A method for designing the power spectrum of a coaxial dual-rotor reducer in fatigue testing

Abstract

This application provides a power spectrum design method for fatigue testing of a coaxial dual-rotor reducer, belonging to the field of helicopter design technology. The method first calculates the power transmitted by the differential planetary gear train under each power state in the power spectrum; obtains the fatigue test power of the planetary gears; sets the ratio of the rotor inner shaft power to the rotor outer shaft power to the critical K value, ensuring that the power of both the rotor inner and outer shafts is provided solely by the differential planetary gear train; calculates the power values ​​of the rotor inner and outer shafts; calculates the reducer input power; and finally determines the reducer fatigue test power spectrum. This invention, by employing a method where the power of both the rotor inner and outer shafts is provided solely by the differential planetary gear train, avoids the generation of closed power in the internal closed differential planetary gear transmission during the reducer fatigue test. While evaluating the planetary gears in the differential planetary gear train, it reduces the risk of premature failure of components in the fixed-axis planetary gear train, simultaneously improving the reducer's working efficiency and the reliability of the reducer fatigue test.

Description

Technical Field

[0001] This application belongs to the field of helicopter design technology, and in particular relates to a method for designing the power spectrum of a coaxial dual-rotor reducer for fatigue testing. Background Technology

[0002] The coaxial dual-rotor helicopter reducer differs in structure from commonly used domestic reducers, employing a closed differential planetary gear transmission mechanism to achieve coaxial reverse torque output. This closed differential planetary gear transmission mechanism consists of a single-stage fixed-axis planetary gear transmission and a single-stage differential planetary gear transmission, offering advantages such as compact structure, large transmission ratio, and smaller size compared to two-stage planetary gear transmissions. However, the internal power transmission of the closed differential planetary gear transmission is complex, and improper design can generate significant closed power. When closed power exists, no effective power flows through the circuit, resulting in a large balancing torque, which increases gear and bearing loads, increases system friction losses, causes reducer temperature, reduces overall transmission efficiency, and affects reducer lifespan. Therefore, the generation of closed power should be avoided as much as possible.

[0003] For coaxial twin-rotor helicopter gearboxes, when conducting fatigue tests on planetary gears in a closed differential planetary gear train, it is crucial to prevent premature damage to components in the fixed-axis planetary gear train during the test. Therefore, the power spectrum design for gearbox fatigue tests must avoid generating closed power to improve the reliability of the fatigue test. Currently, there is no mature and reliable method for designing fatigue test power spectra, lacking a method to guide the design of fatigue test power spectra for coaxial twin-rotor helicopter gearboxes and to conduct fatigue tests on planetary gears. Summary of the Invention

[0004] To avoid the generation of closed power in the internal closed differential planetary gear transmission during the fatigue test of the reducer, and to reduce the risk of premature failure of components in the fixed-axis planetary gear train while evaluating the planetary gears in the differential planetary gear train, thereby improving the working efficiency of the reducer and the reliability of the fatigue test, this invention provides a power spectrum design method for fatigue testing of a coaxial dual-rotor reducer. The technical solution is as follows:

[0005] A method for designing the power spectrum of a coaxial dual-rotor reducer for fatigue testing, the method comprising:

[0006] Step 1: Determine the transmission ratio of the closed differential planetary gear train of the coaxial dual-rotor reducer, including the transmission ratio between the central gear and the fixed-axis transmission gear ring and the transmission ratio between the sun gear and the planet carrier.

[0007] Step 2: Perform power flow analysis on the closed differential planetary gear train to determine the relationship between the load on the star wheel shaft assembly in the fixed-axis planetary gear train and the load on the planetary gears in the differential planetary gear train;

[0008] Step 3: Based on the relationship obtained in Step 3, determine the critical K value corresponding to various scenarios of power distribution between the inner and outer shafts of the reducer rotor. K is the ratio of the load on the outer shaft to the load on the inner shaft.

[0009] Step 4: Based on the overall power spectrum of the coaxial dual-rotor helicopter, calculate the ratio Ki of the power of the outer rotor shaft to the power of the inner rotor shaft corresponding to each power state in the power spectrum;

[0010] Step 5: Determine which of the multiple scenarios in Step 4 the power distribution of the rotor inner shaft and rotor outer shaft in each power state of the power spectrum belongs to;

[0011] Step 6: Calculate the power transmitted by the differential planetary gear train under each power state in the power spectrum;

[0012] Step 7: Determine the maximum power transmitted by the differential planetary gear train and obtain the fatigue test power of the planetary gears;

[0013] Step 8: Set the ratio of the rotor inner shaft power to the rotor outer shaft power to the critical value of K, so that the rotor inner shaft and rotor outer shaft power are provided only by the differential planetary gear train, and calculate the rotor inner shaft and rotor outer shaft power values;

[0014] Step 9: Calculate the input power of the reducer based on the planetary gear fatigue test power obtained in Step 7;

[0015] Step 10: Determine the power spectrum of the reducer fatigue test.

[0016] Step 10 specifically includes:

[0017] Calculate the required gear speed and, based on the requirement of 5 megacycles, calculate the gear testing time.

[0018] Based on the obtained input and output power and the test time, the power spectrum of the reducer fatigue test is determined.

[0019] Furthermore, after step 1, the method also includes: step 2, performing force analysis on the planetary gears in the differential planetary gear train.

[0020] In step 2, the relationship between the load of the star wheel shaft assembly in the fixed-axis planetary gear train and the load of the planetary gears in the differential planetary gear train includes the ratio K of the rotor outer shaft load to the rotor inner shaft load.

[0021] Among them, the various scenarios in step 3 include:

[0022] When K equals the critical value, all the power of the inner and outer rotor shafts is transmitted by the differential planetary gear train, while the power transmitted by the fixed-axis planetary gear train is 0.

[0023] When K is greater than the critical value, all the power of the inner shaft of the rotor is transmitted by the differential planetary gear train, and the output power of the outer shaft of the rotor is transmitted by both the differential planetary gear train and the fixed-axis planetary gear train.

[0024] When K is less than the critical value, all the power of the inner and outer shafts of the rotor is transmitted by the planetary gear train, and the fixed-axis planetary gear train will form an internal power cycle. The existence of the cycled power increases the load on the components and reduces the efficiency of the reducer.

[0025] In step 9, the input power of the reducer is calculated based on the fatigue test power of the planetary gears obtained in step 7, as well as the fatigue test power of the gears at other output parts of the reducer and the power of the accessories.

[0026] In step 7, the maximum power transmitted by the determined differential planetary gear train is multiplied by the safety factor to obtain the fatigue test power of the planetary gears.

[0027] The safety factor is 1.4.

[0028] This invention provides a power spectrum design method for fatigue testing of a coaxial dual-rotor reducer, which can guide the design of the power spectrum for fatigue testing of coaxial dual-rotor reducers. By adopting a method in which the power of both the inner and outer rotor shafts is provided solely by the differential planetary gear train, the closed power generated by the internal closed differential planetary gear transmission can be avoided during the fatigue test of the reducer. While evaluating the planetary gears in the differential planetary gear train, the risk of premature failure of parts in the fixed-axis planetary gear train is reduced, thereby improving the working efficiency of the reducer and the reliability of the reducer fatigue test. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a fixed-axis planetary gear train;

[0030] Figure 2 This is a schematic diagram of a differential planetary gear train;

[0031] Figure 3 A flowchart of the power spectrum design method for fatigue testing of a coaxial dual-rotor reducer provided in an embodiment of the present invention;

[0032] Figure 4 A simplified diagram of the gearbox transmission for a coaxial twin-rotor helicopter;

[0033] Figure 5 This is a schematic diagram of power flow when K = 0.72506;

[0034] Figure 6 This is a schematic diagram of power flow when K > 0.72506;

[0035] Figure 7 This is a schematic diagram of power flow when K < 0.72506.

[0036] in, Figure 1 In the middle, 1-Sun gear, 2-Central gear, 3-Gear chain housing cover, 4-Fixed shaft transmission gear ring, 5-Small star wheel, 6-Large star wheel, 7-Gear chain housing; Figure 2 In the middle, 8-spline flange, 9-planetary drive gear ring, 10-planetary gear, 11-planetary carrier. Detailed Implementation

[0037] The present application will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0038] An embodiment of the present invention provides a method for designing the power spectrum of a coaxial dual-rotor reducer for fatigue testing, comprising the following steps:

[0039] Step 1: Determine the transmission ratio of the closed differential planetary gear train of the coaxial dual-rotor reducer. This transmission ratio includes two parts: the transmission ratio between the central gear and the fixed-axis transmission gear ring and the transmission ratio between the sun gear and the planet carrier.

