JP3659752B2 - Winch hydraulic circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a winch hydraulic circuit that raises and lowers a hook portion by winding and lowering a wire by hydraulic pressure.
[0002]
[Prior art]
Some conventional winch hydraulic circuits are designed to prevent overwinding. This is because, for example, if a winch attached to a truck crane or the like is wound up too much, the boom or winch may be damaged. The overwinding of the winch is caused not only by the overwinding of the winch itself but also by extending or raising the boom while the winch is wound up. In order to prevent such overwinding of the winch, there is a winch hydraulic circuit having an overwinding prevention circuit, which will be described next with reference to FIGS.
[0003]
A hydraulic circuit 1 as shown in FIG. 2 is provided for the operation of the hydraulic truck crane as shown in FIG. The hydraulic circuit 1 includes a boom expansion / contraction switching valve 2, a winch hoisting / lowering switching valve 3, a boom raising / lowering switching valve 4, a boom right / left turning switching valve 5, an up / down switching valve 6, 7 for an outrigger. Have Each of these switching valves is manually operated, and is in a neutral position (indicated by adding a suffix a to the corresponding switching valve drawing symbol) and switching positions on both sides thereof (subscript b in the corresponding switching valve drawing symbol; c)). Each switching valve has an unload passage 10 to which pressure oil is supplied from a pump, a tank passage 11 connected to a tank (pressure release source) , and actuator passages A1 to A6 and B1 to B6 connected to respective corresponding hydraulic actuators. To switch the direction of pressure oil supply and discharge to the actuator. The boom expansion / contraction switching valve 2 shortens at the switching position 2b and extends at 2c. The winch hoisting / lowering switching valve 3 winds up the winch at the switching position 3b and lowers it at 3c. The boom raising / lowering switching valve 4 operates so that the boom rises at the switching position 4b and bends at 4c. The boom right turn left turn switching valve 5 turns the boom left at the switching position 5b and turns right at 5c. The up / down switching valves 6 and 7 of the outriggers move up at the switching positions 6b and 7b and move down at 6c and 7c. In FIG. 2, reference numeral 12 denotes a high pressure relief valve provided on the upstream side of each switching valve in the unload passage 10. Reference numeral 13 denotes a valve device comprising a differential pressure valve 14 and an overwinding prevention valve 15, which constitutes a part of the overwinding prevention circuit, and further reduces the pressure of the unload passage 10 to operate each part at a low pressure. A low pressure relief valve 16 and an electromagnetic opening / closing valve 17 for controlling the pilot pressure of the differential pressure valve 14 are provided. The electromagnetic on-off valve 17 is operated by a push button.
[0004]
The parts constituting the overwinding prevention circuit are the first, second and third pilot valves 31, 32, 33, the valve device 13, and the limit switch 23 (see FIG. 3). The second pilot valve 32 is provided so as to be interlocked with the operation of the boom expansion / contraction switching valve 2, and is located at the neutral position 32n in a shut-off state when the expansion / contraction switching valve 2 is in the neutral position 2a. The switching position 32b is in the shut-off state, and when the switching position 2c is reached, the switching position 32c is in the communication state. The first pilot valve 31 is provided so as to be interlocked with the operation of the winch hoisting / lowering switching valve 3, and is in the neutral position 31n which is in a shut-off state when the winch switching valve 3 is in the neutral position 3a, and the switching position 3b. If it becomes, it will become the switching position 31b which is a communication state, and if it becomes the switching position 3c, it will become the switching position 31c which is a interruption | blocking state. The third pilot valve 33 is provided so as to be interlocked with the boom raising / lowering switching valve 3, and is in the neutral position 33n which is in a shut-off state when the raising / lowering switching valve 4 is in the neutral position 4a. When the switching position 4c is reached, the switching position 33c is in the shut-off state.
[0005]
These second, first and third pilot valves 32, 31 and 33 are provided in parallel between the downstream side of the overwinding prevention valve 15 connected to the pilot passage 34 of the differential pressure valve 14 and the tank passage 11. .
