Future technology trends of commercial vehicle steering components can be divided into three types. Environment-friendly technologies for environment-related regulations such as reducing emissions and improving fuel efficiency, and technology for driving convenience using electric steering control systems, and safety technology to protect drivers, passengers, nearby vehicles and pedestrians. Heavy duty commercial vehicles require a high-power steering system that used engine-driven hydraulic pump systems (generally used min 120bar, 17Liter/min) compared to passenger cars. In recent technical trend, In order to improve fuel efficiency and realize autonomous driving technology, we designed EHPS and Motor driven electric control actuator with the same structure as C-EPS.
Unlike the HPS system, the power used in the EHPS system is the motor, which rotates the gear pump to generate flow and pressure, and the steering oil is delivered to the ball nut gearbox to operate the power steering system through the pitman arm. The advantage of EHPS is that it does not use the engine drive torque, so it improves fuel efficiency by about 1%, and when the pump is connected in parallel, it can secure the flow rate to the main steering. In this process, it is difficult to realize the active autonomous driving technology of the vehicle itself through the steering angle control separately from the driver's steering intention. Therefore, the motor control device directly connected to the steering wheel is essential, and we can design the actuator system by selecting the package and the required output according to the use conditions. The required steering torque as a general auxiliary steering was about 20 Nm, and the C-EPS type actuator using a worm reducer was manufactured and the performance evaluation was carried out.
In this paper, we describe the construction process of the power steering system for commercial vehicles and the design process of the components.