JP2001323904A - Hydraulic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device capable of setting the angle of inclination of a first hydraulic pump and a second hydraulic pump equal to each other when the straight traveling is indicated. SOLUTION: This hydraulic control device is provided with an engine 1, hydraulic pumps 2 and 3, regulators 4 and 5, a traveling left motor 6, a traveling right motor 7, an engine control dial 13 for indicating the target engine speed, and a controller 12 having a base torque computing means 20 for computing the base torque of the hydraulic pumps 2 and 3 on the basis of the target engine speed. The hydraulic control device is also provided with a traveling operation detecting unit 17 for detecting the straight traveling and pressure sensors 18 and 19 for detecting the discharge pressure of the hydraulic pumps 2 and 3. The controller 12 has a correction torque computing means 21 for computing the correction torque larger than the base torque when the discharge pressure detected by the pressure sensors 18 and 19 exist in the predetermined low area L11, and a maximum value selecting means 22 capable of selecting the maximum value of the base torque and the correction torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device provided in a hydraulic shovel or the like, and more particularly to a base torque calculating means for calculating a base torque corresponding to an input torque of a hydraulic pump based on a target engine speed. The present invention relates to a hydraulic control device including:

[0002]

2. Description of the Related Art FIGS. 4 to 7 are explanatory views of the prior art, FIG. 4 is a hydraulic circuit diagram showing the configuration of a conventional hydraulic control device, and FIG. 5 is a diagram of a controller provided in the conventional hydraulic control device shown in FIG. FIG. 6 is a block diagram showing a main part configuration, FIG. 6 is a diagram showing a pump average pressure / pump tilt angle characteristic in the conventional hydraulic control device shown in FIG. 4, and FIG. 7 is an enlarged explanatory view of a portion F in FIG.

[0003] The conventional hydraulic control device shown in FIG. 4 is provided, for example, in a hydraulic excavator. As shown in FIG. 4, the engine 1 is driven by the engine 1.
Variable displacement first and second hydraulic pumps 2 and 3 having the same structure, regulators 4 and 5 for controlling the discharge amounts of these hydraulic pumps 2 and 3, respectively, and discharge from hydraulic pumps 2 and 3 Traveling left motor 6 and traveling right motor 7 driven by pressure oil and traveling left motor 6 and traveling right motor 7 from hydraulic pumps 2 and 3 respectively.
Left directional control valve 8 and right directional control valve 9 for controlling the flow of the pressure oil supplied to the vehicle, and the left directional control valve 9 for switching these directional left control valve 8 and right directional control valve 9 An operating device 10 and an operating device 11 for traveling right are provided.

A target engine speed indicating means for indicating a target engine speed of the engine 1, that is, an engine control dial (hereinafter referred to as "en-con dial").
13, an engine speed control mechanism 14 for controlling the speed of the engine 1, a hydraulic source 16 composed of, for example, a pilot pump, and an oil passage connecting the hydraulic source 16 and each of the regulators 4 and 5 in an oil path. Electromagnetic proportional pressure reducing valve 1
5 and a controller 25.

As shown in FIG. 5, the controller 25 calculates a base torque corresponding to the input torque of the hydraulic pumps 2, 3 based on the target engine speed input from the en-con dial 13. Means 20 are provided. The value of the base torque is set to be small in the predetermined region L1 where the target engine speed is small, and to be large in the predetermined region L2 where the target engine speed is high.

As shown in FIG. 5, the controller 25 performs a calculation for obtaining a control current that becomes smaller as the value of the base torque output from the base torque calculator 20, ie, the value of the command torque becomes larger. The control current calculating means 24 is provided. The control current of the current value obtained by the control current calculation means 24 is output as a drive signal to the control unit of the aforementioned electromagnetic proportional pressure reducing valve 15.

