HYDRAULIC CONTROL SYSTEM FOR A WORKING MACHINE

Abstract

Problem: In a hydraulic control system including a main engine, a plurality of variable capacity hydraulic pumps driven by the main engine, and a plurality of hydraulic actuators driving the hydraulic pumps as a hydraulic source, the merging of the discharged oil of the hydraulic pump is reduced in order to alleviate the reduction in efficiency and operability caused by the merging.Solution: A controller (10) is provided to control the pumping capacity of the hydraulic pumps (P1, P2) and the rotational speed of the main motor (M), and the controller (10) is equipped with a reference pump flow rate setting unit (61) that sets a reference pump flow rate, a target pump flow rate setting unit (64) that sets a target pump flow rate of each hydraulic pump (P1, P2) for each hydraulic pump according to the operation of a manipulator, and a pump flow rate control unit (65) that, when the target pump flow rate of one of the hydraulic pumps (P1, P2) exceeds the reference pump flow rate, maximizes the pumping capacity of the hydraulic pump (P1, P2) and increases the rotational speed of the main motor (M), thereby increasing the pump flow rate to a value greater than the reference pump flow rate.

Description

Technical FieldThe present invention relates to the technical field of hydraulic control systems used in working machines such as hydraulic excavators.Prior ArtIn general, a work machine such as a hydraulic excavator is equipped with a main engine such as an internal combustion engine or an electric motor, a plurality of hydraulic pumps driven by the main engine, and a plurality of hydraulic actuators using the hydraulic pumps as a hydraulic source. In such a hydraulic system, in the case of a high-flow-rate hydraulic actuator in which the hydraulic actuator requires hydraulic oil supplied from a plurality of hydraulic pumps, or in the case of a complex operation in which a plurality of hydraulic actuators are operated simultaneously, the hydraulic oil from the plurality of hydraulic pumps may be merged to supply the hydraulic actuator, but in this case, the hydraulic interference caused by the merging may result in a decrease in efficiency or a deterioration in operability. For example, when hydraulic oil from two hydraulic pumps is supplied to a hydraulic actuator having different load pressure, efficiency is lowered because the discharge pressure of both hydraulic pumps needs to be increased to the pressure of the hydraulic actuator on the high load side in order to prevent the flow of hydraulic oil to the hydraulic actuator on the low load side.On the other hand, there is a known technique for improving operability in complex operations in which the order of supply of hydraulic oil from the first and second hydraulic pumps (a front pump, a rear pump) to each hydraulic actuator is prioritized according to the combination of the simultaneously operated hydraulic actuators to control the timing of supply of hydraulic oil and the amount of supply of hydraulic oil independently of each other (see, e.g., Patent Document 1).There is also a technique that provides a first variable capacity hydraulic pump that is driven by an engine and supplies hydraulic oil to a first hydraulic actuator, second and third hydraulic pumps that are driven by the engine via a continuously variable transmission and supply hydraulic oil to second and third hydraulic actuators, respectively, and a controller that changes the capacity of the first hydraulic pump and a variable speed ratio of each continuously variable transmission according to an operation amount (see, e.g., Patent Document 2).Prior Art DocumentsPatent DocumentsPatent Document 1: JPH 08-23768APatent Document 2: JP 2016-205451ASummary of the InventionProblems to be Solved by the InventionHowever, the invention of Patent Document 1 is configured to be supplied with hydraulic oil from both the first and second hydraulic pumps to each hydraulic actuator that is simultaneously operated during a complex operation, and to be supplied with hydraulic oil from only the first hydraulic pump in a single operation, with hydraulic oil from the second hydraulic pump or from the first and second hydraulic pumps in a complex operation. In addition, in a boom cylinder and an arm cylinder that are high flow rate hydraulic actuators, hydraulic oil is supplied from both the first and second hydraulic pumps when the flow rate exceeds half of the maximum flow rate during the single operation. In other words, in Patent Document 1, merging of the discharged oil of the first and second hydraulic pumps is often performed. Therefore, although it is impossible to avoid the decrease in efficiency and operability caused by the merging, there is a problem that the circuit for supplying merging oil to hydraulic actuators other than large-flow actuators is required and the circuit becomes complicated.On the other hand, the invention of Patent Document 2 is configured such that basically one hydraulic pump is a hydraulic supply source for one or two hydraulic actuators, i.e., each hydraulic pump alone is configured to be able to supply the maximum flow rate of one or two hydraulic actuators. For this reason, a hydraulic pump having a large capacity is required, and there are unfavorable problems in terms of cost and space to be solved by the present invention.Means for Solving the ProblemThe present invention has been developed with the aim of solving these problems in view of the above-mentioned reality. The invention according to claim 1 relates to a hydraulic control system of a working machine, the hydraulic control system comprising a main motor, a plurality of variable capacity hydraulic pumps driven by the main motor, a plurality of hydraulic actuators driving at least one of the hydraulic pumps as a hydraulic source, a working fluid for each hydraulic actuator operated to drive each hydraulic actuator, and a plurality of control valves controlling supply of hydraulic oil from the hydraulic pump to each hydraulic actuator, and provided with a control unit for controlling operation of the control valve, pump capacity of the hydraulic pump, and a rotational speed of the main motor; wherein the control unit comprises: reference pump flow rate setting means that sets a pump flow rate of the hydraulic pump when the pump capacity of the hydraulic pump is maximum and the rotational speed of the main motor is a preset reference rotational speed as the reference pump flow rate; target pump flow rate setting means that sets a target pump flow rate of each hydraulic pump for each hydraulic pump depending on the operation of the operation means for each hydraulic actuator within a range where the pump flow rate of each hydraulic pump does not exceed a preset maximum pump flow rate; and a pump flow rate control means that, when the target pump flow rate of one of the hydraulic pumps set by the target pump flow rate setting means exceeds the reference pump flow rate, maximizes the pump capacity of one of the hydraulic pumps and increases the rotational speed of the main motor to be greater than the reference rotational speed, thereby increasing the pump flow rate of one of the hydraulic pumps to be greater than the reference pump flow rate.The invention according to claim 2, wherein in claim 1, a first hydraulic pump and a second hydraulic pump are included as hydraulic pumps, and a high-flow-rate hydraulic actuator that receives hydraulic oil from both the first and second hydraulic pumps at a time of maximum flow-rate supply is included as the hydraulic actuator; the controller controls either the first or second hydraulic pump as a main pump and supplies hydraulic oil only from the main pump until a flow rate supplied to the high-flow-rate hydraulic actuator reaches a set flow rate set to exceed the reference pump flow rate when the operating medium for the high-flow-rate hydraulic actuator is operated alone, and supplied with the hydraulic oil from both the first and second hydraulic pumps when the flow rate exceeds the set flow rate; and the target pump flow setting means sets the target pump flow rate of the main pump to exceed the reference pump flow rate depending on the supply flow rate of the main pump to the high flow rate hydraulic actuator.The invention according to claim 3, wherein in claim 2, a first high-flow-rate hydraulic actuator using the first hydraulic pump as a main pump and a second high-flow-rate hydraulic actuator using the second hydraulic pump as a main pump are included; when the operating medium for the first and second high-flow-rate hydraulic actuators are simultaneously operated, the controller controls to supply the hydraulic oil from each main pump to the first and second high-flow-rate hydraulic actuators, respectively, and the target pump flow setting means sets the target flow rate of the first