JP5785465B2 - Extrusion molding apparatus and method for producing green molded body for honeycomb structure using the same - Google Patents

Description

The present invention relates to manufacturing technology of the molding, and more particularly to a manufacturing method of an extrusion molding device and a honeycomb structure green moldings using the same for producing a honeycomb structure green compact.

  Conventionally, honeycomb filter structures are widely known for DPF (Diesel particulate filter) and the like. This honeycomb filter structure has a structure in which one end side of some through holes of a honeycomb structure having a large number of through holes is sealed with a sealing material, and the other end side of the remaining through holes is sealed with a sealing material. Patent Documents 1 and 2 disclose a die and an extrusion molding apparatus used for manufacturing a honeycomb structure.

JP 61-5915 A Japanese Patent No. 4099896

  By the way, the honeycomb filter structure for DPF is generally used in a state of being housed in a rigid case. If the dimensional accuracy of the honeycomb filter structure is low, problems such as cracks in the honeycomb filter structure due to thermal stress or the like are likely to occur. Therefore, high dimensional accuracy is required for the green molded body before firing. Some honeycomb structures have a narrow cell pitch (for example, about 1.1 to 2.8 mm), and a high dimensional accuracy is required for the thickness of the partition walls defining a large number of through holes.

  When manufacturing a green molded body with an extrusion molding device, the flow rate of the raw material composition reaching the upstream surface of the die is uneven and the flow rate of the raw material composition in a specific region is high compared to other regions. The formed body is extruded from the die. If this is to be corrected straight afterwards, there arises a problem that the partition walls of the molded body are curved or cracks are formed on the outer surface. Further, even if a straight product is obtained at the initial stage when the production of the molded body is started, the bending of the molded body may become gradually noticeable due to die wear or the like.

The present invention has been made in view of the above problems, an extrusion molding apparatus capable of efficiently producing a green molded body for a honeycomb structure with sufficiently small bending and high dimensional accuracy, and a honeycomb structure using the extrusion molding apparatus It aims at providing the manufacturing method of a green molded object.

An extrusion molding apparatus according to the present invention is for producing a green molded body for a honeycomb structure , provided with a flow path for transferring a paste-like raw material composition and an upstream side of the flow path. A screw for kneading and transferring to the downstream side, a die provided on the downstream side of the flow path, the die for extruding the green molded body for a honeycomb structure made of the raw material composition, and a thickness between the screw and the die. A rectifying plate having a plurality of openings penetrating in the vertical direction, a resistance tube communicating with the die on the downstream side of the rectifying plate, and a length protruding inside the resistance tube so as to penetrate the tube wall of the resistance tube Includes a plurality of freely changeable resistance pins.

The plurality of resistance pins provided in the extrusion molding apparatus of the present invention is for uniformizing the flow velocity distribution of the raw material composition introduced into the die. Check the degree and direction of bending of the extruded green body for honeycomb structure, and if bending exceeding the required accuracy is observed, the bending is sufficiently small by adjusting the protruding length of each resistance pin. A green molded body for a honeycomb structure with high dimensional accuracy can be efficiently manufactured.

The combination of the plurality of resistance pins may be one set or two or more sets. For example, when the resistance tube has a tapered portion in which the flow path cross section decreases from upstream to downstream and a straight tube portion connected to the downstream side of the tapered portion, a plurality of resistance pins include the tapered portion and the straight portion. It is preferable that it is provided on at least one of the tube portions. In addition, when manufacturing a green molded body for a honeycomb structure having a diameter larger than the diameter of the screw, the resistance tube may have an enlarged portion in which the cross section of the flow path increases from upstream to downstream.

The protruding length of each of the plurality of resistance pins may be adjusted manually or may be automatically controlled. In the case of automatic control, the extrusion molding apparatus according to the present invention includes a sensor that detects the degree and direction of bending of a green molded body for a honeycomb structure extruded from a die, and a plurality of resistance pins based on data from the sensor. It is preferable to further include a computer that calculates the length to be projected and a pin drive mechanism that changes the protruding length of each of the plurality of resistance pins based on an output from the computer.

