Accessory drive and electrical generation unit

Abstract

Accessory drive and electrical generation assembly, comprising: a transmission system (7) for mechanical coupling to a gas turbine shaft, and comprising a housing (10) enclosing a gear train having at least two gear lines (L1, L2, L3), each gear line comprising a gear shaft (A1, A2); at least one accessory location (E1, E2, E3, E4) provided on the housing (10) for mounting an accessory intended to be driven in rotation by a gear shaft; and at least one electrical generator provided on one (L2) of the gear lines, the electrical generator being housed in the housing (10), said rotor (11) being disposed around the gear shaft (A2), and an accessory location (E2, E4) being provided at at least one of the two ends of the gear shaft (A2). Figure for the abstract: [Fig. 2]

Description

Title of the invention: Accessory drive and power generation unit. Technical field

[0001] The present exposition relates to the field of auxiliary power transmission systems, and more particularly to the mounting of an electric generator in such systems. Previous technique

[0002] In a gas turbine, a number of components, or accessories, are driven by a mechanical transmission using mechanical power drawn from a turbine shaft. This mechanical transmission typically comprises several sub-assemblies forming a transmission chain, and the final sub-assembly that drives the components includes a gear train housed in a casing, called an accessory gearbox or accessory drive box (AGB). The term "accessory transmission box" is also used. Thus, the AGB, or transmission system described below, is designed to receive mechanical power from the output shaft of the gas turbine and selectively distribute it to the accessories mounted on the casing.

[0003] To this end, the AGB comprises a series of gears formed by pinions of different sizes to transfer mechanical power of a specific value with different ratios so as to ensure a specific rotational speed for each driven piece of equipment. To support the rotating pinions and the transmission shafts, the AGB is equipped with roller bearings designed also to ensure proper alignment of the gear lines, thus extending the service life of the pinion teeth and the splines of the transmission shafts. Following the same logic, the AGB is equipped with lubrication circuits, particularly oil lubrication to reduce wear and friction between its moving components, and optionally with cooling circuits to maintain the operating temperatures of its components at acceptable levels.

[0004] The driven accessories include in particular various pumps for the production of hydraulic power, fuel supply, lubrication, as well as one or more electric generators which may also have an additional starter function.

[0005] Such electric generators may be in the form of an electromagnet electric generator or a permanent magnet alternator (known by the acronym "PMA"). More precisely, a permanent magnet alternator uses its permanent magnets to create a magnetic field in its rotor. This rotating magnetic field induces an electric current in the stator coils, producing electricity. Unlike an electromagnet generator, a PMA does not require an external power supply to create a magnetic field in the rotor thanks to the use of such permanent magnets. Thus, PMAs are used in applications where a source of mechanical energy is available (such as a gas turbine) to generate electricity autonomously. As for an electromagnet generator, it generally uses electromagnets powered by direct current to create a magnetic field in its rotor. This rotating magnetic field induces an alternating current in the stator coils, thus producing electricity.

[0006] As mentioned above, regardless of the type of electric generator (electromagnet or permanent magnet alternator), it can also have a starter function, which is known as a generator / starter (or "Starter / Generator" or S / G in English). When the gas turbine is running, the generator / starter functions as an electric generator and produces an electrical voltage that supplies one or more electrical power distribution centers for the aircraft and its engine(s). Conversely, when the gas turbine is stopped, a generator / starter can function as a starter by being powered by an external energy source to start the gas turbine by rotating the compressor / turbine shaft to which the generator / starter is mechanically coupled via the gearbox.

[0007] However, such an electric generator (or starter / generator by extension) is a relatively bulky piece of equipment due to its components and is usually mounted on the accessory drive housing (AGB), that is, on an external side of the transmission. This results in significant size and weight, especially since several electric generators (or starter / generators by extension) can be mounted on the same transmission. Furthermore, mounting the electric generator in this way reduces the available installation space for connecting an additional accessory to the transmission system.

[0008] Furthermore, it is known that in a turbofan gas turbine, the interflow compartment located between the primary and secondary flow streams houses engine equipment, and may in particular accommodate an accessory drive housing. This is an area, also called the "core zone," where space is generally limited and each component must be carefully designed and positioned. To maximize the efficiency of the installation and minimize propulsive performance losses due to suboptimal aerodynamic lines. Because of this limited space, installing the AGB can be even more challenging with an electrical generator mounted on the accessory drive housing.

