DE102008008492B4 - Method for controlling a motor vehicle internal combustion engine arrangement - Google Patents

Abstract

A method of controlling an automotive internal combustion engine assembly (50) having an internal combustion engine (1) with a charge air inlet (94) and an exhaust outlet (95), a charge air supercharger (64) with a power turbine (12) and a Compressor (3), a coolant circuit (58) with a control element (32, 33) for coolant flow control for demand cooling of the internal combustion engine (1), connected to the outlet (95) exhaust gas catalyst (8), an exhaust gas temperature sensor (9 ) in front of the catalytic converter (8), a low-pressure exhaust gas recirculation line (54) from the exhaust side behind the catalytic converter (8) to the charge air side in front of the compressor turbine (3), an exhaust gas recirculation control valve (2) for controlling the exhaust gas flow through the exhaust gas recirculation -Leitung (54), and a charge air cooler (38) between the compressor turbine (3) and the inlet (94), wherein the charge air cooler (38) has a bypass (52) with a control valve (35) for bypassing the required Intercooler (38) is associated with the method steps of determining the exhaust gas temperature with the exhaust gas temperature sensor (9) when the exhaust gas temperature in the cold-running phase is below a constant threshold: closing the coolant circuit (58) by actuating the coolant circuit control element (32, 33), opening the low pressure exhaust gas recirculation line (54) by opening the exhaust gas recirculation control valve (2), and opening the bypass control valve (35) during the cold running phase.

Description

The invention relates to a method for controlling a cold running phase of a motor vehicle internal combustion engine arrangement.

Modern internal combustion engine arrangements have, in addition to the internal combustion engine and a coolant circuit with a control for demand-controlled coolant flow control for cooling the internal combustion engine on other ancillaries, which have different functions. In particular, in internal combustion engines, a charge air supercharger with a drive turbine in the exhaust gas flow and a compressor turbine on the charge air side is increasingly provided.

Furthermore, for exhaust gas purification both in diesel and gasoline internal combustion engines an exhaust gas catalyst is provided, which is usually associated with an exhaust gas temperature sensor before the inlet of the catalytic converter. Furthermore, for the reduction of nitrogen oxides in particular, a low-pressure exhaust gas recirculation with an exhaust gas recirculation line from the engine exhaust side in the flow direction behind the catalytic converter to the charge air side in the flow direction in front of the compressor turbine is provided. The gas flow through the exhaust gas recirculation line can be controlled by an exhaust gas recirculation control valve.

The requirements for reducing the pollutant emissions of internal combustion engine assemblies are constantly increasing. By far the most emission-rich phase is that between the starting of the cold internal combustion engine and the reaching of the operating temperature of the internal combustion engine and all the aggregates and fluids involved.

In the engine arrangements of the prior art, this requirement is met by appropriate control and regulation of the engine assembly. However, the known controls and regulations for the internal combustion engine arrangement essentially relate to the operation at operating temperature.

In EP 1 403 480 B1 An internal combustion engine arrangement is described in which the coolant circuit is closed as long as the catalytic converter has not reached its operating temperature. Exhaust gas recirculation is controlled as a function of heat losses during combustion.

In JP 11-229973 A An internal combustion engine assembly having a high pressure exhaust gas recirculation line and a low pressure exhaust gas recirculation line is disclosed. As long as the catalytic converter has not reached its operating temperature, the exhaust gas recirculation is basically carried out via the low-pressure exhaust gas recirculation line.

In US 7,261,086 B2 the exhaust gas recirculation on an exhaust gas recirculation cooler, which in turn has a bypass. The exhaust gas recirculation cooler bypass is opened as long as the catalytic converter has not reached its operating temperature.

The object of the invention is to provide a control method for a motor vehicle internal combustion engine arrangement, which ensures a reduction of the pollutant emissions, as long as the internal combustion engine arrangement has not reached the operating temperature.

