Electric field relaxation structure, vacuum valve, method of manufacturing electric field relaxation structure and method of manufacturing vacuum valve

Abstract

The electric field relaxation structure comprises a ceramic insulator (2), a ceramic layer (6) laminated on the ceramic insulator (2) and containing zinc oxide and having voltage nonlinear resistance characteristics, and an insulating layer (7) laminated on the ceramic layer (6), thereby not limiting the current-carrying area and suppressing peeling due to heat generation.

Description

[Technical field]

[0001] The present disclosure relates to an electric field relaxation structure, a vacuum interrupter, a method for manufacturing an electric field relaxation structure, and a method for manufacturing a vacuum interrupter. [Background technology]

[0002] Insulation design is carried out for devices that have high electric field parts. The electric field is a major consideration, and the design is carried out so that the electric field for the applied voltage is below the allowable value. If the structure has a margin for the electric field compared to the allowable value, the insulation distance can be further shortened, making it possible to further miniaturize the device. Therefore, mitigating the electric field is a means of miniaturizing the device.

[0003] A known method for mitigating the electric field is to place a voltage nonlinear resistance material in the high electric field area. For example, in Patent Document 1, a composite material made of a compound (resin) of ZnO or SiC (ceramic voltage nonlinear resistance material filler) is applied to the inner or outer surface of the insulating container of a vacuum valve to improve the electric potential distribution. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 60-75940 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the current flows only through the ZnO or SiC filler, which limits the current-carrying area. The limited current-carrying area can cause the current density to increase in certain areas, generating heat and potentially causing peeling due to differences in thermal expansion.

[0006] The present disclosure has been made in view of the above, and has an object to obtain an electric field relaxation structure that does not limit the current-carrying area and can suppress peeling due to heat generation. [Means for solving the problem]

[0007] In order to solve the above problems and achieve the object, the electric field relaxation structure of the present disclosure has a ceramic insulator and a zinc oxide-containing dielectric laminated on the ceramic insulator, the zinc oxide-containing dielectric laminate having a voltage nonlinear resistance characteristic. Consists entirely of ceramic materials The substrate includes a ceramic layer and an insulating layer laminated on the ceramic layer. Effect of the Invention

[0008] The electric field relaxation structure of the present disclosure has the advantage that the current flow area is not limited and peeling due to heat generation can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing a layer configuration of an electric field relaxation structure according to a first embodiment; [Diagram 2] FIG. 1 is a diagram showing the relationship between the electric field and current characteristics of a varistor according to a first embodiment. [Diagram 3] FIG. 1 is a diagram showing a method for manufacturing a ceramic layer having a voltage nonlinear resistance characteristic of an electric field relaxation structure according to the first embodiment. [Figure 4] FIG. 11 is a cross-sectional view showing a layer configuration of an electric field relaxation structure according to a second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the second embodiment. [Figure 6] FIG. 11 is a cross-sectional view showing a layer configuration of an electric field relaxation structure according to a third embodiment. [Figure 7] FIG. 13 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the third embodiment. [Figure 8] FIG. 11 is a cross-sectional view showing a layer configuration of an electric field relaxation structure according to a fourth embodiment. [Figure 9] FIG. 13 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the fourth embodiment. [Figure 10] FIG. 13 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the fourth embodiment. [Figure 11] FIG. 13 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the fourth embodiment. [Figure 12] FIG. 13 is a cross-sectional view showing the configuration of a vacuum interrupter according to a fifth embodiment. [Figure 13] FIG. 13 is a cross-sectional view showing a configuration of a modified example of the vacuum interrupter according to the fifth embodiment. [Figure 14] FIG. 13 is a cross-sectional view showing a configuration of a modified example of the vacuum interrupter according to the fifth embodiment. [Figure 15] FIG. 13 is a plan view showing a modified example of an electric field relaxation structure used in a vacuum interrupter according to a fifth embodiment. [Figure 16] FIG. 13 is a plan view showing a modified example of an electric field relaxation structure used in a vacuum interrupter according to a fifth embodiment. [Figure 17] FIG. 13 shows experimental results of various performances according to Examples 1 to 17 and Comparative Examples 1 to 3 in the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An electric field relaxation structure, a vacuum interrupter, a method for manufacturing an electric field relaxation structure, and a method for manufacturing a vacuum interrupter according to embodiments will be described in detail below with reference to the drawings.

