Method for operating a combustion machine, combustion machine and motor vehicle

Abstract

A thermal overload of an internal combustion engine and of cooling system of a combustion machine due to a raising of the temperature of the exhaust gas flowing through an exhaust gas line of the combustion machine, which is provided as a measure to desulfurize a NO.sub.x storage catalytic converter and/or to regenerate a particulate filter, is prevented in that before and/or during this measure, the cooling output for the coolant flowing through the cooling system is systematically increased in order to achieve a lowering of the coolant temperature to a value range that lies below what would normallythat is to say, without the simultaneous desulfurization of the NO.sub.x storage catalytic converter and/or without the regeneration of the particulate filterhave been provided for the operation of the combustion machine in a corresponding operating state of the internal combustion engine.

Claims

1. A method of operating a combustion machine comprising an internal combustion engine, a fresh gas line, an exhaust gas line and a cooling system comprising an ambient heat exchanger as well as a cooling channel of the internal combustion engine, whereby a NO.sub.x storage catalytic converter and/or a particulate filter is integrated into the exhaust gas line, comprising: as a measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, temporarily setting a temperature of the exhaust gas flowing through the exhaust gas line to at least a minimum value required for the measure, lowering a temperature of a coolant flowing through the cooling system before and/or during the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, wherein, during the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, a portion of the exhaust gas flowing through the exhaust gas line is conveyed through an exhaust gas recirculation line which comprises an EGR cooler integrated into the cooling system, wherein the temperature of the coolant is lowered only when the portion of the exhaust gas that is being conveyed through the exhaust gas recirculation line is in a volumetric flow fraction that is above a defined limit value, wherein the defined limit value is larger than zero.

2. The method according to claim 1, wherein the lowering of the coolant temperature is brought to an end before, directly at the time of, or shortly after, the termination of the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter.

3. The method according to claim 1, wherein the lowering of the temperature of the coolant is effectuated by increasing the fraction of coolant that is being conveyed through the ambient heat exchanger in comparison to the fraction that is being conveyed through a bypass that bypasses the ambient heat exchanger, and/or; by increasing the throughput rate of a fan associated with the ambient heat exchanger.

4. A combustion machine comprising: an internal combustion engine, a fresh gas line, an exhaust gas line, and a cooling system, the cooling system comprising an ambient heat exchanger, and a cooling channel of the internal combustion engine, wherein a NO storage catalytic converter and/or a particulate filter is integrated into the exhaust gas line, and a regulation unit configured in such a way that it can carry out the method according to claim 1.

5. The combustion machine according to claim 4, further comprising an exhaust gas recirculation line which comprises an EGR cooler integrated into the cooling system.

6. A motor vehicle having the combustion machine according to claim 4.

7. The method according to claim 1, wherein the defined limit value of the volumetric flow fraction is at least 50% of the exhaust gas flowing through the exhaust gas line.

8. A method of operating a combustion machine comprising an internal combustion engine, a fresh gas line, an exhaust gas line and a cooling system comprising an ambient heat exchanger as well as a cooling channel of the internal combustion engine, whereby a NO storage catalytic converter and/or a particulate filter is integrated into the exhaust gas line, comprising: as a measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, temporarily setting a temperature of the exhaust gas flowing through the exhaust gas line to at least a minimum value required for the measure, lowering a temperature of a coolant flowing through the cooling system before and/or during the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, wherein, during the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, a portion of the exhaust gas flowing through the exhaust gas line is conveyed through an exhaust gas recirculation line which comprises an EGR cooler integrated into the cooling system, wherein an extent to which the temperature of the coolant is lowered is varied as a function of a volumetric flow fraction of the exhaust gas that is being conveyed through the exhaust gas recirculation line.

9. The method according to claim 8, wherein the lowering of the coolant temperature is brought to an end before, directly at the time of, or shortly after, the termination of the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter.

10. The method according to claim 8, wherein the lowering of the temperature of the coolant is effectuated by increasing the fraction of coolant that is being conveyed through the ambient heat exchanger in comparison to the fraction that is being conveyed through a bypass that bypasses the ambient heat exchanger, and/or; by increasing the throughput rate of a fan associated with the ambient heat exchanger.

