Tilt-rotor aircraft power transmission structure and gear bending fatigue life evaluation method thereof

Abstract

The application relates to the field of power transmission technology and discloses a tilt-rotor power transmission structure and a gear bending fatigue life evaluation method thereof, wherein the tilt-rotor power transmission structure comprises an interconnection gear pair, a primary gear pair and a secondary gear pair, the interconnection gear pair is provided with an interconnection primary bevel gear set and an interconnection secondary bevel gear set which are connected through a first transmission shaft, the interconnection primary bevel gear set and the interconnection secondary bevel gear set are both composed of two bevel gears which are meshed and connected, the primary gear pair is connected with the interconnection primary bevel gear set through a second transmission shaft, and the secondary gear pair is connected with the interconnection primary bevel gear set through a third transmission shaft. The transmission chain of the interconnection gear pair adopts two-stage bevel gear transmission, and the reduction ratio and the shaft included angle of the two-stage bevel gears can be flexibly adjusted according to the structures of reducers, wings and the like, so as to adapt to the layout requirements of complex spaces. The tilt-rotor power transmission structure provided by the application solves the problem of difficult space layout of the existing interconnection gear transmission chain.

Description

Technical Field

[0001] This invention relates to the field of power transmission system structure technology, specifically to a power transmission structure for tiltrotor aircraft and a method for evaluating the bending fatigue life of its gears. Background Technology

[0002] Tiltrotors are a new type of aircraft that integrates helicopters and fixed-wing aircraft. They are composite aircraft that have the vertical take-off and landing and hovering capabilities of helicopters and the high-speed flight capabilities of fixed-wing aircraft. They have long endurance, high speed and good fuel economy.

[0003] In the existing technology, large and medium-sized tiltrotor aircraft generally use two engines as power sources. The power output of the engines is connected to the main reduction gear to drive the rotor. In order to ensure the synchronization of the rotation speed of the left and right rotors and to achieve power complementarity between the two engines under certain operating conditions, an interconnected gear transmission chain is usually led out from the main transmission chain of the left and right main reduction gears and the power connection between the two engines is realized through the transmission shaft.

[0004] However, existing interconnected gear transmission chains typically employ single-stage cylindrical gear transmission or a two-stage transmission consisting of cylindrical gears and bevel gears. In practical designs, these are often constrained by the design of the wing and frame, making spatial layout of the interconnected gear transmission chain difficult. Summary of the Invention

[0005] This invention provides a power transmission structure for tiltrotor aircraft and a method for evaluating the bending fatigue life of its gears, in order to solve the problem of difficult spatial layout of existing interconnected gear transmission chains.

[0006] In a first aspect, the present invention provides a power transmission structure for a tiltrotor aircraft, comprising: an interconnected gear pair, a primary gear pair, and a secondary gear pair. The interconnected gear pair has an interconnected primary bevel gear set and an interconnected secondary bevel gear set. The interconnected primary bevel gear set and the interconnected secondary bevel gear set are connected by a first transmission shaft. Both the interconnected primary bevel gear set and the interconnected secondary bevel gear set are composed of two meshing bevel gears. The interconnected secondary bevel gear set is connected to a reducer. The primary gear pair is connected to the interconnected primary bevel gear set by a second transmission shaft and is connected to an engine. The secondary gear pair is connected to the interconnected primary bevel gear set by a third transmission shaft and is connected to a rotor output unit.

[0007] Beneficial effects: The interconnected gear pair extracts power from the primary to secondary gear pairs of the main drive train. Both the interconnected primary and secondary bevel gear sets consist of two meshing bevel gears. That is, the transmission train of the interconnected gear pair uses a two-stage bevel gear transmission. The reduction ratio and shaft angle of the two-stage bevel gears can be flexibly adjusted according to the structure of the reducer, wing, etc., to adapt to the layout requirements of complex spaces. The two-stage bevel gears transmit large loads only in a few cases where complementary power from both sides is required, and in some cases do not participate in the power output of the rotor output unit. The tilt rotor power transmission structure provided by this invention solves the problem of difficult spatial layout of existing interconnected gear transmission trains.

[0008] In one optional embodiment, the interconnected first-stage bevel gear set includes: a first bevel gear and a second bevel gear, one end of the first bevel gear being connected to the first-stage gear pair via a second drive shaft, and the other end of the first bevel gear being connected to the second-stage gear pair via a third drive shaft; the second bevel gear meshes with the first bevel gear, and the diameter of the second bevel gear is smaller than the diameter of the first bevel gear.

