Exhaust gas cleaner with catalytic activity, and silencer for internal combustion engines.

The present invention relates to a scrubber of the exhaust gas, having a catalytic activity, for internal combustion engines, also having the function of a silencer.

We know well scrubber exhaust with catalytic activity, for internal combustion engines. In the most common achievements these purifiers include a ceramic mass traversed longitudinally by a large number of small straight channels, the section, usually square, is of the order of 1 mm², which are separated from the another by walls whose thickness is about 0.2 mm and whose surfaces are covered with a platinum layer deposited. The extremely high cost of such a construction is obvious. The exhaust gases are forced through these channels and reduced section, during this course, they effectively lick the platinum coating, which exerts on the gas catalytic action to oxidize carbon monoxide and unburned hydrocarbons, to decompose the nitrogen oxides. As the catalyst is in good conditions, thus obtaining a cleaning of exhaust gas, which can happen to the elimination of 80% to 90% of the harmful impurities. However, this effective provided the catalyst has a relatively short duration, even in the case of fuel carburation engines, which are generally indicates a limit of about 5000 km course, after which the scrubber of the exhaust gas , either due to catalyst poisoning or mostly obstuctions occurring becomes sufficiently effective and should be replaced. On the other hand, such scrubbers are not applied to diesel cycle engines, because the sulfur compounds contained in the exhaust gas of these engines would put off the scrubber already in the course of a few hours. A first very serious drawback of these scrubbers lies in its duration too small compared to the cost, and their inadequacy for diesel cycle engines. But these scavengers also show another very serious drawback, consisting in the high resistance offered to the flow of exhaust gas through the small channels between the ceramic material of the scrubber. This high resistance results in a significant back pressure at the outlet of the engine, and therefore a serious reduction in performance.

Some improvement has been paid to these scrubbers having catalytic activity by replacing the perforated ceramic mass by a folded sheet covered by the catalytic material and folded appropriately to determine a large number of straight channels of reduced section. This construction results considerably more economical, however, the disadvantages of short duration and high resistance to gas flow remain unchanged.

Filters exhaust you mentioned have no specific function as quiet, although in practice they give rise to a certain noise reduction precisely because, and only the high resistance offered to the flow of exhaust gas.

The object of the present invention is to provide a cleaner exhaust gas, for internal combustion engines, which must be of relatively economical construction, which must have high efficiency in purification while not opposing resistance the high flow of exhaust gas, and which must at the same time develop effective action as silenciex, this action is not, too, not accompanied by any high resistance opposed to the flow of exhaust gas.

This object is achieved according to the invention, in that the scrubber comprises in combination: at least one element having a catalytic action, consisting of a sheet metal strip covered with a material having a catalytic activity and wound in spiral, com said strip bearing number stamped projections inclined relative to the longitudinal and transverse directions of the band and acting of spacers between the winding turns of the strip, as well as deflectors for the flow of exhaust gases; and at least one noise absorbing member, substantially non-sink.

Due to these characteristics, the element having a catalytic action can be manufactured relatively economically, and the passages formed within it to the flow of exhaust gas being defined by the inclined projections and therefore extending in a helical manner, give rise to an effective licking catalitiques surfaces by the exhaust gas, even without requiring that these passages are very narrow. It follows on the one hand, that the purifier does not oppose a high resistance to exhaust gas, and does not trouble appreciably engine efficiency, and the other side that the passages are blocked by deposits with a much reduced speed, so that the length of the element is greater than the usual one. On the other hand, the absence of flow resistance has the consequence that the catalytic element, in itself, provides a lower contribution as exhaust silencer, but it provides the combination with a noise-damping member; the latter, in turn, being of a type substantially not sink, do not introduce significant subsequent resistance to flow of exhaust gas. As a result, the exhaust gases can be cleaned and silenced effectively, without introducing any appreciable reduction in engine efficiency, and ensuring that the scrubber-silent a long service life. One consequence of these characteristics is that the following scrubber-quiet the invention can be applied with advantage also in the discharge of the Diesel cycle engines.

Preferably said inclined protrusions stamped into the sheet metal strip intended to constitute the catalytic element has a sinuous conformation, showing in one half of each projecting a directed curvature in one direction and the other half a curvature directed in the opposite direction. This conformation provides particular effectiveness in licking catalytic surfaces by the gas, and at the same time gives projections particularly effective in their function as spacers between the spiral turns of the winding of the strip.

