Hitachi Construction Machinery Co., Ltd.

Hitachi, Ltd.

Eiki Izumi

Hiroshi Watanabe

Yukio Aoyagi

Kichio Nakajima

Kazuo Honma

Toichi Hirata

Yasuo Tanaka

Shigetaka Nakamura

Hiroshi Onoue

Genroku Sugiyama

Sotaro Tanaka

Takeshi Yamaguchi

Hideaki Tanaka

Yusuke Kajita

Masakazu Haga

Yusaku Nozawa

Akira Tatsumi

Gen Yasuda

Yasuharu Gotoh

Kuniaki Yoshida

Hitoshi Kagiwada

Shuichi Ichiyama

Tomohiko Yasuoka

Kunihiko Yoshida

Masaaki Uno

Katsuro Abe

Masahiko Shimotori

Tomohiko Yasudi

Load sensing control system for hydraulic machine

Hydraulic drive traveling system

Control system for hydraulic pump

Hydraulic drive system for construction machine

A load sensing hydraulic drive circuit comprises a variable displacement pump delivering fluid to a flow control valve for controlling flow to an actuator. A pump controller controls a delivery rate of the pump such that a differential pressure between a delivery pressure of the pump and a load pressure of the actuator is equal to a first predetermined value. An unloading valve is connected between the pump and the flow control valve for holding the differential pressure between the delivery pressure of the pump and the load pressure of the actuator less than a second predetermined value. A demanded flow rate of the flow control valve is detected and the unloader valve is controlled based on the demanded flow rate such that when the demanded flow rate is small, the second predetermined value is smaller than the first predetermined value, and when the demanded flow rate increases, the second predetermined value becomes larger than the first predetermined value. This allows stable control of the differential pressure for both large and small changes in operation of the flow control valve.

Control system for load sensing hydraulic drive circuit

Described herein is a variable displacement bent axis type hydraulic machine having a center shaft within a casing in a tilted state along with a valve plate and a cylinder block, and provided with a tilt angle sensor mechanism for detecting the tilt angle of the valve plate. For the purpose of improving the resolution in angle detection, the tilt angle sensor mechanism is constituted by a support shaft rotatably supported on a side wall of the casing at a position deviated toward the valve plate from the pivoting point of the center shaft, a rocking lever having one end thereof securely fixed to the support shaft and the other end pivotally supported at one side of the valve plate, and an angle sensor adapted to detect the rotational angle of the support shaft resulting from rocking movement of the rocking lever. This arrangement permits a wider rotational angle for the support shaft to guarantee higher resolution in the tilt angle detection.

Variable displacement bent axis type hydraulic machine

Hydraulic drive system for construction machines

Control system for a load-sensing hydraulic drive circuit comprising; at least one hydraulic pump; hydraulic actuators driven by the hydraulic pump; and a pressure compensated flow control valve between the pump and each of the actuators, for controlling a flow rate of fluid to each actuator in response to a control signal. The control system has first detection means for detecting a differential pressure between the pump delivery pressure and the maximum load pressure; second detection means for detecting the pump delivery pressure; first means for calculating a differential pressure target pump delivery amount Q.DELTA.p to hold the differential pressure constant; second means for calculating an input limiting target pump delivery amount QT based on at least a pressure signal from the second detection means and an input limiting pump function; third means for selecting one of the differential pressure target delivery amount Q.DELTA.p and the input limiting target delivery amount QT as a pump delivery amount target value Qo, and then controlling the pump delivery amount to not exceed the input amount QT; and fourth means for calculating a compensation value Qns to limit a total consumable actuator flow rate based on at least the input amount QT and the differential pressure target delivery amount Q.DELTA.p when the input amount QT is selected by the third means, and then controlling the pressure compensated flow control valve based on the compensation valve Qns.

