JP6993617B2 - Insulation member and its manufacturing method - Google Patents

Description

The present invention relates to an insulating member used in a drive device and a method for manufacturing the same, and specifically to an insulating member which is lightweight, has high strength, is low in cost, and has excellent workability, and a method for manufacturing the same.

Insulating members are used in devices that rotate at high speed under the application of high voltage. For example, Patent Document 1 discloses that a hybrid insulating member in which a resin and a ceramic are combined is used as an insulating member used in a high voltage generator for radiation technology. Patent Document 2 discloses that an insulating member such as a ceramic shaft is used instead of the metal shaft.

Japanese Unexamined Patent Publication No. 2006-527907 Jikkenhei 05-02540 Japanese Unexamined Patent Publication No. 2009-190959

With the widespread use of electric vehicles, it is expected that the demand for lightweight and high strength will increase for insulating members driven in the space where induced currents and induced magnetic fields are generated.

Currently, non-oxide ceramics such as silicon nitride are used as high-strength insulating members (see Patent Document 3). However, non-oxide ceramics have problems that they are expensive, heavy, and have low processability.

It is also assumed that oxide-based glass with high workability is used as the insulating member. However, oxide-based glass is a brittle material and has a problem of low strength.

The present invention has been made in view of the above circumstances, and its technical problem is to create an insulating member which is lightweight, has high strength and low cost, and has excellent workability, and a method for manufacturing the same.

The present inventors can solve the above technical problems by imparting a substantially perfect circular cross-sectional outer shape to low-density alkali-containing glass and forming a surface compressive stress layer by ion exchange. Is proposed as the present invention. That is, the insulating member of the present invention is an insulating member made of alkali-containing glass, has a cross-sectional outer shape that is substantially a perfect circle, has a density of 2.60 g / cm ³ or less, and is a surface compressive stress layer by ion exchange. It is characterized by having the above and being incorporated in a drive device. Here, the "alkali-containing glass" refers to a glass in which the content of alkali metal oxides (Li ₂ O, Na ₂ O and K ₂ O) in the glass composition is 3% by mass or more in total. The "cross-sectional outer shape that becomes a substantially perfect circle" may mean that the cross-sectional outer shape from at least one direction is a substantially perfect circle. "Approximately perfect circle" means that the dimensional tolerance of the diameter is within 1% (preferably within 0.5%, within 0.1%, within 0.05%, within 0.01%, within 0.005%, in particular. It means that it is within 0.001%). The "dimensional tolerance of diameter" can be measured by, for example, image analysis using an image inspection device. "Density" can be measured by the Archimedes method or the like.

The insulating member of the present invention is made of alkali-containing glass having a density of 2.60 g / cm ³ or less. This makes it possible to improve workability while reducing the weight. On the other hand, alkali-containing glass has high brittleness and therefore low strength. Therefore, the insulating member of the present invention has increased strength by forming a surface compressive stress due to ion exchange.

Further, the insulating member of the present invention has a cross-sectional outer shape that is substantially a perfect circle. This makes it possible to suitably use it as a rolling element incorporated in a drive device. Further, it can be suitably used for a shaft or the like of an electric vehicle or the like. It should be noted that the cross-sectional outer shape that becomes a substantially perfect circle does not have to exist in all the regions of the insulating member, and may exist only in, for example, the portion to be driven.

Secondly, the insulating member of the present invention preferably has a volume resistivity of 10 ^5.0 Ω · cm or more at 150 ° C. Here, the "volume electrical resistance value at 150 ° C." is a value measured based on ASTM C657-78, and is a glass plate having the same glass composition and the same thermal history as the insulating member (for example, a plate thickness of 0.7 mm). ) Is ion-exchanged under the same conditions, and the obtained glass plate is preferably used as a measurement sample. The glass composition (including the glass composition in the minimum region of the compressive stress layer) was determined by standardless quantitative analysis by the ZAF method using SEM-EDX (for example, S4300-SE manufactured by Hitachi High-Technologies Corporation, EX-250 manufactured by HORIBA, Ltd.). Can be measured. Further, if the heat treatment conditions of the glass plate are adjusted so that the densities of the insulating member and the glass plate are matched and the densities of the two are the same, the glass plate can be given the same thermal history as the insulating member. Can be done.

