EP0072059B1 - Supercharged internal-combustion engine with a filter for exhaust gas particles - Google Patents

Abstract

In order to limnit the exhaust particulate emission when supercharging a pressure wave machine-supercharged internal combustion engine, an exhaust particulates filter is arranged in the high-pressure part of the exhaust gas system ahead of the pressure wave machine. By increasing the supply of fuel to the engine itself and/or briefly closing a charge air flap valve a recirculation flap valve and/or brief opening of a exhaust gas by-pass valve, the exhaust gas attains the combustion temperature of soot components deposited on the surface of the filter. These soot components are burned off, and the filter is automatically regenerated.

Description

The present invention relates to a device for limiting the emission of exhaust gas particles in an internal combustion engine according to the preamble of claim 1.

Particulate emissions from internal combustion engines are already legally limited in some countries, while other countries will adopt tougher, more restrictive handling of emissions limit values for exhaust gas particles.

• - Freischwebender Russ.
• - Im Russ angelagerte Kohlenwasserstoffverbindungen und andere organische Substanzen.
• - Sulfatverbindungen.
• - Bleiverbindungen (bei Ottomotoren).

Particle emissions from internal combustion engines essentially consist of the following components:

• - Free-floating soot.
• - Hydrocarbon compounds and other organic substances deposited in the soot.
• - sulfate compounds.
• - Lead compounds (for gasoline engines).

From EP-A-0 010 384 a device for limiting the exhaust gas particle emission is known. The uncharged internal combustion engine shown here is equipped with an exhaust gas particle filter placed in the exhaust system. By increasing the exhaust gas temperature of the filter, its regeneration is initiated by burning the soot deposit on the surface of the filter. The exhaust gas temperature upstream of the filter is increased by increasing the fuel-air ratio, i.e. the air intake quantity is throttled. In order to increase the exhaust gas temperature, one deliberately takes a negative influence on the gas exchange loop, i.e. H. efficiency, with a corresponding deterioration in fuel consumption. Although the circuit resulting from this document has a flap placed after the exhaust gas particle filter, through which part of the exhaust gases can be returned to the engine. A significant temperature increase upstream of the exhaust gas particle filter cannot be achieved with this flap, however, because the pressure difference prevailing in this line compared to the exhaust gas flow after the filter is minimal. This gas recirculation could be increased by regulating the flap in the air inlet line, but this alone would have an additional negative effect on the gas exchange loop.

A device for limiting the exhaust gas particle emission is also known from US Pat. No. 3,937,015. Here, too, the regeneration of the filter is aimed at by burning the soot deposit on its surface. Here, the exhaust gas particle filter can be bypassed via a flap. Although the desired particle combustion temperature can be adjusted, this means that a relative exhaust gas particle filter is accepted.

From DE-A-23 26 989 a circuit of an Otto engine with a turbocharger, a detoxification system (catalyst or reactor) and an exhaust gas blow-off valve arranged between the exhaust pipe and the detoxification system is known.

The interchangeability between the turbocharger and the pressure wave machine is not a given. While there is the same amount of oxygen before and after the turbocharger, the pressure wave machine is still mixed with purge air via the low-pressure suction. A catalytic converter has open, continuous cells and fulfills the task of enabling the conversion of incompletely burned exhaust gases. The reactor is a precursor to the catalyst. Here the incompletely burned exhaust gases are led into a pot, where their combustion takes place with the addition of fuel and oxygen. Exhaust particles are not filtered out either in the catalytic converter or in the reactor. The exhaust gas relief valve fulfills the task of the catalyst. Protect the reactor from excessive pressures or high temperatures.

The invention seeks to remedy this. The invention, as characterized in the claims, has for its object to achieve a filtering of the exhaust gases in a device of the type mentioned during operation, the exhaust gas particle filter being arranged in the high pressure part of the exhaust system in front of the pressure wave machine. In addition, it is an object of the invention to enable the filtered soot to burn off, in the sense of a permanent regeneration of the exhaust gas particle filter.

