Abnormality detection system for hydraulic rotary machine

Abstract

An abnormality detection system (7) for a positive displacement hydraulic rotary machine (1) according to one embodiment, which has a capacity of M excluding a screw pump, includes: a pressure sensor (8) that measures the pressure of a working fluid used in the hydraulic rotary machine (1); and a processing circuit (91) that records time history data, which is a measurement value of the pressure sensor (8). The processing circuit (91) performs frequency analysis on the time history data to create a frequency spectrum, and determines whether there is any abnormality in the hydraulic rotary machine (1) on the basis of at least two amplitude values among rotation order components that are one to (2M-1) times the rotation frequency of the hydraulic rotary machine (1) in the frequency spectrum.

Description

Abnormal Detection System for Hydraulic Rotary Machinery

[0001] The present disclosure relates to an abnormal detection system for hydraulic rotary machinery.

[0002] For hydraulic rotary machines such as hydraulic pumps and hydraulic motors, abnormalities are detected by various methods. For example, Patent Document 1 discloses an abnormal detection device that detects abnormalities in a hydraulic pump using the discharge pressure or drain pressure of the hydraulic pump.

[0003] Specifically, the abnormal detection device of Patent Document 1 measures the discharge pressure or drain pressure of a hydraulic pump with a pressure sensor, performs frequency analysis on the measurement result of the pressure sensor to create a frequency spectrum, and compares the amplitude value of the rotation frequency in the frequency spectrum with a threshold value to determine the presence or absence of an abnormality. Note that the rotation frequency is N / 60 [Hz] when the rotation speed of the hydraulic pump is N [rpm].

[0004] Japanese Patent Application Laid-Open No. 2013-170509

[0005] However, when determining the presence or absence of an abnormality in a hydraulic rotary machine based only on the amplitude value of the rotation frequency in the frequency spectrum as in the abnormal detection device of Patent Document 1, the abnormality of the hydraulic rotary machine cannot be accurately detected.

[0006] Therefore, an object of the present disclosure is to provide an abnormal detection system for a hydraulic rotary machine that can accurately detect abnormalities in the hydraulic rotary machine.

[0007] The present disclosure provides a pressure sensor that measures the pressure of a working fluid used in a positive displacement hydraulic rotary machine with a displacement number M excluding a screw pump, and a processing circuit that records time history data that is the measurement value of the pressure sensor. The processing circuit performs frequency analysis on the time history data to create a frequency spectrum, and is configured to determine the presence or absence of an abnormality in the hydraulic rotary machine based on at least two amplitude values among the rotation order components of 1 to (2M - 1) times the rotation frequency of the hydraulic rotary machine in the frequency spectrum.

[0008] According to this disclosure, a hydraulic rotary machine anomaly detection system is provided that can accurately detect abnormalities in hydraulic rotary machines.

[0009] This figure shows a cross-sectional view of a hydraulic rotary machine and a diagram of an anomaly detection system according to one embodiment. This is a flowchart of the processing performed by the processing circuit of the anomaly detection system. This is a graph showing the frequency spectrum created by frequency analysis of time history data. This is a graph showing the average line of the noise floor. This is a graph superimposed on Figures 3 and 4. This is an enlarged view of the main part of Figure 5. This is a graph showing the reciprocal of the noise floor. This is a graph showing the frequency spectrum corrected so that the noise floor is removed.

[0010] Figure 1 shows an abnormality detection system 7 for a hydraulic rotary machine 1 according to one embodiment. The hydraulic rotary machine 1 is a positive displacement type with a total volume M excluding the screw pump.

[0011] In this embodiment, the hydraulic rotating machine 1 is a hydraulic pump 1A. Furthermore, in this embodiment, the hydraulic pump 1A is an axial piston pump. That is, the volume number M is equal to the number of pistons. However, the hydraulic pump 1A may be a gear pump or a vane pump, etc. In the case of a gear pump, the volume number M is equal to the number of teeth of the gear, and in the case of a vane pump, the volume number M is equal to the number of vanes. Alternatively, the hydraulic rotating machine 1 may be a hydraulic motor.