[0009] Beneficial effects: The first bevel gear extracts power from the first-stage gear pair through the second transmission shaft and from the second-stage gear pair through the third transmission shaft. The power is then transmitted to the second bevel gear through the meshing connection between the first and second bevel gears. The diameter of the second bevel gear is smaller than that of the first bevel gear, which enables speed-increasing transmission. At the same time, it also takes into account key functions such as adapting to spatial layout, matching the speed requirements of power transmission, and ensuring efficient power transmission when the power flow is reversed. The above describes the transmission under the forward power flow condition. When the power flow condition is reversed, the direction of power transmission is opposite.

[0010] In one optional embodiment, the interconnected two-stage bevel gear set includes a third bevel gear and a fourth bevel gear, wherein the third bevel gear is connected to the second bevel gear via a first drive shaft; the fourth bevel gear is meshed with the third bevel gear, and the diameter of the fourth bevel gear is larger than the diameter of the third bevel gear.

[0011] Beneficial effects: The first drive shaft transmits power from the second bevel gear to the third bevel gear. Through the meshing connection of the third and fourth bevel gears, power is then transmitted to the fourth bevel gear. The fourth bevel gear has a larger diameter than the third bevel gear, enabling speed reduction and torque increase. It also plays a crucial role in adapting to the main drivetrain's power extraction, meeting torque requirements under heavy load conditions, adapting to spatial layout, and ensuring transmission stability. The above describes the transmission under forward power flow conditions. Under reverse power flow conditions, the direction of power transmission is opposite.

[0012] In one optional embodiment, the primary gear pair includes a fifth bevel gear and a sixth bevel gear, the fifth bevel gear being connected to the third bevel gear via the second drive shaft, the sixth bevel gear meshing with the fifth bevel gear, and the sixth bevel gear being connected to the drive end of the engine.

[0013] Beneficial effects: The fifth and sixth bevel gears mesh to form a primary gear pair. The engine transmits force to the sixth bevel gear, which in turn transmits force to the fifth bevel gear, and then transmits force to the third bevel gear through the second transmission shaft.

[0014] In one optional embodiment, the secondary gear pair includes a seventh bevel gear and an eighth bevel gear, the seventh bevel gear being connected to the third bevel gear via the third drive shaft, the eighth bevel gear meshing with the seventh bevel gear, and the eighth bevel gear being connected to the rotor output unit.

[0015] Beneficial effects: The seventh and eighth bevel gears mesh to form a two-stage gear pair. The seventh bevel gear transmits power from the third drive shaft and then transmits it to the eighth bevel gear through meshing, thereby driving the rotor to rotate.

[0016] In one alternative embodiment, the first drive shaft, the second drive shaft, and the third drive shaft are all configured as elastic shafts, and the elastic shafts transmit power through floating splines.

[0017] Beneficial effects: Power transmission between primary gear pairs and interconnected gear pairs, and between secondary gear pairs and interconnected gear pairs, is achieved through flexible shafts and floating splines.

[0018] In one alternative implementation, the bevel gear of the interconnected gear pair is configured with a double tooth surface structure.

[0019] Beneficial effects: For interconnected bevel gears subjected to intermittent alternating bending loads and single-engine emergency power exceeding 1.7 times the rated load, a dual-tooth-surface adaptive design is adopted based on the system deformation magnitude under different working conditions, which can improve its reliability and safety.

[0020] Secondly, the present invention also provides a method for evaluating the bending fatigue life of gears, applied to the tilting rotor power transmission structure described in any of the above embodiments, comprising: reducing the allowable bending stress of the bevel gear of the interconnected gear pair by 0.7 times.

[0021] Beneficial effects: By reducing the allowable bending stress of the bevel gears in the interconnected gear pair, its reliability and safety can be improved.

[0022] In one alternative implementation, the bending fatigue life assessment of the bevel gear teeth of the interconnected gear pair adopts the fatigue damage accumulation criterion and reduces the allowable bending fatigue value of the gear material by 0.8-0.95 times.

