Liquid pressure drive system and multi control valve

Abstract

To provide a liquid pressure drive system which can suppress a flow rate of work liquid flowing in a valve body.SOLUTION: A liquid pressure drive system includes: a first liquid pressure pump for ejecting work fluid to a first passage part of a first pump passage; a second liquid pressure pump for ejecting the work fluid to a second passage part of the first pump passage; a first valve block having the first passage part; a main control valve containing a plurality of main valve bodies; a second valve block having the second passage part and provided in the first valve block; and an attach valve containing an attach valve body inserted into the second valve block. The plurality of main valve bodies includes a first main valve body for controlling a flow of the work fluid supplied to a first liquid pressure actuator from the first passage part by a stroke operation. The attach valve body controls a flow of the work fluid supplied to the first liquid pressure actuator from the second passage part by a stroke operation to have the work fluid confluent with the work fluid supplied to the first liquid pressure actuator via the first main valve body from the first passage part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydraulic drive system and a multi-control valve that controls the flow of hydraulic fluid supplied to each of a plurality of hydraulic actuators. [Background technology]

[0002] Hydraulic vehicles such as industrial vehicles and construction vehicles are equipped with various actuators. Hydraulic vehicles perform various tasks by operating the various actuators. Such hydraulic vehicles are equipped with a hydraulic drive system. The hydraulic drive system supplies hydraulic fluid discharged from a hydraulic pump to each hydraulic actuator to drive each hydraulic actuator. The hydraulic drive system also controls the movement of each hydraulic actuator by controlling the flow of the supplied hydraulic fluid. For example, a fluid pressure control device described in Patent Document 1 is known as an example of a hydraulic drive system.

[0003] In the fluid pressure control device of Patent Document 1, a plurality of spools are connected in parallel to a pump passage to which a first hydraulic pump is connected, and the flow of hydraulic fluid supplied to each hydraulic actuator is controlled by stroking the spools. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-78748 A Summary of the Invention [Problem to be solved by the invention]

[0005] The larger the size of a hydraulic vehicle, the greater the flow rate of hydraulic fluid (i.e., the required flow rate) required to drive a hydraulic actuator (e.g., the boom cylinder of an excavator). Therefore, in the fluid pressure control device of Patent Document 1, another hydraulic pump is connected to the first pump passage. This makes it possible to discharge hydraulic fluid at the required flow rate from the two hydraulic pumps to the first pump passage. However, in this case, it is possible that the required flow rate will exceed the rated flow rate of the existing spool. Therefore, it is necessary to enlarge the spool (i.e., the valve body) in order to increase the rated flow rate.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a hydraulic drive system and a multi-control valve that are capable of reducing the flow rate of hydraulic fluid flowing through a valve body. [Means for solving the problem]

[0007] The hydraulic drive system of the present invention is a hydraulic drive system that supplies hydraulic fluid to each of a plurality of hydraulic actuators including a first hydraulic actuator and controls the flow of the supplied hydraulic fluid, and includes a main controller including a first hydraulic pump that discharges hydraulic fluid to a first passage portion of a first pump passage, a second hydraulic pump that discharges hydraulic fluid to a second passage portion of the first pump passage, a first valve block having the first passage portion, and a plurality of main valve bodies that are inserted into the first valve block corresponding to each of the hydraulic actuators and stroke to control the flow of hydraulic fluid supplied from the first passage portion to the corresponding hydraulic actuator. the first valve block having the second passage portion and provided in the first valve block; and an attach valve including an attach valve body inserted into the second valve block, wherein the plurality of main valve bodies include a first main valve body that controls the flow of hydraulic fluid supplied from the first passage portion to the first hydraulic actuator by stroking, and the attach valve body controls the flow of hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and causes the flow of hydraulic fluid to merge with the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator via the first main valve body.

[0008] According to the present invention, the attach valve includes a second valve block having a second passage portion of the first pump passage and a second hydraulic pump connected to the second passage portion, and an attach valve body inserted into the second valve block. The attach valve body controls the hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and merges the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator. Such an attach valve is provided in the first valve block. As a result, the hydraulic fluid discharged from the first hydraulic pump can be supplied to the first hydraulic actuator via the first main valve body, and the hydraulic fluid discharged from the second hydraulic pump can be supplied to the first hydraulic actuator via the attach valve body. That is, since the hydraulic fluid can be supplied to the first hydraulic actuator from two valve bodies, the flow rate of the hydraulic fluid supplied to each valve body can be suppressed. As a result, the size of each valve body can be suppressed. In addition, since the two hydraulic pumps share the first pump passage, an increase in the number of parts constituting the hydraulic drive system can be suppressed. Furthermore, by providing an attach valve to an existing main control valve, a hydraulic drive system can be easily constructed.

[0009] The multi-control valve of the present invention is a multi-control valve that controls a flow of hydraulic fluid supplied to each of a plurality of hydraulic actuators including a first hydraulic actuator, and comprises: a first valve block having a first passage portion of a first pump passage and a first hydraulic pump connected to the first passage portion; a main control valve including a plurality of main valve bodies that are inserted into the first valve block corresponding to each of the hydraulic actuators and that control the flow of hydraulic fluid supplied from the first passage portion to the corresponding hydraulic actuator by stroking; a second valve block having a second passage portion of the first pump passage and a second hydraulic pump connected to the second passage portion; and an attach valve body that is inserted into the second valve block and is provided on the first valve block, wherein the plurality of main valve bodies have a first main valve body that controls the flow of hydraulic fluid supplied from the first passage portion to the first hydraulic actuator by stroking, and the attach valve body controls the flow of hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and causes the flow to merge with the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator via the first main valve body.

[0010] According to the present invention, the attach valve includes a second valve block provided in the first valve block and having a second passage portion formed therein, and an attach valve body inserted into the second valve block. The attach valve body controls the hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and merges the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator. As a result, the hydraulic fluid discharged from the first hydraulic pump can be supplied to the first hydraulic actuator via the main valve body, and the hydraulic fluid discharged from the second hydraulic pump can be supplied to the first hydraulic actuator via the attach valve body. That is, since the hydraulic fluid can be supplied to the first hydraulic actuator from two valve bodies, the flow rate of the hydraulic fluid supplied to each valve body can be suppressed. This can suppress the size of each valve body from increasing. In addition, since the two hydraulic pumps share the first pump passage, the number of parts constituting the hydraulic circuit can be suppressed from increasing. Furthermore, a multi-control valve can be easily constructed by providing an attach valve to an existing main control valve. Effect of the Invention

[0011] According to the present invention, the flow rate of the hydraulic fluid flowing through the valve body can be reduced. [Brief description of the drawings]

[0012] [Figure 1] 1 is a hydraulic circuit diagram showing a hydraulic drive system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing the hydraulic drive system of FIG. 1. [Diagram 3] FIG. 11 is a hydraulic circuit diagram showing a hydraulic drive system according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a hydraulic drive system 1 and a multi-control valve 2 according to an embodiment of the present invention will be described with reference to the drawings mentioned above. Note that the concept of direction used in the following description is used for convenience in the description and does not limit the orientation of the configuration of the invention to that direction. Furthermore, the hydraulic drive system 1 and the multi-control valve 2 described below are merely one embodiment of the present invention. Therefore, the present invention is not limited to the embodiment, and additions, deletions, and modifications are possible within the scope of the spirit of the invention.

