JPH04258505A - Driving control device for hydraulic construction machine - Google Patents

Abstract

PURPOSE:To accurately judge if flow rate is lacking or not for precise rotation number control at all the time and to improve responsiveness at control. CONSTITUTION:In a driving control device for hydraulic construction machine which can carry out load sensing control for holding a discharge pressure of a variable capacity hydraulic pump driven by a prime mover higher than a load pressure of a hydraulic actuator by a certain differential pressure, when a discharge pressure of a hydraulic pump 1 detected by a discharge pressure detecting means 52 is more than a predetermined value, and when the differential pressure detected by a differential pressure detecting means 54 is less than a predetermined value even if the discharge pressure is less than the predetermined value, a rotation number correcting means 100 makes correction so that a target rotation number becomes higher than the target rotation number set by a target rotation number setting means 81.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device used in hydraulic construction machinery such as wheeled hydraulic excavators, and more particularly to a drive control device that improves fuel consumption by controlling the rotational speed of a prime mover depending on the load.

0002

[Prior Art] The present applicant previously proposed the following items 1 and 2 as a drive control device for hydraulic construction machinery that drives a hydraulic actuator using oil discharged from a variable displacement hydraulic pump driven by a prime mover. are doing.

[0003] The load on the hydraulic actuator is detected, and when the load exceeds a predetermined value, it is determined that the pump flow rate is insufficient, and the rotation speed of the prime mover is increased to increase the pump flow rate. 63-167042). According to this, it is possible to operate in a state where fuel consumption is most advantageous while maintaining a desired working speed both under light load and heavy load.

[0004] In devices that employ a load sensing system, if the differential pressure between the discharge pressure of the variable displacement hydraulic pump and the maximum load pressure of the actuator (LS differential pressure) falls below a predetermined value, it is determined that the flow is insufficient and the rotation of the prime mover is stopped. increase the pump flow rate. Alternatively, if the deviation between the displacement volume of the hydraulic pump and the maximum possible displacement volume calculated based on the discharge pressure of the hydraulic pump becomes less than a predetermined value, it is determined that the flow rate is insufficient, and the rotation speed of the prime mover is increased, as described above. Similarly, the pump flow rate is increased (as described in Japanese Patent Application No. 1-318486). According to this, similarly to (2), the vehicle can be operated in a state where the fuel consumption is most advantageous both under light load and heavy load.

[0005]

[Problems to be Solved by the Invention] However, the above-mentioned devices (1) and (3) each have the following problems. In other words, in the device (2), for example, if the discharge pressure of a variable displacement hydraulic pump is detected and the load pressure of the actuator is determined, it is possible to drive multiple actuators when the discharge pressure of the hydraulic pump is low (for example, when driving (When driving the boom or arm at low speed during operation)
When the required flow rate is large despite the low pressure, as in the example shown in FIG.

On the other hand, in the device (2), it is determined whether or not the flow rate is insufficient based on the LS differential pressure or the deviation between the displacement volume of the hydraulic pump and the maximum possible displacement volume. Even if the flow rate is insufficient due to a large value, this can be determined, and the above problem (■) can be resolved.
In control using LS differential pressure, since the detected value of the LS differential pressure fluctuates greatly, a filter is applied to prevent hunting, and the average value of the LS differential pressure over a predetermined period of time is taken, and the pump flow rate is controlled based on that value. Therefore, the response is poorer than the control (2) described above. Furthermore, control using the tilting angle deviation also requires a step of determining the maximum possible displacement volume based on the discharge pressure of the hydraulic pump, and a step of determining the tilting angle deviation, resulting in poor responsiveness.

An object of the present invention is to provide a drive control device for hydraulic construction machinery that can accurately determine whether or not there is a flow shortage in any case and accurately control the rotation speed, and that improves responsiveness during control. It's about doing.

