Patent Application
20110135865
The present invention relates to a component for molding a device used to mold a glass lens or another optical element, and to a method for manufacturing a device which uses the component for molding a device. More specifically, the present invention relates to a component for molding a device for minimizing molding defects, to a method for manufacturing a device which uses the component for molding a device, and also to a device formed using the component and the manufacturing method.
There is an increasing demand for high performance in lenses as optical elements used in digital cameras, cellular telephones, and other various optical elements and optical communications devices and the like, for example. Therefore, aspherical lenses are used as these lenses. Since it is extremely costly to manufacture an aspherical lens by grinding, it is common practice to perform the molding process using a component for molding a device.
Among the techniques for molding an optical element or another such device by a molding process, one technique is to heat a pair of dies for performing molding, the dies being part of the component for molding a device. However, when this heating is performed, air or another gas will sometimes enter and become trapped between the heated parts of the pair of dies and the material constituting the device placed in the dies. If machining proceeds while this gas remains trapped between the dies and the material, then, for example, the material being molded will be compressed by the gas, and the device being molded from the material will have shape defects or other molding defects.
Accordingly, in order to effectively release the gas trapped between the dies and the material out the exterior, there has been disclosed a technique in, e.g., Japanese Laid-open Patent Application No. 8-337428 (hereinafter referred to as “Patent Document 1”) for forming an air groove for removing gas in an area on the external side of the area where the material is disposed (optical effective radius), in the lower die where the material constituting the device is disposed among a pair of upper and lower dies. With this technique, four air grooves, which are used to release the gas to the exterior in a radial pattern outward from a circular shape formed by the outermost area where the material is disposed, are spaced at equal intervals around the circumference of the circle. Since the gas is expelled rather than remaining between the dies and the material, shape defects and other molding defects can be minimized in the lens or other optical element molded from the material, and as a result, the optical characteristics of the molded lens are not compromised.
Japanese Laid-open Patent Application No. 2007-314385 (hereinafter referred to as “Patent Document 2”), for example, discloses a technique for forming a rough surface in an area where the material of the optical element is disposed on the external side (transcriptional range of an optical functional aspect) of an area confined by the upper die and lower die where the optical element main body is formed, in the lower die where the material constituting the optical element is disposed among a pair of upper and lower dies. This rough surface is a surface for releasing gas, which remains between the transcriptional range of the optical functional aspect of the lower die and the material in the transcriptional range of the optical functional aspect, in a radial pattern to the exterior of the die via the rough surface. Since the gas is thereby released rather than remaining between the die and the material, shape defects and other molding defects can be minimized in the lens or other optical element molded from the material, and as a result, the optical characteristics of the molded lens are not compromised.
Furthermore, for example, in the component for molding a device disclosed in Japanese Laid-open Patent Application No. 2007-176707 (hereinafter referred to as “Patent Document 3”), there is a designated space (cavity) in the periphery of the area where the pair of upper and lower dies mesh together and the material of the optical element is disposed. The cavity overlaps with at least some of a plurality of through-holes (straight holes) provided in the external peripheral surface of a hollow body and arranged so as to cover the external peripheral surface of the die, whereby the cavity and the outside area of the body communicate. Therefore, the gas remaining between the die and the material is released to the external area of the body via the communicated through-holes. Patent Document 3 discloses a technique whereby the gas is released in this manner rather than remaining between the die and the material. In Patent Document 3, since shape defects and other molding defects can be minimized in the lens or other optical element molded from the material, the optical characteristics of the molded lens are not compromised.
There is disclosed in, e.g., Japanese Laid-open Patent Application No. 2005-145777 (hereinafter referred to as “Patent Document 4”) a component for molding a device provided with a groove geometry running along a ridge in the external peripheral surface of the lower die, whereby gas remaining between the die and the material is released to the exterior of the die via the groove geometry running along the ridge.
However, in cases in which a groove for letting gas out is provided to the die where the material constituting the optical element is disposed, such as is disclosed in, e.g., Patent Documents 1 and 4, it is possible that the stress applied to the die and the material could be uneven during the process of heating the die and molding the material. In this case, the material constituting the optical element disposed in the die sometimes undergoes a miniscule amount of elastic deformation.
Particularly, providing a groove to the die sometimes causes the die to be asymmetrical with respect to an axis running in the longitudinal axial direction and passing through the center of the cross section. In this case, the stress applied to the die and the material during the molding process is applied disproportionately due to the area of the material. As a result, the deformation of the material is disproportionate, thereby causing a warped shape to be transferred to the lens or other optical element molded from the material, and there is therefore a possibility that shape defects or other molding defects will occur.
As is disclosed in Patent Document 2, for example, providing a rough surface and forming cuts (e.g., irregularities) in the die of the component for molding a device compromises the durability of the die, even if the cuts are formed in an area outside of the transcriptional range of optical functional aspect. As a result of the shorter longevity due to the compromised durability, there is a possibility of the die production costs increasing. Since the material constituting the optical element is disposed on the rough surface, there are cases in which the arrangement of the material becomes unstable. When the molding process is carried out under such unstable conditions, it is difficult to center the die, and as a result, there is a possibility that there will be shape defects or other molding defects in the lens or other optical element molded from the material.
