KR20150076007A - Method and Apparatus for Controlling Power of Construction Machinery - Google Patents

Abstract

The present invention relates to a power control device for a construction machine, comprising: an engine connected to a hydraulic pump so as to drive the hydraulic pump; an engine control unit for controlling the engine, so as to increase an engine RPM command to a predetermined engine RPM and increase or decrease the engine RPM in a hysteresis form according to an engine load factor, when in a heavy-load mode, and to decrease the engine RPM command to the predetermined engine RPM and increase or decrease the engine RPM in the hysteresis form according to the engine load factor, when in a light-load mode; and a pump control unit for controlling the hydraulic pump by using a torque slope map in which engine dynamic characteristics are reflected.

Description

TECHNICAL FIELD [0001] The present invention relates to a power control apparatus for a construction machine,

The present invention relates to a power control apparatus for a construction machine.

BACKGROUND ART Generally, a construction machine such as an excavator drives a plurality of working devices including a boom, an arm and a bucket by using hydraulic oil discharged from a variable displacement hydraulic pump directly connected to an engine.

The discharge flow rate of such a hydraulic pump is controlled by various parameters so as to satisfy various conditions such as efficiency of operation and fuel consumption.

1 is a view for explaining a conventional hydraulic pump control method.

1 (a) is a view for explaining flow control. The flow rate can be controlled according to the P-Q diagram. That is, since the maximum torque output from the engine is determined, the hydraulic pump is operated within a stable range in which the engine is not stopped. For example, the flow rate is decreased when a high pressure is required, and the maximum flow rate is controlled when the pressure is low.

Fig. 1 (b) is a view for explaining horsepower control. The horsepower control is to select the load mode in advance and control the hydraulic pump. That is, when the work performance is to be improved, the upper load mode is selected so that the maximum torque is outputted, and when the work is performed under the light load, the lower load mode is selected so as to lower the maximum torque.

The above-described load mode can be expressed by a light load mode, a standard load mode and a heavy load mode. Also, it can be expressed by a full power mode, a power mode, a standard mode, an economy mode, an idle mode, and the like. That is, the load mode can be expressed according to the magnitude of the load or the magnitude of the output torque.

1 (c) shows the control of the hydraulic pump applied by combining the flow rate control and the horsepower control.

That is, when the work type is heavy, the upper power mode (P mode) is selected and operated. When the work type is light, the lower standard mode (S mode) is selected and operated. As a result, when the mode is changed from the power mode to the standard mode, the maximum discharge flow rate is limited to be controlled to be reduced.

As shown in Fig. 1 (c). The correlation between the pump torque and the engine speed when the hydraulic pump is controlled by combining the flow rate control and the horsepower control will be described with reference to FIG. 2 and FIG.

Fig. 2 is a time-dependent graph of the engine speed and the pump torque. 3 is a graph of the pump torque with respect to the engine speed.

In Fig. 2, A and B are cases in which the required value (flow rate / hydraulic pressure) is suddenly requested by operating the joystick hastily. At this time, the engine speed rpm suddenly drops instantaneously, and the actual pump torque decreases unstably.

Referring to FIG. 3, although the engine speed rpm is linear at around 1800 to 1900 rpm of the rated speed, unstably bouncing occurs as in the C portion. Part C corresponds to portions A and B in Fig. That is, when the joystick is suddenly operated, it can be seen that the pump torque finally outputted is unstable, and the controllability of the working machine is deteriorated.

Part C will be described in detail as follows.

When the joystick is suddenly operated, the maximum required torque (Max Torque) is increased by the joystick lever, and when the engine speed (rpm) is decreased, the output torque T of the hydraulic pump is decreased.

If only the amount of change in the maximum torque required is controlled, the actual engine torque (rpm) decreases at this steep portion of the actual torque change, which may result in a performance degradation limiting the usable energy. In other words, the fuel is injected at a normal injection amount. If the engine speed is lowered, the fuel is consumed because the loss becomes large even though the total amount of energy that can be realized by the consumed fuel is present.

On the other hand, when the engine speed (rpm) is monitored to control the magnitude of the torque, the result value is fed back as a lagging measure, so that a sudden change in the engine speed (rpm) There is a difficulty. In addition, the final torque of the finally outputted hydraulic pump may be unstable, which may result in deterioration of the controllability of the working machine.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power control apparatus for a construction machine capable of improving fuel economy by controlling engine speed and pump torque according to an engine load ratio.

