Abstract: A pump is disclosed. The pump may have a housing, a body rotatably disposed within the housing and at least partially defining a plurality of barrels, a plurality of plungers associated with the plurality of barrels, and a swashplate tiltable by a swivel torque to vary a displacement of the plurality of plungers relative to the plurality of barrels. The pump may also have a port plate with an inlet port, a discharge port, and a protrusion. The port plate may be configured to engage an end of the rotatable body. The pump may further have at least one piston disposed within the housing and configured to selectively engage the protrusion of the port plate to rotate the port plate and adjust the swivel torque.

Abstract: A pump is disclosed. The pump may have a housing, a body rotatably disposed within the housing and at least partially defining a plurality of barrels, a plurality of plungers associated with the plurality of barrels, and a swashplate tiltable by a swivel torque to vary a displacement of the plurality of plungers relative to the plurality of barrels. The pump may also have a port plate with an inlet port, a discharge port, and a protrusion. The port plate may be configured to engage an end of the rotatable body. The pump may further have at least one piston disposed within the housing and configured to selectively engage the protrusion of the port plate to rotate the port plate and adjust the swivel torque.

Abstract: An apparatus and method for controlling a discharge pressure of a variable displacement hydraulic pump. The apparatus and method includes a swashplate pivotally attached to the pump, a control servo operable to increase an angle of the swashplate relative to the pump, a biasing servo operable to decrease the angle of the swashplate relative to the pump, a servo valve having an output port hydraulically connected to the control servo, a divertor line having a first end connected to the pump output port and a second end connected to the biasing servo, and means for controlling the servo valve as a function of the discharge pressure of the pump.

Abstract: A method and apparatus for controlling a pump discharge pressure of a variable displacement hydraulic pump having a swashplate, and a servo valve for controlling an angle of inclination of the swashplate. The method and apparatus includes sensing a value of an actual pump discharge pressure, determining a desired control pressure using a first feedback linearization control law, determining a desired servo valve spool position using a second feedback linearization control law, and controlling the value of the actual pump discharge pressure as a function of the first and second feedback linearization control laws.

Abstract: An apparatus and method for controlling a discharge pressure of a variable displacement hydraulic pump. The apparatus and method includes a swashplate pivotally attached to the pump, a valve plate located on the pump to allow hydraulic fluid to enter the pump through an intake port on the valve plate, and to exit the pump through a discharge port on the valve plate, the hydraulic fluid entering and exiting the pump responsively creating a pressure carry over angle &ggr;, a control servo operable to control an angle of the swashplate relative to the pump, a servo valve having an output port hydraulically connected to the control servo and an input port hydraulically connected to the pump output port, and means for controlling the servo valve as a function of the discharge pressure of the pump and responsively balancing a torque induced by the pressure carry over angle &ggr; with a torque generated by a control pressure Pc at the control servo.

Abstract: An electrohydraulic valve control system which enables simultaneous flow and pressure control for operating an implement or other work element associated with a work machine through the use of a single control valve design, the present control system comparing the actual valve output flow rate of the hydraulic fluid flowing through the valve to a desired valve output flow rate and thereafter modifying the input flow rate to the valve based upon the difference between the actual valve output flow rate and the desired valve output flow rate. The desired valve output flow rate is determined based upon the actual load pressure being exerted against the implement or work element and the operator input signal generated by the operator upon activation of an operator input control mechanism used to control the operation of the implement or work element.

Abstract: A piston for a variable displacement axial piston hydraulic pump has a vibration absorber disposed within a chamber of the piston. The vibration absorber includes a vibration absorber mass suspended between a pair of springs. The vibration absorber offsets the piston inertia created from the oscillatory displacement of the pistons for stabilizing the pump.

Abstract: A pump displacement control for a variable displacement pump includes a torque control valve disposed between a variable torque limiter and a force applying device disposed in axial alignment within a common bore. A sleeve and a valve spool are movable relative to each other to establish a first condition communicating discharge pressure into an actuator chamber to move a swashplate toward a minimum displacement position against the bias of a spring or a second condition communicating the actuating chamber with an exhaust passage to allow the spring to move the swashplate toward its maximum displacement position. A torque control piston disposed between opposing springs resiliently bias the valve spool in a direction to establish the second condition when control fluid is directed into a control chamber.

Abstract: A variable displacement axial piston hydraulic unit includes a flat port plate disposed between a stationery head and a rotatable cylinder barrel. An arcuate actuator piston extends from the port plate and is slidably disposed within an arcuate pocket in the head to define an actuator chamber. Similarly, an arcuate biasing piston extends from the port plate and is slidably disposed within an arcuate pocket defining a biasing chamber which continuously communicates with a discharge passage in the head. By selectably rotating the port plate relative to the head, the amount of fluid pressure carryover through TDC and BDC can be varied, thereby changing the swivel torque acting on the swashplate so that the swivel torque can be utilized to actually control the position of the swashplate. The rotational position of the port plate is controlled by controllably introducing pressurized fluid into the actuating chamber.

Abstract: A pump displacement control for a variable displacement pump includes a torque control valve serially disposed between a remotely controllable displacement control valve and a variable torque limiter in axial alignment within a common bore. A displacement control sleeve is disposed within the bore for normally controlling the fluid pressure in an actuating chamber of an actuator connected to a swashplate of the pump when the pump discharge pressure is below a predetermined high pressure. The torque control valve assumes control of pump displacement when the pump discharge pressure exceeds the predetermined high pressure and includes a sleeve and a valve spool movable relative to each other to establish a first condition communicating discharge pressure into the actuator chamber to move the swashplate toward a minimum displacement position or a second condition communicating the actuating chamber with an exhaust passage so that the swashplate is moved toward its maximum displacement position.