Fluid-apparatus-condition monitoring device

Abstract

Provided is a fluid-apparatus-condition monitoring device that is capable of accurately diagnosing the condition.　A fluid-apparatus-condition monitoring device 102 is for diagnosing the condition of a pressure accumulation device 5 in a fluid pressure circuit 101 that is provided with a pump 2 and said pressure accumulation device 5, and comprises: a pressure detection means 6 capable of detecting the pressure of a working fluid in the fluid pressure circuit 101; and an output means 10 for outputting a determination result at a prescribed frequency among results of detection by the pressure detection means 6.

Description

Fluid equipment condition monitoring device

[0001] The present invention relates to a fluid equipment state monitoring device, for example, a fluid equipment state monitoring device capable of diagnosing the state of a pressure accumulator device.

[0002] In various industrial fields, hydraulic pressure circuits that use a working fluid delivered by a pump to operate a load are known, and some of these hydraulic pressure circuits are provided with a pressure accumulator to prevent pulsation of the working fluid delivered by the pump and to accumulate pressure.

[0003] Pressure accumulators are filled with a sealed fluid such as gas to generate back pressure for discharging the stored working fluid. The pressure of the sealed fluid can decrease due to leakage of the sealed fluid, damage to the pressure accumulator, deterioration over time, etc. If the pressure of the sealed fluid decreases excessively, the pressure accumulator will no longer be able to discharge, so it is necessary to maintain the pressure of the sealed fluid at a certain level or higher. Therefore, fluid equipment status monitoring devices are known for monitoring the status of pressure accumulators.

[0004] For example, the fluid equipment status monitoring device disclosed in Patent Document 1 is mainly composed of a pressure switch and a buzzer. The pressure switch is provided in an accumulator for preventing pulsation, which is provided between the main pump and the breaker. The pressure switch detects the pressure inside the accumulator and is configured to activate a relay when the detected pressure exceeds the installation pressure. The buzzer sounds when the relay is activated. This allows the fluid equipment status monitoring device disclosed in Patent Document 1 to notify the operator that the accumulator has been damaged.

[0005] It is known that the peak pressure of the oil pulsation flowing through the hydraulic piping between the main pump and the breaker is greater when the accumulator is operating abnormally and the back pressure has fallen below the minimum value than when the accumulator is operating normally and the back pressure is normal. Therefore, by setting the set pressure to a value higher than the peak pressure when the accumulator is operating normally, it is possible to identify abnormal accumulator operation.

[0006] Japanese Patent Application Laid-Open No. 10-60953 (page 4, Figure 1)

[0007] To apply a fluid equipment status monitoring device such as that described in Patent Document 1 to a pressure-accumulating accumulator, it is necessary to change the threshold value according to the pressure-accumulation state of the accumulator. However, since the pressure of the working fluid changes in a waveform, it is difficult to identify the pressure-accumulation state. Therefore, a fluid equipment status monitoring device such as that described in Patent Document 1 cannot accurately diagnose the state of the accumulator.

[0008] The present invention has been made in view of the above-mentioned problems, and has an object to provide a fluid equipment state monitoring device that can accurately diagnose the state.

[0009] In order to solve the above-mentioned problems, the fluid equipment status monitoring device of the present invention is a fluid equipment status monitoring device that diagnoses the status of a pressure accumulator in a fluid pressure circuit provided with a pump and the pressure accumulator, and includes: pressure detection means capable of detecting the pressure of the working fluid in the fluid pressure circuit; and output means that outputs a determination result at a predetermined frequency from the detection results by the pressure detection means. This makes it possible to accurately diagnose the status of the pressure accumulator by determining the pressure at the predetermined frequency.

[0010] The predetermined frequency may be a specific frequency based on the characteristics of the pump, which makes it possible to simply improve the accuracy of the determination.

[0011] The pressure detecting means may sample the pressure every 20 msec or less, thereby enabling the state of the pressure accumulator, which is affected by the characteristics of the pump, to be monitored with high accuracy.

[0012] The pressure detection means may sample the pressure every 1 to 3 msec, thereby enabling more accurate monitoring of the state of the pressure accumulator, which is affected by the characteristics of the pump.

