Patent Publication Number: US-2017354913-A1

Title: Honeycomb structured body

Description:
TECHNICAL FIELD 
     The present invention relates to a honeycomb structured body, 
     BACKGROUND ART 
     There is conventionally known, a honeycomb structured body in which flow passages as closing targets are closed not by closing with plugs but by deforming partition walls, that is, by inclining the partition walls at an end part in such a way as to expand the sectional areas of Sow passages adjacent to the flow passages as the closing targets. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Publication No. 2003-166410 
     Patent Literature 2: Japanese Unexamined Patent Publication No. 2003-49631 
     SUMMARY OF INVENTION 
     Technical Problem 
     Although it is expected that such a honeycomb structured body achieves a smaller pressure loss as compared with a honeycomb structured body closed with plugs, the effect of reducing a pressure loss is not sufficient. 
     The present invention is devised in view of the aforementioned problem, and an object thereof is to provide a honeycomb structured body high in effect of reducing a pressure loss. 
     Solution to Problem 
     A honeycomb structured body according to the present invention is a column-shaped porous honeycomb structured body which forms a plurality of first flow passages that are opened on one end face and closed on the other end face and a plurality of second flow passages that are closed on the one end face and opened on the other end face. This honeycomb structured body comprises: central partition walls where sectional areas of each first flow passage and each second flow passage are individually constant in an axial direction; and other-end-side inclined partition walls where the sectional area of each first flow passage is shrank and the sectional area of each second flow passage is expanded from the central partition walls toward the other end face. Further, an axial-directional length of the other-end-side inclined partition wall is  4  mm or more. 
     According to the present invention, since the axial-directional length of the other-end-side inclined, partition wall is secured to be  4  mm or more, an effect of reducing a pressure loss by means of inclined surfaces of the inclined partition walls can be sufficiently secured. 
     Here, since even if the axial-directional length, of the other-end-face-side inclined partition wall is made too large, their production becomes difficult, and in addition, the effect of reducing a pressure loss is not improved very much, it is preferable that the axial-directional length, of the other-end-side inclined partition wail be 20 mm or less. 
     Moreover, the honeycomb structured body further comprises one-end-side inclined, partition walls where the sectional area of each first flow passage is expanded and the sectional area of each second flow passage is shrunk from the central partition walls toward the one end face. 
     Moreover, the one end face can be an inlet side of gas and the other end face can be an outlet side of the gas. 
     Advantageous Effects of Invention 
     According to the present invention, a honeycomb structured body high in effect of reducing a pressure loss is provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a honeycomb filter  100  according to a first embodiment. 
         FIG. 2  is a cross-sectional view of central partition walls  10   cent  of a honeycomb structured body  10  taken along II-II in  FIG. 1 . 
         FIG. 3( a )  is an expanded view of an end face of an inlet (one-end-side) end face  10 E in  in  FIG. 1 , and  FIG. 3( b )  is a cross-sectional view taken along b-b in  FIG. 3( a ) . 
         FIG. 4( a )  is an expanded view of an end face of an outlet (other-end-side) end face  10 E out  in  FIG. 1 , and  FIG. 4( b )  is a cross-sectional view taken along b˜b in  FIG. 4( a )   
         FIG. 5  is a schematic diagram showing a method for producing a honeycomb filter according to the first embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A first embodiment of the present invention is described with reference to the drawings. 
     First Embodiment 
     A honeycomb filter  100  according to the embodiment includes a column-shaped porous honeycomb structured body  10  as shown in  FIG. 1 . The honeycomb structured body  10  has an inlet end face (one end face)  10 E in  and an outlet end face (the other end face)  10 E out . The honeycomb structured body  10  forms a plurality of inlet flow passages (plurality of first flow passages)  70 H in  that are opened on the inlet, end face  10 E in  and closed on the outlet end face  10 E out , and a plurality of outlet flow passages (plurality of second flow passages)  70 H out  that are closed on the inlet end face  10 E in  and opened on the outlet end face  10 E out , and these flow passages extend in the axial direction of the honeycomb structured body  10 . Moreover, the honeycomb structured body  10  has inlet-side inclined partition walls (one-end-side inclined partition walls)  10   in  having the inlet end face  10 E in , outlet-side inclined partition walls (other-end-side inclined partition walls)  10   out  having the outlet end lace  10 E out , and central partition walls  10   cent  between these. 
