Electro-hydraulic actuator

Abstract

The invention relates to an electrohydraulic actuator (1), comprising at least one bidirectionally operable hydraulic pump (2) for conveying a hydraulic fluid, which hydraulic pump has two connection points (6a, 6b) which are designed to alternately supply and / or draw out hydraulic fluid, and a hydraulic actuator component (3) which is designed to alternately supply and / or draw out hydraulic fluid, the hydraulic actuator part (3) has two hydraulic fluid chambers (4a, 4b) into which hydraulic fluid can be supplied in order to actuate the hydraulic actuator part (3), in which: filling one of the hydraulic fluid chambers (4a, 4b) with hydraulic fluid causes the hydraulic fluid to be displaced from the other hydraulic fluid chamber (4b, 4a); a first connection point (6a) of the hydraulic pump (2) is connected by a first line (7a) to a first hydraulic fluid chamber (4a) of the hydraulic actuator part (3) and a second connection point (6b) of the electric hydraulic pump is connected by a second line (7b) to a second hydraulic fluid chamber (4b) of the hydraulic actuator part (3); a first releasable hydraulic closing element (8a) is arranged between the first hydraulic fluid chamber (4a) and the first line (7a) and a second releasable hydraulic closing element (8b) is arranged between the second hydraulic fluid chamber (4b) and the second line (7b); the releasable hydraulic closing element (8a, 8b) prevents an undesired outflow of hydraulic fluid from the hydraulic fluid chamber (4a, 4b); and the releasable hydraulic closing element (8a, 8b) is designed such that, for release, both an electrical release signal and a hydraulic release signal must be present at the releasable hydraulic closing element (8a, 8b).

Description

Technical Field

[0001] The present invention relates to an electro-hydraulic actuator, in particular a linear actuator, which can cause the linear actuator to move. The electro-hydraulic actuator comprises a hydraulic actuator component and an electrically driven hydraulic pump, which provides hydraulic fluid to drive the hydraulic actuator component.

[0002] In particular, the electrohydraulic actuators described herein can operate in up to four quadrants, i.e., the actuators are four-quadrant capable. Four-quadrant capability means that the electrohydraulic actuator can be driven with electrical energy in both directions of motion to produce actuator motion and, in addition, recuperation is also possible in both directions of motion, wherein mechanical energy can be extracted from the actuator motion and converted into electrical energy.

[0003] Such an electrohydraulic actuator is particularly suitable for electrification and increasing the energy efficiency of mobile machines with hydraulic components. Due to the four-quadrant capability of such a linear actuator, a considerable amount of energy can be recovered as electrical energy during the operation of the mobile machine. This would be possible, for example, in the case where an excavator shovel driven by an electrohydraulic actuator is lowered. The potential energy of the excavator shovel can then be dissipated into a hydraulic fluid flow using the hydraulic actuator components. Energy can be extracted from this hydraulic fluid flow and converted into electrical energy using an electric hydraulic pump in generator mode. Background Art

[0004] Hydraulic actuators are often safety-relevant components. For example, in the case of hydraulic actuators in mobile machinery, in the event of a fault, it must be ensured that no unwanted or uncontrolled movements of components of the mobile machine occur. For example, a crane arm or an excavator bucket must not fall in an uncontrolled manner in the event of a fault. The ability to recover from this situation is covered in the field of "functional safety". Summary of the invention

[0005] The object of the present invention is to describe an electrohydraulic actuator which has particularly good properties with regard to operational safety in the event of a possible fault and which at the same time has an advantageous design.

[0006] This object is achieved by the invention according to the features of the independent claims. Further advantageous embodiments are given in the independently formulated claims as well as in the description and in particular also in the description of the drawings. It should be noted that a person skilled in the art will combine the individual features with one another in a technically meaningful manner to arrive at further embodiments of the invention.

[0007] An electrohydraulic actuator will be described herein, the electrohydraulic actuator having at least one bidirectionally operable electrohydraulic pump for conveying hydraulic fluid, the pump having two connection points, the pump being designed to alternately supply and / or remove hydraulic fluid, and the electrohydraulic actuator having a hydraulic actuator component having two hydraulic fluid chambers into which hydraulic fluid can be supplied in order to actuate the hydraulic actuator component, wherein filling one of the hydraulic fluid chambers with liquid fluid simultaneously causes hydraulic fluid to be displaced from the other hydraulic fluid chamber, wherein a first connection point of the hydraulic pump is connected via a first line to the hydraulic actuator component. to a first hydraulic fluid chamber of the hydraulic actuator component, a second connection point of the hydraulic pump is connected to a second hydraulic fluid chamber of the hydraulic actuator component via a second line, wherein a first releasable hydraulic closing element is arranged between the first hydraulic fluid chamber and the first line, and a second releasable hydraulic closing element is arranged between the second hydraulic fluid chamber and the second line, wherein the releasable hydraulic closing element prevents an undesired outflow of hydraulic fluid from the hydraulic fluid chamber, wherein the releasable hydraulic closing element is arranged in such a way that for release both an electrical release signal and a hydraulic release signal have to be applied to the releasable hydraulic closing element.

[0008] The selection of the structure and design of the electrohydraulic actuator (in particular the structure of the hydraulic actuator component and the electrohydraulic pump) is described in detail below. In principle, it is preferred that both the hydraulic pump and the actuator component have two connection points for the hydraulic fluid (as inlet or outlet, respectively), both connection points being connected to each other via a pipeline, thereby forming a transmission circuit for the hydraulic fluid. In addition, various designs of hydraulic pumps and actuator components can be used. It should also be noted that the hydraulic actuator component can also be a parallel connection of several hydraulic (single) actuator components. For example, the hydraulic actuator component can be a pair of hydraulic cylinders acting side by side (in parallel), which together with the electrohydraulic pump form an electrohydraulic actuator and which are referred to as tandem cylinders. Then, the pipeline from the hydraulic pump to the hydraulic (single) actuator component is preferably branched, wherein the branch can be understood as part of the actuator component. In principle, it is possible to divide the actuator component into (single) actuator components, just as it is possible to divide the hydraulic pump into (single) hydraulic pumps.

