JP2002245904A - Hydraulic drive device of breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low cost and highly reliable hydraulic drive device for a breaker having a device capable of preventing a pumping action. SOLUTION: This hydraulic drive device for the breaker comprises a cylinder 4 having fluid sealed therein, a piston 5 slidably disposed in the cylinder, a control valve and a circuit opening pilot valve 37 and a circuit closing pilot valve 39 operated so as to open or close the circuits of the cylinder and the piston. In addition, it comprises a check valve 41 and an anti-pumping piston 42 operated so as to close the check valve 41. When the circuit closing pilot valve 39 is open, an abnormality can be detected by oil leakage from a restriction 48. When a circuit open instruction is given with the circuit closing pilot valve open, the anti-pumping piston 42 closes the check valve 41 so that the pumping action is not performed after the circuit opening operation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device for a circuit breaker, and more particularly to a hydraulic drive device for a power circuit breaker.

[0002]

2. Description of the Related Art A power circuit breaker provided for protecting a power supply system in the event of an emergency such as a lightning strike requires an extremely fast switching operation and a high reliability. In particular,
The pumping operation of performing the closing operation immediately after the opening operation or repeating the opening operation and the closing operation requires a large mechanical and electrical load, which is not preferable. The pumping operation may occur when an opening command is input while the closing command is input, or when the valve body of the pilot valve is stuck due to a long-time stop state. Therefore, an anti-pumping mechanism for preventing pumping is required.

In the prior art, for example, Japanese Patent Application Laid-Open No. 2000-90784
As described in Japanese Patent Publication No.
The secondary side is connected to the switching valve pilot chamber via a check valve, the check valve is provided to prevent flow from the switching valve pilot chamber, and further provided with an anti-pumping piston that closes the check valve, The closing circuit pilot valve 2
A halfway of a pipe connecting from a downstream side and a primary side of the check valve to a fluid return side is connected to an anti-pumping piston operation chamber of an anti-pumping piston, and further connected to a primary side of the check valve. Two throttles are provided in a pipe line connected to the fluid return side from between, and the middle of the two throttles is connected to the anti-pumping piston operation chamber of the anti-pumping piston.

[0004]

In the above prior art, the anti-pumping piston operates even during the normal closing operation. At this time, if the anti-pumping piston operates too fast, the switching valve cannot move to the closing operation state, and if the operation is still slow, there is a problem that pumping cannot be stopped when there is an abnormality. Therefore, the speed was adjusted by the aperture. However, in order to cope with a change in viscosity due to a change in temperature or the like, it has been difficult to accurately design a timing. In addition, since many apertures are required, the cost is high.

Accordingly, an object of the present invention is to provide an anti-pumping piston which operates only when the open-circuit pilot valve is opened with the open-circuit pilot valve open, and in a state where the close-circuit pilot valve is kept open. An object of the present invention is to provide a low-cost and highly reliable fluid pressure drive device for a circuit breaker that can detect an abnormality due to oil leakage.

[0006]

