Construction machinery

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 by pressure oil discharged from a hydraulic pump.

Background Art

[0002] In recent years, in construction machines such as hydraulic excavators, in order to reduce the throttle elements in the hydraulic circuit that drives hydraulic actuators such as hydraulic cylinders and reduce the fuel consumption rate, the 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 by the hydraulic actuator is not returned to the tank but returned to the hydraulic pump. A hydraulic circuit (defined as a closed circuit) has been developed. ru) no Furthermore, in an excavator applying a closed circuit, a configuration in which a pump is connected to the cap chamber side to compensate for the pressure receiving area difference of a single rod cylinder has been proposed.

[0003] In these hydraulic circuits, a configuration has been proposed in which a plurality of pumps can be redundantly connected to one actuator, thereby realizing a composite operation by a plurality of actuators and an increase in speed during single operation. In a hydraulic circuit in which the connection destination actuator of such a pump can be changed, it is necessary to switch the connection and disconnection between the pump and the actuator. At this time, if the differential pressure 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

Summary of the Invention

Problems 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 connecting the pump and actuator. Therefore, if the pressure sensor is faulty, the pump pressure may be increased to a pressure different from the actual actuator pressure before connecting the pump and actuator, which could cause a shock when connecting the pump and actuator and reduce operability.

[0006] The present invention has been made in view of the above 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, in a case where a closed circuit is formed between an actuator for driving a work device and a plurality of hydraulic pumps to drive the actuator. [Means for solving the problem]

[0007] To achieve the above objective, the present invention comprises a work device, an actuator for driving the work device, a plurality of variable displacement closed-circuit pumps having two inlet / outlet ports, a plurality of closed-circuit switching valves capable of switching communication between the actuator and the plurality of closed-circuit pumps, a posture sensor for detecting the posture of the work device, a plurality of closed-circuit pump pressure sensors for detecting the pressure of the plurality of closed-circuit pumps, an actuator pressure sensor for detecting the pressure of the actuator, an operating device for instructing the 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 operating device, wherein the controller closes one of the plurality of closed-circuit switching valves corresponding to one of the closed-circuit pumps when starting to supply hydraulic fluid from one of the plurality of closed-circuit pumps to the actuator, and the controller closes one of the plurality of closed-circuit switching valves corresponding to one of the closed-circuit pumps. In a construction machine that controls one closed-circuit pump so that the differential pressure across the closed-circuit switching valve, which is the difference between the measured value of one closed-circuit pump pressure sensor corresponding to one of the closed-circuit pumps and the measured value of the actuator pressure sensor, is less than or equal to a predetermined first threshold, and then opens one closed-circuit switching valve, the controller determines whether or not the actuator pressure sensor is faulty based on the measured values ​​of two or more closed-circuit pump pressure sensors corresponding to two or more of the closed-circuit pumps and the measured value of the actuator pressure sensor, when two or more of the multiple closed-circuit pumps are connected to the actuator, and if the actuator pressure sensor is determined to be faulty, it calculates a pseudo pressure of the actuator based on the measured value of the attitude sensor, and uses the pseudo pressure instead of the measured value of the actuator pressure sensor to calculate the differential pressure across the closed-circuit switching valve.

[0008] According to the present invention configured as described above, it is possible to correctly determine the failure of the actuator pressure sensor based on the comparison result between the measured value of the actuator pressure sensor and the measured values ​​of two or more closed-circuit pump pressure sensors. Furthermore, if the actuator pressure sensor fails, the differential pressure across the closed-circuit switching valve is calculated using a simulated pressure of the actuator calculated according to the posture of the work device, instead of the measured value of the failed pressure sensor. As a result, the shock when connecting the closed-circuit pump to the actuator is suppressed, thus preventing a decrease in operability. [Effects of the Invention]

[0009] The construction machine according to the present invention makes it possible to suppress the decrease in operability when a pressure sensor that measures the pressure of an actuator driving a work device malfunctions. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view of a hydraulic excavator in an embodiment of the present invention. [Figure 2] This is a hydraulic circuit diagram of a hydraulic drive device mounted on a hydraulic excavator according to an embodiment of the present invention. [Figure 3] This is a functional block diagram of the controller in an embodiment of the present invention. [Figure 4] This is a time chart showing the state changes of the hydraulic drive system when the boom cylinder in an embodiment of the present invention is extended. [Figure 5] This flowchart shows a part of the processing of the pressure sensor fault detection unit in an embodiment of the present invention. [Figure 6] This figure shows the change in posture of the hydraulic excavator when the arm cylinder in an embodiment of the present invention is extended. [Figure 7] This figure shows the relationship between the stroke of the arm cylinder and the pressure in the cap chamber in an embodiment of the present invention. [Figure 8] This flowchart shows the processing of the pressure sensor fault diagnosis input generation device in an embodiment of the present invention. [Figure 9] This is a time chart showing the state changes of the hydraulic drive system in response to the input of the pressure sensor fault diagnosis input generation device in an embodiment of the present invention. [Modes for carrying out the invention]

[0011] The following explanation will use a hydraulic excavator as an example of a construction machine according to the present invention, with reference to the drawings. In each figure, equivalent components are denoted by the same reference numeral, and redundant explanations will be omitted as appropriate.

[0012] Figure 1 is a side view of the hydraulic excavator in this embodiment, and Figure 2 is a hydraulic circuit diagram of the hydraulic drive system mounted on the hydraulic excavator in this embodiment.

[0013] As shown in Figure 1, the hydraulic excavator 100 comprises a lower traveling body 102 equipped with crawler-type traveling devices 101a and 101b on both sides in the left-right direction, and an upper rotating body 103 that is rotatably mounted on the lower traveling body 102. A cab 104 for the operator is provided on the upper rotating body 103. The upper rotating body 103 is connected to the lower traveling body 102 via a slewing device 105. Rotatable It is mounted on the vehicle. The traveling devices 101a and 101b are driven by traveling motors 8a and 8b (shown in Figure 2), and the turning device 105 is driven by a turning motor 7 (shown in Figure 2).

[0014] The base end of a front work implement 106, which is a work device for performing tasks such as excavation, is mounted on the front of the upper slewing body 103 so as to be rotatable in the vertical direction. The front work implement 106 is equipped with a boom 2 whose base end is connected to the front of the upper slewing 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 type hydraulic cylinder driven by hydraulic oil (pressurized oil) as the supplied fluid. The tip of the rod 1c of the boom cylinder 1 is connected to the upper slewing body 103, and the base end of the cylinder tube 1d is connected to the boom 2.

[0015] As shown in Fig. 2, the boom cylinder 1 is located at the proximal end side of the cylinder tube 1d, and when hydraulic oil is supplied, it presses the piston 1e attached to the proximal end portion of the rod 1c to apply a load by hydraulic pressure, and is provided with a cap chamber 1a which is a first hydraulic oil chamber on the cap side for extending the rod 1c. Further, the boom cylinder 1 is located at the distal end side of the cylinder tube 1d, and when hydraulic oil is supplied, it presses the piston 1e to apply a load by hydraulic pressure, and is provided with a rod chamber 1b as a second hydraulic oil chamber on the rod side for retracting the rod 1c.

[0016] Returning to Fig. 1, the proximal end portion of the arm 4 is pivotally connected to the distal end portion of the boom 2. The arm 4 operates via an arm cylinder 3 which is a single-rod hydraulic cylinder. The distal end portion of the rod 3c of the arm cylinder 3 is connected to the arm 4, and the cylinder tube 3d of the arm cylinder 3 is connected to the boom 2.

[0017] As shown in Fig. 2, the arm cylinder 3 is located at the proximal end side of the cylinder tube 3d, and when hydraulic oil is supplied, it presses the piston 3e attached to the proximal end portion of the rod 3c to extend the rod 3c, and is provided with a cap chamber 3a. Further, the arm cylinder 3 is located at the distal end side of the cylinder tube 3d, and when hydraulic oil is supplied, it presses the piston 3e to retract the rod 3c, and is provided with a rod chamber 3b.

[0018] Returning to Fig. 1, the proximal end portion of the bucket 6 is pivotally connected to the distal end portion of the arm 4. The bucket 6 operates via a bucket cylinder 5 which is a single-rod hydraulic cylinder as a hydraulic actuator driven by supplied hydraulic oil. The distal end portion of the rod 5c of the bucket cylinder 5 is connected to the bucket 6, and the proximal end of the cylinder tube 5d of the bucket cylinder 5 is connected to the arm 4.

[0019] As shown in Figure 2, the bucket cylinder 5 is located on the base end side of the cylinder tube 5d and includes a cap chamber 5a that, when hydraulic fluid is supplied, presses against 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 and, when hydraulic fluid is supplied, presses against a piston 5e, thereby retracting the rod 5c.

[0020] The boom cylinder 1, arm cylinder 3, and bucket cylinder 5 each extend and retract in accordance with the supplied hydraulic fluid, and are driven to extend and retract according to the direction in which the hydraulic fluid is supplied. In this embodiment, the hydraulic excavator 100 is a backhoe excavator, and is configured so that the bucket 6 is pulled back by extending the arm cylinder 3 or the bucket cylinder 5.

[0021] The boom 2 is equipped with an attitude sensor 400 capable of measuring the attitude angle. The arm 4 is equipped with an attitude sensor 401 capable of measuring the attitude angle. The bucket 6 is equipped with an attitude sensor 402 capable of measuring the attitude angle. The upper slewing body 103 is equipped with an attitude sensor 403 capable of measuring the slewing angle and the attitude of the upper slewing body. The attitude sensor 403 allows, Hydraulic excavator 100 The attitude angle of the upper rotating body 103 can also be measured when the vehicle is parked on a slope.