[0012] Specifically, the hydraulic pump 1A includes a hollow casing 2 and a rotating shaft 11 extending from the inside to the outside of the casing 2. The rotating shaft 11 is rotated by an engine or electric motor, which is the driving source for the hydraulic pump 1A. Inside the casing 2 are a valve plate 3, a cylinder block 4, a swash plate 61, and a support base 62.

[0013] For the sake of explanation, the axial direction of the rotating shaft 11 will be referred to as the front-rear direction (one end located outside the casing 2 is forward, and the other end is backward), and the two directions perpendicular to the axial direction of the rotating shaft 11 will be referred to as the up-down direction (the upper side of Figure 1 is upward, and the lower side is downward) and the left-right direction.

[0014] The casing 2 includes a container-shaped casing body 21 that opens backward and a valve cover 22 that closes the opening of the casing body 21. The rotating shaft 11 passes through the bottom of the casing body 21. Bearings 12 and 13 that rotatably support the rotating shaft 11 are respectively held in the bottom of the casing body 21 and the valve cover 22.

[0015] The valve plate 3 is mounted on the front surface of the valve cover 22. The valve plate 3 is provided with two arc-shaped ports, a first port 31 and a second port 32, facing in opposite directions. In Figure 1, the first port 31 is depicted as the upper top dead center and the second port 32 as the lower bottom dead center, but the actual positions of the first port 31 and the second port 32 are on both sides of the rotation axis 11 in the left-right direction perpendicular to the distance between the top dead center and the bottom dead center. The top dead center is the position where the piston 51 is most retracted, and the bottom dead center is the position where the piston 51 is most advanced.

[0016] In this embodiment, the rotating shaft 11 rotates in one direction. Therefore, the first port 31 is the intake port and the second port 32 is the discharge port. That is, in the rotational direction of the rotating shaft 11, the first port 31, which is the intake port, is located downstream of the top dead center and upstream of the bottom dead center, and the second port 32, which is the discharge port, is located downstream of the bottom dead center and upstream of the top dead center.

[0017] However, the rotating shaft 11 may rotate in both directions. In this case, when the rotating shaft 11 rotates in one direction, the first port 31 becomes the intake port and the second port 32 becomes the discharge port, and when the rotating shaft 11 rotates in the opposite direction, the second port 32 becomes the intake port and the first port 31 becomes the discharge port. Alternatively, if the hydraulic rotating machine 1 is a hydraulic motor, when the rotating shaft 11 rotates in one direction, the first port 31 becomes the inlet port and the second port 32 becomes the outlet port, and when the rotating shaft 11 rotates in the opposite direction, the second port 32 becomes the inlet port and the first port 31 becomes the outlet port.

[0018] The valve cover 22 is provided with a first passage 2a that communicates with the first port 31 and a second passage 2b that communicates with the second port 32. The first passage 2a and the second passage 2b open to the outer or rear surface of the valve cover 22, and these openings form external connection ports. As described above, in this embodiment the rotating shaft 11 rotates in one direction, so the first passage 2a is the intake passage and the second passage 2b is the discharge passage.

[0019] The cylinder block 4 is fixed to the rotating shaft 11 and slides against the valve plate 3 as it rotates with the rotating shaft 11. The cylinder block 4 is provided with a plurality of forward-opening cylinder bores 41 around the rotating shaft 11. A plurality of pistons 51 are inserted into each of these cylinder bores 41.

[0020] Furthermore, the cylinder block 4 is provided with cylinder ports 42 extending from each cylinder bore 41 to the valve plate 3. Some of these cylinder ports 42 communicate with the first port 31, and some others communicate with the second port 32.

[0021] Multiple shoes 52 are attached to the head of the piston 51. In this embodiment, the shoes 52 slide against the swash plate 61 via an annular shoe plate 53 attached to the swash plate 61. However, the shoe plate 53 may be omitted, and the shoes 52 may slide directly against the swash plate 61. The shoes 52 are held in place by a retaining plate 54 so as to maintain contact with the shoe plate 53.

[0022] The swash plate 61 is supported by a support base 62 provided at the bottom of the casing body 21 so as to be able to swing around a pivot axis extending in the left-right direction. The angle of the swash plate 61 may be fixed or may be changed by a servo piston.

