Hydraulic pump condition monitoring device and hydraulic drive device

Abstract

The purpose of the present invention is to provide a hydraulic pump state monitoring device capable of diagnosing a hydraulic pump on the basis of a force conversion efficiency by measuring a characteristic amount related to the force conversion efficiency from input to output of the hydraulic pump. For this purpose, when the tilt amount of the hydraulic pump has become a predetermined tilt amount and the discharge pressure of the hydraulic pump has become a predetermined pressure, the controller calculates a characteristic amount related to the force conversion efficiency, which is the efficiency of conversion from the rotational force of the prime mover into the discharge pressure of the hydraulic oil of the hydraulic pump at the time when the discharge pressure has become the predetermined pressure.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for monitoring the state of a hydraulic pump that is widely used as a power source for hydraulic excavators, cranes, various other hydraulic machines, and hydraulic devices. [Background Art]

[0002] As prior art documents related to apparatuses for monitoring the state of hydraulic pumps, there are, for example, Patent Documents 1 to 3. Patent Document 1 discloses a construction machine comprising: a prime mover; a tank that stores hydraulic oil; a single-swashplate variable-displacement first hydraulic pump that is driven by the prime mover and discharges hydraulic oil sucked from the tank; a plurality of hydraulic actuators driven by hydraulic oil supplied from the first hydraulic pump; an operation device that instructs operations of the plurality of actuators; and a controller that controls the rotation speed of the prime mover and the tilt of the first hydraulic pump, wherein the construction machine further comprises: a first pressure sensor that detects the pressure of the first hydraulic pump; a first bleed-off adjustment device capable of adjusting the bleed-off flow rate of the first hydraulic pump; and an input device that instructs measurement of the leakage flow rate of the first hydraulic pump, the controller is connected to the operation device, the first pressure sensor, the first bleed-off adjustment device, and the input device, and is programmed to determine the operation state of the operation device based on an input signal from the operation device, convert a detection signal from the first pressure sensor into a pressure value, and output a control signal corresponding to a control command value to the first bleed-off adjustment device, and when it is determined that the operation device is in a non-operation state and a measurement command is input from the input device, the controller measures the pressure of the first hydraulic pump while changing the control command value of the first bleed-off adjustment device with the flow rate of the first hydraulic pump maintained, and calculates the leakage flow rate of the first hydraulic pump based on the control command value of the first bleed-off adjustment device when the pressure of the first hydraulic pump stabilizes at a predetermined pressure. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-95861 [Overview of the project] [Problems that the invention aims to solve]

[0004] A hydraulic pump outputs the input power from the prime mover in the form of the discharge flow rate and discharge pressure of the hydraulic fluid. If the gaps (clearances) between the parts inside the pump increase, the discharge flow rate decreases as the leakage flow rate inside the pump increases. On the other hand, if the frictional force between the sliding parts inside the pump increases, the discharge pressure decreases as the resistance force against the rotational force (torque) of the prime mover increases. Therefore, it is conceivable to introduce indicators such as the speed conversion efficiency (volumetric efficiency) from input to output of the hydraulic pump and the force conversion efficiency (mechanical efficiency) from input to output of the hydraulic pump, and diagnose the hydraulic pump based on these indicators.

[0005] However, while the method described in Patent Document 1 allows for diagnosis based on speed conversion efficiency by measuring the leakage flow rate of the hydraulic pump, it does not allow for diagnosis based on force conversion efficiency.

[0006] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a hydraulic pump condition monitoring device that enables diagnosis of a hydraulic pump based on its force conversion efficiency by measuring characteristic quantities related to the force conversion efficiency from input to output of the hydraulic pump. [Means for solving the problem]

[0008] To achieve the above objectivesThe present invention relates to a hydraulic drive system comprising a prime mover, a tank for storing hydraulic fluid, a variable displacement hydraulic pump driven by the rotation of the prime mover and drawing in and discharging hydraulic fluid from the tank in a capacity corresponding to the amount of tilt, and a controller that acquires information on the rotational force of the prime mover, the amount of tilt of the hydraulic pump, and the discharge pressure of the hydraulic fluid, and controls the amount of tilt of the hydraulic pump, wherein the system is further equipped with a pressure sensor for detecting the discharge pressure of the hydraulic pump, the controller controls the amount of tilt of the hydraulic pump to a predetermined amount of tilt, and when the discharge pressure of the hydraulic pump detected by the pressure sensor reaches a predetermined pressure, it calculates a feature quantity related to the force conversion efficiency, which is the conversion efficiency from the rotational force of the prime mover to the discharge pressure of the hydraulic fluid of the hydraulic pump. The hydraulic drive system is configured to include a bleed-off valve capable of adjusting the flow rate of hydraulic fluid discharged from the hydraulic pump and returned to the tank, a relief valve that regulates the discharge pressure of the hydraulic pump, and a measurement instruction device that instructs the controller to calculate the characteristic quantity, wherein the predetermined pressure is the set pressure of the relief valve, and when an instruction is received from the measurement instruction device, the controller controls the rotational speed of the prime mover to a predetermined rotational speed, controls the tilt amount of the hydraulic pump to the predetermined tilt amount, and closes the bleed-off valve. It shall be considered as such. [Effects of the Invention]

[0009] According to the present invention, by measuring characteristic quantities related to the force conversion efficiency from input to output of the hydraulic pump, it becomes possible to diagnose the hydraulic pump based on the force conversion efficiency. [Brief explanation of the drawing]

[0010] [Figure 1] Side view of a hydraulic excavator in the first embodiment of the present invention [Figure 2] Schematic diagram of the hydraulic drive device in the first embodiment of the present invention [Figure 3] Structural diagram of a variable displacement oblique-shaft hydraulic pump [Figure 4] Functional block diagram of the controller in the first embodiment of the present invention [Figure 5] Flowchart showing the controller processing in the first embodiment of the present invention [Figure 6] A diagram showing the processing of the analysis server in the first embodiment (modified version) of the present invention. [Figure 7] Schematic diagram of the hydraulic drive device in the first embodiment (modified version) of the present invention [Figure 8] Schematic diagram of the hydraulic drive device in the second embodiment of the present invention [Figure 9] Functional block diagram of the controller in the second embodiment of the present invention [Figure 10] Functional block diagram of the controller in the third embodiment of the present invention [Figure 11] Flowchart showing processing of the controller in the third embodiment of the present invention [Figure 12] Schematic configuration diagram of the hydraulic drive device in the fourth embodiment of the present invention Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, equivalent members are denoted by the same reference numerals, and duplicate descriptions will be omitted as appropriate. The present invention is applicable to hydraulic excavators, cranes, other various hydraulic machines and hydraulic devices, and the present embodiment is an example applied to a hydraulic excavator. Examples

[0012] Figure 1 is a side view of a hydraulic excavator according to the first embodiment of the present invention. The hydraulic excavator 100 includes a traveling body 101, a revolving body 102 pivotably mounted on the traveling body 101, and a working device 103 pivotably mounted in the vertical direction on the front side of the revolving body 102.

