JP3074545B2 - Crane boom raising device for construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crane used for a mobile excavator, a trench excavator, and other construction machines, and more particularly to a crane for a construction machine which supports a suspended load with a boom slightly tilted forward.

[0002]

2. Description of the Related Art Conventionally, in such a crane, the boom must be laid substantially horizontally when moving, and a boom elevating cylinder which stands and holds the boom almost vertically during operation hinders handling and lifting and lowering of tools and suspended loads. Since fear must be eliminated, it is common to connect a boom elevating cylinder between the platform and the boom on the boom staying side. (See, for example, Japanese Utility Model Publication No. 37-23637)

However, in this prior art, when increasing or decreasing the working radius of a tool or a suspended load, that is, the boom tilt angle, the winding winch of the stay cable is rotatable and the boom tilt cylinder is controlled to extend and contract to control the boom tilt. It is common to fix the boom in that position by adjusting the angle and then tensioning the stay line by manipulating the winding winch or the like, so the operation of adjusting the boom tilt angle is very troublesome. Not only that, but also a crane operator and an operator of the cable hoisting winch are required, which causes a problem of labor saving.

[0004] Also, when increasing or decreasing the boom tilt angle, the boom tilt cylinder is used only as described above.
If the load on the boom elevating cylinder becomes extremely large, as in a large-diameter deep-hole excavator, oil leakage is likely to occur due to damage to the packing of the boom elevating cylinder, and the boom must be stopped at a predetermined inclination angle. The problem that it becomes impossible to do it occurs.

For example, when the boom at the forward tilt position (a) shown by the chain line in FIG. 3 is raised to a position (b) near the vertical shown by the solid line in FIG. The moment arm of the boom elevating cylinder contraction force, which attempts to raise the boom with the end foot pin as a fulcrum, gradually increases as the boom rises closer to the vertical than when the boom is in the forward leaning position. The moment that the boom is caused to fall by the load gradually decreases as the boom stands closer to the vertical than when the boom is in the forward leaning position.Therefore, the upper oil chamber of the boom elevating cylinder having a small piston pressure receiving area. The hydraulic pressure supplied to the boiler fluctuates significantly, so during drilling work where the boom tilt angle is frequently adjusted, the packing of the boom elevating cylinder is damaged. Will tend to cause oil leakage and,
Until the stay cable is tensioned, the tilt angle of the boom set at the predetermined tilt angle, that is, the digging position, will be out of order.

[0006]

SUMMARY OF THE INVENTION The present invention maintains the stay line in a substantially constant tension state regardless of whether the boom is raised by the boom elevating cylinder, and generates an upper oil chamber when the boom elevating cylinder is contracted. An object of the present invention is to solve the above problem by reducing high pressure by a moment due to a constant stay rope tension.

[0007]

SUMMARY OF THE INVENTION The present invention provides a three-way directional control valve for controlling a boom elevating cylinder, and drives a staying line bobbin in a winding direction only when the boom elevating cylinder is extended or retracted. A hydraulic motor control circuit that is controlled in conjunction with the direction switching valve so as to connect a hydraulic pressure source of the hydraulic motor to be operated and a relief cable for restraining cable tension in parallel to a hydraulic motor control circuit. A constant position is provided for connecting the hydraulic oil chamber of the brake release cylinder of the energized winding cylinder brake device to the tank, and the hydraulic oil chamber is connected to the hydraulic pressure source only when the boom elevating cylinder is extended or retracted. Then, a switching valve that is switched in conjunction with the direction switching valve is inserted into the hydraulic motor control circuit, and the extension and extension of the boom raising cylinder is performed.
When the retracting operation is performed, the stay cable is configured to be always tense.

[0008]

FIG. 1 shows an embodiment of the present invention. A boom raising cylinder control circuit 1 supplies hydraulic pressure of a first hydraulic power source 6 with a relief valve to upper and lower oil chambers 4 and 5 of the boom raising cylinder 3 respectively. A tandem center type three-position directional control valve 7 to be discharged;
Counter balance valves 10, 10 inserted in the middle of supply / drain oil passages 8, 9 to the upper and lower oil chambers on the boom raising cylinder side,
The pilot oil passages 10a and 11a of the counter balance valves are connected to supply / discharge oil passages 9 and 8 on the other side, respectively. T indicates a tank.

