Abstract
A transmission system which is used in conjunction with a microturbine engine for propulsion of a body of air, such as an aircraft wing or fixed propeller based on a plane vertical lift from the rotor, or for a wide variety of other applications. The output shaft microturbine engine preferably operates at a rotational speed in a range between 72,000 and 150,000 RPM RPM with an output power of 150 HP and 5 HP (and most preferably operates in an extended range and 50,000 RPM 200 000 RPM with a power output of 200 HP and 5 HP). The two reduction stages provide a reduction ratio preferably has a value of at least 19, and more preferably greater than 24. The transmission system is small in size, preferably having a maximum diameter of less than twelve inches. The two stages of the transmission system may comprise any (or part) of a number of configurations, including an in-line axis lying configuration, a star configuration-line star a star configuration stimulus offset, moving an idle compound configuration, art inline internal drive and a planetary gear set in drive line. Preferably, the input stage of the transmission system is self-balancing such that the first shaft can be supported without bearings and operatively coupled to the output shaft microturbine engine driven by an outer diameter spline coupling mechanism. For vertical lift applications, a single step together with a drive bevel gear assembly or other axle transmission mechanism can be used to provide the necessary reduction in RPM.
Description
This invention was made with support from the State Government under contract DAAH10 - 03-C -0025 awarded by the U.S. Army . The U.S. Government has certain rights in the invention.Background of the Invention
1. Field of the Invention
This invention relates generally to systems for speed reducing transmission power of a gas turbine engine to a rotary drive element of an aircraft. More particularly, this invention relates to systems for reducing energy transmission speed of a gas turbine engine high speed small size to a rotary actuator slower speed of an airplane
.Two . State of the Art
Unmanned aerial vehicles low cost small (UAVs ) have been developed and deployed to carry out a variety of military roles , including reconnaissance and attack missions . At present , the spark ignition engines 100 HP intermittent (or less ) of power to all low-speed aircraft UAV. Most of these motors driving propellers without the need for a gearbox . However, these burn gasoline engines , which is highly flammable and therefore undesirable for field service operations . Piston engines also have undesirable vibration characteristics and are difficult to start in cold weather operations .
SUMMARY OF THE INVENTION
BRIEF DESCRIPTION OF THE DRAWINGS
. Figure 4 is a cross section showing a third illustrative embodiment of the transmission system of FIG . 1A, which is made by a star configuration - two-stage spur displacement .. 5A is a schematic diagram showing a fourth illustrative embodiment of the transmission system of FIG . 1A, which is made by a configuration of two-stage intermediate - offset.. 5B is a cross section showing the configuration of compound - idler Fig. 5A.. 6A is a schematic diagram depicting a fifth exemplary embodiment of the transmission system of FIG . 1A, which is implemented by a configuration of internal drive train of two stages.. 6B is a cross section showing the configuration of the pulling - Figure internal . 6A.. 7 is a cross section showing a sixth illustrative embodiment of the transmission system of FIG . 1A, which is performed by a train configuration of two-stage planetary drive .Figures . 8A and 8B are schematic diagrams illustrating the principles of a reduction step of self - balance .. 9 is a cross section illustrating an outer diameter driven spline coupling mechanism coupling the output shaft of the microturbine engine to the input shaft of the transmission system according to the present invention.. 10 is a cross section illustrating a coupling mechanism coupling the output shaft of the transmission system to a propeller of a fixed-wing UAV propeller.. 11A is a schematic diagram of a propulsion system based rotor including a microturbine engine and transmission system according to the present invention.. 11B is a pictorial illustration of a vertical elevator which employs exemplary UAV rotor drive system based on the figure. 