[0009] Similar to the inter-vein compartment, space is also limited in the blower compartment and the installation of the AGB equipped with accessories can then be hindered by the lack of available space.

[0010] There is therefore a real need to minimize the size of the AGB (or transmission system) equipped while ensuring its proper functioning within the turbomachine in which it is installed. Description of the invention

[0011] The present description relates to an assembly of accessory drive and electrical generation housing, comprising: - a transmission system intended to be mechanically coupled to a gas turbine shaft, and comprising a casing enclosing a gear train which includes at least two rows of pinions, each row of pinions comprising a pinion shaft; - at least one accessory mounting point on the housing for an accessory intended to be driven in rotation by a pinion shaft; and - at least one electric generator provided on one of the gear lines, comprising a rotor forming an inductor and fixed in rotation to the gear shaft of the gear line, and a stator forming an armature. The assembly is characterized in that the electric generator is housed in the casing, said rotor being arranged around the pinion shaft, and in that an accessory location is provided at at least one of the two ends of the pinion shaft.

[0012] Integrating the electric generator within the gas turbine transmission system allows for a significant reduction in volume and size. This arrangement also allows the electric generator to share the same cooling system as the transmission system.

[0013] According to some embodiments, the stator of said electric generator is mounted on at least one bearing support of the transmission system, said at least one bearing support supporting a bearing intended to guide said pinion shaft in rotation.

[0014] According to some embodiments, said at least one electric generator is permanent magnet.

[0015] According to some embodiments, the accessory location is provided for each of the two ends of the pinion shaft.

[0016] According to some embodiments, the pinion shaft is part of a pinion comprising a toothed wheel, the rotor and the stator being arranged axially on either side of the toothed wheel.

[0017] According to some embodiments, the rotor is formed of two parts arranged axially on either side of the gear wheel, and each part of the rotor is housed in a cavity delimited in part by oil deflectors fixed in rotation to the pinion shaft.

[0018] According to some embodiments, one of the oil deflectors is formed as a single unit with the pinion shaft, and one of the oil deflectors is formed as a single unit with the gear.

[0019] According to some embodiments, the oil deflectors are produced by additive manufacturing.

[0020] According to some embodiments, said rotor is produced at least in part by additive manufacturing.

[0021] Additive manufacturing offers significant advantages in terms of simplifying design and reducing the mass of the transmission system. For this reason, it is used to manufacture the rotor, thereby optimizing its dimensions and reducing its weight.

[0022] According to some embodiments, the pinion shaft of the pinion line comprising the electric generator is guided in rotation by two bearings spaced apart by an inter-bearing distance, and the pinion shaft of an adjacent pinion line is also guided in rotation by two bearings spaced apart by substantially the same inter-bearing distance.

[0023] According to certain embodiments, the stator of the electric generator is at least partly mounted radially inside a substantially cylindrical support housed in the casing coaxially with the pinion shaft, said substantially cylindrical support forming a body of a bearing support whose bearing is intended for the rotational guidance of the pinion shaft.

[0024] The present description further relates to an assembly equipped with an accessory drive and electrical generation unit, comprising an assembly as defined above. A first and a second accessory location are provided for the first and second ends of the pinion shaft, respectively, and further comprising two accessories mounted on said first and second accessory locations.

[0025] The present exposition further relates to an aircraft engine, comprising a gas turbine and an assembly according to one of the two assemblies as defined above, mechanically coupled to a shaft of the gas turbine. Brief description of the drawings

[0026] The accompanying drawings are schematic and are intended primarily to illustrate the principles of the exposition. In these drawings, identical elements (or parts of elements) are identified by the same reference numerals from one figure to another. In addition, elements (or parts of elements) belonging to different embodiments but having a similar function are identified in the figures by numerical reference numerals incremented by 100, 200, etc.

[0027] Other objects, features, and advantages of the invention will be better understood upon reading the following detailed description of various embodiments of the invention given by way of non-limiting examples. This description refers to the accompanying figure pages, on which:

[0028] [Fig. 1] The [Fig. 1] is a simplified diagram of a gas turbine engine according to the state of the art;

[0029] [Fig.2] Fig.2 is a top view of an assembly comprising a transmission system integrating a starter / generator according to a first embodiment of the invention; and

[0030] [Fig.3] The [Fig.3] is a top view of said assembly according to a second embodiment of the invention. Description of the implementation methods

[0031] One field of application of the invention is that of gas turbine aircraft engines, such as that schematically represented in [Fig. 1]. The invention is, however, obviously applicable to other gas turbine aircraft engines, typically helicopter engines, as well as to gas turbine auxiliary power units.

