Construction Machinery

Abstract

To provide a construction machine which can improve responsiveness of another actuator in the state where single-rod type hydraulic cylinders are driven by closed circuit pumps and opened circuit pumps.SOLUTION: A controller 57 performs control of stopping discharge of hydraulic oil of closed circuit pumps 12, 14, 16 and 18, and opened circuit pumps 13, 15, 17 and 19, and controls closed circuit switching valves 43a to 43d, 45a to 45d, 47a to 47d, and 49a to 49d so that connection destinations of the closed circuit pumps 12, 14, 16 and 18 are switched to the other actuator from first single-rod type hydraulic cylinders 1, 3 and 5, at such a timing after signals corresponding to the state where the discharge of the hydraulic oil of the closed circuit pumps 12, 14, 16 and 18 is stopped have been acquired from sensors 12b, 13b, ... and 19b, and before signals corresponding to the state where the discharge of the hydraulic oil of the opened circuit pumps 13, 15, 17 and 19 is stopped are acquired from the sensors 12b, 13b, ... and 19b.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a construction machine such as a hydraulic excavator. [Background technology]

[0002] 2. Description of the Related Art In recent years, in construction machinery such as hydraulic excavators, a hydraulic circuit known as a closed circuit has become known in which hydraulic oil is sent directly from a hydraulic pump, which is a pressure generating source, to a single-rod hydraulic cylinder, which is a hydraulic actuator, and after driving the single-rod hydraulic cylinder to perform a specified task, the hydraulic oil is returned directly to the single-rod hydraulic cylinder, connected in a closed circuit.

[0003] A conventional technique combining this type of closed circuit is disclosed in Patent Document 1. Patent Document 1 discloses a closed circuit hydraulic oil inflow / outflow control section having two inflow / outflow ports that allow hydraulic oil to flow in and out in both directions, and a single-rod hydraulic cylinder having a first hydraulic oil chamber and a second hydraulic oil chamber, in which the two inflow / outflow ports of the closed circuit hydraulic oil inflow / outflow control section are connected in a closed circuit to the first hydraulic oil chamber and the second hydraulic oil chamber, and also discloses an open circuit hydraulic oil inflow / outflow control section having an inflow port for inflowing hydraulic oil from a hydraulic oil tank and an outflow port for outflowing hydraulic oil, and a closed circuit hydraulic oil inflow / outflow control section connected to the open circuit hydraulic oil inflow / outflow control section and configured to supply hydraulic oil flowing out of the open circuit hydraulic oil inflow / outflow control section to a plurality of closed circuits. The drive device for a working machine is described, which is composed of an open circuit having an open circuit and an open circuit switching unit which switches the open circuit hydraulic oil inflow / outflow control unit to one of the closed circuits, and the open circuit switching unit is provided in a plurality of units corresponding to the plurality of closed circuits, and the drive device for a working machine is further provided with a controller which controls each of the plurality of hydraulic oil inflow / outflow control units for the closed circuit, the plurality of hydraulic oil inflow / outflow control units for the open circuit, and the plurality of open circuit switching units, and the controller controls each of the plurality of open circuit switching units so that one of the plurality of open circuits is connected to each of the plurality of closed circuits. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6134614 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional technology disclosed in the above-mentioned Patent Document 1, the response characteristics of the closed circuit pump and the open circuit pump are assumed to be the same, and a method of determining the supply flow rate based on the pressure-receiving area ratio of a single-rod hydraulic cylinder is described. However, when a general swash plate type or bent axis type variable volume axial piston is used for the pump, the closed circuit pump, which can switch the discharge direction in two directions, has a higher response from the maximum tilt to the minimum tilt direction of the swash plate mechanism or the bent axis mechanism. This is because the open circuit pump has a one-way driving force generating mechanism that tilts the swash plate mechanism or the bent axis mechanism from the minimum tilt position to the maximum tilt position, and often uses a spring to return to the minimum tilt, whereas the closed circuit pump has a driving force generating mechanism for changing the tilt in both directions. Thus, although the response of the closed circuit pump from the maximum tilt to the minimum tilt is higher than that of the open circuit pump, the conventional technology has not been able to utilize the high response of the closed circuit pump in operability.

[0006] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a construction machine that is capable of improving the responsiveness of other actuators when a single-rod hydraulic cylinder is driven by a closed circuit pump and an open circuit pump. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a closed circuit pump having two inlet / outlet ports through which hydraulic oil can flow in and out, an open circuit pump having an inlet port and an outlet port for hydraulic oil, a sensor for detecting a signal that changes according to the discharge flow rates of the closed circuit pump and the open circuit pump, a plurality of actuators including a first single-rod hydraulic cylinder and another actuator, each connected to the closed circuit pump and the open circuit pump so that hydraulic oil can be supplied from the closed circuit pump and the open circuit pump, a closed circuit switching valve that switches between conduction and interruption of a flow path of hydraulic oil between the closed circuit pump and the plurality of actuators so that the closed circuit pump is selectively connected in a closed circuit to any one of the plurality of actuators, and an actuator between the open circuit pump and the plurality of actuators so that the hydraulic oil discharged from the open circuit pump is selectively supplied to any one of the plurality of actuators. In a construction machine equipped with an open circuit switching valve that switches between conducting and blocking an oil flow path, and a controller that controls the closed circuit pump, the open circuit pump, the closed circuit switching valve, and the open circuit switching valve, when controlling the connection of the closed circuit pump to be switched to the other actuator from a state in which the closed circuit pump is connected to the first single-rod hydraulic cylinder and the open circuit pump is supplying hydraulic oil to the first single-rod hydraulic cylinder, the controller controls the closed circuit pump and the open circuit pump to stop discharging hydraulic oil, and controls the closed circuit switching valve so that the connection of the closed circuit pump is switched from the first single-rod hydraulic cylinder to the other actuator at a timing after a signal corresponding to a state in which the discharge of hydraulic oil from the closed circuit pump has been stopped is obtained from the sensor and before a signal corresponding to a state in which the discharge of hydraulic oil from the open circuit pump has been stopped is obtained from the sensor.

[0008] According to the present invention configured as described above, when the connection destination of the closed circuit pump is changed to another actuator while the first single-rod hydraulic cylinder is being driven by the closed circuit pump and the open circuit pump, the timing at which the closed circuit pump is connected to the other actuator can be advanced by stopping the discharge of hydraulic oil from the closed circuit pump earlier than the stop of the discharge of the open circuit pump. This allows the timing at which the other actuator starts to be driven to be earlier than when the discharge of the closed circuit pump is stopped in synchronization with the open circuit pump, thereby improving the responsiveness of the other actuator to an operation input. Effect of the Invention

[0009] According to the construction machine of the present invention, it is possible to improve the responsiveness of other actuators when a single-rod hydraulic cylinder is being driven by a closed circuit pump and an open circuit pump. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a hydraulic excavator according to an embodiment of the present invention. [Diagram 2] 1 is a hydraulic circuit diagram of a hydraulic drive system mounted on a hydraulic excavator according to an embodiment of the present invention. FIG. [Diagram 3] FIG. 2 is a functional block diagram of a controller according to the embodiment of the present invention. [Figure 4] 4 is a time chart showing the behavior of a hydraulic drive system to which the present invention is applied. [Diagram 5] 4 is a time chart showing an enlarged view of a portion of the behavior of the hydraulic drive system to which the present invention is applied (at the start of a combined operation of boom raising, swinging, and arm dumping). [Figure 6] 5 is a time chart showing the behavior of a hydraulic drive system to which the present invention is not applied. [Figure 7] 5 is a flowchart showing a process for switching a connection destination of a closed circuit pump by a controller according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a hydraulic excavator will be described as an example of a construction machine according to an embodiment of the present invention with reference to the drawings. In each drawing, the same reference numerals are used to designate the same members, and duplicated descriptions will be omitted as appropriate.

[0012] Fig. 1 is a schematic diagram showing a hydraulic excavator according to this embodiment. Fig. 2 is a hydraulic circuit diagram of a hydraulic drive system mounted on the hydraulic excavator 100.

[0013] As shown in Fig. 1, the hydraulic excavator 100 includes a lower traveling body 102 having crawler-type traveling devices 101a, 101b on both the left and right sides, and an upper rotating body 103 as a main body that is rotatably attached on the lower traveling body 102. A cab 104 for an operator to ride on is provided on the upper rotating body 103. The lower traveling body 102 and the upper rotating body 103 are rotatably attached via a rotating device 105. The traveling devices 101a, 101b are driven by traveling motors 8a, 8b, and the rotating device 105 is driven by a rotating motor 7.

[0014] A base end of a front working implement 106, which is a working device for performing excavation work, for example, is rotatably attached to the front side of the upper rotating body 103. Here, the front side refers to the direction in which an operator sitting in the cab 104 faces (leftward in FIG. 1). The front working implement 106 is equipped with a boom 2, the base end of which is connected to the front side of the upper rotating body 103 so as to be able to move up and down. The boom 2 operates via a boom cylinder 1, which is a single-rod hydraulic cylinder driven by hydraulic oil (pressurized oil) as a supplied fluid. The tip end of a rod 1c of the boom cylinder 1 is connected to the upper rotating body 103, and the base end of a cylinder tube 1d is connected to the boom 2.

[0015] 2, the boom cylinder 1 is provided with a cap chamber 1a, which is a first hydraulic oil chamber on the cap side, located at the base end side of the cylinder tube 1d and which is supplied with hydraulic oil to press a piston 1e attached to the base end of the rod 1c and apply a load due to hydraulic pressure to move the rod 1c in an extended direction. The boom cylinder 1 is also provided with a rod chamber 1b, which is a second hydraulic oil chamber on the rod side, located at the tip end side of the cylinder tube 1d and which is supplied with hydraulic oil to press the piston 1e and apply a load due to hydraulic pressure to move the rod 1c in a retracted direction.

[0016] Returning to FIG. 1, the base end of an arm 4 is connected to the tip of the boom 2 so as to be capable of ascending and descending motion. The arm 4 operates via an arm cylinder 3, which is a single-rod hydraulic cylinder. The tip of the rod 3c of the arm cylinder 3 is connected to the arm 4, and a cylinder tube 3d of the arm cylinder 3 is connected to the boom 2.

[0017] 2, the arm cylinder 3 includes a cap chamber 3a located at the base end side of the cylinder tube 3d, which is supplied with hydraulic oil to press a piston 3e attached to the base end of the rod 3c, thereby extending the rod 3c. The arm cylinder 3 also includes a rod chamber 3b located at the tip end side of the cylinder tube 3d, which is supplied with hydraulic oil to press the piston 3e, thereby retracting the rod 3c.

[0018] Returning to Fig. 1, a base end of a bucket 6 is connected to the tip of the arm 4 so as to be capable of moving up and down. The bucket 6 operates via a bucket cylinder 5, which is a single-rod hydraulic cylinder serving as a hydraulic actuator driven by supplied hydraulic oil. The bucket cylinder 5 has a tip end of a rod 5c connected to the bucket 6, and a base end of a cylinder tube 5d of the bucket cylinder 5 connected to the arm 4.

[0019] 2, the bucket cylinder 5 includes a cap chamber 5a located on the base end side of the cylinder tube 5d, which is supplied with hydraulic oil to press a piston 5e attached to the base end of the rod 5c, thereby extending the rod 5c. The bucket cylinder 5 also includes a rod chamber 5b located on the tip side of the cylinder tube 5d, which is supplied with hydraulic oil to press the piston 5e, thereby retracting the rod 5c.

[0020] The boom cylinder 1, the arm cylinder 3 and the bucket cylinder 5 each perform an extension / retraction operation by the hydraulic oil supplied thereto, and are driven to extend or retract depending on the supply direction of the hydraulic oil.