In order to solve the above-mentioned problems, for example, a contact composed of a movable contact and a fixed contact for interrupting the flow of electric current, a rod connected to the movable contact, and the rod are opened. A fluid pressure cylinder for operating or closing the circuit, at least one control valve for opening or closing the fluid pressure cylinder, and switching of the control valve for switching the fluid pressure cylinder or the control valve to an open circuit operation state or a closed circuit operation state A valve, a switching pilot valve for receiving an open command to switch to an open operation state, a switching pilot valve for receiving a closing command and switching to a closed operation state, a fluid pressure source for pressurizing and supplying a working fluid, A circuit breaker comprising an accumulator for accumulating a working fluid pressurized and supplied from a fluid pressure source and a reservoir for collecting and storing the discharged working fluid. In the pressure driving device, the switching valve is constituted by a two-position three-way valve, and has a switching valve pilot chamber which switches the switching valve to a closed operation state when a high pressure is applied to one end side, and switches to an open operation state when the pressure is reduced to a low pressure. It has a control port connected to the pilot chamber of the valve, both sides are connected to the fluid supply source and the fluid return side, the control port is connected to the switching valve pilot chamber via a throttle, and the pilot valve for open circuit has the primary side On the supply side, the secondary side is connected to a line leading to the switching valve pilot chamber, and the closing pilot valve is connected to a line leading to the switching valve pilot chamber on the primary side.
A secondary valve connected to the return side, and a check valve for preventing flow from the switching valve pilot chamber to the switching valve pilot chamber between the closing pilot valve and the switching valve pilot chamber; and a check valve An anti-pumping piston that performs an operation of closing the anti-pumping piston. The valve side chamber is connected to the switching valve pilot chamber side of the check valve, the anti-pumping piston control chamber is connected to the return side via a throttle, and further connected to the anti-pumping piston control chamber so that the anti-pumping piston does not operate during closing operation. An open cylinder is provided on the return side.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the fluid pressure driving device for a circuit breaker according to the present invention will be described below with reference to FIGS.

FIG. 1 shows a closed state (a state in which electricity is supplied), FIG. 2 shows an initial state of the opening operation, FIG. 3 shows a state in a later stage of the opening operation, and FIG. 5 shows an initial state during the closing operation, FIG. 6 shows a late state during the closing operation, FIG. 7 shows a state in which the closing pilot valve remains open after the closing operation, and FIG. 8 shows a state after the closing operation. 9 shows the initial state of the opening operation with the pilot valve kept open, FIG. 9 shows the middle state of the opening operation, and FIG. 10 shows the latter state of the opening operation.

A fluid pressure driving device 3 for a circuit breaker, which comprises a fixed contact 1 and a movable contact 2 and opens and closes a contact, includes a fluid pressure cylinder 4 for driving the movable contact 2 with a piston 5. The supply pressure of the working fluid discharged from the fluid pressure source 8 and accumulated in the accumulator 9 always acts on the small pressure receiving area 6, and the large pressure receiving area forming the cylinder operating chamber 7 is connected to the open main valve 11 and the closed circuit. The main valve 12 is selectively connected to a high pressure supply pressure side or a low pressure return side connected to the reservoir 10.

The open circuit main valve 11 is a two-way valve for connecting the cylinder operating chamber 7 to the low pressure return side to open the circuit. The control port 14 of the switching valve 13 is connected to the opening main valve pilot chamber 17, and the valve body 15 is closed by the force of the spring 16 and the force acting when the opening main valve pilot chamber 17 is set to a high pressure. Open circuit main valve pilot chamber 17
Is opened by the pressure of the fluid pushed out from the cylinder operation chamber 7 when the pressure is set to a low pressure. A low-pressure chamber 18 is provided on the back surface of the valve body 15 and always has a low pressure through the return side. The inner diameter of the opening main valve pilot chamber 17 is smaller than that of the valve seat 19 by that amount. However, the force for closing the valve by the supply pressure applied to the main valve pilot chamber 17 for opening is greater than the force for opening the valve by the supply pressure acting outward from the valve seat 19 in the closed state. It is configured as follows.

The closing main valve 12 is a two-way valve for connecting the cylinder operating chamber 7 to a high pressure supply side to perform a closing operation, and has a valve body 20 and a piston 21. The force of the spring 22 acts on the valve element 20. Closing main valve pilot chamber 2
The switching valve 13 is provided in the same manner as the opening main valve pilot chamber 17.
The auxiliary port 26 is connected to the valve chamber connected to the cylinder operating chamber 7 via the conduction hole 25 on the back surface of the valve body 20. The diameter of the valve seat 27 is smaller than the inner diameter of the closing main valve pilot chamber 24, that is, the outer diameter of the piston 21, and larger than the inner diameter of the auxiliary chamber 26. Therefore, if the pressure in the closing main valve pilot chamber 24 is reduced, the valve body 20 can use the force of the spring 22, the force due to the supply pressure acting on the portion of the diameter difference between the valve seat 27 and the auxiliary chamber 26, and the auxiliary chamber. It is closed by the force of the pressure acting on the valve 26 and is opened by the force generated here when the closing main valve pilot chamber 24 is set to a high pressure.

