Abstract:
A gas turbine engine assembly comprising, a gearbox including a first housing that includes a first auxiliary gear drive on a first portion thereof, a second housing that includes a second auxiliary gear drive on a second portion thereof, and a third housing that includes a third auxiliary gear drive on a third portion thereof, the housings being interconnected so that the first portion of the first housing, the second portion of the second housing and the third portion of the third housing form a substantially triangular polyhedron shape, with the second portion of the second housing disposed between the first portion of the first housing and the third portion of the third housing. The first auxiliary gear drive, the second auxiliary gear drive and the third auxiliary gear drive project outwardly in mutually divergent directions.

Description:
FIELD 
       [0001]    The present disclosure relates to a gearbox for a gas turbine engine. 
       BACKGROUND 
       [0002]    A typical gas turbine engine for an aircraft may include an accessory drive gearbox. The gearbox is rotationally coupled to at least one spool of the engine by a tower shaft. The gearbox may be coupled to an engine core and enclosed by a core nacelle surrounding the engine core. A compact gearbox configuration may be desirable to fit within the space between the core nacelle and engine core. Reducing inventory of spare parts and the need for multiple dissimilar components is also desirable. 
       SUMMARY 
       [0003]    A system and method for coupling accessories to a gearbox of a turbine engine are described herein. In one exemplary embodiment, a first housing that includes a first auxiliary gear drive on a first portion thereof, a second housing that includes a second auxiliary gear drive on a second portion thereof, and a third housing that includes a third auxiliary gear drive on a third portion thereof. The housings are interconnected so that the first portion of the first housing, the second portion of the second housing and the third portion of the third housing form a substantially triangular polyhedron shape, with the second portion of the second housing disposed between the first portion of the first housing and the third portion of the third housing. The gear drives project outwardly in mutually divergent directions. 
         [0004]    In a further embodiment of any of the above, the first faces of the first and second housing portions are provided respectively by removable first and second covers. 
         [0005]    In a further embodiment of any of the above, a first set of bevel gears interconnects the first and third gear sets. A second set of bevel gears interconnects the second and third gear sets. 
         [0006]    In a further embodiment of any of the above, accessory drive components are secured to the accessory drive component mounts. 
         [0007]    In a further embodiment of any of the above, each of the first faces of the first and second housing portions includes accessory drive component mounts. 
         [0008]    In another exemplary embodiment, a gas turbine engine includes an engine static structure housing a compressor section, a combustor section and a turbine section. A spool supports at least a portion of each of the compressor and turbine sections for rotation about an axis. A gearbox is supported by the engine static structure and is coupled to the spool by a tower shaft. A gas turbine engine assembly comprising, a gearbox including a first housing that includes a first auxiliary gear drive on a first portion thereof, a second housing that includes a second auxiliary gear drive on a second portion thereof, and a third housing that includes a third auxiliary gear drive on a third portion thereof, the housings being interconnected so that the first portion of the first housing, the second portion of the second housing and the third portion of the third housing form a substantially triangular polyhedron shape, with the second portion of the second housing disposed between the first portion of the first housing and the third portion of the third housing. The first auxiliary gear drive, the second auxiliary gear drive and the third auxiliary gear drive project outwardly in mutually divergent directions. 
         [0009]    In a further embodiment of any of the above, gears of the first, second and third auxiliary drives and/or gear sets each include an axis. The gear axes of the first gear set are perpendicular to a first plane. The gear axes of the second gear set are perpendicular to a second plane. The gear axes of the third gear set are perpendicular to a third plane. The first and second planes are non-parallel to one another. The first, second and third planes are transverse to one another. The gear axes of the first and second gear sets are arranged circumferentially with respect to the axis. 
         [0010]    In a further embodiment of any of the above, the intermediate housing portion includes first and second faces opposite one another. The input shaft extends through the first face of the intermediate housing portion and is coupled to the third gear set. 
         [0011]    In a further embodiment of any of the above, the second face of the intermediate housing portion includes a tower shaft cover removably secured to the intermediate housing portion over an opening sized to receive the tower shaft. 
         [0012]    In a further embodiment of any of the above, the first and second faces of each of the first and second housing portions are parallel to one another. 
         [0013]    In a further embodiment of any of the above, the second faces are about 90° apart, and the intermediate housing portion is about 120° apart from each of the first and second housing portions. The forgoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated herein otherwise. These features and elements as well as the operation of the disclosed embodiments will become more apparent in light of the following description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements. 
           [0015]      FIG. 1A  is a cross-sectional view of a gas turbine engine, in accordance with various embodiments; 
           [0016]      FIG. 1B  is a cross-sectional view of a gas turbine engine and diversified gearbox, in accordance with various embodiments; 
           [0017]      FIG. 2  is a perspective view of a gearbox, in accordance with various embodiments; 
           [0018]      FIG. 3  is a view of the gears of a gearbox, in accordance with various embodiments; 
           [0019]      FIG. 4  is a view of gears and bearing of a gearbox, in accordance with various embodiments; 
           [0020]      FIG. 5  is a view of the bevel gearsets of a gearbox, in accordance with various embodiments; and 
           [0021]      FIG. 6  is a view of mounting surface angle options to accommodate components, in accordance with various embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the inventions, it should be understood that other embodiments may be realized and that logical, chemical and mechanical changes may be made without departing from the spirit and scope of the inventions. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. 