This invention is a manufacturing method of the green molded object for honeycomb structures using the said extrusion molding apparatus, and provides the method provided with the process of changing the protrusion length of a resistance pin. According to the method of the present invention, by appropriately adjusting the protruding length of the resistance pin, it is possible to efficiently manufacture a green molded body for a honeycomb structure with sufficiently small bending and high dimensional accuracy. When using an extrusion molding apparatus having a mechanism for automatically controlling the protruding lengths of a plurality of resistance pins, the method according to the present invention includes a step of automatically changing the protruding lengths of the resistance pins. Can do.

According to the present invention, a green molded body for a honeycomb structure with a sufficiently small bend and high dimensional accuracy can be efficiently manufactured.

(A) is a perspective view which shows an example of the green molded object for honeycomb structures, (b) is the elements on larger scale of a green molded object. It is a schematic sectional drawing which shows embodiment of the extrusion molding apparatus which concerns on this invention. It is a fragmentary sectional view which shows the structure of the resistance pin provided so that the resistance tube shown in FIG. 1 and its tube wall might be penetrated. It is a figure which shows the structure of a baffle plate. It is sectional drawing which shows a mode that the front end side of a some resistance pin has protruded inside the resistance tube. It is sectional drawing which shows a mode that the front end side of a some resistance pin has protruded inside the resistance tube. It is other embodiment of the extrusion molding apparatus which concerns on this invention, and is a fragmentary sectional view which shows the form provided with the extension pipe (straight pipe part) in the downstream of the resistance pipe. It is a block diagram which shows the form provided with the mechanism which is other embodiment of the extrusion molding apparatus which concerns on this invention, and automatically controls the protrusion length of a resistance pin. It is a schematic diagram which shows an example of the mechanism which detects the bending of a molded object with a non-contact-type displacement sensor. It is a schematic diagram which shows an example of the mechanism which detects the bending of a molded object with a non-contact-type dimension measuring device.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, prior to description of the extrusion molding apparatus according to the present invention, a green molded body for a honeycomb structure will be described.

<Green molded body>
A green molded body 70 shown in FIG. 1 is obtained by extruding a raw material composition. As shown in FIG. 1A, the green molded body 70 is a cylindrical body in which a large number of through holes 70a are arranged substantially in parallel. The cross-sectional shape of the through hole 70a is a square as shown in FIG. The plurality of through holes 70a are arranged in a square arrangement in the green molded body 70, that is, such that the central axis of the through hole 70a is located at the apex of the square. The square size of the cross section of the through hole 70a can be set to 0.8 to 2.5 mm on a side, for example. A honeycomb structure is manufactured by firing the green molded body 70 at a predetermined temperature.

  The length of the green molded body 70 in the direction in which the through hole 70a extends is not particularly limited, but may be 40 to 350 mm, for example. Moreover, although the outer diameter of the green molded object 70 is not specifically limited, For example, it can be set as 100-320 mm.

  The raw material composition forming the green molded body 70 is not particularly limited. However, when manufacturing a honeycomb structure for DPF, an inorganic compound source powder that is a ceramic raw material, an organic binder such as methylcellulose, and necessary Additives added depending on From the viewpoint of high temperature resistance of the honeycomb structure, suitable ceramic materials include alumina, silica, mullite, cordierite, glass, oxides such as aluminum titanate, silicon carbide, silicon nitride, and the like. The aluminum titanate can further contain magnesium and / or silicon.

  For example, when producing a green molded body of aluminum titanate, the inorganic compound source powder includes an aluminum source powder such as α-alumina powder and a titanium source powder such as anatase type or rutile type titania powder. Furthermore, magnesium source powders such as magnesia powder and magnesia spinel powder and / or silicon source powders such as silicon oxide powder and glass frit can be included.

  Examples of the organic binder include celluloses such as methylcellulose, carboxymethylcellulose, hydroxyalkylmethylcellulose, and sodium carboxymethylcellulose; alcohols such as polyvinyl alcohol; and lignin sulfonate.

  Examples of the additive include a pore former, a lubricant and a plasticizer, a dispersant, and a solvent.

