Transmission system for accessory gearbox of aircraft turbine engine and method of using same

Abstract

A transmission system for driving a device through an accessory gearbox, the transmission system comprising: a gear train comprising a ring gear (5), a planet gear (6) integral with an output shaft (4) and a planet carrier (7) integral with an input shaft (3); a clutch device (10) for the input shaft (3) and the output shaft (4); and a locking device (9), the system comprising a first configuration in which the clutch device (10) is in the engaged position and the locking device (9) is in the disengaged position to drive the output shaft (4) to rotate at the rotational speed of the input shaft (3), and a second configuration (C2) in which the clutch device (10) is in the disengaged position (D) and the locking device (9) is in the connected position (B) to drive the output shaft (4) to rotate at the rotational speed of the input shaft (3). Therefore, the output shaft (4) is driven to rotate at a rotating speed (N4) higher than the rotating speed (N3) of the input shaft.

Description

Technical Field

[0001] The present invention relates to an accessory gearbox for an aircraft turbine engine, and more particularly to a speed change system for the gearbox and a method of using the same. Background Art

[0002] As is known to all, an aircraft turbine engine accelerates a flowing airflow through one (or more) compressors, a combustion chamber and one (or more) turbines to propel the aircraft. The turbine is connected to the compressor through at least one turbine engine shaft.

[0003] As is known, an aircraft turbine engine comprises an accessory gearbox, known to the skilled person by the abbreviation AGB. The accessory gearbox comprises at least one input connected to a number of mutually parallel axes. The input is configured to receive a driving torque from a turbine engine shaft, in particular via radial arms and bevel gears. In operation, the torque received by the input is transmitted to each axis. On each axis one or more devices are mounted in series, such as a lubrication unit, a fuel pump, a generator, a starter and an oil separator.

[0004] As is known, a lubrication unit (GDL) is supplied from a reservoir of lubricating fluid. The lubrication unit generally comprises several pumps, including at least one feed pump designed to supply lubricating fluid to various circuits of an aircraft turbine engine at a flow rate and pressure adapted to the turbine engine speed. The pump is generally driven by an axis with a constant reduction ratio, so that the drive speed is proportional to the rotational speed of the turbine engine shaft.

[0005] In practice, during sub-idling of an aircraft turbine engine, the flow rate and pressure of the lubricating fluid provided by the lubrication unit are insufficient. The rotation speed of the turbine engine shaft is too low to ensure sufficient drive force for certain circuits of the pump, which can lead to damage to the turbine engine, in particular due to seizure. Sub-idling can occur, for example, when an aircraft turbine engine is being started, or when a turbine engine fan or propeller is windmilling (i.e. in automatic rotation), or during maintenance, such as cleaning of the fan.

[0006] One solution is to increase the size of the pump. However, this will undesirably increase the complexity and overall size of the lubrication unit in the accessory gearbox. In particular, pumps are difficult to size to be able to deliver significant flows at very low speeds.

[0007] From US2022010733A1 it is known that torque can be extracted from an aircraft turbine engine to drive an output shaft via a planetary gear train, a clutch and a brake. Above a threshold oil pressure provided by a pump driven by the turbine engine, the brake is activated to block the ring gear of the planetary gear train and increase the speed of the output shaft. The device is not designed for controlled lubrication and even if it is turned on for controlled lubrication, it will result in reduced lubrication at low speeds.

[0008] US2021102499A1 also describes a drive system for driving an accessory gearbox, which can be connected to both a low-pressure shaft and a high-pressure shaft. CN106438880A and US11364797B1 disclose a multi-stage transmission system for a vehicle. Summary of the invention

[0009] The present invention aims to at least partially eliminate these disadvantages.

[0010] The invention relates to a transmission system for driving at least one device through an accessory gearbox of an aircraft turbine engine, the transmission system comprising an input shaft and an output shaft configured to be driven in rotation by the input shaft, the output shaft being configured to be connected to a rotating part of the device.

