DE3743559A1 - Device for removing and burning soot particles present in the exhaust gases from diesel engines - Google Patents

Abstract

A device for removing and burning soot particles present in the exhaust gases from diesel engines has two parallel filter chambers, in each of which a combustion insert is located. The device also has a closure flap, which can be automatically changed over from one end position to the other, for alternate operation of the filter chambers, in such a way that, in one filter chamber closed by the closure flap, the combustion of the soot particles previously deposited therein takes place, while at the same time the other filter chamber, opened by the closure flap and connected to the exhaust gas stream coming from the engine, deals with filtering soot particles out of the exhaust gas stream. The exhaust gas backpressure applying at the inlet of the filter chamber open at the time serves for actuating the closure flap. Furthermore, a first control instrument is provided which interrupts the effect of the exhaust gas backpressure on the closure flap when a predetermined exhaust gas temperature is exceeded. When the exhaust gas backpressure influence is interrupted, the closure flap can automatically be set into a central position, in which both filter chambers are simultaneously connected to the exhaust gas stream. The features described allow an effective automatic change-over of the device in a simple manner, when the latter runs in two-phase operation. Furthermore, however, the device is capable also of ... certain... Original abstract incomplete.

Description

The invention relates to a device for removal and for combustion in the exhaust gases of diesel engines soot particles, with two parallel filter chambers, in which are each arranged a combustion insert, and with a shutter for alternate operation of the filters chambers, such that in one, through the closure flap sealed filter chamber the combustion of the previously there deposited soot particles takes place while at the same time the other, opened by the flap and attached to the connected filter chamber coming from the engine serves to filter out soot particles from the exhaust gas flow, the closure flap when reaching a predetermined Amount of soot particles accumulated in the exhaust gas connected filter chamber automatically into your other End position is reversible, in which the previously locked Open filter chamber and connected to the exhaust gas flow sen is now closed while the previously opened filter chamber sen and for the combustion of the soot particles accumulated there serves.

A device of the aforementioned type is known from DE-OS 28 54 268. The known exhaust gas cleaner is characterized by an unfavorable flow guidance for the exhaust gas flowing out of the cylinders. As a result, the thermal efficiency of the engine deteriorates as a result of an increase in the exhaust gas back pressure. This is expressed in an increase in fuel consumption. Furthermore, the known exhaust gas cleaner is complicated in structure and therefore expensive to manufacture. Because after the burning process, the combustion products from the soot particles are again sent through the second filter, through which the exhaust gas flows. It must be concluded from this that the soot particles have not been completely combusted. Because with a controlled burn off, the soot particles and the hydrocarbons also contained in the exhaust gas would be almost completely oxidized to CO ₂ and H ₂ O, so that a repeated recirculation would then not be necessary.

Another disadvantage of the known exhaust gas cleaner is in that the just regenerated filter insert after completion the burning process is no longer caused by the ignition gas mixture is flowing. The back pressure in the closed filter chamber then sinks and the exhaust gas coming from the engine flows thus also in the return duct and in the closed one Chamber. This can cause soot particles in the flame Store the lock, which can lead to clogging. The Function of the entire soot filter system is ge in question poses. Furthermore, the just regenerated filter (in the closed filter chamber) from the one through the return duct flowing exhaust gas. There can be soot particles deposit on the back of the filter. This leads to when switching to the previously regenerated filter the exhaust gas back pressure is higher than with a completely soot-free filter. The consequence is a deterioration in thermal efficiency.

Finally, a disadvantage of the exhaust gas cleaner mentioned the fact that the external pump, which the Blows the ignition gas mixture into the closed filter chamber, must build up a high pressure so that the exhaust gas from the Re generation process through the return channel and against the exhaust gas back pressure flows out. The external pump is therefore high Power consumption, which in turn affects the efficiency of the engine deteriorates and thus increases fuel consumption.

Based on the described prior art, it is the Object of the present invention, a device of a gangs designated type to create, the constructively uncomplicated graced in the structure, an optimal flow of the Ab gas flow guaranteed and easy control or reversing the closure flap.

