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Patent Searching and Data


Title:
PUMP CONTROL DEVICE AND PUMP CONTROL METHOD
Document Type and Number:
WIPO Patent Application WO/2018/024790
Kind Code:
A1
Abstract:
To provide a pump control device and a pump control method enables to change the setting of a pump flow. The controller (34) is to obtain the sum total value and the maximum value of the demanded flows from the respective hydraulic actuators. The controller (34) is, with respect to the maximum value, to set the pump flow command value based on a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value. By changing the value of the gain, setting of the pump flow is to become easily changeable.

Inventors:
HATA, Yoshihiko (10-1 Yoga 4-chome,Setagaya-k, Tokyo Tokyo 30, 〒1588530, JP)
KISHIDA, Kouji (10-1 Yoga 4-chome,Setagaya-k, Tokyo Tokyo 30, 〒1588530, JP)
MATOBA, Nobuaki (1-14, Wadamiyadouri 7-chome, Hyogo-ku, Kobe-shi Hyogo 63 Japan,Kobe-sh, Hyogo Hyogo 6520863, 〒6520863, JP)
ASANO, Hiroshi (1-14, Wadamiyadouri 7-chome, Hyogo-ku, Kobe-shi, Hyogo 63 Japan,Kobe-sh, Hyogo Hyogo 6520863, 〒6520863, JP)
Application Number:
EP2017/069571
Publication Date:
February 08, 2018
Filing Date:
August 02, 2017
Export Citation:
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Assignee:
CATERPILLAR SARL (Route de Frontenex 76, 1208 Geneva, 1208, CH)
International Classes:
F15B11/16; E02F9/22; F04B49/06; F15B21/08
Foreign References:
EP0587902A11994-03-23
JP2013543086A2013-11-28
EP1655469A12006-05-10
JP2013543086A2013-11-28
Attorney, Agent or Firm:
BRP RENAUD UND PARTNER MBB (Königstraße 28, Stuttgart, 70173, DE)
Download PDF:
Claims:
CLAIMS

[Claim 1]

A pump control device for controlling a flow of a working fluid discharged from a pump with respect to a plurality of flow pressure actuators operated in accordance with respective operations of a plurality of operators, comprising a controller which is to obtain a demanded flow from each flow pressure actuator according to a signal generated by operation of each operator, and while obtaining the sum total value and the maximum value of these demanded flows, with respect to the maximum value, it is to set the pump flow command value on the basis of a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value.

[Claim 2]

A pump control device described in the Claim 1 comprising a switching means for setting by switching the gain in the pump control device .

[Claim 3]

A pump control method for controlling the flow of working fluid discharged from a pump with respect to a plurality of flow pressure actuators, obtaining the sum total value and the maximum value of these demanded flows, with respect to the maximum value, setting the pump flow command value on the basis of a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value.

[Claim 4]

A pump control method described in the Claim 3 that switches the gain in accordance with setting.

Description:
DESCRIPTION

TITLE OF THE INVENTION

Pump control device and pump control method

FIELD OF THE INVENTION

[0001]

The present invention relates to a pump control device and a pump control method for controlling a flow of a working fluid discharged from a pump with respect to a plurality of flow pressure actuators .

BACKGROUND OF THE RELATED ART

[0002]

Conventionally, as a working machine, such as a hydraulic excavator, which is equipped with an engine and a variable capacity pump such as a swashplate type that is driven by said engine and discharges hydraulic fluid and multiple hydraulic actuators such as cylinders and motors that operate by receiving supply of hydraulic fluid discharged from said pump, and also equipped with a hydraulic system that performs positive control in which only the necessary flow corresponding to the lever operation amount for operating these hydraulic actuators is discharged from the pump, is widely known.

[0003]

In such a working machine, there are cases where a compound operation such as interlocking operation of the front working device while rotating is performed as if loading of earth and sand into a truck for example . For such a compound operation, for example, a configuration is known in which the demanded flow of the actuator is predetermined and the square root of the sum of squares of the demanded flows of the actuators is calculated to obtain the pump flow command value (for example, refer to Patent Document 1) .

