Multi-control valve and hydraulic drive device including same

Abstract

A multi-control valve according to the present invention is a hydraulic drive device that controls the flow of working fluid to two ports of a first actuator, said multi-control value comprising: a first control spool that is connected to a first hydraulic pump, a tank, and at least one of the two ports and that controls the flow of the working fluid to said one port; and a second control spool that is connected to the first hydraulic pump, the tank, and the other of the two ports and that controls the flow of the working fluid to the other port, wherein the first and second control spools each independently control the flow rate of the working fluid.

Description

Multi-control valve and hydraulic drive device equipped with same

[0001] The present disclosure relates to a multi-control valve that controls the flow of hydraulic fluid to an actuator having two ports, and a hydraulic drive device including the same.

[0002] Construction machinery such as excavators that are equipped with multiple actuators are equipped with a hydraulic drive device that controls the flow of hydraulic fluid to the actuators. One example of a hydraulic drive device is the hydraulic drive system described in Patent Document 1. In the hydraulic drive system described in Patent Document 1, a meter-in control valve and a meter-out control valve are connected to each actuator. The meter-in control valve controls the flow rate of hydraulic fluid flowing from the pump to the actuator, i.e., the meter-in flow rate, and the meter-out flow rate controls the flow rate of hydraulic fluid discharged from the actuator to a tank, i.e., the meter-out flow rate.

[0003] Japanese Patent Application Laid-Open No. 2022-47627

[0004] The hydraulic drive system of Patent Document 1 controls the flow of hydraulic fluid to an actuator having two ports. That is, in the hydraulic drive system, when a meter-in control valve supplies hydraulic fluid to one of two ports, a meter-out control valve discharges hydraulic fluid from the other port. Also, when the meter-in control valve supplies hydraulic fluid to the other port, the meter-out control valve discharges hydraulic fluid from the other port. Therefore, both the meter-in control valve and the meter-out control valve must be connected to two ports of the actuator. The hydraulic drive system includes, for example, a multi-control valve. Connecting the meter-in control valve and the meter-out control valve to two ports, respectively, complicates the configuration of the passages formed in the multi-control valve. This results in an increase in the size of the multi-control valve.

[0005] Therefore, an object of the present disclosure is to provide a multi-control valve that can be made smaller.

[0006] The multi-control valve of the first disclosure is a multi-control valve that controls the flow of hydraulic fluid to two ports of a first actuator, and includes: a first control spool connected to a first hydraulic pump, a tank, and one of the two ports and controlling the flow of hydraulic fluid to the one port; and a second control spool connected to the first hydraulic pump, the tank, and the other of the two ports and controlling the flow of hydraulic fluid to the other port, wherein the first and second control spools control the flow rates of hydraulic fluid independently of each other.

[0007] According to the first disclosure, the first control spool controls the flow of hydraulic fluid to one port, and the second control spool controls the flow of hydraulic fluid to the other port. Therefore, the passage connecting the first control spool to the other port and the passage connecting the second control spool to the one port can be omitted. This simplifies the configuration of the passages formed in the multi-control valve, allowing for a more compact multi-control valve. Furthermore, the first and second control spools control the flow rate of hydraulic fluid independently of each other. Therefore, the flow rate of hydraulic fluid supplied to and discharged from each port of the actuator can be controlled independently of each other in the multi-control valve, allowing for a more compact design.

[0008] The hydraulic drive device of the present disclosure includes the above-mentioned multi-control valve, which includes a third control spool connected to one of two ports of a second actuator, the second hydraulic pump, and the tank, and controls the flow of hydraulic fluid to the one port of the second actuator, and a fourth control spool connected to the other port of the second actuator, the second hydraulic pump, and the tank, and controls the flow of hydraulic fluid to the other port of the second actuator, the third and fourth control spools controlling the flow rates of hydraulic fluid independently of each other, and a control device, and the multi-control valve further includes a first traveling spool connected to a first traveling motor and the first hydraulic pump, and controls the flow rate of hydraulic fluid supplied to the first traveling motor, and a fourth control spool connected to a second traveling motor and the second hydraulic pump, and controls the flow rate of hydraulic fluid supplied to the second traveling motor. and a second travel spool that controls the flow rate of hydraulic fluid supplied to the first actuator, the first travel motor, and the second travel motor, respectively. The control device controls the openings of the first and second control spools and the first and second travel spools based on an input command and the hydraulic pressures detected by the pressure sensors. When operating the first and second travel spools, if the supply pressure of the first actuator is lower than the supply pressure of the first and second travel motors among the hydraulic pressures detected by the pressure sensors, the control device throttles the openings of the first to fourth control spools, and if the supply pressure of the first and second travel motors is lower than the supply pressure of the first actuator among the hydraulic pressures detected by the pressure sensors, the control device throttles the openings of the first and second travel spools.

[0009] According to the present disclosure, when operating the first and second travel spools, the control device controls the openings of the first to fourth control spools and the first and second travel spools to supply each actuator with a flow rate corresponding to an input command. For example, when the supply pressure of the first and second actuators is low, the control device narrows the openings of the first to fourth control spools. This allows hydraulic fluid to flow more easily through the first and second travel spools, allowing each travel motor to receive a flow rate corresponding to the input command.

[0010] The multi-control valve of the second disclosure is a hydraulic drive device that is connected to a first hydraulic pump and a second hydraulic pump and controls the flow of hydraulic fluid to a first actuator having two ports, and includes a first control spool that controls the flow rate of hydraulic fluid supplied from the first hydraulic pump to one of the two ports, and a second control spool that controls the flow rate of hydraulic fluid discharged from the other of the two ports, and further includes a first sub-spool that controls the flow rate of hydraulic fluid supplied from the second hydraulic pump to the one port, and the first control spool, the first sub-spool, and the second control spool control the flow rates of hydraulic fluid independently of each other.

[0011] According to the second disclosure, a first sub-spool is provided to control the flow rate of hydraulic fluid supplied from the second pump to one of the ports. Therefore, a larger flow rate of hydraulic fluid can be supplied to one of the ports by the first control spool and the first spool. Furthermore, the first control spool, the first sub-spool, and the second control spool control the flow rates of hydraulic fluid independently of each other. Therefore, the flow rate of hydraulic fluid flowing into one of the ports can be controlled independently from the flow rate of hydraulic fluid discharged from the other port. This allows for more accurate control of the flow rate of hydraulic fluid when supplying hydraulic fluid to the actuator via the first control spool and the first sub-spool. Therefore, a larger flow rate of hydraulic fluid can be supplied to the actuator while suppressing an increase in the size of the multi-control valve.

[0012] According to the multi-control valves disclosed in the first and second aspects, the multi-control valve can be made smaller.

[0013] The above and other objects, features, and advantages of the present disclosure will become apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.

[0014] FIG. 1 is a perspective view showing a multi-control valve provided in a hydraulic drive device according to a first embodiment of the present disclosure. FIG. 2 is a circuit diagram showing a hydraulic circuit formed in the multi-control valve. FIG. 3 is a side view of the multi-control valve of FIG. 1 as seen from one side in the width direction. FIG. 4 is a side view of the multi-control valve of FIG. 1 as seen from the other side in the width direction. FIG. 5 is a perspective view of the multi-control valve of FIG. 1 as seen from a different direction. FIG. 6 is a cross-sectional view of the multi-control valve of FIG. 4 taken along line A-A. FIG. 7 is a cross-sectional view of the multi-control valve of FIG. 4 taken along line B-B. FIG. 8 is a cross-sectional view of the multi-control valve of FIG. 4 taken along line C-C. FIG. 9 is a cross-sectional view of the multi-control valve of FIG. 4 taken along line D-D.

[0015] The hydraulic drive system 1 and the multi-control valve 10 according to the embodiment of the present disclosure will be described below with reference to the drawings. Note that the concepts of directions used in the following description are used for convenience of explanation and do not limit the orientation of the configuration of the present disclosure to those directions. Furthermore, the hydraulic drive system 1 and the multi-control valve 10 described below are merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the embodiment, and additions, deletions, and modifications are possible within the scope of the spirit of the present disclosure.

[0016] <Hydraulic Drive System> The hydraulic drive system 1 includes a multi-control valve 10 as shown in FIG. 1 and is installed in a construction machine or the like. The construction machine is, for example, a shovel, and includes multiple actuators 2 to 7 as shown in FIG. 2. In this embodiment, the shovel includes a first travel motor 2, a second travel motor 3, a swing motor 4, a boom cylinder 5, an arm cylinder 6, and a bucket cylinder 7. However, the shovel may include actuators other than the six described above, and the construction machine may also be a wheel loader, a crane, or the like. The first travel motor 2 and the second travel motor 3 operate a pair of crawlers (not shown) provided on the travel device. The swing motor 4 rotates a rotating body (not shown) provided on the travel device. Furthermore, the boom cylinder 5, the arm cylinder 6, and the bucket cylinder 7 operate the boom, the arm, and the bucket (all not shown), respectively. The hydraulic drive system 1 also includes a control device 70 for controlling the multi-control valve 10.

[0017] <Multi-Control Valve> As shown in FIG. 2 , the multi-control valve 10 is, for example, a multi-control valve for a two-pump system, and is connected to two hydraulic pumps 8 and 9. The multi-control valve 10 is supplied with hydraulic fluid from the two hydraulic pumps 8 and 9. The multi-control valve 10 is also connected to a plurality of actuators 2 to 7. Each of the actuators 2 to 7 has two ports 2a to 7a and 2b to 7b. The multi-control valve 10 controls the flow of hydraulic fluid to the two ports 2a to 7a and 2b to 7b in each of the actuators 2 to 7. In other words, the multi-control valve 10 controls the direction (i.e., flow direction) of hydraulic fluid supplied to and discharged from the two ports 2a to 7a and 2b to 7b in each of the actuators 2 to 7, and the flow rate of the hydraulic fluid supplied and discharged. More specifically, the multi-control valve 10 can independently control the flow rates of hydraulic fluid supplied to and discharged from two ports 4a to 7a and two ports 4b to 7b in each of the swing motor 4, boom cylinder 5, arm cylinder 6, and bucket cylinder 7. The multi-control valve 10 configured in this manner includes a valve block 11 and multiple spools 12 to 25, as shown in FIGS. 3 and 4 . In this embodiment, the multi-control valve 10 includes fourteen spools 12 to 25. The number of spools 12 to 25 included in the multi-control valve 10 is not limited to fourteen, and may be thirteen or fewer, or fifteen or more. The multi-control valve 10 also includes multiple pressure sensors 62a to 67a and 62b to 67b. In this embodiment, the multi-control valve 10 also includes a boom regeneration valve element 26.

[0018] As shown in FIGS. 1 and 5 , the valve block 11 is shaped like a rectangular parallelepiped. The valve block 11 has a rectangular shape in a plan view from one side in the height direction. The valve block 11 has various passages 31 to 54, which will be described in detail later. The valve block 11 also has pump ports 31a and 32a on each side surface in the depth direction, which is perpendicular to the height direction. Each of the pump ports 31a and 32a is connected to a hydraulic pump 8 or 9. The valve block 11 also has two tank ports 33a and 33b and four connection ports 35a, 36a, 38a, and 39a on its top surface on one side in the height direction. The tank 30 is connected to the tank port 33a. The valve block 11 also has a plurality of connection ports 41a, 41b, 43a, 45a, 45b, 47a, 49a, 50a, 52a, and 53a on each side surface in the depth direction. The connection ports 41a, 41b, 43a, 45a, 45b, 47a, 49a, 50a, 52a, and 53a are connected to the ports 2a to 7a and 2b to 7b of the plurality of actuators 2 to 7, respectively.

[0019] 3 and 4 control the flow of hydraulic fluid to each of the actuators 2 to 7. Each of the spools 12 to 24, which will be described in more detail, is associated with a corresponding one of the actuators 2 to 7 and controls the flow of hydraulic fluid supplied to and discharged from the corresponding actuator 2 to 7. In this embodiment, the spools 12 to 25 include a first traveling spool 12, a second traveling spool 13, a first boom head side spool 14, a second boom head side spool 15, a boom rod side spool 16, a first arm head side spool 17, a second arm head side spool 18, a first arm rod side spool 19, a second arm rod side spool 20, a bucket head side spool 21, a bucket rod side spool 22, a first swing spool 23, and a second swing spool 24. Each of the spools 12 to 24 is slidably inserted into the valve block 11. In this embodiment, the spools 12 to 24 are inserted into the valve block 11 so as to be slidable in the width direction, which is an example of a first direction. The width direction is a direction perpendicular to the height direction and the depth direction. The spools 12 to 25 control the flow of hydraulic fluid by stroking. In addition to the spools 12 to 24, a confluence spool 25 is also inserted into the valve block 11 so as to be slidable in the width direction.

