U.S. patent application number 13/261508 was filed with the patent office on 2013-03-28 for drive system having at least one hydraulic actuator.
This patent application is currently assigned to Hydac Electronic GMBH. The applicant listed for this patent is Frank Herold, Frank Kattler, Kai Remus. Invention is credited to Frank Herold, Frank Kattler, Kai Remus.
Application Number | 20130074487 13/261508 |
Document ID | / |
Family ID | 44041474 |
Filed Date | 2013-03-28 |
United States Patent
Application |
20130074487 |
Kind Code |
A1 |
Herold; Frank ; et
al. |
March 28, 2013 |
DRIVE SYSTEM HAVING AT LEAST ONE HYDRAULIC ACTUATOR
Abstract
The invention relates to a drive system having at least one
hydraulic actuator (2), which is supplied with pressure medium (4)
by means of at least one pressure-medium pump (3) in a main
circuit, the pressure-medium pump (3) being a
rotational-speed-controlled pressure-medium pump that is driven by
a motor (5) at a variable rotational speed and a controlled torque,
said drive system being characterized in that leakage fluid (7)
that escapes from a displacement chamber (6) of the pressure-medium
pump (3) is discharged through a fluid-conducting connection (8)
having at least one check valve (9, 16), and the at least one check
valve (9, 16) is installed in the fluid-conducting connection (8)
in such a way that the check valve prevents pressure medium from
flowing back out of the main circuit into the displacement chamber
(6) or another interior chamber of the pressure-medium pump (3) and
feeds leakage fluid (7) into the main circuit of the drive system
(1) when there is a slight excess pressure.
Inventors: |
Herold; Frank; (Saarbrucken,
DE) ; Remus; Kai; (Ottweiler, DE) ; Kattler;
Frank; (Puttlingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Herold; Frank
Remus; Kai
Kattler; Frank |
Saarbrucken
Ottweiler
Puttlingen |
|
DE
DE
DE |
|
|
Assignee: |
Hydac Electronic GMBH
Saarbrucken
DE
|
Family ID: |
44041474 |
Appl. No.: |
13/261508 |
Filed: |
March 15, 2011 |
PCT Filed: |
March 15, 2011 |
PCT NO: |
PCT/EP2011/001263 |
371 Date: |
November 29, 2012 |
Current U.S.
Class: |
60/455 |
Current CPC
Class: |
F15B 2211/27 20130101;
F15B 2211/20515 20130101; F15B 2211/625 20130101; F15B 2211/6658
20130101; F15B 2211/7058 20130101; F15B 2211/20561 20130101; F15B
2211/7128 20130101; F15B 2211/7053 20130101; F15B 2211/30505
20130101; F15B 7/006 20130101; F04B 17/00 20130101; F15B 2211/61
20130101 |
Class at
Publication: |
60/455 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 2010 |
DE |
10 2010 020 132.4 |
Claims
1. A drive system having at least one hydraulic actuator (2), which
is supplied with a pressure medium (4) by means of at least one
pressure medium pump (3) in a main circuit, wherein the pressure
medium pump (3) is a speed-controlled pressure medium pump, which
is driven by a motor (5) at a variable speed and a controlled
torque, characterized in that the leakage fluid (7), escaping from
a displacement chamber (6) of the pressure medium pump (3), is
discharged through a fluid-conducting connection (8) having at
least one check valve (9, 16), and that the at least one check
valve (9, 16) is installed in the fluid-conducting connection (8)
in such a way that the check valve prevents the pressure medium
from flowing back out of the main circuit into the displacement
chamber (6) or another interior chamber of the pressure medium pump
(3) and feeds the leakage fluid (7) into the main circuit of the
drive system (1) when there is a slight excess pressure.
2. The drive system according to claim 1, characterized in that the
pressure medium pump (3) has at least one low pressure port (14,
14') and/or at least one high pressure port (15, 15').
3. The drive system according to claim 2, characterized in that the
leakage fluid (7) is discharged at least at one low pressure port
(14, 14') of the pressure medium pump (3).
4. The drive system according to claim 2, characterized in that the
fluid-conducting connection (8) runs through the respective low
pressure port (14, 14') to at least one high pressure port (15,
15'); and that each port (2) of the connection (8) has a check
valve (9, 16).
5. The drive system according to claim 1, characterized in that the
pressure medium pump (3) is an axial piston machine; and that two
check valves (9, 16) that open in opposite directions are activated
in the fluid-conducting connection (8); and the fluid-conducting
connection (8) is connected in parallel to a high pressure port
(15, 15') respectively of the axial piston machine.
