U.S. patent application number 15/328607 was filed with the patent office on 2017-07-27 for camshaft adjuster having a chamber short-circuiting, pressure-controlled control unit.
The applicant listed for this patent is Schaeffler Technologies AG & Co. KG. Invention is credited to Torsten Zschieschang.
Application Number | 20170211430 15/328607 |
Document ID | / |
Family ID | 53610737 |
Filed Date | 2017-07-27 |
United States Patent
Application |
20170211430 |
Kind Code |
A1 |
Zschieschang; Torsten |
July 27, 2017 |
CAMSHAFT ADJUSTER HAVING A CHAMBER SHORT-CIRCUITING,
PRESSURE-CONTROLLED CONTROL UNIT
Abstract
A vane-type camshaft adjuster (1) including a rotor (2) which
has radially projecting vanes (3) and forms vane cells (5) along
with a stator (4) rotatably accommodating the rotor (2), each vane
cell (5) being subdividable by a vane (3) into two adjustable
chambers provided for holding hydraulic fluid; a hydraulic
fluid-controlling device (12) for conducting hydraulic fluid is
disposed and/or connected between the chambers (6, 7) in such a way
that a drop in pressure in the chambers (6, 7) caused or reinforced
by camshaft switching moments occurring during operation is used to
open the hydraulic fluid-controlling device (12) such that fluid
flows therethrough.
Inventors: |
Zschieschang; Torsten;
(Hagenbuechach, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schaeffler Technologies AG & Co. KG |
Herzogenaurach |
|
DE |
|
|
Family ID: |
53610737 |
Appl. No.: |
15/328607 |
Filed: |
June 11, 2015 |
PCT Filed: |
June 11, 2015 |
PCT NO: |
PCT/DE2015/200356 |
371 Date: |
January 24, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 1/46 20130101; F01L
2001/34433 20130101; F01L 1/3442 20130101; F01L 2001/34483
20130101; F01L 2001/34423 20130101 |
International
Class: |
F01L 1/344 20060101
F01L001/344 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2014 |
DE |
DE102014215419.7 |
Claims
1-10. (canceled)
11. A vane-type camshaft adjuster comprising: a rotor having
radially projecting vanes, the rotor, together with a stator
rotatably accommodating the rotor, forming vane cells, each vane
cell divided by a vane into two adjustable chambers provided for
accommodating hydraulic fluid, a hydraulic fluid control device for
conducting hydraulic fluid between the chambers being situated in
such a way that a pressure drop in the chambers is induced or
amplified by camshaft alternating torques occurring during
operation and is used to open the hydraulic fluid control device so
that fluid flows therethrough.
12. The camshaft adjuster as recited in claim 11 wherein the
hydraulic fluid control device includes at least one bypass line
closing device.
13. The camshaft adjuster as recited in claim 11 wherein the
hydraulic fluid control device includes two bypass line closing
devices.
14. The camshaft adjuster as recited in claim 13 wherein the two
bypass line closing devices are situated in parallel to each other
in a fluid-conductible manner.
15. The camshaft adjuster as recited in claim 12 wherein the bypass
line closing device includes a valve and a spring acting
thereupon.
16. The camshaft adjuster as recited in claim 15 wherein the spring
pretensions the valve into a position in which the hydraulic fluid
flow is prevented.
17. The camshaft adjuster as recited in claim 12 wherein the bypass
line closing device is preset in such a way that, when the pressure
in a first of the chambers falls below a limit pressure, a
switching position of the bypass line closing device is forced, the
hydraulic fluid entering the first chamber from the second chamber
through a bypass line in the switching position.
18. The camshaft adjuster as recited in claim 17 wherein the bypass
line closing device includes a valve and a spring acting thereupon,
the spring adapted to the limit pressure.
19. The camshaft adjuster as recited in claim 11 wherein the
hydraulic fluid control device is integrated into the vane.
