JPH07286583A - Hydraulic pump control device for construction machine - Google Patents

Abstract

PURPOSE:To provide pump load torque characteristics suitable for the sort of fuel to drive a prime mover. CONSTITUTION:A device is provided with an instruction device 20 to output an instruction signal corresponding to each sort of fuel among plural sorts of fuel for an engine 1, and an electromagnetic proportional pressure reducing valve 27 to drive a discharge quantity control means 5 to control discharge quantity of a hydraulic pump 2 selectively in one of plural drive modes, and it is also provided with a control device 25 having a logical determination function as a selecting means to select the drive mode of the discharge quantity control means 5 which is changed by drive of the electromagnetic proportional pressure reducing valve 27 in accordance with the instruction signal outputted from the instruction device 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic pump control device for a construction machine such as a hydraulic excavator, in which a pump load torque for a prime mover such as a diesel engine whose output changes according to the type of fuel, The present invention relates to a hydraulic pump control device that is controlled to keep it constant.

[0002]

2. Description of the Related Art FIG. 8 is a circuit diagram showing a conventional hydraulic pump controller of this type. This hydraulic pump control device is provided, for example, in a hydraulic excavator. The hydraulic pump control device shown in FIG. 8 includes a prime mover such as a diesel engine 1, a hydraulic pump driven by the diesel engine 1, for example, a variable displacement hydraulic pump 2, and a hydraulic actuator driven by pressure oil discharged from the hydraulic pump 2. A hydraulic cylinder 4 such as a boom cylinder, a directional control valve 3 for controlling the flow of pressure oil supplied from the hydraulic pump 2 to the hydraulic cylinder 4, and a discharge amount control means 5 for controlling the discharge amount of the hydraulic pump 2. Is equipped with. The discharge amount control means 5 includes a spring 6 and a piston 7 which is biased by the spring 6 and controls the swash plate of the hydraulic pump 2. The control chamber of the piston 7 located on the opposite side of the spring 6 is connected to the discharge line 8 of the hydraulic pump 2 by the pilot line 9, and the piston 7 acts on the force corresponding to the discharge pressure of the hydraulic pump 2 and the force of the spring 6. And the tilt angle of the swash plate is controlled. Diesel engine 1 mentioned above
One of a plurality of fuels, for example, a fuel A capable of obtaining a relatively large engine output T1 and a fuel B having an engine output T2 smaller than the fuel A is selectively used as a fuel for driving the engine. It is like this. In addition, such a difference in engine output (T1> T2) is
Fuel A is based on the difference in fuel quality.
Good quality compared to.

In such a hydraulic pump control device, T = C · P · Q (C is a constant, where T is the pump load torque for the diesel engine 1, P is the pump discharge pressure, and Q is the pump discharge flow rate. ) Have a relationship. That is, the pump load torque T corresponds to the product of the pump discharge pressure P and the pump discharge flow rate Q. In the above-mentioned conventional technique, the pump load torque T is caused by the force of the spring 6 included in the discharge amount control means 5, that is, by the force of a plurality of combined springs, or the force of a non-linearly formed spring. Is set uniquely in advance.

FIG. 9 is a characteristic diagram showing the relationship between the discharge pressure or pressure P of the hydraulic pump 2 and the discharge flow rate or flow rate Q in the hydraulic pump control system shown in FIG. 8. In FIG. Shows the characteristic of the pump load torque T corresponding to the relatively large engine output T1 when using the fuel A, and the characteristic line 11 shows the pump load torque T2 corresponding to the relatively small engine output T2 when using the fuel B. The torque T is shown.

[0005]

By the way, in the prior art having such a configuration, the pump load torque T is set in advance so as to correspond to the characteristic line 10 in FIG. 9 (T = T1).
When using the fuel A, there is no problem, but when using the fuel B, pump load torque T> engine output torque T2. That is, it becomes overtorque. When the overtorque is generated as described above, the engine speed decreases, horsepower is not produced, or engine stall occurs, and the efficiency of predetermined work such as excavation work performed via the hydraulic cylinder 4 decreases.

