JPS6342495Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention is an electrical equipment that is housed in a sealed container and sealed with an insulating fluid. Releases the insulating fluid when the pressure tries to rise,
This invention relates to a return type pressure relief device that returns to normal when the pressure drops to a required level.

[Prior art]

The type shown in FIG. 1 is generally used as a return type pressure relief device. Mounting seat 7 provided in electrical equipment sealed container
Then, the case 1 is provided with a seat 1b for fixing the pressure release cover 2, which is provided with a stud 2a for fixing the pressure release cover 2 at the center part protruding from the inner diameter part, and is fixed with a bolt 6 at the mounting part 1a of the case 1. It has a structure in which a pressure release cover 2 is placed on the end face via a gasket 4 and fixed with a nut 5 via a coil spring 3 as shown.

In this structure, if the compressive force of the coil spring 3 is T, the allowable pressure in the sealed container is _P1 , and the cross-sectional area of the end discharge port of the case 1 is S, then T
The amount of compression of the coil spring 3 is set so that the relationship =P ₁ ×S is established. In this case, the release start pressure is
becomes P ₁ . Let P be the pressure inside the sealed container, and P is P ₁
When the height increases, a gap is generated in the portion of the gasket 4 that is in contact with the end surface of the case 1, and the sealed fluid is released. Due to the discharge, the internal pressure P of the sealed container decreases, and when it becomes lower than _P1 , the discharge stops and the internal pressure P of the sealed container is maintained lower than _P1 .
However, in the pressure relief device of this structure, the pressure to start releasing the pressure and the pressure to stop are almost equal, and there is almost no pressing force against the gasket 4 after the gasket has stopped, which means that the pressure relief device is balanced with almost no pressure, which results in perfect sealing. The condition is not as expected. Furthermore, even a small pressure change due to a temperature change may cause the pressure release operation to be repeated, and there is a possibility that a chattering phenomenon may occur.

The structures shown in FIGS. 2 to 4 have been considered to compensate for the drawbacks of the structure shown in FIG. 1. Second
The structures shown in Figs. 4 to 4 have a structure in which a difference is provided between the discharge start pressure and the discharge stop pressure, and a pressing force is applied to the gasket during normal operation to ensure sealing.

FIG. 2 is a longitudinal sectional view showing the structure. FIG. 3 is a sectional view taken along the line AA shown in FIG. 2. FIG. 4 is a longitudinal sectional view showing the discharge state. This structure will be explained below. As shown in the figure, a pressure relief passage 11a is provided in the center, and a pressure relief hole 11b communicating from this 11a to the outer diameter part is provided, and the fluid in the auxiliary chamber 21 is momentarily released to the outside in the initial state of operation. Pressure relief valve 11 having the shape shown in the figure and having a communication port 11c
Attach the bolt 1 to the mounting seat 20 provided in the sealed container.
The coil spring 14 is inserted into the illustrated position of the case 15 provided with a flange 15a for fixing the coil spring 14 through the gasket 18, and a compressive force is applied to the spring using the spring retaining ring 12 and the nut 13. It is said that In this structure, the internal pressure of the sealed container is P, the allowable pressure in the sealed container is _P1 , the inner area where the sealing action of the gasket 18 is working is _S1 , and the outer diameter of the auxiliary chamber 21, that is, the sealed container side of the case 15. When the inner area of is S ₂ and the compressive force of the coil spring 14 at steady state is T, the force F exerted by the pressure relief valve 11 due to the internal pressure P of the sealed container is (1)
The formula becomes

F= _S1・P...(1) When the compressive force T of the coil spring 14 is strong relative to F, that is, when the relationship shown in equation (2) exists, the pressure relief valve 11
is in the steady state shown in FIG.

T≧F (2) However, when the internal pressure P increases and reaches _P1 , the force ₁ that tries to push out the pressure relief valve 11 becomes the equation (3).

F ₁ =S ₁ ·P ₁ (3) When the relationship between F ₁ and T is expressed as equation (4), the relationship between P ₁ and T is expressed as equation (5).

F ₁ >T (4) P ₁ >T・1/S ₁ (5) When P ₁ satisfies the condition of equation (5), the pressure relief valve 11 tends to be pushed out. The pressure relief valve 11 is pushed out, and the gasket 18 and the gasket 1 of the pressure relief valve 11 are
At the moment when a gap is created between the joints 8 and 8, the fluid in the auxiliary chamber 21 is released to the outside through the communication port 11c.
The pressure in the auxiliary chamber 21 drops to atmospheric pressure. Assuming that the force F ₂ is trying to push out the pressure relief valve 11 at this time,
F ₂ is related to equation (6).

