EP4756237A1

EP4756237A1 - Fluid equipment state monitoring device

Info

Publication number: EP4756237A1
Application number: EP24849173.0A
Authority: EP
Inventors: Yoshiyuki Kagami; Tatsuki Hamada; Masato TAKAZAWA
Original assignee: Eagle Industry Co Ltd
Current assignee: Eagle Industry Co Ltd
Priority date: 2023-08-01
Filing date: 2024-07-30
Publication date: 2026-06-10
Also published as: WO2025028528A1; JPWO2025028528A1; TW202517902A; KR20260030898A; CN121569117A

Abstract

There is provided a fluid machine state monitoring apparatus capable of frequently performing diagnosis. A fluid machine state monitoring apparatus 102 which is used for a fluid pressure circuit 101 including a pump 2, a pressure accumulator 5 and a supplied circuit 8 to which a fluid is supplied from the pump 2 and the pressure accumulator 5, and which is configured to diagnose a state of the pressure accumulator 5 includes: a pressure detection device 6 configured for detecting a pressure of a working fluid in the fluid pressure circuit 101; a timer 10a; and a determination device 10 configured for detecting the pressure of the working fluid at least two arbitrary time points using the pressure detection device 6 and the timer 10a, and determining the state of the pressure accumulator 5.

Description

{TECHNICAL FIELD}

The present invention relates to a fluid machine state monitoring apparatus, for example, a fluid machine state monitoring apparatus capable of diagnosing the state of a pressure accumulator.

{BACKGROUND ART}

In various industrial fields, fluid pressure circuits in which a load is operated using a working fluid delivered from a pump are known. Such fluid pressure circuits may be provided with a pressure accumulator for preventing pulsation of the working fluid delivered from the pump or accumulating pressure.
A sealed fluid such as gas is sealed in the pressure accumulator to obtain back pressure for delivering the accumulated working fluid. The sealed fluid pressure may decrease due to leakage of the sealed fluid, damage to the pressure accumulator, deterioration over time, or the like. Since the pressure accumulator cannot discharge the working fluid when the sealed fluid pressure decreases excessively, and therefore, it is necessary to maintain the sealed fluid pressure at a certain level or higher. Therefore, a fluid machine state monitoring apparatus for monitoring the state of the pressure accumulator is known.
For example, a fluid machine state monitoring apparatus disclosed in Patent Citation 1 is mainly composed of a pressure measurement device, a time measurement device, a computer, and a display device. The pressure measurement device can input the measured operating pressure of an accumulator to the computer. The time measurement device can input the measured time to the computer. The computer stores a minimum operating pressure and a maximum operating pressure. The minimum operating pressure is the minimum pressure required to operate an actuator. The maximum operating pressure is the maximum pressure accumulated in the accumulator.
When the operating pressure input from the pressure measurement device reaches the minimum operating pressure, the computer causes the time measurement device to start measurement. It is assumed that the amount of a fluid supplied from a fluid pressure source is constant per unit time. In addition, when the operating pressure input from the pressure measurement device reaches the maximum operating pressure, the computer causes the time measurement device to end measurement. Then, the computer calculates the difference between the measurement time input from the time measurement device and the standard time.
The standard time is the measurement time required to reach the maximum operating pressure from the minimum operating pressure when the pressure of a sealed gas in the accumulator is at its maximum. It is known that the measurement time becomes shorter than the standard time as the sealed gas pressure decreases. That is, when a difference occurs between the standard time and the measurement time, it is considered that the sealed gas pressure has decreased. When a difference occurs between the standard time and the measurement time, the computer causes the display device to display the difference. Accordingly, the fluid machine state monitoring apparatus disclosed in Patent Citation 1 can notify an operator that the accumulator is damaged or deteriorated.

{CITATION LIST}

{Patent Literature}

Patent Citation 1: JP S63-285301 A (Page 3, FIG. 1)

{SUMMARY OF INVENTION}

{Technical Problem}

In the fluid machine state monitoring apparatus as described in Patent Citation 1, diagnosing the accumulator requires continuing pressure accumulation until the operating pressure reaches the maximum operating pressure from the minimum operating pressure. By the way, when an instruction to operate a load is given in the course of pressure accumulation, it is common to interrupt the pressure accumulation. That is, the fluid machine state monitoring apparatus as described in Patent Citation 1 has few timings at which diagnosis can be performed, and cannot determine the deterioration status in a timely manner, which is a risk.
The present invention has been made in view of such problems, and an object of the present invention is to provide a fluid machine state monitoring apparatus capable of frequently performing diagnosis.

