Hydraulic control systems for work machines

Abstract

To achieve excellent operability by improving a control method, in providing a hydraulic circuit of a work machine with a control circuit for an optional hydraulic actuator.SOLUTION: An optional converging oil passage 22 for joining discharge oils from first and second hydraulic pumps A, B is disposed, the optional converging oil passage 22 is provided with an optional control valve 60 and a compensator valve 61, a variable relief valve 65 is connected to a signal pressure introduction oil passage 62 connector to the compensator valve 61, and a supply pressure to the optional hydraulic actuator 13 can be variably controlled by changing a relief set pressure of the variable relief valve 65. On the other hand, calculation of a distribution flow to the other hydraulic actuators, opening area control of the optional control valve 60 and control valves 23-26 for the other hydraulic actuators, and discharge pressure control of the first and second hydraulic pumps A, B are optimized.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the technical field of hydraulic control systems for work machines such as hydraulic excavators. [Background technology]

[0002] Generally, some work machines, such as hydraulic excavators, are configured to be able to selectively mount a plurality of optional hydraulic actuators. For example, hydraulic excavators are configured to be able to detachably mount optional tools, such as hydraulically driven breakers and crushers, instead of a bucket, which is a commonly used work attachment. When a hydraulic circuit for an optional hydraulic actuator that drives such an optional tool is provided in the hydraulic circuit of a work machine, it is required that the circuit be shared by multiple optional hydraulic actuators in order to save space and reduce the number of parts, while also being able to accommodate control for each individual optional hydraulic actuator. For example, it is required that the circuit be able to control the supply pressure to the optional hydraulic actuator to a pressure that corresponds to the operating pressure of each optional hydraulic actuator, or, in the case of an optional hydraulic actuator that requires a constant flow rate, that the circuit be able to supply a constant flow rate whether the optional hydraulic actuator is operated independently or in conjunction with other hydraulic actuators, or that optional hydraulic actuators that require a small flow rate, such as small breakers or crushers, be supplied with pressurized oil from a single hydraulic pump, and that optional hydraulic actuators that require a large flow rate, such as large breakers or crushers, be supplied with pressurized oil from multiple hydraulic pumps. Therefore, in the past, in order to control the supply pressure to optional hydraulic actuators to a pressure corresponding to the operating pressure of each optional hydraulic actuator, a relief valve is provided in each of a pair of actuator oil lines leading from an option control valve that controls the oil supply and discharge to the optional hydraulic actuator to the optional hydraulic actuator, and the supply pressure to the optional hydraulic actuator is controlled by the set pressure of the relief valve, and a variable relief valve whose set pressure can be changed is used as the relief valve, so that the supply pressure to the optional hydraulic actuator can be changed as desired in accordance with each optional hydraulic actuator (see, for example, Patent Document 1). Meanwhile, a technology has also been proposed in which a hydraulic circuit for a work machine equipped with an optional hydraulic actuator is provided with two hydraulic pumps, a first and a second, as well as first and second flow control valves that control the flow rates supplied from the first and second hydraulic pumps, respectively, and an optional-use direction switching valve that joins the pressure oil supplied from these first and second flow control valves and supplies it to the optional hydraulic actuator (see, for example, Patent Document 2). With this technology, even for an optional hydraulic actuator that uses both the first and second hydraulic pumps as its hydraulic supply sources, it is possible to use only one direction switching valve for the optional hydraulic actuator, and by closing either the first or second flow control valve, it is also possible to use either the first or second hydraulic pump as the hydraulic supply source for the optional hydraulic actuator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-168738 [Patent Document 2] Japanese Patent Application Publication No. 2017-20604 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology of Patent Document 1, in order to control the supply pressure to the optional hydraulic actuators to a pressure corresponding to the operating pressure of each optional hydraulic actuator, a pair of variable relief valves must be arranged in each of a pair of actuator oil passages, which hinders reduction in the number of parts and cost. In addition, in the device of Patent Document 2, even if an optional hydraulic actuator receives hydraulic oil from both the first and second hydraulic pumps, only one directional control valve can be used for the optional hydraulic actuator, but to accommodate an optional hydraulic actuator that receives hydraulic oil from either the first or second hydraulic pump, two flow control valves, one for controlling the supply flow rates from the first and second hydraulic pumps, are required, which again hinders efforts to reduce the number of parts and costs.In addition, in the device of Patent Document 2, when an optional hydraulic actuator is linked to other hydraulic actuators, the discharge flow rate of the hydraulic pump that serves as the hydraulic supply source for these hydraulic actuators is distributed in accordance with the operation amount of the operating device for each hydraulic actuator, but this distribution can result in a shortage of supply flow rate when the optional hydraulic actuator requires a constant flow rate, and these are problems that the present invention aims to solve. [Means for solving the problem]

[0005] The present invention has been made in view of the above-mentioned circumstances and with the objective of solving these problems, and the invention of claim 1 relates to a hydraulic control system for a work machine comprising first and second hydraulic pumps, an optional hydraulic actuator that is selectively attached to the work machine and uses either or both of the first and second hydraulic pumps as a hydraulic supply source, and another hydraulic actuator other than the optional hydraulic actuator that uses either or both of the first and second hydraulic pumps as a hydraulic supply source, the hydraulic control system comprising first and second option supply oil passages that are connected to the first and second hydraulic pumps, respectively, and that serve as pressure oil supply passages to the optional hydraulic actuator and the other hydraulic actuator. a first and second supply oil passage for the other hydraulic actuators; an optional-use confluent oil passage where the first and second supply oil passages for the option are joined; control valves for the optional and other hydraulic actuators that respectively control the supply and discharge of oil to the optional hydraulic actuators and the other hydraulic actuators; and a control device that controls the control valves for the optional and other hydraulic actuators, while the optional-use confluent oil passage is provided with the optional-use control valve and a pressure compensation valve that is arranged upstream of the optional-use control valve and operates to introduce the inlet-side pressure and outlet-side pressure of the optional-use control valve and maintain the differential pressure between the introduced inlet-side pressure and outlet-side pressure at a predetermined pressure; a variable relief valve capable of varying a relief set pressure in response to a control signal from a control device is connected to a signal pressure introduction oil line that introduces the outlet side pressure of the option control valve to the pressure compensating valve, and the pressure in the signal pressure introduction oil line is reduced to the relief set pressure by the variable relief valve and introduced into the pressure compensating valve, thereby making it possible to variably control the pressure in the option joint oil line on the inlet side of the option control valve by changing the relief set pressure of the variable relief valve; The hydraulic control system is further configured to provide first and second bleed valves that control the bleed flow rates from the first and second hydraulic pumps to the oil tank based on control signals output from the control device, respectively, and to control the discharge pressures of the first and second hydraulic pumps by controlling the bleed flow rates using the first and second bleed valves, and the control device, when the optional hydraulic actuator uses only one of the first or second hydraulic pumps as a hydraulic supply source, makes the discharge pressure of the hydraulic pump that serves as the hydraulic supply source higher than the discharge pressure of the other hydraulic pump that is not a hydraulic supply source, and when the optional hydraulic actuator uses both the first and second hydraulic pumps as hydraulic supply sources, controls the bleed flow rates so that the discharge pressures of the first and second hydraulic pumps are equal.This is a hydraulic control system for a work machine, characterized in that The invention of claim 2 relates to a hydraulic control system for a work machine comprising first and second hydraulic pumps, an optional hydraulic actuator selectively attached to the work machine and using either or both of the first and second hydraulic pumps as a hydraulic supply source, and other hydraulic actuators other than the optional hydraulic actuator that use either or both of the first and second hydraulic pumps as a hydraulic supply source, the hydraulic control system comprising first and second option supply oil passages and first and second other hydraulic actuator supply oil passages that are connected to the first and second hydraulic pumps respectively and serve as pressure oil supply passages to the optional hydraulic actuator and the other hydraulic actuators; a control device for controlling the control valves for the option and other hydraulic actuators; and a control device for controlling the control valves for the option and other hydraulic actuators. The option-use confluent oil passage is provided with the first and second option-use supply oil passages joining together, option-use control valves and other hydraulic actuator control valves that respectively control the oil supply and discharge to the option hydraulic actuator and the other hydraulic actuators. The option-use confluent oil passage is provided with the option-use control valve and a pressure compensation valve that is arranged upstream of the option-use control valve and operates to introduce the inlet pressure and outlet pressure of the option-use control valve and maintain the differential pressure between the introduced inlet pressure and outlet pressure at a predetermined pressure. a variable relief valve capable of varying a relief set pressure in response to a control signal from a control device is connected to a signal pressure introduction oil line that introduces the outlet side pressure of the option control valve to the pressure compensating valve, and the pressure in the signal pressure introduction oil line is reduced to the relief set pressure by the variable relief valve and introduced into the pressure compensating valve, thereby making it possible to variably control the pressure in the option joint oil line on the inlet side of the option control valve by changing the relief set pressure of the variable relief valve; The control device calculates first and second required flow rates for the optional and other hydraulic actuators that the optional hydraulic actuators and the other hydraulic actuators request of the first and second hydraulic pumps, respectively, in accordance with the amount of operation of the operating tools for the optional and other hydraulic actuators, and first and second margin added required flow rates for the optional which are calculated by adding a margin flow rate for adjusting the differential pressure of the pressure compensation valve to the first and second required flow rates for the optional, and controls the discharge flow rates of the first and second hydraulic pumps based on these required flow rates, and in controlling the discharge flow rates, uses the first and second required flow rates for the other hydraulic actuators as the required flow rates when the other hydraulic actuators are operated, while uses the first and second margin added required flow rates for the optional. This is a hydraulic control system for a work machine characterized in that The invention of claim 3 relates to a hydraulic control system for a work machine comprising first and second hydraulic pumps, an optional hydraulic actuator selectively attached to the work machine and using either or both of the first and second hydraulic pumps as a hydraulic supply source, and other hydraulic actuators other than the optional hydraulic actuator that use either or both of the first and second hydraulic pumps as a hydraulic supply source, the hydraulic control system comprising first and second option supply oil passages and first and second other hydraulic actuator supply oil passages that are connected to the first and second hydraulic pumps respectively and serve as pressure oil supply passages to the optional hydraulic actuator and the other hydraulic actuators; a control device for controlling the control valves for the option and other hydraulic actuators; and a control device for controlling the control valves for the option and other hydraulic actuators. The option-use confluent oil passage is provided with the first and second option-use supply oil passages joining together, option-use control valves and other hydraulic actuator control valves that respectively control the oil supply and discharge to the option hydraulic actuator and the other hydraulic actuators. The option-use confluent oil passage is provided with the option-use control valve and a pressure compensation valve that is arranged upstream of the option-use control valve and operates to introduce the inlet pressure and outlet pressure of the option-use control valve and maintain the differential pressure between the introduced inlet pressure and outlet pressure at a predetermined pressure. a variable relief valve capable of varying a relief set pressure in response to a control signal from a control device is connected to a signal pressure introduction oil line that introduces the outlet side pressure of the option control valve to the pressure compensating valve, and the pressure in the signal pressure introduction oil line is reduced to the relief set pressure by the variable relief valve and introduced into the pressure compensating valve, thereby making it possible to variably control the pressure in the option joint oil line on the inlet side of the option control valve by changing the relief set pressure of the variable relief valve;The control device calculates first and second required flow rates for the option and other hydraulic actuators that the option hydraulic actuators and the other hydraulic actuators respectively request of the first and second hydraulic pumps in accordance with the operation amounts of the operating tools for the option and other hydraulic actuators, and first and second margin added required flow rates for option obtained by adding a margin flow rate for adjusting the differential pressure of the pressure compensating valve to the first and second required flow rates for option, and controls the opening areas of the control valves for the option and other hydraulic actuators based on these required flow rates, and in controlling the opening area, the control valve for the option controls the opening area so that a total flow rate obtained by adding up the first and second required flow rates for option is supplied to the option hydraulic actuator, while the control valve for the other hydraulic actuators calculates first and second distributed flow rates for the other hydraulic actuators by dividing the discharge flow rates of the first and second hydraulic pumps in accordance with the first and second margin added required flow rates for option and the first and second required flow rates for the other hydraulic actuators, and controls the opening area so that a total flow rate obtained by adding up the first and second distributed flow rates for the hydraulic actuators is supplied to the other hydraulic actuator. [Effects of the Invention]

[0006] By adopting the invention of claim 1, By changing the relief setting pressure of the variable relief valve arranged in the signal pressure introduction oil passage connected to the pressure compensation valve, the upper limit pressure of the pressure oil supplied to the optional hydraulic actuator can be variably controlled to correspond to the pressure of each optional hydraulic actuator, which reduces the number of parts and costs. Even if separate valves for opening and closing the first and second option supply oil passages are not provided in the oil passages, whether the option hydraulic actuator uses either the first or second hydraulic pump as the hydraulic supply source or both hydraulic pumps as the hydraulic supply source, only the supply pressure oil from the hydraulic pump used as the hydraulic supply source can be supplied to the option junction oil passage, thereby reducing the number of parts and costs. By adopting the invention of claim 2, when the optional hydraulic actuator is operated, the first and second margin added required flow rates, which are obtained by adding the margin flow rate for adjusting the differential pressure of the pressure compensation valve, can be secured as the pump flow rate for the optional hydraulic actuator. By adopting the invention of claim 3, the supply flow rate to the optional hydraulic actuator can be reliably secured, thereby reliably avoiding problems such as insufficient supply flow rate to the optional hydraulic actuator when linked with other hydraulic actuators, and ensuring good linked operability with other hydraulic actuators. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a side view of a hydraulic excavator. [Figure 2] FIG. 1 is a hydraulic circuit diagram of a hydraulic excavator. [Figure 3] FIG. 2 is an enlarged hydraulic circuit diagram of a portion relating to an optional hydraulic actuator. [Figure 4] FIG. 4 is a diagram showing the opening characteristics of a switching valve. [Figure 5] FIG. 2 is a block diagram showing the configuration of a controller. [Figure 6] FIG. 3 is a control block diagram of a first and second manipulated variable setting unit. [Figure 7] 10A, 10B, and 10C are diagrams showing the relationship between the operation amount of the operating tool and the required flow rate. [Figure 8] FIG. 3 is a control block diagram of a required flow rate setting unit and a pump control unit. [Figure 9] FIG. 4 is a control block diagram of a valve opening area control unit. [Figure 10] FIG. 4 is a control block diagram of a bleed control unit. [Figure 11] FIG. 4 is a control block diagram of first and second pump target pressure setting in a bleed control unit. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a hydraulic excavator 1, which is an example of a work machine equipped with the hydraulic control system of the present invention. The hydraulic excavator 1 is made up of various parts, such as a crawler-type lower traveling body 2, an upper rotating body 3 that is supported above the lower traveling body 2 so that it can swing freely, and a work implement 4 that is attached to the upper rotating body 3. The work implement 4 is further made up of a boom 5 that has its base end supported on the upper rotating body 3 so that it can swing freely up and down, a stick 6 that is supported at the tip of the boom 5 so that it can swing freely back and forth, and a bucket 7 that is attached to the tip of the stick 6 so that it can swing freely. The hydraulic excavator 1 is also equipped with various hydraulic actuators, such as a boom cylinder 8, a stick cylinder 9, and a bucket cylinder 10 that swing the boom 5, stick 6, and bucket 7, respectively, left and right travel motors (not shown) that travel the lower traveling body 2, and a swing motor (shown in FIG. 2) 11 that swings the upper rotating body 3. Furthermore, the hydraulic excavator 1 is capable of selectively mounting various hydraulically operated optional tools (optional attachments) such as a breaker, crusher, grapple, tilt bucket, rotary cutting attachment (none of which are shown) in place of the bucket 7, depending on the type of work being performed. When an optional tool is mounted, the bucket cylinder 10 operates as a hydraulic cylinder for swinging the optional tool relative to the stick 6.