The switching valve 13 connects the switching valve pilot chamber 28 with a closing pilot valve 37 and an opening pilot valve 39.
The control port 14 communicating with the open main valve pilot chamber 17 and the close main valve pilot chamber 24 is connected to the supply side valve chamber 29 or the low pressure return side which is connected to the high pressure supply side. Is a two-position three-way valve connected to one of the return valve chambers 30 that is connected to. The cylindrical portion 32 of the valve element 31 has a smaller diameter than the supply side valve seat 33 and the back surface of the cylindrical portion 32 is opened to the return side. The pressure receiving area of the switching valve pilot chamber 28 is equal to the return side valve seat 34 and the cylindrical portion 3.
It is configured to be larger than the pressure receiving area of the portion having the diameter difference of 2. Further, the switching valve pilot chamber 28 is
Is connected to a valve chamber having a control port 14.

A holding mechanism 36 is provided on the back surface of the cylindrical portion 32 of the switching valve 31. This mechanism is for mechanically holding the valve element 31 when there is no fluid pressure, and has a holding force that does not affect the normal operation by the fluid pressure.

The open circuit pilot valve 37 and the close circuit pilot valve 39 are both two-way valves configured to open when the open circuit solenoid 38 or the close circuit solenoid 40 is excited, and to be closed by spring force when the excitation is released. Check valve 4
1 are connected in series. Closing pilot valve 3
9 is a high pressure supply side, a secondary side is via a check valve 41 to the primary side of the opening pilot valve 37 and the switching valve pilot chamber 28, and a secondary side of the opening pilot valve 37 is a low pressure side. Connected to the return side.

Further, on the back of the check valve 41, an anti-pumping piston 42 and a spring 43 are provided.
Is provided in the anti-pumping piston check valve side chamber 46. A pipe is provided from the secondary side of the closing pilot valve 39 and is connected to the anti-pumping piston control chamber 44 on the non-return valve side of the anti-pumping piston. The anti-pumping piston control chamber 44 has a throttle 4
It is connected to the return side 10 via a line 49 via 8. A cylindrical portion 45 is provided on the anti-return valve side of the anti-pumping piston 42, and the back surface of the cylindrical portion 45 is opened to the return side to act on the portion of the diameter difference between the anti-pumping piston control chamber 44 and the cylindrical portion 45. The force due to the supply pressure
It is set so that the force acting on the anti-pumping piston check valve side chamber 46 when the switching valve performs the closing operation is smaller.

Next, the operation of this embodiment will be described.

With the above configuration, in the closed state of FIG.
Cylinder operating chamber 7, opening main valve pilot chamber 17 and closing main valve pilot chamber 24, switching valve pilot chamber 28, primary side of closing pilot valve 37 and opening pilot valve 39, secondary of check valve 41 Side is high pressure, the secondary side of the closing pilot valve 37 and the anti-pumping piston control chamber 4
Numeral 4 is connected to the return side via a throttle 49 and has a low pressure, and all valves are closed.