11A according to the present invention.Detailed Description of the Preferred EmbodimentsRecently, turbine engines small ( referred to herein as " microturbine ") have been developed mainly for the control model airplane radio market . An example of such a microturbine engine is disclosed in detail in U.S. Patent . No. 5,727,378 to Seymour . Such microturbines , when used in conjunction with heavy jet fuel ( such as JP- 8) provide a highly advantageous propulsion system for low-cost small unmanned aerial vehicles , . The advantages provided by such microturbines include lighter weight , the less flammable fuels , greater reliability and reduced vibration.However, microturbines operate very high rotational speeds , typically in the range between 72,000 and 150,000 RPM RPM with an output power of 150 HP and 5 HP . Such speeds and output power can be extended to a range of 50,000 RPM and 200 000 rpm with an output power of 200 HP and 5 HP . UAV aircraft operate at much slower speeds of rotation of propeller , typically about 3700 RPM to 4500 RPM . These limitations result in a reduction ratio required of the typical microturbine engine RPM to the propeller RPM by 28:1 to 24:1 .Due to the high speeds of the microturbine (which is 2.5 to 10 times greater than the current state of the turbine engine art production ) , power transmission designs for turbine engines do not provide reduced RPM necessary , nor such designs must integrate RPM reduction functionality in a design of low cost, small and lightweight which is suitable for use in unmanned aerial vehicles .Turning now to FIG . 1A shows a power plant 10 suitable for use in propelling a fixed-wing aircraft , as an unmanned fixed-wing 30 is shown in Fig . 1B. The power plant 10 includes a microturbine engine 12 with an output shaft 14. A coupling mechanism 16 couples the output shaft 14 to the input shaft 18 of a transmission system 20 . The transmission system 20 operates to reduce the speed of the output shaft 14 of the microturbine engine 12 in its own output shaft 22. The output shaft 22 of the transmission system is coupled to a propeller 24 by a coupling mechanism 26. Helix 24 , when driven by the microturbine engine 12 and the transmission system 20 provides a thrust which drives an aircraft body , as the body of the fixed wing aircraft of Figure 30 . 1B. Note that in the configuration shown , the transmission system 20 and the propeller 24 are disposed on the intake side of the microturbine engine 12. This configuration enables the transmission system to be cooled by the engine intake air . Alternatively, the transmission system 20 and the propeller 24 may be disposed on the exhaust side of the microturbine engine 12. In this alternative configuration , the transmission system and the helix must operate in a hot environment, and therefore must be designed to withstand the increased heat load that derives from the operation in the hot environment on the exhaust side engine 12.The output shaft 14 of microturbine 12 operates at very high rotational speeds , typically in the range between 72,000 and 150,000 RPM RPM with an output power of 150 HP and 5 HP . For applications of unmanned aerial vehicles, low speed , the propeller 24 operates at slower rotation speeds , typically about 3700 RPM to 4500 RPM . These restrictions result in a reduction ratio required microturbine engine RPM to the RPM of the propeller in the order of 28:1 to 24:1 . The transmission system 20 provides this required speed reduction in the range of output power ( 150 HP to 5 HP ) microturbine engine .In the preferred embodiment of the present invention , the transmission system 20 and microturbine engine of small size and low weight. Preferably , the maximum diameter of the transmission system is less than 12 inches. Such restrictions on size and weight are suitable for use in advanced unmanned aerial vehicles . Moreover, the transmission system 20 is preferably performed using a two-stage design . There are many different designs of two stages that can be used for the transmission system 20 as described below with respect to FIGS . 2-8.. 2 illustrates a first exemplary embodiment of the transmission system of Figure 20 . 1. The transmission system of two stages, which is labeled 20 ', a driven shaft configuration online. The first reduction stage is provided by an integral pinion P21 to the input shaft 18 and two gears ( each labeled G21) that are spaced 180 degrees apart. The radial center line joining the two pinion gears P21 , and G21 can be in any orientation of the clock, but is preferably disposed in a horizontal orientation to make easier lubrication. The second stage includes two pinions P22 ( which are integral parts of the two intermediate shafts 51, 53 which includes two gears G21 of the first stage ) and a gear G22 which is fixed to an output shaft . The two pinions P22 of the second stage are spaced 180 degrees apart. Since the gear forms a " closed loop " , there should be a relationship between the determined tooth gears and pinions of the two stages , so that the transmission system can be mounted and rotated without interference. Two intermediate shafts 51 and 53, and spline coupled to the output shaft 22 are supported by bearings as shown.The percentage reduction in-line shaft configuration Lay Figure . 2 is provided by:G21 D D D D P21 G22 P22 ,
where DG21 and DP21 are the pitch circle diameters of the teeth of the pinion gears G21 and P21 of the first stage, and
DG22 and DP22 are the pitch circle diameters of the teeth of the gears G22 and pinions P22 of the second stage .
