JPH025679B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Industrial Application The present invention relates to a hydraulic circuit used in winches and the like, which applies a brake when a hydraulic motor is stopped.

(2) Prior Art Conventionally, in a hydraulic winch, two or more fixed-capacity hydraulic motors or two or more fixed-capacity working chambers or two or more fixed-capacity working chambers, or those hydraulic motors are coupled. A hydraulic motor, an automatic switching valve that selectively switches the hydraulic motor or working chamber according to the load so that the hydraulic motor rotates at high speed when the load is light and at low speed when the load is heavy, and the rotation speed of the hydraulic motor. When using a hydraulic closed circuit that uses a hydraulic pump that controls the flow and direction and communicates the sending liquid path and return liquid path when in neutral, and the hydraulic pump that is the driving source for these valves, the automatic switching valve If you lift a load that is likely to operate, set the switching valve to neutral, and operate the brake attached to a drum or other device driven by the hydraulic motor, the load side of the hydraulic motor that was generated by the load will be removed. The pressure decreases due to internal leaks from the hydraulic motor, switching valve, etc., and the automatic switching valve returns to normal. When the brake is released in this state, pressure is generated again on the load side of the hydraulic motor, the automatic switching valve is switched, and the hydraulic fluid is also compressed, albeit slightly. Therefore, a shock occurs when the brake is released. The conventional method used to eliminate this shock when the brake is released is to install a separate booster pump to always generate a constant pressure, connect it to the load side of the hydraulic motor, and connect it to the load side fluid path. The pressure is kept above the return pressure of the automatic switching valve. An example of this conventional hydraulic circuit diagram is shown in FIG. 1 is a hydraulic pump, 2 is a hydraulic motor 3
A switching valve 6 is provided between the sending liquid path 4 and the return liquid path 5 to control the direction and flow rate of the working fluid and to communicate the sending liquid path 4 and the return liquid path 5 in the neutral state, A safety valve 7 that prevents an excessive pressure rise in the hydraulic pump 1 is a tank that applies a constant pressure to the suction side of the hydraulic pump 1. The hydraulic motor 3 has each working chamber 3A,
3B and 3C, and the load due to the cargo is applied by a rope or the like to which the drum 8 is connected.
9 shows a brake device attached to the drum.
10 is a normal rotation liquid path in which pressure is generated due to the load when a load is hoisted by the hydraulic motor 3;
Reference numeral 1 indicates a reversing fluid path that sends hydraulic fluid to the hydraulic motor 3 when lowering a load. Reference numeral 12 indicates an automatic switching valve, which is composed of automatic switching valves 12B and 12C corresponding to the working chambers 3B and 3C of the hydraulic motor 3. When the hydraulic pressure in the forward rotation fluid path 10 is low, the working chamber 3
B and 3C are communicated with the return liquid path 5, and when the normal rotation liquid path 10 achieves a pressure higher than the set pressure, the working chamber 3
B, 3C are communicated with the normal rotation liquid path 10. This automatic switching valve 12 operates using a spring and the pressure of the normal rotation liquid path 10 as pilot pressure, and switches when the pilot pressure exceeds the set spring force, but in order to keep the switching stable, it must be switched once. When the temperature changes, the design is such that the return only occurs at a significantly lower level. The liquid passages of the working chambers 3B and 3C on the side opposite to the connection of the automatic switching valves are communicated with the return liquid passage 5. 13 is a booster pump for applying a constant pressure so that the pressure in the forward rotation liquid path 10 does not drop; 14 is a booster pump provided between the discharge side of the booster pump 13 and the return liquid path 5 for adjusting the liquid pressure of the booster pump 13; The relief valve and booster pump 13 suck the working fluid from the return fluid path 5, and the discharged working fluid communicates with the forward rotation fluid path 10 via the check valve 15. Check valve 1
5 is to prevent problems such as the booster pump 13 being reversed when the pressure in the forward rotation liquid path 10 is higher than the discharge pressure of the booster pump 13.

