Fluid pressure system and method of controlling fluid pressure

Abstract

The present application relates to a fluid pressure system and a fluid pressure control method. A fluid pressure system of an aspect of the present application includes: a merging passage that connects a first flow passage through which working fluid ejected from a first pump flows and a second flow passage through which working fluid ejected from a second pump flows; a merging control valve that has a merging passage through which merged working fluid, which is formed by merging the working fluid from the first pump and the working fluid from the second pump, passes from the merging passage to a downstream, the merging control valve being capable of adjusting an opening degree of the merging passage; a first control valve that drives a first actuator by controlling flows of the working fluid supplied through a supply passage branched from the first flow passage and the merged working fluid supplied from the merging control valve; and a second control valve that drives a second actuator by controlling a flow of the working fluid supplied from the merging passage through the second flow passage.

Description

Technical Field

[0001] This disclosure relates to fluid pressure systems. Background Technology

[0002] A fluid pressure system is known to drive an actuator by merging working fluids ejected from two pumps and controlling the flow rate of the merged working fluid. For example, Japanese Patent Application Publication No. 6-346904 discloses a hydraulic circuit comprising a first circuit using pressurized oil ejected from a first pump to drive a first actuator and a second circuit using pressurized oil ejected from a second pump to drive a second actuator. In this circuit, pressurized oil from the first pump is merged with pressurized oil from the second pump, and the merged pressurized oil is used to drive the second actuator in the second circuit. In this hydraulic circuit, when the second actuator is not driven, pressurized oil from the first pump is not supplied to the second circuit but is discharged to the tank via a bypass path. On the other hand, when the second actuator needs to be driven, the pressurized oil from the first pump is merged with the pressurized oil from the second pump by blocking the bypass path, and the merged pressurized oil can be used to drive the second actuator. Japanese Patent Application Publication No. 2001-349304 also discloses a hydraulic circuit in which the hydraulic oil in the first circuit merges with the hydraulic oil in the second circuit. Such a fluid pressure system is used, for example, in construction machinery.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 6-346904

[0006] Patent Document 2: Japanese Patent Application Publication No. 2001-349304 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In conventional fluid pressure systems, the working fluid from one circuit can merge with the working fluid from another circuit, but merging in the opposite direction is not possible. That is, the merging of the working fluid is unidirectional. For example, when using a merged hydraulic oil formed by merging the hydraulic oil from the first circuit and the hydraulic oil from the second circuit to drive an actuator in the second circuit, this merged hydraulic oil cannot be used as hydraulic oil to operate the actuator in the first circuit.

[0009] One of the objectives of this disclosure is to enable the combined working fluid obtained by combining working fluids that were separately used in two circuits to be used in both circuits. Other objectives of this disclosure will become apparent from the full description herein.

[0010] Solution for solving the problem

[0011] The fluid pressure system of one or more embodiments of the present invention includes: a confluence path connecting a first flow path for working fluid supplied from a first pump and a second flow path for working fluid supplied from a second pump; a confluence control valve having a confluence passage that allows a confluence working fluid formed by the confluence of working fluid from the first pump and working fluid from the second pump to flow downstream from the confluence path, the confluence control valve being capable of adjusting the opening of the confluence passage; a first control valve that drives a first actuator by controlling the flow rates of working fluid supplied via a supply flow path branching from the first flow path and the confluence working fluid supplied from the confluence control valve; and a second control valve that drives a second actuator by controlling the flow rate of working fluid supplied from the confluence path via the second flow path.

[0012] In one or more technical solutions of the present invention, the merging control valve adjusts the opening degree of the merging passage according to the pressure difference between the load pressure of the second actuator and the fluid pressure of the merging passage.

[0013] In one or more of the technical solutions of the present invention, the second control valve blocks the second actuator from the second pump in the neutral position where the second actuator is not driven.

[0014] In one or more of the technical solutions of the present invention, the opening of the merging passage is maximized when the second actuator is not driven.

[0015] In one or more of the technical solutions of the present invention, the confluence path is blocked when the first actuator and the second actuator are driven.

[0016] One or more technical solutions of the present invention provide a fluid pressure system comprising: a third flow path connecting the confluence control valve and the first control valve; and a tank passage connecting the first control valve and a tank. In one or more technical solutions of the present invention, the first control valve has a vent passage connecting the third flow path and the tank passage, and the first control valve is capable of adjusting the opening degree of the vent passage.

[0017] In one or more technical solutions of the present invention, the fluid pressure system includes a flow control valve, which supplies working fluid of a flow rate corresponding to the opening of the vent passage from the first pump to the first control valve via the supply flow path, and supplies the remaining fluid, i.e., the difference between the working fluid from the first pump and the working fluid supplied to the first control valve, to the confluence path.

[0018] The fluid pressure system of one or more embodiments of the present invention includes a third control valve that drives a third actuator by controlling the flow rate of at least a portion of the residual fluid supplied from the first flow path via other supply flow paths and the flow rate of the combined working fluid supplied from the combined control valve.

[0019] One or more technical solutions of the present invention include a fluid pressure system comprising a one-way valve that prevents working fluid from flowing from the confluence path to the first flow path between the first flow path and the confluence path.

[0020] The fluid pressure system of one or more technical solutions of the present invention includes an additional confluence control valve, which is disposed between the first flow path and the confluence path, has a connection passage connecting the first flow path and the confluence path, and is capable of adjusting the opening degree of the connection passage.

[0021] One or more technical solutions of the present invention provide a fluid pressure system comprising: a fourth control valve that drives a fourth actuator by controlling the flow rate of working fluid supplied via the second flow path; and a high-pressure selection unit that supplies the high-pressure portion of the load pressure of the second actuator and the load pressure of the fourth actuator to the confluence control valve. In one or more technical solutions of the present invention, the confluence control valve adjusts the opening degree of the confluence passage based on the pressure difference between the load pressure supplied from the high-pressure selection unit and the fluid pressure of the confluence path.

[0022] In one or more of the technical solutions of the present invention, the fourth control valve blocks the fourth actuator from the second pump in the neutral position where the fourth actuator is not driven.

[0023] One or more technical solutions of the present invention provide a fluid pressure system comprising: a first pump; a second pump; a confluence path connecting a first flow path for working fluid supplied from the first pump and a second flow path for working fluid supplied from the second pump; and a confluence control valve. In one or more technical solutions of the present invention, the confluence control valve has a confluence passage that allows a confluence working fluid, formed by the confluence of working fluid from the first pump and working fluid from the second pump, to flow downstream from the confluence path. In one or more technical solutions of the present invention, the opening degree of the confluence passage is adjustable. One or more technical solutions of the present invention provide a fluid pressure system comprising: a first control valve that drives a first actuator by controlling the flow rates of working fluid supplied via a supply flow path branching from the first flow path and the confluence working fluid supplied from the confluence control valve; and a second control valve that drives a second actuator by controlling the flow rate of working fluid supplied from the confluence path via the second flow path.

