Actuator device and method for operating such an actuator device

Abstract

The invention provides an actuator device, which has: an output element, which is acted on by a fluid and as a result is movable into a holding position; two solid-state actuators, which are able to be activated alternately; a coupling element common to the solid-state actuators; a discharge duct, via which the fluid is able to be discharged from the output element; and at least one valve element, which is adjustable between a blocking closed state and an open state, in which the valve element allows the fluid to be discharged from the output element via the discharge duct and allows the output element to move from the holding position into at least one yielding position, wherein the valve element is actuable, via the coupling element of the respective solid-state actuator, by the respective activation of the solid-state actuator and is able to be moved into the closed state.

Claims

1. An actuator device comprising: at least one output element which can be applied with a fluid and is thereby movable into a holding position, at least two solid-state actuators which can be alternately activated, whereby the fluid can be conveyed to the output element and the output element can be applied with the fluid, a coupling element common to the solid-state actuators, at least one discharge duct via which the fluid can be discharged from the output element, and at least one valve element which is adjustable between at least one closed state blocking the discharge duct and at least one open state unblocking the discharge duct, wherein: in the closed state, the output element can be held in the holding position by the fluid while blocking the discharge duct, and in the open state, the valve element allows discharge of the fluid from the output element via the discharge duct and thereby a movement of the output element from the holding position into at least one yielding position, wherein the valve element can be actuated and thereby brought into the closed state by the respective solid-state actuator via the coupling element by respectively activating the solid-state actuator.

2. The actuator device according to claim 1, wherein at least one reservoir for receiving and storing the fluid is provided.

3. The actuator device according to claim 2, wherein a respective drive element is associated with the respective solid-state actuator, which is actuatable, by the respective solid-state actuator by activating the respective solid-state actuator, whereby the fluid can be conveyed to the output element.

4. The actuator device according to claim 3, wherein in a respective phase of the respective solid-state actuator following the respective activation of the respective solid-state actuator, the fluid can be sucked from the reservoir by the respective drive element, and by subsequent activation of the respective solid-state actuator, it can be conveyed from the respective drive element to the output element by the respective drive element.

5. The actuator device according to claim 4, wherein a first one of the drive elements is actively movable by the solid-state actuator associated with the second drive element via the coupling element as a result of the activation of the solid-state actuator associated with the second drive element in the phase following the activation of the solid-state actuator associated with the first drive element such that the first drive element sucks the fluid from the reservoir.

6. The actuator device according to claim 3, wherein a first area, in which the respective drive element is movable by activating the respectively associated solid-state actuator, is sealed against the respective drive element and/or against a second area, in which the solid-state actuators are arranged, by a membrane.

7. The actuator device according to claim 6, wherein the coupling element is arranged in the first area.

8. The actuator device according to claim 6, wherein the membrane is elastically deformable and/or movable together with the respective drive element.

9. The actuator device according to claim 3, wherein the coupling element engages with a respective recess of the respective drive element and/or is movable together with the respective drive element.

10. The actuator device according to claim 3, wherein the drive elements differ from each other with respect to their respective fluidically active surface for conveying the fluid.

11. The actuator device according to claim 1, wherein the solid-state actuators are coupled to each other via the coupling element.

12. The actuator device according to claim 1, wherein the coupling element is formed as a rocker pivotable around a pivot axis.

13. The actuator device according to claim 1, wherein an electronic computing device is provided, which is formed to alternately activate the solid-state actuators such that upon activation of one of the solid-state actuators, the activation of the other actuator is omitted and vice versa.

14. The actuator device according to claim 13, wherein the computing device is formed to activate the respective solid-state actuator with a sinusoidal, electrical current, wherein the sinusoidal currents for activating the solid-state actuators are phase-shifted relative to each other by 180°.

15. The actuator device according to claim 1, wherein the solid-state actuators are arranged in a housing, which is formed of Invar, and/or wherein the solid-state actuators differ from each other with respect to their respective functional principle.