[0013] The output means may perform a determination at a predetermined frequency when the pump and the accumulator are connected in the circuit. This makes it difficult to obtain a consistent behavior during discharge because the discharge behavior varies depending on the state of the supply circuit. However, during accumulation, the amount of fluid delivered from the pump and the amount supplied to the accumulator are nearly equal, making it easier to stabilize the behavior of the accumulator, obtain a consistent range of behavior, and make determinations. This allows for more accurate monitoring of the state of the accumulator.

[0014] The determination result may be obtained from pressure at a predetermined frequency multiple times. In this way, since the determination result is obtained from pressure at a predetermined frequency multiple times, the accuracy of the determination result can be improved even if an irregularity occurs, such as a large noise being superimposed at any of the detection timings.

[0015] The pressure detection means may directly detect the working fluid pressure of the pressure accumulator, and the output means may output the result of the determination relative to a predetermined reference value as the determination result. In this way, the pressure of the fluid sealed in the pressure accumulator can be estimated from the working fluid pressure, and the degree of normality or abnormality of that value relative to the predetermined reference value can be determined.

[0016] The output means may output the result of the determination relative to the minimum value for safe operation as the determination result, thereby allowing the user to grasp the degree of normality or abnormality of the value of the sealed fluid pressure filled in the pressure accumulator estimated from the working fluid pressure relative to the minimum value for safe operation.

[0017] 1 is a schematic diagram showing a fluid pressure circuit to which a fluid equipment status monitoring device according to a first embodiment of the present invention is applied; FIG. 2 is a flowchart of a diagnostic procedure by the fluid equipment status monitoring device; (a), (c), and (e) are graphs showing pressure changes of a working fluid due to pulsation for each charged gas pressure, and (b), (d), and (f) are graphs showing absolute pressure values ​​at a predetermined frequency for each charged gas pressure; and (a), (b), and (c) are schematic diagrams showing a fluid pressure circuit to which a fluid equipment status monitoring device according to a second embodiment of the present invention is applied.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid equipment state monitoring device according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0019] A fluid pressure circuit to which a fluid equipment status monitoring device according to a first embodiment of the present invention is applied will be described with reference to Figures 1 to 3. In the following description, the left and right sides of Figure 1, as viewed from the front, correspond to the left and right valve positions of an electromagnetic directional control valve.

[0020] The hydraulic circuit as a fluid pressure circuit according to the first embodiment is for sending oil as a working fluid to a supply destination in response to a command in a work machine, a construction machine, a material handling vehicle, an automobile, a train, a wind power generation device, or the like.

[0021] As shown in FIG. 1 , the hydraulic circuit 101 is mainly composed of a drive mechanism 1, a hydraulic pump 2, an electromagnetic directional control valve 3 (hereinafter referred to as the directional control valve 3), a check valve 4, an accumulator 5, a pressure sensor 6, an electromagnetic directional control valve 7, a hydraulic supply circuit 8 as a supply destination, a tank 9, a control device 10, a monitor 11, and a relief valve 12.

[0022] The hydraulic pump 2 is connected to a drive mechanism 1 such as an internal combustion engine, and is rotated by power from the drive mechanism 1 to supply oil as a working fluid downstream. The oil delivered from the hydraulic pump 2 passes through a pipe 18 and flows into the directional control valve 3. Note that although the hydraulic pump 2 in this embodiment is a variable displacement type, it may also be a fixed displacement type.

[0023] The directional control valve 3 is a spring-center type, three-position, four-port solenoid-operated control valve. When the directional control valve 3 is in the neutral position 3-1, it connects the line 18 to the line 19. The line 19 is connected to the tank 9. Therefore, all of the oil delivered from the hydraulic pump 2 is discharged into the tank 9.

[0024] The directional control valve 3 has solenoids 3a and 3b, which are electrically connected to the control device 10 via electric signal lines 13 and 14.

[0025] When an operation command to operate the load provided in the hydraulic pressure supply circuit 8 is not input, the control device 10 outputs an electrical signal to the electrical signal line 13 when the pressure value detected by the pressure sensor 6 described later falls below a predetermined value.

[0026] When solenoid 3a is excited by an electric signal applied through electric signal line 13, the spool of directional control valve 3 moves leftward and switches to right position 3-2. When directional control valve 3 is in right position 3-2, it connects line 18 to line 20 and blocks lines 19 and 21. The return flow path from hydraulic pressure supplied circuit 8 to tank 9 is provided within hydraulic pressure supplied circuit 8.

