Fluid pressure unit

Abstract

A fluid pressure unit comprises: an inverter (17); a motor (10) controlled by the inverter; a pump (11) driven by the motor to discharge a fluid; a detection unit (16) for detecting the pressure and / or flow of the fluid; a controller (20) for controlling the inverter based on a detection value detected by the detection unit so that the pressure and / or flow of the pump becomes a predetermined value; and a suppression unit (33) configured to suppress a change in the output of the inverter caused by a pulsating frequency component of the fluid contained in the detection value.

Description

Technical Field

[0001] The present disclosure relates to a fluid pressure unit. Background Art

[0002] There is known a technique in which, when a hydraulic pump is driven by a motor, pulsation occurs in the discharge pressure of the hydraulic pump due to fluctuations in the discharge volume of the hydraulic pump and torque ripples of the motor (see, for example, Patent Document 1).

[0003] <Prior Art Literature>

[0004] <Patent Document>

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-90669 Summary of the Invention

[0006] <Problems to be Solved by the Invention>

[0007] When pulsation occurs in the discharge pressure of the pump, when an inverter is used to control the motor for driving the pump based on the detection values ​​of the pressure and / or flow of the fluid discharged from the pump, the stability of the pressure and / or flow of the fluid discharged from the pump may sometimes decrease.

[0008] An object of the present disclosure is to provide a fluid pressure unit capable of suppressing a decrease in stability of the pressure and / or flow rate of a fluid discharged from a pump.

[0009] <Methods used to solve the problem>

[0010] The present disclosure provides a fluid pressure unit, comprising: an inverter; a motor controlled by the inverter; a pump driven by the motor to discharge fluid; a detection unit for detecting the pressure and / or flow of the fluid; a controller for controlling the inverter based on a detection value detected by the detection unit so that the pressure and / or flow of the pump becomes a predetermined value; and a suppression unit configured to suppress output changes of the inverter caused by a pulsating frequency component of the fluid contained in the detection value.

[0011] According to this aspect, it is possible to suppress a decrease in the stability of the pressure and / or flow rate of the fluid discharged from the pump.

[0012] In the above-described fluid pressure unit, the suppression unit may set the suppression amount at a frequency component higher than the pulsation frequency component to be lower than the suppression amount at the pulsation frequency component.

[0013] According to this aspect, it is possible to suppress a decrease in the responsiveness of the motor and the pump in a frequency range higher than the pulsation frequency of the fluid.

[0014] In the above-described fluid pressure unit, the suppressing unit may be a band-stop filter that includes the frequency of the pulsation frequency component in a stop band.

[0015] According to this aspect, it is possible to suppress a decrease in the responsiveness of the motor and the pump in a frequency region outside the stop band.

[0016] In the above-mentioned fluid pressure unit, the band rejection filter may be a notch filter that includes the frequency of the pulsation frequency component in a rejection band.

[0017] According to this aspect, it is possible to further suppress a decrease in the responsiveness of the motor and the pump in the frequency region outside the stop band.

[0018] In the above-described fluid pressure unit, the resistance band may be changed according to a rotation speed of the pump.

[0019] According to this aspect, even if the rotation speed of the pump changes, it is possible to suppress a decrease in the stability of the pressure and / or flow rate of the fluid discharged from the pump.

[0020] In the above-described fluid pressure unit, the resistance band may be changed according to a product of a rotation speed of the pump and a number of teeth of the pump.

[0021] According to this aspect, even if the rotation speed of the pump changes, it is possible to accurately suppress a decrease in the stability of the pressure and / or flow rate of the fluid discharged from the pump.

[0022] In the above-described fluid pressure unit, the detection portion may include a pressure sensor that detects the pressure of the fluid.

[0023] According to this aspect, it is possible to accurately suppress a decrease in the stability of the pressure of the fluid discharged from the pump.

[0024] In the above-mentioned fluid pressure unit, the detection portion may include a flow rate sensor that detects a flow rate of the fluid.

[0025] According to this aspect, it is possible to accurately suppress a decrease in the stability of the flow rate of the fluid discharged from the pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a diagram showing a configuration example of a system including a fluid pressure unit according to one embodiment.

[0027] Figure 2 This is a diagram exemplarily showing a stable pressure waveform when the inverter is controlled so as to eliminate pulsation of the discharge pressure of the pump.

[0028] Figure 3This is a diagram exemplarily showing an unstable pressure waveform when the inverter is controlled so as to eliminate pulsation of the discharge pressure of the pump.

[0029] Figure 4 This is a diagram showing an example of changes in the output of the inverter due to the pulsation frequency component of the fluid included in the detection value.

