JP2013022784A - Ceramic sheet punch die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic sheet punch die which is applicable to a manufacturing method in which a ceramic sphere having an excessive thickness to be removed can be manufactured with high efficiency.SOLUTION: There is provided the ceramic sheet punch die which punches a sphere out of a raw material body including ceramic powder and a binder binding the ceramic powder, and includes a first die with a recessed part, a second die with a recessed part, and a cavity formed by combining the recessed parts of the first die and the second die together, a sectional shape of the cavity in a punching direction being a substantially elliptic shape having the major axis in the punching direction.

Description

  The present invention relates to a ceramic sheet punching die for punching a sphere from a ceramic sheet.

  An example of a method for producing a ceramic sphere using a bearing ball as a typical application is disclosed in Patent Document 1 below. In Patent Document 1, “a preformed body in which ceramic powder is pre-formed into a spherical shape is housed in a rubber mold, and the preformed body is densified by pressurizing the inside preformed body through the rubber mold. A ceramic ball comprising: a molding step for obtaining a spherical molded body; and a firing step for firing the spherical molded body, wherein the rubber mold containing the preform has a hardness of 65 or less. Manufacturing method "is disclosed. In addition, the die press molding is illustrated as a formation method of a preforming body.

JP 2002-36216 A

  The manufacturing method of the ceramic sphere disclosed in the above-mentioned Patent Document 1 and densifying the preform formed by molding the ceramic powder by die press molding by cold isostatic pressing (CIP) molding is currently wear resistant. It is widely used as a method for producing ceramic spheres used in bearing balls that require breakage resistance. However, in order to manufacture ceramic spheres by such a manufacturing method, there are mold press molding for spheroidizing ceramic powder, and voids and preforms present in the preform formed by mold press molding. In order to reduce the density unevenness, it is necessary to go through CIP molding and two molding processes, and there is a problem that the manufacturing process becomes long and the manufacturing cost of the ceramic sphere increases. In response to recent environmental problems, the demand for ceramic ball bearings has increased, and there has been an increasing demand for the development of a highly efficient method for producing ceramic spheres.

  In addition, when the ceramic sphere is formed by die press molding as in the method of manufacturing the ceramic sphere of Patent Document 1, a so-called “band” is projected annularly from the spherical surface so as to surround its central portion. A part is inevitably formed. Since this band is a surplus that does not become a product, it is usually removed after grinding by grinding etc., but since sintered ceramics are difficult to process materials, it is necessary to spend a long time for removal processing, There has been a demand for the development of a method for producing ceramic spheres with a small excess to be removed.

  The present invention has been made in view of the above-described problems of the prior art, and provides a punching die that can be applied to a manufacturing method capable of manufacturing a ceramic sphere with a small excess wall to be removed with high efficiency. It is aimed.

  An aspect of the present invention that achieves the above object is a punching die for punching a sphere from a raw material containing a ceramic powder and a binder that binds the ceramic powder, the first mold having a recess, the recess And a cavity formed by a combination of the concave portions of each of the first mold and the second mold, and the cross-sectional shape of the cavity along the punching direction is stamped. A punching die having a substantially elliptical shape whose major axis is a major axis.

  In the punching die of the above aspect, in order to prevent deformation of the punched sphere, at least one of the first mold and the second mold has a deaeration hole communicating with the cavity. desirable.

  In the punching die having the above-described deaeration hole, in order to reduce the surplus by correcting the convex portion formed by the raw material body entering the air vent, in order to press the surplus to the cavity side, It is preferable to have an insertion member having a distal end surface to be inserted into the deaeration hole, and it is desirable that the distal end surface of the insertion member is a part of a spherical surface smoothly connected to the inner surface of the cavity.

  Further, in the punching die having a deaeration hole, the opening of the deaeration hole may be blocked by a plug through which the raw material body can be prevented from entering the deaeration hole, but air can flow therethrough. It is further desirable that the front end surface is a part of a spherical surface that smoothly connects with the inner surface of the cavity.