[0013] The working device 103 includes a boom 104 pivotably mounted in the vertical direction on the front side of the revolving body 102, an arm 105 pivotably mounted in the vertical or longitudinal direction at the distal end of the boom 104, and a bucket 106 pivotably mounted in the vertical or longitudinal direction at the distal end of the arm 105. The boom 104 is driven by a boom cylinder 107 which is a hydraulic actuator. The arm 105 is driven by an arm cylinder 108 which is a hydraulic actuator. The bucket 106 is driven by a bucket cylinder 109 which is a hydraulic actuator. An operator cab 110 for an operator is provided at a front position on the revolving body 102.

[0014] FIG. 2 is a diagram showing a schematic configuration of a hydraulic drive device mounted on a hydraulic excavator 100. The hydraulic drive device 200 includes an engine 20 serving as a prime mover, a single-swash-plate type variable displacement hydraulic pump 21 driven by the engine 20, a hydraulic pilot type tilting mechanism 11 that controls a pump displacement q of the hydraulic pump 21, an electromagnetic proportional valve 22 that outputs pilot pressure generated by reducing a primary pressure from a pilot hydraulic pressure source (not shown) to the tilting mechanism 11, hydraulic actuators 107 to 109, an operation lever 51 that instructs operations of the hydraulic actuators 107 to 109, a measurement instruction device 52, a direction switching valve unit 24, a relief valve 26, a pressure sensor 27, a monitor 50, the engine 20, the electromagnetic proportional valve 22, and a controller 40.

[0015] The direction switching valve unit 24 is connected to a pump discharge oil passage 28 connected to a discharge port of the hydraulic pump 21, and controls a flow of pressure oil supplied from the hydraulic pump 21 to the hydraulic actuators 107 to 109 in accordance with an operation of the operation lever 51. The relief valve 26 is a safety valve that limits a pressure of the pump discharge oil passage 28, and opens when a pressure of the pump discharge oil passage 28 (=pump pressure P) exceeds a relief set pressure Pr, to discharge the pressure oil in the pump discharge oil passage 28 to a tank 29. The pressure sensor 27 is provided in the pump discharge oil passage 28, converts the pressure of the pump discharge oil passage 28 (=pump pressure P) into a pressure signal, and outputs the pressure signal to the controller 40.

[0016] The controller 40 includes an input interface 40a that inputs signals from each device, an arithmetic device 40b configured of a central processing unit (CPU), its peripheral circuits and the like and performing various types of calculation according to a predetermined program, a storage device 40c that stores programs and various data, and an output interface 40d that outputs control signals to each device. The controller 40 controls the engine 20, the tilting mechanism 11, the monitor 50 and the like in accordance with an input signal from the operation lever 51, a pressure signal from the pressure sensor 27, and a measurement command from the measurement instruction device 52.

[0017] Axial piston type pumps are commonly used in construction machinery such as hydraulic excavators, and variable displacement mechanisms include swashplate type and swashplate type. Both achieve variable displacement by changing the displacement volume by changing the piston stroke.

[0018] As an example of a single-tilt variable displacement hydraulic pump, Figure 3 shows the structure of a variable displacement oblique-shaft hydraulic pump. The casing 1 of the hydraulic pump consists of a substantially cylindrical casing body 1A with a bearing portion at one end, and a head casing 1B that closes the other end of the casing body 1A. The rotating shaft 2 is rotatably mounted inside the casing body 1A. The cylinder block 3 is located inside the casing body 1A and rotates together with the rotating shaft 2.

[0019] Multiple cylinders 4 are drilled in the cylinder block 3 along its axial direction. A piston 5 is slidably installed inside each cylinder 4, and a connecting rod 6 is attached to each piston 5. A spherical portion 6A is formed at the tip of each connecting rod 6, and each spherical portion 6A is pivotably supported on a drive disk 7 formed at the tip of the rotating shaft 2. The cylinder block 3, together with the valve plate 8 described later, is arranged with respect to the rotating shaft 2 at an angle of inclination θ, and this angle of inclination θ determines the pump displacement capacity (pump tilt amount).

[0020] The valve plate 8 has one end face that slides against the cylinder block 3, and the other end face of the valve plate 8 slides against a concave, curved tilting sliding surface 9 formed in the head casing 1B. A through hole 8A is drilled in the center of the valve plate 8, and the ends of the center shaft 10 and the oscillating pin 15, which will be described later, are inserted into the through hole 8A from both sides, respectively. The valve plate 8 has a pair of supply and discharge ports (not shown) that intermittently communicate with each cylinder 4 when the cylinder block 3 rotates, and a pair of supply and discharge passages (not shown) that open to the tilting sliding surface 9 of the head casing 1B communicate with these supply and discharge ports regardless of the tilting position (tilting angle θ) of the valve plate 8.

[0021] The center shaft 10 supports the cylinder block 3 between the drive disk 7 and the valve plate 8. A spherical portion 10A is formed at one end of the center shaft 10, and the spherical portion 10A is pivotably supported at the axial center position of the drive disk 7. On the other hand, the other end of the center shaft 10, which protrudes through the center of the cylinder block 3, is slidably inserted into the through hole 8A of the valve plate 8, thereby centering the cylinder block 3 relative to the valve plate 8.

[0022] The tilting mechanism 11 tilts the valve plate 8 along the tilting sliding surface 9. The tilting mechanism 11 is formed within the head casing 1B and consists of a cylinder chamber 12 having oil passages 12A and 12B on both axial ends, a servo piston 14 slidably inserted into the cylinder chamber 12 and defining hydraulic chambers 13A and 13B within the cylinder chamber 12, and a pivoting pin 15 whose base end is fixed to the servo piston 14 and whose tip end is a spherical tip portion 15A that is pivotably inserted into the through hole 8A of the valve plate 8.

