Design and experiment of hydraulically self-excited vibration subsoiler

Abstract: Self-excited vibration subsoilers with springs present the shortages of poor adaptability and failure of vibration in different soil texture because of the constant stiffness and limited adjustment range of pre-tension force. Aiming at improving the working performance of self-excited vibration subsoiler, a new method characterized by hydraulically self-excited vibration source was provided. Meanwhile the self-excited vibration subsoiler with a hydraulic cylinder was designed. The new subsoiler mainly consists of a fixed mount to connect the subsoiler with the machine frame, a hydraulic cylinder served as the self-vibrating source, a connecting plate to connect the tine and the fixed mount, a press roll to compact the tilled soil surface thus reducing the water evaporation. The key design parameters of the hydraulic cylinder were determined by establishing the mechanics and kinematics model of the tine: the diameter D = 40 mm and the stroke S = 130 mm. The adjustable system for hydraulic cylinder pressure was set up. The adjustable system consists of two parts: electric control section and hydraulic section. The hydraulic section mainly includes the hydraulic source, an accumulator, a manual reducing valve and an electromagnetic proportional pressure reducing valve. The hydraulic source can be supplied by the tractor with hydraulic output connector. The accumulator is used to stabilize the system pressure and the electromagnetic proportional pressure reducing valve is used to adjust the working pressure of the hydraulic cylinder continuously and proportionally. The manual reducing valve is set between the electromagnetic proportional pressure reducing valve and the accumulator to obtain desired value closely to the working pressure of the hydraulic cylinder pressure, which is beneficial to avoid pulse impact caused by the electromagnetic proportional pressure reducing valve adjusting the pressure for the hydraulic cylinder. The electric control section is mainly composed of a controller, a touch screen and a DAC module (digital to analog converter). The electric control section communicates with the hydraulic system through the DAC module that transmits the signal volt from the controller to the analog volt for electromagnetic proportional pressure reducing valve to adjust the working pressure of the hydraulic cylinder pressure. The target value of hydraulic pressure is input to the electric control section by the touch screen. The quadratic regression general rotation combination tests were conducted to investigate the influence of hydraulic cylinder pressure, operating speed and soil cone index on the working performance of hydraulically self-excited vibration subsoiler with a hydraulic cylinder. The traction and variation coefficient of tillage depth were selected as evaluation indexes. Results showed that the soil cone index and the operating speed had positive impact on variation index of tillage depth while the working pressure of the hydraulic cylinder pressure had negative impact on variation index of tillage depth. The variation index of tillage depth was more influenced by hydraulic cylinder pressure and operating speed than soil cone index. The traction increased with the increase of the operating speed and hydraulic cylinder pressure and decreased after reaching the maximum value. The impact of the factors on the traction was followed with the soil cone index, the hydraulic cylinder pressure and the operating speed. The regression models with the variation index of tillage depth and the traction as the response value respectively were acquired and the optimal combination of parameters was obtained: the hydraulic cylinder pressure of 3.6 MPa, the operating speed of 1.4 km / h, the soil cone index of 1.18 MPa. Verification test was carried out to testify the regression models using the optimal combination of parameters. The traction and variation index of tillage depth were respectively 1 300.70 N and 3.56% that were better than the results of quadratic regression general rotation combination tests, which verified the reliability of the regression model. This study can provide a theoretical reference for the research of self-excited vibration subsoiling machine.