and second hydraulic pumps for each hydraulic pump depending on the operation amount of the operating medium for the first and second high-flow-rate hydraulic actuators.The invention according to claim 4, wherein in claim 1, the work machine includes a traveling body having a left traveling body and a right traveling body, a working device mounted on the traveling body, a first hydraulic pump and a second hydraulic pump as hydraulic pumps, a left traveling motor and a right traveling motor as hydraulic actuators that drive the left traveling body and the right traveling body, respectively, and a plurality of hydraulic working actuators that drive the working device; when the left and right traveling motors and the operating medium for the hydraulic actuator are simultaneously operated, the controller controls a control valve to direct the hydraulic oil from the first hydraulic pump to the left and right traveling hydraulic motors and the hydraulic oil from the second hydraulic pump to the hydraulic actuator; and the target pump flow rate setting means sets the target pump flow rate of the second hydraulic pump to be larger than the reference pump flow rate.Effect of the inventionAccording to the invention of claim 1, it is possible to reduce the reduction in efficiency and operation caused by the merging and the complexity of the hydraulic circuit, and it is not necessary to provide a hydraulic pump having a large capacity.According to the invention of claim 2, it is possible to reduce the frequency of merging even in high-flow hydraulic actuators supplied with hydraulic oil from both the first and second hydraulic pumps at the time of maximum flow supply.According to the invention of claim 3, when the first and second hydraulic actuators are simultaneously driven at a high flow rate, merging of the discharged oil of the first and second hydraulic pumps can be avoided even if they are high flow rate hydraulic actuators supplied with hydraulic oil from both the first and second hydraulic pumps at the time of maximum flow supply.According to the invention of claim 4, the left and right traveling motors and the operating hydraulic actuator can be supplied with hydraulic oil independently without causing hydraulic interference, and the flow rate supplied to the operating hydraulic actuator can be larger than the reference pump flow rate, which can contribute to improvement of the working efficiency.Brief Description of the DrawingsFIG. 1 is a hydraulic diagram illustrating a first embodiment. FIG. 2 is a side view of a hydraulic excavator. FIG. 3 is a block diagram illustrating input / output of a controller. FIG. 4 is a tabular diagram illustrating examples of a target pump flow rate. FIG. 5 is a diagram illustrating, when the arm manipulator is operated alone, the relationship among the operation of the manipulator, a target supply flow rate from the first and second hydraulic pumps to an arm cylinder, the opening area of the flow rate control valve of the arm, and the opening area of a supply valve passage for a direction switching valve of the arm. FIG. 6 is a hydraulic diagram illustrating a second embodiment.Detailed DescriptionEmbodiments of the present invention will be described below with reference to the drawings.First, FIG. 1 is a hydraulic diagram illustrating the first embodiment of the hydraulic control system of a hydraulic excavator in which this invention has been implemented. In FIG. 1, M represents a main engine; P 1, P 2 each represents a variable capacity hydraulic pump driven by the main engine; P 1 a, P 2 aeach represents a means for changing the capacity of the hydraulic pumps P 1, P 2 based on a control signal transmitted from the controller 10 mentioned later; 3 represents an oil tank; 4 represents a left travel engine; 5 represents a right travel engine; 6 represents a boom cylinder; 7 represents a swing motor; 8 represents an arm cylinder; and 9 represents a bucket cylinder. The left travel motor 4, the right travel motor 5, the boom cylinder 6, the swing motor 7, the arm cylinder 8, and the bucket cylinder 9 are hydraulic actuators using the hydraulic pumps P 1, P 2 as hydraulic supply sources. In these hydraulic actuators, the boom cylinder 6 and the arm cylinder 8 are hydraulic actuators using both hydraulic pumps P 1, P 2 as hydraulic supply sources and corresponding to the high flow rate hydraulic actuator of this invention. Moreover, in the present embodiment, an electric motor driven by a power supply from a battery (not shown) is used as the main motor M, and the drive shafts of the hydraulic pumps P 1 and P 2 are connected to an output shaft of the electric motor.Note that the hydraulic excavator 1 is an example of the working machine of the present invention, and as shown in FIG. 2, the hydraulic excavator is configured to include a lower traveling body 71 having left and right traveling bodies respectively driven by the left and right traveling motors 4, 5, an upper swing body 72 pivotally supported by the lower traveling body 71 and pivotally driven by the swing motor 7, and a front working machine 73 mounted on the upper swing body 72. The work machine 73 is configured to include a boom 74 that is vertically freely supported on the upper swing body 72 and driven by the boom cylinder 6; a arm 75 that is pivotally supported axially on a tip of the boom 74 and driven by the arm cylinder 8; and a bucket 76 that is mounted on a tip of the arm 75 and driven by the bucket cylinder 9. The lower traveling body 71 and the upper swinging body 72 constitute the traveling body of the present invention. In addition, the front work machine 73 corresponds to the working device of the present invention, and the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9 correspond to the hydraulic actuator of the present invention.The hydraulic pump P1 is connected to a pump line C through a straight traveling valve 11 at a later-mentioned first position X and connected to a left traveling direction switching valve 13. In addition, the hydraulic pump P2 is connected to a pump line D and connected to a right travel direction switching valve 14 at the first position X via the straight travel valve 11.The straight traveling valve 11 is a two-position switching valve that switches to a first position X and a second position Y based on a control signal output from the controller 10. When the straight traveling valve 11 is at the first position X, the discharged oil of the hydraulic pump P 1 is supplied to the pump line C and the left traveling direction switching valve 13, and the discharged oil of the hydraulic pump P 2 is supplied to the pump line D and the right traveling direction switching valve 14. When the straight traveling valve 11 is in the second position Y, the discharged oil of the hydraulic pump P 1 is supplied to both the left and right traveling direction switching valves 13, 14, and the discharged oil of the hydraulic pump P 2 is supplied to both the pump lines C and D. The controller 10 then controls the straight traveling valve 11 to be brought to the first position X when only the left and right traveling manipulators (not shown) or when only hydraulic actuators (boom, swing, arm, bucket manipulators, not shown) other than the traveling manipulators are operated. On the other hand, when both the left and right travel manipulators are operated for straight travel and other hydraulic actuators are simultaneously operated, a control signal is output to switch the straight travel valve 11 to the second position Y. When only the left and right travel manipulators are operated and the straight-ahead valve 11 is at the first position X, the discharged oil of the hydraulic pumps P1 and P2 is supplied to the left and right travel motors 4 and 5 via the left and right travel direction switching valves 13 and 14. On the other hand, when the manipulators for the left and right travel movements are simultaneously operated with the other manipulators for the hydraulic actuators, the outflow flow rate of the hydraulic pump P 1 may be distributed only by the left and right travel motors 4 and 5 to balance the supply flow rate to the two travel motors 4 and 5, and the outflow flow rate of the hydraulic pump P 2 may be supplied to the other hydraulic actuators. In the following description, unless specifically stated otherwise, it is explained that the straight traveling valve 11 is at the first position X; that is, the discharged oil of the hydraulic pump P 1 is supplied to the pump line C and the left traveling direction switching valve 13, and the discharged oil of the hydraulic pump P 2 is supplied to the pump line D and the right traveling direction switching valve 14. In addition, the manipulators for the left and right travel, boom, swing, arm, and bucket are similar to the operating means of the present invention.The left and right travel direction switching