[0014] Hydraulic vehicles such as construction vehicles and industrial vehicles are equipped with various hydraulic actuators. The hydraulic vehicles can perform various tasks by operating the various hydraulic actuators. In this embodiment, the hydraulic vehicle is a shovel. However, the hydraulic vehicle is not limited to a shovel, and may be a crane, a wheel loader, or the like. The shovel is equipped with, for example, a traveling device, a revolving body, a boom, an arm, and an attachment (for example, a bucket, a nipper, and a breaker, and in this embodiment, a bucket). The shovel is equipped with a plurality of hydraulic actuators 3 to 9 as shown in FIG. 1 in order to operate the traveling device, the revolving body, the boom, the arm, and the bucket. More specifically, the shovel is equipped with a pair of left and right traveling motors 3 and 4, a revolving motor 5, a boom cylinder 6, an arm cylinder 7, a bucket cylinder 8, and an option cylinder 9. The option cylinder 9 is equipped in the shovel to operate the breaker, the nipper, and the like. In this embodiment, the boom cylinder 6 is an example of a first hydraulic actuator, and the option cylinder 9 is an example of a second hydraulic actuator. The excavator also includes a hydraulic drive system 1 for supplying hydraulic fluid to the eight hydraulic actuators 3-9.

[0015] <Hydraulic drive system> The hydraulic drive system 1 supplies hydraulic fluid to each of the seven hydraulic actuators 3-9. The number of hydraulic actuators to which the hydraulic drive system 1 supplies hydraulic fluid is not limited to seven, but may be two or more. The hydraulic drive system 1 supplies hydraulic fluid to each of the hydraulic actuators 3-9, and controls the flow of the supplied hydraulic fluid. The hydraulic drive system 1 includes three hydraulic pumps 11-13 and a multi-control valve 2. The hydraulic drive system 1 also includes an operating device 17 and a control device 18.

[0016] <Hydraulic pump> The three hydraulic pumps 11-13 discharge hydraulic fluid. More specifically, the three hydraulic pumps 11-13 are driven by a drive source (e.g., an engine and an electric motor) not shown. As a result, the three hydraulic pumps 11-13 discharge hydraulic fluid. In this embodiment, the three hydraulic pumps 11-13 are variable displacement hydraulic pumps, for example, variable displacement swash plate pumps. More specifically, the three hydraulic pumps 11-13 change their discharge capacities in response to an input capacity signal. The three hydraulic pumps 11-13 may be fixed displacement pumps, variable displacement bent axis pumps, etc.

[0017] <Multi-control valve> The multi-control valve 2 controls the flow of hydraulic fluid supplied to each of the hydraulic actuators 3-9. More specifically, the multi-control valve 2 supplies hydraulic fluid discharged from the hydraulic pumps 11-13 to each of the hydraulic actuators 3-9, and also controls the flow of the supplied hydraulic fluid. The multi-control valve 2 includes a main control valve 14 and an attach valve 15. The main control valve 14 includes a plurality of spools 31-38, as described in detail later, and the attach valve 15 includes two spools 39, 40. The multi-control valve 2 supplies hydraulic fluid to each of the hydraulic actuators 3-9 by the spools 31-40, and also controls the flow of the supplied hydraulic fluid. The main control valve 14 and the attach valve 15 will be described in more detail below.

[0018] <Main control valve> The main control valve 14 supplies hydraulic fluid to some of the hydraulic actuators 3-9 (including the boom cylinder 6) and controls the flow of the supplied hydraulic fluid. In this embodiment, the main control valve 14 supplies hydraulic fluid to each of the six hydraulic actuators 3-8 including the boom cylinder 6 and controls the flow of the supplied hydraulic fluid. As shown in FIG. 2, the main control valve 14 includes a first valve block 21 and a plurality of main spools 31-38 (see also FIG. 1). In this embodiment, the main control valve 14 includes at least eight main spools 31-38 as shown in FIG. 1. Furthermore, the main control valve 14 includes two unloading valves 41, 42.

[0019] The first valve block 21 has a first passage portion 22a of the first pump passage 22 (see also FIG. 2). The first valve block 21 also has a second pump passage 23. The first valve block 21 also has a tank passage 24. The first valve block 21 is formed in a generally rectangular parallelepiped shape that is elongated in a first direction that is a predetermined direction. In this embodiment, the first valve block 21 is made up of three block portions 21a to 21c. Each of the block portions 21a to 21c is formed in a generally rectangular parallelepiped shape. The three block portions 21a to 21c are stacked in the first direction to form the first valve block 21.

[0020] The first pump passage 22 is a passage extending from the first valve block 21 to the second valve block 25, which will be described later in detail. In this embodiment, the first pump passage 22 extends in the first direction from the first valve block 21 to the second valve block 25, which will be described later in detail. The first pump passage 22 does not necessarily extend straight from the first valve block 21 to the second valve block 25, and may be curved. The first pump passage 22 has a first passage portion 22a formed in the first valve block 21 and a second passage portion 22b formed in the second valve block 25. That is, the first pump passage 22 has the first passage portion 22a on one side in the first direction and the second passage portion 22b on the other side in the first direction. The first hydraulic pressure pump 11 is connected to the first passage portion 22a, and the second hydraulic pressure pump 12 is connected to the second passage portion 22b.

[0021] The first passage portion 22a extends in a predetermined first direction in the first valve block 21. In this embodiment, the first passage portion 22a extends in the first direction so as to penetrate three block portions 21a to 21c in this embodiment. The first passage portion 22a opens at both end faces of the first valve block 21 in the first direction. The first hydraulic pump 11 is connected to an opening in the first passage portion 22a at one end, which is an end face on one side in the first direction of the first valve block 21.

[0022] The second pump passage 23 extends in the first direction in the first valve block 21. In this embodiment, the second pump passage 23 is formed in the first valve block 21 so as to be parallel to the first passage portion 22a. The second pump passage 23 also opens at one end in the first direction of the first valve block 21. The third hydraulic pump 13 is connected to the opening at one end in the first direction of the first valve block 21 in the second pump passage 23. In addition, the tank passage 24 is a passage formed from the first valve block 21 to the second valve block 25. The tank 19 is connected to the tank passage 24.

[0023] Each of the main spools 31 to 38, which are an example of a main valve body, corresponds to each of the hydraulic actuators 3 to 8. In this embodiment, the eight main spools 31 to 38 include a first traveling spool 31, a second traveling spool 35, a swing spool 36, a bucket spool 32, a first arm spool 33, a second arm spool 37, a first boom spool 34, and a second boom spool 38. The first traveling spool 31 corresponds to the first traveling motor 3, and the second traveling spool 35 corresponds to the second traveling motor 4. The bucket spool 32 corresponds to the bucket cylinder 8, and the swing spool 36 corresponds to the swing motor 5. The first arm spool 33 and the second arm spool 37 correspond to the arm cylinder 7. The first boom spool 34, which is an example of a first main valve body, and the second boom spool 38, which is an example of a second main valve body, correspond to the boom cylinder 6. Each of the four main spools 31-34 is connected in parallel to the first passage portion 22a of the first pump passage 22. The remaining four main spools 35-38 are connected in parallel to the second pump passage 23. Each of the spools 31-38 supplies hydraulic fluid from the passages 22, 23 to the corresponding hydraulic actuators 3-8, respectively, and controls the flow (direction and amount) of the supplied hydraulic fluid by stroking.

[0024] In this embodiment, the first traveling spool 31 supplies hydraulic fluid from the first passage portion 22a to the first traveling motor 3, and controls the flow of hydraulic fluid supplied to the first traveling motor 3 by stroking. The second traveling spool 35 supplies hydraulic fluid from the second pump passage 23 to the second traveling motor 4, and controls the flow of hydraulic fluid supplied to the first traveling motor 3 by stroking. The swing spool 36 supplies hydraulic fluid from the second pump passage 23 to the swing motor 5, and controls the flow of hydraulic fluid supplied to the swing motor 5. The bucket spool 32 supplies hydraulic fluid from the first passage portion 22a to the bucket cylinder 8, and controls the flow of hydraulic fluid supplied to the bucket cylinder 8 by stroking.

