U.S. patent application number 10/771574 was filed with the patent office on 2004-08-12 for high pressure feed pump.
This patent application is currently assigned to CRT Common Rail Technologies AG. Invention is credited to Spinnler, Fritz.
Application Number | 20040156733 10/771574 |
Document ID | / |
Family ID | 4565497 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040156733 |
Kind Code |
A1 |
Spinnler, Fritz |
August 12, 2004 |
High pressure feed pump
Abstract
A high pressure feed pump which includes a cylinder 12 which has
a central bore which mounts a delivery piston 14 for reciprocation.
The delivery piston is reciprocated by a rotating drive shaft 28
which has an eccentric journal 36 formed thereon, and a rolling
ring 40 is rotatably mounted on the eccentric journal. A plate-like
spring element 62 is positioned between the front end of the
delivery piston and the rolling ring. Also, either the front end of
the delivery piston or the side of the spring element which faces
the delivery piston, is a concave configuration, so that at maximum
pressure loading, the spring element is deformed into the concave
region.
Inventors: |
Spinnler, Fritz; (Mellingen,
CH) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
CRT Common Rail Technologies
AG
|
Family ID: |
4565497 |
Appl. No.: |
10/771574 |
Filed: |
February 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10771574 |
Feb 4, 2004 |
|
|
|
PCT/CH02/00374 |
Jul 9, 2002 |
|
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Current U.S.
Class: |
417/470 |
Current CPC
Class: |
F04B 1/0408 20130101;
F04B 1/0426 20130101; F04B 1/0439 20130101; F04B 1/0413
20130101 |
Class at
Publication: |
417/470 |
International
Class: |
F04B 019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2001 |
CH |
2001 1460/01 |
Claims
1. A high pressure feed pump comprising a high pressure cylinder
having a central bore, a delivery piston mounted for reciprocation
within the central bore of the cylinder, a drive shaft for driving
the delivery piston and which includes an eccentric journal formed
thereon, and a rolling ring rotatably mounted about said eccentric
journal, and with said rolling ring having a cambered
circumferential surface, and a plate-like spring element positioned
between a front end of the delivery piston and the rolling ring so
that the spring element rests firstly on the circumferential
surface of the rolling ring via a contact surface, and secondly on
the front end of the delivery piston via an annular surface.
2. The high pressure feed pump of claim 1 wherein the front end of
the delivery piston is of concave configuration.
3. The high pressure feed pump of claim 1 wherein the side of the
spring element which faces the delivery piston is of concave
configuration.
4. The high pressure feed pump of claim 1 wherein the front end of
the delivery piston includes a radial extension.
5. The high pressure feed pump of claim 4 wherein the extension
comprises an adapter which is moveably mounted to the remainder of
the piston.
6. The high pressure feed pump of claim 1 wherein the spring
element is formed by the base of a bucket shaped tappet, with the
bucket shaped tappet having a circumferential wall which is mounted
so as to be guided for movement in the direction of movement of the
delivery piston.
7. The high pressure feed pump of claim 1 wherein one of (1) the
front end of the delivery piston and (2) the side of the spring
element which faces the delivery piston, is of concave
configuration, and wherein at maximum pressure loading, the region
of the spring element which lies opposite said contact surface lies
substantially flat against the front end of the delivery
piston.
8. A high pressure feed pump comprising a main housing mounting a
drive shaft for rotation about a rotational axis, with said main
housing including a chamber which extends radially from said
rotational axis, a high pressure cylinder mounted to said main
housing, with the high pressure cylinder defining a central bore
which is aligned with said radially extending chamber of said main
housing and which is perpendicular to said rotational axis, a
delivery piston mounted for reciprocation within said bore of said
cylinder and defining a front end which faces toward said drive
shaft, an eccentric journal formed on said drive shaft at a
location aligned with the front end of said delivery piston, a
spring biasing member for biasing the delivery piston in a
direction toward said drive shaft, a plate-like spring element
positioned between the front end of the delivery piston and the
eccentric journal so that the spring element rests firstly on the
eccentric journal and secondly on the front end of the delivery
piston, and such that upon rotation of the drive shaft about said
rotational axis the delivery piston is reciprocated in the bore of
said high pressure cylinder, and said spring element being formed
by the base of a bucket shaped tappet, with the bucket shaped
tappet having an outer wall which is mounted within the chamber of
the main housing for movement in a direction parallel to the
reciprocating movement of the delivery piston.
9. The high pressure feed pump of claim 8 wherein one of (1) the
front end of the delivery piston and (2) the side of the spring
element which faces the delivery piston, is of concave
configuration, and such that upon maximum loading the spring
element is deformed into the concave configuration.