DOCUMENT OF PRIOR ART PATENT DOCUMENT

[0004]

[PATENT DOCUMENT 1] Japanese Unexamined Patent Application Publication (Translation of PCT Application) 2013-543086

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0005]

However, in the configuration of the above-mentioned Patent Document 1, since the setting method of the pump flow is fixed to a certain value, it is difficult to change the setting of the pump flow according to different operation modes, for example, when emphasis is placed on fuel efficiency or in the cases where productivity or work speed is emphasized.

[0006]

The present invention has been made in view of the above circumstances, and the objective of the present invention is to provide a pump control device and a pump control method that can easily change the setting of a pump flow.

MEANS FOR SOLVING THE PROBLEM

[0007]

The invention described in claim 1 is a pump control device for controlling a flow of a working fluid discharged from a pump with respect to a plurality of flow pressure actuators operated in accordance with respective operations of a plurality of operators, comprising a controller which is to obtain a demanded flow from each flow pressure actuator according to a signal generated by operation of each operator, and while obtaining the sum total value and the maximum value of these demanded flows, with respect to the maximum value, it is to set the pump flow command value based on a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value.

[0008]

The invention described in the Claim 2 is a pump control device comprising a switching means for setting by switching the gain in the pump control device described in the Claim 1.

[0009]

The invention described in the Claim 3 is a pump control method for controlling the flow of working fluid discharged from a pump with respect to a plurality of flow pressure actuators, obtaining the sum total value and the maximum value of these demanded flows, with respect to the maximum value, setting the pump flow command value based on a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value.

[0010]

The invention described in the Claim 4 is to switch the gain in accordance with setting in the pump control method described in the Claim 3.

EFFECTS OF THE INVENTION

[0011]

According to the Claim 1 of the present invention, the controller obtains the sum total value and the maximum value of the demanded flows from the respective flow pressure actuators, with respect to the maximum value, to set the pump flow command value based on a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value, and by changing the value of the gain, setting of the pump flow is to become easily changeable.

[0012]

According to the Claim 2 of the present invention, by setting the gain for switching by the switching means, for example, switching of the switching means is to be performed by the operator in accordance with the work mode, setting of the pump flow is to become easily changeable depending on the work mode.

[0013]

According to the Claim 3 of the present invention, to obtain the sum total value and the maximum value of the demanded flows from the respective flow pressure, with respect to the maximum value, to set the pump flow command value based on a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value, and by changing the value of the gain, setting of the pump flow is to become easily changeable.

[0014]

According to the Claim 4 of the present invention, for example by switching the gain in accordance with the work mode by the switching means, setting of the pump flow is to become easily changeable depending on the work mode.

BRIEF DESCRIPTION OF THE DRAWING

[0015]

FIG. 1 is a block diagram of a controller showing one embodiment of a pump control device and a pump control method according to the present invention.

FIG. 2 is a block diagram showing an actuator demanded flow calculation unit of the same controller.

FIG. 3 is a block diagram showing a pump demanded flow calculation unit of the same controller.

FIG. 4 is a block diagram showing a pump flow command calculation unit of the same controller.

FIG. 5 is ablock diagram showing the same pump control device .

FIG. 6 is a circuit diagram showing a fluid pressure system equipped with the same pump control device.

FIG. 7 is a schematic diagram showing a hydraulic excavator as a representative example of a work machine equipped with the same hydraulic pressure system.

FIG. 8 is a graph showing an example of a demanded flow during a compound operation of a fluid pressure actuator.

FIG. 9 (a) is a graph showing the calculation result by the pump control device when the gain based on the demanded flow in FIG. 8 is 0, (b) is a graph showing the calculation result when the gain based on the demanded flow in FIG. 8 is 0.3, (c) is a graph showing the calculation result by the pump control device when the gain based on the demanded flow of FIG. 8 is 0.5, (d) is a graph showing the calculation result of the pump control device when the gain based on the demanded flow of FIG. 8 is 1.

DETAILED DESCRIPTION OF THE EMBODIMENT OF THE PRESENT INVENTION

[0016]

Hereinafter, the present invention is to be described in detail on the basis of one embodiment shown in FIGS. 1 to 9.

