KR20030058378A - Hydraulic pump control system for a small excavator - Google Patents

Abstract

PURPOSE: A hydraulic pump control system of a small excavator is provided to prevent the lowering of the speed on a front work by swivel and to prevent unnecessary output loss by outputting the appropriate flow for swivel. CONSTITUTION: The hydraulic pump control system of a small excavator comprises a front working unit containing a boom cylinder(1), a bucket cylinder(2) and an arm cylinder(3), hydraulic pumps(P1,P2) for primary, secondary variable capacities supplying pressure oil to traveling motors(M1,M2), a pump regulator(4) controlling a swash angle of the hydraulic pumps(P1,P2), a swivel motor(M3), a third hydraulic pump(P3) supplying oil pressure to the swivel motor(M3) only, a swiveling direction control valve(7) installed on a discharge hydraulic line(5) of the third hydraulic pump(P3) to change the direction of oil pressure supplied to the swivel motor(M3), a pair of oil grooves(6a,6b) connected to the inlet/outlet of the swiveling direction control valve(7) and the swivel motor(M3), check valves(8a,8b) installed on the oil grooves(6a,6b) to restrain the supply of oil pressure and to allow the discharge of oil pressure, parallel oil grooves(9a,9b) detouring each check valve(8a,8b), swiveling input flow control valves(12a,12b) installed on each parallel oil groove(9a,9b) and communicated when the pressure of pressure oil supplied to the swivel motor(M3) goes over than the appointed pressure, an input flow sensor of a swivel motor connected to each oil groove(9a,9b) of the swiveling input flow control valves(12a,12b) to select the high pressure of the pressure oil on the passages(6a,6b), and an oil groove(10) connecting the detected oil pressure with the pump regulator(4).

Description

Hydraulic pump control system for a small excavator

The present invention relates to an apparatus for controlling a hydraulic pump in a compact excavator. In particular, the present invention includes two main hydraulic pumps for providing a hydraulic source of the front work device and one auxiliary pump for supplying a hydraulic source to the swing motor, and these hydraulic pumps are driven at the output of one engine, It relates to a hydraulic pump control device for controlling the output of the main hydraulic pump is variable according to the output change of the auxiliary pump required for the work.

As shown in the hydraulic circuit of FIG. 1, the small excavator has a flow control of the pressure oil of the first and second variable displacement hydraulic pumps P1 and P2 by each control valve so that the boom cylinder 1 and the bucket cylinder ( 2), the front working device such as the arm cylinder (3) and the driving motors (M1, M2) are supplied, the pressure oil of the third hydraulic pump (P3) is controlled by the turning direction control valve 27 on the hydraulic line (25) And supplied only to the turning motor M3 through the pair of flow paths 26a and 26b, and the three hydraulic pumps P1, P2 and P3 are driven by one engine E, and the first The discharge flow rates of the two variable displacement hydraulic pumps P1 and P2 flow into the hydraulic pressure units 24a, 24b and 24c of the pump regulator 24 through the control lines Pi1, Pi2 and Pi3. The discharge flow rate is controlled in accordance with the total flow rate discharged from the hydraulic pumps P1, P2, and P3.

As described above, the conventional pump control device has an advantage that the engine power can be efficiently used because the total horsepower of one engine is properly distributed and used according to the workload of the plurality of hydraulic pumps, but has the following disadvantages.

As described above, in the conventional hydraulic pump control device, the discharge pressure of the third hydraulic pump P3 which is the driving source of the swing motor M3 and the first hydraulic pump P1 and the second hydraulic pump P2 which are the driving source of the front work device are as follows. Discharge pressures of the first hydraulic pump P1 and the second hydraulic pump P2, which are variable displacement hydraulic pumps, are applied to the work load of the turning motor M3. In the small excavator which frequently turns during operation, the output used to drive the front work apparatus is reduced by the swing operation, so that the operation of the front work apparatus is not sufficient.

