JPH046823B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boom hoisting device for a construction machine, such as a truck crane or a hydraulic excavator, for hoisting a boom.

For example, some truck cranes and hydraulic excavators have a pair of double-acting hoisting cylinders connected to both sides of the boom, and the boom moves up and down by the expansion and contraction of these hoisting cylinders. That is, the pair of undulating cylinders has a first
When pressure oil is supplied from the hydraulic pump to the pressure chamber,
They extend together to perform the raising operation of the boom, and
On the other hand, when pressure oil from the hydraulic pump is supplied to the second pressure chamber, both chambers contract to lower the boom.

By the way, in a boom that is hoisted using a pair of hoisting cylinders, when hoisting the boom is stopped and held at a constant hoisting angle, the holding force of both hoisting cylinders is made equal to prevent the boom from twisting. There is a need. For this reason, in the past, the first pressure chambers of both undulating cylinders were communicated with each other via a communication pipe, thereby making the oil pressure in each first pressure chamber uniform and equalizing the above-mentioned holding force. There is something. However, in this case, if an accident such as breakage occurs in the communication pipe, there is a possibility that the boom cannot be held by both the undulating cylinders. For this reason, both ends of the communication pipe close to each first pressure chamber are normally positioned with a predetermined biasing force in the open position that throttles the communication pipe, and the differential pressure before and after the communication pipe is It is known that each device is provided with a throttle opening/closing valve that is switched to a position that closes the communicating pipeline when the urging force becomes larger than the above-mentioned biasing force, such as in the case of a break in the communicating pipeline. Therefore, if such throttle on-off valves are provided in the communication pipes, oil leakage may occur due to breakage in the communication pipe between these throttle on-off valves. When a large pressure difference occurs in the communication pipe, each throttle opening/closing valve can be closed by this pressure difference, thereby making it possible to hold the boom. For this reason, the above-mentioned throttle opening/closing valve should be one with excellent responsiveness that immediately closes when a large pressure difference occurs in the pressure in the communication pipe before and after it due to a rupture accident, etc. It is being

However, when using such a throttle opening/closing valve with excellent responsiveness, there may be a slight deviation in the timing of its closing operation depending on the fracture position of the communication pipe, so it is necessary to equalize the pressure in each of the first pressure chambers. It is difficult to close the communication pipe in this state. For this reason, after each throttle opening/closing valve is closed, the holding force of the boom of each hoisting cylinder becomes uneven, causing a problem that the boom is twisted.

This invention was made based on the above circumstances, and its purpose is to make it possible to equalize the holding force of the boom in each hoisting cylinder even if a breakage accident occurs in the above-mentioned communication pipe. Our objective is to provide boom hoisting devices for construction machinery.

In other words, in this invention, both ends of the communication pipe adjacent to the first pressure chamber of each undulating cylinder are normally biased to the throttle open position, and when the differential pressure before and after the pressure chamber exceeds a predetermined value. A first throttle opening/closing valve that can be switched to the closed position is provided, and each first throttle opening/closing valve is connected to the communication pipe, and when each first throttle opening/closing valve is switched to the closed position, the first throttle opening/closing valve is connected to the first throttle opening/closing valve. Drain relief pipes are provided in the communication pipes to release the drain, and these drain relief pipes are normally energized to an open position that throttles the drain relief pipes, and when the differential pressure before and after the drain pipes exceeds a predetermined value. The invention is characterized in that a second restrictor opening/closing valve is provided, which can be switched to a closed position in some cases.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a hydraulic circuit that raises and lowers the boom of a truck crane, hydraulic excavator, etc., and numeral 10 in the figure is a hydraulic pump. This hydraulic pump 10 sucks up the oil in the hydraulic tank 11,
Pressure oil is supplied to the double-acting type hoisting cylinders 13, 13 of the boom via a 4-port, 3-position directional control valve 12. That is, the directional control valve 12
One of the output ports of is connected to the first main hydraulic pipe 14, and this first main hydraulic pipe 14 is connected to the first main hydraulic pipe 14.
The undulation cylinders 13, 1 are connected via branch pipes 15, 15.
It is connected to the first pressure chambers 16, 16 of No. 3. On the other hand, the other output port of the directional control valve 12 is connected to the second main hydraulic pipe 17, and the second main hydraulic pipe 17 is connected to the second main hydraulic pipe 17 via the second branch pipes 18, 18 to the second main hydraulic pipe 17. It is connected to two pressure chambers 19, 19. Note that 20 is a relief valve that keeps the pressure of pressure oil sent from the hydraulic pump 10 constant, and 21 is a return pipe for the pressure oil.