• - Die Ansprechbarkeit der Druckwellenmaschine ist gewährleistet.
• - Vorrichtung für die Zufuhr von Fremdenergie und Russ-Abbrenneinrichtungen für das Verbrennen der Russablagerungen an den Oberflächen der Abgaspartikelfilter mittels Fremdenergie entfallen.
• - Regeleinrichtungen, die die Auslösung des Zündvorganges der Fremdenergie in Abhängigkeit des Abgasgegendruckes steuern, entfallen ebenfalls.
• - Das der Druckwellenmaschine eigene Abgasrezirkulationsvermögen wird gesteigert, ohne Verschmutzungsgefahr für den Rotor der Druckwellenmaschine.
• - Nach dem Entzünden der Russablagerungen steigt die Ladeluftdichte sofort wieder an, die Abgastemperatur sinkt, und der Motor wird nicht überhitzt.
• - Trotz herabgesetzter Abgastemperatur, wird wegen der exothermen Reaktion der Russverbrennung dieselbe unvermindert fortgesetzt.

This arrangement of the exhaust gas particle filter has the following advantages:

• - The responsiveness of the pressure wave machine is guaranteed.
• - Device for the supply of external energy and soot burn-off devices for burning the soot deposits on the surfaces of the exhaust gas particle filters by means of external energy are eliminated.
• - Control devices that control the triggering of the ignition process of external energy depending on the exhaust gas back pressure are also omitted.
• - The exhaust gas recirculation capacity of the pressure wave machine is increased without risk of contamination for the rotor of the pressure wave machine.
• - After the soot deposits have ignited, the charge air density increases immediately, the exhaust gas temperature drops and the engine is not overheated.
• - Despite the reduced exhaust gas temperature, the soot combustion continues unabated due to the exothermic reaction of the soot combustion.

Another advantage of the invention is the fact that the gas temperature before the exhaust gas part kelfilter can be increased by briefly closing the recirculation flap and / or by briefly opening the exhaust gas bypass valve. Both when the recirculation flap is closed and when the exhaust gas bypass valve is opened, the excess air in the system becomes smaller. Although the gas temperature rises with the same fuel supply, it is far from increasing to compensate for the performance losses that are traded as a result. In a further driving phase, the power is increased again by increasing the fuel supply; and with it the gas temperature increases even further. Because the recirculation flap is placed in the low-pressure intake of the pressure wave machine, the prevailing pressure difference with respect to the exhaust gas flow does not determine any restriction of the amount of recirculation.

According to claim 2, the filter is arranged in the exhaust gas receiver itself. The advantage of this arrangement can be seen in the fact that the hot exhaust gases flowing out of the internal combustion engine can be used for soot combustion without losses.

According to claim 3, the filter is arranged in a separate section from the actual exhaust gas receiver in the exhaust gas direction immediately before the pressure wave machine.

According to claim 4, the filter is designed as an interchangeable unit.

Due to the arrangements according to claims 3 and 4, the filter can be replaced quickly and easily.

According to claim 5, the filter consists of a monolithic porous and heat-resistant core.

The particles present in the exhaust gas hit the surfaces of the exhaust gas particle filter and agglomerate there to form larger particles, the surface quality and the porosity of the exhaust gas particle filter material playing a crucial role for the accumulation and agglomeration processes of the soot particles and for their combustion.

According to claim 6, the core of the filter is surrounded by a fibrous mat-like and heat-resistant covering.

According to claim 7, the core of the filter together with the casing is arranged in a cylindrical support tube which is held at one end by the retaining ring provided in the exhaust gas receiver and at the other end by the holding cam provided in the exhaust gas receiver.

According to claim 8, the cylindrical support tube is fixed between the flange of the exhaust gas receiver and the flange of the section.

By the arrangement according to claims 6-8, the core of the filter is rigidly integrated with the interposition of the fibrous mat-like covering through the cylindrical support tube and its position is precisely fixed in the axial and radial directions.

According to claims 9-11, the support tube is made of heat-resistant sheet metal and an elastic, heat-resistant layer is arranged between it and the solid jacket of the section of the exhaust gas receiver.

This ensures that the support tube does not warp at a higher temperature and has a high scaling resistance, and that any vibrations that may occur are dampened by the machine due to the elastic, heat-resistant layer and are therefore not transmitted directly to the core of the filter.

According to claims 12 and 13, the monolithic porous core of the filter consists of a ceramic material with high thermal shock resistance or steel wool. With these two materials, optimal filter properties are achieved at higher temperatures, taking into account the temperature change.