[0020] As shown in FIGS. 1 and 5, the multi-control valve 10 also includes a plurality of solenoid valves 12a to 24a and 12b to 25b. The solenoid valves 12a to 24a and 12b to 25b are provided in the valve block 11 in correspondence with the spools 12 to 25 (see also FIGS. 3 and 4, for example). The solenoid valves 12a to 24a and 12b to 25b each output a pilot pressure to the corresponding spool 12 to 25 in response to an input signal. This causes the solenoid valves 12a to 24a and 12b to 25b to stroke the corresponding spool 12 to 25. The multi-control valve 10 configured in this manner includes a hydraulic circuit 10a as follows:

[0021] <Hydraulic Circuit in Multi-Control Valve> The hydraulic circuit 10a in the multi-control valve 10 will be described below with reference to FIG. 2. The valve block 11 has two main passages 31, 32 and a tank passage 33. Each main passage 31, 32 has a pump port 31a, 32a. The first main passage 31 is connected to the first hydraulic pump 8 via a first hydraulic pump port 31a, and the second main passage 32 is connected to the second hydraulic pump 9 via a second hydraulic pump port 32a. The first main passage 31 is connected to the spools 12, 14, 16, 18, 20, 21, and 22 in parallel. The second main passage 32 is connected to the spools 13, 15, 17, 19, 23, and 24 in parallel. The tank passage 33 is connected to the tank 30 via tank ports 33a and 33b (see FIG. 1). Each of the spools 12 to 25 will be described in more detail below.

[0022] [Travel Spool] As described above, the first travel spool 12 is connected to the first hydraulic pump 8. More specifically, the first travel spool 12 is connected to the first main passage 31 via the first travel passage 34, in which the check valve 34a is located, and is further connected to the first hydraulic pump 8 via the first main passage 31. The first travel spool 12 is also connected to the tank passage 33. The first travel spool 12 controls the flow of hydraulic fluid supplied to and discharged from the first travel motor 2. More specifically, the first travel motor 2 has a first supply / discharge port 2a and a second supply / discharge port 2b. The first travel spool 12 is connected to the first supply / discharge port 2a via the first supply / discharge passage 35, and to the second supply / discharge port 2b via the second supply / discharge passage 36. The first traveling spool 12 receives pilot pressures output from the solenoid valves 12a, 12b in opposing directions and strokes to a position corresponding to the pilot pressures of the solenoid valves 12a, 12b. By stroking, the first traveling spool 12 switches the connection destinations of the supply / discharge ports 2a, 2b to the first main passage 31 and the tank passage 33, respectively, and adjusts the opening degree of the first traveling spool 12. In this way, the first traveling spool 12 controls the flow of hydraulic fluid to the first supply / discharge port 2a and the second supply / discharge port 2b of the first traveling motor 2.

[0023] As described above, the second traveling spool 13 is connected to the second hydraulic pump 9. More specifically, the second traveling spool 13 is connected to the second main passage 32 via the second traveling passage 37, in which the check valve 37a is located, and is further connected to the second hydraulic pump 9 via the second main passage 32. The second traveling spool 13 is also connected to the tank passage 33. The second traveling spool 13 controls the flow of hydraulic fluid supplied to and discharged from the second traveling motor 3. More specifically, the second traveling motor 3 has a first supply / discharge port 3a and a second supply / discharge port 3b. The second traveling spool 13 is connected to the first supply / discharge port 3a via the first supply / discharge passage 38, and to the second supply / discharge port 3b via the second supply / discharge passage 39. The second traveling spool 13 receives pilot pressures output from the solenoid valves 13a, 13b in opposing directions and strokes to a position corresponding to the pilot pressures of the solenoid valves 13a, 13b. By stroking, the second traveling spool 13 switches the connection destinations of the supply / discharge ports 3a, 3b to the second main passage 32 and the tank passage 33, respectively, and adjusts the opening degree of the second traveling spool 13. In this way, the second traveling spool 13 controls the flow of hydraulic fluid to the first supply / discharge port 3a and the second supply / discharge port 3b of the second traveling motor 3.

[0024] [Boom Spool] As described above, the first boom head-side spool 14, which is an example of a first control spool, is connected to the first hydraulic pump 8. More specifically, the first boom head-side spool 14 is connected to the first main passage 31 via the first boom passage 40 in which the check valve 40a is located, and is further connected to the first hydraulic pump 8 via the first main passage 31. The first boom head-side spool 14 is also connected to the tank 30 via a tank passage 33. The first boom head-side spool 14 controls the flow of hydraulic fluid to the head-side port 5a of the boom cylinder 5. The boom cylinder 5, which is an example of a first actuator, has two ports 5a and 5b, and the head-side port 5a is, for example, one port 5a of the two ports 5a and 5b. More specifically, the first boom head-side spool 14 is connected to the head-side port 5a via the head-side passage 41. The first boom head-side spool 14 receives pilot pressures output from the solenoid valves 14a, 14b in opposing directions and strokes to a position corresponding to the pilot pressures of the solenoid valves 14a, 14b. By stroking, the first boom head-side spool 14 switches the connection of the head-side port 5a between the first main passage 31 and the tank passage 33. This allows the first boom head-side spool 14 to supply hydraulic fluid from the first hydraulic pump 8 to the head-side port 5a of the boom cylinder 5, or to discharge hydraulic fluid from the head-side port 5a of the boom cylinder 5 to the tank 30. The first boom head-side spool 14 also adjusts its opening. This allows the first boom head-side spool 14 to control the flow rate of hydraulic fluid supplied to or discharged from the head-side port 5a of the boom cylinder 5.

[0025] As described above, the second boom head side spool 15, which is an example of a first sub-spool, is connected to the second hydraulic pump 9. More specifically, the second boom head side spool 15 is connected to the second main passage 32 via the second boom passage 42 in which the check valve 42a is disposed, and is connected to the second hydraulic pump 9 via the second main passage 32. The second boom head side spool 15 is also connected to the tank 30 via the tank passage 33. The second boom head side spool 15 controls the flow of hydraulic fluid to the head side port 5a of the boom cylinder 5. More specifically, the second boom head side spool 15 is connected in parallel to the first boom head side spool 14 via the head side passage 41, which is an example of a first passage. The second boom head side spool 15 is also connected to the head side port 5a via the head side passage 41. The second boom head-side spool 15 receives pilot pressures output from the solenoid valves 15a, 15b in opposing directions and strokes to a position corresponding to the pilot pressures of the solenoid valves 15a, 15b. By stroking, the second boom head-side spool 15 switches the connection destination of the head-side port 5a between the second main passage 32 and the tank passage 33, and adjusts the aperture of the second boom head-side spool 15. This allows the second boom head-side spool 15 to supply hydraulic fluid from the second hydraulic pump 9 to the head-side port 5a of the boom cylinder 5, or to discharge hydraulic fluid from the head-side port 5a of the boom cylinder 5 to the tank 30. The second boom head-side spool 15 also adjusts its aperture. This allows the second boom head-side spool 15 to control the flow rate of hydraulic fluid supplied to or discharged from the head-side port 5a of the boom cylinder 5.

[0026] As described above, the boom rod side spool 16, which is an example of a second control spool, is connected to the first hydraulic pump 8. Explaining in more detail, the boom rod side spool 16 is connected to the first main passage 31 via the first boom passage 40, and is further connected to the first hydraulic pump 8 via the first main passage 31. Explaining in even more detail, the boom rod side spool 16 is connected to the downstream side of the check valve 40a in parallel with the first boom head side spool 14, and is connected to the first main passage 31 together with the first boom head side spool 14 via the check valve 40a. The boom rod side spool 16 is also connected to the tank 30 via a tank passage 33. The boom rod side spool 16 controls the flow of hydraulic fluid to the rod side port 5b, which is the other port 5b of the boom cylinder 5. Explaining in more detail, the boom rod side spool 16 is connected to the rod side port 5b via a rod side passage 43. The boom rod-side spool 16 receives pilot pressures output from the solenoid valves 16a, 16b in opposing directions, and strokes to a position corresponding to the pilot pressures of the solenoid valves 16a, 16b. By stroking, the boom rod-side spool 16 switches the connection destination of the rod-side port 5b to either the first main passage 31 or the tank passage 33. This allows the boom rod-side spool 16 to supply hydraulic fluid from the first hydraulic pump 8 to the rod-side port 5b of the boom cylinder 5, or to discharge hydraulic fluid from the rod-side port 5b of the boom cylinder 5 to the tank 30. The boom rod-side spool 16 also adjusts its opening. This allows the boom rod-side spool 16 to control the flow rate of hydraulic fluid supplied to or discharged from the rod-side port 5b of the boom cylinder 5.

[0027] The spools 14 to 16 configured in this manner stroke independently of one another. Therefore, the spools 14 to 16 can independently control the flow of hydraulic fluid supplied to and discharged from the head-side port 5a and the rod-side port 5b of the boom cylinder 5. That is, the spools 14 to 16 can independently control the meter-in flow rate and the meter-out flow rate for each of the head-side port 5a and the rod-side port 5b of the boom cylinder 5. Furthermore, by stroking both of the boom head-side spools 14, 15, hydraulic fluid from the second hydraulic pump 9 can be supplied to the head-side port 5a of the boom cylinder 5 in addition to hydraulic fluid from the first hydraulic pump 8. Therefore, by stroking both of the spools 14, 15, a greater flow rate can be supplied to the head-side port 5a of the boom cylinder 5 than when only one spool 14 is stroked.

[0028] [Arm Spool] The first arm head-side spool 17, which is an example of a third control spool, is connected to the second hydraulic pump 9. More specifically, the first arm head-side spool 17 is connected to the second main passage 32 via a first arm passage 44 in which a check valve 44a is interposed, and is further connected to the second hydraulic pump 9 via the second main passage 32. The first arm head-side spool 17 is also connected to the tank 30 via a tank passage 33. The first arm head-side spool 17 controls the flow of hydraulic fluid supplied to and discharged from the head-side port 6a of the arm cylinder 6. The arm cylinder 6, which is an example of a second actuator, has two ports 6a, 6b, and the head-side port 6a is one of the two ports 6a, 6b. More specifically, the first arm head-side spool 17 is connected to the head-side port 6a via a head-side passage 45. The first arm head-side spool 17 receives pilot pressures output from the solenoid valves 17a, 17b in opposing directions, and strokes to a position corresponding to the pilot pressures of the solenoid valves 17a, 17b. By stroking, the first arm head-side spool 17 switches the connection destination of the head-side port 6a to either the second main passage 32 or the tank passage 33. This allows the first arm head-side spool 17 to supply hydraulic fluid from the second hydraulic pump 9 to the head-side port 6a of the arm cylinder 6, or to discharge hydraulic fluid from the head-side port 6a of the arm cylinder 6 to the tank 30. The first arm head-side spool 17 also adjusts its opening. This allows the first arm head-side spool 17 to control the flow rate of hydraulic fluid supplied to or discharged from the head-side port 6a of the arm cylinder 6.

[0029] As described above, the second arm head-side spool 18, which is an example of a second sub-spool, is connected to the first hydraulic pump 8. More specifically, the second arm head-side spool 18 is connected to the first main passage 31 via a second arm passage 46 in which a check valve 46a is disposed, and is further connected to the first hydraulic pump 8 via the first main passage 31. The second arm head-side spool 18 is also connected to the tank 30 via a tank passage 33. The second arm head-side spool 18 controls the flow of hydraulic fluid to the head-side port 6a of the arm cylinder 6. More specifically, the second arm head-side spool 18 is connected in parallel to the first arm head-side spool 17 via a head-side passage 45, which is an example of a second passage. The second arm head-side spool 18 is also connected to the head-side port 6a via the head-side passage 45. The second arm head-side spool 18 receives pilot pressures output from the solenoid valves 18a, 18b in opposing directions, and strokes to a position corresponding to the pilot pressures of the solenoid valves 18a, 18b. By stroking, the second arm head-side spool 18 switches the connection of the head-side port 6a to either the first main passage 31 or the tank passage 33. This allows the second arm head-side spool 18 to supply hydraulic fluid from the first hydraulic pump 8 to the head-side port 6a of the arm cylinder 6, or to discharge hydraulic fluid from the head-side port 6a of the arm cylinder 6 to the tank 30. The second arm head-side spool 18 also adjusts its opening. This controls the flow rate of hydraulic fluid supplied to or discharged from the head-side port 6a of the arm cylinder 6.

[0030] As described above, the first arm rod side spool 19, which is an example of a fourth control spool, is connected to the second hydraulic pump 9. More specifically, the first arm rod side spool 19 is connected to the second main passage 32 via the first arm passage 44, and further connected to the second hydraulic pump 9 via the second main passage 32. More specifically, the first arm rod side spool 19 is connected to the downstream side of the check valve 44a in the first arm passage 44 so as to be parallel to the first arm head side spool 17, and is connected to the second main passage 32 together with the first arm head side spool 17 via the check valve 44a. The first arm rod side spool 19 is also connected to the tank 30 via a tank passage 33. The first arm rod side spool 19 controls the flow of hydraulic fluid to the rod side port 6b, which is the other port 6b of the arm cylinder 6. More specifically, the first arm rod side spool 19 is connected to the rod side port 6b via a rod side passage 47. The first arm rod-side spool 19 receives pilot pressures output from the solenoid valves 19a, 19b in opposing directions, and strokes to a position corresponding to the pilot pressures of the solenoid valves 19a, 19b. By stroking, the first arm rod-side spool 19 switches the connection destination of the rod-side port 6b to either the second main passage 32 or the tank passage 33. This allows the first arm rod-side spool 19 to supply hydraulic fluid from the second hydraulic pump 9 to the rod-side port 6b of the arm cylinder 6, or to discharge hydraulic fluid from the rod-side port 6b of the arm cylinder 6 to the tank 30. The first arm rod-side spool 19 also adjusts its opening. This allows the first arm rod-side spool 19 to control the flow of hydraulic fluid supplied to or discharged from the rod-side port 6b of the arm cylinder 6.