A control circuit 2 of a hydraulic motor 13 operatively connected to the winding line 12 of the stay cable controls a second hydraulic power source 14 for rotating the hydraulic motor forward in the winding direction of the stay cable, and limits the tension of the stay cable. A hydraulic pressure inlet 13a of the hydraulic motor 13 includes a relief valve 15 and a brake release cylinder 16 of a winding cylinder brake device which is constantly biased by a compression spring or the like so as to stop the winding cylinder. , The hydraulic oil chamber 16a of the brake release cylinder 16 is connected to the tank T, and the hydraulic oil inlet 13a and the hydraulic oil chamber 1
A switching valve 17 for pilot operation, which has a switching position connecting the second hydraulic pressure source 6a to the second hydraulic pressure source 14 and the relief valve 15, is inserted into the hydraulic motor control circuit 2.

Accordingly, a high pressure selection valve (shuttle valve) 18 for taking out the oil pressure of the high pressure side port is connected between the A and B ports of the directional control valve 7 for controlling the boom raising cylinder.
The switching valve 17 is operated by the pilot pressure 17 by the removal hydraulic pressure.
As a result, the switching valve 17 is switched to the switching position in conjunction with the direction switching valve 7.

As described above, the second hydraulic source (hydraulic pump) is used to drive the hydraulic motor 13 and the brake release cylinder 16.
Although the embodiment provided with 14 has been described, the first hydraulic source (hydraulic pump) 6 can be used instead of providing the second hydraulic source. FIG. 2 shows an embodiment in such a case. In FIG. 2, members denoted by the same reference numerals as those in FIG. 1 indicate corresponding members.

In the embodiment shown in FIG. 2, the diversion valve 1 is connected to the A and B ports of the directional control valve 7 for controlling the boom raising cylinder.
A high-pressure selection valve (shuttle valve) 21 for connecting between the output ports D and D on the non-operating side of the boom elevating cylinders of the two flow dividing valves 19 and 20 to extract the hydraulic pressure of the high-pressure port.
And a hydraulic inlet 13a of the hydraulic motor 13 at the time of take-up rope winding is connected to the hydraulic take-out oil passage 22 of the high-pressure selection valve 21.
, A relief valve 15 and a switching valve 23 with a throttle for controlling the brake release cylinder 16 are connected in parallel, and the switching valve 23 connects the hydraulic oil chamber 16a of the brake release cylinder 16 to the tank T Connected to
When the removal oil pressure of the high-pressure selection valve 21 acts on the hydraulic removal oil passage 22, the switching valve 23 is piloted 23a by the removal oil pressure, and the oil pressure of the hydraulic removal oil passage 22 acts on the hydraulic oil chamber 16a. The release of the winding drum brake device is the same as in the previous embodiment.

Each of the flow dividing valves 19 and 20 is connected to the first hydraulic pressure source 6 respectively.
The input hydraulic pressure supplied from the boom elevating cylinder operating side output port C and the non-operating side output port D is
It is a matter of course that the flow rate is divided and output at a fixed ratio regardless of the magnitude of the load pressure of the output ports C and D.

Reference numeral 24 denotes an emergency valve for releasing the brake. When the emergency valve 24, which is normally switched to the lower position in the figure, is switched to the upper position, the hydraulic pressure of the auxiliary hydraulic source 25 is sequentially applied to the oil passage 2.
6, supplied to the hydraulic oil chamber 16a of the brake release cylinder 16 through the shuttle valve 27 and the switching valve 23 at the switching position to release the brake device for the winding cylinder. When controlling the boom elevating cylinder, the emergency The oil passage 26 is connected to the tank T while the valve 24 is maintained at the lower position in the figure, so that the switching valve 23 can be switched to the switching position only by the hydraulic pressure of the hydraulic oil passage 22.