{Solution to Problem}

In order to solve the foregoing problems, a fluid machine state monitoring apparatus according to the present invention is a fluid machine state monitoring apparatus which is used for a fluid pressure circuit including a pump, a pressure accumulator and a supplied circuit to which a fluid is supplied from the pump and the pressure accumulator, and which is configured to diagnose a state of the pressure accumulator, including: a pressure detection device configured for detecting a pressure of a working fluid in the fluid pressure circuit; a timer; and a determination device configured for detecting the pressure of the working fluid at at least two arbitrary time points using the pressure detection device and the timer, and determining the state of the pressure accumulator. According to the aforesaid feature of the present invention, since it is sufficient that the pressure can be specified at the at least two arbitrary time points, the deterioration state of the pressure accumulator can be frequently diagnosed.
It may be preferable that the at least two arbitrary time points are time points other than a time point at which the working fluid in the fluid pressure circuit reaches a minimum operating pressure and a time point at which the working fluid in the fluid pressure circuit reaches a maximum operating pressure. According to this preferable configuration, by determining the state of the pressure accumulator while reducing the influence of the minimum operating pressure and the maximum operating pressure at which noise is likely to occur, it becomes easier to obtain accurate values.
It may be preferable that the at least two arbitrary time points are time points during pressure accumulation of the pressure accumulator. According to this preferable configuration, during pressure accumulation, since the amount of delivery from the pump substantially coincides with the amount supplied to the pressure accumulator side, the behavior of the pressure accumulator is more likely to be stable. Accordingly, the determination device easily makes a determination based on stable values.
It may be preferable that the pressure detection device is configured to directly detect the pressure of the working fluid in the fluid pressure circuit. According to this preferable configuration, the pressure detection device can be simply provided.
It may be preferable that the pressures detected at a plurality of time points are subjected to a first-order approximation. According to this preferable configuration, even when pulsation or sudden fluctuations occur, the influence thereof can be reduced.
It may be preferable that the determination device is configured to detect the pressure at three or more time points. According to this preferable configuration, even when there is a sudden fluctuation value, a stable determination can be made since the value is not referenced.
It may be preferable that the at least two arbitrary time points are time points during discharge of the pressure accumulator. According to this preferable configuration, it is possible to accurately specify that the pressure accumulator is in a deterioration state.

{BRIEF DESCRIPTION OF DRAWINGS}

FIG. 1 is a schematic diagram illustrating a fluid pressure circuit to which a fluid machine state monitoring apparatus according to a first embodiment of the present invention is applied.
FIGS. 2A, 2B, and 2C are graphs illustrating changes in the pressure of a working fluid for each sealed gas pressure.
FIG. 3 is a graph for describing state diagnosis performed by the fluid machine state monitoring apparatus.
FIG. 4 is a schematic diagram illustrating a fluid pressure circuit to which a fluid machine state monitoring apparatus according to a second embodiment of the present invention is applied.
FIG. 5 is a graph illustrating changes in pressure during discharge that is used for determination by a fluid machine state monitoring apparatus according to a third embodiment of the present invention.

{DESCRIPTION OF EMBODIMENTS}

Modes for implementing a fluid machine state monitoring apparatus according to the present invention will be described below based on embodiments.

{First embodiment}

A fluid pressure circuit to which a fluid machine state monitoring apparatus according to a first embodiment of the present invention is applied will be described with reference to FIGS. 1 to 3. In the following description, the right and left sides when viewed from the front of FIG. 1 correspond to the right and left sides of the valve position of an electromagnetic direction switching valve.
A hydraulic circuit serving as the fluid pressure circuit according to the first embodiment delivers oil serving as a working fluid to a supply destination in response to a command in work machines, construction machines, cargo handling vehicles, automobiles, electric trains, wind power generation systems, or the like.
As illustrated in FIG. 1, a hydraulic circuit 101 is mainly composed of a drive mechanism 1, a hydraulic pump 2, an electromagnetic direction switching valve 3 (hereinafter, referred to as the direction switching valve 3), a check valve 4, an accumulator 5, a pressure sensor 6, an electromagnetic switching valve 7, a hydraulic pressure supplied circuit 8 serving as a supply destination, a tank 9, a control device 10, a monitor 11, and a relief valve 12.
The hydraulic pump 2 is coupled to the drive mechanism 1 such as an internal combustion engine, and is rotated by power from the drive mechanism 1, thereby supplying the oil serving as a working fluid to a downstream side. The oil delivered from the hydraulic pump 2 passes through a pipeline 18, and flows into the direction switching valve 3. Incidentally, the hydraulic pump 2 of the present embodiment is of a variable capacity type, but may be of a fixed capacity type.
The direction switching valve 3 is a spring-centered type three-position, four-port electromagnetic switching valve. The direction switching valve 3 in a neutral position 3-1 connects the pipeline 18 to a pipeline 19. The pipeline 19 is connected to the tank 9. Therefore, the entire amount of oil delivered from the hydraulic pump 2 is discharged to the tank 9.
The direction switching valve 3 includes solenoids 3a and 3b. The solenoids 3a and 3b are electrically connected to the control device 10 through electrical signal lines 13 and 14.
The control device 10 outputs an electrical signal to the electrical signal line 13 when the pressure value detected by the pressure sensor 6 to be described later becomes less than or equal to a minimum operating pressure in a state in which an operation command for operating a load provided in the hydraulic pressure supplied circuit 8 is not input.
In the direction switching valve 3, when the solenoid 3a is energized by an electrical signal applied through the electrical signal line 13, a spool moves in a left direction and switches to a right position 3-2. The direction switching valve 3 in the right position 3-2 connects the pipeline 18 to a pipeline 20, and shuts off the pipeline 19 from a pipeline 21. Incidentally, a return flow passage from the hydraulic pressure supplied circuit 8 to the tank 9 is provided inside the hydraulic pressure supplied circuit 8.
The pipeline 20 is connected to the check valve 4. The check valve 4 is connected to the accumulator 5 through a pipeline 22. The check valve 4 is configured to allow the oil to pass therethrough from the pipeline 20 to the pipeline 22. Accordingly, the oil delivered from the hydraulic pump 2 is accumulated under pressure in the accumulator 5.
In addition, the pipeline 18 is branched and communicably connected to a pipeline 23 with the relief valve 12 interposed therebetween. The pipeline 23 is connected to the tank 9. Accordingly, when the pressure in the pipeline 18 rises to a predetermined level or higher, the relief valve 12 is opened to discharge the oil to the tank 9, so that the circuit can be protected.
The accumulator 5 is mainly composed of a pressure-resistant shell and a balloon-shaped bladder. The shell is connected to the pipeline 22 to the oil to flow in and out. The bladder is disposed inside the shell. In the present embodiment, a sealed fluid sealed in the bladder is nitrogen gas; however, the sealed fluid may be other gases such as air, and may be changed as appropriate. In addition, in the following description, the sealed fluid is simply referred to as "gas". Here, the pressure in the bladder is the back pressure of the accumulator 5.
In the accumulator 5, as the hydraulic pressure in the shell increases, the bladder contracts and the oil in the pipeline 22 flows into the shell. In addition, in the accumulator 5, as the hydraulic pressure in the shell decreases in a state in which the bladder is contracted, the contraction of the bladder is released and the oil in the shell is discharged into the pipeline 22.
In addition, the filling or discharge of the gas from the bladder can be performed through a valve (not illustrated). Incidentally, the accumulator is not limited to a bladder type as in the present embodiment, and may be of a piston type or may be changed as appropriate.
The pipeline 22 is further branched in two directions, and is also connected to the pressure sensor 6 and the electromagnetic switching valve 7.
The pressure sensor 6 is electrically connected to the control device 10 through an electrical signal line 15. The pressure sensor 6 detects the pressure in the pipeline 22, and outputs a pressure signal capable of specifying the pressure to the electrical signal line 15. The pressure in the pipeline 22 is substantially the same as the pressure of the oil accumulated under pressure in the accumulator 5.
The electromagnetic switching valve 7 is a spring-offset type two-position, two-port electromagnetic switching valve. The electromagnetic switching valve 7 in an offset position 7-1 prevents communication between the pipeline 21 and the pipeline 22.
In addition, the solenoid of the electromagnetic switching valve 7 is electrically connected to the control device 10 through an electrical signal line 16. In the electromagnetic switching valve 7, when the solenoid is energized by an electrical signal applied through the electrical signal line 16, a spool moves and switches to an onset position 7-2.
The electromagnetic switching valve 7 in the onset position 7-2 connects the pipelines 21 and 22 to allow the oil to pass from the pipeline 22 side to the pipeline 21. Accordingly, the oil discharged from the accumulator 5 can be supplied to the hydraulic pressure supplied circuit 8. At this time, the control device 10 sets the direction switching valve 3 to the neutral position 3-1.
In addition, when an operation command is input, the control device 10 outputs an electrical signal to the electrical signal line 14.
In the direction switching valve 3, when the solenoid 3b is energized by an electrical signal applied through the electrical signal line 14, a spool moves in a right direction and switches to a left position 3-3. The direction switching valve 3 in the left position 3-3 connects the pipeline 18 to the pipeline 21, and connects the pipeline 19 to the pipeline 20.
The pipeline 21 is branched in two directions, and is connected to the electromagnetic switching valve 7 and the hydraulic pressure supplied circuit 8. Accordingly, the oil delivered from the hydraulic pump 2 flows into the hydraulic pressure supplied circuit 8.
The hydraulic pressure supplied circuit 8 is a circuit in which a load is provided. Incidentally, the load may be an actuator such as a hydraulic cylinder or a hydraulic motor, or may be a pressure increasing device, a power generation device, or the like, and may be changed as appropriate.
Next, a fluid machine state monitoring apparatus 102 of the present embodiment will be described. The fluid machine state monitoring apparatus 102 is mainly composed of the pressure sensor 6 serving as a pressure detection device, the control device 10 serving as an output device, a timer 10a provided in the control device 10, and the monitor 11 serving as a notification device.
The control device 10 estimates the sealed gas pressure in the accumulator 5 based on the pressure value inside the accumulator 5 input from the pressure sensor 6, and outputs, as the determination result, the ratio of the estimated sealed gas pressure to an appropriate sealed gas pressure, such as the sealed gas pressure when fully filled, that is, at the time of factory shipment, or when refilled with the sealed gas, to the monitor 11 through an electrical signal line 17. Hereinafter, a method for diagnosing the accumulator 5 by the fluid machine state monitoring apparatus 102 will be described in detail.
Incidentally, the sealed gas pressure in this specification refers to gas pressure in a state in which no oil flows into the accumulator 5. On the other hand, the sealed gas pressure may be the pressure in a state in which the accumulator 5 is fully filled with the oil, and may be changed as appropriate as long as the sealed gas pressure is a reference gas pressure detected under the same conditions.
The control device 10 diagnoses the accumulator 5 while pressure is accumulated in the accumulator 5. Incidentally, the control device 10 may be configured to determine that pressure accumulation in the accumulator 5 is started and to start diagnosis of the accumulator 5 by outputting an electrical signal to the electrical signal line 13, or the configuration of the control device 10 may be changed as appropriate.
The control device 10 estimates the sealed gas pressure based on the change in pressure value per unit time, that is, the slope, from the pressure value of the oil after the start of pressure accumulation to the pressure value of the oil before the end of pressure accumulation, in detail, from time t2 following pressure accumulation start time t1 to time t3 preceding pressure accumulation end time t4. Incidentally, in the present embodiment, during the diagnosis of the accumulator 5, it is assumed that the amount of oil delivered per unit time from the hydraulic pump 2 is constant.