valves 13, 14 are a center slide valve-closed valve that controls the supply and discharge flow rates for the left and right travel motors 4, 5 and switches the supply and discharge directions, and include forward and reverse pilot ports 13 a, 13 b, 14 a, and 14 bthat are provided with a left travel forward proportional solenoid valve 47 a, a left reverse proportional solenoid valve 47 b, a right forward proportional solenoid valve 48 a, and a right reverse proportional solenoid valve 48 b(see FIG. 3 ) for outputting the control pressure based on the control signal output from the controller 10. When no control pressure is input to the forward and reverse control ports 13a, 13b, 14a and 14b, the left and right travel direction switching valves 13 and 14 are brought into a neutral position N in which the supply and discharge of the left and right travel motors 4 and 5 are not controlled. When the control pressure is input to the front control ports 13a, 14a, the left and right travel direction switching valves 13 and 14 are switched to an operation position X on the forward side to open the supply valve passages 13e, 14e and supply the discharged oil of the hydraulic pumps P1, P2 to the front side ports 4a, 5a of the left and right travel motors 4 and 5, and simultaneously open the discharge valve passages 13f, 14f to allow the discharged oil to flow from the rear ports 4b, 5b to the oil tank 3. In addition, when the control pressure is input to the rear control ports 13b, 14b, the left and right travel direction switching valves 13 and 14 switch to the rear operating position Y to open the supply valve passages 13e, 14e and supply the discharged oil of the hydraulic pumps P1, P2 to the rear ports 4b, 5b of the left and right travel motors 4 and 5, and simultaneously open the drain valve passages 13f, 14f to flow the discharged oil from the front ports 4a, 5a to the oil tank 3. The supply flow rate and the discharge flow rate for the left and right travel motors 4 and 5 when they are positioned at the front operation position X and the rear operation position Y are controlled by the opening area of the supply valve passages 13e, 14e and the discharge valve passages 13f and 14f, and the opening area is controlled to increase and decrease depending on the moving position of the spool, whereby the control pressure input from the travel proportional solenoid valves to the front or rear control ports 13a, 13b, 14a, 14b is increased and decreased. Then, the controller 10 controls the front left side proportional solenoid valve 47 a, the rear left side proportional solenoid valve 47 b, the front right side proportional solenoid valve 48 a, and the rear right side proportional solenoid valve 48 bto output the control pressure that increases or decreases according to the operation amount of the travel manipulators when the left and right travel manipulators are operated, so that the left and right travel motors 4, 5 can be driven at a speed corresponding to the operation amount of the travel manipulators.On the other hand, of the pump line C connected to the hydraulic pump P 1, the main-side boom supply oil passage 17, the lower-side arm supply oil passage 18, and the bucket supply oil passage 19 are branched in parallel with each other, and of the pump line D connected to the hydraulic pump P 2, the lower-side boom supply oil passage 20, the main-side swing supply oil passage 21, and the main-side arm supply oil passage 22 are branched in parallel with each other. The main-side boom supply oil passage 17 and the sub-side boom supply oil passage 20 are oil passages that connect the hydraulic pumps P 1 and P 2 to the pump ports 23 pof the boom directional switching valve 23 described later, and the main-side arm supply oil passage 22 and the sub-side arm supply oil passage 18 are oil passages that connect the hydraulic pumps P 2 and P 1 to the pump port 25 pof the arm directional switching valve 25. The swing supply oil passage 21 is an oil passage that connects the hydraulic pump P 2 to the pump port 24 pof the swing direction switching valve 24, and the bucket oil supply passage 19 is an oil passage that connects the hydraulic pump P 1 to the pump port 26 pof the bucket direction switching valve 26.The lower-side arm supply oil passage 18 is provided with the arm flow control valve 28 that controls supply of a supply flow from the hydraulic pump P 1 to the arm direction switching valve 25. In addition, the lower-side boom supply oil passage 20 is provided with a boom flow rate control valve 29 for controlling the flow rate from the hydraulic pump P 2 to the boom direction switching valve 23. The arm flow rate control valve 28 and the boom flow rate control valve 29 are poppet valves that are operated by the control flow rate proportional solenoid valve 45 and a flow rate proportional solenoid valve 46 (see FIG. 3 ) that are operated to control the flow rate based on a control signal output from the controller 10. It has a function of preventing the backflow that allows the oil flow from the hydraulic pumps P 1 and P 2 to the arm direction switching valve 25 and the boom direction switching valve 23 but prevents the backflow.On the other hand, a flow rate control valve such as the arm flow rate control valve 28 and the boom flow rate control valve 29 described above is not provided in the main-side boom supply oil passage 17, the bucket oil supply passage 19, the swing supply oil passage 21, and the main-side arm supply oil passage 22, and the flow rate from the hydraulic pump P 1 or the hydraulic pump P 2 is supplied to the boom direction switching valve 23, the bucket direction switching valve 26, the swing direction switching valve 24, and the arm direction switching valve 25 without controlling the flow rate. In addition, a check valve 30 is provided in each of the main side boom supply oil passage 17, the bucket oil supply passage 19, the swing oil supply passage 21, and the main side arm supply oil passage 22, and the flow of oil from the hydraulic pumps P 1 and P 2 to the boom direction switching valve 23, the bucket direction switching valve 26, the swing direction switching valve 24, and the arm direction switching valve 25 is allowed, but the backflow is prevented.Thus, the pump port 23 pon the boom direction switching valve 23 can be simultaneously supplied with the hydraulic oil from the hydraulic pump P 1 via the main-side boom supply oil passage 17 and the hydraulic oil from the hydraulic pump P 2 via the lower-side boom supply oil passage 20. In addition, the hydraulic oil from the hydraulic pump P 2 needs to be supplied to the boom direction switching valve 23 in a state (including a shut-off state) of the flow rate controlled by the boom flow rate control valve 29 located in the lower-side boom supply oil passage 20. The pump port 25 pof the arm direction switching valve 25 is to be simultaneously supplied with the hydraulic oil from the hydraulic pump P 2 via the main side arm supply oil passage 22 and the hydraulic oil from the hydraulic pump P 1 via the lower side arm supply oil passage 18, and the hydraulic oil from the hydraulic pump P 1 is to be supplied to the arm direction switching valve 25 in a state (including a shut-off state) of the flow rate controlled by the arm flow rate control valve 28 located in the lower side arm supply oil passage 18.Next, the boom, swing, arm, and bucket direction switching valves 23 to 26 will be explained.First, the swing and bucket direction switching valves 24 and 26 in which the hydraulic oil is supplied from one of the hydraulic pumps P 1 or P 2 will be explained. The swing direction switching valve 24 is a center closed position gate valve for controlling the supply and discharge rates of the swing motor 7 and switching its supply and discharge directions. The swing direction switching valve 24 includes left and right pivotable control ports 24 a, 24 bconnected to the left and right pivotable proportional solenoid valves 44 a, 44 b(see FIG. 3 ), respectively, for outputting a control pressure based on a control signal output from the controller 10; a pump port 24 pconnected to the swing oil supply passage 21; a tank port 24 tconnected to a tank line T to the oil tank 3; a first actuator port 24 cconnected to a left swing port 7 aon the swing motor 7; and a second actuator port 24 dconnected to a right swing port 7 bon the swing motor 7. When no control pressure is input to the left and right swingable control ports 24a, 24b, the swinging direction switching valve 24 is in the neutral position N in which the supply and discharge of the swinging motor 7 are not controlled. When the control pressure is input to the left pivotable control port 24a, the valve 24 is switched to a left pivotable operating position X to open a supply valve passage 24e from a pump port 24p to the first actuator port 24c and open a drain valve passage 