[0023] The control unit 16 controls the tilt of the valve plate 8 via the tilt mechanism 11. The control unit 16 is located on the outside of the head casing 1B and includes a throttle control valve (not shown) that provides feedback control of the amount of pressurized oil (pilot pressure) supplied and discharged from the pilot pump. A sleeve (not shown) is provided on this throttle control valve, and this sleeve and the servo piston 14 are integrally connected by a feedback pin 17 inserted through an elongated hole 1C in the head casing 1B.

[0024] When the throttle control valve of the control unit 16 is switched using an operating lever or the like, pressurized oil (pilot pressure) corresponding to the amount of switching operation is supplied from the pilot pump to the hydraulic chambers 13A and 13B of the tilting mechanism 11 via the oil passages 12A and 12B. The pressure difference between the hydraulic chambers 13A and 13B causes the servo piston 14 to slide and displace, and the servo piston 14 tilts the valve plate 8 and cylinder block 3 in the direction indicated by arrow A with a tilt angle θ via the swing pin 15. The sleeve of the throttle control valve then displaces in accordance with the displacement of the servo piston 14, thereby providing feedback control of the amount of pressurized oil from the pilot pump and maintaining the displacement of the servo piston 14 in a state corresponding to the amount of switching operation of the throttle control valve.

[0025] In an axial piston type variable displacement hydraulic pump with such a configuration, the discharge flow rate of the pump can be changed by increasing or decreasing the amount of piston displacement per revolution by changing the amount of inclination (tilt angle θ) of the oblique shaft or swash plate.

[0026] Next, we will explain the losses that occur in the hydraulic pump. As mentioned above, the main moving and sliding parts of the pump include the bearings, the sliding between each piston 5 and each cylinder 4, the sliding between the cylinder block 3 and the valve plate 8, and the sliding between the valve plate 8 and the head casing 1B. The oil discharged from the pump is transferred from the cylinder block 3 through the valve plate 8 to the discharge port (not shown). If lubrication failure occurs during the sliding of these parts, wear occurs, and the gap between the tilted sliding surfaces becomes larger. This gap is added, and the clearance between parts becomes larger than the specified amount under normal conditions, causing the pump's discharged oil to flow out (leak) into the low-pressure area through this gap. As a result, the pump's discharge flow rate decreases by the amount of leakage compared to the normal discharge flow rate. In addition, if the frictional force increases due to galling, wear, or poor lubrication in the above-mentioned sliding parts, the force acting in a direction that hinders the pump's operation increases, and the hydraulic force decreases accordingly.

[0027] Here, we will explain the power (work rate [J / s=W]) and efficiency of the hydraulic pump 21.

[0028] The rotational power Pwr_e input to the hydraulic pump 21 is expressed by the following formula.

[0029] Pwr_e=Te×Ne / 60×2π ···(1) Te[N·m]: Engine Torque Ne[rpm]: Engine speed The hydraulic power Pwe_p output from the hydraulic pump 21 is expressed by the following formula.

[0030] Pwr_p = P × Q / 60 × 1000 ... (2) P[MPa]: Discharge pressure of hydraulic pump 21 Q [L / min]: Discharge flow rate of hydraulic pump 21 The total efficiency η of the hydraulic pump 21 is expressed by the following formula.

[0031] η = Pwr_p / Pwr_e × 100 ... (3) Here, since power is expressed as the product of force and velocity, the total efficiency η can be expressed as follows.

[0032] η = ηm × ηv ···(4) ηm: Force conversion efficiency ηv: Speed ​​conversion efficiency The force conversion efficiency ηm represents the efficiency of force transmission (mechanical efficiency) from the input to the output of the hydraulic pump 21. In this embodiment, it means the efficiency of converting the rotational force of the engine 20 (prime mover) to the discharge pressure of the hydraulic fluid of the hydraulic pump 21. The speed conversion efficiency ηv represents the efficiency of speed transmission (volumetric efficiency) from the input to the output of the hydraulic pump 21. In this embodiment, it means the efficiency of converting the rotational speed of the engine 20 (prime mover) to the discharge flow rate of the hydraulic fluid of the hydraulic pump 21. In other words, if there is a decrease in output related to "force" from input to output, the force conversion efficiency ηm decreases, and if there is a decrease in output related to "speed", the speed conversion efficiency ηv decreases.

[0033] On the other hand, the force conversion efficiency ηm is expressed by the following formula.

[0034] ηm = Tp / Te ···(5) Tp [N·m]: Reaction torque from pressurized oil The reaction torque Tp can be calculated using the following formula.

[0035] Tp = ΔP × q / 2π × 1000 ... (6) ΔP [MPa]: Pump differential pressure (= pump pressure P - tank pressure (≒ 0)) q[cm 3 / rev]: Pump tilt amount Here, the characteristic quantities related to the force conversion efficiency ηm are the parameters necessary to calculate the force conversion efficiency ηm, and these include engine torque (rotational force of the prime mover) Te, pump tilt amount q, and pump pressure (discharge pressure of the hydraulic fluid) P.

[0036] Conventional technology enables diagnosis of a hydraulic pump based on its speed conversion efficiency ηv by measuring the leakage flow rate Qleak of the hydraulic pump as a feature quantity related to the speed conversion efficiency ηv. In contrast, this embodiment enables diagnosis of the hydraulic pump 21 based on its force conversion efficiency ηm by measuring the feature quantities Te,q,P related to the force conversion efficiency ηm.

[0037] Here, let's discuss the factors that cause a decrease in the force conversion efficiency ηm. The equation of motion for the rotational motion of the hydraulic pump 21 is as follows:

[0038] Jd 2 θ / dt 2 =Te-Tp-Tloss ···(7) J: Moment of inertia of hydraulic pump 21 around its rotation axis θ: Rotation angle of the rotating shaft of the hydraulic pump 21 Te: Engine Torque Tp: Reaction torque Tloss: Torque loss Operating operation with constant rotational angular velocity (d 2 θ / dt 2 When = 0, the left side of equation (7) becomes 0, so the lost torque Tloss can be expressed as follows.

[0039] Tloss = Te - Tp ... (8) By using equation (5) to eliminate the reaction torque Tp in equation (8), the lost torque Tloss can be expressed as follows.

[0040] Tloss = Te × (1 - ηm) ... (9) Lost torque (Tloss) varies depending on the sliding resistance force of the sliding parts inside the pump, the rolling resistance force of the rolling and rotating parts inside the pump, and the hydraulic agitation resistance force during pump operation. As is clear from equation (9), an increase in lost torque (Tloss) reduces the force conversion efficiency (ηm). Therefore, by monitoring the force conversion efficiency (ηm), it is possible to detect an increase in lost torque (Tloss).