[0025] The second arm spool 37 supplies hydraulic fluid from the second pump passage 23 to the arm cylinder 7, and controls the flow of hydraulic fluid supplied to the arm cylinder 7 by stroking. On the other hand, the first arm spool 33 merges hydraulic fluid from the first passage portion 22a with hydraulic fluid supplied from the second pump passage 23 via the second arm spool 37 and supplies it to the arm cylinder 7. The first arm spool 33 controls the flow of hydraulic fluid to be merged by stroking. The first boom spool 34 supplies hydraulic fluid from the first passage portion 22a to the boom cylinder 6, and controls the flow of hydraulic fluid to be supplied to the boom cylinder 6 by stroking. On the other hand, the second boom spool 38 merges hydraulic fluid from the second pump passage 23 with hydraulic fluid supplied from the first passage portion 22a via the first boom spool 34 and supplies it to the boom cylinder 6. The second boom spool 38 controls the flow of hydraulic fluid to be merged by stroking.

[0026] More specifically, each of the eight main spools 31-38 is further connected to the tank passage 24. The four main spools 31-34 switch the connection state between the corresponding hydraulic actuators 3, 6-8 and the first passage portion 22a and the tank passage 24. As a result, the four main spools 31-34 switch the flow direction of the hydraulic fluid supplied to the corresponding hydraulic actuators 3, 6-8. Similarly, the remaining four main spools 35-38 also switch the connection state between the corresponding hydraulic actuators 4-7 and the second pump passage 23 and the tank passage 24. As a result, the remaining four main spools 35-38 also switch the flow direction of the hydraulic fluid supplied to the corresponding hydraulic actuators 4-7.

[0027] Further, electromagnetic proportional control valves 31a to 38a and 31b to 38b are provided corresponding to the main spools 31 to 38, respectively. Each of the electromagnetic proportional control valves 31a to 38a and 31b to 38b outputs a pilot pressure according to an input signal. Each of the electromagnetic proportional control valves 31a to 38a and 31b to 38b applies a pilot pressure to the corresponding main spools 31 to 38 in a direction opposing each other. Further, springs 31c to 38c and 31d to 38d are provided corresponding to the main spools 31 to 38. The springs 31c to 38c bias the corresponding spools 31 to 38 against the pilot pressure from the electromagnetic proportional control valves 31b to 38b. Further, the springs 31d to 38d bias the corresponding spools 31 to 38 against the pilot pressure from the electromagnetic proportional control valves 31a to 38a, respectively. Therefore, the springs 31c to 38c and 31d to 38d can stroke the corresponding main spools 31 to 38 by a stroke amount according to the pilot pressure. As a result, each of the main spools 31 to 38 changes its opening degree according to an input signal.

[0028] For example, electromagnetic proportional control valves 34a, 34b are provided in correspondence with the first boom spool 34. The electromagnetic proportional control valves 34a, 34b apply pilot pressure to the first boom spool 34 in opposing directions. Springs 34c, 34d are provided in correspondence with the first boom spool 34. The springs 34c, 34d bias the first boom spool 34 against the pilot pressures from the electromagnetic proportional control valves 34b, 34a. Therefore, the springs 34c, 34d can stroke the first boom spool 34 by a stroke amount according to the pilot pressure. As a result, the first boom spool 34 changes its opening degree according to an input signal.

[0029] The above-mentioned main spools 31 to 38 are slidably inserted into the first valve block 21. In this embodiment, the eight main spools 31 to 38 are inserted into the first valve block 21 so as to extend in a second direction perpendicular to the first direction as partially shown in FIG. 2. The four main spools 31 to 34 are inserted into the first valve block 21 so as to be aligned in the first direction along the first passage portion 22a as viewed from one side in the second direction. Note that FIG. 2 shows the electromagnetic proportional control valves 31a to 34a provided at one axial end of the four spools 31 to 34. The remaining four main spools 35 to 38 are inserted into the first valve block 21 so as to be aligned in the first direction along the second pump passage 23 as viewed from one side in the second direction. Therefore, the eight main spools 31 to 38 are inserted into the first valve block 21 so as to be aligned in two rows. In this embodiment, in the first valve block 21, four main spools 31-34 are arranged in a row on one side in the third direction when viewed from one side in the second direction, and the remaining four main spools 35-38 are arranged in a row on the other side in the third direction. The third direction is a direction perpendicular to both the first and second directions.

[0030] More specifically, the first valve block 21 has a first block portion 21a, a second block portion 21b, and a third block portion 21c stacked in this order from one side in the first direction. Three main spools 31, 32, and 35 are slidably inserted into the first block portion 21a. Three main spools 33, 36, and 37 are slidably inserted into the second block portion 21b. Furthermore, two main spools 34 and 38 are inserted into the third block portion 21c. In this way, in the first valve block 21, a plurality of spools 31 to 38 are slidably inserted into each of the block portions 21a to 21c.

[0031] The first unloading valve 41 shown in Fig. 1 communicates between the first passage portion 22a and the tank passage 24 in response to an input signal. As a result, the first unloading valve 41 can discharge the hydraulic fluid flowing through the first pump passage 22 to the tank 19 in response to an input signal, thereby placing the first hydraulic pressure pump 11 and the second hydraulic pressure pump 12 in an unloaded state. Furthermore, the second unloading valve 42 communicates between the second pump passage 23 and the tank passage 24 in response to an input signal. As a result, the second unloading valve 42 can discharge the hydraulic fluid flowing through the second pump passage 23 to the tank 19 in response to an input signal, thereby placing the third hydraulic pressure pump 13 in an unloaded state.

[0032] <Attachment valve> The attachment valve 15 merges the hydraulic fluid from the second hydraulic pump 12 with the hydraulic fluid supplied from the main control valve 14 to the boom cylinder 6, and controls the flow of the merged hydraulic fluid. In this embodiment, the attachment valve 15 also supplies hydraulic fluid from the second hydraulic pump 12 to the option cylinder 9, and controls the flow of the supplied hydraulic fluid. The attachment valve 15 includes a second valve block 25 and a third boom spool 39. In this embodiment, the attachment valve 15 further includes an option spool 40.

[0033] The second valve block 25 is provided in the first valve block 21 so as to be stacked in the first direction. In this embodiment, the second valve block 25 is provided in the first valve block 21 so as to be placed on the other end in the first direction, which is the end face on the other side in the first direction of the first valve block 21. In addition, the second valve block 25 has a second passage portion 22b of the first pump passage 22. As described above, the first pump passage 22 is a passage formed from the first valve block 21 to the second valve block 25, and the second passage portion 22b is a portion formed within the second valve block 25. The second hydraulic pump 12 is connected to the second passage portion 22b as described above.

[0034] More specifically, the second valve block 25 is formed in a generally rectangular parallelepiped shape that is long in the first direction. In this embodiment, the length of the second valve block 25 in the third direction is shorter than the length of the first valve block 21 in the third direction, and is, for example, half the length of the first valve block 21 in the third direction. The second valve block 25 may have the same length as the first valve block 21 in the third direction. The second valve block 25 has two block bodies 25a and 25b that are different from each other. Each of the block bodies 25a and 25b is formed in a generally rectangular parallelepiped shape. The two block bodies 25a and 25b are stacked in the first direction to form the second valve block 25. In this embodiment, the first block body 25a is provided at the other end of the first valve block 21 in the first direction, and the second block body 25b is provided on the first block body 25a so as to be stacked in the first direction.

[0035] The second passage portion 22b extends in the first direction in the second valve block 25. That is, in this embodiment, the second passage portion 22b extends in the first direction so as to penetrate the two block bodies 25a, 25b. The second passage portion 22b opens at both end faces of the second valve block 25 in the first direction. The second passage portion 22b abuts an opening at one end of the second valve block 25 in the first direction against an opening at the other side of the first direction of the first passage portion 22a. As a result, the second passage portion 22b is connected to the first passage portion 22a and constitutes the first pump passage 22 together with the first passage portion 22a. The second hydraulic pump 12 is connected to an opening of the second passage portion 22b at the other end of the second valve block 25 in the first direction. In this manner, the two hydraulic pumps 11, 12 are connected to the first pump passage 22.

