Abstract:
The invention relates to an assembly comprising a drive gearbox ( 10 ) for an aircraft ( 1 ) and an accessory ( 30 ), the gearbox comprising: a connecting shaft ( 110 ) adapted to be driven by the propulsion system, a main shaft ( 120 ) adapted to be driven by the connecting shaft ( 110 ), and two bevel gears ( 122, 123 ) which are integral with the main shaft ( 120 ) and have different diameters (d 122 , d 123 ), the accessory comprising: a high-speed accessory shaft ( 31 ) comprising a bevel gear ( 310 ), a low-speed accessory shaft ( 32 ) comprising a bevel gear ( 320 ), such that each gear ( 310, 320 ) on the accessory shafts ( 31, 32 ) meshes with one of the two bevel gears ( 122, 123 ) on the main shaft ( 120 ), so that the two accessory shafts ( 31, 32 ) rotate at different speeds relative to one another.

Description:
GENERAL TECHNICAL FIELD 
       [0001]    The present invention relates to the field of turbine engines. It relates in particular to the mounting of auxiliary equipment and the mechanical transmission of power between a shaft of the engine, in a turbine engine, and this equipment using an accessory gearbox (AGB), or transfer gearboxes (TGB). 
         [0002]    In other words, the invention relates to power transmission architectures allowing the so-called auxiliary equipment of an aircraft to be fed from the power produced by the propulsion unit, as well as the support of this equipment. 
       PRIOR ART 
       [0003]    The accessory gearbox supports different auxiliary equipment, or accessories, mounted on the engine and necessary for its operation or that of the aircraft. These various accessories can in particular comprise a generator, a starter, an alternator, fuel or oil hydraulic-pumps, multistage lubrication units, etc. and are driven mechanically by the engine shaft by means of transmission shafts. The necessary power for driving accessories is generally drawn mechanically at the compressor of the turbine engine. The AGB is adapted to be implemented on an aircraft comprising a propulsion unit allowing setting said aircraft in motion. The propulsion unit is generally a turboprop or a turbojet. 
         [0004]    There currently exist cascades of spur gears P 1 , P 2 , . . . , originating from a transfer shaft TS drawing power from the propulsion unit, each gear offering a different output speed (see  FIG. 1 ). 
         [0005]    Such a solution does not offer the compactness required for integrating the AGB or the reduction ratios necessary for the equipment (the range of speeds extends generally from 6000 to 24000 rpm). 
         [0006]    In addition, there exist certain types of equipment each requiring several different input speeds. For example, the fuel pump has two pump stages each of which has an efficiency optimized at different rotation speeds. Consequently, imposing the same speed on the two stages reduces the performance of the pump and increases the bulk of the system. A two-speed output of the AGB would thus allow reducing the size of the equipment. 
         [0007]    Document US 2013/0247539 describes an AGB  10  having two output speeds (see  FIG. 2 ). A propulsion unit  20 , comprising a low-speed propulsion shaft BS and a high-speed propulsion shaft HS feeds, via bevel gears, a dual power train consisting of concentric transmission shafts over the entire AGB  10 . In fact, a first outer shaft ES 1  is driven by the high-speed shaft HS and a first inner shaft IS is driven by the low-speed shaft LS. Thereafter the first outer shaft ES 1 , respectively inner shaft IS 1 , drives a second outer shaft ES 2 , respectively inner shaft IS 2 , so as to reorient the transmission along the input axes of the equipment. 
         [0008]    As mentioned previously, the first external ES 1  and internal IS 1  shafts—respectively second shafts ES 2 , IS 2 —are concentric and each rotates at a different speed. In this manner, the AGB  10  effectively transmits two rotation speeds for feeding the equipment. 
         [0009]    Such an architecture is cumbersome in terms of design and lifetime (maintenance of alignments, duplication of the transmission power train, hence multiplicity of parts, mechanical loads, etc.). Moreover, it requires adaptation to the propulsion unit  20 , which limits its ability to integrate with existing units  20 . 
         [0010]    Consequently, there is no completely satisfying solution in terms of compactness. In addition, there also does not exist a completely satisfying solution in the case of feeding equipment at several speeds with reduced bulk. Moreover, solutions that can be implemented on aircraft without substantial modification of the propulsion unit or of the equipment are preferable. 
         [0011]    In addition, one direction of the design of AGBs  10  is oriented toward AGBs of the “core” type, as illustrated in  FIG. 3 , demanding in terms of compactness for locating the AGB  10  and the equipment  30 ,  40 ,  50 , . . . . 
       PRESENTATION OF THE INVENTION 
       [0012]    To this end, the invention proposes an assembly comprising a gearbox for driving an aircraft and a piece of equipment, said gearbox being adapted for transmitting the power of a propulsion unit of the aircraft to the piece of equipment, the gearbox comprising:
       A connection shaft, adapted for being driven by the propulsion unit,   A main shaft, adapted for being driven by the connection shaft,   Two bevel gears integral with the main shaft, said gears having different diameters,   the equipment comprising:   a high-speed equipment shaft comprising a bevel gear,   a low-speed equipment shaft, comprising a bevel gear, characterized in that each gear of the equipment shafts is meshed respectively with one of the two bevel gears of the main shaft, so that the two equipment shafts rotate at different speeds from each other.       
 
