Helicopter speed reducer transmission chain structure with composite planetary gear train

Abstract

The invention belongs to the technical field of mechanical structures, and relates to a helicopter speed reducer structure, in particular to a transmission chain structure of a compound planetary gear train helicopter speed reducer. Comprising an input shaft (1); a sun gear (2); a lower-layer duplex planetary gear shaft (3); an upper-layer duplex planetary gear shaft (4); a fixed ring gear (5); a planet carrier (6); a planetary gear in an original planetary gear train is improved into a double-layer planetary gear structure, the improved planetary gear structure is higher in integration level and space utilization rate, under the condition of the same input load, the contact stress of a planetary tooth surface is reduced, the use stress of accessories such as a planetary gear train bearing is also reduced, the failure rate is reduced, and the service life is prolonged. And the floating spline design is adopted between the input shaft and the spline and between the fixed gear ring and the casing, so that the uniformity of the meshing process is improved, and the transmission of the whole structure is more stable.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical structures, relates to the structure of a helicopter reducer, and relates to a transmission chain structure of a compound planetary gear train helicopter reducer. Background Art

[0002] A helicopter reducer is usually installed at a position slightly behind the upper part of the cockpit. Its function is to connect the whole machine platform and transmit the power generated by the engine to the main rotor shaft and then to the main rotor blades, so that the helicopter generates an upward lifting force. For domestic in-service helicopters, the rotational speed output from the engine output shaft is decelerated, combined, and reversed through one or two stages of bevel gears, and then used as the input end of the planetary gear train reduction stage, and is reduced and output to the rotor shaft through the planetary gear train.

[0003] In the existing helicopter reducers, the planetary gears are the key parts to be inspected during each overhaul or when the reducer is disassembled due to special conditions. Increasing the number of planetary gears in the planetary gear train of the reducer can reduce the usage intensity of the planetary gears and extend their service life. However, considering the limited actual assembly space of the planetary gears, it is impossible to increase the number of planetary gears to a certain extent. If the tooth width of the planetary gears is increased, it will cause an increase in the gear strength load coefficient (such as the tooth direction load coefficient) and unstable meshing. In addition, the single-stage reduction ratio of the existing helicopter reducers is limited by space and structural strength, and the reduction ratio is relatively small. To solve the above problems, foreign heavy helicopters adopt a scheme of one-stage bevel gear reduction, two-stage spur gear reduction, and three-stage spur gear split-torque parallel connection, as shown in Figure 1 , all the gears in this scheme are fixed-axis gear trains, and the three-stage reduction ratio is close to 60. In view of the above situation, there is an urgent need for a compound planetary gear reducer with high integration, reliable strength, and large transmission ratio. Summary of the Invention

[0004] Object of the Invention

[0005] The object of the present invention is to provide an arrangement structure of planetary gears for a helicopter reducer, which solves the problems of unstable meshing and small reduction ratio. It is realized that without increasing the external dimensions of the reducer, the number of planetary gears is doubled, the usage intensity of the planetary gears and their accessories is reduced, and the service life is improved, and the reduction ratio is increased.

[0006] Technical Solution

[0007] A compound planetary gear train helicopter reducer transmission chain structure includes an input shaft, a sun gear, a lower double planetary gear shaft, an upper double planetary gear shaft, a fixed ring gear, and a planetary carrier. An external spline is provided on the input shaft to cooperate with the internal spline of the sun gear. The lower end of the sun gear meshes with the lower gear of the lower double planetary gear shaft, and the upper end of the sun gear meshes with the lower gear of the upper double planetary gear shaft. The upper ends of the lower double planetary gear shaft and the upper double planetary gear shaft are at the same height, and their upper gears jointly mesh with the internal teeth of the fixed ring gear. An external spline is provided on the circumferential outer side of the fixed ring gear to cooperate with a spline sleeve fixed on the casing and remains stationary. Constrained by the planetary carrier, the lower double planetary gear shaft and the upper double planetary gear shaft are circumferentially evenly distributed, and the three jointly revolve around the sun gear, and their revolution speed is the final rotor output speed.

[0008] Further, it also includes an output shaft, and the output shaft is fixed to the planetary carrier by screwing.

[0009] Further, the output shaft transmits power to the output hub.

[0010] Further, when the lower double planetary gear shaft and the upper double planetary gear shaft are far apart, the non-working area of the sun gear is set as a connecting rod or a hollow shaft.

