U.S. patent application number 11/569284 was filed with the patent office on 2007-07-26 for camshaft adjuster.
This patent application is currently assigned to SCHAEFFLER KG. Invention is credited to Udo Friedsmann, Mike Kohrs.
Application Number | 20070169730 11/569284 |
Document ID | / |
Family ID | 34966090 |
Filed Date | 2007-07-26 |
United States Patent
Application |
20070169730 |
Kind Code |
A1 |
Kohrs; Mike ; et
al. |
July 26, 2007 |
Camshaft adjuster
Abstract
A camshaft adjuster for relative angle adjustment of a camshaft
with respect to a driving crankshaft, having a hydraulically
operable adjustment apparatus with chambers into which and from
which a hydraulic fluid can be supplied and carried away
alternately for angle adjustment of the chamber-specific
pressure-medium channels, and having a control valve via which the
hydraulic fluid, which is supplied via a pump, can be supplied to
the pressure-medium channels and can be carried away from the
pressure-medium channels into a tank, with operating connections A
and B, which lead to the pressure-medium channels, a pressure
connection P which can be coupled to the pump, and an outlet
connection T which can be coupled to the tank being provided on the
valve body of the control valve, which operating connections A and
B can be selectively coupled to the pressure connection P or to the
outlet connection T, depending on the angle adjustment required,
via a valve piston which can be moved in a controlled manner via a
decoupled pulling or pushing magnet which is arranged externally
with respect to the camshaft adjuster, in which case the fluid
distribution area in the control valve (1, 20, 26, 34) is designed
in such a manner that the hydraulic fluid acts on surfaces of the
valve piston (4, 22, 28, 36) which point essentially in mutually
opposite directions, so that local forces (F.sub.p1, F.sub.p2),
which are essentially in opposite directions to one another, act on
the valve piston (4, 22, 28, 36).
Inventors: |
Kohrs; Mike; (Wilthen,
DE) ; Friedsmann; Udo; (Herzogenaurach, DE) |
Correspondence
Address: |
LUCAS & MERCANTI, LLP
475 PARK AVENUE SOUTH
15TH FLOOR
NEW YORK
NY
10016
US
|
Assignee: |
SCHAEFFLER KG
Industriestrasse 1-3
Herzogenaurach
DE
91074
|
Family ID: |
34966090 |
Appl. No.: |
11/569284 |
Filed: |
May 4, 2005 |
PCT Filed: |
May 4, 2005 |
PCT NO: |
PCT/EP05/04849 |
371 Date: |
November 17, 2006 |
Current U.S.
Class: |
123/90.17 ;
123/90.15 |
Current CPC
Class: |
F01L 1/34 20130101; F01L
2001/34426 20130101; F01L 1/3442 20130101 |
Class at
Publication: |
123/090.17 ;
123/090.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2004 |
DE |
10 2004 025 215.7 |
Claims
1. A camshaft adjuster for relative angle adjustment of a camshaft
with respect to a driving crankshaft, comprising: a hydraulically
operable adjustment apparatus with chambers into which and from
which a hydraulic fluid can be supplied and carried away
alternately for angle adjustment of the chamber-specific
pressure-medium channels, and having a control valve via which the
hydraulic fluid, which is supplied via a pump, can be supplied to
the pressure-medium channels and can be carried away from the
pressure-medium channels into a tank, with operating connections A
and B, which lead to the pressure-medium channels, a pressure
connection P which can be coupled to the pump, and an outlet
connection T which can be coupled to the tank being provided on the
valve body of the control valve, which operating connections A and
B can be selectively coupled to the pressure connection P or to the
outlet connection T, depending on the angle adjustment required,
via a valve piston which can be moved in a controlled manner via a
decoupled pulling or pushing magnet which is arranged externally
with respect to the camshaft adjuster, wherein the fluid
distribution area in the control valve is designed in such a manner
that the hydraulic fluid acts on surfaces of the valve piston which
point essentially in mutually opposite directions, so that local
forces (F.sub.p1, F.sub.p2), which are essentially in opposite
directions to one another, act on the valve piston.
2. The camshaft adjuster as claimed in claim 1, wherein the
mutually opposite forces (F.sub.p1, F.sub.p2) are essentially of
equal magnitude.