[0017] As shown in FIG. 7, the hydraulic excavator 10 serving as a working machine comprises a crawler-type lower driving body 12 driven and run by left and right driving motors 12ml and 12mr as well as an upper rotating body 14 which is rotationally driven by the rotating motor 14m via the rotating bearing section 13 to the lower driving body 12 as a body 11, and on the front side of this upper rotating body 14 , a boom 15 that is rotated by the boom cylinder 15c, an arm 16 that is rotated by the arm cylinder 16c, and a work device 18 equipped with a bucket 17 that is rotated by the bucket cylinder 17c are installed. Additionally, in this working device 18, an attachment operated by an attachment cylinder which is not shown (or an attachment motor) may be detachably provided.

[0018]

Also, as shown in FIG. 6, the driving motors 12ml and 12mr, the rotating motor 14m, the boom cylinder 15c, the arm cylinder 16c, the bucket cylinder 17c and the attachment cylinder (or the attachment motor) are a hydraulic actuator as a flow pressure actuator driven by hydraulic fluid as working fluid discharged from a pump (main pump) 22 driven by an engine 21 mounted on an upper rotating structure 14 (FIG. 7).

[0019]

The pump 22 is, for example, a variable displacement pump respectively equipped with a pump swash plate for variable capacity control. In the present embodiment, a (one) pump 22a and (another) pump 22b are set for this pump 22. The pump 22 is equipped with a swash plate control device 23 ( (one) swash plate control device 23a and (another) swash plate control device 23b) , a proportional solenoid valve 24 ( (one) proportional solenoid valve 24a and

(another) proportional solenoid valve 24b) . Also, the swash plate angle for variable capacity of the pump 22 is controlled by displacement of the swash plate angle adjusting piston of the swash plate control device 23, and these piston displacements are variably controlled by the proportional solenoid valve 24. In addition, the pump 22 is connected to a control valve 25, and pressure oil from the pump 22 is distributed to the respective hydraulic actuators via the control valve 25, and by the pressure oil distributed from the control valve 25, the driving motor 12ml andl2mr, the rotating motor 14m, the boom cylinder 15c, the arm cylinder 16c and the bucket cylinder 17c are to be driven respectively. In the present embodiment, the pump 22a fundamentally discharges pressure oil for driving the left driving motor 12ml, the boom cylinder 15c, the arm cylinder 16c, the bucket cylinder 17c, and the attachment cylinder (or the attachment motor) , and the pump 22b fundamentally discharges pressure oil for driving the right driving motor 12mr, the rotating motor 14m, the boom cylinder 15c and the arm cylinder 16c, however, these can be merged if necessary by using an appropriate merging valve or the like.

[0020]

The control valve 25 is equipped with a plurality of flow control valves (spools) , which are able to freely slide, provided therein for controlling various hydraulic actuators . Specifically, the control valve 25 is equipped with a left driving flow control valve, a right driving flow control valve, a rotating flow control valve, a plurality of boom flow control valves, a plurality of arm flow control valves, and a bucket flow control valve and the like for controlling the flow of pressure oil to be supplied to the driving motors 12ml andl2mr, the swing motor 14m, the boom cylinder 15c, the arm cylinder 16c and the bucket cylinder 17c. Further, this control valve 25 may be provided with an attachment flow control valve for controlling the flow of pressure oil to be supplied to the attachment cylinder (or the attachment motor) . In addition, the control valve 25 is provided with a proportional solenoid valve unit 29 comprising a proportional solenoid valve 29a (FIG. 5) for controlling each flow control valve. Each proportional solenoid valve 29a (FIG. 5) of the proportional solenoid valve unit 29 outputs , by depressurizing, the pilot primary pressure oil supplied from the pilot pump 30, which is a sub pump driven by the engine 21, to the pilot secondary pressure corresponding to the lever operation or the pedal operation by the operator. In other words, the control valve 25 is pilot controlled by lever operation or pedal operation indirectly via the proportional solenoid valve unit 29 in accordance with the operation amount. Furthermore, it is configured so that these flow control valves can be displacement controlled respectively by the pilot secondary pressure oil outputted by the proportional solenoid valve 29a (FIG. 5) being supplied to each flow control valve.

