U.S. patent application number 13/519481 was filed with the patent office on 2013-08-08 for piston pump having an inlet valve.
This patent application is currently assigned to Robert Bosch GmbH. The applicant listed for this patent is Heiko Jahn, Martin Juretko, Marc Zimmermann. Invention is credited to Heiko Jahn, Martin Juretko, Marc Zimmermann.
Application Number | 20130202465 13/519481 |
Document ID | / |
Family ID | 43449187 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130202465 |
Kind Code |
A1 |
Jahn; Heiko ; et
al. |
August 8, 2013 |
Piston Pump having an Inlet Valve
Abstract
A piston pump includes a piston, a sealing element sealing the
piston radially with respect to a cylinder, and an inlet valve
arranged on the piston. The inlet valve includes a valve cage
holding a closing member. The sealing element is integrally
designed with the valve cage.
Inventors: |
Jahn; Heiko; (Tamm, DE)
; Zimmermann; Marc; (Sonthofen, DE) ; Juretko;
Martin; (Hildesheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jahn; Heiko
Zimmermann; Marc
Juretko; Martin |
Tamm
Sonthofen
Hildesheim |
|
DE
DE
DE |
|
|
Assignee: |
Robert Bosch GmbH
Stuttgart
DE
|
Family ID: |
43449187 |
Appl. No.: |
13/519481 |
Filed: |
November 3, 2010 |
PCT Filed: |
November 3, 2010 |
PCT NO: |
PCT/EP10/66723 |
371 Date: |
October 29, 2012 |
Current U.S.
Class: |
417/437 |
Current CPC
Class: |
F04B 1/0408 20130101;
B60T 8/4031 20130101; F04B 53/126 20130101; F04B 39/0016 20130101;
F04B 53/10 20130101 |
Class at
Publication: |
417/437 |
International
Class: |
F04B 53/10 20060101
F04B053/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2009 |
DE |
102009055330.4 |
Claims
1. A piston pump comprising: a piston; a sealing element configured
to seal the piston radially with respect to a cylinder; and an
inlet valve arranged on the piston, said inlet valve including a
valve cage holding a closing member, wherein the sealing element
and the valve cage are one piece.
2. The piston pump as claimed in claim 1, wherein the sealing
element and the valve cage are produced from plastic.
3. The piston pump as claimed in claim 1, wherein a spring support
for a return spring supporting the piston relative to the cylinder
is formed on the sealing element.
4. The piston pump as claimed in claim 3, wherein: the sealing
element includes a sealing lip resting against the cylinder, and
said sealing lip ends in an axially set-back manner relative to the
spring support on the side facing away from the return spring.
5. The piston pump as claimed in claim 1, wherein: the sealing
element includes an axial groove, and the axial groove is open
towards the high-pressure area of the piston/cylinder
arrangement.
6. The piston pump as claimed in claim 1, wherein the sealing
element is configured in a stepped manner on its side facing the
piston.
7. The piston pump as claimed in claim 1, wherein the sealing
element surrounds the piston.
8. The piston pump as claimed in claim 1, wherein the piston is
designed in two parts with a first part turned towards a drive and
a second part turned towards the sealing element.
9. The piston pump as claimed in claim 8, wherein: the first part
is a solid cylinder, and the second part is a hollow cylinder.
10. A vehicle brake system comprising: a piston pump including (i)
a piston, (ii) a sealing element configured to seal the piston
radially with respect to a cylinder, and (iii) an inlet valve
arranged on the piston, said inlet valve including a valve cage
holding a closing member, wherein the sealing element and the valve
cage are one piece.
Description
PRIOR ART
[0001] The invention relates to a piston pump comprising a piston,
a sealing element on the piston sealing radially with respect to a
cylinder, and an inlet valve arranged on the piston, said inlet
valve being designed with a valve cage holding a closing member. In
addition, the invention relates to a vehicle brake system
comprising a piston pump of this type.
[0002] In known vehicle brake systems, the "hydraulic power unit"
is a fixed component. It is used to meter the brake pressure and,
to this end, has a pump, which is generally a piston pump, in which
a piston is displaceable in a cylinder. The piston is displaced in
a two-cycle operation. In a first cycle, a fluid to be conveyed,
for example brake fluid, is sucked up through an inlet valve. In a
second cycle, the fluid is discharged through an outlet valve. The
piston is sealed with respect to the inner surface of the cylinder
by means of a sealing element and is also guided in the cylinder
during its stroke movement by said sealing element. A piston pump
of this type is known for example from DE 10 2005 017 131 A1.
