Abnormality diagnosis system and abnormality diagnosis method

Abstract

An abnormality diagnosis system according to one embodiment of the present invention is an abnormality diagnosis system for a variable capacity hydraulic pump (31 or 35) mounted on a construction machine, and is provided with: a pressure gauge (71 or 72) for detecting the suction pressure, discharge pressure, or discharge pressure of the hydraulic pump (31 or 35); and a control device (6). The control device (6) determines the presence or absence of an abnormality in the hydraulic pump (31 or 35) on the basis of the pressure detected by the pressure gauge (71 or 72) in a state in which the construction machine is operated under predetermined diagnostic conditions. The prescribed diagnostic condition is that the rotational speed and load of the hydraulic pump (31 or 35) are kept constant and the capacity of the hydraulic pump (31 or 35) is kept at a prescribed value greater than the minimum value.

Description

Technical Field

[0001] The present disclosure relates to an abnormality diagnosis system and an abnormality diagnosis method for a hydraulic pump mounted on construction machinery. Background Art

[0002] Hydraulic excavators and other construction machinery are equipped with hydraulic equipment such as hydraulic pumps and hydraulic actuators. Hydraulic pumps are generally variable displacement pumps.

[0003] For example, Patent Document 1 discloses an abnormality detection device that detects the discharge pressure of a hydraulic pump, which is an axial piston pump, and detects abnormality of the hydraulic pump based on the detected discharge pressure.

[0004] Prior art literature: Patent Literature: Patent Document 1: Japanese Patent Application Laid-Open No. 2013-170509. Summary of the Invention

[0005] Problems to be solved by the invention: However, in order to accurately determine whether or not there is an abnormality in the hydraulic pump based on the discharge pressure or other pressure related to the hydraulic pump, it is important to detect the pressure under what circumstances. However, Patent Document 1 does not describe this point.

[0006] Therefore, an object of the present disclosure is to provide an abnormality diagnosis system and an abnormality diagnosis method that can accurately determine whether a hydraulic pump has an abnormality.

[0007] Means of solving the problem: The present disclosure provides, from one aspect, an abnormality diagnosis system for a variable capacity hydraulic pump mounted on engineering machinery, comprising: a pressure gauge for detecting the suction pressure, discharge pressure, or discharge pressure of the hydraulic pump; and a control device for determining whether the hydraulic pump has an abnormality based on the pressure detected by the pressure gauge when the engineering machinery is operating under prescribed diagnostic conditions, wherein the prescribed diagnostic conditions are that the rotational speed and load of the hydraulic pump remain constant and the capacity of the hydraulic pump remains at a prescribed value greater than a minimum value.

[0008] From another aspect, the present disclosure provides an abnormality diagnosis method for a variable capacity hydraulic pump mounted on engineering machinery, wherein the suction pressure, discharge pressure or discharge pressure of the hydraulic pump is detected while the engineering machinery is operating under prescribed diagnostic conditions, and whether the hydraulic pump has an abnormality is determined based on the detected pressures, wherein the prescribed diagnostic conditions are that the rotational speed and load of the hydraulic pump remain constant and the capacity of the hydraulic pump remains at a prescribed value greater than a minimum value.

[0009] Effects of the invention: According to the present disclosure, an abnormality diagnosis system and an abnormality diagnosis method are provided that can determine the presence or absence of an abnormality in a hydraulic pump with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic structural diagram of an abnormality diagnosis system and a hydraulic system including a hydraulic pump according to an embodiment; Figure 2 This is a diagram showing a state in which the left crawler track of the hydraulic excavator is raised. DETAILED DESCRIPTION

[0011] Figure 1 , a hydraulic system including at least one hydraulic pump and an abnormality diagnosis system 1 according to an embodiment of the hydraulic pump are shown. Figure 2 1 shows a hydraulic excavator 10 equipped with the hydraulic system. The abnormality diagnosis system 1 can also be applied to a hydraulic pump installed in a construction machine other than the hydraulic excavator 10, such as a wheel loader.

