JP3346211B2 - Hydraulic circuit of work machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a working machine for controlling the driving of a hydraulic actuator in a working machine such as a hydraulic shovel.

[0002]

2. Description of the Related Art An example of a working machine is a hydraulic excavator as shown in FIG. In the drawing, reference numeral 1 denotes a lower traveling body, and 2 denotes an upper revolving superstructure. A front working mechanism 3 including a boom 3a, an arm 3b, and a bucket 3c is mounted on the upper revolving superstructure 2, and an operator cab 4 in which an operator rides is provided. Further, a machine room 5 containing various devices such as an engine, a hydraulic pump, and a directional control valve unit is installed at a position behind the cab 4.

The traveling of the vehicle by the lower traveling body 1 and the turning of the upper rotating body 2 are driven by a hydraulic motor, and the boom 3a, the arm 3b and the bucket 3c are driven by a hydraulic cylinder. Operating means such as operating levers and operating pedals are provided in the cab 4. An operator in the cab 4 appropriately operates each of these operating means, so that the hydraulic motor and the hydraulic motor described above are operated. By driving a hydraulic actuator composed of a cylinder, a vehicle can be driven or required work can be performed.

When the bucket 3c is used as a front working mechanism, work such as excavation of earth and sand can be performed. Here, when performing work such as open pit mining in a mine, for example, a bucket having a loading capacity of 50 tons or the like is used to improve the efficiency of the work, and a hydraulic cylinder for the boom 3a for driving the bucket is used. A hydraulic cylinder for driving the bucket 3c requires an extremely large driving force. In order to obtain such a large driving force, a configuration is used in which a plurality of hydraulic cylinders are used or the cylinder diameter is increased. For this purpose, a large flow of pressure oil must be supplied to the hydraulic cylinder. In the case of such a super-large hydraulic excavator, a hydraulic circuit for driving a hydraulic actuator of the upper swing body includes:
Based on the conventional concept, for example, a configuration as shown in FIG. 7 can be considered. In FIG. 7, some hydraulic actuators, for example, driving circuit components such as a traveling hydraulic motor are omitted.

As is apparent from FIG. 7, two driving engines 6a and 6b are provided as driving sources (for example, an electric motor or the like can be used as a driving source other than the engines). Each of these engines 6a, 6b provides two hydraulic pumps 7a, 7b and 8a,
8b is driven. Hydraulic pumps 7a, 7b
Is supplied to predetermined hydraulic actuators via direction switching valve units 9a and 9b, and pressure oil supplied from hydraulic pumps 8a and 8b is supplied to predetermined hydraulic actuators via direction switching valve units 10a and 10b. Will be.
The direction switching valve units 9a, 9b, 10
Reference numerals a and 10b denote units of the required number of directional control valves in accordance with the number and type of hydraulic actuators, the applied load, and the like. In the hydraulic circuit shown in FIG. 7, the hydraulic actuators to be driven include boom cylinders 11a and 11b for driving a boom 3a, an arm cylinder 12 for driving an arm 3b, a bucket cylinder 13 for driving a bucket 3c, and a swing. The motor 14 is shown.
Therefore, although each unit is constituted by three directional control valves, in practice, the number of directional control valves constituting each directional control valve unit is further increased due to the provision of a traveling hydraulic motor and the like. .

[0006] Among the actuator described above, the arm cylinder 12, the direction and the pressure oil from the hydraulic pump 7a by the directional control valve 9a ₁ constituting the switching valve unit 9a, the direction switching valve 10a of the directional control valve units 10a ₁ Thus, the pressure oil from the hydraulic pump 8a is joined and supplied. Further, with respect to the turning motor 14, the hydraulic pump 7 by directional control valve 9b ₃ of the directional control valve unit 9b
and pressure oil from b, are supplied by merging the pressure oil from the hydraulic pump 8b by the directional control valve 10b ₃ of the directional control valve unit 10b. On the other hand, pressure oils from four hydraulic pumps 7a, 7b, 8a, 8b are joined to the boom cylinders 11a, 11b and the bucket cylinder 13. That is, the boom cylinders 11a, 11
To drive the b, direction switching valve unit 9a directional control valve 9a ₃ of the directional control valve 9b in the directional control valve unit 9b ₁
And the directional switching valve unit 10
a directional control valve 10a ₃ of a, on which are merged the pressure oil from the directional control valve 10b ₁ of the directional control valve units 10b, further by merging them, will be supplied boom cylinder 11a, and 11b . In order to drive the bucket cylinder 13 also includes a directional control valve 9a ₂ in the directional control valve units 9a, it causes joins the hydraulic fluid between the directional control valve 9b ₂ of the directional control valve unit 9b, the directional control valve units 10a
A directional control valve 10a ₂ of, and so as to merge was merged pressure oil from the directional control valve 10b ₂ of the directional control valve units 10b, moreover two flow paths that these joins.

