt with in any further detail here.
[0021] At least that surface 28 of the piston footplate 18 which is
in contact with the circumferential surface 10 of the running
roller 8 consists of a wear-resistant material, namely of hard
metal, a ceramic material, a cast carbide material or cermet. This
is preferably realized by virtue of the fact that the piston
footplate 18, on its surface 28 facing towards the running roller
8, has at least one, for example disk-like, insert 30 made from the
wear-resistant material. The insert 30 may be positively and/or
cohesively connected to the remaining piston footplate 18, for
example by adhesive bonding or soldering. The insert 30 may, as
shown in FIG. 1, extend over the entire contact surface 28 of the
piston footplate 18 with the running roller 8 or only over part of
this contact surface. Alternatively, it is also possible for the
entire piston footplate 18 to be made from the wear-resistant
material, so that there is no need for an additional insert 30.
[0022] If a ceramic material is used for the piston footplate 18,
it preferably contains silicon nitride Si.sub.3N.sub.4. Hard metals
may, for example, consists of G20, GC37 or GC20, while the cast
carbide material may contain a chilled cast iron material, in
particular GGH or SoGGH.
[0023] Furthermore, the piston 16 itself may be made from
wear-resistant material, for example from an Si.sub.3N.sub.4
ceramic or a ZrO.sub.2 ceramic. The piston 16 may be produced by
extrusion and have a porosity of less than 5%, in which case the
surface is infiltrated with MOS.sub.2. Alternatively, the piston 16
may also be isostatically pressed and sintered.
[0024] Not least, it is also the case that at least part of the
running roller 8, in particular the flat sections 12, consists of a
wear-resistant material, namely of hard metal, a precision-cast
material, a cast carbide material, a sintered tool steel or an
alloyed nitriding steel.
[0025] As in the case of the piston footplate 18, this is
preferably realized by virtue of the fact that the flat sections 12
are each provided with an insert 32 of the wear-resistant material,
as shown in FIG. 1. An insert 32 of this type is in each case held
positively and/or cohesively in a recess 34 of complementary shape
in the flat section 12, for example by adhesive bonding or
soldering. Alternatively, the entire running roller 8 may consist
of the wear-resistant material.
[0026] If hard metal is used for the inserts 32 or for the running
roller 8 itself, examples of suitable materials include G20, GC37
and GC20. A suitable precision-cast material is formed, for
example, by GX-210WCr13H, while a suitable cast carbide material is
locally remelted, carbide SoGGH (gradient material). A suitable
sintered tool steel is ASP23. A nitriding steel which has been
specially alloyed with Cr and/or Mo and/or V and/or C by nitriding
or gas-nitriding is used for a variant with a gradient material.
The basic elements and the process parameters used in the nitriding
lead to deep diffusion with hardnesses of HV 750 to 850 combined,
at the same time, with a higher strength of the base material. The
compound layer which is formed is removed by grinding for
functional reasons.
[0027] The surfaces of the piston footplate 18 and of the running
roller 8 preferably have a surface roughness R.sub.z of between
0.15 .mu.m and 2 .mu.m, depending on the materials used, on the
sliding surfaces. The lower limit applies to ceramic, in particular
a range from 0.15 .mu.m to 0.5 .mu.m, while the upper limit applies
to metals such as SoGGH or ASP23. A surface roughness R.sub.z of
between 0.3 .mu.m and 1 .mu.m is provided for hard metal.
[0028] The table below lists preferred material pairings for the
piston footplate 18, on the one hand, and the running roller 8, on
the other hand. If inserts are used both in the running roller 8
and in the piston footplate 18, any desired combinations of
material pairings are possible with the support bodies in each case
unchanged. In particular, with the pairings in the table in which
the running roller 8 preferably consists entirely of the
wear-resistant material ("solid material"), it is alternatively
also possible to use inserts 32 made from the corresponding
material in the region of the flat sections 12, as has already been
demonstrated in FIG. 1. The running roller 8 as support body for
the inserts 32 may then consist of a different material, for
example 50Cr4, 42CrV4 or 16MnCr5.
[0029] The exemplary embodiment in the third line of the table
plays a particular role. In this case, a carbide zone is in each
case formed in the region of the flat sections 12 of the running
roller 8 consisting of a cast steel material and illustrated
separately in FIG. 5. This carbide zone is produced either by a
targeted solidification rate during casting of the running roller 8
or by remelting and then preferably forms the gradient material
SoGGH. Consequently, the result is a running roller 8 in which a
carbide zone 33 has been formed in the region of the surface
sections 12, while the remaining zones and regions of the running
roller 8 consist of cast steel with unchanged properties.
