JPS6022138B2 - Bucket operation control device for tractor shovels, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control circuit in a loading device for machine tools such as a tractor excavator, and its purpose is to automatically load the load to prevent it from falling when lifting the load. The object of the present invention is to provide a bucket operation control device that controls the loading attitude of a bucket.

Generally, as shown in Fig. 1, the mirror-mounted device for earthmoving machines is attached to a machine frame 1, lifts and lowers a foot arm 2 by operating a lift cylinder 3, and also lifts the tip of the lift arm 2 by operating a bucket cylinder 5. It is constructed so that the supported bucket 4 can be extended or extended, and is used to carry out a series of operations such as excavating, loading, and discharging earth, sand, rocks, and the like.

The present invention is intended to achieve the above object in this type of device, and FIG. 2 shows an embodiment of the operating hydraulic circuit of the present invention in a loading device as shown in FIG. 1, and 6 shows an engine. , 7 is a constant discharge type hydraulic pump driven by the engine 6, and the hydraulic pump 7 supplies pressure oil to the lift cylinder 3 and the bucket cylinder 5.

Reference numeral 8 indicates a directional switching valve for controlling the lift cylinder (hereinafter simply referred to as a lift switching valve); 9 indicates a directional switching valve for controlling a bucket cylinder (hereinafter simply referred to as a bucket switching valve); 10a;
is the switching valve 8 and the piston side chamber 3 of the IJ foot cylinder 3.
10b is a descending flow path that connects the switching valve 8 and the rod side chamber 3b of the lift cylinder 3, and a check valve 14 is interposed in the middle to allow pressure oil to flow only to the rod side chamber 3b. It is being

Reference numeral 11 denotes a flow collecting valve equipped with a pair of throttles 11a and 11b configured to set the flow rate of oil in advance and to flow the oil at an arbitrary ratio.
0b, connected to a first downward branch flow path 20 branched from between the lift switching valve 8 and the check valve 14,
One throttle 11a side suction boat 11d is connected to a second descending branch passage 21 branched from between the rod side chamber 3b and the check valve 14 of the descending passage 10b, and the other throttle 11
The b-side suction boat 11e has a supine flow path 19 that connects the rod side chamber 5b of the bucket cylinder 5 and the bucket flap valve 9.
They are respectively connected to a third descending branch flow path 18 which is further branched.

A second switching valve 13 is disposed in the middle of the branch circuit 18, and this switching valve 13 controls the branch pipe 1 except when high pressure oil is sent to the piston side chamber 3a of the lift cylinder 3.
It has a valve structure that closes 8. Reference numeral 12 denotes a first switching valve that operates in conjunction with the lift switching valve 8, and is branched from a pipe 22 that passes between the pump 7 and the lift switching valve 8, and is located in the middle of a branch pipe 23 connected to the second switching valve 13. It has a valve structure that can open the branch pipe 23 only when the lift switching valve 8 is switched to the lifting boat A.

Reference numeral 24 denotes a foot auxiliary flow path extending from the rod side chamber 3b of the lift cylinder 3, which allows the returned oil in the rod side chamber 3b to flow out to the tank, or from the tank by the suction action from the leaf valve 15 and the rod side chamber 3b. Each of the check valves 16 that can be supplied with oil is connected to the piping and is configured to face the tank.

Reference numeral 25 denotes a bucket auxiliary flow path extending from the piston private chamber 5a of the bucket cylinder 5, and is configured to face the tank via a check valve 17 that can replenish oil from the tank by suction from the piston side chamber 5a. There is.

Note that the first switching valve 12 is not necessarily necessary, and as shown in FIG. As shown in the figure, even if high-pressure oil is branched from the ascending passage 10a and this pressure oil is applied directly to the second switching valve 13, the same functions and effects as described below can be obtained. To explain the operation of the embodiment of the present invention configured as above, first, when lifting the lift cylinder 3,
High pressure oil discharged by a pump 7 driven by an engine 6 is guided to a lift cutoff valve 8 through a check valve.

When the boat of the lift switching valve 8 is switched from the neutral position B to A in order to raise the lift arm 2 (Fig. 1), high pressure oil flows into the piston side chamber 3a of the lift cylinder 3 through the ascending passage 10a. The oil accumulated in the rod side chamber 3b is pushed out and flows through the second descending branch flow path 21 from the suction boat 11d of the flow collecting valve 11 to the throttle 11a side. At this time, the boat of the first switching valve 12 interlocked with the lift switching valve 8 is switched from the closed position E to the open position D, so that the pump 7
The high-pressure oil passes through the branch pipe 23 and operates the second switching valve 13 to open the third descending branch flow path 18, thereby transferring the flow from the rod side chamber 5b of the bucket cylinder 5 to the flow collecting valve 11.
Oil flows into the throttle 11b side. Both apertures 11a, 11b
When the oil flows to the intake boats 11d and 11e, when both throttles reach the set ratio of both throttles 11a and 11b and are balanced,
The oil in the second and third descending branch passages 21 and 18 is transported through the first descending branch passage 21, the descending passage 10b, and the A boat of the lift switching valve 8 to the tank. Reflux. That is, the lifting action of the lift cylinder 3 and the extending action of the bucket cylinder 5 act as a movement. Incidentally, oil is sucked into the piston side chamber 5a of the bucket cylinder 5 from the tank via the check valve 17, and the amount of oil flowing out from the rod side chamber 5b as described above is sufficient to replenish the space created in the piston side chamber 5a when the piston strokes. An amount of oil is inflowed.