[0040] Step 2: Perform force analysis on the planetary gears in the differential planetary gear train.

[0041] Step 3: Perform a power flow analysis of the closed differential planetary gear train. Assuming the ratio of the load on the outer shaft of the rotor to the load on the inner shaft of the rotor is K, derive the expression for the ratio of the load on the star wheel shaft assembly in the fixed-axis planetary gear train to the load on the planetary gears in the differential planetary gear train. This expression uses K to represent the ratio of the above loads.

[0042] Step 4: Using the expressions derived in Step 3, determine the critical values ​​of K for the three scenarios of power distribution between the inner and outer shafts of the reducer rotor. These three scenarios are as follows: When K equals the critical value, all power from the inner and outer shafts is transmitted through the differential planetary gear train, and the power transmitted by the fixed-axis planetary gear train is 0; when K is greater than the critical value, all power from the inner shaft is transmitted through the differential planetary gear train, and the output power from the outer shaft is transmitted jointly by the differential and fixed-axis planetary gear trains; when K is less than the critical value, all power from both the inner and outer shafts is transmitted through the planetary gear trains, and the fixed-axis planetary gear train will form an internal power loop. The existence of this looped power increases the load on the components and reduces the efficiency of the reducer.

[0043] Step 5: Based on the overall power spectrum of the coaxial dual-rotor helicopter, determine the ratio K of the power of the rotor outer shaft to the power of the rotor inner shaft corresponding to each power state in the power spectrum. i .

[0044] Step 6: Determine which of the three scenarios described in Step 4 the power distribution of the rotor inner shaft and rotor outer shaft in each power state of the power spectrum belongs to.

[0045] Step 7: Calculate the power transmitted by the differential planetary gear train under each power state in the power spectrum.

[0046] Step 8: Determine the maximum power transmitted by the differential planetary gear train, multiply it by a safety factor of 1.4, and obtain the fatigue test power of the planetary gears.

[0047] Step 9: Based on the critical value of K calculated in Step 4, set the ratio of the rotor inner shaft power to the rotor outer shaft power to the critical value of K, so that the rotor inner shaft and rotor outer shaft power are provided only by the differential planetary gear system, and calculate the rotor inner shaft and rotor outer shaft power values.

[0048] Step 10: Using the planetary gear fatigue test power obtained in Step 8, plus the fatigue test power of other output gears of the reducer and the power of accessories, while considering power loss, determine the input power of the reducer.

[0049] Step 11: Determine the gear speed to be tested, and determine the gear testing time according to the testing requirement of 5 megacycles.

[0050] Step 12: Based on the input and output power and test time obtained in the above steps, determine the power spectrum of the reducer fatigue test.

[0051] This invention employs a method where the power of both the inner and outer rotor shafts is provided solely by the differential planetary gear system. This avoids the generation of closed power in the internal closed differential planetary gear transmission during the fatigue test of the reducer. While evaluating the planetary gears in the differential planetary gear system, it reduces the risk of premature failure of components in the fixed-axis planetary gear system, thereby improving the working efficiency of the reducer and enhancing the reliability of the reducer fatigue test.

[0052] For example, a coaxial dual-rotor helicopter reducer achieves coaxial reverse torque transmission through a closed planetary gear drive. The closed planetary gear drive consists of a single-stage fixed-axis planetary gear drive and a single-stage differential planetary gear drive. The fixed-axis planetary gear train is a torque-split transmission structure, such as... Figure 1 As shown, the central gear 2 of the fixed-axis planetary gear train simultaneously meshes with the large planetary gears 6 (helical gears) of five planetary gear assemblies to transmit torque. Each large planetary gear 6 is connected to a small planetary gear 5 via a spline pair to transmit torque. The five small planetary gears 5 simultaneously mesh with the fixed-axis transmission ring gear 4 to transmit torque. The central gear 2 of the fixed-axis planetary gear train is connected to the sun gear 1 of the differential planetary gear train via a spline. The differential planetary gear train uses spur gear transmission, such as... Figure 2 As shown, the sun gear 1 of the differential planetary gear train (see...) Figure 1 It simultaneously meshes with 6 planetary gears 10, all of which are installed in the planet carrier 11 and simultaneously mesh with the planetary transmission gear ring 9. The planet carrier 11 drives the inner shaft of the rotor to rotate.

