JPH0251011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a loading shovel with automatic horizontal extrusion function of bucket.

A loading shovel with a bucket automatic horizontal extrusion function is already known and has a structure as shown in FIG. 1 is a lower traveling body, 2 is an upper rotating body, 3 is a boom, 4 is an arm, 5 is a bucket, 6 is a boom cylinder, 7 is an arm cylinder,
8 is a bucket cylinder, and 9 is a level cylinder. The hydraulic circuit is shown in FIG. The rod side oil chamber 9A of the level cylinder 9 is communicated with the rod side oil chamber 6A of the boom cylinder 6 through a pipe 10, and the bottom side oil chamber 9B of the level cylinder 9 is communicated with the bottom side oil chamber 6B of the boom cylinder 6 through a pipe 11. will be communicated to. The main pumps 12, 13 are the directional valves 14A to 14D, 15A of the directional valve groups 14, 15.
Pressure oil is supplied to the arm cylinder 7, boom cylinder 6, bucket cylinder 8, and other actuators (not shown) through 15D, and the return oil is discharged to the tank 16. The pilot pump 17 includes an arm pilot valve 18 and a boom pilot valve 1.
9 and the pilot valve 20 for the bucket. The output ports of each pilot valve 18 to 20 are connected to the directional control valve 1 by pilot pressure signal circuits a to f.
They are connected to pressure receiving parts 4B, 14D, 15A, and 15C, respectively. 21 is a relief valve.

When the arm pilot valve 18 is operated and a pilot pressure signal is sent to the directional switching valve 14B via the pilot pressure signal circuit a, the pressure oil of the main pump 12 is transferred to the bottom side oil chamber 7B of the arm cylinder 7 by the directional switching valve 14B. As a result, the rod of the arm cylinder 7 is extended and the arm 4 is rotated forward. Along with this, the rod of the level cylinder 9 also extends, oil is sent from the rod side oil chamber 9A to the rod side oil chamber 6A of the boom cylinder 6, the rod of the boom cylinder 6 contracts, and the boom 3 lowers. Therefore, only by operating the arm pilot valve 18, the bucket 5 moves horizontally along the ground surface.

However, the excavation operation ends with the rod of the arm cylinder 7 extended, and the boom 3 is raised to raise the bucket 5 to the soil release position above the dump truck bed, and after the soil is released, the arm cylinder 7 is When the rod is retracted and returned to the position at the start of excavation, the boom 3 rises due to the rod retraction of the arm cylinder 7, so an extra operation is required to lower the boom 3 by the amount of the rise. Furthermore, when the rod of the boom cylinder 6 is in the fully extended state, if the arm cylinder 7 is moved in the rod retraction direction, the volume of the bottom side oil chamber 9B of the level cylinder 9 tends to decrease; Since the volume of the bottom side oil chamber 6B cannot be increased, there is nowhere for the oil to go, and the oil pressure in the pipe line 11 increases, and when it reaches the set pressure of a relief valve (not shown), the relief valve opens and drains the oil. Return to tank. Only then does the rod of the arm cylinder 7 contract, allowing the arm 4 to rotate rearward. In this case, the discharge pressure of the main pump 12 becomes considerably high, and energy is wasted.

Furthermore, as the arm 4 rotates forward, the boom 3 necessarily falls and the bucket 5 is pushed out horizontally, but depending on the excavation site, it is better for the boom 4 not to move when the arm 4 rotates forward. There are cases. For example, if there is a sloped concrete surface on the other side of the accumulated earth and sand, it is better to move the bucket 5 in an arc from bottom to top instead of pushing it out horizontally. The conventional device shown in FIG. 2 cannot meet such demands.

The purpose of the present invention is to solve the above-mentioned problems, eliminate the need for the boom to rise when returning from the soil release position to the excavation start position, and make it possible to retract the arm rearward even when the boom cylinder rod is at its maximum extension. It is an object of the present invention to provide a hydraulic circuit for a loading shovel that can select between horizontal movement and arc movement of the bucket.

In order to achieve this object, the present invention provides a pipe line that communicates between a level cylinder and a boom cylinder when the rod is extended and when the bucket horizontal movement is selected. When the rod is opened, the arm cylinder is retracted, or the bucket is moved in an arc, the pipe is closed and the rod-side oil chamber and bottom-side oil chamber of the level cylinder are communicated with the bottom-side oil chamber of the arm cylinder. It is characterized by being equipped with a switching valve.

