Fan drive system and fan drive method

Abstract

To monitor a state of an apparatus of a fan drive system.SOLUTION: A fan drive system includes: a hydraulic pump; a hydraulic motor for rotating a fan based on work fluid supplied from the hydraulic pump; and a controller. The controller includes: a target amount determination unit which determines a target rotational speed of the fan based on a state of an object being cooled by the fan; a comparison unit for calculating a feedback amount indicating a deviation between the target rotational speed of the fan and an actual rotational speed of the fan; and an estimation unit for estimating a state of the hydraulic pump or a state of the hydraulic motor based on the feedback amount, a pump drain pressure which is a pressure of a pump drain line for returning the work fluid from the hydraulic pump to a work fluid tank, and a motor drain pressure which is a pressure of a motor drain line for returning the work fluid from the hydraulic motor to the work fluid tank.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to fan drive systems and methods. [Background technology]

[0002] In the technical field related to fan drive systems, a fan drive system such as that disclosed in Patent Document 1 is known. In Patent Document 1, the fan drive system includes a hydraulic pump and a hydraulic motor that rotates a fan using hydraulic oil supplied from the hydraulic pump. The fan drive system estimates the state of the hydraulic pump or the state of the hydraulic motor based on changes in a feedback amount that indicates the difference between the target rotation speed and the actual rotation speed of the fan. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 131118 Summary of the Invention [Problem to be solved by the invention]

[0004] A fan drive system is composed of multiple devices. If an abnormality occurs in one of the devices, the device in question must be maintained. Therefore, there is a demand for technology that can accurately monitor the status of the devices.

[0005] The present disclosure is directed to monitoring the condition of equipment in a fan drive system. [Means for solving the problem]

[0006] According to the present disclosure, there is provided a fan drive system including a hydraulic pump, a hydraulic motor that rotates a fan based on hydraulic oil supplied from the hydraulic pump, and a controller. The controller has a target amount determination unit that determines a target rotation speed of the fan based on the state of an object to be cooled by the fan, a comparison unit that calculates a feedback amount that indicates the deviation between the target rotation speed of the fan and the actual rotation speed of the fan, and an estimation unit that estimates the state of the hydraulic pump or the state of the hydraulic motor based on the feedback amount, a pump drain pressure that is the pressure in a drain circuit that returns hydraulic oil from the hydraulic pump to a hydraulic tank, and a motor drain pressure that is the pressure in a drain circuit that returns hydraulic oil from the hydraulic motor to the hydraulic tank. [Effects of the Invention]

[0007] According to the present disclosure, the condition of the equipment in the fan drive system can be monitored. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram schematically illustrating a fan drive system according to an embodiment. [Figure 2] FIG. 2 is a hardware configuration diagram showing a controller according to the embodiment. [Figure 3] FIG. 3 is a functional block diagram showing a controller according to the embodiment. [Figure 4] FIG. 4 is a control block diagram of the controller according to the embodiment. [Figure 5] FIG. 5 is a diagram schematically showing the relationship between the feedback amount, the system efficiency, the displacement of the hydraulic pump, and the actual rotation speed of the fan according to the embodiment. [Figure 6] FIG. 6 is a diagram schematically showing the relationship between the feedback amount, the pump drain pressure, and the motor drain pressure according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating types of abnormalities according to the embodiment. [Figure 8] FIG. 8 is a diagram illustrating types of abnormalities according to the embodiment. [Figure 9]FIG. 9 is a diagram illustrating types of abnormalities according to the embodiment. [Figure 10] FIG. 10 is a flowchart showing a method for determining the type of abnormality according to the embodiment. [Figure 11] FIG. 11 is a flowchart showing a method for identifying an abnormal hydraulic pump or hydraulic motor according to this embodiment. [Figure 12] FIG. 12 is a diagram schematically showing the relationship between the feedback amount, the actual rotation speed of the fan, the outside air temperature, the hydraulic oil temperature, and the drain pressure according to the embodiment. [Figure 13] FIG. 13 is a diagram schematically showing the relationship between the feedback amount, the actual rotation speed of the fan, the pump drain pressure, and the motor drain pressure according to the embodiment. [Figure 14] FIG. 14 is a flowchart showing a method for identifying an abnormal fan or drain line according to this embodiment. [Figure 15] FIG. 15 is a diagram schematically showing the relationship between the feedback amount, the actual fan rotation speed, the radiator temperature, the oil cooler temperature, the pump drain pressure, and the motor drain pressure when an abnormality occurs in the cooling core of the radiator according to the embodiment. [Figure 16] FIG. 16 is a diagram schematically showing the relationship between the feedback amount, the actual fan rotation speed, the radiator temperature, the oil cooler temperature, the pump drain pressure, and the motor drain pressure when an abnormality occurs in the cooling core of the oil cooler according to the embodiment. [Figure 17] FIG. 17 is a flowchart showing a method for identifying an abnormal radiator or oil cooler according to this embodiment. [Figure 18] FIG. 18 is a diagram illustrating the relationship between data acquired by the data acquisition unit and devices whose states can be estimated by the estimation unit according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the embodiments. The components of the embodiments described below can be combined as appropriate. In addition, some components may not be used.

[0010] [Fan drive system] FIG. 1 is a diagram schematically illustrating a fan drive system 1 according to an embodiment. The fan drive system 1 is mounted on a work machine having a work implement. Examples of the work machine include a hydraulic excavator, a bulldozer, and a wheel loader. The work machine has an engine 9 and a cooling device 30. The cooling device 30 includes a radiator 31 and an oil cooler 32. Cooling water that cools the engine 9 flows through the radiator 31. The cooling water circulates in a circulation system that includes the engine 9 and the radiator 31. Hydraulic oil flows through the oil cooler 32. The hydraulic oil circulates in a circulation system that includes hydraulic equipment mounted on the work machine and the oil cooler 32. The fan drive system 1 rotates a fan 10. Airflow generated by the rotation of the fan 10 cools the radiator 31 and the oil cooler 32. Cooling the radiator 31 and the oil cooler 32 cools the cooling water and hydraulic oil, thereby cooling the engine 9 and the hydraulic equipment.

[0011] A fan housing 15 is disposed around the fan 10. The fan housing 15 regulates the airflow generated by the rotation of the fan 10.

[0012] As shown in FIG. 1, the fan drive system 1 includes a hydraulic pump 2, a hydraulic motor 3, a hydraulic oil tank 4, a controller 5, a suction line 6, a supply line 7, a tank line 8, a pump drain line 11, and a motor drain line 12.

[0013] The hydraulic pump 2 is the power source for the hydraulic motor 3. The hydraulic pump 2 discharges hydraulic oil. The hydraulic pump 2 has a suction port for sucking in hydraulic oil and a discharge port for discharging the hydraulic oil. The hydraulic pump 2 is connected to the output shaft of the engine 9. The hydraulic pump 2 is driven by the power generated by the engine 9. The hydraulic pump 2 is a variable displacement hydraulic pump. The hydraulic pump 2 has a swash plate 2A and a swash plate drive unit 2B that drives the swash plate 2A. The swash plate drive unit 2B adjusts the angle of the swash plate 2A to adjust the displacement q [cc / rev] of the hydraulic pump 2.

[0014] The hydraulic motor 3 is a power source for the fan 10. The hydraulic motor 3 rotates the fan 10 using hydraulic oil supplied from the hydraulic pump 2. The hydraulic motor 3 has an inlet port through which the hydraulic oil flows in and an outlet port through which the hydraulic oil flows out. The hydraulic motor 3 is a fixed displacement hydraulic motor. The hydraulic motor 3 has an output shaft to which the fan 10 is connected. The fan 10 rotates using the power generated by the hydraulic motor 3.

