DE102019213082A1 - Method for operating a hybrid vehicle - Google Patents

Abstract

The invention relates to a method for operating a hybrid vehicle (100) with an internal combustion engine (110) and a torque-coupled electric machine (120), in which a component (140, 141) can be diagnosed during operation, with and / or or while the diagnosis is being carried out for a predetermined period of time, the internal combustion engine (110) and the electrical machine (120) are operated together in such a way that at least one target variable (T) of the internal combustion engine (110) relevant for carrying out the diagnosis (D) is within a specified area remains.

Description

The present invention relates to a method for operating a hybrid vehicle with an internal combustion engine and a torque-coupled electric machine, in which a component diagnosis can be carried out during operation, as well as a computing unit and a computer program for carrying it out.

State of the art

In a vehicle, especially one with an internal combustion engine, emissions-relevant components or components or systems have to be checked or monitored by the vehicle itself or a corresponding processing unit or a corresponding control unit while driving, i.e. during operation. This is known under the term of on-board diagnosis or OBD (there is also a corresponding legislation for this).

The resulting diagnoses must run both in a reference emissions test and in normal driving (then proven by a so-called IUMPR or “In Use Monitor Performance Ratio”). The diagnoses should run alongside normal driving.

Disclosure of the invention

According to the invention, a method for operating a hybrid vehicle as well as a computing unit and a computer program for its implementation with the features of the independent claims are proposed. Advantageous refinements are the subject matter of the subclaims and the description below.

The invention relates to a method for operating a hybrid vehicle with an internal combustion engine and a torque-coupled electrical machine, in which a component diagnosis can be carried out during operation. Such a diagnosis is, in particular, a diagnosis within the scope of the on-board diagnosis already mentioned above, as is carried out for various components. Components that relate to or influence exhaust gases or emissions from the vehicle or the internal combustion engine, such as a catalytic converter or a lambda probe, are particularly relevant here. In the course of such a diagnosis, it is checked in particular whether certain measured values are within permissible ranges.

It has now been shown that, in particular in the case of an operating state that changes very quickly due to short-term changes in external conditions or a driver's request, undesired interruptions and / or restart of the (once started) diagnosis can occur.

If such a diagnosis is associated, for example, with an active adjustment of the so-called lambda value relative to a value of one, the diagnosis itself can even result in undesirable emissions. For example, in the case of catalytic converter or lambda probe diagnosis, there may be an increase in emissions as a result of a rapid and strong increase in load if the catalytic converter system is completely flowed through with exhaust gas that deviates from lambda one.

In the proposed method, before and / or while the diagnosis is being carried out (during operation of the hybrid vehicle) during a predetermined period, that is to say in particular for a certain minimum duration, the internal combustion engine and the electrical machine are operated together in such a way that at least one is being carried out The target variable relevant to the diagnosis remains within a predetermined range, in particular at least essentially constant.

In this way, conditions that are as constant as possible can be created during operation of the internal combustion engine. This takes into account the requirement that various diagnoses generally require relatively stable and sometimes restricted operating conditions in order to be able to be carried out. For example, the exhaust gas mass flow and the catalytic converter temperature must lie in a certain range and be stable or they must not change too much in order to be able to carry out a catalytic converter diagnosis. Such operating points often do not exist, particularly when driving dynamically or when operating points change significantly for other reasons. So far, there have therefore been a large number of terminations as well as widely scattered diagnostic results.

This is where the invention comes in and integrates the electric machine in a hybrid vehicle in order to keep the operating point of the internal combustion engine as constant as possible. Any changes in a torque request and the like are simply accepted by means of the electrical machine - which has no or at least hardly any influence on such a diagnosis. The electric machine can be operated in a supporting manner (i.e. by outputting torque in motor operation) or under load (i.e. by absorbing torque in generator operation) as required. In this way, better diagnostic results can be achieved overall, and the number of interruptions or new starts of diagnostics is reduced sometimes significantly reduced and emissions can also be reduced.

It should be noted here that a hybrid vehicle can be understood to mean any vehicle with an internal combustion engine and an electric machine, in which the electric machine can at least to a certain extent support and / or burden the internal combustion engine. In this respect, a so-called starter generator can also be considered as a corresponding electrical machine.

Such target variables - which should therefore remain at a certain value or in a certain range of values during the specified period of time - are in particular a (preferably relative) load torque on the internal combustion engine, an air mass flow through, a fuel mass flow, an exhaust gas mass flow, an exhaust gas temperature (in particular in Area of the catalytic converter), a speed of the internal combustion engine and a torque generated by the internal combustion engine into consideration.

