Teijin Seiki Co., Ltd.

Nabtesco Corporation

Ts Corporation

Youji Asano

Nobuaki Shimizu

Haruo Kodama

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 (), a selection valve (), a two-position valve (), a spring () and a hydraulic cylinder () for altering delivery alter delivery of the working oil of a variable delivery hydraulic pump () based on the maximum pressure of the working oil being fed to hydraulic motors () and the delivery pressure of working pump (), and pressure gauges () and a computer (not shown) alter the rotatim speeds of motors () at a substantially same rate for them.

Electro-hydraulic actuation system

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

Electrohydraulic motor and hydraulic driving method

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

Electro-hydraulic servomotor

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. The pressure of the working fluid in the secondary hydraulic chamber is exerted on the brake piston so as to resist the resilient force of the brake spring of the mechanical brake assembly. If the hydraulic system thus constructed is applied, for instance, to a driving apparatus of a crawler vehicle, the hydraulic system is capable of effectively preventing the crawler vehicle from incurring a mighty shock at the time when the crawler vehicle is decelerated and stopped.

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Gifu, Japan

Youji Asano