TABLE-US-00001 TABLE Preferred material pairings Running roller
Piston foot disk Inserts of hard metal, Solid material or inserts
e.g. G20, GC37, GC20 comprising a) ceramic, e.g. Si.sub.3N.sub.4
ceramic b) chilled cast iron, e.g. SoGSH c) Cermet Solid
precision-cast Solid material or inserts material, e.g. GX-
comprising 210WCr13 H a) ceramic, e.g. Si.sub.3N.sub.4 ceramic b)
hard metal, e.g. G20 c) Cermet Solid cast carbide Solid material or
inserts material, e.g. chilled comprising cast iron SoGGH a)
ceramic, e.g. Si.sub.3N.sub.4 ceramic b) hard metal, e.g. G20 c)
Cermet Solid material Solid material or inserts comprising sintered
comprising tool steel, e.g. a) ceramic, e.g. Si.sub.3N.sub.4
ceramic ASP23, b) hard metal, e.g. G20 comprising C, Cr, Mo, c)
Cermet V-alloyed nitriding d) cast carbide material, e.g. steel
SoGGH
[0030] In each case one or more transverse grooves 36 may be formed
in the region of the flat sections 12 of the running roller 8, as
can be seen most clearly from FIG. 6. As can be seen from FIG. 7,
the transverse groove 36 is arranged in the center of a depression
29, forming a groove run-out, in the flat section 12. The
depression 29 is formed by two planes arranged at an angle with
respect to the flat section 12, with the transverse groove 36 at
their intersection line. The depression angle .gamma. of the
depression 29 is, for example, less than 15 degrees. The transition
from the depression 29 to the flat section 12 is rounded with a
radius R.sub.4 of preferably less than or equal to 1 mm. The radius
R.sub.4 is produced for example by grinding. Fuel can accumulate in
this transverse groove 36 or depression 29, which acts as a
build-up gap, which fuel, on account of the sliding velocity
between the flat sections 12 of the running roller 8 and the piston
footplate 18, promotes the formation of a hydrodynamic sliding
film, thereby reducing the wear to the sliding surfaces.
[0031] In the embodiments shown in FIG. 2 to FIG. 4, those parts
which remain the same as and have the same action as in the example
shown in FIG. 1 are denoted by the same reference designations. By
contrast, in the example shown in FIG. 2, the piston footplate 18
is held on the associated piston 16 by a plate holder 38. The
piston footplate 18, on its surface facing the piston 16, has a
circular recess 40, in which the spherically shaped end 42 of the
piston 16 engages, coming into contact with the base of the recess
40. The plate holder 38 is locked on the piston 16 by means of a
circlip 46 engaging in a groove 44 in the piston 16. A circular
insert 30 made from one of the wear-resistant materials described
above is held in a recess 48 of complementary shape in the piston
footplate 18, for example by cohesive bonding, in particular by
soldering. As can be seen from FIG. 2a, the insert 30 is provided
at the edge side, on its surface 31 facing the running roller 8,
with an angled run-out 35, the run-out angle .alpha. amounting to
approximately 15 degrees. Furthermore, the transition between this
surface 31 and the run-out 35 is rounded with a radius R.sub.2 of
approx. 2 mm. The transition between the run-out 35 and the edge
surface 37 of the insert 30 is also rounded by means of a radius
R.sub.1 of less than or equal to 1 mm.
[0032] Similarly to the flat sections 12 of the running roller 8,
the inserts 30 of the piston footplate 18 preferably have at least
two grooves 50 which cross one another, as can be seen most clearly
from FIG. 3. On account of the grooves 50 being arranged so as to
cross one another, there is a high probability that, with regard to
the piston footplate 18 which can rotate with respect to the plate
holder 38, one of the grooves 50 will be oriented transversely with
respect to the direction of movement, in order to promote the
formation of a hydrodynamic lubricating film. The grooves 50 are
preferably produced by pressing. This results in a lower notch
effect compared to chip-forming processes, since the material
fibers are not severed. As can be seen from FIG. 2b, the grooves 50
are each arranged in the center of a depression 39, forming a
groove run-out, in the surface 31. The depression is formed by two
planes arranged at an angle with respect to the surface 31, with
the respective groove 50 located at the intersection line of these
planes. The depression angle .beta. of the depression 39 is, for
example 5 degrees. The transition between the depression 39 and the
surface 31 is rounded with a radius R.sub.3 of preferably less than
or equal to 1 mm.
[0033] In the exemplary embodiment shown in FIG. 4, the piston
footplate 18 consists entirely of one of the wear-resistant
materials mentioned above and is fitted into the passage hole 52 in
an annular bush 54 which consists of steel. The connection between
the annular bush 54 and the piston footplate 18 is preferably
produced by soldering. Of course, there are also other conceivable
options for arranging wear-resistant material on the mutually
associated sliding surfaces 12, 28 of the running roller 8 and
piston footplate 18.
* * * * *