KR20080006667A - Control method of hydraulic pump - Google Patents

Abstract

A hydraulic pump control method is provided to operate an engine with rated rotational frequency by setting the target rotational frequency of an engine according to the pressure variation of fluids discharged from a hydraulic pump and controlling an electronic proportional pressure reducing value according to a difference between the target rotational frequency and the actual rotational frequency of an engine, and controlling the discharge quantity of a hydraulic pump, thereby controlling the output of a hydraulic pump operated with the load of an engine. A hydraulic pump control method comprises the steps of: operating an engine with rated rotational frequency under the order of an electronic control unit if a driver operates an operating unit to perform the appointed work such as excavation work or leveling work(S200); measuring the discharge pressure of a hydraulic pump in a pressure measurement unit, and transferring the measured pressure value to the electronic control unit(S204); calculating the pressure variation with the measured pressure value by the pressure measurement unit, and comparing the pressure variation with standard value in the electronic control unit(S206); in case of heavy load, outputting the varied rotational frequency of the engine according to a difference between the pressure variation of fluids and the standard value in the electronic control unit(S208), and setting the target rotational frequency of the engine by adding the varied rotational frequency to the rated rotational frequency of the engine in the electronic control unit(S210); in case of light load, outputting the varied rotational frequency of the engine according to a difference between the pressure variation of fluids and the standard value in the electronic control unit(S212), and setting the target rotational frequency of the engine by deducting the varied rotational frequency from the rated rotational frequency of the engine in the electronic control unit(S214); comparing the set target rotational frequency of the engine with the measured rotational frequency of the engine, and setting the electric current quantity to be provided to an electronic proportional pressure reducing valve by a proportion and differential calculation in the electronic control unit(S216); providing the calculated electric current value to the electronic proportional pressure reducing value in the electronic control unit(S218); controlling the swash plate swivel angle of the hydraulic pump according to the electric current value provided to the electronic proportional pressure reducing valve, and regulating the discharge quantity of the hydraulic pump with the regulated swivel angle in a pump regulator and rotating the engine in the rated rotational frequency(S220); and stopping the engine under the order of the electronic control unit(S222).

Description

Control method of hydraulic pump

1 is a block diagram showing the configuration of an excavator to which the present invention is applied.

Figure 2 is a flow chart showing a hydraulic pump control method of the present invention.

Figure 3 is a graph showing the setting of the target rotational speed of the engine in the hydraulic pump control method of the present invention.

Figure 4a is a graph showing the current control diagram of the electromagnetic pressure reduction proportional valve according to the target rotational speed of the engine in the case of heavy load in the excavator to which the present invention is applied.

Figure 4b is a graph showing the current control diagram of the electromagnetic pressure reduction proportional valve according to the target rotational speed of the engine at light load in the excavator to which the present invention is applied.

* Explanation of symbols for main parts of the drawings

100: engine 102: engine speed measuring unit

104: hydraulic pump 106: pressure measuring unit

108: electronic pressure proportional valve 110: pump regulator

112: hydraulic actuator 114: electronic control unit

The present invention relates to a hydraulic pump control method in a construction machine.

Construction machinery such as excavators, loaders, dozers, or hydraulic cranes connect hydraulic pumps to the engine, and the hydraulic power output from the hydraulic pump as the engine rotates. By operating the hydraulic actuator (actruator) such as a hydraulic cylinder, a hydraulic motor and the like to perform a predetermined task.

Work performed by the construction machine may be classified into light load work and heavy load work. Taking an excavator as an example, selecting a flat surface or an inclined surface or the like is a light load operation, and a digging operation is a heavy load operation.

The basic requirement for construction machinery such as excavators is the position control technology to perform the work by finding the exact position, but as well as the technology to prevent unnecessary loss of flow is also important.

Accordingly, there is a need for a technology for controlling the current value applied to the electromagnetic pressure reducing valve according to the work performed by the construction machine so that the flow rate can be effectively discharged from the hydraulic pump without overwhelming the engine.