[0021]

The proportional solenoid valve 24 and the proportional solenoid valve unit 29 are controlled by a controller (MECM) 34 shown in FIG. 5. That is to say, a pump control device 35 that controls the pump flow rate is comprised with these proportional solenoid valve 24, the proportional solenoid valve unit 29 (each proportional solenoid valve 29a), and the controller 34. On the input side of the controller 34, a plurality of operators 36 such as the above-mentioned lever (joystick) and pedal operated by an operator to drive the hydraulic actuator, a pressure sensor 37

( (one) pressure sensor 37a and (another) pressure sensor 37b) for detecting the discharge pressure of the pump 22 (FIG. 6), and a work mode changeover switch 38 as an switching means (switching unit) operable by an operator and the like are electrically connected. In addition, on the output side of the controller 34, the proportional solenoid valve 24 and the proportional solenoid valve unit 29 (each proportional solenoid valve 29a) and the like are electrically connected. Therefore, the hydraulic system according to the present embodiment is of the positive control in which the pump flow is controlled on the basis of the operation amount of the operator 36.

[0022]

As shown in FIG. 1, the controller 34 is equipped with an actuator demanded flow rate calculating unit 41, a pump demanded flow rate calculating unit 42 and a pump flow command calculating unit 43, and these calculating units 41 to 43 are, for example, sequentially connected. These calculation units 41 to 43 are provided for the pump 22a (FIG. 6) and the pump 22b (FIG. 6) respectively .

[0023]

The actuator demanded flow rate calculation unit 41 is to calculate and output the demanded flow of each hydraulic actuator on the basis of the operating signal Si inputted according to the operation of the operator 36. The operator 36 for inputting the operating signal Si is electrically connected to the input side of the actuator demanded flow rate calculation unit 41. Further, as shown in FIG. 2, this actuator demanded flow rate calculating unit 41 is equipped with a flow rate setting unit 45 which calculates the demanded flow rate from each hydraulic actuator corresponding to each of the operators 36 and outputs a demanded flow signal Qi indicating said demanded flow. That is to say, this actuator demanded flow rate calculation unit 41 outputs the demanded flow signal Qi via the flow rate setting unit 45.

[0024]

The flow rate setting unit 45 is equipped with a pair of flow rate setting tables 47 and 48 for setting a flow rate on the basis of the operating signal Si. In addition, this flow rate setting unit 45 is provided with a pair of rate limiters 49 and 50 for limiting the startup speed of the demanded flow rate outputted from the flow rate setting tables 47 and 48. Furthermore, the flow rate setting unit 45 is provided with a maximum value selector 51 for selecting a large value of the flow rate outputted from the rate limiters 49 and 50.

[0025]

The flow rate setting tables 47 and 48 are tables that indicate the ratio of the pump flow to the operation amount of the operator 36. One flow rate setting table 47 and the other flow rate setting table 48 correspond to the contradictory actions (expansion and contraction of the cylinder, normal rotation and reverse rotation of the motor, etc.) of the hydraulic actuator

[0026]

Returning to FIG. 1, the pump demanded flow rate calculation unit 42 is to calculate and to output a pump demanded flow (pump demanded flow signal) on the basis of the demanded flow of each actuator outputted from the actuator demanded flow rate calculation unit 41. On the input side of the pump demanded flow rate calculating unit 42, the actuator demanded flow rate calculation unit 41 for inputting the demanded flow signal Qi corresponding to the demanded flow and the work mode changeover switch 38 for inputting the switching signal SS are electrically connected. Also, as shown in FIG. 3, this pump demanded flow calculating unit 42 is equipped with an adder 54 which outputs the sum obtained by adding each demanded flow rate (demanded flow signal Qi) . Furthermore, a maximum value selector 55 for selecting and outputting the maximum value of the demanded flow rate (demanded flow signal Qi) is provided to the pump demanded flow rate calculation unit 42. In addition, a subtractor 56 that outputs the difference between the output of the adder 54 and the output of the maximum value selector 55 is provided to the pump demanded flow rate calculating unit 42. Further, in this pump demanded flow calculating unit 42, a gain switching device 57 for outputting the gain K switched in accordance with the switching signal SS is provided. As this gain K, a predetermined value of 0 to 1 is set. Also, this pump demanded flow calculating unit 42 is provided with a multiplier 58 for multiplying and outputting the output of the subtracter 56 and the output of the gain switching device 57. Additionally, the pump demanded flow rate calculating unit 42 is provided with an adder 59 to output as the pump demanded flow signal Qpr indicating the pump demanded flow rate by adding the output of the multiplier 58 and the output from the maximum value selector 55. hat is to say, this pump demanded flow calculation unit 42 outputs the pump demanded flow (pump demanded flow signal Qpr) via the adder 54, the maximum value selector 55, the subtracter 56, the gain switching device57, the multiplier 58 and the adder 59.

