Abstract: An electrohydraulic actuation system in which the quantity of fluid being fed to hydraulic actuators under higher load pressure among those of a plurality of electrohydraulic actuators can be prevented from becoming deficient. In the electrohydraulic actuation system (100), a selection valve (141), a two-position valve (142), a spring (143) and a hydraulic cylinder (144) for altering delivery alter delivery of the working oil of a variable delivery hydraulic pump (111) based on the maximum pressure of the working oil being fed to hydraulic motors (122, 132) and the delivery pressure of working pump (111), and pressure gauges (145, 146, 147, 148, 149) and a computer (not shown) alter the rotatim speeds of motors (123, 133) at a substantially same rate for them.

Abstract: A hydraulic drive apparatus in which a hydraulic pressure motor is driven and rotated depending on an operation position entered from an operation lever. An oil pressure control circuit and method which detect pressures of operation oils capable of driving the hydraulic pressure motor to rotate and a pressure of an operation oil supplied from a hydraulic pump to a directional control valve. The oil pressure control circuit varies a set pressure of a main relief valve in a manner that feeds current to an electromagnetic relief valve and varies a set pressure of an electromagnetic relief valve. As a result, the oil pressure control circuit carries out such a control that a pressure of an operation oil received from the hydraulic pump is higher than a pressure of an operation oil for driving and rotating the hydraulic pressure motor by a predetermined pressure.

Abstract: An electrohydraulic actuation system in which the quantity of fluid being fed to hydraulic actuators under higher load pressure among those of a plurality of electrohydraulic actuators can be prevented from becoming deficient. In the electrohydraulic actuation system (100), a selection valve (141), a two-position valve (142), a spring (143) and a hydraulic cylinder (144) for altering delivery alter delivery of the working oil of a variable delivery hydraulic pump (111) based on the maximum pressure of the working oil being fed to hydraulic motors (122, 132) and the delivery pressure of working pump (111), and pressure gauges (145, 146, 147, 148, 149) and a computer (not shown) alter the rotatim speeds of motors (123, 133) at a substantially same rate for them.

Abstract: There is provided an electrohydraulic motor that has a spool valve 110 for switching from each of drive positions (111, 112), in each of which a corresponding one of a main oil passage 230 and a return oil passage 240 is connected to a hydraulic actuator 130, to a neutral position, in which the hydraulic actuator 130 and each of the main oil passage 230 and the return oil passage 240 are disconnected, and vice versa. There is also provided a connection switch valve 140, which is connected to the main oil passage 230 and the return oil passage 240, for changing the connection between the main oil passage 230 and the return oil passage 240 in the neutral position 113. In response to an operation of the spool valve 110, the connection switch valve 140 connects the main oil passage 230 to the return oil passage 240 in the neutral position 113 and also disconnects the main oil passage 230 from the return oil passage 240 in the drive positions (111, 112).

Abstract: There is provided an electrohydraulic motor that has a spool valve 110 for switching from each of drive positions (111, 112), in each of which a corresponding one of a main oil passage 230 and a return oil passage 240 is connected to a hydraulic actuator 130, to a neutral position, in which the hydraulic actuator 130 and each of the main oil passage 230 and the return oil passage 240 are disconnected, and vice versa. There is also provided a connection switch valve 140, which is connected to the main oil passage 230 and the return oil passage 240, for changing the connection between the main oil passage 230 and the return oil passage 240 in the neutral position 113. In response to an operation of the spool valve 110, the connection switch valve 140 connects the main oil passage 230 to the return oil passage 240 in the neutral position 113 and also disconnects the main oil passage 230 from the return oil passage 240 in the drive positions (111, 112).

Abstract: An electro-hydraulic servomotor includes: an electric motor (41) which rotates a drive shaft (51) in response to an inputted signal; a hydraulic motor (60) which rotates an output shaft (61) using hydraulic pressure of operation oil; a first geared shaft (53) rotatable along with the output shaft (61); a second geared shaft (52) threadingly engaged with the drive shaft (51) and meshed with the first geared shaft (53); and a spool (71) axially movable along with the second geared shaft (52) depending on a rotational difference between the drive shaft (51) and the first geared shaft (53), to control supply and discharge of the operation oil to and from the hydraulic motor. (60).

Abstract: A hydraulic system comprises a mechanical brake assembly having a brake piston engageable with an output rotation shaft of a hydraulic motor, a cylindrical casing having the brake piston slidably received therein and a brake spring resiliently urging the brake piston to engage with the output rotation shaft of the hydraulic motor. The brake piston and the cylindrical casing collectively define a main hydraulic chamber held in fluid communication with a release fluid passageway which is communicable with a hydraulic pump and a reservoir tank through a shuttle valve and a directional control valve. The brake piston and the cylindrical casing further collectively define a secondary hydraulic chamber held in fluid communication with the release fluid passageway through a fluid feed/return passageway on which a brake resistance restrictor provided for restricting flow of the working fluid in the fluid feed/return passageway.