On the contrary, in advance, the pump load torque T is shown in FIG.
Set so as to correspond to the characteristic line 11 (T = T2)
When using the fuel B, there is no problem, but when using the fuel A, it is not possible to obtain the high performance that should be originally obtained, and from this point of view, a predetermined work performed through the hydraulic cylinder 4 is performed. Efficiency decreases.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to control a hydraulic pump of a construction machine capable of obtaining a pump load torque characteristic suitable for the kind of fuel for driving a prime mover. To provide a device.

[0008]

To achieve this object, the present invention provides a prime mover, a hydraulic pump driven by the prime mover, a discharge amount control means for controlling the discharge amount of the hydraulic pump, and the hydraulic pump. A hydraulic actuator driven by pressure oil discharged from the hydraulic pump, and a directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to the hydraulic actuator, and a plurality of fuels are used as fuel for driving the prime mover. In a hydraulic pump control device for a construction machine, one of which is selectively adopted, an instruction device that outputs an instruction signal corresponding to each of the plurality of fuels, and a plurality of different discharge amount control means are provided. A driving unit that can be selectively driven in one of the driving modes, and a discharge unit that changes according to an instruction signal output from the pointing device. And a selecting means for selecting a driving mode of the output control means.

[0009]

Since the present invention has the above-described structure, for example, as fuel for driving the prime mover, fuel A that provides a relatively large output characteristic of the prime mover and output characteristic of the prime mover smaller than this fuel A are obtained. In the situation where the fuel B can be adopted, as a driving mode of the discharge amount control means by the driving means, a pump discharge amount that can give a first pump load torque suitable for the output characteristic of the prime mover obtained by the fuel A and The first drive mode in which the discharge amount control means is driven so that the discharge amount control means is driven so that the pump discharge amount can provide the second load torque that matches the output characteristic of the prime mover obtained by the fuel B. The second driving mode is set.

In such a situation, if the fuel A is used for driving the prime mover, the fuel A may be indicated by the indicating device. As a result, the instruction signal corresponding to the fuel A is output from the indicating device to the selecting means. The selecting means selects the above-mentioned first drive mode capable of giving the first pump load torque in accordance with the above-mentioned instruction signal (fuel A). The drive means drives the discharge amount control means according to the selected first drive mode. Thus, the desired first pump load torque corresponding to the relatively large output characteristic of the prime mover obtained by the fuel A indicated by the indicating device can be obtained.

Similarly, when the fuel B is used for driving the prime mover, the fuel B may be indicated by the indicating device. As a result, the instruction signal corresponding to the fuel B is output from the instruction device to the selecting means. The selection means selects the above-mentioned second drive mode capable of providing the second pump load torque in accordance with the above-mentioned instruction signal (fuel B). The driving means is
The ejection amount control means is driven according to the selected second driving mode. Thus, the desired second pump load torque corresponding to the relatively small output characteristic of the prime mover obtained by the fuel B indicated by the indicating device can be obtained.

As described above, when the fuel A is used, the first pump load torque corresponding to the relatively large output characteristic of the prime mover is used. When the fuel B is used, the second pump load torque corresponding to the relatively small output characteristic of the prime mover is used. It is possible to obtain appropriate pump load torque characteristics suitable for the type of fuel.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic pump controller for a construction machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic pump control device for a construction machine according to the present invention, FIG. 2 is a plan view showing an indicating device provided in the first embodiment shown in FIG. 1, and FIG. 1 shows the pressure / flow rate characteristic of the hydraulic pump obtained in the first embodiment shown in FIG.
3 is a flowchart showing a procedure of processing executed by a control device provided in the first embodiment shown in FIG.