It has been found through experiments that there is a correlation such that the slope of the pressure value increases, that is, the change in pressure value per unit time increases as the sealed gas pressure decreases. FIG. 2 collectively illustrates one example of the experimental results.
In the experiments illustrated in FIG. 2, the minimum operating pressure is set to 2.2 MPa, and the maximum operating pressure is set to 3.3 MPa. Incidentally, the actual hydraulic pressure before pressure accumulation or the actual hydraulic pressure after pressure accumulation may be slightly higher or lower than the minimum operating pressure or the maximum operating pressure.
FIG. 2A is a graph illustrating the changes in hydraulic pressure and gas pressure during pressure accumulation when the sealed gas pressure is set to 1.6 MPa. In this graph, pressure accumulation starts at approximately 1.0 sec, and pressure accumulation ends at approximately 3.5 sec. The time required to reach the maximum operating pressure from the minimum operating pressure is approximately 2.5 sec.
FIG. 2B is a graph illustrating the changes in hydraulic pressure and gas pressure during pressure accumulation when the sealed gas pressure is set to 1.4 MPa. In this graph, pressure accumulation starts at approximately 1.2 sec, and pressure accumulation ends at approximately 3.3 sec. The time required to reach the maximum operating pressure from the minimum operating pressure is approximately 2.1 sec.
FIG. 2C is a graph illustrating the changes in hydraulic pressure and gas pressure during pressure accumulation when the sealed gas pressure is set to 1.2 MPa. In this graph, pressure accumulation starts at approximately 1.4 sec, and pressure accumulation ends at approximately 3.2 sec. The time required to reach the maximum operating pressure from the minimum operating pressure is approximately 1.8 sec.
From above description, the correlation between the slope of the pressure value and the sealed gas pressure is clear. The control device 10 can specify the sealed gas pressure by looking up, in a table (not illustrated), the slope of pressure values at at least two time points, in more detail, the measurement time required to reach a second predetermined pressure value from a first predetermined pressure value. The table stores the pressure accumulation time and the sealed gas pressure in association in advance.
Incidentally, the present invention is not limited to a configuration in which the measurement time is looked up in the table to specify the corresponding sealed gas pressure, and a configuration in which the corresponding sealed gas pressure is calculated by substituting the measurement time into an equation may be employed, and the method for specifying the estimated sealed gas pressure may be changed as appropriate.
Next, a method for deriving the measurement time by the control device 10 will be described with reference to FIGS. 2 and 3. In FIGS. 2 and 3, the changes in hydraulic pressure are indicated by gray lines, and the gas pressure is indicated by thick black lines. Further, in FIG. 3, the hydraulic pressure moving average is indicated by a thin black line. Incidentally, FIG. 3 is a partially enlarged view of FIG. 2A. In addition, in the present embodiment, the sealed gas pressure when fully filled is 1.6 MPa, and coincides with the sealed gas pressure in FIGS. 2A and 3.
In the present embodiment, the hydraulic pressure moving average is a simple moving average calculated from pressure values for a total of 10 time points including a target time point and nine time points preceding and following the target time point. Incidentally, the hydraulic pressure moving average is not limited to being calculated from pressure values for 10 time points, and the number of time points may be changed as appropriate. In addition, the moving average may be a weighted moving average, an exponential moving average, or the like, and may be changed as appropriate.
In calculating the hydraulic pressure moving average, the control device 10 first obtains pressure values input from the pressure sensor 6 at predetermined time intervals (20 msec) and the times at which the pressure values are input from the timer 10a, and stores the pressure values and the times in correspondence with each other. The times illustrated in FIGS. 2 and 3 are times measured by the timer 10a. Incidentally, the predetermined time at which the pressure value is input from the pressure sensor 6 may be changed as appropriate.
The control device 10 calculates an average value ((P₁ + ... + P₇ + ... + P₁₀)/10) from the hydraulic pressure P₇ detected at a certain time point T₇, the hydraulic pressures P₁ to P₆ detected at six consecutive time points preceding time point T₇, and the hydraulic pressures P₈ to P₁₀ detected at three consecutive time points following time point T₇.
In addition, at time point T₈ immediately following time point T₇, the control device 10 calculates an average value ((P₂ + ... + P₈ + ... + P₁₁)/10) calculated from the hydraulic pressure P₈ detected at time point T₈, the hydraulic pressures P₂ to P₇ detected at six consecutive time points preceding time point T₈, and the hydraulic pressures P₉ to P₁₁ detected at three consecutive time points following time point T₈. The control device 10 also calculates an average value at other time points in the same manner as at time points T₇ and T₈ to obtain the hydraulic pressure moving average.
As illustrated in FIG. 3, the graph illustrating the hydraulic pressure moving average is substantially in proportion to unit time. That is, a value from which pulsation components are removed can be obtained by obtaining the hydraulic pressure moving average.
In addition, in the hydraulic pressure moving average, as illustrated in FIGS. 2A and 2C, the influence of noise such as extremely high pressure values likely to occur immediately after the start of pressure accumulation or extremely low pressure values likely to occur immediately after the end of pressure accumulation is easily reduced.
For these reasons, it is preferable that the measurement time is derived by comparing the hydraulic pressure moving average at each time point with the first predetermined pressure value or the second predetermined pressure value.
Here, the hydraulic pressure moving average is a value obtained by first-order approximation of the pressures detected at a plurality of time points in the present embodiment, in more detail, is a value in which the influence of pulsation on the hydraulic pressure illustrated in a waveform is reduced. Incidentally, if a value in which pulsation components are removed from the hydraulic pressure illustrated in a waveform can be obtained, a first-order approximation may be obtained using a method other than the moving average.
Next, the first predetermined pressure value or the second predetermined pressure value will be described. As described above, a difference occurs between the pressure value at the start of pressure accumulation and the minimum operating pressure and between the pressure value at the end of pressure accumulation and the maximum operating pressure, which is a risk. In addition, extreme fluctuations are likely to occur in hydraulic pressure immediately after the start of pressure accumulation or immediately after the end of pressure accumulation.
In order to reduce these influences, in the present embodiment, the first predetermined pressure value is set to 2.5 MPa, and the second predetermined pressure value is set to 3.0 MPa. These pressure values are obtained by cutting off the upper and lower 20% of the difference of 1.1 MPa between the minimum operating pressure of 2.2 MPa and the maximum operating pressure of 3.3 MPa.
In the present embodiment, as optimal values that balance the reduction in the influence of noise or the like at the start of pressure accumulation and after the end of pressure accumulation and the obtained measurement time, the first predetermined pressure value is set to 2.5 MPa, and the second predetermined pressure value is set to 3.0 MPa. That is, it is preferable that the first predetermined pressure value and the second predetermined pressure value are appropriately set depending on the configuration of the hydraulic circuit to which the fluid machine state monitoring apparatus is applied.
An example in which the upper and lower 20% are cut off has been described above; however, the present invention is not limited thereto. For example, an appropriate value within the range obtained by cutting off the upper and lower 5% or an appropriate value within the range obtained by cutting off the upper and lower 30% may be used, and in any case, the influence of noise or the like at the start of pressure accumulation and after the end of pressure accumulation can be reduced.
In more detail, the wider the cut range is, the easier it is to reduce the influence of noise or the like at the start of pressure accumulation and after the end of pressure accumulation, which is preferable. Meanwhile, the narrower the cut range is, the easier it is to obtain a long measurement time, which is preferable.
For details regarding the derivation of the measurement time in the present embodiment, the difference between the time point corresponding to when the hydraulic pressure moving average exceeds the first predetermined pressure value of 2.6 MPa and the time point corresponding to when the hydraulic pressure moving average exceeds the second predetermined pressure value of 2.9 MPa is set as the measurement time.