[0023] The inside of the casing 2 is filled with working fluid that has leaked from between the valve plate 3 and the cylinder block 4, and from between the piston 51 and the inner surface of the cylinder bore 41. The casing body 21 is provided with a drain port 23, which is connected to a tank by a drain pipe 14. The pressure of the working fluid inside the casing 2 and the drain pipe 14 is the drain pressure of the hydraulic rotary machine 1, which is a hydraulic pump 1A.

[0024] The abnormality detection system 7 includes a pressure sensor 8 that measures the pressure of the working fluid used in the hydraulic rotary machine 1, and a control device 9 electrically connected to the pressure sensor 8. In this embodiment, the pressure sensor 8 is provided on the casing body 21 and measures the pressure of the working fluid inside the casing 2, that is, the drain pressure of the hydraulic rotary machine 1. However, the pressure sensor 8 may also be provided on the drain piping 14.

[0025] The control device 9 includes a processing circuit 91 that records time history data, which is the measured value of the pressure sensor 8, and a user interface 92 having a display screen that functions as an input and display. The user interface 92 is, for example, a touchscreen. However, instead of the control device 9 including the user interface 92, an input and a display may be electrically connected to the control device 9.

[0026] With respect to the control device 9, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, dedicated processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions, or hardware programmed to perform the enumerated functions. The hardware may be hardware disclosed herein, or other known hardware that is programmed or configured to perform the enumerated functions. If the hardware is a processor, which is considered a type of circuit, then the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0027] The processing circuit 91 determines whether or not there is an abnormality in the hydraulic rotary machine 1. The processing performed by the processing circuit 91 will be explained below with reference to Figure 2.

[0028] It is desirable that the time history data recorded in the processing circuit 91 is measured while the pressure in the second flow path 2b, which is the discharge path, i.e., the discharge pressure of the hydraulic pump 1A, is kept constant by a fixed throttle or relief valve. For example, the discharge pressure that is kept constant is in the range of 0.5 MPa to 2 MPaG.

[0029] First, the processing circuit 91 performs frequency analysis on the stored time history data to create the frequency spectrum shown in Figure 3 (step S1). When the rotational speed of the hydraulic rotary machine 1 is N [rpm], the rotational frequency f0 is N / 60 [Hz].

[0030] The frequency on the horizontal axis of the frequency spectrum includes multiple rotational order components that are integer multiples of the rotational frequency f0. For example, the rotational order components include the first rotational order component f1, which is 1 times the rotational frequency f0; the second rotational order component f2, which is 2 times the rotational frequency f0; the third rotational order component f3, which is 3 times the rotational frequency f0; the fourth rotational order component f4, which is 4 times the rotational frequency f0; the fifth rotational order component f5, which is 5 times the rotational frequency f0; the sixth rotational order component f6, which is 6 times the rotational frequency f0; the seventh rotational order component f7, which is 7 times the rotational frequency f0; the eighth rotational order component f8, which is 8 times the rotational frequency f0; and the ninth rotational order component f9, which is 9 times the rotational frequency f0.

[0031] The vertical axis of the frequency spectrum represents the pressure amplitude. In this embodiment, the volume number M, which is equal to the number of pistons, is 9. Therefore, when the hydraulic rotary machine 1 is functioning normally without any abnormalities, the amplitude values ​​P1 to P8 of the first-order rotational component f1 to the eighth-order rotational component f8 are small, and the amplitude values ​​of the rotational order components of the frequency pitch f0 × M, such as the amplitude value P9 of the ninth-order rotational component f9 and the amplitude value P18 of the eighteenth-order rotational component f18, become large. On the other hand, if an abnormality occurs in the hydraulic rotary machine 1, such as wear on the sliding surface between the valve plate 3 and the cylinder block 4, or wear on the piston 51 or shoe 52, the amplitude values ​​P1 to P8 of the first-order rotational component f1 to the eighth-order rotational component f8 become large, as shown in Figure 3.

[0032] The frequency spectrum may contain a noise floor that affects the evaluation of the peak value of the pressure amplitude. For example, in the case of a diaphragm type pressure sensor 8 that guides working fluid to the diaphragm through an inlet tube, resonance causes a portion of the noise floor to protrude.

[0033] The processing circuit 91 calculates the noise floor after creating the frequency spectrum and corrects the frequency spectrum so that the noise floor is removed, as shown in Figure 8 (steps S2 to S6).

