KR101625683B1

KR101625683B1 - Hydraulic circuit for construction machinery

Info

Publication number: KR101625683B1
Application number: KR1020090130687A
Authority: KR
Inventors: 장윤석
Original assignee: 두산인프라코어 주식회사
Priority date: 2009-12-24
Filing date: 2009-12-24
Publication date: 2016-05-31
Also published as: KR20110073887A

Abstract

The hydraulic circuit of the construction machine according to the present invention includes a hydraulic pump 20 driven by an engine 10, a swing motor 30 driven by hydraulic oil discharged from the hydraulic pump 20, The swing control valve 40 controls the flow direction of the hydraulic fluid discharged from the swing motor 20 and the swing motor 30. The swing motor 30 and the swing control valve 40 And when the pressure of the hydraulic line 92 exceeds the swing control reference pressure, the operating fluid of the hydraulic line 92 is discharged to change the pressure of the hydraulic line 92 to the hydraulic pressure A pressure reducing valve (50) for maintaining the pressure below the circulation control reference pressure; And an accumulator 70 connected to the pressure reducing valve 50 through an accumulator line 72 to pressurize the hydraulic fluid discharged from the pressure reducing valve 50.

Swing motor, swing inertia, accumulator, regeneration, starting torque, reduction

Description

HYDRAULIC CIRCUIT FOR CONSTRUCTION MACHINERY

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a construction machine such as an excavator, and more particularly to a hydraulic circuit of a construction machine capable of minimizing operating oil discharged through a swing relief valve by swing inertia.

BACKGROUND ART Generally, a construction machine such as an excavator uses a hydraulic oil discharged from a hydraulic pump to drive a working device. Work machines for construction machines include booms, arms, buckets and upper revolving bodies. Among these working devices, the upper revolving structure has a very high rotational inertia, so that the pressure of the operating oil supplied to the revolving-starting revolving motor of the upper revolving structure abruptly rises.

For this reason, a revolving relief valve is provided in the revolving motor. When the pressure of the hydraulic oil supplied to the swing motor is greater than the swing relief pressure, the swing relief valve drains the hydraulic oil to the tank. Accordingly, at the beginning of the swing drive, the flow rate of the fluid drained through the swing relief valve increases, and an example thereof is shown in Fig.

Referring to FIG. 1, the swing motor supply pressure for driving the swing motor at the swing speed input from the swing operating portion exceeds the swing drive initial swing relief pressure. As described above, in the excess area A, the hydraulic oil is drained through the swing relief valve. At this time, since the pressure of the hydraulic oil drained through the swing relief valve is very high, which is equal to the swing relief pressure, a very large power is lost, which causes the fuel economy of the construction machine to deteriorate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic circuit of a construction machine capable of minimizing a flow rate of hydraulic fluid drained through a swing relief valve and improving fuel economy.

Another object of the present invention is to minimize the starting torque of the engine by compressing the hydraulic oil drained by the swing drive initial swing inertia and by using the pressurized hydraulic oil for controlling the work actuator and the hydraulic pump, And to provide a hydraulic circuit of the construction machine.

In order to achieve the above object, a hydraulic circuit of a construction machine according to the present invention includes a hydraulic pump (20) driven by an engine (10), a swing motor driven by hydraulic oil discharged from the hydraulic pump And a swing control valve (40) for controlling the flow direction of the hydraulic fluid discharged from the hydraulic pump (20) and supplying the hydraulic fluid to the swing motor (30). The swing motor 30 and the swing control valve 40. When the pressure of the hydraulic line 92 exceeds the swing control reference pressure, the operating fluid of the hydraulic line 92 is discharged, A pressure reducing valve (50) for maintaining the pressure of the hydraulic line (92) below the swing control reference pressure; And an accumulator 70 connected to the pressure reducing valve 50 through an accumulator line 72 to pressurize the hydraulic fluid discharged from the pressure reducing valve 50.

