JPH0217722B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a hydraulic circuit that is installed in a hydraulic machine such as a hydraulic excavator or a crane and that drives a hydraulic cylinder by merging pressure oil from a plurality of hydraulic pumps. .

[Background of the invention]

FIG. 2 is a side view showing the external appearance of a hydraulic excavator taken as an example of this type of hydraulic machine, and FIG. 3 is an explanatory diagram illustrating the operation of the working machine portion of the hydraulic excavator shown in FIG.

The hydraulic excavator shown in FIG. 2 includes a traveling body 2 that travels by a traveling device 1, a rotating body 4 that is placed on the traveling body 2 and rotates by a rotating device 3, and a rotating body 4 that is rotated by a rotating device 3. a boom 6 which can be mounted and driven by a boom cylinder 5;
The arm 8 is rotatably mounted on the arm 8 and driven by an arm cylinder 7, and the bucket 10 is rotatably mounted on the arm 8 and driven by a bucket cylinder 9. Reference numeral 11 denotes an operating lever arranged in the driver's cab, which drives the arm cylinder 7, for example. Note that the above-mentioned boom 6, arm 8, bucket 10, etc. constitute a working machine.

The hydraulic excavator configured in this manner is configured such that the arm 8 is retracted by contracting the arm cylinder 7 by operating the operating lever 11, for example.
By extending the arm cylinder 7, the arm 8 can be brought into a cloud (descending) state as shown in FIG. can be carried out.

FIG. 4 is a circuit diagram showing a schematic configuration of a hydraulic circuit provided in the hydraulic excavator shown in FIG. 2. FIG. In this figure, 20 is a first hydraulic pump, and 21 is a second hydraulic pump. 22, 23, 24, 25
are directional control valves arranged in relation to the first hydraulic pump 20, which form a first valve group. Reference numerals 26, 27, 28, and 29 are directional control valves arranged in relation to the second hydraulic pump 21, which form a second valve group. Reference numeral 7 denotes the above-mentioned arm cylinder, which is configured as a single rod type, and the port 24a of the directional control valve (first directional control valve) 24 forming the first valve group and the bottom chamber 30 of the arm cylinder 7 are connected to each other by a pipe. The port 24b of the directional control valve 24 and the rod chamber 32 of the arm cylinder 7 are connected via a pipe 33.

Further, the port 29a of the directional control valve (second directional control valve) 29 forming the second valve group and the aforementioned pipe line 31 are connected through a pipe line 34,
The port 29b of this directional control valve 29 and the aforementioned pipe line 33 are connected through a pipe line 35. Also 3
6 is a supply circuit that supplies pressure oil to the directional control valve 24;
37 is a first check valve disposed in the supply circuit 36 and prevents backflow of pressure oil supplied to the directional control valve 24; 38 is a supply circuit that supplies pressure oil to the directional control valve 29; 39 is a first check valve disposed in the supply circuit 36; This is a second check valve that is disposed in the supply circuit 38 and prevents the pressure oil supplied to the directional control valve 29 from flowing backward. Note that the boom cylinder 5, bucket cylinder 9, etc. described above are omitted from the drawings to simplify the explanation.

In the hydraulic circuit configured as described above, when the operating lever 11 is operated to switch the directional control valves 24 and 29 to the right position in FIG. 36, the first check valve 37, and the port 24a of the directional switching valve 24 to the conduit 31, and the pressure oil of the second hydraulic pump 21 is led to the supply circuit 38, the second check valve 39, and the directional control valve 24. The pressure oil is led to the conduit 31 via the port 29a of the switching valve 29 and the conduit 34, and the combined pressure oil is supplied to the bottom chamber 30 of the arm cylinder 7. Also, part of the pressure oil in the rod chamber 32 of the arm cylinder 7 is in the pipe 3.
3. It is guided to the tank via the port 24b of the directional switching valve 24, and the rest is guided to the tank via the pipe 33, the pipe 35, and the port 29b of the directional switching valve 29, whereby the arm cylinder 7 is extended. For example, the state shown in FIG. 3 described above is achieved.

Further, when the operating lever 11 is operated in the opposite direction to the above and the directional control valves 24 and 29 are respectively switched to the left position in FIG. The pressure oil of the second hydraulic pump 21 is led to the conduit 33 via the check valve 37 and the port 24b of the directional control valve 24, and the pressure oil of the second hydraulic pump 21 is supplied to the supply circuit 38,
Second check valve 39, port 29 of directional valve 29
b. The pressure oil is led to the pipe line 33 via the pipe line 35, and the combined pressure oil flows into the rod chamber 3 of the arm cylinder 7.
2. Further, a part of the pressure oil in the bottom chamber 30 of the arm cylinder 7 is transferred to the pipe 31 and the directional control valve 2.
4 to the tank via port 24a, and the rest are pipe 31, pipe 34, and port 2 of directional control valve 29.
9a to the tank, whereby the arm cylinder 7 is contracted and becomes, for example, in the state shown in FIG. 2 described above.