In the case of the above configuration, when the switching valve 2 is in the neutral position as shown in FIG. It circulates and returns to the hydraulic pump 1. When hoisting a light load by operating the switching valve 2 to the right in the diagram,
The hydraulic fluid discharged from the hydraulic pump 1 is sent to a liquid feed path 4,
It passes through the switching valve 2, the normal rotation liquid path 10, and the hydraulic motor 3.
The liquid enters the working chamber 3A, rotates the hydraulic motor 3 with a pressure commensurate with the load, passes through the reversing liquid path 11, the switching valve 2, and the return liquid path 5, and returns to the hydraulic pump 1. In this case, since the load is light, the pressure in the forward fluid path 10 is low, so the automatic switching valve 12 does not operate, and as shown in the figure, the hydraulic fluid in the forward fluid path 10 is
B, 12C, and the connection side of the check valve 15 are closed, and the flow only flows into the working chamber 3A. Also, the working chamber 3B,
At this time, both the inlet and the outlet of 3C communicate with the return liquid path 5 via the automatic switching valve 12, and are rotated by the torque generated by the working chamber 3A. When the load is heavy and the load applied to the drum 8 is large and the torque of the working chamber 3A cannot hoist it, the pressure in the forward rotation liquid path 10 also increases, and the automatic switching valve 12
B and 12C are sequentially switched so that torque corresponding to the load is generated, working fluid is supplied from the forward rotation fluid passage 10 to the working chambers 3B and 3C, and the torque of the hydraulic motor 3 is increased and it is possible to wind a heavy load. can be raised.
When lowering the load or reversing the load when there is no load, operate the switching valve 2 to the left in the figure, contrary to the case when hoisting. The hydraulic fluid discharged from the hydraulic pump 1 is sent to the working chamber 3A via the feed fluid path 4, the switching valve 2, and the reverse fluid path 11.
enters, reverses the hydraulic motor 3, and switches the forward rotation fluid path 1.
0, switching valve 2, return liquid path 5 to hydraulic pump 1. At this time, when the load is small and the automatic switching valves 12B and 12C are not switching, the working chambers 3B and 3C communicate with the return liquid path 5 at both the inlet and the outlet, and are rotated by the working chamber 3A. However, if the load is large and the automatic switching valve is switching, the working chamber 3
In B and 3C, the hydraulic fluid sucked from the return fluid path 5 is discharged to the forward rotation fluid path 10, merges with the hydraulic fluid in the working chamber 3A, and returns to the switching valve 2 and the return fluid path 5. At this time, the normal rotation liquid path 10 includes a counterbalance valve (not shown),
The liquid returns to the switching valve 2 via a throttle valve or the like, and negative pressure is often prevented from being generated in the reverse liquid path 11.

If you lift a heavy load that activates the automatic switching valve 12 and return the switching valve 2 to neutral while it is still suspended,
A hydraulic motor 3 that stops the load, an automatic switching valve 12,
Due to the internal leakage of the switching valve 2, the load gradually descends. In order to prevent the load from descending, the brake 9 is applied to completely stop the load. However, if the load is stopped for a long time, the pressure in the forward rotation fluid path 10 that was previously generated due to the load of the load will be reduced by the hydraulic motor 3. Since the load no longer needs to be applied, the pressure gradually decreases due to internal leakage of the hydraulic motor 3, automatic switching valve 12, and switching valve 2. When the pressure drops to the return pressure of the automatic switching valve 12, the automatic switching valve 12 returns to its original state. In this state, when the brake 9 is released in an attempt to move the cargo again, the hydraulic motor 3 takes over the load, the pressure in the forward rotation fluid path 10 increases, and the automatic switching valve 12 operates. At this time, a certain amount of hydraulic fluid is required. Although hydraulic fluid is originally incompressible, it contains some air, and as the pressure increases, it compresses, albeit slightly. That is, a certain amount of hydraulic fluid is required to reach the state before the brake 9 is applied, and is replenished by the hydraulic motor 3 being reversed by the cargo. Since this is done instantaneously, a shock will occur.

