US-12618420-B2 - Hydraulic actuator and method for operating

US12618420B2US 12618420 B2US12618420 B2US 12618420B2US-12618420-B2

Abstract

A hydraulic actuator comprising a housing, a piston, first to third pressure chambers, and a plurality of arrangements of piezoelectric elements arranged inside one of the plurality of chambers. A computer implemented internal brake for selectively switching between a braking mode and a non-braking mode of the piston comprises the third chamber, and fluid connections between the first to third chambers with flow control elements.

Inventors

Tanno Zantz

Assignees

AIRBUS OPERATIONS GMBH

Dates

Publication Date: 20260505
Application Date: 20240702
Priority Date: 20230717

Claims (17)

1 . A hydraulic actuator comprising: a housing surrounding a cavity, a piston arranged on a piston rod, a plurality of pressure chambers, and a plurality of arrangements of piezoelectric elements, each of the arrangements arranged adjacent a chamber from the plurality of chambers and configured to selectively contract or expand in order to change a volume of the chamber bordered by the piezoelectric elements of the arrangement; and a braking means configured for a selectively switching between a braking mode and a non-braking mode, wherein in the braking mode the braking means brakes movement of the piston and in the non-braking mode the braking means does not brake movement of the piston, wherein the plurality of pressure chambers includes a first chamber and a second chamber separated by the piston that is movable along an actuation direction, wherein the plurality of arrangements of piezoelectric elements includes a first arrangement of piezoelectric elements arranged adjacent the first chamber and configured to change a volume of the first chamber occupied by the piezoelectric elements of the first arrangement, and wherein the plurality of arrangements of piezoelectric elements includes a second arrangement of piezoelectric elements, wherein the plurality of pressure chambers includes a third chamber, wherein the braking means comprises the third chamber, a first fluid connection with a first flow control means and a second fluid connection with a second flow control means; wherein the first fluid connection connects the third chamber and the first chamber and the first flow control means is configured to selectively vary a flow of a hydraulic fluid through the first fluid connection, and wherein the second fluid connection connects the third chamber and the second chamber and the second flow control means is configured to selectively vary a flow of hydraulic fluid through the second fluid connection, wherein the second arrangement of piezoelectric elements is arranged adjacent the third chamber and is configured to change a volume of the third chamber.
2 . The hydraulic actuator according to claim 1 , wherein the plurality of arrangements of piezoelectric elements includes a third arrangement of piezoelectric elements arranged adjacent the second chamber and configured to change the volume of the second chamber.
3 . The hydraulic actuator according to claim 1 , wherein the third chamber is arranged at one of an axial end of the housing adjacent to one of the first and second chambers, or radially adjacent to the cavity, or around the cavity, or inside the piston.
4 . The hydraulic actuator according to claim 1 , wherein the first flow control means comprises a first valve block including a first valve and a first pipe connecting the first valve block with the second chamber and another first pipe connecting the first valve block with the third chamber, or wherein the first flow control means comprises a first passage in a first wall between the first and third chambers and the first passage contains or is formed by a valve, and wherein the second flow control means comprises a second valve block including a second valve and a second pipe connecting the second valve block with the first chamber and another second pipe connecting the second valve block with the third chamber, or wherein the second flow control means comprises a second passage in a second wall between the second and third chambers and the second passage contains or is formed by a valve.
5 . The hydraulic actuator according to claim 1 , wherein a hydraulic fluid reservoir connected to at least one chamber selected from a group consisting of: the first, second, and third chambers, such that hydraulic fluid flows from the hydraulic fluid reservoir to the at least one chamber or from the at least one chamber to the hydraulic fluid reservoir.
6 . The hydraulic actuator according to claim 1 further comprising: an electronic control unit configured to control the plurality of arrangements of piezoelectric elements and the first and second flow control means of the braking means to conduct a first operation with the following sequence of steps a) to d): a) while the first flow control means is closed, opening the second flow control means, expanding the first arrangement of piezoelectric elements and contracting the second arrangement of piezoelectric elements so that the piston moves in a direction towards the second chamber, the volume of the second chamber is decreased and hydraulic fluid flows from the second chamber via the second fluid connection to the third chamber; b) closing the second flow control means; c) opening the first flow control means, contracting the first arrangement of piezoelectric elements, and expanding the second arrangement of piezoelectric elements so that hydraulic fluid flows from the third chamber via the first fluid connection to the first chamber and the movement of the piston is braked; d) closing the first flow control means.
7 . The hydraulic actuator according to claim 6 , wherein the electronic control unit is configured to control the plurality of arrangements of piezoelectric elements and the first and second flow control means of the braking means such that the first operation is repeated one or several times in order to move the piston in a first actuating direction.
