DE102020201538A1 - Electro-hydraulic actuator arrangement with bladder accumulator and use of a bladder accumulator - Google Patents

Abstract

An electrohydraulic actuator arrangement is disclosed which has a hydrostatic displacement unit which can be driven by an electric motor and which can be operated as a pump and preferably also as a motor. The displacement unit is connected to a hydrostatic actuator, e.g. a differential cylinder, via a closed hydrostatic circuit. A preferably non-prestressed bladder accumulator is provided for the intermediate storage of pendulum or differential volumes.

Description

The invention relates to an actuator arrangement according to the preamble of claim 1 and the use of a bladder accumulator.

Hydraulically open and closed systems are known from the prior art. In the case of hydraulically closed systems, a distinction is made between hydraulic primary and hydraulic secondary driven systems.

• Grundform eines hydraulischen Antriebes, bei dem die Pumpe die Hydraulikflüssigkeit aus einem Vorratsbehälter ansaugt, dessen Oberfläche offen mit dem atmosphärischen Druck verbunden ist. Das Öl wird über Wegeventile zum Verbraucher gefördert und nach Arbeitsleistung wieder in den Behälter zurückgeführt. Eine Richtungsumkehr der Pumpenförderung ist nicht möglich. Ein zu hoher Unterdruck in der Saugleitung sollte vermieden werden. Eine Richtungsumkehr des Aktuators (Zylinder, Motor) erfolgt hier durch ein Wegeventil.

Hydraulically open system:

• Basic form of a hydraulic drive in which the pump sucks in the hydraulic fluid from a reservoir, the surface of which is openly connected to atmospheric pressure. The oil is conveyed to the consumer via directional control valves and returned to the container after work. It is not possible to reverse the direction of the pump delivery. Too high a negative pressure in the suction line should be avoided. A direction reversal of the actuator (cylinder, motor) takes place here by means of a directional valve.

The differential volume of a differential cylinder is taken up in the storage container.

• Grundform für einen hydraulischen Antrieb, bei der der Flüssigkeitsumlauf von der Pumpe zum Aktuator und von dort direkt zurück in die Saugleitung der Pumpe führt. Der hauptsächliche Unterschied zum „Hydraulisch offenen System“ ist damit, dass die Hydraulikpumpe direkt mit der vom Aktuator (Hydraulikmotor bzw.

Hydraulically closed system:

• Basic form for a hydraulic drive in which the fluid circulation leads from the pump to the actuator and from there directly back into the suction line of the pump. The main difference to the "hydraulically open system" is that the hydraulic pump is directly connected to that of the actuator (hydraulic motor or

Differential cylinder) returning hydraulic fluid is fed. The pump is thus "clamped" from two sides - the suction side and the pressure side. This means that an electric motor drives a hydraulic motor. The hydraulic motor generates a volume flow which directly drives a cylinder. The cylinder consequently generates a volume flow which feeds the hydraulic motor. The leakage occurring at the pump and the individual components is absorbed in a low-pressure accumulator, which according to the state of the art is preloaded with respect to the atmosphere, and from there fed back into the hydraulic system.

This means that the differential volume of the differential cylinder is recorded in a memory if required. The drive of the system is reversible.

• Hier wird der Aktuator (z.B. Differenzialzylinder) direkt durch die hydraulische Verdrängereinheit angetrieben. Die Drehrichtung der hydraulischen Verdrängereinheit bestimmt die Wirkrichtung des Aktuators.

Primarily driven:

• Here the actuator (eg differential cylinder) is driven directly by the hydraulic displacement unit. The direction of rotation of the hydraulic displacement unit determines the direction of action of the actuator.

• Hier wird die Wirkrichtung des Aktuators durch ein Ventil bestimmt, welches zwischen hydraulischer Verdrängereinheit und Aktuator (z.B. Differenzialzylinder) verbaut ist.

Secondary driven:

• Here the direction of action of the actuator is determined by a valve which is installed between the hydraulic displacement unit and the actuator (eg differential cylinder).

• Hier wird ein oder mehrere Speicher durch eine hydraulische Verdrängereinheit befüllt mit Betriebsmedium befüllt. Die dort gespeicherte Energie wird im Bedarfsfall durch Ventile dem Aktuator (z.B. Differenzialzylinder) zur Verfügung gestellt und treibt diesen an.