[0031] The second arm rod side spool 20, which is an example of a third sub-spool, is connected to the first hydraulic pump 8, as described above. Explaining in more detail, the second arm rod side spool 20 is connected to the first main passage 31 via the second arm passage 46, and is further connected to the first hydraulic pump 8 via the first main passage 31. Explaining in even more detail, the second arm rod side spool 20 is connected to the downstream side of the check valve 46 a in parallel with the second arm head side spool 18 in the second arm passage 46, and is connected to the first main passage 31 together with the second arm head side spool 18 via the check valve 46 a. Furthermore, the second arm rod side spool 20 is connected to the tank 30 via the tank passage 33. Furthermore, the second arm rod side spool 20 controls the flow of hydraulic fluid to the rod side port 6 b of the arm cylinder 6. More specifically, the second-arm rod-side spool 20 is connected in parallel to the first-arm rod-side spool 19 through a rod-side passage 47, which is an example of a third passage. The second-arm rod-side spool 20 is connected to the rod-side port 6b via the rod-side passage 47. The second-arm rod-side spool 20 receives pilot pressures output from the solenoid valves 20a, 20b in opposing directions and strokes to a position corresponding to the pilot pressures of the solenoid valves 20a, 20b. By stroking, the second-arm rod-side spool 20 switches the connection of the rod-side port 6b to either the first main passage 31 or the tank passage 33. This allows the second-arm rod-side spool 20 to supply hydraulic fluid from the first hydraulic pump 8 to the rod-side port 6b of the arm cylinder 6 and to discharge hydraulic fluid from the rod-side port 6b of the arm cylinder 6 to the tank 30. The second-arm rod-side spool 20 also adjusts its opening. As a result, the second arm rod side spool 20 controls the flow of hydraulic fluid supplied to and discharged from the rod side port 6 b of the arm cylinder 6 .

[0032] The spools 17-20 configured in this manner stroke independently of each other. Therefore, the spools 17-20 can independently control the flow of hydraulic fluid supplied to and discharged from the head side port 6a and the rod side port 6b of the arm cylinder 6. That is, the spools 17-20 can independently control the meter-in flow rate and the meter-out flow rate for each of the head side port 6a and the rod side port 6b of the arm cylinder 6. Furthermore, by stroking both of the arm head side spools 17, 18, hydraulic fluid from the first hydraulic pump 8 can be supplied to the head side port 6a in addition to hydraulic fluid from the second hydraulic pump 9. Therefore, the arm head side spools 17, 18 can supply a larger flow rate to the head side port 6a of the arm cylinder 6 than when only one spool 17 is stroked. The same applies to the arm rod side spools 20, 19.

[0033] [Bucket Spool] As described above, the bucket head-side spool 21 is connected to the first hydraulic pump 8. Explaining in more detail, the bucket head-side spool 21 is connected to the first main passage 31 via a bucket passage 48 in which a check valve 48a is disposed, and is further connected to the first hydraulic pump 8 via the first main passage 31. The bucket head-side spool 21 is also connected to the tank 30 via a tank passage 33. The bucket head-side spool 21 controls the flow of hydraulic fluid to the head-side port 7a of the bucket cylinder 7. The bucket cylinder 7 has two ports 7a, 7b, and the head-side port 7a is one of the two ports 7a, 7b. Explaining in more detail, the bucket head-side spool 21 is connected to the head-side port 7a via a head-side passage 49. The bucket head-side spool 21 receives pilot pressures output from the solenoid valves 21a, 21b in opposing directions, and strokes to a position corresponding to the pilot pressures of the solenoid valves 21a, 21b. By stroking, the bucket head-side spool 21 switches the connection destination of the head-side port 7a to either the first main passage 31 or the tank passage 33. This allows the bucket head-side spool 21 to supply hydraulic fluid from the first hydraulic pump 8 to the head-side port 7a of the bucket cylinder 7, or to discharge hydraulic fluid from the head-side port 7a of the bucket cylinder 7 to the tank 30. The bucket head-side spool 21 also adjusts its opening. This allows the bucket head-side spool 21 to control the flow rate of hydraulic fluid supplied to or discharged from the head-side port 7a of the bucket cylinder 7.

[0034] As described above, the bucket rod side spool 22 is connected to the first hydraulic pump 8. Explaining in more detail, the bucket rod side spool 22 is connected to the first main passage 31 via the bucket passage 48, and is further connected to the first hydraulic pump 8 via the first main passage 31. Explaining in even more detail, the bucket rod side spool 22 is connected in the bucket passage 48 to the downstream side of the check valve 48 a so as to be in parallel with the bucket head side spool 21, and is connected to the first main passage 31 together with the bucket head side spool 21 via the check valve 48 a. The bucket rod side spool 22 is also connected to the tank 30 via a tank passage 33. The bucket rod side spool 22 controls the flow of hydraulic fluid to the rod side port 7 b, which is the other port 7 b of the bucket cylinder 7. Explaining in more detail, the bucket rod side spool 22 is connected to the rod side port 7 b via a rod side passage 50. The bucket rod-side spool 22 receives pilot pressures output from the solenoid valves 22 a, 22 b in opposing directions, and strokes to a position corresponding to the pilot pressures of the solenoid valves 22 a, 22 b. By stroking, the bucket rod-side spool 22 switches the connection destination of the rod-side port 7 b to either the first main passage 31 or the tank passage 33. This allows the bucket rod-side spool 22 to supply hydraulic fluid from the first hydraulic pump 8 to the rod-side port 7 b of the bucket cylinder 7, or to discharge hydraulic fluid from the rod-side port 7 b of the bucket cylinder 7 to the tank 30. The bucket rod-side spool 22 also adjusts its opening. This allows the bucket rod-side spool 22 to control the flow of hydraulic fluid supplied to or discharged from the rod-side port 7 b of the bucket cylinder 7.

[0035] The spools 21, 22 also stroke independently of each other. Therefore, the spools 21, 22 can independently control the flow of hydraulic fluid supplied to and discharged from the head side port 7 a and the rod side port 7 b of the bucket cylinder 7. That is, the spools 21, 22 can independently control the meter-in flow rate and the meter-out flow rate for the head side port 7 a and the rod side port 7 b of the bucket cylinder 7, respectively.

[0036] [Swivel Spool] As described above, the first swing spool 23 is connected to the second hydraulic pump 9. More specifically, the first swing spool 23 is connected to the second main passage 32 via a swing passage 51 having a check valve 51a interposed therein, and is further connected to the second hydraulic pump 9 via the second main passage 32. The first swing spool 23 is also connected to the tank 30 via a tank passage 33. The first swing spool 23 controls the flow of hydraulic fluid to the first supply / discharge port 4a of the swing motor 4. The swing motor 4 has two ports 4a, 4b, and the first supply / discharge port 4a is one of the two ports 4a, 4b, i.e., port 4a. More specifically, the first swing spool 23 is connected to the first supply / discharge port 4a via a first supply / discharge passage 52. The first swing spool 23 receives pilot pressures output from the solenoid valves 23a, 23b in opposing directions and strokes to a position corresponding to the pilot pressures of the solenoid valves 23a, 23b. By stroking, the first swing spool 23 switches the connection of the first supply / discharge port 4a to either the second main passage 32 or the tank passage 33. This allows the first swing spool 23 to supply hydraulic fluid from the second hydraulic pump 9 to the first supply / discharge port 4a of the swing motor 4, or to discharge hydraulic fluid from the first supply / discharge port 4a of the swing motor 4 to the tank 30. The first swing spool 23 also adjusts its opening. This allows the first swing spool 23 to control the flow of hydraulic fluid supplied to or discharged from the first supply / discharge port 4a of the swing motor 4.

[0037] As described above, the second swing spool 24 is connected to the second hydraulic pump 9. More specifically, the second swing spool 24 is connected to the second main passage 32 via the swing passage 51, and further connected to the second hydraulic pump 9 via the second main passage 32. More specifically, the second swing spool 24 is connected in the swing passage 51 downstream of the check valve 51a in parallel with the first swing spool 23, and is connected to the second main passage 32 together with the second swing spool 24 via the check valve 51a. The second swing spool 24 is also connected to the tank 30 via the tank passage 33. The second swing spool 24 controls the flow of hydraulic fluid to the second supply / discharge port 4b, which is the other port 4b of the swing motor 4. More specifically, the second swing spool 24 is connected to the second supply / discharge port 4b via the second supply / discharge passage 53. The second swing spool 24 receives pilot pressures output from the solenoid valves 24a, 24b in opposing directions and strokes to a position corresponding to the pilot pressures of the solenoid valves 24a, 24b. By stroking, the second swing spool 24 switches the connection of the second supply / discharge port 4b to either the second main passage 32 or the tank passage 33. This allows the second swing spool 24 to supply hydraulic fluid from the second hydraulic pump 9 to the second supply / discharge port 4b of the swing motor 4, or to discharge hydraulic fluid from the second supply / discharge port 4b of the swing motor 4 to the tank 30. The second swing spool 24 also adjusts its opening. This allows the second swing spool 24 to control the flow of hydraulic fluid supplied to or discharged from the second supply / discharge port 4b of the swing motor 4.

[0038] The spools 23, 24 also stroke independently of each other. Therefore, the spools 23, 24 can independently control the flow of hydraulic fluid supplied to and discharged from the supply / discharge ports 4a, 4b of the swing motor 4. That is, the spools 23, 24 can independently control the meter-in flow rate and the meter-out flow rate for the supply / discharge ports 4a, 4b of the swing motor 4.

[0039] [Converging Spool] The converging spool 25 is disposed in a converging passage 54 connecting the two main passages 31, 32, and opens and closes the converging passage 54. The converging spool 25 receives pilot pressure output from the solenoid valve 25b in a direction against the biasing force of a spring mechanism 25d, which will be described in detail later, and strokes to a position corresponding to the pilot pressure of the solenoid valve 25b. The converging spool 25 opens and closes the converging passage 54 by stroking, and also adjusts the opening degree of the converging spool 25. In this way, the converging spool 25 merges the hydraulic fluid from the second main passage 32 to the first main passage 31 and in the opposite direction, and also controls the flow rate of the hydraulic fluid to be merged.

[0040] [Boom Regenerative Valve Body] The boom regenerative valve body 26 is connected to the head side passage 41 and the first arm passage 44. More specifically, the boom regenerative valve body 26 is connected to the head side passage 41 so as to be parallel to the spools 14, 15. The boom regenerative valve body 26 is also connected to the first arm passage 44 downstream of the check valve 44a so as to be parallel to the spools 17, 19. The boom regenerative valve body 26 regenerates hydraulic fluid discharged from the head side port 5a of the boom cylinder 5 to the arm cylinder 6. More specifically, the boom regenerative valve body 26 opens and closes in response to the pilot pressure output from the solenoid valve 26a, and adjusts the opening degree of the boom regenerative valve body 26. In this way, the boom regenerative valve body 26 regenerates hydraulic fluid from the head side port 5a of the boom cylinder 5 to the head side port 6a or the rod side port 6b of the arm cylinder 6, and controls the regenerated flow rate.

[0041] <Pressure Sensors> The multiple pressure sensors 61a to 67a and 61b to 67b correspond to the hydraulic pumps 8 and 9 and the ports 2a to 7a and 2b to 7b of the actuators 2 to 7, respectively. The pressure sensors 61a and 61b are connected to the main passages 31 and 32, respectively, and detect the discharge pressure of the corresponding hydraulic pumps 8 and 9. The pressure sensors 62a to 67a and 62b to 67b are also connected to the passages 35, 36, 38, 39, 41, 43, 45, 47, 49, 50, 52, and 53 that lead to the corresponding ports 2a to 7a and 2b to 7b, respectively. The multiple pressure sensors 62a to 67a and 62b to 67b detect the hydraulic pressures of the corresponding ports 2a to 7a and 2b to 7b, i.e., the port pressures. In this embodiment, the multi-control valve 10 is provided with 16 pressure sensors 61a to 67a, 61b to 67b.

[0042] <Control Device> The control device 70 controls the operation of each of the spools 12 to 25 and the boom regeneration valve element 26. The control device 70 controls the operation of each of the spools 12 to 25 and the boom regeneration valve element 26 in response to a command signal input from, for example, an operating device 71. More specifically, the operating device 71 includes a plurality of operating levers and operating pedals (neither of which are shown), and outputs a command signal to the control device 70 in response to operation of the operating levers and operating pedals. The control device 70 also acquires the discharge pressures of the hydraulic pumps 8 and 9 from pressure sensors 61a and 61b, and acquires the port pressures of the ports 2a to 7a and 2b to 7b from pressure sensors 62a to 67a and 62b to 67b, respectively. The control device 70 controls the operation of each of the spools 12 to 25 and the boom regeneration valve element 26 based on the input command signal and the acquired hydraulic pressures of the ports 2a to 7a and 2b to 7b.