In the graph of the hydraulic pressure moving average illustrated in FIG. 3, the first predetermined pressure value of 2.5 MPa and the second predetermined pressure value of 3.0 MPa are values obtained in the period from approximately 1.0 sec to approximately 1.9 sec immediately after the start of pressure accumulation. That is, since the accumulator 5 can be diagnosed immediately after the start of pressure accumulation and in a short period of time, it is easy to increase the number of times the accumulator 5 is diagnosed.
If the sealed gas pressure estimated from the measurement time is lower than the sealed gas pressure of 1.6 MPa when fully filled, the control device 10 can estimate that an abnormality such as gas leakage or deterioration of the bladder has occurred.
The control device 10 calculates the ratio of the estimated sealed gas pressure to the sealed gas pressure of 1.6 MPa when fully filled, regardless of whether the sealed gas pressure estimated from the measurement time is lower than the sealed gas pressure of 1.6 MPa when fully filled. Then, an electrical signal for displaying the calculated ratio is output to the monitor 11. Accordingly, it is possible to grasp the extent to which the estimated sealed gas pressure is located relative to the sealed gas pressure when fully filled, that is, the degree of normality or abnormality.
Incidentally, in the present embodiment, when the estimated sealed gas pressure is equal to the sealed gas pressure when fully filled, the ratio is defined as 100%, and when the estimated sealed gas pressure is equal to atmospheric pressure, the ratio is defined as 0%. The sealed gas pressure when fully filled is a predetermined reference value in the present invention.
In addition, the control device 10 also outputs an electrical signal to the monitor 11 to display the ratio of the minimum value, at which the accumulator 5 is safely operable, to the sealed gas pressure when fully filled, for example, 60%. Accordingly, it is possible to grasp the extent to which the sealed gas pressure estimated from the waveform of hydraulic pressure is located relative to the minimum value at which the accumulator 5 is safely operable, that is, the degree of normality or abnormality.
Incidentally, if the measurement time coincides with the measurement time when fully filled, the monitor 11 or a light-emitting device (not illustrated) such as a light bulb may be caused to emit blue light, if the measurement time is less than or equal to a caution time shorter than the measurement time when fully filled, the monitor 11 or the light-emitting device may be caused to emit yellow light, and if the measurement time is less than or equal to a warning time shorter than the caution time, the monitor 11 and the light-emitting device may be caused to emit red light.
In addition, an alarm corresponding to the measurement time may be sounded, or an alarm may be sounded for a period of time corresponding to the measurement time. That is, the notification mode may be changed as appropriate as long as it is possible to grasp the extent to which the estimated sealed gas pressure is located relative to the minimum value at which the accumulator 5 is safely operable.
As described above, since it is sufficient that the hydraulic pressure moving average can be specified at at least two time points including the time point at which the hydraulic pressure moving average exceeds the first predetermined pressure value as an arbitrary time point and the time point at which the hydraulic pressure moving average exceeds the second predetermined pressure value as an arbitrary time point, the fluid machine state monitoring apparatus 102 of the present embodiment can frequently diagnose the deterioration state of the accumulator 5 compared to a configuration in which it is necessary to specify the measurement time required to reach the maximum operating pressure from the minimum operating pressure.
In addition, the fluid machine state monitoring apparatus 102 can diagnose the accumulator 5 in a short period of time during pressure accumulation. In other words, since it is sufficient that the hydraulic pressure moving average can be specified at at least two time points, the accumulator 5 can be diagnosed even when an operation command or the like is input and pressure accumulation is interrupted after the start of pressure accumulation. Therefore, no maintenance time during which no load is operated needs to be separately provided for diagnosis, thereby making the diagnosis of the accumulator 5 simple.
In addition, during pressure accumulation when the amount of delivery from the hydraulic pump 2 substantially coincides with the amount supplied to the accumulator 5 side, the behavior of the accumulator 5 is more likely to be stable, compared to during discharge when the accumulator 5 is affected by the operating status on the hydraulic pressure supplied circuit 8 side. The fluid machine state monitoring apparatus 102 of the present embodiment that diagnoses the accumulator 5 during pressure accumulation can more accurately monitor the state of the accumulator 5.
In addition, since the pressure sensor 6 is provided in the pipeline 22, the installation thereof is simple. Further, since the pressure sensor 6 directly detects the hydraulic pressure, the hydraulic pressure can be accurately specified compared to a configuration in which the hydraulic pressure is specified from the gas pressure as in a second embodiment to be described later.
Incidentally, in the present embodiment, the output device has been described as being configured to make an operator recognize the determination result through display, sound, or the like; however, the present invention is not limited thereto. For example, a configuration in which the determination result is to restrict the direction switching valve 3 from switching to the right position 3-2 may be employed, and the method may be changed as appropriate.
In addition, in the present embodiment, a configuration in which the state of the accumulator 5 is diagnosed based only on the measurement time specified during one pressure accumulation cycle has been described; however, the present invention is not limited thereto, and the state of the accumulator 5 may be determined based on the average value of the measurement times specified during a plurality of pressure accumulation cycles or the average value of the sealed gas pressures corresponding to the plurality of measurement times. With such a configuration, the influence of irregularities such as pulsation or sudden fluctuations can be further reduced.
In addition, in the present embodiment, a configuration in which the state of the accumulator 5 is diagnosed based on the measurement time from the time point at which the first predetermined pressure value is exceeded to the time point at which the second predetermined pressure value is exceeded; however, the present invention is not limited thereto, and a configuration in which the difference between the pressure value at the time point at which the first predetermined pressure value is exceeded and the hydraulic pressure moving average at a time point after a specified time (for example, 0.5 sec) from that time point may be calculated and the sealed gas pressure is specified from the calculated difference may be employed. With such a configuration, control can be made simple by reducing the number of time points at which the hydraulic pressure moving average is specified.
Further, a configuration in which the sealed gas pressure is specified by calculating the difference between the hydraulic pressure moving average at the time point at which T_a sec has elapsed after the start of pressure accumulation and time point T_b sec following T_a sec, and referring to a table for the calculated difference may be employed. With such a configuration, control can be made simple by further reducing the number of time points at which the hydraulic pressure moving average is specified while easily removing the influence of noise at the start of pressure accumulation.
In addition, in the present embodiment, a configuration in which the accumulator 5 is simply diagnosed during pressure accumulation has been described; however, for example, a configuration in which the detection of pressure by the pressure sensor 6 is performed only during a time period set in advance and the accumulator 5 is diagnosed only during pressure accumulation within this time period may be employed. With such a configuration, the amount of electric power required to diagnose the accumulator 5 can be reduced.
In addition, in the present embodiment, a configuration in which in order to reduce noise at the start of pressure accumulation and after the end of pressure accumulation, the hydraulic pressure moving average is simply calculated has been described; however, for example, a configuration in which the hydraulic pressure moving average is calculated by extracting pressure values that are not affected by noise at the start of pressure accumulation and after the end of pressure accumulation may be employed.
In addition, in the present embodiment, a configuration in which the hydraulic pressure moving average at each time point is adopted as the pressure value to specify the slope of pressure values at at least two time points have been described; however, the present invention is not limited thereto, and the hydraulic pressure itself may be used.
In addition, in the present embodiment, a configuration in which, in diagnosing the accumulator 5, the amount of oil delivered per unit time from the hydraulic pump 2 is constant has been described; however, the present invention is not limited thereto, and the amount of oil may not be constant. With such a configuration, it is preferable that the table for looking up the measurement time is changed in accordance with the amount of oil delivered per unit time from the hydraulic pump 2.