Alternatively, the reduction ratio of the in - line Lay axis configuration of Fig . 2 is provided by:N N G21 N G22 N P21 P22
where NG21 , NP21 , NG22 , NP22 are the number of teeth along the pitch circle of the respective pinions and gears.In the exemplary configuration shown, and DP21 DG21 diameters are 3.731 inches and 0.692 inches, respectively , and tooth counts NG21 and NP21 are 97 and 18 respectively. These values provide a reduction ratio of the first stage of the order of 5.4 . Moreover, DG22 and DP22 diameters are 3.638 inches and 0.785 inches, respectively , and tooth counts NG22 and NP22 are 88 and 18 respectively. These values provide a reduction ratio of the second stage of the order of 4.6. The reduction ratio of the transmission system 20 ' is the product of these two values of reduction , which is ( 5.4 * 4.6 ): 1 and therefore the order of 25:1. With the input shaft 18 rotates at about 104,600 rpm with a power of about 70 HP , the two intermediate shafts 51,53 are rotating at about 19,410 RPM, and the output shaft 22 is rotating at approximately 4191 rpm, which is an appropriate value for driving a propeller of a small fixed-wing UAV propeller .Note that the larger diameter of the configuration of FIG . 2 is formed by the first reduction stage , which is dictated by the outer diameters of the two pinion gears G21 and P21 . In the configuration shown , this amount is provided by ( 2 * 3.731 inch ) 0.692 inch , which is about 9 inches in diameter. The casing requires an additional inch , therefore the larger diameter of the transmission system 20 " is about 10 inches. The width of the transmission system 20 ' is approximately 4.6 inches as shown.
where NR31 , NS31 , NR32 , NS32 are the number of teeth along the pitch circle of the respective ring gears and sun gears of the two stages .
In the exemplary embodiment shown, the diameters DS31 , DS31 and gears DP31 first stage is 0.594 inches, 1.281 inches and 3.156 inches, respectively , and tooth counts NS31 , NP31 , and NR31 first gear stage are 19, 41 , and 101 , respectively. These values provide a reduction ratio of the first stage of the order of 5.3 . Moreover, the diameters DS32 , DP32 and DR32 of the second stage gear are 0.769 inches, 1.423 inches and 3.615 inches, respectively , and tooth counts NS31 , NR32 NP32 and the second gear stage are 20, 37 and 94 respectively. These values provide a reduction ratio of the second stage of 4.7 . The reduction ratio of the system 20 " is the product of these two values of reduction , which is (5.3 * 4.7 ): 1 and therefore the order of 25:1. With the input shaft 18 rotates at about 104,600 rpm with a power of about 70 HP , the intermediate shaft 61 rotates at about 19,677 rPM, and the output shaft rotates at approximately 4187 rpm, which is a value suitable for driving a propeller small propeller fixed wing UAV .Note that the larger diameter of the configuration of FIG . 3 is formed by the second stage, which is dictated by the outer diameter of the ring gear of the second stage R32 . In the configuration shown , this dimension is about 3.6 inches in diameter. The casing requires a few additional inches in diameter , therefore the larger diameter of the transmission system 20 " is about 6 inches. The width of the transmission system 20" is approximately 6.4 inches as shown.Note that it is desirable that planetary systems in star of the first and second stage satisfy well known " hunting tooth " and " meshing sequence " limitations . To " hunting tooth " , the ratio ( NS / NP ) or serving ( NR / NP ) is equal to an integer plus a fraction irreducible . By " sequence meshing " , the ratio ( NR / # of gears ) or the ratio ( NS / # of gears ) is equal to an integer plus a fraction irreducible . On the other hand , you select the number of sprockets to prevent interference between them to satisfy the following restriction :# of arc gears ≤ π sin [ [ dp + 2 a] ds + dp ]
where dp is the pitch diameter of the pinion, ds is the diameter of passage and a sun gear is the addition of the pinion.. Figure 4 illustrates a third exemplary embodiment of the transmission system of Figure 20 . 1. The transmission system of two stages, which is labeled 20 ' "is a star configuration - Offset Spur . The first stage is provided by a star planetary system having a sun gear S41 , a plurality of planetary gears P41 , C41 sets a carrier operatively coupled to P41 planetary gears and an output ring gear R41 . the second stage is provided by a spur pinion and gear P42 G42 . input shaft gear 18 is coupled to the first stage S41 sun . the output ring gear of the first stage R41 is integral intermediate change sprocket 71 with P42 of the second reduction stage integral part thereof. G42 the second stage gear is integral to a spline that is operatively coupled to the output shaft 22 of the transmission system 20 ' " . P41 pinions of the first stage, the intermediate shaft 71, and G42 groove in the second stage gear are supported by bearings as shown.The reduction ratio of the star configuration - Offset Spur figure . 4 is provided by:N R41 N S41 N N G42 P42
where NR41 , NS41 , NG42 , NP42 are the number of teeth along the pitch circle of the respective first stage crown R41, S41 first gear stage , the second stage gear and the second gear P42 stage G42 .
