Construction machine

Abstract

To provide a construction machine that can restrain a decrease in operability in the event of failure of pressure sensors for measuring pressures of actuators for driving a working device when the actuators are driven by constituting closed circuits between the actuators and a plurality of hydraulic pumps.SOLUTION: When determining that actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b are faulty, a controller 57 calculates pseudo pressures of actuators 1, 3, and 5 on the basis of measurement values of attitude sensors 400-403, and calculates closed circuit switching valve front-back differential pressures by using the pseudo pressures instead of measurement values of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a construction machine equipped with a hydraulic circuit that drives a hydraulic actuator with pressure oil discharged from a hydraulic pump. [Background technology]

[0002] In recent years, in construction machinery such as hydraulic excavators, in order to reduce the throttling elements in the hydraulic circuit that drives hydraulic actuators such as hydraulic cylinders and to reduce fuel consumption, development has been underway of a hydraulic circuit (defined as a closed circuit) in which hydraulic oil is sent from a hydraulic drive source such as a hydraulic pump to the hydraulic actuator, and the hydraulic oil that has performed work in the hydraulic actuator is returned to the hydraulic pump instead of being returned to the tank. Furthermore, in an excavator that uses a closed circuit, a configuration has been proposed in which a pump is connected to the cap chamber side to compensate for the pressure-receiving area difference of a single-rod cylinder.

[0003] In these hydraulic circuits, a configuration has been proposed that allows multiple pumps to be redundantly connected to one actuator, thereby enabling combined operation using multiple actuators and increasing the speed when operating alone. In such hydraulic circuits in which the actuator to which the pump is connected can be changed, it is necessary to switch between connecting and disconnecting the pump and the actuator. At this time, if the pressure difference between the actuator and the pump is large, a shock will occur. Patent Document 1 describes a hydraulic drive device that connects the pump and the actuator after reducing the pressure difference between the actuator and the pump. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-203453 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the actuator pressure is measured by a pressure sensor, and the pump pressure is increased to the measured actuator pressure before the pump and actuator are connected. Therefore, if the pressure sensor is broken, the pump pressure is increased to a pressure different from the actual actuator pressure before the pump and actuator are connected, which may cause a shock when the pump and actuator are connected, resulting in reduced operability.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a construction machine that can suppress a decrease in operability when a pressure sensor that measures the pressure of an actuator fails when a closed circuit is formed between an actuator for driving a working device and a plurality of hydraulic pumps to drive the actuator. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a working device, an actuator for driving the working device, a plurality of variable displacement closed circuit pumps each having two inlet / outlet ports, a plurality of closed circuit switching valves capable of switching between communication and cut-off between the actuator and the plurality of closed circuit pumps, a posture sensor for detecting the posture of the working device, a plurality of closed circuit pump pressure sensors for detecting pressures of the plurality of closed circuit pumps, an actuator pressure sensor for detecting pressure of the actuator, an operation device for instructing operation of the actuator, and a controller for controlling the plurality of closed circuit switching valves and the plurality of closed circuit pumps in response to an input signal from the operation device, wherein when starting supply of hydraulic oil from one of the plurality of closed circuit pumps to the actuator, the controller controls one of the plurality of closed circuit switching valves corresponding to the one closed circuit pump among the plurality of closed circuit switching valves to close the one of the plurality of closed circuit switching valves. In a construction machine that controls one closed circuit pump so that a pressure difference across a closed circuit switching valve, which is the difference between a measurement value of one closed circuit pump pressure sensor corresponding to two or more closed circuit pumps and a measurement value of the actuator pressure sensor, is equal to or less than a predetermined first threshold value, and then opens the one closed circuit switching valve. With two or more closed circuit pumps out of the plurality of closed circuit pumps connected to the actuator, the controller determines whether or not the actuator pressure sensor has failed based on the measurement values ​​of two or more closed circuit pump pressure sensors out of the plurality of closed circuit pump pressure sensors corresponding to the two or more closed circuit pumps and the measurement value of the actuator pressure sensor, and if it determines that the actuator pressure sensor has failed, calculates a pseudo pressure of the actuator based on the measurement value of the attitude sensor, and calculates the pressure difference across the closed circuit switching valve using the pseudo pressure instead of the measurement value of the actuator pressure sensor.

[0008] According to the present invention configured as described above, it is possible to correctly determine whether or not the actuator pressure sensor has failed based on the comparison result between the measurement value of the actuator pressure sensor and the measurement values ​​of two or more closed circuit pump pressure sensors. Furthermore, when the actuator pressure sensor fails, the differential pressure across the closed circuit switching valve is calculated using the pseudo pressure of the actuator calculated according to the attitude of the working device instead of the measurement value of the failed pressure sensor. As a result, the shock generated when connecting the closed circuit pump to the actuator is suppressed, making it possible to prevent a decrease in operability. Effect of the Invention

[0009] According to the construction machine of the present invention, it is possible to suppress a decrease in operability when a pressure sensor that measures the pressure of an actuator that drives a working device breaks down. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a side view of 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] 5 is a time chart showing changes in state of the hydraulic drive system when a boom cylinder is extended in an embodiment of the present invention. [Diagram 5] 5 is a flowchart showing a part of a process of a pressure sensor failure detection unit in the embodiment of the present invention. [Figure 6] 11A to 11C are diagrams illustrating a change in posture of the hydraulic excavator when an arm cylinder is extended in an embodiment of the present invention. [Figure 7] 8 is a diagram showing the relationship between the stroke of the arm cylinder and the pressure in a cap chamber in the embodiment of the present invention. FIG. [Figure 8] 5 is a flowchart showing a process of a pressure sensor fault diagnosis input generating unit in the embodiment of the present invention. [Figure 9] 4 is a time chart showing a change in state of the hydraulic drive system in response to an input from the pressure sensor fault diagnosis input generating device in the 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 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 side view of a hydraulic excavator in this embodiment, and FIG. 2 is a hydraulic circuit diagram of a hydraulic drive system mounted on the hydraulic excavator in this embodiment.

[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 rotatably attached to the lower traveling body 102. A cab 104 for an operator to ride in is provided on the upper rotating body 103. The upper rotating body 103 is attached to the lower traveling body 102 via a rotating device 105 so as to be rotatable downward. The traveling devices 101a, 101b are driven by traveling motors 8a, 8b (shown in Fig. 2), and the rotating device 105 is driven by a rotating motor 7 (shown in Fig. 2).

[0014] A front working machine 106, which is a working device for performing excavation work, for example, is attached at its base end to the front of the upper rotating body 103 so as to be rotatable in the vertical direction. The front working machine 106 is equipped with a boom 2, the base end of which is connected to the front of the upper rotating body 103 so as to be rotatable in the vertical direction. 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 boom cylinder 1 has a tip end of a rod 1c connected to the upper rotating body 103, and a base end of a cylinder tube 1d 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, thereby applying a load due to hydraulic pressure and moving 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, thereby applying a load due to hydraulic pressure and moving 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 is provided with 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 is also provided with 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 / retract according to the supply direction of the hydraulic oil. The hydraulic excavator 100 in this embodiment is a backhoe excavator, and is configured such that the bucket 6 is pulled back rearward by extending the arm cylinder 3 or the bucket cylinder 5.