According to the invention the object is achieved in that Actuation of the shutter at the entrance to each open filter chamber prevailing exhaust gas back pressure serves and that a first control device is provided, which at over a predetermined exhaust gas temperature the influence of  Exhaust gas pressure on the shutter interrupts, and that the shut-off valve when the exhaust back pressure is interrupted flow is automatically operable in a central position, in of the two filter chambers simultaneously at the exhaust gas flow are closed.

By actuating the to reverse the Exhaust gas flow from one filter chamber to the other serving The flap through the exhaust back pressure is one as well simple and effective automatic control of exhaust gas cleaning successful. Because the increase in the exhaust gas counter pressure is only due to the soot filter insert prevailing flow resistance determined. This increases with a corresponding filling level of the soot filter insert. In order to ensures that the device is then on the other Filter chamber is reversed when the soot filter insert a filter chamber is filled with soot.

The invention is also characterized in that certain exhaust gas temperatures at a reversal of the closure the flap was deliberately omitted, rather the flap comes to a neutral middle position in this situation, where both filter chambers simultaneously in the exhaust gas flow Filter out the soot particles contained and burn them immediately. The invention takes advantage of the fact that at correspondingly high engine load, for example at vehicle speed speeds of 100 km per hour and above, the exhaust gas temperature becomes so high that ignition and burning in this area of the deposited soot particles in both filter chambers can run continuously, i.e. no more external energy must be led.

In an advantageous embodiment of the basic idea of the inven tion is further proposed that the flap on the closure - to actuate the same - a slidably arranged in a control cylinder, on both sides equally spring loaded control piston attacks and that the two cylinders chambers on both sides of the control piston each with the input of one the two filter chambers are connected by a pressure line and that in each pressure line a device operated by the first control depending on the exhaust gas temperature from shut-off valve, preferably solenoid valve, is arranged.

Because the necessary to reverse the shutter mechanical forces are comparatively small is sufficient for this a relatively small increase in exhaust gas back pressure in front of the filter chamber switched to "filters". The at high exhaust gas temperatures of e.g. more than 500 ° C Interruption of the exhaust gas counter proposed according to the invention pressure influence on the flap can be by Control unit and the shut-off valves actuated by it easily and implement reliably.

To solve the above problem, however, contributes significantly Lich also an idea further developing the invention, which is that in the entrance to the filter chambers one nozzle each for supplying combustion air to which Fenden filter chamber is arranged and that the air supply the nozzles can be controlled by a second control device and that to actuate the second control unit of the control piston serves. It is expedient to generate the necessary Delivery pressure of the combustion supplied to the respective nozzle air an electrical operated by the second control unit Pump provided, and the compressed air coming from the pump line is branched into two compressed air line streams that lead to one of the two nozzles. In every compressed air line strand is an actuatable by the second control unit blocking valve, preferably solenoid valve, arranged.

After only a small amount of energy to ignite a small one According to the invention, part of the deposited soot particles is Combustion process only by supplying cold air into the closed filter chamber of the two-chamber soot filter maintained. So it is only for a short time, at each time start of a burning process, additional (e.g. electrical) Apply energy to generate the ignition temperature. After that  only needs the (electrical) energy to supply the Cold air applied to the filter chamber to be regenerated will. Otherwise, the energy required to blow in Combustion air into the filter chamber to be regenerated only comparatively low. Because the air jet, which through the air nozzle according to the invention in the filter to be regenerated flows into the chamber, only a small counter pressure counteracts it.

In an advantageous development of the invention it is proposed that in the outgoing compressed air line from the pump - prior to its branching - an air heater operable by the second control unit for generating the required ignition temperature is arranged in the entrance to the filter chamber in question.

Further details and advantages of the invention can Claims 6 and 7 are removed.