As described above, the boom cylinders 11a, 1
1b and 4 to drive the bucket cylinder 13.
The hydraulic pumps 7a, 7b, 8a, 8b are joined because a large load acts on the boom 3a and the bucket 3c, and these hydraulic actuators require a large flow rate of hydraulic oil. is there. However, the connection relationship between the hydraulic actuator and the directional control valve is merely an example, and as described above, a hydraulic actuator other than the above may be connected. In such a relationship, an appropriate circuit configuration is adopted depending on the hydraulic excavator as the working machine, for example, the pressure oil may not be merged into the bucket cylinder 13. Further, there is also a hydraulic shovel provided with a hydraulic circuit using three hydraulic pumps driven by a single drive source. In this case, each hydraulic actuator including a boom cylinder and a bucket cylinder has a single hydraulic actuator. It is configured such that pressure oil from a hydraulic pump is supplied, or pressure oil from two or three hydraulic pumps is combined and supplied.

When the hydraulic oil from the four hydraulic pumps shown in FIG. 7 is merged and supplied to the hydraulic actuator, in order to control the supply of the hydraulic oil to the hydraulic actuator, each direction switching valve unit is controlled. From 1 each
Four directional control valves are to be selected, and accordingly, a switching operation of four directional control valves is required to drive a single hydraulic actuator. FIG. 8 shows a configuration of a hydraulic circuit for driving the bucket cylinder 13, for example, in which pressure oils from four hydraulic pumps are combined and supplied to a hydraulic actuator. In the hydraulic circuit diagram of FIG. 8, each of the directional control valve units 9a, 9b, 10
Each of a and 10b is composed of four directional control valves.

As is apparent from FIG. 1, the directional control valves selected to supply the pressure oil to the bucket cylinder 13 include directional control valve units 9a, 9b, 10a, 10
The direction switching valves 9a ₁ , 9b ₂ , 10a ₃ , and 10b ₄ that constitute b. Including these directional control valve _{9a 1, 9b 2, 10a 3} , 10b 4, the directional control valve units 9a, 9b, 10a, 10
All the directional control valves constituting b are switched based on a hydraulic pilot signal. Accordingly, each directional control valve has a hydraulic pilot section P ₁ for switching it in one direction.
When the hydraulic pilot portion P ₂ for switching in the other direction is provided, usually, the directional control valve is held in the neutral position. Switching control of the direction switching valve is performed by the operation lever device 15. The operation lever device 15 has a pair of pilot valves 16a and 16b and an operation lever 17 as its operation means, and the direction switching valves 9a ₁ and 9a.
b _2, 10a _3, the hydraulic pilot portion P ₁ of 10b ₄ is connected to the pilot valve 16 via a pilot pipe 18a, also hydraulic pilot portion P ₂ is a pilot pipe 18b
Is connected to

The pilot valves 16a, 16b are connected to pilot pipes 18a, 1
8b is for supplying a hydraulic pilot signal of a predetermined pressure from the pilot pump 19 to the hydraulic pilot units P ₁ and P ₂ . When the operation lever device 15 is in the neutral position, each of the directional control valves 9a ₁ , 9b ₂ , 10a ₃ ,
The hydraulic pilot portion P ₁ and P ₂ of 10b ₄ are each pilot pipe 18a, from 18b, respectively pilot valve 16a, is connected to the tank via a 16b, thus the hydraulic pilot portion P ₁ and P ₂ No pilot pressure is supplied and the directional control valves 9a ₁ , 9b ₂ , 10a ₃ ,
10b ₄ are all held in the neutral position.

When the operating lever 17 is tilted in the direction of the arrow in FIG. 8 or in the direction opposite to the arrow, the pilot pipe 18a or 18b is connected to the pilot pump 19 via one of the pilot valves 16a or 16b, and the hydraulic pilot section is connected. The hydraulic pilot signal is supplied to either P ₁ or P ₂ , and the other hydraulic pilot section is kept connected to the tank.
a ₁ , 9b ₂ , 10a ₃ , 10b ₄ are simultaneously switched to supply pressure oil to one of the bottom chamber or rod chamber of the bucket cylinder 13 and the other to the tank, so that the bucket cylinder 13 is extended. Or shrink. Then, the pilot valves 16a, 1
6b, the direction switching valve 9a ₁ a hydraulic pilot signal pressure corresponding to the operation amount of the operating lever _{17, 9b 2, 10a 3,} 10b 4
Therefore, the bucket cylinder 13 expands and contracts at a speed corresponding to the operation amount of the operation lever 17.

[0012]

By the way, the operating lever device 15 includes an operating lever 17 and a pilot valve 16.
The operator cab 4 is provided in the operator's cab 4 including the a and 16b, and the operator in the operator's cab 4 operates the operation lever 17. On the other hand, other devices constituting the hydraulic circuit, that is, the direction switching valve unit 9a,
Each device including 9b, 10a, 10b, a pilot pump 19, a tank and the like is provided in the machine room 5. For this purpose, the operating lever device 15 and the direction switching valve units 9a, 9
b, 10a, and pilot pipe 1 connecting between 10b
The pressure oil supply pipes 8a and 18b and the pressure oil supply pipe from the pilot pump 19 and the return pipe to the tank must be routed between the machine room 5 and the operation room 4.

