Patent Publication Number: US-11396821-B2

Title: Turbine engine comprising a rotor supporting variable-pitch blades

Description:
TECHNICAL FIELD 
     The present invention concerns a turbine engine comprising a rotor supporting variable pitch blades, and more precisely an engine architecture optimised and adapted to such a turbine engine. 
     BACKGROUND 
     A turbine engine can comprise a rotor provided with variable pitch blades, i.e. blades whose pitch (and more precisely the pitch angle) can be adjusted according to the flight parameters, so as to optimise the operation of the turbine engine. As a reminder, the pitch angle of a blade corresponds to the angle, in a longitudinal plane perpendicular to the axis of rotation of the blade, between the chord of the blade and the plane of rotation of the rotor. 
     Such a turbine engine comprises a system for controlling the pitch of the blades. The controlling system generally comprises an actuator common to all blades and a mechanism specific to each blade, the mechanism being configured to transform the movement initiated by the actuator into a rotary movement of the corresponding blade. 
     Traditionally, the actuator is secured to the fixed structure of the turbine engine (i.e. placed in a fixed reference frame) and the various mechanisms are secured to the rotor (i.e. placed in a rotating reference frame). In addition, the controlling system comprises a load transfer bearing (LTB) to ensure that the movement initiated by the actuator (fixed reference frame) is transmitted to the mechanisms (rotating reference frame). 
     The movement of the actuator makes it possible to synchronously adjust the pitch of all the blades via the load transfer bearing and the various mechanisms. 
     It is also known from document EP-A1-3165452 that the actuator and the mechanisms are secured to the rotor (rotating reference frame). The controlling system (i.e. the actuator and mechanisms) is positioned in a closed annular enclosure bounded by the rotor. The actuator here is a hydraulic actuator. The controlling system thus comprises a rotary union (or rotary joint) to transfer hydraulic energy from the fixed to the rotating reference frame. 
     Having the actuator in a rotating reference frame means that a load transfer bearing is not required to transmit the movement of the actuator from the fixed to the rotating reference frame, but also means that telescopic servitudes are not required to supply hydraulic power to the actuator. 
     However, the architecture described in the above-mentioned document has disadvantages. The rotor has a high mass and large dimensions. In fact, the rotor has a parallelogram-shaped cross-section defining the enclosure in which the controlling system in particular is placed. In addition, such an architecture presents a disadvantage during a maintenance operation on the controlling system. Indeed, during such a maintenance operation, it is necessary to dismantle the rotor in order to access the controlling system placed inside, to the detriment of productivity. 
     The applicant also noted that it is important to limit the angular displacement of the rotor during operation at the rotary union in order to avoid the appearance of hydraulic leaks and to maximise the service life of the latter. 
     The objective of the present invention is thus to propose a turbine engine with an optimised engine architecture making it possible to remedy the aforementioned drawbacks and meet the aforementioned expectations. 
     SUMMARY OF THE INVENTION 
     For this purpose, the invention provides a turbine engine with a longitudinal axis X comprising:
         a rotor supporting at least one variable pitch blade, said rotor being guided in rotation with respect to a fixed structure of said turbine engine via a first bearing and a second bearing;   a system for controlling the pitch of said at least one blade, said controlling system being secured to said rotor and comprising at least a first actuator set in motion by an energy, said controlling system being arranged axially upstream of said first and second bearings;   a device for transferring said energy disposed axially between the first bearing and the second bearing, said transferring device comprising a fixed member secured to said fixed structure and a moving member secured to said rotor;       

     characterised in that the rotor comprises a ring for supporting said at least one blade and a shaft having a frustoconical portion and a cylindrical portion to which said first and second bearings and said moving member of said transferring device are attached, the frustoconical portion of the shaft extending around the cylindrical portion. 
