Electric hydraulic pitch with reversible pump

Abstract

The invention relates to a mechanism for varying the pitch of a propeller (13) of a turbomachine, the mechanism comprising an electro-hydraulic actuator (11), the mechanism comprising: - an electric motor comprising a rotatable actuation shaft; - a pumping assembly comprising two hydraulic axial piston pumps, each hydraulic axial piston pump comprising: o a barrel housed in a cavity filled with hydraulic fluid; o a set of cylinders formed in the barrel, each cylinder housing a translatable piston and comprising an intake port and a delivery port; o and a tilted disc, the disc of the first pump comprising a crescent intake port for the circulation of hydraulic fluid when the disc is rotated in a first direction, and the disc of the second pump comprising a crescent intake port for the circulation of hydraulic fluid when the disc is rotated in a second direction.

Description

Technical Field

[0001] This invention relates to the field of turbines, including propellers or variable-pitch fans. More specifically, this invention relates to a system for actuating the pitch of the propeller or fan of such a turbine. Background Technology

[0002] Different turbine designs seek propellers (turboprops, open rotors) or fans (turbojet engines) with variable pitch. This variability allows the turbine to adapt to varying flight conditions by maintaining a favorable angle of incidence of air on the blades. Variable pitch is particularly necessary for rotors with low compression ratios, such as fans of turbines and propellers of turboprops, which have high expansion ratios (the ratio of the flow rate of the secondary (cooled) flow to the flow rate of the main (through-body) flow).

[0003] Numerous pitch-changing mechanisms have been envisioned to alter the pitch of propeller or fan blades. These mechanisms typically involve a configuration that rotates the blades about their main axis via kinematic lines (e.g., an eccentric rod assembly actuated by an actuator). The actuator is supplied with hydraulic fluid (e.g., oil) from the turbine's lubrication unit. Variations in the pressure of the delivered hydraulic fluid and the distribution of the fluid within one actuator chamber or another enable the alteration of the blade pitch. To transfer the supply of hydraulic fluid for the pitch-changing mechanism from the turbine's stationary reference frame (lubrication unit) to the rotating reference frame (fan), an oil transfer bearing (OTB) is typically used. In a manner known per se, the OTB comprises a portion fixed relative to the turbine's stator and connected via dedicated channels to servo valves and a pump, and a rotating portion that moves as a unit with the turbine's rotor, the pump itself being connected to an engine lubrication unit comprising an oil reservoir and the pump. However, the OTB is a complex and fragile device, prone to failure, particularly severe oil leaks, which can affect turbine reliability and performance, and require the installation of a return oil pump and an oversized engine oil system. Furthermore, because this configuration relies on the ratings of the turbine's high-pressure body, it is limited in operation at low ratings, and because it depends on the supply of the engine oil circuit, it is susceptible to supply problems during certain maneuvers. Finally, this configuration requires a system to protect it from a hydraulic failure in flight that could close the blade pitch. Two systems are conceivable: a system that locks the blade pitch (“pitch lock”) or a counterweight system to provide feathering to the blades (opening the pitch to limit drag). Both systems are heavy, complex, expensive, and can lead to other failure scenarios, such as improperly set locks.

[0004] Furthermore, when using an irreversible hydraulic pump, it is necessary to use a flow switching valve to allow the pitch changing mechanism to change the pitch in both directions of movement. This switching valve is typically electrically driven; therefore, if such a valve is integrated into the propeller, control current needs to be transmitted from the turbine stator to the turbine rotor (propeller).

[0005] Furthermore, since the start-up of the lubrication unit is usually related to the start-up of the turbine, it is necessary to provide auxiliary systems to offer some protection, especially in cases of overspeed or engine shutdown. Therefore, it is necessary to provide a feathering system that can operate even without hydraulic fluid pressure.

[0006] In addition, the pitch changing mechanism must be able to ensure that it retracts from the feathering position when the engine is stopped. Summary of the Invention

[0007] One object of the present invention is to provide a variable pitch turbine that overcomes the disadvantages of the prior art mentioned below.

[0008] Another object of the present invention is to provide an independent pitch changing mechanism that eliminates the difficulties associated with the delivery of hydraulic fluid from a fixed reference frame to a rotating reference frame.