According to an embodiment of the present invention, the hydraulic circuit includes a regeneration line 73 connecting the accumulator line 72 to a work actuator 74; A pump control line (75) connecting the accumulator line (72) to the regulator (21) of the hydraulic pump (20); A control valve (80) provided on the pump control line (75) for selectively opening and closing the pump control line (75); And a control unit (100) for controlling the starting torque reduction control valve (80) so that the pump control line (75) is opened when the start signal of the engine (10) is inputted.

The oil pressure circuit is provided on the accumulator line 72 and is connected to an accumulator pressure selecting valve 60 for supplying hydraulic oil discharged from the pressure reducing valve 50 to the accumulator 70 or for draining the oil to the drain tank T ); And a pressure sensor 71 for sensing the pressure of the hydraulic oil accumulated in the accumulator 70. The control unit 100 controls the accumulator pressure selection valve 60 so that the pressure sensor 71 The pressure sensor 71 supplies the hydraulic fluid discharged from the pressure reducing valve 50 to the accumulator 70. When the pressure sensed by the pressure sensor 71 is higher than the accumulation control reference pressure And discharges the operating fluid discharged from the pressure reducing valve (50) to the drain tank (T).

The hydraulic circuit may further include a swing pressure varying unit 90 for varying the magnitude of the swing control reference pressure. The swing pressure varying unit 90 may be configured to vary the swing control reference pressure A pilot pump 91 for applying a pilot pressure to the pressure receiving portion 51 of the pressure reducing valve 50; And a pilot control valve 92 provided on a line connecting the pilot pump 91 and the pressure receiving portion 51 of the pressure reducing valve 50 to adjust a pilot pressure applied to the pressure receiving portion 51 do.

According to the above-mentioned problem solving means, by compressing the operating oil discharged from the pressure reducing valve to the accumulator, it becomes possible to reuse the waste energy by the existing swing inertia, thereby improving the fuel consumption of the construction machine.

In this case, by supplying the working oil, which is pressurized by the accumulator, to the working actuator, the fuel consumption of the construction machine can be further improved.

In addition, by using the hydraulic oil accumulated in the accumulator to reduce the discharge flow rate of the hydraulic pump when starting the engine, it is possible to minimize the engine starting torque, thereby improving the startability of the engine and reducing the capacity of the starting motor It can reduce the cost.

Further, when the pressure accumulated in the accumulator through the accumulator pressure selecting valve is increased, the hydraulic fluid discharged from the pressure reducing valve is recovered to the tank, so that the pressure of the hydraulic fluid supplied to the swing motor can be kept constant below the swing control reference pressure.

On the other hand, the swing control reference pressure of the pressure reducing valve can be varied through the swing pressure varying unit, and the swing drive can be efficiently performed in accordance with the swing drive environment.

Hereinafter, a hydraulic circuit of a construction machine according to an embodiment of the present invention will be described in detail.

2, the hydraulic circuit of the construction machine according to the embodiment of the present invention includes a hydraulic pump 20, a swing motor 30, and a control unit 30 for controlling the flow direction of the hydraulic fluid discharged from the hydraulic pump 20 And a swing control valve 40 for supplying the hydraulic pressure to the swing motor 30. The pressure reducing valve 50, the accumulator 70, the axial pressure selecting valve 60, A reducing control valve 80, a turning pressure varying unit 90, a pressure sensor 71 and a control unit 100. [

The pressure reducing valve 50 is provided to maintain the pressure of the hydraulic fluid supplied to the swing motor 30 below the swing control reference pressure and is connected to a hydraulic line for connecting the swing motor 30 and the swing control valve 40 (31). The pressure reducing valve 50 includes first and second pressure reducing valves 50a and 50b installed in the respective hydraulic lines 31a and 31b on both sides of the swing motor 30. [ Here, since the first and second pressure reducing valves 50a and 50b have the same structure and the same operation, only the first pressure reducing valve 50a will be described. Hereinafter, the first pressure reducing valve 50a is referred to as a pressure reducing valve 50. [

The pressure reducing valve 50 determines the turning control reference pressure set in accordance with the signal pressure applied to the spring 52 and the pressure receiving portion 51. When the pressure at the outlet end, If the pressure at the outlet end passing through the pressure reducing valve 50 is higher than the swing control reference pressure, the introduced operating fluid is discharged. With this operation, the pressure reducing valve 50 can maintain the pressure of the operating oil supplied to the swing motor 30 at or below the swing control reference pressure.