[0015] The hydraulic oil tank 4 stores hydraulic oil. The suction line 6 connects the hydraulic oil tank 4 to the suction port of the hydraulic pump 2. The hydraulic pump 2 draws in the hydraulic oil stored in the hydraulic oil tank 4 from the suction port. The hydraulic pump 2 discharges the hydraulic oil drawn in from the suction port from the discharge port. The supply line 7 connects the discharge port of the hydraulic pump 2 to the inlet port of the hydraulic motor 3. The hydraulic oil discharged from the discharge port of the hydraulic pump 2 is supplied to the hydraulic motor 3 via the supply line 7.

[0016] The output shaft of the hydraulic motor 3 rotates based on the hydraulic oil that flows into the inlet port. The rotation of the output shaft of the hydraulic motor 3 rotates a fan 10 connected to the output shaft of the hydraulic motor 3. A tank line 8 connects the outlet port of the hydraulic motor 3 to the hydraulic oil tank 4. The hydraulic oil that flows out from the outlet port of the hydraulic motor 3 is discharged into the hydraulic oil tank 4 via the tank line 8.

[0017] The pump drain line 11 circulates hydraulic oil that leaks from the sliding parts of the hydraulic pump 2. The pump drain line 11 connects the hydraulic pump 2 and the hydraulic oil tank 4. The pump drain line 11 returns hydraulic oil from the hydraulic pump 2 to the hydraulic oil tank 4. When the hydraulic pump 2 is driven, hydraulic oil may leak from the sliding parts of the hydraulic pump 2. Hydraulic oil that leaks from the sliding parts of the hydraulic pump 2 is discharged into the hydraulic oil tank 4 via the pump drain line 11.

[0018] The motor drain line 12 circulates hydraulic oil that leaks from the sliding parts of the hydraulic motor 3. The motor drain line 12 connects the hydraulic motor 3 and the hydraulic oil tank 4. The motor drain line 12 returns hydraulic oil from the hydraulic motor 3 to the hydraulic oil tank 4. When the hydraulic motor 3 is driven, hydraulic oil may leak from the sliding parts of the hydraulic motor 3. Hydraulic oil that leaks from the sliding parts of the hydraulic motor 3 is discharged into the hydraulic oil tank 4 via the motor drain line 12.

[0019] The fan drive system 1 includes an engine rotation speed sensor 21 , an engine water temperature sensor 22 , a hydraulic oil temperature sensor 23 , an outside air temperature sensor 24 , a fan rotation speed sensor 25 , a pump drain pressure sensor 26 , and a motor drain pressure sensor 27 .

[0020] The engine speed sensor 21 detects the number of revolutions of the engine 9 per unit time. The engine speed sensor 21 can detect the number of revolutions of the input shaft of the hydraulic pump 2 by detecting the number of revolutions of the output shaft of the engine 9. The detection data of the engine speed sensor 21 is transmitted to the controller 5. The detection data of the engine speed sensor 21 indicates the engine speed N, which is the number of revolutions of the engine 9 per unit time.

[0021] The engine water temperature sensor 22 detects the temperature of the coolant that cools the engine 9. In the embodiment, the engine water temperature sensor 22 is disposed in the radiator 31. The radiator 31 has a cooling core through which the coolant flows. The engine water temperature sensor 22 detects the temperature of the coolant flowing through the cooling core of the radiator 31. The detected data of the engine water temperature sensor 22 is transmitted to the controller 5. The detected data of the engine water temperature sensor 22 indicates a coolant temperature Tw, which is the temperature of the coolant, or a radiator temperature, which indicates the temperature of the cooling core of the radiator 31. In the embodiment, the coolant temperature Tw detected by the engine water temperature sensor 22 and the radiator temperature are substantially the same.

[0022] The hydraulic oil temperature sensor 23 detects the temperature of hydraulic oil in the fan drive system 1. In the embodiment, the hydraulic oil temperature sensor 23 is disposed in the oil cooler 32. The oil cooler 32 has a cooling core through which hydraulic oil flows. The hydraulic oil temperature sensor 23 detects the temperature of the hydraulic oil flowing through the cooling core of the oil cooler 32. The detection data of the hydraulic oil temperature sensor 23 is transmitted to the controller 5. The detection data of the hydraulic oil temperature sensor 23 indicates a hydraulic oil temperature To, which is the temperature of the hydraulic oil, or an oil cooler temperature, which indicates the temperature of the cooling core of the oil cooler 32. In the embodiment, the hydraulic oil temperature To detected by the hydraulic oil temperature sensor 23 and the oil cooler temperature are substantially the same.

[0023] The outside air temperature sensor 24 detects the temperature outside the work machine. The temperature outside the work machine means the temperature outside the fan drive system 1 and the temperature outside the engine 9. The temperature outside the work machine means the environmental temperatures in which the cooling water and hydraulic oil are used. The detected data from the outside air temperature sensor 24 is transmitted to the controller 5. The detected data from the outside air temperature sensor 24 indicates the outside air temperature Ta, which is the temperature outside the work machine.

[0024] The fan rotation speed sensor 25 detects the rotation speed of the fan 10 per unit time. The fan rotation speed sensor 25 is provided on the output shaft of the hydraulic motor 3. The detection data of the fan rotation speed sensor 25 is transmitted to the controller 5. The detection data of the fan rotation speed sensor 25 indicates the actual rotation speed Fs of the fan 10.

[0025] The pump drain pressure sensor 26 detects the pressure of hydraulic oil leaking from the sliding parts of the hydraulic pump 2. The pump drain pressure sensor 26 is arranged in the pump drain line 11. The hydraulic oil leaking from the sliding parts of the hydraulic pump 2 flows through the pump drain line 11. The pump drain pressure sensor 26 detects the pressure of the pump drain line 11. The pump drain pressure sensor 26 detects the pressure of the hydraulic oil flowing through the pump drain line 11. The greater the amount of hydraulic oil leaking from the sliding parts of the hydraulic pump 2, the higher the pressure of the hydraulic oil flowing through the pump drain line 11. The detection data of the pump drain pressure sensor 26 is transmitted to the controller 5. The detection data of the pump drain pressure sensor 26 indicates the pump drain pressure Pp, which is the pressure of the hydraulic oil leaking from the sliding parts of the hydraulic pump 2.

[0026] The motor drain pressure sensor 27 detects the pressure of hydraulic oil leaking from the sliding parts of the hydraulic motor 3. The motor drain pressure sensor 27 is arranged in the motor drain line 12. The hydraulic oil leaking from the sliding parts of the hydraulic motor 3 flows through the motor drain line 12. The motor drain pressure sensor 27 detects the pressure of the motor drain line 12. The motor drain pressure sensor 27 detects the pressure of the hydraulic oil flowing through the motor drain line 12. The greater the amount of hydraulic oil leaking from the sliding parts of the hydraulic motor 3, the higher the pressure of the hydraulic oil flowing through the motor drain line 12. The detection data of the motor drain pressure sensor 27 is transmitted to the controller 5. The detection data of the motor drain pressure sensor 27 indicates the motor drain pressure Pm, which is the pressure of the hydraulic oil leaking from the sliding parts of the hydraulic motor 3.

[0027] The controller 5 controls the swash plate driver 2B to adjust the angle of the swash plate 2A. Adjusting the angle of the swash plate 2A adjusts the capacity q of the hydraulic pump 2. The controller 5 adjusts the angle of the swash plate 2A based on the engine speed N, the coolant temperature Tw, the hydraulic oil temperature To, the outside air temperature Ta, and the actual rotation speed Fs of the fan 10.

[0028] The relationship expressed by the following equation (1) holds between the capacity q of the hydraulic pump 2, the flow rate Q of the hydraulic oil discharged from the hydraulic pump 2, and the engine speed N. In equation (1), K is the efficiency.

