EP1055813B1 - Liquid cooled combustion engine with an exhaust gas recirculation system - Google Patents

Description

The invention relates to a preamble of claim 1 Liquid-cooled internal combustion engine with an exhaust gas recirculation system, the one with a coolant circulation controlled by a thermostat and a map-controlled Internal combustion engine connected on the inflow and outflow sides for cooling the recirculated into the machine intake air controlled by an EGR valve Exhaust gas comprises, the heat exchanger on the inflow or outflow side a throttle thermostat is controlled.

Such an exhaust gas heat exchanger for an exhaust gas recirculation system of a liquid-cooled Internal combustion engine is for example from DE 28 42 653 A1 known, which serves to cool the recirculated exhaust gas.

Furthermore, from DE 28 32 571 C is an exhaust gas coolant heat exchanger for one Internal combustion engine known in the warm-up phase of the internal combustion engine is used to heat the coolant so as to shorten the warm-up phase. Furthermore, the thermal energy supplied to the coolant in this operating phase can at low outside temperatures also for heating the passenger compartment as well as for windshield defrosting. A cooling the exhaust gas recirculated into the machine intake air is known in this Arrangement not provided.

Furthermore, from DE 25 53 174 A is a liquid-cooled internal combustion engine Known for driving vehicles that have an additional, flowed through by the exhaust gas Includes heat exchanger, both with the line circuit of the Machine cooling as well as in connection with a vehicle heating device stands. This allows the heater to start after the engine is started especially when the outside temperature is low and the engine is still cold become more effective relatively quickly, further via the connection with the machine cooling the warm-up phase of the internal combustion engine is also significantly shortened is. In this known device, too, is a cooling of the recirculated Exhaust gas not provided.

This also applies to the device known from DE 197 26 217 A1 one in the main flow of the exhaust gas of a liquid-cooled internal combustion engine arranged heat exchanger, which in particular in addition to shortening the Warm-up phase also serves an early effective vehicle heating.

Finally, a patent abstract shows and describes the Japanese patent application JP-A-10325368 an internal combustion engine with an exhaust gas recirculation system, the one that can be operated to control the use of exhaust gas heat EGR heat exchanger includes. In one operating mode, this heat exchanger is used the cooling of the exhaust gas supplied to the internal combustion engine and in the other mode of operation of the additional heating of the coolant Internal combustion engine.

As can be seen from the above-described prior art, with the transfer of exhaust heat to the cooling water is associated with a considerable construction effort. With the arrangement of an exhaust gas / water heat exchanger for cooling in the Machine intake air recirculated exhaust gas have functional disadvantages, which both the dimensioning and the arrangement of the EGR cooler within of the coolant circulation of the internal combustion engine. So within the EGR range of coolant throughput through the EGR cooler using a thermostat throttling, because if the EGR amount cools down too much, the advantages of NOx reduction can be partially compensated for by increases in HC emissions. Outside the EGR area with the exhaust gas recirculation line closed into the engine intake air must be caused by gas pulsation, especially in Full load range in the order of magnitude above the actual EGR heat quantity horizontal exhaust gas heat is dissipated to local boiling in the EGR cooler or Avoid heat exchangers. This requires a clearly above the requirements of the EGR cooling function goes beyond radiator dimensioning. Eventually the inlet of the EGR cooler or heat exchanger to the return of the water cooler the internal combustion engine connected to achieve a good cooling effect to be able to feed the EGR heat exchanger with the coldest possible water, this results when the thermostat of the internal combustion engine is closed, ie in an operating area where the internal combustion engine heats up rapidly The EGR heat exchanger is desired or additionally heating requirement is expected or cooler transfers its heat to the external coolant circulation.

The invention has for its object in a generic internal combustion engine using an EGR heat exchanger with little effort in use the heat present in the exhaust gas in a certain operating range. This object is achieved with patent claim 1.

The invention is particularly advantageous with a given EGR heat exchanger to realize in a simple manner for an advantageous rapid heating of the coolant the internal combustion engine after a cold start.

For simultaneous rapid heating of a vehicle heating and / or air conditioning system is proposed in an embodiment of the invention that the EGR heat exchanger upstream of the thermostat of the internal combustion engine with the coolant circulation is connected on the inlet side. This is advantageously the EGR heat exchanger in the warm-up phase of the internal combustion engine after a cold start yourself warming coolant supplied, which in turn heats up by the exhaust gas is. This arrangement allows this in a further advantageous manner by using the Exhaust gas heat cools the coolant more quickly into the internal or short circuit feed the internal combustion engine.