A double check valve 22 and a counterbalance valve 23 are interposed in the first main hydraulic pipe 14 from the side closer to the directional control valve 12, respectively. The counterbalance valve 23 transfers the pilot pressure to the second main hydraulic pipe 1.
7 through a pilot tube 24.

Hydraulic pressure holding valves 25, 25 are interposed in each of the first branch pipes 15, 15, respectively. These oil pressure holding valves 25, 25 are composed of a check valve part 26 directly interposed in the first branch pipes 15, 15, respectively, and a double-acting cylinder part 27 that opens and closes the check plunger of these check valve parts 26. has been done. The operation of these cylinder parts 27, 27 is controlled by the contraction side pilot pipe 28.
This is done by the pilot pressure introduced through the extension side pilot pipe 29.

That is, the contraction side pilot pipe 28 is located between the double check valve 22 and the directional control valve 12.
The extension side pilot pipe 29 is connected to the main hydraulic pipe 14 , and the extension side pilot pipe 29 is connected to a pipe line 30 connecting the first main hydraulic pipe 14 and the second main hydraulic pipe 17 between the counterbalance valve 23 and the double check valve 22 . It is connected to the shuttle valve 31 inside. Therefore, the first and second main hydraulic pipes 14, 1 are connected to each cylinder portion 27, 27.
7 will be led as pilot pressure.

Further, bypass pipes 32, 32 are connected to each of the first branch pipes 15, 15, respectively, to bypass the oil pressure holding valves 25, 25. Therefore, in the case of this embodiment, the first pressure chambers 16, 16 of the undulating cylinders 13, 13 can communicate with each other using the first branch pipes 15, 15 and the bypass pipes 32, 32 as communication pipes. ing. First throttle opening/closing valves 33, 33 are interposed in the bypass pipes 32, 32, respectively. Each first throttle opening/closing valve 33 is connected to a bypass pipe 32
The valve has two positions: a throttle open position X that throttles the flow, and a closed position Y that closes the bypass pipe 32. Normally, each first throttle opening/closing valve 33 is operated by a spring 33a.
The aperture opening position X is biased and positioned by the biasing force. In FIG. 1, the first throttle opening/closing valves 33, 33 are shown as valves that simply switch between two positions, but the throttle amount at the throttle open position X gradually increases until it reaches the closed position Y. It may also be a valve. Further, a first differential pressure pilot pipe 34 is connected to the bypass pipe 32 between each first throttle opening/closing valve 33 and the first pressure chamber 16 of the undulating cylinder 13, and this first differential pressure pilot pipe 3
4, the differential pressure in the bypass pipe 32 before and after each first throttle valve 33 acts in the direction of switching each first throttle valve 33 to the closed position Y against the first biasing force. It's summery. That is,
In the case of this embodiment, in the normal state, the bypass pipes 32, 32 are in a state of communication with each other because the first throttle opening/closing valves 33, 33 are positioned at the respective throttle open positions X. The pressure difference in the bypass pipe 32 before and after the first throttle opening/closing valve 23 is smaller than the first biasing force, so each first throttle opening/closing valve 33 is maintained at the throttle open position X. However, if a portion of the bypass pipes 32, 32 or the first branch pipes 15, 15, which serve as communication pipes connecting the first throttle opening/closing valves 33, 33, is ruptured and oil leaks, each of the first throttle opening/closing valves 33, 33 The pressure difference before and after the valves 33 is larger than the first biasing force, and each first throttle opening/closing valve 33 is switched to the closed position Y by this pressure difference.

Moreover, each of the first throttle opening/closing valves 33, 33 and the bypass pipes 32, 32 are connected to the drain relief pipes 35, 35.
When each first throttle opening/closing valve 33, 33 switches to its closed position Y, the drain is connected to each drain relief pipe 35, 3.
5 to bypass pipes 32, 32. Second throttle opening/closing valves 36, 36 are interposed in the drain relief pipes 35, 35, respectively. Each of these second throttle opening/closing valves 36, 36 is normally operated by a spring 36.
The second biasing force caused by a biases the drain relief pipes 35, 35 to the throttle open position It is set to switch to Y. In addition, in the second throttle opening/closing valves 36, 36, similarly to the first throttle opening/closing valves 33, 33,
Although shown as a valve that simply switches between two positions, it may also be a valve that gradually increases the amount of throttle at the throttle open position X and reaches the closed position Y. Furthermore, in FIG. 1, 37, 37 are second throttle opening/closing valves 36, 36
2 shows the second differential pressure pilot tube.

