JP2001193702A - Hydraulic driving device for construction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain fluctuation of engine speed while limiting a fuel injection amount depending on a drop of boost pressure at the time of application of engine load to reduce dry soot, in a hydraulic driving device for construction equipment. SOLUTION: A pump controller 21 is provided with an operation amount control portion 211, a constant horsepower controlling portion 212, a target absorption torque calculation portion 213, and a minimum value selection portion 214. In the operation amount control portion 211, a target pump inclined rotational angle θc is calculated depending on pressure difference Pc of a restriction 22 detected by a pressure difference detector 23. In the constant horsepower controlling portion 212, a limit value θp is calculated of the target pump inclined rotational angle depending on a coefficient Kc for keeping a constant absorption torque inputted from the absorption torque calculation portion 213. In the minimum value selection portion 214, a smaller one of the target pump inclined rotational angle θc and the limit value θp is outputted to a regulator 20 as a command signal. Further, in the target absorption torque calculation portion 213, the coefficient Kc is calculated based on engine speed deviation ΔN and the boost pressure Pb.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for a construction machine, and more particularly to an engine having a power source, a variable displacement hydraulic pump driven by the engine, and an actuator driven by hydraulic oil supplied from the hydraulic pump. TECHNICAL FIELD The present invention relates to a hydraulic drive device for a construction machine such as a hydraulic shovel that drives a vehicle and performs necessary work.

[0002]

2. Description of the Related Art In a hydraulic drive device of a construction machine such as a hydraulic excavator, when a variable displacement hydraulic pump is used,
The pump control means for controlling the discharge amount of the hydraulic pump includes: 1) controlling the discharge amount of the hydraulic pump in accordance with the operation amount of the operation lever device for controlling the switching direction and the switching amount of the direction switching valve; and
2) It has two functions of keeping the absorption horsepower of the hydraulic pump within the limit value so that the engine is not overloaded.The former is implemented by, for example, negative control, positive control or load sensing control, and the latter is the limitation of input torque. It is implemented by control.

In the latter control, Japanese Patent Laid-Open Publication No.
As described in Japanese Patent No. 171042, there is known a technique of changing the absorption horsepower of a hydraulic pump according to an engine speed deviation. This technique calculates a deviation between the actual engine speed and a target engine speed (engine speed deviation). When the engine speed deviation increases, the fuel injection amount of the engine is increased, and at the same time, the limit value of the absorption torque of the hydraulic pump ( The tilt of the hydraulic pump is controlled so as to reduce the maximum value of the input torque, thereby reducing the absorption horsepower of the hydraulic pump and reducing the fluctuation of the engine speed.

On the other hand, in an engine (usually a diesel engine) which is a power source of a hydraulic drive device of a construction machine, control is generally performed to increase the fuel injection amount of the engine when the engine rotational deviation increases as described above. Prevent stalls. In such an engine, when the engine load suddenly increases, the fuel injection amount also increases, and black smoke is generated in the exhaust gas. In order to prevent this, in an engine equipped with a turbocharger, a supercharging pressure is detected as an intake air amount, and a fuel injection amount is limited according to the supercharging pressure.
In other words, lowering the supercharging pressure means reducing the amount of intake air.Therefore, when the supercharging pressure is reduced, control is performed to reduce the fuel injection amount, and by controlling the ratio of air and fuel to a certain range, black smoke is reduced. Is to be reduced.

[0005]

However, when the technology of engine control for limiting the fuel injection amount in accordance with the supercharging pressure is applied to the technology described in Japanese Patent Application Laid-Open No. 57-171042, the following problem arises. Occurs.

