Die for manufacturing honeycomb bodies

Abstract: A die for manufacturing honeycomb bodies has a die main body (2) having batch supply holes (11) which are open at a backside surface of the die, slit channels (12) which communicate with the batch supply holes and are open at a foreside surface of the die and a taper portion (13) which is formed by working an outer peripheral portion of the foreside surface of the die in a taper manner. A control plate (3) is arranged opposed to the taper portion. Slit channel expanding portions (21) are formed at open ends of the slit channels existing in the taper portion in such a manner that the slit channel is expanded gradually toward the open end. The aim is to strengthen the outermost ribs of the honeycomb structure.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for manufacturing honeycomb bodies used for extruding honeycomb structural bodies. 2. Description of Related Art Generally, various kinds of dies for manufacturing honeycomb bodies are known, which comprise; a die main body including batch supply holes which are opened to a backside surface of the die, slit channels which are communicated with the batch supply holes and are opened to a foreside surface of the die and a taper worked portion which is formed by working an outer peripheral portion of the foreside surface of the die in a taper manner; and a control plate arranged at a portion opposed to the taper worked portion. Fig. 4 is a schematic view showing one embodiment of a known die for manufacturing honeycomb bodies. In the embodiment shown in Fig. 4, a die 51 for manufacturing honeycomb bodies comprises a die main body 52 and a control plate 53. The die main body 52 has a disk-shape and comprises batch supply holes 61 which are opened to its backside surface (lower surface (not shown) in Fig. 4) and slit channels 62 which are opened to its foreside surface (upper surface in Fig. 4). The slit channels 62 have a crisscross shape at the foreside surface of the die main body 52, and the batch supply holes 61 are communicated with alternate intersection points. An outer peripheral portion of the die main body 52 is worked into a taper shape to form a taper worked portion 63. The control plate 53 is connected to the die main body 52 via a spacer 64 in such a manner that one surface 53a is opposed (parallel in Fig. 4) to the taper worked portion 63. In the die 51 for manufacturing honeycomb bodies having the construction shown in Fig. 4, a ceramic batch for example is supplied from the batch supply holes 61 which are opened to the backside surface of the die 51, and the thus supplied ceramic batch is extruded from the slit channels 62 which are opened to the foreside surface of the die 51, so as to obtain a honeycomb structural body. Then, it is possible to reduce an inward batch stress when an outer wall is formed and to prevent a collapsing of outer cells i.e. a generation of wrinkle portions in the honeycomb structural body by forming the taper worked portion 63 at the outer peripheral portion of the die main body 52 and by arranging the control plate 53 at a portion opposed to the taper worked portion 63. However, if a thin wall honeycomb structural body having a thin rib thickness, which is required recently, is to be formed, an isostatic strength of the honeycomb structural body become smaller correspondingly since the rib thickness is thin. Therefore, at the outer portion of the honeycomb structural body to which a pressure is liable to be applied, ribs are deformed and wrinkle portions are liable to be generated. As a result, the honeycomb structural bodies thus obtained are liable to be inferior goods. US 4349329 teaches an extrusion due having grid-shaped extrusion slots and a die mask which covers the outer peripheral portion of the die on the extrudable material outlet side. The extrusion slots at the periphery of the uncovered area are tapered outwardly towards their open ends. A pooling zone is provided in the covered area to provide extrudable material to the uncovered slots. SUMMARY OF THE INVENTION An object of the invention is to eliminate the drawbacks mentioned above and to provide a die for manufacturing honeycomb bodies in which a rib strength can be improved and a generation of wrinkle portions at an outer portion, which is a fatal defect of a thin honeycomb body, can be prevented. According to the invention, there is provided a die for manufacturing honeycomb bodies according to claim 1. In the present invention, since the slit channel expanding portions having the construction mentioned above are arranged at a predetermined portion of the slit channels existing in the taper worked portion of the outer peripheral portions, a larger amount of batch can be supplied to the slit channel expanding portions as compared with that of the other portion, and thus the outermost ribs of the honeycomb structural body can be strengthened. Therefore, an isostatic strength of the honeycomb structural body can be improved even if the honeycomb structural body has a thin wall, and it is possible to prevent a generation of wrinkle portions at the outer portion. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing one embodiment of a die for manufacturing honeycomb bodies according to the invention; Figs. 2a and 2b are schematic views respectively illustrating a part of honeycomb structural bodies according to a comparative example and an example of the present invention; Figs. 3a and 3b are schematic views respectively depicting one embodiment of the die according to the invention which is used in an experiment; and Fig. 4 is a schematic view showing one embodiment of a known die for manufacturing honeycomb bodies. DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 is a schematic view showing one embodiment of a die for manufacturing honeycomb bodies according to the invention. In the embodiment shown in Fig. 1, a die 1 for manufacturing honeycomb bodies comprises a die main body 2 and a control plate 3. The die main body 2 has a disk-shape and comprises batch supply holes 11 which are opened to its backside surface (lower surface (not shown) in Fig. 1) and slit channels 12 which are opened to its foreside surface (upper surface in Fig. 1). The slit channels 12 have a crisscross shape at the foreside surface of the die main body 2, and the batch supply holes 11 are communicated with alternate intersection points. An outer peripheral portion of the die main body 2 is worked into a taper shape to form a taper worked portion 13. The control plate 3 is connected to the die main body 2 via a spacer 14 in such a manner that one surface 3a is opposed (parallel in Fig. 1) to the taper worked portion 13. The construction of the die 1 for manufacturing honeycomb bodies according to the invention mentioned above is the same as that of the known die for manufacturing honeycomb bodies. A different point between the die 1 according to the invention and the known die is that slit channel expanding portions are formed at open ends of the slit channels 12 existing in the taper worked portion 13 of the outer peripheral portion of the die main body 2. In the slit channel expanding portion 21, the slit channel 12 is expanded gradually toward an open end 12a. In this embodiment, the slit channel expanding portion 21 is formed by performing a C-chamfer working for the open end 12a of the slit channel 12. The C-chamfer working can be performed by grinding the slit channel 12 by means of a whetstone which is set with a predetermined angle with respect to the open end 12a of the slit channel 12. Moreover, the slit channel expanding portion 21 is formed locally by a constant distance from the open end 12a of the slit channel 12. In the die 1 for manufacturing honeycomb bodies according to the invention mentioned above, since the slit channel expanding portions 21 are arranged at a predetermined position, a larger amount of batch can be extruded from the slit channels 12, in which the slit channel expanding portions 21 are arranged, as compared with the slit channels 12 in which no slit channel expanding portions 21 are arranged. The batch extruded from the slit channel expanding portions 21, whose amount is larger than that of the other portion, is contacted to the control plate 2 and then integrated inwardly. As a result, in the honeycomb structural body after forming, it is possible to strengthen the ribs existing the outer peripheral portion thereof. One example is shown in Figs. 2a and 2b. Fig. 2 shows a part of the honeycomb structural body extruded by using the known die for manufacturing honeycomb bodies. Fig. 2b illustrates a part of the honeycomb structural body extruded by using the die 1 for manufacturing honeycomb bodies according to the invention. The following is understood from a comparison between Fig. 2a and Fig. 2b. In the honeycomb structural body extruded by using the die 1 for manufacturing honeycomb bodies according to the invention, reinforced portions 33 are formed at connecting portions between ribs 31 and an outer wall 32 and thus an isostatic strength of the honeycomb structural body can be improved. As a result, in the honeycomb structural body extruded by using the die 1 for manufacturing honeycomb bodies according to the invention, the wrinkle portions are not generated at the outer portion. In the embodiment mentioned above, the slit channel expanding portion 21 is formed by performing a C-chamfer on the open end 12a of the slit channel 12. This C-chamfer working can form the slit channel expanding portions 21 at an easiest manner. However, the present invention, of course, is not limited to the C-chamfer working and it is possible to use other working methods if they can expand the slit channel 12 as mentioned above. Moreover, materials of the die main body 2, the control plate 3 and the spacer 14 are not explained, but it is a matter of course that the same materials used in the known die such as stainless can be used. Hereinafter, an actual experiment will be explained. Actually, ceramic honeycomb structural bodies, made of cordierite as a main ingredient, having a dimension of diameter: 103 mm, length: 100 mm, wall thickness: 75µm (3 