[0021] 2, the hydraulic drive system 107 includes four closed circuit pumps configured to form a closed circuit and to be able to supply and discharge hydraulic oil for three types of single-rod hydraulic cylinders and one type of hydraulic motor (swing motor 7 in this embodiment), and four open circuit pumps configured to form an open circuit and to be able to supply and discharge hydraulic oil. The hydraulic drive system 107 also has a configuration that allows flow rate control by combining one closed circuit pump and one open circuit pump when driving a single-rod hydraulic cylinder.

[0022] More specifically, the hydraulic drive unit 107 has a plurality of switching valves that are provided in the hydraulic oil flow paths between the ports of the hydraulic pumps and the cylinders and motors, and that can independently switch between on and off of the flow paths. Each of the switching valves can be controlled, for example, so that a plurality of closed circuit pumps and a plurality of open circuit pumps can join to one single-rod hydraulic cylinder. Furthermore, for example, when joining to one single-rod hydraulic cylinder, the switching valves are controlled by a controller so that one closed circuit pump and one open circuit pump are combined and joined.

[0023] The hydraulic drive unit 107 is a drive unit for driving the hydraulic excavator 100, and is mounted on the upper rotating body 103. The hydraulic drive unit 107 is used to drive the boom cylinder 1, arm cylinder 3, and bucket cylinder 5 that configure the front working machine 106, as well as the swing motor 7 and traveling motors 8a, 8b. The swing motor 7 and traveling motors 8a, 8b are hydraulic motors that are rotationally driven by a supply of hydraulic oil.

[0024] Furthermore, the hydraulic drive unit 107 drives the boom cylinder 1, arm cylinder 3, bucket cylinder 5, swing motor 7, and travel motors 8a, 8b, which are hydraulic actuators, in response to the operation of an operating lever device 56 serving as an operating section installed inside the cab 104. Here, the extension and retraction operations of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, i.e., the operation direction and operation speed, are specified by the operation direction and operation amount of each of the operating levers 56a, 56b, 56c, 56d of the operating lever device 56.

[0025] Furthermore, the hydraulic drive system 107 is equipped with an engine 9 which is a power source. The engine 9 is connected to a power transmission system 10 which is composed of, for example, predetermined gears and the like and which distributes power. The power transmission system 10 is connected to hydraulic pumps 12, 13, . . . , 19 which are variable flow rate hydraulic pumps, and a charge pump 11 which replenishes pressure oil to a flow path 229 which will be described later.

[0026] The hydraulic pumps 12, 14, 16, 18 are first to fourth closed circuit pumps each including a double tilting swash plate mechanism (not shown) having two input / output ports as a pair of inflow / outflow ports that allow hydraulic oil to flow in and out in both directions, and regulators 12a, 14a, 16a, 18a as flow rate adjustment units for adjusting the tilt angle (inclination angle) of the double tilting swash plate constituting the double tilting swash plate mechanism. The regulators 12a, 14a, 16a, 18a are flow rate control units that adjust the tilt angle of the swash plate of the corresponding first to fourth closed circuit pumps 12, 14, 16, 18 in response to an operation signal output from a controller 57 as a control unit, thereby controlling the flow rate of hydraulic oil discharged from the first to fourth closed circuit pumps 12, 14, 16, 18.

[0027] Therefore, the first to fourth closed circuit pumps 12, 14, 16, and 18 are capable of controlling the discharge flow rate and discharge direction of the hydraulic oil from the input and output ports by adjusting the tilt angle of the swash plate. Furthermore, the first to fourth closed circuit pumps 12, 14, 16, and 18 function as hydraulic motors when supplied with hydraulic oil.

[0028] The hydraulic pumps 13, 15, 17, and 19 are first to fourth open circuit pumps each including a one-sided tilting swash plate mechanism (not shown) having an outflow port that allows hydraulic oil to flow in and out in one direction, and regulators 13a, 15a, 17a, and 19a as flow rate adjustment units for adjusting the tilt angle (inclination angle) of the one-sided tilting swash plate constituting the one-sided tilting swash plate mechanism. The regulators 13a, 15a, 17a, and 19a are flow rate control units that adjust the tilt angle of the swash plate of the corresponding one-sided tilting swash plate of the first to fourth open circuit pumps 13, 15, 17, and 19 in response to an operation signal output from a controller 57 as a control unit, thereby controlling the flow rate of hydraulic oil discharged from the first to fourth open circuit pumps 13, 15, 17, and 19.

[0029] Therefore, in the first to fourth open circuit pumps 13, 15, 17, and 19, the flow rate of the hydraulic oil discharged from the outflow port can be controlled by adjusting the tilt angle of the swash plate.

[0030] Furthermore, the tilting swash plate mechanisms of the hydraulic pumps 12, 13, ..., 19 are provided with tilting angle sensors 12b, 13b, ..., 19b that detect the tilting angle, and can be used when the discharge flow rate is used as a trigger for switching the switching valve in the time chart shown in Fig. 4 described later. Alternatively, a means for measuring the control pressure of the regulator of the hydraulic pumps 12, 13, ..., 19 may be provided, and the tilting state of the swash plate and the discharge flow rate of each pump may be calculated from the regulator control pressure.

[0031] In addition, the first to fourth closed circuit pumps 12, 14, 16, and 18 are structured to generate a regulator driving force in both directions, that is, in the direction to maximize and minimize the tilt angle, in order to control the tilt angle of the swash plate in two directions, whereas the first to fourth open circuit pumps 13, 15, 17, and 19 are structured to control the tilt angle of the swash plate in one direction, so the regulator driving force acts only in the direction to maximize the tilt angle, and the return to the minimum angle depends on the restoring force of a spring. Therefore, the first to fourth closed circuit pumps 12, 14, 16, and 18 have higher responsiveness when controlling the tilt angle in the direction to reduce the discharge volume.

[0032] Specifically, a flow path 200 is connected to one input / output port of the first closed circuit pump 12, and a flow path 201 is connected to the other input / output port. A plurality of, for example, four, switching valves 43a, 43b, 43c, 43d are connected to the flow paths 200, 201. The switching valves 43a, 43b, 43c are closed circuit switching valves for switching the supply of hydraulic oil to the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 connected to the first closed circuit pump 12 in a closed circuit. The switching valve 43d is a closed circuit switching valve for a hydraulic motor for switching the supply of hydraulic oil to the swing motor 7 connected to the first closed circuit pump 12 in a closed circuit. The switching valves 43a, 43b, 43c, 43d are configured to switch between the continuity and the cutoff of the flow paths 200, 201 in response to an operation signal output from the controller 57, and are in a cutoff state when there is no operation signal output from the controller 57. The controller 57 controls the switching valves 43a, 43b, 43c, and 43d so that they are not simultaneously in a conductive state.

[0033] Furthermore, the switching valve 43a is connected to the boom cylinder 1 via the flow paths 212 and 213. Therefore, when the switching valve 43a is brought into a conductive state in response to an operation signal output from the controller 57, the first closed circuit pump 12 configures a closed circuit A that is connected in a closed circuit form to the boom cylinder 1 via the flow paths 200 and 201, the switching valve 43a, and the flow paths 212 and 213.

[0034] The pressure sensor 70a connected to the flow path 212 measures the pressure of the flow path 212 and inputs the pressure to the controller 57. The pressure sensor 70b connected to the flow path 213 measures the pressure of the flow path 213 and inputs the pressure to the controller 57.

[0035] In addition, the switching valve 43b is connected to the arm cylinder 3 via the flow paths 214 and 215. Therefore, when the switching valve 43b is brought into a conductive state in response to an operation signal output from the controller 57, the first closed circuit pump 12 configures a closed circuit B that is connected in a closed circuit form to the arm cylinder 3 via the flow paths 200 and 201, the switching valve 43b, and the flow paths 214 and 215.

[0036] The pressure sensor 71a connected to the flow path 214 measures the pressure of the flow path 214 and inputs the result to the controller 57. The pressure sensor 71b connected to the flow path 215 measures the pressure of the flow path 215 and inputs the result to the controller 57.

[0037] Furthermore, the switching valve 43c is connected to the bucket cylinder 5 via the flow paths 216 and 217. Therefore, when the switching valve 43c is brought into a conductive state by an operation signal from the controller 57, the first closed circuit pump 12 configures a closed circuit C that is connected in a closed circuit form to the bucket cylinder 5 via the flow paths 200 and 201, the switching valve 43c, and the flow paths 216 and 217.

[0038] The pressure sensor 72a connected to the flow path 216 measures the pressure of the flow path 216 and inputs the result to the controller 57. The pressure sensor 72b connected to the flow path 217 measures the pressure of the flow path 217 and inputs the result to the controller 57.

[0039] In addition, the switching valve 43d is connected to the swing motor 7 via the flow paths 218 and 219. Therefore, when the switching valve 43d is turned on by an operation signal from the controller 57, the first closed circuit pump 12 forms a closed circuit D that is connected in a closed circuit form to the swing motor 7 via the flow paths 200 and 201, the switching valve 43d, and the flow paths 218 and 219.

[0040] Here, the flow path 212 is also a connection flow path for a hydraulic cylinder for independently connecting the boom cylinder 1 to a plurality of switching valves 44a, 46a, 48a, 50a of the open circuits E, F, G, H described later. The flow path 214 is also a connection flow path for a hydraulic cylinder for independently connecting the arm cylinder 3 to a plurality of switching valves 44b, 46b, 48b, 50b of the open circuits E, F, G, H described later. The flow path 216 is also a connection flow path for a hydraulic cylinder for independently connecting the bucket cylinder 5 to a plurality of switching valves 44c, 46c, 48c, 50c of the open circuits E, F, G, H described later.

[0041] A flow path 203 is connected to one input / output port of the second closed circuit pump 14, and a flow path 204 is connected to the other input / output port. A plurality of, for example, four, switching valves 45a, 45b, 45c, 45d are connected to the flow paths 203, 204. The switching valves 45a, 45b, 45c are closed circuit switching valves for switching the supply of hydraulic oil to the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 connected to the second closed circuit pump 14 in a closed circuit. The switching valve 45d is a closed circuit switching valve for a hydraulic motor for switching the supply of hydraulic oil to the swing motor 7 connected to the second closed circuit pump 14 in a closed circuit. The switching valves 45a, 45b, 45c, 45d are configured to switch between the continuity and the cutoff of the flow paths 203, 204 in response to an operation signal output from the controller 57, and are in a cutoff state when there is no operation signal output from the controller 57. The controller 57 controls the switching valves 45a, 45b, 45c, and 45d so that they are not simultaneously in a conducting state.

[0042] Furthermore, the switching valve 45a is connected to the boom cylinder 1 via the flow paths 212 and 213. Therefore, when the switching valve 45a is brought into a conducting state by an operation signal from the controller 57, the second closed circuit pump 14 configures a closed circuit A connected in a closed circuit form to the boom cylinder 1 via the flow paths 203 and 204, the switching valve 45a, and the flow paths 212 and 213. Furthermore, the switching valve 45b is connected to the arm cylinder 3 via the flow paths 214 and 215. Therefore, when the switching valve 45b is brought into a conducting state by an operation signal from the controller 57, the second closed circuit pump 14 configures a closed circuit B connected in a closed circuit form to the arm cylinder 3 via the flow paths 203 and 204, the switching valve 45b, and the flow paths 214 and 215.

[0043] Further, the switching valve 45c is connected to the bucket cylinder 5 via the flow paths 216 and 217. Therefore, when the switching valve 45c is brought into a conducting state by an operation signal from the controller 57, the second closed circuit pump 14 forms a closed circuit C connected in a closed circuit form to the bucket cylinder 5 via the flow paths 203 and 204, the switching valve 45c, and the flow paths 216 and 217. Furthermore, the switching valve 45d is connected to the swing motor 7 via the flow paths 218 and 219. Therefore, when the switching valve 45d is brought into a conducting state by an operation signal from the controller 57, the second closed circuit pump 14 forms a closed circuit D connected in a closed circuit form to the swing motor 7 via the flow paths 203 and 204, the switching valve 45d, and the flow paths 218 and 219.

