JP3519282B2 - Winch hydraulic circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a winch hydraulic circuit for raising and lowering a hook portion by winding up and down a wire by hydraulic pressure. 2. Description of the Related 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 too hoisted, the boom or winch may be damaged. 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 a winch from being overwound, a winch hydraulic circuit having an overwind prevention circuit (Japanese Patent Laid-Open No. 10-8 / 1998).
No. 7283), which will be described below with reference to FIGS. For the operation of a hydraulic truck crane whose appearance is shown in FIG. 3, a hydraulic circuit 30 as shown in FIG.
Is provided. The hydraulic circuit 30 includes a boom telescopic switching valve 2, a winch hoisting / lowering switching valve 3, a boom up / down switching valve 4, a boom right-turn left-turn switching valve 5, and an outrigger upward / downward switching valve 6,7. Having. Each of these switching valves is manually operated, and is in a neutral position (a suffix a is attached to the corresponding switching valve in the drawing) and a switching position on both sides thereof (a suffix b in the corresponding switching valve in the drawing). c). Each switching valve is connected to an unload passage 10 supplied with pressure oil from a pump, a tank passage 11 connected to a tank, and actuator passages A1 to A6 and B1 to B6 connected to corresponding hydraulic actuators. Thus, the direction of supply and discharge of pressure oil to and from the actuator is switched. Boom telescopic switching valve 2 is in switching position 2
The boom shortens at b and extends at 2c. The winch hoisting / lowering switching valve 3 performs a hoisting operation at the switching position 3b and a lowering operation at 3c. The boom up / down switching valve 4 operates so that the boom rises at the switching position 4b and falls down at 4c, and the boom right turning left turning switching valve 5 turns the boom left at the switching position 5b and turns right at 5c. The upward / downward switching valves 6, 7 of the jacks of the outriggers 24, 25 (see FIG. 3) move upward at the switching positions 6b, 7b.
Move down at c and 7c. In FIG. 2, reference numeral 12 denotes a differential pressure valve, and reference numeral 40 denotes a pilot circuit of the differential pressure valve. The differential pressure valve 12 includes a switching valve 2,
A pressure release passage 39 that connects the upstream side of a series of unload passages 10 of 3, 4, 5, 6, and 7 and a tank passage (pressure release passage) 11 has a pilot port, and the pilot port is provided. It is connected to the tank passage 11 via a pilot circuit 40. The differential pressure valve 12 is opened by a differential pressure between the pressure on the inlet side and the pilot pressure, and changes the pressure on the inlet side connected to the unload passage 10 to a pressure corresponding to the pilot pressure controlled by the pilot circuit 40. I do. The pilot circuit 40 includes a pilot passage 4
3, 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 are provided in series from the pilot port side of the differential pressure valve 12, Connected to passage 11 and said first
Pilot valve 31, on-off valve 41 and low pressure relief valve 42
The second pilot valve 32 and the third pilot valve 33 are connected in parallel to each other. Further, the differential pressure valve 1
A high pressure relief valve 45 is provided in the middle of a pilot passage 43a branched from the pilot passage 43 and connected to the tank passage 11 on the side of the second pilot port. The overwinding prevention valve 44 is a normally closed electromagnetic opening / closing valve, and is opened by a detection signal from the limit switch 23 of the detection means shown in FIG. The limit switch 23 shown in FIG. 3 is provided at the tip of the boom 21 and detects that the hanging hook 22 approaches the tip of the boom. The on-off valve 41 is an electromagnetic on-off valve that is normally opened, and is operated by an external operation, for example, by operating a push button switch.
Switches to the valve closed state. 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. The truck crane having such a winch hydraulic circuit 30 operates in such a manner that the winch wire can be practically hoisted, that is, the boom extension, the winch hoisting, and the boom operation by operating the switching valves 2, 3, and 4. The second, first,
The switching positions are 32c, 31b, and 33b where the third pilot valves 32, 31, and 33 are in the communicating state. This switching valve 2,
If it is assumed that the hook portion 22 is wound up to a predetermined position near the tip of the boom 21 by one or more of the operations of the limit switch 2 and the limit switch 2,
3 detects and outputs a signal to open the overwinding prevention valve 44. As a result, the pilot passage 43 becomes the tank passage 11
, The differential pressure valve 12 is opened, the unload passage 10 is connected to the tank passage 11, and the switching valves 2, 3, 4,.
Since the pressure oil is no longer supplied to the actuator, all the actuators to which the pressure oil has been supplied by operating the switching valve earlier are stopped, and overwinding is prevented. When the switching valves 2, 3, and 4 are operated in such a direction that the overwinding state is released (boom reduction, winch lowering, boom down direction), the corresponding pilot valve shuts off the pilot passage. Since the state is set, each actuator operates in the operated direction. [0008] In the above-mentioned prior art, the overwinding prevention valve 44 and the first pilot valve 31 cut off the pilot passage 43 from the overwinding prevention valve 44.