[0024] The fluid pressure control method of one or more technical solutions of the present invention includes: a merging step, wherein working fluid from the first pump and working fluid from the second pump are merged in a merging path connecting a first flow path for the flow of working fluid from a first pump and a second flow path for the flow of working fluid from a second pump to obtain a merged working fluid; a first driving step, wherein the flow rates of working fluid supplied via a supply flow path branching from the first flow path and the merged working fluid are controlled by a first control valve, thereby driving a first actuator; a second driving step, wherein the flow rate of working fluid supplied from the merging path via the second flow path is controlled by a second control valve, thereby driving a second actuator; and an adjustment step, wherein the flow rate of the merged working fluid supplied from the merging path to the first control valve is adjusted according to the pressure difference between the load pressure of the second actuator and the fluid pressure of the merging path.

[0025] The effects of the invention

[0026] Using the embodiments of the present invention, a combined working fluid obtained by combining working fluids that were used in two separate loops can be used in both loops. Attached Figure Description

[0027] Figure 1 This is a diagram illustrating a fluid pressure system according to one embodiment of the present invention.

[0028] Figure 2 This is a diagram illustrating a fluid pressure system according to another embodiment of the present invention.

[0029] Figure 3 This is a diagram illustrating a fluid pressure system according to another embodiment of the present invention.

[0030] Explanation of reference numerals in the attached figures

[0031] 1. 101, 201, Hydraulic system; 2a, 2b, Hydraulic pump; 3. Tank; 4a~4e, Actuator; 5. Hydraulic circuit; 10. First circuit; 11. 21. 34. 211. 221. 231. Flow control valve; 12. 22. 212. 222. 232. Control valve; 20. Second circuit; 24a, 24b. Shuttle valve; 31. Check valve; 32. Merging control valve; 41. 51. Pump oil circuit; 61. Tank oil circuit; 71. Merging circuit. Detailed Implementation

[0032] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. Elements common to multiple drawings are labeled with the same reference numerals in those drawings.

[0033] Figure 1This diagram illustrates a fluid pressure system 1 according to one embodiment of the present invention. The fluid pressure system 1 is, for example, a hydraulic system that uses pressurized oil as the working fluid. In this specification, it is assumed that the fluid pressure system 1 uses pressurized oil as the working fluid. Therefore, the fluid pressure system 1 is sometimes referred to as a hydraulic system 1. The present invention can also be applied to fluid pressure systems that use working fluids other than pressurized oil (e.g., compressed air or compressed liquids other than pressurized oil).

[0034] The hydraulic system 1 includes: hydraulic pumps 2a and 2b that spray pressurized oil, actuators 4a and 4b driven by the pressurized oil sprayed from the hydraulic pumps 2a and 2b, and a tank 3 for storing the pressurized oil discharged from the actuators 4a and 4b. The flow rate and direction of the pressurized oil sprayed from the hydraulic pumps 2a and 2b are controlled by a hydraulic circuit 5.

[0035] Hydraulic pumps 2a and 2b are driven, for example, by an engine (not shown). Hydraulic pumps 2a and 2b may also be driven by a single engine. Hydraulic pumps 2a and 2b can be either fixed-capacity or variable-capacity pumps.

[0036] Hydraulic system 1 is used, for example, in construction machinery. Actuators 4a and 4b can also be various types of hydraulic actuators used in construction machinery. When hydraulic system 1 is used in construction machinery, actuators 4a and 4b can also be main winch drive motors that drive the main winch, auxiliary winch drive motors that drive the auxiliary winch, boom extension cylinders that extend and retract the boom, boom raising or lowering cylinders that raise or lower the boom, boom rotation cylinders that rotate the boom, and other known actuators.

[0037] The hydraulic circuit 5 has a first circuit 10 and a second circuit 20. The first circuit 10 controls the flow rate of hydraulic oil ejected from the hydraulic pump 2a and supplies the controlled flow rate of hydraulic oil to the actuator 4a. The second circuit 20 controls the flow rate of hydraulic oil ejected from the hydraulic pump 2b and supplies the controlled flow rate of hydraulic oil to the actuator 4b. As described later, sometimes the first circuit 10 supplies a combined hydraulic oil consisting of hydraulic oil ejected from the hydraulic pump 2b and hydraulic oil ejected from the hydraulic pump 2a. In this case, the first circuit 10 controls the flow rate of at least one of the combined hydraulic oil and the hydraulic oil ejected from the hydraulic pump 2a. Similarly, sometimes the second circuit 20 also supplies the combined hydraulic oil. In this case, the second circuit 20 controls the flow rate of at least one of the combined hydraulic oil and the hydraulic oil ejected from the hydraulic pump 2b.

[0038] In the illustrated embodiment, the first loop 10 includes a flow control valve 11, a control valve 12, and unloading valves 13 and 14. The second loop 20 includes a flow control valve 21 and a control valve 22. A check valve 31, a manifold control valve 32, and an unloading valve 33 are disposed between the first loop 10 and the second loop 20. The first loop 10 and the second loop 20 can adopt various loop structures other than those illustrated. Figure 1 The hydraulic circuit 5 shown represents an example of a hydraulic circuit to which the present invention can be applied; however, the present invention is not limited to the illustrated embodiment.

[0039] Control valves 12, 22 and unloading valves 13, 14, 33 can also be pilot-operated valves that operate using pilot pressure supplied from an electromagnetic proportional valve (not shown). This electromagnetic proportional valve, for example, can generate pilot pressure according to a drive signal from a controller (not shown). The controller, for example, receives an operation signal corresponding to the operation amount of an operating lever located in the cab of the construction machinery, and generates a drive signal for actuating the electromagnetic proportional valve based on this operation signal. The electromagnetic proportional valve, operating lever, and controller are not shown in the figures.

[0040] Next, the constituent elements of the first circuit 10 will be described in more detail. The flow control valve 11 is connected upstream to the pump oil passage 41, which supplies pressurized oil flow from the hydraulic pump 2a, and downstream to the supply oil passage 42 and the bypass oil passage 43. Thus, the pump oil passage 41 branches into the supply oil passage 42 and the bypass oil passage 43. The flow control valve 11 has a supply passage connecting the pump oil passage 41 and the supply oil passage 42, and a bypass passage connecting the pump oil passage 41 and the bypass oil passage 43. The flow control valve 11 can gradually change the opening degree of the supply oil passage and the bypass passage between a first connection position 11A and a second connection position 11B. In the first connection position 11A, the opening degree of the supply oil passage connecting the pump oil passage 41 and the supply oil passage 42 is at its maximum, and in the second connection position 11B, the opening degree of the bypass passage connecting the pump oil passage 41 and the bypass oil passage 43 is at its maximum. If the opening of the oil supply passage increases, the opening of the bypass passage decreases, and vice versa.