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

FIG. 3 shows an embodiment of the invention. Components similar to those in FIG. 2 are designated by the same reference numerals. level cylinder 9
and the rod side oil chambers 9A and 6A of the boom cylinder 6
A switching valve 22 is provided in the middle of the pipes 10 and 11 that communicate between the oil chambers 9B and 6B.
The switching valve 22 is switched to the switching position m by receiving a pilot pressure signal from the pilot pressure signal circuit b via the shuttle valve 23, and is held at the return position n when no pilot pressure signal is input. At the return position n, the pipes 10 and 11 are opened, and at the switching position m
Now, the pipes 10 and 11 are closed, and the rod side oil chamber 9A and bottom side oil chamber 9 of the level cylinder 9 are closed.
B is communicated with the bottom side oil chamber 7B of the arm cylinder 7 through part of the pipes 10 and 11 and the pipe 24.

Another pilot pressure signal circuit g is connected to the shuttle valve 23, and a pilot pressure signal generated by the switching valve 25 is transmitted to this pilot pressure signal circuit g. The switching valve 25 is for selecting either horizontal movement or circular movement of the bucket 5. When horizontal movement is selected, the switching valve 25 is at the switching position x, and when circular movement is selected without generating a pilot pressure signal in the pilot pressure signal circuit g. Sometimes the switching position is y,
A pilot pressure signal is generated in the pilot pressure signal circuit g.

In order to rotate the arm 4 forward, when the arm pilot valve 18 is operated and a pilot pressure signal is generated in the pilot pressure signal circuit a, the directional control valve 14B is operated and the pressure oil of the main pump 12 is turned off. is supplied to the bottom side oil chamber 7B of the arm cylinder 7,
The rod of the arm cylinder 7 is extended, and the arm 4 is rotated forward. At this time, pilot pressure signal circuit b
There is no pilot pressure signal, and the switching valve 25
If horizontal movement of the bucket 5 is selected, there is no pilot pressure signal in the pilot pressure signal circuit g, so the switching valve 22 is at the return position n. As a result, the pipes 10 and 11 are opened, and the level cylinder 9 extends the rod as the arm 4 rotates forward, and the hydraulic pressure generated in the rod side oil chamber 9A is transferred to the rod side oil chamber of the boom cylinder 6. 6A, the rod of the boom cylinder 6 is retracted, and the boom 3 is lowered. That is, as the arm 4 is rotated forward, the boom 3 is lowered by the amount that the tip of the arm 4 is raised, and the tip of the arm 4, that is, the bucket 5 can be moved horizontally.

In order to draw the arm 4 backward, when the arm pilot valve 18 is operated to generate a pilot pressure signal in the pilot pressure signal circuit b, the directional control valve 14B operates and the pressure oil of the main pump 12 is turned off. The oil is supplied to the rod side oil chamber 7A of the arm cylinder 7, the rod of the arm cylinder 7 contracts, and the arm 4
is pulled backwards. At this time, the switching valve 22 is activated by the pilot pressure signal from the pilot pressure signal circuit b.
is switched to switching position m. As a result, the pipes 10 and 11 are closed, and the rod side oil chamber 9A and bottom side oil chamber 9B of the level cylinder 9 are closed.
11, the switching position m of the switching valve 22 and the pipe line 2
4 to the bottom oil chamber 7B of the arm cylinder 7, the pressure oil generated in the bottom oil chamber 9B of the level cylinder 9 as the arm 4 is retracted backward is transferred to the bottom oil chamber 7B of the arm cylinder 7. 7B and the directional control valve 14B into the tank 16, allowing the arm 4 to be quickly retracted rearward. In this way, when the arm cylinder 7 is retracted, the level cylinder 9 is disconnected from the boom cylinder 6, so the boom cylinder 6 does not move and the boom 3 can be prevented from rising. The arm 4 can be retracted rearward even when the rod is in its most extended state.