[0008]

[Means for Solving the Problems] To explain in conjunction with FIGS. 1 to 4 showing one embodiment, the invention of claim 1 provides a variable displacement hydraulic pump 1 driven by a prime mover 27, and a variable displacement hydraulic pump 1 driven by a prime mover 27. At least one hydraulic actuator 4, 21 driven by oil discharged from the hydraulic actuator 4, 21, control valves 2, 20 that control the flow rate of pressure oil supplied to the hydraulic actuators 4, 21, and the discharge pressure of the hydraulic pump 1 and the hydraulic actuator. The differential pressure detection means 54 detects the differential pressure between the load pressures of the hydraulic actuators 4 and 21, and the discharge pressure of the hydraulic pump 1 is set to a constant differential pressure than the load pressure of the hydraulic actuators 4 and 21 based on the detected differential pressure. load sensing control means 61 that controls the displacement volume of the hydraulic pump 1 so as to keep it as high as a discharge pressure detection means 52 that detects the discharge pressure of the engine; a rotation speed correction means 100 that corrects the set target rotation speed based on the detected discharge pressure in order to compensate for the insufficient flow rate; The present invention is applied to a drive control device for a hydraulic construction machine, which is equipped with prime mover control means 28 and 88 for controlling the prime mover 27 so that the number of prime movers 27 is the same as that of the prime mover 27. And rotation speed correction means 10
The above problem is solved by configuring 0 as follows. That is, when the detected discharge pressure of the hydraulic pump 1 is above a predetermined value, and even if the discharge pressure is less than the predetermined value, the detected differential pressure is below the predetermined value. Correction is made so that the target rotational speed is higher than the target rotational speed set by the rotational speed setting means 81. The invention of claim 2 also provides the variable displacement hydraulic pump 1, the hydraulic actuators 4 and 21, the control valves 2 and 20, the target rotation speed setting means 81, the discharge pressure detection means 52, and the rotation speed correction means. 100' (FIG. 6), and prime mover control means 28, 88. Then, calculation means 91 calculates a limit value of the maximum displacement volume according to the discharge pressure of the hydraulic pump 1.
The above problem is solved by configuring the rotation speed correcting means 100' as follows. That is, the rotation speed correction means 100' adjusts the displacement volume of the hydraulic pump 1 and the calculated maximum when the detected discharge pressure of the hydraulic pump 1 is equal to or higher than a predetermined value, and even when this discharge pressure is less than a predetermined value. When the deviation from the limit value of the displacement volume is less than or equal to a predetermined value, a correction is made so that the target rotation speed is higher than the target rotation speed set by the target rotation speed setting means 81.

[0009]

[Function] (1) When the detected discharge pressure of the hydraulic pump 1 is equal to or higher than a predetermined value, the rotation speed correction means 100 of the invention according to claim 1 adjusts the target rotation speed setting means 8 to the target rotation speed setting means 8.
Correction is made so that the target rotation speed is higher than the target rotation speed set in step 1. That is, priority is given to the rotation speed control based on the discharge pressure of the hydraulic pump 1 (the control in (2) described above), thereby improving responsiveness. Also, the rotation speed correction means 10
0 means that even if the discharge pressure is less than a predetermined value, when the detected differential pressure is below a predetermined value, the rotation speed is higher than the target rotation speed similarly set by the target rotation speed setting means 81. Output as target rotation speed command value. Therefore, in this case, control (■) will be performed, and even when driving multiple actuators when the discharge pressure of the hydraulic pump is low, it can be determined that the flow rate is insufficient, and the prime mover rotation speed will be increased to increase the pump flow rate. becomes possible. (2) The rotational speed correcting means 100' according to claim 2 is configured to prevent the hydraulic pump 1 from being pushed when the detected discharge pressure of the hydraulic pump 1 is equal to or higher than a predetermined value, and even when this discharge pressure is less than a predetermined value. When the difference between the volume and the calculated maximum displacement limit value is less than a predetermined value, a rotation speed higher than the target rotation speed set by the target rotation speed setting means 81 is output as a target rotation speed command value. . This provides the same effect as described above.