[0021] The boom 2 is provided with an attitude sensor 400 capable of measuring an attitude angle. The arm 4 is provided with an attitude sensor 401 capable of measuring an attitude angle. The bucket 6 is provided with an attitude sensor 402 capable of measuring an attitude angle. The upper rotating body 103 is provided with an attitude sensor 403 capable of measuring the rotation angle and the attitude of the upper rotating body. The attitude sensor 403 can also measure the attitude angle of the upper rotating body 103 when it is parked on a slope.

[0022] As shown in Fig. 2, the hydraulic drive system 107 includes four closed circuit pumps connected in a closed circuit and four open circuit pumps connected in an open circuit for three types of single-rod hydraulic cylinders and three types of hydraulic motors, and when driving a single-rod hydraulic cylinder, one closed circuit pump and one open circuit pump are combined to control the flow rate. In addition, each of these hydraulic pumps is provided with a switching valve, and a configuration is made in which multiple closed circuit pumps and multiple open circuit pumps can be joined to one single-rod hydraulic cylinder. Furthermore, when joining to one single-rod hydraulic cylinder, the controller controls the switching valve 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] 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 device 56 installed in the cab 101. The extension and contraction operations of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, i.e., the operation direction and operation speed, are controlled by the levers 56a to 56c of the operating device 56. The direction and amount of operation of 56d are indicated.

[0025] Furthermore, the hydraulic drive system 107 includes an engine 9 which is a power source. The engine 9 is configured, for example, with predetermined gears and is connected to a power transmission system 10 for distributing 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, and 18 are variable displacement closed circuit pumps equipped with a bi-directional 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, and 18a that adjust the tilt angle (inclination angle) of the bi-directional tilting swash plate that constitutes the bi-directional tilting swash plate mechanism. The regulators 12a, 14a, 16a, and 18a adjust the tilt angle of the swash plate of the corresponding closed circuit pump 12, 14, 16, and 18 in response to an operation signal output from the controller 57, thereby controlling the flow rate of hydraulic oil discharged from the closed circuit pump 12, 14, 16, and 18. When supplied with hydraulic oil, the closed circuit pumps 12, 14, 16, and 18 function as hydraulic motors.

[0027] The hydraulic pumps 13, 15, 17, and 19 are variable displacement open circuit pumps equipped with 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 that adjust the tilt angle (inclination angle) of the one-sided tilting swash plate that constitutes the one-sided tilting swash plate mechanism. The regulators 13a, 15a, 17a, and 19a adjust the tilt angle of the swash plate of the corresponding open circuit pumps 13, 15, 17, and 19 in response to an operation signal output from the controller 57, thereby controlling the flow rate of hydraulic oil discharged from the open circuit pumps 13, 15, 17, and 19.

[0028] Furthermore, the tilting swash plate mechanisms of the hydraulic pumps 12, 13, ..., 19 may be provided with a means (not shown) for detecting the tilt angle, which 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, the hydraulic pumps 12, 13, ..., 19 may be provided with a means for measuring the control pressure of the regulator, and the tilting state of the swash plate and the discharge flow rate of each pump may be calculated from the regulator control pressure.

[0029] In addition, the closed circuit pumps 12, 14, 16, and 18 are structured such that the regulator generates a 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 open circuit pumps 13, 15, 17, and 19 control the tilt angle of the swash plate in one direction, so the regulator's driving force acts only in the direction to maximize the tilt angle, and the return to the minimum angle relies on the restoring force of a spring. Therefore, the closed circuit pumps 12, 14, 16, and 18 have a higher responsiveness when controlling the tilt angle in the direction to reduce the discharge volume.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] 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 provided on 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.

[0048] 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.

[0049] 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.

[0050] 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 provided on 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.

[0051] 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.

[0052] 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.

[0053] 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 provided on a branch flow path 208a, which is a pipe branched off 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.

[0054] 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.

[0055] 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.

[0056] 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 provided on 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.

[0057] 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.

[0058] The hydraulic drive system 107 is composed of closed circuits A, B, C, D in which the 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 from one input / output port of the hydraulic pump to the other input / output port via the actuator, and further composed of open circuit pumps 13, 15, 17, 19, and switching valves 44a, 44b, 44c, 44d, 46a, 46b, 46c, 46d, 48a, 48b, 48c, 48d, 50a, 50b, 50c, 50d, which are connected to one input / output port of the hydraulic pump and to the hydraulic oil tank 25 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 each.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] The pressure sensor 80a connected to the flow path 200 measures the pressure of the flow path 200 and inputs it to the controller 57. The pressure sensor 80a measures the pressure of one of the input / output ports of the first closed circuit pump 12 by measuring the pressure of the flow path 200. The pressure sensor 80b connected to the flow path 201 measures the pressure of the flow path 201 and inputs it to the controller 57. The pressure sensor 80b measures the pressure of the other input / output port of the first closed circuit pump 12 by measuring the pressure of the flow path 201. The pressure sensor 81 connected to the flow path 202 measures the pressure of the flow path 202 and inputs it to the controller 57. The pressure sensor 81 measures the pressure of the flow path 202 to measure the pressure of the discharge port of the first open circuit pump 13.

[0071] The pressure sensor 82a connected to the flow path 203 measures the pressure of the flow path 203 and inputs it to the controller 57. The pressure sensor 82a measures the pressure of one of the input / output ports of the second closed circuit pump 14 by measuring the pressure of the flow path 203. The pressure sensor 82b connected to the flow path 204 measures the pressure of the flow path 204 and inputs it to the controller 57. The pressure sensor 82b measures the pressure of the other input / output port of the second closed circuit pump 14 by measuring the pressure of the flow path 204. The pressure sensor 83 connected to the flow path 205 measures the pressure of the flow path 205 and inputs it to the controller 57. The pressure sensor 83 measures the pressure of the flow path 205 to measure the pressure of the discharge port of the second open circuit pump 15.

[0072] The pressure sensor 84a connected to the flow path 206 measures the pressure of the flow path 206 and inputs it to the controller 57. The pressure sensor 84a measures the pressure of one of the input / output ports of the third closed circuit pump 16 by measuring the pressure of the flow path 206. The pressure sensor 84b connected to the flow path 207 measures the pressure of the flow path 207 and inputs it to the controller 57. The pressure sensor 84b measures the pressure of the flow path 207 to measure the pressure of the other input / output port of the third closed circuit pump 16. A pressure sensor 85 connected to the flow path 208 measures the pressure of the flow path 208 and inputs the pressure to the controller 57. The pressure sensor 85 measures the pressure of the flow path 208, thereby measuring the pressure of the discharge port of the third open circuit pump 17.