[0043] <Specific Configuration of Multi-Control Valve> The specific configuration of the multi-control valve 10 will be described below. As shown in Figures 3 and 4, the multi-control valve 10 includes a valve block 11 and multiple spools 12-25, as described above. Furthermore, as shown in Figures 6 to 9, the multi-control valve 10 includes multiple spool covers 12c-25c, multiple spring mechanisms 12d-25d, and multiple solenoid valves 12a-24a, 12b-25b. The valve block 11 is formed, for example, in a substantially rectangular parallelepiped shape, as shown in Figures 1 and 5. The valve block 11 includes a block main body 11a, multiple first spool holes 11b, and multiple second spool holes 11c.

[0044] The block body 11a is formed, for example, in a roughly rectangular parallelepiped shape. The block body 11a is formed in a rectangular shape in a plan view from one side in the height direction. In this embodiment, the block body 11a includes a first block member 11d and a second block member 11e. The block body 11a can be divided into the first block member 11d and the second block member 11e in the height direction. However, the block body 11a does not necessarily have to be divided into the first block member 11d and the second block member 11e. The block body 11a has a plurality of first spool holes 11b and a plurality of second spool holes 11c formed as follows.

[0045] As shown in FIG. 3 , the plurality of first spool holes 11b are formed on one widthwise side surface of the block body 11a. More specifically, the plurality of first spool holes 11b are arranged in two rows on one widthwise side surface of the block body 11a. In this embodiment, for example, six first spool holes 11b are formed on one widthwise side surface of the block body 11a. The six first spool holes 11b are arranged in two rows in the depth direction, which is an example of a row direction. Each row has three first spool holes 11b arranged in the height direction. In each row, the first spool holes 11b are aligned in a row with respect to each other in the height direction. In this embodiment, two first spool holes 11b are formed in the first block member 11d and four in the second block member 11e. Furthermore, the six first spool holes 11b extend in the width direction from one widthwise side surface of the block body 11a.

[0046] As shown in FIG. 4 , the plurality of second spool holes 11c are formed on the other widthwise side of the block body 11a. More specifically, the plurality of second spool holes 11c are arranged in two rows on the other widthwise side of the block body 11a. In this embodiment, eight second spool holes 11c are formed on the other widthwise side of the block body 11a. The eight second spool holes 11c are arranged in two rows in the depth direction, with four holes in each row in the height direction. In each row, the second spool holes 11c are aligned in a row in the height direction. In this embodiment, four second spool holes 11c are formed in each of the block members 11d and 11e. The eight second spool holes 11c extend in one width direction from the other widthwise side of the block body 11a. Of the eight second spool holes 11c, six are arranged to correspond to the first spool holes 11b and extend toward the corresponding first spool holes 11b. A pair of spool holes 11b, 11c, which are the corresponding first spool hole 11b and second spool hole 11c, are arranged in a line in the width direction. In this embodiment, the pair of spool holes 11b, 11c are aligned in the width direction so that their axes coincide with each other. A partition wall 11f is formed in the valve block 11 between the pair of spool holes 11b, 11c to separate them.

[0047] The spools 12 to 25 are inserted into the valve block 11 as follows. That is, as shown in FIGS. 6 to 9 , each of the spools 12 to 25 is slidably inserted into a first spool bore 11b and a second spool bore 11c of the valve block 11. In this embodiment, each of the spools 16, 19, 20, 22, 24, and 25, which are examples of first spools, is slidably inserted into the first spool bore 11b. Each of the spools 16, 19, 20, 22, and 24 forms an inner pilot chamber 16e, 19e, 20e, 22e, and 24e between itself and the partition wall 11f in the first spool bore 11b. The remaining spools 12 to 15, 17, 18, 21, and 23, which are examples of second spools, are slidably inserted into the second spool bore 11c. Each of the spools 12 and 13 defines an inner pilot chamber 12e, 13e at the bottom of the second spool bore 11c. Each of the spools 14, 15, 17, 18, 21, and 23 defines an inner pilot chamber 14e, 15e, 17e, 18e, 21e, and 23e between the spools and the partition wall 11f in the second spool bore 11c. Pilot pressure is introduced into each of the inner pilot chambers 12e to 24e, and each of the spools 12 to 24 receives the pilot pressure of the inner pilot chambers 12e to 24e in a direction away from the partition wall 11f (hereinafter referred to as "axially outward").

[0048] More specifically, the boom rod spool 16, the second arm rod spool 20, and the bucket rod spool 22 are slidably inserted into the first spool holes 11b in the row on one side in the depth direction, in that order from one side in the height direction. The junction spool 25, the first arm rod spool 19, and the second swing spool 24 are slidably inserted into the first spool holes 11b in the row on the other side in the depth direction, in that order from one side in the height direction. On the other hand, the first traveling spool 12, the first boom head side spool 14, the second arm head side spool 18, and the bucket head side spool 21 are slidably inserted into the second spool holes 11c in the row on one side in the depth direction, in that order from one side in the height direction. In addition, the second traveling spool 13, the second boom head side spool 15, the first arm head side spool 17, and the first swivel spool 23 are slidably inserted into each of the second spool holes 11c in the row on the other side in the depth direction, in that order from one side in the height direction.

[0049] More specifically, the spools 14 to 25 are arranged in the valve block 11 as follows. That is, the first boom head-side spool 14 and the boom rod-side spool 16 are slidably inserted into a pair of spool holes 11b, 11c arranged in a row. Also, the first arm head-side spool 17 and the first arm rod-side spool 19 are slidably inserted into a pair of first spool holes 11b, 11c different from the pair of spool holes 11b, 11c into which the spools 14, 16 are inserted. In addition, each combination of the merging spool 25 and the second boom head-side spool 15, the second arm head-side spool 18 and the second arm rod-side spool 20, the bucket head-side spool 21 and the bucket rod-side spool 22, and the first swivel spool 23 and the second swivel spool 24 is slidably inserted into a pair of spool holes 11b, 11c arranged in a row.

[0050] The spool covers 12c to 25c are provided on the block body 11a so as to cover the openings of the spool holes 11b and 11c. That is, the spool covers 12c to 25c are provided on the block body 11a so as to cover the corresponding spools 12 to 25. More specifically, spool covers 16c, 19c, 20c, 22c, 24c, and 25c are provided on one widthwise side of the block body 11a, and spool covers 12c to 15c, 17c, 18c, 21c, and 23c are provided on the underside of the block body 11a. In this embodiment, two adjacent spool covers 12c to 25c are integrally formed to form a double cover. However, two adjacent spool covers 12c to 25c do not necessarily have to be integrally formed. Additionally, outer pilot chambers 12f to 25f are formed within the spool covers 12c to 25c. The outer pilot chambers 12f to 25f correspond to the respective spools 12 to 25. Pilot pressure is introduced into the outer pilot chambers 12f to 25f, and the pilot pressure in each of the outer pilot chambers 12f to 24f acts on the corresponding spool 12 to 25 in a direction (hereinafter referred to as "axially inward") that resists the pilot pressure in the inner pilot chambers 12e to 24e.

[0051] The spring mechanisms 12d to 25d are housed in the spool covers 12c to 25c, respectively. In this embodiment, the spring mechanisms 12d to 25d are housed in the outer pilot chambers 12f to 25f, respectively. The spring mechanisms 12d to 25d correspond to the spools 12 to 25, and bias the corresponding spools 12 to 25. More specifically, the spring mechanisms 12d to 25d bias the spools 12 to 25 in the direction opposite to the stroke direction of the corresponding spools 12 to 25. This returns the spools 12 to 25 to their neutral positions.

[0052] The first solenoid valves 12a to 24a correspond to the spools 12 to 24, respectively. The first solenoid valves 12a to 24a output pilot pressures corresponding to signals input to the corresponding spools 12 to 24. In this embodiment, the first solenoid valves 12a to 24a are attached to the spool covers 12c to 24c of the corresponding spools 12 to 24, and are connected to the inner pilot chambers 12e to 24e, respectively. The first solenoid valves 12a to 24a output pilot pressures to the corresponding inner pilot chambers 12e to 24e.

[0053] The second solenoid valves 12b to 25b also correspond to the spools 12 to 25, respectively. The second solenoid valves 12b to 25b output pilot pressures according to signals input to the corresponding spools 12 to 25. In this embodiment, the second solenoid valves 12b to 25b are attached to the spool covers 12c to 25c of the corresponding spools 12 to 25, and are connected to the outer pilot chambers 12f to 25f, respectively. The second solenoid valves 12b to 25b output pilot pressures to the corresponding outer pilot chambers 12f to 25f.

[0054] The pilot pressures output from the first solenoid valves 12a to 24a and second solenoid valves 12b to 25b configured in this manner act in opposing directions on the corresponding spools 12 to 25. The biasing forces of the spring mechanisms 12d to 25d also act in opposing directions on the corresponding spools 12 to 25 against the biasing forces of the first solenoid valves 12a to 24a and second solenoid valves 12b to 25b. Therefore, each spool 12 to 25 strokes to a position where the biasing forces of the solenoid valves 12a to 24a, 12b to 25b and the spring mechanisms 12d to 25d balance out. As a result, each spool 12 to 25 controls the flow of hydraulic fluid in accordance with the signals input to the solenoid valves 12a to 24a, 12b to 25b.

[0055] The various passages 31-54 and the pump ports 31a, 32a are formed in the block body 11a as follows. That is, the first main passage 31 and the second main passage 32 are arranged separately on one side and the other side in the depth direction, sandwiching the first spool hole 11b and the second spool hole 11c, as shown in FIG. 6. The first main passage 31 and the second main passage 32 extend in the height direction (see also FIGS. 7 to 9) and open to one side and the other side in the depth direction via the pump ports 31a, 32a, respectively. In addition, the various passages 33-54 are formed in the block body 11a to realize the hydraulic circuit 10a described above. An example of the arrangement of the various passages 33-54 will be described below.

[0056] 6 , the first traveling passage 34 and the second traveling passage 37 are adjacent to the first traveling spool 12 and the second traveling spool 13, respectively, and are spaced apart on one and the other sides in the depth direction. The first traveling passage 34 is connected to the first main passage 31 and the first traveling spool 12, and the second traveling passage 37 is connected to the second main passage 32 and the second traveling spool 13. In addition, in the first traveling spool 12, first and second supply and discharge passages 35, 36 are connected to both axial sides of the first traveling passage 34, and the tank passage 33 is further connected to the axially outer sides of these passages. The first and second supply and discharge passages 35, 36 are connected to the first supply and discharge port 2a and the second supply and discharge port 2b, respectively, via first and second supply and discharge connection ports 35a, 36a that open on the top surface of the valve block 11. Similarly, the second traveling spool 13 has first and second supply / discharge passages 38, 39 connected to both axial sides of the second traveling passage 37, and further connected to the axial outside of these passages 38, 39 is the tank passage 33. The first and second supply / discharge passages 38, 39 are connected to the first supply / discharge port 3a and the second supply / discharge port 3b, respectively, via first and second supply / discharge connection ports 38a, 39a that open on the top surface of the valve block 11.

[0057] As shown in FIG. 7 , the first boom passage 40 and the second boom passage 42 are spaced apart on one and the other sides in the depth direction. The first boom passage 40 is disposed adjacent to the first boom head side spool 14 and the boom rod side spool 16. The first boom passage 40 is connected to the first main passage 31 and branches off midway from the first main passage 31 to connect to the first boom head side spool 14 and the boom rod side spool 16. A check valve 40a is disposed in the first boom passage 40 at its branching point. The first boom head side spool 14 is connected in this order axially outward from the first boom passage 40 to the head side passage 41 and the tank passage 33. The boom rod side spool 16 is connected in this order axially outward from the first boom passage 40 to the rod side passage 43 and the tank passage 33. The rod-side passage 43 is connected to the rod-side port 5b of the boom cylinder 5 via a rod-side connection port 43a that opens on one depth-direction side surface that is a side surface on one depth direction side. The head-side passage 41 extends to the other depth-direction side surface that is a side surface on the other depth direction across the second boom head-side spool 15, and is connected to the head-side port 5a of the boom cylinder 5 via head-side connection ports 41a, 41b that open on both depth-direction side surfaces, respectively.

[0058] The second boom passage 42 is disposed adjacent to the second boom head-side spool 15. The second boom passage 42 is connected to the second main passage 32 and the second boom head-side spool 15 with a check valve 42a interposed therebetween. The second boom head-side spool 15 is also connected to the head-side passage 41 and the tank passage 33 axially outward of the second boom passage 42. Furthermore, the merging passage 54 is disposed adjacent to the other side of the merging spool 25 in the depth direction. The merging passage 54 connects the first main passage 31 and the second main passage 32 with the merging spool 25 interposed therebetween.

[0059] As shown in FIG. 8 , the first arm passage 44 and the second arm passage 46 are disposed at one side and the other side in the depth direction, spaced apart from each other. The second arm passage 46 is disposed adjacent to the second arm head side spool 18 and the second arm rod side spool 20. The second arm passage 46 is connected to the first main passage 31 and branches off midway from the first main passage 31 to connect to the second arm head side spool 18 and the second arm rod side spool 20. A check valve 46a is disposed in the second arm passage 46 at its branching point. The head side passage 45 and the tank passage 33 are connected to the second arm head side spool 18, in that order, axially outward from the second arm passage 46. The rod side passage 47 and the tank passage 33 are connected to the second arm rod side spool 20, axially outward from the second arm passage 46. The head-side passage 45 extends in the depth direction so as to straddle the two arm head-side spools 18, 17. The head-side passage 45 is connected to the head-side port 5a of the arm cylinder 6 via head-side connection ports 45a, 45b that open on both side surfaces in the depth direction. The rod-side passage 43 extends in the other depth direction so as to straddle the first arm rod-side spool 19. The rod-side passage 47 is connected to the rod-side port 5b of the arm cylinder 6 via a rod-side connection port 47a that opens on the other side surface in the depth direction.