[0034] First, the processing circuit 91 calculates the average line of the noise floor as shown in Figure 4 (step S2). Specifically, the processing circuit 91 calculates the average line of the noise floor by applying a moving average to the amplitude values ​​of the pressure amplitude.

[0035] Next, the processing circuit 91 calculates the average value An of the noise floor average line for each rotational order component from the first rotational order component f1 to the eighth rotational order component f8 within a certain range of that rotational order component (step S3). For example, as shown in Figures 5 and 6, the certain range is ±1% of each of the rotational order components from the first rotational order component f1 to the eighth rotational order component f8.

[0036] The processing circuit 91 selects the minimum value An of the average values ​​of the noise floor average lines from the calculated first-order rotation component f1 to the eighth-order rotation component f8 as a reference value (step S4), and divides the reference value by the noise floor average line to calculate the reciprocal of the noise floor average line as shown in Figure 7 (step S5). After calculating the reciprocal of the noise floor average line, the processing circuit 91 multiplies the frequency spectrum by the reciprocal to correct the frequency spectrum as shown in Figure 8 (step S6).

[0037] Subsequently, the processing circuit 91 determines whether or not there is an abnormality in the hydraulic rotating machine 1 based on at least two amplitude values ​​from the rotational (2M-1)th order component f1 to the rotational (1st order) component in the corrected frequency spectrum (step S7). In this embodiment, since the volume number M is 9, the rotational (2M-1)th order component is the rotational 17th order component. Furthermore, in this embodiment, the processing circuit 91 determines whether or not there is an abnormality in the hydraulic rotating machine 1 based on at least two amplitude values ​​from the rotational (M-1)th order component f8 to the rotational (1st order) component f1 to the rotational (8th order) component f8.

[0038] For example, when using all amplitude values ​​P1 to P8 from the first rotational component f1 to the eighth rotational component f8, the processing circuit 91 calculates an index value I using the following formula. After calculating the index value I, the processing circuit 91 compares the index value I with a threshold Pt. If I ≤ Pt, it determines that there is no abnormality in the hydraulic rotating machine 1, and if I > Pt, it determines that there is an abnormality in the hydraulic rotating machine 1.

[0039] After determining whether or not there is an abnormality in the hydraulic rotary machine 10, the processing circuit 91 displays the result of the abnormality determination on the display screen of the user interface 92.

[0040] As described above, in the abnormality detection system 7 of the present embodiment, since the presence or absence of an abnormality in the hydraulic rotary machine 1 is determined based on the amplitude values of at least two rotational order components in the frequency spectrum, the abnormality in the hydraulic rotary machine 1 can be accurately detected.

[0041] In addition, by setting the rotational order components for abnormality determination up to the (2M - 1) - th rotational component, the device cost can be suppressed. In particular, if the rotational order components for abnormality determination are set up to the (M - 1) - th rotational component as in the present embodiment, the device cost can be further suppressed.

[0042] Furthermore, in the present embodiment, since the frequency spectrum is corrected so that the noise floor is removed, stable detection results can be obtained regardless of the structure of the pressure sensor 8.

[0043] <Modification Example> The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0044] For example, when the hydraulic pump 1A is driven by an engine with L cylinders (L is an even number), noise from the engine appears in the amplitude value P(L / 2) of the rotational (L / 2) - th component fL and the amplitude value PL of the rotational L - th component fL. Therefore, the processing circuit 91 may determine the presence or absence of an abnormality in the hydraulic rotary machine 1 based on the amplitude values of rotational order components other than the rotational (L / 2) - th component and the rotational L - th component. According to this configuration, since the rotational (L / 2) - th component and the rotational L - th component are excluded from the rotational order components for abnormality determination, the pulsation of the drain pressure caused by the engine can be ignored.

[0045] The pressure sensor 8 may measure the discharge pressure of the hydraulic pump 1A. Even in this case, if the processing circuit 91 performs the same control as in the above embodiment, the abnormality in the hydraulic rotary machine 1, which is the hydraulic pump 1A, can be accurately detected.

[0046] Alternatively, when the hydraulic rotary machine 1 is a hydraulic motor, the pressure sensor 8 may measure the drain pressure or the inlet pressure.