The first embodiment shown in these figures corresponds to the first, second, third, fourth and sixth aspects of the present invention, and is provided, for example, in a hydraulic excavator. In the first embodiment, as shown in FIG. 1, a prime mover, for example, a diesel engine 1 in which one of a plurality of fuels is selectively adopted,
A hydraulic pump driven by the diesel engine 1, for example, a variable displacement hydraulic pump 2, and a hydraulic actuator driven by pressure oil discharged from the hydraulic pump 2,
For example, a hydraulic cylinder 4 such as a boom cylinder, a directional control valve 3 that controls the flow of pressure oil supplied from the hydraulic pump 2 to the hydraulic cylinder 4, and a discharge amount control means 5 that controls the discharge amount of the hydraulic pump 2. The discharge amount control means 5 is provided with a spring 6 and a piston 7 that is biased by the spring 6 and controls the swash plate of the hydraulic pump 2. The control chamber of the piston 7 located on the opposite side of the spring 6 built in the discharge amount control means 5 is connected to the discharge pipe 8 of the hydraulic pump 2 by the pilot pipe 9,
The discharge pressure of is given. These configurations are the same as those shown in FIG. 8 of the above-mentioned related art.

As the fuel of the diesel engine 1, for example, the fuel A of good quality that can obtain the relatively large engine output characteristic described above, and the fuel of the relatively high quality that the engine output characteristic is smaller than the fuel A are used. The inferior fuel B is selectively adopted.

In particular, the first embodiment is provided with an indicating device 20 having a built-in switch for outputting an instruction signal corresponding to each of the fuels A and B described above, for example, in accordance with a manual operation. As shown in FIG. 2, the pointing device 20 sends an operating lever 21 that can be swung in the direction of arrow 43 and an instruction signal corresponding to the fuel A, for example, an ON signal, when the operating lever 21 is operated in one direction. The switching unit 22 for outputting and the switching unit 23, which is located on the opposite side of the switching unit 22 with the operating lever 21 interposed therebetween, and outputs an instruction signal corresponding to the fuel B, that is, an OFF signal, in response to an operation in the other direction of the operating lever 21. Have and.

Further, a drive means capable of selectively driving the discharge amount control means 5 into one of a plurality of different drive modes, for example, a first pump load adapted to the output characteristic of the engine 1 obtained by the fuel A. A first drive mode in which the discharge amount control means 5 is driven so as to obtain a discharge flow rate capable of giving a torque;
Discharge rate control in either of the second drive modes in which the discharge rate control means 5 is driven so that the discharge flow rate is such that a second load torque suitable for the output characteristics of the engine 1 obtained from the fuel B can be provided. An electromagnetic proportional pressure reducing valve 27 capable of selectively driving the means 5 is provided.

In addition, a selection means, for example, a logic judgment function, which selects the drive mode of the discharge amount control means 5 which changes according to the signal output from the indicating device 20, that is, the drive means, that is, the drive of the electromagnetic proportional pressure reducing valve 27. Control device 25
Is equipped with.

The instruction signal output from the indicating device 20 is guided to the controlling device 25 by the signal line 24, and the controlling device 25
The signal output from is guided to the drive unit of the electromagnetic proportional pressure reducing valve 27 via the signal line 26.

The input side of the electromagnetic proportional pressure reducing valve 27 is connected to the discharge line 8 of the hydraulic pump 2 via the pilot line 28. The output side of the electromagnetic proportional pressure reducing valve 27 is the pilot line 2
It is connected via 9 to the control chamber in which the spring 6 of the discharge amount control means 5 is arranged. That is, one side of the piston 7 of the discharge amount control means 5 (a control chamber on the side opposite to the spring 6)
As described above, the discharge pressure of the hydraulic pump 2 is introduced to the other side of the electromagnetic proportional pressure reducing valve 2 on the other side.
The pilot pressure output from 7 is guided through the pilot pipe line 29. The electromagnetic proportional pressure reducing valve 27 and the tank 31 are connected by a pilot line 30.