  Further, in the punching die of the above aspect, in order to smoothly separate the sphere from the raw material body, a substantially annular protrusion is formed around at least one of the recesses of the first mold and the second mold. It is desirable that a section is provided.

  In addition, in order to prevent deformation of the sphere due to elasticity, the raw material body includes a thermosetting resin as a binder, and has heating means for heating at least one of the first mold and the second mold. desirable.

  According to the present invention, the problem can be solved.

It is a schematic block diagram of the ceramic sphere manufacturing apparatus with which the punching die of the 1st aspect concerning this invention was integrated. FIG. 2 is an enlarged front sectional view of a part A in FIG. 1. It is a figure explaining the malfunction which arises when the cavity of the punching die of FIG. 2 is spherical. It is a figure explaining operation | movement of the punching die of FIG. It is front sectional drawing of another aspect of the punching die of FIG. It is front sectional drawing of the punching die of the 2nd aspect concerning this invention.

  The present invention will be described based on the first and second aspects with reference to the drawings. In the following description, a ceramic green sheet that is a substantially flat ceramic molded body is used as a raw material body that is a raw material for forming a ceramic sphere, but the form of the raw material body is not limited to this, and the raw material body The body may be in a solid form including ceramic powder and a binder that binds the ceramic powder. Furthermore, the present invention is not limited to the first aspect and the second aspect, and can be appropriately modified and implemented within the same scope in the technical idea.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. First, with reference to FIG. 1 which is a schematic configuration diagram, a ceramic sphere manufacturing apparatus 10 in which a punching die according to the first aspect of the present invention (hereinafter sometimes referred to as a die) is incorporated will be described. To do.

  The ceramic sphere manufacturing apparatus 10 is disposed upstream of the left side in FIG. 1, and an unfired ceramic green sheet (hereinafter sometimes simply referred to as a sheet) W, which is a raw material body, is placed to the right from the die at the tip. An auger-type extrusion molding portion 10b that continuously extrudes oppositely, a plurality of feed rollers 10c that conveys the sheet W supplied from the extrusion molding portion 10b to the right side that is the downstream side, and a batting that is conveyed by the feed roller 10c. It is composed of a punching portion 10a that punches a sheet W as a raw material to form a sphere (ceramic sphere). The sheet, which is a substantially flat ceramic molded body, is formed in a single-leaf form by, for example, dry forming press forming or CIP, wet forming casting or injection molding, and the sheets are individually batch-like. The ceramic spheres may be formed by punching. However, it is desirable to form the sheet W continuously by extrusion because the production efficiency is increased. The sheet W may be continuously formed by, for example, a tape forming method. In this case, however, it is necessary to peel the carrier tape from the sheet W immediately before the punching portion 10a.

  The extrusion molding section 10b is supplied with a raw material slurry in which ceramic raw material powder, a solvent composed of water or an organic solvent, and a binder, plasticizer, lubricant, and other molding aids are mixed. It contains kneading by passing through a constant pressure region, compacting and homogenizing while being degassed, and then passing through a die, which contains a ceramic powder having a desired molding density and a binder that binds the ceramic powder with low porosity. A sheet W that is a raw material body is formed.

  Next, the punching part 10a will be described. The punching unit 10a in which the mold 1 of this embodiment is incorporated is a hydraulic or mechanical press device, and is supplied by a lifting unit 10d mounted on the tip of a cylinder rod that moves up and down and a feed roller 10c. The base part 10e is disposed so as to face the lifting part 10d through the sheet W, and the upper mold (first mold) 1a of the mold 1 is connected to the lifting part 10d and the lower mold (second mold). ) 1b is disposed on the base portion 10e.

