JPH0775133B2 - Vacuum valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) [0001] The present invention relates to a vacuum valve, and more particularly to a structure of a bellows capable of obtaining a long fatigue life and high reliability.

(Prior Art) Generally, as shown in FIG. 8, a vacuum valve has a cylindrical end made of an insulating material such as ceramics or glass. The vacuum container 3 is formed by closing the side end plate 2b.
The fixed electrode 5 fixed to the end of the fixed current-carrying shaft 4 serving as the electric path and the movable electrode 7 fixed to the end of the movable current-carrying shaft 6 serving as the electric path are arranged in the inside of the chamber so as to be freely contactable and separable. The movable energizing shaft 6 is fixed to the other end of the bellows 8 whose one end is fixed to the movable end plate 2b, and is movable in the axial direction while maintaining the vacuum degree of the vacuum container 3. There is.
In addition, inside the vacuum container 3, a fixed electrode 5 and a movable electrode 7 are provided.
The metal vapor generated from both electrodes when opening and closing the insulation container 1
A metal shield 9 is provided so as to surround the fixed electrode 5 and the movable electrode 7 in order to prevent the insulation resistance from being reduced by being attached to the inner wall of the. For a vacuum valve that opens and closes frequently, a bellows is used, which is formed by drawing a stainless steel tube as a raw tube to a bellows wall thickness of 0.11 mm.

(Problems to be Solved by the Invention) However, since the bellows 8 expands and contracts when the fixed electrode 5 and the movable electrode 7 are opened and closed, bending stress is generated in the valleys or peaks of each bellows. Therefore, fatigue damage is accumulated in the valleys or ridges due to this stress and repeated opening and closing of the electrodes, resulting in fatigue. When this fatigue develops and penetrates in the plate thickness direction, the degree of vacuum in the vacuum container 3 decreases, the withstand voltage decreases, and the arc generated between the electrodes causes a discharge state and the vacuum valve cannot be shut off. It may cause a malfunction. As can be seen, the bellows 8 is one of the important parts that govern the life of the vacuum valve. In addition, the tendency to cause such a problem is
It is often found in vacuum valves used in vacuum circuit breakers that require frequent opening and closing hundreds of thousands of times.

As described above, in the bellows 8 formed into a bellows having a wall thickness of 0.11 mm, fatigue life occurs and fatigue life until it penetrates in the plate thickness direction (expandable deformation amount of the bellows 8 The fatigue life measured by doubling the above is about 80 to 170,000 times.

Therefore, an object of the present invention is to provide a vacuum valve capable of ensuring frequent opening and closing of several hundred thousand times or more and having high fatigue life and high reliability.

[Structure of Invention]

(Means and Actions for Solving Problems) The present invention forms a vacuum container by closing the openings on both ends of a cylindrical insulating container with fixed-side and movable-side end plates, respectively. A vacuum valve in which both fixed and movable electrodes that can be freely contacted and separated from each other are provided, and the movable current-carrying shaft having the movable electrode fixed to one end and the movable side end plate are airtightly connected by a bellows having peaks and valleys. Uses a stainless steel tube as a raw material and draws the bellows to a thickness of 0.09 to 0.07 mm. When the bellows wall is formed in this way, even if the average stress generated by the pressure difference between the atmospheric pressure acting on the inner side of the bellows and the vacuum acting on the outer side increases, it has little effect on the decrease in the fatigue life of the bellows. Rather, the bending stress amplitude generated in the peaks or valleys of each bellows of the bellows when the electrodes are opened and closed is reduced, and the fatigue life of the bellows is greatly improved.

(Embodiment) An embodiment of the vacuum valve of the present invention will be described below with reference to the drawings. The same parts as in FIG.
A duplicate description will be omitted. In FIG. 1, a vacuum valve
Reference numeral 10 denotes a vacuum container 3, a fixed electrode 5 and a movable electrode 7 which are arranged in the vacuum container 3 so as to be able to come into contact with and separate from each other, a metal shield 9, and one end of which is fixed to a movable side end plate 2b. The bellows 11 has the other end fixed to the movable energizing shaft 6. Here, the bellows 11 is formed by drawing a stainless steel pipe as a raw pipe into a bellows having a wall thickness of 0.09 to 0.07 mm.

Next, the structure of the bellows 11, especially the reason why the wall thickness is 0.09 to 0.07 mm, will be described. Since the bellows usually expands and contracts when the electrodes are opened and closed, bending stress is generated in the valleys or peaks of each bellow of the bellows as shown in FIG.
Bending stress amplitude Δ for the same expansion and contraction deformation amount of this bending stress
σ magnitude of _b increases in proportion to the thickness of the bellows, as shown in FIG. 3 (a). That is, the thickness of the bellows
By making the thickness less than 0.11 mm, the bending stress amplitude Δσ _b is reduced. This is because, as shown in FIG. 4, when the same bellows expands and contracts, the bending stress σ _b generated on the surface of the valleys or peaks of the bellows decreases as the wall thickness t of the bellows decreases. . Further, as the thickness t of the bellows becomes thinner, the weight of the bellows becomes lighter, so that the penetrating force due to high-speed opening and closing becomes smaller and the bellows expands and contracts less. Therefore, the bending stress amplitude Δσ occurring at the valley or peak of the bellows
_b is reduced. The fatigue life of the bellows is largely controlled by this bending stress amplitude, and as the bending stress amplitude Δσ _b decreases, the fatigue life N _f improves as shown in FIG. 3 (b). That is, as the thickness t of the bellows becomes thinner, the bending stress amplitude Δσ _b
Decreases and the fatigue life N _{f of the} bellows increases.

However, as shown in Fig. 5 (a), the bellows thickness t
Becomes thinner, the average stress σ _m based on the pressure difference between the atmospheric pressure acting on the inside of the bellows and the vacuum pressure acting on the outside increases. This average stress σ _m affects the fatigue life N _f as shown in FIG. 7B, and the fatigue life N _f decreases as the average stress σ _m increases. However, the above bending stress amplitude Δσ _b
The effect on the fatigue life N _f is smaller than that of

Therefore, reducing the thickness t of the bellows, reduce the stress amplitude .DELTA..sigma _b bent improve fatigue life N _f, leads to an increase in mean stress sigma _m to reduce the fatigue life N _f.

Figure 6 shows the bending stress amplitude Δ with respect to the fatigue life N _f of 10 ⁷ times.
from sigma _b tolerable line 12 to the average stress sigma _m tolerable line 13, but showing the bending stress amplitude .DELTA..sigma _b and tolerance of a combination of mean stress sigma _m (shaded area), and the dashed line 14, Bending stress amplitude Δσ _b due to thinning of the bellows thickness t
And the change of the combined stress of the average stress σ _m . As is clear from the figure, if the bellows wall thickness t is within the range of 0.09 to 0.07 mm, the fatigue life is 10 ⁷ times or more.

As described above, reducing the bellows thickness t is the fatigue life.
The improvement in N _f is based on the plate thickness effect of fatigue strength characteristics and the bending stress amplitude Δσ _b generated for the same amount of elastic deformation. However, the limit of the improvement is regulated by the increase of the average stress σ _m accompanying the reduction of the bellows thickness t. The thickness t of the bellows
Generally, as shown in FIG. 7, it is managed based on a relational diagram (created by experiment) between the spring constant K of the bellows and the wall thickness t of the bellows. By adjusting (reducing) using means, more sufficient management becomes possible. This makes it possible to obtain a bellows having a high fatigue life and high reliability.

In the bellows formed into a bellows having a wall thickness of 0.09 to 0.07 mm, the present inventors have experienced fatigue and fatigue life until they penetrate in the plate thickness direction. The fatigue life measured by doubling the amount) is about
It has been confirmed by experiments that it is 160 to 4 million times or more, the fatigue life is drastically improved compared to the conventional bellows with a wall thickness of 0.11 mm, and the frequent opening and closing of the electrode several hundred thousand times or more can be sufficiently guaranteed. .

Although the above description has been made on the vacuum valve that opens and closes the electrode at a high frequency of hundreds of thousands of times or more, the vacuum valve for other applications requiring the opening and closing of the electrode at a frequency of 10,000 to 20,000 times can be used for the bellows. Fatigue strength (temporal strength) is improved by using a bellows with a wall thickness of 0.09 to 0.07 mm, so the expansion and contraction amount of the bellows at the time of opening and closing the electrode can be increased and the opening and closing of the electrode can be made faster. be able to.

〔The invention's effect〕

Since the present invention is configured as described above, a vacuum valve with a long fatigue life and high reliability that can guarantee frequent opening and closing of the electrode for hundreds of thousands of times or more can be obtained, and the controlled device can be stable for a long period of time. It is possible to facilitate proper operation and maintenance and inspection.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the vacuum valve of the present invention,
FIG. 2 is an explanatory view showing a temporal change of bending stress generated in a peak portion or a valley portion of a bellows related to the present invention, and FIGS. 3 (a) and (b) are bellows in the bellows related to the present invention. 4 (a) and (b) are bending stresses occurring in the valleys or peaks of the bellows of the bellows related to the present invention. FIG. 5 (a) is an explanatory view showing an enlarged part A and FIG.
(b) is an explanatory view showing the relationship between the thickness of the bellows and the average stress and the fatigue life and the average stress in the bellows related to the present invention, and FIG. 6 is the average for the fatigue life of 10 ⁷ times of the bellows related to the present invention. Explanatory drawing showing the allowable stress range of the combination of stress and bending stress amplitude, FIG. 7 is an explanatory view of the relationship between the bellows wall thickness and the spring constant in the bellows related to the present invention, and FIG. 8 is the structure of a conventional vacuum valve. FIG. 1 ... Insulating container, 2a ... Fixed side end plate 2a ... Movable side end plate, 3 ... Vacuum container 5 ... Fixed electrode, 6 ... Movable energizing shaft 7 ... Movable electrode, 11 ... Bellows

Claims (1)

[Claims] 1. A fixed and movable electrode which can be contacted with and separated from the inside of the vacuum container by forming a vacuum container by closing the openings of both ends of a cylindrical insulating container with fixed and movable end plates. In a vacuum valve in which the movable current-carrying shaft having the movable electrode fixed to one end and the movable side end plate are hermetically connected by a bellows having peaks and valleys. A vacuum valve characterized by forming a bellows wall thickness of 0.09 to 0.07 mm.