[0036] The third boom spool 39, which is an example of a first attachment valve body, is connected to the second passage portion 22b. The third boom spool 39 supplies the hydraulic fluid from the second passage portion 22b to the boom cylinder 6 so that the hydraulic fluid is merged with the hydraulic fluid supplied to the boom cylinder 6 via the first boom spool 34. The third boom spool 39 controls the flow of the hydraulic fluid to be merged by stroking. In this embodiment, the third boom spool 39 merges the hydraulic fluid from the second passage portion 22b with at least one of the hydraulic fluid supplied from the first passage portion 22a via the first boom spool 34 and the hydraulic fluid supplied from the second passage portion 22b via the second boom spool 38. In other words, the third boom spool 39 merges the hydraulic fluid from the second hydraulic pump 12 with the hydraulic fluid from at least one of the first hydraulic pump 11 and the third hydraulic pump 13, and supplies the result to the boom cylinder 6.

[0037] More specifically, the third boom spool 39 is connected to the tank passage 24. The third boom spool 39 switches the connection state between the boom cylinder 6 and the second passage portion 22b and the tank passage 24. As a result, the third boom spool 39 switches the flow direction of the hydraulic fluid supplied from the second passage portion 22b to the boom cylinder 6, and causes the hydraulic fluid from the second passage portion 22b to merge with the above-mentioned hydraulic fluid.

[0038] Further, electromagnetic proportional control valves 39a, 39b are provided in correspondence with the third boom spool 39. Each of the electromagnetic proportional control valves 39a, 39b outputs a pilot pressure according to an input signal. Each of the electromagnetic proportional control valves 39a, 39b applies a pilot pressure to the third boom spool 39 in a direction opposing each other. Further, springs 39c, 39d are provided in correspondence with the third boom spool 39. The springs 39c, 39d bias the third boom spool 39 against the pilot pressures from the electromagnetic proportional control valves 39a, 39b. Therefore, the springs 39c, 39d can stroke the third boom spool 39 by a stroke amount according to the pilot pressure. As a result, the third boom spool 39 changes its opening degree according to the input signal.

[0039] The option spool 40, which is an example of a second attachment valve body, is connected to the second passage portion 22b so as to be in parallel with the third boom spool 39. The option spool 40 supplies hydraulic fluid from the second passage portion 22b to the option cylinder 9. The option spool 40 controls the flow of hydraulic fluid supplied to the option cylinder 9 from the second passage portion 22b by stroking.

[0040] More specifically, the option spool 40 is connected to the tank passage 24. The option spool 40 switches the connection state between the option cylinder 9 and the second passage portion 22b and the tank passage 24. As a result, the option spool 40 switches the flow direction of the hydraulic fluid supplied to the option cylinder 9 from the second passage portion 22b.

[0041] The optional-use spool 40 is provided with electromagnetic proportional control valves 40a and 40b in correspondence with each other. Each of the electromagnetic proportional control valves 40a and 40b outputs a pilot pressure according to an input signal. Each of the electromagnetic proportional control valves 40a and 40b applies a pilot pressure to the optional-use spool 40 in a direction opposing each other. The optional-use spool 40 is provided with springs 40c and 40d in correspondence with each other. The springs 40c and 40d bias the optional-use spool 40 against the pilot pressures from the electromagnetic proportional control valves 40a and 40b. Therefore, the springs 40c and 40d can stroke the optional-use spool 40 by a stroke amount according to the pilot pressure. As a result, the optional-use spool 40 can change its opening degree according to an input signal.

[0042] In addition, the two attachment spools 39, 40 are provided in the second valve block 25 as follows. That is, the third boom spool 39 is slidably inserted into the second valve block 25. The option spool 40 is also slidably inserted into the second valve block 25. To explain in more detail, the third boom spool 39 and the option spool 40 are inserted into the second valve block 25 so as to extend in the second direction (i.e., so as to be parallel to the eight main spools 31 to 38). Each of the two attachment spools 39, 40 is connected to the second passage portion 22b of the first pump passage 22 so as to be in parallel. Each of the two spools 39, 40 is inserted into the first valve block 21 so as to be aligned in the first direction along the second passage portion 22b as viewed from one side in the second direction.

[0043] More specifically, the third boom spool 39 is slidably inserted into the first block body 25a, and the option spool 40 is slidably inserted into the second block body 25b. The second valve block 25 is provided on the first valve block 21 such that the first block body 25a and the second block body 25b are stacked in that order from the first valve block 21 side (i.e., one side in the first direction). In this manner, the attachment spools 39, 40 are inserted into the block bodies 25a, 25b one by one.

[0044] <Operation device> The operating device 17 outputs operation commands to the control device 18 to operate the hydraulic actuators 3-9. The operating device 17 is, for example, an operating valve, an electric joystick, a foot pedal, etc. In this embodiment, the operating device 17 is an electric joystick and a foot pedal. The operating device 17 has a plurality of operating tools 17a-17d. In this embodiment, the operating device 17 includes two operating levers 17a, 17b and two foot pedals 17c, 17d. The operating device 17 outputs operation commands to the hydraulic actuators 3-9 in accordance with the operation of the operating tools 17a-17d (operation direction and operation amount in this embodiment). The operation commands are commands that indicate the operation amount (displacement amount, speed, etc.) of each of the hydraulic actuators 3-9.

[0045] <Control device> The control device 18 controls the movement of each of the spools 31-40. More specifically, the control device 18 controls the movement of each of the spools 31-40 in response to an operation command input from the operating device 17. The control device 18 also calculates the supply flow rate of the hydraulic fluid to be supplied to each of the hydraulic actuators 3-9 based on the input operation command. The control device 18 then calculates the opening degree of each of the spools 31-40 in response to each calculated supply flow rate. Furthermore, the control device 18 controls the movement of each of the spools 31-40 in response to each calculated opening degree. That is, the control device 18 outputs a signal to the electromagnetic proportional control valves 31a-40a, 31b-40b corresponding to each of the spools 31-40, respectively, to stroke each of the spools 31-40.

[0046] Moreover, the control device 18 controls the discharge capacity of the first to third hydraulic pumps 11-13. More specifically, the control device 18 outputs first to third capacity signals in accordance with the calculated supply flow rates to change the respective discharge capacities of the first to third hydraulic pumps 11-13. More specifically, the control device 18 outputs first and second capacity signals in accordance with the respective supply flow rates of the hydraulic actuators 3, 6-9 to control the discharge capacity of the first and second hydraulic pumps 11, 12. Moreover, the control device 18 outputs a third capacity signal in accordance with the respective supply flow rates of the hydraulic actuators 4-7 to control the discharge capacity of the third hydraulic pump 13.

[0047] <Operation of the hydraulic drive system> The hydraulic drive system 1 can cause the shovel to perform various tasks by operating the operating tools 17a to 17d. The following describes the operation of the hydraulic drive system 1 when the operating tools 17a to 17d are each operated.

[0048] When at least one of the operating tools 17a to 17d is operated, the control device 18 controls the movement of each of the spools 31 to 40 in response to the operation command output from the operating device 17. This allows the hydraulic actuators 3 to 9 to be operated in response to the operation command. For example, when the operating levers 17a and 17b are operated, one of the hydraulic actuators 5 to 9 is operated in response to the operation content. On the other hand, when the foot pedals 17c and 17d are operated, the traveling motors 3 and 4 are operated. At this time, the control device 18 calculates the supply flow rate of each of the hydraulic actuators 3 to 9 in response to the operation command. Then, the control device 18 calculates the opening degree of each of the spools 31 to 40 in response to each calculated supply flow rate. Furthermore, the control device 18 controls the movement of each of the spools 31 to 40 in response to each calculated opening degree. That is, the control device 18 outputs a signal to the electromagnetic proportional control valves 31a to 40a and 31b to 40b corresponding to each of the spools 31 to 40, and strokes each of the spools 31 to 40. As a result, the opening of each of the spools 31-40 is controlled to an opening corresponding to the operation command. The control device 18 also controls the discharge capacity of the first to third hydraulic pumps 11-13. More specifically, the control device 18 outputs first to third capacity signals corresponding to the supply flow rates of the hydraulic actuators 3-9, and controls the discharge capacity of each of the first to third hydraulic pumps 11-13. In this way, the control device 18 can operate the hydraulic actuators 3-9 at an operating speed corresponding to the operation command by controlling the opening of each of the spools 31-40 and the discharge capacity of the hydraulic pumps 11-13.

