JPH0452329A - Hydraulic control circuit for hydraulic excavator - Google Patents

Abstract

PURPOSE:To improve the working efficiency by providing a hydraulic control circuit which can change and control a combined and split flow change valve and a swinging load sensing pressure change valve depending on each mode. CONSTITUTION:A change valve 40 for turning on and off swinging load sensing pressure is provided in a load sensing circuit, so that it may be changed and controlled by an electromagnetic pilot valve 52 controlled by a signal circuit 51 in a controller 23. Respective discharge pipe passages 11, 14 for two variable- capacity hydraulic pumps 10, 13 are connected together via a communication pipe passage 46 which is provided with a combined and split flow change valve 47 for pressure oil discharged from both hydraulic pumps 10, 13. For the hydraulic control of a hydraulic excavator with a load sensing system formed in this way, priority modes are preset so as to change the matching of flow distribution work in concurrent swivel operation of a boom and an arm such as in excavating sediment and loading to a dump car through lifting and swinging. The selection of these modes is made by ON and OFF operation of the combined and split flow change valve 47 and the swinging load sensing pressure change valve 40 via a mode change-over switch 54.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a load sensing hydraulic w4r for a hydraulic excavator.
ij when simultaneously operating multiple hydraulic actuators in circuit B! E! In terms of distribution, in detail, when a boom and a swing are used for simultaneous mulberry production, such as when loading excavated earth into a dump truck by lifting and turning, each hydraulic actuator is controlled by changing the control pattern without being affected by the load pressure of the other. This invention relates to a hydraulic $ control circuit for a hydraulic excavator that compensates for the pressure of the supplied flow rate to enable accurate and easy AM to improve workability and save energy.

[Conventional technology]

As shown in FIG. 2, a hydraulic excavator for excavating and loading earth and sand has a hydraulic motor 1 for driving a lower traveling body a. A hydraulic motor 2 for turning the upper revolving body, and a boom 3 as a working machine C mounted on the front part of the upper revolving body. Arm 4. A packet 5 and hydraulic cylinders 6, 7, 8 for operating these working machines C are provided. The hydraulic excavator performs a series of continuous operations such as excavation, lifting rotation, earth removal, lifting rotation, etc. as part of excavation work.
), with worm 3 raised and arm 4 dumped, from the excavation position to 45° and 90° as shown in the same figure (B).
Alternatively, it is a swinging motion onto a loading platform with a dumping force d that is stopped at a position near 180°, but when such simultaneous operations of swing and boom, swing and arm, etc., the pressure of the swing circuit is affected by the arm circuit and boom circuit. Therefore, when the pressure in the boom and arm circuits is low, the turning pressure may also be low and the turning may not be performed smoothly.Since the turning angle differs depending on the stopping position of the dump truck d, the relationship between the turning angle and the boom angle is Conventionally, the operator controls the flow rate supplied to each circuit by adjusting the spool opening of the flow control valve of these hydraulic actuators each time to match the movements of both. The plowing operation was extremely difficult and tiring.

[Problem to be solved by the invention]

In view of the above points, the present invention provides a priority mode according to the work content, in order to ensure the required flow rate without mutual influence of the circuit pressure of each hydraulic actuator when swinging and simultaneously operating the boom, arm, etc. is set in advance to change the flow rate distribution, and the pressure compensation a is controlled by the load sensing pressure 11.
It is an object of the present invention to provide a hydraulic control circuit for a hydraulic excavator, which improves work efficiency by ensuring simultaneous operation by ensuring that m.

[Means to solve the problem]

In order to achieve the above object, the present invention includes two variable displacement hydraulic pumps, a plurality of hydraulic actuators driven by pressure oil discharged from these hydraulic pumps, and a pressure-compensated flow rate for controlling each hydraulic actuator. In the hydraulic 11rB circuit equipped with a control valve and a load sensing system that controls the pump discharge flow rate so as to keep the differential pressure between the pump discharge pressure and the maximum load pressure of the plurality of hydraulic actuators constant, , a switching valve for merging and dividing the discharge pressure oil of both pumps and a switching valve for turning on and off the swing load sensing pressure is provided, and the standard mode, swing priority mode, The above-mentioned purpose is achieved by setting three modes in advance, ie, boom priority and boom priority, and by providing a control hydraulic circuit that switches and controls the merging 9 branch flow switching valve and the swing load sensing pressure switching valve according to each of these modes. achieve.