[0027] The pipe 20 is connected to the check valve 4. The check valve 4 is connected to the accumulator 5 through a pipe 22. The check valve 4 is configured to allow oil to pass from the pipe 20 to the pipe 22. As a result, the oil delivered from the hydraulic pump 2 is accumulated under pressure in the accumulator 5.

[0028] Furthermore, the pipe 18 branches and is connected to a pipe 23 across the relief valve 12 so as to be able to communicate with the pipe 23. The pipe 23 is connected to the tank 9. As a result, when the pressure in the pipe 18 increases above a predetermined level, the relief valve 12 opens to discharge the oil into the tank 9, thereby protecting the circuit.

[0029] The accumulator 5 is mainly composed of a pressure-resistant shell and a balloon-shaped bladder. The shell is connected to a pipe 22 so that oil can flow in and out. The bladder is disposed inside the shell. The fluid sealed in the bladder is nitrogen gas in this embodiment, but it may be other gases such as air, and may be changed as appropriate. In the following description, the sealed fluid will be simply referred to as "gas." Here, the pressure inside the bladder is the back pressure of the accumulator 5.

[0030] In the accumulator 5, as the hydraulic pressure in the shell increases, the bladder contracts, and oil in the conduit 22 flows into the shell. In addition, as the hydraulic pressure in the shell decreases from a contracted state, the bladder of the accumulator 5 is released, and the oil in the shell is discharged into the conduit 22.

[0031] The bladder can be filled with and discharged from the gas supply through a valve (not shown). The accumulator is not limited to the bladder type as in this embodiment, but may be a piston type or may be modified as appropriate.

[0032] The pipe 22 is further branched into two directions and is also connected to a pressure sensor 6 and an electromagnetic switching valve 7 .

[0033] The pressure sensor 6 is electrically connected to the control device 10 through an electric signal line 15. The pressure sensor 6 detects the pressure in the pipe 22 and outputs a pressure signal that can identify the pressure to the electric signal line 15. The pressure in the pipe 22 is approximately the same as the pressure of the oil accumulated in the accumulator 5.

[0034] The solenoid controlled directional control valve 7 is a spring offset type two-position two-port solenoid controlled directional control valve. When the solenoid controlled directional control valve 7 is in the offset position 7-1, the lines 21 and 22 are not in communication with each other.

[0035] Furthermore, the solenoid in the electromagnetic switching valve 7 is electrically connected to the control device 10 through an electric signal line 16. When the solenoid in the electromagnetic switching valve 7 is excited by an electric signal applied through the electric signal line 16, the spool moves and switches to the onset position 7-2.

[0036] The solenoid controlled directional control valve 7 in the onset position 7-2 connects the lines 21 and 22 so that oil can pass from the line 22 to the line 21. This allows oil discharged from the accumulator 5 to be supplied to the hydraulic pressure supplied circuit 8. At this time, the control device 10 sets the directional control valve 3 to the neutral position 3-1.

[0037] Furthermore, when an operation command is input, the control device 10 outputs an electrical signal to the electrical signal line 14 .

[0038] When the solenoid 3b is excited by an electric signal applied through the electric signal line 14, the spool of the directional control valve 3 moves to the right and the directional control valve 3 switches to the left position 3-3. When the directional control valve 3 is in the left position 3-3, the pipe 18 is connected to the pipe 21 and the pipe 19 is connected to the pipe 20.

[0039] The pipeline 21 branches into two directions and is connected to the electromagnetic switching valve 7 and the hydraulic pressure supplied circuit 8. As a result, the oil delivered from the hydraulic pump 2 flows into the hydraulic pressure supplied circuit 8.

[0040] The hydraulic pressure supplied circuit 8 is a circuit provided with a load. The load may be an actuator such as a hydraulic cylinder or a hydraulic motor, or may be a pressure booster, a power generator, or the like, and may be changed as appropriate.

[0041] Next, we will explain the fluid equipment status monitoring device 102 of this embodiment. The fluid equipment status monitoring device 102 is mainly composed of a pressure sensor 6 as a pressure detection means, a control device 10 as an output means, and a monitor 11 as a notification means.

