JP2000154803A - Engine lag-down prevention device for hydraulic construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the lag-down of an engine generated at the urgent operation time of a hydraulic actuator from a non-operation state without generating the deterioration of a fuel consumption and the increase in a black smoke, in a hydraulic construction machine adopting a big engine as a prime mover. SOLUTION: When an operation lever 4a is not operated and a pressure switch 11 is turned OFF, a hydraulic pump 2 is a minimum slant running and an engine 1 runs with a high idle number of rotation. When the operation lever 4a is operated and the pressure switch 11 is turned ON, the control of the hydraulic pump 2 is converted from the minimum slant running control to a torque reduction control and converted to a rated torque control after the elapsing of a prescribed time ΔtA. When the operation lever 4a is returned to a neutral and the pressure switch 11 is turned OFF again, the control of the hydraulic pump 2 is converted from the rated torque control to the minimum slant running control after the elapsing of a prescribed time ΔtB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing engine lug down of a hydraulic construction machine, and more particularly to a device for preventing engine lug down of a hydraulic construction machine such as a hydraulic shovel having an engine having a large lag down as a prime mover.

[0002]

2. Description of the Related Art In a hydraulic construction machine such as a hydraulic shovel, a hydraulic actuator is driven by pressure oil discharged from a hydraulic pump. The hydraulic pump is driven to rotate by a prime mover, and a diesel engine is generally used as the prime mover. In this diesel engine, the fuel injection amount is controlled by a fuel injection device called a governor, and the rotation speed is controlled. The fuel injection device includes a mechanical system and an electronic system. In each of these systems, the fuel injection amount is adjusted in accordance with the deviation between the target rotation speed and the actual rotation speed (rotation speed deviation). That is, when the engine load increases and the rotational speed deviation increases, the fuel injection amount is increased to bring the actual rotational speed closer to the target rotational speed. In this case, when the engine is in a no-load state, the engine speed is a high idle speed higher than the target speed.

[0003] In an engine equipped with such a fuel injection device, when a hydraulic actuator is suddenly operated and a load is suddenly applied to the engine, a phenomenon called lag-down occurs in which the engine rotation drops momentarily. This is because when the engine is in a no-load state, the engine speed is in the high idle state as described above, and the amount of fuel supplied to the engine in this state is small, but a sudden load is applied to the engine. When the fuel injection device attempts to supply a large amount of fuel, a response delay occurs, and the supply of the fuel cannot be made in time, and the engine speed drops momentarily.

[0004] As a technique for preventing such engine lag-down, there is an engine control device of a civil engineering construction machine disclosed in Japanese Patent Application Laid-Open No. 1-222419. In this prior art, a means for detecting an operation state of a control valve for controlling a flow rate supplied to an actuator is provided, and when the control valve is operated and a load is applied to the engine, the control valve is changed to a non-operation state. When detected, the tilt angle of the hydraulic pump is set to a discharge flow rate larger than the minimum discharge flow rate, and a drag load is applied to the engine. By applying a drag load to the engine in this manner, the engine speed is controlled to be slightly lower than the high idle speed, and does not increase to the high idle speed.
Even if a load is applied to the engine by operating the control valve thereafter, the drop in the number of revolutions is reduced, and the lag down is reduced.

[0005]

The engine, which is the prime mover, has been increasing in size with the increase in the size of construction machines. As the size of the engine increases, the lug down speed increases. This is for the following reason.

1) As the size of the engine increases, the inertia of the engine increases and the load increases. Therefore, the number of lag-down rotations increases, and the time until the rotation of the engine returns is lengthened.

2) In the case of a large engine, the input torque limit value of the horsepower control of the hydraulic pump is set to a small value in consideration of the variation in engine output characteristics, and the input torque limit value is increased during load operation by increasing the input torque limit value. There is something to do. In this case, there is an increase in the engine load due to the increased torque, and the decrease in the rotational speed when a sudden load is applied to the engine is further increased.

[0008] 3) In a large engine, high supercharging is often performed by an exhaust turbine in order to produce a high output. In such a high supercharged diesel engine, a load is suddenly applied from a no-load high idle state. In this case, there is a time delay from the low boost pressure state during high idle to the time when the exhaust turbine works effectively and the boost pressure increases, and the engine output rise is delayed, resulting in a large decrease in the engine speed. .

The remarkable decrease in the engine speed due to the above-mentioned lag down and the delay in the rise of the engine speed from that state are perceived as a large change in the engine sound, which gives a discomfort to the machine operator. Also,
The decrease in the rotation speed due to the lug down temporarily reduces the discharge flow rate of the hydraulic pump, and thus affects the workability and operability of the machine.

Conventionally, when a small engine is used, the drop in the lag-down rotation speed is small and the return time is short, so that the influence on workability and operability has not been a serious problem. However, in a hydraulic construction machine equipped with a large engine, the lug-down rotation speed is large as described above, so that the influence on workability and operability becomes a problem.

In the engine control device of the civil engineering construction machine disclosed in Japanese Patent Application Laid-Open No. 1-222419, a drag load is applied as described above to reduce lag down. However, in this method, a load is applied to the engine even when the engine is not operated, so that fuel efficiency is deteriorated and energy efficiency is deteriorated.

In order to prevent the engine lag down, a method of controlling the fuel supply amount to be rapidly increased when a sudden load is applied to the engine may be considered. However, since this method supplies wasteful fuel instantaneously,
As in the case of Japanese Patent Application Laid-Open No. 1-222419, fuel efficiency is deteriorated. Further, when the fuel supply amount is rapidly increased, a problem that black smoke is generated in the exhaust gas also occurs.

An object of the present invention is to provide an engine which is generated when a hydraulic actuator is suddenly operated from a non-operation state without deteriorating fuel consumption and increasing black smoke in a hydraulic construction machine employing a large engine as a prime mover. It is an object of the present invention to provide a device for preventing engine lag down of a hydraulic construction machine, which reduces the lag down of the engine.

[0014]

(1) In order to achieve the above object, the present invention provides an engine, a variable displacement hydraulic pump which is driven to rotate by the engine, and a pressure discharged by the hydraulic pump. Oil is guided through a control valve, a hydraulic actuator driven by the hydraulic oil, and pump control means for controlling the capacity of the hydraulic pump so that the input torque of the hydraulic pump does not exceed a predetermined reference torque. An engine lag down prevention device for a hydraulic construction machine, comprising: a load state detection unit that detects a load state of the hydraulic pump; and a load state detection unit that is provided as a part of the pump control unit. Is detected, the limit value of the input torque of the hydraulic pump is made smaller than the reference torque for a predetermined period to reduce the torque. Shall and a torque reduction control means for performing.

The load state detecting means and the torque reduction control means are provided as described above, and when it is detected that a load is applied to the hydraulic pump, the input torque of the hydraulic pump is reduced for a predetermined period by a limit value of the input torque of the hydraulic pump. When the hydraulic actuator is suddenly operated from a non-operating state, the load applied to the engine is reduced by reducing the engine torque to a value smaller than the reference torque. And the effect on operability is reduced. In addition, the fuel supply amount during that period is also reduced, so that the fuel efficiency is improved and the generation of black smoke is reduced.