[0022] As shown in Figure 2, the hydraulic drive unit 107 is equipped with four closed-circuit pumps connected in closed circuits and four open-circuit pumps connected in open circuits to three types of single-rod hydraulic cylinders and three types of hydraulic motors. When driving a single-rod hydraulic cylinder, flow control is performed by combining one closed-circuit pump and one open-circuit pump. In addition, each of these hydraulic pumps is provided with a switching valve, so that multiple closed-circuit pumps and multiple open-circuit pumps can be combined for a single single-rod hydraulic cylinder. Furthermore, when combining for a single single-rod hydraulic cylinder, the controller controls the switching valve so that one closed-circuit pump and one open-circuit pump are combined for the merger.

[0023] The hydraulic drive unit 107 is a drive unit for driving the hydraulic excavator 100 and is mounted on the upper slewing body 103. The hydraulic drive unit 107 is used to drive the boom cylinder 1, arm cylinder 3, and bucket cylinder 5 that make up the front work implement 106, as well as the slewing motor 7 and the travel motors 8a and 8b. The slewing motor 7 and the travel motors 8a and 8b are hydraulic motors that are driven by the supply of hydraulic fluid.

[0024] Furthermore, the hydraulic drive unit 107 drives the boom cylinder 1, arm cylinder 3, bucket cylinder 5, slewing motor 7, and travel motors 8a, 8b, which are hydraulic actuators, in response to the operation of the operating device 56 installed inside the cab 104. Here, the extension and retraction of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, i.e., the direction and speed of operation, are controlled by each lever 56a of the operating device 56a ~5 This is indicated by the operating direction and amount of 6d.

[0025] Furthermore, the hydraulic drive unit 107 is equipped with an engine 9, which is a power source. The engine 9 is composed of, for example, predetermined gears and is connected to a power transmission unit 10 for distributing power. The power transmission unit 10 includes hydraulic pumps 12, 13, ..., 19, which are variable flow hydraulic pumps, and flow paths, which will be described later. 225 A charge pump 11 for replenishing pressurized oil is connected to each of these.

[0026] The hydraulic pumps 12, 14, 16, and 18 are variable displacement closed-circuit pumps equipped with a double-tilting swashplate mechanism (not shown) having two input / output ports, i.e., a pair of inlet / outlet ports, that allow hydraulic fluid to flow in and out in both directions, and regulators 12a, 14a, 16a, and 18a that adjust the tilt angle (inclination angle) of the double-tilting swashplates constituting this double-tilting swashplate mechanism. The regulators 12a, 14a, 16a, and 18a adjust the tilt angle of the corresponding swashplates of the closed-circuit pumps 12, 14, 16, and 18 in response to the operation signals output from the controller 57, thereby controlling the flow rate of hydraulic fluid discharged from the closed-circuit pumps 12, 14, 16, and 18. Furthermore, the closed-circuit pumps 12, 14, 16, and 18 function as hydraulic motors when supplied with hydraulic fluid.

[0027] The hydraulic pumps 13, 15, 17, and 19 are variable displacement open-circuit pumps equipped with a unidirectional tilting swash plate mechanism (not shown) having an outlet port that allows hydraulic fluid to flow in and out in one direction, and regulators 13a, 15a, 17a, and 19a that adjust the tilt angle (inclination angle) of the unidirectional tilting swash plate constituting this unidirectional tilting swash plate mechanism. The regulators 13a, 15a, 17a, and 19a adjust the tilt angle of the corresponding open-circuit pumps 13, 15, 17, and 19 in response to the operation signal output from the controller 57, thereby controlling the flow rate of hydraulic fluid discharged from the open-circuit pumps 13, 15, 17, and 19.

[0028] Furthermore, the tilting swashplate mechanisms of the hydraulic pumps 12, 13, ..., 19 are equipped with means (not shown) for detecting the tilt angle, which can be used when triggering the switching timing of the switching valve by the discharge flow rate, as shown in the time chart in Figure 4 described later. Alternatively, the hydraulic pumps 12, 13, ..., 19 may be equipped with means for measuring the control pressure of the regulators, and the tilt state of the swashplate of each pump and the discharge flow rate may be calculated from the regulator control pressure.

[0029] Also, closed-circuit pumps 12, 14, 16, and 18 are 、 To control the tilt angle of the swash plate in two directions 、While the structure allows the regulator to generate driving force in both directions—to maximize and minimize the tilt angle—the open-circuit pumps 13, 15, 17, and 19 control the tilt angle of the swash plate in one direction. Therefore, the driving force from the regulator acts only in the direction that maximizes the tilt angle, and the return to the minimum angle depends on the restoring force of the spring. 、 Closed-circuit pumps 12, 14, 16, and 18 exhibit higher responsiveness when controlling the tilt angle in a direction that reduces 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. Multiple, for example, four, switching valves 43a, 43b, 43c, and 43d are connected to the flow paths 200 and 201. Switching valves 43a, 43b, and 43c are closed-circuit switching valves for switching the supply of hydraulic fluid to the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, which are connected in a closed circuit to the first closed-circuit pump 12. Switching valve 43d is a closed-circuit switching valve for a hydraulic motor for switching the supply of hydraulic fluid to the swing motor 7, which is connected in a closed circuit to the first closed-circuit pump 12. The switching valves 43a, 43b, 43c, and 43d are configured to switch between conduction and interruption of the flow paths 200 and 201 in accordance with the operation signal output from the controller 57, and are in an interrupted 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 do not become conductive at the same time.

[0031] Furthermore, the switching valve 43a is connected to the boom cylinder 1 via the passages 212 and 213. Therefore, the first closed-circuit pump 12 constitutes a closed-circuit A, which is connected in a closed-circuit manner to the boom cylinder 1 via the passages 200 and 201, the switching valve 43a, and the passages 212 and 213 when the switching valve 43a becomes conductive in response to the operation signal output from the controller 57.

[0032] Furthermore, the switching valve 43b is connected to the arm cylinder 3 via the flow paths 214 and 215. Therefore, when the switching valve 43b becomes conductive in response to the operation signal output from the controller 57, the first closed-circuit pump 12 forms a closed-circuit B that is connected in a closed-circuit manner 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 becomes conductive due to an operation signal from the controller 57, the first closed-circuit pump 12 forms a closed-circuit C that is connected in a closed-circuit manner to the bucket cylinder 5 via the flow paths 200 and 201, the switching valve 43c, and the flow paths 216 and 217.

[0034] Furthermore, the switching valve 43d is connected to the swivel motor 7 via the flow paths 218 and 219. Therefore, when the switching valve 43d becomes conductive due to 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 manner to the swivel 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 also serves as a connection flow path for hydraulic cylinders to independently connect the boom cylinder 1 to multiple switching valves 44a, 46a, 48a, and 50a of the open circuits E, F, G, and H described later. Furthermore, the flow path 214 also serves as a connection flow path for hydraulic cylinders to independently connect the arm cylinder 3 to multiple switching valves 44b, 46b, 48b, and 50b of the open circuits E, F, G, and H described later. In addition, the flow path 216 also serves as a connection flow path for hydraulic cylinders to independently connect the bucket cylinder 5 to multiple switching valves 44c, 46c, 48c, and 50c of the open circuits E, F, G, and H described later.

[0036] Furthermore, 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. Multiple, for example, four, switching valves 45a, 45b, 45c, and 45d are connected to the flow paths 203 and 204. Switching valves 45a, 45b, and 45c are closed-circuit switching valves for switching the supply of hydraulic fluid to the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, which are connected in a closed circuit to the second closed-circuit pump 14. Switching valve 45d is a closed-circuit switching valve for a hydraulic motor for switching the supply of hydraulic fluid to the swing motor 7, which is connected in a closed circuit to the second closed-circuit pump 14. The switching valves 45a, 45b, 45c, and 45d are configured to switch between conduction and interruption of the flow paths 203 and 204 in accordance with the operation signal output from the controller 57, and are in an interrupted state when there is no output of an operation signal from the controller 57. The controller 57 controls the switching valves 45a, 45b, 45c, and 45d so that they do not become conductive at the same time.

[0037] Furthermore, the switching valve 45a is connected to the boom cylinder 1 via the passages 212 and 213. Therefore, when the switching valve 45a becomes conductive due to an operation signal from the controller 57, the second closed-circuit pump 14 constitutes closed-circuit A, which is connected in a closed-circuit manner to the boom cylinder 1 via the passages 203 and 204, the switching valve 45a, and the passages 212 and 213. Also, the switching valve 45b is connected to the arm cylinder 3 via the passages 214 and 215. Therefore, when the switching valve 45b becomes conductive due to an operation signal from the controller 57, the second closed-circuit pump 14 constitutes closed-circuit B, which is connected in a closed-circuit manner to the arm cylinder 3 via the passages 203 and 204, the switching valve 45b, and the passages 214 and 215.