Preferably, moreover, the band also comprises, in a central region between said projections, openings extending therethrough. These openings help the tape of the production and, in operation, give rise to mutual communication between the gas passages defined by the strip, and hence turbulence phenomena which promote efficient licking catalytic surfaces of the share of gas; furthermore, these openings lead to anastomoses between the various passages, which are very useful in making yet possible acceptable operation when certain parts begin to be blocked. This also helps to extend the life of the scrubber.

Any item not silent heatsink consists of many rooms that are restricted, directed from a central substantially free leads to the periphery of the device. Such a structure ensures effective damping of all the noise frequency components, without resulting in a significant energy dissipation. The structure of the silencer element can be achieved economically through number of annular discs of metal sheet stamped, coupled two by two and finally stacked. Preferably, in addition, these discs are perforated in their areas between the rooms that are restricted. This gives rise to communication between the spaces between the stacked pairs of discs, areas in which occurs the damping of noise carried by the part of the exhaust gas does not affect the rooms that are restricted but located between them on the field.

Preferably, two successive elements having a catalytic action are provided, and the silencer element is interposed between said elements having a catalytic action.

Preferably, finally, at the exit of the scrubber is still provided a collection chamber for solid waste, which communicates through openings with the passage for the exhaust gases. Solid waste resulting from chemical reactions activated by catalysts can thus be collected without discharge into the air, and they can be unloaded from time to time of the collection chamber in which they have accumulated.

These and other features and advantages of the subject of the invention appear more clearly from the following description of a preferred embodiment, but having the character of a non limiting example, shown schematically in the accompanying drawings, wherein:<ul><li>Fig. 1 is a view from the outside in plan, on a reduced scale, the scrubber-quiet device;</li><li>Fig. 2 shows a vertical section taken along the line II-II of Figure 1;</li><li>Fig. 3 shows a cross section taken along the broken line III-III of Figure 2;</li><li>Fig. 4 shows on a larger scale a cross section of an element having a catalytic action, taken along the line IV-IV of Figure 2;</li><li>Fig. 5 shows in plan the development of a section of the metal strip constituting the element having a catalytic action;</li><li>Fig. 6 shows on a larger scale a cross section of the silencer element, taken along the line VI-VI of Figure 2;</li><li>Fig. 7 shows a diametric section of a couple of discs constituting the silencer element, taken along the line VII-VII of Figure 6; and</li><li>Fig. 8 shows a modification to the construction of the muffler housing element.</li></ul>

Referring first to Figures 1 and 2 showing the assembly of a scrubber-exhaust system according to the invention by the reference 0 is specified as a final section of an exhaust pipe of an internal combustion engine which the scrubber is connected by a clamp-on collar 5. the device is defined by a first housing part 1, comprising a first member having a catalytic action, by a second housing part 2 containing a second element having an action catalyst, a third housing part 3 interposed between parts 1 and 2, containing a silencer element, and a fourth housing part 4, for the collection of solid waste and the discharge of clean gas in the air ambient. The housing parts 2 and 4 may advantageously be constituted by a single construction element. The housing parts 1, 2 and 4 are made, preferably, by metal shells pairs of stamped stainless steel, joined together by flanges following the horizontal diameter; the housing part 3 is preferably constituted by a stainless steel pipe section, provided with flanges connected to the housing parts 1 and 2 by clamps 6 provided with clamping means 7.

The input of the device, in correspondence of the collar 5, is begun diverging duct 8 extended by a cylindrical duct 9; these parts are made preferably of stainless steel, and are crossed by holes. The space interposed between the parts 8, 9 and the housing 1 is filled with material such as copper wool 10. In the cylindrical duct 9 is housed the first member having a catalytic action, which will be described further. The cylindrical pipe 9 follows a line converging 11 which opens into the center of the silencer element, housed in part 3 of the housing and which will be described further. Preferably, a thermal-acoustic insulation material 12 is inserted between the converging duct 11 and the outer housing 1.