[0053] like Figure 3 As shown in the figure, the specific implementation process of designing the power spectrum for fatigue testing of a coaxial dual-rotor reducer using the fatigue test power spectrum design method provided in this embodiment of the invention is as follows:

[0054] 1) By Figure 4 Calculate the transmission ratio of the closed differential planetary gear train of the coaxial dual rotor reducer. The transmission ratio includes two parts: the transmission ratio between the central gear 2 and the fixed-axis transmission gear ring 4, and the transmission ratio between the sun gear 1 and the planet carrier 11.

[0055] The transmission ratio between the central gear 2 and the fixed-axis transmission gear ring 4 was calculated to be -0.1594, and the transmission ratio between the sun gear 1 and the planet carrier 11 was 0.1594.

[0056] 2) Perform force analysis on the planetary gears in the differential planetary gear train.

[0057] F 1-10T =1.0337F 9-10T (1)

[0058] F 11 =2.0337F 9-10T (2)

[0059] in:

[0060] F 1-10T The tangential force between the sun gear 1 and the planetary gear 10;

[0061] F 9-10T The tangential force between the planetary transmission ring gear 9 and the planetary gear 10;

[0062] F 11 The tangential force is that of planetary carrier 11.

[0063] 3) Perform power flow analysis on the closed differential planetary gear train, assuming the power of the rotor outer shaft is P. 外 The rotor's internal shaft power is P 内 , let P 外 =K×P 内 ,get:

[0064]

[0065] in:

[0066] P 2-6 The power transmitted between the central gear 2 and the large star wheel 6;

[0067] P 1-10 The power transmitted between the sun gear 1 and the planet gear 10.

[0068] 4) As can be seen from equation (3), the critical value of K is 0.72506. When K = 0.72506, all the power of the inner and outer shafts of the rotor is transmitted by the differential planetary gear train, and the power transmitted by the fixed-axis gear train is 0. The direction of power flow is shown in the figure. Figure 5When K > 0.72506, all the power of the rotor's inner shaft is transmitted by the differential planetary gear train, while the output power of the rotor's outer shaft is transmitted jointly by the differential planetary gear train and the fixed-axis planetary gear train. The power flow direction is illustrated in the diagram. Figure 6 When K < 0.72506, all power to the inner and outer rotor shafts is transmitted through the planetary gear train, and the fixed-axis planetary gear train forms an internal power loop. The direction of power flow is illustrated in the diagram. Figure 7 .

[0069] 5) Based on the helicopter power spectrum, calculate the ratio K of the rotor outer shaft power to the rotor inner shaft power for each power state in the power spectrum. i All are greater than 0.72506, therefore the power of the inner shaft of the rotor in this reducer comes from the differential planetary gear train, and the power of the outer shaft of the rotor comes from both the differential planetary gear train and the fixed-axis planetary gear train. Thus, the power transmitted by the fixed-axis planetary gear train and the differential planetary gear train simultaneously satisfies:

[0070] P 2-6 +P 1-10 =P 外 +P 内 (4)

[0071] in,

[0072] P 2-6 The power transmitted between the central gear 2 and the large star wheel 6;

[0073] P 1-10 The power transmitted between the sun gear 1 and the planetary gear 10;

[0074] P 外 Power of the rotor's outer shaft;

[0075] P 内 This refers to the power of the rotor's inner shaft.

[0076] 6) Calculate the power transmitted by the differential planetary gear train under each power state in the power spectrum. Determine the maximum power transmitted by the differential planetary gear train as 2660.8kW. Multiply by the safety factor of 1.4 to obtain the fatigue test power of the planetary gears as 3725kW.

[0077] 7) Set the ratio of the rotor inner shaft power to the rotor outer shaft power to 0.72506, so that the rotor inner shaft and rotor outer shaft power are provided only by the differential planetary gear system. Calculate the rotor inner shaft and rotor outer shaft power values ​​to be 2167kW and 1558kW, respectively.

[0078] 8) Using the planetary gear fatigue test power obtained in step 6, plus the fatigue test power of other output gears and accessory power of the reducer, assuming a power loss of 3%, calculate the total input power of the reducer:

[0079] Total input power of the reducer = [3725 + 65 (generator transmission gear test power) + 2 (oil pump power) + 51.5 (fan power)] / (1 - 0.03) = 3962kW.