In the exemplary embodiment shown, the diameters DS41 , DP41 and DR41 first gear stage are 0.594 inches, 1.281 inches and 3.156 inches, respectively , and tooth counts NS41 , NP41 , and NR41 first gear stage are 19, 41 , and 101 , respectively. These values provide a reduction ratio of the first stage of the order of 5.3 . Moreover, DP42 and DG42 diameters of the second gear stage are 0.950 inches , 4.50 inches, respectively , and teeth and NG42 NP42 counts of second stage gears are 19 and 92, respectively . These values provide a reduction ratio of the second stage of the order of 4.8. The reduction ratio of the transmission system 20 ' " is the product of these two values of reduction , which is (5.3 * 4.8 ): 1 and therefore the order of 25:1. With the input shaft rotates at about 104,600 rpm with a power of about 70 HP , the intermediate shaft 71 rotates at about 19,677 rPM, and the output shaft 22 is rotating at approximately 4154 rpm, which is a suitable value for driving the propeller a small fixed-wing UAV propeller .Note that the larger diameter of the configuration of FIG . 4 is formed by the second stage, which is dictated by the diameter of the second gear stage G42 . In the configuration shown , this dimension is about 6.5 inches in diameter. The casing requires a few additional inches in diameter , therefore the larger diameter of the transmission system 20 ' " is of the order of 8.8 inches. The width of the transmission system 20' " is of the order of 5.3 inches as shown.Note that it is desirable that the star planetary system to satisfy the first stage well known " hunting tooth " and " meshing sequence " restrictions as described above. Moreover, selecting the number of sprockets in order to avoid interference between them as described above .Figures . 5A and 5B illustrate a fourth embodiment of the transmission system of Figure 20 . 1. The transmission system of two stages, which is labeled 20 " " is a compound idler configuration Offset . The first stage includes a P51 floating input pinion gear drive two diametrically opposed G51 . Each gear G51 is connected to a corresponding intermediate shaft 81 with a second pinion P52 combining stage to drive a single output gear G52 . This arrangement is very similar to the driven shaft arrangement described above with respect to FIG . 2 except that the output gear of the second stage G52 is offset from the inlet. This displacement is possible geometrically because the center distance of the second stage is greater than the center distance of the first stage. The intermediate shafts for the two gears G51 and two pinions P52 (shown as 81 in cross section . 5B ) and spline coupled to the output shaft 22 are supported by bearings as shown.The reduction ratio of the idler configuration Offset Composite figure . 5 provides for the same formulas as Lay line shaft configuration described above with respect to FIG . Two .In the exemplary configuration shown, and DP51 DG51 diameters are 2.767 inches and 0.60 inches, respectively , and tooth counts NG51 and NP51 are 83 and 18 respectively. These values provide a reduction ratio of the first stage of the order of 4.6. Moreover, DG52 and DP52 diameters are 4.020 inches and 0.741 inches, respectively , and teeth and NP52 NG52 counts are 103 and 19, respectively. These values provide a reduction ratio of the second stage of the order of 5.4 . The reduction ratio of the system 20 " " is the product of these two values of reduction , which is ( 4.6 * 5.4 ): 1 and therefore the order of 25:1. With the input shaft 18 rotating at about 104 600 rpm with a power of about 70 HP , the two intermediate shafts 81 are rotating at about 22,684 RPM, and the output shaft 22 is rotating at approximately 4184 rpm, which is a suitable value for driving the propeller of a small fixed-wing UAV propeller .Note that the cross section of Fig . 5B taken through the mesh path as indicated in Fig . 