JPH01170730A - Hydraulic pump controlling method for construction equipment - Google Patents

Abstract

PURPOSE:To speed up the rise of an engine in the beginning of operation by reducing the absorption horse power of a hydraulic pump lower than that in light operation mode when the rotational frequency of engine is less than a set value and at least one of a plurality of operating levers is operated. CONSTITUTION:A plurality of hydraulic actuators 7 of construction equipment are respectively driven through a plurality of hydraulic pumps 5 by an engine 1. Then, when at least one of a plurality of operating levers 9 is under the operated condition, the rotational frequency of engine 1 is commanded by a controller 10 to be set to a set value by throttle layer 11. Also, when the respective operating layers 9 are all under the neutral condition, the rotational frequency of engine 1 is commanded to be less than the set value. Further, when at least one of the respective operating levers 9 is again operated, the absorption horse power of hydraulic pump 5 is reduced lower than that in the light operation mode until the rotational frequency of engine 1 reaches the set value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling a hydraulic system of a hydraulic construction machine.

BACKGROUND ART FIG. 6 is a diagram showing a control device to which a method for controlling a hydraulic system of a hydraulic construction machine is applied. In the figure, 1 is an engine, 2 is a governor control device for the engine 1, 3 is a fuel injection amount control device, 4 is an engine rotation sensor, 5 is a variable displacement hydraulic pump, 6 is a regulator for the hydraulic pump 5, and 7 is a hydraulic pump a plurality of hydraulic actuators operated by pressure oil discharged from 5; 8 a directional switching valve provided between the hydraulic pump 5 and the hydraulic actuator 7; 9 a plurality of operation levers provided corresponding to the hydraulic actuator 7; 10 is a controller, 11 is a throttle lever that sets the rotation speed of the engine 1, and 12 is a state in which low-speed operation control is performed on the engine 1 when all the operating levers 9 are in the neutral position, and a state in which low-speed operation control is not performed. This is a changeover switch that changes between the two states. The fuel injection amount control device 3 receives signals from the throttle lever 11, engine rotation sensor 4, controller 10, and changeover switch 12, and outputs signals to the governor control device 2.

In the above control device, when the operation lever 9 is operated, an output signal corresponding to the operation amount is output from the operation lever 9, and the control signal is processed by the controller 10, and the controller 1o sends the regulator 6 to the directional control valve. A control signal corresponding to the output signal of the operating lever 9 is output to the control lever 8, and the tilting direction and tilting angle of the hydraulic pump 5 and the switching direction and switching amount of the direction switching valve 8 are controlled in accordance with the control signal. ,
The amount of pressure oil supplied to the hydraulic actuator 7 has a value corresponding to the output signal of the operating lever 9, and the speed of the hydraulic actuator tough has a value depending on the amount of pressure oil supplied to the hydraulic actuator tough. Thereby, the hydraulic actuator 7c6
The speed is controlled according to the amount of operation of the operating lever 9. Further, signals from the engine rotation sensor 4, controller 10, throttle lever 11, and changeover switch 12 are input to the fuel injection amount control device 3, and the fuel injection amount of the governor control device 2 is determined by the signals from the fuel injection amount control device 3. The rotational speed of the engine 1 is ultimately controlled by the signal from the fuel injection amount control device 3.

Next, a conventional method of controlling the hydraulic system in the control device shown in FIG. 6 will be explained with reference to FIG. 7. First, when the changeover switch 12 is operated to disable low-speed operation control, by repeating A→D, the rotation speed of the engine 1 is adjusted according to the operation amount of the throttle lever 11, regardless of the operating state of the operating lever 9. The engine 1 is commanded to operate at a set rotation speed at the set value, that is, the set rotation speed, and the engine 1 rotates at the set rotation speed. In this state, if the selector switch 12 is changed to perform low-speed operation control, and all of the operating levers 9 are in the neutral state, the rotation speed of the engine 1 is set to the set rotation speed by repeating steps A-4-B-C. A low-speed rotational operation with a low rotational speed smaller than the number is commanded, and the engine 1 is operated at a low rotational speed. In this state, when at least one of the control levers 9 is activated, the set rotation speed operation is commanded by repeating A-B-D, and the engine 1
is operated at the set rotation speed. In this state, the operating lever 9
When all of the above are in the neutral state, low speed rotational operation is commanded by repeating A→B→C, and the engine 1 is operated at low speed rotation speed. Therefore, when the hydraulic actuator 7 does not operate, such as during a short break in work, the rotation speed of the engine 1 decreases, thereby reducing fuel consumption.Problems to be solved by the invention When operated as shown in FIG. 8a, the rotational speed of the engine 1, the tilt angle of the hydraulic pump 5, and the discharge flow rate of the hydraulic pump 5 change as shown by broken lines in FIGS. 8b to 8d. That is, when all the operating levers 9 are in the neutral state and the engine 1 is at a low rotational speed, when at least one of the operating levers 9 is activated, the state shown in FIG. As shown by the broken line, when the operating lever 9 is operated, the tilting angle of the hydraulic pump 5 increases in accordance with the increase in the operating amount of the operating lever 9, but the torque of the hydraulic pump 5 increases as the discharge of the hydraulic pump 5 increases. Since it is proportional to the product of the pressure and the tilting angle of the hydraulic pump 5, the torque acting on the engine 1 increases as the discharge pressure of the hydraulic pump 5 and the tilting angle increase, so the engine 1 drives the load. As a result, as shown by the broken line in FIG. 8, the rise in the rotation speed of the engine 1 is significantly delayed. The discharge flow rate of the hydraulic pump 5 is proportional to the product of the tilt angle of the hydraulic pump 5 and the rotation speed of the hydraulic pump 5,
Further, the rotation speed of the hydraulic pump 5 is proportional to the rotation speed of the engine 1. Therefore, if the rise in the rotation speed of the engine 1 is significantly delayed, the hydraulic pump 5
The discharge flow rate increases slowly. Therefore, the speed of the hydraulic actuator 7 increases slowly, so that after a long period of time from the time when the operating lever 9 was operated, the speed of the hydraulic actuator 7 reached a value corresponding to the amount of operation of the operating lever 9. As described above, when the engine speed increases, the operability of the control lever 9 is hindered, and the exhaust gas from the engine 1 is discharged as black smoke, which is a problem.

