DE102008015591A1 - Internal-combustion engine i.e. diesel engine, has coolant valve for loading air cooler with coolant from low temperature coolant circuit and engine coolant circuit downstream engine block and upstream to engine cooler - Google Patents

Abstract

The engine has a charge air cooler (58) arranged in an intake system (10). An exhaust manifold (12) and exhaust gas turbochargers (16, 22) are provided in the intake system. An exhaust gas recirculation pipeline (34) discharges exhaust gas into the intake system upstream to the air cooler. A coolant valve loads the air cooler with coolant from a low temperature coolant circuit and an engine coolant circuit downstream an engine block (14) and upstream to an engine cooler of the engine coolant circuit. An independent claim is also included for a method for operating an internal-combustion engine.

Description

The The invention relates to an internal combustion engine having an intake tract, an exhaust tract, an exhaust gas turbocharger, one arranged in the intake tract and from a flowing in a coolant circuit Coolant cooled intercooler, an opening into the intake exhaust gas recirculation line, a Low-temperature coolant circuit and an engine coolant circuit, which flows through an engine block of the internal combustion engine and an engine radiator, wherein the exhaust gas recirculation line flows upstream of the intercooler into the intake tract, according to the preamble of claim 1. The The invention further relates to a method for operating an internal combustion engine with an exhaust tract and an intake tract and an exhaust gas turbocharger, wherein combustion air from a compressor arranged in the intake tract the exhaust gas turbocharger to charge air compressed and over a is cooled in the intake tract intercooler, wherein exhaust gas from the exhaust tract of the internal combustion engine, the intake tract the internal combustion engine supplied upstream of the intercooler and from this recirculated exhaust gas and charge air a suction gas is mixed, wherein the intercooler means a flowing in a cooling circuit cooling medium is cooled, wherein coolant in a low-temperature coolant circuit, which flows over a low temperature radiator, and an engine coolant circuit, which over flows through an engine block and a radiator, is circulated, according to the preamble of claim 9.

From the DE 197 16 566 C1 an internal combustion engine with exhaust gas recirculation is known, wherein recirculated exhaust gas is added upstream of a charge air cooler of the charge air, so that the intercooler cools a mixture of charge air and recirculated exhaust gas.

From the EP 621 921 B1 a method for operating a marine diesel engine is known, wherein charge air is supplied to working cylinder of the internal combustion engine via a charge air cooler cooled with seawater. Here, a portion of the charge air is guided past the intercooler, wherein the amount of charge air carried over is determined such that downstream of the charge air cooler for the entire charge air quantity results in a charge air temperature which is above the dew point and at the same time a maximum temperature for the engine is not exceeds.

From the DE 10 2006 033 314 A1 a heat exchanger system for an internal combustion engine is known, wherein two water-cooled heat exchangers are arranged in an exhaust gas recirculation line. A first of these heat exchanger is flowed through by cooling water from a low-temperature cooling circuit and a second of these heat exchanger of cooling water from an engine cooling circuit. In this case, the flow rate of cooling water through the first heat exchanger is controlled by a temperature controller such that the coolant temperature at the first heat exchanger is not below the dew point of the recirculated exhaust gas or not below 50 ° C.

Of the Invention is the object of an internal combustion engine of o. g. Type and a method of o. G. Sort of cost, Boost pressure buildup and emissions.

These The object is achieved by an internal combustion engine the o. g. Art having the features characterized in claim 1 and by a method of o. g. Type with the marked in claim 9 Characteristics solved. Advantageous embodiments of the invention are described in the further claims.

To it is in an internal combustion engine o. g. Art provided according to the invention, that at least one coolant valve arranged such and is formed, that this coolant valve the intercooler with coolant from the low-temperature coolant circuit and / or from the engine coolant circuit downstream of the Engine block of the internal combustion engine and upstream of the engine radiator and / or with respective partial flows of coolant the low temperature coolant circuit and the engine coolant circuit applied.

This has the advantage that, when the internal combustion engine is at operating temperature, a very low temperature of the charge-air EGR mixture is achieved with a corresponding increase in power and low NO _x raw emissions.

Conveniently, is the at least one coolant valve upstream of the intercooler arranged.

In In a preferred embodiment this is at least one Coolant valve designed as a 2/2-way valve.

The Coolant in the low-temperature coolant circuit and / or in the engine coolant circuit is, for example Water.

Conveniently, connects the at least one coolant valve in dependence from a temperature of a mixture of charge air and recirculated Exhaust gas upstream and / or downstream of the intercooler and / or depending on a temperature of the intercooler flowing through the cooling medium upstream and / or downstream of the intercooler, this optionally with the low-temperature coolant circuit and / or at least partially with the engine coolant circuit.