6. The drive system according to claim 1, characterized in that the
pressure medium pump (3) is bi-directional in the two-quadrant
operating mode or is speed-controlled in the four-quadrant
operating mode.
7. The drive system according to claim 1, characterized in that the
pressure medium pump (3) charges a pressure accumulator (10) with a
pressure medium (4); and this pressure accumulator also charges the
hydraulic actuator (2) with pressure medium (4).
8. The drive system according to claim 1, characterized in that the
hydraulic actuator (2) is an actuating device (11) for a hydraulic
system for roll stabilization of a vehicle.
9. The drive system according to claim 7, characterized in that the
pressure accumulator (10) prestresses the pressure medium (4) on
the intake side (12) of the pressure medium pump (3).
10. The drive system according to claim 7, characterized in that
the pressure accumulator (10) charges the pressure medium (4) in a
working chamber (13, 13') of the hydraulic actuator (2).
11. The drive system according to claim 7, characterized in that
the hydraulic actuator (2) and the pressure medium container are
actuated by a directional control valve in such a way that a
suction process is realized.
12. The drive system according to claim 1, characterized in that
the pressure medium pump (3) is used for supplying pressure medium
to two hydrostatic working cylinders (17) that work in opposite
directions.
13. The drive system according to claim 12, characterized in that
the working cylinders (17) that work in opposite directions are
connected in each instance to a valve (18) for draining the
pressure medium (4) out of each one of their working chambers (13,
13').
14. The drive system according to claim 13, characterized in that a
check valve (R) is arranged parallel to the valve (18) in a
pressure medium line bridging the valve (18); and that at least one
check valve (R) enables the pressure medium (4) to flow out of the
pressure medium container to the respective hydraulic actuator (2).
Description
[0001] The invention relates to a drive system having at least one
hydraulic actuator, which is supplied with a pressure medium by
means of at least one pressure medium pump in a main circuit,
wherein the pressure medium pump is a speed-controlled pressure
medium pump, which is driven by a motor at a variable speed and a
controlled torque.
[0002] Drive systems of a hydraulic nature comprising one or more
actuators, which can also execute different operating movements in
a sequential manner, are often supplied with hydraulic energy by
means of a control valve circuit that is driven by one or more
pressure medium pumps at a constant speed. The technical drawback
of such drive systems is the poor efficiency, because the control
valves convert hydraulic energy into thermal energy in accordance
with the inherent characteristic of the operating principle.
[0003] Such drive systems are also known in suspension systems for
motor vehicles. Hence, DE 199 30 444 C2 describes an active
stabilizer for a motor vehicle that couples two wheels of a vehicle
axle. This stabilizer consists of a first stabilizer part, which is
assigned to one wheel, and a second stabilizer part, which is
assigned to the other wheel, as well as an actuator, which couples
the stabilizer parts. The actuator controls the lateral inclination
of the motor vehicle by bracing the stabilizer parts against each
other. Each stabilizer part extends from one port assigned to the
actuator, to a port that is assigned to the wheel. In the meantime,
there also exist active vehicle suspension systems, which are
further developed to form complex combination systems and enable
not only an active roll stabilization but also a level control of a
top section of the chassis. In this case, the term level control is
understood to mean the active change in the distance between the
top section of the chassis and a vehicle axle.
[0004] As a rule, two-axle passenger vehicles may have a level
control system at both the front axle and the rear axle. In this
case, the level control at the vehicle axles can be carried out
independently of each other.
[0005] DE 10 2004 039 973 A1 describes an active vehicle suspension
system comprising a level control. Such a suspension system
exhibits good spring properties and reduces the vehicle's tendency
to tilt. At the same time, this suspension system makes it possible
to raise and lower the top section of the chassis relative to the
wheels of the vehicle. This lifting and lowering is achieved by
means of the simultaneous possible actuation of a directional
control valve for changing the pressure in the piston-side cylinder
chamber of the active vehicle suspension system in connection with
an adjustable throttle valve and a vehicle part which enables an
adjusting action and is disposed between a piston rod-side cylinder
chamber of the suspension system and a pressure medium pump.
[0006] A drive system of the type described in the introductory
part is known from the prior art US 2008/0190104 A1. The prior art
drive system comprises an actuator with a reversible motor, which
is designed to generate a variable torque. Furthermore, this drive
system comprises a hydraulic transducer, which is connected to the
reversible motor and has a first port and a second port. The
pressure chambers provided in a hydraulic cylinder can be charged
by way of the ports.
