JPH07127605A - Driving control device for oil hydraulic construction machine - Google Patents

Abstract

PURPOSE:To improve fuel consumption a well as to improve eruption of a prime mover, and suppress generation of black smoke by reducing the input torque of a variable displacement hydraulic pump by only a predetermined amount when an incre ment in the number of revolution of the prime mover is corrected according to a load. CONSTITUTION:When discharge pressure Pp of an oil pressure pump detected by a pressure sensor 52 exceeds a predetermined value, and it is detected that an increment in an engine speed is corrected by an engine speed compensation detection means, a high-level signal Sc is outputted and a switching implement 66 for a control section 60 is switched to a contact point side b. As a result, a target tilting rotation angle thetaL of a pump and the reduced target tilting rotation angle thetaTr of the pump are inputted in a selection section 63, and either one of a smaller value is outputted from the selection section 63. If thetaTr<thetaL, is satisfied, displacement of the variable displacement oil pressure pump is set to thetaTr. As a result, only displacement DELTAthetato of the variable displacement oil pressure pump is reduced, and input torque of the pump is reduced so as to reduce an engine load so that eruption for increment of number of revolution is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control for a hydraulic construction machine such as a hydraulic excavator, which adjusts the displacement volume of a variable displacement hydraulic pump when the number of revolutions of a prime mover is adjusted according to the load of a hydraulic actuator. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 57-163.
Japanese Patent No. 701 discloses a drive control device for a hydraulic construction machine that corrects an engine speed preset by a fuel lever or the like according to a load or an operation amount of an operation lever.

[Problems to be Solved by the Invention]

In hydraulic construction machines, especially construction machines equipped with variable displacement hydraulic pumps, the pump displacement volume is controlled so that the input torque of the pump approaches the output torque of the engine in the entire engine speed range. When an instruction to increase the rotation speed is issued according to the load, a so-called drag phenomenon occurs and it takes time for the engine rotation speed to rise. Therefore, even if the fuel injection amount is increased with the increase of the rotation speed, incomplete combustion occurs while the rotation speed does not rise, black smoke is likely to be generated, and fuel consumption is deteriorated. Moreover, since it takes time to increase the rotation speed, a desired actuator speed cannot be obtained, and the work amount does not increase so much.

SUMMARY OF THE INVENTION An object of the present invention is to provide a drive control device for a hydraulic construction machine which suppresses the generation of black smoke by facilitating the speed up when performing the increase correction of the speed of the prime mover due to the load. It is in.

[0005]

1 to 5 showing an embodiment, the invention according to claim 1 relates to a variable displacement hydraulic pump 1 driven by a prime mover 27 and the hydraulic pump 1. A hydraulic actuator 21 driven by oil discharged from the engine, command means 58 and 59 for instructing the operation of the hydraulic actuator 21, and a target rotation speed setting for setting a target rotation speed of the prime mover 27 according to the operation of the operating member 57a. Means 81, load detection means 52 for detecting the load of the hydraulic actuator 21, rotation speed correction means 82, 87 for correcting the set target rotation speed according to the detected load, and corrected target rotation speed. The present invention is applied to a drive control device for a hydraulic construction machine including prime mover control means 28 and 88 for controlling the prime mover 27 so that And
Rotation speed correction detection means 84, 85 for detecting that the rotation speed correction means 82, 87 perform correction for increasing the rotation speed.
When it is detected by the rotation speed correction detecting means 84, 85 that the increase in the rotation speed is corrected, the displacement volume reducing means 6 for reducing the displacement volume of the variable displacement hydraulic pump 1 is removed.
The above objects are achieved by including 5, 66, and 67. According to the invention of claim 2, the load sensing control for controlling the displacement volume of the variable displacement hydraulic pump 1 and the input torque of the hydraulic pump 1 within the output range of the prime mover so that the pressure difference upstream and downstream of the control valve 20 becomes constant. The present invention is applied to a drive control device for a hydraulic construction machine including a displacement volume control means 80 for controlling the displacement volume of the hydraulic pump by any one of the torque limitation control and the rotation speed correction means 82, 87. The rotational speed correction detection means 84, 85 for detecting that the rotational speed increase correction is performed, and the rotational speed correction detection means 84, 85 detect that the rotational speed increase correction is performed, and the torque limit is set. When control is being performed,
The displacement volume of the variable displacement hydraulic pump 1 is reduced, and when the load sensing control is being performed, the displacement volume is detected by the revolution speed correction detection means 84, 85 even if it is detected that the revolution speed increase correction is performed. The above-described object is achieved by including the non-reducing displacement volume reducing means 65, 66, 67.