The operation in this first embodiment is as follows. That is, when the fuel A is used as the fuel for driving the diesel engine 1, the operator of this hydraulic excavator may swing the operating lever 21 of the instruction device 20 to the switching portion 22 side corresponding to the fuel A. This activates the switch built in the pointing device 20,
The instruction device 20 outputs an instruction signal corresponding to the fuel A. As shown in step S1 of FIG. 4, the above-described instruction signal is input to the control device 25 via the signal line 24. Next, as shown in step S2, it is determined whether the instruction signal input by the control device 25 corresponds to the fuel A. Since the instruction signal now corresponds to fuel A, step S
3, the selection is made to turn on the electromagnetic proportional pressure reducing valve 27, that is, the driving mode of the discharge amount control means 5 by the electromagnetic proportional pressure reducing valve 27 is adapted to the output characteristic of the engine 1 obtained by the fuel A. A process of selecting the first drive mode for driving the discharge amount control means 5 so that the discharge flow rate is such that a load torque can be given is performed. An ON signal corresponding to the first mode is output from the control device 25, and the signal line 2
6 to the drive unit of the electromagnetic proportional pressure reducing valve 27.
As a result, the electromagnetic proportional pressure reducing valve 27 shown in FIG. 1 tends to be connected to the pilot line 28, and the pilot pressure of the input pilot line 28 is reduced, but a relatively large pilot pressure is output and this is output. The pilot pressure is applied via the pilot line 29 to the control chamber in which the spring 6 of the discharge amount control means 5 is arranged.

A force generated by the discharge pressure of the hydraulic pump 2 is applied to one side of the piston 7 of the discharge amount control means 5, and a force of the spring 6 is applied to the other side of the piston 7 for comparison with the electromagnetic proportional pressure reducing valve 27. The force due to the relatively large pilot pressure is applied, and the swash plate of the hydraulic pump 2 changes in the direction of increasing the discharge amount due to the force relationship. Therefore, the flow rate discharged from the hydraulic pump 2 increases, and the pump load torque T (= C · P
-Q) is a relatively large first pump load torque corresponding to the output of the engine 1 obtained from the fuel A. The characteristic line 32 of FIG. 3 shows the characteristic of the first pump load torque obtained at this time.

Further, when the fuel B whose quality is lower than that of the fuel A is adopted as the fuel for driving the diesel engine 1, the operator of this hydraulic excavator makes the operating lever 21 of the indicating device 20 correspond to the fuel B. It may be rocked to the switching unit 23 side. As a result, the switch built in the indicating device 20 is activated, and the fuel B
An instruction signal corresponding to is output. In this case,
No in step S2, the procedure moves to step S4, the electromagnetic proportional pressure reducing valve 27 is turned off, that is, the drive mode of the discharge amount control means 5 by the electromagnetic proportional pressure reducing valve 27 is obtained by the fuel B. Processing for selecting the second drive mode for driving the discharge amount control means 5 so that the discharge flow rate can provide the second pump load torque that matches the output characteristic of the above. OFF corresponding to this second mode
A signal is output from the control device 25 and given to the drive unit of the electromagnetic proportional pressure reducing valve 27 via the signal line 26. As a result, the electromagnetic proportional pressure reducing valve 27 shown in FIG. 1 tends to be connected to the pilot conduit 30 connected to the tank 31, and the pilot pressure in the pilot conduit 29 is reduced. Therefore, the pilot pressure applied to the control chamber in which the spring 6 of the discharge amount control means 5 is arranged becomes small.

Compared with the force due to the discharge pressure of the hydraulic pump 2 applied to one side of the piston 7 of the discharge amount control means 5,
The force of the spring 6 applied to the other side and the pilot line 2
The resultant force with the pilot pressure of 9 becomes small, and the hydraulic pump 2
The swash plate changes in the direction of decreasing the discharge amount. Therefore, the flow rate discharged from the hydraulic pump 2 is reduced, and the pump load torque T (= C · P · Q) becomes a relatively small second pump load torque corresponding to the output of the engine 1 obtained by the fuel B. Become. The characteristic line 33 in FIG. 3 shows the characteristic of the second pump load torque obtained at this time.

In the first embodiment constructed as described above, when the engine 1 is driven by the fuel A by appropriately operating the operating lever 21 of the indicating device 20, the relatively large engine 1 obtained by the fuel A is obtained. When the engine 1 is driven by the fuel B, a relatively large first pump load torque corresponding to the output characteristic of the engine 1 is used. The pump load torque can be used to realize efficient driving of the engine 1 adapted to the quality of fuel, and along with this, the efficiency of various work such as excavation work performed via the hydraulic cylinder 4 can be improved. be able to.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention, and FIG. 6 is a flow chart showing a procedure of processing executed by a control device provided in the second embodiment shown in FIG. This second embodiment is defined by claims 1, 2, 3, and 3 of the present invention.
Corresponds to items 4 and 7.