Furthermore, as is disclosed in Patent Document 3, for example, when through-holes are provided in the hollow body disposed on the external side of the external peripheral surface of the die, the strength of the body is significantly reduced. Since the body is formed to be hollow with only the external peripheral surface being a rigid component, even if the die body had no through-holes, the strength would still be less than that of a non-hollow cylindrical object. Therefore, when the molding process is carried out using this type of body having through-holes and insufficient strength, there is a possibility that the body will be damaged by the stress being applied to the body.
The present invention was contrived in view of the problems described above, and an object thereof is to provide a component for molding a device whereby gas remaining between the die and the material is minimized as are molding defects originating in the structure of the component for molding a device, a manufacturing method which uses the component for molding a device, and a device formed using the component and the manufacturing method.
The component for molding a device according to the present invention is a component for molding a device used to mold a device, comprising a pair of dies for performing molding, a hollow body disposed so as to enclose external peripheral surfaces of the pair of dies, and a frame die for adjusting the position of the material constituting the device between the pair of dies. In the component for molding a device, a concavity is formed in an area constituting at least part of an internal peripheral surface of the body facing the external peripheral surface of the dies.
The pair of dies are dies vertically arranged as a pair in the usual state of use. Designating the vertical direction as a longitudinal axial direction, a cross section intersecting the longitudinal axial direction is a cylindrical shape forming a circle, for example. The curved surfaces of the dies, which extend in the longitudinal axial direction and cover the external surfaces, are herein defined as the external peripheral surfaces. In the components for molding a device disclosed in the aforementioned Patent Documents, a groove for expelling gas remaining between the dies and the material for molding a device is provided to the die in which the material is disposed. Meanwhile, in the component for molding a device according to the present invention, the groove (concavity) is provided in the hollow body disposed so as to enclose the external peripheral surfaces of the dies. Therefore, since a groove is not provided to the dies where the material for molding the device is disposed, a uniform state of stress applied to the dies and the material can be preserved when the molding process is performed on the material.
Since the hollow body is disposed so as to cover the external peripheral surfaces of the pair of dies, the groove (concavity) for expelling the gas to be expelled from the external peripheral surfaces of the dies to the exterior of the component for molding a device is formed in an area constituting at least part of the internal peripheral surface of the body, which faces the external peripheral surfaces of the dies. The internal peripheral surface herein refers to a curved surface extending in the longitudinal axial direction of the body and covering the internal surface. If this configuration is used, gas can be efficiently expelled to the exterior of the component for molding a device via the groove in the internal peripheral surface of the body.
In cases where a concavity is provided to the body, as with cases where a through-hole is provided, the extent by which the strength of the body is reduced is small. Therefore, it is possible to provide a component for molding a device which has adequate durability and expels gas efficiently. With this type of component, the occurrence of shape defects and other molding defects can be minimized.
The external shape of the cross section intersecting the longitudinal axial direction of the dies, the body, and the frame die is preferably circular, as previously described. The term “intersecting” used herein indicates the state of being orthogonal to the longitudinal axial direction, for example.
Since the component for molding a device according to the present invention is used to mold lenses as optical elements used in various optical elements, optical communication devices, and the like, the component for molding a device preferably has a circular cross section in order to mold circular lenses.
The dimension of the above-described groove (concavity) formed in the internal peripheral surface of the body preferably satisfies the equation:
L=R
m−√(Rm2−D2)−{Rs−√(Rs2−D2)}≦0.001
where 2D (mm) is the width of the concavity that extends in a direction intersecting the longitudinal axial direction of the dies, Rm (mm) is the radius of the dies from the center of a circular shape formed by the cross section of the dies to the external peripheral surfaces of the dies, and Rs (mm) is the radius of the body from the center of a circular shape formed by the cross section of the body to the internal peripheral surface of the body.
If the opposing upper and lower paired dies are disposed so as to have point symmetry about the center of a cross section intersecting the longitudinal axial direction of the body, the device formed by performing the molding process will have an ideal shape having no decenter. However, in actuality, since there is a groove in the internal peripheral surface of the body, there are cases in which an area of the dies in the external peripheral surface vicinity fits into the groove. When the dies fit into the groove, the dies become decentered with respect to the body, and the device formed by the molding process therefore has a shape with a specified amount of decenter. To make the area where the dies fit into the groove as small as possible, the previously described distance L over which the body fits into the concavity is preferably 0.001 mm or less, and more preferably 0.0005 mm or less.
The following relationships are preferably satisfied:
α1<α2
α1<α3
0.030≧(α1Di−α2Dp)ΔT+(Di−Dp)≧0.005
0.150≧(α1Di−α3Dr)ΔT+(Di−Dr)≧0.015
where T (° C.) is the sintering temperature when the material is molded, Di (mm) is the inside diameter of a circular shape formed by a cross section intersecting the longitudinal axial direction of the body, Dp (mm) is the outside diameter of a circular shape formed by a cross section intersecting the longitudinal axial direction of the dies, Dr (mm) is the outside diameter of a circular shape formed by a cross section intersecting the longitudinal axial direction of the frame die, α1 (/° C.) is the average coefficient of thermal expansion of the body from room temperature at which the material is disposed between the pair of dies to T (° C.), α2 (/° C.) is the average coefficient of thermal expansion of the dies from room temperature to T (° C.), α3 (/° C.) is the average coefficient of thermal expansion of the frame die from room temperature to T (° C.), and ΔT (° C.) is the difference between the sintering temperature T (° C.) and the room temperature at which the material is disposed between the pair of dies.
As described above, the molding process is preferably performed during a state in which the pair of opposing dies are not decentered in relation to the body, but it is possible to achieve a highly satisfactory accuracy of decenter at the heating temperature T (° C.) for performing molding, by effectively using the difference in thermal expansion between the pair of dies and the body when the dies are actually being heated. However, when the inside diameter Di (mm) of the body viewed in a cross section is less than the outside diameter Dp (mm) of the cross section of the pair of dies at T (° C.), sometimes a thermal insert state arises and the sliding capacity in the component for molding a device is severely reduced. In view of this, between the body and the pair of dies at T (° C.), there is preferably a gap of a specified dimension or greater as viewed in a cross section. However, when the inside diameter Di (mm) of the body when viewed in a cross section at T (° C.) is too large in comparison with the outside diameter Dp (mm) of the cross section of the pair of dies, the accuracy of decenter in the device is compromised. The aforementioned mathematical relationships show that it is preferable that this gap be from 0.005 mm or greater to 0.030 mm or less.
Similarly, there is preferably a gap of a specified dimension or greater between the body and the frame die when viewed in a cross section at T (° C.). The frame die is used in order to adjust the position where the material constituting the device is disposed, and is a component formed using a high-strength (high flexural strength) material. Because of this, when the frame die becomes thermally inserted in the body, the durability of the body poses a serious problem. Therefore, the frame die preferably has an even larger gap to the body than the previously described pair of dies. However, when the gap is too large, the precision of positioning the device is compromised. The aforementioned mathematical relationships show that it is preferable that this gap be from 0.015 mm or greater to 0.150 mm or less.
The above-described concavity of the body preferably extends in a direction coinciding with the longitudinal axial direction of the body. For example, processing the concavity of the body so that the concavity extends in a direction coinciding with the longitudinal axial direction is easier and has better merit in terms of processing costs than processing the concavity so that the concavity extends in a direction intersecting the longitudinal axial direction (i.e., in a direction substantially coinciding with the peripheral direction of the internal peripheral surface of the body).
The above-described concavity of the body may also extend in a direction intersecting the longitudinal axial direction of the body. The term “intersect” herein includes, for example, both a structure in which the concavity extends in an inclined direction at a specified angle relative to the longitudinal axial direction of the body, and a structure in the concavity extends in a direction substantially perpendicular to the longitudinal axial direction of the body. If the concavity extends in a direction intersecting the longitudinal axial direction of the body in this manner, the amount by which the dies fit into the concavity is reduced even if the width of the concavity is substantially the same as that of the previously described concavity extending in a direction coinciding with the liquid substance, for example. Therefore, suitable accuracy of decenter can be preserved. The concavity may also be disposed so as to describe a spiraling shape in the internal peripheral surface of the body, for example. In this case as well, the amount by which the dies fit into the concavity can be reduced, similar to the previously described case in which the concavity of the body extends in a direction intersecting the longitudinal axial direction of the body.
This concavity disposed in the internal peripheral surface of the body may also be formed in a plurality throughout the internal peripheral surface of the body. In this case, the concavities are preferably disposed at equal intervals in the circumferential direction of the internal peripheral surface of the body. The term “equal intervals” herein includes cases of substantially equal intervals (for example, cases in which the difference in distance between concavities along the circumferential direction of the body is within ±15% of the average value). Thus, if the concavities are disposed at equal intervals, the action of expelling gas remaining between the die and the material can be performed uniformly throughout the entire die. The stress applied to the entire component for molding a device when the molding process is performed can also be made uniform.
The materials constituting the constituent elements of the component for molding a device according to the present invention will now be described. First, to satisfy the mathematical relationships previously described, the body preferably includes at least 90 mass % or more of a material whose coefficient of thermal expansion is from 1.0×10−7 (/° C.) or greater to 3.5×10−6 (/° C.) or less, e.g., the body preferably includes 90 mass % or more of quartz glass. Commonly, quartz glass is often used as the material of the body. Possible examples of another material whose coefficient of thermal expansion value is within the aforementioned range are glass carbon; Adceram, which is a composite ceramic material of lithium aluminum silicate (LiAlSi2O6) and wollastonite (CaO—SiO2); and the like. These materials may be used as the material of the body.
Alternatively, the material of the body may include 90 mass % or more of silicon nitride. Using a material containing silicon nitride for the body can make the strength of the formed body greater than cases in which the above-described quartz glass is used.
It is also preferred that at least the sliding surfaces of the pair of dies facing the internal peripheral surface of the body be formed from a carbon-containing material. The carbon-containing material herein preferably includes any one material selected from the group consisting of graphite, glass carbon, diamond-like carbon (DLC), and diamond.
The pair of dies are preferably formed entirely from a carbon-containing material, not merely in the sliding surfaces facing the internal peripheral surface of the body. Including carbon can improve the degree of demolding (ease of removal from the dies) by which the formed device is removed from dies after the device has been molded. Particularly, by forming at least the sliding surfaces facing the internal peripheral surface of the body from a material containing predominantly carbon, the ease with which the dies and the body slide against each other can be improved, and the above-described ease of removal can be further improved. Possible allotropes of carbon include graphite, glass carbon, DLC, and diamond. At least the above-described sliding surfaces of the pair of dies facing the internal peripheral surface of the body may be formed from a material including these allotropes.