[0041] Figure 4 is a functional block diagram of the controller 40 in the first embodiment. The controller 40 in this embodiment includes a measurement condition determination unit 41 and a feature quantity calculation unit 42. The controller 40 consists of an arithmetic processing unit such as a CPU, a storage device such as ROM and RAM, and an input / output interface for signal input and output to and from external devices, and realizes the functions of each part by executing a program stored in the storage device. Note that in Figure 4, only the functions related to the measurement of feature quantities Te, q, and P related to the force conversion efficiency ηm of the hydraulic pump 21 are shown, and functions related to the driving of hydraulic actuators 107 to 109 are omitted.

[0042] The measurement condition determination unit 41 receives a measurement command from the measurement instruction device 52 and determines whether the measurement conditions for the feature quantities Te, q, and P are met. If it determines that the measurement conditions are met, it instructs the feature quantity calculation unit 42 to calculate the feature quantities Te, q, and P. Here, the measurement instruction device 52 may be newly added to the machine, or it may utilize a timer provided in the machine or an external device that can communicate with the controller 40. In this embodiment, the measurement conditions are that the engine speed Ne is within the range of the target engine speed Nt ± tolerance, the pump tilt amount q is within the range of the target pump tilt amount qt ± tolerance, and the pump pressure P is within the range of the target pump pressure Pt ± tolerance. Therefore, by setting these tolerances to small values, it is possible to suppress variations in the measurement conditions.

[0043] The feature calculation unit 42 receives instructions from the measurement condition determination unit 41 and calculates representative values ​​of engine torque Te, pump tilt amount q, and pump pressure P as feature quantities Te, q, and P, respectively. The feature calculation unit 42 stores the calculated feature quantities Te, q, and P together with time information in the storage device 40c, outputs them to a monitor 50 or the like located in the driver's cab 110, and also notifies the vehicle manager, service department, etc. via wireless communication or the like.

[0044] Figure 5 is a flowchart showing the processing of the controller 40 in the first embodiment. Each step will be described in order below.

[0045] The controller 40 first determines whether or not a measurement command has been input (step S101).

[0046] If the result of step S101 is No, the flow is terminated.

[0047] If the result of step S101 is Yes, the engine speed Ne and pump tilt amount q are obtained, and the pump pressure P is measured (step S102).

[0048] Following step S102, it is determined whether or not the measurement conditions for the features Te, q, and P have been met (step S103).

[0049] If the result of step S103 is No, return to step S101.

[0050] If the result of step S103 is Yes, the engine torque Te and pump tilt amount q are obtained, and the pump pressure P is measured (step S104).

[0051] Following step S104, representative values ​​of engine torque Te, pump tilt amount q, and pump pressure P are calculated as feature quantities Te, q, and P (step S105). Possible methods for calculating representative values ​​include averaging the most recent multiple measurements and smoothing the measurements with a low-pass filter, but the calculation method is not limited to these.

[0052] Following step S105, the feature quantities Te, q, and P, along with time information, are stored in the memory device 40c, output to the monitor 50, etc., and notified to the vehicle manager, service department, etc. via wireless communication, etc. (step S106), and the flow ends.

[0053] (summary) In the first embodiment, a hydraulic pump state monitoring device monitors the state of a variable displacement hydraulic pump 21 that is driven by the rotation of a prime mover 20 and discharges hydraulic fluid at a capacity corresponding to the tilt amount q. The device includes a controller 40 that has a calculation function for acquiring information on the rotational force Te of the prime mover 20, the tilt amount q of the hydraulic pump 21, and the discharge pressure P of the hydraulic fluid, and for monitoring the state of the hydraulic pump 21. When the tilt amount q of the hydraulic pump 21 becomes a predetermined tilt amount qt and the discharge pressure P of the hydraulic pump 21 becomes a predetermined pressure Pt, the controller 40 measures characteristic quantities Te, q, and P related to the force conversion efficiency ηm, which is the conversion efficiency from the rotational force Te of the prime mover 20 to the discharge pressure P of the hydraulic fluid of the hydraulic pump 21 when the discharge pressure P becomes the predetermined pressure Pt.

[0054] In the first embodiment, a hydraulic drive device 200 is provided, comprising a prime mover 20, a tank 29 for storing hydraulic fluid, a variable displacement hydraulic pump 21 driven by the rotation of the prime mover 20 and sucking in and discharging hydraulic fluid from the tank 29 in a capacity corresponding to the tilt amount q, and a controller 40 that acquires information on the rotational force Te of the prime mover 20, the tilt amount q of the hydraulic pump 21 and the discharge pressure P of the hydraulic fluid, and controls the tilt amount q of the hydraulic pump 21. The device is further provided with a pressure sensor 27 for detecting the discharge pressure of the hydraulic pump 21. The controller 40 controls the tilt amount q of the hydraulic pump 21 to a predetermined tilt amount qt, and when the discharge pressure P of the hydraulic pump 21 detected by the pressure sensor 27 reaches a predetermined pressure Pt, it calculates feature quantities Te, q, and P related to the force conversion efficiency ηm, which is the conversion efficiency from the rotational force Te of the prime mover 20 to the discharge pressure P of the hydraulic fluid of the hydraulic pump 21.

[0055] According to the first embodiment configured as described above, when the operating state of the hydraulic pump 21 satisfies the desired measurement conditions, the feature quantities Te, q, and P related to the force conversion efficiency ηm are measured, making it possible to diagnose the hydraulic pump 21 based on the force conversion efficiency ηm. Note that the measurement conditions for the feature quantities Te, q, and P are not limited to one, but multiple conditions may be set. For example, the main operating operations of the hydraulic excavator 100 include high-power operation during excavation work (high engine speed Ne, high pump pressure P, high pump tilt q), medium-power operation such as leveling work (medium engine speed Ne, medium pump pressure P, medium pump tilt q), and low-power operation such as slow-speed work (medium engine speed Ne, low pump pressure P, low pump tilt q). By setting measurement conditions corresponding to these operating operations, it becomes possible to appropriately diagnose the hydraulic pump 21 mounted on the hydraulic excavator 100.

