HYDRAULIC SYSTEM FOR A VEHICLE, SUCH AS AN AIRCRAFT

Abstract

A hydraulic system for reducing mechanical loads or noise development is disclosed having at least two hydraulic pumps including a pump element, such as a piston or rotary gear. The hydraulic pumps can be speed-controlled by a pump controller to achieve a nominal pressure P.sub.0. The pump controller further includes an offset (x) between the pump elements and controls one of the hydraulic pumps such that the pump elements move in an anti-cyclic manner, that is, a phase shift of about 180.

Claims

1. A hydraulic system for a vehicle, comprising: a plurality of hydraulic pump apparatus configured for generating hydraulic pressure, each hydraulic pump apparatus comprising a hydraulic pump, wherein the hydraulic pump has a pump discharge and at least one pump element that is configured to displace hydraulic fluid through the pump discharge to generate the hydraulic pressure, wherein the pump discharges are fluidly connected to form a common discharge; and a pump controller configured to determine an offset between a pair of pump elements, wherein the pump controller is configured to adjust the offset such that the pair of pump elements moves in an anti-cyclic manner.

2. The hydraulic system according to claim 1, wherein the pump controller is configured to adjust the offset such that one of the pair of pump elements discharges hydraulic fluid, when the other of the pair of pump elements draws in hydraulic fluid.

3. The hydraulic system according to claim 1, wherein at least one pump discharge and/or the common discharge comprises a pressure sensor that is configured for measuring the pressure of the hydraulic fluid, and the pump controller is configured to control each hydraulic pump apparatus by controlling a speed of the hydraulic pump, such that a nominal pressure is kept at the respective pump discharge and/or common discharge.

4. The hydraulic system according to claim 1, wherein the hydraulic pump apparatus comprises an electric pump motor that is operatively coupled to the pump controller to be controlled and that drives the hydraulic pump.

5. The hydraulic system according to claim 1, further comprising a position determining unit that is configured to determine a pump element position of each pump element, and the pump controller is configured to determine the offset based on the pump element positions of the pair of pump elements.

6. The hydraulic system according to claim 5, wherein the position determining unit comprises a position sensor that is configured to measure a quantity that is indicative of the pump element position.

7. The hydraulic system according to claim 6, wherein the position sensor is chosen from a group consisting of an optical position sensor, a magnetic position sensor, a resolver, an electrical power sensor, and an electrical current sensor.

8. The hydraulic system according to claim 6, wherein the position sensor is disposed on the hydraulic pump, the pump element, or the electric pump motor.

9. The hydraulic system according to claim 1, wherein the pump controller is configured to adjust the offset by controlling the speed of the hydraulic pump.

10. The hydraulic system according to claim 1, further comprising at least one hydraulic actuator that is supplied with hydraulic fluid from the common discharge.

11. An aircraft comprising a hydraulic system according to claim 1, wherein the hydraulic system is configured to drive any of a high-lift device, a door or freight door, a landing gear, and a control surface.

12. A method for operating a hydraulic system according to claim 1, the method comprising: a plurality of hydraulic pump apparatus generating hydraulic pressure, each hydraulic pump apparatus comprising a hydraulic pump, wherein the hydraulic pump has least one pump element that displaces hydraulic fluid through a pump discharge to generate the hydraulic pressure, and the pump discharges are combined into a common discharge; and a pump controller determining an offset between a pair of pump elements, wherein the pump controller adjusts the offset such that the pair of pump elements moves in an anticyclic manner.

13. The method according to claim 12, further comprising: a position determining unit determining a pump element position of each pump element, and the pump controller determining the offset based on the pump element positions of the pair of pump elements.

14. The method according to claim 13, wherein the pump controller adjusts the offset by controlling the speed of the hydraulic pump.

15. The method according to claim 12, further comprising at least one hydraulic actuator being supplied with hydraulic fluid from the common discharge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] For an understanding of embodiments of the disclosure, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0052] FIG. 1 illustrates an embodiment of an aircraft;

[0053] FIG. 2 illustrates an embodiment of a hydraulic system;

[0054] FIG. 3 illustrates a function of the hydraulic system of FIG. 2;

[0055] FIG. 4 illustrates a time-pressure diagram of a single hydraulic pump; and,

[0056] FIG. 5 illustrates a time-pressure diagram of the hydraulic system of FIG. 2.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0057] Some embodiments will now be described with reference to the Figures.