[0006] During the operation of the construction machine, the engine load changes suddenly. In the technique described in Japanese Patent Application Laid-Open No. 57-171042, a change in the engine load is regarded as an engine speed deviation, and when the engine load suddenly changes (increases) and the engine speed deviation increases, the fuel injection amount of the engine is reduced. Since the control is performed so as to increase the amount to a corresponding amount, fluctuations in the rotational speed of the engine are minimized. However, in order to reduce the black smoke in the exhaust gas of the engine, when applying the technology of restricting the fuel injection amount according to the supercharging pressure, when the supercharging pressure decreases due to a sudden change (increase) in the engine load, Since the fuel injection amount is limited according to the supercharging pressure, black smoke in the exhaust gas is reduced, but the fuel injection amount cannot be secured according to the engine speed deviation, and the engine speed fluctuation becomes larger than before. Would.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic drive device for a construction machine capable of suppressing fluctuations in engine speed while reducing black smoke by limiting a fuel injection amount in response to a decrease in supercharging pressure when an engine load is applied. It is to provide.

[0008]

(1) In order to achieve the above object, the present invention provides an engine as a power source, a variable displacement hydraulic pump driven by the engine, and a pump pumped out of the hydraulic pump. An actuator driven by pressurized oil, a direction switching valve for controlling the direction and flow rate of the pressure oil discharged from the hydraulic pump, operating means for controlling the switching direction and the amount of switching of the direction switching valve, Pump discharge amount control means for controlling the discharge amount of the hydraulic pump according to the operation amount of the means, a turbocharger for increasing the intake amount of the engine, and a supercharging pressure detecting means for detecting the intake amount as pressure, Engine speed detecting means for detecting the actual speed of the engine; engine speed command means for commanding the target speed of the engine; actual engine speed and target speed of the engine; A deviation of the engine speed and an engine speed control means for controlling the engine speed in accordance with the supercharging pressure. But,
There is a horsepower control means for changing the maximum value of the absorption horsepower of the hydraulic pump according to the engine speed deviation and the supercharging pressure, and limiting the discharge amount so that the absorption horsepower of the hydraulic pump becomes equal to or less than the maximum value. Shall be.

As described above, the horsepower control means is provided in the pump discharge amount control means, and the maximum value of the absorption horsepower of the hydraulic pump is changed according to the engine speed deviation and the supercharging pressure, thereby limiting the discharge amount of the hydraulic pump. When the load is applied to the engine by the input operation of the operating means and the engine speed decreases, the absorption horsepower of the hydraulic pump can be reduced not only by the engine speed deviation but also by the reduction of the supercharging pressure. The control means can restrict the fuel injection amount in accordance with the decrease of the supercharging pressure and reduce the black smoke and suppress the fluctuation of the engine speed as in the past.

(2) In the above (1), preferably,
The horsepower control means includes a calculating means for calculating a target absorption torque based on the engine speed deviation and the supercharging pressure, and a tilt angle of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the target absorption torque. And restricting means for restricting

Thus, the horsepower control means changes the maximum value of the absorption horsepower of the hydraulic pump according to the engine speed deviation and the supercharging pressure, and adjusts the discharge amount so that the absorption horsepower of the hydraulic pump becomes less than the maximum value. It will be restricted.

(3) In the above (2), preferably,
The calculating means calculates to reduce the target absorption torque as the engine rotational speed deviation increases and to reduce the target absorption torque as the supercharging pressure decreases.

Thus, the horsepower control means reduces the absorption horsepower of the hydraulic pump as the engine speed deviation increases and as the supercharging pressure decreases.

(4) In the above (2), the limiting means includes means for detecting a discharge pressure of the hydraulic pump,
Means for calculating a limit value of the target pump tilt angle corresponding to the target absorption torque obtained by the calculating means based on the pump discharge pressure; and means for limiting the tilt angle of the hydraulic pump to the limit value or less. Having.

Thus, the limiting means can be constituted by the arithmetic function of the controller.

(5) In the above (2), the calculating means is configured to output an electric signal according to the target absorption torque, and the limiting means is configured to control the electromagnetic proportional valve operated by the electric signal, The output pressure of the proportional valve is input to a hydraulic port for tilt angle increasing operation of the hydraulic pump, and the discharge pressure of the hydraulic pump is input to a hydraulic port for tilt angle decreasing operation of the hydraulic pump. And a tilt control actuator for controlling the tilt angle of the hydraulic pump so that the discharge pressure does not exceed a set value determined by the output pressure of the electromagnetic proportional valve.