[0011] Embodiment 1 1 is a cross-sectional view showing a layer configuration of the electric field relaxation structure according to the first embodiment. The electric field relaxation structure includes a ceramic insulator 2, a ceramic layer 6 having voltage nonlinear resistance characteristics, and an insulating layer 7. In this electric field relaxation structure, the ceramic layer 6 is laminated on the ceramic insulator 2, and the insulating layer 7 is laminated on the ceramic layer 6.

[0012] The voltage nonlinear resistor realized by the ceramic layer 6 has a characteristic of being an insulator when a low electric field is applied and a conductor when a high electric field is applied, and is a material that reversibly shows an insulator and a conductor at the threshold electric field. Therefore, the voltage nonlinear resistor does not follow Ohm's law and is called a varistor. Figure 2 is a diagram showing the relationship between the electric field and the current characteristic of the varistor according to the first embodiment. As shown in Figure 2, the varistor has an electric characteristic in which the resistance changes at the threshold electric field Ec beyond the low electric field region, and a current flows suddenly in the electric field region above the threshold electric field Ec. The varistor is a material that is mainly composed of zinc oxide and is sintered after adding small amounts of several types of subcomponents. The varistor is a material that can control performance such as the magnitude of the threshold electric field Ec and the volume resistance when it is an insulator by the composition.

[0013] The ceramic layer 6, which is the voltage nonlinear resistor in the first embodiment, is manufactured as follows. First, zinc oxide powder, which is the main raw material, is weighed. Next, as auxiliary components, bismuth oxide, antimony oxide, chromium oxide, nickel oxide, manganese oxide, cobalt oxide, and silicon oxide are added so that the total amount becomes 100 mol% together with the zinc oxide, which is the main raw material, and they are crushed and mixed using water as a medium. At this time, a binder for adhering the raw materials to each other and a dispersant for uniformly dispersing the raw materials are added. For example, the zinc oxide powder is 96.5 mol%, bismuth oxide 0.5 mol%, antimony oxide 0.5 mol%, chromium oxide 0.5 mol%, nickel oxide 0.5 mol%, manganese oxide 0.5 mol%, cobalt oxide 0.5 mol%, and silicon oxide 0.5 mol%. At this time, it is better to crush and mix the raw materials uniformly and to have the same average particle size.

[0014] The mixed material is then sprayed into a high-temperature atmosphere of 100°C or higher to spray-dry the raw materials, thereby obtaining spherical granules 1 in which the raw materials, such as zinc oxide, bismuth oxide, antimony oxide, chromium oxide, nickel oxide, manganese oxide, cobalt oxide, and silicon oxide, are uniformly aggregated.

[0015] Next, the ceramic insulator 2 and the spherical granules 1 are integrated using a mold. FIG. 3 is a diagram showing a method for manufacturing a ceramic layer 6 having voltage nonlinear resistance characteristics of an electric field relaxation structure according to the first embodiment. As shown in FIG. 3, for example, a mold consisting of a die 3, an upper punch 4, and a lower punch 5 is used. First, the ceramic insulator 2 is placed on the lower punch 5 of the mold, and the spherical granules 1 are poured onto the ceramic insulator 2. Next, the upper punch 4 is lowered to apply pressure to the spherical granules 1 to form a molded body. This integrates the ceramic insulator 2 and the molded body. Then, the ceramic layer 6 having voltage nonlinear resistance characteristics is obtained by firing, which will be described later.

[0016] As the ceramic insulator 2, various ceramics such as aluminum oxide, titanium oxide, chromium oxide, silicon oxide, glass, silicon nitride, silicon carbide, zirconium dioxide, mullite, stearite, forsterite, cordierite, and aluminum nitride can be used, but aluminum oxide is preferable from the viewpoint of cost. In this case, if the ceramic insulator 2 is a material having an uneven surface, a higher adhesion to the ceramic layer 6 can be obtained due to the anchor effect. Thereafter, the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics are fired at a temperature of 1000° C. or higher while they are integrated, thereby making it possible to produce the ceramic layer 6 having voltage nonlinear resistance characteristics from the compact.

[0017] For the insulating layer 7, various insulating materials such as resin, ceramic, glass, etc. can be used.