Storage - charging mode:

• Here, one or more accumulators are filled with operating medium by a hydraulic displacement unit. If necessary, the energy stored there is made available to the actuator (eg differential cylinder) by valves and drives it.

• Passive Entgasung:
  • Hier wird der innere Aufbau eines Ausgleichsbehälters, welcher gegenüber Atmosphäre offen gestaltet ist, so ausgeführt, dass eine optimale passive Entgasung des Druckmittels stattfinden kann.
• Aktive Entgasung:
  • Hier wird mittels eines Entgasungsmoduls der Partialdruck des Druckmittels so weit reduziert, dass nur noch gelöstes und kein freies Gas mehr im Druckmittel vorhanden ist.

Size reduction through passive and active degassing in the hydraulically open system:

• Passive degassing:
  • Here, the internal structure of an expansion tank, which is designed to be open to the atmosphere, is designed in such a way that optimal passive degassing of the pressure medium can take place.
• Active degassing:
  • Here, by means of a degassing module, the partial pressure of the pressure medium is reduced to such an extent that only dissolved and no free gas is left in the pressure medium.

The disadvantage of electrohydraulic actuator arrangements with an open circuit is the high pressure medium requirement and the resulting large space requirement for the low-pressure accumulator arrangement.

In contrast, the invention is based on the object of creating an electrohydraulic actuator arrangement using a bladder accumulator which is more compact than all of the above.

This object is achieved by an electrohydraulic actuator arrangement with the features of claim 1 and by the use of a bladder accumulator with the features of claim 19.

Further advantageous embodiments of the invention are described in the dependent claims.

The claimed electrohydraulic actuator assembly has an electric motor, a hydrostatic displacement unit and a rotary or linear hydrostatic actuator. The displacement unit can be driven by means of a coupling or coupled directly to the electric motor. The displacement unit supplies the actuator with pressure medium, with at least one bladder accumulator being provided for the intermediate storage of pendulum or differential volumes of the pressure medium. According to the invention, the displacement unit and the actuator and the bladder accumulator are arranged in a closed hydraulic system. Since there is no open tank, but the bladder accumulator closed off from the environment, there is a significantly reduced permeability of the overall system to the environment (partial pressure, undesired gas components in the pressure medium).

This also solves the problem, because there is a three to five times lower pressure medium requirement and thus a reduced space requirement of the actuator arrangement according to the invention compared to an open hydraulic system.

The actuator arrangement according to the invention also results in a reduced need for maintenance, since there is no need to change the pressure medium if the actuator arrangement has a low number of load changes over the life of the actuator arrangement. This system can be implemented as a plug & play solution. A controlled version with a soft start function can enable the actuator to start up smoothly. A controlled version, e.g. by means of a frequency converter, enables auto-sequential control.

If the displacement unit can be operated as a bidirectional pump, and if the actuator is designed to be bidirectional, the actuator arrangement can be operated bidirectionally. For energy recovery, the displacement unit can preferably be operated in four-quadrant operation.

According to the prior art, low-pressure accumulators are preloaded on their gas side higher than the ambient pressure so that they fulfill their function. Here, a bladder is filled with gas pressure and the pressure medium is stored under pressure between the bladder and the pressure medium container. The higher the partial pressure difference between the gas in the bladder and the pressure medium, the higher the probability that undesired permeability will occur and an increase in the partial pressure in the pressure medium will result, which means that gas will pass through the bladder into the pressure medium. which can have a detrimental effect on the overall hydraulic system.

In the case of the invention listed here, the pressure medium is collected in the bladder, which is preferably exposed to atmospheric pressure. Therefore, in a particularly preferred development of the actuator arrangement according to the invention, the bladder accumulator has a non-prestressed bladder, on the outside of which there is only ambient pressure and the permeability is less pronounced due to the less pronounced partial pressure difference.

In comparison to an open circuit of the prior art, in which active and / or passive degassing of the pressure medium is required permanently, in the case of the bladder accumulator with a non-pretensioned bladder, the actuator arrangement is only filled with a defined undersaturated pressure medium during the initial start-up, since the value of the Atmospheric oxygen in the pressure medium is below the limit at which dissolved air in the pressure medium changes into undissolved air and so no free gas bubbles form in the pressure medium, which can damage the entire actuator arrangement.

If the actuator does not have to change the number of load changes over its lifetime, it is not necessary to change the pressure medium.

