Construction machinery, construction machinery system, and pump load reduction method

Abstract

To provide a technology capable of suppressing the acceleration of failure of a hydraulic pump that shows signs of failure. [Solution] The construction machine 100 is equipped with an on-off valve 40 arranged in a flow path FP3 connecting a first pump 21 and a second pump 22, a first unloading valve 51 that adjusts the flow rate of hydraulic oil from the first pump 21 to a tank 25, a second unloading valve 52 that adjusts the flow rate of hydraulic oil from the second pump 22 to the tank 25, a first check valve 61 that blocks the flow of hydraulic oil from the on-off valve 40 to the first pump 21, a second check valve 62 that blocks the flow of hydraulic oil from the on-off valve 40 to the second pump 22, and a controller 10 that performs pump load reduction control by increasing the opening of the unloading valve connected to the failure symptom pump out of the first unloading valve 51 and the second unloading valve 52, when either the first pump 21 or the second pump 22 is a failure symptom pump that shows signs of failure, and by increasing the opening of the on-off valve 40.

Description

[Technical Field]

[0001] The present disclosure relates to technology for construction machines such as hydraulic excavators. [Background technology]

[0002] Patent Document 1 discloses a control system, which includes an engine, a first hydraulic pump and a second hydraulic pump driven by the engine, an opening and closing device provided in a flow path connecting the first hydraulic pump and the second hydraulic pump and capable of switching between a confluence state in which the flow path is open and a branch state in which the flow path is closed, a first hydraulic actuator to which hydraulic oil discharged from the first hydraulic pump is supplied in the branch state, a second hydraulic actuator to which hydraulic oil discharged from the second hydraulic pump is supplied in the branch state, a determination unit that determines whether or not output of the engine is limited, and a confluence / branch control unit that controls the opening and closing device to enter the confluence state when the determination unit determines that output of the engine is limited. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 188460 Summary of the Invention [Problem to be solved by the invention]

[0004] In the control system of Patent Document 1, when one of the first hydraulic pump and the second hydraulic pump shows signs of failure, when the opening and closing device is switched to the confluence state, the pump pressure of the hydraulic pump that is not showing signs of failure acts on the hydraulic pump that is showing signs of failure (failure sign pump), accelerating the failure of the failure sign pump.

[0005] The present disclosure aims to provide a technology that can prevent the acceleration of failure of a hydraulic pump that shows signs of failure. [Means for solving the problem]

[0006] A construction machine according to a first aspect includes a first pump, a second pump, a first actuator that receives hydraulic oil from the first pump, a second actuator that receives hydraulic oil from the second pump, an on-off valve arranged in a flow path connecting the first pump and the second pump, a first unloading valve that adjusts the flow rate of hydraulic oil from the first pump to a tank, a second unloading valve that adjusts the flow rate of hydraulic oil from the second pump to the tank, a first check valve that blocks the flow of hydraulic oil from the on-off valve to the first pump, and a second check valve that blocks the flow of hydraulic oil from the on-off valve to the second pump, and a controller that performs pump load reduction control by increasing the opening of the unloading valve connected to the failure symptom pump, of the first unloading valve and the second unloading valve, when either the first pump or the second pump is a failure symptom pump that is showing signs of failure.

[0007] In this first aspect, the construction machine is equipped with the first check valve and the second check valve, and the controller performs the pump load reduction control, so that the acceleration of failure of the pump showing a sign of failure is suppressed. This makes it possible to extend the life of the pump showing a sign of failure compared to when the pump load reduction control is not performed. Specifically, this is as follows.

[0008] For example, if the first pump is the symptom-of-failure pump, even if the controller increases the aperture of the on-off valve during the pump load reduction control, the first check valve blocks the flow of hydraulic oil from the on-off valve toward the first pump, so the pump pressure of the second pump, which is a normal pump, does not act on the first pump. Moreover, the controller can increase the aperture of the first unload valve during the pump load reduction control to increase the flow rate of hydraulic oil from the first pump toward the tank, thereby reducing the load acting on the symptom-of-failure pump. This suppresses the progression of a failure of the symptom-of-failure pump (e.g., the first pump). Moreover, because the controller increases the aperture of the on-off valve during the pump load reduction control, hydraulic oil can be supplied from the normal second pump to both the first actuator and the second actuator to operate the first actuator and the second actuator. That is, in the first aspect, the progression of a failure of the symptom-of-failure pump can be suppressed while operating the first actuator and the second actuator. This allows the life of the failure indication pump to be extended while continuing work using the first actuator and the second actuator.

[0009] A construction machine according to a second aspect is preferably the construction machine according to the first aspect further including the following configuration. That is, in the construction machine according to the second aspect, it is preferable that each of the first pump and the second pump is a variable displacement hydraulic pump, and the controller reduces the displacement of the failure indication pump in the pump load reduction control. The torque of a hydraulic pump is proportional to the product of the pump pressure of the hydraulic pump and the displacement of the hydraulic pump. In this second aspect, in the pump load reduction control, the controller can reduce the torque of the failure indication pump by reducing the displacement of the failure indication pump, thereby further reducing the load acting on the failure indication pump. This can further suppress the progression of a failure in the failure indication pump.

[0010] A construction machine according to a third aspect is preferably the construction machine according to the first or second aspect further including the following configuration. That is, in the construction machine according to the third aspect, it is preferable that each of the first pump and the second pump is a variable displacement hydraulic pump, and the controller increases the displacement of the normal pump, which is not showing signs of failure, of the first pump and the second pump in the pump load reduction control. In this third aspect, the pump load reduction control can increase the flow rate of hydraulic oil discharged from the normal pump compared to when the displacement of the normal pump is not increased. Therefore, when the first actuator and the second actuator are operated by supplying hydraulic oil to both the normal pump (e.g., the second pump), the speed of one or both of the first actuator and the second actuator can be increased compared to when the displacement of the normal pump is not increased.

[0011] A construction machine according to a fourth aspect is preferably the construction machine according to any one of the first to third aspects, further comprising the following configuration: That is, in the construction machine according to the fourth aspect, it is preferable that, in the pump load reduction control, the controller reduces the aperture of an unloading valve connected to a normal pump of the first pump or the second pump that is not showing signs of failure. In this fourth aspect, the pump load reduction control can reduce the flow rate of hydraulic oil returning to the tank via the unloading valve connected to the normal pump, compared to when the aperture of the unloading valve connected to the normal pump is not reduced, and therefore the speed of one or both of the first actuator and the second actuator can be increased.

[0012] A construction machine according to a fifth aspect may be the construction machine according to any one of the first to fourth aspects, further including the following configuration: That is, in the construction machine according to the fifth aspect, the controller may determine signs of a failure of the first pump using a first pump pressure that is the discharge pressure of the first pump, and may determine signs of a failure of the second pump using a second pump pressure that is the discharge pressure of the second pump.

[0013] A construction machine according to a sixth aspect is preferably the construction machine according to any one of the first to fifth aspects, further comprising the following configuration: That is, in the construction machine according to the sixth aspect, the controller may determine signs of a failure of the first pump using the flow rate of hydraulic oil discharged from the first pump or a physical quantity correlated to the flow rate, and may determine signs of a failure of the second pump using the flow rate of hydraulic oil discharged from the second pump or a physical quantity correlated to the flow rate.