In An advantageous development of the invention is at least one second coolant valve downstream of the intercooler arranged, which is preferably designed as a 2/2-way valve.

In a particularly preferred embodiment is a the Intercooler bridging bypass channel arranged with bypass valve such that this bypass channel at opened bypass flap the charge air, the recirculated Exhaust gas or the mixture of charge air and recirculated Exhaust gas at least partially past the intercooler passes.

• – der Ladeluftkühler mit dem Strom des Kühlmittels im Niedertemperatur-Kühlmittelkreislauf beaufschlagt wird, falls die momentane Temperatur des Ansauggases t_lnkk gleich oder größer der minimalen Solltemperatur des Ansauggases t_lnkk-min ist, und
• – der Ladeluftkühler wenigstens teilweise mit dem Strom des Kühlmittels im Motor-Kühlmittelkreislauf stromab des Motorblocks und stromauf des Motorkühlers beaufschlagt wird und/oder die Ladeluft, das rückgeführte Abgas und/oder das Ansauggas an dem Ladeluftkühler vorbei geleitet wird, falls die momentane Temperatur des Ansauggases t_lnkk für eine vorbestimmte erste Zeitpanne unterhalb der minimalen Solltemperatur des Ansauggases t_lnkk-min liegt.

Furthermore, it is provided according to the invention in a method of the aforementioned type that depending on an ambient pressure, an intake temperature, a boost pressure, a mass flow of the charge air upstream of the charge air cooler m _lvkk , a temperature of the charge air upstream of the intercooler t _lvkk , a modeled exhaust gas recirculation rate, a measured exhaust gas recirculation rate and / or a temperature of the exhaust gas upstream of the turbine of the turbocharger t _abgmm a minimum target temperature of the intake gas t _lnkk-min min is determined so that this is above the dew point of the intake gas, and a current temperature of the intake gas t _lnkk with this minimum Target temperature of the intake gas t is _{compared lnkk-min} , wherein

• - The charge air cooler is supplied with the flow of the coolant in the low-temperature coolant circuit, if the current temperature of the intake gas t _{lnkk is} equal to or greater than the minimum target temperature of the intake gas t _lnkk-min , and
• - The intercooler is at least partially acted upon by the flow of coolant in the engine coolant circuit downstream of the engine block and upstream of the engine radiator and / or the charge air, the recirculated exhaust gas and / or the intake gas is passed to the intercooler, if the current temperature of the intake gas t _{lnkk is} below the minimum target temperature of the intake gas t _lnkk-min for a predetermined first time period.

This has the advantage that the formation of liquid condensate in the intercooler and the subsequent suction section due to cooling below the dew point in a low-temperature and short-distance operation of the internal combustion engine is effectively avoided. This prevents ice formation even at low ambient temperatures and thus partial or complete obstruction of the suction path between the point of admixture of recirculated exhaust gas into the intake manifold and working cylinder intake valves. For example, the instantaneous temperature of the intake gas t _{lnkk is} a measured or modeled temperature.

The recirculated exhaust gas is expediently upstream of a turbine arranged in the exhaust tract of the exhaust gas turbocharger branched off from the exhaust system and downstream of the compressor of the exhaust gas turbocharger fed to the intake.

In a preferred embodiment, the minimum target temperature of the intake gas t _{lnkk-min is} determined such that it is 1 ° K to 5 ° K above the dew point.

Conveniently, the predetermined first time interval is dependent on the ambient temperature, ambient humidity, an engine operating point, a coolant temperature in the engine coolant circuit, a coolant temperature in the low-temperature coolant circuit and / or the number of cold reboots with a coolant temperature in the engine coolant circuit when switching off the internal combustion engine determined below a predetermined temperature threshold.

If the first measure for increasing the temperature in the charge air cooler is insufficient, a mass flow rate of the coolant flow through the charge air cooler is reduced if the instantaneous temperature of the intake gas t _{lnkk falls} below the minimum setpoint temperature of the intake _gas for a predetermined second time span which is greater than the first time span Intake gas t _lnkk-min is.

If the above measure is insufficient to increase the temperature in the charge air cooler, a flow of refrigerant through the charge air cooler will be cut off if the instantaneous temperature of the intake gas t _lnkk is below the minimum target intake gas temperature t for a predetermined third time period greater than the second time period _lnkk-min is.

