Pressure compensating valve, unloading pressure control valve and hydraulically operated device

Abstract

A pressure compensating valve ( 7 ) comprises a main valve ( 20 ) that is operated in such a way as to increase the area of the opening between an inlet port ( 24 ) and an outlet port ( 25 ) by means of pressure acting on a first pressure receiving component ( 21 ), that is also operated in such a way as to reduce the area of the opening by means of pressure acting on a second pressure receiving component ( 22 ) and pressure acting on a third pressure receiving component ( 23 ), and that is designed to allow the pressure (Pa) of the pressured oil flowing to the inlet port ( 24 ) to act on the first pressure receiving component ( 21 ) and the pressure (Pb) of the load driven by the pressured oil flowing from the outlet port ( 25 ) to act on the second pressure receiving component ( 22 ); and control pressure producer ( 7 B) for allowing control pressure (Pe) resulting from a reduction in the pressure (Pa) of the inlet port ( 24 ) to act on the third pressure receiving component ( 23 ). An unloading pressure control valve comprises a main valve ( 100 ) that is constructed in such a way as to operate in the communicating direction by means of the discharge pressure (P P ) of the hydraulic pump ( 1 ) acting on a first pressure receiving component ( 123 ), to operate in the cut-off direction upon load pressure (P LS ) to a second pressure receiving component ( 124 ), and to change the balance of the operating force in each direction by means of control pressure (Pg) acting on a third pressure receiving component ( 125 ); and control pressure producer ( 101 ) for producing the control pressure (Pg). A hydraulically operated device has a variable bleed valve ( 11 ) located in a load pressure sensing passage ( 9 ). This allows pressure compensated characteristics to be changed as desired. The unloading start pressure is also preset so as to improve response in terms of the hydraulic actuators. Energy loss can also be minimized, allowing the rapid start-up of the hydraulic actuators to be controlled, machines can be made smaller, and high precision control can be achieved.

What is claimed is:  
     
         1 . A pressure compensating valve through which pressured oil fed from a hydraulic pump ( 1 ) to a hydraulic actuator ( 5 ) passes, comprising: 
 a main valve ( 20 ), that operates in such a way as to increase an area of an opening between an inlet port ( 24 ) and an outlet port ( 25 ) thereof by means of pressure acting on a first pressure receiving component ( 21 ), and operates in such a way as to reduce the area of the opening by means of pressure acting on a second pressure receiving component ( 22 ) and pressure acting on a third pressure receiving component ( 23 ), and that allows pressure (Pa) of the pressured oil flowing into the inlet port ( 24 ) to act on the first pressure receiving component ( 21 ) and pressure (Pb) of a load driven by the pressured oil flowing out from the outlet port ( 25 ) to act on the second pressure receiving component ( 22 ); and    control pressure producing means ( 7 B) for allowing control pressure (Pe) resulting from a reduction in the pressure (Pa) of the inlet port ( 24 ) to act on the third pressure receiving component ( 23 ).    
     
     
         2 . An unloading pressure control valve for introducing a pressured oil discharged from a hydraulic pump ( 1 ) to a tank according to pressure difference between discharge pressure (P P ) of the hydraulic pump ( 1 ) and load pressure (P LS ) of a hydraulic actuator ( 5 ), comprising: 
 a main valve ( 100 ), that operates toward a communicating direction by means of discharge pressure (P P ) of the hydraulic pump ( 1 ) acting on a first pressure receiving component ( 23 ), to operate toward a cut-off direction by means of load pressure (P LS ) acting on a second pressure receiving component ( 24 ), and that changes balance of an operating force in each of the directions by means of control pressure (Pg) acting on a third pressure receiving component ( 25 ); and    control pressure producing means ( 101 ) for producing the control pressure (Pg).    
     
     
         3 . A hydraulically operated device comprising: 
 a plurality of hydraulic actuators ( 5 ) to which pressured oil discharged from a variable delivery hydraulic pump ( 1 ) is supplied via a pressure compensating valve ( 7 ) and a directional control valve ( 4 );    pressure output means ( 8 ) for outputting pressure (P LS ) to a load pressure sensing passage ( 9 ) according to maximum load pressure among load pressures acting on the actuators ( 5 ); and    pump discharge pressure control means ( 12 ) for controlling discharge pressure of the variable delivery hydraulic pump ( 1 ) based on the pressure (P LS ) output from the pressure output means ( 8 ),    characterized in that a variable bleed valve ( 11 ) is provided in the load pressure sensing passage ( 9 ).    
     