[0023] Beneficial effects: It can achieve precise gear fatigue life, ensure high reliability and safety, reduce the weight of interconnected gears, and improve the power density of tiltrotor gearboxes. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a tilting rotor power transmission structure according to an embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the power transmission structure of the tilt rotor shown. Figure 3 for Figure 1 Schematic diagram of power flow direction when a tilting rotor power transmission structure transmits a small load; Figure 4 for Figure 1 Schematic diagram of power flow direction when a tilt rotor power transmission structure transmits large amounts of power. Figure 5 for Figure 1 Design of the tooth convex surface imprint of the intermediate gear in the interconnected gear pair; Figure 6 for Figure 1 Design of concave tooth surface imprints for intermediate interconnected gear pairs.

[0026] Explanation of reference numerals in the attached figures: 1. Interconnected gear pair; 11. Interconnected first-stage bevel gear set; 111. First bevel gear; 112. Second bevel gear; 12. First drive shaft; 13. Interconnected second-stage bevel gear set; 131. Third bevel gear; 132. Fourth bevel gear; 2. First-stage gear pair; 21. Fifth bevel gear; 22. Sixth bevel gear; 3. Second drive shaft; 4. Second-stage gear pair; 41. Seventh bevel gear; 42. Eighth bevel gear; 5. Third drive shaft; 6. Reducer; 7. Engine; 8. Rotor output unit. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In related technologies, to avoid interference between the interconnecting shaft and the tilting unit of the main reducer 6, the interconnecting stage gears must be larger in size, thus increasing the weight of the transmission chain. Furthermore, given the forward and reverse power flow of the interconnecting stage gears and the intermittent cross-beam bending loads on the teeth, there is a lack of corresponding assessment methods for predicting gear bending fatigue life. Using previous calculation methods would result in excessively large safety margins for the gears, increasing their weight.

[0029] The following is combined with Figures 1 to 6 The following describes embodiments of the present invention.

[0030] According to an embodiment of the present invention, in one aspect, a power transmission structure for a tiltrotor aircraft is provided, comprising: an interconnected gear pair 1, a primary gear pair 2, and a secondary gear pair 4. The interconnected gear pair 1 has an interconnected primary bevel gear set 11 and an interconnected secondary bevel gear set 13. The interconnected primary bevel gear set 11 and the interconnected secondary bevel gear set 13 are connected by a first transmission shaft 12. Both the interconnected primary bevel gear set 11 and the interconnected secondary bevel gear set 13 are composed of two meshing bevel gears. The interconnected secondary bevel gear set 13 is connected to a reducer 6. The primary gear pair 2 is connected to the interconnected primary bevel gear set 11 by a second transmission shaft 3 and is connected to an engine 7. The secondary gear pair 4 is connected to the interconnected primary bevel gear set 11 by a third transmission shaft 5 and is connected to a rotor output unit 8.

[0031] In use, the interconnected gear pair 1 extracts power from the primary gear pair 2 to the secondary gear pair 4 of the main drive train. Both the interconnected primary bevel gear set 11 and the interconnected secondary bevel gear set 13 consist of two meshing bevel gears. That is, the drive train of the interconnected gear pair 1 uses a two-stage bevel gear transmission. The reduction ratio and shaft angle of the two-stage bevel gears can be flexibly adjusted according to the reducer 6, wing, and other structures to adapt to complex spatial layout requirements. The two-stage bevel gears only transmit large loads when complementary power from both sides is needed, and in some cases do not participate in the power output of the rotor output unit 8. The tilt rotor power transmission structure provided in this embodiment solves the problem of difficult spatial layout of existing interconnected gear drive trains.

[0032] In one embodiment, the interconnected primary bevel gear set 11 includes: a first bevel gear 111 and a second bevel gear 112. One end of the first bevel gear 111 is connected to the primary gear pair 2 via the second transmission shaft 3, and the other end of the first bevel gear 111 is connected to the secondary gear pair 4 via the third transmission shaft 5. The second bevel gear 112 meshes with the first bevel gear 111, and the diameter of the second bevel gear 112 is smaller than the diameter of the first bevel gear 111. The first bevel gear 111 extracts power from the primary gear pair 2 via the second transmission shaft 3 and from the secondary gear pair 4 via the third transmission shaft 5. Through the meshing connection of the first bevel gear 111 and the second bevel gear 112, the power is transmitted to the second bevel gear 112. The smaller diameter of the second bevel gear 112 enables speed-increasing transmission while also adapting to spatial layout, matching power transmission speed requirements, and ensuring efficient power transmission when the power flow is reversed. The above describes the transmission under forward power flow conditions. Under reverse power flow conditions, the power transmission direction is opposite. Alternatively, as an alternative implementation, the diameters of the first bevel gear 111 and the second bevel gear 112 may be equal.