[0018] In this way, in the first embodiment, since the voltage nonlinear resistor is made only of ceramic and does not contain resin, the current-carrying area is not limited, and peeling due to heat generation can be suppressed.

[0019] Embodiment 2 4 is a cross-sectional view showing the layer configuration of the electric field relaxation structure according to embodiment 2. In embodiment 2, a glass layer 8 is provided between ceramic insulator 2 and ceramic layer 6 having voltage nonlinear resistance characteristics, thereby improving the adhesion between ceramic insulator 2 and ceramic layer 6 having voltage nonlinear resistance characteristics.

[0020] The glass layer 8 acts as an adhesive that connects the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics, and can improve adhesion. For example, by using the ceramic insulator 2 that has the glass layer 8 on its surface in advance and carrying out the manufacturing method described with reference to FIG. 3, for example, the electric field relaxation structure shown in FIG. 4 is created.

[0021] FIG. 5 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the second embodiment. The molded body is in a state where pressure is applied to the spherical granules 1, and there are voids between the spherical granules 1. The voids are expelled to the outside by firing, and the molded body becomes dense. Therefore, when a ceramic insulator 2 having a glass layer 8 between the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics is used, as shown in FIG. 5, the glass layer 8 enters the voids, and after firing, an interface layer 9 can be formed in which the glass contained in the glass layer 8 and the ceramic contained in the ceramic layer 6 having voltage nonlinear resistance characteristics coexist.

[0022] According to the configuration of FIG. 5, the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics can be bonded more firmly. Such a layer configuration can be created by slowing down the firing rate of the ceramic layer 6 having voltage nonlinear resistance characteristics, softening the glass before firing the molded body, and allowing the glass to penetrate into the gaps in the molded body. From the viewpoint of the permeability of the glass layer 8, the porosity is preferably 20% or more. Also, from the viewpoint of handling the molded body, the porosity is preferably 80% or less. The porosity can be calculated, for example, by calculating the bulk density from the weight and apparent volume of the molded body, and then calculating the ratio of the calculated bulk density to the true density after firing.

[0023] Thus, according to embodiment 2, a glass layer 8 is provided between the ceramic insulator 2 and the ceramic layer 6 having voltage-nonlinear resistance characteristics, or an interface layer 9 is provided in which the glass contained in the glass layer 8 and the ceramic contained in the ceramic layer 6 having voltage-nonlinear resistance characteristics coexist, thereby making the adhesion between the ceramic insulator 2 and the ceramic layer 6 having voltage-nonlinear resistance characteristics stronger.

[0024] Embodiment 3 6 is a cross-sectional view showing the layer configuration of the electric field relaxation structure according to embodiment 3. The method for forming the insulating layer 7 includes a first method in which the insulating layer 7 is newly formed after the ceramic layer 6 having the voltage nonlinear resistance characteristic is formed, and a second method in which the insulating layer 7 is simultaneously formed when the ceramic layer 6 having the voltage nonlinear resistance characteristic is formed.

[0025] In the first method, after firing the ceramic layer 6 having voltage nonlinear resistance characteristics, a resin can be applied to the surface by spraying or brushing and then cured to form the insulating layer 7. Alternatively, the insulating layer 7 can be made of glass by spraying a glass paste and firing the glass.

[0026] In the second method, after making a molded body from the spherical granules 1, a precursor material of the insulating layer 7 is applied to the upper surface of the molded body, and the precursor and the molded body are reacted to make the insulating layer 7. The precursor material is a mixture of at least one of bismuth oxide, antimony oxide, and silicon oxide, mixed with an organic material, and made into a paste. The molded body and the precursor react with each other by firing when making the ceramic layer 6 having voltage nonlinear resistance characteristics, and the insulating layer 7 is made. When the firing temperature exceeds 1100°C, the reaction between the molded body and the precursor becomes active, and as shown in FIG. 6, an interface layer 10 in which the insulator contained in the insulating layer 7 and the ceramic contained in the ceramic layer 6 having voltage nonlinear resistance characteristics coexist can also be provided. This interface layer 10 strengthens the adhesion between the ceramic layer 6 having voltage nonlinear resistance characteristics and the insulating layer 7, making it less likely that peeling will occur.

