Basis

Open circuitIn an open circuit the pump delivers oil from the hydraulic tank to the consumer. From the consumer the oil runs back to the hydraulic tank.Fixed displacement pumpFixed displacement motorCylinder2002/09Folie * Basic Training / Travel Hydraulic

With a distributing valve, the hydraulic motor or a cylinder can be triggered two sides.Distributing valve2002/09Fixed displacement pumpFixed displacement motorCylinderOpen circuitFolie * Basic Training / Travel Hydraulic

Closed circuitIn a closed circuit the pump delivers oil to the consumer. From the consumer the oil is running back to the suction side of the pump.The pump can deliver oil in both directions. Variable displacement pumpVariable displacement motor2002/09Folie * Basic Training / Travel Hydraulic

Pressure relief valves protect the closed circuit against to high pressure in both directions.Pressure relief valves2002/09Variable displacement pumpVariable displacement motorClosed circuitFolie * Basic Training / Travel Hydraulic

The leakage from the variable displacement pump and the variable displacement motor flows to the hydraulic tank. 2002/09Pressure relief valvesVariable displacement pumpClosed circuitVariable displacement motorFolie * Basic Training / Travel Hydraulic

Closed circuitThe leakage from the closed circuit will be replaced by fresh oil. The feed pump delivers oil on the low pressure side into the closed circuit.Var. displ. Pump with feed pumpVar. displ. motorfiltercooler2002/09Folie * Basic Training / Travel Hydraulic

Folie * Basic Training / Travel HydraulicHydrostatic drive:Variable displacement pump A4VG .. DAVariable displacement motor A6VM .. DAHydrostatic travel drive

Variable displacement pump A4VG .. DAPressure relief valveFeeding pumpPerformance adjustment screwRegulator valveFeedingpressurerelief valvePressure cut off valveFolie * Basic Training / Travel Hydraulic

Var. Displacement pump - A4VG .. DA2002/02During activated Solenoid 3, the directional valve 4 is pushed down. In This time, the control oil is running to the servo piston. From approx. 6 bar control pressure on, the servo piston is pushing against the pressure springs and the pump is swivelling out.1 Pressure springs2 Servo piston3 Solenoid for drive direction forward4 Directional valveFolie * Basic Training / Travel Hydraulic

Var. displacement pump / DA-RegulationPressure cut-off valveRegulator valveFeeding pumpFeeding pressure relief valveDirectional solenoid valveInching valveFolie * Basic Training / Travel Hydraulic

Var. displacement pump - A4VG .. DA2002/09RPM-depending, the feed pump delivers oil to the regulator valve. Corresponding to this, a certain differential pressure occur on the orifice. The differential pressure effects a force against the spring in the regulator valve and the control pressure. This adjust a certain, RPM-depending control pressure. DA regulator valveFolie * Basic Training / Travel Hydraulic

Servo piston with directional valveInching valveVariable displacement pump A4VG .. DAFolie * Basic Training / Travel Hydraulic

Var. displacement pump - A4VG .. DA2003/09Pressure cut-offThe pressure cut-off limits the maximum pressure in the closed circuit. The high pressure acts through the shuttle valve 4 on the piston 3 and valve 2 against the pressure spring 1. If the high pressure exceeds the adjusted value, the control pressure will be reduced to the tank channel and the variable displacement pump reduces the flow rate.Folie * Basic Training / Travel Hydraulic

2002/09Pressure relief and replenishing valveAt high pressureLow pressure side with replenishingVar. displacement pump - A4VG 71-180 DAFolie * Basic Training / Travel Hydraulic

2002/09High pressure valve at high pressureHigh pressure valve at feedingHigh pressure valve at bypass function (for tow off procedure)Var. displacement pump - A4VG 40 / 56 DAFolie * Basic Training / Travel Hydraulic

Var. displacement motor - A6VM .. DA2002/02During reverse travel, the solenoid valve travel direction is power-suppliedDuring 1. travel range, the solenoid valve 1. travel range is power-supplied. 1 Drive shaft2 Housing3 Rotary group4 Valve travel direction5 Valve 1. travel range6 Control unit7 Discharge valveBig swash angle 25:High torque = high tractive forceLow revolutions = low speedSmall swash angle:Low torque = low tractive forceHigh revolutions = High speedFolie * L 506 - L 510 Fahrhydraulik

During full speed, the control pressure reaches approx. 30 bar. In this time, the control valve is pushed down and the var. displacement motor regulates to Q-min.If the high pressure reaches approx. 220 bar, the control valve is moved up, against the control pressure. In this time, the oil is running from the large side of the servo piston to the tank and the var. displacement motor regulates to Q-max. 2002/09 Var. displacement motor - A6VM .. DAFolie * L 506 - L 510 Fahrhydraulik

Var. displ. motor - A6VM 80 HA1R11 Drive shaft2 Housing3 Rotary group4 Discharge valve 5 Control unit6 Adjusting unit 2002/09Big swash angel 25:High torque = high tractive forceLow revolutions = low speedSmall swash angel:Low torque = low tractive forceHigh revolutions = High speedFolie * Basic Training / Travel Hydraulic

M1Servo pistonControl unitThe discharge valve prevent high temperatures in the closed circuit of the hydrostat.Discharge valveSolonoid valve 1. travel rangeSol. valve travel direction2002/09 Var. displ. motor - A6VM 80 HA1R1Folie * Basic Training / Travel Hydraulic

Var. displ. motor / HP-RegulationThe high pressure works on the ring surface of the regulating valve. After reaching a certain high pressure, the regulating valve will be pushed against the spring.Now the high pressure oil flows to the servo piston surface M1 and the var. displ. motor regulates in direction Q max. At activated Solenoid valve 1. travel range, the regulating valve will be pushed against the spring. The var. displ. motor regulates in direction Q max. 2002/09Folie * Basic Training / Travel Hydraulic

Performance curve / Travel hydraulicPerformance = Flow x PressureCalculation of performancekW =l/min x bar600

kW =200 x 300600

= 100 kWPrinciple:When pressure increases, the flow volumemust decrease, or visa-versa!Pressure is always build up by resistance(Inclination, stock-pile)Tractive force [kN]Speed [km/h]Hydrostatic 3-shift gear boxFolie * Basic Training / Travel Hydraulic