According to claim 14, in order to increase the exhaust gas temperature upstream of the filter, the charge air flap in the charge air line is briefly closed and operated again after the filter has been regenerated.

The invention is explained below with reference to exemplary embodiments shown in the drawing.

• Figur 1 eine schematische Darstellung einer ersten Variante der Abgaspartikelfilteranordnung bei der Aufladung einer Brennkraftmaschine mittels Druckwellenmaschine.
• Figur 2 eine schematische Darstellung einer zweiten Variante der Abgaspartikelfilteranordnung bei der Aufladung einer Brennkraftmaschine mitteis Druckweiienmaschine.
• Figur 3 einen Schnitt durch die Abgaspartikelfilteranordnung gemäss der beispielsweisen Ausführungsform der ersten Variante in Fig. 1.
• Figur 4 einen Schnitt durch eine Abgaspartikelfilteranordnung gemäss der beispielsweisen Ausführungsform der zweiten Variante in Fig. 2.

The drawing shows:

• Figure 1 is a schematic representation of a first variant of the exhaust gas particle filter arrangement when charging an internal combustion engine by means of a pressure wave machine.
• Figure 2 is a schematic representation of a second variant of the exhaust gas particle filter arrangement when charging an internal combustion engine by means of a pressure welding machine.
• FIG. 3 shows a section through the exhaust gas particle filter arrangement according to the exemplary embodiment of the first variant in FIG. 1.
• FIG. 4 shows a section through an exhaust gas particle filter arrangement according to the exemplary embodiment of the second variant in FIG. 2.

1 shows a cylinder head 1 with six cylinders 2. In the cylinder head 1, an inlet / suction channel 3 is arranged for each cylinder, which open into a manifold 4. The manifold 4 is connected to the pressure wave machine 7 through the charge air line 5, in which the charge air flap 6 is located.

In the cylinder head 1 there are also one exhaust gas channel 8 for each cylinder, to which the exhaust manifolds 9 are connected and which open into an exhaust gas receiver 10. In a manner known per se, the exhaust housing 13 of the pressure wave machine 7 is connected to the exhaust gas receiver 10 through the intermediate piece 11 connected. As already mentioned, the charge air line 5 opens into the pressure wave machine 7, and the fresh air intake line 14 with recirculation flap 37 and the exhaust line 15 are also connected. The exhaust gas bypass valve 36 is located in a bypass 35 between the exhaust gas housing 13 and the exhaust line 15. The mode of operation of the charge air flap 6, the recirculation flap 37 and the exhaust gas bypass valve 36 is subsequently described in more detail in connection with the description of FIG. 4 in connection with the mode of operation of the filter 18 during driving operation explained. The pressure wave machine 7 is driven via a pulley 16 by the motor shaft 17, the connection of V-belts 16 'between the pulley 16 and the motor shaft 17 or the motor pulley 17' being shown only schematically in the drawing for reasons of better clarity.

In this first variant, the exhaust gas particle filter 18 is arranged in the exhaust gas receiver 10 itself. The particle filter 18 is only indicated in FIG. 1, but is shown and explained in detail in FIG. 3.

For easier handling and better accessibility when replacing the filter 18, on the one hand the end plate 27 by means of a screw bolt 29, washer 30 and nut 31 with the flange 22 of the exhaust gas receiver 10 and on the other hand the flange 21 of the exhaust gas receiver 10 is also screwed to the flange 19 of the intermediate piece 11 releasably connected.

The intermediate piece 11 in turn connects the exhaust gas receiver 10 to the exhaust gas housing 13 of the pressure wave machine 7 and is arranged such that it can be removed by the flange connection 19, 21 and the flange connection 20, 23.

FIG. 2 shows a schematic illustration of a second variant of the exhaust gas particle filter arrangement. Here, the filter 18 is arranged in a section 12 separated from the actual exhaust gas receiver 10 in the exhaust gas direction directly in front of the pressure wave machine 7.

In the exemplary illustration according to FIG. 2, the exhaust gas receiver 10 has a smaller diameter than the first variant (FIG. 1) and extends to the section 12. The intermediate piece 11 is omitted in this arrangement.

For ease of handling and better accessibility when replacing the filter 18, the section 12 is also arranged to be removable. On the one hand, the flange 12 'of the section 12 is detachably connected to one another by a screw connection with the flange 21 of the exhaust gas receiver 10 and, on the other hand, the flange 12 "is also connected to the flange 23 of the exhaust gas housing 13 of the pressure wave machine 7 with a screw connection.