[0009] Next, a hydraulic control system provided in the hydraulic excavator 1 will be described based on the hydraulic circuit diagram shown in Fig. 2. In Fig. 2, the hydraulic circuit related to the traveling motor is omitted. In Fig. 2, A and B are variable displacement first and second hydraulic pumps, Aa and Ba are displacement varying means for varying the displacements of the first and second hydraulic pumps A and B, and 12 is an oil tank. Also, 8, 9, 10, and 11 are the boom cylinder, stick cylinder, bucket cylinder, and swing motor, which are hydraulic actuators permanently installed in the hydraulic excavator 1. Furthermore, 13 is an optional hydraulic actuator. Optional hydraulic actuator 13 is a hydraulic actuator provided on an optional tool to drive an optional tool selectively attached to the hydraulic excavator 1. For example, if a breaker is attached as an optional tool, optional hydraulic actuator 13 is a breaker hydraulic actuator (hereinafter simply referred to as the breaker), and if a grapple is attached, optional hydraulic actuator 13 is a grapple hydraulic actuator. In this embodiment, boom cylinder 8 and stick cylinder 9 use both the first and second hydraulic pumps A and B as hydraulic supply sources, bucket cylinder 10 uses first hydraulic pump A as a hydraulic supply source, and swing motor 11 uses second hydraulic pump B as a hydraulic supply source. Furthermore, as will be described later, the optional hydraulic actuator 13 is configured to use either one or both of the first and second hydraulic pumps A and B as the hydraulic pressure supply source, depending on the flow rate required by the optional hydraulic actuator 13 and whether the optional hydraulic actuator 13 is operated independently or in conjunction with (simultaneous operation with) other hydraulic actuators. Furthermore, in this embodiment, the boom cylinder 8, stick cylinder 9, bucket cylinder 10, and swing motor 11 correspond to other hydraulic actuators other than the optional hydraulic actuator of the present invention.

[0010] 2, C is a first pump line connected to the discharge side of first hydraulic pump A, and first boom supply oil passage 14, first bucket supply oil passage 15, first stick supply oil passage 16, and first option supply oil passage 17 are connected to first pump line C in parallel with one another. Also, D is a second pump line connected to the discharge side of second hydraulic pump B, and second boom supply oil passage 18, second stick supply oil passage 19, second swing supply oil passage 20, and second option supply oil passage 21 are connected to second pump line D in parallel with one another. The first and second boom supply oil passages 14, 18 are oil passages that connect the first and second hydraulic pumps A, B, respectively, to a boom control valve 23, which will be described later, the first bucket supply oil passage 15 is an oil passage that connects the first hydraulic pump A to a bucket control valve 25, the first and second stick supply oil passages 16, 19 are oil passages that connect the first and second hydraulic pumps A, B, respectively, to a stick control valve 24, and the second swing supply oil passage 20 is an oil passage that connects the second hydraulic pump B to a swing control valve 26. In addition, the first and second option supply oil passages 17, 21 are oil passages that connect the first and second hydraulic pumps A, B, respectively, to an option joint oil passage 22, which will be described later. The first boom, first bucket, and first stick supply oil passages 14, 15, and 16 correspond to the first other hydraulic actuator supply oil passages of the present invention, and the second boom, second stick, and second swing supply oil passages 18, 19, and 20 correspond to the second other hydraulic actuator supply oil passages of the present invention. Also, the boom, stick, bucket, and swing control valves 23 to 26 correspond to the other hydraulic actuator control valves of the present invention.

[0011] A boom flow control valve 31 is disposed in the second boom supply oil passage 18, controlling the supply flow rate from the second hydraulic pump B to the boom control valve 23, and first and second stick flow control valves 32 and 33 are disposed in the first and second stick supply oil passages 16 and 19, controlling the supply flow rates from the first and second hydraulic pumps A and B to the stick control valve 24, respectively. These boom flow control valve 31 and first and second stick flow control valves 32 and 33 are poppet valves that control the flow rates by pilot operation using a boom flow control electromagnetic proportional valve 41 and first and second stick flow control electromagnetic proportional valves 42 and 43 (all shown in Figures 5 and 9), which operate based on control signals output from the controller 30, and have a backflow prevention function that allows oil to flow from the first and second hydraulic pumps A and B to the boom control valve 23 and stick control valve 24, but prevents backflow.

[0012] On the other hand, no flow control valves such as the boom flow control valve 31 or the first and second stick flow control valves 32 and 33 described above are disposed in the first boom supply oil passage 14, first bucket supply oil passage 15, second swing supply oil passage 20, and first and second option supply oil passages 17 and 21, and the pressure oil supplied from first hydraulic pump A or second hydraulic pump B via these first boom supply oil passage 14, first bucket supply oil passage 15, second swing supply oil passage 20, and first and second option supply oil passages 17 and 21 is supplied directly to the boom control valve 23, bucket control valve 25, swing control valve 26, and option joint oil passage 22 without being flow rate controlled. Furthermore, check valves 34 are provided in the first boom supply oil passage 14, the first bucket supply oil passage 15, the second swing supply oil passage 20, and the first and second option supply oil passages 17, 21, respectively, so that oil is permitted to flow from the first and second hydraulic pumps A, B to the boom control valve 23, the bucket control valve 25, the swing control valve 26, and the option joint oil passage 22, but reverse flow is prevented.

[0013] Thus, pressure oil from the first hydraulic pump A via the first boom supply oil passage 14 and pressure oil from the second hydraulic pump B via the second boom supply oil passage 18 can be supplied to the pump port 23p of the boom control valve 23, and the pressure oil from the second hydraulic pump B is supplied to the boom control valve 23 in a state where its flow rate is controlled (including a shut-off state) by a boom flow control valve 31 arranged in the second boom supply oil passage 18. Furthermore, pressure oil from the first hydraulic pump A via the first stick supply oil passage 16 and pressure oil from the second hydraulic pump B via the second stick supply oil passage 19 can be supplied to the pump port 24p of the stick control valve 24, and the pressure oil from these first and second hydraulic pumps A and B is supplied to the stick control valve 24 in a state where its flow rate is controlled (including a shut-off state) by first and second stick flow control valves 32 and 33 arranged in the first and second stick supply oil passages 16 and 19, respectively.

[0014] The control valves 23-26 for the boom, stick, bucket, and swing are closed center spool valves that control the supply and discharge flow rate for the boom cylinder 8, stick cylinder 9, bucket cylinder 10, and swing motor 11, and switch the supply and discharge direction. They are equipped with pairs of pilot ports 23a, 23b-26a, 26b that are respectively connected to electromagnetic proportional valves 44a, 44b-47a, 47b (shown in FIGS. 5 and 9) for the boom, stick, bucket, and swing that output pilot pressure based on a control signal from the controller 30, supply valve passages 23c-26c that supply pressure oil from first and / or second hydraulic pumps A, B to the boom cylinder 8, stick cylinder 9, bucket cylinder 10, and swing motor 11, and discharge valve passages 23d-26d that allow discharged oil from the boom cylinder 8, stick cylinder 9, bucket cylinder 10, and swing motor 11 to flow to a tank line T that leads to an oil tank 12. When pilot pressure is not input to both pilot ports 23a, 23b to 26a, 26b, the supply valve paths 23c to 26c and the discharge valve paths 23d to 26d are closed and the valves are positioned in a neutral position N where supply and discharge control is not performed for the corresponding hydraulic actuators (boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11). However, when pilot pressure is input to one or the other pilot port 23a, 23b to 26a, 26b, the valves are configured to switch to an operating position X or Y where the supply valve paths 23c to 26c and the discharge valve paths 23d to 26d are opened and supply and discharge control for the hydraulic actuators is performed. The opening areas of the supply valve passages 23c to 26c and the discharge valve passages 23d to 26d when they are located at the operating positions X or Y are controlled to increase or decrease in accordance with the movement stroke of the spool that accompanies an increase or decrease in pilot pressure output from the electromagnetic proportional valves 44a, 44b to 47a, 47b for the boom, stick, bucket, and swing to the pilot ports 23a, 23b to 26a, 26b of the control valves 23 to 26 for the boom, stick, bucket, and swing.

[0015] The supply flow rate and discharge flow rate to the bucket cylinder 10 and the swing motor 11 are controlled by the opening areas of the supply valve passages 25c, 26c and discharge valve passages 25d, 26d of the bucket and swing control valves 25, 26. Furthermore, with regard to the supply flow rate to boom cylinder 8, the supply flow rate from first hydraulic pump A via first boom supply oil passage 14, which is not provided with a flow control valve, is controlled by the opening area of ​​supply valve passage 23c of boom control valve 23, while the supply flow rate from second hydraulic pump B via second boom supply oil passage 18, which is provided with boom flow control valve 31, is "zero" when boom flow control valve 31 is closed, and is controlled by the opening area of ​​boom flow control valve 31 and the opening area of ​​supply valve passage 23c of boom control valve 23 when boom flow control valve 31 is open. On the other hand, the discharge flow rate from boom cylinder 8 is controlled by the opening area of ​​discharge valve passage 23d of boom control valve 23. Furthermore, with regard to the supply flow rate to the stick cylinder 9, the supply flow rate from the first hydraulic pump A via the first stick supply oil passage 16 in which the first stick flow control valve 32 is provided is "zero" when the first stick flow control valve 32 is closed, and is controlled by the opening area of ​​the first stick flow control valve 32 and the opening area of ​​the supply valve passage 24c of the stick control valve 24 when the first stick flow control valve 32 is open, while the supply flow rate from the second hydraulic pump B via the second stick supply oil passage 19 in which the second stick flow control valve 33 is provided is "zero" when the second stick flow control valve 33 is closed, and is controlled by the opening area of ​​the second stick flow control valve 33 and the opening area of ​​the supply valve passage 24c of the stick control valve 24 when the second stick flow control valve 33 is open. On the other hand, the discharge flow rate from the stick cylinder 9 is controlled by the opening area of ​​the discharge valve passage 24d of the stick control valve 24.

[0016] On the other hand, the optional equipment confluence oil passage 22 is an oil passage formed by the merging of the downstream side of the first optional equipment supply oil passage 17 connected to the first hydraulic pump A and the downstream side of the second optional equipment supply oil passage 21 connected to the second hydraulic pump B, and the optional equipment confluence oil passage 22 is provided with an optional equipment control valve 60 (described later) and a compensator valve (corresponding to the pressure compensation valve of the present invention) 61 located upstream of the optional equipment control valve 60.

[0017] The option control valve 60 is a closed center spool valve that controls the supply / discharge flow rate for the option hydraulic actuator 13 and switches the supply / discharge direction, and as shown in the enlarged hydraulic circuit diagram of FIG. 3, is equipped with first and second pilot ports 60a, 60b connected to first and second option solenoid proportional valves 48a, 48b (shown in FIGS. 5 and 9) respectively that output pilot pressure based on a control signal output from the controller 30, a pump port 60p connected to the option hydraulic junction oil passage 22, a tank port 60t connected to the tank line T, one actuator port 60c connected to one port 13a of the option hydraulic actuator 13, the other actuator port 60d connected to the other port 13b of the option hydraulic actuator 13, and a load pressure output port 60e connected to a second pilot port 61b of a compensator valve 61 (described later) via a signal pressure introduction oil passage 62. When pilot pressure is not input to the first and second pilot ports 60a, 60b, the option control valve 60 does not control the supply and discharge of the option hydraulic actuator 13, and is located in a neutral position N in which the load pressure output port 60e is connected to the tank port 60t. However, when pilot pressure is input to the first pilot port 60a, the option control valve 60 switches to a first operating position X, and a supply valve path 60f from the pump port 60p to one of the actuator ports 60c and a supply valve path 60f from the other actuator port 60d to the tank port 60t are connected to the first pilot port 60a. The second operating position Y is configured to open a discharge valve passage 60g leading to the tank port 60t and a load pressure valve passage 60h leading from the downstream side of the supply valve passage 60f to the load pressure output port 60e, and when pilot pressure is input to the second pilot port 60b, the second operating position Y is switched to open the supply valve passage 60f leading from the pump port 60p to the other actuator port 60d, the discharge valve passage 60g leading from one actuator port 60c to the tank port 60t, and the load pressure valve passage 60h leading from the downstream side of the supply valve passage 60f to the load pressure output port 60e.The opening areas of the supply valve passage 60f and the discharge valve passage 60g are controlled to increase or decrease according to the movement position of a spool that is moved by the pilot pressure output from the first and second option-operated solenoid proportional valves 48a and 48b, and the supply flow rate and discharge flow rate for the option hydraulic actuator 13 are controlled by the opening areas of the supply valve passage 60f and the discharge valve passage 60g, respectively. Furthermore, when the option-operated control valve 60 is in the first or second operating position X or Y, the outlet side pressure of the option-operated control valve 60 (the pressure downstream of the supply valve passage 60f, the load pressure of the option hydraulic actuator 13) is introduced into the signal pressure introducing oil passage 62 by opening the load pressure valve passage 60h.