In a further embodiment of the invention it can also be provided that the EGR heat exchanger with exhaust gas heat recirculation controlled upstream of the Thermostats of the internal combustion engine with the coolant circulation and subsequent Exhaust gas cooling controlled on the inlet side downstream of a cooler Internal combustion engine can be connected to the coolant circulation. With this configuration can be used in an exhaust gas recirculation mode following the warm-up phase in partial load mode the EGR heat exchanger is charged with relatively cool coolant become.

With regard to the simple design, it is further proposed that the first Switch as exhaust switch and the second switch as coolant switch each as a control valve device are designed.

To the gas dynamics of the engine exhaust pipe through the bypass over the EGR heat exchanger with open exhaust switch is not to be significantly disturbed Another embodiment of the invention downstream of the exhaust switch in the connection arranged a throttle point with the engine exhaust pipe. This arrangement is in particular in the case of an exhaust gas turbocharger arranged in the engine exhaust line of importance, the throttled connection according to another proposal downstream of the turbine of the exhaust gas turbocharger into the engine exhaust pipe empties. For the advantageous rapid heating of the coolant circulation in the internal Circuit of the internal combustion engine is also proposed that the EGR heat exchanger on the outlet side with a return line with the coolant circulation of the Internal combustion engine controlled connectable vehicle heating and / or air conditioning in Connection is established. Since this heating return line is usually in the internal or Short circuit of the internal combustion engine opens upstream of a water pump thus including rapid and intensive heating of the internal combustion engine the controllable vehicle heating achieved.

Finally, for an internal combustion engine equipped with an exhaust gas turbocharger in the cold start area the effect of the exhaust gas turbocharger through the exhaust gas bypass path not adversely affected by the EGR heat exchanger, it is further proposed that the exhaust gas switch and the coolant switch as well the EGR valve on a charger provided in the engine exhaust pipe Machine start are controlled open delayed. This is the start of the Exhaust gas turbocharger ensured in all cases.

The invention is based on a coolant circuit shown schematically in the drawing a liquid-cooled internal combustion engine with an exhaust gas recirculation system described.

A liquid-cooled, map-controlled internal combustion engine 1 with an exhaust gas recirculation system 2 comprises one controlled by a thermostat 3 Coolant circulation connected to the EGR heat exchanger on the inlet and outlet side 5 for cooling the controlled in the machine intake air 7 via an EGR valve 6 recirculated exhaust gas, the EGR heat exchanger 5 on the discharge side via a Throttle thermostat 8 is controlled.

In order to use this EGR heat exchanger in this internal combustion engine 1 5 Using the heat contained in the exhaust gas in the cold start phase is invented proposed that the EGR heat exchanger 5 to use exhaust heat can be operated in a controlled manner, with an exhaust gas recirculation line 9 downstream of the EGR valve 6 a first switch 10 for connection to an engine exhaust pipe 11 and in the drain line 12 of the EGR heat exchanger 5 in one of them Throttle thermostats 8 bypass line 13 a second switch 14 are provided for the coolant circulation of the internal combustion engine 1, the EGR valve 6 and the two switches 10 and 14 for exhaust gas heat recirculation in the Coolant circulation 4 are map-controlled on a free, respective medium passage.

In order to rapidly warm up the internal combustion engine 1 during the warm-up phase To achieve circulating coolant, the EGR heat exchanger 5 is upstream of the Thermostats 3 of the internal combustion engine 1 with the coolant circulation 4 on the inlet side Connection with which coolant heated on the machine side to the EGR heat exchanger 5 is supplied, the temperature of which is further increased by using the exhaust gas heat is.

In order, if necessary, in the exhaust gas recirculation following the warm-up phase To achieve greater cooling of the recirculated exhaust gas in the partial load range, The internal combustion engine 1 can be further equipped so that with exhaust gas cooling the EGR heat exchanger 5 on the inlet side - not shown - is controlled downstream of one Radiator 15 of the internal combustion engine 1 can be connected to the coolant circulation 4.