When an opening command is issued in this state, as shown by an arrow in FIG. 2, the opening solenoid 38 is excited, the opening pilot valve 37 is pushed open, and the switching valve pilot chamber 28 is returned to the low pressure return side. Connected to
The switching valve 13 is switched to the open operation state by the high pressure acting on the valve chamber having the supply side valve chamber 29 and the control port 14. At this time, since the anti-pumping piston control chamber 44 has a low pressure, the anti-pumping piston does not operate, and the check valve 41 remains closed. When the switching valve is switched to the open-circuit operation state, the control port 14 and the open-circuit main valve pilot chamber 17 connected to the control port 14 are connected to the return side to have a low pressure. Is opened by the high pressure acting from the cylinder operation chamber 7 to connect the cylinder operation chamber 7 to the return side, and the piston 5 and the movable contact 2 start the opening operation. After that, when the fluid in the cylinder operation chamber 7 is pushed out by the high pressure applied to the small pressure receiving area side 6 of the cylinder 4, the opening main valve 11 is kept open due to the pressure difference generated before and after the opening main valve 11. 3 is in the later stage of the opening operation shown in FIG. Further, since the flow from the cylinder operation chamber 7 to the return side stops, the pressure difference between the front and rear of the opening main valve 11 disappears.
1 is closed by a spring 16. On the other hand, since the excitation of the opening solenoid 38 is released, the opening pilot valve 3 is opened.
7 is also closed by the spring force, and all the valves are closed again as shown in FIG.

Since the closing main valve pilot chamber 24 together with the opening main valve pilot chamber 17 has a low pressure, the piston 21 of the closing main valve 12 once moves upward, but the closing main valve 12 is closed from the beginning. Since it remains closed even when only the piston 21 moves, it does not affect the above-described opening operation.

Next, when a closing command is issued in the open state shown in FIG. 4, as shown in FIG.
0 is excited, and the closing pilot valve 39 is pushed and opened to flow from the primary side connected to the supply side to the secondary side, and the check valve 41 is pushed open to set the switching valve pilot chamber 28 to a high pressure. To switch the switching valve 13 to the closing operation state. At this time, the pressure in the switching valve pilot chamber 28 does not increase to the supply pressure during the switching valve operation. That is, the valve seat 33 and the cylindrical portion 32
The switching valve pilot chamber 28 generates enough pressure to drive the switching valve 13 by overcoming the load such as the supply pressure acting due to the diameter difference of the above and the frictional force of the packing around the switching valve 32. The supply pressure is applied to the anti-pumping piston control chamber 44 and the anti-pumping piston check valve side chamber 46 is provided.
Is substantially the same as the pressure in the switching valve pilot chamber 28. At this time, the force acting on the anti-pumping piston control chamber 44 is configured to be smaller than the force acting on the anti-pumping piston check valve side chamber 46 by providing the cylindrical portion 45, so that the anti-pumping piston 42 Do not work. As shown in FIG. 6, the operation of the switching valve causes the control port 14 and the closing main valve pilot chamber 24 connected thereto to have a high pressure, so that the piston 21 and the valve body 20 of the closing main valve 12 move downward. Then, the valve is opened, the cylinder operation chamber 7 is connected to the high pressure side, and the piston 5 and the movable contact 2 start the closing operation. At this time, the pressure in the cylinder operation chamber 7 becomes high instantaneously at the start of the cylinder operation.

As the pressure in the cylinder operating chamber 7 rises, the pressure in the auxiliary chamber 26 increases through the through hole 25.
While the is moving, it does not rise to the supply pressure. That is,
The pressure sufficient to drive the piston 5 by overcoming loads such as the supply pressure acting on the small pressure receiving area side 6, the mass of the movable contact and the like, and the frictional force of the packing around the piston 5, is generated in the cylinder operation chamber 7, This pressure is generally determined by the ratio of the pressure receiving area of the small pressure receiving area side 6 to the pressure receiving area of the cylinder operating chamber 7, but since the cylinder operating chamber 7 has a larger pressure receiving area, this pressure is lower than the supply pressure. Therefore, at this pressure, the piston 21
Is pressed downward by the supply pressure acting on the closing main valve pilot chamber 24, and this force is applied to the auxiliary chamber 26 and the spring 22.
It is configured to be larger than the force acting upward from above. Therefore, during the closing operation of the piston 5, the closing main valve 1 is closed.
2 is kept open and continues the closing operation.

At this time, when the switching valve 13 is switched to the closing operation state, the opening main valve pilot chamber 17 also becomes high in pressure, but the opening main valve 11 is closed before the start of operation, and the closing force of the valve is reduced. It does not affect the operation at all because it only increases.