According to an embodiment of the present invention, a power control apparatus for a construction machine according to the present invention includes an engine connected to a hydraulic pump to drive the hydraulic pump; In the case of the heavy load state, the engine speed command is increased or decreased in the hysteresis type in accordance with the engine load rate after the engine speed command is increased by the predetermined engine speed, and in the case of the light load condition, An engine control device for controlling the engine such that the engine speed is raised or lowered in a hysteresis form in accordance with the engine load ratio after descending by the engine speed; And a pump control device for controlling the hydraulic pump using a torque slope map reflecting the engine dynamic characteristics.

Preferably, the engine load factor is calculated by the engine load factor (%) = actual engine torque / engine maximum torque * 100.

Preferably, the engine control device limits the operation of raising or lowering the engine speed in the hysteresis mode in accordance with the engine load ratio in the command region where the engine speed command is lower than the maximum rating.

Preferably, the heavy load state is a digging or a boom up + swing state, and the light load state is a dumping or a turn + return state.

Preferably, the pump control device divides the engine load factor into a plurality of sections and generates the torque slope map by obtaining each of the torque slopes at the time when the engine load drop phenomenon is stabilized when the engine load is generated for each section .

As described above, according to the present invention, by providing the power control device for a construction machine that controls the engine speed in the hysteresis type in accordance with the engine load ratio and controls the pump torque using the torque slope map reflecting the engine dynamic characteristics, The work efficiency can be improved while minimizing the work performance limit of the machine.

1 is a view for explaining a conventional hydraulic pump control method,
Fig. 2 is a time-dependent graph of the engine speed and the pump torque. 3 shows a pump torque graph for the engine speed,
3 shows a pump torque graph for the engine speed,
4 is a graph showing the engine load ratio according to the engine speed,
5 is a diagram illustrating a configuration of a power control apparatus for a construction machine according to an embodiment of the present invention,
6 is a view for explaining control of a hydraulic pump in a hydraulic system of a construction machine,
7 is a view for explaining an engine speed control region of a power control apparatus for a construction machine according to an embodiment of the present invention,
8 is a view for explaining a change in the engine speed when the engine load is increased step by step in the power control apparatus of the construction machine according to the embodiment of the present invention,
9 is a view for explaining an example of setting a torque slope for each load range in a power control apparatus for a construction machine according to an embodiment of the present invention;
10 is a view of a dashboard of a construction machine according to an embodiment of the present invention,
11 is a graph showing the number of revolutions of the engine in each working section of the construction machine.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. Further, when a technical term used herein is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art are replaced. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In the present application, the term "comprising" or "comprising" or the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

Further, the suffix "module" and "part" for components used in the present specification are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

Furthermore, terms including ordinals such as first, second, etc. used in this specification can be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the purpose of facilitating understanding of the present invention, and should not be construed as limiting the scope of the present invention with reference to the accompanying drawings.

The power control apparatus of a construction machine according to an embodiment of the present invention controls engine speed and pump torque in accordance with the engine load ratio. The engine load factor can be calculated by the following equation (1).

[Equation 1]

Engine load factor (%) = actual engine torque / engine maximum torque * 100

4 is a graph showing the engine load ratio according to the engine speed.

Referring to FIG. 4, it is a heavy load area when the engine load ratio is 80 to 100%, and a light load area when the engine load ratio is less than 50%.

The power control apparatus for a construction machine according to an embodiment of the present invention changes the heavy load mode to the light load mode when the engine load ratio is located in the heavy load region to adjust the hydraulic power to the operation maximum performance, , It maintains the heavy load mode.

Also, the power control device of the construction machine maximizes the fuel efficiency by entering the light load mode when the engine load rate is reduced to less than 50%, and maintains the light load mode when the engine load rate is maintained at 80% or less.

5 is a diagram illustrating a configuration of a power control apparatus for a construction machine according to an embodiment of the present invention.

Referring to FIG. 5, the hydraulic pump 10 has a swash plate r, and increases or decreases the discharge flow rate according to the inclination angle of the swash plate. Here, the inclination angle of the swash plate is regulated by the pump regulator 40.

The hydraulic fluid discharged from the hydraulic pump 10 is supplied to the main control valve 20 and the actuator 30 connected to the spool is supplied with the hydraulic fluid / RTI > Accordingly, the actuator 30 operates according to the operating oil to perform a desired work.