[0030] Figure 5 This is a diagram showing an example of a case where a change in the inverter output caused by a pulsation frequency component of the fluid included in the detection value is suppressed.

[0031] Figure 6 This is a diagram exemplarily showing a pressure waveform when a change in the inverter output caused by a pulsation frequency component of the fluid included in the detection value is suppressed.

[0032] Figure 7 1 is a diagram showing a first configuration example of the fluid pressure unit.

[0033] Figure 8 This is a diagram showing an example of a pressure-flow rate diagram.

[0034] Figure 9 1 is a diagram showing a second configuration example of the fluid pressure unit. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments will be described.

[0036] Figure 1 1 is a diagram showing a configuration example of a system including a fluid pressure unit according to one embodiment. Figure 1 The illustrated system 100 causes the actuator 13 to perform desired motions using fluid supplied from a fluid pressure unit 200. The system 100 includes the fluid pressure unit 200, a control valve 19, and the actuator 13. The actuator 13 is an example of a load that is actuated by the fluid supplied from the fluid pressure unit 200. The actuator 13 is connected to the fluid pressure unit 200 via the control valve 19.

[0037] Fluid pressure unit 200 uses motor 10 controlled by inverter 17 to drive pump 11, supplying fluid in tank 12 to actuator 13, such as a cylinder. When the fluid is oil, the fluid pressure unit is also referred to as an oil pressure unit. The fluid is not limited to liquids such as oil; it can also be gas.

[0038] The fluid pressure unit 200 includes an inverter 17 , a motor 10 , a pump 11 , a tank 12 , a pressure sensor 16 , a controller 20 , and a suppressor 33 .

[0039] The inverter 17 controls the motor 10 according to a command (control signal) supplied from the controller 20. The inverter 17 is a circuit for adjusting the power supplied to the motor 10, and has, for example, a three-phase bridge circuit for outputting a three-phase AC current.

[0040] The motor 10 is a synchronous electric motor controlled by an inverter 17 , and is driven by an alternating current output from the inverter 17 .

[0041] The pump 11 is driven by the motor 10 controlled by the inverter 17 to discharge the fluid. For example, the pump 11 draws the fluid from the tank 12 via the suction path 14 and compresses it, and discharges the compressed fluid to the actuator 13 via the discharge path 15 and the control valve 19. The fluid output from the actuator 13 returns to the tank 12 via the control valve 19 and the return path 9.

[0042] exist Figure 1 In the illustrated example, discharge path 15 includes discharge pipes 15b, 15c, 15d, and 15e through which fluid discharged from pump 11 passes. The discharge path via discharge pipes 15b and 15c on the fluid pressure unit 200 side is connected to the discharge path via discharge pipes 15d and 15e on the actuator 13 side at connection point 15a. Meanwhile, return path 9 includes return pipes 9a and 9b through which fluid output from actuator 13 passes.

[0043] For example, discharge pipes 15b and 15c may have higher rigidity than discharge pipes 15d and 15e. For example, discharge pipes 15d and 15e may be hoses formed from an elastomer such as rubber or resin, while discharge pipes 15b and 15c may be tubes formed from a metal block having higher rigidity than the elastomer. Return path 9 (return pipes 9a and 9b) may be made of the same material as discharge path 15, or a different material.

[0044] The pressure sensor 16 is an example of a detection unit that detects the pressure of the fluid discharged from the pump 11 and outputs the detected fluid pressure (hereinafter also referred to as detection pressure Pd). The pressure sensor 16 detects the pressure of the fluid flowing through the discharge path 15. In this example, the pressure of the fluid discharged from the pump 11 to the discharge pipe 15b of the discharge path 15 via the discharge pipe 15c is detected.

[0045] The controller 20 is based on the pressure detection value detected by the pressure sensor 16 (in Figure 1In the example shown, a command for controlling the inverter 17 is output to control the pressure of the fluid discharged from the pump 11 (discharge pressure Po) so that it reaches a predetermined value (for the detection pressure Pd). For example, based on the pressure detection value detected by the pressure sensor 16, the controller 20 activates the inverter 17 to control the motor 10 so that the discharge pressure Po of the pump 11 reaches a target pressure. The target pressure is specified, for example, by a pressure command supplied from outside the controller 20. Furthermore, the pressure at the input end of the actuator 13 of the pump 11 via the discharge path 15 is referred to as the load pressure Pa.