[0027]

Returning to FIG. 1, the pump flow command calculation unit 43 is to calculate the pump flow command signal Qpc indicating the pump flow command value for controlling the discharge flow from the pump 22 (FIG. 6) on the basis of the pump demanded flow outputted from the pump demanded flow rate calculation unit 42. Specifically, the pump flow command calculation unit 43 limits the pump demanded flow (pump demanded flow signal Qpr) outputted from the pump demanded flow rate calculation unit 42 by the constant horsepower flow obtained from the pump pressure, and outputs it as the pump flow command value (Pump flow command signal Qpc) . On the input side of this pump flow command calculation unit 43, the pump demanded flow rate calculation unit 42 for inputting the pump demanded flow (pump demanded flow signal Qpr) and the pressure sensor 37 for inputting the pump pressure (pump pressure signal Pp) are electrically connected. In addition, in this pump flow command calculation unit 43, as shown in FIG. 4, a constant horsepower flow table 61 for setting a constant horsepower flow on the basis of the pump pressure (pump pressure signal Pp) is provided. Furthermore, in this pump flow command calculation unit 43, a minimum value selector 62 for outputting as the pump flow command value (pump flow command signal Qpc) by selecting the minimum value of the output of constant horsepower flow table 61 and the pump demanded flow (pump demanded flow signal Qpr) is provided. That is to say, this pump flow command calculation unit 43 outputs the pump flow command value (pump flow command signal Qpc) via the constant horsepower flow table 61 and the minimum value selector 62.

[0028]

The constant horsepower flow table 61 is a table that indicates the ratio of the pump flow to the pump pressure.

[0029]

In addition, it should be noted that the above-described calculation units 41 to 43 fundamentally have the same configuration for the pump 22a and the pump 22b, respectively. Therefore, only the pump 22a is to be described in details below, and the description for the pump 22b is to be omitted.

[0030]

In the present embodiment, as shown in FIG. 2, on the input side of the actuator demanded flow rate calculation unit 41, an operator 36tl for driving left that inputs the driving left operation signal Stl, an operator 36bm for the boom operation that inputs the boom operation signal Sbm, an operator 36am for the arm operation that inputs the arm operation signal Sam, and an operator 36bk for the bucket operation that inputs the bucket operation signal Sbk are electrically connected, respectively. In addition, in the flow rate setting unit 45, a left driving flow rate setting unit 45tl, a boom flow rate setting unit 45bm, an arm flow rate setting unit 45am, and a bucket flow rate setting unit 45bk are set corresponding to the operators 36tl, 36bm, 36am, and 36bk.

[0031]

To the left driving flow rate setting unit 45tl, the boom flow rate setting unit 45bm, and the bucket flow rate setting unit 45bk, the driving left signal Stl, the boom operation signal Sbm, and the bucket operation signal Sbk are directly inputted from the operator 36tl, the operator 36bm, and the operator 36bk respectively. Also, to the arm flow rate setting unit 45am, a signal of which the arm operation signal Sam inputted from the operator 36am is restricted by the boom operation signal Sbm inputted from the operator 36bm is inputted. Specifically, the minimum value selector 65 is electrically connected to the arm flow rate setting unit 45am. To the minimum value selector 65, a signal in which the boom operation signal Sbm is limited by the arm restriction table 66 and the arm operation signal Sam are inputted. Then, the minimum value selector 65 selects and outputs a small value of these signals .