Currently, in an electro-hydraulic drive unit for primarily regulated or controlled (direct) hydrostatic transmissions, e.g. for maritime applications, low-pressure accumulators are used to compensate for the differential volume in linear transmissions (differential cylinders). These low-pressure accumulators must be preloaded higher than the ambient pressure on the gas side so that they fulfill their function. Furthermore, permeabilitation can occur due to the partial pressure difference between the gas and pressure medium side. Using an expansion tank with a non-pretensioned bladder, it is possible to absorb the differential volume of the differential cylinder at ambient pressure and to build this up with a design that is up to three times more compact than with a pretensioned low-pressure bladder accumulator.

The advantage of the further development with the bladder accumulator which is only atmospherically preloaded is that its pneumatic side or gas side is not limited by a pressure vessel, since the gas - in particular air - can escape from an installation space or housing, and thus the entire volume of the installation space or Housing can be used as a compensating volume for the pressure medium, since no volume is required for pretensioned gas. The pressure medium is nevertheless separated from the pneumatic pressure medium or gas, so that it absorbs less of it.

This electro-hydraulic actuator arrangement for primarily regulated or controlled (direct) hydrostatic transmissions with non-preloaded expansion tanks should preferably be used in maritime applications Applications (e.g. in DAVIT systems) are used. This replaces hydraulic systems with open hydraulic circuits or secondary-driven hydraulic circuits (valve-operated). There is the possibility of building the actuator arrangement with standard components, which also contains bladder accumulators for the low pressure range to compensate for the differential volume. According to the state of the art, these bladder accumulators must be pressurized on the gas side in order to ensure the correct functioning of the bladder accumulator. As a result of the pretensioned pressure on the gas side, the volume of the bladder accumulator increases in comparison to a system according to the preferred development that is not pretensioned on the gas side. These bladder accumulators for the low pressure range can be replaced by an expansion tank with a non-pretensioned bladder in order to make the expansion tank more compact. Since there is a small difference in partial pressure between the gas side and the hydraulic side, permeabilitation (gas diffuses through a partition, also due to the partial pressure difference) is avoided or reduced in an expansion tank with a non-preloaded bladder, which means that no gas passes through the reservoir into the pressure medium got.

It is also possible with this type of expansion tank with a non-pretensioned bladder to design open systems according to the invention closed and to replace the expansion tank with an expansion tank with a non-pretensioned bladder. In comparison to an open system, which undergoes permanent pressure medium conditioning through active and / or passive degassing, in the case of the expansion tank with a non-pretensioned bladder it is only necessary to switch the hydraulic system into unsaturated (the value of the air oxygen in the pressure medium is below Limit at which dissolved air in the pressure medium changes into undissolved air) to fill pressure medium.

Thus, this invention can be used not only in a maritime environment, but in all fields of application of hydraulics.

In order to protect the bladder, it is particularly preferred if the bladder accumulator has a housing which surrounds the bladder at least in sections. The housing of the bladder accumulator can be roughly cuboid. Here the pressure medium is in the bladder and the housing (e.g. metal housing) does not have to be designed as a pressure vessel.

A hydraulic block or a valve block is preferably provided. The displacement unit and the bladder accumulator are attached to the hydraulic block. The electric motor can be attached to the hydraulic block or valve block either directly or indirectly via the displacement unit. Alternatively, the electric motor hydraulic pump unit can also be connected by a pump support.

The electric motor and / or the hydraulic block and / or the displacement unit can be covered by a hood. This provides protection against pollution and soundproofing.

A sensor, e.g. a temperature or pressure sensor, can be attached to the displacement unit or the hydraulic block or the actuator (e.g. differential cylinder).

A measuring connection can be provided on the displacement unit or on the hydraulic block or on the actuator (e.g. differential cylinder).

In a first design variant (with a somewhat slimmer shape) the bladder accumulator is attached to a side of the hydraulic block opposite the electric motor.

Then a compact design is preferred in which the design of the accumulator housing of the bladder accumulator transversely to an output shaft of the electric motor and / or transversely to a drive shaft of the displacement unit corresponds maximally, preferably approximately, to the extent of the hydraulic block and / or the electric motor.

In a second design variant (with a somewhat shorter, wider shape), the bladder accumulator is arranged to the side of and / or parallel to an output shaft of the electric motor and / or a drive shaft of the displacement unit.

In the second structural variant, too, a compact design (viewed in the transverse direction) is preferred in which the extent of the housing of the bladder accumulator transversely to the output shaft of the electric motor and / or transversely to the drive shaft of the displacement unit is at a maximum, preferably approximately the extent of the hydraulic block and / or the Electric motor corresponds.