[0027] 7 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the third embodiment. In the electric field relaxation structure of FIG. 7, the insulating layer 7 has a two-layer structure of an insulating layer 71 and an insulating layer 72. The insulating layer 71 and the insulating layer 72 are made of different materials. One of the insulating layers 71 and 72 is made of Zn2SiO4 or Zn7Sb2O 12 If the structure includes the above, the insulating characteristics can be further improved, and the adhesion between the ceramic layer 6 having the voltage nonlinear resistance characteristics and the insulating layer 7 can be further strengthened.

[0028] Thus, according to embodiment 3, an interface layer 10 is provided between the ceramic layer 6 having voltage-nonlinear resistance characteristics and the insulating layer 7, in which the insulator contained in the insulating layer 7 and the ceramic contained in the ceramic layer 6 having voltage-nonlinear resistance characteristics coexist, thereby making the adhesion between the ceramic layer 6 having voltage-nonlinear resistance characteristics and the insulating layer 7 stronger.

[0029] Embodiment 4 Fig. 8 is a cross-sectional view showing a layer configuration of an electric field relaxation structure according to a fourth embodiment. The electric field relaxation structure of Fig. 8 includes a ceramic insulator 2, a glass layer 8, a ceramic layer 6 having a voltage nonlinear resistance characteristic, an interface layer 10 in which the insulating layer 7 and the ceramic layer 6 having a voltage nonlinear resistance characteristic coexist, and an insulating layer 7. In this electric field relaxation structure, the glass layer 8, the ceramic layer 6, the interface layer 10, and the insulating layer 7 are sequentially stacked on the ceramic insulator 2. The electric field relaxation structure of Fig. 8 is produced by combining the manufacturing method of the electric field relaxation structure of Fig. 4 and the manufacturing method of the electric field relaxation structure of Fig. 6.

[0030] 9 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the fourth embodiment. The electric field relaxation structure of FIG. 9 includes a ceramic insulator 2, a glass layer 8, a ceramic layer 6 having a voltage nonlinear resistance characteristic, an interface layer 10 in which an insulating layer 71 and a ceramic layer 6 having a voltage nonlinear resistance characteristic coexist, and insulating layers 71 and 72 having a two-layer structure. In this electric field relaxation structure, the glass layer 8, the ceramic layer 6, the interface layer 10, and the insulating layers 71 and 72 having a two-layer structure are sequentially stacked on the ceramic insulator 2. The electric field relaxation structure of FIG. 9 is produced by combining the manufacturing method of the electric field relaxation structure of FIG. 4, the manufacturing method of the electric field relaxation structure of FIG. 6, and the manufacturing method of the electric field relaxation structure of FIG. 7.

[0031] Fig. 10 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the fourth embodiment. The electric field relaxation structure of Fig. 10 includes a ceramic insulator 2, a glass layer 8, an interface layer 9 in which the glass layer 8 and a ceramic layer 6 having a voltage nonlinear resistance characteristic coexist, a ceramic layer 6 having a voltage nonlinear resistance characteristic, an interface layer 10 in which the insulating layer 7 and a ceramic layer 6 having a voltage nonlinear resistance characteristic coexist, and an insulating layer 7. In this electric field relaxation structure, the glass layer 8, the interface layer 9, the ceramic layer 6, the interface layer 10, and the insulating layer 7 are sequentially stacked on the ceramic insulator 2. The electric field relaxation structure of Fig. 10 is produced by combining the manufacturing method of the electric field relaxation structure of Fig. 5 and the manufacturing method of the electric field relaxation structure of Fig. 6.

[0032] FIG. 11 is a cross-sectional view showing a layer structure of a modified example of the electric field relaxation structure according to the fourth embodiment. The electric field relaxation structure of FIG. 11 includes a ceramic insulator 2, a glass layer 8, an interface layer 9 in which the glass layer 8 and a ceramic layer 6 having a voltage nonlinear resistance characteristic coexist, a ceramic layer 6 having a voltage nonlinear resistance characteristic, an interface layer 10 in which an insulating layer 71 and a ceramic layer 6 having a voltage nonlinear resistance characteristic coexist, and insulating layers 71 and 72 of a two-layer structure. In this electric field relaxation structure, the glass layer 8, the interface layer 9, the ceramic layer 6, the interface layer 10, and the insulating layers 71 and 72 of a two-layer structure are sequentially stacked on the ceramic insulator 2. The electric field relaxation structure of FIG. 11 is produced by combining the manufacturing method of the electric field relaxation structure of FIG. 5, the manufacturing method of the electric field relaxation structure of FIG. 6, and the manufacturing method of the electric field relaxation structure of FIG. 7.