The second embodiment is the same as the first embodiment except for the arrangement of the discharge amount control means 34 of the hydraulic pump 2 and the pilot pipe lines 9 and 29 connected to the discharge amount control means 34. This is equivalent to the first embodiment. That is, this second
In this embodiment, the discharge amount control means 34 is configured to include a stepped piston 36 that controls the swash plate of the hydraulic pump 2 and a spring 35 that biases the stepped piston 36. A pilot pipe line 9 connected to the discharge pipe line 8 and a pilot pipe line 29 connected to the electromagnetic proportional pressure reducing valve 27 are connected to one side of the stepped piston 36. The resultant force of the force and the pilot pressure output from the electromagnetic proportional pressure reducing valve 27 is
A stepped piston 36 is provided to oppose the force of the spring 35. Also in the second embodiment configured as described above, when the fuel A is used as the fuel for driving the diesel engine 1, the operator of this hydraulic excavator operates the operating lever 21 of the indicating device 20 to switch the fuel corresponding to the fuel A. 22
It is only necessary to swing the switch to the side, whereby the switch incorporated in the indicating device 20 is activated, and the indicating device 20 outputs an instruction signal corresponding to the fuel A. Step S11 in FIG.
As shown in, the instruction signal is input to the control device 25 via the signal line 24. Next, as shown in step S12, it is determined whether the instruction signal input by the control device 25 corresponds to the fuel A. Since the instruction signal now corresponds to the fuel A, the procedure proceeds to step S13, and the selection of turning off the electromagnetic proportional pressure reducing valve 27, that is, the driving mode of the discharge amount control means 5 by the electromagnetic proportional pressure reducing valve 27 is changed to the fuel. A process of selecting the first drive mode for driving the discharge amount control means 5 so that the discharge flow rate that can give the first pump load torque that matches the output characteristic of the engine 1 obtained by A is performed. An OFF signal corresponding to the first mode is output from the control device 25 and given to the drive unit of the electromagnetic proportional pressure reducing valve 27 via the signal line 26. As a result, FIG.
The electromagnetic proportional pressure reducing valve 27 shown in FIG. 2 tends to be connected to the pilot pipe line 28, and although the pilot pressure of the input pilot line 28 is reduced, a relatively large pilot pressure is output, and this output pilot pressure is It is given to the control chamber located on the opposite side of the control chamber in which the spring 6 of the discharge amount control means 5 is arranged via the pilot conduit 29.

The discharge pressure of the hydraulic pump 2 is also applied to the same control chamber. Therefore, the stepped piston 36 opposes the force of the spring 6 to give a resultant force of a force due to the relatively large pilot pressure output from the electromagnetic proportional pressure reducing valve 27 and a force due to the discharge pressure of the hydraulic pump 2, Due to these force relationships, the swash plate of the hydraulic pump 2 changes to increase the discharge amount. Therefore, the flow rate discharged from the hydraulic pump 2 increases, and the pump load torque T becomes a relatively large first pump load torque corresponding to the output of the engine 1 obtained by the fuel A.

When the fuel B is used as the fuel for driving the diesel engine 1, the instruction device 20 outputs an instruction signal corresponding to the fuel B. In this case, the determination in step S12 of FIG. 6 is NO, and step S14
The second pump load is selected so that the electromagnetic proportional pressure reducing valve 27 is turned on, that is, the driving mode of the discharge amount control means 5 by the electromagnetic proportional pressure reducing valve 27 is adapted to the output characteristic of the engine 1 obtained by the fuel B. A process of selecting the second drive mode for driving the discharge amount control means 5 so that the discharge flow rate that can give the torque is achieved is performed. An ON signal corresponding to the second mode is output from the control device 25, and the signal line 26
Is supplied to the drive unit of the electromagnetic proportional pressure reducing valve 27 via. As a result, the electromagnetic proportional pressure reducing valve 27 shown in FIG.
Will tend to be connected to the pilot line 30 connected to
The pilot pressure in the pilot line 29 becomes smaller. Therefore, the force of the spring 6 of the discharge amount control means 5 becomes relatively strong. Therefore, the flow rate discharged from the hydraulic pump 2 is reduced, and the pump load torque T becomes a relatively small second pump load torque corresponding to the output of the engine 1 obtained by the fuel B.

