Method for filling a hydraulic circuit of an electro-hydraulic system using a filling device

Abstract

The invention relates to a device for filling a hydraulic circuit of an electro-hydraulic system, the hydraulic circuit being provided with a drain valve and a fill valve. According to the invention, the device comprises: - a vacuum generator designed to be connected to the drain valve via a first shut-off valve, to eliminate the air or gas present in the circuit, and - a supply of pressurized hydraulic fluid, the source being designed to be connected to the fill valve via a second shut-off valve, and to the drain valve and to the first shut-off valve via a third shut-off valve, to fill the hydraulic fluid circuit.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of electro-hydrostatic systems, also known as electro-hydraulic systems, and more particularly to a device for filling the hydraulic circuit of an electro-hydrostatic system, and to a filling method using such a device. BACKGROUND

[0002] It is known to equip aircraft with electro-hydrostatic systems (EHA - electro-hydrostatic actuators) to locally generate hydraulic energy with a view to actuating moving parts of the aircraft, such as ailerons, rudders or landing gear. Such a system is known from, for example, document FR-A-2 836 671. The EHA system makes it possible to dispense with a hydraulic network covering the entire aircraft, thereby improving the reliability of the aircraft while significantly reducing its weight.

[0003] The EHA system generally comprises a hydraulic actuator such as a pneumatic cylinder, a hydraulic pump driven by an electric motor, and a hydraulic circuit connecting the pump to the cylinder. The hydraulic pump pressurizes the working fluid, typically hydraulic oil, contained in the circuit to increase the pressure in the chamber of the cylinder and to operate it. The EHA system thus forms an independent hydraulic unit, which contains its own fluid reserve, which facilitates maintenance.

[0004] However, the hydraulic pump is sensitive to the cavitation phenomenon. Thus, when filling the circuit of the EHA system, it is necessary to evacuate as much as possible the air present in the circuit, otherwise the pump will be severely damaged. To do this, it is common practice to "manually" actuate the cylinder several times when filling the circuit. However, performing such actuations can be difficult and complex, in particular in the case where the EHA system is dedicated to lifting the landing gear. In addition, their effectiveness is limited, air often remaining trapped in the circuit and / or in the cavities of the cylinder.

[0005] In addition, when the hydraulic pump is a booster pump, it is necessary to fill the circuit of the EHA system to a predetermined pressure to ensure proper operation of the pump. SUMMARY

[0006] The present invention therefore aims to propose a device for reliably and effectively filling the circuit of an electro-hydrostatic system without requiring a large number of maintenance operations.

[0007] To this end, a device for filling the hydraulic circuit of an electro-hydrostatic system is provided, the hydraulic circuit being provided with a drain valve and a fill valve. According to the invention, the filling device comprises:

[0008] - a vacuum generator designed to be connected to the drain valve via a first shut-off valve, to eliminate the air or gas present in the circuit, and

[0009] - a supply of pressurized hydraulic fluid designed to be connected to the filling valve via the second shut-off valve and to the discharge valve and to the first shut-off valve via the third shut-off valve, so as to fill the hydraulic fluid circuit.

[0010] The vacuum generator is used to establish a vacuum in the hydraulic circuit of the electro-hydraulic system, so as to effectively evacuate the air or gas contained in said circuit before filling it by means of the supply of hydraulic fluid. It is thus not necessary to manually actuate the electro-hydraulic system in order to protect it from cavitation phenomena. This facilitates the maintenance and replacement of the electro-hydraulic system.

[0011] According to a particular feature of the invention, the vacuum generator comprises a vacuum pump connected to the first shut-off valve by means of a liquid / gas separator.

[0012] According to another particular feature of the invention, the supply of hydraulic fluid comprises a filling pump connected to a reservoir whose capacity is greater than that of the hydraulic circuit of the electro-hydraulic system.

[0013] According to a particular embodiment of the invention, the vacuum generator and the supply of hydraulic fluid are mounted on a mobile carriage.

[0014] In particular, this carriage is an elevating carriage (chariot élévateur).

[0015] The invention also relates to a method of filling a circuit of an electro-hydraulic system using such a device.