On the other hand, the operator can operate the joystick, the pedal and the like to generate the flow rate control signal. The flow control signal moves the specific spool of the main control valve 20 along the flow control signal line pi.

That is, when the operator operates the joystick, the flow control signal opens and closes the spool of the main control valve 20. When the spool is opened, the hydraulic fluid is supplied to the actuator 30 to perform a desired operation.

On the other hand, the hydraulic pump 10 receives power from the engine 100. The engine 100 is controlled by the control of the engine control device 104. [

The engine speed (rpm) may be preset by the engine speed control unit 102 and may be varied by the command of the pump control unit 50. [

When the engine speed command is input to the engine control device 104, the engine control device 104 operates the engine governor 106 to supply the engine 100 with fuel. For example, when a command for raising the engine speed is issued, the fuel injection amount is increased. When a command for lowering the engine speed is issued, the fuel injection amount is decreased. When the specific engine speed is to be maintained, .

When the engine load factor exceeds 80%, the engine control device 104 raises the engine speed command by a predetermined engine speed (for example, 100 rpm) and sets the engine speed to a hysteresis type Up or down to a low load mode. If the engine load factor is less than 50%, the engine control device 104 decreases the engine speed command by a predetermined engine speed (for example, 100 rpm) and increases or decreases the engine speed in a hysteretic manner Down operation mode. 7, the engine control unit 104 sets the variable width of the engine speed to 100 rpm without any problem in the continuous operation, and in the command region where the engine speed command is lower than the maximum rated speed by 300 rpm, The engine speed control described above is limited in consideration of the speed.

The pump control device 50 controls the horsepower of the pump regulator 40 according to the load state of the engine. Here, the pump controller 50 generates a torque slope map reflecting the engine dynamic characteristics, and controls the horsepower of the pump regulator 40 using the generated torque slope map. A method of generating the torque slope map by the pump control apparatus 50 according to the present invention will be described in detail with reference to FIGS. 8 and 9. FIG.

The hydraulic pump 10 is further provided with a gear pump 70, which is an auxiliary pump. The gear pump 70 provides a pilot hydraulic fluid to a joystick / pedal, and generates a flow control signal when operating the joystick / pedal to transmit the pressure of the flow control signal.

On the other hand, the pilot hydraulic fluid discharged from the gear pump 70 is supplied to the shuttle valve 80 through the first hydraulic line L1 via the electron proportional pressure reducing valve 60. [ The other end of the shuttle valve 80 receives the flow control signal pi. The shuttle valve 80 selects a large pressure in the pressure of the first hydraulic line L1 and the pressure of the flow control signal line and the selected pressure is provided to the pump regulator 40 via the second hydraulic line L2 .

The electronic proportional pressure reducing valve 60 receives the control signal from the pump control device 50 through the first signal line s1. In detail, when an optional operation (eg Breaker / Shear) is performed in the construction machine, the pilot pressure of the flow control signal line pi and the flow rate set for the optional operation using the electron proportional pressure reducing valve 60 After comparing the pressures, the flow rate is controlled by using the high pressure.

Hereinafter, a pump regulator 40 for controlling the hydraulic pump 10 will be described with reference to Figs. 5 and 6. Fig.

6 is a view for explaining the control of the hydraulic pump in the hydraulic system of the construction machine.

The control of the hydraulic pump 10 includes a flow rate control, an equi-horsepower control, and a horsepower control, and each control will be described in detail below.

[Flow Control]

The flow control generates the required flow rate by operating the joystick, and the flow control signal pi is generated by the displacement obtained by operating the joystick. For example, when the flow control signal pi increases from p1 to p2 as shown in Fig. 6 (a), the pump regulator 40 increases the flow rate Qp from q1 to q2, . As a result, the discharge flow rate of the hydraulic pump 10 is increased.

[Constant Horse Power Control]

The back horsepower control is controlled so as to maintain the constant pump horsepower set by the load pressure (Pd).

In the back horsepower control, the correlation between the pressure and the flow rate is set in the PQ map, and the load pressure Pd applied to the hydraulic line between the hydraulic pump 10 and the main control valve 20 is received, So that the discharge flow rate can be varied.

6 (b), when the load pressure Pd increases from p1 to p2, for example, the pump regulator 40 changes the swash plate r so that the flow rate Qp is reduced from q1 to q2 . Thereby, although the discharge flow rate of the hydraulic pump 10 is controlled to be reduced, the pump horsepower is kept constant.