Furthermore, in the second structural variant, a compact design (viewed in the longitudinal direction) is preferred in which the expansion of the housing of the bladder accumulator along the output shaft of the electric motor and along the drive shaft of the displacement unit corresponds to a maximum, preferably approximately that of the hydraulic block plus that of the electric motor.

The displacement unit and the actuator are connected to one another via two working lines. In the bidirectional configuration of the actuator arrangement (already addressed above) an additional low-pressure line is preferably provided, which can be connected, preferably automatically, to the working line to which low-pressure is applied. The bladder accumulator is then connected to the low-pressure line and connected to this bar.

In a fail-safe further development of the actuator arrangement according to the invention, a high-pressure accumulator - e.g. a piston accumulator - is provided which is charged in normal operation and which can supply the actuator with pressure medium instead of the displacement unit in emergency operation. In emergency operation, the high-pressure accumulator can be connected to the working line that is effective in the safety-relevant direction, e.g. in the direction of lifting, without external energy supply.

In connection with the non-pretensioned bladder (already mentioned above), there is the possibility of constructing the actuator arrangement with components in such a way that a repeated test of the accumulator in the low-pressure range is not necessary.

In emergency mode, ducts or hoses should be short. The high-pressure accumulator is therefore preferably attached to the actuator.

The displacement unit is e.g. an axial piston machine. The actuator is e.g. a motor or a cylinder e.g. a differential cylinder. The cylinder and the high-pressure accumulator are preferably aligned parallel to one another.

The actuator arrangement is preferably designed for a maritime application, in particular it is suitable for salt water and designed for maritime environmental influences. In the maritime application, the actuator arrangement according to the invention can be attached or attached in a davit system or a launching device for boats or on a hedge cover or on a hatch or on a lid or on a loading flap or on a safety bulkhead.

In addition, partially open hydraulic systems can be built as small as possible independently of maritime applications by designing them as a closed system and replacing the expansion tank open to the atmosphere in the open system with the bubble that is not pretensioned here with respect to the atmosphere and then the entire electrohydraulic actuator arrangement as a closed hydraulic one System executes.

In a preferred development, the actuator arrangement is initially filled with an unsaturated pressure medium whose partial pressure of dissolved gas is more than 0 mbar, but below a value at which the dissolved gas changes into free gas in the pressure medium.

The hydrostatic actuator is preferably a hydraulic differential cylinder, and the bladder accumulator is arranged to accommodate a differential volume which is released from or received into the differential cylinder when the differential cylinder is actuated.

For example, the bladder can be pillow-shaped or pocket-shaped.

The inventive use of an atmospheric bladder accumulator serves as a compensating volume in a closed hydraulic system for receiving or releasing a pendulum volume or a differential volume that is released from or received into the actuator when an actuator is actuated.

Also in the use according to the invention, the bladder accumulator is preferably initially filled with an unsaturated pressure medium whose partial pressure of dissolved gas is more than 0 mbar, but below a value at which the dissolved gas changes into free gas in the pressure medium.

Several exemplary embodiments of the actuator arrangement according to the invention are shown in the figures.

• 1 in einer perspektivischen schematischen Ansicht eine Anwendung der erfindungsgemäßen Aktuatoranordnung in einem Davit-System,
• 2 in einer perspektivischen Ansicht die Aktuatoranordnung gemäß einem ersten Ausführungsbeispiel,
• 3 einen Schaltplan der erfindungsgemäßen Aktuatoranordnung gemäß einem zweiten Ausführungsbeispiel,
• 4 in einer perspektivischen Ansicht die Aktuatoranordnung gemäß dem zweiten Ausführungsbeispiel in einer ersten konstruktiven Variante,
• 5 in einer Ansicht die Aktuatoranordnung gemäß dem zweiten Ausführungsbeispiel in einer zweiten konstruktiven Variante,
• 6 in einer weiteren Ansicht die Aktuatoranordnung aus 5, und
• 7 in einer teils geschnittenen Ansicht einen Ausschnitt der Aktuatoranordnung aus 6.