[0018] Incidentally, there are various types of optional hydraulic actuators 13, such as those that supply pressure oil in one direction, such as a unidirectional motor or a single-acting cylinder (e.g., a breaker), those that supply pressure oil in both directions, such as a bidirectional motor or a double-acting cylinder (e.g., a crusher), those that require a large flow rate (e.g., a large breaker or crusher), and those that only require a small flow rate (e.g., a small breaker or crusher), and the optional control valve 60 is used commonly with these various optional hydraulic actuators 13. In other words, by switching the optional control valve 60 between the first operating position X and the second operating position Y, pressure oil can be supplied in both directions to the optional hydraulic actuator 13, and by using only one of the operating positions, either the first operating position X or the second operating position Y, pressure oil can be supplied in one direction. However, in this embodiment, the first operating position X is used when pressure oil is supplied in one direction.

[0019] On the other hand, the signal pressure introduction oil passage 62 is an oil passage that extends from the load pressure output port 60e of the option-operated control valve 60 to the second pilot port 61b of the compensator valve 61, and a first orifice 63 is provided in the signal pressure introduction oil passage 62. A signal pressure relief oil passage 66 branches off from the signal pressure introduction oil passage 62 that extends from the load pressure output port 60e of the option-operated control valve 60 to the first orifice 63, via a second orifice 64 and an adjustable relief valve 65, and leads to the tank line T. The adjustable relief valve 65 is an electromagnetic proportional relief valve that can change a set relief pressure LP based on a control signal from the controller 30, and when the set relief pressure LP of the adjustable relief valve 65 is lower than the load pressure of the option hydraulic actuator 13 that is introduced into the signal pressure introduction oil passage 62, the load signal pressure input to the second pilot port 61b of the compensator valve 61 drops to the set relief pressure LP.

[0020] The compensator valve 61 is equipped with a first pilot port 61a to which a first pilot pressure is input that presses the valve element of the compensator valve 61 to the closing side, a second pilot port 61b to which a second pilot pressure that presses the valve element to the opening side is input, and a spring 61c that presses the valve element to the opening side, and the opening area is controlled so that the differential pressure between the first pilot pressure and the second pilot pressure is maintained at a predetermined pressure K determined by the spring 61c. The first pilot port 61a of the compensator valve 61 is connected to the optional equipment joint oil passage 22 on the inlet side of the optional equipment control valve 60, and the pressure of the optional equipment joint oil passage 22 is input thereto. The second pilot port 61b is connected to the signal pressure introducing oil passage 62, and when the load pressure of the optional hydraulic actuator 13 is equal to or lower than the relief set pressure LP of the variable relief valve 65, the load pressure of the optional hydraulic actuator 13 is input, whereas when the load pressure of the optional hydraulic actuator 13 is higher than the relief set pressure LP, a load signal pressure reduced to the relief set pressure LP is input. Thus, when the load pressure of the optional hydraulic actuator 13 is equal to or lower than the relief set pressure LP, the pressure PO in the optional-use joined oil passage 22 is controlled by the action of the compensator valve 61 to be higher by a predetermined pressure K than the load pressure of the optional hydraulic actuator 13, whereas when the load pressure of the optional hydraulic actuator 13 is higher than the relief set pressure LP, the pressure PO in the optional-use joined oil passage 22 is controlled to be higher by the predetermined pressure K than the relief set pressure LP. This makes it possible to variably control the relief set pressure LP of the variable relief valve 65 based on a control signal from the controller 30, thereby controlling the pressure PO of the option confluence oil passage 22 on the inlet side of the option control valve 60 to be equal to or lower than the pressure (LP+K) that is higher than the relief set pressure LP by a predetermined pressure K (PO≦(LP+K)).

[0021] 2 and 3, reference numeral 67 denotes a first actuator oil passageway extending from one actuator port 60c of the option control valve 60 to one port 13a of the option hydraulic actuator 13, and 68 denotes a second actuator oil passageway extending from the other actuator port 60d of the option control valve 60 to the other port 13b of the option hydraulic actuator 13. First and second option relief oil passageways 71 and 72 branch off from these first and second actuator oil passageways 67 and 68 and lead to the tank line T via first and second option relief valves 69 and 70. The first and second option relief valves 69 and 70 operate to release high-pressure oil into the oil tank 12 when the first and second actuator oil passageways 67 and 68 become high pressure due to dynamic pressure fluctuations such as when surge pressure is generated due to an external force such as a collision, and the set relief pressures of the first and second option relief valves 69 and 70 are set to a value exceeding the highest driving pressure of the optional hydraulic actuators 13 selectively attached to the hydraulic excavator 1. It should be noted that inexpensive valves whose relief set pressure cannot be electrically changed are used for the first and second option relief valves 69, 70. Relief valves are also connected to the oil passages that connect the boom control valve 23, stick control valve 24, bucket control valve 25, and swing control valve 26 to the boom cylinder 8, stick cylinder 9, bucket cylinder 10, and swing motor 11, respectively, but are omitted from Figure 2.

[0022] 2 and 3, reference numeral 73 denotes a bypass oil passage branching off from the first or second actuator oil passage 67, 68 and leading to the oil tank 12, and a selector valve 74 is disposed in the bypass oil passage 73. As shown in FIG. 4, the selector valve 74 is a two-position selector valve that is turned ON / OFF by a voltage applied from the controller 30 and switches between a closed position N and an open position X. When the selector valve 74 is switched to the open position X, oil discharged from the optional hydraulic actuator 13 can flow directly to the oil tank 12 without passing through the discharge valve passage 60g of the option control valve 60. When an optional hydraulic actuator 13 that requires back pressure reduction, such as a breaker, is installed and pressure oil is supplied in one direction, the selector valve 74 can be opened (set to the open position X) to allow oil discharged from the optional hydraulic actuator 13 to flow from the bypass oil passage 73 to the oil tank 12, thereby reliably reducing the back pressure acting on the optional hydraulic actuator 13. As mentioned above, the switching valve 74 is an inexpensive device that switches ON / OFF, and is capable of performing back pressure reduction control at a lower cost than, for example, when a variable relief valve is used. Furthermore, the bypass oil passage 73 is formed by branching off from an actuator oil passage that serves as a return oil passage from the optional hydraulic actuator 13 when an optional hydraulic actuator 13 that has a unidirectional pressure oil supply direction and requires back pressure reduction is installed, and in this embodiment, the bypass oil passage 73 is formed by branching off from the second actuator oil passage 68, but when the first actuator oil passage 67 serves as a return oil passage from the optional hydraulic actuator 13, the bypass oil passage 73 is formed by branching off from the first actuator oil passage 67.

[0023] 2, E and F denote first and second bleed lines that branch off from upstream positions of all of the supply oil passages 14-21 connected to the first and second pump lines C and D and lead to the tank line T. First and second bleed valves 75 and 76 are provided in the first and second bleed lines E and F, respectively. These first and second bleed valves 75 and 76 are actuated by pilot pressures output from first and second bleed electromagnetic proportional valves 49a and 49b (shown in FIGS. 5 and 10) to increase or decrease their opening areas, thereby controlling the increase or decrease of the bleed flow rates that flow from the first and second hydraulic pumps A and B to the oil tank 12 via the first and second bleed lines E and F. The pressures in the first and second pump lines C and D (the discharge pressures of the first and second hydraulic pumps A and B) are controlled by controlling the bleed flow rates using the first and second bleed valves 75 and 76.

[0024] 2, reference numeral 77 denotes a valve block incorporating various valves for controlling the oil supply and discharge to the various hydraulic actuators (boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11, and optional hydraulic actuator 13). The valve block 77 is formed by integrally assembling a main valve block 77X incorporating various valves for controlling the permanently installed hydraulic actuators (boom, stick, bucket, and swing control valves 23-26, boom and first and second stick flow control valves 31-33, etc.) and first and second bleed valves 75, 76, etc., to an optional valve block 77Y incorporating various valves for controlling the optional hydraulic actuators (option control valve 60, compensator valve 61, variable relief valve 65, first and second option relief valves 69, 70, etc.). The bypass oil passage 73 and the switching valve 74 are provided outside the valve block 77.

[0025] On the other hand, as shown in the block diagram of FIG. 5, the controller 30 (corresponding to the control means of the present invention) has connected to it on its input side boom operation detection means 80, stick operation detection means 81, bucket operation detection means 82, swing operation detection means 83, option operation detection means 84, which detect the operation direction and operation amount of the boom operation tool, stick operation tool, bucket operation tool, swing operation tool and option operation tool, respectively, optional hydraulic actuator notification means 85 described later, pressure sensors (not shown) which detect the pump pressure of the first and second hydraulic pumps A and B, pressure sensors (none shown) which detect the load pressure of the boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11 and optional hydraulic actuator 13, etc., and on its output side capacity varying means Aa, Ba of the first and second hydraulic pumps A and B, boom flow control solenoid proportional valve 41 which outputs pilot pressure to the boom flow control valve 31, first and second stick flow control valves 32, 33 which output pilot pressure to the first and second stick flow control valves 32, 33, respectively. solenoid proportional valves 42 and 43 for controlling tick flow, solenoid proportional valves 44a, 44b to 47a, 47b for boom, stick, bucket and swing which output pilot pressure to control valves 23 to 26 for boom, stick, bucket and swing, first and second option solenoid proportional valves 48a, 48b which output pilot pressure to option control valve 60, first and second bleed solenoid proportional valves 49a, 49b which output pilot pressure to first and second bleed valves 75, 76, and variable relief valve 65 , switching valve 74, etc. are connected, and a first and second operation amount setting unit 90, a required flow rate setting unit 91, a pump control unit 92, a valve opening area control unit 93, a bleed control unit 94, an option control unit 95, etc., which will be described later, are configured to control the discharge flow rates of the first and second hydraulic pumps A and B, control the bleed flow rates of the first and second bleed lines E and F, and control the oil supply and discharge to and from the boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11, and option hydraulic actuator 13.The optional hydraulic actuator notifying means 85 is a means for notifying the controller 30 of various information such as the type and specifications of the optional hydraulic actuator 13 when the optional hydraulic actuator 13 is installed, or the value of an optional upper limit pressure PU, which will be described later. In this embodiment, a monitor device (not shown) disposed in the cab 3 a of the hydraulic excavator 1 is provided as the optional hydraulic actuator notifying means 85, and various information about the optional hydraulic actuator 13 can be notified to the controller 30 and various pieces of information can be changed by operating the monitor device. Also, although the optional hydraulic actuator notifying means 85 is provided external to the controller 30 in FIG. 5 , it is also possible to configure the controller 30 to have at least some of the information and functions stored in the optional hydraulic actuator notifying means 85.

[0026] Next, the control performed by the setting section and control section provided in the controller 30 will be described. When operation signals are input from the operation detection means 80-84 for the boom, stick, bucket, swing, and option, the first and second operation amount setting unit 90 sets, based on these operation signals, a first operation amount to be performed by the first hydraulic pump A and a second operation amount to be performed by the second hydraulic pump B for each operation tool operation amount. The first and second operation amounts are set based on pre-stored data according to the first and second hydraulic pumps A and B that serve as hydraulic supply sources for the operated hydraulic actuators (boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11, and optional hydraulic actuator 13), the operation tool operation amount, the hydraulic actuators to be operated in conjunction (simultaneously), and the type and specifications of the optional hydraulic actuator 13. For example, in this embodiment, since the bucket cylinder 10 uses only the first hydraulic pump A as a hydraulic supply source, when the bucket operation tool is operated, only the first bucket operation amount is set. Furthermore, since the swing motor 11 uses only the second hydraulic pump B as a hydraulic supply source, when the swing operation tool is operated, only the second swing operation amount is set. For the boom cylinder 8, first and second boom operation amounts are set when pressure oil is supplied from both the first and second hydraulic pumps A and B, but only the first boom operation amount is set when pressure oil is supplied only from the first hydraulic pump A. For the stick cylinder 9, first and second stick operation amounts are set when pressure oil is supplied from both the first and second hydraulic pumps A and B, but only the first stick operation amount is set when pressure oil is supplied only from the first hydraulic pump A, and only the second stick operation amount is set when pressure oil is supplied only from the second hydraulic pump B. For the optional hydraulic actuator 13, first and second option operation amounts are set when pressure oil is supplied from both the first and second hydraulic pumps A and B, but only the first option operation amount is set when pressure oil is supplied only from the first hydraulic pump A, and only the second option operation amount is set when pressure oil is supplied only from the second hydraulic pump B (see FIG. 6).The data for setting the first and second manipulated variables is stored as control parameters in the first and second manipulated variable setting unit 90, and can be changed using the monitor device or the like, for example, depending on the type of work to be performed by the hydraulic excavator 1 and the type and specifications of the optional hydraulic actuator 13.

