DE4414904C1 - Temperature-controlled exhaust catalytic converter system for an internal combustion engine - Google Patents

Abstract

Know strategies for avoiding an exhaust-gas temperature too low for a catalytic converter are to sheathe the exhaust feed line with insulation or to control the temperature of the body of the catalytic converter itself by means of an additional exhaust-gas heat exchanger flow. The invention proposes an exhaust catalytic converter system with a temperature control line which emerges from an outflow space in the body of the catalytic converter downstream of the said body and extends in the upstream direction of the main flow in thermal contact with an exhaust-gas feedline section adjoining the region of the catalytic converter up to a reversal point and, from there, is taken back in the downstream direction of the main flow, opening into an exhaust-gas removal line downstream of a flow-control valve. Together with the valve, the temperature control line permits flow in the exhaust-gas temperature-control line which regulates the temperature of the exhaust gas upstream of the catalytic converter, thus avoiding excessively high or excessively low exhaust-gas temperatures in the inlet region of the catalytic converter. This system can be employed, for example, for passenger vehicles with a direct-injection diesel engine.

Description

The invention relates to a temperature-controlled exhaust gas catalyst system for an internal combustion engine according to the Oberbe handle of claim 1 as z. B. general for strength vehicle internal combustion engines can be used and specifically for Cars with modern diesel engines with direct input spraying is of particular benefit.

It is generally known that after a cold start of a vehicle engine there is first a strong heat transfer from the gas to the still cold exhaust pipe section located upstream of a catalytic converter, so that the exhaust gas in the entrance area of the catalytic converter is already too low a temperature for an optimal catalytic effect having. It is known ter ter to counter this fact by insulating the pipes of this exhaust pipe section. However, this insulation on the other hand has the consequence that in the warm operating state of the system there is only a relatively low exhaust gas cooling along the exhaust section in front of the catalytic converter by heat contact with the outside air flowing past. As a result, when the engine is warm, e.g. B. in a Vollastbe operated modern car diesel engine with direct injection, exhaust gas temperatures in the catalyst arise which are above the optimal working range of modern NO _x -Reduktionskata analyzers. On the other hand, even with a warm engine in a system without pipe insulation and temperature control measures for the exhaust gas, the exhaust gas temperature may be too low in the catalytic converter area if the engine is operated in the lower part-load range.

To get an optimal catalyze as quickly as possible after starting the engine To reach sat temperature, it is also known, the Kata lysator body area with an additional, exhaust gas Temperature control line. So in the disclosure document DE 41 09 227 A1 a temperature-controlled catalytic converter Gate system shown in the main flow upstream of the catalytic converter gate body arranged a controllable 2-way valve and the Catalyst body at the same time out as a heat exchanger body forms is. By controlling the valve accordingly the incoming exhaust gas can be used directly for pollutant conversion sion in the catalyst area or first over a Tempe rierleitung are passed through the catalytic converter shear area and then into the catalyst line opens in front of the catalyst body.

A similar catalyst body temperature control is given by the in JP 55-19939 (A), generic appropriate catalytic converter system effects. The Tempe flows there rier line downstream of the catalyst body in front of an in the shut-off valve arranged in the exhaust gas discharge line then in the catalyst body area to temper it back and then flows downstream of the Ab shut-off valve in the exhaust gas discharge line. With this measure the catalyst body can do one even in a shorter time suitable operating temperature after a cold engine start enough, but the difficulty remains that the Ab gas has already cooled down considerably before the catalytic converter and therefore no op., especially in the catalyst entrance area maximum catalyst effect for the inflowing, still ratio Exhaust gas is moderately cool.

The invention is a technical problem of providing a temperature-controlled catalytic converter system at the beginning  mentioned type, which in the various operating conditions achieved the best possible catalyst effect and ins special as much as possible both too high and too low Temperatures of the exhaust gas flowing into the catalyst ver avoids.

This problem is caused by a temperature-controlled exhaust gas catalytic converter Sator system solved with the features of claim 1. There in particular it is provided that the main streams direction behind the catalyst body and in front of the control valve that leads to the exhaust gas and carries the temperature control line in Thermal contact to the main flow upstream of the catalyst body Exhaust gas supply line extends. This doesn't only the catalyst body itself at a more optimal tempera is held, but also what is flowing to it Exhaust gas. Through the thermal contact of the temperature control line with it Exhaust gas supply line section, the exhaust gas remains in this area tempered, in particular due to excessive cooling Thermal contact to the outside is prevented. At the same time remains by eliminating the insulation of the exhaust gas supply line Possibility to do this if the exhaust gas flow is very hot to cool to the outside by thermal contact, then the valve is controlled so that none in the temperature control line valued exhaust gas flow is present and this in which the exhaust gas supply line opposite area therefore even through the Thermal contact to the outside is largely cooled. In to cool exhaust gas flow, on the other hand, becomes direct through the valve Outflow of the exhaust gas from the catalyst outflow space into the Exhaust gas discharge line shut off and this from the Kataly exhaust gas escaping through the temperature control line. By appropriately controlling intermediate valve positions is also the exhaust gas outflow from the catalyst outflow space in any ratio between temperature control line and direct Outflow into the exhaust gas discharge line, which is a appropriate temperature control of the catalytic converter system means.  

