Patent Publication Number: US-7721461-B2

Title: Method and apparatus for drying honeycomb formed body

Description:
TECHNICAL FIELD 
   The present invention relates to a method and an apparatus for drying a honeycomb formed body and, more particularly, to a method and an apparatus for drying a honeycomb formed body which prevent deformation such as warpage of partition walls of the honeycomb formed body during drying thereof. 
   BACKGROUND ART 
   Generally, ceramic-based honeycomb structures are produced through a procedure of, for example, molding (e.g., extruding) a raw material composition containing a predetermined ceramic source and water to thereby form a honeycomb formed body having a plurality of cells defined by partition walls, each cell serving as a fluid conduit; drying the honeycomb formed body; and firing the dried honeycomb formed body. 
   Among the above production steps for a ceramic honeycomb structure, drying of a honeycomb formed body is carried out by means of, for example, hot air or high-frequency heating employing an electromagnetic wave. In electromagnetic wave drying, an electromagnetic wave of high-frequency region (high-frequency wave) capable of heating water is applied to a honeycomb formed body, whereby water is vaporized so as to dry the honeycomb formed body (see, for example, Patent Document 1). As compared with drying with hot air, electromagnetic wave drying more effectively dries from an inner part of a honeycomb formed body. However, in this case, the outer part of the formed body is difficult to dry as compared with the inner part, which is problematic. 
   In addition, when a honeycomb formed body has a thin outer wall or partition walls, drying by means of high-frequency heating employing an electromagnetic wave raises a problem. Specifically, due to the structural nature, the outer part of the thus-dried formed body is not readily dried as compared with the inner part thereof, wrinkles and dents generate in the outer periphery, whereby warpage of partition walls, and other deformation are problematically generated. The characteristic feature of the method for drying a honeycomb formed body described in Patent Document 1 is that the humidity of an atmosphere including a honeycomb formed body is elevated during electromagnetic wave drying so as to prevent cracking and other deformation of the outer wall. However, the method makes it more difficult to dry the outer peripheral part. In the case where the honeycomb formed body has a thin outer wall and partition walls and a large percent opening (i.e., poor strength of the honeycomb formed body), wrinkles and dents in the outer periphery, warpage of partition walls, and other deformation are difficult to prevent, which is problematic. 
   Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2002-283330 
   DISCLOSURE OF THE INVENTION 
   In the case where a honeycomb formed body, which is generally in the cylinder form, is dried by means of electromagnetic waves (high-frequency waves), the inner part of the structure is dried more rapidly than the outer peripheral wall (outer part) thereof. The reason why the above difference in drying speed is provided is as follows. When electromagnetic wave drying is performed, the honeycomb formed body is rapidly heated, in contrast to the case of thermal drying such as hot air drying. During evaporation of water, the temperature of the formed body reaches an equilibrium at about 100° C. When drying is performed only through high-frequency heating, the inside temperature of a drying apparatus is generally lower than the drying formed body. Therefore, releasing of heat from a part of the formed body in the vicinity of the outer peripheral wall thereof, which is in contact with the atmosphere in the drying apparatus, is promoted, resulting in temperature drop of the part, whereby vaporization of water in the part is suppressed. Thus, in order to uniformly dry the entirety of the honeycomb formed body, the inside temperature of the drying apparatus must be regulated to a temperature almost equivalent to that of the drying honeycomb formed body, and the inside humidity must be relatively lowered, during drying, whereby drying of the outer peripheral wall is promoted. In addition, essentially, hot air is applied to the outer peripheral wall so as to locally heat the outer peripheral wall part and remove water vapor residing in the vicinity of the outer peripheral wall, thereby lowering humidity around the outer peripheral wall. 
   The present invention has been conceived in order to solve the aforementioned problems, and objects of the invention are to provide a method and an apparatus for drying a honeycomb formed body which prevent deformation such as warpage of partition walls of a honeycomb formed body during drying thereof. 
   In order to attain the aforementioned objects, the present invention provides methods and apparatuses for drying a honeycomb formed body as follows. 
   [1] A method for drying a honeycomb formed body including subjecting, to high-frequency heating through electromagnetic wave irradiation, a honeycomb formed body in an undried state (i.e., undried honeycomb formed body) which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls, in a drying space of a humidified and heated atmosphere, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed bodies so as to dry the undried honeycomb formed body, thereby producing a dried honeycomb formed body, 
   wherein the humidified and heated atmosphere in the drying space is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. through feeding water vapor into and forcedly discharging the drying space; and the undried honeycomb formed body is subjected to high-frequency heating in the atmosphere through electromagnetic wave irradiation such that 50 to 99 mass % of water contained in the formed body is evaporated at the end of high-frequency heating, 
   whereby the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased, 
   thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body and that of the outer part thereof, 
   thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed (first mode of the honeycomb formed body drying method of the present invention). 
   [2] A method for drying a honeycomb formed body as described in [1], wherein, after drying of the honeycomb formed body through high-frequency heating, the honeycomb formed body is further dried through application of hot air thereto. 
   [3] A method for drying a honeycomb formed body as described in [2], wherein the hot air has a temperature of 100 to 130° C. 
   [4] A method for drying a honeycomb formed body as described in any of [1] to [3], wherein the electromagnetic wave has a frequency of 900 to 10,000 MHz. 
   [5] A method for drying a honeycomb formed body as described in any of [1] to [4], wherein the honeycomb formed body has a percent cell opening of 80% or more, and each of the partition walls has a thickness of 0.18 mm or less. 
   [6] A method for drying a honeycomb formed body including subjecting, to high-frequency heating through electromagnetic wave irradiation, a honeycomb formed body in an undried state (i.e., undried honeycomb formed body) which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls, in a drying space of a humidified and heated atmosphere, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed bodies so as to dry the undried honeycomb formed body, thereby producing a dried honeycomb formed body, 
   wherein the undried honeycomb formed body is subjected to high-frequency heating in the atmosphere through electromagnetic wave irradiation such that 50 to 99 mass % of water contained in the formed body is evaporated at the end of high-frequency heating, while the humidified and heated atmosphere in the drying space is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C.; and hot air is fed into the drying space so as to apply the hot air to the undried honeycomb formed body, 
   whereby the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased, 
   thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body and that of the outer part thereof, 
   thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed (second mode of the honeycomb formed body drying method of the present invention). 
   [7] A method for drying a honeycomb formed body as described in [6], wherein hot air is fed into the drying space at a velocity of 0.5 to 10 m/s and a flow rate of 3 to 60 m 3 /s. 
   [8] A method for drying a honeycomb formed body as described in [6] or [7], wherein the hot air fed into the drying space has a temperature of 80 to 135° C. 
   [9] A method for drying a honeycomb formed body as described in any of [6] to [8], wherein the hot air fed into the drying space has a humidity level of 20% or less. 
   [10] A method for drying a honeycomb formed body as described in any of [6] to [9], wherein the honeycomb formed body is dried in the drying space while the structure is rotated about the center axis thereof. 
   [11] A method for drying a honeycomb formed body as described in any of [6] to [10], wherein, in addition to the hot air fed into the drying space, hot air (second hot air) is further applied to an outer peripheral wall of the undried honeycomb formed body at a predetermined distance from the wall, to thereby dry the undried honeycomb formed body.
 
[12] A method for drying a honeycomb formed body as described in [11], wherein the second hot air applied to the outer peripheral wall of the undried honeycomb formed body has a velocity of 0.5 to 10 m/s.
 
[13] A method for drying a honeycomb formed body as described in [11] or [12], wherein the second hot air applied to the outer peripheral wall of the undried honeycomb formed body has a temperature of 80 to 135° C.
 
[14] A method for drying a honeycomb formed body as described in any of [11] to [13], wherein the second hot air applied to the outer peripheral wall of the undried honeycomb formed body has a humidity level of 20% or less.
 
[15] A method for drying a honeycomb formed body as described in any of [6] to [14], wherein the humidity and temperature of the drying space are controlled through feeding hot air into and forcedly discharging the drying space.
 
[16] A method for drying a honeycomb formed body as described in any of [6] to [15], wherein after drying of the honeycomb formed body through high-frequency heating, the honeycomb formed body is further dried through application of hot air (hot air for post-drying) thereto.
 
[17] A method for drying a honeycomb formed body as described in [16], wherein the hot air for post-drying has a temperature of 100 to 130° C.
 
[18] A method for drying a honeycomb formed body as described in any of [6] to [17], wherein the electromagnetic wave has a frequency of 900 to 10,000 MHz.
 
[19] A method for drying a honeycomb formed body as described in any of [6] to [18], wherein the honeycomb formed body has a percent cell opening of 80% or more, and each of the partition walls has a thickness of 0.18 mm or less.
 
[20] An apparatus for drying a honeycomb formed body, in use, which is capable of performing subjecting, to high-frequency heating through electromagnetic wave irradiation, a honeycomb formed body in an undried state (i.e., undried honeycomb formed body) which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls, in a drying space of a humidified and heated atmosphere, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed bodies so as to dry the undried honeycomb formed body, thereby producing a dried honeycomb formed body,
 
   the apparatus comprising a drying chamber having a drying space for accommodating the undried honeycomb formed body in a humidified and heated atmosphere; an electromagnetic wave generator for generating the electromagnetic wave with which the undried honeycomb formed body accommodated in the drying chamber is to be irradiated such that 50 to 99 mass % of water contained in the undried formed body is evaporated at the end of irradiation; and an atmosphere controlling unit having a water vapor feeding means and a forced discharge means and allowing the humidified and heated atmosphere in the drying space to maintain at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C., 
   wherein the undried honeycomb formed body accommodated in the drying chamber in which the humidified and heated atmosphere is maintained by means of the atmosphere controlling unit is irradiated with an electromagnetic wave generated by the electromagnetic wave generator, 
   whereby the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased, 
   thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body and that of the outer part thereof, 
   thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed (first mode of the honeycomb formed body drying apparatus of the present invention). 
   [21] An apparatus for drying a honeycomb formed body as described in [20], wherein the drying chamber has a heat insulating material covering the same. 
   [22] An apparatus for drying a honeycomb formed body as described in [20] or [21], wherein the electromagnetic wave has a frequency of 900 to 10,000 MHz. 
   [23] An apparatus for drying a honeycomb formed body as described in any of [20] to [22], which further comprises a hot air drying chamber having a hot air drying space for accommodating the honeycomb formed body which has been dried in the drying space included in the drying chamber wherein the honeycomb formed body is further dried through application of hot air thereto in the hot air drying space, and a hot air generator for generating the hot air.
 
[24] An apparatus for drying a honeycomb formed body as described in [23], wherein the hot air has a temperature of 100 to 130° C.
 
[25] An apparatus for drying a honeycomb formed body as described in any of [20] to [24], wherein the honeycomb formed body has a percent cell opening of 80% or more, and each of the partition walls has a thickness of 0.18 mm or less.
 
[26] An apparatus for drying a honeycomb formed body, in use, which is capable of performing subjecting, to high-frequency heating through electromagnetic wave irradiation, a honeycomb formed body in an undried state (i.e., undried honeycomb formed body) which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls, in a drying space of a humidified and heated atmosphere, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed bodies so as to dry the undried honeycomb formed body, thereby producing a dried honeycomb formed body,
 
   the apparatus comprising a drying chamber having a drying space for accommodating the undried honeycomb formed body in a humidified and heated atmosphere; an electromagnetic wave generator for generating the electromagnetic wave with which the undried honeycomb formed body accommodated in the drying chamber is to be irradiated for high-frequency heating thereof; and a hot air feeding unit for feeding hot air into the drying chamber, which hot air feeding unit being provided so that the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased synergistic with the high-frequency heating performed by means of the electromagnetic wave generator, such that 50 to 99 mass % of water contained in the undried formed body is evaporated at the end of irradiation, and the humidified and heated atmosphere in the drying space is maintain at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C., 
   wherein the undried honeycomb formed body accommodated in the drying chamber in which the humidified and heated atmosphere is maintained by means of the hot air feeding unit is irradiated with an electromagnetic wave generated by the electromagnetic wave generator, thereby performing high-frequency heating, and the hot air fed by the hot air feeding unit is applied to the undried honeycomb formed body, thereby increasing the amount of water vaporized from the outer part, 
   thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body and that of the outer part thereof, 
   thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed (second mode of the honeycomb formed body drying apparatus of the present invention). 
   [27] An apparatus for drying a honeycomb formed body as described in [26], wherein the hot air feeding unit has a hot air generator and a hot air introduction member for introducing, into the drying chamber, the hot air generated by means of the hot air generator.
 
[28] An apparatus for drying a honeycomb formed body as described in [26] or [27], wherein hot air is fed by means of the hot air feeding unit at a velocity of 0.5 to 10 m/s and a flow rate of 3 to 60 m 3 /s.
 
[29] An apparatus for drying a honeycomb formed body as described in any of [26] to [28], wherein the hot air fed by means of the hot air feeding unit has a temperature of 80 to 135° C.
 
[30] An apparatus for drying a honeycomb formed body as described in any of [26] to [29], wherein the hot air fed by means of the hot air feeding unit has a humidity level of 20% or less.
 
[31] An apparatus for drying a honeycomb formed body as described in any of [26] to [30], which further comprises a hot air application apparatus for further applying hot air (second hot air) to an outer peripheral wall of the undried honeycomb formed body accommodated in the drying chamber at a predetermined distance from the wall, to thereby heat the undried honeycomb formed body.
 
[32] An apparatus for drying a honeycomb formed body as described in [31], wherein the hot air application apparatus has a second hot air application section for applying a second hot air; and the second hot air application section is formed such that the second hot air is applied to the outer peripheral wall in two directions opposing each other and being normal to the center axis of the undried honeycomb formed body, whereby the second hot air is applied to the undried honeycomb formed body in two directions so as to sandwich the outer peripheral wall.
 
[33] An apparatus for drying a honeycomb formed body as described in [31] or [32], wherein the second hot air is applied by means of the hot air application apparatus to the outer peripheral wall of the undried honeycomb formed body at a velocity of 0.5 to 10 m/s.
 
[34] An apparatus for drying a honeycomb formed body as described in any of [31] to [33], wherein the second hot air applied by means of the hot air application apparatus to the outer wall of the undried honeycomb formed body has a temperature of 80 to 135° C.
 
[35] An apparatus for drying a honeycomb formed body as described in any of [31] to [34], wherein the second hot air applied by means of the hot air application apparatus to the outer wall of the undried honeycomb formed body has a humidity level of 20% or less.
 
[36] An apparatus for drying a honeycomb formed body as described in any of [26] to [35], which further comprises a stand having a rotatable receiving member and a support for rotatably supporting the receiving member,
 