In general, depending on the type of diagnosis, it may be necessary for the target variable to remain as constant as possible before, during or before and during the diagnosis. In this respect, the relevant, predetermined period of time can be selected accordingly before and / or during the diagnosis. The length of the period can also be selected according to the type of diagnosis and can depend on the duration of the implementation of the diagnosis, but also on the duration until the conditions relevant for the diagnosis are present.

It is also preferred if the internal combustion engine and the electrical machine continue to be operated together during the specified period of time in such a way that a sum of the torques output by the internal combustion engine and the electrical machine corresponds to a torque request to the hybrid vehicle that is specified, for example, by a driver's request . Ultimately, this means that any torque changes are primarily made by the electrical machine. In this way, dynamic operation of the hybrid vehicle can still be made possible - at least within certain limits - while the diagnosis can be carried out reliably. It is of course also conceivable that the torque request corresponds to a constant torque, i.e. that the sum of the torques output by the internal combustion engine and the electrical machine remains constant or at least essentially constant during the specified period.

Before the diagnosis is carried out - and in particular also before the aforementioned operation of the internal combustion engine and electrical machine - it is advantageously checked which maximum torque the electrical machine can absorb and / or output, the diagnosis only being carried out if, taking into account the maximum The torque that can be absorbed or emitted by the electrical machine, the internal combustion engine and the electrical machine can be operated together during the predetermined period of time in such a way that the target variable of the internal combustion engine remains within the predetermined range. In other words, it can first be checked whether the electrical machine is even able to balance the operation of the internal combustion engine to such an extent that the latter can be operated as required.

If this is not the case, this check can be carried out again at a later point in time, for example. This is because the conditions for both the internal combustion engine and the electrical machine can then have changed. The maximum torque that the electric machine can absorb and / or output also depends, for example, on the current state of a battery, an inverter used or other operating limits that can possibly also be influenced by the temperature or other ambient conditions. In this way, any interruptions to diagnoses can be prevented even more effectively.

It is also conceivable that a diagnosis is only carried out when a specific minimum torque can be output and / or absorbed by the electrical machine. This ensures that sufficient torque from the internal combustion engine can be compensated for in order to operate it at the relevant operating point.

If the internal combustion engine is assigned an automatic transmission (with a number of gears), it is also preferred if the internal combustion engine continues to be operated during the predetermined period of time such that a speed of the internal combustion engine is within a predetermined range by selecting a suitable gear. In this way, for example, a preferred speed range for a certain type of diagnosis can be selected. For example, it can make sense to increase the speed in order to achieve higher exhaust gas temperatures. These are often useful for diagnosing the catalytic converter.

If a continuously variable automatic transmission is assigned to the internal combustion engine, the Internal combustion engine continues to be operated in such a way that a speed of the internal combustion engine remains at least substantially constant. Diagnosis can thus be made even more efficient, since the conditions are even more stable.

The operating point of an internal combustion engine is defined by its speed and torque. If both are preferably kept essentially constant or within a permissible tolerance range, the internal combustion engine and the electrical machine are preferably operated together in such a way that the operating point of the internal combustion engine remains constant within the scope of an operating point tolerance. As a result, numerous target variables relevant for diagnoses can be kept essentially constant at the same time.

It is particularly preferred or a preferred goal that - depending on the intervention options - the operating point of the internal combustion engine, that is to say speed and torque, are kept constant as a target variable or at least as constant as possible or at least in the range mentioned. If this is not or not sufficiently possible, for example due to the lack of possibility to keep the speed constant or to vary it in a targeted manner, it is preferred or a preferred goal to adjust the exhaust gas mass flow and / or the torque of the internal combustion engine - depending on the specific application. to be kept constant or at least as constant as possible or at least in the range mentioned. Further preferred target variables such as air mass flow, fuel mass flow, exhaust gas mass flow and exhaust gas temperature will, for example and generally also remain constant at a constant operating point.

A computing unit according to the invention, for example a control unit of a motor vehicle, is set up, in particular in terms of programming, to carry out a method according to the invention.

The implementation of a method according to the invention in the form of a computer program or computer program product with program code for performing all method steps is advantageous, since this causes particularly low costs, especially if an executing control device is used for other tasks and is therefore available anyway. Suitable data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard drives, flash memories, EEPROMs, DVDs, etc. A program can also be downloaded via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention emerge from the description and the accompanying drawing.

The invention is shown schematically in the drawing using an exemplary embodiment and is described below with reference to the drawing.

Figure list

• 1 shows schematically a hybrid vehicle in which a method according to the invention can be carried out.
• 2 shows schematically a sequence of a method according to the invention in a preferred embodiment.

