JP3044879B2 - Method for firing ceramic molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for firing ceramic molded articles, and more particularly, to a method for firing ceramic molded articles having a small thickness in a stacked state in the thickness direction.

[0002]

2. Description of the Related Art Conventionally, in order to fire a ceramic molded body used for forming a positive temperature coefficient thermistor element or the like, as shown in FIG. Are stacked in a box-shaped firing box 3 having only an open top surface, and the stack 2 is stacked in a firing furnace (not shown) at a preset temperature. Is generally adopted.

[0003]

According to the above-described conventional method, each of the ceramic molded bodies 1 constituting each of the stacked bodies 2 housed in parallel in the firing casing 3 is described.
Baking proceeds from the outside in contact with the high-temperature furnace atmosphere toward the inside. However, since these ceramic molded bodies 1 have the characteristic of shrinking as firing proceeds, each of the ceramic molded bodies 1 constituting the stacked body 2, particularly, the ceramic molded body 1 located above the stacked body 2. As a result, the product shrinks more and the warpage accompanying the shrinkage becomes larger. As a result, there is an inconvenience that the product yield deteriorates.

The present invention has been made in view of such inconvenience, and it is possible to effectively suppress the occurrence of warpage due to shrinkage of a ceramic molded body, and to easily improve the product yield. It is an object of the present invention to provide a method for firing a ceramic molded body.

[0005]

According to the present invention, in order to achieve the above object, a stacked body obtained by stacking a plurality of ceramic molded bodies along a thickness direction is stored in a firing box in parallel. wherein in the firing process of firing to the ceramic molded body, a drop lid made of pre-Symbol ceramic molding the same composition of the ceramics, in said firing Napishtim
Place on the stack, and stack the stack by its own weight.
It is characterized in that the body is fired while being pressed along its thickness direction .

[0006]

According to the above construction, the weight of the drop lid is dispersed and added to the individual ceramic molded bodies constituting the stacked body, and each ceramic molded body is pressed along the thickness direction. It will be fired in the state where it was.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method of the present invention will be described below with reference to the drawings.

FIG. 1 is a cutaway perspective view for explaining the method of the present embodiment, and is a cutaway perspective view of a firing box in a state in which a ceramic molded body is housed. In FIG. 1, parts and portions that are the same as or correspond to those in FIG. 3 showing the conventional example are denoted by the same reference numerals.

In the method of this embodiment, a ceramic molded body used for forming a positive temperature coefficient thermistor element or the like is fired. As shown in FIG. 1, a ceramic molded body 1 to be fired, for example, barium titanate or the like is used. Is formed by stacking a required plurality of sheets along the thickness direction. Each of the stacked bodies 2 is stored in parallel in a box-shaped firing box 3 having an open top only, with a predetermined space therebetween. In this case, since the firing box 3 is generally made of alumina, a powder or a rug made of zirconia is spread on the bottom surface of the box 3 in order to prevent a reaction with the ceramic molded body 1. A zirconia coating is applied. By the way, the shape of the firing casing 3 shown in FIG. 1 in plan view is rectangular, but is not limited to this, and it is needless to say that the firing casing 3 may be circular.

[0010] Further, the stacks 2 thus housed in parallel in the firing box 3 are collectively covered on each of the stacks 2 and the stacks 2 are placed under their own weight in the stacking direction. A drop lid 5 to be pressed is placed. That is, the drop lid 5 is attached to the ceramic molded body 1.
It is formed by firing a ceramic material having the same composition as, for example, barium titanate, and is formed as a flat plate having a certain weight. In addition, this drop lid 5
Is similar to the inner shape of the firing box 3 and its outer dimensions are smaller than the inner dimensions of the firing box 3. By the way, at this time, the drop lid 5 may be formed of alumina, mullite, or the like. In this case, however, a measure for preventing the reaction between the drop lid 5 and the ceramic molded body 1 is required. The drop lid 5 is preferably made of a ceramic material having the same composition as that of the ceramic molded body 1 to be fired, since it is required separately and the work required for the firing operation increases. Further, depending on the composition of the molded body, there is also an effect of preventing component volatilization during firing.

