Ceramic honeycomb structure and method of production thereof

Stock material or miscellaneous articles – Structurally defined web or sheet – Honeycomb-like

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Details

422180, 502439, 50252719, 21050021, 210506, 264433, B32B 1700

Patent

active

059520795

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a ceramic honeycomb structure (hereinafter referred to simply as the honeycomb structure) and its manufacturing method, and more particularly, to a ceramic honeycomb structure and its manufacturing method that is used in catalyst supports for internal combustion engines, filters and so forth.


BACKGROUND ART

For example, honeycomb structures used as catalyst supports for internal combustion engines have in recent years come to be required to have low pressure loss accompanying the increased performance of internal combustion engines, as well as high purification performance in consideration of environmental issues and so forth.
As can be seen in Japanese Unexamined Patent Publication (Kokai) No. 7-39761, in the prior art, attempts have been made to maintain compression strength while maintaining a low thickness for the partition walls that compose the honeycomb structure by using predetermined values for numerical aperture, bulk density and so forth.
However, it was still difficult to obtain a honeycomb structure free of chipping in the constitution of the prior art.
Therefore, the present invention was obtained in consideration of the above-mentioned problems, and is characterized by the obtaining of a honeycomb structure having thin partition walls that suppresses the occurrence of chipping.


DISCLOSURE OF THE INVENTION

To begin with, the inventors of the present invention earnestly researched the mechanism of chipping in honeycomb structures in which the partition wall thickness is 0.13 mm or less.
As a result, the following matters were found.
Namely, in the honeycomb structure of the prior art, external force is applied during drying of the honeycomb support extruded from an extrusion mold, when dragging at the time of handling and transport (such as when the honeycomb structure is hooked at the outlet of the dryer during removal work from the dryer or when the honeycomb structure is taken off of the dryer belt while dragging), when clamping during cutting of both ends, and when taking the honeycomb support in and out of the kiln during firing to form a honeycomb structure.
At these times, there are cases in which force is produced within the honeycomb structure from the inside to the outside to the partition walls and peripheral wall, resulting in the application of point-contact force to the peripheral wall of the honeycomb structure. In such a case, in the honeycomb structure of the prior art, the circumference of the peripheral wall dissipates force by micro-chipping, resulting in a structure that is able to withstand external impacts.
However, in a honeycomb structure 80 having an extremely thin wall thickness as shown in FIG. 1, in the case force is produced from the inside to the outside relative to the partition walls and peripheral wall, it was found that a large edge chipping 82 is induced by the resulting micro-chipping of the peripheral wall.
In the case of having thick partition walls as in the prior art, the occurrence of edge chipping is inhibited by the sufficient joining strength as a result of the contact width between the peripheral wall and partition walls being large relative to a force like that which tries to pull apart the outer peripheral wall. In contrast, it was found that in the case the partition walls are extremely thin, and particularly in cases in which the partition walls are 0.13 mm or less in thickness, due to the small contact width between the peripheral wall and partition walls, the honeycomb structure is extremely weak with respect to force applied from the inside to the outside of the honeycomb structure, thereby resulting in the occurrence of edge chipping.
Here, the relationship between partition wall thickness and the occurrence of edge chipping is shown in FIG. 2.
As is also clear from FIG. 2, when partition wall thickness is 0.13 mm or less, there is a sudden increase in the occurrence of edge chipping.
Therefore, claim 1 of the invention of the present application discloses a honeycomb structure having

REFERENCES:
patent: 4448833 (1984-05-01), Yamaguchi
patent: 4550005 (1985-10-01), Kato

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