(2) In the above (1), preferably,
The pump control unit includes a minimum displacement control unit that controls the hydraulic pump to a minimum displacement when the load state detection unit detects that the hydraulic pump is not in the load-in state. When the load state detecting means detects that a load has been applied to the hydraulic pump, the hydraulic pump is switched from the minimum displacement control to the reduced torque control, and the predetermined time is maintained for the reduced torque control. Thereafter, it is means for shifting to control based on the reference torque.

Thus, by providing the pump control means having the minimum displacement control and the torque reduction control means,
When the hydraulic actuator is suddenly operated, the above (1)
As described in, the drop in engine speed due to lug down can be suppressed, the recovery time of engine speed can be shortened, and unnecessary hydraulic oil is not discharged from the hydraulic pump when the hydraulic actuator is not operated, reducing the engine load I do.

(3) In the above (1), preferably, the pump control means detects a rotational speed of the engine, and when the detected engine rotational speed exceeds a predetermined rotational speed, the input of the hydraulic pump is preferably performed. A torque increase control unit configured to increase a torque limit value to be larger than the reference torque to perform a torque increase control; wherein the load torque detection unit detects that the hydraulic pump is not in a load input state by the load state detection unit; When the load state detecting means detects that a load has been applied to the hydraulic pump, the torque reduction control is maintained for the predetermined period, and thereafter, the control shifts to control based on the reference torque. It is a means to do.

As described above, when the hydraulic actuator is suddenly operated by providing the pump control means provided with the torque increasing means and the torque reducing means provided with the torque increasing means, as described in (1) above, the engine rotation of the lag-down state is performed. The number of drops can be suppressed and the return time of the engine speed can be shortened, and when the hydraulic actuator is not operated, the hydraulic pump is torque-reduced to reduce the engine load. Then, the hydraulic pump is controlled to increase the torque.

(4) Further, in the above (1), preferably, the pump control means includes: a pressure sensor for detecting a discharge pressure of the hydraulic pump; and a discharge pressure of the hydraulic pump detected by the pressure sensor. A controller that calculates a target displacement for providing the reference torque and outputs an electric signal corresponding thereto, and a displacement control actuator that operates by the electric signal from the controller and controls the hydraulic pump so as to obtain the target displacement. And
The torque reduction control means is provided in the controller, and when the load state detection means detects that a load is applied to the hydraulic pump, the input torque of the hydraulic pump is reduced from the reference torque for the predetermined time. This is a means for calculating a target capacity to be reduced.

As a result, the pump control means is configured using the controller, and the torque reduction control can be performed as described in (1) above.

(5) Further, in the above (1), the pump control means may guide the discharge pressure of the hydraulic pump,
A hydraulic regulator that controls the capacity of the hydraulic pump so that the input torque of the hydraulic pump does not exceed the reference torque by the discharge pressure;
When the load state detecting means detects that a load has been applied to the hydraulic pump, the controller outputs a drive current for torque reduction control for the predetermined time, and operates by the drive current to generate a control pressure. A solenoid valve; and setting adjustment means for adjusting a set value of the hydraulic regulator so that a limit value of an input torque of the hydraulic pump is made smaller than the reference torque when the control pressure is introduced.

Thus, the pump control means is constituted by a hydraulic regulator, and the torque reduction control can be performed as described in the above (1).

(6) In the above (1), preferably, the pump control means guides the discharge pressure of the hydraulic pump, and the discharge pressure does not cause the input torque of the hydraulic pump to exceed the reference torque. A hydraulic regulator for controlling the displacement of the hydraulic pump, a rotational speed detecting means for detecting the rotational speed of the engine, and a torque increasing control when the engine rotational speed detected by the rotational speed detecting device exceeds a predetermined rotational speed. A controller provided with a torque increasing control calculating means for outputting a first drive current, a first solenoid valve operated by the first drive current to generate a first control pressure;
A first setting adjusting unit that adjusts a setting value of the hydraulic regulator so that a limit value of an input torque of the hydraulic pump becomes larger than the reference torque when a control pressure is guided, and the reduction torque control unit includes: A predetermined torque reduction control unit that is provided in the controller and outputs a second drive current for reduced torque control when the load state detection unit detects that a load has been applied to the hydraulic pump; A second solenoid valve that operates with the second drive current to generate a second control pressure, and a hydraulic regulator that reduces the input torque of the hydraulic pump to be smaller than the reference torque when the second control pressure is introduced. Second setting adjusting means for adjusting the set value.

Thus, the pump control means is constituted by a hydraulic regulator and has a torque increasing control function.
The torque reduction control can be performed as in the above (1).

[0026]

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

FIGS. 1 to 5 are views for explaining an engine lug down prevention device according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a diesel engine, and a fuel injection amount of the engine 1 is controlled by a governor (fuel injection device) not shown. A variable displacement hydraulic pump 2 is connected to an output shaft 1a of the engine 1, and the hydraulic pump 2 is driven to rotate by the engine 1 to discharge pressure oil. The pressure oil discharged from the hydraulic pump 2 is supplied to an actuator, for example, a hydraulic cylinder 5 via a center bypass type control valve 3 to drive the hydraulic cylinder 5. The control valve 3 is operated by the operation lever device 4 and controls the flow rate and direction of the pressure oil supplied from the hydraulic pump 2 to the hydraulic cylinder 5.

The operating lever device 4 is, in this example, a hydraulic pilot system having an operating lever 4a and pressure reducing valves 4b, 4c. The pressure reducing valves 4b, 4c have primary ports that are rotationally driven by the engine 1 together with the hydraulic pump 2. The pilot drive unit 3 of the control valve 3 is connected to a pilot pump 6 through a pilot port 6 through a pilot line 7a, 7b.
a, 3b. When the operating lever 3a is tilted to the right in the figure, the pressure reducing valve 4b operates, and an operating pilot pressure corresponding to the operation amount of the operating lever 3a is applied to the pilot drive unit 3a of the control valve 3, whereby the control valve 3 is moved to the left side in the figure. The position is switched to the position, and the flow rate according to the operation amount of the operation lever 4a is supplied to the rod side of the hydraulic cylinder 5. When the operating lever 3a is tilted to the left in the figure, the pressure reducing valve 4c is activated, and the operating pilot pressure corresponding to the operation amount of the operating lever 3a is applied to the control valve 3.
, The control valve 3 is switched to the position on the right side in the figure, and a flow rate corresponding to the operation amount of the operation lever 4a is supplied to the bottom side of the hydraulic cylinder 5.

The hydraulic pump 2 has, for example, a swash plate 2a as a variable capacity member, and the tilt angle of the swash plate 2a is controlled by a tilt control actuator 8 (described later).
, The pump displacement is controlled.

The above-described hydraulic drive system is provided with the engine lag down prevention device of the present embodiment. This engine lag down prevention device is configured as a part of pump control means, and is connected to pilot lines 7a and 7b, and is a check valve 10a as a shuttle valve 10 for selecting a pressure on a high pressure side of the pilot lines 7a and 7b. , 10
b, a pressure switch 11 that operates when the pressure selected by the shuttle valve 10 is the operating pilot pressure, and a pressure sensor 12 that is provided in the discharge path 2 b of the hydraulic pump 2 and detects the discharge pressure of the hydraulic pump 2. , A controller 13 that receives signals from the pressure switch 11 and the pressure sensor 12 and performs predetermined arithmetic processing, an electromagnetic valve 14 that is operated by a drive current output from the controller 13,
And the tilt control actuator 8 described above that is operated by the control pressure generated by the above.

