Hydraulic system for construction machine
First Claim
1. A hydraulic system for a construction machine, comprising:
- a first traveling motor and a second traveling motor adapted to actuate a pair of travel devices;
actuators adapted to actuate working attachments including a boom and an arm;
a first hydraulic pump and a second hydraulic pump adapted to supply pressure oil for actuating said first and second traveling motors and said actuators;
a first traveling control valve and a second traveling control valve adapted to control amount of pressure oil to be supplied to said first and second traveling motors in accordance with operation of operating means for the first and second traveling motors;
working control valves provided correspondingly to said actuators, said working control valves being classified into a first group including said first traveling control valve and a second group including said second traveling control valve, bleed-off passages in all the control valves belonging to said first group being mutually communicated in series as a first center bypass passage toward an oil tank when all the control valves are in their neutral positions, and bleed-off passages in all the control valves belonging to said second group being mutually communicated in series as a second center bypass passage toward an oil tank when all the control valves are in their neutral positions;
a straight-travel valve adapted to switch each flowing direction of pressure oil discharged from said first and second hydraulic pumps, said straight-travel valve supplying pressure oil discharged from said first and second hydraulic pumps to said first and second bypass passages respectively when all of said traveling motors and said actuators are not in operation, while in a simultaneous operation mode in which the traveling motor and the actuator associated with the traveling control valve and the working control valve belonging to one of said first and second groups are operated simultaneously, supplying pressure oil discharged from one of said first and second hydraulic pumps to both said first and second traveling control valves and further supplying pressure oil discharged from the other hydraulic pump to the working control valve; and
a cut-off valve and an opening valve provided on a downstream side of each of the bleed-off passages in said traveling control valves, said cut-off valve cutting off the center bypass passage located between the traveling control valve and the working control valve associated with the traveling motor and the actuator which are in operation in said simultaneous operation mode of the traveling motor and the actuator being operated simultaneously, said opening valve causing a downstream side of the bleed-off valve in said traveling control valve to be opened to the oil tank.
1 Assignment
0 Petitions
Accused Products
Abstract
According to the invention, traveling bypass cut-off valves are disposed in center bypass passages respectively which are located between traveling direction control valves and working direction control valves disposed downstream of the valves, wherein, when at least a traveling motor and any of working actuators are operated simultaneously, the traveling bypass cut-off valves are switched from neutral position to another position. Thereby, when travel and work by working actuators are performed simultaneously, interference between pressure oil fed to traveling motors and pressure oil fed to the working actuators is to be prevented.
-
Citations
19 Claims
-
1. A hydraulic system for a construction machine, comprising:
-
a first traveling motor and a second traveling motor adapted to actuate a pair of travel devices;
actuators adapted to actuate working attachments including a boom and an arm;
a first hydraulic pump and a second hydraulic pump adapted to supply pressure oil for actuating said first and second traveling motors and said actuators;
a first traveling control valve and a second traveling control valve adapted to control amount of pressure oil to be supplied to said first and second traveling motors in accordance with operation of operating means for the first and second traveling motors;
working control valves provided correspondingly to said actuators, said working control valves being classified into a first group including said first traveling control valve and a second group including said second traveling control valve, bleed-off passages in all the control valves belonging to said first group being mutually communicated in series as a first center bypass passage toward an oil tank when all the control valves are in their neutral positions, and bleed-off passages in all the control valves belonging to said second group being mutually communicated in series as a second center bypass passage toward an oil tank when all the control valves are in their neutral positions;
a straight-travel valve adapted to switch each flowing direction of pressure oil discharged from said first and second hydraulic pumps, said straight-travel valve supplying pressure oil discharged from said first and second hydraulic pumps to said first and second bypass passages respectively when all of said traveling motors and said actuators are not in operation, while in a simultaneous operation mode in which the traveling motor and the actuator associated with the traveling control valve and the working control valve belonging to one of said first and second groups are operated simultaneously, supplying pressure oil discharged from one of said first and second hydraulic pumps to both said first and second traveling control valves and further supplying pressure oil discharged from the other hydraulic pump to the working control valve; and
a cut-off valve and an opening valve provided on a downstream side of each of the bleed-off passages in said traveling control valves, said cut-off valve cutting off the center bypass passage located between the traveling control valve and the working control valve associated with the traveling motor and the actuator which are in operation in said simultaneous operation mode of the traveling motor and the actuator being operated simultaneously, said opening valve causing a downstream side of the bleed-off valve in said traveling control valve to be opened to the oil tank. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
-
-
12. A hydraulic system for a construction machine, comprising:
-
a first traveling motor and a second traveling motor adapted to actuate a pair of travel devices;
actuators adapted to actuate working attachments;
a first hydraulic pump and a second hydraulic pump adapted to supply pressure oil for actuating said traveling motors and said actuators;
a first traveling control valve and a second traveling control valve adapted to control amount of pressure oil to be supplied to said first and second traveling motors in accordance with operation of operating means for the first and second traveling motors, bleed-off passages of said traveling control valves being fully open when said traveling control valves assume their neutral positions, and said bleed-off passages being fully closed when the traveling control valves assume their non-neutral positions;
working control valves provided correspondingly to said actuators, said working control valves being classified into a first group including said first traveling control valve and a second group including said second traveling control valve, bleed-off passages in all the control valves belonging to said first group being mutually communicated in series as a first center bypass passage toward an oil tank when all the control valves are in their neutral positions, and bleed-off passages in all the control valves belonging to said second group being mutually communicated in series as a second center bypass passage toward an oil tank when all the control valves are in their neutral positions;
a straight-travel valve adapted to switch each flowing direction of pressure oil discharged from said first and second hydraulic pumps, said straight-travel valve supplying pressure oil discharged from said first and second hydraulic pumps to said first and second bypass passages respectively when all of said traveling motors and said actuators are not in operation, while in a simultaneous operation mode in which the traveling motor and the actuator associated with the traveling control valve and the working control valve belonging to one of said first and second groups are operated simultaneously, supplying pressure oil discharged from one of said first and second hydraulic pumps to both said first and second traveling control valves and supplying pressure oil discharged from the other hydraulic pump to the working control valve;
an opening valve which, when said first or said second traveling motor is in operation, causes the oil passage located between the traveling control valve associated with the traveling motor in operation and the hydraulic pump for supply of pressure oil to said traveling control valve to be opened to the oil tank; and
means which makes control so that the area of opening of said opening valve becomes smaller with an increase in the amount of operation of operating means for said traveling motor. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
-
Specification