[0012] like Figure 2 As shown, the hydraulic excavator 10 includes a traveling body 11 and a revolving body 14 rotatably supported by the traveling body 11. The traveling body 11 includes a pair of crawler tracks, a left crawler track 12 and a right crawler track 13. Furthermore, the hydraulic excavator 10 includes a boom 15 that pitches relative to the revolving body 14; an arm 16 swingably connected to the tip of the boom 15; and a bucket 17 swingably connected to the tip of the arm 16.

[0013] The oil pressure system, such as Figure 1 As shown, the hydraulic actuators include a left travel motor 21, a right travel motor 22, a boom cylinder 23, an arm cylinder 24, a bucket cylinder 25, and a swing motor 26. The left travel motor 21 and the right travel motor 22 drive the left crawler track 12 and the right crawler track 13, respectively. The boom cylinder 23 pitches the boom 15. The arm cylinder 24 and the bucket cylinder 25 swing the arm 16 and the bucket 17, respectively. The swing motor 26 rotates the rotating structure 14.

[0014] In this embodiment, the hydraulic system includes two hydraulic pumps, namely, a first hydraulic pump 31 and a second hydraulic pump 35. The first hydraulic pump 31 supplies hydraulic oil to the left travel motor 21, the arm cylinder 24, and the swing motor 26, while the second hydraulic pump 35 supplies hydraulic oil to the right travel motor 22, the boom cylinder 23, and the bucket cylinder 25. However, the number of hydraulic pumps mounted on the hydraulic excavator 10 may be one or three or more.

[0015] More specifically, the first hydraulic pump 31 is connected to the tank via a suction line 33 and is connected to a left travel control valve 42, an arm control valve 43, and a swing control valve 44 via a supply line 41. The left travel control valve 42, the arm control valve 43, and the swing control valve 44 are each connected to the left travel motor 21, the arm cylinder 24, and the swing motor 26 via a pair of supply and discharge lines.

[0016] The left travel control valve 42 changes the rotational direction and speed of the left travel motor 21 according to the operation direction and amount of the left travel operating device 81, described later. The arm control valve 43 changes the operation direction and speed of the arm cylinder 24 according to the operation direction and amount of the arm operating device 84, described later. The swing control valve 44 changes the rotational direction and speed of the swing motor 26 according to the operation direction and amount of the swing operating device 86, described later.

[0017] In this embodiment, a center bypass line 45 branches from the supply line 41, and the center bypass line 45 extends to the tank through the left travel control valve 42, the arm control valve 43, and the swing control valve 44. However, instead of the center bypass line 45, an unloading line provided with an unloading valve connecting the supply line 41 and the tank may be used.

[0018] Similarly, the second hydraulic pump 35 is connected to the tank via a suction line 37 and is connected to a right travel control valve 52, a boom control valve 53, and a bucket control valve 54 via a supply line 51. The right travel control valve 52, the boom control valve 53, and the bucket control valve 54 are connected to the right travel motor 22, the boom cylinder 23, and the bucket cylinder 25, respectively, via a pair of supply and discharge lines.

[0019] The right travel control valve 52 changes the rotational direction and speed of the right travel motor 22 according to the operation direction and amount of the right travel operating device 82, described later. The boom control valve 53 changes the movement direction and speed of the boom cylinder 23 according to the operation direction and amount of the boom operating device 83, described later. The bucket control valve 54 changes the movement direction and speed of the bucket cylinder 25 according to the operation direction and amount of the bucket operating device 85, described later.

[0020] In this embodiment, a center bypass line 55 branches from the supply line 51, and the center bypass line 55 extends to the tank through the right travel control valve 52, the boom control valve 53, and the bucket control valve 54. However, instead of the center bypass line 55, an unloading line having an unloading valve connected to the supply line 51 and the tank may be used.

[0021] In this embodiment, the first hydraulic pump 31 and the second hydraulic pump 35 are driven by the engine 30. The engine 30 drives the first hydraulic pump 31 and the second hydraulic pump 35 at a constant rotation speed. However, the first hydraulic pump 31 and the second hydraulic pump 35 may also be driven by an electric motor.