     The outer diameter of the honeycomb structured body  10  can be sets for example, to be 50 to 250 mm. The axial-directional length of the honeycomb structured body  10  can be set, for example, to be 50 to 300 mm. 
       FIG. 2  is a cross-section of the central partition walls  10   cent  of the honeycomb structured body  10 . The central partition walls  10   cent  form many inlet flow passages  70 H in  and many outlet flow passages  70 H out  sectional areas of which are individually substantially constant along the axial direction. In the embodiment, the inlet flow passages  70 H in  and the outlet flow passages  70 H out  are regularly arranged in such a way that in the central partition walls  10   cent , one inlet flow passage  70 H in  is adjacent to three other inlet flow passages  70 H in  and adjacent to three outlet flow passages  70 H out . One outlet flow passage  70 H out  is adjacent to six inlet flow passages  70 H in  and not adjacent to the other outlet flow passages  70 H out . Each flow passage Is adjacent to totally six flow passages respectively via the partition walls. In the central partition walls  10   cent  the sectional shapes of the inlet flow passages  70 H in  and the outlet flow passages  70 H out  are substantially hexagonal. The thickness of a portion W that separates two flow passages in the central partition wall  10   cent  can be set, for example, to be 0.10 to 0.35 mm. The density of the flow passages can be set, for example, to be 150 to 400 cpsi. 
     Next, referring to  FIGS. 3( a )  and  FIG. 3( b ) , a structure of the inlet-side inclined partition walls (one-end-side inclined partition walls)  10   in  is shown. The inlet-side inclined partition wails  10   in  are inclined relative to the axis of the inlet flow passages  70 H in  and the outlet flow passages  70 H out  in such a way as to gradually expand the sectional areas of the inlet flow passages  70 H in  and to gradually shrink and close the sectional areas of the outlet flow passages  70 H out  as compared with the central partition walls  10   cent , from the central partition walls  10   cent  toward the inlet end face  10 E in . Specifically, the inlet-side inclined partition walls  10   in  gradually expand the sectional areas of the inlet flow passages  70 H in  which are substantially hexagonal in the central partition walls  10   cent  and make the sectional shapes triangular on the inlet end face  10 E in , and make the sectional areas of the outlet flow passages  70 H out    0  before reaching the inlet end face  10 E in , from the central partition walls  10   cent  toward the inlet end face  10 E in . On the inlet end face  10 E in , the vertices of each triangle forming the expanded inlet flow passage  70 H in  reach the centers of the outlet flow passages  70 H out , and in this way, the outlet flow passages  70 H out  are closed. In the inlet-side inclined partition walls  10   in , the thickness of a plate-like portion separating two flow passages can be set, for example, to be 0.10 to 0.35 mm. This thickness can be a thickness within ±10% relative to the thickness of the partition wall in the central partition walls  10   cent . 
     Next, referring to  FIG. 4( a )  and  FIG. 4( b ) , a structure of the outlet-side inclined partition wails (other-end-side inclined partition walls)  10   out  is shown. The outlet-side inclined partition walls  10   out  are inclined relative to the axis of the inlet flow passages  70 H in  and the outlet flow passages  70 H out  in such a way as to gradually expand the sectional areas of the outlet flow passages  70 H out  and to gradually shrink and close the sectional areas of the inlet flow passages  70 H in  as compared with the central partition walls  10   cent , from the central partition walls  10   cent  toward the outlet end face  10 E out . Specifically, the outlet-side inclined partition walls  10   out  gradually expand the sectional areas of the outlet flow passages  70 H out  which are substantially hexagonal in the central partition walls  10   cent  into hexagons, side portions of each of the outlet flow passages  70 H out  becoming the corners of the hexagon, and make the sectional areas of the outlet flow passages  70 H out    0  before reaching the outlet end face  10 E out , from the central partition walls  10   cent  to the outlet end face  10 E out . On the outlet end face  10 E out , the vertices of each hexagon of the expanded outlet flow passage  70 H out  reach the vicinities of the centers of the inlet flow passages  70 H in , and in this way, the inlet flow passages  70 H in  are closed. In the outlet-side inclined partition walls  10   out , the thickness of a plate-like portion separating two flow passages can be set, for example, to be 0.10 to 0.8 mm. This thickness can set to be a thickness equivalent to (for example, not less than 0.9 times) the thickness of the partition wall in the central partition walls  10   cent  or not less than the thickness of the partition wall and its upper limit can be made large up to the length of opposite sides (see  FIG. 2 ) out of the contour lines of substantial hexagons of two adjacent Met flow passages  70 H in  in the central partition walls  10   cent . 