[0044] Next, a flow path 206 is connected to one input / output port of the third closed circuit pump 16, and a flow path 207 is connected to the other input / output port. A plurality of, for example, four, switching valves 47a, 47b, 47c, 47d are connected to the flow paths 206, 207. The switching valves 47a, 47b, 47c are closed circuit switching valves for switching the supply of hydraulic oil to the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 connected in a closed circuit to the third closed circuit pump 16. The switching valve 47d is a closed circuit switching valve for a hydraulic motor for switching the supply of hydraulic oil to the swing motor 7 connected in a closed circuit to the third closed circuit pump 16. The switching valves 47a, 47b, 47c, 47d are configured to switch between conduction and cutoff of the flow paths in response to an operation signal output from the controller 57, and are in a cutoff state when there is no operation signal output from the controller 57. The controller 57 controls the switching valves 47a, 47b, 47c, and 47d so that they are not simultaneously in a conducting state.

[0045] Furthermore, the switching valve 47a is connected to the boom cylinder 1 via the flow paths 212 and 213. Therefore, when the switching valve 47a is brought into a conducting state by an operation signal from the controller 57, the third closed circuit pump 16 constitutes a closed circuit A connected in a closed circuit form to the boom cylinder 1 via the flow paths 206 and 207, the switching valve 47a, and the flow paths 212 and 213. Furthermore, the switching valve 47b is connected to the arm cylinder 3 via the flow paths 214 and 215. Therefore, when the switching valve 47b is brought into a conducting state by an operation signal from the controller 57, the third closed circuit pump 16 constitutes a closed circuit B connected in a closed circuit form to the arm cylinder 3 via the flow paths 206 and 207, the switching valve 47b, and the flow paths 214 and 215.

[0046] Moreover, the switching valve 47c is connected to the bucket cylinder 5 via the flow paths 216 and 217. Therefore, when the switching valve 47c is brought into a conducting state by an operation signal from the controller 57, the third closed circuit pump 16 constitutes a closed circuit C connected in a closed circuit form to the bucket cylinder 5 via the flow paths 206 and 207, the switching valve 47c, and the flow paths 216 and 217. Furthermore, the switching valve 47d is connected to the swing motor 7 via the flow paths 218 and 219. Therefore, when the switching valve 47d is brought into a conducting state by an operation signal from the controller 57, the third closed circuit pump 16 constitutes a closed circuit D connected in a closed circuit form to the swing motor 7 via the flow paths 206 and 207, the switching valve 47d, and the flow paths 218 and 219.

[0047] Next, a flow path 209 is connected to one input / output port of the fourth closed circuit pump 18, and a flow path 210 is connected to the other input / output port. A plurality of, for example, four, switching valves 49a, 49b, 49c, 49d are connected to the flow paths 209, 210. The switching valves 49a, 49b, 49c are closed circuit switching valves for switching the supply of hydraulic oil to the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 connected in a closed circuit to the fourth closed circuit pump 18. The switching valve 49d is a closed circuit switching valve for a hydraulic motor for switching the supply of hydraulic oil to the swing motor 7 connected in a closed circuit to the fourth closed circuit pump 18. The switching valves 49a, 49b, 49c, 49d are configured to switch between conduction and cutoff of the flow paths in response to an operation signal output from the controller 57, and are in a cutoff state when there is no operation signal output from the controller 57. The controller 57 controls the switching valves 49a, 49b, 49c, and 49d so that they are not simultaneously in a conducting state.

[0048] The switching valve 49a is connected to the boom cylinder 1 via the flow paths 212 and 213. Therefore, when the switching valve 49a is brought into a conducting state by an operation signal from the controller 57, the fourth closed circuit pump 18 constitutes a closed circuit A connected in a closed circuit form to the boom cylinder 1 via the flow paths 209 and 210, the switching valve 49a, and the flow paths 212 and 213. Furthermore, the switching valve 49b is connected to the arm cylinder 3 via flow paths 214 and 215. Therefore, when the switching valve 49b is brought into a conducting state by an operation signal from the controller 57, the fourth closed circuit pump 18 constitutes a closed circuit B connected in a closed circuit form to the arm cylinder 3 via the flow paths 209 and 210, the switching valve 49b, and the flow paths 214 and 215.

[0049] Furthermore, the switching valve 49c is connected to the bucket cylinder 5 via the flow paths 216 and 217. Therefore, when the switching valve 49c is brought into a conducting state by an operation signal from the controller 57, the fourth closed circuit pump 18 constitutes a closed circuit C connected in a closed circuit form to the bucket cylinder 5 via the flow paths 209 and 210, the switching valve 49c, and the flow paths 216 and 217. Furthermore, the switching valve 49d is connected to the swing motor 7 via the flow paths 218 and 219. Therefore, when the switching valve 49d is brought into a conducting state by an operation signal from the controller 57, the fourth closed circuit pump 18 constitutes a closed circuit D connected in a closed circuit form to the swing motor 7 via the flow paths 209 and 210, the switching valve 49d, and the flow paths 218 and 219.

[0050] Furthermore, one input / output port of the first open circuit pump 13 is connected to a plurality of, for example, four, switching valves 44a, 44b, 44c, and 44d and a relief valve 21 via a flow path 202. The other input / output port of the first open circuit pump 13 is connected to a hydraulic oil tank 25 to form an open circuit E. The switching valves 44a, 44b, 44c, and 44d are open circuit switching valves that switch between conductive and blocked states of the flow path 202 in response to an operation signal output from a controller 57, and switch the supply destination of the hydraulic oil discharged from the first open circuit pump 13 to connecting flow paths 301, 302, 303, and 304 described below, and are in a blocked state when there is no operation signal output from the controller 57. The controller 57 controls the switching valves 44a, 44b, 44c, and 44d so that they are not in a conductive state at the same time.

[0051] The switching valve 44a is connected to the boom cylinder 1 via a connecting flow path 301 and a flow path 212. The connecting flow path 301 is a connecting pipe provided by branching off from the flow path 212. The switching valve 44b is connected to the arm cylinder 3 via a connecting flow path 302 and a flow path 214. The connecting flow path 302 is a connecting pipe provided by branching off from the flow path 214. The switching valve 44c is connected to the bucket cylinder 5 via a connecting flow path 303 and a flow path 216. The connecting flow path 303 is a connecting pipe provided by branching off from the flow path 216. The switching valve 44d is connected to proportional switching valves 54 and 55, which are control valves that control the supply and discharge of hydraulic oil to the traveling motors 8a and 8b, via a connecting flow path 304 and a flow path 220. On the other hand, when the hydraulic pressure in the flow path 202 reaches or exceeds a predetermined pressure, the relief valve 21 releases the hydraulic oil in the flow path 202 to the hydraulic oil tank 25 to protect the flow path 202 and, ultimately, the hydraulic drive device 107 (hydraulic circuit).

[0052] In addition, a proportional valve 64 serving as a pressure-compensated flow rate control valve is connected between the flow path 202 and the hydraulic oil tank 25. The proportional valve 64 is connected to a branch flow path 202a, which is a pipe branched from the flow path 202, which is a pipe connecting the switching valves 44a, 44b, 44c, and 44d and the first open circuit pump 13, and connected to the hydraulic oil tank 25. Thus, the proportional valve 64 controls the flow rate of hydraulic oil flowing from the flow path 202 to the hydraulic oil tank 25 in response to an operation signal output from the controller 57. In addition, the proportional valve 64 is in a shutoff state when no operation signal is output from the controller 57.

[0053] Furthermore, one input / output port of the second open circuit pump 15 is connected to a plurality of, for example, four, switching valves 46a, 46b, 46c, 46d and a relief valve 22 via a flow path 205. The other input / output port of the second open circuit pump 15 is connected to a hydraulic oil tank 25 to form an open circuit F. The switching valves 46a, 46b, 46c, 46d are open circuit switching valves that switch between conductive and blocked states of the flow path 205 in response to an operation signal output from a controller 57, and switch the supply destination of the hydraulic oil discharged from the second open circuit pump 15 to the connecting flow paths 301, 302, 303, 304, and are in a blocked state when no operation signal is output from the controller 57. The controller 57 controls the switching valves 46a, 46b, 46c, 46d so that they are not in a conductive state at the same time.

[0054] Moreover, the switching valve 46a is connected to the boom cylinder 1 via a connecting passage 301 and a passage 212. The switching valve 46b is connected to the arm cylinder 3 via a connecting passage 302 and a passage 214. The switching valve 46c is connected to the bucket cylinder 5 via a connecting passage 303 and a passage 216. The switching valve 46d is connected to the proportional switching valves 54, 55 via a connecting passage 304 and a passage 220. On the other hand, the relief valve 22 protects the passage 205 by releasing the hydraulic oil in the passage 205 to the hydraulic oil tank 25 when the hydraulic pressure in the passage 205 reaches or exceeds a predetermined pressure.

[0055] In addition, a proportional valve 65 serving as a pressure-compensated flow rate control valve is connected between the flow path 205 and the hydraulic oil tank 25. The proportional valve 65 is connected to a branch flow path 205a, which is a pipe branched from the flow path 205, which is a pipe connecting the switching valves 46a, 46b, 46c, and 46d and the second open circuit pump 15, and connected to the hydraulic oil tank 25. Thus, the proportional valve 65 controls the flow rate of hydraulic oil flowing from the flow path 205 to the hydraulic oil tank 25 in response to an operation signal output from the controller 57. In addition, the proportional valve 65 is in a shutoff state when no operation signal is output from the controller 57.

[0056] Furthermore, one input / output port of the third open circuit pump 17 is connected to a plurality of, for example, four, switching valves 48a, 48b, 48c, 48d and the relief valve 23 via a flow path 208. The other input / output port of the third open circuit pump 17 is connected to the hydraulic oil tank 25 to form an open circuit G. The switching valves 48a, 48b, 48c, 48d are open circuit switching valves that switch between conductive and blocked states of the flow path 208 in response to an operation signal output from the controller 57, and switch the supply destination of the hydraulic oil discharged from the third open circuit pump 17 to the connecting flow paths 301, 302, 303, 304, and are in a blocked state when no operation signal is output from the controller 57. The controller 57 controls the switching valves 48a, 48b, 48c, 48d so that they are not in a conductive state at the same time.

[0057] Moreover, switching valve 48a is connected to boom cylinder 1 via connecting passage 301 and passage 212. Switching valve 48b is connected to arm cylinder 3 via connecting passage 302 and passage 214. Switching valve 48c is connected to bucket cylinder 5 via connecting passage 303 and passage 216. Switching valve 48d is connected to proportional switching valves 54, 55 via connecting passage 304 and passage 220. On the other hand, relief valve 23 protects passage 208 by releasing the hydraulic oil in passage 208 to hydraulic oil tank 25 when the hydraulic pressure in passage 208 reaches or exceeds a predetermined pressure.

[0058] In addition, a proportional valve 66 serving as a pressure-compensated flow rate control valve is connected between the flow path 208 and the hydraulic oil tank 25. The proportional valve 66 is connected to a branch flow path 208a, which is a pipe branched from the flow path 208, which is a pipe connecting the switching valves 48a, 48b, 48c, 48d and the third open circuit pump 17, and connected to the hydraulic oil tank 25. Thus, the proportional valve 66 controls the flow rate from the flow path 208 to the hydraulic oil tank 25 in response to an operation signal output from the controller 57. In addition, the proportional valve 66 is in a shutoff state when no operation signal is output from the controller 57.