         [0023]    Different cross-hatching and/or surface shading may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
         [0024]      FIG. 1A  schematically illustrates an example gas turbine engine  20  that includes a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section  22  drives air along a bypass flow path B while the compressor section  24  draws air in along a core flow path C where air is compressed and communicated to a combustor section  26 . In the combustor section  26 , air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through the turbine section  28  where energy is extracted and utilized to drive the fan section  22  and the compressor section  24 . 
         [0025]    Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines; for example a turbine engine including a three-spool architecture in which three spools concentrically rotate about a common axis and where a low spool enables a low pressure turbine to drive a fan via a gearbox, an intermediate spool that enables an intermediate pressure turbine to drive a first compressor of the compressor section, and a high spool that enables a high pressure turbine to drive a high pressure compressor of the compressor section. 
         [0026]    The example gas turbine engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis X relative to an engine static structure  36  via various bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0027]    The low speed spool  30  generally includes an inner shaft  40  that connects a fan  42  and a low pressure (or first) compressor  44  section to a low pressure (or first) turbine  46  section. The inner shaft  40  drives the fan  42  through a speed change device, such as a geared architecture  48 , to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure (or second) compressor  52  section and a high pressure (or second) turbine section  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via the various bearing systems  38  about the engine central longitudinal axis X. 
         [0028]    A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . In one example, the high pressure turbine  54  includes at least two stages to provide a double stage high pressure turbine  54 . In another example, the high pressure turbine  54  includes only a single stage. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine. 
         [0029]    The example low pressure turbine  46  has a pressure ratio that is greater than about 5. The pressure ratio of the example low pressure turbine  46  is measured prior to an inlet of the low pressure turbine  46  as related to the pressure measured at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. 
         [0030]    A mid-turbine frame  57  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  57  further supports various bearing systems  38  in the turbine section  28  as well as setting airflow entering the low pressure turbine  46 . 
         [0031]    The core airflow C is compressed by the low pressure compressor  44  then by the high pressure compressor  52  mixed with fuel and ignited in the combustor  56  to produce high speed exhaust gases that are then expanded through the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  57  includes vanes  59 , which are in the core airflow path and function as an inlet guide vane for the low pressure turbine  46 . Utilizing the vane  59  of the mid-turbine frame  57  as the inlet guide vane for low pressure turbine  46  decreases the length of the low pressure turbine  46  without increasing the axial length of the mid-turbine frame  57 . Reducing or eliminating the number of vanes in the low pressure turbine  46  shortens the axial length of the turbine section  28 . Thus, the compactness of the gas turbine engine  20  is increased and a higher power density is achieved. 
         [0032]    The disclosed gas turbine engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the gas turbine engine  20  includes a bypass ratio greater than about six (6), with an example embodiment being greater than about ten (10). The example geared architecture  48  is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about 2.3. 
         [0033]    In one disclosed embodiment, the gas turbine engine  20  includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor  44 . It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines. 
         [0034]    With continuing reference to  FIG. 1B , a gearbox  62  coupled to a gas turbine engine  20  is illustrated. A core nacelle is arranged about the engine static structure  36  and encloses the gearbox  62 . 
         [0035]    As illustrated in  FIG. 2 , the gearbox  62  is operatively coupled to the high spool by a tower shaft. For example, the tower shaft is rotationally driven by a high spool via a gear set, which is provided by beveled gears. The tower shaft is connected to an input shaft  80  that is supported by the gearbox  62 . The input shaft  80  provides the rotational coupling to various accessory drive components  84 ,  86 ,  88 ,  90 ,  92 , and  94 . Gearbox  62  assists with external line connection and maintenance due to components being mounted on the axial surface. Stated another way, gearbox  62  assists with external line connection and maintenance due to components being mounted parallel with the engine axis. Gearbox  62  adds flexibility to a gas turbine engine assembly. Mounting surfaces are angled in various positions to fit the components in the package envelope. 
         [0036]    The gearbox  62  is provided by a generally a triangular polyhedron shaped structure housing  68  having a first housing portion  70  and second housing portion  72  interconnected to one another by an intermediate housing portion  74 . The intermediate housing portion  74  supports the input shaft  80 . The first housing portion  70  includes a first face  76 A. The second housing portion  72  includes a first face  76 B. The intermediate housing portion  74  includes a first face  76 C. The first faces  76 A-C are adjacent to the engine static structure  36 , with brief reference to  FIG. 1A . The first face  76 C of intermediate housing portion  74  forms a triangle bounded on two sides by an edge  625 ,  635  of the first face of the first and second housing portions (with brief reference to  FIG. 6 ). 