10. The high pressure pump of claim 9 further comprising a valve
housing which includes a delivery chamber which communicates with
the end of the delivery piston opposite said front end, and an
inlet valve and an outlet valve both communicating with the
delivery chamber.
11. The high pressure pump of claim 10 wherein the drive shaft
further comprises a rolling ring rotatably mounted about said
eccentric journal and with said rolling ring having a cambered
circumferential surface.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation of international
application PCT/CH02/00374, filed 9 Jul., 2002, and which
designates the U.S. The disclosure of the referenced application is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a high pressure feed pump
of the type which operates according to the reciprocating piston
principle. More particularly, a pump of this type may be used to
produce the injection pressure in fuel injection systems, for
example common rail systems, for internal combustion engines. A
high pressure feed pump of the general type is disclosed in EP-A-1
058 001 and corresponding U.S. Pat. No. 6,205,980.
[0003] High pressure feed pumps of the described type have a high
pressure cylinder or plunger cylinder and a cylindrical delivery
piston or plunger piston which can be reciprocated therein, the
volume of the delivery chamber within the high pressure cylinder
being varied by the reciprocating movement of the plunger piston.
During a filling stroke of the plunger piston, it is possible to
connect the delivery chamber to a reservoir chamber for a delivery
medium via a filling valve, in order to fill the delivery chamber
whose reciprocating volume is increasing with the delivery medium.
During a subsequent delivery stroke with the filling valve closed,
the pressure rises in the delivery chamber until a pressure valve
opens and as a result connects the delivery chamber to a high
pressure chamber, for example the common rail.
[0004] The plunger piston is driven by an eccentric drive which
comprises an eccentric which is mounted on an eccentric shaft and
on which a rolling ring is rotatably mounted. The latter has a
cambered circumferential surface to reduce its moment of inertia.
During the rotation of the eccentric, the delivery piston, which is
pretensioned in the direction toward the eccentric shaft, rests on
the rolling ring with a plate-like extension which is provided at
that end of said delivery piston. During operation, the rolling
ring rotates to and fro and changes its direction of rotation twice
per revolution of the eccentric shaft. The design and function of
the high pressure pump is further described in EP-A-1 058 001 and
corresponding U.S. Pat. No. 6,205,980, the disclosures of which are
expressly incorporated herein by this reference.
[0005] In high pressure feed pumps of the above-mentioned type, in
particular when they are used for diesel injection systems, the
material loads are high in those parts which come into contact with
one another between the rolling ring and the delivery piston. As a
result, either the delivery pressures which can be achieved with
such pumps are limited, or the relevant elements must be designed
with large dimensions.
[0006] It is therefore an object of the present invention to
provide a high pressure delivery pump which overcomes the
abovementioned problems.
SUMMARY OF THE INVENTION
[0007] The above and other objects and advantages of the present
invention are achieved by the provision of a high pressure feed
pump which includes a plate-like spring element positioned between
the front end of the delivery piston and the rolling ring. The
rolling ring has a cambered circumferential surface, and the spring
element rests firstly on the circumferential surface of the rolling
ring via a contact surface, and secondly on the front end of the
delivery piston via an annular surface.
[0008] By this construction, the Hertzian surface stress between
the rolling ring and the delivery piston (plunger) is considerably
reduced compared with known high pressure feed pumps. This is
because load dependent adaptation to the camber of the rolling ring
takes place as a result of the plate-like spring element. The
contact surface between the rolling ring and the spring element
which is moved by the delivery piston also becomes greater as the
load becomes greater, which keeps the Hertzian surface stress
within acceptable limits, both between the rolling ring and the
spring element and also between the latter and the delivery piston,
even at very high delivery pressures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention will be explained in greater detail using
embodiments shown in the drawing, in which, purely
diagrammatically:
[0010] FIG. 1 shows a transverse section through a high pressure
feed pump according to the invention along the section line I-I of
FIG. 2;
[0011] FIG. 2 shows the high pressure feed pump shown in FIG. 1 in
a longitudinal section along the line II-II of FIG. 1;
[0012] FIG. 3 shows, partially in section, part of the high
pressure feed pump shown in FIGS. 1 and 2 having a delivery piston
which is of concave shape at the front end and rests on a bucket
shaped tappet which at the other end interacts with a rolling ring
of a drive shaft;
[0013] FIG. 4 shows, in the same representation as FIG. 3, a
further embodiment of the high pressure feed pump according to the
invention having an adapter head which is movably mounted on a
shaft of the delivery piston;
[0014] FIG. 5 shows a section along the line V-V of the embodiment
shown in FIG. 4; and
[0015] FIG. 6 shows, in the same representation as FIG. 3, a
further embodiment, in which the front end of the delivery piston
is of planar design and the bucket shaped tappet has a concave
recess.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] FIGS. 1 and 2 show a transverse section and a longitudinal
section through a high pressure feed pump having a main housing 10,
which has a radial chamber into which a high pressure cylinder 12
(also called a plunger cylinder) is positioned. A delivery piston
14 (also called a plunger piston) can move to and fro in the
direction of the longitudinal axis 14'.