[0011] The present invention is remarkable in that the speed change system comprises:

[0012] a planetary gear train comprising a freely rotating ring gear, a sun gear fixed to the output shaft and a planet carrier comprising at least one planet gear, the planet carrier being fixed to the input shaft,

[0013] a clutch device configured to connect the input shaft and the output shaft in an engaged position and to disconnect the input shaft and the output shaft in a disengaged position,

[0014] - a locking device configured to prevent the ring gear from rotating in the connected position and to allow the ring gear to rotate in the disconnected position,

[0015] The transmission system has:

[0016] o a first configuration in which the clutch device is in an engaged position and the locking device is in a disengaged position, thereby driving the output shaft to rotate at a speed equal to the speed of the input shaft, and

[0017] o a second configuration in which the clutch device is in the disengaged position and the locking device is in the connected position, thereby driving the output shaft to rotate at a speed greater than the input shaft speed,

[0018] Advantageously, the speed change system enables the output shaft to be driven with two different constant transmission ratios relative to the input shaft. Due to the planetary gear train, the speed change system also has small overall dimensions, making it easy to integrate into the accessory gearbox of an aircraft turbine engine. The invention thus makes it possible to provide several different drive speeds for aircraft equipment installed in the accessory gearbox without significantly increasing the overall dimensions.

[0019] According to one aspect of the invention, the clutch device is configured to automatically decouple the input shaft from the output shaft when the rotational speed of the output shaft is greater than the rotational speed of the input shaft. Advantageously, no digital control or manual intervention is required to control the clutch device. This makes switching from the disengaged position to the engaged position and vice versa simple, convenient and direct. In this way, control of the locking device enables the clutch device to be directly controlled.

[0020] According to one aspect of the invention, the clutch device is of the flywheel type, preferably of the overrunning clutch type. Such a clutch device is simple and cheap.

[0021] According to one aspect of the invention, the locking device is configured to cooperate with the ring gear in the connected position by a positive locking connection. This ensures an effective mechanical locking in a simple and practical manner.

[0022] According to one aspect of the invention, the locking device comprises a piston that can translate between a connection position and a disconnection position, and the piston is preferably equipped with a return spring. The restoring force of the spring and the pressure of the lubricating fluid together enable the piston to automatically and effectively move between the connection position and the disconnection position.

[0023] The invention also relates to an aircraft turbine engine accessory gearbox comprising a speed change system as described above.

[0024] According to one aspect of the invention, the accessory gearbox comprises at least one lubrication unit connected to the output shaft of the transmission system, the lubricating fluid flowing in the lubrication unit at a variable pressure which is a function of the rotational speed of the output shaft, the locking device being configured to automatically move from the connected position to the disconnected position when the lubricating fluid pressure is greater than a first preset lubricating fluid pressure threshold. Advantageously, no digital control or manual intervention is required to control the locking device. This makes switching from the connected position to the disconnected position and vice versa simple, convenient and straightforward. The automatic movement of the clutch device and the locking device cooperate to provide fully automatic operation of the transmission system. Advantageously, the invention enables a faster build-up of pressure and flow rate in the lubrication circuit.

[0025] According to a preferred aspect, the locking device is configured to automatically move from the disconnected position to the connected position when the pressure of the lubricating fluid is below a second preset threshold, preferably below the first threshold. Therefore, due to the hysteresis phenomenon, the switching between the first configuration and the second configuration of the transmission system is quickly performed.

[0026] According to one aspect of the invention, the accessory gearbox comprises at least one aircraft device connected to the output shaft, said aircraft device preferably being a lubrication unit. Thus, the invention makes it possible to provide several different drive speeds for the aircraft device installed in the accessory gearbox, in particular depending on the speed of the aircraft turbine engine. In the case of the lubrication unit, this makes it possible to ensure sufficient lubrication of the aircraft turbine engine at low speeds, in order to avoid the risk of wear due to seizure as in the prior art.

[0027] The invention also relates to an aircraft turbine engine comprising an accessory gearbox as described above.

[0028] The invention also relates to a method of using a transmission system as described above, wherein the transmission system is initially in a first configuration in which the clutch device is in an engaged position and the locking device is in a disengaged position, the method comprising:

[0029] - a step of moving the locking device to the connected position, and

[0030] - The step of moving the clutch device to a disengaged position so that the transmission system is in a second configuration.

[0031] The invention also relates to a method of using a transmission system as described above, wherein the transmission system is initially in a second configuration in which the clutch device is in a disengaged position and the locking device is in a connected position, the method comprising:

[0032] - a step of moving the locking device to the open position, and

[0033] - The step of moving the clutch device to an engaged position so that the transmission system is in a first configuration.

