Honeycomb structure forming tool

Abstract

Honeycomb structure forming tool (100, 300) comprising: a first mold (10) disposed on an upstream side in an extrusion direction (X) of a kneaded material of a molding raw material, and in which a central portion (15) on the side of a kneaded material discharge surface has a convex portion (16) projecting toward a downstream side in the extrusion direction (X); and an annular second mold (20) arranged on the downstream side of the first mold (10) and having a shape complementary to the convex region (16), wherein first kneading material introduction holes (12) and first grid slots (11) communicating with the first kneading material introduction holes (12) are formed in the central region (15) of the first mold (10), in a peripheral region (17) surrounding the central region (15) of the first mold (10), the first kneading material introduction holes (12) are formed such that they extend through the peripheral region (17) of the first mold (10), and second kneading material introduction holes (22) are formed in the annular second mold (20), into which the kneading material discharged from the first kneading material introduction holes (12) formed in the peripheral region (17) of the first mold (10) is introduced, and second grid slots (21) communicating with the second kneading material introduction holes (22), the honeycomb structure forming tool (100, 300) has a gap region (55) between an outer peripheral surface of the convex portion (16) of the first mold (10) and an inner peripheral surface of the annular second mold (20) in order to extrude the kneaded material into a ring shape, the honeycomb structure forming tool (100, 300) further includes a mesh member (30, 30A) interposed between the first mold (10) and the second mold (20) and formed from a plurality of interwoven linear materials (33) and having a cavity portion (36) corresponding to the convex portion (16) of the first mold (10), the movement of the kneading material between the first kneading material introduction hole (12) and the second kneading material introduction hole (22) is carried out through the meshes of the net element (30, 30A), wherein passage channels (31) formed by the meshes of the net element (30, 30A) are connected to the gap region (55), and the mesh element (30) is configured such that linear materials (33) extending in a lateral direction are interwoven with linear materials (33) extending in a direction perpendicular thereto to allow movement of the kneaded material through the meshes of the mesh element (30, 30A) in a region in which the interwoven linear materials (33) are not superimposed.

Description

[0001] This application is an application based on JP-2016-156975, filed on August 9, 2016, and JP-2016-220875, filed on November 11, 2016, with the Japan Patent Office, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTIONField of the invention

[0002] The present invention relates to a honeycomb structure forming die, and more particularly, it relates to a honeycomb structure forming die capable of forming a honeycomb formed body having a central part different from a peripheral part in terms of honeycomb structure with high quality. Description of the state of the art

[0003] Conventionally, a catalyst-impregnated honeycomb structure is used for treatment to remove pollutants such as HC, CO, and NOx contained in exhaust gases emitted from an internal combustion engine of a motor vehicle or the like. Furthermore, the honeycomb structure is also used as a filter for purifying exhaust gases by sealing the open ends of honeycombs formed with porous partition walls.

[0004] Honeycomb structures are columnar structures each including partition walls forming a plurality of honeycombs that become flow channels for exhaust gas. Such a honeycomb structure has a honeycomb structure in which a plurality of honeycombs are regularly arranged in predetermined cycles in a plane perpendicular to an extending direction of the honeycombs. Heretofore, there has been one type of honeycomb structure in the above-mentioned plane of a honeycomb structure, but recently, for the purpose of improving the purification efficiency of exhaust gas or the like, a honeycomb structure having two or more types of honeycomb structures in the above-mentioned plane has been proposed.For example, a honeycomb structure has been proposed in which a central part is different from a peripheral part in a plane perpendicular to a honeycomb extending direction in honeycomb density or honeycomb shape, thus having two kinds of honeycomb structures in the above-mentioned plane.

[0005] This honeycomb structure is manufactured by molding a wrought material containing a ceramic molding raw material with an extrusion die to produce a honeycomb molded body, and then drying and firing the resulting honeycomb molded body. For example, the mold is manufactured as a honeycomb molding die by forming back holes into a metal molding substrate, into which the wrought material is introduced, and slits communicating with the back holes (see, for example, Patent Documents 1 to 4). Hereinafter, the honeycomb molding die is simply referred to as a "molding die" or occasionally as a "mold."

[0006] Further prior art is also known from patent documents 5 to 10. [Patent Document 1] JP 2015-096 310 A [Patent Document 2] JP 2013-132 879 A [Patent Document 3] JP 2013-132 881 A [Patent Document 4] JP H04-332 604 A [Patent document 5] US 2015 / 0 137 431 A [Patent document 6] EP 2 617 541 A1 [Patent document 7] DE 1 238 198 B [Patent Document 8] US 3,900,546 A [Patent Document 9] US 5,108,685 A [Patent Document 10] US 6,039,908 A BRIEF DESCRIPTION OF THE INVENTION

[0007] For example, a mold described in Patent Document 1 includes a first mold part located on an upstream side in an extrusion direction of a raw material and a second mold part located on a downstream side. The above-mentioned first mold part has convex portions protruding from a periphery on the downstream side in the extrusion direction, and the above-mentioned second mold part has through holes that fit with the convex portions. In the mold described in Patent Document 1, the convex portions of the first mold part are inserted into the through holes of the second mold part to combine the first mold part and the second mold part into one mold.

[0008] However, the mold described in Patent Document 1 has a problem that there are design limitations when the mold for molding a honeycomb molded article is used to form a honeycomb structure having two types of honeycomb structures. In other words, usually, in the mold for molding the honeycomb molded article, "mesh slits" are formed on the side of a kneading material discharge surface of a molding substrate, which correspond to a honeycomb structure of the honeycomb molded article. Further, in such a mold, back holes are formed as raw material supply holes, which communicate with intersection points of the lattice slits. In Patent Document 1 described, in situations where the first mold part is different from the second mold part in terms of the shape of the respective slits, it is difficult to connect all the back holes (i.e., first raw material supply holes) in the first mold part with all the back holes (i.e.,second raw material supply holes) in the second mold part. If all the back holes do not align with each other, and when the first mold part and the second mold part are combined into one piece, the movement of the molded material in the mold is hindered, and uniform extrusion becomes difficult. Consequently, in the mold described in Patent Document 1, it is necessary to select the shapes of the slits formed in the first mold part and the second mold part, respectively, so that the above-mentioned movement of the molded material is not hindered, and the degree of freedom of design is very low.

[0009] The molds described in Patent Documents 2 and 3, respectively, are not molds for forming a honeycomb formed article having two types of honeycomb structures, but are molds for improving honeycomb quality only in an outermost peripheral part. Furthermore, the molds described in Patent Documents 2 and 3 have a problem in that they are not compatible with the formation of various honeycomb formed articles in which the shapes of two types of honeycomb structures and their formation areas vary widely. For example, a honeycomb structure having two types of honeycomb structures occasionally has a boundary wall arranged to surround the honeycomb structure of a central part at a boundary between the honeycomb structure of the central part and the honeycomb structure of a peripheral part.During extrusion, the boundary wall requires a large amount of molding raw material compared to the partition walls constituting the honeycomb structures of the central part and the peripheral part. When the honeycomb formed body having such a boundary wall as described above is formed using any of the molds described in Patent Documents 2 and 3, the demand exceeds the supply of the molding raw material for forming the boundary wall, and molding defects may be caused in the boundary wall and its surroundings. Furthermore, the molds described in Patent Documents 2 and 3 were each developed to improve the honeycomb quality only in the outermost peripheral part, and thus a problem arises regarding the strength of a shell portion. If the problem is to be solved only by simply increasing the molding area of ​​a shell portion, there is a risk of the shell portion being deformed.

[0010] A mold described in Patent Document 4 has a structure in which adjacent mold bodies are tightened with wedges or engaged with each other using pressing pressure. Thus, there is a problem that the pressure resistance properties of a wrought material are low and the mold is prone to breakage. The mold described in Patent Document 4 also has a problem that positional displacement of back holes is easily caused and there is a likelihood of generating molding defects.

