Engine Exhaust Particulate Filter

Technical Field

This invention relates to a filter for removing particulates from exhaust gases of engines, such as diesel engines, so as to deliver substantially parti¬ culate-free exhaust gases to the ambient atmosphere.

Background Art

Internal combustion engines, and particularly diesel engines, emit exhaust gases that carry substan¬ tial amounts of particulate material- Such material adds to the air pollution produced by internal combustion engines which lack an effective particulate filter. In¬ sofar as applicant is aware, none of the diesel engines now in use have a particulate filter in the exhaust system.

A problem with most particulate filters is that if they are sufficiently compact and are really effec¬ tive in particulate removal they tend to create excessively high engine exhaust back pressure which reduces engine efficiency, resulting in excessive fuel use which increases operating cost. In addition, con¬ ventional particulate filters gradually become clogged with particulates in operation which causes excessive back pressure resulting in poor engine performance or damage to the engine or the filter. Ultimately the filter must be changed or rejuvenated by a difficult cleaning operation.

The devices of United States patents known to applicant which purport to provide a particulate filter for internal combustion engine exhaust gases all suffer either from the defect of creating excessive back

pressure especially after prolonged operation or of be¬ ing unacceptably complex, or being inefficient in the removal of particulates, or being excessively large.

The foregoing illustrates limitations of the known prior art. Thus, it is apparent that it would be advantageous to provide an alternative directed to over¬ coming one or more of the limitations as set forth above.

Disclosure of the Invention

In one aspect of the present invention, this is accomplished by providing a filter apparatus including a housing within which a fluid conduit is mounted. At least one pair of opposed filter elements are disposed axially along the conduit. The elements extend radially outwardly from the conduit. Means are provided for directing fluid from the conduit outwardly between the pair of•elements. One of the elements is in fluid flow inhibiting relationship with the other of the elements. At least one of the elements is of a construction suffi¬ cient for movement relative to the other element to a fluid flow permitting relationship in response to pressure changes of the fluid between the elements.

Brief Description of Drawings

Fig. 1 is a longitudinal sectional view illustrating a first embodiment of the invention; Fig. 2 is a fragmentary plan view of an annular perforate clip which encircles a filter element;

Fig. 3 is a fragmentary sectional view illus¬ trating a modified type of filter element for said first embodiment; Fig. 4 is a fragmentary transverse sectional view illustrating a second embodiment of the invention;

Fig. 5 is a fragmentary sectional view illus¬ trating more clearly the interrelationship between the filter elements of the second embodiment;

Fig. 6 is a view like -Fig. 5 illustrating the filter elements of a third embodiment of the invention;

Fig. 7 is a fragmentary sectional view illus¬ trating a fourth embodiment of the invention; and Fig. 8 is a fragmentary sectional view illus¬ trating in greater detail the relationship between the filter elements of the embodiment of Fig. 7.

Best Mode for Carrying out the Invention

Referring- to the drawings in detail, and referring first to Fig. 1, a housing, indicated generally at 10, has an inlet end wall 11 provided with an inlet opening 12 through which a pipe 12a delivers exhaust gases to a fluid conducting manifold 13. A cylindrical housing side wall 14 has an opening 15 communicating with a discharge pipe 15a;- and the end of the housing opposite the wall 11 is 'supplied with a closure plate 16 which may be conveniently removably mounted upon the end of the cylindrical housing side wall 14 by a collar 17, although other common means may be used such as screws or bolts in overlapping circumferential flanges. Preferably the housing 10 is fabricated from sheet metal which is pro¬ tected from the corrosive effect of hot exhaust gases by ceramic- lining elements 11a, 14a and 16a on the respective end wall 11, cylindrical side wall 14, and end plate 16.

Suitable means such as an abutment 18 is employ¬ ed to fixedly secure one end of the manifold 13 to the end wall 11, and the opposite end portion of the manifold 13 extends through an axial hole 19 in the end plate 16 and the ceramic liner 16a. A sleeve 20 having a thrust ring 21 makes a sliding fit on an outer end portion 22 of the manifold 13.