The swing control reference pressure of the pressure reducing valve 50 is adjusted according to a signal pressure applied to the pressure receiving portion 51 and the swing control reference pressure is adjusted through the swing pressure varying unit 90. The swing pressure varying unit 90 will be described later in detail.

The accumulator 70 is for accumulating hydraulic oil discharged from the pressure reducing valve 50 and is connected to the pressure reducing valve 50 through an accumulating pressure line 72. As described above, the pressure of the hydraulic fluid discharged through the pressure reducing valve 50 is accumulated through the accumulator 70, and the hydraulic pressure accumulated in the accumulator 70 is reused to utilize the hydraulic oil that has been abandoned through the revolving relief valve . Therefore, the fuel efficiency of the construction machine is improved compared to the conventional hydraulic circuit.

The accumulator 70 is connected to the working actuator 74 through the regeneration line 73 so as to utilize the hydraulic oil that has been pressurized and connected to the regulator 21 of the hydraulic pump 20 through the pump control line 75 do. Accordingly, the hydraulic oil that is pressurized by the accumulator 70 can be used not only to drive the working actuator 74 but also to control the flow rate of the hydraulic pump 20. [

However, if the pressure accumulated in the accumulator 70 is higher than the swing control reference pressure, the pressure of the hydraulic fluid supplied to the swing motor 30 may be higher than the swing control reference pressure. For this reason, when pressure accumulated in the accumulator (70) rises, the hydraulic fluid discharged from the pressure reducing valve (50) must be drained to the drain tank (T). For this function, the axial pressure-selecting valve 60 is installed on the axial-pressure line 72.

The accumulator pressure selection valve 60 is for accumulating hydraulic fluid discharged from the pressure reducing valve 50 to the accumulator 70 or draining the hydraulic fluid to the drain tank T. In response to a signal output from the controller 100, . The axial pressure selecting valve 60 is constituted by the first and second axial pressure selecting valves 60a and 60b but since both the axial pressure selecting valves 60a and 60b have the same structure and operation, (60) will be described.

More specifically, when the pressure of the accumulator 70 sensed by the pressure sensor 71 is smaller than the accumulator pressure control reference pressure, the accumulator pressure selecting valve 60 is operated such that the hydraulic fluid discharged from the pressure reducing valve 50 is supplied to the accumulator 70, When the pressure of the accumulator 70 sensed by the pressure sensor 71 is equal to or greater than the accumulator pressure control reference pressure, the accumulator pressure selector valve 60 is switched to the pressure reducing valve 50, Is drained to the drain tank (T).

The control valve 80 for reducing the starting torque is used to use hydraulic oil that is pressurized by the accumulator 70 as a pump control signal input to the regulator 21. The control valve 80 is provided in the pump control line 75, And selectively opens and closes the control line 75. More specifically, the startup torque reduction control valve 80 receives a signal from the control unit 100 at engine startup, converts the pump control line 75 to open, and supplies the hydraulic oil from the accumulator 70 to the regulator 21). Then, the swash plate is driven in a direction in which the flow rate of the hydraulic pump 20 is minimized, thereby minimizing the torque applied to the engine 10 at the start. That is, the starting torque of the engine 10 can be minimized. By minimizing the starting torque of the engine 10, it is possible to smoothly start the engine 10, reduce the capacity of the starting motor of the engine 10, and reduce the cost. Particularly, in the harsh region, the viscosity of oil or the like in the engine 10 is increased, so that the starting torque of the engine 10 is increased, which makes it difficult to start the engine 10. Therefore, by reducing the swash plate angle of the hydraulic pump 20 to reduce the starting torque, the starting performance of the engine 10 can be improved.

On the other hand, the regeneration line 73 is provided with a selection valve 76 for selectively opening and closing the regeneration line 73. The selection valve 76 determines whether or not to supply the working oil, which is pressurized by the accumulator 70, to the working actuator 74.