[0038] Furthermore, the switching valve 45c is connected to the bucket cylinder 5 via the passages 216 and 217. Therefore, when the switching valve 45c becomes conductive due to an operation signal from the controller 57, the second closed-circuit pump 14 constitutes a closed-circuit C, which is connected in a closed-circuit manner to the bucket cylinder 5 via the passages 203 and 204, the switching valve 45c, and the passages 216 and 217. Also, the switching valve 45d is connected to the slewing motor 7 via the passages 218 and 219. Therefore, when the switching valve 45d becomes conductive due to an operation signal from the controller 57, the second closed-circuit pump 14 constitutes a closed-circuit D, which is connected in a closed-circuit manner to the slewing motor 7 via the passages 203 and 204, the switching valve 45d, and the passages 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. Multiple, for example, four, switching valves 47a, 47b, 47c, and 47d are connected to the flow paths 206 and 207. Switching valves 47a, 47b, and 47c are closed-circuit switching valves for switching the supply of hydraulic fluid to the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, which are connected in a closed circuit to the third closed-circuit pump 16. Switching valve 47d is a closed-circuit switching valve for a hydraulic motor for switching the supply of hydraulic fluid to the swing motor 7, which is connected in a closed circuit to the third closed-circuit pump 16. The switching valves 47a, 47b, 47c, and 47d are configured to switch between conducting and blocking the flow paths in accordance with the operation signal output from the controller 57, and are in a blocked state when there is no output of an operation signal from the controller 57. The controller 57 controls the switching valves 47a, 47b, 47c, and 47d so that they do not become conductive at the same time.

[0040] Furthermore, the switching valve 47a is connected to the boom cylinder 1 via the passages 212 and 213. Therefore, when the switching valve 47a becomes conductive due to an operation signal from the controller 57, the third closed-circuit pump 16 constitutes closed-circuit A, which is connected in a closed-circuit manner to the boom cylinder 1 via the passages 206 and 207, the switching valve 47a, and the passages 212 and 213. Also, the switching valve 47b is connected to the arm cylinder 3 via the passages 214 and 215. Therefore, when the switching valve 47b becomes conductive due to an operation signal from the controller 57, the third closed-circuit pump 16 constitutes closed-circuit B, which is connected in a closed-circuit manner to the arm cylinder 3 via the passages 206 and 207, the switching valve 47b, and the passages 214 and 215.

[0041] Furthermore, the switching valve 47c is connected to the bucket cylinder 5 via the passages 216 and 217. Therefore, when the switching valve 47c becomes conductive due to an operation signal from the controller 57, the third closed-circuit pump 16 constitutes a closed-circuit C, which is connected in a closed-circuit manner to the bucket cylinder 5 via the passages 206 and 207, the switching valve 47c, and the passages 216 and 217. In addition, the switching valve 47d is connected to the slewing motor 7 via the passages 218 and 219. Therefore, when the switching valve 47d becomes conductive due to an operation signal from the controller 57, the third closed-circuit pump 16 constitutes a closed-circuit D, which is connected in a closed-circuit manner to the slewing motor 7 via the passages 206 and 207, the switching valve 47d, and the passages 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. Multiple, for example, four, switching valves 49a, 49b, 49c, and 49d are connected to the flow paths 209 and 210. Switching valves 49a, 49b, and 49c are closed-circuit switching valves for switching the supply of hydraulic fluid to the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, which are connected in a closed circuit to the fourth closed-circuit pump 18. Switching valve 49d is a closed-circuit switching valve for a hydraulic motor for switching the supply of hydraulic fluid to the swing motor 7, which is connected in a closed circuit to the fourth closed-circuit pump 18. The switching valves 49a, 49b, 49c, and 49d are configured to switch between conducting and blocking the flow paths in accordance with the operation signal output from the controller 57, and are in a blocked 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 do not become conductive at the same time.

[0043] Furthermore, the switching valve 49a is connected to the boom cylinder 1 via the passages 212 and 213. Therefore, when the switching valve 49a becomes conductive due to an operation signal from the controller 57, the fourth closed-circuit pump 18 constitutes closed-circuit A, which is connected in a closed-circuit manner to the boom cylinder 1 via the passages 209 and 210, the switching valve 49a, and the passages 212 and 213. Also, the switching valve 49b is connected to the arm cylinder 3 via the passages 214 and 215. Therefore, when the switching valve 49b becomes conductive due to an operation signal from the controller 57, the fourth closed-circuit pump 18 constitutes closed-circuit B, which is connected in a closed-circuit manner to the arm cylinder 3 via the passages 209 and 210, the switching valve 49b, and the passages 214 and 215.

[0044] Furthermore, the switching valve 49c is connected to the bucket cylinder 5 via the passages 216 and 217. Therefore, when the switching valve 49c becomes conductive due to an operation signal from the controller 57, the fourth closed-circuit pump 18 constitutes a closed-circuit C, which is connected in a closed-circuit manner to the bucket cylinder 5 via the passages 209 and 210, the switching valve 49c, and the passages 216 and 217. Also, the switching valve 49d is connected to the slewing motor 7 via the passages 218 and 219. Therefore, when the switching valve 49d becomes conductive due to an operation signal from the controller 57, the fourth closed-circuit pump 18 constitutes a closed-circuit D, which is connected in a closed-circuit manner to the slewing motor 7 via the passages 209 and 210, the switching valve 49d, and the passages 218 and 219.

[0045] Furthermore, one input / output port of the first open-circuit pump 13 is connected to a relief valve 21 via a flow path 202 to a plurality of, for example, four, switching valves 44a, 44b, 44c, and 44d. The other input / output port of the first open-circuit pump 13 is connected to the hydraulic oil tank 25 and is considered an open-circuit E. The switching valves 44a, 44b, 44c, and 44d are open-circuit switching valves that switch the conduction and blockage of the flow path 202 in accordance with the operation signal output from the controller 57, and switch the supply destination of the hydraulic oil flowing out of the first open-circuit pump 13 to the connected flow paths 301, 302, 303, and 304, which will be described later. They are in a blocked state when there is no output of an operation signal from the controller 57. The controller 57 controls the switching valves 44a, 44b, 44c, and 44d so that they do not enter a conduction state at the same time.

[0046] Furthermore, the switching valve 44a is connected to the boom cylinder 1 via the connecting passage 301 and the passage 212. The connecting passage 301 is a connecting pipe branched off from the passage 212. Also, the switching valve 44b is connected to the arm cylinder 3 via the connecting passage 302 and the passage 214. The connecting passage 302 is a connecting pipe branched off from the passage 214. In addition, the switching valve 44c is connected to the bucket cylinder 5 via the connecting passage 303 and the passage 216. The connecting passage 303 is a connecting pipe branched off from the passage 216. Furthermore, 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 fluid to the travel motors 8a and 8b, via the connecting passage 304 and the passage 220. On the other hand, the relief valve 21 protects the passage 202 and, consequently, the hydraulic drive unit 107 (hydraulic circuit) by releasing the hydraulic fluid in the passage 202 to the hydraulic fluid tank 25 when the operating hydraulic pressure in the passage 202 exceeds a predetermined pressure.

[0047] Furthermore, a proportional valve 64, which functions as a pressure-compensated flow control valve, is connected between the flow path 202 and the hydraulic oil tank 25. The proportional valve 64 is located on the branch flow path 202a, which is a pipeline that branches off from the flow path 202, which is a pipeline connecting the switching valves 44a, 44b, 44c, and 44d to the first open-circuit pump 13, and connects to the hydraulic oil tank 25. Therefore, the proportional valve 64 controls the flow rate of hydraulic oil that flows from the flow path 202 to the hydraulic oil tank 25 in accordance with the operation signal output from the controller 57. The proportional valve 64 is also shut off when there is no operation signal output from the controller 57.

[0048] Furthermore, one input / output port of the second open-circuit pump 15 is connected to a relief valve 22 via a flow path 205 to a plurality of, for example, four, switching valves 46a, 46b, 46c, and 46d. The other input / output port of the second open-circuit pump 15 is connected to the hydraulic oil tank 25 and is configured as an open circuit F. The switching valves 46a, 46b, 46c, and 46d are open-circuit switching valves that switch the conduction and blockage of the flow path 205 in accordance with the operation signal output from the controller 57, and switch the supply destination of the hydraulic oil flowing out of the second open-circuit pump 15 to the connected flow paths 301, 302, 303, and 304. They are in a blocked state when there is no output of an operation signal from the controller 57. The controller 57 controls the switching valves 46a, 46b, 46c, and 46d so that they do not enter a conduction state simultaneously.

[0049] Furthermore, the switching valve 46a is connected to the boom cylinder 1 via the connecting passage 301 and passage 212. The switching valve 46b is connected to the arm cylinder 3 via the connecting passage 302 and passage 214. The switching valve 46c is connected to the bucket cylinder 5 via the connecting passage 303 and passage 216. The switching valve 46d is connected to the proportional switching valves 54 and 55 via the connecting passage 304 and passage 220. On the other hand, the relief valve 22 protects the passage 205 by releasing the hydraulic fluid in the passage 205 to the hydraulic fluid tank 25 when the hydraulic pressure in the passage 205 exceeds a predetermined pressure.

[0050] Furthermore, a proportional valve 65, which functions as a pressure-compensated flow control valve, is connected between the flow path 205 and the hydraulic oil tank 25. The proportional valve 65 is located on the branch flow path 205a, which is a pipeline that branches off from the flow path 205, which is the pipeline connecting the switching valves 46a, 46b, 46c, and 46d to the second open-circuit pump 15, and connects to the hydraulic oil tank 25. Therefore, the proportional valve 65 controls the flow rate of hydraulic oil that flows from the flow path 205 to the hydraulic oil tank 25 in accordance with the operation signal output from the controller 57. The proportional valve 65 is also shut off when there is no operation signal output from the controller 57.

