U.S. patent application number 13/196017 was filed with the patent office on 2012-02-02 for hydraulic backlash compensating element.
This patent application is currently assigned to SCHAEFFLER TECHNOLOGIES GMBH & CO. KG. Invention is credited to Markus FISCHER, Rainer FUHRMANN, Marco KOWALSKI.
Application Number | 20120024249 13/196017 |
Document ID | / |
Family ID | 45470997 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120024249 |
Kind Code |
A1 |
FUHRMANN; Rainer ; et
al. |
February 2, 2012 |
HYDRAULIC BACKLASH COMPENSATING ELEMENT
Abstract
A hydraulic backlash compensating element for an internal
combustion engine, which has a housing in which a pressure-actuated
piston is mounted The piston has a check valve via which oil can
flow into the housing, and the check valve has a valve seat and a
valve element arranged movably therein. The valve element is a
hollow ball.
Inventors: |
FUHRMANN; Rainer;
(WAISCHENFELD, DE) ; KOWALSKI; Marco;
(HERZOGENAURACH, DE) ; FISCHER; Markus; (HESSDORF,
DE) |
Assignee: |
SCHAEFFLER TECHNOLOGIES GMBH &
CO. KG
|
Family ID: |
45470997 |
Appl. No.: |
13/196017 |
Filed: |
August 2, 2011 |
Current U.S.
Class: |
123/90.57 |
Current CPC
Class: |
F01L 1/2405 20130101;
F01L 2820/01 20130101; F16H 2007/0859 20130101; F01L 1/024
20130101; F01L 2303/00 20200501; F16H 2007/0806 20130101; F16H
7/0848 20130101; F01L 1/24 20130101; F01L 2250/04 20130101; F01L
2301/00 20200501; F01L 2250/02 20130101 |
Class at
Publication: |
123/90.57 |
International
Class: |
F01L 1/14 20060101
F01L001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2010 |
DE |
10 2010 033 091.4 |
Claims
1-8. (canceled)
9. A hydraulic backlash compensating element for an internal
combustion engine, comprising: an elongated housing having a bore
therein; a pressure-actuated piston, which is mounted in the bore
of the housing; and a check valve mounted at one end of the housing
to allow oil to flow into the housing, the check valve having a
valve seat and a hollow ball arranged movably within the check
valve.
10. The hydraulic backlash compensating element according to claim
9, wherein the hollow ball is produced from a sintered inorganic
material.
11. The hydraulic backlash compensating element according to claim
9, wherein the hollow ball has a filling.
12. The hydraulic backlash compensating element according to claim
11, wherein the filling comprising a gas, gel or colloid.
13. The hydraulic backlash compensating element according to claim
11, wherein the filling is composed of solids.
14. The hydraulic backlash compensating element according to claim
13, wherein the solids are sand or powder.
15. The hydraulic backlash compensating element according to claim
11, wherein the filling comprises at least one liquid.
16. The hydraulic backlash compensating element according to claim
9, wherein the hollow ball has a wall comprised of a porous
material.
17. The hydraulic backlash compensating element according to claim
9, wherein the hollow ball has a wall comprised of layers of
different materials.
18. A check valve for hydraulic backlash compensating element for
an internal combustion engine which has an elongated housing with a
bore therein and a pressure-actuated piston mounted in the bore of
the housing, comprising: a housing; a valve seat; and a hollow
ball, the valve seat and the hollow ball being arranged movably
within the housing.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of DE 2010 033 091.4
filed Aug. 2, 2010, which is incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to a hydraulic backlash
compensating element for an internal combustion engine.
BACKGROUND OF THE INVENTION
[0003] A hydraulic backlash compensating element of the
abovementioned type is known from the general prior art. The
hydraulic backlash compensating element has an oil-filled
piston/cylinder unit, a check valve and a spring. Hydraulic
backlash compensating elements are encountered in valves, support
elements or tensioning elements for tensioning a traction means in
a traction drive of an internal combustion engine, for example.
[0004] Inside a housing there is a piston with an integrated check
valve. The two elements can be moved relative to one another, form
a defined leakage gap at the contact surface and are pushed apart
by an internal spring. While the piston enters the housing under
the action of an external force, a high pressure arises in the
oil-filled pressure chamber formed by the housing and the piston
when the check valve is closed. A small quantity of oil is
discharged to the surroundings through the very narrow leakage gap.