   the receiving member being capable of rotating the undried honeycomb formed body placed on an upper surface thereof virtually about the center axis of the receiving member, wherein 
   the undried honeycomb formed body is placed on the receiving member of the stand during drying of the undried honeycomb formed body in the drying chamber; 
   the undried honeycomb formed body and the stand are transferred into the drying chamber; 
   the undried honeycomb formed body is dried while the undried honeycomb formed body is rotated through rotation of the receiving member, to thereby provide a dried honeycomb formed body; and 
   the dried honeycomb formed body and the stand are removed from the drying chamber. 
   [37] An apparatus for drying a honeycomb formed body as described in [36], wherein the receiving member forming the stand has a pinion part for allowing the receiving member to rotate about the center axis; 
   the drying chamber further contains a conveyer and a rod-like rack part provided along the conveyer, 
   the conveyer being adapted such that the undried honeycomb formed body placed on the stand is placed thereon and transferred to the drying chamber; the undried honeycomb formed body is dried while being transferred, to thereby provide a dried honeycomb formed body; and the dried honeycomb formed body is removed from the drying chamber, and 
   the rod-like rack part being disposed along the conveyer, being aligned in the longitudinal direction of the conveyer, and having rack part teeth formed on one side facing the stand and along the conveyer such that the rack part teeth are engaged with the pinion part of the receiving member during transfer of the undried honeycomb formed body placed on the stand by means of the conveyer, 
   wherein, during transfer of the undried honeycomb formed body placed on the stand by means of the conveyer in the drying chamber, the stand is transferred while the rack part teeth are engaged with the pinion part of the receiving member, thereby rotating the receiving member about the center axis thereof, whereby the undried honeycomb formed body placed on the stand is transferred in the drying chamber while rotating virtually about the center axis of the receiving member. 
   [38] An apparatus for drying a honeycomb formed body as described in any of [26] to [37], wherein the drying chamber has a heat insulating material covering the same. 
   [39] An apparatus for drying a honeycomb formed body as described in any of [26] to [38], wherein the electromagnetic wave has a frequency of 900 to 10,000 MHz. 
   [40] An apparatus for drying a honeycomb formed body as described in any of [26] to [39], which further comprises a post-drying chamber having a post-drying space for accommodating the honeycomb formed body which has been dried in the drying space included in the drying chamber wherein the honeycomb formed body is further dried through application of hot air (for post-drying) thereto, and a post-drying hot air generator for generating the hot air for post-drying. 
   [41] An apparatus for drying a honeycomb formed body as described in [40], wherein the hot air for post-drying generated by means of the post-drying hot air generator has a temperature of 100 to 130° C. 
   [429] An apparatus for drying a honeycomb formed body as described in any of [26] to [41], wherein the honeycomb formed body has a percent cell opening of 80% or more, and each of the partition walls has a thickness of 0.18 mm or less. 
   In the first mode of the honeycomb formed body drying method of the present invention, an undried honeycomb formed body which is formed from a raw material composition containing a ceramic raw material and water is irradiated with an electromagnetic wave for high-frequency heating in a predetermined space whose inside atmosphere has been controlled to a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. through feeding of water vapor and forcedly discharging the inside atmosphere, to thereby dry the undried honeycomb formed bodies such that 50 to 99 mass % of water contained in the formed body is evaporated. Therefore, the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased through employment of the aforementioned humidified and heated atmosphere, thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body and that of the outer part thereof, thereby suppressing deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part. 
   In the second mode of the honeycomb formed body drying method of the present invention, an undried honeycomb formed body which is formed from a raw material composition containing a ceramic raw material and water is irradiated with an electromagnetic wave for high-frequency heating in a predetermined space whose inside atmosphere has been controlled to a humidity level as low as 30 to 65% and a temperature of 75 to 130° C., and hot air is fed into the aforementioned predetermined space, to thereby dry the undried honeycomb formed bodies such that 50 to 99 mass % of water contained in the formed body is evaporated. Therefore, the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased through employment of the aforementioned humidified and heated atmosphere and feeding the hot air, thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body and that of the outer part thereof, thereby suppressing deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part. 
   In the first mode of the honeycomb formed body drying apparatus of the present invention, the drying space of the drying chamber is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. through an atmosphere controlling unit for feeding water vapor into and forcedly discharging the drying space; and the undried honeycomb formed body placed in the drying space is irradiated with an electromagnetic waver generated by an electromagnetic wave generator for high-frequency heating in the atmosphere such that 50 to 99 mass % of water contained in the formed body is evaporated at the end of high-frequency heating, to thereby dry the undried honeycomb formed body. Therefore, the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased through employment of the aforementioned humidified and heated atmosphere, thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof, thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by a difference between drying degree of the inner part and that of the outer part is suppressed. 
   In the second mode of the honeycomb formed body drying apparatus of the present invention, the drying space of the drying chamber is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. through a hot air feeding unit; and the undried honeycomb formed body is irradiated with an electromagnetic waver generated by an electromagnetic wave generator for high-frequency heating in the atmosphere such that 50 to 99 mass % of water contained in the formed body is evaporated at the end of high-frequency heating, and the hot air generated by the hot air generator is applied to the undried honeycomb molded unit, to thereby dry the undried honeycomb formed body. Therefore, the amount of water vaporized from the outer part of the undried honeycomb formed body, which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased through employment of the aforementioned humidified and heated atmosphere and application of hot air, thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body and that of the outer part thereof, thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  A schematic cross-sectional view of a honeycomb formed body drying apparatus employed in an embodiment according to a first mode of the honeycomb formed body drying method of the present invention. 
       FIG. 2  A cross-section taken along line A-A′ in  FIG. 1 . 
       FIG. 3  A schematic cross-sectional view of an apparatus for drying a honeycomb formed body employed in an embodiment according to a second mode of the method of the present invention for drying a honeycomb formed body. 
       FIG. 4  A cross-section taken along line AA-AA′ in  FIG. 3 . 
       FIG. 5  A schematic plan view showing that the receiving member of the stand on which an undried honeycomb formed body is placed is rotated by means of the rack part. 
       FIG. 6  A schematic plan view showing that hot air is applied to an undried honeycomb formed body which is rotating. 
       FIG. 7  A schematic cross-sectional view showing an embodiment according to a first mode of the honeycomb formed body drying apparatus of the present invention. 
       FIG. 8  A cross-section taken along line B-B&#39; in  FIG. 7 . 
       FIG. 9  A schematic cross-sectional view showing an embodiment according to a second mode of the honeycomb formed body drying apparatus of the present invention. 
       FIG. 10  A cross-section taken along line BB-BB&#39; in  FIG. 9 . 
       FIG. 11  A schematic plan view showing that the receiving member of the stand on which an undried honeycomb formed body is placed is rotated by means of the rack part. 
       FIG. 12  A schematic plan view showing that hot air is applied to an undried honeycomb formed body which is rotating. 
   