         [0019]    Thus the proposed architecture is compact, thanks to a downstream division of the power train of the transmission into two rotations with different speeds. Moreover, it makes it possible to feed equipment requiring two input speeds. 
         [0020]    The invention also comprises the following features, taken alone or in combination:
       the bevel gears are placed facing one another, so that driving the two equipment shafts occurs in opposite directions,   the connection shaft is tilted with respect to the main shaft, the equipment is a multistage fuel pump,   the equipment is a multistage lubrication unit.       
 
         [0024]    The invention also proposes a system comprising an assembly as previously described, further comprising a propulsion system, said propulsion system driving the connection shaft. 
         [0025]    In addition, the assemblies or systems as previously described can comprise at least two pieces of equipment, the two pieces of equipment being driven by the same bevel gears of the gearbox. 
         [0026]    In addition, the assemblies or systems as previously described have at least one bevel gear which is a spiral bevel gear. 
         [0027]    The invention also proposes an aircraft comprising a system according to the foregoing presentation, wherein the propulsion system is a turboprop. 
         [0028]    Independently, the invention also proposes an assembly comprising a gearbox for driving an aircraft and a piece of equipment, said gearbox being adapted for transmitting the power of a propulsion unit to the piece of equipment,
       the gearbox comprising:
           A connection shaft, adapted for being driven by the propulsion unit,   A main shaft, adapted for being driven by the connection shaft,   A bevel gear integral with the main shaft,   
           the equipment comprising:
           a high-speed equipment shaft,   a low-speed equipment shaft,   
           characterized in that a epicyclic gear train comprising an input shaft and an output shaft is positioned between the main shaft and the equipment, the input shaft comprising a bevel gear connected to the bevel gear of the main shaft and being integral in rotation with one of the two equipment shafts and the output shaft being integral in rotation with the other equipment shaft, so that the two drive shafts have different rotation speeds.       
 
         [0037]    Independently, the invention also proposes a gearbox for driving the equipment of an aircraft adapted for transmitting the power of a propulsion unit to at least one piece of equipment, the transmission gearbox comprising:
       A connection shaft, adapted for being driven by the propulsion unit, comprising a bevel gear,   A main shaft, comprising:
           a reception member in the form of a first bevel gear, adapted for being driven by the bevel gear of the connection shaft, and   a second bevel gear, adapted to drive a piece of equipment,   
           A secondary shaft, mounted coaxially on the main shaft and independent in rotation, comprising:
           a first bevel gear, adapted for being driven by the bevel gear of the connection shaft, and   a second bevel gear, adapted to drive another piece of equipment,   
           wherein the axis of the connection shaft and the axis of the main shaft are concurrent and form a non-right angle, and the bevel gear of the main shaft and the bevel gear of the secondary shaft, both adapted for being driven by the bevel gear of the connection shaft, have different geometries, so that the rotation speeds of the main shaft and of the secondary shaft are different.       
 