[0014] A construction machine system according to a seventh aspect includes the construction machine according to any one of the first to sixth aspects and an external device located at a location remote from the construction machine, and it is preferable that the controller transmits information about the fault symptom pump to the external device. In this seventh aspect, for example, even when an operator remotely operates the construction machine at a location remote from the construction machine, or when a worker involved in work monitors the automatically operated construction machine at a location remote from the construction machine, the operator or the worker involved in work can grasp the status of the fault symptom pump in the construction machine based on the information transmitted from the controller and can quickly take necessary measures.

[0015] A pump load reduction method according to an eighth aspect is a pump load reduction method for a construction machine comprising a first pump, a second pump, a first actuator that receives hydraulic oil from the first pump, a second actuator that receives hydraulic oil from the second pump, an on-off valve arranged in a flow path connecting the first pump and the second pump, a first unloading valve that adjusts the flow rate of hydraulic oil from the first pump to a tank, a second unloading valve that adjusts the flow rate of hydraulic oil from the second pump to the tank, a first check valve that blocks the flow of hydraulic oil from the on-off valve to the first pump, and a second check valve that blocks the flow of hydraulic oil from the on-off valve to the second pump, and when either the first pump or the second pump is a failure symptom pump that is showing signs of failure, the method includes a controller increasing the opening degree of the unloading valve connected to the failure symptom pump, of the first unloading valve and the second unloading valve, and the controller increasing the opening degree of the on-off valve. [Effects of the Invention]

[0016] According to the present disclosure, a technique is provided that can suppress the acceleration of failure of a hydraulic pump that shows signs of failure. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a side view showing a construction machine according to an embodiment. [Figure 2] FIG. 2 is a diagram showing a hydraulic circuit of the construction machine. [Figure 3] 1 is a graph showing an example of a relational expression representing the relationship between an operation amount (operation signal) of an operation received by an operating device and a pump command flow rate (target flow rate). [Figure 4] 10 is a graph showing an example of a relational expression that represents the relationship between an operation amount (operation signal) of an operation received by an operating device and an unloading valve opening command (current value). [Figure 5] 4 is a flowchart showing an example of a calculation process performed by a controller of the construction machine. [Figure 6] FIG. 1 is a diagram illustrating a construction machine system. DETAILED DESCRIPTION OF THE INVENTION

[0018] A construction machine according to an embodiment of the present disclosure will be described with reference to the drawings.

[0019] Fig. 1 is a side view showing a construction machine 100 according to an embodiment. In the specific example shown in Fig. 1, the construction machine 100 is a shovel. However, the construction machine in this disclosure may be other construction machines such as a crane or a bulldozer.

[0020] As shown in FIG. 1, the construction machine 100 includes a lower body 1, an upper rotating body 2, and a work implement 3.

[0021] The lower body 1 is a self-propelled lower traveling body equipped with a crawler-type traveling device. However, the lower body 1 may be configured with a base member such as a foundation or a pillar that is fixed to a fixed object such as the ground or a structure.

[0022] The upper rotating body 2 is supported on the lower body 1 so as to be rotatable around the Z axis in the vertical direction. The upper rotating body 2 includes a rotating frame, a cabin supported by the rotating frame, and a counterweight disposed behind the cabin.

[0023] The working device 3 includes a boom 4 supported on a swivel frame so that it can be raised and lowered, an arm 5 supported rotatably at the tip of the boom 4, and a bucket 6 supported rotatably at the tip of the arm 5.

[0024] 2 is a diagram showing the main parts of the hydraulic circuit of the construction machine 100. The construction machine 100 is equipped with a controller 10, multiple hydraulic pumps, an on-off valve 40 (confluence valve), multiple hydraulic actuators, an operation device 12, multiple directional control valves, a boom acceleration control valve 44, multiple unloading valves, multiple check valves, and multiple detectors.

[0025] The controller 10 includes a computer including a processing unit and a memory. The controller 10 performs pump load reduction control, which will be described later. The pump load reduction control by the controller 10 is realized by the processing unit executing a control program stored in the memory.

[0026] The plurality of hydraulic pumps include a first pump 21 and a second pump 22. Each of the first pump 21 and the second pump 22 is a variable displacement hydraulic pump. Each of the first pump 21 and the second pump 22 is driven by a drive source (not shown). The drive source may be, for example, an engine or an electric motor.

[0027] The capacity (displacement volume) of the first pump 21 is adjusted by a first regulator 91, and the capacity (displacement volume) of the second pump 22 is adjusted by a second regulator 92. The first regulator 91 adjusts the capacity of the first pump 21 in accordance with a tilt command (current value) input from the controller 10. The second regulator 92 adjusts the capacity of the second pump 22 in accordance with the tilt command (current value) input from the controller 10.

[0028] The on-off valve 40 is disposed in a connection flow path FP3, which is a flow path connecting the first pump 21 and the second pump. A first discharge flow path FP1 is connected to the first pump 21, and the hydraulic oil discharged from the first pump 21 flows into this first discharge flow path FP1. A second discharge flow path FP2 is connected to the second pump 22, and the hydraulic oil discharged from the second pump 22 flows into this second discharge flow path FP2. The connection flow path FP3 is a flow path connecting the first discharge flow path FP1 and the second discharge flow path FP2, and the on-off valve 40 is disposed midway along the connection flow path FP3.

[0029] The on-off valve 40 is configured to be switchable between an open state in which the hydraulic oil is allowed to flow through the connection flow path FP3 and a closed state in which the hydraulic oil is prevented from flowing through the connection flow path FP3. The on-off valve 40 is configured to perform an opening / closing operation in response to an on-off valve opening command (current value) input from the controller 10. The on-off valve 40 may be configured such that the opening degree of the on-off valve 40 is adjusted to a magnitude in accordance with the magnitude of the on-off valve opening command (current value).

[0030] 1 and 2, the plurality of hydraulic actuators include a boom cylinder 31, an arm cylinder 34, a bucket cylinder 33, and a swing motor 32. The boom cylinder 31 and the bucket cylinder 33 are each an example of a first actuator in the present disclosure. The swing motor 32 is an example of a second actuator in the present disclosure.

[0031] The boom cylinder 31 is a hydraulic cylinder that operates when supplied with hydraulic oil to raise and lower the boom 4 relative to the upper rotating body 2. The boom cylinder 31 has a base end that is rotatably attached to the rotating frame of the upper rotating body 2, and a tip end that is rotatably attached to the boom 4.

[0032] The arm cylinder 34 is a hydraulic cylinder that operates when supplied with hydraulic oil to rotate the arm 5 relative to the boom 4. The arm cylinder 34 has a base end that is rotatably attached to the boom 4 and a tip end that is rotatably attached to the arm 5.

[0033] The bucket cylinder 33 is a hydraulic cylinder that operates when supplied with hydraulic oil to rotate the bucket 6 relative to the arm 5. The bucket cylinder 33 has a base end that is rotatably attached to the arm 5, and a tip end that is rotatably attached to a link member that is connected to the bucket 6.

[0034] The swing motor 32 is a hydraulic motor that operates by receiving a supply of hydraulic oil and swings the upper swing body 2 relative to the lower body 1.

[0035] In FIG. 2, only the circuits for operating the boom cylinder 31, the swing motor 32, and the bucket cylinder 33 are shown as representatives, and the circuits for operating other actuators such as the arm cylinder 34 are not shown.