[0006]
The overwinding prevention valve 15 of the valve device 13 is excited by the detection signal of the limit switch 23 to switch from the valve closed state to the valve open state. As shown in FIG. 3, the limit switch 23 is provided at the distal end portion of the boom 21 and detects that the hanging hook portion 22 has approached the boom distal end portion. Reference numerals 24 and 25 in FIG. 3 denote outriggers.
[0007]
The hydraulic circuit 1 having such an overwinding prevention circuit performs an operation in which the wire of the winch is effectively wound up, that is, the boom is extended by operating the switching valves 2, 3 and 4, the winch is wound up, and the boom is raised. If it does, it will become switching position 32c, 31b, 33b which the 2nd, 1st, 3rd pilot valve 32, 31, 33 corresponding to this will be in a communication state. If the hook portion 22 is wound up to a predetermined position near the tip of the boom 21 by the operation of any one of the switching valves 2, 3 and 4, the limit switch 23 detects this and outputs a signal. Then, the electromagnetic on-off valve 15 is opened. As a result, since the pilot passage 34 communicates with the tank passage 11, the downstream side of the pilot passage 34 of the differential pressure valve 14 becomes the tank pressure, the differential pressure valve 14 is opened, the unload passage 10 is connected to the tank passage 11, Since the pressure oil is not supplied to the switching valves 2, 3, 4 and so, the actuator that has previously been supplied with the pressure oil by operating the switching valve stops its operation to prevent overwinding.
[0008]
In this state, when the operation of lowering the winch wire, that is, when the boom is shortened, the winch is lowered, or the boom is lowered by the operation of the switching valves 2, 3, 4, the second interlocked with the second operation is performed. The first and third pilot valves 32, 31, 33 are switched to the switching positions 32 b, 31 c, 33 c where they are cut off, pressure is generated downstream of the pilot passage of the differential pressure valve 14, and the differential pressure valve 14 is closed. Accordingly, pressure is also generated in the unload passage 10, pressure oil is also supplied to the actuator whose switch valve is operated, and the actuator quickly operates to wind down the winch.
[0009]
In addition, the hydraulic circuit 1 opens the electromagnetic on- off valve 17 to reduce the pressure in the pilot passage 25 to the set pressure of the low-pressure relief valve 16, whereby the pressure in the unload passage 10 is also reduced. The pressure is lowered to the set pressure. When the on-off valve 17 is opened, the overwinding prevention valve 15 is maintained in a closed state. By doing so, the so-called hook-in operation of fixing the hook portion in close contact with the tip of the boom is facilitated.
[0010]
[Problems to be solved by the invention]
In the conventional hydraulic circuit, when the on-off valve 17 is opened to perform a hook-in operation, the inside of the unload passage 10 is reduced to a predetermined low pressure regardless of the operation of each switching valve, and overwinding prevention is also achieved. Since the valve 15 is maintained in the closed state, the overwinding stop function is released, and any actuator can be operated at a low pressure exceeding the limit of overwinding regardless of which switching valve is operated. It becomes possible. This is because, when the hook-in operation is performed, if the expansion / contraction switching valve 2 or the undulation switching valve 4 is erroneously operated for some reason and the boom 21 moves in the direction in which the boom 21 extends or is raised, There is a problem that the winch is damaged. The hook-in operation is performed, for example, when the truck crane moves to another place after the crane work is completed, and the boom 21 is shortened and placed in a lying state. At this time, the hook 22 normally approaches the tip of the boom. The boom 21 and the winch may be damaged because the boom 21 is in an overwound state when the boom 21 is slightly moved in the extending or rising direction.