Within the housing 10 the manifold 13 has a series of exhaust openings, such as the openings 23

which may be circular or elongated slots which are spaced longitudinally along the manifold so as to dis¬ charge exhaust gases from the manifold 13 radially out¬ wardly into housing 10. Conveniently, openings 23 are arranged in a spiral pattern, as shown, so as to eliminate any need for matching filter maze members to a particular spacing between openings.

Surrounding the manifold is at least one and preferably a plurality of pairs of filter maze members, indicated generally at 27, axially disposed along manifold 13 within housing 10. Each of the filter maze members consists of two opposed, radially extending filter elements 28 and 29 having inner periphery encircl¬ ing the manifold 13 adjacent the exhaust openings 23. The filter elements 28,29 comprise relatively thin plates of porous, preferably refractory material which are spaced apart at a first end 101 adjacent manifold 13 and which converge toward each other as they extend radially outwardly from manifold 13 and have outer peri- pheral portions 28a and 29a lightly in contact with one another at a second end 102 for inhibiting fluid flow between elements 28,29. By relatively thin is meant that elements 28,29 are of a construction sufficient to flex and separate at outer peripheral portions 28a,29a in response to increased back pressures and pressures exerted by heavy engine load. As shown in Figures 1 and 2, a perforated annular clip 30, which may conveniently be in the form of a split collar having a plurality of openings 30a formed therein, loosely embraces the outer peripheral portions 28a and 29a of the filter elements in juxtaposition to permit elements 28,29 to relatively move apart at the abutting second end 102 in response to pressure changes in exhaust gases between elements 28,29. The filter elements 28 and 29 may consist of a material such, for example, as ceramic, compressed stainless steel wire, foamed metal, or any other material which

may be fabricated into a plate having pores small enough to effectively filter soot particles as small as 0.01 to 1 micron in diameter.

The series of openings 23, in the manifold 13 divide exhaust gases entering the manifold 13 into several independent streams, with each of- the streams entering one of the filter maze members 27 between the spaced elements 28,29.

The filter maze members 27 are held firmly in stacked relationship between the sleeve 20 and the annular abutment 18 by means of a spring 31 which is compressed between the thrust ring 21 of the sleeve and a spring seat flange 32 that screws onto a thread 33 on the outer end portion 22 of the manifold. A closure cap 34 also screws onto the thread 33 and serves as a retainer for the spring seat flange 32. Included also is a gas seal 35 between ring 21 and plate 16.

In normal operation an internal combustion engine is periodically so heavily loaded that the exhaust gases are discharged at a temperature high enough to burn out the particulate material which is trapped on the surface and i the pores of the filter maze members 27. However, if an engine is operated for an extended period of time under light loads, as when idling, there may be a sufficient buildup of particulate material in the filter elements 28 and 29 as to cause undesirable back pressure. When this occurs, the increased pressure forces outer peripheral portions 28a,29a, slightly apart so that exhaust gases and possibly some particulate material may escape past loose fitting clip 30 to the ambient atmosphere.

When the engine is next operated under heavy load, the temperature of the exhaust gases is ordinarily high enough to oxidize the collected particulates and rejuvenate the filter mazes. The particulates deposited at the inner surfaces of the filter elements, and prob-

ably those nearest to the manifold, .are ignited at high load; and the combustion spreads rapidly throughout the trapped particulates and consumes them all. Under these circumstances, peripheral portions 28a,29a may also be forced slightly apart.

Referring to Fig. 3, there is illustrated a modified filter maze member 127 consisting of filter elements 128 and 129 which are like the filter elements previously described except for respective combustion points 128a and 129a on their facing surfaces. The combustion points project into the stream of hot gases entering the filter maze member and are quickly heated at high load to a high enough temperature to ignite any particles built up on the inner surfaces of the filter elements.

Referring now to Figs. 4 to 8, several alterna¬ tive forms of filter maze members are illustrated. In each case, there is a housing, indicated generally at 10, which is the same as the housing previously described except that, as seen in Figs. 4 and 7, an inlet end wall 11 is at the bottom, so that an inlet pipe 12 communi¬ cates with an upright manifold 13,213 which has a series of exhaust openings such as the openings 223, seen in Fig. 4. Each of the openings 223 consists of several coplanar holes, rather than the spirally arranged holes illustrated in Fig. 1.