[0011] On the other hand, the honeycomb molded article with two types of honeycomb structures occasionally has a boundary wall that defines the two types of honeycomb structures at a boundary between a central part of the honeycomb molded article and its peripheral part. The amount of kneading material consumed for the boundary wall during extrusion differs from that of the kneading material consumed for the partition walls to be formed around the boundary wall. Consequently, the honeycomb molded article with two types of honeycomb structures has a problem that molding defects are likely to form, particularly around the boundary wall. For example, if the type or the like of the kneading material of the molding raw material is changed during extrusion, the flowability of the kneading material varies. Therefore, the mold for extruding the honeycomb molded article with the boundary wall greatly limits versatility.

[0012] The present invention has been developed in consideration of the above-mentioned problems, and its object is to provide a honeycomb structure forming die capable of forming a honeycomb formed body having a central part different from a peripheral part in terms of honeycomb structure with high quality.

[0013] According to the present invention, the following honeycomb structure forming tool is provided. [1] A honeycomb structure forming tool comprising: a first mold disposed on an upstream side in an extrusion direction of a kneaded material of a molding raw material, and in which a central portion on the side of a kneaded material discharge surface has a convex portion projecting toward a downstream side in the extrusion direction; and an annular second shape arranged on the downstream side of the first shape and having a shape complementary to the convex region, wherein first wrought material introduction holes and first grid slots communicating with the first wrought material introduction holes are formed in the central region of the first mold, in a peripheral region surrounding the central region of the first mold, the first wrought material introduction holes are formed so as to pass through the peripheral region of the first mold, and second kneading material introduction holes are formed in the annular second mold, into which the kneading material discharged from the first kneading material introduction holes formed in the peripheral region of the first mold is introduced, and second grid slots communicating with the second kneading material introduction holes, wherein the honeycomb structure forming tool has a gap portion between an outer peripheral surface of the convex portion of the first mold and an inner peripheral surface of the annular second mold to extrude the kneaded material into a ring shape, wherein the honeycomb structure forming tool further includes a mesh member interposed between the first mold and the second mold and formed of a plurality of interwoven linear materials and having a cavity portion corresponding to the convex portion of the first mold, wherein the movement of the kneading material between the first kneading material introduction hole and the second kneading material introduction hole is carried out through the meshes of the net element, whereby passage channels formed by the meshes of the net element are connected to the gap area, and the mesh element is configured such that linear materials extending in a lateral direction are interwoven with linear materials extending in a direction perpendicular thereto to allow movement of the kneading material through the meshes of the mesh element in a region where the interwoven linear materials are not superimposed. [2] The honeycomb structure forming tool according to the above item [1], wherein a shape of the first slits is different from a shape of the second slits. [3] The honeycomb structure forming tool according to the above items [1] or [2], wherein a diameter of the linear materials constituting the mesh member is from 0.030 to 0.500 mm. [4] The honeycomb structure forming tool according to any one of the above items [1] to [3], wherein the number of meshes per centimeter of the mesh element is from 3.9 to 130. [5] The honeycomb structure forming die according to any one of the above items [1] to [4], including two or more mesh members, wherein the mesh member inserted between the first die and the second die is replaced, wherein a distance between the first die and the second die is changeable in the extrusion direction. [6] The honeycomb structure forming tool according to any one of the above items [1] to [5], including two or more kinds of second molds different in the shape of the second slits, wherein the second molds are interchangeable. [7] The honeycomb structure forming tool according to any one of the above items [1] to [6], wherein a ratio of an area of ​​the central region of the first mold to an area of ​​an end face of a honeycomb molded body to be extruded is 30 to 70%. [8] The honeycomb structure forming tool according to any one of the above items [1] to [7], wherein honeycomb surrounding slits extend from the first slits and honeycomb surrounding slits extend from the second slits in mutually crossing directions. [9] The honeycomb structure forming die according to any one of the above items [1] to [8], wherein an arrangement direction of a honeycomb structure of the honeycomb formed body to be extruded through the first slits and an arrangement direction of a honeycomb structure of the honeycomb formed body to be extruded through the second slits are in directions crossing each other.

[10] The honeycomb structure forming die according to any one of the above items [1] to [9], further comprising an annular space-gathering member interposed between the first mold and the second mold, wherein the mesh member is disposed in an inner region of the annular space-gathering member.

[11] The honeycomb structure forming tool according to any one of the above items [1] to

[10] , wherein in the first mold, the central region is equal to the peripheral region with respect to an opening diameter of the first wrought material introduction hole and an interval between the first wrought material introduction holes.

[0014] A honeycomb structure forming die according to the present invention includes a first die in which a central portion on the side of a molded material discharge surface has a convex portion protruding toward a downstream side in a molded material extrusion direction, and an annular second die having a shape complementary to the convex portion of the first die. Furthermore, the honeycomb structure forming die includes a mesh member interposed between the first die and the second die. Thus, the mesh member is arranged such that the meshes of the mesh member form passageways in which the movement of a molded material between a first molded material introduction hole and a second molded material introduction hole is carried out between a surface of a peripheral portion of the first die on the downstream side and a surface of the second die on the upstream side.

[0015] The honeycomb structure forming die according to the present invention is capable of forming a honeycomb formed body with high quality, having a central portion different from a peripheral portion in terms of honeycomb structure. In other words, in the honeycomb structure forming die according to the present invention, the first molded material introduction holes communicate with the second molded material introduction holes through the meshes of the mesh member. Consequently, even if the positions of the first molded material introduction holes of the first die do not coincide with the positions of the second molded material introduction holes of the second die in the extrusion direction, the movement of the molded material between the first molded material introduction hole and the second molded material introduction hole is performed via the meshes of the mesh member.Particularly, in a region other than a region where the linear materials of the mesh member are superimposed, the movement of the kneaded material is also performed between the meshes of the mesh member. Thus, when the movement of the kneaded material is performed through the meshes, a distribution of the flow rate of the kneaded material to be introduced into the second kneaded material introduction holes can be made uniform. Therefore, the honeycomb structure forming die according to the present invention is capable of uniformizing the amount of the kneaded material ejected from the second slits of the second die and forming the honeycomb formed body with high quality.

[0016] Furthermore, according to the honeycomb structure molding die of the present invention, even if a back pressure is generated in the mold upon exchanging the mold or stopping the piston extrusion, it is possible to effectively prevent the deformation of the second mold.

[0017] Furthermore, in the honeycomb structure forming die according to the present invention, the mesh member is a member separated from the first die and the second die, and thus, the size of a space formed by the mesh member can be easily changed. In other words, when the thickness of the mesh member is changed, a distance of the space in the extrusion direction is adjustable. Furthermore, by adjusting the distance of the space in the extrusion direction, it is possible to adjust the amount of molded material to be introduced into a gap portion to extrude a boundary wall.For example, when a type of molded material is changed or when the second mold is replaced with another second mold having a different second slit shape, it is possible to appropriately adjust the amount of molded material to be introduced into the above-mentioned gap area, and it is possible to mold the honeycomb molded article with high quality. The honeycomb structure molding die according to the present invention has excellent versatility. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view schematically illustrating a kneaded material discharge surface side of an embodiment of a honeycomb structure forming die according to the present invention; Fig. 2 is a plan view of the side of a wrought material introduction surface of the Fig. 1 shown honeycomb structure forming tool; Fig.3 is a plan view of the side of a kneading material exit surface of a first mold, which Fig. 1 shown honeycomb structure forming tool; Fig. 4 is a plan view of the side of a wrought material exit surface of a second mold, showing the Fig. 1 shown honeycomb structure forming tool; Fig. 5 is a plan view of the side of a wrought material introduction surface of the second mold, showing the Fig. 1 shown honeycomb structure forming tool; Fig. 6 is a plan view of a mesh element that supports the Fig. 1 shown honeycomb structure forming tool; Fig. 7 is a cross-sectional view showing a cross section along the line AA' of the Fig. 1 schematically shows the honeycomb structure forming tool shown; Fig. 8 is an enlarged cross-sectional view of an enlarged part of Fig. 7; Fig.Fig. 9 is an enlarged cross-sectional view showing a state in which the mesh member in the Fig. 8 shown honeycomb structure forming tool; Fig. 10 is a perspective view schematically illustrating an example of a honeycomb structure manufactured with the honeycomb structure forming die according to the present invention; Fig. 11 is a plan view showing an inlet end face of the Fig. 10 schematically shows the honeycomb structure; Fig. 12 is a cross-sectional view showing a cross section along the line BB' in Fig. 11 schematically; Fig. 13 is a plan view schematically illustrating the kneading material discharge surface side of another embodiment of the honeycomb structure forming die according to the present invention; and Fig.14 is a plan view schematically illustrating a mesh member and a space gaining member for use in another embodiment of the honeycomb structure forming die according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Embodiments of the present invention will be described in more detail below with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that design changes, improvements, and the like may be appropriately added based on common knowledge without departing from the spirit of the present invention. (1) Honeycomb structure forming tool:

[0019] An embodiment of a honeycomb structure forming tool according to the present invention will be described. Here, Fig.1 is a plan view schematically illustrating a kneaded material discharge surface side of one embodiment of the honeycomb structure forming die according to the present invention. Fig. 2 is a plan view of the side of a wrought material introduction surface of the Fig. 1 shown honeycomb structure forming tool. Fig. 3 is a plan view of the side of a kneading material exit surface of a first mold, which Fig. 1 shown honeycomb structure forming tool. Fig. 4 is a plan view of the side of a wrought material exit surface of a second mold, showing the Fig. 1 shown honeycomb structure forming tool. Fig. 5 is a plan view of the side of a wrought material introduction surface of the second mold, showing the Fig. 1 shown honeycomb structure forming tool. Fig. 6 is a plan view of a mesh element that supports the Fig. 1 shown honeycomb structure forming tool. Fig.7 is a cross-sectional view showing a cross section along the line AA' of the Fig. 1 shows a schematic representation of the honeycomb structure forming tool. Fig. 8 is an enlarged cross-sectional view of an enlarged part of Fig. 7. It should be noted that in Fig. 3, Fig. 5 and Fig. 6 areas of the first shape, the second shape and the mesh element are each shown hatched.

[0020] As in the Fig.1 to 8, a honeycomb structure forming die 100 according to the present invention includes a first die 10, a second die 20, and a mesh member 30. The first die 10 is disposed on an upstream side in an extrusion direction X of a kneaded material of a molding raw material, and a central portion on the side of a kneaded material discharge surface 18 has a convex portion 16 protruding toward a downstream side in the extrusion direction. The second die 20 is an annular die disposed on the downstream side of the first die 10 and having a shape complementary to the convex portion 16 of the first die 10. The mesh member 30 is interposed between the first die 10 and the second die 20.The mesh member 30 acts as a spacer to form a space between the surface (a downstream surface 14) of a peripheral portion 17 of the first die 10 on the downstream side and the surface (an upstream surface 24) of the second die 20 on an upstream side. Hereinafter, the honeycomb structure forming die 100 according to the present embodiment will occasionally be referred to simply as the "forming die 100." The extrusion direction X of the wrought material is an extrusion direction when performing extrusion using the forming die 100 according to the present embodiment, and the direction extends from a wrought material introduction surface 19 to the wrought material discharge surface 18.

[0021] According to the molding die 100 of the present embodiment, first molded material introduction holes 12 and first mesh slots 11 communicating with the first molded material introduction holes 12 are formed in the central region 15 of the first mold 10. The first molded material introduction holes 12 are formed coaxially with intersection points of the first mesh slots 11 in the extrusion direction X. In other words, the first molded material introduction holes 12 communicate with the intersection points of the first mesh slots 11. In the peripheral region 17 surrounding the central region 15 of the first mold 10, the first molded material introduction holes 12 are formed to pass through the peripheral region 17 of the first mold 10.

[0022] The annular second mold 20 includes second molding material introduction holes 22 into which the molding material emerging from the first molding material introduction holes 12 formed in the peripheral region 17 of the first mold 10 is introduced, and second mesh slots 21 communicating with the second molding material introduction holes 22. The second molding material introduction holes 22 are formed coaxially with intersection points of the second mesh slots 21 in the extrusion direction X. In other words, the second kneading material introduction holes 22 communicate with the intersection points of the second lattice slots 21. The molding tool 100 according to the present embodiment is formed such that the opening positions of the first kneading material introduction holes 12 of the peripheral portion 17 of the first mold do not coincide with the opening positions of the second kneading material introduction holes 22 of the second mold 20 in at least a part of the molding tool.

[0023] In the molding die 100 of the present embodiment, the first die 10 and the second die 20 are combined to sandwich the mesh member 30 therebetween. Hereinafter, an end surface of the peripheral portion 17 of the first die 10 on the downstream side in the extrusion direction X will be referred to as the "downstream surface 14 in the peripheral portion 17 of the first die 10," and an end surface of the annular second die 20 on the upstream side in the extrusion direction X will occasionally be referred to as the "upstream surface 24 of the second die 20." Furthermore, when simply mentioning the upstream side, it means the upstream side in the extrusion direction X, and when simply mentioning the downstream side, it means the downstream side in the extrusion direction X.

[0024] The molding tool 100 according to the present invention has through-channels 31 formed by meshes of the mesh element 30, through which the kneaded material moves between the first kneaded material introduction hole 12 and the second kneaded material introduction hole 22 between the downstream surface 14 in the peripheral region 17 of the first mold 10 and the upstream surface 24 of the second mold 20. In the Fig. 6 to 8, reference numeral 33 denotes a linear material 33 which forms the mesh element 30. As Fig. 6, a central region of the mesh member 30 has a hollow region 36 obtained by cutting out a region corresponding to the convex region 16 of the first mold 10 in a round shape.

[0025] The molding die according to the present embodiment has a gap portion 55 between an outer peripheral surface of the convex portion 16 of the first die 10 and an inner peripheral surface of the annular second die 20 to extrude the kneaded material into a ring shape. In other words, in the molding die 100 according to the present embodiment, a cavity portion 26 is formed in a central portion 25 of the second die 20 to be slightly larger than a peripheral edge of the convex portion 16 of the first die 10. According to this structure, when the first die is combined with the second die with the convex portion 16 of the first die 10 inserted into the cavity portion 26 of the annular second die 20, the annular gap portion 55 is formed between the convex portion 16 of the first die 10 and the second die 20.The annular gap portion 55 functions as a gap portion 55 for forming a boundary wall of a honeycomb molded body. In the present invention, "the annular second mold having a shape complementary to the convex portion 16 of the first mold 10" means an annular mold having the cavity portion 26 slightly larger than the convex portion 16 of the first mold 10.