     Such an arrangement of the controlling system, i.e. upstream of the first and second bearings and in other words outside the oil enclosure, makes it possible to simplify the rotor, and consequently to reduce the weight and size of the latter, but also to significantly simplify the maintenance of the controlling system. In fact, to access the controlling system, the inlet cone simply has to be removed. This shape of the rotor, and in particular the shaft whose frustoconical portion extends around the cylindrical portion, significantly reduces the axial dimensions of the engine architecture. 
     In addition, the axial arrangement of the transferring device between the first bearing and the second bearing prevents hydraulic leakage (when the energy transferred is hydraulic energy) and maximises the service life of the latter. This is because the angular displacement is minimised at the portion of the rotor axially between the first and second bearing. Thus, when the turbine engine is in operation, the mechanical stresses of the moving member on the fixed member are minimised. 
     The turbine engine according to the invention may comprise one or more of the following characteristics, taken in isolation from each other or in combination with each other:
         the rotor is annular and defines an open internal space in which said controlling system is placed;   the frustoconical portion of the shaft flares from upstream to downstream;   said first actuator is a hydraulic actuator, said transferring device being a rotary union, said controlling system comprising a mechanism configured to transform the movement initiated by said hydraulic actuator into a rotary movement of said at least one blade;   said first actuator is an electric actuator, said transferring device being a rotary transformer, said controlling system comprising a mechanism configured to transform the movement initiated by said electric actuator into a rotary movement of said at least one blade;   said first actuator is an electric motor comprising a rotary output shaft, said at least one blade being rotatable about a axis Y substantially perpendicular to said axis X, said mechanism comprising a crank having a first end centered on said axis Y and rotatably coupled to said at least one blade and a second end having a cam follower eccentric to said axis Y, said cam follower cooperating with a cam in the form of a groove made in a ring, said ring being rotationally coupled to said output shaft of said electric motor;   said transferring device is a rotary transformer, said first actuator is an electric motor configured to actuate a pump of a hydraulic circuit secured to said rotor, said circuit comprising a liquid tank connected with said pump, said circuit comprising a second hydraulic actuator supplied with pressurised liquid by said pump, said controlling system comprising a mechanism configured to transform the movement initiated by said second actuator into a rotary movement of said at least one blade;   said circuit comprises an accumulator configured to feather said at least one blade, in particular in the event of failure of the rotary transformer;   the rotor is guided in rotation with respect to an annular support of said fixed structure, said support being attached to an inner hub of an intermediate casing, said support comprising a frustoconical upstream wall, a frustoconical downstream wall and a tubular cylindrical wall in which the first bearing and the fixed member of said transferring device are housed, the cylindrical wall being disposed axially between said upstream wall and said downstream wall;   the first bearing is disposed upstream of the second bearing;   said rotor is coupled in rotation to a planet carrier of a reduction gear.       

    
    
     
       DESCRIPTION OF THE FIGURES 
       The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly when reading the following description made as an non-limiting example and with reference to the annexed drawings in which: 
         FIG. 1  is a schematic axial (or longitudinal) half-section view of a partially represented aircraft turbine engine, according to a first embodiment; 
         FIG. 2  is a schematic axial half-section view of a partially represented aircraft turbine engine in a second embodiment; 
         FIG. 3  is a schematic axial half-section view of a partially represented aircraft turbine engine in a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 3  show a partial representation of a turbine engine  1  with longitudinal axis X and a ducted fan  2 . The fan  2  comprises a rotor  3  which is movable (about the axis X) relative to a fixed structure  4 , with the rotor  3  supporting a series of variable pitch blades  5 . The fan  2  is located upstream of a gas generator comprising, for example, a low-pressure compressor, a high-pressure compressor, a combustor, a high-pressure turbine and a low-pressure turbine. 
     By convention, in this application the terms “upstream” and “Downstream” are defined in relation to the direction of gas flow in the fan  2  (or turbine engine  1 ). Similarly, by convention in this Application, “internal”, “external”, “inner” and “outer” are defined radially with respect to the longitudinal axis X of the turbomachine  1 , which is in particular the axis of rotation of the compressor and turbine rotors. 