[0073] The pressure sensor 86a connected to the flow path 209 measures the pressure of the flow path 209 and inputs it to the controller 57. The pressure sensor 86a measures the pressure of one of the input / output ports of the fourth closed circuit pump 18 by measuring the pressure of the flow path 209. The pressure sensor 86b connected to the flow path 210 measures the pressure of the flow path 210 and inputs it to the controller 57. The pressure sensor 86b measures the pressure of the other input / output port of the fourth closed circuit pump 18 by measuring the pressure of the flow path 210. The pressure sensor 87 connected to the flow path 211 measures the pressure of the flow path 211 and inputs it to the controller 57. The pressure sensor 87 measures the pressure of the flow path 211 to measure the pressure of the discharge port of the fourth open circuit pump 19.

[0074] Pressure sensor 70a connected to flow path 212 measures the pressure of flow path 212 and inputs the result to controller 57. Pressure sensor 70a measures the pressure of flow path 212, thereby measuring the pressure of cap chamber 1a of boom cylinder 1. Pressure sensor 70b connected to flow path 213 measures the pressure of flow path 213, thereby inputting the result to controller 57. Pressure sensor 70b measures the pressure of flow path 213, thereby measuring the pressure of rod chamber 1b of boom cylinder 1.

[0075] The pressure sensor 71a connected to the flow path 214 measures the pressure of the flow path 214 and inputs it to the controller 57. The pressure sensor 71a measures the pressure of the flow path 214, thereby measuring the pressure of the cap chamber 3a of the arm cylinder 3. The pressure sensor 71b connected to the flow path 215 measures the pressure of the flow path 215, thereby inputting it to the controller 57. The pressure sensor 71b measures the pressure of the flow path 215, thereby measuring the pressure of the rod chamber 3b of the arm cylinder 3.

[0076] The pressure sensor 72a connected to the flow path 216 measures the pressure of the flow path 216 and inputs the pressure to the controller 57. The pressure sensor 72a measures the pressure of the flow path 216, thereby measuring the pressure of the cap chamber 5a of the bucket cylinder 5. The pressure sensor 72b connected to the flow path 217 measures the pressure of the flow path 217, thereby inputting the pressure to the controller 57. The pressure sensor 72b measures the pressure of the flow path 217, thereby measuring the pressure of the rod chamber 5b of the bucket cylinder 5.

[0077] Pressure sensor 73a connected to flow path 218 measures the pressure of flow path 218 and inputs it to controller 57. Pressure sensor 73a measures the pressure of one input / output port of the swing motor 7 by measuring the pressure of flow path 218. Pressure sensor 73b connected to flow path 219 measures the pressure of flow path 219 and inputs it to controller 57. Pressure sensor 73b measures the pressure of flow path 219 to measure the pressure of the other input / output port of the swing motor 7.

[0078] 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 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.

[0079] 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 also performs the above-mentioned pressure-receiving area control for the arm cylinder 3 and the bucket cylinder 5.

[0080] 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 to 50a, 43b to 50b, 43c to 50c, 43d, to 50d to supply hydraulic oil discharged from the same number of open circuit pumps 13, 15, 17, and 19 as the corresponding closed circuit pumps 12, 14, 16, and 18 to at least one of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5 being operated.

[0081] Furthermore, the boom lever 56a of the operating device 56 gives the controller 57 a command value for the extension direction and extension speed of the boom cylinder 1. The arm lever 56b gives the controller 57 a command value for the extension direction and extension speed of the arm cylinder 3, and the bucket lever 56c gives the controller 57 a command value for the extension direction and extension speed of the bucket cylinder 5. Furthermore, the swing lever 56d gives the controller 57 a command value for the rotation direction and rotation speed of the swing motor 7. The operating device 56 is also provided with an operating lever (not shown) that gives the controller 57 a command value for the rotation direction and rotation speed of the travel motors 8a, 8b. A display device 58 is connected to the controller 57 to display the state of the vehicle body to the operator.

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

[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] The pressure calculation unit 57b calculates the pressure of each part from the measurement values ​​of the pressure sensors 70a to 73b, 80 to 87 provided in each part, and inputs the calculated pressure to the actuator allocated flow rate calculation unit 57c and the display device 58.

[0085] The pressure sensor failure detection unit 57d detects a failure of a pressure sensor according to the flowchart shown in Figure 5 from the measurement values ​​of the pressure sensors 70a to 73b, 80 to 87 and the connection state between the pressure sensors determined from the command values ​​to the switching valves 43a to 49d, and inputs the detected failure to the actuator allocated flow rate calculation unit 57c and the display device 58.

[0086] The pseudo pressure calculation unit 57e calculates the pseudo pressures of the actuators 1, 3, and 5 based on the measurement values ​​of the attitude sensors 400 to 403, and inputs the calculated pseudo pressures to the actuator allocated flow rate calculation unit 57c and the display device 58.

[0087] Actuator allocated flow rate calculation unit 57c normally calculates command values ​​for switching valves 43a-50d, proportional valves 64-67, and regulators 12a-19a based on inputs from lever operation amount calculation unit 57a and pressure calculation unit 57b. On the other hand, when pressure sensor failure detection unit 57d detects a failure of a pressure sensor, it calculates command values ​​for switching valves 43a-50d, proportional valves 64-67, and regulators 12a-19a based on inputs from pseudo pressure calculation unit 57e and lever operation amount calculation unit 57a.

[0088] Display device 58 displays the measurement values ​​of each pressure sensor input from pressure calculation unit 57b, the failure state of each pressure sensor input from pressure sensor failure detection unit 57d, and the pseudo pressure input from pseudo pressure calculation unit 57e.

[0089] The pressure sensor fault diagnosis input generating device 59 connected to the controller 57 is a device for improving the accuracy of fault detection by the pressure sensor fault detecting unit 57d. The pressure sensor fault diagnosis input generating device 59 outputs a lever operation signal to the lever operation amount calculating unit 57a for making the hydraulic excavator 100 take a predetermined posture (diagnosis posture) suitable for diagnosing the pressure sensor based on the measurement values ​​of the posture sensors 400 to 403, and outputs an open command to the switching valves 43a to 50d in a state where the hydraulic excavator 100 is stationary in the diagnosis posture. In this embodiment, the pressure sensor fault diagnosis input generating device 59 is configured as a device independent of the controller 57, but may be configured as a part of the function of the controller 57. Details of the pressure sensor fault diagnosis input generating device 59 will be described later.

[0090] Next, the operation of the hydraulic drive device 107 shown in FIG. 2 will be described. (1) When not in operation In FIG. 2, when levers 56a to 56d are not operated, hydraulic pumps 12 to 19 are controlled to the minimum tilt angle, switching valves 43a to 50d are all closed, and boom cylinder 1, arm cylinder 3, bucket cylinder 5, and swing motor 7 are held in a stopped state. (2) When the boom is raised Fig. 4 shows the state change of the hydraulic drive unit 107 when the boom cylinder 1 is extended. Fig. 4 shows the measurement values ​​of the pressure sensors 70a, 80a, 82a, 84a, and 86a when the pressure sensor 70a is normal and when the pressure sensor 70a has failed and the measurement value has drifted to the positive side.