Thirdly, in the insulating member of the present invention, the volume resistivity at 150 ° C. is preferably 10 times or more the volume resistivity before ion exchange.

Fourth, in the insulating member of the present invention, it is preferable that the compressive stress value of the surface compressive stress layer on the outer shape of a substantially perfect circle is 300 MPa or more and the stress depth is 25 μm or more. Here, the "compressive stress value" and the "stress depth" are determined from the number of interference fringes observed and their intervals when the sample is observed using a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho). Can be calculated. When the insulating member has a flat portion of 1 cm square or more, the compressive stress value of the surface compressive stress layer on the outer shape of a substantially perfect circle can be measured by measuring the compressive stress value and stress depth of the surface compressive stress layer of the flat portion. And the stress depth can be estimated accurately. When the insulating member does not have a flat portion of 1 cm square or more, a glass plate having the same glass composition and the same thermal history as the insulating member is subjected to ion exchange treatment under the same conditions, and the surface compressive stress layer of the obtained glass plate is compressed. By measuring the stress value and stress depth, it is possible to accurately estimate the compressive stress value and stress depth of the surface compressive stress layer on the outer shape of the cross section of a substantially perfect circle.

Fifth, in the insulating member of the present invention, the alkali-containing glass contains SiO ₂ 40 to 75%, Al ₂ O ₃ 10 to 30%, and Na ₂ O 5 to 25% by mass in terms of glass composition. Is preferable.

Sixth, the method for manufacturing an insulating member of the present invention is a method for manufacturing an insulating member made of alkali-containing glass, which has a cross-sectional outer shape that is substantially a perfect circle and has a density of 2.60 g / cm ³ or less. After producing the alkali-containing glass, the alkali-containing glass is ion-exchanged to form a surface compressive stress layer.

It is a conceptual diagram which shows an example of the insulating member of this invention. It is a conceptual diagram which shows an example of the insulating member of this invention. It is a conceptual diagram which shows an example of the insulating member of this invention.

The insulating member of the present invention has a cross-sectional outer shape that is substantially a perfect circle. By doing so, stable driving can be expected even under harsh conditions such as high-speed rotation, high friction, and high load. Further, such a cross-sectional shape can be easily formed from molten glass and can be polished while rotating the glass, so that scratches on the glass surface are reduced and the strength tends to be high.

The insulating member of the present invention is preferably an annular (or cylindrical) insulating member having a substantially perfect circular cross-sectional shape. In this case, the outer diameter of the annulus is preferably 100 mm or less, 80 mm or less, 50 mm or less, particularly 30 mm or less, and preferably 1 mm or more, 2 mm or more, 4 mm or more, and particularly 5 mm or more. In this way, it can be suitably applied to a shaft or the like incorporated in a drive device. The inner diameter of the annulus is not particularly limited and can be adjusted according to the design of the drive device. FIG. 1 is a conceptual diagram showing an example of the insulating member of the present invention, FIG. 1 (a) is a perspective conceptual diagram of an annular insulating member having a substantially perfect circular cross-sectional shape, and FIG. 1 (b) is a perspective diagram. It is a cross-sectional conceptual diagram when the insulating member shown in FIG. 1A is cross-sectionally cross-sectionally.

The insulating member of the present invention is preferably a columnar insulating member having a substantially perfect circular cross-sectional shape. In this case, the diameter of the cylinder is preferably 100 mm or less, 80 mm or less, 50 mm or less, particularly 30 mm or less, and preferably 1 mm or more, 2 mm or more, 4 mm or more, and particularly 5 mm or more. In this way, it can be suitably applied to rollers, shafts and the like incorporated in a drive device. FIG. 2 is a conceptual diagram showing an example of the insulating member of the present invention, FIG. 2A is a perspective conceptual diagram of a columnar insulating member having a substantially perfect circular cross-sectional shape, and FIG. 2B is a perspective diagram. It is a cross-sectional conceptual diagram when the insulating member shown in FIG. 2 (a) is cross-sectionally cross-sectionally.