  Reference numerals 10f and 10h are a pair of flat plate-shaped holding members disposed on the elevating part 10d and the base part 10e so as to sandwich the upper mold 1a and the lower mold 1b. The holding members 10f and 10h, which are preferable components disposed in the punching portion 10a, sandwich the sheet W from the top and bottom before punching when the elevating portion 10a is lowered to punch the sheet W. When the die 1 is punched, the movement of the sheet W is restricted so that the sheet W does not move in the vertical direction. Reference numerals 10g and 10i denote elevating means for elevating an insertion member as a preferred component arranged in the upper mold 1a and the lower mold 1b as will be described later. Reference numerals 10j and 10k are heating means for heating the upper mold 1a and the lower mold 1b, respectively. As will be described later, the heating means 10j and 10k are elements that need to be disposed when punching a sheet W containing a thermosetting resin as a binder which is a preferred embodiment, and are not an essential component in the punching portion 10a. .

  Next, the configuration of the mold 1 incorporated in the punching portion 10a will be described with reference to FIG. 2 which is an enlarged front sectional view of the portion A in FIG. As shown in FIG. 2, the substantially cylindrical upper mold 1a and lower mold 1b arranged so as to be coaxial with each other in the horizontal direction are concave portions formed so as to penetrate through the pressing surfaces 1m and 1n as the tip surfaces. 1c and 1h. When the upper mold 1a is lowered and the pressure surfaces 1m and 1n are brought into contact with each other and the upper mold 1a and the lower mold 1b are combined, a cavity 1L, which is a sealed space, is formed in the mold 1. When the upper mold 1a is lowered, the sheet W is cut by the outer peripheral edges of the upper mold 1a and the lower mold 1b and punched into a circular shape, and a part of the sheet W is filled in the cavity 1L and filled P1. Form. In order to reliably separate the filling body P1 from the sheet W and to prevent the sheet W from being caught between the pressing surfaces 1m and 1n of the upper mold 1a and the lower mold 1b, the concave portion of the upper mold 1a is used. It is desirable that a substantially annular projection 1e be provided around 1c, and the tip surface of the projection 1e be a pressure surface 1m. The protrusion 1e may be provided around the recess 1h of the lower mold 1b instead of the upper mold 1a, or may be provided on both the upper mold 1a and the lower mold 1b. Further, in order to suppress the biting of the sheet W between the pressing surfaces 1m and 1n of the upper mold 1a and the lower mold 1b, the sheet W that is pressure-deformed by the upper mold 1a and the lower mold 1b is connected to the outside. In order to make the flow smooth, it is desirable to form a tapered surface inclined upwards around the protrusion 1m.

  Here, as described above, the upper mold 1a of the cavity 1L formed by the combination of the recesses 1c and 1h of the upper mold 1a and the lower mold 1b moves up and down, that is, along the punching direction by the mold 1. The cross-sectional shape has a major axis diameter L1 along the punching direction larger than the minor axis diameter T in the direction orthogonal to the punching direction (hereinafter sometimes referred to as the horizontal direction), and the punching direction is the major axis. It has an elliptical shape, and the cross-sectional shape of the cavity 1L around the center line C is substantially the same. In FIG. 2, the long axis diameter L1 is drawn extremely large with respect to the short axis diameter T for the sake of understanding. However, the cross-sectional shape of the cavity 1L may be a substantially elliptical shape with the long axis in the punching direction. . The reason why the cavity 1L is configured as described above will be described with reference to FIG.

  FIG. 3A shows a state in which the sheet W is punched with a mold 9 configured to form a spherical cavity 9L by a combination of the upper mold 9a and the lower mold 9b, instead of the cavity 1L having the above-described configuration. FIG. When the sheet W is punched with the mold 9 having such a configuration, the sheet W is filled into the cavity 9L by the same process as described above, and the spherical filling body P1 is formed. Here, the sheet W containing a binder, a plasticizer, and other organic components has elasticity even if it is molded by any of the above-described dry molding and wet molding methods, and the filling body P1 filled in the cavity 9L is It is in a state of being elastically deformed and compressed by pressurization by the mold 1. Since this filling body P1 is spherical, the amount of elastic deformation in the punching direction in the horizontal direction varies from place to place, and as indicated by arrows B1 and B2 in FIG. It is the lowest and becomes higher as it goes outward from the center line C, and the outer edge is the highest with the elastic deformation amount B2. When the filler P1 is removed from the cavity 9L, the diameter of the filler P1 is increased in the punching direction and the horizontal direction due to elastic return (springback) due to elastic deformation. Since the amount of elastic deformation varies depending on the position in the horizontal direction, as shown in FIG. 3B, the elastic return amount D1 is small in the portion along the center line C, and the elastic return amount D2 is increased toward the outer edge. As a result, the filler P1 after being removed from the cavity 9L and elastically deformed is not a sphere, but a distorted elliptical sphere Z.