[0006]

When the rotation speed correction detecting means 84 and 85 detect that the rotation speed is increased, the displacement volume of the variable displacement hydraulic pump 1 is reduced and the pump input torque is reduced. In the drive control device according to the second aspect, when the increase correction of the rotational speed is performed during the execution of the input torque limit control, the displacement volume of the variable displacement hydraulic pump is reduced, but during the execution of the load sensing control. The displacement volume is not reduced when the rotational speed is increased.

Incidentally, in the section of means and action for solving the above problems for explaining the constitution of the present invention, the drawings of the embodiments are used for making the present invention easy to understand. It is not limited to.

[0008]

【Example】

-First Embodiment- An embodiment in which the present invention is applied to a wheel hydraulic excavator will be described with reference to Figs. 2 is a diagram showing the overall configuration of the drive control device for the hydraulic excavator, FIG. 3 is a diagram showing its pilot operation circuit, and 1 is an engine (motor).
It is a variable displacement hydraulic pump driven by 27. The rotation speed of the engine 27 is the governor lever 27 of the governor 27a.
It is controlled by rotating b by the pulse motor 28. Then, the discharge oil of the variable displacement hydraulic pump 1 according to the engine speed is guided to the hydraulic motor 4 via the traveling control valve 2 and to the arm hydraulic cylinder 21 via the arm control valve 20. .

Now, for example, when the forward / reverse switching valve 8 (FIG. 3) is switched to the forward (F position) and the pedal 6a of the pilot valve 6 is operated, the oil discharged from the hydraulic pump 5 is pilot port 2a of the pilot type control valve 2. The control valve 2 is switched by the stroke amount according to the pilot hydraulic pressure. As a result, the oil discharged from the variable displacement hydraulic pump 1 is transferred to the conduit 9
1, the pressure compensating valve 23, and the control valve 2 are supplied to the hydraulic motor 4 to drive the vehicle. The speed of the vehicle depends on the depression amount of the traveling pedal 6a.

When the pedal 6a is released during traveling, the pilot valve 6 shuts off the pressure oil, and its outlet port communicates 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 of the slow return valve 7, the pilot control valve 2 is gradually switched to the neutral position and the vehicle is gradually decelerated.

When the arm lever 58 is operated, the hydraulic pilot type arm 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 supplied to the conduit 92. , Is guided to the arm cylinder 21 via the pressure compensating valve 24 and the control valve 20, and the arm cylinder 21 expands and contracts to move the arm up and down.

Although not shown in FIG. 1, a boom lever, a bucket lever, and a turning lever are provided in addition to the arm lever 58 and the traveling pedal 6a. Like the arm lever 58, the pilot corresponding to the operation amount of each lever is provided. A pressure reducing valve that discharges pressure oil, a control valve that is switched by the discharge pilot pressure oil, and an actuator that is driven by the pressure oil from the control valve are provided.

The pressure compensating valves 23 and 24 are provided for independently compensating the operation of the hydraulic motor 4 and the arm cylinder 21, and when the difference between the inlet and outlet pressures of the respective control valves is a predetermined value or more, the hydraulic pump 1 is operated. Supply pressure oil to each actuator. A pressure compensating valve of this kind is also provided for each actuator (not shown) described above.