11. A combustion machine comprising: an internal combustion engine, a fresh gas line, an exhaust gas line, and a cooling system, the cooling system comprising an ambient heat exchanger, and a cooling channel of the internal combustion engine, wherein a NO.sub.x storage catalytic converter and/or a particulate filter is integrated into the exhaust gas line, and a regulation unit configured in such a way that it can carry out the method according to claim 8.

12. The combustion machine according to claim 11, further comprising an exhaust gas recirculation line which comprises an EGR cooler integrated into the cooling system.

13. A motor vehicle having the combustion machine according to claim 11.

14. A method of operating a combustion machine comprising an internal combustion engine, a fresh gas line, an exhaust gas line and a cooling system comprising an ambient heat exchanger as well as a cooling channel of the internal combustion engine, whereby a NO.sub.x storage catalytic converter and/or a particulate filter is integrated into the exhaust gas line, comprising: as a measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, temporarily setting a temperature of the exhaust gas flowing through the exhaust gas line to at least a minimum value required for the measure, lowering a temperature of a coolant flowing through the cooling system before and/or during the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter, wherein, for a given operating state of the internal combustion engine, a temperature value range of the coolant during the measure to desulfurize the NO.sub.x storage catalytic converter and/or to regenerate the particulate filter is lower than a temperature value range of the coolant not during the measure to desulfurize the NOx storage catalytic converter and/or to regenerate the particulate filter.

15. The method of operating a combustion machine according to claim 14, wherein the lowering of the temperature of the coolant is achieved by increasing a cooling output for the coolant flowing through the cooling system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in greater detail below making reference to an embodiment shown in the drawings. The drawings show the following:

(2) FIG. 1: a motor vehicle according to the invention; and

(3) FIG. 2: a combustion machine according to the invention, depicted schematically in a diagram.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a motor vehicle according to the invention, having a combustion machine 10 according to the invention.

(5) Such a combustion machine 10 according to the invention as shown in FIG. 2 can have an internal combustion engine 12 that can especially be configured as a reciprocating-piston internal combustion engine that works in accordance with the Diesel principle and that comprises a cylinder housing 14 with cylinders 16 configured therein as well as a cylinder head 18. Moreover, the combustion machine 10 as shown in FIG. 2 also has a main cooling system and a secondary cooling system.

(6) The main cooling system serves to (directly) cool the internal combustion engine 12, the motor oil that lubricates the internal combustion engine 12, the transmission oil of a (manual or automatic) transmission (not shown here) belonging to the internal combustion engine 12, an exhaust gas turbocharger 20, especially a bearing block or an exhaust gas turbine 96 of the exhaust gas turbocharger 20, as well as exhaust gas that is recirculated either via an exhaust gas recirculation line 22 of a low-pressure exhaust gas recirculation system or via an exhaust gas recirculation line 24 of a high-pressure exhaust gas recirculation system. For this purpose, the main cooling system has cooling channels 26, 28 of the cylinder housing 14 and of the cylinder head 18, a motor oil cooler 30, a transmission oil cooler 32, a cooler for the exhaust gas turbocharger 20, specifically, a cooling channel of the exhaust gas turbine 96 of the exhaust gas turbocharger (ETC cooler) 34, a cooler for (or a cooling channel in) an exhaust gas recirculation valve 36 as well as an EGR cooler in the exhaust gas recirculation line 22 of the low-pressure exhaust gas recirculation system (LP-EGR cooler 38) and another one in the exhaust gas recirculation line 24 of the high-pressure exhaust gas recirculation system (HP-EGR cooler 40). Moreover, the main cooling system comprises a main cooler 42, three coolant pumps 46, 48, 50 as well as a heating heat exchanger 44. The main cooler 42 serves to re-cool this flowing coolant by transferring thermal energy to the ambient air that likewise flows through the main cooler 42. The heating heat exchanger 44, in contrast, serves to warm, and thus control the temperature of, the ambient air, whenever necessary, specifically, the air that is provided to regulate the interior temperature of a motor vehicle comprising the combustion machine 10 (as shown, for example, in FIG. 1). Of the three coolant pumps 46, 48, 50 of the main cooling system, one is provided as the main coolant pump 46 and it can be powered either by an electric motor or, preferably, directly or indirectly by a drive shaft (especially a crankshaft; not shown here) of the internal combustion engine 12, that is to say, it can be powered mechanically. Also if the main coolant pump 46 is mechanically powered, it can be controlled or regulated in terms of its specific throughput rate (that is to say, in each case relating to the drive rotational speed), and it can also be switched off (that is to say, without generating any appreciable throughput in spite of the rotary drive). In this context, it can be provided that, when the main coolant pump 46 is in the switched-off state, the flow of medium through it can be either prevented or permitted. The two other (additional) coolant pumps 48, 50 of the main cooling system, in contrast, are powered by electric motors.