[0032]

In addition, the flow rate setting table 47 and the flow rate setting table 48 correspond, for example, to the forward flow rate and the reverse flow rate in the left driving flow rate setting unit 45tl. Similarly, the flow rate setting table 47 and the flow rate setting table 48 correspond to the boom raising flow rate and the boom lowering flow rate in the boom flow rate setting unit 45bm, also correspond to the arm-in flow rate and the arm-out flow rate in the arm flow rate setting unit 45am, and correspond to the bucket-in flow rate and the bucket-out flow rate in the bucket flow rate setting unit 45bk.

[0033]

Further, an operator for attachment operation, which is not shown, for inputting an attachment operation signal may be electrically connected to the input side of the demanded flow rate calculation unit 41. In this case, the flow rate setting unit 45 may further be provided with an attachment flow rate setting unit.

[0034]

Also, as shown in FIG. 3, on the input side of the pump demanded flow rate calculation unit 42, the flow rate setting unit 45 (flow rate setting units 45tl, 45bm, 45am, and 45bk) of the actuator demanded flow rate calculation unit 41 (FIG. 2) as well as the work mode changeover switch 38 are electrically connected. A plurality of, for example, three different gains Kl, K2, and K3 having different values are preset in the gain switching device 57 according to the work mode. Therefore, the work mode changeover switch 38 can select, for example, three kinds of work modes.

[0035]

Also, as shown in FIG. 4, on the input side of the pump flow command calculation unit 43, the pump demanded flow rate calculation unit 42 as well as the pressure sensor 37a for inputting the pump pressure signal Ppa are electrically connected

[0036]

Next, the operation of the illustrated embodiment is to be described .

[0037]

As an outline, the controller 34 of the pump control device 35 obtains the sum total value and the maximum value of these demanded flows, with respect to the maximum value, sets the pump flow command value on the basis of a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value. More specifically, the controller 34 obtains the sum total value and the maximum value of these demanded flows, with respect to the maximum value, a value obtained by adding a value obtained by multiplying a difference between the sum total value and the maximum value by a predetermined gain as the pump demanded flow rate, and sets the pump flow command value by limiting the pump demanded flow by the constant horsepower flow rate.

[0038]

Specifically, when the operator operates the operator 36, as shown in FIG. 2, the operation signal Si corresponding to the operation amount of the operator 36 is inputted to the flow rate setting unit 45 of the actuator demanded flow rate calculation unit 41. In the flow rate setting unit 45, the demanded flow is set by the flow rate setting tables 47 and 48 in accordance with the operation signal Si, and the startup speed of the output of these flow rate setting tables 47 and 48 is limited by the rate limiters 49 and 50, and by selecting the maximum value of the outputs of the rate limiters 49 and 50 by the maximum value selector 51, the demanded flow (demanded flow signal Qi) is to be set. For example, in FIG. 2, on the basis of the operation amount of the operator 36tl, the operator 36bm, the operator 36am, and the operator 36bk (the driving left operation signal Stl, the boom operation signal Sbm, the arm operation signal Sam, and the bucket operation signal Sbk) , the driving left demanded flow (the driving left demanded signal Qtl) , the boom demanded flow (the boom demanded flow signal Qbm) , the arm demanded flow (the arm demanded flow signal Qam) , and the bucket demanded flow (the bucket demanded flow signal Qbk) are to be set respectively. These set demanded flow rates (the demanded flow signal Qi) are inputted to the pump demanded flow rate calculation unit 42 shown in FIG. 3, respectively.

[0039]

In this pump demanded flow rate calculation unit 42, the adder 54 calculates the sum (∑Qi) of the demanded flow rate (the demanded flow signal Qi) . In addition, the maximum value selector 55 selects the maximum value (Max (Qi) ) of these demanded flow rates (the demanded flow signal Qi) . Further, the subtracter 56 subtracts the output of the maximum value selector 55 from the output of the adder

54 (∑Qi - Max (Qi) ) .

[0040]

Here, as the work mode changeover switch 38 is switched in accordance with the work mode selected by the operator, the gain switching device 57 in which the switching signal SS from the work mode changeover switch 38 is inputted is to output one of the predetermined gains Kl, K2, and K3 as the gain K. It is to output by the outputted gain K and the output of the subtractor 56 are multiplied by the multiplier 58 (K (∑Qi-Max (Qi) ) ) and this output of the multiplier 58 and the output of the maximum value selector

55 are added by the adder 59 to calculate the pump demanded flow (pump demanded flow signal Qpr (= Max (Qi) + K (∑Qi - Max (Qi) ) .