If the aforementioned measure for increasing the temperature in the intercooler is insufficient, the exhaust gas recirculation is reduced, in particular switched off, if the instantaneous temperature of the intake gas t _Inkk for a predetermined fourth time period, which is greater than the third period, below the minimum target temperature of the intake gas t _lnkk-min is.

Conveniently, the instantaneous temperature of the intake gas t _{Inkk is compared} with a predetermined maximum temperature of the intake gas t _Inkk-max , wherein the exhaust gas recirculation is reduced, in particular switched off, the boost pressure is limited and / or an injected amount of fuel is limited, if the current temperature of the intake gas t _{lnkk is} equal to or greater than the predetermined maximum temperature of the intake gas t _lnkk-max .

The The invention will be explained in more detail below with reference to the drawing explained. This shows in

1 a first preferred embodiment of an internal combustion engine according to the invention in a schematic representation,

2 the first preferred embodiment of the internal combustion engine according to the invention 1 with a cooling circuit in a schematic representation,

3 a detailed representation of the cooling circuit of the internal combustion engine according to 2 in a first operating state in a schematic representation,

4 a detailed representation of the cooling circuit of the internal combustion engine according to 2 in a second operating state in a schematic representation,

5 an alternative embodiment of a guide of an intake gas in an intake tract of the internal combustion engine according to the invention in a schematic representation,

6 a further alternative embodiment of a guide of a suction gas in an intake tract of the internal combustion engine according to the invention in a schematic representation and

7 a schematic flow diagram for a preferred embodiment of the method according to the invention.

In the 1 illustrated, preferred embodiment of an internal combustion engine according to the invention comprises an intake 10 , an exhaust tract 12 , an engine block 14 , a first exhaust gas turbocharger 16 a low-pressure stage with one in the intake tract 12 arranged first compressor 18 and one in the exhaust tract 14 arranged first turbine 20 , a second exhaust gas turbocharger 22 a high-pressure stage with one in the intake tract 12 arranged second compressor 24 and one in the exhaust tract 14 arranged second turbine 26 , one in the intake tract 10 arranged suction tube 28 , one in the exhaust tract 10 arranged exhaust manifold 30 and one in the intake tract 10 arranged intercooler 32 , The intercooler 32 is either an air-air or an air-water cooler.

Upstream of the second turbine 26 branches off the exhaust tract 12 an exhaust gas recirculation line (EGR line) 34 from which downstream of the second compressor 24 in the intake tract 10 opens and an electrically or pneumatically actuated EGR valve 36 for adjusting an exhaust gas recirculation rate (EGR rate).

A compressor bypass line 38 bridges the second compressor 24 and has a compressor bypass valve 40 on, which works passively mechanically or can be actively controlled in multiple stages and preferably steplessly the compressor bypass line 38 opens or closes.

A first turbine bypass line 42 bridges the first turbine 20 and has an example active and / or pneumatically controllable turbine bypass valve (wastegate) 44 on. A second turbine bypass line 54 bridges the second turbine 26 and has a pneumatic exhaust flap 56 with warehouse confirmation on.

In the intake tract 10 flows downstream of the compressor 18 and 24 charge air 46 , In the EGR leadership 34 flows recirculated exhaust gas 48 , Downstream of the EGR line 34 in the intake tract 10 flows in the intake tract 10 a mixture of charge air 46 and recirculated exhaust gas 48 , which is hereinafter referred to as suction gas 50 referred to as. In the exhaust tract 12 flows exhaust 52 ,

Downstream of the EGR line 34 in the intake tract 10 and upstream of the suction pipe 28 is a combination cooler 58 for the intake gas 50 arranged. This combination cooler 58 is circulated by one in a cycle. Coolant flows through. For this purpose, the combination cooler 58 a lead 60 in which the coolant is the combi cooler 58 flows in, and a return 62 in which the coolant from the combi cooler 58 flows out, up.

The following values are measured or modeled: A mass flow m _lvkk and a temperature t _{lvkk of} the charge air 46 upstream of the EGR line 34 in the intake tract. A mass flow m _egrvkk and a temperature t _{egrvkk of} the recirculated exhaust gas 48 in the EGR leadership 34 downstream of the EGR valve 36 , A mass flow m _kmvkk and a temperature t _kmvkk of the combi cooler 58 flowing through cooling fluid in the flow 60 of the combination cooler 58 , A mass flow m _kmnkk and a temperature t _kmnkk of the Kombikühler 58 flowing through cooling fluid in the return 62 of the combination cooler 58 , A mass flow m _lnkk and a temperature t _{lnkk of} the intake gas (mixture of charge air 46 and recirculated exhaust 48 ) downstream of the combination cooler 58 and upstream of the suction pipe 28 , A temperature t _{abgnm of} the exhaust gas 52 in the exhaust manifold 30 downstream of the engine block 14 ,

