Method for Reducing Emissions in a Motor Vehicle by Controlling the Generator Output

Abstract

A method for influencing exhaust-gas characteristics of a motor vehicle having a combustion engine in which the exhaust-gas composition and/or the exhaust-gas temperature are/is influenced with the aid of an emission management system that includes a control device having an emission management algorithm and at least one control element. The exhaust-gas values are able to be optimized, and the fuel consumption lowered if the generator output is increased or lowered by the emission management system within the framework of an emission management measure.

Description

FIELD OF THE INVENTION

The present invention relates to a method for controlling exhaust-gas characteristics of a motor vehicle having a combustion engine, and to a corresponding device.

BACKGROUND INFORMATION

Modern vehicles usually include an emission-reduction system, which is used to reduce the emissions, especially of carbon-monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NO_x) in the exhaust gas of the combustion engine. The measures for reducing the emissions are normally subdivided into “engine measures”, “post-engine measures” and “secondary treatment measures”.

Among the engine measures are, for example, a load-dependent mixture adjustment, the mixture generation, exhaust-gas recirculation (EGR) or injection control etc.

Among the post-engine measures are, in particular, the generally known exhaust-gas catalysts, exhaust-gas particle filters (DPF), especially for diesel vehicles, as well as thermal afterburning of the exhaust gases.

Exhaust-Gas Catalyst

Various catalyst types, such as, for example, TWO, NSC, SOR, DOC are known from the related art. In an adsorption catalyst NSC (nitrogen oxide adsorption catalyst) the catalyst must be regenerated at regular intervals in order to ensure proper functioning of the catalyst. In the regeneration procedure the mixture is usually set to leaner values and the NO_x emissions are thereby reduced, but there is a rise in the fuel consumption, and the CO and HC emissions increase. A catalyst regeneration typically takes less than five seconds.

Exhaust-Gas Particle Filter

With the aid of special filter structures, a particle filter DPF mechanically catches the soot particles produced in the combustion. In order to ensure proper functioning of the particle filter in the long term, the filter must be regenerated regularly. In doing so a regeneration temperature is set that is several 100K above the exhaust-gas temperature prevailing during normal operation. A DPF regeneration phase lasts approximately 5 to 10 minutes.

To implement the various emission-reducing measures or to regenerate catalytic converters or particle filters, modern vehicles include an emission reduction system, which essentially is made up of a control device having an emission management algorithm (EMA) and a number of sensors. Within the scope of reducing emissions, the EMA acts on a number of control devices such as the injection, throttle valve, an exhaust-recirculation valve etc. As a rule, all measures taken for the purpose of reducing emissions are not torque-neutral, i.e., they affect the torque and thus the output of the combustion engine. This is not intended since the output changes produced in this manner interfere with the driving operation.

To avoid torque changes, the emission reduction system therefore implements suitable compensating measures. While the various compensating measures cause the torque to remain essentially constant, the fuel consumption rises and the efficiency of the engine drops accordingly.

SUMMARY OF THE INVENTION

Therefore it is an object of the present invention to enhance the effectiveness of an emission management system and simultaneously improve, in particular, the energy balance of emission management measures.

An important idea of the present invention is to make use of the operation of the vehicle generator as an additional degree of freedom within the scope of the measures for reducing emissions. The vehicle generator is driven by the combustion engine and requires a more or less powerful torque from the combustion engine, depending on the generator output provided. By modifying the generator output, it is therefore possible to modify the torque requirement of the generator and thereby compensate for a change in the engine torque caused by emission-reducing measures. Furthermore, a modification of the generator output, or the retrospective effect on the combustion engine, also allows the chemical composition of the exhaust-gas flow or the exhaust-gas temperature (in the following: exhaust gas characteristics) to be influenced. In particular with emission management measures in which the engine torque increases, the integration of the vehicle generator into the emission management also has the advantage that this additional engine output is able to be converted into electrical power by a corresponding increase in the generator output. The energy stored in the fuel is therefore not wasted but converted into electric energy and stored, for instance in a battery.