[0010] In the section of means and effects for solving the above-mentioned problems that explains the structure of the present invention, figures of embodiments are used to make the present invention easier to understand. It is not limited to.

[0011]

[Embodiment] - First Embodiment - An embodiment of the present invention will be explained with reference to FIGS. 1 to 5. FIG. Figure 2 is a diagram showing the overall configuration of the drive control device of a hydraulic excavator, and Figure 3
is a diagram showing a part of the enlarged view, and 1 is the engine (
This is a variable displacement hydraulic pump driven by a prime mover) 27. The rotation speed of the engine 27 is controlled by rotating the governor lever 27b of the governor 27a with the pulse motor 28. The oil discharged from the variable displacement hydraulic pump 1 according to the engine rotational speed is guided to the hydraulic motor 4 via the travel control valve 2, and is also guided to the working hydraulic cylinder 21 via the working control valve 20. .

Now, for example, if the forward/reverse switching valve 8 is moved forward (position F) and the pedal 6a of the pilot valve 6 is operated,
Discharged oil from the hydraulic pump 5 is guided to the pilot port 2a of the pilot type control valve 2, and the control valve 2 is switched at a stroke amount depending on the pilot oil pressure. This results in
The oil discharged from the variable displacement hydraulic pump 1 is supplied to the hydraulic motor 4 through the pipe line 91, the pressure compensation valve 23, and the control valve 2, and the vehicle runs. The speed of the vehicle depends on the amount of depression of the travel pedal 6a.

When the pedal 6a is released while the vehicle is running, the pilot valve 6 shuts off the pressure oil and its outlet port is communicated with the tank 10. As a result, the pressure oil acting on the pilot port 2a returns to the tank 10 via the forward/reverse switching valve 8, the slow return valve 7, and the pilot valve 6. At this time, since the return oil is throttled by the throttle 7a of the slow return valve 7, the pilot type control valve 2 is gradually switched to the neutral position and the vehicle is gradually decelerated.

When the work lever 58 is operated, the hydraulic pilot type work control valve 20 is switched by the pressure reduced by the pressure reducing valve 59 according to the amount of operation, and the oil discharged from the hydraulic pump 1 is transferred to the pipe 92. , a pressure compensation valve 24 and a control valve 20 to a working hydraulic cylinder 21, and as the hydraulic cylinder 21 expands and contracts, a working attachment such as a boom moves up and down. Here, the pressure compensation valves 23 and 24 are
The operations of the hydraulic motor 4 and the hydraulic cylinder 21 are compensated for independently, and the hydraulic pump 1 supplies a pressure higher than the load pressure of each of them by a predetermined pressure.

The tilting angle, ie, the displacement volume, of the variable displacement hydraulic pump 1 is controlled by a tilting angle control device 40. The tilting angle control device 40 includes a hydraulic pump 41 driven by an engine 27, a pair of electromagnetic valves 42 and 43, and a piston position controlled by pressure oil from the hydraulic pump 41 according to switching of the electromagnetic valves 42 and 43. The tilting angle of the hydraulic pump 1 is controlled according to the piston position of the servo cylinder 44. Here, the pair of solenoid valves 42 and 43 are switched and controlled by a controller 50.

Reference numeral 51 denotes a tilting angle sensor for detecting a tilting angle θs of the hydraulic pump 1; 52 denotes a discharge pressure Pp of the hydraulic pump 1;
A pressure sensor 53 detects the rotation speed N of the engine 27.
A rotation speed sensor 54 detects the discharge pressure of the hydraulic pump 1 and the maximum load pressure of the actuator (hydraulic motor 4
This is a differential pressure sensor that detects the differential pressure between the load pressure of the hydraulic cylinder 21 and the load pressure of the hydraulic cylinder 21, which is the larger value selected by the shuttle valve 29, that is, the LS differential pressure ΔPLS. Further, 55 is a potentiometer that detects the amount of rotation Nθ of the governor lever 27b, and the detection results of each of these sensors are input to the controller 50. 5
Reference numeral 7 denotes a rotation speed setting device that commands a target rotation speed X according to manual operation of the fuel lever 57a, and the command signal is also input to the controller 50.