[0034] According to a preferred aspect, the driving step of the locking device is performed before the driving step of the clutch device. Preferably, the driving step of the clutch device is automatically performed after the driving step of the locking device. Advantageously, the execution of the driving step of the locking device causes the speed difference between the input shaft and the output shaft to be adjusted, thereby automatically triggering the execution of the driving step of the clutch device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be better understood on reading the following description, given by way of example, with reference to the following drawings, given by way of non-limiting example, in which like references indicate similar objects.

[0036] Figure 1 is a schematic longitudinal section through an aircraft turbine engine including an accessory gearbox according to an embodiment of the invention.

[0037] Figure 2 Schematic diagram of an accessory gearbox with a speed change system in a first configuration according to an embodiment of the present invention.

[0038] Figure 3 Schematic diagram of an accessory gearbox with a speed change system in a second configuration according to an embodiment of the present invention.

[0039] Figure 4 is used to Figure 2 Schematic diagram of a locking device in which the ring gear of a transmission system is locked in a disengaged position.

[0040] Figure 5 is used to Figure 3 Schematic diagram of a locking device for locking the ring gear of a transmission system in a connected position.

[0041] Figure 6 The output shaft speed varies with Figure 2 and Figure 3 Schematic diagram of the functional change in the pressure of the lubricating fluid in the lubrication unit of the accessory gearbox.

[0042] Figure 7 is a schematic diagram of a method of using a speed change system when traveling in a second configuration according to an embodiment of the present invention.

[0043] Figure 8 is a schematic diagram of a method of using a speed change system during movement in a first configuration according to an embodiment of the present invention.

[0044] Fig. 9 Schematic diagram of an accessory gearbox with a speed change system in a first configuration according to another embodiment of the present invention.

[0045] It should be noted that the accompanying drawings illustrate the invention in detail in order to implement the invention and, if necessary, said drawings can of course serve to better define the invention. DETAILED DESCRIPTION

[0046] The present invention relates to an accessory gearbox for an aircraft turbine engine, and in particular to a speed change system for the gearbox and a method of using the same.

[0047] like Figure 1As shown, in this example, an aircraft turbine engine 100 of the dual-flow type extends along a longitudinal axis X and provides propulsion for the aircraft by accelerating the airflow flowing in the turbine engine 100, in particular by one or more compressors 300, 310, a combustion chamber 400 and one or more turbines 500, 510. The turbines 500, 510 are connected to the compressors 300, 310 by at least one turbine engine shaft 200, 210.

[0048] like Figure 1 As shown, the aircraft turbine engine 100 comprises an accessory gearbox 1 known to those skilled in the art by its abbreviation AGB. The accessory gearbox 1 is usually located radially outside the compressor or compressors 300, 310 with respect to the longitudinal axis X, in this example radially outside the auxiliary duct VS.

[0049] refer to Figure 1 The accessory gearbox 1 includes at least one connected to a plurality of parallel axes ( Figure 2 and Figure 3 800 and bevel gear 900. The input end is configured to receive, in particular, receive a driving torque from the turbine engine shaft 200, 210 through a radial arm 800 and a bevel gear 900. In this example, the radial arm 800 extends into a guide member, which is called an "exit guide vane" or abbreviated OGV and extends radially into the auxiliary duct VS. In operation, the torque received by the input end is transmitted to each axis. One or more devices are installed in series on each axis, such as a lubrication unit, a fuel pump, a generator, a starter and an oil separator.

[0050] Figure 2 and Figure 3 The axis L of the accessory gearbox 1 is shown, on which the lubrication unit GDL is mounted. The lubrication unit GDL is supplied by a reservoir of lubricating fluid (not shown). The lubrication unit GDL comprises several pumps, including at least one feed pump (not shown) dimensioned to supply lubricating fluid to various circuits of the aircraft turbine engine at a flow rate and pressure suitable for the speed of the turbine engine 100. The pump is driven by the torque of the turbine engine shaft 200, 210, which is transmitted by the radial arm 800 and the bevel gear 900.