[0042] The control device 10 estimates the pressure of the gas charged in the accumulator 5 based on the pressure value in the accumulator 5 input from the pressure sensor 6, and outputs the ratio of the estimated charged gas pressure to an appropriate charged gas pressure such as the charged gas pressure when the accumulator is fully charged, i.e., the charged gas pressure at the time of shipment from the factory or when the charged gas is recharged, as a judgment result to the monitor 11 via the electrical signal line 17. The diagnostic procedure for the accumulator 5 by the fluid equipment state monitoring device 102 will be described below with reference to Figures 2 and 3.

[0043] In this specification, the charged gas pressure refers to the gas pressure when no oil has flowed into the accumulator 5. On the other hand, the charged gas pressure may be the pressure when the accumulator 5 is filled with oil, and may be changed as appropriate as long as it is a reference gas pressure detected under the same conditions.

[0044] 2, the control device 10 repeatedly executes step S1 (step S1: N) until an electric signal is output to the electric signal line 13. When the pressure detected by the pressure sensor 6 increases to a certain level or more, it determines that pressure is being accumulated (step S1: Y) and proceeds to step S2.

[0045] Regarding the method of determining whether or not pressure is being accumulated, the control device 10 may determine that pressure is being accumulated by outputting an electric signal to the electric signal line 13, or the method may be changed as appropriate.

[0046] When the control device 10 proceeds to step S2, pressure values ​​sampled every 2 msec are input from the pressure sensor 6, and the control device 10 performs a fast Fourier transform (hereinafter referred to as "FFT") on the waveform obtained from these values ​​to derive the absolute pressure value at a specified frequency.

[0047] 3(a), 3(c), and 3(e), which are made up of detection values ​​sampled every 2 msec by the pressure sensor 6, are the detection results of the pressure detection means of the present invention. More specifically, the start time of step S2 is set to 0.00 sec, and the period up to 0.10 sec is set as a detection result of 1. The control device 10 performs FFT on this detection result of 1. The same applies to step S4, which will be described later.

[0048] 3(a), (c), and (e) for more details on steps S2 and S4, it can be seen that the pressure value input from the pressure sensor 6 to the control device 10 during pressure accumulation changes in a waveform over time. It can also be seen that there is a regularity in which multiple successive cycles with large amplitude are followed by one successive cycle with small amplitude. In other words, it can be seen that the oil delivered from the hydraulic pump 2 is pulsating.

[0049] It has been found that the pulsation of oil delivered from the hydraulic pump 2 has a frequency specific to the pump. When the frequency of the hydraulic pump 2 is measured with the hydraulic circuit 101 configured, the predetermined frequency to be measured can be identified. Specifically, in an experiment described below, when a hydraulic pump 2 with a pulsation of 225 Hz was used, the predetermined frequency was approximately 223.1 Hz (see FIGS. 3(b), (d), and (f)).

[0050] Experiments have shown that there is a correlation between the absolute pressure value at a given frequency and the pressure of the enclosed gas, such that the lower the enclosed gas pressure, the higher the absolute pressure value at the given frequency. Figure 3 shows an example of the experimental results.

[0051] 3(a), (c), and (e) show pressure changes detected by the pressure sensor 6 in order to clearly show increases and decreases in pressure, and the pressure units and scales are the same. That is, the pressure units and scales on the vertical axes are the same.

[0052] Fig. 3(a) shows a waveform of the pressure value detected by the pressure sensor 6 when the hydraulic pump 2 is operated with the charged gas pressure set to 2.0 MPa. Fig. 3(b) shows the absolute pressure value, i.e., the amplitude, extracted near a predetermined frequency obtained by FFT of the waveform shown in Fig. 3(a). The absolute pressure value at the predetermined frequency was approximately 0.015 MPa.

[0053] Figure 3(c) shows the waveform of the pressure value obtained as the detection result when the filled gas pressure was set to 1.8 MPa. Figure 3(d) shows the absolute pressure value extracted near a predetermined frequency obtained by FFT of the waveform shown in Figure 3(c). The absolute pressure value at the predetermined frequency was approximately 0.019 MPa.

[0054] Figure 3(e) shows the waveform of the pressure value obtained as the detection result when the filled gas pressure was set to 1.6 MPa. Figure 3(f) shows the absolute pressure value extracted near a predetermined frequency obtained by FFT of the waveform shown in Figure 3(e). The absolute pressure value at the predetermined frequency was approximately 0.022 MPa.

