JP2008091142A - Functionally gradient material for sealing, manufacturing method therefor, and bulb - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a functionally gradient material for sealing in which cracking is suppressed, even with few number of layers, for facilitating manufacturing. <P>SOLUTION: The functionally gradient material FGM for sealing includes an insulating layer 1 and a conductive layer 2. The interface B between the insulating layer 1 and the conductive layer 2 contains an insulating substance and conductive substance, and is formed into a roughened shape. Accordingly, even if tensile stress is produced in the direction along the interface B, excessive deformation in the direction along the interface B will be suppressed by the drag generated by the roughened shape, and the occurrence of cracks are effectively suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a functionally gradient material for sealing, a method for producing the functionally gradient material for sealing, and a tube sealed using the functionally gradient material for sealing.

  Tubes with airtight containers made of quartz glass, such as halogen bulbs and high-pressure discharge lamps, have conventionally used a foil sealing structure that seals the airtight container using molybdenum foil as the sealing metal foil. Yes. However, an attempt has been made to use a functionally graded material instead of the sealed metal foil for reasons such as the limit of the allowable current value in the sealed metal foil (see, for example, Patent Document 1).

In order to easily manufacture this functionally gradient material and suppress the occurrence of cracks, the use of a plasma sintering method has also been studied (see, for example, Patent Document 1).
JP 2000-260395 A JP 2006-49269 A

  In Patent Document 1, since it is necessary to increase the number of buffer layers in order not to generate cracks, the number of functionally graded materials is increased, which is troublesome to manufacture and yields a good product rate during sintering. However, the cost is high and the practicality is poor.

  As in Patent Document 2, by using the plasma sintering method, the powder as the material for forming each layer can be melted in a short time to form an airtight functional gradient material for sealing. The generation of cracks has not been effectively suppressed.

  The present invention uses a functionally graded sealing material that is less prone to cracking with a small number of layers and is easy to manufacture, a method for producing the functionally graded sealing material, and the functionally graded material for sealing. An object of the present invention is to provide a sealed tube.

  The functionally graded material for sealing according to claim 1 comprises a first layer having an insulating substance and a sealing function, and a second layer having an insulating substance and a conductive substance, The first and second layers are connected so that the boundary surface between the first and second layers forms an uneven shape.

  In the present invention, the functional gradient material for sealing has a multilayer structure having at least an insulating layer as a first layer and a conductive layer as a second layer, and is mainly used as a sealing member for a tube. The The conductive layer as the second layer may have a multilayer structure of two layers or three or more layers. As the second layer, an intermediate layer for reducing the difference in thermal expansion coefficient or improving the strength can be used. However, if the intermediate layer is used, the sealing member becomes large. Is preferably made as thin as possible or omitted.

  Since the thermal expansion coefficients of the insulating layer and the conductive layer are clearly different, a tensile stress is generated in the direction along the boundary surface between the insulating layer and the conductive layer when a large change in heat is repeated. This is considered to be one of the major causes of cracks.

  In the present invention, since the boundary surface between the insulating layer as the first layer and the conductive layer as the second layer is formed so as to have an uneven shape, it is pulled in the direction along the boundary surface. Even when stress is generated, excessive deformation in the interface direction is suppressed by the drag generated by the uneven shape, and the generation of cracks is effectively suppressed. In addition, a diffusion bonding layer is formed in the vicinity of the boundary surface by diffusing substances constituting each layer, but by making the boundary surface uneven, the diffusion distribution of the diffusion bonding layer can be spread over the entire uneven shape. Therefore, the functionally graded material can be formed so that the difference in thermal expansion coefficient between the layers increases or decreases in a gradient manner.

  As for the uneven shape of the boundary surface, a material for forming one of the first or second layer is formed in advance using a molding die or the like, and then the other material is filled from above, and then sintered. Although it can manufacture by ligating, as long as the uneven | corrugated shape which can achieve the effect of this invention can be formed, you may form uneven | corrugated shape using another method.

  The functional gradient material for sealing according to claim 1, wherein the first and second layers are connected along the axial direction to form a cylindrical structure as a whole, and the boundary surface is The concave-convex shape orthogonal to the axial direction is characterized by having a rotationally symmetric shape around this axis.

  In the functionally graded sealing material having a cylindrical structure, a shift due to tensile stress occurs along the boundary surface from the axial center. For this reason, by making the concavo-convex shape a rotationally symmetric shape around the axis of the cylindrical structure, the drag based on the concavo-convex shape is evenly generated, effectively suppressing the occurrence of cracks due to the local occurrence of deviation. be able to.

  A third aspect of the present invention is the functionally gradient material for sealing according to the first or second aspect, wherein the first and second layers are formed so as to be connected by a plasma sintering method.

  The present invention defines the configuration of a highly reliable sealing member manufactured by a suitable manufacturing method. That is, by sealing the sealing member by the discharge plasma method, a good diffusion bonding layer is formed, and the insulating layer and the conductive layer are directly strong and securely and reliably bonded. Can be obtained. The discharge plasma method is a method in which sintering is performed by the heat generated by plasma of spark discharge generated in the particle gap and the Joule heat generated by energization when a DC pulse voltage is applied to the particle gap of the powder in the compressed state.

  According to the discharge plasma method, vaporization and melting occur on the surface of the compressed powder particles, and the powder particles are densely welded to obtain a homogeneous sintered body in which the insulating layer and the conductive layer are joined together. Can do. In the process of sintering the insulating layer and the conductive layer, part of the material constituting both layers moves at the junction between the insulating layer and the conductive layer by diffusion to reach the other layer, And since the diffusion bonding layer in which the substances constituting both layers are intertwined in three dimensions is formed, it is strong despite the difference in thermal expansion coefficient between the insulating layer and the conductive layer. In addition, highly reliable bonding can be obtained over a long period of time.

  The tube of claim 4 includes an airtight container having an opening; and a first layer mainly composed of the same kind of material as the airtight container, and seals the opening of the airtight container at a portion of the first layer. The functionally gradient material for sealing according to any one of claims 1 to 3, wherein the functionally gradient material for sealing is sealed inside an airtight container, and the airtight container passes through the second layer of the functionally gradient material for sealing. A tube operating member that is fed from the outside.

  The tube is an electric actuating means in which a sealing member is hermetically sealed inside an airtight container. According to the present invention, a tube suitable for various uses can be obtained. For example, in the case of a lighting tube, this includes a halogen bulb, a high-pressure discharge lamp, and the like. In addition, in the case of a non-illuminating tube, for example, various electron tubes and the like are included.

The airtight container has an opening. When the functional gradient material for sealing is stored in the hermetic container, the opening can be passed through. Moreover, the opening is sealed with the functionally gradient material for sealing, so that the inside of the airtight container becomes airtight. Further, in the case of a lighting tube, the hermetic container can be configured to be translucent mainly with metal oxide or metal nitride. As the metal oxide, for example, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), yttrium oxide (YOX), yttrium-aluminum-garnet (YAG), or the like can be used. As the metal nitride, aluminum nitride (AlN) or the like can be used. Each of the above substances is a material having translucency and heat resistance, and can be obtained as a polycrystalline body, that is, a ceramic or a single crystal. In the case of a non-illuminating tube, the hermetic container may be either translucent or non-translucent.

  The insulating layer of the functional gradient material for sealing is mainly composed of the same material as that of the hermetic container. Similarly, since it is mainly composed of metal oxide or metal nitride, the thermal expansion coefficient is almost the same as that of the hermetic container. On the other hand, the conductive layer has conductivity enough to function as a conductor, and the coefficient of thermal expansion is relatively different from that of the insulating layer. In addition, the conductive layer is allowed to be composed of a mixture of a metal oxide or metal nitride and a conductive metal, which is preferably the same material as that constituting the insulating layer. In this case, it has been confirmed by experiments that the conductive metal exhibits the required conductivity if it is mixed by about 30% by mass or more of the conductive layer. However, if necessary, the conductive layer may be substantially composed only of a conductive metal. The sealing member is a member that is housed in the hermetic container and is supplied with electric power from the outside of the hermetic container through the conductive layer of the sealing member, and performs a desired electrical operation in the hermetic container. For example, in the case of a halogen bulb, the sealing member is an incandescent filament. In the case of a high pressure discharge lamp, the sealing member is a discharge electrode.