[0059] Furthermore, one input / output port of the fourth open circuit pump 19 is connected to a plurality of, for example, four, switching valves 50a, 50b, 50c, and 50d and a relief valve 24 via a flow path 211. The other input / output port of the fourth open circuit pump 19 is connected to a hydraulic oil tank 25 to form an open circuit H. The switching valves 50a, 50b, 50c, and 50d are open circuit switching valves that switch between conductive and blocked states of the flow path 211 in response to an operation signal output from a controller 57, and switch the supply destination of the hydraulic oil discharged from the fourth open circuit pump 19 to the connecting flow paths 301, 302, 303, and 304, and are in a blocked state when no operation signal is output from the controller 57. The controller 57 controls the switching valves 50a, 50b, 50c, and 50d so that they are not in a conductive state at the same time.

[0060] Moreover, the switching valve 50a is connected to the boom cylinder 1 via a connecting passage 301 and a passage 212. The switching valve 50b is connected to the arm cylinder 3 via a connecting passage 302 and a passage 214. Moreover, the switching valve 50c is connected to the bucket cylinder 5 via a connecting passage 303 and a passage 216. The switching valve 50d is connected to the proportional switching valves 54, 55 via a connecting passage 304 and a passage 220. On the other hand, the relief valve 24 protects the passage 211 by releasing the hydraulic oil in the passage 211 to the hydraulic oil tank 25 when the hydraulic pressure in the passage 211 reaches or exceeds a predetermined pressure.

[0061] In addition, a pressure-compensated proportional valve 67 is connected between the flow path 211 and the hydraulic oil tank 25. The proportional valve 67 is connected to a branch flow path 211a, which is a pipe branched from the flow path 211, which is a pipe connecting the switching valves 50a, 50b, 50c, and 50d and the fourth open circuit pump 19, and connected to the hydraulic oil tank 25. Thus, the proportional valve 67 controls the flow rate of hydraulic oil flowing from the flow path 211 to the hydraulic oil tank 25 in response to an operation signal output from the controller 57. In addition, the proportional valve 67 is in a shutoff state when no operation signal is output from the controller 57.

[0062] Here, the connecting flow path 301 is composed of open circuit connecting flow paths 305a, 306a, 307a, 308a connected to the discharge side, which is the side from which the hydraulic oil flows out, of at least one switching valve 44a, 46a, 48a, 50a among the multiple open circuits E, F, G, H, and a closed circuit connecting flow path 309a connected to the flow path 212 constituting the closed circuit A. The connecting flow path 302 is composed of open circuit connecting flow paths 305b, 306b, 307b, 308b connected to the discharge side, which is the side from which the hydraulic oil flows out, of at least one switching valve 44b, 46b, 48b, 50b among the multiple open circuits E, F, G, H, and a closed circuit connecting flow path 309b connected to the flow path 214 constituting the closed circuit B. The connecting flow path 303 is composed of open circuit connecting flow paths 305c, 306c, 307c, 308c connected to the discharge side, which is the side from which the hydraulic oil flows out, of at least one switching valve 44c, 46c, 48c, 50c among the multiple open circuits E, F, G, H, and a closed circuit connecting flow path 309c connected to the flow path 216 constituting the closed circuit C. The connecting flow path 304 is composed of open circuit connecting flow paths 305d, 306d, 307d, 308d connected to the discharge side, which is the side from which the hydraulic oil flows out, of at least one switching valve 44d, 46d, 48d, 50d among the multiple open circuits E, F, G, H, and a connecting flow path 309d connected to the flow path 220.

[0063] The hydraulic drive system 107 is composed of closed circuits A, B, C, D in which the first to fourth closed circuit pumps 12, 14, 16, 18, the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the swing motor 7 are connected in a closed circuit form from one input / output port of the hydraulic pump to the other input / output port via the actuator, and further composed of open circuits E, F, G, H in which the first to fourth open circuit pumps 13, 15, 17, 19, the switching valves 44a, 44b, 44c, 44d, 46a, 46b, 46c, 46d, 48a, 48b, 48c, 48d, 50a, 50b, 50c, 50d are connected to one input / output port of the hydraulic pump, and the hydraulic oil tank 25 is connected to the other input / output port. Furthermore, the closed circuits A, B, C, D and the open circuits E, F, G, H are provided in pairs, for example, four circuits each.

[0064] On the other hand, the discharge port of charge pump 11 is connected to charge relief valve 20 and charge check valves 26, 27, 28, 29, 40a, 40b, 41a, 41b, 42a, and 42b via flow path 229. The suction port of charge pump 11 is connected to hydraulic oil tank 25. Here, charge relief valve 20 adjusts the charge pressure of charge check valves 26, 27, 28, 29, 40a, 40b, 41a, 41b, 42a, and 42b.

[0065] In addition, the charge check valve 26 supplies hydraulic oil from the charge pump 11 to the flow paths 200, 201 when the hydraulic pressure in the flow paths 200, 201 falls below the pressure set by the charge relief valve 20. Similarly, the charge check valve 27 supplies hydraulic oil from the charge pump 11 to the flow paths 203, 204 when the hydraulic pressure in the flow paths 203, 204 falls below the pressure set by the charge relief valve 20. In addition, the charge check valve 28 supplies hydraulic oil from the charge pump 11 to the flow paths 206, 207 when the hydraulic pressure in the flow paths 206, 207 falls below the pressure set by the charge relief valve 20. Similarly, the charge check valve 29 supplies hydraulic oil from the charge pump 11 to the flow paths 209, 210 when the hydraulic pressure in the flow paths 209, 210 falls below the pressure set by the charge relief valve 20.

[0066] Furthermore, the charge check valves 40a, 40b supply hydraulic oil from the charge pump 11 to the flow paths 212, 213 when the hydraulic pressure in the flow paths 212, 213 falls below the pressure set by the charge relief valve 20. Similarly, the charge check valves 41a, 41b supply hydraulic oil from the charge pump 11 to the flow paths 214, 215 when the hydraulic pressure in the flow paths 214, 215 falls below the pressure set by the charge relief valve 20. Furthermore, the charge check valves 42a, 42b supply hydraulic oil from the charge pump 11 to the flow paths 216, 217 when the hydraulic pressure in the flow paths 216, 217 falls below the pressure set by the charge relief valve 20.

[0067] In addition, a pair of relief valves 30a, 30b are connected between the flow paths 200, 201. When the hydraulic pressure in the flow paths 200, 201 reaches or exceeds a predetermined pressure, the relief valves 30a, 30b release the hydraulic oil in the flow paths 200, 201 to the hydraulic oil tank 25 via the charge relief valve 20 to protect the flow paths 200, 201. Similarly, a pair of relief valves 31a, 31b are connected between the flow paths 203, 204. When the hydraulic pressure in the flow paths 203, 204 reaches or exceeds a predetermined pressure, the relief valves 31a, 31b release the hydraulic oil in the flow paths 203, 204 to the hydraulic oil tank 25 via the charge relief valve 20 to protect the flow paths 203, 204.

[0068] Further, relief valves 32a and 32b are also connected between the flow paths 206 and 207. When the hydraulic pressure in the flow paths 206 and 207 reaches or exceeds a predetermined pressure, the relief valves 32a and 32b release the hydraulic oil in the flow paths 206 and 207 to the hydraulic oil tank 25 via the charge relief valve 20 to protect the flow paths 206 and 207. Further, relief valves 33a and 33b are also connected between the flow paths 209 and 210. When the hydraulic pressure in the flow paths 209 and 210 reaches or exceeds a predetermined pressure, the relief valves 33a and 33b release the hydraulic oil in the flow paths 209 and 210 to the hydraulic oil tank 25 via the charge relief valve 20 to protect the flow paths 209 and 210.

[0069] Next, the flow path 212 is connected to the cap chamber 1a of the boom cylinder 1. The flow path 213 is connected to the rod chamber 1b of the boom cylinder 1. Relief valves 37a and 37b are connected between the flow paths 212 and 213. When the hydraulic pressure in the flow paths 212 and 213 reaches or exceeds a predetermined pressure, the relief valves 37a and 37b release the hydraulic oil in the flow paths 212 and 213 to the hydraulic oil tank 25 via the charge relief valve 20 to protect the flow paths 212 and 213. Furthermore, a flushing valve 34 is connected between the flow paths 212 and 213. The flushing valve 34 discharges the excess hydraulic oil (excess oil) in the flow paths 212 and 213 to the hydraulic oil tank 25 via the charge relief valve 20.

[0070] Moreover, the flow path 214 is connected to the cap chamber 3a of the arm cylinder 3. The flow path 215 is connected to the rod chamber 3b of the arm cylinder 3. Furthermore, the relief valves 38a, 38b are connected between the flow paths 214, 215. When the hydraulic pressure in the flow paths 214, 215 reaches or exceeds a predetermined pressure, the relief valves 38a, 38b release the hydraulic oil in the flow paths 214, 215 to the hydraulic oil tank 25 via the charge relief valve 20 to protect the flow paths 214, 215. Furthermore, the flushing valve 35 is connected between the flow paths 214, 215. The flushing valve 35 discharges excess hydraulic oil in the flow paths 214, 215 to the hydraulic oil tank 25 via the charge relief valve 20.

[0071] Moreover, the flow path 216 is connected to the cap chamber 5a of the bucket cylinder 5. The flow path 217 is connected to the rod chamber 5b of the bucket cylinder 5. Furthermore, relief valves 39a and 39b are connected between the flow paths 216 and 217. When the hydraulic pressure in the flow paths 216 and 217 reaches or exceeds a predetermined pressure, the relief valves 39a and 39b release the hydraulic oil in the flow paths 216 and 217 to the hydraulic oil tank 25 via the charge relief valve 20 to protect the flow paths 216 and 217. Furthermore, a flushing valve 36 is connected between the flow paths 216 and 217. The flushing valve 36 discharges excess hydraulic oil in the flow paths 216 and 217 to the hydraulic oil tank 25 via the charge relief valve 20.

[0072] Furthermore, the flow paths 218, 219 are each connected to the swing motor 7. Furthermore, relief valves 51a, 51b are connected between the flow paths 218, 219. When the pressure difference (flow path pressure difference) of the hydraulic oil between the flow paths 218, 219 becomes equal to or greater than a predetermined pressure, the relief valves 51a, 51b release the hydraulic oil in the high-pressure side flow paths 218, 219 to the low-pressure side flow paths 219, 218 to protect the flow paths 218, 219.

[0073] The proportional switching valve 54 and the travel motor 8a are connected through the flow paths 221, 222. Relief valves 52a, 52b are connected between the flow paths 221, 222. When the pressure difference of the hydraulic oil between the flow paths 221, 222 becomes equal to or greater than a predetermined pressure, the relief valves 52a, 52b release the hydraulic oil in the high-pressure side flow paths 221, 222 to the low-pressure side flow paths 222, 221 to protect the flow paths 221, 222. The proportional switching valve 54 is configured to switch the connection destination between the flow path 220 and the hydraulic oil tank 25 to either the flow path 221 or the flow path 222 in response to an operation signal output from the controller 57, and is capable of adjusting the flow rate.

[0074] Furthermore, the proportional switching valve 55 and the travel motor 8b are connected through the flow paths 223, 224. Relief valves 53a, 53b are connected between the flow paths 223, 224. When the pressure difference of the hydraulic oil between the flow paths 223, 224 becomes equal to or greater than a predetermined pressure, the relief valves 53a, 53b release the hydraulic oil in the high-pressure side flow paths 223, 224 to the low-pressure side flow paths 224, 223 to protect the flow paths 223, 224. The proportional switching valve 55 is configured to switch the connection destination between the flow path 220 and the hydraulic oil tank 25 to either the flow path 223 or the flow path 224 in response to an operation signal output from the controller 57, and is capable of adjusting the flow rate.

[0075] The controller 57 controls each regulator 12a, 13a, ..., 19a, switching valves 43a, 44a, ..., 50a, 43b, 44b, ..., 50b, 43c, 44c, ..., 50c, 43d, 44d, ..., 50d, and proportional switching valves 54, 55 based on command values ​​for the extension direction and extension speed of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5 from the operating lever device 56, command values ​​for the rotation direction and rotation speed of the swing motor 7 and traveling motors 8a, 8b, and various sensor information within the hydraulic drive unit 107.