[0041] When the hydraulic pump 2a is not supplying pressurized oil, the flow control valve 11 remains in the first connection position 11A under the action of a spring. The flow control valve 11 has: a first pressure chamber into which the load pressure of the actuator 4a is introduced via a downstream passage of the control valve 12 and a load pressure detection passage 81; and a second pressure chamber into which pressurized oil from a branch of the oil supply line 42 is introduced. When the control valve 12 is in the neutral position, the downstream passage of the control valve 12 is maintained at the tank pressure, so the tank pressure also acts on the first pressure chamber of the flow control valve 11. In addition, when the control valve 12 is in the neutral position, the oil supply line 42 is blocked by the control valve 12. Therefore, when the control valve 12 is in the neutral position, if pressurized oil is ejected from the hydraulic pump 2a, the second pressure chamber is pressurized, and the flow control valve 11 switches from the first connection position 11A to the second connection position 11B. In response, if control valve 12 is switched to supply pressurized oil to actuator 4a, the load pressure of actuator 4a acts on the first pressure chamber. Thus, the pressure acting on the first pressure chamber varies depending on the stroke of control valve 12. As will be described later, the larger the stroke of control valve 12, the smaller the opening of the venting passage, and the higher the load pressure of actuator 4a. Therefore, the position of flow control valve 11 can be controlled according to the stroke of control valve 12. When the load pressure of actuator 4a is sufficiently large, flow control valve 11 switches to the first connection position 11A.

[0042] The control valve 12 has a vent 12a, an inlet throttling opening 12b, and openings A1 and B1 for supplying discharge pressure oil relative to the actuator 4a. The vent 12a is connected to the merge control valve 32 (described later) via a central oil passage 44. The vent 12a is connected to the tank oil passage 61 via a vent passage located inside the control valve 12. The inlet throttling opening 12b is connected to the oil supply passage 42. The central oil passage 44 has a branch oil passage 45 that branches off upstream of the vent 12a and is connected to the oil supply passage 42. A check valve 15 is provided between the oil supply passage 42 and the branch oil passage 45 of the central oil passage 44 to prevent backflow from the oil supply passage 42 to the central oil passage 44.

[0043] Control valve 12 is switched to any of the neutral position 12A, the first supply position 12B, and the second supply position 12C by means of pilot pressure from the solenoid proportional valve. In the illustrated embodiment, control valve 12 is a neutral fully open type valve. For the neutral fully open type control valve 12, in the neutral position 12A, the vent passage is fully open, and the vent opening 12a is connected to the tank oil passage 61. If pilot pressure is supplied to control valve 12 from the solenoid proportional valve, the opening of the vent passage is reduced according to the stroke of the spool of control valve 12. When the spool moves to the end of its stroke, control valve 12 switches to the first supply position 12B or the second supply position 12C.

[0044] The control valve 12 has a hydraulic oil supply passage that connects the inlet throttling opening 12b to openings A1 and B1. For example, when the control valve 12 is switched to the first supply position 12B, the inlet throttling opening 12b is connected to opening A1 via the hydraulic oil supply passage of the control valve 12, and the tank oil passage 61 is connected to opening B1 via the hydraulic oil discharge passage of the control valve 12. Similarly, when the control valve 12 is switched to the second supply position 12C, the inlet throttling opening 12b is connected to opening B1 via the hydraulic oil supply passage of the control valve 12, and the tank oil passage 61 is connected to opening A1 via the hydraulic oil discharge passage of the control valve 12. Thus, depending on the switching position of the control valve 12, the hydraulic oil supplied from the hydraulic pump 2a and the connection between the tank 3 and the actuator 4a are switched. Alternatively, when actuator 4a is an auxiliary winch drive motor that drives an auxiliary winch, when control valve 12 is switched to the first supply position 12B, the auxiliary winch drive motor is driven in the winding direction; when control valve 12 is switched to the second supply position 12C, the auxiliary winch drive motor is driven in the winding direction. Alternatively, when actuator 4a is a boom extension cylinder that extends the boom, when control valve 12 is switched to the first supply position 12B, the boom extension cylinder is driven in the extension direction; when control valve 12 is switched to the second supply position 12C, the boom retraction cylinder is driven in the boom retraction direction.

[0045] An unloading valve 13 is positioned between the pump oil circuit 41 and the tank oil circuit 61. The unloading valve 13 operates when the oil pressure in the pump oil circuit 41 exceeds a set pressure, causing the pressurized oil in the pump oil circuit 41 to return to the tank oil circuit 61. That is, when the oil pressure in the pump oil circuit 41 exceeds the set pressure, the unloading valve 13 is used to unload the hydraulic pump 2a. An unloading valve 14 is positioned between the bypass oil circuit 43 and the tank oil circuit 61. When the oil pressure in the bypass oil circuit 43 exceeds a set pressure, it causes the pressurized oil to return from the bypass oil circuit 43 to the tank oil circuit 61.

[0046] Next, the components of the second circuit 20 will be described. The flow control valve 21 is connected upstream to a branch oil passage 52 and downstream to a supply oil passage 53. The branch flow passage 52 is a branch of the pump oil passage 51, which supplies pressurized oil ejected from the hydraulic pump 2b. The branch flow passage 52 can also be a branch of the confluence passage 71, described later. The branch flow passage 52 is always connected to the confluence passage 71. The supply oil passage 53 is connected to the inlet throttling opening 22a of the control valve 22.

[0047] The flow control valve 21 has a pressurized oil supply passage connecting the branch flow path 52 and the oil supply passage 53. The flow control valve 21 can gradually change the opening of the pressurized oil supply passage between a connection position 21A (maximum opening) and a blocking position 21B (blocking the supply passage). When the hydraulic pump 2b is not supplying pressurized oil, the flow control valve 21 is in the connection position 21A due to the force of the spring. The flow control valve 21 has: a first pressure chamber connected to a downstream passage of the control valve 22, into which the load pressure of the actuator 4b is introduced; and a second pressure chamber into which the pressurized oil branch of the oil supply passage 53 is introduced. When the control valve 22 is in the neutral position, the oil supply passage 53 is blocked by the control valve 22. Therefore, when control valve 22 is in the neutral position, if pressurized oil is ejected from hydraulic pump 2b, the second pressure chamber is pressurized, and flow control valve 21 switches from connected position 21A to disconnected position 21B. Conversely, if control valve 22 is switched to supply pressurized oil to actuator 4b, the first pressure chamber is pressurized, and flow control valve 21 switches to a position corresponding to the pressure difference between the first and second pressure chambers.