   DESCRIPTION OF REFERENCE NUMERALS 
     1 ,  51 ,  101 , and  151  • • • drying chamber;  2 ,  52 ,  102 , and  152  • • • drying space;  3 ,  53 ,  103 , and  153  • • • electromagnetic wave generator;  4  and  54  • • • water vapor feeding means;  104  and  154  • • • hot air generator;  5  and  55  • • • forced discharge means;  105  and  155  • • • hot air introducing member;  6  and  56  • • • atmosphere controlling unit;  106  and  156  • • • hot air feeding unit;  11 ,  61 ,  111 , and  161  • • • blower for forced discharge;  12 ,  62 ,  112 , and  162  • • • duct for forced discharge;  113  and  163  • • • forced discharge means;  21 ,  71 ,  121 , and  171  • • • conveyer;  23 ,  73 ,  123 , and  173  • • • ceiling;  24 ,  74 ,  124 , and  174  • • • outer frame;  25 ,  75 ,  125 , and  175  • • • roof;  26 ,  76 ,  126 , and  176  • • • side surface;  127  and  177  • • • rack part;  128  and  178  • • • hot air application apparatus;  129  and  179  • • • rack part teeth;  31  and  81  • • • hot air drying chamber;  131  and  181  • • • post-drying chamber;  32  and  82  • • • hot air generator;  132  and  182  • • • hot air generator for post-drying;  33 ,  83 ,  133 , and  183  • • • hot air feeding piping;  34 ,  84 ,  134 , and  184  • • • hot air feeding nozzle;  35 ,  85 ,  135 , and  185  • • • hot air discharge duct;  36 ,  86 ,  136 , and  186  • • • piping for preliminary heating;  37  and  87  • • • hot air drying space;  137 ,  187  • • • post-drying space;  41 ,  91 ,  141 , and  191  • • • undried honeycomb formed body;  42 ,  92 ,  142 , and  192  • • • dried honeycomb formed body;  43  and  93  • • • honeycomb formed body in drying;  44 ,  94 ,  144 , and  194  • • • outer peripheral surface wall;  45 ,  95 ,  145 , and  195  • • • top end;  146  and  196  • • • support;  147  and  197  • • • receiving member;  148  and  198  • • • stand;  149  and  199  • • • pinion part;  100 ,  200 ,  300 , and  400  • • • drying apparatus; D, E, DD, and EE • • • honeycomb formed body moving direction; H,h • • • second hot air; and R and S • • • rotational direction. 
   BEST MODES FOR CARRYING OUT THE INVENTION 
   Best modes for Carrying Out the present invention (hereinafter may be referred to as “embodiment”) will next be described with reference to the drawings. However, these embodiments should not be construed as limiting the invention thereto. It is also understood by those skilled in the art that appropriate changes and modifications in arrangement of the embodiments may be made in the invention without departing from the scope of the present invention. In the drawings, the same reference numerals denote components common to each of the drawings. 
   Best modes for Carrying Out the present invention (hereinafter may be referred to as “embodiment”) will next be described with reference to the drawings. However, these embodiments should not be construed as limiting the invention thereto. It is also understood by those skilled in the art that appropriate changes and modifications in arrangement of the embodiments may be made in the invention without departing from the scope of the present invention. In the drawings, the same reference numerals denote components common to each of the drawings. 
     FIG. 1  is a schematic cross-sectional view of an apparatus for drying a honeycomb formed body employed in an embodiment according to a first mode of the honeycomb formed body drying method of the present invention. 
   The embodiment of the first mode of the honeycomb formed body drying method of the present invention can be carried out by means of a honeycomb formed body drying apparatus  100  (hereinafter may be referred to simply as “drying apparatus  100 ”) shown in  FIG. 1 . However, the drying apparatus to be employed in the embodiment of the first mode of the honeycomb formed body drying method of the present invention is not limited to the drying apparatus  100  shown in  FIG. 1 . 
   Through employment of the drying apparatus  100  shown in  FIG. 1 , a honeycomb formed body in an undried state (i.e., undried honeycomb formed body)  41  which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls is subjected to high-frequency heating through electromagnetic wave irradiation, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed body  41  so as to dry the undried honeycomb formed body  41 , thereby producing a dried honeycomb formed body  41 . As used herein, when the undried honeycomb formed body  41  assumes a cylinder, the term “an outer part of the undried honeycomb formed body  41 ” refers to a part in the vicinity of the outer peripheral surface wall of the cylinder. The outer part represents an area about 20-mm inside from the outermost periphery when viewed in a cross-section of the cylinder. The term “an inner part of the undried honeycomb formed body  41 ” refers to a part other than the outer part, and the inner part includes a center axis. When the undried honeycomb formed body  41  assumes a shape other than a cylinder, the inner part refers to a part in the vicinity of the center axis or the center, and the outer part refers to a part in the vicinity of the outer periphery or the outer surface. In this case, the outer part represents an area about 20-mm inside from the outer periphery (outer surface), and the inner part of the undried honeycomb formed body  41  is a part other than the outer part. 
   The drying apparatus  100  includes, in a cylindrical outer frame  24 , a drying chamber  1  having a drying space  2  for accommodating an undried honeycomb formed body  41  in a humidified and heated atmosphere; an electromagnetic wave generator  3  for generating an electromagnetic wave with which the undried honeycomb formed body  41  accommodated in the drying chamber  1  is to be irradiated such that 50 to 99 mass % of water contained in the undried formed body  41  is evaporated at the end of irradiation; and an atmosphere controlling unit  6  having a water vapor feeding means  4  and a forced discharge means  5  and allowing the humidified and heated atmosphere in the drying chamber  1  to maintain at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. 
   The outer frame  24  forming the drying apparatus  100  is formed in a cylindrical shape such that the center axis is oriented virtually in the horizontal direction. An undried honeycomb formed body  41  is transferred into the drying apparatus through one end of the cylinder, and the dried honeycomb formed body  42  is removed through the other end thereof. In the outer frame  24 , a ceiling  23  is disposed virtually in the horizontal direction so as to provide a space between the ceiling and a roof  25  of the outer frame, and divides the outer frame  24  into two chambers. The drying chamber  1  is formed into a cylinder, and the center axis of the cylinder virtually aligns the center axis of the outer frame  24 . The drying chamber is disposed under (in the vertical direction) the roof  25  formed in the outer frame  24 . In the drying chamber  100 , a conveyer  21  is disposed so as to extend from one end (inlet end) of the outer frame  24  to the other end (outlet end) of the outer frame  24  through the inside of the cylindrical drying chamber  1  so that the undried honeycomb formed bodies  41  are continuously transferred into the chamber and the thus-dried honeycomb formed bodies  42  are continuously removed to the outside. No particular limitation is imposed on the type of the conveyer  21 , and a belt conveyer, a roller conveyer, and other conveyers may be employed. 
   The embodiment of the honeycomb formed body drying method is carried out through employment of the drying apparatus  100 . Specifically, an undried honeycomb formed body  41  is subjected to high-frequency heating through electromagnetic wave irradiation in a drying space  2  of a humidified and heated atmosphere, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed body  41  so as to dry the undried honeycomb formed body  41 , thereby producing a dried honeycomb formed body  42 . 
   In the embodiment of the honeycomb formed body drying method, the humidified and heated atmosphere in the drying space  2  is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. by means of an atmosphere controlling unit  6 , and the undried honeycomb formed body  41  is subjected to high-frequency heating in the atmosphere through an electromagnetic wave generated by an electromagnetic wave generator  3  such that 50 to 99 mass % of water contained in the formed body  41  is evaporated at the end of high-frequency heating, whereby the amount of water vaporized from the outer part of the undried honeycomb formed body  41 , which amount is smaller than that of water vaporized from the inner part of the formed body  41  through high-frequency heating alone, is increased through employment of the aforementioned predetermined humidified and heated atmosphere, thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body  41  and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body  41  and that of the outer part thereof, thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed. 
   Deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part occurs by the following mechanism. During drying of the undried honeycomb formed body  41 , partition walls are shrunken. If the honeycomb formed body is not dried uniformly, difference in shrinkage degree of partition walls is provided. The difference causes warpage. Thus, deformation of partition walls such as warpage occurs. In the embodiment of the honeycomb formed body drying method, such deformation of partition walls can be prevented. The term “deformation of partition walls” is used to refer to warpage of partition walls, generation of wrinkles, generation of wrinkles in the outermost peripheral surface wall, formation of dents, etc. 
   When the humidity level in the drying space  2  is lower than 30%, an outer peripheral surface wall  44  (see  FIG. 2 ) of the undried honeycomb formed body  41  is dried excessively rapidly. Thus, defects are generated in the outer peripheral surface wall  44 , which is problematic. A humidity level in the drying space of higher than 65% is also problematic. Specifically, the amount of water vaporized from the outer part of the undried honeycomb formed body  41  is generally smaller than that of vaporized from the inner part at an initial drying stage, providing a difference in drying degree between the inner part and the outer part, resulting in deformation of partition walls such as wrinkles. When the humidity level is excessively high, the difference in drying degree between the inner part and the outer part increases, resulting in deformation of partition walls, which is problematic. As used herein, the term “defects in the outer peripheral surface wall” refers to a cracking of the outer peripheral surface wall having a length corresponding to 20% or more the thickness. In addition, when the humidity level is high, the amount of water vaporized from the undried honeycomb formed body problematically decreases due to loss of the energy of the input electromagnetic wave. Therefore, the humidity level in the drying space  2  is more preferably 30 to 50%. 
   When the inside temperature of the drying space  2  is lower than 75° C., the undried honeycomb formed body  41  is difficult to dry, resulting in problematic wrinkles in the outer peripheral surface wall, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  41  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  41 , and the organic binder may be burnt. Needless to say, both cases are problematic. Thus, the inside temperature of the drying space  2  is preferably 90 to 110° C. When the inside temperature falls within a range of 75 to 90° C., the produced honeycomb formed bodies have no problem in quality. However, difference in water content between the inner part of the honeycomb formed body and the outer part thereof as low as less than 10 mass % may result. In addition, a longer drying time may be required so as to compensate drop in drying efficiency. 
   When the percent vaporized water amount of the undried honeycomb formed body is less than 50 mass %, shrinkage of the honeycomb formed body is not complete. When water is further vaporized, the honeycomb formed body further shrinks not uniformly, resulting in deformation of partition walls of the honeycomb formed body, which is problematic. When the percent vaporized water amount of the undried honeycomb formed body is more than 99 mass %, the honeycomb formed body is over dried locally, and scorching may occur due to burning of a binder, which is also problematic. As used herein, the term “percent vaporized water amount of the undried honeycomb formed body” refers to a value obtained by dividing the mass of vaporized water by the mass of water contained in the undried honeycomb formed body and multiplying 100. 
   In the embodiment of the honeycomb formed body drying method, when the undried honeycomb formed body  42  is dried by means of the drying apparatus  100 , the following procedure is employed. Firstly, the undried honeycomb formed body  41  is transferred into the chamber through one end of the outer frame  24  and placed on the conveyer  21 . The undried honeycomb formed body  41  is conveyed through driving force of the conveyer  21  so as to move in the honeycomb formed body conveyance direction D, followed by transferring into the drying chamber  1  through one end of the drying chamber  1  by means of the conveyer  21 . While the undried honeycomb formed body  41  is conveyed by means of the conveyer  21  in the drying chamber  1  as a honeycomb formed body  43  in a drying state, the undried honeycomb formed body  41  is subjected to high-frequency heating for drying through irradiation with an electromagnetic wave generated by the electromagnetic wave generator  3  in the drying space  2  of which atmosphere is controlled to a predetermined humidity and temperature by means of the atmosphere controlling unit  6 , to thereby form the dried honeycomb formed body  42 . Subsequently, the thus-dried honeycomb formed body  42  is removed from the drying chamber  1  through the other end thereof and transferred to a hot air drying chamber  31 . The dried honeycomb formed body  42  is conveyed by means of the conveyer  21  in the hot air drying chamber  31 , while further dried through application of hot air to the formed body  42 . Subsequently, the formed body  42  is removed from the hot air drying chamber  31  and the drying apparatus  100 . 
   As shown in  FIG. 1 , the drying apparatus  100  includes the atmosphere controlling unit  6  for controlling the drying space  2  in the drying chamber  1  to a predetermined humidity and temperature. The atmosphere controlling unit  6  has a water vapor feeding means  4  for feeding water vapor into the drying chamber  1 , and a forced discharge means  5  for discharging the drying chamber  1 . The water vapor feeding means  4  is a piping having at the tip nozzles through which water vapor is discharged, and the tip is inserted in the drying chamber  1 . Water vapor to be employed is generated by means of, for example, a water vapor generator and fed through the piping. In the forced discharge means  5 , the piping connected to a blower for forced discharge  11  is branched into two. The tip of one branch is inserted into the space near one end of the drying chamber  1 , and the tip of the other branch is inserted into a space near the other end of the drying chamber  1 . The gas present in the drying chamber  1  is discharged by means of the blower for forced discharge  11  to the outside in accordance with need through the piping. 
   The water vapor that is fed through the water vapor feeding means  4  into the drying chamber  1  preferably has a temperature of 100 to 120° C. The amount of water vapor fed into the drying chamber  1  and the amount of discharge from the drying chamber  1  to the outside through the blower for forced discharge  11  are appropriately determined in accordance with factors such as the capacity of the drying chamber  1 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  1 . For example, when the capacity of the drying chamber  1  is about 7 m 3 , the amount of water vapor is preferably 90 to 120 kg/Hr, and the discharge rate is preferably 20 to 50 m 3 /min. 
   As shown in  FIG. 1 , electromagnetic wave generators  3  are disposed on the inner surface of the ceiling  23  of the drying chamber  1  along the center axis of the outer frame  24 . The electromagnetic wave generators  3  are distributed in ten zones located with virtually the same intervals. In each zone, as shown in  FIG. 2 , two electromagnetic wave generators are disposed on the ceiling  23  and one electromagnetic wave generator on each side surface  26 ; i.e., total four electromagnetic wave generators  3  are disposed. Thus, 40 electromagnetic wave generators  3  are disposed in the drying chamber  1 .  FIG. 2  is a cross-section taken along line A-A′ in  FIG. 1 . According to the embodiment of the honeycomb formed body drying method, the drying honeycomb formed body  43  is irradiated with an electromagnetic wave of the outer peripheral surface wall  44  side and the top end  45  side. Thus, the inside of the honeycomb formed body is more uniformly irradiated with an electromagnetic wave, and the entirety of the honeycomb formed body more uniformly undergoes high-frequency heating, which is preferred. No particular limitation is imposed on the place and number of the electromagnetic wave generators  3  to be disposed. For example, in each zone, one electromagnetic wave generator  3  may be placed at any place. Alternatively, five or more electromagnetic wave generators  3  may be disposed at any places. The number of the zones where an electromagnetic wave generator  3  is disposed is not limited to ten, and may be appropriately determined in accordance with factors such as the length of the drying chamber  1 . Preferably, the drying chamber  1  is covered with a heat insulating material, whereby the inside temperature of the drying chamber  1  is maintained. In addition, the outer frame  24  is preferably surrounded by a heat insulating material. 
   In the embodiment of the honeycomb formed body drying method, the electromagnetic wave employed for drying preferably has a frequency of 900 to 10,000 MHz, more preferably 2,000 to 10,000 MHz. When the frequency is lower than 900 MHz, water is difficult to undergo high-frequency heating, and a honeycomb formed body may be difficult to dry. In contrast, when the frequency is higher than 2,000 MHz, water effectively undergoes high-frequency heating. As shown in  FIG. 2 , the electromagnetic wave generators  3  may be disposed inside the drying chamber  1 . Alternatively, electromagnetic wave generators  3  may be disposed outside the drying chamber  1 , and the generated electromagnetic wave is guided through a predetermined site of the drying chamber  1  into the drying chamber  1  via a waveguide so as to apply the electromagnetic wave to the drying honeycomb formed body  43 . 
   The energy of the electromagnetic wave applied to the honeycomb formed body is appropriately determined in accordance with factors such as the capacity of the drying chamber  1 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  1 . For example, when the capacity of the drying chamber  1  is about 7 m 3 , the total energy is preferably 150 to 300 kW. When the energy is smaller than 150 kW, the honeycomb formed body may fail to be dried to a predetermined drying degree, whereas when the energy is higher than 300 kW, the vaporization speed of water from the honeycomb formed body is elevated, difficulty may be encountered in reduction of the difference in drying condition between the inner part of the honeycomb formed body and the outer part thereof, even though the drying space is heated and humidified. 
   In the embodiment of the honeycomb formed body drying method, as mentioned above, preferably, an undried honeycomb formed body is dried through electromagnetic wave irradiation to form a dried honeycomb formed body, and hot air is applied to the dried honeycomb formed body for further drying. Through this procedure, the remaining water content can be reduced to 0.5% or lower. In a preferred manner for applying hot air to the dried honeycomb formed body for further drying, as shown in  FIG. 1 , the dried honeycomb formed body  42  is transferred by means of a conveyer to a hot air drying chamber  31  having a hot air drying space  37  and provided in the vicinity of the outlet of the outer frame  24 . The hot air fed through hot air feeding nozzles  34  disposed under the hot air drying chamber  31  is applied to the dried honeycomb formed body  42  in the direction from the bottom to the top end. The hot air fed through hot air feeding nozzles  34  to the hot air drying chamber  31  is discharged to the outside through a hot air discharge duct  35  disposed above the hot air drying chamber  31  (space between the ceiling  23  and the roof  25 ). The aforementioned hot air preferably has a temperature of 100 to 130° C. When the temperature is lower than 100° C., the dried honeycomb formed body may be difficult to dry, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  41  are vaporized, causing deformation of partition walls of the undried honeycomb formed body  41  and burning of the organic binder and other substances, which are problematic. 
   The hot air feeding nozzles  34  are linked to the hot air generator  32  via the hot air feeding piping  33  so that the hot air generated by the hot air generator  32  is transferred via the hot air feeding piping  33  and discharged through the hot air feeding nozzles  34 . No particular limitation is imposed on the type of the hot air generator  32  so long as the generator attains predetermined temperature and flow rate. For example, a hot air generator having a heater employing high-temperature water vapor or an electric heater and a blower may be used. In the generator, a blow generated by the blower is heated to provide hot air. The hot air generated by the hot air generator  32  may be used for preliminarily heating the unheated drying chamber  1  before the start of electromagnetic wave drying of the undried honeycomb formed body. In  FIG. 1 , hot air is fed into the drying chamber  1  via a piping for preliminary heating  36  connected to the hot air generator  32 . 
   The embodiment of the honeycomb formed body drying method is suitable for drying a honeycomb formed body made of ceramic material, having a percent opening of 80% or more and a partition wall thickness of 0.18 mm or less. As used herein, the term “percent opening” refers to a ratio (percent) of the total cross-sectional area of the cell through-holes to the cross-sectional area of the honeycomb formed body in which the cell through-holes are located, as viewed in a cross-section of a honeycomb formed body cut in a direction normal to the center axis. 
   The drying apparatus employed in the embodiment of the honeycomb formed body drying method continuously dries honeycomb formed bodies and may be a batch-type. In use, the batch-type drying apparatus is such that a predetermined number of undried honeycomb formed bodies are accommodated therein and irradiated with an electromagnetic wave to thereby dry the honeycomb formed bodies; irradiation of the electromagnetic wave is stopped; the thus-dried honeycomb formed bodies are removed; another predetermined number of undried honeycomb formed bodies are accommodated therein; and irradiation of an electromagnetic wave is started. 
     FIG. 3  is a schematic cross-sectional view of an apparatus for drying a honeycomb formed body employed in an embodiment according to a second mode of the honeycomb formed body drying method of the present invention. 
   The embodiment of the second mode of the honeycomb formed body drying method of the present invention can be carried out by means of a honeycomb formed body drying apparatus  200  (hereinafter may be referred to simply as “drying apparatus  200 ”) shown in  FIG. 3 . However, the drying apparatus to be employed in the embodiment of the second mode of the honeycomb formed body drying method of the present invention is not limited to the drying apparatus  200  shown in  FIG. 3 . 
   Through employment of the drying apparatus  200  shown in  FIG. 3 , a honeycomb formed body in an undried state (i.e., undried honeycomb formed body)  141  which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls is subjected to high-frequency heating through electromagnetic wave irradiation, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed body  141  so as to dry the undried honeycomb formed body  141 , thereby producing a dried honeycomb formed body  142 . As used herein, when the undried honeycomb formed body  141  assumes a cylinder, the term “an outer part of the undried honeycomb formed body  141 ” refers to a part in the vicinity of the outer peripheral surface wall of the cylinder. The outer part represents an area about 20-mm inside from the outermost periphery when viewed in a cross-section of the cylinder. The term “an inner part of the undried honeycomb formed body  141 ” refers to a part other than the outer part, and the inner part includes a center axis. When the undried honeycomb formed body  141  assumes a shape other than a cylinder, the inner part refers to a part in the vicinity of the center axis or the center, and the outer part refers to a part in the vicinity of the outer periphery or the outer surface. In this case, the outer part represents an area about 20-mm inside from the outer periphery (outer surface), and the inner part of the undried honeycomb formed body  141  is a part other than the outer part. 
   The drying apparatus  200  includes, in a cylindrical outer frame  124 , a drying chamber  101  having a drying space  102  for accommodating an undried honeycomb formed body  141  in a humidified and heated atmosphere; an electromagnetic wave generator  103  for generating an electromagnetic wave with which the undried honeycomb formed body  141  accommodated in the drying chamber  101  is to be irradiated for performing high-frequency heating of the undried honeycomb formed body  141 ; a hot air feeding unit  106  for feeding hot air into the drying space, which hot air feeding unit being provided so that the amount of water vaporized from the outer part of the undried honeycomb formed body  141 , which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased synergistic with the high-frequency heating performed by means of the electromagnetic wave generator  103 , such that 50 to 99 mass % of water contained in the undried formed body  141  is evaporated at the end of irradiation, and the humidified and heated atmosphere in the drying space  102  is maintain at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C.; and a hot air application apparatus  128  for applying hot air for heating to the outer peripheral surface wall of the undried honeycomb formed body  141  accommodated in the drying chamber  101 . 
   The outer frame  124  forming the drying apparatus  200  is formed in a cylindrical shape such that the center axis is oriented virtually in the horizontal direction. An undried honeycomb formed body  141  is transferred into the drying apparatus through one end of the cylinder, and the dried honeycomb formed body  142  is removed through the other end thereof. In the outer frame  124 , a ceiling  123  is disposed virtually in the horizontal direction so as to provide a space between the ceiling and a roof  125  of the outer frame, and divides the outer frame  124  into two chambers. The drying chamber  101  is formed into a cylinder, and the center axis of the cylinder virtually aligns the center axis of the outer frame  124 . The drying chamber is disposed under (in the vertical direction) the roof  125  formed in the outer frame  124 . 
   In the drying chamber  200 , a conveyer  121  is disposed so as to extend from one end (inlet end) of the outer frame  124  to the other end (outlet end) of the outer frame  124  through the inside of the cylindrical drying chamber  101  so that the undried honeycomb formed bodies  141  are continuously transferred into the chamber and the thus-dried honeycomb formed bodies  142  are continuously removed to the outside. 
   In the vicinity of the inlet end of the drying chamber  101  for transferring the undried honeycomb formed bodies  141 , there is provided a hot air feeding unit  106  having a hot air generator  104  for generating hot air and a hot air introducing member  105  for feeding hot air generated by the hot air generator  104  into the drying space  102  of the drying chamber  101 . The hot air fed into the drying space  102  through the hot air feeding unit  106  is applied to the undried honeycomb formed body  141  transferred into the drying space  102 , thereby drying the undried honeycomb formed body  141 . 
   In the vicinity of the outlet end of the drying chamber  101  for removing the undried honeycomb formed bodies  141 , there is provided a forced discharge means  113  having a blower for forced discharge  111  and a duct for forced discharge  112 , through which means the drying space  102  is discharged. 
   In the drying chamber  101 , a hot air application apparatus  128  is disposed so as to sandwich the conveyer  121  along the direction DD of transferring the undried honeycomb formed body  141 . The hot air application apparatus  128  has a second hot air application section (not illustrated) for applying hot air (second hot air). The second hot air application section (not illustrated) is formed such that the second hot air is applied to the outer peripheral wall  144  in two directions opposing each other and being normal to the center axis of the undried honeycomb formed body  141 , whereby the second hot air is applied to the undried honeycomb formed body  141  in two directions so as to sandwich the outer peripheral wall  144 . Preferably, the second blow application section has a plurality of tubular nozzles (hot air application nozzles), through which hot air is applied to the outer peripheral surface wall  144  of the undried honeycomb formed body  141 . More preferably, the hot air application nozzles are aligned along the center axis (top to bottom) of the undried honeycomb formed body  141 , while the axis of each hot air application nozzle is aligned in the horizontal direction and the tip of the nozzle faces the outer peripheral surface wall  144 , whereby the second hot airs are simultaneously applied to the outer peripheral surface wall  144  from the top end to the bottom thereof. In this case, preferably, the line passing through the nozzle tips is virtually aligned in the center axis of the undried honeycomb formed body  141 . Through employment of the configuration, the second hot air can be applied to the entire outer peripheral surface wall  144  during movement of the undried honeycomb formed body  141 . Preferably, a plurality of sets of nozzles being aligned in the center axis of the undried honeycomb formed body  141  are arranged in the direction DD of transferring the undried honeycomb formed body  141  such that the nozzle lines are arranged virtually in parallel one another, whereby second hot airs provided by the nozzle sets are sequentially applied to the outer peripheral surface wall  144  during transfer of the undried honeycomb formed body  141 . However, the nozzles in each nozzle set are not necessarily in the same line, and a zigzag or an irregular arrangement may also be employed, so long as the second hot air can be applied to the outer peripheral surface wall  144  uniformly from the top end to the bottom thereof. The second hot air application section does not necessarily have hot air application nozzles and, instead, may have a piping having a plurality of holes through which the hot air is applied. 