[0056] Furthermore, the feature quantities Te, q, and P in the first embodiment include the rotational force Te of the prime mover 20, the tilt amount q of the hydraulic pump, and the discharge pressure P of the hydraulic pump 21. By measuring the rotational force Te of the prime mover 20, the tilt amount q of the hydraulic pump 21, and the discharge pressure P of the hydraulic pump 21, it becomes possible to diagnose the hydraulic pump 21 based on the force conversion efficiency ηm.

[0057] In this embodiment, a configuration in which one hydraulic pump 21 is driven by one engine 20 has been described, but construction machinery is generally equipped with multiple hydraulic pumps. Figure 6 shows a schematic configuration of a hydraulic drive unit 200 equipped with two hydraulic pumps. In this configuration, one engine 20 drives two hydraulic pumps 21a and 21b. In this case, the hydraulic power Pwr_p output from the hydraulic pumps 21a and 21b is the sum of the hydraulic power output from each hydraulic pump, and can be calculated as follows.

[0058] Pwr_p = P × Q =P1×Q1+P2×Q2 =Ne × (P1 × q1 + P2 × q2) ... (10) P1: Discharge pressure of hydraulic pump 21a P2: Discharge pressure of hydraulic pump 21b Q1: Discharge flow rate of hydraulic pump 21a Q2: Discharge flow rate of hydraulic pump 21b q1: Tilt amount of hydraulic pump 21a q2: Tilt amount of hydraulic pump 21b Therefore, even in a hydraulic drive system equipped with multiple hydraulic pumps, it is possible to diagnose the hydraulic pumps based on the force conversion efficiency ηm, just as in a hydraulic drive system equipped with a single hydraulic pump.

[0059] Furthermore, in this embodiment, the hydraulic excavator 100 calculates the feature quantities Te, q, and P related to the force conversion efficiency ηm and outputs them together with time information to the monitor 50 in the operator's cab 110. However, the data may be transferred to an analysis server installed at another location using communication means such as satellite communication, and the analysis server may perform the diagnostic processing. Figure 7 shows an example of a configuration when the analysis server performs the diagnostic processing. In this example, the hydraulic pump 21 is judged to be abnormal when the feature quantities exceed a judgment threshold. By performing the diagnostic processing on the analysis server in this way, signs of malfunction related to the decrease in the force conversion efficiency of the hydraulic pump can be grasped even at a remote location. The judgment threshold can be easily changed on the analysis server, so the level of malfunction for diagnosis can be easily adjusted. For example, the analysis server can collect data not only from one machine but also from many machines of the same type, same class, etc., so the judgment threshold may be determined by relative value comparisons such as the degree of deviation or deviation from the population. In this case, the judgment threshold can be adjusted to an optimal value while operating the machine. [Examples]

[0060] A second embodiment of the present invention will be described, focusing on the differences from the above embodiment. In the first embodiment, the configuration was such that feature quantities Te, q, and P related to the force conversion efficiency ηm were measured when the operating state of the hydraulic pump 21 met predetermined measurement conditions. However, construction machinery such as a hydraulic excavator 100 performs various operations according to the operator's actions, and the operating state of the hydraulic pump 21 fluctuates accordingly, so it is almost impossible to expect the operating state of the hydraulic pump 21 to stably meet the measurement conditions. As a result, there is a risk that the measured values ​​of the feature quantities Te, q, and P will vary, and the reliability of the diagnosis of the hydraulic pump 21 based on the force conversion efficiency ηm may decrease. This embodiment realizes an operating state of the hydraulic pump 21 in which the measurement conditions of the feature quantities Te, q, and P are stably met.

[0061] Figure 8 is a schematic diagram of the hydraulic drive unit 200 in the second embodiment. The hydraulic drive unit 200 in this embodiment further includes a bleed-off valve 25 located in the pump discharge oil passage 28. The bleed-off valve 25 is configured to block the flow of hydraulic fluid discharged from the pump discharge oil passage 28 and returned to the tank 29 via the directional control valve unit 24, and is located upstream or downstream of a control spool (not shown) in the directional control valve unit 24. Figure 8 shows an example in which the bleed-off valve 25 is located upstream of the control spool. The bleed-off valve 25 opens and closes in response to a control signal from the controller 40, opening or closing the pump discharge oil passage 28. The bleed-off valve 25, together with the directional control valve unit 24 and the relief valve 26, is often configured as a single valve unit, sometimes referred to as a directional flow control valve.

[0062] The controller 40 receives measurement commands from the measurement instruction device 52, controls the opening area Ab of the bleed-off valve 25, the engine speed Ne, and the pump tilt amount q, and calculates characteristic quantities Te, q, and P related to the force conversion efficiency ηm of the hydraulic pump 21 based on the pump pressure P detected by the pressure sensor 27, stores them in the storage device 40c, outputs them to the monitor 50, and notifies vehicle managers, service departments, etc. via wireless communication.

[0063] Figure 9 is a functional block diagram of the controller 40 in the second embodiment. In addition to the configuration of the first embodiment (shown in Figure 4), the controller 40 includes a measurement control unit 43, an engine speed control unit 44, a pump tilt control unit 45, and a bleed-off valve control unit 46.

[0064] The measurement control unit 43 receives the measurement command and the lever neutral signal and outputs commands to the engine speed control unit 44, the pump tilt control unit 45, and the bleed-off valve control unit 46 to satisfy the measurement conditions for the feature quantities Te, q, and P. The measurement command may be generated by operating an input device such as a switch located in the driver's cab 110, or it may be generated automatically immediately after the engine 20 starts and the controller 40 is powered on. In that case, the power signal input from the power supply unit (not shown) of the controller 40 corresponds to the measurement command. The lever neutral signal is a signal that occurs when the hydraulic actuators 107 to 109 are not being operated and is generated in response to the input signal from the operating lever 51.

[0065] The engine speed control unit 44 receives a command from the measurement control unit 43 and outputs a control signal to match the engine speed Ne with the target engine speed Nt. The pump tilt control unit 45 receives a command from the measurement control unit 43 and outputs a control signal to match the pump tilt amount q with the target pump tilt amount qt. The bleed-off valve control unit 46 receives a command from the measurement control unit 43 and outputs a control signal to close the bleed-off valve 25. As a result, the engine speed Ne becomes constant at the target engine speed Nt, the pump tilt amount q becomes constant at the target pump tilt amount qt, and the pump pressure P becomes constant at the set pressure of the relief valve 26, so that the measurement conditions for the feature quantities Te, q, and P are stably met.

