JP2773511B2 - Control method of pump displacement for construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a tilting amount of a pump of a construction machine such as a hydraulic shovel, which is provided with a variable pump driven by an engine and determines a discharge amount of the variable pump according to a displacement amount of an operation lever. About.

[0002]

2. Description of the Related Art FIG. 4 shows an engine 1 and a variable pump mounted on a hydraulic shovel (more specifically, a variable displacement hydraulic pump).
2 is a diagram illustrating a control circuit of FIG. In FIG. 4, reference numeral 3 denotes a work attachment mounted on the front portion of the hydraulic excavator, 4 denotes an arm cylinder as a representative example of a plurality of hydraulic actuators arranged on the work attachment 3, and 5 denotes a pilot switching valve for an arm. , 6 is a hydraulic remote control valve, 7 is an operation lever of the hydraulic remote control valve 6, 8 is a pilot pump, 9 is a regulator for adjusting the swash plate tilt angle of the variable pump 2, 10 is a governor device of the engine 1, and 11 is a governor device. 10 is a governor lever, 12 is a control motor such as a so-called stepping motor, 13 is a drive lever of the control motor 12, 14 is a rotation speed detector for detecting the rotation speed of the engine 1, 16 is a controller, 17 is a mode switch, and 18 is a mode switch. An accelerator lever device, 19 is an accelerator lever of the accelerator lever device 18, and 20 is an accelerator. Potentiometer for detecting an operation position of the bar 19, reference numeral Lee -
(A) and (b) show the connection of a pilot line connecting the hydraulic remote control valve 6 and the arm pilot switching valve 5.
By switching the engine speed control mode changeover switch 17 according to the magnitude of the work load during the operation of the hydraulic excavator, H (for heavy load), S (for normal load), FC (fine operation work) ) Can be selected respectively. By operating the accelerator lever 19 in the direction of the arrow L, the engine speed becomes low idling rotation (low-speed engine rotation), and when operating in the direction of arrow H, the engine speed becomes high idling (high-speed engine rotation).

As shown in FIG. 4, a control circuit of a conventional hydraulic excavator includes an engine 1 and a variable pump 2 driven by the engine 1, and a rotation speed detector for detecting the rotation speed of the engine 1. 14 is provided, and a rotation speed detection signal from the rotation speed detector 14 is sent to the controller 1.
6 and a mode changeover switch 17 and an accelerator lever device 17 near a driver's seat (not shown).
Is provided. Then, when the driver operates the mode changeover switch 17 and the accelerator lever device 18 as required during work, the operation position signals of the mode changeover switch 17 and the accelerator lever 19 are input to the controller 16. The controller 16 makes a determination based on the operation position signal, and outputs a control command signal from the controller 16 to the control motor 12. The control motor 12 rotates to rotate the governor lever, and the engine speed is adjusted.

When the pump pressure of the variable pump 2 changes in response to the increase or decrease of the work load, the pump pressure changes
Acting on the regulator 9 via 1, 22, the throttle 23 and the conduit 24. Since the regulator 9 operates to adjust the swash plate tilt angle (tilt amount) of the variable pump 2, the discharge flow rate of the pump can be automatically changed.

[0005]

When a hydraulic excavator performs a work, the engine speed is adjusted to a high-speed high idle rotation or a low-speed low idle rotation according to the working condition.

FIG. 5 is a table showing the relationship between the operation angle θ of the working operation lever and the pump flow rate Q at the time of high idle rotation and low idle rotation of the engine. As shown in FIG. 5, when the engine speed is high and when the engine speed is low,
If the swash plate tilt angle is not changed, the pump flow rate will be different. Even at the start of operation of the operation lever for work, the pump flow rate is the flow rate Q discharged during high idle rotation.
2 decreases to the flow rate Q1 during low idle rotation. Therefore, even when the operation lever is operated by the same operation angle (not shown, but the operation angle at which the opening area of the spool of the pilot switching valve changes in the same manner) at the start of operation of the operation lever, if the pump flow rate is small, for example, the hydraulic pressure such as an arm cylinder The generated pressure for operating the actuator decreases. Therefore, when working at a low engine speed, the operating lever (including the pedal) must be operated to a considerably large angular position to increase the operating pressure of the hydraulic actuator. There is a problem that the area becomes narrow, and the responsiveness and the inching property of the hydraulic actuator for driving the arm or the boom are deteriorated.

In view of such circumstances, the present invention provides a construction machine having a wide operation control area of an operation lever and good responsiveness and inching property of a hydraulic actuator even when the engine is rotating at a low speed. It is an object of the present invention to provide a method of controlling a pump tilt amount.