[0016] According to the invention, the method comprises the following steps:

[0017] - connecting the first shut-off valve and the third shut-off valve to the discharge valve and the second shut-off valve to the filling valve;

[0018] - opening the filling valve, the discharge valve and the first shut-off valve and operating the vacuum generator when the second shut-off valve and the third shut-off valve are closed;

[0019] - once a vacuum has been established in the circuit, opening the second shut-off valve so as to fill the circuit with pressurized hydraulic fluid while the vacuum generator is still operating;

[0020] - once the circuit has been filled with fluid, closing the first shut-off valve and then opening the third shut-off valve so as to bypass the vacuum generator and circulate the fluid through the electro-hydraulic system until the fluid contained in the circuit reaches a predetermined pressure;

[0021] - closing the discharge valve and the filling valve.

[0022] In particular, the electro-hydraulic system comprises a plurality of actuators selectable by at least two distributors, while the method comprises a step of controlling the distributors one after the other in succession to establish a vacuum in the hydraulic circuit, and a step of controlling the distributors according to a predetermined sequence to fill the hydraulic circuit. BRIEF DESCRIPTION OF DRAWINGS

[0023] The application will be better understood from the following description, which is purely illustrative and non-limiting, and should be read in reference to the only attached drawings, in which:

[0024] - Figure 1 is a schematic view of a filling device according to a specific embodiment of the application, connected to a hydraulic circuit of an electro-hydraulic system. DETAILED DESCRIPTION

[0025] Reference Figure 1 The following describes the application applied to the filling of a hydraulic circuit of an electro-hydraulic system 20, with the aim of actuating a mobile component of an aircraft.

[0026] The electro-hydraulic system 20 comprises a motor-pump unit 21, three hydraulic cylinders 22.1, 22.2, 22.3, a hydraulic accumulator 23 and a hydraulic fluid distribution circuit 24 connecting the motor-pump unit 21 to the cylinders 22.1, 22.2, 22.3 and to the accumulator 23.

[0027] The motor-pump unit 21 comprises a hydraulic pump 21.1 driven by an electric motor 21.2. The pump 21.1 is a rotary pump with two flow directions, configured to draw in hydraulic fluid through one orifice and to expel it through another orifice. The motor 21.2 is a three-phase motor configured to receive electrical energy supplied by an electrical source and controlled by a controller (not shown).

[0028] In a conventional manner, each cylinder 22.1, 22.2, 22.3 comprises a cylinder defining a volume divided into two chambers, isolated from each other by a piston. Two orifices make it possible to insert or expel fluid into one or the other of the two chambers by means of the pressure differential induced by the pump 21.1, thus moving the piston. A rod is fixed to the piston and transmits the force for actuating one of the mobile components of the aircraft.

[0029] The distribution circuit 24 comprises a high-pressure circuit HP connecting the pump 21.1 to the cylinders 22.1, 22.2, 22.3, to supply them with pressurized fluid. The high-pressure circuit HP comprises two monostable distributors D1, D2, making it possible to selectively move the pistons of the cylinders 22.1, 22.2, 22.3.

[0030] The distributor D1 has two first ports, which are connected to the orifice of the pump 21.1, and four second ports, two of which are connected to the chambers of the cylinder 22.1, while the other two are connected to two first ports of the distributor D2. The distributor D2 has four second ports, two of which are connected to the chambers of the cylinder 22.2, while the other two are connected to the chambers of the cylinder 22.3.

[0031] In a conventional manner, the distributor D1 comprises a spool which can adopt two states: a rest state (shown in Figure 1 ), in which the spool provides a connection between the pump 21.1 and the cylinder 22.1, and a bypass state, in which the spool provides a connection between the pump 21.1 and the distributor D2.

[0032] The state of the distributor D1 is controlled by an electromagnet arranged at one end of said distributor D1, so that a voltage generated by a control unit moves the spool to enable the distributor D1 to switch from the rest state to the bypass state.

[0033] In a conventional manner, the distributor D2 comprises a spool which can adopt two states: a rest state (shown in Figure 1 ), in which the spool provides a connection between the distributor D1 and the cylinder 22.2, and a bypass state, in which the spool provides a connection between the distributor D1 and the cylinder 22.3.

[0034] The state of the distributor D2 is controlled by an electromagnet arranged at one end of said distributor D2, so that a voltage generated by a control unit moves the spool to enable the distributor D2 to switch from the rest state to the bypass state.