FIG. 2 shows the structure of the tilt control actuator 8. The tilt control actuator 8 has a piston 8b reciprocating in a cylinder body 8a, a swash plate 2a is operatively connected to a piston rod 8c, and a spring 8d is built in a bottom side in the cylinder body 8a. The control pressure from the solenoid valve 14 is introduced into the rod-side chamber 8e. When the solenoid valve 14 is at the position shown in the figure and the rod side chamber 8e is at the tank pressure, the piston rod 8c moves leftward in the figure by the force of the spring 8, and the tilt angle (pump capacity) of the swash plate 2a decreases. Let it. When a current flows through the solenoid valve 14, a control pressure is introduced into the rod-side chamber 8e, and the piston rod 8c moves rightward in the figure to increase the tilt angle (pump capacity) of the swash plate 2a.

The controller 13 performs a calculation process as shown in the flowchart of FIG. In the flowchart of FIG. 3, Fa is a first switching determination flag used to determine the switching of the pressure switch 11 from OFF to ON, and Fb is used to determine the switching of the pressure switch 11 from ON to OFF. A second switching determination flag, Ca is a torque reduction control counter indicating a torque reduction control time, and Cb is a control switching delay counter indicating a delay time of switching from rated torque control to minimum displacement control. ΔtA is the duration of the torque reduction control, for example, about 0.5 seconds, and ΔtB is the delay time from the rated torque control to the minimum displacement control, for example, about 3 seconds.

The limit value Tra of the input torque of the hydraulic pump 2 as shown in FIG.
t and Tdec are stored. The horizontal axis in FIG. 4 is the discharge pressure of the hydraulic pump 2 (the value detected by the pressure sensor 12), and the vertical axis is the target tilt of the swash plate 2a of the hydraulic pump 2, which is denoted by reference symbols Pd and q, respectively. . The input torque limit value Trat is a normal limit value, and the input torque limit value Tdec
Is a limit value at the time of torque reduction control. Since the product of the pump discharge pressure and the pump discharge flow rate is the input horsepower (work amount) of the hydraulic pump 2, if the rotational speed of the hydraulic pump 2 is constant, the above control eventually results in the input of the hydraulic pump 2. The horsepower is controlled so as not to exceed the limit values corresponding to the limit values Trat and Tdec.

Hereinafter, the operation of the present embodiment will be described while explaining the processing contents of the controller 13 with reference to FIG.

When the power of the controller 13 is turned on,
First, in steps 100 and 102, the first and second switching determination flags Fa and Fb are set to Fa = 0 and F, respectively, as initialization processing.
b = 0, and the torque reduction control counter Ca and the control switching delay counter Cb are set to Ca = 0 and Cb = 0, respectively. Next, after reading the state of the pressure switch 11 and the detection value of the pressure sensor 12 in step 104, it is determined in step 106 whether the pressure switch 11 is ON. This determination is based on whether or not the operating lever 4a of the operating lever device 4 has been operated and an operating pilot pressure has been generated.
This is the part that checks whether the load has been applied to or not. When the power of the controller 13 is turned on, the pressure switch 11 is not turned on (is not operated), so the determination result is No, and the procedure proceeds to step 108. In step 108, it is determined whether or not the second switching determination flag Fb is Fb = 1. Also in this case, since the initialization process is performed in the above-described procedure 100 and Fb = 0, the determination result is No, the minimum displacement control is performed in the procedure 110, and the first switching determination flag Fa is set to Fa = 1 in the procedure 112. After that, the process returns to step 104.

Here, the minimum tilt control performed in step 110 is control for maintaining the tilt angle of the swash plate 2a of the hydraulic pump 2 at the minimum tilt angle qmin shown in FIG.
Outputs a drive current corresponding to the minimum tilt angle qmin to the solenoid valve 14, and the tilt angle of the hydraulic pump 2 is reduced to the minimum tilt angle qmin.
Control so that

While the operation lever 4a of the operation lever device 4 is not operated, the above procedures 104, 106, 108, 110, and
Step 112 is repeated, and the minimum displacement control is continued. Thus, when the operation lever 4a is not operated, useless pressure oil is not discharged from the hydraulic pump 2, and the load on the engine 1 is reduced.

When the operating lever 4a of the operating lever device 4 is operated and the operating pilot pressure rises in the pilot line 7a or 7b, the pressure switch 11 is turned on, and the above procedure 1 is performed.
At 06, the determination result is Yes, and the routine proceeds to step 120.
In step 120, it is determined whether the first switching determination flag Fa is Fa = 1. In this case, Fa =
Since it is set to 1, the determination result is Yes, and the torque reduction control is performed in step 122. Here, the torque reduction control performed in step 122 is to control the input torque of the hydraulic pump 2 to be limited to the limit value Tdec in FIG. 4, and the controller 13 reads the pressure sensor read in step 104 at that time. 12, the discharge pressure Pd of the hydraulic pump 2 is obtained, and this discharge pressure Pd is used as the input torque limit value Tdec of FIG.
, The corresponding target tilt angle q is calculated, and the corresponding drive current is output to the solenoid valve 14.

Next, at step 124, it is determined whether or not the torque reduction control counter Ca has a predetermined set value ΔtA. In this case, the initialization process is performed in the above procedure 102,
Since Ca = 0, the result of the determination is No. After adding 1 to the counter Ca in step 126, step 104
Return to

When the torque reduction control counter Ca has the set value Δt A
While smaller than the above steps 104, 106, 120 and 12
2, 124 and 126 are repeated, the torque reduction control is continued, and when the counter Ca becomes Ca = ΔtA, the procedure 12
The determination result of step 4 becomes Yes, the first switching determination flag Fa is set to Fa = 0 in step 128, the torque reduction control counter Ca is set to Ca = 0 in step 130, and the process returns to step 104. In this case, the result of determination in step 120 is No, the rated torque control is performed in step 140, the second switching determination flag Fb is set to Fb = 1 in step 142, and
Return to 4.

Here, the rated torque control performed in step 140 means that the input torque of the hydraulic pump 2 is limited to the limit value Trat in FIG.
Controller 1
3 is the pressure sensor 12 at that time read in step 104
, The discharge pressure Pd of the hydraulic pump 2 is obtained from the detected value, and the discharge pressure Pd is referred to the input torque limit value Trat in FIG. 4 to calculate a corresponding target tilt angle q. Output to

While the operation lever 4a is in the operating state, the above steps 104, 106, 120, 140 and 142 are repeated, and the rated torque control is continued.

As a result, when the operating lever 4a is switched from the non-operating state to the operating state, the input torque of the hydraulic pump 2 does not suddenly increase to the rated torque, but instead of the hydraulic pump 2 for a predetermined time ΔtA. Is limited to a limit value Tdec, which is lower than the rated torque, for a predetermined time ΔtA.
After the lapse of time, control is performed such that the rated torque becomes the limit value Trat.