The second embodiment constructed as described above also has the same effect as that of the first embodiment.

FIG. 7 is a circuit diagram showing a third embodiment of the present invention. This third embodiment is characterized by claims 1, 2 and 3 of the present invention.
It corresponds to 3, 5, and 6.

Particularly in the third embodiment shown in this figure, the discharge amount control means 5 is driven in synchronization with the hydraulic pump 2 as a drive means capable of selectively driving one of a plurality of different drive modes. Pilot pump 37, a pilot relief valve 42 that regulates the magnitude of pilot pressure discharged from the pilot pump 37, and a discharge amount of the pressure discharged from the pilot pump 37 in accordance with a signal output from the control device 25. An ON-OFF type electromagnetic switching valve 39 that selectively outputs as pilot pressure for driving the control means 5 is provided.

The pilot pump 37 and the input port of the electromagnetic switching valve 39 are connected by a pilot line 38,
The output port of the electromagnetic switching valve 39 and the control chamber in which the spring 6 of the discharge amount control means 5 is arranged are connected by a pilot line 40, and the electromagnetic switching valve 39 and the tank 31 are connected by a pilot line 41. I am allowed. The other structure is the same as that of the first embodiment shown in FIG.

Even in the third embodiment constructed as described above, when the operating lever 21 of the indicating device 20 is switched to the switching portion 22 corresponding to the fuel A, as in the first embodiment described above, An instruction signal corresponding to the fuel A is output to the control device 25 via the signal line 24, the control device 25 performs substantially the same processing as that shown in the flow chart of FIG. 4, and the electromagnetic switching is performed via the signal line 26. The operation of switching the valve 39 to the lower position of FIG. 7 is performed. As a result, the pilot pressure of the pilot pump 37 is reduced to the pilot line 3
The piston 7 is guided to the pilot line 40 via 8 and the piston 7 moves to the right in the figure, and the tilt angle of the swash plate changes so that the discharge amount of the hydraulic pump 2 increases. As a result, a relatively large first pump load torque corresponding to the fuel A equivalent to the characteristic line 32 of FIG. 3 described above can be obtained.

On the contrary, the operating lever 21 of the pointing device 20
Is switched to the switching unit 23 corresponding to the fuel B, an instruction signal corresponding to the fuel B is output to the control device 25, and the operation of switching the electromagnetic switching valve 39 to the upper position of FIG. Is performed. This allows
While the pilot pipe line 38 is blocked, the pilot pipe line 40 communicates with the tank 31 to generate tank pressure, the piston 7 moves to the left in the drawing, and the swash plate tilts so that the discharge amount of the hydraulic pump 2 decreases. The turning angle changes. As a result, a relatively small second pump load torque corresponding to the fuel B equivalent to the characteristic line 33 of FIG. 3 described above can be obtained.

Even in the third embodiment thus constructed, the engine 1 is driven by the fuel A by appropriately operating the operating lever 21 of the indicating device 20 as in the first embodiment. When the engine 1 is driven by the fuel B, a relatively small first pump load torque corresponding to the relatively large output characteristic of the engine 1 obtained by the fuel A is obtained. A relatively small second pump load torque corresponding to the output characteristic of No. 1 can be achieved, and efficient driving of the engine 1 that matches the quality of fuel can be realized.
It is possible to improve the efficiency of various work such as excavation work performed via the.

In place of the discharge amount control means 5 shown in the third embodiment, the discharge amount control means 34 having the stepped piston 36 of the second embodiment shown in FIG. 5 is provided. May be.

[0038]

Since the present invention has the above-mentioned structure, it is possible to obtain a pump load torque characteristic suitable for the type of fuel for driving the prime mover, and thereby to realize efficient drive of the prime mover. It is possible to improve the efficiency of various works performed via the hydraulic actuator driven by the pressure oil discharged from the hydraulic pump.