That is, in a small excavator, the swinging operation is frequently performed due to the characteristics of the work. The engine output is partially used to operate the swinging motor, and only the remaining output is required for the front work. There was a tendency for the back speed to decrease.

In addition, when the operation mainly in the swinging operation, a flow rate higher than the flow rate required for the swinging operation is supplied to the swinging motor, and the flow rate is used to relieve unnecessary flow loss.

Therefore, the present invention is designed to solve the disadvantages of the conventional hydraulic pump control device of the compact excavator, to prevent the phenomenon of lowering the speed of the front operation by the swinging operation frequently during the swing compounding operation, the swinging operation during the swinging operation It is an object of the present invention to provide a hydraulic pump control device capable of preventing unnecessary output loss by outputting only an appropriate flow rate required for the engine.

1 is a schematic hydraulic circuit diagram of a conventional hydraulic pump control apparatus for a compact excavator;

2 is a schematic hydraulic circuit diagram of a hydraulic pump control apparatus according to the present invention.

※ Explanation of code about main part of drawing ※

P1: variable displacement first hydraulic pump P2: variable displacement second hydraulic pump

P3: 3rd hydraulic pump M1: space motor

M2: left motor M3: turning motor

1: boom cylinder 2: bucket cylinder

3: dark cylinder 4: pump regulator

4a, 4b, 4c: Hydraulic chamber 5: Hydraulic line

L1, L2: Hydraulic line 6a, 6b: Euro

7: Slewing direction control valve 8a, 8b: check valve

9a, 9b: Parallel line 10: Euro

12a, 12b: Swivel input flow control valve

The present invention for achieving the above object is a compact having a variable displacement first and second hydraulic pump for supplying pressure oil to the front work device and the traveling motor, and a pump regulator for controlling the swash plate angle of the first and second hydraulic pump In the hydraulic control device of the excavator,

A turning motor, a third hydraulic pump for independently supplying hydraulic oil only to the turning motor, a turning direction control valve installed on the discharge hydraulic line of the third hydraulic pump to switch the direction of the hydraulic oil supplied to the turning motor; A pair of flow paths connecting the swing direction control valve and the inlet / outlet of the swing motor, check valves respectively provided on the flow paths to suppress the supply of pressurized oil and allow discharge, and each parallel to bypass the check valves. A swing input flow control valve installed on each of the parallel flow paths and connected only when the pressure of the hydraulic oil supplied to the swing motor is equal to or greater than a predetermined pressure, and connected to each inlet side flow path of the swing input flow control valve. The swing motor input flow rate detection means for selecting the pressure oil having the higher pressure in the oil pressure on the flow path, and the pressure oil detected from the swing motor input flow rate detection means A flow path is connected to the pump regulator.

The swing motor input flow rate detecting means is constituted by a shuttle valve that selects the pressure oil having the higher pressure among the inlet pressure oils of the swing input flow control valve. The flow path connecting the swing motor input flow rate sensing means and the pump regulator is connected to the pump regulator in a direction of reducing the swash plate angle of the first and second variable displacement hydraulic pumps.

Accordingly, the present invention drives the first hydraulic pump and the second hydraulic pump as the output of the engine except for the output of the third hydraulic pump driven to operate the swing motor, and the full output of the engine when the swing motor is not operated. Since it is used to drive the first hydraulic pump and the second hydraulic pump, it is possible to improve the front workability by supplying a sufficient flow rate to the front work device, and in the case of a complex work that simultaneously performs turning and front work, the first Since the output of the hydraulic pump and the second hydraulic pump is reduced to operate the third hydraulic pump for turning operation, the output of the engine can be efficiently utilized.

Hereinafter, an embodiment of a hydraulic pump control device of a small excavator according to the present invention will be described in detail according to the accompanying drawings.

2 is a hydraulic circuit diagram schematically showing an embodiment of a hydraulic pump control apparatus of a small excavator according to the present invention.