To illustrate and explain the invention is an embodiment shown in the drawing and is described in detail below. The drawing shows (schematically) an embodiment of a fiction Appropriate device for removing and burning in soot particles contained in the exhaust gases of diesel engines, in Side view (partly in longitudinal section), together with one Block diagram representation from which the function of the front direction can be seen.

The exhaust gas cleaning device for diesel engines shown has a housing designated overall by 10 , which consists of a cylindrical middle part 11 and two adjoining ends on the end face, frustoconically formed side parts 12 and 13 . At the side parts 12 , 13 each has a pipe socket 14 or 15 with connection flange 16 or 17 . The direction of flow of the exhaust gas is indicated by arrows 18 , 19 . Accordingly, the side part 12, which widens towards the middle part 11 of the housing 10 , forms the input side into which the exhaust-gas-laden exhaust gas coming from the engine (not shown) enters. In the side part 13 , which tapers conically in the direction of flow 19, on the other hand, the exhaust gases cleaned in the central part 11 of the device are collected and subsequently discharged into the open through the exhaust (not shown).

In the middle part 11 of the housing 10 , two filter chambers 20 and 21 are formed, in each of which a filter insert 22 or 23 is arranged. The filter chambers 20 , 21 are separated from one another by a central partition wall 24 . The filter inserts 22 , 23 are expediently commercially available ceramic monoliths with a catalytically active coating. The two filter chambers 20 , 21 with the filter inserts 22 , 23 arranged therein are of the same design and are suitable for both alternate and simultaneous operation.

In the plane 25, which forms the transition between the input part 12 and the central part 11 of the device, a closure flap 27 designed as a double-armed lever is mounted at 26 . The closure flap 27 can assume three different positions, through which the exhaust gas flow coming from the engine (see arrow 18 ) can be influenced in a certain way. In the one end position of the closure flap 27 , which is shown in solid lines in the drawing, the filter chamber 21 located below is closed, and the exhaust gas flow thus only enters the (upper) filter chamber 20 . In a second possible end position of the closure flap 27 - indicated in the drawing by dashed lines and identified by 27 ' -, conversely, the (upper) filter chamber 20 is closed, and the exhaust gas accordingly only reaches the (lower) filter chamber 21 . Finally, a middle position of the closure flap 27 is also provided. This is also indicated in dashed lines and designated 27 '' . In this latter position, both filter chambers 20 and 21 are opened, so that the particulate exhaust gas coming from the engine can reach both filter chambers 20 , 21 simultaneously. As the drawing also shows, are at the transition level between the pipe socket 14 and the input part 12 - diametrically zueinan - two permanent magnets 28 , 29 arranged, which ensure a safe and tight closing of the closure flap 27 in the two end positions 27 and 27 ' .

To actuate the closure flap 27 , a control cylinder, shown schematically and designated 30, is used, in which a control piston 31 is displaceably arranged. In two in the control cylinder 30 on both sides of the control piston 31 bil-forming cylinder chambers 32 , 33 , a pressure spring 34 or 35 acting on the control piston 31 is arranged. The pressure springs 34 , 35 are of equal strength, so that they keep the control piston 31 in equilibrium unless this is influenced by other forces. The control piston 31 articulates on the closure flap 27 by means of a piston rod 36 at 37 . It should be noted in this regard that the relevant lever part of the closure flap 27, numbered 38 , is located laterally outside the housing 10 .

To actuate the control piston 31 and thus also the closing flap 27 , the exhaust gas back pressure p ₃ building up within the input part 12 is now used. For this purpose, two pressure lines 39 , 40 indicated by dash-dotted lines are provided, both of which open into the control cylinder 30 . The one pressure line, numbered 39 , is assigned to the filter chamber 20 and accordingly starts from the upper part of the inlet part 12 . It opens into the cylinder chamber 33 located above the control piston 31 . The other pressure line 40 , on the other hand, is assigned to the lower filter chamber 21 and accordingly takes its exit from the lower part of the inlet part 12 . It is connected to the cylinder chamber 32 located below the control piston 31 . In the pressure lines 39 , 40 - before their junctions in the control cylinder 30 - a shut-off valve 41 and 42 , respectively, is arranged as a solenoid valve. The shut-off valves 41 , 42 can be actuated by a first control device 43 , indicated schematically as a box.