5A This gives the appearance of a large set . But in fact , the intermediate shafts are in the same center line as the input gear so that the total height of the transmission system is approximately 7.5 inches. The width of the transmission system is in the order of 4.6 inches as shown. Costs are expected idler configuration and weight compound in the figures. 5A and 5B will be lower with respect to other configurations discussed herein. Therefore, it is expected that the configuration of the idler wheel is advantageous compound for use in lightweight applications , such as in small unmanned aerial vehicles fixed wing propeller.Figures . 6A and 6B illustrate a fifth embodiment of the transmission system of Figure 20 . 1. The transmission system of two stages, which is labeled 20 ' " " is a drive gear configuration - internal online. The first step is performed by a traction unit . A traction unit using rollers (not mesh teeth ) for the transfer of energy. Is based on the principle of creating a normal force between two rollers which can bear a tangential load equal to the normal force of traction coefficient . The traction coefficient is similar to the coefficient of friction. The drive unit is cooled and lubricated with specially developed traction fluids . The traction fluid , combined with the rolling elements, acts as a spur gear , which has the advantage of a cushioning effect on the transmission. The cutting force of an oil film lubrication elasto - hydrodynamic between the two rotating surfaces achieves traction drive . A device for automatic adjustment of the speed / load gets high efficiency to provide the right amount of radial force to enable the unit. The radial force automatically adjusts torque. The drive unit is typically lower in the cost of a reduction step oriented as it avoids the cost of a mesh of teeth.As shown in the figure. 6A, two of the three pinions (labeled A P61 , P61 B) of the traction stage are fixed in position and one of the three pinions ( P61 labeled C) is dissolved a small amount of space ( for example, 0 , 0031 inches). Central loose sprocket position P61 in the holder C is moved in a direction such that critical when torque is applied to the traction sun S61 , P61 loose pinion attempts C away from its rest position and the line contact between the inner cylinder and the message is moved away from the center line between the traction sun S61 and subsequent release the member . This creates a larger force and normal preloads all three rollers pinion P61 A, B P61 , P61 C. Varies with the adjustment torque so that it provides the correct amount of normal force to transmit the torque applied . As torque increases , the P61 C loose roller automatically adjusts to a new position and provides the correct new normal force required .In the configuration shown, there is a pull ring R61 . However , its only purpose is to provide a reaction element radial load and therefore is limited to rotate along nonpareil . The three sprockets P61 A, B P61 , P61 C are bonded to a backing of C61 via bearings so that they can rotate about there own centers , and the carrier is fixed in position C61 . Integral to each drive gear is a pinion external stimulus P62 (shown in cross section . Figure 6B ) . The three external sprocket drive an output P62 R62 internal ring gear drives the output shaft 22. The three external sprocket P62 and the output inner ring gear R62 provide the second stage of the transmission system 2 ' " ."The percentage reduction of the traction device configuration - internal line of figures . 6A and 6B is provided by: D D D D P61 S61 R62 P62
where DP61 and DS61 are the roll diameters of the respective teeth of the sun gears P61 and D61 of the first stage traction and DP62 and DR62 are the pitch circle diameters of the teeth of the ring gear and pinions respectively R62 P62 for the second stage .
Moreover, the percentage reduction of the pulling configuration - internal line of figures . 6A and 6B is provided by:D D P61 N R62 N S61 P62
where DP61 and DS61 are the roll diameters of the respective teeth of the sun gears P61 and S61 of the first stage traction and NR62 and NP62 are the number of teeth on the pitch circle for the respective gear ring of R62 and pinions P62 for the second stage .