(7) The various heat exchanger components as well as the coolant pumps 46, 48, 50 are integrated into different cooling circuits of the main cooling system. A main cooling circuit comprises the cooling channels 26, 28 of the cylinder head 18 and of the cylinder housing 14, the main cooler 42, a bypass 52 that bypasses the main cooler 42, as well as the main coolant pump 46. The cooling channels 26, 28 of the cylinder head 18 and of the cylinder housing 14 here are integrated into the main cooling circuit in parallel. A first control unit 54 in the form of a (self-regulating) thermostat valve (opening temperature: 105 C.) as well as a second control unit 56 in the form of a control valve that can be actuated by a regulation unit 58 can influence whether and to what extent coolant flows through the cooling channel 26 of the cylinder housing 14 when coolant is flowing through the cooling channel 28 of the cylinder head 18. A third control unit 60, which is likewise configured in the form of a control valve that can be actuated by a regulation unit 58, can influence whether and, if so, to what extent coolant that is flowing, among other things, in the main cooling circuit, is being conveyed through the main cooler 42 or through the bypass 52 associated with it. The first, second and third control units 54, 56, 60 as well as a fourth control unit 62 each constitute part of a coolant distribution module 108.

(8) Moreover, a first secondary cooling circuit is provided, which comprises a secondary segment that branches off directly downstream (relative to a specified direction of flow of the coolant in the main cooling circuit) from an outlet of the cooling channel 28 of the cylinder head 18 from a section of the main cooling circuit and it opens up again upstream from the third control unit 60 into a section of the main cooling circuit. The section of the main cooling circuit between the branch-off and the opening of this secondary segment of the first secondary cooling circuit can be closed by means of the fourth control unit 62, which is configured in the form of a control valve that can be actuated by means of the regulation unit 58, so that, whenever needed, any flow through this section of the main cooling circuit (and consequently the entire main cooling circuit) can be suppressed by means of this fourth control unit 62. A first additional coolant pump 48 of the additional coolant pumps 48, 50 is integrated into the first secondary cooling circuit. Downstream from this first additional coolant pump 48, the first secondary cooling circuit divides into two parallel lines, whereby the LP-EGR cooler 38 and, downstream from there, the heating heat exchanger 44 are integrated into the first of these lines while the ETC cooler 34 is integrated into the second line. The two lines of the secondary segment of the first secondary cooling circuit are reunited once again before they open up into the main cooling circuit.

(9) The main cooling system also comprises a second secondary cooling circuit. A secondary segment of the second secondary cooling circuit into which the cooler (cooling channel) for the exhaust gas recirculation valve 36 is integrated branches off in the vicinity of the outlet of the cooling channel 28 of the cylinder head 18, whereby a throttle 64 that serves to limit the amount of coolant flowing through the second secondary cooling circuit is integrated into this branch-off. The secondary segment of the second secondary cooling circuit opens up upstream from the main coolant pump 46 (as well as downstream from the main cooler 42 and upstream from the opening of the bypass 52 associated with the main cooler 46) into a section of the main cooling circuit.

