A drive, which permits a lowering in the feed pressure provided by the feed pump and, at the same time, effects a supply to the displacement unit of the drive which meets the demand with regard to pressure and delivery volume. This is achieved in that the displacement unit (5) is supplied with hydraulic energy by an electro-hydraulic supply unit (6) wherein the supply unit (6) comprises a hydraulic reservoir (9) and a non-return valve (18) and is connected to the feed pressure limiting valve (12), which is implemented as an electrically adjustable pressure limiting valve, wherein the hydraulic reservoir (9) is also connected to an electro-hydraulic pressure sensor (10), which outputs the electric signal thereof to an electric auxiliary controller (11), and wherein the electric auxiliary controller (11) drives the feed pressure limiting valve (12). These hydraulic drives are used for example, in self-propelled working machines.

The aim of the invention of for the hydrostatic drive to enable a lowering of the feed pressure provided by the feed pump and, at the same time, to effect a supply of the adjustment unit of the drive that is proper with respect to the pressure and the delivery rate. This aim is achieved in that the adjustment unit (5) of the drive is supplied with hydraulic energy by an electrohydraulic supply unit (6), wherein the supply unit (6) consists of an electric motor (7) and an auxiliary pump (8) coupled thereto and wherein the outlet of the auxiliary pump (8) is connected to the adjustment unit (5) directly or by means of a check valve (18). Hydrostatic drives according to the invention are used, for example, in self-propelled working machines.

The aim of the invention of for the hydrostatic drive to enable a lowering of the feed pressure provided by the feed pump and, at the same time, to effect a supply of the adjustment unit of the drive that is proper with respect to the pressure and the delivery rate. This aim is achieved in that the adjustment unit (5) of the drive is supplied with hydraulic energy by an electrohydraulic supply unit (6), wherein the supply unit (6) consists of an electric motor (7) and an auxiliary pump (8) coupled thereto and wherein the outlet of the auxiliary pump (8) is connected to the adjustment unit (5) directly or by means of a check valve (18). Hydrostatic drives according to the invention are used, for example, in self-propelled working machines.

A vehicle may include an electric motor, a variable displacement hydraulic pump having a swash plate, driven traction members, a transmission operably coupling the electric motor to the driven traction members and to the hydraulic pump, a hydraulic pressure consumer fluidly coupled to an output of the hydraulic pump, a battery to receive energy produced by the electric motor during braking of the driven traction members by the electric motor and a controller. The controller is configured to adjust an angle of the swash plate in response to a sensed state of the battery and braking of the driven traction members.

A vehicle may include an electric motor, a variable displacement hydraulic pump having a swash plate, driven traction members, a transmission operably coupling the electric motor to the driven traction members and to the hydraulic pump, a hydraulic pressure consumer fluidly coupled to an output of the hydraulic pump, a battery to receive energy produced by the electric motor during braking of the driven traction members by the electric motor and a controller. The controller is configured to adjust an angle of the swash plate in response to a sensed state of the battery and braking of the driven traction members.

A pump operation piston biased by a neutral spring mechanism and a larger volume operation spring biased by a larger volume operation spring in a larger volume direction operatively move pump and motor volume adjusting members, respectively, is provided. A first pressure control valve commonly controls supply-discharge of pressure oil that presses the pump operation piston in a first slide direction and the motor operation piston in a smaller volume direction. A second pressure control valve controls supply-discharge of pressure oil that presses the pump operation piston in a second slide direction. Biasing forces of the neutral spring mechanism and the larger volume operation spring are so set that, after the pump operation piston is moved in the first slide direction by a predetermined distance, the motor operation piston starts moving.

A pump operation piston biased by a neutral spring mechanism and a larger volume operation spring biased by a larger volume operation spring in a larger volume direction operatively move pump and motor volume adjusting members, respectively, is provided. A first pressure control valve commonly controls supply-discharge of pressure oil that presses the pump operation piston in a first slide direction and the motor operation piston in a smaller volume direction. A second pressure control valve controls supply-discharge of pressure oil that presses the pump operation piston in a second slide direction. Biasing forces of the neutral spring mechanism and the larger volume operation spring are so set that, after the pump operation piston is moved in the first slide direction by a predetermined distance, the motor operation piston starts moving.

A bi-directional pump connected to a motor by a pair of supply/discharge lines; a regulator changes the bi-directional pump tilting angle; and a controller controls the regulator based on a turning signal outputted from a turning operation valve. At the turning acceleration, at which the signal increases, the controller calculates a motor flow rate passing through the motor and an instruction flow rate determined based on the turning signal. If the instruction flow rate is greater than a reference flow rate obtained by adding a predetermined value to the motor flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the reference flow rate. If the instruction flow rate is not greater than the reference flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the instruction flow rate.

A compact wheel loader having a hydrostatic transmission and two modes of operation. In a normal mode, a demand lever is used to set the engine speed, and displacement of the swash plate of the hydraulic pump of the transmission is set by a hydraulic pilot pressure (Ps) that increases with engine speed, so that the transmission ratio automatically decreases as the engine speed increased. In a creeper mode, the engine is set to operate at a high speed to meet the demand of powered implements of the loader, and the wheel speed is controlled by the demand lever setting the transmission ratio by varying the hydraulic pilot pressure (Ps).

A compact wheel loader having a hydrostatic transmission and two modes of operation. In a normal mode, a demand lever is used to set the engine speed, and displacement of the swash plate of the hydraulic pump of the transmission is set by a hydraulic pilot pressure (Ps) that increases with engine speed, so that the transmission ratio automatically decreases as the engine speed increased. In a creeper mode, the engine is set to operate at a high speed to meet the demand of powered implements of the loader, and the wheel speed is controlled by the demand lever setting the transmission ratio by varying the hydraulic pilot pressure (Ps).