JP2006242136A - Pump control method and pump control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump control method capable of obtaining stable load operating speed in response to a different power source frequency. <P>SOLUTION: Power source frequency of a three-phase induction motor 23 is detected by a frequency detector 41, and the pressure corresponding to the detected power source frequency is led to each of capacity variable means 24a, and discharge flow rate of the operating fluid of each of hydraulic pumps 24 is controlled to stabilize the maximum discharge flow rate. The three-phase induction motor 23 is continuously operated, regardless of the power source frequency, and the maximum operating speed of each of the hydraulic cylinders 28 and each of hydraulic motors 29 are stabilized to obtain stable load operating speed in response to a different power source frequency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pump control method and a pump control device for driving a variable displacement pump by an induction motor.

  Conventionally, in a working machine such as an electric excavator, for example, as shown in FIG. 4, a three-phase induction motor 3 is electrically connected to an electric control panel 2 connected to a power supply line 1. Some hydraulic cylinders 7 and various hydraulic motors 8 are operated by operating the hydraulic pumps 4 and 4 and controlling the flow rate and direction of the hydraulic oil discharged from the hydraulic pumps 4 and 4 with the control valve 6. .

Here, the rotational speed N [rpm] of the rotor of the induction motor is defined as follows: the power frequency is f [Hz], the slip is s, and the number of magnetic poles is p.
N = 120f (1-s) / p (1)
And is proportional to the power supply frequency.

Therefore, a control method is known in which the number of revolutions of a compressor or the like is changed by changing the power supply frequency to change the operation of the apparatus (see, for example, Patent Document 1).
JP 2003-336889 A (page 3-4, FIG. 2)

  As described above, since the operation of the induction motor changes in proportion to the power supply frequency, for example, when a commercial AC power supply is used as the power supply of the induction motor, the frequency varies depending on the region, for example, 50 Hz in eastern Japan and 60 Hz in western Japan. , The rotational speed of the three-phase induction motor 3 changes depending on the region in which the apparatus is operated, the amount of hydraulic oil discharged from the hydraulic pumps 4 and 4 changes, and the operating speed of the hydraulic cylinder 7 and the hydraulic motor 8 changes. Changes, and there is a problem that work performance may be lowered or workability may be deteriorated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a pump control method and a pump control device capable of obtaining a stable load operating speed with respect to different power supply frequencies. .

  The invention according to claim 1 detects the power supply frequency of the induction motor that drives the variable displacement pump including the variable displacement means, and guides the signal corresponding to the detected power supply frequency to the displacement variable means, thereby providing the variable displacement pump. Is a pump control method for controlling the discharge flow rate of the working fluid of the variable displacement type by detecting the power frequency of the induction motor that drives the variable capacity pump and introducing a signal corresponding to the detected power frequency to the capacity variable means By controlling the discharge flow rate of the working fluid of the pump, it is possible to make the maximum operating speed of the load constant and to obtain a stable operating speed of the load for different power supply frequencies.

  According to a second aspect of the present invention, in the pump control method according to the first aspect, a flow rate setting signal is output corresponding to the detected power supply frequency, a pressure is output corresponding to the flow rate setting signal, and the pressure and variable The high-pressure side is selected from the negative control pressure generated by the fluid control valve that controls the working fluid supplied to the load from the capacity type pump, and is supplied to the capacity variable means, corresponding to the detected power supply frequency Output the pressure corresponding to the output flow rate setting signal, select the high pressure side from this pressure and the negative control pressure generated by the fluid control valve and supply it to the capacity variable means, the capacity by the existing negative control pressure Effectively using variable means, the discharge flow rate of the variable displacement pump is adjusted with the pressure and fluid control valve corresponding to the flow rate setting signal output corresponding to the power supply frequency. Corrected in response to the power supply frequency different at any one of the negative control pressure raw, it is possible to obtain the operating speed of the stable load.