[0009] Another object of the present invention is to provide a passive pitch changing mechanism, that is, a mechanism that does not require any electrical system and controller to change the pitch of a turbine propeller (or fan).

[0010] Another object of the present invention is to provide a pitch changing mechanism that can be used regardless of the turbine's operating state. Furthermore, the pitch changing mechanism can realize the protection function and feathering function of the turbine's propeller / fan blades without relying on the electrical control system.

[0011] Another object of the present invention is to provide a pitch changing mechanism that can be implemented in an open rotor type turbine including a propeller or a turboprop type turbine, and in a turbojet engine including a fan.

[0012] Therefore, according to a first aspect, the present invention provides a pitch changing mechanism for a turbine propeller, the turbine including a stator and a rotor, the pitch changing mechanism including an electro-hydraulic actuator, the pitch changing mechanism comprising:

[0013] - An electric motor, which is fixedly mounted on the stator portion of the turbine and includes an actuation shaft capable of rotating about a rotational axis;

[0014] - Pumping assembly, comprising two axial piston hydraulic pumps adapted to pressurize hydraulic fluid, each hydraulic pump including:

[0015] o-Cylinder section, which is housed in a cavity that is fully or partially filled with hydraulic fluid, and is fixedly connected to the stator section of the turbine to prevent the cylinder section from rotating about the actuation shaft;

[0016] o A set of cylinders formed inside the cylinder, each cylinder housing a piston capable of translational movement within the cylinder and including a feed port and a discharge port, the feed port being configured to receive hydraulic fluid from the cavity, and the discharge port being configured to deliver the hydraulic fluid to the actuator of the propeller.

[0017] The disc is tilted relative to the axis of rotation and rotatably fixed to the actuation shaft, with each piston supported on the surface of the disc;

[0018] The first pump disc in the pump includes a curved feed opening that extends circumferentially relative to the axis of rotation and is configured to allow hydraulic fluid to flow from the cavity of the first pump to the cylinder of the first pump when the pump disc is driven in a first rotational direction. The second pump disc in the pump also includes a curved feed opening that extends circumferentially relative to the axis of rotation and is configured to allow hydraulic fluid to flow from the cavity of the second pump to the cylinder of the second pump when the pump disc is driven in a second rotational direction opposite to the first rotational direction.

[0019] Advantageously, the invention is achieved by the following features, which are employed individually or in any combination of technically possible combinations of these features:

[0020] - When the disc of the first pump is driven in the second rotation direction, the feed port of the cylinder is closed by the surface of the disc of the first pump; when the disc of the second pump is driven in the first rotation direction, the feed port of the cylinder is closed by the surface of the disc of the second pump.

[0021] - The pump's discharge port is adjacent to and leads to the central area of ​​the pumping assembly;

[0022] - Each cylinder also includes a drain valve, which is mounted on a drain port and configured to prevent hydraulic fluid from flowing in the direction of the cylinder;

[0023] - The pitch changing mechanism also includes an annular groove formed in the body of each pump, the annular groove being in fluid communication with the discharge port of the corresponding pump cylinder;

[0024] - The propeller actuator includes two chambers, the first chamber of which is in fluid communication with the annular groove of the first pump, and the second chamber of which is in fluid communication with the annular groove of the second pump.

[0025] -The pitch changing mechanism also includes:

[0026] o A first hydraulic valve, configured to fluidly communicate a first chamber of the actuator with an annular groove of a first pump when the actuator shaft is driven in a first rotational direction, or to fluidly communicate a first chamber of the actuator with a hydraulic accumulator when the actuator shaft is driven in a second rotational direction; and

[0027] The second hydraulic valve is configured to fluidly communicate the second chamber of the actuator with the annular groove of the second pump when the actuator shaft is driven in the second rotational direction, or to fluidly communicate the second chamber of the actuator with the hydraulic accumulator when the actuator shaft is driven in the first rotational direction.

[0028] - The first hydraulic valve and the second hydraulic valve are controlled by the pressure at the discharge port of the first pump and the pressure at the discharge port of the second pump, respectively.

[0029] - The motor (29) is an asynchronous motor;

[0030] - The propeller pitch is controlled by the torque of the motor. Attached Figure Description

[0031] Other features and advantages of the invention will become apparent from the following description of preferred embodiments. This description will be given with reference to the accompanying drawings, in which:

[0032] Figure 1 This is a schematic cross-sectional view of an example turbine, which includes a fan or propeller with variable pitch and a pitch changing mechanism according to an embodiment of the invention.