[0058] Referring to FIG. 1, an aircraft 10 comprises a fuselage 12. A pair of wings 14 is attached to the fuselage. Each wing 14 comprises an engine 16 for propulsion. The aircraft 10 comprises a tail plane section 18.

[0059] The aircraft 10 typically comprises a plurality of high-lift devices 20, which are attached to each wing 14. The high-lift device 20 on the leading edge of the wing 14 is typically called a slat 22, whereas the high-lift device 20 on the trailing edge of the wing is typically called a flap 24.

[0060] Each wing 14 and the tail plane section 18 typically comprise control surfaces 26. The control surfaces 26 which are attached to the wings 14 are called ailerons 28. The control surface 26 on the tail plane section 18 which controls the pitch of the aircraft 10 is called an elevator 30. The control surface 26 that is attached to the tail plane section 18 and controls the yaw angle is called a rudder 32.

[0061] Furthermore, the aircraft 10 may comprise a plurality of doors 34, in particular freight doors or loading doors, to access the freight space of the aircraft 10. Furthermore, the aircraft 10 comprises a plurality of landing gears (not shown) which are typically arranged near the cockpit section 36 and below the wings 14. The front landing gear near the cockpit section 36 is typically configured such that the aircraft 10 can be steered on the ground.

[0062] The aircraft 10 comprises a hydraulic system 40. The hydraulic system 40 can be operatively coupled to any of the previously mentioned components of the aircraft 10 in order to provide a means to move and steer the respective components. As depicted in FIG. 1, for example, the hydraulic system 40 can be operatively connected to the doors 34 in order to open and close them.

[0063] Referring to FIG. 2, the hydraulic system 40 is explained in more detail. The hydraulic system 40 comprises a fluid tank 42 for storing hydraulic fluid.

[0064] The hydraulic system 40 comprises a plurality of hydraulic pump apparatus 44. The hydraulic pump apparatus 44 may be configured identically. Each hydraulic pump apparatus 44 comprises a pump discharge 46 through which hydraulic fluid that was drawn in from the fluid tank 42 is discharged from the hydraulic pump apparatus 44.

[0065] Each pump discharge 46 may comprise a pressure sensor 48. The pressure sensor 48 is arranged to measure the pressure generated by the respective hydraulic pump apparatus 44. Downstream of the pressure sensors 48, the pump discharges 46 are combined into a single common discharge 50. The common discharge 50 is coupled to hydraulic actuators which drive one of the doors 34, for example. In a variant that is not shown explicitly, it is possible to have one pressure sensor 48 that is arranged to measure the pressure generated by all hydraulic pump apparatus 44. The pressure sensor 48 may be disposed on the common discharge 50.

[0066] The hydraulic system 40 comprises a pump controller 52 that is operatively coupled to each hydraulic pump apparatus 44 and each pressure sensor 48.

[0067] The hydraulic pump apparatus 44 comprises a hydraulic pump 54 which is fluidly connected to the fluid tank 42 and the pump discharge 46.

[0068] The hydraulic pump apparatus 44 may further comprise an electric pump motor 56 that is mechanically connected to the hydraulic pump 54 in order to drive it. The electric pump motor 56 is operatively connected to the pump controller 52 in order to be controlled. The electric pump motor 56 may be capable of being speed controlled.

[0069] The hydraulic pump 54 may be configured as a piston pump or a rotary gear pump. The piston and the rotary gear are examples of a pump element that is used to displace the hydraulic fluid in order to generate hydraulic pressure.

[0070] The hydraulic pump apparatus 44 comprises a position sensor 58 that is suitable to measure a quantity that is indicative of the position of the pump element. The position sensor 58 can be arranged on the hydraulic pump 54 or the electric pump motor 56. The position sensor 58 may be an optical sensor or a magnetic type sensor, such as a Hall sensor. Other sensor types are also possible. In particular, the position sensor 58 may be a power sensor or a current sensor that is connected to the electrical pump motor 56 and capable of inferring the position of the pump element based on the consumed power and or current. These methods are generally known for electric motors so they are not described here in more detail.