[0076] Specifically, the controller 57 performs pressure-receiving area control to control the first flow rate, which is the flow rate of the first closed circuit pump 12 on the side of the flow path 212 connected to the cap chamber 1a and the rod chamber 1b of the boom cylinder 1, and the second flow rate, which is the flow rate of the first open circuit pump 13 connected to the connecting flow path 301 via the switching valve 44a, so that the ratio between these first flow rate and second flow rate becomes a predetermined value set in advance according to the pressure-receiving areas of the cap chamber 1a and the rod chamber 1b of the boom cylinder 1. Similarly, the controller 57 performs the above-mentioned pressure-receiving area control for the arm cylinder 3 and the bucket cylinder 5 other than the boom cylinder 1.

[0077] In addition, when at least one of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5 is operated, the controller 57 appropriately controls the switching valves 43a, 44a,...,50a, 43b, 44b,...,50b, 43c, 44c,...,50c, 43d, 44d,...,50d to supply hydraulic oil discharged from the first to fourth open circuit pumps 13, 15, 17, 19, which are in the same number as the corresponding first to fourth closed circuit pumps 12, 14, 16, 18, to at least one of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5 being operated.

[0078] Furthermore, the operation lever 56a of the operation lever device 56 gives the controller 57 command values ​​for the extension and retraction direction and speed of the boom cylinder 1. The operation lever 56b gives the controller 57 command values ​​for the extension and retraction direction and speed of the arm cylinder 3, and the operation lever 56c gives the controller 57 command values ​​for the extension and retraction direction and speed of the bucket cylinder 5. Furthermore, the operation lever 56d gives the controller 57 command values ​​for the rotation direction and rotation speed of the swing motor 7. The configuration also includes an operation lever (not shown) that gives command values ​​for the rotation direction and rotation speed of the traveling motors 8a, 8b to the controller 57.

[0079] As described above, the hydraulic drive system 107 includes a closed circuit pump (e.g., the first to fourth closed circuit pumps 12, 14, 16, 18) and an open circuit pump (e.g., the first to fourth open circuit pumps 13, 15, 17, 19), each of which discharges hydraulic oil, and a plurality of actuators (e.g., the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, the swing motor 7) hydraulically connected to the closed circuit pumps and the open circuit pumps so that hydraulic oil can be supplied from the closed circuit pumps and the open circuit pumps to each of the actuators.

[0080] The hydraulic drive device 107 also has, for example, closed circuit switching valves (e.g., switching valves 43a-43d, 45a-45d, 47a-47d, 49a-49d) that switch between conducting and blocking a flow path of hydraulic oil between the closed circuit pump and the multiple actuators so that the closed circuit pump is selectively connected in a closed circuit to any one of the multiple actuators (forming closed circuits A-D), and open circuit switching valves (e.g., switching valves 44a-44d, 46a-46d, 48a-48d, 50a-50d) that switch between conducting and blocking a flow path of hydraulic oil between the open circuit pump and the multiple actuators so that the hydraulic oil discharged from the open circuit pump is selectively supplied to any one of the multiple actuators (for example, supplied to any one of the connecting flow paths 301-304).

[0081] In addition, the controller 57 receives operation input via the operating lever device 56 and controls each component in the hydraulic drive device 107, including the closed circuit pump, the open circuit pump, the closed circuit switching valve, and the open circuit switching valve, for example, to perform the operations described above.

[0082] 3 shows a functional block diagram of the controller 57. The controller 57 is composed of a lever operation amount calculation unit 57a, an actuator pressure calculation unit 57b, and an actuator allocated flow rate calculation unit 57c.

[0083] The lever operation amount calculation unit 57a calculates the movement direction and movement speed target of each actuator in response to the lever input of the operator, and inputs them to the actuator allocated flow rate calculation unit 57c.

[0084] Actuator pressure calculation unit 57b calculates the pressure of each actuator from the values ​​of pressure sensors 70a, 70b, 71a, 71b, 72a, 72b provided on boom cylinder 1, arm cylinder 3, and bucket cylinder 5, and inputs the calculated pressure to actuator allocated flow rate calculation unit 57c.

[0085] Based on inputs from lever operation amount calculation unit F11 and actuator pressure calculation unit 57b, actuator allocated flow rate calculation unit 57c calculates command values ​​to the switching valve, proportional valve, and regulator so that the actuator speed is as input from lever operation amount calculation unit 57a. Actuator allocated flow rate calculation unit 57c calculates the discharge flow rate based on a signal indicating the pump state from the regulator, such as the tilt angle and regulator pressure. Furthermore, actuator allocated flow rate calculation unit 57c of controller 57 controls the switching valve based on the discharge flow rate, and controls switching between the actuator and the pump.

[0086] In this embodiment, the discharge flow rate is calculated based on the signals of the tilt angle sensors 12b to 19b, but sensors for detecting the tilt angle and regulator pressure are not essential, and it is also possible to calculate the discharge flow rate based on a regulator command value calculated by the controller 57.

[0087] Furthermore, when changing the connection destination of a pump and an actuator using a switching valve, the actuator allocated flow rate calculation unit 57c of the controller 57 first performs control to stop the discharge of hydraulic oil from the pump. Then, when the actuator allocated flow rate calculation unit 57c detects that the calculated discharge flow rate of each pump has reached a predetermined arbitrary value, it determines that the stop of the discharge of hydraulic oil to the previous connection destination has been completed, and at a later timing performs control to switch the connection destination of the pump to the new actuator. Then, after detecting that the pump has been connected to the new actuator based on the operating state of the switching valve, the actuator allocated flow rate calculation unit 57c performs control to start the discharge of hydraulic oil to the pump.

[0088] In the following embodiment, a case will be described in which the completion condition for stopping the discharge of the pump, which is the switching condition set by the controller 57, is set to the discharge flow rate of the pump becoming almost zero. More specifically, in this embodiment, for each pump, when the detection value of the tilt angle sensor (i.e., the actual tilt angle of the pump) is a value (angle) corresponding to a discharge flow rate equal to or less than a predetermined amount (for example, equal to or less than a few cc), the actuator allocated flow rate calculation unit 57c determines that the pump is in a state in which the discharge of hydraulic oil has been stopped. In other words, the actuator allocated flow rate calculation unit 57c determines whether the pump is in a state in which the discharge of hydraulic oil is being discharged or in a state in which the discharge of hydraulic oil has been stopped, based on a signal acquired from the tilt angle sensor. For example, when the acquired signal value (sensor value) is within a range corresponding to a predetermined tilt angle or less (equal to or less than a threshold value of the signal value), the actuator allocated flow rate calculation unit 57c determines that the pump is in a state in which the discharge of hydraulic oil has been stopped, and when the acquired signal value (sensor value) is within a range corresponding to a tilt angle exceeding the predetermined tilt angle, the actuator allocated flow rate calculation unit 57c determines that the pump is in a state in which the discharge of hydraulic oil has been stopped.

[0089] Next, regarding the driving method of the hydraulic drive unit 107 according to the above embodiment, the behavior of the combined operation of the hydraulic pumps 12, 13, . . . , 19 when the present invention is applied and when the present invention is not applied will be described with reference to Figs. 4, 5, and 6, taking as an example an independent operation in which the boom cylinder 1 is operated independently and a combined operation in which the boom cylinder 1, the swing motor 7, the arm cylinder 3, and the bucket cylinder 5 are operated in a combined manner. In the following description, it is assumed that the first to fourth closed circuit pumps 12, 14, 16, and 18 connected to the closed circuits A, B, C, and D have the same capacity. Furthermore, it is assumed that the pressure-receiving area ratios (rod chamber pressure-receiving area / cap chamber pressure-receiving area) of the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 are the same.

[0090] 4, 5, and 6 are time charts showing the state of the hydraulic drive device 107 during operation. In the figures, (a) is the operation amount of the operating lever 56a, (b) is the operation amount of the operating lever 56b, (c) is the operation amount of the operating lever 56c, (d) is the operation amount of the operating lever 56d, and (e) is the state of the switching valves 43a and 44a. (f) is the flow rate of the first closed circuit pump 12, (g) is the flow rate of the first open circuit pump 13, (h) is the state of the switching valves 45a and 46a, (i) is the state of the switching valve 45d, and (j) is the flow rate of the second closed circuit pump 14. (k) is the flow rate of the second open circuit pump 15, (l) is the state of the switching valves 47a and 48a, (m) is the state of the switching valves 47b and 48b, (n) is the flow rate of the third closed circuit pump 16, and (o) is the flow rate of the third open circuit pump 17. (p) is the flow rate of the proportional valve 66, (q) is the state of the switching valves 49a and 50a, (r) is the state of the switching valves 49c and 50c, (s) is the flow rate of the fourth closed circuit pump 18, (t) is the flow rate of the fourth open circuit pump 19, and (u) is the pressure of the arm cylinder 3 (cap chamber 3a, rod chamber 3b). Also, Fig. 4 shows the behavior when the present invention is applied, and Fig. 6 shows the behavior when the present invention is not applied. Furthermore, Fig. 5 shows an enlarged view of the behavior at the start of a combined operation of boom raising, swinging, and arm dumping.

[0091] <When stopped: t0~t11> 4, when the operating levers 56a, 56b, 56c, 56d of the operating lever device 56 are not being operated at all (t0 to t11), the hydraulic pumps 12, 13, ..., 19 are controlled to have the minimum tilt angle of their swash plates, and the discharge flow rates of the hydraulic pumps 12, 13, ..., 19 are set to approximately zero (0) (control to stop the discharge of hydraulic oil from the hydraulic pumps is maintained). At this time, the switching valves 43a, ..., 50d and the proportional switching valves 54, 55 are all controlled to be in a shutoff state, and the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, the swing motor 7, and the traveling motors 8a, 8b are each held in a stopped state.

[0092] <Boom raising only: t11~t21> 4, when the operating lever 56a of the operating lever device 56 is operated (t11), the controller 57 controls the regulator 12a of the first closed circuit pump 12 to drive the swash plate of the first closed circuit pump 12 so that the discharge port of the first closed circuit pump 12 becomes the flow path 200. At the same time, the controller 57 controls the regulator 13a of the first open circuit pump 13 to drive the swash plate so that the hydraulic oil is discharged from the first open circuit pump 13 to the flow path 202. At this time, the controller 57 controls the conduction of the switching valves 43a, 44a.

[0093] Then, at time t12, the discharge flow rate of the first closed circuit pump 12 becomes Qcp1, and the discharge flow rate of the first open circuit pump 13 becomes Qop1. At this time, the controller 57 performs the above-mentioned pressure receiving area control, and determines the discharge flow rates (Qcp1, Qop1) of the first closed circuit pump 12 and the first open circuit pump 13 so that the area ratio (Aa1:Aa2) of the pressure receiving area (Aa1) of the cap chamber 1a of the boom cylinder 1 to the pressure receiving area (Aa2) of the rod chamber 1b is equal to the flow rate ratio {(Qcp1+Qop1):Qcp1} of the first closed circuit pump 12 and the first open circuit pump 13. Furthermore, the controller 57 controls the discharge flow rates of the first closed circuit pump 12 and the first open circuit pump 13 so that the ratio of the discharge flow rate of the first closed circuit pump 12 to the discharge flow rate of the first open circuit pump 13 changes while maintaining the relationship Qcp1:Qop1.

[0094] Furthermore, when the amount of operation of the operating lever 56a further increases (t12), the controller 57 controls the regulator 14a of the second closed circuit pump 14 to drive the swash plate of the second closed circuit pump 14 so that the discharge port of the second closed circuit pump 14 becomes the flow path 203. At the same time, the controller 57 controls the regulator 15a of the second open circuit pump 15 to drive the swash plate so that the hydraulic oil is discharged from the second open circuit pump 15 to the flow path 205. At this time, the controller 57 controls the conduction of the switching valves 45a, 46a.

