For years, gear and gerotor type pumps have been common in Continuously Variable Transmissions (CVT). In their efforts to improve power density and efficiency of the CVT, engineers are showing interest in other pump types that can better cope with the increasing demands. The raising of CVT pressure levels, to enable higher torque and increased variator efficiency, makes that issues like the hydraulic system effectiveness and efficiency have become increasingly important.
Dual stroke vane pumps provide an answer. They basically form two independent, not necessarily identical, pumps that can work at different pressure levels. They enable the design of cost-effective solutions like switch-able or separated high/low pressure circuits within a single pump unit. This offers a better answer to the hydraulic power requirements of the CVT. Furthermore, the vane design is compact and provides high volumetric efficiency at low speeds even without measures like axial pressure compensation.
Understanding CVT requirements, Van Doorne's Transmissie has focussed on the development of the roller vane (RV) pump to avoid the unfavorable start-up performance, the typical wear behavior and the relatively high production cost accompanying traditional vane pump designs. This has led to several built designs for prototype CVT transmissions showing that the RV pump is ready for the market.