16. A method for operating an actuator device comprising: applying a fluid to at least one output element which is thereby movable into a holding position; alternately activating at least one first solid-state actuator and at least one second solid-state actuator, whereby the fluid is conveyed to the output element and the output element is applied with the fluid; a coupling element being common to the solid-state actuators; discharging the fluid via at least one discharge duct from the output element; and actuating at least one valve element by the respective solid-state actuator via the coupling element by respectively activating the respective solid-state actuator and thereby bringing the valve element into a closed state blocking the discharge duct, in which the output element is held in the holding position by the fluid while blocking the discharge duct, wherein the valve element shifts from the closed state into an open state unblocking the discharge duct, in which the valve element allows discharge of the fluid from the output element via the discharge duct, if both activation of the first solid-state actuator and activation of the second solid-state actuator are omitted at the same time, whereby the output element moves from the holding position into at least one yielding position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings show in:

(2) FIG. 1 a schematic representation of a first embodiment of an actuator device according to the invention, in particular for a system such as for example a brake system; and

(3) FIG. 2 a schematic representation of a second embodiment of the actuator device.

(4) In the figures, identical or functionally identical elements are provided with identical reference characters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) FIG. 1 shows an actuator device denoted by 10 as a whole in a schematic representation, which is for example used in or for a system, in particular safety system. The mentioned system for example comprises at least one component, which provides a load and exerts it on the actuator device 10, in particular in a first state of the system. This load is illustrated in FIG. 1 by an arrow F also referred to as force arrow. The system for example occupies the first state during a normal operation of the system, wherein the system does not have an error or defect during the normal operation. In the first state, the system is for example under tension and/or force or braking the system is omitted in the first state.

(6) The actuator device 10 comprises at least or exactly one output element 12, which is for example coupled or can be coupled to the mentioned component. Thus, the component exerts the load denoted by the arrow F and for example formed as a force on the output element 12. The output element 12 is for example a bellows. Alternatively or additionally, the output element 12 for example comprises at least or exactly one chamber 14, which can be supplied with a fluid, in particular with a liquid. This means that the fluid can for example be introduced into the chamber 14 and conducted out of the chamber 14 or discharged from the chamber 14. By introducing the fluid into the chamber 14, the output element 12 is applied with the fluid. At least a partial area 16 of the output element 12 also referred to as part at least partially bounds the chamber 14 such that at least the partial area 16 can be applied with the fluid, in particular in that the fluid is conducted or introduced into the chamber 14.

(7) Thus, the output element 12, in particular the partial area 16, can be applied with the fluid and is thereby movable into a holding position H shown in FIG. 1 as well as can be held in the holding position for example against the load.

(8) For example, if the fluid is discharged from the chamber 14 such that the fluid is discharged from the output element 12 or from the partial area 16, thus, the partial area 16 or the output element 12 can evade or yield to the load, whereby the partial area 16 or the output element 12, in particular translationally, moves from the holding position H into a yielding position A for example illustrated by a dashed line. Thus, the partial area 16 is for example, in particular translationally, movable between the holding position H and the yielding position A along a direction of movement illustrated by a double arrow 18 in FIG. 1.

(9) The actuator device 10 comprises at least one first solid-state actuator 20 and at least one second solid-state actuator 22. The solid-state actuators 20 and 22 are also simply referred to as actuators and are for example formed as piezoelectric actuators. Thus, the respective actuator is for example also referred to as piezo actuator. Within the scope of a method for operating the actuator device 10, the actuators are alternately activated by an electronic computing device 24 of the actuator device 10 particularly schematically illustrated in FIG. 1, whereby the fluid is conveyed, in particular pumped, to the output element 12 and therein for example into the chamber 14 by the respective actuator. Hereby, the output element 12, in particular the partial area 16, is applied with the fluid. The respective solid-state actuator 20 and 22, respectively, can be formed as a piezo actuator or else as a polymer actuator or else as a shape memory alloy actuator, that is as such an actuator, which comprises and uses at least one shape memory alloy to convey the fluid.

(10) Within the scope of the activation, an electrical energy, in particular an electrical current or an electrical voltage, is for example applied to the respective actuator. In that the respective actuator is alternately activated, inactive phases and active phases of the respective actuator consecutively alternate, wherein during or in the respective active phase of the respective actuator, activation of the respective actuator is effected or the respective actuator is activated. In or during the respective inactive phase of the respective actuator, an activation of the respective actuator is omitted. By activating the respective actuator, a deformation of the respective actuator is effected, in particular such that a deformation of the respective actuator occurs along a deformation direction illustrated by a double arrow 26 in FIG. 1. For example, the respective actuator is enlarged along the deformation direction by activating the respective actuator such that a length increase of the respective actuator extending along the deformation direction is effected by activating the respective actuator. By terminating the activation of the respective actuator, a length reduction of the respective actuator along the deformation direction for example occurs.

(11) Moreover, the actuator device 10 comprises a coupling element 28 common to the solid-state actuators 20 and 22, which is for example formed as a rocker pivotable around a pivot axis 30, in particular in relation to a housing 32 particularly schematically illustrated in FIG. 1. Further, the coupling element 30 and thus the pivot axis 30 can for example be translationally moved, in particular in relation to the housing 32, along the deformation direction. For example, the actuators are at least partially, in particular at least predominantly or completely, accommodated in the housing 32 also referred to as actuator housing. The respective actuator is at least indirectly, in particular directly, supported on the housing 32 on the one hand. On the other hand, the respective actuator is coupled to the coupling element 28 and to the respectively other actuator via it.

(12) Moreover, the actuator device 10 comprises at least one discharge duct 34, via which the fluid can be discharged from the chamber 14 and thus from the output element 12, in particular the partial area 16. Thus, if the fluid for example first received in the chamber 14 is discharged from the chamber 14 via the discharge duct 34, thus, the partial area 16 can thereby be moved from the holding position H into the yielding position A by the load.

(13) Furthermore, the actuator device 10 comprises a valve element 36 for example formed as a ball, which is presently a constituent of a check valve 38. The check valve 38 is arranged in the discharge duct 34 and comprises the valve element 36 and a corresponding second valve element 40. The valve element 40 for example forms a valve seat for the valve element 36. The valve element 36 is movable, in particular along the deformation direction and/or in translational manner, in relation to the valve element 40 and/or in relation to the housing 32 between at least one open position unblocking the discharge duct 34 and at least one closed position fluidically blocking the discharge duct 34. In the closed position, the valve element 36 seats on the corresponding valve seat formed by the valve element 40. If the valve element 36 is in the closed position, thus, the valve element 36 is in a closed state. If the valve element 36 is in the open position, thus, the valve element 36 is in the open state. The valve element 36 is also coupled to the coupling element 28 and thus coupled to the actuators via the coupling element 28.

(14) In the closed state or in the closed position, the output element 12, in particular the partial area 16, is held in the holding position H by the fluid located in the chamber 14 while blocking the discharge duct 34 effected by the valve element 36. In the open state or in the open position, the valve element 36 allows discharging the fluid from the output element 12 or from the chamber 14 and thus from the partial area 16 via the discharge duct 34, whereby the valve element 36 allows a movement of the output element 12 or of the partial area 16 from the holding position H into the yielding position A. Therein, the valve element 36 can be actuated by the respective solid-state actuator 20 or 22 via the coupling element 28 by the respective activation of the respective solid-state actuator 20 or 22 and thereby can be brought into the closed state or is movable into the closed position and can be held in the closed state or in the closed position.

(15) Moreover, the actuator device 10 comprises at least one reservoir 42 for receiving and storing the fluid. In particular, under the effect of a load acting on the reservoir 42 and illustrated by an arrow F2 in FIG. 1, the reservoir 42 for example formed as a bellows can provide the fluid first received in the reservoir 42. Preferably, the fluid is a liquid such that the actuator device 10 can be a hydraulic actuator device.

(16) Moreover, a first drive element 44 for example formed as a piston is associated with the first solid-state actuator 20, and a second drive element 46 for example formed as a piston is associated with the second solid-state actuator 22. The respective drive element 44 and 46, respectively, is for example, in particular translationally, movable along the deformation direction. The piston is for example translationally movably accommodated in a drive housing 48 and 50, respectively. For example, if the respective solid-state actuator 20 and 22, respectively, is activated, thus, the respective piston is thereby for example displaced in a first displacement direction coinciding with the deformation direction in particular in relation to the drive housing 48 and 50, respectively. Thereby, fluid is conveyed out of the drive housing 48 and 50, respectively, and conveyed to the output element 12 and therein into the chamber 14. Hereby, the partial area 16 is for example applied with the fluid. If a length reduction of the respective actuator occurs in the respective inactive phase of the respective actuator, thus, the respective drive element 44 and 46, respectively, moves in a second displacement direction opposite to the first displacement direction and coinciding with the deformation direction in relation to the drive housing 48 and 50, respectively. Hereby, fluid is for example sucked from the reservoir 42 by the respective drive element 44 and 46, respectively, via a respective conduit 52 and 54, respectively, and sucked into the respective drive housing 48 and 50. In moving the respective drive element 44 and 46, respectively, in the first displacement direction, the fluid flows from the respective drive housing 48 and 50, respectively, into a respective conduit 56 and 58, respectively, through which the fluid is conducted from the respective drive housing 48 and 50, respectively, to the output element 12 and therein for example into the chamber 14. Overall, it is apparent that the respective drive element 44 and 46, respectively, is actuatable, in particular movable, by activating the respective actuator and therein by the respective actuator itself, whereby the fluid can be conveyed or is conveyed from the respective drive element 44 and 46, respectively, to the output element 12.

(17) During the first state, the actuators are alternatively activated such that the solid-state actuator 20 is for example in its active phase, while the solid-state actuator 22 is in its inactive phase, and such that the solid-state actuator 22 is in its active phase, while the solid-state actuator 20 is in an inactive phase. Hereby, the valve element 36 is held in the closed state in the first state of the system and the partial area 16 is held in the holding position H.

(18) If and preferably only if both activation of the solid-state actuator 20 and activation of the solid-state actuator 22 are omitted at the same time, the valve element 36 moves, in particular by a pressure of the fluid acting on the valve element 36, from the closed position into the open position, whereby the partial area moves from the holding position H into the yielding position A. As a result, the system is for example switched to zero-voltage and/or zero-force and/or the system is braked.

(19) The previously mentioned pressure of the fluid acting on the valve element 36 for example results from the fact that the load illustrated by the arrow F acts on the fluid received in the chamber 14 via the partial area 16, which can for example act on the valve element 36 via the discharge duct 34 for example formed as a discharge conduit. Thus, the valve element 36 can for example be held in the closed position against the load by alternately activating the actuators. If activation of the solid-state actuator 20 and activation of the solid-state actuator 22 are omitted at the same time, thus, the valve element 36 and also the partial area 16 can yield to the load and move into the open position or into the initial position A.

(20) It is apparent from FIG. 1 that a check valve 60 is arranged in the conduit 52, which opens in the direction of the drive element 44 or in the direction of the drive housing 48 and closes in opposite direction. Thereby, the drive element 44, if it moves in the second displacement direction, can suck fluid from the reservoir 42 via the conduit 52. In the conduit 54, a check valve 62 is arranged, which opens in the direction of the drive element 46 or opens in the direction of the drive housing 50 and closes in the opposite direction. Thereby, the drive element 46 can, if it moves in the second displacement direction, suck fluid from the reservoir 42 via the conduit 54 and the check valve 62.

(21) A check valve 64 is arranged in the conduit 56, which opens in the direction of the output element 12 and closes in opposite direction. Thereby, the drive element 44 can, if it moves in the first displacement direction, convey fluid out of the drive housing 48 and convey it through the conduit 56 and convey it to the or into the output element 12. Accordingly, a check valve 66 is also arranged in the conduit 58, which blocks in the direction of the drive element 46 and opens in the opposite direction. Thereby, the drive element 46 can, if it moves in the first displacement direction, convey the fluid out of the drive housing 50 and convey it through the conduit 58, whereby the drive element 46 can convey the fluid from the drive housing 50 to the or into the output element 12.

(22) The coupling element 28 is preferably rigid or not elastic, in particular not rubbery-elastic. In particular, the coupling element 28 is inherently rigid and dimensionally stable, respectively. In particular, the coupling element 28 can be formed as a rocker arm. Therein, the valve element 36 functions as a switch valve, which is actuated with the aid of the two solid-state actuators 20 and 22 connected to each other by the coupling element 28.

(23) In an initial state, the switch valve is for example first open. In this initial state, activation of the actuators is omitted. In other words, the actuators are at zero-voltage in the initial state. In order to close the switch valve, that is to move the valve element 36 from the open position into the closed position, an electrical voltage is applied to the actuators or an electrical voltage is applied to only one of the actuators such that both actuators are for example half deflected or only one of the actuators is completely deflected. Hereby, the valve element 36 is closed and pretensioned. Due to the kinematics realizable by the use of the coupling element 28, it does not make a difference if one of the actuators is fully deflected or both actuators are half deflected. For the operation of the actuators, a sinusoidal activation of the actuators offset or phase-shifted to each other by 180 degrees is selected, whereby a pump is realized without opening the switch valve, since a closing force for holding the switch valve in the closed position is realized via the mechanical coupling element 28 and not via a hydraulic pressure in the actuator device 10. This means that the fluid can be pumped to and into the output element 12 by the actuators, while the valve element 36 remains in the closed position.

(24) In the presently shown embodiment, the actuator device 10 comprises the exactly two actuators. Alternatively thereto, it is conceivable that at least one or more further solid-state actuators are provided in addition to the two actuators, which are coupled to each other via the coupling element 28, such that the valve element 36 can be actuated by the respective solid-state actuator via the coupling element 28. For the operation of the actuators, the number of which is at least two, three, four or greater, a sinusoidal activation of the actuators offset or phase-shifted to each other by an angular amount is selected, whereby the previously described pump is realized. Therein, the angular amount results from 360 degrees divided by the number of the actuators.

(25) Only if both solid-state actuators 20 and 22 are switched to zero-voltage at the same time, the valve element 36 (switch valve) opens, whereby a pressure, in particular of the fluid, also referred to as system pressure and for example existing in the chamber 14 is relieved. By pumping the fluid, a pressure build-up is effected in the hydraulic output element 12, in particular the chamber 14. This pumping and thereby the pressure build-up in the output element 12 are effected via the alternate activation, also referred to as actuation, of the actuators, whereby an alternate actuation of the two hydraulic drive elements 44 and 46 is realized. By the use of the check valves 60, 62, 64 and 66 and by the arrangement thereof, it is ensured that in each cycle, that is in each activation of the respective actuator, either fluid is pumped from the respective drive housing 48 and 50, respectively, into the output element 12 for pressure increase or fluid is sucked and thus re-conveyed from the reservoir 42 functioning as a hydraulic compensation element into the respective drive housing 48 and 50, respectively.

(26) The activation of the actuators offset or phase-shifted to each other by 180 degrees can be presented by particularly simple and thus inexpensive power electronics since the activation can be effected at least nearly without reactive power. The reason for this is that the electrical energy can always be shifted back and forth between the two capacitances of the actuators by this activation. For example, if a fixed turnaround frequency is selected with the aid of an inductance, a clocked final stage along with the filters required thereto can additionally be omitted.

(27) Preferably, the valve element 36 comprises at least one hydraulically active surface. A pressure of the fluid acting on the valve element 36 can be captured via this surface and for example by a pressure sensor. As a result, the system pressure can be captured, in particular determined, by the good electromechanical coupling, whereby, in particular permanent, pressure monitoring is allowed.