[0060] The first arm passage 44 is disposed adjacent to the first arm head side spool 17 and the first arm rod side spool 19. The first arm passage 44 is connected to the second main passage 32, branches off from the second main passage 32 midway, and is connected to the first arm head side spool 17 and the first arm rod side spool 19. A check valve 44a is disposed in the first arm passage 44 at the branching point. A head side passage 45 and a tank passage 33 are connected in this order to the first arm head side spool 17 axially outward from the first arm passage 44. A rod side passage 47 and a tank passage 33 are connected in this order to the first arm rod side spool 19 axially outward from the first arm passage 44.

[0061] As shown in FIG. 9 , the bucket passage 48 and the swing passage 51 are arranged separately on one and the other sides in the depth direction. The bucket passage 48 is arranged adjacent to the bucket head-side spool 21 and the bucket rod-side spool 22. The bucket passage 48 is connected to the first main passage 31 and branches off from the first main passage 31 midway to connect to the bucket head-side spool 21 and the bucket rod-side spool 22. A check valve 48a is disposed in the bucket passage 48 at its branching point. A head-side passage 49 and a tank passage 33 are connected in this order to the bucket head-side spool 21 axially outward from the bucket passage 48. A rod-side passage 50 and a tank passage 33 are connected in this order to the bucket rod-side spool 22 axially outward from the bucket passage 48. The head-side passage 49 is connected to the head-side port 7a of the bucket cylinder 7 via a head-side connection port 49a that opens on one side surface in the depth direction. The rod-side passage 50 is connected to the rod-side port 7b of the bucket cylinder 7 via a rod-side connection port 50a that opens on one side surface in the depth direction.

[0062] The swing passage 51 is disposed adjacent to the first swing spool 23 and the second swing spool 24. The swing passage 51 is connected to the second main passage 32 and branches off midway from the second main passage 32 to connect to the first swing spool 23 and the second swing spool 24. A check valve 51a is disposed in the swing passage 51 at its branching point. A first supply / discharge passage 52 and a tank passage 33 are connected to the first swing spool 23 axially outward from the swing passage 51. A second supply / discharge passage 53 and a tank passage 33 are connected to the second swing spool 24 axially outward from the swing passage 51. The first supply / discharge passage 52 is connected to the first supply / discharge port 4a of the swing motor 4 via a first supply / discharge connection port 52a that opens on the other side surface in the depth direction. The second supply / discharge passage 53 is connected to the second supply / discharge port 4b of the swing motor 4 via a second supply / discharge connection port 53a that opens on the other side surface in the depth direction.

[0063] <Flow of Hydraulic Fluid in the Multi-Control Valve> In the hydraulic drive system 1, when the actuators 2 to 7 are driven based on a command from the operating device 71 (in this embodiment, a command signal that is an electrical signal such as a current or voltage), the control device 70 controls the multi-control valve 10 as follows. That is, when driving the traveling device, the control device 70 outputs pilot pressure from at least one of the solenoid valves 12a, 12b, 13a, and 13b. For example, when pilot pressure is output from the first solenoid valves 12a and 13a, the pilot pressure is directed to the inner pilot chambers 12e and 13e, respectively, and the traveling spools 12 and 13 are actuated. As a result, hydraulic fluid is supplied from the hydraulic pump 8 to the first traveling motor 2 via the first traveling spool 12, and from the hydraulic pump 9 to the second traveling motor 3 via the second traveling spool 13. This drives the traveling device.

[0064] When outputting pilot pressure from the first solenoid valves 12a, 13a, the control device 70 acquires the discharge pressures of the hydraulic pumps 8, 9 and the port pressures of the ports 2a, 3a detected by the pressure sensors 61a, 61b, 62a, 63a. The control device 70 then operates the solenoid valves 12a, 13a based on the input command signals and the acquired discharge pressures and port pressures. As a result, the control device 70 supplies a flow rate corresponding to the input command signals to the travel motors 2, 3, driving the travel motors 2, 3 at a speed corresponding to the amount of operation of the operating device 71. The control device 70 also operates the solenoid valves 14a-24a, 14b-24b for the actuators 4-7 described below based on the acquired discharge pressures and port pressures and command signals. Therefore, a detailed description of the actuators 4-7 will be omitted.

[0065] Furthermore, when rotating the swing body, the control device 70 operates as follows. That is, the control device 70 outputs pilot pressure from one of the solenoid valves 23a, 23b, 24a, and 24b. For example, when pilot pressure is output from the solenoid valves 23a and 24b, the pilot pressure is introduced into the pilot chambers 23f and 24e, and the swing motor 4 is activated. At this time, hydraulic fluid is supplied from the hydraulic pump 8 to the first supply / discharge port 4a via the first swing spool 23, and further discharged from the second supply / discharge port 4b to the second swing spool 24 and into the tank 30. The first swing spool 23 and the second swing spool 24 can independently stroke, and their respective openings can be adjusted independently. Therefore, the multi-control valve 10 can independently control the flow rates of the first supply / discharge port 4a and the second supply / discharge port 4b, enabling more precise control of the swing motor 4.

[0066] Furthermore, when driving the boom, the control device 70 operates as follows. For example, when extending the boom cylinder 5, the control device 70 outputs pilot pressure from the solenoid valves 14b and 16a. This leads to the pilot pressure being directed to the pilot chambers 14f and 16e. As a result, hydraulic fluid from the first hydraulic pump 8 is directed to the head-side port 5a, and the boom cylinder 5 is extended. Furthermore, when a larger flow rate is required through the head-side port 5a of the boom cylinder 5, pilot pressure is also output from the solenoid valve 15b. This leads to the pilot pressure being directed to the pilot chamber 15f, and hydraulic fluid from the second hydraulic pump 9 is also directed to the head-side port 5a of the boom cylinder 5 via the second boom head-side spool 15. This allows a larger flow rate to be supplied through the head-side port 5a of the boom cylinder 5. On the other hand, when retracting the boom cylinder 5, the control device 70 outputs pilot pressure from the solenoid valves 14a and 16b. As a result, pilot pressure is introduced into the pilot chambers 14e and 16f, causing the boom cylinder 5 to contract.

[0067] In the boom cylinder 5 that extends and retracts in this manner, hydraulic fluid is supplied to and discharged from the head side port 5a via the boom head side spools 14, 15, and hydraulic fluid is supplied to and discharged from the rod side port 5b via the rod side spool 16. The spools 14 to 16 can stroke independently of one another, and their respective openings can be adjusted independently of one another. Therefore, with the multi-control valve 10, the flow rates supplied to and discharged from the head side port 5a and the rod side port 5b can also be controlled independently, allowing for more precise control of the boom cylinder 5.

[0068] Furthermore, when operating the arm, the control device 70 operates as follows. For example, when extending the arm cylinder 6, the control device 70 outputs pilot pressure from the solenoid valves 17b and 19a. This leads to the pilot pressure being directed to the pilot chambers 17f and 19e. As a result, hydraulic fluid from the second hydraulic pump 9 is directed to the head side port 6a, and the arm cylinder 6 is extended. Furthermore, when a larger flow rate is required through the head side port 6a of the arm cylinder 6, pilot pressure is also output from the solenoid valves 18b and 20a. This leads to the pilot pressure being directed to the pilot chambers 18f and 20e, and hydraulic fluid from the first hydraulic pump 8 can also be directed to the head side port 6a of the arm cylinder 6 via the second arm head side spool 18. This allows a larger flow rate of hydraulic fluid to flow through the head side port 6a of the arm cylinder 6. On the other hand, when retracting the arm cylinder 6, the control device 70 outputs pilot pressure from the solenoid valves 17a and 19b. As a result, pilot pressure is introduced into pilot chambers 17e and 19f, contracting the arm cylinder 6. Furthermore, pilot pressure is output from solenoid valves 18a and 20b, allowing a larger flow rate of hydraulic fluid to flow into the rod-side port 6b of the arm cylinder 6.

[0069] In the arm cylinder 6 that extends and retracts in this manner, hydraulic fluid is supplied to and discharged from the head side port 6a via the arm head side spools 17, 18, and from the rod side port 6b via the arm rod side spools 19, 20. Each spool 17-20 can stroke independently of the others, and their respective openings can be adjusted independently of each other. Therefore, with the multi-control valve 10, the flow rates supplied to and discharged from the head side port 6a and the rod side port 6b can also be controlled independently, allowing for more precise control of the arm cylinder 6.

[0070] Furthermore, when operating the bucket, the control device 70 operates as follows. For example, when extending the bucket cylinder 7, the control device 70 causes the solenoid valves 21b and 22a to output pilot pressure. This leads to the pilot pressure being introduced into the pilot chambers 21f and 22e, causing the bucket cylinder 7 to extend. On the other hand, when retracting the bucket cylinder 7, the control device 70 causes the solenoid valves 21b and 22a to output pilot pressure. This leads to the pilot pressure being introduced into the pilot chambers 21e and 22f, causing the bucket cylinder 7 to retract.

[0071] Furthermore, when the arm and boom are moved simultaneously and the boom is retracted, the control device 70 outputs pilot pressure from the solenoid valve 26 a, thereby allowing the hydraulic fluid discharged from the head side port 5 a of the boom cylinder 5 to be regenerated in the arm cylinder 6 via the boom regeneration valve body 26.

[0072] Furthermore, when the traveling gear and the boom are moved simultaneously, the control device 70 operates as follows. For example, the control device 70 outputs pilot pressure from the solenoid valves 12a and 13a and also outputs pilot pressure from the solenoid valves 14b and 16a. This drives the traveling gear and the boom. More specifically, the control device 70 acquires the discharge pressures of the hydraulic pumps 8 and 9 and the port pressures of the ports 2a, 3a, and 5a from the pressure sensors 61a, 61b, 62a, 62b, and 65a. The control device 70 then calculates the pilot pressures to be output from the solenoid valves 12a, 13b, 14b, and 16a based on the acquired discharge pressures and port pressures and command signals, and operates the spools 12, 13, 14, and 16.

[0073] The control device 70 also acquires the port pressures of the ports 2a, 3a, and 5a and controls the movement of the spools 12, 13, 14, and 16 as follows. That is, when the supply pressure, which is the hydraulic fluid pressure supplied to the boom cylinder 5, is lower than the supply pressure to the first and second travel motors 2 and 3, the control device 70 throttles the opening of the first boom head-side spool 14 and the boom rod-side spool 16. More specifically, the control device 70 outputs pilot pressure from the solenoid valves 14b and 16a to throttle the opening of the first boom head-side spool 14 and the boom rod-side spool 16. This ensures a flow rate corresponding to the command signal for the first and second travel motors 2 and 3. On the other hand, when the supply pressure to the first and second travel motors 2 and 3 is lower than the supply pressure to the boom cylinder 5, the control device 70 throttles the opening of the first and second travel spools 12 and 13. More specifically, the control device 70 outputs pilot pressure from the solenoid valves 12b, 13b so as to reduce the opening of the first and second traveling spools 12, 13. This ensures a flow rate corresponding to the command signal for the boom cylinder 5.

[0074] In this way, when the traveling gear and boom are moved simultaneously, the control device 70 secures the flow rate supplied to the traveling motors 2 and 3 and the boom cylinder 5 by narrowing the openings of the spools 12, 13, 14, and 16. This allows the traveling motors 2 and 3 and the boom cylinder 5 to move at speeds according to command signals. Additionally, the control device 70 similarly controls the operation of the spools 12 to 24 when the traveling gear and the arm, bucket, or rotating body are moved simultaneously.

[0075] Furthermore, when the travel device is used to cause the excavator to travel straight, the control device 70 opens the junction passage 54 using the junction spool 25. This connects the first hydraulic pump 8 and the second hydraulic pump 9. More specifically, the two main passages 31, 32 are connected to each other. This reduces the difference in hydraulic pressure between the hydraulic fluid flowing through the two main passages 31, 32, and also reduces the difference in hydraulic pressure between the hydraulic fluid guided to the first and second travel spools 12, 13. This makes it easy to guide the same flow rate of hydraulic fluid to each travel motor 2, 3 during straight travel, thereby improving straight-line travel performance.

[0076] In the multi-control valve 10 of this embodiment, the first boom head-side spool 14 controls the flow of hydraulic fluid to the head-side port 5a, and the boom rod-side spool 16 controls the flow of hydraulic fluid to the rod-side port 5b. Therefore, the passage connecting the first boom head-side spool 14 to the rod-side port 5b and the passage connecting the boom rod-side spool 16 to the head-side port 5a can be omitted. This simplifies the configuration of the passages formed in the multi-control valve 10, allowing the multi-control valve 10 to be made more compact. Furthermore, the first boom head-side spool 14 and the boom rod-side spool 16 control the flow rate of hydraulic fluid independently of each other. Therefore, the multi-control valve 10 can independently control the flow rate of hydraulic fluid supplied to and discharged from the ports 5a, 5b of the boom cylinder 5, and can be made more compact.