In the prior art having such a configuration, FIG.
As shown in FIG.
3 and the base torque corresponding to the target engine speed input by the base torque calculating means 20 is input to the control current calculating means 24 as a command torque, and here corresponds to the corresponding command torque. The current value is calculated. The control current of the current value is output to the control unit of the electromagnetic proportional pressure reducing valve 15 as a drive signal. The control current calculating means 24 increases the current value as the command torque is smaller. The electromagnetic proportional pressure reducing valve 15 is appropriately switched according to the above-described control current, reduces the primary pressure of the hydraulic pressure source 16, and supplies the pilot pressure Pt to the regulators 4 and 5. The regulators 4 and 5 include an electromagnetic proportional pressure reducing valve 15.
The tilt angle θ of the hydraulic pumps 2 and 3 is controlled by the pilot pressure Pt supplied via the controller and the discharge pressures of the hydraulic pumps 2 and 3. For example, as the discharge pressure of the hydraulic pumps 2 and 3 and the pilot pressure Pt increase, the tilt angle θ of the hydraulic pumps 2 and 3 increases.
Is controlled to be smaller.

Returning to FIG. 4, the electromagnetic proportional pressure reducing valve 15
The valve opening increases as the value of the control current output from the controller 25 increases, and the pilot pressure Pt to the regulators 4 and 5 increases. The regulators 4 and 5 operate so that the tilt angle θ of the hydraulic pumps 2 and 3 decreases as the pilot pressure Pt increases. Therefore, the pilot pressure Pt increases as the target engine speed of the engine 1 decreases, and the regulators 4 and 5 operate to reduce the tilt angle θ. Conversely, the pilot pressure Pt decreases as the target engine speed increases. And the tilt angle θ tends to increase.

On the other hand, the discharge pressures of the hydraulic pumps 2 and 3 also act on the regulators 4 and 5, and the tilting of the hydraulic pumps 2 and 3 is performed by a synergistic effect of these pump discharge pressures and the pilot pressure Pt. Is controlled.

The pump average pressure / pump tilt angle characteristic in the above-mentioned conventional technique will be described with reference to FIG.

The horizontal axis in FIG. 6 shows the pump average pressure, which is the average value of the discharge pressures of the hydraulic pumps 2 and 3, and the vertical axis shows the tilt angle θ of the hydraulic pumps 2 and 3. This FIG.
It corresponds to what is called a -Q curve. Curves A and B indicated by dashed lines are iso-horsepower curves corresponding to the engine speed, that is, curves indicating the horsepower that can be produced by the engine 1. Curve A is an iso-horsepower curve at a high speed, for example, the maximum speed, 4 is an iso-horsepower curve when the rotational speed is low. The pump input torque is determined by the product of the discharge pressures of the hydraulic pumps 2 and 3 and the discharge flow rates of the hydraulic pumps 2 and 3, and is set so as not to exceed the engine output horsepower corresponding to the equal horsepower curve described above.
The tilt angles θ of these hydraulic pumps 2 and 3 are controlled. That is, as shown in FIG. 6, when the engine rotational speed is the maximum rotational speed, the tilt angle θ on the line indicated by the solid line
Is controlled. Note that the solid straight line G corresponds to the maximum tilt angle, which is set mechanically.
This is a region where the tilt angle θ cannot be increased any more.

The polygonal line is determined so as to be substantially tangent to the curve A. This is to make effective use of the engine output horsepower. On the other hand, as the engine speed decreases, the iso-horsepower curve shifts to the left side of FIG. 6 (translation).
In response, the solid line hofer also shifts to the left. At this time, on the low rotational speed side, it is set so as to contact the constant horsepower curve B with a straight line having a gentle slope. what if,
If they are set to be in contact with each other with a steep straight line d, there is a possibility that the engine may stall beyond the constant horsepower curve when the discharge pressure of the hydraulic pumps 2 and 3 increases. For this reason, it is set so as to substantially contact the constant horsepower curve B with a gentle straight line.

When the target engine speed decreases and the pilot pressure pt shown in FIG. 4 increases with the operation of the en-con dial 13, the pump average pressure-pump tilt angle characteristic line (FIG. 6) as shown in FIG. (PQ line) shifts to the left, and the break point where the tilt angle θ decreases from the maximum tilt angle shifts from the break point A to the break point B. Thus, the input torque of the hydraulic pumps 2, 3 does not exceed the output horsepower of the engine 1, and engine stall is prevented.

A known technique of this kind is disclosed, for example, in JP-A-4-5487.