An object of the present invention is to set the target rotational speed of the engine according to the pressure change amount of the fluid discharged from the hydraulic pump, and to control the hydraulic pressure proportional valve in accordance with the difference between the set target rotational speed and the actual rotational speed of the engine hydraulic pump It is to provide a control method of the hydraulic pump to control the output of the hydraulic pump that ultimately acts as the load of the engine by adjusting the discharge flow rate of the engine to drive the engine at the rated speed.

Hydraulic pump control method of the present invention for achieving this object is, by controlling the discharge flow rate of the hydraulic pump by the electromagnetic pressure reduction proportional valve, the rotation speed of the engine for driving the hydraulic pump by the adjusted discharge flow rate is controlled A hydraulic pump control method, comprising: an engine speed measuring unit measuring an actual rotational speed of an engine, a pressure measuring unit measuring a pressure of a fluid discharged from a hydraulic pump, and calculating a pressure change amount using the measured pressure of the fluid; Setting a target rotational speed of the engine according to the calculated pressure change amount of the fluid; And adjusting the discharge flow rate of the hydraulic pump by controlling the electromagnetic pressure reduction proportional valve according to the difference value between the set target rotational speed of the engine and the measured actual rotational speed of the engine.

Hereinafter, the present invention will be described in detail with an example of an excavator in construction machinery in order to make the present invention easier to understand.

However, in describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

1 is a block diagram showing the configuration of an excavator to which the present invention is applied.

As shown in FIG. 1, the configuration of an excavator is an engine corresponding to a power source.

Reference numeral 102 denotes an engine rotation speed measurement unit that measures an actual rotation speed of the engine 100 using a speed sensor.

Reference numeral 104 denotes a hydraulic pump driven by the rotational force of the engine 100. The hydraulic pump 104 is a variable displacement hydraulic pump having a variable discharge flow rate.

Reference numeral 106 is a pressure measuring unit that measures the pressure of the fluid discharged from the hydraulic pump 104 using a pressure sensor.

Reference numeral 108 is an electromagnetic pressure reduction proportional valve for driving a pump regulator 110 by applying a current value corresponding to a difference between a target rotational speed and an actual rotational speed of the engine 100.

Reference numeral 110 is a pump regulator for adjusting the discharge flow rate by adjusting the swash plate oblique angle of the hydraulic pump 104 according to the current value applied to the electromagnetic pressure proportional valve 108.

Reference numeral 112 is a hydraulic actuator driven by the fluid discharged from the hydraulic pump 104. The hydraulic actuator 112 includes a hydraulic cylinder or a hydraulic motor.

Reference numeral 114 denotes an electronic control unit that manages the entire system of the excavator and controls each unit.

2 is a flowchart illustrating a method for controlling the electromagnetic depressurization proportional valve of the present invention, and FIG. 3 is a graph showing a target rotational speed of the engine in the method for controlling the electromagnetic depressurization proportional valve of the present invention.

Figure 4a is a graph showing the current control diagram of the electromagnetic pressure reduction proportional valve according to the target rotational speed of the engine in the case of heavy load in the excavator according to the present invention, Figure 4b is a view of the engine at light load in the excavator to which the present invention is applied This is a graph showing the current control diagram of the proportional solenoid valve according to the target speed.

When the solenoid pressure reduction valve 108 increases the discharge flow rate of the hydraulic pump 104, the engine 100 receives a lot of load, and when the solenoid pressure reduction valve 108 reduces the discharge flow rate of the hydraulic pump 104, the engine ( 100) is less loaded. Therefore, it is possible to control the number of revolutions of the engine through the control of the electromagnetic pressure reduction proportional valve (108).

As illustrated in FIG. 2, the operation of the excavator to which the present invention is applied will be described in detail by way of example. When the driver manipulates the operation unit to perform a predetermined operation such as an excavation operation or a stop operation, the engine 100 It is operated at the rated speed by the command of the electronic control unit 114. (S200)

When the engine 100 operates as described above, the hydraulic pump 104 is driven by the rotational force of the engine 100. The hydraulic pump 104 is a variable displacement pump in which the discharge flow rate is controlled by the electromagnetic pressure reduction proportional valve 108.