The integration of the vehicle generator into the emissions management system according to the present invention allows a multitude of applications of which a few are listed in the following text:

According to a first specific embodiment of the present invention, the generator output is increased in a regeneration process for an adsorption catalyst (NSC). The injection quantity of the main injection is normally increased over several seconds in a regeneration of an adsorption catalyst, the excess-air factor (Lambda) dropping in the process. However, this simultaneously means higher fuel consumption and an increase in the engine torque. By a corresponding increase in the generator output, this engine torque is able to be partially compensated. The additional electric energy generated in the process may be stored, for instance in a battery or some other electric storage device. The electric energy may then be used in a subsequent lean phase of the combustion engine, for instance, to operate electric consumers, and the generator output reduced accordingly. This makes it possible to save fuel in the subsequent lean phase.

According to a second specific embodiment of the present invention, the generator output is increased in a regeneration process for an exhaust-gas particle filter. Particle filters are regenerated by, among others, an accumulated late injection, which causes the exhaust-gas temperature to rise and the soot mass to be combusted. Due to the additional late injection, the fuel consumption increases during the particle filter regeneration as well, for a period of approximately 5 to 10 minutes. The additional engine torque may once again be compensated by setting a higher generator output. The electrical energy obtained in the process is preferably stored again.

The generator output may be varied, for instance by direct control of a generator controller or by control of an energy management system, which then is able to initiate various measures that influence the generator output, such as the activation or deactivation of consumers. The emission management system preferably has an interface to an energy management system for this purpose.

According to a third specific embodiment of the present invention, the generator output is reduced in an acceleration phase of the vehicle, and the ERR (ERR: exhaust-recirculation rate) is increased accordingly. A high ER rate is usually set in stationary driving operation of a vehicle in order to reduce the NO_x emissions. In contrast, in acceleration phases, the ER rate must be reduced so that enough oxygen is available for an additional fuel combustion. If the loading of the combustion engine is reduced by the vehicle generator in such an acceleration phase, a relatively higher ER rate may simultaneously be implemented and the NO_x emissions reduced in this manner.

According to a fourth specific embodiment of the present invention, in a cold-start phase or in phases having a low exhaust-gas temperature, e.g., in longer overrun phases, the generator output is increased in order to raise the exhaust-gas temperature. The efficiency of an exhaust-gas catalyst drops at an exhaust-gas temperature that is too low. The additional loading of the combustion engine by the vehicle generator entails higher fuel consumption, and the exhaust gas heats up more rapidly. This shortens the cold-start phase or phases during which a low exhaust-gas temperature prevails.

According to a fifth specific embodiment of the present invention, the generator output is increased in the cold-start phase in order to reduce the HC and CO emissions of the combustion engine. In the cold-start phase the engine temperature is lower than during normal operation so that the HC and CO emissions of the combustion engine increase. If the generator output and thus the torque requested from the combustion engine is increased during the cold-start phase, the cold-start phase is able to be shortened correspondingly.

An emission management system by which the methods described above are able to be implemented includes a control device having an emission management algorithm and at least one control element connected to the control device with whose aid the chemical exhaust-gas composition and/or the exhaust-gas temperature are/is able to be influenced. Also included in this system is a generator having a generator controller, which is controllable by the control device, so that the generator output is able to be increased or lowered within the scope of an emission management.

Prior to modifying the generator output, the emission management system communicates preferably with an energy management system, which is utilized to administer the electric power in an electrical network. In this way the requirements of the emission management system may be coordinated with those of the energy management system. This makes it possible, for instance, that the energy management system rejects a request to increase the generator output if the generator is loaded to capacity or if the battery is already fully charged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic block representation of an emission management system connected to an energy management system.

FIG. 2 shows a schematic representation of a vehicle electrical network having an emission management system and an energy management system.

DETAILED DESCRIPTION

FIG. 1 shows an emission management system (left side), which is connected to an energy management system (right side). The emission management system includes a control device 1 having an emission management algorithm (EMA), which is stored in control device 1 in the form of software. Control device 1 is connected to various control elements, in the case at hand, to throttle valve 2, injection 4, and an exhaust-gas recirculation system 5, by way of example. The individual subsystems 3-5 may be controlled within the framework of engine or post-engine measures for the purpose of reducing emissions or for regeneration, and the emission values optimized as a result.

Emission management system 1,3,4,5 is able, for instance, to actuate throttle valve 3, modify the injection quantity or the injection timing, or influence the exhaust-gas recirculation rate in order to modify the chemical exhaust-gas composition or the exhaust-gas temperature. The relationships between the influence variables and the emission values are sufficiently known from the related art.