When the closing operation is completed and the piston 5 stops and the flow stops, the cylinder operating chamber 7 and the communication hole 2
5. Since the auxiliary chamber 26 rises to the supply pressure, the valve body 20 and the piston 21 are pushed up and closed by the force of the spring 22.
When the closing command by the solenoid 40 is cut off, the closing pilot valve 40 closes, and the secondary side of the closing pilot valve 40,
Since the anti-pumping piston control chamber 44 is connected to the return side through the throttle 48, the pressure becomes low. As a result of these series of operations, the closed state shown in FIG. 1 is reached.

Next, a description will be given of an operation when an opening command is input in a state where the closing pilot valve is kept open (FIG. 7) due to some abnormal state or manual operation. In the state of FIG. 7, the secondary side of the closing pilot valve is connected to the return side 10 via the throttle 48, so that the oil continues to leak, and an abnormality can be detected. When an opening command is issued in this state, the opening pilot valve 37 is opened as shown in FIG.
The pressure at 8 is reduced and the switching valve is switched to the open state by the high pressure acting on the supply-side valve chamber 29 and the valve chamber having the control port 14. However, as shown in FIG. 9, when the operation of the switching valve is completed, the pressure in the switching valve pilot chamber 28 becomes lower than the closing pilot valve and the check valve 41 and the opening pilot valve 3.
7, the pressure of the anti-pumping piston check valve side chamber 46 connected to the switching valve pilot chamber 28 decreases, and the force of the anti-pumping piston control chamber 44 is reduced by the anti-pumping piston reverse pressure. The anti-pumping piston 42 operates to overcome the force of the stop valve side chamber 46 and closes the check valve. As shown in FIG. 10, after the switching valve operation, the circuit is opened as in the normal operation. Even if the opening command is cut off after the switching valve operation and the opening pilot valve 37 closes, the check valve 41 remains closed, the anti-pumping piston check valve side chamber 46 is kept at a low pressure, and the anti-pumping piston control chamber 44 is closed. Since the supply pressure is constantly applied, the check valve 41 is kept closed. Therefore, the open circuit state is maintained. After the operation is completed, the oil continues to leak through the throttle 48, so that an abnormality can be detected. Further, when the abnormality of the closing pilot valve 39 is resolved and closed, the anti-pumping piston returns to the original position, and can return to the normal closed state of FIG.
As described above, according to the present embodiment, the anti-pumping mechanism is configured to operate only when the open-circuit pilot valve is opened with the anti-pumping mechanism kept open while the anti-pumping piston operates. Therefore, it is possible to provide a low-cost and highly reliable fluid pressure drive device for a circuit breaker, which can be easily manufactured and has high reliability.

Next, another embodiment of the present invention is shown in FIGS.

In this embodiment, the main valve 11 for opening and the main valve 12 for closing are removed from the embodiment shown in FIGS. 1 to 10, and the control port 14 of the switching valve 13 is changed to the cylinder operating chamber 7 of the hydraulic cylinder 4. In this embodiment, the fluid pressure cylinder is directly driven by a switching valve. 11 shows a closed state, FIG. 12 shows an initial state of the opening operation, FIG. 13 shows a state of the latter half of the opening operation, FIG. 14 shows an initial state of the closing operation, and FIG. 16 shows an initial state of the opening operation in a state where the closing pilot valve remains open after the closing operation, and FIG. 17 shows a state of the latter half of the opening operation, respectively.

Except that the opening main valve 11 and the closing main valve 12 are not provided, the configuration is the same as that of the embodiment shown in FIGS. 1 to 10, and the opening operation, the closing operation, and the closing operation in the normal state are performed. The opening operation when the pilot valve 39 is kept open due to an abnormality is the same as in the above-described embodiment.

The present embodiment is suitable for a fluid pressure drive device for driving a small to medium capacity circuit breaker. According to this embodiment, the same effects as those of the embodiment shown in FIGS. 1 to 10 can be obtained. Further, since the main valve is not required, the size can be further reduced and the production can be facilitated.