[0051] Furthermore, one input / output port of the third open-circuit pump 17 is connected to a relief valve 23 via a flow path 208 to a plurality of, for example, four, switching valves 48a, 48b, 48c, and 48d. The other input / output port of the third open-circuit pump 17 is connected to the hydraulic oil tank 25 and is configured as an open circuit G. The switching valves 48a, 48b, 48c, and 48d are open-circuit switching valves that switch the conduction and blockage of the flow path 208 in accordance with the operation signal output from the controller 57, and switch the supply destination of the hydraulic oil flowing out of the third open-circuit pump 17 to the connected flow paths 301, 302, 303, and 304. They are in a blocked state when there is no output of an operation signal from the controller 57. The controller 57 controls the switching valves 48a, 48b, 48c, and 48d so that they do not enter a conduction state simultaneously.

[0052] Furthermore, the switching valve 48a is connected to the boom cylinder 1 via the connecting passage 301 and passage 212. The switching valve 48b is connected to the arm cylinder 3 via the connecting passage 302 and passage 214. The switching valve 48c is connected to the bucket cylinder 5 via the connecting passage 303 and passage 216. The switching valve 48d is connected to the proportional switching valves 54 and 55 via the connecting passage 304 and passage 220. On the other hand, the relief valve 23 protects the passage 208 by releasing the hydraulic fluid in the passage 208 to the hydraulic fluid tank 25 when the hydraulic pressure in the passage 208 exceeds a predetermined pressure.

[0053] Furthermore, a proportional valve 66, which acts as a flow control valve with pressure compensation, is connected between the flow path 208 and the hydraulic oil tank 25. The proportional valve 66 is installed on the branch flow path 208a, which is a pipeline that branches off from the flow path 208, which is a pipeline connecting the switching valves 48a, 48b, 48c, 48d and the third open-circuit pump 17, and connects to the hydraulic oil tank 25. Therefore, the proportional valve 66 controls the flow from the flow path 208 to the hydraulic oil tank 25 in accordance with the operation signal output from the controller 57. Hydraulic fluid The flow rate is controlled. Furthermore, the proportional valve 66 is shut off if there is no output of an operation signal from the controller 57.

[0054] Furthermore, one input / output port of the fourth open-circuit pump 19 is connected via a flow path 211 to a plurality of, for example, four, switching valves 50a, 50b, 50c, and 50d, and a relief valve 24. The other input / output port of the fourth open-circuit pump 19 is connected to the hydraulic oil tank 25 and is configured as an open circuit H. The switching valves 50a, 50b, 50c, and 50d are open-circuit switching valves that switch the conduction and blockage of the flow path 211 in accordance with the operation signal output from the controller 57, and switch the supply destination of the hydraulic oil flowing out of the fourth open-circuit pump 19 to the connected flow paths 301, 302, 303, and 304. When there is no output of an operation signal from the controller 57, they are in a blocked state. The controller 57 controls the switching valves 50a, 50b, 50c, and 50d so that they do not enter a conduction state simultaneously.

[0055] Furthermore, the switching valve 50a is connected to the boom cylinder 1 via the connecting passage 301 and passage 212. The switching valve 50b is connected to the arm cylinder 3 via the connecting passage 302 and passage 214. The switching valve 50c is connected to the bucket cylinder 5 via the connecting passage 303 and passage 216. The switching valve 50d is connected to the proportional switching valves 54 and 55 via the connecting passage 304 and passage 220. On the other hand, the relief valve 24 protects the passage 211 by releasing the hydraulic fluid in the passage 211 to the hydraulic fluid tank 25 when the operating hydraulic pressure in the passage 211 exceeds a predetermined pressure.

[0056] Furthermore, a pressure-compensated proportional valve 67 is connected between the flow path 211 and the hydraulic oil tank 25. The proportional valve 67 is installed on the branch flow path 211a, which is a pipeline that branches off from the flow path 211, which is a pipeline connecting the switching valves 50a, 50b, 50c, 50d and the fourth open-circuit pump 19, and connects to the hydraulic oil tank 25. Therefore, the proportional valve 67 controls the flow rate of hydraulic oil that flows from the flow path 211 to the hydraulic oil tank 25 in accordance with the operation signal output from the controller 57. In addition, the proportional valve 67 is shut off when there is no output of an operation signal from the controller 57.

[0057] Here, the connecting passage 301 consists of open-circuit connecting passages 305a, 306a, 307a, and 308a connected to the discharge side of at least one of the multiple open circuits E, F, G, H switching valves 44a, 46a, 48a, and 50a, which is the side from which the hydraulic fluid is discharged, and a closed-circuit connecting passage 309a connected to the passage 212 that constitutes closed circuit A. The connecting passage 302 consists of open-circuit connecting passages 305b, 306b, 307b, and 308b connected to the discharge side of at least one of the multiple open circuits E, F, G, H switching valves 44b, 46b, 48b, and 50b, which is the side from which the hydraulic fluid is discharged, and a closed-circuit connecting passage 309b connected to the passage 214 that constitutes closed circuit B. The connecting passage 303 consists of open-circuit connecting passages 305c, 306c, 307c, and 308c, which are connected to the discharge side of at least one of the multiple open circuits E, F, G, and H switching valves 44c, 46c, 48c, and 50c, on which the hydraulic fluid is discharged, and a closed-circuit connecting passage 309c, which is connected to the passage 216 that constitutes the closed circuit C. The connecting passage 304 consists of open-circuit connecting passages 305d, 306d, 307d, and 308d, which are connected to the discharge side of at least one of the multiple open circuits E, F, G, and H switching valves 44d, 46d, 48d, and 50d, on which the hydraulic fluid is discharged, and a connecting passage 309d, which is connected to the passage 220.

[0058] The hydraulic drive unit 107 is composed of closed circuits A, B, C, and D, in which closed-circuit pumps 12, 14, 16, and 18, a boom cylinder 1, an arm cylinder 3, a bucket cylinder 5, and a swing motor 7 are connected in a closed circuit manner from one input / output port of the hydraulic pump to the other input / output port via an actuator. Furthermore, it is composed of open circuits E, F, G, and H, in which open-circuit pumps 13, 15, 17, and switching valves 44a, 44b, 44c, 44d, 46a, 46b, 46c, 46d, 48a, 48b, 48c, 48d, 50a, 50b, 50c, and 50d are connected to one input / output port of the hydraulic pump and the hydraulic oil tank 25 is connected to the other input / output port. In addition, closed circuits A, B, C, and D and open circuits E, F, G, and H are provided in pairs, for example, in sets of four.

[0059] On the other hand, the discharge port of the charge pump 11 is Flow path 225 It is connected via to the charge relief valve 20 and the charge check valves 26, 27, 28, 29, 40a, 40b, 41a, 41b, 42a, and 42b. The suction port of the charge pump 11 is connected to the hydraulic oil tank 25. Here, the charge relief valve 20 adjusts the charge pressure of the charge check valves 26, 27, 28, 29, 40a, 40b, 41a, 41b, 42a, and 42b.

[0060] Furthermore, the charge check valve 26 supplies hydraulic fluid from the charge pump 11 to passages 200 and 201 when the operating hydraulic pressure in passages 200 and 201 falls below the pressure set by the charge relief valve 20. Similarly, the charge check valve 27 supplies hydraulic fluid from the charge pump 11 to passages 203 and 204 when the operating hydraulic pressure in passages 203 and 204 falls below the pressure set by the charge relief valve 20. Also, the charge check valve 28 supplies hydraulic fluid from the charge pump 11 to passages 206 and 207 when the operating hydraulic pressure in passages 206 and 207 falls below the pressure set by the charge relief valve 20. Similarly, the charge check valve 29 supplies hydraulic fluid from the charge pump 11 to passages 209 and 210 when the operating hydraulic pressure in passages 209 and 210 falls below the pressure set by the charge relief valve 20.

[0061] Furthermore, the charge check valves 40a and 40b supply hydraulic fluid from the charge pump 11 to passages 212 and 213 when the operating hydraulic pressure in passages 212 and 213 falls below the pressure set by the charge relief valve 20. Similarly, the charge check valves 41a and 41b supply hydraulic fluid from the charge pump 11 to passages 214 and 215 when the operating hydraulic pressure in passages 214 and 215 falls below the pressure set by the charge relief valve 20. In addition, the charge check valves 42a and 42b supply hydraulic fluid from the charge pump 11 to passages 216 and 217 when the operating hydraulic pressure in passages 216 and 217 、 When the pressure falls below the pressure set by the charge relief valve 20, hydraulic fluid is supplied from the charge pump 11 to the passages 216 and 217.

[0062] Furthermore, a pair of relief valves 30a and 30b are connected between passages 200 and 201. When the hydraulic pressure in passages 200 and 201 exceeds a predetermined pressure, the relief valves 30a and 30b release the hydraulic fluid in passages 200 and 201 to the hydraulic fluid tank 25 via the charge relief valve 20, thereby protecting passages 200 and 201. Similarly, a pair of relief valves 31a and 31b are connected between passages 203 and 204. When the hydraulic pressure in passages 203 and 204 exceeds a predetermined pressure, the relief valves 31a and 31b release the hydraulic fluid in passages 203 and 204 to the hydraulic fluid tank 25 via the charge relief valve 20, thereby protecting passages 203 and 204.

[0063] Furthermore, relief valves 32a and 32b are also connected between passages 206 and 207. When the hydraulic pressure in passages 206 and 207 exceeds a predetermined pressure, the relief valves 32a and 32b release the hydraulic fluid in passages 206 and 207 to the hydraulic fluid tank 25 via the charge relief valve 20, thereby protecting passages 206 and 207. Additionally, relief valves 33a and 33b are connected between passages 209 and 210. When the hydraulic pressure in passages 209 and 210 exceeds a predetermined pressure, the relief valves 33a and 33b release the hydraulic fluid in passages 209 and 210 to the hydraulic fluid tank 25 via the charge relief valve 20, thereby protecting passages 209 and 210.