[0008]

The present invention according to claim 1 is provided with an engine and a variable pump driven by the engine, and determines a pump discharge amount according to a displacement amount of an operation lever for operating a hydraulic actuator. And controlling the amount of tilt of the variable pump in accordance with the work load acting on the hydraulic actuator, in the method of controlling the amount of tilt of the pump of the construction machine, wherein the operation of the operation lever at the start of movement at the time of low-speed rotation of the engine is performed. The amount of tilt of the variable pump during low-speed rotation of the engine is made larger than the amount of tilt of the variable pump during high-speed engine idling so that the amount is approximately the same as the operation amount at the start of movement during high engine idling. is there.

The present invention according to claim 2 provides the present invention as claimed in claim 1.
When the amount of tilt of the variable pump during low-speed rotation of the engine is determined, the amount of tilt of the variable pump during low-speed rotation of the engine is determined by the amount of tilt of the variable pump during high-speed engine rotation. The value is obtained by multiplying a value obtained by dividing the engine speed during rotation by the engine speed during low-speed rotation of the engine.

Further, according to the present invention, a correction is made such that the value approaches 0 as the engine speed approaches the engine high idling speed and increases as the engine speed decreases. Is applied to the engine speed at the time of high engine idling when the amount of tilt of the variable pump at the time of low speed engine rotation is determined in the invention according to claim 2.

[0011]

According to the first aspect of the present invention, the engine low-speed rotation is performed so that the operation amount at the start of movement of the operation lever during low-speed rotation of the engine is substantially the same as the operation amount at the start of movement during high-idling rotation of the engine. The amount of tilt of the variable pump at the time of rotation is larger than the amount of tilt of the variable pump at the time of engine high idling, so that the operation control area of the operation lever is wide, and the responsiveness and inching performance of the hydraulic actuator are good.

According to the second aspect of the present invention, the amount of tilt of the variable pump during low-speed rotation of the engine is converted into the amount of tilt of the variable pump during high-speed idle rotation of the engine, and the number of engine rotations during high engine idle rotation. Multiplied by the value obtained by dividing by the engine speed at low engine speed, the operation amount at the start of operation of the operation lever at low engine speed is almost the same as the operation amount at the start of engine high idle rotation. , The control of the pump displacement can be executed only by detecting the engine speed. Therefore, no extra measuring means is required, and the control of the pump tilt amount can be executed by a simple calculation.

Further, according to the third aspect of the present invention,
A correction is made to the engine speed at the time of the engine high idling speed so that the value approaches 0 as the engine speed at the engine high idling speed approaches and increases as the engine speed decreases. Therefore, the operation amount at the start of movement of the operation lever during low-speed rotation of the engine can be more accurately matched with the operation amount at the start of movement during high-idle rotation of the engine.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a main part control circuit diagram according to the present invention. In FIG. 1, the same components as those described with reference to FIG. 7 in the related art section are denoted by the same reference numerals.
9 'is a regulator of the variable pump 2, 25 is a controller, 26 is a memory, and 27 is an electromagnetic proportional pressure reducing valve which is an electro-oil converter.

FIG. 2 shows the pilot secondary pressure derived from the hydraulic remote control valve 6 by operating the operation lever 7 and the tilt amount of the variable pump 2 (the pump discharge flow rate per one rotation of the pump shaft (CC / rev). FIG.

Next, the control method of this embodiment will be described with reference to FIGS.
Is described. The regulator 9 ′ of the variable pump 2 is connected to the controller 25 via the electromagnetic proportional pressure reducing valve 27, and the controller 27 stores a pump characteristic curve that determines the pump discharge amount according to the displacement amount of the operation lever 7. The ratio of the engine speed at the time of the engine high idling to the current target speed of the engine 1 is calculated. When the engine speed is reduced to a low speed, the controller 25 operates the operating lever 7 at the time of the engine high idling. A calculation is performed by multiplying the amount of displacement of the pump at the start of movement by the above ratio, and a command signal for increasing the amount of displacement of the variable pump 2 is output to the regulator 9 ′ via the electromagnetic proportional pressure reducing valve 27 based on the calculation result. I did it.

