1. Hydraulic system noise. The noise of the hydraulic system is mainly generated by the pump. During the working process of the excavator, due to the continuous change of the load, the pressure and flow of the pump change with the load, and the pressure and flow change to form pressure pulsation, Cause vibration and noise. The noise of the main control valve is another noise source of the hydraulic system. During the hydraulic excavation process, each spool of the main control valve is continuously opened and closed. During the opening and closing process, hydraulic shock will be generated, causing vibration and producing Noise. In addition, when the excavator performs actions at the same time, it is necessary to throttle the actuator control spool with light load. Therefore, there are many throttle orifices inside the main control valve. When the oil flows through the throttle orifice and the valve port, the Cavitation noise is generated due to changes in pressure.
2. Fan noise. Fan noise is mainly aerodynamic noise, and aerodynamic noise is mainly composed of rotational noise and eddy current noise . Rotational noise is caused by air pressure pulsation formed by fan blades, mainly low-frequency components, and fan blades. It is proportional to the 10th power of the peripheral speed. The eddy current noise is caused by the random pulsation acting on the blade, and is proportional to the 5-6th power of the peripheral speed of the fan blade. The higher the peripheral speed of the fan blade, the greater the noise, the same diameter The higher the fan speed, the louder the noise.
3. Intake and exhaust noise. In the first half of the intake stroke of the engine, due to the downward movement of the piston, a negative pressure is generated in the cylinder, and the gas flows in from the intake pipe, generating a negative pressure wave, which propagates through the valve and along the intake pipe, and when it reaches the open end, it flows from The open end reflects back the positive pressure wave. Therefore, there is a pressure wave in the intake pipe, and this fluctuation will generate fundamental frequency noise. In addition, when the intake air flows through the intake passage at a high speed, eddy current noise will also be generated. The exhaust gas is discharged through the exhaust pipe and muffler. At the initial stage of the exhaust valve opening, with the influx of gas, a large positive pressure wave is generated at the exhaust valve and propagates to the outlet end of the exhaust pipe, and returns to the negative pressure wave at the outlet end. Therefore, there is a pressure wave in the exhaust pipe, and this fluctuation will also generate fundamental frequency noise. In addition, when exhausting, the high-speed flow of the airflow will generate eddy current noise, and the noise will be radiated when flowing through the wall pipe and the shell.
4. Diesel engine body noise. Diesel engines for hydraulic excavators generally have larger displacement and power, and the noise generated during operation is also larger, mainly including the explosion sound caused by the ignition of the diesel engine, and the impact noise generated by the periodic impact of the piston on the cylinder head, etc. It is radiated through the casing of the diesel engine. Another important component is the noise caused by the vibration of the diesel engine. During the operation, due to the imbalance caused by the inertia moment of the piston, the diesel engine is stimulated to produce vertical vibration and severe horizontal, front and rear shaking. Resulting in the vibration of the diesel engine casing and radiated noise.