[0011] Further, the number of teeth of each stage of gears is expressed as: the number of teeth of the sun gear - Z S ; the number of teeth of the ring gear - Z r ; the number of teeth of the large planetary gear - Z P1 ; the number of teeth of the small planetary gear - Z P2 ; then the transmission ratio of the output shaft 7 to the input shaft 1 is expressed as: In this transmission system, the relative speed of the fixed ring gear is zero, v = 0. After the input shaft is given an input speed V1, the output shaft speed is expressed as V2 = i × V1.

[0012] Further, the tooth width of the sun gear is 2.5 times that of the single-layer double planetary gear. To better adapt to the equal load requirement during the transmission process, the sun gear is split into two parts, the input shaft and the sun gear. An involute spline connection is used between the two. The spline can axially float while transmitting torque and motion, and the floating amount between the two is controlled by the structural dimensions.

[0013] Further, the sun gear and the fixed ring gear are circumferentially connected by 6 upper double planetary gear shafts and 6 lower double planetary gear shafts; the outside of the fixed ring gear also has a spline allowing floating and is fixed to the casing.

[0014] Further, its feature is that 12 double gear shafts are installed on the planetary carrier through bearings, and the planetary carrier and the output shaft are connected by bolts.

[0015] The beneficial effects of this application are as follows:

[0016] In the structural design of the double-layer planetary gear chain of the main reducer of the helicopter in the present invention, the planetary gears in the original planetary gear train are improved into a double-layer planetary gear structure. The improved planetary gear structure has higher integration and space utilization rate. Under the condition of the same input load, the contact stress of the planetary tooth surface is reduced, and the stress of the accessories such as the bearings of the planetary gear train is also reduced, the failure rate is reduced, and the service life is extended. The floating spline design is adopted between the input shaft and the spline, and between the fixed gear ring and the casing, which improves the uniformity during the meshing process and makes the overall structure transmission more stable.

[0017] Compared with the existing planetary gear train reducer, the double-layer composite planetary gear train reducer has 4 main advantages:

[0018] 1. The planetary gear shafts in the helicopter reducer are designed in layers. Without increasing the contour dimensions of each casing, the number of planetary gear shafts is doubled. When working, the number of meshing teeth increases by one time, effectively reducing the use strength of the planetary gear shafts and the mating parts, extending the service life, reducing the failure rate of the planetary gears, planetary bearings and accessories, and increasing the integration and space utilization rate.

[0019] 2. The number of planetary gears is doubled, and the load that can be borne is also doubled, improving the overall transmission capacity of the reducer. Compared with the existing reducer, under the condition of the same external expansion size, a larger transmission ratio can be borne, meeting the problem of the future high power density transmission demand.

[0020] 3. The floating spline method is adopted between the input shaft and the sun gear, and between the fixed gear ring and the casing. The floating space is ensured through the structural dimensions, improving the load sharing and stability of the transmission and reducing the load sharing coefficient.

[0021] 4. In order to make the tooth surface meshing more stable, when the planetary gear and the sun gear use helical gears to mesh, the helix angle directions of the lower ends of the upper double-connected gears and the lower double-connected gears are opposite, and the axial forces generated by the helical gears can be offset between the two, without axial load. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the transmission chain structure of the main reducer of the prior art;

[0023] Figure 2 It is a schematic diagram of the structure implemented by the present invention;

[0024] 1 - input shaft, 2 - sun gear, 3 - lower double-connected planetary gear shaft, 4 - upper double-connected planetary gear shaft, 5 - fixed gear ring, 6 - planetary carrier, 7 - output shaft;

[0025] Figure 3 It is a schematic diagram of the structure evolved from the embodiment of the present invention;

[0026] Figure 4 Schematic diagram of other perspectives of the structure implemented for the present invention;

[0027] Figure 5 Schematic diagram of other perspectives of the structure evolved from the embodiments of the present invention. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the implementation of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below in conjunction with the embodiments of the present invention. In the examples, the same or similar reference numerals throughout denote the same or similar elements or elements having the same or similar functions. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments described below by reference are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. The embodiments of the present invention are described in detail below.

[0029] The structure of the present invention is based on the "Pre-research Special Project for Enhancing the Capability of Helicopter Transmission Systems" and, in accordance with the requirements of the sub-topic "Research on High-Integrity and High Transmission Ratio Compound Planetary Gear Train Transmission Technology", conducts research on the processing technology of component-level verification parts and completes the trial production of component-level test verification parts. The trial-produced parts are expected to meet the 50-hour operation test assessment with a reduction ratio of not less than 6 and a transmission efficiency of not less than 98.5% under the conditions of an input power of not less than 2500 KW and an input speed of (1000 - 2000) r / min. At present, the drawing of the part level has been completed, and the rough machining process of some parts has been completed. It is expected to complete the machining, assembly, and the above-mentioned test assessment in 2025.