     An aperture ratio on the inlet end face  10 E in  can be made larger than an aperture ratio on the outlet end face  10 E out . 
     In the embodiment, an axial-directional length H out  of the outlet-side inclined partition wall  10   out  is 4 mm or more. The upper limit of H out  does not specially exist but it can be set, for example, to be 20 mm or less. An axial-directional length H in  of the inlet-side inclined partition wall  10   in  is not specially limited but it can be set, for example, to be 4 mm or more, and also, to be 20 mm or less. 
     Notably, the axial-directional, lengths H in  and H out  of the inclined partition walls can also have dispersions on the individual flow passages, and in such a case, the arithmetic mean of those only has to satisfy the aforementioned requirement. 
     The material of the honeycomb structured body  10  is porous ceramics, which have pores that gas can pass through, and on the other hand, that can capture particles such as soot. Examples of the ceramics include aluminum titanate, silicon carbide and cordierite. Aluminum titanate can contain magnesium, silicon and the like. The porosity of the partition wall of the honeycomb structured body  10  can be set, for example, to be 40 to 70%. 
     A catalyst may be supported on the surface of the honeycomb structured body  10 . Examples of the catalyst include particles of at least one metal element selected from the group consisting of Pt, Pd, Rh, silver, vanadium, chromium, manganese, iron, cobalt, nickel and copper, or a zeolite catalyst. The particle diameter of the catalyst can be set, for example, to be 1 nm to 10 μm. 
     While the catalyst may be directly supported on the surface of the honeycomb structured body  10 , it can also be held on a support held on the honeycomb structured body. The support sometimes functions as a co-catalyst. 
     Examples of the support include particles of oxides such as alumina, silica, magnesia, titania, zirconia, ceria, La 2 O 3 , BaO and zeolite, or composite oxides containing one or more of these. The particle diameter of the support can be set, for example, to be 0.1 to 100 μm. 
     Subsequently, operation of the honeycomb filter according to the embodiment is described. As compared with a honeycomb filter  100  in which flow passages are closed with plugs, the honeycomb filter  100  as above can have a lower initial pressure loss. Specifically, the effect of reducing a pressure loss by an end surface of the inlet flow passage  70 H in  being set to be an inclined surface by the outlet-side inclined partition wall  10   out  is high. In particular, since in the embodiment the axial-directional length H out  of the outlet-side inclined partition wall  10   out  is 4 mm or more, the end surface is sufficiently inclined relative to the axis as compared with, the case where the end surface of the inlet flow passage  70 H in  is orthogonal to the axis of the flow passage as in conventional plug closing, and hence, sufficient reduction of the pressure loss is possible. Accordingly, an initial pressure loss of the honeycomb filter  100  can be suppressed. 
     Subsequently, a method for producing such a honeycomb filter is described. First, a ceramic raw material undergoes extrusion molding by an extrusion molding machine to produce a honeycomb compact having the same sectional shape as that of the central partition wails  10   cent . This honeycomb compact has unclosed inlet flow passages  70 H in  and unclosed outlet flow passages  70 H out  in the state of these being penetrated. 
     The composition of the ceramic raw material only has to be one with which porous ceramics are given after firing it. For example, it can contain Hie ceramic raw material, an organic binder, a pore-forming agent, a solvent, and an additive which is added as needed. 
     The ceramic raw material is powder containing elements composing the ceramics. The binder can be an organic binder, and examples thereof include: celluloses such as methylcelluloses, carboxymethylcelluloses, hydroxyalkylmethylcelluloses and sodium carboxymethylcelluloses; alcohols such as polyvinyl alcohol); and lignin sulfonate salts. Examples of the additive include, for example, lubricants, plasticizers and dispersants. 
     Subsequently, as shown in  FIG. 5 , the inlet-side inclined partition walls  10 in are formed on the inlet end face  10 E of  an obtained unfired honeycomb compact  100 ′. Specifically, a closing jig  400  having many triangular pyramidal projections  410   a  is prepared. Then, the closing jig  400  is moved in such a way that each projection  410   a  comes into the inlet flow passage  70 H in . In this way, the partition walls of the inlet flow passage  70 H in  are deformed and the sectional area of the flow passage is expanded, and meanwhile, the sectional areas of the outlet flow passages  70 H out  are shrank. Then, finally, as shown in  FIG. 3( a )  and  FIG. 3( b ) , the sectional shapes of the inlet flow passages  70 H in  become triangular, and the partition walls are completely crimped in the outlet flow passages  70 H out  and the outlet flow passages  70 H out  are sealed. Namely, the outlet flow passages  70 H out  are closed on the inlet end face  10 E in . Notably, vibration or ultrasonic waves may be given to the closing jig  400 . 