[0029]

As described above, according to the present invention, the anti-pumping mechanism is configured such that the anti-pumping piston operates only when the opening pilot valve is opened while the closing pilot valve is kept open. In addition, it is possible to eliminate a throttle for adjusting the time and detect an abnormality of the closing pilot valve. For this reason, it is easy to manufacture, and it is possible to provide a low-cost and highly-reliable circuit breaker fluid pressure driving device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a closed state of a circuit breaker according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an initial state during an opening operation of the circuit breaker.

FIG. 3 is a configuration diagram showing a state in a later stage during an opening operation of the circuit breaker.

FIG. 4 is a configuration diagram showing an open circuit state of the circuit breaker.

FIG. 5 is a configuration diagram showing an initial state during a closing operation of the circuit breaker.

FIG. 6 is a configuration diagram showing a later state of the circuit breaker during a closing operation;

FIG. 7 is a configuration diagram showing a state in which the closing pilot valve is kept open in the closed state of the circuit breaker.

FIG. 8 is a configuration diagram showing an initial state of an opening operation from a state where the closing pilot valve is kept open in the closed state of the circuit breaker.

FIG. 9 is a configuration diagram showing a middle state of an opening operation from a state in which a closing pilot valve is kept open in a closed state of the circuit breaker.

FIG. 10 is a configuration diagram illustrating a state in a later stage of the opening operation from a state in which the closing pilot valve is kept open in a closed state of the circuit breaker.

FIG. 11 is a configuration diagram showing a closed state of a circuit breaker according to a second embodiment of the present invention.

FIG. 12 is a configuration diagram showing an initial state during an opening operation of the circuit breaker.

FIG. 13 is a configuration diagram showing a later state of the circuit breaker during an opening operation;

FIG. 14 is a configuration diagram showing an initial state during a closing operation of the circuit breaker.

FIG. 15 is a configuration diagram showing a later state of the circuit breaker during a closing operation;

FIG. 16 is a configuration diagram showing an initial state of an opening operation from a state in which the closing pilot valve is kept open in a closed state of the circuit breaker.

FIG. 17 is a configuration diagram showing a later state of an opening operation from a state in which the closing pilot valve is kept open in a closed state of the circuit breaker.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixed contact, 2 ... Movable contact, 3 ... Fluid pressure drive, 4 ... Fluid pressure cylinder, 5 ... Piston, 6 ... Small pressure receiving area chamber, 7 ... Cylinder operation chamber, 8 ... Fluid pressure source, 11 ... Opening main valve, 12: closing main valve, 13: switching valve, 28: switching valve pilot chamber, 37: opening pilot valve, 39: closing pilot valve, 41: check valve, 42: anti-pumping piston.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhide Takeda 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Electric Systems Division, Hitachi, Ltd. (72) Inventor Daisuke Ebisawa 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture No. 1 F-term in the Electric Systems Division, Hitachi, Ltd. (Reference) 3H089 AA90 BB16 CC01 DA02 DA04 DA14 DB33 DB47 DB49 DB75 EE15 EE31 GG02 HH05 HH29 JJ20

Claims (4)