   The embodiment of the honeycomb formed body drying method is carried out through employment of the drying apparatus  200 . Specifically, an undried honeycomb formed body  141  is subjected to high-frequency heating through electromagnetic wave irradiation in a drying space  102  which is maintained at a humidified and heated atmosphere through hot air, and the supplied hot air is applied to the undried honeycomb formed body  141 , whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed body  141  so as to dry the undried honeycomb formed body  141 , thereby producing a dried honeycomb formed body  142 . 
   In the embodiment of the honeycomb formed body drying method, the humidified and heated atmosphere in the drying space  102  is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. by means of a hot air feeding unit  106 , and the undried honeycomb formed body  141  is subjected to high-frequency heating in the atmosphere through an electromagnetic wave generated by an electromagnetic wave generator  103  and also, the hot air fed through the hot air feeding unit  106  is applied to the undried honeycomb formed body  141 , such that 50 to 99 mass % of water contained in the formed body  141  is evaporated at the end of high-frequency heating, whereby the amount of water vaporized from the outer part of the undried honeycomb formed body  141 , which amount is smaller than that of water vaporized from the inner part of the formed body  141  through high-frequency heating alone, is increased through employment of the aforementioned predetermined humidified and heated atmosphere and application of hot air to the formed body  141 , thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body  141  and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body  141  and that of the outer part thereof, thereby producing a dried honeycomb formed body in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed. In addition to the hot air fed by means of the hot air feeding unit  106 , hot air (second hot air) is applied to the outer peripheral surface wall  144  of the undried honeycomb formed body  141  at a predetermined distance from the wall, to thereby further reduce a difference between drying degree of the inner part of the undried honeycomb formed body  141  and that of the outer part thereof, thereby further suppressing deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part. In order to promote drying of the outer part, which is difficult to dry through sole high-frequency, and to control the drying state to that of the inner part, which is readily dried through sole heating high-frequency heating, preferably, application of the second hot air applied to the outer peripheral surface wall  144  of the undried honeycomb formed body  141  is carried out only to the outer peripheral surface wall  144  of the undried honeycomb formed body  141  and not to the top end and the bottom thereof. If the second hot air is applied to the top end and the bottom, the difference in the amount of water vaporization between the inner part of the undried honeycomb formed body  141  and the outer part thereof may be difficult to reduce. 
   Deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part occurs by the following mechanism. During drying of the undried honeycomb formed body  141 , partition walls are shrunken. If the honeycomb formed body is not dried uniformly, difference in shrinkage degree of partition walls is provided. The difference causes warpage. Thus, deformation of partition walls such as warpage occurs. In the embodiment of the honeycomb formed body drying method, such deformation of partition walls can be prevented. The term “deformation of partition walls” is used to refer to warpage of partition walls, generation of wrinkles, generation of wrinkles in the outermost peripheral surface wall, formation of dents, etc. 
   When the humidity level in the drying space  102  is lower than 30%, an outer peripheral surface wall  144  of the undried honeycomb formed body  141  is dried excessively rapidly. Thus, defects are generated in the outer peripheral surface wall  144 , which is problematic. A humidity level in the drying space of higher than 65% is also problematic. Specifically, the amount of water vaporized from the outer part of the undried honeycomb formed body  141  is generally smaller than that of vaporized from the inner part at an initial drying stage, providing a difference in drying degree between the inner part and the outer part, resulting in deformation of partition walls such as wrinkles. When the humidity level is excessively high, the difference in drying degree between the inner part and the outer part increases, resulting in deformation of partition walls, which is problematic. As used herein, the term “defects in the outer peripheral surface wall” refers to a cracking of the outer peripheral surface wall having a length corresponding to 20% or more the thickness. In addition, when the humidity level is high, the amount of water vaporized from the undried honeycomb formed body problematically decreases due to loss of the energy of the input electromagnetic wave. Therefore, the humidity level in the drying space  2  is more preferably 30 to 50%. 
   When the inside temperature of the drying space  102  is lower than 75° C., the undried honeycomb formed body  141  is difficult to dry, resulting in problematic wrinkles in the outer peripheral surface wall, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  141  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  141 , and the organic binder may be burnt. Needless to say, both cases are problematic. Thus, the inside temperature of the drying space  102  is preferably 90 to 110° C. When the inside temperature falls within a range of 75 to 90° C., the produced honeycomb formed bodies have no problem in quality. However, difference in water content between the inner part of the honeycomb formed body and the outer part thereof as low as less than 10 mass % may result, and drying of the honeycomb formed body may be slightly insufficient. 
   When the percent vaporized water amount of the undried honeycomb formed body is less than 50 mass %, shrinkage of the honeycomb formed body is not complete. When water is further vaporized after completion of drying in the drying apparatus  200 , the honeycomb formed body further shrinks not uniformly, resulting in deformation of partition walls of the honeycomb formed body, which is problematic. When the percent vaporized water amount of the undried honeycomb formed body is more than 99 mass %, the honeycomb formed body is over dried locally, and scorching may occur due to burning of a binder, which is also problematic. As used herein, the term “percent vaporized water amount of the undried honeycomb formed body” refers to a value obtained by dividing the mass of vaporized water by the mass of water contained in the undried honeycomb formed body and multiplying 100. 
   The hot air fed through the hot air feeding unit  106  into the drying space  102  preferably has a velocity of 0.5 to 10 m/s, more preferably 2 to 10 m/s, and preferably has a flow rate of 3 to 60 m 3 /s, more preferably 12 to 60 m 3 /s. When the velocity is less than 0.5 m/s, heating of the outer part of the undried honeycomb formed body  141  through the hot air may be insufficient, whereas when the velocity is more than 10 m/s, the undried honeycomb formed body  141  may undesirably be moved, or the outer peripheral surface wall  144  may be deformed. When the flow rate is less than 3 m 3 /s, heating of the outer part of the undried honeycomb formed body  141  through the hot air may be insufficient, whereas when the flow rate is more than 60 m 3 /s, the undried honeycomb formed body  141  may undesirably be moved, or the outer peripheral surface wall  144  may be deformed. 
   The hot air fed through the hot air feeding unit  106  into the drying space  102  preferably has a temperature of 80 to 135° C., more preferably 95 to 110° C. When the temperature is lower than 80° C., the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  141  may be reduced, whereas when the temperature is higher than 135° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  141  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  141 , and the organic binder may be burnt, which are problematic. 
   The hot air fed through the hot air feeding unit  106  into the drying space  2  preferably has a humidity level of 20% or less, more preferably 15% or less. When the humidity level is higher than 20%, the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  141  may be reduced. 
   In the present embodiment, in addition to the aforementioned hot air fed through the hot air feeding unit  106 , a second hot air is preferably applied to the outer peripheral surface wall  144  of the undried honeycomb formed body  141  at a predetermined distance from the wall. In this case, the second hot air preferably has a velocity of 0.5 to 10 m/s, more preferably 2 to 10 m/s. When the velocity is less than 0.5 m/s, heating of the outer part of the undried honeycomb formed body  141  through the second hot air may be insufficient, the effect of promoting vaporization of water from the outer peripheral surface wall  144  of the undried honeycomb formed body  141  by virtue of the second hot air may be reduced, the effect being based on blowing out water vapor residing in the vicinity of the outer peripheral surface wall  144  of the undried honeycomb formed body  141 , whereby the humidity around the outer peripheral surface wall  144  is reduced. When the velocity is more than 10 m/s, the undried honeycomb formed body  141  may undesirably be moved, or the outer peripheral surface wall  144  may be deformed. Upon application of the second hot air to the outer peripheral surface wall  144  of the undried honeycomb formed body  141 , the second hot air is preferably applied to the entire outer peripheral surface wall  144 . Thus, the second hot air can be applied to the entire outer peripheral surface wall  144  at the aforementioned predetermined velocity, whereby vaporization of water from the outer peripheral surface wall  144  of the undried honeycomb formed body  141  can be effectively promoted. 
   The second hot air fed through the hot air application apparatus  128  to the outer peripheral surface wall  144  preferably has a temperature of 80 to 135° C., more preferably 95 to 110° C. When the temperature is lower than 80° C., the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  141  may be reduced, whereas when the temperature is higher than 135° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  141  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  141 , and the organic binder may be burnt, which are problematic. 
   The second hot air fed through the hot air application apparatus  128  to the outer peripheral surface wall  144  preferably has a humidity level of 20% or less. When the humidity level is higher than 20%, the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  141  may be reduced. 
   The distance between a blow application site of the second hot air application section of the hot air application apparatus  128  and the outer peripheral surface wall  144  of the undried honeycomb formed body  141  (i.e., a predetermined distance from the hot air feeding unit  106  upon application of the second hot air to the outer peripheral surface wall  144 ) is preferably 0.1 to 1.0 m. When the distance is smaller than 0.1 m, the hot air may be excessively applied to a part of the outer peripheral surface wall  144 , whereas when the distance is in excess of 1.0 m, the second hot air which cannot be applied to the outer peripheral surface wall  144  but which is fed to the other sites predominates, possibly reducing the second hot air application efficiency. 
   In the present embodiment, the aforementioned hot air feeding unit  106  has a hot air generator  104  for generating hot air and a hot air introducing member  105  for feeding hot air generated by the hot air generator  104  into the drying space  102  of the drying chamber  101 . No particular limitation is imposed on the type of the hot air generator  104  so long as the generator attains predetermined temperature and flow rate. For example, a hot air generator having a heater employing high-temperature water vapor or an electric heater and a blower may be used. In the generator, a blow generated by the blower is heated to provide hot air. The temperature of the hot air low may be controlled basically by means of the above heater, and the humidity thereof may be controlled by means of a demoisturizer or a similar device. 
   As shown in  FIG. 3 , the tubular nozzle of the hot air introducing member  105  may be inserted into the drying chamber  101 . Alternatively, the drying chamber  101  may be provided with a hole; the hot air generated by the hot air generator  104  is transferred to the hole through a piping; and the hot air is introduced into the drying chamber  101  through the hole. When the nozzle is inserted into the drying chamber  101 , the nozzle is preferably oriented in a desired direction. 
   In the embodiment of the honeycomb formed body drying method, when the undried honeycomb formed body  142  is dried by means of the drying apparatus  200 , the following procedure is employed. Firstly, the undried honeycomb formed body  141  placed on a stand  148  is transferred into the chamber through one end of the outer frame  124  and placed on the conveyer  121 . The undried honeycomb formed body  141  is conveyed through driving force of the conveyer  121  so as to move in the honeycomb formed body conveyance direction DD, followed by transferring into the drying chamber  101  through one end of the drying chamber  101  by means of the conveyer  121 . While the undried honeycomb formed body  141  is conveyed by means of the conveyer  121  in the drying chamber  101 , the undried honeycomb formed body  141  is subjected to high-frequency heating for drying through irradiation with an electromagnetic wave generated by the electromagnetic wave generator  103  in the drying space  102  of a predetermined humidity and temperature, and the hot air fed through the hot air feeding unit  106  is applied to the honeycomb formed body. In addition, the second hot air is applied to the outer peripheral wall  144  through the hot air application apparatus  128  so as to promote drying the outer part, to thereby form the dried honeycomb formed body  142  of which entirety is almost uniformly dried. Subsequently, the thus-dried honeycomb formed body  142  is removed from the drying chamber  101  through the other end thereof and transferred to a post-drying chamber  131 . The dried honeycomb formed body  142  is conveyed by means of the conveyer  121  in the post-drying chamber  131 , while further dried through application of hot air to the formed body  142 . Subsequently, the formed body  142  is removed from the post-drying chamber  131  and the drying apparatus  200 . 
   In the embodiment of the honeycomb formed body drying method, preferably, hot air is applied to the outer peripheral surface wall  144  of the undried honeycomb formed body  141  in the drying space  102 , while the undried honeycomb formed body  141  is rotated about the center axis thereof. Since hot air is applied to the undried honeycomb formed body  141  in a rotating state, the hot air is uniformly applied to the entire outer peripheral surface wall  141 , which is preferred. For the similar reason, preferably, the second hot air is applied to the undried honeycomb formed body  141  in a rotating state. 
   A preferred embodiment of the method for rotating the undried honeycomb formed body  141  will be described with reference to  FIG. 4 . The stand  148  is configured to have a rotatable receiving member  147  and a support  146  for rotatably supporting the receiving member  147 , the receiving member  147  being capable of rotating the undried honeycomb formed body  141  placed on an upper surface thereof virtually about the center axis of the receiving member  147 . The receiving member  147  forming the stand  148  is provided so as to have a pinion part  149  for allowing the receiving member  147  to rotate about the center axis. A rod-like rack part  127  is disposed along a conveyer  121 , which is aligned in the longitudinal direction of the conveyer  121  and has rack part teeth  129  formed on one side facing the stand  148  and along the conveyer  121  such that the rack part teeth  129  are engaged with the pinion part  149  of the receiving member  147  during transfer of the undried honeycomb formed body  141  placed on the stand  148  by means of the conveyer  121 . During transfer of the undried honeycomb formed body  141  placed on the stand  148  by means of the conveyer  121  in the drying chamber  101 , the stand  148  is transferred while the rack part teeth  129  are engaged with the pinion part  149  of the receiving member  147 , thereby rotating the receiving member  147  about the center axis thereof, whereby the undried honeycomb formed body  141  placed on the stand  148  is transferred in the drying apparatus  200  while rotating virtually about the center axis of the receiving member  147 . According to the above method, the energy used to move the undried honeycomb formed body  141  partially serves as a driving source for rotating the undried honeycomb formed body  141 . Therefore, an additional driving source is not required, which is preferred.  FIG. 4  is a cross-section taken along line AA-AA′ in  FIG. 3 . 
     FIG. 5  is a schematic plan view showing that the receiving member  147  of the stand on which the undried honeycomb formed body  141  is placed is rotated by means of the rack part  127 . As shown in  FIG. 5  and mentioned above, the mechanism for rotating the undried honeycomb formed body  141  involves transferring of the stand in the DD direction while the pinion part  149  of the receiving member  147  is engaged with the rack part teeth  129  of the rack part  127  affixed to the inside of the drying chamber; rotating the receiving member  147  about the center axis thereof in a rotational direction R; and rotating the undried honeycomb formed body  141  placed on the stand virtually about the center axis of the receiving member in the rotational direction R. 
   As shown in  FIG. 6 , the undried honeycomb formed body  141  is transferred in the direction DD while being supported by means of the support  146  of the stand and rotating in the rotational direction R. Preferably, a second hot air H is applied to the undried honeycomb formed body  141  in two directions so as to sandwich the structure by means of the hot air application apparatus  128  disposed so as to be aligned the direction DD and sandwich the undried honeycomb formed body  141 .  FIG. 6  is a schematic plan view showing that a second hot air is applied to the undried honeycomb formed body  141  which is rotating. 
   Although the aforementioned combination of the pinion part and the rack part is employed as a mechanism for rotating the undried honeycomb formed body, other methods may also be employed. Examples include a method in which the member on which the undried honeycomb formed body is placed (i.e., receiving member) is directly rotated through a rotational driving system such as a motor; and a method in which a magnet or a like means is buried in the member on which the undried honeycomb formed body is placed (i.e., receiving member) and the member is rotated in a non-contact manner by means of an electromagnetic circuit. 
   As shown in  FIG. 3 , the drying apparatus  200  is provided with a hot air feeding unit  106  and an discharge means  113  for discharging the drying chamber  101 . In the embodiment of the honeycomb formed body drying method, the drying space  102  of the drying chamber  101  can be controlled to a predetermined humidity and temperature through employment of the hot air feeding unit  106  and the forced discharge means  113 . The atmosphere of the drying space  102  may be controlled through adjusting of the properties (i.e., temperature, humidity level, flow rate, and velocity) of the hot air fed through the hot air feeding unit  106 . However, combination of the hot air feeding unit  106  and the forced discharge means  113  is preferred, since the atmosphere can be more precisely controlled. In addition, through provision of a water vapor feeding means (not illustrated) for feeding water vapor into the drying space  102 , more precise atmosphere control can be realized. The forced discharge means  5  has a blower for forced discharge  111  and a duct for forced discharge  112  connected to the blower for forced discharge  111 , and the duct for forced discharge  112  is communicated with the drying chamber  101 . The atmosphere of the drying chamber  101  is discharged in accordance with needs through the blower for forced discharge  111  via the duct for forced discharge  112 . 
   In the case where the water vapor that is fed through the water vapor feeding means into the drying chamber  101 , the water vapor preferably has a temperature of 100 to 120° C. The amount of water vapor fed into the drying chamber  101  and the amount of discharge from the drying chamber  101  to the outside through the blower for forced discharge  111  are appropriately determined in accordance with factors such as the capacity of the drying chamber  101 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  101 . For example, when the capacity of the drying chamber  101  is about 7 m 3 , the amount of water vapor is preferably 90 to 120 kg/Hr, and the discharge rate is preferably 20 to 50 m 3 /min. 
   As shown in  FIG. 3 , electromagnetic wave generators  103  are disposed on the inner surface of the ceiling  123  of the drying chamber  101  along the center axis of the outer frame  124 . The electromagnetic wave generators  103  are distributed in ten zones located with virtually the same intervals. In each zone, as shown in  FIG. 4 , two electromagnetic wave generators are disposed on the ceiling  123  and one electromagnetic wave generator on each side surface  126 ; i.e., total four electromagnetic wave generators  103  are disposed. Thus, 40 electromagnetic wave generators  103  are disposed in the drying chamber  101 . According to the embodiment of the honeycomb formed body drying method, the undried honeycomb formed body  141  is irradiated with an electromagnetic wave of the outer peripheral surface wall  144  side and the top end  145  side. Thus, the inside of the honeycomb formed body is more uniformly irradiated with an electromagnetic wave, and the entirety of the honeycomb formed body more uniformly undergoes high-frequency heating, which is preferred. No particular limitation is imposed on the place and number of the electromagnetic wave generators  103  to be disposed. For example, in each zone, one electromagnetic wave generator  103  may be placed at any place. Alternatively, five or more electromagnetic wave generators  103  may be disposed at any places. The number of the zones where an electromagnetic wave generator  103  is disposed is not limited to ten, and may be appropriately determined in accordance with factors such as the length of the drying chamber  101 . Preferably, the drying chamber  101  is covered with a heat insulating material, whereby the inside temperature of the drying chamber  101  is maintained. In addition, the outer frame  124  is preferably surrounded by a heat insulating material. 
   In the embodiment of the honeycomb formed body drying method, the electromagnetic wave employed for drying preferably has a frequency of 900 to 10,000 MHz, more preferably 2,000 to 10,000 MHz. When the frequency is lower than 900 MHz, water is difficult to undergo high-frequency heating, and a honeycomb formed body may be difficult to dry. In contrast, when the frequency is higher than 2,000 MHz, water effectively undergoes high-frequency heating. As shown in  FIG. 4 , the electromagnetic wave generators  103  may be disposed inside the drying chamber  101 . Alternatively, electromagnetic wave generators  103  may be disposed outside the drying chamber  101 , and the generated electromagnetic wave is guided through a predetermined site of the drying chamber  101  into the drying chamber  101  via a waveguide so as to apply the electromagnetic wave to the undried honeycomb formed body  141 . 
   The energy of the electromagnetic wave applied to the honeycomb formed body is appropriately determined in accordance with factors such as the capacity of the drying chamber  101 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  101 . For example, when the capacity of the drying chamber  1  is about 7 m 3 , the total energy is preferably 150 to 300 kW. When the energy is smaller than 150 kW, the honeycomb formed body may fail to be dried to a predetermined drying degree, whereas when the energy is higher than 300 kW, the vaporization speed of water from the honeycomb formed body is elevated, difficulty may be encountered in reduction of the difference in drying condition between the inner part of the honeycomb formed body and the outer part thereof, even though the drying space is heated and humidified. 
   In the embodiment of the honeycomb formed body drying method, as mentioned above, preferably, an undried honeycomb formed body is dried through electromagnetic wave irradiation to form a dried honeycomb formed body, and hot air (hot air for post-drying) is applied to the dried honeycomb formed body for further drying. Through this procedure, the remaining water content can be reduced to 0.5% or lower. In a preferred manner for applying hot air (hot air for post-drying) to the dried honeycomb formed body for further drying, as shown in  FIG. 3 , the dried honeycomb formed body  142  is transferred by means of a conveyer  121  to a post-drying chamber  131  having a post-drying space  137  and provided in the vicinity of the outlet of the outer frame  124 . The hot air for post-drying fed through hot air feeding nozzles  134  disposed under the post-drying chamber  131  is applied to the dried honeycomb formed body  142  in the direction from the bottom to the top end. The hot air fed through hot air feeding nozzles  134  to the post-drying chamber  131  is discharged to the outside through a hot air discharge duct  135  disposed above the post-drying chamber  131  (space between the ceiling  123  and the roof  125 ). The aforementioned hot air for post-drying preferably has a temperature of 100 to 130° C. When the temperature is lower than 100° C., the dried honeycomb formed body  142  may be difficult to dry, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the dried honeycomb formed body  142  are vaporized, causing deformation of partition walls of the dried honeycomb formed body  142  and burning of the organic binder and other substances, which are problematic. 
   The hot air feeding nozzles  134  are linked to the post-drying hot air generator  132  via the hot air feeding piping  133  so that the hot air for post-drying generated by the post-drying hot air generator  132  is transferred via the hot air feeding piping  133  and discharged through the hot air feeding nozzles  134 . No particular limitation is imposed on the type of the post-drying hot air generator  132  so long as the generator attains predetermined temperature and flow rate. For example, a hot air generator having a heater employing high-temperature water vapor or an electric heater and a blower may be used. In the generator, a blow generated by the blower is heated to provide hot air. The hot air for post-drying generated by the post-drying hot air generator  132  may be used for preliminarily heating the unheated drying chamber  101  before the start of electromagnetic wave drying of the undried honeycomb formed body. In  FIG. 3 , hot air is fed into the drying chamber  101  via a piping for preliminary heating  136  connected to the post-drying hot air generator  132 . 
   The embodiment of the honeycomb formed body drying method is suitable for drying a honeycomb formed body made of ceramic material, having a percent opening of 80% or more and a partition wall thickness of 0.18 mm or less. As used herein, the term “percent opening” refers to a ratio (percent) of the total cross-sectional area of the cell through-holes to the cross-sectional area of the honeycomb formed body in which the cell through-holes are located, as viewed in a cross-section of a honeycomb formed body cut in a direction normal to the center axis. 
   The drying apparatus employed in the embodiment of the honeycomb formed body drying method continuously dries honeycomb formed bodies and may be a batch-type. In use, the batch-type drying apparatus is such that a predetermined number of undried honeycomb formed bodies are accommodated therein and irradiated with an electromagnetic wave to thereby dry the honeycomb formed bodies; irradiation of the electromagnetic wave is stopped; the thus-dried honeycomb formed bodies are removed; another predetermined number of undried honeycomb formed bodies are accommodated therein; and irradiation of an electromagnetic wave is started. 
   An embodiment of the first mode of the honeycomb formed body drying apparatus of the present invention will next be described.  FIG. 7  is a schematic cross-sectional view showing an embodiment according to the first mode of the honeycomb formed body drying apparatus of the present invention. 
