JPH09166101A - Circuit pressure holding device for hydraulic closing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform non-smooth operation of a hydraulic actuator due to abnormal reduction of a circuit pressure during movement of an object when an object having high inertia is moved from a stop state by the hydraulic actuator. SOLUTION: A hydraulic circuit is constituted in such a manner that the ports 1a and 1b of a hydraulic pump 1 are communicated with the ports 3a and 3b, having different pressure receiving areas, of a hydraulic actuator 3 through lines 4 and 5. Discharge of a surplus flow rate and supply of an insufficient flow rate, occurring to the lines 4 and 5 due to operation of a hydraulic pump 1, are effected by control valves 6 and 7 to which pilot pressures in the lines 5 and 4 are guided. In this case, by inserting a pair of check valves 11 and 12, different in a flow direction, in parallel in the line 4, the flows of the lines 4 and 5 form a flow accompanied by a cracking pressure to prevent abnormal reduction of a circuit pressure, and the control valves 6 and 7 are stabilized to smooth operation of the hydraulic actuator 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention communicates first and second ports of a reciprocating actuator having different pressure receiving areas with first and second ports which are suction and discharge ports of a hydraulic pump. The present invention relates to a circuit pressure holding device in a closed hydraulic circuit.

[0002]

2. Description of the Related Art An example of this type of hydraulic closed circuit is shown in FIG. The hydraulic pump 1 capable of sucking and discharging from both the first port 1a and the second port 1b is driven by an electric motor 2 whose rotation speed is controllable. The first and second ports 1a, 1b of the hydraulic pump 1 are the rod-side first rod 3a and the first port 3a located on the head side of the reciprocating hydraulic actuator 3 having different pressure-receiving areas, which are the return rod cylinders. The first port 4 and the second port 5 are in communication with the second port 3b located at, respectively.

Between the first conduit 4 and the second conduit 5,
The first and second control valves 6 and 7 which allow a natural flow from the hydraulic tank 10 to the first and second pipe lines 4 and 5 are inserted, and these first and second control valves 6 and 6 are inserted. 7 is controlled by pilot pressures of pilot lines 9 and 8 communicating with the second and first pipelines 5 and 4 on the opposite side, respectively.

With such a configuration, the hydraulic actuator 3
When the hydraulic pump 1 is rotated by the electric motor 2 in a predetermined direction in an attempt to displace the rod 3c of the hydraulic actuator 3 to the right in the figure, the hydraulic actuator 3 of the hydraulic actuator 3 passes from the first port 1a through the first pipe line 4. Flow to the first port 3a occurs. At this time, the flow rate supplied to the first port 3a and the second port 3
Since the flow rates discharged from b differ, a surplus flow rate occurs in one side and a shortage flow rate occurs in the other side.

The discharge of the excess flow rate and the supplementation of the insufficient flow rate are
First and second control valves 6 and 7 connected to hydraulic tank 10
By using the pilot pressure of the second and first conduits 5 and 4 via the hydraulic pump 3 and the electric motor 2 for driving the hydraulic pump 1 using the hydraulic actuators 3 having different pressure receiving areas.
This makes it possible to move the object forward and backward and control its speed.

[0006]

However, in such a conventional hydraulic closed circuit, when an object having a large inertia is moved forward or backward by a hydraulic actuator, the circuit is moved when the object starts to move from a stationary state. A phenomenon occurs in which the pressure temporarily decreases abnormally and the pilot pressure controlling the other control valve also decreases. If this circuit pressure falls below the minimum required pilot pressure of the first and second control valves, the first and second control valves will not operate normally and the hydraulic actuator will not operate smoothly. . The present invention has been made in view of the above points,
It is an object of the present invention to always maintain the circuit pressure at a predetermined value or more and smoothly control the operation of the hydraulic actuator.

[0007]

In order to achieve the above object, the present invention provides a hydraulic pump capable of sucking and discharging from both the first and second ports, and an electric motor for driving the hydraulic pump. Hydraulic actuators having different pressure receiving areas, which are provided with first and second ports respectively communicating with the first and second ports of the hydraulic pump by first and second conduits,
The operation of the hydraulic pump is performed to discharge the excess flow amount or replenish the insufficient flow amount generated in the first and second pipelines.
A circuit pressure holding device in a hydraulic closed circuit comprising a first and a second control valve, which is operated by pilot pressure in a first pipeline, wherein at least one of the first and second pipelines is free from each other. A circuit pressure holding device in a hydraulic closed circuit in which a pair of check valves having different flow directions are inserted in parallel.

[0008]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and the portions corresponding to those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, the first port 1a of the hydraulic pump 1 and the first port 3a of the hydraulic actuator 3 are used.
A pair of check valves 11 and 12 having different free flow directions are inserted in parallel on the first conduit 4 communicating with each other, that is, on the head side of the hydraulic actuator 3. The other configuration is the same as that of FIG.

