R900345330 Bosch Rexroth Proportional pressure relief valve

Pressure valves of type DBG are pilot-operated pressure relief valves. They are used for system pressure limitation. The pressure relief valves from this series mainly consist of a pilot control valve with electric motor as pressure adjustment element and main valve with main spool insert. The system pressure is set by means of a DC motor (16) with speed reduction transmission (17). The output shaft of the speed reduction transmission (17) turns the cam (14) that tensions the spring (8) via the spring plate (15) and thereby causes a pressure change. The pressure applied to channel A acts on the main spool (1.1). Simultaneously, pressure is applied to the spring-loaded side of the main spool (1.1) and to the pilot poppet (6) in the pilot control valve (7) via the control lines (4) and (5) which are equipped with nozzles (2.1, 2.2) and (3). If the system pressure exceeds the value set at the spring (8), the pilot poppet (6) opens. The signal for this is provided internally - with type DBG..–1X/.. via the control lines (12) and (4) from channel A; or externally – with type DBG..–1X/..X (XY) via the connection (13) and the control line (4). The pilot oil now flows via nozzle (2.1), control line (4), nozzle (2.2) and pilot poppet (6) into the spring chamber. From here, it is fed into the tank, either internally – with type DBG..–1X/.. via control line (10), or externally – with type DBG..–1X/..Y (XY) via control line (11). The compression spring (1.2) acts on the main spool (1.1) in closing direction, i. e. there is a pressure drop between side “A” and the spring-loaded side of the main spool (1.1). The flowing pilot oil volume is determined by the cross-section of the nozzles (2.1, 2.2) and by the pressure drop at the main spool (1.1). When the pressure in “A” has increased by the pressure drop at the main spool (1.1) in relation to the cracking pressure at the pilot poppet (6), the main spool (1.1) opens from “A” to “B”. The oil now flows from channel “A” to channel “B”, whilst the set operating pressure is maintained. The cam position (14) is reported back by the actual value potentiometer (18). Optionally, electric end switches can be installed instead of the actual value potentiometer (18) to limit the min. and max. pressure. For the version with limit switch, the min. adjustment time is 12 seconds for the pressure range pmin to pmax. The adjustment time of 12 seconds facilitates a sensitive start-up of the desired pressure in jog mode. For the version with actual value potentiometer, the min. adjustment time is 0.65 seconds for the pressure range pmin to pmax. The integrated amplifier type VT-VRM1-1 enables program control. With 2 additional pressure switches, the min. and max. pressure can be limited. If the energy supply is interrupted (cable break, fuse defect, short-circuit, etc.), the pressure adjusted at the valve remains unchanged for the version with limit switch.