In an embodiment of the invention, the temperature control line in the area in which they are in thermal contact with the exhaust gas supply line lies, a coaxially surrounding this ring channel, so that the Ab gas supply line in this area on all sides from this tempering line section is shielded. In the river The reversal point of the temperature control line goes this ring channel then into a pipe that bypasses the catalyst body in parallel tung about.

An embodiment of the invention according to claim 3 has the front part that either the exhaust pipe or with the valve the temperature control line can be actively shut off or the respective active flow components through appropriate valve position let set.

In one embodiment of the invention according to claim 4, the Temperature control line formed by a longitudinally divided ring channel. The individual Ringlängska formed by this longitudinal division channels are connected to each other upstream and on the other hand partly lead into the catalyst outflow space and the rest of the flow downstream of the valve into the exhaust gas discharge line. The exhaust gas flow thus takes place in the temperature rierleitung by opening out of the catalyst outflow in the part of the longitudinal channels, from where the exhaust gas counteracts the main flow direction and along the corresponding Ab gas supply line section flows back until it is at the main flow upstream reversal point into the other Ringlängska channels is diverted and in these downstream to the Ab gas supply line is routed behind the valve. Through this Temperature control line design as a divided ring channel can consequently the flow and return of the temperature control exhaust gas in take place within this ring channel, so that a very short tem perierleitungsweg reached or a separate pipe to Bypassing the catalyst body area is avoided.

Preferred embodiments of the invention are in the drawing are shown and are described below.

Fig. 1 shows a temperature-controlled catalytic converter system with a radial flow catalyst in longitudinal section and

Fig. 2 shows a temperature-controlled exhaust gas catalytic converter system with an axially flowed catalyst in longitudinal section.

In the exhaust gas catalytic converter system shown in FIG. 1, a radial flow catalytic converter body 1 is arranged for converting pollutants, which annularly surrounds a central catalytic converter antechamber 2 , into which an exhaust gas supply pipe 3 opens. In the supply pipe 3 , the exhaust gas flows in the main flow direction 15 defined in this way. The catalyst body 1 is surrounded by a catalytic converter housing 14, wherein the space between Kataly sator body 1 and the housing 14 defines a Katalysatorausströmraum 4, enters the exhaust gas after flowing through the Kataly sator body 1 in the location indicated by the arrows radial direction. At the main downstream of the rear end of the catalyst housing 14 is attached to the housing 14, a Abgasab supply pipe 5 is added, in which the Katalysatorausströmraum 4 opens at this end. In this mouth a controllable valve is arranged in the form of a positionable throttle valve 6 . Upstream of the main flow, the catalyst housing 14 passes into a ring channel section 8 of a tempering line 7 . This tempering line ring channel section 8 surrounds the exhaust gas supply pipe 3 in its section located in front of the catalytic converter body 1 and extends upstream of the main flow to a vertex 9 , in which the ring channel section 8 merges into a parallel pipe section 11 of the tempering line 7 , which extends from this vertex 9 bypassing the catalyst housing 14 to a main flow located from the throttle valve 6 junction 10 in the exhaust pipe 5 he stretches. In this way, there is a temperature control line flow 13 from the annular gap of the catalyst outflow space 4 between the catalyst body 1 and the catalyst housing 14 through the annular channel section 8 coaxially and opposite to the flow in the exhaust gas supply pipe 3 to the ring channel apex point 9 and from there through the parallel pipe 11 into the exhaust gas discharge pipe 5 .

With the exhaust gas catalytic converter system constructed in this way, the temperature of the catalyst body 1 and in particular also of the exhaust gas flowing into it can be regulated as follows. With a comparatively cold exhaust gas supply flow, the throttle valve 6 is controlled in its position in the exhaust gas discharge pipe 5 against the catalyst outflow space 4 . As a result, the exhaust gas is completely diverted into the temperature control line 7 after passing through the catalyst body 1 . The exhaust gas flowing back here on the catalyst body 1 initially ensures thermal insulation of the catalyst body 1 to the outside and thus to the same temperature control. At the same time, the temperature flow in the adjoining annular channel section 8 provides heat shielding of the exhaust gas supply pipe 3 in this area in front of the catalytic converter body 1 and thus ensures a temperature of the incoming exhaust gas. This means that the passing into the Katalysatorvorraum 2 gas is maintained substantially at the temperature which upstream has at the level of Temperierleitungsscheitelpunktes 9, since a significant further cooling in the waste gas supply line portion between the sem apex 9 and the Katalysatorvorraum 2 by the Temperierströmung in the annular channel section 8 is prevented. It is understood that the location of the Temperierleitungsscheitelpunk tes 9 and thus the length of the Temperierleitungs-Ringkanalab section 8 is matched to the present application in such a way that there is sufficient temperature control of the inflowing exhaust gas.