With the above configuration, when the hydraulic pump 1 is rotated in a predetermined direction by the electric motor 2 in an attempt to displace the hydraulic actuator 3 to the right in the figure, the first hydraulic pump 1 is moved.
Flow from the port 1a of the hydraulic actuator 3 to the first port 3a of the hydraulic actuator 3 through the first conduit 4. At this time, the first port connected to the first port 1a of the hydraulic pump 1
Of the load device (not shown) that engages with the rod 3c of the hydraulic actuator 3 as a free flow with a predetermined cooking pressure in the direction of the hydraulic actuator 3 via the check valve 11. It is possible to avoid an abnormally low pressure in the first conduit 4 caused by inertia.

Also, the rod 3c of the hydraulic actuator 3
When the hydraulic pump 1 is rotated in the reverse direction by the electric motor 2 in an attempt to displace it to the left in the figure, the second port of the hydraulic actuator 3 passes from the second port 1b through the second pipe line 5. Flow to 3b occurs. As a result, a return flow rate from the first port 3a of the hydraulic actuator 3 is generated,
This return flow rate becomes a free flow with a predetermined cracking pressure by the check valve 12, and the abnormal low pressure of the second pipe line 5 caused by the inertia of the load device (not shown) that engages with the rod 3c of the hydraulic actuator 3. Can be avoided.

As described above, the circuit pressures of the first and second pipelines 4 and 5 are always maintained at a predetermined pressure or more, so that the first and second control valves connected to the tank line of the hydraulic tank 10 are connected. The operations of 6 and 7 are stable, and the hydraulic actuator 3 can be operated smoothly.

Next, FIG. 2 is a hydraulic circuit diagram showing another embodiment of the present invention. In this embodiment, the hydraulic pump 1
On the second conduit 5 that connects the second port 1b of the hydraulic actuator 3 to the second port 3b of the hydraulic actuator 3, that is, on the rod side of the hydraulic actuator 3, a pair of check valves 11 having different free flow directions, 12 are inserted in parallel,
Other configurations are the same as those in FIG. Even in the hydraulic closed circuit configured as described above, it is possible to obtain the same operation and effect as in the previous embodiment.

FIG. 3 is a hydraulic circuit diagram showing still another embodiment of the present invention. In this embodiment, a pair of check valves 11, 12 and 13, 14 having different free flow directions from each other are inserted in parallel in the first pipe line 4 and the second pipe line 5, respectively. The configuration is the same as in FIG. With such a configuration, the circuit pressures of the first and second conduits 4 and 5 are more favorably maintained, the operations of the first and second control valves 6 and 7 are further stabilized, and the inertial force is extremely high. Even with a large load, the hydraulic actuator 3 can operate smoothly.

[0015]

As described above, the circuit pressure holding device in the hydraulic closed circuit according to the present invention flows through at least one of the first and second pipelines connecting the hydraulic pump and the hydraulic actuator. Since the pair of check valves having different directions are inserted in parallel, the flow in the first and second conduits becomes a free flow with a predetermined cracking pressure by either of the pair of check valves. As a result, even if the circuit pressure fluctuates,
A predetermined circuit pressure is maintained, the first and second control valves using the circuit pressure as a pilot pressure are reliably operated, and the hydraulic actuator can be operated smoothly.

[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 showing another embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram showing still another embodiment of the present invention.

FIG. 4 is a hydraulic circuit diagram illustrating a conventional hydraulic closed circuit.

[Explanation of symbols]

 1: hydraulic pump 1a: first port 1b: second port 2: electric motor 3: hydraulic actuator 3a: first port 3b: second port 3c: rod 4: first pipe 5: first Pipeline 2 6: First control valve 7: Second control valve 8, 9: Pilot line 10: Hydraulic tank 11, 12, 13, 14: Check valve

Claims (1)

[Claims] 1. A hydraulic pump capable of sucking and discharging from both of the first and second ports, an electric motor for driving the hydraulic pump, and a first and second ports of the hydraulic pump. ，
Hydraulic actuators having different pressure receiving areas, which are provided with first and second ports that communicate with each other through a second pipeline, and discharge of excess flow rates generated in the first and second pipelines by operating the hydraulic pump. Alternatively, replenishing the insufficient flow rate is the second, first
Circuit pressure holding device in a hydraulic closed circuit consisting of a first and a second control valve, which is operated by pilot pressure in the pipeline of the above, wherein at least one of the first and second pipelines has a free flow direction with respect to each other. A circuit pressure holding device in a hydraulic closed circuit, characterized in that a pair of check valves of different types are inserted in parallel.