[0047] <Summary> As a first aspect, the present disclosure provides a pressure sensor that measures the pressure of a working fluid used in a positive-displacement hydraulic rotary machine having a displacement number of M excluding a screw pump, and a processing circuit that records time history data which is a measured value of the pressure sensor. The processing circuit performs frequency analysis on the time history data to create a frequency spectrum, and is configured to determine the presence or absence of an abnormality in the hydraulic rotary machine based on at least two amplitude values of rotational order components from 1 times to (2M - 1) times the rotational frequency of the hydraulic rotary machine in the frequency spectrum.

[0048] According to the above configuration, since the presence or absence of an abnormality in the hydraulic rotary machine is determined based on the amplitude values of at least two rotational order components in the frequency spectrum, the abnormality in the hydraulic rotary machine can be accurately detected. Further, by setting the rotational order components for abnormality determination up to the (2M - 1) - order component, the device cost can be suppressed.

[0049] As a second aspect, in the first aspect, the processing circuit may be configured to determine the presence or absence of an abnormality in the hydraulic rotary machine based on at least two amplitude values of rotational order components from 1 times to (M - 1) times the rotational frequency of the hydraulic rotary machine in the frequency spectrum. According to this configuration, the device cost can be further suppressed.

[0050] As a third aspect, in the first or second aspect, the hydraulic rotary machine is a hydraulic pump driven by an engine with L cylinders (L is an even number), and the processing circuit may be configured to determine the presence or absence of an abnormality in the hydraulic rotary machine based on the amplitude values of rotational order components other than the (L / 2) - order component and the L - order component. According to this configuration, since the (L / 2) - order component and the L - order component are excluded from the rotational order components for abnormality determination, the pulsation of the drain pressure caused by the engine can be ignored.

[0051] In a fourth embodiment, in any of the first to third embodiments, the processing circuit may be configured to calculate a noise floor after creating the frequency spectrum, correct the frequency spectrum so that the noise floor is removed, and determine whether or not there is an abnormality in the hydraulic rotary machine using the amplitude value of the rotational order component in the corrected frequency spectrum. With this configuration, a stable detection result can be obtained regardless of the structure of the pressure sensor.

[0052] In a fifth embodiment, in any of the first to fourth embodiments, for example, the hydraulic rotary machine may include a casing whose interior is filled with the working fluid, and the sensor may measure the pressure of the working fluid inside the casing.

[0053] 1. Hydraulic rotary machine, 1A. Hydraulic pump, 7. Anomaly detection system, 8. Pressure sensor, 91. Processing circuit

Claims

1. A hydraulic rotary machine abnormality detection system comprising: a pressure sensor for measuring the pressure of the working fluid used in a positive displacement hydraulic rotary machine with a volume of M, excluding screw pumps; and a processing circuit for recording time history data which is the measured value of the pressure sensor, wherein the processing circuit is configured to perform frequency analysis on the time history data to create a frequency spectrum, and to determine whether or not there is an abnormality in the hydraulic rotary machine based on at least two amplitude values ​​of rotational order components in the frequency spectrum that are 1 to (2M-1) times the rotational frequency of the hydraulic rotary machine.

2. The hydraulic rotary machine abnormality detection system according to claim 1, wherein the processing circuit is configured to determine whether or not there is an abnormality in the hydraulic rotary machine based on at least two amplitude values ​​of rotational order components in the frequency spectrum that are 1 to (M-1) times the rotational frequency of the hydraulic rotary machine.

3. The hydraulic rotary machine is a hydraulic pump driven by an L-cylinder (L is an even number) engine, and the processing circuit is configured to determine whether or not there is an abnormality in the hydraulic rotary machine based on the amplitude values ​​of rotational (L / 2)th order component and rotational Lth order component. This is the abnormality detection system for a hydraulic rotary machine according to claim 1 or 2.

4. The hydraulic rotary machine abnormality detection system according to claim 1 or 2, wherein the processing circuit is configured to calculate the noise floor after creating the frequency spectrum, correct the frequency spectrum so that the noise floor is removed, and determine whether or not there is an abnormality in the hydraulic rotary machine using the amplitude value of the rotational order component in the corrected frequency spectrum.

5. The hydraulic rotary machine includes a casing whose interior is filled with the working fluid, and the sensor measures the pressure of the working fluid in the casing, an abnormality detection system for a hydraulic rotary machine according to claim 1 or 2.

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