By the way, in the case of this embodiment, the region 38 surrounded by the dashed line in FIG. 1 is 1 as shown in FIG.
The holding valve is configured as one holding valve, and the specific structure of this holding valve will be briefly explained below.

Reference numeral 40 in FIG. 2 is the housing, and this housing 40 is provided with ports A, B, C, and D, respectively.
D corresponds to the position with the same symbol in the hydraulic circuit shown in FIG. In other words, 4 in Figure 2
Reference numeral 1 designates a check plunger 41 of a check valve portion 26 in the oil pressure holding valve 25, and this check plunger 41 is capable of closing a valve hole 43 formed in the middle of an internal passage 42 connecting ports A and B.
Note that 44 is a valve spring that urges the check plunger 41 in a direction to close the valve hole 43. Also, 4
5 is a piston of the cylinder portion 27 in the oil pressure holding valve 25, and a rod 46 of this piston 45
extends coaxially toward the check plunger 41. Further, the bypass pipe 32 is connected to the inner hole 47 in FIG. 2, the housing 40 and the check plunger 4.
1, and a passage 50 in the spool 49 slidably inserted into the check plunger 41.
and a passage 51 communicating with an internal passage 42 in the check plunger 41, and a throttle 52 of the first throttle opening/closing valve 33 is formed in the middle of this passage 51. Further, in this embodiment, the opening portion 53 of the passage 51 that communicates with the passage 50 in the spool 49 is long and has a predetermined length in the sliding direction of the spool 49. Therefore, as shown in FIG. 2, when the passages 50 and 51 are in communication with each other, the first throttle opening/closing valve 33 is in the throttle open position
When the passages 50 and 51 are moved to the left in the figure and the communication between them is cut off, the first throttle opening/closing valve 33 moves to the closed position Y.

On the other hand, in the case of FIG. 2, the drain relief conduit 35 includes a hole 55 formed in the head 54 of the check plunger 41, a space 57 between the holder 56 housed in the check plunger 41 and the check plunger 41, and a space 57 between the holder 56 and the check plunger 41. It is constituted by the formed hole 58, a space 59 within the holder 56, a passage 61 within the plunger 60 slidably fitted into the holder 56, and a space 62 between the spool 49 and the holder 56. In this embodiment, the passage 61
A throttle 63 of the second throttle opening/closing valve 36 is provided in the middle. Therefore, when the hole 58 of the holder 56 is in communication with the space 59 inside the holder 56 as shown in FIG. If the communication between the hole 58 and the space 59 is cut off by moving to the left in FIG.
6 moves to its closed position Y.

Next, the operation of an embodiment with such a configuration will be explained based on FIG. 1.

First, when raising the boom, pressure oil is supplied from the hydraulic pump 10 to the first main hydraulic pipe 14 via the directional control valve 12 . In this case, the luffing cylinder 1 is connected to the first main hydraulic pipe 14 via the double check valve 22, the counterbalance valve 23, the oil pressure holding valves 25, 25, and the first branch pipes 15, 15.
Pressure oil is supplied to each of the first pressure chambers 16, 16 of the first pressure chambers 16, 13, whereby both the undulating cylinders 13, 13 are extended, and the boom can be raised. In addition, as the hoisting cylinders 13, 13 expand, the second branch pipes 18, 18, the second main hydraulic pipe 17, the directional control valve 12, and the return pipe 21 are connected to the second pressure chambers 19 of the hoisting cylinders 13, 13. Oil is returned to the hydraulic tank 11 via. In this case, the oil pressure of the first main hydraulic pipe 14 is transferred to each cylinder part 27 of the oil pressure holding valve 25 via the contraction side pilot pipe 28.
Since the pilot pressure is introduced as pilot pressure, each cylinder portion 27 is in a contracted state.
Only the flow of pressure oil toward each of the first pressure chambers 16 of No. 3 and 13 is allowed. In other words, if we consider Figure 2,
The pressure of the pressure oil flowing from port A moves the check plunger 41 to the right in FIG. and flows out from port B. In addition, the return oil from each cylinder part 27 is sent to the extension side pilot pipe 29, the shuttle valve 31,
It is returned to the hydraulic tank 11 via the pipe line 30, the second main hydraulic pipe 17, the directional control valve 12, and the return pipe 21.