The controller 50 has a first control circuit section 60 as shown in FIG. , a selection section 63, and a servo control section 64. The LS control unit 61 sets a target differential pressure ΔPLSR,
The deviation Δ(PLS) from the LS differential pressure ΔPLS detected by the differential pressure sensor 54 is calculated, the amount of change ΔθL of the target value is calculated from this deviation Δ(PLS), and this is integrated for load sensing control. The target pump tilt angle θL is determined and output.

The torque control section 62 controls the engine rotation speed Nr detected by the rotation speed sensor 53 and the potentiometer 5.
Speed sensing is performed by calculating the deviation ΔT from the governor lever position Nθ detected in step 5, and a target torque Tpo for preventing engine stall is calculated from this deviation ΔT. A tilting angle is calculated by multiplying the pump discharge pressure Pp by the reciprocal of the pump discharge pressure Pp, and the value θps is filtered by a temporary delay element to obtain a target pump tilting angle θT for input torque limiting control.

The selection unit 63 selects the two target tilt angles θL.
, θT is selected and the servo control unit 64
Output to. The servo control unit 64 compares the selected tilting angle command value θr with the tilting angle feedback value θs detected by the tilting angle sensor 51, and determines that the pump tilting angle θs is determined by the tilting angle command value θs. The tilt angle control device 40 is controlled so as to match the value θr.

Here, according to the load sensing control described above, the displacement volume (hereinafter also referred to as tilt angle) of the variable displacement hydraulic pump 1 is controlled so that the LS differential pressure becomes a constant value,
Since the pump pressure is maintained higher than the load sensing pressure by a predetermined target value, the pump tilting angle is controlled so that the pump discharge flow rate becomes the required flow rate of the control valve 2 or 20, and the excess flow rate is discharged. This eliminates waste due to throttling loss and improves fuel efficiency and operability. Further, according to the input torque limit control, the torque of the hydraulic pump 1 is maintained within the range of the output torque of the engine 27, and overload on the engine 27 is prevented.

On the other hand, the controller 50 has a second control circuit section 80 shown in FIG. Second control circuit section 8
0, 81 is a target rotation speed calculation unit, which determines a target rotation speed Nx according to the displacement amount X from a signal corresponding to the displacement amount X of the fuel lever 57a of the rotation speed setting device 57. The displacement amount X and the target rotational speed Nx are set in a relationship such that as the displacement amount X increases, the target rotational speed Nx increases linearly from the idle rotational speed Ni.

Reference numeral 82 denotes a first corrected rotation speed calculating section, which calculates the discharge pressure Pp of the hydraulic pump 1 which is the output of the pressure sensor 52.
The increment value Δα of the corrected rotational speed α is determined from the characteristics shown in the figure in accordance with the above. According to this characteristic, the above-mentioned increment value Δα becomes negative in a range where the discharge pressure Pp is less than or equal to the first predetermined value Pp1, and in a range where the discharge pressure Pp is greater than or equal to the second predetermined value Pp2 which is greater than the first predetermined value Pp1. In this case, the increment value Δα becomes positive, and in other ranges, that is, Pp1<Pp<Pp2, the increment value Δα becomes positive.
α becomes zero. The increment value Δα of the corrected rotational speed α obtained by the first corrected rotational speed calculating section 82 is added to the corrected rotational speed α obtained in the previous control cycle by an adding section 85,
It is set as a new corrected rotation speed α.

