Hydrostatic drive having a closed circuit and method for operating the drive

Hydrostatic drive unit, comprising

• a variable flow pump,
• a hydraulic motor,
• a feed pump,
• a supply pressure limiting valve,
• an adjustment unit, and
• a drive control controlling the adjustment unit,
• wherein the adjustment unit is supplied with hydraulic energy by an electrohydraulic supply unit,
• wherein the supply unit comprises at least one hydraulic accumulator and a check valve and is connected to the supply pressure limiting valve, which is configured as an electrically adjustable pressure limiting valve,
• wherein the hydraulic accumulator also is connected to an electrohydraulic pressure sensor, which delivers its electrical signal to an electrical auxiliary control,
• wherein the electrical auxiliary control controls the supply pressure limiting valve,
• wherein the electrical auxiliary control is configured as a program-controlled control system and controls the supply pressure limiting valve so that the supply unit supplies the adjustment unit with hydraulic energy as needed, and
• wherein the demand is determined based on electrical signals from at least one of the adjustment unit, a drive control overriding the auxiliary control and signals from operating pressure sensors connected to outlets of the variable flow pump.

Hydrostatic drive unit, comprising

• a variable flow pump,
• a hydraulic motor,
• a feed pump,
• a supply pressure limiting valve,
• an adjustment unit, and
• a drive control controlling the adjustment unit,
• wherein the adjustment unit is supplied with hydraulic energy by an electrohydraulic supply unit,
• wherein the supply unit comprises at least one hydraulic accumulator and a check valve and is connected to the supply pressure limiting valve, which is configured as an electrically adjustable pressure limiting valve,
• wherein the hydraulic accumulator also is connected to an electrohydraulic pressure sensor, which delivers its electrical signal to an electrical auxiliary control,
• wherein the auxiliary control controls the supply pressure limiting valve electrically so that the supply pressure and therewith also the pressure of the supply unit is increased or decreased in consideration of the supply pressure demand of the variable flow pump in case of a fluctuating power requirement of the adjustment unit,
• wherein the power requirement of the adjustment unit is determined from the signal from the pressure sensor in the auxiliary control, and
• wherein the power requirement of the variable flow pump is determined from signals received from operating pressure sensors.