JPH07122275B2 - Boom cylinder control circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic control circuit for a work machine such as a power shovel, and more particularly to a boom cylinder control circuit.

(Prior Art) Conventionally, in power shovels and the like, scraping work such as earthmoving and slope work are performed in addition to excavation work, but the scraping work is performed by using the dead weight of the entire work machine. During work and slope work, three complex operations are performed that simultaneously operate the boom, arm, bucket, and so on.

(Problems to be Solved by the Invention) However, the above-mentioned scraping work and slope work require a considerable amount of precision for finishing, and therefore, the three-complex operation involves fine operations and the like, and thus requires high skill. Only a person could do it. In view of this, the present invention aims to solve the drawbacks of the prior art by providing a boom cylinder control circuit capable of performing the above-mentioned operations without requiring skill and improving finishing accuracy. It was made.

(Means for Solving the Problem) In order to achieve the above object, the first claim of the present invention is that the bottom side receives the amount of oil from the pump when the boom is raised and returns the amount of oil on the head side to the tank, and the head side when lowered. Is the hydraulic circuit of the boom cylinder that receives the amount of oil from the pump and returns the amount of oil to the tank on the bottom side. When the arm is rolled in during scraping and slope work, the boom rises due to the reaction force from the ground. In order to maintain the bucket position at a certain level, a valve that can adjust the flow rate is installed in the return circuit from the head side of the boom cylinder to the tank, and the bottom side circuit has a check that allows suction from the tank. A valve is provided, and in the second aspect, the bottom side and the pump, and the head side and the pump are separately connected from a main circuit. A variety of tank circuits are formed, and a pilot control valve that can adjust the flow rate by an electric signal is installed in the middle of each circuit, and a check valve that can suck from the tank is installed in the main circuit on the bottom side, and the pressing force by the current is applied. The feature is that can be adjusted.

(Operation) With the above structure, when the arm is wound, the boom is always lifted because the boe rises due to the reaction force from the ground. Therefore, the bucket position can be maintained at a horizontal height, and the ground is pressed with appropriate stress, so that scraping work and slope work can be performed.

(Example) Hereinafter, the present invention will be described with reference to the examples shown in FIGS. 1 and 2.

As shown in FIG. 1, the boom cylinder control circuit according to the first aspect of the present invention is arranged such that when the boom 1 rises, the bottom 4 side receives the oil amount from the pump 2 and the head 5 side receives the oil amount.
In the hydraulic circuit of the boom cylinder 3 in which the head 5 side receives the oil amount from the pump 2 when returning and the bottom 4 side returns the oil amount to the tank 6, the arm 13 is used during the scraping work and the slope work. The flow rate provided in the return circuit 7 from the head 5 side of the boom cylinder 3 to the tank 6 so that the boom 1 can be lifted by the reaction force from the ground when the operation is performed so as to keep the position of the bucket 14 at a constant height. Adjustable proportional solenoid valve 8 and check valve 10 that can be sucked from the tank 6 provided in the circuit 9 on the bottom 4 side
Etc.

The proportional solenoid valve 8 is designed so that its opening is determined in proportion to the current value, and is operated by turning on / off a separately provided changeover switch 11. When not operating, it is turned off by a spring 12. It has become. And the changeover switch 11 is ON
That is, the flow rate on the side of the head 5 is reduced during operation.

An arm 13 is provided at the tip of the boom 1, and a bucket 14 (a slope bucket during slope work) is provided at the tip of the arm 13. The arm 13 and the bucket 14 are respectively an arm cylinder 15 and a bucket cylinder 16 respectively. It is designed to be moved by.

The circuits 17 and 18 from the pump 2 to the boom cylinder 3 have a directional switching valve 19 in three positions, and when the switching is made by pushing to the right around the neutral position shown in FIG. The amount of oil enters the bottom 4 side of the boom cylinder 3, the boom 1 rises, and when switched to pull to the left, the oil amount of the pump 2 enters the head 5 side and the boom 1 descends. .

Further, when the direction switching valve 19 is neutral, when the proportional electromagnetic valve 8 is turned on, the boom 1 tries to descend by its own weight, but the hydraulic pressure of the circuit 7 is throttled by the valve 8 and the circuit 7 is closed.
The pressure of becomes high and it floats. The degree of this throttling is such that the boom 1, arm 13, bucket 14 and other work machines maintain a certain height due to their own weight, and when the bucket 14 hits a stone etc. The aperture is like this.

In the present invention, the check valve 10 compensates for the shortage of the amount of oil on the bottom 4 side.