The turning pressure varying unit 90 is for varying the magnitude of the turning control reference pressure. In a situation where a large swing drive force is required by the swing pressure varying unit 90, the drive torque of the swing motor 30 can be increased to improve workability. In a situation where a large swing drive force is not required, The driving torque can be reduced and unnecessary energy consumption can be minimized. The orbiting pressure variable unit 90 includes a pilot pump 91 for applying a pilot pressure to the pressure receiving portion 51 of the pressure reducing valve 50 and a hydraulic pump 91 for applying a hydraulic pressure of the pilot pump 91 and the pressure reducing valve 50 And a pilot control valve (92) provided on a line connecting the pilot valve (51) to adjust the pilot pressure. The pilot control valve 92 is composed of the first and second pilot control valves 92a and 92b, but the structure and operation of the pilot control valve 92 are the same. Therefore, only one pilot control valve 92 will be described below.

The pilot control valve 92 is converted according to a signal output from the control unit 100. That is, when the opening amount of the pilot control valve 92 is increased and the signal pressure applied to the pressure receiving portion 51 is increased, the swing control reference pressure is increased. On the contrary, the opening amount of the pilot control valve 92 is decreased When the signal pressure applied to the pressure receiving portion 51 becomes small, the swing control reference pressure becomes small.

The pressure sensor 71 is for detecting the pressure of the hydraulic oil that is accumulated in the accumulator 70 and the pressure detected by the pressure sensor 71 is output to the controller 100.

The control unit 100 is for controlling the axial pressure selection valve 60, the startup torque reduction control valve 80, and the pilot control valve 92. The control unit 100 will be described in detail in the description of the hydraulic circuit operation process of the present embodiment.

Hereinafter, the operation of the hydraulic circuit having the above-described configuration will be described in detail.

2, when the swing operation signal is inputted from the swing operation portion, the swing control valve 40 is changed as shown in Fig. The hydraulic fluid discharged from the hydraulic pump 20 is supplied to the swing motor 30 through the swing control valve 40 and the first pressure reducing valve 50a to drive the swing motor 30, 50b and the swing control valve 40 to the tank T. In this state, the inertia of the swing motor 30 is large, so that the pressure at the outlet end of the first pressure reducing valve 50a gradually rises and exceeds the swing control reference pressure. Then, as shown in Fig. 4, the first pressure reducing valve 50a discharges the working oil through the pressure accumulating line 72. As shown in Fig. At this time, the axial pressure-selecting valve 60 is in the converted state as shown in FIG. 4, so that the hydraulic fluid discharged through the axial pressure line 72 is accumulated in the accumulator 70. However, when the pressure accumulated in the accumulator 70 sensed by the pressure sensor 71 exceeds the axial pressure control reference pressure, the control unit 100 converts the first axial pressure selection valve 60a to the first pressure reducing valve 50a to the tank (T).

Meanwhile, the control unit 100 outputs a control signal to the first pilot control valve 92a according to a signal input by the rotation speed increasing button or the like. In this case, the signal pressure input to the pressure receiving portion 51 of the first pressure reducing valve 50a is varied to vary the swing control reference pressure.

When the starter key 11 is turned ON to start the engine 10, the controller 100 converts the starter torque reduction control valve 80 to open the pump control line 75 . Then, the pressure of the operating oil, which is pressurized by the accumulator 70, is input to the regulator 21 of the hydraulic pump 20 to reduce the discharge flow rate of the hydraulic pump 20. [ As a result, the starting torque of the engine 10 can be minimized and the starting performance can be maximized.

On the other hand, the working oil that is pressurized by the accumulator (70) can be supplied to the working actuator (74). A selection valve for opening and closing the regeneration line 73 may be provided on the regeneration line 73. The regeneration line 73 is controlled by the selector valve so as to be synchronized with the operation of the corresponding actuator 74, 70) can be used for work.

The operation of the oil pressure circuit is limited to the case where the swing control valve 40 is changed to one side. However, even when the swing control valve 40 is changed to the other side, the operation of the pressure reducing valve 50, And the pilot regulating valve 92 and the hydraulic fluid flow in the same direction as described above.