In the component for molding a device according to the present invention, the edges of the pair of upper and lower dies constituting the component for molding a device, where the sliding surfaces and pressing surfaces for pressing the material intersect, are preferably surfaces having an R-chamfer or C-chamfer of from 0.2 mm or greater to 1.0 mm or less. The term “R-chamfered surface” herein refers to a surface formed into a curved shape having a certain radius (R) at the border between two surfaces. The term “C-chamfered surface” herein refers to a surface provided so as to intersect two intersecting surfaces. In the case of an R-chamfered surface, the aforementioned radius (R) is preferably from 0.2 mm or greater to 1.0 mm or less. In the case of a C-chamfered surface, the length of the section over which the C-chamfered portion spans the two intersecting surfaces is preferably from 0.2 mm or greater to 1.0 mm or less.
The ease with which the dies and the body slide against each other can be improved by providing this manner of R-chamfered surfaces or C-chamfered surfaces. This R-chamfering or C-chamfering also fulfills the role of minimizing galling or catching of the dies in the body.
The frame die preferably includes at least 90 mass % or more of a ceramic having a flexural strength of 300 MPa or greater. More specifically, the frame die is preferably configured from a material including any one ingredient selected from the group consisting of silicon carbide, silicon nitride, alumina, boron carbide, zirconia, and tantalum carbide.
The frame die is used in order to adjust the position where the material constituting the device is disposed between the pair of dies. The pressure of pressing during molding acts directly on the frame die as lateral pressure. Therefore, the frame die is preferably formed using a high-strength (high flexural strength) material. Therefore, the frame die is preferably configured from a material including any material selected from the group described above. It is also preferred that the frame die commonly include the strong materials described above.
The method for manufacturing a device using the component for molding a device described above comprises a step for preparing a material, a step for disposing the material in a die, a step for heating the die, and a step for pressing the material. In the step for pressing the material, even if the die fits into the groove (concavity) provided in the internal peripheral surface of the body as previously described, if the die is heated in the step for heating the die, the position of the die relative to the body can be corrected via the difference in coefficients of thermal expansion between the die and the body. Therefore, the device formed via these steps has a highly favorable accuracy of decenter.
According to the component for molding a device of the present invention, gas remaining between the dies and the material can be minimized, as can molding defects in the formed device, which originate in the structure of the component for molding a device. As a result, a device formed using the component for molding a device of the present invention has a highly favorable accuracy of decenter.
Embodiments of the present invention are described hereinbelow with reference to the drawings. In these embodiments, elements which carry out the same functions are denoted by the same symbols, and descriptions thereof are not repeated if they are not particularly necessary.
The component 10 for molding a device shown in
A material 13 constituting the device is disposed in an area inside the frame die 16 disposed on the lower die 12, as shown in the cross-sectional view of
A sleeve 15 is disposed so as to cover the entire external peripheral surface of the body 14, as shown in
Rm (mm) denotes the radius of the circular shape formed by the cross section of the upper die 11, and Rs (mm) (0′ is the center of the body internal peripheral surface 14b) denotes the radius of the body internal peripheral surface 14b, as shown in
BO=√(Rm2−PB2)≦√(Rm2−D2)
Focusing on the right triangle BO′P:
BO′=√(Rs2−PB2)=√(Rs2−D2)
Also, A′O′=Rs, therefore:
A′B=A′O′−BO′=R
s−√(Rs2−D2)
AO=Rm, therefore:
L=AA′=AO−BO−A′B=R
m−√(Rm2−D2)−{R2−√(Rs2−D2)}
The width of the groove 14c, the radius of the cross section of the pair of dies, and other dimensions are preferably designed so that the distance L over which the upper die 11 fits into the groove 14c is 0.001 mm or less, i.e. 1 μm or less. If the molded lens or other device has a large amount of decenter, the performance of the lens suffers. Specifically, to preserve the definition of images captured through the lens, it is ideal that there be no (zero) decenter in the molded device.
Taking into account the circumstances described above, and also the machining precision of the upper die 11, the lower die 12, and other constituent elements of the component 10 for molding a device, as well as the handling precision when the upper die 11 is set on the lower die 12; the margin of deviation of L, which is a reference of the amount of decenter when the upper die external peripheral surface 11c is fitted into the groove 14c, is approximately 1 μm of the allowable amount of decenter 10 μm. Therefore, since L is preferably 1 μm or less, it is preferable that L≦0.001 (mm) as described above. It is even more preferable that L≦0.0005 (mm), i.e. that L be 0.5 μm or less. Therefore, the actual amount of decenter is presumably greater than L as described above.
The possibility of the body internal peripheral surface 14b being thermally inserted in the upper die external peripheral surface 11c after molding was described above, but the occurrence of a thermal insert can be prevented by effectively using the difference in coefficients of thermal expansion between the materials of the body 14 and the pair of dies, or other constituent elements of the component 10 for molding a device.