[0033] Figure 2 This is a partial schematic cross-sectional view of an exemplary embodiment of a planetary mechanical reducer, which can be used in a turbine including a pitch changing mechanism according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic cross-sectional view of the propeller pitch changing mechanism according to the present invention.

[0035] Figure 4 This is a schematic diagram of an example of an annular groove formed in the body of the pump;

[0036] Figure 5 This is a schematic diagram of an example of a curved feed opening formed in the disc of a pump;

[0037] Figure 6This is a schematic diagram of the propeller pitch changing mechanism according to an embodiment; and

[0038] Figure 7 This is a schematic diagram of the propeller pitch changing mechanism according to an embodiment. Detailed Implementation

[0039] This invention is applicable to any turbine with variable pitch, which includes a pitch-changing mechanism. In particular, this invention relates to... Figure 1 The illustrations include turbines with propellers (e.g., turboprops) or other open rotors (ductless propellers) and ducted turbojet engines including fans, wherein the pitch of the fan or propeller blades can be varied according to flight conditions. For the remainder of this application, for the sake of simplicity in the specification and claims, the term "propeller" will be used to refer to the propeller or fan of the turbojet engine as described above.

[0040] Typically, in addition to the propeller, a turbine also includes a mechanical reduction gear 50, such as... Figure 2 As shown, a mechanical reducer is configured to rotatably drive a propeller. The reducer 50 is housed within the turbine housing. The turbine is configured to be fixedly mounted on the aircraft by suitable attachment means (e.g., pylons). For the remainder of this document, the term "stator portion of the turbine" will refer to any portion of the turbine fixed relative to the housing, which is configured to be connected to a pylon, and "rotor portion of the turbine" will refer to any portion that can move about an axis when the turbine is in operation, and by definition, the rotor portion of the turbine is therefore movably mounted relative to the stator portion. As an example, the stator portion includes the turbine housing, within which means for driving the propeller, etc., are housed. For example, the rotor portion includes a propeller and a drive shaft for the propeller.

[0041] Finally, in this application, upstream and downstream are defined relative to the conventional flow direction of gas in and through the propeller. Furthermore, "axis A" of the hydraulic pump refers to the axis of rotation of the hydraulic pump. The axial direction corresponds to the direction of axis A, and the radial direction is the direction perpendicular to and through the axis. Additionally, the circumferential (or transverse) direction corresponds to the direction perpendicular to axis A and does not cross the axis. Unless otherwise stated, the terms "inner" and "outer" are used with reference to the radial direction, such that the inner portion or inner surface of an element is closer to axis A than the outer portion or outer surface of the same element. Furthermore, when an element rotates relative to axis A, the element is considered "in a fixed reference frame," while when an element can be driven to rotate relative to axis A, the element is considered "in a rotating reference frame."

[0042] The reducer 50 is planetary and includes:

[0043] -Sun gear 51, the sun gear is centered on the rotation axis of the reducer and is configured to be rotated and driven by the drive input shaft of the turbine.

[0044] - Ring gear 52, the ring gear being coaxial with the sun gear 51 and configured to drive the propeller shaft about the axis of rotation, and

[0045] - Planetary gear train 53, which is circumferentially distributed around the axis of rotation of the reducer between the sun gear 51 and the ring gear 52. Each planetary gear meshes with the sun gear 51 on the inner side and with the ring gear 52 on the outer side. The planetary gear train 53 is mounted on a planet carrier 54, which is fixed relative to the stator of the turbine.

[0046] In a variant, the reducer 50 can be planetary type, in which case the ring gear 52 is fixedly mounted on the stator of the turbine, and the drive shaft is rotatably driven by the planet carrier 54.

[0047] like Figure 3 As shown, the pitch changing mechanism includes an electro-hydraulic actuator 11 (EHA), a pumping assembly 2, and a motor 29. The electro-hydraulic actuator is configured to actuate actuator 15, which is mechanically connected to propeller 13 to change the propeller pitch. The pumping assembly is configured to pressurize a fluid (typically oil).