Although the volumes of the individual hydraulic pilot sections P ₁ and P ₂ are relatively small, the four directional control valves 9 a ₁ , 9
The total volumes of the hydraulic pilot portions P ₁ and P ₂ of b ₂ , 10a ₃ and 10b ₄ are considerably large, and the total supply flow rate of the hydraulic pilot signals is considerably large. In this manner, the pipe through which the large-volume hydraulic pilot signal flows is generally configured to flow using a merged pipe from at least a portion connected to the operation lever device 15 to a position immediately before the direction switching valve. Therefore, four hydraulic pipes connected to the operation lever device 15, that is, two pilot pipes 18a, 1
8 b, a pressure oil supply pipe and a return pipe from the pilot pump 19 extend from the machine room 5 into the operation room 4. In order to improve the responsiveness of the directional control valve to the operation of the operation lever 17, these pipes must be made thick to increase the flow rate.

In order to route four thick pipes to one operation lever device in the cab 4, a large space is required, and other hydraulic actuators (not shown) such as an arm cylinder and Since a plurality of other operation lever devices for operating the swing motor and the like are provided in the same manner, not only does the living space in the cab 4 be pressed, but also the arrangement of other devices is restricted. There is. In addition, there is a disadvantage that the longer the entire length of the pipe, the greater the pressure loss due to an increase in pipe resistance and the like, and the lower the response speed of the directional control valve.

Here, as the pilot signal sent from the operating means provided in the operator's cab to the direction switching valve, an electric signal can be used instead of the hydraulic pilot signal described above. In order to switch the directional control valve by an electric signal, the directional control valve is constituted by an electromagnetic proportional valve. When an electromagnetic proportional valve is used, the signal transmission path is simplified and the response is extremely good because the operating means and the pilot portion of the directional control valve need only be connected by a signal cable. If a required number of electromagnetic proportional valves are used to control the driving of a large number of hydraulic actuators, the cost will increase significantly. Therefore, from the viewpoint of cost and the like, it is far more advantageous to use a hydraulic pilot type directional control valve than to control a directional control valve using an electromagnetic proportional valve.

The present invention has been made in view of the above points, and an object thereof is to supply a large flow rate hydraulic pilot signal to a hydraulic pilot section using a hydraulic pilot type directional switching valve. In such a configuration, the length of the thick pipe is reduced to a minimum length, the pipe passing through the cab can be made thinner, and the pressure loss is reduced to improve the responsiveness to switching of the directional control valve. It is in.

[0017]

In order to achieve the above-mentioned object, the present invention provides a plurality of hydraulic pumps,
Multiple hydraulic pressures driven by pressure oil supplied from the pump
Actuator and hydraulic oil
Includes multiple hydraulic pilot type directional control valves for supply / discharge control
And a plurality of directional control valves respectively connected to the respective hydraulic pumps.
The unit, the operation lever, and the operation amount of this operation lever
System with a pilot valve that supplies a corresponding hydraulic signal
Control means for reducing the number of the plurality of hydraulic actuators.
At least one hydraulic actuator has
Two or more directional switching valve units among directional switching valve units
From the directional valves selected from
Supply by merging,
Pressure control valve to which these pipes are connected, and this pressure control valve
Hydraulic pilot from the pilot pump connected
A signal for each hydraulic pyro of the selected one of the plurality of directional control valves.
Pipes for supplying oil to each oil section from the pressure control valve.
Pressure of hydraulic pilot signal supplied to pressure pilot section
To control the hydraulic pressure from the pilot valve.
Signal supplied to this pressure control valve as a hydraulic control signal
And a supply pipe .

Here, in a hydraulic circuit including a hydraulic pump and a hydraulic actuator, if a plurality of hydraulic pumps are provided, a plurality of directional control valves are connected to each hydraulic pump. Generally, the plurality of directional control valves are configured as a unitized directional control valve unit. In such a configuration, a desired directional control valve is selected from all the directional control valve units or some of the directional control valve units, and the pressure oil from the selected directional control valves is discharged. Merge and supply to the hydraulic actuator,
Further, the branch pipes on the downstream side of the respective pressure control valves are branched, and the respective branch flow paths are connected to the respective hydraulic pilot portions of the selected direction switching valves.

An example of the pressure control valve provided between the pilot pump and the hydraulic pilot portion of the direction switching valve includes, for example, an outlet port communicating with the hydraulic pilot portion,
A hydraulic control signal supplied to the control port in a valve casing having an inlet port communicating with the pilot pump, a tank port communicating with the tank, and a control port to which a hydraulic control signal is supplied from the pilot pump via a pilot valve. Based on the above, it is possible to provide a configuration in which a valve body that displaces the outlet port into a state communicating with the tank port, a state communicating with the inlet port, and a state blocking the communication with the tank port and the inlet port is provided. it can.

The selected plurality of directional control valves may be switched at the same time. However, the flow of each of the selected directional control valves for driving the hydraulic actuator to the hydraulic pilot unit is controlled. If a throttle is provided in at least a part of the flow path so that the switching timing of each of the directional control valves has a difference of a plurality of steps, there is an advantage that smooth movement of the hydraulic actuator is achieved. is there.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. Thus, the same or equivalent components as those described in the related art described above are denoted by the same reference numerals, and description thereof will be omitted.