[0027] Furthermore, a required flow rate setting unit 91 determines the required flow rates (first required flow rate for boom, second required flow rate for boom, first required flow rate for stick, second required flow rate for stick, first required flow rate for bucket, second required flow rate for swing, first required flow rate for option, and second required flow rate for option) that each hydraulic actuator (boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11, optional hydraulic actuator 13) requires of the first and second hydraulic pumps A and B, based on the first and second manipulated variable set by the first and second manipulated variable setting unit 90. Furthermore, the required flow rate setting unit 91 sets first and second margin added required flow rates for option by adding a margin flow rate α to the first and second required flow rates for option, respectively (see FIG. 8). Note that the margin flow rate α is a flow rate added to the first and second required flow rates for option to avoid a shortage of pressurized oil supplied to the optional hydraulic actuator 13 due to flow rate control performed by the compensator valve 61 for adjusting the differential pressure when pressurized oil is supplied from the first and second hydraulic pumps A and B to the optional hydraulic actuator 13. Furthermore, when the first and second option-use requested flow rates are "zero," the first and second option-use margin-added requested flow rates also become "zero." 7(A), (B), and (C) show examples of the relationship between the first and second option-use operating device operation amounts, the first and second option-use required flow rates, and the total option-use required flow rate (the sum of the first option-use required flow rate and the second option-use required flow rate). FIG. 7(A) shows a case in which, in the first and second operation amount setting unit 90, when the operation amount of the operating device is small, only the first option-use operating amount is set (pressurized oil is supplied only from the first hydraulic pump A), and when the operation amount of the operating device is large, the first and second option-use operating amounts are set (pressurized oil is supplied from both the first and second hydraulic pumps A and B). FIG. 7(B) shows a case in which the first and second option-use operating amounts are set to the same value (the same amount of pressurized oil is supplied from the first and second hydraulic pumps A and B). FIG. 7(C) shows a case in which only one of the first or second operation amounts is set (pressurized oil is supplied from only either the first hydraulic pump A or the second hydraulic pump B). The required flow rate setting unit 91 is provided with data such as a map showing the relationship between the first and second operation amounts and the required flow rate for each hydraulic actuator, and uses this data to determine the required flow rate according to the operation amount of the operating tool. Such data is incorporated into the required flow rate setting unit 91 as a control parameter, and it is possible to change the value of the required flow rate corresponding to the first and second operation amounts using the monitor device, etc., depending on, for example, the work content to be performed by the hydraulic excavator 1 and the type and specifications of the optional hydraulic actuator 13.

[0028] The pump control unit 92 also calculates target discharge flow rates for the first and second hydraulic pumps A and B based on the required flow rates set by the required flow rate setting unit 91. In this case, the first and second required boom flow rates, the first and second required stick flow rates, the first required bucket flow rate, and the second required swing flow rate set by the required flow rate setting unit 91 are used for the required flow rates for the boom cylinder 8, the stick cylinder 9, the bucket cylinder 10, and the swing motor 11, and the first and second margin added required flow rates for option, to which a margin flow rate α is added, are used for the required flow rate for the optional hydraulic actuator 13. The target discharge flow rate for the first hydraulic pump A is set to the sum of the first required flow rates and first margin added required flow rates for the first hydraulic pump A of each operated hydraulic actuator (first required boom flow rate + first required stick flow rate + first required bucket flow rate + first margin added required flow rate for option), and if the total flow rate exceeds the maximum discharge flow rate of the first hydraulic pump A, the maximum discharge flow rate is set to the target discharge flow rate. Similarly, the target discharge flow rate of the second hydraulic pump B is set to the sum of the second required flow rates and second margin added required flow rates for the second hydraulic pump B of each operated hydraulic actuator (second required flow rate for boom + second required flow rate for stick + second required flow rate for swing + second margin added required flow rate for option), and if the total flow rate exceeds the maximum discharge flow rate of the second hydraulic pump B, the maximum discharge flow rate is set to the target discharge flow rate. Then, the pump control unit 92 outputs control signals to the capacity varying means Aa and Ba of the first and second hydraulic pumps A and B so as to obtain the target discharge flow rates (see FIG. 8). Note that if the first operation amounts of the hydraulic actuators are all "zero" and if the second operation amounts are all "zero", the first and second hydraulic pumps A and B are each controlled to have a minimum flow rate.

[0029] Furthermore, the valve opening area control unit 93 calculates the opening areas of the supply valve passages 23c to 26c of the boom, stick, bucket and swing control valves 23 to 26, the boom flow control valve 31, the first and second stick flow control valves 32 and 33, and the supply valve passage 60f of the option control valve 60, based on the required flow rates for the first and second hydraulic pumps A and B of each hydraulic actuator calculated by the required flow rate setting unit 91. In this case, the control process for determining the opening area differs between the control valves (control valves for boom, stick, bucket, and swing) 23-26 and flow control valves (flow control valves for boom, first and second stick) 31-33 for the permanently installed hydraulic actuators (boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11) and the optional control valve 60, so first, the opening area control of the control valves 23-26 and flow control valves 31-33 for the permanently installed hydraulic actuators will be described. When calculating the opening areas of the control valves 23-26 and the flow control valves 31-33 for the permanent hydraulic actuators, the valve opening area control unit 93 first calculates the distributed flow rates for each permanent hydraulic actuator. The distributed flow rates are calculated separately for the first hydraulic pump A and the second hydraulic pump B. That is, for the distributed flow rates for the permanent hydraulic actuators supplied with pressure oil from the first hydraulic pump A, the target discharge flow rate of the first hydraulic pump A is distributed in the ratio of the first margin added required flow rate for option, the first required flow rate for boom, the first required flow rate for stick, and the first required flow rate for bucket to calculate the first distributed flow rate for boom, the first distributed flow rate for stick, and the first distributed flow rate for bucket. Furthermore, for the distributed flow rates for the permanent hydraulic actuators supplied with pressure oil from the second hydraulic pump B, the target discharge flow rate of the second hydraulic pump B is distributed in the ratio of the second margin added required flow rate for option, the second required flow rate for boom, the second required flow rate for stick, and the second required flow rate for swing to calculate the second distributed flow rate for boom, the second distributed flow rate for stick, and the second distributed flow rate for swing. If the first and second option margin addition required flow rates are "zero," a distributed flow rate calculation is performed to distribute the entire amount of the target discharge flow rate to the permanent hydraulic actuators. The valve opening area control unit 93 calculates the opening areas of the supply valve paths 23c-26c of the boom, stick, bucket, and swing control valves 23-26 and the boom, first, and second stick flow control valves 31-33 for supplying the first and second boom distributed flow rates, the first and second stick distributed flow rates, the bucket first distributed flow rate, and the swing second distributed flow rate from the first and second hydraulic pumps A and B to the boom cylinder 8, the stick cylinder 9, the bucket cylinder 10, and the swing motor 11, respectively, and outputs control signals to the boom, stick, bucket, and swing solenoid proportional valves 44a, 44b-47a, 47b, the boom flow rate control solenoid proportional valve 41, and the first and second stick flow rate control solenoid proportional valves 42, 43 so as to achieve the opening areas (see FIG. 9 ). In this way, when controlling the opening areas of the control valves 23-26 and the flow control valves 31-33 for the permanent hydraulic actuators, the discharge flow rates of the first and second hydraulic pumps A, B are divided between the first and second optional margin addition required flow rates and the required flow rate of the permanent hydraulic actuators. This means that even when the optional hydraulic actuator 13 is operated in conjunction with other hydraulic actuators (permanent hydraulic actuators) that share hydraulic pumps A and / or B, the first and second optional margin addition required flow rates are supplied to the optional hydraulic junction oil passage 22, ensuring a reliable supply flow rate to the optional hydraulic actuator 13. As an example of control, it is also possible to adjust the first and second optional margin addition required flow rates by multiplying the first and second optional margin addition required flow rates by a flow rate restriction coefficient dedicated to the conjunction operation, thereby controlling the supply flow rate to the optional hydraulic actuator 13 to be constant. On the other hand, when determining the opening area of ​​the option control valve 60, the valve opening area control unit 93 calculates the opening area of ​​the supply valve passage 60f of the option control valve 60 for supplying the total flow rate of the first and second option required flow rates set by the required flow rate setting unit 91 to the option hydraulic actuator 13, and outputs control signals to the first and second option solenoid proportional valves 48a, 48b so as to achieve this opening area (see FIG. 9). In this case, the differential pressure before and after the supply valve passage 60f of the option control valve 60 is kept constant (predetermined pressure K) by the compensator valve 61 described above, so the supply flow rate from the option control valve 60 to the option hydraulic actuator 13 is controlled with high precision so as to be the total flow rate of the first and second option required flow rates.

[0030] In addition, the bleed control unit 94 controls the bleed flow rate flowing from the first and second hydraulic pumps A, B to the oil tank 12 based on the first and second operation amounts calculated by the first and second operation amount setting unit 90, and controls the discharge pressure of the first and second hydraulic pumps A, B by controlling the bleed flow rate. In this case, the bleed control unit 94 first determines the first and second required pressures (first required boom pressure, second required boom pressure, first required stick pressure, second required stick pressure, first required bucket pressure, second required swing pressure, first required option pressure, second required option pressure) that the corresponding hydraulic actuators require of the first and second hydraulic pumps A and B based on the first and second boom operation amounts, the first and second stick operation amounts, the first bucket operation amount, the second swing operation amount, and the first and second option operation amounts. Note that the bleed control unit 94 has data for each hydraulic actuator, such as a map showing the relationship between the first and second operation amounts and the required pressures, and determines the required pressure corresponding to the operation amount of the control tool using this data. Such data is incorporated into the bleed control unit 94 as control parameters, and it is possible to change the value of the required pressure corresponding to the operation amount depending, for example, on the work content performed by the hydraulic excavator 1 and the type and specifications of the optional hydraulic actuator 13. Next, the bleed control unit 94 calculates the first and second pump required pressures based on the first and second required pressures. In this case, the maximum value of the required pressures (first boom required pressure, first stick required pressure, first bucket required pressure, and first option required pressure) that the hydraulic actuators require of the first hydraulic pump A is set as the first pump required pressure PR1, and the maximum value of the required pressures (second boom required pressure, second stick required pressure, second swing required pressure, and second option required pressure) that the hydraulic actuators require of the second hydraulic pump B is set as the second pump required pressure PR2. Then, target pressures (first and second pump target pressures) PT1 and PT2 of the first and second hydraulic pumps A and B are set based on the first and second pump required pressures PR1 and PR2 (see FIG. 10).

[0031] In setting the first and second pump target pressures PT1, PT2, the bleed control unit 94 first determines whether or not an option operation device is being operated, and if the option operation device is not being operated (if the first and second option operation amounts are both "zero"), it sets the first and second pump required pressures PR1, PR2 as the target pressures PT1, PT2 of the first and second hydraulic pumps A, B. On the other hand, if the option operation device is being operated (if at least one of the first and second option operation amounts is not "zero"), it performs option priority control, which will be described later.

[0032] When the option priority control is performed, the bleed control unit 94 first determines whether the hydraulic pump supplying pressure oil to the option hydraulic actuator 13 is the first hydraulic pump A only (only the first option operation amount is set), the second hydraulic pump B only (only the second option operation amount is set), or both the first and second hydraulic pumps A and B (first and second option operation amounts are set).The bleed control unit 94 then compares the first pump required pressure PR1 with the second pump required pressure PR2 in each of the cases where the determination result is the first hydraulic pump A only (hereinafter referred to as determination result (A)), the second hydraulic pump B only (hereinafter referred to as determination result (B)), or both the first and second hydraulic pumps A and B (hereinafter referred to as determination result (A+B)). And when in the determination result (A), the first pump required pressure PR1 is greater than the second pump required pressure PR2 (PR1 > PR2), these first and second pump required pressures PR1 and PR2 are respectively set as the target pressures PT1 and PT2 of the first and second hydraulic pumps A and B. On the other hand, when in the determination result (A), the first pump required pressure PR1 is less than or equal to the second pump required pressure PR2 (PR1 ≤ PR2), the pressure obtained by adding the margin pressure β to the second pump required pressure PR2 (PR2 + β) is set as the first pump target pressure PT1, and the second pump required pressure PR2 is set as the second pump target pressure PT2. Thereby, in the case of the determination result (A), that is, when the hydraulic pump for supplying pressure oil to the optional hydraulic actuator 13 is only the first hydraulic pump A, the target pressure PT1 of the first hydraulic pump A is set to be higher than the target pressure PT2 of the second hydraulic pump B. Incidentally, the margin pressure β is the pressure added to make the discharge pressure of the hydraulic pump for supplying pressure oil to the optional hydraulic actuator 13 surely higher than the discharge pressure of the hydraulic pump that does not supply pressure oil to the optional hydraulic actuator 13. Also, when in the determination result (B), the first pump required pressure PR1 is greater than or equal to the second pump required pressure PR2 (PR1 ≥ PR2), the first pump required pressure PR1 is set as the first pump target pressure PT1, and the pressure obtained by adding the margin pressure β to the first pump required pressure PR1 (PR1 + β) is set as the second pump target pressure PT2. On the other hand, when in the determination result (B), the first pump required pressure PR1 is less than the second pump required pressure PR2 (PR1 < PR2), these first and second pump required pressures PR1 and PR2 are set as the target pressures PT1 and PT2 of the first and second pumps. Thereby, in the case of the determination result (B), that is, when the hydraulic pump for supplying pressure oil to the optional hydraulic actuator 13 is only the second hydraulic pump B, the target pressure PT2 of the second hydraulic pump B is set to be higher than the target pressure PT1 of the first hydraulic pump A. Also, when in the determination result ( A+B ), the first pump required pressure PR1 is greater than the second pump required pressure PR2 (PR1 > PR2), the first pump required pressure PR1 is set as the first and second pump target pressures PT1 and PT2. On the other hand, when in the determination result ( A+B), if the first pump required pressure PR1 is equal to or less than the second pump required pressure PR2 (PR1≦PR2), the second pump required pressure PR2 is set as the first and second pump target pressures PT1 and PT2. A+B ), that is, when the hydraulic pumps supplying pressure oil to the optional hydraulic actuator 13 are both the first and second hydraulic pumps A and B, the target pressures PT1 and PT2 of these first and second hydraulic pumps A and B are set to be equal to the higher of the first and second pump required pressures PR1 and PR2 (see FIG. 11). In this way, when the hydraulic pump supplying pressure oil to the optional hydraulic actuator 13 is either the first or second hydraulic pump A, B (in the case of the judgment result (A) or (B)), the discharge pressure of the one hydraulic pump supplying pressure oil is controlled to be higher than the discharge pressure of the other hydraulic pump not supplying pressure oil, so that the pressure oil supplied from one hydraulic pump flows preferentially to the optional equipment merged oil passage 22, and the pressure oil supplied from the other hydraulic pump does not flow to the optional equipment merged oil passage 22. On the other hand, when the hydraulic pumps supplying pressure oil to the optional hydraulic actuator 13 are both the first and second hydraulic pumps A, B (in the case of the judgment result (A+B)), the discharge pressures of both hydraulic pumps A, B are controlled to be the same, so that the pressure oil supplied from both the first and second hydraulic pumps A, B is supplied to the optional equipment merged oil passage 22 and merges.