     
         4 . A hydraulically operated device comprising: 
 a pressure compensating valve through which pressured oil that is fed from a hydraulic pump ( 1 ) to a hydraulic actuator ( 5 ) passes; and    an unloading pressure control valve for introducing discharged pressured oil from the hydraulic pump ( 1 ) to a tank according to the pressure difference between discharge pressure (P P ) of the hydraulic pump ( 1 ) and load pressure (P LS ) of the hydraulic actuator ( 5 ),    characterized by further comprising:    a pressure compensating valve ( 7 ), that is operated in such a way as to increase area of an opening between an inlet port ( 24 ) and an outlet port ( 25 ) by means of pressure acting on a first pressure receiving component ( 21 ) for the pressure compensating valve, that is also operated in such a way as to reduce the area of the opening by means of pressure acting on a second pressure receiving component ( 22 ) for the pressure compensating valve and pressure acting on a third pressure receiving component ( 23 ) for the pressure compensating valve, and comprises: 
 a main valve ( 20 ) for the pressure compensating valve for allowing pressure (Pa) of the pressured oil flowing into the inlet port ( 24 ) to act on the first pressure receiving component ( 21 ) for the pressure compensating valve and pressure (Pb) of a load driven by the pressured oil flowing out from the outlet port ( 25 ) to act on the second pressure receiving component ( 22 ) for the pressure compensating valve; and  
 control pressure producing means ( 7 B) for allowing control pressure (Pe) resulting from a reduction in the pressure (Pa) of the inlet port ( 24 ) to act on the third pressure receiving component ( 23 ) for the pressure compensating valve, and an unloading pressure control valve ( 10 ), comprising:  
 a main valve ( 100 ), that operates toward communicating direction by means of discharge pressure (P P ) of the hydraulic pump ( 1 ) acting on a first pressure receiving component ( 123 ) for the unloading pressure control valve, and toward cut-off direction by means of load pressure (P LS ) acting on-a second pressure receiving component ( 124 ) for an unloading pressure control valve, and changes balance of operating forces in each of the directions by means of control pressure (Pg) acting on a third pressure receiving component ( 125 ) for an unloading pressure control valve; and  
 control pressure producing means ( 101 ) for producing the control pressure (Pg).  
   
     
     
         5 . A hydraulically operated device comprising: 
 a plurality of hydraulic actuators ( 5 ) to which pressured oil discharged from a variable delivery hydraulic pump ( 1 ) is supplied via a pressure compensating valve ( 7 ) and a directional control valve ( 4 );    pressure output means ( 8 ) for outputting pressure (P LS ) to a load pressure sensing passage ( 9 ) according to maximum load pressure among load pressures acting on the actuators ( 5 ); and    pump discharge pressure control means ( 12 ) for controlling discharge pressure of the variable delivery hydraulic pump ( 1 ) based on the pressure (P LS ) output from the pressure output means ( 8 ),    characterized by further comprising:    a pressure compensating valve ( 7 ) comprising: 
 a main valve ( 20 ), that operates in such a way as to increase an area of an opening between an inlet port ( 24 ) and an outlet port ( 25 ) thereof by means of pressure acting on a first pressure receiving component ( 21 ), and operates in such a way as to reduce the area of the opening by means of pressure-acting on a second pressure receiving component ( 22 ) and pressure acting on a third pressure receiving component ( 23 ), and that allows pressure (Pa) of the pressured oil flowing into the inlet port ( 24 ) to act on the first pressure receiving component ( 21 ) and pressure (Pb) of a load driven by the pressured oil flowing out from the outlet port ( 25 ) to act on the second pressure receiving component ( 22 ); and  
 control pressure producing means ( 7 B) for allowing control pressure (Pe) resulting from a reduction in the pressure (Pa) of the inlet port ( 24 ) to act on the third pressure receiving component ( 23 ), and  
   a variable bleed valve ( 11 ) provided in the load pressure sensing passage ( 9 ).    
     