20. The camshaft adjuster as recited in claim 18 wherein the bypass
line closing device includes a pilot line establishing a
pressure-transmitting connection between the first chamber and a
closing element, the spring, in its basic position, forcing the
closing element into the bypass line connecting the two chambers in
a hydraulic fluid-suppressing manner, and the bypass line being
open in an activating position, when the pressure in the first
chamber reaches or falls below the limit pressure.
21. The camshaft adjuster as recited in claim 11 wherein two
pistons movable toward and away from each other are situated in a
channel or bore, the pistons being situated in such a way that the
pistons are activated only by a pilot line assigned to them.
Description
[0001] The present invention relates to a vane-type camshaft
adjuster, including a rotor, which has radially projecting vanes,
the rotor, together with a stator rotatably accommodating the
rotor, forming vane cells, each of which is divided by a vane into
two adjustable chambers provided for accommodating hydraulic
fluid.
BACKGROUND
[0002] Camshaft adjusters of this type are used in valve train
assemblies of internal combustion engines, as known, for example,
from DE 102 39 748 A1. Camshaft adjusters as valve timing control
units are also known from the prior art, for example US
2008/0173267 A1 or U.S. Pat. No. 7,182,052 B2 or DE 10 2008 000 083
A1. In these publications, a valve timing control unit controls a
valve timing of an inlet/outlet valve of an internal combustion
engine. The device includes a housing which is rotated with the aid
of a drive shaft. The housing has a chamber space which
accommodates a vane rotor, which is rotatable toward a retard and
an advance side relative to the housing with the aid of a driven
shaft, in that a hydraulic pressure is applied thereto in a retard
and advance chamber in the chamber space. A filter is provided in a
fluid channel for removing foreign substances, which extends from a
sliding section between the driven shaft and a bearing to both the
housing and the vane rotor through a connected section between the
driven shaft and the vane rotor. The filter is provided on the side
of both the housing and the vane rotor with respect to the sliding
section.
[0003] Camshaft adjusters are furthermore known from the
publications U.S. Pat. No. 7,245,077 B2, U.S. Pat. No. 7,318,401 B2
and U.S. Pat. No. 7,000,580 B1. Slide valve devices for a camshaft
adjuster including integrated check valves are described
therein.
[0004] The present invention is in the field of accumulators and
additional control functions in the switching valve. It therefore
relates to pressure-driven adjusters, which are also known as oil
pressure-activated (OPA) adjusters.
SUMMARY OF THE INVENTION
[0005] At excessively high torsional moments, an underpressure
currently occurs periodically on the pump side in a camshaft
adjuster. This results in dynamic problems and in additional air
intake due to suction from leakage gaps and/or a degassing of a
hydraulic fluid, such as a hydraulic liquid, e.g., oil, such as
pressure oil/motor oil.
[0006] An object of the present invention is to avoid these
disadvantages, to provide a particularly dynamically optimized
camshaft adjuster and to eliminate or at least mitigate the
disadvantages known from the prior art.
[0007] The present invention provides that a hydraulic fluid
control device/hydraulic fluid regulating device is situated and/or
connected between the chambers for conducting hydraulic fluid in
such a way that a pressure drop, preferably below a predetermined
limit pressure in the chambers, caused or amplified by camshaft
alternating torques occurring during operation, is used to open the
hydraulic fluid control device so that fluid flows
therethrough.
[0008] The pressure at which the system begins to suck in air, or
at which oil begins to degas, may be understood to be the critical
pressure, in certain situations equal to a limit pressure. A limit
pressure is understood to be the pressure which is the pressure set
via the spring pretension and piston active surface.
[0009] It is advantageous if the hydraulic fluid control device
includes at least one bypass line closing device or preferably two
bypass line closing devices. In this way, hydraulic fluid may be
transported both from the one chamber into the other chamber during
a pressure drop and from the other chamber into the one chamber. An
optimization in both adjusting directions of the camshaft adjuster
is then achievable.