Reference numeral 83 denotes a second correction rotation speed calculation section, and this second correction rotation speed calculation section 83 includes the differential pressure sensor 5.
The LS differential pressure ΔPLS detected by 4 is inputted via the filter 89, and the increment Δα of the corrected rotational speed α is determined from the characteristics shown in the figure in accordance with the LS differential pressure ΔPLS. Here, as mentioned above, the LS differential pressure ΔPLS detected by the differential pressure sensor 54 fluctuates greatly in a short period of time, so in order to prevent hunting, the filter 89 calculates the average value over a predetermined period of time. I am trying to use the value. Note that since the detected value of the discharge pressure Pp is relatively stable, there is no need to use such a filter. This second
According to the characteristics of the corrected rotation speed calculation unit 83, the LS differential pressure ΔP
In the range where LS is greater than the target differential pressure ΔPLSR, the corrected rotation speed α
The increment value Δα becomes negative, and in the range where the LS differential pressure ΔPLS is equal to or less than the target differential pressure ΔPLSRΔ, the increment value Δα becomes positive, and the increment value Δα increases as the LS differential pressure ΔPLS decreases.

The increment value Δα of the corrected rotational speed α obtained by the second corrected rotational speed calculation section 83 can be input to the addition section 86 via a switch 84 . The switch 84 is turned on only when the increment value Δα determined by the first corrected rotation speed calculation section 82 is zero, and the output of the second correction rotation speed calculation section 83 is turned on only when this switch 84 is on. Δα is the adder 8
6 is added to the corrected rotation speed α. The output of the adder 86 is added by the adder 85, and the output of the adder 85 is added by the adder 85.
7, it is added to the target rotation speed Nx, and is set as the target rotation speed command value Ny. Here, the reason why each control characteristic is provided with hysteresis and the increment value Δα of the corrected rotational speed α is determined and added to the previous corrected rotational speed α is to prevent hunting.

The target rotational speed command value Ny is compared with the signal of the displacement Nθ of the governor lever 27b detected by the potentiometer 55 in the servo control section 88, and the two are made to match according to the procedure shown in FIG. Pulse motor 28 is controlled.

In FIG. 5, first, in step S21, the target rotational speed command value Ny and the governor lever displacement amount Nθ are respectively read, and the process proceeds to step S22. In step S22, the result of Nθ-Ny is stored in the memory as the rotational speed difference A, and in step S23, it is determined whether |A|≧K using a predetermined reference rotational speed difference K. If affirmative, the process proceeds to step S24, where it is determined whether the rotation speed difference A>0 or not. If A>0, the governor lever displacement amount Nθ is larger than the target rotation speed command value Ny, that is, the control rotation speed is the target rotation. Since the number of revolutions is higher than the number of revolutions, a signal instructing the motor to reverse rotation is sent to the pulse motor 2 in step S25 in order to lower the engine revolution speed.
Output to 8. As a result, the pulse motor 28 rotates in reverse, and the rotational speed of the engine 27 decreases.

On the other hand, if A≦0, the governor lever displacement amount N
Since θ is smaller than the target rotational speed command value Ny, that is, the control rotational speed is lower than the target rotational speed, a signal instructing normal rotation of the motor is output in step S26 in order to increase the engine rotational speed. As a result, the pulse motor 28 rotates normally, and the rotational speed of the engine 27 increases. If step S23 is negative, the process proceeds to step S27, where a motor stop signal is output, thereby maintaining the rotational speed of the engine 27 at a constant value. After steps S25 to S27 are executed, the process returns to the beginning.

In the above configuration, the discharge pressure Pp of the hydraulic pump 1 detected by the pressure sensor 52 is a predetermined value Pp2.
(FIG. 1) When Pp≧Pp2, the increment value Δα of the corrected rotational speed α obtained by the first corrected rotational speed calculating section 82
is on the + side, and the corrected rotation speed α to which this Δα is added is added to the target rotation speed Nx set by the target rotation speed calculating section 81. Therefore, the target rotational speed command value Ny becomes higher than the target rotational speed Nx by the corrected rotational speed α, the actual rotational speed of the engine 27 increases accordingly, and the discharge flow rate of the hydraulic pump 1 increases. Also, Pp1<Pp<Pp2
When , the increment value Δα of the corrected rotation speed α becomes zero, and Pp
When ≦Pp1, Δα is on the − side, so Pp<P
At the time of p2, the target rotation speed command value Ny is the target rotation speed N
It will be less than or equal to x. In other words, according to this control, the actual pump flow rate is controlled according to the required flow rate of the hydraulic pump 1, and the operation is performed in a state where the fuel consumption is most advantageous while maintaining the desired working speed under both light and heavy loads. becomes possible. Here, this control based on the discharge pressure Pp of the hydraulic pump 1 does not require a filter to prevent hunting, so it has the effect of good responsiveness.