The tilt angle of the variable displacement hydraulic pump 1, that is, the displacement volume, is controlled by a tilt angle control device 40.
The tilt angle control device 40 controls the piston position by the hydraulic pump 41 driven by the engine 27, the pair of electromagnetic valves 42, 43, and the pressure oil from the hydraulic pump 41 according to the switching of the electromagnetic valves 42, 43. The servo cylinder 44 is configured to control the tilt angle of the hydraulic pump 1 according to the piston position of the servo cylinder 44. Here, the pair of solenoid valves 42 and 43 is switch-controlled by the controller 50.

Reference numeral 51 is a tilt angle sensor for detecting a tilt angle θs of the hydraulic pump 1, and 52 is a discharge pressure Pp of the hydraulic pump 1.
Is a pressure sensor, 53 is the number of revolutions N of the engine 27.
A rotation speed sensor for detecting r, 54 is the discharge pressure of the hydraulic pump 1 and the maximum load pressure of the actuator (hydraulic motor 4
Of the load pressure of the arm cylinder 21 and the other actuators, which is the maximum value selected by the shuttle valve 29), that is, L
A differential pressure sensor for detecting an S differential pressure ΔPLS. Also, 5
Reference numeral 5 denotes a potentiometer that detects the amount of rotation Nθ of the governor lever 27b, and the detection results of these sensors are input to the controller 50. 57 is a fuel lever 57a
Is a rotation speed setting device for instructing the target rotation speed X according to the manual operation of, and the command signal is also input to the controller 50.

The controller 50 includes a first control circuit section 60 as shown in FIG. 1 and a second control circuit section 80 as shown in FIG.
And have. In the second control circuit unit 80 shown in FIG. 4, reference numeral 81 denotes a target rotation speed calculation unit, which determines the target rotation speed Nx according to the signal X corresponding to the displacement amount of the fuel lever 57a of the rotation speed setting device 57. . The displacement amount X and the target rotation speed Nx are the target rotation speed Nx as the displacement amount X increases.
Is set to linearly increase from the idle speed Ni.

Reference numeral 82 denotes a rotation speed correction value calculation unit, which outputs a rotation speed correction value ΔN according to the discharge pressure Pp of the hydraulic pump 1 which is the output of the pressure sensor 52. When the pump pressure increases above the rotation speed increase pressure set value Pu, the rotation speed correction value calculation unit 82 outputs the rotation speed correction value ΔN according to the pump pressure according to the illustrated increase characteristic. On the other hand, when the pump pressure decreases by a predetermined value or more, that is, when the current value decreases by (Pu-Pd) or more, the rotation speed correction value ΔN according to the pump pressure according to the illustrated reduction characteristic.
Is output. Here, the pressure Pd when the rotation speed correction value ΔN becomes zero is called a rotation speed down set value, and Pu and Pd
Is a hysteresis, and once the rotational speed has been increased, the rotational speed is not decreased unless the pump pressure decreases by the difference or more, which prevents hunting.

The output ΔN of the rotation speed correction value calculation unit 82 is input to an adder 87 described later. Rotation speed correction value calculation unit 82
A selection switch that can be freely turned on / off from the driver's seat may be provided between the adder 87 and the adder 87. Reference numeral 83 is a memory for storing the rotation speed correction value ΔN as the previous value ΔNold, and 84
Is a deviation device that calculates and outputs a deviation ΔΔN between the current value ΔN and the previous value ΔNold. Reference numeral 85 denotes a first control unit 60 to be described later, which outputs a high level signal Sc when the deviation ΔΔN is a predetermined value or more and a low level signal Sc when the deviation ΔΔN is less than the predetermined value.
When a high level signal is output from the function generator 85, the displacement volume of the variable displacement hydraulic pump 1 is reduced by a predetermined value. The details will be described later. It should be noted that the signal Sc is for detecting the presence / absence of the increase correction of the rotation speed, and it is desirable to hold the high level signal for a predetermined time by the delay timer. Preferably, the delay time is controlled so that the high level is maintained until the rotation speed is increased.