[0033] Embodiment 5. In the fifth embodiment, a vacuum interrupter to which the above-mentioned electric field relaxation structure is applied will be described. Fig. 12 is a cross-sectional view showing the configuration of a vacuum interrupter 11 according to the fifth embodiment. Fig. 12 shows the state in which the contacts of the vacuum interrupter 11 are closed. The vacuum interrupter 11 includes a fixed electrode bar 12, a movable electrode bar 13, a fixed contact 14, a movable contact 15, a bellows 16, a fixed end plate 17, a movable end plate 18, an arc shield 19, a ceramic insulator 21, and a ceramic insulator 22. The ceramic insulator 21 and the ceramic insulator 22 correspond to the ceramic insulator 2 in the first to fourth embodiments. The first electrode corresponds to the fixed electrode bar 12 and the fixed contact 14, and the second electrode corresponds to the movable electrode bar 13 and the movable contact 15.

[0034] The vacuum valve 11 comprises an arc shield 19, ceramic insulators 21, and ceramic insulators 22, which constitute, for example, a cylindrical vacuum insulating container. A fixed end plate 17 and a movable end plate 18 are sealed to the circular openings at both ends of the vacuum insulating container. The fixed electrode bar 12 is fixed to the fixed end plate 17 by brazing while passing through the plate. A fixed contact 14 is fixed to the end of the fixed electrode bar 12 inside the vacuum insulating container by brazing.

[0035] The movable electrode bar 13 is provided so as to penetrate the movable end plate 18. A movable contact 15, which is freely movable into and out of contact with the fixed contact 14, is fixed to the end of the movable electrode bar 13 by brazing, facing the fixed contact 14. That is, the movable contact 15 comes into contact with the fixed contact 14 or moves away from the fixed contact 14 in accordance with the movement of the movable electrode bar 13. A freely expandable bellows 16 is provided in the middle of the movable electrode bar 13.

[0036] The ceramic insulator 21 is fixed to the fixed end plate 17 by brazing, and the ceramic insulator 22 is fixed to the movable end plate 18 by brazing. In the vacuum insulating container, the arc shield 19 is fixed to the divided ceramic insulators 21, 22 by brazing so as to be sandwiched between them. In other words, the arc shield 19 is provided between the ceramic insulators 21, 22 so as to surround the fixed contact 14 and the movable contact 15. The arc shield 19 is made of a metal such as stainless steel.

[0037] In the fifth embodiment, an electric field relaxation layer 20 is laminated and fixed to the outer peripheral surfaces of ceramic insulators 21 and 22 . 1, the glass layer 8, the ceramic layer 6 and the insulating layer 7 having voltage nonlinear resistance characteristics in FIG. 4, the glass layer 8, the interface layer 9, the ceramic layer 6 and the insulating layer 7 having voltage nonlinear resistance characteristics in FIG. 5, the ceramic layer 6, the interface layer 10 and the insulating layer 7 having voltage nonlinear resistance characteristics in FIG. 6, the ceramic layer 6, the interface layer 10 and the insulating layer 7 having voltage nonlinear resistance characteristics in FIG. 7, the glass layer 8, the ceramic layer 6, the interface layer 10 and the insulating layer 7 having voltage nonlinear resistance characteristics in FIG. 8, the glass layer 8, the ceramic layer 6, the interface layer 10 and the insulating layer 7 having voltage nonlinear resistance characteristics in FIG. 9, the glass layer 8, the ceramic layer 6, the interface layer 10 and the insulating layer 7 having voltage nonlinear resistance characteristics in FIG. 10, or the glass layer 8, the interface layer 9, the ceramic layer 6, the interface layer 10 and the insulating layer 71 and 72 in FIG. 11.

[0038] Fig. 13 is a cross-sectional view showing the configuration of a modified example of the vacuum interrupter 11a according to the fifth embodiment. In the vacuum interrupter 11a of Fig. 13, the vacuum insulating container is made of an undivided ceramic insulator 23. The arc shield 19 is disposed on the inner peripheral surface of the ceramic insulator 23. In addition, the electric field relaxation layer 20 similar to that described above is laminated and fixed to the outer peripheral surface of the ceramic insulator 23.