Show it

• 1 in a perspective schematic view an application of the actuator arrangement according to the invention in a davit system,
• 2 in a perspective view the actuator arrangement according to a first embodiment,
• 3 a circuit diagram of the actuator arrangement according to the invention according to a second embodiment,
• 4th in a perspective view the actuator arrangement according to the second embodiment in a first structural variant,
• 5 in a view the actuator arrangement according to the second embodiment in a second structural variant,
• 6th in a further view the actuator assembly 5 , and
• 7th a section of the actuator arrangement in a partially sectioned view 6th .

1 shows an application of all the exemplary embodiments of the actuator arrangement according to the invention shown in the following figures in one Davit system. The davit system is used to move a boat 1 from an inside to an outside of a side wall of a ship (not shown in detail) and for lowering the boat 1 to the water surface. For this purpose, the davit system has two cranes, which run along the side wall and in the longitudinal direction of the boat 1 are spaced from each other. Each crane has an actuator arrangement according to the invention, by means of which a boom 2 the crane can be extended or swiveled transversely to the drop side.

2 shows the actuator arrangement according to a first embodiment. Only a hood is shown 4th and directly adjacent to it a bladder accumulator arrangement consisting of three prestressed bladder accumulators 6th . Furthermore, the actuator arrangement has a differential cylinder 8th , the one hand pivotable to the boom 2 (see. 1 ) and on the other hand is pivotably coupled to the ship. By extending and retracting the differential cylinder 8th becomes the boom 2 extended or retracted.

Inside the hood 4th are an in 3 shown electric motor M, a hydraulic block 12th and a displacer unit P. arranged. The hood 4th protects these components from environmental influences and reduces the sound pressure level of the electric motor M and the displacement unit P. .

As the displacer unit P. and the differential cylinder 8th are connected to one another via a closed hydraulic circuit, the pressure medium requirement and thus the installation space requirement of the actuator arrangement is reduced compared to the prior art.

The electric motor M (e.g. direct current motor or alternating current motor (e.g. asynchronous motor, servo motor ...) is via a coupling or in a closed coupled variant with the hydraulic displacement unit P. connected for multi-quadrant operation and drives them.

In parallel with the differential cylinder 8th is a high-pressure accumulator designed as a piston accumulator 10 intended. This serves as a redundant pressure medium supply for the differential cylinder 8th and is related to 3 explained in more detail.

The hydraulic block 12th serves as a carrier to accommodate the electric motor M and the displacement unit P. . In the hydraulic block 12th becomes the suction option, the pressure protection of the displacement unit P. , pilot operated check valves as well as the adaptation for the bladder accumulator 6th ; 106 ; 206 to compensate for the differential volume of the differential cylinder 8th , as well as the connection option for the high-pressure accumulator 10 realized for redundant operation.

3 shows a circuit diagram of the actuator arrangement according to the invention according to a second embodiment, which is also shown in FIG 4th to 7th is shown. The difference between the second exemplary embodiment and the first exemplary embodiment can only be seen in the changed bladder accumulator.

The circuit of the actuator arrangement has two high-pressure-resistant working lines A. , B. via which the displacer unit P. with the differential cylinder 8th are connected according to the invention in a closed circuit. There is also a central low-pressure line ND provided via valves 13th with the working line leading to low pressure A. , B. is connected.

The hydraulic block 12th also serves as a holder for a hydraulic filter 14th between the valve 13th the respective low-pressure working line A. , B. and the central low pressure line ND . Furthermore are on the hydraulic block 12th Valves built to realize various extended hydraulic functions.

So is the central low pressure line ND via a respective spring-loaded check valve 16 with the two working lines A. , B. connected via which the suction function of the differential cylinder 8th is executed. Furthermore, the two working lines A. , B. via a respective pressure relief valve 18th to the central low pressure line ND relieved. There is a lowering brake valve in each of the two working lines 20th intended.

The work management A. is with a piston crown space of the differential cylinder 8th connected while the other working line B. with an annulus of the differential cylinder 8th connected is. The work management A. and the piston head space act in a safety-related priority in the lifting direction, while the other working line B. with the annulus in the lowering direction of the differential cylinder 8th Act.

If the electric motor M and / or the displacement unit acting as a pump P. should fail, the piston head space of the differential cylinder acting in the lifting direction can 8th via the corresponding work line prioritized in terms of safety A. from the high pressure accumulator 10 are supplied. With an application of the actuator arrangement in the davit system according to FIG 1 the boat 1 The ship can also be moved out and lowered in an emergency.

