JPH08302752A - Boom-lifting priority hydraulic circuit for hydraulic shovel - Google Patents

Abstract

PURPOSE: To improve operatability by increasing the speed of boom lifting when the composite operation of the boom lifting and bucket closing of a hydraulic shovel is conducted. CONSTITUTION: A piston 20 for controlling a bucket-closing stroke is installed at one end of a spool for a directional control valve 13 for a bucket. A boom- lifting pilot oil path 21 is branched, and connected to the inlet port 20a of the piston 20. when the composite operation of boom lifting and bucket closing is performed, the piston 20 is extended by the pilot secondary pressure of boom lifting, and the spool for the directional control valve 13 for the bucket is controlled so as not to be moved up to a full stroke to the bucket-closing side. Accordingly, the quantity of oil passed through the directional control valve 13 for the bucket and supplied to a hydraulic cylinder 18 for the bucket is reduced, and the quantities of oil fed to hydraulic cylinders 16a, 16b for a boom are augmented, thus increasing the speed of boom lifting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a hydraulic excavator, and more particularly to a boom raising priority for increasing the amount of oil supplied to the boom directional control valve when performing a combined boom raising and bucket closing operation. It relates to a hydraulic circuit.

[0002]

2. Description of the Related Art A hydraulic circuit of a conventional hydraulic excavator is shown in FIG. A boom directional control valve 2 and a bucket directional control valve 3 are connected in parallel to the first hydraulic pump 1, and an arm directional control valve 5 is connected to the second hydraulic pump 4.

By operating the boom remote control valve, the spool of the boom directional control valve 2 is switched, and the oil discharged from the first hydraulic pump 1 is supplied to the boom hydraulic cylinders 6a, 6b. Further, the spool of the bucket directional control valve 3 is switched by the operation of the bucket remote control valve, and the oil discharged from the first hydraulic pump 1 is supplied to the bucket hydraulic cylinder 8 through the supply oil passage 7. Further, the spool of the arm directional control valve 5 is switched by operating the remote control valve for the arm, and the oil discharged from the second hydraulic pump 4 is supplied to the arm hydraulic cylinder 9.

[0004]

SUMMARY OF THE INVENTION In a hydraulic excavator in which a boom directional control valve and a bucket directional control valve are connected in parallel to a hydraulic pump, a combined operation of raising the boom and closing the bucket is performed when loading the dump truck with sediment. In the case of carrying out, the boom raising speed became slow due to the large amount of oil supplied to the bucket side, and the operability was not good.

Therefore, when a combined operation of raising the boom of the hydraulic excavator and closing the bucket is performed, the amount of oil supplied to the directional control valve for the boom is increased to increase the boom raising speed to improve the operability during the combined operation. A technical problem to be solved in order to improve the situation arises, and an object of the present invention is to solve this problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above object, and is a hydraulic excavator in which a boom directional control valve and a bucket directional control valve are connected in parallel to a hydraulic pump. A piston for restricting the closing stroke of the bucket is installed at one end of the spool of the bucket directional control valve, and the boom raising pilot oil passage of the boom directional control valve is branched to connect to the piston inlet port. In a hydraulic excavator in which a boom directional control valve and a bucket directional control valve are connected in parallel to a circuit and a hydraulic pump, a switching valve having a throttle position and an open position is provided on an oil passage supplied to the bucket directional control valve. Install a pressure switch in the boom raising pilot oil passage of the directional control valve for the boom, and insert the bucket directional control valve into the bucket. Closed pilot oil passages are equipped with pressure switches, each pressure switch is connected to the AND circuit input terminal, and the switching valve is operated to the throttle position by the output signal of the AND circuit. A circuit is provided.

[0007]

In the invention according to claim 1, when the remote control valve for the boom is operated to the raising side, the pilot secondary pressure is supplied to the boom raising pilot oil passage, and the spool of the boom directional control valve is opened. It switches and the boom rises. At this time, the piston provided at one end of the spool of the bucket directional control valve extends due to the secondary pilot pressure.

When the combined operation of raising the boom and closing the bucket is performed, when the spool of the directional control valve for the bucket moves to the closing side, the spool comes into contact with the piston and the stroke of the spool toward the closing side of the bucket is restricted. It is impossible to move to the full stroke. Therefore, the oil passage of the bucket directional control valve is throttled to reduce the amount of oil supplied to the bucket hydraulic cylinder, the amount of oil supplied to the boom hydraulic cylinder is increased, and the boom raising speed is increased.

According to the second aspect of the invention, when the remote control valve for the boom is operated to the raising side, the secondary pilot pressure is supplied to the boom raising pilot oil passage,
The boom directional control valve spool switches and the boom rises. At this time, the pressure switch provided in the boom raising pilot oil passage senses the pilot secondary pressure and turns on. Further, if the remote control valve for the bucket is operated to the closing side, the pilot secondary pressure is supplied to the bucket closing pilot oil passage, the spool of the bucket directional control valve is switched, and the bucket is closed. At this time, the pressure switch provided in the bucket closing pilot oil passage senses the secondary pilot pressure and turns on.