[0030] The structures of the parts in this solution are similar to those of the same type of parts in the existing helicopter transmission systems. The materials of the input shaft, sun gear, lower double planetary gear shaft, upper double planetary gear shaft, and output shaft are 9310 steel, and the machining accuracy is grade 5. The gear tooth surfaces, spline tooth surfaces, and mating surfaces of the bearings are carburized to increase hardness and wear resistance. The material of the fixed gear ring is 32Cr3MoVE, and the machining accuracy is grade 5. The gear tooth surfaces and spline tooth surfaces are nitrided to improve wear resistance. The material of the planet carrier is aluminum alloy 2618A, and the machining accuracy is grade 6. The machining surface is chromate anodized to improve corrosion resistance. The lubrication method is to introduce pressurized oil externally, and after passing through the casing oil circuit, each transmission component is lubricated by spraying oil through an oil injector. The assembly principle and assembly process can follow those of the existing helicopters.

[0031] Therefore, all the machining processes, surface treatment processes, machining accuracies, lubrication methods, assembly principles, etc. of the parts in the present invention can follow those of the existing helicopters, without adding new types of materials and without increasing the implementation difficulty.

[0032] The present invention aims to provide a hierarchical structure of the planetary gears of a helicopter reducer, which is not limited to the structure introduced in this article. For example, after the sun gear (2) is stratified, the upper and lower sun gears are respectively meshed with the upper double planetary gear shaft (3) and the lower double planetary gear shaft (4), that is, the non-working area is transitioned by a columnar structure, as shown in Figure 3 , and all are within the scope of the transmission principle of the present invention.

[0033] Embodiment

[0034] The transmission chain structure of the compound planetary gear train helicopter reducer is shown in Figure 2 , including: input shaft (1); sun gear (2); lower double planetary gear shaft (3); upper double planetary gear shaft (4); fixed ring gear (5); planet carrier (6); an external spline is provided on the input shaft (1) to cooperate with the internal spline of the sun gear (2); the lower end of the sun gear (2) is meshed with the lower gear of the lower double planetary gear shaft (3), and the upper end of the sun gear (2) is meshed with the lower gear of the upper double planetary gear shaft (4); the upper ends of the lower double planetary gear shaft (3) and the upper double planetary gear shaft (4) are at the same height, and the upper gears of the two are jointly meshed with the internal teeth of the fixed ring gear (5); an external spline is provided on the circumferential outer side of the fixed ring gear (5) to cooperate with the spline sleeve fixed on the casing and remains stationary. Under the constraint of the planet carrier (6), the lower double planetary gear shaft (3) and the upper double planetary gear shaft (4) are circumferentially evenly distributed, and the three jointly revolve around the sun gear (2), and the revolution speed is the final rotor output speed.

[0035] In a certain embodiment of the present invention, an output shaft (7) is further included, and the output shaft (7) is fixed to the planet carrier (6) by screwing.

[0036] In a certain embodiment of the present invention, the output shaft (7) transmits power to the output hub.

[0037] In a certain embodiment of the present invention, when the lower double planetary gear shaft (3) and the upper double planetary gear shaft (4) are far apart, the non-working area of the sun gear (2) is set as a connecting rod or a hollow shaft, as shown in Figure 3 .

[0038] In a certain embodiment of the present invention, the number of teeth of each stage of gear is represented as: number of teeth of the sun gear - Z S ; number of teeth of the ring gear - Z r ; number of teeth of the large planetary gear - Z P1; Number of teeth of the planet gear - Z P2 . Then the transmission ratio between the output shaft 7 and the input shaft 1 is expressed as: In this transmission system, the relative rotational speed of the fixed ring gear is zero (v = 0). After the input shaft (1) is given an input rotational speed V1, the rotational speed of the output shaft can be expressed as V2 = i × V1.

[0039] In a certain embodiment of the present invention, the tooth width of the sun gear is 2.5 times that of the single - layer double - row planet gear. To better meet the requirement of load sharing during the transmission process, the sun gear is split into two parts, the input shaft and the sun gear, which are connected by an involute spline. The spline can axially float while transmitting torque and motion, and the floating amount between the two is controlled by the structural dimensions.