  According to a third aspect of the present invention, in the pump control method according to the first aspect, when the detected power supply frequency is the first frequency set in advance, the working fluid supplied to the load from the variable displacement pump is controlled. When the negative control pressure generated by the fluid control valve is supplied to the capacity variable means and the detected power supply frequency is preset and is a second frequency higher than the first frequency, the negative control pressure is preset corresponding to the second frequency. The high pressure side is selected from the generated pressure and the negative control pressure and supplied to the capacity varying means. When the detected power supply frequency is the first preset frequency, the negative control pressure is supplied to the capacity varying means. When the supplied and detected power supply frequency is a second frequency that is preset and greater than the first frequency, a pressure that is preset corresponding to the second frequency is set. And by supplying to the variable capacitance means to select the high pressure side of the negative control pressure, it is possible to obtain the operating speed of the load stable corresponding to the two given supply frequency different from each other.

  The invention according to claim 4 includes a variable displacement pump provided with a capacity variable means, driven by an induction motor, a frequency detection means for detecting a power supply frequency of the induction motor, and a power supply frequency detected by the frequency detection means. And a control means for controlling the discharge flow rate of the working fluid of the variable displacement pump by guiding the signal to the variable displacement means, and detecting the power supply frequency of the induction motor that drives the variable displacement pump by the frequency detection means. Then, by controlling the discharge flow rate of the working fluid of the variable displacement pump by guiding the signal corresponding to the detected power supply frequency to the capacity variable means by the control means, the maximum operating speed of the load is made constant, and the different power supply frequencies It is possible to obtain a stable load operating speed.

  According to a fifth aspect of the present invention, in the pump control device according to the fourth aspect, the control unit outputs a flow rate setting signal corresponding to the power supply frequency detected by the frequency detection unit, and the flow rate setting output from the controller. High pressure from the solenoid valve that outputs the pressure according to the signal, the solenoid valve pressure output from the solenoid valve, and the negative control pressure generated by the fluid control valve that controls the working fluid supplied to the load from the variable displacement pump And a high pressure selection valve that selects the side and supplies it to the capacity variable means. The solenoid valve generates an electromagnetic signal corresponding to the flow rate setting signal output by the controller corresponding to the power supply frequency detected by the frequency detecting means. The valve pressure is output, and the capacity can be varied by selecting the high pressure side using the high pressure selection valve from the solenoid valve pressure and the negative control pressure generated by the fluid control valve. By supplying to the stage, it becomes possible to easily configure the control means by effectively using the capacity variable means by the existing negative control pressure, and the maximum discharge flow rate of the variable capacity pump is set to the solenoid valve pressure and the fluid control valve. It is possible to obtain a stable operating speed of the load by correcting the power supply frequency in accordance with either one of the negative control pressure generated in response to a different power supply frequency.

  According to a sixth aspect of the present invention, in the pump control device according to the fourth aspect, the control means selectively sets the switching valve for selectively switching the passage between the communication state and the cutoff state, and the power supply frequency detected by the frequency detection means. The passage is blocked by the switching valve when the first frequency is set, and the passage is blocked by the switching valve when the power supply frequency detected by the frequency detection means is a second frequency that is preset and higher than the first frequency. A controller that outputs a switching signal for setting a communication state, a pressure control valve that outputs a preset pressure corresponding to the second frequency, and a pressure control valve that is connected to the pressure control valve via the switching valve and outputs from the pressure control valve The high pressure side is selected from the generated pressure and the negative control pressure generated by the fluid control valve that controls the working fluid supplied to the load from the variable displacement pump, and is supplied to the variable capacity means. When the power supply frequency detected by the frequency detecting means is a preset first frequency, the switching valve is closed by a controller switching signal and output from the pressure control valve. When the power supply frequency detected by the frequency detecting means is a preset second frequency that is greater than the first frequency, the controller controls the controller when the negative pressure is supplied to the capacity varying means by shutting off the detected pressure from the high pressure selection valve. The switching valve is opened by the switching signal, and the pressure output from the pressure control valve is output to the high pressure selection valve. The high pressure selection valve selects the high pressure side between the pressure output from the pressure control valve and the negative control pressure. By supplying the capacity variable means, it is possible to obtain a stable load operating speed corresponding to two different predetermined power supply frequencies.

  According to the first aspect of the present invention, the power supply frequency of the induction motor is detected, and a signal corresponding to the detected power supply frequency is guided to the displacement variable means to control the discharge flow rate of the working fluid of the variable displacement pump. Thus, the maximum operating speed of the load is constant, and a stable operating speed of the load can be obtained for different power supply frequencies.