[0046] However, when the motor 10 drives the pump, the discharge pressure Po of the pump 11 pulsates due to the driving of the pump 11. Therefore, the pressure pulsation frequency component of the fluid may be included in the pressure detection value of the pressure sensor 16. In this case, if the controller 20 controls the inverter 17 based on the pressure detection value of the pressure sensor 16, the pressure pulsation frequency component included in the pressure detection value may reduce the stability of the discharge pressure Po of the pump 11.

[0047] For example, the controller 20 performs a method (pulsation compensation method) of controlling the inverter 17 based on the pressure detection value of the pressure sensor 16 to eliminate the pulsation of the discharge pressure Po, thereby Figure 2 As shown in FIG. 1 , the pulsation of the discharge pressure Po and the load pressure Pa can be suppressed. However, in the pulsation compensation method, if the frequency band of the pulsation of the discharge pressure Po is high, the control frequency band of the controller 20 for the inverter 17 will be insufficient, and thus Figure 3 As shown, the discharge pressure Po and the load pressure Pa may become unstable. For example, if the controller 20 controls the inverter 17 in a manner that eliminates pulsation above the control band, the command (control signal) supplied from the controller 20 to the inverter 17 may vibrate, and the discharge pressure Po and the load pressure Pa may hunt.

[0048] Figure 1 The illustrated fluid pressure unit 200 according to one embodiment includes a suppressing unit 33 configured to suppress changes in the output of the inverter 17 caused by a pressure pulsation frequency component of the fluid included in the pressure detection value of the pressure sensor 16. Since the suppressing unit 33 suppresses changes in the output of the inverter 17 caused by the pressure pulsation frequency component of the fluid included in the pressure detection value of the pressure sensor 16, it is possible to suppress a decrease in the stability of the discharge pressure Po and the load pressure Pa of the pump 11.

[0049] Figure 4This diagram illustrates an example of how inverter output changes due to the pulsation frequency component of the fluid included in the detection value. When controller 20 controls inverter 17 based on the pressure detection value of pressure sensor 16, the pressure pulsation frequency component of the fluid included in the pressure detection value of pressure sensor 16 may be superimposed on the AC current output from inverter 17. Figure 4 The waveform is shown as an example of a fluid pressure pulsation frequency component included in the pressure detection value of pressure sensor 16 superimposed on one phase of AC current iu output from inverter 17. The same pressure pulsation frequency component is also superimposed on the other phase of AC current output from inverter 17 (for example, AC currents iv and iw).

[0050] because Figure 1 The suppression unit 33 shown suppresses the change in the output AC current of the inverter 17 caused by the pressure pulsation frequency component of the fluid contained in the pressure detection value of the pressure sensor 16, so that Figure 5 As shown in FIG. 1 , the pressure pulsation frequency component superimposed on the output AC current can be suppressed. Since the inverter 17 is not controlled in a manner to eliminate the pulsation of the discharge pressure Po, Figure 6 As shown, slight pulsation may sometimes remain in the discharge pressure Po. However, since the pressure pulsation is attenuated in the discharge path from the connection point 15a to the actuator 13, the load pressure Pa at the input end of the actuator 13 is substantially constant.

[0051] The suppression unit 33 can set the suppression amount for frequency components higher than the pressure pulsation frequency component of the fluid included in the pressure detection value of the pressure sensor 16 to be lower than the suppression amount for the pressure pulsation frequency component. This approach can suppress a decrease in the responsiveness of the motor 10 and pump 11 in a frequency range higher than the pressure pulsation frequency of the fluid. For example, it can suppress the situation where the rapid operation of the motor 10 and pump 11 is hindered.

[0052] The suppressor 33 may be a band-stop filter that includes the frequency of the fluid pressure pulsation frequency component included in the pressure detection value of the pressure sensor 16 within the stop band. This configuration can suppress the reduction in the responsiveness of the motor 10 and pump 11 in the frequency range outside the stop band.

[0053] The band-stop filter may be a notch filter that includes the frequency of the fluid pressure pulsation frequency component included in the pressure detection value of the pressure sensor 16 within the stop band. Since signals in frequency regions outside the stop band are less likely to be attenuated, the notch filter can further suppress any reduction in the responsiveness of the motor 10 and pump 11 in frequency regions outside the stop band.

[0054] The stop band of the band-rejection filter or notch filter can be changed according to the rotation speed of the pump 11. According to this embodiment, even if the rotation speed of the pump 11 changes, the stop band is adjusted to an appropriate stop band according to the rotation speed, thereby suppressing the decrease in the stability of the discharge pressure Po of the pump 11.

[0055] The stop band can be changed by multiplying the rotation speed of the pump 11 by the number of teeth of the pump 11. According to this configuration, even if the rotation speed of the pump 11 changes, a decrease in the stability of the discharge pressure Po of the pump 11 can be accurately suppressed.