Furthermore, control device 1 is connected to a vehicle generator 7 or its generator controller 13 via a control line 10. In this way, emission management system 1,3,4,5 is able to also incorporate generator 7 into the emission management as an additional degree of freedom. This results in a multitude of possibilities for utilizing generator 7 within the framework of an emission management process.

For instance, the generator may be used to compensate for a higher engine output or a higher engine torque that would be produced by the implementation of emission management measures. At the same time, the energy contained in the fuel is partially converted into electrical energy. If the electrical energy is stored or utilized, fuel is able to be saved at an average over time. Furthermore, generator 7, or the retrospective effect of the generator on the combustion engine, may be used to create the preconditions for further improvement of the emission values.

Via a second communication connection 9, control device 1 is also connected to control device 2 of the energy management system. The energy management system is used to administer the electrical energy available or required in the electrical network, and essentially includes control device 2 to which a plurality of consumers 6, vehicle generator 7 and a battery 8 are connected. Connection 9 may be used to coordinate the power requirements of emission management system 1,3,4,5 with energy management system 2,6,7,8, which likewise has access to vehicle generator 7.

The integration of the vehicle generator into the emission management system according to the present invention allows a multitude of applications such as those listed in the introduction to the specification by way of example.

Within the framework of emission management measures, control device 1 or 2 increases or lowers the generator output depending on the application. optionally, upon request by the EMA, energy management system 2,6,7,8 may even initiate measures on its own in order to increase or lower the generator output, e.g., to activate or deactivate consumers 6.

FIG. 2 shows a vehicle electrical system 14 in which lines 9,10 have been drawn in more precisely. In this case, EMS control device 1 is connected to EEM control device 2 via a CAN bus 9. Via a CAN bus, EEM control device 2 is also connected to a switch 12 by which consumers 6b are able to be activated and deactivated.

Here, the control of generator 7 or generator controller 13 is implemented via a bit-synchronous interface (BSS) on EMS control device 1.

Algorithms EMA and EEM of the two control devices 1,2 may alternatively also be provided in a single control device. The interfaces would then lie within the control device.

LIST OF REFERENCE NUMERALS

• 1 EMS control device
• 2 EEM control device
• 3 throttle valve
• 4 injection
• 5 exhaust-gas recirculation
• 6 consumers
• 7 generator
• 8 battery
• 9 communication line
• 10 control line
• 11 combustion engine
• 12 controllable switch
• 13 generator controller
• 14 vehicle electrical system
• BSS bit-synchronous interface
• EMA emission management algorithm
• EEM electrical energy management
• CAN bus

Claims

1-8. (canceled)

9. A method for influencing exhaust-gas characteristics of a motor vehicle having a combustion engine, the method comprising:

influencing at least one of an exhaust-gas composition and an exhaust-gas temperature by a specified control of control elements with the aid of an emission management system that includes a control device having an emission management algorithm and at least one control element; and

one of increasing and decreasing a generator output within the framework of an emission management measure.

10. The method as recited in claim 9,

wherein the emission management algorithm increases the generator output in a regeneration process for an adsorption catalyst.

11. The method as recited in claim 9,

wherein the emission management algorithm increases the generator output in a regeneration process for an exhaust-gas particle filter.

12. The method as recited in claim 9,

wherein the emission management algorithm reduces the generator output in an acceleration phase of the vehicle and thereby enables a higher exhaust-gas recirculation rate.

13. The method as recited in claim 9,

wherein the emission management algorithm increases the generator output in a cold-start phase or in phases having a low exhaust-gas temperature in order to raise the exhaust-gas temperature or to shorten a warm-up phase of the engine.

14. A device for influencing exhaust-gas characteristics of a vehicle having a combustion engine, comprising:

a control device having an emission management algorithm;

at least one control element connected to the control device, with whose aid at least one of an exhaust-gas composition and an exhaust-gas temperature is able to be influenced; and

a generator controller interconnected with the control device, so that a generator output is able to be at least one of increased and decreased within the framework of an emission management.

15. The device as recited in claim 14,

further comprising a communication interface situated between the emission management algorithm and an energy management algorithm.

16. The device as recited in 14,

further comprising a big-synchronous interface for providing a connection between the control device and the generator controller.