mil), cell number: 62 cells per square centimetre (400 cpsi) were extruded by using dies according to a comparative example and examples 1-2 to form ceramic honeycomb structural bodies. Then, with respect to the thus formed ceramic honeycomb structural bodies, ISO (isostatic) strengths in a radial direction were measured and compared. Here, as a comparative example, use was made of a die in which no C-chamfer working was performed with respect to all the open ends of the slit channels existing in the taper worked portion. As an example 1, use was made of a die in which a C-chamfer working was performed with respect to all the open ends of the slit channels existing in the taper worked portion. That is to say, all the open ends of the slit channels existing in a diagonal line region 41 shown in Fig. 3a, i.e. the open ends of the slit channels along both X axis and Y axis if X axis and Y axis were assumed to be extended along crisscross slit channels, were worked by a C(0.5)-chamfer working. As an example 2, use was made of a die in which a C-chamfer working was performed with respect to all the open ends of the slit channels existing in the taper worked portion. That is to say, a C(0.5)-chamfer working was performed only for the open ends of the slit channels along Y axis existing in a diagonal line region 42 in Fig. 3b, only for the open ends of the slit channels along X axis existing in a diagonal line region 43 in Fig. 3b and for all the open ends of the slit channels along both X axis and Y axis existing in a diagonal line region 41 in Fig. 3b. The results are shown in the following Table 1. From the results show in Table 1, it is understood that the examples 1 and 2 according to the invention show better ISO strength as compared with the comparative example. Comparative example 1 Example 1 Example 2 ISO strength 10kg/cm 2 level more than 10kg/cm 2 more than 10kg/cm 2 As is clearly understood from the explanations mentioned above, according to the invention, since the slit channel expanding portions having the construction mentioned above are arranged at a predetermined portion of the slit channels existing in the taper worked portion of the outer peripheral portions, a larger amount of batch can be supplied to the slit channel expanding portions as compared with that of the other portion, and thus the outermost ribs of the honeycomb structural body can be strengthened. Therefore, an isostatic strength of the honeycomb structural body can be improved even if the honeycomb structural body has a thin wall, and it is possible to prevent a generation of wrinkle portions at the outer portion.

Claims: A die (1) for manufacturing honeycomb bodies including: a die main body (2) having batch supply holes (11) which open to a backside surface of the die (1); slit channels (12) in communication with the batch supply holes (11) and open to a foreside surface of the die (1) ; a taper portion (13) forming an outer peripheral portion of the foreside surface of the die (1) in a tapered manner; and a control plate (3) arranged at a position opposed to the taper portion (13) ; characterised in that : the slit channels (12) opening into the taper portion (13) have slit channel expanding portions (21) formed at their open ends (12a) in such a manner that the slit channels (12) expand gradually toward their open ends (12a). A die (1) for manufacturing honeycomb bodies according to claim 1, wherein each said slit channel expanding portions (21) is a C-chamfer at the open ends of the slit channel (12). A die (1) for manufacturing honeycomb bodies according to claim 2, wherein: the slit channels (12) have a crisscross shape at the foreside surface of the die main body (2), the direction of the lines in the crisscross defining an X axis and a Y axis respectively; and said slit channel expanding portions (21) are provided at the open ends of all the slit channels (12) opening into the taper portion (13) and extending along the X axis and at the open ends of all the slit channels (12) opening into the taper portion (13) and extending along the Y axis. A die (1) for manufacturing honeycomb bodies according to claim 2, wherein the slit channels (12) have a crisscross shape at the foreside surface of the die main body (2), the direction of the lines in the crisscross defining an X axis and a Y axis respectively; and said slit channel expanding portions (21) are provided, at respective different circumferential regions (41, 42, 43) of the taper portion, (a) at the open ends of only the slit channels (12) opening into the taper portion (13) and extending along the X axis, (b) at the open ends of only the slit channels (12) opening into the taper portion (13) and extending along the Y axis, and (c) at the open ends of the slit channels (12) opening into the taper portion (13) and extending along the X axis and at the open ends of the slit channels (12) opening into the taper portion (13) and extending along the Y axis.

Inventors: MIYAZAKI MAKOTO, MIYAZAKI, MAKOTO
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1999
Main classification: B28B3
IPC codes: B28B3