[Brief description of drawings]

FIG. 1 is a first hydraulic pump control device for a construction machine according to the present invention.
3 is a circuit diagram showing an embodiment of FIG.

FIG. 2 is a plan view showing an indicating device provided in the first embodiment shown in FIG.

FIG. 3 is a diagram showing pressure / flow rate characteristics of the hydraulic pump obtained in the first embodiment shown in FIG.

FIG. 4 is a flowchart showing a procedure of processing executed by a control device provided in the first embodiment shown in FIG.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

FIG. 6 is a flowchart showing a procedure of processing executed by a control device provided in the second embodiment shown in FIG.

FIG. 7 is a circuit diagram showing a third embodiment of the present invention.

FIG. 8 is a circuit diagram showing a conventional pump control device for a construction machine.

9 is a diagram showing pressure / flow rate characteristics of the hydraulic pump in the conventional technique shown in FIG.

[Explanation of symbols]

 1 Diesel Engine (Motor) 2 Variable Capacity Hydraulic Pump 3 Directional Control Valve 4 Hydraulic Cylinder (Hydraulic Actuator) 5 Discharge Amount Control Means 6 Spring 7 Piston 8 Discharge Pipeline 9 Pilot Pipeline 20 Indication Device 25 Control Device (Selection Means) 27 Electromagnetic proportional pressure reducing valve (driving means) 28 Pilot line 29 Pilot line 30 Pilot line 31 Tank 34 Discharge amount control means 35 Spring 36 Stepped piston 37 Pilot pump (driving means) 38 Pilot line 39 Electromagnetic switching valve (drive) Means) 40 pilot conduit 41 pilot conduit 42 pilot relief valve (driving means)

Claims (7)

[Claims] 1. A prime mover, a hydraulic pump driven by the prime mover, discharge amount control means for controlling a discharge amount of the hydraulic pump, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, and the hydraulic pressure. A hydraulic pump for a construction machine, comprising: a directional control valve that controls a flow of pressure oil supplied from the pump to the hydraulic actuator, and one of a plurality of fuels is selectively adopted as a fuel that drives the prime mover. In the control device, an instruction device that outputs an instruction signal corresponding to each fuel of the plurality of fuels, and a drive that can selectively drive the discharge amount control means into one of a plurality of different drive modes. Means and a selecting means for selecting a drive mode of the discharge amount control means which is changed by the drive means in accordance with an instruction signal output from the indicating device. A hydraulic pump control device for construction machinery. 2. The hydraulic pump control device for a construction machine according to claim 1, wherein the prime mover is a diesel engine. 3. The hydraulic pump control device for a construction machine according to claim 1, wherein the selection means is a control device having a logical judgment function. 4. The electromagnetic proportional pressure reducing valve for outputting a pilot pressure for driving the discharge amount control means in accordance with a signal output from the control device, wherein the drive means is an electromagnetic proportional pressure reducing valve. Hydraulic pump controller for construction machinery. 5. The driving means selectively outputs the pressure discharged from the pilot pump according to a signal output from the pilot pump and the control device, as a pilot pressure for driving the discharge amount control means. The hydraulic pump control device for a construction machine according to claim 3, further comprising an electromagnetic switching valve. 6. The hydraulic pump is a variable displacement hydraulic pump, and the discharge amount control means includes a piston for controlling a tilt angle of a swash plate of the variable displacement hydraulic pump, and one side of the piston is provided. 6. A pilot line for guiding the pump discharge pressure as a pilot pressure, and a pilot line for guiding the pilot pressure output from the drive means on the other side of the piston. Hydraulic pump controller for construction machinery. 7. The hydraulic pump is a variable displacement hydraulic pump, and the discharge amount control means includes a stepped piston for controlling a tilt angle of a swash plate of the variable displacement hydraulic pump, and A pilot line for guiding the pump discharge pressure as a pilot pressure to the one side, and a pilot line for guiding the pilot pressure output from the drive means to the one side of the stepped piston are provided. The hydraulic pump control device for a construction machine according to claim 4 or 5.