[0029] Q = K×q×N …(1)

[0030] When the engine 9 is rotating at a constant engine speed N, the controller 5 can adjust the flow rate Q of hydraulic oil supplied from the hydraulic pump 2 to the hydraulic motor 3 by adjusting the angle of the swash plate 2A to adjust the capacity q. The rotation speed of the fan 10 is adjusted based on the flow rate Q of hydraulic oil supplied from the hydraulic pump 2 to the hydraulic motor 3. The flow rate Q of hydraulic oil flowing into the inlet port of the hydraulic motor 3 is proportional to the rotation speed of the fan 10. The greater the flow rate Q of hydraulic oil supplied from the hydraulic pump 2 to the hydraulic motor 3, the higher the rotation speed of the fan 10. The smaller the flow rate Q of hydraulic oil supplied from the hydraulic pump 2 to the hydraulic motor 3, the lower the rotation speed of the fan 10. If hydraulic oil is not supplied from the hydraulic pump 2 to the hydraulic motor 3, the fan 10 stops rotating.

[0031] [controller] FIG. 2 is a hardware configuration diagram showing a controller 5 according to an embodiment. The controller 5 includes a computer system. The controller 5 has a processor 5A such as a CPU (Central Processing Unit), a main memory 5B including a nonvolatile memory such as a ROM (Read Only Memory) and a volatile memory such as a RAM (Random Access Memory), a storage 5C, and an input / output interface 5D including an input / output circuit. The functions of the controller 5 are stored in the storage 5C as a computer program. The processor 5A reads the computer program from the storage 5C, loads it into the main memory 5B, and executes processing in accordance with the computer program. The computer program may be distributed to the controller 5 via a network.

[0032] 3 is a functional block diagram showing a controller 5 according to an embodiment. The controller 5 includes a data acquisition unit 51, a target amount determination unit 52, a comparison unit 53, a calculation unit 54, a control unit 55, an estimation unit 56, an output unit 57, and a storage unit 58.

[0033] The data acquisition unit 51 acquires the engine rotation speed N from the engine rotation speed sensor 21. The data acquisition unit 51 acquires the coolant temperature Tw from the engine water temperature sensor 22. The data acquisition unit 51 acquires the hydraulic oil temperature To from the hydraulic oil temperature sensor 23. The data acquisition unit 51 acquires the outside air temperature Ta from the outside air temperature sensor 24. The data acquisition unit 51 acquires the actual rotation speed Fs of the fan 10 from the fan rotation speed sensor 25. The data acquisition unit 51 acquires the pump drain pressure Pp from the pump drain pressure sensor 26. The data acquisition unit 51 acquires the motor drain pressure Pm from the motor drain pressure sensor 27.

[0034] The target amount determination unit 52 determines the target rotation speed Fr of the fan 10 based on the state of the object to be cooled by the fan 10. In the embodiment, the object to be cooled by the fan 10 includes coolant and hydraulic oil.

[0035] The state of the object to be cooled by the fan 10 changes from moment to moment based on the operating state of the work machine and the ambient temperature. The state of the object to be cooled includes the coolant temperature Tw and the hydraulic oil temperature To. The operating state of the work machine includes the engine speed N. The ambient temperature includes the outside air temperature Ta. That is, the coolant temperature Tw and the hydraulic oil temperature To change from moment to moment based on the engine speed N and the outside air temperature Ta. The target rotation speed Fr of the fan 10 determined by the target amount determination unit 52 changes from moment to moment based on the engine speed N, the coolant temperature Tw, the hydraulic oil temperature To, and the outside air temperature Ta.

[0036] The comparison unit 53 compares the target rotation speed Fr of the fan 10 determined by the target amount determination unit 52 with the actual rotation speed Fs of the fan 10 acquired by the data acquisition unit 51. The comparison unit 53 calculates a feedback amount Fa indicating the deviation between the target rotation speed Fr of the fan 10 and the actual rotation speed Fs of the fan 10.

[0037] The calculation unit 54 calculates the command rotation speed Ft by adding the feedback amount Fa to the target rotation speed Fr. The command rotation speed Ft is a rotation speed for controlling the swash plate driving unit 2B of the hydraulic pump 2. The feedback amount Fa includes a deviation between the target rotation speed Fr and the command rotation speed Ft.

[0038] The control unit 55 controls the swash plate driver 2B based on the command rotation speed Ft. In this embodiment, the control unit 55 calculates a control current i for the swash plate driver 2B so that the swash plate driver 2B rotates at the command rotation speed Ft. The swash plate driver 2B is driven based on the control current i calculated by the control unit 55 to adjust the angle of the swash plate 2A.

[0039] The estimation unit 56 estimates the state of the hydraulic pump 2 or the state of the hydraulic motor 3 based on a change in the feedback amount Fa. In the embodiment, the state of the hydraulic pump 2 or the state of the hydraulic motor 3 includes a system efficiency indicating the product of the volumetric efficiency of the hydraulic pump 2 and the volumetric efficiency of the hydraulic motor 3.

[0040] The estimation unit 56 estimates the state of the hydraulic pump 2 or the state of the hydraulic motor 3 based on changes in the feedback amount Fa, changes in the pump drain pressure Pp, and changes in the motor drain pressure Pm. The state of the hydraulic pump 2 includes a state in which hydraulic oil is leaking from a sliding part of the hydraulic pump 2. The state of the hydraulic motor 3 includes a state in which hydraulic oil is leaking from a sliding part of the hydraulic motor 3.

[0041] The output unit 57 outputs the result of estimation by the estimation unit 56 to the output device 40. Examples of the output device 40 include a display device and an audio output device.

[0042] The memory unit 58 stores multiple correlation data regarding the target rotation speed Fr of the fan 10. The correlation data is obtained in advance by experiment or simulation. As disclosed in International Publication No. 2018 / 131118, the memory unit 58 stores first correlation data indicating the relationship between the engine rotation speed N and the target rotation speed Fr1 of the fan 10 required at that engine rotation speed N. The memory unit 58 stores second correlation data indicating the relationship between the coolant temperature Tw and the target rotation speed Fr2 of the fan 10 required at that coolant temperature Tw. The memory unit 58 stores third correlation data indicating the relationship between the hydraulic oil temperature To and the target rotation speed Fr3 of the fan 10 required at that hydraulic oil temperature To. The memory unit 58 stores fourth correlation data indicating the relationship between the outside air temperature Ta and the target rotation speed Fr4 of the fan 10 required at that outside air temperature Ta.

[0043] The target quantity determination unit 52 derives a target rotation speed Fr1 for the fan 10 based on the engine rotation speed N detected by the engine rotation speed sensor 21 and first correlation data stored in the memory unit 58. The calculation unit 54 derives a target rotation speed Fr2 for the fan 10 based on the coolant temperature Tw detected by the engine water temperature sensor 22 and second correlation data stored in the memory unit 58. The calculation unit 54 derives a target rotation speed Fr3 for the fan 10 based on the hydraulic oil temperature To detected by the hydraulic oil temperature sensor 23 and third correlation data stored in the memory unit 58. The calculation unit 54 derives a target rotation speed Fr4 for the fan 10 based on the outside air temperature Ta detected by the outside air temperature sensor 24 and fourth correlation data stored in the memory unit 58. The target amount determination unit 52 selects an arbitrary target rotation speed from the target rotation speeds Fr1, Fr2, Fr3, and Fr4, and determines the selected target rotation speed as the final target rotation speed Fr of the fan 10.

[0044] [Feedback control] 4 is a control block diagram of the controller 5 according to the embodiment. As shown in FIG. 4, the controller 5 controls the swash plate driving unit 2B by feedback control.