[0036] The operating device 12 includes a plurality of operating levers. Any one of the plurality of operating levers receives a boom operation by the operator to operate the boom cylinder 31. The boom operation includes a boom-raising operation to cause the boom 4 to perform a boom-raising operation, and a boom-lowering operation to cause the boom 4 to perform a boom-lowering operation. Any one of the plurality of operating levers receives an arm operation by the operator to operate the arm cylinder. The arm operation includes an arm-pushing operation to cause the arm 5 to perform an arm-pushing operation, and an arm-pulling operation to cause the arm 5 to perform an arm-pulling operation. Any one of the plurality of operating levers receives a bucket operation by the operator to operate the bucket cylinder 33. The bucket operation includes a bucket-pushing operation to cause the bucket 6 to perform a bucket-pushing operation (soil-discharging operation), and a bucket-pulling operation to cause the bucket 6 to perform a bucket-pulling operation (excavation operation). Any one of the plurality of operating levers receives a swing operation by the operator to operate the swing motor 32. The turning operation includes a right turning operation for making the upper turning body 2 turn right, and a left turning operation for making the upper turning body 2 turn left.

[0037] The boom-raising operation is an operation in which the tip of the boom 4 moves away from the ground, and the boom-lowering operation is an operation in which the tip of the boom 4 moves closer to the ground. The arm-pushing operation is an operation in which the tip of the arm 5 moves away from the boom 4, and the arm-pulling operation is an operation in which the tip of the arm 5 moves closer to the boom 4. The bucket-pushing operation is an operation in which the tip of the bucket 6 moves away from the upper rotating body 2, and the bucket-pulling operation is an operation in which the tip of the bucket 6 moves closer to the upper rotating body 2.

[0038] When the operation device 12 receives a lever operation (the boom operation, the arm operation, the bucket operation, or the swing operation) by the operator, it inputs an operation signal to the controller 10 according to the amount of the lever operation.

[0039] FIG. 3 is a graph showing an example of a relational expression representing the relationship between the operation amount (operation signal) of the lever operation received by the operation device 12 and the pump command flow rate, which is the target flow rate of the pump. The controller 10 stores the relational expression shown in FIG. 3 in advance. Using the relational expression shown in FIG. 3, the controller 10 calculates a larger target flow rate (pump command flow rate) as the operation amount of the lever operation received by the operation device 12 increases. Then, the controller 10 inputs a tilt command corresponding to the calculated pump command flow rate to the first regulator 91 or the second regulator 92. As a result, the pump capacity increases as the operation amount of the lever operation increases.

[0040] When the operation device 12 receives, for example, the boom operation, the controller 10 calculates a pump command flow rate, which is a target flow rate for the first pump 21, based on an operation signal corresponding to the operation amount of the boom operation input from the operation device 12 and the relational expression shown in FIG. 3, and inputs a tilt command (current value) corresponding to the calculated pump command flow rate to the first regulator 91. This adjusts the capacity of the first pump 21 to a magnitude corresponding to the operation amount of the boom operation. Furthermore, when the operation device 12 receives, for example, the bucket operation, the controller 10 calculates a pump command flow rate, which is a target flow rate for the first pump 21, based on an operation signal corresponding to the operation amount of the bucket operation input from the operation device 12 and the relational expression shown in FIG. 3, and inputs a tilt command (current value) corresponding to the calculated pump command flow rate to the first regulator 91. This adjusts the capacity of the first pump 21 to a magnitude corresponding to the operation amount of the bucket operation. Furthermore, when the operating device 12 receives, for example, the swing operation, the controller 10 calculates a pump command flow rate, which is a target flow rate for the second pump 22, based on an operation signal corresponding to the amount of operation of the swing operation input from the operating device 12 and the relational expression shown in Fig. 3, and inputs a tilt command (current value) corresponding to the calculated pump command flow rate to the second regulator 92. This adjusts the capacity of the second pump 22 to a magnitude corresponding to the amount of operation of the swing operation.

[0041] The plurality of directional control valves include a boom directional control valve 41, an arm directional control valve (not shown), a bucket directional control valve 43, and a swing directional control valve 42. Each of the boom directional control valve 41 and the bucket directional control valve 43 is an example of a first control valve in the present disclosure. The swing directional control valve 42 is an example of a second control valve in the present disclosure. The first control valve is a control valve for adjusting the direction and flow rate of hydraulic oil supplied from the first pump 21 to the first actuator. The second control valve is a control valve for adjusting the direction and flow rate of hydraulic oil supplied from the second pump 22 to the second actuator.

[0042] Each of the plurality of directional control valves may be configured to operate in response to an opening command output from the operating device 12 and input to the directional control valve in response to the amount of operation received by the operating device 12. In this case, the opening command input from the operating device 12 may be a pilot pressure output from a remote control valve of the operating device 12 in response to the amount of operation received by the operating device 12 and input to the directional control valve, or may be a current value output from the operating device 12 and input to the directional control valve in response to the amount of operation received by the operating device 12. Furthermore, each of the plurality of directional control valves may be configured to operate in response to an opening command (current value) output from the controller 10 in response to the amount of operation received by the operating device 12 and input to the directional control valve.

[0043] Each of the plurality of directional control valves may be a three-position directional control valve having a P port which is a port to which hydraulic oil is supplied from the pump, a T port which is a port connected to a tank flow path for returning hydraulic oil to the tank 25, an A port which is a port connected to a flow path through which hydraulic oil is supplied to the hydraulic actuator or a flow path through which hydraulic oil is discharged from the hydraulic actuator, and a B port which is a port connected to a flow path through which hydraulic oil is discharged from the hydraulic actuator or a flow path through which hydraulic oil is supplied to the hydraulic actuator. Each of the plurality of directional control valves has a spool which operates in response to an opening command input from the operating device 12 or the controller 10.

[0044] The first discharge flow path FP1 branches into a flow path FP4 and a flow path FP5, the flow path FP4 is connected to the P port of the boom direction control valve 41, and the flow path FP5 is connected to the P port of the bucket direction control valve 43. The second discharge flow path FP2 branches into a flow path FP6 and a flow path FP7, the flow path FP6 is connected to the P port of the swing direction control valve 42, and the flow path FP7 is connected to the P port of the boom acceleration control valve 44.

[0045] The A port of the boom direction control valve 41 is connected to the head side chamber 31A of the boom cylinder 31 via a flow path FP21. The B port of the boom direction control valve 41 is connected to the rod side chamber 31B of the boom cylinder via a flow path FP22. The A port of the bucket direction control valve 43 is connected to the head side chamber 33A of the bucket cylinder 33 via a flow path FP25. The B port of the bucket direction control valve 43 is connected to the rod side chamber 33B of the bucket cylinder via a flow path FP26. The A port of the swing direction control valve 42 is connected to the first port 32A of the swing motor 32 via a flow path FP23. The B port of the swing direction control valve 42 is connected to the second port 32B of the swing motor 32 via a flow path FP24.

[0046] The boom direction control valve 41 opens to change the direction and flow rate of hydraulic oil supplied to the boom cylinder 31 by displacing a spool in accordance with a boom opening command input from the operating device 12 or the controller 10. The arm direction control valve opens to change the direction and flow rate of hydraulic oil supplied to the arm cylinder by displacing a spool in accordance with an arm opening command input from the operating device 12 or the controller 10. The bucket direction control valve 43 opens to change the direction and flow rate of hydraulic oil supplied to the bucket cylinder 33 by displacing a spool in accordance with a bucket opening command input from the operating device 12 or the controller 10. The swing direction control valve 42 opens to change the direction and flow rate of hydraulic oil supplied to the swing motor 32 by displacing a spool in accordance with a swing opening command input from the operating device 12 or the controller 10.