By the way, since the above-mentioned arm cylinder 7 is a single rod type, the bottom chamber 30 and the rod chamber 3
There is a difference in the pressure receiving area of 2, for example, the rod chamber 32
The pressure receiving area of the bottom chamber 30 is set to be approximately 1/2 of the pressure receiving area of the bottom chamber 30. Therefore, even if an equal load W acts on the bucket 10 portion during the arm dump shown in FIG. 2 and the arm cloud state shown in FIG. 3, the load W generated in the rod chamber 32 during the arm dump shown in FIG. The holding pressure is set at the bottom chamber 3 at the time of arm crowding as shown in Fig. 3.
The holding pressure generated at 0 is multiplied by the pressure receiving area ratio, that is, 2
About twice as much. On the other hand, leakage of pressure oil from the ports of the directional control valves 24 and 29 to the low pressure side is generally unavoidable due to the design, and especially during the arm dump shown in FIG. 2 where the holding pressure is high, the two directional control valves 24,
29, the amount of leakage is large, and since the area on the rod side is small, even with the same amount of leakage, the amount of movement of the arm cylinder becomes larger. For this reason, there is a problem in that the amount of natural movement, that is, the amount of natural descent of the arm 8 becomes large.

Note that although the arm 8 has been described above, the same thing can happen to the bucket 10 as well.

[Object of the Invention] The present invention has been made in view of the actual situation in the prior art, and its purpose is to solve the problem of pressure oil leakage that occurs when a work machine component such as an arm is held in a predetermined stopped state. The object of the present invention is to provide a hydraulic circuit for a hydraulic machine that can suppress the amount of water.

[Summary of the invention]

To achieve this objective, the present invention provides a plurality of hydraulic pumps, a first directional control valve, a second directional control valve connected to each of these hydraulic pumps,
A hydraulic cylinder connected to the first directional control valve and the second directional control valve, a first check valve that prevents backflow of pressure oil supplied to the first directional control valve, and a second directional control valve. A second check valve that prevents backflow of pressure oil supplied to the directional switching valve, and the hydraulic cylinder is driven by merging the pressure oil of a plurality of hydraulic pumps, the above-mentioned hydraulic cylinder The bottom chamber of the hydraulic cylinder communicates with both the first directional control valve and the second directional control valve, and the rod chamber of the hydraulic cylinder communicates only with the first directional control valve, and
A conduit connecting the first check valve and the first directional control valve and a conduit connecting the second check valve and the second directional control valve communicate with each other, An output port of the second directional control valve that is different from the output port connected to the bottom chamber of the hydraulic cylinder is formed as a closing port, and the pressure oil of the plurality of hydraulic pumps is combined to drive the hydraulic cylinder, and the hydraulic cylinder When a holding pressure is generated in the rod chamber, the structure is such that the holding pressure affects only the first directional control valve.

[Embodiments of the invention]

Hereinafter, the hydraulic circuit of the hydraulic machine of the present invention will be explained based on the drawings. FIG. 1 is a circuit diagram showing an embodiment of a hydraulic circuit of a hydraulic machine according to the present invention. It should be noted that this FIG. 1 is drawn corresponding to the above-mentioned FIG. 4, and the same parts in this FIG. 1 as those shown in the above-mentioned FIGS.

In the embodiment shown in FIG. 1, a pipe line 31 connecting the bottom chamber 30 of the arm cylinder 7 and the port 24a of the directional control valve (first directional control valve) 24, The port 29a of the directional control valve 29 (No. 2) is connected through a pipe 40, and the rod chamber 32 of the arm cylinder 7 is connected via a pipe 33 to the port 24b of the directional control valve 24.
Further, a pipe line connecting the first check valve 37 and the directional control valve 24, which prevents the backflow of the pressure oil supplied to the directional control valve 24, and a pipe line which prevents the backflow of the pressure oil supplied to the directional control valve 29, are provided. A conduit 41 is provided that connects the second check valve 39 to prevent this from happening and the directional control valve 29 . Furthermore, an output port different from the port 29a, which is connected to the bottom chamber 30 of the arm cylinder 7 of the directional control valve 29 via the pipes 40 and 31, is formed as a closed port. The other configurations are equivalent to, for example, the circuit shown in FIG. 4 described above.

In the hydraulic circuit configured as described above, when the operating lever 11 is operated to switch the directional control valves 24 and 29 to the right position in FIG. 1, for example, the pressure oil of the first hydraulic pump 20 is supplied. Circuit 36, first
The second hydraulic pump 2
The pressure oil of No. 1 is led to the pipe line 31 through the supply circuit 38, the second check valve 39, the port 29a of the directional control valve 29, and the pipe line 40, and the combined pressure oil flows to the bottom of the arm cylinder 7. It is supplied to the chamber 30. Further, the pressure oil in the rod chamber 32 of the arm cylinder 7 is led to the tank via the pipe line 33 and the port 24b of the directional control valve 24, thereby causing the arm cylinder 7 to extend, for example, as shown in FIG. It becomes cloud state.