First, FIG. 1 shows a configuration of a hydraulic circuit for driving a large-capacity hydraulic cylinder such as a boom cylinder or a bucket cylinder. In this figure, as shown in FIG. 7, a configuration is shown in which the hydraulic oil from the four hydraulic pumps 20a to 20d is joined to drive the hydraulic cylinder 21. In addition, each hydraulic pump 20a ~
A plurality of directional control valves (four in the figure) are unitized as directional control valves provided to control the supply of pressure oil from 20d.
2d, each directional switching valve unit 22a to 22d
d is connected to each of the hydraulic pumps 20a to 20d. All the directional control valves constituting the directional control valve units 22a to 22d are configured by hydraulic pilot type directional control valves that perform switching control based on hydraulic pilot signals. Accordingly, the directional control valve is provided with a hydraulic pilot section at both ends.

The directional control valves constituting the directional control valve units 22a to 22d are connected to hydraulic actuators.
The hydraulic cylinder 21 has four hydraulic pumps 20a to 20d.
An example is shown in which pressure oil from
One directional switching valve is selected from each of the directional switching valve units 22a to 22d, and the hydraulic oil supplied from the hydraulic pumps 20a to 20d is merged via the four directional switching valves to form the hydraulic cylinder 21. Is supplied to the bottom chamber 21B or the rod chamber 21R. In the figure, reference numerals 22a ₁ , 2
The directional control valves indicated by 2b ₂ , 22c ₃ and 22d ₄ are directional control valves selected to drive the hydraulic cylinder 21. These directional control valves 22a ₁ , 22b ₂ , 2
In order to perform switching control of 2c ₃ and 22d ₄ , hydraulic pilot sections to which a hydraulic pilot signal is supplied are provided at both ends, but all these directional switching valves 22a ₁ , 22b ₂ ,
Per 22c _3, 22d _4, respectively show a hydraulic pilot portion of the one side by the sign of P _1, also showing the other hydraulic pilot portion by the sign of P _2. In addition, in the figure, 23 is a tank.

The directional control valves 22a to 22d are normally held at neutral positions, and their respective hydraulic pilot portions P
_When the pilot pressure is supplied to ₁ , the directional control valves 22a ₁ , 2
2b ₂ , 22c ₃ and 22d ₄ are switched to one side. As a result, for example, pressure oils from the four hydraulic pumps 20a to 20d are combined and supplied to the bottom chamber 21B side of the hydraulic cylinder 21, and the rod chamber 21R is kept connected to the tank 23, and The cylinder 21 operates in the extension direction. Conversely, when supplying a pilot pressure to the hydraulic pilot portion P _2, the directional control valve _{22a 1, 22b 2, 22c 3} , 22d 4
Is switched to the other side, the hydraulic cylinder 21 is supplied with pressure oil to the rod chamber 21R, and the hydraulic oil in the bottom chamber 21B is returned to the tank 23, so that the hydraulic cylinder 21 contracts.

A pilot pump 24 is provided for controlling the supply of the pilot pressure, and the pressure oil from the pilot pump 24 is supplied to the directional control valves 22a ₁ , 22b ₂ , 22
An operation lever device 25 is provided for controlling the supply to the hydraulic pilot portions P ₁ and P ₂ in c ₃ and 22d ₄ .
The operation lever device 25 includes a pair of pilot valves 26.
a, 26b and an operation lever 27, and have the same configuration as the operation lever device 15 described in the related art. When the operating lever 27 is held at the neutral position, the pilot pressure does not act on any of the hydraulic pilot portions P ₁ and P ₂ of the direction switching valves 22a ₁ , 22b ₂ , 22c ₃ and 22d ₄ , and therefore, each direction switching valve 22a ₁ , 22b ₂ , 22c ₃ , 22
d ₄ is held in the neutral position. When the operating lever 27 is tilted to one side, each of the directional control valves 22a ₁ , 22b ₂ , 22c ₃ ,
22 d ₄ is switched to one side, tilting the other, the direction switching valves _{22a 1, 22b 2, 22c 3} , 22d 4 also will be switched to the other side. In addition, the pressure of the hydraulic pilot signal changes in accordance with the angle of the operation lever 27, and the direction switching valves 22a ₁ , 2 correspond to the pressure of the hydraulic pilot signal.
Strokes 2b ₂ , 22c ₃ and 22d ₄ are performed. As a result, when the operation lever 27 is tilted at the maximum angle, the entire flow rate is supplied to the hydraulic cylinder 21, and the hydraulic cylinder 21 is displaced at a high speed. On the other hand, when the operation angle of the operation lever 27 is reduced, the flow rate supplied to the hydraulic cylinder 21 decreases accordingly, and the speed of movement of the hydraulic cylinder 21 also decreases. In the figure, reference numeral 28 denotes the pilot pump 2
4 is a relief valve for setting the maximum pressure of the circuit including the pressure control valve 4. In addition to this relief valve, a low-pressure relief valve for setting the maximum pressure of the hydraulic pilot signal for the hydraulic cylinder 21 can be provided in the circuit.

