Experimental Investigation of the Suction Capabilities of an Innovative High Speed External Gear Pump for Electro-Hydraulic Actuated Automotive Transmissions

In this paper, the suction capabilities of an innovative high speed external gear pump have been measured and analyzed for verifying its potential use as a reliable and efficient power unit for electro-hydraulic actuated automotive transmissions. In particular, with the aim to face extremely challenging operating conditions, mainly in terms of rotational speed, this specific type of volumetric machine is designed with both two suction and delivery ports. All the experimental measurements have been performed by using a specifically tailored test bench, equipped with a double Cardan joint and an overdrive, designed for running the pump over a wide range of rotational speeds, spanning between 400 and 7000 rpm, and applying a delivery pressure of about 45 bar, very close to a typical actuation value of a high-performance automotive hydraulic transmission. Furthermore, with the aim to confirm the consistency of the experimental measurements, two identical prototypes of the high speed external gear pump have been tested and compared for two different values of the operating temperature, respectively equal to 40 and 60 °C. First of all, the higher efficiency of the pump primary suction port has been clearly highlighted and evaluated. Moreover, for rotational speed values higher than 4000 rpm, a significant increase of the volumetric flow rate delivered by the pump can be achieved using both the suction ports together and, thus, this particular hydraulic configuration can be considered as a very promising design solution for the entire actuation system.