Variable Displacement Pump A4VG - Group VH A/S

12/52 Bosch Rexroth AG | Mobile Hydraulics A4VG | RE 92 003/05.03DA - Hydraulic Control, Speed RelatedThe DA control is an engine speed-dependent, or automotive,type control system. The built-in DA regulating cartridgegenerates a pilot pressure that is proportional to pump (engine)drive speed. This pilot pressure is directed to the positioningcylinder of the pump by a solenoid actuated 4/3 way directionalvalve. Pump displacement is infinitely variable in each directionof flow, and is influenced by both pump drive speed anddischarge pressure. Flow direction (i.e. machine forward orreverse) is controlled by energizing solenoid a or b.Increasing pump drive speed generates a higher pilot pressurefrom the DA cartridge, with a subsequent increase in pumpflow and/or pressure.Dependent on the selected pump operating characteristics,increasing system pressure (i.e. machine load) causes thepump to swivel back towards a smaller displacement. Engineoverload (anti-stall) protection is achieved by the combinationof this pressure-related pump de-stroking, and the reduction ofpilot pressure as the engine speed droops.Any additional power requirement, such as implementhydraulics, may result in further engine pull down. This causesa further reduction in pilot pressure and therefore pumpdisplacement. Automatic power division and full utilization ofavailable power is thus achived for both the vehicletransmission and the implement hydraulics, with priority givento the implement hydraulics.To provide controllable reduced vehicle speed operation whenhigh engine speeds are required for fast implement hydraulics,various inching options are available.The DA regulating cartridge can also be used in pumps withconventional control devices, such as EP, HW or HD, toprovide an engine anti-stall function, or as a combination ofautomotive and displacement control functions.Application of the DA control is only appropriate on certaintypes of vehicle drive systems, and requires a review of theengine and vehicle parameters to ensure proper application ofthe pump, and safe and efficient machine operation. All DAapplications must therefore be reviewed by a RexrothApplication Engineer.Hydraulic control, speed related,DA-control valve, fixed setting, DA1D2/DA2D2 1 )) size 28 and 250 without port F a1 and F S GraphDirection of rotation – Control – Direction of through put flowSize Solenoid Control Through put Operatingpressure flow pressurea X 2B to A M A28...56b X 1A to B M Ba X 2A to B M B71...250b X 1B to A M Aa X 2A to B M B28...56b X 1B to A M Aa X 2B to A M A71...250b X 1A to B M BSizes 28, 250 Sizes 40...180BM B(size 250)BM BAM AM A (size 250)Aswitching solenoid aView ZX Zswitching solenoid a1M A (size 28)anticlockwiseXanticlockwise1BclockwiseclockwiseX 2 M B (size 250) M B (size 28)X 2switching solenoid bswitching solenoid bTechnical data - solenoidsDA1DA2Voltage 12 V (±20 %) 24 V (±20 %)Zero position V g 0 solenoid solenoidde-energized de-energizedPosition V g max solenoid solenoidenergized energizedNominal resistance (at 20°C) 5,5 Ω 21,7 ΩNominal power 26,2 W 26,5 WCurrent required, minimum effective 1,32 A 0,67 ADuty cycle 100 % 100 %Insulation class see connector design, page 48Standard: Switching solenoid without manual emergencyoperation. Manual emergency operation with resetby valve spring on demand.Direction of rotationanti-clockwise clockwise