In order to allow the combustion of the soot particles stored in the filter inserts 22 , 23 , the filter chambers 20 and 21 must be supplied with combustion air. For this purpose, two air nozzles 44 , 45 are provided, which are arranged in the input part 12 at two diametrically opposite points. The air nozzle 44 is assigned to the filter chamber 20 , whereas the second air nozzle 45 serves to supply combustion air to the other filter chamber 21 . The air nozzles 44 , 45 are supplied with ambient air, which is conveyed by an electric air pump 46 into a compressed air line 47 . The compressed air line 47 branches at 48 into two compressed air lines 49 and 50 . The compressed air line 49 leads to the air nozzle 44 , whereas the air nozzle 45 is fed by the compressed air line 50 . Between the electric air pump 46 and the branch 48 , an air heater 51 is arranged in the compressed air line 47 , which preferably works according to the "hot air dryer" principle. The function of the electric air pump 46 and the air heater 51 are controlled by a second control device 52 . The second control device 52 also serves to actuate two in the compressed air lines 49 , 50 arranged shut-off valves 53 , 54 , which are expediently designed as solenoid valves.

In the position of the closure flap 27 shown in the drawing in solid lines - as in the other end position 27 '- the exhaust gas purification device operates in the so-called two-phase operation. This is intended for low engine loads, e.g. for vehicle speeds of less than 100 km per hour. In this case, the one filter chamber, for example the upper filter chamber 20 in the exemplary embodiment shown, operates in filter mode, ie it filters out the soot particles contained in the incoming exhaust gas stream and deposits them in the filter insert 22 . The other filter chamber, on the other hand, because of the locked position of the flap 27 is not accessible to the exhaust gas flow - in the example shown this is the lower filter chamber 21 - is at the same time busy with the soot particles previously deposited in the filter insert concerned (eg 23 ) burn and regenerate the filter insert again. The combustion air required for this is supplied to the filter chamber 21 or the filter insert 23 through the air nozzle 45 . For this purpose, the shut-off valve 54 is held in the open position and the other shut-off valve 53 in the closed position by the second control device 52 . In order to start the burning process in the filter chamber 21 , an increased temperature of the combustion air emerging from the air nozzle 45 is required. For this purpose, the electric heater is briefly activated by the second control unit 52 . As soon as the burning process is in progress, the supply of unheated ambient air is sufficient. The air heater 51 can thus be switched off again after the combustion process has ignited.

During this time, the exposure to filtered soot particles increases continuously in the other filter chamber 20 . As a result, the exhaust gas back pressure p ₃ rises accordingly in the inlet area 12 located in front of the filter chamber 20 . As soon as the exhaust gas back pressure p ₃ in the (upper) input area 55 becomes greater than in the (lower) input area 56 - the two shut-off valves 41 , 42 are open here - the control piston is moved from its upper end position 31 shown in the drawing to its dashed line and moved with 31 ' be numbered lower end position. This also means a reversal of the closure flap 27 in the other end position 27 '. The exhaust gas stream containing soot particles coming from the engine is now controlled in the lower filter chamber 21 , and the regeneration process (combustion of the deposited soot particles) can now be initiated in the upper filter chamber 20 . When it reaches its lower end position 31 ', the control piston 31 actuates a contact switch 57 which controls the second control unit 52 so that it starts the air pump 46 and the air heater 51 , the shut-off valve 53 opens and the shut-off valve 54 closes. Now he gets heated ambient air through the pressure line 49 into the air nozzle 44 , and the combustion process in the filter chamber 20 can begin.