In the component 10 for molding a device at room temperature before heating is performed (such as when the material 13 is pressed) for molding, for example, Di (mm) denotes the inside diameter of the circular shape formed by a cross section intersecting the longitudinal axial direction (the vertical direction) of the body 14, Dp (mm) denotes the outside diameter of the circular shape formed by a cross section intersecting the longitudinal axial direction of the upper die 11 and the lower die 12, Dr (mm) denotes the outside diameter of the circular shape formed by a cross section intersecting the longitudinal axial direction of the frame die 16, α1 (/° C.) denotes the average coefficient of thermal expansion of the body 14 between room temperature and T (° C.), α2 (/° C.) denotes the average coefficient of thermal expansion of the upper die 11 and the lower die 12 between room temperature and T (° C.), and α3 (/° C.) denotes the average coefficient of thermal expansion of the frame die 16 between room temperature and T (° C.), as shown in
The following is a description of the dimensions of the constituent elements of the component 10 for molding a device in a case in which the component 10 for molding a device of
0.030≧(Di+α1DiΔT)−(Dp+α2DpΔT)=(α1Di−α2Dp)ΔT+(Di−Dp)≧0.005 (mm).
In other words, the gap is preferably from 5 μm or greater to 30 μm or less. If so, it is possible to prevent the above-described problem of a thermal insert as well as a loss of accuracy of decenter in the device.
Similarly, it is preferred that there be a fixed gap between the body 14 and the frame die 16, which is a ring. Moreover, the frame die 16 is used to position the material 13 to be molded, which is disposed in the area inside the internal peripheral surface of the frame die, and a high-strength material is used for the frame die; therefore, when a thermal insert forms due to heating during molding, there is a possibility that the durability of the body 14 will be severely reduced. In view of this, it is preferred that the gap between the body 14 and the frame die 16 be equal to or greater than the gap between the body 14 and the upper die 11 (the lower die 12). Specifically:
0.150≧(Di+α1DiΔT)−(Dr+α3DrΔT)=(α1Di−α3Dr)ΔT+(Di−Dr)≧0.015 (mm)
In other words, it is preferred that the gap be from 15 μm or greater to 150 μm or less. Providing a gap having at least the dimensions described above makes it possible to prevent a thermal insert from forming during molding as well as loss of device-positioning precision.
When the respective materials for the body 14, the upper die 11 (the lower die 12), and the frame die 16 are selected, it is preferred that α1<α2 and α1<α3. If so, the step of arranging the material 13 can be made easier by providing adequately wide gaps between the body 14 and the frame die 16 and between the body 14 and the upper die 11 (the lower die 12) at room temperature, for example, using the difference in coefficients of thermal expansion. At the same time, a high accuracy of decenter can be preserved by adequately reducing the size of the gaps between the body 14 and the frame die 16 and between the body 14 and the upper die 11 (the lower die 12) at the molding temperature T (° C.), for example.
Specific materials for forming the constituent elements of the component 10 for molding a device are described herein. First, it is preferred that the body 14 be formed using a material containing at least 90 mass % or more of a material whose coefficient of thermal expansion is from 1.0×10−7 (/° C.) or greater to 3.5×10−6 (/° C.) or less. It is particularly preferable to use a material containing at least 90 mass % or more of quartz glass whose coefficient of thermal expansion is 5.0×10−7 (/° C.). It is even more preferable to use a material composed of the above-described quartz glass (containing 100 mass % of quartz glass) as the material of the body 14.
If quartz glass is used as the body 14, since quartz glass has a low coefficient of thermal expansion, the step of arranging the material 13 can be made easier by providing an adequately large gap between the body 14 and the upper die 11 (the lower die 12) at room temperature, for example. Since heating light or radiant light permeates the quartz glass, the quartz glass has the effect of making it easier to control the temperature of the entire die set.
Alternatively, a material containing at least 90 mass % or more of silicon nitride may be used as the body 14. By using a material containing silicon nitride as the material of the body 14, the strength of the body 14 formed can be increased more so than in cases of using a material containing the above-described quartz glass.
The sleeve 15 disposed so as to cover the external peripheral surface in the longitudinal axial direction of the body 14 is preferably made of any one material selected from the following group: glass carbon, graphite, silicon nitride, silicon carbide, alumina, boron carbide, zirconia, tantalum carbide, molybdenum, and tungsten, for example. Using these materials for the sleeve 15 has the effect of blocking the heating light and using the radiant heat or transferred heat to heat the entire component 10 for molding a device including the upper die 11, the lower die 12, and the material 13.
The pair of dies, which are the upper die 11 and the lower die 12, are preferably formed from a material containing carbon. The material containing carbon herein preferably includes any one material selected from the following group: graphite, glass carbon, DLC, and diamond.
It is preferred that in addition to the sliding surfaces facing the body internal peripheral surface 14b, e.g., the upper die external peripheral surface 11c (the lower die external peripheral surface 12c), the pair of dies also be entirely formed from a material containing carbon such as those described above. This is because including carbon can improve the degree of demolding (ease of removal from the die) by which the formed device is removed from the upper die 11 (lower die 12) after the material 13 has been molded by the upper die 11 and the lower die 12, which are the constituent elements subjected to heating. Since the coefficient of thermal expansion of glass carbon is 2.8×10−6 (/° C.) and the coefficient of thermal expansion of diamond is 1.1×10−6 (/° C.), for example, it is easy for the coefficients of thermal expansion of the pair of dies to be α1<α2 as described above.
Particularly, by forming at least the sliding surfaces facing the internal peripheral surface of the body 14, e.g., the upper die external peripheral surface 11c (the lower die external peripheral surface 12c) from a material containing predominantly carbon, the ease with which the pair of dies and the body 14 slide against each other can be improved, and the above-described ease of removing the mold from the die can be further improved.