Since this shock is dangerous, a booster pump 13 is used as a method to prevent this, and the pressure in the forward rotation liquid path 10 is maintained at a level higher than the return pressure of the automatic switching valve 12 when the switching valve 2 is in the neutral position. . That is, the booster pump 13 discharges the working fluid sucked in from the return fluid path 5 at high pressure, pushes up the check valve 15, and supplies the hydraulic fluid to the forward rotation fluid path 10.

The hydraulic fluid in an amount greater than the flow rate due to internal leakage from the hydraulic motor 3 passes through the relief valve 14, acts to maintain a constant pressure, and returns to the return fluid path 5. In this way, even if the brake 9 is applied during lifting when the automatic switching valve 12 is activated and the brake 9 is applied, the pressure in the forward rotation liquid path 10 will not become lower than the return pressure of the automatic switching valve 12 due to the booster pump 13. Automatic switching valve 12 does not return. Even if the brake 9 is released at this point, the hydraulic fluid will only be compressed due to the pressure difference between the pressure set by the relief valve 14 and the load generated by the load, so the shock will be small and will not be dangerous.

Note that even if the switching valve 2 is operated while the booster pump 13 is still rotating, the operation will be the same as when the booster pump 13 is not present. When hoisting and lowering a load, the pressure in the forward rotation fluid path 10 increases due to the load of the load, but the hydraulic fluid is closed by the check valve 15, and the entire discharge amount of the booster pump 13 passes through the relief valve 14. I will do it. When hoisting or lowering when there is no cargo, the entire discharge amount of the booster pump 13 flows to the normal rotation liquid path 10 if the pressure in the normal rotation liquid path 10 is lower than the set pressure of the leaf valve 14. Since the discharge amount of the booster pump 13 is considerably smaller than that of the hydraulic pump 1,
There is no problem with its operation. Also, automatic switching valve 12
The return is performed when the cargo lands on the ground and the pressure in the forward rotation liquid path 10 becomes lower than the return pressure of the automatic switching valve 12. At this time as well, the booster pump 13 is supplying working fluid to the forward rotation fluid path 10, but since the forward rotation fluid path 10 is communicated with the return fluid path 5 by the switching valve 2, the pressure is controlled by the automatic switching valve. The automatic switching valve 12 easily returns because the pressure has not risen above the return pressure of the switch 12.

(3) Problems to be solved by the invention By adding the booster pump 13,
Although the shock when releasing the brake 9 when a load is suspended inside has been eliminated, the following problem has occurred due to the installation of the booster pump. One is that the installation of the booster pump 13 necessitates a driving device for this pump. Although various types of drive devices can be used, a method is used in which an electric motor and its starting device, and a method in which the output shafts of the electric motor for driving the hydraulic pump 1 are used as both shafts, are used. However, both required energy for the booster pump 13, increasing the overall energy requirements used by the winch. In addition, these drive devices are expensive, and those that require separate drive devices, such as those using an electric motor and a starter, require maintenance and inspection of those devices. 2 is booster pump 1
3 is consumed by internal leakage from the relief valve 14 or the hydraulic motor 3, and is converted into heat, which increases the amount of heat generated and causes a rise in the temperature of the hydraulic fluid.
If a cooler is installed, its capacity must be increased.

(4) Means for solving the problems The present invention was made with the aim of solving the above problems and providing an inexpensive hydraulic circuit without adding a booster pump.
Between the pressure intensifier and the inflow side of the pressure intensifier from the fluid path that circulates when the switching valve 2 is neutral, there is a high pressure shutoff valve that stops the flow to the pressure intensifier when the pressure of the hydraulic pump 1 exceeds a certain pressure, and a pressure intensifier. It is configured as a hydraulic circuit that communicates with the normal rotation hydraulic path via a check valve.