[0091] From time t0 to time t1, the input to the boom lever 56a is 0, and the boom cylinder 1 is stationary.

[0092] From time t1 to time t5, the input of the boom lever 56a is increased to the maximum command value for extending the boom cylinder 1. As the input of the boom lever 56a increases, the number of pumps connected increases. The switching valves 43a, 45a, 47a, and 49a open at the same time that the closed circuit pumps 12, 14, 16, and 18 are connected to the boom cylinder 1.

[0093] At time t1, the boom lever 56a is input. At this time, before the first closed circuit pump 12 and the boom cylinder 1 are connected, the discharge pressure of the first closed circuit pump 12 is boosted to the pressure of the cap chamber 1a of the boom cylinder 1, and then the switching valve 43a opens. The boosting operation is performed based on values ​​measured by the pressure sensors 70a and 80a, and the switching valve 43a opens after the difference between the measurement value of the pressure sensor 80a and the measurement value of the pressure sensor 70a becomes equal to or less than a threshold value (first threshold value).

[0094] When the pressure sensor 70a is normal, the discharge pressure of the first closed circuit pump 12 measured by the pressure sensor 80a immediately before the switching valve 43a opens due to the pressure boost process is sufficiently boosted. When the discharge flow rate of the first closed circuit pump 12 increases from time t1 to time t2, the measurement value of the pressure sensor 80a becomes larger than the measurement value of the pressure sensor 70a by the amount of the pressure loss occurring when passing through the pipeline and the switching valve 43a.

[0095] If the pressure sensor 70a fails and the measurement value drifts to the positive side, the discharge pressure of the first closed circuit pump 12 measured by the pressure sensor 80a immediately before the switching valve 43a opens due to the pressure boost process will be higher than the pressure in the cap chamber 1a of the boom cylinder 1. This will cause a shock when the switching valve 43a is opened.

[0096] From time t2 to time t3, the second closed circuit pump 14 is also pressurized and then the switching valve 45a is opened, but if the pressure sensor 70a fails, the pressure is excessively increased, causing a shock when each switching valve is opened. Since three or more pressure sensors are connected to the same pipe line until time t3, a failure of the pressure sensor 70a is detected by processing by the pressure sensor failure detection unit 57d described later.

[0097] From time t3 to time t5, a failure of the pressure sensor 70a is detected, so the pseudo pressure calculated by the pseudo pressure calculation unit 57e is used instead of the measurement value of the pressure sensor 70a to calculate the differential pressure across the switching valves 47a, 49a. By using the pseudo pressure instead of the measurement value of the failed pressure sensor 70a, it is possible to prevent the closed circuit pumps 16, 18 from being excessively pressurized, and therefore it is possible to suppress shock when the switching valves 47a, 49a are opened.

[0098] FIG. 5 is a flowchart showing a part of the process of the pressure sensor failure detection unit 57d. FIG. 5 shows only the process of detecting a failure of the pressure sensor 70a of the boom cylinder 1. The failure detection of the pressure sensor 70a of the boom cylinder 1 is performed by comparing the measured value of the pressure sensor 70a with the measured values ​​of the pressure sensors 80a, 82a, 84a, 86a of the closed circuit pumps 12, 14, 16, 18 connected to the boom cylinder 1 through the same pipe line and the pressure sensors 81, 83, 85, 87 of the open circuit pumps 13, 15, 17, 19. Note that FIG. 5 omits the process of comparing the measured value of the pressure sensor 70a with the measured values ​​of the pressure sensors 81, 83, 85, 87 of the open circuit pumps 13, 15, 17, 19. Each step of FIG. 5 will be described below in order.

[0099] The pressure sensor failure detection unit 57d first determines whether the boom cylinder 1 and the closed circuit pump 12 are connected (step S11). If the result of the determination in step S11 is YES, the process proceeds to step S21 described later. If the result of the determination in step S11 is YES, the process calculates the absolute value (differential pressure) of the difference between the measurement values ​​of the pressure sensors 70a and 80a (step S12). Following step S12, the process determines whether the differential pressure is smaller than a predetermined threshold value Plim (step S13). Here, the threshold value Plim is a value that is determined in advance in consideration of the measurement error of the pressure sensor and the flow rate pressure loss characteristics. In addition, although the threshold value Plim is a constant value in this embodiment, it may be a value that changes depending on the pump discharge flow rate. If the result of the determination in step S13 is NO, the process proceeds to step S21 described later. If the result of the determination in step S13 is NO, the process adds 1 to the failure flag of the pressure sensor 70a (step S14).

[0100] Following step S14, it is determined whether or not the boom cylinder 1 and the closed circuit pump 14 are connected (step S21). If the determination in step S21 is YES, the absolute value of the difference between the measurement values ​​of the pressure sensors 70a, 82a (differential pressure) is calculated (step S22). Following step S22, it is determined whether or not the differential pressure is smaller than a threshold value Plim (step S23). If the determination in step S23 is NO, the process proceeds to step S31 described below. If the determination in step S23 is NO, 1 is added to the failure flag of the pressure sensor 70a (step S24).

[0101] Following step S24, it is determined whether or not the boom cylinder 1 and the closed circuit pump 16 are connected (step S31). If the determination in step S31 is YES, the absolute value of the difference between the measurement values ​​of the pressure sensors 70a, 84a (differential pressure) is calculated (step S32). Following step S32, it is determined whether or not the differential pressure is smaller than a threshold value Plim (step S33). If the determination in step S33 is NO, the process proceeds to step S41 described below. If the determination in step S33 is NO, 1 is added to the failure flag of the pressure sensor 70a (step S34).

[0102] Following step S34, it is determined whether or not the boom cylinder 1 and the closed circuit pump 18 are connected (step S41). If the determination in step S41 is YES, the absolute value of the difference between the measurement values ​​of the pressure sensors 70a, 86a (differential pressure) is calculated (step S42). Following step S42, it is determined whether or not the differential pressure is smaller than a threshold value Plim (step S43). If the determination in step S43 is NO, the process proceeds to step S51 described below. If the determination in step S43 is NO, 1 is added to the failure flag of the pressure sensor 70a (step S44).

[0103] Following step S44, it is determined whether the failure flag is greater than 1 (step S51). If the determination in step S51 is NO, the flow ends. If the determination in step S51 is YES, the pressure sensor 70a is determined to be malfunctioning (step S52), and the flow ends.

[0104] The above has described the processing related to detecting a fault in pressure sensor 70a. However, pressure sensor fault detection unit 57d can also detect faults in the other actuator pressure sensors 70b, 71a, 71b, 72a, 72b, 73a, 73b and pump pressure sensors 80a, 80b, 81, 82a, 82b, 83, 84a, 84b, 85, 86a, 86b, 87 by comparing the measurement values ​​for each combination of two pressure sensors included in three or more pressure sensors that detect the pressure in a connected pipeline.