The insulating member of the present invention is preferably a spherical insulating member having a substantially perfect circular cross-sectional shape, that is, a substantially perfect circular insulating member. In this case, the diameter of the sphere is preferably 100 mm or less, 80 mm or less, 50 mm or less, particularly 30 mm or less, and preferably 1 mm or more, 2 mm or more, 4 mm or more, particularly 5 mm or more. By doing so, it becomes possible to suitably apply to a driving device, particularly a spacer, a sphere or the like incorporated in a rolling device. FIG. 3 is a conceptual diagram showing an example of the insulating member of the present invention, FIG. 3A is a perspective conceptual diagram of a spherical insulating member having a substantially perfect circular cross-sectional shape, and FIG. 3B is a perspective diagram. It is sectional drawing conceptual diagram when the insulating member shown in FIG. 3A is cross-sectionally cross-sectionally.

It is preferable that the surface of the insulating member of the present invention is a polished surface, and in particular, the surface on the outer shape of a substantially perfect circular cross section is a polished surface. By doing so, since molding defects such as burrs are removed, it is possible to improve the dimensional accuracy while increasing the strength. The surface roughness Ra of the polished surface is preferably 1 nm or less, 0.5 nm or less, 0.4 nm or less, 0.3 nm or less, and particularly 0.2 nm or less. If the surface roughness Ra of the polished surface is too large, the insulating member is liable to be damaged under severe conditions such as high-speed rotation, high friction, and high load. Here, the "surface roughness Ra" can be measured by a method based on JIS B0601: 2001 with the insulating member fixed by a jig or the like.

In the insulating member of the present invention, the density is 2.60 g / cm ³ or less, preferably 2.55 g / cm ³ or less, 2.5 g / cm ³ or less, 2.49 g / cm ³ or less, and particularly 2.48 g / cm. It is cm ³ or less. The lower the density, the lighter the insulating member can be. In order to reduce the density, the content of SiO ₂ , P ₂ O ₅ , B ₂ O ₃ in the glass composition may be increased, or an alkali metal oxide, an alkaline earth metal oxide, ZnO, ZrO ₂ , etc. The content of TiO ₂ may be reduced.

The volumetric electrical resistance at 150 ° C. is preferably 10 ^5.0 Ω · cm or more, 10 ^5.5 Ω · cm or more, 10 ^6.0 Ω · cm or more, 10 ^6.5 Ω · cm or more, and 10 ^{7. 0} Ω · cm or more, 10 ^7.5 Ω · cm or more, 10 ^8.0 Ω · cm or more, 10 ^8.5 Ω · cm or more, 10 ^8.7 Ω · cm or more, 10 ^9.0 Ω · cm or more Especially, it is ^109.5 Ω · cm or more. If the volume resistivity is too low, the insulation tends to decrease.

The volume resistivity at 150 ° C. is preferably 10 times or more, 50 times or more, 100 times or more, 200 times or more, 250 times or more, particularly 300 times or more, the volume resistivity before ion exchange. When the volume resistivity at 150 ° C. is less than 10 times the volume resistivity before ion exchange, it becomes difficult to achieve both strength and insulation at a high level.

The coefficient of thermal expansion in the temperature range of 30 to 380 ° C is preferably 70 × ^10-7 to 110 × ^10-7 / ° C, 75 × ^10-7 to 110 × ^10-7 / ° C, 80 × ^10-7 to 110. × 10 ^-7 / ° C, especially 85 × 10 ^-7 to 110 × 10 ^-7 / ° C. If the coefficient of thermal expansion is regulated as described above, even if the surrounding metal members expand due to the heat generated during high-speed rotation, they can be properly driven. Here, the "coefficient of thermal expansion" is an average value measured by a dilatometer in a temperature range of 30 to 380 ° C.

The strain point is preferably 520 ° C. or higher, 550 ° C. or higher, 560 ° C. or higher, and particularly 570 ° C. or higher. The higher the strain point, the better the heat resistance. Further, when the strain point is high, stress relaxation is less likely to occur during the ion exchange process, so that it becomes easy to secure a high compressive stress value.

The temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is preferably 1650 ° C. or lower, 1600 ° C. or lower, 1580 ° C. or lower, 1550 ° C. or lower, 1540 ° C. or lower, and particularly 1530 ° C. or lower. The lower the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s, the lower the temperature at which the glass can be melted. Therefore, the lower the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s, the smaller the burden on the glass manufacturing equipment such as the melting kiln, and the higher the foam quality of the insulating member.

The liquid phase temperature is preferably 1200 ° C. or lower, 1150 ° C. or lower, 1130 ° C. or lower, 1110 ° C. or lower, 1090 ° C. or lower, and particularly 1070 ° C. or lower. If the liquidus temperature is too high, it becomes difficult to form the desired shape.

The Young's modulus is 65 GPa or more, preferably 69 GPa or more, preferably 71 GPa or more, preferably 75 GPa or more, and particularly preferably 77 GPa or more. If the Young's modulus is too low, the insulating member is easily deformed, so that the drive tends to be unstable under severe conditions such as high-speed rotation, high friction, and high load. Here, the "Young's modulus" can be measured by, for example, a well-known resonance method or the like.

The insulating member of the present invention has a surface compressive stress layer due to ion exchange. Thereby, the strength of the insulating member can be increased. As a method of forming a surface compressive stress layer by ion exchange, a method of immersing alkali-containing glass in an ion exchange solution and introducing alkaline ions having a large ionic radius into the glass surface is preferable. By doing so, the surface compressive stress layer can be formed in a short time. Further, as a method for forming the surface compressive stress layer by ion exchange, a method for forming the surface compressive stress layer by ion exchange between K ions in the KNO ₃ molten salt and the Na component in the alkali-containing glass is particularly preferable. By doing so, K ions and Na ions are mixed in the surface compressive stress layer, and the volume resistivity of the glass surface can be significantly increased by the mixed alkali effect.

In the insulating member of the present invention, the compressive stress value of the surface compressive stress layer is preferably 300 MPa or more, 600 MPa or more, 800 MPa or more, 900 MPa or more, 1000 MPa or more, and particularly 1100 MPa or more. The larger the compressive stress value, the higher the mechanical strength of the insulating member. However, if the compressive stress value is too large, the tensile stress inherent in the insulating member may become extremely high. Therefore, the compressive stress value of the compressive stress layer is preferably 2500 MPa or less. The compressive stress value can be increased by shortening the ion exchange time or lowering the ion exchange temperature.

The stress depth is preferably 25 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 60 μm or more, and particularly 70 μm or more. The larger the stress depth, the more difficult it is for the insulating member to crack even if the surface of the insulating member is deeply scratched due to wear at high rotation or foreign matter. On the other hand, if the stress depth is too large, the tensile stress inherent in the insulating member may become extremely high. Therefore, the stress depth is preferably 500 μm or less, 300 μm or less, 200 μm or less, and particularly 150 μm or less. The stress depth can be increased by lengthening the ion exchange time or raising the ion exchange temperature.

The internal tensile stress value is preferably 200 MPa or less, 150 MPa or less, 100 MPa or less, and particularly 50 MPa or less. The smaller the internal tensile stress value, the more difficult it is for the insulating member to be damaged due to internal defects in the insulating member. However, when the internal tensile stress value becomes extremely small, the compressive stress value and stress depth decrease, and the insulating member The mechanical strength is reduced. Therefore, the internal tensile stress value is preferably 1 MPa or more, 10 MPa or more, and particularly 15 MPa or more. The "internal tensile stress value" refers to a value calculated by the following formula 1. The thickness t of the insulating member in Equation 1 refers to the shortest distance among the distances between the opposing surfaces of the insulating member. For example, in the case of a rod shape (cylindrical column) whose cross-sectional shape is a substantially perfect circle, it refers to the diameter of a substantially perfect circle. In the case of a disk shape whose cross-sectional shape is approximately a perfect circle, it refers to the thickness of the disk.

[Formula 1]
CT = CS x DOL / (t x 1000-2 x DOL)
CT: Internal tensile stress value (MPa)
t: Thickness of insulating member (mm)
CS: Compressive stress value (MPa)
DOL: Depth of compressive stress layer (μm)

In the insulating member of the present invention, the alkali-containing glass preferably contains SiO ₂ 40 to 75%, Al ₂ O ₃ 10 to 30%, and Na ₂ O 5 to 25% by mass as a glass composition. The reason for limiting the content range of each component as described above will be described below. In the description of the content range of each component, the following% indication indicates mass% unless otherwise specified.

SiO ₂ is a component that forms a network of glass, and its content is preferably 40 to 75%, 45 to 70%, 45 to 65%, 45 to 63%, and particularly 48 to 61%. If the content of SiO ₂ is too large, the meltability, moldability, and coefficient of thermal expansion tend to decrease. On the other hand, if the content of SiO ₂ is too small, it becomes difficult to vitrify, and the coefficient of thermal expansion becomes unreasonably high, so that it becomes difficult to match the coefficient of thermal expansion of peripheral members, and the thermal shock resistance tends to decrease.

Al ₂ O ₃ is a component that enhances ion exchange performance, strain point, and Young's modulus. However, if the content of Al ₂ O ₃ is too large, devitrified crystals are likely to precipitate on the glass, making it difficult to form a desired shape. In addition, the meltability and the coefficient of thermal expansion tend to decrease. Therefore, the suitable upper limit range of Al ₂ O ₃ is 30% or less, 28% or less, 24% or less, 23% or less, 22% or less, 21.5% or less, particularly 21% or less, and the suitable lower limit range is. 10% or more, 12% or more, 13% or more, 15% or more, 17% or more, especially 18% or more.

Na ₂ O is an ion exchange component and a component that enhances meltability and moldability. It is also a component that improves devitrification resistance. However, if the Na ₂ O content is too high, the volume resistivity will be low and the coefficient of thermal expansion will be unreasonably high, making it difficult to match the coefficient of thermal expansion of peripheral members and reducing thermal shock resistance. It becomes easier to do. In addition, the balance of the glass composition may be lost, and the devitrification resistance may decrease. Therefore, the content of Na ₂ O is preferably 5 to 25%, 10 to 25%, 11 to 22%, 12 to 20%, 13 to 19%, and particularly 14 to 18%.

In addition to the above components, for example, the following components may be introduced.

P ₂ O ₅ is a component that enhances the ion exchange performance, and is particularly a component that increases the stress depth. As described above, in order to improve the ion exchange performance, it is effective to increase the amount of Al ₂ O ₃ , but if the content of Al ₂ O ₃ is too large, the devitrification resistance tends to decrease. Therefore, there is a limit to the amount of Al ₂ O ₃ introduced. However, when P ₂ O ₅ is introduced, even if the amount of Al ₂ O ₃ is increased, the glass is less likely to be devitrified, so that the allowable amount of Al ₂ O ₃ introduced can be increased. As a result, the ion exchange performance can be dramatically improved. On the other hand, if the content of P ₂ O ₅ is too large, the glass tends to be phase-separated, and the water resistance and devitrification resistance tend to decrease. Based on the above points, the suitable upper limit range of P ₂ O ₅ is 17% or less, 10% or less, 9% or less, 8% or less, 7% or less, particularly 6% or less, and the suitable lower limit range is 0. .1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, especially 4% or more.

B ₂ O ₃ is a component that lowers the liquid phase temperature, high temperature viscosity, and density, and is a component that enhances ion exchange performance, especially the compressive stress value. Burning may occur, and water resistance, liquid phase viscosity, and stress depth may decrease. Therefore, the content of B ₂ O ₃ is preferably 0 to 6%, 0 to 4%, 0 to 3%, 0 to 2%, and particularly less than 0-1%.

Li ₂ O is an ion exchange component and a component that lowers high-temperature viscosity and enhances meltability and moldability. It is a component that further enhances Young's modulus. However, if the content of Li ₂ O is too large, the volume resistivity tends to decrease. In addition, the liquidus viscosity is lowered, and the glass is easily devitrified. Further, the low-temperature viscosity is lowered too much, stress relaxation is likely to occur during the ion exchange treatment, and there is a possibility that the compressive stress value is rather lowered. Therefore, the Li ₂ O content is preferably 0 to 10%, 0 to 8%, 0 to 5%, less than 0 to 3%, 0 to 2%, less than 0-1%, 0 to 0.1%. Less than, especially less than 0-0.01%.

K ₂ O is a component that promotes ion exchange, and is a component that has a high effect of increasing the stress depth, especially among alkali metal oxides. In addition, it is a component that lowers the high-temperature viscosity, enhances meltability and moldability, and improves devitrification resistance. However, if the content of K ₂ O is too large, the volume resistivity tends to decrease. In addition, since the coefficient of thermal expansion becomes unreasonably high, it becomes difficult to match the coefficient of thermal expansion of peripheral members, and the thermal impact resistance tends to decrease. Further, the strain point may be lowered too much, or the balance of the glass composition may be lost, and conversely, the devitrification resistance may be lowered. Suitable upper limit ranges of K2O _are 10% or less, 9% or less, 8% or less, 7% or less, particularly 6% or less, and suitable lower limit ranges are 0% or more, 0.5% or more, 1% or more. 2% or more, 3% or more, especially 4% or more.

The suitable upper limit range of the total amount of Li ₂ O, Na ₂ O and K ₂ O is 30% or less, 25% or less, particularly 22% or less, and the suitable lower limit range is 8% or more, 10% or more, 13%. Above, especially 15% or more. If the total amount of Li ₂ O, Na ₂ O and K ₂ O is too large, the volume resistivity and devitrification resistance tend to decrease. In addition, since the coefficient of thermal expansion becomes unreasonably high, it becomes difficult to match the coefficient of thermal expansion of peripheral members, and the thermal impact resistance tends to decrease. On the other hand, if the total amount of Li ₂ O, Na ₂ O and K ₂ O is too small, the ion exchange performance and the meltability tend to deteriorate.

The molar ratio K ₂ O / Na ₂ O is preferably 0 to 1, 0 to 0.8, 0.05 to 0.7, 0.1 to 0.5, 0.15 to 0.4, 0.15. ~ 0.3, especially 0.15 to 0.25. By doing so, the volume resistivity can be increased by the mixed alkali effect. In addition, "K ₂ O / Na ₂ O" is a value obtained by dividing the content of K ₂ O by the content of Na ₂ O.

MgO and CaO are components that reduce high-temperature viscosity, improve meltability and moldability, and increase strain points and Young's modulus, and among alkaline earth metal oxides, they have a large effect of improving ion exchange performance. It is an ingredient. However, when the contents of MgO and CaO are high, the density and the coefficient of thermal expansion become high, and the glass tends to be devitrified. Therefore, the content of MgO is preferably 10% or less, 8% or less, 6% or less, 5% or less, and particularly 4% or less. The CaO content is preferably 8% or less, 6% or less, 4% or less, 2% or less, and particularly less than 1%.

SrO and BaO are components that lower the high-temperature viscosity, improve the meltability and moldability, and increase the strain point and Young's modulus. However, when the contents of SrO and BaO are large, the density and the coefficient of thermal expansion tend to be high, and the ion exchange performance tends to be deteriorated. Therefore, the content of SrO is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly less than 0.1%. The content of BaO is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly less than 0.1%.

The total amount of MgO, CaO, SrO and BaO is preferably 0 to 15%, 0 to 9%, 0 to 6%, and particularly 0 to 5%. If the total amount of MgO, CaO, SrO and BaO is too large, the density and the coefficient of thermal expansion become unreasonably high, and the devitrification resistance and the ion exchange performance tend to deteriorate.

The mass ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.5 or less, 0.4 or less, and particularly 0.3 or less from the viewpoint of enhancing devitrification resistance. In addition, "(MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O)" is a value obtained by dividing the total amount of MgO, CaO, SrO and BaO by the total amount of Li ₂ O, Na ₂ O and K ₂ O. ..

ZnO is a component that enhances ion exchange performance. It is also a component that lowers the high temperature viscosity without lowering the low temperature viscosity. However, when the amount of ZnO is increased in the presence of P ₂ O ₅ , the glass tends to be phase-separated or devitrified. Therefore, the ZnO content is preferably 8% or less, 4% or less, 1% or less, 0.1% or less, and particularly 0.01% or less.

ZrO ₂ is a component that enhances ion exchange performance, Young's modulus, and strain point, and is a component that lowers high-temperature viscosity. However, as the content of ZrO ₂ increases, the devitrification resistance tends to decrease. Therefore, the content of ZrO ₂ is preferably 0 to 10%, 0 to 5%, 0 to 3%, less than 0-1%, 0 to 0.4%, and particularly less than 0 to 0.1%.

TiO ₂ is a component that enhances ion exchange performance and is a component that lowers high-temperature viscosity. However, when the content of TiO ₂ is high, the glass tends to be devitrified. Therefore, the content of TiO ₂ is preferably 0 to 4%, 0 to less than 1%, 0 to less than 0.1%, and particularly 0 to less than 0.01%.