(5) Effect According to the present invention having the above configuration, when the switching valve 2 is in the neutral position, the hydraulic fluid discharged from the hydraulic pump 1 circulates through the feed liquid path 4, the switching valve 2, and the return liquid path 5. At this time, a small amount of resistance is generated between the switching valve 2 and the piping, and there is a pressure difference between the inflow and outflow sides of the switching valve 2. This pressure difference activates the pressure intensifier, increasing the pressure. By generating a pressure higher than the return pressure of the automatic switching valve 12 in the normal rotation fluid path 10 using the working fluid, a shock when the brake 9 is released when the load is suspended is eliminated.

(6) First Embodiment An embodiment of the present invention will be described based on the drawings. 1st
The figure shows a first embodiment according to the invention. 1 is a hydraulic pump; 2 is a switching valve that controls the direction and flow rate of the hydraulic fluid to the hydraulic motor 3; and communicates the liquid supply path 4 and return liquid path 5 in the neutral state; and 6 is the liquid supply path 4. A safety valve 7 is provided between the hydraulic pump 1 and the return liquid path 5 to prevent an excessive pressure rise in the hydraulic pump 1.
This is a tank that applies constant pressure to the suction side of the The hydraulic motor 3 has working chambers 3A, 3B, and 3C, to which a drum 8 is connected, and is loaded with cargo by a rope or the like. 9 shows a brake device attached to the drum. 10 is a normal rotation liquid path in which pressure is generated due to the load when hoisting a load by the hydraulic motor 3; 11 is a forward rotation liquid path when hoisting a load;
A reversing fluid path for sending hydraulic fluid to the hydraulic motor 3 is shown. Reference numeral 12 indicates an automatic switching valve, and the automatic switching valve 12 is arranged so as to correspond to the working chambers 3B and 3C of the hydraulic motor 3.
B and 12C, and when the hydraulic pressure in the normal rotation liquid path 10 is low, the working chambers 3B and 3C are communicated with the return liquid path 5, and when the normal rotation liquid path 10 reaches a set pressure or higher, The working chambers 3B and 3C are communicated with the normal rotation liquid path 10. This automatic switching valve 12 operates using a spring and the pressure of the normal rotation liquid path 10 as pilot pressure, and switches when the pilot pressure exceeds the set spring stored force, but in order to keep the switching stable, it is temporarily switched off. It is designed in such a way that once the temperature changes, its recovery will only occur at a considerably lower level. Working chamber 3B, 3
The liquid path on the side opposite to the connection of the automatic switching valve C is communicated with the return liquid path 5. 15 is a check valve.

In the present invention, instead of the conventional booster pump 13 and relief valve 14, a pressure intensifier 16 and a high pressure valve 17 are provided with the configuration shown in FIG. That is, in FIG. 1, the pressure intensifier 16 is the hydraulic motor 16.
A configuration in which the output shaft and input shaft of each of the hydraulic pump A and the hydraulic pump 16B are linked is used, and compared to the inflow flow rate of the hydraulic motor 16A, the discharge amount of the hydraulic pump 16B is smaller, and the hydraulic motor The discharge pressure of the hydraulic pump 16B is higher than the inlet pressure of the hydraulic pump 16A. This pressure intensifier 16 may be of any type as long as it can continuously increase the pressure, such as a shunt valve or a pressure intensifier using a reciprocating piston. The high-pressure shutoff valve 17 automatically closes the liquid path when the inlet pressure exceeds the set pressure. A hydraulic motor 16 is provided between the fluid path and the inflow side, and when the pressure in the liquid feeding path 4 exceeds the circulation pressure, the hydraulic motor 16
Stop the flow to A. The outflow side of the hydraulic motor 16A communicates with the return liquid path 5, the suction side of the hydraulic pump 16B communicates with the return liquid path 5, and the discharge side of the hydraulic pump 16B communicates with the forward rotation liquid path 10 via the check valve 15. are doing. The connection between the intake port of the high pressure valve 17 from the feed liquid path 4 and the return liquid path on the outlet side of the hydraulic pump 16 has a large differential pressure, which has the advantage that the capacity of the pressure intensifier can be small. Therefore, if only one hydraulic pump 1 and one switching valve 2 are connected as shown in Fig. 1, it is preferable to install it near the discharge side and suction side of the hydraulic pump 1. . This is because passage resistance such as the sending liquid path 4, the returning liquid path 5, and a cooler (not shown) can also be effectively utilized.

