DE19948148B4 - Motor vehicle with an internal combustion engine - Google Patents

Abstract

Motor vehicle with an internal combustion engine with catalytic exhaust gas purification via at least one catalytic converter inserted behind an exhaust manifold, wherein in the motor vehicle an air duct (1) is arranged, which has an inlet opening (2) in an area of the front of the motor vehicle and with its end in an exhaust manifold ( 9) associated heat shield (11) opens, extending between the internal combustion engine (10) and catalyst (7), characterized in that in the air duct (1) is provided a flexible element (16) for vibration-decoupling of internal combustion engine (10) and body ,

Description

The The invention relates to a motor vehicle with an internal combustion engine with catalytic emission control via at least one rear an exhaust manifold used catalyst, in particular pre-catalyst, wherein im Motor vehicle an air duct is arranged in an area the front of the motor vehicle has an inlet opening and with his End in an exhaust manifold associated heat shield flows, that extends between the internal combustion engine and the catalyst, according to the preamble of claim 1.

Known Automotive engines operate with direct fuel injection in a large part of an engine operating map with an excess of air, which allows a significant reduction in fuel consumption. Under these conditions can to convert the nitrogen oxides no conventional three-way catalysts be used. For The nitrogen oxide conversion of lean exhaust gas are therefore under used other NOx storage catalysts.

With Such NOx storage catalysts can have sufficiently high conversion rates however only be achieved in a narrow exhaust gas temperature window, whereby the efficiency increasing lean operating range of the Motors is severely limited. Thus, it is necessary to engine operation and to coordinate the catalyst system so that the exhaust gas temperatures at the entrance to the storage catalyst (s) via a the largest possible engine operating range lie within this temperature window. At higher vehicle speeds is in this regard the upper temperature limit is problematic. For the extension of the engine operating range at higher Engine speeds and engine loads are therefore appropriate measures, for cooling the exhaust gas and thus the lowering of the catalyst temperature to lead.

From the generic DE 41 27 634 A1 an exhaust system with a covered tube is known, wherein in response to a temperature in an exhaust gas purification device cooling air is guided into the enclosure. The cooling air flow is guided in a cooling air pipe, which runs next to the exhaust pipe to a tail pipe of the exhaust system.

A motor vehicle with an internal combustion engine, a catalytic converter used in an exhaust system and an air duct arranged in the motor vehicle, which has an inlet opening in an area of the front of the motor vehicle, is known from US Pat JP 07-275 653 A known. For better NOx conversion here a comparatively complicated, double-walled exhaust system, namely with an inner exhaust pipe and an outer cooling air pipe, proposed by the internal combustion engine to the converter. The outer tube also envelops the converter. In the outer tube of this double-walled arrangement, two Luftleitschächte can open, wherein the one is disposed in an upper region of the exhaust pipe downstream of a cooling air fan and the second in a geodetically lower lying area of the body.

In a second embodiment this known arrangement, the exhaust system is executed only single-walled, and an outgoing from the vehicle front Luftleitschacht leads in a separate line cooling air to a circular converter surrounding radiator.

From the JP 08-189 334 A To improve an exhaust gas cooling, a downstream of the cooling water heat exchanger air guiding device is known, wherein the exhaust pipe has additional cooling fins. The exhaust manifold immediately adjacent to the cylinder head of the internal combustion engine is not used for cooling purposes.

The DE 2 305 377 A discloses an exhaust manifold, which is flowed around at higher part loads or full load operation of the internal combustion engine of a gaseous cooling medium. For this purpose, the exhaust manifold on a corresponding sheath through which the gaseous cooling medium flows.

The GB 1 361 910 A describes an internal combustion engine with a catalytic converter for exhaust gas purification. Respective exhaust manifolds are provided with Wärmeleitblechen and a sheath. Through the envelope cooling air is blown by fans.

From the US Pat. No. 3,820,327 a device for regulating the temperature of a catalyst for exhaust gas purification of an internal combustion engine is known. By means of an air flow heat exchanger surfaces of the catalyst and the exhaust manifold are cooled. The flow rate of the air flow is proportional to a temperature increase of the catalyst, wherein the air flow is completely inhibited when the temperature of the catalyst falls below a predetermined value.