In Fig. 3 - here the same reference numerals apply as in Fig. 1 - a section through the exhaust gas particle filter arrangement according to the first variant in Fig. 1 is shown. For the sake of clarity, however, only the exhaust gas receiver ends and part of the exhaust gas receiver 10 and part of the filter 18 are shown.

The filter 18 consists of a monolithic, porous, heat-resistant and cylindrical core made of ceramic material cf. e.g. B. SAE Paper No. 810114 of February 23, 1981 "Cellufar Ceramic Diesel Particulate Filters by John S. Howitt et al., And is provided with a fibrous and heat-resistant mat-like covering 24 made of ceramic or mineral fiber material, the ends 24 'of the mat-like covering 24 having the cylindrical filter 18 in protrude axially and are inclined inwards towards the axis, whereby the position of the filter 18 is fixed in the longitudinal direction. The filter 18 together with the cover 24 is fastened in a support tube 25, which consists of heat-resistant sheet metal, which encloses the filter 18 together with the cover 24 under contact pressure, the ends of the support tube 25 being welded along a surface line. The annular exhaust gas inflow space 39 is located between the support tube 25 and the solid casing of the exhaust gas receiver 10. According to the direction of the arrows with the reference number 40, the exhaust gas flows from the exhaust gas channels 8 into the exhaust gas inflow space 39 and from there into the filter antechamber 41. The exhaust gas inflow space 39 and the filter anteroom 41 are connected to one another. After the exhaust gas has passed through the filter 18, it reaches the intermediate piece 11 and is fed from there to the exhaust gas housing 13 of the pressure wave machine 7.

To attach the support tube 25, a retaining ring 26 is arranged at the downstream end of the exhaust gas receiver 10 and at least four retaining cams 28 are each arranged concentrically at the other end of the exhaust gas receiver 10. An asbestos seal 33 is located between the holding ring 26 and the support tube 25 in order to prevent exhaust gas from getting directly into the intermediate piece 11 bypassing the filter 18, while the asbestos seals 33 ′ take over the sealing against the environment.

In Fig. 4 - here the essentially the same reference numerals as in Fig. 3 apply - a section through the exhaust gas particle filter arrangement according to the variant in Fig. 2 is shown. The construction of the filter 18 is the same as described in detail in FIG. 3. At one end of the support tube 25, a flange 25 'is provided, which is clamped between the flange 21 of the exhaust gas receiver 10 and the flange 12' of the section 12 and is fastened by screw connections 29, 30, 31. An elastic heat-resistant layer 34 made of wire mesh is located between the support tube 25 and the solid jacket of the section 12. The one-sided fastening of the support tube 25 and the lining with the elastic, heat-resistant layer 34 was chosen in order to dampen any vibrations of the machine that might occur and to allow vibrations already transmitted to the support tube 25 to subside more quickly. In addition, the different thermal expansions of the different materials caused by thermal influence must be taken into account sufficiently. If the support tube 25 were fixed on both sides, thermal stresses would possibly destroy the Guide attachment of the support tube 25. The flange 12 ″ of the section 12 is connected to the flange 23 of the exhaust gas housing 13 of the pressure wave machine 7 by means of a screw connection 29, 30, 31 with the interposition of a seal 33 ′.

• Tritt bei Teillast eine Verstopfung des Filters 18 auf, dann bewirkt der Druckverlust des Filters 18 primär eine Behinderung des Gaswechsels des Motors, was eine Reduktion der Nutzleistung zur Folge hat. Die Leistungseinbusse wird der Fahrer durch mehr Brennstoff wettmachen ; dadurch steigt die Gastemperatur stark an. Fordert der Fahrer dem Fahrzeug genügend Leistung ab, kommt es automatisch zum Abbrennen des Russes. Die Entflammtemperatur von Russ beträgt ca. 650 °C.

The operation of the filter 18 during driving is described below:

• If the filter 18 becomes blocked at partial load, the pressure loss of the filter 18 primarily causes an impediment to the gas exchange of the engine, which results in a reduction in the useful power. The driver will make up for the drop in performance with more fuel; this causes the gas temperature to rise sharply. If the driver demands sufficient power from the vehicle, the soot burns off automatically. The flame temperature of soot is approx. 650 ° C.

An increase in the gas temperature also takes place if, with a predetermined degree of occupancy of the exhaust gas particle filter, the recirculation flap 37 and / or the charge air flap 6 close briefly. With this measure, it is clear that with a constant fuel supply quantity, the excess air becomes smaller because there is less charge air in the system. If the charge air flap 6 and the recirculation flap 37 close, then the engine is only supplied with air via the snifting valve: this is equivalent to a suction operation. If there is less charge air, the performance of the engine generally drops. Although the gas temperature rises somewhat here, the increase is far from being so marked that it can compensate for the loss in performance. In the subsequent driving phase, the driver then takes care of the increase in performance himself, by trying to compensate for the loss in performance through more accelerator pressure.

The same is true if the exhaust gas bypass valve 36, whether individually or in connection with charge air flap 6 and / or recirculation flap 37, opens briefly. The charge air in the system also decreases here. The loss in performance is compensated for by the supply of a larger amount of fuel.

The pressure wave machine 7 tolerates the high temperature peaks because the rotor is flushed with fresh air. The shock wave machine 7's own exhaust gas recirculation capacity can be increased by temperature surges without risk of contamination of the rotor.

Claims (14)

1. Device for limitation of the exhaust gas particle emission in an internal combustion engine with an exhaust gas particle filter in the exhaust gas system, filter regeneration being performed by an increase in the exhausfgas temperature ahead of the filter as the result of increasing the fuel/air ratio and thus by a combustion of the soot deposit on the surface of the filter, characterised in that a gas-dynamic pressure-wave machine (7) is provided in the exhaust gas system of the internal combustion engine, the exhaust gas particle filter (18) in the high-pressure part of the exhaust gas system being arranged ahead of the pressure-wave machine (7) and, for increasing the exhaust gas temperature ahead of the filter (18)

- a briefly closable recirculation flap (37) being placed in the low-pressure intake line (14) of the pressure-wave machine (7),

- and/or an exhaust gas bypass valve (36), to be opened briefly, being provided in a bypass (35) downstream of the filter (18) - as known per se - between exhaust gas casing (13) and exhaust pipe (15).

2. Device according to Claim 1, characterised in that the filter (18) is arranged in the exhaust gas receiver (10) itself.

3. Device according to Claim 1, characterised in that the filter (18) is arranged in a segment (12) separate from the actual exhaust gas receiver (10), directly ahead of the pressure-wave machine (7) in the exhaust gas direction.

4. Device according to Claim 1, 2 or 3, characterised in that the filter (18) is designed as an exchangeable module.

5. Device according to one of Claims 1 to 4, characterised in that the filter (18) consists of a monolithic, porous and heat-resistant core.

6. Device according to Claim 5, characterised in that the core of the filter (18) is surrounded by a fibrous, matt-like and heat-resistant covering (24).

7. Device according to Claims 1 to 6, characterised in that the core of the filter (18), together with the covering (24), is arranged in a cylindrical suspension tube (25) which is retained at one end by the remaining ring (26) provided in the exhaust gas receiver (10) and at the other end by the retaining cams (28) provided in the exhaust gas receiver (10).

8. Device according to Claims 1 to 6, characterised in that the core of the filter (18), together with the covering (24), is arranged in a cylindrical suspension tube (25), which is secured between the flange (21) of the exhaust gas receiver (10) and the flange (12') of the segment (12).

9. Device according to Claim 8, characterised in that the suspension tube (25) is made of heat-resistant sheet metal.

10. Device according to one of Claims 1 to 8, characterized in that a resilient, heat-resistant layer (34) is arranged between the suspension tube (25) and the solid jacket of the segment (12) of the exhaust gas receiver (10).

11. Device according to Claim 10, characterised in that the layer (34) is formed by a resilient, heat-resistant wire mesh.

12. Device according to Claims 5 to 8, characterised in that the monolithic, porous core of the filter (18) is made of a ceramic material of high spalling resistance.

13. Device according to Claims 2 to 4, characterised in that the monolithic, porous core of the filter (18) is made of steel wool.

14. Device according to Claim 1, characterised in that a briefly closable charge-air flap (6) is provided in the charge-air duct (5) to the internal combustion engine.

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