  Therefore, the cavity 1L of the present embodiment takes into account the difference in the elastic return amount of the filling body P1 in the punching direction due to the elasticity of the sheet W, and the filling body P1 is removed after being taken out from the cavity 1L. The cross-sectional shape along the punching direction was a substantially elliptical shape having a long axis in the punching direction so as to form a sphere. According to the filling body P1 formed by the cavity 1L, as shown in FIG. 3 (c), the elastic return amount is D1, and the length on the center line C is the smallest L1, and from the center line C, The distance between the upper hemisphere and the lower hemisphere in the punching direction of the filler P1 is reduced to L2 to L4 according to the amount of elastic return that increases toward the outside. The difference in elastic return amount of the filler P1 is complemented by the distribution of the distances L1 to L4 of the filler P1 in the horizontal direction, and the filler P1 after being removed from the cavity 1L and elastically deformed becomes a sphere P.

  The specific shape of the cavity 1L is appropriately set depending on the elastic modulus of the sheet W, but the sheet W was obtained by punching with the mold 9 having the spherical cavity 9L shown in FIG. You may determine based on the elastic return amount computed from the shape of the ellipsoidal sphere Z.

  Next, the deaeration holes 1d and 1i and the insertion members 1f and 1j arranged as preferable components in the mold 1 of this aspect will be described. Deaeration holes 1d and 1i arranged in the upper mold 1a and the lower mold 1b are opened on the inner surfaces of the recesses 1c and 1h so as to communicate with the cavity 1L. By arranging such deaeration holes 1d and 1i, when the upper mold 1a contacts the lower mold 1b and the sheet W is filled, the air in the cavity 1L escapes to the outside through the deaeration holes 1d and 1i. Therefore, the sheet W is smoothly filled into the cavity 1L, and the occurrence of the shape defect of the filling body P1 can be suppressed. A plurality of the deaeration holes 1d and 1j may be provided in the upper mold 1a and the lower mold 1b, or may be provided in at least one of the upper mold 1a and the lower mold 1b.

  Here, when the deaeration holes 1d and 1i are provided as described above, as shown in FIG. 4B, a part of the sheet W filled in the cavity 1L enters the deaeration holes 1d and 1i, There is a possibility that protrusions P2 and P3 are formed as surplus on the top and bottom of the filler P1. The protrusions P2 and P3 have a smaller volume than the band formed by the conventional method of manufacturing ceramic spheres, so that the removal process is less, but it is not enough to manufacture bearing balls at low cost. It is desirable that the volume of the protrusions P2 and P3 that are meat is small. Therefore, in the mold 1 of the present embodiment provided with the deaeration holes 1d and 1i, the columnar insertion members 1f and 1j having the tip surfaces 1g and 1k at one end inserted into the deaeration holes 1d and 1i are arranged. Yes. The other ends of the insertion members 1f and 1j are connected to the elevating means 10g and 10i shown in FIG. 1, and are moved up and down in the deaeration holes 1d and 1i while being position-controlled in the vertical direction. According to the insertion members 1f and 1j, the volumes of the protrusions P2 and P3 can be reduced by pressing the protrusions P2 and P3 entering the deaeration holes 1d and 1i with the tip surfaces 1g and 1k. In order to eliminate the protrusions P2 and P3, as shown in FIG. 2, the shape of the distal end surfaces 1g and 1k of the insertion members 1f and 1j is a part of a spherical surface that is smoothly connected to the inner surface of the cavity 1L. It is desirable to push the insertion members 1f and 1j toward the cavity 1L so that the front end surfaces 1g and 1k coincide with the open ends of the deaeration holes 1d and 1i.