[0077] The multi-control valve 10 of this embodiment further includes a second boom head-side spool 15 that is connected to the second hydraulic pump 9 and the head-side port 5a and controls the flow of hydraulic fluid supplied to the head-side port 5a. Therefore, a larger flow rate of hydraulic fluid can be supplied to the head-side port 5a by the first boom head-side spool 14 and the second boom head-side spool 15. The second boom head-side spool 15 also controls the flow rate of hydraulic fluid independently of the first boom head-side spool 14 and the boom rod-side spool 16. Therefore, the flow rate of hydraulic fluid supplied to the head-side port 5a via the second boom head-side spool 15 can be controlled independently from the flow rate of hydraulic fluid discharged from the rod-side port 5b. This allows the flow rate of hydraulic fluid to be controlled with greater precision when hydraulic fluid is supplied to the head-side port 5a via the first boom head-side spool 14 and the second boom head-side spool 15.

[0078] Furthermore, in the multi-control valve 10 of this embodiment, the first arm head-side spool 17 controls the flow of hydraulic fluid to the head-side port 6a of the arm cylinder 6, and the first arm rod-side spool 19 controls the flow of hydraulic fluid to the rod-side port 6b of the arm cylinder 6. Therefore, it is possible to omit a passage connecting the first arm head-side spool 17 to the rod-side port 6b of the arm cylinder 6 and a passage connecting the first arm rod-side spool 19 to the head-side port 6a of the arm cylinder 6. This simplifies the configuration of the passages formed in the multi-control valve 10, allowing the multi-control valve 10 to be made more compact. Furthermore, the first arm head-side spool 17 and the first arm rod-side spool 19 control the flow rate of hydraulic fluid independently of each other. Therefore, the multi-control valve 10 can independently control the flow rate of hydraulic fluid supplied to and discharged from the ports 6a, 6b of the arm cylinder 6, and can be made more compact.

[0079] Furthermore, the multi-control valve 10 of this embodiment further includes a second-arm head-side spool 18 that is connected to the head-side port 6a of the arm cylinder 6 and the first hydraulic pump 8 and controls the flow of hydraulic fluid supplied to the head-side port 6a of the arm cylinder 6. Therefore, a larger flow rate of hydraulic fluid can be supplied to the head-side port 6a by the first-arm head-side spool 17 and the second-arm head-side spool 18. Furthermore, the second-arm head-side spool 18 controls the flow rate of hydraulic fluid independently of the first-arm head-side spool 17 and the first-arm rod-side spool 19. Therefore, the flow rate of hydraulic fluid supplied to the head-side port 6a via the second-arm head-side spool 18 can be controlled independently from the flow rate of hydraulic fluid discharged from the rod-side port 6b. This allows the flow rate of hydraulic fluid to be controlled with higher accuracy when hydraulic fluid is supplied to the head-side port 6a via the first-arm head-side spool 17 and the second-arm head-side spool 18.

[0080] Furthermore, the multi-control valve 10 of this embodiment further includes a second-arm rod-side spool 20 that is connected to the first hydraulic pump 8 and the rod-side port 6b of the arm cylinder 6 and controls the flow of hydraulic fluid to the rod-side port 6b. Therefore, a larger flow rate of hydraulic fluid can be supplied to and discharged from the rod-side port 6b by the first-arm rod-side spool 19 and the second-arm rod-side spool 20. Furthermore, the second-arm rod-side spool 20 controls the flow rate of hydraulic fluid independently of the first-arm head-side spool 17, the first-arm rod-side spool 19, and the second-arm head-side spool 18. Therefore, the flow rate of hydraulic fluid supplied to and discharged from the rod-side port 6b can be controlled independently from the flow rate of hydraulic fluid supplied to and discharged from the head-side port 6a. As a result, when hydraulic fluid is supplied to and discharged from the rod-side port 6b via the first-arm rod-side spool 19 and the second-arm rod-side spool 20, the flow rate of the supplied and discharged hydraulic fluid can be controlled with higher accuracy.

[0081] Furthermore, in the multi-control valve 10 of this embodiment, the spools 15, 18, 20 are connected to the passages 41, 45, 46 in parallel with the spools 14, 17, 19. This allows the hydraulic fluid from the first and second hydraulic pumps 8, 9 to be combined and supplied to the head-side port 5a of the boom cylinder 5, and the hydraulic fluid from the first and second hydraulic pumps 8, 9 to be combined and supplied to the ports 6a, 6b of the arm cylinder 6. This reduces the number of passages formed in the multi-control valve 10. This simplifies the configuration of the passages formed in the multi-control valve 10, allowing the multi-control valve 10 to be made more compact.

[0082] Furthermore, in the multi-control valve 10 of this embodiment, the valve block 11 includes a pair of spool holes 11b, 11c that extend in the width direction and are aligned in the width direction with a partition wall 11f sandwiched therebetween. The first boom head-side spool 14 and the boom rod-side spool 16 are slidably inserted into the spool holes 11b, 11c. This allows the two spools 14, 15, which can independently control the flow rates of hydraulic fluid supplied to and discharged from the ports 5a, 5b of the boom cylinder 5, to be aligned in the width direction. This allows the valve block 11, which can independently control the flow rates of hydraulic fluid supplied to and discharged from the ports 5a, 5b of the boom cylinder 5, to be miniaturized.

[0083] Furthermore, in the multi-control valve 10 of this embodiment, the valve block 11 includes a plurality of spool holes 11b, 11c, which extend in the width direction and are arranged side by side in the width direction with corresponding spool holes 11b, 11c sandwiching a partition wall 11f therebetween. The first and boom rod-side spools 16, the first arm head-side spool 17, and the first arm rod-side spool 19 are slidably inserted into the corresponding two spool holes 11b, 11c, respectively. Therefore, two spools 14, 16 that can independently control the flow rate of hydraulic fluid supplied to and discharged from the ports 5a, 5b of the boom cylinder 5 can be arranged side by side in the width direction, and two spools 17, 19 that can independently control the flow rate of hydraulic fluid supplied to and discharged from the ports 6a, 6b of the arm cylinder 6 can be arranged side by side in the width direction. This allows the valve block 11, which can independently control the flow rates of the hydraulic fluid supplied to and discharged from the ports 5a, 5b, 6a, 6b of the boom cylinder 5 and the arm cylinder 6, to be made smaller.

[0084] Furthermore, in the hydraulic drive system 1 of this embodiment, when operating the first traveling spool 12 and the second traveling spool 13, the control device 70 controls the openings of the spools 12 to 19 so as to supply a flow rate corresponding to the input command signal to each traveling motor 2, 3. For example, when the supply pressure of the boom cylinder 5 is lower than the supply pressure to the first and second traveling motors 2, 3, the control device 70 narrows the openings of the spools 14, 16. This makes it easier for hydraulic fluid to flow to the first traveling spool 12 and the second traveling spool 13, allowing the flow rate corresponding to the input command signal to flow to each traveling motor 2, 3.

[0085] Furthermore, in the hydraulic drive system 1 of this embodiment, when the control device 70 operates the first traveling spool 12 and the second traveling spool 13, it opens the merging spool 25 to connect the first hydraulic pump 8 and the second hydraulic pump 9. This makes it possible to equalize the supply pressures to the two traveling motors 2, 3 connected to the first hydraulic pump 8 and the second hydraulic pump 9, thereby improving straight-line running ability when the two traveling motors 2, 3 are operated simultaneously.

[0086] Furthermore, the multi-control valve 10 of this embodiment is provided with a second boom head-side spool 15 that controls the flow rate of hydraulic fluid supplied from the second hydraulic pump 9 to the head-side port 5a. Therefore, a larger flow rate of hydraulic fluid can be supplied to one port by the first boom head-side spool 14 and the second boom head-side spool 15. Furthermore, the first boom head-side spool 14, the second boom head-side spool 15, and the boom rod-side spool 16 control the flow rate of hydraulic fluid independently of each other. Therefore, the flow rate of hydraulic fluid flowing into the head-side port 5a can be controlled independently from the flow rate of hydraulic fluid discharged from the rod-side port 5b. This allows for more accurate control of the flow rate of hydraulic fluid when supplying hydraulic fluid to the actuator via the first boom head-side spool 14 and the second boom head-side spool 15. Therefore, a larger flow rate of hydraulic fluid can be supplied to the boom cylinder 5 while preventing the multi-control valve from becoming larger.

[0087] Furthermore, the multi-control valve 10 of this embodiment further includes a second arm head-side spool 18 that controls the flow rate of hydraulic fluid supplied from the first hydraulic pump 8 to the head-side port 6a of the arm cylinder 6. Therefore, a larger flow rate of hydraulic fluid can be supplied to the head-side port 6a of the arm cylinder 6 by the two arm head-side spools 17, 18. Furthermore, the first arm head-side spool 17, the second arm head-side spool 18, and the first arm rod-side spool 19 control the flow rate of hydraulic fluid independently of each other. Therefore, the flow rate of hydraulic fluid flowing into the head-side port 6a of the arm cylinder 6 can be controlled independently from the flow rate of hydraulic fluid discharged from the rod-side port 6b. This allows for more accurate control of the flow rate of hydraulic fluid when supplying hydraulic fluid to the arm cylinder 6 via the first arm head-side spool 17 and the second arm head-side spool 18. Therefore, a larger flow rate of hydraulic fluid can be supplied to the arm cylinder 6 while suppressing an increase in the size of the multi-control valve.

[0088] Furthermore, the multi-control valve 10 of this embodiment further includes a second-arm rod-side spool 20 that, together with the first-arm rod-side spool 19, discharges hydraulic fluid from the rod-side port 6b and controls the flow rate of hydraulic fluid discharged from the rod-side port 6b. Therefore, the two arm rod-side spools 19, 20 allow a larger flow rate of hydraulic fluid to be discharged from the other port. Furthermore, the second-arm rod-side spool 20 controls the flow rate of hydraulic fluid independently of the first-arm head-side spool 17, the second-arm head-side spool 18, and the first-arm rod-side spool 19. Therefore, the flow rate of hydraulic fluid discharged from the rod-side port 6b can be controlled independently of the flow rate flowing into the head-side port 6a. This allows the flow rate of hydraulic fluid to be controlled with greater precision when hydraulic fluid is discharged from the arm cylinder 6 via the two arm rod-side spools 19, 20.

[0089] Furthermore, in the multi-control valve 10 of this embodiment, an example of one port of the first actuator is the head side port 5a of the boom cylinder 5, and an example of one port of the second actuator is the head side port 6a of the arm cylinder 6. Therefore, the multi-control valve 10 that supplies hydraulic fluid to the boom cylinder 5 and the arm cylinder 6 can achieve the functions described above.

[0090] Furthermore, in the multi-control valve 10 of this embodiment, the boom regenerative valve element 26 regenerates the hydraulic fluid discharged from the head-side port 5a of the boom cylinder 5 to the first arm passage 44. Therefore, it is possible to omit a portion of the passage connecting the boom regenerative valve element 26 to the ports 6a, 6b of the arm cylinder 6, thereby simplifying the configuration of the passages formed in the multi-control valve 10. This allows the multi-control valve 10 to be made more compact.

[0091] Furthermore, in the multi-control valve 10 of this embodiment, the bucket head-side spool 21 controls the flow of hydraulic fluid to the head-side port 7a of the bucket cylinder 7, and the bucket rod-side spool 22 controls the flow of hydraulic fluid to the rod-side port 7b of the bucket cylinder 7. Therefore, it is possible to omit a passage connecting the bucket head-side spool 21 to the rod-side port 7b and a passage connecting the bucket rod-side spool 22 to the head-side port 7a. This simplifies the configuration of the passages formed in the multi-control valve 10, allowing the multi-control valve 10 to be made more compact. Furthermore, the bucket head-side spool 21 and the bucket rod-side spool 22 control the flow rate of hydraulic fluid independently of each other. Therefore, the multi-control valve 10 can independently control the flow rate of hydraulic fluid supplied to and discharged from the ports 7a, 7b of the bucket cylinder 7, and can be made more compact.

[0092] Furthermore, in the multi-control valve 10 of this embodiment, the first rotation spool 23 controls the flow of hydraulic fluid to the first supply / discharge port 4a, and the second rotation spool 24 controls the flow of hydraulic fluid to the second supply / discharge port 4b. Therefore, the passage connecting the first rotation spool 23 and the second supply / discharge port 4b and the passage connecting the second rotation spool 24 and the first supply / discharge port 4a can be omitted. This simplifies the configuration of the passages formed in the multi-control valve 10, allowing the multi-control valve 10 to be made more compact. Furthermore, the first and second rotation spools 23, 24 control the flow rate of hydraulic fluid independently of each other. Therefore, the multi-control valve 10 can independently control the flow rate of hydraulic fluid supplied to and discharged from each port 4a, 4b of the swing motor 4, and can be made more compact.

[0093] [Other Embodiments] In the hydraulic drive unit 1 and the multi-control valve 10 of this embodiment, the boom cylinder 5 is given as an example of the first actuator, but the first actuator may be the travel motors 2 and 3, the swing motor 4, the arm cylinder 6, or the bucket cylinder 7. Similarly, the arm cylinder 6 is given as an example of the second actuator, but the second actuator may be the travel motors 2 and 3, the swing motor 4, the boom cylinder 5, or the bucket cylinder 7. Furthermore, one port of each actuator may be the rod-side port 5b or 6b, and the other port may also be the head-side port 5a or 6a.