• • Der Kühlmittelkreislauf wird durch Betätigung des Kühlmittelkreislauf-Steuerelementes geschlossen, d. h. das Kühlmittel zum Kühlen des Verbrennungsmotors zirkuliert nicht mehr, sondern steht jedenfalls weitgehend still. Hierdurch werden während der Kaltlaufphase der Verbrennungsmotor und alle Aggregate, die darüber hinaus im Kühlmittelstrom angeordnet sind, nicht aktiv gekühlt. Das Kühlwasser entzieht dem Verbrennungsmotor und den von ihm darüber hinaus durchströmten Aggregaten nur ein unvermeidliches Minimum an Wärme. Auf diese Weise wird der Verbrennungsmotor durch den Verbrennungsprozess schnellstmöglich erwärmt und werden insbesondere auch die entstehenden Verbrennungsgase geringstmöglich durch den Verbrennungsmotor gekühlt. Im Ergebnis weisen die aus dem Abgas-Auslass des Verbrennungsmotors austretenden Gase eine höhere Temperatur auf, als dies bei bereits zirkulierendem Kühlmittel der Fall wäre.
• • Ferner wird während der Kaltlaufphase das Abgasrückführungs-Steuerventil der Niederdruck-Abgasrückführung geöffnet. Das aus dem Abgaskatalysator austretende Abgas wird mit der größtmöglichen Rate zurückgeführt auf die Ladeluftseite der Verbrennungsmotoranordnung. Hierdurch wird jedenfalls ein Teil des Abgases und damit jedenfalls ein Teil der Abgas-Wärme in die Ladeluftseite eingespeist. Die Wärme des aus dem Abgaskatalysator austretenden Abgases geht also nicht vollständig verloren, sondern wird zu einem erheblichen Teil der Ladeluft zugeführt, so dass diese Wärme der Verbrennungsmotoranordnung erhalten bleibt.

This object is achieved in that after starting the engine continuously the exhaust gas temperature is determined with the exhaust gas temperature sensor. As long as the exhaust gas temperature determined with the exhaust gas temperature sensor is below a constant limit of over 200 ° C, the cold running phase continues, and the following measures are carried out:

• • The coolant circuit is closed by actuation of the coolant circuit control, ie the coolant for cooling the engine no longer circulates, but is at least largely quiet. As a result, during the cold running phase of the internal combustion engine and all units, which are also arranged in the coolant flow, not actively cooled. The cooling water draws the internal combustion engine and the power from him through aggregates only an unavoidable minimum of heat. In this way, the internal combustion engine is heated as quickly as possible by the combustion process and, in particular, the resulting combustion gases are cooled as little as possible by the internal combustion engine. As a result, the gases exiting the exhaust gas outlet of the internal combustion engine have a higher temperature than would be the case with already circulating coolant.
• • Furthermore, during the cold running phase, the exhaust gas recirculation control valve of the low-pressure exhaust gas recirculation is opened. Exhaust gas exiting the catalytic converter is returned at the highest possible rate to the charge air side of the engine assembly. In this way, in any case a part of the exhaust gas and thus at least part of the exhaust gas heat is fed into the charge air side. The heat of the exhaust gas emerging from the catalytic converter is therefore not completely lost, but is supplied to a considerable part of the charge air, so that this heat of the internal combustion engine arrangement is maintained.

In the cold running phase, in which the exhaust gas temperature is below a constant limit of over 200 ° C, the exhaust gas is the only heat carrier. By the two measures, namely closing the coolant circuit and opening the low-pressure exhaust gas recirculation is ensured that the exhaust gas heats up as quickly as possible. In turn, this ensures that the exhaust gas catalyst is heated as quickly as possible to the threshold temperature. The catalytic converter according to the prior art begins to work for physical reasons only at temperatures above 200 ° C, ie to reduce the pollutant emissions considerably. The limit value corresponds approximately to the minimum operating temperature of the catalytic converter. For present day catalytic converters, the limit is a value above 250 ° C.