As soon as the temperature of the inflowing exhaust gas and / or the Ka talysatorkörpers 2 threatens to be too high, the throttle valve 6 is partially or fully opened, so that part of the exhaust gas or the entire exhaust gas flow past the throttle valve 6 directly into the exhaust gas discharge line 5 . Only an exhaust gas fraction that can be reduced to zero then still flows through the temperature control line 7 , since the exhaust gas emerging from the catalyst body 1, due to the resulting pressure and flow conditions, tends to leave the catalyst outlet chamber 4 past the throttle valve 6 and into the exhaust gas discharge pipe 5 as is pushed over the temperature control line 7 . Due to the missing or only slight temperature control line flow 13 , the temperature control line 7 and the catalyst housing 14 are cooled noticeably by the outside air flowing past, which in turn corresponds to a corresponding cooling of the exhaust gas in the exhaust gas supply pipe 3 also in the area surrounded by the temperature control line ring channel section 8 as well Catalyst body 1 leads, whereby the flowing into the Kata lysatorvorraum 2 exhaust gas and the catalyst body 1 are brought back to an optimal working temperature.

In this way, the exhaust gas catalytic converter system shown permits a temperature control which avoids both a too low and, for example, a too high working temperature of the catalyst body 1 and the exhaust gas flowing into it for a modern NO _x reduction catalytic converter. It also enables an improved light-off behavior of the catalytic converter and variable temperature control of the exhaust gas flowing into the catalytic converter inlet, which is of great benefit particularly in the part-load operation of a diesel engine with direct injection. There is no need to attach insulation materials to the exhaust gas supply pipe and around the catalytic converter body. The coaxial sheathing of the exhaust gas supply pipe section in front of the catalyst body by 1 through the temperature control line 7 also reduces the airborne sound radiation. Furthermore, the volume and the coating of the catalyst body 1 can be optimally adapted to the conditions. The somewhat increased catalyst back pressure in the cold start due to the closing of the throttle valve 6 counteracts that of excessive exhaust gas cooling in the region of the catalyst body.

The same advantages mentioned above also result for the exhaust gas catalytic converter system shown in FIG. 2, which functionally corresponds essentially to that of FIG. 1, in which an axial flow-through catalyst body 21 is provided instead of the radial flow catalyst, which is radially sealed from a catalyst housing 34 is limited, the housing 34 delimiting a catalyst space 22 , into which a gas supply pipe 23 opens. The exhaust gas flows in this feed pipe 23 in the main flow direction 32 defined in this way. The main flow downstream of the catalytic converter body 21 , the catalytic converter housing 34 delimits a catalytic converter outflow chamber 24 , from which both an exhaust gas discharge pipe 25 and a pipe 36 open, which is part of a temperature control line 27 . The opening 35 in the temperature control line pipe 36 is adjacent to that in the exhaust gas discharge pipe 25 , a pivoting flap 26 being mounted as a controllable valve on the housing 34 in the adjoining area, the lungs between two end positions, in which it blocks one of the two openings, is pivotable. The temperature control line tube 36 opening out of the catalyst outflow space 24 bypasses the catalytic converter housing 34 upstream of the main flow and, at the level of the confluence of the exhaust gas supply tube 23 and the catalyst antechamber 22, passes into an annular channel section 28 of the temperature control line 27 , which flows upstream - the exhaust gas supply tube 23 in this area in front of the catalyst housing 34 coaxially bend - extends to an apex 29 . At this apex 29 , the temperature control line 27 passes from the ring duct section surrounding the corresponding exhaust gas pipe section 28 again into a parallel pipe 31 which, bypassing the catalyst housing 34 , essentially in the main flow direction 32 from the apex 29 to a main flow downstream of the swivel flap 26 , is an orifice 30 extends into the exhaust pipe 25 .