Only when only the pilot passage 43 communicates with the pilot passage 43 and then the pilot passage 43 is shut off again, the hydraulic pressure is confined between the overwind prevention valve 44 and the first pilot valve 31. The contained hydraulic pressure acts on the first pilot valve 31 and presses the spool of the first pilot valve 31 in the radial direction. If this radial pressing force is biased,
The sliding resistance between the spool of the first pilot valve 31 and the inner hole in which the spool slides increases, so that a large operating force is required when operating the winch switching valve 3 linked with the first pilot valve 31. However, there is a problem that operability is deteriorated. An object of the present invention is to provide a hydraulic circuit that can improve operability. According to the present invention, there is provided an unload passage connected to a pump, and pressurized oil supplied to the winch for raising and lowering a hook portion of the winch connected to the unload passage. A winch switching valve operated by an operator for discharging, a pressure release passage connecting the unload passage between the pump and the winch switching valve to a tank, and a balance piston provided in the pressure release passage and type of the main relief valve, a first pilot passage connecting the secondary <br/> side chamber of said main relief valve, and detecting means for detecting that the hook is raised to a predetermined position, said detecting means The first pilot passage according to the detection signal.
An overwinding prevention valve communicating from the shut-off state to a second pilot passage connected to the tank, and the second pilot passage between the overwinding prevention valve and the tank interlocked with the winch switching valve. in the hydraulic circuit of the winch and a spool-type pilot valve in communication or block, the over winding protection valve, the said first pilot passage path second pilot
When blocking the passage, characterized in that to connect the second pilot passage of the pilot valve side of the over-winding prevention valve to the third pilot passage that communicates with the tank (claim 1). In a state where the winch switching valve is operated and the winch is hoisting, the pilot valve is in communication with the second pilot passage, but the overwind prevention valve is closed and the second pilot passage is shut off. is there. In other words, the
(2) The main relief valve shuts off the pressure release passage due to the shut-off state of the pilot passage, and the hydraulic pressure of the unload passage can rise, and pressure oil is supplied to and discharged from the winch by operating the winch switching valve. The winch is hoisting. Assuming that the winch winding operation is continued as it is, the hook portion rises to a predetermined position and is detected by the detection means, and the detection signal activates the overwinding prevention valve to move the first pilot passage and the second pilot passage . Because of the communication, the secondary side chamber of the main relief valve is connected to the tank, the main relief valve is opened, and the unload passage communicates with the tank via the pressure release passage. As a result, the pressure in the unload passage is released, and the winch winding operation is stopped to prevent overwinding. In this state, when the winch switching valve is operated to lower the winch, the hook portion is lowered and the detection means is no longer detected, so that the overwind prevention valve is closed. When the winch is being lowered, the winch switching valve is in the lowered switching position, the second pilot passage is shut off by the pilot valve, the main relief valve is closed, and high-pressure hydraulic oil is Has been introduced. Therefore, assuming that the overwinding prevention valve has only a function of simply shutting off between the first and second pilot passages , the high-pressure hydraulic oil introduced into the second pilot passage before the overwinding prevention valve closes. Is closed in the second pilot passage by closing the overwinding prevention valve. However, the pilot valve side the excessive winding valve is in the cutoff state
Since the second pilot passage communicates with the tank via the third pilot passage, the containment of the high-pressure oil is avoided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a hydraulic circuit which can be used in place of the hydraulic circuit 30 (FIG. 2) of the truck crane in the conventional example described above. This is a corresponding configuration of a pilot circuit 40a of the main relief valve 14. This pilot circuit will be mainly described, and other parts equivalent to those in FIG. 2 will be denoted by the same reference numerals and description thereof will be omitted. As the main relief valve 14, a balance piston type relief valve is used, and the switching valves 2, 3, 4,
A pressure release passage 39 connecting the upstream side of the series of unload passages 10, 5, 6 and 7 to the tank passage 11,
It has a secondary side chamber 14a, and the secondary side chamber 14a is connected to the pilot circuit 40a. Main relief valve 14
The valve is opened by the pressure difference between the inlet pressure and the pilot pressure, and the pressure on the inlet connected to the unload passage 10 is controlled to a pressure corresponding to the pilot pressure. The pilot circuit 40a includes a first pilot valve 31, a second pilot valve 32, and a third pilot valve 3.