   The apparatus  300  of the present embodiment for drying a honeycomb formed body (hereinafter may be referred to simply as “drying apparatus  300 ”) shown in  FIG. 7  is such that a honeycomb formed body in an undried state (i.e., undried honeycomb formed body)  91  which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls is subjected to high-frequency heating through electromagnetic wave irradiation, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed body  91  so as to dry the undried honeycomb formed body  91 , thereby producing a dried honeycomb formed body  92 . The inner part and outer part of the undried honeycomb formed body  91  are the same as the inner part and outer part of the undried honeycomb formed body  41  shown in  FIG. 1  dried through the aforementioned honeycomb formed body drying method of the present invention. 
   The drying apparatus  300  of the embodiment includes, in a cylindrical outer frame  74 , a drying chamber  51  having a drying space  52  for accommodating an undried honeycomb formed body  91  in a humidified and heated atmosphere; an electromagnetic wave generator  53  for generating an electromagnetic wave with which the undried honeycomb formed body  91  accommodated in the drying chamber  51  is to be irradiated such that 50 to 99 mass % of water contained in the undried formed body  91  is evaporated at the end of irradiation; and an atmosphere controlling unit  56  having a water vapor feeding means  54  and a forced discharge means  55  and allowing the humidified and heated atmosphere in the drying space  52  to maintain at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. 
   The outer frame  74  forming the drying apparatus  300  is formed in a cylindrical shape such that the center axis is oriented virtually in the horizontal direction. An undried honeycomb formed body  91  is transferred into the drying apparatus through one end of the cylinder, and the dried honeycomb formed body  92  is removed through the other end thereof. In the outer frame  74 , a ceiling  73  is disposed virtually in the horizontal direction so as to provide a space between the ceiling and a roof  75  of the outer frame, and divides the outer frame  74  into two chambers. The drying chamber  51  is formed into a cylinder, and the center axis of the cylinder virtually aligns the center axis of the outer frame  74 . The drying chamber is disposed under (in the vertical direction) the roof  75  formed in the outer frame  74 . In the drying chamber  300 , a conveyer  71  is disposed so as to extend from one end (inlet end) of the outer frame  74  to the other end (outlet end) of the outer frame  74  through the inside of the cylindrical drying chamber  51  so that the undried honeycomb formed bodies  91  are continuously transferred into the chamber and the thus-dried honeycomb formed bodies  92  are continuously removed to the outside. No particular limitation is imposed on the type of the conveyer  71 , and a belt conveyer, a roller conveyer, and other conveyers may be employed. 
   In the embodiment, the honeycomb formed body drying apparatus  300  has the above configuration. The humidified and heated atmosphere in the drying space  52  is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. by means of an atmosphere controlling unit  56 . In order to evaporate 50 to 99 mass % of water contained in the formed body  91  at the end of high-frequency heating, the amount of water vaporized from the outer part of the undried honeycomb formed body  91 , which amount is smaller than that of water vaporized from the inner part of the formed body  91  through high-frequency heating alone, is increased (in the aforementioned humidified and heated atmosphere), thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body  91  and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body  91  and that of the outer part thereof, thereby producing a dried honeycomb formed body  92  in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed. The difference in water content between the inner part of the dried honeycomb formed body  92  and the outer part thereof (the amount of water of the undried honeycomb formed body from which the amount of vaporized water has been subtracted is divided by the amount of water which the undried honeycomb formed body has contained, and the value is multiplied with 100) is preferably 10 mass % or less. Through controlling the water content, deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part can be suppressed. 
   Deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part occurs by the following mechanism. During drying of the undried honeycomb formed body  91 , partition walls are shrunken. If the honeycomb formed body is not dried uniformly, difference in shrinkage degree of partition walls is provided. The difference causes warpage. Thus, deformation of partition walls such as warpage occurs. In the embodiment of the honeycomb formed body drying method, such deformation of partition walls can be prevented. The term “deformation of partition walls” is used to refer to warpage of partition walls, generation of wrinkles, generation of wrinkles in the outermost peripheral surface wall, formation of dents, etc. 
   When the humidity level in the drying space  52  is lower than 30%, an outer peripheral surface wall  94  (see  FIG. 4 ) of the undried honeycomb formed body  91  is dried excessively rapidly. Thus, defects are generated in the outer peripheral surface wall  94 , which is problematic. A humidity level in the drying space of higher than 65% is also problematic. Specifically, the amount of water vaporized from the outer part of the undried honeycomb formed body  91  is generally smaller than that of vaporized from the inner part at an initial drying stage, providing a difference in drying degree between the inner part and the outer part, resulting in deformation of partition walls such as wrinkles. When the humidity level is excessively high, the difference in drying degree between the inner part and the outer part increases, resulting in deformation of partition walls, which is problematic. In addition, when the humidity level is high, the amount of water vaporized from the undried honeycomb formed body problematically decreases due to loss of the energy of the input electromagnetic wave. Therefore, the humidity level in the drying space  52  is more preferably 30 to 50%. 
   When the inside temperature of the drying space  52  is lower than 75° C., the undried honeycomb formed body  91  is difficult to dry, resulting in problematic wrinkles in the outer peripheral surface wall, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  91  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  91 , and the organic binder may be burnt. Needless to say, both cases are problematic. Thus, the inside temperature of the drying space  52  is preferably 90 to 110° C. When the inside temperature falls within a range of 75 to 90° C., the produced honeycomb formed bodies have no problem in quality. However, difference in water content between the inner part of the honeycomb formed body and the outer part thereof as low as less than 10 mass % may result. In addition, a longer drying time may be required so as to compensate drop in drying efficiency. 
   When the percent vaporized water amount of the undried honeycomb formed body is less than 50 mass %, shrinkage of the honeycomb formed body is not complete. When water is further vaporized, the honeycomb formed body further shrinks not uniformly, resulting in deformation of partition walls of the honeycomb formed body, which is problematic. When the percent vaporized water amount of the undried honeycomb formed body is more than 99 mass %, the honeycomb formed body is over dried locally, and scorching may occur due to burning of a binder, which is also problematic. As used herein, the term “percent vaporized water amount of the undried honeycomb formed body” refers to a value obtained by dividing the mass of vaporized water by the mass of water contained in the undried honeycomb formed body and multiplying 100. 
   When the undried honeycomb formed body  92  is dried by means of the drying apparatus  300  of the present embodiment, the following procedure is employed. Firstly, the undried honeycomb formed body  91  is transferred into the chamber through one end of the outer frame  74  and placed on the conveyer  71 . The undried honeycomb formed body  91  is conveyed through driving force of the conveyer  71  so as to move in the honeycomb formed body conveyance direction E, followed by transferring into the drying chamber  51  through one end of the drying chamber  51  by means of the conveyer  71 . While the undried honeycomb formed body  91  is conveyed by means of the conveyer  71  in the drying chamber  51  as a honeycomb formed body  93  in a drying state, the undried honeycomb formed body  91  is subjected to high-frequency heating for drying through irradiation with an electromagnetic wave generated by the electromagnetic wave generator  53  in the drying space  52  of which atmosphere is controlled to a predetermined humidity and temperature by means of the atmosphere controlling unit, to thereby form the dried honeycomb formed body  92 . Subsequently, the thus-dried honeycomb formed body  92  is removed from the drying chamber  51  through the other end thereof and transferred to a hot air drying chamber  81 . The dried honeycomb formed body  92  is conveyed by means of the conveyer  71  in the hot air drying chamber  81 , while further dried through application of hot air to the formed body  92 . Subsequently, the formed body  92  is removed from the hot air drying chamber  81  and the drying apparatus  200 . 
   As shown in  FIG. 7 , the drying apparatus  300  includes the atmosphere controlling unit  56  for controlling the drying space  52  in the drying chamber  51  to a predetermined humidity and temperature. The atmosphere controlling unit  56  has a water vapor feeding means  54  for feeding water vapor into the drying chamber  51 , and a forced discharge means  55  for discharging the drying chamber  51 . The water vapor feeding means  54  is a piping having at the tip nozzles through which water vapor is discharged, and the tip is inserted in the drying chamber  51 . Water vapor to be employed is generated by means of, for example, a water vapor generator and fed through the piping. In the forced discharge means  55 , the piping connected to a blower for forced discharge  61  is branched into two. The tip of one branch is inserted into the space near one end of the drying chamber  61 , and the tip of the other branch is inserted into a space near the other end of the drying chamber  51 . The gas present in the drying chamber  51  is discharged so as to control the atmosphere of the drying space  52  by means of the blower for forced discharge  61  to the outside in accordance with need through the piping. 
   The water vapor that is fed through the water vapor feeding means  54  into the drying chamber  51  preferably has a temperature of 100 to 120° C. The amount of water vapor fed into the drying chamber  51  and the amount of discharge from the drying chamber  51  to the outside through the blower for forced discharge  61  are appropriately determined in accordance with factors such as the capacity of the drying chamber  51 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  51 . For example, when the capacity of the drying chamber  51  is about 7 m 3 , the water vapor in flow is preferably 90 to 120 kg/Hr, and the discharge rate is preferably 20 to 50 m 3 /min. 
   As shown in  FIG. 7 , electromagnetic wave generators  53  are disposed on the inner surface of the ceiling  73  of the drying chamber  51  along the center axis of the outer frame  74 . The electromagnetic wave generators  53  are distributed in ten zones located with virtually the same intervals. In each zone, as shown in  FIG. 8 , two electromagnetic wave generators are disposed on the ceiling  73  and one electromagnetic wave generator on each side surface  76 ; i.e., total four electromagnetic wave generators  53  are disposed. Thus, 40 electromagnetic wave generators  53  are disposed in the drying chamber  51 .  FIG. 8  is a cross-section taken along line B-B′ in  FIG. 7 . According to the embodiment of the honeycomb formed body drying method, the drying honeycomb formed body  93  is irradiated with an electromagnetic wave of the outer peripheral surface wall  94  side and the top end  95  side. Thus, the inside of the honeycomb formed body is more uniformly irradiated with an electromagnetic wave, and the entirety of the honeycomb formed body more uniformly undergoes high-frequency heating, which is preferred. No particular limitation is imposed on the place and number of the electromagnetic wave generators  53  to be disposed. For example, in each zone, one electromagnetic wave generator  53  may be placed at any place. Alternatively, five or more electromagnetic wave generators  53  may be disposed at any places. The number of the zones where an electromagnetic wave generator  53  is disposed is not limited to ten, and may be appropriately determined in accordance with factors such as the length of the drying chamber  51 . The electromagnetic wave generator  53  is preferably disposed at such a place that the electromagnetic wave is applied to the honeycomb formed body  93  as uniformly as possible. Preferably, the drying chamber  51  is covered with a heat insulating material, whereby the inside temperature of the drying chamber  51  is maintained. In addition, the outer frame  74  is preferably surrounded by a heat insulating material. 
   In the embodiment of the honeycomb formed body drying method, the electromagnetic wave employed for drying preferably has a frequency of 900 to 10,000 MHz, more preferably 2,000 to 10,000 MHz. When the frequency is lower than 900 MHz, water is difficult to undergo high-frequency heating, and a honeycomb formed body may be difficult to dry. In contrast, when the frequency is higher than 2,000 MHz, water effectively undergoes high-frequency heating. As shown in  FIG. 4 , the electromagnetic wave generators  53  may be disposed inside the drying chamber  51 . Alternatively, electromagnetic wave generators  53  may be disposed outside the drying chamber  51 , and the generated electromagnetic wave is guided through a predetermined site of the drying chamber  51  into the drying chamber  51  via a waveguide so as to apply the electromagnetic wave to the drying honeycomb formed body  93 . 
   The energy of the electromagnetic wave applied to the honeycomb formed body is appropriately determined in accordance with factors such as the capacity of the drying chamber  51 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  51 . For example, when the capacity of the drying chamber  51  is about 7 m 3 , the total energy is preferably 150 to 300 kW. When the energy is smaller than 150 kW, the honeycomb formed body may fail to be dried to a predetermined drying degree, whereas when the energy is higher than 300 kW, the vaporization speed of water from the honeycomb formed body is elevated, difficulty may be encountered in reduction of the difference in drying condition between the inner part of the honeycomb formed body and the outer part thereof. 
   As shown in  FIG. 7 , the drying apparatus  300  of the embodiment includes a hot air drying chamber  81  provided in the vicinity of the outlet of the outer frame  74 . The hot air drying chamber  81  is present in the vicinity of the outlet of the outer frame  74  and has a space between the ceiling  73  and the conveyer  71  (hot air drying space  87 ). As mentioned above, in the hot air drying chamber  81 , hot air is applied to the dried honeycomb formed body  92  for further drying. Upon performance of further drying in the hot air drying chamber  81 , the dried honeycomb formed body  92  is transferred by means of a conveyer  71  to a hot air drying chamber  81 . Preferably, the hot air fed through hot air feeding nozzles  84  disposed under the hot air drying chamber  81  is applied to the dried honeycomb formed body  92  in the direction from the bottom to the top end. The hot air fed through hot air feeding nozzles  84  to the hot air drying chamber  81  is discharged to the outside through a hot air discharge duct  85  disposed above the hot air drying chamber  81  (space between the ceiling  73  and the roof  75 ). The aforementioned hot air preferably has a temperature of 100 to 130° C. When the temperature is lower than 100° C., the dried honeycomb formed body may be difficult to dry, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  91  are vaporized, causing deformation of partition walls of the undried honeycomb formed body  91  and burning of the organic binder and other substances, which are problematic. 
   The hot air feeding nozzles  84  are linked to the hot air generator  82  via a piping so that the hot air generated by the hot air generator  82  is transferred via the piping and discharged through the hot air feeding nozzles  84 . No particular limitation is imposed on the type of the hot air generator  82  so long as the generator attains predetermined temperature and flow rate. For example, a hot air generator having a heater employing high-temperature water vapor or an electric heater and a blower may be used. In the generator, a blow generated by the blower is heated to provide hot air. The hot air generated by the hot air generator  82  may be used for preliminarily heating the unheated drying chamber  51  before the start of electromagnetic wave drying of the undried honeycomb formed body. In  FIG. 7 , hot air is fed into the drying chamber  51  via a piping for preliminary heating  86  connected to the hot air generator  82 . 
   The honeycomb formed body to be suitably dried in the embodiment is made of ceramic material, having a percent opening of 80% or more and a partition wall thickness of 0.18 mm or less. As used herein, the term “percent opening” refers to a ratio (percent) of the total cross-sectional area of the cell through-holes to the cross-sectional area of the honeycomb formed body in which the cell through-holes are located, as viewed in a cross-section of a honeycomb formed body cut in a direction normal to the center axis. 
   The drying apparatus of the embodiment continuously dries honeycomb formed bodies and may be a batch-type. In use, the batch-type drying apparatus is such that a predetermined number of undried honeycomb formed bodies are accommodated therein and irradiated with an electromagnetic wave to thereby dry the honeycomb formed bodies; irradiation of the electromagnetic wave is stopped; the thus-dried honeycomb formed bodies are removed; another predetermined number of undried honeycomb formed bodies are accommodated therein; and irradiation of an electromagnetic wave is started. 
   An embodiment of the second mode of the honeycomb formed body drying apparatus of the present invention will next be described.  FIG. 9  is a schematic cross-sectional view showing an embodiment according to the second mode of the honeycomb formed body drying apparatus of the present invention. 
   The apparatus  400  of the present embodiment for drying a honeycomb formed body (hereinafter may be referred to simply as “drying apparatus  400 ”) shown in  FIG. 9  is such that a honeycomb formed body in an undried state (i.e., undried honeycomb formed body)  191  which is formed from a raw material composition containing a ceramic raw material and water and which has a plurality of cells defined by partition walls is subjected to high-frequency heating through electromagnetic wave irradiation, whereby water is vaporized from an inner part and an outer part of the undried honeycomb formed body  191  so as to dry the undried honeycomb formed body  191 , thereby producing a dried honeycomb formed body  192 . The inner part and outer part of the undried honeycomb formed body  191  are the same as the inner part and outer part of the undried honeycomb formed body  141  shown in  FIG. 3  dried through the aforementioned honeycomb formed body drying method of the present invention. 
   The drying apparatus  400  includes, in a cylindrical outer frame  174 , a drying chamber  151  having a drying space  152  for accommodating an undried honeycomb formed body  191  in a humidified and heated atmosphere; an electromagnetic wave generator  153  for generating an electromagnetic wave with which the undried honeycomb formed body  191  accommodated in the drying chamber  151  is to be irradiated for performing high-frequency heating of the undried honeycomb formed body  191 ; and a hot air feeding unit  156  for feeding hot air into the drying space  152 , which hot air feeding unit being provided so that the amount of water vaporized from the outer part of the undried honeycomb formed body  191 , which amount is smaller than that of water vaporized from the inner part of the formed body through high-frequency heating alone, is increased, such that 50 to 99 mass % of water contained in the undried formed body  191  is evaporated at the end of irradiation, and the humidified and heated atmosphere in the drying space  152  is maintain at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. The drying apparatus  400  of the embodiment further has a hot air application apparatus  178  for applying hot air for heating to the outer peripheral surface wall of the undried honeycomb formed body  191  accommodated in the drying chamber  151 , and a forced discharge means  163  for forcedly discharging the drying space  152 . 
   The outer frame  174  forming the drying apparatus  400  is formed in a cylindrical shape such that the center axis is oriented virtually in the horizontal direction. An undried honeycomb formed body  191  is transferred into the drying apparatus through one end of the cylinder, and the dried honeycomb formed body  192  is removed through the other end thereof. In the outer frame  174 , a ceiling  173  is disposed virtually in the horizontal direction so as to provide a space between the ceiling and a roof  175  of the outer frame, and divides the outer frame  174  into two chambers. The drying chamber  151  is formed into a cylinder, and the center axis of the cylinder virtually aligns the center axis of the outer frame  174 . The drying chamber is disposed under (in the vertical direction) the roof  175  formed in the outer frame  174 . In the drying chamber  400 , a conveyer  171  is disposed so as to extend from one end (inlet end) of the outer frame  174  to the other end (outlet end) of the outer frame  174  through the inside of the cylindrical drying chamber  151  so that the undried honeycomb formed bodies  191  are continuously transferred into the chamber and the thus-dried honeycomb formed bodies  192  are continuously removed to the outside. 
   In the vicinity of the inlet end of the drying chamber  151  for transferring the undried honeycomb formed bodies  191 , there is provided a hot air feeding unit  156  having a hot air generator  154  for generating hot air and a hot air introducing member  155  for feeding hot air generated by the hot air generator  154  into the drying space  152  of the drying chamber  151 . The hot air fed into the drying space  152  through the hot air feeding unit  156  is applied to the undried honeycomb formed body  191  transferred into the drying space  152 , thereby drying the undried honeycomb formed body  191 . 
   In the vicinity of the outlet end of the drying chamber  151  for removing the undried honeycomb formed bodies  191 , there is provided a forced discharge means  163  having a blower for forced discharge  161  and a duct for forced discharge  162 , through which means the drying space  152  is discharged. 
   In the drying chamber  151 , a hot air application apparatus  178  is disposed so as to sandwich the conveyer  171  along the direction EE of transferring the undried honeycomb formed body  191 . The hot air application apparatus  178  has a second hot air application section (not illustrated) for applying hot air (second hot air). The second hot air application section (not illustrated) is formed such that the second hot air is applied to the outer peripheral wall  144  in two directions opposing each other and being normal to the center axis of the undried honeycomb formed body  191 , whereby the second hot air is applied to the undried honeycomb formed body  191  in two directions so as to sandwich the outer peripheral wall  194 . 
   Preferably, the distance between the application site of the second hot air application section and the outer peripheral surface wall of the honeycomb formed body is 0.1 to 1.0 m. When the distance is less than 0.1 m, the hot air may applied to a portion of the outer peripheral surface wall, whereas when the distance is in excess of 1.0 m, the second hot air which cannot be applied to the outer peripheral surface wall but which is fed to the other sites predominates, possibly reducing the second hot air application efficiency. 
   Preferably, the second blow application section of the hot air application apparatus  178  has a plurality of tubular nozzles (hot air application nozzles), through which hot air is applied to the outer peripheral surface wall  194  of the undried honeycomb formed body  191 . More preferably, the hot air application nozzles are aligned along the center axis (top to bottom) of the undried honeycomb formed body  191 , while the axis of each hot air application nozzle is aligned in the horizontal direction and the tip of the nozzle faces the outer peripheral surface wall  194 , whereby the second hot airs are simultaneously applied to the outer peripheral surface wall  194  from the top end to the bottom thereof. In this case, the line passing through the nozzle tips is virtually aligned in the center axis of the undried honeycomb formed body  191 . Through employment of the configuration, the second hot air can be applied to the entire outer peripheral surface wall  194  during movement of the undried honeycomb formed body  191 . Preferably, a plurality of sets of nozzles being aligned in the center axis of the undried honeycomb formed body  191  are arranged in the direction EE of transferring the undried honeycomb formed body  191  such that the nozzle lines are arranged virtually in parallel one another, whereby second hot airs provided by the nozzle sets are sequentially applied to the outer peripheral surface wall  194  during transfer of the undried honeycomb formed body  191 . However, the nozzles in each nozzle set are not necessarily in the same line, and a zigzag or an irregular arrangement may also be employed, so long as the second hot air can be applied to the outer peripheral surface wall  194  uniformly from the top end to the bottom thereof. 
   The second hot air application section does not necessarily have hot air application nozzles and, instead, may have a piping having a plurality of holes through which the hot air is applied. No particular limitation is imposed on the position and number of the hot air application nozzles and the holes of the piping so long as the hot air can be effectively applied to the entire outer peripheral surface wall  194  of the undried honeycomb formed body  191 . Preferably, the position and number of the hot air application nozzles and the holes of the piping can be altered in accordance with the dimensions undried honeycomb formed body  191 . 
   In the embodiment, the honeycomb formed body drying apparatus  400  has the above configuration. The humidified and heated atmosphere in the drying space  152  is maintained at a humidity level as low as 30 to 65% and a temperature of 75 to 130° C. by means of hot air. In order to evaporate 50 to 99 mass % of water contained in the formed body  141  at the end of heating, the amount of water vaporized from the outer part of the undried honeycomb formed body  191 , which amount is smaller than that of water vaporized from the inner part of the formed body  191  through high-frequency heating alone, is increased through high-frequency heating of the undried honeycomb formed body  191  and application of the hot air to the undried honeycomb formed body  191  (in the aforementioned humidified and heated atmosphere with application of the hot air to the outer peripheral wall  194 ), thereby reducing a difference between amount of water vaporized from the inner part of the undried honeycomb formed body  191  and that of water vaporized from the outer part thereof as well as reducing a difference between drying degree of the inner part of the undried honeycomb formed body  191  and that of the outer part thereof, thereby producing a dried honeycomb formed body  192  in which deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part is suppressed. The difference in water content between the inner part of the dried honeycomb formed body  192  and the outer part thereof (the amount of water of the undried honeycomb formed body from which the amount of vaporized water has been subtracted is divided by the amount of water which the undried honeycomb formed body has contained, and the value is multiplied with 100) is preferably 10 mass % or less. Through controlling the water content, deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part can be suppressed. 
   In addition to the hot air fed by means of the hot air feeding unit  156 , hot air (second hot air) is applied to the outer peripheral surface wall  194  of the undried honeycomb formed body  191  at a predetermined distance from the wall, to thereby further reduce a difference between drying degree of the inner part of the undried honeycomb formed body  191  and that of the outer part thereof, thereby further suppressing deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part. In order to promote drying of the outer part, which is difficult to dry through sole high-frequency, and to control the drying state to that of the inner part, which is readily dried through sole heating high-frequency heating, preferably, application of the second hot air applied to the outer peripheral surface wall  194  of the undried honeycomb formed body  191  is carried out only to the outer peripheral surface wall  194  of the undried honeycomb formed body  191  and not to the top end and the bottom thereof. If the second hot air is applied to the top end and the bottom, the difference in the amount of water vaporization between the inner part of the undried honeycomb formed body  191  and the outer part thereof may be difficult to reduce. 