[0105] With reference to FIG. 4, a failure detection operation will be described for the cases where pressure sensor 70a that measures the cap chamber pressure of boom cylinder 1 is normal and where it is broken.

[0106] <When the pressure sensor 70a is normal> In the state from time t1 to time t5, with the switching valves 43a, 45a, 47a, 49a open, it is determined in steps S11, S21, S31, and S41 whether the boom cylinder 1 and the closed circuit pumps 12, 14, 16, and 18 are connected. If they are connected, the differential pressure between the pressure of the boom cylinder 1 and the pressure of the pumps 12, 14, 16, and 18 is calculated in steps S12, S22, S32, and S42. At this time, the pressure sensor 70a is normal, and the differential pressure with respect to the pump pressure is smaller than the threshold value Plim, so the failure flag of the pressure sensor 70a is not counted up. In other words, since the failure flag is zero, the pressure sensor 70a is not determined to be broken in step S51.

[0107] <When the pressure sensor 70a fails> In the state from time t1 to time t5, with the switching valves 43a, 45a, 47a, and 49a open, it is determined in steps S11, S21, S31, and S41 whether the boom cylinder 1 and the closed circuit pumps 12, 14, 16, and 18 are connected. If they are connected, the differential pressure between the boom cylinder 1 and the pumps 12, 14, 16, and 18 is calculated in steps S12, S22, S32, and S42. At this time, the pressure sensor 70a is broken, and the differential pressure with respect to the pump pressure becomes greater than the threshold value Plim, so the failure flag of the pressure sensor 70a is counted up in steps S14, S24, S34, and S44. After time t2, in a situation where two or more pumps are connected to the boom cylinder 1, the failure flag of the pressure sensor 70a becomes greater than 1, so that the pressure sensor 70a is determined to be broken in step S51.

[0108] Next, a description will be given of the processing of the pseudo pressure calculation unit 57e shown in Fig. 3. The pseudo pressure calculation unit 57e determines the pseudo pressures of the actuators 1, 3, and 5 that drive the work implement 106 based on the attitude of the hydraulic excavator 100. A method of determining the pseudo pressure will be described below using the arm cylinder 3 as an example.

[0109] Fig. 6 shows the change in posture of the hydraulic excavator 100 when the arm cylinder 3 is extended, and Fig. 7 shows the relationship between the stroke of the arm cylinder 3 and the cap chamber 3a. In the postures (a) to (b) of Fig. 6, the pressure in the cap chamber 3a of the arm cylinder 3 is constant as shown in Fig. 7. This is because the force supporting the arm 4 and the bucket 6 against gravity acts on the rod chamber 3b of the arm cylinder 3, causing the pressure in the rod chamber 3b to be higher than the pressure in the cap chamber 3a, and the cap chamber 3a on the low-pressure side is maintained at the charge pressure by the flushing valve 34. Therefore, in the stroke range of the postures (a) to (b), the pseudo pressure in the cap chamber 3a of the arm cylinder 3 may be set to the charge pressure.

[0110] In the postures (b) to (c) of FIG. 6, the pressure in the cap chamber 3a of the arm cylinder 3 increases according to the stroke as shown in FIG. 7. This is to exert a force necessary to support the arm 4 and the bucket 6 against gravity. At this time, the pressure differs depending on whether the bucket 6 is empty or fully loaded. Taking this characteristic into consideration, the pseudo pressure is set to a value greater than the pressure in the empty state (unloaded state) with respect to the cylinder stroke so that the difference between the pseudo pressure and the actual pressure is small even in the loaded state. Note that, in this embodiment, the boom cylinder 1, the bucket cylinder 5, and the upper rotating body 103 are in a constant posture as shown in FIG. 6, but a pseudo pressure table is also provided for cases where the postures of the actuators other than the arm cylinder 3 and the upper rotating body 103 are different.

[0111] 3 is provided in the controller 57, so that even if the actuator pressure sensors 70a-73b fail, the hydraulic excavator 100 can be operated without a significant decrease in operability by calculating the differential pressure across the switching valves 43a-50d using the pseudo pressure. Furthermore, the information displayed on the display device 58 allows the operator to recognize the failure state of the pressure sensor, and prompts the operator to repair the pressure sensor early.

[0112] The pressure sensor fault diagnosis input generating device 59 shown in FIG. 3 makes the hydraulic excavator 100 take a predetermined diagnostic posture (for example, a posture in which the pressure in the cap chamber 3a of the arm cylinder 3 is low as shown in FIG. 6(a) or a posture in which the pressure in the cap chamber 3a of the arm cylinder 3 is high as shown in FIG. 6(c)) to compare the outputs of a normal pressure sensor and a faulty pressure sensor at various pressure levels, thereby improving the probability of fault detection. Also, unlike detection during operation, the accuracy of fault detection can be improved by comparing the outputs of the pressure sensors when the hydraulic excavator 100 is stationary in the diagnostic posture, that is, when the influence of the flow rate pressure loss characteristic is removed and the pressure in the pipeline is made uniform. In this embodiment, the pressure sensor fault diagnosis input generating device 59 is configured as a device independent of the controller 57, but it may be configured as a part of the functions of the controller 57.

[0113] 8 is a flowchart showing the processing of the pressure sensor fault diagnosis input generating device 59. The processing of this flow is carried out in a state where the hydraulic excavator 100 is placed on a horizontal ground surface. Each step will be described in order below.

[0114] The pressure sensor fault diagnosis input generating device 59 first calculates the stroke (detection stroke) of the boom cylinder 1 from the measurement values ​​of the posture sensors 400 to 403, and judges whether or not the detection stroke coincides with the stroke (diagnosis stroke) of the boom cylinder 1 in the diagnosis posture (step S101). If the result of the judgment in step S101 is NO, the input of the boom lever 56a is adjusted so that the difference between the detection stroke and the diagnosis stroke becomes small (step S102), and the process returns to step S101. Here, the input of the boom lever 56a is adjusted to a value obtained by multiplying the difference between the diagnosis stroke and the detection stroke by a predetermined gain, for example. In addition, the predetermined gain is set to a small value such that two or more closed circuit pumps are not connected to the boom cylinder 1. This allows the posture of the boom 2 to be gradually changed toward the diagnosis posture.

[0115] If the answer is YES in step S101, the stroke (detection stroke) of the arm cylinder 3 is calculated from the measurement values ​​of the posture sensors 400 to 403, and it is determined whether the detection stroke coincides with the stroke (diagnosis stroke) of the arm cylinder 3 in the diagnosis posture (step S103). If the answer is NO in step S103, the input of the arm lever 56b is adjusted so that the difference between the detection stroke and the diagnosis stroke becomes small (step S104), and the process returns to step S103. Here, the input of the arm lever 56b is adjusted to a value obtained by multiplying the difference between the diagnosis stroke and the detection stroke by a predetermined gain, for example. In addition, the predetermined gain is set to a small value such that two or more closed circuit pumps are not connected to the arm cylinder 3. This allows the posture of the arm 4 to be gradually changed toward the diagnosis posture.

