JPH0240019B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for firing a ceramic honeycomb structure. (Prior art) Conventionally, as a method for manufacturing ceramic products by firing a green body molded body, in order to prevent cracks and adhesion, the green body molded body was not placed directly on a shelf board, but was placed on the top of the shelf. There is a known method of baking the product by placing it on a baking tray called a baking tray. In addition, a method for manufacturing a ceramic honeycomb structure by firing a green ceramic honeycomb structure (hereinafter abbreviated as a raw honeycomb structure) involves firing the raw honeycomb structure in a state in which the axis of the cells is approximately horizontal (horizontal firing). ) and a method in which a raw honeycomb structure is fired (standing firing) in a state where the axis of the cells is substantially perpendicular. Specifically, in the case of stand-up firing, the horse chestnut is placed on a shelf board, and the raw honeycomb structure is placed on top of it with the axis of the cells approximately perpendicular, that is, one open end surface of the raw honeycomb structure is in contact with the horse chestnut. , placed and fired. (Problem to be solved by the invention) In standing firing, since high temperature gas generally tends to gather upward, the temperature of the raw honeycomb structure is lower on the upper end surface side (upper side) than on the lower end surface side (lower side). The lower part is in contact with shelf boards, horse chestnuts, etc., so it is not exposed to combustion gas, whereas the upper end surface is exposed to the combustion gas flow and becomes hot. There were cases where the temperature distribution was different between the upper and lower parts. If the temperature distribution is uneven in this manner, firing shrinkage occurs unevenly in the upper and lower portions, and cuts are likely to occur on the upper end surface, which is easily heated. Alternatively, if temperature non-uniformity occurs when the binder, pore-forming material, etc. contained in the raw honeycomb structure is burned out, abnormal expansion occurs in the overheated part, resulting in the disadvantage that breakage is likely to occur on the upper end surface, which is easily heated. It was hot. When the raw honeycomb structure is large or fired in large quantities, such as in a tunnel kiln, it is difficult to solve these drawbacks by adjusting the kiln temperature distribution, airflow, etc. When I dealt with it using this method, productivity decreased. In side firing, when the raw honeycomb structure is overheated by exposing its end faces to combustion gas, etc., and the temperature rises locally, uneven temperature distribution may occur; For the same reason as the above-mentioned standing firing, cuts were likely to occur at the end surface, which is easily heated. (Means for Solving the Problems) The present inventors solved these drawbacks by applying a conker to both open end surfaces of the green ceramic honeycomb structure when firing the green ceramic honeycomb structure using a conker. This problem can be solved by firing using a ceramic honeycomb structure for at least one of the horse chestnuts. Therefore, in the case of standing firing, a local temperature rise occurs, and by placing a conker on the upper end surface, which is easily cut, it is possible to suppress a local temperature rise on the upper end surface even if it is exposed to combustion gas or the like. In addition, in the case of horizontal firing, a local temperature rise occurs,
Place a conker against the edge that is easy to break. For example, when the end face faces the direction of the flame of the ignition burner and the end face is susceptible to local overheating, the conker may be brought into contact with the burner side, or may be brought into contact with one end face or both end faces. The conker that comes into contact with the end face can be the same as in the case of standing firing. The contact surface of the horse chestnut may be a flat surface, a curved surface, or a shape that contacts both open end surfaces of the raw honeycomb structure so as to prevent hot gas from entering. In addition to making horse chestnut into a honeycomb structure, the weight can be reduced.A common effect between standing and horizontal firing is that when the cell openings of the honeycomb structure of horse chestnut correspond to the cell openings of the raw honeycomb structure, it is possible to reduce the weight when the binder and pore-forming agent are burned away. This makes it easier to dissipate the gas generated, making it easier to remove binders and the like. As long as there are no problems with the material of the conker, such as cutting or adhesion,
Although any ceramic can be used, it is preferable to use one in which the coefficient of thermal expansion of the horse chestnut and the raw honeycomb structure are approximately the same, so that breakage due to expansion and contraction during firing can be prevented. For example, it is preferable to use the same material of ceramics as the raw honeycomb structure for the conker, mullite for mullite, and cordierite conker for cordierite. The opening of the honeycomb-structured horse chestnut cells is approximately 0.8~
310 cells/cm ² (5 to 2000 cells/square inch) is acceptable. The size of the horse chestnut is preferably approximately the same as that of the raw honeycomb structure, and the thickness is selected in consideration of the temperature or temperature distribution and weight of the raw honeycomb structure. Also,
In the case of standing firing, if the weight of the horse chestnut placed on the upper end surface is too heavy, the frictional force generated when the raw honeycomb structure contracts or expands during firing on the lower end surface will increase, which may cause breakage. It goes without saying that the lighter the conker on the upper end surface is, the more preferable it is. The horse chestnut has a chamfered part on the outer periphery of the abutting surface, and the outer edge of the abutting surface is 3 times larger than the outer edge of the open end surface of the raw honeycomb structure.
When the conker is brought into contact with the open end surface of the raw honeycomb structure so that it is located 5 to 15 mm or more inward, firing shrinkage or The frictional resistance force that occurs during expansion can be reduced, and this has the effect of preventing cuts that occur on the open end surfaces of the raw honeycomb structure due to the frictional resistance force.
This chamfering has a great effect on preventing the lower end face of the standing fire from being cut, where the frictional resistance between the horse chestnut and the opening end face is large. The chamfered part has a chamfer angle θ of 3 to 45° or a chamfer angle θ
It may be rounded with an angle approximating . If a groove is provided on the abutting surface of one or both of the conkers and this groove is extended to the chamfered part, the heating gas will circulate better and the temperature will rise faster, which is almost the same as making the conkers have a honeycomb structure. A similar effect can be obtained. If a chamfer is also provided at the upper edge of the groove, cuts during firing of the raw honeycomb structure are reduced. The chamfer angle and radius of curvature of the chamfered portion of the groove may be set to the same value as the chamfered angle θ of the chamfered portion of the conker, but may be set to different values. The horse chestnut may be a live horse chestnut or a permanent horse chestnut, and it is preferable to use a shape that matches the shape of the raw honeycomb structure to which it comes into contact, such as an ellipse, circle, or rectangle. When standing firing a raw honeycomb structure, inserting a spacer between it and the shelf board under the lower horse chestnut improves air permeability, shortens firing time, and reduces breakage. (Function) Since the conker is brought into contact with both open end faces of the raw honeycomb structure and fired, it is possible to prevent the occurrence of breaks due to uneven temperature distribution due to overheating at the end faces of the raw honeycomb structure, and the temperature rises quickly. Firing with uniform distribution becomes possible, increasing productivity. (Example) Hereinafter, the present invention will be described in further detail with reference to Examples. Examples 1 to 7 Horse chestnuts 1 having the shapes, dimensions, structures, and materials shown in Table 1 below were obtained. The lower horse chestnut has an angle θ = 15 ~ on the upper edge
It had a 30° annular chamfer 2, and the chamfer 2 was in contact with the contact surface 3 at an outer edge _R2 . This horse chestnut 1 is the 12th to 1st
As shown in FIG. 7, the raw honeycomb structure 7 shown in Table 1 was fired by using it vertically or horizontally. The outer edge R ₂ of the contact surface 3 of the horse chestnut 1 is located inward from the outer edge of the open end surface of the raw honeycomb structure 7 by a of 3 mm or more, usually 5 to 15 mm. As shown in Table 1, the ceramic honeycomb structure obtained by firing in this manner had no breakage at all. When a spacer 8 is inserted between the bottom edge and the shelf board 9 as shown in FIG.
No cuts occurred at all. 6 to 9 show other examples of horse chestnuts used in the present invention. When a horse chestnut without a chamfered portion 2 is brought into contact with the left and right sides (Fig. 10) or the top and bottom (Fig. 11) of the raw honeycomb structure and fired horizontally or vertically, the cut was eliminated, but the The precision of shape and dimensions was higher for the actual model. Note that Table 1 also shows, as Reference Examples 1 and 2, cases in which a conker was brought into contact with the left and right end faces and side-burned as a modification example of the present invention. Reference Examples 1 and 2 have breakage rates of 10%, so they can barely be used, but this shows that they are not as good as the results of the present invention.