[0011]
[Means for Solving the Problems]
The means of the present invention includes an unload passage connected to a pressure source, and a winch switching valve connected to the unload passage for supplying and discharging pressure oil to the winch so as to raise and lower the hook portion of the winch according to a switching operation. A pressure release passage connecting the upstream side of the winch switching valve of the unload passage to a pressure release source, one connected to the pressure release source, and the other connected to a pilot portion of the differential pressure valve described later of the pressure release passage. A pilot passage, a differential pressure valve that is provided in the pressure release passage and opens due to a pressure difference between the pressure in the unload passage and the pressure in the pilot passage, and the hook portion approaches the tip of the boom to a predetermined position. In a winch hydraulic circuit comprising a detecting means for detecting this and an overwinding prevention valve provided in the pilot passage that opens in response to a signal from the detecting means, A first pilot valve that is disposed on the pressure release source side of the overwinding prevention valve of the pilot passage and that opens in response to an operation in the direction of winding up the winch of the winch switching valve in conjunction with the operation of the winch switching valve; An opening / closing valve that opens and closes in response to an external operation is provided on the pressure release source side of the first pilot valve, and a relief valve that reduces the inside of the pilot passage to a predetermined pressure in parallel with the opening / closing valve. To do.
[0012]
An opening / closing valve that opens and closes by an external operation on the pressure release source side of the first pilot valve and a relief valve that reduces the inside of the pilot passage to a predetermined pressure in parallel with the opening / closing valve are provided. When the valve is closed, the pilot passage is connected to the pressure release source only through the relief valve. In this state, when the winch switching valve is operated in the winch winding direction, the winch winds up with normal hydraulic pressure when the overwinding prevention valve is not opened. When detection by the detecting means, that is, a state immediately before overwinding is detected, the overwinding prevention valve is opened, and at this time, the first pilot valve is opened, so that the pilot passage is connected to the pressure release source via the relief valve. The pressure of the pilot passage is controlled by the relief valve and is maintained at a predetermined low pressure, whereby the differential pressure valve maintains the unload passage at the predetermined low pressure, so that the winch winds up at that low pressure. . Further, when the winch switching valve is operated in the winch winding direction and the overwinding is detected, the winch is wound up at a low pressure from the beginning. Therefore, if the predetermined low pressure controlled by the relief valve is set appropriately, the hook-in operation can be performed with a hoisting force that does not cause damage to the winch. Further, in the normal winch operation, the on-off valve is opened, and there is no influence on the operation of the winch due to the operation of the winch switching valve.
[0013]
The hook portion of the winch is attached to the tip of a boom that can be extended and retracted hydraulically by hydraulic pressure, and pressure oil is supplied to and discharged from the extension cylinder to extend and retract the boom in response to a switching operation. A telescopic switching valve and a hoisting switching valve for supplying and discharging pressure oil to and from the hoisting cylinder to raise and lower the boom in response to the switching operation are connected, and the boom is interlocked with the operation of the telescopic switching valve in the pilot passage. A second pilot valve that opens in response to an operation in the extending direction and a third pilot valve that opens in response to an operation in the direction in which the boom is raised in conjunction with the operation of the undulation switching valve are the first pilot. It is good to set it as the structure connected in parallel with respect to a valve, the said on-off valve, and the said relief valve.
[0014]
Since the second pilot valve and the third pilot valve are connected in parallel to the circuit composed of the first pilot valve, the on-off valve and the relief valve, respectively, and are directly connected to the pressure release source, That is, when the overwinding detection state and the on-off valve are closed, the second or third pilot valve can be operated even if the undulation switching valve is operated in the direction in which the boom occurs or the expansion / contraction switching valve is operated in the direction in which the boom extends. Since the pilot passage is connected to the pressure release source, the unload passage is connected to the pressure release source via the differential pressure valve, so that the boom does not operate.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a hydraulic circuit 30 that can be used in place of the hydraulic circuit 1 (see FIG. 2) of the truck crane in the conventional example described with reference to FIGS. 2 and 3, and is different from that of FIG. the main point is the structure of the pilot circuit 40 of the differential pressure valve 14, without directly connecting the downstream side of the first pilot valve 31 to the tank passage 11, to connect the open closing 41 and the low-pressure relief valve 42 to the parallel circuit It is connected to the tank passage 11 via The pilot circuit 40 will be described, and other parts equivalent to those in FIG.
