Fluid-flow control valve

A fluid-flow control valve device comprising:

• a spool chamber;
• an outlet passage being adapted to fluidly connected to an inlet port of an hydraulic actuator;
• an inlet passage being adapted to fluidly connected to a pump outlet;
• a drain passage being adapted to be fluidly connected to a reservoir;
• a control orifice being fluidly disposed upstream of said outlet passage for variably restricting a flow of working fluid from said inlet passage to said outlet passage;
• a valve spool slidably accommodated in said spool chamber and defining a first pressure chamber and a second pressure chamber in cooperation with an inner peripheral wall of said spool chamber;
• said first pressure chamber to which said inlet passage and said drain passage open to communicate said inlet passage with said outlet passage via said control orifice and to control a size of drain-passage opening in conjunction with one end of said valve spool;
• and said second pressure chamber into which a pressure in said outlet passage is introduced;
• a control spring disposed in said second pressure chamber for biasing said valve spool toward said first pressure chamber;
• said control spring being in cooperation with said valve spool and said control orifice, to feed a required flow rate of working fluid from said inlet passage via said control orifice to said outlet passage and to return a remainder working fluid to said drain passage;
• said control orifice consisting of a main fixed orifice and a sub-orifice being arranged parallel to said main fixed orifice, said sub-orifice being responsive to a pressure in said first pressure chamber to variably meter an opening size of said sub-orifice;
• and
• means for variably adjusting a set spring-bias of said control spring associated said valve spool in response to a change in the pressure in said outlet passage,
• wherein said spring-bias adjustment means comprises a control pressure chamber communicating said second pressure chamber, a movable spring-seat member disposed between said control pressure chamber and said second pressure chamber so that a first pressure surface of said movable spring-seat member facing said second pressure and so that a second pressure surface of said movable spring-seat member facing said control pressure chamber having a pressure-receiving surface area greater than said first pressure surface, and a return spring attached to said movable spring-seat member for biasing said movable spring-seat member toward said control pressure chamber.

A fluid-flow control valve device comprising:

• a spool chamber;
• an outlet passage being adapted to fluidly connected to an inlet port of an hydraulic actuator;
• an inlet passage being adapted to fluidly connected to a pump outlet;
• a drain passage being adapted to be fluidly connected to a reservoir;
• a control orifice being fluidly disposed upstream of said outlet passage for variably restricting a flow of working fluid from said inlet passage to said outlet passage;
• a valve spool slidably accommodated in said spool chamber and defining a first pressure chamber and a second pressure chamber in cooperation with an inner peripheral wall of said spool chamber;
• said first pressure chamber to which said inlet passage and said drain passage open to communicate said inlet passage with said outlet passage via said control orifice and to control a size of drain-passage opening in conjunction with one end of said valve spool;
• and said second pressure chamber into which a pressure in said outlet passage is introduced;
• a control spring disposed in said second pressure chamber for biasing said valve spool toward said first pressure chamber;
• said control spring being in cooperation with said valve spool and said control orifice, to feed a required flow rate of working fluid from said inlet passage via said control orifice to said outlet passage and to return a remainder working fluid to said drain passage;
• said control orifice consisting of a main fixed orifice and a sub-orifice being arranged parallel to said main fixed orifice, said sub-orifice being responsive to a pressure in said first pressure chamber to variably meter an opening size of said sub-orifice;
• and
• means for variably adjusting a set spring-bias of said control spring associated said valve spool in response to a change in the pressure in said outlet passage,
• wherein said spring-bias adjustment means comprises an essentially cylindrical-hollow movable sleeve slidable disposed between an outer periphery of said valve spool and an inner peripheral wall of said spool chamber and having a through-opening for communicating the opening of said inlet passage with the opening of said drain passage, a first pressure surface of said movable sleeve facing to said first pressure chamber and a second pressure surface of said movable sleeve facing to a low-pressure chamber formed opposite to said first pressure chamber, and a return spring attached to said movable sleeve for biasing said movable sleeve toward said first pressure chamber.

A fluid-flow control valve device comprising:

• a spool chamber;
• an outlet passage being adapted to fluidly connected to an inlet port of an hydraulic actuator;
• an inlet passage being adapted to fluidly connected to a pump outlet;
• a drain passage being adapted to be fluidly connected to a reservoir;
• a control orifice being fluidly disposed upstream of said outlet passage for variably restricting a flow of working fluid from said inlet passage to said outlet passage;
• a valve spool slidably accommodated in said spool chamber and defining a first pressure chamber and a second pressure chamber in cooperation with an inner peripheral wall of said spool chamber;
• said first pressure chamber to which said inlet passage and said drain passage open to communicate said inlet passage with said outlet passage via said control orifice and to control a size of drain-passage opening in conjunction with one end of said valve spool;
• and said second pressure chamber into which a pressure in said outlet passage is introduced;
• a control spring disposed in said second pressure chamber for biasing said valve spool toward said first pressure chamber;
• said control spring being in cooperation with said valve spool and said control orifice, to feed a required flow rate of working fluid from said inlet passage via said control orifice to said outlet passage and to return a remainder working fluid to said drain passage;
• said control orifice consisting of a main fixed orifice and a sub-orifice being arranged parallel to said main fixed orifice, said sub-orifice being responsive to a pressure in said first pressure chamber to variably meter an opening size of said sub-orifice;
• and
• means for variably adjusting a set spring-bias of said control spring associated said valve spool in response to a change in the pressure in said outlet passage,
• wherein said valve spool comprises an outer spool having a cylindrical portion and a bottom portion formed with an axial through-opening and an inner spool having a large-diameter portion slidably fitted onto an inner peripheral wall of said cylindrical portion of said outer spool and a small-diameter portion slidably fitted into said axial through-opening, said bottom portion of said outer spool facing to said second pressure chamber, and said control spring acting on said inner spool, and
• wherein said spring-bias adjustment means comprises at least a low-pressure chamber being defined between an inner peripheral wall of said cylindrical portion of said outer spool and an outer peripheral wall of said small-diameter portion of said inner spool, and a return spring disposed between said inner and outer spools for biasing said inner spool toward said first pressure chamber and biasing said outer spool toward said second pressure chamber.