(10) A third secondary cooling circuit comprises a secondary segment that branches off in the vicinity of the branch-off between the cooling channels 26, 28 of the cylinder head 18 and of the cylinder housing 14 and upstream from the main coolant pump 46 (as well as downstream from the main cooler 42 and the opening of the bypass 52 associated with the main cooler 42) again into a section of the main cooling circuit. The motor oil cooler 30 is integrated into this secondary segment.

(11) A fourth secondary cooling circuit comprises a secondary segment that branches off from the secondary segment of the third cooling circuit and into which a fifth control unit 66 in the form of a thermostat valve (opening temperature: e.g. 75 C.) is integrated as well as the transmission oil cooler 32. The secondary segment of the fourth secondary cooling circuit likewise opens up upstream from the main coolant pump 46 (as well as downstream from the main cooler 42 and upstream from the opening of the bypass 52 associated with the main cooler 42) again into a section of the main cooling circuit.

(12) A fifth secondary cooling circuit of the main cooling system comprises a secondary segment that branches off upstream from the first additional coolant pump 48 out of the secondary segment of the first secondary cooling circuit and into which the second additional coolant pump 50 as well as the HP-EGR cooler 40 are integrated downstream therefrom. A sixth control unit 68 in the form of a thermostat valve (switchover temperature, for instance, between 70 C. and 80 C.) is arranged downstream from the HP-EGR cooler 40. As a function of the temperature, this sixth control unit can distribute coolant that has flowed through the HP-EGR cooler 40 into either an end section of the secondary segment of the EGR cooling circuit or into a short-circuit line 70 that, upstream from the second additional coolant pump 50, opens up into an initial section of the secondary segment of the fifth secondary cooling circuit.

(13) The secondary cooling system serves to cool the fresh gas (charge air) that has been charged by means of a compressor 98 of the turbocharger 20 and that is fed to the internal combustion engine 12 via a fresh gas line 74 of the combustion machine 10 and also serves to cool a metering valve 72 by means of which a reducing agent can be introduced into exhaust gas that is flowing through an exhaust gas line 76 of the combustion machine 10, so that a selective catalytic reduction can reduce the pollutants, especially nitrogen oxides, contained in the exhaust gas. The intercooler 78 provided to cool the charge air on the one hand and the cooling channel provided to cool the metering valve 72 on the other hand are integrated into parallel lines of a cooling circuit of the secondary cooling system. Moreover, a coolant pump 80, which can be powered by an electric motor, as well as an additional cooler 82, which serves to re-cool the coolant flowing through the cooling circuit of the secondary cooling system by transferring thermal energy to the ambient air that is flowing through the additional cooler 82, are integrated into this cooling circuit (in the section that is not divided into two lines). The additional cooler 82 can be bypassed by means of a bypass 84, whereby a seventh control unit 86, which can be configured either as a thermostat valve or as a control valve that can be actuated by means of the control unit, can change the distribution of the coolant flowing through the cooling circuit of the secondary cooling system either into the additional cooler 82 or into the bypass 82 associated with it.

(14) The temperature of the coolant in the main cooling system during regular operation of the combustion machine 10 can be considerably higher in the main cooling system than in the secondary cooling system, at least in certain sections, so that the former can also be referred to as a high-temperature cooling system and the latter as a low-temperature cooling system.

(15) The cooling system also comprises a compensation tank 88 that is partially filled with coolant and partially with air. The compensation tank 88 is fluidically connected to the main cooling circuit of the main cooling system as well as to the cooling circuit of the secondary cooling system by means of a connecting line 90 that starts at a (lower) section of the compensation tank 88 which holds the coolant. Moreover, vent lines 92, which are fitted with one or more non-return valves 94 or a throttle 64, connect the HP-EGR cooler 40, the main cooler 42, the cooling channel 28 of the cylinder head 18 as well as the intercooler 78 to the (upper) section of the compensation tank 88 which holds the air.

(16) The main cooling system of the cooling system as shown in FIG. 1 can be operated, for example, in the following manner.