SnO ₂ is a component that enhances ion exchange performance, particularly compressive stress value. However, when the content of SnO ₂ is large, devitrification due to SnO ₂ is likely to occur. Therefore, the content of SnO ₂ is preferably 0 to 3%, 0.01 to 2%, 0.05 to 1%, and particularly 0.1 to 0.5%.

As the clarifying agent, one or more selected from the group of As ₂ O ₃ , Sb ₂ O ₃ , CeO ₂ , F, Cl and SO ₃ may be contained. However, in consideration of the environment, it is preferable not to add As ₂ O ₃ and Sb ₂ O ₃ , and the content of As ₂ O ₃ and Sb ₂ O ₃ is less than 0.1%, particularly less than 0.01%, respectively. Is preferable. The content of F is preferably less than 0.1%, particularly preferably less than 0.01%, in order to suppress stress relaxation due to a decrease in low temperature viscosity.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase Young's modulus. However, when the total amount of rare earth oxides is large, the raw material cost rises and the devitrification resistance tends to decrease. Therefore, the total amount of rare earth oxides is preferably 3% or less, 2% or less, less than 1%, 0.5% or less, and particularly 0.1% or less.

The contents of PbO and Bi ₂ O ₃ are preferably less than 0.1%, respectively, in consideration of the environment.

In the insulating member of the present invention, the content of K ₂ O at a depth of 2.5 μm from the surface is preferably higher than the content of K ₂ O in the internal region deeper than the surface compressive stress layer. The content of K ₂ O at a depth of 2.5 μm from the surface is 1 mol% or more, 3 mol% or more, 5 mol% or more, 7 mol% or more, 8 mol% or more, 9 mol% or more than the content of K ₂ O in the internal region. In particular, it is preferably 10 mol% or more. The content of K ₂ O at a depth of 2.5 μm from the surface and the content of K ₂ O in the internal region are ZAF using SEM-EDX (for example, S4300-SE manufactured by Hitachi High-Technologies Corporation, EX-250 manufactured by HORIBA, Ltd.). It can be measured by standardless quantitative analysis by the method.

The insulating member of the present invention can be manufactured, for example, as follows. First, a glass batch prepared so as to have an alkali-containing glass having a specific composition is put into a continuous melting furnace and melted by heating at 1500 to 1600 ° C. to obtain molten glass, and then via a clarification container and a stirring container. After supplying to a molding container, it is molded into various shapes and slowly cooled. Next, the surface of the obtained alkali-containing glass is polished. Subsequently, the alkali-containing glass is immersed in an ion exchange solution to form a surface compressive stress layer by ion exchange on the surface of the alkali-containing glass.

As a molding method, various molding methods can be adopted. The Dunner method is preferable when molding into an annular shape (or a cylindrical shape). When molding into a columnar shape, the drawing method is preferable. When molding into a spherical shape, a marble molding method or a droplet molding method is preferable. By doing so, the dimensional accuracy of the insulating member is improved, and it becomes easy to reduce the amount of polishing on the glass surface. It is also possible to process the bulk glass into a predetermined shape by grinding and polishing it.

The ion exchange treatment can be carried out, for example, by immersing the alkali-containing glass in a molten salt of potassium nitrate at 360 to 480 ° C. for 1 to 100 hours. From the viewpoint of production efficiency, it is preferable to perform ion exchange treatment of a plurality of insulating members at the same time, and the plurality of insulating members are arranged on a metal jig at equal intervals so that the insulating members do not come into contact with each other. It is more preferable to carry out an ion exchange treatment in a state in which the above-mentioned materials are laminated.

The present invention will be described with reference to examples. However, the present invention is not limited to the following examples. The following examples are merely examples.

Table 1 shows the glass composition and characteristics of Examples (Nos. 1 to 8) of the present invention.

Each sample in Table 1 was prepared as follows. First, glass raw materials were prepared so as to have the glass composition in the table, and melted at 1580 ° C. for 8 hours using a platinum container. Then, the molten glass was poured onto a carbon plate and formed into a plate shape, and then machined into a predetermined shape to obtain a glass plate having a size of 5 cm square and a plate thickness of 0.7 mm. Further, the glass plate was machined to obtain a glass rod having a diameter of φ0.6 mm (within a dimensional tolerance of 0.01%), a glass rod having a length of 5 cm, and a glass ball having a diameter of φ0.6 mm (within a dimensional tolerance of 0.01%).

