Abstract: A hydraulic drive apparatus includes: an electric motor; a variable displacement pump driven by the electric motor, the pump including a pair of pump ports whose delivery side and suction side are switched with each other in accordance with a rotation direction of the electric motor; a hydraulic actuator connected to the pair of pump ports by a first supply/discharge line and a second supply/discharge line; and a control device that controls the electric motor based on an actuator position command value for the hydraulic actuator. The pump is configured such that a volume of the pump decreases in accordance with increase in a pressure difference between the first supply/discharge line and the second supply/discharge line.

Abstract: A piston accommodated in an internal space of a cylinder and forming a pair of pressure chambers together with the cylinder, the piston being configured to move relative to the cylinder; a first actuator connected to one pair of pressure chambers; a second actuator connected to the other of the pair of pressure chambers; a position detector configured to detect a position of the piston relative to the cylinder; a pressure detector configured to detect a pressure of one pair of pressure chambers; and a controller configured to control the first actuator and the second actuator. The controller controls one of the first actuator and the second actuator that the position detected by the position detector is made close to a target position and controls the other of the first actuator and the second actuator that the pressure detected by the pressure detector is made close to a target pressure.

Abstract: A hydraulic drive apparatus includes: an electric motor; a variable displacement pump driven by the electric motor, the pump including a pair of pump ports whose delivery side and suction side are switched with each other in accordance with a rotation direction of the electric motor; a hydraulic actuator connected to the pair of pump ports by a first supply/discharge line and a second supply/discharge line; and a control device that controls the electric motor based on an actuator position command value for the hydraulic actuator. The pump is configured such that a volume of the pump decreases in accordance with increase in a pressure difference between the first supply/discharge line and the second supply/discharge line.

Abstract: A piston accommodated in an internal space of a cylinder and forming a pair of pressure chambers together with the cylinder, the piston being configured to move relative to the cylinder; a first actuator connected to one pair of pressure chambers; a second actuator connected to the other of the pair of pressure chambers; a position detector configured to detect a position of the piston relative to the cylinder; a pressure detector configured to detect a pressure of one pair of pressure chambers; and a controller configured to control the first actuator and the second actuator. The controller controls one of the first actuator and the second actuator that the position detected by the position detector is made close to a target position and controls the other of the first actuator and the second actuator that the pressure detected by the pressure detector is made close to a target pressure.

Abstract: An end part of a piston on a front edge side is formed so as to have a crowning of a 1.2-order to 2.5-order curve where a length is 10% or more and 80% or less of a length of a cylindrical part and a height is 10% or more and 160% or less of a clearance. An end part of a cylinder block on a front edge side is formed so as to have a crowning of a 1.2-order to 2.5-order curve where a length is 8% or more and 60% or less of the length of a cylindrical part and a height is 12% or more and 125% or less of the clearance.

Abstract: A regulator includes a feedback lever configured to move a compensating sleeve in an axial direction of a compensating spool. The compensating spool and the compensating sleeve form: a self-pressure introduction chamber, into which a self-pressure of a pump is introduced; and a pressure adjuster configured to output a control pressure from the self-pressure introduction chamber to a large-diameter pressure receiver of a servo piston. The compensating sleeve includes a stepped portion, to which a pressure in a direction in which a control spring urges the compensating spool is applied when the self-pressure is introduced into the self-pressure introduction chamber.

Abstract: An end part of a piston on a front edge side is formed so as to have a crowning of a 1.2-order to 2.5-order curve where a length is 10% or more and 80% or less of a length of a cylindrical part and a height is 10% or more and 160% or less of a clearance. An end part of a cylinder block on a front edge side is formed so as to have a crowning of a 1.2-order to 2.5-order curve where a length is 8% or more and 60% or less of the length of a cylindrical part and a height is 12% or more and 125% or less of the clearance.

Abstract: An austenitic stainless steel having excellent corrosion resistance in hot aqueous medium is disclosed. The steel essentially consists by weight ofC: not more than 0.08%Si: 2.5-4.0%Mn: not more than 0.8%P: not more than 0.045%S: not more than 0.005%Cr: 16-25%Ni: 6-20%Cu: 1.5-4.0%N: not more than 0.05%and the balance Fe and unavoidable incidental impurities.