2 additionally illustrates the cooling circuit of the internal combustion engine according to 1 , wherein functionally identical parts are provided with the same reference numerals, as in 1 so that their explanation to the above description of 1 is referenced. The internal combustion engine has a low-temperature coolant circuit 64 in which one Coolant via a low-temperature radiator 66 is circulated, and an engine coolant circuit 68 , in which a coolant via a radiator 70 and the engine block 14 is circulated. The engine cooler 70 is for the dissipation of thermal energy additionally with a radiator fan 72 fitted. The engine coolant circuit 68 has an engine coolant circuit bypass line 74 for bridging the engine cooler 70 on.

The low-temperature coolant circuit 64 is via an inlet valve 76 with the lead 60 of the combination cooler 58 connected and the return 62 of the combination cooler 58 is either directly or via a return valve 78 also in such a way with the low-temperature coolant circuit 64 connected to that, the combination cooler 58 in the cycle of the low-temperature coolant circuit 64 is looped. This in the low-temperature coolant circuit 64 circulated coolant thus flows through the combination cooler 58 , Furthermore, the inlet valve connects 76 the lead 60 of the combination cooler 58 optionally with the engine coolant circuit 68 over a first branch line 80 which coolant from the engine coolant circuit 68 after flowing through the engine block 14 , So from the engine block heated coolant, the combination cooler 58 supplies. A second branch line 82 connects the return 62 of the combination cooler 58 if necessary via the return valve 78 with the engine coolant circuit 68 so that the coolant from the engine coolant circuit 68 after flowing through the combi cooler 58 to the engine cooler 70 is directed.

The inlet valve 76 is designed such that this optional coolant only from the low-temperature coolant circuit 64 or only from the engine coolant circuit 68 or both coolant from the low-temperature coolant circuit 64 and the engine coolant circuit 68 in a certain proportion to the flow 60 of the combination cooler 58 supplies.

3 and 4 show an exemplary embodiment of the arrangement of combination cooler 58 , Inlet valve 76 and return valve 78 , wherein additionally a coolant bypass line 84 is provided. Here are the inlet valve 76 and the return valve 78 each designed as a 2-2-way valve. In the in 3 illustrated position of the valves 76 . 78 are the feed 60 and the return 62 of the combination cooler 58 exclusively with the low-temperature coolant circuit 64 connected, leaving only coolant from the low-temperature coolant circuit 64 through the combi cooler 58 flows. In the in 4 illustrated position of the valves 76 . 78 are the feed 60 and the return 62 of the combination cooler 58 exclusively with the engine coolant circuit 68 leading branch line 80 and 82 connected so that only from the engine block preheated coolant from the engine coolant circuit 68 through the combi cooler 58 flows.

5 illustrates an advantageous development of the intake system 10 , Here is also a combined radiator bypass line 86 with a combination radiator bypass flap 88 provided, which the combination cooler 58 bridged and near the confluence of the EGR pipeline 34 upstream of the combi cooler 58 from the intake tract 10 branches off and downstream of the combi cooler 58 and upstream of the suction pipe 28 back to the intake system 10 opens. This is controlled by the combination radiator bypass flap 88 the suction gas 50 partly on the combi cooler 58 Passed over to prevent a cooling effect of the Kombikühlers 58 the suction gas 50 cooled to a temperature below the dew point.

6 illustrates an alternative embodiment for the combined radiator bypass line 68 with combination radiator bypass flap 88 , In this case, the combined radiator bypass line branches 68 from the EGR leadership 34 upstream of their confluence with the intake tract 10 as well as downstream of the EGR valve 36 from and flows downstream of the Kombikühlers 58 and upstream of the suction pipe 28 back to the intake system 10 one. In this way, only part of the recirculated exhaust gas 48 on the combi cooler 58 Passed over to prevent a cooling effect of the Kombikühlers 58 the suction gas 50 cooled to a temperature below the dew point.