Possible allotropes of carbon include graphite, glass carbon, DLC, and diamond. If at least the upper die external peripheral surface 11c (lower die external peripheral surface 12c) of the above-described pair of dies, which is a surface that slides against the internal peripheral surface of the body 14, is formed from a material containing these allotropes, sufficient slidability against the body 14 can be ensured.
In the step of pressing the material against the frame die 16, which is a ring, during molding, the surface of the upper die 11 which faces the lower die 12 applies a large amount of lateral pressure. Therefore, the material used for the frame die 16 preferably is high in strength, and particularly in flexural strength, assuming there will be cases in which a large amount of stress is applied from the side. Specifically, the frame die 16 is preferably formed from a ceramic having a flexural strength of 300 MPa or greater, or the frame die 16 preferably includes at least 90 mass % or more of a ceramic. If the frame die 16 is formed using such a material, high durability can be maintained even if a large amount of pressure is applied during molding (during pressing).
Specifically, it is preferred that the frame die 16 be configured from a material including any one ingredient selected from the group consisting of silicon carbide, silicon nitride, alumina, boron carbide, zirconia, and tantalum carbide.
If this structure is used, even if the upper die external peripheral surface 11c is in contact with the internal peripheral surface of the body 14, the possibility of the edge interfering with the internal peripheral surface of the body 14 can be reduced because there is a space (draft) formed between the edge and the internal peripheral surface of the body 14. It is also easy to expel gas, which forms between the upper die 11 and the lower die 12 when the pair of dies are heated in order to perform molding, for example, to the groove 14c (see
The radius of the R-chamfered portion of the edge as shown in
If the radius of the R-chamfered portion or the dimension of the C-chamfered cut portion is increased by too much, it poses a problem in that machining costs could increase. Furthermore, if the radius of the R-chamfered portion or the dimension of the C-chamfered cut portion is increased by too much, there will be a greater ratio of sections where the value of the outside diameter (e.g. Dp (mm) in
With a component 10 for molding a device having any of the configurations described above, the upper die 11 and the lower die 12 slide satisfactorily against the body 14, and gas remaining between the upper die 11 and the lower die 12 can be easily expelled when heating is performed during the molding process. To easily expel the gas remaining between the upper die 11 and the lower die 12 further outside of the body 14 after the gas has been expelled outside of the upper die 11 or the lower die 12, the groove 14c, which is a concavity, is disposed in an area constituting at least part of the internal peripheral surface of the body 14.
For example, when the area with the material 13 between the upper die 11 and lower die 12 shown in
The groove 14c is preferably formed across the entire longitudinal axial direction of the body 14 (i.e., from the upper end of the body 14 to the lower end), as shown in
A groove 14c having a fixed width is disposed in a direction coinciding with the longitudinal axial direction of the body 14 only from the center vicinity of the longitudinal axial direction of the body 14 (i.e., the area enclosed between the upper die 11 and the lower die 12) to the top side (i.e., the area facing the upper die external peripheral surface 11c, which is the external peripheral surface of the upper die 11), as shown in
Disposing the groove 14c in only the top half of the body 14 reduces the amount by which the pair of dies (the upper die 11) facing the groove 14c fits into the groove 14c, in comparison with cases in which the groove 14c is disposed from the top end of the body 14 to the bottom end, as shown in
A groove 14c having a fixed width is disposed in a direction coinciding with the longitudinal axial direction of the body 14 only from the center vicinity of the longitudinal axial direction of the body 14 (i.e., the area enclosed between the upper die 11 and the lower die 12) to the bottom side (i.e., the area facing the lower die external peripheral surface 12c, which is the external peripheral surface of the lower die 12), as shown in
If this configuration is used, the gas led into the groove 14c is efficiently expelled to the exterior of the component 10 for molding a device. Since the gas led into the groove 14c flows downward through the groove 14c, the effect of gravity helps the gas to be expelled smoothly to the exterior.
In this case, similar to the groove 14c shown in
The groove 14c shown in
Even if the groove 14c extends at an incline in relation to the longitudinal axial direction in this manner, the groove still has the function of expelling the gas remaining between the upper die 11 and the lower die 12, similar to the cases in which the groove 14c extends in a direction coinciding with the longitudinal axial direction. Although the width of the groove 14c in
The groove 14c in
The groove 14c in
The groove 14c shown in
With the spiraling shape formed by the grooves 14c in
In cases in which a plurality of grooves 14c is disposed in the internal peripheral surface of the body 14 as shown in
Experiments for confirming the molded state were conducted on devices molded using the component 10 for molding a device according to the embodiment of the present invention, in which the previously described groove 14c as a concavity was disposed in at least part of the internal peripheral surface of the body 14; and devices molded using a component 10 for molding a device having no groove 14c.
The component 10 for molding a device shown in
In the component 10 for molding a device having the groove 14c, the width 2D (see
The inside diameters (mm) of the upper die 11 and the lower die 12, for example are not recorded in Table 1 because the structures of the upper die 11 and the lower die 12 do not have inside diameters. Furthermore, the inside diameter (mm) of the frame die 16, the outside diameter (mm) of the body 14, and other parameters, for example, are not recorded because they are not considered essential points when implementing an example according to the present invention.