[0045] As described above, the target amount determination unit 52 determines the target rotation speed Fr of the fan 10. The data acquisition unit 51 acquires the actual rotation speed Fs of the fan 10 from the fan rotation speed sensor 25. The comparison unit 53 calculates a feedback amount Fa indicating the deviation between the target rotation speed Fr and the actual rotation speed Fs. The calculation unit 54 adds the feedback amount Fa to the target rotation speed Fr to calculate the command rotation speed Ft. The estimation unit 56 monitors the feedback amount Fa calculated by the comparison unit 53.

[0046] The calculation unit 54 calculates the required flow rate Qr, which indicates the flow rate Q of hydraulic oil required to achieve the command rotation speed Ft. As described above, the flow rate Q of hydraulic oil supplied to the hydraulic motor 3 is proportional to the rotation speed of the fan 10. Therefore, the calculation unit 54 can calculate the required flow rate Qr to achieve the command rotation speed Ft.

[0047] The calculation unit 54 calculates the capacity q of the hydraulic pump 2 required to achieve the required flow rate Qr. As shown in equation (1), the flow rate Q changes based on the engine speed N. Therefore, the calculation unit 54 can calculate the capacity q of the hydraulic pump 2 required to achieve the required flow rate Qr based on the current engine speed N and the required flow rate Qr acquired by the data acquisition unit 51.

[0048] The control unit 55 calculates the control current i required for the swash plate driving unit 2B to achieve the displacement q calculated by the calculation unit 54. The angle of the swash plate 2A is adjusted based on the control current i. By adjusting the angle of the swash plate 2A, the displacement q of the hydraulic pump 2 is adjusted.

[0049] As disclosed in International Publication No. 2018 / 131118, the memory unit 58 stores fifth correlation data indicating the relationship between the engine speed N, the required flow rate Qr, and the control current i. The memory unit 58 stores a large number of fifth correlation data indicating the control current i for achieving the required flow rate Qr at each of a plurality of engine speeds N (Na, Nb, Nc, etc.). The control unit 55 calculates the control current i to be output to the swash plate driver 2B to achieve the command rotation speed Ft of the fan 10 based on the target rotation speed Fr, the current engine rotation speed N acquired by the data acquisition unit 51, and the fifth correlation data stored in the memory unit 58. The control unit 55 outputs a control signal including the calculated control current i to the swash plate driver 2B.

[0050] [Feedback amount] In the fan drive system 1, when the hydraulic pump 2 and the hydraulic motor 3 are both normal, the control unit 55 outputs a control current i, causing the fan 10 to rotate at the target rotation speed Fr. The hydraulic pump 2 being normal includes the hydraulic pump 2 being new, and for example, including the degradation level of the parts of the hydraulic pump 2 being at an acceptable level. The hydraulic motor 3 being normal includes the hydraulic motor 3 being new, and for example, including the degradation level of the parts of the hydraulic motor 3 being at an acceptable level.

[0051] If at least one of the hydraulic pump 2 and the hydraulic motor 3 is abnormal, the system efficiency of the fan drive system 1 decreases. An abnormality in the hydraulic pump 2 includes an unacceptable level of deterioration of components of the hydraulic pump 2 and an unacceptable level of leakage of hydraulic oil from sliding parts of the hydraulic pump 2. An abnormality in the hydraulic motor 3 includes an unacceptable level of deterioration of components of the hydraulic motor 3 and an unacceptable level of leakage of hydraulic oil from sliding parts of the hydraulic motor 3. If at least one of the hydraulic pump 2 and the hydraulic motor 3 is abnormal, even if a control current i is output from the control unit 55, the fan 10 cannot rotate at the target rotation speed Fr, and the actual rotation speed Fs of the fan 10 becomes lower than the target rotation speed Fr. In other words, if at least one of the hydraulic pump 2 and the hydraulic motor 3 is abnormal, even if a control current i is output from the control unit 55, the feedback amount Fa becomes large.

[0052] As disclosed in International Publication No. 2018 / 131118, the estimation unit 56 estimates the system efficiency of the fan drive system 1 based on changes in the feedback amount Fa.

[0053] 5 is a diagram schematically illustrating the relationship between the feedback amount Fa, the system efficiency, the capacity q of the hydraulic pump 2, and the actual rotation speed Fs of the fan 10 according to the embodiment. As shown in FIG. 5, the feedback amount Fa and the system efficiency are correlated.

[0054] In FIG. 5, time t0 is the time when use of a new hydraulic pump 2 and hydraulic motor 3 begins. During a period P1 between time t0 and time t1, a predetermined time after time t0, the feedback amount Fa does not change substantially. The estimation unit 56 estimates that the system efficiency is normal during the period P1 based on the change in the feedback amount Fa. Normal system efficiency means that both the hydraulic pump 2 and the hydraulic motor 3 are normal. Normal system efficiency means that the fan 10 rotates according to the target rotation speed Fr.

[0055] During a period P2 between time t1 and time t2, which is a predetermined time after time t1, the feedback amount Fa increases. The estimation unit 56 estimates that the system efficiency is decreasing during the period P2 based on the change in the feedback amount Fa. The decrease in the system efficiency means that at least one of the hydraulic pump 2 and the hydraulic motor 3 is abnormal.

[0056] If at least one of the hydraulic pump 2 and the hydraulic motor 3 is abnormal, the actual rotation speed Fs of the fan 10 decreases. When a situation occurs in which the actual rotation speed Fs of the fan 10 decreases, the feedback amount Fa increases. When the feedback amount Fa increases, the command rotation speed Ft increases in order to rotate the fan 10 at the target rotation speed Fr. As the command rotation speed Ft increases, the angle of the swash plate 2A is adjusted so that the capacity q of the hydraulic pump 2 increases. When the capacity q of the hydraulic pump 2 increases, the flow rate Q of hydraulic oil supplied from the hydraulic pump 2 to the hydraulic motor 3 increases, and the actual rotation speed Fs of the fan 10 increases. During a period P2 in which the system efficiency decreases, the control unit 55 increases the flow rate Q of hydraulic oil supplied to the hydraulic motor 3, thereby allowing the fan 10 to rotate at the target rotation speed Fr.

[0057] The estimation unit 56 can estimate whether an abnormality has occurred in at least one of the hydraulic pump 2 and the hydraulic motor 3 based on the rate of change of the feedback amount Fa, which indicates the amount of change of the feedback amount Fa per unit time. In the example shown in Fig. 5, the feedback amount Fa increases sharply at time point t1. Therefore, the estimation unit 56 can estimate that an abnormality has occurred in at least one of the hydraulic pump 2 and the hydraulic motor 3 at time point t1.

[0058] [Identifying abnormal hydraulic pumps or hydraulic motors] As described above, the estimation unit 56 can estimate that at least one of the hydraulic pump 2 and the hydraulic motor 3 is abnormal based on the change in the feedback amount Fa. In the embodiment, the estimation unit 56 can identify the abnormal device (hydraulic pump 2 or hydraulic motor 3) based on the change in the feedback amount Fa, the change in the pump drain pressure Pp, and the change in the motor drain pressure Pm. The estimation unit 56 can identify the abnormal hydraulic pump 2 or hydraulic motor 3 based on the change in the feedback amount Fa, the change in the pump drain pressure Pp, and the change in the motor drain pressure Pm. The estimation unit 56 can determine whether the hydraulic pump 2 or the hydraulic motor 3 is abnormal based on the change in the feedback amount Fa, the change in the pump drain pressure Pp, and the change in the motor drain pressure Pm.

[0059] 6 is a diagram schematically showing the relationship between the feedback amount Fa, pump drain pressure Pp, and motor drain pressure Pm according to the embodiment. The estimation unit 56 monitors the feedback amount Fa, pump drain pressure Pp, and motor drain pressure Pm. The estimation unit 56 determines whether the hydraulic pump 2 or the hydraulic motor 3 is abnormal, based on changes in the feedback amount Fa, the pump drain pressure Pp, and the motor drain pressure Pm.