  Examples of the pore-forming agent include carbon materials such as graphite; resins such as polyethylene, polypropylene and polymethyl methacrylate; plant materials such as starch, nut shells, walnut shells and corn; ice; and dry ice.

  Lubricants and plasticizers include alcohols such as glycerol; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, arachidic acid, oleic acid and stearic acid; metal stearates such as Al stearate, polyoxyalkylene alkyl And ether (POAAE).

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid, and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid, and lactic acid; alcohols such as methanol, ethanol, and propanol; ammonium polycarboxylate; Surfactants such as oxyalkylene alkyl ethers are listed.

  As the solvent, for example, alcohols such as methanol, ethanol, butanol and propanol; glycols such as propylene glycol, polypropylene glycol and ethylene glycol; and water can be used.

<Extrusion molding equipment>
A preferred embodiment of the extrusion molding apparatus according to the present invention will be described with reference to FIGS. The extrusion molding apparatus 10 shown in FIG. 2 is for producing a green molded body 70 from a powdery or pasty raw material composition.

  The extrusion molding apparatus 10 includes a screw 2A provided at the upper stage in the housing 1 and a screw 2B provided at the lower stage. The screws 2A and 2B are for kneading the raw material composition supplied from the inlet 1a and transferring it downstream through the flow path 1b. A vacuum chamber 3 is provided between the screws 2A and 2B, and the raw material composition can be degassed by reducing the pressure in the vacuum chamber 3. The raw material composition in the vacuum chamber 3 is introduced into the lower screw 2B by a roller 3a.

  The extrusion molding apparatus 10 includes a rectifying plate 5 provided on the downstream side of the screw 2B, a die 8 from which a molded body 70A made of a raw material composition is extruded, a resistance tube 9 that communicates the flow path 1b and the die 8, and a resistance. It further includes 16 resistance pins P which are provided so as to penetrate the tube wall of the tube 9 and whose lengths protrude inside the resistance tube 9 can be changed (see FIGS. 3 and 5). The resistance tube 9 has an internal flow path tapered (tapered portion), and the flow path cross-sectional area gradually decreases from the upstream side toward the downstream side. In addition, a support base 15 for supporting the molded body 70A is installed next to the extrusion molding apparatus 10 so that the molded body 70A extruded from the die 8 is not deformed. Prior to the introduction of the raw material composition into the die 8, the rectifying plate 5 and the plurality of resistance pins P are intended to make the flow velocity distribution uniform.

The rectifying plate 5 is detachably attached to the housing 1 and is disposed between the screw 2B and the die 8. 4A is a front view of the current plate 5, and FIG. 4B is a cross-sectional view of the current plate 5. The rectifying plate 5 has a plurality of openings 5a penetrating in the thickness direction. The rectifying plate 5 may have a net-like resistor (not shown) in order to enhance the effect of adjusting the flow rate. As the net-like resistor, for example, a wire net having a mesh number of 5 to 200 mesh (more preferably 50 to 150 mesh) can be used. By arranging one or a plurality of wire meshes on the upstream surface of the rectifying plate 5, a higher rectifying effect can be obtained and foreign substances contained in the raw material composition can be removed. The number of meshes (mesh) of the metal mesh here means the number of meshes between 1 inch (25.4 mm). When selecting the mesh to be used, the first condition is that the mesh opening W is small with respect to the opening (slit width) of the die. Good. The number of meshes N can be calculated by the following formula.
N = 25.4 / (W + d)
In the formula, W represents the mesh opening (mm), and d represents the wire diameter (mm) of the mesh.

  The rectifying plate 5 is preferably a structure that hardly causes distortion even when pressure is received from the upstream side. From this viewpoint, the material of the rectifying plate 5 is preferably carbon steel, for example. Examples of suitable materials other than carbon steel include special steels containing nickel, chromium, tungsten and the like. The thickness of the current plate 5 is preferably 10 to 100 mm from the viewpoint of ensuring sufficient strength.