3. The camshaft adjuster as claimed in claim 1, wherein the
pressure connection P is at an angle, preferable at right angles,
to the valve axis and opens into an annular channel which is formed
between the valve piston and the valve body, can be connected to
the operating connection A as a function of position, and leads
into the hollow-cylindrical valve piston, which is closed at both
ends and whose cavity can be connected as a function of position to
the operating connection B, with pressure being applied to the end
cavity surfaces via the hydraulic fluid.
4. The camshaft adjuster as claimed in claim 3, wherein the two
operating connections A, B can be connected as a function of
position to the outlet connection T, which is at right angles to
the valve longitudinal axis, via an annular channel which is formed
between the valve piston and the valve body.
5. The camshaft adjuster as claimed in claim 3, wherein the
pressure connection P, the outlet connection T and the operating
connections A and B are arranged running at right angles to the
valve longitudinal axis and in the sequence B-T-A-P, or
A-T-B-P.
6. The camshaft adjuster as claimed in claim 1, wherein the
pressure connection P is at an angle, preferably at right angles,
to the valve longitudinal axis and opens into an annular space
which is formed between the valve piston and the valve body and can
be connected as a function of position to the operating connection
A or B, in which case the operating connections A, B can be
connected as a function of position via connecting openings to the
cavity in the hollow-cylindrical valve piston, and the cavity leads
to the outlet connection T.
7. The camshaft adjuster as claimed in claim 6, wherein the
pressure connection P and the operating connections A and B are
arranged such that they run at right angles to the valve
longitudinal axis and in the sequence A-P-B.
8. The camshaft adjuster as claimed in claim 1, wherein the
pressure connection P is on the valve longitudinal axis and opens
via guide channels into an annular space which is formed between
the valve piston and the valve body and can be connected as a
function of position to the operating connection A or B, in which
case the operating connections A, B can be connected as a function
of position via connecting openings to the cavity in the
hollow-cylindrical valve piston and the cavity leads to the outlet
connection T.
9. The camshaft adjuster as claimed in claim 1, wherein the
pressure connection P runs aligned with the valve longitudinal axis
and opens into the hollow-cylindrical valve piston on which radial
openings are provided through which the hydraulic fluid enters the
annular space which is formed between the valve piston and the
valve body and is bounded by the end face of the valve piston.
10. The camshaft adjuster as claimed in claim 1, wherein the
control valve is integrated centrally in the adjustment apparatus,
and rotates with it.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a camshaft adjuster for relative
angle adjustment of a camshaft with respect to a driving
crankshaft, having a hydraulically operable adjustment apparatus
with chambers into which and from which a hydraulic fluid can be
supplied and carried away alternately for angle adjustment of the
chamber-specific pressure-medium channels, and having a control
valve via which the hydraulic fluid, which is supplied via a pump,
can be supplied to the pressure-medium channels and can be carried
away from the pressure-medium channels into a tank, with operating
connections A and B, which lead to the pressure-medium channels, a
pressure connection P which can be coupled to the pump, and an
outlet connection T which can be coupled to the tank being provided
on the valve body of the control valve, which operating connections
A and B can be selectively coupled to the pressure connection P or
to the outlet connection T, depending on the angle adjustment
required, via a valve piston which can be moved in a controlled
manner via a decoupled pulling or pushing magnet which is arranged
externally with respect to the camshaft adjuster.
BACKGROUND OF THE INVENTION
[0002] In known internal combustion engines, the camshaft by means
of which the valve movement of the inlet and outlet valves of the
internal combustion engine is controlled is movement-coupled to the
crankshaft of the machine via a control chain or a control belt,
that is to say the camshaft is driven via the crankshaft. In order
to allow the operating time of the inlet and/or outlet valves to be
adjusted as a function of the operating situation, so that the
valves open somewhat earlier or later in time with respect to the
respective operating cycle, camshaft adjusters are integrated, via
which the relative angle which the camshaft assumes with respect to
the crankshaft can be adjusted. This means that the two shafts can
be rotated somewhat relative to one another, with the consequence
that the operating time of the valves which are operated via the
camshaft is varied.