[0051] refer to Figure 2 and Figure 3 The present invention relates to a transmission system 2 for driving one or more devices (such as a lubrication unit GDL) by an accessory gearbox 1. The transmission system 2 comprises:

[0052] an input shaft 3 and an output shaft 4, the output shaft 4 being configured to be driven in rotation by the input shaft 3,

[0053] a planetary gear train comprising a freely rotating ring gear 5 , a sun gear 6 fixed to the output shaft 4 , and a planet carrier 7 fixed to the input shaft 3 and comprising one or more planet gears 8 ,

[0054] a clutch device 10 configured to connect the input shaft 3 and the output shaft 4 in an engaged position E and to disconnect the input shaft 3 and the output shaft 4 in a disconnected position D, and

[0055] A locking device 9 configured to prevent the ring gear 5 from rotating in the connected position B and to allow the ring gear 5 to rotate in the disconnected position A.

[0056] Also according to the present invention, the transmission system 2 has:

[0057] - Figure 2 The first configuration C1 shown, in which the clutch device 10 is in the engaged position E and the locking device 9 is in the disengaged position A, thereby driving the output shaft 4 to rotate at a speed N4 equal to the speed N3 of the input shaft 3, and

[0058] - Figure 3 The second configuration C2 is shown, in which the clutch device 10 is in the disengaged position D and the locking device 9 is in the connected position B, so that the output shaft 4 is driven to rotate at a rotation speed N4 greater than the rotation speed N3 of the input shaft 3.

[0059] The transmission system 2 enables the output shaft 4 to be driven by the rotation of the input shaft 3 according to two different constant reduction ratios, namely a first transmission ratio R1 verified as R1=N4 / N3=1 in the first configuration C1 and a second transmission ratio R2 verified as the relationship R2>R1 in the second configuration C2. Preferably, the second transmission ratio R2 is R2=N4 / N3 and R2>3. The planetary gear train also means that the transmission system 2 has a very small overall size.

[0060] Figure 2 and Figure 3 In the example shown, a preferred embodiment of the invention is shown, in which the transmission system 2 is integrated into the accessory gearbox 1 and is mounted on the axis L of the lubrication unit GDL. The lubrication unit GDL is mounted on an output shaft 4, corresponding to the output end of the planetary gear train. An input shaft 3, corresponding to the input end of the planetary gear train, is connected to the input end of the accessory gearbox 1 and receives the input from the turbine engine shafts 200, 210 ( Figure 1 ) of torque.

[0061] according to Fig. 9In the preferred aspect shown, the transmission system 2 also includes a single gear train 20, which is equipped with two pinions of different diameters in order to adjust the speed received by the lubrication unit GDL according to a constant transmission ratio R, preferably verifying a transmission ratio R>1 and preferably R<2. The single gear train 20 can be installed between the input end of the accessory gearbox 1 and the input shaft 3 of the planetary gear train (see Fig. 9 ), or installed between the output shaft 4 of the planetary gear train and the lubrication unit GDL. The total transmission ratio Rtot between the lubrication unit GDL and the input end of the accessory gearbox 1 is therefore verified as Rtot=R*R1=R in the first configuration C1, and as Rtot=R*R2>R*R1 in the second configuration C2.

[0062] It goes without saying that the transmission system 2 can be mounted on any axis of the accessory gearbox 1, in addition to the axis of the lubrication unit GDL, so as to be able to drive one or more other aircraft devices with two different transmission ratios. Advantageously, in the case of an axis with several devices, the transmission system 2 enables all devices to be shifted simultaneously. Moreover, according to another aspect of the invention, the transmission system 2 can be integrated into the aircraft device instead of into the accessory gearbox 1.

[0063] The gear system 2 enables the drive of the lubrication unit GDL to be adjusted according to the speed of the aircraft turbine engine 100. The second configuration C2 has a higher transmission ratio R2 than the transmission ratio R1 of the first configuration C1 and is therefore particularly suitable for the low idle speed of the aircraft turbine engine 100 in order to compensate for the low rotation speed of the turbine engine shaft 200, 210. This ensures that the pump of the lubrication unit GDL is fully driven with a suitable flow rate and pressure, thereby avoiding the risk of damaging the turbine engine 100, in particular due to seizure, as in the prior art. The sub-idle state is observed in particular when the aircraft turbine engine 100 is started or when the turbine engine is windmilling, that is, when the turbine engine 100 is stationary and rotates only at a very low rotation speed under the influence of the wind, better known as "windmilling". Low idle speeds can also be observed during maintenance of the aircraft turbine engine 100. The first configuration C1 with a reduction ratio R1=1 enables the pump of the lubrication unit GDL to be driven at the speed of the turbine engine 100 in the same way as in the prior art (except for sub-idle).