     The rotor  3  is guided in rotation relative to the fixed structure  4  of the turbine engine  1  via a first bearing  6  and a second bearing  7 . The turbine engine  1  comprises a pitch  8  for at least one blade  5 . The controlling system  8  is secured to the rotor  3  and comprises at least a first actuator  9  which is moved (or actuated) by an energy. The controlling system  8  is arranged axially upstream of the first and second bearings  6 ,  7 . The turbine engine  1  further comprises a device  10  for transferring the energy arranged axially between the first bearing  6  and the second bearing  7 . The transferring device  10  comprises a fixed member  11  secured to the fixed structure  4  and a moving member  12  secured to the rotor  3 . The rotor  3  comprises a support ring  14  of said at least one blade  5  and a shaft  15  having a frustoconical portion  16  and a cylindrical portion  17  on which the first and second bearings  6 ,  7  and the moving member  12  of the transferring device  10  are attached, the frustoconical portion  16  of the shaft  15  extending around the cylindrical portion  17  of the shaft  15 . 
     It should be noted that the embodiments illustrated in  FIGS. 1 to 3  are in no way limiting, the engine architecture according to the invention could, for example, be incorporated into the rotor of a non-ducted fan of a turbine engine, and in particular a turbine engine better known as “Open Rotor” which generally comprises a non-ducted fan or two non-ducted fans that are counter-rotating. In the case of an “Open Rotor” with two counter-rotating non-ducted fans called “Pusher” (i.e. with the fans placed downstream of the gas generator), the engine architecture according to the invention could be adapted more particularly to the rotor of the downstream fan. In the case of an “Open Rotor” with two counter-rotating non-ducted fans called “Puller” (i.e. with the fans placed upstream of the gas generator), the engine architecture according to the invention could be adapted more particularly to the rotor of the upstream fan. 
     According to the embodiments illustrated in  FIGS. 1 to 3 , the rotor  3  is annular and defines an open internal space  13  in which the controlling system  8  is placed. The ring  14  is arranged around the shaft  15 . The ring  14  has a larger diameter than the cylindrical portion  17  of the shaft  15 . The ring  14  is connected to the frustoconical portion  16  of the shaft  15  via for example fastening means. The frustoconical portion  16  of the shaft  15  flares out from upstream to downstream. The frustoconical portion  16  and the cylindrical portion  17  of the shaft  15  form an axial half-cut pin. The rotor  3  is guided in rotation relative to an annular support  18  of the fixed structure  4 . The rotor  3  is rotated by a turbine shaft via a speed reduction gear  19 . The reduction gear  19  is an epicyclic reduction gear. The rotor  3  is rotationally coupled to a planet carrier of the reduction gear  19 , the planet carrier forming the output shaft of the reduction gear  19 . In addition, the rotor  3  comprises an inlet cone  20  which is centred on the axis X and flares from upstream to downstream. 
     According to the embodiments illustrated in  FIGS. 1 to 3 , the support  18  is mounted on an inner hub  21  of an intermediate casing  22 . The support  18  comprises a frustoconical-shaped upstream wall  23 , a frustoconical-shaped downstream wall  24  and a tubular cylindrical wall  25  in which the first bearing  6  and the fixed member  11  of the transferring device  10  are housed. The second bearing  7  is housed in an opening provided in the downstream wall  24 . The cylindrical wall  25  is arranged axially between the upstream wall  23  and the downstream wall  24 . The upstream and downstream walls  23 ,  24 , and the cylindrical portion  17  of the shaft  15  define between them an annular enclosure  26  (commonly known as the “oil enclosure”) in which the first and second bearings  6 ,  7  are housed and lubricated. The upstream and downstream walls  23 ,  24  flare from upstream to downstream. The cylindrical wall  25  extends here from the inner end of the upstream wall  23 . The first and second bearings  6 ,  7  respectively guide the shaft  15  of the rotor  3  in rotation relative to the cylindrical wall  25  and the downstream wall  24  of the support  18 . The first bearing  6  is located upstream of the second bearing  7 . The first bearing  6  is for example a roller bearing. The second bearing  7  is for example a ball bearing. The sealing means  27  are placed upstream of the first bearing  6  between the cylindrical wall  25  and the cylindrical portion  17  of the shaft  15 , so that the enclosure  26  is sealed. 
