JPH0232881Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an impact prevention valve device that prevents impact pressure from being generated due to opening and closing of valves in a hydraulic pump equipped with a plurality of hydraulic pumps.

Conventionally, in this type of hydraulic circuit, as shown in the first diagram, an unload circuit e equipped with a pilot valve c and an unload valve d is provided in a merging circuit b of a plurality of hydraulic pumps a, a, and an unload circuit e is provided in the merging circuit b. When the flow rate is no longer needed, it is discharged to the tank at low pressure to reduce the power of the pumps a and a and to prevent the oil temperature from rising. In this case, the unload valve d is Since large-diameter pumps are used for discharging the flow rate of the plurality of pumps a, opening and closing of the pumps creates an undesirable impact on the hydraulic circuit. Therefore, as shown in the second diagram, each discharge circuit f, f of each hydraulic pump a, a is provided with an unload circuit as described above, and a small unload valve is used.
Although each unload valve is closed in sequence to prevent a shock from occurring in the hydraulic circuit, since pressure oil is trapped in the merging circuit b, a shock still occurs when the actuator is started. In order to prevent such entrapment of pressure oil, if the flow rate of the merging circuit is small, the switching valve of the circuit should be a tandem center type, and the pressure oil can be discharged to the tank via the switching valve.
In a confluence circuit where a large flow rate of several thousand per minute flows from a plurality of pumps, switching of a tandem center type switching valve has the disadvantage of causing a shock to the hydraulic circuit.

The purpose of this invention is to prevent the occurrence of shock by preventing the entrapment of pressure oil in a hydraulic circuit equipped with a plurality of hydraulic pumps. It is a hydraulic circuit in which an unload circuit is provided in each of the discharge circuits 2, and the flow rates of the respective discharge circuits 2 are combined in a merging circuit 3 and supplied to the actuator.The merging circuit 3 has a line check valve, a closed center In a device that is configured to be closed by the intervention of a circuit closing device of a type switching valve, each discharge circuit 2 is connected to a shuttle valve 4.
to extract the highest pressure of each discharge circuit 2 and transfer the pressure to the pilot circuit 5.
The pressure of the merging circuit 3 acts on the closing side of the logic valve 7 which opens to connect the circuit 3 to the tank 6 through the merging circuit 3.

Figure 3 shows an example where four hydraulic pumps 1 are provided; in this case, two hydraulic pumps 1 and 1 are installed.
The discharge circuits 2 and 2 of each set are connected to each other via a shuttle valve 4, and the pressure extraction port of each shuttle valve 4 of each set is connected to the logic valve 7 via a pilot circuit 5. The highest pressure in the discharge circuit 2 is made to act on the logic valve 7. The logic valve 7 has a general configuration of a cartridge type seat valve, and its valve body 7a resists the elasticity of the spring 7b behind it and the pressure acting through the pilot circuit 5 to close the merging circuit 3. A valve opening operation is applied by the pressure of , so that the pressure fluid in the merging circuit 3 can be discharged to the tank 6.
8 is a slow return valve device constructed by combining a check valve and a throttle valve, and 9 is an unload valve that controls the operation of a pilot valve 10 having a relief valve function.

To explain its operation, when each unload valve 9 is operated all at once to discharge the pressure in each discharge circuit 2 and each hydraulic pump 1 is placed in a no-load state, the logic valve 7
The chamber of the spring 7b is connected to the tank via the slow return valve device 8, the pilot circuit 5 and the shuttle valve 4, similar to the discharge circuit 2, and has an unload pressure close to the tank pressure. On the other hand, the load pressure of the actuator is blocked by the line check valve and cannot be discharged from the unload valve 9, as in the case shown in the second figure, in the merge circuit 3, but the pressure in the merge circuit 3 is If the pressure is higher, the valve body 7a of the logic valve 7 is pushed open because the chamber on the spring 7b side is connected to the tank, and the pressure in the merging circuit 3 can be discharged to the tank 6, so that the pressure is not trapped. Therefore, when the actuator connected to the merging circuit 3 is activated, no shock is generated due to the confinement pressure. When all the pumps 1 are operated under load at the same time, the actuator can be started without shock by closing each unload valve 9 one after another. In this case, the logic valve 7 is automatically closed by the pressure extracted from the shuttle valve 4. The shuttle valve 4 is connected to each discharge circuit 2.
Since the highest pressure is extracted and applied to the logic valve 7, the logic valve 7 will not open even if, for example, two of the pumps 1 are unloaded and the remaining two pumps are in operation. Further, since each unload valve 9 has a relatively small diameter corresponding to the flow rate of each pump 1, operation can be started without causing a shock to the hydraulic system. Note that a deceleration valve may be provided in the merging circuit 3 as a circuit closing device.

In this way, according to the present invention, the logic valve 7 is provided in the merging circuit 3 of a plurality of hydraulic pumps 1, and this is connected via the shuttle valve 4 to each discharge circuit 2 having an unload circuit. It is possible to prevent pressure oil from being trapped in the closed merging circuit 3 and generate an impact, and its structure is relatively simple and can be manufactured at low cost.

[Brief explanation of the drawing]

1 and 2 are diagrams of a conventional example, and FIG. 3 is a diagram of an example of the present invention. 1... Hydraulic pump, 2... Discharge circuit, 3... Merging circuit, 4... Shuttle valve, 5... Pilot circuit, 6... Tank, 7... Logic valve.

Claims (1)

[Scope of utility model registration request] A hydraulic circuit is provided with an unload circuit for each discharge circuit 2 of a plurality of hydraulic pumps 1, and the flow rates of each discharge circuit 2 are combined in a merging circuit 3 and supplied to an actuator. The confluence circuit 3 is configured to be closed by a circuit closing device such as a line check valve or a closed center type switching valve, and each discharge circuit 2 is connected to each other via a shuttle valve 4 to close each discharge circuit. Acts on the closing side of the logic valve 7 which extracts the highest pressure of the circuit 2 and passes it through the pilot circuit 5 to open the circuit 3 to the tank 6 by the pressure of the merging circuit 3. Shock prevention valve device for hydraulic circuit.