  According to the invention of claim 2, the pressure corresponding to the flow rate setting signal output corresponding to the detected power supply frequency is output, and the high pressure side is selected from this pressure and the negative control pressure generated by the fluid control valve By supplying the capacity variable means to the existing capacity variable means using the negative control pressure, the maximum discharge flow rate of the variable displacement pump can be output corresponding to the power frequency. It is possible to obtain a stable operating speed of the load by correcting with either one of the pressure corresponding to the flow rate setting signal and the negative control pressure generated by the fluid control valve.

  According to the invention of claim 3, when the detected power supply frequency is the first frequency, the negative control pressure is supplied to the capacity varying means, and when the detected power supply frequency is the second frequency, the second frequency is supplied. By selecting the high pressure side of the preset pressure and the negative control pressure corresponding to the frequency and supplying it to the capacity variable means, it is possible to achieve a stable load operating speed corresponding to two different predetermined power supply frequencies. Obtainable.

  According to the fourth aspect of the present invention, the power supply frequency of the induction motor is detected by the frequency detecting means, and a signal corresponding to the detected power supply frequency is guided to the capacity variable means by the control means, and the working fluid of the variable capacity pump By controlling the discharge flow rate, the maximum operating speed of the load can be made constant, and a stable operating speed of the load can be obtained for different power supply frequencies.

  According to the fifth aspect of the present invention, the solenoid valve pressure output from the solenoid valve in response to the flow rate setting signal output from the controller corresponding to the power supply frequency detected by the frequency detecting means, and the fluid control valve By selecting the high pressure side from the negative control pressure to be supplied to the capacity variable means by using the high pressure selection valve, it is possible to easily configure the control means by effectively using the capacity variable means based on the existing negative control pressure, and The maximum discharge flow rate of the variable displacement pump is corrected corresponding to the different power supply frequency by either the solenoid valve pressure or the negative control pressure generated by the fluid control valve to obtain a stable load operating speed. be able to.

  According to the sixth aspect of the present invention, when the power supply frequency detected by the frequency detecting means is the first frequency, the switching valve is closed by the switching signal of the controller and the pressure output from the pressure control valve is applied to the high pressure selection valve. When the power supply frequency detected by the frequency detection means is the second frequency, the switching valve is opened by the controller switching signal and output from the pressure control valve. The pressure is output to the high-pressure selection valve, and the high-pressure selection valve selects the high-pressure side of the pressure output from the pressure control valve and the negative control pressure and supplies the selected pressure to the capacity variable means. It is possible to obtain a stable load operating speed corresponding to the power supply frequency.

  Hereinafter, the present invention will be described in detail with reference to the embodiment shown in FIGS.

  FIG. 2 shows a hydraulic excavator A as a work machine. In this excavator A, an upper swing body 13 is provided on an upper portion of a lower traveling body 11 via a swing bearing portion 12 so as to be rotatable. A cab 14 is mounted, and a working device 15 is provided on the side of the cab 14 so as to be operable.

  Further, the upper swing body 3 is equipped with a pump control device shown in FIG. This pump control device includes an electric control panel 22 that is electrically connected to a power supply line 21 from a commercial AC power supply (not shown). The electric control panel 22 is provided with a three-phase induction motor 23 as an induction motor. The three-phase induction motor 23 is provided with hydraulic pumps 24 and 24 as variable displacement pumps so that they can be driven.

  Each hydraulic pump 24 has a pump passage 25 led out from the discharge port, and these pump passages 25 are controlled as fluid control valves that control the direction and flow rate of the hydraulic fluid discharged from each hydraulic pump 24 as the hydraulic fluid. The valves 26 communicate with supply ports to a number of spools 26a as movable valve bodies.

  The output ports from these spools 26a allow the hydraulic cylinders 28, 28, 28, 28, which are fluid pressure actuators as loads for operating the working device 15 and the like, and the lower traveling body 11 to travel or to the lower traveling body 11. The upper revolving unit 13 communicates with hydraulic motors 29 and 29 that are fluid pressure actuators as loads for driving the upper revolving unit 13 to rotate.

  Further, the discharge port from each spool 26a communicates with the tank 31.

  The spools 26a control the direction and the flow rate of the hydraulic oil discharged from the hydraulic pumps 24, whereby the operating directions and operating speeds of the hydraulic cylinders 28 and the hydraulic motors 29 are controlled.