[0049] Specifically, when the boom cylinder 6 is operated in response to an operation command from the operating device 17, the control device 18 controls the hydraulic pumps 11 to 13 and the multi-control valve 2 in accordance with the calculated supply flow rate of the boom cylinder 6 as follows. That is, when the supply flow rate of the boom cylinder 6 is small, the control device 18 controls the discharge capacity of the first and second hydraulic pumps 11, 12 in accordance with the calculated supply flow rate. For example, the control device 18 controls the discharge capacity of the second hydraulic pump 12 to the minimum discharge capacity, and controls the discharge capacity of the first hydraulic pump 11 in accordance with the calculated supply flow rate. Note that the discharge capacity of the first hydraulic pump 11 may be controlled to the minimum discharge capacity, and the discharge capacity of the second hydraulic pump 12 may be controlled in accordance with the calculated supply flow rate. This reduces the energy consumption of the second hydraulic pump 12. The control device 18 also outputs a signal in accordance with the opening degree calculated based on the supply flow rate to the electromagnetic proportional control valves 34a, 34b. As a result, the opening degree of the first boom spool 34 is controlled to the calculated opening degree, and the boom cylinder 6 operates at an operating speed according to the operation command.

[0050] Next, when the supply flow rate of the boom cylinder 6 is slightly larger, the control device 18 controls the discharge capacity of the first and third hydraulic pumps 11, 13 according to the calculated supply flow rate. The discharge capacity of the second hydraulic pump 12 is maintained at, for example, the minimum discharge capacity. The control device 18 also outputs a signal according to the opening calculated based on the supply flow rate to the electromagnetic proportional control valves 34a, 38a, 34b, 38b. This controls the opening of the first and second boom spools 34, 38 to the calculated opening. Then, the hydraulic drive system 1 can supply the hydraulic fluid from the first hydraulic pump 11 and the hydraulic fluid from the third hydraulic pump 13 to the boom cylinder 6 by merging them together. This allows a larger amount of hydraulic fluid to be supplied to the boom cylinder 6 than when the hydraulic fluid is supplied to the boom cylinder 6 only from the first hydraulic pump 11. This allows the boom cylinder 6 to operate at a high operating speed according to an operation command.

[0051] Furthermore, when the supply flow rate of the boom cylinder 6 is even larger, the control device 18 controls the discharge capacity of the first to third hydraulic pumps 11 to 13 according to the calculated supply flow rate. The control device 18 also outputs a signal according to the opening calculated based on the supply flow rate to the electromagnetic proportional control valves 34a, 38a, 39a, 34b, 38b, and 39b. As a result, the openings of the first to third boom spools 34, 38, and 39 are controlled to the calculated openings. Then, the hydraulic drive system 1 can supply the hydraulic fluid from the first hydraulic pump 11 to the boom cylinder 6 by merging the hydraulic fluid from the second and third hydraulic pumps 12 and 13. As a result, a larger amount of hydraulic fluid is supplied to the boom cylinder 6 than when the hydraulic fluid is supplied to the boom cylinder 6 from the two hydraulic pumps 11 and 13. As a result, the boom cylinder 6 can be operated at a high operating speed according to an operation command.

[0052] At this time, the hydraulic fluid is discharged from the two hydraulic pumps 11, 12 to the first pump passage 22. Of the discharged hydraulic fluid, the hydraulic fluid from the first hydraulic pump 11 is supplied to the boom cylinder 6 mainly via the first boom spool 34. Meanwhile, the hydraulic fluid from the second hydraulic pump 12 is supplied to the boom cylinder 6 mainly via the third boom spool 39. In this manner, the large flow rate of hydraulic fluid discharged from the two hydraulic pumps 11, 12 is supplied to the boom cylinder 6 via the two spools 34, 39. Therefore, it is possible to prevent hydraulic fluid from flowing at a flow rate exceeding the rated flow rate of each of the two spools 34, 39. Therefore, it is possible to supply hydraulic fluid at a larger flow rate to the boom cylinder 6 while preventing the two spools 34, 39 from becoming larger.

[0053] Moreover, when the optional cylinder 9 is operated in response to an operation command, the control device 18 controls the hydraulic pumps 11, 12 and the multi-control valve 2 as follows. That is, the control device 18 controls the discharge capacity of the first and second hydraulic pumps 11, 12 in response to the supply flow rate of the optional cylinder 9 calculated based on the operation command. For example, the control device 18 controls the discharge capacity of the first hydraulic pump 11 to a minimum discharge capacity, and controls the discharge capacity of the second hydraulic pump 12 in response to the calculated supply flow rate. This reduces the energy consumption of the first hydraulic pump 11. Note that the discharge capacity of the second hydraulic pump 12 may be controlled to a minimum discharge capacity, and the discharge capacity of the first hydraulic pump 11 may be controlled in response to the calculated supply flow rate. In addition, the control device 18 outputs a signal corresponding to the opening calculated based on the supply flow rate to the electromagnetic proportional control valves 40a, 40b. As a result, the opening of the optional spool 40 is controlled to the calculated opening, and the optional cylinder 9 is operated at an operating speed corresponding to the operation command.

[0054] Furthermore, when a plurality of hydraulic actuators, for example, the boom cylinder 6, the arm cylinder 7, and the bucket cylinder 8, are operated in response to an operation command, the control device 18 controls the hydraulic pumps 11-13 and the multi-control valve 2 as follows. That is, the control device 18 controls the discharge capacity of the first to third hydraulic pumps 11-13 in response to the supply flow rates of the respective cylinders 6-8 calculated based on the operation command. The control device 18 also outputs signals in response to the openings calculated based on the supply flow rates to each of the electromagnetic proportional control valves 33a, 34a, 36a-39a, 33b, 34b, and 36b-39b. For example, the control device 18 outputs signals to each of the electromagnetic proportional control valves 33a, 34a, 36a-38a, 33b, 34b, and 36b-38b. As a result, the opening degrees of each of first arm spool 33, first boom spool 34, bucket spool 32, second arm spool 37, and second boom spool 38 are controlled to the calculated opening degrees. At this time, hydraulic fluid is discharged from two hydraulic pumps 11, 12 to first pump passage 22. Therefore, even when a large supply flow rate is required in response to an operation command, a sufficient flow rate of hydraulic fluid can be supplied to boom cylinder 6 and arm cylinder 7. As a result, each of cylinders 6 to 8 can be operated at an operating speed in response to the operation command.

[0055] Furthermore, the control device 18 outputs first and second unload signals when the operating devices 17a to 17d are not being operated. Then, the first unload valve 41 connects the first pump passage 22 to the tank passage 24 based on the first unload signal. This causes the first and second hydraulic pumps 11, 12 to be in an unloaded state. On the other hand, the second unload valve 42 connects the second pump passage 23 to the tank passage 24 based on the second unload signal. This causes the third hydraulic pump 13 to be in an unloaded state.

[0056] Furthermore, in the hydraulic drive system 1, the two hydraulic pumps 11, 12 discharge hydraulic fluid to the first pump passage 22. Therefore, as long as at least one of the two hydraulic pumps 11, 12 can discharge hydraulic fluid, the hydraulic fluid can be supplied from the first passage portion 22a to each of the hydraulic actuators 3, 6 to 9. Therefore, the hydraulic drive system 1 can achieve a fail-safe for the two hydraulic pumps 11, 12.