[0064] Next, passage 212 is connected to the cap chamber 1a of the boom cylinder 1. Passage 213 is connected to the rod chamber 1b of the boom cylinder 1. Relief valves 37a and 37b are connected between passages 212 and 213. When the operating hydraulic pressure in passages 212 and 213 exceeds a predetermined pressure, the relief valves 37a and 37b release the hydraulic fluid in passages 212 and 213 to the hydraulic fluid tank 25 via the charge relief valve 20, thereby protecting passages 212 and 213. Furthermore, a flushing valve 34 is connected between passages 212 and 213. The flushing valve 34 discharges any excess hydraulic fluid (excess oil) in passages 212 and 213 to the hydraulic fluid tank 25 via the charge relief valve 20.

[0065] Furthermore, passage 214 is connected to the cap chamber 3a of the arm cylinder 3. Passage 215 is connected to the rod chamber 3b of the arm cylinder 3. In addition, relief valves 38a and 38b are connected between passages 214 and 215. When the operating hydraulic pressure in passages 214 and 215 exceeds a predetermined pressure, the relief valves 38a and 38b release the hydraulic fluid in passages 214 and 215 to the hydraulic fluid tank 25 via the charge relief valve 20, thereby protecting passages 214 and 215. Furthermore, a flushing valve 35 is connected between passages 214 and 215. The flushing valve 35 discharges any excess hydraulic fluid in passages 214 and 215 to the hydraulic fluid tank 25 via the charge relief valve 20.

[0066] Furthermore, passage 216 is connected to the cap chamber 5a of the bucket cylinder 5. Passage 217 is connected to the rod chamber 5b of the bucket cylinder 5. In addition, relief valves 39a and 39b are connected between passages 216 and 217. When the operating hydraulic pressure in passages 216 and 217 exceeds a predetermined pressure, the relief valves 39a and 39b release the hydraulic fluid in passages 216 and 217 to the hydraulic fluid tank 25 via the charge relief valve 20, thereby protecting passages 216 and 217. Furthermore, a flushing valve 36 is connected between passages 216 and 217. The flushing valve 36 discharges any excess hydraulic fluid in passages 216 and 217 to the hydraulic fluid tank 25 via the charge relief valve 20.

[0067] Furthermore, passages 218 and 219 are connected to the swing motor 7, respectively. Relief valves 51a and 51b are also connected between passages 218 and 219. When the pressure difference of the hydraulic fluid between passages 218 and 219 (flow path pressure difference) exceeds a predetermined pressure, the relief valves 51a and 51b release the hydraulic fluid in the high-pressure passages 218 and 219 to the low-pressure passages 219 and 219, thereby protecting passages 218 and 219.

[0068] Furthermore, the proportional switching valve 54 and the travel motor 8a are connected by passages 221 and 222. Relief valves 52a and 52b are connected between passages 221 and 222. When the pressure difference of the hydraulic fluid between passages 221 and 222 exceeds a predetermined pressure, the relief valves 52a and 52b release the hydraulic fluid in the high-pressure passages 221 and 222 to the low-pressure passages 222 and 221, thereby protecting passages 221 and 222. The proportional switching valve 54 is configured to switch the connection destination between passage 220 and the hydraulic fluid tank 25 to either passage 221 or passage 222 in accordance with the operation signal output from the controller 57, and the flow rate is adjustable.

[0069] Furthermore, the proportional switching valve 55 and the travel motor 8b are connected by passages 223 and 224. Relief valves 53a and 53b are connected between passages 223 and 224. When the pressure difference of the hydraulic fluid between passages 223 and 224 exceeds a predetermined pressure, the relief valves 53a and 53b release the hydraulic fluid in the high-pressure passages 223 and 224 to the low-pressure passages 224 and 223, thereby protecting passages 223 and 224. The proportional switching valve 55 is configured to switch the connection destination between passage 220 and the hydraulic fluid tank 25 to either passage 223 or passage 224 in response to an operation signal output from the controller 57, and the flow rate is adjustable.

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

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

[0072] The pressure sensor 84a connected to the flow path 206 measures the pressure in the flow path 206 and inputs it to the controller 57. By measuring the pressure in the flow path 206, the pressure sensor 84a measures the pressure at one of the input / output ports of the third closed-circuit pump 16. The pressure sensor 84b connected to the flow path 207 measures the pressure in the flow path 207 and inputs it to the controller 57. By measuring the pressure in the flow path 207, the pressure sensor 84b measures the pressure at one of the input / output ports of the third closed-circuit pump 16. 、 The pressure at the other input / output port of the third closed-circuit pump 16 is measured. The pressure sensor 85 connected to the flow path 208 is 、 Measure the pressure in flow path 208. 、 Input to controller 57. Pressure sensor 85 、 By measuring the pressure in the flow path 208, the pressure at the discharge port of the third open-circuit pump 17 is measured.

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

[0074] The pressure sensor 70a connected to the flow path 212 measures the pressure in the flow path 212 and inputs it to the controller 57. By measuring the pressure in the flow path 212, the pressure sensor 70a measures the pressure in the cap chamber 1a of the boom cylinder 1. The pressure sensor 70b connected to the flow path 213 measures the pressure in the flow path 213 and inputs it to the controller 57. By measuring the pressure in the flow path 213, the pressure sensor 70b measures the pressure in the rod chamber 1b of the boom cylinder 1.

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

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

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

[0078] Based on command values ​​from the operating device 56 for the extension and retraction direction and extension and retraction speed of the boom cylinder 1, arm cylinder 3 and bucket cylinder 5, command values ​​for the rotation direction and rotation speed of the slewing motor 7 and travel motors 8a and 8b, and various sensor information in the hydraulic drive unit 107, 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 and 55.

[0079] Specifically, the controller 57 performs pressure-receiving area control to control the first flow rate and the second flow rate so that the ratio of the first flow rate, which is the flow rate of the first closed-circuit pump 12 on the flow path 212 side connected to the cap chamber 1a and 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 a switching valve 44a, becomes a predetermined value set in advance according to the pressure-receiving area of ​​the cap chamber 1a and rod chamber 1b of the boom cylinder 1. Similarly, the controller 57 also performs the above pressure-receiving area control for the arm cylinder 3 and the bucket cylinder 5.

[0080] Furthermore, when the controller 57 operates at least one of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5, the switching valves 43a~50a, 43b~50b, 43c~50c ,43d~50d By appropriately controlling the system, the hydraulic fluid discharged from the same number of open-circuit pumps 13, 15, 17, 19 as the corresponding closed-circuit pumps 12, 14, 16, 18 is supplied to at least one of the boom cylinder 1, arm cylinder 3, and bucket cylinder 5 that are to be operated.

[0081] Furthermore, the boom lever 56a of the operating device 56 provides the controller 57 with command values ​​for the extension / retraction direction and extension / retraction speed of the boom cylinder 1. The arm lever 56b provides the controller 57 with command values ​​for the extension / retraction direction and extension / retraction speed of the arm cylinder 3, and the bucket lever 56c provides the controller 57 with command values ​​for the extension / retraction direction and extension / retraction speed of the bucket cylinder 5. Furthermore, the slewing lever 56d provides the controller 57 with command values ​​for the rotation direction and rotation speed of the slewing motor 7. The operating device 56 is The system also includes an operating lever (not shown) that provides command values ​​for the rotation direction and rotation speed of the travel motors 8a and 8b to the controller 57. Furthermore, a display device 58 is connected to the controller 57 to show the operator the status of the vehicle.

[0082] Figure 3 shows a functional block diagram of the controller 57. The controller 57 consists of a lever operation amount calculation unit 57a, a pressure calculation unit 57b, an actuator allocation flow rate calculation unit 57c, a pressure sensor fault detection unit 57d, and a pseudo-pressure calculation unit 57e.

[0083] The lever operation amount calculation unit 57a calculates the operating direction and target operating speed of each actuator in response to the operator's lever input, and inputs this information to the actuator allocation flow rate calculation unit 57c.

[0084] The pressure calculation unit 57b controls the pressure sensors 70a to 73b provided in each section. 80a The pressure in each part is calculated from the measured values ​​up to 87 and input to the actuator allocation flow rate calculation unit 57c and the display device 58.

[0085] The pressure sensor fault detection unit 57d uses the measured values ​​of pressure sensors 70a~73b, 80a~87 and the switching valve 43a~ 50d Based on the connection status of the pressure sensors determined from the command values, a fault in a pressure sensor is detected according to the flowchart shown in Figure 5, and this information is input to the actuator allocation flow rate calculation unit 57c and the display device 58.

[0086] The simulated pressure calculation unit 57e calculates the simulated pressure of actuators 1, 3, and 5 based on the measured values ​​of attitude sensors 400 to 403, and inputs this information to the actuator allocation flow rate calculation unit 57c and the display device 58.

[0087] Under normal circumstances, the actuator allocation flow rate calculation unit 57c calculates command values ​​for the switching valves 43a to 50d, proportional valves 64 to 67, and regulators 12a to 19a based on inputs from the lever operation amount calculation unit 57a and the pressure calculation unit 57b. On the other hand, if the pressure sensor failure detection unit 57d detects a failure in the pressure sensor, it calculates command values ​​for the switching valves 43a to 50d, proportional valves 64 to 67, and regulators 12a to 19a based on inputs from the pseudo-pressure calculation unit 57e and the lever operation amount calculation unit 57a.