When a combined operation of raising the boom and closing the bucket is performed, both of the pressure switches are turned on, and a signal is output from the output terminal of the AND circuit. The output signal operates the switching valve to restrict the throttle. Switch to position. Therefore, the amount of oil supplied from the hydraulic pump to the bucket directional control valve decreases, the amount of oil supplied to the boom hydraulic cylinder via the boom directional control valve increases, and the boom raising speed increases.

[0011]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a boom-up priority hydraulic circuit for a hydraulic excavator according to claim 1, wherein a boom directional control valve 12 and a bucket directional control valve 13 are connected in parallel to a first hydraulic pump 11. The directional control valve 15 for the arm is connected to the second hydraulic pump 14.

By operating a boom remote control valve (not shown), the spool of the boom directional control valve 12 is switched, and the oil discharged from the first hydraulic pump 11 is supplied to the boom hydraulic cylinders 16a, 16b. Also,
By operating a remote control valve (not shown) for the bucket, the spool of the bucket directional control valve 13 is switched, and the oil discharged from the first hydraulic pump 11 is supplied to the oil supply passage 17.
And is supplied to the bucket hydraulic cylinder 18. Further, the spool of the arm directional control valve 15 is switched by the operation of the arm remote control valve (not shown), and the oil discharged from the second hydraulic pump 14 is supplied to the arm hydraulic cylinder 19.

A piston 20 is provided at one end of the spool of the bucket directional control valve 13. The piston 2
0 is installed in the direction in which the spool of the bucket directional control valve 13 moves toward the bucket closing side. Then, the boom raising pilot oil passage 21 of the boom directional control valve 12 is branched and connected to the inlet port 20a of the piston 20.

If the remote control valve for the boom is operated to the raising side, the boom raising pilot oil passage 2
The secondary pilot pressure is supplied to 1, and the spool of the boom directional control valve 12 moves to the left in the drawing to switch to the boom raising position. Therefore, hydraulic fluid is supplied from the first hydraulic pump 11 to the oil passage 22 via the boom directional control valve 12, the boom hydraulic cylinders 16a and 16b extend, and the boom rises. At this time, the secondary pilot pressure is also supplied to the inlet port 20a of the piston 20, and the piston 20 extends and approaches one end of the spool of the bucket directional control valve 13.

On the other hand, if the remote control valve for the bucket is operated to the closing side, the pilot secondary pressure is supplied to the bucket closing pilot oil passage 23, and the spool of the bucket directional control valve 13 moves to the right in the figure. Switch to the bucket closing position. Therefore, the hydraulic oil that has passed through the supply oil passage 17 from the first hydraulic pump 11 is supplied to the bucket hydraulic cylinder 18 via the bucket directional control valve 13,
The bucket hydraulic cylinder 18 extends to close the bucket.

When a combined operation of raising the boom and closing the bucket is performed, the piston 20 extends due to the secondary pilot pressure in the boom raising pilot oil passage 21, and the spool of the bucket directional control valve 13 closes. When it moves to, it comes into contact with the piston 20 and the stroke of the spool toward the bucket closing side is restricted, and the spool cannot move to the full stroke. Therefore, the oil passage of the bucket directional control valve 13 is throttled, the amount of oil supplied to the bucket hydraulic cylinder 18 is reduced, the amount of oil supplied to the boom hydraulic cylinders 16a, 16b is increased, and the boom raising speed is increased. Get faster

FIG. 2 shows a boom hoisting priority hydraulic circuit for a hydraulic excavator according to a second aspect of the present invention. The same components as those of the hydraulic circuit shown in FIG. As shown in the figure, the bucket directional control valve 13
A switching valve 24 having a throttle position and an open position is provided on a supply oil passage 17 for supplying pilot oil discharged from a pilot pump 25 to a pilot oil passage 27 by controlling it with a solenoid valve 26.

When the solenoid valve 26 is turned on,
The spool is switched to the open position and the pilot oil passage 27
Pilot oil is supplied to the pilot port 24a of the switching valve 24, and pilot pressure is applied to the switching port 24 to switch the switching valve 24 to the throttle position. On the other hand, when the solenoid valve 26 is turned off, the spool is switched to the closed position to shut off the pilot oil, the pilot oil in the pilot oil passage 27 returns to the tank, and the switching valve 24 returns to the open position.

Here, the boom raising pilot oil passage 2
1 is provided with a pressure switch 28 for detecting the secondary pilot pressure for raising the boom, and the pressure switch 28 is connected to an AND circuit 29.
Connect to one of the input terminals. Further, a pressure switch 30 for detecting the pilot secondary pressure when the bucket is closed is provided in the bucket closing pilot oil passage 23.
0 is connected to the other input terminal of the AND circuit 29. Further, the output terminal of the AND circuit 29 is connected to the solenoid valve 26.
Connect to the solenoid of.