[0022] The first and second hydraulic pumps 31, 35 are each variable displacement pumps. In this embodiment, the first and second hydraulic pumps 31, 35 are each axial piston pumps with variable tilt angles, such as a swash plate pump or a bent axis pump. However, the first and second hydraulic pumps 31, 35 may also be other types of pumps, such as vane pumps.

[0023] The capacity of the first hydraulic pump 31 is varied by a regulator 32, while the capacity of the second hydraulic pump 35 is varied by a regulator 36. In this embodiment, regulators 32 and 36 are controlled by the control device 6. For example, if the first hydraulic pump 31 is a swash plate pump, the regulator 32 may be a regulator that electrically varies the oil pressure acting on the servo piston connected to the swash plate of the first hydraulic pump 31, or it may be an electric actuator connected to the swash plate of the first hydraulic pump 31. Similarly, if the second hydraulic pump 35 is a swash plate pump, the regulator 36 may be a regulator that electrically varies the oil pressure acting on the servo piston connected to the swash plate of the second hydraulic pump 35, or it may be an electric actuator connected to the swash plate of the second hydraulic pump 35.

[0024] However, the regulators 32 and 36 do not necessarily need to be controlled by the control device 6 and may be operated by the pressure of the hydraulic oil. For example, the regulators 32 and 36 may be of a negative control type or a load sensing type.

[0025] Regarding the control device 6, the functions of the elements disclosed in this specification can be performed using a circuit or processing circuit that includes a general-purpose processor, a dedicated processor, an integrated circuit, an ASIC (Application Specific Integrated Circuits), an existing circuit and / or a combination thereof that is constructed or programmed to perform the disclosed functions. The processor is considered to be a processing circuit or circuit because it includes transistors or other circuits. In the present disclosure, a circuit, unit or means is hardware that performs the listed functions, or hardware that is programmed to perform the listed functions. The hardware can be the hardware disclosed in this specification, or other known hardware that is programmed or constructed to perform the listed functions. When the hardware is considered to be a processor that is a type of circuit, the circuit, means or unit is a combination of hardware and software, and the software is used in the construction of the hardware and / or processor.

[0026] The swing body 14 of the hydraulic excavator 10 includes a cab, and a left travel operating device 81 , a right travel operating device 82 , a boom operating device 83 , an arm operating device 84 , a bucket operating device 85 , and a swing operating device 86 are arranged in the cab.

[0027] The left travel operating device 81 and the right travel operating device 82 each have a pedal that outputs an operating signal corresponding to the amount of pedal operation. The boom operating device 83, the arm operating device 84, the bucket operating device 85, and the rotation operating device 86 each have a handle that outputs an operating signal corresponding to the amount of handle operation. Alternatively, the boom operating device 83 and the bucket operating device 85 may be integrated so as to share a common handle, and the arm operating device 84 and the rotation operating device 86 may be integrated so as to share a common handle.

[0028] In this embodiment, the left travel operating device 81, the right travel operating device 82, the boom operating device 83, the arm operating device 84, the bucket operating device 85, and the rotation operating device 86 output electrical signals as operating signals, and the output operating signals are input to the control device 6. However, the left travel operating device 81, the right travel operating device 82, the boom operating device 83, the arm operating device 84, the bucket operating device 85, and the rotation operating device 86 can also output pilot pressures to corresponding control valves as operating signals. In this case, the pilot pressures output to the control valves are detected by pressure gauges and input to the control device 6.

[0029] When the left travel control device 81, the right travel control device 82, the boom control device 83, the arm control device 84, the bucket control device 85, and the rotation control device 86 are not operated, the control device 6 controls the regulators 32 and 36 so that the capacities of the first hydraulic pump 31 and the second hydraulic pump 35 are at their minimum values. In this embodiment, the minimum capacity of the first hydraulic pump 31 and the second hydraulic pump 35 is 0%, and the maximum capacity is 100%. Furthermore, when the capacity of the first hydraulic pump 31 and the second hydraulic pump 35 is 0%, the discharge flow rate of the first hydraulic pump 31 and the second hydraulic pump 35 is greater than zero.