[0048] In addition to the inlet throttling opening 22a, control valve 22 has openings A2 and B2 for supplying discharge pressure oil relative to actuator 4b. If pilot pressure is supplied to control valve 22 from the solenoid proportional valve, the opening degree of the pressure oil supply passage connecting inlet throttling opening 22a to opening A2 or opening B2 gradually changes according to the stroke of the spool of control valve 22. Pressure oil corresponding to the opening degree of this supply passage flows from inlet throttling opening 22a to opening A2 or opening B2. When the spool moves to the end of one stroke, control valve 22 switches to the first supply position 22B; when the spool moves to the end of the other stroke, control valve 22 switches to the second supply position 22C. When control valve 22 switches to the first supply position 22B, the pressure oil supply passage connecting inlet throttling opening 22a and opening A2 becomes fully open, and tank oil passage 61 is connected to opening B2 via the pressure oil discharge passage of control valve 22. When control valve 22 is switched to the second supply position 22C, the inlet throttling opening 22a is connected to opening B2 via the internal pressure oil supply passage of control valve 22, and the tank oil passage 61 is connected to opening A2 via the internal pressure oil discharge passage of control valve 22. Thus, actuator 4b is driven according to the switching position of control valve 22.

[0049] Next, the merging of the pressurized oil ejected from pressure pump 2a and pressure pump 2b will be explained. The pressurized oil ejected from pressure pump 2a at a flow rate corresponding to the opening area of ​​the oil supply passage of flow control valve 11 flows through oil supply passage 42 to the inlet throttling opening 12b of control valve 12, while the remaining oil flows to bypass passage 43. This remaining oil is introduced from bypass passage 43 through check valve 31 into merging passage 71. When flow control valve 11 is switched to the second connection position 11B, the pressurized oil ejected from pressure pump 2a does not branch into other oil passages but is introduced into merging passage 71. Additionally, the pressurized oil ejected from pressure pump 2b is also introduced into merging passage 71. Thus, the pressurized oil ejected from pressure pump 2a and pressure pump 2b merges in merging passage 71. In this specification, the pressure oil obtained by combining the pressure oil ejected from pressure pump 2a and pressure oil ejected from pressure pump 2b in the confluence circuit 71 is referred to as "confluenced pressure oil" or more commonly as "confluenced working fluid".

[0050] A confluence control valve 32 is provided downstream of the confluence path 71. The confluence control valve 32 is connected upstream to the confluence path 71 and downstream to the central oil passage 44. The confluence control valve 32 controls the flow rate of the confluence pressurized oil flowing from the confluence path 71 to the central oil passage 44. Specifically, the confluence control valve 32 has a confluence pressurized oil passage connecting the confluence path 71 and the central oil passage 44, and can gradually change the opening degree of the confluence pressurized oil passage between a blocked position 32A and a fully open connection position 32B. When no pressurized oil is supplied from the hydraulic pumps 2a and 2b, the confluence control valve 32 is held in the blocked position 32A by the force of a spring. The merge control valve 32 has: a first pressure chamber into which the load pressure of the actuator 4b is introduced from the downstream passage of the control valve 22 via the load pressure detection passage 82; and a second pressure chamber into which the pressurized oil from the merge passage 71 is introduced. The operation of the merge control valve 32 will be described later.

[0051] An unloading valve 33 is positioned between the manifold 71 and the tank oil circuit 61. The unloading valve 33 operates when the oil pressure in the manifold 71 exceeds a set pressure, causing the combined pressurized oil to return from the manifold 71 to the tank oil circuit 61. That is, when the oil pressure in the manifold 71 exceeds the set pressure, the unloading valve 33 is used to unload the hydraulic pumps 2a and 2b.

[0052] Regarding the operation of the hydraulic system 1, the operation of the hydraulic system 1 is explained in four scenarios: (1) neither actuator 4a nor 4b is driven; (2) neither actuator 4a is driven but actuator 4b is driven; (3) actuator 4a is driven but actuator 4b is not driven; and (4) both actuator 4a and 4b are driven.

[0053] First, when neither actuators 4a nor 4b are driven (1), control valves 12 and 22 are maintained in the neutral position. If control valve 12 is in the neutral position, the oil supply line 42 is blocked, thus the second pressure chamber of flow control valve 11 is pressurized, thereby switching flow control valve 11 to the second connection position 11B. As a result, the pressurized oil ejected from pressure pump 2a is not directed to other oil line branches, but is introduced into the manifold 71 via bypass oil line 43. In the second circuit 20, control valve 22 is in the neutral position, thus the flow control valve 21 is switched to the blocking position 21B. As a result, the pressurized oil ejected from pressure pump 2b is not directed to other oil line branches, but is introduced into the manifold 71. The combined pressurized oil formed by the combination of the pressurized oil ejected from pressure pump 2a and the pressurized oil ejected from pressure pump 2b is introduced into the second pressure chamber of the manifold control valve 32. At this time, since the downstream of control valve 22 becomes the tank pressure, the first pressure chamber of the merge control valve 32 also becomes the tank pressure. Therefore, the merge control valve 32 switches from the blocking position 32A to the connecting position 32B, and the merged pressurized oil flows from the merge passage 71 to the central oil passage 44. Since control valve 12 is in the neutral position, the merged pressurized oil flows from the central oil passage 44 through the vent passage of control valve 12 to the tank oil passage 61, and is discharged from the tank oil passage 61 to the tank 3. Thus, when actuators 4a and 4b are not driven, the pressurized oil sprayed from pressure pumps 2a and 2b merges in the merge passage 71 to become merged pressurized oil, which is discharged to the tank 3 through the central oil passage 44 and the tank oil passage 61. At this time, no pressurized oil is supplied to actuators 4a and 4b.

[0054] Next, the operation of the hydraulic system 1 in the case where actuator 4a is not driven but actuator 4b is driven will be explained. Since actuator 4a is not driven, control valve 12 is in the neutral position. Therefore, the pressurized oil ejected from pressure pump 2a is introduced into the manifold 71 in the same way as in case (1) above. In manifold 71, the pressurized oil ejected from pressure pump 2a merges with the pressurized oil ejected from pressure pump 2b. In the second circuit 20, since actuator 4b needs to be driven, pilot pressure is supplied to control valve 22, and control valve 22 is switched to the first supply position 22B or the second supply position 22C using this pilot pressure. As a result, the supply passage of flow control valve 21 is opened, and the merged pressurized oil in manifold 71 is supplied to actuator 4b through control valve 22. At this time, the load pressure of actuator 4b is introduced into the first pressure chamber of the manifold control valve 32 through the load pressure detection passage 82. Therefore, the manifold passage of the manifold control valve 32 becomes the opening degree determined by the pressure difference between the load pressure of actuator 4b introduced into the first pressure chamber and the pressure of the manifold oil introduced into the second pressure chamber through the manifold passage 71. Thus, when actuator 4a is not driven but actuator 4b is driven, the manifold oil is supplied to actuator 4b from the manifold passage 71 through the flow control valve 21 and the control valve 22. The remaining oil not used by the drive of actuator 4b is discharged from the manifold control valve 32 through the central oil passage 44 and the tank oil passage 61 to the tank 3.