On the other hand, when the increment value Δα of the corrected rotation speed α obtained by the first correction rotation speed calculation unit 82 is zero, the switch 84 is turned on, so that the increment value obtained by the second correction rotation speed calculation unit 83 Δα is added to the corrected rotation speed α by an adding section 86. Since this increment value Δα is positive in the range where the LS differential pressure ΔPLS is equal to or less than the target differential pressure ΔPLSR, in this case, the target rotation speed command value Ny becomes higher than the target rotation speed Nx, and the actual rotation of the engine 27 The number also increases accordingly, and the discharge flow rate of the hydraulic pump 1 increases.

That is, according to the above, since priority is given to control based on the discharge pressure Pp, the engine speed can normally be increased quickly with good responsiveness. Further, when the required flow rate is large despite the low pressure, such as when driving a plurality of actuators when the discharge pressure of the hydraulic pump 1 is low, the first target rotation speed calculation section 81 using the discharge pressure Pp Although the control cannot determine whether the flow is insufficient, the second correction rotation speed calculation unit 83 that uses the LS differential pressure ΔPLS can determine the insufficient flow, and the discharge flow of the hydraulic pump 1 can be increased to the required amount, although the responsiveness is poor. becomes possible.

In the configuration of the above embodiment, the hydraulic motor 4 and working hydraulic cylinder 21 act as a hydraulic actuator, the LS control section 61 acts as a load sensing control means, the fuel lever 57a acts as an operating means, and the target rotation speed calculation section 81 acts as a control means. is the target rotation speed setting means, the first and second corrected rotation speed calculating sections 82, 83, the switch 84 and the addition sections 85 to 87 are the rotation speed correction means 100, and the pulse motor 28 and the servo control section 88 are the prime mover control unit. The pressure sensor 52 constitutes a discharge pressure detection means, and the differential pressure sensor 54 constitutes a differential pressure detection means.

-Second Embodiment- A second embodiment of the present invention will be explained with reference to FIG. FIG. 6 is a diagram corresponding to FIG. 1 described above, and parts similar to those in FIG. 1 are given the same reference numerals. The second control circuit section 90 in this embodiment includes a tilt angle calculation section 91, an addition section 92, and a second correction rotation speed calculation section 93 instead of the second correction rotation speed calculation section 83. is provided. The tilt angle calculation unit 91 is
Input the discharge pressure Pp of the hydraulic pump, and
Maximum tilt angle of hydraulic pump 1 according to (maximum displacement volume)
Find the limit value θp. According to this characteristic, the discharge pressure P
The smaller p is, the larger the maximum tilt angle limit value θp becomes.

The adding section 92 calculates the deviation Δθ (=θp−θs) between this limit value θp and the pump tilting angle θs detected by the tilting angle sensor 51, and performs a second correction rotation speed calculation. In a section 93, an increment value Δα of the corrected rotational speed α is determined from the illustrated characteristics in accordance with this deviation Δθ. According to this characteristic, in a range where the deviation Δθ is greater than or equal to a predetermined value Δθ0, the increment value Δα of the corrected rotation speed α is negative, and in a range where the deviation Δθ is less than or equal to the predetermined value Δθ0, the increment value Δα is positive.
The increment value Δα increases as the deviation Δθ decreases. Then, the determined increment value Δα is added to the corrected rotational speed α by the adding section 86 only when the switch 84 is on, as described above.