  The rectifying plate 5 has a plurality of openings 5a having a diameter of 1 to 10 mm penetrating in the thickness direction. The opening ratio of the rectifying plate 5 is preferably 30 to 80%. When the current plate 5 having an opening ratio of less than 30% is used, a sufficient amount of the raw material composition cannot be passed per unit time unless the upstream pressure is excessively increased, and the pressure is the allowable pressure of the apparatus. It is easy to become more. On the other hand, the current plate 5 having an aperture ratio exceeding 80% tends to have insufficient strength. The opening ratio of the rectifying plate 5 is preferably 40 to 80%, and more preferably 50 to 80%.

  Here, the “aperture ratio” means a value calculated by dividing the total area of the openings on one surface of the current plate 5 by the area of the one surface (excluding the peripheral edge covered by the housing). . In addition, in the case of a rectifying plate in which the flow passage cross-sectional area of the opening is not constant, the total area of the opening may vary depending on the position of the rectifying plate in the thickness direction (feeding direction of the raw material composition). This means a value calculated using the minimum value of the sum.

  As shown in FIGS. 3 and 5, the 16 resistance pins P are provided so as to penetrate the tube wall of the resistance tube 9, and are arranged at substantially equal intervals in the circumferential direction of the resistance tube 9. The length of the resistance pin P protruding inside the resistance tube 9 can be freely changed. More specifically, the resistance pin P has a seal mechanism that does not leak the raw material composition from between the resistance pin 9 and the resistance tube 9, and is slidable with respect to the resistance wall 9. Note that, as a configuration that allows the protruding length to be changed, a screw rotation type mechanism using a screw provided in the resistance pin P and a screw hole provided in the resistance tube 9 may be used instead of the slide type mechanism. Further, the number of resistance pins P is not limited to 16, but 6 to 36 are preferably used for one set in order to obtain a sufficient flow rate adjustment effect.

  From the viewpoint of obtaining a sufficient flow rate adjustment effect, the plurality of resistance pins P are preferably arranged at predetermined positions on the upstream side of the die 8. That is, it is preferable that the central axes of the plurality of resistance pins P are installed in the range of 10 to 100 mm (more preferably 10 to 50 mm) from the upstream surface of the die 8.

  The protruding length of the resistance pin P can be changed. By increasing the protruding length, the flow rate of the raw material composition flowing through the region can be reduced, and the bending of the green molded body 70 can be reduced. The protruding length can be 0 to 120% (see FIG. 6), preferably 0 to 100% based on the radius of the position where the resistance pin P of the resistance tube 9 is provided (see FIG. 5). reference).

  For example, when the extruded green molded body 70 is curved upward, it is considered that the flow rate of the raw material composition flowing in the lower region of the resistance tube 9 is higher than in other regions. In this case, as shown in FIG. 5, a plurality of resistance pins P located in the region may be projected. In FIG. 5, the ratio of the protrusion length (radius reference of the resistance tube 9) is 100% for the resistance pin P1 located at the lower end, 70% for the adjacent resistance pin P2, and further for the adjacent resistance pin. P3 is set to 30%. The green molded body 70 having sufficiently high dimensional accuracy can be continuously manufactured by checking the degree and direction of bending of the extruded molded body and changing the protruding length of each resistance pin P.

  It is preferable that the tip of the resistance pin P is tapered. By adopting such a configuration, even when each resistance pin P protrudes to the center of the resistance tube 9, it is possible to sufficiently suppress the adjacent resistance pins P from interfering with each other. When all the resistance pins P are projected to the center, that is, when the ratio of the projection lengths of all the resistance pins P is 100%, the flow path at the position where the resistance pins P of the resistance tube 9 are provided. Assuming that the cross-sectional area is 100, the cross-sectional area of the flow path excluding the portion blocked by the resistance pin P is preferably about 10-50. Setting the ratio of the flow path cross-sectional area to less than 10 tends to complicate the mechanism of the apparatus, and if it exceeds 50, the effect of adjusting the flow velocity by the resistance pin P tends to be insufficient.

  As shown in FIG. 3, the resistance pin P may be arranged so that the angle formed with the central axis of the resistance tube 9 is 90 °, or may be arranged so as to be inclined upstream or downstream. When the resistance pin P is inclined to the upstream side or the downstream side, the inclination angle of the resistance pin P is preferably within 30 ° with respect to a plane whose normal is the central axis of the resistance tube 9.