[0088] The display device 58 displays the measured values ​​of each pressure sensor input from the pressure calculation unit 57b, the fault status of each pressure sensor input from the pressure sensor fault detection unit 57d, and the simulated pressure input from the simulated pressure calculation unit 57e.

[0089] The pressure sensor fault diagnosis input generation device 59, connected to the controller 57, is a device for improving the accuracy of fault detection by the pressure sensor fault detection unit 57d. Based on the measured values ​​of the attitude sensors 400 to 403, the pressure sensor fault diagnosis input generation device 59 outputs a lever operation signal to the lever operation amount calculation unit 57a to cause the hydraulic excavator 100 to assume a predetermined attitude (diagnosis attitude) suitable for diagnosing the pressure sensor, and outputs an open command to the switching valves 43a to 50d when the hydraulic excavator 100 is stationary in the diagnosis attitude. In this embodiment, the pressure sensor fault diagnosis input generation device 59 is configured as a device independent of the controller 57, but it may also be configured as part of the functions of the controller 57. Details of the pressure sensor fault diagnosis input generation device 59 will be described later.

[0090] Next, the operation of the hydraulic drive unit 107 shown in Figure 2 will be explained. (1) When not in operation In Figure 2, when levers 56a to 56d are not operated 、 The hydraulic pumps 12-19 are controlled to the minimum tilt angle, all switching valves 43a-50d are closed, and the boom cylinder 1, arm cylinder 3, bucket cylinder 5, and slewing motor 7 are held in a stopped state. (2) When the boom is raised Figure 4 shows the state changes of the hydraulic drive unit 107 when the boom cylinder 1 is extended. Figure 4 shows the measured values ​​of pressure sensors 70a, 80a, 82a, 84a, and 86a when pressure sensor 70a is functioning normally and when pressure sensor 70a malfunctions and the measured value drifts to a positive value.

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

[0092] Between time t1 and time t5, the input to the boom lever 56a is raised to the maximum value of the command to extend the boom cylinder 1. As the input to the boom lever 56a increases, the number of connected pumps increases. The timing at which the switching valves 43a, 45a, 47a, and 49a open is the timing at which 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 pressed. 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 increased to the pressure in the cap chamber 1a of the boom cylinder 1 before the switching valve 43a opens. The pressure-boosting operation is performed based on the values ​​measured by the pressure sensors 70a and 80a, and the switching valve 43a opens after the difference between the measured value of pressure sensor 80a and the measured value of pressure sensor 70a falls below a threshold (first threshold).

[0094] When the pressure sensor 70a is functioning normally, the discharge pressure of the first closed-circuit pump 12, measured by the pressure sensor 80a just before the switching valve 43a opens due to the pressure boosting process, is sufficiently increased. As the discharge flow rate of the first closed-circuit pump 12 increases from time t1 to time t2, the pipeline and the switching valve 43a are... Hydraulic fluid The pressure loss that occurs as the material passes through causes the measurement value of pressure sensor 80a to be greater than the measurement value of pressure sensor 70a.

[0095] If the pressure sensor 70a malfunctions and the measured value drifts to the positive side, the discharge pressure of the first closed-circuit pump 12, measured by the pressure sensor 80a just before the switching valve 43a opens due to the boosting process, will become higher than the pressure in the cap chamber 1a of the boom cylinder 1. This will cause a shock when the switching valve 43a opens.

[0096] Between time t2 and time t3, the second closed-circuit pump 14 is also increased in pressure before opening the switching valve 45a. However, if the pressure sensor 70a malfunctions, excessive pressure increase will occur, causing a shock when opening each switching valve. Since three or more pressure sensors are connected to the same pipeline by time t3, the malfunction of the pressure sensor 70a is detected by the processing of the pressure sensor malfunction detection unit 57d described later.

[0097] Between time t3 and time t5, a malfunction of the pressure sensor 70a is detected. Therefore, instead of the measured value from the pressure sensor 70a, the pseudo-pressure calculated by the pseudo-pressure calculation unit 57e is used to calculate the differential pressure across the switching valves 47a and 49a. By using a pseudo-pressure instead of the measured value from the malfunctioning pressure sensor 70a, it is possible to prevent the closed-circuit pumps 16 and 18 from being excessively pressurized, thereby suppressing the shock when opening the switching valves 47a and 49a.

[0098] Figure 5 is a flowchart showing part of the processing of the pressure sensor fault detection unit 57d. Figure 5 shows only the process for detecting a fault in the pressure sensor 70a of the boom cylinder 1. The fault 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 and the pressure sensors 81, 83, 85, 87 of the open-circuit pumps 13, 15, 17, 19, which are connected to the boom cylinder 1 via the same pipeline. Note that in Figure 5, the process of comparing the measured values ​​with the pressure sensors 81, 83, 85, 87 of the open-circuit pumps 13, 15, 17, 19 is omitted. The steps in Figure 5 will be explained in order below.

[0099] The pressure sensor fault detection unit 57d first determines whether the boom cylinder 1 and the closed-circuit pump 12 are connected (step S11). NOIf it is determined that the condition is not met, the process proceeds to step S21 described below. If the result in step S11 is YES, the absolute value of the difference between the measured values ​​of pressure sensors 70a and 80a (differential pressure) is calculated (step S12). Following step S12, it is determined whether the differential pressure is less than a predetermined threshold Plim (step S13). Here, the threshold Plim is a value predetermined considering the measurement error of the pressure sensor and the flow rate pressure loss characteristics. In this embodiment, the threshold Plim is set to a constant value, but it may also be a value that changes according to the pump discharge flow rate. If the result in step S13 is YES, the process proceeds to step S21 described below. If the result in step S13 is NO, 1 is added to the fault flag of pressure sensor 70a (step S14).

[0100] Following step S14, it is determined whether the boom cylinder 1 and the closed-circuit pump 14 are connected (step S21). If it is determined to be YES in step S21, the absolute value of the difference between the measured values ​​of the pressure sensors 70a and 82a (differential pressure) is calculated (step S22). Following step S22, it is determined whether the differential pressure is less than the threshold Plim (step S23). YES If it is determined that it is not true, proceed to step S31 described below. If it is determined to be NO in step S23, add 1 to the fault flag of the pressure sensor 70a (step S24).

[0101] Following step S24, it is determined whether the boom cylinder 1 and the closed-circuit pump 16 are connected (step S31). If it is determined to be YES in step S31, the absolute value of the difference between the measured values ​​of the pressure sensors 70a and 84a (differential pressure) is calculated (step S32). Following step S32, it is determined whether the differential pressure is less than the threshold Plim (step S33). YES If it is determined that it is not true, proceed to step S41 described below. If it is determined to be NO in step S33, add 1 to the fault flag of the pressure sensor 70a (step S34).

[0102] Following step S34, it is determined whether the boom cylinder 1 and the closed-circuit pump 18 are connected (step S41). If it is determined to be YES in step S41, the absolute value of the difference between the measured values ​​of the pressure sensors 70a and 86a (differential pressure) is calculated (step S42). Following step S42, it is determined whether the differential pressure is less than the threshold Plim (step S43). YES If it is determined that it is not true, proceed to step S51 described below. If it is determined to be NO in step S43, add 1 to the fault flag of the pressure sensor 70a (step S44).

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

[0104] The above describes the process related to fault detection of the pressure sensor 70a. However, the pressure sensor fault detection unit 57d can also detect faults in 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 measured values ​​for each combination of two pressure sensors included in the three or more pressure sensors that detect the pressure of the pipeline in communication.

[0105] Referring to Figure 4, the fault detection operation of the pressure sensor 70a, which measures the cap chamber pressure of the boom cylinder 1, will be explained in both the normal and faulty cases.

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

[0107] <If pressure sensor 70a malfunctions> In the state from time t1 to time t5, with the switching valves 43a, 45a, 47a, and 49a open, steps S11, S21, S31, and S41 determine 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 faulty, and the differential pressure with the pump pressure becomes greater than the threshold Plim, so the fault flag of the pressure sensor 70a is incremented in steps S14, S24, S34, and S44. From time t2 onward, if two or more pumps are connected to the boom cylinder 1, the fault flag of the pressure sensor 70a becomes greater than 1, so the pressure sensor 70a is determined to be faulty in step S51.

[0108] Next, the processing of the pseudo-pressure calculation unit 57e shown in Figure 3 will be explained. The pseudo-pressure calculation unit 57e determines the pseudo-pressures of the actuators 1, 3, and 5 that drive the work device 106 based on the posture of the hydraulic excavator 100. The method for determining the pseudo-pressure will be explained below using the arm cylinder 3 as an example.

[0109] Figure 6 shows the change in posture of the hydraulic excavator 100 when the arm cylinder 3 is extended, and Figure 7 shows the stroke of the arm cylinder 3 and the cap chamber 3a pressureThis shows the relationship. In the postures (a) and (b) of Figure 6, the pressure in the cap chamber 3a of the arm cylinder 3 remains constant, as shown in Figure 7. This is because the force supporting the arm 4 and bucket 6 against gravity acts on the rod chamber 3b of the arm cylinder 3, causing the pressure in the rod chamber 3b to become higher than the pressure in the cap chamber 3a, and the low-pressure side of the cap chamber 3a acts as a flushing valve. 35 This is because it is maintained at the charge pressure. Therefore, in the stroke range of positions (a) to (b), the pseudo pressure in the cap chamber 3a of the arm cylinder 3 should be set to the charge pressure.