         [0037]    Instead of mounting the accessory drive components such that their rotational axes are in the same direction as the core engine axis X, with brief reference to  FIG. 1A , the accessory drive components are mounted on both of the first faces  76 A,  76 B, on the first and second housing portions  70 ,  72 , as desired. That is, the axes of the accessory drive components  84 ,  86 ,  88 , 90 ,  92 , and  94  are arranged circumferentially relative to the engine static structure  36  (with brief reference to  FIG. 1A ). The gearbox  62  comprises a plurality of independent gear trains with a triangle shaped intermediate housing portion  74  to give more space for long components. The gearbox  62  can be adjusted in any direction by changing the shaft angle of bevel gearsets  116  and  118 , rotate the mounting surfaces around input shaft  80  or moving the first set of first and second idler gears  122  and  124 , also known a spur gears, forward or aft to allow the long component fit in given space, with brief reference to  FIG. 3 ). 
         [0038]    As illustrated in  FIG. 2 , a variable frequency generator (VFG)  88 , air turbine starter  90 , and a lubrication pump  84  are mounted to the first face  76 A. A hydraulic pump  86 , a fuel pump  92 , and a permanent magnet alternator (PMA)  94  are mounted to the first face  76 B. 
         [0039]    An integrated drive generator (IDG), and/or a deoiler is optionally mounted to at least one of first face  76 A or first face  76 B. In this manner, the axial length of the gearbox  62  and its arrangement of accessory drive components  84 ,  86 ,  88 ,  90 ,  92 ,  94  are reduced compared to axially oriented accessory drive components. As a result, the gearbox  62  and accessory drive components  84 ,  86 ,  88 ,  90 ,  92 ,  94  are positioned easily along the length of the engine static structure  36  to more desirable locations where more space and/or cooler temperatures are provided. 
         [0040]    The mounting locations  84 M,  86 M,  88 M,  90 M,  92 M,  94 M for the accessory drive components  84 ,  86 ,  88 ,  90 ,  92 ,  94  are shown in more detail as  84 M,  86 M,  88 M,  90 M,  92 M,  94 M in  FIG. 3 . Like numerals are used to indicate an association amongst components. The first faces  76 A,  76 B of the first housing portion  70  and second housing portion  72  are provided by removable a first cover  310  and a second cover  320  that selectively provide access to an interior of the generally a triangular polyhedron shaped housing  68  within which the gear train is mounted. 
         [0041]    The covers are removable to provide access to any gear  130 , which are mounted to the shafts  126 , which are supported by bearings  128  relative to the housing  68 , as shown in  FIG. 4 . In this manner, the bearings  128  and gears  130  are easily serviced. 
         [0042]    With reference to  FIG. 3 , the first, second and intermediate housing portions  70 ,  72 ,  74  respectively house first, second and third gear sets  110 ,  112 ,  114 . The first gear set  110  is operatively connected to the third gear set  114  by a first bevel gear set  116 . The second gear set  112  is operatively coupled to the third gear set  114  by the second bevel gear set  118 , with reference to  FIG. 5 . The input shaft  80  rotationally drives an input gear  120  which rotationally drives the first and second gear sets  110 ,  112  via first and second idler gears  122 ,  124 . The first gear set  110  includes gears  86 G,  92 G,  94 G, that respectively rotationally drive the hydraulic pump  86 , a fuel pump  92 , a permanent magnet alternator (PMA)  94 . The second gear set  112  includes second gears  84 G,  88 G,  90 G,  88 G that respectively drive the back-up variable frequency generator (VFG)  88 , air turbine starter  90 , and the lubrication pump  84 . 
         [0043]    As can be appreciated by  FIG. 3 , the gears of the first gear set  110  are parallel with one another relative to a plane P 1 . The gears of the second gear set  112  are parallel with one another with respect to a second plane P 2 . First face  76 A intersects with first face  76 B along common edge  81 . The gears of the third gear set  114  are parallel with one another with respect to a third plane P 3 . The planes P 1 -P 3  are independent and not parallel relative to one another. 
         [0044]    As illustrated in  FIG. 6 , first face  76 A or first face  76 B are angled at desired orientations to accommodate accessory drive components  84 ,  86 ,  88 ,  90 ,  92 ,  94 , such as the distance measured from the first face  76 A or first face  76 B of accessory drive components  84 ,  86 ,  88 ,  90 ,  92 ,  94 . Narrowing dimensions of first face of  76 C of the intermediate housing portion  74  of gearbox  62  assists with creating space in location A and location B for further component extension from first face  76 A or first face  76 B. 
         [0045]    Accordingly the mounting surfaces of gearbox  62  can be adjusted in any direction by changing the shaft angle of bevel gearsets and rotating the mounting surfaces around the input shaft in kind. Also, the mounting surfaces of gearbox  62  can be adjusted by moving the first set of spur gears forward or aft to allow a long component to fit in given space. 
         [0046]    Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. The scope of the disclosure, however, is provided in the appended claims.