As shown in Figure 2, the hydraulic pump control apparatus of the present invention includes a variable displacement first hydraulic pump (P1) and the second hydraulic pump (P2), the first hydraulic pump (P1) and the second hydraulic pressure The oil pressure of the pump P2 is controlled by the control valve so that the flow direction is controlled, which is selective for the front and rear driving motors M1 and M2, the boom cylinder 1, the bucket cylinder 2, the arm cylinder 3, and the like. These front work equipment are operated by supplying

In addition, the compact excavator according to the present invention includes a third hydraulic pump (P3) for supplying the hydraulic oil to the doser cylinder or the swing motor (M3), the third hydraulic pump (P3) is the first hydraulic pump (P1) and The second hydraulic pump P2 is connected to be driven by one engine E. Thus the full power of the engine is distributed and used to drive the three hydraulic pumps.

Control lines Pi1 and Pi2 are branched into the outlet hydraulic lines L1 and L2 of the first hydraulic pump P1 and the second hydraulic pump P2, so that the first hydraulic pump P1 and the second hydraulic pump are branched. It is connected to each hydraulic chamber 4a, 4b of the pump regulator 4 which controls the swash plate angle of P2. When the discharge flow rate of the first hydraulic pump P1 or the second hydraulic pump P2 acts on the hydraulic chamber of the pump regulator 4 through the control lines Pi1 and Pi2, the pump regulator 4 is connected to the hydraulic pump. The swash plate angle of (P1, P2) is reduced.

The outlet hydraulic line 5 of the third hydraulic pump P3 is provided with a turning direction control valve 7 for switching the direction of the pressurized oil supplied to the turning motor M3 and the turning direction control valve 7. Is connected to the inlet and outlet of the swing motor M3 through a pair of flow paths 6a and 6b. On the pair of flow paths 6a and 6b for connecting the check valves 8a and 8b to suppress the supply of pressurized oil to the swing motor M3 and to allow discharge thereof, the check valves 8a and 8b bypass the check valves 8a and 8b. Parallel lines 9a and 9b are provided. Therefore, the hydraulic oil of the third hydraulic pump P3 is supplied to the swing motor M3 through one parallel line 9a and 9b to operate the swing motor, and then the flow paths 6a and 8 provided with the check valves 8a and 8b. Through 6b).

Swivel input flow control valves 12a and 12b are provided on the parallel lines 9a and 9b to communicate only when the pressure of the hydraulic oil supplied to the swing motor M3 is equal to or greater than a predetermined pressure. Swivel motor input flow rate sensing means is connected to each inlet side flow path 6a, 6b of 12b to select and detect the higher pressure oil in the pressure oil flowing into each swing input flow rate control valve 12a, 12b. have.

The swing motor input flow rate detection means is composed of a shuttle valve 13 connected to the flow path (6a, 6b). The outlet of the shuttle valve 13 is connected to the hydraulic part 4c of the pump regulator 4 for controlling the swash plate angle of the first hydraulic pump P1 and the second hydraulic pump P2 through the flow path 10. do.

Referring to the process of controlling the pump of the compact excavator according to the present invention configured as described above are as follows.

<Front work only without turning>

In this case, the turning direction control valve 7 is placed in a neutral position, and the discharge pressure oil of the third hydraulic pump P3 is drained into the tank via the turning direction control valve 7 to provide the turning motor input flow rate sensing means. Since there is no flow rate detected at, there is no signal pressure input to the pump regulator 4 of the first hydraulic pump P1 and the second hydraulic pump P2. Therefore, in this case, the horsepower of the engine driving the three hydraulic pumps (P1, P2, P3) is used only to operate the first hydraulic pump (P1) and the second hydraulic pump (P2) for driving the front work equipment. Therefore, even when the work load of the front work device is increased to increase the output of the first hydraulic pump P1 or the second hydraulic pump P2, the horsepower of the engine is equal to the first hydraulic pump P1. It can be used to drive the second hydraulic pump (P2), thereby supplying sufficient pressure oil to the front work device is able to smoothly perform the front work.