[0041]

Next, in the pump flow command calculation unit 43 shown in FIG. 4, the constant horsepower flow rate (constant horsepower flow signal) is set in the constant horsepower flow rate table 61 on the basis of the pump pressure (pump pressure signal Pp) detected by the pressure sensor 37, the pump demanded flow (the pump demanded flow signal Qpr) that is outputted from the pump demanded flow rate calculation unit 42 by the minimum value selector 62 is calculated by limiting with the constant horsepower flow rate (the constant horsepower flow signal) . Then by outputting this pump flow command value (the pump flow command signal Qpc) to the proportional solenoid valve 24 shown in FIG. 6, the flow rate of the pump 22 is to be controlled by the proportional solenoid valve 24 operating the swash plate control device 23.

[0042]

Specifically, the pump flow rate in the case of the gain being switched when a plurality of hydraulic actuators are combined is calculated. For example, examples of demanded flow rates of the boom cylinder 15c, the arm cylinder 16c, and the bucket cylinder 17c when the boom 15 (the operator 36bm) , the arm 16 (the operator 36am) , and the bucket 17 (the operator 36bk) are operated in combination are shown in FIGS. 8, and the calculation results by the controller 34 on the basis of these demanded flow rates are shown in FIG. 9 (a) to FIG. 9 (d) . The dotted lines in FIGS. 9 (a) to 9 (d) show calculation results in which the upper limit of the square root of the sum of the respective demanded flow rates is limited by the pump maximum flow rate as a comparative example. Here, FIG. 9 (a) shows the case where the gain is 0 (mere maximum value of each demanded flow), FIG. 9 (b) shows the case where the gain is 0.3, FIG. 9 (c) shows the case where the gain is 0.5, and FIG. 9 (d) shows the case where the gain is 1 (mere sum of the demanded flow rates) . When the gain is 0.3, it mostly matches with the comparative example.

[0043]

As shown in FIGS. 9 (a) to 9 (d) , for example, in the case of work focusing on fuel consumption, by setting the gain low, it is possible to improve the fuel consumption by controlling the loss of energy due to loss of pressure of the flow control valve setting the pump flow rate lower than the opening area of each flow control valve of the control valve 25 in the combined operation. On the other hand, in the case where the emphasis is placed on productivity and work speed, by setting the gain to a higher value, it is possible to secure the productivity and work speed setting the pump flow rate according to the work in the combined operation.

[0044]

Thus, according to one example of the embodiment above, the controller 34 obtains the sum total value and the maximum value of the demanded flows from the respective flow pressure actuators, with respect to the maximum value, to set the pump flow command value on the basis of a value obtained by adding a value obtained by multiplying a predetermined gain of the difference between the sum total value and the maximum value, and by changing the value of the gain, setting of the pump flow is to become easily changeable.

[0045]

For example, by setting the gain for switching by the work mode changeover switch 38, switching of the work mode changeover switch 38 is to be performed by the operator in accordance with the work mode, setting of the pump flow is to become easily changeable depending on the work mode. Therefore, it is possible to perform pump flow control in conformity with the work mode desired by the operator, particularly in the combined operation of a plurality of hydraulic actuators.

[0046]

In addition, in one example of the embodiment above, the gain may be set to an arbitrary value from 0 to 1, or may be set linearly in addition to selection from a plurality of fixed values.

INDUSTRIAL APPLICABILITY

[0047]

The present invention has industrial applicability for operators involved in the manufacturing industry, sales industry and the like of a pump control device or work machine. DESCRIPTION OF THE SYMBOL

[0048]

12ml, 12mr A driving motor as a fluid pressure actuator

14m A pivot motor as a fluid pressure actuator

15c A boom cylinder as a fluid pressure actuator

16c An arm cylinder as a fluid pressure actuator

17c A bucket cylinder as a fluid pressure actuator

22 A pump

34 A controller

35 A pump control device

36 An operator

38 A work mode changeover switch for switching means