[0030] On the other hand, when any one of the left travel operating device 81, the arm operating device 84, and the rotation operating device 86 is operated, the control device 6 increases the capacity of the first hydraulic pump 31 as the amount of operation of the operating device increases. Furthermore, when any one of the right travel operating device 82, the boom operating device 83, and the bucket operating device 85 is operated, the control device 6 increases the capacity of the second hydraulic pump 35 as the amount of operation of the operating device increases.

[0031] The pressure of the first hydraulic pump 31 is detected by a pressure gauge 71 and input to the control device 6 . Similarly, the pressure of the second hydraulic pump 35 is detected by a pressure gauge 72 and input to the control device 6 .

[0032] In this embodiment, a pressure gauge 71 is provided on the discharge line 34 of the first hydraulic pump 31 to detect the discharge pressure of the first hydraulic pump 31. A pressure gauge 72 is provided on the discharge line 38 of the second hydraulic pump 35 to detect the discharge pressure of the second hydraulic pump 35. The pressure gauge 71 can be mounted on the housing of the first hydraulic pump 31 or on the discharge pipe connecting the first hydraulic pump 31 to the tank. Similarly, the pressure gauge 72 can be mounted on the housing of the second hydraulic pump 35 or on the discharge pipe connecting the second hydraulic pump 35 to the tank.

[0033] However, the pressure gauge 71 may be provided in the suction line 33 to detect the suction pressure of the first hydraulic pump 31, or in the supply line 41 to detect the discharge pressure of the first hydraulic pump 31. Similarly, the pressure gauge 72 may be provided in the suction line 37 to detect the suction pressure of the second hydraulic pump 35, or in the supply line 51 to detect the discharge pressure of the second hydraulic pump 35.

[0034] The discharge pressure of the first hydraulic pump 31 is detected by the pressure gauge 71 while the hydraulic excavator 10 is operating under predetermined diagnostic conditions for the first hydraulic pump 31. The predetermined diagnostic conditions for the first hydraulic pump 31 are that the rotational speed and load of the first hydraulic pump 31 remain constant, and that the capacity of the first hydraulic pump 31 is maintained at a predetermined value α greater than a minimum value. In this embodiment, the predetermined value α is between 50% and 100%. However, the predetermined value α may alternatively be between 70% and 100%.

[0035] In this embodiment, the state of the hydraulic excavator 10 is operated under the prescribed diagnostic conditions regarding the first hydraulic pump 31, such as Figure 2 The figure shows the hydraulic excavator 10 in a state where the left crawler track 12 is suspended and driven. Specifically, the operator rotates the rotating body 14 counterclockwise relative to the traveling body 11, and in this state, presses the bucket 17 against the ground. The pedal of the left travel control device 81 can be depressed in either the forward or reverse direction. Furthermore, the pedal can be depressed to the maximum amount or a certain amount less than the maximum amount.

[0036] In this manner, while the left crawler track 12 is being driven in mid-air, the pressure gauge 71 detects the discharge pressure of the first hydraulic pump 31. The control device 6 determines whether the first hydraulic pump 31 has any abnormality based on the detected discharge pressure. For example, the control device 6 can determine whether the first hydraulic pump 31 has any abnormality by comparing the waveform of the detected discharge pressure with a normal waveform, or by comparing the discharge pressure at a specific moment within the detected discharge pressure with a threshold value. Alternatively, the control device 6 can determine whether the first hydraulic pump 31 has any abnormality by performing frequency analysis on the detected discharge pressure.

[0037] It is desirable that the control device 6 determine whether the first hydraulic pump 31 has an abnormality after confirming that the discharge pressure of the first hydraulic pump 31 is maintained at a predetermined value β. For example, the predetermined value β is 1 MPa to 20 MPa. Alternatively, the predetermined value β may be 1 MPa to 10 MPa.