In the exemplary configuration shown, and DS61 DP61 diameters are 1.680 inches and 0.40 inches, respectively . These values provide a reduction ratio of the first stage of the traction unit around 4 . Moreover, DR62 and DP62 diameters are 2.50 inches and 0.421 inches, respectively , and tooth counts are NR62 and NP62 95 and 16 respectively. These values provide a reduction ratio of the second stage of the order of 5.9 . The reduction ratio of the transmission system is the product of these two values of reduction , which is (4 * 5.9 ): 1 and therefore the order of 24:1 . With the input shaft 18 rotating at about 104 600 rpm with a power of about 70 HP , P61 sprockets are rotating at about 24,905 RPM, and the output shaft 22 is rotating at approximately 4195 rpm, which is a suitable value for driving the propeller of a small fixed-wing UAV propeller .
where DR71 and DS71 are the roll diameters of the respective teeth of the ring and sun R71 S71 of the first stage traction and DR72 and DS72 are the pitch circle diameters of the teeth of the respective sprocket and gear R72 S72 plot for the second stage .
Moreover, the percentage reduction of the pulling configuration - internal line of figures . 6A and 6B is provided by:S71 R71 D D ( 1 + N N S72 R72 )
where DR71 and DS71 are the diameters of the respective rollers to the ring and sun R71 S71 of the first stage traction and NP72 and NS72 is the number of teeth on the pitch circle for the respective ring gear equipment R72 and S72 for the second stage.In the exemplary configuration shown, and DS71 DR71 diameters are 3.775 inches and 0.675 inches, respectively . These values provide a reduction ratio of the first stage of the drive unit of the order of 5.6. Moreover, DR72 and DS72 diameters are 3.64 inches and 1.16 inches, respectively , and tooth counts are NR72 and NS72 91 and 29, respectively. These values provide a reduction ratio of the second stage of the order of 4.1. The reduction ratio of the transmission system is the product of these two values of reduction , which is ( 5.6 * 4.1 ): 1 and therefore the order of 23:01 . With the input shaft 18 rotating at about 104 600 RPM , the first stage R1 ring is rotating at about 17,318 RPM, and the output shaft 22 is rotating at approximately 4185 rpm, which is a value suitable for driving a propeller of a small fixed-wing UAV propeller .Note that the total height of the transmission system 20 "" " is approximately 4.3 inches , and the width of the transmission system is in the order of 3.5 inches as shown.Another consideration for the design of the transmission system of the present invention is the high speed operation of the input shaft 18. The design of the bearings to operate at such high speeds in a challenge. However, it is very difficult to design bearings suitable for use with radial and / or thrust at such high speeds . Therefore, it is an objective to have the input shaft of the transmission torque and carry only have no radial or thrust loads ( and if possible have no bearings) . In order to reduce the radial and thrust loads on the input shaft of the transmission, it is preferable that the first stage of reduction of the transmission system to provide auto - balanced . This condition is provided by equally spaced apart from the roller gear and outputs a given pinion such that the resultant load on the pinion is zero. Figures . 8A and 8B illustrates the physical configuration provided by auto - balance . For example, consider the two gear system of FIG . 8A. Suppose the tangential load on the gear tooth is higher than that in the lowest gear . Radial loads of the teeth are the resultant of the tangential loads teeth, therefore the radial load on the gear teeth will also be higher than that at the bottom . This difference in load will force the pinion in mesh in the load lighter side (eg lower gear side ) until the loads are balanced exactly . Therefore, if the pinion is allowed to "float " so that it is trapped by gears or rollers equally spaced around the loads are equal resulting in the desired cancellation . In this configuration, the input shaft 18 of the transmission system does not need the support of high bearing , eliminating the need for loaded bearings at high speeds.Note also that when using a planetary system in the first stage of the transmission system 20 , should be considered with a fixed support . This is necessary to prevent the centrifugal forces acting on the pinions of a swivel , which may substantially reduce the life of the bearing.Preferably, the input shaft 18 of the transmission system 20 is coupled to the output shaft 14 of microturbine 12 via an outer diameter driven splined coupling mechanism (sometimes referred to as a " root diameter flat spline fit coupler " ) as shown in Fig . 