7 schematically illustrates a flow chart diagram of an exemplary embodiment of a method according to the invention. First, a predetermined value for a maximum target temperature t _lnkk-max and a predetermined value for a minimum target temperature t _{Inkk-min of} the intake gas (mixture of charge air 46 and recirculated exhaust 48 ) downstream of the combination cooler 58 and upstream of the suction pipe 28 certainly. This determination of the values for the maximum setpoint temperature t _Inkk-max and / or the minimum setpoint temperature t _{Inkk-min of} the intake gas, for example, depending on an ambient pressure, an intake temperature, a boost pressure, the mass flow of the charge air upstream of the intercooler m _lvkk , the temperature the charge air upstream of the charge air cooler t _lvkk , a modeled exhaust gas recirculation rate, a measured exhaust gas recirculation rate and / or the temperature of the exhaust gas upstream of the turbine of the exhaust gas turbocharger t _abgnm . in one step 100 " _Lnkk <t _lnkk-min ", it is checked whether the temperature of the intake gas 50 after the combi cooler 58 is less than the predetermined minimum target temperature t _lnkk-min . If not, it will have a first branch 102 to step 104 " _Lnkk > t _lnkk-max " jumped. In step 104 it checks if the temperature of the intake gas 50 after the comm bikühler 58 is greater than the predetermined maximum target temperature t _lnkk-max . If not, it will be over a branch 106 to step 108 Jumped "package of measures". In this step 108 becomes the combination cooler 58 flowing portion of the coolant from the engine coolant circuit 68 reduced, the coolant mass flow through the combination cooler 58 raised, a fan request to the radiator fan 72 is reduced, a value for the maximum permissible EGR rate is raised, a value for the maximum permissible boost pressure is raised, and an existing power limit is canceled. After completing step 108 is about branch 110 again to step 100 jumped.

Is in step 100 the result of the test t _lnkk <t _lnkk-min "yes", is about branch 112 to step 114 "Proportion of engine coolant with flow through Specify combination radiator" and the one by the combination radiator 58 flowing proportion of the coolant from the engine coolant circuit 86 raised. After that is about branch 116 to step 118 "Proportion of engine coolant = 100%?" Jumped and checked whether the proportion of the through the combination cooler 58 flowing coolant from the engine coolant circuit 86 is already 100%, ie from already exclusively coolant from the engine coolant circuit 86 over the combi cooler 58 flows. If not, will be over branch 120 back to step 100 jumped. Does the test "Engine coolant ratio = 100%?" In step 118 however, "yes", then becomes over branch 122 to step 124 "T _mot > t _lnkk-min ?", Where t _{mot is} a temperature of the coolant in the engine coolant circuit 86 is, and checked whether the engine temperature, which is represented by t _mot , greater than the predetermined minimum target temperature t _{lnkk-min of} the intake gas downstream of the combined radiator 58 , If this is the case then it will be over branch 126 to step 128 "Specify coolant mass flow throughflow Combi cooler; Max. permissible EGR rate indicated ", in which the coolant mass flow through the combination cooler 58 is raised and a value for the maximum allowable EGR rate is increased. Subsequently, by step 128 over branch 130 to step 100 jumped back. If, on the other hand, in the test "t _mot > t _lnkk-min ?" In step 124 the result is "no" is about branch 132 to step 134 "Coolant mass flow throughflow Combi cooler" jumped and the mass flow of the coolant through the combination cooler 58 reduced. Connecting will be via branch 136 to step 138 "Coolant mass flow = 0?" Jumped and checked whether the coolant mass flow through the combination cooler 58 is zero. If this is not the case then it will be about branch 140 back to step 100 jumped. Is the result of the test "Coolant mass flow = 0?" In step 138 "Yes", then will about branch 142 to step 144 "Max. perm. EGR rate decrease "and a value for the maximum permissible EGR rate is reduced. Subsequently, over branch 146 back to step 100 jumped.

Is in step 104 the result from the test "t _lnkk > t _lnkk-max ""yes", then becomes over branch 148 to step 150 "Proportion of engine coolant at flow rate Combi cooler" jumped and the proportion of the through the combination cooler 58 flowing coolant from the engine coolant circuit 68 reduced. Subsequently, over branch 152 to step 154 "Proportion of engine coolant = 0?" Jumped and checked whether the through the combination cooler 58 flowing proportion of coolant from the engine coolant circuit 68 is zero. If not, will be over branch 156 back to step 100 jumped. On the other hand, is the result of the test "engine coolant percentage = 0?" In step 154 "Yes", then will about branch 158 to step 160 "Fan request raised" and a request to the radiator fan 71 elevated. Subsequently, over branch 162 to step 164 "Fan = 100%?" Jumped and checked, whether the radiator fan 72 already running at 100%. If not, will be over branch 166 back to step 100 jumped. On the other hand, is the result of the test "Fan = 100%?" In step 164 "Yes", then will about branch 168 to step 170 "Max. perm. decrease EGR rate "and a value for the maximum permissible EGR rate is reduced. Subsequently, over branch 172 to step 174 "EGR rate = 0?" Jumped and checked whether the EGR rate is already zero. If not, will be over branch 176 back to step 100 jumped. On the other hand, is the result from the check "EGR rate = 0?" In step 174 "Yes", then will about branch 178 to step 180 "Max. perm. boost pressure "jumped and a value for the maximum. permissible charge pressure reduced. Connecting will be via branch 182 to step 184 "Boost pressure ≤ ambient pressure?" Jumped and checked whether the instantaneous boost pressure is less than or equal to the ambient pressure. If this is not the case then it will be about branch 186 back to step 100 jumped. On the other hand, is the result of the test "boost pressure ≤ ambient pressure?" In step 184 "Yes", then will about branch 188 to step 190 "Power limit" jumped and set a power limit for the output from the engine power to further increase the temperature of the intake gas 50 downstream of the combi cooler 58 to avoid. Subsequently, over branch 192 back to step 100 jumped.

