JPS61204427A - Hydraulic circuit for civil engineering and construction machine - Google Patents

Abstract

PURPOSE:To vary a flow rate, by a method wherein a switching valve is located on plural discharge amount control circuits for controlling the sweeping volume varying mechanism of a hydraulic pump, and the control circuits are energized and shut off according to a working condition. CONSTITUTION:When a normal excavating work is conducted, with switcheds 50 and 51 closed, electromagnetic valves 46 and 47 are switched to a position on the left side, and oblique plates 14a and 15a of hydraulic pumps 14 and 15 are brought to a minimum inclination. This causes a boom cylinder 9 and an arm cylinder 10 to be driven by hydraulic pumps 16 and 17, and running motors 6 and 7 to be respectively driven only by the single pump. Meanwhile, when an attachment having a low volume is driven by an empty switching valve 19, if only the switch 50 is closed and the switching valve 46 is shifted to a position on the right side, the attachment is driven only by the single hydraulic pump, and breakage due to an excessive flow rate is prevented from occurring. In this case, the cylinders 9 and 10 are driven at a high speed with the aid of the three pumps.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a hydraulic circuit for a civil engineering/construction machine such as a hydraulic excavator, which is used by attaching and detaching special attachments as necessary.

[Background of the invention]

In general, civil engineering and construction machines are equipped with a running body, a revolving body, and attachments specific to the civil engineering and construction machines, each of which is used for a specific purpose. This will be explained using a hydraulic excavator as an example.

2 and 3 are side views and plan views of the schematic structure of a hydraulic excavator, in which 1 is a running body; 2 is a running body 1;
A revolving body is rotatably installed on the revolving body, 3 is a boom rotatably attached to the revolving body 2, 4 is an arm rotatably attached to the boom 3, and 5 is rotatably attached to the arm 4. This is the packet that was sent.

These boom 3, arm 4. The packet 5 constitutes a front mechanism. 6 is a left travel motor, and 7 is a right travel motor, which causes the traveling body 1 to travel.

Reference numeral 8 designates a swing motor for rotating the revolving structure 2, 9 a boom cylinder, 1O an arm cylinder, and 11 a packet cylinder. A hydraulic excavator performs normal work such as excavation work by driving these actuators. These actuators are usually driven by a plurality of hydraulic pumps. Hereinafter, a hydraulic circuit for driving these actuators will be explained using diagrams.

FIG. 4 is a hydraulic circuit diagram of a conventional hydraulic excavator. In the figure, actuators that are the same as those shown in FIG. 2 are given the same reference numerals. 12 is the first engine mounted on the hydraulic excavator, and <13 is the second engine. 14 is a first hydraulic pump, and 15 is a second hydraulic pump, which are mechanically driven by the first engine 12. 16 is a third hydraulic pump, and 17 is a fourth hydraulic pump, which are driven by the second engine 13. Each of the hydraulic pumps 14 to 17VC has a variable displacement mechanism (hereinafter represented by a swash plate) 14a, '15
a, 16a.

17a is provided. Reference numeral 18 designates a first multiple valve, which includes a left travel directional control valve ρ, a first boom directional control valve 21. Directional switching valve for first arm, empty directional switching valve 1
9 are integrally connected, and the first hydraulic pump 14
and is interposed in the confluence and discharge circuit 23 of the third hydraulic pump 16. Sae is the second multiple valve, and the right travel direction switching valve 25 and the second boom direction switching valve are the second arm circumferential direction switching valve! , a packet directional switching valve section is integrally connected and interposed between the second hydraulic pump 15 and the fourth hydraulic pump 11 and the merging discharge circuit 29. The left travel motor 6 is connected to the output circuit 30 of the left travel direction switching valve 4.
connected to. The right travel motor 7 is connected to the output circuit 31 of the right travel direction switching valve. The boom cylinder 9 is connected to the output circuit 32 of the first boom directional control valve 21 and the second boom directional control valve. The arm cylinder cylinder O is connected to the output circuit blade of the first arm directional switching valve and the second arm directional switching valve.

The packet cylinder 11 is connected to the output circuit 34 of the packet directional control valve. In addition, empty directional control valve 1
Output circuit 9 is closed and no actuator is connected to it. Each direction switching valve '1, 21, 22 . included in the first multiple valve 18 and the second multiple valve 24.
25128.27.2!3 are operation signals A and B generated in pilot circuits, which will be described later.

Pilot pipes for sending C, D, and E are connected to the hydraulic pumps 14, 15, 16, and 17, and the swash plates 14a, 15a, 16a, 1
In order to control the tilting of the pump 7a, a pilot pipe 41 is connected to send a discharge amount control signal F generated in the pilot circuit.

Note that the work on the turning directional control valve is omitted because it is not necessary for explaining the present invention.

FIG. 4 shows a conventional pilot circuit for operating the hydraulic circuit of the civil engineering/construction machine shown in FIG.