[0026] In the molding die 100 according to the present embodiment, an end surface of the first die 10 on the upstream side in the extrusion direction X is the kneaded material introduction surface 19 of the entire molding die 100. Therefore, during extrusion, the kneaded material of the molding raw material is initially introduced into the first kneaded material introduction holes 12 opened in the kneaded material introduction surface 19 of the first die 10. The kneaded material introduced into the first kneaded material introduction holes 12 of the central portion 15 of the first die 10 moves to the first mesh slits 11 communicating with the first kneaded material introduction holes 12 and is ejected from the kneaded material discharge surface 18 of the first die as a molded body corresponding to a shape of the first slits 11.On the other hand, the kneaded material introduced into the first kneaded material introduction holes 12 of the peripheral portion 17 of the first die 10 is ejected on the downstream surface 14 side of the first die 10 and introduced into the second kneaded material introduction holes 22 of the second die 20 through the meshes of the mesh member 30. Consequently, even if the positions of the first kneaded material introduction holes 12 of the first die 10 do not coincide with the positions of the second kneaded material introduction holes 22 of the second die 20, the movement of the kneaded material between the first kneaded material introduction hole 12 and the second kneaded material introduction hole 22 is properly performed.The mesh member 30 is formed, for example, by interweaving the linear materials 33 extending in the lateral direction with the linear materials 33 extending in a perpendicular direction. Thus, in a region other than the region where the interwoven linear materials 33 are superimposed, the movement of the kneaded material is also performed through the meshes of the mesh member 30. Consequently, when the kneaded material moves through the meshes of the mesh member 30, it is possible to uniformly distribute the flow rate of the kneaded material to be introduced into the second kneaded material introduction holes 22.The kneaded material introduced into the second kneaded material introduction holes 22 of the second mold 20 moves to the second mesh slots 21 communicating with the second kneaded material introduction holes 22 and is ejected from the kneaded material discharge surface 28 of the second mold as a molded body corresponding to a shape of the second slots 21. Therefore, the molding die 100 according to the present embodiment is capable of uniformizing the amount of kneaded material ejected from the second slots 21 of the second mold 20 and molding the honeycomb molded body with high quality.Furthermore, the through-channels 31 formed by the meshes of the mesh member 30 also communicate with the gap region 55 to extrude the kneaded material into a ring shape, and thus, the kneaded material introduced into the first kneaded material introduction holes 12 of the peripheral portion 17 of the first die 10 is also introduced into the gap region 55 through the meshes of the mesh member 30. This also makes it possible to make a flow rate distribution of the kneaded material to be introduced into the gap region 55 more uniform, and it is also possible to particularly effectively prevent the generation of molding defects around the boundary wall of the honeycomb molded body to be extruded.Consequently, the molding die 100 according to the present invention is capable of molding the honeycomb molded body having a central part different from a peripheral part in terms of the honeycomb structure and having the boundary wall at a boundary between the central part and the peripheral part with high quality.

[0027] In this specification, the "honeycomb structure" refers to a honeycomb structure aligned according to a partition wall thickness, a honeycomb density, and a honeycomb shape. Furthermore, the "slit shape" refers to the shape of the slots aligned according to a width, a depth, and a length of each slot formed in the mold and a configuration of the interconnection of the slots.

[0028] Furthermore, if a space is to be provided between the first mold 10 and the second mold 20 without interposing the mesh member 30 between the first mold 10 and the second mold 20, the second mold is brought into a state similar to a one-sided suspension. Thus, when the second mold comes into the state similar to a one-sided suspension, if back pressure is generated in the die 100 upon exchanging the die or stopping the piston extrusion, the second mold 20 may be deformed. In the die 100 according to the present embodiment, the mesh member 30 is interposed between the first mold 10 and the second mold 20, and thus the back pressure generated in the second mold 20 can be absorbed by the mesh member 30, so that the back pressure is dispersed.

[0029] Furthermore, although not shown in the drawings, according to the molding die of the present embodiment, a plurality of types of second molds different in the shape of the second slits can be separately manufactured, and the second mold is interchangeable for use in accordance with the honeycomb structure of the honeycomb molded article to be molded. The second kneaded material introduction holes of the second mold are formed coaxially with the intersection points of the second mesh slits in the extrusion direction, and thus the respective opening positions of the second kneaded material introduction holes in the upstream surface of the second mold vary in accordance with the shape of the second slits of the second mold.Even when a second die having a different shape of the second slits is used, uniform extrusion in the central region and the peripheral region can always be achieved without hindering the movement of the kneading material in the die because the net member is placed between the first die and the second die.

[0030] Furthermore, in the molding die 100 according to the present embodiment, the mesh member 30 is a separate member from the first die 10 and the second die 20, so that when the mesh member 30 is replaced, the thickness of the mesh member 30, the mesh size, or the like can be easily changed. For example, when the thickness of the mesh member 30 is changed in the extrusion direction X, a distance between the first die 10 and the second die 20 in the extrusion direction X is adjustable. Then, the above-mentioned distance in the extrusion direction X is adjusted, whereby an amount of the kneaded material to be introduced into the gap portion 55 can be adjusted. For example, the distance between the first die 10 and the second die 20 in the extrusion direction X is adjustable by Fig. 9 shown network element' 30A is used. The Fig.9 is the mesh element 30A formed using a linear material 33A having a larger diameter than the linear material 33 of the mesh element 30A shown in Fig. 8 shown network element 30. Here, Fig. 9 is an enlarged cross-sectional view showing a state in which the mesh member in the Fig. 8 shown honeycomb structure forming tool. In the Fig. 9 are components corresponding to the mold shown in Fig. 8 are similar to the mold 100 shown, with the same reference numerals as in Fig. 8 and their description is occasionally omitted. In Fig. 9, reference numeral 31A denotes passage channels formed by the meshes of the net element 30A.

[0031] For example, if the type of kneading material of the mold base material during the use of the Fig.8 is changed, the flowability of the kneading material varies, and the flow rate distribution of the kneading material to be introduced into the gap region 55 may vary. Consequently, if the type of kneading material is changed, the balance of consumption of kneading material between the second slits 21 and the gap region 55 may be lost. Furthermore, even if the second mold 20 is replaced with another second mold (not shown) having a different shape of the second slits, the amount of kneading material to be ejected from the second slits 21 of the second mold 20 varies, and the balance of consumption of the kneading material between the second slits 21 and the gap region 55 may be lost.When the balance of the consumption of the kneaded material between the second slits 21 and the gap portion 55 is lost, the thickness of the mesh member 30 is adjusted and the amount of the kneaded material to be introduced into the gap portion 55 is adjusted, whereby it is possible to effectively prevent the generation of molding defects around the boundary wall of the honeycomb formed body. Furthermore, in addition to adjusting the thickness of the mesh member 30, for example, the amount of the kneaded material to be introduced into the gap portion 55 can be adjusted by adjusting the mesh size of the mesh member 30. In the molding die 100 of the present embodiment, even when changing the type of the kneaded material, replacing the second die, and the like, the thickness of the mesh member 30 or the mesh size is adjusted, whereby the flow rate distribution of the kneaded material in the molding die 100 can be appropriately adjusted.Therefore, the mold 100 of the present embodiment not only has the effect that the second mold is interchangeable, but also has the particularly extraordinary effect that the mold has extraordinarily excellent versatility.

[0032] Here, the honeycomb structure manufactured by the honeycomb structure forming die according to the present embodiment will be described. Fig. 10 is a perspective view schematically illustrating an example of a honeycomb structure manufactured with the honeycomb structure forming die according to the present invention. Fig. 11 is a plan view showing an inlet end face of the Fig. 10 shows a schematic representation of the honeycomb structure. Fig. 12 is a cross-sectional view showing a cross section along the line BB' in Fig. 11 shows schematically.

[0033] One in Fig. 10 to Fig.The honeycomb structure 200 shown in Figure 12 comprises a columnar honeycomb structural body 204 with porous partition walls 201 and a peripheral wall 203 arranged around a periphery of the partition walls 201. The partition walls 201 of the honeycomb structural body 204 form a plurality of honeycombs 202 that extend from an inlet end face 211 to an outlet end face 212 and become passageways for a fluid. Furthermore, the honeycomb structural body 204 has a central honeycomb structure 215, a peripheral honeycomb structure 216, and a boundary wall 208 arranged in a boundary region between the peripheral honeycomb structure 216 and the central honeycomb structure 215. In the honeycomb structure body 204, the central honeycomb structure 215 and the peripheral honeycomb structure 216 are different honeycomb structures.