A 'the outlet of the silencer element housed in the part 3 of the housing is provided a diverging duct 13, extended by a cylindrical conduit 15 perforated. Preferably, the space between the diverging duct 13 and the outer casing 2 is filled with a thermo-acoustic insulation material 14, while the space between the perforated cylindrical conduit 15 and the outer casing 2 is filled, preferably by of copper wool 16. in the cylindrical conduit 15 is housed the second element having a catalytic action, which will be described further.

The fourth part 4 of the housing is restricted to a discharge opening 17 which opens into the ambient air. The lower part of this section of the housing is penetrated by openings 18 which open into a crop drawer 19. A pipe 21 is connected at 20 to the slider 19 and extends towards the anterior part of the device, inside of which it ends in an opening 22 directed in the direction of the flow of gas so as to receive a suction action. In the interior of the fourth part 4 of the housing accommodates a central spindle body 23 shaped so to accompany the flow of gas, which body can be manufactured from sheet stainless steel.

The first member having a catalytic action, disposed in the cylindrical duct 9 is formed (Figure 4) by winding spirally a metal strip 24, whose conformation detail from FIG 5. In the tape sheet 24 are pressed at regular intervals and in a direction inclined, projections 25 which preferably, as shown, comprise two successive portions of the opposite curvature, so that they show a curvy general form, in extended S. The strip 24 can be cut from a stainless steel sheet 5/10 mm thick, and the height of the projections 25 may be of the order of 2 mm, with a pitch of about 26 mm. Preferably the projections 25 extend between the end holes 26, making it easier machining. Furthermore it is advantageous if the openings 27 are provided along the longitudinal centerline of the web 24. These openings 27 are made before the drawing of the projections 25, so that, under the presence of the openings 27, the sheet strip 24 can not be machined to a not very economical and precise way. 24 thus shaped strip is wound spirally around a core consisting of a tube 38 closed at one of its ends by a plug 39. As will be understood, during the winding of the ban 24 the projections 25 establish exactly the distance between the turns of the coil, and then they define between said coils of considerable section of passages, during winding. For their part, the holes 26 and openings 27 provide limited communication between different winding turns of the tape 24.

The second element having a catalytic action, disposed in the cylindrical conduit 15 is formed itself as by a sheet metal strip 40 wound spirally on a central core 41 closed by a plug 42. The structure of the sheet metal strip 40 may be similar at all from that of the sheet metal strip 24 already described, except for the proportions, which generally can be somewhat reduced. In view of this, this strip 40 will not be described in more detail. The central core 41 of the second element having a catalytic action can be advantageously constituted by an extension of fusiform body 23 already described.

The strips 24 and 40 which are produced by the elements having a catalytic action are covered by a deposit of a suitable material, having an effective catalytic action on the exhaust, either in the direction of oxidizing carbon monoxide and unburned hydrocarbons, either in the direction of reducing nitrogen oxides, is still in the direction of decomposing or modifying other substances, such as sulfur compounds, which are present especially in the exhaust cycle engines diesel. The catalytic substances applied to the sheet 24 and the sheet 40 may be the same or different between them, and they may differ according to the intended application of the scrubber. As a preferred example it is indicated that the band 24 constituting the first element having a catalytic action may be advantageously covered by palladium, to specifically act on the carbon monoxide, the unburned substances and nitrogen oxides, while the sheet 40 constituting the second element having a catalytic action can be advantageously covered by tantalum, specifically for action on sulfur compounds.

The silencer element housed in Part 3 of the housing is made for an annular discs pressed steel, eg stainless steel, shaped as shown in Figure 6. Each disc 28 has a central opening 29 free, which will begin pressings 30 digs led to the periphery, which will restrict ess and end with much smaller openings 31 central mouths digs, for example having a diameter equal to 1/4 the diameter of the mouths. These disks, thus stamped are coupled symmetrically two by two, as shown in Figure 7, by attaching them by welding at several points. The corresponding digs two discs and form chambers which extend from the free central opening 29, by restricting to the periphery, where they are connected to the openings 31, thus becoming overturned tubes. In the embodiment shown the discs have an octagonal symmetry. Couples of discs can be stacked by moving angularly 22 ° 30 'relative to the other, thereby providing that the spring arrangement of Figure 2. To facilitate mounting of the pairs of discs of battery each disc has along its periphery sixteen notches 32 arranged at uniform distances, which are made to correspond to the slides 34 applied to part 3 of the housing, so as to ensure an orderly superposition of pairs of discs. In addition, the discs are drilled with many holes 33 (eighty holes in the example) that cross in non-restricted areas concerned by the recesses 30.