[0016]
The differential pressure valve 14 is provided in a pressure release passage 39 that connects the upstream side of the series of unload passages 10 of the switching valves 2, 3, 4, 5, 6, 7 and the tank passage (pressure release passage) 11, and is a pilot The pilot port is connected to the tank passage 11 via the pilot circuit 40. The differential pressure valve 14 is opened by the differential pressure between the pressure on the inlet side and the pilot pressure, and the pressure on the inlet side connected to the unload passage 10 is changed to a pressure corresponding to the pilot pressure controlled by the pilot circuit 40. To do.
[0017]
The pilot circuit 40 includes an overwinding prevention valve 44, a first pilot valve 31, an on-off valve 41 and a low-pressure relief valve 42 connected in parallel in the pilot passage 43 from the pilot port side, Finally, it is connected to the tank passage, and the second pilot valve 32 and the third pilot valve 33 are connected in parallel to the circuit of the first pilot valve 31, the on-off valve 41 and the low pressure relief valve 42, respectively. A high-pressure relief valve 45 is provided in the middle of a pilot passage 43 a that branches off from the pilot passage 43 on the pilot port side and connects to the tank passage 11.
[0018]
The overwinding prevention valve 44 is an electromagnetic on-off valve that is normally closed, and is opened by a detection signal from the limit switch 23 of the detection means described with reference to FIG. The on-off valve 41 is an electromagnetic on-off valve that is normally open, and is switched to a closed state by an external operation, for example, by a push button switch operation. The low pressure relief valve 42 maintains the upstream side at a predetermined low pressure. The high pressure relief valve 45 maintains the upstream side at a predetermined high pressure.
[0019]
Such a truck crane having the hydraulic circuit 30 of the winch is operated so that the wire of the winch is effectively wound up, that is, the boom is extended by the operation of the switching valves 2, 3, 4, the winch is wound up, and the boom is raised. If it does, it will become switching position 32c, 31b, 33b which the 2nd, 1st, 3rd pilot valve 32, 31, 33 corresponding to this will be in a communication state. If the hook portion 22 is wound up to a predetermined position near the tip of the boom 21 by one or a plurality of operations of the switching valves 2, 3, 4, the limit switch 23 detects this, A signal is output to open the overwinding prevention valve 44. As a result, since the pilot passage 43 communicates with the tank passage 11, the differential pressure valve 14 is opened, the unload passage 10 is connected to the tank passage 11, and pressure oil is supplied to each switching valve 2, 3, 4. Therefore, all the actuators previously supplied with pressure oil by operating the switching valve stop operating, and overwinding is prevented. In this state, when the switching valves 2, 3, 4 are operated in the direction in which the winch is lowered, the corresponding pilot valve puts the pilot passage 43 in the shut-off state, so that each actuator quickly winds the winch. Operates in the downward direction.
[0020]
When performing the hook-in operation, the on-off valve 41 is closed by an external operation. When the switching valve 3 is operated in the direction to wind up the winch, the first pilot valve 31 is in the communication state, but the on-off valve 41 is closed, so that the low-pressure relief valve 42 is in the operating state, and the upstream side thereof is since maintaining a predetermined low pressure, the differential pressure valve 14 acts low pressure pilot pressure to maintain the unload passage 10 to a predetermined low pressure in the differential pressure valve 14. Accordingly, the winch is driven by the low pressure hydraulic pressure to perform a hoisting operation, thereby performing a hook-in operation. The set pressure of the low pressure relief valve 42 is set as low as possible so that the hook-in operation is possible.
[0021]
Further, when the boom expansion / conversion switching valve 2 or the boom raising / lowering switching valve 4 is mistakenly operated in the direction in which the winch is wound up during the hook-in operation, the second or third pilot valves 32, 33 corresponding to the switching valve are operated. Since the pilot passage 43 is connected to the tank passage 11 and the on-off valve 41 is closed, the differential pressure valve 14 opens and connects the unload passage 10 to the tank passage 11. The actuator does not operate, the winch is not rolled up, and damage to the winch and boom is reliably prevented.