When the combined operation of raising the boom and closing the bucket is performed, the secondary pilot pressure is supplied to the boom raising pilot oil passage 21 to cause the boom directional control valve 12 to operate.
The spool is switched to the raised position, the boom hydraulic cylinders 16a and 16b extend, the boom rises, and the secondary pilot pressure is supplied to the bucket closing pilot oil passage 23 so that the bucket directional control valve 13 spools. Switching to the closed position, the bucket hydraulic cylinder 18 extends and the bucket closes.

At this time, the pressure switch 28 is turned on by detecting the pilot secondary pressure for raising the boom, and the pressure switch 3 is detected by detecting the pilot secondary pressure for closing the bucket.
0 turns on. When both pressure switches 28 and 30 are turned on, a signal is output from the output terminal of the AND circuit 29, and this output signal causes the solenoid valve 26 to
Turns on.

As described above, when the solenoid valve 26 is turned on, the switching valve 24 is switched to the throttle position, and the amount of oil supplied to the bucket directional control valve 13 is reduced. Therefore, the boom hydraulic cylinders 16a, 16b are supplied from the first hydraulic pump 11 via the boom directional control valve 12.
The amount of oil supplied to the boom hydraulic cylinder 16 increases.
The extension speeds of a and 16b are increased.

Thus, when a combined operation of raising the boom and turning is performed, the boom raising speed is increased and the operability is improved. Since the switching valve 24 is switched to the throttle position by the output signal of the AND circuit 29, the switching valve 24 is not switched only by the boom raising operation or the bucket closing operation, which adversely affects other combined operations or single operations. Never give.

Although the pilot operated switching valve 24 is used in this embodiment, a solenoid operated switching valve (not shown) may be used instead. And
An AND circuit 2 is used for the solenoid of the solenoid operated switching valve.
If the output terminal of 9 is connected, the switching valve is directly operated by the output signal of the AND circuit 29 during the combined operation of raising the boom and closing the bucket, and the switching valve switches to the throttle position to the bucket directional control valve 13. The amount of oil supplied to is reduced.

Therefore, the present invention can be variously modified without departing from the spirit of the present invention, and it is obvious that the present invention covers the modifications.

[0026]

As described in detail in the above-mentioned one embodiment, the present invention according to claim 1 is such that when the boom raising and bucket closing operations are combined, a boom raising pilot secondary operation is performed. The piston extends due to the pressure, and the piston restricts the spool of the bucket directional control valve from moving to the bucket closing side to the full stroke. Therefore, the amount of oil that passes through the bucket directional control valve and is supplied to the bucket hydraulic cylinders decreases, the amount of oil supplied to the boom hydraulic cylinders increases, and the boom raising speed increases.

According to the second aspect of the invention, when the boom raising and the bucket closing are combined, both the pressure switch on the boom raising pilot oil passage and the pressure switch on the bucket closing pilot oil passage are operated. When turned on, the switching valve is operated to the throttle position by the output signal of the AND circuit. Therefore, the amount of oil supplied to the bucket directional control valve decreases, the amount of oil supplied to the boom hydraulic cylinder via the boom directional control valve increases, and the boom raising speed increases.

Thus, in both the invention of claim 1 and the invention of claim 2, the boom raising speed at the combined operation of boom raising and bucket closing is increased, and the operability is remarkably improved. .

[Brief description of drawings]

FIG. 1 shows an embodiment of the invention according to claim 1, and is a boom raising priority hydraulic circuit diagram of a hydraulic excavator.

FIG. 2 is a boom hydraulic circuit diagram of a boom of a hydraulic excavator, showing an embodiment of the invention according to claim 2;

FIG. 3 is a hydraulic circuit diagram of a conventional hydraulic excavator.

[Explanation of symbols]

 11 First Hydraulic Pump 12 Boom Directional Control Valve 13 Bucket Directional Control Valve 17 Supply Oil Path 20 Piston 20a Inlet Port 21 Boom Raising Pilot Oil Path 23 Bucket Closing Pilot Oil Path 24 Changeover Valve 26 Solenoid Valve 28 Pressure Switch 29 AND Circuit 30 Pressure switch

Claims (2)

[Claims] 1. In a hydraulic excavator in which a boom directional control valve and a bucket directional control valve are connected in parallel to a hydraulic pump, a bucket closing stroke regulating piston is provided at one end of a spool of the bucket directional control valve, and a boom is provided. A boom raising priority hydraulic circuit for a hydraulic excavator, characterized in that the boom raising pilot oil passage of the directional control valve is branched and connected to the inlet port of the piston. 2. In a hydraulic excavator in which a boom directional control valve and a bucket directional control valve are connected in parallel to a hydraulic pump, a switching valve having a throttle position and an open position on an oil passage supplied to the bucket directional control valve. And a pressure switch in the boom raising pilot oil passage of the boom directional control valve, and a pressure switch in the bucket closing pilot oil passage of the bucket directional control valve.Each pressure switch is connected to the AND circuit input terminal. And a boom raising priority hydraulic circuit for a hydraulic excavator, wherein the switching valve is operated to a throttle position by an output signal from an AND circuit.