24f from the second actuator port 24d to the tank port 24t. Also, when the control pressure is input to the right pivotable control port 24 b, the valve 24 is configured to switch to a right pivotable operation position Y to open the supply valve passage 24 efrom the pump port 24 pto the second actuator port 24 dand the drain valve passage 24 ffrom the first actuator port 24 cto the tank port 24 t. When the valve 24 is at the left or right swing position X or Y for operation, the flow rates for supply and discharge of the swing motor 7 are controlled by the opening area of the supply and discharge valve passages 24e, 24f, and the opening area is controlled to increase or decrease depending on the moving position of the spool, increasing or decreasing the control pressure from the left and right pivotable proportional solenoid valves 42a, 42b to the left and right pivotable control ports 24a, 24b.The bucket direction switching valve 26 is a center slide valve closed for controlling the supply and discharge flow rates of the bucket cylinders 9 and switching the supply and discharge directions. The valve 26 has an extended-side control port 26 aand a retracted-side control port 26 bconnected to the retracted-side and extended-side proportional solenoid valve 44 aand the retracted-side proportional solenoid valve of the bucket 44 b, respectively (see FIG. 3 ) to output the control pressure based on a control signal output from the controller 10, a pump port 26 pconnected to the supply oil passage 19 of the bucket, a tank port 26 tconnected to the tank passage T, a first actuator port 26 cconnected to a head-side port 9 aon the bucket cylinder 9, and a second actuator port 26 dconnected to a rod-side port 9 bon the bucket cylinder 9. The bucket direction switching valve 26 has the same structure as the above-mentioned swing direction switching valve 24. When the valve 26 changes from a neutral position N to an extended or retracted lateral operating position X or Y, the valve 26 is configured to open a supply valve passage 26 efrom the pump port 26 pto the actuator port 26 cor 26 dand open a drain valve passage 26 ffrom the actuator port 26 dor 26 cto the tank port 26 t, and control the supply and drain rates depending on the opening area of the supply and drain valve passages 26 e, 26 fof the bucket cylinder 9. The opening area is controlled to increase or decrease depending on the movement position of the spool with increase or decrease of the control pressure output from the extended-side and retracted-side proportional solenoid valves 44 a, 44 b.Next, the boom and arm direction switching valves 23, 25 in which the hydraulic oil is supplied from both the first and second hydraulic pumps P 1, P 2 will be explained. The bucket direction switching valve 25 is a center slide valve closed for controlling the supply and discharge rates of the arm cylinder 10 and switching the supply and discharge directions. The valve 25 has an extended-side control port 25 aand a retracted-side control port 25 bconnected to the bucket extended and contracted lateral proportional solenoid valves 43 a, 43 b(see FIG. 3 ) for outputting the control pressure based on a control signal output from the controller 10, a pump port 25 pconnected to the main supply oil passage 22 and the lower-side arm supply oil passage 18, a tank port 25 tconnected to the tank line T, a first actuator port 25 cconnected to a head-side port 8 aof the arm cylinder 8, and a second actuator port 25 dconnected to a rod-side port 8 bof the arm cylinder 8. When the control pressure is not input to the extended and retracted side control ports 25 a, 25 b, the arm direction switching valve 25 is in a neutral position N in which the supply and the discharge for the arm cylinder 8 are not controlled. When the control pressure is input to the extended-side control port 25 a, the valve 25 is configured to be switched to an extended-side operating position X to open a supply valve passage 25 efrom the pump port 25 pto the first actuator port 25 cand open a drain valve passage 25 ffrom the second actuator port 25 dto the tank port 25 t. When the control pressure is input to the retracted-side control port 25 b, the valve 25 is configured to be switched to the retracted-side operating position Y to open the supply valve passage 25 efrom the pump port 25 pto the second actuator port 25 dand open the drain valve passage 25 ffrom the first actuator port 25 cto the tank port 25 t. The opening area of the supply valve passage 25 eand the drain valve passage 25 fis controlled to increase or decrease depending on the moving position of the spool moved by the control pressure of the arm extended side proportional solenoid valve 43 aand the arm retracted side proportional solenoid valve 43 b, and the outflow rate from the arm cylinder 8 is controlled by the opening area of the drain valve passages 25 f. When the arm flow rate control valve 28 closes the lower side arm supply oil passage 18, the supply flow rate to the arm cylinder 8 is controlled by the opening area of the supply valve passage 25 eon the arm direction switching valve 25. When the arm flow rate control valve 28 opens the arm supply lower side oil passage 18, the supply flow rate of the arm cylinder 8 is controlled by the opening area of the arm flow rate control valve 28 and the opening area of the supply valve passage 25 eof the arm direction switching valve 25.The boom direction switching valve 23 is a center slide valve closed for controlling the supply and discharge rates of the boom cylinder 6 and switching the supply and discharge directions. The valve 23 has an extended-side control port 23 aand a retracted-side control port 23 bconnected to the proportional solenoid valves 41 aand 41 b(see FIG. 3 ) for outputting the control pressure based on a control signal output from the controller 10, a pump port 23 pconnected to the main-side supply oil passage 17 and the lower-side boom supply oil passage 20, a tank port 23 tconnected to the tank pipe T, a first actuator port 23 cconnected to a head-side port 6 aon the boom cylinder 6, and a second actuator port 23 dconnected to a rod-side port 6 bon the boom cylinder 6, respectively. The boom direction switching valve 23 has a similar structure to the above-mentioned arm direction switching valve 25, and is configured to open a supply valve passage 23 efrom the pump port 23 pto the actuator port 23 cor 23 dand open a drain valve passage 24 ffrom the actuator port 23 dor 23 cto the tank port 23 tby switching from a neutral position N to an extended side operation position X and a retracted side operation position Y. The opening area of the supply and discharge valve passages 23 eand 23 fis controlled to increase or decrease depending on the moving position of the spool moved by the control pressure of the proportional solenoid valves 41 a, 41 bfor the boom extended and retracted sides. The flow rate of the boom cylinder 6 is controlled by the opening area of the drain valve passage 23 f. When the boom flow rate control valve 29 closes the lower-side boom supply oil passage 20, the supply flow rate to the boom cylinder 6 is controlled by the opening area of the supply valve passage 23 eof the boom direction switching valve 23. When the boom flow rate control valve 29 opens the boom supply lower side oil passage 20, the flow rate to the boom cylinder 6 is controlled by the opening area of the boom flow rate control valve 29 and the opening area of the supply valve passage 23 eof the boom direction switching valve 23.Note that the straight traveling valve 11, the left and right traveling valves, the boom, swing, arm, and bucket direction switching valves 13, 14, 23- 26, the boom and arm flow rate control valves 28, 29 correspond to the control valves of the present invention.In addition, in the present embodiment, the hydraulic pumps P 1, P 2 correspond to the pumps or the first and second hydraulic pumps of the present invention, and the boom cylinder 6 and the arm cylinder 8 are hydraulic actuators corresponding to the high-flow-rate hydraulic actuators or the first and second high-flow-rate hydraulic actuators of the present invention as described above, and both the first and second hydraulic pumps of the present invention are used as hydraulic supply sources. In addition, the main pump of the present invention is a hydraulic pump to which the main-side supply oil passage (the main-side boom supply oil passage 17, the main-side arm supply oil passage 22) is connected. In the present embodiment, the main pump of the boom cylinder 6 is the hydraulic pump P 1, and the main pump of the arm cylinder 8 is the hydraulic pump P 2.As shown in the block diagram of FIG. 3, the controller 10 (corresponding to the control means in this invention) is connected at an input side to a boom operation detecting means 50 for detecting an operation direction