3. Overwind prevention valve 50, solenoid on-off valve 52, relief valve 5
3. It is composed of a relief valve 45 and the like. A first pilot passage 54, one end of which is connected to the secondary side chamber 14a of the main relief valve 14, is connected to the second pilot passage 51 via the overwinding prevention valve 50, and branches off at two points on the way to each other. Valve 32, first pilot valve 31, third
Although the downstream side is connected to the tank passage 11 via the pilot valve 33, the solenoid valve 52 and the relief valve 52 are inserted in parallel downstream of the first pilot valve 31. Further, a pilot passage 54 a branched from the middle of the first pilot passage 54 is connected to the tank passage 11 via a relief valve 45. The overwinding prevention valve 50 is an electromagnetic valve that can be switched to two positions, and includes first and second pilot passages 54.
And a communication position 50b for connecting the first pilot passage 54 and the third pilot passage 55 and the second pilot passage 51 connected to the separately provided tank passage 11, respectively . It is normally at the cutoff position 50a, and is switched to the communication position 50b by an overwinding detection signal from the limit switch 23. The electromagnetic valve 52 is an electromagnetic valve that is normally opened, and is switched to a closed state by an external operation, for example, by operating a push button switch. The relief valve 53 is a low pressure relief valve that maintains the upstream side at a predetermined low pressure. The relief valve 45 is a high-pressure relief valve that maintains the upstream side at a predetermined high pressure. The hydraulic circuit provided with the above-described pilot circuit 40a includes a supply block body 56 and a boom expansion / contraction switching valve 2 as generally shown in FIG. The block bodies such as the provided block body 57, the block body 58 provided with the winch hoisting / lowering switching valve 3, the block body 59 provided with the boom up / down switching valve 4, and the like are sequentially connected and formed. Each valve constituting the pilot circuit 40a is provided in one of the block bodies. That is, the main relief valve 1
4. The high-pressure relief valve 45 and the overwind prevention valve 50 are provided in the supply block body 56, the electromagnetic on-off valve 52 is provided in the block body 57, and the low-pressure relief valve 53 is provided in the block body 58. In some cases, the block body 58
May be provided together with the low-pressure relief valve 53. The arrangement of such a valve is dependent on the supply block 56
Since the valves are not concentrated on each block, the size of each block body can be equalized. Further, it is possible to reduce or omit a passage for connecting a pilot valve and an electromagnetic on-off valve or a low-pressure relief valve provided in separate block bodies as in the related art. This can reduce the number of passage connection seals and ports between the block bodies. A truck crane having such a winch hydraulic circuit is operated in such a manner that the winch wire can be practically hoisted, that is, the boom is extended by operating the switching valves 2, 3, and 4, the winch is hoisted, and the boom is lifted. When standing up, the second, first, and third
The switching positions are 32c, 31b, and 33b where the pilot valves 32, 31, and 33 are in the communicating state. The switching valves 2, 3,
4, the hook portion 22
Is wound up to a predetermined position near the tip of the boom 21, the limit switch 23 detects this, and outputs a detection signal to switch the overwinding prevention valve 50 to the communicating position. As a result, since the first and second pilot passages 54 and 51 communicate with each other, the main relief valve 14
Is opened, the unload passage 10 is connected to the tank passage 11, and no pressure oil is supplied to each of the switching valves 2, 3, and 4. Therefore, the actuator which has been supplied with the hydraulic pressure by operating the switching valve first However, both stop the operation and prevent overwinding. When the switching valves 2, 3, and 4 are operated in such a direction as to release the over-wound state (boom reduction, winch down, boom down direction), the corresponding pilot valve is switched to the second pilot passage. Because 51 is in the cutoff state,
Each actuator operates in the operated direction. When the hook-in operation is performed, the on-off valve 52 is closed by an external operation. When the switching valve 3 is operated in the direction of winding the winch, the first pilot valve 31 is in a communicating state, but the on-off valve 52 is closed, so that the low-pressure relief valve 53 is in the operating state.
Since the upstream side is maintained at a predetermined low pressure, a low-pressure pilot pressure acts on the secondary side chamber 14a of the main relief valve 14, and the main relief valve 14 maintains the unload passage 10 at a predetermined low pressure. Accordingly, the winch is driven by the low hydraulic pressure to perform a hoisting operation, thereby performing a hook-in operation. Note that the set pressure of the low-pressure relief valve 53 is set as low as possible so that the hook-in operation can be performed. If the boom extension / reduction switching valve 2 or the boom up / down switching valve 4 is erroneously operated in the direction of promoting the overwinding state during the hook-in operation, the second or third valve corresponding to the switching valve is operated. Since the pilot valves 32 and 33 are in a communicating state, the second pilot passage 51 is connected to the tank passage 11 and the main relief valve 14 is opened to open the unload passage 10 even when the on-off valve 52 is in the closed state. Tank passage 1
1, the actuator does not operate and the winch and the boom are reliably prevented from being damaged. The high-pressure relief valve 45 of the pilot passage 54a is effective when the first pilot passage 54 is in the shut-off state, and is set to the allowable limit pressure of the unload passage 10 when the switching valve is operated and the actuator operates. The value is set to a corresponding value, and the limit pressure of the unload passage is controlled by controlling the main relief valve 14 with the pilot pressure. For this reason, the relief valve can be formed smaller than when a high-pressure relief valve is provided directly in the unload passage 10. In this embodiment, since a balance piston type relief valve is used as the main relief valve, the hydraulic pressure acting on the pilot valve is the pump pressure.