[0009] In order to achieve particularly good protection with regard to functional safety by means of a releasable hydraulic closing element, it is advantageous if the releasable hydraulic closing element is arranged directly at the transition of the line to the hydraulic fluid chamber of the actuator component. Several releasable hydraulic closing elements arranged at corresponding connection points of (individual) actuator components connected in parallel to one another of a hydraulic (monolithic) actuator component can then also be understood as a (common) releasable hydraulic closing element.

[0010] Therefore, the releasable hydraulic closing element is arranged between the pipeline connecting the actuator component and the hydraulic pump and the hydraulic fluid chamber. The releasable hydraulic closing element is designed to hydraulically separate the hydraulic fluid chamber of the actuator component from the pipeline. If the releasable hydraulic closing element is locked or released, the escape of hydraulic fluid from the hydraulic fluid chamber can be reliably prevented by the releasable hydraulic closing element. The releasable hydraulic closing elements are designed to be locked in the idle state (no release signal acts on them).

[0011] The term "released" means that the releasable hydraulic closing element is open. In this case, the releasable hydraulic closing element preferably has no effect or a small effect on the flow of hydraulic fluid into or out of the hydraulic fluid chamber or in the pipeline. In order to release the releasable hydraulic closing element, both the release signal (electrical release signal and hydraulic release signal) must be applied to the releasable hydraulic closing element. In normal operation, the hydraulic closing element is released and therefore both the release signal (electrical release signal and hydraulic release signal) are applied to the releasable hydraulic closing element. At least one release signal can also be applied indirectly, for example via the releasable hydraulic closing element, and the electrohydraulic actuator is arranged in such a way that the hydraulic release signal is only forwarded to the releasable hydraulic closing element if the electrical release signal is also present.

[0012] The arrangement of a releasable hydraulic closure element between the line connecting the actuator component to the hydraulic pump and the hydraulic fluid chamber meets all or part of the following characteristics:

[0013] Advantageously, no further branches to other hydraulic components (such as expansion tanks, intermediate circuits, etc.) are provided between the releasable hydraulic closing element and the hydraulic fluid chamber. However, compensating lines can be provided to other parallel cylinders, together forming the actuator component. Such compensating lines are common, for example, between two individual cylinders of a tandem cylinder chain, as is often used, for example, in the lowest stage of an excavator arm.

[0014] - The hydraulic fluid carrying part on the side of the releasable hydraulic closure element facing the hydraulic fluid chamber preferably has a very high leakage resistance. Preferably, this hydraulic fluid carrying part is not made of a flexible material such as a hose or the like,

[0015] And can be completely metal.

[0016] -If the electrical release signal required for release and the hydraulic release signal required for release are not present, the hydraulic closing element is advantageously arranged to be closed, regardless of other boundary conditions. Such a further boundary condition is, for example, a maximum permissible pressure in the actuator component, which, if exceeded, can cause the actuator component to burst. Another such boundary condition is, for example, a maximum permissible braking acceleration of the actuator component, which, due to the mass inertia, can trigger forces and / or torques exceeding the permissible limit values ​​on the mobile machine. Many other such boundary conditions usually exist. When the hydraulic closing element is closed due to a missing in the release signal, this boundary condition is not taken into account. If this boundary condition is exceeded or violated, regardless of the possible effects, locking is performed to ensure the safety of the electrohydraulic actuator. Preferably, however, the hydraulic closing element has an additional function, which is integrated in the valve and ensures that the actual exceeding of this boundary condition does not occur. This additional function is in particular a bypass function, which takes effect when a certain limit pressure is exceeded and is explained in more detail below.

[0017] It is particularly advantageous if the releasable hydraulic closing element is a releasable non-return valve.

[0018] Preferably, when the aforementioned release signal is absent, the releasable hydraulic closing element acts as a non-return valve, in particular within the working pressure range. This means that within the working pressure range, hydraulic fluid can flow into the hydraulic fluid chamber, but hydraulic fluid cannot flow out. The "working pressure range" here refers to the pressure range of the hydraulic fluid in the line and the hydraulic fluid chamber, which usually occurs during the operation of the electrohydraulic actuator, wherein pressure peaks that occur, for example, due to sudden valve closing and / or acceleration of the hydraulic fluid volume in the line are preferably not within the working pressure range. Such pressure peaks are preferably outside the working pressure range. Preferably, the releasable hydraulic closing element has an additional function in the form of a bypass channel and / or a bypass function, which opens at a pressure above the working pressure range and then, although acting as a non-return valve within the working pressure range, allows a limited amount of hydraulic fluid to pass through in order to buffer such pressure peaks and prevent the working pressure range from being permanently covered. This function is mainly used for component protection, for example, in order to prevent hydraulic actuator components from bursting due to pressure peaks that occur in the hydraulic fluid chamber, which pressure peaks occur due to sudden deceleration caused by the closing of the releasable hydraulic closing element.