[0071] Referring to FIG. 3, the functioning of the pump controller 52 is described in more detail. The pump controller 52 takes in the pump element position X.sub.1, X.sub.2 of each pump element. Furthermore, the pump controller 52 takes in the hydraulic pressure P.sub.1, P.sub.2 generated by each hydraulic pump apparatus 44 and measured by the respective pressure sensor 48.

[0072] The pump element positions X.sub.1 and X.sub.2 are fed to a comparator unit 60, which determines an offset AX between the pump elements.

[0073] The pump controller 52 further comprises a first motor controller 62 and a second motor controller 63. Each motor controller 62, 63 is coupled to one hydraulic pump apparatus 44 in order to control its operation. Each motor controller 62, 63 in particular controls the speed of the respective electric pump motor 56.

[0074] The first and second motor controllers 62, 63 receive the respective measured pressure P.sub.1 and P.sub.2. In a manner known per se, the first and second motor controllers 62, 63 generate an initial control signal Ci.sub.1 and Ci.sub.2 that defines the speed at which the respective electric pump motor 56 should run. The initial control signals Ci.sub.1, Ci.sub.2 are determined such that a nominal pressure P.sub.0 can be maintained at each pump discharge 46.

[0075] The initial control signals Ci.sub.1, Ci.sub.2 are fed to an adjustment unit 64. The adjustment unit 64 also receives the offset Ax determined by the comparator unit 60. From these inputs, the adjustment unit 64 generates an adjusted control signal Ca for the second motor controller 63, for example. The adjusted control signal Ca is generated such that the offset Ax between the pair of pump elements is changed. The adjusted control signal Ca is fed to the second motor controller 63 which controls the respective electric pump motor 56 accordingly.

[0076] As a result, the offset Ax between the pump elements of the hydraulic pump apparatus 44 can be adjusted in a manner that allows for the pump elements to move anti-cyclically. For example, when one of the pump elements performs a discharge stroke the other pump element does exactly the opposite and performs a drawing in stroke.

[0077] Referring to FIGS. 4 and 5, the consequences of this type of operation is illustrated. In particular it is possible to adjust the offset Ax to allow reduction of pressure fluctuations in the hydraulic system 40.

[0078] FIG. 4 depicts a time-pressure diagram and illustrates the pressure fluctuations that are typically caused by the operation of a hydraulic pump apparatus 44. The currently measured pressure P.sub.1 oscillates around the nominal pressure P.sub.0. As may be gathered from FIG. 4, the measured pressure P.sub.1 typically increases when the pump element displaces the hydraulic fluid and decreases when the pump element draws in new hydraulic fluid from the fluid tank 42. Each of the hydraulic pump apparatus 44 has a similar build and therefore, the pressure fluctuations are also similar.

[0079] FIG. 5 depicts the optimal result of an optimal adjustment of the offset Ax between the pump elements of both hydraulic pump apparatus 44. As may be gathered from the diagram, the offset x is not zero but has a certain value that is typically given by the configuration of the hydraulic pumps 54 which causes the pressure fluctuations to align in a destructive interference pattern. The pressure peaks and pressure valleys of the hydraulic pump apparatus 44 meet at the same time but with opposite amplitude, which allows at least a reduction of the pressure fluctuations, or ideally as illustrated in FIG. 5, a complete elimination.

[0080] In order to reduce mechanical loads or noise development, a hydraulic system 40 is proposed that comprises at least two hydraulic pumps 54 having pump element, e.g., a piston or rotary gear. The hydraulic pumps 54 can be speed controlled by a pump controller 52 to achieve a nominal pressure P.sub.0. The pump controller 52 further determines an offset (x) between the pump elements and controls one of the hydraulic pumps 54 such that the pump elements move in an anticyclic manner, i.e. with a phase shift of about 180.

[0081] While at least one exemplary embodiment is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.