[0033] In one embodiment, the interconnected two-stage bevel gear set 13 includes a third bevel gear 131 and a fourth bevel gear 132. The third bevel gear 131 is connected to the second bevel gear 112 via a first drive shaft 12. The fourth bevel gear 132 meshes with the third bevel gear 131, and the diameter of the fourth bevel gear 132 is larger than that of the third bevel gear 131. The first drive shaft 12 transmits power from the second bevel gear 112 to the third bevel gear 131. Through the meshing connection of the third bevel gear 131 and the fourth bevel gear 132, power is transmitted to the fourth bevel gear 132. The larger diameter of the fourth bevel gear 132 enables speed reduction and torque increase, and also plays a crucial role in adapting to the power extraction of the main drive chain, meeting the torque requirements of high-load conditions, adapting to spatial layout, and ensuring transmission stability. The above describes the transmission under forward power flow conditions. Under reverse power flow conditions, the direction of power transmission is opposite. Alternatively, as an alternative implementation, the diameters of the third bevel gear 131 and the fourth bevel gear 132 may be equal.

[0034] In one embodiment, the primary gear pair 2 includes a fifth bevel gear 21 and a sixth bevel gear 22. The fifth bevel gear 21 is connected to the third bevel gear 131 via the second drive shaft 3. The sixth bevel gear 22 meshes with the fifth bevel gear 21 and is connected to the drive end of the engine 7. The meshing of the fifth bevel gear 21 and the sixth bevel gear 22 forms the primary gear pair 2. The engine 7 transmits force to the sixth bevel gear 22, which in turn transmits force to the fifth bevel gear 21, and then transmits force to the third bevel gear 131 via the second drive shaft 3. Alternatively, as an alternative embodiment, the primary gear pair 2 can also be configured as two spur gear transmission structures.

[0035] In one embodiment, the secondary gear pair 4 includes a seventh bevel gear 41 and an eighth bevel gear 42. The seventh bevel gear 41 is connected to the third bevel gear 131 via the third drive shaft 5. The eighth bevel gear 42 meshes with the seventh bevel gear 41 and is connected to the rotor output unit 8. The meshing of the seventh bevel gear 41 and the eighth bevel gear 42 forms the secondary gear pair 4. The seventh bevel gear 41 transmits power from the third drive shaft 5 to the eighth bevel gear 42 through the meshing connection, thereby driving the rotor to rotate. Alternatively, as an alternative embodiment, the secondary gear pair 4 can also be configured as two spur gear transmission structures.

[0036] In one embodiment, the first drive shaft 12, the second drive shaft 3, and the third drive shaft 5 are all configured as flexible shafts, which transmit power via floating splines. Power transmission between the primary gear pair 2 and the interconnected gear pair 1, and between the secondary gear pair 4 and the interconnected gear pair 1, is achieved through the flexible shafts and floating splines.

[0037] In one embodiment, the bevel gear of the interconnected gear pair 1 is configured with a double tooth surface structure. For operating conditions where the teeth of the interconnected bevel gear are subjected to intermittent alternating bending loads and the single-engine emergency power is more than 1.7 times the rated load, a double tooth surface adaptive design is adopted according to the system deformation magnitude under different operating conditions, which can improve its reliability and safety.

[0038] Working principle: In one embodiment, the power transmission condition of the tilt rotor power transmission structure is as follows: Figure 3 As shown, the interconnected gear pairs 1 on both sides extract power from the primary gear pair 2 to the secondary gear pair 4 of the main drive chain on their respective sides, and transmit the power to the intermediate reducer 6 through the interconnected shaft. Under this condition, the load transmitted by the tiltrotor power transmission structure is relatively small, and it mainly provides power to the various accessories of the aircraft.

[0039] In one embodiment, the second power transmission condition of the tilt rotor power transmission structure is as follows: Figure 4 As shown, the interconnected gear pair 1 on either side extracts power from the primary gear pair 2 to the secondary gear pair 4 of the main drive chain on its own side, transmits the power to the intermediate reducer 6 through the interconnected shaft, and transmits most of the power to the rotor output unit 8 on the other side through the power transmission structure of the tilting rotor on the other side. Under this condition, the load transmitted by the tilting rotor power transmission structure is large, mainly because the rotor provides the power output, ensuring that both rotors can provide sufficient upward lift or forward thrust.

