Havrylenko O. Improvement of the hydraulic engines motion synchronization process

Synchronization of several working bodies operation to ensure the precise movement of one working element (the implementation of multi-engine hydraulic units) is an urgent problem in many industries: pressing and forging equipment, hoist and transport devices, vibration generators, earth-moving machines etc. The efficiency to use the modern technological equipment including complex automated aggregates with a large number of executive bodies greately depends on the ability to predict the properties of the power drivers used in it. The schemes of the hydraulic engines synchronization are analyzed, the factors that influence the motion coordination of the output units in the engines (rods of hydraulic cylinders, rotors of hydraulic engines) are considered. The schemes of hydraulic engines synchronization are characterized by a constant error of the hydraulic engines motion velocity in the steady mode. It is established that at the asymmetrical loading the synchronization error by the position of the output link of the hydraulic engine is proportional to the amount of movement (motion time). According to the results of the analysis, tasks to improve the synchronization process regarding the movement of the hydraulic engines in a multi-engine hydraulic unit are set. The hydraulic drive with two hydraulic cylinders is investigated, the motion velocity of rods is synchronized by the divider of the working fluid flow. Based on the investigated mathematical model, the operation of synchronized hydraulic cylinders in unsteady mode with a sudden change of load on one of the hydraulic cylinders is calculated. The motion velocities of the rods of the hydraulic cylinders and the pressure in the inter-throttle chambers of the flow divider are determined. It is established that during transient operation modes of the drive, caused by a sudden change in the load of the hydraulic cylinders, there are oscillations of pressure in the inter-throttle chambers of the flow divider and, as a result, the synchronization error of the motion velocity of the cylinders rods at the initial stage. The relative pressure drop in the inter-throttle chambers reaches 1, and the relative difference of motion velocities - up to 0.43. In order to improve the accuracy of the hydraulic engines synchronization, a flow divider is proposed, which added extra feedback regarding the pressure drop in the inter-throttle chambers of the divider. Additional feedback is realized through the use of a double-slotted spool-type throttle valve. Based on the conditions of minimum synchronization error, the necessary dependence to change the working gap of the regulated throttles is determined and the recommendations on the profiling of the working gaps of the spool-type throttle are given. It is established through calculation and confirmed in the experiment that the use of adjustable throttles reduces the error regarding the synchronization of movement velocity of the cylinders rods to 0.27, and the pressure drop in the inter-throttle chambers of the flow divider - to 0.53. In the transition process for the velocity and pressure, there are higher-order harmonics, caused by the movement of the spool valve of the double-slot distributor. The presence of higher-order harmonics in pressure and velocity oscillations does not significantly affect the hydraulic motors operation, since the amplitude of oscillations is negligible. The reduction of the velocity synchronization error is due to the simultaneous change of the throttle area, which stabilizes the pressure drop and the adjustable throttle area.