         [0046]    The invention also proposes an assembly comprising a gearbox as previously described, further comprising a piece of equipment comprising a high-speed equipment shaft and a low-speed equipment shaft, characterized in that the two shafts are coaxial and in that the two shafts each have a bevel gear, wherein:
       one of the two gears is driven by the second bevel gear of the secondary shaft, and   the other gear is driven by the second bevel gear of the main shaft,   so that the two equipment shafts rotate at different speeds.       
 
     
    
     
       PRESENTATION OF THE FIGURES 
         [0050]    Other features, aims and advantages of the invention will be revealed by the description that follows, which is purely illustrative and not limiting, and which must be read with reference to the appended drawings, wherein: 
           [0051]      FIGS. 1 and 2  show AGBs conforming to the prior art, 
           [0052]      FIG. 3  shows a 3D view of an AGB conforming to the invention, 
           [0053]      FIG. 4  shows a schematic of an AGB architecture conforming to a first embodiment, 
           [0054]      FIG. 5  shows a geometric feasibility schematic, 
           [0055]      FIGS. 6 and 7  show a second embodiment, 
           [0056]      FIGS. 8 and 9  show a third embodiment, 
           [0057]      FIG. 10  shows several pieces of equipment driven by a single bevel gear, 
           [0058]      FIG. 11  shows the first and the third embodiments integrated in the same AGB. 
       
    
    
     DETAILED DESCRIPTION 
     1 st  Embodiment 
       [0059]    Referring to  FIGS. 3 and 4 , the AGB  10  comprises first of all:
       a connection shaft  110  adapted to be meshed with the propulsion unit, said connection shaft  110  comprising a leading meshing member  111 ,   a main shaft  120 , comprising a receiving meshing member  121 . The leading  111  and receiving  121  meshing members form a first bell crank R 1 .       
 