[0056] The number of teeth of the pump 11 is generally about 9 to 10 or more. For example, when the pump 11 is a positive displacement pump, pulsation corresponding to the product of the rotation speed of the pump 11 and the number of teeth of the pump 11 occurs in the discharge pressure Po. Figure 4 The waveform is shown as an example of a waveform in which a pulsation frequency of 5 to 100 [Hz]×13 [tooths] is superimposed on the output AC current of the inverter 17 when the number of teeth of the pump 11 is 13.

[0057] It should be noted that the suppression unit 33 may be configured by hardware or by the cooperative operation of hardware and software.

[0058] Figure 7 1 is a diagram showing a first configuration example of a fluid pressure unit. Figure 7 The composition shown in Figure 1 The description of the same configuration as that shown will be omitted by citing the above description. Figure 7 The illustrated fluid pressure unit 200A may include a speed sensor 18. The speed sensor 18 detects the speed of the motor 10 and outputs the detected speed ωd.

[0059] The controller 20 includes a notch filter 32 that includes the frequencies of the pulsation frequency components included in the detected pressure Pd within a stopband. The notch filter 32 changes the stopband (notch frequency) based on the speed ωd detected by the speed sensor 18. Alternatively, the notch filter 32 changes the stopband (notch frequency) based on the command speed ω* (more preferably, the old speed ω^ a unit time prior to the command speed ω*), described later. These configurations allow the notch filter 32 to adjust the stopband to include the frequencies of the pulsation frequency components that vary with the rotational speed of the pump 11, thereby suppressing any decrease in the stability of the pressure and / or flow rate of the fluid discharged from the pump 11.

[0060] The controller 20 controls the operation of the inverter 17 for driving the motor 10 based on the pressure Pd detected by the pressure sensor 16, the flow rate Qd calculated based on the speed ωd detected by the speed sensor 18, and a map 21 consisting of target pressure, target flow rate, and horsepower limit (also referred to as a PQ map). The flow rate Qd calculated by the controller 20 represents an estimated value of the flow rate Q of the fluid discharged from the pump 11 to the discharge path 15.

[0061] The controller 20 multiplies the detected speed ωd [1 / s] by the volume q [m 3 ] to calculate the flow rate Qd[m 3 / s]. Since the volume q of the pump 11 is constant, it is a fixed value. The controller 20 derives the target horsepower Rr from the PQ diagram 21 based on the target pressure Pr supplied from the outside and the flow rate Qd calculated by the multiplier 31. On the other hand, the controller 20 derives the detected horsepower Rd (=Pd×Qd) by multiplying the pressure Pd detected by the pressure sensor 16 by the flow rate Qd calculated by the multiplier 31 using the multiplier 23. The controller 20 derives the error Re (=Rr-Rd) between the target horsepower Rr and the detected horsepower Rd using the subtractor 22. The controller 20 has a PID control unit 24, which derives the command speed ω* (in PID, P represents proportional, I represents integral, and D represents differential) for making the error Re close to zero through PID control. The command speed ω* can be derived by PI control.

[0062] The controller 20 can calculate the old speed ω^ before the unit time (for example, the control cycle) by delaying the command speed ω* using a delay device (not shown), and multiply the old speed ω^ [1 / s] by the volume q [m 3 ] to calculate the flow rate Qd[m 3 / s].

[0063] The controller 20 includes a voltage setting unit 29 that sets a command voltage Vr for operating the inverter 17 that drives the motor 10 based on the command speed ω*.

[0064] The functions of each unit of the controller 20 , such as the PID control unit 24 , are realized by operating a processor (eg, a CPU (Central Processing Unit)) using a program stored in a memory in a readable manner.

[0065] Figure 8This diagram shows an example of a pressure-flow rate diagram. PQ diagram 21 consists of a maximum flow rate line corresponding to the maximum set flow rate Q0, a maximum horsepower curve consisting of a curve corresponding to the maximum horsepower limit L0, and a maximum pressure line corresponding to the maximum set pressure P0. Since flow rate Q is equivalent to the product of the rotational speed ω (rotational speed) of motor 10 and the volume q of pump 11, it is equivalent to the rotational speed ω.

[0066] The controller 20 operates the inverter 17 for driving the motor 10 in such a manner that the pressure Pd detected by the pressure sensor 16 and the flow rate Qd calculated based on the detection speed ωd or the command speed ω* operate on the line formed by the set pressure Pn-set flow rate Qn-set horsepower curve Ln in the PQ diagram 21.