[0055] Next, the operation of the hydraulic system 1 in the case where actuator 4a is driven but actuator 4b is not driven will be explained. In this case, since actuator 4b is not driven, control valve 22 is in the neutral position. Therefore, pressurized oil ejected from pressure pump 2b is introduced into manifold 71. On the other hand, since actuator 4a needs to be driven, pilot pressure is supplied to control valve 12, and the spool of control valve 12 travels with a stroke corresponding to the pilot pressure. According to the stroke of the spool, the opening of the relief passage of control valve 12 decreases, and the opening of the passage between inlet throttling opening 12b and opening A1 or opening B1 increases. As a result, the first pressure chamber of the flow control valve 11 is pressurized, and the second pressure chamber is depressurized. Consequently, the opening of the oil supply passage connecting the pump oil passage 41 and the oil supply passage 42 of the flow control valve 11 increases. This allows the pressurized oil ejected from the pressure pump 2a to be supplied from the flow control valve 11 through the oil supply passage 42 at a flow rate corresponding to the opening of this oil supply passage, and then to the inlet throttling opening 12b. Additionally, the remaining oil in the pressurized oil ejected from the pressure pump 2a, excluding the oil flowing into the oil supply passage 42, flows through the bypass oil passage 43 to the manifold 71. In the manifold 71, the remaining oil supplied from the bypass oil passage 43 merges with the pressurized oil ejected from the pressure pump 2b. Since the control valve 22 is in the neutral position, the first pressure chamber of the manifold control valve 32 experiences pressure, and the second pressure chamber experiences the pressure of the manifold oil in the manifold 71. Since the pressurized oil flowing from the first circuit 10 to the merge circuit 71 is only the residual oil from the pressurized oil ejected from the pressure pump 2a, the opening of the merge passage of the merge control valve 32 is reduced compared to the case where the actuator 4a is not driven. Thus, the merged pressurized oil in the merge circuit 71 flows to the central oil circuit 44 through the merge passage with a reduced opening area. A portion of the merged pressurized oil in the central oil circuit 44 merges with the pressurized oil flowing in the supply oil circuit 42 via the branch oil circuit 45. The residual oil in the merged pressurized oil in the central oil circuit 44 that is not supplied to the branch oil circuit 45 is discharged to the tank 3 through the vent passage of the control valve 12. Thus, the pressurized oil supplied from the supply oil circuit 42 and the pressurized oil supplied from the central oil circuit 44 via the branch oil circuit 45 are supplied to the inlet throttle opening 12b, forming a merged pressurized oil. This merged pressurized oil is supplied to the actuator 4a from the inlet throttle opening 12b through the pressurized oil supply passage of the control valve 12. Thus, when actuator 4a is driven but actuator 4b is not driven, the pressurized oil supplied by the oil supply line 42 in the pressurized oil ejected from the pressure pump 2a merges with the pressurized oil supplied by the merge line 71 via the merge control valve 32, the central oil line 44 and the branch oil line 45, and the actuator 4a is driven by the merged pressurized oil.

[0056] Next, the operation of the hydraulic system 1 when both actuators 4a and 4b are driven will be explained (4). The operation of the hydraulic system 1 when one of actuators 4a and 4b is driven is as described in (2) and (3) above. If actuator 4b is driven when actuator 4a is driven, as explained in (3) above, the remaining oil in the pressurized oil ejected from pressure pump 2a, except for the pressurized oil flowing into the oil supply line 42, flows into the manifold 71 through the bypass line 43. In addition, similar to the case in (2) above, the manifold pressurized oil (the manifold pressurized oil from the remaining oil from pressure pump 2a and the pressurized oil from pressure pump 2b) in the manifold 71 is supplied to actuator 4b through control valve 22. At this time, the load pressure of actuator 4b is introduced into the first pressure chamber of the manifold control valve 32 through the load pressure detection passage 82. Additionally, the remaining oil supplied from the pressure pump 2a to the confluence passage 71 via the bypass oil passage 43 and the remaining oil in the pressurized oil ejected from the pressure pump 2b that was not utilized by the actuator 4b are introduced into the second pressure chamber of the confluence control valve 32 to form confluence pressurized oil. Therefore, the confluence passage of the confluence control valve 32 becomes an opening determined by the pressure difference between the load pressure of the actuator 4b introduced into the first pressure chamber and the pressure of the confluence pressurized oil introduced into the confluence passage 71 into the second pressure chamber. According to this opening, the confluence pressurized oil in the confluence passage 71 flows into the central oil passage 44. Similar to the explanation above (3), a portion of the confluence pressurized oil in the central oil passage 44 merges with the pressurized oil flowing in the supply oil passage 42 via the branch oil passage 45. Therefore, the confluence pressurized oil formed by the combination of the pressurized oil supplied from the supply oil passage 42 and the pressurized oil supplied from the central oil passage 44 via the branch oil passage 45 is supplied to the inlet throttle opening 12b. The combined pressurized oil is supplied to actuator 4a from the inlet throttling opening 12b through the pressurized oil supply passage of control valve 12. Thus, when both actuators 4a and 4b are driven, the residual oil in the pressurized oil from hydraulic pump 2a and the combined pressurized oil from hydraulic pump 2b are supplied to actuator 4b from the confluence passage 71 through flow control valve 21 and control valve 22. The pressurized oil ejected from pressure pump 2a and supplied through oil supply passage 42 are combined with the pressurized oil supplied from confluence passage 71 through confluence control valve 32, central oil passage 44 and branch oil passage 45, and the combined pressurized oil is used to drive actuator 4a.

[0057] Next, the method for controlling the hydraulic pressure of the hydraulic system 1 described above will be explained. In the hydraulic system 1, the pressurized oil ejected from the hydraulic pump 2a (the remaining oil in the pressurized oil ejected from the pressure pump 2a when the hydraulic pump 2a is loaded, excluding the pressurized oil supplied to the control valve 12 via the oil supply line 42) and the pressurized oil ejected from the hydraulic pump 2b are combined in the confluence line 71 to form confluenced pressurized oil. When the hydraulic pump 2a is loaded, the position of the spool of the control valve 12 is switched according to the pilot pressure from the electromagnetic proportional valve, and the opening degree of the vent passage is determined by the position of the spool. The pressurized oil flow rate corresponding to the opening degree of the vent passage is output from the control valve 12 to the actuator 4a, and the actuator 4a is driven by the pressurized oil. The pressurized oil supplied to the actuator 4a is supplied from the flow control valve 11 through the oil supply line 42 to the inlet throttling opening 12b. The flow rate of pressurized oil in the confluence circuit 71, corresponding to the opening degree of the confluence passage of the confluence control valve 32, merges with the pressurized oil flowing in the supply oil circuit 42. Since the opening degree of the confluence passage of the confluence control valve 32 is determined by the pressure difference between the load pressure of the actuator 4b introduced into the first pressure chamber and the pressure of the confluence pressurized oil in the confluence circuit 71 introduced into the second pressure chamber, the flow rate of the confluence pressurized oil supplied from the confluence circuit 71 via the confluence control valve 32 to the inlet throttling opening 12b of the control valve 12 is adjusted according to the pressure difference between the load pressure of the actuator 4b and the pressure of the confluence pressurized oil in the confluence circuit 71. Furthermore, when the hydraulic pump 2b is loaded, the position of the spool of the control valve 22 is switched according to the pilot pressure from the electromagnetic proportional valve. The flow rate of pressurized oil corresponding to the switched position of the control valve 22 is output to the actuator 4b, and the actuator 4b is driven by this pressurized oil.