and an operation amount of a boom manipulator, a swing operation detecting means 51 for detecting an operation direction and an operation amount of a swing manipulator, an arm operation detecting means 52 for detecting an operation direction and an operation amount of an arm manipulator, a bucket operation detecting means 53 for detecting an operation direction and an operation amount of a bucket manipulator, a travel operation detecting means 54 for detecting an operation direction and an operation amount of a travel manipulator, and a plurality of pressure sensors each for detecting, not shown in the figures, the discharge pressure of the hydraulic pumps P 1, P2 and load pressure of each hydraulic actuator (boom cylinder 6, swing motor 7, arm cylinder 8, bucket cylinder 9, and left and right travel motors 4 and 5); and on an output side connected to the booms, swing, arm, and bucket direction switching valves 23 to 26, the extended and retracted side proportional solenoid valves 41 a, 41 b, the left and right swing side proportional solenoid valves 42 a, 42 b, the extended and retracted side proportional solenoid valves 43 a, 43 b, the extended and retracted side proportional solenoid valves 44 a, 44 b, the left forward and backward travel proportional solenoid valves 47 a, 47 b, the proportional solenoid valves for right forward and backward travel 48a, 48b, the proportional solenoid valve for flow rate control of the arm 45 outputting control pressure to the arm flow rate control valve 28 located on the lower side arm supply oil passage 18, the proportional solenoid valve for controlling the boom flow rate 46 outputting control pressure to the boom flow rate control valve 29 located on the lower side arm supply oil passage 20, the travel valve 11 for straight travel, and the means for changing P1a, P2a the capacity of the hydraulic pump P1, P2 controlling control pressure to the control ports 23a, 23b-26a, 26b, 13a, 13b, 14a, 14b of the directional switching valves 23-26 of the boom, slewing gear, arm, respectively, the bucket and the left and right traveling direction switching valves 13, 14. The controller 10 can freely control the input / output from the control device of the main motor. Further, the controller 10 includes various setting units and control units such as a reference pump flow rate setting unit (corresponding to a reference pump flow rate setting means of the present invention) 61, a target supply flow rate setting unit 62, a supply flow rate control unit 63, a target pump flow rate setting unit (corresponding to a target pump flow rate setting means of the present invention) 64, and a pump flow rate control unit (including a pump capacity control unit 65 aof a main motor speed control unit 65 bcorresponding to a pump flow rate control means of the present invention) 65. the setting units and the control units are configured to control the oil supply and oil discharge of each of the hydraulic actuators 4 to 9, the power control of the hydraulic pumps P 1 and P 2, and the speed control of the main motor M, and the like.Next, the control executed by each setting unit, control unit 61- 65 of the controller 10 will be described.First, in the reference pump flow rate setting unit 61, the controller 10 sets the flow rate of the hydraulic pumps P 1 and P 2 as the reference pump flow rate Ls when the pump capacity of the hydraulic pumps P 1 and P 2 is maximum and the rotation speed of the main motor M corresponds to the preset reference rotation speed Ns. In this case, during the normal operation of the hydraulic excavator, the operation speed range of the main motor M is set in advance, and the reference speed Ns is set to a speed within the operation speed range and less than the maximum speed Nm within the operation speed range. The reference pump flow rate Ls is to be integrated as a control parameter into the reference pump flow rate setting unit 61 and may be changed with, for example, a monitoring device (not illustrated) disposed in the cab of the hydraulic excavator 1.In addition, the flow rate of the hydraulic pumps P 1 and P 2 is set as the maximum flow rate Lm of each hydraulic pump P 1 and P 2 when the capacity of the hydraulic pumps P 1 and P 2 is maximum and the rotation speed of the main motor M is the maximum rotation speed Nm.In addition, the controller 10 sets the target supply flow rate for each hydraulic actuator in the target supply flow rate setting unit 62, and sets the target pump flow rate Lt of the hydraulic pumps P 1 and P 2 in the target pump flow rate setting unit 64 when a detection signal is input from the respective operation detection means 50 to 54 for boom, swing, arm, bucket, and travel.The target supply flow rate setting unit 62 sets a target supply flow rate supplied to each hydraulic actuator of each hydraulic pump P 1, P 2 according to the combination of the operated hydraulic actuators and the operation amount of each manipulator. In this case, the sum of the target supply flow rates supplied from each hydraulic pump P 1 and P 2 is set so that the pump flow rates of the hydraulic pumps P 1 and P 2 are distributed to each hydraulic actuator according to the operation of the manipulator of each hydraulic actuator with the hydraulic pumps P 1 and P 2 as hydraulic supply sources within a range not exceeding the maximum pump flow rate Lm of each hydraulic pump P 1 and P 2, respectively.In addition, the target pump flow rate setting unit 64 sets the target pump flow rate Lt of each hydraulic pump P 1 and P 2 based on the sum of the target supply flow rates to each hydraulic actuator carried by each hydraulic pump P 1 and P 2, respectively. In this case, the target pump flow rate Lt of each hydraulic pump P 1, P 2 is set so that the preset maximum pump flow rate Lm of each hydraulic pump P 1, P 2 is not exceeded.Moreover, in the supply flow control unit 63, the controller 10 outputs a control signal to each of the proportional solenoid valves 41 a, 41 b- 44 a, 44 b, 47 a, 47 b- 48 a, 48 b, 45, 46 to output the control pressure for the opening area and the opening area of the swing, arm, bucket, left and right direction switching valves 23- 26, 13, 14 corresponding to the target supply flow rate, so that the target supply flow rate set by the target supply flow rate setting unit 62 is supplied from each hydraulic pump P 1, P 2 to each hydraulic actuator.Further, the controller 10 controls the pump capacity of the hydraulic pumps P 1 and P 2 and the rotational speeds of the main motor M in the pump flow rate control unit 65 (including a pump capacity control unit 65 athat controls the pump capacity of the hydraulic pumps P 1 and P 2 and a main motor rotational speed control unit 65 bthat outputs a control signal to the main motor controller 60 to control the rotational speed of the main motor M) so that the pump flow rate of the hydraulic pumps P 1 and P 2 corresponds to the target pump flow rate Lt set by the target pump flow rate setting unit 64. In this case, the pump flow rate control unit 65 controls the rotation speed of the main motor M to be the reference rotation speed Ns when the target pump flow rate Lt of both the hydraulic pumps P 1 and P 2 set in the target pump flow rate setting unit 64 is equal to or less than the reference pump flow rate Ls, and controls the pump capacity to be the flow rate of the hydraulic pumps P 1 and P 2 to be the target pump flow rate Lt. On the other hand, when the target pump flow rate Lt of one hydraulic pump P 1 or P 2 exceeds the reference pump flow rate Ls, the pump capacity of one of the hydraulic pumps P 1 and P 2 is maximized and the rotation speed of the main motor M is increased to more than the reference pump flow rate Ns, the maximum rotation speed Nm being the upper limit, so that the pump flow rate Lt of one of the hydraulic pumps P 1 and P 2 is controlled to be the target pump flow rate Lt exceeding the reference pump flow rate Ls. Also, each other of the hydraulic pumps P 2 and P 1 is controlled to be the target pump flow rate Lt by adjusting the pump capacity according to the increased rotational speeds of the main motor M.Next, the control executed by the controller 10 will be described in more detail.For example, when the maximum pump capacity of the hydraulic pumps P 1 and P 2 is set to 125 cm 3 / U and the reference rotational speed Ns of the main motor M is set to 1600 U / min, the reference pump flow rate Ls is set to 200 L / m. When the maximum rotation speed Nm is set to 2400 U / min within the normal rotation speed range of the main motor M, the maximum flow rate Lm of the hydraulic pumps P 1, P 2 is set to 300 L / m.The table in FIG. 4 shows an example of the target pump flow rate Lt of the hydraulic pumps P 1 and P 2 set when the manipulator is operated for each hydraulic actuator in a case where the reference pump flow rate Ls is set to 200 L / m and the maximum pump flow rate Lm is set to 300 L / m as described above. The "A" to "F" in the table are respectively the target pump flow rates Lt when the left travel manipulator, the right travel manipulator, the boom manipulator, the arm manipulator, the bucket manipulator, and the swing manipulator are fully operated separately, and "G" is the target pump flow rate Lt when the left and right travel manipulator, the boom manipulator, the arm manipulator, and the bucket manipulator are fully operated simultaneously. Note that the straight-ahead travel valve 11 is controlled to be in the first position X in the case of "A" to "F" and in the second position in the case of "G".Here, the reference pump flow rate Ls is set to correspond to the maximum supply flow rate to each of the left and right travel motors 4, 5 in the present embodiment. The maximum flow rate to the left and right traveling motors 4, 5 is set so as to limit the maximum value of the flow rate to the left and right traveling motors 4, 5 so that cornering does not occur when the hydraulic excavator 1 is traveling straight. Then, by setting the reference pump flow rate Ls to the maximum supply flow rate to the traveling motors 4 and 5, and by setting the target pump flow rate Lt to the reference pump flow rate Ls (200 L / m), when the left and right traveling manipulators are fully operated, as illustrated in "A" in FIG. 4, the maximum flow rate can be uniformly supplied from the hydraulic pumps P 1 and P 2 to the left and right motors 4 and 5 when only the left and right traveling manipulators are fully operated simultaneously.In addition, "C" and "D" in FIG. 4 show an example of the target pump flow rate Lt of the hydraulic pumps P 1 and P 2 when the boom and arm manipulators alone are fully operated. As described above, the boom cylinder 6 and the arm cylinder 8 are high-flow-rate hydraulic actuators that use both the hydraulic pumps P 1 and P 2 as hydraulic sources, and when the boom and arm manipulators are operated alone, the target supply flow rate and the target pump flow rate Lt are set separately for the hydraulic pumps P 1 and P 2. With respect to the control, in this case, the arm cylinder 8 will be described with reference to FIG. 5 as an example, since the case of the boom cylinder 6 and the case of the arm cylinder 8 are the same. The controller 10 sets the target supply flow rate (the target supply flow rate is zero) not from the hydraulic pump P 1 connecting the supply oil passage 18 of the lower-side arm supply, but sets only the target supply flow rate from the hydraulic pump (main pump) P 2 connecting the main-side arm supply oil passage 22 with the increase in the operation of the manipulator, controls the opening area of the supply valve passage 25 eof the arm direction switching valve 25 to increase with the increase in the operation of the manipulator, and controls the arm flow rate control valve 28 to be closed. On the other hand, when the operation of the manipulator exceeds the set value D, the target supply flow rate of both hydraulic pumps P2 and P1 is set, and in addition to the supply valve passage 25e of the arm direction switching valve 25, the arm flow rate control valve 28 is also controlled to open. The set value D of the operation amount of the manipulator is set to a value exceeding 50% of the operation amount of the manipulator when the operation amount is 100% in a state of full operation, for example, 70% to 90% of the operation amount, and the target supply flow rate when the operation amount of the manipulator is the set value D is set to the set flow rate Ld, and the set flow rate Ld is set to approach the maximum pump flow rate Lm exceeding the reference pump flow rate Ls of the hydraulic pump P 2. As a result, when the flow rate supplied to the arm cylinder 8 is below the set flow rate Ld set to exceed the reference pump flow rate Ls, only the hydraulic oil of the hydraulic pump P 2 is supplied to the arm cylinder 8, and when the flow rate exceeds the set flow rate Ld, the hydraulic oil is supplied from both the hydraulic pumps P 1 and P 2 to the arm cylinder 8. Moreover, the controller 10 sets the target pump flow rate Lt of the hydraulic pumps P 2, P 1 so that the target supply flow rate can be supplied, but in this case, the target pump flow rate Lt of the hydraulic pump P 2 is set to exceed the reference pump flow rate Ls corresponding to the target supply flow rate. Then, when the target supply flow rate and the target pump flow rate Lt are set in this manner and the operation amount of the manipulator exceeds the set value D, that is, when the supply flow rate to the arm cylinder 8 exceeds the set flow rate Ld set to exceed the reference pump flow rate Ls, the hydraulic oil from the hydraulic pumps P 2 and P 1 is gathered and supplied to the arm cylinder 8, so that the frequency at which the gathering is performed can be reduced.On the other hand, when the boom manipulator and the arm manipulator are simultaneously operated, i.e., when the boom cylinder 6 and the arm cylinder 8 which are high-flow-rate hydraulic actuators are simultaneously driven, the controller 10 calculates the distribution flow rate to the boom cylinder 6 and the arm cylinder 8 according to the operation amount of the manipulators, sets the target supply flow rate to allow the distribution flow rate to be supplied only from the main hydraulic pumps P 1 and P 2, respectively, to the boom cylinder 6 and the arm cylinder 8, and further sets the target pump flow rate Lt according to the target supply flow rate. That is, only the target supply flow rate from the hydraulic pump P 1 is set for the boom cylinder 6, and the target pump flow rate Lt of the hydraulic pump P 1 is set according to the target supply flow rate to the boom cylinder 6; and only the target supply flow rate from the hydraulic pump P 2 is set for the arm cylinder 8, and the target pump flow rate Lt of the hydraulic pump P 2 is set according to the target supply flow rate to the arm cylinder 8. Then, the directional switching valves 23 and 25 of the boom and the arm are controlled to open the supply valve passages 23 e, 25 ein the opening portion corresponding to the target supply flow rate, while the flow rate control valves 29 and 28 of the boom and the arm are controlled to close. In addition, the pump output control of the hydraulic pumps P 1 and P 2 and the rotation speed control of the main motor M are executed such that the pump flow rates of the hydraulic pumps P 1 and P 2 respectively correspond to the target pump flow rate Lt. In this way, when the boom cylinder 6 and the arm cylinder 8 are simultaneously driven, merging of the discharged oil of the hydraulic pumps P 1 and P 2 can be prevented even if they are high-flow hydraulic actuators supplied with hydraulic oil from both the hydraulic pumps P 1 and P 2 at the time of maximum flow supply.In addition, an example of the target pump flow rate Lt of the hydraulic pump P 1 when the bucket manipulator alone is fully operated is illustrated in "E" of FIG. 4, but the target pump flow rate Lt is set to be larger than the reference pump flow rate Ls of the hydraulic pump P 1. Thereby, it is possible to supply a flow rate exceeding the reference pump flow rate Ls to the bucket cylinder 9 when the bucket operation tool alone is fully operated, and even the bucket cylinder 9 having only one hydraulic pump P 1 as a hydraulic supply source can increase the supply flow rate without increasing the capacity of the hydraulic pump P 1 to improve the working efficiency.In addition, an example of the target pump flow rate Lt of the hydraulic pumps P 1 and P 2 when the left and right travel manipulators and the boom, arm, and bucket manipulators are fully operated simultaneously is illustrated in "G" of FIG. 4, in which case the travel valve 11 is controlled to be at the second position Y as described above, so that the left and right travel motors 4, 5 are supplied with the hydraulic oil from the hydraulic pump P 1, and the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9 are supplied with the hydraulic oil from the hydraulic pump P 2. In this case, by setting the target pump flow rate Lt of the hydraulic pump P 2 to a value larger than the reference pump flow rate Ls as shown in "G" in FIG. 4, the supply flow rate to the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9 can be increased, which can contribute to the improvement in the working efficiency.In the present embodiment configured as described, the hydraulic control system of the hydraulic excavator 1 is configured to include a main motor M, a plurality of variable capacity hydraulic pumps P 1, P 2 driven by the main motor M, and a plurality of hydraulic actuators 4- 9 (left and right travel motors 4, 5, the boom cylinder 6, the swing motor 7, the arm cylinder 8, the bucket cylinder 9) that drive at least one of the hydraulic pumps P 1, P 2 as a hydraulic source; Operating means for each hydraulic actuator (the left and right travel manipulator, the boom manipulator, the swing manipulator, the arm manipulator, the bucket manipulator) operated to drive each hydraulic actuator 4-9, and a plurality of control valves (the straight travel valve 11, the left and right travel, boom, swing, arm, and bucket direction switching valves 13, 14, 23-26, the flow rate control valves 28, 29 of the boom and the arm) that control the supply of hydraulic oil from the hydraulic pumps P1 and P2 to each hydraulic actuator 4-9. When the controller 10 is provided for controlling the operation of the control valve, the pump capacity of the hydraulic pumps P 1, P 2, and the rotation speed of the main motor M, the controller 10 includes the reference pump flow rate setting unit 61 that sets the reference pump flow rate Ls as the pump flow rate of the hydraulic pumps P 1, P 2 when the pump capacity of the hydraulic pumps P 1, P 2 is maximum and the rotation speed of the main motor M is the preset reference rotation speed Ns; and the target pump flow rate setting unit 64 that sets, for each of the hydraulic pumps, the target pump flow rates Lt of each of the hydraulic pumps P 1 and P 2 sin accordance with the operation of an operation medium for each of the hydraulic actuators within a range, in which the pump flow rates of each of the hydraulic pumps P 1 and P 2 do not exceed the preset maximum pump flow rate Lm, and the pump flow control portion 65 that maximizes the pump capacity of each hydraulic pump P 1 or P 2 and makes the rotational speed of the main motor M greater than the reference rotational speed Ns when the target pump flow rate Lt of each hydraulic pump P 1 or P 2 set by the target pump flow rate setting unit 64 exceeds the reference pump flow rate Ls, whereby the pump flow rate of the hydraulic pump P 1 or P 2 becomes greater than the reference pump flow rate Ls.However, by controlling the setting unit 61 for the reference pump flow rate setting unit 64 for the target pump flow rate and the pump flow rate control unit 65 provided in the controller 10, the flow rate of the hydraulic pump P 1 or P 2, which is the hydraulic source of the hydraulic actuator operated by the manipulator, can be increased to be larger than the reference pump flow rate Ls when the pump capacity is maximum and the rotational speed of the main motor M is the reference rotational speed Ns, so that the need and frequency of merging the discharged oil of the hydraulic pumps P 1 and P 2 can be reliably reduced to ensure the flow rate supplied to the operated hydraulic actuator, thereby reducing the efficiency, operability, and complexity of the circuit caused by the merging. In addition, since the configuration increases the pump flow rate of the hydraulic pumps P 1 and P 2 to be larger than the reference pump flow rate Ls by increasing the rotational speed of the main motor M to be larger than the reference rotational speed Ns, it is not necessary to provide a hydraulic pump with a large capacity.In addition, in the present embodiment, the hydraulic pump P 1 and the hydraulic pump P 2 (the first and second hydraulic pumps) are provided as hydraulic pumps, and the boom cylinder 6 and the arm cylinder 8 (high flow rate hydraulic actuator) are provided as hydraulic actuators supplied with the hydraulic oil from both the hydraulic pumps P 1 and P 2 at the time of maximum flow supply. On the other hand, when the boom and arm manipulators are operated independently of each other, the controller 10 controls one of the hydraulic pumps P 1 and P 2 as the main pump to supply hydraulic oil only from the main pump until the flow rate to the boom cylinder 6 and the arm cylinder 8 reaches the set flow rate Ld set to exceed the reference pump flow rate Ls, and when the set flow rate Ld is exceeded, controls the amount of hydraulic oil to be supplied from the two hydraulic pumps P 1 and P 2; and the target pump flow rate setting unit 64 sets the target pump flow rate Lt of the main pump to exceed the reference pump flow rate Ls corresponding to the flow rate from the main pump to the boom cylinder 6 and the arm cylinder 8. That is, only when the flow rate supplied to the boom cylinder 6 and the arm cylinder 8 exceeds the set flow rate Ld set to exceed the reference pump flow rate Ls, the hydraulic oil from the two hydraulic pumps P 1 and P 2 is merged and supplied to the boom cylinder 6 and the arm cylinder 8, so that even a high-flow-rate hydraulic actuator is supplied with the hydraulic oil from both hydraulic pumps P 1 and P 2 at the time of the maximum flow rate, so that the frequency of merging can be reduced.In addition, in the present embodiment, the boom cylinder 6 uses the hydraulic pump P 1 as a main pump and the arm cylinder 8 uses the hydraulic pump P 2 as a main pump. However, when the boom manipulator and the arm manipulator are simultaneously operated, the controller 10 controls the boom cylinder 6 and the arm cylinder 8 to be supplied only with the hydraulic oil from the main pump, and the target pump flow rate setting unit 64 sets the target pump flow rate Lt of the hydraulic pumps P 1 and P 2 for the hydraulic pump according to the operation of the boom and arm manipulators. As a result, when the boom cylinder 6 and the arm cylinder 8 are simultaneously driven, merging of the discharged oil of the hydraulic pumps P 1 and P 2 can be prevented even if they are high-flow-rate hydraulic actuators in which both the hydraulic pumps P 1 and P 2 serve as a source of hydraulic oil at the time of maximum flow supply.In addition, the hydraulic excavator 1 includes a traveling body (the lower traveling body 71 and the upper swing body 72) including left and right traveling bodies and a working device (the front working machine 73) mounted on the traveling body, and includes the hydraulic pump P 1 and the hydraulic pump P 2 as hydraulic pumps and the left and right traveling motors 4 and 5 that respectively drive the left and right traveling bodies as hydraulic actuators. On the one hand, the hydraulic excavator includes the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9 as a plurality of operating hydraulic actuators that drive the working device. On the other hand, when the left and right travel manipulators, the boom, the arm, and the bucket manipulators are simultaneously operated, the controller 10 controls the forward travel valve 11 to supply the hydraulic oil from the hydraulic pump P 1 to the left and right travel motors 4 and 5 and to supply the hydraulic oil from the hydraulic pump P 2 to the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9, and the target pump flow rate setting unit 64 sets the target pump flow rate Lt of the hydraulic pump P 2 to be larger than the reference pump flow rate Ls. As a result, the left and right traveling motors 4, 5 and the hydraulic actuator (boom cylinder 6, arm cylinder 8, bucket cylinder 9) can be supplied with hydraulic oil independently of each other without causing hydraulic interference. By setting the target pump flow rate Lt of the hydraulic pump P 2 to a value larger than the reference pump flow rate Ls, the supply flow rate to the hydraulic actuator can be increased, which can contribute to improvement in the working efficiency.A second embodiment of the present invention will be described below with reference to FIG. 6. In the second embodiment, the parts common to the first embodiment are assigned the same reference numerals, and the description is omitted.In the second embodiment, three hydraulic pumps, P1, P2, and P3, are provided as hydraulic pumps driven by the main motor M. In addition, as in the first embodiment, the hydraulic pump P 1 is connected to the pump line C via the straight traveling valve 11 located at the first position and is connected to the left traveling direction switching valve 13. In addition, the hydraulic pump P 2 is connected to the pump line D and connected to the right travel direction switching valve 14 via the straight travel valve 11 located at the first position X. On the other hand, the hydraulic pump P 3 is connected to the main-side boom supply oil passage 17.From the pump line C connected to the hydraulic pump P 1, the lower-side arm supply oil passage 18 and the bucket oil supply passage 19 branch off in parallel with each other, and from the pump line D connected to the hydraulic pump P 2, the lower-side boom supply oil passage 20, the swing oil supply passage 21, and the main-side arm supply oil passage 22 branch off in parallel with each other. The lower-side arm supply oil passage 18 and the lower-side boom supply oil passage 20 are provided with the arm flow rate control valve 28 and the boom flow rate control valve 29, respectively, as in the first embodiment.The hydraulic oil from the hydraulic pump P 3 is supplied to the pump port 23 pof the boom direction switching valve 23 via the main-side boom supply oil passage 17 and the hydraulic oil from the hydraulic pump P 2 is supplied to the pump port 23 pof the boom direction switching valve 23 via the sub-side boom supply oil passage 20, and the hydraulic oil from the hydraulic pump P 2 is supplied to the boom direction switching valve 23 in a state (including a shut-off state) in which the flow rate is controlled by the boom flow control valve 29 located in the sub-side boom supply oil passage 20. Further, the hydraulic oil from the hydraulic pump P 2 is supplied to the pump port 25 pof the arm direction switching valve 25 via the main side arm supply oil passage 22 and the hydraulic oil from the hydraulic pump P 1 is supplied to the arm direction switching valve 25 via the lower side arm supply oil passage 18, and the hydraulic oil from the hydraulic pump P 1 is supplied to the arm direction switching valve 25 in a state (including a shut-off state) in which the flow rate is controlled by the arm flow rate control valve 28 provided in the lower side arm supply oil passage 18. Further, the hydraulic oil from the hydraulic pump P 1 is supplied to the pump port 26 pof the bucket direction switching valve 26 via the bucket oil supply passage 19, and the hydraulic oil from the hydraulic pump P 2 is supplied to the pump port 24 pvia the supply oil passage 21 of the swing direction switching valve 24. The boom, swing, arm, and bucket direction switching valves 23 to 26, and the boom and arm flow control valves 29 and 28 are the same as in the first embodiment.And in the second embodiment, as in the first embodiment, the control of the oil supply and discharge of each hydraulic actuator 4 to 9, the control of the capacity of the hydraulic pumps P 1, P 2, P 3, the control of the rotation speed of the main motor M, etc. are executed by the controller 10, but in the second embodiment, the hydraulic pump P 3 is only the hydraulic supply source of the boom cylinder 6, Then, when the boom manipulator, the arm manipulator, and the bucket manipulator are simultaneously operated, i.e., the so-called front triple complex operation, the controller 10 controls the closing of the boom and arm flow rate control valves 29 and 28, respectively. As a result, during the front triple complex operation, the boom cylinder 6 is supplied with hydraulic oil only from the hydraulic pump P 3, the arm cylinder 8 only of the hydraulic pump P 2 and the bucket cylinder 9 only of the hydraulic pump P 1, so that the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9 can be supplied with hydraulic oil in an independent cycle without any hydraulic interference therebetween. In this case, the pump delivery amounts of the hydraulic pumps P 3, P 2, and P 1 may be increased or decreased by the pump output control and the rotation speed control of the main motor M according to the operation amounts of the boom, arm, and bucket manipulators, so that the pump delivery amounts of each of the hydraulic pumps P 3, P 2, and P 1 may be a flow rate corresponding to the operation amounts of the manipulators of the boom cylinder 6, arm cylinder 8, and bucket cylinder 9.Note that the present invention is not limited to the first and second embodiments described above, and for example, in setting the target pump flow rate of each hydraulic pump, it may be configured to set an upper limit to the sum of the target pump flow rates of all hydraulic pumps. In this case, the upper limit of the sum of the target pump flow rates may be arbitrarily set in a range not exceeding the sum of the maximum pump flow rates of each hydraulic pump. In addition, in the above embodiment, an electric motor is used as the main motor, but the present invention can be implemented even when a motor is used as the main motor.In addition, this invention can be obviously implemented in various working machines having a plurality of hydraulic pumps driven by the main engine, without being limited to hydraulic excavators.Industrial applicabilityThis invention can be applied to the hydraulic control system of a working machine such as a hydraulic excavator.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2016-205451A

[0004]

Claims

A hydraulic control system of a working machine, characterized by comprising: a main motor; a plurality of variable capacity hydraulic pumps driven by the main motor; a plurality of hydraulic actuators driving at least one of the hydraulic pumps as a hydraulic source; operating means for each hydraulic actuator operated to drive each hydraulic actuator; and a plurality of control valves controlling supply of hydraulic oil from the hydraulic pump to each hydraulic actuator; and providing a control device for controlling operation of the control valve, pump capacity of the hydraulic pump, and a rotational speed of the main motor; wherein the control device comprises: reference pump flow rate setting means that sets a pump flow rate of the hydraulic pump when the pump capacity of the hydraulic pump is maximum and the rotational speed of the main motor is a preset reference rotational speed as the reference pump flow rate; target pump flow rate setting means that sets a target pump flow rate of each hydraulic pump for each hydraulic pump depending on the operation of the operation means for each hydraulic actuator within a range in which the pump flow rate of each hydraulic pump does not exceed a preset maximum pump flow rate; a pump flow rate control means that, when the target pump flow rate of one of the hydraulic pumps set by the target pump flow rate setting means exceeds the reference pump flow rate, maximizes the pump capacity of the one of the hydraulic pumps and increases the rotational speed of the main motor to be greater than the reference rotational speed, thereby increasing the pump flow rate of the one of the hydraulic pumps to be greater than the reference pump flow rate.The hydraulic control system in the work machine according to claim 1, characterized in that a first hydraulic pump and a second hydraulic pump are included as hydraulic pumps, and a high-flow-rate hydraulic actuator that supplies hydraulic oil from the first and second hydraulic pumps simultaneously at a maximum flow rate is included as a hydraulic actuator; the controller controls one of the first and second hydraulic pumps to a main pump and supplies hydraulic oil only from the main pump until a flow rate supplied to the high-flow-rate hydraulic actuator reaches a set flow rate set to exceed the reference pump flow rate when the operating medium for the high-flow-rate hydraulic actuator is operated alone and supplied with the hydraulic oil from both the first and second hydraulic pumps when the flow rate exceeds the set flow rate; and the target pump flow rate setting means sets the target pump flow rate of the main pump to exceed the reference pump flow rate depending on the supply flow rate of the main pump to the high flow rate hydraulic actuator.The hydraulic control system in the work machine according to claim 2, characterized in that a first high-flow-rate hydraulic actuator using the first hydraulic pump as a main pump and a second high-flow-rate hydraulic actuator using the second hydraulic pump as a main pump are included; when the operating media for the first and second high-flow-rate hydraulic actuators are simultaneously operated, the controller controls supply of the hydraulic oil from each main pump to the first and second high-flow-rate hydraulic actuators, respectively; and the target pump flow-rate setting means sets the target pump flow rate of the first and second hydraulic pumps for each hydraulic pump depending on the operation amount of the operating media for the first and second high-flow-rate hydraulic actuators.The hydraulic control system in the working machine according to claim 1, characterized in that the working machine includes a traveling body having a left traveling body and a right traveling body, a working device mounted on the traveling body, a first hydraulic pump and a second hydraulic pump as hydraulic pumps, a left traveling motor and a right traveling motor as hydraulic actuators that drive the left traveling body and the right traveling body, respectively, and a plurality of hydraulic working actuators that drive the working device; when the left and right traveling motors and the operating medium for the hydraulic working actuator are simultaneously operated, the controller controls a control valve to supply the hydraulic oil from the first hydraulic pump to the left and right traveling hydraulic motors and the hydraulic oil from the second hydraulic pump to the hydraulic working actuator; and the target pump flow rate setting means sets the target pump flow rate of the second hydraulic pump to be larger than the reference pump flow rate.

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