The DE 44 10 022 A1 describes an exhaust system for an internal combustion engine with an exhaust gas converter. For rapid temperature control of a housing having exhaust gas converter for the exhaust gases of an internal combustion engine, the converter and a waste gas supply serving Vorrohr are arranged in a container which is provided with a demand-controlled cooling air supply. The Vorrohr runs in the container in the immediate vicinity of the exhaust gas converter approximately U-shaped to ensure large heat transfer surfaces.

task The invention is not only a motor vehicle with an internal combustion engine to disposal to provide, the catalytic exhaust gas purification in comparatively simple and space-saving way over an extended engine operating range can be optimized, but at the same time measures for vibration engineering Decoupling of internal combustion engine and body and to compensate specify installation tolerances. The task is performed by a motor vehicle of the type mentioned above with the features characterized in claim 1 solved. Advantageous developments of the invention are specified in the dependent claims.

at A motor vehicle of the above type is thus provided that the exhaust manifold a heat shield is assigned, in which the end of the Luftleitschachtes opens, wherein yourself this heat shield extends between the engine and the catalyst. According to the invention is in Air duct a flexible element for vibration control Decoupling of internal combustion engine and body arranged. The Arrangement of this element in the air duct and not on his Ends gives it a flexibility that compensates for Installation tolerances and a slight shaping of the element in addition to the ensures vibration-decoupling.

The Vibration decoupling by the flexible element in the Air duct ensures that in almost all engine operating ranges, d. H. even with abrupt load changes and corresponding relative movements the engine opposite the motor vehicle, a sufficient, catalytic emission control made available is.

Of the Air duct, which is located in an area of the front of the motor vehicle an entrance opening may be provided with a controllable switching flap. This has the advantage that the controllable switching flap in one Operating position the cooling air flow towards a cooling water heat exchanger diverted and can be ensured that, for example, at an uphill ride of the motor vehicle under high load and high Coolant temperature the internal combustion engine, the air flow can be used for additional cooling of the cooling water heat exchanger can. In such an operating case then the component protection for the Pre-catalyst and the storage catalyst via an increased enrichment ensured the combustion mixture become.

On the Air duct allows especially at higher levels Travel speeds of the exhaust manifold and thus the exhaust cool down, so that also the temperatures of a pre-storage and storage catalyst reduce. Another advantage of the exhaust gas cooling is that at high engine speeds and loads, the thermal load of and storage catalyst is lowered, which significantly prolongs the component life contributes.

If in the text below a pre-catalyst and / or a main catalyst is mentioned, so can Including in each case several such catalysts at a single Motor vehicle meant.

The in the area of the entrance opening arranged the Luftleitschachtes switching flap can either two Switching states, open and closed, have or be continuously adjustable.

to Magnification of the effectiveness the exhaust gas cooling can the entrance opening Air guiding holes have funnel-shaped are formed, and arranged in the region of the inlet opening a fan, even at lower speeds a satisfactory cooling of the To ensure exhaust gas or the catalysts.

In addition, besides these measures to increase the air flow and the flow velocity in the air duct air ducts be arranged to purposefully guide the flow of air around the ones to be cooled To realize components. Furthermore, the entire exhaust system additional or optionally optimized, for example via a Ribbing or over the Use of special pipe geometries with larger surface area, over one Coating the exhaust system to increase the emission coefficient and thus the heat emission by radiation as well as measures to increase the heat transfer can be provided between exhaust and exhaust system.

The switching flap is preferably operated via an electronic control of the engine management, wherein the switching flap is opened in a rest position or a default position and is controlled during the operating conditions enumerated below: during the heating of the pilot and main catalytic converter after an engine start or if a desulfurization of the Pre- and main catalyst is required; when the exhaust gas temperature after the main catalyst is lower than the dew point or when the coolant temperature is lower than a minimum threshold; if the exhaust gas temperature upstream of the precatalyst is less than a minimum threshold and the exhaust gas temperature downstream of the precatalyst is less than a minimum mumschwelle and at the same time the temperature of the main catalyst is less than a minimum threshold or when the vehicle speed is less than a minimum threshold.

The Switching flap is controlled in a deflection position when the coolant temperature the internal combustion engine is larger as a maximum threshold and the exhaust gas or catalyst temperature is greater than a maximum threshold.

following is an embodiment the invention described in more detail with reference to the drawings. Show it:

1 a schematic diagram of an exhaust gas cooling,

2 a schematic diagram of a version with air deflection,

3 another version of exhaust gas cooling in side view,

4 a representation of 3 in a plan view,

5 another version of the exhaust gas cooling in side view and

6 a representation of two air currents according to the version 5 ,

A motor vehicle with an internal combustion engine 10 with catalytic exhaust purification with one immediately behind an exhaust manifold 9 arranged pre-catalyst 7 and a main catalyst arranged behind the exhaust gas flow and configured as a NOx storage catalyst 8th has a Luftleitschacht for cooling the exhaust gas 1 on, in the area of the front of a motor vehicle, an inlet opening 2 owns and its end on the exhaust manifold 9 and / or a graphically not shown exhaust gas cooler is directed and in the region of the inlet opening 2 , which prefers behind a radiator grille 12 is arranged, a controllable switching flap 3 ; 4 having. This switching flap 3 ; 4 has either two switching states, a controlled state and a controlled state or is infinitely adjustable, whereby the exhaust gas temperature can be adjusted particularly precisely to the optimum operating range of the NOx storage catalytic converter.