[0116] If the answer to the question in step S103 is YES, the stroke (detection stroke) of the bucket cylinder 5 is calculated from the measured values ​​of the attitude sensors 400 to 403, and it is determined whether or not the detection stroke coincides with the stroke (diagnosis stroke) of the bucket cylinder 5 in the diagnosis attitude (step S105). If the answer to the question in step S105 is NO, the input of the bucket lever 56c is adjusted so that the difference between the detection stroke and the diagnosis stroke becomes small (step S106), and the process returns to step S105. Here, the input of the bucket lever 56c is adjusted to a value obtained by multiplying the difference between the diagnosis stroke and the detection stroke by a predetermined gain, for example. In addition, the predetermined gain is set to a small value such that two or more closed circuit pumps are not connected to the bucket cylinder 5. This allows the attitude of the bucket 6 to be gradually changed toward the diagnosis attitude.

[0117] If the result of the determination in step S105 is YES, an open command is output to the switching valves 43a, 44a, 45a, 46a, 47a, 48a, 49a, and 50a (step S107). As a result, with the hydraulic excavator 100 stationary in the diagnosis posture and the closed circuit pumps 12, 14, 16, and 18 connected to the boom cylinder 1, the pressure sensor failure detection unit 57d performs failure diagnosis processing (step S108).

[0118] Following step S108, a close command is output to the switching valves 43a, 44a, 45a, 46a, 47a, 48a, 49a, and 50a (step S109), and an open command is output to the switching valves 43b, 44b, 45b, 46b, 47b, 48b, 49b, and 50b (step S110). As a result, with the hydraulic excavator 100 stationary in the diagnosis posture and the closed circuit pumps 12, 14, 16, and 18 connected to the arm cylinder 3, a failure diagnosis process is performed by the pressure sensor failure detection unit 57d (step S111).

[0119] Following step S111, a close command is output to the switching valves 43b, 44b, 45b, 46b, 47b, 48b, 49b, and 50b (step S112), and an open command is output to the switching valves 43c, 44c, 45c, 46c, 47c, 48c, 49c, and 50c (step S113). As a result, with the hydraulic excavator 100 stationary in the diagnosis posture and the closed circuit pumps 12, 14, 16, and 18 connected to the bucket cylinder 5, a failure diagnosis process is performed by the pressure sensor failure detection unit 57d (step S114).

[0120] Following step S114, a close command is output to the switching valves 43c, 44c, 45c, 46c, 47c, 48c, 49c, and 50c (step S115), and an open command is output to the switching valves 43d, 44d, 45d, 46d, 47d, 48d, 49d, and 50d (step S116). As a result, with the excavator 100 stationary in the diagnosis posture and the closed circuit pumps 12, 14, 16, and 18 connected to the swing motor 7, a failure diagnosis process is performed by the pressure sensor failure detection unit 57d (step S117).

[0121] Following step S117, a close command is output to the switching valves 43d, 44d, 45d, 46d, 47d, 48d, 49d, and 50d (step S118), and the flow ends.

[0122] Fig. 9 shows state changes of the hydraulic drive system 107 in response to input from the pressure sensor fault diagnosis input generating device 59. Fig. 9 shows only the operation during fault diagnosis of the pressure sensor 70a on the cap side of the boom cylinder 1. It is also assumed that the arm 4 and the bucket 6 are already in the diagnostic posture.

[0123] From time t10 to time t11, the pressure sensor fault diagnosis input generating device 59 is not activated, the input of the boom lever 56a is 0, and the boom cylinder 1 is stationary.

[0124] At time t11, pressure sensor fault diagnosis input generating device 59 starts, and adjusts the input of boom lever 56a until the stroke of boom cylinder 1 reaches the diagnosis stroke toward time t12. Shortly after the input of boom lever 56a starts at time t11, switching valve 43a opens and closed circuit pump 12 is connected to boom cylinder 1. The input of boom lever 56a becomes smaller as the stroke of boom cylinder 1 approaches the diagnosis stroke.

[0125] When the stroke of boom cylinder 1 reaches the diagnosis stroke at time t12, changeover valve 43a closes, and from time t12 to time t13, changeover valves 43a, 45a, 47a, and 49a open.

[0126] From time t13 to time t14, a failure diagnosis of the pressure sensor 70a is performed, and from time t14 to time t15, the switching valves 43a, 45a, 47a, and 49a are closed.

[0127] (summary) In this embodiment, the working device 106, actuators 1, 3, and 5 that drive the working device 106, a plurality of variable displacement closed circuit pumps 12, 14, 16, and 18 each having two inlet / outlet ports, a plurality of closed circuit switching valves 43a to 43d, 45a to 45d, and 47a to 47d that can switch between communication or cut-off between the actuators 1, 3, and 5 and the plurality of closed circuit pumps 12, 14, 16, and 18, attitude sensors 400 to 403 that detect the attitude of the working device 106, and a plurality of closed circuit pump pressure sensors 80a, 80b, 82a, 82b, 82c, 82d, 82e, 82f, 82g, 82h, 82h, 82i, 82j ... and a controller 57 for controlling the closed circuit switching valves 43a to 43d, 45a to 45d, 47a to 47d and the closed circuit pumps 12, 14, 16, 18 in response to an input signal from the operation device 56. The controller 57 controls the actuators 1, 3, 5 from one of the closed circuit pumps 12, 14, 16, 18. In a construction machine in which, when starting the supply of hydraulic oil to 3, 5, one closed circuit switching valve corresponding to the one closed circuit pump among a plurality of closed circuit switching valves 43a to 43d, 45a to 45d, 47a to 47d is closed, the one closed circuit pump is controlled so that a pressure difference across the closed circuit switching valve, which is a difference between a measurement value of a closed circuit pump pressure sensor corresponding to the one closed circuit pump and a measurement value of an actuator pressure sensor 70a, 70b, 71a, 71b, 72a, 72b, becomes equal to or less than a predetermined first threshold value, and then the one closed circuit switching valve is opened. When two or more of the pumps 12, 14, 16, 18 are connected to the actuators 1, 3, 5, a determination is made as to whether or not the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b have failed based on the measurement values ​​of two or more of the closed-circuit pump pressure sensors 80a, 80b, 82a, 82b, 84a, 84b, 86a, 86b corresponding to the two or more closed-circuit pumps and the measurement values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, and a determination is made as to whether or not the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b have failed based on the measurement values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b.When 71b, 72a, and 72b are determined to be faulty, the pseudo pressures of the actuators 1, 3, and 5 are calculated based on the measurement values ​​of the attitude sensors 400 to 403, and the differential pressure across the closed circuit switching valve is calculated using the pseudo pressures instead of the measurement values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b.