As an alternative to the determination and the evaluation of the exhaust gas temperature for determining the activity of the catalytic converter, this can also be determined with two λ probes, which are arranged in front of and behind the exhaust gas catalytic converter. If the difference in the oxygen content determined by the λ probes falls below a certain limit value, it is assumed that the catalytic converter is not working, which is a prerequisite for determining the cold-running phase. Instead of the condition relating to the exhaust gas temperature, the condition in this case would be that the difference of the oxygen concentrations determined by the two λ probes before and after the catalytic converter falls below a limit which indicates a non-exhaust gas purifying effect of the catalytic converter. In any case, the non-activity of the catalyst should be noted for the determination of the cold-start phase.

By the two described method steps, namely the closing of the coolant circuit and the opening of the low-pressure exhaust gas recirculation thermal or thermal management is realized, which has the fastest possible heating of the exhaust gas in the cold running phase, since in this way the exhaust gas catalyst in the shortest possible time its Minimum operating temperature reached. In this way, it is achieved that at a cold start, especially at low outside temperatures, the pollutant emissions in the exhaust gas are reduced as quickly as possible.

Until the combustion engine, the ancillaries and fluids have reached operating temperature pass on small gasoline engines only a few minutes. During this time, however, up to 90% of the pollutant emissions measured in the normalized driving cycles arise. Since the nominal exhaust emissions of internal combustion engine assemblies or motor vehicles are determined with specified driving cycles, and the cold running phase, for example, in the valid for the EU NEDZ a relatively high proportion, which contributes significantly to the accounted pollutant emission, especially in a large internal combustion engine, contributes to the heat-optimized thermal management and thus the fastest possible heating of the catalytic converter significantly to improve the nominal emissions of pollutants.

The coolant circulation control element in the coolant circuit can be realized as a valve and / or as a coolant pump. Great advantages here can provide an electric coolant pump, which can shut off the coolant circuit by switching off in a simple manner, if not completely enough. In addition, a corresponding valve can be arranged in the coolant circuit, which prevents any appreciable flow within the coolant circuit. It is crucial that when the coolant circuit is closed by appropriate actuation of the coolant circuit control element, the coolant no longer circulates appreciably.

In particular, in diesel internal combustion engines, the exhaust gas has relatively low temperatures, so that the heating of the internal combustion engine and the units and the fluids takes a relatively long time. Especially with large diesel internal combustion engines, the time until the catalytic converter reaches its operating temperature is considerably shortened with the described control strategy and the exhaust gases determined in the normalized driving cycle are considerably reduced.

The internal combustion engine assembly includes an intercooler between the compressor turbine and the charge air inlet of the internal combustion engine. The intercooler is associated with a bypass valve with a control valve for bypassing the intercooler as required. During the cold run phase, the bypass control valve is open, so that the charge air does not flow through the intercooler, but bypasses it through the bypass. In this way, an unnecessary cooling of the charge air is avoided in the charge air cooler and the charge air is withdrawn as little heat, as is possible.

According to a preferred embodiment, the limit is in a range between 250 and 300 ° C. Conventional catalytic converters of the prior art begin to operate at an operating temperature of about 270 degrees to 280 ° C. The heat-optimized control of the coolant circuit and the low-pressure exhaust gas recirculation is only terminated when an exhaust gas temperature of at least 250-300 ° C is reached.

According to a preferred embodiment, the internal combustion engine arrangement has a high-pressure exhaust gas recirculation line from the exhaust gas Outlet of the internal combustion engine and before the catalytic converter to the charge air side behind the compressor turbine on. According to the present method, during the cold running phase, the engine assembly is provided in such an arrangement that the high pressure exhaust gas recirculation control valve that opens the high pressure exhaust gas recirculation line closes and regulates to close during the cold running phase. Since the high-pressure exhaust gas recirculation line branches off in the direction of flow upstream of the exhaust gas catalyst in the internal combustion engine heated exhaust gas, the branched exhaust gas would initially not directly the heating of the catalytic converter to good. Therefore, when a high-pressure exhaust gas recirculation line is provided, during the cold-running phase, the high-pressure exhaust gas recirculation control valve must be closed.