[0040] In a certain embodiment of the present invention, the sun gear and the fixed ring gear are circumferentially connected by 6 upper - layer double - row planet gear shafts and 6 lower - layer double - row planet gear shafts. The outer side of the fixed ring gear is also provided with a spline that allows floating and is fixed to the casing to meet the load sharing requirement.

[0041] In a certain embodiment of the present invention, 12 double - row gear shafts are installed on the planet carrier through bearings, and the planet carrier is connected to the output shaft by bolts.

[0042] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application should have the ordinary meaning understood by those of ordinary skill in the art to which this application belongs. The words indicating directions such as "upper", "lower", "left", "right", "center", "vertical", "horizontal", "inner", "outer", etc. used in the description of this application are only used to represent relative directions or position relationships, rather than implying that the device or component must have a specific orientation, be constructed and operated in a specific orientation. When the absolute position of the described object changes, its relative position relationship may also change accordingly. Therefore, it should not be understood as a limitation to this application. The terms "first", "second", "third" and similar terms used in the description of this application are only for descriptive purposes to distinguish different components, and cannot be understood as indicating or implying relative importance. The words "a", "one" or "the" and similar words used in the description of this application should not be understood as an absolute limitation on the quantity, but should be understood as having at least one. The words "including" or "comprising" and similar words used in the description of this application are intended to mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects.

[0043] In addition, it should be noted that, unless otherwise clearly specified and defined, the similar terms such as "installed", "connected", and "coupled" used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two components. Those skilled in the art can understand its specific meaning in this application according to specific circumstances.

[0044] The above are only specific embodiments of the present invention and are not used to limit the present invention. Any person skilled in the art may, within the spirit and principle of the present invention, use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims

1. A compound planetary gear train helicopter reducer transmission chain structure, characterized in that: It includes an input shaft, a sun gear, a lower double planetary gear shaft, an upper double planetary gear shaft, a fixed gear ring, and a planet carrier; the input shaft is provided with an external spline that cooperates with the internal spline of the sun gear; the lower end of the sun gear is meshed with the lower end gear of the lower double planetary gear shaft, and the upper end of the sun gear is meshed with the lower end gear of the upper double planetary gear shaft; the upper end of the lower double planetary gear shaft is at the same height as the upper end of the upper double planetary gear shaft, and the upper end gears of the two are meshed with the internal teeth of the fixed gear ring; an external spline is provided on the circumferential outer side of the fixed gear ring to cooperate with the spline sleeve fixed on the casing and remain stationary; under the constraint of the planet carrier, the lower double planetary gear shaft and the upper double planetary gear shaft are evenly distributed in the circumference, and the three revolve around the sun gear together, and their revolution speed is the final rotor output speed.

2. The structure according to claim 1, characterized in that It also includes an output shaft, which is fixed to the planet carrier by screw connection.

3. The structure according to claim 2, characterized in that The output shaft transmits power to the output hub.

4. The structure according to claim 1, characterized in that When the lower double planetary gear shaft and the upper double planetary gear shaft are far apart, the sun gear non-working area is set as a connecting rod or a hollow shaft.

5. The structure according to claim 4, characterized in that The number of teeth on each gear is expressed as: number of teeth on the sun gear - Z S ;Number of teeth on ring gear - Z r ; Number of teeth of large planetary gear - Z P1 ; Number of teeth of asteroid gear - Z P2 ; The transmission ratio of the output shaft 7 to the input shaft 1 is expressed as: In this transmission system, the relative speed of the fixed ring gear is zero, v=0. After the input shaft is given an input speed V1, the output shaft speed is expressed as V2=i×V1.

6. The structure according to claim 5, characterized in that The tooth width of the sun gear is 2.5 times that of the single-layer double-coupled planetary gear. In order to better adapt to the load-sharing requirements of the transmission process, the sun gear is split into two parts, the input shaft and the sun gear. The two are connected by an involute spline. The spline can float axially while transmitting torque and motion, and the floating amount between the two is controlled by the structural size.

7. The structure according to claim 6, characterized in that The sun gear and the fixed gear ring are connected circumferentially through 6 upper double planetary gear shafts and 6 lower double planetary gear shafts; the outer side of the fixed gear ring also has splines that allow floating and is fixed to the casing to meet the load-balancing requirements.

8. The structure according to claim 7, characterized in that The 12 double gear shafts are mounted on the planetary carrier through bearings, and the planetary carrier and the output shaft are connected with bolts.

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