     Next, likewise, the outlet-side inclined partition walls  10   out  are formed on the outlet end face  10 E out . Projections of a closing jig inserted into the outlet flow passages  70 H out  can be set to be hexagonal pyramidal. After that, alter drying as needed, the honeycomb compact  100 ′ both of whose end faces have been sealed is fired to obtain the honeycomb structured body. 
     Subsequently, the catalyst can be supported on the honeycomb structured body  10  as needed by a known method. 
     Notably, the present invention is not limited to the aforementioned embodiment but various modifications thereof are possible. For example, arrangements of the inlet flow passages and the outlet flow passages, that is, the numbers of flow passages adjacent to each flow passage are also not limited to those in the aforementioned embodiment. For example, each flow passage can be arranged in such a way that one inlet flow passage  70 H in  is adjacent to four other inlet flow passages  70 H in  and adjacent to two outlet flow passages  70 H out  and that one outlet flow passage  70 H out  is adjacent to six inlet flow passages  70 H in  and not adjacent to the other outlet flow passages  70 H out . Notably, in the present specification, that “two flow passages are adjacent to each other” can mean that two flow passages are separated from each other via one partition wall in the thickness direction of the partition wall. 
     Moreover, any shapes of the inclined partition walls are sufficient as long as the sectional area of each inlet flow passage is shrunk and the sectional area of each outlet flow passage is expanded from the central partition walls toward the other end face, and detailed shapes can be properly modified in accordance with the sectional shape of each flow passage and the arrangement of the flow passages. 
     Moreover, the sectional shape of the flow passage is not specially limited to that in the aforementioned embodiment but a polygon such as a tetragon or an octagon, a circle, or the like is possible. 
     Moreover, while the honeycomb structured body  10  of the aforementioned embodiment has a structure having inlet inclined partition walls on the inlet side, implementation thereof is possible even with a structure in which the inlet flow passages are closed with plugs at the inlet end and which does not have the inlet-side inclined partition walls. 
     Furthermore, the external shape of the filter does not have to be a cylindrical body but may be, for example, a quadrangular prism. 
     EXAMPLES 
     Reference Example 1 
     A cordierite-made porous honeycomb structured body onto which a catalyst was not adhered and that had a structure as shown in  FIG. 1  to  FIG. 4  for the aforementioned embodiment was prepared. The outer diameter was 118.4 mm, the length was 113.4 mm, the cell density was 360 cpsi, the wall thickness was 10 mil (0.25 mm), the aperture ratio at the inlet end was 42%, the aperture ratio at the outlet end was 27%, the porosity of the partition walls was 58%, and the average pore diameter was 18 μm. The axial-directional length H in  of the inlet-side inclined partition walls and the axial-directional length H out  of the outlet-side inclined partition walls were set to be 2 to 3 mm (2.5 mm on average) and 2 to 3 mm (2.5 mm on average), respectively. A pressure loss when air at 600 Nm 3 /h was fed at room temperature was 5.80 kPa. 
     Reference Example 2 
     This was set to be the same as Reference Example 1 except that the axial-directional length H in  of the inlet-side inclined partition walls was set to be 0, that is, the inlet side was closed with plugs. The pressure loss was 6.00 kPa. 
     Reference Example 3 
     This was set to be the same as Reference Example 1 except that the axial-directional length H out  of the outlet-side Inclined partition walls was set to be 0, that is, the outlet side was closed with plugs. The pressure loss was 6.86 kPa. 
     Reference Example 4 
     This was set to be the same as Reference Example 1 except that the axial-directional length H in  of the inlet-side inclined partition walls was set to be 0 and the axial-directional length H out  of the outlet-side inclined partition walls, that is, both the inlet side and the outlet side were closed with plugs. The pressure loss was 7.67 kPa. 
     It is found from these experiments that to provide the inclined partition walls on the outlet side is more effective for reduction of a pressure loss than to provide the inclined partition walls on the inlet side. 
     Comparative Example 1 
     The cell density was changed from 360 cpsi to 250 cpsi. Due to the change of the cell density, the inlet-side aperture ratio became 43% from 42%, and the outlet-side aperture ratio became 30% from 27%. This was set to be the same as Reference Example 1 except the above. The pressure loss was 4.46 kPa. 
     This was set to be the same as Comparative Example 1 except that the axial-directional length H out  of the outlet-side inclined partition walls was set to be 4 to 5 mm (4.5 mm on average). The pressure loss was 4.18 kPa. 
     Table 1 presents the results. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Pressure 
               
