U.S. patent application number 10/560465 was filed with the patent office on 2006-10-05 for radial piston pump for generating high pressure for fuel in fuel injection systems of combustion engines.
Invention is credited to Gerhard Breuer, Claudia Kohler, Franz Ruckert, Karl-Heinz Thiemann.
Application Number | 20060222517 10/560465 |
Document ID | / |
Family ID | 33482902 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060222517 |
Kind Code |
A1 |
Breuer; Gerhard ; et
al. |
October 5, 2006 |
Radial piston pump for generating high pressure for fuel in fuel
injection systems of 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 hard metal, a ceramic
material, a cast carbide material or cermet, and/or that at least
part of the running roller (8), in particular at least part of the
circumferential surface (10, 12) of the running roller (8),
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 and/or that the piston (16)
consists of a ceramic material.
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
|
Family ID: |
33482902 |
Appl. No.: |
10/560465 |
Filed: |
June 9, 2004 |
PCT Filed: |
June 9, 2004 |
PCT NO: |
PCT/EP04/06207 |
371 Date: |
March 31, 2006 |
Current U.S.
Class: |
417/273 |
Current CPC
Class: |
F02M 59/06 20130101;
F02M 59/102 20130101; F05C 2203/0843 20130101; F05C 2203/08
20130101; F05C 2251/10 20130101; F04B 1/0426 20130101; F02M 59/445
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 |
10326880.4 |
Claims
1-13. (canceled)
14. 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
surface (28, 31) of the piston footplate (18) which is in contact
with the circumferential surface (10, 12) of the running roller (8)
has at least one insert (30) made from a wear-resistant material,
namely of hard metal, a ceramic material, a cast carbide material
or cermet, and/or in that at least part of the running roller (8),
in particular at least part of the circumferential surface (10, 12)
of the running roller (8), consists of a wear-resistant material,
namely of hard metal, a sintered tool steel or an alloyed nitriding
steel.
15. The radial piston pump as claimed in claim wherein the piston
(16) consists of a ceramic material.
16. The radial piston pump as claimed in claim 14, wherein the
running roller (8) consists of a heat-treated steel and has inserts
(32) made from hard metal, such as G20, GC37 or GC20, and in that
the piston footplate (18) has inserts (30) made from ceramic, such
as Si.sub.3N.sub.4 ceramic, from chilled cast iron, such as SoGGH,
or from cermet.
17. The radial piston pump as claimed in claim 14, wherein the
running roller (8) consists of a precision-cast material, such as
GX-210WCr13 H, and in that the piston footplate (18) has inserts
(30) made from ceramic, such as Si.sub.3N.sub.4 ceramic, from hard
metal, such as G20, or from cermet.
18. The radial piston pump as claimed in claim 14, wherein the
running roller (8) consists of a cast carbide material, such as
chilled cast iron SoGGH, and in that the piston footplate (18) has
inserts (30) made from ceramic, such as Si.sub.3N.sub.4 ceramic,
from hard metal, such as G20, or from cermet.
19. The radial piston pump as claimed in claim 14, wherein the
running roller (8) consists of sintered tool steel, such as ASP23,
or of an alloyed nitriding steel, and in that the piston footplate
(18) has inserts (30) made from ceramic, such as Si.sub.3N.sub.4
ceramic, from hard metal, such as G20, from cermet or from a cast
carbide material, such as SoGGH.
20. The radial piston pump as claimed in claim 14, wherein the
alloyed nitriding steel contains C and/or Cr and/or V and/or Mo, is
gas-nitrided and does not have a compound layer in the region of
contact with the piston footplate (18).
21. The radial piston pump as claimed in claim 14, wherein the
running roller (8), on its circumferential surface (10, 12), has at
least one insert (32) made from the respective wear-resistant
material.
22. The radial piston pump as claimed in claim 14, wherein the
running roller (8), on its circumferential surface (12), has at
least one transverse groove (36) extending transversely to the
direction of movement.
23. The radial piston pump as claimed in claim 14, wherein the
piston footplate (18) has at least two grooves (50) which cross one
another on its surface (31) facing the running roller (8).
24. The radial piston pump as claimed in claim 14, 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.
25. The radial piston pump as claimed in claim 14, wherein the
piston consists of an Si.sub.3N.sub.4 ceramic or a ZrO.sub.2
ceramic.
26. The radial piston pump as claimed in claim 14, wherein the
piston (16) is produced by extrusion and has a porosity of less
than 5%, the surface being infiltrated with MOS.sub.2.
27. The radial piston pump as claimed in claim 14, wherein the
piston (16) is isostatically extruded and sintered.
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 and of the piston/cylinder 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, and/or at
least part of the running roller, in particular at least part of
the circumferential surface of the running roller, 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 and/or the piston consists of a ceramic
material. 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 a role, which results in a low mass inertia of the running
roller, the piston and the piston footplate.