{Second embodiment}

Next, a fluid machine state monitoring apparatus according to a second embodiment will be described with reference to FIG. 4. Incidentally, the description of configurations that are the same as and overlap with the configurations of the first embodiment will be omitted.
As illustrated in FIG. 4, a fluid machine state monitoring apparatus 202 provided in a hydraulic circuit 201 of the second embodiment is mainly composed of a pressure sensor 106 serving as the pressure detection device, the control device 10, the timer 10a, and the monitor 11.
The pressure sensor 106 is connected to the accumulator 5. In addition, the pressure sensor 106 is electrically connected to the control device 10 through an electrical signal line 115. The pressure sensor 106 detects the gas pressure in the bladder, and outputs a pressure signal capable of specifying the gas pressure to the electrical signal line 115.
Referring to FIG. 3, it can be seen that the pressure value input from the pressure sensor 106 to the control device 10 during pressure accumulation, that is, the gas pressure changes in accordance with changes in the hydraulic pressure or the hydraulic pressure moving average. That is, it can be seen that the gas sealed in the bladder is affected by the hydraulic pressure. That is, the pressure sensor 106 can detect changes in hydraulic pressure from changes in gas pressure.
In addition, the gas pressure shows smaller pressure fluctuations per unit time compared to the hydraulic pressure, and changes approximately linearly. Accordingly, the fluid machine state monitoring apparatus202 of the present embodiment can estimate the sealed gas pressure from the slope of pressure values at at least two time points input from the pressure sensor 106.
In addition, referring also to FIG. 2, it can be seen that the extreme fluctuations seen in the hydraulic pressure hardly occurs in the gas pressure immediately after the start of pressure accumulation and immediately after the end of pressure accumulation. Therefore, the first predetermined pressure value and the second predetermined pressure value can be appropriately set from pressure values included within the range of 2.3 MPa to 3.2 MPa obtained by cutting of the upper and lower 5% of the difference of 1.1 MPa between the minimum operating pressure of 2.2 MPa and the maximum operating pressure of 3.3 MPa.
Incidentally, the sealed gas pressure estimated from the pressure value detected by the pressure sensor 106 as in the present embodiment and the sealed gas pressure estimated from the pressure value detected by the pressure sensor 6 as in the first embodiment may be used in combination. That is, two pressure sensors 6 and 106 may be used in combination as the pressure detection device.