(17) During a warm-up phase, especially after a cold start of the internal combustion engine, when the coolant in the entire cooling system consequently has a relatively low temperature, it can be provided that the main coolant pump 46 is not operated, as a result of which or whereby it is also switched off and therefore no coolant can flow through it. At the same time, during this warm-up phase, the first additional coolant pump 48 (with a variable throughput rate) can be operated, as a result of which coolant (in conjunction with an interrupting setting of the fourth control unit 62) is conveyed in the first secondary cooling circuit. In this process, the coolant flows through the ETL cooler 34, the LP-EGR cooler 38 and the heating heat exchanger 44 which are all integrated into the secondary segment of the first secondary cooling circuit. Moreover, this coolant flows (completely) through the bypass 52 that likewise constitutes a section of the first secondary cooling circuit to the main water cooler 42 (due to an appropriate setting of the third control unit 60), also through the secondary segment of the third secondary cooling circuit (in a flow direction counter to that during regular operation; see the arrow tip without shading), whereby, optionally through the integration of an appropriate bypass (not shown here) into this secondary segment, coolant can be prevented from flowing through the motor oil cooler 30 as well as through the cooling channel 28 of the cylinder head 18. As a rule, appropriate settings of the first control unit 54 and of the second control unit 56 prevent coolant from also flowing through the cooling channel 26 of the cylinder housing 14, except for a relatively small pilot flow that serves to control the temperature of the first control unit 54, which is configured as a thermostat valve. In exceptional situations, especially in cases of the operation of the internal combustion engine 12 at high loads, particularly at a full load, in spite of the warm-up phase, however, it can also be provided for the second control unit 56 to be changed to a opening setting by means of the regulation unit 58 in order to ensure that the coolant also flows through the cooling channel 26 of the cylinder housing 14. As a function of the temperature of the coolant flowing through the first secondary cooling circuit, the fifth control unit 66 is used during the warm-up phase to prevent coolant from flowing through the secondary segment of the fourth secondary cooling circuit and consequently through the transmission oil cooler 32, at least initially.

(18) Since the coolant flows through the cooling channel 28 of the cylinder head 18, whereby said cooling channel 28 likewise constitutes a section of the first secondary cooling circuit, the coolant also flows through the second secondary cooling circuit into which the cooler (cooling channel) for the exhaust gas recirculation valve 36 is integrated.

(19) During the warm-up phase, it is also provided for the sixth control unit 68 to be set in such a way that, by means of the second additional coolant pump 50, which is operated for this purpose, coolant is conveyed in the short-circuit system which, for the rest, only comprises the HP-EGR cooler 40 and the short-circuit line 70.

(20) During regular operation of the combustion machine 10, the main coolant pump 46 (with a variable specific throughput rate) is operated and coolant is conveyed through all of the cooling circuits of the main cooling system, at least at times. In this process, the two additional coolant pumps 48, 50 of the main cooling system can, if needed, likewise be operated in order to assist the main coolant pump 46. When it comes to the second additional coolant pump 50, however, this only applies after the sixth control unit 68 has been switched over in such a way that coolant is allowed to flow in the fifth cooling circuit. Before this is provided for, the second additional coolant pump 50 is operated in order to convey coolant (also still during regular operation of the combustion machine 10) inside the short-circuit system.

(21) During regular operation of the combustion machine 10, coolant flows continuously through the main cooling circuit, a process in which coolant is always flowing through the cooling channel 28 of the cylinder head 18, in contrast to which the flow of coolant also through the cooling channel 26 of the cylinder housing 14 (provided that the second control unit 56 has not been changed to the opening setting in exceptional situations) is only released by means of the first control unit 54 once the temperature of the coolant in the cooling channel 26 of the cylinder housing 14 has reached a temperature of approximately 105 C.

(22) During regular operation of the combustion machine 10, the third control unit 60 is also used to effectuate a variable distribution of the coolant flowing through the main cooling circuit into either the main cooler 42 or the associated bypass 52, as a result of which a target temperature of approximately 90 C. can be set for the coolant that is leaving the cooling channel 28 of the cylinder head 18.