Both the drive turbine and the turbine-type compressor of the charge air supercharger can each be assigned a bypass with a bypass valve, which essentially serve to limit the pressure. The drive turbine removes heat from the exhaust gas. The compressor initially has the same temperature as the charged charge air during cold start. During operation, the compressor turbine heats the charge air through the compression.

If the engine assembly has an exhaust manifold with a cooling device connected to its own cooling circuit or to the engine coolant circuit and a coolant supply control device of the coolant device, the control of the exhaust manifold cooling device during the cold running phase is not made unnecessary to the exhaust gas much heat to escape.

Basically, it applies to all heat exchangers of the engine assembly that they are not in operation. Examples of further heat exchangers are engine oil heat exchangers or transmission oil heat exchangers which have an oil line, an exhaust line and / or a coolant line. All cooling functions of the combustion engine arrangement must therefore be switched off, so that all usable heat is supplied to the engine and the catalytic converter.

In the following an embodiment of the invention is explained in more detail with reference to the drawing:
The drawing shows a schematic representation of an internal combustion engine arrangement.

In the figure is schematically a complex internal combustion engine arrangement 50 shown. In the arrangement 50 All essential components are shown, which are around the internal combustion engine 1 around with the charge air, the exhaust gas, several coolant circuits as well as two oil circuits.

Fresh charge air is through an air filter 5 sucked in and then passes an air mass meter 4 , The sucked charge air then enters a charge air supercharger 64 one in which they are in a turbine-like compressor 3 possibly compressed. The charge air then flows to a cooled with a coolant intercooler 38 which has a bypass 52 with a bypass valve 35 assigned. From there, the charge air flows through the gas control valve 42 in the form of a throttle to a mixer 43 in which the charge air is possibly mixed with recirculated exhaust gas from the high-pressure exhaust gas recirculation.

From the mixer 43 the charge air reaches via the intake manifold 34 and through a charge air inlet 94 in the internal combustion engine 1 , There, the charge air is enriched with fuel, and ignited the mixture obtained in this way. The resulting exhaust gas flows from an exhaust outlet 95 from the internal combustion engine 1 out.

That from the outlet 95 Exhaust gas is emitted in a water-cooled exhaust manifold 11 cooled and flows with its main stream on to a drive turbine 12 the charge air charger 64 , The drive turbine 12 drives the compressor turbine 3 at. The drive turbine 12 is a bypass 68 with a bypass valve 60 and the compressor turbine 3 is a bypass 66 with a bypass valve 61 assigned. From the charge air charger 64 Coming the exhaust gas passes an exhaust gas temperature sensor 9 , which is just before a catalytic converter 8th is arranged. From the catalytic converter 8th the exhaust gas flows through a first gas control valve 7 and a second gas control valve 6 in an exhaust, not shown. The stream of gas shown here is the main gas stream from the inlet of the air filter to the outlet into a muffler or exhaust.

This main gas flow has three branches, namely a low-pressure exhaust gas recirculation, a high-pressure exhaust gas recirculation and a branch for the supply of two three-way heat exchangers 21 . 26 ,

The low pressure exhaust gas recirculation is from a pipe 54 formed in the exhaust branch between the catalytic converter 8th and the first gas control valve 7 branches off and in its course an exhaust gas recirculation control valve 2 having. This exhaust gas recirculation line 54 discharges into the charge air line in front of the charge air supercharger 64 ,