In this way, it is possible to control the attitude of the bucket cylinder 3 by moving the bucket cylinder 5 when the lift cylinder 3 is raised, thereby making it possible to prevent the cargo from falling due to the tilt during the raising process of the bucket. .

Note that the piston position of the bucket cylinder 5 when attempting to raise the lift cylinder 3 is not always constant; for example, if you try to raise the lift cylinder when the bucket cylinder is at the end of its descent, the piston position may move toward the bucket cylinder side. There is no flow of oil, and the two throttles 11a and 11b are not balanced, and the cold flow valves are not operated to maintain the closed state of both the suction boats 11d and 11e and the collecting and discharging boat 11c.

In the present invention, in such a case, the return oil in the rod side chamber 3b of the lift cylinder 3 is returned to the tank from the lift auxiliary flow path 24 through the relief valve 15. Therefore, the lift cylinder can move upward. Next, when lowering the lift sill 3, move the boat of the lift switching valve 8 to C.
When switching to
It flows into the rod side chamber 3b of the lift cylinder 3 through the check valve 14.

At this time, high-pressure oil also flows into the first and second descending branch channels 20 and 21, but since the third descending branch channel 18 is in a blocked state, oil does not flow into the throttle 11b of the flow collecting valve 11, and both Aperture 11a
, 11b are not balanced, so the suction boats 11d and 11
e and the collector discharge boat 11c are both shut off, and the collector valve 11
does not operate and oil does not flow. Note that the check valve 14 is provided to pass only the high-pressure oil at this time, and the check valve 16 in the lift auxiliary flow path 24 prevents oil flowing out from the piston side chamber 3a and the rod from the lift cylinder 3, especially when the load is lowered. When the quantitative balance of oil flowing into the side chamber 3b collapses and oil supply is insufficient, the rod side chamber 3 of the cylinder
It acts to replenish oil in b. As described in detail above, according to the hydraulic control circuit of the present invention, when the lift cylinder is raised, the bucket cylinder can be interlocked to smoothly and automatically control the attitude of the bucket, and the throttle of the flow collecting valve can be controlled. The bucket operation can be controlled freely by setting the ratio to any desired ratio, so the load will not fall while the bucket is rising, and there is no need for parts that obstruct visibility, such as mechanical leveling. Ta.

Also, the circuit can be installed in any small space,
Furthermore, by disposing the second check valve 13 in the third descending branch flow path 18, the flow through the branch flow path 18 is completely blocked except when the lift cylinder is raised, so that the flow collecting valve is activated against one's will. There is nothing to do, and it improves workability and safety, and is also excellent in terms of economy.

[Brief explanation of drawings]

FIG. 1 is a side view of a tractor shovel, FIG. 2 is a hydraulic circuit diagram showing one embodiment of the hydraulic control circuit of the present invention, and FIGS. 3 and 4 are hydraulic circuit diagrams showing other embodiments. 3... Lift cylinder, 5... Bucket cylinder, 8.
...Directional switching valve for lift cylinder control, 9...
...Directional switching valve for bucket cylinder control, 1 1...
...Collection valve, 11a, 11b... Throttle of the flow collection valve, 12... First switching valve, 13...
Second switching valve, 14, 16, 17...Check valve, 1
5...Relief/LF. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 A lift cylinder that raises and lowers the lift arm, a bucket cylinder that raises and lowers the bucket supported at the tip of the lift arm, a hydraulic pump that supplies pressure oil to both of the cylinders, and a hydraulic pump that supplies pressure oil to the lift cylinder. In a truck shovel, etc. equipped with a directional control valve for controlling the lift cylinder and a directional control valve for controlling the bucket cylinder that switches the pressure oil to the bucket cylinder, the rod side chamber of the lift cylinder and the directional control valve for controlling the lift cylinder are communicated. A supine flow path 1 that connects the front and rear portions of the check valve 14 in the downward flow path 10b, the rot side chamber of the bucket cylinder, and the bucket cylinder control directional switching valve.
9 to the first, second, and third descending branch channels 20, 2, respectively.
1 and 18, and one end of the second and third branch channels 21 and 18 is formed into a flow collecting valve.
1e, one end of the first downward branching flow path 20 is connected to the flow collecting discharge port 11c of the flow collecting valve, and the third downward branching flow path is controlled by the lift cylinder control directional switching valve. At the same time, a bucket auxiliary flow path 25 is provided in the piston side chamber of the bucket cylinder to supply oil from a tank, and a bucket auxiliary flow path 25 is provided in the rod side chamber of the lift cylinder to supply return oil from the rod side chamber. A bucket operation control device for a tractor shovel or the like, characterized in that each lift auxiliary flow path 24 is connected to a relief valve that allows the flow to flow into a tank.