Procedure for heating-up and keeping warm an emission control assembly of a motor vehicle

Abstract

The invention concerns a procedure to heat up or keep warm an exhaust gas emission control assembly of a motor vehicle with a drive train containing one transmission. The drive train is powered by an internal combustion engine and at least one second drive unit.

Description

SHORT DESCRIPTION OF THE DRAWING

Additional forms of embodiment, aspects and advantages of the invention also result independently from their summarization in claims without restriction of the generality of the following description using the only FIGURE of the example of embodiment of the invention depicted in the drawing.

FORM OF EMBODIMENT OF THE INVENTION

The only FIGURE shows in a sectional representation a schematic depiction of a drive train of a motor vehicle designed as a parallel hybrid.

The motor vehicle 10 comprises a drive train 11, which can be engaged with an internal combustion engine 12 and an electric machine 13, which is connected to a battery 14, and a transmission 15, a decoupler 16, a clutch 17 and a drive 18, preferably a differential drive 18.

An exhaust gas emission control assembly is not depicted in the FIGURE, which comprises at least one catalytic converter, and which must have a certain operating temperature for optimal performance, i.e. for the optimal purification of the exhaust gases fed through the exhaust gas emission control assembly.

The optimal operating temperature is set as quickly as possible, if the internal combustion engine 12 is operated with an optimum engine rotational speed, which is an engine rotational speed optimized for the control of exhaust gases, or with an optimum torque, which is a torque optimized for the control of exhaust gases. When cold starting, if the exhaust gas emission control assembly is still cold, only an insufficient conversion, i.e. an insufficient control of the exhaust gases in the assembly, takes place, so that the emission of the exhaust gasses is high.

In order to quickly heat up or to keep the catalytic converter warm, as much waste heat as possible must be given off to the exhaust gas emission control assembly by way of the exhaust gases. This is attained, in that the internal combustion engine 12 is operated with an optimal rotational speed, which is designated as optimum engine rotational speed, or is operated with an optimal torque, which is designated as optimum torque.

In order to meet the demand of the driving performance requirements, which mean, for example the motor vehicle's speed, a drive unit, preferably the internal combustion engine 12, in a motor vehicle with two drive units is deployed to heat up the exhaust gas emission control assembly; and the other drive unit, preferably the electric machine 13, is deployed to implement the demands of the driver, i.e. the motor vehicle's speed.

Among other things two concepts are known for a hybrid vehicle: the so-called power-split-concept, also known as the power-split hybrid, and the concept of the parallel hybrid. In both concepts it is possible to significantly detach the internal combustion engine 12 from the driver's input and to design a rotational speed of the internal combustion engine 12 quasi uncompromisingly to an optimal emission control. By means of the corresponding open loop control of the electric machine 13, the input of the driver can nevertheless be implemented in a broad scope, so that the driver does not notice any difference in the performance of the vehicle between the heating-up phase and a normal operating mode.

Claims

1. A method of heating-up and keeping warm an exhaust gas emission control assembly of a motor vehicle with a drive train, containing one transmission, which is powered by an internal combustion engine and at least one second drive unit, the method comprising: setting a rotational speed or a torque of the internal combustion engine in an operating state, which lies outside of the idling speed and deviates from values for rotational speed or torque, during an identical driving operational state without the heating-up or keeping warm of the exhaust gas emission control assembly.

2. A method according to claim 1, further comprising disengaging the internal combustion engine from the drive train and providing a rotational speed or a torque from the second drive unit.

3. A method according to claim 1, further comprising calculating an optimum engine rotational speed or an optimum torque required for the heating-up or keeping warm of the exhaust gas emission control assembly.

4. A method according to claim 1, further comprising calculating a minimum engine rotational speed or a minimum torque, which in each case represent a lower threshold value for the heating-up of the exhaust gas emission control assembly.

5. A method according to claim 1, further comprising calculating a maximum engine rotational speed or a minimum engine rotational speed, which in each case represent an upper threshold value for the heating-up of the exhaust gas emission control assembly.

6. A method according to claim 1, further comprising assigning priority for an optimum engine rotational speed, a minimum engine rotational speed, or a maximum engine rotational speed.

7. A method according to claim 1, further comprising assigning a priority for an optimum torque, a minimum torque, or a maximum torque.

8. A method according to claim 1, further comprising allowing demands from varying functional units different from the exhaust gas emission control assembly in a motor vehicle control system with regard to engine rotational speed and assigning, in each case, a priority to the demands of the varying functional units.

9. A method according to claim 8, wherein the demands, which do not themselves originate with the heating-up or keeping warm of the exhaust gas emission control assembly, are only then taken into account, if their priority is higher, or an engine rotational speed demanded or a torque demanded lies above a minimum engine rotational speed or beneath a maximum engine rotational speed.

10. A method according to claim 8, wherein the demands, which do not themselves originate from the heating-up or the keeping warm of the exhaust gas emission control assembly, are only then taken into account, if their priority is higher, or a torque demanded lies above a minimum torque or beneath a maximum torque.

11. A method according to claim 1, wherein setting includes setting the engine rotational speed such that an open loop control of an automatic transmission is adapted to selection of a gear ratio in such a manner that a rotational speed lying as close as possible to an optimum engine rotational speed results or that a minimum engine rotational speed is not undershot or that a maximum engine rotational speed is not exceeded.

12. A method according to claim 1, wherein setting includes setting the engine rotational such that in a power-split system, rotational speeds of both of the internal combustion engine and the second drive unit are adjusted in such a manner that a rotational speed of the internal combustion engine lies as close as possible to an optimum engine rotational speed, or that a minimum engine rotational speed is not undershot or that a maximum engine rotational speed is not exceeded.

13. A method according to claim 1, further comprising adjusting the second drive unit in such a manner that when interacting with torques of the internal combustion engine and the second drive unit, a torque demanded is set, whereby the internal combustion engine is operated in such a way that a torque emitted from it corresponds to an optimum torque calculated for the heating-up of the exhaust gas emission control system or is greater than the minimum torque or smaller than the maximum torque.

14. A method according to claim 1, wherein optimum engine rotational speed, minimum engine rotational speed, maximum engine rotational speed, optimum torque, minimum torque, or maximum torque are variably dependent on ambient conditions or on an already implemented heating progression of the exhaust gas emission control assembly.

15. A motor vehicle with an exhaust gas emission control assembly and a drive train in which the internal combustion engine and at least one second drive unit are connected, whereby the drive train has a transmission, wherein the internal combustion engine can be disengaged from the drive train depending upon an engine rotational speed for heating-up and keeping warm of the exhaust gas emission control assembly or a torque of the drive train, whereby in an operating state, which lies outside of the idling speed, an engine rotational speed or a torque of the internal combustion engine, deviating from the values for the engine rotational speed or the torque, is adjustable and setting the engine rotational speed or torque during an identical driving condition without the heating-up or keeping warm of the exhaust gas emission control assembly.

16. A motor vehicle according to claim 15, wherein a second drive unit is an electric machine.

17. A motor vehicle according to claim 15, wherein the internal combustion engine can be disengaged from the drive train by means of a decoupler.