Furthermore, a high-pressure exhaust gas recirculation is provided, wherein the high-pressure exhaust gas recirculation line 56 on the exhaust side between the water cooled exhaust manifold 11 and the charge air charger 64 branches. After the branch is in Course of the line 56 an exhaust gas mass and temperature sensor 13 arranged, which detects the exhaust gas mass and the exhaust gas temperature at this point. The exhaust stream then flows through a high pressure exhaust gas recirculation cooler 15 which is a gas control valve 16 upstream. Furthermore, it is parallel to the radiator 15 a bypass 15 ' provided by the exhaust gas bypassing the radiator 15 can flow when the relevant gas control valves 16 . 17 . 18 are closed or opened accordingly. In the high pressure exhaust gas recirculation cooler 15 can that be through the pipe 56 recirculated exhaust gas can be cooled if necessary to the thermal load of the internal combustion engine 1 and reduce the lying in the main exhaust stream units, and to reduce nitrogen oxides in the exhaust gas.

In the flow direction behind the radiator 15 is in the course of the line 56 a high pressure exhaust gas recirculation cooler sensor 19 arranged, with the help of the cooling capacity of the exhaust gas recirculation cooler 15 can be regulated. The exhaust gas flows from there into the mixer 43 in which the charge air with the exhaust gas from the high-pressure exhaust gas recirculation line 56 is mixed.

Another exhaust pipe 70 branches in the exhaust main flow between the first gas control valve 7 and the second gas control valve 6 to the two three-way heat exchangers 21 . 26 from. In the first three-way heat exchanger 21 can be heated with the help of the warm exhaust gas, a target medium and cooled with the help of the also supplied coolant the same target medium as needed. Both three-way heat exchangers therefore have not only their exhaust gas inlets but also inlets for the coolant. The first three-way heat exchanger is via a lubricant supply line 80 and derivation 81 connected to corresponding lubricant connections of the internal combustion engine 1 , In the first three-way heat exchanger 21 Thus, the internal combustion engine lubricant is cooled by the cooling water or heated by the exhaust gas when needed.

The second three-way heat exchanger 26 is via a lubricant supply line 83 and a lubricant discharge 84 with a gear 62 connected. Through the lubricant supply and drain 83 . 84 and the associated three-way heat exchanger 26 If necessary, the gear lubricant can be cooled or heated. This is particularly useful in automatic transmissions, in which the amount of lubricant can often be 10 liters and more, and of which at low lubricant temperature, a high portion of the drive power is absorbed, and too high slip occurs too high a temperature.

In the present case, two coolant circuits are provided, namely a first high-temperature coolant circuit 58 and a second low temperature circuit 59 , The low temperature circuit 59 serves to cool the intercooler 38 and has for this purpose a low-temperature radiator 45 and a low temperature coolant pump 41 on.

The high-temperature coolant circuit 58 has a cooler 46 , a coolant pump 33 and a variety of lines and valves. The main coolant flow is from the radiator 46 coming from a coolant line 88 to the coolant pump 33 when operating the coolant in the internal combustion engine 1 inflated. That from the internal combustion engine 1 escaping coolant flows through a coolant control valve 32 back to the radiator 46 ,

Between the coolant outlet of the internal combustion engine 1 and the coolant control valve 32 branch several coolant lines to the exhaust manifold radiator 11 , the high pressure exhaust gas recirculation cooler 15 , to the first three-way heat exchanger 21 and to the second three-way heat exchanger 26 from there each to the radiator cooler 46 flow back.

The coolant flows are controlled by control valves 10 . 14 . 20 . 90 controlled or regulated as needed.

In the course of the lubricant lines 80 . 81 . 83 . 84 are each in front of and behind the three-way heat exchangers 21 . 26 temperature sensors 22 . 24 . 27 . 28 arranged, with the help of the relevant lubricant temperature can be controlled.

The two coolers 45 . 46 The two coolant circuits are cooled by outside incoming cooling air 64 cooled by a closable cooling air blind 44 passes through.