When the operating lever is returned to the neutral position from the operating state of the operating lever 4a as described above, the pilot line 7
Since the operating pilot pressure of a or 7b decreases, the pressure switch 11 is turned off, the result of the determination in the above step 106 becomes No, and the procedure proceeds to step 108. In this case, since Fb = 1 was set in the previous step 142, the determination result is Yes, and the procedure proceeds to step 150. In step 150, it is determined whether or not the control switching delay counter Cb is equal to a predetermined set value ΔtB. In this case, since the initialization process is performed in the above-described step 102 and Cb = 0, the determination result is No. The rated torque control is performed in step 152, and 1 is added to the counter Cb in step 154. Return to step 104.

When the control switching delay counter Cb has the set value Δt B
While smaller than the above steps 104, 106, 108 and 15
0, 152 and 154 are repeated, the rated torque control is continued, and when the counter Cb becomes Cb = ΔtB, the procedure 1
The determination result at 50 is Yes, and the procedure proceeds to step 110. In step 110, the minimum tilt control is performed as described above, and in step 1
After setting the first switch determination flag Fa to 1 in step 12, the process returns to step 104.

When the operating lever 4a is returned to the neutral position and the operating lever 4a is operated again during the predetermined time ΔtB, the rated torque control is maintained without switching to the minimum tilt control, and the predetermined time is maintained. Only after the lapse of ΔtB has the mode switched to the minimum tilt control, the operation lever 4a
The operation of returning the hydraulic pump to the neutral position little by little, and unnecessary control of the hydraulic pump to the minimum tilt at the time of operating the reverse lever are avoided.

In the above, the shuttle valve 10 and the pressure sensor 11 constitute load state detecting means for detecting the load state of the hydraulic pump 2, and the pressure sensor 12 and the controller 1
3. The solenoid valve 14 and the tilt control actuator 8 constitute pump control means for controlling the capacity of the hydraulic pump 2 so that the input torque of the hydraulic pump 2 does not exceed a predetermined reference torque (rated torque). The processing functions of steps 122 to 130 shown in FIG. 3 are provided as a part of the pump control means, and when it is detected that the load is applied to the hydraulic pump 2 by the load state detecting means 10 and 11,
The limit value of the input torque of the hydraulic pump 2 is set to a predetermined period Δt
A, A torque reduction control means for performing torque reduction control with a torque smaller than the reference torque is configured.

The processing function of the controller 13 in the procedure 110 shown in FIG. 3 is to control the hydraulic pump 2 to the minimum capacity when the load state detecting means 10 and 11 detect that the hydraulic pump 2 is not in the load applied state. With this processing function and the processing functions of steps 122 to 130, the torque reduction control means detects that a load has been applied to the hydraulic pump 2 by the load state detection means 10 and 11. Then, the hydraulic pump 2 is switched from the minimum displacement control to the torque reduction control, the torque reduction control is maintained for the predetermined time, and thereafter, the control is shifted to the control based on the reference torque.

When the operation lever 4a is operated from the non-operation state,
FIG. 5 shows changes in the engine speed and pump torque control and changes in the pressure switch 11 when the operation state is returned to the non-operation state.
Shown in In the figure, “minimum displacement”, “reduced torque”, and “rated torque” are, for convenience, the procedure 110 (minimum displacement), the procedure 122 (reduced torque), the procedures 140 and 15 in FIG.
The state at 2 (rated torque) is indicated by [ON], and the other cases are indicated by "OFF".

When the operating lever 4a is not operated and the pressure switch 11 is turned off, the hydraulic pump 2 is at a minimum tilt, and the engine 1 is at a high idle speed. When the operating lever 4a is operated and the pressure switch 11 is turned on, the control of the hydraulic pump 2 is switched from the minimum displacement control to the reduced torque control, and is switched to the rated torque control after a lapse of a predetermined time ΔtA. When the operation lever 4a is returned to the neutral position and the pressure switch 11 is turned off again, the control of the hydraulic pump 2 switches from the rated torque control to the minimum displacement control after a lapse of a predetermined time ΔtB.

As a comparative example, when the control of the hydraulic pump 2 is immediately switched from the minimum displacement control to the rated torque control when the operation lever 4a is operated, the engine 1 suddenly changes from the no-load state to a high load. , The fall in the engine speed due to engine lag down is ΔN1
And the time delay before returning to the rated speed is also t1
And long, affect the operability. On the other hand, if the predetermined time ΔtA and the torque reduction control are interposed as described above, the lag down of the engine 1 can be suppressed to ΔN2, and the return time of the engine rotation is also shortened to t2. Less.

Therefore, according to the present embodiment, a hydraulic construction machine employing an engine with a large lag down
When the operating lever 4a is in a non-operating state and the operating lever 4a is suddenly operated from a state in which the engine 1 is at a high idle speed, a drop in the rotating speed of the engine 1 due to a lag down can be reduced, and the return time can be shortened. The effect of engine lag down on operability can be reduced. Further, when a sudden load is applied from the state where the engine 1 is at the idling speed, the fuel supply amount is not rapidly increased, so that deterioration of fuel efficiency can be prevented and generation of black smoke can be reduced. Further, discomfort of the operator is reduced, and a comfortable operation can be performed.

A second embodiment of the present invention will be described with reference to FIGS. In FIG. 6, components that are the same as those shown in FIG. 1 are given the same reference numerals.

In FIG. 6, the hydraulic drive system according to this embodiment is substantially the same as that of the first embodiment.

Tilt (capacity) of the swash plate 2a of the hydraulic pump 2
Is controlled by a hydraulic regulator 24 having a power shift control function.

Further, the engine lag down prevention device of the present embodiment is provided with a shuttle valve 10 for selecting the pressure on the high pressure side of the pilot lines 7a and 7b, and when the pressure selected by the shuttle valve 10 is the operating pilot pressure. A pressure switch 11 that operates, a rotation sensor 21 that detects the number of rotations of the engine 1, and a controller 13A that receives signals from the pressure switch 11 and the rotation sensor 21 and performs predetermined arithmetic processing.
And solenoid valves 22 and 23 operated by a drive current output from the controller 13A, and these solenoid valves 22 and 23
And a hydraulic regulator 24 having the above-described power shift control function.

The hydraulic regulator 24 is connected to the horsepower port 2
4a and a reduced horsepower port 24b,
a is connected to the solenoid valve 11, the horsepower reducing port 24b is connected to the solenoid valve 12, and the horsepower increasing port 24a is connected from the solenoid valve 11.
When the control pressure is introduced into the motor, the torque increase control is performed, and when the control pressure is introduced from the solenoid valve 12 to the horsepower reduction port 23b, the torque reduction control is performed.