[0055] From the above, the correlation between the absolute pressure value at a predetermined frequency and the pressure of the gas sealed in the bladder is clear. Therefore, the absolute pressure value at a predetermined frequency obtained when the bladder is fully filled with gas is set as a set value, and the set value is compared with the absolute pressure value at the predetermined frequency obtained in step S2 (step S3).

[0056] If the absolute pressure value at the predetermined frequency obtained in step S2 is equal to or less than the set value, it is determined that the bladder is fully filled with gas (step S3: N). Next, the control device 10 proceeds to step S8, where it outputs an electrical signal to the monitor 11 to display 100%.

[0057] The term "100%" used here refers to the ratio when the charged gas pressure at full filling is equal to the estimated charged gas pressure. The ratio of the estimated charged gas pressure to the charged gas pressure at full filling is set to 0% when the estimated charged gas pressure is equal to atmospheric pressure. The charged gas pressure at full filling is a predetermined reference value in the present invention.

[0058] Furthermore, when comparing the absolute pressure value at a specified frequency with the set value, it may be determined whether the absolute pressure value at the specified frequency is included within a certain range including the set value, for example, a range of ±5% of the set value, or this may be changed as appropriate.

[0059] Thereafter, the control device 10 completes the diagnosis of the accumulator 5. After the diagnosis is completed, if pressure is being accumulated (step S1: Y), steps S2 and S3 are newly executed.

[0060] On the other hand, if the absolute pressure value at the predetermined frequency obtained in step S2 is greater than the set value, it can be assumed that an abnormality such as gas leakage or bladder deterioration has occurred (step S3: Y). In this case, pressure values ​​sampled every 2 msec are input from the pressure sensor 6, and the waveform obtained from these values ​​is subjected to FFT to identify the absolute pressure value at the predetermined frequency (step S4).

[0061] In step S5, the control device 10 compares the set value with the absolute pressure value at the predetermined frequency obtained in step S4. If the absolute pressure value at the predetermined frequency obtained in step S4 is equal to or less than the set value (step S5: N), the control device 10 proceeds to step S8 and outputs an electrical signal to the monitor 11 to display 100%. Then, the diagnosis of the accumulator 5 is completed.

[0062] If the absolute pressure value at the predetermined frequency obtained in step S4 is greater than the set value (step S5: Y), the control device 10 proceeds to step S6.

[0063] In step S6, the control device 10 refers to a table (not shown) for the absolute pressure value at the predetermined frequency obtained in step S2, and identifies a corresponding pressure value that has been set in advance based on experimental results, etc. Similarly, the control device 10 refers to the same table for the absolute pressure value at the predetermined frequency obtained in step S4, and identifies a corresponding pressure value. Then, an average value is calculated from the pressure values ​​identified from the absolute pressure values ​​at the predetermined frequencies in steps S2 and S4. This average value is identified as the estimated filler gas pressure.

[0064] In addition, the configuration is not limited to one in which the absolute pressure value at a specified frequency is referenced in a table to identify the corresponding pressure value, but may also be one in which the absolute pressure value at a specified frequency is substituted into a formula to calculate the corresponding pressure value, and the method of identifying the estimated enclosed gas pressure may be changed as appropriate.

[0065] In step S7, the control device 10 calculates the ratio of the estimated charged gas pressure to the charged gas pressure when the tank is fully filled.

[0066] Thereafter, the control device 10 proceeds to step S8, and outputs an electric signal to the monitor 11 to display the ratio of the estimated charged gas pressure to the charged gas pressure at full filling, for example, 70%, thereby allowing the user to grasp the extent to which the estimated charged gas pressure is located relative to the charged gas pressure at full filling, i.e., the degree of normality or abnormality.

[0067] In step S8, the control device 10 also outputs an electric signal to the monitor 11 to display the ratio of the minimum value at which the accumulator 5 can safely operate to the charged gas pressure when the accumulator 5 is fully charged, for example, 60%. This allows the user to understand to what extent the charged gas pressure estimated from the hydraulic waveform is located relative to the minimum value at which the accumulator 5 can safely operate, that is, the degree of normality or abnormality.