In the exemplary embodiment of an internal combustion engine according to the invention, the recirculated exhaust gas is 48 in the field of admixture with the charge air 46 uncooled. However, it is also possible in the EGR line 34 to provide an additional EGR cooler.

The maximum cooling capacity of the combi cooler 58 is 0.03 ... 0.4, better 0.1 ... 0.3, ideally 0.15 ... 0.25 kW per kW rated motor power to a gas mass flow of 300 kg / h, a gas inlet temperature of 250 ° C and a gas outlet temperature of 50 ° C.

Preferably, the combination cooler is designed as an air-water cooler, ie the Ansauggasstrom 50 transfers its heat to a coolant circuit 64 in turn, its heat through another air-water heat exchanger 66 dissipates to the environment. This coolant circuit is connected to the engine cooling circuit 68 For example, connected in the region of a surge tank, but preferably the flowing media or coolant, as in 2 represented, at least largely decoupled from each other. The advantage of this procedure is a temperature of the intake gas that is significantly reduced when the engine is warm and ambient temperatures above 0 ° C 50 with resulting increase in output and lower NO _x raw emissions, especially in diesel engines.

The return of exhaust gas 48 through the low temperature cooler 58 However, increases the risk of cooling below the dew point in the low-temperature and short-distance operation of the internal combustion engine, ie it forms liquid condensate in the radiator 58 and the subsequent intake manifold 28 , For this reason, a monitoring of condensate formation is provided according to the invention, in particular so that at low ambient temperatures no extensive ice formation and thus a partial or complete blocking of the suction between EGR Zumischstelle and intake valves takes place. For this purpose, depending on ambient pressure, intake temperature, boost pressure, m _lvkk , t _lvkk , modeled or measured exhaust gas recirculation rate and t _abgnm, a minimum setpoint temperature of the intake gas t _{lnkk-min is} determined. This minimum setpoint temperature is advantageously at least slightly (1 ° K to 5 ° K) above the dew point.

If the actual measured or modeled exhaust gas temperature t _{lnkk is} below the minimum setpoint temperature t _lnkk-min for an applicable period of time (step 100 ), it is first tried, the coolant temperature in the flow of the combi cooler 58 t _kmvkk raise by the combi cooler 58 to a greater extent by the engine block 14 returning coolant instead of coolant from the low-temperature circuit 64 is flowed through (step 114 ). This is preferably done via a continuously or 2 or multi-stage switchable valve 76 in the lead 60 dis Combi cooler 58 ,

Optional is also in the return 62 of the combination cooler 58 a corresponding valve 78 arranged. In the worst case, ie short-distance operation with a cold engine and low outside temperatures, is thus the combination cooler 58 complete with from the engine block 14 partially heated coolant from the engine coolant circuit 68 , such as water, flows through.

Of the The above-mentioned period becomes dependent, for example the ambient temperature and humidity, the engine operating point, the coolant temperature and the number of cold reboots with a coolant temperature when parking below set a predeterminable temperature threshold.

If the minimum setpoint temperature t _{lnkk-min is} not reached even with this measure, the coolant flow through the combined radiator becomes 58 reduced (step 134 ), ideally until the complete suppression of the flow, provided that the temperature of the coolant from the engine coolant circuit 68 below the minimum target temperature of the intake gas 50 t _lnkk-min . Otherwise, a maximum flow of the combi cooler will continue 58 with the warm coolant from the engine coolant circuit 68 sought. If the engine is cold, this measure will not suffice to heat the intake gas 50 beyond the dew point, the exhaust gas recirculation is withdrawn (step 144 ), optimally completely switched off, to the combi cooler 58 a sufficient amount of heat over the heating time-consuming coolant from the engine coolant circuit 68 can be provided. Exceeds the temperature of the coolant from the engine coolant circuit 68 the default t _lnkk-min , so is both the coolant flow through the combination cooler 58 as well as the maximum allowable EGR rate again set high (step 128 ).