Devices were molded in practice using each of the components for molding a device described above.
The state of the device formed by the steps described above was evaluated by measuring the relative density using Archimedes' Principle. Table 2 is a table showing the results of measuring samples of devices formed using the component 10 for molding a device having a groove 14c and a component for molding a device having no groove 14c. “Yes” indicates measurement results of samples of devices formed using the component 10 for molding a device having the groove 14c, and “No” indicates measurement results of samples of devices formed using a component for molding a device having no groove 14c. As shown in Table 2, the relative densities of the samples were measured for all of the total of 200 devices formed, 100 being formed using each component for molding a device, and samples whose relative densities were 99% or greater were designated as successful. The number of successful samples whose relative densities were 99% or greater is shown in Table 2.
As shown in Table 2, of the samples of devices formed using the component 10 for molding a device having the groove 14c, all 100 were “successful” samples whose relative densities were 99% or greater. Meanwhile, of the samples of devices formed using the component for molding a device having no groove 14c, 0 were “successful” samples whose relative densities were 99% or greater; in other words, all 100 of the 100 samples had relative densities less than 99%.
From the above results, gas remaining in the area enclosed by the pair of dies in the process of molding the device can be expelled to the exterior more efficiently via the groove 14c when the device has been formed using the component 10 for molding a device according to the present invention, in which a groove 14c is disposed in at least part of the area in the internal peripheral surface of the body 14. Therefore, it can be said that the ratio whereby gas is contained in the formed device is reduced. Consequently, when the device is formed using the component 10 for molding a device according to the present invention, a higher quality device having a greater relative density can be formed in comparison with cases of forming the device using a component for molding a device having no groove in the body.
In Example 2, a test was conducted to evaluate the amount of decenter in devices formed using the component 10 for molding a device having a groove 14c in the body 14.
In Example 2, a component 10 for molding a device having a groove 14c extending in the longitudinal axial direction of the body 14 was prepared, as shown in
Similar to the previous Example 1, 100 samples of devices using ZnS as the material 13 were formed using the bodies 14 having grooves 14c of different widths, based on the sequence in the flowchart of
As shown in Table 4, the best results of 0.2 μm and 0.3 μm for the average value of increase in the amount of decenter of the 100 samples were obtained with the devices molded using the components 10 for molding a device having bodies 14 whose groove 14c widths were 1.5 mm and 2 mm, respectively. In the devices formed using the component 10 for molding a device having a body 14 whose groove 14c width was 3 mm, the average value of increase in the amount of decenter of the 100 samples was 0.7 μm, which was still less than 1 μm, the allowable amount of increase in the amount of decenter. In the devices formed using the body 14 whose groove 14c width was 4 mm, the result was that the average value of increase in the amount of decenter of the 100 samples exceeded 1 μm.
From the above results, it can be said that if a device is formed using the component 10 for molding a device according to the present invention and the width of the groove 14c in the body 14 is 3 mm or less, or more preferably 2 mm or less, a high-quality device can be formed in which the increase in the amount of decenter of the formed device is kept within the allowable range.
In Example 3, a test was conducted similar to Example 2, using a component 10 for molding a device in which the materials and dimensions of the pair of dies, the body, and the frame die had been changed from those in Example 2. Table 5 below is a table showing the materials and dimensions of the constituent elements of the component for molding a device prepared in Example 3. As shown in Table 5, the component 10 for molding a device prepared in Example 3 had a groove 14c, and, as shown in
A circular shape formed by a cross section intersecting the longitudinal axial direction of the upper die 11 and the lower die 12 has an outside diameter (see Dp in
Similar to the previous Example 2, 100 samples of devices using ZnS as the material 13 were formed using the bodies 14 having grooves 14c of different widths, based on the sequence in the flowchart of
As shown in Table 6, the best results of 0.2 μm and 0.5 μm for the average value of increase in the amount of decenter of the 100 samples were obtained with the devices molded using the components 10 for molding a device having bodies 14 whose groove 14c widths were 2 mm and 3 mm, respectively. In the devices formed using the component 10 for molding a device having a body 14 whose groove 14c width was 4 mm, the average value of increase in the amount of decenter of the 100 samples was 0.9 μm, which was still less than 1 μm, the allowable amount of increase in the amount of decenter. In the devices formed using the body 14 whose groove 14c width was 5 mm, the result was that the average value of the amount of decenter of the 100 samples exceeded 1 μm.
From the above results, it can be said that if a device is formed using the component 10 for molding a device according to the present invention and the width of the groove 14c in the body 14 is 4 mm or less or more preferably 3 mm or less, a high-quality device can be formed in which the increase in the amount of decenter of the formed device is kept within the allowable range.
