Method for operating an internal combustion engine of a vehicle's drive train at start-up and vehicle

Abstract

The invention relates to a method for operating an internal combustion engine of a drive train of a vehicle at start-up and to a vehicle having an exhaust gas aftertreatment system for purifying exhaust gas of a combustion engine, wherein after starting the internal combustion engine, the drive train is operated in a first operating state, wherein in the first operating state the internal combustion engine is operated at idle speed, the exhaust gas aftertreatment system is heated by the internal combustion engine, and a start-up lock is activated, wherein the activated start-up lock in the first operating state prevents starting with the internal combustion engine, wherein after reaching a predefined state of the exhaust gas aftertreatment system, the drive train is operated in a second operating state, wherein in the second operating state the start-up lock is deactivated, so that starting with the internal combustion engine is possible in the second operating state.

Description

Technical Field

[0001] The invention relates to a method for operating an internal combustion engine (Verbrennungskraftmaschine, combustion engine) of a drive train of a vehicle when starting off and to a vehicle. Background Art

[0002] In particular, in order to meet future motor vehicle emission requirements, it is necessary to avoid operating conditions of motor vehicles in which high exhaust emissions are generated, especially operating conditions of motor vehicles, especially combustion-powered vehicles in which high exhaust emissions are generated. In particular, during the heating phase of the exhaust gas aftertreatment system, that is, during the phase in which the exhaust gas aftertreatment system cannot yet play its full role, high emissions, so-called cold emissions, are generated. Here, the level of cold emissions is largely related to the user's driving style and the heating capacity of the exhaust gas aftertreatment system. In particular, such cold emissions are generated when the vehicle is started for the first time after the internal combustion engine of the motor vehicle is started for the first time, because the temperature of the exhaust gas aftertreatment system when the motor vehicle is stopped for a long time or when it is started for the first time is lower than the original operating temperature or operating temperature window of the exhaust gas aftertreatment system, wherein the exhaust gas aftertreatment system only plays its full role or at least an acceptable role at this operating temperature. Therefore, under the condition of being lower than the operating temperature of the exhaust gas aftertreatment system, exhaust gas with a high content of harmful substances is discharged from the exhaust gas aftertreatment system.

[0003] A hybrid vehicle having an internal combustion engine and a catalytic converter is known from DE 11 2011 104 708 B4. This document describes a method for operating a hybrid vehicle, wherein the hybrid vehicle is started at least electrically when the internal combustion engine is cold for the first time, and the internal combustion engine is started before, during or after the start and is operated in a combustion mode independent of the electric operation of the electric motor to heat the catalytic converter.

[0004] DE 10 2009 027 642 A1 also describes a method for controlling a drive train of a hybrid vehicle, wherein the hybrid vehicle is started at least electrically when the hybrid drive is started for the first time when the internal combustion engine is cold, and the internal combustion engine is started before, during or after the start and is operated in a combustion mode independent of the electric operation of the electric motor to heat the catalytic converter.

[0005] DE 10 2009 027 641 A1 and DE 103 33 210 A1 form further prior art. Summary of the invention

[0006] The object of the present invention is to provide a method and a vehicle which are distinguished by particularly low emissions when starting or starting. The method according to the invention is in particular a method for operating an internal combustion engine during a cold start, ie starting when the internal combustion engine is relatively cold.

[0007] This object is achieved by a method for operating an internal combustion engine of a drive train of a vehicle when the vehicle is moving off, as described in the next two paragraphs, and by a vehicle described below, which is particularly suitable for carrying out the method and one or more advantageous embodiments of the method.

[0008] The method according to the invention relates to a method for operating an internal combustion engine of a drive train of a vehicle when the vehicle is starting. The vehicle has an exhaust gas aftertreatment system for purifying the exhaust gas of a combustion engine (Verbrennungmotor, internal combustion engine), wherein after starting the internal combustion engine, the drive train is operated in a first operating state, wherein in this first operating state, the internal combustion engine is operated at idle speed. The exhaust gas aftertreatment system is heated by the internal combustion engine, in particular by the exhaust gas of the internal combustion engine. In this first operating state, the starting lock is enabled, wherein the starting lock enabled in the first operating state prevents starting with the internal combustion engine. As a result, the vehicle cannot start or the vehicle cannot be started. The starting lock can be designed in particular so that the driver of the motor vehicle cannot shift gears when the starting lock is enabled.

[0009] After reaching a predefined state of the exhaust gas aftertreatment system, in particular a predefined operating temperature of the exhaust gas aftertreatment system, the drive train is operated in a second operating state, wherein the start lock is deactivated in the second operating state so that the internal combustion engine can be used for starting.

[0010] The method according to the invention thus ensures that after starting the internal combustion engine, the exhaust gas aftertreatment system first reaches a predefined state, in particular a predefined temperature, thereby increasing the efficiency of the exhaust gas aftertreatment system. During this time, the vehicle cannot use the internal combustion engine for starting, thereby avoiding a request for high power from the internal combustion engine for the purpose of starting the vehicle, which is accompanied by high emissions.