{Third embodiment}

Next, a fluid machine state monitoring apparatus according to a third embodiment of the present invention will be described with reference to FIG. 5. Incidentally, the description of configurations that are the same as and overlap with the configurations of the first embodiment will be omitted.
As illustrated in FIG. 5, the fluid machine state monitoring apparatus of the third embodiment differs from that of the first embodiment in that the accumulator 5 is diagnosed based on changes in pressure when the oil is discharged from the accumulator 5.
FIG. 5 illustrates changes in hydraulic pressure during discharge. It has been found through inventors' experiments that the ratio of the decrease in pressure during discharge increases as the abnormality progresses. Therefore, attention is focused on changes in pressure immediately after the start.
In the present embodiment, pressure values are input to the control device 10 from the pressure sensor 6 at predetermined time intervals (20 msec).
The graph illustrated in FIG. 5 schematically illustrates the pressure value at each time measurement in both normal and abnormal states. In addition, the pressure value at time t31 corresponding to the start of discharge is the maximum operating pressure of 3.3 MPa in both normal and abnormal states. In the present embodiment, as two arbitrary time points for diagnosing the deterioration state of the pressure accumulator, time t32 that is two seconds after time t31 and time t33 that is 10 seconds after time t32 are adopted. The time between times t32 and t33 is 10 sec.
Accordingly, the reflection of noise, such as sudden pressure fluctuations that can occur for a short period of time after the start of discharge or sudden pressure fluctuations that can occur for a short period of time before and after the minimum operating pressure of 2.2 MPa is reached, in the diagnosis result can be suppressed.
Incidentally, time t32 as one arbitrary time point in the course of the decrease in pressure may be changed as appropriate. For example, when no sudden pressure fluctuation occurs within a short period of time from the start of discharge, when the influence of noise on the diagnosis result is small, or the like, time t31 may be adopted.
In addition, time t33 that is separately set as one arbitrary time point in the course of the decrease in pressure may be changed as appropriate. For example, when no sudden pressure fluctuation occurs within a short period of time before and after the minimum operating pressure of 2.2 MPa is reached, when the influence of noise on the diagnosis result is small, or the like, the time at which the minimum operating pressure of 2.2 MPa is reached may be adopted.
The control device 10 diagnose gas leakage, faults, or the like in the accumulator 5 by comparing the amount of change in pressure value per unit time from time t32 to time t33, that is, the slope, with a threshold value Kt. In the present embodiment, 0.06 MPa/sec calculated from trial results is adopted as the threshold value Kt; however, threshold value Kt may be changed as appropriate depending on the performance of the accumulator, the usage environment, and the like. In addition, the threshold value Kt may be automatically calculated by the control device 10 through trials, and may be set or corrected. Incidentally, in FIG. 5, in order to facilitate comparison between the threshold value Kt and a slope Kn, a reference line with a slope of the threshold value Kt is illustrated by an alternate long and short dash line.
In the change in pressure in a normal state illustrated in FIG. 5, the pressure difference between the pressure at time t32 and the pressure at time t33 was substantially 0.5 MPa. As a result, the slope Kn is approximately 0.05 MPa/sec, and is smaller than the threshold value Kt.
In the change in pressure in an abnormal state illustrated in FIG. 5, the time between times t32 and t33 was approximately 10 sec. In addition, the pressure difference between the pressure at time t32 and the pressure at time t33 was substantially 0.7 MPa. As a result, the slope Ka is approximately 0.07 MPa/sec, and is larger than the threshold value Kt.
As described above, by comparing the threshold value Kt with the newly obtained slope, it is possible to accurately specify that the accumulator 5 is in a deterioration state.
Incidentally, in the present embodiment, a configuration in which the threshold value Kt is compared with the slope between times t32 and t33 has been described; however, the present invention is not limited thereto. The pressure difference between the pressure at time t32 and the pressure at a time after a predetermined time (for example, 5 seconds) from time t32 may be compared with the threshold value, or the time until the pressure decreases from the pressure at start time t32 by a predetermined pressure (for example, 0.5 MPa) may be compared with the threshold value, and the comparison parameter may be changed as appropriate.
In addition, in the present embodiment, the diagnosis of the accumulator 5 has been described as being performed based on the changes in hydraulic pressure during discharge; however, the present invention is not limited thereto, and the diagnosis may be performed based on the changes in gas pressure during discharge. In addition, diagnosis may be performed based on the change in a value obtained by first-order approximation of the hydraulic pressure moving average or the like during discharge is calculated in the same manner as in the first embodiment.
The embodiments of the present invention have been described above with reference to the drawings; however, the specific configurations are not limited to these embodiments, and modifications or additions that are made without departing from the scope of the present invention are also included in the present invention.
For example, in the first to third embodiments, the fluid pressure circuit has been described as a hydraulic circuit in which oil is pumped; however, the present invention is not limited thereto. The working fluid may be a fluid other than oil, and the fluid to be applied may be changed as appropriate.
In addition, in the first to third embodiments, a configuration in which the working fluid delivered from the pump is directly supplied to the pressure accumulator has been described; however, the present invention is not limited thereto, and a configuration in which an actuator is provided between the pump and the pressure accumulator and the working fluid delivered from the actuator is supplied to the pressure accumulator may be employed. Even with such a configuration, the state of the pressure accumulator can be diagnosed based on the slope of the pressure value corresponding to the amount of working fluid per unit time supplied to the pressure accumulator.
In addition, in the first to third embodiments, an example of the type of pressure accumulator that accumulates the working fluid, which is delivered from the pump, under pressure in order to discharge the working fluid when needed has been provided; however, the present invention is not limited thereto, and the pressure accumulator may be used for pulsation prevention or may be used for energy regeneration. In addition, the pressure accumulator in the present invention may be any device capable of temporarily storing and discharging the working fluid, such as an air chamber or a damper, and may be changed as appropriate.
In addition, in the first to third embodiments, the determination result has been described as the ratio of the estimated sealed gas pressure to the sealed gas pressure when fully filled; however, the present invention is not limited thereto. The determination result may be the estimated sealed gas pressure itself, may be the amount of sealed gas corresponding to the estimated sealed gas pressure, or may be the ratio of the estimated amount of sealed gas to the amount of sealed gas when fully filled, the ratio of the estimated sealed gas pressure to the minimum value for safe operation may be output as the determination result, or the determination result may simply be whether the sealed gas pressure has decreased, and the type of determination result may be changed as appropriate.
In addition, in the first to third embodiments, the pressure detection device has been described as being configured as a pressure sensor; however, the present invention is not limited thereto, and the pressure detection device may be composed of a pressure sensor and a control device. That is, a configuration in which the control device samples pressure data, which is sequentially input to the control device from the pressure sensor, at predetermined time intervals to obtain a pressure value may be employed.
In addition, in the first to third embodiments, the control device serving as the output device has been described as being configured to also control the direction switching valve, the electromagnetic switching valve, and the like; however, the present invention is not limited thereto. The control device may be provided separately from a control device that controls the direction switching valve, the electromagnetic switching valve, and the like, and may be, for example, a cloud server or the like. If the output device is configured as a cloud server, the pressure detection device or the notification device may be wirelessly connected to the cloud server. In other words, the pressure detection device or the notification device may include a communication device.
Further, the notification device may be a smartphone or a tablet terminal. With such a configuration, the determination result may be transmitted from the cloud server as a notification or email, or a user may access the cloud server and receive the determination result, and the notification method may be changed as appropriate. In addition, if the pressure detection device includes a wireless communication device, a microcontroller that is am output device, or the like, the determination result may be output to the cloud server.
In addition, in the first to third embodiments, tests were performed at room temperature; however, in consideration of climate or temperature changes to which the internal fluid is subjected, values obtained by applying temperature correction to the test results may be used.