[0039] Fig. 14 is a cross-sectional view showing the configuration of a modified example of the vacuum interrupter 11b according to the fifth embodiment. In the vacuum interrupter 11b of Fig. 14, the electric field relaxation layer 20 is laminated and fixed to the outer peripheral surface of one of the divided ceramic insulators 21, 22. In the case of Fig. 14, the electric field relaxation layer 20 is laminated and fixed to the outer peripheral surface of the ceramic insulator 22.

[0040] FIG. 15 is a plan view showing a modified example of the electric field relaxation structure used in the vacuum interrupter according to the fifth embodiment. FIG. 16 is a plan view showing a modified example of the electric field relaxation structure used in the vacuum interrupter according to the fifth embodiment. In the electric field relaxation structure of FIG. 15, the electric field relaxation layers 20 are dispersedly disposed on the ceramic insulators 21, 22, and 23 of FIG. 12 to FIG. 14. In the electric field relaxation structure of FIG. 15, a plurality of elongated electric field relaxation layers 20 extending in the direction in which the fixed electrode bar 12 or the movable electrode bar 13 extends are disposed intermittently along the circumferential direction. In the electric field relaxation structure of FIG. 16, a plurality of elongated electric field relaxation layers 20 extending in the direction in which the fixed electrode bar 12 or the movable electrode bar 13 extends are formed in a meandering wave shape, and a plurality of wave-shaped electric field relaxation layers 20 are disposed intermittently along the circumferential direction.

[0041] The ceramic insulators 21, 22, 23 and the electric field relaxation layer 20 are manufactured by the method of the first embodiment, but in the case of a cylindrical shape such as a vacuum valve, they can be created by cold isostatic pressing using a rubber mold. In the cold isostatic pressing, the ceramic insulators 21, 22, 23 are set in a rubber mold, and the spherical granules 1 are poured into the gap between the ceramic insulators 21, 22, 23 and the rubber mold to fill it, and after filling, the inlet for putting in the spherical granules 1 is sealed, and then isotropic pressure is applied by water pressure. This results in a molded body that has been subjected to the same pressure as a uniaxial press using a mold. Thereafter, firing is performed as described in the first embodiment, and an insulating layer 7 is provided in the same manner as in the first embodiment, thereby making it possible to create a vacuum valve having an electric field relaxation structure in which a layer configuration of a ceramic layer 6 having voltage nonlinear resistance characteristics and an insulating layer 7 is provided on the surface of the ceramic insulator 2.

[0042] Embodiment 6 In the sixth embodiment, performance comparison is made between Examples 1 to 17 and Comparative Examples 1 to 3. Fig. 17 is a diagram showing experimental results of various performances according to Examples 1 to 17 and Comparative Examples 1 to 3 in the sixth embodiment.

[0043] For the layer structures of Examples 1 to 17 and Comparative Examples 1 to 3, "present" in the figures indicates that the layer structure is included, whereas a "hyphen" indicates that the layer structure is not included. For example, Example 1 has a layer structure including a ceramic insulator 2, a ceramic layer 6 having voltage nonlinear resistance characteristics, and an insulating layer 7. For each of Examples 1 to 17 and Comparative Examples 1 to 3, the performance such as the electric field relaxation effect, the insulating performance of the insulating layer, the peel strength of the layer, and the handling of the molded body were investigated.

[0044] The electric field relaxation effect was investigated using the vacuum interrupter 11 shown in Fig. 12. With the fixed electrode 12 connected to the voltage application side and the movable electrode 13 connected to the ground, a voltage was applied and the potential of the arc shield 19 was measured to determine the electric field relaxation effect.

[0045] The ceramic insulator 2 was made of alumina with a thickness of 10 mm. The glass layer 8 was made of glass with a thickness of 1 mm and mainly composed of silicon oxide. The ceramic layer 6 having voltage nonlinear resistance characteristics was made of the material with the composition described in the first embodiment and had a thickness of 2 mm. The main component of the insulating layer 7 was Zn2SiO4 and the thickness was 200 μm. When the insulating layer 7 is composed of two layers, the insulating layers 71 and 72, the main component of the insulating layer 71 was Zn2SiO4 with a thickness of 100 μm and the main component of the insulating layer 72 was Zn7Sb2O 12 A material having a thickness of 100 μm was used. In interface layer 9 where glass layer 8 and ceramic layer 6 having voltage nonlinear resistance characteristics coexist, glass containing silicon oxide as a main component and ceramic layer 6 having voltage nonlinear resistance characteristics made of a material with the composition described in embodiment 1 coexist, and the thickness is 10 μm. In interface layer 10 where insulating layer 7 and ceramic layer 6 having voltage nonlinear resistance characteristics coexist, ceramic layer 6 having voltage nonlinear resistance characteristics made of a material with the composition described in embodiment 1 and Zn2SiO4 coexist, and the thickness is 10 μm.