[0048] The motor 29 is fixedly mounted on the stator portion of the turbine, and the motor includes an actuation shaft 21 that is rotatable about the rotation axis A.

[0049] The pumping assembly 2 includes two axial piston hydraulic pumps 20a and 20b, which are adapted to pressurize hydraulic fluid and share an identical body 22, which is driven to rotate by a propeller 13.

[0050] Each of pumps 20a and 20b includes a cylinder 23a (23b) and a disc 26a (26b), the cylinder being housed in a cavity 221a (221b) which is wholly or partially filled with hydraulic fluid. An orifice assembly is formed in the cylinder 23a (23b), defining a cylinder configured to slidably receive a piston 24. The translation axis of the piston 24 is generally parallel to the rotation axis A. Each piston 24 includes a sliding pad 25, which is thus configured to be supported on the disc 26a (26b).

[0051] The cylinder portion 23a (23b) and associated piston 24 of each of the two pumps 20a and 20b are fixedly connected to the stator portion of the turbine to prevent the cylinder portion and piston from rotating about the drive shaft 21. Therefore, the cylinder portions 23 and 23b cannot rotate about axis A (and are thus in a fixed reference frame). Specifically, the cylinder portions 23a and 23b can be mechanically connected. In an embodiment, when the reducer 50 is a planetary reducer, the two cylinder portions 23a and 23b are securely attached to the planet carrier 54 of the reducer 50 to secure the second cylinder portion. In a variant, when the reducer 50 is a planetary reducer (the drive shaft is driven by the planet carrier 54), the cylinder portion can be mounted on the ring gear 52.

[0052] Two disks 26a and 26b are mounted around the actuation shaft 21, tilted relative to the axis of rotation A, and rotatably fixed to the actuation shaft 21. Therefore, disks 26a and 26b are rotatably driven by the actuation shaft 12. The sliding pad 25 of the piston 24 is configured to slide freely along the disks 26a (26b), while the sliding pad is supported on the disks (constant contact) regardless of the angular position of the piston 24 about the axis of rotation A.

[0053] Two cylindrical portions 23a and 23b are mounted around an actuation shaft 21. Since the cylindrical portions 23a and 23b are in a fixed reference frame, and the actuation shaft 21 is configured to be driven by a motor 29 rotating about axis A, each cylindrical portion includes through-holes 234a and 234b configured to receive the actuation shaft 21 of the motor 29. The through-holes 234a and 234b are coaxial and, where applicable, connected.

[0054] To enable rotational blocking of the cylinder portions 23a and 23b, the electro-hydraulic actuator 11 includes a first bearing 27a (27c) and a second bearing 27b (27d). The first bearing 27a (27c) is configured to support the disc 26a (26b) of the first pump 20a (second pump 20b), and the second bearing 27b (27d) is configured to support the cylinder portion 23a (23b) of the first pump 20a (second pump 20b). For example, the first bearing 27a (27c) may be installed between the disc 26a (26b) and the cylinder portion 23a (23b), particularly at the portion connecting the cylinder portion to a fixed reference system for the first pump 20a, while the second bearing 27b (27d) is installed between the cylinder portion 23a (23b) and the body 22.

[0055] During operation of the electro-hydraulic actuator 11, the two discs 26a, 26b are driven rotatably by the actuation shaft 21 about the rotation axis A. The two cylinders 23a, 23b are fixed. Since the pistons 25 of the two pumps 20a, 20b are constantly supported on the corresponding discs 26a, 26b of the pistons, this rotational motion has the effect of displacing the sliding pads 25 of the piston 24 along an axis parallel to the rotation axis A, thereby producing a reciprocating motion whose amplitude is determined by the inclination of the discs 26a, 26b relative to the rotation axis A.

[0056] In this embodiment, the discharge holes 232 of pumps 20a and 20b are adjacent and lead to the central region of the pumping assembly 2. Therefore, discs 26a and 26b are each located at opposite ends of the pumping assembly 2 and are coaxial with the rotation axis A. Thus, the pumping assembly 2 sequentially includes a first disc 26a, a cylindrical portion 23a, a discharge hole 232 of pump 20a, an annular groove of pump 20a, an annular groove of pump 20b, a discharge hole 232 of pump 20b, a cylindrical portion 23b, and a second disc 26b along the rotation axis A. Therefore, the cylindrical portions 23a and 23b are configured such that the sliding pad 25 of the piston 24 is oriented towards the end along the rotation axis A of the pumping assembly 2.