[0010] If the two bypass line closing devices are situated in
parallel to each other in a fluid conducting manner, the reaction
times may be minimized.
[0011] A particularly efficient camshaft adjuster optimization is
achieved if the bypass line closing device includes a valve, such
as a 2/2-way valve, and a spring acting thereupon, such as a
pressure or tension spring. In this case, two open/close valves may
be situated on/in the camshaft adjuster, which are actuated when
the pressure in the first chamber falls. The actuated valve then
opens a channel to allow oil to flow from the other chamber to the
first chamber.
[0012] If the spring pretensions the valve into a position in which
the hydraulic fluid flow is prevented, simple means may be used to
facilitate a complex actuation.
[0013] A hydraulic fluid control unit is thus proposed, which
connects chambers A and B, i.e., a first chamber and a second
chamber, only when the pressure in one chamber falls below the
pressure (p.sub.krit) set via a controller/switch. A pressure
compensation between the chambers may then take place. In this
process, the pressure gradient between the chambers is utilized,
which is induced in any case by the (camshaft) alternating
torques.
[0014] As long as the pressure in the relevant chamber is above the
critical pressure (limit pressure), the relevant controller/switch
ensures a blocking of the short-circuit between the chambers. Each
path A or B having the particular connected chambers requires a
separate control unit, which varies the pressure in the
corresponding path or opens the bypass to the other chamber if the
pressure falls below the critical pressure in the one chamber. The
pressure difference between the chambers is not an issue. It is
additionally possible that a bypass/bypass line is opened when the
pressure falls below a level set via the control unit (limit
pressure). An overflow through this bypass line then occurs. The
pressure level is not "equalized," but instead the camshaft
adjuster takes in the additional oil available to it (i.e., the oil
"that it can get") and thus increases the speed of its adjusting
movement.
[0015] It is desirable if the bypass line closing device is preset
in such a way that, when the pressure in a first of the chambers
falls below a limit pressure (p.sub.krit), a switching position of
the bypass line closing device is forced, in which the hydraulic
fluid enters the one, first chamber from the other, second chamber
through a bypass line.
[0016] It is advantageous if the spring is adapted to the limit
pressure/the pressure (p.sub.krit) set via the controller. This
precise limit pressure is set with the aid of the spring, the area
ratios and/or the active surfaces on the piston.
[0017] It is also advantageous if the hydraulic fluid conducting
device is integrated or built into a vane. In this way, a very
compact camshaft adjuster may be achieved.
[0018] It is advantageous if the bypass line closing device
includes a pilot line, which establishes a pressure-transmitting
connection between the first chamber and a closing element, the
spring, in its basic position, forcing the closing element into the
bypass line connecting the two chambers in a hydraulic
fluid-suppressing manner and, in an activating position, opening
the bypass line, when the pressure in the first chamber reaches
and/or falls below the limit pressure.
[0019] One advantageous exemplary embodiment is also characterized
in that two pistons, which are movable toward and away from each
other, are situated in a channel, the pistons being situated in
such a way that they are activated only by the pilot line assigned
to them. The two pistons are thus hydraulically controllable
separately from each other. A pressure-impermeable separation is
thus to be maintained in the channel, which may be designed in the
manner of a bore. In this way, a specific embodiment in a vane may
be used as an insertion element which includes two separate
chambers and pistons/cups. The insertion element may be provided
with two sections having bores in a sleeve. Internally, the
spring-loaded pistons or cups close the bores in a basic position,
the pressure in both chambers being above the critical pressure. If
the pressure in one of the two chambers falls below the critical
pressure, the piston located on this chamber side moves, whereby
the piston exposes a bore, and an overflow into the chamber having
the lower pressure from the other chamber occurs via the bypass
line.
[0020] A camshaft adjuster of this type may also be refined in that
the switching area is the area of the shared pilot line which
ensures a hydraulic fluid-permeable connection between the two
bypass lines in a pressure difference-/pressure drop-dependent
displacement of one of the pistons.