[0019] If necessary, an additional function or a bypass function can be realized by a pressure reducing valve acting in parallel with the hydraulic closing element, which opens at a pressure above the working pressure limit value, thereby allowing a certain braking distance of the actuator part. At pressures in the working pressure range or below the working pressure limit value, such a pressure reducing valve is preferably ineffective. If the closing element closes as quickly as possible and as a result the working pressure limit value is exceeded, the parallel-acting pressure reducing valve opens, for example, in such a way (as far as possible and / or as long as possible) that a compromise is achieved between the "braking distance" and the load on the actuator part.

[0020] Another alternative to the pressure relief valve in the bypass is that a releasable hydraulic closing element can be provided for damped closing. This can also reduce pressure peaks. Therefore, if one of the release signals is omitted, the releasable hydraulic closing element preferably closes after a certain time delay, which can also depend on the applied / occurring pressure.

[0021] In principle, hydraulic closing elements are designed so that in normal operation (in the open state when the release signal is applied), they cause the lowest possible flow resistance and pressure drop when hydraulic fluid flows into or out of the hydraulic fluid chamber. This is beneficial for the best possible energy efficiency of the electrohydraulic actuator.

[0022] It is advantageous if the hydraulic actuator component has a displaceable element, the hydraulic fluid chambers are connected to each other via the displaceable element, and wherein the hydraulic actuator component at least partially forms a transmission circuit with the pipeline and the hydraulic pump, so that hydraulic fluid separated from one hydraulic fluid chamber can flow directly into another hydraulic fluid chamber via the pipeline and the hydraulic pump.

[0023] In this case, the term "directly" flowing into a cavity means, in particular, that the hydraulic fluid flowing out of the hydraulic fluid cavity does not first flow into a reservoir for hydraulic fluid, but flows via the hydraulic pump directly into another hydraulic fluid cavity of the same hydraulic actuator component, wherein several hydraulic actuator components are connected to a reservoir for hydraulic fluid.

[0024] Therefore, when using an electrohydraulic actuator, preferably there is a cyclic transmission of hydraulic fluid in the transmission circuit, in which the displaceable element in the hydraulic actuator component participates. The term "communication" of the hydraulic fluid chamber means that, in particular, the change in the volume of one hydraulic fluid chamber always necessarily causes the change in the volume of another hydraulic fluid chamber. On the one hand, the displaceable element is moved by the hydraulic fluid. On the other hand, the displaceable element also transmits the movement of the hydraulic fluid in one of the hydraulic fluid chambers to another hydraulic fluid chamber, and vice versa. By driving the hydraulic pump with different transmission directions, the displaceable element can be moved by the hydraulic fluid. The actuator movement of the actuator component is the movement of the displaceable element and the components connected to it. Preferably, the transmission circuit is not completely independent, but is connected to the intermediate hydraulic circuit via other hydraulic components. However, this intermediate circuit itself does not directly participate in the cyclic transmission of the hydraulic fluid in the transmission circuit, but is arranged to ensure the suitable operating conditions for the cyclic transmission in the transmission circuit. Further explanation is provided below and in particular in the description of the figure.

[0025] Furthermore, it is advantageous if the hydraulic fluid chambers of the hydraulic actuator components have hydraulic cross-sections that differ from one another so that when the displaceable element is displaced, a volume change (deltavolume) occurs as the total volume of the hydraulic fluid chamber changes, wherein the hydraulic pump has a two-part pump chamber, a first part of the pump chamber being connected to a pipeline to form a transmission circuit, and a second part of the pump chamber being connected to a pipeline to a hydraulic fluid chamber having a larger hydraulic cross-section and to a hydraulic fluid reservoir, the volume change can be compensated by the hydraulic fluid reservoir.

[0026] Hydraulic actuator components, in which two corresponding hydraulic fluid chambers have different hydraulic cross-sections, are common. They are often referred to as differential components (e.g. differential cylinders). The different volumes are caused, for example, by the fact that one of the two hydraulic fluid chambers accommodates a feed rod which transmits the movement of the displaceable element to a component of the mobile machine (e.g. to the arm of an excavator).

[0027] For hydraulic actuator components of this type, the principle of cyclic transmission and transmission circuits is only possible for the part of the hydraulic fluid that can be absorbed into the hydraulic fluid chamber with the smaller hydraulic cross section. The additional amount of fluid escaping from the hydraulic fluid chamber with the larger hydraulic cross section is referred to herein as "volume change". The volume change must not only be discharged when the displaceable element moves towards the hydraulic fluid chamber with the larger hydraulic cross section and the volume of this hydraulic fluid decreases. The volume change must also be supplied when the displaceable element moves towards the hydraulic fluid chamber with the smaller hydraulic cross section and the volume of the hydraulic fluid chamber with the larger hydraulic cross section increases.

[0028] To achieve this, a hydraulic pump with a two-part pump chamber is proposed herein. The first partial pump chamber forms part of a transfer circuit. The size of the first partial pump chamber is determined so that the volume that can flow from one hydraulic fluid chamber to another hydraulic fluid chamber is transported with it. The second partial pump chamber is used to pump hydraulic fluid from a hydraulic fluid reservoir into the circuit, or to discharge hydraulic fluid from the circuit into a hydraulic fluid reservoir. This is used to balance the volume change, i.e. supply or discharge, according to the direction in which the displaceable element is moved. Preferably, both partial pump chambers are connected to a common pump drive motor, possibly via a common shaft. Via the two partial pump chambers, energy can be supplied to and extracted from the hydraulic fluid flow so as to be converted (recovered) into electrical energy.

[0029] It is also advantageous if the first line and the second line are each connected to a reservoir for the hydraulic fluid, which reservoir is arranged in a closed hydraulic system to compensate for function-related fluctuations with a minimum system pressure.

[0030] It is also advantageous if the reservoir is connected to the first line and the second line via further hydraulic closing elements, wherein these further hydraulic closing elements prevent the operating pressure generated by the hydraulic pump in one of the two lines from being transmitted to the reservoir.