[0003] known camshaft adjusters are, for example, in the form of
vane cell adjusters and have a rotor, which is connected to the
camshaft such that they rotate together, and a stator, which is
coupled to the crankshaft via the control chain or the control
belt. Vanes which project radially outwards are provided on the
rotor and engage between stops which project radially inwards on
the stator, on the one hand limit the rotation movement and on the
other hand form chamber walls. The chambers are bounded by the
respective side of a rotor-side vane and by the sides of the
stator-side stops. In order to rotate the rotor with respect to the
stator and thus with respect to the angled setting, a hydraulic
fluid is now forced into or drawn out of these chambers--a
plurality of chamber pairs are in each case provided depending on
the number of vanes--with a control valve being used for this
purpose, generally a 4/3-way valve. Operating connections A and B
are provided on this valve and respectively lead to a chamber A and
a chamber B of a respective chamber pair. In the camshaft adjuster
embodiment under discussion, the control valve is itself in the
form of a central valve, that is to say it is inserted centrally,
in the middle, in the camshaft adjuster or in its rotor and is
connected to the camshaft, that is to say the control valve thus
rotates with the adjuster and the rotor.
[0004] A valve piston is integrated in the control valve itself and
moves axially, with its movement being controlled via a pulling or
pushing magnet which is positioned externally with respect to the
camshaft adjuster and, for example, is arranged on a motor or other
third object. In this embodiment, the magnet is thus not integrated
in the adjuster. Depending on the position of the valve piston, one
or the other of the operating connections A or B is now coupled to
the pressure connection P, so that hydraulic fluid is passed into
the associated chamber A or B, while the respective other chamber
is connected to the valve-side outlet connection, so that the fluid
located in the chamber to which no pressure is applied can be drawn
out towards the tank via the outlet connection. This allows the
rotor to be rotated hydraulically with respect to the stator. In
order to hold a rotation angle that has been set between the stops,
the valve piston can also virtually close both operating
connections A and B, and thus the associated chambers.
[0005] In known camshaft adjusters with the control valve under
discussion, the pressure connection P is provided on the valve
body, with its end aligned with the valve longitudinal axis. The
hydraulic fluid, which is supplied under pressure, presses against
an end surface of the frequently hollow-cylindrical valve body,
before passing into the respective operating connection A or B,
depending on the piston position. This leads to a considerable
force being exerted on the piston, as a result of the fluid supply,
which the external control magnet has to overcome in order to move
the valve piston in an opposite direction. The magnetic force
counteracts the spring acting on the valve piston and, when no
current is flowing through the electromagnet, moves the valve
piston to its basic position (P-B-A-T). The spring is matched to
the system (magnetic force, flow and pressure forces of the
hydraulics, piston movement, piston friction, etc). If the
fluid-dependent force acting in the opposite direction now also has
to be overcome in addition, this can lead in the worst case, when
the applied fluid pressure is high, to the magnetic force that is
acting not being strong enough to move the valve piston or to the
valve piston not completely covering the movement distance
associated with the electrical power applied to the magnet.
SUMMARY OF THE INVENTION
[0006] The invention is based on the object of specifying a
camshaft adjuster which allows reliable positioning of the valve
piston even when the applied fluid pressure is high.
[0007] In order to solve this problem for a camshaft adjuster of
the type mentioned initially, the invention provides that the fluid
distribution area in the control valve, that is to say in the valve
body or the valve piston or between the two--is designed in such a
manner that the hydraulic fluid acts on surfaces of the valve
piston which point essentially in mutually opposite directions, so
that local forces, which are essentially in opposite directions to
one another, act on the valve piston.
[0008] In the camshaft adjuster according to the invention, the
fluid path for the hydraulic fluid, as soon as it enters the valve
body and before it passes to one of the operating connections A or
B, is designed such that the valve piston is loaded by the fluid on
two surfaces which point in mutually opposite directions, so that
this directional load results in forces which project in the
opposite direction, act on the valve piston and at least partially
compensate for one another. As a result of this flow guidance, the
total force which results from the fluid supply and acts on the
valve piston is in consequence considerably reduced in comparison
to the embodiments according to the prior art, which means that the
force to be exerted by the external control magnet on the valve
piston or on its extended control rod which points towards the
magnet is considerably reduced. This means that any pressure surges
in the supply of hydraulic fluid can never have any disadvantageous
effect on the valve control.