[0047] When the operating lever of the operating device 12 receives a boom-raising operation, a boom opening command corresponding to the amount of operation of the boom-raising operation is input from the operating device 12 or the controller 10 to the boom direction control valve 41, and the spool of the boom direction control valve 41 is displaced from the neutral position in the direction corresponding to the boom-raising operation by a stroke corresponding to the amount of operation of the boom-raising operation. As a result, the boom direction control valve 41 opens to allow hydraulic oil from the first pump 21 to be supplied to the head-side chamber 31A of the boom cylinder 31 and to allow hydraulic oil discharged from the rod-side chamber 31B of the boom cylinder 31 to return to the tank 25. As a result, the boom cylinder 31 extends, and the boom 4 performs a boom-raising operation.

[0048] When the operating lever of the operating device 12 is operated to lower the boom, a boom opening command corresponding to the amount of operation of the boom lowering operation is input from the operating device 12 or the controller 10 to the boom direction control valve 41, and the spool of the boom direction control valve 41 is displaced from the neutral position in the direction corresponding to the boom lowering operation by a stroke corresponding to the amount of operation of the boom lowering operation. As a result, the boom direction control valve 41 opens to allow hydraulic oil from the first pump 21 to be supplied to the rod side chamber 31B of the boom cylinder 31 and to allow hydraulic oil discharged from the head side chamber 31A of the boom cylinder 31 to return to the tank 25. As a result, the boom cylinder 31 retracts, and the boom 4 performs a boom lowering operation.

[0049] The operations of the arm direction control valve and bucket direction control valve 43 are similar to the operation of the boom direction control valve 41 described above, and therefore detailed explanations thereof will be omitted.

[0050] When the operation lever of the operation device 12 receives a right swing operation, a swing opening command corresponding to the amount of operation of the right swing operation is input from the operation device 12 or the controller 10 to the swing direction control valve 42, and the spool of the swing direction control valve 42 is displaced from the neutral position in the direction corresponding to the right swing operation by a stroke corresponding to the amount of operation of the right swing operation. As a result, the swing direction control valve 42 opens to allow hydraulic oil from the second pump 22 to be supplied to the first port 32A of the swing motor 32 and to allow hydraulic oil discharged from the second port 32B of the swing motor 32 to return to the tank 25. As a result, the swing motor 32 rotates in the direction corresponding to the right swing, and the upper swing body 2 performs a right swing operation.

[0051] When the operation lever of the operation device 12 is operated to swing left, a swing opening command corresponding to the amount of operation of the left swing operation is input from the operation device 12 or the controller 10 to the swing direction control valve 42, and the spool of the swing direction control valve 42 is displaced from the neutral position in the direction corresponding to the left swing operation by a stroke corresponding to the amount of operation of the left swing operation. As a result, the swing direction control valve 42 opens to allow hydraulic oil from the second pump 22 to be supplied to the second port 32B of the swing motor 32 and to allow hydraulic oil discharged from the first port 32A of the swing motor 32 to return to the tank 25. As a result, the swing motor 32 rotates in the direction corresponding to the left swing, and the upper swing body 2 performs a left swing operation.

[0052] When the on-off valve 40 is in a closed state, the hydraulic oil discharged from the first pump 21 is supplied to the boom cylinder 31 via the boom direction control valve 41 and to the bucket cylinder 33 via the bucket direction control valve 43, and the hydraulic oil discharged from the second pump 22 is supplied to the swing motor 32 via the swing direction control valve 42. In other words, when the on-off valve 40 is in a closed state, the hydraulic oil discharged from the first pump 21 and the hydraulic oil discharged from the second pump 22 do not join together via the on-off valve 40.

[0053] On the other hand, when the on-off valve 40 is in the open state, the hydraulic oil discharged from the first pump 21 and the hydraulic oil discharged from the second pump 22 are supplied to the bucket cylinder 33 via the bucket directional control valve 43, thereby increasing the operating speed of the bucket 6. In this embodiment, when the swing motor 32 is operated, the on-off valve 40 is closed. However, even when the swing motor 32 is operated, the on-off valve 40 may be opened and the hydraulic oil discharged from the first pump 21 and the hydraulic oil discharged from the second pump 22 may be supplied to the swing motor 32.

[0054] The boom acceleration control valve 44 is a control valve that opens when the boom 4 performs a boom-raising operation to increase the speed of the boom-raising operation of the boom 4. When the operating lever of the operating device 12 receives a boom-raising operation, a boom opening command corresponding to the amount of operation of the boom-raising operation is input from the operating device 12 or the controller 10 to the boom acceleration control valve 44, and the spool of the boom acceleration control valve 44 is displaced from the neutral position by a stroke corresponding to the amount of operation of the boom-raising operation. As a result, the boom acceleration control valve 44 opens to allow hydraulic oil from the second pump 22 to be supplied to the head-side chamber 31A of the boom cylinder 31 and to allow hydraulic oil discharged from the rod-side chamber 31B of the boom cylinder 31 to return to the tank 25. As a result, not only is hydraulic oil discharged from the first pump 21 supplied to the boom cylinder 31 via the boom direction control valve 41, but hydraulic oil from the second pump 22 is also supplied to the boom cylinder 31 via the boom acceleration control valve 44, thereby increasing the speed of the boom-raising operation of the boom 4.

[0055] The plurality of unloading valves include a first unloading valve 51 and a second unloading valve 52. The first unloading valve 51 is configured to adjust the flow rate of hydraulic oil from the first pump 21 to the tank 25. The second unloading valve 52 is configured to adjust the flow rate of hydraulic oil from the second pump 22 to the tank 25.

[0056] The first unloading valve 51 is configured to open and close in accordance with a first unloading valve opening command (current value) input from the controller 10. The second unloading valve 52 is configured to open and close in accordance with a second unloading valve opening command (current value) input from the controller 10. The first unloading valve 51 may be configured so that the opening degree of the first unloading valve 51 is adjusted to a magnitude corresponding to the magnitude of the first unloading valve opening command (current value). The second unloading valve 52 may be configured so that the opening degree of the second unloading valve 52 is adjusted to a magnitude corresponding to the magnitude of the second unloading valve opening command (current value).

[0057] Fig. 4 is a graph showing an example of a relational expression representing the relationship between the operation amount (operation signal) of the lever operation received by the operating device 12 and the unloading valve opening command (current value). The controller 10 stores the relational expression shown in Fig. 4 in advance. Using the relational expression shown in Fig. 4, the controller 10 calculates a smaller current value (unloading valve opening command) as the operation amount of the lever operation received by the operating device 12 increases, and inputs the calculated unloading valve opening command to the unloading valve. As a result, the opening degree of the unloading valve decreases as the operation amount of the lever operation increases.

[0058] When the operation device 12 receives, for example, the boom operation, the controller 10 calculates a first unloading valve opening command based on an operation signal corresponding to the operation amount of the boom operation input from the operation device 12 and the relational expression shown in FIG. 4, and inputs the calculated first unloading valve opening command (current value) to the first unloading valve 51. As a result, the opening degree of the first unloading valve 51 is adjusted to a magnitude corresponding to the operation amount of the boom operation. Also, when the operation device 12 receives, for example, the bucket operation, the controller 10 calculates a first unloading valve opening command based on an operation signal corresponding to the operation amount of the bucket operation input from the operation device 12 and the relational expression shown in FIG. 4, and inputs the calculated first unloading valve opening command (current value) to the first unloading valve 51. As a result, the opening degree of the first unloading valve 51 is adjusted to a magnitude corresponding to the operation amount of the bucket operation. Furthermore, when the operating device 12 receives, for example, the swing operation, the controller 10 calculates a second unloading valve opening command based on an operation signal corresponding to the amount of swing operation input from the operating device 12 and the relational expression shown in Fig. 4, and inputs the calculated second unloading valve opening command (current value) to the second unloading valve 52. As a result, the opening degree of the second unloading valve 52 is adjusted to a magnitude corresponding to the amount of swing operation.

