Hydrostatic breaking concept

A method for decelerating a hydrostatic transmission with a closed hydraulic fluid circuit, in which a hydraulic pump drivable by a drive engine and a hydraulic motor are arranged and connected fluidly through two working lines, whereas, alternately, depending on the operational mode and the conveying direction of the hydraulic pump, one working line is a low pressure line and the other working line is a high pressure line, and whereby the hydraulic pump as well as the hydraulic motor are adjustable in their respective displacement volumes by means of a control unit, and whereas the hydraulic motor comprises a housing containing a hydrostatic drive mechanism having an inlet and an outlet connected by a connecting line where a pressure control valve is arranged, which can be flown through in direction to the inlet and which pressure control valve opens if the high pressure present at the outlet exceeds a predetermined pressure limit of the pressure relief valve, wherein during coasting operation of the hydrostatic transmission the displacement volume of the hydraulic pump and/or of the hydraulic motor are adjustable by means of the control unit a function of the speed of the drive motor or of the speed of the hydraulic pump,

• whereby the hydrostatic transmission is in a coasting mode and whereby the displacement volume of a hydraulic pump is adjusted such that neither the rotational speed limit of the hydraulic pump nor the rotational speed limit of a drive engine which propulses the hydraulic pump is exceeded, whereas by means of the control unit the displacement volume of a hydraulic motor is adapted for adjusting the braking power and, at the same time, a partial flow of the hydraulic fluid volume flow rate is conducted via a connecting line running from an outlet to an inlet of the drive mechanism of the hydraulic motor, if the high pressure at the outlet of the drive mechanism is exceeding a predetermined pressure limit of a pressure relief valve arranged in connecting line, whereas the high pressure is released by means of the pressure relief valve under dissipation of heat to a low pressure being present at the inlet of the drive mechanism, and during coasting operation, the rotational speed of the drive engine or of the hydraulic pump is held in a range of 5% to 15% below the respective rotational speed limit, whichever is the lower rotational speed limit.

A method for decelerating a hydrostatic transmission with a closed hydraulic fluid circuit, in which a hydraulic pump drivable by a drive engine and a hydraulic motor are arranged and connected fluidly through two working lines, whereas, alternately, depending on the operational mode and the conveying direction of the hydraulic pump, one working line is a low pressure line and the other working line is a high pressure line, and whereby the hydraulic pump as well as the hydraulic motor are adjustable in their respective displacement volumes by means of a control unit, and whereas the hydraulic motor comprises a housing containing a hydrostatic drive mechanism having an inlet and an outlet connected by a connecting line where a pressure control valve is arranged, which can be flown through in direction to the inlet and which pressure control valve opens if the high pressure present at the outlet exceeds a predetermined pressure limit of the pressure relief valve, wherein during coasting operation of the hydrostatic transmission the displacement volume of the hydraulic pump and/or of the hydraulic motor are adjustable by means of the control unit a function of the speed of the drive motor or of the speed of the hydraulic pump,

• whereby the hydrostatic transmission is in a coasting mode and whereby the displacement volume of a hydraulic pump is adjusted such that neither the rotational speed limit of the hydraulic pump nor the rotational speed limit of a drive engine which propulses the hydraulic pump is exceeded, whereas by means of the control unit the displacement volume of a hydraulic motor is adapted for adjusting the braking power and, at the same time, a partial flow of the hydraulic fluid volume flow rate is conducted via a connecting line running from an outlet to an inlet of the drive mechanism of the hydraulic motor, if the high pressure at the outlet of the drive mechanism is exceeding a predetermined pressure limit of a pressure relief valve arranged in connecting line, whereas the high pressure is released by means of the pressure relief valve under dissipation of heat to a low pressure being present at the inlet of the drive mechanism, whereas the pressure limit is adaptable during the coasting operation of the hydrostatic transmission, and wherein the pressure limit being adaptable during the coasting operation of the hydrostatic transmission is in dependency on the rotational speed of the hydraulic pump or of the drive engine propelling the hydraulic pump and/or in dependency on the conveying performance of the hydraulic motor.