9. In this configuration, the input shaft of the transmission system 16 includes a driven spline outer diameter section 91 . The output shaft 14 of microturbine 12 includes projections 93 which project radially inwardly from the inner diameter surface of engaging section 91 piloted . A retaining ring 95 or other suitable retention mechanism is used to hold the input shaft 95 in the horizontal direction as shown. Alternatively, the outer surface of the groove may be provided on the output shaft 14 of the microturbine engine 12 with a surface groove provided in the inner input shaft 16 of the transmission system .An accessory unit may be operatively coupled to the drive train of the transmission system . For example, the accessory unit may be a starter / generator that has a 4-pole brushless permanent magnet AC type architecture with a plurality (eg, four ) magnets mounted around a perimeter of the rotor. A power control unit converts the alternating current output output current generation mode , and converts the input dc to ac power input into bootloader mode . The accessory unit can be coupled to the drive train of the transmission system in many ways.For example, the accessory can be mounted directly on the input shaft of the transmission system (or the motor output shaft microturbine ) . This configuration can be problematic in designs that are based on a floating input shaft for the purpose of load sharing self - balancing and cancellation of the radial load as described above due to the weight and any imbalance in the shaft fitting transmission system input . Moreover, for a design which uses a pull type unit in the first stage of the transmission system , the accessory mounted on the transmission input shaft will have very little influence on the charge exchange due to the fact that radial loads are greater traction than ten times the tangential load and the three equidistant sprockets rigidly maintain traction sun instead. The radial stiffness of the sun Traction can easily handle any influence of attachment on the input shaft .Alternatively , the accessory unit can be mounted on a separate mounting platform and driven by the drive train transmission system . For example, consider the configuration Compound Idler displacement of the figures. 5A and 5B. In this configuration, a pinion may be integral with the rotation shaft of the accessory unit and driven by an intermediate gear engaged with one of the gears G1 of the first stage. Preferably, the number of pinion teeth which is integral to the rotation axis of the accessory unit equals the number of sprocket teeth of the first step P1 to allow the axis of rotation of the accessory unit to be driven at the same rotational speed as the input shaft 18 of the transmission system 20 . Furthermore, the intermediate gear provides clearance between the accessory mounting and the stage (s) of the transmission system .The transmission system also requires a lubrication system . Preferably, the lubrication system includes a conventional oil filter and the pump system . The oil pump can be a vane type pump , gear pump or gerotor pump , which are all well known . Moreover, the system preferably includes a lubrication oil cooler device as is well known . In the event that the requirements of the type of oil, the system temperature and pressure of the engine and transmission are similar , the lubrication system of the transmission system can be combined with the engine lubrication system , as is well known .For fixed wing applications , the output shaft of the transmission system is coupled to a propeller. The gyroscopic moment induced by the expected rate of pitch and yaw rate and the mass moment of inertia of the coil dictates the size of the output shaft of the transmission system . An exemplary mechanism for coupling the output shaft of the transmission system to a propeller is shown in Fig . 10 . Note that the coupling mechanism can be integrated into the housing of the transmission system for a compact design.The exemplary embodiments of the transmission system ( and the propulsion system based on microturbine employ such transmission systems ) described above are suitable for use in small applications in fixed-wing aircraft , such as small UAVs . Transmission systems (and the microturbine propulsion system based on the use of such transmission systems ) may also be readily adapted for use in other applications than aircraft, such as in small aircraft applications vertical elevation as shown in figure . 11A. In such applications, a power plant 110 suitable for use in a jet aircraft vertical lift includes a microturbine engine 112 with output shaft 114 . A coupling mechanism 116 couples the output shaft 114 to the input shaft 118 of a transmission system 120. The transmission system 120 operates to reduce the speed of the output shaft 114 of the microturbine engine 112 in its own output shaft 122. The output shaft 122 of the transmission system 120 is coupled to a bevel gear assembly 124 or other suitable drive mechanism that transmits power of the rotation shaft 122 to a vertical axis of rotation 126. A rotor 128 is coupled to the vertical axis of rotation 126. The rotor 128, when driven by the microturbine engine 112 and transmission system 120, provides a thrust drives an aircraft body , as the body of the vertical lift aircraft 130 of FIG. 11B. Note that in the configuration shown , the drive system 120 and the