When the external force acting on the piston weakens, the internal
spring pushes the hydraulic element apart. This gives rise to a
differential pressure which opens the check valve, and the extra
quantity of oil required for the compensating process flows in. The
check valve has a valve element which interacts with a valve seat.
In general, a valve spring is provided in the check valve, pressing
on the valve element in the direction of the valve seat in order in
this way to close an inlet duct. In order to obtain effective
damping in the hydraulic backlash compensating element, it is
important that the check valve should open and close precisely. The
opening and closing times and the speed of response of the check
valve depend, inter alia, on the mass of the valve element. With
increasingly dynamic processes in the internal combustion engine,
various malfunctions occur in conventional check valves having
steel balls as valve elements, e.g. noise, bouncing of the valve
element, inadequate closure and wear on the valve element and the
valve seat.
OBJECT OF THE INVENTION
[0005] It is therefore the underlying object of the invention to
specify a hydraulic backlash compensating element which has a check
valve that avoids the above-mentioned disadvantages.
SUMMARY OF THE INVENTION
[0006] According to the invention, which relates to a hydraulic
backlash compensating element for an internal combustion engine,
which comprises a housing that has an opening and a
pressure-actuated piston which is mounted in the opening of the
housing that has a check valve which can allow oil to flow into the
housing and has a valve seat and a valve element arranged movably
within therein, the object is achieved by virtue of the fact that
the valve element of the check valve is a hollow ball. The
particular advantage here is that a hollow ball is lighter than a
ball made of solid material. Owing to the lower mass, there is an
improvement in the dynamic response of the valve element, leading
to improvements in the response times of the check valve of the
hydraulic backlash compensating element. Another advantage is that
the force with which the valve element strikes against the valve
seat decreases with the weight of the valve element. As a result,
the wear on the valve seat and on the valve element is reduced.
[0007] As a specific embodiment of the invention, it is proposed
that the hollow ball be produced from a sintered inorganic
material. In general, the valve elements used in hydraulic backlash
compensating elements are solid steel balls having a diameter of
2-3 mm. To enable a robust hollow ball of such a size to be
produced, a special manufacturing process is required. This process
has been developed only recently by IFAM (Fraunhofer--Institut fur
Fertigungstechnik und Angewandte Materialforschung) and hollomet
GmbH, see also WO 2001/54846 A2. Expanded polystyrene balls are
used as the starting material. In a fluidized bed process, an air
stream blows the balls upwards and keeps them suspended while a
suspension of metal powder and binder is sprayed onto them from
above. Once the metal layer is thick enough, a heat treatment is
carried out: in a first step, all the organic constituents, the
polystyrene and the binder vaporize. The residual materials are
gaseous and escape through the pores in the metal layer. What
remains is a fragile metal ball. This is sintered at just below the
melting temperature. During this process, the metal powder granules
combine and the shell becomes hard and impermeable. The ball is now
sufficiently robust to be ground in a grinding machine. The wall
thickness can be set to thicknesses of between a few tenths of a
millimeter and one millimeter. A hollow ball produced in the manner
described has a low inertia, on the one hand, and, given the
appropriate wall thickness, also has the required robustness, on
the other. A hollow ball produced by this process is therefore
eminently suitable as a valve element in a check valve subjected to
dynamic loading in a hydraulic backlash compensating element.
[0008] According to a preferred development of the invention, it is
proposed that the hollow ball have a filling. A partially filled
hollow ball makes it possible to optimize the noise behavior of the
valve since the noises associated with the impact of the valve
element in the valve seat are attenuated. The rebounding of the
valve element during closure onto the valve seat is likewise
reduced. As a result, there is an improvement in the closing
behavior and hence also in the response time of the valve. The
filling can be composed of various materials. Gases, gels or
colloids can be used as a filling, for example, depending on the
application. Solids, sand, powder or even liquids are likewise
conceivable, and the liquids in turn may differ in their
viscosity.