[0068] In addition, the ratio of the minimum value at which the accumulator 5 can safely operate to the charged gas pressure when fully filled may be displayed on the monitor 11 even if the conditions are not met in step S3 or step S5 (S3, S5: N).

[0069] Furthermore, if the ratio of the estimated filled gas pressure to the filled gas pressure at full capacity is 100%, the monitor 11 and a light-emitting device such as a light bulb (not shown) may be made to emit blue light, and if it falls below 90%, the monitor 11 and the light-emitting device may be made to emit yellow light, and if it falls below 70%, the monitor 11 and the light-emitting device may be made to emit red light.

[0070] Furthermore, an alarm may be sounded according to the ratio of the estimated charged gas pressure to the charged gas pressure when the tank is fully filled, or the alarm may be sounded for a period of time according to the ratio. In other words, the notification method may be changed as appropriate as long as it allows the user to understand to what extent the estimated charged gas pressure is located relative to the minimum value at which safe operation is possible.

[0071] As described above, the fluid equipment state monitoring device 102 of this embodiment is capable of accurately diagnosing the state of the accumulator 5 by determining the absolute pressure value at a predetermined frequency.

[0072] Furthermore, while the absolute pressure value at a given frequency changes depending on the pressure of the enclosed gas, it is hardly affected by the pressure accumulation state of the accumulator 5. Therefore, the state can be diagnosed with high accuracy whether the accumulator 5 is for accumulating pressure as in this embodiment or an accumulator for preventing pulsation as in Patent Document 1.

[0073] Furthermore, while the absolute pressure value at a specified frequency changes depending on the pressure of the enclosed gas, it is hardly affected by the amount of pressure delivered per unit time from the hydraulic pump 2. Therefore, even if the amount of pressure delivered per unit time changes, that is, if the pump is changed, there is no effect. For example, even if the pump is replaced with one with different delivery performance, the condition of the accumulator 5 can be diagnosed with high accuracy.

[0074] Furthermore, since the predetermined frequency in this embodiment is a specific frequency based on the characteristics of the hydraulic pump 2, the accuracy of the determination can be easily improved.

[0075] Furthermore, since the pressure sensor 6 samples the pressure value every 2 msec, which is less than 20 msec, the state of the accumulator 5, which is affected by the characteristics of the hydraulic pump 2, can be monitored with higher accuracy.

[0076] It is preferable that the pressure sensor 6 samples the pressure value every 20 msec or less, and more preferably every 1 to 3 msec. This is because the shorter the sampling interval, the easier it is to identify the absolute pressure value of high frequencies by FFT.

[0077] Furthermore, the fluid equipment status monitoring device 102 determines the maximum pressure value at a predetermined frequency when the hydraulic pump 2 and accumulator 5 are connected in the circuit. The behavior of the accumulator 5 is more likely to be stable, with constant behavior and less noise, and easier to determine when it is accumulating pressure, when the amount of hydraulic fluid delivered from the hydraulic pump 2 and the amount of hydraulic fluid supplied to the accumulator 5 are nearly equal, than when it is discharging, when it is difficult to achieve constant behavior due to the operating conditions of the hydraulic pressure supplied circuit 8, for example, when it operates intermittently and is otherwise unstable. This allows the status of the accumulator 5 to be monitored more accurately.

[0078] In this embodiment, when diagnosing the accumulator 5, the absolute pressure value of a predetermined frequency is determined in steps S2 and S3, and then the absolute pressure value of the predetermined frequency is determined in steps S4 and S5. For example, even if an irregularity such as an impact occurs in steps S2 and S3 and the process proceeds to step S4, the absolute pressure value of the predetermined frequency in a state where no irregularity is included can be obtained in steps S4 and S5, and a determination can be made. This improves the accuracy of the determination result.

[0079] Furthermore, since the average value of the pressure value corresponding to the absolute pressure value of the predetermined frequency identified in step S2 and the pressure value corresponding to the absolute pressure value of the predetermined frequency identified in step S4 is identified as the estimated enclosed gas pressure, it is easier to reduce the error with the actual enclosed gas pressure compared to a configuration that uses only one of the pressure values.

[0080] In this embodiment, the output means has been described as being configured to make the operator aware of the judgment result by displaying it, making a sound, etc., but this is not limited to this, and the judgment result may be, for example, to restrict the directional control valve 3 from switching to the right position 3-2, or may be modified as appropriate.