  Each spool 26a is pilot-operated by a pilot pressure output from a remote control valve (not shown) operated by an operator, displaces a stroke proportional to the pilot pressure, and receives a pilot pressure from the opposite side. Each hydraulic cylinder 28 and each hydraulic motor 29 are switched to operate in the opposite directions.

  Further, a center bypass passage 33 is branched from each pump passage 25. The center bypass passage 33 is a throttle for taking out each spool 26a in a neutral state and a negative control pressure (hereinafter referred to as a negative control pressure). It is connected to the tank 31 via 34.

  From the upstream side of the throttle 34 of the center bypass passage 33, a negative control passage 36 (hereinafter referred to as a negative control passage 36) for guiding the negative control pressure that increases as the spool stroke returns to the neutral position to the displacement varying means 24a of each hydraulic pump 24. , Called negative control passage 36).

  Here, the capacity varying means 24a controls the tilt angle of the pump swash plate by the regulator 24b, and decreases the tilt angle of the pump swash plate as the negative control pressure supplied from the negative control passage 36 increases. And control to reduce the pump discharge flow rate.

  Further, the negative control passage 36 is provided with a control means 37 for controlling the discharge amount of the hydraulic oil of each hydraulic pump 24.

  This control means 37 is a controller 42 electrically connected to a frequency detector 41 as a frequency detection means connected to the power line 21, and the pressure is reduced as a signal in accordance with a flow rate setting signal from the controller 42. An electromagnetic proportional pressure reducing valve 43 as a solenoid valve that outputs pressure and a shuttle valve 44 as a high pressure selection valve are provided.

  Here, the frequency detector 41 detects the power supply frequency via the power supply line 21 and outputs the detected power supply frequency to the controller 42 as a signal.

  Further, the controller 42 outputs a flow rate setting signal to the solenoid of the electromagnetic proportional pressure reducing valve 43 corresponding to the power supply frequency output from the frequency detector 41.

  Further, the electromagnetic proportional pressure reducing valve 43 uses a secondary pressure obtained by reducing the primary pressure supplied from the pilot hydraulic power source 46 according to the flow rate setting signal output from the controller 42 as a negative signal as the electromagnetic valve pressure. The pressure is output as a pressure reducing valve pressure.

  Then, the controller 42 controls to increase the valve opening of the electromagnetic proportional pressure reducing valve 43 as the power supply frequency increases, so as to increase the pressure reducing valve pressure.

  In addition, each shuttle valve 44 selects either the high pressure side of the negative control pressure generated through the spool 26a or the pressure reducing valve pressure output from the electromagnetic proportional pressure reducing valve 43 to change the capacity varying means 24a of each hydraulic pump 24. Each of the negative control passages 36 is connected to one inlet, the output passage 48 of the electromagnetic proportional pressure reducing valve 43 is connected to the other inlet, and each hydraulic pressure is supplied to the outlet. The regulators 24b of the pump 24 are communicated with each other.

  Next, the operation of the embodiment shown in FIGS. 1 and 2 will be described.

  When power is supplied from the power line 21 to the three-phase induction motor 23 via the electric control panel 22 and the three-phase induction motor 23 is driven, each hydraulic pump 24 is driven by the three-phase induction motor 23 and hydraulic oil is supplied. It is discharged into the pump passage 25.

  The discharged hydraulic oil is subjected to direction control and flow rate control by each spool 26a of the control valve 26, and each hydraulic cylinder 28 and each hydraulic motor 29 are operated.

  At this time, if all the spools 26a are in a neutral state, the maximum negative control pressure is generated in the negative control passage 36, and this maximum negative control pressure is input to the regulator 24b through one inlet of each shuttle valve 44, and the pump discharge flow rate Is controlled to a minimum. Further, when the spool 26a is displaced, the negative control pressure decreases and the pump discharge flow rate increases.

  On the other hand, in the control means 37, a flow rate control signal is output from the controller 42 to the electromagnetic proportional pressure reducing valve 43 corresponding to the power supply frequency detected by the frequency detector 41, and the solenoid of the electromagnetic proportional pressure reducing valve 43 is responded to this output. Is excited to change the valve opening of the electromagnetic proportional pressure reducing valve 43, and the pressure reducing valve pressure changed in accordance with the valve opening is input to the shuttle valve 44 from the other inlet of each shuttle valve 44.