F ₂ = S ₂ · P ₁ ...(6) F ₂ becomes S ₂ /S ₁ times that of F ₁ , and the pressure relief valve 11 moves instantaneously to the position shown in Fig. 4, and the insulation inside the sealed container is removed. Fluid is released. The compressive repulsive force T ₂ of the coil spring 14 when the pressure relief valve 11 is in the position shown in Fig. 4 is expressed as (7) where K is the spring constant and L is the amount of movement.
It becomes like the formula.

T ₂ = T + KL …(7) The insulating fluid is released, the internal pressure P decreases, (8)
When the relationship expressed by the equation is reached, the pressure relief valve 11 attempts to return to the state shown in FIG.

P<1/S ₂・(T+KL) ...(8) The pressure relief valve 11 gradually returns from the position shown in Fig. 3 to the position shown in Fig. 2, and the internal pressure when it reaches the position shown in Fig. 2 is
When P ₂ , the relationship is expressed by equation (9).

P ₂ = 1/S ₂ ·T (9) At the moment when the state shown in FIG. The pressure is equal to the internal pressure of the sealed capacity, and the force F ₃ that tries to push out the pressure relief valve 11 has the relationship shown in equation (10).

F ₃ =S ₁ ·P ₂ (10) The force F ₀ that attempts to seal the pressure relief valve 11 is the difference between the compressive repulsion force T of the coil spring 14 and F ₃ and has the relationship of equation (11).

F ₀ =T−F ₃ =S ₂ P ₂ −S ₁ P ₂ =(S ₂ −S ₁ )P ₂ (11) F ₀ acts as a force that compresses the gasket 18 and has a sealing effect.

In the pressure relief device having this structure, friction between the pressure relief valve 11 and the case 15 and between the sliding parts of the presser ring 12 and the inner diameter of the case 15 may impede the movement. Providing the opening 11c in the pressure relief valve 11 has the drawback of requiring special processing.

[Summary of the idea]

The present invention provides a configuration in which the pressure relief valve can be easily slid and a connecting port between the auxiliary chamber and the outside air can be easily provided.

[Example of idea]

An embodiment of the present invention will be described in detail below with reference to FIG. In contrast to the conventional structure shown in FIG. 3, the pressure relief passage 11a and the pressure relief port 11b of the pressure relief valve 11 are provided at the same positions as in the conventional structure, and the connection port is not provided on the pressure relief valve 11 but on the inner diameter side of the case 15. A connecting port 15b is provided at the position shown at 15b in FIG. It has a structure with

[Effect of idea]

With this structure, the connection port 15b connecting the auxiliary chamber 21 and the outside air can be provided by a simple process such as cutting grooves in 2 to 4 places with a file after processing the inner diameter of the case 15. Butsuyu 16,1
7 has the effect of eliminating sliding friction during operation and improving the accuracy of the relief pressure and stop pressure.

Needless to say, if the sliding parts are smooth and friction-free, there will be no need for a bushing.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a conventional pressure relief device, Fig. 2 is a longitudinal sectional view of another conventional pressure relief device, Fig. 3 is a sectional view taken along the - line in Fig. 2, and Fig. 4 is a longitudinal sectional view of another conventional pressure relief device. FIG. 5 is a longitudinal sectional view showing an embodiment of the present invention, and FIG. 6 is a sectional view taken along the - line in FIG. 5. In the figure, 11 is a pressure relief valve, 11a is a pressure relief passage, 11
b is a pressure release hole, 12 is a spring holding ring, 13 is a nut, 14 is a coil spring, 15 is a case, 15a is a flange, 15b is a connection port, 16 and 17 are bushings for bearings, 18 is a gasket, 19 is a bolt, 2
0 is a mounting seat, and 21 is an auxiliary chamber. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) If the internal pressure of an electrical device that is sealed with insulating fluid rises abnormally, the insulating fluid is released, and the range within which the insulating fluid is discharged does not exceed the withstand pressure of the container. An auxiliary chamber is provided in the pressure relief device that maintains the pressure inside the chamber, and the fluid in the auxiliary chamber is released during the initial stage of internal pressure rise.The force that pushes out the pressure relief valve at the time of pressure relief is calculated by multiplying the cross section of the outside diameter of the auxiliary chamber by the internal pressure. A pressure relief device characterized in that a connection passage is provided in the inner diameter portion of the pressure relief valve insertion portion on the case side. (2) The pressure relief device according to claim 1 of the utility model registration claim, characterized in that a bushing for smooth sliding is provided on the inner diameter of the case having a connecting passage.