As shown in FIG. 4, the rotational speed correction value calculation unit 8
The rotation speed correction value ΔN obtained in 2 is input to the + input terminal of the adder 87, where it is added to the target rotation speed Nx to obtain the target rotation speed command value Ny. The target rotation speed command value Ny is compared with the signal of the displacement amount Nθ of the governor lever 27b detected by the potentiometer 55 by the servo control unit 88, and the pulse motor 28 is made to match them according to the procedure shown in FIG. Is controlled.

In FIG. 5, first, in step S21, the target rotation speed command value Ny and the governor lever displacement amount Nθ are read, and the flow proceeds to step S22. In step S22, the result of Nθ-Ny is stored in the memory as the rotation speed difference A, and in step S23, it is determined whether or not | A | ≧ K using a predetermined reference rotation speed difference K. If affirmative, the routine proceeds to step S24, where it is determined whether or not the rotational speed difference A> 0. If A> 0, the governor lever displacement amount Nθ is larger than the target rotational speed command value Ny, that is, the control rotational speed is the target rotational speed. Since it is higher than the number, the pulse motor 2 outputs a signal for instructing the motor reverse rotation in step S25 in order to reduce the engine speed.
Output to 8. As a result, the pulse motor 28 rotates in the reverse direction and the rotation 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 rotation speed command value Ny, that is, the control rotation speed is lower than the target rotation speed, a signal instructing normal rotation of the motor is output in step S26 in order to increase the engine rotation speed. As a result, the pulse motor 28 rotates in the normal direction and the rotation speed of the engine 27 increases. When step S23 is denied, the routine proceeds to step S27, where a motor stop signal is output, whereby the rotation speed of the engine 27 is maintained at a constant value. When steps S25 to S27 are executed, the process returns to the beginning.

The first control circuit section 60 shown in FIG. 1 comprises a load sensing control section (hereinafter, LS control section) 61, a torque control section 62, a selection section 63, and a servo control section 64. The LS control unit 61 controls the deviation Δ between the target differential pressure ΔPLSR and the LS differential pressure ΔPLS detected by the differential pressure sensor 54.
(PLS) is calculated, the amount of change ΔθL of the target value is calculated from this deviation Δ (PLS), and this is integrated to obtain and output the target pump tilt angle θL for load sensing control.

The torque control unit 62 detects the engine speed Nr detected by the speed sensor 53 and the potentiometer 5.
The deviation ΔN from the governor lever position Nθ detected in 5 is calculated, and the target torque Tpo for preventing the engine stall is calculated from the deviation ΔN, and the target torque Tpo is calculated.
Is multiplied by the reciprocal of the pump discharge pressure Pp detected by the pressure sensor 52 to perform tilt angle calculation, and the value θps is filtered by a temporary delay element to obtain the target pump tilt angle θT for input torque limit control. Ask.

Reference numeral 65 is a subtracter, which subtracts the reference pump tilt angle θto from the target pump tilt angle θT output from the torque control unit 62 to output the reduced target pump tilt angle θTr, and 66 is a subtracter. Is a switching device that selects one of the target pump tilt angle θT and the reduced target pump tilt angle θTr and sends it to the selection unit 63. The reference pump tilt angle θto is output from the reference pump tilt angle output unit 67.

The selection unit 63 uses the two target tilt angles θL.
And θT or θL and θTr, whichever is smaller, is selected and output to the servo control unit 64. Servo control unit 64
Indicates the selected tilt angle command value θr and the tilt angle sensor 51.
The tilt angle control device 40 is controlled so that the pump tilt angle θs matches the tilt angle command value θr. This switching is switched so as to select θTr in accordance with the above-described correction for increasing the rotation speed.

According to the load sensing control, 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 tilt 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. It is possible to improve fuel efficiency and operability by eliminating waste due to diaphragm loss. According to the input torque limit control, the torque of the hydraulic pump 1 is kept within the range of the output torque of the engine 27, and the engine 27 is prevented from being overloaded.