     By way of concrete example, the support  18  could be broken down into two separate assemblies, namely a first assembly comprising the upstream wall  23  and the cylindrical wall  25  and a second assembly comprising only the downstream wall  24 . Both sets would then be flanged to the inner hub using common fastening means such as screws. 
     According to the embodiments illustrated in  FIGS. 1 to 3 , each blade  5  comprises a root  28  mounted in a housing  29  of the ring  14  via two bearings  30  so that the blade  5  is mobile in rotation around an axis Y substantially perpendicular to the axis X. 
     According to the first embodiment illustrated in  FIG. 1 , the controlling system  8  comprises at least a first actuator  9  and a mechanism  31  specific to each of the blades  5 . 
     The controlling system  8  comprises either a first actuator  9  for each blade  5  or one or more first actuators  9  for all the blades  5 . 
     Advantageously, the controlling system  8  comprises a first actuator  9  common to all blades  5  and a mechanism  31  specific to each of the blades  5 , this mechanism  31  making it possible to transform the movement initiated by the first actuator  9  into a rotary movement of the corresponding blade  5 . The movement of the first actuator  9  makes it possible to synchronously adjust the pitch of all the blades  5  via in particular the various mechanisms  31 . 
     The first actuator  9  can be either a hydraulic or an electric actuator. 
     If the first actuator  9  is a hydraulic actuator, the energy to be transported to the actuator is hydraulic energy, i.e. a pressurised liquid such as oil. The actuator is supplied with hydraulic energy via a power supply unit  32 . The power supply unit  32  comprises the device  10  for transferring the hydraulic energy from the fixed reference frame (connected to the fixed structure  4 ) to the rotating reference frame (connected to the rotor  3 ), this transferring device  10  being here a rotary union  33  (or rotating joint). The rotary union  33  comprises a fixed member  11  secured to the support  18  (and more precisely to the cylindrical wall  25 ) and a moving member  12  secured to the rotor  3  (and more precisely to the cylindrical portion  17 ). The rotary union  33  ensures the transmission of hydraulic energy from the fixed member  11  to the moving member  12  (or vice versa) in a sealed manner. The rotary union  33  can comprise one or more tracks. The supply assembly  32  further comprises at least one pipe  34  connected to the fixed member  11  of the rotary union  33 , and at least one pipe  35  connected to both the moving member  12  of the rotary union  33  and the first actuator  9 . 
     If the first actuator  9  is an electric actuator, the energy to be transported to the actuator is electrical energy, i.e. electricity. The actuator is supplied with electrical energy via a power supply unit  32 . The power supply unit  32  comprises the device  10  for transferring the electrical energy from the fixed reference frame (connected to the fixed structure  4 ) to the rotating reference frame (connected to the rotor  3 ), this transferring device  10  being here a rotary transformer  36  (or rotary transformer). The rotary transformer  36  ensures the transmission of electrical energy by means of electromagnetic induction. Such a transformer is, for example, described in more detail in documents EP-A1-1306558 and FR-A1-2712250. The rotary transformer  36  comprises a fixed member  11  secured to the support  18  and a moving member  12  secured to the rotor  3 . The power supply unit  32  also comprises at least one cable  37  connected to the fixed member  11  of the rotary transformer  36  and at least one cable  38  connected to both the moving member  12  of the rotary transformer  36  and the first actuator  9 . 
     The first actuator  9  comprises a fixed element in relation to the rotor  3  and a moving element in relation to the fixed element (and therefore in relation to the rotor  3 ). The fixed element of the first actuator  9  is fixed to the rotor  3 . The moving element is linked to at least one mechanism  31 . The first actuator  9  can be linear or rotary. 