FIG. 3 shows an embodiment of a large-diameter and deep-hole excavator to which the present invention is applied. A pair of left and right boom elevating cylinders 3 are connected to the gate-shaped or frame-shaped boom 30 on the side of the staying cable extension side of the boom, and the upper end is fixed or locked 32 to the upper end of the boom 30. The lower ends of the pair of left and right stay lines 33 are wound around a pair of left and right winding drums 12 attached to the rear end of the machine base 29, respectively. In the embodiment shown in FIGS. 1 and 2, only one boom raising cylinder 3 and one winding drum 12 are shown for simplification of drawing, but these are provided on both sides of the machine base 29, respectively. And

Numeral 34 denotes a hydraulically driven winch mounted on the machine base 29. One of the ropes 35 extended from the winch 34 suspends a hammer grab bucket 36 via a pulley device at the upper end of the boom 30. A crown 37 for lowering and controlling opening and closing of a lower excavating blade 36a of the hammer club bucket in cooperation with the winding cable 35 is suspended and supported by a pair of left and right suspension cables 38 passing through a pulley device at the upper end of the boom. A crown elevating and lowering adjusting device 39 for adjusting the length of the sling cable between the crown 37 and the upper end of the boom as shown in a chain-line front boom falling position (a) and a solid line near vertical position (b) is provided at the top of the boom. The hole is dug by raising and lowering the hammer grab bucket 36 with the winch 34 at the (b) position of the boom 30, and the excavated soil is tilted to the forward falling position (b). Although for discharging it is lowered as the chain line indicates the Baketsuto 36 and crown 37 from beam,
Such a technique has been disclosed in Japanese Patent Application Laid-Open No. 3-208982 and the like.

Reference numeral 29a denotes a flat U-shaped work table attached to the front end of the machine base 29, 40 denotes four front jacks which horizontally support the work table 29a, and 41 denotes a work table which can be pushed down or pulled up to the work table 29a. A rotary press-fitting device that is pushed in while rotating the casing tube 42 prior to digging,
43 denotes a rear jack supporting the rear end of the machine base 29, and 44 denotes an operator cab.

[0018]

In order to increase the angle of inclination of the boom with the load hung forward, a three-position directional control valve in the neutral position applies a high-pressure operating oil pressure corresponding to the load to the upper oil chamber side of the boom elevating cylinder. When the boom elevating cylinder is switched to the retracted position of the boom elevating cylinder that supplies oil and discharges the oil in the lower oil chamber to the tank, the hydraulic oil chamber of the hydraulic motor and the hydraulic oil chamber of the brake release cylinder are operated in conjunction with this. At the same time, hydraulic pressure is supplied from a hydraulic source (hydraulic pump), and the hydraulic motor causes the bobbin to wind and tighten the stay line.

At this time, in a hydraulic pump (a positive displacement pump), the discharge pressure is determined by the load, and the discharge pressure rises when the load, that is, the stay cable tension becomes excessive, but the maximum discharge pressure is limited by the relief valve. Therefore, when the boom is retracted due to the contraction of the boom elevating cylinder and the winding of the stay cable by the bobbin while the boom is tilted forward, there is no possibility that the load carried by the stay cable becomes excessive. The boom elevating cylinder contraction force is reduced according to the moment causing the boom by force (this is usually much larger than the moment arm of the boom elevating cylinder contraction force causing the boom), The operating oil pressure of the upper oil chamber is reduced accordingly, and damage to the packing of the boom elevating cylinder can be prevented.

When the boom is raised to a predetermined position and the three-position directional control valve is returned to the neutral position to stop the boom elevating cylinder from contracting, the hydraulic motor for driving the winding drum is operated in conjunction with the directional control valve. At the same time as being stopped,
Since the operating oil pressure of the brake release cylinder is discharged to the tank, the bobbin of the stay cable is fixed with a constant frictional force by the brake device. On the other hand, the discharge hydraulic pressure of the hydraulic pressure source is discharged from the relief valve to the tank.