[For production]

Therefore, when lifting the boom to load earth and sand into a dump truck by lifting and turning, or turning 180 degrees by arm dumping, by switching to the turning priority mode, the two hydraulic pump circuits are turned off so that the convergence and branch flow switching valves are turned off. The circuits are now independent of each other, and one hydraulic pump is used exclusively for the boom. Load sensing and a pressure-compensated flow rate 11m valve ensure the necessary discharge flow rate for the boom without being affected by the circuit pressure of the swing circuit. The large flow rate required for the rotation is ensured by increasing the discharge volume by the rotation load sensing of the other hydraulic pump circuit and the flow rate control valve with pressure compensation.

In addition, during the slight 45° turn in the above-mentioned lifting turn, the boom supply flow rate is prioritized by switching to boom priority mode, and the two hydraulic pump circuits are also switched to branch flow, each becoming an independent circuit. The swing load sensing is also turned off, and the necessary discharge amount is ensured by the load sensing and pressure-compensated flow control valve of one hydraulic pump circuit of the boom, and the swing and arm are controlled by pressure compensation by the other hydraulic pump circuit. The required flow rate is ensured.

For work that includes 90° turning 9 and 1M of normal excavation, the switch can be switched to standard mode to create a merging circuit, and depending on the work, it can be switched to boom priority mode to adjust the boom movement during simultaneous operations. It is possible to match and simultaneously operate smoothly without performing matching operations.

〔Example〕

An embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a hydraulic V4 control circuit of a hydraulic excavator, particularly a boom operating hydraulic cylinder 6 (hereinafter simply referred to as a boom cylinder) and an arm operating hydraulic cylinder 7 according to the present invention.
This figure shows a preferred embodiment of a hydraulic control circuit for three hydraulic actuators: a hydraulic actuator (hereinafter simply referred to as an arm cylinder) and a swing drive hydraulic motor 1 (hereinafter simply referred to as a swing motor). A boom cylinder 6 is connected to the discharge circuit 11 of one variable displacement hydraulic pump 1O, and the boom cylinder 6 is connected to this discharge circuit 11. A pressure compensated flow control valve 12 with a length of 11 m is installed, and the arm cylinder 7 is connected to the discharge circuit 14 of the other variable displacement hydraulic pump 13 via a branch circuit 14a, and to the other branch circuit 14b. The swing motor 1 is connected, and each of these branch circuits 14a, 14b is provided with a pressure-compensated flow rate viirm valve 15, 16. In this way, boom cylinder 6, arm cylinder 7
The swing motor 1 is connected in parallel to two hydraulic pumps l0113, and is connected to the tank 1 via a return circuit 17.
8 is connected. Each flow Il control valve 12, 15.
Reference numeral 16 is a pilot operation type, and the main pipe 20 of the pilot pump ■9 is connected to the pilot pipes 21a to 21a, respectively.
It is connected to both ends of the answer via 21r. and,
Boom, arm, and rotation operating levers 22a, 22b
, 22c are controlled by pilot valves 25a to 25f, which are electromagnetic proportional control valves that are opened and closed by signal lines 24a to 24f from the controller 23. Note that 26 is a return pipe for pilot hydraulic pressure.

Each of the pressure compensation control valves 12.15.16 also includes pressure compensation valves 27a, 27b, 27c that detect and compensate the discharge pressure of the hydraulic pump 10.13 for the required flow rate of the respective hydraulic actuator 6.7.1. A load sensing regulator 28a2 of each hydraulic pump 1013 is provided.
8b and pyro 7) A pilot pipe 111 that detects the maximum load pressure of the swirling motor 1 from the outlet boat 30 of the control valve 16 for controlling the swirling flow as a zero-order load sensing circuit connected via pipes 27a and 27b. ! +31 and the biloft conduit 33 that detects the maximum load pressure of the arm cylinder 7 from the outlet boat 32 of the arm river flow 1tt4 control valve 15, and the biloft conduit 35 whose maximum load pressure side pressure is detected by the shuttle valve 34, and the biloft conduit 35 for the boom. The shuttle valve 38 detects the pressure on the maximum load pressure side between the outlet port 36 of the flow rate l11m valve 12 and the viroft pipe 37 that detects the maximum load pressure of the boom cylinder 6. Hydraulic pump l is connected by pilot line 29a.
The hydraulic pump 13 is connected to the load sensing regulator 28a of the other hydraulic pump 13 via a pilot line 29b.

A switching valve 40 for swing load sensing pressure is interposed in the load sensing circuit. The switching valve 40 is an electromagnetic pyro controlled by a signal circuit 51 of the controller 23 via a pyroft pipe 41.

It is designed to be switched to AM by a gate valve 52.