         [0062]    The main shaft  120 , due to its rotation, transmits mechanical power to the equipment  30 ,  40 , . . . ,  60 . For this purpose, the mains shaft  120  further comprises a first bevel gear  122  and a second bevel gear  123  integral with the main shaft  120 . What is meant by integral is integral in rotation due to a screw, welding or clamping connection. The two bevel gears  122 ,  123  have different respective diameters d 122 , d 123  and different pitch angles δ 122 , δ 123 . The pitch angle is defined with respect to the shaft on which the bevel gear is mounted (see  FIG. 5 ). 
         [0063]    The pitch angles δ 122 , δ 123  define axes Δ 122 , Δ 123  which are concurrent at one point P. 
         [0064]    The first bevel gear  122  comprises Z 122  teeth and the second bevel gear comprises Z 123  teeth. It is well understood that the number of teeth is directly correlated to the diameter of the gear. 
         [0065]    According to a first variant, the bevel gears  122 ,  123  are placed facing one another, in other words the point P is situated between the two wheels  122 ,  123  (see  FIG. 4 ) or the pitch angles δ 122 , δ 123  defined in an oriented manner have opposite signs. 
         [0066]    According to a second variant, the bevel gears  122 ,  123  are placed in series, in other words the point P is located outside the two gears  122 ,  123  (not shown in the figures) or the pitch angles δ 122 , δ 123  defined in an oriented manner, have the same sign. 
         [0067]    In this manner, the bevel gears  122 ,  123  are adapted for receiving a piece of equipment  30  requiring two input speeds. To that end, the equipment  30  comprises a first equipment shaft  31  and a second equipment shaft  32 , the two shafts being concentric. When the equipment  30  is installed on the AGB  10 , the axis defined by the two equipment shafts runs through the point P defined previously. 
         [0068]    The first equipment shaft  31  comprises a bevel gear  310 , with  2310  teeth, which is meshed with the first bevel gear  122  of the main shaft  120 . Said two bevel gears  122 ,  310  thus form a second bell crank R 2 . 
         [0069]    The second equipment shaft  32  comprises a bevel gear  320 , with  2   320  teeth, which is meshed with the second bevel gear  123  of the main shaft  120 . Said two bevel gears  123 ,  320  thus form a third bell crank R 3 . 
         [0070]    In order to allow the equipment  30  to be assembled, it is naturally necessary that the axes defined by the pitch angles δ 30 , δ 320  of the bevel gears  310 ,  320  of the equipment shafts  31 ,  32  join at said point P. 
         [0071]    Preferably, the equipment shafts  31 ,  32  are orthogonal to the main shaft  120  but such a condition is not necessary. 
         [0072]      FIG. 5  illustrates the geometric feasibility of the architecture as well as the rotation speeds of the various shafts. 
         [0073]    The speed of rotation of part i is designated ω i . Setting d 122 &gt;d 123  (and consequently Z 122 &gt;Z 123 ) and, arbitrarily δ 122 &lt;δ 123  with δ 122 +δ 310 =δ 123 +δ 320a =90° (orthogonality of the shafts); 
         [0074]    Thus, we have: 
         [0000]      ω 31   =Z   310   /Z   122 ·ω 120 =tan (δ 122 );
 
         [0000]    Ω 32   =Z   320   /Z   123 ·ω 120 =tan (δ 123 );
 
but δ 122 &gt;δ 123 , hence ω 31 &gt;ω 32 .
 