FIG. 7 shows details of the hydraulic regulator 24. The hydraulic regulator 24 is provided with the swash plate 2 of the hydraulic pump 2.
a tilt control actuator 31 for adjusting the tilt angle of a;
And a horsepower control servo valve 32 for controlling the operation of the tilt control actuator 31. The tilt control actuator 31 includes a servo piston 31a having different pressure receiving areas on both end faces, a pressure receiving chamber 31b in which the small diameter end face of the servo piston 31a is located, and a pressure receiving chamber 3 in which the large diameter end face is located.
1c, the pressure receiving chamber 31b at the small diameter side end face is connected to the discharge path 2b of the hydraulic pump 2, and the pressure receiving chamber 31c at the large diameter side end face is provided.
Is connected to either the discharge path 2b of the hydraulic pump 2 or the tank via the servo valve 32. When the pressure receiving chamber 31c on the large-diameter side end face is connected to the tank by the control of the servo valve 32, the servo piston 31a moves to the left in the drawing by the discharge pressure of the hydraulic pump 2 loaded on the pressure receiving chamber 31b, and the hydraulic pump 2 When the pressure receiving chamber 31c is connected to the discharge path 2b, the piston pressure receiving area in the pressure receiving chamber 31c is larger than the piston pressure receiving area in the pressure receiving chamber 31b. Therefore, the servo piston 1a moves rightward in the figure, and increases the tilt angle (pump capacity) of the swash plate 2a of the hydraulic pump 2.

The servo valve 32 includes a spool 32a, a feedback sleeve 32b linked to the servo piston 31a via a feedback lever 33, and a spool 3a.
A setting spring 32c acting on one end of the spool 2a;
a hydraulic drive unit 32d acting on the end opposite to the end of the large-diameter piston 34, an operating rod 35 provided at the end of the large-diameter piston 34 on the spool 32a side. A small-diameter piston 36 provided at the opposite end of the large-diameter piston 34, a pressure-receiving chamber 37 in which the small-diameter piston 36 end of the large-diameter piston 34 is located, and a small-diameter piston 36 of the large-diameter piston 34. Pressure receiving chamber 3 where the end is located
8 and a pressure receiving chamber 39 in which the end of the small-diameter piston 36 is located. The pressure receiving chamber 37 is connected to the discharge path 2b of the hydraulic pump 2, and the pressure receiving chamber 38 includes the above-described horsepower increasing port 24a.
The pressure increasing chamber 39 is connected to the secondary port of the solenoid valve 22 through the horsepower increasing port 23a, and the pressure receiving chamber 39 is connected to the horsepower reducing port 24b.
And is connected to the secondary port of the solenoid valve 23 via the horsepower reduction port 24b.

When neither of the solenoid valves 22 and 23 is operated, the spool 32a is controlled by the force of the setting spring 32c and the hydraulic pressure by the pump discharge pressure acting on the end of the large-diameter piston 34 in the pressure receiving chamber 37. When the balance operates and the hydraulic pressure is smaller than the spring force, the tilt control actuator 31
Is connected to the tank, the pump capacity is increased as described above, and when the hydraulic pressure becomes larger than the spring force,
The pressure receiving chamber 31c of the tilt control actuator 31 is connected to the discharge path 2
b, the pump capacity is reduced as described above, whereby the input torque of the hydraulic pump 2 is controlled so as not to exceed the limit value determined by the setting spring 32c.

FIG. 8 shows the limit value of the input torque of the hydraulic pump 2 at this time by Trat. Control using this limit value Trat is referred to as rated torque control. Since the product of the pump discharge pressure and the pump discharge flow rate is the input horsepower (work amount) of the hydraulic pump 2, if the rotational speed of the hydraulic pump 2 is constant, the above control eventually results in the input of the hydraulic pump 2. The horsepower is controlled so as not to exceed the limit value determined by the setting spring 32c.

When the solenoid valve 22 is actuated, a control pressure is introduced into the pressure receiving chamber 38, and the hydraulic pressure by the control pressure is applied to the end of the large-diameter piston 34 in a direction opposite to the hydraulic pressure by the pump discharge pressure of the pressure receiving chamber 37. Additionally acts on the spool 32a so that the sum of the force of the setting spring 32c and the additional oil pressure of the pressure receiving chamber 38 balances the oil pressure by the pump discharge pressure in the pressure receiving chamber 37. For this reason, the hydraulic pump 2 can output a larger flow rate for the same pump discharge pressure as compared with when the solenoid valve 22 is not operated, and the limit value of the input torque of the hydraulic pump 2 is shown in FIG. It increases from the indicated limit value Trat to Tinc. Control using this limit value Tinc is referred to as increased torque control.

When the solenoid valve 23 operates, the pressure receiving chamber 39
The control pressure is introduced to the end of the small-diameter piston 36, and the hydraulic pressure by the control pressure additionally acts in the same direction as the hydraulic pressure by the pump discharge pressure of the pressure receiving chamber 37. As a result, the spool 32a The operation is such that the hydraulic pressure due to the pump discharge pressure in the pressure receiving chamber 37 is balanced with the force obtained by subtracting the additional hydraulic pressure in the pressure receiving chamber 39 from the force of the pressure. For this reason, the hydraulic pump 2 can output a smaller flow rate for the same pump discharge pressure as compared with when the solenoid valve 23 is not operated, and the limit value of the input torque of the hydraulic pump 2 is shown in FIG. The indicated limit value Trat is reduced to Tdec. Control using this limit value Tdec is referred to as torque reduction control.

The controller 13A performs a calculation process as shown in the flowchart of FIG. In FIG. 9, the same steps as those shown in FIG. Hereinafter, the operation of the present embodiment will be described while the processing contents of the controller 13A are described with reference to FIG.

When the power of the controller 13A is turned on, first, in the procedures 100 and 102, the first
And the second switching determination flags Fa and Fb are set to Fa =
0, Fb = 0, and the torque reduction control counter Ca and the control switching delay counter Cb are respectively Ca = 0, Cb =
Set to 0. Next, after reading the state of the pressure switch 11 and the detection value of the rotation sensor 21 in step 104A, step 1
At 06, it is determined whether or not the pressure switch 11 is ON. This judgment is a part for checking whether the operation lever 4a of the operation lever device 4 is operated and the operation pilot pressure is generated, that is, whether the load is applied to the hydraulic pump 2 or not. When the power of controller 1A3 is ON, pressure switch 1
Since 1 is not ON (when not operating), the judgment result is N
o and proceed to step 108. In step 108, it is determined whether or not the second switching determination flag Fb is Fb = 1. Also in this case, the initialization process is performed in the above procedure 100 and Fb = 0, so the determination result is No, the torque reduction control is performed in the procedure 110A, and the first switching determination flag Fa is performed in the procedure 112.
Is set to Fa = 1, and the process returns to step 104.

Here, in the torque reduction control performed in step 110A, a drive current is output to the solenoid valve 23, whereby the hydraulic pump 2 is controlled so that the input torque does not exceed the limit value Tdec of the torque reduction control as described above. You.

While the operation lever 4a of the operation lever device 4 is not operated, the above procedures 104, 106, 108, 110
A and 112 are repeated, and the torque reduction control is continued.
Thus, when the operation lever 4a is not operated, the load on the engine 1 is reduced.

When the operating lever 4a of the operating lever device 4 is operated and the operating pilot pressure rises in the pilot line 7a or 7b, the pressure switch 11 is turned on, and the above procedure 1 is performed.
At 06, the determination result is Yes, and the routine proceeds to step 120.
In step 120, it is determined whether the first switching determination flag Fa is Fa = 1. In this case, Fa =
1, the determination result is Yes, and the procedure 122A
Performs torque reduction control. The processing content of this torque reduction control is the same as the procedure 110A.