[0058] Next, refer to Figure 2 Another embodiment of the hydraulic system 101 of the present invention will be described. Figure 2 The hydraulic system 101 shown differs from hydraulic system 1 in that it uses a flow control valve 34 instead of a check valve 31. Furthermore, since the flow control valve 34 in hydraulic system 101 is connected to a pump oil passage 41, hydraulic system 101 differs from hydraulic system 1 in that it uses a flow control valve 16 that does not perform the aforementioned branch, instead of a flow control valve 11 that controls the oil pressure branch from hydraulic pump 2a.

[0059] A flow control valve 16 is located between the hydraulic pump 2a and the control valve 12. The upstream of the flow control valve 16 is connected to the pump oil passage 41, and the downstream is connected to the supply oil passage 42. Inside the flow control valve 16, a supply passage connecting the pump oil passage 41 and the supply oil passage 42 is provided. The flow control valve 16 can gradually change the opening of the supply passage between a maximum opening position 16A and a blocking position 16B. When no pressurized oil is supplied from the hydraulic pump 2a, the flow control valve 16 is maintained in the connected position 16A by the force of a spring. The flow control valve 21 has: a first pressure chamber connected to the downstream passage of the control valve 12, into which the load pressure of the actuator 4a is introduced; and a second pressure chamber into which pressurized oil from the supply oil passage 42 is introduced. When control valve 12 is in the neutral position, the oil supply line 42 is blocked by control valve 12. In this case, if control valve 12 is switched to supply pressurized oil to actuator 4a, the first pressure chamber is pressurized, thereby the flow control valve 16 is switched to a position corresponding to the pressure difference between the first and second pressure chambers.

[0060] The flow control valve 34 is connected upstream to the pump oil passage 41 and downstream to the manifold 71. The flow control valve 34 controls the flow rate of pressurized oil flowing from the pump oil passage 41 to the manifold 71. Specifically, the flow control valve 34 has a connection passage connecting the pump oil passage 41 and the manifold 71, and the opening of this connection passage can be gradually changed between a blocked position 34A (blocking the opening) and a fully open connection position 34B. When pressurized oil is not supplied by the hydraulic pump 2a, the flow control valve 34 is held in the blocked position 34A by the force of a spring. The flow control valve 34 has: a first pressure chamber into which the load pressure of the actuator 4a is introduced from the downstream passage of the control valve 12 via the load pressure detection passage 81; and a second pressure chamber into which pressurized oil from the pump oil passage 41 is introduced. When control valve 12 is in the neutral position, if pressurized oil is ejected from pressure pump 2a and the oil pressure in pump oil passage 41 acts on the second pressure chamber of flow control valve 34, the second pressure chamber will be pressurized. On the other hand, tank pressure acts on the first pressure chamber, so flow control valve 34 switches to connection position 34B. If flow control valve 34 switches to connection position 34B, the pressurized oil ejected from pressure pump 2a flows to the junction passage 71 via pump oil passage 41 and flow control valve 34.

[0061] Next, the operation of the hydraulic system 101 will be explained. When the actuator 4a is not driven, the flow control valve 34, like the check valve 31 of the hydraulic system 1, causes the pressurized oil ejected from the pressure pump 2a to flow into the manifold 71, so the hydraulic system 101 operates in the same way as the hydraulic system 1.

[0062] The operation of the hydraulic system 1 is the same when actuator 4a is driven and actuator 4b is not driven. That is, the pressurized oil ejected from pressure pump 2b merges with the pressurized oil ejected from pressure pump 2a in the confluence passage 71, and the merged pressurized oil flows into the central oil passage 44 through the confluence control valve 32. When actuator 4a is driven, the load pressure of actuator 4a is introduced into the first pressure chamber of flow control valve 34 through load pressure detection passage 81.

[0063] The flow control valve 34 can also switch to the blocking position 34A when the load pressure of the actuator 4a acts on the first pressure chamber. By switching the flow control valve 34 to the blocking position 34A when the load pressure of the actuator 4a acts on the first pressure chamber, the flow of pressurized oil ejected from the pressure pump 2a into the manifold 71 can be prevented when the actuator 4a is to be driven. Thus, the pressurized oil ejected from the pressure pump 2a can be prevented from flowing into the manifold 71 when the actuator 4a is driven but the actuator 4b is not driven, and when both actuators 4a and 4b are driven. Thus, when both actuators 4a and 4b are driven, the actuator 4a can be driven solely by the pressurized oil ejected from the pressure pump 2a, and the actuator 4b can be driven solely by the pressurized oil ejected from the pressure pump 2b.

[0064] Next, refer to Figure 3 Another embodiment of the hydraulic system 201 of the present invention will be described. In the hydraulic system 201, the first circuit 10 controls the flow rate of pressurized oil ejected from the pressure pump 2a, thereby driving actuator 4c in addition to driving actuator 4a, and the second circuit 20 controls the flow rate of pressurized oil ejected from the pressure pump 2b, thereby driving actuators 4d and 4e in addition to driving actuator 4b. Figure 3 In one embodiment, actuator 4a may be an auxiliary winch drive motor that drives the auxiliary winch, actuator 4c may be a main winch drive motor that drives the main winch, actuator 4b may be a boom extension cylinder that extends and retracts the boom, actuator 4d may be a boom raising or lowering cylinder that raises or lowers the boom, and actuator 4e may be a boom slewing cylinder that rotates the boom. Actuator 4c is an example of the third actuator, and actuators 4d and 4e are examples of the fourth actuator. In hydraulic system 201, detailed descriptions of components shared with or similar to hydraulic system 1 are omitted.

[0065] The first circuit 10 of the hydraulic system 201 includes a flow control valve 211 and a control valve 212 that controls the flow rate of pressurized oil supplied to the actuator 4c. Control valve 212 is arranged in series with control valve 12 along the central oil passage 44. Control valve 212 is constructed similarly to control valve 12. Control valve 212 can also be a neutral, fully open type valve. Control valve 212 has: a vent opening 212a, an inlet throttling opening 212b, and an opening for supplying discharge pressurized oil relative to the actuator 4c (reference numerals omitted). For control valve 212, in the neutral position 12A, the vent passage is fully open, and vent opening 212a is connected to the tank oil passage 61 via the vent passage of control valve 12. The greater the stroke of control valve 212, the smaller the opening of the vent passage, and the higher the load pressure on actuator 4c; therefore, the position of flow control valve 211 is controlled according to the stroke of control valve 212.