The operation lever device 25 is provided with a direction switching valve 22a ₁ ,
The operation lever device 25 is for performing switching control of the direction switching valves 22b ₂ , 22c ₃ and 22d _4.
2a ₁ , 22b ₂ , 22c ₃ , and 22d ₄ are not directly supplied with pilot pressure, but a pilot pipe 30 from the pilot pump 24 is branched on the way, and a signal supply pipe 31 is connected to the operation lever device 25. Connected. The pilot pipe 30 is further branched into branch pipes 30a and 30b, and the branch pipe 30a is further branched into _four , and each hydraulic pilot of the _four directional control valves 22a ₁ , 22b ₂ , 22c ₃ and 22d ₄ respectively. It is connected to part P _1, also the branch pipe 30b
A flow path branched from is connected to the hydraulic pilot portion P _2. Moreover, each of the directional control valves 22a ₁ , 22b ₂ , 22
c ₃ , 22d ₄ hydraulic pilot sections P ₁ , P ₂ and branch pipe 3
0a, 30b between the pressure control valves 32a, 32a, respectively.
32b are provided. The signal supply pipe 31, which is another type of pipe, is connected to these pressure control valves 32a, 32a.
2b for controlling the pump 2
Signal pipe 31 for supplying a hydraulic control signal to the hydraulic oil from 4
The pressures a and 31b are supplied to the pressure control valves 32a and 32b via the pilot valves 26a and 26b of the operation lever device 25.

The structure and operation of the pressure control valves 32a and 32b will be described with reference to FIGS.
Here, since the pressure control valves 32a and 32b have the same configuration, 32 is used as a reference of the pressure control valve in these figures. 2 shows a state where the hydraulic pilot signal is not supplied, FIG. 3 shows a state where the hydraulic pilot signal is supplied, and FIG. 4 shows a state where the hydraulic pilot signal and the hydraulic control signal are balanced. Is shown.

In the figure, reference numeral 33 denotes a valve casing of the pressure control valve 32, in which a spool valve element 34 is provided. Also, the valve casing 3
3 has an inlet port A leading to the pilot pump 24 and a tank port T leading to the tank 23;
2a ₁ , 22b ₂ , 22c ₃ , 22d ₄ hydraulic pilot section P ₁
Or an outlet port B communicating with P _2, and a control port P leading to the pilot valve 26a or 26b is formed. The spool valve body 34 is slid and displaced in accordance with the pressure supplied to the control port P, so that the outlet port B is connected to the tank port T shown in FIG. 2 and the inlet port shown in FIG. A for switching to a state in which both the inlet port A and the tank port T are shut off, as shown in FIG.

For this purpose, the lands 34a and 34b provided on the spool valve body 34 allow the chambers 33A, 33B, 33T, 33P and 33
S can be sectioned. Chamber 33
A, 33B, 33T, and 33P are inlet ports A,
The outlet port B, the tank port T, and the control port P are always open.
3B communicates with the chamber 33T, communicates with the chamber A, or shuts off both the chamber 33T and the chamber A. Also, the chamber 33S
Is provided with a valve element urging means 35, and the spool valve element 34
In the direction of the control port P, and the chamber 33S is always in communication with the chamber B by a communication passage 36 provided in the spool valve element 34.

As described above, the pressure in the control port P acts on the one end surface of the spool valve element 34, the pressure in the chamber B acts on the other end side, and the spool valve element 34 is provided with a valve element. The pressing force of the urging means 35 is acting. Here, although not essential, the pressure receiving areas at both ends of the spool valve 34 are equal, and in FIG. 2, a rightward pressing force F ₁ is generated in the spool valve 34 by the pressure in the control port P. ,
The total pressing force F ₂ of the pressure and the valve body urging means 35 in the outlet port B, and presses the spool valve 34 to the left in FIG. Here, the urging force of the valve body urging means 35 changes in proportion to the amount of displacement, but when at least one of the pressure in the control port P or the pressure in the outlet port B changes, the spool valve body 34 The inside of the valve casing 33 is slid and displaced.

When the control pressure is not applied to the control port P, the spool valve element 34 is held at the position shown in FIG.
The outlet port B communicates with the tank 23 through the tank port T. Further, since the chamber 33S is also in communication with the chamber 33S via the communication passage 36, both the chamber 33B and the chamber 33S are maintained at the tank pressure. From this state, the signal pipe 31a or 3
1b supplies a hydraulic control signal to the control port P, and when the pressure in the control port P rises, the spool valve 3
A pressure difference is generated between the chamber 33P and the chamber 33S, which face both ends of the chamber 4. As a result, the control port when the pressing force F ₁ based on the pressure in the P becomes larger than the pressing force F ₂ based on the biasing force of the spool valve body 34 the valve body urging means 35 acting on the spool valve body 34 valve By sliding displacement in the direction against the body urging means 35, the outlet port B is cut off from the tank port T, and then the outlet port B communicates with the inlet port A as shown in FIG. Become. Thus, the pilot pump 24 will be communicated with the hydraulic pilot portion P ₁ or P ₂ of the directional control valve _{22a 1, 22b 2, 22c 3} , 22d 4 via the inlet port A and an outlet port B,
A hydraulic pilot signal is supplied.