When the hydraulic pump 104 is driven, the pressure measuring unit 106 measures the discharge pressure of the hydraulic pump 104 and transmits the measured pressure value to the electronic control unit 114 (S204).

In addition, the engine speed measuring unit 102 measures the actual rotation speed of the engine 100, and transmits the measured actual rotation speed to the electronic controller 114.

The electronic control unit 114 calculates the pressure change amount using the pressure value measured by the pressure measuring unit 106, compares the pressure change amount with a reference value (S206), and when the pressure change amount shows a sharp change beyond the reference value, Judging by

The electronic controller 114 calculates the change rotation speed X of the engine 100 according to the difference between the pressure change amount of the fluid and the reference value.

The electronic controller 114 sets the target rotational speed of the engine 100 by adding the change rotational speed to the rated rotational speed of the engine 100. (S210)

On the other hand, the electronic control unit 114 compares the pressure change amount with the reference value (S206), and determines the light load when the pressure change amount shows a change less than the reference value.

The electronic controller 114 calculates the change rotation speed X of the engine 100 according to the difference between the pressure change amount of the fluid and the reference value.

The electronic control unit 114 sets the target rotational speed of the engine 100 by subtracting the change rotational speed to the rated rotational speed of the engine 100. (S214)

 For example, as shown in FIG. 3, when the pressure change amount of the fluid discharged from the hydraulic pump 104 is a heavy load larger than a reference value, the rated rotation of the engine 100 is added to the rated rotation speed of the engine 100 by adding the change rotation speed. The target rotation speed of the engine 100 is set higher than the number. In addition, in the case of a light load in which the pressure change amount of the fluid discharged from the hydraulic pump 104 is smaller than the reference value, the change in rotation speed is subtracted from the rated rotation speed of the engine 100 so as to be lower than the rated rotation speed of the engine 100. Set the target speed.

The electronic control unit 114 compares the target rotational speed of the engine 100 set above with the measured rotational speed of the engine, and calculates an amount of current to be applied to the electromagnetic pressure reduction proportional valve 108 through proportional differential calculation as the difference value. (S216) Proportional differential operation control is a method of agile control by increasing the amount of manipulation when the deviation from the sudden external change is large.

The proportional differential equation is the same as Equation 1.

[Equation 1]

u (t) = Kp * e (t) + Kd * (de (t) / dt)

Here, "Kp" is Proportional Gain, "Kd" is Derivative Gain, "e (t)" is the difference between the target rotational speed and the actual rotational speed of the engine 100, u (t) is an operation value for adjusting the difference between the target rotational speed and the actual rotational speed of the engine 100 and is an amount of current applied to the electromagnetic pressure reduction proportional valve 108. The manipulated value "u (t)" is multiplied by the proportional gain "Kp" multiplied by the difference "e (t)" between the target rotational speed and the actual rotational speed of the engine 100 and the target of the engine 100 by the derivative gain "Kd". It is calculated as the sum of the product of the time derivative "(de (t) / dt)" for the difference between the revolutions and the actual revolutions.

The electronic controller 114 applies the current value calculated above to the electromagnetic pressure reduction proportional valve 108 (S218), and the electronic pressure reduction proportional valve 108 is the pump regulator 110 with the current value calculated by the electronic control portion 114. ).

The pump regulator 110 adjusts the swash plate tilt angle of the hydraulic pump 104 according to the current value applied to the electromagnetic pressure reduction valve 108, and adjusts the discharge flow rate of the hydraulic pump 104 by the adjusted tilt angle. (S220).

For example, when the pressure change amount of the hydraulic pump 104 is a heavy load larger than the reference value, the actual rotation speed of the engine 100 is dropped by the pressure of the load. As illustrated in FIG. 4, the electronic control unit 114 sets the target rotation speed Nr + X of the engine by adding the change rotation speed X to the rated rotation speed Nr of the engine 100. In addition, as described above, the target rotational speed of the engine 100 is set high, and as shown in FIG. 4, the discharge pressure is controlled by controlling the electromagnetic pressure reduction proportional valve 108 along the corresponding current control diagram.