Next, at step 124, it is determined whether or not the torque reduction control counter Ca has a predetermined set value ΔtA. In this case, the initialization process is performed in the above procedure 102,
Since Ca = 0, the result of the determination is No. After adding 1 to the counter Ca in step 126, step 104
Return to

When the reduction torque control counter Ca has the set value Δt A
While it is smaller, the above procedures 104A, 106, 120, 1
22A, 124, and 126 are repeated, the torque reduction control is continued, and when the counter Ca becomes Ca = ΔtA, the determination result of step 124 becomes Yes, and the first switching determination flag Fa is set to Fa = 0 in step 128, and After setting the torque reduction control counter Ca to Ca = 0 at 130, the procedure 104A is executed.
Return to Thus, after the operation of the operation lever 4a, ΔtA
The non-operation torque reduction control is continued for a predetermined time.

After returning to step 104A, the next step 12
The determination result at 0 is No, and the procedure proceeds to step 160. In step 160, the rotational speed N of the engine 1 and a change in the rotational speed are obtained from the detected value of the rotation sensor 21 at that time read in step 104A, and when the rotational speed N is increasing and is equal to or higher than the preset rotational speed Nset. It is determined whether or not there is, and if the determination result is No, the rated torque control is performed in step 140A, and the process returns to step 104A.

Here, in the rated torque control performed in step 140A, the drive current is not output to either of the solenoid valves 22 and 23, so that the hydraulic pump 2 has the input torque determined by the set spring 32c as described above. Control limit value Tra
It is controlled not to exceed t.

Check whether the number of revolutions N of the engine 1 is increasing or not.
While the rotational speed is lower than the set rotational speed Nset, the above procedures 104A, 10A
6, 120, 160, and 140A are repeated, the rated torque control is continued, and when the rotation speed N is increasing and reaches the set rotation speed Nset, the determination result of the procedure 160 is Yes.
Then, the torque increase control is performed in step 162, and step 142
After setting the second switching determination flag Fb to Fb = 1, the procedure 1
Return to 04.

Here, in the torque increase control performed in step 162, a drive current is output to the solenoid valve 22, whereby the hydraulic pump 2 is controlled so that the input torque does not exceed the limit value Tinc of the torque increase control as described above. You.

While the operation lever 4a is in the operating state and the engine speed N is equal to or higher than Nset, the above procedure 104 is executed.
A, 106, 120, 160, 162, 142 are repeated, and the torque increase control is continued.

Thus, when the operating lever 4a is switched from the non-operating state to the operating state, the input torque of the hydraulic pump 2 is not controlled by the increased torque, but is set to the set value Δt.
For a predetermined time A, the input torque of the hydraulic pump 2 is limited to the limit value Tdec of the torque reduction control, and after a lapse of the predetermined time ΔtA, the torque becomes the limit value Trat of the rated torque.

When the operation lever is returned to the neutral position from the operation state of the operation lever 4a as described above, the pilot line 7
Since the operating pilot pressure of a or 7b decreases, the pressure switch 11 is turned off, the result of the determination in the above step 106 becomes No, and the procedure proceeds to step 108. In this case, since Fb = 1 was set in the previous step 142, the determination result is Yes, and the procedure proceeds to step 150. In step 150, it is determined whether or not the control switching delay counter Cb is equal to a predetermined set value ΔtB. In this case, since the initialization process is performed in the above procedure 102 and Cb = 0, the determination result is No. The torque increase control is performed in the procedure 164, and 1 is added to the counter Cb in the procedure 154. It returns to procedure 104A.

When the control switching delay counter Cb has the set value Δt B
While smaller than the above steps 104A, 106, 108, 1
50, 164 and 154 are repeated, the torque increase control is continued, and when the counter Cb becomes Cb = ΔtB, the procedure 1
The determination result at 50 is Yes, and the procedure proceeds to procedure 110A.
In step 110A, the torque reduction control is performed as described above. In step 112, the first switching determination flag Fa is set to Fa = 1, and the process returns to step 104A.

When the operating lever 4a is returned to the neutral position and the operating lever 4a is operated again during the predetermined time ΔtB, the torque increasing control is maintained without switching to the reduced torque control, and the predetermined time ΔtB is maintained. Is switched to the torque reduction control only after the lapse of the operation, and the work of returning the operation lever 4a to the neutral position in small increments and the unnecessary torque reduction control of the hydraulic pump during the reverse lever operation are avoided.

In the above, the shuttle valve 10 and the pressure sensor 11 constitute load state detecting means for detecting the load state of the hydraulic pump 2 as in the first embodiment, and the tilt control actuator of the hydraulic regulator 24 31, the spool 32 a of the horsepower control servo valve 32, the feedback sleeve 32 b, the setting spring 32 c, the large-diameter piston 34 of the hydraulic drive unit 32 d, the operating rod 35, and the pressure receiving chamber 37
The pump control means controls the capacity of the hydraulic pump 2 so that the input torque of the hydraulic pump 2 does not exceed a predetermined reference torque (rated torque). The solenoid valve 23 and the horsepower reduction servo port of the horsepower control servo valve 32 24b, small diameter piston 3
6, the pressure receiving chamber 39 and the processing function of the controller 13A in the steps 122A to 130 shown in FIG. 9 are provided as a part of the pump control means, and the load is applied to the hydraulic pump 2 by the load state detecting means 10 and 11. Is detected, the limit value of the input torque of the hydraulic pump 2 is changed to a predetermined period Δ
tA, a torque reduction control means for performing torque reduction control by making the torque smaller than the reference torque.

The rotation sensor 21 and the solenoid valve 22
The horsepower control port 32a of the horsepower control servo valve 32, the large-diameter piston 34, the pressure receiving chamber 38, and the processing functions of the procedures 162, 162, and 142 shown in FIG. When the engine speed becomes equal to or higher than a predetermined speed, the limit value of the input torque of the hydraulic pump 2 is made larger than the reference torque to constitute a torque increase control means for performing torque increase control.
According to the procedure 110A and the procedures 122A to 130 shown in FIG.
When it is detected that the hydraulic pump 2 is not in the load input state, the torque reduction control is performed, and the load state detection means 1
When it is detected by 0 and 11 that a load is applied to the hydraulic pump 2, the torque reduction control is maintained for the above-mentioned predetermined period, and thereafter, the control is shifted to the control based on the reference torque.

Further, the horsepower increasing port 24 a of the horsepower control servo valve 32, the large-diameter piston 34, and the pressure receiving chamber 38 are connected to the solenoid valve 2.
When the control pressure from the hydraulic pump 2 is introduced, the first setting adjusting means for adjusting the set value of the hydraulic regulator 24 so that the limit value of the input torque of the hydraulic pump 2 becomes larger than the reference torque (rated torque) is constituted, and the horsepower control is performed. The reduced horsepower port 24b of the servo valve 32, the small diameter piston 36, and the pressure receiving chamber 39 are connected to the solenoid valve 2
When the control pressure from 3 is introduced, a second setting adjusting means for adjusting the set value of the hydraulic regulator 24 so that the limit value of the input torque of the hydraulic pump 2 is made smaller than the reference torque.

When the operation lever 4a is operated from the non-operation state,
FIG. 1 shows a change in the engine speed and pump torque control and a change in the pressure switch 11 when returning to the non-operation state.
0 is shown.