A controllable switching flap 4 , as in 2 is designed as an air deflecting device, which can be brought into a flow position in which the cooling air flow is aligned in the direction of a cooling water heat exchanger, which may be the case especially in the case of a climb under high load and high cooling water temperature in the rare case in which case, however, an increased accumulation of the combustion mixture becomes necessary for component protection.

A more concrete embodiment, as in the 3 and 4 shown behind a radiator grille 12 which is above a bumper 15 and below a hood 14 is arranged, an entrance opening 2 of the air duct 1 on which on its front air baffles 6 has, which are arranged funnel-shaped.

Inside the ventilation shaft 1 is a controllable switching flap 3 Arranged in the air duct 1 a flexible element 16 for vibration engineering decoupling of internal combustion engine 10 and body connects, with the Luftleitschacht 1 in one on the manifold 9 directed heat shield 11 leads to the hot exhaust gases in front of the pre-catalyst 7 to cool down to a desired temperature. Inside the heat shielding plate 11 Further air baffles may be provided which serve to equalize the flow of the exhaust pipes of the individual cylinders, which is particularly useful in oblique flow of the exhaust pipes.

The control of the switching flap 3 via a control unit 17 which, in addition to the known engine operating data via a temperature sensor arranged in front of and / or behind the primary catalytic converter and / or upstream of the main catalytic converter 18 is supplied with process data to be evaluated.

Furthermore, as in 1 shown, in addition, the front pipe of the main catalyst designed as a storage catalyst 8th be cooled in a known manner, for example by additional baffles 13 in the underbody of the motor vehicle, which can optionally be designed switchable.

According to further, not graphically illustrated embodiments of the invention can either increase the air flow and the flow velocity through the Luftleitschacht 1 in the area of its entrance opening 2 or downstream of the switching flap 3 an additional blower be provided or to improve the heat dissipation exhaust system have an additional ribbing or the use of special tube geometries with a larger surface done as well as a coating of the exhaust system to increase the emission coefficient and thus the heat emission by radiation can contribute to or more Known measures to increase the heat transfer between the exhaust and the exhaust pipe wall or between this and the Environment are taken.

At the in 5 Version shown, the cooling air is below the bumper 15 taken. This embodiment may be particularly advantageous in vehicles with very heavily pulled down hood 14 when an air inlet in the radiator grille 12 only has a small cross-section. It is also advantageous in this embodiment that the cooling air is removed in the region of the highest dynamic pressure. An air duct 1 leads next to or over a cooler obliquely upwards and is arcuate on the heat shield 11 directed. To a setting of the switching flap 3 To prevent this is preferably in obliquely upward leading Luftleitschacht 1 to arrange.

In the 5 represented version can lead by the multiple deflection of the cooling air flow to an inhomogeneous formation of the air flow. 6 illustrated by different stake arrows, as by a suitable inclination of the switching flap 3 , right representation, a part of the vorkatnahen area more pronounced cooling air flow, left view, can be directed into the upper part of the Luftleitschachtes and thus contributes to a homogenization of the flow. The inclination of the switching flap 3 can in the controlled rest position by appropriate structural design of the maximum adjustment of this flap 3 be ensured. It is also conceivable to provide a stop buffer, which can be made fixed or adjustable. The inclination of the flap 3 in the rest position can then be adjusted depending on the driving speed and / or the exhaust gas or catalyst temperatures.

A further homogenization of the air flow in the exhaust gas cooling in the version according to 1 . 2 . 3 . 4 or 5 is possible by further upstream or downstream of the switching flap arranged fixed or adjustable baffles 22 as exemplified in 6 shown.

Claims (4)

Motor vehicle with an internal combustion engine with catalytic exhaust gas purification via at least one catalytic converter used behind an exhaust manifold, wherein in the motor vehicle an air duct ( 1 ) is arranged, in an area of the front of the motor vehicle, an inlet opening ( 2 ) and with its end in a the exhaust manifold ( 9 ) associated heat shield ( 11 ), which is located between internal combustion engine ( 10 ) and catalyst ( 7 ), characterized in that in Luftleitschacht ( 1 ) a flexible element ( 16 ) for vibration engineering decoupling of internal combustion engine ( 10 ) and body is provided. Motor vehicle according to claim 1, characterized in that in the region of the inlet opening ( 2 ) a controllable switching flap ( 3 . 4 ) is used. Motor vehicle according to claim 1, characterized in that the controllable switching flap ( 3 . 4 ) has two switching states, open and closed, has or is infinitely adjustable. Motor vehicle according to claim 3, characterized in that in the switching state "on" the switching flap ( 3 . 4 ) is at least approximately parallel to the surrounding air flow.