[0060] 6, time t0 is the time when the use of a new hydraulic pump 2 and hydraulic motor 3 begins. During a period P1 between time t0 and time t1, which is a predetermined time after time t0, the feedback amount Fa does not change substantially. Furthermore, during the period P1, the pump drain pressure Pp and the motor drain pressure Pm do not change substantially either.

[0061] During a period P2 between time t1 and time t2, which is a predetermined time after time t1, the feedback amount Fa increases. During the period P2, the motor drain pressure Pm does not substantially change, but the pump drain pressure Pp increases. The estimation unit 56 estimates that the system efficiency is decreasing during the period P2 based on the change in the feedback amount Fa. The estimation unit 56 also estimates that the hydraulic pump 2 is abnormal based on the pump drain pressure Pp. An increase in the pump drain pressure Pp means that a large amount of hydraulic oil has leaked from the hydraulic pump 2. Therefore, the estimation unit 56 can estimate that the hydraulic pump 2 is abnormal.

[0062] Furthermore, in the embodiment, the estimation unit 56 can identify the type of abnormality based on the change in the feedback amount Fa. The types of abnormality include aging deterioration and sudden failure. An example of a sudden failure is when a foreign object enters the equipment (hydraulic pump 2 and hydraulic motor 3) causing the equipment to malfunction.

[0063] 7, 8, and 9 are diagrams illustrating types of abnormalities according to the embodiment. FIG. 7 shows changes in the feedback amount Fa when the estimation unit 56 estimates that there is no abnormality in the hydraulic pump 2 and the hydraulic motor 3. FIG. 8 shows changes in the feedback amount Fa when the estimation unit 56 estimates that at least one of the hydraulic pump 2 and the hydraulic motor 3 has deteriorated over time. FIG. 9 shows changes in the feedback amount Fa when the estimation unit 56 estimates that a sudden failure has occurred in at least one of the hydraulic pump 2 and the hydraulic motor 3.

[0064] In this embodiment, a feedback threshold value, which is a threshold value for the feedback amount Fa, is determined in advance and stored in the storage unit 58. In this embodiment, the feedback threshold value is determined to be 20[%] of the feedback limit value.

[0065] The estimation unit 56 calculates the average value of the feedback amount Fa at each of five points in time after a predetermined period (e.g., 500 hours) has elapsed since the start of use of the new hydraulic pump 2 and hydraulic motor 3. The estimation unit 56 sets the calculated average value as the reference value of the feedback amount Fa.

[0066] 7, when the reference value of the feedback amount Fa does not exceed the feedback threshold value, the estimation unit 56 determines that the system efficiency is normal. Normal system efficiency means that the hydraulic pump 2 and the hydraulic motor 3 are normal.

[0067] 8 and 9, when the reference value of the feedback amount Fa gradually increases and exceeds the feedback threshold, the estimation unit 56 determines that the system efficiency is decreasing. The decrease in the system efficiency means that at least one of the hydraulic pump 2 and the hydraulic motor 3 is abnormal.

[0068] As shown in FIG. 8, when the reference value of the feedback amount Fa exceeds the feedback threshold value, the estimation unit 56 determines that at least one of the hydraulic pump 2 and the hydraulic motor 3 has deteriorated over time.

[0069] 9, the estimation unit 56 counts the number of times that the reference value of the feedback amount Fa exceeds the feedback threshold value during a retroactive period between the present time and a predetermined time (e.g., 500 hours) from the present time. If the reference value of the feedback amount Fa exceeds the feedback threshold value at least three times in a row, the estimation unit 56 determines that a sudden failure has occurred in at least one of the hydraulic pump 2 and the hydraulic motor 3.

[0070] 10 is a flowchart showing a method for determining the type of abnormality according to this embodiment. The data acquisition unit 51 acquires the actual rotation speed Fs of the fan 10 from the fan rotation speed sensor 25 (step SA1). The target amount determination unit 52 determines the target rotation speed Fr of the fan 10 based on the state of the coolant and hydraulic oil that are the objects to be cooled by the fan 10 (step SA2). The comparison unit 53 calculates a feedback amount Fa that indicates the deviation between the target rotation speed Fr and the actual rotation speed Fs (step SA3).

[0071] The estimation unit 56 sets a reference value for the feedback amount Fa (step SA4). As described above, the estimation unit 56 sets the reference value to the average value of the feedback amount Fa at each of five points in time after a predetermined period has elapsed since the start of use of the brand new hydraulic pump 2 and hydraulic motor 3.

[0072] The estimation unit 56 determines whether the reference value of the feedback amount Fa exceeds a predetermined feedback threshold value (step SA5). If it is determined in step SA5 that the reference value of the feedback amount Fa does not exceed the feedback threshold value (step SA5: No), the estimation unit 56 determines that there is no abnormality in the hydraulic pump 2 and the hydraulic motor 3 (step SA6).

[0073] If it is determined in step SA5 that the reference value of the feedback amount Fa has exceeded the feedback threshold value (step SA5: Yes), the estimation unit 56 determines whether the reference value of the feedback amount Fa has exceeded the feedback threshold value in a retroactive period going back 500 hours from the present time (step SA7).

[0074] In step SA7, if it is determined that the reference value of the feedback amount Fa does not exceed the feedback threshold value during the retrospective period (step SA7: No), the estimation unit 56 determines that at least one of the hydraulic pump 2 and the hydraulic motor 3 has deteriorated over time (step SA8).

[0075] In step SA7, if it is determined that the reference value of the feedback amount Fa has exceeded the feedback threshold during the retrospective period (step SA7: Yes), the estimation unit 56 determines whether the reference value of the feedback amount Fa has exceeded the feedback threshold three times in a row (step SA9).

[0076] In step SA9, if it is determined that the reference value of the feedback amount Fa has not exceeded the feedback threshold value three consecutive times (step SA9: No), the estimation unit 56 determines that at least one of the hydraulic pump 2 and the hydraulic motor 3 has deteriorated over time (step SA8).

[0077] In step SA9, if it is determined that the reference value of the feedback amount Fa has exceeded the feedback threshold value three consecutive times (step SA9: No), the estimation unit 56 determines that at least one of the hydraulic pump 2 and the hydraulic motor 3 has experienced a sudden failure (step SA10).

[0078] 11 is a flowchart showing a method for identifying an abnormal hydraulic pump 2 or hydraulic motor 3 according to an embodiment. The data acquisition unit 51 acquires the pump drain pressure Pp from the pump drain pressure sensor 26 (step SB1). The data acquisition unit 51 acquires the motor drain pressure Pm from the motor drain pressure sensor 27 (step SB2).

[0079] Drain pressure thresholds, which are thresholds for the pump drain pressure Pp and the motor drain pressure Pm, are determined in advance and stored in the storage unit 58. In the embodiment, the drain pressure thresholds are determined to be design performance limit values.

[0080] The estimation unit 56 determines whether the pump drain pressure Pp has exceeded a predetermined drain pressure threshold (step SB3). If it is determined in step SB3 that the pump drain pressure Pp has exceeded the drain pressure threshold (step SB3: Yes), the estimation unit 56 estimates that the hydraulic pump 2 is abnormal (step SB4). If it is determined in step SB3 that the pump drain pressure Pp has not exceeded the drain pressure threshold (step SB3: No), the estimation unit 56 determines that the hydraulic pump 2 is normal (step SB5).

[0081] The estimation unit 56 determines whether the motor drain pressure Pm has exceeded a predetermined drain pressure threshold (step SB6). If it is determined in step SB6 that the motor drain pressure Pm has exceeded the drain pressure threshold (step SB6: Yes), the estimation unit 56 estimates that the hydraulic motor 3 is abnormal (step SB7). If it is determined in step SB6 that the motor drain pressure Pm has not exceeded the drain pressure threshold (step SB6: No), the estimation unit 56 determines that the hydraulic motor 3 is not abnormal (step SB8).