[0032] The engine of [Fig.1] comprises a combustion chamber 1, the combustion gases from the combustion chamber 1 driving a high-pressure turbine 2 and a low-pressure turbine 3. The turbine 2 is coupled by a shaft to a high-pressure compressor 4 supplying the combustion chamber 1 with pressurized air while the turbine 3 is coupled by another shaft to a blower 5 at the inlet of the engine.

[0033] A transmission system 7 (or gearbox, or accessory drive unit) is connected by a mechanical power take-off 9 to a turbine shaft. Such a transmission system may also be located, but not limited to, within a compartment of the blower 5. In this latter case, the transmission system 7 is connected to a shaft of the blower 5.

[0034] This system comprises a set of gears for driving various accessories. These gears are arranged in the transmission system 7 for To form a gear train, each gear is used to drive at least one accessory whose axis of rotation is coaxial with the gear's axis. This constitutes a gear train, a term well-known to those in the trade. Each gear train has a specific configuration of its gears to provide power tailored to a given accessory. These gears can vary in size, shape, and transmission ratio to ensure a specific rotational speed for each driven accessory.

[0035] By way of example and not limitation, the transmission system 7 may comprise between two and 20 gear lines and be integrated into a turbojet engine whose fan diameter is between 20 and 140 inches. The turbojet engine may further have a compression ratio of between 20 and 60, and be of the single-flow, twin-flow, single-spool, twin-spool, or triple-spool type. Such a turbojet engine may further comprise one to eight low-pressure turbine stages.

[0036] Figure 2 shows a top view of an assembly comprising the transmission system 7 and a plurality of accessory locations E1, E2, E3, and E4, each suitable for mounting an accessory AX, AY, AZ, and AW (the latter being illustrated in Figure 3). More specifically, such a transmission system 7 comprises a housing 10 containing a gear train comprising, here only as an example, three separate rows of gears, designated respectively by L1, L2, and L3. Each location E1, E2, E3, and E4 is thus provided on the housing 10.

[0037] In this example, each gear line L1, L2 has been specifically designed to drive one or a plurality of particular accessories. The first gear line L1 is configured to drive accessory AX, the second gear line L2 is configured to drive accessories AY and AW, and the third gear line L3 is configured to drive accessory AZ. As such, each gear line has a gear shaft. The first gear line L1 has a gear shaft A1 and the second gear line L2 has a gear shaft A2 as illustrated in [Fig. 2]. Each gear shaft is guided in rotation by bearings, for example roller bearings, supported in the transmission system 7 by bearing supports 13. To avoid cluttering [Fig. 2], the bearing supports for the gear shaft A1 are not shown.

[0038] More specifically, each pinion shaft is intended to drive one of the accessories in rotation. An accessory location is thus provided at at least one of the two ends of the pinion shaft, and this does not therefore exclude the possibility of an accessory location being provided for each of the two ends of the pinion shaft.

[0039] Such accessories may include various pumps for hydraulic power generation, fuel supply, lubrication, and one or more electric generators that may have an additional starter function. However, as explained above, the electric generator (or starter / generator by extension) is a relatively bulky accessory due to its components. If mounted on one side of the housing 10, outside the transmission system 7, the electric generator creates a significant obstruction and reduces the possibility of obtaining sufficient installation space to couple an additional accessory to the transmission system 7.

[0040] Thus, in this embodiment of the invention, the electric generator, as an accessory, is mounted inside the housing 10 of the transmission system 7. In other words, it cannot be one of the accessories AX, AY, and AZ mounted on the accessory drive housing 7. This electric generator is provided on one of the gear lines, here the second gear line L2. This gear line L2 is guided in rotation by two bearings 17 spaced apart by an inter-bearing distance DR. This inter-bearing distance DR can also be substantially the distance between two bearings guiding another adjacent gear line L1 or L3. This makes it possible to produce gear shafts of substantially the same length. Preferably, the difference between the inter-bearing distance of an adjacent pinion line L1 or L3 and the inter-bearing distance DR of the pinion line L2 is between -10% x DR and +10% x DR.This arrangement can promote a compact assembly, including the accessory drive and electrical generation unit, all aligned axially with the L2 pinion line. With this arrangement, the housing 10 can comprise two substantially flat and parallel faces, 10A and 10B, which house the accessory locations. A housing with two faces, each formed by several axially offset flat surfaces, is also possible.