This makes it possible to hydraulically configure the limiting means.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing a hydraulic drive device of a construction machine according to a first embodiment of the present invention.

In FIG. 1, the hydraulic drive device of this embodiment has a variable displacement type hydraulic pump 1, and an actuator 4 is connected to a discharge path 2 of the hydraulic pump 1 via a directional switching valve 3. The actuator 4 is driven by the pressure oil sent from. The actuator 4 includes a load 5 and performs a predetermined operation by driving the load 5.

The directional control valve 3 is, for example, a center bypass type having a center bypass passage 3a. When the directional control valve 4 is at the neutral position, the center bypass passage 3a is fully opened, and the center is switched as the directional control valve 3 is operated. The bypass passage 3a is throttled, and the center bypass passage 3a is fully closed at the full operation position of the direction switching valve 3. The input side of the center bypass passage 3a is connected to the discharge path 2 of the hydraulic pump 1 via a center bypass line 7a, and the output side is connected to the tank 8 via a center bypass line 7b.

The direction switching valve 3 is of a pilot operation type, and the switching direction and the amount of switching are controlled by a control pilot pressure generated by the operating lever device 10, and the flow direction and flow rate of the pressure oil supplied to the actuator 4 are controlled. Control. The operation lever device 10 is connected to the pilot pump 11 and generates a pilot pressure according to the operation direction and the operation amount of the operation lever 10a by using the pressure oil from the pilot pump 11 as a source pressure.

The hydraulic pump 1 is, for example, a swash plate pump.
A swash plate 1a is provided as a displacement displacement mechanism, and the swash plate 1a is controlled by a regulator 20, thereby changing the tilt angle of the hydraulic pump 1 and controlling the pump discharge amount.
The regulator 20 operates according to a command signal from the pump controller 21.

The hydraulic pump 1 and the pilot pump 11 are connected to an output shaft 13 of a motor 12 and are driven to rotate by the motor 12. The prime mover 12 is a diesel engine, and includes a turbocharger 14 and a fuel injection device 30. The fuel injection device 30 controls the fuel injection amount supplied to the engine 12, and is constituted by, for example, an electronic governor unit. The electronic governor unit is operated by a command signal from the engine controller 31.

The center bypass line 7b has an aperture 22
A differential pressure detector 23 for detecting a differential pressure across the throttle 22 is connected before and after the throttle 22. The directional control valve 3 is of the center bypass type as described above, and as a result of the opening area of the center bypass passage 3a changing according to the switching amount (stroke) of the directional control valve 3, the pressure flowing through the center bypass line 7b is correspondingly changed. The oil flow also changes. That is, the flow rate of the hydraulic oil flowing through the center bypass line 7b is maximum when the directional control valve 3 is at the neutral position, and the flow rate of the hydraulic oil flowing through the center bypass line 7b decreases as the directional control valve 3 is operated. At the full operation position of the directional control valve 3, the flow rate of the pressure oil flowing through the center bypass line 7b becomes zero. Since the differential pressure across the throttle 22 changes according to the flow rate of the pressure oil flowing through the center bypass line 7b, the switching amount of the direction switching valve 3 can be detected by detecting the differential pressure across the throttle 22. That is, the differential pressure detector 23 constitutes means for detecting the switching amount of the direction switching valve 3. The switching amount of the direction switching valve 3 corresponds to the operation amount of the operation lever 10a of the operation lever device 10, and detecting the switching amount of the direction switching valve 3 detects the operation amount of the operation lever 10a, that is, the required flow rate. Will be.

The hydraulic pump 1 has a discharge passage 2
Is provided with a pressure detector 24 for detecting the discharge pressure.

The hydraulic pump 1 and the pilot pump 11 are connected to an output shaft 13 of a motor 12 and are driven to rotate by the motor 12. The prime mover 12 is a diesel engine, and includes a turbocharger 14 and a fuel injection device 30. The fuel injection device 30 controls the fuel injection amount supplied to the engine 12, and is constituted by, for example, an electronic governor unit. The electronic governor unit is operated by a command signal from the engine controller 31.

