The working environment of shearer is bad, and the gear fault data of rocker transmission system is not easy to collect, so the gear fault simulation experiment of rocker transmission system is carried out by using the shearer rocker loading experimental platform. The loading test bench of shearer rocker arm is composed of eddy current dynamometer, test rocker arm, test rocker arm, connecting components, coupling and mechanical fastening device, as shown in Figure 1. The eddy current dynamometer is responsible for providing the load torque required by the rocker arm loading. There is a motor in the test rocker arm, which can convert low speed and large torque into high speed and small torque. There is a motor in the test rocker arm, which is the power source of the test bench. The coupling connects the test rocker arm with the test rocker arm to transmit torque. The mechanical fastening device is used to support and fix the test rocker arm and test rocker arm.
The transmission principle of test rocker arm is shown in Fig. 2, and z1-z14 are gears. The output shaft of the motor of the cutting part is connected with the gear Z1 through the slender flexible torque shaft. The output torque of the motor is transmitted to the first stage planetary reducer through the gear z1-z8. The planetary carrier of the first stage planetary reducer transmits the power to the second stage planetary reducer. The power output from the second stage planetary reducer is transmitted to the square coupling sleeve, and finally to the cutting drum.
The loading process of shearer rocker arm is as follows
(1) The loaded double rocker arm is fixed on the support, the output end of the test rocker arm and the input end of the eddy current dynamometer are connected and fixed through the connecting components, and the input end of the test rocker arm and the output end of the test rocker arm are connected and fixed through the coupling, and the appropriate adjustment is made to make the rotation center of each component connected and fixed consistent as far as possible, so as to prevent the vibration of the rocker arm.
(2) The acceleration sensor is used to realize the vibration signal acquisition of shearer rocker armin different states. The transmission path of vibration energy in the rocker arm can be expressed by the power flow. Therefore, the arrangement point of the sensor can be selected according to the distribution of the power flow in the rocker arm. When collecting gear vibration signal, the effect is better when the monitoring point is near the support of the shaft and the shell. Therefore, the acceleration sensor is installed on the shell near the straight gear side of the rocker arm. At the same time, the acceleration sensor is connected with the vibration signal acquisition equipment. The sampling frequency is 12khz and the sensitivity is 500mv / g. the installation position of acceleration sensor and data acquisition equipment are shown in Fig. 3.
(3) After the loading platform and the test system are installed, the motor in the test rocker arm is connected with the power supply to carry out the loading experiment. By adjusting the load button of eddy current dynamometer, the load is adjusted to 25%, 50% and 75% respectively. The loading time of each loading amount was set as 1 h. In the loading time range, the vibration signal of the rocker arm is collected and saved to the computer.
(4) Repeat the above steps to collect the vibration signals of rocker arm spur gear under five states: normal, wear, fracture, pitting and crack. By observing the vibration signals of different loads, it is found that the fault vibration signal of rocker arm under 50% load is obvious. Therefore, five states with 50% load are selected to draw the vibration signal waveforms under various gear states, as shown in Figure 4.
It can be seen from Figure 4 that the acceleration of the vibration signal of the rocker gear changes little under the normal state, and its value fluctuates within – 0.2 ~ 0.2m/s2, with less impact vibration; When the gear pitting fault occurs, the acceleration range of vibration signal increases, but the increase range is small, and there is no obvious impact vibration signal; When the gear wear fault occurs, the amplitude of acceleration fluctuation begins to increase, and the impact vibration is more obvious; When the gear cracks and broken teeth occur, the acceleration range increases greatly, and there is a very obvious and regular impact vibration signal. Therefore, from the time-domain signal analysis, the vibration signal characteristics of gear under five states have obvious differences, which is conducive to the subsequent gear fault classification.