Surrounding the manifold 213 is a series of filter maze members, indicated generally at 227, each of which consists of two opposed, radially extending filter elements 228 and 229. Each of the filter elements 228 consists of a thin, rigid bottom plate 230 having an internal annular collar 230a which makes an easy sliding fit upon the manifold 213. Secured to the upper surface of the plate 230 by any suitably heat- resistant means is a rug-like member consisting of a backing 231 and pile 231a. Both the backing 231 and

the pile 231a must, of course, consist of material which is effectively immune to the high temperatures of the gases discharged into the manifold 213.

The filter element 229 consists only of a rug- like member having a backing 231 and a pile 231a. A mounting annulus 232 makes an easy sliding fit on the manifold 213 and has a plurality of circumferentially spaced narrow posts 233, so that the inner margin of the filter element 229 is supported in predetermined spaced relationship to the inner margin of the filter element 228. The rug-like element of the filter element 229 is sufficiently limp that all but its innermost portion is supported upon the lower filter element 228 as seen in Fig. 5, so the pile 231a of the two rug-like members tends to intermesh in a fluid flow inhibiting relation¬ ship and form a very effective filter maze.

In the event of extended low temperature operation, the accumulation of particulate matter in the pile fibers of the two rug-like members ultimately causes a development of enough pressure to lift the outer portion of the upper filter element 229 off the lower filter element 228 a sufficient distance that the particulate buildup is relieved and exhaust gases may continue to pass between the filter elements as indi- cated by the arrows in Fig. 4. When normal high temperature operation is resumed the heat of the exhaust gases will be sufficient to burn out the deposited car¬ bon particulates, thus rejuvenating the filter maze members 227. Fig. 6 illustrates a third embodiment of a filter maze member, indicated generally at 327, which consists of a lower filter element 328 having a face 328b and an upper filter element 329 having a face 329b opposite face 328b which are rigid plates having inter- meshing stiff bristles 328a and 329a in a fluid flow inhibiting relationship. This structure may be used

^' _) - ^' - .-- ^■■• - ϋ

with a manifold like the manifold 13, in which the openings consist of spirally arranged holes. Successive filter maze members 327 have their respective adjacent filter elements in contact with one another, or separat- ed by resilient bellows members such as those illustrat¬ ed in Fig. 7 where they are given a reference numeral 450. The resilient bellows members permit the filter elements 328 and 329 to move apart under increased back pressure caused by any accumulation of particulates in the filter maze formed by the bristles 328a and 329a.

Referring now to Figs. 7 and 8, filter maze members, indicated generally at 427, consist of ceramic filter elements 428 and 429 having opposed faces 428c, 429c, which have concentric, tapered lands 428a and grooves 428b which intermesh with lands 429a and grooves 429b in a fluid flow inhibiting relationship. Resilient bellows members 450 are mounted between adjacent filter maze members 427, both to act as gas seals between the filter maze members and to allow for separation between the filter elements under the increased back pressure caused by an accumulation of particulates o the lands and in the grooves.

The assemblies illustrated in Figs. 4 and 7 have upright manifolds; but it is obvious that they could have horizontal manifolds provided a means were provided, such as the compression spring 31 in Fig. 1, to force all the filter maze members toward the inlet end of the housing.

Industrial Applicability The engine exhaust particulate filter of the present invention, in any of its several embodiments, may be installed in the exhaust line of an internal combustion engine where the particulate-bearing exhaust gases must pass through it.

In operation, the apparatus in any one of its embodiments functions to divide particulate-laden exhaust gases into several independent streams which flow out of the manifold 13 or 213, as the case may be, through the exhaust openings 23, etc., or 223, etc.

Each of the streams of particulate-laden exhaust gases is directed into a filter maze member which traps the majority of the particulates in the stream and passes the effectively particulate-free gases to the ambient atmosphere.

Under heavy loads gases are directed into the filter maze members at a high enough temperature to oxidize or burn out the trapped particulates and thereby rejuvenate those members. Furthermore, the structure of the present particulate filter in any of its disclosed embodiments causes it to function as a fairly effective muffler or noise suppressant for the engine exhaust.

It is anticipated that aspects of the present invention, other than those specifically defined in the appended claims, can be obtained from the foregoing description and the drawings.

Λ ^* -,