Search Results

This article describes a design method for improving the mechanical efficiency in a small vane pump, which is driven by an electric motor with a battery for a conventional vehicle. An aim of designing is a decrease in friction torque without decreasing the volumetric efficiency. The influence of two important factors concerning the friction torque, i.e. the dimensions of pump parts such as a cam ring, a rotor and a vane, and the coefficient of friction between the cam contour and the vane tip on the mechanical efficiency is clarified in two stages. In the experimental analysis, the coefficient of friction between the vane and the cam contour in the actual pumps is estimated and the influence of the pump-operating conditions such as oil temperature is also investigated. Furthermore, the relationship between the coefficient of friction and the mechanical efficiency is demonstrated.

This paper deals with a mathematical analysis of pump efficiencies in an internal gear and balanced vane pumps. They are commonly used in current automatic transmissions including a continuously variable transmission. For these pumps, the influence of oil temperature as well as pump-operating pressures and pump speeds is clarified by using mathematical models taking oil temperature into consideration, which are constructed on the basis of actual measured flow and torque data under various pump-operating conditions. For fuel economy in a vehicle, because the pump should be operated under conditions to obtain higher pump efficiencies, it is very important to understand the relationship between the pump efficiencies and the pump-operating conditions.

This paper deals with an advanced electro-hydraulic power steering (EHPS) system compactly integrating a hydraulic pump with an electric motor, a steering gearbox with a center-closed servo valve and an accumulator. In this EHPS system, the hydraulic pump with an electronically controlled motor works only during steering operation. Stopping the hydraulic pump during non-steering operation is extremely effective for reducing energy consumption in power steering because steering operations are infrequent. The EHPS system described in this paper is suitable for pollution free vehicles such as electric vehicle having no engine-driven accessories and has the advantages of reduced power consumption and ease of installation. This EHPS system may be also used for engine-driven vehicles and has been tested on a conventional gasoline engine vehicle with an 810 kg front weight. Test results demonstrate its effectiveness.