Search Results

A novel hydraulic transmission system-Hydraulic Energystorage Transmission System(HESTS) which contains a Hydraulic Continuously Variable Transmission(HCVT) and a flow controllable accumulator is proposed. The power flows of the HESTS has been analyzed. Computer simulations show the potentialities of improving fuel economy of a vehicle with a HESTS. A fuzzy logic controller with two regulating factors is developed to improve the performance of the HESTS with variable loads.

In View of the performance of high output torque moment, good response and continuously variable transmission of hydrostatic transmission, a new concept of Hydraulic Energy Storage Transmission System (HESTS) of city bus was put forward, although the hydraulic-mechanical split power hybrid city bus had run effectively in some cities, such as Copenhagen, Stockholm and Berlin, etc.[1][2]. HESTS was comprised of a variable displacement pump, a variable displacement pump/motor unit, two accumulators and an Electrical Control Unit (ECU). The high pressure accumulator could be controlled to absorb braking energy in hydraulic energy and reuse the stored energy to restart the prime mover or accelerate the vehicle. HESTS could operate in seven modes while the ECU outputs different combined control signals to pump, pump/motor and directional valves. The mathematical model of a HESTS for a city bus was established.

A low cost, anti-pollution pump/motor displacement-varying mechanism was studied in this paper. In the hydrostatic energy storage transmission system(HESTS), a variable pump (motor) unit was used to transfer the energy. A new pump/motor displacement-varying mechanism was obtained based on low price manual manipulating variable pump with high-speed on-off solenoid valves supporting pressure oil. Simulation results showed that the position precision and the ability of following sinusoidal wave signal of the new mechanism met the requirement of the pump/motor unit. Experiment results proved that the new pump/motor displacement-varying mechanism operated precisely and reliably.