[0007] Based on this prior art, the object of the present invention
is to provide a hydraulic drive system which is designed in a
simple way, has good control properties, and avoids the throttling
losses of the control valves that are inherent in the operating
principle, so that very good efficiency is achieved, as
required.
[0008] This object is achieved with a drive system having the
features specified in claim 1 in its entirety.
[0009] According to the characterizing part of claim 1, the leakage
fluid, escaping from a displacement chamber of the pressure medium
pump, is discharged through a fluid-conducting connection having at
least one check valve, wherein the at least one check valve is
installed in the fluid-conducting connection in such a way that the
check valve prevents the pressure medium from flowing back out of
the main circuit into the displacement chamber or another interior
chamber of the pressure medium pump and feeds the leakage fluid
into the main circuit of the drive system when there is a slight
excess pressure.
[0010] In order to compensate for the leakage losses in the
hydraulic circuit between the hydraulic actuator and the pressure
medium pump, the invention provides that the leakage fluid,
escaping from the pressure medium pump, is discharged through a
check valve by means of a fluid-conducting connection to the
pressure medium flow generated by said connection. The use of a
check valve makes it possible to actuate, on the one hand, the
leakage fluid flow; and, on the other hand, the leakage oil in the
entire pressure medium flow can be kept in circulation with any
other quantity of fluid.
[0011] Furthermore, it is advantageous to discharge the leakage
fluid at a low pressure port of the pressure medium pump or to feed
the leakage fluid to the low pressure side of such a pressure
medium flow of the pressure medium pump. Furthermore, it is
advantageous to feed the leakage fluid flow to a high pressure port
of the pressure medium pump. In this case, the check valve or the
two check valves, which prestress the leakage fluid flow as a
function of the direction of flow of the pressure medium pump,
prevent the pressure medium from flowing, subject to a high
pressure, into the corresponding interior chamber of the housing of
the pressure medium pump. In this respect, it is provided that the
check valves have mutually opposite opening directions. Each of the
fluid-conducting connections that discharge the leakage fluid is
connected to a high pressure port of the pressure medium pump, so
that the overall result is a parallel connection of the
fluid-conducting connecting lines to the high pressure fluid lines
to the consumers or the hydraulic actuators that are supplied by
the pressure medium pump. The leakage is recirculated, as required,
through the respective low pressure fluid line, which is designed
in the form of the high pressure fluid line and, at this point, is
not needed for the high pressure guide.
[0012] The pressure medium pump can drive a whole variety of
different kinds of hydraulic actuators, such as a double-acting
actuating cylinder or a hydraulic motor, which can also be used to
actuate stabilizers of a roll stabilization system of a
vehicle.
[0013] Due to the fact that the pressure medium pump, which
supplies the hydraulic actuator with a pressure medium, is operated
preferably as a bi-directional speed-controlled pump, preferably
without a control valve and, thus, with extremely low losses, in a
two or four-quadrant operating mode, and is driven by a motor with
variable speed and controlled torque, the result is a drive system
that delivers pressure medium from a pressure medium container to
the respective hydraulic actuator and vice versa, only as required
and in such a way that the pressure medium is adapted to the
desired actuation.
[0014] Furthermore, it is advantageous to charge a pressure
accumulator with a pressure medium; and this pressure accumulator
can be used for compensating a volume of the pressure medium on the
consumer side or also on the intake side of the pressure medium
pump. The pressure accumulator can also be used to directly charge
a working chamber of a hydraulic actuator. If the intake side of
the pressure medium pump is charged from the pressure accumulator,
then cavitation in the drive system is avoided by means of this
measure of prestressing the system.
[0015] The pressure medium pump has a constant displacement volume,
so that in combination with the torque-controlled, speed-variable
drive of the pressure medium pump, variable flow rates are made
possible. As a result, there is no need for valves to control the
flow rate and the direction of flow of the pressure medium pump.
Check valves, which have an impact on the leakage fluid outflow,
are adequate to operate the drive system. However, it may be
advantageous to connect fast switching directional control valves
between the pressure medium pump and the hydraulic actuator or
between a plurality of hydraulic actuators.
