JPH0217723B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit in which a plurality of hydraulic actuators are driven by a plurality of hydraulic pumps, and in particular,
The present invention relates to a hydraulic circuit suitable for a hydraulic system of a construction machine equipped with a large number of hydraulic actuators.

[Traditional background]

In construction machines such as hydraulic excavators, a large number of hydraulic actuators are used to drive working mechanisms and traveling mechanisms, and a plurality of hydraulic pumps are mounted to drive these hydraulic actuators. A directional switching valve for controlling the drive of each of the hydraulic actuators is installed for each hydraulic pump, and is composed of a plurality of single blocks. In such construction machines, working mechanisms are often expanded, modified, partially replaced, and functions are changed, and along with this, it may be necessary to add directional switching valves. In this way, one of the hydraulic circuits with an additional directional control valve compared to the conventional hydraulic system.
An example is shown in FIG.

FIG. 2 is a circuit diagram of a hydraulic circuit of a conventional construction machine. In the figure, 1 is a first hydraulic pump mounted on a construction machine, and 2 is a second hydraulic pump.
Reference numeral 3 designates a first monoblock type four-way directional valve group, which includes directional valves 3A, 3B, 3C, and 3.
It is composed of D. The output ports of each of the directional control valves 3A to 3D are connected to various hydraulic actuators. 3e is a pump port connecting the first directional valve group 3 to the first hydraulic pump 1; 3g;
is a center bypass that communicates the directional control valves 3A to 3D at their neutral positions. Reference numeral 4 denotes a second directional valve group of monoblock type four-way type, which is composed of directional valves 4A, 4B, 4C, and 4D, and the output ports of each of these directional valves 4A to 4D are connected to various hydraulic actuators. ing.
4e is a pump port that connects the second directional valve group 4 to the second hydraulic pump 2, 4f is a carryover port, and 4g is a center bypass.
A hydraulic cylinder 5 is connected to the output port of the directional control valve 3A, and drives, for example, a bucket of a hydraulic excavator. 6 is a pilot valve for switching the directional control valve 3A, and 6a is its operating lever. Directional switching valve 3 depending on the operation of operating lever 6a.
Pilot pressure oil is supplied to the pilot port A, and the directional control valve 3 is switched. 7 and 8 are relief valves, 9 and 10 are hydraulic pumps that drive hydraulic actuators other than the hydraulic actuators controlled by the first directional valve group and the second directional valve group, 11 and 12 are filters, and 13 14 is an oil cooler, and 14 is a hydraulic oil tank.

In such a hydraulic system, when the function of the hydraulic cylinder 5 is changed to increase the speed in its extension direction, a mechanism that is added accordingly will be described below. Furthermore, before this expansion,
The carryover port 4f is connected to the tank 14. Now, in the figure, 15 is an added directional control valve. The pump port of the directional control valve 15 is the second
Like the directional control valve group 4, it is connected to the second hydraulic pump 2, and its output port is connected to the bottom side of the hydraulic cylinder 5. 16 is a logic valve. This logic valve 16 includes a pressure chamber 16a, a valve body 16b, and a communication hole 16 formed in the valve body 16b.
c, a return spring 16d, a discharge port 16e, etc. The communication hole 16c is connected to the carryover port 4f of the second directional valve group 4. 17 is a switching valve, its input port is connected to the pressure chamber 16a of the logic valve 16, and its output port is connected to the filter 12, the oil cooler 1, as well as the discharge port 16e of the logic valve 16.
3 to the tank 14. The additional directional switching valve 15 and switching valve 17 are switched by pilot pressure from the pilot valve 6.

Next, the operation of the above hydraulic circuit will be explained. When the operating lever 6a is operated, pilot pressure is transmitted from the pilot valve 6 to the directional control valves 3A, 15, and the directional control valve 17, and the directional control valve 3A is moved, for example, to the left position in the figure, or to the directional control valve 17. The valve 15 is switched to the left position in the figure, and the switching valve 17 is switched to the cutoff position. By switching the switching valve 17 to the cutoff position, the pressure chamber 16a of the logic valve 16 and the tank 14 are cut off, and the oil from the second hydraulic pump 2 passes through the center bypass 4g, the carryover port 4f, and the communication hole 16c. It enters the pressure chamber 16a and presses the valve body 16b of the logic valve 16 to shut off the logic valve 16, thereby cutting off the circuit from the carrier port 4f to the tank 14 via the discharge port 16e of the logic valve 16. On the other hand, by switching the directional control valve 3A, the pressure oil of the first hydraulic pump 1 is supplied to the bottom side of the hydraulic cylinder 5, and at the same time, by switching the directional control valve 15, the pressure oil of the second hydraulic pump 2 is also supplied. It is supplied to the bottom side of the hydraulic cylinder 5. Therefore, the hydraulic cylinder 5
The pressure oil of the first hydraulic pump 1 and the pressure oil of the second hydraulic pump 2 are combined and discharged to the bottom side of the hydraulic cylinder 5, and the speed of the hydraulic cylinder 5 in the extension direction is increased. In this case, since the center bypass 4g is cut off from the tank 14 by the logic valve 16, pressure oil can be supplied from the second hydraulic pump 2 without any problem. When the operating lever 6a is returned to the neutral position, the directional control valves 3A and 15 return to the neutral position, and the hydraulic cylinder 5 is held at that position. At the same time, the switching valve 17 also returns to the conducting position, the pressure chamber 16a of the logic valve 16 and the tank 14 are connected, the valve body 16b is pushed to the right in the figure, and the carryover port 4f is connected to the discharge port 1 of the logic valve 16.
It is connected to the tank 14 via 6e and enters the normal state.