When the operating lever 4a is not operated and the pressure switch 11 is OFF, the hydraulic pump 2 is in the torque reduction control, and the engine 1 is at the high idle speed. When the operation lever 4a is operated and the pressure switch 11 is turned on, the reduced torque control of the hydraulic pump 2 is maintained for a predetermined time ΔtA, and then the control is switched to the rated torque control. Thereafter, when the drop in the engine speed is restored and reaches the set speed Nset, the hydraulic pump 2 switches to the increased torque control.
When the operation lever 4a is returned to the neutral position and the pressure switch 11 is turned off again, the control of the hydraulic pump 2 is switched from the torque increase control to the torque decrease control after a lapse of a predetermined time ΔtB.

FIG. 10 shows a comparative example in which torque increase control is performed.
FIG. 11 shows a change similar to. In this comparative example, when the operation lever 4a is not operated, the hydraulic pump is in torque increase control, the operation lever 4a is operated, and the engine speed is reduced to Nse.
When it falls to t1, it switches from increasing torque control to rated torque control. When the engine speed further decreases to Nset2, it switches from rated torque control to reduced torque control, and then when the engine speed recovers and reaches Nset2, the rated torque is restored again. Control is switched to, and when the engine speed further recovers to Nset1, the control returns to the torque increase control.

When the engine 1 is controlled so as to suddenly apply a high load from the no-load state, the lag-down speed of the engine 1 is as large as ΔN1A, and the time delay before returning to the rated speed is as long as t1A. Affects operability. On the other hand, if the torque reduction control is interposed for the predetermined time ΔtA as described above, the lag down of the engine 1 is reduced by ΔN
2A, and the engine rotation recovery time is t2A
Therefore, the influence on the operability is reduced.

Therefore, according to this embodiment, when the operation lever 4a is not operated and the operation lever 4a is suddenly operated from the state where the engine 1 is at the high idling speed, the rotation speed of the engine 1 drops due to the lug down. And the return time can be shortened, and the effect of engine lag down on operability can be reduced. Also, Engine 1
When a sudden load is applied from a state where the engine speed is at the idling speed, the fuel supply amount is not suddenly increased, so that it is possible to prevent the fuel consumption from deteriorating and reduce the generation of black smoke. Further, discomfort of the operator is reduced, and a comfortable operation can be performed.

Furthermore, according to the present embodiment, when the engine speed is restored and becomes equal to or higher than the predetermined speed Nset, the hydraulic pump 2 is controlled to increase the torque, so that the output horsepower of the engine 1 can be used effectively.

In the above embodiment, the means (shuttle valve 10 and pressure switch 11) for detecting the state of the operating pilot pressure of the operating lever device 4 has been described as an example of the load state detecting means of the hydraulic pump 2. The state detection means is not limited to this. Hereinafter, other examples regarding this point will be described with reference to FIGS.
4 will be described. In the figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals.

FIG. 12 shows an example of the load state detecting means when the electric lever system is used as the operating means of the control valve.

In FIG. 12, as an operating means for the control valve 3, an electric lever device 4B is provided instead of the hydraulic pilot type operating lever device 4 (see FIG. 1) of FIG. The electric lever device 4B includes an operation amount detection device 4d that detects an operation amount of the operation lever 4a, and a detection signal (electric signal) is input to the controller 13B. The controller 13B converts a signal from the operation amount detection device 4d into a drive current for the solenoid valves 40 and 41, and outputs the drive current. Solenoid valve 4
0, 41 are operated by the drive current, and the operation lever 4a
A secondary pressure corresponding to the operation amount is generated and output to the pilot drive units 3a and 3b of the control valve 3.

Further, the controller 13B performs the pressure switch 1 in step 104 of the flowchart shown in FIG.
Instead of reading the state of 1 (see FIG. 1), a signal from the operation amount detection device 4d is read, and it is determined whether or not the operation lever 4a is operated. Thus, when the electric lever device 4B is used, the load state detecting means can be configured without using a special sensor.

FIG. 13 shows an example of the load state detecting means for detecting the displacement of the operation lever instead of the operation pilot pressure.

In FIG. 13, limit switches 42 and 43 which operate when the operation lever 4a is operated are provided instead of the shuttle valve 10 and the pressure switch 11 of FIG. 1, and signals from the limit switches 42 and 43 are provided. This is input to the controller 13C. The controller 13C
In step 104 of the flowchart shown in FIG. 3, instead of reading the state of the pressure switch 11 (see FIG. 1),
The state of the limit switches 42 and 43 is read, and it is determined whether or not the operation lever 4a has been operated. As described above, the load state of the hydraulic pump 2 can be detected by detecting not the signal from the operating means but the displacement of the operating means.

FIG. 14 shows an example of the load state detecting means for detecting not the operation pilot pressure from the operation means but other state quantities.

In FIG. 14, instead of the shuttle valve 10 and the pressure switch 11 of FIG. 1, a throttle 46 disposed downstream of the control valve 3 in a center bypass line 45 passing through the control valve 3, and a throttle 46 A pressure switch 47 for detecting the pressure on the upstream side is provided.
7 is input to the controller 13D. The controller 13D performs the procedure 1 of the flowchart shown in FIG.
At 04, instead of reading the state of the pressure switch 11 (see FIG. 1), the state of the pressure switch 47 is read to determine whether the operation lever 4a has been operated.
In this case, when the control valve 3 is not operated, the pressure on the upstream side of the throttle 46 is high, and when the control valve 3 is operated, the pressure decreases. Therefore, when the pressure switch 47 is turned off from ON, the operation lever 4a is turned on. Is determined to have been operated. When the pressure downstream of the center bypass line changes in accordance with the operation amount of the operation means, the load state of the hydraulic pump can be detected by detecting the pressure.

Although not shown, the following state variables other than those described above can be used to detect the load state of the hydraulic pump 2.

When the minimum displacement control of the hydraulic pump is performed by the hydraulic regulator, the discharge flow rate or the displacement angle of the hydraulic pump. The discharge pressure of the hydraulic pump. The displacement of the spool of the pump regulator. The displacement of the control valve.・ Boost pressure of turbocharger

[0100]

According to the present invention, in a hydraulic construction machine employing an engine having a large lag down, a decrease in the number of revolutions of the engine lag down which occurs when the hydraulic actuator is suddenly operated from the non-operation state is reduced. It can be made smaller and the return time can be shorter. Therefore, the influence of engine lag down on operability is reduced. Further, when a sudden load is applied to the engine, the supply amount of fuel is not rapidly increased, so that deterioration of fuel efficiency can be prevented and generation of black smoke can be reduced.
Further, since the discomfort of the operator is reduced, a comfortable operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hydraulic drive system including an engine lag down prevention device according to a first embodiment of the present invention.

FIG. 2 is a view showing details of a tilt control actuator of the hydraulic pump shown in FIG. 1;

FIG. 3 is a flowchart showing a process performed by a controller shown in FIG. 1;

4 is a diagram showing a limit value Trat for rated torque control and a limit value Tdec for torque reduction control of the input torque of the hydraulic pump stored in the memory of the controller shown in FIG. 1;

FIG. 5 is a time chart showing changes in the engine speed and pump torque control and changes in the pressure switch according to the present embodiment when the operation lever is operated from the non-operation state and then returned to the non-operation state.