In the case of the above configuration, when the switching valve 2 is set to neutral, the hydraulic fluid discharged from the hydraulic pump 1 is transferred to the feed liquid path 4,
The liquid is circulated through the switching valve 2, the return liquid path 5, and the suction side of the hydraulic pump 1, but as described above, due to the resistance, the pressure on the discharge side of the hydraulic pump 1 is higher than that on the suction side. In other words, the hydraulic fluid is branched from the feed liquid path 4 and introduced into the high pressure valve 17, but since the pressure is below the set pressure, part of the hydraulic fluid discharged from the hydraulic pump 1 is introduced into the high pressure valve 17. Passing through valve 17, pressure intensifier 1
The liquid enters the hydraulic motor 16A of No. 6, rotates the hydraulic motor 16A, and returns to the liquid path 5. The hydraulic pump 16B is rotated by the rotational force of the hydraulic motor 16A of the pressure intensifier 16, and the hydraulic fluid sucked from the return fluid path 5 is discharged from the feed fluid path 4 at high pressure. The pressure intensifier 16 is designed to exceed the pressure. The hydraulic fluid discharged from the hydraulic pump 16B passes through the check valve 15 and is supplied to the forward rotation fluid path 10. When the load on which the automatic switching valve 12 operates is hoisted up and placed in a suspended state neutral to the switching valve 2, and the brake 9 is applied, the pressure in the normal fluid passage 10 gradually decreases, but unlike the conventional booster pump shown in FIG. 13, the pressure is maintained above a certain level by the discharge pressure of the hydraulic pump 16B of the pressure intensifier 16, so the pressure does not drop below the return pressure of the automatic switching valve 12, and the automatic switching valve 12 does not return. . Therefore, here brake 9
Even if it is opened, the shock is small.

The amount of working fluid supplied by the pressure intensifier 16 is only the amount necessary for internal leakage of the hydraulic motor 3, and is smaller than the discharge amount of a conventional booster pump, so no waste occurs.

Next, the action of the high pressure valve 17 will be explained. When the switching valve 2 is switched to the hoisting side, the hydraulic pump 1 discharges the working fluid at a pressure commensurate with the load of the cargo, but at this time, the high pressure shutoff valve 17 is switched to stop the flow into the pressure intensifier 16. If high pressure valve 17
If there is no direct connection, the pressure discharged from the pressure intensifier 16 is the same as that of the normal rotation liquid path 10 which is its outlet, and the inflow pressure of the hydraulic motor 16A of the pressure intensifier 16 and the hydraulic pump 16B are the same. The discharge pressures of both will be almost the same. Then, the difference between the inflow flow rate of the hydraulic motor 16A and the discharge rate of the hydraulic pump 16B wastefully returns to the liquid path 5, and a part of the discharge rate of the hydraulic pump 1 is reduced. Similarly, the rotation of the hydraulic motor 3 becomes slower due to the installation of the pressure booster 16. In addition, unlike the neutral case of the switching valve 2, the forward rotation fluid path 10, which is the connection side of the discharge side of the pressure intensifier 16, is no longer a dead-end circuit, so the discharge amount of the pressure intensifier 16 can be infinitely increased. The rotation may exceed the permissible rotation of the pressure vessel, so it is necessary to install a flow regulating valve or the like to prevent over rotation. In the case of reverse rotation, when the switching valve 2 is operated in the lowering direction, the discharge pressure of the hydraulic pump 1 becomes higher than the circulating pressure when the switching valve 2 is in the neutral state, and the high-pressure stop valve 17 releases the pressure to the pressure intensifier 16. Stop the influx. If there is no high pressure valve 17 and the direct pressure intensifier 16 is directly connected to the feed liquid path 4, the discharge amount of the hydraulic pump 1 will be wasted because the normal rotation liquid path 10 is not a dead end circuit, as in the case of hoisting. There is a risk of it returning to the liquid path and causing over-rotation. However, in the case of lowering a heavy load, a counterbalance valve (not shown) is installed in the forward rotation liquid path 10 to prevent negative pressure from being generated in the reverse rotation liquid path 11. In some cases, the pressure is higher than the discharge pressure of 16, and at this time, the pressure intensifier 16 remains stopped.