[0011] In the second operating state, that is, in the state where the exhaust gas aftertreatment system has reached the required efficiency, the internal combustion engine can be used to start. Thus, high emissions caused by starting under the condition of reduced efficiency of the exhaust gas aftertreatment system are avoided.

[0012] It is entirely conceivable that in the first operating state the vehicle driver cannot influence the rotational speed of the internal combustion engine, for example pressing the accelerator pedal does not lead to an increase in the rotational speed of the internal combustion engine.

[0013] It is considered particularly advantageous if the exhaust gas aftertreatment system is electrically heatable, in particular has an electrically heatable catalytic converter, wherein the exhaust gas aftertreatment system is electrically heated before the internal combustion engine is started. This has the advantage that the exhaust gas aftertreatment system already has an increased operating temperature before the exhaust gas of the internal combustion engine reaches the exhaust gas aftertreatment system. This also accelerates the heating of the exhaust gas aftertreatment system and thus the second operating state of the drive train is reached more quickly. It is entirely conceivable to also introduce a carrier mass flow into the exhaust gas aftertreatment system in order to distribute the heat generated during the electrical heating in the exhaust gas aftertreatment system.

[0014] It is also considered to be advantageous if the combustion engine can be started or is started only after a predefined second state of the exhaust-gas aftertreatment system has been reached.

[0015] In particular, it is proposed that in the second operating state, the maximum power of the combustion engine that can be requested by the driver is limited to a value below the maximum possible power of the combustion engine. This is particularly advantageous if, although the predefined state of the exhaust gas aftertreatment system is sufficient to avoid high emissions when starting, the efficiency of the exhaust gas aftertreatment system is further increased by further warming of the exhaust gas aftertreatment system. By limiting the maximum power that can be requested by the driver to a value below the maximum possible power value of the combustion engine, high emissions due to a high power output of the combustion engine are avoided. It is entirely conceivable that in the second operating state, the maximum power of the combustion engine that can be requested by the driver continues to increase over time.

[0016] It is considered advantageous if the maximum power that can be requested by the driver is dependent on the state of the exhaust-gas aftertreatment system, and the driver can request the maximum possible power of the combustion engine in particular after reaching a further, predefined state of the exhaust-gas aftertreatment system.

[0017] It is considered to be advantageous if the state of the exhaust-gas aftertreatment system is determined as a function of the temperature of the exhaust-gas aftertreatment system, in particular as a function of the temperature of the catalytic converter.

[0018] It is considered particularly advantageous if the vehicle has an electric motor, wherein the electric motor can be used for starting independently of the state of the exhaust gas aftertreatment system.

[0019] However, it is also entirely conceivable that the drive train does not have any further drive units besides the internal combustion engine. In this respect, the vehicle is a pure combustion engine.

[0020] The vehicle according to the invention is particularly suitable for carrying out the method according to the invention and one or more advantageous embodiments thereof. The vehicle has a drive train with an internal combustion engine, wherein the vehicle has an exhaust gas aftertreatment system for purifying the exhaust gas of the combustion engine and further has a control device, wherein the control device is configured such that after starting the internal combustion engine, the drive train is operated in a first operating state, wherein in the first operating state the internal combustion engine is idle, the exhaust gas aftertreatment system is heated by the internal combustion engine, and a start lock is activated, wherein the activated start lock in the first operating state prevents starting the vehicle using the internal combustion engine. The control device is further configured such that: after reaching a predefined state of the exhaust gas aftertreatment system, the drive train is operated in a second operating state, wherein in the second operating state the start lock is deactivated, so that starting using the internal combustion engine is possible in the second operating state.

[0021] In an advantageous embodiment of the vehicle, it is provided that the vehicle has a display for displaying the operating state of the drive train and / or the state of the starting lock and / or the maximum power that can be requested.

[0022] Additional advantageous embodiments are also provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention is explained in more detail in the following figures with reference to exemplary embodiments, without being restricted thereto.

[0024] In the attached picture:

[0025] Figure 1 A graph is shown for comparing different launch types.

[0026] List of Reference Numerals

[0027] 1 Power curve during a sporty start

[0028] 2 Upper limit when starting in compliance with emission standards

[0029] 3 Power curve when starting according to WLTC

[0030] 4 Power curve when starting according to the invention

[0031] 5 First time interval

[0032] 6 Second time interval DETAILED DESCRIPTION

[0033] Figure 1The following are exemplary diagrams of different power curves for different vehicle start types after starting the internal combustion engine of the vehicle. The curve with reference numeral 1 shows the power curve for a sporty start. Curve 2 shows the upper limit for a start in compliance with emission standards. Curve 3 shows the power curve for a start according to the WLTC test cycle (Worldwide harmonized Lightduty Test Cycle). The curve with reference numeral 4 shows the power curve for a start according to the invention.

[0034] according to Figure 1 The area region of the graph of corresponds to the region with high emissions above curve 2 and the region below curve 2 corresponds to the region with low emissions. Correspondingly, the power curve in the region below curve 2 can be regarded as favorable in terms of emissions.