[0095] Then, when the operation value of the operating lever 56a is further increased (t13), the discharge flow rate of the second closed circuit pump 14 becomes Qcp1, and the discharge flow rate of the second open circuit pump 15 becomes Qop1. At this time, the controller 57 also performs the above-mentioned pressure-receiving area control, and controls the discharge flow rates of the second closed circuit pump 14 and the second open circuit pump 15 so that the ratio of the discharge flow rate of the second closed circuit pump 14 to the discharge flow rate of the second open circuit pump 15 changes while maintaining the relationship Qcp1:Qop1.

[0096] Furthermore, when the amount of operation of the operating lever 56a further increases (t13), the controller 57 controls the regulator 16a of the third closed circuit pump 16 to drive the swash plate of the third closed circuit pump 16 so that the discharge port of the third closed circuit pump 16 becomes the flow path 206. At the same time, the controller 57 controls the regulator 17a of the third open circuit pump 17 to drive the swash plate so that the hydraulic oil is discharged from the third open circuit pump 17 to the flow path 208. At this time, the controller 57 controls the conduction of the switching valves 47a, 48a.

[0097] Then, when the amount of operation of the operating lever 56a is further increased (t14), the discharge flow rate of the third closed circuit pump 16 becomes Qcp1, and the discharge flow rate of the third open circuit pump 17 becomes Qop1. At this time, the controller 57 also performs the above-mentioned pressure-receiving area control, and controls the discharge flow rates of the third closed circuit pump 16 and the third open circuit pump 17 so that the ratio of the discharge flow rate of the third closed circuit pump 16 to the discharge flow rate of the third open circuit pump 17 changes while maintaining the relationship Qcp1:Qop1.

[0098] Furthermore, when the amount of operation of the operating lever 56a further increases (t14), the controller 57 controls the regulator 18a of the fourth closed circuit pump 18 to drive the swash plate of the fourth closed circuit pump 18 so that the discharge port of the fourth closed circuit pump 18 becomes the flow path 209. At the same time, the controller 57 controls the regulator 19a of the fourth open circuit pump 19 to drive the swash plate so that the hydraulic oil is discharged from the fourth open circuit pump 19 to the flow path 211. At this time, the controller 57 controls the conduction of the switching valves 49a, 50a.

[0099] Then, when the operation amount of the operating lever 56a reaches +X (t15), the discharge flow rate of the fourth closed circuit pump 18 becomes Qcp1, and the discharge flow rate of the fourth open circuit pump 19 becomes Qop1. At this time, the controller 57 also performs the above-mentioned pressure-receiving area control, and controls the discharge flow rates of the fourth closed circuit pump 18 and the fourth open circuit pump 19 so that the ratio of the discharge flow rate of the fourth closed circuit pump 18 to the discharge flow rate of the fourth open circuit pump 19 changes while maintaining the relationship Qcp1:Qop1.

[0100] <Boom raising + rotation combined: t21~t31> In FIG. 4, when the operation amount of the operating lever 56a is X and the boom cylinder 1 is operating independently, the operating lever 56d is operated (t21), the controller 57 performs control to switch the actuator to which the second closed circuit pump 14 is connected from the boom cylinder 1 to the swing motor 7.

[0101] More specifically, first, the controller 57 performs (starts) control to stop the discharge of hydraulic oil from the second closed circuit pump 14. This controls the regulator 14a, and drives the second closed circuit pump 14 so that the tilt angle of the swash plate becomes the minimum tilt angle. Then, the controller 57 calculates from a signal acquired from the tilt angle sensor that the tilt angle of the second closed circuit pump 14 has actually become the minimum tilt angle, and thereby determines that the second closed circuit pump 14 has completed stopping the discharge of hydraulic oil (time t22).

[0102] In this embodiment, the controller 57 performs (starts) control to stop the discharge of hydraulic oil from the second open circuit pump 15 simultaneously with (at time t21) the control to stop the discharge of hydraulic oil from the second closed circuit pump 14. This controls the regulator 15a of the second open circuit pump 15, and the second open circuit pump 15 is driven so that the tilt angle of the swash plate becomes the minimum tilt angle. The controller 57 then calculates from a signal acquired from the tilt angle sensor that the tilt angle of the second open circuit pump 15 has actually become the minimum tilt angle, thereby determining that the stop of the discharge of hydraulic oil from the second open circuit pump 15 has been completed (time t24).

[0103] In the conventional technology shown in Fig. 6, the swash plate of the second closed circuit pump 14 and the swash plate of the second open circuit pump 15 are simultaneously at the minimum tilt angle. In contrast, in the present invention, the control for returning the tilt of the closed circuit pump is switched depending on the next connection of the closed circuit pump according to the flowchart shown in Fig. 7. At t21, the operation lever 56d is input, so that the next connection is the swing motor 7.

[0104] First, in step S1, it is determined whether the new connection destination is a single-rod hydraulic cylinder and the requested operation is a cylinder extension operation. Since the new connection destination is the swing motor 7, the process proceeds to step S4. In step S4, the closed circuit pump is brought to a discharge stop state as quickly as possible. Therefore, as shown in FIG. 4, in the present invention, the discharge flow rate of the second closed circuit pump 14 becomes almost zero from t21 to t22. In contrast, it takes the time from t21 to t24 for the discharge flow rate of the second open circuit pump 15, which has low responsiveness, to become almost zero.

[0105] On the other hand, in this embodiment, as shown in FIG. 4, when the discharge stop of the second closed circuit pump 14 is completed (t22), the controller 57 controls the switching valve 45a to be closed and then controls the switching valve 45d to be open. As a result, the second closed circuit pump 14 and the swing motor 7 are connected in a closed circuit. Then, in this embodiment, at the same time (time t22), the controller 57 proceeds to step S6 according to the flowchart shown in FIG. 7 because the connection destination after the change in step S5 is the swing motor 7, and controls the second closed circuit pump 14 to start discharging hydraulic oil, and also controls the inflow flow rate of the swing motor 7 with the second closed circuit pump 14. As a result, the regulator 14a of the second closed circuit pump 14 is controlled, and the swash plate of the second closed circuit pump 14 is driven so that the discharge port of the second closed circuit pump 14 becomes the flow path 203.

[0106] In addition, at the timing when the second open circuit pump 15 has stopped discharging hydraulic oil (t24), which is the timing after the second closed circuit pump 14 has been connected to the swing motor 7 (after time t22), the controller 57 controls the switching valve 46a to be shut off.

[0107] Note that at the timing before the second open circuit pump 15 has completely stopped discharging the hydraulic oil (before time t24), that is, at time t23 when the second open circuit pump 15 is discharging the hydraulic oil to the boom cylinder 1, which is the actuator before switching, the second closed circuit pump 14 starts discharging the hydraulic oil to the swing motor 7, and the discharge flow rate is Qcp1. That is, when the control lever 56d is operated, the hydraulic oil supplied to the boom cylinder 1 at t24 is reduced by the discharge flow rate (Qcp1) of the second closed circuit pump 14 and the discharge flow rate (Qop1) of the second open circuit pump 15, so that the operating speed of the boom cylinder 1 decreases. Note that, when the operation amount of the control lever 56d is set to zero (0) in this state, the state is restored to the previous original state (t21), and the operating speed of the boom cylinder 1 also returns (not shown).

[0108] 6 is not applied, the timing at which the discharge of the second closed circuit pump 14 is stopped is t24, which is the same as the timing at which the discharge of the second open circuit pump 15 is stopped. On the other hand, when the present invention is applied, the supply of flow rate to the swing motor 7 can start at t22, whereas when the present invention is not applied, this is delayed until t24.

[0109] Therefore, by applying the present invention, the time from the rotation lever input to the supply of flow to the rotation motor 7 during combined operation can be shortened, thereby shortening the time from the rotation lever input to the operation of the rotation motor 7 during combined operation.

[0110] <Boom raising + rotation + arm dump combined: t31~t41> In FIG. 4, when the operating amount of the operating levers 56a, 56d is X and the boom cylinder 1 and the swing motor 7 are performing combined operation, and then the operating lever 56b is operated (t31), the controller 57 performs control to switch the actuator to which the third closed circuit pump 16 is connected from the boom cylinder 1 to the arm cylinder 3.

[0111] More specifically, first, the controller 57 starts control to stop the discharge of hydraulic oil from the third closed circuit pump 16 and the third open circuit pump 17. This controls the regulator 16a of the third closed circuit pump 16 to drive the third closed circuit pump 16 so that the tilt angle of the swash plate becomes the minimum tilt angle, and when the tilt angle of the third closed circuit pump 16 actually becomes the minimum tilt angle, the discharge of hydraulic oil from the third closed circuit pump 16 is stopped (time t32).

[0112] Furthermore, the regulator 17a of the third open circuit pump 17 is controlled to drive the third open circuit pump 17 so that the tilt angle of the swash plate of the third open circuit pump 17 becomes the minimum tilt angle. Then, when the tilt angle of the third open circuit pump 17 actually becomes the minimum tilt angle, the third open circuit pump 17 completes stopping the discharge of hydraulic oil (time t34).

[0113] In the conventional technology shown in Fig. 6, the swash plate of the third closed circuit pump 16 and the swash plate of the third open circuit pump 17 are simultaneously at the minimum tilt angle. In contrast, in the present invention, the control for returning the tilt of the closed circuit pump is switched depending on the next connection of the closed circuit pump according to the flowchart shown in Fig. 7. At t31, the operation lever 56b is input, so that the next connection is the arm cylinder 3.

[0114] First, in step S1, it is determined whether the new connection destination is a single-rod hydraulic cylinder and the requested operation is a cylinder extension operation. Since the requested operation is a contraction operation (arm dump operation) of the arm cylinder 3 this time, the process proceeds to step S4. In step S4, the closed circuit pump is brought to a discharge stop state as quickly as possible. Therefore, as shown in FIG. 4, in the present invention, the discharge flow rate of the third closed circuit pump 16 becomes almost zero from t31 to t32. In contrast, it takes the third open circuit pump 17, which has low responsiveness, from t31 to t34 until the discharge flow rate becomes almost zero.

[0115] On the other hand, in the case of Fig. 4 in which the present invention is applied, when the discharge flow rate of the third closed circuit pump 16 becomes almost zero (t32), the controller 57 controls the switching valve 47a to be shut off, and then controls the switching valve 47b to be turned on. At the same time, the controller 57 proceeds to step S7 according to the flowchart shown in Fig. 7 because the connection destination after the change in step S5 is the arm cylinder 3. As shown in Fig. 5, the pressure of the cap chamber 3a is higher than the pressure of the rod chamber 3b in the arm cylinder 3 from t32 to t33.5, so the process proceeds to step S8 as shown in Fig. 7, and the outflow flow rate from the cap chamber 3a of the arm cylinder 3 for the required speed of the arm cylinder 3 is controlled by the third closed circuit pump 16. At this time, the maximum flow rate of the third closed circuit pump 16 becomes -Qcp1 at t33. Also, as shown in Fig. 5, since the pressure of the arm cylinder 3 after t33.5 is such that the pressure in the cap chamber 3a is lower than the pressure in the rod chamber 3b, the process proceeds to step S9 as shown in Fig. 7, and the inflow flow rate into the rod chamber 3b of the arm cylinder 3 for the required speed of the arm cylinder 3 is controlled by the third closed circuit pump 16. At this time, the maximum flow rate of the third closed circuit pump 16 is Qcp2. When the same cylinder speed is to be realized, -Qcp1<-Qcp2.

[0116] The regulator 16 a of the third closed circuit pump 16 is controlled by the controller 57 , and the swash plate of the third closed circuit pump 16 is driven so that the discharge port of the third closed circuit pump 16 is aligned with the flow path 207 .