bevel gear assembly 124 are arranged on the intake side of the microturbine engine 112. This configuration enables the transmission system 120 and the bevel gear assembly 124 to be cooled by the engine intake air . Alternatively, the transmission system 120 and the bevel gear assembly 124 may be disposed on the exhaust side of the microturbine engine 112. In this alternative configuration , the drive system 120 and the bevel gear assembly 124 must operate in a hot environment , and therefore must be designed to withstand the increased heat load that derives from the operation in the hot environment on the exhaust side of the engine 112.The output shaft 114 of the microturbine 112 operates at very high rotational speeds , typically in the range between 72,000 and 150,000 RPM RPM with an output power of 150 HP and 5 HP . For applications of unmanned aerial vehicles , the rotor 128 operates at slower rotation speeds , typically about 3700 RPM to 4500 RPM . These restrictions result in a reduction ratio required microturbine engine RPM to the rotor RPM in the range of 28:1 to 24:1 . The transmission system 120 and the bevel gear assembly 124 provides this required speed reduction in the output power range (150 HP to 5 HP ) microturbine engine .In the preferred embodiment of the present invention , the transmission system 120 and the microturbine engine 112 has a small size and low weight. Preferably , the maximum diameter of the transmission system 120 is less than 12 inches. Such restrictions on size and weight are suitable for use in advanced unmanned aerial vehicles .Moreover, the transmission system 120 may be performed by a two-stage design . There are many different designs of two stages that can be used for the transmission system 120 as described above with respect to FIGS . 2-8. Note that the bevel gear assembly 124 typically provide a reduction ratio of about 2:1 to 3:1 . Therefore, the reduction ratio of the two designs stage transmission Figs . 2-8 as described above are readily adapted to provide a lower reduction ratio ( for example , of about 9:01 ) to provide a total reduction ratio of about 28:1 to 24:1 . Preferably, the reduction ratio of each stage of the designs of two-stage transmission Figs . 2-8 are of the order of 03:01 .Note that the design of the drive unit of the figures. 6A - 6B and 7, the first stage planetary drive can easily be adapted to provide any reduction ratio of up to 13:01 in the step of pulling only . Thus, for vertical lift applications , the second planetary stage can be eliminated completely oriented , thereby providing significant cost advantages .Have been described and illustrated herein several embodiments of a transmission system of high speed and small microturbine power systems based on the use of improved transmission system . While we have described particular embodiments of the invention, it is not intended that the invention be limited thereto , as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise . Therefore, while certain shaft speeds , horsepower and reduction factors are described , it is appreciated that the transmission systems described herein can be readily adapted for use in a wide range of shaft speeds , horses power and reduction ratios . For example, transmission systems described herein may be readily adapted for use with microturbines operate over an extended range between 50,000 and 200,000 RPM RPM with an output power of 200 HP and 5 HP . In these systems, is likely to increase the reduction ratio provided by the transmission system for certain applications, such as applications of unmanned aerial vehicles described in this document. Furthermore, while the particular types of transmission stages have been described , it is understood that other well known transmission stage designs can be used . For example, and not by way of limitation, the transmission system can be realized by a harmonic drive stage . The harmonic drive includes three basic elements ( a spline circulate a Flexspline , and wave generator ) utilizing non-circular rotation to drive the Flexspline Circular Spline . Also , while the transmission system and the drive system based on microturbine of the present invention are preferably used together with a propellant to drive a fixed-wing aircraft small size, be appreciated that can be easily adapted for other small size aircraft applications such as vertical lift aircraft or hybrid tilt rotor aircraft . Moreover, the transmission system and the drive system based on microturbine of the present invention may be readily adapted for use in other applications, such as marine propulsion systems , automotive applications, generation of power electric applications , HVAC applications based on micro - turbine and hydraulic applications. Finally , while the microturbine power systems based on the present invention can consume a wide variety of fuels, including liquid (such as liquefied natural gas) or gaseous fuel (such as natural gas or propane ) . Therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed .
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