Abstract: A hydraulic excavator drive system includes: a first pump connected to a head-side chamber of a boom cylinder; and a second pump that supplies hydraulic oil to one of, or both, an arm cylinder and a bucket cylinder. The first pump is driven by an electric motor. The drive system further includes a switching valve that is in a first position at a boom raising operation and in a second position at a vehicle body lifting operation. The first position is a position in which the switching valve brings a rod-side chamber of the boom cylinder into communication with a tank, and the second position is a position in which the switching valve brings the rod-side chamber into communication with the second pump.

Abstract: A hydraulic excavator drive system includes: a first pump that is connected to a head-side chamber of a boom cylinder by a head-side line and to a rod-side chamber of the boom cylinder by a rod-side line to form a closed circuit; and a second pump that supplies hydraulic oil to at least one of an arm cylinder or a bucket cylinder. The hydraulic excavator drive system further includes a switching valve located on a relay line that connects a supply line extending from the second pump to the rod-side line. The switching valve opens the relay line at a boom raising operation and blocks the relay line except at the boom raising operation.

Abstract: A hydraulic excavator drive system (1) includes an arm control valve (31) and an arm switching valve (41). The arm switching valve (41) is connected to an arm pushing supply line (34) by a rod-side line (42) and to an arm crowding supply line (35) by a head-side line (43). The arm switching valve (41) is switched between a neutral position, a recycling position in which the arm switching valve (41) allows the rod-side line (42) to communicate with the head-side line (43) and a second tank line (44), and a meter-out control position in which the arm switching valve (41) allows the head-side line (43) to communicate with the tank line (44). The arm switching valve (41) incorporates therein a check valve (45) that allows a flow from the rod-side line (42) toward the head-side line (43) when the arm switching valve (41) is in the recycling position.

Abstract: A housing of a multi-control valve includes an arm parallel passage, an arm crowding supply passage, an arm pushing supply passage, a boom parallel passage, a boom raising supply passage, and a boom lowering supply passage. The housing further includes: a slide hole; a head-side passage that is branched off from the boom raising supply passage and extends to the slide hole; a rod-side passage that is branched off from the boom lowering supply passage and extends to the slide hole; and a regeneration passage that extends from the slide hole to the arm parallel passage. The slide hole receives a boom sub spool therein. The boom sub spool is either a boom recycling spool or a boom regeneration spool.

Abstract: A hydraulic excavator drive system (1) includes an arm control valve (31) and an arm switching valve (41). The arm switching valve (41) is connected to an arm pushing supply line (34) by a rod-side line (42) and to an arm crowding supply line (35) by a head-side line (43). The arm switching valve (41) is switched between a neutral position, a recycling position in which the arm switching valve (41) allows the rod-side line (42) to communicate with the head-side line (43) and a second tank line (44), and a meter-out control position in which the arm switching valve (41) allows the head-side line (43) to communicate with the tank line (44). The arm switching valve (41) incorporates therein a check valve (45) that allows a flow from the rod-side line (42) toward the head-side line (43) when the arm switching valve (41) is in the recycling position.

Abstract: A hydraulic excavator drive system includes: a first pump connected to a head-side chamber of a boom cylinder; and a second pump that supplies hydraulic oil to at least one of an arm cylinder or a bucket cylinder. The first pump is driven by an electric motor. The drive system further includes: a first switching valve located on a rod-side line; and a second switching valve located on a relay line. The first switching valve opens the rod-side line at a boom raising operation, but blocks the rod-side line except at the boom raising operation. The second switching valve blocks the relay line at the boom raising operation, but opens the relay line at a vehicle body lifting operation.

Abstract: A housing of a multi-control valve includes an arm parallel passage, an arm crowding supply passage, an arm pushing supply passage, a boom parallel passage, a boom raising supply passage, and a boom lowering supply passage. The housing further includes: a slide hole; a head-side passage that is branched off from the boom raising supply passage and extends to the slide hole; a rod-side passage that is branched off from the boom lowering supply passage and extends to the slide hole; and a regeneration passage that extends from the slide hole to the arm parallel passage. The slide hole receives a boom sub spool therein. The boom sub spool is either a boom recycling spool or a boom regeneration spool.

Abstract: A valve unit according to one embodiment includes valve equipment and control circuitry. The valve equipment includes a spool valve and a poppet-type logic valve. The spool valve switches a direction of supply and discharge of hydraulic oil to and from a hydraulic actuator. The logic valve is located between the spool valve and a hydraulic pump. The control circuitry controls the spool valve and the logic valve, such that if a supply flow rate of the hydraulic oil to the hydraulic actuator is less than a predetermined value, an opening area of a meter-in passage of the spool valve is less than an opening area of the logic valve, whereas if the supply flow rate of the hydraulic oil to the hydraulic actuator is greater than the predetermined value, the opening area of the meter-in passage of the spool valve is greater than the opening area of the logic valve.