[0110] In the postures (b) to (c) of Figure 6, as shown in Figure 7, the pressure in the cap chamber 3a of the arm cylinder 3 increases with the stroke. This is because it exerts the force necessary to support the arm 4 and bucket 6 against gravity. At this time, the pressure differs depending on whether the bucket 6 is empty or fully loaded. The simulated pressure is set to take this characteristic into account, so that even when the bucket is loaded, the difference between the simulated pressure and the actual pressure is small, and the simulated pressure is set to a value greater than the pressure in the empty (unloaded) state relative to the cylinder stroke. In this embodiment, the case where the posture of the boom cylinder 1, bucket cylinder 5, and upper slewing body 103 is constant as shown in Figure 6 has been described, but a simulated pressure table will also be provided for cases where the posture of actuators other than the arm cylinder 3 and the upper slewing body 103 are different.

[0111] By providing the functions shown in Figure 3 to the controller 57, even if the actuator pressure sensors 70a to 73b fail, the hydraulic excavator 100 can be operated without significantly reducing operability by calculating the differential pressure across the switching valves 43a to 50d using simulated pressure. In addition, the information displayed on the display device 58 allows the operator to recognize the failure status of the pressure sensor and promptly repair the pressure sensor.

[0112] The pressure sensor fault diagnosis input generation device 59 shown in Figure 3 can improve the probability of fault detection by comparing the output of a normal pressure sensor and a faulty pressure sensor at various pressure levels by having the hydraulic excavator 100 assume 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 Figure 6(a), or a posture in which the pressure in the cap chamber 3a of the arm cylinder 3 is high, as shown in Figure 6(c)). Furthermore, unlike detection during operation, the accuracy of fault detection can be improved by comparing the output of the pressure sensors when the hydraulic excavator 100 is stationary in a diagnostic posture, i.e., when the influence of flow pressure loss characteristics is eliminated and the pressure in the pipeline is made uniform. In this embodiment, the pressure sensor fault diagnosis input generation device 59 is configured as a device independent of the controller 57, but it may also be configured as part of the functions of the controller 57.

[0113] Figure 8 is a flowchart showing the processing of the pressure sensor fault diagnosis input generation device 59. This flowchart is performed with the hydraulic excavator 100 installed on level ground. Each step will be explained in order below.

[0114] The pressure sensor fault diagnosis input generation device 59 first calculates the stroke of the boom cylinder 1 (detection stroke) from the measured values ​​of the attitude sensors 400 to 403, and determines whether the detection stroke matches the stroke of the boom cylinder 1 (diagnosis stroke) in the diagnosis posture (step S101). If NO is determined in step S101, 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. 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 attitude of the boom 2 to be gradually changed toward the diagnosis posture.

[0115] If the result in step S101 is YES, the stroke of the arm cylinder 3 (detection stroke) is calculated from the measured values ​​of the attitude sensors 400 to 403, and it is determined whether the detection stroke matches the stroke of the arm cylinder 3 (diagnosis stroke) in the diagnostic posture (step S103). If the result in step S103 is NO, the input of the arm lever 56b is adjusted so that the difference between the detection stroke and the diagnosis stroke is 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. 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 attitude of the arm 4 to be changed gradually toward the diagnostic posture.

[0116] If the result in step S103 is YES, the stroke of the bucket cylinder 5 (detection stroke) is calculated from the measured values ​​of the attitude sensors 400 to 403, and it is determined whether the detection stroke matches the stroke of the bucket cylinder 5 (diagnosis stroke) in the diagnostic posture (step S105). If the result in step S105 is NO, the input to the bucket lever 56c is adjusted so that the difference between the detection stroke and the diagnosis stroke is small (step S106), and the process returns to step S105. Here, the input to 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. 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 changed gradually toward the diagnostic posture.

[0117] If the result 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, the hydraulic excavator 100 is stationary in the diagnostic position and closed-circuit pumps 12, 14, 16, and 18 and open-circuit pumps 13, 15, 17, 19With the boom cylinder 1 connected, the pressure sensor fault detection unit 57d performs fault 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, the hydraulic excavator 100 comes to a standstill in the diagnostic position and the closed-circuit pumps 12, 14, 16, and 18 and open-circuit pumps 13, 15, 17, 19 With the arm cylinder 3 connected, the pressure sensor fault detection unit 57d performs fault diagnosis processing (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, the hydraulic excavator 100 is stationary in the diagnostic position and closed-circuit pumps 12, 14, 16, 18 and open-circuit pumps 13, 15, 17, 19 With the bucket cylinder 5 connected, a fault diagnosis process is performed by the pressure sensor fault 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, the hydraulic excavator 100 comes to a standstill in the diagnostic position and the closed-circuit pumps 12, 14, 16, and 18 and open-circuit pumps 13, 15, 17, 19 With the slewing motor 7 connected, the pressure sensor fault detection unit 57d performs fault diagnosis processing (step S117).

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

[0122] Figure 9 shows the state changes of the hydraulic drive unit 107 in response to the input of the pressure sensor fault diagnosis input generation device 59. Figure 9 only shows 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 bucket 6 are already in the diagnostic position.

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

[0124] At time t11, the pressure sensor fault diagnosis input generation device 59 is activated, and at time t12 at The input to the boom lever 56a is adjusted until the stroke of boom cylinder 1 reaches the diagnostic stroke. Shortly after the input to the boom lever 56a begins at time t11, the switching valve 43a opens and the closed-circuit pump 12 is connected to boom cylinder 1. The input to the boom lever 56a decreases as the stroke of boom cylinder 1 approaches the diagnostic stroke.

[0125] When the stroke of boom cylinder 1 reaches the diagnostic stroke at time t12, the switching valve 43a closes, and between time t12 and time t13, the switching valves 43a, 45a, 47a, and 49a open.

[0126] Between time t13 and time t14, a fault diagnosis of the pressure sensor 70a is performed, and between time t14 and time t15, the switching valves 43a, 45a, 47a, and 49a are closed.

[0127] (summary) In this embodiment, the system includes a work device 106, actuators 1, 3, and 5 that drive the work device 106, a plurality of variable displacement closed-circuit pumps 12, 14, 16, and 18 having two inlet and outlet ports, and a plurality of closed-circuit switching valves 43a to 43d, 45a to 45d, and 47a to 47d that can switch the communication between the actuators 1, 3, and 5 and the plurality of closed-circuit pumps 12, 14, 16, and 18. ,49a~49d The system includes posture sensors 400-403 for detecting the posture of the work device 106, multiple closed-circuit pump pressure sensors 80a, 80b, 82a, 82b, 84a, 84b, 86a, 86b for detecting the pressure of multiple closed-circuit pumps 12, 14, 16, 18, actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b for detecting the pressure of actuators 1, 3, 5, an operating device 56 for instructing the operation of actuators 1, 3, 5, and multiple closed-circuit switching valves 43a- 43c ,45a~ 45c ,47a~ 47c, 49a~49c The system also includes a controller 57 that controls multiple closed-circuit pumps 12, 14, 16, 18, and when the controller 57 starts supplying hydraulic fluid from one of the multiple closed-circuit pumps 12, 14, 16, 18 to the actuators 1, 3, 5, it controls multiple closed-circuit switching valves 43a~ 43c ,45a~ 45c ,47a~ 47c, 49a~49cIn a construction machine in which, with one of the closed-circuit pumps, one closed-circuit switching valve, closed, the controller 57 controls the closed-circuit pump so that the differential pressure across the closed-circuit switching valve, which is the difference between the measured value of the closed-circuit pump pressure sensor corresponding to one of the closed-circuit pumps and the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, becomes less than or equal to a predetermined first threshold, and then opens the closed-circuit switching valve, the controller 57 controls the closed-circuit pump so that, with two or more of the multiple closed-circuit pumps 12, 14, 16, 18 connected to actuators 1, 3, 5, the multiple closed-circuit pump pressure sensors 80a, 80b, 82a, 82b, 84a, 84b, 86a, 86 Based on the measured values ​​of two or more closed-circuit pump pressure sensors corresponding to the two or more closed-circuit pumps mentioned above, and the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b, it is determined whether or not the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b are malfunctioning. If it is determined that the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b are malfunctioning, the simulated pressure of actuators 1, 3, and 5 is calculated based on the measured values ​​of the attitude sensors 400 to 403, and the differential pressure across the closed-circuit switching valve is calculated using the simulated pressure instead of the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b.

[0128] According to this embodiment configured as described above, the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72 b Based on the comparison results between the measured value and the measured values ​​of two or more closed-circuit pump pressure sensors, actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72 b This makes it possible to correctly determine malfunctions. Furthermore, if actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b fail, the simulated pressure of actuators 1, 3, and 5, calculated according to the posture of the work device 106, is used instead of the measured value of the failed pressure sensor to control the closed-circuit switching valve 43a~ 43c ,45a~ 45c ,47a~ 47c, 49a~49cThe differential pressure across the circuit is calculated. As a result, the shock when connecting the closed-circuit pumps 12, 14, 16, and 18 to actuators 1, 3, and 5 is suppressed, thus preventing a decrease in operability.