Here, in this control using the deviation Δθ between the limit value θp of the maximum tilting angle and the pump tilting angle θs, a step of determining the limit value θp from the discharge pressure Pp and a step of determining the deviation Δθ are required. Therefore, the response is poor compared to the control based on the discharge pressure Pp (first corrected rotational speed calculation section 82), but even if the required flow rate is large at low pressure and the flow rate is insufficient, it is possible to determine whether the flow rate is insufficient. Can be done.

In the above configuration, the detected discharge pressure Pp of the hydraulic pump 1 is equal to or higher than the predetermined value Pp2 (FIG. 1) (Pp
≧Pp2), the increment value Δα of the value corrected rotation speed α obtained by the first correction rotation speed calculating section 82 is +
side, and the target rotational speed command value Ny becomes higher than the target rotational speed Nx. Therefore, the actual rotational speed of the engine 27 increases accordingly, and the discharge flow rate of the hydraulic pump 1 can be rapidly increased.

Further, when the increment value Δα of the corrected rotational speed α obtained by the first corrected rotational speed calculating section 82 is zero, the switch 8
4 is turned on, the increment value Δα obtained by the second correction rotation speed calculating section 93 is added to the correction rotation speed α by the addition section 86. This increment value Δα is determined by the maximum tilt angle limit value θp obtained by the tilt angle calculation section 91 and the tilt angle sensor 51.
Since the deviation Δθ from the pump tilt angle θs detected by is positive in the range below the predetermined value Δθ0, the target rotation speed command value Ny is lower than the target rotation speed Nx set by the target rotation speed calculation section 81. The discharge flow rate of the hydraulic pump 1 increases.

That is, according to this embodiment, as in the first embodiment, priority is given to control based on the discharge pressure Pp, and therefore the engine speed can normally be increased quickly with good responsiveness. Furthermore, when the required flow rate is large despite the low pressure, such as when driving a plurality of actuators when the discharge pressure of the hydraulic pump 1 is low, the second correction rotation speed calculation section that uses the tilt angle deviation Δθ is used. 93, it is possible to determine whether the flow rate is insufficient, and it becomes possible to increase the discharge flow rate of the hydraulic pump 1 to the required amount, although the responsiveness is poor.

In the configuration of the above embodiment, the tilt angle calculation section 91 serves as the calculation means, and the first and second correction rotation speed calculation sections 82, 93, the switch 84, and the addition sections 85 to 87 serve as the rotation speed correction means. 100' respectively.

Although the above example shows an example in which the engine speed is controlled according to the amount of operation of the fuel lever, the operating means is not limited to the fuel lever, and for example, the engine speed can be controlled according to the amount of operation of the travel pedal. The present invention can also be applied to those that do. Further, the present invention can be similarly applied to hydraulic construction machines other than hydraulic excavators. Further, in the second embodiment, the deviation Δθ was calculated from the tilt θs detected by the tilt angle sensor 51, but θL (LS target tilt) in FIG. 3 may be used instead of this θs. .

[0040]

According to the invention of claim 1, in a device that performs load sensing control, when the discharge pressure of the hydraulic pump is equal to or higher than a predetermined value, and even when this discharge pressure is less than a predetermined value, the LS differential pressure is When the rotation speed is below a predetermined value, the target rotation speed command value is set to a rotation speed higher than the target rotation speed set according to the operation of the operating means, so responsiveness during control is improved, and in any case However, it is possible to accurately determine whether the flow rate is insufficient and to control the rotation speed accurately. According to the invention of claim 2, when the discharge pressure of the hydraulic pump is equal to or higher than a predetermined value, and even when this discharge pressure is less than a predetermined value, the difference between the displacement volume of the hydraulic pump and the maximum possible displacement volume is a predetermined value. Since the target rotation speed command value is set to a rotation speed higher than the target rotation speed when the rotation speed is less than the target rotation speed, the same effect as described above can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an engine control circuit section according to a first embodiment.