[Problem to be solved by the invention]

In the above description of the hydraulic circuit, an example was explained in which there is a new requirement to increase the speed of the hydraulic cylinder 5, and for this purpose, the directional control valve 15 is added separately from the second directional control valve group 4. However, the present invention is not limited to this example, and a directional control valve may be added in conjunction with new installation or modification of a hydraulic actuator. If a directional control valve is added in addition to the directional control valve group 4, if the carry over port 4f is always connected to the tank 14, control by the added directional control valve will be impossible. In the case of a hydraulic circuit, it is necessary to install a logic valve 16 and a switching valve 17.

In this way, in conventional hydraulic circuits, when adding a new directional switching valve, it is necessary to install a logic valve 16 and a switching valve 17, making the configuration of the hydraulic circuit complicated. It also has the disadvantage of being expensive due to the use of complex valves such as logic valves.

The present invention has been made in view of the above circumstances, and its purpose is to provide an inexpensive hydraulic circuit in which directional switching valves can be easily added.

[Means to solve the problem]

To achieve the above object, the present invention provides a plurality of directional valves each having a center bypass circuit including a first directional valve, the first directional valve being connected to a first hydraulic pump. a plurality of directional valves having a center bypass circuit including a second directional valve group and a second directional valve group connected to a second hydraulic pump; The pressure oil of the first hydraulic pump is passed through the first directional switching valve to the second hydraulic pump via the second directional switching valve.
a hydraulic actuator to which the pressure oil of the hydraulic pumps is combined and supplied;
a third directional switching valve that is connected to the hydraulic pump in parallel with the second directional switching valve group to drive and control another hydraulic actuator; an operating device that operates the third directional switching valve; and an operating device that operates the third directional switching valve. [Function] The device is characterized in that it is provided with a switching means for switching the second directional switching valve to a non-discharge side position according to the operating signal whenever the device is operated. When the third directional valve is operated in one direction or the other by the device, no matter which direction the third directional control valve is operated,
The second directional control valve is switched to the non-discharge side position.
As a result, the connection between the center bypass pipe of the second directional valve group and the tank is cut off, and the supply of pressure oil from the second hydraulic pump to the other hydraulic actuators via the third directional valve is interrupted. It becomes possible.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a circuit diagram of a hydraulic circuit according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 2 are given the same reference numerals, and explanations thereof will be omitted. Reference numeral 20 denotes an existing hydraulic cylinder, the driving of which is controlled by the directional switching valve 3B in the first directional switching valve group 3 and the directional switching valve 4C in the second directional switching valve group 4. 21 is a check valve interposed between the hydraulic cylinder 20 and the directional switching valve 4C. 22 is a newly added hydraulic cylinder, 2
Reference numeral 3 designates a directional switching valve newly added to control the drive of this hydraulic cylinder 22. A pilot valve 24 generates pilot pressure according to the amount of operation of the operating lever 24a. 25a,
Reference numeral 25b denotes a pilot line for transmitting the pilot pressure of the pilot valve 24 to pilot ports at both ends of the directional control valve 23. 26 is a shuttle valve that selects the higher pressure among the pressures generated in both pilot pipes 25a and 25b; 27 is a shuttle valve 2;
This is a pilot pipe line that guides the pilot pressure selected in step 6 to the pilot port on the non-discharge side of the directional control valve 4C.