The load sensor regulators 28a and 28b are connected to the pump discharge line 11.14 and the hydraulic pump 10.13, respectively.
The pilot t! is connected by pilot pipes glI29a, 29b between the hydraulic cylinders 42a, 42b that control the amount of tilting of the swash plate. 6-type load sensing valve 44a
, 44b, and the pilot pipes 29a, 43a are connected to both ends of one load sensing valve 44a, and the viroft pipes 29b, 43b are connected to both ends of the other load sensing valve 44b, respectively.

When the maximum load pressure guided by the pilot pipes 29a, 29b becomes larger than the sum of the discharge pressure of the hydraulic pump 10.13 guided by the pilot pipes 43a, 43b and the spring 45, the load sensing valve 44a,
When 44b switches from the (A) position to the (B) position, the pyro.

Pressure oil flows from the top pipes 43a and 43b to the hydraulic cylinders 42a and 4.
2b, increase the tilting amount of the hydraulic pump 10.13 (
to increase the discharge flow rate, and conversely, the maximum load pressure is smaller than the pump discharge pressure (when the load sensor song valve 4
4a 44b switches from (B) position to (A) position,
The pressure oil in the hydraulic nolinders 42a and 42b is returned to the tank 18, and the hydraulic pump 10.132m rotation amount is reduced to discharge fL.
i1 will be decreased. In this way, hydraulic pump 1
The differential pressure between the delivery pressure of 0.13 and the maximum load pressure of the hydraulic actuator 6.7.1 is maintained at a constant value set by the spring 45.

By using the pressure-compensated flow IAM valves 12, 15, and 16 together with the load sensing system described above, the pressure oil discharged from the hydraulic pump 10, 13 can be suppressed to the required flow rate to save energy and achieve pressure compensation control. Ensure the required minimum differential pressure and supply it to the hydraulic actuator 6.7.1 $1
01. The two variable displacement hydraulic pumps 10.13 are connected to their respective discharge pipes 11.14 by a communication pipe 11346, and the communication pipe 4
6 is provided with a merging and branching switch 47 for the pressure oil discharged from both hydraulic pumps 10 and 13. And this switching valve 47
The pyro 7)
IF! The switching is controlled by the pilot oil pressure of 2148. In addition, the confluence.

The load sensing press-fitting switching valve 53 is interposed in the load sensing circuit.

The hydraulic AM of a hydraulic excavator with a load sensing system configured in this way is capable of matching work by distributing flow rate during simultaneous operation of the boom, arm, and swing, such as excavating earth and sand during lifting and turning, and loading into a dump truck. The priority modes shown in the table below are set in advance so that the mode can be changed, and these modes can be selected by switching the above-mentioned merge 9 branch flow switching valve 47 and swing load sensing pressure switching valve 40 to the mode switching valve 47.
The turning load sensing pressure switching valve 40 is turned on and off by turning the mode switching switch 54 on and off.

(1) Standard mode This mode is used to set the mode selector switch 54 to the standard mode when the work equipment and the swing are required to have approximately the same amount of flow rate, but not so much that one takes priority over the other, such as when raising a boom with an approximately 90° turn. When the switch is made, the merging 1 branching switching valve 47 is turned ON via the biloft valve 50 in response to a command from the controller, and the discharge pressure oils of both hydraulic pumps 10 and 13 are combined, and the swing load sensing switching valve 40 is also turned ON. It is turned off via the valve 52 to be in the "off" state.

As a result, each actuator 6.7.1 of the boom arm and swing is operated by the respective pressure compensating valve 12.15.16 to achieve the required Ij without prioritizing one over the other.
! The quantity is guaranteed.

(n) Swing priority mode In this mode, when the maximum load pressure of the swing motor 1 is large, such as when turning 180°, and a large amount of flow is required, switching to the swing priority mode allows the flow to merge into one branch via the biloft valve 50. The switching valve 47 turns OFF and becomes a shunt circuit,
The pressure pumps 10.13 on both sides become independent circuits, and the load sensing circuits that operate simultaneously on the switching valve 47 also become independent in both pumps 10.13.

As a result, both pumps TO and 13 circuits are divided into independent circuits, and one hydraulic pump lO secures the required flow rate for lifting the boom cylinder 6 while compensating the pressure, and the other hydraulic pump 13 secures the required flow rate for swinging. In order to secure a large weight, the swing load sensing valve 40 is turned ON via the biloft valve 52, and the maximum load pressure of the swing motor 1 and arm cylinder 6 is fed back to the load sensing cylinder regulator 28b of the hydraulic pump 13. The discharge flow rate increases to match the maximum load pressure.