[0046] Regarding the peel strength, the peel strength between the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics, and the peel strength between the ceramic layer 6 having voltage nonlinear resistance characteristics and the insulating layer 7 are shown separately. Furthermore, for the ceramic layer 6 having voltage nonlinear resistance characteristics, the porosity of the molded body before firing was also investigated, and the relationship with handling of the molded body was examined.

[0047] Regarding the electric field relaxation effect, if it is effective, it is indicated with a circle, and if it is not effective, it is indicated with an x. Regarding the insulating performance of the insulating layer, excellent means excellent, good means good and indicates that it is above the allowable level, and poor means poor and indicates that it does not reach the allowable level. Regarding the peel strength, excellent means outstanding, excellent means excellent, and good means good. All of these levels exceed the allowable value and are usable, with excellent being the best in that order. Poor means poor. Regarding the handling of the molded body, excellent means excellent, and good means good and indicates that it is above the allowable level.

[0048] As shown in Fig. 17, Examples 1 to 17 all include at least the ceramic insulator 2, the ceramic layer 6 having voltage nonlinear resistance characteristics, and the insulating layer 7, and all have an electric field relaxation effect. On the other hand, Comparative Examples 1, 2, and 3 lacking any one of the ceramic insulator 2, the ceramic layer 6 having voltage nonlinear resistance characteristics, and the insulating layer 7 did not have an electric field relaxation effect. Note that in Comparative Example 1, since there was no ceramic insulator 2, it was not possible to manufacture the ceramic layer 6 having voltage nonlinear resistance characteristics.

[0049] Comparing among Examples 1 to 17, by providing the glass layer 8, the peel strength between the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics was improved from good to excellent. Furthermore, by providing the interface layer 9 in which the glass layer 8 and the ceramic layer 6 having voltage nonlinear resistance characteristics coexist, the peel strength between the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics was improved from excellent to excellent, and the strength was further increased. Furthermore, by providing the interface layer 10 in which the insulating layer 7 and the ceramic layer 6 having voltage nonlinear resistance characteristics coexist, the peel strength between the ceramic layer 6 having voltage nonlinear resistance characteristics and the insulating layer 7 was improved to excellent or higher. Furthermore, by providing the insulating layers 71 and 72, the peel strength became excellent, and the insulating performance of the insulating layers 71 and 72 was also improved from good to excellent.

[0050] Examples 2, 10, 11, 12, and 13 have the same layer structure, but the porosity before firing is different, 60%, 20%, 80%, 19%, and 81%, respectively. No difference was observed in performance and handling of the molded body between Examples 2, 10, and 11. On the other hand, in Example 12, which has a porosity of 19% before firing, the peel strength between the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics was lowered to good. In Example 13, which has a porosity of 81% before firing, the handling of the molded body was lowered to good.

[0051] In Examples 8, 14, 15, 16, and 17, which have layer structures different from those of Examples 2, 10, 11, 12, and 13, the porosity before firing is 60%, 20%, 80%, 19%, and 81%, respectively. In Examples 8, 14, and 15, no difference was observed in performance and handling of the molded body. On the other hand, in Example 16, which has a porosity of 19% before firing, the peel strength between the ceramic insulator 2 and the ceramic layer 6 having voltage nonlinear resistance characteristics was significantly reduced. In Example 17, which has a porosity of 81% before firing, the handling of the molded body was significantly reduced. Therefore, it was found that the porosity before firing is preferably 20% or more and 80% or less.

[0052] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the gist of the present disclosure. [Explanation of symbols]

[0053] 1 spherical granules, 2,21,22,23 ceramic insulator, 3 die, 4 upper punch, 5 lower punch, 6 ceramic layer, 7,71,72 insulating layer, 8 glass layer, 9,10 interface layer, 11,11a,11b vacuum valve, 12 fixed electrode bar, 13 movable electrode bar, 14 fixed contact, 15 movable contact, 16 bellows, 17 fixed end plate, 18 movable end plate, 19 arc shield, 20 electric field relaxation layer.