[0016] If the hydraulic actuator is, for example, a double-acting
cylinder, then both ports of the pressure medium pump are connected
in each instance to a working chamber of the pressure medium pump,
so that in the event of a rotational direction or direction of flow
of the pressure medium pump in the one direction, for example, the
rod chamber is filled and the working chamber on the piston base
side is emptied and vice versa. The result of this feature is an
exact control and travel movement of the actuating element of the
hydraulic actuator as a function of the direction of rotation and
the rotational speed of the pressure medium pump. The motor,
preferably an electric motor, which is driving the pressure medium
pump, is torque-controlled and driven as a function of the sensor
signals of a control and/or regulating device, which determines the
demand requirement of the hydraulic actuator. In this respect, the
motor can be, for example, an electric motor with pulse width
modulation.
[0017] In order to superimpose a level control function on the
functions of the roll stabilization, it is advantageous to assign a
valve to each hydraulic actuator that is associated with the drive
system. This valve can be used to empty or fill a working chamber
of the respective hydraulic actuator, so that, for example, the
absolute position of a piston of an actuating cylinder can be
displaced.
[0018] As a result, the absolute position of the wheels of a motor
vehicle relative to a chassis can be changed in terms of their
height; and the top section of the chassis of a motor vehicle can
be raised or lowered.
[0019] Hydraulic actuators, for example, in the manner of actuating
cylinders, can also be coupled so that the result is a sequence
control or a coupling in the opposite direction. For example, a
vehicle wheel on the inside of a curve can be raised; and the
vehicle wheel that is on the outside of a curve can be lowered.
[0020] Additional advantages, features, and details of the
invention will be apparent from the dependent claims and the
following description, in which a number of exemplary embodiments
are described with reference to the drawings. In this context, the
features mentioned in the claims and the description may be
essential to the invention individually or in any combination.
[0021] FIG. 1 is a schematic circuit diagram of a drive system
comprising a double-acting actuating cylinder and a pressure
accumulator as the consumer;
[0022] FIG. 2 is a schematic circuit diagram of a drive system
comprising a double-acting actuating cylinder and a pressure
accumulator, which charges a working chamber of the actuating
cylinder;
[0023] FIG. 3 shows a drive system, the consumer of which is an
oscillating motor for a roll stabilization system, with a pressure
accumulator for compensating for the leakage fluid and for
prestressing the pressure medium on the intake side;
[0024] FIG. 4 shows a drive system, as in FIG. 3, but without a
pressure accumulator;
[0025] FIG. 5 shows a drive system, the consumers of which are two
actuating cylinders with a cross-connected working chamber, and a
pressure accumulator for compensating for the leakage fluid and for
prestressing the pressure medium on the intake side;
[0026] FIG. 6 shows a drive system, which corresponds to the one in
FIG. 5, but without a pressure accumulator; and
[0027] FIG. 7 is a schematic circuit diagram of a drive system with
two actuating cylinders as the consumers in conformity with the
drawing according to FIG. 6, where the supply of pressure medium to
the actuating cylinders can be overridden by one 2/2-way valve
respectively in order to remove the pressure medium from each
working chamber respectively of each actuating cylinder.
[0028] FIG. 1 shows a schematic circuit diagram of a hydraulic
drive system 1 comprising a hydraulic actuator 2, which is designed
as a double-acting actuating cylinder 19. The hydraulic actuator 2
is provided, as is generally known, with a piston 20, which is
guided in a cylinder housing 21 in such a way that it can be
displaced in the axial direction; and this hydraulic actuator forms
two working chambers 13, 13' in the cylinder housing 21. A pressure
medium pump 3, which is provided with a constant displacement
volume, is used to supply pressure medium to the actuator 2. The
pressure medium pump 3 is driven by a motor 5, constructed in the
form of a torque-controlled, speed-variable electric motor, by
means of a shaft 22, which is merely indicated symbolically.
However, the electric motor 5 can also be replaced with a
conventional internal combustion engine, for example, in the form
of a diesel engine. Furthermore, it is possible to use an axial
piston machine (not illustrated), which is the subject matter of DE
10 2007 058 859 A1, where the electric motor and the pressure
medium pump are combined as a module in a common housing.
[0029] In the exemplary embodiment according to FIG. 1, the two
working chambers 13, 13' of the actuating cylinder 19 are connected
in a fluid-conducting manner to the high pressure port 15 of the
pressure medium pump 3; and in the embodiment according to FIG. 2,
each working chamber 13, 13' of the actuating cylinder 19 is
connected to a high pressure port 15 or 15' respectively of the
pressure medium pump 3. In this respect, the pressure medium 4 is
conveyed, as a function of the direction of rotation of the motor 5
and the rotational speed, into the one or the other working chamber
13, 13' of the actuating cylinder 19 by the pressure medium pump 3
in a closed hydraulic circuit without the interconnection of
switching valves or directional control valves. The result is a
travel movement or, if desired, a blocking of the position of the
piston 20 of the respective actuating cylinder 19. A four-quadrant
drive of the motor 5 or more specifically a four-quadrant operation
of the pressure medium pump 3 is provided, a feature that clearly
demonstrates a use of the drive system 1 in a motor vehicle (not
illustrated) as an active stabilization system.