Higher than normal pilot pressure. Therefore, when pressure oil is confined between the pilot valve and the overwinding prevention valve 50, the pressing force for pressing the spool of the pilot valve in the radial direction is large, so that the sliding resistance is smaller than the operating force or the spring force. Increase and differential failure (hydraulic lock)
May occur. However, in this embodiment,
When the overwinding prevention valve 50 is switched to the shut-off position, the second pilot passage 51 is connected to the third pilot passage 55 at the shut-off position even if the hydraulic pressure is acting on the second pilot passage 51 before that . It communicates with the tank passage 11.
Thereby, the overwinding prevention valve 5 of the second pilot passage 51
No pressure oil is confined between 0 and the pilot valves 31, 32, 33, so that a large pressing force for pressing the pilot valve in the radial direction does not act, and the sliding of the pilot valve linked to the switching valve. Because the resistance does not increase,
The operability of the switching valves 2, 3, and 4 is not impaired. Further, when the overwinding prevention valve 50 and the pilot valves 2, 3, and 4 are formed in separate blocks as in the embodiment, the above-described hydraulic pressure is not confined and the overwinding is prevented. Oil leakage from the block body mating surface between the prevention valve and the first pilot valve can be reduced. According to the first aspect of the present invention, when the overwind prevention valve shuts off the pilot passage, pressure is not confined in the pilot passage between the overwind prevention valve and the tank. In the pilot valve, no radial pressing force acts on the spool, and the sliding resistance does not increase. Therefore, it is possible to prevent an increase in the operating force of the winch switching valve that is linked to the pilot valve, and to improve the operability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a hydraulic circuit diagram showing one embodiment of the present invention. FIG. 2 is a hydraulic circuit diagram of a winch having conventional overwinding prevention means. FIG. 3 is a schematic front view showing the appearance of a truck crane having a conventional hydraulic circuit. [Description of Signs] 2 Boom telescopic switching valve 3 Winch hoisting / lowering switching valve 4 Boom up / down switching valve 5 Boom left / right turning switching valve 6 Outrigger vertical movement switching valve 7 Outrigger vertical movement switching valve 10 Unload passage 11 Tank passage 14 Main relief valve 31 First pilot valve 32 Second pilot valve 33 Third pilot valve 40a Pilot circuit 45 Relief valve 50 Overwind prevention valve 50a Shut off position 50b Communication position 51 Pilot passage 52 Electromagnetic on-off valve 53 Relief valve 54 Pilot passage 54a Branch pilot passage 55 Pilot passage 56 Supply block 57 Expansion / contraction block 58 Winch block 59 Up / down block

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Jun Nakano 1-16-117, Fukuyoshidai, Nishi-ku, Kobe-shi, Hyogo Nabco Seishin Plant Co., Ltd. (56) References JP-A-9-255286 (JP, A) Kaihei 10-87283 (JP, A) JP-A-9-329107 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F15B 11/00-11/22 B66C 13/20 B66D 1/54

Claims (1)

(57) [Claim 1] An unload passage connected to a pump,
A winch switching valve connected to the unload passage and operated by a pilot to supply and discharge pressure oil to the winch to raise and lower a hook portion of the winch; and an unloading valve between the pump and the winch switching valve. a pressure relief passage connecting the load passage into the tank, and balance piston of the main relief valve provided in said pressure relief passageway, a first pilot passage connecting the secondary side chamber of said main relief valve, the hook portion Detecting means for detecting that has risen to a predetermined position; and
Connect the first pilot passage to the tank from the shut-off state.
A winch having an overwind prevention valve communicating with the pilot passage and a spool type pilot valve interlocking with the winch switching valve and communicating or blocking the second pilot passage between the overwind prevention valve and the tank; in the hydraulic circuit, the over winding protection valve, the first pilot passage channel
When disconnected from the second pilot passage is tangent to the second pilot passage of the pilot valve side of the over-winding prevention valve to the third pilot passage that communicates with the tank
Hydraulic circuit of winches, characterized in that to continue.