If arc movement of Bucket 5 is selected,
The switching valve 25 is switched to the switching position y. This generates a pilot pressure signal in the pilot pressure signal circuit, which passes through the shuttle valve 23 to the switching valve 22.
, and switches the switching valve 22 to the switching position m. Therefore, even when the arm cylinder 7 is extended by the rod, the level cylinder 9 is disconnected from the boom cylinder 6, and the boom cylinder 6 does not move. Then, the pressure oil of the main pump 12 is supplied to both the bottom side oil chambers 7B and 9B of the arm cylinder 7 and level cylinder 9 by the operation of the directional control valve 14B, the arm 4 rotates forward, and the bucket 5 is moved from below. Move upward in an arc.

When the arc movement of the bucket 5 is selected and the arm cylinder 7 is extended in a rod manner,
The volume of the bottom side oil chamber 9B of the level cylinder 9 becomes larger and requires oil to flow in from the outside.
Since the pressure in the bottom side oil chamber 7B of the arm cylinder 6 is high and oil is supplied from there, there is no possibility that negative pressure will be generated in the bottom side oil chamber 9B.

The switching valve 22 shown in the embodiment of FIG. 3 is switched to the switching position m by a pilot pressure signal that commands the rod retraction operation of the arm cylinder 7 or a pilot pressure signal that indicates the selection of arc movement of the bucket 5. However, there is also a switching valve that is switched to position n by a pilot pressure signal that commands the rod extension operation of arm cylinder 7 or a pilot pressure signal that indicates horizontal movement selection of bucket belt 5, and is otherwise held at position m. good.

As a means for switching the switching valve 22, the switching valve 2
5 is used, but the present invention is not limited to this, and it can be performed by mechanical means or electrical means. Further, the switching valve 25 is not limited to a manual type, but may be one that detects resistance to horizontal excavation and automatically switches to circular excavation, for example.

As explained above, according to the present invention, during the rod extension operation of the arm cylinder and when the horizontal movement of the bucket is selected, the switching valve provided in the middle of the pipe connecting the level cylinder and the boom cylinder Since the opening is opened, the bucket can be pushed out horizontally by rotating the arm forward, similar to a conventional loading shovel.
When the arm cylinder is retracting the rod, the switching valve closes the pipe, and the rod-side oil chamber and bottom-side oil chamber of the level cylinder are communicated with the bottom-side oil chamber of the arm cylinder. This eliminates the need for the boom to rise when returning from the excavation start position, and the arm can be retracted rearward even when the boom cylinder is at its maximum extension. And when selecting Bucket's arc movement,
Since the pipe is closed by the switching valve and both oil chambers of the level cylinder are communicated with the bottom side oil chamber of the arm cylinder, the bucket can be rotated forward in an arc by the rod extension movement of the arm cylinder. Can be done. This allows you to choose between horizontal movement and arc movement of the bucket.
A variety of excavations can be performed.

[Brief explanation of the drawing]

FIG. 1 is a side view of a conventional loading shovel, FIG. 2 is a hydraulic circuit diagram of a conventional loading shovel, and FIG. 3 is a circuit diagram of an embodiment of the present invention. 3...Boom, 4...Arm, 5...Bucket, 6...Boom cylinder, 7...Arm cylinder, 8...Bucket cylinder, 9...Level cylinder, 6A, 7A, 9A...Rod side oil room, 6
B, 7B, 9B...Bottom side oil chamber, 10, 11...
...Pipeline, 22...Switching valve, 25...Switching valve.

Claims (1)

[Claims] 1.Equipped with a boom cylinder, an arm cylinder, and a bucket cylinder that drive the boom, arm, and bucket, respectively, and a level cylinder installed between the boom and the arm, and between the rod side oil chambers of the level cylinder and the boom cylinder, In the hydraulic circuit of the loading shovel, which communicates between the bottom side oil chamber and the bottom side oil chamber, there is a pipe in the middle of the pipe connecting the level cylinder and the boom cylinder, during the rod extension operation of the arm cylinder, and when the bucket is When horizontal movement is selected, the pipe is opened, and when the arm cylinder rod retracts or when the bucket is moved in an arc, the pipe is closed and the rod-side oil chamber and bottom-side oil chamber of the level cylinder are closed to the arm. A hydraulic circuit for a loading shovel characterized by being provided with a switching valve that communicates with the bottom side oil chamber of the cylinder.