[0057] In each pump, the cylinder includes a feed port 242 and a discharge port 232. The feed port is configured to receive hydraulic fluid from cavities 211a, 211b, and the discharge port is configured to pass through annular grooves 223a, 223b formed in the body 22. Figure 4 The hydraulic fluid contained in the cylinder is discharged to the propeller actuator 15. The use of this annular groove, which is in fluid communication with the discharge port 232 of the cylinder, allows the pump to operate regardless of the angular position of the body 22 and therefore the angular position of the discharge port 232 during the movement of the piston 24.

[0058] Furthermore, the disk 26a of the first pump 20a in the pump includes a curved feed opening 261a extending circumferentially relative to the axis of rotation A. Figure 5 The curved opening is configured such that when the disc 26a of the pump 20a is driven in a first rotational direction about the axis of rotation A, hydraulic fluid can flow from the cavity 221a of the first pump 20a in the pump to the cylinder of the first pump in the pump.

[0059] Symmetrically, the disc 26b of the second pump 20b in the pump includes a curved feed opening 261b extending circumferentially relative to the axis of rotation A. This curved opening is configured such that when the disc 26b of the pump 20b is driven in a second rotational direction about the axis of rotation A, hydraulic fluid can flow from the cavity 221b of the second pump 20b in the pump to the cylinder of the second pump in the pump, the second rotational direction being opposite to the first rotational direction.

[0060] For example, each curved feed opening 261a, 261b extends circumferentially relative to the axis of rotation A to form a semicircle. Therefore, curved feed opening 261a is symmetrical with respect to curved feed opening 261b, that is, curved feed opening 261a and curved feed opening 261b are opposite each other in the diametrical direction.

[0061] Pumps 20a and 20b also include a closing device configured to close the feed port 242 of the cylinder to prevent hydraulic fluid from entering the cylinder when pumps 20a and 20b must not discharge, i.e., when the rotational axis of the first pump 20a rotates in the second direction and the rotational axis of the pump 20b rotates in the second direction. In a first variant embodiment, the closing device includes a feed valve mounted at the feed port 242 of each cylinder. Each feed valve has an open configuration and a closed configuration. In the open configuration, the feed valve opens and allows hydraulic fluid to flow from the cylinder portion to the cylinder. In the closed configuration, the discharge valve closes the cylinder and prevents hydraulic fluid from flowing between the cylinder and the corresponding cylinder portion 23a, 23b. In the closed configuration, the feed valve thus prevents pressurized hydraulic fluid from the cylinder from returning along the direction of the cylinder portion 23a, 23b. Since the cylinder sections 23a and 23b are rotatable, preferably, the feed valve 241 is installed inside the cylinder, and the feed valve automatically (passively) positions itself in an open or closed configuration depending on the position of the piston 24 in the cylinder. Where applicable, in particular, the feed valve 241 may be installed close to the sliding pad 25.

[0062] In a variant embodiment that can be combined with the first variant, the function of the closing device is directly implemented by the discs 26a, 26b of pumps 20a, 20b. For this purpose, each disc 26a, 26b can be configured such that when disc 26a is driven in the rotational direction in which the corresponding pump 20a, 20b is not discharging (i.e., the second rotational direction in the case of the first pump 20a, and the second rotational direction in the case of the second pump 20b), the surface of the disc closes the feed port 242 of the cylinder. For example, the surface of each disc 26a, 26b may include curved feed openings 261a, 261b that extend circumferentially relative to the rotation axis A in a first semicircle to form a semicircle, and are solid or even include circumferential protrusions relative to the rotation axis A in a second semicircle.

[0063] Therefore, depending on the rotation direction of the actuation shaft 21, only one of the two pumps 20a and 20b discharges. Specifically, when the actuation shaft rotates in the first rotation direction, when the piston is in the feeding phase, the feed port 242 of the cylinder of the first pump 20a is positioned to face the curved feed opening 261a, allowing hydraulic fluid to enter the hole of the cylinder 23a. On the other hand, the feed port 242 of the cylinder of the second pump 20b is positioned to face the solid portion of the disc 26b, which closes the feed port 242, thus preventing hydraulic fluid from entering the hole of the cylinder 23b. Therefore, only the first pump 20a is discharging.