5 is a graph schematically showing the swing motor supply pressure by an operating hydraulic circuit as described above. Referring to FIG. 5, it can be seen that the supply pressure of the swing motor can be kept lower than the swing reel leaf pressure. Although not shown in FIG. 5, in this embodiment, since the revolving relief valve is eliminated and the pressure reducing valve is used, the supply pressure of the revolving motor can be maintained higher than the revolving relief pressure.

1 is a graph schematically showing a change amount of a conventional swing motor supply pressure,

2 is a hydraulic circuit diagram schematically showing a hydraulic circuit of a construction machine according to an embodiment of the present invention,

3 and 4 are hydraulic circuit diagrams for explaining the operation process of the hydraulic circuit shown in FIG. 2,

Fig. 5 is a graph schematically showing a supply pressure change amount of the swing motor operated by the hydraulic circuit shown in Fig. 2. Fig.

DESCRIPTION OF THE REFERENCE NUMERALS OF THE DRAWINGS

10; Engine 20; Hydraulic pump

21; A regulator 30; Swing motor

40; A swing control valve 50; Pressure reducing valve

60; An axial pressure selection valve 70; Accumulator

71; Pressure sensor 80; Control valve for starting motor reduction

90; A turning pressure varying unit 91; Pilot pump

92; Pilot regulating valve 100; The control unit

Claims

A hydraulic pump 20 driven by the engine 10, a swing motor 30 driven by hydraulic oil discharged from the hydraulic pump 20, And a swing control valve (40) for controlling the swing motor (30) to supply the hydraulic pressure to the swing motor (30)

Is provided on a hydraulic line (92) connecting the swing motor (30) and the swing control valve (40). When the pressure of the hydraulic line (92) exceeds the swing control reference pressure, A pressure reducing valve (50) for discharging the hydraulic line (92) to maintain the pressure of the hydraulic line (92) below the swing control reference pressure;

An accumulator (70) connected to the pressure reducing valve (50) through an accumulating pressure line (72) to accumulate hydraulic fluid discharged from the pressure reducing valve (50);

A pump control line (75) connecting the accumulator line (72) to the regulator (21) of the hydraulic pump (20);

A control valve (80) provided on the pump control line (75) for selectively opening and closing the pump control line (75); And

And a control unit (100) for controlling the starting torque reduction control valve (80) so that the pump control line (75) is opened when the engine start signal is input. .

delete

The method according to claim 1,

An axial pressure selection valve 60 provided on the axial line 72 to supply hydraulic fluid discharged from the pressure reducing valve 50 to the accumulator 70 or to drain the hydraulic fluid discharged from the pressure reducing valve 50 to the drain tank T;

A pressure sensor (71) for sensing the pressure of the hydraulic oil accumulated in the accumulator (70); And

When the pressure sensed by the pressure sensor 71 is smaller than the accumulation control reference pressure, the hydraulic fluid discharged from the pressure reducing valve 50 is supplied to the accumulator 70, And a control unit (100) for controlling the axial pressure selection valve (60) to discharge the hydraulic fluid discharged from the pressure reducing valve (50) to the drain tank (T) when the pressure is higher than the axial pressure control reference pressure Hydraulic circuit of construction machinery.

The method according to claim 1,

Further comprising a turning pressure varying unit (90) for varying the magnitude of the turning control reference pressure.

5. The apparatus according to claim 4, wherein the orbiting-pressure varying unit (90)

A pilot pump 91 for applying a pilot pressure to the pressure receiving portion 51 of the pressure reducing valve 50 such that the swing control reference pressure can be varied; And

And a pilot control valve (92) provided on a line connecting the pilot pump (91) and the pressure receiving portion (51) of the pressure reducing valve (50) to adjust a pilot pressure applied to the pressure receiving portion And the hydraulic circuit of the construction machine.

The method according to claim 1,

A regeneration line 73 connecting the accumulator line 72 to the working actuator 74; And

And a selector valve (76) for selectively opening and closing the regeneration line (73).