[0128] According to the present embodiment configured as described above, it is possible to correctly determine the failure of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, 73a, 73b based on the comparison result between the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, 73a, 73b and the measured values ​​of two or more closed circuit pump pressure sensors. In addition, when the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b fail, the differential pressures before and after the closed circuit switching valves 43a-43d, 45a-45d, 47a-47d are calculated using the pseudo pressures of the actuators 1, 3, 5 calculated according to the attitude of the working device 106 instead of the measured values ​​of the failed pressure sensors. As a result, the shock when the closed circuit pumps 12, 14, 16, 18 are connected to the actuators 1, 3, 5 is suppressed, so that it is possible to prevent the operability from deteriorating.

[0129] The hydraulic excavator 100 in this embodiment also includes a plurality of variable displacement open circuit pumps 13, 15, 17, 19 each having an inlet port and an outlet port, a plurality of open circuit switching valves 44a to 44d, 46a to 46d, 48a to 48d, 50a to 50d capable of connecting the plurality of open circuit pumps 13, 15, 17, 19 to the actuators 1, 3, 5, and a plurality of open circuit pump pressure sensors 81, 83, 85, 87 for detecting the pressures of the plurality of open circuit pumps 13, 15, 17, 19. When starting the supply of hydraulic oil from one of the plurality of open circuit pumps 13, 15, 17, 19 to the actuators 1, 3, 5, the controller 57 closes one of the plurality of open circuit switching valves 44a to 44d, 46a to 46d, 48a to 48d, 50a to 50d corresponding to the one open circuit pump, and compares the measurement value of one open circuit pump pressure sensor corresponding to the one open circuit pump with the actuator pressure sensors 70a, 70b, 71a, 71b, 71c, and 71d. a, 71b, 72a, 72b are controlled so that a differential pressure before and after the open circuit switching valve, which is a difference between the measured values ​​of the open circuit switching valve and the actuators, is equal to or less than the first threshold value, and then the open circuit switching valve is opened, and in a state in which two or more open circuit pumps out of the plurality of open circuit pumps 13, 15, 17, 19 are connected to the actuators 1, 3, 5, the measured values ​​of two or more open circuit pump pressure sensors out of the plurality of open circuit pump pressure sensors 81, 83, 85, 87 corresponding to the two or more open circuit pumps are compared with the actuators. The presence or absence of a failure of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b is determined based on the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, and when it is determined that the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b are faulty, the open circuit switching valve upstream / downstream differential pressure is calculated using the pseudo pressure instead of the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b. This makes it possible to correctly determine the failure of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, 73a, 73b based on the results of comparison between the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, 73a, 73b and the measured values ​​of two or more open circuit pump pressure sensors.Furthermore, if the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b fail, the pressure differentials across the open circuit switching valves 44a-44d, 46a-46d, 48a-48d are calculated using the pseudo pressures of the actuators 1, 3, 5 calculated in accordance with the attitude of the working device 106, instead of the measured values ​​of the failed pressure sensors. As a result, shocks that occur when the open circuit pumps 13, 15, 17, 19 are connected to the actuators 1, 3, 5 are suppressed, making it possible to prevent deterioration in operability.

[0130] In addition, the controller 57 in this embodiment calculates the difference between the measured values ​​of each of the two pressure sensors included in the actuator pressure sensors 70a-72b, the two or more closed circuit pump pressure sensors, and the two or more open circuit pump pressure sensors, with the two or more closed circuit pumps and the two or more open circuit pumps connected to the actuators 1, 3, and 5, and determines that the pressure sensor included in the two or more combinations in which the difference is greater than a predetermined second threshold value Plim is faulty. This makes it possible to detect faults in the closed circuit pump pressure sensors 80a, 80b, 82a, 82b, 84a, 84b, 86a, 86b, and the open circuit pump pressure sensors 81, 83, 85, and 87, in addition to the actuator pressure sensors 70a-72b.

[0131] Furthermore, the hydraulic excavator 100 in this embodiment is equipped with a display device 58 capable of displaying information output from the controller 57, and when the controller 57 determines that one of the pressure sensors included in the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, the two or more closed circuit pump pressure sensors, and the two or more open circuit pump pressure sensors has failed, it outputs identification information of the one pressure sensor to the display device 58. This makes it possible to shorten the time until a failed pressure sensor is repaired or replaced.

[0132] Furthermore, the controller 57 in this embodiment calculates the pseudo pressure so that the pseudo pressure is greater than the pressure of the actuators 1, 3, and 5 when the working device 106 assumes the posture detected by the posture sensors 400-403 in an unloaded state. This makes it possible to suppress shocks that occur when the switching valves 43a-49d are opened even if the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, 73a, and 73b fail while the working device 106 is under load.

[0133] Furthermore, the hydraulic excavator 100 in this embodiment is equipped with a pressure sensor fault diagnosis input generating device 59 capable of adjusting the input / output of the controller 57, and the controller 57 controls the multiple closed circuit pumps 12, 14, 16, 18, the multiple closed circuit switching valves, the multiple open circuit pumps 13, 15, 17, 19, and the multiple open circuit switching valves so that the working device 106 takes a predetermined posture (diagnosis posture) by adjusting the input / output by the pressure sensor fault diagnosis input generating device 59, and then maintains a state in which the multiple closed circuit pumps 12, 14, 16, 18 are connected to the actuators 1, 3, 5 with the discharge flow rates of the multiple closed circuit pumps 12, 14, 16, 18 set to zero, and maintains a state in which the multiple open circuit pumps 13, 15, 17, 19 are connected to the actuators 1, 3, 5 with the discharge flow rates of the multiple open circuit pumps 13, 15, 17, 19 set to zero. This allows the pressure sensor fault diagnosis process to be performed while the hydraulic excavator 100 is stationary in the diagnostic position, i.e., while the effects of the flow rate pressure loss characteristics are removed and the pressure in the pipeline is uniform, thereby improving the accuracy of fault detection.

[0134] Although the embodiment of the present invention has been described above in detail, the present invention is not limited to the above-mentioned embodiment and includes various modified examples. For example, the above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to an embodiment having all of the configurations described. [Explanation of symbols]