From this structure of the exhaust gas catalytic converter system, the fol lowing, essentially identical to that of the system of FIG. 1, results. Subsequent to a cold start or at partial load operation of a diesel engine with direct injection, the swivel flap 26 is controlled so that it blocks the exhaust gas discharge pipe 25 from the catalyst outflow chamber 24 , thereby simultaneously opening the outlet 35 from the catalyst outflow chamber 24 into the temperature control line 27 . The exhaust gas flowing through the catalyst body 21 is then guided through the tempering line 27 in the manner indicated by the flow arrows 33 , first in the catalyst housing 34 bypassing the main flow upstream temperature control tube 36 , from there through the annular channel section 28 to the tele point 29 where it is deflected, and then we sentlichen in häuses in the main flow direction 32 through the second Tem perierleitungseinzelrohr 31 bypassing the Katalysatorge 34 in the Abgasabführrohr 25th

With this measure, the prevention of excessive cooling of the exhaust gas flowing in the exhaust gas supply pipe 23 is achieved by the exhaust gas supply pipe section lying in front of the catalytic converter housing 34 being isolated from the outside temperature by the exhaust gas flow in the tempering line annular duct section 28 , so that the catalyst chamber 22 inflowing exhaust gas essentially remains at the temperature it has at the level of the temperature control line peak 29 . As described for the system of FIG. 1, the degree of temperature can be adjusted by the choice of the length of the Temperierleitungsringka channel 28 , ie the position of the Temperierleitungsleitungspunktes 29 to the particular application. When a Abgastem is temperature reached after warming up the engine, and in particular in the full load of said diesel engine with direct injection, which is higher than the favorable working Tempera ture, the pivoting flap is ert gesteu to a position 26 which space the direct orifice from the Katalysatorausström 24 in the Exhaust pipe 25 at least partially releases. Depending on the position of the swivel flap 26 , the mouth 35 in the temperature control line 27 also remains partially open or it is completely shut off. Depending on the situation, an exhaust gas flow that can be regulated in terms of its flow intensity is maintained through the temperature control line 27 . The reduced or completely stopped flow through the temperature control line results in a weaker or completely non-existent heat insulation of the exhaust gas supply line section coaxially surrounded by the temperature control line annular duct section 28 with respect to the outside temperature, so that the exhaust gas flowing in the exhaust gas supply pipe 32 also flows through the area encased by the temperature control line ring duct section 28 through the outside is further cooled so that the temperature of the exhaust gas entering the catalyst housing 34 is reduced again.

It follows from this functional description that, with regard to the exhaust gas catalytic converter system of FIG. 2, the same functional advantages result with regard to achieving the best possible temperature of the exhaust gas entering the inlet area of the catalyst as were detailed above for the system of FIG. 1, which is referred to again here. Of course, a suitable control or regulating device in addition to the sensor system, z. B. for detecting the exhaust gas temperature, provided for automatic exhaust gas temperature regulation, for which purpose a common device of this type can be used, so that it need not be discussed in more detail here.

It is understood that the person skilled in the art in addition to the exhaust gas shown catalyst systems further implementations of the invention, such as it is defined by the appended claims can increase. In particular, the invention is also for belie  other than the types and forms of catalyst shown body applicable.

Claims (5)

1. Temperature-controlled catalytic converter system for an internal combustion engine, with

• - a catalyst body ( 1 ),
• - an exhaust gas supply line ( 3 ) supplying the exhaust gas to the catalyst body,
• - A exhaust gas discharge line ( 5 ) opening out from a catalyst body outflow space ( 4 ),
• - A controllable valve ( 6 ) for regulating the flow cross-section for flue gas flowing directly into the exhaust gas discharge line from the catalyst body and
• - A from the catalyst body outflow space and main flow downstream of the valve bypassing the same in the exhaust gas discharge line tempering line ( 7 ),

characterized in that

• - The temperature control line ( 7 ) leg section holds ( 8 ) which is in thermal contact with the exhaust gas supply line ( 3 ).

2. Exhaust gas catalytic converter system according to claim 1, further characterized in that the line section of the temperature control line ( 7 ) arranged in thermal contact with the exhaust gas supply line forms an exhaust gas supply line ( 3 ) coaxially surrounding ring channel ( 8 ), which at its most upstream end face ( 9 ) into a separate pipeline section ( 11 ) of the temperature control line ( 7 ) which is arranged between this front end and the junction point ( 10 ) in the exhaust gas discharge line ( 5 ). 3. catalytic converter system according to claim 1 or 2, further characterized in that

• - The temperature control line ( 27 ) in an opening ( 35 ) from the catalyst body outflow chamber ( 24 ) Be rich as a separate, the catalyst body ( 21 ) parallel tube section ( 36 ) is formed and
• - With the controllable valve either the tempering line mouth ( 35 ) or the exhaust gas discharge line mouth can be shut off.

4. Exhaust gas catalyst system according to claim 1, further characterized in that designed the temperature control line as a longitudinally divided ring channel is either the catalyst body and the upstream downstream, exhaust gas in thermal contact with it supply line section or only surrounds the latter, the longitudinal channels separated from each other at their furthest main upstream end communicating with each other stand and part of it with its opposite end open out of the catalyst body outflow space, while the remaining longitudinal channels with their opposite end in the exhaust gas discharge line downstream of the controllable Open the valve.