To achieve a simple structure of the arrangement for exhaust gas heat use are the first switch 10 as an exhaust switch and the second switch 14 as a coolant switch each designed as a control flap device, each controlled by a map are operated.

In order not to significantly disturb the gas dynamics of the engine exhaust pipe 11 by the exhaust gas bypass flow through the EGR heat exchanger 5 with effective use of exhaust gas heat through the open-controlled exhaust switch 10 is the exhaust switch downstream 10 in a connection 16 with the engine exhaust pipe 11 a Throttle point 17 arranged.

In an internal combustion engine 1 designed in particular as a diesel engine Exhaust gas turbocharger 18 arranged in the engine exhaust line 11 is essential here that the throttled connection 16 downstream of the turbine of the exhaust gas turbocharger 18 opens into the machine exhaust pipe 11.

To achieve rapid heating of the coolant in the coolant circulation 4 is the EGR heat exchanger 5 on the discharge side with a return line 19 one with the Coolant circulation 4 of the internal combustion engine 1 controlled connectable vehicle and / or Air conditioning unit 20 in connection, with the heating return line 19 downstream of the thermostat 3 of the internal combustion engine 1 upstream of an inlet a water pump 21 opens.

To start the exhaust gas turbocharger 18 of the internal combustion engine 1 after a To ensure a cold start, the exhaust switch 10 and the coolant switch 14 and the EGR valve 6 is openly delayed open after an engine start.

Otherwise, the EGR heat exchanger 5 can be equipped with a separate, water-cooled one Charge air cooler (not shown) can be structurally combined.

Claims (8)

1. A liquid-cooled internal combustion engine comprising an exhaust-gas recirculation system,

   which comprises an AGR heat exchanger (5) connected on the inflow and the outflow side to a thermostat (3)-controlled coolant circuit (4) of an internal combustion engine (1) controlled by performance characteristics for cooling the exhaust gas recirculated under the control of an AGR valve (6) into the engine intake air (7), wherein

   the AGR heat exchanger (5) is controlled by a throttle thermostat (8) on the inflow or outflow side,

   characterised in that

   in order to use the heat of the exhaust gas, the AGR heat exchanger (5) can be controlled in operation in per se known manner, wherein

   a first switch (10) for connecting to an engine exhaust pipe (11) is provided in an exhaust gas recirculation line (9) downstream of the AGR valve (6) and

   a second switch (14) for circulating coolant (4) is provided in an inflow or outflow pipe (12) of the AGR heat exchanger (5) in a line (13) bypassing the throttle thermostat (8) therein, wherein

   when the heat of exhaust gas is recirculated into the coolant circuit (4), the AGR valve (6) and the two switches (10, 14) are controlled in accordance with performance characteristics to obtain a free passage of medium in each case.
2. An engine according to claim 1, characterised in that upstream of the thermostat (3) of the internal combustion engine (1), the AGR heat exchanger (5) is connected to the coolant circuit (4) on the inflow side.
3. An engine according to claim 1, characterised in that

   in the case where the heat of the exhaust gas is circulated, the AGR heat exchanger (5) can be connected to the coolant circuit (4) on the inlet side and under control upstream of the thermostat (3) of the engine (1), and

   in the case of exhaust gas cooling, the AGR heat exchanger can be connected to the coolant circuit (4) on the inlet side under control downstream of a radiator (15) of the engine (1).
4. An engine according to any of claims 1 to 3, characterised in that

   the first switch (10) is an exhaust-gas switch and

   the second switch (14) is a coolant switch, both being in the form of a control-shutter device.
5. An engine according to any of claims 1 to 4, characterised in that a restrictor (17) is disposed downstream of the exhaust-gas switch (10) in a connection (16) to an engine exhaust pipe (11).
6. An engine according to claim 5, characterised in that the connection (16) opens into the engine exhaust pipe (11) downstream of the turbine of an exhaust-gas turbocharger (18).
7. An engine according to any of claims 1 to 6, characterised in that on the outflow side the AGR heat exchanger (5) is connected to a return line (19) of a vehicle-heating and/or air-conditioning system (20) connectable in controlled manner to the coolant circuit (4) of the engine (1).
8. An engine according to any of claims 1 to 7, characterised in that when a turbocharger (18) is provided in the engine exhaust pipe (11), the exhaust-gas switch (10), the coolant switch (14) and the AGR valve (6) are controlled open and with time delay after an engine start.

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