  Refer to FIG. 5 which is a front sectional view showing an enlarged part of the mold 2 of another embodiment in which the protrusions P2 and P3 which are surplus portions generated in the mold 1 provided with the deaeration holes 1d and 1i are reduced. I will explain. In FIG. 5, the same components as those of the mold 1 of the above aspect are denoted by the same reference numerals, and detailed description thereof is omitted (the mold 3 of the second aspect described with reference to FIG. 6 is also omitted). The same).

  The mold 2 shown in FIG. 5 has basically the same configuration as the mold 1, but the opening of the deaeration holes 1 d and 1 i on the side of the cavity 1 L is connected to the deaeration holes 1 d and 1 i. The sheet W is prevented from entering, but the air is blocked by the flowable plugs 2m and 2n. The plugs 2m and 2n may be disposed at positions where the front end surfaces 1g and 1k are separated from the opening ends of the deaeration holes 1d and 1i. However, in order not to generate the protrusions P2 and P3, as shown in FIG. In addition, the shape of the tip surfaces 1g and 1k is a part of a spherical surface that is smoothly connected to the inner surface of the cavity 1L, and the tip surfaces 1g and 1k are arranged so as to coincide with the open ends of the deaeration holes 1d and 1i. desirable.

  As the plugs 2m and 2n for closing the deaeration holes 1d and 1i, plugs 2m and 2n made of a porous metal or ceramic having air permeability may be used. Further, the stoppers 2m and 2n formed along the center line C may be used as long holes having a minute diameter that are difficult for the sheet W to enter. In this case, the deaeration holes 1d and 1i are formed as bottomed blind holes. In addition, a long hole may be provided in the remaining portion so that the plugs 2m and 2n are integrated with the upper molds 1a and 1b. Thus, even when it is configured integrally with the upper molds 1a and 1b, it can function as the stoppers 2m and 2n.

  A method for manufacturing a ceramic sphere using the mold 1 of the first aspect will be described with reference to FIG. First, as shown in FIG. 4 (a), a sheet W formed by an unillustrated extrusion molding portion is placed between the upper mold 1a and the lower mold 1b in a state where the upper mold 1a as the initial position is raised. The sheet W is supplied to the gap formed in the above. Next, as shown in FIG. 4B, the upper mold 1a is lowered to a position where the pressing surfaces 1m and 1n of the upper mold 1a and the lower mold 1b come into contact with each other, and the sheet W is formed at the outer peripheral edges of the upper mold 1a and the lower mold 1b. Is punched into a circular shape, and the sheet W is filled into the cavity 1L to form a compacted filling body P1. At this time, the air in the cavity 1L escapes to the outside through the deaeration holes 1d and 1i, but the sheet W enters the deaeration holes 1d and 1i to form projections P2 and P3.

  Next, as shown in FIG. 4 (c), the insertion members 1f and 1j are inserted into the deaeration holes 1d and 1i so that the front end faces the opening ends of the deaeration holes 1d and 1i, and the deaeration holes 1d and 1i are inserted. The formed protrusions P2 and P3 are lost. Thereafter, as shown in FIG. 4D, when the upper die 1a is raised to the initial position and the filler P1 is taken out from the recess 1c of the upper die 1a, the filler P1 expands due to elastic deformation, and the desired ceramics are obtained. A sphere P is formed. In addition, when taking out the filling body P1 from the upper mold | type 1a, as shown in the figure, the insertion member 1f inserted in the deaeration hole 1d may be dropped, and the filling body P1 may be extruded from the recessed part 1c. Further, after the sheet W containing a thermosetting resin as a binder is punched to form the filling body P1, the upper mold 1a and the lower mold 1b are heated by the heating means 10j and 10k to form the ceramic sphere P. This is desirable because the elastic deformation of the filler P1 is alleviated by the thermoset resin. In this case, the cavity 1L of the mold 1 has a form closer to a sphere.