[0117] When the discharge flow rate of third open circuit pump 17 becomes substantially zero (t34), controller 57 controls to shut off switching valve 48a. That is, when control lever 56b is operated, the hydraulic oil supplied to boom cylinder 1 at t34 is reduced by approximately the discharge flow rate (Qcp1) of third closed circuit pump 16 and the discharge flow rate (Qop1) of third open circuit pump 17, and the operating speed of boom cylinder 1 decreases. Note that, when the operation amount of control lever 56b is set to zero (0) in this state, the state is restored to the previous original state (t31), and the operating speed of boom cylinder 1 also returns (not shown).

[0118] 5, at t34, the controller 57 controls the switching valve 48a to be shut off, and then controls the switching valve 48b to be turned on. At the same time, the controller 57 controls the proportional valve 66 so that the flow rate through the proportional valve 66 becomes Qpv1. At this time, the controller 57 controls the pressure-receiving area, and the discharge flow rate Qcp2 of the third closed circuit pump 16 and the flow rate Qpv1 through the proportional valve 66 are determined so that the area ratio (Aa3:Ab3) of the pressure-receiving area (Aa3) of the cap chamber 3a of the arm cylinder 3 to the pressure-receiving area (Ab3) of the rod chamber 3b and the flow rate ratio {(Qcp2+Qpv1):Qcp2} of the flow rates through the third closed circuit pump 16 and the proportional valve 66 become equal. Furthermore, the controller 57 controls the discharge flow rate of the third closed circuit pump 16 and the flow rate through the proportional valve 66 so that the ratio between the discharge flow rate of the third closed circuit pump 16 and the flow rate through the proportional valve 66 changes while maintaining the relationship Qcp2:Qpv1.

[0119] 6, when the present invention is not applied, the timing when the discharge flow rate of the third closed circuit pump 16 becomes almost zero is t34, which is the same as the timing when the discharge flow rate of the third open circuit pump 17 becomes almost zero. When the present invention is applied, the supply of flow rate to the arm cylinder 3 can start at t32, whereas when the present invention is not applied, it is delayed until t34.

[0120] Therefore, by applying the present invention, the time from the arm lever input to the supply of flow rate to the arm cylinder 3 during combined operation can be shortened, thereby shortening the time from the arm lever input to the operation of the arm cylinder 3 during combined operation.

[0121] <Boom lift + rotation + arm dump + bucket cloud combination: t41~t52> In FIG. 4, when the operation amounts of the operation levers 56a, 56b, 56d are each X and the boom cylinder 1, arm cylinder 3, and swing motor 7 are in a combined operation, and then the operation lever 56c is operated (t41), the controller 57 performs control to switch the actuator to which the fourth closed circuit pump 18 and the fourth open circuit pump 19 are connected from the boom cylinder 1 to the bucket cylinder 5.

[0122] More specifically, the regulator 18a of the fourth closed circuit pump 18 is controlled to drive the fourth closed circuit pump 18 so that the tilt angle of the swash plate of the fourth closed circuit pump 18 becomes the minimum tilt angle, and the discharge of the fourth closed circuit pump 18 is stopped (time t42). At the same time, the regulator 19a of the fourth open circuit pump 19 is controlled by the controller 57 to drive the fourth open circuit pump 19 so that the tilt angle of the swash plate of the fourth open circuit pump 19 becomes the minimum tilt angle, and the discharge of the fourth open circuit pump 19 is stopped (time t42).

[0123] In the present invention, the control for returning the tilt of the closed circuit pump is switched depending on the next connection of the closed circuit pump according to the flowchart shown in Fig. 7. At t41, the operation lever 56c is input, so that the next connection is the bucket cylinder 5.

[0124] First, in step S1, it is determined whether the new connection destination is a single-rod hydraulic cylinder and the requested operation is a cylinder extension operation. Since the requested operation is an extension operation (bucket crowding operation) of the bucket cylinder 5 this time, the process proceeds to step S2. In step S2, the discharge of the closed circuit pump is stopped in synchronization with the open circuit pump. Therefore, as shown in FIG. 4, the discharge of the fourth closed circuit pump 18 is stopped from t41 to t42 in accordance with the fourth open circuit pump 19, which has low responsiveness.

[0125] When the discharge flow rates of the fourth closed circuit pump 18 and the fourth open circuit pump 19 become substantially zero (t42), the controller 57 controls the switching valves 49a, 50a to be shut off, and then controls the switching valves 49c, 50c to be open. At the same time, the controller 57 proceeds to step S3 according to the flowchart shown in FIG. 7, and controls the inflow flow rate into the cap chamber 5a of the bucket cylinder 5 for the required speed of the bucket cylinder 5 by the fourth closed circuit pump 18. At this time, the maximum flow rate of the fourth closed circuit pump 18 becomes Qcp1 at t43. The controller 57 controls the regulator 18a of the fourth closed circuit pump 18, and the swash plate of the fourth closed circuit pump 18 is driven so that the discharge port of the fourth closed circuit pump 18 becomes the flow path 209.

[0126] When the operating lever 56b is operated, at t42 the hydraulic oil supplied to the boom cylinder 1 is reduced by approximately the discharge flow rate (Qcp1) of the fourth closed circuit pump 18 and the discharge flow rate (Qop1) of the fourth open circuit pump 19, and the operating speed of the boom cylinder 1 decreases. Note that when the operation amount of the operating lever 56c is set to zero (0) in this state, the state is restored to the previous original state (t41), and the operating speed of the boom cylinder 1 also returns (not shown).

[0127] As shown in Fig. 4, at t43, the controller 57 controls the switching valves 49a and 50a to be shut off, and then controls the switching valves 49c and 50c to be open. At this time, the controller 57 controls the pressure-receiving area, and determines the discharge flow rates Qcp1 and Qop1 of the fourth closed circuit pump 18 and the fourth open circuit pump 19 so that the area ratio (Aa5:Ab5) of the pressure-receiving area (Aa5) of the cap chamber 5a of the bucket cylinder 5 to the pressure-receiving area (Ab5) of the rod chamber 5b is equal to the flow rate ratio {(Qcp1+Qop1):Qcp1} of the flow rates passing through the fourth closed circuit pump 18 and the fourth open circuit pump 19. Furthermore, the controller 57 controls the discharge flow rates of the fourth closed circuit pump 18 and the fourth open circuit pump 19 so that the ratio of the discharge flow rates of the fourth closed circuit pump 18 and the fourth open circuit pump 19 changes while maintaining the relationship Qcp1:Qop1.

[0128] As described above, even when the present invention is applied, if the operation after the connection change is the cylinder extension operation, the closed circuit pumps 12, 14, 16, 18 operate in synchronization with the open circuit pumps 13, 15, 17, 19, so the responsiveness is the same as that of the conventional technology shown in FIG. 6. This is because, when the closed circuit pumps 12, 14, 16, 18 perform the cylinder extension operation alone, especially when the cylinder cap chamber pressure is higher than the cylinder rod chamber pressure, the return flow rate from the cylinder rod chamber side is small compared to the discharge flow rate of the closed circuit pumps 12, 14, 16, 18, so that the suction side of the closed circuit pumps 12, 14, 16, 18 becomes negative pressure, which causes equipment failure. This can be solved by making the charge pump 11 larger, but this requires installation space and causes problems such as increased energy consumption during standby. Therefore, it is most effective to apply this patent when the pump connection change is for an operation other than the cylinder extension operation.

[0129] (summary) In this embodiment, the system includes closed circuit pumps 12, 14, 16, 18 each having two inlet / outlet ports through which hydraulic oil can flow in and out, open circuit pumps 13, 15, 17, 19 each having an inlet port and an outlet port for hydraulic oil, sensors 12b, 13b, . . . , 19b for detecting signals that change according to the discharge flow rates of the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19, first single-rod hydraulic cylinders 1, 3, 5, and other actuators, and the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, a plurality of actuators 1, 3, 5, 7 connected to the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19 so that hydraulic oil can be supplied from the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19; closed circuit switching valves 43a to 43d, 45a to 45d, 47a to 47d, 49a to 49d for switching between conduction and interruption of a flow path of hydraulic oil between the closed circuit pumps 12, 14, 16, 18 and the plurality of actuators 1, 3, 5, 7 so that the closed circuit pumps 12, 14, 16, 18 are selectively connected in a closed circuit to any one of the plurality of actuators 1, 3, 5, 7; open circuit switching valves 44a-44d, 46a-46d, 48a-48d, 50a-50d for switching between on and off a flow path of hydraulic oil between the open circuit pumps 13, 15, 17, 19 and the actuators 1, 3, 5, 7 so that hydraulic oil discharged from the pumps 13, 15, 17, 19 is selectively supplied to any one of the actuators 1, 3, 5, 7; closed circuit pumps 12, 14, 16, 18, open circuit pumps 13, 15, 17, 19, closed circuit switching valves 43a-43d, 45a-45d, 47a-47d, 49a-49d, and open circuit switching valve 44a In the construction machine 100 having the controller 57 for controlling the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19, when controlling the connection destination of the closed circuit pumps 12, 14, 16, 18 to the other actuator from a state in which the closed circuit pumps 12, 14, 16, 18 are connected to the first single-rod hydraulic cylinders 1, 3, 5 and the open circuit pumps 13, 15, 17, 19 are supplying hydraulic oil to the first single-rod hydraulic cylinders 1, 3, 5, the controller 57 controls the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17,The control unit 10 controls the closed circuit switching valves 43a-43d, 45a-45d, 47a-47d, 49a-49d so that the connection destination of the closed circuit pumps 12, 14, 16, 18 is switched from the first single-rod hydraulic cylinders 1, 3, 5 to the other actuators at a timing after a signal corresponding to a state in which the discharge of hydraulic oil from the closed circuit pumps 12, 14, 16, 18 has been stopped is obtained from the sensors 12b, 13b, . . . , 19b and before a signal corresponding to a state in which the discharge of hydraulic oil from the open circuit pumps 13, 15, 17, 19 has been stopped is obtained from the sensors 12b, 13b, . . . , 19b.

[0130] According to the present embodiment configured as described above, when changing the connection destination of the closed circuit pumps 12, 14, 16, 18 to another actuator while the first single-rod hydraulic cylinders 1, 3, 5 are driven by the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19, the timing of connecting the closed circuit pumps 12, 14, 16, 18 to the other actuator can be advanced by stopping the discharge of hydraulic oil from the closed circuit pumps 12, 14, 16, 18 earlier than the stop of the discharge of the open circuit pumps 13, 15, 17, 19. This allows the timing of starting the drive of the other actuator to be earlier than when the discharge of the closed circuit pumps 12, 14, 16, 18 is stopped in synchronization with the open circuit pumps 13, 15, 17, 19, and therefore the responsiveness of the other actuator to the operation input can be improved.

[0131] In this embodiment, the other actuator is the second single-rod hydraulic cylinder 1, 3, 5 that receives an operation input to perform a contracting operation, and the construction machine 100 is equipped with pressure sensors 70a, 70b, 71a, 71b, 72a, 72b that detect the cap chamber pressure and the rod chamber pressure of the second single-rod hydraulic cylinder 1, 3, 5. When the second single-rod hydraulic cylinder 1, 3, 5 is contracted by the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19, the controller 57 acquires from the sensors 12b, 13b, . . . , 19b a signal corresponding to a state in which the discharge of hydraulic oil from the open circuit pumps 13, 15, 17, 19 has been stopped. At a timing after the open circuit switching valve is controlled so that the supply destination of the hydraulic oil from the open circuit pumps 13, 15, 17, 19 is switched from the first single-rod hydraulic cylinder 1, 3, 5 to the second single-rod hydraulic cylinder 1, 3, 5, and the discharge flow rate of the closed circuit pumps 12, 14, 16, 18 is controlled so that the drive speed of the second single-rod hydraulic cylinder 1, 3, 5 does not change in accordance with the magnitude relationship between the cap chamber pressure and the rod chamber pressure during the period from when the closed circuit pumps 12, 14, 16, 18 are connected to the second single-rod hydraulic cylinder 1, 3, 5 to when the open circuit pumps 13, 15, 17, 19 start supplying hydraulic oil to the second single-rod hydraulic cylinder 1, 3, 5. As a result, immediately after switching the connection of the closed circuit pumps 12, 14, 16, 18 from the first single-rod hydraulic cylinders 1, 3, 5 to the second single-rod hydraulic cylinders 1, 3, 5, it is possible to make the drive speed of the second single-rod hydraulic cylinders 1, 3, 5 the same regardless of the pressure state of the second single-rod hydraulic cylinders 1, 3, 5.