Next, when the boom is to be lowered, pressure oil from the hydraulic pump 10 is supplied to the second main hydraulic pipe 17 via the directional control valve 12. Than this,
From this second main hydraulic pipe 17 to second branch pipes 18, 18
Pressure oil is supplied to each second pressure chamber 19 of the undulating cylinders 13, 13 via the undulating cylinders 13, 13. Therefore, both the hoisting cylinders 13, 13 can be retracted to perform the hoisting motion of the boom. In this case, at the same time as the pressure oil is supplied to the second main hydraulic pipe 17, the pressure oil in the second main hydraulic pipe 17 is supplied as pilot pressure to each hydraulic pressure via the pipe line 30, the shuttle valve 31, and the extension side pilot pipe 29. Guided to each cylinder portion 27 of the holding valve 25,
Each cylinder portion 27 is extended to forcibly open its check valve portion 26. If you look at this in Figure 2, port C
The piston 45 is moved to the right in the figure by the pressure oil flowing in from the piston 45, so that the rod 46 of the piston 45 comes into contact with the check plunger 41, causing the check plunger 41 to be separated from the valve hole 43. Become. In this case, each cylinder part 2
The return oil from 7 is returned to the first main hydraulic pipe 14 via the contraction side pilot pipe 28.

Further, the pressure oil in the second main hydraulic pipe 17 is guided as pilot pressure to the counterbalance valve 23 via the pilot pipe 24.
open. Note that this counterbalance valve 23 is opened after the check valve portion 26 of each oil pressure holding valve 25 is forcibly opened.
Therefore, when both the undulation cylinders 13, 13 are contracted, the return oil from the first pressure chambers 16, 16 of the undulation cylinders 13, 13 flows into the first branch pipe 1.
5, 15, oil pressure holding valves 25, 25, counter balance valve 23, and double check valve 22.
It returns to the main hydraulic pipe 14 and is returned to the hydraulic tank 11 from this first main hydraulic pipe 14 via the directional switching valve 12 and the return pipe 21. In this case, the double check valve 22 will generate a pressure difference before and after it due to the internal throttle, but this pressure difference will be transmitted to each oil pressure holding valve 25 via the shuttle valve 31 and the expansion side pilot pipe 29. It is guided to each cylinder part 27.

In addition, when the hoisting cylinders 13, 13 are extended, the directional control valve 12 is set to the neutral position, and the hoisting cylinder 1
3 and 13, the pressure in each first pressure chamber 16 of the undulation cylinders 13 and 13 is maintained by the oil pressure holding valves 25 and 25 and the counterbalance valve 23, and the pressure in each first pressure chamber 16 of each Since the first throttle opening/closing valves 33, 33 are in communication with each other via the throttle opening position X, the pressures of the first throttle opening/closing valves 33, 33 are uniformly adjusted. Furthermore, when the directional control valve 12 is set to the neutral position and the operation of the hoisting cylinders 13, 13 is stopped from the time of contraction of the hoisting cylinders 13, 13,
The pilot pressure guided from the second main hydraulic pipe 17 to each cylinder part 27 of the hydraulic pressure holding valves 25, 25 disappears, but as mentioned above, the double check valve 2
2, a pressure difference is generated in the first main hydraulic pipe 14 due to the restriction, and this pressure difference is applied to the pipe line 30 and the shuttle valve 3 as pilot pressure.
1 and an extension-side pilot pipe 29 to each cylinder portion 27 of the oil pressure holding valves 25, 25, and hold these oil pressure holding valves 25, 25 open. In other words, the oil pressure holding valves 25, 25 are closed only after the pilot pressure from the second main hydraulic pipe 17 disappears, the counterbalance valve 23 closes, and as a result, no oil flows through the double check valve 22. . Note that after this, the undulation cylinders 13, 1
The pressure in each of the first pressure chambers 16 of 3 is controlled by a hydraulic pressure holding valve 25,
25 and the counterbalance valve 23, and since each of the first throttle opening/closing valves 33, 33 is in the throttle open position X, it goes without saying that they are mutually evenly balanced.