[0064] Conversely, when the actuation shaft rotates in the second rotational direction, and when the piston is in the feeding phase, the feed port 242 of the cylinder of the second pump 20b is positioned to face the curved feed opening 261b, allowing hydraulic fluid to enter the hole in the cylinder 23b. On the other hand, the feed port 242 of the cylinder of the first pump 20a is positioned to face the solid portion of the disc 26a, which closes the feed port 242, thus preventing hydraulic fluid from entering the hole in the cylinder 23a. Therefore, only the second pump 20b is discharging.

[0065] In an embodiment, each cylinder includes means configured to close or open the drain port 232. In an embodiment, these means include a drain valve 231 mounted at the drain port 232. Each drain valve 231 has an open configuration and a closed configuration. In the open configuration, the drain valve 231 opens and allows hydraulic fluid to flow from the cylinder to the annular groove. In the closed configuration, the drain valve 231 closes the cylinder and prevents hydraulic fluid from flowing between the cylinder and the annular groove. In the closed configuration, the drain valve 231 thus prevents pressurized hydraulic fluid from the annular grooves 223a, 223b from returning along the cylinder direction. Since the body 22 is rotatable, preferably, the drain valve 231 is mounted inside the cylinder, and the drain valve automatically (passively) positions itself in the open or closed configuration depending on the position of the piston 24 in the cylinder.

[0066] Preferably, the actuator 15 includes a dual-acting cylinder comprising a first chamber 151 and a second chamber 152. Furthermore, the actuator 15 is rotatably fixed to and connected to the propeller 13, such that actuation of the actuator 15 (by successively filling and emptying the first and second chambers) has the effect of changing the pitch of the propeller 13 in one or the other direction.

[0067] Reference Figure 6The electro-hydraulic actuator 11 also includes two-way valves 153 and 154 and a hydraulic accumulator 16. The two-way valves have two positions fluidly connected to each pump 20a, 20b, and the hydraulic accumulator is mounted in the rotating reference frame of the propeller. Each valve 153, 154 is controlled between a first position (the so-called actuated position) and a second position by the pressure of hydraulic fluid at an annular groove in the corresponding pump 20a, 20b. In the first position, valves 153, 154 fluidly communicate one chamber of the actuator 15 with the annular groove of the corresponding pump, and in the second position, valves 153, 154 fluidly communicate the same chamber of the actuator 15 with the hydraulic accumulator. Valves 153, 154 position themselves in the first position when the pressure at the outlet of pumps 20a, 20b overcomes the rigidity of the spring associated with the valves 153, 154. Therefore, each valve 153, 154 is passively shifted between a first position and a second position according to the pressure of the hydraulic fluid at the outlet of the corresponding pump 20a, 20b, the pressure of the hydraulic fluid at the outlet of the corresponding pump depending on the rotation direction of the actuation shaft 21.

[0068] More specifically, the first valve 153, controlled by the pressure at the outlet of the first pump 20a, is configured to fluidly communicate the first chamber 151 of the actuator 15 with the annular groove of the first pump 20a (through which the first pump 20a discharges pressurized fluid), when the actuator shaft 21 rotates in the first rotational direction, or to fluidly communicate the first chamber of the actuator with the hydraulic accumulator 16 when the actuator shaft 21 is driven in the second rotational direction. Similarly, the valve 154, fluidly connected to the second pump 20b, is configured to fluidly communicate the second chamber 152 of the actuator 15 with the annular groove of the second pump 20b (through which the second pump 20b discharges pressurized fluid), when the actuator shaft 21 rotates in the second rotational direction, or to fluidly communicate the second chamber of the actuator with the hydraulic accumulator 16 when the actuator shaft rotates in the first rotational direction.

[0069] Therefore, when the motor 29 actuates the actuation shaft 21 of the pumping assembly 2 in the first rotational direction, it has the effect of filling the first chamber 151 of the actuator 15 and emptying the second chamber 152 of the actuator, while when it actuates the second actuation shaft 21 in the second rotational direction, it has the effect of filling the second chamber 152 of the actuator 15 and emptying the first chamber 151 of the actuator. Therefore, the propeller pitch, depending on the fluid pressure in the first chamber 151 and the second chamber 152 of the actuator 15, can be completely controlled by the motor 29. Thus, this operating mode eliminates the need for a flow switching valve to select the chamber of the actuator that is guided with pressurized hydraulic fluid.