[0009] It is expedient if the mutually opposite forces which are
produced by the application of pressure to a surface according to
the invention are essentially of equal magnitude, for which
purposes the areas to which pressure is applied should expediently
also be essentially of the same magnitude.
[0010] According to a first refinement of the invention, the
pressure connection P may be at right angles to the valve axis and
may open into an annular channel which is formed between the valve
piston and the valve body, can be connected to the operating
connection A as a function of position, and leads into the
hollow-cylindrical valve piston, which is closed at both ends and
whose cavity can be connected as a function of position to the
operating connection B, with pressure being applied to the end
cavity surfaces via the hydraulic fluid. The surfaces via which the
forces in opposite directions are introduced into the valve piston
are in this embodiment the end surfaces which bound the cavity at
the end. Assuming that this is a hollow-cylindrical piston part
with a constant cavity diameter, the areas are also in consequence
essentially of the same magnitude, so that this also results in
forces essentially of the same magnitude acting in opposite
directions.
[0011] It should be noted at this point that, of course, depending
on the configuration of the control valve and of the adjustment
apparatus, the operating connection B may also be connected to the
annular channel instead of the operating connection A, and the
operating connection A may be connected to the cavity instead of
the operating connection B, that is to say the respective operating
connections can also be interchanged. This applies to all of the
embodiments described in the following text.
[0012] In the described embodiment, it is also possible to provide
that the two operating connections can be connected as a function
of position to the outlet connection which is at an angle,
preferably at right angles, to the valve longitudinal axis, via an
annular channel which is formed between the valve piston and the
valve body. Expediently, in this valve embodiment, all of the
connections, that is to say both the pressure connection P and the
outlet connection T and the operating connections A and B are
arranged such that they run at right angles to the valve axis and
in the sequence B-T-A-P or A-T-B-P, with a tension spring being
used in the last-mentioned case in order to switch the valve to the
basic position P-B-A-T when no current is flowing that is to say
when the magnet is not active.
[0013] One alternative embodiment of a control valve provides that
the pressure connection P is at an angle, preferably at right
angles, to the valve axis and opens into an annular space which is
formed between the valve piston and the valve body and can be
connected as a function of position to the operating connection A
or B, in which case the operating connections A, B can be connected
as a function of position via connecting holes to the cavity in the
hollow-cylindrical valve piston, and the cavity leads to the outlet
connection T, which in this embodiment runs aligned axially with
the valve longitudinal axis. In this case as well, the pressure
connection P and the operating connections A and B can expediently
be arranged such that they run at right angles to the valve
longitudinal axis and in the sequence A-P-B.
[0014] A further embodiment variant provides that the pressure
connection P is on the valve longitudinal axis and opens via guide
channels into an annular space which is formed between the valve
piston and the valve body and can be connected as a function of
position to the operating connection A or B, in which case the
operating connections A, B can be connected as a function of
position via connecting holes to the cavity in the
hollow-cylindrical valve piston, and the cavity leads to the outlet
connection T.
[0015] Finally, a further valve embodiment provides that the
pressure connection P runs aligned with the valve longitudinal axis
and opens into the hollow-cylindrical valve piston on which radial
openings are provided through which the hydraulic fluid enters the
annular space which is formed between the valve piston and the
valve body and is bounded by the end face of the valve piston. In
this embodiment--in a similar manner to that in the prior art--the
hydraulic fluid is passed axially into the hollow-cylindrical valve
piston. Because of the piston openings which are provided according
to the invention, the fluid emerges from the piston into the rear
annular space which is formed between the piston and the valve
body, or it is effectively diverted and presses against the piston
outer surface, which is located opposite the cavity end wall. Thus,
in this embodiment as well, the pressure acts on surfaces which are
effectively mutually opposite thus resulting in local forces in
opposite directions acting on the valve piston.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a section view of a first embodiment of a
control valve,
[0017] FIG. 2 shows a camshaft adjuster according to the invention
with the integrated control valve shown in FIG. 1,
[0018] FIG. 3 shows a second embodiment of a camshaft adjuster
according to the invention, with a second embodiment of an
integrated control valve,
[0019] FIG. 4 shows a third embodiment of a control valve, and
[0020] FIG. 5 shows a fourth embodiment of a control valve.