     
         6 . A hydraulically operated device comprising: 
 a plurality of hydraulic actuators ( 5 ) to which pressured oil discharged from a variable delivery hydraulic pump ( 1 ) is supplied via a pressure compensating valve ( 7 ) and a directional control valve ( 4 );    pressure output means ( 8 ) for outputting pressure (P LS ) to a load pressure sensing passage ( 9 ) according to maximum load pressure among load pressures acting on the actuators ( 5 );    pump discharge pressure control means ( 12 ) for controlling discharge pressure of the variable delivery hydraulic pump ( 1 ) based on the pressure (P LS ) output from the pressure output means ( 8 ); and    an unloading pressure control valve ( 10 ) for introducing a pressured oil discharged from a hydraulic pump ( 1 ) to a tank according to pressure difference between discharge pressure (P P ) of the hydraulic pump ( 1 ) and load pressure (P LS ) of a hydraulic actuator ( 5 ),    characterized in that    the unloading pressure control valve ( 10 ) comprises: 
 a main valve ( 100 ), that operates toward a communicating direction by means of discharge pressure (P P ) of the hydraulic pump ( 1 ) acting on a first pressure receiving component ( 123 ), to operate toward a cut-off direction by means of load pressure (P LS ) acting on a second pressure receiving component ( 124 ), and that changes balance of an operating force in each of the directions by means of control pressure (Pg) acting on a third pressure receiving component ( 125 ); and  
 control pressure producing means ( 101 ) for producing the control pressure (Pg), and  
   a variable bleed valve ( 11 ) is provided in the load pressure sensing passage ( 9 ).    
     
     
         7 . A hydraulically operated device comprising: 
 a plurality of hydraulic actuators ( 5 ) to which pressured oil discharged from a variable delivery hydraulic pump ( 1 ) is supplied via a pressure compensating valve ( 7 ) and a directional control valve ( 4 );    pressure output means ( 8 ) for outputting pressure (P LS ) to a load pressure sensing passage ( 9 ) according to maximum load pressure among load pressures acting on the actuators ( 5 );    pump discharge pressure control means ( 12 ) for controlling discharge pressure of the variable delivery hydraulic pump ( 1 ) based on the pressure (P LS ) output from the pressure output means ( 8 ); and    an unloading pressure control valve ( 10 ) for introducing a pressured oil discharged from a hydraulic pump ( 1 ) to a tank according to pressure difference between discharge pressure (P P ) of the hydraulic pump ( 1 ) and load pressure (LS) of a hydraulic actuator ( 5 ),    characterized by further comprising:    a pressure compensating valve ( 7 ), that is operated in such a way as to increase area of an opening between an inlet port ( 24 ) and an outlet port ( 25 ) by means of pressure acting on a first pressure receiving component ( 21 ) for the pressure compensating valve, that is also operated in such a way as to reduce the area of the opening by means of pressure acting on a second pressure receiving component ( 22 ) for the pressure compensating valve and pressure acting on a third pressure receiving component ( 23 ) for the pressure compensating valve, and comprises: 
 a main valve ( 20 ) for the pressure compensating valve for allowing pressure (Pa) of the pressured oil flowing into the inlet port ( 24 ) to act on the first pressure receiving component ( 21 ) for the pressure compensating valve and pressure (Pb) of a load driven by the pressured oil flowing out from the outlet port ( 25 ) to act on the second pressure receiving component ( 22 ) for the pressure compensating valve; and  
 control pressure producing means ( 7 B) for allowing control pressure (Pe) resulting from a reduction in the pressure (Pa) of the inlet port ( 24 ) to act on the third pressure receiving component ( 23 ) for the pressure compensating valve;  
 an unloading pressure control valve ( 10 ), comprising:  
   a main valve ( 100 ), that operates toward communicating direction by means of discharge pressure (P P ) of the hydraulic pump ( 1 ) acting on a first pressure receiving component ( 123 ) for the unloading pressure control valve, and toward cut-off direction by means of load pressure (P LS ) acting on a second pressure receiving component ( 124 ) for an unloading pressure control valve, and changes balance of operating forces in each of the directions by means of control pressure (Pg) acting on a third pressure receiving component ( 125 ) for an unloading pressure control valve; and 
 control pressure producing means ( 101 ) for producing the control pressure (Pg.), and  
   a variable bleed valve ( 11 ) provided in the load pressure sensing passage ( 9 ).