[0033] After setting the target pressures PT1, PT2 of the first and second hydraulic pumps A, B, the bleed control unit 94 calculates the opening areas of the first and second bleed valves 75, 76 to achieve the target pressures PT1, PT2, and outputs control signals to the first and second bleed electromagnetic proportional valves 49a, 49b to achieve the opening areas, thereby controlling the bleed flow rates that flow from the first and second hydraulic pumps A, B to the oil tank 12 (see FIG. 10). Note that when the first operation amounts of the hydraulic actuators are all "zero" and when the second operation amounts are all "zero", the bleed flow rates are controlled so that the discharge pressures of the first and second hydraulic pumps A, B become the minimum discharge pressures that are set in advance.

[0034] Furthermore, the option control section 95 performs control to set the set relief pressure LP of the variable relief valve 65 based on information input from the option hydraulic actuator notification means 85 . In this case, the option control unit 95 receives, from the option hydraulic actuator notification means 85, the value of an option upper limit pressure PU that is set in advance as the upper limit pressure of each option hydraulic actuator 13 in accordance with the type, specifications, etc. of the option hydraulic actuator 13. Then, it outputs a control signal to the variable relief valve 65 so as to set the relief setting pressure LP of the variable relief valve 65 to a pressure (LP = PU - K) obtained by subtracting the predetermined pressure K (a pressure determined by the spring 61c of the compensator valve 61) from the option upper limit pressure PU. As a result, the inlet side pressure PO of the option control valve 60 is controlled by the action of the compensator valve 61 described above to be equal to or lower than (LP + K) a pressure higher than the relief setting pressure LP of the variable relief valve 65 by the predetermined pressure K (PO ≦ (LP + K)), in other words, equal to or lower than the option upper limit pressure PU (PO ≦ PU). In this way, by setting the relief set pressure LP of the variable relief valve 65 to control the inlet side pressure of the option control valve 60 to be equal to or less than the option upper limit pressure PU, it is possible to make the supply pressure to the option hydraulic actuator 13 less than the option upper limit pressure PU set for each option hydraulic actuator 13, even without providing variable relief valves in the pair of first and second actuator oil passages 67, 68 leading from the option control valve 60 to the option hydraulic actuator 13.

[0035] Furthermore, the option control unit 95 determines whether the optional hydraulic actuator 13 is a hydraulic actuator that has a one-way pressure oil supply direction and that requires back pressure reduction, such as a breaker, based on information input from the option hydraulic actuator notification means 85. If it is determined to be an applicable hydraulic actuator, it outputs a control signal to position the switching valve 74 in the open position X. This allows return oil from the optional hydraulic actuator 13 to the oil tank 12 to flow directly to the oil tank 12 without passing through the option control valve 60, thereby ensuring that back pressure can be reduced.

[0036] Next, the control that is performed when the option operating tool is operated will be described using examples 1 to 7. In each example, the control that is the same as in other examples will be explained briefly or omitted. [Example 1] First, a case where the optional operation tool is operated independently and pressure oil is supplied to the optional hydraulic actuator 13 only from the first hydraulic pump A will be described as Example 1. In this case, when an operation signal is input from the option-related operation detection means 84, the controller 30 first sets a first option-related operation amount, which is the operation amount to be performed by the first hydraulic pump A. Furthermore, in accordance with the first option-related operation amount, the controller 30 calculates a first option-related required flow rate that the option hydraulic actuator 13 requests of the first hydraulic pump A, and a first option-related margin-added required flow rate, which is the first option-related required flow rate plus a margin flow rate α. The controller then controls the discharge flow rate of the first hydraulic pump A using the first option-related margin-added required flow rate as a target discharge flow rate. Furthermore, the controller 30 sets a first option-related required pressure that the option hydraulic actuator 13 requests of the first hydraulic pump A in accordance with the first option-related operation amount, sets the first option-related required pressure as a first pump required pressure PR1, and further sets the first pump required pressure PR1 to a target pressure PT1 of the first hydraulic pump A, and controls the opening area of ​​the first bleed valve 75 so as to achieve the target pressure PT1. Meanwhile, the discharge flow rate and discharge pressure of the second hydraulic pump B are controlled to be minimum. The pressure oil supplied from the first hydraulic pump A flows through the first pump line C and the first optional-option supply oil passage 17 to the optional-option junction oil passage 22, and is supplied to the optional hydraulic actuator 13 through a compensator valve 61 and optional-option control valve 60 disposed in the optional-option junction oil passage 22. Furthermore, the controller 30 controls the supply pressure to the optional-option control valve 60 to be equal to or lower than the optional-option upper limit pressure PU by setting the set pressure LP of the variable relief valve 65 to a pressure (LP=PU-K) obtained by subtracting a predetermined pressure K from the optional-option upper limit pressure PU, which is set based on the type, specifications, etc. of the optional hydraulic actuator 13.Furthermore, the opening area of ​​the supply valve passage 60f of the optional equipment control valve 60 is controlled to be an opening area corresponding to the first optional equipment required flow rate, and in this case, the differential pressure before and after the optional equipment control valve 60 is maintained at a predetermined pressure K by the compensator valve 61, so that highly accurate supply flow rate control can be performed. In addition, the supply flow rate from the first hydraulic pump A is the first optional equipment margin added required flow rate, which is the first optional equipment required flow rate plus a margin flow rate α, so that even if the flow rate is controlled by the compensator valve 61 to adjust the differential pressure, the supply flow rate to the optional equipment control valve 60 will not be insufficient. Furthermore, if the optional equipment hydraulic actuator 13 is a hydraulic actuator that requires back pressure reduction, a control signal is output to the switching valve 74 to switch to the open position X, so that return oil from the optional equipment hydraulic actuator 13 can flow to the oil tank 12 via the bypass oil passage 73 without passing through the optional equipment control valve 60. In this way, in Example 1, pressure oil is supplied to the optional hydraulic actuators 13 only from the first hydraulic pump A, but in this case, the supply pressure to the optional control valve 60 is controlled to be equal to or less than the optional upper limit pressure PU set for each optional hydraulic actuator 13, and the supply flow rate to the optional hydraulic actuators 13 can be controlled with high precision.

[0037] [Example 2] Next, a case where the option operating tool is operated independently and pressure oil is supplied to the option hydraulic actuator 13 from both the first and second hydraulic pumps A and B will be described as Example 2. In this case, when an operation signal is input from the option-specific operation detection means 84, the controller 30 first sets first and second option-specific operation variables. Furthermore, the controller 30 calculates first and second option-specific required flow rates and first and second option-specific margin-added required flow rates in accordance with the first and second option-specific operation variables. The controller 30 then controls the discharge flow rates of the first and second hydraulic pumps A and B using the first and second option-specific margin-added required flow rates as target discharge flow rates. Furthermore, the controller 30 sets first and second option-specific required pressures in accordance with the first and second option-specific operation variables, and sets the first and second option-specific required pressures as first and second pump required pressures PR1 and PR2, respectively. Furthermore, the controller 30 sets the higher of the first and second pump required pressures PR1 and PR2 as target pressures PT1 and PT2 (PT1 = PT2) for both the first and second hydraulic pumps A and B, and controls the opening areas of the first and second bleed valves 75 and 76 to achieve the target pressures PT1 and PT2. This controls the discharge pressures of the first and second hydraulic pumps A and B to be equal. The pressure oil supplied from the first and second hydraulic pumps A, B passes through first and second pump lines C, D and first and second optional-unit supply oil passages 17, 21, respectively, to join at an optional-unit joint oil passage 22. In this case, because the discharge pressures of the first and second hydraulic pumps A, B are equal, the pressure oil supply from either one of the hydraulic pumps A, B is not given priority at the time of joining, and the oil supplied from both hydraulic pumps A, B flows into the optional-unit joint oil passage 22 and is supplied to the optional-unit hydraulic actuator 13 via a compensator valve 61 and an optional-unit control valve 60 disposed in the optional-unit joint oil passage 22. The opening area of ​​the supply valve passage 60f of the optional-unit control valve 60 is controlled so as to be the opening area corresponding to the total flow rate of the first and second optional-unit required flow rates. In this case, as in the case of Example 1 described above, highly accurate supply flow rate control can be performed. Furthermore, the controller 30 sets the relief set pressure LP of the variable relief valve 65 and controls the switching of the switching valve 74 as necessary, but these are the same as in Example 1 and therefore will not be described here. In this way, in Example 2, pressure oil is supplied to the optional hydraulic actuator 13 from both the first and second hydraulic pumps A and B, but in this case as well, as in Example 1, the supply pressure to the optional control valve 60 is controlled to be equal to or less than the optional upper limit pressure PU set for each optional hydraulic actuator 13, and the supply flow rate to the optional hydraulic actuator 13 can be controlled with high precision. Moreover, in this case, the discharge pressures of the first and second hydraulic pumps A and B are controlled to be equal, so that the supply oil from both hydraulic pumps A and B can be joined in the optional-option joint oil passage 22 without priority being given to the supply of pressure oil from either one of the hydraulic pumps A or B.

[0038] [Example 3] Next, we will explain, as Example 3, a case in which the option operating tool is operated in conjunction with the stick operating tool and the swing operating tool, and pressure oil is supplied to the option hydraulic actuator 13 from a first hydraulic pump A, and pressure oil is supplied to the stick cylinder 9 and swing motor 11 from a second hydraulic pump B. In this case, when operation signals are input from the option-related, stick-related, and swing-related operation detection means 84, 81, and 83, the controller 30 first sets the first option-related, second stick-related, and second swing-related operation amounts. Furthermore, the controller 30 calculates the first option-related, second stick-related, and second swing-related required flow rates and the first option-related margin-added required flow rate according to the first option-related, second stick-related, and second swing-related operation amounts. The controller 30 then controls the discharge flow rate of the first hydraulic pump A using the first option-related margin-added required flow rate as the target discharge flow rate, and controls the discharge flow rate of the second hydraulic pump B using the sum of the second stick-related required flow rate and the second swing-related required flow rate as the target discharge flow rate (or, if the total flow rate exceeds the maximum discharge flow rate of the second hydraulic pump B, the maximum discharge flow rate as the target discharge flow rate). Furthermore, the controller 30 sets the first option-related, second stick-related, and second swing-related required pressures according to the first option-related, second stick-related, and second swing-related operation amounts. The first optional-use required pressure is set to the first pump required pressure PR1, and the higher of the second stick-use and second swing-use required pressures is set to the second pump required pressure PR2. Furthermore, the first pump required pressure PR1 and the second pump required pressure PR2 are compared, and target pressures PT1 and PT2 of the first and second hydraulic pumps A and B are set based on the comparison result. In this case, by control of the above-mentioned bleed control unit 94, the target pressure PT1 of the first hydraulic pump A that supplies pressure oil to the optional hydraulic actuator 13 is set to a higher pressure than the target pressure PT2 of the second hydraulic pump B that does not supply pressure oil to the optional hydraulic actuator 13, and the opening areas of the first and second bleed valves 75 and 76 are controlled to achieve the target pressures PT1 and PT2. The pressure oil supplied from the first hydraulic pump A flows through the first pump line C and the first option supply oil passage 17 to the option joint oil passage 22. In this case, however, the discharge pressure of the first hydraulic pump A is higher than the discharge pressure of the second hydraulic pump B, so the pressure oil supplied from the first hydraulic pump A flows preferentially to the option joint oil passage 22, and the pressure oil supplied from the second hydraulic pump B does not flow to the option joint oil passage 22.The supply pressure oil from the first hydraulic pump A that flows into the optional accessory joint oil passage 22 is supplied to the optional accessory hydraulic actuator 13 via the compensator valve 61 and optional accessory control valve 60, which are arranged in the optional accessory joint oil passage 22. In this case, the control of the opening area of ​​the supply valve passage 60f of the optional accessory control valve 60, the setting of the relief set pressure LP of the variable relief valve 65, and the switching control of the switching valve 74 that is performed as needed are the same as in Example 1, so explanations will be omitted. On the other hand, the supply pressure oil from the second hydraulic pump B flows from the second pump line D to the second stick supply oil passage 19, and is supplied to the stick cylinder 9 via the second stick flow control valve 33 and the stick control valve 24, and also flows from the second pump line D to the second swing supply oil passage 20, and is supplied to the swing motor 11 via the swing control valve 26. In this case, the second stick flow control valve 33 and the opening areas of the supply valve passages 24c, 26c of the stick and swing control valves 24, 26 are controlled by the above-mentioned valve opening area control unit 93 so as to provide opening areas corresponding to the second stick distributed flow rate and the second swing distributed flow rate obtained by distributing the discharge flow rate of the second hydraulic pump B at the ratio of the second stick required flow rate and the second swing required flow rate.In addition, in Example 3, since pressure oil is supplied to the stick cylinder 9 only from the second hydraulic pump B, the first stick flow control valve 32 arranged in the first stick supply oil passage 16 is controlled to close. As described above, in Example 3, the optional operation tool is operated in conjunction with the operation tools for the other hydraulic actuators (stick cylinder 9, swing motor 11), and pressure oil is supplied to the optional hydraulic actuator 13 from the first hydraulic pump A, and pressure oil is supplied to the other hydraulic actuators from the second hydraulic pump B. However, in this case as well, as in Examples 1 and 2, the supply pressure to the optional control valve 60 is controlled to be equal to or lower than the optional upper limit pressure PU set for each optional hydraulic actuator 13, and the supply flow rate to the optional hydraulic actuator 13 can be controlled with high precision. Moreover, in this case, the discharge pressure of the first hydraulic pump A that supplies pressure oil to the optional hydraulic actuator 13 is controlled to be higher than the discharge pressure of the second hydraulic pump B, so that only the supply pressure oil from the first hydraulic pump A can be reliably flowed into the optional hydraulic junction oil path 22. Meanwhile, the discharge flow rate of the second hydraulic pump B is distributed to the other hydraulic actuators, thereby ensuring good interlocking operability between the optional hydraulic actuator 13 and the other hydraulic actuators (stick cylinder 9, swing motor 11).