[0009] According to another embodiment of the invention, it is
envisaged that the wall of the hollow ball be composed of layers of
different materials and/or that the wall be composed of a porous
material. With surface layers of different hardness, it is possible
to reduce both the wear on the valve element and the wear on the
valve seat. A wall of porous material, on the other hand, can
optimize the rebound behavior. Another variant envisages combining
a layer of porous material with a hardened layer. It is likewise
conceivable to use a harder substrate material, which is provided
with a rubber coating in order to protect the valve seat and the
valve element from wear.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Illustrative embodiments of the invention are depicted in
the figures, which are described in detail below, although the
invention is not restricted to these illustrative embodiments. In
the drawing:
[0011] FIG. 1 shows a hydraulic backlash compensating element
embodied as a hydraulic belt tensioner,
[0012] FIG. 2 shows a hydraulic backlash compensating element
embodied as a hydraulic chain tensioner,
[0013] FIG. 3 shows a hydraulic backlash compensating element
embodied as a support element,
[0014] FIG. 4 shows a check valve in cross section,
[0015] FIG. 5 shows a valve element as a hollow ball,
[0016] FIG. 6 shows a hollow ball with filling material, and
[0017] FIG. 7 shows a hollow ball, the wall of which is composed of
layers of different materials.
DETAILED DESCRIPTION OF THE DRAWINGS
[0018] Various embodiments of hydraulic backlash compensating
elements are depicted in FIGS. 1 to 3. Since the construction of
all three embodiments is virtually identical, the description of
the figures will be given by way of example for FIG. 2, which shows
a hydraulic backlash compensating element 1 designed as a hydraulic
chain tensioner. Inside a housing 2 there is a piston 3 with an
integrated check valve 4. The piston 3 is arranged within the
housing 2 in a manner which allows longitudinal movement, and the
two elements are pushed apart by an internal spring 6. A defined
leakage gap 10 is formed between the outer surface of the piston 3
and the inner surface of the housing 2. While the piston 3 enters
the housing 2 under the action of an external force, e.g. that of a
traction means or a cam (not shown here), a high pressure arises in
a pressure chamber 12 enclosed by the housing and the piston when
the check valve 4 is closed. A small quantity of oil passes into
the engine compartment through the very narrow leakage gap 10. When
the external force acting on the piston 3 weakens, the internal
spring 6 pushes the backlash compensating element 1 apart. This
gives rise to a differential pressure which opens the check valve
4. The extra quantity of oil required for the compensating process
can flow in via an oil feed opening 13 arranged in the housing
2.
[0019] The check valve 4 has a valve element 7 which interacts with
a valve seat 5. In general, a valve spring 11 is provided in the
check valve 4. This pushes the valve element 7 in the direction of
the valve seat 5 and thus closes the oil feed opening 13 as the
differential pressure falls. In order to obtain effective damping
in the hydraulic backlash compensating element 1, it is important
that the check valve 4 should open and close precisely. The opening
and closing times and the speed of response of the check valve 4
depend on the mass of the valve element 4. The lighter the valve
element 7, the more rapid is the response of the check valve 4. For
this reason, the valve element 7 is embodied as a hollow ball in
order to reduce the mass.
[0020] FIG. 4 shows a detail view of the check valve 4 in the
closed state when the valve spring 11 is pressing the valve element
7 into the valve seat 5. FIG. 5 shows the valve element 7 as a
hollow ball in cross section. The wall thickness 9 of the hollow
ball can vary, depending on requirements. FIGS. 6 and 7 show
further possible embodiments of the valve element 7 for achieving
optimum closing and opening behavior of the check valve 4 of the
hydraulic backlash compensating element 1. FIG. 6 shows a valve
element 7 as a filled hollow ball. The filling 8 makes it possible
to optimize the noise behavior of the check valve 4 since the
noises associated with the impact of the valve element 7 in the
valve seat 5 are attenuated. The rebounding of the valve element 7
during closure onto the valve scat 5 is likewise reduced. As a
result, there is an improvement in the closing behavior and hence
also in the response time of the check valve 4. FIG. 7 shows a
valve element 7 embodied as a hollow ball, the wall 9 of which is
composed of layers of different materials. With surface layers of
different hardness, it is possible to reduce both the wear on the
valve element 7 and the wear on the valve seat 5.
LIST OF REFERENCE SIGNS
[0021] 1 Hydraulic Backlash Compensating Element [0022] 2 Housing
[0023] 3 Piston [0024] 4 Check Valve [0025] 5 Valve Seat [0026] 6
Spring [0027] 7 Valve Element [0028] 8 Filling [0029] 9 Wall [0030]
10 Leakage Gap [0031] 11 Valve Spring [0032] 12 Pressure Chamber
[0033] 13 Oil Feed Opening
* * * * *