[0017] The high pressure cylinder 12 is clamped with a flange-like
extension between the main housing 10 and a valve housing 16. The
valve housing 16 is joined to the housing 10 by means of threaded
bolts 17. An inlet valve 18 and an outlet valve 20 are provided in
the valve housing 16. The inlet valve 18 opens and closes a passage
22 to a storage container for the medium to be delivered, and the
outlet valve 20 opens and closes a passage 24 to a high pressure
container. In the case of a high pressure injection system for
internal combustion engines, fuel such as diesel or gasoline is
situated in the storage container, and the high pressure container
is, for example, a common rail.
[0018] Furthermore, an eccentric drive 26 for driving the delivery
piston 14 is arranged in the housing 10 of the high pressure feed
pump. The eccentric drive 26 has a drive shaft 28 which is
continuously driven in the direction of the arrow and is mounted in
a generally known manner in the housing 10 which includes a cover
32 which closes the latter. Bearings (not shown) may be provided
such that the drive shaft 28 can freely rotate about a rotational
axis 30.
[0019] Between the bearing points 34, 34', the drive shaft 28 bears
an eccentric journal 36 which is arranged eccentrically with regard
to the rotational axis 30 of the drive shaft 28 and whose center
axis 38 runs parallel to the rotational axis 30. A rolling ring 40
is mounted on the eccentric journal 36 in a rotatable manner with
respect to the eccentric journal 36. The radially outer
circumferential surface 42 of the rolling ring 40 is cambered, that
is to say is of convex design, as best seen in FIG. 2.
[0020] A through bore 44, in the shape of a circular cylinder, is
formed in the high pressure cylinder 12, and the bore 44 is coaxial
with the axis 14', which preferably extends perpendicular to the
rotational axis 30 of the draft shaft. The delivery piston 14 is
displaceably guided in the bore with a sliding seal. Its end region
facing the drive shaft 28 engages in a bucket shaped tappet 46, on
whose base 48 it rests with the front end 50 of a mushroom shaped
or plate shaped extension 52. The base 48 of the bucket shaped
tappet 46 sits on the rolling ring 40 at the other side. The
reference numeral 54 denotes the point of contact or contact area
between the rolling ring 40 and the base 48 of the bucket shaped
tappet 46. The delivery piston 14 is pretensioned in the direction
toward the rolling ring 40 by means of a compression spring 56
which is supported at one end on the high pressure cylinder 12 and
at the other end on the extension 52.
[0021] The outer circumferential wall 58 of the bucket shaped
tappet 46 is guided in a sliding manner in a radial chamber formed
in the housing 10 for sliding movement in the longitudinal
direction and hence in the direction of movement of the delivery
piston 14. The transverse forces which act on the bucket shaped
tappet 46 from the drive shaft 28 and the rolling ring 40 are
absorbed by the bucket shaped tappet 46 and are not transmitted to
the delivery piston 14, or only to a very small degree.
[0022] In order to compress and deliver the delivery medium, the
delivery piston 14 is reciprocated up and down by the eccentric
drive 26 and the compression spring 56. When the delivery piston 14
moves downward during a filling stroke, the delivery chamber 60 is
filled with the delivery medium via the inlet valve 18. When the
delivery piston 14 is moved in the upward direction during the
following delivery stroke, the pressure in the delivery chamber 60
rises with the inlet valve 18 closed, until the outlet valve 20
opens and as a result connects the delivery chamber 60 to the high
pressure container (e.g. a common rail). In the process, the
delivery medium is delivered into the high pressure container.
[0023] In a manner enlarged with regard to FIGS. 1 and 2, FIG. 3
shows the delivery piston 14, the compression spring 56, the bucket
shaped tappet 46, the rolling ring 40 and part of the drive shaft
28, which can be driven in the direction of the arrow, having the
eccentric journal 36.
[0024] The bucket shaped tappet 46 is preferably made from hardened
roller bearing steel. The plate shaped base 48 of the bucket shaped
tappet 46, which is flat in the unloaded state, has spring
properties and serves as a spring element 62 in its interaction on
one side with the cambered circumferential surface 42 of the
rolling ring 40 and on the other side with the concavely designed
front end 50 of the delivery piston 14. The depression 64 in the
end of the delivery piston 14 can be shaped, for example, as a
spherical cap or part of the circumferential surface of a torus.