[0030] A pressure accumulator 10 serves to compensate for the fluid
with respect to the differential volume between the two chamber
sides of the actuating cylinder 19 or the pressure medium pump 3 as
well as to prestress the pressure medium 4 on the high pressure
side of the pressure medium pump 3. In the drive system 1 shown in
FIG. 1, the two working chambers 13, 13' are charged to the same
degree with the pressure of the pressure accumulator 10, whereas in
the exemplary embodiment of a drive system 1 shown in FIG. 2, the
piston rod-side working chamber 13' of the actuating cylinder 19 is
directly charged with the pressure of the pressure accumulator 10
without the interconnection of the pressure medium pump 3. The
pressure medium pump 3 has a low pressure port 14 in both of the
possible directions of flow. The low pressure port is effective
whenever the respectively other, opposite high pressure port 15,
15' makes the high pressure that is required for the hydraulic
circuit available. The respective low pressure port 14 produces a
port for a fluid-conducting connection 8, which returns again the
leakage fluid 7 from a displacement chamber 6 of the pressure
medium pump 3, and, in particular, over the low pressure port to
the respective high pressure side and, as required, to the high
pressure ports 15, 15'. This approach represents a design feature
for an overall hydraulically closed drive system 1 without a
pressure medium container.
[0031] The fluid-conducting connection 8 runs through the
respective low pressure port 14 to each high pressure port 15, 15';
and each connecting branch of the connection 8 has a check valve 9,
16. Each check valve 9, 16 is installed in the fluid-conducting
connection 8 in such a way that the check valve prevents the
pressure medium from flowing back out of the main circuit into the
displacement chamber 6 or another interior chamber of the pressure
medium pump 3; and in the event of a slight excess pressure, the
leakage fluid 7 is fed into the main stream or more specifically
into the main circuit of the drive system 1.
[0032] FIGS. 3 and 4 show schematic circuit diagrams of a hydraulic
drive system 1 comprising a hydraulic actuator 2, which is designed
as an oscillating motor 23. Oscillating motors, in particular
so-called single bladed oscillating motors, are known. They are
used, for example, in connection with stabilizers for roll
stabilization of a motor vehicle. Such an oscillating motor also
has a housing and a rotor, which comprises a shaft and at least one
blade. The blade is used to divide a working chamber, enclosed by
the housing, into at least two pressure chambers. The two pressure
chambers are, as shown, connected in each instance to the one high
pressure port 15, 15' of the pressure medium pump 3. In order to
cause the blade to rotate relative to the housing, a chamber is
charged with more or less pressure medium 4, so that the result is
a defined relative position between the housing and a rotor that is
connected in a rotationally rigid manner to the blade.
[0033] When the pressure medium pump is in a neutral position, the
position of the blade and the rotational position of the rotor are
also fixed. The rotor can be rigidly attached to stabilizer rods of
a suspension system of a motor vehicle and, as a result, can raise
or lower the position of a wheel relative to the top section of the
chassis of the vehicle.
[0034] In order to be able to implement with low losses such
actuating tasks with a drive system 1 that largely dispenses with
valves, preference is given to a pulse width modulated electric
motor 5 that lends itself well to the drive of the pressure medium
pump 3. The actuation of such an electric motor is advantageously
performed by a control and/or regulating device (not shown in
detail) that processes the sensor signals in the form of
measurement values that relate specifically to the trip and the
vehicle; and these measurement values are passed on accordingly. In
addition, an adaptive control can be realized to the effect that
the torque is measured at an output shaft of the electric motor or
the oscillating motor and also flows into the actuation of the
motor 5. It is also possible to replace the said electric motor
with an internal combustion engine of the conventional design, for
example, a diesel engine.
[0035] The electric motor can also be electronically commutated, so
that the result is an improvement in efficiency in addition to an
increase in reliability and operational safety. Moreover, such
electronically commutated motors are not only less demanding to
design, but also less complicated to manufacture. See also in this
respect the disclosure of DE 10 2007 058 859 A1.