In this state, the three-position directional control valve is switched to the extension position of the boom elevating cylinder, and the operating oil pressure is supplied to the lower oil chamber side, so that the oil in the upper oil chamber is released by the corresponding counterbalance valve. When discharging to the tank and tilting the boom forward while applying back pressure, the operating hydraulic pressure is low because the boom is biased forward by the load, and the packing of the boom elevating cylinder may not be damaged. Absent. Also, in conjunction with the switching of the direction switching valve, the discharge hydraulic pressure of the hydraulic power source urges the bobbin driving hydraulic motor in the retracting line winding direction, but the retracting line tension may increase due to the above-described forward tilting of the boom. Therefore, the hydraulic motor is driven in reverse by the tension of the stay cable to extend the stay cable from the bobbin, and the hydraulic pressure of the hydraulic source is discharged from the relief valve to the tank to maintain the stay cable tension substantially constant. .

When the boom is to be raised and lowered between, for example, a horizontal falling position (C) shown by a chain line in FIG. 3 and a vertical falling position (B) shown by a solid line in FIG. Since no load is applied, the operating oil pressure of the boom elevating cylinder is relatively low even if a predetermined tension is applied to the stay cable, and there is no danger of damaging the packing of the boom elevating cylinder.

The mechanism for controlling the hydraulic motor for driving the bobbin and the brake release cylinder of the brake for the bobbin in conjunction with the direction switching valve of the boom elevating cylinder is limited to the pilot operating mechanism shown in the illustrated embodiment. It is needless to say that any mechanism can be adopted.

[0024]

As described above, the boom elevating device of the present invention operates the three-position directional control valve for controlling the boom elevating cylinder connected between the machine base and the boom on the boom staying side. Not only can the boom be lowered while maintaining the tension of the boom staying cable approximately constant, but also prevent damage to the packing due to an increase in operating oil pressure when the boom raising cylinder contracts, and reduce the boom tilt angle. Deterioration can be prevented.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of one embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of another embodiment of the present invention.

FIG. 3 is a side view of a large-diameter deep-hole excavator to which the present invention is applied.

[Explanation of symbols]

 2 Hydraulic motor control circuit 3 Boom elevating cylinder 4 Upper oil chamber of boom elevating cylinder 5 Lower oil chamber of boom elevating cylinder 6 Hydraulic power source of boom elevating cylinder control circuit 7 3 direction switching valve 10 Upper oil chamber side counter balance valve DESCRIPTION OF SYMBOLS 11 Counterbalance valve at the lower oil chamber side 12 Rewinding line winding cylinder 13 Hydraulic motor 13a Hydraulic motor inlet for hydraulic motor 14 Hydraulic motor control circuit 15 Hydraulic motor control circuit 15 Relief valve for restraining line tensioning device 16 Brake release cylinder 17 Switching valve 18 High pressure selection Valve (shuttle valve) 23 Switching valve 30 Boom 33 Stay cable

Claims (1)

(57) [Claims] 1. A construction machine crane having a boom elevating cylinder connected between a machine base and a boom on a boom staying cable laying side, a three-position directional control valve for controlling the boom elevating cylinder, and the boom elevating. Only when the cylinder is being extended or retracted, the operating hydraulic power source and the relief cable tension limiting relief valve are connected in parallel to the hydraulic inlet of the hydraulic motor that should drive the winding rope in the winding direction in the winding direction. A hydraulic motor control circuit controlled in conjunction with the direction switching valve,
The hydraulic oil chamber of the brake release cylinder of the winding cylinder brake device which is constantly biased is provided with a permanent position for connecting the hydraulic oil chamber to the tank, and the hydraulic oil chamber is connected to the hydraulic power source only when the boom elevating cylinder is extended or retracted. A switching valve that is switched in conjunction with the direction switching valve is inserted into the hydraulic motor control circuit so that the extension cable is always taut when the boom elevating cylinder is extended or retracted. Boom lifting device for construction machinery cranes.