[0059] The first unloading valve 51 is connected to the first discharge flow path FP1 via a first unloading flow path FP8. The second unloading valve 52 is connected to the second discharge flow path FP2 via a second unloading flow path FP9. A location P1 where the first unloading flow path FP8 is connected to the first discharge flow path FP1 is located between the first pump 21 and a location P3 where the connection flow path FP3 is connected to the first discharge flow path FP1. A location P2 where the second unloading flow path FP9 is connected to the second discharge flow path FP2 is located between the second pump 22 and a location P4 where the connection flow path FP3 is connected to the second discharge flow path FP2.

[0060] The plurality of check valves include a first check valve 61 and a second check valve 62. The first check valve 61 blocks the flow of hydraulic oil from the on-off valve 40 toward the first pump 21. The second check valve 62 blocks the flow of hydraulic oil from the on-off valve 40 toward the second pump 22.

[0061] The first check valve 61 is disposed in the first discharge flow path FP1. Specifically, the first check valve 61 is disposed in the first discharge flow path FP1 between a position P1 where the first unloading flow path FP8 is connected to the first discharge flow path FP1 and a position P3 where the connection flow path FP3 is connected to the first discharge flow path FP1. The first check valve 61 allows hydraulic oil discharged from the first pump 21 to flow from the position P1 to the position P3 in the first discharge flow path FP1, while preventing hydraulic oil from flowing in the opposite direction in the first discharge flow path FP1. The first check valve 61 prevents the pump pressure of the second pump 22 from acting on the first pump 21 when the on-off valve 40 is open. Furthermore, the first check valve 61 prevents hydraulic oil discharged from the second pump 22 from flowing into the first unloading flow path FP8 via the on-off valve 40 when the on-off valve 40 is open.

[0062] The second check valve 62 is disposed in the second discharge flow path FP2. Specifically, the second check valve 62 is disposed in the second discharge flow path FP2 between a position P2 where the second unloading flow path FP9 is connected to the second discharge flow path FP2 and a position P4 where the connection flow path FP3 is connected to the second discharge flow path FP2. The second check valve 62 allows hydraulic oil discharged from the second pump 22 to flow from the position P2 to the position P4 in the second discharge flow path FP2, while preventing hydraulic oil from flowing in the reverse direction in the second discharge flow path FP2. The second check valve 62 prevents the pump pressure of the first pump 21 from acting on the second pump 22 when the on-off valve 40 is open. Furthermore, the second check valve 62 prevents hydraulic oil discharged from the first pump 21 from flowing into the second unloading flow path FP9 via the on-off valve 40 when the on-off valve 40 is open.

[0063] The plurality of check valves may further include check valves 63, 64, 65, and 66.

[0064] The check valve 63 is disposed in the flow path FP4 connected to the P port of the boom direction control valve 41. The check valve 63 allows the hydraulic oil to flow in the flow path FP4 toward the P port of the boom direction control valve 41, while preventing the hydraulic oil from flowing in the opposite direction in the flow path FP4.

[0065] The check valve 64 is disposed in a flow path FP6 connected to the P port of the swing direction control valve 42. The check valve 64 allows the hydraulic oil to flow in the flow path FP6 toward the P port of the swing direction control valve 42, while preventing the hydraulic oil from flowing in the opposite direction in the flow path FP6.

[0066] The check valve 65 is disposed in the flow path FP5 connected to the P port of the bucket direction control valve 43. The check valve 65 allows the hydraulic oil to flow in the flow path FP5 toward the P port of the bucket direction control valve 43, while preventing the hydraulic oil from flowing in the opposite direction in the flow path FP5.

[0067] The check valve 66 is disposed in the flow path FP7 connected to the P port of the boom acceleration control valve 44. The check valve 66 allows hydraulic oil to flow through the flow path FP7 toward the P port of the boom acceleration control valve 44, while preventing hydraulic oil from flowing in the opposite direction through the flow path FP7.

[0068] The plurality of detectors includes a first pump pressure detector 71, a second pump pressure detector 72, a boom speed detector 81, a swing speed detector 82, a bucket speed detector 83, and an arm speed detector (not shown). Each of the plurality of detectors inputs a detection result to the controller 10.

[0069] The first pump pressure detector 71 is a pressure sensor that detects the first pump pressure, which is the discharge pressure of the first pump 21. The first pump pressure detector 71 may detect, for example, the pressure of the hydraulic oil in the first discharge flow path FP1.

[0070] The second pump pressure detector 72 is a pressure sensor that detects the second pump pressure, which is the discharge pressure of the second pump 22. The second pump pressure detector 72 may detect, for example, the pressure of the hydraulic oil in the second discharge flow path FP2.

[0071] The boom speed detector 81 is a speed sensor that detects the operating speed of the boom cylinder 31. The swing speed detector 82 is a speed sensor that detects the operating speed of the swing motor 32. The bucket speed detector 83 is a speed sensor that detects the operating speed of the bucket cylinder 33. The arm speed detector is a speed sensor that detects the operating speed of the arm cylinder 34.

[0072] When either the first pump 21 or the second pump 22 is a fault symptom pump that shows signs of failure, the controller 10 performs pump load reduction control by increasing the opening degree of the unloading valve connected to the fault symptom pump, either the first unloading valve 51 or the second unloading valve 52, and increasing the opening degree of the opening / closing valve 40.

[0073] In this embodiment, the construction machine 100 is equipped with the first check valve 61 and the second check valve 62, and the controller 10 performs the pump load reduction control, so that the acceleration of failure of the pump showing signs of failure is suppressed. This makes it possible to extend the life of the pump showing signs of failure compared to when the pump load reduction control is not performed. Specifically, this is as follows.

[0074] For example, if the first pump 21 is the fault-indicating pump, even if the controller 10 increases the aperture of the on-off valve 40 during the pump load reduction control, the first check valve 61 blocks the flow of hydraulic oil from the on-off valve 40 toward the first pump 21, so that the pump pressure of the second pump 22, which is a normal pump, does not act on the first pump 21. Moreover, the controller 10 can increase the aperture of the first unload valve 51 during the pump load reduction control to increase the flow rate of hydraulic oil from the first pump 21 toward the tank 25, thereby reducing the load acting on the fault-indicating pump. This suppresses the progression of a failure of the fault-indicating pump (e.g., the first pump 21). Moreover, because the controller 10 increases the aperture of the on-off valve 40 during the pump load reduction control, hydraulic oil can be supplied from the normal second pump 22 to the boom cylinder 31, the swing motor 32, and the bucket cylinder 33, thereby operating the boom cylinder 31, the swing motor 32, and the bucket cylinder 33. That is, in this embodiment, the progression of failure of the failure indication pump can be suppressed while operating the boom cylinder 31, the swing motor 32, and the bucket cylinder 33. This makes it possible to extend the life of the failure indication pump while continuing work using the boom cylinder 31, the swing motor 32, and the bucket cylinder 33.