In the above structure, when the discharge pressure Pp of the hydraulic pump 1 detected by the pressure sensor 52 exceeds the predetermined value Pu (FIG. 1), the rotation speed correction value Δ corresponding to the pressure Pu is increased.
N is output from the rotation speed correction value calculation unit 82. This correction value ΔN is calculated by the adder 87 in the target rotation speed calculation unit 81.
It is added to the target rotation speed Nx set in. Therefore, the target rotation speed command value Ny becomes higher than the target rotation speed Nx, the actual rotation speed of the engine 27 also rises accordingly, and the discharge amount of the hydraulic pump 1 is increased in a range in which the passage flow rate of the control valve is not saturated. The flow rate increases.

At this time, if the deviation ΔΔN between the current rotational speed correction value ΔN and the previous rotational speed correction value ΔNold is equal to or greater than a predetermined value, the function generator 84 outputs the high level signal Sc, and the first control is performed. The switch 66 of the portion 60 is switched to the b contact side. As a result, the target pump tilt angle θL and the reduced target pump tilt angle θTr for load sensing control are input to the selection unit 63, and the smaller value is output from the selection unit 63.

When the increase in the rotational speed is corrected while the selection unit 63 is selecting θT, if θTr <θL, the displacement volume of the variable displacement hydraulic pump 1 is set to θTr. As a result, the displacement volume of the variable displacement hydraulic pump 1 is reduced by Δθto as the number of revolutions is increased, the pump input torque is reduced, and the load on the engine 27 is reduced.
Therefore, the increase in the number of revolutions is improved and the effect of increasing the number of revolutions becomes remarkable. Even if the rotation speed is increased during the load sensing control, the torque is not reduced and the operation feeling of the load sensing control is not impaired.

-Second Embodiment- FIG. 6 shows a second embodiment of the first controller 60. The difference from FIG. 1 is that the reference pump tilt angle θto is set to the rotation speed correction value ΔN.
The point is that it is changed according to the above, and the other is configured in the same manner. That is, the rotation speed correction value ΔN is input to the function generator 67A, and the reference pump tilt angle θto corresponding to this rotation speed correction value is output. In this second embodiment,
The larger the rotational speed correction value ΔN, the more the target pump tilt angle θTr
Is smaller, that is, the larger the rotational speed correction value ΔN is, the smaller the pump input torque is, the jet of the rotational speed becomes constant regardless of the rotational speed correction amount, and the operation feeling is improved.

In the construction of the above embodiment, the hydraulic motor 4 and the working hydraulic cylinder 21 etc. are hydraulic actuators, the traveling pedal 6a, the operating lever 58 etc. are commanding means, the fuel lever 57a is an operating member, and the target rotational speed. The calculation unit 81 is a target rotation speed setting unit, the adder 87 is a rotation speed correction unit, the pulse motor 28 and the servo control unit 88 are prime mover control units, and the pressure sensor 52 is a load detection unit.
The deviation device 84, the function generator 85, etc. serve as a rotation speed correction means,
The first control unit 60 constitutes displacement volume reducing means and displacement volume control means, respectively.

In the above description, the load of the actuator is detected by the pump pressure. However, the load of the actuator is detected from the pressure of the hydraulic actuator or the deviation between the actual engine speed and the target speed (governor lever position). May be. Further, in the above, an example in which the engine target speed is set as the operation member according to the operation amount of the fuel lever has been shown, but the operation member is not limited to the fuel lever, and for example, the engine target speed may be set according to the travel pedal operation amount. The present invention can be applied to a device for setting. Also, the one that sets the engine target speed with the up / down switch, or
A switch for heavy load, a switch for light load, and a switch for idle may be provided, and each switch may be operated to set a predetermined target rotation speed. Furthermore, the present invention can be similarly applied to hydraulic construction machines other than hydraulic excavators. Furthermore, although the load sensing hydraulic drive control device has been described, the present invention is not limited to this control method in an invention that does not require load sensing control.

