Exhaust system

1. An exhaust system for an internal combustion engine, the exhaust system comprising:

at least one catalytic converter unit with at least one catalytic converter device through which internal combustion engine exhaust gas flows and the at least one catalytic converter unit comprising a heat exchanger volume; and

a fuel-operated heater with an operative connection between a heater exhaust of the fuel-operated heater and the heat exchanger volume, whereby heater exhaust gas leaving the heater flows through the heat exchanger volume, the at least one catalytic converter unit comprising an internal combustion engine exhaust gas flow space through which internal combustion engine exhaust gas flows, the at least one catalytic converter device being arranged in the internal combustion engine exhaust gas flow space, the heat exchanger volume comprising a heater exhaust gas flow space enclosing the internal combustion engine exhaust gas flow space at least in a length area of the internal combustion engine exhaust gas flow space containing the at least one catalytic converter device.

2. The exhaust system in accordance with claim 1 , wherein the heater exhaust gas flow space extends over an entire circumference of the internal combustion engine exhaust gas flow space.

3. The exhaust system in accordance with claim 1 , wherein at least one catalytic converter device of the at least one catalytic converter unit is an oxidation catalytic converter device.

4. The exhaust system in accordance with claim 1 , wherein the at least one catalytic converter unit comprises at least one particle filter device which is arranged downstream of the at least one catalytic converter device.

5. The exhaust system in accordance with claim 4 , wherein:

the at least one catalytic converter unit comprises an internal combustion engine exhaust gas flow space through which internal combustion engine exhaust gas flows;

the heater exhaust gas flow space encloses a length area of the internal combustion engine exhaust gas flow space, which length area contains the at least one particle filter device, over an entire circumference of the internal combustion engine exhaust gas flow space.

6. The exhaust system in accordance with claim 1 , wherein at least one catalytic converter unit is at least one first catalytic converter unit and further comprising at least one second catalytic converter unit provided in an internal combustion engine exhaust gas flow direction downstream of the at least one first catalytic converter unit, and the at least one second catalytic converter unit is an SCR catalytic converter unit.

7. The exhaust system in accordance with claim 1 , further comprising:

at least one muffler unit connected to the at least one catalytic converter unit in an internal combustion engine exhaust gas flow direction downstream of the at least one catalytic converter unit, wherein heater exhaust gas flowing through the heat exchanger volume is introduced into the internal combustion engine exhaust gas stream in the internal combustion engine exhaust gas flow direction upstream of at least one muffler unit.

8. The exhaust system in accordance with claim 7 , further comprising at least another muffler unit wherein a plurality of muffler units following one another in an internal combustion engine exhaust gas flow direction, and that the heater exhaust gas is introduced into the internal combustion exhaust gas stream between a last muffler unit in the internal combustion engine exhaust gas flow direction and a next-to-last muffler unit in the internal combustion engine exhaust gas flow direction.

9. The exhaust system in accordance with claim 1 , wherein the fuel-operated heater comprises:

a combustion air feed device for feeding combustion air into a combustion chamber;

a fuel feed device for feeding fuel into the combustion chamber; and

a heat exchanger unit through which heater exhaust gas and heat exchanger medium to be heated can flow.

10. The exhaust system in accordance with claim 9 , further comprising a heater exhaust gas catalytic converter device, through which heater exhaust flows.

11. The exhaust system in accordance with claim 10 , wherein the heater exhaust gas catalytic converter device is arranged in a heater exhaust gas flow direction essentially downstream of the heat exchanger unit.

12. The exhaust system in accordance with claim 1 , wherein the at least one catalytic converter unit comprises a housing and an outer wall, the outer wall surrounding at least a portion of the housing, the housing comprising an outer housing surface and an inner housing surface, the outer wall comprising an outer wall inner surface, the outer wall inner surface and the outer housing surface defining at least a portion of the heater exhaust gas flow space, the inner housing surface defining at least a portion of the internal combustion engine exhaust gas flow space.

13. A method for operating an exhaust system, the method comprising:

providing an exhaust system for an internal combustion engine, the exhaust system comprising:

at least one catalytic converter unit with at least one catalytic converter device through which internal combustion engine exhaust gas flows, the at least one catalytic converter unit comprising an internal combustion engine exhaust gas flow space through which internal combustion engine exhaust gas flows, the at least one catalytic converter device being arranged in the internal combustion engine exhaust gas flow space;

a heat exchanger volume; and

a fuel-operated heater with an operative connection between a heater exhaust of the fuel-operated heater and the heat exchanger volume, wherein heater exhaust gas leaving the heater flows through the heat exchanger volume, the heat exchanger volume comprising a heater exhaust gas flow space enclosing the internal combustion engine exhaust gas flow space at least in a length area of the internal combustion engine exhaust gas flow space containing the at least one catalytic converter device;

operating the fuel operated heater in a catalytic converter unit temperature control mode at least if a temperature in the area of the at least one first catalytic converter unit is below a first threshold temperature in a combustion operation generating heater exhaust gas flowing through the heat exchanger volume.

14. The method in accordance with claim 13 , further comprising:

providing a heater exhaust gas catalytic converter device, through which heater exhaust flows;

arranging the heater exhaust gas catalytic converter device in a heater exhaust gas flow direction essentially downstream of the heat exchanger unit;

operating the heater at least some times with a hypostoichiometric fuel/combustion air mixture in the combustion operation.

15. The method in accordance with claim 14 , wherein the heater is alternatingly operated with a hypostoichiometric fuel/combustion air mixture and a hyperstoichiometric fuel/combustion air mixture.

16. The method in accordance with claim 13 , wherein the heater is operated at least some times with a hyperstoichiometric fuel/combustion air mixture after the combustion has ended.

17. The method in accordance with claim 13 , wherein the heater is operated in a catalytic converter unit temperature control mode at least if the temperature in the area of the at least one first catalytic converter unit is above a second threshold temperature in an air feed operation for generating an air stream flowing through the heat exchanger volume.

18. A drive system for a vehicle, the drive system comprising:

an internal combustion engine; and

an exhaust system comprising:

at least one catalytic converter unit with at least one catalytic converter device through which internal combustion engine exhaust gas flows;

a heat exchanger volume; and

a fuel-operated heater with an operative connection between a heater exhaust of the fuel-operated heater and the heat exchanger volume, whereby heater exhaust gas leaving the heater flows through the heat exchanger volume, the at least one catalytic converter unit comprising an internal combustion engine exhaust gas flow space through which internal combustion engine exhaust gas flows, the at least one catalytic converter device being arranged in the internal combustion engine exhaust gas flow space, the heat exchanger volume comprising a heater exhaust gas flow space enclosing the internal combustion engine exhaust gas flow space at least in a length area of the internal combustion engine exhaust gas flow space containing the at least one catalytic converter device.

19. The drive system in accordance with claim 18 , wherein:

the heater exhaust gas flow space extends over at least a portion of a circumference of the internal combustion engine exhaust gas flow space.

20. The drive system in accordance with claim 19 , wherein the fuel-operated heater comprises:

a combustion air feed device for feeding combustion air into a combustion chamber;

a fuel feed device for feeding fuel into the combustion chamber; and

a heat exchanger unit through which heater exhaust gas and heat exchanger medium to be heated can flow.