[0066] The second circuit 20 of the hydraulic system 201 includes flow control valves 21, 221, and 231, and control valves 22, 222, and 232. Since flow control valves 21 and 22 have already been described with respect to hydraulic system 1, their description is omitted. Flow control valves 221 and 231 are both connected upstream to branch oil passages 52 and are configured similarly to flow control valve 21. Flow control valve 221 controls the flow rate of pressurized oil ejected from pressure pump 2b and outputs to control valve 222, while flow control valve 231 controls the flow rate of pressurized oil ejected from pressure pump 2b and outputs to control valve 232. Control valves 222 and 232 are configured similarly to control valve 22. Control valve 222 drives actuator 4d by controlling the flow rate and direction of pressurized oil supplied from flow control valve 221 to the inlet throttling opening. Control valve 232 drives actuator 4e by controlling the flow rate and direction of pressurized oil supplied from flow control valve 231 to the inlet throttling opening.

[0067] The second circuit 20 includes shuttle valves 24a and 24b. The two supply ports of shuttle valve 24a are connected to the downstream passages of control valves 222 and 232, respectively. Shuttle valve 24a outputs the higher pressure from its outlet to shuttle valve 24b. Shuttle valve 24b supplies the higher pressure from the outlet of shuttle valve 24a and the pressure from the downstream passage of control valve 22 to the first pressure chamber of the confluence control valve 32. Thus, shuttle valves 24a and 24b constitute a maximum pressure selection unit. This maximum pressure selection unit selects the highest pressure from the downstream passages of control valves 22, 222, and 232 and supplies the selected pressure to the first pressure chamber of the confluence control valve 32.

[0068] The operation of the hydraulic system 201 is explained. When none of the actuators 4a to 4e are driven, control valves 12, 212, 22, 222, and 232 are all maintained in the neutral position. In this case, the pressurized oil injected from pressure pump 2a is introduced into the manifold 71 via bypass oil passages 43 and 243, and the pressurized oil injected from pressure pump 2b is also introduced into the manifold 71. The combined pressurized oil formed in the manifold 71 flows from the central oil passage 44 through the vent passages of control valves 212 and 12 into the tank oil passage 61, and is discharged from the tank oil passage 61 into the tank 3. Thus, when none of the actuators 4a to 4e are driven, the pressurized oil injected from pressure pumps 2a and 2b merges in the manifold 71 to become combined pressurized oil, which is discharged into the tank 3 via the central oil passage 44 and the tank oil passage 61. At this time, no pressurized oil is supplied to actuators 4a to 4e. That is, pressure pumps 2a and 2b are unloaded.

[0069] When actuators 4a and 4c are not driven, but any one of actuators 4b, 4d, and 4e is driven, the actuator being driven is driven by the combined pressure oil from the combined passage 71. For example, when only actuator 4d is driven, combined pressure oil is supplied from the combined passage 71 to actuator 4d via flow control valve 221 and control valve 222. At this time, the remaining oil is discharged from the combined control valve 32 to the tank 3 via the central oil passage 44 and the tank oil passage 61. When actuator 4b or actuator 4e is driven, or when two or more actuators 4b, 4d, and 4e are driven simultaneously, combined pressure oil is similarly supplied from the combined passage 71 to the actuator being driven, and the remaining oil is discharged via the combined control valve 32.

[0070] Next, when actuator 4a or actuator 4c is driven while actuators 4b, 4d, and 4e are not driven, control valves 22, 222, and 232 are in the neutral position, and the pressurized oil ejected from pressure pump 2b is introduced into the manifold 71. On the other hand, pilot pressure is supplied to control valve 12 or 212 corresponding to the actuator being driven. This pilot pressure causes the spool valve to travel, reducing the opening of the control valve's venting passage. In addition, the opening of the passage between the inlet throttling opening and the opening connected to the actuator increases. For example, when actuator 4c is driven, the pressurized oil ejected from pressure pump 2a, supplied through oil supply passage 242, merges with the pressurized oil supplied from manifold 71 via manifold control valve 32, central oil passage 44, and branch oil passage 245, and drives actuator 4c using this merged pressurized oil. It is also possible to drive actuators 4a and 4c simultaneously.

[0071] Next, when any one of actuators 4a and 4c is driven and at least one of actuators 4b, 4d, and 4e is driven, the actuator being driven is driven by the combined hydraulic oil. For example, when actuators 4c and 4d are driven, the residual oil in the hydraulic oil from hydraulic pump 2a and the combined hydraulic oil from hydraulic pump 2b are supplied to actuator 4d from the combined passage 71 via flow control valve 221 and control valve 222. The hydraulic oil injected from pressure pump 2a and supplied through oil supply passage 242 are combined with the hydraulic oil supplied from the combined passage 71 via combined control valve 32, central oil passage 44, and branch oil passage 245. This combined hydraulic oil is then supplied to actuator 4c. More specifically, the remaining oil from the pressurized oil ejected from pressure pump 2a, excluding the pressurized oil flowing into the oil supply line 242, flows through bypass lines 43 and 243 to the confluence line 71. The confluence pressurized oil in the confluence line 71 (the confluence pressurized oil from the remaining oil from pressure pump 2a and the pressurized oil from pressure pump 2b) is supplied to actuator 4d through control valve 222. At this time, the load pressure of actuator 4d is introduced into the first pressure chamber of confluence control valve 32 through load pressure detection passage 82. In addition, the confluence pressurized oil formed by the remaining oil supplied from pressure pump 2a to confluence passage 71 via bypass lines 43 and 243 and the remaining oil from the pressurized oil ejected from pressure pump 2b that is not used for the drive of actuator 4d is introduced into the second pressure chamber of confluence control valve 32. Therefore, the opening of the confluence control valve 32 is determined by the pressure difference between the load pressure of the actuator 4d introduced into the first pressure chamber and the pressure of the confluence oil introduced into the confluence passage 71 into the second pressure chamber. The confluence oil in the confluence passage 71 flows into the central oil passage 44 according to this opening. In addition, a portion of the confluence oil in the central oil passage 44 merges with the pressure oil flowing in the supply oil passage 242 via the branch oil passage 245. Therefore, the confluence oil formed by the confluence of the pressure oil supplied from the supply oil passage 242 and the pressure oil supplied from the central oil passage 44 via the branch oil passage 245 is supplied to the inlet throttle opening 212b. This confluence oil is supplied to the actuator 4c from the inlet throttle opening 212b through the pressure oil supply passage of the control valve 212. Actuators 4c and 4d are driven by the confluence oil supplied in this way. When other combinations of actuators are driven, the actuator that is driven is driven by the combined hydraulic pressure in the same manner as described above. The combination of actuators that can be driven simultaneously can include any combination of actuators 4a to 4e.