The present invention solves the above problems and provides a hydraulic pump control method for construction machinery that can reduce fuel consumption, shorten the engine speed rise time, and provide good operability. purpose.

Means for Solving the Problems The means of the present invention taken to solve the above-mentioned problems are as follows: (i) At least one of the plurality of operation levers for commanding the operation of the hydraulic actuator is in an activated state. When the engine rotation speed is commanded to operate at the set rotation speed set by the throttle lever, and when all of the above operating levers are in the neutral state while the set rotation speed operation command is being issued, the engine rotation speed is When at least one of the operating levers is activated while the low speed rotation speed operation command is issued, the engine The absorption horsepower of the hydraulic pump was set significantly lower than in the light work mode until the rotational speed of the hydraulic pump reached a predetermined control rotational speed.

Operation a. When at least one of the control levers is activated while a low speed operation command is given to the engine, the hydraulic pressure is maintained until the engine speed reaches the predetermined control speed. The absorption horsepower of the pump has been set significantly higher than in light work mode.

As a result, the load on the engine is significantly smaller than the torque of the hydraulic pump in the light work mode, and the time required for the engine speed to rise is significantly shorter than in the prior art.

At the same time, the discharge amount of the hydraulic pump is rapidly increased, so that the speed of the hydraulic actuator reaches a value corresponding to the amount of operation of the operating lever within a short time.

EXAMPLE Hereinafter, the hydraulic pump control method according to this invention will be explained in detail based on the drawings. FIG. 1 is a pump horsepower control curve diagram of the hydraulic pump 5. In the diagram of FIG. 1, the X-axis shows the hydraulic pump discharge pressure, and the Y-axis shows the hydraulic pump discharge flow rate. The curve H is the absorption horsepower curve used for the heavy work mode with a heavy load, the curve S is the standard work mode with a standard load, and the curved line is the light work mode with a light load. The H, S, and L modes are modes in which the driver selects the above mode depending on the magnitude of the work load when working on the construction machine, and changes the engine horsepower without reducing the engine speed. For example, when the L mode is selected during light work with a light load, engine horsepower is reduced and used, so fuel consumption can be reduced in proportion. Curve Z
is the Z mode used in the hydraulic pump control method according to the present invention. This Z mode has an absorption horsepower curve set significantly lower than that of the L mode, or the absorption horsepower has been reduced to an extremely low level.

Next, in the control device shown in FIG. 6 according to FIG.
A hydraulic pump control method according to the present invention will be explained. First, when the changeover switch 12 is operated to disable low-speed operation control, by repeating A-+D, the set rotation speed operation is commanded regardless of the operating state of the operating lever 9, and when the operating lever 9 is operated, the regulator 6
is activated, and the tilting angle of the hydraulic pump 5 becomes a value corresponding to the amount of operation of the operating lever 9. In this state, selector switch 12
When the control levers 9 are all in the neutral state when switching to the state where low-speed operation control is performed, A-4B-4
By repeating 0, low speed rotation speed operation is commanded, and the engine 1 is operated at low speed rotation speed. In this state, when at least one of the operating levers 9 is activated, the engine 1
A-+B-+E until the rotation speed reaches the control rotation speed.
-) By repeating D, even if the operating lever 9 is operated, the hydraulic pump 5 maintains the reduced horsepower state for a certain period of time, and the set rotation speed is commanded. When the rotational speed of the engine 1 reaches the set rotational speed, the absorption horsepower of the hydraulic pump 5 has also increased.