Control system for load-sensing hydraulic drive circuit

A hydraulic drive system has first and second flow control valves. Each of the control valves has a main valve of the seat valve type with a valve body for controlling communication between an inlet port and an outlet port which are both connected to a main circuit. Each further have a variable restrictor capable of changing an opening degree thereof in response to displacements of the valve body, and a back pressure chamber communcating with the inlet port through the variable restrictor and producing a control pressure to urge the valve body in the valve-closing direction. A pilot valve is connected to a pilot circuit which is connected between the back pressure chamber and the outlet port of the main valve; and an auxiliary valve is connected to the pilot circuit for controlling a differential pressure between the inlet pressure and the outlet pressure of the pilot valve. The auxiliary valve is controlled such that the differential pressure between the inlet pressure and the outlet pressure of the pilot valve has a relationship expressed by a certain equation including constants .alpha., .beta. and .gamma., with respect to a differential pressure between the delivery pressure of a hydraulic pump and the maximum load pressure of the first and second hydraulic actuators, a differential pressure between that maximum load pressure and the self-load pressure of each of the hydraulic actuators, and the self-load pressure, wherein the constants .alpha., .beta. and .gamma. are set to respective predetermined values.

Flow control valves for hydraulic motor system

A control system for controlling input power to hydraulic pumps of a hydraulic system including a prime mover and a plurality of variable displacement hydraulic pumps driven by said prime mover. The control system comprises: a first computing unit for computing, for each of the hydraulic pumps, an input torque control value concerning a distribution of input torques of said hydraulic pumps from a representative pressure obtained on the basis of a discharge pressure of at least one other hydraulic pumps; a second computing unit for determining an input torque for each of the hydraulic pumps on the basis of a corresponding one of the input torque control values determined by the first computing unit; and a third computing unit for determining an object discharge rate of each of the hydraulic pumps from the input torque obtained by the second computing unit and an own discharge pressure of each of the hydraulic pumps.

Control system for controlling input power to variable displacement

Method of and system for controlling hydraulic power system

A control system for a hydraulic circuit having a variable displacement hydraulic pump, and an actuator driven by the pump, in which a pump control controls a displacement volume varying member of the pump based on an operating signal giving a command with respect to the position thereof and a detector signal indicative of the actual position thereof while restricting the operating speed of the member to a level below a predetermined maximum speed. The control system has maximum speed setting device previously setting a first predetermined maximum speed and a second predetermined maximum speed higher than the first predetermined maximum speed for the operating speed of the variable displacement volume varying member and operative to select the first predetermined maximum speed when the direction of operation of the actuator commanded by the operating signal agrees with the actual direction of operation thereof, and select the second predetermined maximum speed when the position of the displacement volume varying member commanded by the operating signal is neutral or when the direction of operation of the actuator commanded by the operating signal is opposite to the actual direction of operation thereof. The pump control is constructed to effect the speed control of the displacement volume varying member based on the first or second predetermined maximum speed selected by the maximum speed setting device.

Control system for hydraulic circuit means

A control system for a hydraulic circuit including at least first and second variable displacement volume type hydraulic pumps, at least first and second hydraulic actuators driven by the pumps, and valves for controlling hydraulic connections between the pumps and the actuators. The control system includes a device for deciding the order of priority of hydraulic connections between the first actuator and the first and second hydraulic pumps and the order of priority of hydraulic connections between the second pump and the first and second actuators. A first sensor is provided for sensing maximization of the displacement volume of the first pump, sensing that the displacement volume of the second pump has become substantially zero. A device decides target displacement volumes of the first and second pumps based on information supplied at least by the priority order deciding device and first and second sensor. When the flow rate of hydraulic fluid supplied to the first actuator is increased, the displacement volume of the second pump is increased from substantially zero after the displacement volume of the first pump is maximized. When the flow rate of hydraulic fluid supplied to the first actuator is reduced, the displacement volume of the first pump is reduced after the displacement volume of the second pump has become substantially zero.

Control system for hydraulic circuit apparatus

A hydraulic power system having a variable displacement hydraulic pump, a hydraulic motor driven by the hydraulic pump for actuating a load, with the pump and motor being connected to constitute a closed hydraulic circuit. A hydraulic servo controls the displacement volume of the pump, and a motor stop arrangement prevents, in its operative position, the motor from rotating. The system includes a control valve responsive to a main line pressure in the closed hydraulic circuit for controlling a hydraulic fluid supply to the hydraulic servo to prevent the main line pressure from substantially exceeding a predetermined level, and a control is responsive to the operation of the hydraulic servo for releasing the motor stop arrangement from the operative position when the hydraulic servo is operating.

Hydraulic power system

Control valve assembly

Growing community of inventors

Ibaraki, Japan

Eiki Izumi