[0031] Such a reservoir is preferably part of the hydraulic intermediate circuit described above. Preferably, this reservoir is connected to the line via a further hydraulic closing element, in particular a non-return valve, and via which the hydraulic fluid can flow into the line if the minimum pressure is no longer maintained there. However, the reservoir is designed in such a way that no leaks in the line can be compensated by the reservoir, but only possible function-related fluctuations, for example due to fluctuating ambient pressure, thermal expansion behavior of the hydraulic fluid and similar phenomena.

[0032] Preferably, the reservoir is also connected to the delivery circuit in such a way that excess pressure can also be discharged from the delivery circuit into the reservoir. The reservoir and the hydraulic intermediate circuit are preferably connected to a hydraulic fluid supply which provides the reservoir and the intermediate circuit with the amount of hydraulic fluid required to support the pumping operation.

[0033] It is also advantageous if the releasable hydraulic closing element has a hydraulic release signal input, to which the hydraulic signal line is connected, via which the presence of a hydraulic system pressure of the electrohydraulic actuator is monitored as hydraulic release signal.

[0034] The hydraulic signal line is a functional connection to a hydraulic and / or hydraulic-mechanical component. The signal-conducting connection can be implemented using any technical means. During normal operation of the electrohydraulic actuator, the signal-conducting connection represents a connection to a component in which or on which a hydraulic system is present. The hydraulic system pressure is transmitted via the signal-conducting connection to the hydraulic release signal and there serves as a hydraulic release signal. If the hydraulic system pressure drops or falls below a threshold value, this is transmitted via the signal-conducting connection to the hydraulic release signal. There, the hydraulic release signal disappears and the releasable hydraulic closing element closes.

[0035] The hydraulic release signal input is preferably an active surface on the releasable hydraulic closure element to which a minimum pressure must be applied for release. If necessary, the release signal input can also be arranged so that a maximum pressure must not be exceeded. The hydraulic release signal will thus be an applied pressure signal in a specific pressure range.

[0036] For monitoring the hydraulic system pressure, it is also advantageous if the hydraulic release signal input is connected to the reservoir via a hydraulic signal line.

[0037] Preferably, there is a pressure transmission line from the reservoir to the two releasable hydraulic closing elements. If necessary, the pressure transmission line can be realized in several parts. If necessary, the pressure transmission line can also be interrupted by a pressure transmission element, which prevents the hydraulic fluid from escaping, but transmits pressure changes to the release signal input. The connection between the reservoir and the hydraulic release signal input is also in particular a purely functional connection, which enables the pressure or pressure changes in the reservoir to be transmitted to the hydraulic release signal input.

[0038] It has been found that the pressure in the reservoir using the intermediate circuit is a very effective parameter for determining whether there is a fault in the hydraulic components of the electrohydraulic actuator, which justifies or necessitates the closing of the releasable hydraulic closing element. Operation-related pressure fluctuations in the transmission circuit are compensated by the reservoir. As long as the reservoir (only) compensates for operating fluctuations in the transmission circuit that are not the cause of a fault (leakage, etc.), the hydraulic fluid supplier preferably facilitates maintaining the pressure in the reservoir. If the fluctuations can no longer be compensated by the reservoir, it can be assumed that the fluctuations are due to a fault (leakage, etc.). In this case, it is desirable to block the hydraulic closing elements that can be released or to stop releasing them. This behavior can be achieved by connecting the reservoir to the hydraulic release signal input.

[0039] It is also advantageous if the releasable hydraulic closing element has at least one electric release signal input, at least one electric release signal input is connected to an electric signal line and via at least one electric release signal input the presence of a functional signal of a driving power supply and / or a controller of the electric hydraulic pump and / or a functional signal of the electric hydraulic pump is monitored as an electric release signal.

[0040] This electrical signal line is preferably also a functional connection, which is preferably at least partially implemented with the electrical component.

[0041] The electrical release signal is preferably used to monitor whether there is a fault in the electrical components of the electrohydraulic actuator, such as the absence of the supply voltage of the control unit, an interruption in the drive power supply, etc. In an embodiment, the presence and absence of other voltages and / or signals (in particular several voltages) can also be monitored or monitored at the electrical release signal input.

[0042] In particular, the electrical release signal is used to monitor whether overvoltage and / or undervoltage occurs in a drive power supply of the control unit and / or in power electronics in the drive power supply (eg in an inverter for supplying power to an electric hydraulic pump).

[0043] Preferably, a control unit for self-monitoring the inverter is present in the driver power supply. Preferably, this control unit issues a so-called "enable signal" which can be used as a release signal and is connected to the electrical release signal input via a line.

[0044] Such a control unit in a driver power supply monitors internal signals and states and detects (more or less reliably) a "runaway".

[0045] If necessary, a setpoint / actual value deviation provided by an external (safety) electronic device which monitors the movements of the actuator component can, for example, be taken into account as an electrical release signal. The external (safety) electronic system is in particular an electronic system which is located on the electrohydraulic actuator component described herein and is preferably arranged to monitor the functioning of the electrohydraulic actuator component in its intended function. For example, if the electrohydraulic actuator component is used to actuate an excavator arm, then the external (safety) electronic device can, for example, be connected to a sensor which monitors the movements of the excavator arm and determines whether these movements are moved as expected and desired due to the control signals to the electrohydraulic actuator.