[0070] Furthermore, since the propeller pitch is directly controlled by the hydraulic fluid generated by the hydraulic pump 20 (which depends on the displacement speed of the piston 24), the control of the propeller pitch 13 can be achieved using the torque control of the motor 29. In this embodiment, the motor 29 is an asynchronous motor, which does not generate any resistive torque in the event of a short circuit, thus reducing the risk of fire.

[0071] It should be noted that the pumping assembly 2 consists only of passively actuated devices, and the valves are controlled solely by the pressure at the outlets of pumps 20a and 20b. Therefore, no controller or electrical system is required other than the electrical devices necessary to control the electric motor 29.

[0072] Typically, the pitch-changing mechanism may also include a feathering system that operates without hydraulic fluid pressure. In an embodiment, the feathering system includes a lightweight type of counterweight.

[0073] Therefore, this configuration of the pitch changing mechanism eliminates the need for an oil-transmitted bearing (OTB), thereby eliminating the risk of leakage and the associated size limitations of the turbine's lubrication circuit and pitch actuation system. Furthermore, this circuit is independent of the lubrication unit, and more generally, independent of the turbine's lubrication circuit. Since the solution provided is based on a closed hydraulic circuit independent of the turbine's lubrication circuit, there is, in particular, no longer a supply problem based on flight maneuvers. Specifically, the pressure transmitted by the hydraulic pump 20 can reach a significant level (approximately 300 bar), which simplifies the size of the actuator 15. Furthermore, the pump is driven by an electric motor. Therefore, it is conceivable to power the system from various electrical sources, allowing it to operate independently of the turbine's main HP rotational speed.

[0074] It should be noted that the feathering mechanism here only includes passive actuation devices, and the safety valve 18 and auxiliary valve 19 are controlled solely by pressure in the hydraulic circuit of the pitch changing mechanism. Therefore, no controller or electrical system is required other than the electrical devices needed to control the flow switching valve and the electric motor 29.

Claims

1. A pitch changing mechanism for a propeller (13) of a turbine, the turbine comprising a stator and a rotor, the pitch changing mechanism comprising an electro-hydraulic actuator (11), the pitch changing mechanism comprising: - Motor (29), which is configured to be fixedly mounted on the stator portion of the turbine and includes an actuation shaft (21) capable of rotating about a rotation axis (A). - Pumping assembly (2), which includes two axial piston hydraulic pumps (20) adapted to pressurize hydraulic fluid. The first axial piston hydraulic pump of the two axial piston hydraulic pumps includes: - A first cylinder (23a), which is housed in a first cavity (221a) that is fully or partially filled with hydraulic fluid, the first cylinder (23a) being configured to be fixedly connected to the stator portion of the turbine to prevent the first cylinder from rotating about the actuation shaft (21); - A first set of cylinders, formed inside the first cylindrical section (23a), each cylinder housing a piston (24) capable of translational movement within the cylinder and including a feed port (242) and a discharge port (232), the feed port being configured to receive hydraulic fluid from the first cavity (221a), and the discharge port being configured to deliver hydraulic fluid to the actuator (15) of the propeller. - A first disc (26a), which is tilted relative to the axis of rotation (A) and rotatably fixed to the actuation shaft (21), with each piston (24) supported on the surface of the first disc (26a); The second axial piston hydraulic pump of the two axial piston hydraulic pumps includes: - A second cylinder (23b), which is housed in a second cavity (221b) that is fully or partially filled with hydraulic fluid, the second cylinder (23b) being configured to be fixedly connected to the stator portion of the turbine to prevent the second cylinder from rotating about the actuation shaft (21); - A second set of cylinders is formed inside the second cylindrical section (23b), each cylinder housing a piston (24) capable of translational movement within the cylinder and including a feed port (242) and a discharge port (232), the feed port being configured to receive hydraulic fluid from the second cavity (221b), and the discharge port being configured to deliver hydraulic fluid to the actuator (15) of the propeller. - A second disc (26b), which is tilted relative to the axis of rotation (A) and rotatably fixed to the actuation shaft (21), with each piston (24) supported on the surface of the second disc (26b); The first disc of the first axial piston hydraulic pump (20a) includes a first curved feed opening (261a) that extends circumferentially relative to the axis of rotation (A) and is configured such that when the first disc (26a) of the first axial piston hydraulic pump (20a) is driven in a first rotational direction, hydraulic fluid can flow from the first cavity (221a) of the first axial piston hydraulic pump (20a) to the cylinder of the first axial piston hydraulic pump. The second disc (26b) of the second axial piston hydraulic pump (20b) includes a second curved feed opening (261b) that extends circumferentially relative to the axis of rotation (A) and is configured such that when the second disc (26b) of the second axial piston hydraulic pump (20b) is driven in a second rotational direction, the hydraulic fluid can flow from the second cavity (221b) of the second axial piston hydraulic pump (20b) to the cylinder of the second axial piston hydraulic pump. The second rotational direction is opposite to the first rotational direction.