[0072] Next, the effects of the above-described embodiments will be explained. According to the hydraulic system 1 of the above-described embodiments, the pressurized oil ejected from pressure pump 2a and the pressurized oil ejected from pressure pump 2b are combined in the confluence path 71 to obtain confluenced pressurized oil. In the first circuit 10, the flow rate of the confluenced pressurized oil supplied from the confluence path 71 via the confluence control valve 32 can be controlled by the control valve 12, thereby controlling the first actuator 4a. In the second circuit 20, the flow rate of the confluenced pressurized oil supplied from the branch oil passage 52 connected to the confluence path 71 can be controlled by the control valve 22, thereby controlling the second actuator 4b. Thus, the confluenced pressurized oil obtained by combining the pressurized oil ejected from pressure pump 2a and the pressurized oil ejected from pressure pump 2b can be used in both the first circuit 10 and the second circuit 20. The fluid pressure systems 101 and 201 also achieve the same effect.

[0073] In one embodiment described above, the opening adjustment of the merge control valve 32 is not performed using a pilot pressure that varies according to the operator's operation. Therefore, even if the operator does not perform any operation, the actuator can be driven using merged hydraulic pressure in both circuits.

[0074] In one embodiment described above, the remaining oil, depending on the load pressure of the actuator 4b, can be discharged to the tank 3 via the manifold control valve 32. Thus, the actuator 4b can be driven with an appropriate load pressure.

[0075] In one embodiment described above, since the opening of the manifold passage of the manifold control valve 32 is increased when the actuator 4b is not driven in the second circuit 20, the pressurized oil ejected from the pressure pump 2b can be applied to the first circuit.

[0076] In one embodiment described above, multiple actuators 4a and 4c can be driven using combined hydraulic pressure in the first circuit 10.

[0077] In one of the above embodiments, it is possible to prevent the confluence pressure oil from flowing back from the confluence path 71 to the first circuit 10.

[0078] The dimensions, materials, and configurations of the constituent elements described in this specification are not limited to those explicitly stated in the embodiments. These constituent elements can be modified to have any dimensions, materials, and configurations that fall within the scope of this invention. Furthermore, constituent elements not explicitly described in this specification can be added to the embodiments described herein, and some constituent elements described in each embodiment can be omitted. Additionally, the above-described embodiments can be appropriately combined. Configurations formed by combining these embodiments can also be included within the scope of this invention. For example, in the fluid pressure system 201, a configuration in which a flow control valve 34 is provided instead of a check valve 31 is also considered one embodiment of this invention.

Claims

1. A fluid pressure system, wherein the fluid pressure system includes: a merging passage that connects a first flow passage through which working fluid ejected from a first pump flows and a second flow passage through which working fluid ejected from a second pump flows; a merging control valve that has a merging passage through which merged working fluid, which is a mixture of working fluid from the first pump and working fluid from the second pump, flows downstream from the merging passage, the merging control valve being capable of adjusting an opening degree of the merging passage; a first control valve that drives a first actuator by controlling a flow rate of working fluid supplied from the merging control valve and working fluid supplied via a supply passage that branches from the first flow passage; and a second control valve that drives a second actuator by controlling a flow rate of working fluid supplied from the merging passage via a branch passage that is always in communication with the merging passage.

2. The fluid pressure system according to claim 1, wherein the merging control valve adjusts the opening degree of the merging passage in accordance with a pressure difference between a load pressure of the second actuator and a fluid pressure of the merging passage.

3. The fluid pressure system according to claim 1 or 2, wherein the second control valve blocks the second actuator from the second pump in a neutral position in which the second actuator is not driven.

4. The fluid pressure system according to claim 1 or 2, wherein the opening degree of the merging passage becomes maximum in a case where neither the first actuator nor the second actuator is driven.

5. The fluid pressure system according to claim 1 or 2, wherein the fluid pressure system includes: a third flow passage that connects the merging control valve and the first control valve; and a tank passage that connects the first control valve and a tank, the first control valve has a bleed passage that connects the third flow passage and the tank passage, the first control valve being capable of adjusting an opening degree of the bleed passage.

6. The fluid pressure system according to claim 5, wherein the fluid pressure system includes a flow control valve that supplies working fluid, which corresponds to the opening degree of the bleed passage, of working fluid ejected from the first pump to the first control valve via the supply passage, and supplies a remaining fluid, which is a difference between working fluid ejected from the first pump and working fluid supplied to the first control valve, to the merging passage.

7. The fluid pressure system according to claim 6, wherein the fluid pressure system includes a third control valve that drives a third actuator by controlling a flow rate of at least a part of the remaining fluid supplied from the first flow passage via another supply passage and the merged working fluid supplied from the merging control valve.

8. The fluid pressure system according to claim 1 or 2, wherein the fluid pressure system includes a check valve that prevents working fluid from flowing from the merging passage to the first flow passage.

9. The fluid pressure system according to claim 1 or 2, wherein The fluid pressure system includes another merging control valve provided between the first flow path and the merging path, having a connection passage connecting the first flow path and the merging path, and capable of adjusting an opening degree of the connection passage.

10. The fluid pressure system according to claim 1 or 2, wherein The fluid pressure system includes: a fourth control valve that drives a fourth actuator by controlling a flow rate of working fluid supplied via the second flow path; and a high-pressure selection section that supplies one of a load pressure of the second actuator and a load pressure of the fourth actuator, which is higher in pressure, to the merging control valve, the merging control valve adjusts an opening degree of the merging passage in accordance with a pressure difference between the load pressure supplied from the high-pressure selection section and a fluid pressure of the merging path.

11. The fluid pressure system according to claim 10, wherein the fourth control valve blocks the fourth actuator from the second pump in a neutral position in which the fourth actuator is not driven.

12. A fluid pressure system, wherein The fluid pressure system includes: a first pump; a second pump; a merging path that connects a first flow path through which working fluid ejected from the first pump flows and a second flow path through which working fluid ejected from the second pump flows; a merging control valve that has a merging passage through which merged working fluid, which is a result of merging working fluid from the first pump and working fluid from the second pump, passes from the merging path to a downstream, the merging control valve being capable of adjusting an opening degree of the merging passage; a first control valve that drives a first actuator by controlling flow rates of working fluid supplied via a supply flow path branched from the first flow path and the merged working fluid supplied from the merging control valve; and a second control valve that drives a second actuator by controlling a flow rate of working fluid supplied from the merging path via a branched flow path that is always in communication with the merging path.

13. A fluid pressure control method, wherein The fluid pressure control method includes: a merging process of merging working fluid ejected from a first pump and working fluid ejected from a second pump to obtain merged working fluid in a merging path that connects a first flow path through which the working fluid ejected from the first pump flows and a second flow path through which the working fluid ejected from the second pump flows; a first driving process of driving a first actuator by controlling flow rates of working fluid supplied via a supply flow path branched from the first flow path and the merged working fluid using a first control valve; a second driving process of driving a second actuator by controlling a flow rate of working fluid supplied from the merging path via a branched flow path that is always in communication with the merging path using a second control valve; and an adjusting process of adjusting a flow rate of the merged working fluid supplied from the merging path to the first control valve in accordance with a pressure difference between a load pressure of the second actuator and a fluid pressure of the merging path.

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