[0046] For example, travel and speed signals can be determined and monitored. For example, such signals can be transmitted from external (safety) electronics to the control unit of the electric hydraulic pump, where, if necessary, these signals can be collected and evaluated. As long as the target values ​​or target value ranges for these signals are maintained by the actual values ​​of these signals, an electrical release signal is preferably output, which is applied to the electrical release signal input. As soon as the actual value exceeds or leaves these target values ​​and / or target value ranges, the electrical release signal is preferably no longer provided. The releasable hydraulic closing element is then blocked.

[0047] External (safety) electronics can also preferably be used to evaluate measured values ​​about the operation of the electrohydraulic actuator itself. For example, pressure sensors, force sensors, acceleration sensors, etc. can be provided on components of the electrohydraulic actuator to monitor its function. This allows very high safety standards to be maintained.

[0048] The electric hydraulic pump is preferably controlled by a controller. Preferably, the controller has at least one output stage, which drives the electric drive power for the hydraulic pump in response to a control signal from a higher-level control component of the mobile work performing machine, so that the hydraulic actuator component performs the desired actuator movement. The supply voltage can be, for example, an input voltage of the output stage, which is used by the control system in response to the control signal to transmit the electric drive power to the hydraulic pump. Electrical parameters that can be determined in the output stage and are essential for the operation of the electrohydraulic actuator can also be used as electrical release signals.

[0049] In a preferred embodiment, the electrical release signal is a digital signal, which is formed from various individual release signals, wherein the individual release signals are associated with each other in a suitable manner, for example by an AND link, so that several individual release signals must be present simultaneously to form the electrical release signal, or by an OR link, so that several individual release signals must be present alternatively to each other to form the electrical release signal. If necessary, more complex networks can exist, which form the electrical release signal from a large number of individual signals.

[0050] It is particularly advantageous if the hydraulic pump is arranged in such a way that it can also act as a generator in order to convert the mechanical energy of the hydraulic fluid flow from one connection point to another connection point into electrical energy.

[0051] The electrohydraulic actuator is particularly preferably arranged to transmit the mechanical energy via lines to the hydraulic actuator component and via the hydraulic fluid to an electrohydraulic pump and to recover the mechanical energy as electrical energy using the hydraulic pump.

[0052] The possibility of operating the hydraulic pump in generator mode has been explained above in conjunction with the four-quadrant capability of the electrohydraulic actuator. The electrohydraulic actuator described here is a four-quadrant actuator with recuperation capability and at the same time a high level of functional safety (due to the releasable hydraulic closing elements and their association with the electrical and hydraulic release signals).

[0053] It is also advantageous if the hydraulic actuator component is a linear actuator.

[0054] The described design is particularly suitable for providing an actuator that can be used to generate very large linear forces.

[0055] The electrohydraulic actuators described herein are preferably arranged to produce a mechanical output in excess of 10 kW (kilowatts).

[0056] A mobile work performing machine will also be described herein, which comprises at least one electrohydraulic actuator as described.

[0057] For example, the mobile work performing machine may be an excavator or similar machine. However, the electrohydraulic actuator described herein may also be used in other applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention and the technical content of the present invention are explained in more detail below with reference to the accompanying drawings. The accompanying drawings show preferred exemplary embodiments to which the present invention is not limited. In particular, it should be pointed out that the accompanying drawings and in particular the scaling shown in the accompanying drawings are only schematic. The accompanying drawings show:

[0059] Figure 1 : a first variant of the described electrohydraulic actuator, and

[0060] Figure 2 : A second variant of the described electrohydraulic actuator. DETAILED DESCRIPTION

[0061] Figure 1 A variant of the described electrohydraulic actuator 1 is shown in which the hydraulic actuator part 3 has hydraulic fluid chambers 4a, 4b with identical hydraulic cross sections 20a and 20b. The total actuator volume 5 is here independent of the position of the displaceable element between the two hydraulic fluid chambers 4a and 4b. Figure 2A variant of the described electrohydraulic actuator 1 is shown, in which the hydraulic actuator component 3 has hydraulic fluid chambers 4a, 4b having different hydraulic cross-sections 20, 20b. The total actuator volume 5 here depends on the position of the displaceable element between the two hydraulic fluid chambers 4a and 4b and is variable. Such a hydraulic actuator component 3 is also called, for example, a differential hydraulic actuator component 3 or (in the case of a hydraulic cylinder as hydraulic actuator component 3) also a "differential cylinder". Such differential hydraulic actuator components 3 are widely used. The invention described here does not differ fundamentally with respect to whether the hydraulic actuator component 3 is a differential hydraulic actuator component 3 or not. However, some differences need to be pointed out in order to make it clear in detail. Figure 1 and Figure 2 In the embodiment of the present invention, the electrohydraulic actuator 1 according to the invention is described once in the case of a differential hydraulic actuator component 3 and once in the case of a non-differential hydraulic actuator component 3. However, the same features in both variants will be described together here.

[0062] The electrohydraulic actuator 1 has a hydraulic actuator part 3 and an electric hydraulic pump 2, which can be driven by an electric pump drive motor 26. The hydraulic actuator part 3 usually has two hydraulic fluid chambers 4a, 4b, between which there is a displaceable element 19, which can be moved by filling one hydraulic fluid chamber 4a, 4b and simultaneously emptying the other hydraulic fluid chamber 4b, 4a to produce an actuator movement 24. In this way, large forces can be generated in the hydraulic actuator part 3, which can be used, for example, to drive an excavator arm or a crane arm.