(23) Moreover, during regular operation of the combustion machine 10, coolant flows continuously through the first secondary cooling circuit into which the ETC cooler 34, the LP-EGR cooler 38 and the heating heat exchanger 44 are integrated. Here, owing to an adapted operation of the first additional coolant pump 48, the volumetric flow of the coolant through the secondary line of the first secondary cooling circuit can also be adapted so as to also be superimposed onto the throughput of the main coolant pump 46. This can be especially relevant in order to achieve a sufficient heat transfer in the heating heat exchanger 44 and thus sufficient heating functionality for heating the interior of a motor vehicle comprising the combustion machine 10.

(24) Coolant also flows continuously through the second secondary cooling circuit into which the cooler (cooling channel) for the exhaust gas recirculation valve 36 is integrated and through the third secondary cooling circuit into which the motor oil cooler 30 is integrated.

(25) When it comes to the fourth secondary cooling circuit into which the transmission oil cooler 32 is integrated, in contrast, this only applies if the temperature of the coolant present at the fifth control unit 66, which is likewise integrated into the secondary segment of the fourth secondary cooling circuit, amounts to at least 75 C., so that the fifth control unit 66 (which can be varied depending on the temperature) then allows the coolant to also flow through the transmission oil cooler 32. Here, too, in the closing setting, a relatively small pilot flow can be provided, serving to control the temperature of the fifth control unit 66, which is configured as a thermostat valve.

(26) Coolant only flows through the fifth secondary cooling circuit as well if the temperature of the coolant previously being conveyed in the short-circuit system has reached at least the applicable limit temperature, which can be between 70 C. and 80 C. Once the sixth control unit 68 has released at least a partial flow of coolant through the fifth cooling circuit 68, the HP-EGR cooler 49 is continuously charged with coolant whose temperature corresponds essentially to the one that had been reached in the outlet of the cooling channel 28 of the cylinder head 18 and that can especially be approximately 90 C.

(27) Regarding the cooling channel 26 of the cylinder housing 14, the secondary segment of the fourth secondary cooling circuit and thus the transmission oil cooler 32 as well as the secondary segment of the EGR cooling circuit, it applies that the appertaining flow of coolant can be interrupted once again by means of the appropriate control units 54, 66, 68 if the value has fallen below the applicable limit temperature or opening temperature.

(28) The flow of coolant through the cooling circuit of the secondary cooling system is effectuated as needed by means of the coolant pump 80 integrated therein and independently of the control or regulation means of the main cooling system.

(29) The cooling system of the combustion machine 10 also allows an after-heating functionality for the internal combustion engine 12 that is no longer being operated, and this is achieved in that coolant is conveyed by means of the first additional coolant pump 48 in the first main cooler 42 that then optionally also comprises the main cooler 42, as a result of which thermal energy that is especially still present in the main cooler 42, in the cylinder head 18 and in the LP-EGR cooler 38 can be utilized in the heating heat exchanger 44 in order to control the temperature of the interior of a motor vehicle comprising the combustion machine 10.

(30) Moreover, the cooling system also allows an after-cooling functionality for the internal combustion engine 12 that is no longer being operated and that was previously under a high thermal load, and this is achieved in that coolant is conveyed by means of the first additional cooling pump 48 in the first secondary cooling circuit that also comprises the main cooler 42, as a result of which the thermally critical components of the cooling system, especially the cylinder head 18 and the exhaust gas turbocharger 20, can be after-cooled by means of the ETC cooler 34 and the LP-EGR cooler 38.