   Deformation of the partition walls caused by the difference between drying degree of the inner part and that of the outer part occurs by the following mechanism. During drying of the undried honeycomb formed body  191 , partition walls are shrunken. If the honeycomb formed body is not dried uniformly, difference in shrinkage degree of partition walls is provided. The difference causes warpage. Thus, deformation of partition walls such as warpage occurs. In the embodiment of the honeycomb formed body drying method, such deformation of partition walls can be prevented. The term “deformation of partition walls” is used to refer to warpage of partition walls, generation of wrinkles, generation of wrinkles in the outermost peripheral surface wall, formation of dents, etc. 
   When the humidity level in the drying space  152  is lower than 30%, an outer peripheral surface wall  194  of the undried honeycomb formed body  191  is dried excessively rapidly. Thus, defects are generated in the outer peripheral surface wall  194 , which is problematic. A humidity level in the drying space of higher than 65% is also problematic. Specifically, the amount of water vaporized from the outer part of the undried honeycomb formed body  191  is generally smaller than that of vaporized from the inner part at an initial drying stage, providing a difference in drying degree between the inner part and the outer part, resulting in deformation of partition walls such as wrinkles. When the humidity level is excessively high, the difference in drying degree between the inner part and the outer part increases, resulting in deformation of partition walls, which is problematic. In addition, when the humidity level is high, the amount of water vaporized from the undried honeycomb formed body problematically decreases due to loss of the energy of the input electromagnetic wave. Therefore, the humidity level in the drying space  52  is more preferably 30 to 50%. 
   When the inside temperature of the drying space  152  is lower than 75° C., the undried honeycomb formed body  191  is difficult to dry, resulting in problematic wrinkles in the outer peripheral surface wall, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  191  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  191 , and the organic binder may be burnt. Needless to say, both cases are problematic. Thus, the inside temperature of the drying space  152  is preferably 90 to 110° C. When the inside temperature falls within a range of 75 to 90° C., the produced honeycomb formed bodies have no problem in quality. However, difference in water content between the inner part of the honeycomb formed body and the outer part thereof as low as less than 10 mass % may result. In addition, drying of the entire molded body may be insufficient. 
   When the percent vaporized water amount of the undried honeycomb formed body is less than 50 mass %, shrinkage of the honeycomb formed body is not complete. When water is further vaporized, the honeycomb formed body further shrinks not uniformly, resulting in deformation of partition walls of the honeycomb formed body, which is problematic. When the percent vaporized water amount of the undried honeycomb formed body is more than 99 mass %, the honeycomb formed body is over dried locally, and scorching may occur due to burning of a binder, which is also problematic. As used herein, the term “percent vaporized water amount of the undried honeycomb formed body” refers to a value obtained by dividing the mass of vaporized water by the mass of water contained in the undried honeycomb formed body and multiplying 100. 
   The hot air fed through the hot air feeding unit  156  into the drying space  52  preferably has a velocity of 0.5 to 10 m/s, more preferably 2 to 10 m/s, and preferably has a flow rate of 3 to 60 m 3 /s, more preferably 12 to 60 m 3 /s. When the velocity is less than 0.5 m/s, heating of the outer part of the undried honeycomb formed body  191  through the hot air may be insufficient, whereas when the velocity is more than 10 m/s, the undried honeycomb formed body  191  may undesirably be moved, or the outer peripheral surface wall  194  may be deformed. When the flow rate is less than 3 m 3 /s, heating of the outer part of the undried honeycomb formed body  191  through the hot air may be insufficient, whereas when the flow rate is more than 60 m 3 /s, the undried honeycomb formed body  191  may undesirably be moved, or the outer peripheral surface wall  194  may be deformed. 
   The hot air fed through the hot air feeding unit  156  into the drying space  152  preferably has a temperature of 80 to 135° C., more preferably 95 to 110° C. When the temperature is lower than 80° C., the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  191  may be reduced, whereas when the temperature is higher than 135° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  191  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  191 , and the organic binder may be burnt, which are problematic. 
   The hot air fed through the hot air feeding unit  156  into the drying space  152  preferably has a humidity level of 20% or less, more preferably 15% or less. When the humidity level is higher than 20%, the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  191  may be reduced. 
   In the present embodiment, in addition to the aforementioned hot air fed through the hot air feeding unit  156 , a second hot air is preferably applied to the outer peripheral surface wall  194  of the undried honeycomb formed body  191  at a predetermined distance from the wall. In this case, the second hot air preferably has a velocity of 0.5 to 10 m/s, more preferably 2 to 10 m/s. When the velocity is less than 0.5 m/s, heating of the outer part of the undried honeycomb formed body  191  through the second hot air may be insufficient, the effect of promoting vaporization of water from the outer peripheral surface wall  194  of the undried honeycomb formed body  191  by virtue of the second hot air may be reduced, the effect being based on blowing out water vapor residing in the vicinity of the outer peripheral surface wall  194  of the undried honeycomb formed body  191 , whereby the humidity around the outer peripheral surface wall  194  is reduced. When the velocity is more than 10 m/s, the undried honeycomb formed body  191  may undesirably be moved, or the outer peripheral surface wall  194  may be deformed. Upon application of the second hot air to the outer peripheral surface wall  194  of the undried honeycomb formed body  191 , the second hot air is preferably applied to the entire outer peripheral surface wall  194 . Thus, the second hot air can be applied to the entire outer peripheral surface wall  194  at the aforementioned predetermined velocity, whereby vaporization of water from the outer peripheral surface wall  194  of the undried honeycomb formed body  191  can be effectively promoted. 
   The second hot air fed through the hot air application apparatus  178  to the outer peripheral surface wall  194  preferably has a temperature of 80 to 135° C., more preferably 95 to 110° C. When the temperature is lower than 80° C., the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  191  may be reduced, whereas when the temperature is higher than 135° C., substances other than water such as an organic binder contained in the undried honeycomb formed body  191  are vaporized, leading to deformation of partition walls of the undried honeycomb formed body  191 , and the organic binder may be burnt, which are problematic. 
   The second hot air fed through the hot air application apparatus  178  to the outer peripheral surface wall  194  preferably has a humidity level of 20% or less. When the humidity level is higher than 20%, the effect of promoting vaporization of water from the outer part of the undried honeycomb formed body  191  may be reduced. 
   In the present embodiment, the aforementioned hot air feeding unit  156  has a hot air generator  154  for generating hot air and a hot air introducing member  155  for feeding hot air generated by the hot air generator  154  into the drying space  152  of the drying chamber  151 . No particular limitation is imposed on the type of the hot air generator  154  so long as the generator attains predetermined temperature and flow rate. For example, a hot air generator having a heater employing high-temperature water vapor or an electric heater and a blower may be used. In the generator, a blow generated by the blower is heated to provide hot air. The temperature of the hot air low may be controlled basically by means of the above heater, and the humidity thereof may be controlled by means of a demoisturizer or a similar device. 
   As shown in  FIG. 9 , the tubular nozzle of the hot air introducing member  155  may be inserted into the drying chamber  151 . Alternatively, the drying chamber  151  may be provided with a hole; the hot air generated by the hot air generator  154  is transferred to the hole through a piping; and the hot air is introduced into the drying chamber  151  through the hole. When the nozzle is inserted into the drying chamber  151 , the nozzle is preferably oriented in a desired direction. 
   During drying of an undried honeycomb formed body in the drying chamber, when a second hot air is applied by means of a hot air application apparatus to the undried honeycomb formed body in an initial drying stage, the outer peripheral surface wall of the undried honeycomb formed body may be more rapidly dried as compared with the inner part thereof. Therefore, the second hot air is preferably applied, while whether or not the undried honeycomb formed body is sufficiently heated through high-frequency heating is checked by means of an IR sensor or a similar means. Alternatively, high-frequency heating is performed in an initial drying stage, and the second hot air is applied to the undried honeycomb formed body when the structure has reached a predetermined position in the drying chamber (i.e., position where the structure is in a sufficiently heated state through high-frequency heating). 
   When the undried honeycomb formed body  192  is dried by means of the drying apparatus  400  of the present embodiment, the following procedure is employed. Firstly, the undried honeycomb formed body  191  is transferred into the chamber through one end of the outer frame  174  and placed on the conveyer  171 . The undried honeycomb formed body  191  is conveyed through driving force of the conveyer  171  so as to move in the honeycomb formed body conveyance direction E, followed by transferring into the drying chamber  151  through one end of the drying chamber  151  by means of the conveyer  171 . While the undried honeycomb formed body  191  is conveyed by means of the conveyer  171  in the drying chamber  151 , the undried honeycomb formed body  191  is subjected to high-frequency heating for drying through irradiation with an electromagnetic wave generated by the electromagnetic wave generator  153  in the drying space  152  of a predetermined humidity and temperature, and the hot air fed through the hot air feeding unit  156  is applied to the honeycomb formed body. In addition, the second hot air is applied to the outer peripheral wall  194  through the hot air application apparatus  178  so as to promote drying the outer part, to thereby form the dried honeycomb formed body  192  of which entirety is almost uniformly dried. Subsequently, the thus-dried honeycomb formed body  192  is removed from the drying chamber  151  through the other end thereof and transferred to a post-drying chamber  181 . The dried honeycomb formed body  192  is conveyed by means of the conveyer  171  in the post-drying chamber  181 , while further dried through application of hot air to the formed body  192 . Subsequently, the formed body  192  is removed from the post-drying chamber  181  and the drying apparatus  400 . 
   The drying apparatus of the embodiment is preferably configured as shown in  FIG. 10 . Specifically, the drying apparatus has a stand  198  having a rotatable receiving member  197  and a support  196  for rotatably supporting the receiving member  197 , the receiving member  197  being capable of rotating an undried honeycomb formed body  191  placed on an upper surface thereof virtually about the center axis of the receiving member  197 , wherein the undried honeycomb formed body  191  is placed on the receiving member  197  of the stand  198  during drying of the undried honeycomb formed body  191  in a drying chamber  151 ; the undried honeycomb formed body  191  and the stand  198  are transferred into the drying chamber  151 ; the undried honeycomb formed body  191  is dried while the undried honeycomb formed body  191  is rotated in the rotational direction S through rotation of the receiving member  197  in the rotational direction S, to thereby provide a dried honeycomb formed body; and the dried honeycomb formed body and the stand  198  are removed from the drying chamber  151 . Since hot air is applied to the undried honeycomb formed body  191  in a rotating state, the hot air is uniformly applied to the entire outer peripheral surface wall  194 , which is preferred. For the similar reason, preferably, the second hot air is applied to the undried honeycomb formed body  191  in a rotating state. 
   In a preferred configuration for rotating the undried honeycomb formed body  191  in the drying chamber  151 , the receiving member  197  forming the stand  198  has a pinion part  199  for allowing the receiving member  197  to rotate about the center axis, and the drying apparatus  400  further has, in the drying chamber  151 , a rod-like rack part  177  is disposed along a conveyer  171 , which is aligned in the longitudinal direction of the conveyer  171  and has rack part teeth  179  formed on one side facing the stand  198  and along the conveyer  171  such that the rack part teeth  179  are engaged with the pinion part  199  of the receiving member  197  during transfer of the undried honeycomb formed body  191  placed on the stand  198  by means of the conveyer  171 . Through employment of the configuration, during transfer of the undried honeycomb formed body  191  placed on the stand  198  by means of the conveyer  171  in the drying chamber  151 , the stand  198  is transferred while the rack part teeth  179  are engaged with the pinion part  199  of the receiving member  197 , thereby rotating the receiving member  197  about the center axis thereof, whereby the undried honeycomb formed body  191  placed on the stand  198  is transferred in the drying apparatus  400  while rotating virtually about the center axis of the receiving member  197 . Through employment of the drying apparatus  400  having the above configuration, the energy used to move the undried honeycomb formed body  191  partially serves as a driving source for rotating the undried honeycomb formed body  191 . Therefore, an additional driving source is not required, which is preferred.  FIG. 10  is a cross-section taken along line BB-BB′ in  FIG. 9 . 
     FIG. 11  is a schematic plan view showing that the receiving member  197  of the stand on which the undried honeycomb formed body  191  is placed is rotated by means of the rack part  177 . As shown in  FIG. 11  and mentioned above, the mechanism for rotating the undried honeycomb formed body  191  involves transferring of the stand in the EE direction while the pinion part  199  of the receiving member  197  is engaged with the rack part teeth  179  of the rack part  177  affixed to the inside of the drying chamber; rotating the receiving member  197  about the center axis thereof in a rotational direction S; and rotating the undried honeycomb formed body  191  placed on the stand virtually about the center axis of the receiving member in the rotational direction S. 
   As shown in  FIG. 12 , the undried honeycomb formed body  191  is transferred in the direction EE while being supported by means of the support  196  of the stand and rotating in the rotational direction S. Preferably, a second hot air h is applied to the undried honeycomb formed body  191  in two directions so as to sandwich the structure by means of the hot air application apparatus  178  disposed so as to be aligned the direction EE and sandwich the undried honeycomb formed body  191 .  FIG. 12  is a schematic plan view showing that a second hot air h is applied to the undried honeycomb formed body  191  which is rotating. 
   Although the aforementioned combination of the pinion part and the rack part is employed as a mechanism for rotating the undried honeycomb formed body, other methods may also be employed. Examples include a method in which the member on which the undried honeycomb formed body is placed (i.e., receiving member) is directly rotated through a rotational driving system such as a motor; and a method in which a magnet or a like means is buried in the member on which the undried honeycomb formed body is placed (i.e., receiving member) and the member is rotated in a non-contact manner by means of an electromagnetic circuit. 
   As shown in  FIG. 9 , the drying apparatus  400  is provided with a hot air feeding unit  156  and an discharge means  163  for discharging the drying chamber  151 . The drying space  152  of the drying chamber  151  can be controlled to a predetermined humidity and temperature through employment of the hot air feeding unit  156  and the forced discharge means  163 . The atmosphere of the drying space  152  may be controlled through adjusting of the properties (i.e., temperature, humidity level, flow rate, and velocity) of the hot air fed through the hot air feeding unit  156 . However, combination of the hot air feeding unit  156  and the forced discharge means  163  is preferred, since the atmosphere can be more precisely controlled. In addition, through provision of a water vapor feeding means (not illustrated) for feeding water vapor into the drying space  152 , more precise atmosphere control can be realized. The forced discharge means  163  has a blower for forced discharge  161  and a duct for forced discharge  162  connected to the blower for forced discharge  161 , and the duct for forced discharge  162  is communicated with the drying chamber  151 . The atmosphere of the drying chamber  151  is discharged in order to control the atmosphere in the drying chamber  152  through the blower for forced discharge  161  via the duct for forced discharge  112 . 
   In the case where the water vapor that is fed through the water vapor feeding means into the drying chamber  151 , the water vapor preferably has a temperature of 100 to 120° C. The amount of water vapor fed into the drying chamber  151  and the amount of discharge from the drying chamber  151  to the outside through the blower for forced discharge  161  are appropriately determined in accordance with factors such as the capacity of the drying chamber  151 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  151 . For example, when the capacity of the drying chamber  151  is about 7 m 3 , the water vapor in flow is preferably 90 to 120 kg/Hr, and the discharge rate is preferably 20 to 50 m 3 /min. 
   As shown in  FIG. 9 , electromagnetic wave generators  153  are disposed on the inner surface of the ceiling  173  of the drying chamber  151  along the center axis of the outer frame  174 . The electromagnetic wave generators  153  are distributed in ten zones located with virtually the same intervals. In each zone, as shown in  FIG. 10 , two electromagnetic wave generators are disposed on the ceiling  173  and one electromagnetic wave generator on each side surface  176 ; i.e., total four electromagnetic wave generators  153  are disposed. Thus, 40 electromagnetic wave generators  153  are disposed in the drying chamber  151 . According to the embodiment of the honeycomb formed body drying method, the undried honeycomb formed body  191  is irradiated with an electromagnetic wave of the outer peripheral surface wall  194  side and the top end  195  side. Thus, the inside of the honeycomb formed body is more uniformly irradiated with an electromagnetic wave, and the entirety of the honeycomb formed body more uniformly undergoes high-frequency heating, which is preferred. No particular limitation is imposed on the place and number of the electromagnetic wave generators  153  to be disposed. For example, in each zone, one electromagnetic wave generator  153  may be placed at any place. Alternatively, five or more electromagnetic wave generators  153  may be disposed at any places. The number of the zones where an electromagnetic wave generator  153  is disposed is not limited to ten, and may be appropriately determined in accordance with factors such as the length of the drying chamber  151 . The electromagnetic wave generators  153  are preferably disposed at such positions that an electromagnetic wave is applied to the undried honeycomb formed bodies  191  as uniformly as possible. Preferably, the drying chamber  151  is covered with a heat insulating material, whereby the inside temperature of the drying chamber  151  is maintained. In addition, the outer frame  174  is preferably surrounded by a heat insulating material. 
   In the embodiment of the honeycomb formed body drying method, the electromagnetic wave employed for drying preferably has a frequency of 900 to 10,000 MHz, more preferably 2,000 to 10,000 MHz. When the frequency is lower than 900 MHz, water is difficult to undergo high-frequency heating, and a honeycomb formed body may be difficult to dry. In contrast, when the frequency is higher than 2,000 MHz, water effectively undergoes high-frequency heating. As shown in  FIG. 10 , the electromagnetic wave generators  153  may be disposed inside the drying chamber  151 . Alternatively, electromagnetic wave generators  153  may be disposed outside the drying chamber  151 , and the generated electromagnetic wave is guided through a predetermined site of the drying chamber  151  into the drying chamber  151  via a waveguide so as to apply the electromagnetic wave to the undried honeycomb formed body  191 . 
   The energy of the electromagnetic wave applied to the honeycomb formed body is appropriately determined in accordance with factors such as the capacity of the drying chamber  151 , and the number and dimensions of honeycomb formed bodies accommodated in the drying chamber  151 . For example, when the capacity of the drying chamber  151  is about 7 m 3 , the total energy is preferably 150 to 300 kW. When the energy is smaller than 150 kW, the honeycomb formed body may fail to be dried to a predetermined drying degree, whereas when the energy is higher than 300 kW, the vaporization speed of water from the honeycomb formed body is elevated, difficulty may be encountered in reduction of the difference in drying condition between the inner part of the honeycomb formed body and the outer part thereof. 
   As shown in  FIG. 9 , the drying apparatus  400  of the present embodiment has a post-drying chamber  181  provided in the vicinity of the outlet of the outer frame  174  through which dried honeycomb formed bodies  192  are removed. The post-drying chamber  181  is disposed in the vicinity of the outlet of the outer frame  174  and has a space (post-drying space  187 ) between the ceiling  173  and the conveyer  171 . As mentioned above, in the post-drying chamber  181 , the dried honeycomb formed body  192  can be further dried through application of hot air (hot air for post-drying) thereto. Upon drying in the post-drying chamber  181 , the dried honeycomb formed body  192  is transferred by means of a conveyer  171  to a post-drying chamber  181 . The hot air for post-drying fed through hot air feeding nozzles  184  disposed under the post-drying chamber  181  is applied to the dried honeycomb formed body  192  in the direction from the bottom to the top end. The hot air fed through hot air feeding nozzles  184  to the post-drying chamber  181  is discharged to the outside through a hot air discharge duct  185  disposed above the post-drying chamber  181  (space between the ceiling  173  and the roof  175 ). The aforementioned hot air for post-drying preferably has a temperature of 100 to 130° C. When the temperature is lower than 100° C., the dried honeycomb formed body may be difficult to dry, whereas when the temperature is higher than 130° C., substances other than water such as an organic binder contained in the dried honeycomb formed body  192  are vaporized, causing deformation of partition walls of the dried honeycomb formed body  92  and burning of the organic binder and other substances, which are problematic. 
   The hot air feeding nozzles  184  are linked to the post-drying hot air generator  182  via a piping so that the hot air for post-drying generated by the post-drying hot air generator  182  is transferred via the piping and discharged through the hot air feeding nozzles  184 . No particular limitation is imposed on the type of the post-drying hot air generator  182  so long as the generator attains predetermined temperature and flow rate. For example, a hot air generator having a heater employing high-temperature water vapor or an electric heater and a blower may be used. In the generator, a blow generated by the blower is heated to provide hot air. The hot air for post-drying generated by the post-drying hot air generator  182  may be used for preliminarily heating the unheated drying chamber  151  before the start of electromagnetic wave drying of the undried honeycomb formed body. In  FIG. 9 , hot air is fed into the drying chamber  151  via a piping for preliminary heating  186  connected to the post-drying hot air generator  182 . 
   The honeycomb formed body to be dried by means of the drying apparatus of the embodiment is made of ceramic material, having a percent opening of 80% or more and a partition wall thickness of 0.18 mm or less. As used herein, the term “percent opening” refers to a ratio (percent) of the total cross-sectional area of the cell through-holes to the cross-sectional area of the honeycomb formed body in which the cell through-holes are located, as viewed in a cross-section of a honeycomb formed body cut in a direction normal to the center axis. 
   The drying apparatus of the embodiment continuously dries honeycomb formed bodies and may be a batch-type. In use, the batch-type drying apparatus is such that a predetermined number of undried honeycomb formed bodies are accommodated therein and irradiated with an electromagnetic wave to thereby dry the honeycomb formed bodies; irradiation of the electromagnetic wave is stopped; the thus-dried honeycomb formed bodies are removed; another predetermined number of undried honeycomb formed bodies are accommodated therein; and irradiation of an electromagnetic wave is started. 
   EXAMPLES 
   The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto. 
   Example 1 
   Through employment of the drying apparatus  300  of the present invention (first mode) shown in  FIG. 7 , drying of honeycomb formed bodies was performed in accordance with the honeycomb formed body drying method according to the first mode of the present invention. 
   The following drying conditions were employed. An electromagnetic wave having a frequency of 2.45 GHz was generated by means of electromagnetic wave generators  53  each having an output power of 5 kW. As shown in  FIG. 7 , the electromagnetic wave generators  53  were distributed in ten zones located with virtually the same intervals. In each zone, as shown in  FIG. 8 , two electromagnetic wave generators were disposed on the ceiling  73  and one electromagnetic wave generator on each side surface  76 ; i.e., total four electromagnetic wave generators  53  were disposed. Thus, 40 electromagnetic wave generators (4 per zone)  53  were disposed so as to provide a total output power of 200 kW. The type of the electromagnetic wave generators  53  was a magnetron. 
   The inside humidity level of the drying space  52  was adjusted to 50%, and water vapor (120° C.) was fed into the drying space through a water vapor feeding means  54  at 120 kg/Hr. Air was discharge through a forced discharge means  55  at 60 m 3 /min. The inside temperature of the drying space  52  was adjusted to about 105° C. 
   Each of the honeycomb formed bodies subjected to drying was made of cordierite and had a cell partition wall thickness of 0.15 mm, a percent opening of 80%, and a mass of about 6 kg. 
   Drying of honeycomb formed bodies was performed continuously by means of the drying apparatus  300  under such conditions that the drying chamber  51  had an accommodation capacity of 10 honeycomb formed bodies and the residence time of one honeycomb formed body in the drying space  52  was controlled to about 3 minutes. 
   Comparative Example 1 
   The same drying conditions as those of Example 1 were employed, except that the humidity level of the drying space was adjusted to 70%, water vapor (110° C.) was fed into the drying space through a water vapor feeding means at 30 kg/Hr, air was discharged through a forced discharge means at 60 m 3 /min, and the inside temperature of the drying space was adjusted to about 90° C. 
   Visual Observation 
   The honeycomb formed bodies dried through the honeycomb formed body drying method of Example 1 or Comparative Example 1 were visually observed. In the honeycomb formed body obtained in Example 1, no wrinkles or defects of the outer peripheral surface walls or no deformations of the cell partition walls of the outer part of the honeycomb formed bodies were observed. In contrast, in the honeycomb formed bodies obtained in Comparative Example 1, wrinkles were generated in outer peripheral surface walls, and deformations in cell partition walls present in the outer part of the honeycomb formed bodies were observed. The deformation of the partition wall of each of the honeycomb formed bodies obtained in Comparative Example 1 was found to be 20 mm inside from the outer peripheral surface wall. 
   Water Content Distribution in Honeycomb Formed Body 
   The honeycomb formed bodies dried through the honeycomb formed body drying method of Example 1 or Comparative Example 1 were investigated in terms of water content distribution (water content: mass %). In each of the dried honeycomb formed bodies, water content was determined in a center axis region, an outer peripheral surface wall region, and an intermediate region therebetween. In each region, the honeycomb formed body was divided into seven blocks along the center axis thereof from the top end to the bottom with the same intervals (1st block including the top end, 7th block including the bottom, and 2nd to 6th blocks being arranged from the top to the bottom). Thus, water content was determined in total 21 blocks. From each block, a sample (about 10 mm×10 mm) was cut out, and the weights of the sample immediately after cutting and that after complete drying were measured, thereby calculating water content immediately after cutting. The results are shown in Table 1. 
   