[Claims] 1. A contact comprising a movable contact and a fixed contact for interrupting the flow of electric current, a rod connected to the movable contact, a fluid pressure cylinder for opening or closing the rod, and A switching valve for opening or closing a fluid pressure cylinder, an opening pilot valve for setting the switching valve to an open operation state upon receiving an opening command, and a closing valve for switching the switching valve to a closed operation state upon receiving a closing command. A shutoff system including a pilot valve, a fluid pressure source for pressurizing and supplying a working fluid, an accumulator for accumulating the working fluid pressurized and supplied from the fluid pressure source, and a reservoir for collecting and storing the discharged working fluid. In the fluid pressure drive device of the vessel, the switching valve is constituted by a two-position three-way valve, and when a high pressure is applied to one end side, the switching valve is brought into a closed operation state, and when a low pressure is applied, the switching valve is opened. Comprising a switching valve pilot chamber changing, a control port connected to the pilot chamber of the control valve in the center, on both sides is connected to a fluid supply and a fluid return side,
The control port is connected to the switching valve pilot chamber via a restrictor, and the closing pilot valve is connected to a supply side on the primary side and to a pipeline leading to the switching valve pilot chamber on the secondary side, and is used for the open circuit. The pilot valve has a primary side connected to a pipeline leading to the switching valve pilot chamber, a secondary side connected to a return side, and further between the closing circuit pilot valve and the switching valve pilot chamber, from the switching valve pilot chamber to the switching valve pilot chamber. A check valve for preventing flow to the switching valve for closing circuit pilot chamber, and an anti-pumping piston for performing an operation of closing the check valve, the anti-pumping piston, the secondary side of the pilot valve for closing circuit the said The anti-pumping piston is connected to the anti-pumping piston control chamber on the non-return valve side of the anti-pumping piston, and the anti-pumping piston check valve side chamber is connected to the switching valve pi of the check valve. A fluid pressure drive device for a circuit breaker, wherein the device is connected to a lot chamber, and the anti-pumping piston control chamber is connected to a return side via a throttle. 2. A contact comprising a movable contact and a fixed contact for interrupting the flow of current, a rod connected to the movable contact, a fluid pressure cylinder for opening or closing the rod, and At least one control valve for opening or closing the fluid pressure cylinder, a switching valve for switching the control valve between an open operation state and a closed operation state, and an open circuit for setting the switching valve to an open operation state in response to an open command. A pilot valve, a closing pilot valve for switching the switching valve to a closed operation state in response to a closing command, a fluid pressure source for pressurizing the working fluid, and accumulating the working fluid pressurized and supplied from the fluid pressure source. A hydraulic drive device for a circuit breaker, comprising an accumulator that performs the operation and a reservoir that collects and stores the discharged working fluid, wherein the switching valve includes a two-position three-way valve. A switching valve pilot chamber for switching the switching valve to a closed operation state when high pressure is applied to one end side, and a switching valve pilot chamber for switching to an open circuit operation state when low pressure is applied, and a control port connected to a pilot chamber of the control valve in the center, Connected to the fluid supply and the fluid return,
The control port is connected to the switching valve pilot chamber via a restrictor, and the closing pilot valve is connected to a supply side on the primary side and to a pipeline leading to the switching valve pilot chamber on the secondary side, and is used for the open circuit. The pilot valve has a primary side connected to a pipeline leading to the switching valve pilot chamber, a secondary side connected to a return side, and further, between the closing circuit pilot valve and the switching valve pilot chamber, from the switching valve pilot chamber to the switching valve pilot chamber. A check valve for preventing flow to the switching valve for closing circuit pilot chamber, and an anti-pumping piston for performing an operation of closing the check valve, the anti-pumping piston, the secondary side of the pilot valve for closing circuit the said The anti-pumping piston is connected to the anti-pumping piston control chamber on the non-return valve side of the anti-pumping piston, and the anti-pumping piston check valve side chamber is connected to the switching valve pi of the check valve. A fluid pressure drive device for a circuit breaker, wherein the device is connected to a lot chamber side, and the anti-pumping piston control chamber is connected to a return side via a throttle. 3. The fluid pressure drive device for a circuit breaker according to claim 1, wherein a spring is provided in the anti-pumping piston check valve side chamber. 4. The anti-pumping piston includes a cylindrical portion in the anti-pumping piston control chamber, the back surface of which is open to the return side. The force acting on the anti-pumping piston check valve side chamber at the time of switching to the closing operation state is smaller than the force acting on the check valve side chamber. The fluid pressure drive device for a circuit breaker according to any one of claims 1 to 3, wherein the force is set to be larger than a force acting on the pumping piston check valve side chamber.