In the ensuing period now begins simultaneously in the input part 56 due to the deposition of soot particles in the filter 23 of the exhaust gas back pressure p ₃ to continuously increase. As soon as it exceeds the pressure value in the other input part 55 , the control piston 31 is again reversed in the manner described above, this time in its upper end position. The closure flap 27 now resumes its position shown in the drawing in solid lines. In this position, the control piston 31 actuates a contact switch 58 which , similar to the contact switch 57 , controls the second control device 52 . This then actuates the air pump 46 and the air heater 51 , closes the shut-off valve 53 and opens the shut-off valve 54 . The regeneration process described above can thus begin again. At the same time, the filtering process begins in the upper filter chamber 20 again.

If the engine is now driven with a higher load, for example at vehicle speeds in the range above 100 km per hour, the temperature of the exhaust gas flowing at 18 increases accordingly. To measure this exhaust gas temperature, a temperature sensor designated 59 is arranged in the pipe socket 14 . This is in operative connection with the already mentioned first control device 43 . If the exhaust gas temperature now reaches a predetermined value, for example 500 ° C. or above, the temperature sensor 59 inputs a corresponding signal into the first control device 43 , and this causes the two shut-off valves 41 and 42 to close. So that the flow of the exhaust gas back pressure p ₃ to the position of the control piston 31 is prevented. The control piston 31 is now only under the force of the equally strong compression springs 34 and 35 . This means that the control piston 31 and thus also the closure flap 27 is moved into a central position 31 '' or 27 ''. The entire device is no longer working in two-phase operation, because both filter chambers 20 and 21 are simultaneously the incoming exhaust gas stream opens ge. At such a high exhaust gas temperature, it is no longer necessary to supply external energy to initiate the combustion process in the two filter chambers 20 , 21 . The residual oxygen content in the exhaust gas is sufficient to completely burn the soot particles deposited in the filter inserts 22 and 23 . Accordingly, the electric air pump 46 and the electric air heater 51 can remain switched off. The two shut-off valves 53 , 54 remain closed.

The so-called one-phase operation described above, which comes into operation at high exhaust gas temperatures, is thus characterized in that both filter chambers 20 and 21 are acted upon by exhaust gas or soot particles, but regenerate continuously at the same time by combustion of the soot particles. In this operating state, because of the sufficiently high exhaust gas temperatures, for example above 500 ° C., the soot particles in both filter chambers 20 , 21 can burn off independently. This does not require spark ignition anymore.

After the exhaust gas flow has been filtered in one or both filter chambers 20 , 21 , it passes through the end part 13 and the connecting piece 15 into the exhaust pipe (not shown) of the vehicle. This creates a vacuum area in the end part 13 . This has a particularly favorable effect when the device according to the invention operates in what is known as two-phase operation. This is because the combustion products arising during the regeneration of the filter insert ( 22 or 23 ) concerned are also sucked off by the exhaust gas stream filtered in the other filter chamber ( 20 or 21 ). This has a favorable effect in that the electric air pump 46 , which supplies the regeneration filter chamber ( 20 or 21 ) combustion air, only has to work against a comparatively low back pressure. This advantageously means minimizing the electrical energy to be applied for driving the electric air pump.

Claims (7)