[0064] According to a preferred aspect of the present invention, the clutch device 10 is configured to automatically engage and disconnect the input shaft 3 and the output shaft 4 according to the speed difference between the input shaft 3 and the output shaft 4. More specifically, the clutch device 10 is configured to automatically disconnect the input shaft 3 and the output shaft 4 when the rotation speed N4 of the output shaft 4 is greater than the rotation speed N3 of the input shaft 3.

[0065] No manual intervention is required. The movement of the clutch device 10 between the engaged position E and the disengaged position D is preferably effected by a mechanical mechanism directly triggered by the speed difference between the input shaft 3 and the output shaft 4. Advantageously, the clutch device 10 is simple in structure, low in cost, easy to integrate and has no electrical or electronic control components.

[0066] Preferably, the clutch device 10 is in the form of a flywheel, preferably of the overrunning clutch type. The flywheel comprises a first ring fixed to the input shaft 3 and a second ring fixed to the output shaft 4 and mounted coaxially opposite to the first ring. The flywheel comprises one or more elements for connecting the second ring, preferably via an abutment (such as a joint or a roller), to the first ring in rotation. In the engaged position E, the second ring is blocked relative to the first ring. In the disengaged position D, the second ring is oversteered relative to the first ring. The output shaft 4 rotates in the same direction in the engaged position E and the disengaged position D. No further description will be given of the overrunning clutch type flywheel known to those skilled in the art.

[0067] refer to Figure 4 and Figure 5 As mentioned above, the locking device 9 comprises:

[0068] - Figure 4 The disconnected position A shown, in which the locking device 9 allows the ring gear 5 of the planetary gear train to rotate, and

[0069] - Figure 5 A connection position B is shown, in which the locking device 9 prevents the ring gear 5 of the planetary gear train from rotating.

[0070] according to Figure 4 and Figure 5 In the preferred aspect shown, the locking device 9 is configured to cooperate with the ring gear 5 by clutching, preferably by positive locking connection, in the connection position B. Therefore, the locking device 9 comprises a dog clutch member 15, which comprises a groove 13 configured to cooperate with a complementary spline 14 on the ring gear 5 to prevent the ring gear 5 from rotating.

[0071] according to Figure 4 and Figure 5 In the preferred aspect shown, the locking device 9 comprises a piston 16 mounted so as to be able to move in translation between a connected position B and a disconnected position A. The dog clutch member 15 is mounted on the piston 16 so as to enable movement between a connected position B, in which the splines 13 cooperate with complementary splines 14 on the ring gear 5, and a disconnected position A, in which the splines 13 are kept at a distance from the complementary splines 14 on the ring gear 5. The ring gear 5 is mounted so as not to move in translation.

[0072] Preferably, the piston 16 further includes a return spring 17, the return force of which enables the piston 16 to move in coordination with the pressure P of the lubricating fluid.

[0073] according to Figure 4 and Figure 5 In the preferred aspect shown, the locking device 9, more precisely the piston 16, moves automatically under the action of the pressure P of the lubricating fluid flowing in the lubricating unit GDL and the return spring 17. The pressure P of the lubricating fluid varies according to the speed of the aircraft turbine engine 100 and increases with the rotation speed N3 of the input shaft 3.

[0074] refer to Figure 6 When the pressure P of the lubricating fluid is greater than the first threshold value S1, the pressure P is configured to cause the locking device 9 to move from the connection position B ( Figure 5 ) moves to the disconnect position A( Figure 4 ). The pressure P of the lubricating fluid also acts on the return spring 17. Figure 4 In the disconnected position A shown, the pressure P of the lubricating fluid is configured to act on the piston 16 to keep the dog clutch member 15 away from the ring gear 5. Figure 4 In the disconnected position A shown, the pressure P of the lubricating fluid holds the spring 17 in the deformed state.