[0034] Here, the central honeycomb structure 215 is a honeycomb structure formed by a plurality of honeycombs 202a formed in a central part of the honeycomb structural body 204 in a plane of the honeycomb structural body 204 that is perpendicular to an extending direction of the honeycombs 202. The peripheral honeycomb structure 216 is a honeycomb structure formed by a plurality of honeycombs 202b formed closer to a periphery of the honeycomb structural body 204 than to a central part of the honeycomb structural body 204 in the plane described above.

[0035] The "honeycomb structure" is a structure formed by a group of repeating units, and one repeating unit corresponds to one honeycomb 202 formed by the partition walls 201, or to a combination of a plurality of honeycombs 202 in the plane perpendicular to the extending direction of the honeycombs 202. For example, when the honeycombs having the same shape are regularly arranged in the above-mentioned plane, a region where honeycombs having the same shape exist becomes a honeycomb structure. Further, when a combination of a plurality of honeycombs having different honeycomb shapes forms a repeating unit, a region where the repeating unit exists forms a honeycomb structure.

[0036] When two honeycomb structures are described as "different honeycomb structures," it means that when comparing the two honeycomb structures, the structures differ in either the partition thickness, the honeycomb density, or the honeycomb shape. Here, when "the structures differ in partition thickness," it means that when comparing the partition thicknesses of the two honeycomb structures, there is a difference of 25 µm or more. Furthermore, when "the structures differ in honeycomb density," it means that when comparing the honeycomb densities of two honeycomb structures, there is a difference of 7 honeycombs / cm. 2 or more.

[0037] The molding tool according to the present embodiment can be suitably used for molding a honeycomb molded body for producing the Fig.10 to 12. A more suitable configuration of the mold according to the present embodiment will be described below.

[0038] In the molding tool according to the present embodiment, it is preferable that the shape of the first slots 11 is different from the shape of the second slots 21, as shown in the Fig.1 to 8. There are no particular restrictions on the shape of the first slits 11 and the shape of the second slits 21, and the shapes can be appropriately selected in accordance with the honeycomb structure of the honeycomb formed body to be formed. Further, the molding die may include two or more types of second molds 20 that are different in the shape of the second slits 21, and may be configured so that the second mold 20 is interchangeable. Further, the molding die may include two or more types of first molds 10 that are different in the shape of the first slits 11, and may be configured so that the first mold 10 is interchangeable.

[0039] An example of the mesh member 30 is a mesh member formed by weaving a plurality of linear materials 33. However, the mesh member 30 may be formed only by meshes such that the thickness of a portion where the meshes intersect is large, and another portion is thinner than this intersecting portion. Another example of the mesh member 30 may be a mesh member composed of a plurality of linear materials 33 monolithically formed in advance by molding or the like. Note that, as a substitute for the mesh member, a perforated member may be used, such as a punching plate comprising a plate-shaped member in which a plurality of holes are formed. However, in this perforated member, the respective holes are formed separately, and thus the kneaded material is difficult to move in the plurality of holes.Consequently, compared with the mesh member 30 of the molding die 100 of the present embodiment, it is difficult to achieve the effect of making the flow rate distribution of the kneading material uniform with the perforated member such as the punch plate or the like.

[0040] There is no particular limitation on the diameter of the linear material 33 constituting the mesh member 30, and for example, it is preferable that the diameter be from 0.030 to 0.500 mm. If the diameter of the linear material 33 is less than 0.030 mm, the thickness of the mesh member 30 will be excessively small, and it may be difficult to make the flow rate distribution of the kneaded material uniform. Furthermore, the linear material 33 may be thin, and the strength of the mesh member 30 may deteriorate. If the diameter of the linear material 33 exceeds 0.500 mm, the meshes for the kneaded material introduction holes will be excessively large, and therefore, a difference in flow velocity between the introduction holes may arise, and the molding properties may be disadvantageously deteriorated.It should be noted that the thickness of the mesh element 30 usually has a value that is twice the above-mentioned diameter of the linear material 33.

[0041] The mesh size of the mesh member 30 is not particularly limited. For example, it is preferable that the number of meshes per centimeter is from 3.9 to 130. If the number of meshes per centimeter is less than 3.9, the strength of the mesh member 30 deteriorates, and the mesh member 30 is easily deformed. In particular, if the diameter of the linear material 33 is small, the mesh member 30 is more likely to be deformed. On the other hand, if the number of meshes per centimeter exceeds 130, the meshes of the mesh member 30 become excessively dense, and the resistance during the passage of the kneaded material may increase. Furthermore, as the number of meshes per centimeter increases, the diameter of the usable linear material 33 is limited, and an upper limit of the thickness of the mesh member 30 may be restricted.

[0042] The mold 100 according to the present embodiment may include two or more mesh elements 30. For example, as shown in Fig. 8 and Fig. 9, two or more mesh elements 30 and 30A having different thicknesses may be prepared in advance. Furthermore, the mesh element in which the distance between the first die 10 and the second die 20 in the extrusion direction X is optimal may be appropriately selected for use from the two or more mesh elements 30 and 30A according to the molding conditions during extrusion. Although not shown in the drawings, the two or more mesh elements may be different in the number of meshes per centimeter, that is, the mesh size.

[0043] A ratio of an area of ​​the central region 15 of the first mold 10 to an area of ​​an end face of the honeycomb molded body to be extruded can be appropriately determined in accordance with the honeycomb structures of the central part and the peripheral part of the honeycomb molded body to be formed (see, for example, Fig. 10 to Fig. 12). It should be noted that in the mold according to the present embodiment, the above ratio is preferably from 30 to 70%, and more preferably from 40 to 60%.

[0044] As described above, in the molding die 100, the cavity portion 26 in the central portion 25 of the second mold 20 is formed to be slightly larger than the peripheral edge of the convex portion 16 of the first mold 10, and the annular gap portion 55 is formed between the convex portion 16 of the first mold 10 and the second mold 20. There is no particular limitation on a distance between the above-mentioned annular gap portions 55, and the distance can be appropriately selected in accordance with a thickness of the boundary wall of the honeycomb formed body to be formed. For example, it is preferable that the distance between the annular gap portions 55 is from 0.04 to 0.50 mm.

[0045] In the first mold 10, it is preferable that the central region 15 be equal to the peripheral region 17 in terms of the opening diameter of the first kneaded material introduction hole 12 and a distance between the first kneaded material introduction holes 12. According to such a structure, for example, it is possible to easily manufacture the first mold 10 at low cost.

[0046] Furthermore, in the molding tool according to the present embodiment, honeycomb-enclosing slits from the first slits and honeycomb-enclosing slits from the second slits may extend in mutually intersecting directions. Here, the "honeycomb" means a space defined by partition walls in the honeycomb molded body to be molded. For example, a Fig. 13 is manufactured in a state in which the first slots 11 of the first mold are 10 to 45° from the Fig.1 are rotated clockwise. Consequently, in the mold 300, honeycomb surrounding slits among the first slits 11 and honeycomb surrounding slits among the second slits 21 do not have a parallel positional relationship. In the mold of the present embodiment, even when the respective honeycomb surrounding slits intersect at the first slits and the second slits as described above, it is possible to uniform the flow rate distribution of the kneaded material. Therefore, it is possible to uniform the amount of kneaded material ejected from the second slits of the second mold, and it is possible to mold the honeycomb molded article with high quality.

[0047] In the mold 100 of the present embodiment, as shown in Fig.1, an arrangement direction of the honeycomb structure of the honeycomb molded body to be extruded through the first slits 11 is parallel to an arrangement direction of the honeycomb structure of the honeycomb molded body to be extruded through the second slits 21. In other words, an extending direction of the first slits 11 of the first mold 10 is parallel to an extending direction of the second slits 21 of the second mold 20. As shown in the Fig. However, in the molding tool 300 shown in Fig. 13, the arrangement direction of the honeycomb structure of the honeycomb molded body to be extruded through the first slits 11 and the arrangement direction of the honeycomb structure of the honeycomb molded body to be extruded through the second slits 21 may be in mutually intersecting directions. Fig. 13 is a plan view schematically illustrating the side of a kneaded material discharge surface of another embodiment of the honeycomb structure forming die according to the present invention. Fig. 13 are components which are similar to those of the mold shown in Fig. 1 are similar, are designated by the same reference numerals and their description is occasionally omitted.

