Reducing the fluid loss in case of depressurization of tractors’ hydraulic drive

BACKGROUND: The operation of hydraulic drives of agricultural machinery is associated with the problem of leakage of fuel and lubricants, leading to contamination of water and soil. The most intense oil spill occurs when high-pressure hoses of hydraulic equipment are destroyed. The existing methods of solving the problem of oil leakage from high-pressure hoses have severe restrictions and high costs of their implementation. One of the effective methods of solving the problem is the use of hydraulic drive protection devices that disconnect the unpressurised section from the pressure source.

AIMS: To develop an improved protection device – an emergency stop device that controls a hydraulic drive with several types of hydraulic motors with a minimum number of device elements.

MATERIALS AND METHODS: The design of a hydraulic drive emergency stop device (RUF Patent No. 2522013) installed in the hydraulic system of a tractor with single- and double-acting hydraulic cylinders has been developed. The method in use is a morphological analysis of the structure and distinctive features of existing engineering solutions.

RESULTS: The shutdown unit and the terminal sensor of the emergency stop device compare the value of the hydraulic pump supply with the flow rate in the drain line. At the same time, the device is able to automatically adjust itself to their permissible difference, ensuring that there are no false responses when using double-cavity hydraulic cylinders with one rod. False responses when connecting a single-cavity hydraulic cylinder are prevented by using an additional flow sensor that blocks the shutdown unit. The fluid flow is throttled in the annular gaps between the pistons, sensor and shutdown unit housings; in this case, both pistons are mutually balanced.

CONCLUSIONS: The proposed solution is aimed to eliminate significant oil throw-out form high-pressure hoses and makes it possible to use a single device for controlling the whole tractor hydraulic system. As a result, the weight and cost of the protection device reduce and the hydraulic drive scheme does not complicate significantly. The developed device does not demand additional power supply from the tractor’s on-board power circuit, as it operates with use of hydraulic energy. The protection device is applicable to hydraulic cylinders and hydraulic motors of various sizes thanks to ability of self-adjustment to the greatest difference in flow rate.