[0039] [Example 4] Next, as Example 4, we will explain a case where the option operating tool is operated in conjunction with the boom operating tool and the bucket operating tool, and pressure oil is supplied to the option hydraulic actuator 13 from the second hydraulic pump B, and pressure oil is supplied to the boom cylinder 8 and the bucket cylinder 10 from the first hydraulic pump A. In this case, when operation signals are input from the option-operated, boom-operated, and bucket-operated operation detection means 84, 80, and 82, the controller 30 first sets the option-operated second, boom-operated first, and bucket-operated first manipulated variables. Furthermore, the controller 30 calculates the option-operated second, boom-operated first, and bucket-operated first required flow rates and the option-operated second margin added required flow rate according to the option-operated second, boom-operated first, and bucket-operated first manipulated variables. The controller 30 then controls the discharge flow rate of the second hydraulic pump B using the option-operated second margin added required flow rate as a target discharge flow rate, and controls the discharge flow rate of the first hydraulic pump A using the sum of the boom-operated first required flow rate and the bucket-operated first required flow rate as a target discharge flow rate (or, if the total flow rate exceeds the maximum discharge flow rate of the first hydraulic pump A, the controller 30 sets the option-operated second, boom-operated first, and bucket-operated first required pressures according to the option-operated second, boom-operated first, and bucket-operated first manipulated variables. The controller 30 then sets the option-operated second required pressure as the second pump required pressure PR2, and the higher of the boom-operated first and bucket-operated first required pressures as the first pump required pressure PR1. Furthermore, the first pump required pressure PR1 and the second pump required pressure PR2 are compared, and target pressures PT1, PT2 of the first and second hydraulic pumps A, B are set based on the comparison result. In this case, the target pressure PT2 of the second hydraulic pump B that supplies pressure oil to the optional hydraulic actuator 13 is set to a higher pressure than the target pressure PT1 of the first hydraulic pump A that does not supply pressure oil to the optional hydraulic actuator 13 by control of the above-mentioned bleed control unit 94, and the opening areas of the first and second bleed valves 75, 76 are controlled so as to achieve the target pressures PT1, PT2. Then, the pressure oil supplied from the second hydraulic pump B flows via the second pump line D and the second optional-unit supply oil passage 21 to the optional-unit joint oil passage 22. In this case, since the discharge pressure of the second hydraulic pump B is higher than the discharge pressure of the first hydraulic pump A, the pressure oil supplied from the second hydraulic pump B flows preferentially to the optional-unit joint oil passage 22, and the pressure oil supplied from the first hydraulic pump A does not flow to the optional-unit joint oil passage 22.The supply pressure oil from second hydraulic pump B that has flowed into optional accessory joint oil passage 22 is supplied to optional accessory hydraulic actuator 13 via compensator valve 61 and optional accessory control valve 60, which are arranged in optional accessory joint oil passage 22. In this case, the control of the opening area of ​​supply valve passage 60f of optional accessory control valve 60, the setting of relief set pressure LP of variable relief valve 65, and the switching control of switching valve 74 that is performed as needed are the same as in example 1, and therefore description thereof will be omitted. Meanwhile, supply pressure oil from first hydraulic pump A flows from first pump line C to first boom supply oil passage 14 and is supplied to boom cylinder 8 via boom control valve 23, and also flows from first pump line C to first bucket supply oil passage 15 and is supplied to bucket cylinder 10 via bucket control valve 25. In this case, the opening areas of supply valve passages 23c, 25c of boom and bucket control valves 23, 25 are controlled to be opening areas corresponding to the first distributed boom flow rate and the first distributed bucket flow rate obtained by distributing the discharge flow rate of first hydraulic pump A at the ratio of the first required boom flow rate and the first required bucket flow rate. Note that in Example 4, because pressure oil is supplied to boom cylinder 8 only from first hydraulic pump A, boom flow control valve 31 disposed in second boom supply oil passage 18 is controlled to close. As described above, in Example 4, the optional-element operating tool is operated in conjunction with the operating tools for the other hydraulic actuators (boom cylinder 8, bucket cylinder 10), and pressure oil is supplied to the optional hydraulic actuator 13 from the second hydraulic pump B, and pressure oil is supplied to the other hydraulic actuators from the first hydraulic pump A. However, in this case, as in Examples 1 to 3, the supply pressure to the optional-element control valve 60 is controlled to be equal to or lower than the optional-element upper limit pressure PU set for each optional hydraulic actuator 13, and the supply flow rate to the optional hydraulic actuator 13 can be controlled with high precision. Moreover, in this case, the discharge pressure of the second hydraulic pump B that supplies pressure oil to the optional hydraulic actuator 13 is controlled to be higher than the discharge pressure of the first hydraulic pump A, so that only the supply pressure oil from the second hydraulic pump B can be reliably flowed into the optional-element joint oil passage 22. Meanwhile, the discharge flow rate of the first hydraulic pump A is distributed to the other hydraulic actuators, thereby ensuring good interlocking operability between the optional hydraulic actuator 13 and the other hydraulic actuators (boom cylinder 8, bucket cylinder 10).

[0040] [Example 5] Next, we will explain, as Example 5, a case in which the option operating tool is operated in conjunction with the boom operating tool, stick operating tool, and bucket operating tool, and pressure oil is supplied to the option hydraulic actuator 13 from the second hydraulic pump B, and pressure oil is supplied to the boom cylinder 8, stick cylinder 9, and bucket cylinder 10 from the first hydraulic pump A. In this case, when operation signals are input from the option, boom, stick, and bucket operation detection means 84, 80, 81, and 82, the controller 30 first sets the option-second, boom-first, stick-first, and bucket-first operation amounts. Furthermore, the controller 30 calculates the option-second, boom-first, stick-first, and bucket-first required flow rates and the option-second margin-added required flow rate according to the option-second, boom-first, stick-first, and bucket-first operation amounts. The controller 30 then controls the discharge flow rate of the second hydraulic pump B using the option-second margin-added required flow rate as a target discharge flow rate, and controls the discharge flow rate of the first hydraulic pump A using the sum of the first boom required flow rate, the first stick required flow rate, and the first bucket required flow rate as a target discharge flow rate (if the total flow rate exceeds the maximum discharge flow rate of the first hydraulic pump A, the controller 30 sets the maximum discharge flow rate as the target discharge flow rate). Furthermore, the controller 30 sets the option-second, boom-first, stick-first, and bucket-first required pressures according to the option-second, boom-first, stick-first, and bucket-first operation amounts. The second optional-unit required pressure is set to the second pump required pressure PR2, and the highest pressure among the first boom-unit, first stick-unit, and first bucket-unit required pressures is set to the first pump required pressure PR1. Furthermore, target pressures PT1 and PT2 of the first and second hydraulic pumps A and B are set in the same manner as in Example 4 above, and the opening areas of the first and second bleed valves 75 and 76 are controlled to achieve the target pressures PT1 and PT2, but in this case, the target pressure PT2 of the second hydraulic pump B that supplies pressure oil to the optional hydraulic actuator 13 is set to a higher pressure than the target pressure PT1 of the first hydraulic pump A that does not supply pressure oil to the optional hydraulic actuator 13. The supply pressure oil from the second hydraulic pump B flows through the second pump line D and the second optional-unit supply oil passage 21 to the optional-unit joint oil passage 22, but in this case, as in Example 4, the supply pressure oil from the second hydraulic pump B flows preferentially to the optional-unit joint oil passage 22, and the supply pressure oil from the first hydraulic pump A does not flow.The supply pressure oil from second hydraulic pump B that flows into optional accessory joint oil passage 22 is supplied to optional accessory hydraulic actuator 13 via compensator valve 61 and optional accessory control valve 60, but in this case, the control of the opening area of ​​supply valve passage 60f of optional accessory control valve 60, the setting of relief set pressure LP of variable relief valve 65, and the switching control of switching valve 74 that is performed as needed are the same as in Example 1, and therefore description thereof will be omitted. Meanwhile, the supply pressure oil from first hydraulic pump A flows from first pump line C to first boom supply oil passage 14 and is supplied to boom cylinder 8 via boom control valve 23, and also flows from first pump line C to first stick supply oil passage 16 and is supplied to stick cylinder 9 via first stick flow control valve 32 and stick control valve 24, and further flows from first pump line C to first bucket supply oil passage 15 and is supplied to bucket cylinder 10 via bucket control valve 25. In this case, the opening areas of supply valve passages 23c, 24c, 25c of boom, stick, and bucket control valves 23, 24, 25 and first stick flow control valve 32 are controlled by the above-mentioned valve opening area control unit 93 so as to be opening areas corresponding to the first distributed boom flow rate, first distributed stick flow rate, and first distributed bucket flow rate obtained by distributing the discharge flow rate of first hydraulic pump A in the ratio of the first required boom flow rate, first required stick flow rate, and first required bucket flow rate. Note that in example 5, because pressure oil is supplied to boom cylinder 8 and stick cylinder 9 only from first hydraulic pump A, boom flow control valve 31 disposed in second boom supply oil passage 18 and second stick flow control valve 33 disposed in second stick supply oil passage 19 are controlled to close. As described above, in Example 5, the optional accessory operating tool is operated in conjunction with the operating tools for the other hydraulic actuators (boom cylinder 8, stick cylinder 9, bucket cylinder 10), and pressure oil is supplied to the optional hydraulic actuator 13 from the second hydraulic pump B, and pressure oil is supplied to the other hydraulic actuators from the first hydraulic pump A. However, in this case as well, as in Examples 1 to 4, the supply pressure to the optional accessory control valve 60 is controlled to be equal to or lower than the optional accessory upper limit pressure PU set for each individual optional hydraulic actuator 13, and the supply flow rate to the optional hydraulic actuator 13 can be controlled with high precision. Moreover, as in Example 4, it is possible to ensure that only the supply pressure oil from the second hydraulic pump B flows into the optional accessory junction oil path 22, and good interlocking operability between the optional hydraulic actuator 13 and the other hydraulic actuators (boom cylinder 8, stick cylinder 9, bucket cylinder 10) can be ensured. Furthermore, as in Example 5, by configuring the optional hydraulic actuator 13 to be supplied with pressurized oil from either the first or second hydraulic pump (second hydraulic pump B in Example 5), and the boom cylinder 8, stick cylinder 9, and bucket cylinder 10 to be supplied with pressurized oil from the other hydraulic pump (first hydraulic pump A in Example 5), even if the optional hydraulic actuator 13 is a hydraulic actuator that requires almost the discharge flow rate of one hydraulic pump, it can be configured to be supplied with pressurized oil from only one hydraulic pump.