When controlling in this way, move the operating lever 9 as shown in Fig. 3a.
When operated as shown in FIG.
It changes as shown by the solid line d. That is, when all of the operating levers 9 are in a neutral state and the engine 1 is at a low rotational speed, when at least one of the operating levers 9 is activated, the engine 1's rotational speed becomes low. Until the number of rotations reaches the control rotation speed N, the hydraulic pump 5 is under horsepower reduction control. For this purpose, the engine 1 is
The rotation speed rises quickly. Then, when the rotation speed of the engine 1 reaches the set rotation speed, the discharge flow rate of the hydraulic pump 5 becomes a value corresponding to the operation amount of the operation lever 9, and the speed of the hydraulic actuator tough changes according to the operation amount of the operation lever 9. The operability is very good. In addition, FIG. 4 shows that the engine control rotation speed N in FIG. 4 is a diagram showing a state in which the state is maintained until immediately after reaching . In the case of FIG. 4, as in the case of FIG. 3,
The rotational speed of the engine 1 rises very quickly, and the operability of the hydraulic actuator 7 is very good.

Next, another hydraulic pump control method according to the present invention in the control device shown in FIG. 6 will be explained with reference to FIG. First, when the changeover switch 12 is operated to disable low-speed operation control, the engine 1 is commanded to operate at the set rotation speed by repeating A-D, regardless of the operating state of the operating lever 9. In this state, when the selector switch 12 is changed to perform low-speed operation control and all the operating levers 9 are in the neutral state, A→B−
By repeating C, low speed rotation speed operation is commanded, and the engine 1 is operated at low speed rotation speed. In this state, when at least one of the operating levers 9 is activated, the engine 1
A-B-+E until the rotational speed and control rotational speed are reached.
By repeating '→F→D, even if the operating lever 9 is operated, the hydraulic pump 5 maintains the reduced horsepower state for a certain period of time.When the engine 1 reaches the control speed, the engine 1
At the same time, the absorption horsepower of the hydraulic pump 5 is also increased.

Effects of the Invention In the conventional control method for the hydraulic system of construction machinery, all of the operating levers are in a neutral state, and at least one of the operating levers is in an operating state when the engine speed is low. When this happens, the torque of the hydraulic pump acting on the engine is large, so the engine speed slowly increases while driving the load. As a result, there was a significant delay in the rise of the engine speed, which impeded the operability of the control lever, and the exhaust gas from the engine was emitted as black smoke, which was a problem.

However, in the hydraulic pump control method according to the present invention, when at least one of the control levers is activated while the engine speed is at a low speed as described above, the engine speed is set in advance. The absorption horsepower of the hydraulic pump was set significantly lower than in the light work mode until the predetermined control rotation speed was reached. Therefore, when at least one of the control levers is activated while a low-speed engine speed operation command is issued, the absorption horsepower of the hydraulic pump to the engine is extremely small, so the engine speed rises at the start of operation. It is extremely fast and can also prevent black smoke from the exhaust gas emitted by the engine. Furthermore, since the speed of the hydraulic actuator reaches a value corresponding to the operating amount of the operating lever after a short time has elapsed from the time when the operating lever is operated, the operability is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a pump horsepower control curve diagram of a hydraulic pump according to the present invention, and FIG. 2 is a flowchart for explaining a hydraulic pump control method according to the present invention. Graph for explaining the operation, FIG. 5 is a flowchart for explaining another hydraulic pump control method according to the present invention, FIG. FIG. 7 is a flowchart for explaining the conventional control method, and FIG. 8 is a graph for explaining the operation in the conventional control method. 1---------1 engine 2--111--Governor control device 3--------
(1) Fuel injection amount control device 4 ---------1
Engine rotation sensor 5 -==--Hydraulic pump 6--Regulator 7--Hydraulic actuator 8--
---One-way switching valve 9--1 Operation lever 10--1--Controller 11 --=--Throttle lever 12--=
= - changeover switch or more

Claims (1)

[Claims] An engine, a variable displacement hydraulic pump driven by the engine, a plurality of hydraulic actuators operated by pressure oil discharged from the hydraulic pump, a throttle lever that sets the rotation speed of the engine, and a regulator for the hydraulic pump. and a plurality of operating levers provided corresponding to the hydraulic actuator and for commanding the operation of the hydraulic actuator by operating at least the regulator, and when all of the operating levers are in neutral positions,
In a method for controlling a hydraulic system of construction machinery that enables switching of an engine governor from a high speed rotation position to a low speed rotation position, when at least one of the operation levers is activated, the rotation speed of the engine is controlled by the throttle lever. When all of the above control levers are in the neutral state while the set rotation speed operation command is issued, the rotation speed of the engine is set to a low speed lower than the set rotation speed. When at least one of the operating levers is activated while the low-speed rotational speed operation command is issued, the rotational speed of the engine is set to a predetermined control rotational speed. A method for controlling a hydraulic pump for construction machinery, characterized in that the absorption horsepower of the hydraulic pump is set significantly lower than in a light work mode until the number reaches the maximum number.