[0038] The discharge pressure of the second hydraulic pump 35 is detected by the pressure gauge 72 while the hydraulic excavator 10 is operating under predetermined diagnostic conditions for the second hydraulic pump 35. The predetermined diagnostic conditions for the second hydraulic pump 35 are that the rotational speed and load of the second hydraulic pump 35 remain constant, and that the capacity of the second hydraulic pump 35 is maintained at a predetermined value γ greater than a minimum value. In this embodiment, the predetermined value γ is greater than 50% and less than 100%. However, the predetermined value γ may alternatively be greater than 70% and less than 100%.

[0039] In this embodiment, the hydraulic excavator 10 is operated in a state where the predetermined diagnostic conditions for the second hydraulic pump 35 are satisfied. Figure 2 Conversely, the right crawler track 13 of the hydraulic excavator 10 is in a floating, driven state. Specifically, the operator rotates the revolving body 14 clockwise relative to the traveling body 11, and in this state, presses the bucket 17 against the ground. The pedal of the right travel operating device 82 can be depressed in either the forward or reverse direction. Furthermore, the pedal can be depressed to the maximum amount or a certain amount less than the maximum amount.

[0040] In this manner, while the right track 13 is being driven in mid-air, the pressure gauge 72 detects the discharge pressure of the second hydraulic pump 35. The control device 6 determines whether the second hydraulic pump 35 has any abnormality based on the detected discharge pressure. For example, the control device 6 can determine whether the second hydraulic pump 35 has any abnormality by comparing the waveform of the detected discharge pressure with a normal waveform. Alternatively, the control device 6 can determine whether the second hydraulic pump 35 has any abnormality by comparing the discharge pressure at a specific moment within the detected discharge pressure with a threshold value. Alternatively, the control device 6 can determine whether the second hydraulic pump 35 has any abnormality by performing frequency analysis on the detected discharge pressure.

[0041] It is desirable that the control device 6 determine whether the second hydraulic pump 35 has an abnormality after confirming that the discharge pressure of the second hydraulic pump 35 is maintained at a predetermined value ε. For example, the predetermined value ε is 1 MPa to 20 MPa. Alternatively, the predetermined value ε may be 1 MPa to 10 MPa.

[0042] As described above, in this embodiment, the discharge pressure of the first hydraulic pump 31 is detected while the hydraulic excavator 10 is operating under predetermined diagnostic conditions for the first hydraulic pump 31. Therefore, the presence of an abnormality in the first hydraulic pump 31 can be determined with high accuracy. Furthermore, the discharge pressure of the second hydraulic pump 35 is detected while the hydraulic excavator 10 is operating under predetermined diagnostic conditions for the second hydraulic pump 35. Therefore, the presence of an abnormality in the second hydraulic pump 35 can be determined with high accuracy.

[0043] Furthermore, in this embodiment, the discharge pressure of the first hydraulic pump 31 is detected while the left crawler 12 of the hydraulic excavator 10 is being driven in a floating manner, and the discharge pressure of the second hydraulic pump 35 is detected while the right crawler 13 of the hydraulic excavator 10 is being driven in a floating manner. Therefore, the predetermined diagnostic conditions for the first hydraulic pump 31 and the predetermined diagnostic conditions for the second hydraulic pump 35 can be easily achieved in the hydraulic excavator 10.

[0044] <Modification> The present disclosure is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present disclosure.

[0045] The hydraulic excavator 10 does not necessarily need to be operated with the left crawler 12 of the hydraulic excavator 10 lifted and driven under the prescribed diagnostic conditions for the first hydraulic pump 31. For example, the hydraulic excavator 10 can also be operated in a rotational manner or traveling on a flat surface under the prescribed diagnostic conditions for the first hydraulic pump 31. When the hydraulic excavator 10 is rotationally driven, the rotating body 14 can be rotated with the boom 15 and arm 16 folded. When the hydraulic excavator 10 is traveling, the traveling body 11 can be moved forward or backward. However, since the pressure of the first hydraulic pump 31 may be unstable when the hydraulic excavator 10 is traveling on a flat surface, the above embodiment is desirable.