[0132] In this embodiment, the other actuator is the hydraulic motor 7. This makes it possible to improve the responsiveness of the hydraulic motor 7 in a state in which the first single-rod hydraulic cylinders 1, 3, 5 are driven by the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19.

[0133] Furthermore, the construction machine 100 in this embodiment is equipped with operation levers 56a-56d capable of setting the drive direction and drive speed of the first single-rod hydraulic cylinder and the hydraulic motor 7, and the controller 57 determines the connection destinations of the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19 in response to inputs from the operation levers 56a-56d. This makes it possible to improve the responsiveness of the other actuators to inputs from the operation levers 56a-56d, which improves the responsiveness of the other actuators in a state in which the single-rod hydraulic cylinder is driven by the closed circuit pump and the open circuit pump.

[0134] In addition, the multiple actuators 1, 3, 5, 7 in this embodiment include second single-rod hydraulic cylinders 1, 3, 5, and the controller 57 controls the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19 so that the discharge of the closed circuit pumps 12, 14, 16, 18 is stopped in synchronization with the open circuit pumps 13, 15, 17, 19 when switching the connection destinations of the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19 from the first single-rod hydraulic cylinders 1, 3, 5 to the second single-rod hydraulic cylinders 1, 3, 5 that have received an operation input for performing an extension operation. The control circuit 40 controls the discharge flow rates of the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19, and controls the closed circuit switching valves 43a-43d, 45a-45d, 47a-47d, 49a-49d and the open circuit switching valves 44a-44d, 46a-46d, 48a-48d, 50a-50d so that the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19 are connected to the second single-rod hydraulic cylinders 1, 3, 5 at a timing after the discharge of the closed circuit pumps 12, 14, 16, 18 and the open circuit pumps 13, 15, 17, 19 has been stopped. This makes it possible to prevent the suction side of the closed circuit pumps 12, 14, 16, 18 from becoming negative pressure immediately before switching the connection destination of the closed circuit pumps 12, 14, 16, 18 from the first single-rod hydraulic cylinders 1, 3, 5 to another actuator.

[0135] (others) It should be noted that the present invention is not limited to the above-described embodiment, but includes various modified embodiments. For example, the above-described embodiment has been described in order to easily explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations.

[0136] In each of the above embodiments, the hydraulic drive unit 107 is mounted on a hydraulic excavator 100 as an example. However, the present invention is not limited to this. The hydraulic drive unit 107 according to the present invention can be used in construction machines other than the hydraulic excavator 1, for example, construction machines equipped with at least one single-rod hydraulic cylinder that can be driven by a hydraulic circuit, such as a hydraulic crane or a wheel loader.

[0137] In addition, in each of the above embodiments, a hydraulic pump equipped with a double-tilting slanting plate mechanism capable of controlling the inflow / outflow direction and flow rate was used as the first to fourth open circuit pumps 13, 15, 17, 19, but it is also possible to use a hydraulic pump equipped with a single-tilting slanting plate mechanism capable of discharging hydraulic oil in only one direction from the hydraulic oil tank 25 to the switching valves 44a, 44b, 44c, 44d, 46a, 46b, 46c, 46d, 48a, 48b, 48c, 48d, 50a, 50b, 50c, 50d.

[0138] Furthermore, in each of the above embodiments, each of the multiple hydraulic pumps 12, 13, ..., 19 equipped with a double tilt swash plate mechanism is connected to one engine 9 via the power transmission device 10, but it is also possible to prepare multiple fixed displacement hydraulic pumps as the hydraulic pumps 12, 13, ..., 19, connect electric motors whose rotation direction and rotation speed can be controlled to these fixed displacement hydraulic pumps, and control these electric motors by the controller 57 to control the discharge inlet / outlet direction and discharge flow rate of the hydraulic oil depending on the rotation direction and rotation speed of each fixed displacement hydraulic pump. [Explanation of symbols]

[0139] Reference Signs List 1...Boom cylinder (first single-rod hydraulic cylinder, second single-rod hydraulic cylinder), 1a...cap chamber, 1b...rod chamber, 1c...rod, 1d...cylinder tube, 1e...piston, 2...boom, 3...arm cylinder (first single-rod hydraulic cylinder, second single-rod hydraulic cylinder), 3a...cap chamber, 3b...rod chamber, 3c...rod, 3d...cylinder tube, 3e...piston, 4...arm, 5...bucket cylinder (first single-rod hydraulic cylinder, second single-rod hydraulic cylinder), 5a...cap chamber, 5b...rod chamber, 5c...rod, 5d...cylinder Tube, 5e... piston, 6... bucket, 7... swing motor (hydraulic motor), 8a, 8b... travel motor, 9... engine, 10... power transmission device, 11... charge pump, 12... first closed circuit pump, 12a... regulator, 12b... tilt angle sensor, 13... first open circuit pump, 13a... regulator, 13b... tilt angle sensor, 14... second closed circuit pump, 14a... regulator, 14b... tilt angle sensor, 15... second open circuit pump, 15a... regulator, 15b... tilt angle sensor, 16... third closed circuit pump, 16a... regulator, 16b... tilt angle sensor, 17... third Open circuit pump, 17a...regulator, 17b...tilt angle sensor, 18...fourth closed circuit pump, 18a...regulator, 18b...tilt angle sensor, 19...fourth open circuit pump, 19a...regulator, 19b...tilt angle sensor, 20...charge relief valve, 21-24...relief valve, 25...hydraulic oil tank, 26-29...charge check valve, 30a, 30b, 31a, 31b, 32a, 32b, 33a, 33b...relief valve, 34-36...flushing valve, 37a, 37b, 38a, 38b, 39a, 39b...relief valve, 40a, 40b, 41a, 41b, 42 a, 42b... Charge check valve, 43a to 43d, 45a to 45d, 47a to 47d, 49a to 49d... Switching valve (closed circuit switching valve), 44a to 44d, 46a to 46d, 48a to 48d, 50a to 50d... Switching valve (open circuit switching valve), 51a, 51b, 52a, 52b, 53a, 53b... Relief valve, 54, 55... Proportional switching valve, 56... Operating lever device, 56a to 56d... Operating lever, 57... Controller, 57a... Lever operation amount calculation unit, 57b... Actuator pressure calculation unit, 57c... Actuator allocation flow rate calculation unit, 64 to 67... Proportional valve, 70a, 70b,71a, 71b, 72a, 72b...pressure sensor, 100...hydraulic excavator (construction machine), 101a, 101b...traveling device, 102...lower traveling body, 103...upper rotating body, 104...cab, 105...rotating device, 106...front working machine, 107...hydraulic drive unit, 200-202...flow path, 202a...branch flow path, 203-205...flow path, 205a...branch flow path, 206-208... Flow path, 208a... branch flow path, 209 to 211... flow path, 211a... branch flow path, 212 to 224, 229... flow path, 301 to 304... connecting flow path, 305a to 305d, 306a to 306d, 307a to 307d, 308a to 308d... connecting flow path for open circuit, 309a to 309c... connecting flow path for closed circuit, 309d... connecting flow path, A, B, C, D... closed circuit, E, F, G, H... open circuit.

Claims

1. a closed circuit pump having two inlet / outlet ports through which hydraulic oil can flow in and out; an open circuit pump having an inlet port and an outlet port for hydraulic fluid; a sensor for detecting a signal that changes depending on the discharge flow rate of the closed circuit pump and the open circuit pump; a plurality of actuators including a first single rod hydraulic cylinder and other actuators, each actuator being connected to the closed circuit pump and the open circuit pump such that hydraulic fluid can be supplied from the closed circuit pump and the open circuit pump; a closed circuit switching valve that switches between conduction and interruption of a flow path of hydraulic oil between the closed circuit pump and the plurality of actuators so that the closed circuit pump is selectively connected in a closed circuit to any one of the plurality of actuators; an open circuit switching valve that switches between a conducting state and a blocking state of a flow path of hydraulic oil between the open circuit pump and the plurality of actuators so that the hydraulic oil discharged from the open circuit pump is selectively supplied to any one of the plurality of actuators; A construction machine including the closed circuit pump, the open circuit pump, the closed circuit switching valve, and a controller that controls the open circuit switching valve, When the controller performs control to switch the connection destination of the closed circuit pump to the other actuator from a state in which the closed circuit pump is connected to the first single-rod hydraulic cylinder and the open circuit pump is supplying hydraulic oil to the first single-rod hydraulic cylinder, A control is performed to stop the discharge of hydraulic oil from the closed circuit pump and the open circuit pump, and the closed circuit switching valve is controlled so that a connection destination of the closed circuit pump is switched from the first single-rod hydraulic cylinder to the other actuator at a timing after a signal corresponding to a state in which the discharge of hydraulic oil from the closed circuit pump has been stopped is obtained from the sensor and before a signal corresponding to a state in which the discharge of hydraulic oil from the open circuit pump has been stopped is obtained from the sensor. A construction machine characterized by:

2. 2. The construction machine according to claim 1, the other actuator is a second single rod hydraulic cylinder that receives an operation input to perform a contraction operation; a pressure sensor for detecting a cap chamber pressure and a rod chamber pressure of the second single-rod hydraulic cylinder; The controller: When the second single-rod hydraulic cylinder is contracted by the closed circuit pump and the open circuit pump, the open circuit switching valve is controlled so that a destination of the hydraulic oil from the open circuit pump is switched from the first single-rod hydraulic cylinder to the second single-rod hydraulic cylinder at a timing after a signal corresponding to a state in which the open circuit pump has stopped discharging the hydraulic oil is acquired from the sensor, and During the period from when the closed circuit pump is connected to the second single-rod hydraulic cylinder until when the open circuit pump starts to supply hydraulic oil to the second single-rod hydraulic cylinder, the discharge flow rate of the closed circuit pump is controlled so that the drive speed of the second single-rod hydraulic cylinder does not change according to the magnitude relationship between the cap chamber pressure and the rod chamber pressure. A construction machine characterized by:

3. 2. The construction machine according to claim 1, The other actuator is a hydraulic motor. A construction machine characterized by:

4. The construction machine according to claim 3, an operation lever capable of setting a drive direction and a drive speed of the first single-rod hydraulic cylinder and the hydraulic motor; The controller determines a connection destination of the closed circuit pump and the open circuit pump in response to an input from the operation lever. A construction machine characterized by:

5. 2. The construction machine according to claim 1, the plurality of actuators includes a second single rod hydraulic cylinder; When switching the connection destination of the closed circuit pump and the open circuit pump from the first single rod hydraulic cylinder to the second single rod hydraulic cylinder that has received an operation input to perform an extension operation, controlling a discharge flow rate of the closed circuit pump so that the discharge of the closed circuit pump is stopped in synchronization with the open circuit pump; The closed circuit switching valve and the open circuit switching valve are controlled so that the closed circuit pump and the open circuit pump are connected to the second single-rod hydraulic cylinder at a timing after the discharge of the closed circuit pump and the open circuit pump is stopped. A construction machine characterized by:

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