[0075] Furthermore, in this embodiment, the controller 10 reduces the displacement of the symptom-of-failure pump in the pump load reduction control. The torque of a hydraulic pump is proportional to the product of the pump pressure of the hydraulic pump and the displacement of the hydraulic pump. In the pump load reduction control, the controller 10 can reduce the torque of the symptom-of-failure pump by reducing the displacement of the symptom-of-failure pump, thereby further reducing the load acting on the symptom-of-failure pump. This can further suppress the progression of failure of the symptom-of-failure pump.

[0076] Furthermore, in this embodiment, the controller 10 may increase the capacity of a normal pump (e.g., the second pump 22) that does not show signs of failure, out of the first pump 21 and the second pump 22, during the pump load reduction control. In this case, the flow rate of hydraulic oil discharged from the normal pump can be increased compared to when the capacity of the normal pump is not increased during the pump load reduction control. Therefore, when hydraulic oil is supplied from the normal second pump 22 to the boom cylinder 31 and / or the bucket cylinder 33 and the swing motor 32 to operate these actuators, the speed of at least one of the boom cylinder 31, the swing motor 32, and the bucket cylinder 33 can be increased compared to when the capacity of the normal second pump 22 is not increased.

[0077] Furthermore, in the present embodiment, the controller 10 may, in the pump load reduction control, reduce the aperture of an unloading valve (e.g., second unloading valve 52) connected to a normal pump (e.g., second pump 22) that does not show signs of failure, out of the first pump 21 and the second pump 22. In this case, the flow rate of hydraulic oil that is discharged from the second pump 22 and returns to the tank 25 via the second unloading valve 52 can be reduced compared to when the aperture of the second unloading valve 52 connected to the normal second pump 22 is not reduced in the pump load reduction control, and therefore the speed of at least one of the boom cylinder 31, the swing motor 32, and the bucket cylinder 33 can be increased.

[0078] In addition, in this embodiment, the controller 10 determines signs of failure of the first pump 21 using the first pump pressure detected by the first pump pressure detector 71, and determines signs of failure of the second pump 22 using the second pump pressure detected by the second pump pressure detector 72.

[0079] The controller 10 may determine that the first pump 21 is the failure symptom pump when the first pump pressure is less than a first pressure threshold, which is a predetermined threshold, and may determine that the second pump 22 is the failure symptom pump when the second pump pressure is less than a second pressure threshold, which is a predetermined threshold.

[0080] In addition, in this embodiment, the controller 10 determines signs of failure of the first pump 21 using a first physical quantity, which is the flow rate of the hydraulic oil discharged from the first pump 21 or a physical quantity correlated to that flow rate, and determines signs of failure of the second pump 22 using a second physical quantity, which is the flow rate of the hydraulic oil discharged from the second pump 22 or a physical quantity correlated to that flow rate.

[0081] The first physical quantity may be the operating speed of a hydraulic actuator, among the plurality of hydraulic actuators, that is supplied with hydraulic oil discharged from first pump 21. The operating speed of a hydraulic actuator correlates with the flow rate of hydraulic oil supplied to that hydraulic actuator. Controller 10 may store a relational expression that expresses the relationship between the flow rate of hydraulic oil and the operating speed of that hydraulic actuator. In this case, controller 10 can calculate an actual flow rate (first actual flow rate), which is the actual flow rate of hydraulic oil discharged from first pump 21, based on the operating speed of that hydraulic actuator.

[0082] Similarly, the second physical quantity may be the operating speed of a hydraulic actuator, among the plurality of hydraulic actuators, that is supplied with hydraulic oil discharged from the second pump 22. The operating speed of a hydraulic actuator correlates with the flow rate of hydraulic oil supplied to the hydraulic actuator. The controller 10 may store a relational expression that expresses the relationship between the flow rate of hydraulic oil and the operating speed of the hydraulic actuator. In this case, the controller 10 can calculate an actual flow rate (second actual flow rate), which is the actual flow rate of hydraulic oil discharged from the second pump 22, based on the operating speed of the hydraulic actuator.

[0083] Specifically, when the operating device 12 receives, for example, a boom-lowering operation, the controller 10 calculates a pump command flow rate, which is a target flow rate for the first pump 21 determined in accordance with the amount of operation of the boom-lowering operation, and inputs a tilt command corresponding to the pump command flow rate to the first regulator 91. This adjusts the capacity of the first pump 21 to a magnitude corresponding to the pump command flow rate. The controller 10 then calculates an actual flow rate (first actual flow rate), which is the actual flow rate of hydraulic oil discharged from the first pump 21, based on the operating speed of the boom cylinder 31 input from the boom speed detector 81. The controller 10 may determine that the first pump 21 is the failure symptom pump when the absolute value of the difference between the pump command flow rate and the first actual flow rate is greater than a first flow rate threshold, which is a predetermined threshold.

[0084] Furthermore, when the operating device 12 is subjected to, for example, a swing operation, the controller 10 calculates a pump command flow rate, which is a target flow rate for the second pump 22 determined according to the amount of operation of the swing operation, and inputs a tilt command corresponding to the pump command flow rate to the second regulator 92. This adjusts the capacity of the second pump 22 to a magnitude corresponding to the pump command flow rate. The controller 10 then calculates an actual flow rate (second actual flow rate), which is the actual flow rate of hydraulic oil discharged from the second pump 22, based on the operating speed of the swing motor 32 input from the swing speed detector 82. The controller 10 may determine that the second pump 22 is the failure symptom pump when the absolute value of the difference between the pump command flow rate and the second actual flow rate is greater than a second flow rate threshold, which is a predetermined threshold.

[0085] FIG. 5 is a flowchart showing an example of the calculation process performed by the controller 10.

[0086] When the flow shown in FIG. 5 is started, the displacements of the first pump 21 and the second pump 22 are, for example, at the minimum displacement (idling state).

[0087] In step S11, the controller 10 determines whether the operation device 12 has received a lever operation based on an operation signal input from the operation device 12 (operation signal determination process). If the operation device 12 has not received a lever operation (NO in step S11), the controller 10 performs the process of step S11 again. If the operation device 12 has received a lever operation (YES in step S11), the controller 10 performs the pump control process of step S12.

[0088] In the following, an example will be described in which the operation device 12 receives the boom lowering operation and the swing operation at the same time.

[0089] In step S12, the controller 10 calculates a tilt command (current value) using the operation signal input from the operation device 12 and the relational expression shown in Fig. 3. Specifically, in step S12, the controller 10 calculates a pump command flow rate (first pump command flow rate) that is a target flow rate of the first pump 21 using the operation signal corresponding to the boom lowering operation input from the operation device 12 and the relational expression shown in Fig. 3, and calculates a first tilt command (current value) that corresponds to the calculated first pump command flow rate. In addition, the controller 10 calculates a pump command flow rate (second pump command flow rate) that is a target flow rate of the second pump 22 using the operation signal corresponding to the swing operation input from the operation device 12 and the relational expression shown in Fig. 3, and calculates a second tilt command (current value) that corresponds to the calculated second pump command flow rate.

[0090] Next, in step S13, the controller 10 performs unloading control processing. The controller 10 calculates an unloading valve opening command (current value) using the operation signal input from the operation device 12 and the relational expression shown in Fig. 4. Specifically, in step S13, the controller 10 calculates a first unloading valve opening command (current value) using the operation signal corresponding to the boom lowering operation input from the operation device 12 and the relational expression shown in Fig. 4, and calculates a second unloading valve opening command (current value) using the operation signal corresponding to the swing operation input from the operation device 12 and the relational expression shown in Fig. 4.