[0094] Furthermore, in the multi-control valve 10 of this embodiment, the spools 14 and 15 are connected only to the head side port 5a, but they may also be connected to the rod side port 5b to control the meter-in flow rate of the rod side port 5b. Similarly, the spool 16 may also be connected to the head side port 5a to control the meter-out flow rate of the head side port 5a. Furthermore, both the spools 17 and 18 may be connected to the rod side port 6b to control the meter-in flow rate of the rod side port 6b. Furthermore, the spools 19 and 20 may also be connected to the head side port 6a to control the meter-out flow rate of the head side port 6a.

[0095] The number of spool holes 11b, 11c in the multi-control valve 10 in this embodiment is not limited to the above-described number and may be five or less, or eight or more. Furthermore, while the spools 14, 15 are inserted into the corresponding spool holes 11b, 11c, they may be inserted into two different first spool holes 11b or two different second spool holes 11c, or into offset spool holes 11b, 11c. The same applies to the spools 17, 18, spools 19, 20, spools 21, 22, and spools 23, 24. The control device 70 does not necessarily need to control the multi-control valve 10 as described above; it is sufficient that the control device 70 controls the actuators 2 to 7 so that the flow rates corresponding to the command signals are supplied to and discharged from the actuators 2 to 7.

[0096] <Exemplary Embodiment> A multi-control valve in a first aspect is a multi-control valve that controls the flow of hydraulic fluid to two ports of a first actuator, and includes: a first control spool connected to a first hydraulic pump, a tank, and one of the two ports and controlling the flow of hydraulic fluid to the one port; and a second control spool connected to the first hydraulic pump, the tank, and the other of the two ports and controlling the flow of hydraulic fluid to the other port, wherein the first and second control spools control the flow rates of hydraulic fluid independently of each other.

[0097] According to the above aspect, the first control spool controls the flow of hydraulic fluid to one port, and the second control spool controls the flow of hydraulic fluid to the other port. Therefore, a passage connecting the first control spool to the other port and a passage connecting the second control spool to the one port can be omitted. This simplifies the configuration of the passages formed in the multi-control valve, allowing for a more compact multi-control valve. Furthermore, the first and second control spools control the flow rate of hydraulic fluid independently of each other. Therefore, the flow rate of hydraulic fluid supplied to and discharged from each port of the actuator can be controlled independently of each other in the multi-control valve, allowing for a more compact design.

[0098] In a second aspect, the multi-control valve is the multi-control valve of the first aspect, further comprising a second hydraulic pump different from the first hydraulic pump, and a first sub-spool connected to the one port and controlling the flow rate of hydraulic fluid supplied from the second hydraulic pump to the one port, the first sub-spool controlling the flow rate of hydraulic fluid independently of the first and second control spools.

[0099] According to the above aspect, the hydraulic fluid supply device further includes a second pump and a first sub-spool connected to one of the ports and controlling the flow of hydraulic fluid supplied to the one port. Therefore, a larger flow rate of hydraulic fluid can be supplied to the one port by the first control spool and the first sub-spool. Furthermore, the first sub-spool controls the flow rate of hydraulic fluid independently of the first and second control spools. Therefore, the flow rate of hydraulic fluid supplied to the one port via the first sub-spool can be controlled independently from the flow rate of hydraulic fluid discharged from the other port. This allows for more accurate control of the flow rate of hydraulic fluid supplied to the one port via the first control spool and the first sub-spool.

[0100] A multi-control valve in a third aspect is the multi-control valve of the second aspect, further comprising: a third control spool connected to one of two ports of the second actuator, the second hydraulic pump, and the tank, and controlling the flow of hydraulic fluid to the one port of the second actuator; and a fourth control spool connected to the other port of the second actuator, the second hydraulic pump, and the tank, and controlling the flow of hydraulic fluid to the other port of the second actuator, wherein the third and fourth control spools control the flow rates of hydraulic fluid independently of each other.

[0101] According to the above aspect, the third control spool controls the flow of hydraulic fluid to one port of the second actuator, and the fourth control spool controls the flow of hydraulic fluid to the other port of the second actuator. Therefore, a passage connecting the third control spool to the other port of the second actuator and a passage connecting the fourth control spool to the one port of the second actuator can be omitted. This allows the multi-control valve to be made more compact. Furthermore, the third and fourth control spools control the flow rates of hydraulic fluid independently of each other. Therefore, the flow rates of hydraulic fluid supplied to and discharged from each port of the second actuator can be controlled independently of each other for the multi-control valve, and the multi-control valve can be made more compact.

[0102] In a fourth aspect, the multi-control valve is the multi-control valve of the third aspect, further comprising a second sub-spool connected to one port of the second actuator and the first hydraulic pump, and controlling the flow rate of hydraulic fluid supplied to the one port, wherein the second sub-spool controls the flow rate of hydraulic fluid independently of the third and fourth control spools.

[0103] According to the above aspect, the hydraulic control device further includes a second sub-spool connected to one port of the second actuator and the first pump, for controlling the flow of hydraulic fluid supplied to the one port of the second actuator. Therefore, a larger flow rate of hydraulic fluid can be supplied to the one port by the third control spool and the second sub-spool. Furthermore, the second sub-spool controls the flow rate of hydraulic fluid independently of the third and fourth control spools. Therefore, the flow rate of hydraulic fluid supplied to the one port via the second sub-spool can be controlled independently from the flow rate of hydraulic fluid discharged from the other port. This allows for more accurate control of the flow rate of hydraulic fluid when hydraulic fluid is supplied to the one port via the third control spool and the second sub-spool.

[0104] In a fifth aspect, the multi-control valve is the multi-control valve of the fourth aspect, further comprising a third sub-spool connected to the other port of the first hydraulic pump and the other port of the second actuator and controlling the flow rate of hydraulic fluid supplied to the other port, wherein the third sub-spool controls the flow rate of hydraulic fluid independently of the third and fourth control spools and the second sub-spool.

[0105] According to the above aspect, the hydraulic pump further includes a third sub-spool connected to the other port of the first pump and the second actuator and controlling the flow of hydraulic fluid to the other port. Therefore, a larger flow rate of hydraulic fluid can be supplied to or discharged from the other port by the fourth control spool and the third sub-spool. Furthermore, the third sub-spool controls the flow rate of hydraulic fluid independently of the third and fourth control spools and the second sub-spool. Therefore, the flow rate of hydraulic fluid supplied to or discharged from the other port can be controlled independently from the flow rate of hydraulic fluid supplied to or discharged from one port. This allows for more accurate control of the flow rate of hydraulic fluid supplied or discharged to the other port via the fourth control spool and the third sub-spool.

[0106] In a sixth aspect, the multi-control valve is the multi-control valve of the fifth aspect, wherein the first sub-spool is connected to a first passage connecting the first control spool and one port of the first actuator, the second sub-spool is connected to a second passage connecting the third control spool and one port of the second actuator, and the third sub-spool is connected to a third passage connecting the fourth control spool and the other port of the second actuator.

[0107] According to the above aspect, each sub-spool is connected to a respective one of the first to third passages. Therefore, hydraulic fluid from the first and second pumps can be combined and supplied to one port of the first actuator, and hydraulic fluid from the first and second pumps can be combined and supplied to each port of the second actuator. This reduces the number of passages formed in the multi-control valve. This simplifies the configuration of the passages formed in the multi-control valve, allowing for a more compact multi-control valve.

[0108] In a seventh aspect, the multi-control valve is the multi-control valve of any one of the first to sixth aspects, further comprising a valve block including a pair of spool holes extending in a first direction and arranged in a row with a partition wall therebetween, and the first control spool and the second control spool are slidably inserted into each of the pair of spool holes.

[0109] According to the above aspect, the valve block includes a pair of spool holes extending in a first direction and arranged in a row in the first direction with a partition wall sandwiched therebetween. The first and second control spools are slidably inserted into the spool holes arranged in the first direction. Therefore, two control spools that can independently control the flow rates of hydraulic fluid supplied to and discharged from the respective ports of the actuator can be arranged in a row in the first direction. This makes it possible to reduce the size of the valve block that can independently control the flow rates of hydraulic fluid supplied to and discharged from the respective ports of the actuator.

[0110] In an eighth aspect, the multi-control valve is the multi-control valve of any one of the third to sixth aspects, further comprising a valve block including a plurality of spool holes extending in a first direction, the plurality of spool holes being arranged in a row in the first direction with corresponding spool holes sandwiched between partitions, wherein the first and second control spools are slidably inserted into pairs of the spool holes arranged in a row, and the third and fourth control spools are slidably inserted into another pair of spool holes different from the pair of spool holes.

[0111] According to the above aspect, the valve block includes a plurality of spool holes extending in a first direction and arranged in a row in the first direction with corresponding spool holes sandwiched between them by a partition wall. The first and second control spools and the third and fourth control spools are slidably inserted into different pairs of spool holes, respectively. Therefore, two control spools that can independently control the flow rates of hydraulic fluid supplied to and discharged from the ports of the first actuator can be arranged in a row, and two control spools that can independently control the flow rates of hydraulic fluid supplied to and discharged from the ports of the second actuator can be arranged in a row in the first direction. This allows the valve block that can independently control the flow rates of hydraulic fluid supplied to and discharged from the ports of the first and second actuators to be made smaller.

[0112] A hydraulic drive device in a ninth aspect further includes the multi-control valve of any one of the third to sixth aspects and a control device, wherein the multi-control valve further includes: a first traveling spool connected to a first traveling motor and the first hydraulic pump and configured to control a flow rate of hydraulic fluid supplied to the first traveling motor; a second traveling spool connected to a second traveling motor and the second hydraulic pump and configured to control a flow rate of hydraulic fluid supplied to the second traveling motor; and a plurality of pressure sensors configured to respectively detect supply pressures of hydraulic fluid supplied to the first actuator, the first traveling motor, and the second traveling motor. The control device controls the openings of the first and second control spools and the first and second traveling spools based on input commands and hydraulic pressures detected by the pressure sensors, and when operating the first and second traveling spools, if the supply pressure of the first actuator is lower than the supply pressure of the first and second traveling motors among the hydraulic pressures detected by the pressure sensors, the control device reduces the openings of the first to fourth control spools, and if the supply pressure of the first and second traveling motors is lower than the supply pressure of the first actuator among the hydraulic pressures detected by the pressure sensors, the control device reduces the openings of the first and second traveling spools.

[0113] According to the above aspect, when operating the first traveling spool and the second traveling spool, the control device controls the openings of the first to fourth control spools and the first traveling spool and the second traveling spool to supply a flow rate corresponding to an input command to each actuator. For example, when the supply pressure of the first and second actuators is low, the control device narrows the openings of the first to fourth control spools. This makes it easier for hydraulic fluid to flow to the first traveling spool and the second traveling spool, allowing a flow rate corresponding to the input command to flow to each traveling motor.

[0114] In a tenth aspect, the hydraulic drive device is the hydraulic drive device of the ninth aspect, wherein the multi-control valve further includes a junction spool that opens and closes a junction passage connecting the first hydraulic pump and the second hydraulic pump, and when operating the first traveling spool and the second traveling spool, the control device connects the first hydraulic pump and the second hydraulic pump by opening the junction passage with the junction spool.

[0115] According to the above aspect, when the control device operates the first traveling spool and the second traveling spool, the control device connects the first hydraulic pump and the second hydraulic pump by opening the merging spool. This makes it possible to equalize the supply pressures to the two traveling motors that were previously connected separately, thereby improving straight-line running performance when the two traveling motors are operated simultaneously.

[0116] In an eleventh aspect, a multi-control valve is a hydraulic drive device that is connected to a first hydraulic pump and a second hydraulic pump and controls the flow of hydraulic fluid to a first actuator having two ports, and includes a first control spool that controls the flow rate of hydraulic fluid supplied from the first hydraulic pump to one of the two ports, and a second control spool that controls the flow rate of hydraulic fluid discharged from the other of the two ports, and further includes a first sub-spool that controls the flow rate of hydraulic fluid supplied from the second hydraulic pump to the one port, and the first control spool, the first sub-spool, and the second control spool control the flow rates of hydraulic fluid independently of each other.

[0117] According to the above aspect, the multi-control valve includes a first sub-spool that controls the flow rate of hydraulic fluid supplied from the second pump to one of the ports. Therefore, a larger flow rate of hydraulic fluid can be supplied to one of the ports by the first control spool and the first spool. Furthermore, the first control spool, the first sub-spool, and the second control spool control the flow rates of hydraulic fluid independently of each other. Therefore, the flow rate of hydraulic fluid flowing into one of the ports can be controlled independently from the flow rate of hydraulic fluid discharged from the other port. This allows for more accurate control of the flow rate of hydraulic fluid when supplying hydraulic fluid to the actuator via the first control spool and the first sub-spool. Therefore, a larger flow rate of hydraulic fluid can be supplied to the actuator while suppressing an increase in size of the multi-control valve.

[0118] In a twelfth aspect, the multi-control valve is the multi-control valve of the eleventh aspect, further comprising a third control spool that controls the flow rate of the hydraulic fluid supplied from the second hydraulic pump to one port of the second actuator, a fourth control spool that controls the flow rate of the hydraulic fluid discharged from the other port of the second actuator, and a second sub-spool that controls the flow rate of the hydraulic fluid supplied from the first hydraulic pump to the one port of the second actuator, wherein the third control spool, the second sub-spool, and the fourth control spool control the flow rates of the hydraulic fluid independently of each other.