[0057] In the hydraulic drive system 1 of this embodiment, the attachment valve 15 includes a second valve block 25 having the second passage portion 22b of the first pump passage 22 and to which the second hydraulic pump 12 is connected, and a third boom spool 39 inserted through the second valve block 25. The third boom spool 39 controls the hydraulic fluid supplied from the second passage portion 22b to the boom cylinder 6 by stroking, and merges the hydraulic fluid supplied from the first passage portion 22a to the boom cylinder 6. Such an attachment valve 15 is provided in the first valve block 21. Thereby, the hydraulic fluid discharged from the first hydraulic pump 11 can be supplied to the boom cylinder 6 via the first boom spool 34, and the hydraulic fluid discharged from the second hydraulic pump 12 can be supplied to the boom cylinder 6 via the third boom spool 39. That is, since hydraulic fluid can be supplied to the boom cylinder 6 from the two attach spools 34, 39, the flow rate of hydraulic fluid supplied to each of the attach spools 34, 39 can be reduced. This makes it possible to prevent each of the attach spools 34, 39 from becoming larger. In addition, since the two hydraulic pumps 11, 12 share the first pump passage 22, it is possible to prevent an increase in the number of parts constituting the hydraulic drive system 1. Furthermore, by providing the attach valve 15 to the existing main control valve 14, the hydraulic drive system 1 can be easily constructed.

[0058] In addition, in the hydraulic drive system 1 of this embodiment, the second boom spool 38 strokes to control the flow of hydraulic fluid supplied from the second pump passage 23 to the boom cylinder 6 and merges it with the hydraulic fluid supplied from the first passage portion 22a to the boom cylinder 6. Therefore, the hydraulic fluid discharged from the first to third hydraulic pumps 11 to 13 can be supplied to the boom cylinder 6 via the respective spools 34, 38, 39. That is, since the hydraulic fluid can be supplied to the boom cylinder 6 from the three spools 34, 38, 39, the flow rate of the hydraulic fluid supplied to each of the spools 34, 38, 39 can be suppressed. This makes it possible to suppress an increase in size of each of the spools 34, 38, 39.

[0059] Furthermore, in the hydraulic drive system 1 of this embodiment, the first unloading valve 41 connects the first pump passage 22 and the tank passage 24 in response to an input first unloading signal. Therefore, the first and second hydraulic pumps 11, 12 can share the first unloading valve 41. This makes it possible to reduce the number of parts in the hydraulic drive system 1.

[0060] Furthermore, in the hydraulic drive system 1 of this embodiment, the second valve block 25 includes a first block body 25a and a second block body 25b provided in the first block body 25a. The second passage portion 22b extends between the first block body 25a and the second block body 25b. The attachment valve 15 further includes an option spool 40 inserted into the second block body 25b. The option spool 40 controls the flow of hydraulic fluid supplied from the second passage portion 22b to the option cylinder 9 by stroking. Therefore, the hydraulic fluid from the second hydraulic pump 12 can be supplied from the second passage portion 22b to the option cylinder 9 via the option spool 40. Therefore, in the hydraulic drive system 1, by providing the second block body 25b in the first block body 25a, the option spool 40 can be easily added to control the hydraulic fluid supplied to the option cylinder 9.

[0061] Furthermore, in the hydraulic drive system 1 of this embodiment, the first hydraulic pump 11 is connected to the first passage portion 22a on one side in the first direction of the first pump passage 22, and the second hydraulic pump 12 is connected to the second passage portion 22b on the other side in the first direction of the first pump passage 22. Therefore, in the first pump passage 22, the hydraulic fluid discharged from each of the two hydraulic pumps 11, 12 can be supplied to the boom cylinder 6 via separate spools 34, 39. Therefore, it is possible to reduce pressure loss in the hydraulic fluid supplied to the boom cylinder 6 from each of the hydraulic pumps 11, 12. Also, since each of the hydraulic pumps 11, 12 is connected to each of the one side and the other side in the predetermined direction of the first pump passage 22, connection of the hydraulic pumps 11, 12 is easy.

[0062] Furthermore, in the hydraulic drive system 1 of this embodiment, the control device 18 calculates the opening degree of the first boom spool 34 and the third boom spool 39 according to the supply flow rate calculated based on the input operation command, and controls the movement of the first boom spool 34 and the third boom spool 39 according to the calculated opening degree. Therefore, the control device 18 can control the flow rate of the hydraulic fluid supplied to the boom cylinder 6 via each of the spools 34, 39 even when the hydraulic fluid is discharged from the two hydraulic pumps 11, 12 and a large flow rate of the hydraulic fluid flows into the first pump passage 22 and is supplied to each of the spools 34, 39. This allows the control device 18 to suppress the flow rate of the hydraulic fluid supplied to each of the spools 34, 39.

[0063] Furthermore, in the hydraulic drive system 1 of this embodiment, the control device 18 outputs a first displacement signal and a second displacement signal in accordance with the supply flow rate to change the discharge displacements of the first hydraulic pump 11 and the second hydraulic pump 12. This makes it possible to reduce the energy consumption in the first hydraulic pump 11 and the second hydraulic pump 12.

[0064] In the multi-control valve 2 of this embodiment, the attachment valve 15 includes a second valve block 25 provided in the first valve block 21 and having the second passage portion 22b formed therein, and a third boom spool 39 inserted into the second valve block 25. The third boom spool 39 controls the hydraulic fluid supplied from the second passage portion 22b to the boom cylinder 6 by stroking, and merges the hydraulic fluid supplied from the first passage portion 22a to the boom cylinder 6. This allows the hydraulic fluid discharged from the first hydraulic pump 11 to be supplied to the boom cylinder 6 via the first boom spool 34, and the hydraulic fluid discharged from the second hydraulic pump 12 to be supplied to the boom cylinder 6 via the third boom spool 39. That is, since the hydraulic fluid can be supplied to the boom cylinder 6 from the two spools 34, 39, the flow rate of the hydraulic fluid supplied to each spool 34, 39 can be suppressed. This allows the size of each spool 34, 39 to be suppressed. In addition, since the two hydraulic pumps 11, 12 share the first pump passage 22, it is possible to prevent an increase in the number of parts constituting the multi-control valve 2. Furthermore, the multi-control valve 2 can be easily constructed by providing the attachment valve 15 to the existing main control valve 14.

[0065] <Other embodiments> In the hydraulic drive system 1 and the multi-control valve 2 of this embodiment, a pump port of the second passage portion 22b to which the second hydraulic pump 11 is connected is formed at the other end in the first direction of the second block body 25b of the second valve block 25. However, the pump port of the second passage portion 22b may be formed in the first block body 25a (see, for example, FIG. 3). In the hydraulic drive system 1 of this embodiment, the main valve body is a main spool, but it may be a poppet-type valve body or a piston-type valve body. In addition, the main valve body may be something like flow control spools 34A, 34B that can independently control the meter-in flow rate and the meter-out flow rate of the boom cylinder 6, as shown in the hydraulic drive system 1A and the multi-control valve 2A of FIG. 3. Furthermore, the main valve body may be a valve body of a flow control valve. The flow control valve has, for example, a piston-type valve body. One flow control valve is provided between the first passage portion 22a and the head port of the boom cylinder 6, and another flow control valve is provided between the first passage portion 22a and the rod port of the boom cylinder 6. Each of the flow control valves controls the flow rate of hydraulic fluid supplied from the first passage portion 22a to the head port, and also controls the flow rate of hydraulic fluid supplied from the first passage portion 22a to the rod port. Furthermore, the number of block bodies of the attachment valve 15 is not limited to two, and may be three or more. And, the block body does not necessarily need to be provided with a spool, as long as it is provided with at least the third boom spool 39.