[0066] (summary) The hydraulic drive unit 200 in the second embodiment includes a bleed-off valve 25 that can adjust the flow rate of the hydraulic fluid discharged from the hydraulic pump 21 and returned to the tank 29, a relief valve 26 that regulates the discharge pressure P of the hydraulic pump 21, and a measurement instruction device 52 that instructs the controller 40 to calculate characteristic quantities Te, q, and P. The predetermined pressure Pt is the set pressure Pr of the relief valve 26, and when an instruction is received from the measurement instruction device 52, the controller 40 controls the rotational speed Ne of the prime mover 20 to a predetermined rotational speed Nt, controls the tilt amount q of the hydraulic pump 21 to a predetermined tilt amount qt, and closes the bleed-off valve 25.

[0067] According to the second embodiment configured as described above, the measurement conditions for the feature quantities Te, q, and P can be stably met, thereby improving the reliability of the diagnosis of the hydraulic pump 21 based on the force conversion efficiency ηm. [Examples]

[0068] A third embodiment of the present invention will be described, focusing on the differences from the above embodiments. In the first and second embodiments, by measuring the characteristic quantities Te, q, and P related to the force conversion efficiency ηm, it is possible to diagnose the hydraulic pump 21 based on the force conversion efficiency ηm, but diagnosis based on the speed conversion efficiency ηv is not possible. This embodiment enables diagnosis of the hydraulic pump 21 based on both the force conversion efficiency ηm and the speed conversion efficiency ηv. Note that the circuit configuration of the hydraulic drive device 200 in the third embodiment is the same as in the second embodiment (shown in Figure 8), so a description will be omitted.

[0069] Figure 10 is a functional block diagram of the controller 40 in the third embodiment. In addition to the configuration of the second embodiment (shown in Figure 9), the controller 40 in this embodiment includes a feature calculation unit 48 that calculates feature quantities related to the speed conversion efficiency ηv from the input to the output of the hydraulic pump 21.

[0070] The speed conversion efficiency ηv is expressed by the following formula.

[0071] ηv = Qout / Qin ... (11) Qout[L / min]: Pump discharge flow rate Qin [L / min]: Pump suction flow rate The pump suction flow rate Qin can be calculated using the following formula.

[0072] Qin = q × Ne / 1000 ... (12) q[cm 3 / rev]: Pump tilt amount Ne[rpm]: Engine speed The pump discharge flow rate Qout can be calculated using the following formula.

[0073] Qout=Qb=C×Ab×√(2×ΔPb / ρ) ···(13) Qb: Flow rate through bleed-off valve C: coefficient Ab: Bleed-off valve opening area ΔPb: Differential pressure across the bleed-off valve (= pump pressure P - tank pressure (≒ 0)) ρ: Hydraulic oil density The features related to the speed conversion efficiency ηv are the parameters necessary to calculate the speed conversion efficiency ηv, and these include the pump tilt amount q, engine speed Ne, pump pressure P, and bleed-off valve opening area Ab.

[0074] Here, the leakage flow rate Qleak can be expressed as follows:

[0075] Qleak = Qin - Qout ···(14) By using equation (11) to eliminate the pump discharge flow rate Qout in equation (14), the leakage flow rate Qleak can be expressed as follows.

[0076] Qleak = Qin × (1 - ηv) ... (15) As is clear from equation (15), the velocity conversion efficiency ηv decreases as the leakage flow rate Qleak increases. Therefore, by monitoring the velocity conversion efficiency ηv, it is possible to detect an increase in the leakage flow rate Qleak.

[0077] The measurement control unit 43 receives the measurement command and the lever neutral signal and outputs commands to the engine speed control unit 44, the pump tilt control unit 45, and the bleed-off valve control unit 46 to satisfy the measurement conditions for the feature quantities Te, q, and P, and also outputs a measurement command to the measurement condition determination unit 41. The functions of the feature quantity calculation unit 42, the engine speed control unit 44, the pump tilt control unit 45, and the bleed-off valve control unit 46 are the same as in the second embodiment (Figure 9), so their explanation is omitted.

[0078] The measurement condition determination unit 41 receives a measurement command from the measurement control unit 43 and determines whether the measurement conditions for the feature quantities Te, q, and P are met. If it determines that the measurement conditions are met, it instructs the feature quantity calculation unit 42 to calculate the feature quantities Te, q, and P, and also instructs the feature quantity calculation unit 48 to calculate the feature quantities q, Ne, P, and Ab.

[0079] The feature calculation unit 48 receives instructions from the measurement condition determination unit 41 and calculates representative values ​​of the pump tilt amount q, engine speed Ne, pump pressure P, and bleed-off valve opening area Ab as feature quantities q, Ne, P, and Ab. The feature calculation unit 48 stores the calculated feature quantities q, Ne, P, and Ab together with time information in the storage device 40c, outputs them to a monitor 50 or the like located in the driver's cab 110, and also notifies the vehicle manager, service department, etc. via wireless communication or the like.

[0080] Figure 11 is a flowchart showing the processing of the controller 40 in the third embodiment. Note that in Figure 11, only the measurement process of the feature quantities q, Ne, P, and Ab related to the velocity conversion efficiency ηv is shown, and the measurement process of the feature quantities Te, q, and P related to the velocity conversion efficiency ηv is omitted. Each step will be explained in order below.

[0081] The controller 40 first determines whether the operating lever 51 is in the neutral (non-operated) position (step S301).

[0082] If the result of step S301 is No, the flow is terminated.

[0083] If the result of step S301 is Yes, the engine speed Ne and the pump tilt amount q are adjusted so that the suction flow rate Qin of the hydraulic pump 21a becomes the specified flow rate (step S302).

[0084] Following step S302, the pump pressure P is measured (step S303).

[0085] Following step S303, it is determined whether the pump pressure P is equal to the target pump pressure Pt (step S304).

[0086] If the result of step S304 is No, the bleed-off valve opening area Ab is adjusted (step S305), and the process returns to step S303. Specifically in step S305, if the pump pressure P is lower than the target pump pressure Pt, the bleed-off valve opening area Ab is reduced, and if the pump pressure P is higher than the target pump pressure Pt, the bleed-off valve opening area Ab is increased.

[0087] If the result of step S304 is Yes, the bleed-off valve opening area Ab, pump tilt amount q, and engine speed Ne are obtained, and the pump pressure P is measured (step S306).

[0088] Following step S306, it is determined whether the number of executions of step S304 has reached a predetermined number (step S307). If the result of the determination in step S307 is No, the process returns to step S303. This determination is made to ensure that there is enough data to perform moving average processing, filtering, etc., later on, taking into account that there may be variations in the data acquired or measured in step S306. The predetermined number of executions is set according to the processing content and the data acquisition rate.