  In each shuttle valve 44, either the input negative control pressure or pressure reducing valve pressure is selected and supplied to each regulator 24b, and these regulators 24b are connected to each pump 24 of each hydraulic pump 24 by each variable capacity means 24a. Since the tilt angle of each plate is controlled, even if the negative control pressure decreases due to the displacement of the spool 26a, the pressure reducing valve pressure from the electromagnetic proportional pressure reducing valve 43 is input to the regulator 24b as a pseudo negative control pressure, so that the hydraulic pump It is possible to control the maximum flow rate of 24.

  Specifically, when the power supply frequency is 50 Hz and 60 Hz, for example, when the operation when the power supply frequency is 50 Hz is used as a reference, when the power supply frequency increases to 60 Hz or the like, Since the pump speed is increased, the pressure reducing valve pressure from the electromagnetic proportional pressure reducing valve 43 is applied, so that the pressure reducing valve pressure from the electromagnetic proportional pressure reducing valve 43 that has passed through the shuttle valve 44 is changed to a low pseudo negative control pressure. The tilt angle is made smaller than the maximum value to reduce the pump capacity, and the pump discharge flow rate is controlled to a predetermined maximum value that is substantially equal regardless of whether the power supply frequency is 50 Hz or 60 Hz.

  On the other hand, for example, when the operation when the power supply frequency is 60 Hz is used as a reference, the pump speed of each hydraulic pump 24 decreases when the power supply frequency decreases to 50 Hz or the like. By eliminating the valve pressure, the swash plate tilt angle of the hydraulic pump 24 is increased to the maximum value to increase the pump capacity, and the pump discharge flow rate is set to a predetermined maximum that is substantially equal regardless of whether the power supply frequency is 50 Hz or 60 Hz. Control to value.

  Next, effects of the embodiment shown in FIGS. 1 and 2 are listed.

  The frequency detector 41 detects the power supply frequency of the three-phase induction motor 23, and guides the pressure corresponding to the detected power supply frequency to each capacity variable means 24a to control the discharge flow rate of the hydraulic oil of each hydraulic pump 24. By making the maximum discharge flow rate of each hydraulic pump 24 constant, the three-phase induction motor 23 operates as it is regardless of the power supply frequency, the maximum operating speed of each hydraulic cylinder 28 and each hydraulic motor 29 is made constant, and different power supply frequencies In contrast, a stable load operating speed can be obtained.

  Specifically, the pressure reducing valve pressure obtained by reducing the primary pressure in response to the flow rate setting signal output corresponding to the power supply frequency detected by the frequency detector 41 is output by the electromagnetic proportional pressure reducing valve 43, and this pressure reducing valve pressure is output. By selecting the high pressure side from the negative pressure and the negative control pressure by the shuttle valve 44 and supplying it to the capacity variable means 24a, each hydraulic pump can be used effectively corresponding to different power supply frequencies by effectively using the capacity variable means 24a by the existing negative control pressure. The discharge flow rate of 24 can be corrected by either the pressure reducing valve pressure from the electromagnetic proportional pressure reducing valve 43 or the negative control pressure, and a stable load operating speed can be obtained.

  In particular, by using the electromagnetic proportional pressure reducing valve 43 to generate the pseudo negative control pressure, it is possible to cope with a plurality of continuously different power supply frequencies.

  Moreover, since the control means 37 and the frequency detector 41 can be retrofitted to the negative control passage 36 and the power supply line 21, respectively, it can be easily applied to an existing fluid pressure circuit or the like.

  Further, by using such a pump control device for a working machine such as the hydraulic excavator A, it is possible to obtain stable operating speeds of the hydraulic cylinders 28 and the hydraulic motors 29 as loads, and therefore, for example, power supply frequencies are different. When working machines are used in areas, etc., it is possible to reliably prevent deterioration of work capacity or workability, and there is no need to change the design corresponding to each of different power supply frequencies. The manufacturing cost can be suppressed by improving the property.

  Next, another embodiment of the pump control device will be described with reference to FIG. In addition, about the structure and effect | action similar to embodiment shown by the said FIG.1 and FIG.2, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the embodiment shown in FIG. 3, instead of the electromagnetic proportional pressure reducing valve 43 of the embodiment shown in FIGS. 1 and 2, a pressure reducing valve 51 as a pressure control valve and an electromagnetic wave as a switching valve are used. The switching valve 52 is provided, and corresponds to two power supply frequencies different from 50 Hz as a preset first frequency and 60 Hz as a preset second frequency.