[0015]

In the prior art shown in FIGS. 4 to 6 described above, when straight running is instructed in a state where the target engine speed is low, the vehicle generally tilts on a straight line d in FIG. The turning angle θ is controlled. At this time, hydraulic oil is supplied from the corresponding hydraulic pumps 2 and 3 to the traveling left motor 6 and the traveling right motor 7 shown in FIG. These two hydraulic pumps 2 and 3 have basically the same structure and are made to have the same performance, but in reality, their respective performances are slightly different from each other due to manufacturing errors and the like. There is also a difference. In FIG. 7 in which the F portion of FIG. 6 is enlarged, for example, 30 is the pump average pressure of the first hydraulic pump 2.
A pump tilt angle characteristic line 31 indicates a pump average pressure / pump tilt angle characteristic line of the second hydraulic pump 3. This FIG.
As can be seen from the figures, although the same pilot pressure Pt and the same pump discharge pressure act on the regulators 4 and 5, respectively, there is a slight difference in the tilt angle θ. This causes a difference in the flow rate of the pressure oil supplied to each of the traveling left motor 6 and the traveling right motor 7. That is,
A flow rate difference corresponding to the difference 32 in the tilt angle θ in FIG. 7 occurs. Therefore, in the above-described prior art shown in FIGS.
There is a problem that the workability of the work performed through the straight traveling is reduced. In particular, the portion of the straight line d in FIG. 6 in which the rotation speed of the engine 1 is relatively low has a larger inclination than the portion of the straight line, so that the tilt angle θ of the hydraulic pumps 2 and 3 tends to be different.

The present invention has been made in view of the above situation in the prior art, and an object of the present invention is to set the respective tilt angles of the first hydraulic pump and the second hydraulic pump when the straight traveling is instructed. An object of the present invention is to provide a hydraulic control device that can be made equal.

[0017]

In order to achieve the above object, an invention according to claim 1 of the present application is directed to an engine and a variable displacement first hydraulic pump driven by the engine and having the same structure, A second hydraulic pump and these first
A regulator for controlling the discharge amounts of the hydraulic pump and the second hydraulic pump, a traveling left motor driven by pressure oil discharged from the first hydraulic pump, and a drive motor driven by pressure oil discharged from the second hydraulic pump. A traveling right motor, and target engine speed instruction means for instructing a target engine speed, and a base torque corresponding to the input torque of the first hydraulic pump and the second hydraulic pump based on the target engine speed. In a hydraulic control device including a controller having a base torque calculating means for calculating, a travel detecting means for detecting that a straight running is instructed, and discharge pressures of the first hydraulic pump and the second hydraulic pump are respectively detected. Discharge pressure detecting means, wherein the controller detects that the discharge pressure detected by the discharge pressure detecting means has a predetermined low level. A correction torque calculating means for calculating a correction torque having a value larger than the base torque corresponding to the target engine speed corresponding to the corresponding discharge pressure, and a base torque output from the base torque calculating means, And a maximum value selecting means capable of selecting a maximum value of the correction torques output from the correction torque calculating means. The controller detects that the straight running is instructed by the running detecting means. With
When the discharge pressure detecting means detects that the discharge pressure is in the predetermined low area, the maximum value selecting means selects the correction torque calculated by the correction torque calculating means, and sets the correction torque to It is configured to output a drive signal for driving each of the regulators accordingly.

According to the first aspect of the present invention, the hydraulic oil from the first hydraulic pump is supplied to the traveling left motor, and the hydraulic oil from the second hydraulic pump is supplied to the traveling right motor. When the vehicle is going to travel straight ahead, it is detected by the travel detecting means that this straight traveling is instructed. It is empirically known that the discharge pressure of each of the first hydraulic pump and the second hydraulic pump is generally within a predetermined low range in such a straight running. Therefore, at this time, the discharge pressure detecting means detects that the discharge pressures of the first hydraulic pump and the second hydraulic pump are within the above-described predetermined low range.

In the controller, as described above, it is detected by the travel detecting means that straight traveling is instructed, and at the same time, the discharge pressure detecting means sets the discharge pressures of the first hydraulic pump and the second hydraulic pump in a predetermined low range. When the presence is detected, the built-in maximum value selecting means performs a process of selecting the correction torque calculated by the correction torque calculating means.

The correction torque at this time is a torque larger than the base torque corresponding to the target engine speed obtained by the base torque calculation means. That is, it is possible to shift the pump average pressure / pump tilt angle characteristic line in the direction of higher engine rotation than before. Thus, the tilt angle of each of the first hydraulic pump and the second hydraulic pump can be set to the maximum tilt angle.