[0089] If the result of step S307 is Yes, the acquired values ​​of the bleed-off valve opening area Ab, pump tilt amount q, and engine speed Ne for a specified number of times, as well as the measured value of the pump pressure P, are averaged and calculated as a feature quantity (step S308).

[0090] Following step S308, the feature quantities q, Ne, P, and Ab are stored in the memory device 40c along with time information, output to the monitor 50, etc., and notified to the vehicle manager, service department, etc. via wireless communication, etc. (step S309).

[0091] Following step S309, the bleed-off valve opening area Ab, pump tilt amount q, and engine speed Ne are returned to their state before the start of the flow (step S310), and the flow is terminated.

[0092] (summary) In the third embodiment, the controller 40 includes a bleed-off valve 25 that can adjust the flow rate of the hydraulic fluid discharged from the hydraulic pump 21 and returned to the tank 29, and a measurement instruction device 52 that instructs the controller 40 to calculate characteristic quantities Te, q, and P. When an instruction is received from the measurement instruction device 52, the controller 40 controls the rotational speed Ne of the prime mover 20 to a predetermined rotational speed Nt, controls the tilt amount q of the hydraulic pump 21 to a predetermined tilt amount qt, and adjusts the opening area Ab of the bleed-off valve 25 so that the discharge pressure P of the hydraulic pump 21 detected by the pressure sensor 27 matches a predetermined pressure Pt.

[0093] According to the third embodiment configured as described above, the measurement conditions for the feature quantities Te, q, and P can be stably met, similar to the second embodiment, thereby improving the reliability of the diagnosis of the hydraulic pump 21 based on the force conversion efficiency ηm.

[0094] Furthermore, in the third embodiment, the controller 40 controls the rotational speed Ne of the prime mover 20 to a predetermined rotational speed Nt, controls the tilt amount q of the hydraulic pump 21 to a predetermined tilt amount qt, and adjusts the opening area Ab of the bleed-off valve 25 so that the discharge pressure P of the hydraulic pump 21 detected by the pressure sensor 27 matches a predetermined pressure Pt. In this state, it calculates feature quantities Te, q, and P related to the force conversion efficiency ηm, and also calculates feature quantities q, Ne, P, and Ab related to the speed conversion efficiency ηv, which is the conversion efficiency from the rotational speed Ne of the prime mover 20 to the discharge flow rate Qout of the hydraulic fluid of the hydraulic pump 21. This makes it possible to diagnose the hydraulic pump 21 based on the speed conversion efficiency ηv.

[0095] Furthermore, the characteristic quantities q, Ne, P, and Ab related to the speed conversion efficiency ηv in the third embodiment include the tilt amount q of the hydraulic pump 21, the rotational speed Ne of the prime mover 20, the discharge pressure P of the hydraulic pump 21, and the opening area Ab of the bleed-off valve 25. As a result, by measuring the tilt amount q of the hydraulic pump 21, the rotational speed Ne of the prime mover 20, the discharge pressure P of the hydraulic pump 21, and the opening area Ab of the bleed-off valve 25, it becomes possible to diagnose the hydraulic pump 21 based on the speed conversion efficiency ηv. [Examples]

[0096] A fourth embodiment of the present invention will be described, focusing on the differences from the above embodiments. In the first or second embodiment, diagnosis of the hydraulic pump 21 based on the force conversion efficiency ηm is possible, and in the third embodiment, diagnosis of the hydraulic pump 21 based on the force conversion efficiency ηm and the speed conversion efficiency ηv is possible. However, in machinery that operates outdoors in various regions, such as construction machinery, the characteristic quantities related to the force conversion efficiency ηm and the speed conversion efficiency ηv fluctuate due to the influence of the external environment, so it may not be possible to correctly evaluate the force conversion efficiency ηm and the speed conversion efficiency ηv. For example, in a hydraulic excavator, it is generally known that the viscosity of the hydraulic fluid changes with temperature. When the oil temperature decreases, the viscosity of the hydraulic fluid increases, the lost torque consumed to agitate the hydraulic fluid inside the pump increases, the force required to push the hydraulic fluid to the outside of the pump increases, and the leakage flow rate inside the pump increases. Therefore, it is assumed that the force conversion efficiency ηm and the speed conversion efficiency ηv will fluctuate depending on the operating temperature of the hydraulic excavator 100. This embodiment maintains the reliability of the diagnosis of the hydraulic pump 21 based on the force conversion efficiency ηm and speed conversion efficiency ηv by suppressing fluctuations in the force conversion efficiency ηm and speed conversion efficiency ηv due to changes in the temperature of the hydraulic fluid.

[0097] Figure 12 is a schematic diagram of the hydraulic drive unit 200 in the fourth embodiment. The hydraulic drive unit 200 in this embodiment further includes a temperature sensor 30 capable of detecting the temperature of the hydraulic fluid during operation. The output value of the temperature sensor 30 is input to the controller 40. The controller 40 is configured to avoid evaluating the feature quantities in temperature ranges where malfunctions of the hydraulic pump 21 are expected, by understanding the temperature of the hydraulic fluid when measuring the feature quantities described in the first to third embodiments.

[0098] Generally, the operating oil temperature range for the hydraulic excavator 100 during normal operation is 30°C to 70°C. Therefore, in this embodiment, the controller 40 measures feature quantities when the oil temperature detected by the temperature sensor 30 is within this range, but does not measure feature quantities when it is outside this range. As a result, feature quantities related to the force conversion efficiency ηm and speed conversion efficiency ηv are measured only when the oil temperature is within the normal range, making it possible to suppress fluctuations in the force conversion efficiency ηm and speed conversion efficiency ηv due to changes in oil temperature.

[0099] (summary) In the fourth embodiment, the hydraulic drive unit 200 is equipped with a temperature sensor 30 that detects the temperature of the hydraulic fluid circulating in the hydraulic pump 21. The controller 40 stops calculating the feature quantities Te,q,P related to the force conversion efficiency ηm and the feature quantities q,Ne,P,Ab related to the speed conversion efficiency ηv when the temperature of the hydraulic fluid detected by the temperature sensor 30 falls outside a predetermined temperature range.