[0003] The object of the invention is to create a vehicle brake
system comprising a piston pump, in which the seal between the
piston and the cylinder is designed so as to be permanently
reliable whilst, at the same time, creating an arrangement which is
particularly cost-effective on the whole.
DISCLOSURE OF THE INVENTION
[0004] In accordance with the invention, a piston pump comprising a
piston, a sealing element sealing the piston radially with respect
to a cylinder, and an inlet valve arranged on the piston is
created, said inlet valve being designed with a valve cage holding
a closing member. The sealing element and the valve cage are
designed in one piece.
[0005] With the solution according to the invention, the one-piece
component formed from the sealing element and valve cage of the
inlet valve can be produced in a more cost-effective manner
compared to two individual components. In addition however, the
solution according to the invention affords further surprising
advantages. In particular, the assembly of the sealing element is
also simplified considerably with this solution, because the
sealing element is additionally stabilized in terms of shape by
means of the valve cage. In addition, the valve cage can be used in
an automatic assembly device as a position recognition means for
the sealing element. Lastly, the one-piece component can be held
particularly easily on the respective piston by a respective return
spring and can thus be fastened to said piston in a very simple and
cost-effective manner. This will be explained in greater detail
hereinafter as a development of the solution according to the
invention.
[0006] In accordance with a first advantageous development of the
piston pump according to the invention, the sealing element and the
valve cage are produced from plastic.
[0007] Due to the selective choice of a plastic which is
sufficiently dimensionally stable for the valve cage and also
sufficiently resilient for the sealing element, it is possible to
produce the one-piece component according to the invention in only
a single manufacturing process.
[0008] In accordance with a second advantageous development of the
piston pump according to the invention, a spring support for a
return spring supporting the piston relative to the cylinder is
formed on the sealing element.
[0009] The spring support designed in such a way enables a
particularly space-saving arrangement of the return spring, wherein
said return spring may, at the same time, be selected to be
particularly long and large in diameter. The return spring can
therefore develop high restoring forces with a small installation
space.
[0010] In accordance with a third advantageous development of the
piston pump according to the invention, the sealing element has a
sealing lip resting against the cylinder, said sealing lip ending
in an axially set-back manner relative to the spring support on the
side facing away from the return spring.
[0011] The spring support axially set back in such a way compared
to the effective surface of the return spring prevents the
respective sealing lip from being damaged due to the applied return
spring and the restoring forces thereof.
[0012] In accordance with a fourth advantageous development of the
piston pump according to the invention, the sealing element is
designed with an axial groove, which is open towards the
high-pressure area of the piston/cylinder arrangement.
[0013] During operation of the piston pump, in the axial groove
open in such a way towards the high-pressure area of the
piston/cylinder arrangement, the pressure prevailing in the
high-pressure area may infiltrate the axial groove and thus expand
it. At the same time, the radially outer part of the sealing
element, that is to say the part which lies radially outwardly
beside the axial groove, is then pressed against the adjacent inner
wall of the cylinder. With increasing pressure in the high-pressure
area, a reinforcement of the support of the sealing element against
the cylinder also thus develops, and therefore an improved seal. At
the same time, the leakage behavior in the piston and also the
guidance of the piston in the cylinder are improved.
[0014] In accordance with a fifth advantageous development of the
piston pump according to the invention, the sealing element is
designed in a stepped manner on its side facing the piston.
[0015] The stepped design of the sealing element leads to a
comparatively large contact area between the piston and the sealing
element. This large contact area improves the fastening of the
sealing element. In particular, the sealing element can be fixed by
being pressed on against the axially extending flanks of the
step(s). At the same time, the sealing element is centered at these
flanks relative to the piston. The radially directed flanks of the
step(s) are used to support the sealing element with respect to the
piston, which is particularly advantageous when the piston is reset
by means of the above-mentioned return spring.
[0016] In accordance with a sixth advantageous development of the
piston pump according to the invention, the sealing element
surrounds the piston.
[0017] The sealing element surrounds a portion of the piston in
this manner in particular at a step, a groove or a phase of the
piston in such a way that the sealing element hooks behind the
piston in the axial direction by means of a pawl, which is
peripheral or peripheral over portions. A positive-fit connection
between the piston and sealing element is thus created, which can
be easily produced or pre-assembled, even in an automatic
manufacturing process, due to the above-mentioned slightly
resilient property of the material of the sealing element.
[0018] In accordance with a seventh advantageous development of the
piston pump according to the invention, the piston is designed in
two parts with a first part turned towards a drive and a second
part turned towards the sealing element.