(I[l) Boom Priority Mode This mode is used when the turning angle is relatively small, such as approximately 45° turning, and a large amount of flow is required for raising the boom and dumping the arm. When the mode selector switch 54 is switched to the boom priority mode, the merging 9 branch flow switching valve 47 is turned OFF and becomes "off" to form a branch flow circuit, and both pumps 10.13 The circuits are independent, and the pressure oil from one hydraulic pump 10 is exclusively supplied to the boom cylinder 6, and the pressure oil from the other pump 13 is supplied to the swing motor 1 and arm cylinder 7, as well as the swing load sensor song switching valve 40. When the load sensing circuit is turned off, the flow rate is prioritized to be supplied to the boom side while ensuring the necessary flow rate for the swing and arm. In this way, the priority mode is selected and switched according to the work content, and the boom lever 22al, the boom lever 22al, the boom lever 2Zb, and the swing lever 22, each consisting of an electric lever, are selected and switched according to the work content.
By operating a, each pressure-compensated flow rate is controlled from the controller 23 through each pilot valve 25a to 25f! 4
Operate control valves 12, 15, and 16 to open the boom, arm,
and each hydraulic actuator 67 of the swing. We will be manipulating l. Note that 55 is a monitor, and each priority mode setting is displayed on the monitor 55.

〔Effect of the invention〕

As described above, in each discharge circuit of the two hydraulic pumps connected to each hydraulic actuator for the boom, arm, and swing, the present invention provides an important connection between the confluence and branch flow switching valves and the swing load sensing pressure in each hydraulic pump circuit. By installing a switching valve, the required flow rate of each hydraulic actuator can be secured by selecting a priority mode consisting of boom priority, swing priority, and standard, which are preset according to the work content. Since the simultaneous operation of the arm rotation can be smoothly performed, the operator can avoid the trouble of controlling the flow rate supplied to each circuit by adjusting the spool opening of the flow rate l1yl valve to 1il111 each time the arm is rotated. This eliminates the need for tiring operations, further improving work efficiency. Moreover, since the load sensing pressure is controlled according to the work content, the energy saving effect is further improved.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic $1111 circuit diagram showing one embodiment of the present invention. FIG. 2(A) is an explanatory view showing the boom raising arm dumping state of the hydraulic excavator, and FIG. 2(B) is an explanatory view showing the rotating state for loading excavated earth and sand to the dump truck stop position. 1......Swivel motor 6...Boom cylinder 7...Arm cylinder 10.13...Variable displacement hydraulic pump 12 ,15
．． 16--Flow rate am valve with pressure compensation 19・・・・
・・Pilot pumps 22a, b, c...Operating lever 23...Controller 25a-f...Pilot valve 27 a+b+c...Pressure compensation valve 28a,
b...Load sensing cylinder regulator 40...Swivel load sensing pressure switching valve 44a, b...Load sensing valve 47...
... Merging 1 branch flow switching valve 50.52 ... Pilot valve

Claims (2)

[Claims] (1) Two variable displacement hydraulic pumps, a plurality of hydraulic actuators driven by the pressure oil discharged from each of these hydraulic pumps, a flow control valve with pressure compensation that controls each hydraulic actuator, and a pump discharge pressure and a load sensing system that controls the pump discharge flow rate so as to keep the differential pressure between the maximum load pressures of the plurality of hydraulic actuators constant; A switching valve is installed to switch on and off the load sensing pressure of the merging and dividing flow, as well as the swing load sensing pressure.In addition, the standard mode, swing priority mode, and boom priority mode can be set in advance according to the work content when simultaneously operating the boom, arm, and swing. A hydraulic control circuit for a hydraulic excavator, characterized in that the settings are made, each of these modes is selected according to the work content, and the merge/separate flow switching valve and the swing load sensing pressure switching valve are switched and controlled. . (2) In the above setting mode, raise the boom of the work equipment,
When the turning angle is approximately 180° during lift turning in the arm dump state, turn off the merging and dividing switching valves as turning priority mode.
F to set it as a shunt circuit, turn on the swing load sensing switching valve, input the load sensing pressure, merge as boom priority mode when the swing angle is about 45 degrees, turn off the split flow switching valve to set it as a shunt circuit, and turn on the swing load sensing switching valve to input the load sensing pressure. Turn off the sensing switching valve and turn off the load sensing pressure.
Further, when the swing angle is about 90 degrees, the standard mode is set, and the merging and branching switching valves are turned on to form a splitting circuit, and the swinging load sensing switching valve is turned off, and the load sensing pressure is turned off. (1) A hydraulic control circuit for the hydraulic excavator described in (1).