Claims

1. A ceramic insulator; a ceramic layer laminated on the ceramic insulator and made only of a ceramic material containing zinc oxide and having voltage nonlinear resistance characteristics; an insulating layer laminated on the ceramic layer; An electric field relaxation structure characterized by:

2. A glass layer is provided between the ceramic insulator and the ceramic layer.

2. The electric field relaxation structure according to claim 1.

3. An interface layer in which glass and ceramic having voltage nonlinear resistance characteristics coexist is provided between the glass layer and the ceramic layer.

3. The electric field relaxation structure according to claim 2.

4. An interface layer is provided between the ceramic layer and the insulating layer, in which the ceramic containing zinc oxide and having voltage nonlinear resistance characteristics and the insulator contained in the insulating layer coexist.

2. The electric field relaxation structure according to claim 1.

5. The insulating layer is composed of at least two layers, and one of the two layers contains Zn2SiO4 or Zn7Sb2O12.

5. The electric field relaxation structure according to claim 4.

6. an insulating container made of the ceramic insulator; end plates fixed to both ends of the insulating container; a first electrode housed in the insulating container from one of the end plates; a second electrode that is accommodated in the insulating container from the other end plate and moves toward and away from the first electrode; an arc shield provided in a middle portion of the insulating container; Equipped with The layer structure excluding the ceramic insulator in the electric field relaxation structure according to any one of claims 1 to 5 is laminated on the outer peripheral surface of the insulating container. A vacuum valve characterized by:

7. A step of placing spherical granules of a material having voltage nonlinear resistance characteristics on a ceramic insulator and pressing the material to form a compact layer of the material having voltage nonlinear resistance characteristics; firing the ceramic insulator and the compact layer to form the ceramic insulator and a ceramic layer having voltage nonlinear resistance characteristics; providing an insulating layer on the ceramic layer having voltage nonlinear resistance characteristics.

10. A method for manufacturing an electric field relaxation structure comprising:

8. A step of placing spherical granules of a material having voltage nonlinear resistance characteristics on a ceramic insulator and pressing the material to form a compact layer of the material having voltage nonlinear resistance characteristics; Applying a precursor material of an insulating layer to a surface of the molded body layer; and firing the precursor materials of the ceramic insulator, the compact layer, and the insulating layer to create a layer structure of the ceramic insulator, the ceramic layer having voltage nonlinear resistance characteristics, and the insulating layer.

10. A method for manufacturing an electric field relaxation structure comprising:

9. The ceramic layer having voltage nonlinear resistance characteristics has a porosity of 20% or more and 80% or less before firing.

9. The method for manufacturing an electric field relaxation structure according to claim 7 or 8.

10. 7. A method for manufacturing a vacuum valve according to claim 6, comprising the steps of: a step of placing spherical granules of a material having voltage nonlinear resistance characteristics on the ceramic insulator as the insulating container and pressing the material to form a compact layer of the material having voltage nonlinear resistance characteristics; firing the ceramic insulator and the compact layer to form the ceramic insulator and a ceramic layer having voltage nonlinear resistance characteristics; and providing an insulating layer on the ceramic layer having voltage nonlinear resistance characteristics, thereby providing an electric field relaxation structure. A method for manufacturing a vacuum valve.

11. 7. A method for manufacturing a vacuum valve according to claim 6, comprising the steps of: a step of placing spherical granules of a material having voltage nonlinear resistance characteristics on the ceramic insulator as the insulating container and pressing the material to form a compact layer of the material having voltage nonlinear resistance characteristics; Applying a precursor material of an insulating layer to a surface of the molded body layer; and a step of firing the precursor materials of the ceramic insulator, the compact layer, and the insulating layer to create a layer structure of the ceramic insulator, the ceramic layer having voltage nonlinear resistance characteristics, and the insulating layer, thereby providing an electric field relaxation structure. A method for manufacturing a vacuum valve.

12. The ceramic layer having voltage nonlinear resistance characteristics has a porosity of 20% or more and 80% or less before firing.

11. The method for manufacturing a vacuum valve according to claim 10.

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