At the same time, monitoring also takes place for exceeding a maximum permissible setpoint temperature t _lnkk-max (step 104 ). If this temperature t _{lnkk-max is} exceeded, the low-temperature component in the combi cooler advance gradually increases 60 started up (step 150 ), the fan request is set high (step 160 ), the maximum EGR rate is lowered (step 170 ), as well as the boost pressure (step 180 ) and the injection quantity (step 190 ) limited. In the range t _Inkk between the minimum and maximum temperature is possible as low as possible charge air temperature or temperature of the intake gas 50 regulated. Therefore, a maximum flow of the combined radiator with coolant from the low-temperature coolant circuit 64 sought.

Alternatively or additionally, to solve the dew point problem, the bypass 86 around the combi cooler 57 provided around, which opens passively with appropriate differential pressure in front of and behind the combi cooler, for example via a spring-loaded flap or actively with an example electrically, pneumatically or hydraulically operated actuator continuously, multi-stage or as a pure on-off circuit is switched. This bypass 86 conducts entwe the suction gas 50 (EGR charge air mixture) around the combi cooler 58 or alternatively feeds only the recirculated exhaust gas 48 behind the combi cooler 58 one. In the actively switchable variant, the bypass is at coolant temperatures below a predeterminable temperature threshold (preferably 50 ° C) 86 actively open and at least a partial flow recirculated exhaust gas 46 (EGR) or intake gas 50 (Mixture EGR + charge air) around the combination cooler 58 guided around.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 19716566 C1 [0002]
• - EP 621921 B1 [0003]
• DE 102006033314 A1 [0004]

Claims (17)