When the spool valve element 34 switches to the state shown in FIG. 3, the pressure in the chamber 33B is guided to the chamber 33S via the communication passage 36. The inlet port A is connected to the pilot pump 24, and the discharge pressure of the pilot pump 24 acts, and this pressure is also supplied to the inside of the chamber 33S. On the other hand, the pressure supplied from the control port P to the chamber 33P is a hydraulic control signal of a pressure controlled from one of the pilot valves 25a and 25b constituting the operation lever device 25. This hydraulic control signal is a pressure corresponding to the angle of the operation lever 27, and is a control pressure of the relief valve 28 even when the control lever 27 is tilted at the maximum angle.
If the angle of the operation lever 27 is smaller than that, the pressure of the hydraulic control signal is also reduced accordingly.

From the above, the spool valve element 34 is
Switched to the state, the pressure in the output port B is increased, the pressing force F ₂ of the spool valve body 34 is raised, the spool valve body 34 is slidably displaced in a direction in which the state of FIG. Eventually, the spool valve element 34 becomes the chamber 33B and the chamber 3
The state shown in FIG. 4 is established in which communication with the chamber 3A is interrupted and communication with the chamber T is not established. In this state, since the hydraulic oil does not flow in and out of the output port B, the spool valve body 34 is held at that position. As a result, the pressure at the outlet port B is kept constant.

Therefore, the operating lever device 2 provided in the cab is
When the operating lever 27 of 5 holds the neutral position, the pressure control valve 32a, 32b are both pilot pump 24 and the directional control valve _{22a 1, 22b 2, 22c 3} , hydraulic pilot portion P ₁ of the 22 d _4, P ₂ Is kept unconnected.
Accordingly, the directional control valve _{22a 1, 22b 2, 22c 3} , 22d 4 becomes neutral position, the hydraulic cylinder 21 is held stationary. From this state, it is assumed that, for example, the operation lever 27 is tilted in one direction by a predetermined angle and operated to supply a control hydraulic signal from the pilot valve 26a. by this,
A control oil pressure signal of a pressure corresponding to the operation angle of the operation lever 27 is supplied from the signal pipe 31a to the pressure control valve 32a. However, no control oil pressure signal is supplied to the pressure control valve 32b. As a result, the spool valve element 34 of the pressure control valve 32a is slid and displaced, and pressure oil from the pilot pump 24 is supplied from the inlet port A to the outlet port B to generate pressure, which is output as a hydraulic pilot signal. You. The pressure of the hydraulic pilot signal is controlled so as to be a pressure corresponding to the operation angle of the operation lever 27. As a result, the hydraulic pilot signal from the pilot pump 24 is transmitted through the pilot pipe 30 to the direction switching valve unit 22a.
Directional switching valves 22a ₁ , 22b ₂ , 22
c _3, it is supplied to all of the hydraulic pilot portion P ₁ of the 22 d _4. Further, since the control pressure signal to the pressure control valve 32b which is the other hydraulic pilot portion P ₂ is connected is not supplied, the outlet port B is kept in communication with the tank port T, all of the hydraulic pilot portion P ₂ is kept in communication with the tank 23. As a result, the direction switching valves 22a ₁ , 2 in the direction switching valve units 22a to 22d
2b ₂ , 22c ₃ , and 22d ₄ are all switched, so that a large amount of pressure oil is supplied from the hydraulic pumps 20a to 20d to the hydraulic cylinder 21.
And the piston rod of the hydraulic cylinder 21 is extended. When the operation lever 27 is tilted in the opposite direction, the hydraulic cylinder 21 operates in the opposite direction.

As described above, the directional control valves 22a ₁ , 22a
In order to control b ₂ , 22c ₃ , and 22d ₄ , two systems of pipes, a pilot pipe 30 and a signal supply pipe 31, are provided. Of these two systems, branch pipes 30a and 30d are provided.
b, the directional switching valve 22a ₁ , in which an extremely high pressure oil for directly driving the hydraulic cylinder 21 flows.
22b ₂ , 22c ₃ , 22d ₄ hydraulic pilot sections P ₁ , P ₂
The operation control is carried out by supplying the pressure oil to the hydraulic pump, and the flow rate of the hydraulic pilot signal becomes considerably large. And 4
Since hydraulic pilot signals are supplied to the hydraulic pilot sections P ₁ and P ₂ , it is necessary to supply a large flow rate hydraulic signal,
The diameter of the pipe also increases. On the other hand, the signal supply pipe 31 and the signal pipe 3 downstream of the operation lever device 25 are provided.
1a and 31b need only selectively supply a hydraulic control signal to the two pressure control valves 32a and 32b. In addition, the control targets are the pressure control valves 32a and 32b on which a pressure extremely lower than the driving pressure of the hydraulic cylinder 21 acts. is there. Therefore, since the control hydraulic signal supplied to the pressure control valves 32a and 32b may be a small flow rate, a thin pipe can be used.