[0021] It should be noted that it is possible to provide the
springs on the two slide valves with tensile or pressure
pretensioning or to eliminate them altogether, depending on how the
critical pressure level is to be set, at which the slide valve is
to be deflected out of its initial position (closed without
pressure). For example, no spring is necessary if the slide valve
is to open upon falling below 0 bar, the underpressure in the
chamber connected to the corresponding port "pulling open" the
slide valve.
[0022] A spring having pressure pretensioning is sensible if the
slide valve is to be moved only starting at a certain
underpressure, e.g., at a pilot pressure of -0.1 bar. A tensile
pretensioning is theoretically also conceivable if the slide valve
is to open the bypass upon falling below a certain positive
pressure, such as above 0 bar. A pilot pressure would then be
detectable, e.g., at 0.1 bar. However, this design is risky,
because both slide valves are set to "through-flow" upon the
startup of the internal combustion engine, i.e., they are open
without pressure, and are thus able to generate an undesirable
short circuit via the two slide valves. One may try to compensate
for this state with the aid of additional switching elements. This
design is still technically very critical, since there is the risk
of the bypass unintentionally opening or being open in the first
place with each torque zero crossing/alternating torque, causing a
backflow of the fluid. The variant without a spring is also
critical, since the indifferent position of the cups/pistons/slide
valves may also cause the wrong bypass to open unintentionally.
From a technical perspective, therefore, the variant with spring
pretensioning is sensible and preferred, because it permits a
defined basic position of the valve, and a secure sealing against
chamber pressures may thus occur.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The present invention is explained in greater detail below
with the aid of a drawing in which four exemplary embodiments are
illustrated.
[0024] FIG. 1 shows a circuit diagram for a first specific
embodiment of a camshaft adjuster according to the present
invention, a first chamber A being supplied with hydraulic fluid
via a pump, the pressure in first chamber A being above the
critical pressure, the torsional moments being uncritical, the
system functioning as an OPA system, and a short circuit A-B being
closed at a main valve;
[0025] FIG. 2 shows the camshaft adjuster from FIG. 1 in the
situation in which the pressure in first chamber A falls below
critical pressure p.sub.krit, i.e. a suction phase is present, the
torsional moments dominating the behavior of the camshaft adjuster
in a driving manner, the pressure supply from the pump furthermore
no longer being sufficient, a hydraulic fluid control
device/pressure regulating unit releasing a short-circuit via a
bypass line from second chamber B to first chamber A as long as the
system ensures that the pressure rises again above the critical
pressure in the first chamber by compensating the pressure and
resupplying hydraulic fluid from the second chamber to the first
chamber;
[0026] FIG. 3 shows another type of representation of the camshaft
adjuster from FIGS. 1 and 2, second chamber B being supplied with
hydraulic fluid by the pump, the pressure in chamber B being above
the critical pressure, the torsional moments being uncritical, the
adjusting direction of the camshaft adjuster being opposite the
adjusting direction of the specific embodiment in FIGS. 1 and 2,
and short circuit A-B also being closed;
[0027] FIG. 4 shows the situation in the adjusting direction as
shown in FIG. 3, however the pressure in second chamber B falling
below the critical pressure (suction phase), the torsional moments
dominating the behavior of the camshaft adjuster in a driving
manner, the pressure regulating unit/hydraulic fluid control device
releasing the short circuit/bypass line from chamber A to chamber
B, the system continuing to compensate the pressure and resupply
the hydraulic fluid from chamber A to chamber B until the pressure
in chamber B is again above the critical pressure;
[0028] FIG. 5 shows another exemplary embodiment, in which two
valves are integrated into a rotor vane and spring-loaded
cups/pistons are used;
[0029] FIG. 6 shows the exemplary embodiment from FIG. 5 but in an
open switching position of the bypass line;
[0030] FIG. 7 shows another specific embodiment for positioning the
valves in the vane, where the pilot bore may also be provided
centrically with respect to the piston or cup axis, so that the
bypass line does not have to be offset but may also be drilled in a
single pass, if the piston or the cup sufficiently blocks the
opposite chamber in a blocking position and sufficiently releases
the channel for the through flow in an open position;
[0031] FIG. 8 shows another specific embodiment in the closed
position of the bypass line; and
[0032] FIG. 9 shows the exemplary embodiment from FIG. 8 in the
open position of the bypass line.