[0035] The distribution circuit 24 also comprises a low-pressure circuit BP connecting the accumulator 23 to the pump 21.1, to guarantee a reserve of pressurized hydraulic fluid in said distribution circuit 24, to compensate for the asymmetry of the chambers of the cylinders 22.1, 22.2, 22.3, to ensure the pressurization of the pump 21.1, and to compensate for the thermal expansion of the distribution circuit 24. The low-pressure circuit BP has a filling valve VR at the bottom and a discharge valve VP at the top. Two check valves AC1, AC2 connect the low-pressure circuit BP to the high-pressure circuit HP to achieve a flow balance, to ensure the pressurization of the pump 21.1, and the re- supply of the chambers 22.1, 22.2, 22.3.

[0036] The filling device according to the application, overall referenced 1, comprises a vacuum generator 2 and a supply of pressurized hydraulic fluid 3.

[0037] The vacuum generator 2 comprises a vacuum pump 4 connected to a first shut-off valve VI by means of a liquid / gas separator 5. The vacuum pump 4 provides a minimum pressure of 10 mbar for the suction operation.

[0038] The vacuum generator 2 is connected by a first shut-off valve V1 to the discharge valve VP of the electro-hydraulic system 20.

[0039] The hydraulic fluid supply source 3 comprises a filling pump 6 driven by an electric motor 7. The filling pump 6 has an inlet orifice connected to a reservoir 8 of hydraulic fluid H complying with the AS4059 standard to allow its circulation and connected to a third shut-off valve V3 via a check valve CV3 and has an outlet orifice connected to a second shut-off valve V2 via a check valve CV1. The capacity of the reservoir 8 is greater than the capacity of the distribution circuit 24 of the electro-hydraulic system 20. The pressure provided by the filling pump 6 is greater than or equal to a predetermined pressure of the distribution circuit 24 at rest.

[0040] A filter 9 is arranged between the outlet orifice of the filling pump 6 and the inlet orifice of the check valve CV1 to avoid contaminating the hydraulic fluid H injected into the distribution circuit 24 of the electro-hydraulic system 20. A pressure gauge 10 and a check valve CV2 are also arranged between the outlet orifice of the check valve CVT1 and the outlet orifice of the check valve CV3 to control the pressure and the direction of flow of the hydraulic fluid H in the hydraulic fluid supply source 3.

[0041] The hydraulic fluid supply source 3 also comprises a pressure regulator 11 arranged between the outlet orifice of the check valve CV3 and the inlet orifice of the filling pump 6 to make it possible to manually adjust the pressure of the hydraulic fluid H contained in the distribution circuit 24 by means of the pressure gauge 10.

[0042] The operation of the filling device 1 is described in detail below.

[0043] The discharge valve VP of the electro-hydraulic system 20 is connected to the first shut-off valve V1 of the vacuum generator 2 and to the third shut-off valve V3 of the hydraulic fluid supply source 3.

[0044] The filling valve VR of the electro-hydraulic system 20 is connected to the second shut-off valve V2 of the hydraulic fluid supply source 3.

[0045] When the second shut-off valve V2 and the third shut-off valve V3 are closed, the filling valve VR, the discharge valve VP and the first shut-off valve V1 are opened. The vacuum generator 2 is then started to create a vacuum in the low-pressure circuit BP and in the part of the high-pressure circuit HP that communicates with the vacuum generator 2 when the dispensers D1 are in the rest state.

[0046] To create a vacuum in the entire high-pressure circuit HP, the dispensers D1, D2 are controlled one after the other to switch from the rest state to the bypass state.

[0047] To measure the degree of vacuum, the pressure gauge 30 is placed as close as possible to the discharge valve VP.

[0048] When a vacuum is established in the entire distribution circuit 24 (the pressure is substantially equal to 10 mbar), the distributors D1, D2 are controlled to switch from the bypass state to the rest state and the second shut-off valve V2 is opened. Then, when the vacuum generator 2 is still running, the filling pump 6 of the hydraulic fluid supply source 3 is started, the pressure regulation being set to minimum. In this way, when the distributors D1 are in the rest state, the portions of the low-pressure circuit BP and of the high-pressure circuit HP communicating with the hydraulic fluid supply source are naturally filled with hydraulic fluid H.

[0049] To fill the entire high-pressure circuit HP, the distributors D1, then the distributors D2 are controlled to switch from the rest state to the controlled state.

[0050] In the case where the liquid / gas separator 5 is full, it can be emptied by closing the first shut-off valve V1 and opening the third shut-off valve V3. To determine that the distribution circuit 24 has been completely filled, it is necessary to repeat the filling of the liquid / gas separator 5.