DETAILED DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows a control valve 1 comprising a valve body 2 on
which, in the illustrated exemplary embodiment, an external thread
3 is provided, via which the valve body is screwed on, on the
camshaft side, after insertion into the rotor of an adjustment
device. A valve piston 4 is guided such that it can move axially in
the valve body 2, and can be moved against a return force which is
produced by a spring 5. A stem rod 6 is arranged on the valve
piston 4 for movement and interacts with an external control
magnet, which is not shown in any more detail, in order to move the
valve piston in the other direction, against the spring or with
spring assistance. As described, the control magnet is arranged
externally, for example on the motor, that is to say it does not
move, in contrast to the control valve 1, which rotates with the
rotor. The control valve 1 is held encapsulated in the housing of
the camshaft adjuster, and the stem rod 6 interacts with the magnet
via this housing.
[0022] A plurality of different connections are provided on the
valve body 2. On the one hand, an operating connection A and an
operating connection B are shown, via which hydraulic fluid can be
passed into corresponding chambers in the apparatus, which is in
the form of a vane-cell adjustment apparatus, depending on the
position of the valve piston 4. The illustration also shows a
pressure connection P, via which the hydraulic fluid is supplied by
a pump, which is not illustrated in any more detail. Furthermore,
an outlet connection T is shown, via which hydraulic fluid to be
carried away is passed to a tank, which is not shown in any more
detail.
[0023] Various control edges 7a (which are associated with the
operating connection A) and 7b (which are associated with the
operating connection B) are provided on the valve piston 4.
Depending on the position of the valve piston, the operating
connections A and B are connected via these control edges either to
the pressure connection P or to the outlet connection T via the
channel 41, depending on whether fluid is intended to be supplied
into the chambers which are associated with the operating
connection A and fluid is intended to be carried away from the
chambers which are associated with the operating connection B, and
is intended to be passed to the tank via the outlet connection T,
or vice versa. The position is controlled by the magnet, which is
not shown in any more detail.
[0024] In order to prevent the hydraulic fluid, which is supplied
at a relatively high pressure, from exerting a force on the valve
piston which would additionally have to be overcome by the magnet
which is moved against the spring force in order to move the valve
piston 4, an annular channel 8 is provided in the control valve 1,
and the pressure connection P opens into it. The annular channel
8--which can be connected to the operating connection A if required
depending on the piston position--opens via openings 9 on the valve
piston side into the cavity 10 in the valve piston 4. The cavity 10
can be connected via appropriate openings 11 to the operating
connection B, when the aim is to supply the hydraulic fluid to it,
depending on the piston position.
[0025] The hydraulic fluid in the cavity 10 presses against two
mutually opposite end surfaces 12, 13 which bound the cavity, seen
in the axial direction. This results in a force F.sub.p1 or
F.sub.p2, which in each case acts in the direction of the valve
piston, with these forces being in opposite directions to one
another, as can be seen. The two forces--which in the ideal case
are of equal magnitude--thus compensate for one another, so that
the valve piston 4 effectively has no pressure applied to it in the
ideal case, to the extent that forces act on it from the fluid
supply.
[0026] FIG. 2 shows a camshaft adjuster 14 according to the
invention having a rotor 15 and a stator 16. The rotor 15 is
connected to the control valve 1 such that they rotate together,
and this assembly can rotate with respect to the stator 16, which
is connected to the crankshaft by means of the control chain or the
control belt. A plurality of vanes 17 are provided in a known
manner on the rotor, rest closely against the inner wall 18 of the
stator, and are bounded by the two chambers in each case, to which
fluid is respectively applied via one operating connection A or B
or from where fluid can be drawn away via the respective operating
connections. There is no need to describe further details relating
to this, because the basic design of such camshaft adjusters is
well known.