               
                   
                 Cell 
                 Wall 
                 Inlet-Side 
                 Outlet-Side 
                   
                   
                 Loss at 
               
               
                   
                 Density 
                 Thickness 
                 Aperture 
                 Aperture 
                 Hin 
                 Hout 
                 600 Nm 3 /h 
               
               
                   
                 [cpsi] 
                 [mil] 
                 Ratio [%] 
                 Ratio [%] 
                 [mm] 
                 [mm] 
                 [kPa] 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Reference 
                 360 
                 10 
                 42 
                 27 
                 2.5 mm 
                 2.5 mm 
                 5.80 
               
               
                 Example 1 
                   
                   
                   
                   
                 on 
                 on 
               
               
                   
                   
                   
                   
                   
                 Average 
                 Average 
               
               
                 Reference 
                 360 
                 10 
                 42 
                 27 
                 0 
                 2.5 mm 
                 6.00 
               
               
                 Example 2 
                   
                   
                   
                   
                   
                 on 
               
               
                   
                   
                   
                   
                   
                   
                 Average 
               
               
                 Reference 
                 360 
                 10 
                 42 
                 27 
                 2.5 mm 
                 0 
                 6.86 
               
               
                 Example 3 
                   
                   
                   
                   
                 on 
               
               
                   
                   
                   
                   
                   
                 Average 
               
               
                 Reference 
                 360 
                 10 
                 42 
                 27 
                 0 
                 0 
                 7.67 
               
               
                 Example 4 
               
               
                 Comparative 
                 250 
                 10 
                 43 
                 30 
                 2.5 mm 
                 2.5 mm 
                 4.46 
               
               
                 Example 1 
                   
                   
                   
                   
                 on 
                 on 
               
               
                   
                   
                   
                   
                   
                 Average 
                 Average 
               
               
                 Example 1 
                 250 
                 10 
                 43 
                 30 
                 2.5 mm 
                 4.5 mm 
                 4.18 
               
               
                   
                   
                   
                   
                   
                 on 
                 on 
               
               
                   
                   
                   
                   
                   
                 Average 
                 Average 
               
               
                   
               
            
           
         
       
     
     REFERENCE SIGNS LIST 
       70 H in  Inlet flow passage (first flow passage) 
       70 H out  Outlet flow passage (second flow passage) 
       10  Honeycomb structured body 
       10   cent  Central partition wall 
       10   out  Outlet-side inclined partition wall (other-end-side inclined partition wall) 
       10   in  Inlet-side inclined partition wall (one-end-side inclined partition wall) 
       10 E in  Inlet end face (one end face) 
       10 E out  Outlet end face (the other end face) 
       100  Honeycomb filter 
     W Portion separating two flow passages 
     H in  Axial-directional length of the inlet-side inclined partition wall (one-end-side inclined partition wall) 
     H out  Axial-directional length of fee outlet-side inclined partition wall (other-end-side inclined partition wall) 
       400  Closing jig 
       410   a  Projection