Gas separation – With means securing or retaining separating media – Internal frame or support means
Reexamination Certificate
2001-10-19
2004-08-17
Smith, Duane (Department: 1724)
Gas separation
With means securing or retaining separating media
Internal frame or support means
C055S282300, C055S385300, C055S486000, C055S495000, C055S498000, C055S501000, C055S502000, C055S520000, C055S521000, C055S523000, C055S527000, C055SDIG001, C055SDIG003, C060S311000
Reexamination Certificate
active
06776815
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a particulate filter for scavenging particulate matters (which will hereinafter be abbreviated to PMs if not especially specified) typified by soot defined as suspended particulate matters contained in an exhaust gas of, e.g., a diesel engine.
BACKGROUND ARTS
The diesel engine has a high economical merit and is, while on the other hand, highly required to purge the exhaust gas of the PMs. What is known for attaining this is a technology of providing a particulate filter for scavenging the PMs in an exhaust system of the diesel engine so that the PMs are not discharged into the atmospheric air (see Japanese Patent Application Laying-Open Publication No.9-262414).
The particulate filter basically includes N-sheets of (N is an even-number of 2 or larger) composed of heat resisting metal fibers and having a filter function, and the same number of heat resisting metal plates as that of the non-woven fabrics, each having a widthwise dimension somewhat smaller than the non-woven fabric, taking a corrugated shape in vertical section and therefore generally called a corrugated sheet.
The following is an outline of the method of forming the particulate filter.
An elongate rectangular multi-layer member is formed by piling up alternately the corrugated sheets and the non-woven fabrics in same direction, and is thereafter wound in roll as to be a cylindrical shape (what the elongate rectangular multi-layer member is formed in the cylindrical shape will hereinafter be called a [cylindrical multi-layer body]).
Note that a configuration of the cylindrical multi-layer body is kept in the cylindrical shape owing to a rigidity of the corrugated sheet. Namely, the corrugated sheet functions as a bone member of the cylindrical multi-layer body.
Then, the cylindrical multi-layer body has a sealing portion that seals by welding the leading edges of the non-woven fabrics adjacent to each other in the radial direction, and a non-sealing portion that keeps open the leading edges of the non-woven fabrics similarly adjacent to each other, these sealing and non-sealing portions being formed alternately.
To describe it in depth, the cylindrical multi-layer body is formed alternately with the sealing portion at which the corrugated sheet positioned between the non-woven fabrics is closed and invisible when viewed from is one side end thereof, and with the non-sealing portion at which the corrugated sheet is visible because of its being opened. Then, the sealing portion and the non-sealing portion are also formed alternately at the other side end thereof. The positions of forming the sealing and non-sealing portions are, however, different at one side end and at the other side end.
Namely, with respect to a couple of adjacent non-woven fabrics with the sealing portions at one side end of the cylindrical multi-layer body, the other side end is provided with no sealing portion. With respect to another couple of adjacent non-woven fabrics with no sealing portion formed at one side end, the other side end is provided with the sealing portion.
As a result, portions with the corrugated sheets inserted into spaces, of which one side end closed and the other side end opened, surrounded by the non-woven fabrics, (hereinafter be called a [layer portion]), are formed spirally in multi-layers in the cylindrical multi-layer body. Then, the thus configured cylindrical multi-layer body is inserted into the heat resisting metal container having substantially the same diameter as an inside diameter of the exhaust pipe and opened at both of side ends thereof. The inner surface of the heat resisting metal container and the outer peripheral surface of the cylindrical multi-layer body, are welded at proper portions, thereby fixing the cylindrical multi-layer body to the heat resisting metal container. The particulate filter is thus formed. Note that the particulate filter is formed so that no gap is formed to the greatest possible degree between the cylindrical multi-layer body and the heat resisting metal container in order to ensure the durability against vibrations.
The particulate filter is attached to the exhaust pipe by fitting the filter into a joint portion between the exhaust pipes.
Further, the heat resisting metal container is charged with the cylindrical multi-layer body so as to not form any gap within the heat resisting metal container, and the exhaust gas flows through the cylindrical multi-layer body without any leakage. It can be therefore said that the outside diameter of the cylindrical multi-layer body has, though slightly smaller, substantially the same dimension as the inside diameter of the heat-resistant metal container.
The thus configured particulate filter attached to the exhaust pipe is coaxial with the exhaust pipe.
Then, in a state where the particulate filter is attached to the exhaust pipe, the exhaust gas flowing through the exhaust pipe towards the particulate filter enters the layer portion from the non-sealing portion provided upstream of the exhaust gas in the non-woven fabric, and thereafter flows downstream of the exhaust pipe. The downstream side within this layer portion is sealed by welding, and extremely minute gaps formed between the fibers of the non-woven fabric are closed at this portion. Accordingly, the exhaust gas flowing nowhere flows from the layer portion sealed downstream towards other layer portion adjacent to the former layer portion and having the non-sealing portion on the downstream side. At this time, the PMs are scavenged in between the minute gaps of the non-woven fabric, thereby purging the exhaust gas of the PMs.
The exhaust gas with the PMs removed flows into the other layer portion and is thereafter, because of the other layer portion with the non-sealing portion provided downstream and opened, discharged into the atmospheric air.
On the other hand, when a quantity of the PMs scavenged by the particulate filter becomes large enough to cause clogging in the metal fiber non-woven fabric, an exhaust resistance rises with the result that the flow of the exhaust gas becomes unsmoothed Besides, no further scavenging of the PMs can be attained.
Such being the case, the scavenged PMs are removed by periodically burning PMs with the heat of the exhaust gas or the heat of an electric heater, etc., thereby preventing the clogging. This serves to eliminate an obstacle against scavenging the PMs by the particulate filter. This is called a recycling of the particulate filter.
By the way, according to the prior art disclosed in Japanese Patent Application Laying-Open Publication No.9-262414, the elongate rectangular multi-layer member composed of the non-woven fabric and the corrugated sheet is wound in roll, and needed to slightly bend a start-of-winding portion of the elongate rectangular multi-layer member because of such a configuration. Therefore, an excessive stress occurs on the bent portion as the start-of-winding portion of the elongate rectangular multi-layer member, and as a result cracks and creases are, though minute, easy to form in that portion.
Further, when forming the cylindrical multi-layer body, though feasible to obtain a strength in the radial direction with the corrugated plate, the non-woven fabric and the corrugated plate are held in the axial direction only by a frictional resistance due to a contact therebetween with only an arrangement that the elongate rectangular multi-layer member is wound in roll by simply piling up the non-woven fabric and the corrugated sheet. Hence, if a pressure of the exhaust gas that acts in the axial direction abruptly changes, a deviation between the non-woven fabric and the corrugated plate might occur. If the deviation therebetween occurs, the rigidity of the cylindrical multi-layer body that is kept by the corrugated plates decreases, and it is considered that the cracks and the damages are caused in the cylindrical multi-layer body.
Next, the particulate filter is, as described above, coaxial with the exhaust pipe, and the outer peripheral portion o
Itsuaki Satoru
Kato Zenichiro
Nagai Youichi
Shibutani Kazutoshi
Shimoda Kohei
Greene Jason M.
Oliff & Berridg,e PLC
Smith Duane
Toyota Jidosha & Kabushiki Kaisha
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