Internal combustion engine with an intake tract ( 10 ), an exhaust tract ( 12 ), an exhaust gas turbocharger ( 16 . 22 ), one in the intake tract ( 10 ) and cooled by a coolant flowing in a coolant circuit intercooler ( 58 ), an exhaust gas recirculation line opening into the intake tract ( 34 ), a low-temperature coolant circuit ( 64 ) and an engine coolant circuit ( 68 ), which an engine block ( 14 ) flows through the internal combustion engine and a radiator ( 70 ), wherein the exhaust gas recirculation line ( 34 ) upstream of the intercooler ( 58 ) opens into the intake tract, characterized in that at least one coolant valve ( 76 ) is arranged and configured such that this coolant valve ( 76 ) the intercooler ( 58 ) with coolant from the low-temperature coolant circuit ( 64 ) and / or from the engine coolant circuit ( 68 ) downstream of the engine block ( 14 ) of the internal combustion engine and upstream of the engine radiator ( 70 ) and / or with respective partial flows of coolant from the low-temperature coolant circuit ( 64 ) and the engine coolant circuit ( 68 ). Internal combustion engine according to claim 1, characterized in that the at least one coolant valve ( 76 ) upstream of the intercooler ( 58 ) is arranged. Internal combustion engine according to at least one of the preceding claims, characterized in that the at least one coolant valve ( 76 ) is designed as a 2/2-way valve. Internal combustion engine according to at least one of the preceding claims, characterized in that the coolant in the low-temperature coolant circuit ( 64 ) and / or in the engine coolant circuit ( 68 ) Water is. Internal combustion engine according to at least one of the preceding claims, characterized in that the at least one coolant valve ( 76 ) as a function of a temperature (t _lvkk , t _lnkk ) of a mixture of charge air and recirculated exhaust gas ( 50 ) upstream and / or downstream of the intercooler ( 58 ) and / or as a function of a temperature (t _kmvkk , t _kmnkk ) of the intercooler ( 58 ) flowing through the cooling medium upstream and / or downstream of the intercooler ( 58 ) this optionally with the low-temperature coolant circuit ( 64 ) and / or at least partially with the engine coolant circuit ( 68 ) connects. Internal combustion engine according to at least one of the preceding claims, characterized in that at least one second coolant valve ( 78 ) downstream of the intercooler ( 58 ) is arranged. Internal combustion engine according to claim 6, characterized in that the second coolant valve ( 78 ) is designed as a 2/2-way valve. Internal combustion engine according to at least one of the preceding claims, characterized in that the charge air cooler ( 58 ) bridging bypass channel ( 86 ) with bypass flap ( 88 ) is arranged such that this bypass channel ( 86 ) with opened bypass flap ( 88 ) the charge air ( 46 ), the recirculated exhaust gas ( 48 ) or the mixture ( 50 ) from charge air and recirculated exhaust gas at least partially on the intercooler ( 58 ) passes by. Method for operating an internal combustion engine having an exhaust tract and an intake tract and an exhaust gas turbocharger, wherein combustion air is compressed by a compressor of the exhaust gas turbocharger arranged in the intake manifold to charge air and cooled via a charge air cooler arranged in the intake tract, wherein exhaust gas from the exhaust tract of the internal combustion engine upstream of the intake tract of the internal combustion engine the charge air cooler is supplied and from this recirculated exhaust gas and charge air, a suction gas is mixed, wherein the charge air cooler is cooled by means of a cooling medium flowing in a cooling medium, wherein coolant in a low-temperature coolant circuit, which flows through a low-temperature radiator, and an engine coolant circuit, which flows over an engine block and a radiator, is circulated, characterized in that in dependence on an ambient pressure, a suction temperature, a boost pressure, a mass flow of Charge air upstream of the intercooler m _lvkk , a temperature of the charge air upstream of the intercooler t _lvkk , a modeled exhaust gas recirculation rate, a measured exhaust gas recirculation rate and / or a temperature of the exhaust gas upstream of the turbine of the exhaust gas turbocharger t _abgnm a minimum target temperature of the intake gas t _{lnkk-min is} determined in that it is above the dew point of the intake gas, and a current temperature of the intake gas t _{lnkk is compared} with this minimum target temperature of the intake gas t _lnkk-min , wherein - the charge air cooler is charged with the flow of the coolant in the low-temperature coolant circuit, if the instantaneous Temperature of the intake gas t _{lnkk is} equal to or greater than the minimum target temperature of the intake gas t _lnkk-min , and - the intercooler is at least partially supplied with the flow of coolant in the engine coolant circuit downstream of the engine block and upstream of the engine radiator and / or the charge air, the recirculated exhaust gas and / or the intake gas is passed past the charge air cooler, if the instantaneous temperature of the intake gas t _lnkk for a predetermined first time period below the minima len target temperature of the intake gas t _lnkk-min is. A method according to claim 9, characterized in that the instantaneous temperature of the intake gas t _{lnkk is} a measured or modeled temperature. Method according to claim 9 or 10, characterized that the recirculated exhaust gas upstream of a in Exhaust tract arranged turbine of the exhaust gas turbocharger from the exhaust tract branched off and downstream of the compressor of the exhaust gas turbocharger Intake tract is supplied. Method according to at least one of claims 9 to 11, characterized in that the minimum setpoint temperature of the intake gas t _{lnkk-min is} determined such that it is 1 ° K to 5 ° K above the dew point. Method according to at least one of the claims 9 to 12, characterized in that the predetermined first time span depending on the ambient temperature, ambient humidity, a Engine operating point, a coolant temperature in the engine coolant circuit, a coolant temperature in the low-temperature coolant circuit and / or the number of cold reboots with a coolant temperature in the engine coolant circuit when switching off the internal combustion engine is determined below a predetermined temperature threshold. Method according to at least one of claims 9 to 13, characterized in that a mass flow rate of the refrigerant flow through the charge air cooler is reduced when the instantaneous temperature of the intake gas t _lnkk for a predetermined second time period, which is greater than the first time period, below the minimum target temperature of the intake gas t _lnkk-min . Method according to at least one of claims 9 to 14, characterized in that a coolant flow through the charge air cooler is interrupted when the instantaneous temperature of the intake gas t _Inkk for a predetermined third time period, which is greater than the second period, below the minimum target temperature of the intake gas t _lnkk-min . Method according to at least one of claims 9 to 15, characterized in that the exhaust gas recirculation is reduced, in particular switched off, when the instantaneous temperature of the intake gas t _Inkk for a predetermined fourth time period, which is greater than the third period, below the minimum target temperature of the intake gas t _lnkk-min . Method according to at least one of claims 9 to 16, characterized in that the instantaneous temperature of the intake gas t _{Inkk is compared} with a predetermined maximum temperature of the intake gas t _Inkk-max , whereby the exhaust gas recirculation is reduced, in particular switched off, the charge pressure is limited and / or an injected amount of fuel is limited when the instantaneous temperature of the intake gas t _{lnkk is} equal to or greater than the predetermined maximum temperature of the intake gas t _lnkk-max .