[0033] The figures are only of a schematic nature and are used only
for the sake of understanding the present invention. Identical
elements are provided with identical reference numerals.
[0034] Features of the individual exemplary embodiments are also
interchangeable with each other.
DETAILED DESCRIPTION
[0035] A first specific embodiment of a camshaft adjuster 1
according to the present invention is illustrated in FIG. 1. This
camshaft adjuster 1 is provided for use in a valve train assembly
on an internal combustion engine. This camshaft adjuster 1 includes
a rotor 2, which has radially projecting vanes 3. Three or more
vanes 3 are usually used. Four vanes 3 are particularly
preferred.
[0036] Rotor 2 is rotatably situated in a stator 4, which may be
connected to an endless traction mechanism, such as a chain, e.g.
via a gear wheel. Rotor 2 and stator 4 form vane cells 5, which are
each divided into a first chamber 6 and a second chamber 7 by a
vane 3. The first chamber may also be referred to as chamber A, and
the second chamber may also be referred to as chamber B, and vice
versa. A main shutoff/switchover valve 9 is provided in a line
system 8. This main shutoff/switchover valve 9 is situated between
a pump (P) 10 and a tank (T) 11. A hydraulic fluid control device
12 is additionally provided.
[0037] Hydraulic fluid control device 12 preferably includes two
bypass line closing devices 13. The two bypass line closing devices
13 include a valve 14, such as a 2/2-way valve 15. This valve 14,
which may also be referred to as a slide valve, is pretensioned
with the aid of a spring 16.
[0038] Bypass line closing devices 13 are each situated in one
bypass line 17 or situated in a shared bypass line 17. There is
also a pilot line 18 for each bypass line closing device 13. Upon
falling below limit pressure/critical pressure p.sub.krit in first
chamber 6, an opening action is ultimately applied to one of the
two 2/2-way valves 15 via pilot line 18, so that, as illustrated in
FIG. 2, e.g. hydraulic fluid, such as oil, enters first chamber 6
from second chamber 7 via bypass line 17. Bypass line 17 remains
open, due to valve 14 on the right in the figure, until pressure P
in first chamber 6 falls below critical pressure p.sub.krit.
[0039] The adjusting direction of rotor 2 relative to stator 4 is
symbolized by arrow 19.
[0040] FIGS. 3 and 4 show a modified type of representation in
opposite adjusting direction 19 of rotor 2 relative to stator
4.
[0041] However, a variant of the specific embodiments illustrated
in FIGS. 1 through 4 is shown in FIGS. 5 and 6. In FIG. 5, both a
first bypass line 17 and a second bypass line 17 are closed,
whereas a bypass line 17 is opened based on the pressure
transmission from first chamber 6 due to a closing element 20
pretensioned by spring 16, so that hydraulic fluid is able to enter
first chamber 6 from second chamber 7.
[0042] The two bypass line closing devices 13, which are separated
from each other, are mounted alternatingly in vane 3. Each bypass
line closing device 13 includes a pilot line 18 to particular
assigned first or second chamber 6 or 7, which facilitates an
opening and closing of particular assigned bypass/bypass line 17 in
coordination with active spring 16. Pilot line 18 may also be
referred to as a pilot channel.