         [0075]    Two coaxial equipment shafts  31 ,  32  are thus obtained, which rotate at different speeds. The speeds of the two shafts  31 ,  32  are thus independent, that is to say that by selecting suitable parameters, the speeds can be adjusted independently of one another, even if the two equipment shafts  31 ,  32  are driven by the same main shaft  120 . 
         [0076]    In fact, the reduction ratios depend directly on the number of teeth of the bevel gears  122 ,  123  of the main shaft  120  and the bevel gears  310 ,  320  of the equipment  30 . 
       2 nd  Embodiment 
       [0077]    The structure of the AGB is similar to that of the first embodiment, with the connection shaft  110  and the main shaft  120  with the first bell crank R 1 . 
         [0078]    The main shaft  120  comprises a bevel gear  124 . 
         [0079]    An epicyclic gear train  13  is meshed with the bevel gear  124 . The epicyclic gear train  13  comprises an entry sun gear  131 , an output sun gear  132 , at least one planet gear  133  and a planet carrier  134 . The output sun gear also comprises an output shaft  132   a.    
         [0080]    According to a first alternative (see  FIG. 6 ), the planet carrier  134  comprises a shaft  134   a  and a bevel gear  134   b  which is meshed with the bevel gear  124  of the main shaft  120 . The equipment shafts  31 ,  32  are integral in rotation with respectively the planet carrier  134  and the output sun gear  132  (or the reverse), which for their part are rotating along the same axis at different speeds. 
         [0081]    According to a second alternative (see  FIG. 7 ), the input sun gear  131  comprises a shaft  131   a  and a bevel gear  131   b  which is meshed with the bevel gear  124  of the main gear  120 . The equipment shafts  31 ,  32  are integral in rotation respectively with the input sun gear  131  and the output sun gear  132  (or the reverse), which are themselves rotating on the same axis at different speeds. 
         [0082]    These alternatives are not limiting and are adaptable without difficulty for a person skilled in the art to different types of epicyclic gear trains. In fact, an epicyclic gear train is defined by three values of angular rotation (those of the input sun gear  131 , of the output sun gear  132 , and of the satellite carrier  133 ). Consequently, there exists a plurality of alternatives. 
         [0083]    More generally, an input shaft  131   a,    134   a  and an output shaft  132   a,  integral in rotation respectively with one of the two equipment shafts  31 ,  32  are defined. Moreover, the input shaft  131   a  comprises a bevel gear  131   b,    134   b  driven by the bevel gear  124  of the main shaft. 
       3 rd  Embodiment 
       [0084]    Referring to  FIG. 8 , the bell crank R 1  is strictly comprised between 0 and 90°, that is to say that the axes of the transfer shaft  110  and of the main shaft  120  do not define a right angle. To that end, the leading meshing member  111  of the connection shaft  110  is a bevel gear with pitch angle δ 111  and the receiving meshing member  121  of the main shaft is a bevel gear with pitch angle δ 121  and with diameter d 121 . Recall that the pitch angle is defined with the shaft on which the bevel gear is mounted. 
         [0085]    The pitch angles δ 111 , δ 121  define axes Δ 111 , Δ 121  which are concurrent at a point Q. 
         [0086]    The connection shaft  110  is tilted with respect to the mains shaft  120 , which means that the sum of the pitch angles δ 111 +δ 121  is not equal to 90°. 
         [0087]    In this embodiment, a secondary shaft  150  is assembled, concentric with the main shaft  120 . This secondary shaft  150  comprises a first bevel gear  151  with diameter d 151  which is meshed with the bevel gear  111  of the connection shaft  110 . For reasons of geometry, the axis Δ 151  defined by the pitch angle δ 151  also runs through the point Q. 
         [0088]    Due to the non-orthogonality of the connection shaft  111  and of the main shaft  120 , diameter d 121  is less than diameter d 151 . Consequently, given that the bevel gears  121 ,  151  mesh with a common meshing part—the bevel gear  111 , the rotation speeds of the main shaft  120  and of the secondary shaft  150  are different. Note also that the direction of rotation are different. The secondary shaft  150  comprises at least one second bevel gear  152 , which feeds a piece of equipment  40  through the equipment shaft  41  and a bevel gear  42  on said shaft  41 . In the present case, the equipment  40  requires only needs to be fed at one speed. 
         [0089]    In a complementary fashion, the main shaft  120  comprises at least one other bevel gear  125  which meshes with another piece of equipment  50 . 
         [0090]    Thus, the architecture presented makes it possible to have different speeds for supplying different equipment. 
         [0091]    According to a variant of the third embodiment, the equipment  30  as defined in the first embodiment can be fed by the third embodiment. As shown in  FIG. 9 , in this variant, the bevel gear  152  of the secondary shaft  150  meshes with the bevel gear  310  of the equipment shaft  31  and the bevel gear  125  of the main shaft meshes with the bevel gear  320  of the equipment shaft  32 . 
         [0092]    In this manner, the third embodiment also makes it possible to feed a piece of equipment requiring two input speeds. 
         [0093]    In the foregoing description, each bevel gear of the main shaft  120  drives only one piece of equipment  30 ,  40 ,  50 . For reasons of optimizing space and bulk, each bevel gear of the main shaft  120  can drive several pieces of equipment, by positioning them around the shaft, either at regular angular intervals (between 30° and 180° for example, see  FIGS. 3 and 10 ) via multiple meshing. 
         [0094]    Finally, the three embodiments are not exclusive and can be implemented two by two, or all three in the same AGB  10 .  FIG. 11  thus shows for example the first and third embodiments (with the two variants) on one AGB  10 . 
         [0095]    Advantageously, the bevel gears used to drive the different elements are spiral bevel gears, or Zérol® type gears, or hypoid gears, or more generally helical gearing. 
         [0096]    Combinations of different types of gearing can be contemplated, depending on the type of power transfer, speeds of rotation and mechanical constraints.