[0040] According to an embodiment of the present invention, another aspect provides a method for evaluating the bending fatigue life of gears, applied to the tilting rotor power transmission structure described in the above embodiments, comprising: reducing the allowable bending stress of the bevel gears in the interconnected gear pair 1 by a factor of 0.7. By reducing the allowable bending stress of the bevel gears in the interconnected gear pair 1, its reliability and safety can be improved.

[0041] In one embodiment, the bending fatigue life assessment of the bevel gear teeth of the interconnected gear pair 1 adopts the fatigue damage accumulation criterion and reduces the allowable bending fatigue value of the gear material by 0.8-0.95 times. This enables the obtaining of accurate gear finite fatigue life, ensuring its high reliability and safety, reducing the weight of the interconnected gear pair 1, and increasing the power density of the tiltrotor reducer 6.

[0042] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A tilting rotor power transmission structure, characterized in that, include: The interconnected gear pair (1) has an interconnected first-stage bevel gear set (11) and an interconnected second-stage bevel gear set (13). The interconnected first-stage bevel gear set (11) and the interconnected second-stage bevel gear set (13) are connected by a first transmission shaft (12). Both the interconnected first-stage bevel gear set (11) and the interconnected second-stage bevel gear set (13) are composed of two bevel gears meshing together. The interconnected second-stage bevel gear set (13) is connected to a reducer (6). The primary gear pair (2) is connected to the interconnected primary bevel gear set (11) via the second drive shaft (3), and the primary gear pair (2) is connected to the engine (7). The secondary gear pair (4) is connected to the interconnected primary bevel gear set (11) via the third transmission shaft (5), and the secondary gear pair (4) is connected to the rotor output unit (8).

2. The tilting rotor power transmission structure according to claim 1, characterized in that, The interconnected first-stage bevel gear set (11) includes: The first bevel gear (111) has one end connected to the first-stage gear pair (2) via the second transmission shaft (3), and the other end connected to the second-stage gear pair (4) via the third transmission shaft (5). The second bevel gear (112) meshes with the first bevel gear (111), and the diameter of the second bevel gear (112) is smaller than the diameter of the first bevel gear (111).

3. The tilting rotor power transmission structure according to claim 2, characterized in that, The interconnected two-stage bevel gear set (13) includes: The third bevel gear (131) is connected to the second bevel gear (112) via the first drive shaft (12); The fourth bevel gear (132) meshes with the third bevel gear (131), and the diameter of the fourth bevel gear (132) is larger than the diameter of the third bevel gear (131).

4. The tilting rotor power transmission structure according to claim 3, characterized in that, The first-stage gear pair (2) includes a fifth bevel gear (21) and a sixth bevel gear (22). The fifth bevel gear (21) is connected to the third bevel gear (131) via the second transmission shaft (3). The sixth bevel gear (22) meshes with the fifth bevel gear (21). The sixth bevel gear (22) is connected to the drive end of the engine (7).

5. The tilting rotor power transmission structure according to claim 3, characterized in that, The secondary gear pair (4) includes a seventh bevel gear (41) and an eighth bevel gear (42). The seventh bevel gear (41) is connected to the third bevel gear (131) via the third transmission shaft (5). The eighth bevel gear (42) meshes with the seventh bevel gear (41). The eighth bevel gear (42) is connected to the rotor output unit (8).

6. The tilting rotor power transmission structure according to any one of claims 1-5, characterized in that, The first drive shaft (12), the second drive shaft (3) and the third drive shaft (5) are all configured as elastic shafts, and the elastic shafts transmit power through floating splines.

7. The tilting rotor power transmission structure according to any one of claims 1-5, characterized in that, The bevel gear of the interconnected gear pair (1) is configured with a double tooth surface structure.

8. A method for evaluating the bending fatigue life of gears, characterized in that, The tilt rotor power transmission structure applied to any one of claims 1-7 includes: the bevel gear of the interconnected gear pair (1) having a bending allowable stress reduced by 0.7 times.

9. The gear bending fatigue life assessment method according to claim 8, characterized in that, The assessment of the bending fatigue life of the bevel gear teeth in the interconnected gear pair (1) adopts the fatigue damage accumulation criterion and reduces the allowable bending fatigue value of the gear material by 0.8-0.95 times.

Images