[0081] Next, a fluid equipment state monitoring device according to a second embodiment will be described with reference to Figures 4 and 5. Note that a description of the same configuration as in the first embodiment will be omitted.

[0082] As shown in FIG. 4, the fluid equipment state monitoring device 202 provided in the hydraulic circuit 201 of this embodiment 2 is mainly composed of a pressure sensor 106 as a pressure detection means, a control device 10, and a monitor 11.

[0083] The pressure sensor 106 is connected to the accumulator 5. The pressure sensor 106 is also electrically connected to the control device 10 through an electric signal line 115. The pressure sensor 106 detects the gas pressure in the bladder and outputs a pressure signal that can identify the gas pressure to the electric signal line 115.

[0084] As shown in Figure 5, the pressure value input from the pressure sensor 106 to the control device 10 during pressure accumulation changes in a waveform over time. In other words, it can be seen that the gas sealed in the bladder is affected by the pulsation of the oil delivered from the hydraulic pump 2. More specifically, it can be seen that the gas pressure changes in the same way as the oil pressure changes in the accumulator 5. In other words, the pressure sensor 106 can detect changes in oil pressure from changes in gas pressure.

[0085] As a result, similar to the first embodiment, the control device 10 can perform FFT on the waveform obtained from the multiple pressure values ​​input from the pressure sensor 106 and derive the absolute pressure value at a predetermined frequency.

[0086] It is also possible to use a combination of the absolute pressure value at a predetermined frequency derived by FFTing the waveform obtained from the pressure value detected by the pressure sensor 106 as in this embodiment and the absolute pressure value at a predetermined frequency derived by FFTing the waveform obtained from the pressure value detected by the pressure sensor 6 as in the first embodiment. In other words, the two pressure sensors 6 and 106 may be used in combination as pressure detection means.

[0087] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0088] For example, in the first and second embodiments, the fluid pressure circuit has been described as a hydraulic circuit in which oil is pumped, but this is not limited to this, and the working fluid may be a fluid other than oil, and the fluid to be applied may be changed as appropriate.

[0089] In addition, in the first and second embodiments, the working fluid discharged from the pump is directly supplied to the pressure accumulator, but the present invention is not limited to this. An actuator may be provided between the pump and the pressure accumulator, and the working fluid discharged from the actuator may be supplied to the pressure accumulator. Even in such a configuration, it is possible to diagnose the condition of the pressure accumulator by identifying a predetermined frequency in the fluid pressure circuit and obtaining the pressure of that frequency.

[0090] In the first and second embodiments, the pressure accumulator is of the type that accumulates pressure in the working fluid delivered from the pump for discharge when necessary, but the present invention is not limited to this and may be used for preventing pulsation or for energy regeneration. The pressure accumulator in the present invention may be any device that can temporarily hold and discharge the working fluid, such as an air chamber or a damper, and may be modified as appropriate.

[0091] In addition, in the first and second embodiments, the state of the pressure accumulating device is diagnosed based on the pulsation during pressure accumulation. However, the present invention is not limited to this, and the pulsation during discharge or the pulsation at a constant pressure may be used.

[0092] Furthermore, in the above-described first and second embodiments, the judgment result was described as the ratio of the estimated enclosed gas pressure to the enclosed gas pressure at full filling, but it is not limited to this and may be the absolute pressure value at a predetermined frequency, the estimated enclosed gas pressure itself, the enclosed gas amount corresponding to the estimated enclosed gas pressure, the ratio of the estimated enclosed gas amount to the enclosed gas amount at full filling, or the ratio of the estimated enclosed gas pressure to the minimum value for safe operation may be output as the judgment result, or it may simply be whether or not the enclosed gas pressure has decreased, and may be changed as appropriate.

[0093] Furthermore, in the above-described first and second embodiments, a configuration has been described in which an abnormality is diagnosed in the pressure accumulator when it is determined that the absolute pressure value at a predetermined frequency is greater than the set value for two consecutive times. However, this is not limited to this, and an abnormality may be diagnosed in the pressure accumulator when it is determined that the absolute pressure value at a predetermined frequency is greater than the set value for three or more consecutive times, or an abnormality may be diagnosed in the pressure accumulator when it is determined once that the absolute pressure value at a predetermined frequency is greater than the set value, and this may be modified as appropriate.

[0094] Furthermore, in the first and second embodiments, an average value is calculated from each pressure value identified from the absolute pressure values ​​at two predetermined frequencies, but this is not limited to this. Pressure values ​​that are thought to more strongly reflect irregularities than the multiple identified pressure values ​​may be eliminated by a filter, and values ​​other than the average value may be used as long as they can reduce the influence of irregularities.

[0095] In addition, in the first and second embodiments, the pressure detection means is described as being a pressure sensor, but the present invention is not limited to this and may be configured as a pressure sensor and a control device. In other words, the control device may sample pressure data sequentially input from the pressure sensor to the control device at predetermined time intervals to obtain a pressure value.

[0096] In addition, in the first and second embodiments, one detection result was described as a plurality of pressure values ​​constituting a waveform from 0.00 sec to 0.10 sec, but this is not limited to this, and as long as it is possible to identify the pressure at a predetermined frequency, one detection result may be one pressure value, a plurality of pressure values ​​corresponding to one cycle, a plurality of pressure values ​​corresponding to a predetermined number of cycles, a plurality of pressure values ​​obtained per another unit time, or may be changed as appropriate. Furthermore, the greater the number of cycles, the better, as it is possible to reduce the influence of irregularities.

[0097] In addition, in the first and second embodiments, the control device as the output means has been described as being configured to also control the directional control valve, the solenoid control valve, etc., but this is not limited thereto and may be provided separately from the control device that controls the directional control valve, the solenoid control valve, etc., and may be, for example, a cloud server. If the output means is configured as a cloud server, the pressure detection means and the notification means may be wirelessly connected to the cloud server. In other words, the pressure detection means and the notification means may have a communication device.

[0098] Furthermore, the notification means may be a smartphone or a tablet terminal, and in such a configuration, the determination result may be sent from the cloud server as a notification or email, or the user may access the cloud server to receive the determination result, or other appropriate configurations may be used. In addition, if the pressure detection means is configured to have a wireless communication device and a microcontroller or the like as output means, the determination result may be output to the cloud server.

[0099] Furthermore, in the first and second embodiments, the tests were carried out at room temperature, but taking into consideration the climate and temperature changes to which the internal fluid is subjected, it is also possible to use values ​​that have been temperature-corrected from the test results.

[0100] DESCRIPTION OF SYMBOLS 2 Hydraulic pump (pump) 5 Accumulator (pressure accumulation device) 6 Pressure sensor (pressure detection means) 8 Hydraulic pressure supplied circuit (supply destination) 10 Control device (output means) 11 Monitor (notification means) 101 Hydraulic circuit (fluid pressure circuit) 102 Fluid equipment status monitoring device 106 Pressure sensor (pressure detection means) 201 Hydraulic circuit (fluid pressure circuit) 202 Fluid equipment status monitoring device

Claims

1. A fluid equipment status monitoring device for diagnosing the status of a pressure accumulator in a fluid pressure circuit provided with a pump and a pressure accumulator, the fluid equipment status monitoring device comprising: a pressure detection means capable of detecting the pressure of a working fluid in the fluid pressure circuit; and an output means for outputting a judgment result at a specified frequency from the detection results by the pressure detection means.

2. The fluid equipment status monitoring device according to claim 1, wherein the predetermined frequency is a specific frequency based on the characteristics of the pump.

3. A fluid equipment status monitoring device according to claim 1 or 2, wherein the pressure detection means samples the pressure every 20 msec or less.

4. The fluid equipment status monitoring device according to claim 3, wherein the pressure detection means samples the pressure every 1 to 3 msec.

5. A fluid equipment status monitoring device as set forth in claim 1, wherein said output means performs a determination at a predetermined frequency when said pump and said pressure accumulator are connected on a circuit.

6. The fluid equipment status monitoring device according to claim 1, wherein the judgment result is obtained from pressure at a predetermined frequency multiple times.

7. A fluid equipment status monitoring device as described in claim 1, wherein the pressure detection means directly detects the working fluid pressure of the pressure accumulator, and the output means outputs, as the judgment result, a result of judgment against a predetermined reference value.

8. A fluid equipment status monitoring device as described in claim 7, wherein the output means outputs, as the judgment result, a judgment result relative to a minimum value for safe operation.

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