To the central low-pressure line that is always carrying low pressure ND is a bladder accumulator 106 ; 206 in particular for the differential volume between the two pressure chambers of the differential cylinder 8th connected. The bladder accumulator 106 ; 206 has a bubble 22nd , which is filled with pressure medium on the inside, and which is only exposed to ambient air and therefore ambient pressure on the outside. That’s the bubble 22nd in contrast to the prior art and in contrast to the first exemplary embodiment 2 not biased. It is therefore sufficient if the second exemplary embodiment of the actuator arrangement according to FIGS 3 to 7th is only filled with undersaturated pressure medium during the initial start-up.

Since - as in the first embodiment 2 - the displacer unit P. and the differential cylinder 8th via a closed hydraulic circuit with the two working lines A. , B. are connected to each other, and there - different from the first embodiment 2 - In addition, the bladder accumulator 106 ; 206 a non-pretensioned bladder 22nd has, the pressure medium requirement in the second embodiment is greatly reduced compared to that of the prior art, whereby the space requirement of the actuator arrangement is reduced.

4th shows a first structural variant of the second exemplary embodiment of the actuator arrangement according to the invention according to FIG 3 in a perspective view, with connecting hoses of the working lines A. , B. from the hydraulic block 12th to the differential cylinder 8th are not shown. Furthermore, the attachment of the high pressure accumulator 10 on the differential cylinder 8th and lines running therebetween are not shown.

It can be seen that the hydraulic block 12th is roughly cuboid and has an approximately square base. On an approximately square top of the hydraulic block 12th the electric motor M is arranged, while, in contrast, the displacement unit is initially arranged on an approximately square underside P. and then an enclosure 24 of the bladder accumulator 106 are set. The case 24 has a shape similar to that of the hydraulic block 12th is similar. More precisely, a cuboid housing is on an approximately square base 24 built up. In this first constructive variant of the second exemplary embodiment, there is thus a comparatively slim assembly made up of an electric motor M and a hydraulic block 12th , Displacement unit P. and bladder accumulators 106 educated.

The 5 and 6th show, in different views, an alternative structural variant of the second exemplary embodiment of the actuator arrangement according to the invention. When shown in 5 runs an output shaft 26th of the electric motor M or a drive shaft of the displacement unit P. perpendicular to the plane of the drawing. The housing extends transversely thereto 124 of the bladder accumulator 206 about as far as the hydraulic block 12th .

In 6th runs the output shaft of the electric motor M and the drive shaft of the displacement unit P. roughly across the plane of the drawing. The housing extends parallel to this 124 about as far as the hydraulic block 12th and the electric motor M together.

7th shows the second design variant according to 5 and 6th of the second embodiment of the actuator arrangement according to the invention, wherein the differential cylinder 8th and the high pressure accumulator 10 have been omitted. In a partly translucent representation of the hydraulic block 12th is the output shaft 26th of the electric motor M or the drive shaft 26th the displacement unit P. to recognize. As in 6th was visible, the case extends 124 of the bladder accumulator 206 in this direction about as far as the electric motor M and the hydraulic block 12th together.

Due to the cut representation of the bladder accumulator 206 is the elongated, non-prestressed bladder arranged in it 22nd to recognize. The bladder 22nd is via a connecting line 23 to the hydraulic block 12th connected.

The hydraulic block also serves 12th as a holder for measuring points and measuring sensors 28 .

The respective housing 24 ; 124 the non-preloaded bladder accumulators 106 ; 206 of the second embodiment are smaller than the total volume of the three prestressed bladder accumulators 6th of the first embodiment. The case 124 of the non-preloaded bladder accumulator 206 the second variant of the second embodiment is according to 7th flatter than the preloaded bladder accumulators 6th of the first embodiment according to 2 .

The respective housing 24 ; 124 the non-preloaded bladder accumulators 106 ; 206 of the second embodiment have through openings, so that the ambient pressure on the outside of the respective base 22nd is present.

An electrohydraulic actuator arrangement is disclosed which has a hydrostatic displacement unit that can be driven by an electric motor M P. which can be operated as a pump and preferably also as a motor. The displacement unit P. is for example an axial piston machine. Via a closed hydrostatic circuit A. , B. is the displacer unit P. connected to a hydrostatic actuator, for example a differential cylinder 8th is. A preferably non-prestressed bladder accumulator is used for the intermediate storage of pendulum or differential volumes 6th ; 106 ; 206 intended. The bladder accumulator, especially its housing 24 ; 114, is attached to a hydraulic block of the actuator arrangement in a space-saving manner.