Next, the operation will be described. In normal work such as excavation, the changeover switch 11 is not used and kept in the OFF state.

Next, in the scraping work and the slope work, the direction switching bareb 19 is returned to the neutral position, the boom 1 is kept at a constant height, and the bottom of the bucket 14 is pressed against the ground so as to be balanced by its own weight. Do as if you are involved.

If a lever (not shown) of the arm 13 and the bucket 14 is operated in this state, a reaction force from the ground is received, but since the head pressure of the boom 1 has escaped, the boom 1 is lifted by the reaction force. It can be in a floating mode that automatically moves in the direction. At this time, when the change-over switch 11 is turned on, the proportional electromagnetic valve 8 is switched against the spring 12 so that the passage to the tank 6 which has been closed until now and the head 5 side are communicated while being squeezed, and the head is closed by this throttle. 5
Is kept at a suitable pressure.

That is, when the bucket 14 hits a large stone or the like during the above work, the boom 1 rises and escapes, and in the case of a small stone, the work can be automatically pushed into the ground without escaping.

Then, the check valve 10 replenishes the shortage of the oil amount on the bottom 4 side.

This allows the operator to operate only the arm 13 and the bucket 14 without moving the boom lever.

FIG. 2 shows an embodiment of the second claim of the present invention, and parts common to those in FIG. 1 will be described with the same reference numerals as in FIG.

There is no directional valve as shown in FIG. 1 between the pump 2 and the boom cylinder 3, and between the bottom 4 side and the pump 2,
Further, tank circuits 23 and 24 are respectively provided in the main circuits 21 and 22 between the head 5 side and the pump 2 in a branched manner, and the oil amount is adjusted in the middle of the main circuits 21 and 22 and the tank circuits 23 and 24. Possible pilot control valves (in this embodiment, meter-in valves 25A, 25B in the main circuit and meter-out valves 25C, 25D in the tank circuit) are respectively provided as shown. The meter-in valves 25A and 25B and the meter-out valves 25C and 25D are exactly the same in structure. Further, this arrangement is generally called a logic valve system.

The meter-in valves 25A, 25B and meter-out valves 25C, 25D provided in the main circuits 21, 22 and the tank circuits 23, 24 are electrically connected to an electric operation lever 26 and an operation controller 27, for example, as shown in the figure. Thus, the currents A, B, C, D are connected to the respective valves 25A, 25B, 25C, 25D.

Therefore, when a voltage corresponding to the operation amount is sent to the operation controller 27 by the operation lever 26, it is converted into a current corresponding to the voltage, and the currents A, B, C, D are used to control the valves. The amount of oil passing through 25A, 25B, 25C and 25D is controlled. As a result, during normal work such as excavation, the flow rate from the pump 2 passes through the meter-in valve 25A to the bottom 4
The boom 1 goes up when it goes into the head side through the meter-in valve 25B.

The controller 27 is electrically connected to the signal generator 29 via the changeover switch 28. However, the signal generator 29 is in the OFF state in the case of normal excavation work, etc. When 28 is turned on, it is connected to the controller 27.

A constant current flows when the signal generator 29 is turned on. In this embodiment, the changeover switch 28 is turned off during the scraping work or the slope work, and the current D
Due to this, the meter-out valve of the tank circuit 24 on the head 5 side
It operates 25D to adjust the flow rate.

Each current from the controller 27 causes the meter-in valve 25A, which is in the closed state by the spring 30 when not operating, to operate the meter-in valve 25A against the spring 30 when the oil amount of the pump 2 is supplied to the bottom 4 side. 4 and at the same time, in order to flow from the head 5 side to the tank 6, the current D operates so that the meter-out valve 25D operates against the spring 30 to communicate with the tank 6. Therefore, in this state, no current flows through the meter-in valve 25B and the meter-out valve 25C.

When the meter-in valve 25B and the meter-out valve 25C are operated in exactly the same manner, the amount of oil from the pump 2 enters the head 5, and at the same time, the oil on the bottom 4 side flows into the tank 6. In this state, no current flows through the meter-in valve 25A and the outer-in valve 25D.

In the case of the present invention, the check valve 10 is capable of compensating for the shortage of the amount of oil on the bottom 4 side and adjusting the pressing force by the electric current.

Next, the operation of this embodiment will be described. During normal work such as excavation, the changeover switch 28 is kept on and the signal generator 29 is kept off. Therefore, the signal generator 2
9 does not work. When the boom 1 is raised, the operating lever 26 is operated and a voltage corresponding to the operation amount is sent to the controller 27, which converts the current into a current and the current A operates the meter-in valve 25A against the spring 30. So pump 2
Of oil flows to the bottom 4 of the boom cylinder 3, and at the same time the current D actuates the meter-out valve 25D so that the oil quantity of the head 5 flows to the tank 6 and, as a result, the boom 1 rises.