[0066] Furthermore, in the hydraulic drive system 1 and the multi-control valve 2 of this embodiment, the main control valve 14 may be provided with spools other than the eight spools 31 to 38. For example, the main control valve 14 may be provided with a straight-line travel spool that switches the connection destinations of the first and third hydraulic pumps 11, 13 so that hydraulic fluid can be supplied from one hydraulic pump 11 to the two travel motors 3, 4. The option spool 40 may be provided in the main control valve 14, and is not necessarily provided in the multi-control valve 2. Furthermore, the arrangement of the main spools 31 to 38 of the main control valve 14 is merely an example, and is not limited to the above description.

[0067] Furthermore, in the hydraulic drive system 1 and the multi-control valve 2 of this embodiment, the first unloading valve 41 is connected to the first hydraulic pump 11 side in the first pump passage 22. However, the first unloading valve 41 may be connected to the second hydraulic pump 12 side in the first pump passage 22, or may be connected to any position in the first pump passage 22. The same applies to the second unloading valve 42.

[0068] Furthermore, in the hydraulic drive system 1 and the multi-control valve 2 of this embodiment, a pressure compensating valve may be provided corresponding to each of the main spools 32-34, 37, 38-40. Each of the pressure compensating valves maintains a constant pressure difference across the corresponding main spool 32-34, 37, 38-40. Therefore, each of the main spools 32-34, 37, 38-40 can supply hydraulic fluid at a flow rate corresponding to the opening degree of each to the corresponding hydraulic actuator 6-9. That is, each of the main spools 32-34, 37, 38-40 can supply hydraulic fluid at a flow rate corresponding to an input signal to the corresponding hydraulic actuator 6-9.

[0069] Exemplary embodiments A hydraulic drive system in a first aspect is a hydraulic drive system that supplies hydraulic fluid to each of a plurality of hydraulic actuators including a first hydraulic actuator and controls a flow of the supplied hydraulic fluid, the hydraulic drive system including a first hydraulic pump that discharges hydraulic fluid to a first passage portion of a first pump passage, a second hydraulic pump that discharges hydraulic fluid to a second passage portion of the first pump passage, a first valve block having the first passage portion, and a plurality of main valve bodies that are inserted into the first valve block corresponding to each of the hydraulic actuators and stroke to control the flow of hydraulic fluid supplied from the first passage portion to the corresponding hydraulic actuator. the first valve block having the second passage portion and provided in the first valve block, and an attach valve including an attach valve body inserted into the second valve block, wherein the plurality of main valve bodies include a first main valve body that controls the flow of hydraulic fluid supplied from the first passage portion to the first hydraulic actuator by stroking, and the attach valve body controls the flow of hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and causes the flow to merge with the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator via the first main valve body.

[0070] According to the above aspect, the attach valve includes a second valve block having a second passage portion of the first pump passage and a second hydraulic pump connected to the second passage portion, and an attach valve body inserted into the second valve block. The attach valve body controls the hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and merges the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator. Such an attach valve is provided in the first valve block. As a result, the hydraulic fluid discharged from the first hydraulic pump can be supplied to the first hydraulic actuator via the first main valve body, and the hydraulic fluid discharged from the second hydraulic pump can be supplied to the first hydraulic actuator via the attach valve body. That is, since the hydraulic fluid can be supplied to the first hydraulic actuator from two valve bodies, the flow rate of the hydraulic fluid supplied to each valve body can be suppressed. As a result, the size of each valve body can be suppressed. In addition, since the two hydraulic pumps share the first pump passage, an increase in the number of parts constituting the hydraulic drive system can be suppressed. Furthermore, by providing an attach valve to an existing main control valve, a hydraulic drive system can be easily constructed.

[0071] A hydraulic drive system in a second aspect is the hydraulic drive system of the first aspect, further comprising a third hydraulic pump that discharges hydraulic fluid to a second pump passage, the first valve block further has the second pump passage, the plurality of main valve bodies has a second main valve body inserted into the first valve block, and the second main valve body controls the flow of hydraulic fluid supplied from the second pump passage to the first hydraulic actuator by stroking to merge the hydraulic fluid with the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator.

[0072] According to the above aspect, the second main valve body strokes to control the flow of hydraulic fluid supplied from the second pump passage to the first hydraulic actuator and merges the hydraulic fluid supplied from the first passage to the first hydraulic actuator. Therefore, the hydraulic fluid discharged from the first to third hydraulic pumps can be supplied to the first hydraulic actuator via each valve body. In other words, since the hydraulic fluid can be supplied to the first hydraulic actuator from three valve bodies, the flow rate of the hydraulic fluid supplied to each valve body can be reduced. This makes it possible to prevent each valve body from becoming large.

[0073] In a third aspect, the hydraulic drive system is the hydraulic drive system of the first or second aspect, wherein the main control valve further includes an unloading valve, the first valve block is formed with a tank passage leading to a tank, and the unloading valve connects the first passage portion with the tank passage in response to an input signal.

[0074] According to the above aspect, the unloading valve communicates the first passage portion with the tank passage 24 in response to an input signal. Therefore, the first and second hydraulic pumps can share the unloading valve. This makes it possible to reduce the number of parts in the hydraulic drive system.

[0075] A hydraulic drive system in a fourth aspect is the hydraulic drive system of any of the first to third aspects, wherein the second valve block includes a first block body into which a first attachment valve body which is the attachment valve body is inserted, and a second block body provided on the first block body, the attachment valve further includes a second attachment valve body which is inserted into the second block body, the second passage portion extends to the first block body and the second block body, and the second attachment valve body controls, by stroking, the flow of hydraulic fluid supplied from the second passage portion to a second hydraulic actuator which is one of the plurality of hydraulic actuators.

[0076] A hydraulic drive system in a fifth aspect is the hydraulic drive system of any of the first to fourth aspects, wherein the first valve block and the second valve block are stacked in a predetermined direction, the first pump passage extends in a predetermined direction in the first valve block and the second valve block, the first hydraulic pump is connected to the first passage portion on one side of the first pump passage in the predetermined direction, and the second hydraulic pump is connected to the second passage portion on the other side of the first pump passage in the predetermined direction.

[0077] According to the above aspect, the first hydraulic pump is connected to the first passage portion on one side of the first pump passage in the predetermined direction, and the second hydraulic pump is connected to the second passage portion on the other side of the first pump passage in the predetermined direction. Therefore, in the first pump passage, the hydraulic fluid discharged from each of the two hydraulic pumps can be supplied to the first hydraulic actuator via separate valve bodies. Therefore, it is possible to reduce pressure loss in the hydraulic fluid supplied from each hydraulic pump to the first hydraulic actuator. Furthermore, since each hydraulic pump is connected to each of the one side and the other side of the first pump passage in the predetermined direction, connection of the hydraulic pumps is easy.

[0078] A hydraulic drive system in a sixth aspect is the hydraulic drive system of any one of the first to fifth aspects, further comprising a control device that controls movement of the first main valve body and the attachment valve body, wherein the control device calculates the opening degree of the first main valve body and the attachment valve body in accordance with a supply flow rate of working fluid to be supplied to the first hydraulic actuator, the supply flow rate being calculated based on an input command, and controls the movement of the first main valve body and the attachment valve body in accordance with the calculated opening degree.

[0079] According to the above aspect, the control device calculates the opening degree of the first main valve element and the attachment valve element according to the supply flow rate calculated based on the input command, and controls the movement of the first main valve element and the attachment valve element according to the calculated opening degree. Therefore, the control device can control the flow rate of the hydraulic fluid supplied to the first hydraulic actuator via each valve element even when the hydraulic fluid is discharged from the two hydraulic pumps and flows into the first pump passage at a large flow rate and is supplied to each valve element. This allows the control device to reduce the flow rate of the hydraulic fluid supplied to each valve element.

[0080] A hydraulic drive system in a seventh aspect is the hydraulic drive system of the sixth aspect, wherein the first hydraulic pump changes its discharge capacity in response to a first capacity signal, and the second hydraulic pump changes its discharge capacity in response to a second capacity signal, and the control device outputs a first capacity signal and a second capacity signal in response to a supply flow rate calculated based on an input command, thereby controlling the discharge capacities of the first hydraulic pump and the second hydraulic pump.