[0067] Figure 9 : is a diagram showing a second configuration example of a fluid pressure unit. Figure 9 The composition shown in Figure 1 、 Figure 7 The description of the same configuration as that shown will be omitted by citing the above description. Figure 9 The fluid pressure unit 200B shown may include a flow sensor 8. The flow sensor 8 is an example of a detection unit for detecting the flow rate Q of the fluid discharged from the pump 11 to the discharge path 15, and outputs the detected flow rate Qd of the fluid (hereinafter also referred to as the detected flow rate Qd). Although the flow sensor 8 detects the flow rate Q of the fluid flowing through the discharge pipe 15b of the discharge path 15, for example, it may also detect the flow rate Q of the fluid flowing through the discharge pipe 15d or the discharge pipe 15e. The controller 20 divides the detected flow rate Qd [m 3 / s] divided by the volume q[m 3 ], thereby calculating the detection speed ωd[1 / s].

[0068] The controller 20 includes a notch filter 32 that includes the frequencies of the pulsation frequency components included in the detected pressure Pd within a stopband. The notch filter 32 changes the stopband (notch frequency) based on the speed ωd detected by the divider 34 of the controller 20. This configuration allows the notch filter 32 to adjust the stopband to include the frequencies of the pulsation frequency components that vary with the rotational speed of the pump 11, thereby suppressing any decrease in the stability of the pressure and / or flow rate of the fluid discharged from the pump 11.

[0069] Although the above embodiments are described, it should be understood that various changes in form or details may be made without departing from the spirit and scope of the claims. Various modifications and improvements such as combination with or replacement of part or all of other embodiments may be made.

[0070] For example, the controller 20 can control the inverter so that the pressure and / or flow rate of the pump reaches a predetermined value based on the flow rate detected by the flow sensor 8. This is because the controller 20 can use the pipe resistance of the discharge path 15 to calculate the pressure of the fluid based on the flow rate detected by the flow sensor 8.

[0071] This international application claims priority based on Japanese Patent Application No. 2020-115853 filed on July 3, 2020, and incorporates the entire contents of Japanese Patent Application No. 2020-115853 into this international application.

[0072] Explanation of symbols

[0073] 8: Flow sensor;

[0074] 9: return path;

[0075] 10: Motor;

[0076] 11: Pump;

[0077] 12: slot;

[0078] 13: actuator;

[0079] 14: Inhalation path;

[0080] 15: discharge path;

[0081] 16: pressure sensor;

[0082] 17: Inverter;

[0083] 18: speed sensor;

[0084] 19: control valve;

[0085] 20: controller;

[0086] 32: Notch filter;

[0087] 33: inhibitory part;

[0088] 100: system;

[0089] 200, 200A, 200B: Fluid pressure unit.

Claims

1. A fluid pressure unit comprising: Inverter; a motor controlled by the inverter; a pump driven by the motor to discharge the fluid; a detection unit, for detecting the pressure and / or flow of the fluid; a controller configured to control the inverter based on the detection value detected by the detection unit so that the pressure and / or flow rate of the pump becomes a predetermined value; as well as The suppressing unit is configured to suppress a pulsation component having a higher frequency than the output AC current and superimposed on the output AC current of the inverter due to the pulsation frequency component of the fluid included in the detection value.

2. The fluid pressure unit according to claim 1, wherein: The suppression unit sets the suppression amount at a frequency component higher than the pulsation frequency component to a suppression amount lower than the pulsation frequency component.

3. The fluid pressure unit according to claim 2, wherein: The suppressing unit is a band-stop filter that includes the frequency of the pulsation frequency component in a stop band.

4. The fluid pressure unit according to claim 3, wherein: The band rejection filter is a notch filter that includes the frequency of the pulsation frequency component in a rejection band.

5. The fluid pressure unit according to claim 3, wherein: The stop band varies depending on the rotational speed of the pump.

6. The fluid pressure unit according to claim 4, wherein: The stop band varies depending on the rotational speed of the pump.

7. The fluid pressure unit according to claim 5, wherein: The stop band varies according to the product of the rotational speed of the pump and the number of teeth of the pump.

8. The fluid pressure unit according to claim 6, wherein: The stop band varies according to the product of the rotational speed of the pump and the number of teeth of the pump.

9. The fluid pressure unit according to any one of claims 1 to 8, wherein: The detection unit includes a pressure sensor that detects the pressure of the fluid.

10. The fluid pressure unit according to any one of claims 1 to 8, wherein: The detection unit includes a flow sensor for detecting a flow rate of the fluid.

Images