【table】

[Table] (Effects of the Invention) According to the present invention, a ceramic honeycomb structure having a complex shape, precise dimensions, and uniform quality can be easily obtained in a short time and with high yield without occurrence of breakage. . Therefore, the present invention is extremely useful industrially. Of course, various changes and modifications may be made without departing from the broader spirit, scope, and spirit of the invention.

[Brief explanation of drawings]

FIG. 1 is a partial side view diagrammatically explaining a horse chestnut used in the present invention, and FIGS. 2 to 5 are diagrammatic side views showing embodiments of the method of the present invention. Figures 6 to 8 are diagrammatic plan views showing examples of the horse chestnut used in the present invention, Figure 9 is a diagrammatic perspective view of the horse chestnut shown in Figure 6, and Figure 10 is the method of the present invention in the case of standing firing. Fig. 11 is an exploded perspective view diagrammatically showing another embodiment of the method of the present invention in the case of side firing;
12-17 are diagrammatic side views showing embodiments of the method of the present invention. 1... Horse chestnut, 2... Chamfered portion, 3... Contact surface, 4
...Groove, 5...Cell wall or rib, 6...Cell, 7
...Raw honeycomb structure, 8...Spacer, 9...
Shelf board, R ₁ ... Lower end outer edge of raw honeycomb structure 7, R ₂
...Outer edge of the contact surface 3 of the horse chestnut 1.

Claims (1)

[Scope of Claims] 1. When firing a green ceramic honeycomb structure using a conker, a conker is brought into contact with both open end surfaces of the green ceramic honeycomb structure, and a conker of the ceramic honeycomb structure is attached to at least one of the conkers. 1. A method for firing a ceramic honeycomb structure, characterized by firing using a ceramic honeycomb structure. 2. The method according to claim 1, wherein the cell openings of the horse chestnut honeycomb structure correspond to the cell openings of the green ceramic honeycomb structure. 3. The method according to claim 1, wherein the conker is made of the same material as the green ceramic honeycomb structure. 4. The method according to claim 1, wherein at least one of the conkers has a chamfered portion on the outer periphery of the contact surface. 5. The outer edge of the abutting surface of at least one of the conkers is 3.3 mm wider than the open end surface of the green ceramic honeycomb structure.
The method according to claim 1, wherein the method is located more than mm inward. 6. The method according to claim 1, wherein one or both of the conkers have a groove on the contact surface.