[0036] The exemplary embodiments according to the FIGS. 3 and 4
show in each instance a drive system 1 with a fluid-conducting
connection 8 that is provided for discharging the leakage oil 7 out
of the displacement chamber or the low pressure chamber of the
pressure medium pump in the same way as shown in the FIGS. 1 and 2,
specifically, by way of check valves 9, 16, which are connected to
the high pressure ports 15, 15'. FIG. 3 shows the drive system 1,
which is provided with an additional pressure accumulator 10, which
is connected to the respective low pressure port 14 as a function
of the operating direction of the pressure medium pump 3, which
overall provides for an absolute compensation of the pressure
medium losses in the drive system 1 as a whole. The pressure
accumulator 10 guarantees a low hydraulic pressure at the point
that the leakage fluid is recirculated. At the same time, the drive
system 1 is hydraulically prestressed to the extent that a negative
pressure and, thus, the cavitation associated with such a negative
pressure cannot occur in the drive system 1. In the exemplary
embodiment of the drive system 1 shown in FIG. 4, this prestressing
function takes on the elasticity of the fluid-conducting connection
between the individual components of the drive system 1 itself.
[0037] In the exemplary embodiments of a drive system 1 shown in
FIGS. 5 and 6, two working cylinders 17 that work in opposite
directions are shown as the consumers or as the actuating device
11; and these working cylinders can be used as the actuating
cylinder 19 for an active suspension system of a motor vehicle that
is not shown in detail. Owing to the cross connected connection of
the working chambers 13, 13' of the cylinders, the pistons 20 of
the cylinders 17 can move together in an inactive operating phase
of the drive system 1, in which the position of the displacement
elements of the pressure medium pump 3 is not fixed; and, hence,
the pistons enable an unimpeded movement of the wheels of a motor
vehicle in the vertical direction.
[0038] In the exemplary embodiment according to FIG. 5, a pressure
accumulator 10 is shown in the same way and in order to elucidate
the same function as in the exemplary embodiment shown in the FIG.
3.
[0039] In the exemplary embodiment of a hydraulic drive system 1
shown in FIG. 7, a valve 18, which is designed as a 2/2-way valve,
is connected to each high pressure port 15, 15' of the pressure
medium pump 3. Each of the valves 18 is arranged in a
fluid-conducting connection 24 between the high pressure ports 15,
15' and a pressure medium container in the form of a hydraulic
tank. Each fluid-conducting connection 24 has a check valve R,
which can be traversed with flow in the direction of the high
pressure ports 15, 15' and blocks in the opposite direction. This
switching technique makes it possible to securely clamp a piston 20
of a working cylinder 17 at an end stop point and at the same time
enables a controlled movement of the other piston 20 of the other
working cylinder 17. In this case, a working chamber of the
respective cylinder 17 can be supplied with pressure medium 4 from
the pressure medium container (tank). This design measure is
necessary, because the required volume of pressure medium cannot be
taken from a working chamber 13, 13' of the piston 20, which in
this respect is fixed in position.
[0040] The valves 18 can be actuated by the control and/or
regulating device. The actuation takes place when the one or the
other cylinder 17 demands a rolling moment. A signal for such an
actuation of the valve 18 can be obtained through the measurement
of a rolling moment at the respective piston 20 or through a
pressure signal at a valve 18 or, in addition, from a torque signal
of the motor 5.
[0041] Just the various check valves alone that are employed are
adequate for the function. In practice, they should be check valves
with a so-called minimum AP. As an alternative, directional control
valves with a very fast activation could be provided. Even
combinations of a directional control valve and a check valve (see
FIG. 7) are possible and constitute a good solution. For the
actuation signal, this signal has to correspond to the direction of
the rolling moment; and the magnitude of the rolling moment is
immaterial. In summary, it should also be pointed out that the
proposed solution provides a very energy-efficient circuit for the
hydraulic roll stabilization system. In this respect, only that
amount of energy is provided that is actually needed for the roll
stabilization. In the previous systems, the pump is connected, as
explained, to the drive train, which means that there is always a
volumetric flow to be transported, hence a large amount of energy
is required. If no roll stabilization is necessary, the volumetric
flow is pumped in a circuit at a low pressure, a state that denotes
a loss. If roll stabilization is required, then the solutions known
from the prior art transport the volumetric flow at a pressure that
corresponds to the rolling moment, even though in reality, after
the pressure for the rolling moment has been reached, it would only
be necessary to compensate for the leakage. The solution according
to the invention minimizes such energy losses in an effective
way.
* * * * *