[0080] 9) Calculate the required gear speed, and based on the requirement of 5 megacycles, calculate the gear testing time. Gear testing time = 5 × 10⁻⁶ 6 / Gear speed.

[0081] 10) Based on the input and output power and test time obtained from the above steps, determine the power spectrum of the reducer fatigue test.

[0082] In practical applications, step 10) needs to be performed according to actual needs. For example, you can refer to Table 1 to complete this step.

[0083] Table 1 Power spectrum of fatigue test of reducer

[0084]

[0085]

[0086] The above description merely illustrates the embodiments of this application, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Furthermore, any parts of this invention not described in detail are conventional techniques.

Claims

1. A method for designing the power spectrum of a coaxial dual-rotor reducer for fatigue testing, characterized in that, The method includes: Step 1: Determine the transmission ratio of the closed differential planetary gear train of the coaxial dual-rotor reducer, including the transmission ratio between the central gear and the fixed-axis transmission gear ring and the transmission ratio between the sun gear and the planet carrier. Step 2: Perform power flow analysis on the closed differential planetary gear train to determine the relationship between the load on the star wheel shaft assembly in the fixed-axis planetary gear train and the load on the planetary gears in the differential planetary gear train; Step 3: Based on the relationship obtained in Step 3, determine the critical K value corresponding to various scenarios of power distribution between the inner and outer shafts of the reducer rotor. K is the ratio of the load on the outer shaft to the load on the inner shaft. Step 4: Based on the overall power spectrum of the coaxial twin-rotor helicopter, calculate the ratio K of the power of the rotor outer shaft to the power of the rotor inner shaft corresponding to each power state in the power spectrum. i ; Step 5: Determine which of the multiple scenarios in Step 4 the power distribution of the rotor inner shaft and rotor outer shaft in each power state of the power spectrum belongs to; Step 6: Calculate the power transmitted by the differential planetary gear train under each power state in the power spectrum; Step 7: Determine the maximum power transmitted by the differential planetary gear train and obtain the fatigue test power of the planetary gears; Step 8: Set the ratio of the rotor inner shaft power to the rotor outer shaft power to the critical value of K, so that the rotor inner shaft and rotor outer shaft power are provided only by the differential planetary gear train, and calculate the rotor inner shaft and rotor outer shaft power values; Step 9: Calculate the input power of the reducer based on the planetary gear fatigue test power obtained in Step 7; Step 10: Determine the power spectrum of the reducer fatigue test.

2. The method according to claim 1, characterized in that, Step 10 specifically involves: Calculate the required gear speed and, based on the requirement of 5 megacycles, calculate the gear testing time. Based on the obtained input and output power and the test time, the power spectrum of the reducer fatigue test is determined.

3. The method according to claim 1, characterized in that, Following step 1, the method further includes: step 2, performing force analysis on the planetary gears in the differential planetary gear train.

4. The method according to claim 1, characterized in that, The relationship between the load on the star wheel shaft assembly in the fixed-axis planetary gear train and the load on the planetary gears in the differential planetary gear train in step 2 includes the ratio K of the rotor outer shaft load to the rotor inner shaft load.

5. The method according to claim 1, wherein The various scenarios in step 3 include: When K equals the critical value, all the power of the inner and outer rotor shafts is transmitted by the differential planetary gear train, while the power transmitted by the fixed-axis planetary gear train is 0. When K is greater than the critical value, all the power of the inner shaft of the rotor is transmitted by the differential planetary gear train, and the output power of the outer shaft of the rotor is transmitted by both the differential planetary gear train and the fixed-axis planetary gear train. When K is less than the critical value, all the power of the inner and outer shafts of the rotor is transmitted by the planetary gear train, and the fixed-axis planetary gear train will form an internal power cycle. The existence of the cycled power increases the load on the components and reduces the efficiency of the reducer.

6. The method according to claim 1, characterized in that, In step 9, the input power of the reducer is calculated based on the fatigue test power of the planetary gears obtained in step 7, as well as the fatigue test power of the gears at other output parts of the reducer and the power of the accessories.

7. The method according to claim 1, characterized in that, In step 7, the maximum power transmitted by the determined differential planetary gear train is multiplied by the safety factor to obtain the fatigue test power of the planetary gears.

8. The method according to claim 7, characterized in that, The safety factor is 1.4.

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