The cold running phase of the internal combustion engine is as follows:
The cold run phase is defined by the exhaust gas temperature from the exhaust gas temperature sensor 9 in front of the catalytic converter 8th is measured. The cold running phase lasts as long as that of the exhaust gas temperature sensor 9 measured temperature is below 280 ° C. During the cold-running phase, the coolant circuit is activated by actuation of the coolant circulation control element, in this case by the coolant pump 33 is formed, closed. In this way it is ensured that no appreciable flow of coolant flows through the coolant lines. In particular, the internal combustion engine 1 not significantly active cooled. Also all other accessories supplied with coolant ancillaries, so the exhaust manifold 11 , the high pressure exhaust gas recirculation cooler 15 and the two three-way heat exchangers 21 . 26 are not actively cooled, which is done by closing the relevant control valves 10 . 14 . 20 . 90 is realized.

Further, the coolant control valve 32 closed, the return flow of the coolant to the cooling water cooler 46 controls. Also this control valve 32 represents an alternative or supplementary refrigerant circuit control element in the sense of the claims. As a second important measure during the cold running phase, the low-pressure exhaust gas recirculation by opening the exhaust gas recirculation control valve 2 open. This can be achieved by the low-pressure exhaust gas recirculation line 54 the exhaust from a branch behind the catalytic converter 8th and pressure increased by the subsequent throttling gas control valve 7 be returned and fed into the charge air line 92 between the compressor turbine 3 and the intercooler 38 , In this way, the residual heat, which from the exhaust catalyst 8th exiting exhaust still has, to a large extent the charge air fed back so that this heat is not lost. As a result, a total of faster heating of the in the catalytic converter 8th incoming exhaust gas reaches, so that the exhaust catalyst 8th faster reaches its operating temperature of about 270 to 280 ° C, starting from the catalytic converter a large part of the internal combustion engine 1 helps to convert exiting harmful emissions into harmless emissions.

During the cold running phase, the high pressure exhaust gas recirculation remains closed, which in particular by closing all the control valves 16 . 17 . 18 in the pipes 56 the high-pressure exhaust gas recirculation is realized.

Claims (2)

Method for controlling a motor vehicle internal combustion engine arrangement ( 50 ) with an internal combustion engine ( 1 ) with a charge air inlet ( 94 ) and an exhaust outlet ( 95 ), a charge air charger ( 64 ) with a drive turbine ( 12 ) and a compressor ( 3 ), a coolant circuit ( 58 ) with a control ( 32 . 33 ) to the coolant flow control for the required cooling of the internal combustion engine ( 1 ), one with the outlet ( 95 ) associated exhaust gas catalyst ( 8th ), an exhaust gas temperature sensor ( 9 ) in front of the catalytic converter ( 8th ), a low-pressure exhaust gas recirculation line ( 54 ) from the exhaust side behind the catalytic converter ( 8th ) to the charge air side in front of the compressor turbine ( 3 ), an exhaust gas recirculation control valve ( 2 ) for controlling the exhaust gas flow through the exhaust gas recirculation line ( 54 ), and a charge air cooler ( 38 ) between the compressor turbine ( 3 ) and the inlet ( 94 ), wherein the intercooler ( 38 ) a bypass ( 52 ) with a control valve ( 35 ) for bypassing the intercooler as required ( 38 ), with the method steps: determination of the exhaust gas temperature with the exhaust gas temperature sensor ( 9 ), if the exhaust gas temperature in the cold-running phase is below a constant limit: closing the coolant circuit ( 58 ) by actuation of the coolant circulation control element ( 32 . 33 ), Opening the low pressure exhaust gas recirculation line ( 54 ) by opening the exhaust gas recirculation control valve ( 2 ), and opening the bypass control valve ( 35 ) during the cold running phase. Method for controlling a motor vehicle internal combustion engine arrangement ( 50 ) according to claim 1, characterized in that the cold-running phase at an exhaust gas temperature above a limit of 200 ° C, and preferably at a threshold between 250 and 300 ° C.

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