[0035] In a sporty start, i.e. a start with a very high engine power being requested shortly after the engine is started, the exhaust gas aftertreatment system has not yet reached the required temperature, so that the exhaust gas aftertreatment is relatively poor or incomplete, so that an increase in the emission of harmful emissions occurs in a sporty start according to curve 1.

[0036] In the method according to the invention, it is provided that after starting the internal combustion engine, the drive train is operated in a first operating state, wherein the internal combustion engine is operated at idle speed in this first operating state. Correspondingly, in this first operating state, the exhaust gas aftertreatment system is heated by the internal combustion engine, wherein only a small amount of exhaust gas reaches the exhaust gas aftertreatment system due to the idle speed, so that the exhaust gas aftertreatment system can adequately treat the exhaust gas. In this first operating state, the starting lock is activated, thus preventing starting with the internal combustion engine.

[0037] Based on the current Figure 1 In the exemplary example of , in a first time interval 5 after starting the engine, i.e. from time 0 until a time of approximately 6 seconds, the drive train is operated in a first operating state. This is followed by a second time interval 6, in which the drive train is operated in a second operating state, in which the starting lock is deactivated, so that in the second operating state, i.e. from a time of approximately 6 seconds after starting the engine, the internal combustion engine can be used for starting.

[0038] Furthermore, in the second operating state, i.e. in the second time interval 6, the maximum power of the combustion engine that can be requested by the driver is limited to a value below the maximum possible power of the combustion engine. As a result, the exhaust gas aftertreatment system can be heated further in order to increase the efficiency of the exhaust gas aftertreatment system. In the region of the second time interval 6, the maximum power of the combustion engine that can be requested by the driver increases continuously.

Claims

1. A method for operating an internal combustion engine of a drive train of a vehicle at start-up, wherein the vehicle has an exhaust gas aftertreatment system for purifying exhaust gas of the internal combustion engine, wherein after starting the internal combustion engine, the drive train is operated in a first operating state, wherein in the first operating state, the internal combustion engine is idling, the exhaust gas aftertreatment system is heated by the internal combustion engine, and a start-up lock is activated, wherein the start-up lock activated in the first operating state prevents starting with the internal combustion engine, wherein after reaching a predefined state of the exhaust gas aftertreatment system, the drive train is operated in a second operating state, wherein in the second operating state the start-up lock is deactivated, so that in the second operating state the internal combustion engine can be used for starting, wherein in the second operating state a maximum power of the internal combustion engine that can be requested by a driver is limited to a value below a maximum possible power of the internal combustion engine, wherein the maximum power that can be requested by the driver is dependent on the state of the exhaust gas aftertreatment system and the driver can request the maximum possible power of the internal combustion engine after reaching another, predefined state of the exhaust gas aftertreatment system. 2 . The method according to claim 1 , wherein the exhaust gas aftertreatment system is electrically heatable, wherein the exhaust gas aftertreatment system is electrically heated before starting the internal combustion engine. 3 . The method according to claim 1 , wherein the exhaust gas aftertreatment system has an electrically heatable catalytic converter. 4 . The method according to claim 1 , wherein the internal combustion engine can only be started after a predefined second state of the exhaust-gas aftertreatment system has been reached. 5 . The method according to claim 1 , wherein the state of the exhaust-gas aftertreatment system is determined as a function of a temperature of the exhaust-gas aftertreatment system. 6 . The method as claimed in claim 1 , wherein the vehicle has an electric motor, wherein the electric motor can be used for starting independently of the state of the exhaust gas aftertreatment system.

7. The method according to claim 1 or 2, wherein the drive train does not have any further drive units besides the internal combustion engine.

8. A vehicle having a drive train with an internal combustion engine, wherein the vehicle has an exhaust gas aftertreatment system for purifying exhaust gas of the internal combustion engine, and further comprising a control device, wherein the control device is configured such that after starting the internal combustion engine, the drive train is operated in a first operating state, wherein in the first operating state, the internal combustion engine is idling, the exhaust gas aftertreatment system is heated by the internal combustion engine, and a start-up lock is activated, wherein the start-up lock activated in the first operating state prevents the use of the internal combustion engine for starting the vehicle, wherein the control device is configured such that: after reaching a predefined state of the exhaust gas aftertreatment system, the drive train is operated in a second operating state, wherein in the second operating state, the start-up lock is deactivated, so that in the second operating state the internal combustion engine can be used for starting, wherein in the second operating state a maximum power of the internal combustion engine that can be requested by a driver is limited to a value below a maximum possible power of the internal combustion engine, wherein the maximum power that can be requested by the driver is dependent on the state of the exhaust gas aftertreatment system, and the driver can request the maximum possible power of the internal combustion engine after reaching another, predefined state of the exhaust gas aftertreatment system. 9 . The vehicle according to claim 8 , wherein the vehicle is a vehicle for performing the method according to any one of claims 1 to 7 . 10 . The vehicle according to claim 8 , wherein the vehicle has a display for displaying the operating state of the drive train and / or the state of the start-off lock and / or the maximum power that can be requested by the driver.

11. The vehicle of claim 8, wherein the exhaust aftertreatment system is electrically heatable, wherein the exhaust aftertreatment system is electrically heated prior to starting the internal combustion engine.

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