[0011] Next, the inventors of the present invention have proposed a drop lid 5.
In order to compare the advantages and disadvantages of the method of this embodiment using the method of the present invention and the conventional method without using the dropping lid 5, a large number of ceramic molded bodies 1 made of barium titanate having a diameter of 16.8 mm and a thickness of 0.6 mm were prepared. Since the baking experiment was prepared and performed, the baking experiment will be described.

First, in this firing experiment, the inner dimensions were 88 mm long × 88 mm wide × 24 mm high (thickness 6 m
The firing case 3 of m) was used, and a stacked body 2 formed by stacking 20 pieces of the ceramic molded bodies 1 having the above dimensions was stored in 5 columns and 5 rows in the firing case 3. . As the drop lid 5, a plate made of barium titanate and formed as a flat plate having a length of 84.5 mm, a width of 84.5 mm, and a thickness of 1 mm was used. In this firing experiment, the firing case 3 containing the ceramic molded body 1 pressed by the dropping lid 5 (the method of the present embodiment) and the firing casing 3 containing only the ceramic molded body 1 without using the dropping lid 5 were used. After firing both Box 3 (conventional method) at a temperature of 1350 ° C. for 1 hour,
When the ceramic molded body 1 located at the uppermost part of the stacked body 2 where the adverse effect of sintering appears most greatly was taken out and the warpage generated was measured, the results shown in Table 1 were obtained. Here, x and y in Table 1 represent the average value of the dimensions of each portion of the fired ceramic molded body 1 as shown in FIG. 2, and xy represents the average value of the degree of warpage. σ indicates the standard deviation of xy.

[0013]

[Table 1]

According to Table 1, which shows the results of the firing experiment, the ceramics fired by the method of the present embodiment using the dropping lid 5 is less than the warpage of the ceramic molded body 1 fired without using the dropping lid 5. It is clear that the warpage appearing in the molded body 1 is greatly reduced. Furthermore, in the method of this embodiment, since each of the stacked bodies 2 stored in parallel in the firing box 3 is dropped and pressed by the lid 5, external force such as vibration during transportation is applied to the firing box 3. Even if the ceramic molded body 1
It has also been confirmed that there is no mutual displacement or the like, and that there is an advantage that cracking or chipping in the ceramic molded body 1 can be prevented.

[0015]

As described above, according to the present invention,
On the stacked body stored in parallel in the firing box, a ceramic material of the same composition as the ceramic molded body is used,
In addition, since the drop lids that press each stack along the stacking direction are placed, the weight of the drop lid is dispersed and added to the individual ceramic molded bodies that constitute the stack. Thus, each ceramic molded body is fired while being pressed along the thickness direction. As a result, it is possible to effectively suppress the occurrence of warpage due to shrinkage of the ceramic molded body, and it is possible to obtain an effect that the product yield can be easily improved.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view of a firing box in a state in which a ceramic molded body is stored according to a method of the present embodiment.

FIG. 2 is a side view showing a warped state of a fired ceramic molded body.

FIG. 3 is a cutaway perspective view of a firing box in a state in which a ceramic molded body is stored according to a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic molded body 2 Stacked body 3 Sintering box 5 Drop lid

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C04B 35/64 F27D 3/12

Claims (1)

(57) [Claims] 1. A firing method for a ceramic molded body in which a plurality of ceramic molded bodies (1) are stacked in a thickness direction and a stacked body (2) is stored in a firing casing (3) in parallel and fired. in the previous SL ceramic molded body (1) off the lid made of ceramics of the same composition as (5), said firing Napishtim- (3) in the previous in
Place on the stack (2), and remove the drop lid (2).
Press the stack (2) with its weight along the thickness direction.
A method for firing a ceramic molded body, characterized in that the firing is performed in a heated state .