Next, the operation of this embodiment will be explained. First, when the existing hydraulic cylinder 20 is driven in the direction in which its rod contracts, the directional switching valve 3B is switched to the right position in the figure. Then, the first hydraulic pump 1
The pressure oil is transferred to the hydraulic cylinder 2 via the directional control valve 3B.
At the same time, the oil on the bottom side of the hydraulic cylinder 20 is discharged to the tank 14 via the directional control valve 3B, and as a result, the rod of the hydraulic cylinder 20 is contracted. When driving the rod of the hydraulic cylinder 20 in the extension direction, the directional control valve 3B is switched to the left position in the figure, and at the same time, the directional control valve 4B is switched to the left position in the figure.
C is switched to the right position in the figure. Therefore,
Pressure oil from the first hydraulic pump 1 and the second hydraulic pump 2 is supplied to the bottom side of the hydraulic cylinder 20 through directional control valves 3B and 4C, respectively. That is, the hydraulic cylinder 20 is driven at increased speed by the directional switching valve 4C only when the rod is driven in the extension direction.

Next, a case will be described in which the additional hydraulic cylinder 22 is driven. When the operating lever 24a is operated to drive the hydraulic cylinder 22, pilot pressure is outputted from the pilot valve 24 to, for example, the pilot pipe 25a in response to the operation.
This pilot pressure causes the directional control valve 23 to be switched to the right position in the figure. At the same time, the pilot pressure in the conduit 25a is selected by the shuttle valve 26 and output to the pilot conduit 27, and the directional control valve 4C is switched to the left position in the figure. By switching the left side position of the directional switching valve 4C, that is, switching to the side (anti-discharge side) where pressure oil is not merged and discharged with respect to the hydraulic cylinder 20, the center bypass 4g is switched to the directional switching valve 4C.
It is cut off from the tank 14 at this point. At this time, the pressure oil on the bottom side of the hydraulic cylinder 20 is transferred to the directional control valve 4.
The oil tries to flow to the tank 14 via C, but this flow is blocked by the check valve 21, so switching the directional control valve 4C to the opposite side has no effect on the hydraulic cylinder 20. . As mentioned above, the center bypass 4g is connected to the directional control valve 4C.
is shut off from the tank 14 by switching to the opposite discharge side, so that the pressure oil of the second hydraulic pump 2 is transferred to the hydraulic cylinder 22 via the right side position of the directional control valve 23.
The hydraulic cylinder 22 is driven in the direction of retracting the rod. Note that when the pilot pressure of the pilot valve 24 is output to the pilot pipe line 25b by the operating lever 24a,
The directional control valve 4C is also switched to the anti-discharge side,
The hydraulic cylinder 22 is driven in the direction of extending its rod without any hindrance.

In this way, in this embodiment, when there is a directional switching valve that allows pressure oil to join only when the existing hydraulic cylinder is driven in the rod extension direction, this directional switching valve is reversed by the pilot pressure that operates the added directional switching valve. Since the center bypass is cut off from the tank by switching to the discharge side, directional switching valves can be easily and inexpensively added without using logic valves, switching valves, etc.

In addition, in the description of the above embodiment, the case where one directional control valve is added is explained, but it is of course applicable to the case where a plurality of directional control valves are added. Further, the operation of the directional control valve is not limited to the above-mentioned pilot pressure, but may also be performed by an electric signal or a link mechanism. Furthermore, instead of providing a separate check valve, a directional switching valve having a built-in check valve function may be used.

〔Effect of the invention〕

As described above, in the present invention, when there is a directional valve group having a directional valve that allows pressure oil to join an existing hydraulic actuator only when the actuator is driven in a predetermined direction, this directional valve can be used in the direction of the additionally installed hydraulic actuator. The operation signal of the switching valve is used to switch to the anti-discharge side and cut off the center bypass from the tank.
There is no need to install logic valves, switching valves, etc., and directional switching valves can be easily and inexpensively added using a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a hydraulic circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional hydraulic circuit. 1...First hydraulic pump, 2...Second hydraulic pump, 3...First directional valve group, 4...
second directional valve group, 3A, 3B, 3C,
3D, 4A, 4B, 4C, 4D, 23... Directional switching valve, 20, 22... Hydraulic cylinder, 21... Check valve, 24... Pilot valve, 26...
shuttle valve.

Claims (1)

[Claims] 1 A plurality of directional valves having a center bypass circuit including a first directional valve, and a first directional valve group connected to a first hydraulic pump, and a second directional valve group.
a plurality of directional switching valves having a center bypass circuit including directional switching valves, and a second directional switching valve group connected to a second hydraulic pump; and a hydraulic actuator to which pressure oil of the first hydraulic pump via a valve is supplied by merging pressure oil of the second hydraulic pump via the second directional switching valve, the hydraulic circuit comprising: a third directional valve that does not belong to any of the directional valve groups and is connected to the second hydraulic pump in parallel with the second directional valve group to drive and control another hydraulic actuator; Third
A hydraulic system comprising: an operating device for operating the second directional switching valve; and a switching means for switching the second directional switching valve to a non-discharge side position in response to an operating signal whenever the operating device is operated. circuit.