8 . The hydraulic actuator according to claim 6 , wherein the plurality of arrangements of piezoelectric elements includes a third arrangement of piezoelectric elements arranged adjacent the second chamber and configured to change the volume of the second chamber, and wherein the electronic control unit is configured to further control the plurality of arrangements of piezoelectric elements and the first and second flow control means of the braking means to conduct a second operation with the following sequence of steps: e1) while the second flow control means is closed, opening the first flow control means, expanding the third arrangement of piezoelectric elements and contracting the second arrangement of piezoelectric elements so that the piston moves in a direction towards the first chamber, the volume of the first chamber is decreased and hydraulic fluid flows from the first chamber via the first fluid connection to the third chamber; f1) closing the first flow control means; g1) opening the second flow control means, contracting the third arrangement of piezoelectric elements, and expanding the second arrangement of piezoelectric elements so that hydraulic fluid flows from the third chamber via the first fluid connection to the first chamber while movement of the piston is braked; h1) closing the second flow control means.
9 . The hydraulic actuator according to claim 6 , wherein the electronic control unit is configured to further control the plurality of arrangements of piezoelectric elements and the first and second flow control means of the braking means to conduct a second operation with the following sequence of steps: e2) while the first flow control means is closed, opening the second flow control means, contracting the first arrangement of piezoelectric elements and expanding the second arrangement of piezoelectric elements so that the piston moves in a direction towards the first chamber, the volume of the first chamber is decreased and hydraulic fluid flows from the third chamber via the second fluid connection to the second chamber; f2) closing the second flow control means; g2) opening the first flow control means, expanding the first arrangement of piezoelectric elements, and contracting the second arrangement of piezoelectric elements so that hydraulic fluid flows from the first chamber via the first fluid connection to the third chamber and the movement of the piston is braked; h2) closing the first flow control means.
10 . The hydraulic actuator according to claim 9 , wherein the electronic control unit is configured to control the plurality of arrangements of piezoelectric elements and the first and second flow control means of the braking means such that the second operation is repeated one or several times in order to move the piston in a second actuating direction.
11 . The hydraulic actuator according to claim 1 , wherein the first, second, and third chambers and the first and second fluid connection form a closed volume.
12 . A method for operating a hydraulic actuator comprising a housing surrounding a cavity, a piston arranged on a piston rod, a plurality of pressure chambers, and a plurality of arrangements of piezoelectric elements, each of the arrangements arranged adjacent a chamber from the plurality of chambers and configured to selectively contract or expand in order to change a volume of said chamber, and a braking means configured for a selectively switching between a braking mode and a non-braking mode, wherein in the braking mode the braking means brakes movement of the piston and in the non-braking mode does not brake movement of the piston, wherein the plurality of pressure chambers includes a first chamber and a second chamber separated by the piston that is movable along an actuation direction, wherein the plurality of arrangements of piezoelectric elements includes a first arrangement of piezoelectric elements arranged adjacent the first chamber and configured to change the volume of the first chamber, and wherein the plurality of arrangements of piezoelectric elements includes a second arrangement of piezoelectric elements, wherein the braking means comprises a third chamber, a first fluid connection with a first flow control means and a second fluid connection with a second flow control means, wherein the first fluid connection connects the third chamber and the first chamber and the first flow control means is configured to selectively vary a flow of a hydraulic fluid through the first fluid connection, and wherein the second fluid connection connects the third chamber and the second chamber and the second flow control means is configured to selectively vary the flow of hydraulic fluid through the second fluid connection, wherein the second arrangement of piezoelectric elements s arranged adjacent the third chamber and is configured to change the volume of the third chamber occu, the method comprising the following sequence of steps: a) while the first flow control means is closed, opening the second flow control means, expanding the first arrangement of piezoelectric elements and contracting the second arrangement of piezoelectric elements so that the piston moves in a direction towards the second chamber, the volume of the second chamber is decreased and hydraulic fluid flows from the second chamber via the second fluid connection to the third chamber; b) closing the second flow control means; c) opening the first flow control means, contracting the first arrangement of piezoelectric elements, and expanding the second arrangement of piezoelectric elements so that hydraulic fluid flows from the third chamber via the first fluid connection to the first chamber and the movement of the piston is braked; d) closing the first flow control means.
13 . The method according to claim 12 , wherein the plurality of arrangements of piezoelectric elements includes a third arrangement of piezoelectric elements arranged adjacent the second chamber and configured to change the volume of the second chamber occupied by the piezoelectric elements of the third arrangement, and the method further comprising the following sequence of steps: e1) while the second flow control means is closed, opening the first flow control means, expanding the third arrangement of piezoelectric elements and contracting the second arrangement of piezoelectric elements so that the piston moves in a direction towards the first chamber, the volume of the first chamber is decreased and hydraulic fluid flows from the first chamber via the first fluid connection to the third chamber; f1) closing the first flow control means; g1) opening the second flow control means, contracting the third arrangement of piezoelectric elements, and expanding the second arrangement of piezoelectric elements so that hydraulic fluid flows from the third chamber via the first fluid connection to the first chamber while movement of the piston is braked; h1) closing the second flow control means.
14 . The method according to claim 12 further comprising: repeating the steps e1) to h1) one or several times for moving the piston in a second actuation direction.
15 . The method according to claim 12 , further comprising the following sequence of steps: e2) while the first flow control means is closed, opening the second flow control means, contracting the first arrangement of piezoelectric elements and expanding the second arrangement of piezoelectric elements so that the piston moves in a direction towards the first chamber, the volume of the first chamber is decreased and hydraulic fluid flows from the third chamber via the second fluid connection to the second chamber; f2) closing the second flow control means; g2) opening the first flow control means, expanding the first arrangement of piezoelectric elements, and contracting the second arrangement of piezoelectric elements so that hydraulic fluid flows from the first chamber via the first fluid connection to the third chamber and the movement of the piston is braked; h2) closing the first flow control means.
16 . The method according to claim 12 further comprising: repeating steps e2) to h2) one or several times for moving the piston in a second actuation direction.
17 . The method according to claim 12 further comprising: repeating steps a) to d) one or several times for moving the piston in a first actuation direction.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS This application claims the benefit of European Patent Application Number 23185853.1 filed on Jul. 17, 2023, the entire disclosure of which is incorporated herein by way of reference. FIELD OF THE INVENTION The invention relates to a hydraulic actuator and an operation method for such a hydraulic operator. BACKGROUND OF THE INVENTION A hydraulic actuator is known from EP 3 324 055 B1 which discloses a hydraulic actuator with an integrated piezo stack powered hydraulic pump. The known actuator comprises a piston supported on a piston rod that extends into the housing of the actuator. The piston forms two hydraulic chambers within the actuator housing. The volume of each chamber is changed by the operation of an associated piezo stack per chamber and a set of valves that selectively enable fluid flow between first and second chambers. An external mechanical brake is also provided at the end of the piston rod to brake its position. A controller controls the operation of the stacks and valves in order to achieve a pumping cycle that results in controlled movement of the piston in the actuator housing. SUMMARY OF THE INVENTION An object of the invention is to improve such a hydraulic actuator with regard to a reduced complexity, a higher reliability and a compact design. For achieving such object, the invention provides a hydraulic actuator according to one or more embodiments described herein. An operating method for such a hydraulic actuator is also described herein. The invention provides according to a first aspect thereof a hydraulic actuator comprising a housing, a piston, a plurality of pressure chambers, a plurality of arrangements of piezoelectric elements, and a braking means. The housing surrounds a cavity. The piston is arranged on a piston rod and is movable within the cavity along an actuation direction. Each of the arrangements of piezoelectric elements is arranged inside one of the plurality of chambers and is configured to selectively contract or expand in order to change the volume of this chamber occupied by the piezoelectric elements of the arrangement. The braking means is configured for a selectively switching between a braking mode and a non-braking mode. In the braking mode, the braking means brakes movement of the piston. In the non-braking mode, the braking means does not brake movement of the piston. The plurality of pressure chambers includes a first chamber and a second chamber separated by the piston. The plurality of arrangements of piezoelectric elements includes a first arrangement of piezoelectric elements arranged inside the first chamber and configured to change the volume of the first chamber occupied by the piezoelectric elements of the first arrangement. The plurality of arrangements of piezoelectric elements further includes a second arrangement of piezoelectric elements. The braking means comprises a third chamber, a first fluid connection with a first flow control means and a second fluid connection with a second flow control means. The first fluid connection connects the third chamber and the first chamber, and the first flow control means is configured to selectively varying flow of a hydraulic fluid through the first fluid connection. The second fluid connection connects the third chamber and the second chamber, and the second flow control means is configured to selectively vary the flow of hydraulic fluid through the second fluid connection. The second arrangement of piezoelectric elements is arranged inside the third chamber and is configured to change the volume of the third chamber occupied by the piezoelectric elements of the second arrangement. In some embodiments the plurality of arrangements of piezoelectric elements includes a third arrangement of piezoelectric elements arranged inside the second chamber and configured to change the volume of the second chamber occupied by the piezoelectric elements of the third arrangement. In some embodiments a diaphragm or membrane is arranged in at least one of the chambers containing an arrangement of piezoelectric elements. The diaphragm or membrane separates the arrangement of piezoelectric elements (such as a piezo stack) from a hydraulic fluid part of the chamber which can be filled with a hydraulic fluid. In some embodiments, the third chamber is arranged at an axial end of the housing adjacent to one of the first and second chambers. In some embodiments, the third chamber is arranged radially adjacent to the cavity. In some embodiments, the third chamber is arranged around the cavity. In some embodiments, the third chamber is arranged inside the piston which is then a hollow piston. In some embodiments, the flow control means are selected from a group consisting of valves, active MEMS valves, active disc valves, active one-way disc valves, and magnetorheological valves. In some embodiments, the first fluid connection comprises a first valve block including at least one first