[0082] The estimation unit 56 can determine whether the hydraulic pump 2 or the hydraulic motor 3 is abnormal and estimate the type of abnormality by combining the determination result of the type of abnormality described with reference to Figure 10 and the identification result of the abnormal equipment (hydraulic pump 2 or hydraulic motor 3) described with reference to Figure 11.

[0083] [Fan and drain line abnormality detection] In the embodiment, the estimation unit 56 estimates the state of the fan 10 based on changes in the feedback amount Fa, changes in the actual rotation speed Fs of the fan 10, changes in the outside air temperature Ta, changes in the coolant temperature Tw or the hydraulic oil temperature To, and changes in the motor drain pressure Pm. The estimation unit 56 estimates whether the fan 10 is abnormal. The estimation unit 56 estimates whether the fan 10 is damaged.

[0084] In the embodiment, an abnormality in the fan 10 refers to an abnormal noise being generated from the fan 10, even though there is no abnormality in the cooling capacity of the fan 10 or the hydraulic motor 3. Abnormalities in the fan 10 include loosening of the fan boss fixing bolts and a missing part of the fan 10. When an abnormality occurs in the fan 10, the unbalanced moment of the rotating body increases, causing rotational wobble of the fan 10. When rotational wobble of the fan 10 occurs, rotational wobble of the output shaft of the hydraulic motor 3 connected to the fan 10 occurs, causing a change in the motor drain pressure Pm.

[0085] In the embodiment, damage to the fan 10 refers to a decrease in the cooling capacity of the fan 10 and an abnormality occurring in the hydraulic motor 3. When the abnormality level of the fan 10 increases, the fan 10 is damaged. If the rotational deviation of the fan 10 increases and the fan 10 rotates with a rotational deviation greater than the tip clearance, the fan 10 may come into contact with the fan housing 15, potentially damaging the fan 10. The tip clearance refers to the dimension of the gap between the fan 10 and the fan housing 15 when the fan 10 is rotating normally. If the fan 10 is damaged, the rotational deviation of the output shaft of the hydraulic motor 3 connected to the fan 10 increases, causing a significant change in the motor drain pressure Pm. Furthermore, if the rotational deviation of the output shaft of the hydraulic motor 3 increases, components of the hydraulic motor 3, such as bearings and seals, may be damaged.

[0086] FIG. 12 is a diagram showing a schematic relationship between the feedback amount Fa, the actual rotation speed Fs of the fan 10, the outside air temperature Ta, the hydraulic oil temperature To, and the motor drain pressure Pm according to the embodiment.

[0087] 12, time t0 is the time when the use of a new hydraulic pump 2 and hydraulic motor 3 begins. At time t0, the fan 10 is normal. During the period between time t0 and time t3, which is a predetermined time after time t0, the feedback amount Fa, the actual rotation speed Fs of the fan 10, the outside air temperature Ta, the hydraulic oil temperature To, and the motor drain pressure Pm do not substantially change.

[0088] If the fan 10 breaks at time t3, the cooling capacity of the fan 10 decreases, and therefore the actual rotation speed Fs of the fan 10 increases in order to maintain the cooling capacity. If the fan 10 breaks, the rotational deviation of the output shaft of the hydraulic motor 3 connected to the fan 10 increases, resulting in a large change in the motor drain pressure Pm. Although the actual rotation speed Fs of the fan 10 increases, the cooling capacity of the fan 10 decreases due to the breakage of the fan 10, and therefore the hydraulic oil temperature To increases. Even if the fan 10 breaks, the outside air temperature Ta and the feedback amount Fa do not change substantially. If the outside air temperature Ta and the feedback amount Fa do not change, the actual rotation speed Fs of the fan 10 and the hydraulic oil temperature To increase, and the motor drain pressure Pm changes, the estimation unit 56 can estimate that the fan 10 has broken.

[0089] 12, the estimation unit 56 may determine whether the fan 10 is damaged based on the coolant temperature Tw instead of the hydraulic oil temperature To. The estimation unit 56 may determine whether the fan 10 is damaged based on both the hydraulic oil temperature To and the coolant temperature Tw. The estimation unit 56 may determine whether the fan 10 is damaged based on, for example, the average value of the hydraulic oil temperature To and the coolant temperature Tw. In the following description, one or both of the hydraulic oil temperature To and the coolant temperature Tw will be referred to as the coolant temperature, as appropriate.

[0090] The estimation unit 56 also estimates the states of the pump drain line 11 and the motor drain line 12 based on the change in the feedback amount Fa, the change in the pump drain pressure Pp, and the change in the motor drain pressure Pm.

[0091] In the embodiment, abnormalities in the drain lines (11, 12) include clogging of the drain lines (11, 12), an excessive increase in the pressure of the hydraulic oil tank 4, and clogging of a filter in a breather cap provided in the hydraulic oil tank 4. The breather cap is disposed to close the opening of the hydraulic oil tank 4, and has a ventilation structure for maintaining a constant pressure in the hydraulic oil tank 4.

[0092] FIG. 13 is a diagram schematically showing the relationship between the feedback amount Fa, the actual rotation speed Fs of the fan 10, the pump drain pressure Pp, and the motor drain pressure Pm according to the embodiment.

[0093] 13, time t0 is the time when the use of a new hydraulic pump 2 and hydraulic motor 3 begins. At time t0, the pump drain line 11 and the motor drain line 12 are normal. During the period between time t0 and time t4, which is a predetermined time after time t0, the feedback amount Fa, the actual rotation speed Fs of the fan 10, the pump drain pressure Pp, and the motor drain pressure Pm do not substantially change.

[0094] If an abnormality occurs in the pump drain line 11 at time t4, the pump drain pressure Pp rises. Because the hydraulic pump 2 and the hydraulic motor 3 are both normal, the feedback amount Fa and the actual rotation speed Fs of the fan 10 do not change substantially. Because the pump drain pressure Pp rises and the motor drain pressure Pm does not change substantially, the estimation unit 56 can determine that the pump drain line 11 is abnormal and the motor drain line 12 is normal.

[0095] 14 is a flowchart showing a method for identifying an abnormal fan 10 or a drain line (11, 12) according to this embodiment. In the identification method described with reference to FIG. 14, it is assumed that the hydraulic pump 2 and the hydraulic motor 3 are normal. In other words, it is assumed that the hydraulic pump 2 and the hydraulic motor 3 have been determined to be normal by the identification method described with reference to FIG. 11.

[0096] A rotation speed threshold, which is a threshold for the actual rotation speed Fs of the fan 10, is determined in advance and stored in the storage unit 58. In this embodiment, the rotation speed threshold is set to the design performance limit value. A temperature threshold, which is a threshold for the coolant temperature, is determined in advance and stored in the storage unit 58. In this embodiment, the temperature threshold is set to the design performance limit value.

[0097] The data acquisition unit 51 acquires the pump drain pressure Pp from the pump drain pressure sensor 26 and the motor drain pressure Pm from the motor drain pressure sensor 27 (step SC1). The data acquisition unit 51 acquires the actual rotation speed Fs of the fan 10 from the fan rotation speed sensor 25 (step SC4). The data acquisition unit 51 acquires the coolant temperature from one or both of the engine water temperature sensor 22 and the hydraulic oil temperature sensor 23 (step SC7).

[0098] The estimation unit 56 determines whether the pump drain pressure Pp and the motor drain pressure Pm have each exceeded a predetermined drain pressure threshold (step SC2). If it is determined in step SC2 that the pump drain pressure Pp and the motor drain pressure Pm have not exceeded the drain pressure threshold (step SC2: No), the estimation unit 56 determines that there is no abnormality in the hydraulic pump 2 and the hydraulic motor 3 (step SC3).