Similarly, when lowering the boom 1, the current B operates the meter-in valve 25B against the spring 30, so that the oil amount of the pump 2 flows to the head 5, and at the same time, the current C changes the meter-out valve.
Since 25C is operated, the amount of oil in the bottom 4 flows into the tank 6 and, as a result, the boom 1 descends.

Next, for scraping and slope work, meter-in valve 25A
The operation is stopped and the boom 1 is kept at a constant height so that the bottom surface of the bucket 14 is pressed against the ground so as to be balanced by its own weight, and then the arm 13 is wound.

When the arm 13 and the bucket 14 are operated by levers (not shown) in this state, the reaction force is received from the ground as described above. The reaction force causes the boom 1 to be automatically moved in the raising direction. be able to.

That is, in the logic system having independent valves such as the meter-in valves 25A and 25B and the meter-out valves 25C and 25D according to the present invention, the changeover switch 28 is turned off.
By turning on the signal generator 29 and passing a certain current, the hydraulic pressure of the head 5 of the boom cylinder 3 is released to the tank 6 while being appropriately throttled by the operation of the meter-out valve 25C. As a result, when the bucket 14 hits a large stone during the above work, the boom 1 rises and escapes,
In the case of small stones, the work of pushing it into the ground can be done automatically without escaping. And this is the bottom 4
Check valve 10 replenishes the oil shortage. Therefore, the operator need only operate the arm 13 and the bucket 14 without moving the lever of the boom 1.

In the above embodiment, the flow control valve in the first claim is a proportional electromagnetic valve, and the pilot control valve in the second claim is a variable flow meter-in valve and a meter-out valve. However, the present invention is not limited to this. It may be a substitute for this instead of the above.

Further, as the operation means of each valve, the one for turning on / off the changeover switch or the signal generator has been shown, but it is not limited to this.

Especially in the case of the logic system in the embodiment of the second claim, it is naturally possible to correspond the changeover switch and the signal generator with software and hardware of the controller.

(Effects of the Invention) Since the present invention is configured as described above, it is not necessary to move the boom lever as in the conventional case in the scraping work and the slope work, and only the arm or the operation of the arm and the bucket is required. Therefore, the work can be facilitated and made more efficient, and the finishing accuracy is improved.

[Brief description of drawings]

FIG. 1 is a boom cylinder control circuit diagram showing one embodiment of the first claim of the present invention, and FIG. 2 is a boom cylinder control circuit diagram showing one embodiment of the second claim. 1 …… Boom, 2 …… Pump, 3 …… Boom cylinder, 4 ……
Bottom, 5 ... Head, 6 ... Tank, 7 ... Circuit (return), 8
…… Valve (proportional solenoid valve), 9 …… Circuit (bottom side), 10 …… Check valve, 13 …… Arm, 14 …… Bucket, 21,22 …… Main circuit, 23,24 …… Tank circuit, 25A, 25B ...
… Pilot control valve (meter-in valve), 25C, 25D
...... Pilot control valve (meter-out valve), 26
…… Operating lever, 27 …… Controller.

Claims (2)

[Claims] 1. When the boom is raised, the bottom side receives the amount of oil from the pump, the head side returns the amount of oil to the tank, and the lower side receives the amount of oil from the pump, and the bottom side returns the amount of oil to the tank. In the hydraulic circuit of the boom cylinder
During scraping work and slope work, the boom is lifted by the reaction force from the ground when the arm is rolled in, so that the bucket position can be maintained at a constant height. A boom cylinder control circuit that is equipped with a valve that can adjust the flow rate, and a check valve that can suck air from the tank in the bottom circuit. 2. When the boom is raised, the bottom side receives the amount of oil from the pump, the head side returns the amount of oil to the tank, and when the boom is lowered, the head side receives the amount of oil from the pump and the bottom side returns the amount of oil to the tank. In the hydraulic circuit of the boom cylinder
A tank circuit branched from a main circuit in which the bottom side and the pump and a head side and the pump are separately connected is formed, and a pilot control valve whose flow rate can be adjusted by an electric signal is provided in the middle of each circuit and the bottom circuit is provided. The control circuit of the boom cylinder is characterized in that the main circuit on the side is equipped with a check valve that can suck in from the tank, and the pressing force can be adjusted by the current.