(28) FIG. 2 shows a second embodiment of the actuator device 10. In the second embodiment, two output elements 12 are for example provided and the output element 12 comprises two output parts. In the second embodiment, the housing 32 is formed of Invar such that an advantageous temperature compensation is realizable. Therein, the actuators are accommodated in the housing 32. In the second embodiment, the actuator device 10 comprises an, in particular elastically deformable, membrane 68. For example, a first area 70, in which the respective drive element 44 and 46, respectively, is movable, is sealed against the respective drive element 44 and 46, respectively, or against the respective drive housing 48 and 50, respectively, and/or against the housing 32 and/or against a second area 72, in which the solid-state actuators 20 and 22 are arranged, by the membrane 68. In other words, sealing of the two hydraulic drive elements 44 and 46 is effected by the membrane 68 in the second embodiment.

(29) In the second embodiment, the coupling element 28 is connected to the drive elements 44 and 46 such that the coupling element 28 engages with a respective recess 74 and 76, respectively, for example formed as a milled groove of the respective drive element 44 and 46, respectively, for example formed as a piston.

(30) The previously mentioned temperature compensation for the solid-state actuators 20 and 22 is implemented such that the for example parallel housing 32 is formed of an advantageous material such as for example Invar. Thereby, upon a temperature variation, an undesired opening of the switch valve caused by different temperature expansion coefficients, in particular of the actuators, can be prevented.

(31) The actuator device 10 can be formed as an integrating actuator unit with quick release function, wherein the actuator device 10 is an integrating actuator unit in that the fluid is pumped to the and in particular into the output element 12 by alternately activating the solid-state actuators 20 and 22. The previously mentioned quick release function can be simply presented without integrating process in that the solid-state actuators 20 and 22 are switched to zero-voltage such that both activation of the first solid-state actuator 20 and activation of the second solid-state actuator 22 are omitted at the same time. Thereby, a fast transition of the system from the first state into the second state can be allowed or effected.

(32) The actuators can function or be operated like a so-called electronic vane. By activating the respective actuator, that is by applying an electrical current to the respective actuator, the respective actuator for example expands. If the activation is terminated, thus, the respective actuator again contracts. Then or at the moment when or at which one of the actuators contracts, electrical charge is shifted from the one actuator to the or into the other actuator and vice versa. Thereby, the mentioned electronic vane is realized.

(33) A further advantage of the invention is in that the actuators can be operated or alternately activated with a very low frequency of less than 10 Hertz to remain in position. Thereby, depolarization or reverse polarization of the actuators for example formed as piezo actuators can be avoided.

(34) Furthermore, it is possible to realize a force limitation via corresponding arrangement of the actuators. In particular, there are at least two possibility of presenting such an advantageous force limitation: In a first one of the possibilities, the realization of a force limitation is effected by correspondingly dimensioning the actuators. Thereby, it can be ensured that the valve element 36 is, in particular always, opened, that is adjusted into the open state, if a force for example acting on the output element 12 reaches or exceeds a threshold value. By correspondingly dimensioning the actuators, the threshold value dan be adjusted or preset. In other words, if the force reaches or exceeds the threshold value, thus, the valve element 36 opens.

(35) Hereby, the valve element 36 is for example adjusted into the open state, in particular also, if the force exceeds the threshold value, while the actuators or at least or exactly one of the actuators is activated. In the second possibility, the force limitation can be realized via a so-called offset or basic voltage, in particular of the activation of the respective actuator. The activation of the respective actuator has at least or exactly two voltage portions: A first one of the voltage portions is the basic voltage, which is a basic voltage increase above the zero line. The second voltage portion is a sine wave for realizing the sinusoidal activation or the sinusoidal current. The sine wave for example adjusts the speed, with which it is pumped. By adjusting the basic voltage, the threshold value or the force limitation can for example be adjusted. Thereby, the actuators can be formed as inherently safe actuators.