(31) This after-cooling functionality can especially be relevant in conjunction with an automatic stop function of the internal combustion engine 12. Thanks to the automatic stop function, the internal combustion engine 12 is automatically switched off during operation of the combustion machine 10 or of the motor vehicle comprising the combustion machine 10 whenever the engine is not supposed to deliver any drive output. In order to prevent a local thermal overload of the main cooling system and of the components integrated therein, especially the internal combustion engine 12, the LP-EGR cooler 38 and the ETC cooler 34, which can have been subject to high thermal loads to a great extent during the preceding operation of the internal combustion engine 12, while the stop function is activated and consequently while the internal combustion engine 12 is not operating, it is provided for coolant to be conveyed in the first secondary cooling circuit by operating the first additional coolant pump 48. Depending on the settings of the control units 66, 68 and the switching setting that allow coolant to flow through the main coolant pump 46, it is also possible here for coolant to flow through the transmission oil cooler 32, through the motor oil cooler 30, through the main coolant pump 46 as well as through the cooling channels 26 of the cylinder housing 14. At times, the direction of flow (see the directional arrows without shading in FIG. 2) is opposite from the direction of the flow (see the directional arrows with shading in FIG. 2) during operation of the internal combustion engine 12. During the after-cooling, it can be provided for all of the coolant flowing in the first secondary cooling circuit to be conveyed via the main cooler 42. However, the third control unit 60 can also convey a variable fraction (all the way up to the total amount) of this coolant via the bypass 52. In particular, this makes it possible to prevent an excessive cooling of the coolant if the internal combustion engine 12 remains non-operational for a prolonged period of time because the stop function has been activated.

(32) As an alternative or in addition, it is provided for the coolant to also be conveyed in the cooling circuit of the secondary cooling system by means of the coolant pump 80 when the internal combustion engine 12 is not being operated due to an activated stop function, thereby avoiding excessive heating of the intercooler 78. When the internal combustion engine 12 is put back in operation following a manual or automatic deactivation of the automatic stop function, the intercooler 78 can thus once again immediately deliver sufficient output for cooling the charge air that is to be fed to the internal combustion engine 12, so that the charge air is fed to the combustion chambers of the internal combustion engine 12 within the temperature range prescribed for this purpose. The seventh control unit 86 can vary the fraction of coolant flowing in the cooling circuit of the secondary cooling system via the additional cooler 82 or via the associated bypass 84, on the one hand, in order to attain a sufficient cooling output especially for the intercooler 78 and, on the other hand, in order to prevent excessive cooling of the coolant.

(33) Furthermore, it is provided for the combustion machine 10 that, in the case of certain instationary operating states of the internal combustion engine 12, specifically in those cases when the load demand that is made of the operation of the internal combustion engine 12 is increased by at least 20% relative to the full load, the temperature of the coolant flowing in the cooling circuit of the secondary cooling system is lowered, for example, by approximately 20 C. in comparison to that during the preceding stationary operation in order for such an implemented increase in the cooling output of the intercooler 78 to achieve an improved filling of the combustion chambers of the internal combustion engine 12 and consequently an improved build-up of the charge pressure, as a result of which the dynamic operating behavior of the internal combustion engine 12 is improved.

(34) In order to lower the temperature of the coolant flowing in the cooling circuit of the secondary cooling system, to the extent possible, a greater fraction of coolant arriving at the seventh control unit 86 is conveyed via the additional cooler 82. It can also be provided for a fan 106 associated with the additional cooler 82 to be put into operation or for its drive output to be increased, as a result of which the cooling output of the additional cooler 82 can be increased.

(35) A NO.sub.x storage catalytic converter 100 as well as a particulate filter 102 are also integrated into the exhaust gas line 76 of the combustion machine 10. The NO.sub.x storage catalytic converter 100 serves to store nitrogen oxides contained in the exhaust gas when these cannot be reduced to a sufficient extent by the reducing agent that is supplied in combination with a reduction catalytic converter or SCR catalytic converter (not shown here). This can be the case, for instance, after a cold start of the combustion machine 10 or in the case of a relatively prolonged operation of the internal combustion engine 12 at low loads and rotational speeds, as a result of which the SCR catalytic converter does not yet have or no longer has an operating temperature required for a sufficient reduction. The particulate filter 102, in contrast, serves to filter particles out of the exhaust gas.

(36) For the NO.sub.x storage catalytic converter 100 as well as for the particulate filter 102, it applies that, once they have reached a defined load limit, they have to be regenerated in order to retain their functionality. In the case of the NO.sub.x storage catalytic converter 100, there is the additional aspect that it has to be desulfurized at regular intervals since the sulfur normally present in fuel reacts with the storage material of the NO.sub.x storage catalytic converter 100, as a result of which the amount of storage material available for storing the nitrogen oxides diminishes. For purposes of the desulfurization, the NO.sub.x storage catalytic converter 100 has to be heated up, among other things by systematic measures, to a temperature that lies between 600 C. and 650 C. Comparable temperatures are also needed to regenerate the particulate filter 102.