[0041] Electric generators can take the form of a permanent magnet alternator (PMA) or an electromagnet electric generator. More specifically, and as mentioned above, a permanent magnet alternator uses its permanent magnets to create a magnetic field in its rotor. This rotating magnetic field induces an electric current in the coils of its stator, producing electricity. As for the electric generator, it generally uses electromagnets powered by a direct current to create a magnetic field in its rotor. This rotating magnetic field induces an alternating current in the coils of its stator, thus producing electricity. Such an electric generator can generate, for example, a mechanical power output of between 0.5 and 3 kW.

[0042] The electric generator may also have a starter function, which is known as a generator / starter. It may also have a low-speed electric motor function, designed to be activated when the engine is off in order to rotate the high-pressure engine casing very slowly to prevent bowed rotor (a phenomenon known as "bowed rotor") and thus avoid thermal imbalance in the engine before restarting. Its operation is described above and repeated here for the sake of completeness. When the gas turbine is running, the generator / starter then functions as an electric generator and produces an electrical voltage that supplies one or more electrical power distribution centers for the aircraft and its engine(s).Conversely, when the gas turbine is stopped, a generator / starter can function as a starter by being powered by an external energy source to start the gas turbine by rotating the turbine shaft to which the generator / starter is mechanically coupled via the gearbox (or transmission system 7). As an example, the generator / starter can have a rotational speed of up to 30,000 rpm.

[0043] Whether it is a permanent magnet alternator or an electric generator with electromagnets (possibly with a generator function), the rotor 11 of the electric generator which forms the inductor is arranged around the pinion shaft A2, so as to extend transversely on either side of the pinion line, here the pinion line L2.

[0044] As for the stator 12 of the electric generator, it is mounted on one or more bearing supports 13 intended to guide the rotation of the pinion shaft A2 of the pinion line L2. Each bearing is, for example, a rolling bearing 17, but a plain bearing is also possible. More particularly, the stator 12 can be mounted at least partially radially inside a substantially cylindrical body 13A of a bearing support 13, housed in the casing 10 coaxially with the pinion shaft A2. In this case, the substantially cylindrical body 13A forms part of the bearing support 13 for guiding the rotation of the pinion shaft A2.

[0045] The rotor 11 and the stator 12 are therefore housed in the available and unused spaces of the transmission system 7.

[0046] It should be noted that the pinion shaft A2 can be part of a pinion comprising a gear 40. The electric generator is then formed of two parts, each comprising the rotor 11 and the stator 12, arranged axially on either side of the gear 40. Each part of the rotor 11 is then housed in a cavity partially delimited by oil deflectors 16 that are rotationally fixed to the pinion shaft A2. These oil deflectors 16 prevent the rotor 11 from being immersed in the oil, which could conversely lead to overheating due to the continuous stirring of oil through the rotor. By preventing lubrication and cooling oil from the bearings 17 and / or the teeth of the gear 40 from being projected onto the rotor 11, they also prevent oil from entering the air gap between the rotor and the stator.

[0047] As a reminder, the oil deflectors 16 are components that allow the flow of oil to be diverted or channeled, in order to prevent it from entering certain sensitive areas or from affecting the operation of the rotor 11.

[0048] By way of example, one of the oil deflectors 16 can be formed in one piece with the pinion shaft A2 and one of the deflectors 16 can be formed in one piece with the gear 40.

[0049] Thus, integrating the electric generator within the transmission system 7 allows for a reduction in volume and overall size. Furthermore, by freeing up this installation space on at least one side of the pinion line L2, another accessory can be installed there, for example, accessory AY. Moreover, such an assembly also allows the electric generator to share the same cooling systems with the transmission system 7.

[0050] It should be emphasized that the operation of the electric generator (or generator / starter) is in no way compromised by this arrangement. Indeed, connectors 14 of the electric generator, which serve to transmit the electricity produced by it, are positioned outside the transmission system 7, more precisely on the housing 10 of the AGB, between two accessories for example. These connectors 14 ensure the connection with the electric generator via a specially designed wiring connection 15 in the housing 10, thus allowing the connectors to pass through the housing and maintain the connection between the electric generator and the outside of the transmission system 7.

[0051] Of course, a person skilled in the art is able to use other means of connection to ensure the link between the electric generator and the outside of the transmission system 7.

[0052] Figure 3 presents a second top view of said assembly comprising the transmission system 7 according to a second embodiment. In this example, the rotor 11 of the electric generator is produced, at least in part, by additive manufacturing, which offers significant advantages in terms of design simplification and reduction of the mass of the transmission system 7.