  The die 8 is for producing a molded body having the shape shown in FIG. 1 from the raw material composition, and has a grid-like flow path (not shown) corresponding thereto. A die used for manufacturing a molded body having a cell structure such as the green molded body 70 needs to set the flow path precisely, and is generally expensive. For this reason, it is desirable to reduce the frequency of die replacement work as much as possible. In the present embodiment, the frequency of changing the setting of the die 8 can be reduced by changing the protruding length of the resistance pin P in the resistance tube 9, and the life of the die 8 is extended by uniformizing the flow rate of the raw material composition. And the replacement frequency can be lowered.

  In the above embodiment, the case where a plurality of resistance pins P are provided on the tube wall of the resistance tube 9 is exemplified. However, if the position where the plurality of resistance pins are provided is between the rectifying plate 5 and the die 8, It is not limited. For example, when an extension tube (straight tube portion) 9a is connected to the downstream side of the resistance tube (tapered portion) 9, a plurality of resistance pins P may be provided on the resistance tube 9 or the extension tube 9a (see FIG. 7). A plurality of resistance pins P may be provided on both the resistance tube 9 and the extension tube 9a.

<Method for producing green molded body>
Next, a method for manufacturing the green molded body 70 using the extrusion molding apparatus 10 will be described. First, the raw material composition is introduced into the flow path 1b from the inlet 1a. By operating the screws 2A, 2B and the roller 3a, the raw material composition is kneaded and transferred downstream. The kneaded material is passed through the opening 5 a of the rectifying plate 5 to make the flow velocity distribution uniform, and then introduced into the die 8 through the resistance tube 9. The linear velocity of the raw material composition on the downstream side of the die 8 can be about 10 to 150 cm / min.

  The raw material composition having a uniform flow velocity distribution is extruded from the die 8 and the compact 70 </ b> A is collected on the support base 15. The green molded body 70 is obtained by cutting the molded body 70A into a predetermined length.

  When the flow rate distribution is not sufficiently uniformed only by the rectifying action of the rectifying plate 5, and the degree of bending of the green molded body 70 becomes significant, a step of changing the protruding length of the resistance pin P is performed. This step can be performed without stopping the supply of the raw material composition to the extrusion molding apparatus 10, whereby the green molded body 70 having sufficiently high dimensional accuracy without changing or changing the setting of the die 8. Can be efficiently produced over a sufficiently long period of time. In particular, if an extrusion molding apparatus having a mechanism for automatically controlling the protruding lengths of the plurality of resistance pins P is used, the protruding lengths of the resistance pins P can be automatically changed.

  The extrusion molding apparatus 20 shown in FIG. 8 has the same configuration as the above-described extrusion molding apparatus 10 except that it further includes a mechanism that automatically controls the protruding lengths of the plurality of resistance pins P. The extrusion molding device 20 is a computer 12 that detects the degree and direction of bending of the molded body 70 </ b> A extruded from the die 8, and a computer that calculates the length of the plurality of resistance pins P to be projected based on data from the sensor 12. 13 and a pin drive mechanism 14 that changes the protruding length of each of the plurality of resistance pins P based on the output from the computer 13. As the sensor 12, a non-contact type displacement sensor using a laser beam or LED light L, a non-contact type size measuring device, or the like can be used. As the pin drive mechanism 14, when the resistance pin P is a slide type or a screw rotation type, a mechanism that reciprocates or rotates the resistance pin P with a gear or the like can be adopted.

  FIG. 9 is a diagram illustrating a configuration of a bending detection mechanism when a non-contact displacement sensor LK-G (trade name, manufactured by Keyence Corporation) is used as the sensor 12. By using four sets (non-contact type displacement sensors 12A to 12D) of sensors including a light emitting element 12a that emits laser light or LED light L and a light receiving element 12b, the bending of the molded body 70A is detected. A circle Y consisting of a broken line in FIG. 9 shows a cross-sectional position of the green body when a straight green body 70A is obtained, and a circle N consisting of a solid line shows the cross-sectional position of the green body where bending has occurred. is there. Two sets of non-contact type displacement sensors 12A and 12B may be used.