[0046] Similarly, the hydraulic excavator 10 operating under the prescribed diagnostic conditions for the second hydraulic pump 35 does not necessarily need to be operating with the right crawler 13 of the hydraulic excavator 10 lifted and driven. For example, the hydraulic excavator 10 operating under the prescribed diagnostic conditions for the second hydraulic pump 35 may also be operating while the hydraulic excavator 10 is traveling on a flat surface. In this case, the traveling body 11 can be driven forward or backward. However, since the pressure of the second hydraulic pump 35 may be unstable when the hydraulic excavator 10 is traveling on a flat surface, the above embodiment is preferable.

[0047] Summary As a first embodiment, the present disclosure provides, from one aspect, an abnormality diagnosis system for a variable capacity hydraulic pump mounted on engineering machinery, comprising: a pressure gauge for detecting the suction pressure, discharge pressure or discharge pressure of the hydraulic pump; and a control device for determining whether the hydraulic pump has an abnormality based on the pressure detected by the pressure gauge when the engineering machinery is operating under prescribed diagnostic conditions, wherein the prescribed diagnostic conditions are that the rotational speed and load of the hydraulic pump remain constant and the capacity of the hydraulic pump remains at a prescribed value greater than a minimum value.

[0048] According to the above configuration, since the pressure of the hydraulic pump is detected while the construction machine is operating under predetermined diagnostic conditions, the presence or absence of an abnormality in the hydraulic pump can be determined with high accuracy.

[0049] As a second aspect, in the first aspect, for example, when the minimum capacity of the hydraulic pump is 0% and the maximum capacity of the hydraulic pump is 100%, the predetermined value may be 50% or more and 100% or less.

[0050] As a third aspect, in the first or second aspect, for example, the predetermined value may be a first predetermined value, and the control device may determine whether the hydraulic pump has an abnormality after confirming that the discharge pressure of the hydraulic pump is maintained at a second predetermined value.

[0051] As a fourth aspect, in the third aspect, for example, the second predetermined value may be equal to or greater than 1 MPa and equal to or less than 20 MPa.

[0052] As a fifth aspect, in any of the first to fourth aspects, the construction machine may be a hydraulic excavator including a pair of crawler tracks, and the construction machine may be operated in a state where one crawler track of the hydraulic excavator is driven and floated. This configuration allows the hydraulic excavator to easily achieve the predetermined diagnostic condition.

[0053] As a sixth aspect, in any of the first to fourth aspects, the construction machine may be a hydraulic excavator including a pair of crawler tracks, and the operation of the construction machine may be a state in which the hydraulic excavator is rotationally driven or driven on a flat surface. This configuration allows the hydraulic excavator to easily achieve predetermined diagnostic conditions.

[0054] As a seventh method, the present disclosure provides an abnormality diagnosis method from another aspect, which is an abnormality diagnosis method for a variable capacity hydraulic pump mounted on engineering machinery, wherein, when the engineering machinery is operating under specified diagnostic conditions, the suction pressure, discharge pressure or discharge pressure of the hydraulic pump is detected, and whether the hydraulic pump has an abnormality is determined based on the detected pressure, and the specified diagnostic conditions are that the speed and load of the hydraulic pump remain constant and the capacity of the hydraulic pump is maintained at a specified value greater than the minimum value.

[0055] According to the above configuration, since the pressure of the hydraulic pump is detected while the construction machine is operating under predetermined diagnostic conditions, the presence or absence of an abnormality in the hydraulic pump can be determined with high accuracy.

[0056] As an eighth aspect, in the seventh aspect, for example, when the minimum capacity of the hydraulic pump is 0% and the maximum capacity of the hydraulic pump is 100%, the predetermined value may be 50% or more and 100% or less.

[0057] As a ninth aspect, in the seventh or eighth aspect, for example, the predetermined value may be a first predetermined value, and the control device may determine whether the hydraulic pump has an abnormality after confirming that the discharge pressure of the hydraulic pump is maintained at a second predetermined value.

[0058] As a tenth aspect, in the ninth aspect, for example, the second predetermined value may be equal to or greater than 1 MPa and equal to or less than 20 MPa.