[0053] Of course, in this embodiment, the rotor 11 and the stator 12 of the electric generator (or generator / starter) are housed inside the casing 10. The difference with the embodiment of [Fig. 2] lies in the fact that the rotor 11 is produced by additive manufacturing. It is also possible that the permanent magnets of the electric generator are produced by additive manufacturing. For this purpose, and solely by way of example, the permanent magnets may be manufactured by implementing a process called direct energy deposition (DED for "Direct Energy Deposition" according to the Anglo-Saxon term).

[0054] Other components of the transmission system 7 can also be produced by additive manufacturing, for example, the oil deflectors 16.

[0055] In the example illustrated in [Fig.3], each of the locations E2 and E4 which are provided at each end of the pinion shaft A2, allow the mounting of accessories AY and AW.

[0056] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

[0057] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Demands

1. Accessory drive and electrical generation housing assembly, comprising: - a transmission system (7) intended to be mechanically coupled to a gas turbine shaft, and comprising a housing (10) containing a gear train which has at least two rows of pinions (L1, L2, L3), each row of pinions comprising a pinion shaft (A1, A2); - at least one accessory location (E1, E2, E3, E4) provided on the housing (10) for mounting an accessory (AX, AY, AZ, AW) intended to be driven in rotation by a pinion shaft;and - at least one electric generator provided on one (L2) of the gear rows, comprising a rotor (11) forming an inductor and fixed in rotation to the gear shaft (A2) of the gear row (L2), and a stator (12) forming an armature, the assembly being characterized in that the electric generator is housed in the casing (10), said rotor (11) being arranged around the gear shaft (A2), and in that an accessory location (E2, E4) is provided at at least one of the two ends of the gear shaft (A2).

2. Assembly according to claim 1, wherein the stator (12) of said electric generator is mounted on at least one bearing support (13) of the transmission system (7), said at least one bearing support (13) supporting a bearing (17) intended to guide the rotation of said pinion shaft (A2).

3. Assembly according to claim 1 or 2, wherein said at least one electric generator is permanent magnet.

4. Assembly according to any one of the preceding claims 1 to 3, wherein an accessory location (E2, E4) is provided for each of the two ends of the pinion shaft (A2).

5. Assembly according to any one of the preceding claims, 1 to 4, wherein the pinion shaft (A2) is part of a pinion comprising a gear wheel (40), and wherein the rotor (11) and the stator (12) are each arranged axially on either side of the gear wheel (40).

6. Assembly according to claim 5, wherein the rotor (11) is formed of two parts arranged axially on either side of the gear wheel, and each part of the rotor (11) is housed in a cavity delimited in part by oil deflectors (16) rotationally fixed to the pinion shaft (L2).

7. Assembly according to claim 6, wherein one of the oil deflectors (16) is formed as one piece with the pinion shaft (L2), and wherein one of the oil deflectors (16) is formed as one piece with the gear.

8. Assembly according to claim 7, wherein the oil deflectors (16) are made by additive manufacturing.

9. Assembly according to any one of the preceding claims 1 to 8, wherein said rotor (11) is made at least in part by additive manufacturing.

10. Assembly according to any one of the preceding claims 1 to 9, wherein the pinion shaft (A2) of the pinion line (L2) comprising the electric generator is guided in rotation by two bearings (17) spaced apart by an inter-bearing distance (DR), and the pinion shaft (Al) of an adjacent pinion line (Ll) is also guided in rotation by two bearings spaced apart substantially by the same inter-bearing distance (DR).

11. Assembly according to any one of the preceding claims 1 to 10, wherein the stator (12) of the electric generator is at least partly mounted radially inside a substantially cylindrical support (13A) housed in the casing (10) coaxially with the pinion shaft (L2), said substantially cylindrical support (13A) forming a body of a bearing support (13) the bearing of which (17) is intended for the rotational guidance of the pinion shaft.

12. Assembly equipped with accessory drive and electrical generation housing, comprising an assembly according to any one of claims 1 to 11 wherein a first and a second accessory location (E2, E4) are provided for respectively the first and second ends of the pinion shaft (A2), and further comprising two accessories (AW, AY) mounted on said first and second accessory locations (E2, E4).

13. Aircraft engine, comprising a gas turbine and an assembly according to any one of claims 1 to 11, or an assembly equipped according to claim 12, mechanically coupled to a shaft of the gas turbine.

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