[0051] When the entire distribution circuit 24 is filled with hydraulic fluid H, the first shut-off valve V1 is closed and then the third shut-off valve V3 is opened to bypass the vacuum generator 2 and to increase the pressure H of the hydraulic fluid contained in the distribution circuit 24 to the pressure determined by means of the pressure regulator 11 and the pressure gauge 10.

[0052] Once the hydraulic fluid H has reached the predetermined pressure in the entire distribution circuit 24, the discharge valve VP and the filling valve VR are closed. Thereby, the process of filling the electro-hydraulic system 20 has been completed. Subsequently, the electro-hydraulic system 20 can be disconnected from the filling device 1.

[0053] Approximately 15 minutes are required to fill the electro-hydraulic system 20. This duration depends, inter alia, on the length of the distribution circuit 24, the size of the cylinders 22.1, 22.2, 22.3, the power of the filling pump 6, etc.

[0054] It should be noted that:

[0055] - the check valves CV1 and CV3 make it possible to maintain the pressure of the hydraulic fluid H contained in the distribution circuit 24 when the filling pump 6 is not running; and

[0056] - the check valve CV2 makes it possible to force the flow of hydraulic fluid H towards the pressure regulator 11 and the filter 9.

[0057] Of course, the application is not limited to the described embodiments, but covers any variants falling within the scope of the application as defined by the claims.

[0058] The filling device can be mounted on a mobile carriage so that it is installed as close as possible to the electro-hydraulic system.

[0059] In particular when the electro-hydrostatic system is at a high level (rudder, aileron, etc.), the carrier can advantageously be a lifting carrier.

[0060] Although the distributors D1, D2 are monostable herein, they can have different properties (bistable, etc.)

[0061] The electro-hydrostatic system does not necessarily have to be provided with distributors, which simplifies the filling method.

[0062] Although the filling method is manual herein, it can be automated by using electronic sensors and shut-off valves, in particular connected to a control unit.

[0063] Depending on the structure and the position of the cylinders, they can be equipped with exhaust valves.

[0064] The number of actuators can be less than or greater than three. The electro-hydrostatic system can in particular comprise only one or two cylinders.

[0065] The cylinders can have different properties from those shown (single-acting cylinders, etc.), and are not necessarily identical.

Claims

1. A method for filling a hydraulic circuit (24) of an electro-hydraulic system (20), said hydraulic circuit being provided with a drain valve (VP) and a fill valve (VR), said method using a filling device (1) comprising: - a vacuum generator (2) designed to be connected to the drain valve via a first shut-off valve (VI) to eliminate the air or gas present in the circuit, and - a hydraulic fluid supply source (3) for supplying pressurized hydraulic fluid designed to be connected to the fill valve via a second shut-off valve (V2) and to the drain valve and to the first shut-off valve via a third shut-off valve (V3) to fill the hydraulic fluid circuit, and said method comprising the steps of: - connecting the first and third shut-off valves (VI, V3) to the drain valve (VP) and the second shut-off valve (V2) to the fill valve (VR); - opening the fill valve, the drain valve and the first shut-off valve and operating the vacuum generator (2) when the second and third shut-off valves are closed; - once a vacuum has been established in the circuit, opening the second shut-off valve in order to fill the circuit with pressurized hydraulic fluid while the vacuum generator is still operating; - once the circuit has been filled with fluid, closing the first shut-off valve and then opening the third shut-off valve to bypass the vacuum generator and circulate the fluid through the electro-hydraulic system until the fluid contained in the circuit reaches a predetermined pressure; - closing the drain valve and the fill valve.

2. The method of claim 1, wherein, The electro-hydraulic system (20) comprises a plurality of actuators selectable by at least two distributors (Dl, D2) and the method comprises a step of controlling the distributors one after the other in succession to establish a vacuum in the hydraulic circuit (24) and a step of controlling the distributors according to a predetermined sequence to fill the hydraulic circuit.

3. The method according to claim 1 or 2, characterized in that, The vacuum generator (2) comprises a vacuum pump (4) connected to the first shut-off valve by means of a liquid / gas separator (5).

4. The method according to claim 1 or 2, characterized in that, The hydraulic fluid supply source (3) comprises a filling pump (6) connected to a reservoir whose capacity is greater than that of the hydraulic circuit (24) of the electro-hydraulic system.

5. The method according to claim 1 or 2, characterized in that, The vacuum generator (2) and the hydraulic fluid supply source (3) are mounted on a mobile carriage.

6. The method of claim 5, wherein, The mobile carriage is a lifting carriage.

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