In the calculation by the controller 27, the amount of tilt of the variable pump 2 (the theoretical discharge amount CC / rev per one rotation of the pump shaft) at the time of high engine idling is represented by q.
0, the engine speed during engine high idle is Nma
x, the pump flow rate Q0 in this case is Q0 = q0
× Nmax. Here, assuming that the target rotation speed when the engine rotation speed is reduced to a low speed is N1 and the pump tilt amount at that time is q1, q1 = q0 × Nmax / N1. As a result, the pump flow rate Q1 at the time of lowering to the low speed is Q1 = q1 × N1 = (q0 × Nma
x / N1) × N1 = q0 × Nmax. The ratio in the above equation is Nmax / N1> 1. Even when the engine speed is reduced to a low speed as described above, the same pump flow rate as in the case of high engine idle speed can be obtained. Therefore, by implementing the control method of the present invention, even when the engine speed is reduced to a low speed, the operation amount at the start of movement of the working operation lever is made substantially the same as the operation amount at the start of movement during high idle rotation. Can be.

FIG. 3 shows a correction value curve of the target engine speed. Next, a control method according to a third aspect of the present invention will be described.

According to the control method of the second aspect, the output current characteristics from the controller 25, the pilot pressure (specifically, the pilot secondary pressure) characteristics derived from the electromagnetic proportional pressure reducing valve, and the pump tilt characteristics due to the pilot pressure are obtained. Since it is not taken into consideration, it is necessary to correct the theoretical target engine speed. Therefore, as shown in FIG.
Engine speed Nmax at high engine idle speed
The controller 25 sets the correction value to the theoretical target rotation speed based on a correction value curve that approaches a value of 0 (zero) as the vehicle speed approaches, and increases as the engine rotation speed decreases. Was added to set the target engine speed. Therefore, by calculating the ratio of the engine high idle speed to the current corrected target engine speed of the engine 1, the operation amount of the operation lever 7 at the start of movement at the time of the engine low speed is reduced to the operation amount at the start of the engine high idle speed. The manipulated variable can be further equalized.

[0020]

According to the present invention, the operation amount of the operation lever at the start of movement at the time of low engine rotation is substantially the same as the operation amount of the movement start at the time of high engine idling, thereby expanding the operation control range of the operation lever. And the responsiveness and inching operability of the hydraulic actuator can be improved.

Therefore, regardless of whether the engine speed is high or low, the operation amount of the operation lever at the start of movement can be made the same, so that the operability and workability of the construction machine can be improved.

According to the second aspect of the present invention, the control of the pump displacement can be executed only by detecting the engine speed.
This means that the control of the pump displacement can be executed with a simple calculation without the need for extra measuring means, and the cost of the construction machine can be reduced.

Further, according to the third aspect of the present invention, it is possible to more accurately match the operation amount at the start of movement of the operation lever during low-speed rotation of the engine with the operation amount at start of movement during high-idle rotation of the engine. Claim 3
In the invention according to the second aspect as well, since the calculation can be performed only by detecting the engine speed, there is an effect that the cost of the construction machine can be reduced.

[Brief description of the drawings]

FIG. 1 is a main part control circuit diagram according to the present invention.

FIG. 2 is a table showing a relationship between a pilot secondary pressure derived from a hydraulic remote control valve and a pump displacement.

FIG. 3 is a correction value curve of an engine target speed according to the present invention.

FIG. 4 is a diagram showing a control circuit of the related art.

FIG. 5 is a prior art chart showing a relationship between an operation angle of a working operation lever and a pump flow rate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 engine 2 variable pump 7 work operation lever 9, 9 'regulator 10 governor device 12 control motor 16, 25 controller 17 mode changeover switch 18 accelerator lever device 26 memory 27 electromagnetic proportional pressure reducing valve

Claims (3)

(57) [Claims] [Claim 1] equipped with a variable pump driven by the engine and that engine, so as to determine the pump discharge amount in accordance with the displacement amount of the operating lever for the hydraulic actuator operation, also the working load acting on the hydraulic actuator In the control method of the pump displacement amount of the construction machine, the displacement amount of the variable pump is adjusted in accordance with the operation amount of the operation lever at the time of low speed rotation of the engine. Variable at the time of low-speed rotation of the engine so that
Pump displacement during engine high idle rotation
A method for controlling a pump displacement of a construction machine, wherein the displacement is increased from a displacement of the variable pump . 2. A variable pump at the time of low-speed rotation of an engine.
Variable pump during engine high idle rotation
Engine rotation during engine high idle rotation
Value obtained by dividing the number of turns by the engine speed at low engine speed
2. The construction according to claim 1, wherein the value is multiplied by
How to control the amount of pump tilt of the machine . 3. The engine at high engine idle speed
As the speed approaches, the value approaches 0 and the engine
So that it becomes larger as the rotation speed of the
Adjustment of the variable pump at low engine speed.
When calculating the rotation amount, the engine
3. The construction according to claim 2, wherein the rotation is applied to a gin rotation speed.
How to control the amount of pump tilt of the machine .