[0091] Next, the controller 10 performs the pump failure determination process of steps S14 to S17.

[0092] In step S14, the controller 10 determines whether the absolute value of a first flow rate difference (|first pump command flow rate−first actual flow rate|), which is the difference between the first pump command flow rate and a first actual flow rate, which is the actual flow rate discharged from the first pump 21, is equal to or less than a predetermined first flow rate threshold. The controller 10 also determines whether the absolute value of a second flow rate difference (|second pump command flow rate−second actual flow rate|), which is the difference between the second pump command flow rate and a second actual flow rate, which is the actual flow rate discharged from the second pump 22, is equal to or less than a predetermined second flow rate threshold. The controller 10 can calculate the first actual flow rate based on the operating speed of the boom cylinder 31 input from the boom speed detector 81, and can calculate the second actual flow rate based on the operating speed of the swing motor 32 input from the swing speed detector 82.

[0093] If the absolute value of the first flow rate difference is greater than the first flow rate threshold (NO in step S14), or if the absolute value of the second flow rate difference is greater than the second flow rate threshold (NO in step S14), the controller 10 performs the process of step S17.

[0094] Specifically, if the absolute value of the first flow rate difference is greater than the first flow rate threshold, in step S17 the controller 10 determines that the first pump 21 is a symptom-of-failure pump that is showing signs of failure, and stores the fact that the first pump 21 is the symptom-of-failure pump. If the absolute value of the second flow rate difference is greater than the second flow rate threshold, in step S17 the controller 10 determines that the second pump 22 is a symptom-of-failure pump that is showing signs of failure, and stores the fact that the second pump 22 is the symptom-of-failure pump. Note that because the probability that both the first pump 21 and the second pump 22 will simultaneously show signs of failure is low, the flowchart in FIG. 5 omits processing for the case where both the first pump 21 and the second pump 22 are simultaneously determined to be the symptom-of-failure pumps.

[0095] If the absolute value of the first flow rate difference is equal to or less than the first flow rate threshold and the absolute value of the second flow rate difference is equal to or less than the second flow rate threshold (YES in step S14), the controller 10 performs the process of step S15.

[0096] In step S15, the controller 10 determines whether the first pump pressure, which is the pump pressure of the first pump 21, is equal to or greater than a predetermined first pressure threshold, based on the detection result input from the first pump pressure detector 71. The controller 10 also determines whether the second pump pressure, which is the pump pressure of the second pump 22, is equal to or greater than a predetermined second pressure threshold, based on the detection result input from the second pump pressure detector 72.

[0097] If the first pump pressure is lower than the first pressure threshold (NO in step S15), or if the second pump pressure is lower than the second pressure threshold (NO in step S15), the controller 10 performs the process of step S17.

[0098] Specifically, if the first pump pressure is lower than the first pressure threshold, in step S17 the controller 10 determines that the first pump 21 is a symptom-of-failure pump that is showing a symptom of failure, and stores the fact that the first pump 21 is the symptom-of-failure pump. If the second pump pressure is lower than the second pressure threshold, in step S17 the controller 10 determines that the second pump 22 is a symptom-of-failure pump that is showing a symptom of failure, and stores the fact that the second pump 22 is the symptom-of-failure pump. Note that, because the probability that both the first pump 21 and the second pump 22 will simultaneously show symptoms of failure is low, the flowchart in FIG. 5 omits processing for the case where both the first pump 21 and the second pump 22 are simultaneously determined to be the symptom-of-failure pumps.

[0099] If the first pump pressure is equal to or greater than the first pressure threshold and the second pump pressure is equal to or greater than the second pressure threshold (YES in step S15), the controller 10 performs the process of step S16.

[0100] In step S16, the controller 10 determines that both the first pump 21 and the second pump 22 are normal pumps that do not show any signs of failure, and stores the fact that both the first pump 21 and the second pump 22 are normal pumps.

[0101] Next, the controller 10 performs the pump failure control process of steps S18 to S21.

[0102] In step S18, the controller 10 determines whether or not there is a pump showing signs of failure.

[0103] If there is no pump showing a failure symptom (NO in step S18), the controller 10 performs the process of step S22. In this case, in step S22, the controller 10 inputs the first tilting command and the second tilting command calculated in step S12 to the first regulator 91 and the second regulator 92, respectively. Also in step S22, the controller 10 inputs the first unloading valve opening command and the second unloading valve opening command calculated in step S13 to the first unloading valve 51 and the second unloading valve 52, respectively. Also in step S22, the controller 10 inputs an on-off valve opening command to the on-off valve 40 such that the opening degree of the on-off valve 40 becomes fully closed (zero opening degree).

[0104] If it is determined in step S11 that the operating device 12 has received the boom lowering operation and the swing operation, regardless of the presence or absence of the failure indication pump, a boom opening command corresponding to the boom lowering operation is input to the boom direction control valve 41 from the operating device 12 or the controller 10, and a swing opening command corresponding to the swing operation is input to the swing direction control valve 42 from the operating device 12 or the controller 10. Then, the boom direction control valve 41 opens so as to change the direction and flow rate of hydraulic oil supplied to the boom cylinder 31 by displacing its spool in accordance with the boom opening command, and the swing direction control valve 42 opens so as to change the direction and flow rate of hydraulic oil supplied to the swing motor 32 by displacing its spool in accordance with the swing opening command.

[0105] If there is a pump showing signs of failure (YES in step S18), the controller 10 performs the processes of steps S19 to S22.

[0106] In step S19, the controller 10 determines a displacement command for reducing the displacement of the pump determined to be the failure symptom pump, either the first pump 21 or the second pump 22.

[0107] In the following, an example will be described in which the first pump 21 is the faulty pump and the second pump 22 is the normal pump.

[0108] In this case, in step S19, the controller 10 determines a failure-time tilt command (current value) that is a tilt command that makes the displacement of the first pump 21 smaller than the displacement corresponding to the first tilt command calculated in step S12. Specifically, for example, the controller 10 determines a tilt command corresponding to the minimum displacement of the first pump 21 as the failure-time tilt command.

[0109] Next, in step S20, the controller 10 determines an unloading opening command (current value) during failure to increase the opening degree of the first unloading valve 51. Specifically, for example, the controller 10 determines, as the unloading opening command during failure, an unloading valve opening command that maximizes the opening degree of the first unloading valve 51 (fully open).

[0110] Next, in step S21, the controller 10 determines an on-off valve opening command (current value) during failure to increase the opening degree of the on-off valve 40. Specifically, for example, the controller 10 determines an on-off valve opening command during failure that maximizes the opening degree of the on-off valve 40 (fully open).

[0111] Next, in step S22, the controller 10 inputs the failure-time tilt command determined in step S19 to the first regulator 91, and inputs the second tilt command calculated in step S12 to the second regulator 92. Also in step S22, the controller 10 inputs the failure-time unloading opening command determined in step S20 to the first unloading valve 51, and inputs the second unloading valve opening command calculated in step S13 to the second unloading valve 52. Also in step S22, the controller 10 inputs the failure-time on-off valve opening command determined in step S21 to the on-off valve 40.

[0112] [Variations] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and includes, for example, the following modified examples.