[Power Shift Control]

The horsepower control is a control to adjust the pump horsepower according to the load condition of the engine. That is, the horsepower control is performed by setting a plurality of P-Q maps and controlling the hydraulic pump by selecting one of a plurality of P-Q maps according to the load. The plurality of P-Q maps can be selected by a command of the pump control device 50 through the second signal line s2.

For example, as shown in FIG. 6C, the PQ map can be provided as a heavy load map, a standard load map, a light load map, and a specific PQ map is selected in accordance with the workload to control the hydraulic pump can do.

Thus, even when the same load pressure Pd is applied, a large amount of flow corresponding to q1 is discharged when the heavy load map is selected. On the other hand, when the standard load map is selected, the flow rate corresponding to q2 smaller than q1 is discharged. Also, when the light load map is selected, the flow amount corresponding to q3 smaller than q2 is discharged.

That is, in the case where it is determined that the load of the work subject is large, the PQ map near the heavy load is selected, and when the work load is determined to be general, the standard load map is selected, When it is judged, the PQ map near the light load is selected and the hydraulic pump 10 is controlled.

FIG. 8 is a view for explaining a change in the engine speed when the engine load of the construction machine is increased according to an embodiment of the present invention. FIG. Fig. 5 is a view for explaining an example of setting a torque slope for each load range in a power control device of a machine. Fig.

First, the pump control device 50 according to the present invention calculates the pump torque by the following equation (2).

&Quot; (2) "

T: The size of the pump torque realized by the hydraulic pump.

P: Pressure of the hydraulic fluid discharged from the hydraulic pump.

Q: The flow rate of the hydraulic fluid discharged per unit of rotation from the hydraulic pump.

A: It is a constant for converting power unit into power unit.

The torque slope map is a torque slope generated by checking the engine dynamic characteristics according to the engine load. Hereinafter, a method of generating the torque slope map will be described with reference to FIGS. 8 and 9. FIG.

As shown in FIG. 8, when the maximum engine load factor that can be implemented is assumed to be 100%, the engine load factor is set step by step, and the change in the engine speed is confirmed while providing the set engine load ratio to the construction machine (equipment).

When the set engine load ratio suddenly acts, the engine speed (rpm) is temporarily restored and then restored. At this time, it is confirmed whether or not the engine speed is restored.

For example, when the drop amount of the engine speed (rpm) is higher than the rated engine speed when the engine load ratio of 50% is applied, the process proceeds to the next step.

If the drop amount D1 of the engine speed (rpm) is lower than the rated engine speed when the engine load ratio of 75% is applied in the next step, the drop point of the engine speed (rpm) Find the point higher than the number of revolutions.

In the next step, the drop amount D2 of the engine speed (rpm) may remarkably drop when the 100% engine load ratio operates. At this time, a point where the drop point of the engine speed (rpm) is stabilized higher than the rated engine speed is found while changing the torque slope.

As described above, when the drop point is higher than or equal to the rated engine speed, the dynamic characteristics of the engine load ratio and the engine speed are matched with each other while observing the change in the engine speed (rpm) while gradually increasing the engine load factor I think.

In the embodiment of the present invention, the engine load ratios are 50%, 70%, and 100%. However, as shown in FIG. 9, the engine load ratios are 20%, 40%, 60% The torque slope map can also be generated by dividing by five segments including%.

Referring to FIG. 9, as shown in FIG. 9A, a time point at which the engine speed is stabilized by initially applying a low engine load factor is found, and the slope at this time is defined as a first torque slope R1 do.

Thereafter, as shown in FIG. 9B, a time point at which the engine speed is stabilized by applying an engine load ratio of 20% is found, and the slope at this time is defined as a second torque slope R2.

Likewise, as shown in Figs. 9C, 9D and 9E, the third to fifth torque gradients R3 to R5 are detected stepwise.

The first to fifth torque tilts R1 to R5 defined as described above constitute a contrast torque slope map for each load section as shown in FIG. 9 (f).

The pump control device 50 controls the horsepower of the pump regulator 40 using the above-described torque gradient map. That is, the pump control device 50 controls the hydraulic pump 10 by reflecting the torque gradient to the previously calculated torque value.

Since the torque slope map is a value reflecting the engine dynamic characteristics, the pump controller 50 controls the hydraulic pump 10 in accordance with the engine dynamic characteristics.

On the other hand, although the engine dynamics can be more accurately found by dividing the engine load factor into sub-segments, it takes 3 to 5 sub-segments because it takes much time to find the dynamics of the engine.