[0081] According to the above aspect, the control device outputs the first displacement signal and the second displacement signal in accordance with the supply flow rate to change the discharge displacements of the first hydraulic pump and the second hydraulic pump, thereby reducing the energy consumption in each of the first hydraulic pump and the second hydraulic pump.

[0082] In an eighth aspect, a multi-control valve controls a flow of hydraulic fluid supplied to each of a plurality of hydraulic actuators including a first hydraulic actuator, the multi-control valve including: a first valve block having a first passage portion of a first pump passage and a first hydraulic pump connected to the first passage portion; a main control valve including a plurality of main valve bodies inserted into the first valve block corresponding to each of the hydraulic actuators and stroking to control the flow of hydraulic fluid supplied from the first passage portion to the corresponding hydraulic actuator; a second valve block having a second passage portion of the first pump passage and a second hydraulic pump connected to the second passage portion; and an attach valve body inserted into the second valve block, the plurality of main valve bodies including a first main valve body stroking to control the flow of hydraulic fluid supplied from the first passage portion to the first hydraulic actuator, and the attach valve body stroking to control the flow of hydraulic fluid supplied from the second passage portion to the first hydraulic actuator and to merge the flow of hydraulic fluid supplied from the first passage portion to the first hydraulic actuator via the first main valve body.

[0083] According to the above aspect, the attach valve includes a second valve block provided in the first valve block and having a second passage portion formed therein, and an attach valve body inserted into the second valve block. The attach valve body controls the hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and merges the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator. As a result, the hydraulic fluid discharged from the first hydraulic pump can be supplied to the first hydraulic actuator via the main valve body, and the hydraulic fluid discharged from the second hydraulic pump can be supplied to the first hydraulic actuator via the attach valve body. That is, since the hydraulic fluid can be supplied to the first hydraulic actuator from two valve bodies, the flow rate of the hydraulic fluid supplied to each valve body can be suppressed. This can suppress an increase in size of each valve body. In addition, since the two hydraulic pumps share the first pump passage, an increase in the number of parts constituting the hydraulic circuit can be suppressed. Furthermore, a multi-control valve can be easily configured by providing an attach valve to an existing main control valve. [Explanation of symbols]

[0084] 1,1A Hydraulic Drive System 2,2A Multi-Control Valve 3. First travel motor (hydraulic actuator) 4. Second travel motor (hydraulic actuator) 5 Swing motor (hydraulic actuator) 6 Boom cylinder (first hydraulic actuator) 7 Arm cylinder (hydraulic actuator) 8 Bucket cylinder (hydraulic actuator) 9 Optional cylinder (second hydraulic actuator) 11 First hydraulic pump 12 Second hydraulic pump 13. 3rd hydraulic pump 14 Main control valve 15 Attachment valve 18 Control device 19. Tank 21 First valve block 22 First pump passage 22a 1st passage section 22b 2nd passage section 23 Second pump passage 24 Tank Passage 25 Second valve block 25a 1st block 25b 2nd block 31 First traveling spool (main valve body) 32 Bucket spool (main valve body) 33 First arm spool (main valve body) 34 First boom spool (first main valve body) 34A Flow Control Spool 35 Second traveling spool (main valve body) 36 Swing spool (main valve body) 37 Second arm spool (main valve body) 38 Third boom spool (second main valve body) 39 Spool for third boom (first attachment valve body) 40 Option spool (second attachment valve body) 41 Unloading valve

Claims

1. A hydraulic drive system that supplies hydraulic fluid to each of a plurality of hydraulic actuators including a first hydraulic actuator and controls a flow of the supplied hydraulic fluid, a first hydraulic pump that discharges hydraulic fluid to a first passage portion of a first pump passage; a second hydraulic pump that discharges hydraulic fluid to a second passage portion of the first pump passage; a main control valve including a first valve block having the first passage portion, and a plurality of main valve bodies each inserted into the first valve block corresponding to each of the hydraulic actuators and stroking to control the flow of hydraulic fluid supplied from the first passage portion to the corresponding hydraulic actuator; a second valve block having the second passage portion and provided in the first valve block, and an attachment valve including an attachment valve body inserted into the second valve block, the plurality of main valve bodies include a first main valve body that controls a flow of hydraulic fluid supplied from the first passage portion to the first hydraulic actuator by stroking, the attach valve body controls the flow of hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and causes the hydraulic fluid to merge with the hydraulic fluid supplied from the first passage portion to the first hydraulic actuator via the first main valve body.

2. a third hydraulic pump that discharges hydraulic fluid to the second pump passage; the first valve block further includes the second pump passage; the plurality of main valve bodies include a second main valve body inserted into the first valve block, 2. The hydraulic drive system according to claim 1, wherein the second main valve body controls a flow of hydraulic fluid supplied from the second pump passage to the first hydraulic actuator by stroking, and causes the flow to merge with hydraulic fluid supplied from the first passage portion to the first hydraulic actuator.

3. The main control valve further includes an unloading valve; The first valve block is formed with a tank passage that is connected to a tank, 2. The hydraulic drive system according to claim 1, wherein the unloading valve connects the first passage portion and the tank passage in response to an input signal.

4. The second valve block includes a first block body through which a first attachment valve body serving as the attachment valve body is inserted, and a second block body provided in the first block body, The attachment valve further includes a second attachment valve body that is inserted into the second block body, The second passage portion extends through the first block body and the second block body, 2. The hydraulic drive system according to claim 1, wherein the second attachment valve body controls a flow of hydraulic fluid supplied from the second passage portion to a second hydraulic actuator that is one of the plurality of hydraulic actuators by stroking.

5. the first valve block and the second valve block are stacked in a predetermined direction, the first pump passage extends in a predetermined direction in the first valve block and the second valve block, the first hydraulic pump is connected to the first passage portion located on one side of the first pump passage in a predetermined direction, 2. The hydraulic drive system according to claim 1, wherein the second hydraulic pump is connected to the second passage portion located on the other side of the first pump passage in the predetermined direction.

6. A control device that controls the movement of the first main valve body and the attachment valve body is further provided.

2. The hydraulic drive system according to claim 1, wherein the control device calculates openings of the first main valve body and the attachment valve body in accordance with a supply flow rate of hydraulic fluid to be supplied to the first hydraulic actuator, the supply flow rate being calculated based on an input command, and controls movement of the first main valve body and the attachment valve body in accordance with the calculated openings.

7. the first hydraulic pump changes its discharge capacity in response to a first capacity signal; the second hydraulic pump changes its discharge capacity in response to a second capacity signal; 7. The hydraulic drive system according to claim 6, wherein the control device outputs a first displacement signal and a second displacement signal in accordance with a supply flow rate calculated based on an input command to control the discharge displacements of the first hydraulic pump and the second hydraulic pump.

8. A multi-control valve that controls a flow of hydraulic fluid supplied to each of a plurality of hydraulic actuators including a first hydraulic actuator, a first valve block having a first passage portion of a first pump passage and a first hydraulic pump connected to the first passage portion; and a main control valve including a plurality of main valve bodies each inserted into the first valve block corresponding to each of the hydraulic actuators and stroking to control a flow of hydraulic fluid supplied from the first passage portion to the corresponding hydraulic actuator; a second valve block having a second passage portion of the first pump passage and a second hydraulic pressure pump connected to the second passage portion; and an attachment valve provided in the first valve block, the attachment valve including an attachment valve body inserted into the second valve block, the plurality of main valve bodies include a first main valve body that controls a flow of hydraulic fluid supplied from the first passage portion to the first hydraulic actuator by stroking; The attach valve body is a multi-control valve that controls the flow of hydraulic fluid supplied from the second passage portion to the first hydraulic actuator by stroking, and causes the flow to merge with the hydraulic fluid supplied from the first passage portion via the first main valve body to the first hydraulic actuator.

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