[0063] In the electrohydraulic actuator 1 described here, the two hydraulic fluid chambers 4a and 4b are connected to the connection points 6a and 6b of the electric hydraulic pump 2 via the lines 7a and 7b, respectively. The hydraulic actuator component 3 or the two hydraulic fluid chambers 4a, 4b of the hydraulic actuator component 3, the lines 7a, 7b and the electric hydraulic pump 2 together form a transfer circuit 10. The electric hydraulic pump 2 can be used to build up pressure at one of its connection points 6a, 6b and provide hydraulic fluid under pressure at this connection point 6a, 6b so that the hydraulic fluid flows via the corresponding lines 7a, 7b into the corresponding hydraulic fluid chamber 4a, 4b of the actuator component. In the process, the hydraulic pump 2 transfers hydraulic fluid, which is provided to the hydraulic pump 2 at the corresponding other connection point 6b, 6a and is thus removed from the corresponding other hydraulic fluid chamber 4b, 4a via the corresponding other lines 7b, 7a. The hydraulic pump 2 can be operated selectively in two conveying directions, i.e. to provide hydraulic fluid under pressure at the first connection point 6a or at the second connection point 6b, thereby generating an actuator movement 24 in different directions with the hydraulic actuator part 3. In this way, the electrohydraulic actuator 1 can be used to convert electrical energy into mechanical energy, which is provided at the hydraulic actuator part 3. The electrical energy is first converted into hydraulic energy by the electrohydraulic pump 2 and then into mechanical energy by the hydraulic actuator part 3 with the actuator movement 24. The actuator movement 24 can be used, for example, to move an excavator shovel driven by the hydraulic actuator part 3. The electrohydraulic pump 2 is operated here in a so-called conveying mode. The pump drive motor 26 is driven electrically here. This is preferably possible in two conveying directions.

[0064] With the help of the electrohydraulic actuator 1, it is also preferably possible to convert the mechanical energy of the actuator movement 24 into electrical energy. First, the mechanical energy of the actuator movement 24 is converted or recovered into hydraulic energy with the actuator part 3 and then converted into electrical energy with the electrohydraulic pump 2 or the electric pump drive motor 26. This can be used, for example, to convert the potential energy of an excavator shovel driven by the hydraulic actuator part 3 into electrical energy. The electrohydraulic pump 2 then operates in a so-called generator mode. This is also preferably possible in both conveying directions.

[0065] An electric hydraulic pump 2 which can operate in both directions in the transmission mode and in the generator mode is also referred to as having four-quadrant capability. Thus, the transmission circuit 10 formed by the lines 7a, 7b, the hydraulic pump 2 and the hydraulic actuator component 3 or its hydraulic fluid chambers 4a, 4b can be operated in both directions in the transmission mode or in the generator mode.

[0066] The electrohydraulic actuator 1 or the transmission circuit and in particular the lines 7a, 7b are connected to the hydraulic intermediate circuit 25. The hydraulic intermediate circuit 25 has only an indirect effect on the generation of electrical energy into mechanical energy at the hydraulic actuator component 3 and the recovery of mechanical energy into electrical energy at the hydraulic actuator component 3, i.e. ensuring suitable hydraulic conditions in the transmission circuit 10 so that both the transmission operation and the generator operation are possible with the highest possible efficiency of the conversion of electrical energy into mechanical energy and vice versa.

[0067] The intermediate circuit 25 comprises a plurality of further hydraulic components 9, the most important of which are briefly explained here. The hydraulic intermediate circuit 25 is connected to the lines 7a and 7b with further hydraulic closing elements 12a and 12b. If the pressure in one of the two lines 7a and 7b of the delivery line 10 is too low, the additional closing elements 12a and 12b allow the hydraulic fluid to flow into the delivery circuit 10. However, the hydraulic intermediate circuit 25 is arranged in such a way that no hydraulic fluid losses exceeding a threshold value are compensated in the delivery circuit 10, but only fluctuations which are acceptable during normal operation.

[0068] Preferably, the hydraulic intermediate circuit 25 has a reservoir 11 which contains a hydraulic fluid reservoir which is prepared for receiving hydraulic fluid from the transmission circuit 10 via closing elements 12a, 12b and pressure relief and for releasing the hydraulic fluid to the transmission circuit 10, where it remains in conditions suitable for operation. The intermediate circuit 25 and in particular the reservoir 11 itself are supplied with hydraulic fluid, for example by a hydraulic fluid supply 18.

[0069] At the connection between the hydraulic fluid chambers 4a, 4b and the lines 7a, 7b, there are releasable hydraulic closing elements 8a, 8b, which are in particular non-return valves. When this releasable hydraulic closing element 8a, 8b is closed, the hydraulic fluid can no longer escape from the hydraulic fluid chambers 4a and 4b. In this way, the hydraulic actuator component 3 is locked. Therefore, the releasable hydraulic closing element 8a, 8b ensures that if the hydraulic actuator component 3 or other components of the mobile work performing machine 15 fail, the hydraulic actuator component 3 or the components driven by it (such as an excavator shovel) do not perform any undesired (uncontrolled) movements.

[0070] The releasable hydraulic closing elements 8a, 8b are arranged so that they are closed unless two independent release signals, namely the electrical release signal and the hydraulic release signal, are present. The electrical release signal and the hydraulic release signal are thus linked to one another at the releasable hydraulic closing elements 8a, 8b or are preferably linked to one another in a logical AND operation by the structure of the releasable hydraulic closing elements 8a, 8b. Preferably, the releasable hydraulic closing elements 8a, 8b have a hydraulic release signal input 13 for the hydraulic release signal and an electrical release signal input 14 for the electrical release signal.