[0043] The arrangement is selected in such a way that the first and
second chambers are hydraulically separated from each other in a
valve basic position, i.e. when the pilot pressure is above the
critical pressure. Neither the (over)pressure in first chamber 6
nor the pressure in second chamber 7 may cause closing element 12
to open in the manner of a piston or a cup, nor cause a pressure
gradient between the two chambers 6 and 7.
[0044] A suitable recess in the sense of an indentation for the
end-face accommodation of closing element 20 may support the secure
closing of the closing element/valve body/cup/piston.
[0045] The pressure in both chambers is above the critical
pressure, as shown in FIG. 5. The valves are in their basic
positions, whereby bypass/bypass line 17 is closed.
[0046] In FIG. 6, on the other hand, the pressure in first chamber
6 has fallen below the critical pressure. However, the torsional
moments carry along camshaft adjuster 1, in particular rotor 2. The
supply of volume flow through pump 10 is then no longer
sufficiently ensured. As a result, a pressure which falls below the
critical pressure sets in in chamber A, i.e. in first chamber 6.
Closing element 20 is now pulled out of its seat or recess against
illustrated spring 16 due to this "underpressure" in first chamber
6. The short circuit from second chamber 7 to first chamber 6 is
thus opened. This opening is also hydraulically supported by the
chamber pressure in second chamber 7, which acts upon the now
exposed end face of closing element 20.
[0047] If a pressure compensation occurs between the two chambers 6
and 7, valve/closing element 20 returns to its seat and closes
bypass/bypass line 17. A slight recess for accommodating closing
element 20 ensures a secure sealing against a laterally acting
pressure from chambers 6 and 7.
[0048] The system operates like a traditional adjuster in pure OPA
mode until the pressure in one chamber 6 or 7 falls as a result of
the present alternating torques and critical pressure p.sub.krit
set via spring 16 and an active surface of the closing element
interior or the piston surface. Up to this point, the system is
operated by oil pressure control and is not dependent on
"repumping" between the chambers, which has an advantageous effect
on the adjusting speed or the adjusting behavior at low torsional
moments.
[0049] As the moments increase, the adjustment is then additionally
supported by the repumping between the chambers, in the sense of a
CTA adjustment, i.e. a cam torque actuation. The pressure gradient
between chambers 6 and 7 additionally helps achieve higher
adjusting speeds. The potential for air intake or outgassing from
the oil is minimized. Of course, this also depends on the set pilot
pressure.
[0050] FIG. 7 shows another specific embodiment, pilot lines 18
being present, which extend (orthogonally) from the two chambers 6
and 7 and which act upon adjusting devices 19/closing elements 20
which are in an operative relationship with springs 16. Closing
elements 20 close sloping bypass lines 17.
[0051] FIGS. 8 and 9 show two closing elements 20, which are
movable independently of each other, in a bore, which connects the
two chambers 6 and 7 orthogonally to the surface of vane 3. If the
pressure drops below the limit pressure in second chamber 7, for
example closing element 20 which is closer to second chamber 7,
i.e. the corresponding piston, is sucked/displaced in the direction
of second chamber 7. A passage for oil from the one section of
bypass line 17 to the other section of bypass line 17 is
facilitated thereby, so that hydraulic fluid is transported from
first chamber 6 to second chamber 7 according to the arrow
direction shown in bypass line 17 in FIG. 9.
LIST OF REFERENCE NUMERALS
[0052] 1 camshaft adjuster [0053] 2 rotor [0054] 3 vane [0055] 4
stator [0056] 5 vane cell [0057] 6 first chamber [0058] 7 second
chamber [0059] 8 line system [0060] 9 main shutoff/switchover valve
[0061] 10 pump [0062] 11 tank [0063] 12 hydraulic fluid control
device [0064] 13 bypass line closing device [0065] 14 valve [0066]
2/2-way valve [0067] 16 spring [0068] 17 bypass line [0069] 18
pilot line [0070] 19 adjusting direction [0071] 20 closing
element
* * * * *