(37) The NO.sub.x storage catalytic converter 100 and the particulate filter 102 are heated up to the temperatures needed for a desulfurization or regeneration by appropriately raising the temperature of the exhaust gas, for which purpose various fundamentally known, especially engine-internal, measures are provided.

(38) While the temperature of the exhaust gas is being raised accordingly in order to bring about the desulfurization of the NO.sub.x storage catalytic converter 100 and the regeneration of the particulate filter 102, a thermal output which has been increased to the commensurate extent is introduced into the internal combustion engine 12 (especially directly on the basis of the engine-internal measures that bring about the rise in the temperature of the exhaust gas) as well as into the entire main cooling system or at least into one or more sections thereof, namely, via the internal combustion engine 12 on the one hand and via the two EGR coolers 38, 40 on the other hand.

(39) In order to prevent a local overload of the cooling system, especially in the area of the internal combustion engine 12 (in this context, it is particularly important to prevent the coolant from boiling), it is provided for the temperature of the coolantspecifically of the coolant that is to be subsequently conveyed via the main cooling pump 46 into the internal combustion engine 12to be lowered shortly before as well as at least at times during the rise in the temperature of the exhaust gas prescribed for the desulfurization of the NO.sub.x storage catalytic converter 100 and/or for the regeneration of the particulate filter 102, in order to compensate for the increased thermal load of the internal combustion engine 12 as well as of the main cooling system due to the rise in the temperature of the exhaust gas. In this process, the temperature of the coolant is measured by means of a temperature sensor 104 that is integrated into the outlet of the cooling channel 28 of the cylinder head 18.

(40) In order to lower the temperature of the coolant flowing into the internal combustion engine 12, to the extent possible, a greater fraction of coolant arriving at the third control unit 60 is conveyed via the main cooler 42. It can also be provided for a fan 106 associated with the main cooler 42 to be put into operation or for its drive output to be increased, as a result of which the cooling output of the main cooler 42 can be increased.

(41) Shortly before, at the same time as, or shortly after, the raising of the temperature of the exhaust gas prescribed as the measure for the desulfurization of the NO.sub.x storage catalytic converter 100 and/or for the regeneration of the particulate filter 102 has been ended, the lowering of the temperature of the coolant is also ended or reversed in order to prevent the coolant from excessively cooling the components that are integrated into the main cooling system.

LIST OF REFERENCE NUMERALS

(42) 10 combustion machine 12 internal combustion engine 14 cylinder housing 16 cylinder 18 cylinder head 20 exhaust gas turbocharger 22 exhaust gas recirculation line of the low-pressure exhaust gas recirculation system 24 exhaust gas recirculation line of the high-pressure exhaust gas recirculation system 26 cooling channel of the cylinder housing 28 cooling channel of the cylinder head 30 motor oil cooler 32 transmission oil cooler 34 ETC cooler 36 exhaust gas recirculation valve 38 LP-EGR cooler 40 HP-EGR cooler 42 ambient heat exchanger/main cooler 44 heating heat exchanger 46 main coolant pump 48 first additional coolant pump 50 second additional coolant pump 52 bypass to the main cooler 54 first control unit 56 second control unit 58 regulation unit 60 third control unit 62 fourth control unit 64 throttle 66 fifth control unit 68 sixth control unit 70 short-circuit line 72 metering valve 74 fresh gas line 76 exhaust gas line 78 intercooler 80 coolant pump of the secondary cooling system 82 ambient heat exchanger/additional cooler 84 bypass to the additional cooler 86 seventh control unit 88 compensation tank 90 connecting line 92 vent line 94 non-return valve 96 exhaust gas turbine of the exhaust gas turbocharger 98 compressor of the exhaust gas turbocharger 100 NO.sub.x storage catalytic converter 102 particulate filter 104 temperature sensor 106 fan 108 coolant distribution module