[0075] Still reference Figure 6 When the pressure P of the lubricating fluid is lower than the second threshold value S2, the return spring 17 applies a reverse restoring force greater than the pressure P, thereby causing the locking device 9 to move from the disconnected position A ( Figure 4 ) toward connection position B( Figure 5 ) sports. Figure 5 In the connection position B shown, the restoring force of the spring 17 causes the saw teeth 13 of the dog clutch member 15 to cooperate with the complementary saw teeth 14 of the ring gear 5 .

[0076] Preferably, the first threshold value S1 of the pressure P is selected so that the speed of the low-pressure turbine engine shaft 200 is greater than the maximum spool speed, such as about 600 rpm, and less than the average idling speed, such as about 10,000 rpm. Preferably, the second threshold value S2 of the pressure P is lower than the first threshold value S1, this hysteresis being generated by the hydraulic system of the lubrication unit GDL and depending on the hydraulic load. This hysteresis enables a fast movement from the first configuration C1 to the second configuration C2 and vice versa, as will be described below.

[0077] Therefore, no manual intervention is required to actuate the locking device 9. The automatic movement of the locking device 9 and the clutch device 10 enables coordinated and automatic switching from the first configuration C1 to the second configuration C2 of the transmission system 2 and vice versa.

[0078] Figure 7A method is shown for changing from a first configuration C1 to a second configuration C2 using a transmission system 2, such as during deceleration of an aircraft turbine engine 100 to a low idle speed. The aircraft turbine engine 100 has an initial speed higher than a sub-idle speed, such as at ground idle or cruising speed, and the lubricating fluid flowing in the lubrication unit GDL has a pressure P higher than a second threshold value S2. The transmission system 2 is initially in the first configuration C1. In fact, the input shaft 3, the ring gear 5 and the output shaft 4 move together at the same rotation speed N3, N4.

[0079] refer to Figure 6 and Figure 7 , the method comprising:

[0080] - a step E1 of moving the locking device 9 to the connection position B. The driving step E1 is preferably performed automatically when the pressure P of the lubricating fluid drops below a second threshold value S2, preferably due to the restoring force of the spring 17 pressing the dog clutch member 15 against the ring gear 5. At the end of the driving step E1, the ring gear 5 is blocked from rotating, preferably by a positive locking connection. The input shaft 3 then moves in the ring gear 5 and drives the output shaft 4 to rotate at a rotation speed N4 greater than the rotation speed N3 of the input shaft 3.

[0081] - a step E2 of moving the clutch device 10 to the disengaged position D. Preferably, after the driving step E1, the driving step E2 is automatically performed by coasting when the rotation speed N4 of the output shaft exceeds the rotation speed N3 of the input shaft 3. The driving step E1 automatically and without delay causes the driving step E2. At the end of the driving step E2, the transmission system 2 is in the second configuration C2, which provides the best performance of the lubrication unit GDL during the sub-idle period of the aircraft turbine engine 100.

[0082] Figure 8 A method is shown for changing the second configuration C2 to the first configuration C1 using the transmission system 2, for example when the speed of the aircraft turbine engine 100 increases from sub-idle. The aircraft turbine engine 100 is initially at sub-idle and the lubricating fluid flowing in the lubrication unit GDL has a pressure P below the first threshold S1. The transmission system 2 is initially in the second configuration C2. In practice, the output shaft 4 is driven at a rotation speed N4 greater than the rotation speed N3 of the input shaft 3, and the ring gear 5 is stationary.

[0083] refer to Figure 6 and Figure 8 , the method comprising:

[0084] - a step E3 of moving the locking device 9 to the disengaged position A. The driving step E3 is preferably performed automatically when the pressure P of the lubricating fluid becomes greater than the first threshold S1 and drives the piston 16 to move the dog clutch member 15 away from the ring gear 5. At the end of the driving phase E1, the ring gear 5 rotates freely, which reduces the speed of the output shaft 4 relative to the input shaft 3.