1. Device for removing and burning soot particles contained in the exhaust gases of diesel engines, with two parallel filter chambers, in each of which a combustion insert is arranged, and with a closure flap for alternate operation of the filter chambers, such that in one, by the flap-closed filter chamber the combustion of the soot particles previously deposited there takes place, while at the same time the other filter chamber, opened by the flap and connected to the exhaust gas stream coming from the engine, serves to filter out soot particles from the exhaust gas stream, the flap when a predetermined amount of soot particles has been reached in the filter chamber just connected to the exhaust gas flow can be automatically reversed into its other end position, in which the previously closed filter chamber is now open and connected to the exhaust gas flow, while the previously opened filter chamber is now closed un d is used for combustion of accumulated there soot particles, characterized in that flap for actuating the closure (27) at the input (55 or 56) back-pressure to the respectively open filter chamber (20 or 21) prevailing exhaust gas (p ₃₎ is used and that a first control unit ( 43 ) is provided, which interrupts the influence of the exhaust gas back pressure ( p ₃ ) on the closure flap ( 27 ) when a predetermined exhaust gas temperature is exceeded, and that the closure flap ( 27 ) automatically in an intermediate position upon interruption of the exhaust gas back pressure influence ( 27 '') can be actuated, in which both filter chambers ( 20 , 21 ) are connected to the exhaust gas stream ( 18 ) at the same time. 2. Apparatus according to claim 1, characterized in that on the closure flap ( 27 ) - for actuating the same - a slidably arranged in a control cylinder ( 30 ) arranged on both sides equally spring-loaded ( 34, 35 ) control piston ( 31 ) engages and that the two cylinder chambers ( 32 , 33 ) on both sides of the control piston ( 31 ) are each connected to the inlet ( 55 or 56 ) of one of the two filter chambers ( 20 or 21 ) by a pressure line ( 39 or 40 ) and that in each pressure line ( 39 or 40 ) a shut-off valve ( 41 or 42 ), preferably a solenoid valve, which can be actuated by the first control device ( 43 ) as a function of the exhaust gas temperature. 3. Apparatus according to claim 1 and 2, characterized in that in the input ( 55 or 56 ) to the filter chambers ( 20 or 21 ) each have a nozzle ( 44 or 45 ) for supplying combustion air to the filter chamber in question ( 20th or 21 ) and that the air supply to the nozzles ( 44 , 45 ) can be controlled by a second control device ( 52 ) and that for actuating the second control device ( 52 ) - by contact switches ( 57 , 58 ) - the control piston ( 31 ) serves. 4. The device according to claim 3, characterized in that for generating the required delivery pressure of the respective nozzle ( 44 or 45 ) supplied combustion air, an actuatable by the second control device ( 52 ) electric pump ( 46 ) is provided and that the Pump ( 46 ) outgoing compressed air line ( 47 ) (at 48 ) branches into two compressed air line lines ( 49 , 50 ), each leading to one of the two nozzles ( 44 , 45 ), and that in each line of compressed air line ( 49 and 50 ) through the second control device ( 52 ) actuatable shut-off valve ( 53 or 54 ), preferably a solenoid valve, is arranged. 5. Apparatus according to claim 3 and 4, characterized in that in the outgoing from the pump ( 46 ) compressed air line ( 47 ) - before its branching ( 48 ) - by the second control unit ( 52 ) actuatable air heater ( 51 ) for Generation of the required Zündtempe temperature is arranged in the input ( 55 or 56 ) to the relevant filter chamber ( 20 or 21 ). 6. Device according to one or more of the preceding claims, with a flap designed as a double-armed lever, characterized in that the input ( 12 or 55 , 56 ) to the two filter chambers ( 20 , 21 ) is cone-shaped as a whole, whereby it expands from the end of the exhaust pipe ( 14 or 15 ) to the filter chambers ( 11 or 20 , 21 ), and that at the transition from the exhaust pipe ( 14 ) into the filter chamber inlet ( 12 or 55 , 56 ), at two diametrically opposed points each a permanent magnet ( 28 or 29 ) is arranged and that each permanent magnet ( 28 , 29 ) in the relevant end position ( 27 or 27 ') of the closure flap ( 27 ) with the associated free end thereof cooperates and that the closure flap ( 27 ) engages with its other end (at 37 ) on the control piston ( 31 ). 7. The device according to one or more of the preceding claims, in particular according to claim 1, characterized in that the connecting lines ( 39 , 40 ) from the filter chamber input ( 55 , 56 ) to the control cylinder ( 30 ) by the first control unit ( 43 ) at exhaust gas temperatures of equal to or greater than 500 ° C who the (at 41, 42 ) and that at the transition of the exhaust pipe ( 14 ) into the filter chamber inlet ( 55 , 56 ) a protruding into the exhaust gas temperature sensor ( 59 ) is arranged, which is in operative connection with the first control device ( 43 ).