[0048] The Fig. 13 also contains a mesh element 30 (see Fig. 8) between a first form 10 and a second form 20. Consequently, even if, as in the Fig. 13, an extending direction of the first slits 11 of the first mold 10 and an extending direction of the second slits 21 of the second mold 20 intersect each other, making it possible to uniformly distribute the flow rate of the kneaded material. Therefore, it is possible to uniformly distribute the amount of kneaded material ejected from the second slits 21 of the second mold 20, and it is possible to mold the honeycomb molded body with high quality.

[0049] Furthermore, the Fig. 13 is prepared in advance so that the first slots 11 of the first mold 10 are rotated clockwise by 45°. Fig. However, the mold 100 shown in Figure 1 can be used by rotating the first mold 10 clockwise to 45°. Even if the first mold 10 of the Fig. 1 is rotated clockwise by 45°, the movement of the kneading material in the mold 100 is not hindered because the mesh member 30 is present between the first mold 10 and the second mold 20, as shown in the Fig. 7 and Fig.8. A conventional molding tool that does not include the mesh member 30 is designed such that, for example, the first molding material introduction holes of the first mold align with the second molding material introduction holes of the second mold align in the extrusion direction of the molding material. Consequently, if only the first mold aligns during operation, the movement of the molding material within the mold may be hindered.

[0050] In the Fig. 1 to Fig.8 according to the present embodiment, there are no particular restrictions on the thickness of the first mold 10, a protrusion height of the convex portion 16 of the first mold 10, and a thickness of the second mold 20. It is preferable that the thickness of the first mold 10 is from 10 to 50 mm. It is preferable that the protrusion height of the convex portion 16 of the first mold 10 is from 10 to 30 mm. It is preferable that the thickness of the second mold 20 is from 10 to 30 mm. Note that the protrusion height of the convex portion 16 of the first mold 10 may be the same as or different from the thickness of the second mold 20.For example, when the convex portion 16 of the first mold 10 is inserted into the cavity portion 26 of the annular second mold 20, a position of the wrought material exit surface 18 of the first mold 10 may coincide with a position of the wrought material exit surface 28 of the second mold 20, but need not coincide therewith.

[0051] Furthermore, the mold according to the present invention may comprise an annular space recovery element 40 as shown in Fig. 14 shown. Fig.14 is a plan view schematically illustrating a mesh member and the space-gathering member for use in another embodiment of the honeycomb structure forming tool according to the present invention. In the space-gathering member 40, a central portion of a substrate 43 is cut into a circular shape, so that a space 41 is formed in the central portion of the space-gathering member 40. The space-gathering member 40 is sandwiched between a first mold 10 (see Fig. 8) and a second form 20 (see Fig.8). Therefore, the space-gathering element 40 acts as a spacer to form a space between a surface (a downstream surface) in a peripheral region of the first mold on the downstream side and the surface (an upstream surface) of the second mold on an upstream side. In an inner region of the space-gathering element 40, ie, in the space formed in the substrate 43, a previously described mesh element 30 is preferably inserted. The mesh element 30 shown in Fig. 14 has, for example, a toroidal shape, in which a peripheral area of ​​the Fig. 6 shown network element is adapted in a round shape. In Fig. 14, the toroidal mesh element 30 is received in the space 41 of the space-gaining element 40 and both the mesh element 30 and the space-gaining element 40 are sandwiched between the first mold 10 (see Fig.8) and the second form 20 (see Fig. 8) is used.

[0052] Thus, the honeycomb structure forming tool further contains the Fig. 14, whereby it is possible to relieve compressive loads acting on the mesh element 30 during extrusion and to effectively prevent deformation or damage to the mesh element 30. Preferably, the Fig. 14 shown network element 30 similar to that in Fig. 6, except that the network element has the toroidal shape in which the peripheral area of ​​the Fig. 6 shown network element 30 is adapted to a round shape. In the Fig. 14 are components which are similar to those of the network element 30 shown in Fig. 6 are designated by the same reference numerals and their description is omitted.

[0053] An example of a material of a first mold substrate 13 constituting the first mold 10 and a second mold substrate 23 constituting the second mold 20 is a metal or alloy commonly used as a material of a honeycomb structure mold. Hereinafter, the first mold substrate and the second mold substrate are generally referred to simply as the "mold substrate" on occasion. An example of the material of the mold substrate is a metal or alloy containing at least one metal selected from the group consisting of iron (Fe), titanium (Ti), nickel (Ni), copper (Cu), and aluminum (Al).

[0054] An example of an alloy used as a mold substrate material is a stainless alloy, specifically SUS630. This stainless alloy is an inexpensive material that is relatively easy to process. Another example of an alloy used as a mold substrate is a tungsten carbide-based cemented carbide, which has excellent wear resistance. By using a mold substrate made of a tungsten carbide-based cemented carbide or the like, it is possible to produce a honeycomb mold in which the slots are subject to less wear.

[0055] There is no particular limitation on a material of the mesh member 30, but an example of the material is any kind of metal or alloy.

[0056] There is no particular limitation on the method for manufacturing the mold of the present embodiment. For example, the mold according to the present embodiment can be manufactured according to a conventional mold manufacturing method.

[0057] The first wrought material introduction holes and the second wrought material introduction holes can be formed using known machining methods such as drilling machining, discharge machining, electrolytic machining or laser machining of the first mold substrate and the second mold substrate.

[0058] The first slots and the second slots may be formed using known machining methods such as grinding machining, discharge machining, electrolytic machining, or laser machining of the first mold substrate and the second mold substrate.

[0059] The convex area forming the central area of ​​the first shape can be formed by grinding, discharge machining or joining two elements.

[0060] The mesh member can be manufactured, for example, by manufacturing a wire mesh formed by weaving a plurality of linear materials and forming a hole in a central portion of the manufactured wire mesh having a size corresponding to that of the convex portion of the first mold. Examples

[0061] Hereinafter, the present invention will be described in further detail with reference to examples, but the present invention is not limited by these examples. Example 1

[0062] In Example 1, a mold for producing a honeycomb structure 200 was produced, which has a honeycomb structure body 204 having a central honeycomb structure 215 different from a peripheral honeycomb structure 216 in the honeycomb structure, as shown in Fig. 10 to Fig. 12. Specifically, in Example 1, the mold was manufactured so that the honeycomb structure of the final product was constructed as follows. The honeycomb structure of the final product had a round column shape, in which the diameter of each end face was 100 mm, and the diameter of the central honeycomb structure in the end face was 70 mm. The honeycomb structure had a boundary wall with a thickness of 0.1 mm at the boundary between the central honeycomb structure and the peripheral honeycomb structure. In the central honeycomb structure, the honeycomb shape was quadrangular, the thickness of the partition wall was 0.09 mm, and the honeycomb density was 93 combs / cm. 2. In the circumferential honeycomb structure, the honeycomb shape was square, the thickness of the partition wall was 0.11 mm and a honeycomb density was 62 honeycombs / cm 2 . It should be noted that the respective dimensions of the honeycomb structure described above do not include any manufacturing tolerances.

[0063] First, in Example 1, a plate-shaped first mold substrate with a vertical dimension of 200 mm, a lateral dimension of 200 mm, and a thickness of 20 mm was prepared. The mold substrate was made of stainless steel. A surface of the prepared first mold substrate was defined as a wrought material discharge surface, and a convex portion was formed in a central region on the wrought material discharge surface side by discharge machining such that the protrusion length was 10 mm.