[0135] Reference Signs List 1... boom cylinder (actuator), 1a... cap chamber, 1b... rod chamber, 1c... rod, 1d... cylinder tube, 1e... piston, 2... boom, 3... arm cylinder (actuator), 3a... cap chamber, 3b... rod chamber, 3c... rod, 3d... cylinder tube, 3e... piston, 4... arm, 5... bucket cylinder (actuator), 5a... cap chamber, 5b... rod chamber, 5c... rod, 5d... cylinder tube, 5e... piston, 6... bucket, 7... swing motor (actuator), 8a, 8b... travel motor, 9... engine, 10... drive Force transmission device, 11... charge pump, 12... first closed circuit pump, 12a... regulator, 13... first open circuit pump, 13a... regulator, 14... second closed circuit pump, 14a... regulator, 15... second open circuit pump, 15a... regulator, 16... third closed circuit pump, 16a... regulator, 17... third open circuit pump, 17a... regulator, 18... fourth closed circuit pump, 18a... regulator, 19... fourth open circuit pump, 19a... regulator, 20... charge relief valve, 21 to 24... relief valve, 25... hydraulic oil tank, 26 to 29... charge charge Check valves, 30a, 30b, 31a, 31b, 32a, 32b, 33a, 33b...Relief valves, 34-36...Flushing valves, 37a, 37b, 38a, 38b, 39a, 39b...Relief valves, 40a, 40b, 41a, 41b, 42a, 42b...Charge check valves, 43a-43d, 45a-45d, 47a-47d, 49a-49d...Switching valves (closed circuit switching valves), 44a-44d, 46a-46d, 48a-48d, 50a-50d...Switching valves (open circuit switching valves), 51a, 51b, 52a, 52b, 53a, 53b...Relief valves, 54, 55...Proportional switching valves , 56 ... operation device, 56a ... boom lever, 56b ... arm lever, 56c ... bucket lever, 56d ... rotation lever, 57 ... controller, 57a ... lever operation amount calculation unit, 57b ... pressure calculation unit, 57c ... actuator allocation flow rate calculation unit, 57d ... pressure sensor failure detection unit, 57e ... pseudo pressure calculation unit, 58 ... display device, 59 ... pressure sensor failure diagnosis input generation device, 64 ~ 67 ... proportional valve, 70a, 70b, 71a, 71b, 72a, 72b, 73a, 73b ... pressure sensor (actuator pressure sensor), 80a, 80b, 82a, 82b, 84a, 84b, 86a,86b...pressure sensor (closed circuit pump pressure sensor), 81, 83, 85, 87...pressure sensor (open circuit pump pressure sensor), 100...hydraulic excavator, 101...cab, 101a, 101b...traveling device, 102...lower traveling body, 103...upper rotating body, 104...cab, 105...rotating device, 106...front work machine (working device), 107...hydraulic drive unit, 200-202...flow path, 202a...branch flow path, 203-2 05...flow path, 205a...branch flow path, 206-208...flow path, 208a...branch flow path, 209-211...flow path, 211a...branch flow path, 212-225...flow path, 301-304...connecting flow path, 305a-305d, 306a-306d, 307a-307d, 308a-308d...connecting flow path for open circuit, 309a-309c...connecting flow path for closed circuit, 400-403...position sensor, A-D...closed circuit, E-H...open circuit. ,

Claims

1. A working device; An actuator that drives the working device; A plurality of variable displacement closed circuit pumps each having two inlet and outlet ports; a plurality of closed circuit switching valves capable of switching between communication and cut-off between the actuator and the plurality of closed circuit pumps; a posture sensor for detecting a posture of the working device; a plurality of closed circuit pump pressure sensors for detecting pressures of the plurality of closed circuit pumps; an actuator pressure sensor for detecting a pressure of the actuator; An operation device for instructing an operation of the actuator; a controller that controls the plurality of closed circuit switching valves and the plurality of closed circuit pumps in response to an input signal from the operation device, a controller for controlling one closed circuit pump of the plurality of closed circuit switching valves corresponding to the one closed circuit pump so that a pressure difference across the closed circuit switching valve, which is a difference between a measurement value of a closed circuit pump pressure sensor corresponding to the one closed circuit pump and a measurement value of the actuator pressure sensor, is equal to or less than a predetermined first threshold value when starting to supply hydraulic oil from the one closed circuit pump of the plurality of closed circuit switching valves to the actuator, while keeping the one closed circuit switching valve of the plurality of closed circuit switching valves closed, and then opening the one closed circuit switching valve; The controller: determining whether or not the actuator pressure sensor has a failure based on measurement values ​​of two or more closed circuit pump pressure sensors among the plurality of closed circuit pumps corresponding to the two or more closed circuit pumps and a measurement value of the actuator pressure sensor, with two or more closed circuit pumps among the plurality of closed circuit pump pressure sensors being connected to the actuator; When it is determined that the actuator pressure sensor has failed, a pseudo pressure of the actuator is calculated based on the measurement value of the attitude sensor, and the pseudo pressure is used instead of the measurement value of the actuator pressure sensor to calculate the pressure difference across the closed circuit switching valve. A construction machine characterized by:

2. 2. The construction machine according to claim 1, a plurality of variable displacement open circuit pumps having inlet and outlet ports; a plurality of open circuit switching valves capable of connecting the plurality of open circuit pumps to the actuator; a plurality of open circuit pump pressure sensors detecting pressures of the plurality of open circuit pumps; The controller: when starting to supply hydraulic oil from one open circuit pump of the plurality of open circuit pumps to the actuator, one open circuit switching valve corresponding to the one open circuit pump among the plurality of open circuit switching valves is closed, and then the one open circuit switching valve is controlled so that a pressure difference across the open circuit switching valve, which is a difference between a measurement value of one open circuit pump pressure sensor corresponding to the one open circuit pump and a measurement value of the actuator pressure sensor, becomes equal to or less than the first threshold value, and then the one open circuit switching valve is opened; With two or more open circuit pumps among the plurality of open circuit pumps connected to the actuator, determining whether or not the actuator pressure sensor has a failure based on measurement values ​​of two or more open circuit pump pressure sensors among the plurality of open circuit pump pressure sensors corresponding to the two or more open circuit pumps and a measurement value of the actuator pressure sensor; When it is determined that the actuator pressure sensor is faulty, the differential pressure across the open circuit switching valve is calculated using the pseudo pressure instead of the measured value of the actuator pressure sensor. A construction machine characterized by:

3. The construction machine according to claim 2, The controller calculates a difference between measured values ​​for each combination of two pressure sensors included in the actuator pressure sensor, the two or more closed circuit pump pressure sensors, and the two or more open circuit pump pressure sensors, with the two or more closed circuit pumps and the two or more open circuit pumps connected to the actuator, and determines that a pressure sensor included in two or more combinations for which the difference is greater than a predetermined second threshold value is faulty. A construction machine characterized by:

4. The construction machine according to claim 3, a display device capable of displaying information output from the controller, When the controller determines that one of the pressure sensors included in the actuator pressure sensor, the two or more closed circuit pump pressure sensors, and the two or more open circuit pump pressure sensors is faulty, it outputs identification information of the one pressure sensor to the display device. A construction machine characterized by:

5. 2. The construction machine according to claim 1, The controller calculates the pseudo pressure so that the pseudo pressure is equal to or greater than the pressure of the actuator when the working device assumes the posture detected by the posture sensor in an unloaded state. A construction machine characterized by:

6. 2. The construction machine according to claim 1, a pressure sensor fault diagnosis input generating device capable of adjusting an input / output of the controller; The controller controls the plurality of closed circuit pumps, the plurality of closed circuit switching valves, the plurality of open circuit pumps, and the plurality of open circuit switching valves so that the working device takes a predetermined posture by adjusting input and output by the pressure sensor fault diagnosis input generating device, and then maintains a state in which the plurality of closed circuit pumps are connected to the actuator with the discharge flow rates of the plurality of closed circuit pumps set to zero, and maintains a state in which the plurality of open circuit pumps are connected to the actuator with the discharge flow rates of the plurality of open circuit pumps set to zero. A construction machine characterized by:

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