Energy consumption of parallel type hybrid electric vehicle with continuously variable transmission using electric oil pump

This paper presents a design of electrified hydraulic control system for a parallel type hybrid electric vehicle (HEV) with continuously variable transmission (CVT). Considering the hybrid characteristics and CVT feature which requires high line pressure to supply the demanded clamping force, three electrified hydraulic system: (1) 1-MOP+1-EOP, (2) 2-EOP and (3) 1-EOP were proposed and the energy consumption was evaluated. The EOP displacement was designed considering the demanded flow rate and pump efficiency. To investigate the amount of flow, pressure and energy consumption of the electrified hydraulic control system, an AMESim-MATLAB/Simulink co-simulator was developed for the target HEV, which consists of the vehicle powertrain and hydraulic system model. From the simulation results, it was found that 2-EOP system shows the smallest energy consumption while satisfying the required control, lubrication and leakage flow.

I. Introduction

As global warming becomes severe, regulations for environment protection are being strengthened. EU will impose a penalty of 95 per 1g/km when CO2 emission exceeds 95g/km from 2020. The United States announced a penalty of $5.5 for a deficit of 0.1mpg when the fuel consumption does not meet 46.6mpg from 2020 [1]. In response to these regulations, hybrid electric vehicles (HEVs) have been actively developed in automobile industry. Toyota introduced its 4th generation ‘Prius’ in 2016. ‘Prius’ is a power split type which is first commercially successful HEV. The power split type HEV can achieve the improved fuel economy by electric continuously variable function using motor-generator (MG). However, it is mentioned that the power split type has a drawback of low efficiency at high vehicle speed due to the power circulation. In addition, two relatively large size MG are required to implement the power split function.