FIG. 6 is a diagram illustrating a hydraulic drive system including an engine lag down prevention device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing details of a pump regulator shown in FIG. 6;

8 is a diagram showing input torque control characteristics of the pump regulator shown in FIG.

FIG. 9 is a flowchart illustrating processing performed by a controller illustrated in FIG. 6;

FIG. 10 is a time chart showing changes in the engine speed and pump torque control and changes in the pressure switch according to the present embodiment when the operation lever is operated from the non-operation state and then returned to the non-operation state.

FIG. 11 is a time chart showing changes in the engine speed and pump torque control and changes in the pressure switch according to the related art when the operation lever is operated from the non-operation state and then returned to the non-operation state.

FIG. 12 is a diagram showing a hydraulic drive system showing another embodiment of the no-load detecting means in the engine lag down prevention device of the present invention.

FIG. 13 is a diagram showing a hydraulic drive system showing still another embodiment relating to a no-load detecting means in the engine lag down prevention device of the present invention.

FIG. 14 is a view showing a hydraulic drive system showing still another embodiment relating to a no-load detecting means in the engine lag down prevention device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 2 Hydraulic pump 3 Control valve 4 Operating lever device 4a Operating lever 5 Hydraulic cylinder 6 Pilot pump 7a, 7b Pilot line 8 Tilt control actuator (pump control means) 10 Shuttle valve (load state detecting means) 11 Pressure switch (load) State detecting means) 12 Pressure sensor (pump control means) 13 Controller (pump control means; torque reduction control means) 14 Solenoid valve (pump control means) 13A Controller (pump control means; torque reduction control means; torque increase control means) 22 Solenoid valve (increased torque control means) 23 Solenoid valve (decreased torque control means) 24 Hydraulic regulator (pump control means) 24a Increased horsepower port (increased torque control means) 24b Reduced horsepower port (decreased torque control means) 31 Tilt control Actuator (pump control means) 32 Horsepower control servo valve (pump control means) 32a spool (pump control means) 32b feedback sleeve (pump control means) 32c setting spring (pump control means) 32d hydraulic drive section (pump control means; reduced torque control means; increased torque control means) 34) Large-diameter piston (pump control means; increasing torque control means) 35 Operating rod (pump control means) 36 Small-diameter piston (reducing torque control means) 37 Pressure receiving chamber (pump control means) 38 Pressure receiving chamber (increase torque control means) 39 Pressure receiving chamber (torque reduction control means)

 ──────────────────────────────────────────────────の Continuing on the front page (72) Gen Yasuda, Inventor 650, Kandamachi, Tsuchiura-shi, Ibaraki Pref.Hitachi Construction Machinery Co., Ltd. (72) Inventor Yoshinori Owada 650, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. F-term (reference) in Tsuchiura Plant of the formula company

Claims (6)

[Claims] 1. An engine, a variable displacement hydraulic pump rotationally driven by the engine, and hydraulic oil discharged from the hydraulic pump are guided through a control valve and driven by the hydraulic oil. And a pump control means for controlling a capacity of the hydraulic pump so that an input torque of the hydraulic pump does not exceed a predetermined reference torque. And a load state detecting means for detecting the load on the hydraulic pump when the load state detecting means detects that a load has been applied to the hydraulic pump. A torque reduction control means for reducing the value to a value smaller than the reference torque for a predetermined period to perform torque reduction control. Machinery of the engine lug-down prevention device. 2. The apparatus according to claim 1, wherein the pump control means detects the hydraulic pressure when the load state detecting means detects that the hydraulic pump is not in the load-on state. A minimum displacement control unit that controls a pump to a minimum displacement; wherein the torque reduction control unit sets the hydraulic pump to a minimum displacement when the load state detection unit detects that a load is applied to the hydraulic pump. An engine lag down prevention device for a hydraulic construction machine, which is means for switching from control to the reduced torque control, maintaining the reduced torque control for the predetermined time, and thereafter shifting to control based on the reference torque. 3. The engine lug down prevention device for a hydraulic construction machine according to claim 1, wherein said pump control means detects a rotational speed of said engine, and said engine rotational speed becomes equal to or higher than a predetermined rotational speed. The system further includes a torque increase control unit that performs a torque increase control by increasing a limit value of an input torque of the hydraulic pump to be larger than the reference torque. Is detected, the torque reduction control is performed. When the load state detecting means detects that a load is applied to the hydraulic pump, the torque reduction control is maintained for the predetermined period, and thereafter, the reference torque is reduced. An engine lag down prevention device for a hydraulic construction machine, characterized in that it is means for shifting to control by an engine. 4. The engine lag down prevention device for a hydraulic construction machine according to claim 1, wherein said pump control means includes: a pressure sensor for detecting a discharge pressure of said hydraulic pump; A controller that calculates a target displacement that gives the reference torque based on the discharge pressure and outputs an electric signal corresponding thereto; and operates the electric pump from the controller to control the hydraulic pump so that the target displacement is obtained. A displacement control actuator that is provided in the controller, and when the load state detection unit detects that a load has been applied to the hydraulic pump, the hydraulic control unit controls the hydraulic pressure for the predetermined time. Means for calculating a target displacement for making the input torque of the pump smaller than the reference torque. Pressure construction machinery of the engine lug-down prevention device. 5. The apparatus according to claim 1, wherein said pump control means guides a discharge pressure of said hydraulic pump, and the input pressure of said hydraulic pump is determined by said discharge pressure. A hydraulic regulator for controlling a capacity of the hydraulic pump so as not to exceed a torque, wherein the torque reduction control unit is configured to perform the predetermined operation when the load state detection unit detects that a load is applied to the hydraulic pump. A controller that outputs a drive current for controlling time and torque reduction, a solenoid valve that operates by the drive current to generate a control pressure, and, when the control pressure is guided, sets a limit value of an input torque of the hydraulic pump to the reference torque. And a setting adjusting means for adjusting a set value of the hydraulic regulator so as to be smaller. Gudaun prevention device. 6. The engine lag down prevention device for a hydraulic construction machine according to claim 1, wherein said pump control means guides a discharge pressure of said hydraulic pump, and the input pressure of said hydraulic pump is determined by said discharge pressure. A hydraulic regulator for controlling the capacity of the hydraulic pump so as not to exceed the torque, a rotation speed detection means for detecting the rotation speed of the engine, and an increase in the engine rotation speed detected by the rotation speed detection device when the rotation speed exceeds a predetermined rotation speed. A controller having a torque increasing control calculating means for outputting a first driving current for torque control, a first solenoid valve which is operated by the first driving current to generate a first control pressure, And a first setting adjusting means for adjusting the set value of the hydraulic regulator so that the limit value of the input torque of the hydraulic pump becomes larger than the reference torque. The torque reduction control means is provided in the controller, and when the load state detection means detects that a load is applied to the hydraulic pump, the second drive for torque reduction control is performed for the predetermined time. A torque reduction operation control means for outputting a current; a second solenoid valve which operates by the second drive current to generate a second control pressure; and when the second control pressure is introduced, the input torque of the hydraulic pump is set to the reference value. Adjusting the set value of the hydraulic regulator to be smaller than the torque;
An engine lug down prevention device for a hydraulic construction machine, comprising: a setting adjustment unit.