[0059] As an eleventh aspect, in any one of the seventh to tenth aspects, the construction machine may be a hydraulic excavator including a pair of crawler tracks, and the operation state of the construction machine may be a state in which one crawler track of the hydraulic excavator is driven and floated. This configuration allows the hydraulic excavator to easily achieve the predetermined diagnostic condition.

[0060] As a twelfth aspect, in any of the seventh to tenth aspects, the construction machine may be a hydraulic excavator including a pair of crawler tracks, and the operation of the construction machine may be a state in which the hydraulic excavator is rotationally driven or driven on a flat surface. This configuration allows the hydraulic excavator to easily achieve predetermined diagnostic conditions.

Claims

1. An abnormality diagnosis system for a variable displacement hydraulic pump mounted on a construction machine, characterized in that: have: a pressure gauge for detecting the suction pressure, discharge pressure, or discharge pressure of the hydraulic pump; and a control device that determines whether the hydraulic pump has an abnormality based on the pressure detected by the pressure gauge while the construction machine is operating under predetermined diagnostic conditions; The predetermined diagnostic condition is that the rotation speed and load of the hydraulic pump are kept constant and the displacement of the hydraulic pump is kept at a predetermined value greater than a minimum value.

2. The abnormality diagnosis system according to claim 1, characterized in that: When the minimum value of the capacity of the hydraulic pump is set to 0% and the maximum value of the capacity of the hydraulic pump is set to 100%, the predetermined value is 50% or more and 100% or less.

3. The abnormality diagnosis system according to claim 1 or 2, characterized in that: The prescribed value is a first prescribed value, The control device determines whether or not there is an abnormality in the hydraulic pump after confirming that the discharge pressure of the hydraulic pump is maintained at a second predetermined value.

4. The abnormality diagnosis system according to claim 3, characterized in that: The second predetermined value is not less than 1 MPa and not more than 20 MPa.

5. The abnormality diagnosis system according to claim 1 or 2, characterized in that: The engineering machine is a hydraulic excavator including a pair of crawlers. The state in which the construction machine is operated is a state in which one crawler track of the hydraulic excavator is driven to float.

6. The abnormality diagnosis system according to claim 1 or 2, characterized in that: The engineering machine is a hydraulic excavator including a pair of crawlers. The state in which the construction machine is operated is a state in which the hydraulic excavator is rotationally driven or traveled on a flat surface.

7. A method for diagnosing abnormality of a variable displacement hydraulic pump mounted on a construction machine, characterized in that: In a state where the construction machine is operated under predetermined diagnostic conditions, the suction pressure, discharge pressure or discharge pressure of the hydraulic pump is detected, and whether the hydraulic pump has an abnormality is determined based on the detected pressure. The predetermined diagnostic condition is that the rotation speed and load of the hydraulic pump are kept constant and the displacement of the hydraulic pump is kept at a predetermined value greater than a minimum value.

8. The abnormality diagnosis method according to claim 7, characterized in that: When the minimum value of the capacity of the hydraulic pump is set to 0% and the maximum value of the capacity of the hydraulic pump is set to 100%, the predetermined value is 50% or more and 100% or less.

9. The abnormality diagnosis method according to claim 7 or 8, characterized in that: The prescribed value is a first prescribed value, The control device determines whether or not there is an abnormality in the hydraulic pump after confirming that the discharge pressure of the hydraulic pump is maintained at a second predetermined value.

10. The abnormality diagnosis method according to claim 9, characterized in that: The second predetermined value is not less than 1 MPa and not more than 20 MPa.

11. The abnormality diagnosis method according to claim 7 or 8, characterized in that: The engineering machine is a hydraulic excavator including a pair of crawlers. The state in which the construction machine is operated is a state in which one crawler track of the hydraulic excavator is driven to float.

12. The abnormality diagnosis method according to claim 7 or 8, characterized in that: The engineering machine is a hydraulic excavator including a pair of crawlers. The state in which the construction machine is operated is a state in which the hydraulic excavator is rotationally driven or traveled on a flat surface.

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