  According to the present invention, since the boundary between the first layer and the second layer is formed so as to have an uneven shape, the tensile stress in the direction along the boundary due to the difference in thermal expansion coefficient. Even if this occurs, excessive deformation in the direction of the boundary surface is suppressed by the drag generated by the uneven shape, and the generation of cracks is effectively suppressed.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment for carrying out the functionally gradient material for sealing of the present invention, FIG. 1 (a) is a conceptual cross-sectional view, and FIG. 1 (b) is a view of the boundary surface from the axial direction. It is a conceptual front view. In this embodiment, the functional gradient material FGM for sealing has a two-layer configuration including a first layer (hereinafter referred to as an insulating layer) 1 and a second layer (hereinafter referred to as a conductive layer) 2. It is a sintered member, and adjacent layers are joined and integrated with a cylindrical structure by sintering using a discharge plasma sintering method (hereinafter referred to as SPS method).

  The insulating layer 1 has a sealing function. This sealing function is used when sealing the sealed portion by sealing the insulating layer 1 in a sealed portion of an appropriate member to be sealed, for example, an opening of a tube airtight container. Contribute to. The insulating layer 1 is an airtight sintered body by compressing and sintering an insulating substance powder.

The insulating layer 1 can be mainly composed of an insulating material having the same quality as the portion to be sealed, such as a metal oxide or a metal nitride. If it does so, since the thermal expansion coefficient of the to-be-sealed part and the insulating layer 1 will approach, it will become easy to perform sealing reliably. If the sealed portion is made of quartz glass, the insulating layer 1 is preferably formed using silica (SiO ₂ ) or a material mainly composed of silica. Moreover, if it is a product made from translucent ceramics, for example, translucent alumina ceramics, the insulating layer 1 is formed using the same material as the translucent ceramics, for example, alumina (Al ₂ O ₃ ) or a material mainly composed of alumina. It is good to form.

  The conductive layer 2 is assumed to have at least conductivity that can function as a conductor. For this purpose, the conductive substance and the insulating substance are contained in an appropriate content ratio, and generally the conductive substance has a content ratio of 20% by mass or more, preferably 30% by mass or more of the entire conductive layer 3. The conductive layer 2 is preferably configured. In the case where the current flowing through the conductive layer 2 is relatively small, the conductive substance powder may be contained at 20% by mass or more of the conductive layer. On the other hand, when the current flowing through the conductive layer 2 is relatively large, it is better to configure the content ratio of the conductive material to 30% by mass or more. There is no upper limit for the mixing ratio of the conductive materials, and if necessary, the conductive material may be substantially composed of only the conductive materials. However, it is preferable to add an insulating material to be a binder at an appropriate content ratio. Note that as the conductive substance, a metal having a heat resistance that can be sintered and a relatively good conductivity, preferably a powder of a heat resistant metal such as molybdenum (Mo) or tungsten (W) is used. On the other hand, it is preferable to use the same material as the constituent material of the insulating layer 1 as the insulating material.

  The conductive layer 2 may be provided with a buffer layer that absorbs the difference in thermal expansion coefficient between the insulating layer 1 and the conductive layer 2. That is, the buffer layer is set to an intermediate thermal expansion coefficient between the thermal expansion coefficient of the insulating layer 1 and the thermal expansion coefficient of the conductive layer 2. In order to adjust the coefficient of thermal expansion, the conductive material may be mixed at an appropriate content ratio. The number of buffer layers may be extremely small compared to the prior art, allowing 0 to 2 layers. In this embodiment, no buffer layer is provided. When a plurality of buffer layers are provided, the coefficient of thermal expansion may be changed so as to increase sequentially from the insulating layer 1 toward the conductive layer 2.

  In the state where the functional gradient material FGM for sealing is sealed to the sealed portion and the sealed portion is hermetically sealed, the conductive layer 2 is sealed inside and outside of the sealed portion via the insulating layer 1 hermetically. It becomes a means for electrically connecting. For example, as will be described later, if a conductive metal member 4 made of a heat-resistant metal such as molybdenum or tungsten is connected to the conductive layer 2 through the insulating layer 1, the insulating layer of the functionally gradient material FGM for sealing is used. The inside and outside of the sealing portion can be conductively connected in a state where the space between 1 and the conductive layer 2 is kept airtight. In addition, since the difference in coefficient of thermal expansion between the conductive metal member 4 and the insulating layer 1 and the conductive layer 2 is relatively large, a slight gap is formed so as not to be fused during sintering. It is better to take into consideration.

  Note that the conductive metal member 5 can be connected to the conductive layer 2 in order to introduce an electric current or the like from the outside. In the present invention, the conductive metal members 4 and 5 are not essential, and may be connected by sintering at the same time as necessary, or may be connected after sintering.

  The boundary surface B between the insulating layer 1 and the conductive layer 2 has an uneven shape, and both are connected via the boundary surface B. The concavo-convex shape is alternately formed with annular convex portions and concave portions having a large diameter in the cross-sectional direction around the central axis of the cylindrical functional gradient material for sealing FGM. That is, the concavo-convex shape is a shape to be rotated around the central axis of the cylindrical functional gradient material for sealing FGM. For this reason, it is possible to effectively suppress the occurrence of cracks due to the local occurrence of the shift generated at the boundary surface B between the insulating layer 1 and the conductive layer 2 by the uniform generation of the drag force based on the uneven shape. Can do.

  The protruding height of the boundary surface B (difference between the concave portion and the convex portion) is 0.5 to 5 mm, and the interval between the concave portion and the convex portion is 0.5 to 5 mm. By forming the boundary surface B having such an uneven shape, even if a tensile stress is generated in the direction along the boundary surface B, excessive deformation in the direction of the boundary surface B is caused by the drag generated by the uneven shape. And the occurrence of cracks is effectively suppressed. In addition, the materials constituting each layer diffuse to each other near the boundary surface B to form a diffusion bonding layer (not shown). By making the boundary surface B uneven, the diffusion distribution of the diffusion bonding layer is uneven. Since it can be spread over the whole, the functionally graded material can be formed so that the difference in thermal expansion coefficient between the layers increases or decreases in a gradient manner.

  As for the uneven shape of the boundary surface B, a desired uneven shape is formed in advance using a mold or the like for the fine particle material forming the insulating layer 1 (or conductive layer 2), and then the conductive layer 2 (or insulating layer) is formed thereon. It can be produced by filling the fine particle material of 1) and then sintering.

The conductive layer 2 is a mixture of an insulating material (SiO ₂ ) and a conductive material (Mo), but contains 30% by mass of the conductive material, so that the insulating material (SiO ₂ ) is 100% insulating. There is a 30% difference in the content ratio of the conductive metal between the layer 1 and the layer 1. However, a good bond is formed by being sintered by the SPS method.

The functionally gradient material for sealing FGM of the example will be described. The functionally graded sealing material FGM of Example has a cylindrical shape with a diameter of 10 mm and a thickness of 30 mm (thickness is 10 mm for each layer). The layer structure may be a three-layer structure of insulating layer (SiO ₂ 100%) + buffer layer (SiO ₂ 85%, Mo 15%) + conductive layer (SiO ₂ 70%, Mo 30%). The manufacturing method is based on the spark plasma sintering method (pressure 40 MPa, firing temperature 1400 ° C., 10 minutes).

  As a comparative example, 20 samples in which the boundary surface B is a flat surface orthogonal to the axial direction were manufactured, applied as a sealing material for a 400 W type high pressure mercury lamp, and tested for 500 hours. As a result, Example 1 was a non-defective product, but in the comparative example, cracks were observed in nearly 50% of the sample products.

  FIG. 2 is a front sectional view showing a tube which is a second embodiment of the present invention. This embodiment is an example applied to a high-pressure discharge lamp as a tube, wherein 3 is an airtight container, FGM is a sealing member, and 4 is a power supply member, and these constitute a high-pressure discharge lamp. The hermetic vessel 3 is made of a light-transmitting and fire-resistant material, for example, quartz glass, and is made of quartz glass having an outer shape substantially in a spindle shape, and a discharge space 3a having a substantially spheroid shape inside thereof. Is formed. A pair of openings 3b and 3b are formed at both ends of the airtight container 3 in the tube axis direction.

  The sealing member FGM is the same as that of the first embodiment, and is formed by a discharge plasma sintering method belonging to the rapid sintering method. The boundary surface B is formed by three-dimensionally intertwining the materials constituting the insulating layer 1 as the first layer and the conductive layer 2 as the second layer by diffusing and moving with each other. is there.

  The sealing member FGM seals the airtight container 3 in an airtight manner by being fitted and sealed in the opening 3 b of the airtight container 3. In FIG. 2, the initial boundary between the opening 3b and the sealing member FGM is indicated by a dotted line.

The insulating layer 1 of the sealing member FGM is mainly composed of metal oxide or metal nitride, but in this embodiment, since the hermetic container 3 is made of quartz glass, it is mainly composed of silica (SiO ₂ ). Yes. On the other hand, the conductive layer 2 is mainly composed of a mixture of a conductive metal and a metal oxide. In this embodiment, the conductive metal is made of molybdenum (Mo) or tungsten (W), and the metal oxide is oxidized. The material is made of silica which is the same material as the constituent material of the insulating layer 1. The mixing ratio of the conductive metal and the metal oxide is selected at a predetermined ratio within the range of 30% by mass or more so that the conductive layer 2 has a conductivity that exhibits a required low resistance value. ing.

  The sealing member 5 is a discharge electrode made of a tungsten (W) rod-shaped body, and the base end thereof is inserted into and fixedly supported from one end face of the conductive layer 2 in the sealing member FGM. Is conducting.

  The power supply member 4 is a lead member made of a molybdenum rod-like body, and the tip thereof is inserted and fixedly supported from the other end face of the conductive layer 2 in the sealing member FGM and penetrates the insulating layer 1. is doing.

  Therefore, the sealing member FGM, the sealing member 5 and the power supply member 4 described above are integrated around the sealing member FGM to constitute an electrode mount.

  Thus, the tube constitutes a high-pressure discharge lamp, and the discharge electrodes of the pair of sealing members 5 and 5 are opposed to each other in the discharge space 3a in the translucent airtight container 1, and the discharge space. A discharge medium is enclosed in 3a.

The conceptual cross section which shows the 1st form for implementing the functional gradient material for sealing of this invention. Front sectional drawing which shows the tube which is the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Insulating layer as 1st layer, 2 ... Conductive layer as 2nd layer, 4, 5 ... Conductive metal member, FGM ... Functional gradient material

Claims (4)

  An insulating material having a first layer having a sealing function and a second layer having an insulating material and a conductive material, and the boundary surface between the first and second layers is uneven. A functionally graded material for sealing, wherein the first and second layers are connected so as to form.   The first and second layers are connected along the axial direction to form a cylindrical structure as a whole, the boundary surface is orthogonal to the axial direction, and the concavo-convex shape is rotationally symmetric about this axis The functionally graded material for sealing according to claim 1, wherein:   The functional gradient material for sealing according to claim 1, wherein the first and second layers are formed so as to be connected by a plasma sintering method. An airtight container with an opening;
The sealing function according to any one of claims 1 to 3, further comprising a first layer mainly composed of the same kind of material as that of the hermetic container, wherein the opening of the hermetic container is sealed at a portion of the first layer. A graded material;
A tube actuating member sealed inside the hermetic container and fed from the outside of the hermetic container via the second layer of the functionally graded sealing material;
A tube characterized by comprising:

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