[0064] Subsequently, first mesh slits were formed in the molded material exit surface of the convex portion of the first molding substrate. The first mesh slits were formed in a slit shape to extrude the partition walls that form the central honeycomb structure of the aforementioned honeycomb structure of the final product. The first slits were formed by grinding.

[0065] Next, first mastic material introduction holes with an opening diameter of 1.2 mm were formed in a mastic material introduction surface of the first mold substrate so as to communicate with the intersection points of the first slits. Also, in a peripheral region of the first mold substrate that did not have a convex portion, first mastic material introduction holes were formed with the same pitch as in a central region having the convex portion. The first mastic material introduction holes of the peripheral region of the first mold substrate were through holes extending from a mastic material introduction surface of the first mold substrate to a downstream surface of the peripheral region. As described above, a first mold was manufactured in the mold of Example 1.

[0066] Subsequently, a plate-shaped second mold substrate with a vertical dimension of 200 mm, a lateral dimension of 200 mm, and a thickness of 10 mm was prepared. The mold substrate was made of stainless steel. A central region of the prepared second mold substrate was cut out in a circular shape, thus forming the second mold substrate with a ring shape.

[0067] Subsequently, second mesh slits were formed in the molded material exit surface of a convex portion of the second mold substrate. The second mesh slits were formed in a slit shape to extrude the partition walls that form the peripheral honeycomb structure of the aforementioned honeycomb structure of the final product. The second slits were formed by grinding.

[0068] Subsequently, second kneaded material introduction holes with an opening diameter of 1.2 mm were formed in the surface of the second mold substrate opposite to the kneaded material exit surface so that they were connected to the intersection points of the second slits.

[0069] A wire mesh was then created by interweaving linear materials with a diameter of 0.2 mm so that the number of meshes per centimeter was seven. The wire mesh was made of stainless steel. A central region of the fabricated wire mesh was cut out in a circular shape with a diameter of 80 mm to produce a mesh element with a space in an area corresponding to a central region of the first shape.

[0070] Subsequently, in a state where the mesh member was disposed on the kneaded material discharge surface side at an outer side of a peripheral portion of the first mold, a convex portion of the center portion of the first mold was inserted into a cavity portion of a center portion of a second mold so that the mesh member was sandwiched between the first mold and the second mold, and thus the molding die according to Example 1 was manufactured.

[0071] Table 1 shows a "mold structure," a "pitch (mm) of the second slits," and a "distance (mm) between gap regions for confinement part formation." Table 1 also shows the "presence" of the mesh member, a "diameter (mm) of the linear material" constituting the mesh member, and the "number of meshes per centimeter (meshes)" of the mesh member. Note that the table shows a mold as a "two-part structure" in a "Mold Structure" column when the mold is manufactured by combining the first mold and the second mold into a mold with the mesh member sandwiched therebetween, as in the mold of Example 1.On the other hand, the table shows the mold as a “one-piece structure” in the “Mold Structure” column when the mold is manufactured by manufacturing a single mold substrate such that a central region differs from a peripheral region in terms of the shape of the slits.

[0072] The total operating time required to manufacture the mold according to Example 1 was 70 hours. "Molded body quality" and "occurrence of deformation of the second mold" were evaluated using the mold according to Example 1 by a method described below. Table 1 shows the results. Molded body quality

[0073] A honeycomb structure formed from a cordierite composition was extruded using the manufactured mold. The extruded honeycomb structure was visually inspected, and the quality of the honeycomb structure was evaluated according to the following evaluation standards. If there are no defects in the appearance, a molded article is rated as "good." If there is a defect in the appearance or molding cannot be performed, the molded article is rated as "rejected." Here, the "defect in the appearance" means that the partition walls constituting the honeycomb structure are bent due to deviations in the extrusion speed in the respective areas of the mold. Presence of a deformation of the second form

[0074] Using the manufactured mold, extrusion was performed three times under the same conditions as in the molded article quality evaluation. In the state after extrusion, the presence of deformation of the second mold was confirmed by visual inspection. If deformation is confirmed in the second mold, the table displays "Present" in the corresponding column. If no deformation of the second mold could be confirmed, the table displays "No" in the corresponding column. Table 1 Mold construction Pitch of the second slots (mm) Distance (mm) between gap areas for boundary wall formation (mm) Network element Total operating time required for production (hours) Molded body quality Presence of a deformation of the second form available Diameter of the linear material (mm) Number of stitches per cm (stitches) Example 1 Two-part construction 1,4 0,1 Yes 0,1 7 70 Good No Example 2 Two-part construction 1,4 0,1 Yes 0,2 7 70 Good No Example 3 Two-part construction 1,4 0,1 Yes 0,1 12 70 Good No Comparison example 1 One-piece construction 1,4 0,1 - - - 100 Committee No Comparison example 2 Two-part construction 1,4 0,1 No - - 70 Committee No Comparison example 3 Two-part construction 1,4 0,1 No (space available) - - 80 Good Yes Examples 2 and 3

[0075] The procedure of Example 1 was repeated, except that a "diameter (mm) of the linear material" of the mesh member and the "number of meshes per centimeter (meshes)" were changed to the values ​​shown in Table 1, and molds were prepared. The procedure of Example 1 was repeated to conduct evaluations of "molded article quality" and "presence of second-shape deformation" using the molds according to Examples 2 and 3. Table 1 shows the results. Comparison example 1

[0076] In Comparative Example 1, a plate-shaped molding substrate having a vertical dimension of 200 mm, a lateral dimension of 200 mm, and a thickness of 20 mm was prepared. The molding substrate was made of stainless steel. A surface of the prepared molding substrate was defined as a wrought material discharge surface, and slits having the same shape as the first slits in Example 1 were formed in a central region on the wrought material discharge surface side. Subsequently, slits having the same shape as the second slits of the molding die of Example 1 were formed in a peripheral region on the wrought material discharge surface side of the molding substrate. Then, an annular slit was formed at a position corresponding to a gap region of Example 1 to connect one end of each first slit to one end of each second slit.Subsequently, molding material introduction holes with an opening diameter of 1.2 mm were formed from the molding material introduction surface side of the molding substrate so that they communicated with the intersection points of the respective slits. As described above, a mold according to Comparative Example 1 was manufactured.

[0077] The total operating time required to manufacture the mold according to Comparative Example 1 was 100 hours. The procedure of Example 1 was repeated to evaluate the "molded body quality" and the "presence of second-shape deformation" using the mold according to Comparative Example 1. Table 1 shows the results. Comparison example 2

[0078] In Comparative Example 2, a first mold and a second mold constructed in the same manner as the first mold and the second mold of the molding die according to Example 1 were initially prepared. Then, in Comparative Example 2, the second mold was combined with the first mold, and a convex portion of a central portion of the first mold was inserted into a cavity portion of a central portion of the prepared second mold, thus manufacturing a molding die according to Comparative Example 2. In other words, according to Comparative Example 2, the molding die was manufactured without inserting a mesh member between the first mold and the second mold.

[0079] The total operating time required to manufacture the mold according to Comparative Example 2 was 70 hours. The procedure of Example 1 was repeated to evaluate the "molded body quality" and the "presence of second-shape deformation" using the mold according to Comparative Example 2. Table 1 shows the results. Comparison example 3

[0080] In Comparative Example 3, a first mold constructed in the same manner as the first mold of the molding die of Example 1 was initially prepared. Subsequently, in Comparative Example 3, a second mold was prepared in which a portion of 0.1 mm was removed from an upstream surface of a second molding substrate in an extrusion direction by grinding. The second mold was combined with the first mold, and a convex portion of a central portion of the first mold was inserted into a cavity portion of a central portion of the second mold, thus manufacturing a molding die of Comparative Example 3. In the molding die of Comparative Example 3, a downstream surface of a peripheral portion of the first mold did not abut against an upstream surface of the second mold, and the second mold was combined with the first mold in a state similar to a one-sided suspension.