[0019] The individual parts of the piston thus designed in two
parts can be assigned specific functions. The first part is thus
used to transfer the thrust generated at the drive to the second
part, which in turn ensures the flow of fluid, in particular brake
fluid, into the inlet valve. The high-pressure area inside the
cylinder is then defined by means of the sealing element and sealed
with respect to the low-pressure area. The second part pushes the
sealing element into the cylinder and is in turn pushed by the
first part. The piston is reset starting from the return spring by
transferring the restoring thrust forces via the sealing element
and the second part onto the first part. The individual parts can
be optimized in a simpler manner in view of the material selection
and possible production methods, as would be the case with a
one-part piston.
[0020] In accordance with an eighth advantageous development of the
piston pump according to the invention, the first part is designed
as a solid cylinder and the second part is designed as a hollow
cylinder.
[0021] The first part designed as a solid cylinder can be produced
in a very cost-effective manner and, in particular, can transfer
high thrust forces. It is advantageously produced from plastic, to
which reinforcing fibers are preferably added. The second part
designed as a hollow cylinder may advantageously already be formed
as a blank with a cylindrical hollow chamber. The second part is
preferably produced from metal and in particular is designed as a
sinter cast part or as a deep-drawn part. In a part of this type,
merely at least one radial opening is to be formed, through which
the fluid to be sucked up can then flow radially from the outside
in, in the direction of the inlet valve during operation of the
piston pump.
[0022] The above-mentioned object is furthermore also achieved by a
vehicle brake system comprising a piston pump of this type
according to the invention, wherein corresponding advantages are
achieved, as already described above for the piston pump.
[0023] An exemplary embodiment of the solution according to the
invention will be explained in greater detail hereinafter on the
basis of the accompanying schematic drawings, in which:
[0024] FIG. 1 shows a longitudinal section of a piston pump
according to the prior art,
[0025] FIG. 2 shows the detail II in FIG. 1 in an enlarged
scale,
[0026] FIG. 3 shows a longitudinal section of a first exemplary
embodiment of a piston pump according to the invention,
[0027] FIG. 4 shows the detail IV in FIG. 3 in an enlarged
scale,
[0028] FIG. 5 shows a longitudinal section of a second exemplary
embodiment of a piston pump according to the invention, and
[0029] FIG. 6 shows the detail VI in FIG. 5 in an enlarged
scale.
[0030] A piston pump 10 according to the prior art is illustrated
in FIGS. 1 and 2 and comprises, inter alia, a piston arrangement
12, which is formed from a cylinder 14 and a piston 16 mounted
displaceably therein. The piston arrangement 12 further comprises
an inlet valve 18 and an outlet valve 20. These valves 18 and 20
are provided so that, during its stroke movement in the cylinder
14, the piston 16 can suck a fluid through an inlet 22 into a
high-pressure chamber or high-pressure area 24 inside the cylinder
14 and can discharge this fluid again, under pressure, from the
high-pressure area 24 through an outlet 26. The fluid is a brake
fluid in the present case.
[0031] The piston 16 is biased resiliently in the axial direction
by means of a return spring 28 located in the high-pressure area
24. On the basis of FIG. 1, the return spring 28 is supported at
its left end against the end face of the cylinder 14 and presses at
its right end against a spring support 30. The spring support 30 is
coupled fixedly to the piston 16 so that the return spring 28
presses accordingly against the piston 16 via the spring support
30.
[0032] A sealing element 32 is also arranged between the piston 16
and the cylinder 14 and seals the high-pressure area 24 in the
cylinder 14. The sealing element 32 is annular and surrounds the
piston 16 at the outer surface thereof. The sealing element 32 is
held fixedly on this outer surface by means of a valve cage or
valve housing 34 of the inlet valve 18, said valve cage or valve
housing being slid over the piston 16. At the valve housing 34, the
spring support 30 is also shaped in the form of a shoulder. The
sealing element 32 retained in such a way lies radially inwardly
against the inner surface of the cylinder 14, so as to slide along
and seal said inner surface of the cylinder.
[0033] The valve housing 34 is designed in a beaker-shaped manner
as a cage, in the interior of which a screw-shaped return spring 36
is located and presses against a spherical closing member 38. The
closing member 38 thus lies (in the operating state illustrated in
FIGS. 1 and 2) against a valve seat 40, which is formed on the end
face of the piston 16. The closing member 38 is lifted from this
valve seat 40, against the force of the return spring 36, when the
piston 16 is withdrawn to the right from the cylinder 14, based on
FIG. 1. With this movement, the inlet valve 18 is thus opened and
fluid is sucked into the high-pressure area 24.