The maximum tilt angle is determined by the first hydraulic pump and the second hydraulic pump.
It is unique to each of the hydraulic pumps, and is set mechanically as described above. Now, since the first hydraulic pump and the second hydraulic pump have the same structure, the maximum tilt angles of these hydraulic pumps are equal to each other.
That is, when the straight running is instructed in this way, the first
The tilt angles of the hydraulic pump and the second hydraulic pump can be kept equal to each other.

In the above arrangement, the controller includes a switch for conducting the correction torque calculating means and the maximum value selecting means when the traveling detecting means detects that the straight running is instructed. It may be configured.

In the above-mentioned configuration, a configuration may be adopted in which an electromagnetic proportional pressure reducing valve is interposed between the hydraulic pressure source and each of the regulators and is switched by the drive signal output from the controller.

In the above-mentioned configuration, the travel detecting means may comprise a travel operation detector for detecting that the travel operating device has been operated.

The hydraulic control device may be provided in a hydraulic shovel having a structure including a traveling body.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic control device according to the present invention will be described below with reference to the drawings. 1 to 3 are explanatory views of an embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram showing an overall configuration of the embodiment, and FIG. 2 is a main part of a controller provided in the embodiment shown in FIG. FIG. 3 is a block diagram showing the configuration, and FIG. 3 is a graph showing the average pressure of the pump obtained in the embodiment shown in FIG.
It is a figure showing a pump tilt angle characteristic.

In these figures, those equivalent to those shown in FIGS. 4 to 7 are denoted by the same reference numerals. That is, even in the present embodiment, the engine 1, the variable displacement first hydraulic pump 2, the second hydraulic pump 3, and the regulators 4 and 5, which have the same structure, drive the traveling body (not shown). The vehicle includes a left motor 6, a traveling right motor 7, a traveling left direction control valve 8, a traveling right direction control valve 9, a traveling left operating device 10, and a traveling right operating device 11.

Further, an encon dial 13, which constitutes a target engine speed instruction means, an engine speed control mechanism 14, and a hydraulic source 16 comprising, for example, a pilot pump
, An electromagnetic proportional pressure reducing valve 15 and a controller 12.

As shown in FIG. 2, the controller 12
A base torque calculating means 20 for calculating a base torque corresponding to the input torque of the hydraulic pumps 2 and 3 based on a target engine speed input from the encon dial 13; and a smaller value as the value of the command torque increases. And a control current having a current value calculated by the control current calculating means 24 is output to the control unit of the electromagnetic proportional pressure reducing valve 15 described above. . For the above configuration,
It is equivalent to that shown in FIGS.

FIG. 3A shows an iso-horsepower curve when the engine speed is high, for example, the maximum engine speed, B is an iso-horsepower curve when the engine speed is low, and solid line Toe-ho is the engine speed. Pump average pressure / pump tilt angle characteristic line when the rotation speed is the maximum rotation speed, and the solid line Toni shows the pump average pressure / pump tilt angle characteristic line when the engine rotation speed is low.
B is a turning point where the tilt angle θ decreases from the maximum tilt angle at the maximum rotation speed and the low rotation speed, respectively. These are also the same as those shown in FIGS.

In the present embodiment, in particular, the travel detecting means for detecting that the straight traveling is instructed, for example, the travel operation for detecting that the travel left operating device 10 and the travel right operating device 11 shown in FIG. Detector 17, hydraulic pump 2,
3 is provided with discharge pressure detecting means for detecting the respective discharge pressures, for example, pressure sensors 18 and 19.

The controller 12 includes the pressure sensor 1
Pump pressure average calculating means 25 which receives pressure signals PS1 and PS2 output from 8 and 19 and calculates an average pressure thereof, and a correction torque corresponding to the pump average pressure calculated by the pump average pressure calculating means 25. And a correction torque calculating means 21 for calculating. The correction torque calculating means 21 determines whether the pump average pressure is in a predetermined low region L11.
When the average pressure of the pump is in a predetermined high region L22, the calculation is performed so as to have a small correction torque. The predetermined low region L11 of the pump average pressure means that the discharge pressures of the hydraulic pumps 2 and 3 are in the predetermined low region L11, and thus the discharge pressure of the hydraulic pumps 2 and 3 is in the predetermined low region L11. This means that the target engine speed for driving these hydraulic pumps 2 and 3 is in a predetermined low region L1. In other words, the predetermined low region L1 of the target engine speed in the base torque calculating means 20 and the predetermined low region L11 of the average pump pressure in the correction torque calculating means 21 are set so as to substantially coincide with each other. Further, the value of the correction torque in the correction torque calculating means 21 is determined in the region L1 where the pump average pressure is a predetermined low value.
When it is 1, it is preset so that the target engine speed of the base torque calculation means 20 becomes larger than the value of the base torque when it is in the predetermined low region L1. When the pump average pressure is in the predetermined high region L22, the value of the correction torque is set to be smaller than the value of the base torque when the target engine speed of the base torque calculating means 20 is in the predetermined high region L2. Is set in advance.

The controller 12 is closed when a signal indicating that a traveling operation has been performed (traveling ON) is further output from the traveling operation detector 17, and a signal indicating that no traveling operation has been performed (traveling OFF) is output. A switch means 23 which is opened when output, a correction torque calculated by the correction torque calculation means 21 output through the switch means 23, and a maximum of the base torque calculated by the base torque calculation means 20. A maximum value selecting means capable of selecting a value is provided.

When the travel OFF signal is output from the travel operation detector 17, the switch means 23 is open, so that the base torque calculated by the base torque calculation means 20 is always the maximum value. It is selected by the selection means 22. When the traveling ON signal is output from the traveling operation detector 17, the switch means 23 is closed, and therefore the base torque calculated by the base torque calculating means 20 or the correction torque calculated by the correction torque calculating means 21 is used. One of the torques is selected by the maximum value selecting means 22 as the maximum value. In this case, the pressure sensor 1
The average value of the discharge pressures of the hydraulic pumps 2 and 3 detected at 8 and 19, that is, the average pump pressure is lower than a predetermined low region L11.
, The correction torque calculated by the correction torque calculation means 21 is larger than the base torque calculated by the base torque calculation means 20, so that this correction torque is selected by the maximum value selection means 22 as the maximum value. You.
Further, for example, when the boom, the arm, and the like are operated together with the traveling body and the discharge pressures of the hydraulic pumps 2 and 3 increase, and the pump average pressure reaches a predetermined high region L22, compared with the correction torque. Therefore, the base torque becomes larger, and therefore, this base torque is selected by the maximum value selecting means 22 as the maximum value.

The base torque or the correction torque selected by the maximum value selection means 22 is output to the control current calculation means 24 as a command torque. The control current calculation means 24 calculates a current value according to the command torque output from the maximum value selection means 22 and outputs a control current of the current value to the control unit of the electromagnetic proportional pressure reducing valve 15. In this case, as described above, the control current calculating means 24 increases the current value as the command torque is smaller. Thereby, the electromagnetic proportional pressure reducing valve 15
And the regulators 4 and 5 operate to reduce the tilt angle θ of the hydraulic pumps 2 and 3. Conversely, the current value decreases as the command torque increases. As a result, the valve opening of the electromagnetic proportional pressure reducing valve 15 decreases, and the regulators 4 and 5 operate to increase the tilt angle θ of the hydraulic pumps 2 and 3.

The operation of the present embodiment configured as described above is as follows.

Now, a relatively low target engine speed, ie, a target engine speed in the low region l1 of the base torque calculating means 20 in FIG. It is assumed that both of the operation devices 11 are operated and straight running is about to be performed.

The controller 13 outputs a drive signal corresponding to the target engine speed indicated by the en-con dial 13 to the engine speed control mechanism 14. As a result, the engine speed control mechanism 14 operates, and the speed of the engine 1 becomes a speed corresponding to the target engine speed, and the hydraulic pumps 2 and 3 are driven according to this speed. The pressure of the pressure oil discharged from the hydraulic pumps 2 and 3 is determined by a pressure sensor 1
8, 19, and pressure signals PS1, PS2, respectively.
Is input to the controller 12.

In the controller 12, a base torque corresponding to the target engine speed indicated by the en-con dial 13 is calculated by the base torque calculating means 20. In this case, the target engine speed is relatively low, and therefore belongs to a predetermined low region L1, and a small value of the base torque is calculated accordingly.

The pressure signals PS1 and PS2 output from the pressure sensors 18 and 19 are used as pump average pressure calculating means 2.
The average value of the discharge pressures of the hydraulic pumps 2 and 3 is obtained by the average pump pressure calculating means 25 as the average pump pressure. The correction torque is calculated by the correction torque calculation means 20 according to the pump average pressure. In this case, the hydraulic pump 2,
3 has a relatively low discharge pressure, and thus has a predetermined low region L.
1, and a correction torque having a large value, that is, a correction torque having a value larger than the corresponding base torque is calculated accordingly.

During this time, the operation of the traveling left operating device 10 and the traveling right operating device 11 is detected by the traveling operation detector 17, whereby the switch means 23 of the controller 12 is closed.

Therefore, when the base torque output from the base torque calculation means 20 and the correction torque output from the correction torque calculation means 21 via the switch means 23 are input to the maximum value selection means 22, the maximum value A correction torque is selected. A relatively large correction torque of this torque value is given to the control current calculation means 24 as a command torque.

In this case, since the command torque has a large torque value, a relatively small current value is calculated, and the control current of the small calculated value is output to the control unit of the electromagnetic proportional pressure reducing valve 15 shown in FIG. . As a result, the electromagnetic proportional pressure reducing valve 15 is switched so that the valve opening becomes relatively small. Therefore, a small pilot pressure Pt is supplied from the hydraulic pressure source 16 to the regulators 4 and 5 via the electromagnetic proportional pressure reducing valve 15.

Accordingly, the tilt angle θ of the hydraulic pumps 2, 3
Is larger than the tilt angle θ based on the base torque corresponding to the target engine speed. The characteristic line of the average pressure of the pump and the tilt angle of the pump at this time is shown by a solid line in FIG. Therefore, assuming that the tilt angle θ based on the base torque corresponding to the corresponding target engine speed is the CO point on the solid line toni of FIG.
At the same pump average pressure in this case, that is, based on a correction torque larger than the base torque, the tilt angle θ
Can be shifted to the point C1 on the maximum tilt angle.

For the above reasons, the tilt angles θ of the hydraulic pumps 2 and 3 in the present embodiment are equal to each other at the mechanically set maximum tilt angle. In response, hydraulic oils of the same flow rate are supplied from the hydraulic pumps 2 and 3 to the traveling left motor 6 and the traveling right motor 7 via the traveling left direction control valve 8 and the traveling right direction control valve 9. Thereby, a desired straight traveling can be realized. Therefore, the workability of the work performed through the straight running can be improved without meandering.

In the above-described embodiment, for example, a combined operation of traveling and a boom or an arm is intended, a high target engine speed is instructed from the en-con dial 13, and the discharge pressures of the hydraulic pumps 2 and 3 are controlled. That is, when the pump average pressure increases and reaches the predetermined high region L22 of the correction torque calculation means 21, the base torque calculation means 20 calculates the correction torque compared to the correction torque calculated by the correction torque calculation means 21. The base torque becomes larger, and the base torque is selected by the maximum value selection means 22.
This base torque is input to the control current calculation means 24 as a command torque, and a corresponding current value is obtained. The control current of the current value is supplied to the control unit of the electromagnetic proportional pressure-reducing valve 15, and the hydraulic pumps 2 and 3 are controlled so that the tilt angle θ increases. The iso-horsepower curve at this time is shown, for example, in FIG. 3A, and the pump average pressure-pump tilt angle characteristic line is shown in FIG.
The solid line of FIG.

When, for example, the boom, the arm or the like is driven in a state where the traveling left operating device 10 and the traveling right operating device 11 are not operated, the signal output from the traveling operation detector 17 is OFF. As described above, the switching means 23 shown in FIG. 2 is opened. Therefore, the base torque output from the base torque calculating means 20 is always selected by the maximum value selecting means 22 irrespective of whether or not the target engine speed is low. This base torque is input to the control current calculation means 24 as a command torque, and a corresponding current value is obtained. The control current of the current value is supplied as a drive signal to the control unit of the electromagnetic proportional pressure reducing valve 15, and the tilt angle θ of the hydraulic pumps 2, 3 is calculated as shown in FIG.
7 are controlled in the same manner as the conventional ones.

Although an example in which the present invention is applied to a hydraulic excavator has been described above, the present invention is not limited to such an application to a hydraulic excavator, but may be applied to a working machine such as a crane having a traveling body. Is also good.

[0049]

According to the present invention, the tilt angle of each of the first hydraulic pump and the second hydraulic pump when the straight traveling is instructed is set to the maximum tilt set mechanically. The corners can be made equal to each other, so that the meandering that has conventionally occurred can be prevented, and the workability of the work performed through this straight traveling can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an overall configuration of a hydraulic control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a main configuration of a controller provided in the embodiment shown in FIG. 1;

FIG. 3 is a view showing a pump average pressure / pump tilt angle characteristic obtained in the embodiment shown in FIG. 1;

FIG. 4 is a hydraulic circuit diagram showing a configuration of a conventional hydraulic control device.

FIG. 5 is a block diagram showing a main configuration of a controller provided in the conventional hydraulic control device shown in FIG.

FIG. 6 is a diagram showing characteristics of a pump average pressure and a pump tilt angle in the conventional hydraulic control device shown in FIG. 4;

FIG. 7 is an enlarged explanatory view of a portion F in FIG. 6;

[Explanation of symbols]

Reference Signs List 1 engine 2 first hydraulic pump 3 second hydraulic pump 4 regulator 5 regulator 6 traveling left motor 7 traveling right motor 8 traveling left direction control valve 9 traveling right direction control valve 10 traveling left operating device 11 traveling right operating device 12 controller 13 Encon dial (Target engine speed indicating means) 14 Engine speed control mechanism 15 Electromagnetic proportional pressure reducing valve 16 Hydraulic power source 17 Running operation detector (Running detecting means) 18 Pressure sensor (Discharge pressure detecting means) 19 Pressure sensor (Discharge pressure) Detecting means) 20 base torque calculating means 21 correction torque calculating means 22 maximum value selecting means 23 switch means 24 control current calculating means 25 pump average pressure calculating means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoichi Furutari 650, Kandamachi, Tsuchiura-shi, Ibaraki Prefecture Inside the Tsuchiura Plant of Hitachi Construction Machinery Co., Ltd. (72) Inventor Koji Ishikawa 650 Kandamachi, Tsuchiura-shi, Ibaraki Prefecture Hitachi Construction Machinery Co., Ltd.F-term in Tsuchiura Plant (reference) BB17 CC10 DA03 DA13 DB05 DB43 EE22 FF03 FF08 GG02 JJ02

Claims (5)

[Claims] 1. An engine, a variable displacement first hydraulic pump and a second hydraulic pump driven by the engine and having the same structure, and a first hydraulic pump and a second hydraulic pump.
A regulator for controlling the discharge amount of the hydraulic pump, a traveling left motor driven by pressure oil discharged from the first hydraulic pump, and a traveling right motor driven by pressure oil discharged from the second hydraulic pump; A target engine speed indicating means for indicating a target engine speed, and a base torque calculation for calculating a base torque corresponding to the input torque of the first hydraulic pump and the second hydraulic pump based on the target engine speed. In a hydraulic control device provided with a controller having means, a travel detection means for detecting that straight traveling is instructed; a discharge pressure detection means for detecting discharge pressures of the first hydraulic pump and the second hydraulic pump, respectively; The discharge pressure detected by the discharge pressure detecting means is in a predetermined low region. A correction torque calculating means for calculating a correction torque larger than the base torque corresponding to the target engine speed corresponding to the corresponding discharge pressure; a base torque output from the base torque calculating means; A maximum value selection unit that can select a maximum value of the correction torques output from the correction torque calculation unit, wherein the controller detects that the straight traveling is instructed by the traveling detection unit, When the discharge pressure is detected by the discharge pressure detecting means to be in the predetermined low region, the maximum value selecting means selects the correction torque calculated by the correction torque calculating means, and according to the correction torque, And outputting a drive signal for driving each of the regulators. 2. The controller according to claim 1, wherein said controller includes a switch for electrically connecting said correction torque calculating means to said maximum value selecting means when it is detected by said travel detecting means that straight traveling is instructed. The hydraulic control device according to claim 1, wherein 3. The hydraulic control according to claim 1, further comprising an electromagnetic proportional pressure reducing valve interposed between a hydraulic pressure source and each of the regulators and switched by the drive signal output from the controller. apparatus. 4. The hydraulic control device according to claim 1, wherein said travel detecting means comprises a travel operation detector for detecting that the travel operating device has been operated. 5. The hydraulic control device according to claim 1, wherein the hydraulic control device is provided in a hydraulic shovel.