     
       
         
             
           
             
               TABLE 1 
             
           
          
             
                 
             
             
               (Unit: mass %) 
             
          
         
         
             
             
             
          
             
                 
               Ex. 1 
               Comp. Ex. 1 
             
          
         
         
             
             
             
             
             
             
             
          
             
                 
                 
               Inter- 
               Outer 
                 
               Inter- 
               Outer 
             
             
                 
               Center 
               mediate 
               peripheral 
               Center 
               mediate 
               peripheral 
             
             
                 
               axis 
               region 
               surface 
               axis 
               region 
               surface 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
             
             
          
             
               1st block 
               22 
               23 
               23 
               30 
               33 
               40 
             
             
               2nd block 
               19 
               22 
               23 
               20 
               22 
               38 
             
             
               3rd block 
               19.5 
               21 
               25 
               20 
               22 
               40 
             
             
               4th block 
               18 
               22 
               23 
               20 
               23 
               42 
             
             
               5th block 
               19 
               21 
               24 
               21 
               24 
               40 
             
             
               6th block 
               20 
               22 
               22.5 
               20 
               22 
               35 
             
             
               7th block 
               15 
               18.5 
               19.5 
               15 
               18 
               30 
             
             
               Average 
               18.9 
               21.4 
               22.9 
               20.9 
               23.4 
               37.9 
             
          
         
         
             
             
             
          
             
               In-carrier 
               21 
               25 
             
             
               average 
             
             
                 
             
          
         
       
     
   
   As is clear from Table 1, the honeycomb formed bodies obtained in Example 1 had almost same water content in the center axis region, the intermediate region, and the outer peripheral surface wall region, whereas the honeycomb formed bodies obtained in Comparative Example 1 had a water content of the outer peripheral surface wall about 15 to 20 mass % higher as compared with the center axis region and the intermediate region. The results along with the above visual observation results indicate that drying performed in Example 1 reduces the water content of the outer peripheral surface wall through drying in a high-temperature, low-humidity atmosphere, thereby inhibiting wrinkles and defects of the outer peripheral surface wall and deformations of partition walls. These results also indicate that drying performed in Comparative Example 1 increases the water content of the outer peripheral surface wall through drying in a high-humidity atmosphere, thereby generating wrinkles the outer peripheral surface wall and deformations of cell partition walls. The average water content (in-carrier average) of each of the honeycomb formed bodies obtained in Example 1 is about 4 mass %-lower as compared with those obtained in Comparative Example 1, indicating that drying in Example 1 enhances drying efficiency by virtue of reduced humidity. As used herein, the term “in-carrier average” refers to a water content of the entirety of one honeycomb formed body. 
   Example 2 to 10 
   The procedure of Example 1 was repeated, except that the inside humidity and temperature of the drying space  2  were modified as specified in Table 2, to thereby dry honeycomb formed bodies. In each Example, the number of honeycomb formed bodies dried was 300. 
   Comparative Example 2 to 22 
   The procedure of Comparative Example 1 was repeated, except that the inside humidity and temperature of the drying space were modified as specified in Table 2, to thereby dry honeycomb formed bodies. In each Comparative Example, the number of honeycomb formed bodies dried was 300. 
   Visual Observation 
   In each of the Examples 2 to 10 and the Comparative Examples 2 to 22, 300 dried honeycomb formed bodies were visually observed. The results are shown in Table 2. In Table 2, the term “outer wall wrinkle” refers to a ratio (%) of the number of dried honeycomb formed body having wrinkles in the outer peripheral surface walls to the number of the dried honeycomb formed body in each of the Examples and Comparative Examples. The term “outer wall defect” refers to a ratio (%) of the number of dried honeycomb formed body having defects in the outer peripheral surface walls to the number of the dried honeycomb formed body in each of the Examples and Comparative Examples. As shown in Table 2, through controlling the inside humidity of the drying space to 30 to 65% at 75 to 130° C., wrinkles and defects of the outer peripheral surface wall can be prevented. 
   