[0099] In step SC2, if it is determined that the pump drain pressure Pp and the motor drain pressure Pm exceed the drain pressure threshold (step SC2: Yes), the estimation unit 56 determines whether the actual rotation speed Fs of the fan 10 has exceeded a predetermined rotation speed threshold (step SC5).

[0100] If it is determined in step SC5 that the actual rotation speed Fs of the fan 10 does not exceed the rotation speed threshold (step SC5: No), the estimation unit 56 determines that there is an abnormality in the drain lines (11, 12) (step SC6).

[0101] If it is determined in step SC5 that the actual rotation speed Fs of the fan 10 exceeds the rotation speed threshold (step SC2: Yes), the estimation unit 56 determines whether the coolant temperature has exceeded a predetermined temperature threshold (step SC8).

[0102] If it is determined in step SC8 that the coolant temperature does not exceed the temperature threshold value (step SC8: No), the estimation unit 56 determines that there is an abnormality in the fan 10 (step SC9).

[0103] If it is determined in step SC8 that the coolant temperature exceeds the temperature threshold value (step SC8: Yes), the estimation unit 56 determines that the fan 10 is broken (step SC10).

[0104] [Detecting abnormalities in the cooling system] In the embodiment, the estimation unit 56 estimates the state of the cooling device 30 based on changes in the feedback amount Fa, changes in the actual rotation speed Fs of the fan 10, changes in the coolant temperature Tw, changes in the hydraulic oil temperature To, changes in the pump drain pressure Pp, and changes in the motor drain pressure Pm. The state of the cooling device 30 includes the state of the cooling core of the radiator 31 or the state of the cooling core of the oil cooler 32.

[0105] 15 is a diagram showing the relationship between the feedback amount Fa, the actual rotation speed Fs of the fan 10, the radiator temperature, the oil cooler temperature, the pump drain pressure Pp, and the motor drain pressure Pm when an abnormality occurs in the cooling core of the radiator 31 according to the embodiment. The radiator temperature is equal to the coolant temperature Tw. The oil cooler temperature is equal to the hydraulic oil temperature To.

[0106] 15, time t0 is the time when use of a new hydraulic pump 2 and hydraulic motor 3 begins. At time t0, the fan 10, radiator 31, and oil cooler 32 are all normal. During the period between time t0 and time t5, which is a predetermined time after time t0, the feedback amount Fa, the actual rotation speed Fs of the fan 10, the oil cooler temperature, the radiator temperature, the pump drain pressure Pp, and the motor drain pressure Pm do not substantially change.

[0107] If an abnormality occurs in the cooling core of the radiator 31 at time t5, the radiator temperature rises. As the radiator temperature rises, the command rotation speed Ft increases, and the actual rotation speed Fs of the fan 10 increases. As the actual rotation speed Fs of the fan 10 increases, the rise in the radiator temperature is suppressed, and the radiator temperature remains substantially unchanged.

[0108] Because the cooling core of the oil cooler 32 is normal, an increase in the actual rotation speed Fs of the fan 10 causes a decrease in the oil cooler temperature. Because the feedback amount Fa, the pump drain pressure Pp, and the motor drain pressure Pm have not substantially changed, the estimation unit 56 can determine that the cooling core of the radiator 31 is abnormal.

[0109] In the embodiment, the radiator 31 and the oil cooler 32 are each cooled by one fan 10. Therefore, when the radiator temperature is constant and the oil cooler temperature drops, the estimation unit 56 can determine that an abnormality has occurred in the cooling core of the radiator 31.

[0110] Figure 16 is a diagram showing a schematic diagram of the relationship between the feedback amount Fa, the actual rotation speed Fs of the fan 10, the radiator temperature, the oil cooler temperature, the pump drain pressure Pp, and the motor drain pressure Pm when an abnormality occurs in the cooling core of the oil cooler 32 according to the embodiment.

[0111] At time t0 shown in Figure 16, the fan 10, radiator 31, and oil cooler 32 are all normal. If an abnormality occurs in the cooling core of the oil cooler 32 at time t5, the oil cooler temperature will rise. When the oil cooler temperature rises, the command rotation speed Ft increases, and the actual rotation speed Fs of the fan 10 increases. As the actual rotation speed Fs of the fan 10 increases, the rise in the oil cooler temperature is suppressed, and the oil cooler temperature remains substantially unchanged.

[0112] Because the cooling core of the radiator 31 is normal, the radiator temperature decreases as the actual rotation speed Fs of the fan 10 increases. Because the feedback amount Fa, the pump drain pressure Pp, and the motor drain pressure Pm do not substantially change, the estimation unit 56 can determine that an abnormality has occurred in the cooling core of the oil cooler 32.

[0113] As described above, the radiator 31 and the oil cooler 32 are each cooled by one fan 10. Therefore, when the oil cooler temperature is constant and the radiator temperature drops, the estimation unit 56 can determine that an abnormality has occurred in the cooling core of the oil cooler 32.

[0114] Fig. 17 is a flowchart showing a method for identifying an abnormal radiator 31 or oil cooler 32 according to this embodiment. In the identification method described with reference to Fig. 17, it is assumed that the hydraulic pump 2 and the hydraulic motor 3 are normal. In other words, it is assumed that the hydraulic pump 2 and the hydraulic motor 3 are determined to be normal by the identification method described with reference to Fig. 11.

[0115] A radiator threshold value, which is a threshold value for the radiator temperature, is determined in advance and stored in the storage unit 58. In an embodiment, the radiator threshold value is set to a design performance limit value. An oil cooler threshold value, which is a threshold value for the oil cooler temperature, is determined in advance and stored in the storage unit 58. In an embodiment, the oil cooler threshold value is set to a design performance limit value.

[0116] The data acquisition unit 51 acquires the actual rotation speed Fs of the fan 10 from the fan rotation speed sensor 25 (step SD1). The data acquisition unit 51 acquires the radiator temperature from the engine water temperature sensor 22 (step SD4). The data acquisition unit 51 acquires the oil cooler temperature from the hydraulic oil temperature sensor 23 (step SD8).

[0117] The estimation unit 56 determines whether the actual rotation speed Fs of the fan 10 exceeds a predetermined rotation speed threshold (step SD2). If it is determined in step SD2 that the actual rotation speed Fs of the fan 10 does not exceed the rotation speed threshold (step SD2: No), the estimation unit 56 determines that there is no abnormality in the fan 10 (step SD3).

[0118] If it is determined in step SD2 that the actual rotation speed Fs of the fan 10 exceeds the rotation speed threshold (step SD2: Yes), the estimation unit 56 determines whether the radiator temperature is equal to or lower than the radiator threshold (step SD5).

[0119] If it is determined in step SD5 that the radiator temperature is not equal to or lower than the radiator threshold value (step SD5: No), the estimation unit 56 determines that there is no abnormality in the radiator 31 (step SD6).

[0120] If it is determined in step SD5 that the radiator temperature is equal to or lower than the radiator threshold value (step SD5: Yes), the estimation unit 56 determines that there is an abnormality in the oil cooler 32 (step SD7).

[0121] If it is determined in step SD2 that the actual rotation speed Fs of the fan 10 exceeds the rotation speed threshold (step SD2: Yes), the estimation unit 56 determines whether the oil cooler temperature is equal to or higher than the oil cooler threshold (step SD9).

[0122] If it is determined in step SD9 that the oil cooler temperature is not equal to or lower than the oil cooler threshold value (step SD9: No), the estimation unit 56 determines that there is no abnormality in the oil cooler 32 (step SD10).