The pilot pipe 30 requiring a thick pipe is
It is not necessary to connect to the operation lever device 25 provided in the cab 4, and only the thin signal supply pipe 31 for controlling the pressure control valves 32a and 32b may be connected to the operation lever device 25. Is extremely thin. As a result, the installation space for the piping in the cab 4 can be saved, and the cab 4 can be widely used.
In addition, since the directional switching valve units 22a to 22d are arranged in the normal machine room 5 at positions close to the hydraulic pumps 20a and 20b and the pilot pump 24 and the tank 23, a large flow of pressure oil flows and switching valves 22a _1, 2
2b _2, 22c _3, 22d ₄ to a hydraulic pilot signal directly supplied pilot pipe 30a, the total length of 30b can be significantly shortened. Therefore, the pressure loss at the time of switching the directional control valve is suppressed to a minimum, and the supply of the pilot pressure and the return to the tank 23 can be performed at an extremely high speed, so that there is no problem of a response delay.

In addition, a directional control valve for controlling each hydraulic actuator constituting the hydraulic shovel or a directional control valve unit selected from a directional control valve unit including a plurality of directional control valves is switched to provide a plurality of hydraulic pumps to one actuator. It is sufficient to provide two pressure control valves each when the pressure oils are combined from each other, and the structure of the pressure control valves is extremely simple, so that the overall configuration of the hydraulic circuit can be simplified. The cost can be reduced and the reliability can be improved as compared with the case where an electromagnetic proportional valve is used.

Here, the direction switching valve units 22a to 22
d, four directional control valves 22a ₁ , 22b ₂ , 22
Although c ₃ and 22d ₄ may be configured to be switched at the same time, the operation lever 27 of the operation lever device 25 is then changed.
The when operated in order as indicated by the solid line, which at the same time the directional control valve _{22a 1, 22b 2, 22c 3} , hydraulic pilot signal to the hydraulic pilot portion P ₁ or P ₂ of 22 d ₄ is supplied to the Figure 5, pressure oil is dispersed, will be the pressure of the hydraulic pilot portion P ₁ or P ₂ is increased with a t ₁ delay some time, yet with the pressure increase of the hydraulic pilot signal, reaches a maximum flow rate in a short time of Δt . For this reason, the hydraulic actuator may start moving suddenly.

From the above, in order to make the movement of the hydraulic actuator smooth, the hydraulic pilot portions P ₁ and P ₂ of the _four directional switching valves 22 a ₁ , 22 b ₂ , 22 c ₃ and 22 d 4 are provided. The supplied hydraulic pilot signal has a time difference. For this, as shown in FIG. 1, the directional control valve _{22a 1, 22b 2, 22c 3} , 22d 4 of providing the aperture C in the respective flow path to the hydraulic pilot portion P ₁ and P ₂ of. Each of the apertures C is a variable aperture, and according to the type of the hydraulic actuator, the work content, and the like,
Change the aperture. For example, the directional control valve 22a ₁
The throttle C is fully opened, has substantially no throttle effect, and has a directional control valve 22b ₂ , a directional control valve 22c ₃ ,
To reduce the opening area aperture in the forward direction switching valve 22 d _4.

[0040] Thus, when the operation lever 27 of the operating lever device 25 is operated, as shown in FIG. 5, with T ₁ delay short time, first switching of the directional control valve 22a ₁ begins, the time T _{After 2} seconds, the direction switching valve 2
In addition to 2a _1, now switched the direction switching valve 22b _2, further time T ₃ has elapsed, the direction switching valve 22c _3,
Time T ₄ passes the directional control valve 22 d ₄ also become switched, the whole, so that the characteristics shown by the dashed line in the figure is obtained. As a result, hydraulic actuator, since from the beginning of the operation lever 27 and the time T ₁ has elapsed, will be the motion begins, faster than when responsiveness is not provided a throttle C. In addition, the time ΔT from when the supply of the pressure oil to the hydraulic actuator is started to when the maximum flow rate becomes the maximum flow rate according to the operation angle of the operation lever 27 is later than when the throttle C is not provided, and the flow rate until the maximum flow rate is increased. The movement of the hydraulic actuator becomes smoother to the extent that the rate is suppressed.

Here, by forming the stop C with a variable stop, the stop opening area can be appropriately adjusted according to the characteristics of the work, etc. However, if there is no need for adjustment, the stop openings will be different from each other. , Or a configuration in which a diaphragm is provided only at a desired position. Furthermore, for hydraulic cylinders and the like,
Depending on the mounting direction, there is a case where a load is always applied to only one side. In such a case, the hydraulic pilot unit on the side receiving the load and the hydraulic pilot unit on the opposite side are restricted by the throttle. It can also be configured to vary the amount. Further, by providing an open / close valve on the upstream side or downstream side of any of the throttles, by opening / closing the open / close valve as appropriate according to the working mode or the like, the joining of the directional switching valve to the hydraulic actuator is reduced. It can be set to be performed, a part to be merged, or a setting not to be merged.

