The meshing frequency and its double frequency of each pair of wheels constitute the main vibration excitation components of the planetary gear transmission system, and the strength of the system vibration is directly affected by the relationship between the excitation components and the natural frequency of the transmission system. In order to study the influence of various excitation components on the vibration of the system, this paper calculates the dynamic response of the planetary gear transmission system at different speeds, as shown in the figure, where FM is the meshing frequency (and FM = NZ / 60), near the natural frequency of the sun wheel’s torsion (412hz, second-order repetition frequency, corresponding speed is 706r / min), the frequency of the meshing force between the sun wheel and the planet wheel has obvious peak value. Under the influence of the meshing frequency at 2500 R / min ~ 3000 R / min, the second harmonic at 1500 R / min and the third harmonic at 1000 R / min, there are peaks near the lateral vibration (889 Hz, third-order repetition frequency, 919 Hz) and the torsional vibration natural frequency (1046 Hz) of the planet gear, among which the peak value corresponding to the meshing frequency at 3000 R / min is the largest. Near the natural frequency (1791hz) of the lateral vibration of the inner ring gear, the frequency spectrum affected by the second harmonic wave at 280r / min also shows an obvious peak.
Due to the time-varying stiffness of gear engagement and the contact force of tooth profile, the frequency distribution of meshing force of planetary gear transmission system becomes more complex, and the input speed will also affect the frequency components of the system. In this paper, the change of the first-order meshing force FSP1 between the sun wheel and the planet wheel and the first-order meshing force frp1 between the planet wheel and the inner ring gear in the range of 500r / min ~ 3000r / min is calculated, as shown in the figure.
The frequency variation of the first-order engagement force can be divided into three intervals: A, B and C. A range is 500r / min ~ 105r / min, and there is only one order natural frequency of the sun wheel in this range. In a range, with the increase of rotating speed, FSP1 and frp1 gradually increased, accompanied by fluctuations.
Because the torsional vibration of the sun wheel directly affects the engagement between the sun wheel and the planet, the increase rate of FSP1 in this region is larger than that of frp1, so that the engagement frequency of FSP1 gradually approaches to frp1 until the frequency of 105r / min is equal. B interval is 105r / min ~ 2000r / min. in this interval, the number of natural frequencies of the system increases, including 889hz, 919hz of the lateral vibration frequency of the planetary gear, and 1046hz of the torsional vibration frequency of the planetary carrier. Each vibration mode directly affects the Meshing Effect of the sun gear and the planetary gear, so the FSP1 in B interval increases greatly.
Because the torsional vibration of the sun gear does not directly affect the Meshing Effect of the inner ring gear and the planetary gear, frp1 experienced the process of first reducing and then increasing, but the increasing amplitude is not obvious. In Section C, the number of modes of the system is reduced, and the modal density is relatively low. Only the transverse vibration mode of the inner ring gear (1791 Hz) exists. Therefore, the frequency of the first-order meshing force in Section B decreases first and then increases.