The following characteristics were evaluated using a sample of each glass plate.

Density is a value measured by the well-known Archimedes method.

The coefficient of thermal expansion α is an average value measured by a dilatometer in the temperature range of 30 to 380 ° C.

Young's modulus E is a value measured by a well-known resonance method.

The strain point Ps and the slow cooling point Ta are values measured by the method of ASTM C336.

The softening point Ts is a value measured by the method of ASTM C338.

The temperature corresponding to the high temperature viscosity of 10 ^4.0 dPa · s, 10 ^3.0 dPa · s, and 10 ^2.5 dPa · s is a value measured by the platinum ball pulling method.

The liquidus temperature TL passes through a standard sieve of 30 mesh (seam opening of 500 μm), and the glass powder remaining in 50 mesh (screen opening of 300 μm) is placed in a platinum boat and held in a temperature gradient furnace for 24 hours to crystallize. It is a value measured by the temperature at which the crystals are deposited.

The volume resistivity ρ _before at 150 ° C. is a value measured according to ASTM C657-78.

Subsequently, both surfaces of each glass plate were optically polished and then ion-exchanged. The ion exchange treatment was carried out by immersing each glass plate in KNO ₃ molten salt at 430 ° C. for 4 hours. Similarly, the above ion exchange treatment was performed on each glass rod and glass ball. After the ion exchange treatment, the surface of each glass plate is cleaned, and the compressive stress value CS and stress depth of the compressive stress layer are determined from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho) and their intervals. The DOL was calculated. In the calculation, the refractive index of each glass plate was 1.50, and the optical elastic constant was 30 [(nm / cm) / MPa]. Although the glass composition of the glass surface fluctuates microscopically before and after the ion exchange treatment, the effect is minor when viewed as a whole glass.

Subsequently, the volume resistivity ρ _after at 150 ° C. was measured for each glass plate after the ion exchange treatment in accordance with ASTM C657-78.

As can be seen from Table 1, the sample No. The glass plates of Nos. 1 to 8 had a low density, and the compressive stress value CS and the stress depth DOL of the compressive stress layer were large. In addition, sample No. The glass plates according to 1 and 2 had a high volume resistivity ρ _after after the ion exchange treatment. Therefore, the sample No. It is considered that the glass rods and glass spheres according to 1 to 8 also have a low density, a large compressive stress value CS and a large stress depth DOL of the compressive stress layer, and a high volume resistance ρ _after after the ion exchange treatment.

The insulating member of the present invention is lightweight, has high strength, is low in cost, and is excellent in workability. Therefore, the insulating member of the present invention is also suitable for applications incorporated in a drive device, for example, an insulating member such as a rolling element, a shaft, a motor member, a roller member, etc. used in an electric vehicle or the like.

Claims (5)

As a glass composition, it is an insulating member made of alkali-containing glass containing SiO ₂ 40 to 75%, Al ₂ O ₃ 10 to 30%, and Na ₂ O 5 to 25% by mass.
An insulating member having a spherical shape having a substantially perfect circular cross-sectional shape, a density of 2.60 g / cm ³ or less, a surface compressive stress layer by ion exchange, and being incorporated into a drive device. .. The insulating member according to claim 1, wherein the volume resistivity at 150 ° C. is 10 ^5.0 Ω · cm or more. The insulating member according to claim 1 or 2, wherein the surface compressive stress layer on the outer shape of a substantially perfect circle has a compressive stress value of 300 MPa or more and a stress depth of 25 μm or more. The invention according to claim 1 to 3, wherein the alkali-containing glass contains SiO ₂ 40 to 75%, Al ₂ O ₃ 18 to 30%, and Na ₂ O 5 to 25% by mass as a glass composition. The insulating member described in any one. As a glass composition, it is a method for manufacturing an insulating member made of alkali-containing glass, which contains SiO ₂ 40 to 75%, Al ₂ O ₃ 10 to 30%, and Na ₂ O 5 to 25% in mass%.
After producing an alkali-containing glass having a spherical shape with a substantially perfect cross-sectional shape and a density of 2.60 g / cm ³ or less, the alkali-containing glass is ion-exchanged to form a surface compressive stress layer. A method of manufacturing an insulating member, which is characterized by being incorporated in a drive device.

Images