[0033]

As described above, according to the present invention, the input torque of the variable displacement hydraulic pump is reduced by a predetermined amount when the engine rotational speed is increased and corrected in accordance with the load. Blow-up is improved, the generation of graphite is suppressed, and fuel efficiency is improved. Further, since the increase in the number of revolutions becomes faster, the amount of increase in the discharge flow rate of the pump due to this exceeds the amount of decrease in the pump discharge flow rate due to the reduction of the input torque during this period, and as a result, the actuator speed becomes faster and the work amount improves. In the drive control device that performs the load sensing control and the torque limiting control, the displacing volume reduction control is performed only during the torque limiting control, so that the operation feeling during the load sensing control is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing details of a pump control circuit unit according to an embodiment.

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

FIG. 3 is a diagram showing the pilot operation circuit of FIG. 2;

FIG. 4 is a block diagram of a rotation speed control circuit unit.

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

FIG. 6 is a block diagram showing details of another embodiment of the pump control circuit unit.

[Explanation of symbols]

 1 Variable Capacity Hydraulic Pump 2 Travel Control Valve 4 Travel Hydraulic Motor 4a-4c Pressure Sensor 6 Pilot Valve 6a Travel Pedal 8 Forward / Reverse Switching Valve 20 Arm Control Valve 21 Arm Cylinder 21a-21d Pressure Sensor 27 Engine (Motor) 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 unit 61 LS control unit 62 Torque control unit 63 Selection unit 64 Servo control unit 65 Deviation device 66 Switcher 67 Reference pump tilt angle output unit 67A Function generator 80 Second control circuit unit 81 Target rotation speed calculation unit 82 Rotation speed correction value calculation unit 83 memory 84 deviation device 85 function generator

Claims (2)

[Claims] 1. A variable displacement hydraulic pump driven by a prime mover, a hydraulic actuator driven by oil discharged from the hydraulic pump, command means for instructing the operation of the hydraulic actuator, and load of the hydraulic actuator is detected. Load detection means, a target rotation speed setting means for setting a target rotation speed of the prime mover according to an operation of an operating member, and a rotation speed correction means for correcting the set target rotation speed according to a detected load. And a drive control device for a hydraulic construction machine including a prime mover control means for controlling the prime mover so as to obtain the corrected target rotation speed, the rotation speed correction means performs an increase correction of the rotation speed. The rotation speed correction detecting means for detecting, and when the rotation speed correction detecting means detects that the rotation speed increase correction is to be performed, Hydraulic construction machine drive control unit, characterized in that it comprises a displacement volume reduction means for reducing the displacement volume of the variable displacement hydraulic pump. 2. A variable displacement hydraulic pump driven by a prime mover, a hydraulic actuator driven by oil discharged from the hydraulic pump, command means for commanding the operation of the hydraulic actuator, and a command of this command means. A control valve that controls the pressure oil supplied from the hydraulic pump to the hydraulic actuator, a load detection unit that detects the load of the hydraulic actuator, and a target rotation speed that sets the target rotation speed of the prime mover according to the operation of the operating member. Setting means, rotation speed correction means for correcting the set target rotation speed according to the detected load, prime mover control means for controlling the prime mover to reach the corrected target rotation speed, and the control A load sensing system for controlling the displacement volume of the variable displacement hydraulic pump so that the pressure difference upstream and downstream of the valve becomes constant. Control and a displacement control means for controlling the displacement volume of the hydraulic pump by any one of the torque limit control for limiting the input torque of the hydraulic pump within the output range of the prime mover. In the drive control device, a rotation speed correction detection unit that detects that the rotation speed correction unit performs the rotation speed increase correction, and that the rotation speed correction detection unit detects that the rotation speed increase correction is performed, In addition, the displacement volume of the variable displacement hydraulic pump is reduced when the torque limit control is being performed, and the rotational speed correction is performed by the rotational speed correction detecting means when the load sensing control is being performed. A drive control device for a hydraulic construction machine, comprising: a displacement volume reducing means that does not reduce the displacement volume even if it is detected.