List of reference symbols

1

boat

2

boom

4th

Hood

6th

preloaded bladder accumulator

8th

Actuator / differential cylinder

10

High pressure accumulator

12th

Hydraulic block

13th

Valve

14th

Hydraulic filter

16

check valve

18th

Pressure relief valve

20th

Counterbalance valve

22nd

bladder

23

Connecting line

24; 124

casing

26th

Output shaft / drive shaft

28

Measuring sensors

106; 206

non-preloaded bladder accumulator

A, B

Work management

ND

Low pressure line

P.

Displacement unit

Claims (20)

Electro-hydraulic actuator arrangement with an electric motor (M), by which a hydrostatic displacement unit (P) can be driven, from which a hydrostatic actuator (8) can be supplied, with at least one bladder accumulator (6; 106; 206) being provided for the intermediate storage of a pressure medium, thereby characterized in that the displacement unit and the actuator (8) are arranged in a closed hydraulic system. Actuator arrangement according to Claim 1 , wherein the bladder accumulator (106; 206) has a non-pretensioned bladder (22), on the outside of which there is ambient pressure. Actuator arrangement according to one of the preceding claims, wherein the bladder accumulator (106; 206) has a housing (24; 124) which surrounds the bladder (22) at least in sections. Actuator arrangement according to one of the preceding claims, having a hydraulic block (12) to which the displacement unit (P) and the bladder accumulator (6; 106) are attached. Actuator arrangement according to Claim 4 , wherein the bladder accumulator (106) is attached to a side of the hydraulic block (12) opposite the electric motor (M) Actuator arrangement according to Claim 4 , wherein the bladder accumulator surrounds the electric motor (M). Actuator arrangement according to Claim 4 , wherein the bladder accumulator (6; 206) is aligned parallel to the electric motor (M). Actuator arrangement according to Claim 4 and after Claim 5 or 7th , wherein the extension of the housing (24; 124) of the bladder accumulator (106; 206) transversely to an output shaft (26) of the electric motor (M) and / or transversely to a drive shaft (26) of the displacement unit (P) approximately the extension of the hydraulic block (12) corresponds. Actuator arrangement according to one of the preceding claims, wherein the displacement unit (P) and the actuator (8) are connected to one another via two working lines (A, B), and wherein a low-pressure line (ND) is provided which is connected to the working line ( A, B) can be connected, the bladder accumulator (6; 106; 206) being connected to the low-pressure line (ND). Actuator arrangement according to one of the preceding claims, with a high-pressure accumulator (10) for the redundant supply of pressure medium to the actuator (8). Actuator arrangement according to the Claims 9 and 10 , wherein the high-pressure accumulator (10) can be connected to that working line (A) which is prioritized in terms of safety. Actuator arrangement according to Claim 10 or 11 , wherein the high-pressure accumulator (10) is attached to the actuator (8). Actuator arrangement according to one of the Claims 10 to 12th , wherein the actuator (8) is a cylinder, and wherein the cylinder and the high-pressure accumulator (10) are aligned parallel to one another. Actuator arrangement according to Claim 4 and after one of the Claims 10 to 13th , wherein the high pressure accumulator (10) is a piston accumulator and is attached to the hydraulic block (12). Actuator arrangement according to one of the preceding claims, which is designed for a maritime application. Actuator arrangement according to one of the preceding claims, which is initially filled with an unsaturated pressure medium whose partial pressure of dissolved gas is more than 0 mbar, but below a value at which the dissolved gas changes into free gas in the pressure medium. Actuator arrangement according to one of the Claims 1 to 16 characterized in that the actuator (8) is a hydraulic differential cylinder, and that the bladder accumulator (6; 106; 206) is arranged to accommodate a differential volume that is released from the actuator (8) when the actuator (8) is actuated or in this is recorded. Actuator arrangement according to one of the preceding claims, wherein the bladder (22) is pillow-shaped or pocket-shaped. Use of an atmospheric bladder accumulator (6; 106; 206) as a compensating volume in a closed hydraulic system for receiving or releasing a pendulum volume or a differential volume that is released from or received into the actuator (8) when an actuator (8) is actuated. Use of a bladder accumulator (6; 106; 206) according to Claim 19 , wherein the bladder (22) is initially filled with an unsaturated pressure medium whose partial pressure of dissolved gas is more than 0 mbar, but below a value at which the dissolved gas changes into free gas in the pressure medium.

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