On the other hand, when the amount of pressure change of the hydraulic pump 104 is a light load smaller than the reference value, the actual rotation speed of the engine 100 increases. As shown in FIG. 5, the electronic control unit 114 sets the target rotation speed Nr-X of the engine 100 by subtracting the change rotation speed X from the rated rotation speed Nr of the engine 100. In addition, as described above, the target rotational speed of the engine 100 is set low, and as shown in FIG. 5, the discharge pressure is controlled by controlling the electromagnetic pressure reduction proportional valve 108 along the corresponding current control diagram.

As described above, the discharge flow rate of the hydraulic pump 104 is adjusted, and the engine 100 rotates at the rated rotation speed.

As described above, when the driver manipulates the operation unit to perform a predetermined task and terminate the task, the engine 100 is stopped by the command of the electronic controller 114 (S222).

On the other hand, while the invention has been shown and described with respect to specific preferred embodiments, those skilled in the art to which the present invention pertains without departing from the scope of the present invention with respect to the above-described embodiment It will be readily appreciated that various modifications and variations can be made. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

When the pressure change amount of the fluid discharged from the hydraulic pump is larger than the reference value, the target rotational speed of the engine is set high to increase the amount of current applied to the electromagnetic pressure reducing valve to quickly reduce the discharge flow rate. This has the effect of reducing the width of the engine speed falls below the rated speed.

If the pressure change of the fluid discharged from the hydraulic pump is less than the reference value, set the target rotational speed of the engine lower and control the amount of current applied to the solenoid pressure reducing valve to increase the discharge flow rate, so that the operation can be performed under the optimum conditions. It has the effect of being performed.

By controlling as described above, there is no effect on the engine and unnecessary loss of flow rate is eliminated.

Claims (4)

In the hydraulic pump control method of controlling the discharge flow rate of the hydraulic pump by the electromagnetic pressure reduction proportional valve, the rotation speed of the engine for driving the hydraulic pump by the controlled discharge flow rate, An engine rotation speed measurement unit measuring an actual rotation speed of the engine, a pressure measurement unit measuring a pressure of the fluid discharged from the hydraulic pump, and calculating a pressure change amount by the measured pressure of the fluid; Setting a target rotational speed of the engine according to the calculated pressure change amount of the fluid; And And adjusting the discharge flow rate of the hydraulic pump by controlling the electromagnetic pressure reduction proportional valve according to the difference value between the set target rotational speed of the engine and the measured actual rotational speed of the engine. . According to claim 1, Setting a target rotational speed of the engine; Calculate a change rotation speed of the engine according to the pressure change amount of the fluid, and set a target rotation speed by adding the change rotation speed of the engine to the rated rotation speed of the engine when the pressure change amount of the fluid is larger than a reference value, And setting a target rotation speed by subtracting the change rotation speed of the engine from the rated rotation speed of the engine when the pressure change amount of the fluid is smaller than the reference value. According to claim 1, wherein the control of the electromagnetic pressure reduction proportional valve; And a proportional differential calculation of the difference between the target rotational speed of the engine and the actual rotational speed of the engine to calculate the amount of current, and supply the calculated amount of current to the electromagnetic pressure reduction proportional valve. The method of claim 3, wherein the proportional differential operation is; Hydraulic pump control method characterized in that calculated by the formula (1). Equation  One u (t) = Kp * e (t) + Kd * (de (t) / dt) Here, "Kp" is Proportional Gain, "Kd" is Derivative Gain, "e (t)" is the difference between the target rotational speed and the actual rotational speed of the engine 100, u (t) is an operation value for adjusting the difference between the target rotational speed and the actual rotational speed of the engine 100 and is an amount of current applied to the electromagnetic pressure reduction proportional valve 108.

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