[0071] When the hydraulic components of the electrohydraulic actuator 1 are operating normally, there is a hydraulic release signal. For example, if there is a leak in the first line 7a and / or the second line 7b, the hydraulic release signal is omitted. The hydraulic release signal is preferably derived at the reservoir 11 of the hydraulic intermediate circuit 25 described previously. If the pressure in the reservoir 11 is higher than a predetermined threshold pressure, there is a hydraulic release signal. The pressure in the reservoir 11 can be used to monitor the tightness of the entire system consisting of the transmission circuit 10 and the intermediate circuit 25. If the pressure in the reservoir 11 is higher than the threshold pressure, it can be confirmed that there is no leak in the transmission circuit 10 and / or the intermediate circuit 25. Preferably, the reservoir 11 is directly connected to the hydraulic release signal input 13 of the releasable hydraulic closing elements 8a, 8b via a hydraulic signal line 27.

[0072] When the electrical components of the electrohydraulic actuator 1 and possibly also the higher-level components of the mobile work performing machine 15 are functioning properly, the electrical release signal is present. The electrical release signal can be obtained, for example, at the electrical control unit 17 of the electrohydraulic pump 2, which controls the pump drive motor 26 of the electrohydraulic pump 2. Preferably, the electrical control unit 17 is arranged to produce the electrical release signal from the drive power supply 16, internal electrical variables of the electrical control unit 17 and other variables that may be received by the electrical control unit from external safety electronics. The electrical release signal can preferably be formed by individual release signals, which are connected to each other by suitable links (AND links or OR links) to form an electrical release signal that represents the complete functionality of the electrical components of the electrohydraulic actuator 1. If the electrical release signal is applied to the releasable hydraulic closing elements 8a, 8b, it can be assumed that the electrical components of the electrohydraulic actuator 1 (in particular the pump drive motor 26, the control unit 17 and the drive power supply 16) are fully functional. Preferably, the electrical release signal is directly forwarded to the release signal input 14 of the releasable hydraulic closing element 8a, 8b via the electrical signal line 28. The control unit 17 is preferably supplied with electrical energy for the electrohydraulic actuator 1 by the drive power supply 16, which provides a supply current or a supply voltage. Preferably, the control unit 17 and the drive power supply 16 are also capable of recovery. This means that the energy recovered from the electrohydraulic actuator 1 can be fed back into the drive power supply 16.

[0073] The above explanation first describes the use of Figure 1 The operating mode of the electrohydraulic actuator 1 of the illustrated variant is shown. Figure 2 The electrohydraulic actuator 1 shown with a differential cylinder as actuator member 3 has further (in some cases slightly different) characteristics which will be briefly discussed here.

[0074] exist Figure 2 In the variant shown, the electrohydraulic pump 2 preferably has a first partial pump chamber 21a and a second partial pump chamber 21b. The different hydraulic cross sections 20a, 20b result in a volume change 22, which is shown here at the inlet of the second partial pump chamber 21b, because during operation of the electrohydraulic actuator 1, the volume change 22 is conveyed through the second partial pump chamber 21b. Preferably, both partial pump chambers 21a, 21b are driven by a common pump drive motor 26. The first partial pump chamber 21a substantially corresponds to the embodiment according to Figure 1 The pump chamber (not shown separately) of the electric hydraulic pump 2 of the embodiment of FIG. 21 is connected to two pipelines 7a and 7b and forms a transmission circuit 10 with the pipelines 7a and 7b and the hydraulic fluid chambers 4a and 4b of the hydraulic actuator component 3.

[0075] The second partial pump chamber 21 b is connected only to the first line 7 a to the first hydraulic fluid chamber 4 a, which has a larger first hydraulic cross section 20 a. The second partial pump chamber 21 b is also connected to a hydraulic fluid reservoir 23, into which or from which hydraulic fluid is drawn during operation of the electrohydraulic actuator 1, depending on the direction of delivery. The hydraulic fluid reservoir 23 can also be pressurized in order to store hydraulic energy in the hydraulic fluid. Recovery of mechanical energy 24 from the actuator movement 24 into electrical energy is also preferably possible.