Further, when the operating lever 11 is operated in the opposite direction to the above and the directional control valves 24 and 29 are respectively switched to the left position in FIG. is led to the pipe line 33 through the check valve 37 and the port 24b of the directional switching valve 24,
Further, the pressure oil of the second hydraulic pump 21 is supplied to the directional control valve 2.
Since the closed state is formed in 9 parts, the pressure oil is guided to the pipe line 33 via the supply circuit 38, the second check valve 39, the pipe line 41, and the port 24b of the directional control valve 24, and the combined pressure oil is supplied to the rod chamber 32 of the arm cylinder 7. Part of the pressure oil in the bottom chamber 30 of the arm cylinder 7 is led to the tank via the pipe 31 and the port 24a of the directional control valve 24, and the rest is led to the tank via the pipe 31, the pipe 40, and the port 29a of the directional control valve 29. As a result, the arm cylinder 7 contracts and enters the arm dump state shown in FIG. 2 described above, for example.

In the embodiment configured as described above, when the arm is clouded as shown in FIG. The arm cylinder 7 can be extended by merging the pressure oil of the hydraulic pump 21, and when the arm is dumped as shown in FIG. The pressure oil of the two hydraulic pumps 21 can be combined to contract the arm cylinder 7, and the direction of the pressure oil in the bottom chamber 30 of the arm cylinder 7 can be changed during arm dumping, which requires particularly fast arm speed. Valve 24 and directional valve 29
It is possible to return to the tank through both of the above, and it is possible to obtain good workability equivalent to conventional methods. In addition,
When the arm is clouded, arm cylinder 7
Pressure oil in the rod chamber 32 is returned to the tank only through the directional control valve 24, but in this case, for practical purposes,
No pressure loss problems arise.

In addition, in this embodiment, as shown in FIG. 2, when the arm 8 is held in the inoperative state in the arm dump state, a holding pressure is generated in the rod chamber 32 of the arm cylinder 7 shown in FIG. , this holding pressure is transmitted via the conduit 33, but the conduit 33
Only the directional control valve 24 is connected to the directional control valve 24, that is, the holding pressure at this time is not transmitted to the directional control valve 29. Therefore, the leakage of pressure oil due to this holding pressure is caused by the directional control valve 24. Therefore, the amount of leakage can be suppressed.

In addition, although the embodiment related to the drive of the arm 8 has been given above, the present invention is not limited to this, and the embodiment related to the drive of the arm 8 is described.
It is also possible to apply the present invention to a hydraulic circuit for driving other working machine components corresponding to the above.

〔Effect of the invention〕

Since the hydraulic circuit of the hydraulic machine of the present invention is configured as described above, it is possible to ensure good workability of the work machine constituent members such as the arm as in the conventional case, and also to ensure that the work machine constituent members are controlled in a specified manner. The amount of leakage of pressure oil that occurs when the work machine is held in a stopped state can be suppressed compared to the conventional method, and there is an effect that the amount of natural movement such as the amount of natural descent of the components of the working machine can be reduced.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the hydraulic circuit of the hydraulic machine of the present invention, Fig. 2 is a side view showing the external appearance of a hydraulic shovel taken as an example of the hydraulic machine, and Fig. 3 is similar to Fig. 2. FIG. 4 is a circuit diagram showing a schematic configuration of a conventional hydraulic circuit provided in the hydraulic excavator shown in FIG. 2. 7...Arm cylinder, 8...Arm, 20...
...First hydraulic pump, 21... Second hydraulic pump, 24... Directional switching valve (first directional switching valve),
29... Directional switching valve (second directional switching valve), 30
... bottom chamber, 31, 33, 40, 41 ... pipe line, 36 ... supply circuit, 37 ... first check valve,
38... Supply circuit, 39... Second check valve.

Claims (1)

[Claims] 1 A plurality of hydraulic pumps, a first directional control valve and a second directional control valve connected to each of these hydraulic pumps, and the first directional control valve and the second directional control valve connected to each of these hydraulic pumps.
a hydraulic cylinder connected to the directional control valve, a first check valve that prevents backflow of pressure oil supplied to the first directional control valve, and a pressure oil supplied to the second directional control valve. In the hydraulic circuit of the hydraulic machine, the hydraulic circuit includes a second check valve that prevents backflow of the hydraulic fluid, and drives the hydraulic cylinder by merging the pressure oils of the plurality of hydraulic pumps, wherein the bottom chamber of the hydraulic cylinder is The hydraulic cylinder is connected to both the first directional valve and the second directional valve, and the rod chamber of the hydraulic cylinder is connected only to the first directional valve, and the first check valve and the second directional valve are connected to each other. A pipe line communicating with the first directional control valve and a pipe line communicating the second check valve with the second directional control valve are connected to each other, and the hydraulic cylinder of the second directional control valve A hydraulic circuit for a hydraulic machine, characterized in that an output port connected to a bottom chamber of the hydraulic machine and a different output port are formed as closed ports.