[0041] [Example 6] Next, we will explain Example 6, which shows a case where the option operating tool is operated in conjunction with the boom operating tool and the swing operating tool, and where pressurized oil is supplied to the option hydraulic actuator 13 and boom cylinder 8 from a first hydraulic pump A, and pressurized oil is supplied to the swing motor 11 from a second hydraulic pump B. In this case, when operation signals are input from the option-related, boom-related, and swing-related operation detection means 84, 80, and 83, the controller 30 first sets the first option-related, first boom-related, and second swing-related operation variables. Furthermore, the controller 30 calculates the first option-related, first boom-related, and second swing-related required flow rates and the first option-related margin added required flow rate according to the first option-related, first boom-related, and second swing-related operation variables. The controller 30 then controls the discharge flow rate of the first hydraulic pump A using the sum of the first option-related margin added required flow rate and the first boom-related required flow rate as the target discharge flow rate (if the total flow rate exceeds the maximum discharge flow rate of the first hydraulic pump A, the maximum discharge flow rate is set as the target discharge flow rate), and also controls the discharge flow rate of the second hydraulic pump B using the second swing-related required flow rate as the target discharge flow rate. Furthermore, the controller 30 sets the first option-related, first boom-related, and second swing-related required pressures according to the first option-related, first boom-related, and second swing-related operation variables. The higher of the first option-operated and first boom-operated required pressures is set as the first pump required pressure PR1, and the second swing required pressure is set as the second pump required pressure PR2. Furthermore, the first pump required pressure PR1 and the second pump required pressure PR2 are compared, and target pressures PT1 and PT2 of the first and second hydraulic pumps A and B are set based on the comparison result, but in this case, by control of the above-mentioned bleed control unit 94, the target pressure PT1 of the first hydraulic pump A that supplies pressure oil to the optional hydraulic actuator 13 is set to a higher pressure than the target pressure PT2 of the second hydraulic pump B that does not supply pressure oil to the optional hydraulic actuator 13, and the opening areas of the first and second bleed valves 75 and 76 are controlled to achieve the target pressures PT1 and PT2. The pressure oil supplied from the first hydraulic pump A flows from the first pump line C to the first boom supply oil passage 14, and is supplied to the boom cylinder 8 via the boom control valve 23, and also flows from the first pump line C to the option joint oil passage 22 via the first option supply oil passage 17. In this case, however, since the discharge pressure of the first hydraulic pump A is higher than the discharge pressure of the second hydraulic pump B, the pressure oil supplied from the first hydraulic pump A flows preferentially to the option joint oil passage 22, and the pressure oil supplied from the second hydraulic pump B does not flow to the option joint oil passage 22.The supply flow rate of the pressure oil from the first hydraulic pump A supplied from the first boom supply oil passage 14 to the boom control valve 23 to the boom cylinder 8 is controlled by the opening area of ​​the supply valve passage 23c of the boom control valve 23. In this case, the opening area of ​​the supply valve passage 23c of the boom control valve 23 is controlled by the control of the valve opening area control unit 93 described above so as to be an opening area corresponding to the first boom distributed flow rate obtained by distributing the discharge flow rate of the first hydraulic pump A in the ratio of the first option-use margin added requested flow rate to the first boom-use requested flow rate. As a result, the first option-use margin added requested flow rate, which is the first option-use requested flow rate plus the margin flow rate α, flows from the first hydraulic pump A to the optional-use joined oil passage 22. The supply pressure oil from the first hydraulic pump A flowing to the optional-use joined oil passage 22 is then supplied to the optional hydraulic actuator 13 via the compensator valve 61 and the optional-use control valve 60 arranged in the optional-use joined oil passage 22. In this case, the opening area of ​​the supply valve passage 60f of the option-operated control valve 60 is controlled to be an opening area corresponding to the first required flow rate for option-operated, but the control of the opening area, the setting of the relief set pressure LP of the variable relief valve 65, the operation of the compensator valve 61, and the switching control of the selector valve 74 performed as needed are the same as in Example 1, so explanations will be omitted. Meanwhile, supply pressure oil from the second hydraulic pump B flows from the second pump line D to the second swing supply oil passage 20 and is supplied to the swing motor 11 via the swing control valve 26. In this case, the opening area of ​​the supply valve passage 26c of the swing control valve 26 is controlled to be an opening area corresponding to the second required flow rate for swing, because the swing motor 11 is the only hydraulic actuator to which pressure oil is supplied from the second hydraulic pump B. In addition, in Example 6, pressure oil is supplied to the boom cylinder 8 only from the first hydraulic pump A, so the boom flow control valve 31 arranged in the second boom supply oil passage 18 is controlled to close. In this way, in Example 6, the optional accessory operating tool is operated in conjunction with operating tools for the two other hydraulic actuators (boom cylinder 8, swing motor 11), and pressure oil is supplied to the optional accessory hydraulic actuator 13 and one of the other hydraulic actuators from the first hydraulic pump A, while pressure oil is supplied to the other other hydraulic actuator from the second hydraulic pump B. However, even when the optional accessory hydraulic actuator 13 shares the first hydraulic pump A with the other hydraulic actuator in this way, the optional accessory first margin added required flow rate, which is the first optional accessory required flow rate plus the margin flow rate α, is supplied to the optional accessory junction oil passage 22. Therefore, even when the flow rate is controlled by the compensator valve 61 to adjust the differential pressure, the supply flow rate to the optional accessory control valve 60 does not become insufficient, and even in this case, as in Examples 1 to 5 above, the supply pressure to the optional accessory control valve 60 is controlled to be equal to or lower than the optional accessory upper limit pressure PU set for each individual optional accessory hydraulic actuator 13, and the supply flow rate to the optional accessory hydraulic actuator 13 can be controlled with high precision. Moreover, in this case, the discharge pressure of the first hydraulic pump A that supplies pressure oil to the optional hydraulic actuator 13 is controlled to be higher than the discharge pressure of the second hydraulic pump B, so that only the pressure oil supplied from the first hydraulic pump A can be reliably flowed into the optional-use junction oil passage 22. On the other hand, the discharge flow rate of the second hydraulic pump B is supplied to the other hydraulic actuator, thereby ensuring good interlocking operability between the optional hydraulic actuator 13 and the other hydraulic actuators (boom cylinder 8, swing motor 11).

[0042] [Example 7] Next, we will explain Example 7, which shows a case where the option operating tool is operated in conjunction with the boom operating tool and the stick operating tool, and where pressurized oil is supplied to the option hydraulic actuator 13 and stick cylinder 9 from the second hydraulic pump B, and pressurized oil is supplied to the boom cylinder 8 from the first hydraulic pump A. In this case, when operation signals are input from the option, stick, and boom operation detection means 84, 81, and 80, the controller 30 first sets the second option, second stick, and first boom operation amounts. Furthermore, the controller 30 calculates the second option, second stick, and first boom required flow rates and the second option margin added required flow rate according to the second option, second stick, and first boom operation amounts. The controller then controls the discharge flow rate of the second hydraulic pump B using the sum of the second option margin added required flow rate and the second stick required flow rate as the target discharge flow rate (if the total flow rate exceeds the maximum discharge flow rate of the second hydraulic pump B, the maximum discharge flow rate is set as the target discharge flow rate). The controller 30 also controls the discharge flow rate of the first hydraulic pump A using the first boom required flow rate as the target discharge flow rate. Furthermore, the controller 30 sets the second option, second stick, and first boom required pressures according to the second option, second stick, and first boom operation amounts. The higher of the second option and second stick required pressures is set as the second pump required pressure PR2, and the first boom required pressure is set as the first pump required pressure PR1. Furthermore, the first pump required pressure PR1 and the second pump required pressure PR2 are compared, and target pressures PT1, PT2 of the first and second hydraulic pumps A, B are set based on the comparison result. In this case, under the control of the bleed control unit 94 described above, the target pressure PT2 of the second hydraulic pump B that supplies pressure oil to the optional hydraulic actuator 13 is set to a higher pressure than the target pressure PT1 of the first hydraulic pump A that does not supply pressure oil to the optional hydraulic actuator 13, and the opening areas of the first and second bleed valves 75, 76 are controlled to achieve the target pressures PT1, PT2.The pressure oil supplied from the second hydraulic pump B flows from the second pump line D to the second stick supply oil passage 19, and is supplied to the stick cylinder 9 via the second stick flow control valve 33 and the stick control valve 24, and also flows from the second pump line D to the optional equipment joint oil passage 22 via the second optional equipment supply oil passage 21. In this case, however, since the discharge pressure of the second hydraulic pump B is higher than the discharge pressure of the first hydraulic pump A, the pressure oil supplied from the second hydraulic pump B flows preferentially to the optional equipment joint oil passage 22, and the pressure oil supplied from the first hydraulic pump A does not flow to the optional equipment joint oil passage 22. The flow rate of oil discharged from the second hydraulic pump B, which is supplied from the second stick supply oil passage 19 to the stick control valve 24 via the second stick flow control valve 33, to the stick cylinder 9 is controlled by the opening areas of the second stick flow control valve 33 and the supply valve passage 24c of the stick control valve 24. In this case, the opening areas of the second stick flow control valve 33 and the supply valve passage 24c of the stick control valve 24 are controlled by the control of the valve opening area control unit 93 described above so as to become the opening areas corresponding to the second stick distributed flow rate obtained by distributing the discharge flow rate of the second hydraulic pump B in the ratio of the second option margin added required flow rate and the second stick required flow rate. As a result, the second option margin added required flow rate, which is the second option required flow rate plus the margin flow rate α, flows from the second hydraulic pump B to the option confluent oil passage 22. Then, the supply pressure oil from the second hydraulic pump B that has flowed into the optional accessory joint oil passage 22 is supplied to the optional accessory hydraulic actuator 13 via the compensator valve 61 and the optional accessory control valve 60, which are arranged in the optional accessory joint oil passage 22. In this case, the opening area of ​​the supply valve passage 60f of the optional accessory control valve 60 is controlled to be an opening area corresponding to the second optional accessory required flow rate, but the control of the opening area, the setting of the relief set pressure LP of the variable relief valve 65, the operation of the compensator valve 61, and the switching control of the switching valve 74 that is performed as needed are the same as in Example 1, so explanations will be omitted.On the other hand, the pressure oil supplied from first hydraulic pump A flows from first pump line C to first boom supply oil passage 14 and is supplied to boom cylinder 8 via boom control valve 23. In this case, the opening area of ​​supply valve passage 23c of boom control valve 23 is controlled to be an opening area corresponding to the first required boom flow rate, because the only hydraulic actuator to which pressure oil is supplied from first hydraulic pump A is boom cylinder 8. In Example 7, since pressure oil is supplied to boom cylinder 8 only from first hydraulic pump A, boom flow control valve 31 arranged in second boom supply oil passage 18 is controlled to close, and since pressure oil is supplied to stick cylinder 9 only from second hydraulic pump B, first stick flow control valve 32 arranged in first stick supply oil passage 16 is controlled to close. In this way, in Example 7, the optional accessory operating tool is operated in conjunction with operating tools for the two other hydraulic actuators (stick cylinder 9, boom cylinder 8), and pressure oil is supplied to the optional accessory hydraulic actuator 13 and one of the other hydraulic actuators from the second hydraulic pump B, while pressure oil is supplied to the other other hydraulic actuator from the first hydraulic pump A. However, even when the optional accessory hydraulic actuator 13 shares the second hydraulic pump B with the other hydraulic actuator in this way, the optional accessory first margin added required flow rate, which is the first optional accessory required flow rate plus the margin flow rate α, is supplied to the optional accessory junction oil passage 22. Therefore, even when the flow rate is controlled by the compensator valve 61 to adjust the differential pressure, the supply flow rate to the optional accessory control valve 60 does not become insufficient. Furthermore, even in this case, as in Examples 1 to 6 above, the supply pressure to the optional accessory control valve 60 is controlled to be equal to or lower than the optional accessory upper limit pressure PU set for each individual optional accessory hydraulic actuator 13, and the supply flow rate to the optional accessory hydraulic actuator 13 can be controlled with high precision. Moreover, in this case, the discharge pressure of the second hydraulic pump B that supplies pressure oil to the optional hydraulic actuator 13 is controlled to be higher than the discharge pressure of the first hydraulic pump A, so that only the pressure oil supplied from the second hydraulic pump B can be reliably flowed into the optional-use junction oil passage 22. On the other hand, the discharge flow rate of the first hydraulic pump A is supplied to the other hydraulic actuator, thereby ensuring good interlocking operability between the optional hydraulic actuator 13 and the other hydraulic actuators (stick cylinder 9, boom cylinder 8).

[0043] In the embodiment configured as described above, the hydraulic control system of the hydraulic excavator 1 includes first and second hydraulic pumps A and B, an optional hydraulic actuator 13 that is selectively attached to the hydraulic excavator 1 and uses either or both of the first and second hydraulic pumps A and B as a hydraulic supply source, and a boom cylinder 8, a stick cylinder 9, a bucket cylinder 10, and a swing motor 11 (other hydraulic actuators) that use either or both of the first and second hydraulic pumps as a hydraulic supply source. First and second option supply oil passages 17, 21 are connected to the second hydraulic pumps A, B, respectively, and serve as pressure oil supply passages to the option hydraulic actuator 13; first and second boom supply oil passages 14, 18, first and second stick supply oil passages 16, 19, first bucket supply oil passage 15, and second swing supply oil passage 20 (supply oil passages for the first and second other hydraulic actuators) are connected to the first and second hydraulic pumps A, B, respectively, and serve as pressure oil supply passages to the boom cylinder 8, stick cylinder 9, bucket cylinder 10, and swing motor 11; and the first and second option supply oil passages The oil passages 17 and 21 join together in a joint oil passage 22 for optional equipment, an optional control valve 60 that controls the oil supply and discharge for the optional hydraulic actuator 13, and control valves 23 to 26 (control valves for other hydraulic actuators) for the boom, stick, bucket, and swing that respectively control the oil supply and discharge for the boom cylinder 8, stick cylinder 9, bucket cylinder 10, and swing motor 11. 26, and a controller 30 for controlling the optional equipment control valve 60 is provided in the optional equipment joint oil passage 22. In this configuration, the optional equipment control valve 60 and a compensator valve 61 are provided in the optional equipment joint oil passage 22. The compensator valve 61 is arranged upstream of the optional equipment control valve 60 and operates to introduce the inlet side pressure and the outlet side pressure of the optional equipment control valve 60 and maintain the differential pressure between the introduced inlet side pressure and the outlet side pressure at a predetermined pressure K. A signal pressure introducing oil passage 62 that introduces the outlet side pressure of the optional equipment control valve 60 to the compensator valve 61 is provided.A variable relief valve 65 is connected, which can vary the relief set pressure LP based on a control signal from the controller 30, and the pressure in the signal pressure introduction oil passage 62 is reduced to the relief set pressure LP by the variable relief valve 65 and introduced into the compensator valve 61, so that the pressure in the option-use junction oil passage 22 on the inlet side of the option-use control valve 60 can be variably controlled based on the control signal output from the controller 30 to the variable relief valve 65.

[0044] As a result, the upper limit pressure of the pressurized oil that is flow rate controlled by the option control valve 60 and supplied to the option hydraulic actuator 13 can be variably controlled to a pressure that corresponds to each option hydraulic actuator 13 by changing the relief setting pressure LP of the variable relief valve 65 connected to the signal pressure introducing oil line 62 with a control signal from the controller 30. Therefore, compared to a configuration in which variable relief valves are provided in each of the pair of first and second hydraulic actuator oil lines 67, 68 leading from the option control valve 60 to the option hydraulic actuator 13 to variably control the upper limit pressure of the pressurized oil supplied to the option hydraulic actuator 13, the number of variable relief valves can be reduced, contributing to cost reduction. Moreover, the compensator valve 61 maintains the differential pressure between the inlet pressure and outlet pressure of the option control valve 60 at a predetermined pressure K, so the flow rate supplied to the option hydraulic actuator 13 can be controlled with high precision.

[0045] Furthermore, the hydraulic control system is provided with first and second bleed valves 75, 76 which respectively control the bleed flow rates flowing from the first and second hydraulic pumps A, B to the oil tank 12 based on control signals output from the controller 30, and is configured to control the discharge pressures of the first and second hydraulic pumps A, B by controlling the bleed flow rates using the first and second bleed valves 75, 76. In this case, when the optional hydraulic actuator 13 uses only one of the first and second hydraulic pumps A, B as its hydraulic supply source, the controller 30 makes the discharge pressure of the hydraulic pump that serves as the hydraulic supply source higher than the discharge pressure of the other hydraulic pump that is not a hydraulic supply source, and when the optional hydraulic actuator 13 uses both the first and second hydraulic pumps A, B as its hydraulic supply sources, the controller 30 controls the bleed flow rates so that the discharge pressures of the first and second hydraulic pumps A, B are equal. As a result, when the optional hydraulic actuator 13 uses only one of the first and second hydraulic pumps A, B as the hydraulic supply source, the supply pressure oil from that one hydraulic pump that is the hydraulic supply source can be preferentially made to flow to the optional device junction oil passage 22, and the supply pressure oil from the other hydraulic pump that is not the hydraulic supply source does not flow to the optional device junction oil passage 22. Furthermore, when the optional hydraulic actuator 13 uses both the first and second hydraulic pumps A, B as hydraulic supply sources, the supply pressure oil from both hydraulic pumps A, B can be made to merge in the optional device junction oil passage 22. Therefore, even if valves for opening and closing the first and second optional device supply oil passages 17, 21 are not provided in the first and second optional device supply oil passages 17, 21, respectively, only the supply pressure oil from the hydraulic pump that is the hydraulic supply source can be supplied to the optional device junction oil passage 22, whether either one of the first and second hydraulic pumps A, B is used as the hydraulic supply source or both hydraulic pumps are used as hydraulic supply sources, which allows for a reduction in the number of parts and contributes to cost reduction.

[0046] Furthermore, the controller 30 also controls the discharge flow rates of the first and second hydraulic pumps A and B. In this case, the controller 30 calculates the first and second required option flow rates, the first and second required boom flow rates, the first and second required stick flow rates, the first required bucket flow rate, and the second required swing flow rate that are required by each hydraulic actuator from the first and second hydraulic pumps A and B, respectively, in accordance with the operation amounts of the control tools for the option, boom, stick, bucket, and swing, as well as first and second margin added required option flow rates obtained by adding a margin flow rate for adjusting the differential pressure of the compensator valve 61 to the first and second required option flow rates, and controls the discharge flow rates of the first and second hydraulic pumps A and B based on these required flow rates. When the boom cylinder 8, stick cylinder 9, bucket cylinder 10, or swing motor 11 is operated, the controller 30 uses the first and second required boom flow rates, the first and second required stick flow rates, the first required bucket flow rate, and the second required swing flow rate as the required flow rates, while when the option hydraulic actuator 13 is operated, the controller 30 uses the first and second margin added required option flow rates as the required flow rates. As a result, the discharge flow rates of the first and second hydraulic pumps A and B can be controlled in accordance with the amount of operation of the operating tool, and when the optional hydraulic actuator 13 is operated, the first and second margin added required flow rates, which are the first and second required flow rates required by the optional hydraulic actuator 13 plus a margin flow rate α for differential pressure adjustment, can be secured as the pump flow rate for the optional hydraulic actuator 13.

[0047] Furthermore, the controller 30 controls the opening areas of the option control valve 60 and the boom, stick, bucket and swing control valves 23 to 26 based on the first and second option required flow rates, the first and second boom required flow rates, the first and second stick required flow rates, the first bucket required flow rate, the second swing required flow rate, and the first and second option margin added required flow rates obtained by adding a margin flow rate α to the first and second option required flow rates. In this case, the option control valve 60 controls the opening area so that the total flow rate obtained by adding the first and second option required flow rates to the option hydraulic actuator 13. Meanwhile, for the boom, stick, bucket and swing control valves 23 to 26, the first and second distributed flow rates for the boom, the first and second distributed flow rates for the stick, the first distributed flow rate for the bucket and the second distributed flow rate for the swing are determined by distributing the discharge flow rates of the first and second hydraulic pumps A and B according to the first and second margin added required flow rates for the option, the first and second required flow rates for the boom, the first and second required flow rates for the stick, the first required flow rate for the bucket and the second required flow rate for the swing, and the opening area is controlled so that the total flow rate obtained by adding up the first and second distributed flow rates for each hydraulic actuator is supplied to the boom cylinder 8, stick cylinder 9, bucket cylinder 10 and swing motor 11. As a result, even when the optional hydraulic actuator 13 is operated in conjunction with other hydraulic actuators (boom cylinder 8, stick cylinder 9, bucket cylinder 10, swing motor 11) that share hydraulic pump A and / or B, the first and second optional margin added required flow rate is supplied to the optional confluent oil passage 22, so the supply flow rate to the optional hydraulic actuator 13 can be reliably secured. Thus, for example, if the optional hydraulic actuator 13 is a hydraulic actuator that requires a constant flow rate, problems such as insufficient supply flow rate to the optional hydraulic actuator 13 when it is operated in conjunction with the other hydraulic actuators can be reliably avoided, and good interlocking operability with the other hydraulic actuators can be secured. [Industrial Applicability]

[0048] The present invention can be used in a hydraulic control system for a work machine such as a hydraulic excavator when an optional hydraulic actuator is installed on the work machine. [Explanation of symbols]

[0049] 8 Boom cylinder 9 Stick Cylinder 10 Bucket cylinder 11 Swing motor 12 Oil Tank 13 Optional Hydraulic Actuators 14 First boom oil supply line 15. First bucket oil supply line 16 First stick supply oil passage 17 First option oil supply line 18 Second boom oil supply line 19 Second stick supply oil passage 20 Second turning oil supply line 21 Second option oil supply line 22 Optional confluence oil passage 23 Boom control valve 24 Stick control valve 25 Bucket control valve 26 Swing control valve 30 Controllers 60 Optional control valve 61 Compensator valve 62 Signal pressure introduction oil passage 65 Variable Relief Valve 75 First bleed valve 76 Second bleed valve 91 Requested flow rate setting section 92 Pump control section 93 Valve opening area control unit 94 Bleed control section A First hydraulic pump B Second hydraulic pump

Claims

1. A hydraulic control system for a work machine comprising first and second hydraulic pumps, an optional hydraulic actuator selectively attached to the work machine and using either or both of the first and second hydraulic pumps as a hydraulic pressure supply source, and another hydraulic actuator other than the optional hydraulic actuator that uses either or both of the first and second hydraulic pumps as a hydraulic pressure supply source, The hydraulic control system is provided with first and second option supply oil passages and first and second other hydraulic actuator supply oil passages, which are connected to the first and second hydraulic pumps respectively and serve as pressure oil supply passages to the option hydraulic actuator and other hydraulic actuators, an option junction oil passage where the first and second option supply oil passages join, option and other hydraulic actuator control valves that respectively control oil supply and discharge to the option hydraulic actuator and other hydraulic actuator, and a control device that controls these option and other hydraulic actuator control valves, The optional equipment control valve and a pressure compensation valve, which is disposed upstream of the optional equipment control valve and operates to introduce the inlet pressure and outlet pressure of the optional equipment control valve and maintain the differential pressure between the introduced inlet pressure and outlet pressure at a predetermined pressure, are provided in the optional equipment joint oil line, and a variable relief valve, which can vary the relief set pressure according to a control signal from a control device, is connected to a signal pressure introduction oil line that introduces the outlet pressure of the optional equipment control valve to the pressure compensation valve, and the pressure in the signal pressure introduction oil line is reduced to the relief set pressure by the variable relief valve and introduced into the pressure compensation valve, thereby making it possible to variably control the pressure in the optional equipment joint oil line on the inlet side of the optional equipment control valve by changing the relief set pressure of the variable relief valve, The hydraulic control system is further configured to provide first and second bleed valves that control the bleed flow rates from the first and second hydraulic pumps to the oil tank based on control signals output from the control device, and to control the discharge pressures of the first and second hydraulic pumps by controlling the bleed flow rates using the first and second bleed valves, and the control device, when the optional hydraulic actuator uses only one of the first or second hydraulic pumps as a hydraulic supply source, makes the discharge pressure of the hydraulic pump that serves as the hydraulic supply source higher than the discharge pressure of the other hydraulic pump that is not a hydraulic supply source, and when the optional hydraulic actuator uses both the first and second hydraulic pumps as hydraulic supply sources, controls the bleed flow rates so that the discharge pressures of the first and second hydraulic pumps are equal.

2. A hydraulic control system for a work machine comprising first and second hydraulic pumps, an optional hydraulic actuator selectively attached to the work machine and using either or both of the first and second hydraulic pumps as a hydraulic pressure supply source, and another hydraulic actuator other than the optional hydraulic actuator that uses either or both of the first and second hydraulic pumps as a hydraulic pressure supply source, The hydraulic control system is provided with first and second option supply oil passages and first and second other hydraulic actuator supply oil passages, which are connected to the first and second hydraulic pumps respectively and serve as pressure oil supply passages to the option hydraulic actuator and other hydraulic actuators, an option junction oil passage where the first and second option supply oil passages join, option and other hydraulic actuator control valves that respectively control oil supply and discharge to the option hydraulic actuator and other hydraulic actuator, and a control device that controls these option and other hydraulic actuator control valves, The optional equipment control valve and a pressure compensation valve, which is disposed upstream of the optional equipment control valve and operates to introduce the inlet pressure and outlet pressure of the optional equipment control valve and maintain the differential pressure between the introduced inlet pressure and outlet pressure at a predetermined pressure, are provided in the optional equipment joint oil line, and a variable relief valve, which can vary the relief set pressure according to a control signal from a control device, is connected to a signal pressure introduction oil line that introduces the outlet pressure of the optional equipment control valve to the pressure compensation valve, and the pressure in the signal pressure introduction oil line is reduced to the relief set pressure by the variable relief valve and introduced into the pressure compensation valve, thereby making it possible to variably control the pressure in the optional equipment joint oil line on the inlet side of the optional equipment control valve by changing the relief set pressure of the variable relief valve, The control device calculates first and second required flow rates for the optional and other hydraulic actuators that the optional hydraulic actuators and the other hydraulic actuators request of the first and second hydraulic pumps, respectively, in accordance with the amount of operation of the operating tools for the optional and other hydraulic actuators, and first and second margin added required flow rates for the optional hydraulic actuators, which are calculated by adding a margin flow rate for adjusting the differential pressure of the pressure compensation valve to the first and second required flow rates for the optional hydraulic actuators, and controls the discharge flow rates of the first and second hydraulic pumps based on these required flow rates, and in controlling the discharge flow rates, uses the first and second required flow rates for the other hydraulic actuators as the required flow rates when the other hydraulic actuators are operated, and uses the first and second margin added required flow rates for the optional hydraulic actuators as the required flow rate when the optional hydraulic actuators are operated.

3. A hydraulic control system for a work machine comprising first and second hydraulic pumps, an optional hydraulic actuator selectively attached to the work machine and using either or both of the first and second hydraulic pumps as a hydraulic pressure supply source, and another hydraulic actuator other than the optional hydraulic actuator that uses either or both of the first and second hydraulic pumps as a hydraulic pressure supply source, The hydraulic control system is provided with first and second option supply oil passages and first and second other hydraulic actuator supply oil passages, which are connected to the first and second hydraulic pumps respectively and serve as pressure oil supply passages to the option hydraulic actuator and other hydraulic actuators, an option junction oil passage where the first and second option supply oil passages join, option and other hydraulic actuator control valves that respectively control oil supply and discharge to the option hydraulic actuator and other hydraulic actuator, and a control device that controls these option and other hydraulic actuator control valves, The optional equipment control valve and a pressure compensation valve, which is disposed upstream of the optional equipment control valve and operates to introduce the inlet pressure and outlet pressure of the optional equipment control valve and maintain the differential pressure between the introduced inlet pressure and outlet pressure at a predetermined pressure, are provided in the optional equipment joint oil line, and a variable relief valve, which can vary the relief set pressure according to a control signal from a control device, is connected to a signal pressure introduction oil line that introduces the outlet pressure of the optional equipment control valve to the pressure compensation valve, and the pressure in the signal pressure introduction oil line is reduced to the relief set pressure by the variable relief valve and introduced into the pressure compensation valve, thereby making it possible to variably control the pressure in the optional equipment joint oil line on the inlet side of the optional equipment control valve by changing the relief set pressure of the variable relief valve, a control device that calculates first and second required flow rates for the option and other hydraulic actuators that the option hydraulic actuators and the other hydraulic actuators respectively request of the first and second hydraulic pumps in accordance with the operation amounts of the operating tools for the option and other hydraulic actuators, and first and second margin added required flow rates for option obtained by adding a margin flow rate for adjusting the differential pressure of the pressure compensating valve to the first and second required flow rates for option, and controls the opening areas of the control valves for the option and other hydraulic actuators based on these required flow rates, and in controlling the opening area, controls the opening area of ​​the option control valve so that a total flow rate obtained by adding up the first and second required flow rates for option, and calculates first and second distributed flow rates for the other hydraulic actuators by dividing the discharge flow rates of the first and second hydraulic pumps in accordance with the first and second margin added required flow rates for option and the first and second required flow rates for the other hydraulic actuators, and controls the opening area of ​​the other hydraulic actuator control valve so that a total flow rate obtained by adding up the first and second distributed flow rates for the hydraulic actuators is supplied to the other hydraulic actuator.

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