  The pressure reducing valve 51 communicates with the other inlet of each shuttle valve 44 through the output passage 54, and is a secondary pressure obtained by reducing the primary pressure supplied from the pilot hydraulic power source 46 in accordance with the power frequency of 60 Hz. The pressure reducing valve pressure is output as a negative signal pressure.

  The electromagnetic switching valve 52 is provided in the output passage 54, and when the power supply frequency detected by the frequency detector 41 is 50 Hz based on the switching signal output from the controller 42, the pressure reducing valve 51 and each shuttle valve 44. And the other inlet of each shuttle valve 44 is connected to the tank 31 via a line 55, and the pressure reducing valve 51 and each shuttle valve 44 are connected when the power frequency detected by the frequency detector 41 is 60 Hz. The communication state is established.

  The operation of the embodiment shown in FIG. 3 will be described.

  When power is supplied from the power line 21 to the three-phase induction motor 23 via the electric control panel 22 and the three-phase induction motor 23 is driven, each hydraulic pump 24 is driven by the three-phase induction motor 23 and hydraulic oil is supplied. The discharged hydraulic oil is discharged to the pump passage 25, and the direction and flow rate of the discharged hydraulic oil are controlled by the spools 26a of the control valve 26, and the hydraulic cylinders 28 and the hydraulic motors 29 are operated.

  At this time, if all the spools 26a are in a neutral state, the maximum negative control pressure is generated in the negative control passage 36, and this maximum negative control pressure is input to the regulator 24b through one inlet of each shuttle valve 44, and the pump discharge flow rate Is controlled to a minimum. Further, when the spool 26a is displaced, the negative control pressure decreases and the pump discharge flow rate increases.

  On the other hand, in the control means 37, a switching signal is output from the controller 42 to the electromagnetic switching valve 52 corresponding to the power supply frequency detected by the frequency detector 41.

  For example, when the power supply frequency is 50 Hz, the electromagnetic switching valve 52 is switched to the closed state by the switching signal output from the controller 42, the pressure reducing valve 51 and the shuttle valve 44 are shut off, and the output passage 54 is opened. The line 55 communicates with the tank 31 and only the negative control pressure is output from the shuttle valve 44 to the capacity varying means 24a.

  When the power supply frequency becomes 60 Hz, the electromagnetic switching valve 52 is switched to the open state by the switching signal output from the controller 42, and the pressure reducing valve 51 and the shuttle valve 44 are in communication with each other. The high pressure side of the outputted pressure reducing valve pressure and negative control pressure is selected by the shuttle valve 44 and outputted to the capacity varying means 24a. For this reason, even if the negative control pressure drops due to the displacement of the spool 26a, the pressure reduction valve pressure from the pressure reduction valve 51 is input to the regulator 24b as a pseudo negative control pressure, so that the maximum flow rate of the hydraulic pump 24 is 50 Hz It is controlled to be substantially equal to the case of.

  As described above, in the embodiment shown in FIG. 3, when the power supply frequency detected by the frequency detector 41 is the first frequency, for example, 50 Hz, the electromagnetic switching valve 52 is closed by the switching signal of the controller 42. The pressure output from the pressure reducing valve 51 is cut off with respect to the shuttle valve 44, the negative control pressure is supplied to the capacity varying means 24a, and the power frequency detected by the frequency detector 41 is a frequency higher than the first frequency, for example, 60 Hz. In response to this, the electromagnetic switching valve 52 is opened by the switching signal of the controller 42, and the pressure reducing valve pressure output from the pressure reducing valve 51 is output to the shuttle valve 44. The pressure reducing valve output from the pressure reducing valve 51 is output from the shuttle valve 44. The high pressure side of the valve pressure and the negative control pressure is selected and supplied to the capacity varying means 24a.

  In other words, only the negative control pressure is applied to the power frequency having the smaller value among the two different power frequencies, so that the swash plate tilt angle of the hydraulic pump 24 can be used up to the maximum value, and the value is For the larger power supply frequency, by applying the high pressure side of the negative control pressure and the pressure reducing valve output from the pressure reducing valve 51, the low pressure reducing valve pressure is set as the pseudo negative control pressure even when the negative control pressure decreases. The configuration is such that the swash plate tilt angle of the hydraulic pump 24, which increases the speed compared with the case of operating at the power frequency with the smaller value, is suppressed to be smaller than the maximum value.