[0123] If it is determined in step SD9 that the oil cooler temperature is equal to or lower than the oil cooler threshold value (step SD9: Yes), the estimation unit 56 determines that there is an abnormality in the radiator 31 (step SD11).

[0124] [effect] As described above, according to the embodiment, the fan drive system 1 includes the hydraulic pump 2, the hydraulic motor 3 that rotates the fan 10 based on the hydraulic oil supplied from the hydraulic pump 2, and the controller 10. The controller 10 includes a target amount determination unit 52 that determines a target rotation speed Fr of the fan 10 based on the state of an object to be cooled by the fan 10, a comparison unit 53 that calculates a feedback amount Fa that indicates the deviation between the target rotation speed Fr of the fan 10 and the actual rotation speed Fs of the fan 10, and an estimation unit 56 that estimates the state of the hydraulic pump 2 or the state of the hydraulic motor 3 based on the feedback amount Fa, a pump drain pressure Pp that is the pressure in the pump drain line 11 that returns hydraulic oil from the hydraulic pump 2 to the hydraulic oil tank 4, and a motor drain pressure Pm that is the pressure in the motor drain line 12 that returns hydraulic oil from the hydraulic motor 3 to the hydraulic oil tank 4.

[0125] According to the embodiment, the states of the hydraulic pump 2 and the hydraulic motor 3, which are components of the fan drive system 1, are monitored with high accuracy. Furthermore, when the system efficiency decreases, the estimation unit 56 can identify whether the hydraulic pump 2 or the hydraulic motor 3 is abnormal, based on the pump drain pressure Pp and the motor drain pressure Pm. Therefore, the component in which an abnormality has occurred (the hydraulic pump 2 or the hydraulic motor 3) is maintained at an appropriate time, and maintenance of components that do not require maintenance is suppressed.

[0126] 18 is a diagram showing the relationship between data acquired by the data acquisition unit 51 according to the embodiment and devices whose states can be estimated by the estimation unit 56. As shown in FIG. 18, the estimation unit 56 can estimate whether an abnormality has occurred in the hydraulic pump 2 or the hydraulic motor 3, based on the actual rotation speed Fs of the fan 10, the feedback amount Fa, and the drain pressure (pump drain pressure Pp or motor drain pressure). The controller 5 can estimate the state of the device by double-checking the feedback amount Fa and the drain pressure, and therefore can monitor the state of the device with high accuracy.

[0127] The estimation unit 56 can estimate whether an abnormality has occurred in the fan 10 based on the actual rotation speed Fs of the fan 10, the feedback amount Fa, the outside air temperature Ta, the coolant temperature Tw, the hydraulic oil temperature To, and the drain pressure. This prevents damage to the fan 10 or the hydraulic motor 3, and the output unit 57 can output an error alert to the output device 40 before a fatal failure occurs. Furthermore, the controller 5 can bring the work machine to an emergency stop when the fan 10 or the hydraulic motor 3 is damaged. Furthermore, the occurrence of unexpected situations caused by broken pieces of the fan 10 is prevented.

[0128] The estimation unit 56 can estimate whether or not an abnormality has occurred in the drain lines (11, 12) based on the feedback amount Fa and the drain pressure, thereby preventing damage to the drain lines (11, 12).

[0129] The estimation unit 56 can estimate whether an abnormality has occurred in the radiator 31 or the oil cooler 32 based on the actual rotation speed Fs of the fan 10, the feedback amount Fa, the outside air temperature Ta, the coolant temperature Tw, the hydraulic oil temperature To, and the drain pressure. As a result, maintenance of the device in which an abnormality has occurred (the radiator 31 or the oil cooler 32) is performed at an appropriate time, and maintenance of devices that do not require maintenance is suppressed. [Explanation of symbols]

[0130] 1...fan drive system, 2...hydraulic pump, 2A...swash plate, 2B...swash plate drive unit, 3...hydraulic motor, 4...hydraulic oil tank, 5...controller, 5A...processor, 5B...main memory, 5C...storage, 5D...input / output interface, 6...suction line, 7...supply line, 8...tank line, 9...engine, 10...fan, 11...pump drain line, 12...motor drain line, 15...fan housing, 21...engine speed sensor, 22...engine water temperature sensor, 23...hydraulic oil temperature sensor, 24...outside air temperature sensor, 25 ...Fan rotation speed sensor, 26...Pump drain pressure sensor, 27...Motor drain pressure sensor, 30...Cooling device, 31...Radiator, 32...Oil cooler, 40...Output device, 51...Data acquisition unit, 52...Target quantity determination unit, 53...Comparator, 54...Calculation unit, 55...Control unit, 56...Estimation unit, 57...Output unit, 58...Memory unit, Fa...Feedback amount, Fr...Target rotation speed, Fs...Actual rotation speed, Ft...Command rotation speed, N...Engine rotation speed, Pm...Motor drain pressure, Pp...Pump drain pressure, Ta...Outside air temperature, To...Hydraulic oil temperature, Tw...Cooling water temperature.

Claims

1. A hydraulic pump; a hydraulic motor that rotates a fan using hydraulic oil supplied from the hydraulic pump; a controller; The controller a target amount determination unit that determines a target rotation speed of the fan based on a state of an object to be cooled by the fan; a comparison unit that calculates a feedback amount indicating a deviation between a target rotation speed of the fan and an actual rotation speed of the fan; an estimation unit that estimates a state of the hydraulic pump or a state of the hydraulic motor based on the feedback amount, a pump drain pressure that is a pressure in a pump drain line that returns hydraulic oil from the hydraulic pump to a hydraulic oil tank, and a motor drain pressure that is a pressure in a motor drain line that returns hydraulic oil from the hydraulic motor to the hydraulic oil tank, Fan drive system.

2. The estimation unit estimates that the hydraulic pump is abnormal when the pump drain pressure exceeds a drain pressure threshold. The fan drive system of claim 1 .

3. The estimation unit estimates that the hydraulic motor is abnormal when the motor drain pressure exceeds a drain pressure threshold. The fan drive system of claim 1 .

4. The objects to be cooled by the fan include cooling water flowing through a radiator and hydraulic oil flowing through an oil cooler, the estimation unit estimates the state of the fan based on the feedback amount, the actual rotation speed of the fan, an outside air temperature, the temperature of the cooling water or the temperature of the hydraulic oil, and the motor drain pressure. The fan drive system of claim 1 .

5. the estimation unit estimates states of the pump drain line and the motor drain line based on the feedback amount, the pump drain pressure, and the motor drain pressure. The fan drive system of claim 1 .

6. The objects to be cooled by the fan include cooling water flowing through a radiator and hydraulic oil flowing through an oil cooler, the estimation unit estimates the state of the radiator or the state of the oil cooler based on the feedback amount, the actual rotation speed of the fan, the temperature of the cooling water, the temperature of the hydraulic oil, the pump drain pressure, and the motor drain pressure. The fan drive system of claim 1 .

7. The state of the hydraulic pump or the state of the hydraulic motor includes a system efficiency indicating a product of a volumetric efficiency of the hydraulic pump and a volumetric efficiency of the hydraulic motor. The fan drive system of claim 1 .

8. Supplying hydraulic oil from a hydraulic pump to a hydraulic motor; rotating a fan with the hydraulic motor; determining a target rotation speed of the fan based on a state of an object to be cooled by the fan; calculating a feedback amount indicating a deviation between a target rotation speed of the fan and an actual rotation speed of the fan; and estimating a state of the hydraulic pump or a state of the hydraulic motor based on the feedback amount, a pump drain pressure which is the pressure of a pump drain line that returns hydraulic oil from the hydraulic pump to a hydraulic oil tank, and a motor drain pressure which is the pressure of a motor drain line that returns hydraulic oil from the hydraulic motor to a hydraulic oil tank. Fan drive method.

Images