[0027] FIG. 3 shows a further embodiment according to the invention
of a camshaft adjuster 19 whose basic design corresponds to that of
the camshaft adjuster 14 shown in FIG. 2, but with the integrated
control valve 20 being of a different design. This likewise has a P
pressure connection as well as the two operating connections A and
B and an outlet connection T. However, in this case, the pressure
connection P, which is passed from the outside via the valve body
21 inwards, can be connected effectively centrally between the
operating connections A and B, which can be connected to the
pressure connection P or to the outlet connection T, which is this
case runs axially with the valve longitudinal axis, via the
position of the valve piston 22 in a corresponding manner to that
described for the control valve 1. In this embodiment as well, in
which the valve piston 22 can likewise be moved by a control
magnet, which is not shown in any more detail, against a return
spring, which is not shown in any more detail, the fluid is
supplied in such a manner that forces which largely compensate for
one another and result from the fluid that is forced in act on the
valve piston 22. The pressure connection P opens into an annular
channel 23 which is bounded by the control flanks 24, 25, by means
of which the connection to the operating connections A and B,
respectively, is opened or closed. The fluid thus presses against
the flanks, which point in opposite directions to one another, so
that this necessarily results in forces in opposite directions to
one another, which compensate for one another. In this case as
well, a fluid distribution area is thus provided, which allows
force compensation.
[0028] Finally, FIG. 4 shows a further control valve 26 which can
be integrated in the same way in a camshaft adjuster as is shown in
the previous figures. This control valve as well has a valve body
27 and a valve piston 28. In this case, the pressure connection P
is axial with respect to the valve longitudinal axis, while the
operating connections A and B, which are not shown in any more
detail, as well as the outlet connection T are vertical with
respect to the valve longitudinal axis.
[0029] As can be seen, in this case as well, the valve piston is
mounted with respect to a return spring 29. This is
hollow-cylindrical, and the fluid that is supplied enters it.
However, a plurality of openings 40 are provided on the opposite
side so that the fluid can enter the annular space 31 which
surrounds this piston end, where the fluid presses against the
piston outer surface 32 which is opposite the end surface 33 in the
interior of the piston. Thus, in this case as well, two surfaces
which point in mutually opposite directions once again have the
fluid applied to them, thus resulting in forces in mutually
opposite directions acting on the valve piston 28.
[0030] Finally, FIG. 5 shows a further control valve 34 according
to the invention, whose pressure connection P likewise runs axially
and whose operating connections A and B emerge from the valve body
35 at right angles to the longitudinal axis, while the outlet
connection T emerges from the valve piston 36 vertically with
respect to the longitudinal axis. In this case as well, the
hydraulic fluid is initially diverted via appropriate guide
channels 37 and is then passed into an annular space 38, which is
bounded by two surfaces 39, 40 on the valve piston 36. This
embodiment corresponds essentially to the valve embodiment shown in
FIG. 3, and this once again results in forces of the same magnitude
but in opposite directions acting on the valve piston 36. However,
in this case, the hydraulic fluid is supplied axially, while it is
supplied from the side in the case of the valve in FIG. 3.
REFERENCE NUMBERS
[0031] 1 Control valve [0032] 2 Valve body [0033] 3 External thread
[0034] 4 Valve piston [0035] 5 Spring [0036] 6 Stem rod [0037] 7a,
7b Control edges [0038] 8 Annular channel [0039] 9 Openings [0040]
10 Cavity [0041] 11 Openings [0042] 12 End surfaces [0043] 13 End
surfaces [0044] 14 Camshaft adjuster [0045] 15 Rotor [0046] 16
Stator [0047] 17 Vane [0048] 18 Inner wall [0049] 19 Camshaft
adjuster [0050] 20 Control valve [0051] 21 Valve body [0052] 22
Valve piston [0053] 23 Annular channel [0054] 24 Control flanks
[0055] 25 Control flanks [0056] 26 Control valve [0057] 27 Valve
body [0058] 28 Valve piston [0059] 29 Return spring [0060] 30
Openings [0061] 31 Annular space [0062] 32 Piston outer surface
[0063] 33 End surface [0064] 34 Control valve [0065] 35 Valve body
[0066] 36 Valve piston [0067] 37 Guide channels [0068] 38 Annular
space [0069] 39 Surfaces [0070] 40 Surfaces [0071] 41 Channel
[0072] A Operating connection [0073] B Operating connection [0074]
P Pressure connection [0075] T Outlet connection [0076] F.sub.p1
Force [0077] F.sub.p2 Force
* * * * *