<In case of swing combined operation (when supplying hydraulic oil to swing motor and front work equipment at the same time)>

In this case, the first hydraulic pump P1 and the second hydraulic pump P2 supply the pressurized oil to the front work device, and the front work device and the third hydraulic pump P3 also supply the pressurized oil to the turning motor M3. .

In this case, the flow rate of the third hydraulic pump P3 supplied through the turning direction control valve 7 to the inlet side of the turning motor M3 is only higher than a predetermined pressure by the turning input flow control valves 12a and 12b. It is supplied to the swing motor (M3), the flow rate input to the swing motor is detected by the shuttle valve 13 and the pump regulator of the first hydraulic pump (P1) and the second hydraulic pump (P2) through the flow path (10) It acts on the pressure receiving part 4a of (4). Accordingly, the pump regulator 4 reduces the maximum warp angle of the first hydraulic pump P1 and the second hydraulic pump P2 so that the front work load increases, but the first hydraulic pump P1 and the second hydraulic pump P2 are increased. The maximum discharge flow rate is reduced, which reduces the load on the engine required for front work.

Therefore, even when the swing combined operation is performed, the horsepower of the engine can be efficiently used to drive three hydraulic pumps.

As described above, according to the hydraulic pump control apparatus of the present invention, since the output of the engine is distributed and used to drive the hydraulic pump for driving the front work device according to the load of the hydraulic pump for driving the swing motor, the front work and the swing operation. In the case of performing the turning composite operation at the same time smoothly and performing only the front work, the front work is smoothed because the full power of the engine is used to drive the corresponding hydraulic pump.

Claims (3)

Front work device including boom cylinder (1), bucket cylinder (2), arm cylinder (3), etc. and first and second variable displacement hydraulic pumps (P1, P2) for supplying pressure oil to the traveling motors (M1, M2). And a pump regulator (4) for controlling the swash plate angles of the first and second variable displacement hydraulic pumps (P1, P2), The swing motor M3, the third hydraulic pump P3 for supplying pressure oil only to the swing motor M3 independently, and the discharge hydraulic line 5 of the third hydraulic pump P3 are installed on the swing motor. A turning direction control valve 7 for switching the direction of the pressure oil supplied to the M3, a pair of flow paths 6a and 6b connecting the turning direction control valve 7 and the inlet and outlet of the turning motor M3, Check valves 8a and 8b respectively installed on the flow paths 6a and 6b to suppress the supply of pressurized oil and permit discharge, and each parallel flow path 9a bypassing the respective check valves 8a and 8b. And 9b), swing input flow control valves 12a and 12b installed on the respective parallel flow paths 9a and 9b and communicating only when the pressure of the hydraulic oil supplied to the swing motor M3 is equal to or higher than a predetermined pressure. Swivel cap connected to the inlet side flow paths 6a and 6b of the swing input flow control valves 12a and 12b to select the pressure oil having the higher pressure among the hydraulic oils on the flow paths 6a and 6b. Type flow rate detecting means, the turning a small hydraulic pump control system of the excavator, characterized in that with a flow passage 10 connecting the pump regulator (4), the pressure oil from the detected motor type flow rate detecting means. The small excavator according to claim 1, wherein the swing motor input flow rate detecting means is a shuttle valve (13) which selects the pressure oil having the higher pressure among the inlet pressure oils of the swing input flow control valves (12a, 12b). Hydraulic pump control system. The small-size device according to claim 1 or 2, wherein the flow path (10) is connected to the pump regulator (4) in a direction of reducing the swash plate angle of the first and second variable displacement hydraulic pumps (P1, P2). Hydraulic Pump Control System of Excavator.