{REFERENCE SIGNS LIST}

2: Hydraulic pump (pump)
5: Accumulator (pressure accumulator)
6: Pressure sensor (pressure detection device)
8: Hydraulic pressure supplied circuit (supply destination)
10: Control device (output device)
10a: Timer
11: Monitor (notification device)
101: Hydraulic circuit (fluid pressure circuit)
102: Fluid machine state monitoring apparatus
106: Pressure sensor (pressure detection device)
201: Hydraulic circuit (fluid pressure circuit)
202: Fluid machine state monitoring apparatus

Claims

A fluid machine state monitoring apparatus which is used for a fluid pressure circuit including a pump, a pressure accumulator and a supplied circuit to which a fluid is supplied from the pump and the pressure accumulator, and which is configured to diagnose a state of the pressure accumulator, comprising:
a pressure detection device configured for detecting a pressure of a working fluid in the fluid pressure circuit;

a timer; and

a determination device configured for detecting the pressure of the working fluid at at least two arbitrary time points using the pressure detection device and the timer, and determining the state of the pressure accumulator.
The fluid machine state monitoring apparatus according to claim 1,
wherein the at least two arbitrary time points are time points other than a time point at which the working fluid in the fluid pressure circuit reaches a minimum operating pressure and a time point at which the working fluid in the fluid pressure circuit reaches a maximum operating pressure.
The fluid machine state monitoring apparatus according to claim 1 or 2,
wherein the at least two arbitrary time points are time points during pressure accumulation of the pressure accumulator.
The fluid machine state monitoring apparatus according to claim 3,
wherein the pressure detection device is configured to directly detect the pressure of the working fluid in the fluid pressure circuit.
The fluid machine state monitoring apparatus according to claim 1,
wherein the pressures detected at a plurality of time points are subjected to a first-order approximation.
The fluid machine state monitoring apparatus according to claim 1,
wherein the determination is configured to detect the pressure at three or more time points.
The fluid machine state monitoring apparatus according to claim 1 or 2,
wherein the at least two arbitrary time points are time points during discharge of the pressure accumulator.