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

Hydrostatic drive unit, comprising

• a variable flow pump,
• at least one hydraulic motor,
• a feed pump,
• an adjustable 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 an electric motor, which is controlled by an auxiliary control regarding at least one of its speed and its torque, and an auxiliary pump coupled to the electric motor,
• wherein the outlet of the auxiliary pump is connected to the adjustment unit,
• wherein the supply pressure limiting valve is configured as an electrohydraulic valve,
• wherein an electrical actuator adjusts the supply pressure limiting valve, and
• wherein the electrical actuator is electrically connected to the auxiliary control.

Hydrostatic drive unit, comprising

• a variable flow pump,
• a hydraulic motor,
• a feed pump,
• an adjustable 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 an electric motor, which is controlled by an auxiliary control regarding at least one of its speed and its torque, and an auxiliary pump coupled to the electric motor,
• wherein the outlet of the auxiliary pump is connected to the adjustment unit,
• wherein the electrical auxiliary control is configured as a programmed control which controls the electric motor in such a way that the auxiliary pump connected to the electric motor supplies the adjustment unit with hydraulic energy as needed,
• wherein the need is determined from at least one of electrical signals from the adjustment unit, electrical signals of the drive control overriding the auxiliary control and from electrical signals of operating pressure sensors connected to the outlets of the variable flow pump.

Hydrostatic drive unit, comprising

• a variable flow pump,
• a hydraulic motor,
• a feed pump,
• an adjustable 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 an electric motor, which is controlled by an auxiliary control regarding at least one of its speed and its torque, and an auxiliary pump coupled to the electric motor,
• wherein the outlet of the auxiliary pump is connected to the adjustment unit,
• wherein the supply pressure limiting valve is configured as a proportionally operating electrohydraulic valve,
• wherein the auxiliary control emits a proportional electrical signal to the electrical actuator, and
• wherein the electrical actuator is configured so that the nominal value of the supply pressure is decreased with increasing electric current and the nominal value of the supply pressure is increased with decreasing electric current.