[0006] The running roller and/or the piston footplate may be made
entirely from the wear-resistant material, or else these parts
consist, as hitherto, of case-hardened steel or heat-treated steel
but bear at least one insert made from the wear-resistant material.
The use of inserts brings the advantage of a modular structure,
i.e. a standardized running roller and a standardized piston
footplate can each be provided with inserts made from different
material, so that numerous pairing variants can be produced.
[0007] On account of the materials properties of the wear-resistant
materials used, the following sliding pairings are particularly
preferred:
[0008] The running roller consists of a heat-treated steel and has
inserts of hard metal, such as G20, GC37 or GC20, and the piston
foot disk consists of ceramic, such as Si.sub.3N.sub.4 ceramic, of
chilled cast iron, such as SoGSH, or of cermet, or it has inserts
made from the above-mentioned materials.
[0009] The running roller consists of a precision-cast material,
such as GX-210WCr13 H, and the piston foot disk consists of
ceramic, such as Si.sub.3N.sub.4 ceramic, of hard metal, such as
G20, or of cermet, or it has inserts made from the abovementioned
materials.
[0010] The running roller consists of a cast carbide material, such
as chilled cast iron SoGGH, and the piston foot disk consists of
ceramic, such as Si.sub.3N.sub.4 ceramic, of hard metal, such as
G20, or of cermet, or it has inserts made from the abovementioned
materials.
[0011] The running roller consists of sintered tool steel, such as
ASP23, or of an alloyed nitriding steel, and the piston foot disk
consists of ceramic, such as Si.sub.3N.sub.4 ceramic, of hard
metal, such as G20, of cermet or of a cast carbide material, such
as SoGGH, or it has inserts made from the abovementioned materials.
The alloyed nitriding steel may contain C and/or Cr and/or V and/or
Mo, is gas-nitrided and does not have a compound layer in the
region of contact with the piston footplate.
[0012] A further measure provides for the surface of the piston
footplate and/or of the running roller to have a surface roughness
R.sub.z of between 0.15 .mu.m and 2 .mu.m. More specifically, the
ceramic material has a surface roughness R.sub.z of between 0.15
.mu.m and 0.5 .mu.m, the hard metal has a surface roughness R.sub.z
of between 0.3 .mu.m and 1.0 .mu.m and the cast carbide material
has a surface roughness R.sub.z of between 0.5 .mu.m and 2.0
.mu.m.
[0013] It is particularly preferable for the running roller, on its
circumferential surface, to have at least one transverse groove
extending transversely to the direction of movement. In addition,
the piston footplate may also have at least two grooves which cross
one another on its surface facing the running roller. Fuel can
accumulate in these grooves, which each act as a build-up gap, and
this fuel, on account of the sliding movement between the
circumferential surface of the running roller and the piston
footplate, promotes the formation of a hydrodynamic sliding film,
which further reduces the wear to the sliding surfaces.
[0014] Not least, the piston preferably consists of an
Si.sub.3N.sub.4 ceramic or a ZrO.sub.2 ceramic, is produced by
extrusion and has a porosity of less than 5%, with the surface
being infiltrated with MOS.sub.2. In particular, the piston is
isostatically extruded and sintered. The result is a very smooth
surface with a low coefficient of friction, which is also of
benefit to the wear properties.
[0015] Exemplary embodiments of the invention are illustrated in
the drawings and explained in more detail in the description which
follows. In the drawings:
[0016] 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;
[0017] FIG. 2 shows a large cross-sectional illustration of a
piston and piston footplate in accordance with a further
embodiment.
[0018] FIG. 2a shows an enlarged excerpt from FIG. 2;
[0019] FIG. 2b shows a further enlarged excerpt from FIG. 2;
[0020] FIG. 3 shows a view of the piston footplate from FIG. 2 from
below;
[0021] FIG. 4 shows a cross-sectional illustration of a piston with
piston footplate and a drive shaft in accordance with a further
embodiment;
[0022] FIG. 5 shows a cross-sectional illustration of a drive shaft
in accordance with a further embodiment;
[0023] FIG. 6 shows a view on line VI-VI from FIG. 5;
[0024] FIG. 7 shows a view on line VII-VII from FIG. 6.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] If hard metal is used for the inserts 32 or for the running
roller 8 itself, a particularly wear-resistant hard metal with a
Vickers hardness of at least HV 1100 and a fracture toughness
K.sub.IC>=10 MPa/m.sup.3/2 with binder contents of 12 to 20% is
suitable, particularly preferably G20, GC37 or GC20. In particular
hard metals which have low adhesion coefficients are used here. A
suitable precision-cast material is formed, for example, by
GX-210WCr13 H, 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. 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.
[0033] 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. 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. SoGGH 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
[0034] 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 y 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.
[0035] 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 a 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.
[0036] 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 P 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.
[0037] 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.
* * * * *