     The mechanism  31  comprises, for example, for each blade, a crank with a first end centred on the axis Y and rotationally coupled to the corresponding blade and a second end eccentric to the axis Y and secured to the moving element of the first actuator  9 . The crank handle is used to multiply the force required to adjust the pitch of the corresponding blade. 
     According to the second embodiment illustrated in  FIG. 2 , the controlling system  8  comprises at least a first actuator  9  and a mechanism  31  specific to each of the blades  5 . 
     The controlling system  8  comprises either a first actuator  9  for each blade  5  or one or more first actuators  9  for all blades  5 . 
     Advantageously, the controlling system  8  comprises a first actuator  9  common to all blades  5  and a mechanism  31  specific to each of the blades  5 . This mechanism  31  makes it possible to transform the movement initiated by the first actuator  9  into a rotary movement of the corresponding blade  5 . 
     More precisely, the first actuator  9  is an electric motor comprising a rotating output shaft  39 . For each blade  5 , the mechanism  31  comprises a crank  40  with a first end centred on the axis Y and rotationally coupled with the corresponding blade  5 , and a second end with a cam follower  41  eccentric to the axis Y. The cam follower  41  cooperates with a cam  42  in the form of a groove made in a ring  43 , the ring  43  being rotationally coupled to the output shaft  39  of the electric motor. 
     The rotary movement of the output shaft  39  of the electric motor allows synchronised adjustment of the pitch of all the blades  5 , in particular via the various mechanisms  31  (for each mechanism  31 , a cam  42 /cam follower  41  assembly and a crank  40 ). 
     The stator of the electric motor is fixed to the rotor  3 . 
     The electric motor may comprise a reduction gear. For example, the ring  43  is rotationally coupled to the motor output shaft  39  via a spline or serrated connection. 
     The power supply unit  32  of the electric motor is identical to that of an electric actuator detailed above in connection with the first embodiment. 
     According to the third embodiment illustrated in  FIG. 3 , the controlling system  8  comprises a first actuator  9  common to all blades  5  and a mechanism  31  specific to each blade  5 . 
     Specifically, the first actuator  9  is an electric motor configured to drive a pump  44  of a hydraulic circuit  45  secured to the rotor  3 . The circuit  45  comprises a liquid tank (or reservoir) connected to the pump  44 . The circuit  45  comprising a second hydraulic actuator  46  supplied with pressurised liquid by the pump  44 . The mechanism  31  is configured to transform the movement initiated by the second actuator  46  into a rotary movement of the corresponding blade  5 . 
     Advantageously, the second actuator  46  is common to all blades  5 . 
     The rotary movement of the rotor of the electric motor makes it possible to synchronously adjust the pitch of all the blades  5  via the hydraulic circuit  45  and the various mechanisms  31 . 
     The hydraulic circuit  45  is said to be autonomous (or independent) in terms of hydraulic energy, and in other words the hydraulic circuit  45  does not receive hydraulic energy from the fixed reference frame. 
     The stator of the electric motor is fixed to the rotor  3 . 
     The second actuator  46  comprises a fixed element in relation to the rotor  3  and a moving element in relation to the fixed element (and therefore in relation to the rotor  3 ). The moving element is linked to the mechanisms  31 . The second actuator  46  can be linear or rotary. 
     Mechanism  31  comprises, for example, for each blade, a crank with a first end centred on the axis Y and coupled in rotation with the corresponding blade and a second end eccentric with respect to the axis Y and secured to the moving element of the second actuator  46 . 
     Advantageously, the circuit  45  comprises an accumulator configured to feather the blades, particularly in the event of failure of the rotary transformer  36 . The accumulator is, for example, a pressurised liquid reservoir. 
     In addition, the circuit  45  can comprise one or more pre-actuators configured to, among other things, control the flow of pressurised liquid within the circuit  45 . A pre-actuator is, for example, a distributor, valve or servo valve. The electric motor may comprise a reduction gear. 
     The power supply  32  of the electric motor is identical to that of an electric actuator detailed above in relation to the first embodiment.