[0076] Reference numerals list

[0077] 1Electro-hydraulic actuator

[0078] 2 Electric hydraulic pump

[0079] 3 Hydraulic Actuator Components

[0080] 4a First hydraulic fluid chamber

[0081] 4b Second hydraulic fluid chamber

[0082] 5Total actuator volume

[0083] 6a First connection point

[0084] 6b Second connection point

[0085] 7a First pipeline

[0086] 7b Second pipeline

[0087] 8a First releasable hydraulic closure element

[0088] 8b Second releasable hydraulic closure element

[0089] 9Other hydraulic components

[0090] 10 Transmission circuit

[0091] 11 Storage

[0092] 12a Another first hydraulic closing element

[0093] 12b Another second hydraulic closing element

[0094] 13 Hydraulic release signal input terminal

[0095] 14 Electric release signal input terminal

[0096] 15Mobile work execution machines

[0097] 16 driving power supply

[0098] 17 Controller

[0099] 18 Hydraulic fluid supplier

[0100] 19 Displaceable elements

[0101] 20a First hydraulic cross section

[0102] 20b Second hydraulic cross section

[0103] 21a First part pump chamber

[0104] 21b Second part pump chamber

[0105] 22Volume change

[0106] 23 Hydraulic fluid reservoir

[0107] 24 Actuator Movement

[0108] 25 Hydraulic intermediate circuit

[0109] 26 Pump drive motor

[0110] 27 Hydraulic signal line

[0111] 28 electrical signal lines

Claims

1. An electrohydraulic actuator (1) comprising at least one bidirectionally operable hydraulic pump (2) for conveying hydraulic fluid, the pump having two connection points (6a, 6b), the two connection points (6a, 6b) being designed to alternately supply and / or remove hydraulic fluid, the electrohydraulic actuator (1) also having a hydraulic actuator component (3), the hydraulic actuator component (3) having two hydraulic fluid chambers (4a, 4b), hydraulic fluid being able to be supplied to the two hydraulic fluid chambers (4a, 4b) in order to actuate the hydraulic actuator component (3), wherein filling one of the hydraulic fluid chambers (4a, 4b) with hydraulic fluid simultaneously causes hydraulic fluid to be displaced from the other hydraulic fluid chamber (4b, 4a), the first connection point (6a) of the electrohydraulic pump (2) being connected to the hydraulic actuator component via a first line (7a) (3), a first hydraulic fluid chamber (4a) of the hydraulic pump (2), a second connection point (6b) of the hydraulic pump (2) is connected to a second hydraulic fluid chamber (4b) of the hydraulic actuator component (3) via a second pipeline (7b), wherein a first releasable hydraulic closing element (8a) is arranged between the first hydraulic fluid chamber (4a) and the first pipeline (7a), and a second releasable hydraulic closing element (8b) is arranged between the second hydraulic fluid chamber (4b) and the second pipeline (7b), wherein the releasable hydraulic closing elements (8a, 8b) prevent undesired outflow of hydraulic fluid from the hydraulic fluid chambers (4a, 4b), wherein the releasable hydraulic closing elements (8a, 8b) are designed in such a way that in order to release, both an electrical release signal and a hydraulic release signal must be applied to the releasable hydraulic closing elements (8a, 8b).

2. An electrohydraulic actuator (1) as claimed in claim 1, wherein the releasable hydraulic closing element (8a, 8b) is a releasable non-return valve.

3. An electro-hydraulic actuator (1) as claimed in claim 1 or 2, wherein the hydraulic actuator component (3) has a displaceable element (19), the hydraulic fluid chambers (4a, 4b) are connected to each other via the displaceable element (19), and wherein the hydraulic actuator component (3) at least partially forms a transmission circuit (10) with the pipeline (7a, 7b) and the electric hydraulic pump (2) so that the hydraulic fluid separated from one hydraulic fluid chamber (4a, 4b) can flow directly into the other hydraulic fluid chamber (4b, 4a) via the pipeline (7a, 7b) and the electric hydraulic pump (2).

4. An electrohydraulic actuator (1) according to claim 3, wherein the hydraulic fluid chambers (4a, 4b) of the hydraulic actuator member (3) have hydraulic cross-sections (20a, 20b) that are different from each other, so that when the displaceable element (19) is displaced, a volume change (22) is generated as a function of the total volume of the hydraulic fluid chambers (4a, 4b), wherein: The electric hydraulic pump (2) has a two-part pump chamber, a first part pump chamber (21a) is connected to the pipeline (7a, 7b) to form a transmission circuit (10), and a second part pump chamber (21b) is connected to the pipeline (7a, 7b) to the hydraulic fluid chamber (4a, 4b) with a larger hydraulic cross-section (20a, 20b) and is connected to a hydraulic fluid reservoir (23), and the volume change (22) can be compensated by the hydraulic fluid reservoir (23).

5. An electrohydraulic actuator (1) as claimed in claim 3 or 4, wherein the first line (7a) and the second line (7b) are respectively connected to a reservoir (11) for hydraulic fluid, the reservoir (11) being arranged to compensate function-related fluctuations with a minimum system pressure in a closed hydraulic system.

6. An electrohydraulic actuator (1) as claimed in claim 5, wherein the reservoir (11) is connected to the first line (7a) and the second line (7b) via further hydraulic closing elements (12a, 12b), wherein these further hydraulic closing elements (12a, 12b) prevent the operating pressure generated by the electrohydraulic pump (2) in one of the two lines (7a, 7b) from being transmitted to the reservoir (11).

7. An electro-hydraulic actuator (1) as claimed in one of the preceding claims, wherein the releasable hydraulic closing element (8a, 8b) has a hydraulic release signal input terminal (13), the hydraulic signal line (27) is connected to the hydraulic release signal input terminal (13), and via the hydraulic release signal input terminal (13), the presence of hydraulic system pressure of the electro-hydraulic actuator (1) is monitored as a hydraulic release signal.

8. The electro-hydraulic actuator (1) according to claim 7, wherein the hydraulic release signal input (13) is connected to the reservoir (11) via a hydraulic signal line (27) to monitor the hydraulic system pressure.

9. An electro-hydraulic actuator (1) as claimed in one of the preceding claims, wherein the releasable hydraulic closing element (8a, 8b) has an electrical release signal input terminal (14), an electrical signal line (28) is connected to the electrical release signal input terminal (14), and via the electrical release signal input terminal (14), the presence of a functional signal of a driving power supply (16) and / or a controller (17) of the electric hydraulic pump (2) and / or a functional signal of the electric hydraulic pump (2) is monitored as an electrical release signal.

10. An electrohydraulic actuator (1) as claimed in one of the preceding claims, wherein the electrohydraulic pump (2) is arranged such that the electrohydraulic pump (2) can act as a generator to convert the mechanical energy of the flow of hydraulic fluid from one connection point (6a, 6b) to the other connection point (6b, 6a) into electrical energy.

11. An electrohydraulic actuator (1) according to one of the preceding claims, arranged to transmit mechanical energy at the hydraulic actuator component (3) to an electrohydraulic pump (2) via a pipeline (7a, 7b) and via a hydraulic fluid, and to recover the mechanical energy as electrical energy using the electrohydraulic pump (2).

12. Electrohydraulic actuator (1) according to one of the preceding claims, wherein the hydraulic actuator component (3) is a linear actuator.

13. A mobile work performing machine (15) comprising at least one electrohydraulic actuator (1) according to one of the preceding claims.

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