Embodiment (s) of the invention

In 1 is schematically a hybrid vehicle 100 shown, in which a method according to the invention can be carried out. The hybrid vehicle 100 has an internal combustion engine 110 as well as a torque-coupled electrical machine 120 on. The electrical machine can be operated in such a way that it supports the internal combustion engine, that is to say additionally emits torque, or also takes up torque, that is to say is operated as a generator. The internal combustion engine 110 is also an example of a continuously variable automatic transmission 150 assigned.

There is also a computing unit designed as an engine control unit 130 shown, by means of which the internal combustion engine 110 and the electrical machine can be controlled and operated with it. In addition, a diagnosis can be carried out with it, for example a diagnosis of a catalytic converter 140 or a lambda probe 141 , each of which is only indicated schematically.

In 2 a sequence of a method according to the invention is shown schematically in a preferred embodiment, as is the case, for example, in the hybrid vehicle or on its engine control unit according to FIG 1 can be carried out.

In one step 200 it is first established that a specific diagnosis D. should be carried out. Then in one step 210 checked whether the electrical machine - currently - can output or absorb a certain minimum torque Mmin and what maximum torque Mmax it can output or absorb.

Then in one step 220 an operating point B. (and thus the torque and, if possible with the existing transmission or transmission concept, the speed) of the internal combustion engine is set to a predefined value within a predefined range W so that at least one is required to carry out the diagnosis D. relevant target variable, such as an exhaust gas temperature T , remains within a specified range. Within this range W becomes the operating point B. then for a specified period of time Δt held. Then it is done in one step 230 the diagnosis started.

During the period Δt the electrical machine is operated or controlled in such a way that a possible torque request M _F to the hybrid vehicle by means of a buzzer of the torques currently provided by the internal combustion engine and the electrical machine. After completion of the diagnosis can be done in one step 240 then go back to the regular operation of the hybrid vehicle.

In this way, diagnostics can be carried out significantly more efficiently in a hybrid vehicle, since the number of interruptions or new starts of diagnostics can be significantly reduced.

Claims (10)

Method for operating a hybrid vehicle (100) with an internal combustion engine (110) and a torque-coupled electric machine (120), in which a diagnosis with regard to a component (140, 141) can be carried out during operation, with before and / or during execution of the diagnosis (D), the internal combustion engine (110) and the electrical machine (120) are operated together during a predetermined period of time (Δt) in such a way that at least one target variable (T) of the internal combustion engine (110) relevant for carrying out the diagnosis (D) remains within a specified range. Procedure according to Claim 1 , wherein the at least one target variable relevant for performing the diagnosis is selected from: a load torque, a generated torque, a speed, an air mass passed through, a fuel mass flow, an exhaust gas mass flow and an exhaust gas temperature (T). Method according to one of the preceding claims, wherein during the predetermined time period (Δt) the internal combustion engine (110) and the electrical machine (120) continue to be operated together in such a way that a sum of the torques output by the internal combustion engine and the electrical machine of a torque request (M _F ) corresponds to the hybrid vehicle (100). Method according to one of the preceding claims, wherein, before the diagnosis (D) is carried out, it is checked which maximum torque (M _max ) the electrical machine can absorb and / or output, and the diagnosis (D) is only carried out if below _{Taking into account the maximum torque (M max} ) that can be absorbed and / or emitted by the electrical machine, the internal combustion engine (110) and the electrical machine (120) can be operated together during the specified period (Δt) in such a way that the at least one for performing the Diagnosis (D) relevant target variable (T) remains within the specified range. Method according to one of the preceding claims, wherein, if the internal combustion engine (110) is assigned an automatic transmission, the internal combustion engine continues to be operated during the predetermined time period (Δt) in such a way that a speed of the internal combustion engine (110) within within a given range. Method according to one of the preceding claims, wherein, if the internal combustion engine (110) is assigned a continuously variable automatic transmission (150), the internal combustion engine continues to be operated during the predetermined period of time in such a way that a speed of the internal combustion engine (110) remains at least substantially constant . Method according to one of the preceding claims, wherein during the predetermined time period (Δt) the internal combustion engine (110) and the electrical machine (120) are operated together in such a way that an operating point (B) of the internal combustion engine (110) is within a predetermined range (W) remains. Computing unit (130) which is set up to carry out all method steps of a method according to one of the preceding claims. Computer program that causes a computing unit (130) to perform all method steps of a method according to one of the Claims 1 to 7th perform when it is executed on the computing unit (130). Machine-readable storage medium with a computer program stored thereon Claim 9 .

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