[0113] (A) Construction Machinery Systems FIG. 6 is a diagram showing a construction machine system. This construction machine system includes a construction machine 100 and an external device 200 located remotely from the construction machine 100. When the pump showing a fault symptom is identified, the controller 10 of the construction machine 100 transmits information about the pump showing a fault symptom to the external device 200. In this modification, for example, even when an operator remotely operates the construction machine 100 from a location remote from the construction machine 100, or when a worker monitors an automatically operated construction machine 100 from a location remote from the construction machine 100, the operator or the worker can grasp the status of the pump showing a fault symptom in the construction machine 100 based on the information transmitted from the controller 10, and can quickly take necessary measures. The information transmitted from the controller 10 to the external device 200 may include, for example, information that enables the operator or the worker to determine which of the first pump 21 and the second pump 22 is showing a fault symptom.

[0114] The construction machine 100 and the external device 200 are configured to be able to communicate with each other, for example, via a network. The network is an information communication network such as the Internet, a telephone network, a satellite communication network, a wide area network (WAN), a local area network (LAN), or a dedicated line. The network 50 may be any one of these communication networks, or may be configured by combining multiple types of communication networks.

[0115] The external device 200 may be, for example, an information terminal such as a tablet computer, a smartphone, a laptop personal computer, or a desktop personal computer.

[0116] (B) Criteria for determining failure symptoms In the flowchart shown in Figure 5, the controller 10 determines signs of failure of the first pump 21 using the flow rate of hydraulic oil discharged from the first pump 21, and determines signs of failure of the second pump 22 using the flow rate of hydraulic oil discharged from the second pump 22, but the determination of signs of failure may also be made using a physical quantity correlated to the flow rates.

[0117] Specifically, the controller 10 may determine a failure symptom of the first pump 21 using the operating speed (an example of a first physical quantity) of a hydraulic actuator to which hydraulic oil discharged from the first pump 21 is supplied. In this case, in step S14, the controller 10 may convert the first pump command flow rate, which is a target flow rate of the first pump 21, into a first target operating speed, which is a target operating speed of the hydraulic actuator, using a relational expression that represents the relationship between the flow rate of hydraulic oil and the operating speed of the hydraulic actuator, and may determine that the first pump 21 is the failure symptom pump when the absolute value of the difference between the first target operating speed and a first actual operating speed, which is the actual operating speed of the hydraulic actuator (|first target operating speed−first actual operating speed|), is greater than a first speed threshold, which is a predetermined threshold.

[0118] Similarly, the controller 10 may determine a failure symptom of the second pump 22 using the operating speed (an example of a second physical quantity) of a hydraulic actuator to which hydraulic oil discharged from the second pump 22 is supplied. In this case, in step S14, the controller 10 may convert the second pump command flow rate, which is a target flow rate of the second pump 22, into a second target operating speed, which is a target operating speed of the hydraulic actuator, using a relational expression that represents the relationship between the flow rate of hydraulic oil and the operating speed of the hydraulic actuator, and may determine that the second pump 22 is the failure symptom pump when the absolute value of the difference between the second target operating speed and a second actual operating speed, which is the actual operating speed of the hydraulic actuator (|second target operating speed−second actual operating speed|), is greater than a second speed threshold, which is a predetermined threshold.

[0119] In the above embodiment, the controller 10 determines whether or not the pump is exhibiting a fault symptom by comparing the absolute value with a threshold value, but the determination method is not limited to this. Specifically, in step S14, the controller 10 may determine that the first pump 21 is the pump exhibiting a fault symptom if the difference between the first pump command flow rate and the first flow rate (first pump command flow rate - first actual flow rate) is greater than a predetermined first flow rate threshold value, or may determine that the second pump 22 is the pump exhibiting a fault symptom if the difference between the second pump command flow rate and the second actual flow rate (second pump command flow rate - second actual flow rate) is greater than a predetermined second flow rate threshold value.

[0120] Similarly, in step S14, the controller 10 may determine that the first pump 21 is the failure symptom pump if the difference between the first target operating speed and the first actual operating speed (first target operating speed - first actual operating speed) is greater than a predetermined first speed threshold, and may determine that the second pump 22 is the failure symptom pump if the difference between the second target operating speed and the second actual operating speed (second target operating speed - second actual operating speed) is greater than a predetermined second speed threshold. [Explanation of symbols]

[0121] 10: Controller 21: First pump 22: Second pump 31: Boom cylinder 32: Swing motor 33: Bucket cylinder 40: On-off valve 41: Boom directional control valve 42: Swing directional control valve 43: Bucket directional control valve 44: Boom acceleration control valve 51: First unloading valve 52: Second unloading valve 61: First check valve 62: Second check valve 71: First pump pressure detector 72: Second pump pressure detector 81: Boom speed detector 82: Turning speed detector 83: Bucket speed detector 91: First regulator 92: Second regulator 100: Construction machinery FP3: Connecting channel

Claims

1. A first pump; A second pump; a first actuator that receives hydraulic fluid from the first pump; a second actuator that receives hydraulic fluid from the second pump; an on-off valve disposed in a flow path connecting the first pump and the second pump; a first unloading valve that adjusts the flow rate of hydraulic oil from the first pump to a tank; a second unloading valve that adjusts the flow rate of hydraulic oil from the second pump to the tank; a first check valve that blocks the flow of hydraulic oil from the on-off valve toward the first pump; a second check valve that blocks the flow of hydraulic oil from the on-off valve toward the second pump; a controller that, when either the first pump or the second pump is a failure symptom pump that is showing signs of failure, performs pump load reduction control by increasing the opening degree of the unloading valve, of the first unloading valve or the second unloading valve, that is connected to the failure symptom pump, and by increasing the opening degree of the on-off valve.

2. each of the first pump and the second pump is a variable displacement hydraulic pump; The construction machine according to claim 1 , wherein the controller reduces the capacity of the pump showing the failure indication in the pump load reduction control.

3. each of the first pump and the second pump is a variable displacement hydraulic pump; 3. The construction machine according to claim 1, wherein the controller increases the capacity of one of the first pump and the second pump that is in good working order and shows no signs of failure, in the pump load reduction control.

4. 3. The construction machine according to claim 1, wherein the controller, in the pump load reduction control, reduces the opening of an unloading valve connected to a normal pump of the first pump and the second pump that does not show signs of failure.

5. 3. The construction machine according to claim 1, wherein the controller determines signs of a failure of the first pump using a first pump pressure that is a discharge pressure of the first pump, and determines signs of a failure of the second pump using a second pump pressure that is a discharge pressure of the second pump.

6. 3. The construction machine according to claim 1, wherein the controller determines signs of a failure of the first pump using a flow rate of hydraulic oil discharged from the first pump or a physical quantity correlated to the flow rate, and determines signs of a failure of the second pump using a flow rate of hydraulic oil discharged from the second pump or a physical quantity correlated to the flow rate.

7. The construction machine according to claim 1; an external device that is placed at a location remote from the construction machine, The construction machine system, wherein the controller transmits information about the failure symptom pump to the external device.

8. A first pump; A second pump; a first actuator that receives hydraulic fluid from the first pump; a second actuator that receives hydraulic fluid from the second pump; an on-off valve disposed in a flow path connecting the first pump and the second pump; a first unloading valve that adjusts the flow rate of hydraulic oil from the first pump to a tank; a second unloading valve that adjusts the flow rate of hydraulic oil from the second pump to the tank; a first check valve that blocks the flow of hydraulic oil from the on-off valve toward the first pump; a second check valve that blocks a flow of hydraulic oil from the on-off valve toward the second pump, A pump load reduction method including, when either the first pump or the second pump is a failure symptom pump that is showing signs of failure, increasing the opening degree of the unloading valve, of the first unloading valve or the second unloading valve, that is connected to the failure symptom pump, and increasing the opening degree of the on-off valve.

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