The operation of this cleaner-quiet is as follows. The exhaust gas from the exhaust pipe 0 enter the diverging duct 8 which carries them to the first member 24 having a catalytic action. A part of these gases flows through the perforations of the ducts 8 and 9 in the copper wool filler 10, where it is subjected to a chemical action capable of neutralizing a part of the nitrogen oxides. Then the gas run through the passages defined by the winding projections 25 between the turns of the sheet 24 wound in a spiral, forming the first element having a catalytic action. These passages are relatively wide (with the dimensions shown they have a law through section 50 mm²), so they do not result in considerable loss of load, but the angled arrangement and the sinuous shape of passages ensure effective licking the catalytic surface deposited on the sheet 24, so that the treated gas with efficiency by the catalytically active substance, and they are purified.

The conduit 11 carries the converging and depurated gas 29 of the silencer element interior passageway 28 formed by the stacked discs. Although they cover this element without suffering losses, under the presence of the free central passage 29, the gases that carry sound waves produced by the engine transmit their pressure variations with 30 rooms which, by their form restricted shaped horn reversed, effectively weaken, but a non-dissipative way the noise carried. Under the shape of the rooms, which will restrict it does not meet the real phenomena of resonance, and the weakening extends substantially the entire frequency range up the noise. The mouths of rooms 30 to the central passage 29 occupy most of the perimeter area of ​​the passage, but they can not occupy completely; therefore, part of the pressure disturbances carried by the gas must penetrate the spaces between the discs 28. In these disturbances act the holes 33 of the disks 28, allowing a transmission of pressure variations in the longitudinal direction of the silencer element , and therefore compensation of these pressures among the various e spaces, therefore, the neutralization of the transported background noise.

Downstream of the silencer element 28, the diverging duct 13 again distributes the flow of exhaust gas to the second member 40 having catalytic activity, which repeats the action already done by the first member having a catalytic action 24 of an entire way ment similar to the physical point of view, but with different chemical characteristics of intervention if, as is preferred, catalytic substances deposited on the two elements are different. By using catalytic materials able to perform actions in a way complementary between them, as in the preferred case of the use of palladium and tantalum, it can reach a depuration extremely thrust exhaust, compared to all the different classes of pollutants contained.

Parts of the substances formed by chemical reactions activated by the catalysts are solid. At the output of the second element having a catalytic action 40 the gas which, under the inclination of the projections pressed into the sheet metal strip forming the element having catalytic activity, have a whirl, have the tendency to accumulate solids heavier against the inner surface of the duct converging defined by the fourth part 4 of the housing; the presence of fusiform body 23 promotes this phenomenon. For this reason the solid parts, meeting the openings 18, pass into the tray 19, where they are deposited, instead of being released into the ambient air through the outlet 17 with the purified exhaust gas. The tube 21 which, by its mouth 22, receives a light aerodynamic suction action on the part of the exhaust gases entering the scrubber-exhaust system, keeps the drawer 19 in a slight depression which favors the entry and maintaining said solid waste. Then these, at times, can be discharged only by removing the tray 19, without the need to disassemble the entire device of the vehicle on which it is installed.

Of course, various modifications may be brought to the embodiment has been described by way of example. For example, as shown in Figure 8, the different housing parts 1 'to 4', and therefore also the housing 3 'of the silencer element can be defined by two coupled half-shells, which may also constitute the joints 11 'and 13'. The choice among the various possible construction systems can be made by the designer in the light of various assessments, it included those relating to the means of production available. The inclined arrangement and optionally the winding shape of the projections 25 can be modified in different ways and, if necessary, also in a different way for the two elements having a catalytic action. In some cases an element having a catalytic action may be sufficient on its own, and in this case may be disposed either upstream or downstream of the silencer element. The latter may also have a different structure from that described, provided that substantially caused not sink or, at least, no heat sink. Finally, the choice of catalytically active substances deposited on the strips constituting the elements having a catalytic action may be differently directed, besides that on the specified substances, and for example may be considered platinum employment, so-said platinum black, palladium-carbon or other catalysts known or developed especially for this job. Of course, on the other hand, any detail of the embodiment may be replaced by its technical equivalents.