Abstract: A multi-control valve device includes: a valve block including a plurality of valve holes; a plurality of spools movably housed in the plurality of valve holes in a one-to-one correspondence; one or more attachment parts provided on the valve block; and a plurality of solenoid valves provided on the one or more attachment parts in a one-to-one correspondence with the plurality of spools and each of which reduces a primary pressure, outputs a secondary pressure to a corresponding one of the plurality of spools, and moves the spool. The valve block includes a primary pressure supply passage through which the primary pressure is supplied to each of the plurality of solenoid valves.

Abstract: A directional and flow control valve includes: a housing with a pump port, a first supply/discharge port, a second supply/discharge port, and a tank port, the housing including therein a first pilot chamber, a second pilot chamber, and a third pilot chamber; and a first spool and a second spool, which are independent of each other. The first spool includes a first end surface facing the first pilot chamber and a second end surface facing the third pilot chamber. The second spool includes a first end surface facing the second pilot chamber and a second end surface facing the third pilot chamber. The first spool brings the first supply/discharge port into one of the pump port or the tank port, and the second spool brings the second supply/discharge port into the other one of the pump port or the tank port.

Abstract: A multi-control valve includes: spools that are located side by side in a particular direction; and a housing including slide holes that receive therein the respective spools. The housing includes a first and second pump passages that extend in the particular direction, the first and second pump passages being located at both sides of the spools, respectively. Among the spools, a common spool that is used in common for the first and second pump passages is received in a merging slide hole. The housing includes: a first communication passage that is located at the first pump passage side of the merging slide hole and that extends from the first pump passage to the merging slide hole; and a second communication passage that is located at the second pump passage side of the merging slide hole and that extends from the second pump passage to the merging slide hole.

Abstract: A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: a brake for a slewing motor; and a second solenoid proportional valve connected to a brake release port of the brake by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

Abstract: A hydraulic excavator drive system includes: a first pump connected to a head-side chamber of a boom cylinder; and a second pump that supplies hydraulic oil to at least one of an arm cylinder or a bucket cylinder. The first pump is driven by an electric motor. The drive system further includes: a first switching valve located on a rod-side line; and a second switching valve located on a relay line. The first switching valve opens the rod-side line at a boom raising operation, but blocks the rod-side line except at the boom raising operation. The second switching valve blocks the relay line at the boom raising operation, but opens the relay line at a vehicle body lifting operation.

Abstract: A hydraulic excavator drive system includes: a first pump that is connected to a head-side chamber of a boom cylinder by a head-side line and to a rod-side chamber of the boom cylinder by a rod-side line to form a closed circuit; and a second pump that supplies hydraulic oil to at least one of an arm cylinder or a bucket cylinder. The hydraulic excavator drive system further includes a switching valve located on a relay line that connects a supply line extending from the second pump to the rod-side line. The switching valve opens the relay line at a boom raising operation and blocks the relay line except at the boom raising operation.

Abstract: A hydraulic excavator drive system includes: a first pump connected to a head-side chamber of a boom cylinder; and a second pump that supplies hydraulic oil to one of, or both, an arm cylinder and a bucket cylinder. The first pump is driven by an electric motor. The drive system further includes a switching valve that is in a first position at a boom raising operation and in a second position at a vehicle body lifting operation. The first position is a position in which the switching valve brings a rod-side chamber of the boom cylinder into communication with a tank, and the second position is a position in which the switching valve brings the rod-side chamber into communication with the second pump.

Abstract: A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: a relief valve for the main pump, the relief valve including a pilot port; and a second solenoid proportional valve connected to the pilot port of the relief valve by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

Abstract: A multi-control valve device includes: a valve block including a plurality of valve holes; a plurality of spools movably housed in the plurality of valve holes in a one-to-one correspondence; one or more attachment parts provided on the valve block; and a plurality of solenoid valves provided on the one or more attachment parts in a one-to-one correspondence with the plurality of spools and each of which reduces a primary pressure, outputs a secondary pressure to a corresponding one of the plurality of spools, and moves the spool. The valve block includes a primary pressure supply passage through which the primary pressure is supplied to each of the plurality of solenoid valves.

Abstract: A multi-control valve unit includes a housing with built-in spools that are parallel to each other. The housing includes pilot chambers formed therein, the pilot chambers corresponding to both ends of the spools. Solenoid proportional valves are mounted to the housing, such that the solenoid proportional valves are connected to the respective pilot chambers. A hydraulic pressure generator is mounted to the housing, such that the hydraulic pressure generator is connected to the solenoid proportional valves. The hydraulic pressure generator includes an electric motor and a pump.

Abstract: A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: a relief valve for the main pump, the relief valve including a pilot port; and a second solenoid proportional valve connected to the pilot port of the relief valve by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

Abstract: A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: a brake for a slewing motor; and a second solenoid proportional valve connected to a brake release port of the brake by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.