FIG. 2 is a diagram showing the overall configuration of a drive control device for hydraulic construction machinery.

FIG. 3 is an enlarged view of a portion of FIG. 2;

FIG. 4 is a block diagram of a pump control circuit section.

FIG. 5 is a flowchart showing a procedure for engine speed control.

FIG. 6 is a block diagram of an engine control circuit section according to a second embodiment.

[Explanation of symbols]

1 Variable capacity hydraulic pump 2 Traveling control valve 4 Traveling hydraulic motor 6 Pilot valve 6a Traveling pedal 8 Forward/backward switching valve 20 Working control valve 21 Working cylinder 27 Engine (prime mover) 28 Pulse motor 40 Tilt control device 50 Controller 51 Tilt angle sensor 52 Pressure sensor 53 Rotation speed sensor 54 Differential pressure sensor 55 Potentiometer 57 Rotation speed setting device 57a Fuel lever 60 First control circuit section 61 LS control section 62 Torque control section 63 Selection section 64 Service Bo control section 80, 90 Second control circuit section 81 Target rotation speed calculation section 82 First correction rotation speed calculation section 83, 93 Second correction rotation speed calculation section 84 Switches 85 to 87 Addition section 88 Servo control section 91 Tilt angle calculation section 92 Addition section 100, 100' Rotation speed correction means

Claims (2)

[Claims] 1. A variable displacement hydraulic pump driven by a prime mover, at least one hydraulic actuator driven by oil discharged from the hydraulic pump, and a control valve that controls the flow rate of pressure oil supplied to the hydraulic actuator. a differential pressure detection means for detecting a differential pressure between the discharge pressure of the hydraulic pump and the load pressure of the hydraulic actuator; load sensing control means for controlling the displacement of the hydraulic pump so as to maintain it higher than the pressure by a certain differential pressure; and target rotation speed setting means for setting the target rotation speed of the prime mover in accordance with the operation of the operating means. , a discharge pressure detection means for detecting the discharge pressure of the hydraulic pump; a rotation speed correction means for correcting the set target rotation speed based on the detected discharge pressure in order to compensate for the insufficient flow rate; and the correction means. In the drive control device for hydraulic construction machinery, the drive control device for hydraulic construction machinery includes a prime mover control means for controlling the prime mover so as to achieve a target rotation speed, wherein the rotation speed correction means is configured to control the detected hydraulic pump discharge pressure to a predetermined value or higher. When, and even if this discharge pressure is less than a predetermined value, when the detected differential pressure is below a predetermined value, the target rotation speed becomes higher than the target rotation speed set by the target rotation speed setting means. A drive control device for hydraulic construction machinery, which is characterized by adding corrections such as: 2. A variable displacement hydraulic pump driven by a prime mover, at least one hydraulic actuator driven by oil discharged from the hydraulic pump, and a control valve that controls the flow rate of pressure oil supplied to the hydraulic actuator. a target rotation speed setting means for setting a target rotation speed of the prime mover in accordance with the operation of the operating means; a discharge pressure detection means for detecting the discharge pressure of the hydraulic pump; and based on the detected discharge pressure, Driving a hydraulic construction machine, comprising: rotation speed correction means for correcting the set target rotation speed to compensate for insufficient flow; and prime mover control means for controlling the prime mover so as to achieve the corrected target rotation speed. The control device includes a calculation means for calculating a maximum displacement limit value according to the discharge pressure of the hydraulic pump, and the rotation speed correction means is configured to calculate a limit value of the maximum displacement according to the discharge pressure of the hydraulic pump, and the rotation speed correction means is configured to calculate a limit value of the maximum displacement according to the discharge pressure of the hydraulic pump. and even if this discharge pressure is less than a predetermined value, when the deviation between the displacement volume of the hydraulic pump and the calculated maximum displacement limit value is equal to or less than a predetermined value, the target rotation speed setting means A drive control device for hydraulic construction machinery, characterized in that a correction is made so that the target rotational speed is higher than a target rotational speed set.