No abstract

Water hydraulics is developed toward widening application especially in food processing systems. Water hydraulic pushing cylinder system used in meat slicer is recently paid attention by both academic and industrial researchers in Japan. Due to very fast working cycle (0.5-1 seconds per cycle corresponding to 120-60 meat slices per minute), in conventional systems, methods to make a supply pressure track a load pressure for saving energy cannot be used. Supply pressure is normally set around a constant value by a relief valve. Thus, the energy loss in such system is huge because of much surplus supply pressure. This research introduces a novel energy-saving water hydraulic pushing cylinder system in meat slicer, which uses a 2/2 flow control valve for controlling the pressure in high-pressure chamber of the cylinder and 3 On/Off valves mainly for adjusting working direction of the piston rod. This system made the supply pressure nearly equal to the load pressure. As a result, the energy consumption reduced much, the reduction is approximately 50% based on the simulation result and control performance is acceptable.

Recently, the application of water hydraulics has received considerable attention because of its inherent merits such as environmental friendliness, hygiene, washability, high safety against fire hazard, lower running cost, and availability of tap water. However, water hydraulic systems have lower energy efficiencies than oil hydraulic systems, and this prevents its wider application. The water hydraulic variable displacement pump is yet to be made available in the market as it requires advanced technology and high manufacturing cost. Currently, water hydraulic servo/proportional valve systems or independent metering systems incorporating fixed displacement pumps lose large amounts of energy because of surplus pressure and flow rate. This study is aimed at designing a novel water hydraulic transmission technique to improve the efficiency of motor systems. The proposed system uses two two-way, two-position flow control valves for controlling the pressure at the input port of the hydraulic motor by releasing small amounts of surplus flow rate to a reservoir through these valves. The surplus pressure in such systems can be minimized and made equal to the hose pressure drop. The simulation results showed that the proposed transmission system can improve the energy efficiency of the independent metering system and conventional system to approximately twice and thrice the current value, respectively. In this study, the energy losses in the three systems were also analyzed in detail. Pham and Ito, Journal of Advanced Mechanical Design, Systems, and Manufacturing, Vol.10, No.4 (2016)

Low energy efficiency and high installed cost are the two main problems that prevent water hydraulics to be popular in application. This research introduces two novel systems: water hydraulic fluid switching transmission (FST) and pump motor transmission (PMT) that only use cheap ON/OFF valves for lessening the initial cost and reducing the energy consumption; beside, this paper also introduces a conventional servo motor system (SMS) for comparison. Moreover, both FST and PMT systems can recover the kinetic energy of a flywheel in a deceleration process and store it into an accumulator for using in the next working cycle. The experimental results show that the FST system only need from 33.2 to 47.3% of total energy consumption of the SMS to complete a full cycle and even much reducing in PMT system with the reduction from 76.0 to 86.0%. A method to estimate the saved energy stored in the accumulator will be introduced in this study as well and found out that from 8.2 to 11.6% and from 8.7 to 13.7% of the total energy consumption of the FST and PMT systems were recovered. The SMS shows advantage in transient response with the shortest rise time and smallest overshoot while the steady state error is only slightly smaller than the PMT system. The steady state error of FST system is quite large, but it keeps almost same value for all reference velocity; thus, such system is appropriate for applying in high velocity systems. With acceptable velocity response and extremely improving in energy efficiency, the PMT system is promising to replace conventional water hydraulic system in many applications.