[0100] According to the fourth embodiment configured as described above, the feature quantities Te,q,P related to the force conversion efficiency ηm and the feature quantities q,Ne,P,Ab related to the speed conversion efficiency ηv are measured only when the temperature of the hydraulic fluid is within a predetermined temperature range. Therefore, it is possible to suppress fluctuations in the force conversion efficiency ηm or the speed conversion efficiency ηv due to changes in the temperature of the hydraulic fluid.

[0101] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to add parts of the configuration of one embodiment to the configuration of another embodiment, and it is also possible to delete parts of the configuration of one embodiment or replace parts of parts of another embodiment. [Explanation of Symbols]

[0102] 1…Casing, 1A…Casing body, 1B…Head casing, 1C…Slotted hole, 2…Rotating shaft, 3…Cylinder block, 4…Cylinder, 5…Piston, 6…Connecting rod, 6A…Spherical part, 7…Drive disk, 8…Valve plate, 8A…Through hole, 9…Tilting sliding surface, 10…Center shaft, 10A…Spherical part, 11…Tilting mechanism, 12…Cylinder chamber, 12A…Oil passage hole, 12B…Oil passage hole, 13A…Hydraulic chamber, 13B…Hydraulic chamber, 14…Servo piston, 15…Oscillation pin, 15A…Spherical tip, 16…Control unit, 17…Feedback pin, 20…Engine (prime mover), 20…Engine, 21,21a,21b…Hydraulic pump, 22…Solenoid proportional valve, 24…Directional control valve unit, 25…Bleed-off valve, 26…Relief valve 27...Pressure sensor, 28...Pump discharge oil passage, 29...Tank, 30...Temperature sensor, 40...Controller, 40a...Input interface, 40b...Calculation unit, 40c...Storage device, 40d...Output interface, 41...Measurement condition determination unit, 42...Feature calculation unit, 43...Measurement control unit, 44...Engine speed control unit, 45...Pump tilt control unit, 46...Bleed-off valve control unit, 48...Feature calculation unit, 50...Monitor, 51...Operating lever, 52...Measurement instruction device, 100...Hydraulic excavator, 101...Traveling body, 102...Slewing body, 103...Working device, 104...Boom, 105...Arm, 106...Bucket, 107...Boom cylinder, 108...Arm cylinder, 109...Bucket cylinder, 110...Operator's cab, 200...Hydraulic drive unit.

Claims

1. A prime mover, A tank for storing hydraulic fluid, A variable displacement hydraulic pump, driven by the rotation of the aforementioned prime mover, sucks in and discharges hydraulic fluid from the tank in a capacity corresponding to the amount of tilt, A hydraulic drive system comprising a controller that acquires information regarding the rotational force of the prime mover, the tilt amount of the hydraulic pump, and the discharge pressure of the hydraulic fluid, and controls the tilt amount of the hydraulic pump, The hydraulic pump is equipped with a pressure sensor for detecting the discharge pressure, The controller is configured to control the tilt amount of the hydraulic pump to a predetermined tilt amount, and when the discharge pressure of the hydraulic pump detected by the pressure sensor reaches a predetermined pressure, it calculates a characteristic quantity related to the force conversion efficiency, which is the conversion efficiency from the rotational force of the prime mover to the discharge pressure of the hydraulic fluid of the hydraulic pump. The hydraulic drive device is A bleed-off valve capable of adjusting the flow rate of the hydraulic fluid that is discharged from the hydraulic pump and then returned to the tank, A relief valve that regulates the discharge pressure of the hydraulic pump, The system includes a measurement instruction device that instructs the controller to calculate the aforementioned feature quantities, The predetermined pressure is the set pressure of the relief valve. When the controller receives an instruction from the measurement instruction device, it controls the rotational speed of the prime mover to a predetermined rotational speed, controls the tilt amount of the hydraulic pump to the predetermined tilt amount, and closes the bleed-off valve. A hydraulic drive device characterized by the following features.

2. A prime mover, A tank for storing hydraulic fluid, A variable displacement hydraulic pump, driven by the rotation of the aforementioned prime mover, sucks in and discharges hydraulic fluid from the tank in a capacity corresponding to the amount of tilt, A hydraulic drive system comprising a controller that acquires information regarding the rotational force of the prime mover, the tilt amount of the hydraulic pump, and the discharge pressure of the hydraulic fluid, and controls the tilt amount of the hydraulic pump, The hydraulic pump is equipped with a pressure sensor for detecting the discharge pressure, The controller is configured to control the tilt amount of the hydraulic pump to a predetermined tilt amount, and when the discharge pressure of the hydraulic pump detected by the pressure sensor reaches a predetermined pressure, it calculates a characteristic quantity related to the force conversion efficiency, which is the conversion efficiency from the rotational force of the prime mover to the discharge pressure of the hydraulic fluid of the hydraulic pump. The hydraulic drive device is A bleed-off valve capable of adjusting the flow rate of the hydraulic fluid that is discharged from the hydraulic pump and then returned to the tank, The system includes a measurement instruction device that instructs the controller to calculate the aforementioned feature quantities, When the controller receives an instruction from the measurement instruction device, it controls the rotational speed of the prime mover to a predetermined rotational speed, controls the tilt amount of the hydraulic pump to the predetermined tilt amount, and adjusts the opening area of ​​the bleed-off valve so that the discharge pressure of the hydraulic pump detected by the pressure sensor matches the predetermined pressure. A hydraulic drive device characterized by the following features.

3. In the hydraulic drive device according to claim 2, The controller controls the rotational speed of the prime mover to the predetermined rotational speed, controls the tilt amount of the hydraulic pump to the predetermined tilt amount, and adjusts the opening area of ​​the bleed-off valve so that the discharge pressure of the hydraulic pump detected by the pressure sensor matches the predetermined pressure, and calculates the feature quantities related to the force conversion efficiency, as well as the feature quantities related to the speed conversion efficiency, which is the conversion efficiency from input to output of the hydraulic pump. A hydraulic drive device characterized by the following features.

4. In the hydraulic drive device according to claim 3, The characteristic quantities related to the speed conversion efficiency include the tilt amount of the hydraulic pump, the rotational speed of the prime mover, the discharge pressure of the hydraulic pump, and the opening area of ​​the bleed-off valve. A hydraulic drive device characterized by the following features.

5. In the hydraulic drive device according to claim 1 or 2, The hydraulic pump is equipped with a temperature sensor for detecting the temperature of the hydraulic fluid circulating through it. The controller stops calculating the feature quantity when the temperature of the hydraulic fluid detected by the temperature sensor falls outside a predetermined temperature range. A hydraulic drive device characterized by the following features.

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