In the above description, the directional switching valves provided for controlling the driving of the hydraulic actuators when driving the respective operating portions of the working machine with the hydraulic actuators are each configured as a directional switching valve unit. . It is preferable that the directional control valves constituting the directional control valve unit have the same structure in terms of manufacturing, and from the viewpoint of mass productivity of the directional control valve unit, the hydraulic oil from a plurality of hydraulic pumps is preferable. This is because, in order to control the direction, it is more preferable that the same number of direction switching valve units are provided as the hydraulic pumps. On the other hand, the flow rate required for each hydraulic actuator differs depending on the load of each operating unit. Therefore, the flow rate of the pressure oil flowing through the direction switching valve changes according to each hydraulic actuator. That is, when a large flow rate is required, the directional control valves installed in the working machine are all of the same configuration by joining the hydraulic oil flowing through the directional control valves of the number corresponding to the required flow rate. Even
The required flow rate can be supplied to each hydraulic actuator. In addition, in the present invention, even when the number of directional switching valves to be selected is large in order to cause the converging of the pressure oils, it is necessary to control the switching by the operation lever device provided in the cab. In this case, the responsiveness to the operation of the operation lever device is improved with thin piping. Therefore, the present invention is not limited to the hydraulic circuit shown in FIG. 1. For example, the number of provided hydraulic pumps and directional switching valve units is arbitrary, and pressure oil from any directional switching valve is combined with any hydraulic actuator. Or how to configure the piping for that, etc.
Various circuit designs are possible.

[0043]

As described above, the present invention provides a
Hydraulic actuator by combining pressure oil from directional control valve
When supplying the power to the
The hydraulic signal of each direction switching valve is applied to the hydraulic signal according to the work volume.
Instead of supplying it directly to the
This signal is supplied to the pressure control valve as a signal,
Hydraulic pilot from pilot pump to each directional control valve
Since a signal is supplied, a hydraulic pilot type directional switching valve is used to supply a large flow rate hydraulic pilot signal to the hydraulic pilot unit.
The responsiveness is improved by minimizing the routing length of the thick pipes, and the pipes passing through the cab are made thinner, so that the installation space can be reduced.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a pressure control valve.

FIG. 3 is a sectional view of the pressure control valve showing an operation state different from that of FIG. 2;

FIG. 4 is a sectional view showing still another operation state of the pressure control valve.

FIG. 5 is a diagram comparing a case where a throttle is provided in a flow path to each hydraulic pilot unit and a case where no throttle is provided.

FIG. 6 is an external view of a hydraulic shovel as an example of a working machine.

FIG. 7 is a hydraulic circuit diagram for driving a hydraulic actuator according to the related art.

8 is a hydraulic circuit configuration diagram that extracts and shows a circuit portion for driving a bucket cylinder from the hydraulic circuit diagram of FIG. 7;

[EXPLANATION OF SYMBOLS] 20a~20d hydraulic pump 21 hydraulic cylinders _{22a 1, 22b 2, 22c 3} , 22d 4 directional valve P _1, P ₂ hydraulic pilot portion 23 tank 24 pilot pump 25 operating lever device 30 pilot pipe 30a, 3
0b Branch pipe 31 Signal supply pipe 32, 32a, 32b Pressure control valve 33 Valve casing 34 Spool valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E02F 9/20-9/22 E02F 3/43 F15B 11/00-11/22

Claims (4)

(57) [Claims] A plurality of hydraulic pumps and a hydraulic pump
Hydraulic actuators driven by pressure oil supplied from the pump
Supply and discharge of hydraulic oil to the tutor and each of the hydraulic actuators
Including a plurality of hydraulic pilot type directional control valves for controlling,
A plurality of directional control valve units respectively connected to the respective hydraulic pumps;
And the operating lever and the operating amount of this operating lever.
Control with pilot valve to supply hydraulic pressure signal
And the plurality of hydraulic actuators
Each of the hydraulic actuators has the plurality of direction disconnections.
From two or more directional switching valve units
Merges pressure oil from multiple selected directional valves
In supplies by the pressure control valve the pipe from the pilot pump is connected
When connected to the pressure control valve, from the pilot pump
Switching the hydraulic pilot signal of the selected plurality of directions
A pipe for supplying to each hydraulic pilot section of the valve, and a pipe supplied to each hydraulic pilot section from the pressure control valve.
To control the pressure of the hydraulic pilot signal
The hydraulic signal from the pilot valve is used as the hydraulic control signal.
And a signal supply pipe for supplying the pressure control valve to the pressure control valve . 2. The hydraulic pressure control valve according to claim 1, wherein the pressure control valve includes an outlet port communicating with the hydraulic pilot unit, an inlet port communicating with the pilot pump, a tank port communicating with the tank, and a hydraulic control signal from the pilot pump via the pilot valve. In a valve casing provided with a control port supplied with, based on a hydraulic control signal supplied to the control port, the outlet port communicates with a tank port, a state communicates with an inlet port, and 2. The hydraulic circuit for a working machine according to claim 1, wherein a valve body is provided which is displaced between a state in which communication with the tank port and the inlet port is interrupted. 3. A throttle is provided in at least a part of a flow path to a hydraulic pilot portion of each of the plurality of directional control valves selected for driving the hydraulic actuator, and a throttle is provided for each of the directional control valves. 2. The hydraulic circuit for a working machine according to claim 1, wherein the switching timing has a plurality of steps. 4. The method according to claim 1, wherein each of said stops is constituted by a variable stop.
The hydraulic circuit of a working machine according to claim 3, wherein: