Motivation

In load-sensing (LS) systems with a variable displacement pump, the volume flow of the hydraulic pump is regulated according to the demand of the consumers, with the system pressure being based on the highest load pressure. Energetically unfavorable operating points always occur in the system when several consumers with different load pressures are operated simultaneously.

These losses can be reduced by raising the lower load pressure by increasing the return pressure at the consumer. This reduces the pressure difference to be throttled at the pressure compensators, which represents the relevant power loss. Technically, this solution can be implemented, for example, by increasing the return pressure of the lower-load consumers by using a storage tank. The stored energy can later be made available to the system again.

Project objectives

The basic functionality of the system described was investigated in the project "Reduction of system-related energy losses at pressure compensators in load-sensing systems through series connection of a hydraulic accumulator (reduction of system-related pressure losses)". A simulation model of the system was first set up. The simulations carried out showed that with the selected cycle (90° working cycle of an excavator), a reduction in power loss of up to 24 % is possible compared to the conventional LS system. The calculation does not take into account the efficiency of the components required for regenerative braking.

To ensure that the aforementioned potential for increasing efficiency can be achieved in a real system, the possibility of using the energy stored in the storage tank in the system must be investigated in this project. On the other hand, the 3/2-way proportional valve, which controls the connection of the return line to the storage tank, must be optimized with regard to jerk-free cylinder movement.

Project results
The project results are documented in the final report.

Funding
The IGF project 20950 N / 1 was funded from 01.12.2019 to 28.02.2022 via the AiF as part of the program for the promotion of joint industrial research and development (IGF) by the Federal Ministry of Economics and Climate Protection on the basis of a resolution of the German Bundestag.