Example 4 is a test conducted in order to verify the range of materials which can be used in the constituent elements constituting the component 10 for molding a device. Table 7 is a table showing the materials and dimensions of the constituent elements of the component for molding a device prepared in one aspect of Example 4 of the present invention, as well as the evaluation results. As shown in Table 7, in the component 10 for molding a device prepared in one aspect of Example 4 of the present invention, the upper die 11 and the lower die 12 were formed using carbide. In both the upper die 11 and the lower die 12, a thin film of diamond was formed as their external peripheral surfaces; respectively, the upper die external peripheral surface 11c and the lower die external peripheral surface 12c, from the standpoint that these surfaces would be the sliding surfaces facing the body 14. Each of the thin films of diamond had a thickness of 3 μm. A circular shape formed by a cross section intersecting the longitudinal axial direction of the upper die 11 and lower die 12 had an outside diameter (see Dp in
As with the previous Example 3, 100 samples of devices using ZnS as the material 13 were formed using the component 10 for molding a device described above, based on the sequence in the flowchart of
As shown in Table 7, the average value of increase in the amount of decenter was 0.1 μm, which is less than 0.5 μm, and the evaluation result is therefore ⊙ (best). Specifically, a carbon-containing material is used in the main bodies and external peripheral surfaces of the dies, even by using carbide, for example, instead of glass carbon as the pair of dies and forming thin films of diamond on the external peripheral surfaces of the pair of dies. Therefore, even if the component 10 for molding a device is configured using the materials of the constituent elements in the above-described aspect of Example 4 of the present invention, the component 10 for molding a device is capable of being used to form satisfactory devices in which the increase in the amount of decenter is small.
Table 8 is a table showing the materials and dimensions of the constituent elements of the component for molding a device prepared in a second aspect of Example 4 of the present invention, as well as the evaluation results. As shown in Table 8, in the component 10 for molding a device prepared in one aspect of Example 4 of the present invention, the upper die 11 and the lower die 12, including the upper die external peripheral surface and the lower die external peripheral surface 12c, were formed using graphite. A circular shape formed by a cross section intersecting the longitudinal axial direction of the upper die 11 and the lower die 12 had an outside diameter (Dp in
As shown in Table 8, the average value of increase in the amount of decenter was 0.3 μm, which is less than 0.5 μm, and the evaluation result is therefore ⊙ (best). A carbon-containing material is used in the main bodies and external peripheral surfaces of the dies, even if graphite is used instead of glass carbon or carbide as the pair of dies. Therefore, even if the component 10 for molding a device is configured using the materials of the constituent elements in the above-described second aspect of Example 4 of the present invention, the component 10 for molding a device is capable of forming satisfactory devices in which the increase in the amount of decenter is small.
Table 9 is a table showing the materials and dimensions of the constituent elements of the component for molding a device prepared in a third aspect of Example 4 of the present invention, as well as the evaluation results. As shown in Table 9, in the component 10 for molding a device prepared in one aspect of Example 4 of the present invention, the upper die 11 and the lower die 12 were formed using carbide. DLC having a thickness of 3 μm was formed on the upper die external peripheral surface 11c and the lower die external peripheral surface 12c. A circular shape formed by a cross section intersecting the longitudinal axial direction of the upper die 11 and the lower die 12 had an outside diameter (Dp in
As shown in Table 9, the average value of increase in the amount of decenter was 0.6 μm, which is less than 1.0 μm, and the evaluation result is therefore ◯ (good). A carbon-containing material is used in the main bodies and external peripheral surfaces of the dies, even by using carbide, for example, instead of glass carbon as the pair of dies and forming thin films of DLC on the external peripheral surfaces of the pair of dies. Therefore, even if the component 10 for molding a device is configured using the materials of the constituent elements in the above-described third aspect of Example 4 of the present invention, the component 10 for molding a device is capable of forming satisfactory devices in which the increase in the amount of decenter is small.
Example 5 was a test on the effects of varying the shape and number of grooves 14c formed in the body 14. Table 10 is a table showing the materials and dimensions of the elements constituting the component for molding a device prepared in Table 5. As shown in Table 10, in the component 10 for molding a device prepared in order to form the devices in Example 5 of the present invention, the materials and dimensions of the constituent elements are all kept the same while only the shape of the groove 14c is varied. Specifically, as shown in Table 10, the materials and dimensions (outside diameter, inside diameter) of the constituent elements are all identical to those of the component 10 for molding a device prepared in Example 2 previously described. The material 13 of the devices molded in Example 5 is also ZnS, similar to Examples 1 through 4 previously described. The widths of the formed grooves 14c are all 2 mm. The devices were also formed based on the sequence in the flowchart shown in
Table 11 is a table showing the shape and number of grooves in different bodies in Example 5, as well as the results of evaluating decenter in the devices formed using these bodies. As shown in Table 11, the shapes of the grooves are the shapes of the grooves 14c of the body development views 24 of
One hundred device samples were formed using each of the bodies 14 having the respective groove 14c shapes, and the amount of decenter in the samples formed was measured using laser probe 3D measuring equipment (Mitaka Kohki Co., Ltd.). The average values of the measured amounts of decenter were calculated and evaluated for each body 14 used. The evaluation results are expressed by the same system as that of the previous Examples 2 through 4.
As shown in Table 11, in cases in which the extending direction of the groove 14c was an intersecting direction (inclined direction) relative to the longitudinal axial direction of the body 14 (the vertical direction of the drawing) as in
As shown in Table 11, even if any of the shapes shown in
The embodiments and examples disclosed herein are given by way of example in all regards and should not be construed as being restrictive. The scope of the present invention is defined not by the foregoing descriptions but by the claims, and the scope of the present invention is intended to include the claims, their equivalent meanings, and all modifications within the scope of the claims.
The present invention has value particularly as a technique for forming a satisfactory device which is high in quality while having a high relative density and a small amount of decenter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-291279 | Nov 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/068336 | 10/26/2009 | WO | 00 | 2/17/2011 |