The intervals of the above-described load ratio of the engine load ratio can be set at equal intervals. For example, in the case of setting to five intervals, the load interval can be set to an equal range by 20%.

On the other hand, as described above, the intervals of the load of the engine load can be set at equal intervals, but may be set at unequal intervals. For example, the engine load can be set to be wide, while the engine load can be set to be relatively narrow and subdivided. More specifically, when the engine load is set to five intervals, the first load section is 0 to 30%, the second load section is 30% to 55%, the third load section is 55% to 75% 4, the load section may be set to 75% to 90%, and the fifth load section may be set to 90 to 100%.

In addition, when the engine load is low, the drop of the engine speed may not be conspicuous, but when the engine load is large, the drop amount of the engine speed may be large. Therefore, it is possible to find the coincidence of the dynamic characteristics between the engine load and the engine speed by setting the engine load to be smaller in a larger section. This makes it possible to more accurately grasp the dynamics of the engine. That is, by setting the load range narrower for a larger load section and setting the load range wider for a relatively smaller load section, the weight can be set to a larger value in a section sensitive to the load reaction, .

10 is a view showing an instrument panel of a construction machine according to an embodiment of the present invention.

On the construction machine, the user can select the mode through the mode selection button, and the mode is turned on in the default state to save fuel economy.

Referring to FIG. 10, when a mode is selected, an S character is added to a power mode icon 1010 located at the lower left of the instrument panel to identify whether the function is selected. You can also add a memory function for the corresponding function in the menu of the instrument panel to set whether the always-on mode is remembered or the previous operation mode is memorized when restarting.

11 is a graph showing the number of revolutions of the engine in each working section of the construction machine.

Referring to FIG. 11, the digging or boom up + swing section during the 180-degree excavation or cargo operation is a heavy load section. In order to ensure the maximum power performance of the set power mode, And the damping or turning + return section is a section under light load, and it is understood that the fuel efficiency is maximized by reducing the engine speed. In order to prevent the pump torque from being limited due to the difference between the actual engine speed and the command when the engine speed rises, it is necessary to lower the control point 1110 to prevent excessive power shift control, It can be seen that the torque slope Ramp is given to the pump torque control 1120 with the profile taking into account the dynamic characteristics of the engine, thereby reducing the drop in the engine speed and preventing the fuel from being overpowered.

The embodiments disclosed herein have been described with reference to the accompanying drawings. Thus, the embodiments shown in the drawings are not to be construed as limiting, and those skilled in the art will understand that the present invention can be combined with each other, and when combined, some of the components may be omitted.

Here, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings, but should be construed as meaning and concept consistent with the technical idea disclosed in the present specification.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only examples described in the present specification, and not all of the technical ideas disclosed in the present specification are described. Therefore, various modifications It is to be understood that equivalents and modifications are possible.

10: Hydraulic pump 20: Main control valve
30: actuator 40: pump regulator
50: Pump control device 60: Electronic proportional pressure reducing valve
70: Gear pump 80: Shuttle valve
100: engine 102: engine speed control unit
104: engine control device 106: engine governor

Claims (5)

An engine connected to the hydraulic pump to drive the hydraulic pump;
In the case of the heavy load state, the engine speed command is increased or decreased in the hysteresis type in accordance with the engine load rate after the engine speed command is increased by the predetermined engine speed, and in the case of the light load condition, An engine control device for controlling the engine such that the engine speed is raised or lowered in a hysteresis form in accordance with the engine load ratio after descending by the engine speed; And
A pump controller for controlling the hydraulic pump using a torque slope map reflecting the engine dynamic characteristics;
The power control device of the construction machine. The method according to claim 1,
Wherein the engine load factor is calculated by the following equation (1).
[Equation 1]
Engine load factor (%) = actual engine torque / engine maximum torque * 100 The method according to claim 1,
Wherein the engine control unit limits the operation of raising or lowering the engine speed in the hysteresis mode in accordance with the engine load ratio in the command region where the engine speed command is lower than the maximum rating. The method according to claim 1,
Wherein the heavy load state is a digging or a boom up + swing state, and the light load state is a dumping or a turn + return state. The method according to claim 1,
Wherein the pump control device divides the engine load factor into a plurality of sections and generates the torque slope map by obtaining the respective torque slopes at the time when the engine speed drop phenomenon is stabilized when the engine load is generated for each section Power control device for construction machinery.

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