Next, in the case of an emergency situation such as a rupture in the pipeline between the oil pressure holding valves 25, 25 and the counterbalance valve 23 from the normal operating state as described above,
Due to oil leakage from the rupture point, a large pressure difference is generated in the bypass pipes 32, 32 before and after each of the first throttle opening/closing valves 33. Therefore, these first throttle opening/closing valves 33, 33 move from the normal throttle open position X to the closed position Y.
However, in this case, the flow rate of the drain released from each first throttle opening/closing valve 33 to each bypass pipe 32 via the drain relief pipe 35 is such that the second throttle opening/closing valve 36 is in the throttle open position X. It will be narrowed down because of this. Therefore, the pressure difference generated before and after each of the second throttle valves 36 is the same as that of each of the first throttle valves 3.
3. Each first throttle opening/closing valve 3 serves as a back pressure to resist the closing operation.
3, the timing of the closing operation when each first throttle opening/closing valve 33 switches from the throttle open position X to the closed position Y is delayed. Therefore,
During the delay time of the closing operation of each first throttle opening/closing valve 33, the pressure in each first pressure chamber 16 of the undulating cylinders 13, 13 is made uniform, and then each first throttle opening/closing valve 33 is closed and each of the first The pressure in the pressure chamber 16 can be maintained. As a result, even in an emergency situation such as a rupture of a pipe, the boom can be held securely by equalizing the holding force of the boom by the luffing cylinders 13, 13, without twisting the boom. .

In this case, referring to FIG. 2, the drains that are released from each of the first throttle opening/closing valves 33 to each of the bypass pipes 32 are from the space 62 to the passage 61, the throttle 63, the space 59, the hole 58, the space 57, and the hole 55. On the other hand, by cutting off the communication between the hole 50 of the spool 49 and the passage 51,
Each first throttle opening/closing valve 33 is switched to its closed position Y.

In addition, in the case of this embodiment, a passage 51 communicating with the hole 50 of the spool 49 is clearly shown in FIG.
Since the opening portion 53 is formed long along the sliding direction of the spool 49, when a large load is applied to one of the luffing cylinders 13, for example, when the boom swings, pressure is applied to each first pressure chamber 16. Even if the flow rate of oil flowing through each first throttle on-off valve 33 is somewhat large, the difference in the flow rate of the oil flowing through each first throttle on-off valve 33 may vary.
3 will not malfunction and switch to the closed position Y. Therefore, the reliability of the operation of each first throttle opening/closing valve 33 can be increased.

In this embodiment, the oil pressure holding valve 25,
Since the first and second throttle opening/closing valves 33 and 36 are built into one holding valve, assembly to the hydraulic piping is easy.
Moreover, it is also suitable for preventing pipe breakage accidents.

As detailed above, in this invention, in addition to the first throttle on-off valve, a second throttle on-off valve is provided that delays the closing timing of the first throttle on-off valve, so that in the unlikely event that a rupture accident occurs in the communicating pipe, Even in this case, the boom can be held by equalizing the pressure in the first pressure chamber of each undulating cylinder. Furthermore, since the second throttle opening/closing valve is eventually closed, the boom can be held securely, resulting in excellent reliability.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, with FIG. 1 being an overall hydraulic circuit diagram and FIG. 2 being a sectional view of a holding valve. 13... undulating cylinder, 16... first pressure chamber,
19...Second pressure chamber, 32...Bypass pipe (communication pipe), 33...First throttle opening/closing valve, 35...Drain relief pipe, 36...Second throttle opening/closing valve.

Claims (1)

[Claims] 1 A pair of double-acting type hoisting cylinders are connected to the boom of a construction machine, and by supplying pressure oil to the first pressure chamber of each hoisting cylinder, both hoisting cylinders are extended together to perform the boom raising operation, and each By supplying pressure oil to the second pressure chamber of the undulation cylinder,
In a boom hoisting device for construction machinery in which both hoisting cylinders are contracted together to perform a boom lodging operation, a communication pipe is provided that allows the first pressure chambers to communicate with each other, and each of the first pressure chambers is Both ends close to the first pressure chamber are normally biased to an open position that throttles the communication pipe, maintaining each first pressure chamber in communication with each other, and maintaining a predetermined differential pressure between the two pressure chambers before and after the communication pipe. A first throttle opening/closing valve is provided, which is switched to a position where the communication pipe is closed when the value exceeds the value, and each first throttle opening/closing valve is connected to the communicating pipe, so that each first throttle opening/closing valve is switched to the closing position. When switching to the drain relief line, a drain relief line is provided to release the drain from the first throttle opening/closing valve to the communication line. , characterized in that a second restrictor opening/closing valve is provided, which is switched to a position that closes each drain relief pipe when the differential pressure before and after the drain relief pipe becomes larger than a predetermined value. boom hoisting device for construction machinery.