The target rotation speed of the engine 12 is commanded by an engine speed command device 32. The engine speed instruction device 32 is, for example, a dial type.

The output shaft 13 of the engine 12 has an engine 1
The turbocharger 14 is provided with a supercharging pressure detector 34.

The pump controller 21 includes the differential pressure detector 2
3. The signals from the pressure detector 24 and the engine controller 31 are input, and predetermined arithmetic processing is performed.
A command signal is output to 0.

The engine controller 31 receives signals from an engine speed command device 32, an engine speed detector 33, and a supercharging pressure detector 34, performs predetermined arithmetic processing, and sends a command signal to the fuel injection device 30. Output.

FIG. 2 is a functional block diagram showing the control functions of the pump controller 21 and the engine controller 31.

In FIG. 2, the pump controller 21
Has the functions of an operation amount control unit 211, a constant horsepower control unit 212, a target absorption torque calculation unit 213, and a minimum value selection unit 214.

The manipulated variable control unit 211 inputs the signal from the differential pressure detector 23 as the differential pressure Pc before and after the diaphragm 22 and refers to this to a table stored in the memory. The corresponding target pump tilt angle θc is calculated.
Here, the differential pressure Pc before and after the throttle 22 is high when the switching amount of the directional control valve 3 (the operation amount of the operation lever 10a; required flow rate) is small, and decreases as the operation amount increases. The table shows the corresponding differential pressure P
c and the target pump tilt angle θc, that is, when the differential pressure Pc is large, the target pump tilt θc is small and the differential pressure Pc
The relationship between the differential pressure Pc and the target pump tilt angle θc is set so that the target pump tilt angle θc increases as the value becomes smaller.

The constant horsepower control section 212 includes a pressure detector 24
Is input as the pump discharge pressure Pp.
A coefficient Kc signal for keeping the absorption torque constant is input from the absorption torque calculation unit 213, and these signals are referred to a table stored in a memory, and the pump discharge pressure P at that time is referred to.
Limit value θp of target pump tilt angle according to p and coefficient Kc
Is calculated. Here, the following relationship between θp, Pp, and Kc is set in the memory table.

Θp = Kc / Pp By modifying the above equation, θp · Pp = Kc. That is, K
c represents a target absorption torque to be made constant.

The target absorption torque calculation unit 213 is provided with an engine speed deviation ΔN (described later) from the engine controller 31.
And a signal of a supercharging pressure Pb (described later) are input, and a coefficient Kc is calculated based on a predetermined function f (ΔN, Pb). Here, the function f (ΔN, Pb) is determined so that Kc decreases as the engine speed deviation ΔN increases, and Kc decreases as the supercharging pressure Pb decreases. .

Kc = K−aΔN + bPb−C where K: reference target absorption torque a, b: coefficient C: constant or Kc = K−d (ΔN / Pb) where K: reference target absorption torque d: coefficient minimum The value selection unit 214 selects the smaller of the target pump tilt angle θc calculated by the operation amount control unit 211 and the limit value θp of the target pump tilt angle obtained by the horsepower constant control unit 212, and controls the pump tilt angle. To the regulator 20 as a command signal.

The engine controller 31 has the functions of a difference calculation unit 311, a control compensation unit 312, a fuel injection amount restriction control unit 313, and a minimum value selection unit 314.

The difference calculation unit 311 is for performing engine control by negatively feeding back the engine speed, and receives a signal from the engine speed command device 32 and a signal from the engine speed detector 33, A deviation between the target engine speed and the engine speed (engine speed deviation) is calculated.

The control compensator 312 is inserted in series with respect to the engine speed deviation, performs differential integration and multiplication of the engine speed deviation, and optimizes the response characteristic of the engine speed. A target fuel injection amount is determined.

The fuel injection amount restriction control unit 313 inputs a signal from the supercharging pressure detector 34 as the supercharging pressure Pb, refers to the table stored in the memory, and obtains the supercharging pressure Pb at that time. Calculates the limit value M of the target fuel injection amount according to. Here, if the air intake amount is small, the supercharging pressure Pb is low, and if the air intake amount is increased, the supercharging pressure Pb becomes high. Therefore, the ratio of air and fuel is kept within a certain range to reduce black smoke. Therefore, when the supercharging pressure Pb is low, the limiting value M of the fuel injection amount is small, and the supercharging pressure Pb and the limiting value of the fuel injection amount are increased such that the limiting value M of the fuel injection amount increases as the supercharging pressure Pb increases. The relationship of M is set.

The minimum value selection unit 314 includes the target fuel injection amount calculated by the control compensation unit 312 and the fuel injection amount restriction control unit 31
3. Select the smaller of the limit value M of the fuel injection amount obtained in 3,
It outputs to the fuel injection device 30 as a fuel injection control signal.

In the above, the operating lever device 10 constitutes operating means for controlling the switching direction and the switching amount of the direction switching valve 3, and includes a regulator 20, a pump controller 21, a throttle 22, a differential pressure detector 23, and a pressure detector 24. Constitutes a pump discharge amount control means, among which a regulator 20, an operation amount control unit 211 of a pump controller 21, a throttle 22,
The differential pressure detector 23 has a function of controlling the discharge amount of the hydraulic pump 1 in accordance with the operation amount of the operation means, a constant horsepower control unit 212 of the pump controller 21, and a target absorption torque calculation unit 2
13, the minimum value selection unit 214 and the pressure detector 24 change the maximum value of the absorption horsepower of the hydraulic pump 1 according to the engine speed deviation and the supercharging pressure, and determine that the absorption horsepower of the hydraulic pump 1 is equal to or less than the maximum value. The horsepower control means for limiting the discharge amount is configured as follows.

The target absorption torque calculator 213 of the pump controller 21 constitutes calculation means for calculating the target absorption torque based on the engine speed deviation and the supercharging pressure.
The constant horsepower control unit 212 and the minimum value selection unit 214 of the pump controller 21 constitute limiting means for limiting the tilt angle of the hydraulic pump 1 so that the absorption torque of the hydraulic pump 1 does not exceed the target absorption torque.

Next, the operation of the present embodiment configured as described above will be described.

When the operating lever 10a of the operating lever device 10 is not operated while the construction machine is operating, the directional control valve 3 is in the neutral position, and the hydraulic oil discharged from the hydraulic pump 1 is supplied to the center bypass lines 7a, 7b. All return to the tank 8. At this time, the differential pressure across the throttle 22 becomes maximum. This differential pressure is detected by the differential pressure detector 23 and input to the operation amount control unit 211 of the pump controller 21, and the target pump tilt angle θc is calculated to a minimum value. For this reason, the minimum value selection unit 214 selects the target pump tilt angle θc calculated by the operation amount control unit 211 and outputs it to the regulator 20 as a command signal, so that the hydraulic pump 1 is controlled to the minimum discharge amount. You.

On the other hand, as a result of controlling the discharge amount of the hydraulic pump 1 to the minimum, the absorption torque of the hydraulic pump 1 also becomes the minimum, and the load on the engine 12 also becomes the minimum. Therefore, the difference between the target engine speed calculated by the difference calculation unit 311 of the engine controller 31 and the engine speed (engine speed difference) is also minimized, and the control compensation unit 31 is controlled.
The target fuel injection amount obtained in step 2 is also minimized. For this reason, the target injection amount is selected by the minimum value selection section 314 and is output to the fuel injection device 30 as a fuel injection control signal.

Next, the operation lever 1 of the operation lever device 10 will be described.
When 0a is operated, the direction switching valve 3 switches from the neutral position, and the pressure oil discharged from the hydraulic pump 1 is distributed to the actuator 4 according to the operation amount. Actuator 4
Is connected to the load 5, the hydraulic pump 1 has a discharge pressure corresponding to the load 5, and the discharge pressure is
And is input to the constant horsepower control unit 212 of the pump controller 21. In the horsepower constant control unit 212,
From the signal (discharge pressure) and the coefficient Kc at that time, a limit value θp of the target pump tilt angle is calculated. Further, as a result of the directional control valve 3 switching from the neutral position, the differential pressure across the throttle 22 decreases according to the amount of operation, and the pump controller 21
The operation amount control unit 211 calculates a target pump tilt angle θp having a magnitude corresponding to the differential pressure across the throttle 22. The minimum value selection unit 214 selects the target pump tilt angle θc and outputs it to the regulator 20 as a command signal until the target pump tilt angle θc reaches the target pump tilt angle limit value θp, and outputs the target pump tilt angle θc. Reaches the limit value θp of the target pump tilt angle, the target pump tilt angle limit value θp is selected and output to the regulator 20 as a command signal to control the hydraulic pump 1 to increase the discharge amount.

On the other hand, as a result of such control that the discharge amount of the hydraulic pump 1 is increased, the absorption torque of the hydraulic pump 1 is also increased, and the load on the engine 12 is also increased. Therefore, the engine speed starts to decrease, and the difference between the target engine speed and the engine speed (engine speed difference) increases. Difference calculation unit 311 of engine controller 31
Then, the engine speed deviation is calculated, and the control compensator 31
In step 2, the target fuel injection amount is increased so as to maintain the target engine speed.

At this time, since the fuel injection amount has been kept to a minimum, the supercharging pressure has also been reduced. This supercharging pressure is detected by the supercharging pressure detector 34 and the fuel injection of the engine controller 31 is performed. Is input to the quantity limit control unit 313,
A small value is calculated as the limit value M of the target fuel injection amount. Therefore, until the target fuel injection amount calculated by the difference calculation unit 311 reaches the target fuel injection amount limit value M, the former target fuel injection amount is selected by the minimum value selection unit 314 and the fuel injection control signal is used as the fuel injection control signal. When the target fuel injection amount reaches the limit value M, the minimum value selection unit 314 selects the limit value M of the target fuel injection amount, and outputs the fuel injection control signal. Is output to the fuel injection device 30, and the fuel injection amount is limited. In other words, the maximum value of the target fuel injection amount is limited by the fuel injection amount restriction control unit 313, and conventionally, the reduction amount and the reduction time of the engine speed are large due to the limitation.

In the present embodiment, when the maximum value of the target fuel injection amount is limited as described above, the signal of the engine speed deviation ΔN and the signal of the supercharging pressure are output from the engine controller 31 to the target absorption torque of the pump controller 21. Arithmetic unit 21
3 and the target absorption torque calculation unit 213 calculates the target absorption torque Kc that decreases as the engine speed deviation ΔN increases and as the supercharging pressure Pb decreases, as described above. Output to
For this reason, the limit value θp of the target pump tilt angle calculated by the constant horsepower control unit 212 is reduced not only by an increase in the engine speed deviation ΔN but also by a decrease in the supercharging pressure Pb. The reduced target pump tilt angle limit value θp is selected and output as a command signal. As a result, an increase in the discharge amount of the hydraulic pump is limited, and the absorption torque of the hydraulic pump 1 is reduced. In other words, when the operating lever 10a of the operating lever device 10 is operated, the absorption torque of the hydraulic pump 1 increases and the engine speed decreases, but while the supercharging pressure is decreasing, the supercharging pressure decreases. As a result, the absorption torque of the hydraulic pump 1 is reduced depending on the amount, and as a result, the reduction amount and the reduction time of the engine speed are reduced.

Therefore, according to the present embodiment, when the engine load is turned on, the fuel injection amount is limited in accordance with the reduction of the supercharging pressure, so that the black smoke is reduced and the fluctuation of the engine speed can be suppressed.

A second embodiment of the present invention will be described with reference to FIG. In the figure, the same reference numerals are given to members and functions equivalent to those shown in FIGS. In the present embodiment, the first
In this embodiment, the functions of the operation amount control unit, the horsepower constant control unit, and the minimum value selection unit provided in the pump controller 21 are hydraulically configured together with the regulator.

In FIG. 3, a regulator 20A for controlling the swash plate 1a of the hydraulic pump 1 includes a tilt control actuator 201 for controlling the operation amount and a tilt control actuator 202 for controlling the horsepower constant. The pressure on the upstream side of the throttle 22 of the center bypass line 7b is guided as control pressure to the tilt control actuator 201 of the operation amount control, and the tilt control actuator 201 reduces the tilt angle of the hydraulic pump 1 when the control pressure increases. When the control pressure decreases, the swash plate 1a is negatively controlled to increase the tilt angle of the hydraulic pump 1. The tilt control actuator 202 for constant horsepower control has a hydraulic port 202a for increasing the pump tilt angle and a hydraulic pump 202b for decreasing the pump tilt angle, and the output pressure of the electromagnetic proportional valve 26 changes the pump tilt angle. A setting in which the discharge pressure of the hydraulic pump 1 is input to the hydraulic port 202a of the increasing direction operation, the discharge pressure of the hydraulic pump 1 is input to the hydraulic port 202b of the pump tilt angle decreasing operation, and the discharge pressure of the hydraulic pump 11 is determined by the output pressure of the electromagnetic proportional valve 26. The tilt angle of the hydraulic pump 1 is controlled so as not to exceed the value.

Further, the pump controller 21A has a target absorption torque calculation section 213, and the target absorption torque calculation section 213 uses the engine rotation speed deviation sent from the engine controller 31 as described in the first embodiment. A function f determined in advance from the signal of ΔN and the signal of the supercharging pressure Pb
A coefficient Kc (target absorption torque) is calculated based on (ΔN, Pb), and an electric signal corresponding to the coefficient Kc is transmitted to the electromagnetic proportional valve 2.
6 is output.

In the above, the regulator 20A (the tilt control actuator 201 for controlling the operation amount and the tilt control actuator 202 for constant horsepower control), the pump controller 21A, the throttle 22, and the electromagnetic proportional valve 26 constitute a pump discharge amount control means. Among them, the tilt control actuator 201 for controlling the operation amount of the regulator 20A and the throttle 22 have a function of controlling the discharge amount of the hydraulic pump 1 according to the operation amount of the operation means (the operation lever device 10).
The tilt control actuator 202, the pump controller 21A, and the electromagnetic proportional valve 26 for the constant horsepower control of A change the maximum value of the absorption horsepower of the hydraulic pump 1 according to the engine speed deviation and the supercharging pressure. A horsepower control means for limiting the discharge amount so that the absorbed horsepower is equal to or less than the maximum value.

The target absorption torque calculation section 213 of the pump controller 21A constitutes calculation means for calculating the target absorption torque based on the engine speed deviation and the supercharging pressure, and the tilt control of the horsepower constant control of the regulator 20A. The actuator 202 and the electromagnetic proportional valve 26 constitute limiting means for limiting the tilt angle of the hydraulic pump 1 so that the absorption torque of the hydraulic pump 1 does not exceed the target absorption torque.

Also in this embodiment configured as described above, it is possible to suppress the fluctuation of the engine speed while reducing the black smoke by limiting the fuel injection amount in accordance with the decrease of the supercharging pressure when the engine load is applied.

In the above embodiment, as means for controlling the discharge amount of the hydraulic pump in accordance with the operation amount of the operation lever of the operation lever device, the hydraulic pressure is controlled in accordance with the differential pressure across the throttle provided in the center bypass line. A negative control system that controls the tilt angle of the pump was used.However, a positive control method that controls the tilt angle of the pump with pilot pressure generated by the operating lever device, or the pump discharge pressure is higher than the maximum load pressure by a predetermined value A load sensing control method for controlling the pump tilt angle may be used, and the same effect can be obtained.

[0061]

According to the present invention, when the engine load is turned on, the fuel injection amount is limited in accordance with the decrease of the supercharging pressure, thereby reducing black smoke and suppressing the engine speed fluctuation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hydraulic drive device according to a first embodiment of the present invention.

FIG. 2 is a functional block diagram showing details of processing functions of a pump controller and an engine controller shown in FIG.

FIG. 3 is a functional block diagram illustrating a hydraulic drive device according to a second embodiment of the present invention with respect to processing functions of a pump controller and an engine controller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 1a Swash plate 2 Discharge path 3 Direction switching valve 4 Actuator 5 Load 10 Operating lever device 10a Operating lever 11 Pilot pump 12 Motor (engine) 13 Output shaft 14 Supercharger 20, 20A Regulator 21, 21A Pump controller 22 Throttle Reference Signs List 23 Differential pressure detector 24 Pressure detector 26 Electromagnetic proportional valve 30 Fuel injection device 31 Engine controller 32 Revolution command device 33 Engine revolution detector 34 Supercharging pressure detector 201 Tilt control actuator for operation amount control 202 Constant horsepower control Displacement control actuator 202a Hydraulic port for pump tilt angle increasing operation 202b Hydraulic pump for pump tilt angle decreasing operation 211 Operating amount control unit 212 Horsepower constant control unit 213 Target absorption torque calculation unit 214 Minimum value selection unit 311 Difference Arithmetic unit 312 Control compensation unit 313 Fuel injection amount limitation control unit 314 Minimum value selection unit

Continued on front page F-term (reference) 2D003 AA01 AB05 AB06 BA08 CA03 DA03 DA04 DB02 DB03 3H089 AA83 BB30 CC08 DA03 DA13 DB03 DB47 DB49 EE22 FF07 FF10 GG02 JJ01 JJ02

Claims (5)

[Claims] 1. An engine as a power source, a variable displacement hydraulic pump driven by the engine, an actuator driven by pressure oil sent from the hydraulic pump, and pressure oil discharged from the hydraulic pump Directional control valve for controlling the direction and flow rate of the directional control valve, operating means for controlling the switching direction and the amount of switching of the directional switching valve, and a pump discharge amount for controlling the discharge amount of the hydraulic pump in accordance with the operating amount of the operating means Control means, a turbocharger for increasing the intake air amount of the engine, a supercharging pressure detecting means for detecting the intake air amount as a pressure, an engine speed detecting means for detecting an actual engine speed, Engine speed command means for commanding a target speed, and a deviation between the actual speed and the target speed of the engine is determined, and a deviation is calculated according to the engine speed deviation and the supercharging pressure. A hydraulic drive device for a construction machine, comprising: an engine speed control means for controlling an engine speed; wherein the pump discharge amount control means absorbs the hydraulic pump in accordance with the engine speed deviation and a supercharging pressure. A hydraulic drive device for a construction machine, comprising: a horsepower control unit that changes a maximum value of a horsepower and limits a discharge amount so that an absorption horsepower of the hydraulic pump is equal to or less than the maximum value. 2. A hydraulic drive system for a construction machine according to claim 1, wherein said horsepower control means calculates a target absorption torque based on said engine rotational speed deviation and supercharging pressure, and Limiting means for limiting the tilt angle of the hydraulic pump so that the absorption torque does not exceed the target absorption torque. 3. The hydraulic drive system for a construction machine according to claim 2, wherein said calculating means decreases the target absorption torque as said engine rotational speed deviation increases, and said target absorption torque as said supercharging pressure decreases. A hydraulic drive for a construction machine, wherein the hydraulic drive is operated to reduce the torque. 4. A hydraulic drive system for a construction machine according to claim 2, wherein said limiting means detects a discharge pressure of said hydraulic pump, and a target absorption calculated by said arithmetic means based on said pump discharge pressure. A hydraulic drive device for a construction machine, comprising: means for calculating a limit value of a target pump tilt angle corresponding to torque; and means for limiting the tilt angle of the hydraulic pump to the limit value or less. 5. The hydraulic drive device for a construction machine according to claim 2, wherein said calculating means outputs an electric signal corresponding to said target absorption torque, and said limiting means operates an electromagnetic signal operated by said electric signal. The output pressure of the proportional valve and the electromagnetic proportional valve is input to a hydraulic port for tilt angle increasing operation of the hydraulic pump, and the discharge pressure of the hydraulic pump is applied to a hydraulic port for tilt angle decreasing operation of the hydraulic pump. And a tilt control actuator for controlling a tilt angle of the hydraulic pump so that the discharge pressure of the hydraulic pump is not exceeded a set value determined by the output pressure of the electromagnetic proportional valve. Hydraulic drive.