[0119] According to the above aspect, the multi-control valve further includes a second sub-spool that controls the flow rate of hydraulic fluid supplied from the first pump to one port of the second actuator. Therefore, a larger flow rate of hydraulic fluid can be supplied to one port of the second actuator by the third control spool and the second sub-spool. Furthermore, the third control spool, the second sub-spool, and the fourth control spool control the flow rates of hydraulic fluid independently of each other. Therefore, the flow rate of hydraulic fluid flowing into one port of the second actuator can be controlled independently from the flow rate of hydraulic fluid discharged from the other port. This allows for more accurate control of the flow rate of hydraulic fluid when supplying hydraulic fluid to the actuator via the third control spool and the second sub-spool. Therefore, a larger flow rate of hydraulic fluid can be supplied to the actuator while preventing the multi-control valve from becoming too large.

[0120] In a thirteenth aspect, the multi-control valve is the multi-control valve of the twelfth aspect, further comprising a third sub-spool that, together with the fourth control spool, discharges hydraulic fluid from the other port and controls the flow rate of the hydraulic fluid discharged from the other port, and the third sub-spool controls the flow rate of the hydraulic fluid independently of the third control spool, the second sub-spool, and the fourth control spool.

[0121] According to the above aspect, the actuator further includes a third sub-spool that, together with the fourth control spool, discharges hydraulic fluid from the other port and controls the flow rate of hydraulic fluid discharged from the other port. Therefore, a larger flow rate of hydraulic fluid can be discharged from the other port by the fourth control spool and the third sub-spool. Furthermore, the third sub-spool controls the flow rate of hydraulic fluid independently of the third control spool, the second sub-spool, and the fourth control spool. Therefore, the flow rate of hydraulic fluid discharged from the other port can be controlled independently from the flow rate flowing into one port. This allows the flow rate of hydraulic fluid to be controlled with greater precision when discharging hydraulic fluid from the actuator via the fourth control spool and the third sub-spool.

[0122] In a fourteenth aspect, the multi-control valve is the multi-control valve of the third or twelfth aspect, wherein the first actuator is a boom cylinder of a construction machine, the second actuator is an arm cylinder of the construction machine, one port of the first actuator is a head side port of the boom cylinder, the other port of the first actuator is a rod side port of the boom cylinder, one port of the second actuator is a head side port of the arm cylinder, and the other port of the second actuator is a rod side port of the arm cylinder.

[0123] According to the above aspect, one port of the first actuator is a head-side port of the boom cylinder, and one port of the second actuator is a head-side port of the arm cylinder, so that the above-described function can be achieved in a hydraulic drive device that supplies hydraulic fluid to the boom cylinder and the arm cylinder.

[0124] In a fifteenth aspect, the multi-control valve is the multi-control valve of the fourteenth aspect, further comprising a boom regeneration valve element that regenerates hydraulic fluid discharged from a head-side port of the boom cylinder to the arm cylinder.

[0125] According to the above aspect, the boom regenerative valve element regenerates hydraulic fluid discharged from the head-side port of the boom cylinder into the arm passage. This makes it possible to omit a portion of the passage connecting the boom regenerative valve element and each port of the arm cylinder, thereby simplifying the configuration of the passages formed in the hydraulic drive device. This allows the hydraulic drive device to be made more compact.

[0126] In a sixteenth aspect, the multi-control valve is the multi-control valve of the fourteenth aspect, further including: a bucket head-side spool connected to the first hydraulic pump, a tank, and a head-side port of the bucket cylinder, and controlling the flow of hydraulic fluid to the head-side port of the bucket cylinder; and a bucket rod-side spool connected to the first hydraulic pump, the tank, and a rod-side port of the bucket cylinder, and controlling the flow of hydraulic fluid to the rod-side port of the bucket cylinder, wherein the bucket head-side spool and the bucket rod-side spool control the flow rates of hydraulic fluid independently of each other.

[0127] According to the above aspect, the bucket head-side spool controls the flow of hydraulic fluid to the head-side port of the bucket cylinder, and the bucket rod-side spool controls the flow of hydraulic fluid to the rod-side port of the bucket cylinder. Therefore, a passage connecting the bucket head-side spool and the rod-side port, and a passage connecting the bucket rod-side spool and the head-side port can be omitted. This simplifies the configuration of the passages formed in the hydraulic drive unit, thereby enabling the hydraulic drive unit to be made more compact. Furthermore, the bucket head-side spool and the bucket rod-side spool control the flow rate of hydraulic fluid independently of each other. Therefore, the flow rates of hydraulic fluid supplied to and discharged from the ports of the bucket cylinder can be controlled independently of each other, and the hydraulic drive unit can be made more compact.

[0128] In a seventeenth aspect, the multi-control valve is the multi-control valve of the fourteenth aspect, further comprising: a first swing spool connected to the second hydraulic pump, the tank, and a first supply / discharge port of the swing motor, and controlling the flow of hydraulic fluid to the first supply / discharge port of the swing motor; and a second swing spool connected to the second hydraulic pump, the tank, and a second supply / discharge port of the swing motor, and controlling the flow of hydraulic fluid to the second supply / discharge port of the swing motor, wherein the first and second swing spools control the flow rate of hydraulic fluid independently of each other.

[0129] According to the above aspect, the first rotation spool controls the flow of hydraulic fluid to the first supply / discharge port, and the second rotation spool controls the flow of hydraulic fluid to the second supply / discharge port. Therefore, a passage connecting the first rotation spool and the second supply / discharge port and a passage connecting the second rotation spool and the first supply / discharge port can be omitted. This simplifies the configuration of the passages formed in the hydraulic drive unit, thereby enabling the hydraulic drive unit to be made more compact. Furthermore, the first and second rotation spools control the flow rate of hydraulic fluid independently of each other. Therefore, the flow rates of hydraulic fluid supplied to and discharged from each port of the swing motor can be controlled independently of each other, and the hydraulic drive unit can be made more compact.

[0130] From the above description, many modifications and other embodiments of the present disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present disclosure. Details of the structure and / or function thereof can be substantially changed without departing from the spirit of the present disclosure.

Claims

1. A multi-control valve for controlling the flow of hydraulic fluid to two ports of a first actuator, comprising: a first control spool connected to a first hydraulic pump, a tank, and one of the two ports, for controlling the flow of hydraulic fluid to the one port; and a second control spool connected to the first hydraulic pump, the tank, and the other of the two ports, for controlling the flow of hydraulic fluid to the other port, wherein the first and second control spools independently control the flow rate of the hydraulic fluid.

2. The multi-control valve according to claim 1, further comprising a second hydraulic pump different from the first hydraulic pump, and a first sub-spool connected to the one port for controlling the flow rate of the hydraulic fluid supplied from the second hydraulic pump to the one port, wherein the first sub-spool independently controls the flow rate of the hydraulic fluid from the first and second control spools.

3. The multi-control valve according to claim 2, comprising: a third control spool connected to one of the two ports of a second actuator, the second hydraulic pump, and the tank, for controlling the flow of hydraulic fluid to the one port of the second actuator; and a fourth control spool connected to the other port of the second actuator, the second hydraulic pump, and the tank, for controlling the flow of hydraulic fluid to the other port of the second actuator, wherein the third and fourth control spools independently control the flow rate of the hydraulic fluid.

4. The multi-control valve according to claim 3, further comprising a second sub-spool connected to one of the ports of the second actuator and the first hydraulic pump for controlling the flow rate of the hydraulic fluid supplied to the one port, wherein the second sub-spool independently controls the flow rate of the hydraulic fluid from the third and fourth control spools.

5. The multi-control valve according to claim 4, further comprising a third sub-spool connected to the first hydraulic pump and the other port of the second actuator for controlling the flow rate of the hydraulic fluid supplied to the other port, wherein the third sub-spool independently controls the flow rate of the hydraulic fluid from the third and fourth control spools and the second sub-spool.

6. The first sub-pool is connected to a first passage connecting the first control spool and one port of the first actuator; the second sub-pool is connected to a second passage connecting the third control spool and one port of the second actuator; and the third sub-pool is connected to a third passage connecting the fourth control spool and the other port of the second actuator. The multi-control valve according to claim 5.

7. The multi-control valve according to claim 1, further comprising a valve block including a pair of spool holes extending in a first direction and arranged in a row with a partition therebetween, wherein the first control spool and the second control spool are slidably inserted into each of the pair of spool holes.

8. The multi-control valve according to claim 3, further comprising a valve block including a plurality of spool holes extending in a first direction, wherein corresponding spool holes are arranged in a row in the first direction with a partition therebetween. The first and second control spools are slidably inserted into a pair of spool holes arranged in a row, respectively, and the third and fourth control spools are slidably inserted into another pair of spool holes different from the pair of spool holes, respectively.

9. The hydraulic drive device further comprises the multi-control valve according to claim 3 and a control device, wherein the multi-control valve further comprises: a first traveling spool connected to the first traveling motor and the first hydraulic pump and configured to control the flow rate of the hydraulic fluid supplied to the first traveling motor; a second traveling spool connected to the second traveling motor and the second hydraulic pump and configured to control the flow rate of the hydraulic fluid supplied to the second traveling motor; and a plurality of pressure sensors configured to respectively detect the supply pressures of the hydraulic fluid supplied to the first actuator, the first traveling motor, and the second traveling motor. The control device controls the opening degrees of the first and second control spools and the first and second traveling spools based on an input command and the hydraulic pressures detected by the respective pressure sensors. When operating the first and second traveling spools, if the supply pressure of the first actuator is lower than the supply pressures of the first and second traveling motors at the hydraulic pressures detected by the respective pressure sensors, the control device reduces the opening degrees of the first to fourth control spools; and if the supply pressures of the first and second traveling motors are lower than the supply pressure of the first actuator at the hydraulic pressures detected by the respective pressure sensors, the control device reduces the opening degrees of the first and second traveling spools.

10. The multi-control valve further comprises a confluence spool configured to open and close a confluence passage connecting the first hydraulic pump and the second hydraulic pump. When operating the first traveling spool and the second traveling spool, the control device connects the first hydraulic pump and the second hydraulic pump by opening the confluence passage with the confluence spool. The hydraulic drive device according to claim 9.

11. A hydraulic drive device that is connected to a first hydraulic pump and a second hydraulic pump and controls the flow of hydraulic fluid to a first actuator having two ports, the hydraulic drive device comprising: a first control spool that controls the flow rate of the hydraulic fluid supplied from the first hydraulic pump to one of the two ports; and a second control spool that controls the flow rate of the hydraulic fluid discharged from the other of the two ports, further comprising a first sub-spool that controls the flow rate of the hydraulic fluid supplied from the second hydraulic pump to the one port, wherein the first control spool, the first sub-spool, and the second control spool independently control the flow rate of the hydraulic fluid, and is a multi-control valve.

12. A third control spool that controls the flow rate of the hydraulic fluid supplied from the second hydraulic pump to one port of a second actuator; a fourth control spool that controls the flow rate of the hydraulic fluid discharged from the other port of the second actuator; and a second sub-spool that controls the flow rate of the hydraulic fluid supplied from the first hydraulic pump to one port of the second actuator, wherein the third control spool, the second sub-spool, and the fourth control spool independently control the flow rate of the hydraulic fluid, and is the multi-control valve according to claim 11.

13. Further comprising a third sub-spool that discharges the hydraulic fluid from the other port together with the fourth control spool and controls the flow rate of the hydraulic fluid discharged from the other port, wherein the third sub-spool independently controls the flow rate of the hydraulic fluid from the third control spool, the second sub-spool, and the fourth control spool, and is the multi-control valve according to claim 12.

14. The first actuator is a boom cylinder of a construction machine, the second actuator is an arm cylinder of the construction machine, one port of the first actuator is a head-side port of the boom cylinder, the other port of the first actuator is a rod-side port of the boom cylinder, one port of the second actuator is a head-side port of the arm cylinder, and the other port of the second actuator is a rod-side port of the arm cylinder, and is the multi-control valve according to claim 3 or 12.

15. The multi-control valve according to claim 14, further comprising a boom regeneration valve body that regenerates the hydraulic fluid discharged from the head-side port of the boom cylinder to the arm cylinder.

16. A bucket head-side spool that is connected to the first hydraulic pump, the tank, and the head-side port of the bucket cylinder and controls the flow of hydraulic fluid to the head-side port of the bucket cylinder; and a bucket rod-side spool that is connected to the first hydraulic pump, the tank, and the rod-side port of the bucket cylinder and controls the flow of hydraulic fluid to the rod-side port of the bucket cylinder. The bucket head-side spool and the bucket rod-side spool independently control the flow rate of the hydraulic fluid. The multi-control valve according to claim 14.

17. A first swing spool that is connected to the second hydraulic pump, the tank, and the first supply / discharge port of the swing motor and controls the flow of hydraulic fluid to the first supply / discharge port of the swing motor; and a second swing spool that is connected to the second hydraulic pump, the tank, and the second supply / discharge port of the swing motor and controls the flow of hydraulic fluid to the second supply / discharge port of the swing motor. The first and second swing spools independently control the flow rate of the hydraulic fluid. The multi-control valve according to claim 14.

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