[0022]
The high pressure relief valve 45 in the pilot passage 43a is effective when the pilot passage 43 is in a shut-off state, and is a value corresponding to the allowable limit pressure of the unload passage 10 when the switching valve is operated and the actuator operates. The differential pressure valve 14 is controlled by the pilot pressure to control the limit pressure of the unload passage. For this reason, a relief valve can be formed in a small size compared with the case where a high pressure relief valve is provided directly in the unload passage 10.
[0023]
【The invention's effect】
The invention according to claim 1 has an effect that the work of hook-in can be easily performed.
According to the second aspect of the present invention, when the open / close valve is closed and the relief valve is in an operating state for the hook-in operation, the raising / lowering switching valve is set in the direction in which the boom occurs or the extension switching valve is set in the direction in which the boom extends. Even if it is operated erroneously, the pilot passage is connected to the pressure release source, and the boom does not operate in the direction where it is raised or extended, so that the winch and the boom can be reliably prevented from being damaged.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.
FIG. 2 is a hydraulic circuit diagram of a winch having conventional overwinding preventing means.
FIG. 3 is a schematic front view showing the appearance of a conventional truck crane having a winch hydraulic circuit.
[Explanation of symbols]
2 Telescopic switching valve (boom)
3 winch selector valve (winding up and down)
4 Undulating valve (boom)
5 Rotation direction switching valve (boom)
6 Outrigger up / down switching valve 7 Outrigger up / down switching valve 10 Unload passage 11 Tank passage 14 Differential pressure valve 21 Boom 22 Hook 23 Limit switch 30 Hydraulic circuit 31 First pilot valve 32 Second pilot valve 33 Third pilot valve 40 Pilot circuit 41 open closing 42 low-pressure relief valve 43 pilot passage 44 over winding prevention valve 45 pressure relief valve

Claims (2)

An unload passage connected to the pressure source, a winch switching valve connected to the unload passage for supplying and discharging pressure oil to the winch so as to raise and lower a hook portion of the winch according to a switching operation, and an unload passage of the unload passage A pressure release passage that connects the upstream side of the winch switching valve to a pressure release source, a pilot passage that one is connected to the pressure release source and the other is connected to a pilot portion of a differential pressure valve of the pressure release passage. A differential pressure valve provided in a pressure release passage and opened by a differential pressure between the pressure in the unload passage and the pressure in the pilot passage; and a detecting means for detecting that the hook portion has approached a boom tip to a predetermined position. And an overwinding prevention valve provided in the pilot passage that opens in response to a signal from the detection means. A first pilot valve is provided which is disposed on the pressure release source side of the overwinding prevention valve and opens in response to the operation of the winch switching valve in the direction of winding up the winch in conjunction with the operation of the winch switching valve. An opening / closing valve that opens and closes according to an external operation on the pressure release source side of the pilot valve, and a relief valve that reduces the inside of the pilot passage to a predetermined pressure in parallel with the opening / closing valve. Hydraulic circuit. The hook portion of the winch is attached to the tip of a boom that can be extended and retracted hydraulically by hydraulic pressure, and pressure oil is supplied to and discharged from the extension cylinder to extend and retract the boom in response to a switching operation. A telescopic switching valve and a hoisting switching valve for supplying and discharging pressure oil to and from the hoisting cylinder to raise and lower the boom in response to the switching operation are connected, and the boom is interlocked with the operation of the telescopic switching valve in the pilot passage. A second pilot valve that opens in response to an operation in the extending direction and a third pilot valve that opens in response to an operation in the direction in which the boom is raised in conjunction with the operation of the undulation switching valve are the first pilot. 2. The winch hydraulic circuit according to claim 1, wherein the hydraulic circuit is connected in parallel to the valve, the on-off valve and the relief valve.

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