As explained above, the high pressure shutoff valve 17 prevents the discharge amount of the hydraulic pump 1 from flowing into the pressure intensifier 16 needlessly during forward or reverse rotation, prevents the pressure intensifier 16 from over-rotating, and prevents the switching valve 2 from flowing into the pressure intensifier 16. The hydraulic fluid flows into the pressure intensifier 16 only in the neutral state.

Second Embodiment In the second embodiment, explanations of the same components as those in the first embodiment will be omitted.

In the first embodiment, one hydraulic pump and one switching valve are used.
The hydraulic circuit according to the present invention can also be applied when two or more switching valves are arranged in series in one hydraulic pump. Indicate the case. At this time, the pressure difference acting on the hydraulic pumps 16A, 16A of the pressure intensifiers 16, 16 is effectively utilized for the passage resistance of the sending liquid path 4, return liquid path 5, cooler, etc. (not shown), as in the case of the first embodiment. It is impossible to do this because the operation of the switching valves 2 and 2 interferes with each other, and the switching valves 2 and 2 interfere with each other.
It is supplied only by the passing resistance of 2. however,
The pressure intensifier 16 near the suction side of the hydraulic pump 1 can even utilize the passage resistance of a cooler (not shown).

Other embodiments (a) Hydraulic motor 16 used in the first embodiment
A. Pressure intensifier 1 in conjunction with hydraulic pump 16B
6, the suction side connection of the hydraulic pump 16B is connected to the return liquid path 5, but the high pressure valve 1
7 and the hydraulic motor 16A. In this case, the discharge pressure of the hydraulic pump 16B is increased by adding pressure to the pressure in the liquid supply path 4, and efficiency is improved accordingly. This is the second
This is also possible in the embodiment and is more efficient.

(b) In the first and second embodiments, an example was shown in which one switching valve was connected to one hydraulic motor having three fixed capacities, and necessary automatic switching valves were provided. But 2
A winch hydraulic circuit may be used, in which the output shafts of one or more fixed capacity hydraulic motors rotate the drum in conjunction with each other, and one switching valve and a required number of automatic switching valves are provided. In addition, the output shafts of a hydraulic motor with multiple working chambers and a hydraulic motor with one working chamber are linked to form a winch hydraulic circuit equipped with one switching valve and the required number of automatic switching valves. Also good.

(C) In the first and second embodiments and the above-mentioned embodiments, one or more hydraulic motors are operated by one switching valve;
More than one switching valve may be used and operated in conjunction with each other.

(7) Effects of the Invention As described above, the present invention provides a system between the pressure intensifier and the inflow side of the pressure intensifier from the fluid path that circulates when the switching valve is in the neutral state, and prevents the flow into the pressure intensifier when the pressure of the hydraulic pump exceeds a certain level. By configuring the system as a liquid path that communicates with the high-pressure shut-off valve and the forward rotation liquid path from the pressure intensifier via a check valve, (a) the booster pump can be driven more easily than when a conventional booster pump is installed. This eliminates the need for drive means such as an electric motor and a starting circuit.

(b) When a booster pump was installed, the hydraulic fluid often passed through the relief valve, generating a large amount of heat; however, according to the present invention, the minimum necessary hydraulic fluid is supplied, so the temperature rise in the hydraulic fluid is small. The capacity of the cooler will also be smaller.

