A travel drive apparatus for a hydraulic drive work vehicle and control method therefor, the apparatus including: a travel hydraulic pump driven by the power of an engine; a hydraulic motor that receives discharged oil from the travel hydraulic pump and causes the vehicle to travel; a travel changeover valve that receives the discharged oil from the travel hydraulic pump, supplies the discharged oil to the hydraulic motor and discharges return oil from the hydraulic motor to a tank, in which the travel drive apparatus comprises; an accelerator for controlling an engine rotational speed; an operation unit for selecting vehicle forward travel, stop, and reverse travel; the travel changeover valve being adapted for receiving signals from the operation unit, switching the discharge oil supplied from the travel hydraulic pump to the hydraulic motor, and controlling vehicle forward travel, stop and reverse travel; a relief valve that regulates pressure for controlling the hydraulic motor when the vehicle has decelerated, positioned between the travel changeover valve and the hydraulic motor; and a pressurizing unit for raising the set pressure at the relief valve controlling the hydraulic motor when the engine rotational speed is increased, while switching the vehicle from forward travel to reverse travel, or from reverse travel to forward travel, so that the work vehicle may switch over from forward to reverse travel; or vice versa, while exhibiting good acceleration performance.

Travel drive apparatus for hydraulic drive work vehicle and control method therefor

A composite hydraulic system for a work vehicle which has two separate hydraulic circuits. Included in the composite system are three pumps, two of which supply the two circuits on the vehicle. A third pump transfers hydraulic fluid between the two hydraulic circuits. An engine operates all three pumps simultaneously and means are provided whereby the third pump under certain conditions operates as a motor to provide regeneration.

Composite hydraulic system

The invention concerns a hydrostatic drive with a closed hydraulic fluid circuit comprising a hydraulic motor and a variable displacement pump. A feed pump feeds hydraulic fluid under pressure. A control device regulates pressure to a double-sided servo control unit comprising a control piston in a double-sided control cylinder so that the control piston can open a feed line for hydraulic fluid to one side while opening a discharge line on the other. The control device comprises an actuator at the cylinder by means of which force can be exerted onto the piston. A preload element exerts force onto the piston. The pressure generated by the variable displacement pump returns via a return line such that force is exerted in the direction of the piston, if inactive, the piston is maintained by the preload element and the pressure of the variable displacement pump.

Control device for hydrostatic drives

The invention relates to a hydrostatic machine having an actuating device for adjusting a displacement volume of the hydrostatic machine, wherein the actuating device has a return element (3) for actuating a control valve (15) as a function of a position of the actuating device, wherein a valve unit (6) is further provided for adjusting an actuating pressure of the actuating device, which is activated mechanically by means of the return element (3).

Hydrostatic machine having an actuating device comprising a return element for actuating a control valve

A hydrostatic machine having an actuating device for adjusting a displacement volume of the hydrostatic machine is provided. The actuating device has a return element for actuating a control valve as a function of a position of the actuating device. A valve unit is further provided for adjusting an actuating pressure of the actuating device, which is activated mechanically by means of the return element.

Hydrostatic machine having a control device having a return element for controlling a regulating valve

Hydrostatic drive system with a pressure supply line (1), in which pressure medium is conducted at a predetermined pressure, and a consumer (4, 126) of hydraulic energy which is connected to this pressure supply line (1) and in which the ratio of pressure gradient to force on the output side is constant, a control arrangement being provided for the velocity of motion of this consumer, which control arrangement has a displacement machine (61, 92, 100) which can be adjusted with regard to the displacement volume per revolution, is provided with a speed-regulating device (22, 29, 41, 35, 37) and has a rotating shaft, the shaft being connected to a second displacement machine and the control arrangement being hydraulically coupled to the consumer.

Hydrostatic drive system with a consumer of hydraulic energy connected to a pressure supply line

Steuereinrichtung zum steuern der bewegungsgeschwindigkeit eines kolbens

Control arrangement for regulating the speed of movement of a hydrostatic energy consumer is provided in which the ratio between pressure supplied and power on the output side is constant, in particular, a piston capable of sliding in a cylinder connected to a pressure main line, characterized in that an initial hydrostatic displacement machine is connected between the pressure main line and the consumer and is coupled with a second hydrostatic displacement machine on the shaft side, the second hydrostatic displacement machine is adjustable with respect to its displacement volume per revolution and is connected on the one hand to the pressure main line and on the other hand to a chamber carrying a lower pressure, where the adjusting element of this second displacement machine is connected with an r.p.m.-regulating device.

Control arrangements for regulating the speed of a hydrostatic energy consumer

Hydrostatic drive system with a pressure main in which the pressure is regulated to as constant a pressure as possible and into which is passed a delivery flow which is at least equal to the sum of the flows which all the connected loads can accept simultaneously, a hydraulic motor being connected to this pressure main and, to prevent this hydraulic motor from reaching an impermissibly high speed, a safety device which limits the flow passing through being connected in series with the said motor, it preferably being possible to set the safety device to a particular displacement volume per revolution as a function of the setting given to the hydraulic motor.

Backe Wolfgang Prof Dr Ing

Papers

Hydrostatic drive system with a consumer of hydraulic energy connected to a pressure supply line

Steuereinrichtung zum steuern der bewegungsgeschwindigkeit eines kolbens

Control arrangements for regulating the speed of a hydrostatic energy consumer

Hydrostatic drive system with a hydraulic motor connected to a pressure main