[0034] The sealing element 32 according to FIGS. 1 and 2 has a main
body 42, which is basically square in cross-section and on which a
sealing lip 44 facing the high-pressure area 24 is formed.
[0035] FIGS. 3 and 4 show a piston pump 10 according to the
invention. This piston pump likewise has a piston arrangement 12
comprising a cylinder 14 and a piston 16 displaceable therein.
Furthermore, an inlet valve 18 and an outlet valve 20 are likewise
provided. The piston 16 is biased resiliently by a return spring 28
located in a high-pressure area 24, said return spring pressing
against a spring support 46 according to the invention coupled
fixedly to the piston 16.
[0036] A sealing element 48 according to the invention is also
located between the piston 16 and the cylinder 14, said sealing
element being retained fixedly on the piston 16 and being able to
slide along the inner surface of the cylinder 14. This sealing
element 48 is formed in one piece with a valve housing 50 according
to the invention, in such a way that the spring support 46 and the
sealing element 48 are also designed in one piece. The one-piece
design of the spring support 46 and sealing element 48 enables an
axially very short, more compact design with a smaller dead space
volume. The sealing element 48 can additionally be biased by the
return spring 28. A radially very wide support surface is also
provided for the return spring 28 at the spring support 46.
[0037] As can be seen in FIG. 4, the sealing element 48 is designed
with an axial groove 52, which is open in the direction of the
high-pressure area 24. The pressurized fluid located in the
high-pressure area 24 accordingly also infiltrates this axial
groove 52. The two inner, mutually opposed side faces or flanks 54
and 56 of the axial groove 52 are pressed radially away from one
another by this fluid. In particular, the lip-shaped part or
portion 58 of the sealing element 48 located radially outwardly
from the axial groove 52 and which can also be referred to as a
sealing lip is pressed radially outwardly and therefore against the
inner surface of the cylinder 14. As the pressure increases in the
high-pressure area 24, this portion 58 of the sealing element 48
thus also rests more heavily against the cylinder 14, where it thus
provides an improved seal. In addition, the guidance of the piston
16 in the cylinder 14 is improved.
[0038] FIGS. 5 and 6 illustrate an exemplary embodiment of a
sealing element 48, in which the end of the lip-shaped portion 58
or the sealing lip of the sealing element 48 is set back axially
towards the side facing away from the return spring 28, relative to
the radially directed plane of the spring support 46. A distance
from the return spring 28 is thus also produced axially, so that
the return spring 28 cannot damage the lip-shaped portion 58. The
return spring 28 also presses the core of the sealing element 48
axially together, however, so that it is pressed radially
outwardly.
[0039] In both exemplary embodiments shown in FIGS. 3 to 6, the
piston 16 is formed in two parts from a first part 60 and a second
part 62. The first part 60 is a solid cylindrical, rod-shaped
structure, which is injection molded from plastic and is
specifically adapted to transfer axially directed shear forces from
an eccentric drive (not illustrated) to the second part 62 and thus
to the sealing element 48. The second part 62 is a hollow
cylindrical sinter cast part, which has a shoulder or a step 64 and
66 at each of its two ends. The step 64 encompasses the first part
60 radially outwardly at the end region thereof, wherein the first
part 60 is fixed non-positively in the interior of the step 64 by
means of a press fit. The step 66 is located adjacent to the
sealing element 48 and is surrounded thereby radially outwardly in
the axial direction. A portion 68 of the sealing element 48, which
forms the core thereof, rests radially outwardly against the step
66 and forms a press fit therewith. A further portion 70 of the
sealing element 48, which is located radially completely outwardly,
surrounds the step 66 of the second part 62 completely in the form
of a type of arm or sleeve. A plurality of pawls 72 is formed
peripherally on this portion 70, said pawls hooking behind the
radially outer region of the step 66 and thus producing a
positive-fit connection to the second part 62 in the axial
direction.
[0040] Furthermore, an annular chamber 74 widened in the radial
direction is created in the border area between the sealing element
48 and the valve cage or valve housing 34 thus formed in one piece.
This annular chamber 74 enables fluid to flow off temporarily, said
fluid passing through the gap formed between the valve seat 40 and
the closing member 38 when the inlet valve is opened. The annular
chamber 74 receives this fluid and thus reduces the pressure surges
which would otherwise occur. It thus acts in a damping manner in
terms of the pressure impulses produced. An undercut in the valve
housing 34 is not necessary for the annular chamber 74, but is
created merely by a stepped recess in the valve housing 34 in
cooperation with the adjacent second part 62 of the piston 16,
which is particularly favorable in terms of manufacture.
* * * * *