  For this reason, the pump discharge flow rate can be controlled to a substantially equal predetermined maximum value even for two different predetermined power supply frequencies, and a stable load operating speed can be obtained corresponding to the two different predetermined power supply frequencies. be able to.

  In particular, since the switching of two different power supply frequencies corresponds to the switching of the electromagnetic switching valve 52, the control of the control means 37 is facilitated.

  In the embodiment shown in FIG. 3, the power supply frequency is not limited to 50 Hz and 60 Hz, but can correspond to any two power supply frequencies having different values.

  Further, in each of the above embodiments, the pump control device can be used in correspondence with any electric variable displacement pump or variable displacement pump driven by an electric device other than a work machine such as an electric hydraulic excavator. It is.

It is a circuit diagram showing one embodiment of a pump control device concerning the present invention. It is a side view which shows the working machine provided with the pump control apparatus same as the above. It is a circuit diagram which shows other embodiment of the pump control apparatus which concerns on this invention. It is a circuit diagram which shows the pump control apparatus of a prior art example.

Explanation of symbols

23 Three-phase induction motors as induction motors
24 Hydraulic pump as variable displacement pump
24a Variable capacity means
26 Control valve as fluid control valve
37 Control means
41 Frequency detector as frequency detection means
42 Controller
43 Pressure reducing valve as solenoid valve
44 Shuttle valve as high pressure selection valve
51 Pressure reducing valve as pressure control valve
52 Solenoid switching valve as switching valve

Claims (6)

Detecting the power frequency of the induction motor that drives the variable displacement pump equipped with variable capacity means,
A pump control method characterized by controlling a discharge flow rate of a working fluid of a variable displacement pump by guiding a signal corresponding to the detected power supply frequency to a displacement variable means. Outputs a flow rate setting signal corresponding to the detected power frequency,
Pressure is output in response to this flow setting signal,
2. The high pressure side is selected from this pressure and a negative control pressure generated by a fluid control valve for controlling the working fluid supplied to the load from the variable displacement pump, and supplied to the variable capacity means. The pump control method as described. When the detected power supply frequency is a preset first frequency, a negative control pressure generated by a fluid control valve that controls the working fluid supplied from the variable displacement pump to the load is supplied to the displacement variable means, When the detected power supply frequency is a second frequency that is set in advance and is greater than the first frequency, the capacity variable means is selected by selecting the high pressure side from the pressure set in advance corresponding to the second frequency and the negative control pressure. The pump control method according to claim 1, wherein the pump control method is provided. A variable displacement pump having a capacity variable means and driven by an induction motor;
Frequency detection means for detecting the power supply frequency of the induction motor;
A pump control apparatus comprising: control means for controlling the discharge flow rate of the working fluid of the variable displacement pump by guiding a signal corresponding to the power supply frequency detected by the frequency detection means to the displacement variable means. The control means
A controller that outputs a flow rate setting signal corresponding to the power supply frequency detected by the frequency detection means;
A solenoid valve that outputs pressure according to the flow rate setting signal output from the controller;
High pressure supplied to the variable capacity means by selecting the high pressure side from the solenoid valve pressure output from the solenoid valve and the negative control pressure generated by the fluid control valve that controls the working fluid supplied to the load from the variable displacement pump The pump control device according to claim 4, further comprising a selection valve. The control means
A switching valve for selectively switching the passage between a communication state and a cutoff state;
When the power supply frequency detected by the frequency detection means is the first preset frequency, the passage is shut off by the switching valve, and the power supply frequency detected by the frequency detection means is preset and greater than the first frequency. A controller that outputs a switching signal that causes the passage to communicate with the switching valve when there are two frequencies;
A pressure control valve that outputs a preset pressure corresponding to the second frequency;
This pressure control valve is connected via a switching valve, and is high pressure from the pressure output from the pressure control valve and the negative control pressure generated by the fluid control valve that controls the working fluid supplied to the load from the variable displacement pump. The pump control device according to claim 4, further comprising a high-pressure selection valve that selects a side and supplies the variable capacity means to the displacement variable means.

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