[0129] Furthermore, the hydraulic excavator 100 in this embodiment includes a plurality of variable displacement open-circuit pumps 13, 15, 17, 19 having inlet and outlet ports, a plurality of open-circuit switching valves 44a~44d, 46a~46d, 48a~48d, 50a~50d that can connect the plurality of open-circuit pumps 13, 15, 17, 19 to actuators 1, 3, 5, and a plurality of open-circuit pump pressure sensors 81, 83, 85, 87 that detect the pressure of the plurality of open-circuit pumps 13, 15, 17, 19. When the controller 57 starts supplying hydraulic fluid from one of the open-circuit pumps 13, 15, 17, 19 to the actuators 1, 3, 5, it closes one of the open-circuit switching valves 44a~44d, 46a~46d, 48a~48d, 50a~50d that corresponds to the one open-circuit pump, and uses the measured value of the open-circuit pump pressure sensor corresponding to the one open-circuit pump and the actuator pressure sensors 70a, 70b, 71 After controlling one open-circuit pump so that the differential pressure across the open-circuit switching valve, which is the difference between the measured values ​​of a, 71b, 72a, and 72b, is less than or equal to the first threshold, the one open-circuit switching valve is opened, and with two or more of the open-circuit pumps 13, 15, 17, and 19 connected to actuators 1, 3, and 5, the measured values ​​of two or more open-circuit pump pressure sensors 81, 83, 85, and 87 corresponding to the two or more open-circuit pumps are compared with the actuators Based on the measured values ​​of the inverter pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b, it is determined whether or not the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b are faulty. If it is determined that the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b are faulty, the differential pressure across the open-circuit switching valve is calculated using the simulated pressure instead of the measured values ​​of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b. b Based on the comparison results between the measured value and the measured values ​​of two or more open-circuit pump pressure sensors, actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 7 2b This makes it possible to correctly determine the malfunction. Furthermore, if the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, and 72b fail, the simulated pressure of actuators 1, 3, and 5, calculated according to the posture of the work device 106, is used instead of the measured value of the faulty pressure sensor to control the open-circuit switching valves 44a-44d, 46a-46d, and 48a-48d. ,50a~50d The differential pressure across the circuit is calculated. As a result, the shock when connecting the open-circuit pumps 13, 15, 17, and 19 to actuators 1, 3, and 5 is suppressed, thus preventing a decrease in operability.

[0130] Furthermore, in this embodiment, the controller 57 calculates the difference in measured values ​​for each combination of two pressure sensors included in the actuator pressure sensors 70a to 72b, the two or more closed-circuit pump pressure sensors, and the two or more open-circuit pump pressure sensors, while the two or more closed-circuit pumps and the two or more open-circuit pumps are connected to the actuators 1, 3, and 5. The controller determines that any pressure sensor included in two or more combinations where the difference is greater than a predetermined second threshold Plim is faulty. This makes it possible to detect faults not only in the actuator pressure sensors 70a to 72b, but also 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.

[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. When the controller 57 determines that one of the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72b, the two or more closed-circuit pump pressure sensors, or the two or more open-circuit pump pressure sensors is faulty, it outputs identification information of the one pressure sensor to the display device 58. This makes it possible to shorten the time until the faulty pressure sensor is repaired or replaced.

[0132] Furthermore, in this embodiment, the controller 57 calculates the simulated pressure such that the position detected by the position sensors 400-403 is greater than the pressure of the actuators 1, 3, and 5 when the work device 106 is in an unloaded state. As a result, when a load is applied to the work device 106, the actuator pressure sensors 70a, 70b, 71a, 71b, 72a, 72 b Even in the event of a malfunction, it is possible to suppress the shock when opening the switching valves 43a to 49d.

[0133] Furthermore, the hydraulic excavator 100 in this embodiment is equipped with a pressure sensor fault diagnosis input generation device 59 that can adjust the input and output of the controller 57, and the controller 57 adjusts the input and output of the pressure sensor fault diagnosis input generation device 59 so that the working device 106 takes a predetermined posture (diagnostic posture) by supplying multiple closed-circuit pumps 12, 14, 16, 18 and multiple closed-circuit switching valves 43a~ 43c ,45a~ 45c ,47a~47 c, 49a~49c After controlling the pumps, the discharge flow rates of the multiple closed-circuit pumps 12, 14, 16, and 18 are set to zero, and the multiple closed-circuit pumps 12, 14, 16, and 18 are maintained connected to the actuators 1, 3, and 5. This allows the hydraulic excavator 100 to be stationary in a diagnostic position, i.e., the pressure on the pipeline is made uniform by eliminating the effects of flow rate pressure loss characteristics, thereby improving the accuracy of fault detection.

[0134] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and includes various modifications. For example, the embodiments described above have been described in detail for the purpose of explaining the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described above. [Explanation of Symbols]

[0135] 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... Swivel motor (actuator), 8a, 8b... Travel motor, 9... Engine, 10... Drive Power 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... Relief valve for charging, 21~24... Relief valve, 25... Hydraulic oil tank, 26~29... Charge chain 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… Check valves for charging, 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...Operating device, 56a...Boom lever, 56b...Arm lever, 56c...Bucket lever, 56d...Slewing lever, 57...Controller, 57a...Lever operation amount calculation unit, 57b...Pressure calculation unit, 57c...Actuator assigned flow rate calculation unit, 57d...Pressure sensor fault detection unit, 57e...Simulated pressure calculation unit, 58...Display device, 59...Pressure sensor fault 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, Ru, 1 01a, 101b... Traveling device, 102... Lower traveling body, 103... Upper slewing body, 104... Cab, 105... Slewing device, 106... Front work equipment (working device), 107... Hydraulic drive device, 200~202... Flow channels, 202a... Branching flow channels, 203~205... Flow channels, 205a... Branching flow channels, 206~208... Flow channels, 208a... Branching flow channels, 209~211... Flow channels, 211a... Branching flow channels, 212~225... Flow channels, 301~304... Connecting flow channels, 305a~305d, 306a~306d, 307a~307d, 308a~308d... Open circuit connecting flow channels, 309a~309c... Closed circuit connecting flow channels, 400~403... Attitude sensors, A~D... Closed circuits, E~H... Open circuits.

Claims

1. Work equipment and An actuator that drives the aforementioned work device, Multiple variable displacement closed-circuit pumps having two inlet / outlet ports, Multiple closed-circuit switching valves capable of switching the connection between the actuator and the multiple closed-circuit pumps, A posture sensor for detecting the posture of the work device, Multiple closed-circuit pump pressure sensors for detecting the pressure of the multiple closed-circuit pumps, An actuator pressure sensor for detecting the pressure of the actuator, An operating device for instructing the operation of the actuator, The system includes a controller that controls the plurality of closed-circuit switching valves and the plurality of closed-circuit pumps in response to input signals from the operating device, In a construction machine, when the controller starts supplying hydraulic fluid from one of the plurality of closed-circuit pumps to the actuator, the controller controls the one closed-circuit switching valve so that the differential pressure across the closed-circuit switching valve, which is the difference between the measured value of the closed-circuit pump pressure sensor corresponding to the one closed-circuit pump and the measured value of the actuator pressure sensor, becomes less than or equal to a predetermined first threshold value, while the one closed-circuit switching valve is closed, and then opens the one closed-circuit switching valve. The aforementioned controller, With two or more of the multiple closed-circuit pumps connected to the actuator, the presence or absence of a malfunction in the actuator pressure sensor is determined based on the measured values ​​of two or more closed-circuit pump pressure sensors corresponding to the two or more closed-circuit pumps and the measured value of the actuator pressure sensor. If the actuator pressure sensor is determined to be faulty, a pseudo-pressure of the actuator is calculated based on the measurement value of the attitude sensor, and the differential pressure across the closed-circuit switching valve is calculated using the pseudo-pressure instead of the measurement value of the actuator pressure sensor. A construction machine characterized by the following features.

2. In the construction machine described in claim 1, Multiple open-circuit pumps with variable displacement having inlet and outlet ports, Multiple open-circuit pumps and multiple open-circuit switching valves that can be connected to the actuator, The system includes a plurality of open-circuit pump pressure sensors that detect the pressure of the plurality of open-circuit pumps, The aforementioned controller, When supplying hydraulic fluid to the actuator from one of the multiple open-circuit pumps, the open-circuit switching valve corresponding to the one open-circuit pump is closed, and the open-circuit switching valve is controlled so that the differential pressure across the open-circuit switching valve, which is the difference between the measured value of the open-circuit pump pressure sensor corresponding to the one open-circuit pump and the measured value of the actuator pressure sensor, becomes less than or equal to the first threshold, and then the open-circuit switching valve is opened. With two or more of the multiple open-circuit pumps connected to the actuator, the presence or absence of a malfunction in the actuator pressure sensor is determined based on the measured values ​​of two or more open-circuit pump pressure sensors corresponding to the two or more open-circuit pumps and the measured value of the actuator pressure sensor. If the actuator pressure sensor is determined to be faulty, the differential pressure across the open-circuit switching valve is calculated using the simulated pressure instead of the measured value from the actuator pressure sensor. A construction machine characterized by the following features.

3. In the construction machine described in claim 1, The controller calculates the simulated pressure such that the position detected by the position sensor is greater than or equal to the pressure of the actuator when the work device is in an unloaded state. A construction machine characterized by the following features.

4. In the construction machine described in claim 1, The controller is equipped with a pressure sensor fault diagnosis input generation device that allows adjustment of input and output, The controller, by adjusting the input and output of the pressure sensor fault diagnosis input generation device, controls the plurality of closed-circuit pumps and the plurality of closed-circuit switching valves so that the work device assumes a predetermined posture, and then maintains the state in which the plurality of closed-circuit pumps are connected to the actuator with the discharge flow rate of the plurality of closed-circuit pumps set to zero. A construction machine characterized by the following features.

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