Around the depression 64, the front end 50 of the delivery piston
14 has a flat annular surface 66, with which it rests on the base
48 in the unloaded or lightly loaded state and which can have the
shape of a circular ring, oval or other shape depending on the
shape of the depression 64.
[0025] Preferably, the longitudinal axis 14' of the delivery piston
14 should run centrally with respect to the depression 64 or
annular surface 66 and with respect to the bucket shaped tappet 46.
Furthermore, the axis 14' preferably runs in a plane extending at
right angles to the rotational axis 30 of the drive shaft 28, said
plane extending centrally through the contact area 54.
[0026] The base 48, acting as a spring element 62, of the bucket
shaped tappet 46 is deformed into the depression 64 as a function
of the loading of the delivery piston 14 in such a way that, when
the load becomes greater, firstly the contact area 54 between the
base 48 and the rolling ring 40 and secondly the area over which
the base 48 rests on the delivery piston 14 are enlarged. As a
result, the Hertzian surface stress in the relevant parts is kept
within limits which permits a long service life of the high
pressure feed pump. The base 48 is preferably dimensioned in such a
way that its entire area rests in the depression 64 on the delivery
piston 14 in the case of a specific load.
[0027] In the embodiment shown in FIGS. 4 and 5, only the delivery
piston 14 is different in comparison with the embodiment shown in
FIGS. 1 to 3. The functioning is the same as described further
above. There is therefore only a detailed description of the
delivery piston 14.
[0028] The delivery piston 14 shown in FIGS. 4 and 5 has a shaft
68, on whose end region, which is shaped like a hemisphere and
faces the rolling ring 40, sits an adapter head 70 of substantially
circular cylindrical shape. The front end 50, which interacts with
the base 48 of the bucket shaped tappet 46, of the head adapter 70
is of the same design as that in the case of the delivery piston 14
according to FIG. 3. A recess 72 of the adapter head 70 for
accommodating the end region of this side of the shaft 68 is shaped
to be diametrically opposed to said end region and has a peripheral
groove 74 in a cylindrical outer part adjoining the hemispherical
surface.
[0029] The shaft 68 is correspondingly provided with a
circumferential groove 76. As best seen in FIG. 5, a rectilinear
through hole 78 runs through the adapter head 70, whose axis is
tangent to the circular center line of the toroidal chamber
delimited by the groove 74 and the circumferential groove 76. A
section of a securing element formed from spring steel wire 80
extends through the through hole 78, and a further section of said
securing element extends around the adapter head 70 in order to
fasten it. In this manner, the adapter head 70 is mounted on the
shaft 68 in the manner of a sphere with limited mobility. This
makes it possible for exclusively axial forces and no bending
forces to act on the delivery piston 14.
[0030] The compression spring 56 is supported on a flange ring 82
which engages around two half flanges 84 and is for its part
supported on the latter. A bead 86 of the half flanges 84 engages
in a circumferential groove of the shaft 68 and the half flanges 84
are attached in this way to the shaft 68 in the axial
direction.
[0031] The embodiment shown in FIG. 6 of the high pressure feed
pump according to the invention is very similar to that according
to FIG. 3, the front end 50 of the delivery piston 14 being of flat
design and the base 48 of the bucket shaped tappet 46 being of
concave shape as a result of a recess 64' on the side facing the
delivery piston 14. Here too, the delivery piston 14 rests in the
unloaded and lightly loaded state with an annular surface 66 on the
base 48, acting as a spring element 62, of the bucket shaped tappet
46. The method of operation is the same as described further above
in conjunction with the other embodiments.
[0032] In the embodiment shown in FIG. 6, the delivery piston 14
can be of the same design as shown in FIG. 3 or 4. The transition
between the annular surface 66 and the depression 64' is itself
preferably shaped in a manner corresponding to the spring
characteristic of the spring element 62, such that the area with
which the spring element rests on the delivery piston is
continuously enlarged as the load rises.
[0033] The depression 64' can be matched to the camber of the
rolling ring 40 in such a way that, when at least approximately the
whole area of the spring element 62 rests in the depression 64',
the spring element 62 also rests on the rolling ring 40 across at
least approximately the whole width of the latter.
[0034] Many modifications and other embodiments of the inventions
set forth herein will come to mind to one skilled in the art to
which these inventions pertain having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. Therefore, it is to be understood that the inventions are
not to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
* * * * *