  FIG. 10 is a diagram illustrating a configuration of a bending detection mechanism when a non-contact type dimension measuring device LS-7000 (trade name, manufactured by Keyence Corporation) is used as the sensor 12. Sixteen non-contact type dimension measuring devices 12a to 12p are arranged so as to surround the molded body 70A. A circle Y consisting of a broken line in FIG. 10 indicates the cross-sectional position of the molded body when a straight molded body 70A is obtained, and a circle N consisting of a solid line indicates the cross-sectional position of the molded body where bending has occurred. is there. In the case where non-contact size measuring devices are arranged as shown in FIG. 10, the number thereof is not particularly correlated with the number of resistance pins P, but is preferably larger than the number of resistance pins P. Moreover, only either one of a pair of opposing measuring devices may be sufficient, for example, only measuring device 12a-12h shown in FIG. 10 may be sufficient.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the cylindrical green molded body 70 is illustrated, but the shape and structure of the molded body are not limited thereto. The outer shape of the green molded body 70 may be, for example, a rectangular column such as a quadrangular column or an elliptical column. Further, the arrangement of the through holes 70a may not be a square arrangement, and may be, for example, a substantially triangular arrangement, a substantially hexagonal arrangement, or the like. Furthermore, the shape of the through hole 70a may not be square, and may be, for example, a substantially triangular shape, a substantially hexagonal shape, a substantially octagonal shape, or a substantially circular shape.

  According to the present invention, it is possible to efficiently produce a molded body with sufficiently small bending and high dimensional accuracy.

DESCRIPTION OF SYMBOLS 1 ... Housing, 1b ... Flow path, 2B ... Screw, 5 ... Current plate, 5a ... Opening, 8 ... Die, 9 ... Resistance pipe (taper part), 9a ... Extension pipe (straight pipe part) 10, 20 ... Extrusion Molding device, 12 ... sensor, 12A, 12B ... non-contact displacement sensor (sensor), 12a to 12p ... non-contact dimension measuring device (sensor), 13 ... computer, 14 ... pin drive mechanism, 70 ... green molded body, 70A: Molded body, P (P1, P2, P3): Resistance pin.

Claims (6)

An extrusion molding apparatus for producing a green molded body for a honeycomb structure,
A flow path for transferring a paste-like raw material composition;
A screw provided on the upstream side of the flow path, kneading the raw material composition and transferring it downstream;
A die that is provided on the downstream side of the flow path and from which the green molded body for a honeycomb structure made of the raw material composition is extruded;
A rectifying plate provided between the screw and the die and having a plurality of openings penetrating in the thickness direction;
A resistance tube communicating with the downstream side of the current plate and the die;
A plurality of resistance pins provided so as to pass through the tube wall of the resistance tube, and the length protruding inside the resistance tube can be changed respectively;
An extrusion apparatus comprising:   The resistance tube has a tapered portion whose flow path cross section decreases from upstream to downstream, and a straight tube portion connected to the downstream side of the tapered portion, and the plurality of resistance pins include the tapered portion and the straight portion. The extrusion molding apparatus according to claim 1, wherein the extrusion molding apparatus is provided on at least one of the pipe portions. The extrusion molding apparatus according to claim 1 or 2, further comprising a sensor that detects a degree and a direction of bending of the green molded body for a honeycomb structure extruded from the die. A computer for calculating a length to be projected of the plurality of resistance pins based on data from the sensor;
A pin drive mechanism for changing the protruding length of each of the plurality of resistance pins based on an output from the computer;
The extrusion apparatus according to claim 3, further comprising: It is a manufacturing method of the green molded object for honeycomb structures using the extrusion molding apparatus as described in any one of Claims 1-4 , The method provided with the process of changing the protrusion length of the said resistance pin. It is a manufacturing method of the green molded object for honeycomb structures using the extrusion molding apparatus of Claim 4 , Comprising: The method provided with the process of changing the protrusion length of the said resistance pin automatically.

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