[Second Embodiment]
The metal mold | die 3 which is 2nd Embodiment of this invention is demonstrated with reference to FIG. The mold 3 according to the second aspect is basically constituted by the same technical idea as the mold 1 according to the first aspect, but has a structure in which the mass productivity of the ceramic sphere is further improved. That is, the mold 3 of the second mode is disposed so as to face the upper roll 3a through the cylindrical upper roll (first mold) 3a having the hollow portion 3o and the sheet W supplied from the left side. A cylindrical lower roll (second mold) having a hollow portion 3p is provided, and the positions of the two are adjusted so that the contact 3r is disposed at a position connecting the central axes. The upper roll 3a and the lower roll 3b are formed with a plurality of recesses 1c and 1h identical to those in the first aspect at equal angles on the outer peripheral surfaces thereof. The upper roll 3a and the lower roll 3b are arranged so that the cavity 1L is formed when the concave portions 1c and 1h are combined at the contact point 3r of the two. The diameter of the sheet W filled in the cavity 1L is smaller than that of the deaeration holes 1d and 1i of the mold 1 of the first mode so that the sheet W does not enter the deaeration holes 3d and 3i.

  According to the mold 3, the supplied sheet W is first filled in the concave portions 1c and 1h existing on the left side of the contact 3r in the rotating upper roll 3a and the lower roll 1b, and both the contact 3r. In the cavity 1L formed in the above, it is consolidated and becomes the filling body P1. Next, when the outer peripheral surfaces of the upper roll 3a and the lower roll 3b are separated on the left side of the contact 3r, the filler P1 is detached from the concave portion 1c of the upper roll 3a, and is expanded in diameter by elastic deformation. Ceramic spheres are formed. In the mold 3, a plurality of recesses 1 c and 1 h are formed on the outer peripheral surfaces of the cylindrical upper roll 3 a and lower roll 3 b, so that the above process is continuously repeated and the ceramic spheres P become more efficient one after another. Well formed.

1 (2, 3) Mold 1a (3a) First mold 1b (3b) Second mold 1c (1h) Recess 1d (1i, 3d, 3i) Deaeration hole 1f (1j) Insert member 1m (1n) Addition Pressure surface 1L (3L) Cavity 10 Ceramic sphere manufacturing apparatus 10a Punching part 10b Extrusion part 10c Feed roller

Claims (8)

  A punching die for punching a sphere from a raw material body including a ceramic powder and a binder that binds the ceramic powder, the first mold having a recess, the second mold having a recess, and the first mold A cavity formed by a combination of the concave portions of the mold and the second mold, and the cross-sectional shape of the cavity along the punching direction is a substantially elliptical shape with the punching direction being the long axis. Punching die characterized by having   The punching die according to claim 1, wherein at least one of the first die and the second die has a deaeration hole communicating with the cavity.   The punching die according to claim 2, further comprising an insertion member having a distal end surface to be inserted into the deaeration hole.   The punching die according to claim 3, wherein a distal end surface of the insertion member is a part of a spherical surface that is smoothly connected to an inner surface of the cavity.   3. The punching die according to claim 2, wherein the opening of the deaeration hole on the cavity side prevents the raw material from entering the deaeration hole, but the air is closed with a plug through which air can flow.   The punching die according to claim 5, wherein a distal end surface of the stopper is a part of a spherical surface smoothly connected to an inner surface of the cavity.   The punching die according to any one of claims 1 to 6, wherein a substantially annular protrusion is provided around at least one of the concave portion of the first die and the concave portion of the second die.   The punching die according to any one of claims 1 to 7, wherein the raw material body includes a thermosetting resin as a binder, and has heating means for heating at least one of the first mold and the second mold.

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