[0085] - a step E4 of moving the clutch device 10 to the engaged position E. Preferably, after the driving step E3, the driving step E4 is automatically performed by locking the freewheel when the rotation speed N4 of the output shaft 4 is equal to the rotation speed N3 of the input shaft 3. The driving step E3 automatically and without delay causes the driving step E4. At the end of the driving step E4, the transmission system 2 is in the first configuration C1 and enables the lubrication pump to be operated at speeds of the aircraft turbine engine 100 other than sub-idle in a manner similar to the prior art.

[0086] In this way, the movement of the transmission system 2 is completely controlled by the speed of the aircraft turbine engine, or moves automatically as a function of the rotation speed of the input shaft N3 .

[0087] According to an alternative aspect of the invention, the drive E2 of the clutch device 10 to the disengaged position D occurs before the drive E1 of the locking device 9 to the disconnected position B, wherein the return spring 17 has an adapted spring constant. Similarly, the drive E4 of the clutch device 10 to the engaged position E occurs before the drive E3 of the locking device 9 to the connected position A.

Claims

1. An accessory gearbox (1) of an aircraft turbine engine (100), comprising at least one lubrication unit (GDL) and a transmission system (2) for driving the lubrication unit (GDL), the transmission system (2) comprising an input shaft (3) and an output shaft (4) configured to be driven in rotation by the input shaft (3), the output shaft (4) being connected to a rotating part of the lubrication unit (GDL), a lubricating fluid flowing in the lubrication unit (GDL) at a variable pressure (P) which is a function of the rotation speed of the output shaft (4), characterized in that The speed change system (2) comprises: - a planetary gear train comprising a freely rotating ring gear (5), a sun gear (6) fixed to the output shaft (4) and a planet carrier (7) comprising at least one planet gear (8), the planet carrier (7) being fixed to the input shaft (3), a clutch device (10) configured to connect the input shaft (3) and the output shaft (4) in an engaged position (E) and to disconnect the input shaft (3) and the output shaft (4) in a disconnected position (D), - a locking device (9) configured to prevent the ring gear (5) from rotating in the connected position (B) and to allow the ring gear (5) to rotate in the disconnected position (A), the locking device (9) comprising a piston (16) capable of translation between the connected position (B) and the disconnected position (A), the piston (16) being equipped with a return spring and configured to automatically move from the connected position (B) to the disconnected position (A) under the action of the pressure (P) of the lubricating fluid and the return spring (17), the pressure (P) being higher than a predetermined first pressure threshold (S1) of the lubricating fluid, - The transmission system (2) has: a first configuration (C1), in which the clutch device (10) is in the engaged position (E) and the locking device (9) is in the disengaged position (A), thereby driving the output shaft (4) to rotate at a speed (N4) equal to the speed (N3) of the input shaft (3), and ○ A second configuration (C2), in which the clutch device (10) is in the disengaged position (D) and the locking device (9) is in the connected position (B), thereby driving the output shaft (4) to rotate at a speed (N4) greater than the speed (N3) of the input shaft (3).

2. The accessory gearbox (1) according to claim 1, characterized in that The clutch device (10) is configured to automatically separate the input shaft (3) and the output shaft (4) when the rotation speed (N4) of the output shaft (4) is greater than the rotation speed (N3) of the input shaft (3).

3. The accessory gearbox (1) according to claim 1 or 2, characterized in that The clutch device (10) is of flywheel type, preferably of overrunning clutch type.

4. The accessory gearbox (1) according to any one of claims 1 to 3, characterized in that The locking device (9) is configured to cooperate with the ring gear (5) in the connection position (B) through a positive locking connection.

5. The accessory gearbox (1) according to any one of claims 1 to 4, characterized in that The piston (16) of the locking device (9) is configured to automatically move from the disconnected position (A) to the connected position (B) under the action of the pressure (P) of the lubricating fluid and the return spring (17) when the pressure (P) of the lubricating fluid is lower than a second preset threshold value (S2), preferably lower than a first threshold value (S1).

6. A method for using the accessory gearbox (1) according to any one of claims 1 to 5, characterized in that: The transmission system (2) is initially in a first configuration (C1), in which the clutch device (10) is in the engaged position (E) and the locking device (9) is in the disengaged position (A), and the method of use comprises: - a step (E1) of moving said locking device (9) into said connection position (B), and - a step (E2) of moving the clutch device (10) to the disengaged position (D) so as to place the transmission system (2) in the second configuration (C2).

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