In FIG. 4, 35s36s37 is a joystick lever type pilot valve, which is interposed in a parallel row in the discharge circuit 39 of the pilot hydraulic pump vane. By opening the pilot valve and operating the operating lever 35a,
An operation signal A for operating the first arm directional switching valve and the second arm directional switching valve 4; and an operation signal A for operating the first arm directional switching valve 21 and the second boom directional switching valve 4; At the same time, at least one of the operation signals B for operating the hydraulic pumps 14 and 15 is generated.
, 16.

A discharge amount control signal F for adjusting the discharge amount of 17 is generated.

By opening the pilot valve and manipulating the operating lever 36a, at least one of the operation signal C for operating the left-hand travel direction switching valve 4 and the operation signal C for operating the right-hand travel direction change-over valve 3 is generated. At the same time, each of the hydraulic pumps 14, 15.

A discharge amount control signal F that adjusts the discharge amount of 16 and 17 is generated. By operating the operating lever 37a, the pilot valve 37 generates an operating signal E for operating the packet directional valve blade, and at the same time adjusts the discharge amount of each of the hydraulic pumps 14, 15, 16, and 17. A discharge amount control signal F is generated. The tochi is a shuttle block, and each of the built-in shuttle blocks is connected to three pilot pipes in which a discharge amount control signal F is generated by each of the pilot valves 35#36#37&C, and from the outlet pipe. A combined discharge amount control signal F is supplied to each of the hydraulic pumps 14, 15, 16, and 17K.

Reference numerals 42, 43, 44, and 45 in FIG.
This is a pilot pipe leading to each swash plate 16 and 17.

By the way, when carrying out work with a hydraulic excavator, if the work is to be carried out in a confined space, or if the work is wall excavation, slope excavation, etc., it is easier to carry out the work by driving the actuator slowly at a slow speed. be. However, in the above-mentioned hydraulic circuit, the pressure oil of the hydraulic pumps for each actuator Km is combined and supplied via the directional control valve, so it is difficult to drive the actuators at the desired slow speed. . Also, with hydraulic excavators.

Special tasks may be performed using various attachments. For example, add or remove packet 5.

A breaker is attached as an attachment to the tip of the arm 4, and is used as a drive side via the empty direction switching valve 19 to perform work such as breaking the road surface. In this case, if the attached attachment operates with small miscarriage pressure oil, the flow rate of the pressure oil supplied to the attachment in the hydraulic circuit becomes excessive, and there is a risk that the attachment will be damaged.

Conventionally, in order to solve these problems, the engine 12,
However, measures have been taken to lower the rotational speed of the hydraulic pump 13 and reduce the overall discharge flow rate of each hydraulic pump.

With such a means, the operating speed of all the actuators is uniformly slowed down, so the operating speed in the case of compound operation is also slowed down, resulting in a drawback that the inherent working performance is degraded.

Furthermore, the above-mentioned hydraulic circuit is configured to supply pressure oil to the actuator using multiple hydraulic pumps, so if a hydraulic pump fails, it is difficult to determine which hydraulic pump has failed. It was difficult to determine. Conventionally, this determination has been made by measuring oil pressure or flow rate, but with these methods, it takes a considerable amount of time to determine which pump has failed, and cropping must be stopped during that time. However, there was a drawback that work efficiency was reduced.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to be able to supply pressure oil to an actuator at a flow rate depending on the work situation and attached attachments without reducing the drive speed of the hydraulic pump drive source. It is an object of the present invention to provide a hydraulic circuit for civil engineering and construction machinery that can easily identify a hydraulic pump that has failed.

[Summary of the invention]

In order to achieve the above object, the present invention operates a directional control valve using an operating section, drives a corresponding actuator,
At the same time, the hydraulic circuit with 5 VC controls the variable displacement mechanism of the corresponding hydraulic pump via the discharge amount control circuit.1. The present invention is characterized in that a switching valve is interposed in the discharge amount control circuit, and pressure is applied to conduct and cut off the discharge amount control circuit.

[Embodiments of the invention]

The present invention will be described below based on illustrated embodiments. FIG. 1 is a hydraulic circuit diagram of a hydraulic excavator according to an embodiment of the present invention. In the figure, the same parts as those shown in FIGS. 4 and 5 are designated by the same reference numerals, and the explanation thereof will be omitted. 46, 4
7, 48 and 49 are pilot pipes 42 and 49, respectively.
This is an electromagnetic switching valve equipped with 43, 44, and 45K. Also, 50, 51, 52, 53! Value switching valve 4
This is a switch connected to terminals 6, 47, 48, and 49 for switching between them.

Each of the switches 50 , 51 , 52 , and 53 is arranged in the operator's cab of the hydraulic excavator.

Now, when each switch 50, 51, 52, 53 is open, each electromagnetic switching valve 46, 47, 48,
49 is located on the left side of the figure, and each pilot pipe 42, 4
3, 44, and 45 become conductive. This state is the same as the state shown in FIG. 4, and normal work can be carried out without any trouble.

