Design of a Hydraulic Control Unit for a Two-Speed Dedicated Electric Vehicle Transmission

Two-speed automatic transmission is one solution to increase the economic efficiency and dynamic performance of battery electric vehicles(BEV).Hydraulic control unit(HCU)is a key component in automatic transmissions,which determines the quality of shifting directly.Based on the structural scheme and shift logic of a two-speed dedicated electric vehicles transmission(2DET)with two wet clutches,we designs a 2DET hydraulic control unit composed of three subsystems:pressure regulating and flow control system,shift operated and control system and cooling and lubrication system.The results of the experiments,including the valve body bench test,transmission bench test and vehicle test,show that the design of hydraulic control unit meets the requirements.

Dual-pump Control Algorithm of Two-speed Powershift Transmissions in Electric Vehicles

A high-speed motor in a drive system causes several challenges to the reliability of the mechanical parts of electric vehicles and leads to issues with noise,vibration and harshness(NVH).Thus,a two-speed powershift transmission is considered an effective way to improve the dynamic,economic and comfort performance of electric vehicles.A newly designed dual-pump hydraulic control system for a two-speed powershift transmission with two wet clutches is presented,in which the mechani-cal oil pump is linearly affected by the vehicle speed and the electric oil pump is controllable.By integrating the dynamic model of the hydraulic system into one of the powertrains with a two-speed transmission,a co-simulation dynamic model is proposed.To satisfy the flow and pressure demand of the hydraulic system,a dual-pump control strategy is presented,in which the electric oil pump is controlled by the mechanical oil pump following the minimum energy consumption principle.The World Light Vehicle Test Procedure(WLTP)cycle simulation results show that the energy consumption of the proposed hydraulic system can be reduced by 58.2%compared to the previous single-pump system developed by the authors with a constant main-line pressure control strategy.On the basis,the best configuration of the two pumps can further reduce the energy consumption of the hydraulic system by 23.2%compared to that of two-oil pumps with preset displacement.

Temperature and structural responses of a single-section utility tunnel throughout fire exposure

In this study,fire tests of four single-section scaled-down utility tunnels were conducted.By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure,the effects on the fire behavior of two different construction methods,cast-in-situ and prefabricated,and of two different materials,ordinary concrete and full lightweight concrete,were explored.The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate,and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete.As the temperature increased,the temperature gradient along the thickness direction of the tunnel became apparent.The maximum temperature difference between the inner and outer wall surfaces was 531.7°C.The highest temperature occurred in the cooling stage after stopping the heating,which provided a reference for the fire protection design and rescue of the utility tunnel.The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm,which was 41.8%larger than that of the cast-in-situ utility tunnel.The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27%and 16.8%,respectively.The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance.