Combined design method of two-degree-of-freedom planetary gear transmission


The planetary transmission consists of several NGW-type epicyclic gear trains and a number of shift operating elements (brake B, clutch C). The shifting is achieved by the separation or combination of clutches and brakes coupled to the gears or shafts. It is widely used as a vehicle and construction machinery. Variable speed drive. If you do not learn from the existing design, it is difficult for general engineers to design a schematic diagram of the mechanism according to the required number of gears and the ratio of the gear ratio, and calculate the number of teeth. Therefore, this paper proposes a design method that combines the schematic diagrams of planetary rows. The example shows the combination design and the calculation method of the number of teeth of the four-speed and five-speed planetary transmission with two degrees of freedom.
2 Theoretical basis Single planetary row and planetary row diagrams are shown in the diagram shown by b. Black dots indicate basic components, a is the sun gear, b is the ring gear, and H is the boom. The three basic components are closed and form a closed train. The transmission ratio is derived as follows: By screening 72 transmission schemes, more than ten dual planetary transmission schemes suitable for the transmission can be obtained.
Table 1 Appropriate diagram of the planetary row and the transmission ratio Planetary row Applicable diagrams The ratio of the transmission ratio and the transmission ratio when the brake is combined (A:=2~3) Stone 1 combined i=\擂忍2 combination = Table 1 only A sketch of five dual planetary transmission schemes is presented for the designer to combine design and gear count calculations.
3 two-degree-of-freedom planetary transmission combination design example Two-degree-of-freedom planetary transmissions work, in addition to a given one, must also be combined with only one operating element, then the movement of other components can be determined.
example. Design 3 forward gear planetary transmissions, requiring the gear ratio of each gear. Forward 1 block i, 3. 8 forward 2 block i2 1 (direct gear), reverse gear i down "-6. Solution. It is known that the range of the gear ratios of each scheme in Table 1 can be combined with a double planetary row that can provide the reverse gear ratio on the double planetary row that meets the requirements of the forward gear. There are several design schemes.
a is a three-planetary diagram that satisfies the requirements. It adds a third planetary row to the simplified version of the sequence number 1, and the third and second planetary rows form exactly the two planets in the serial number 4 that provide the reverse gear ratio. row. It is easy to draw a schematic diagram of the mechanism shown in figure b from the figure a.
When the clutch C is combined, it is the direct gear. When the brakes B1, B2 and B3 are respectively combined, the transmission realizes the 2nd gear, the 1st gear and the reverse gear respectively, which should be according to the two formulas in the serial number 1 and one of the formulas in the serial number 4. Calculate the k value. That is, i2=1 initial value of k and according to the concentric condition and assembly condition of the planetary transmission (according to the number of planetary wheels is 3), it is determined by repeated calculation.
Then calculate the actual gear ratio by substituting each k value into the above three formulas.
Table 2 The relative error between the actual gear ratio of the four-speed planetary transmission combined component and the corresponding gear ratio and the original expected value is less than 2%, which meets the design requirements. If a displacement gear is used, the error will be smaller.
Another design of this problem is to use the planetary rows of Nos. 5 and 4 to form a three-planetary structure, which is a combination diagram and mechanism diagram.
Then the actual gear ratio and corresponding combined components are shown in Table 4. Table 4 Five-speed planetary transmission combined components and corresponding gear ratio according to the formula in a and serial numbers 5 and 4, the following formula is listed: i = from the above three, and according to the previous The method is determined as follows: h 2 Z8 2 actual transmission ratio and corresponding combined components are shown in Table 3 Table 3 4 gear planetary transmission coupling components and corresponding gear ratios. If combined with the schematic diagrams of serial numbers 3 and 4 into four planetary rows, not only can it be satisfied The three forward gears required by this question can also be added according to the formulas of Tables 3 and 4 and can be obtained by comparing a: i=k2/(k2+1)1-left 3 left 4.1-6 by the above four formulas, and According to the method described above: ki II after designing the mechanism diagram of the planetary transmission and determining the number of teeth of each gear, the meshing efficiency of each gear should be accounted for. The transmission requirement for the vehicle is 92.5% of the forward gear, and the reverse gear meshing efficiency is calculated the most. The convenient method is the KpeiHec method, also known as the gear ratio method.

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