2. The pitch changing mechanism according to claim 1, wherein, When the first disc (26a) of the first axial piston hydraulic pump (20a) is driven in the second rotation direction, the feed port (242) of the cylinder is closed by the surface of the first disc of the first axial piston hydraulic pump (20a), and when the second disc (26b) of the second axial piston hydraulic pump (20b) is driven in the first rotation direction, the feed port (242) of the cylinder is closed by the surface of the second disc of the second axial piston hydraulic pump (20b).

3. The pitch changing mechanism according to claim 1, wherein, The discharge port (232) of the axial piston hydraulic pump is adjacent to and leads to the central region of the pumping assembly (2).

4. The pitch changing mechanism according to claim 1, wherein, Each cylinder also includes a discharge valve (231) mounted on the discharge port (232) and configured to prevent hydraulic fluid from the actuator (15) from flowing in the direction of the cylinder.

5. The pitch changing mechanism according to claim 1 further includes a first annular groove (222a) formed in the body (22) of the first axial piston hydraulic pump and a second annular groove (222b) formed in the body of the second axial piston hydraulic pump, each of the first annular groove (222a) and the second annular groove (222b) being in fluid communication with the discharge port (232) of the cylinder of the corresponding axial piston hydraulic pump.

6. The pitch changing mechanism according to claim 5, wherein, The propeller actuator (15) includes two chambers, the first chamber of which is in fluid communication with the first annular groove (222a) of the first axial piston hydraulic pump (20a), and the second chamber of which is in fluid communication with the second annular groove (222b) of the second axial piston hydraulic pump (20b).

7. The pitch changing mechanism according to claim 6 further includes: - A first hydraulic valve (153), configured to fluidly communicate the first chamber (151) of the actuator with the first annular groove (222a) of the first axial piston hydraulic pump (20a) when the actuating shaft (21) is driven in the first rotational direction, or to fluidly communicate the first chamber of the actuator with the hydraulic accumulator (16) when the actuating shaft (21) is driven in the second rotational direction; and - A second hydraulic valve (154) configured to fluidly communicate the second chamber (152) of the actuator with the second annular groove (222b) of the second axial piston hydraulic pump (20b) when the actuator shaft (21) is driven in the second rotational direction, or to fluidly communicate the second chamber of the actuator with the hydraulic accumulator (16) when the actuator shaft (21) is driven in the first rotational direction.

8. The pitch changing mechanism according to claim 7, wherein, The first hydraulic valve (153) and the second hydraulic valve (154) are controlled by the pressure at the discharge port (232) of the first axial piston hydraulic pump (20a) and the pressure at the discharge port of the second axial piston hydraulic pump (20b), respectively.

9. The pitch changing mechanism according to claim 1, wherein, The motor (29) is an asynchronous motor.

10. The pitch changing mechanism according to claim 1, wherein, The pitch of the propeller (13) is controlled by the torque control of the motor (29).

11. A turbine comprising a propeller (13) and a pitch changing mechanism according to any one of claims 1 to 10, the pitch changing mechanism being configured to actuate an actuator (15) mechanically connected to the propeller (13).

12. An aircraft comprising at least one turbine according to claim 11, the turbine being connected to the aircraft via a pylon.

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