     
       
         
             
             
             
             
             
           
             
                 
               TABLE 2 
             
             
                 
                 
             
             
                 
                 
               Humidity 
                 
                 
             
             
                 
               Temperature 
               level in 
                 
               Wrinkles 
             
             
                 
               in drying 
               drying 
               Defects in 
               in outer 
             
             
                 
               chamber 
               chamber 
               outer wall 
               wall 
             
             
                 
               (° C.) 
               (%) 
               (%) 
               (%) 
             
             
                 
                 
             
           
          
             
                 
             
          
         
         
             
             
             
             
             
          
             
               Ex. 2 
               95 
               30 
               0 
               0 
             
             
               Ex. 3 
               95 
               50 
               0 
               0 
             
             
               Ex. 4 
               95 
               65 
               0 
               0 
             
             
               Ex. 5 
               75 
               30 
               0 
               0 
             
             
               Ex. 6 
               75 
               50 
               0 
               0 
             
             
               Ex. 7 
               75 
               65 
               0 
               0 
             
             
               Ex. 8 
               130 
               30 
               0 
               0 
             
             
               Ex. 9 
               130 
               50 
               0 
               0 
             
             
               Ex. 10 
               130 
               65 
               0 
               0 
             
             
               Comp. Ex. 2 
               95 
               0 
               100 
               0 
             
             
               Comp. Ex. 3 
               95 
               10 
               80 
               0 
             
             
               Comp. Ex. 4 
               95 
               20 
               10 
               0 
             
             
               Comp. Ex. 5 
               95 
               70 
               0 
               3 
             
             
               Comp. Ex. 6 
               95 
               80 
               0 
               10 
             
             
               Comp. Ex. 7 
               95 
               90 
               0 
               20 
             
             
               Comp. Ex. 8 
               95 
               100 
               0 
               55 
             
             
               Comp. Ex. 9 
               75 
               0 
               15 
               0 
             
             
               Comp. Ex. 10 
               75 
               10 
               8 
               0 
             
             
               Comp. Ex. 11 
               75 
               20 
               3 
               0 
             
             
               Comp. Ex. 12 
               75 
               70 
               0 
               10 
             
             
               Comp. Ex. 13 
               75 
               80 
               0 
               25 
             
             
               Comp. Ex. 14 
               75 
               90 
               0 
               50 
             
             
               Comp. Ex. 15 
               75 
               100 
               0 
               100 
             
             
               Comp. Ex. 16 
               130 
               0 
               100 
               0 
             
             
               Comp. Ex. 17 
               130 
               10 
               90 
               0 
             
             
               Comp. Ex. 18 
               130 
               20 
               25 
               0 
             
             
               Comp. Ex. 19 
               130 
               70 
               0 
               3 
             
             
               Comp. Ex. 20 
               130 
               80 
               0 
               5 
             
             
               Comp. Ex. 21 
               130 
               90 
               0 
               15 
             
             
               Comp. Ex. 22 
               130 
               100 
               0 
               35 
             
             
                 
             
          
         
       
     
   
   Example 11 
   Through employment of the drying apparatus  400  of the present invention (second mode) shown in  FIG. 9 , drying of honeycomb formed bodies was performed in accordance with the honeycomb formed body drying method according to the second mode of the present invention. 
   The following drying conditions were employed. An electromagnetic wave having a frequency of 2.45 GHz was generated by means of electromagnetic wave generators  153  each having an output power of 5 kW. As shown in  FIG. 9 , the electromagnetic wave generators  153  were distributed in ten zones located with virtually the same intervals. In each zone, as shown in  FIG. 10 , two electromagnetic wave generators were disposed on the ceiling  173  and one electromagnetic wave generator on each side surface  176 ; i.e., total four electromagnetic wave generators  153  were disposed. Thus, 40 electromagnetic wave generators (4 per zone)  153  were disposed so as to provide a total output power of 200 kW. The type of the electromagnetic wave generators  153  was a magnetron. 
   The employed hot air generator  154  of the hot air feeding unit  156  was an electric heater, and the heated air was fed by means of a blower. The hot air generated by means of the hot air generator  154  was introduced into the drying space  152  through the hot air introducing member  155 . The hot air introduced into the drying space  152  was controlled to have a flow rate of 12 m 3 /s, a velocity of 2 m/s, and a temperature of 105° C. 
   The hot air application apparatus  178  was disposed such that four nozzles whose tips facing the outer peripheral surface wall of the honeycomb formed body are aligned along the center axis (top to bottom) of the undried honeycomb formed body. Ten sets of four nozzles were aligned in parallel in the direction of transferring the undried honeycomb formed body. The total flow rate of the second hot air applied by means of a nozzle set of four nozzles aligned in the top-to-bottom direction was adjusted to 0.002 m 3 /s. The second hot air fed through each nozzle was controlled to have a velocity of 3 m/s and a temperature of 105° C. 
   Air was discharged through a forced discharge means  63  at 60 m 3 /min. 
   The inside humidity and temperature of the drying space  152  were adjusted to 50% and about 105° C., respectively. 
   Each of the honeycomb formed bodies subjected to drying was made of cordierite and had a cell partition wall thickness of 0.13 mm, a percent opening of 83%, and a mass of about 6 kg. 
   Drying of honeycomb formed bodies was performed continuously by means of the drying apparatus  400  under such conditions that the drying chamber  151  had an accommodation capacity of 10 honeycomb formed bodies and the residence time of one honeycomb formed body in the drying space  152  was controlled to about 3 minutes. 
   Comparative Example 23 
   The same drying conditions as those of Example 11 were employed, except that the humidity level of the drying space was adjusted to 70%, water vapor (110° C.) was fed into the drying space through a water vapor feeding means at 30 kg/Hr, air was discharged through a forced discharge means at 60 m 3 /min, the inside temperature of the drying space was adjusted to about 90° C., and feeding of hot air through the hot air feeding unit and application of the second hot air through the hot air application apparatus were not performed. 
   Visual Observation 
   The honeycomb formed bodies dried through the honeycomb formed body drying method of Example 11 or Comparative Example 23 were visually observed. In the honeycomb formed body obtained in Example 11, no wrinkles or defects of the outer peripheral surface walls or no deformations of the cell partition walls of the outer part of the honeycomb formed bodies were observed. In contrast, in the honeycomb formed bodies obtained in Comparative Example 23, wrinkles were generated in outer peripheral surface walls, and cell partition walls in the outer part of the honeycomb formed bodies were observed. The deformation of the partition wall of each of the honeycomb formed bodies obtained in Comparative Example 23 was found to be 20 mm inside from the outer peripheral surface wall. 
   Water Content Distribution in Honeycomb Formed Body 
   The honeycomb formed bodies dried through the honeycomb formed body drying method of Example 11 or Comparative Example 23 were investigated in terms of water content distribution (water content: mass %). In each of the dried honeycomb formed bodies, water content was determined in a center axis region, an outer peripheral surface wall region, and an intermediate region therebetween. In each region, the honeycomb formed body was divided into seven blocks along the center axis thereof from the top end to the bottom with the same intervals (1st block including the top end, 7th block including the bottom, and 2nd to 6th blocks being arranged from the top to the bottom). Thus, water content was determined in total 21 blocks. From each block, a sample (about 10 mm×10 mm) was cut out, and the weights of the sample immediately after cutting and that after complete drying were measured, thereby calculating water content immediately after cutting. The results are shown in Table 1. Complete drying was performed in a hot air atmosphere at 120° C. for 24 hours. 
   
     
       
         
             
           
             
               TABLE 3 
             
           
          
             
                 
             
             
               (Unit: mass %) 
             
          
         
         
             
             
             
          
             
                 
               Ex. 11 
               Comp. Ex. 23 
             
          
         
         
             
             
             
             
             
             
             
          
             
                 
                 
               Inter- 
               Outer 
                 
               Inter- 
               Outer 
             
             
                 
               Center 
               mediate 
               peripheral 
               Center 
               mediate 
               peripheral 
             
             
                 
               axis 
               region 
               surface 
               axis 
               region 
               surface 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
             
             
          
             
               1st block 
               20 
               21 
               21 
               30 
               33 
               40 
             
             
               2nd block 
               18 
               19 
               19 
               20 
               22 
               38 
             
             
               3rd block 
               18 
               19 
               19 
               20 
               22 
               40 
             
             
               4th block 
               17.5 
               19.5 
               19 
               20 
               23 
               42 
             
             
               5th block 
               18 
               19 
               19.5 
               21 
               24 
               40 
             
             
               6th block 
               18.5 
               19 
               19.5 
               20 
               22 
               35 
             
             
               7th block 
               15 
               18.5 
               19.5 
               15 
               18 
               30 
             
             
               Average 
               17.9 
               19.3 
               19.5 
               20.9 
               23.4 
               37.9 
             
          
         
         
             
             
             
          
             
               In-carrier 
               19.5 
               25.7 
             
             
               average 
             
             
                 
             
          
         
       
     
   
   As is clear from Table 3, the honeycomb formed bodies obtained in Example 11 had almost same water content in the center axis region, the intermediate region, and the outer peripheral surface wall region, whereas the honeycomb formed bodies obtained in Comparative Example 23 had a water content of the outer peripheral surface wall about 15 to 20 mass % higher as compared with the center axis region and the intermediate region. The results along with the above visual observation results indicate that drying performed in Example 11 reduces the water content of the outer peripheral surface wall through drying in a high-temperature, low-humidity atmosphere, thereby inhibiting wrinkles and defects of the outer peripheral surface wall and deformations of partition walls. These results also indicate that drying performed in Comparative Example 23 increases the water content of the outer peripheral surface wall through drying in a high-humidity atmosphere, thereby generating wrinkles the outer peripheral surface wall and deformations of cell partition walls. The average water content (in-carrier average) of each of the honeycomb formed bodies obtained in Example 11 is about 6.2 mass %-lower as compared with those obtained in Comparative Example 23, indicating that drying in Example 11 enhances drying efficiency by virtue of reduced humidity. As used herein, the term “in-carrier average” refers to a water content of the entirety of one honeycomb formed body, and is calculated by subtracting the mass (B) of the completely dried honeycomb formed body from the mass (A) of the entire honeycomb formed body, dividing the difference (B-A) by the mass (A) of the entire honeycomb formed body before drying, and multiplying 100. 
   Example 12 to 20 
   The procedure of Example 11 was repeated, except that the inside humidity and temperature of the drying space  152  were modified as specified in Table 4, to thereby dry honeycomb formed bodies. In each Example, the number of honeycomb formed bodies dried was 300. 
   Comparative Example 24 to 44 
   The procedure of Comparative Example 23 was repeated, except that the inside humidity and temperature of the drying space were modified as specified in Table 4, to thereby dry honeycomb formed bodies. In each Comparative Example, the number of honeycomb formed bodies dried was 300. 
   Visual Observation 
   In each of the Examples 12 to 20 and the Comparative Examples 24 to 44, 300 dried honeycomb formed bodies were visually observed. The results are shown in Table 4. In Table 4, the term “outer wall wrinkle” refers to a ratio (%) of the number of dried honeycomb formed body having wrinkles in the outer peripheral surface walls to the number of the dried honeycomb formed body in each of the Examples and Comparative Examples. The term “outer wall defect” refers to a ratio (%) of the number of dried honeycomb formed body having defects in the outer peripheral surface walls to the number of the dried honeycomb formed body in each of the Examples and Comparative Examples. As shown in Table 4, through controlling the inside humidity of the drying space to 30 to 65% at 75 to 130° C., wrinkles and defects of the outer peripheral surface wall can be prevented. 
   
     
       
         
             
             
             
             
             
           
             
                 
               TABLE 4 
             
             
                 
                 
             
             
                 
                 
               Humidity 
                 
                 
             
             
                 
               Temperature 
               level in 
                 
               Wrinkles 
             
             
                 
               in drying 
               drying 
               Defects in 
               in outer 
             
             
                 
               chamber 
               chamber 
               outer wall 
               wall 
             
             
                 
               (° C.) 
               (%) 
               (%) 
               (%) 
             
             
                 
                 
             
           
          
             
                 
             
          
         
         
             
             
             
             
             
          
             
               Ex. 12 
               95 
               30 
               0 
               0 
             
             
               Ex. 13 
               95 
               50 
               0 
               0 
             
             
               Ex. 14 
               95 
               65 
               0 
               0 
             
             
               Ex. 15 
               75 
               30 
               0 
               0 
             
             
               Ex. 16 
               75 
               50 
               0 
               0 
             
             
               Ex. 17 
               75 
               65 
               0 
               0 
             
             
               Ex. 18 
               130 
               30 
               0 
               0 
             
             
               Ex. 19 
               130 
               50 
               0 
               0 
             
             
               Ex. 20 
               130 
               65 
               0 
               0 
             
             
               Comp. Ex. 24 
               95 
               0 
               100 
               0 
             
             
               Comp. Ex. 25 
               95 
               10 
               80 
               0 
             
             
               Comp. Ex. 26 
               95 
               20 
               10 
               0 
             
             
               Comp. Ex. 27 
               95 
               70 
               0 
               3 
             
             
               Comp. Ex. 28 
               95 
               80 
               0 
               10 
             
             
               Comp. Ex. 29 
               95 
               90 
               0 
               20 
             
             
               Comp. Ex. 30 
               95 
               100 
               0 
               55 
             
             
               Comp. Ex. 31 
               75 
               0 
               15 
               0 
             
             
               Comp. Ex. 32 
               75 
               10 
               8 
               0 
             
             
               Comp. Ex. 33 
               75 
               20 
               3 
               0 
             
             
               Comp. Ex. 34 
               75 
               70 
               0 
               10 
             
             
               Comp. Ex. 35 
               75 
               80 
               0 
               25 
             
             
               Comp. Ex. 36 
               75 
               90 
               0 
               50 
             
             
               Comp. Ex. 37 
               75 
               100 
               0 
               100 
             
             
               Comp. Ex. 38 
               130 
               0 
               100 
               0 
             
             
               Comp. Ex. 39 
               130 
               10 
               90 
               0 
             
             
               Comp. Ex. 40 
               130 
               20 
               25 
               0 
             
             
               Comp. Ex. 41 
               130 
               70 
               0 
               3 
             
             
               Comp. Ex. 42 
               130 
               80 
               0 
               5 
             
             
               Comp. Ex. 43 
               130 
               90 
               0 
               15 
             
             
               Comp. Ex. 44 
               130 
               100 
               0 
               35 
             
             
                 
             
          
         
       
     
   
   INDUSTRIAL APPLICABILITY 
   The invention provides a method and an apparatus for drying a honeycomb formed body which prevent deformation such as warpage of partition walls of a honeycomb formed body during drying thereof in the production of the honeycomb formed body, particularly a ceramic honeycomb formed body, whereby a high-quality honeycomb formed body free of deformation can be produced.