[0081] The total operating time required to manufacture the mold according to Comparative Example 3 was 80 hours. The procedure of Example 1 was repeated to evaluate the "molded body quality" and the "presence of second-shape deformation" using the mold according to Comparative Example 3. Table 1 shows the results. Results

[0082] In the molds according to Examples 1 to 3, it was possible to shorten the production time, and the molded article quality evaluations were adequate compared to the mold according to Comparative Example 1. Furthermore, in the molds according to Examples 1 to 3, deformation of the second shape was not confirmed.

[0083] As a result, the molding die of Comparative Example 1 resulted in rejects during the molded product quality evaluation. The reason for this result is presumably that when the central portion of the mold differs from its peripheral portion in terms of the slit shape, the flow rate distribution of the molded material in the molding die tends to become uneven, and the amount of molded material ejected from the slits is not uniform. In particular, when extrusion was performed using the molding die of Comparative Example 1, the demand for molded material for forming the boundary wall exceeded the supply, and numerous molding defects were confirmed in the boundary wall and its surroundings.

[0084] In the mold according to Comparative Example 2, in an area where the positions of the first molding material introduction holes of the first mold did not match those of the second molding material introduction holes of the second mold, the movement of the molding material was hindered, and as a result, only rejects were obtained in the molded article quality evaluation. Furthermore, when extrusion was performed using the mold according to Comparative Example 2, the demand for molding the boundary wall exceeded the supply, and numerous molding defects were confirmed in the boundary wall and its surroundings.

[0085] For the mold according to Comparative Example 3, the evaluation of the molded article quality was adequate, but when evaluating the presence of deformation of the second mold, the deformation of the second mold was confirmed. If the second mold is significantly deformed, the molded article quality may be affected. Furthermore, if the second mold is easily deformed, there is a concern that the manufacturing cost of a product will increase due to mold replacement or the like.

[0086] A honeycomb structure forming die according to the present invention can be used to produce a honeycomb formed body having a central part different from a peripheral part in terms of the honeycomb structure. List of reference symbols

[0087] 10: first mold, 11: first slit, 12: first wrought material introduction hole, 13: first mold substrate, 14: downstream surface (the downstream surface of a peripheral portion of the first mold), 15: central portion, 16: convex portion, 17: peripheral portion, 18: wrought material exit surface (the wrought material exit surface of the first mold), 19: wrought material introduction surface, 20: second mold, 21: second slit, 22: second wrought material introduction hole, 23: second mold substrate, 24: upstream surface (the upstream surface of the second mold), 25: central portion, 26: cavity portion, 27: peripheral portion, 28: wrought material exit surface (the wrought material exit surface of the second shape), 30 and 30A: mesh element, 31 and 31A: through-channel, 33 and 33A: linear material, 36: cavity region, 40: space-gathering element, 41: space, 43: substrate, 55: gap region (a gap region for forming a boundary wall),100 and 300: honeycomb structure forming tool (the forming tool), 201: partition wall, 202: honeycomb, 202a: honeycomb (honeycombs of a central honeycomb structure), 202b: honeycomb (honeycombs of a peripheral honeycomb structure), 203: peripheral wall, 204: honeycomb structure body, 208: boundary wall, 211: inlet end face, 212: outlet end face, 215: central honeycomb structure, 216: peripheral honeycomb structure, 200: honeycomb structure, and X: extrusion direction.

Claims

[1] Honeycomb structure forming tool (100, 300) comprising: a first mold (10) disposed on an upstream side in an extrusion direction (X) of a kneaded material of a molding raw material, and in which a central portion (15) on the side of a kneaded material discharge surface has a convex portion (16) projecting toward a downstream side in the extrusion direction (X); and an annular second mold (20) arranged on the downstream side of the first mold (10) and having a shape complementary to the convex region (16), wherein first kneading material introduction holes (12) and first grid slots (11) communicating with the first kneading material introduction holes (12) are formed in the central region (15) of the first mold (10), in a peripheral region (17) surrounding the central region (15) of the first mold (10), the first kneading material introduction holes (12) are formed such that they extend through the peripheral region (17) of the first mold (10), and second kneading material introduction holes (22) are formed in the annular second mold (20), into which the kneading material discharged from the first kneading material introduction holes (12) formed in the peripheral region (17) of the first mold (10) is introduced, and second grid slots (21) communicating with the second kneading material introduction holes (22), the honeycomb structure forming tool (100, 300) has a gap region (55) between an outer peripheral surface of the convex portion (16) of the first mold (10) and an inner peripheral surface of the annular second mold (20) in order to extrude the kneaded material into a ring shape, the honeycomb structure forming tool (100, 300) further includes a mesh member (30, 30A) interposed between the first mold (10) and the second mold (20) and formed from a plurality of interwoven linear materials (33) and having a cavity portion (36) corresponding to the convex portion (16) of the first mold (10), the movement of the kneading material between the first kneading material introduction hole (12) and the second kneading material introduction hole (22) is carried out through the meshes of the net element (30, 30A), wherein passage channels (31) formed by the meshes of the net element (30, 30A) are connected to the gap region (55), and the mesh element (30) is configured such that linear materials (33) extending in a lateral direction are interwoven with linear materials (33) extending in a direction perpendicular thereto to allow movement of the kneaded material through the meshes of the mesh element (30, 30A) in a region in which the interwoven linear materials (33) are not superimposed. [2] The honeycomb structure forming tool (100, 300) according to claim 1, wherein a shape of the first lattice slots (11) is different from a shape of the second lattice slots (21). [3] The honeycomb structure forming tool (100, 300) according to claim 1 or 2, wherein a diameter of the linear materials (33, 33A) constituting the mesh member (30, 30A) is from 0.030 to 0.500 mm. [4] Honeycomb structure forming tool (100, 300) according to one of claims 1 to 3, wherein the number of meshes per centimeter of the mesh element (30, 30A) is from 3.9 to 130. [5] A honeycomb structure forming tool (100, 300) according to any one of claims 1 to 4, comprising two or more mesh members (30, 30A), wherein the mesh member (30, 30A) inserted between the first mold (10) and the second mold (20) is replaced, whereby a distance between the first mold (10) and the second mold (20) in the extrusion direction (X) is variable. [6] A honeycomb structure forming tool (100, 300) according to any one of claims 1 to 5, comprising two or more types of second molds (20) which differ in the shape of the second lattice slots (21), the second molds (20) being interchangeable. [7] Honeycomb structure forming tool (100, 300) according to one of claims 1 to 6, wherein a ratio of an area of ​​the central region (15) of the first mold (10) to an area of ​​an end face of a honeycomb molded body to be extruded is 30 to 70%. [8] Honeycomb structure forming tool (100, 300) according to one of claims 1 to 7, wherein grid slots surrounding a honeycomb (202) extend from the first grid slots (11) and grid slots surrounding a honeycomb (202) extend from the second grid slots (21) in mutually crossing directions. [9] The honeycomb structure forming tool (100, 300) according to any one of claims 1 to 8, wherein an arrangement direction of a honeycomb structure of the honeycomb formed body to be extruded through the first lattice slots (11) and an arrangement direction of a honeycomb structure of the honeycomb formed body to be extruded through the second lattice slots (21) extend in mutually crossing directions. [10] Honeycomb structure forming tool (100, 300) according to one of claims 1 to 9, further comprising an annular space recovery element (40) which is inserted between the first mold (10) and the second mold (20), wherein the mesh element (30, 30A) is arranged in an inner region of the annular space recovery element (40). [11] The honeycomb structure forming tool (100, 300) according to any one of claims 1 to 10, wherein in the first mold (10), the central region (15) is equal to the peripheral region (17) in terms of the opening diameter of the first kneading material introduction hole (12) and a distance between the first kneading material introduction holes (12).

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