From this state, for example, if the switch force 51 is closed,
The solenoid valves 46 and 47 are respectively switched to the right position in the figure, the pilot lines 42 and 43 are shut off, and the hydraulic pump side line is connected to the tank. As a result, the swash plate 14 a of the hydraulic pump 14 and the swash plate 1 of the hydraulic pump 15
5a is the minimum tilting, and each of these hydraulic pumps 14,
The discharge flow rate of No. 15 is the minimum flow rate. This causes the boom cylinder 9. The arm cylinder 10 is 2 ho: / 7” (
The left traveling motor 6 is driven by only one hydraulic pump 16, the right traveling motor 7 is driven by only one hydraulic pump 17, and the packet cylinder 11 is driven by only one hydraulic pump. It is driven by only one pump, No. 17, and the driving speed of both is reduced by half.

On the other hand, when a small-capacity attachment is attached and the drive of this attachment is controlled by the idle direction switching valve 19, when the switch blade is closed and the electromagnetic switching valve 46 is switched to the right position, the small-capacity attachment is controlled by the hydraulic pump 1.
Only one pump of No. 6 is driven, and the flow rate of the pressure oil supplied to it is reduced, making it possible to prevent damage due to excessive flow rate. In this case, the boom cylinder 9 and arm cylinder 10 are equipped with three pumps (hydraulic pumps 15, 16, 17).
)K, so it can be driven at high speed.

The above-mentioned selection of hydraulic pumps can be made arbitrarily, and each actuator can be driven at various speeds between 4 pumps and 1 pump without reducing the rotational speed of the carrot.

Furthermore, in the normal state where each switch 50, 51, 52, 53 is open, if a failure occurs in any of the hydraulic pumps and the discharge flow rate of that hydraulic pump decreases, this will cause the 1 appears as the driving speed decreases. Therefore, in order to determine which hydraulic pump is malfunctioning, switch 50, 51, 52
, 53 in sequence and enter. In this case, the hydraulic pump corresponding to the switch whose drive speed of the actuator does not change is determined to be the hydraulic pump in which a failure has occurred.

As described above, in this embodiment, an electromagnetic switching valve is interposed in the pilot line that drives the swash plate of each hydraulic pump, and this is switched by a switch, so that the actuator can be driven by four pumps or one pump. This makes it possible to supply pressure oil to the actuator at a flow rate depending on the work situation and attachment without reducing the engine speed. Also, if a failure occurs in the hydraulic pump.

A malfunctioning hydraulic pump can be easily and quickly identified by simply opening and closing the switches in sequence.

Furthermore, since the above switch is located in the driver's cab,
Only a small amount of effort is required to control the flow rate of pressure oil supplied to the actuator and to determine a failure.

In addition, in the description of the above-mentioned embodiment, although the hydraulic excavator was illustrated and explained, it is not limited to a hydraulic excavator, and it is natural that it can be applied to other civil engineering and construction machines. or,
It is also possible to use a pilot type switching valve or a manual switching valve instead of the electromagnetic switching valve.

〔Effect of the invention〕

As described above, in the present invention, a switching valve is interposed in the discharge amount control circuit that controls the variable displacement mechanism of the hydraulic pump, and the discharge amount control circuit is made conductive or disconnected. The flow rate of pressure oil supplied to the actuator can be increased (changed) depending on the work situation and attachment without reducing the drive speed of the actuator.Also, when a failure occurs in the hydraulic pump, it is possible to identify the failed pump. It can be done easily.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram of a hydraulic excavator according to an embodiment of the present invention, Figs. 2 and 3 are a side view and a plan view of a schematic configuration of the hydraulic excavator, and Figs. 4 and 5 are a diagram of a conventional hydraulic excavator. FIG. 14, 15, 16, 17--Hydraulic pump, 14a, 15a. 16a, 17a... Swash plate' ” #36 *
37...Pilot valve, 35a, 36a
, 37a...Operating lever, A...Pilot hydraulic pump, 40...Shuttle block, 41, 42, 43, 44 #45...
...Pilot pipe, 46, 47°, 49...
...Solenoid switching valve, 50, 51, 52, 53.
...Switch Figure 1! 4 ρ 1
6 ITTE0 1O Figure 3 Figure 4 Figure 41! Figure 5

Claims (1)

[Claims] A plurality of hydraulic pumps having a variable displacement mechanism, a plurality of actuators driven by these hydraulic pumps, each directional switching valve that controls the drive of each of these actuators, and each operation unit that operates each of these directional switching valves. and,
In a hydraulic circuit equipped with a discharge amount control circuit that controls a displacement variable mechanism of a corresponding hydraulic pump among the plurality of hydraulic pumps when each of these operating units is operated, each of the discharge amount control circuits is turned on and off. A hydraulic circuit for civil engineering and construction machinery, characterized by being equipped with a switching valve that