(c) Since the amount of working fluid discharged from the pressure intensifier is the minimum necessary, a rotary pressure intensifier has a low rotation speed and low noise. Furthermore, if the pressure intensifier is of a reciprocating type, the sliding speed is low, so the noise is even lower. In the conventional case where a booster pump was used, the hydraulic fluid always passed through the relief valve, which generated noise, but this is also eliminated. If a pressure compensator type variable discharge pump is used as the booster pump, noise and heat generation can be minimized, but it is expensive.

(d) There is no need for maintenance and inspection of the electric motor that drives the booster pump, the starting circuit, etc.

(e) The energy used for the drive means used for the booster pump is no longer required, and the energy required for the winch as a whole can be reduced.

(f) The brake device 9 is not described in detail, but for reasons such as maintenance and inspection, it is usually composed of a hydraulic brake cylinder with a spring inside.For safety reasons, the brake acts on the spring, and the hydraulic brake cylinder It is desirable that the brake be released by

Conventionally, such braking has been performed using a separate small hydraulic pump unit as a drive source and a brake switching valve linked to switching valve 2, and when switching valve 2 is in neutral, the hydraulic brake cylinder is operated. is connected to the tank of the hydraulic pump unit, and when the switching valve 2 is operated to raise or lower, the piping from the hydraulic pump unit that is always under pressure is connected to the hydraulic brake cylinder. It will be done. This hydraulic pump unit for brakes is of a type that maintains a constant pressure during operation because it is necessary to release the brake instantly and smoothly.

When the hydraulic circuit of the present invention is used, it is possible to perform the same function using self-pressure without using the brake hydraulic pump unit. This is because when the conventional neutral brake 9 of the switching valve 2 was applied, there was no hydraulic pressure source sufficient to open the brake cylinder on the hydraulic circuit.In the case of the hydraulic circuit according to the present invention, the switching valve This is because even if the brake 9 is applied during the neutral state of the vehicle 2, the pressure intensifier 16 can secure a hydraulic pressure source sufficient to open the brake cylinder.

Specifically, the hydraulic pressure source for opening the brake cylinder is connected to the feed liquid path 4 on the outlet side of the hydraulic pump 1.
and the normal rotation liquid path 10 via the high pressure selection valve. In other words, even when the discharge pressure of the hydraulic pump 1 is suspended in a cargo and the brake is applied, the pressure intensifier 16 always uses the higher pressure of the normal rotation liquid path 10, which has a pressure above a certain level, as the hydraulic pressure source. As a result, the brake cylinder is operated by a brake switching valve linked to the switching valve 2.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of the first embodiment, FIG. 2 is a hydraulic circuit diagram of the second embodiment, and FIG. 3 is a conventional hydraulic circuit diagram. 1... Hydraulic pump, 2... Switching valve, 3... Hydraulic motor, 3A, 3B, 3C... Each working chamber, 4... Liquid supply path, 5... Return liquid path, 6... Safety valve, 7... Tank, 8
...Drum, 9...Brake device, 10...Normal rotation liquid path,
11... Reverse liquid path, 12... Automatic switching valve, 13... Booster pump, 14... Relief valve, 15... Check valve,
16...Pressure booster, 16A...Hydraulic pressure pump, 16B...Hydraulic pressure motor, 17...High pressure shield valve.

Claims (1)

[Claims] 1 Controlling the rotation direction and rotation speed of two or more fixed-capacity hydraulic motors that are linked together, or a hydraulic motor that has two or more fixed-capacity working chambers, or the hydraulic motors that are linked together, and the hydraulic motors. A switching valve that communicates the sending liquid path and a returning liquid path when in neutral, an automatic switching valve that selectively switches the hydraulic motor or the working chamber of the hydraulic motor according to the load, and a hydraulic pump that is the driving source. In the winch hydraulic closed circuit configured, when the operating fluid of the hydraulic pump circulates when the switching valve is in the neutral state, the hydraulic fluid returns from the high pressure side to the low pressure side via the cutoff valve and the pressure intensifier; 1. A winch hydraulic circuit characterized in that a hydraulic fluid path is added to communicate high-pressure hydraulic fluid, which is the output of a pressure intensifier, to the load side of the hydraulic motor via a check valve.